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Environmental and Natural Resource Management Consultantsvia emailAugust 22, 2008Mr. Drew SquyresSenior Project ManagerPacific Gas and Electric Company, Environmental Services4325 South Higuera StreetSan Luis Obispo, CA 93401RE: Pacific Gas & Electric (PG&E) Company, Diablo Canyon Power Plant(DCPP) Water Resources Evaluation: Well Installation and Aquifer Testing | |||
==Dear Drew:== | |||
Please find enclosed the revised Water Resources Evaluation Phase II report forDiablo Canyon Power Plant. We are providing this to you in accordance withPG&E Contract #46000 16684 and Contract Work Authorization #35007983 13.This draft includes results from additional aquifer testing conducted in June, 2008which improve and expand upon the assessment of any connectivity betweengroundwater pumping and flows within Diablo Creek.We have enjoyed working with you on the important project, and look forward toproviding additional support in the future.Sincerely,Timothy ThompsonVice President -Water Resource Sciencescc: Mr. Mark Coleman, Diablo Canyon Power PlantMr. John Giambastiani, ENTRIX, Concord DIABLO CANYON POWER PLANTWATER RESOURCES EVALUATIONPHASE II REPORT:WELL REHABILITATION,MONITORING WELL INSTALLATION,AND AQUIFER TESTINGPrepared by:Environmental and Natural Resource Management consultantsAugust 22, 2008 ENTRIX, Inc, -Environmental and Natural Resource Management ConsultantsAugust 22, 2008TABLE OF CONTENTSEXECUTIVE SUMMARY ........................................................................................ 11. INTRODUCTION ............................................................................................... 11.1 BACKGROUND......................................................................................................... 11.2 HYDROGEOLOGY .................................................................................................... 21.3 WELL SITE SELECTION.............................................................................................. 32. MONITORING WELL INSTALLATION (WELL #4 AND WELL #5) ................................ 12.1 DRILLER AND DRILLING METHODS................................................................................ 12.2 WELL #4........................................................................................................ 22.2.1 Site Description ........................................................................................ 22.2.2 Well Construction ...................................................................................... 22.2.3 Well Logging............................................................................................ 22.2.4 Well Development and Testing .................................................................... 32.3 WELL#5 .............................................................................................................. 62.3.1 Site Description ........................................................................................ 62.3.2 Well Construction ...................................................................................... 62.3.3 Well Logging............................................................................................ 62.3.4 Well Development and Testing........................................................................ 83. WELL #2 REHABILITATION AND TESTING .......................................................... 113.1 WELL REHABILITATION....................................................................... :.................... 113.1.1 Results of Pump, Motor, and Column Pipe Inspection............................................. 113.1.2 Video Log Results .................................................................:.................... 113.1.3 Description of Well Rehabilitation Tasks Performed .............................................. 113.2 SPINNER TEST........................................................................................................ 123.3 PUMP TESTS FOR EVALUATING WELL YIELD................................................................... 133.3.1 Step Drawdown Test.................................................................................. 133.3.2 Constant Rate Tests................................................................................... 153.5 PUMP SPECIFICATIONS............................................................................................. 164. AQUIFER RESPONSE TO PUMPING TEST......................................................... 174.1 MONITORING LOCATIONS ......................................................................... 2............ 174.1.1 2007 Constant Rate Pumping Test............................................................... 174.1.2 2008 Constant Rate Pumping Test............................................................... 174.1.3 Effect of Constant Rate Pumping Test at Monitoring Wells ................................... 184.1.4 Effect of Constant Rate Pumping Test at Surface Water Monitoring Locations.....'......... 194.2 WATER QUALITY ................................................................................................... 244.2.1 Relative Water Quality of Wells #2, #4 and #5...................................................... 244.2.2 Well #2 -Water Quality vs. Depth.................................................................... 284.2.3 Comparison of Suiface Water and Groundwater Composition .................................... 334.2.4 Summary of Water Quality Results................................................................... 375. SUMMARY AND CONCLUSIONS......................................................................... 385.1 WELL #2 REHABILITATION ....................................................................................... 385.2 EFFECTS OF GROUNDWATER PUMPING ON DIABLO CREEK .................................................. 385.3 RECOMMENDATIONS FOR GROUNDWATER USE............................................................... 385.3.1 Well #2 Construction, Operations and Maintenance............................................... 385.3.2 Monitoring Wells .................................................................................. 395.4 MONITORING PROGRAM RECOMMENDATIONS ................................................................. 39DCPP Water Resources Report Page TOC- 1 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008FIGURESFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.Figure 7.Figure 8.Figure 9.Figure 10.Figure 11.Figure 12a.Figure 12b.Figure 13a.Figure 13b.Figure 14a.Figure 14b.Table 1.Table 2.Table 3.Table 4.Table 5.Table 6.Table 7.Table 8.Table 9.Map of project site showing location of wells.Photograph of Well #4.Schematic diagram showing Well #4 construction and lithology.Drawdown at Well #4 during development and testing.Photograph of Well #5.Schematic diagram showing Well #5 construction and lithology.Drawdown at Well #5 during development and testing.Graph of Step Drawdown Test at Well #2.Water levels at Well #2 during the constant rate pumping test.Water levels in DCPP Wells during November 2007 constant ratetest.Water levels in DCPP Wells during June 2008 constant rate test)Water levels at Pumping Well and Diablo Creek Locations (June/July 2008Pump Test).Water levels at pumping well and Diablo Creek locations focused ontime period of test.Constituent concentrations as a function of depth at Well #2.Constituent concentrations as a function of depth at Well #2.Constituent concentrations as a function of depth at Well #2 andDiablo Creek.Constituent concentrations as a function of depth at Well #2 andDiablo Creek.TABLESDCPP Well Locations.Construction Parameters for Well #4 and Well #5.Development of Well #4 (November 8, 2007).Development of Well #5 (November 10, 2007).Well #2 Spinner Log Analysis.DCPP Well #2 -Step Rate Test.Comparison of Well #4, Well #5 and Well #2 Composite Samples.Well #2 Depth-Specific Water Quality Results.Water quality in Diablo Creek compared to groundwater.DCPP Water Resources Report Page TOC-2DCPP Water Resources ReportPage TOC-2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Attachment A:Attachment B:Attachment C:Attachment D:Attachment E:ATTACHMENTSWell 4 DocumentationWell 5 DocumentationWell 2 DocumentationWater Quality Data TablesDCPP Water Resources Monitoring PlanDCPP Water Resources Report Page TOC-3DCPP Water Resources ReportPage TOC-3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Executive SummaryThe PG&E Diablo Canyon Power Plant ("DCPP") has historically utilized threeindependent water supplies for plant water needs, listed in order of volumetric priority:(a) seawater, treated by a large reverse osmosis system ("SWRO"), (b) diversions fromDiablo Creek, and (c) groundwater produced by a single on-site well ("Well #2"). As aresult of a directive by the California Coastal Commission, diversions from Diablo Creekwill be ceased. This change in supply options increases the dependence upongroundwater and therefore generates a need for the groundwater to be both more reliableand pumped at a slightly greater rate than historically. Given this context, the purpose ofthis Water Resources Evaluation is to develop a better understanding of on-sitegroundwater resources in terms of potential yield, water quality and relationship betweengroundwater pumping and flows in Diablo Creek. This work is based in part on a 2007study ("Phase I: Evaluation of Groundwater and Surface Water Data") that was preparedto identify appropriate steps for refurbishing and testing existing groundwater productionfacilities, evaluating groundwater water quality issues, and installing monitoring wells.The Phase II scope-of-services included: (1) installation of two monitoring wells (Well #4and Well #5), (2) evaluation and rehabilitation Of Well #2, (3) aquifer testing at Well #2,and (4) water quality sampling and analysis. The proposed new monitoring wells willprovide valuable information needed for (a) understanding current groundwater basinconditions, (b) assessing future groundwater production potential and water quality at theproposed locations, and (c) comparing groundwater water levels with flow levels inDiablo Creek to demonstrate if any hydraulic connection is apparent.The two monitoring wells, known as Wells #4 and #5, were drilled and completed to 500ft and 400 ft, respectively. The wells were logged, tested and evaluated for water quality.Well #4 was pumped for two hours at a rate of 30 gallons per minute, had 21 ft ofdrawdown and has a potential yield of 80 gallons per minute (gpm) or more. Waterquality at Well #4 was satisfactory, but poorer than the other wells. Well #5 was pumpedfor over two hours at a rate of 49 gallons per minute, had a drawdown of approximately 8ft and has a potential yield of 150 gpm or more. Water quality at Well #5 was better thanthat at Well #2 in many, but not all, respects.The pre-existing and historically productive Well #2 was rehabilitated, including cleaningof the casing, and replacement of the pump, motor, column pipe and surface controls. Thewell was tested and sampled to determine if the well's inflow rates and water qualitydiffered at different depths. Based upon the results of this work, it is evident thatsignificant inflow rates occur at different depths within the well and that the water qualityat these various depths is also different in certain respects. The majority of the well'swater enters in the 190-275 ft zone, and is of reasonably good water quality. A shallowerzone was identified as contributing approximately 20% of the well's flow and containingelevated concentrations of total dissolved solids, chloride, iron and silica.DCPP Water Resources ReportPaeE-Page EC- I ENTRIX, Inc.- Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well #2 was initially tested from November 26 through December 7, 2007, a 10-dayconstant rate pumping test that included monitoring at Well #2, three monitoring wellsand in Diablo Creek. The test was run at 150 gpm which proved to be an acceptable long-term, sustainable pumping rate for the well, even with the preceding years of limitedrainfall and associated lowered water levels. During wetter climatic periods, the well hasa capacity to produce at a greater flow rate.A second constant rate pump test was conducted at Well #2 from June 25 to July 2, 2008to evaluate the relationship between groundwater pumping and creek water levels. Well#2 was pumped at a rate between 150 and 200 gpm for seven days. Changes in waterlevels were monitored in Wells #2 and #5 as well as at two locations in Diablo Creek.Just before the end of the test, water quality samples were collected from Well #2 and thecreek. The data collected do not show a correlative water level response between waterlevels in Diablo Creek and pumping water levels in Well #2. During the course of thepumping test, water levels in the Creek did not exhibit a drawdown or rebound signaturecorresponding to the start and end of the pump test, respectively. If the creek and wellwere connected, measurable changes in the creek water levels would likely occur. Theabsence of these trends supports the conclusion that there is no discernable connectionbetween creek water levels and pumping at Well #2.Water quality comparisons were also conducted to determine if a relationship existsbetween groundwater pumping at Well #2 and flows within Diablo Creek. Concentrationsof several key constituents from samples collected contemporaneously during the multipletests were markedly different indicating distinct water sources.Finally, a water resource monitoring program was initiated to collect and track hydrologicdata in an effort to ensure adequate understanding of this valuable resource is developedand maintained.Recommendations of this work include continuance of the water resources monitoringprogram, evaluating factors associated with future production use of Wells #4 or #5, andevaluate implementation of downhole well modifications to improve water quality in Well#2.DCPP Water Resources ReportPaeE-Page EC-2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20081. IntroductionThis report provides a summary of well rehabilitation, monitoring well installation,aquifer testing, and water quality analyses conducted at the PG&E Diablo Canyon PowerPlant ("DCPP") from October 2007 through July, 2008. The services were conducted aspart of the Phase II and Phase III Water Resources Evaluation scope of work which, inturn, is based upon the June 30, 2007 technical report entitled: "Phase I: Evaluation ofGroundwater and Surface Water Data". The work provides data and recommendations tosupport increased reliability of groundwater production and an evaluation of whether aconnection exists between groundwater pumping from the existing Well #2 and flowsassociated with Diablo Creek. Also included is a section of the report that summarizesrecommendations for groundwater use and facilities management and provides elementsof a long-term groundwater resource monitoring program.This work is part of a larger effort by DCPP staff to increase reliability of available watersupplies, which also includes modifications to the DCPP seawater reverse osmosis("SWRO") treatment plant system. Properly managed and monitored development oflocal groundwater resources can provide a highly reliable water supply that will continueto supplement the SWRO supply. As part of this ongoing groundwater developmentactivity, groundwater monitoring data will be collected to establish a body of informationto better understand the water resources of the area. Appropriate work to follow the taskssummarized in this document includes implementation of a groundwater monitoringprogram to initiate the collection of water related data that will increase the understandingand forecasting of this valuable resource. Additional phases of work may also include theconversion of one or both of the new monitoring wells to production wells dependingupon future determination of DCPP groundwater supply needs.1.1 BackgroundWater supply for DCPP steam generation is currently acquired from three sources: reverseosmosis treatment of seawater ("SWRO"), surface diversions from Diablo Creek, andpumped groundwater. SWRO is the primary water supply source, with the surface waterand groundwater resources used in supporting roles for augmentation during normalSWRO operations or for temporary backup supply during SWRO outages. Because of aregulatory mandate to cease Diablo Creek diversions, groundwater will be elevated in itsrelative importance to meet the water supply needs of DCPP and it is therefore appropriateto increase groundwater production capability and reliability.Given that context, a study was prepared ("Phase I: Evaluation of Groundwater andSurface Water Data") to identify appropriate steps for refurbishing and testing existingDCPP Water Resources Report PgPage 1 ENTRIX, Inc. -Environmental and Natural Resource Management Cons~ultantsAugust 22, 2008groundwater production facilities, evaluating groundwater water quality issues, andinstalling monitoring wells.The monitoring wells were recommended to gain a broader understanding of thegroundwater conditions present at the DCPP site and to develop information on futureproduction well locations. These wells will provide information needed for (a)understanding current groundwater basin conditions, (b) assessing future groundwaterproduction potential and water quality at the proposed locations, and (c) comparinggroundwater water levels with flow levels in Diablo Creek to demonstrate if any hydraulicconnection is apparent. If replacement of the existing Well #2 or augmentation of theexisting DCPP groundwater pumping capacity is needed at a future date, one or both ofthese monitoring wells could be converted to production wells.In order to comply with the aforementioned regulatory mandate to cease Diablo Creekdiversions, increased groundwater production will be needed. The cessation of creekdiversions generates two considerations:1. Increased dependence upon Well #2 to provide all the water needed toaugment the SWRO system; and,2. The technical concept of demonstrating that both existing and futuregroundwater pumping does not extract subsurface water associatedwith Diablo Creek flows.For these considerations, a series of diagnostic aquifer tests were conducted. These testsinvolved pumping at Well #2 at similar rates to historical and planned usage andcontemporaneous water level monitoring at other wells and at locations within DiabloCreek.1.2 HydrogeologyThe primary aquifer established by existing groundwater extractions is the fracturedsandstone (possibly dolomitic) of the lower to middle Miocene-aged Obispo Formation.This unit also contains siltstones and finer grained beds that are less productive than thefractured sandstones. The brittle nature of the sandstones produces discrete fracture setsthat can form a prolific bedrock aquifer. Because the aquifer material in this region isrelatively hard and locally brittle bedrock, essentially all groundwater production will bederived from fractures within the rock, not from the pore spaces between the sand grainsas occurs in an alluvial (i.e., uncemented, unlithified) aquifer.DCPP Water Resources Report PgPage 2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20081.3 Well Site SelectionSite selection in bedrock aquifers is highly dependent upon the existence of fracturedzones that allow groundwater collection and conveyance from upgradient source areas.For the purpose of monitoring well site selection, a local and regional scale fracture studywas conducted, as described in the Phase I report. This study combined with site accessand other considerations resulted in the identification of three (3) favorable drillinglocations, two (2) of which (site "4" and site "5 b") were selected by PG&E staff for themonitoring wells installed as part of this Phase II work. (see Table 1, Figure 1). Site "5b"of the Phase I report will be referenced as site "5" in this report and all future references.As a historical note, Well #3 was drilled contemporaneously with wells 1 and 2, yetbecause of insufficient yield was abandoned before well completion. It is located in thesmall turn-around circle near the current Diablo Creek diversion and pumping facilities*(see Figure 1). The wellhead is no longer visible in the field, and its elevation in Table 1is approximate.Table 1. DCPP Well LocationsNorth East EeainWell No. Descriptive Location Coordinate* Coordinate* lvainfIt mslWell #1 Near Diablo Creek 2277056.86 5711903.64 251.36Well #2 On Deer Trail Rd. 2276517.11 5712241.45 333.3Well #3 On Turnaround near SempSemp ~ ~ 8Well #3 Lower Weir SempSemp-8On Deer Trail Rd. atWell #4 troftwaetnk 2276209.20 5712999.92 452.35Well 115 Near Man Camp area 2276658.80 5712413.70 303.93*Coordinates and Elevations were surveyed by GraniteConstruction staff. Coordinates are consistent with other DCPPsurveying data. Elevations represent the top of the concrete padat each well.DCPP Water Resources Report PgPage 3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008-~ IrTh~r~ ~ FIgure______________________________________ 6 v~AI L~23t~ofl~ w~-~H lt~oi~ M~,pN A C). k -~ C)r),~, 42~ 1CC)t pidIIo (2afl~o~ Vowe, ~3fltUXD~Figure 1. Map of project site showing location of monitoring stations.DCPP Water Resources Report Pg ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082. Monitoring Well Installation (Well #4 and Well #5)The initial task conducted during this phase of the project involved the installation of two(2) monitoring wells. The design and installation approach for the wells included theprovision that each monitoring well could be converted to a production well at a futuredate. Therefore, careful monitoring was conducted during drilling of the monitoring wellsto assess the potential well yield and water quality. Additionally, upon completion of eachwell, a short-term pumping test was conducted to provide an estimate of yield and allowfor collection of a water sample for water quality analysis.Both wells were drilled to relatively deep depths (506 ft and 409 ft, respectively) to allowfor penetration of a significant depth of bedrock, which greatly increases the potential tointersect fracture zones that have regional connectivity and hence increased yield anddrought-period tolerance. Also, deep sanitary seals were installed at the wells to provideincreased assurance that shallow groundwater that could potentially be tributary to DiabloCreek is not captured by the wells. Additional details of well construction are provided inTable 2 and Figures 3 and 6, below.Table 2. Construction Parameters for Well #4 and Well #5.Well Construction Parameter Well #4 Well #5Drilled Depth 506 ft 409 ftBorehole Diameter 10.5 inches 10.5 inchesDirect Air Rotary/Drilling Method Direct Air Rotary Mud RotarySanitary Seal 230 ft 75 ftCasing Size (OD) 5 inch 5 inchCasing Material PVC (Sch. 80) PVC (Sch. 80)Screen Interval 250 -500 ft 100 -400 ftSlot size 0.050 in 0.050 inGravel Pack #8 mesh sand #8 mesh sandInitial Water Level (below ground) 219 ft 40 ftWellhead Elevation (ft MSL) 452.35 ft 303.93 ftGeophysical Logs SP, Resistivity, Sonic SP, Resistivity, Sonic2.1 Driller and Drilling MethodsCascade Drilling of La Habra, CA was contracted to conduct the monitoring wellinstallation based upon previous experience, qualifications, safety record and familiaritywith PG&E projects. Cascade was directed to employ rotary air-hammer drilling methodswhich are appropriate for hard, fractured bedrock aquifer materials as present at the site.Cascade provided a crew of 3, an auxiliary air compressor and other ancillary drillingequipment for the installation of the two (2) monitoring wells. Geophysical well loggingat Wells #4 and #5 was conducted by Welenco of Bakersfield, CA.DCPP Water Resources Report PgPage 1 ENTRIX, Inc. -Environmnental and Natural Resource Management ConsultantsAugust 22, 20082.2 Well#42.2.1 Site DescriptionWell #4 (Figure 2) is located 0.2 miles up Sky View Road from its intersection with DeerRun Road near the Man Camp, and is at the junction of Sky View Road and the water tankroad. This site was selected because it represents a high potential for sufficient flow ratesto provide supplemental water production, it will likely have at most a limited effect onthe existing Well #2, and its effect on Diablo Creek will likely be very limited. It is alsoat a sufficient distance from Well #2 and Diablo Creek to allow monitoring of up-gradientaquifer conditions that can support development of a broader understanding of aquiferwater levels and possible variability in aquifer water quality.2.2.2 Well ConstructionWell #4 was drilled from October 24 to October 26, 2007 to a total depth of 506 ft beneathground surface. Water was first encountered at 245 ft, and stabilized to a static level of219 ft. In consideration of the depth to water, and the interest in ensuring limitedconnectivity to Diablo Creek, the sanitary seal was constructed to 230 ft deep. PerforatedPVC casing was installed from 230-500 ft. By the time the total depth of drilling wasreached, the well was naturally producing approximately 40 gpm, as evidenced by theflow resulting from the air injection employed as part of the air-hammer drilling method.2.2.3 Well LoggingSediments encountered during drilling included abundant clay, shale and siltstone withinterspersed layers of sandstone (see State Well Drillers Report, Attachment A). Evidenceof fracturing increased below 240 feet and correlates with increased water production ofthe well during drilling. This observation is particularly relevant because in fracturedbedrock aquifers, essentially all the groundwater that is available to enter the well will bederived from fractures within the rock, rather than from the pore spaces between the sandgrains. Geophysical logs run in the hole included electrical log (resistivity andspontaneous potential [SP]), gamma, sonic velocity and temperature. These logs illustratethe stratified nature of the formation and an increase in the proportion of sandstone-richbeds in the lower 60 feet of the well. The indications provided by the e-logs are largelycorroborated with the lithologic monitoring conducted by ENTRIX during well drilling.Initial stabilized water levels in the well were measured at 219 ft deep. Confined aquiferconditions are evident based upon this static water level in relation to the 230 ft depth ofthe sanitary seal and top of slotted casing at 250 ft deep.DCPP Water Resources Report PgPage 2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008ioto of Monitoring Well #42.2.4 Well Development and TestingWell #4 was developed for a full day following well construction, including severaliterations of surging and bailing at deep, medial and shallow portions of the well.Development was continued until the produced water was clear. Next, in an effort toestablish potential well yield, Well #4 was pumped for two hours at a rate of 30 gallonsper minute, which results in a drawdown of approximately 21 ft. Based on these data, thespecific capacity of the well is approximately 1.4 gpm/ft of drawdown. Given that thereare at least 200 feet of additional available drawdown, flow rates of 80 gpm are attainableif needed at a future date; although the pumping lift would be substantially greater thanthat needed at either Well #2 or Well #5 for this production rate.As indicated in Table 3 below, by the end of the test, the turbidity in the water was greatlyreduced and the pumping water level had nearly stabilized (Table 3, Figure 4). A waterquality sample was collected at Well #4 at the end of the test, on November 8, 2007.Water quality results are provided below in Section 4.DCPP Water Resources ReportPage 3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008If it is determined in the future that production from this well is needed, we suggestconducting, depth-specific water quality sampling to determine if a portion of the well'sproduced water is of the poorer quality than from other depths. If it is determined that aspecific zone (i.e. the deepest zone, for example) is of particularly poor water quality,changes in well construction parameters may aid in controlling water quality from thiswell, although production rates will likely be reduced. Also, although this well still has alower specific capacity than Well #5, it is sufficiently distant from Well #2 so as to reducethe potential for interfering cones of depression from multiple pumping wells, and isworthy of consideration to meet future production needs.Table 3. Development of Well #4 on November 8, 2007.Elapsed Depth Electrical Trity VolumeTime Time to Conductivity Triiy Pumped_______Water___ (mai) (ft bgcs) (NTU) (gallons)12:49 0 217 _ ____ 012:50 1 221.85 1635 53 I13:10 21 234.44 1488 271 60013:30 41 237.03 1463 10.9 120013:50 61 237.05 1483 0 180014:10 81 237.69 1464 0 240014:30 101 238.05 1465 0.7 300014:50 121 238.3 1478 0 3600Well 4 Development and Testing215220"Z 225*9°2302352400 20 40 60 80 100 120 140Elapsed Time (min)Figure 4. Drawdown at Well #4 during development and testing.DCPP Water Resources Report PgPage 4 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Figure 3. Schematic diagram showing Well #4 construction and lithology.DCPP Water Resources Report PgPage 5 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082.3 Well #52.3.1 Site DescriptionWell #5 (Figure 5) is located in the northeast corner of the Man Camp yard. Based uponthe structural geologic work conducted in the Phase I study, this site is located southeastof a throughgoing N75°E structure which may represent a hydrologic barrier, andtherefore the well likely encountered favorable aquifer materials with groundwaterproduction characteristics similar to Well #2. Also, because this monitoring well isrelatively close to Well #2, drawdown during the Well #2 pumping will be evident andthereby helpful in the aquifer analysis efforts.2.3.2 Well ConstructionWell #5 was drilled from October 28 to November 2, 2007 to a total depth of 409 ftbeneath ground surface. Unstable downhole conditions between 50 and 250 ft requiredconversion from air rotary drilling methods to bentonite mud-based drilling methods.Using drilling mud is a common solution to bedrock wells having unstable sections thatwon't stay open with the viscosity of water only. Water was first encountered at 45 fi, andstabilized to a static level of 40 ft. In consideration of the depth to water, and the interestin ensuring limited connectivity to Diablo Creek, the sanitary seal was constructed to 75 ftdeep. Blank PVC casing was installed from 75 to 100 ft; perforated PVC casing wasinstalled from 100-400 ft. By the time the total depth of drilling was reached, the wellwas naturally producing over 100 gpm, as evidenced by the flow resulting from the airinjection employed as part of the air-hammer drilling method.2.3.3 Well LoggingNear surface sediments encountered during drilling of Well #5 included both siltstonewith clay and/or sandy components as present at Well #4 and also a larger proportion ofpoorly-lithified sandstone beds (see State Well Drillers Report, Attachment B). Overall,the sediments in the upper 100 ft+ in this well were poorly consolidated which resulted inunstable hole conditions as mentioned above. Evidence of fracturing was present fromapproximately 50 feet and throughout the depth of the hole, and likely corresponds withthe structural geologic evidence from analysis of aerial photographs that this site is withina northeast-trending fracture system.DCPP Water Resources Report Page 6DCPP Water Resources ReportPage 6 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008gure 5. Photograph of Well #5.Geophysical logs run in the hole included electrical log (resistivity and spontaneouspotential), gamma, sonic velocity and temperature. Collectively, these logs illustrate thestratified nature of the formation and an increase in the proportion of sandstone-rich bedsin the upper and lower portions of the well. The indications provided by the e-logs arelargely corroborated with the lithologic monitoring conducted by ENTRIX during welldrilling.Initial stabilized water levels in the well were measured at approximately 80 ft deep.Confined aquifer conditions are evident based upon this static water level in relation to the250 ft depth to the top of slotted casing.DCPP Water Resources Report PgPage 7 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082.3.4 Well Development and TestingWell #5 was developed for 7.5 hours following well construction, including severaliterations of surging and bailing at deep, medial and shallow portions of the well.Development was continued until the produced water was clear. Next, in an effort toestablish potential well yield, Well #5 was pumped for over two hours at a rate of 49gallons per minute, which resulted in a drawdown of approximately 9 ft (Figure 7). Basedon these data, the specific capacity of the well is approximately 5.9 gpm/ft of drawdown,which represents a higher specific capacity than that measured at Well #4. Based uponthis, albeit limited, production test, this well likely has a production capacity equal to orgreater than that of Well #2. Given that there are at least 300 feet of additional availabledrawdown, flow rates of 150 gpm may be possible if needed at a future date. Note thatthe initial recovery of the well's water level is illustrated in the graph to show the rapidwater level response when pumping stopped.For the second half of the test, the measured turbidity in the water was "0" (see Table 4)indicating that the well development was successful to remove turbid material from boththe drilling process and from the use of drilling mud.A water quality sample was also collected at Well #5 on November 10, 2007. Waterquality results are provided in Section 4 below.Based on this pumping test and water quality data, Well #5 has a higher specific capacityand better water quality than Well #4, and represents a more viable alternative if at afuture date conversion to a production well is needed. However, because Well #5 islocated near the existing Well #2, and approximately 9 feet of drawdown was observed atWell #5 during the pump test of Well #2, consideration and planning of the combineddrawdown effects is needed to adequately forecast the combined yield of the two wellsoperating together.DCPPWate Reourcs ReortPage 8 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Figure 6. Schematic diagram showing Well #5 construction and lithology.DCPP Water Resources Report Page 9DCPP Water Resources Report ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 4. Development of Well #5 (November 10, 2007).Easd Depth Electrical Triiy VlmTime Time to Conductivity Triiy Pumped_______Water(mini) (ft bgs) (NTU) (gallons)7:25 80_____7:30 0 80 ____7:50 20 85.3 1020 3.31 10008:10 40 86.35 962 1.65 20008:30 60 87.12 948 1.3 30008:50 80 88.31 943 1.2 40009:10 100 88.4 941 0 50009:30 120 88.41 935 0 60009:52 142 83.55 930 0 7000Well 5 Development and TestingI-79808182838485868788890 20 40 60 80 100 120 140 160Elapsed Time (min)Figure 7. Drawdown at Well #5 during development2007.and testing on November 10,DCPP Water Resources ReportPae1Page 10 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083. Well #2 Rehabilitation and Testing3.1 Well RehabilitationWell #2 was rehabilitated to provide a series of benefits such as increased reliability,potential for increased yield, and increased operating efficiency of the well. Withcessation of Diablo Creek diversions, the increased dependence upon groundwater can besupported by ensuring Well #2 is mechanically and physically sound.Well #2 was originally installed in 1985 to a total depth of 350 feet by Floyd V. Wells, Incof Santa Maria, California. The 10-inch diameter Schedule 200 PVC casing is perforatedfrom 90 ft bgs to total depth, with 0.040 full-flow horizontal-slot well screen.3.1.1 Results of Pump, Motor, and Column Pipe InspectionThe existing pump and motor on Well #2 were removed by Fisher Pump of Santa Maria,CA, under contract to Woodward Drilling Co. of Rio Vista, CA. The motor, pump andpump column although marginally operational all exhibited signs of wear and debilitationtypical of 20-year old equipment. It was determined that replacement of thesecomponents was in the best interest of DCPP and a greater reliability of the groundwatersupply produced by this facility.3.1.2 Video Log ResultsFollowing pump removal, a video logging tool was used to visually inspect the downholeconditions of Well #2. This video file provided evidence of the presence of encrustationof the well casing, mainly below 238 ft, and the existence of an approximately 20 ft thickpile of debris at the bottom of the well (Attachment C). Using these data, wellrehabilitation was recommended to include swabbing, brushing, air jetting and bailing.3.1.3 Description of Well Rehabilitation Tasks PerformedBased upon results of the video investigation, described above, the following steps wereperformed:* Bail out most of accumulated sediment from bottom of well.* Brush well with plastic-bristle brush to remove major areas of encrustation.* Additional sediment removed by bailing followed by air lifting.* Swab well with dispersant and detergent to clean casing encrustation andre-open clogged perforations.* Re-develop well with swab tool and conduct additional air lifting toremove all dispersant and suspended material.DCPP Water Resources ReportPage 11 ENTRIX, Inc.- Environmental and Natural Resource Management ConsultantsAugust 22, 20083.2 Spinner TestUpon completion of well rehabilitation work, velocity logging of the well was conductedby Pacific Surveys of Claremont, CA to determine the depth-distribution of groundwaterinflow into the well. This involves lowering a flow-metering logging tool into the welland pulling it up past the productive zones during active pumping. The relative inflowrates at the various depths of the well are evident from this effort and can provide valuableinformation if certain zones exhibit dominant flow rates and/or associated water qualityissues. The actual logs provided by the contractor are included as Attachment C.For the spinner test, the well was pumped at a rate of 90 gpm for 2.5 hours prior to andduring the survey. During the test; the pumping water level was 149 ft bgs. The results ofthe velocity logging, summarized in Table 5, indicate that there are two primaryproductive zones that produce over 90% of the flow into the well. The top loggedinterval, from the top of the perforations at 100 ft bgs to 158 ft bgs, producesapproximately 30% of the flow. This zone is underlain by an approximately 30-foot thicklow productivity zone. The most productive zone is located from 190-275 ft bgs.Water quality samples were collected at 158 ft bgs, 190 ft bgs, and 275 ft bgs. The pumpwas set at a depth of 160 ft bgs during this test, which is a fundamental considerationbecause the pump set-depth influences flow direction within the well, and this is animportant consideration for assessing the representativeness of depth-specific waterquality samples. Given the direction of flow within the well, the water quality samplecollected at 158 feet represents water from the 100-158 foot interval; the sample collectedat 190 feet represents water from the 190-275 foot flow zone; and water collected at 275 ftbgs represents the lowest flow zone sampled (275-3 50). Discussion of the water qualitysample analytical results is provided in section 4 below.Table 5. Well #2 Spinner Log Analysis[Flow Rate = 90 gpm1Zone Depths Production % of Flow Zones gpm/ft Thickness(ft bgs) (gpm) (t100-158 20 26% 0.34 58158-190 4 4% 0.13 32190-275 63 67% 0.74 85275-350 3 3% 0.04 75DCPP Water Resources ReportPae1Page 12 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083.3 Pump Tests for Evaluating Well YieldA series of diagnostic pumping tests were conducted to evaluate the Well #2 yield, as wellas its water quality. Results for these tests were used to establish the well's sustainableyield, specify a new submersible well pump and motor, evaluate if groundwater pumpingeffects flows in Diablo Creek, and assess groundwater water quality.A step drawdown test and a constant rate test were performed at Well #2 betweenNovember 20 and December 6, 2008 using a temporary test pump, installed at a depth of300 ft bgs. For over 4 weeks prior to this test, monitoring of water levels was conductedat Well #1, #2, and at the Diablo Creek facilities. Monitoring data was also collected atthe newly constructed Wells #4 and #5 soon after their respective completion dates.These data provide a trend and variation history of water levels at these various locationswhich is useful to establish the natural variability of these water resources in comparisonwith the stresses imposed by the pumping tests.A final pumping test was run in June and July, 2008 to provide specific data to evaluate ifgroundwater pumping affects water levels in Diablo Creek and also to comparegroundwater water quality between these two water bodies.3.3.1 Step Drawdown TestA step drawdown test was conducted to assess the Well #2 optimal and maximumpotential sustainable yields. This test involved pumping the well at a series of four (4)increasingly higher pumping rates for 60 minutes each. The graph of the drawdown andproduction data was used to determine the well's highest sustainable yield and also todetermine the optimal pumping rate for the multi-day constant rate test.On November 20, 2007, a step-rate test was conducted at the rehabilitated Well #2. Thepump set depth was 300 ft bgs. A total of 36,300 gallons were pumped during the courseof the test. The rates used in the test are provided below in Table 6.A graph of the results of the step drawdown test is provided in Figure 8. Drawdownstabilized during the two lower flow rate portions of the test, but not at the two higherflow rate portions. As is relatively common for wells producing from fracture systems ofa bedrock aquifer, extended time is needed at moderate to high flow rates to achievestabilized pumping water levels.In this well, during the 175 gpm pumping of Step 3, water levels continued to declinefrom 208.2 ft bgs after 5 minutes of pumping to 216 ft bgs after 58 minutes of pumping.It is possible, but not assured that the well could have stabilized its drawdown over alonger duration. Additionally, the well was unable to sustain the 215 gpm pumping ratefor Step 4, which is useful information to understand the upper limit of the well's potentialyield. The well recovered quickly after the pump was shut down. At the end of the step-rate test, the water level in the well was 268 ft bgs. The well achieved 90% recoveryDCPP Water Resources ReportPae1Page 13 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008within 10 minutes after pumping ceased and water levels in the well fully recovered inapproximately four (4) hours. Based upon these data, it was determined that a rate of 150gpm would be sustainable for the duration of the planned constant rate pump test.Table 6. DCPP Well #2 -Step Rate TestPumpingDate Start Time Rate_______ _______ (gpm)Step 1 11/20/2007 10:00 75Step 2 11:00 125Step 3 12:00 175Step 4 13:00 21513:03 21513:05 20513:10 20013:20 19513:40 195______________ 13:55 195Diablo Canyon Power Plant -Well 2 Step Drawdown Test4J00.100120140160180200220240260280300Start of Test:November 20, 2007 10:00 AM120 180 240 300360Elapsed Time (min)Figure 8. Graph of Step Drawdown Test at Well #2.DCPP Water Resources Report Page 14DCPP Water Resources ReportPage 14 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083.3.2 Constant Rate TestsA constant rate pumping test was conducted at Well #2 starting at 14:30 on November 26,2007 and ending at noon on December 6, 2007. The static water level at Well #2 at thestart of the test was 112.7 ft bgs and the water level just before the pump was stopped was238.6 ft bgs. A total of 2,321,000 gallons were pumped during the 10-day constant ratetest at a relatively constant rate of 150 gpm. Based on these data, the specific capacity ofthe well is 1.2 gpm/ft of drawdown.As illustrated in Figure 9, the pumping water level at the well dropped steadily andstabilized at approximately 223 ft bgs by the second day of the test. Two additional,discrete steps in the drawdown occur at approximately 48 hours and at approximately 214hours. These are related to minor adjustments of the gate valve on the discharge pipe inan effort to re-establish the target pumping rate of 150 gpm. The well achieved 80%recovery within three (3) hours of the end of the constant rate test, and 94% recovery onweek later.Diablo Canyon Power PlantWell 2 Constant Rate Test100120140*} 160a- 180220S2402602803000 24 48 72 96 120 144 168 192 216 240 264 288 312Start of Test: Elapsed Time (hours)November 26, 200? 2:30 PMFigure 9. Water levels at Well #2 during the constant rate pumping test.336 360 384 408DCPP Water Resources ReportPae1Page 15 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008In addition to recording pumping water levels at Well #2, several other wells on theproperty and two surface water monitoring stations on Diablo Creek were monitoredbefore and during the constant rate test. A further discussion of water level monitoringresults at these monitoring stations is provided in Section 4.Water quality sampling was conducted during the test at the middle and just before shut-down. Results are provided and analyzed in Section 5.Collectively, these data indicate the firm reliability of Well #2 to produce 150 gpm on along-term basis under normal operating conditions. Currently, normal well operationsrequire the well to be operated at intervals of several hours per day. With the futuredecommissioning of the Diablo Creek diversion, an increased demand may be establishedon Well #2 for water supply. Based upon the results of these tests, Well #2 could beoperated at its design flow rate of 150 gpm for significantly longer periods per day whilestill maintaining acceptable margins of safety with respect to pumping water levels.Importantly, because of the limited rainfall in the years preceding this test, drought-typeconditions exist and the results of this testing can be considered representative of limitedwater availability conditions. Although not necessarily worst-case conditions, the yield ofthe well and response of the aquifer will not be any worse than that exhibited during thistest except during periods of even more extreme drought conditions. In a multi-yeardrought, if a greater amount of groundwater is needed than is produced from the wellunder its typical operating patterns, the well could be (a) run for more hours per dayand/or (b) retrofitted with a higher capacity pump set at a deeper level. Finally, duringperiods of higher rainfall and therefore more "average" water supply within the aquifer,the yield of the well as currently equipped will likely be greater and the associateddrawdown effects on the aquifer will be less.3.5 Pump SpecificationsUpon inspection, the condition of the pump, motor and column pipe were determined tobe sufficiently degraded to warrant replacement. A replacement pump, motor and columnpipe was specified, as described below. Installation and operability testing of thesecomponents was conducted on April 18, 2008 by Fisher Pump of Santa Maria, CA.Pump: Grundfos Submersible model # 150S 150-7Pump Serial Number: 07L 19-06-6129Motor: 15 hp FranklinMotor Protector: Franklin SubMonitorControl Panel: Siemens, Class 87Column Pipe: 300 ft of 4-inchProbe access tube: 1-inch PVC (300 ft)DCPP Water Resources ReportPae1Page 16 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084. Aquifer Response to Pumping TestThe response of the aquifer to pumping at Well #2 was evaluated using water level datacollected from Wells # 1, #4, and #5 during the constant rate pumping test conducted in2007. In addition, a second constant rate pumping test was conducted from June 25 toJuly 2, 2008 to evaluate the response of water levels in Diablo Creek to pumping waterfrom Well #2. As part of this analysis, groundwater and creek water level data werecollected before, during and after a test with contemporaneous measurements from thepumping well. Data collected during the 2008 pumping test were also compared with datafrom the 2007 pump test to further evaluate the aquifer response to pumping at Well #2.4.1 Monitoring LocationsWater levels at several wells and two surface water monitoring sites on Diablo Creek weremonitored before and during the constant rate tests at Well #2 (Figures 10 and 11). Inaddition, meteorological conditions were noted at the site and were also reviewed asavailable from the nearest gauging station, the Nipomo CIMIS station. The Nipomostation provides comprehensive data, but its inland setting records different climatologicconditions than the coastal conditions at DCPP.4.1.1 2007 Constant Rate Pumping TestDuring the first constant rate test water levels were monitored in Well #1, near DiabloCreek; Well #4, up the hill from Well #2; and Well #5, near the Man Camp. These wellswere outfitted with pressure transducer devices that automatically collected water leveldata at a programmed frequency of one measurement every 30 minutes.Data was also collected at two locations in Diablo Creek during this test. However, DCPPwater diversions from the creek during the pumping test created water level variations thatprevented determination of any relationship between pumping at Well #2 and creek flow.4.1.2 2008 Constant Rate Pumping TestWater levels at wells #1, #2, #4, and #5, and two surface monitoring sites on Diablo Creekwere monitored before and during the 2008 constant rate test. Wells #2 and #5 as well asthe two creek locations were monitored with pressure transducers that automaticallycollect and record water level data at programmed frequencies. Water levels in Well #1and Well #4 were measured manually with a water level meter just prior to the start of thetest and periodically during the pump test. For the duration of the pumping test,diversions from the Lower Weir pond were stopped.Diablo Creek water levels were monitored throughout the test at the Lower Weir andapproximately 1,000 feet downstream of the Lower Weir, before the creek enters aDCPP Water Resources ReportPage 17 ENTRIX, Inc. -Environ men tal and Natural Resource Management ConsultantsAugust 22, 2008drainage culvert. Where the stream enters the drainage culvert a notched wooden plankestablishes a small pool which flows into the drainage culvert.4.1.3 Effect of Constant Rate Pumping Test at Monitoring Wells4.1.3.1 2007 Constant Rate Pump TestWater levels in Monitoring Wells #1 and 4 did not show drawdown effects related topumping at Well #2 during the course of the constant rate pumping test (Figure 10). Thegreatest observed effect was approximately 9 feet of drawdown at Well #5, which is theclosest monitoring well to the pumping well, at a distance of approximately 250 feet.Water levels in Well #4 remained unchanged throughout the test. This is indicative ofboth the source of the Well #2 water being largely from aquifer zones that may not bephysically connected to Well #4, and also because the upgradient position and distance ofWell #4 relative to #2 minimizes the influence of the Well #2 drawdown.Water levels in Well #1 show a slight and very gradual rise that corresponds in timingwith the pumping at Well #2. This is likely related to the discharge point of the pumpedwater which occurred approximately 200 feet southwest of Well #1, and thereforeprobably induced recharge to the shallow, unconfined sediments in which Well #1 iscompleted.4.1.3.2 2008 Constant Rate Pump TestWater levels in Monitoring Wells #1 and #4 dropped from approximately 27.4 ft bgs and223 ft bgs, respectively, just before the test down to 31.8 ft bgs and 232.4 at the end of thetest (Figure 11). During the second constant rate test the discharge point of the pumpedwater was relocated to a point inside a drainage culvert which is downstream of allsampling locations. This a distinct difference in the response of Well #1 water levelsbetween the two constant rate tests.The water level in Well #5 dropped from approximately 80 ft bgs before the test toapproximately 98 feet just before the test was halted. This is greater drawdown ascompared with the 2007 test is a result of the higher Well #2 pumping rate maintainedduring the 2008 test which resulted in approximately :20 ft more drawdown in that well ascompared with the 2007 test.DCPP Water Resources ReportPae1Page 18 ENTRIX, Inc, -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels at Monitoring Wells During Well 2 Constant Rate Test10356085a. 110160185210235-24 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408Start of Test."November 26, 2007 2.30 PMElapsed Time (hours)Figure 10. Water levels in DCPP Wells during November 2007 constant rate test.4.1.4 Effect of Constant Rate Pumping Test at Surface WaterMonitoring LocationsA pumping test was conducted from 13:30 on June 25, 2008 to 13:45 July 2, 2008 toinvestigate any existing relationships betwveen water levels in Diablo Creek and pumpingwater from Well #2.Data were collected in both creek locations using pressure transducers automaticallyprogrammed to collect water level data. Data collection began on April 18, 2008 and wasterminated on July 3, 2008. An overall saw-tooth trend of declining water levels can beseen in the data set, consistent with a baseline-recession trend of a stream in transitionfrom the wet to dry season (Figure 1 2a).DCPP Water Resources ReportPae1Page 19 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008The data collected before the pumping test show correlations between water levels at theLower Weir and the culvert with frequent drops in water levels at the lower weir,presumably resulting from diverting water from the Lower Weir to the holding tanks on-Site. For the duration of the pumping test, diversions from the Lower Weir pond werestopped. The characteristic drop in water levels at the Lower Weir is not present and thewater levels at both creek sampling points follow the same trend (Figure 1 2b).Creek water level variability during the pump test is within the normal range captured inthe dataset. Approximately 26 hours into the pumping test, a water level drop ofapproximately 0.16 feet occurred. Because fluctuations of this magnitude over similartimescales are present in the non-pumping background data extending back to April 18,2008, this water level change is not related to the groundwater pumping. Additionally,when the pump test was terminated at 13:45 on July 2, 2008, water levels in the creekcontinue in a downward trend for approximately 5 hours without a significant rebound orchange in water levels compared to levels seen over the duration of the test (Figure 12b).Based upon these test data, there is no evidence that creek water levels are affected bypumping at Well #2.DCPPWate Reourcs ReortPage 20 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels in Nearby Wells During 2008 Well#2 Constant Rate Test300250200S150,,0"10050024 48 72 96 120 144 168Elapsed Time (hours) --Well 2 --Well 5Well 4 -Well 1Figure 11. Water Levels in DCPP wells during June 2008 Constant Rate Test.DCPP Water Resources Report Page 21DCPP Water Resources ReportPage 21 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels at Diablo Creek During Well 2 Constant Rate Test1O00120140S1601802402260-70 60 50 40 30Elapsed Time (Days)Start Time: June 25, 2008 13.302.51.50.5-0.5-1CA0).000-25 15 5 0 5 10-Well 2 -----Well 5Well 2 PreTest Data Lower WeirFigure 12a. Water levels at pumping well and Diablo Creek locations (0 hour represents Test start on 6/25/08).DCPP Water Resources ReportPae2Page 22 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diabio Canyon Power PlantWater Levels in Diablo Creek during Well #2 Constant Rate Test1001201401802020.2603.52.0"1.51 £0.500-0.5-1-3 1 0 1 2 3 4 5 6 7 8Start Time: June 25, 2008 13:30Elapsed Time (Days)-Well 2 --Lower Weir-CulvertFigure 1 2b. Water levels at pumping well and Diablo Creek locations focused on time period of test (0 hourrepresents Test start on 6/25/08).DCPP Water Resources ReportPae2Page 23 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2 Water QualityWater quality samples were collected at several intervals throughout the study period.Samples were collected at wells #4 and #5 during development and pumping tests.Multiple samples were collected at Well #2, as follows:* Three sets of paired discrete depth-specific and surface (composite)samples were collected during the spinner test;* Four samples were collected during the step test, near the end of eachpumping step;* Two paired samples from Well #2 and Diablo Creek Upper Weir werecollected at the mid-point and at the end of the first constant rate pumpingtest (December 3 and December 6, 2007); and,* Samples were collected at Well #2 and at Diablo Creek Lower Weir duringthe second constant rate pumping test (June 30, 2008).The water quality data were then reviewed to evaluate:* Similarity of the groundwater extracted from Well #2, Well #4 and Well #5to assist in future water resources planning decisions;* Water quality as a function of depth at Well #2; and,* Similarity of surface water and groundwater composition.A comprehensive series of tables listing all water quality data collected in this phase of theproject are provided in Attachment D of this report.4.2.1 Relative Water Quality of Wells #2, #4 and #5In general, constituent concentrations in the water extracted from Well #5 are similar tothose of the water extracted from Well #2 (Table 7). For most constituents,concentrations are lower at Well #5 than at Well #2. Water chemistry of Well #4 differssignificantly from that of Wells #2 and #5 for many of the constituents sampled. Waterfrom Well #4 is harder (it has a higher specific conductivity, and higher concentrations oftotal dissolved solids, alkalinity, bicarbonate, total hardness, calcium, chloride,magnesium, potassium, sodium, and sulfate) than Well #2. Water from Well #5 has alower concentration than Well #2 for all of these constituents.There are a few other notable differences in the water quality signature of the Well #4water. Water from Well #4 was the only groundwater sample that was found to have adetectable odor. Nitrate was detected in all groundwater samples except for the Well #4sample. The concentration of chromium at Well #4 was more than double the nexthighest concentration detected, as found at Well #2.DCPP Water Resources ReportPae2Page 24 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well #2 was the only well with detectable arsenic concentrations and Well #2 also hadsignificantly higher (by a factor of 4) nickel concentrations than Well #4 or #5, althoughboth nickel and arsenic were below detection limits in the samples collected on June 30,2008.Iron and aluminum concentrations are quite variable (by an order of magnitude) from wellto well, and among the various samples collected at Well #2. A more detailed review ofconcentrations of these constituents with regard to aquifer depth is provided in thefollowing section.Well #2 had the highest silica concentration of any of the wells (at 27 mag/I). Well #2 andWell #4 had concentrations ranging from 19-27 mg/I.DCPP Water Resources Report Page 25DCPP Water Resources ReportPage 25 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 7. Comparison of Well #4, Well #5 and Well #2 Composite SamplesWell #2 Well #2 Well #2 Well #2 Well #2 Well #2 Well #4 Well #5Composite 1 Composite 2 Composite 3Analyte Units PQL (Surface) (Surface) (Surface)11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 11/8/07 11/10/07___________15:40 15:50 16:05pH S.U. -6.6 6.7 6.7 6.9 6.5 7.3 6.6 6.9Color Color Unit 5 <5 <5 <5 <5 <5 <5 <5 <5MBAS Surfactants mg/L 0.1 BQL BQL BQL BQL BQL BQL BQL BQLOdor T.O.N. 1 ND ND ND ND ND ND 2 NDSpec. Conductivity umhos/cm 1 1300 1300 1290 1280 1270 1200 1610 1050T.D.S. mg/L 10 790 790 790 760 780 810 1020 640Turbidity N.T.U. 0.1 4.5 0.69 1.4 0.39 0.4 0.1 1.4 1.8Nitrate (as N) mg/L 0.1 0.2 0.2 0.2 0.3 0.5 0.1 BQL 0.2Alkalinity (CaCO3) mg/L 10 410 400 410 390 390 400 520 380Bicarbonate(CaCO3) mg/L 10 410 400 410 390 390 400 520 380Carbonate (CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQLHardness (as CaCO3) mg/L 10 520 510 520 580 560 590 710 440Hydroxide (as CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQLAluminum ug/L 5 170 46 100 5.8 BQL 52 120Antimony ug/L I BQL BQL BQL BQL BQL BQL BQLArsenic ug/L 0.5 2.2 1.8 2 0.66 BQL BQL BQLBarium ug/L 0.5 30 27 28 38 BQL 33 30Beryllium ug/L 0.5 BQL BQL BQL BQL BQL BQ BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQLCalcium mg/L 0.1 97 94 95 120 110 120 150 90Chloride mg/b 0.2 100 100 100 94 95 91 120 69Chromium ug/L 1 2.8 1.7 1.9 1.3 BQL 6.1 2.2Copper mg/b 0.02 BQL BQL BQL 0.024 BQL BQL BQ BQLFluoride mg/b 0.1 0.4 0.4 0.4 0.5 0.5 0.7 0.3 0.4DCPP Water Resources ReportPae2Page 26 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 7. Comnarisnn nf Well #4. Well #.5 and Well #2 (ennt'd.AWell #2 Well #2 Well #2 Well #2 Well #2 Well #2 Well #4 Well #5Composite 1 Composite 2 Composite 3Analyte Units PQL (Surface) (Surface) (Surface)11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 11/8/07 11/10/07______________15:40 15:50 16:05______ ____Iron mg/L 0.1 0.71 0.12 22 BQL BQL BQL 0.13 0.11Lead ug/L 0.5 1.5 0.63 0.62 BQL BQL 0.65 BQLMagnesium mg/b 0.1 61 60 60 70 68 69 91 57Manganese mg/b 0.005 0.041 0.017 0.018 0.028 0.026 0.02 0.015 0.021Mercury ug/L 0.5 BQL BQL BQL BQL BQL BQ BQLNickel ug/b 1 9.5 8.2 8.5 7.8 BQL 1.5 2.6Potassium mg/b 0.2 2.7 2.7 2.7 2.9 2.8 3.1 8.2 2.3Selenium ug/b 1 2.7 2.1 2.4 3.2 BLQL15Silica mg/L 20 20 19 _ ___ ____ 27 20 25Silver ugiL 0.5 BQL BQL BQL BQL BQL BQ BQLSodium mg/b 0.5 70 69 68 53 50 63 83 51Sulfate mg/b 0.5 140 150 150 160 170 150 210 87Thallium ug/L 0.5 BQL BQL BQL BQL BQ BQ BQLZinc mg/b 0.05 0.15 0.11 0.11 0.43 0.32 0.32 0.2 0.34DCPP Water Resources Report Page 27DCPP Water Resources ReportPage 27 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2.2 Well #2 -Water Quality vs. DepthThree pairs of depth-specific and composite water quality samples were collected at Well#2 during the velocity logging of the well conducted on November 15, 2007. Thesediscrete depth samples provide an opportunity to evaluate water quality from specificdepths within the aquifer and to determine whether changes in pumping practices and/orchanges to well construction parameters may be appropriate for improving the quality ofthe pumped water.Water quality samples were collected at 158 ft bgs, 190 ft bgs, and 275 ft bgs. The pumpwas set at a depth of 160 ft bgs during this test. Because the pump set depth influencesflow direction within the well, this is an important consideration for assessing therepresentativeness of depth-specific water quality samples. Given the direction of flowwithin the well, the water quality sample collected at 158 feet represents water from the100-158 foot interval (which represents approximately 26% of the flow into the well); thesample collected at 190 feet represents water from the 190-275 foot interval (whichproduces approximately 66% of the flow into the well); and water collected at 275 ft bgsrepresents the deepest zone in the well from 275-350 ft bgs (which representsapproximately 3% of the flow in the well).Based upon these data (Table 8), the shallow productive zone (from 100-158 feet bgs) hassubstantially higher turbidity and higher concentrations of silica, total dissolved solids,nickel, aluminum and iron than the deeper productive zone (190-275 ft bgs). Figures 12aand 12b below illustrate these values. Arsenic and bicarbonate concentrations are slightlylower in the shallow productive zone as compared to the deeper productive zone. Forother constituents sampled, concentrations do not differ significantly between these twoproduction zones.Considering these water quality differences between the uppermost zone and the lowerzones, economic analysis may be needed to determine the costs and benefits of specificwell construction modifications to isolate zones. If in the future one or more of theseconstituents adversely affects the water treatment operations, well modificationapproaches can be considered. First, a temporary packer could be installed to prevent theshallowest zone of poor water quality groundwater from entering the well. This device isan elongated, thick-rubber balloon that is attached to a section of column pipe and can beinflated or deflated using an air value at the wellhead. Materials and installation for thisdevice would cost approximately $10,000. Second, the well screen adjacent to theshallowest zone of poor water quality groundwater could be permanently sealed withcement. This is a more complex operation than installation of the packer but is stillviable. This approach has a similar cost to the packer option, but has an advantage ofbeing a permanent solution, whereas the packer may need to be rehabilitated or replacedevery 5 to 10 years.DCPPWate Reourcs ReortPage 28 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008In both cases, the well's produced water quality would improve and its drawdown wouldincrease to maintain the target flow rate of 150 gpm. Because the pump operates at afixed rate, the well would operate at a flow rate approximately 10-20 gpm less and from apumping water level of approximately 5 to 10 feet deeper.Well 2 -Concentration vs. Depth100120140'" 160180G'2005220240260280300Conce ntrationFigure 1 3a. Constituent concentrations as a function of depth at Well #2.DCPP Water Resources Report Page 29DCPP Water Resources ReportPage 29 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well 2 -Concentration vs. Depth100120140'~160.01804-* 200.=2200.240 -*--- Alkalinity (CaCO3)260 Bicarbonate (CaCt-0-Alurninum (ugi)260 -Chloride (rngl)3000 100 200 300 400 500 600 700 800 900 1000ConcentrationFigure 1 3b. Constituent concentrations as a function of depth at Well #2.DCPP Water Resources Report Page 30DCPP Water Resources ReportPage 30 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Tahle 8. Well #~2 Denth-Sneeifie Water Ouialitv Cornposite 1 Discrete 1 Composite 2 Discrete 2 Composite 3 Discrete 3(Surface) (275 Ft.) (Surface) (190 Ft.) (Surface) (158 Ft.)nayeUis PL 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07________________15:40 _______ 15:50 16:05Depth (or Pumping Water Level) _____275 190 158-pH S.U. -6.6 6.9 6.7 6.8 6.7 6.7Color Color Unit S <5 <5 <5 <5 <5 <5MBAS Surfactants mg/L 0.1 BQL BQL BQL BQL BQL BQLOdor T.O.N. 1 ND ND ND ND ND NDSpec. Conductivity umhos/cm 1 1300 1420 1300 1340 1290 1300T.D.S. mg/L 10 790 860 790 800 790 810Turbidity N.T.U. 0.1 4.5 4.7 0.69 3.6 1.4 7Alkalinity (CaCO3) mg/L 10 410 440 400 420 410 400Bicarbonate(CaCO3) mg/L 10 410 440 400 420 410 400Carbonate (CaCO3) mg/b 10 BQL BQL BQL BQL BQL BQLHardness (as CaCO3) mg/L 10 520 530 510 520 520 530Hydroxide (as CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQLAluminum ug/L 5 170 240 46 110 100 300Antimony ug!L I BQL BQL BQL BQL BQL BQLArsenic ug/L 0.5 2.2 4 1.8 2.5 2 1.4Barium ug/L 0.5 30 26 27 27 28 35Beryllium ug/L 0.5 BQL BQL BQL BQL BQL BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQLCalcium mg/L 0.1 97 95 94 96 95 100Chloride mg/L 0.2 100 120 100 110 100 110Chromium ug/L 1 2.8 6.4 1.7 4.3 1.9 4.3Copper mg/b 0.02 BQL 0.037 BQL BQL BQL BQLFluoride mg/b 0.1 0.4 0.5 0.4 0.4 0.4 0.5DCPP Water Resources Report Page 31DCPP Water Resources ReportPage 31 TbeNT.RWel #2 Det-SEvionentalc anWaturQalit Resource MangemntCnsltntTable 8. Well #2 Depth-Specific Water Quality Results (cont'd.)Well 2 Well 2 Well 2 Well 2 Well 2 Well 2Composite 1 Discrete 1 Composite 2 Discrete 2 Composite 3 Discrete 3Analyte Units PQL (Surface) (275 Ft.) (Surface) (190 Ft.) (Surface) (158 Ft.)11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07_______________15:40 15:50 ______ 16:05Depth (or Pumping Water Level) _____________ 275 190 158Iron mgiL 0.1 0.71 0.73 0.12 0.43 22 62Lead ug/L 0.5 1.5 0.78 0.63 0.99 0.62 1Magnesium mg/L 0.1 61 64 60 62 60 69Manganese mg/L 0.005 0.041 0.056 0.017 0.03 0.018 0.0087Mercury ug/L 0.5 BQL BQL BQL BQL BQL BQLNickel ug/L 1 9.5 16 8.2 8.9 8.5 11Potassium mg/L 0.2 2.7 3.2 2.7 3.1 2.7 2.1Selenium ug/L 1 2.7 3.2 2.1 2.2 2.4 6Silica mg/L ___ 20 22 19 20 19 24Silver ug/L 0.5 BQL BQL BQL BQL BQL BQLSodium mg/b 0.5 70 100 69 80 68 59Sulfate mg/L 0.5 140 150 150 150 150 160Thallium ug/L 0.5 BQL BQL BQL BQL BQL BQLZinc mg/L 0.05 0.15 0.07 0.11 0.069 0.11 0.099Total Sulfide mg/L __Ammonia (as N) mg/b 0.1 _____Nitrate (as N) mg/L 0.1 0.2 BQL 0.2 BQL 0.2 0.9Nitrate (as NO3) mg/b 1_________________________________________o-Phosphate-P mg/b 0.05 _______T.K.N. mg/b 1 _________DCPP Water Resources Report Page 32DCPP Water Resources ReportPage32 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2.3 Comparison of Surface Water and GroundwaterCornpositionA significant aspect of this study is to determine if a connection exists betweengroundwater from the existing DCPP production well and surface water in Diablo Creek.In addition to reviewing water level data during the pumping tests in an effort to detecttrends that might indicate a significant connectivity between the extracted groundwaterand the Creek, water quality data were reviewed to assess if any connectivity existsbetween the surface water and the shallow groundwater production zone.Two methods are used to review the water quality data that were collected from Well #2and the creek. The first is the comparison of paired water quality samples collected at thepumping well and at the creek on December 3, 2007, December 6, 2007 and June 30,2008 (Table 9). For these sampling dates which occurred during the constant ratepumping tests at Well #2, samples were collected contemporaneously, so as to provide aninstantaneous snapshot of water quality at both locations for comparison purposes.The second method used to examine the water quality data for trends that indicate thedegree of connectivity between extracted groundwater at Well #2 and the Creek was tocompare the depth-specific water quality samples collected at Well #2 with water qualitysamples collected at the Upper Creek sampling site (Figure 14a and Figure 14b, below).If there is a significant degree of connectivity between water in the upper productive zoneof Well #2 and surface water, it would be expected that the shallowest water qualitysample collected from the well could have a geochemical composition similar to that ofthe surface water sample for a number of constituents (or more similar to the surface waterthan that of the deeper groundwater).The most definitive result of this water quality comparison is the considerable variation inseveral key constituents, such as TDS, Chloride, Sodium, Iron, which are all substantiallylower in concentration in the creek water than in groundwater. The difference is evidentin comparison to both the various composite well samples as well as the depth-specificsamples. The water quality difference evident in these constituents, most of which aregenerally considered "conservative" (i.e., they do not tend to vary with time or reactionsin the subsurface), is diagnostic of largely if not entirely different water source. As oneline of evidence, these data indicate limited, if any, connection between the groundwaterpumping at Well #2 and creek flows.Also, the presence of bacteria (Total Coliform and E Coli) in the creek water and itsabsence in well #2 water (although the Total Coliform results from the December 6, 2007well sample was "present" but this could be a contaminated sample and thereforeanomalous), is additional corroboration that groundwater pumping at Well #2 is notdirectly extracting water from the creek.DCPP Water Resources Report Page 33DCPP Water Resources ReportPage 33 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 9. Water Quality in Diablo Creek Compared to Groundwater ___Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Upper Upper CulvertWeir WeirDiscrete 1 Composite Discrete 2 Discrete 3Analyte Units PQL Composite 1 (7Ft) 2(9F.) Composite 3 (158 Ft.)11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 12/3/07 12/6/07 6/30/0815:40 15:50 16:05pH S.U. -6.6 6.9 6.7 6.8 6.7 6.7 6.9 6.5 7.3 8.2 7.9 8.2Color Color Unit 5 <5 <5 <5 <5 <5 <5 <5 <5 <5 10 10 30Spec. Conductivity umhos/cm 1 1300 1420 1300 1340 1290 1300 1280 1270 1200 870 870 860T.D.S. mgfL 10 790 860 790 800 790 810 760 780 810 530 540 540Turbidity N.T.U, 0.1 4.5 4.7 0.69 3,6 1.4 7 0.39 0.4 0.1 2.1 2 9.5Alkalinity (CaCO3) mg/L 1 0 410 440 400 420 410 400 390 390 400 350 340 370Bicarbonate(CaCO3) mg/L 10 410 440 400 420 410 400 390 390 400 350 340 360Carbonate (CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL 10Hardness (as mg/L 10 520 530 510 520 520 530 580 560 BQL 430 430 420CaCO3)Hydroxide (as mg/'L 10 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLCaCO3) ____Aluminum ug/L 5 170 240 46 110 100 300 5.8 BQL 63 0.25Arsenic ug/L 0.5 2.2 4 1.8 2.5 2 1.4 0.66 BQL 2.1 BQLBarium ug/L 0.5 30 26 27 27 28 35 38 BQL 57 BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL 0.61 0.001Calcium mg/L 0.1 97 95 94 96 95 100 120 110 120 99 89 90Chloride mg/L 0.2 100 120 1 00 110 100 110 94 95 91 33 33 33Chromium ug/L 1 2.8 6.4 1,7 4.3 1.9 4.3 1.3 BQL 1.7 BQLCopper mg/L 0.02 BQL 0.037 BQL BQL BQL BQL 0.024 BQL BQL BQL BQL BQLFluoride mg/L 0.1 0.4 0.5 0.4 0.4 0.4 0.5 0.5 0.5 0.7 0.3 0.3 0.4Iron mg/L 0.1 0.71 0.73 0.12 0,43 0.22 0.62 BQL BQL BQL BQL 0.00011 0.27Lead ug/L 0.5 1.5 0.78 0.63 0.99 0.62 1 BQL BQL BQL BQLMagnesium mg/L 0.1 61 64 60 62 60 69 70 68 69 54 50 47Manganese mg/L 0.005 0.041 0.056 0.017 0.03 0.018 0.0087 0.028 0.026 0.02 BQL BQL BQLDCPP Water Resources ReportPage 34 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 9. Water Quality in Diablo Creek Compared to Groundwater (cont'd.)Nickel ug/L 1 9.5 16 8.2 8.9 8.5 11 7.8 BQL 11 0.01Potassium mg/L 0.2 2.7 3.2 2.7 3.1 2.7 2.1 2.9 2.8 3.1 2.9 2.6 2.5Selenium ug/L 1 2.7 3.2 2.1 2.2 2.4 6 3.2 BQL 1.2 BQLSilica mgIL 20 22 19 20 19 24 24 23 27 31l 29 33Silver ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLSodium mg/L 0.5 70 100 69 80 68 59 53 50 63 22 19 23Sulfate mg/L 0.5 140 150 150 150 150 160 160 170 150 88 89 82Thallium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLZinc mg/L. 0.05 0.15 0.07 0.11 0.069 0.11 0.099 0.43 0.32 0.32 0.13 0.065 BQLNitrate (as N) mg/IL 0.1 0.2 BQL 0.2 BQL 0.2 0.9 0.3 0.5 0.1 BQL BQL BQLE. Coli _____ absent absent present presentTotal Coliform present absent present presentDCPP Water Resources Report Page 35DCPP Water Resources ReportPage 35 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsMay 23, 2008Well 2 -Depth-Specific Samples and Creek Samples-101540I6590115140165190215240265;290ConcentrationFigure 1 4a. Constituent concentrations as a function of depth at Well #2 and Diablo Creek.Well 2 -Depth-Specific Samples and Creek Samples--Alkalinity (CaC;O3) (mgl)140 -NE Bicarbonate (CaCO3) (nrigl)--Aluminum (ugi)165 -a-Chloride (ngl)(6 -Creek-TDS215 A Creek-Alkalinity:: Creek-Bicarbonate* Creek-Alurrinum265 A Creek -Chloride*Cr'ee k-k-on0 100o 200 300 400 500 600 700 800 900 1000Conce ntra tionFigure 14b. Constituent concentrations as a function of depth at Well #2 and Diablo Creek.DCPP Water Resources Report Page 36DCPP Water Resources ReportPage 36 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsMay 23, 20084.2.4 Summary of Water Quality ResultsDepth-specific water quality testing indicates that the water extracted from the deepproduction zone is higher quality (i.e., generally lower in constituent concentrationsimportant to plant operations) than water extracted from the shallow production zone. Inorder to reduce concentrations of certain constituents in extracted groundwater, such assilica, the upper screened portion of Well #2 could be temporarily or permanently sealed.Doing so would improve the quality of pumped groundwater from Well #2. However,this upper productive zone represents approximately 20% of the flow in the well and ifthis portion of the well is sealed, DCPP can expect a 10-20 gpm reduction in groundwaterproduction.The presence of a series of diagnostic constituents with significantly differentconcentrations in Diablo Creek compared with Well #2 groundwater represents a strongline of evidence that groundwater pumping does not draw from Diablo creek.DCPP Water Resources Report Page 37DCPP Water Resources ReportPage 37 C)I0N) | |||
Environmental and Natural Resource Management Consultantsvia emailAugust 22, 2008Mr. Drew SquyresSenior Project ManagerPacific Gas and Electric Company, Environmental Services4325 South Higuera StreetSan Luis Obispo, CA 93401RE: Pacific Gas & Electric (PG&E) Company, Diablo Canyon Power Plant(DCPP) Water Resources Evaluation: Well Installation and Aquifer Testing | |||
==Dear Drew:== | |||
Please find enclosed the revised Water Resources Evaluation Phase II report forDiablo Canyon Power Plant. We are providing this to you in accordance withPG&E Contract #46000 16684 and Contract Work Authorization #35007983 13.This draft includes results from additional aquifer testing conducted in June, 2008which improve and expand upon the assessment of any connectivity betweengroundwater pumping and flows within Diablo Creek.We have enjoyed working with you on the important project, and look forward toproviding additional support in the future.Sincerely,Timothy ThompsonVice President -Water Resource Sciencescc: Mr. Mark Coleman, Diablo Canyon Power PlantMr. John Giambastiani, ENTRIX, Concord DIABLO CANYON POWER PLANTWATER RESOURCES EVALUATIONPHASE II REPORT:WELL REHABILITATION,MONITORING WELL INSTALLATION,AND AQUIFER TESTINGPrepared by:Environmental and Natural Resource Management consultantsAugust 22, 2008 ENTRIX, Inc, -Environmental and Natural Resource Management ConsultantsAugust 22, 2008TABLE OF CONTENTSEXECUTIVE SUMMARY ........................................................................................ 11. INTRODUCTION ............................................................................................... 11.1 BACKGROUND......................................................................................................... 11.2 HYDROGEOLOGY .................................................................................................... 21.3 WELL SITE SELECTION.............................................................................................. 32. MONITORING WELL INSTALLATION (WELL #4 AND WELL #5) ................................ 12.1 DRILLER AND DRILLING METHODS................................................................................ 12.2 WELL #4........................................................................................................ 22.2.1 Site Description ........................................................................................ 22.2.2 Well Construction ...................................................................................... 22.2.3 Well Logging............................................................................................ 22.2.4 Well Development and Testing .................................................................... 32.3 WELL#5 .............................................................................................................. 62.3.1 Site Description ........................................................................................ 62.3.2 Well Construction ...................................................................................... 62.3.3 Well Logging............................................................................................ 62.3.4 Well Development and Testing........................................................................ 83. WELL #2 REHABILITATION AND TESTING .......................................................... 113.1 WELL REHABILITATION....................................................................... :.................... 113.1.1 Results of Pump, Motor, and Column Pipe Inspection............................................. 113.1.2 Video Log Results .................................................................:.................... 113.1.3 Description of Well Rehabilitation Tasks Performed .............................................. 113.2 SPINNER TEST........................................................................................................ 123.3 PUMP TESTS FOR EVALUATING WELL YIELD................................................................... 133.3.1 Step Drawdown Test.................................................................................. 133.3.2 Constant Rate Tests................................................................................... 153.5 PUMP SPECIFICATIONS............................................................................................. 164. AQUIFER RESPONSE TO PUMPING TEST......................................................... 174.1 MONITORING LOCATIONS ......................................................................... 2............ 174.1.1 2007 Constant Rate Pumping Test............................................................... 174.1.2 2008 Constant Rate Pumping Test............................................................... 174.1.3 Effect of Constant Rate Pumping Test at Monitoring Wells ................................... 184.1.4 Effect of Constant Rate Pumping Test at Surface Water Monitoring Locations.....'......... 194.2 WATER QUALITY ................................................................................................... 244.2.1 Relative Water Quality of Wells #2, #4 and #5...................................................... 244.2.2 Well #2 -Water Quality vs. Depth.................................................................... 284.2.3 Comparison of Suiface Water and Groundwater Composition .................................... 334.2.4 Summary of Water Quality Results................................................................... 375. SUMMARY AND CONCLUSIONS......................................................................... 385.1 WELL #2 REHABILITATION ....................................................................................... 385.2 EFFECTS OF GROUNDWATER PUMPING ON DIABLO CREEK .................................................. 385.3 RECOMMENDATIONS FOR GROUNDWATER USE............................................................... 385.3.1 Well #2 Construction, Operations and Maintenance............................................... 385.3.2 Monitoring Wells .................................................................................. 395.4 MONITORING PROGRAM RECOMMENDATIONS ................................................................. 39DCPP Water Resources Report Page TOC- 1 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008FIGURESFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.Figure 7.Figure 8.Figure 9.Figure 10.Figure 11.Figure 12a.Figure 12b.Figure 13a.Figure 13b.Figure 14a.Figure 14b.Table 1.Table 2.Table 3.Table 4.Table 5.Table 6.Table 7.Table 8.Table 9.Map of project site showing location of wells.Photograph of Well #4.Schematic diagram showing Well #4 construction and lithology.Drawdown at Well #4 during development and testing.Photograph of Well #5.Schematic diagram showing Well #5 construction and lithology.Drawdown at Well #5 during development and testing.Graph of Step Drawdown Test at Well #2.Water levels at Well #2 during the constant rate pumping test.Water levels in DCPP Wells during November 2007 constant ratetest.Water levels in DCPP Wells during June 2008 constant rate test)Water levels at Pumping Well and Diablo Creek Locations (June/July 2008Pump Test).Water levels at pumping well and Diablo Creek locations focused ontime period of test.Constituent concentrations as a function of depth at Well #2.Constituent concentrations as a function of depth at Well #2.Constituent concentrations as a function of depth at Well #2 andDiablo Creek.Constituent concentrations as a function of depth at Well #2 andDiablo Creek.TABLESDCPP Well Locations.Construction Parameters for Well #4 and Well #5.Development of Well #4 (November 8, 2007).Development of Well #5 (November 10, 2007).Well #2 Spinner Log Analysis.DCPP Well #2 -Step Rate Test.Comparison of Well #4, Well #5 and Well #2 Composite Samples.Well #2 Depth-Specific Water Quality Results.Water quality in Diablo Creek compared to groundwater.DCPP Water Resources Report Page TOC-2DCPP Water Resources ReportPage TOC-2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Attachment A:Attachment B:Attachment C:Attachment D:Attachment E:ATTACHMENTSWell 4 DocumentationWell 5 DocumentationWell 2 DocumentationWater Quality Data TablesDCPP Water Resources Monitoring PlanDCPP Water Resources Report Page TOC-3DCPP Water Resources ReportPage TOC-3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Executive SummaryThe PG&E Diablo Canyon Power Plant ("DCPP") has historically utilized threeindependent water supplies for plant water needs, listed in order of volumetric priority:(a) seawater, treated by a large reverse osmosis system ("SWRO"), (b) diversions fromDiablo Creek, and (c) groundwater produced by a single on-site well ("Well #2"). As aresult of a directive by the California Coastal Commission, diversions from Diablo Creekwill be ceased. This change in supply options increases the dependence upongroundwater and therefore generates a need for the groundwater to be both more reliableand pumped at a slightly greater rate than historically. Given this context, the purpose ofthis Water Resources Evaluation is to develop a better understanding of on-sitegroundwater resources in terms of potential yield, water quality and relationship betweengroundwater pumping and flows in Diablo Creek. This work is based in part on a 2007study ("Phase I: Evaluation of Groundwater and Surface Water Data") that was preparedto identify appropriate steps for refurbishing and testing existing groundwater productionfacilities, evaluating groundwater water quality issues, and installing monitoring wells.The Phase II scope-of-services included: (1) installation of two monitoring wells (Well #4and Well #5), (2) evaluation and rehabilitation Of Well #2, (3) aquifer testing at Well #2,and (4) water quality sampling and analysis. The proposed new monitoring wells willprovide valuable information needed for (a) understanding current groundwater basinconditions, (b) assessing future groundwater production potential and water quality at theproposed locations, and (c) comparing groundwater water levels with flow levels inDiablo Creek to demonstrate if any hydraulic connection is apparent.The two monitoring wells, known as Wells #4 and #5, were drilled and completed to 500ft and 400 ft, respectively. The wells were logged, tested and evaluated for water quality.Well #4 was pumped for two hours at a rate of 30 gallons per minute, had 21 ft ofdrawdown and has a potential yield of 80 gallons per minute (gpm) or more. Waterquality at Well #4 was satisfactory, but poorer than the other wells. Well #5 was pumpedfor over two hours at a rate of 49 gallons per minute, had a drawdown of approximately 8ft and has a potential yield of 150 gpm or more. Water quality at Well #5 was better thanthat at Well #2 in many, but not all, respects.The pre-existing and historically productive Well #2 was rehabilitated, including cleaningof the casing, and replacement of the pump, motor, column pipe and surface controls. Thewell was tested and sampled to determine if the well's inflow rates and water qualitydiffered at different depths. Based upon the results of this work, it is evident thatsignificant inflow rates occur at different depths within the well and that the water qualityat these various depths is also different in certain respects. The majority of the well'swater enters in the 190-275 ft zone, and is of reasonably good water quality. A shallowerzone was identified as contributing approximately 20% of the well's flow and containingelevated concentrations of total dissolved solids, chloride, iron and silica.DCPP Water Resources ReportPaeE-Page EC- I ENTRIX, Inc.- Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well #2 was initially tested from November 26 through December 7, 2007, a 10-dayconstant rate pumping test that included monitoring at Well #2, three monitoring wellsand in Diablo Creek. The test was run at 150 gpm which proved to be an acceptable long-term, sustainable pumping rate for the well, even with the preceding years of limitedrainfall and associated lowered water levels. During wetter climatic periods, the well hasa capacity to produce at a greater flow rate.A second constant rate pump test was conducted at Well #2 from June 25 to July 2, 2008to evaluate the relationship between groundwater pumping and creek water levels. Well#2 was pumped at a rate between 150 and 200 gpm for seven days. Changes in waterlevels were monitored in Wells #2 and #5 as well as at two locations in Diablo Creek.Just before the end of the test, water quality samples were collected from Well #2 and thecreek. The data collected do not show a correlative water level response between waterlevels in Diablo Creek and pumping water levels in Well #2. During the course of thepumping test, water levels in the Creek did not exhibit a drawdown or rebound signaturecorresponding to the start and end of the pump test, respectively. If the creek and wellwere connected, measurable changes in the creek water levels would likely occur. Theabsence of these trends supports the conclusion that there is no discernable connectionbetween creek water levels and pumping at Well #2.Water quality comparisons were also conducted to determine if a relationship existsbetween groundwater pumping at Well #2 and flows within Diablo Creek. Concentrationsof several key constituents from samples collected contemporaneously during the multipletests were markedly different indicating distinct water sources.Finally, a water resource monitoring program was initiated to collect and track hydrologicdata in an effort to ensure adequate understanding of this valuable resource is developedand maintained.Recommendations of this work include continuance of the water resources monitoringprogram, evaluating factors associated with future production use of Wells #4 or #5, andevaluate implementation of downhole well modifications to improve water quality in Well#2.DCPP Water Resources ReportPaeE-Page EC-2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20081. IntroductionThis report provides a summary of well rehabilitation, monitoring well installation,aquifer testing, and water quality analyses conducted at the PG&E Diablo Canyon PowerPlant ("DCPP") from October 2007 through July, 2008. The services were conducted aspart of the Phase II and Phase III Water Resources Evaluation scope of work which, inturn, is based upon the June 30, 2007 technical report entitled: "Phase I: Evaluation ofGroundwater and Surface Water Data". The work provides data and recommendations tosupport increased reliability of groundwater production and an evaluation of whether aconnection exists between groundwater pumping from the existing Well #2 and flowsassociated with Diablo Creek. Also included is a section of the report that summarizesrecommendations for groundwater use and facilities management and provides elementsof a long-term groundwater resource monitoring program.This work is part of a larger effort by DCPP staff to increase reliability of available watersupplies, which also includes modifications to the DCPP seawater reverse osmosis("SWRO") treatment plant system. Properly managed and monitored development oflocal groundwater resources can provide a highly reliable water supply that will continueto supplement the SWRO supply. As part of this ongoing groundwater developmentactivity, groundwater monitoring data will be collected to establish a body of informationto better understand the water resources of the area. Appropriate work to follow the taskssummarized in this document includes implementation of a groundwater monitoringprogram to initiate the collection of water related data that will increase the understandingand forecasting of this valuable resource. Additional phases of work may also include theconversion of one or both of the new monitoring wells to production wells dependingupon future determination of DCPP groundwater supply needs.1.1 BackgroundWater supply for DCPP steam generation is currently acquired from three sources: reverseosmosis treatment of seawater ("SWRO"), surface diversions from Diablo Creek, andpumped groundwater. SWRO is the primary water supply source, with the surface waterand groundwater resources used in supporting roles for augmentation during normalSWRO operations or for temporary backup supply during SWRO outages. Because of aregulatory mandate to cease Diablo Creek diversions, groundwater will be elevated in itsrelative importance to meet the water supply needs of DCPP and it is therefore appropriateto increase groundwater production capability and reliability.Given that context, a study was prepared ("Phase I: Evaluation of Groundwater andSurface Water Data") to identify appropriate steps for refurbishing and testing existingDCPP Water Resources Report PgPage 1 ENTRIX, Inc. -Environmental and Natural Resource Management Cons~ultantsAugust 22, 2008groundwater production facilities, evaluating groundwater water quality issues, andinstalling monitoring wells.The monitoring wells were recommended to gain a broader understanding of thegroundwater conditions present at the DCPP site and to develop information on futureproduction well locations. These wells will provide information needed for (a)understanding current groundwater basin conditions, (b) assessing future groundwaterproduction potential and water quality at the proposed locations, and (c) comparinggroundwater water levels with flow levels in Diablo Creek to demonstrate if any hydraulicconnection is apparent. If replacement of the existing Well #2 or augmentation of theexisting DCPP groundwater pumping capacity is needed at a future date, one or both ofthese monitoring wells could be converted to production wells.In order to comply with the aforementioned regulatory mandate to cease Diablo Creekdiversions, increased groundwater production will be needed. The cessation of creekdiversions generates two considerations:1. Increased dependence upon Well #2 to provide all the water needed toaugment the SWRO system; and,2. The technical concept of demonstrating that both existing and futuregroundwater pumping does not extract subsurface water associatedwith Diablo Creek flows.For these considerations, a series of diagnostic aquifer tests were conducted. These testsinvolved pumping at Well #2 at similar rates to historical and planned usage andcontemporaneous water level monitoring at other wells and at locations within DiabloCreek.1.2 HydrogeologyThe primary aquifer established by existing groundwater extractions is the fracturedsandstone (possibly dolomitic) of the lower to middle Miocene-aged Obispo Formation.This unit also contains siltstones and finer grained beds that are less productive than thefractured sandstones. The brittle nature of the sandstones produces discrete fracture setsthat can form a prolific bedrock aquifer. Because the aquifer material in this region isrelatively hard and locally brittle bedrock, essentially all groundwater production will bederived from fractures within the rock, not from the pore spaces between the sand grainsas occurs in an alluvial (i.e., uncemented, unlithified) aquifer.DCPP Water Resources Report PgPage 2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20081.3 Well Site SelectionSite selection in bedrock aquifers is highly dependent upon the existence of fracturedzones that allow groundwater collection and conveyance from upgradient source areas.For the purpose of monitoring well site selection, a local and regional scale fracture studywas conducted, as described in the Phase I report. This study combined with site accessand other considerations resulted in the identification of three (3) favorable drillinglocations, two (2) of which (site "4" and site "5 b") were selected by PG&E staff for themonitoring wells installed as part of this Phase II work. (see Table 1, Figure 1). Site "5b"of the Phase I report will be referenced as site "5" in this report and all future references.As a historical note, Well #3 was drilled contemporaneously with wells 1 and 2, yetbecause of insufficient yield was abandoned before well completion. It is located in thesmall turn-around circle near the current Diablo Creek diversion and pumping facilities*(see Figure 1). The wellhead is no longer visible in the field, and its elevation in Table 1is approximate.Table 1. DCPP Well LocationsNorth East EeainWell No. Descriptive Location Coordinate* Coordinate* lvainfIt mslWell #1 Near Diablo Creek 2277056.86 5711903.64 251.36Well #2 On Deer Trail Rd. 2276517.11 5712241.45 333.3Well #3 On Turnaround near SempSemp ~ ~ 8Well #3 Lower Weir SempSemp-8On Deer Trail Rd. atWell #4 troftwaetnk 2276209.20 5712999.92 452.35Well 115 Near Man Camp area 2276658.80 5712413.70 303.93*Coordinates and Elevations were surveyed by GraniteConstruction staff. Coordinates are consistent with other DCPPsurveying data. Elevations represent the top of the concrete padat each well.DCPP Water Resources Report PgPage 3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008-~ IrTh~r~ ~ FIgure______________________________________ 6 v~AI L~23t~ofl~ w~-~H lt~oi~ M~,pN A C). k -~ C)r),~, 42~ 1CC)t pidIIo (2afl~o~ Vowe, ~3fltUXD~Figure 1. Map of project site showing location of monitoring stations.DCPP Water Resources Report Pg ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082. Monitoring Well Installation (Well #4 and Well #5)The initial task conducted during this phase of the project involved the installation of two(2) monitoring wells. The design and installation approach for the wells included theprovision that each monitoring well could be converted to a production well at a futuredate. Therefore, careful monitoring was conducted during drilling of the monitoring wellsto assess the potential well yield and water quality. Additionally, upon completion of eachwell, a short-term pumping test was conducted to provide an estimate of yield and allowfor collection of a water sample for water quality analysis.Both wells were drilled to relatively deep depths (506 ft and 409 ft, respectively) to allowfor penetration of a significant depth of bedrock, which greatly increases the potential tointersect fracture zones that have regional connectivity and hence increased yield anddrought-period tolerance. Also, deep sanitary seals were installed at the wells to provideincreased assurance that shallow groundwater that could potentially be tributary to DiabloCreek is not captured by the wells. Additional details of well construction are provided inTable 2 and Figures 3 and 6, below.Table 2. Construction Parameters for Well #4 and Well #5.Well Construction Parameter Well #4 Well #5Drilled Depth 506 ft 409 ftBorehole Diameter 10.5 inches 10.5 inchesDirect Air Rotary/Drilling Method Direct Air Rotary Mud RotarySanitary Seal 230 ft 75 ftCasing Size (OD) 5 inch 5 inchCasing Material PVC (Sch. 80) PVC (Sch. 80)Screen Interval 250 -500 ft 100 -400 ftSlot size 0.050 in 0.050 inGravel Pack #8 mesh sand #8 mesh sandInitial Water Level (below ground) 219 ft 40 ftWellhead Elevation (ft MSL) 452.35 ft 303.93 ftGeophysical Logs SP, Resistivity, Sonic SP, Resistivity, Sonic2.1 Driller and Drilling MethodsCascade Drilling of La Habra, CA was contracted to conduct the monitoring wellinstallation based upon previous experience, qualifications, safety record and familiaritywith PG&E projects. Cascade was directed to employ rotary air-hammer drilling methodswhich are appropriate for hard, fractured bedrock aquifer materials as present at the site.Cascade provided a crew of 3, an auxiliary air compressor and other ancillary drillingequipment for the installation of the two (2) monitoring wells. Geophysical well loggingat Wells #4 and #5 was conducted by Welenco of Bakersfield, CA.DCPP Water Resources Report PgPage 1 ENTRIX, Inc. -Environmnental and Natural Resource Management ConsultantsAugust 22, 20082.2 Well#42.2.1 Site DescriptionWell #4 (Figure 2) is located 0.2 miles up Sky View Road from its intersection with DeerRun Road near the Man Camp, and is at the junction of Sky View Road and the water tankroad. This site was selected because it represents a high potential for sufficient flow ratesto provide supplemental water production, it will likely have at most a limited effect onthe existing Well #2, and its effect on Diablo Creek will likely be very limited. It is alsoat a sufficient distance from Well #2 and Diablo Creek to allow monitoring of up-gradientaquifer conditions that can support development of a broader understanding of aquiferwater levels and possible variability in aquifer water quality.2.2.2 Well ConstructionWell #4 was drilled from October 24 to October 26, 2007 to a total depth of 506 ft beneathground surface. Water was first encountered at 245 ft, and stabilized to a static level of219 ft. In consideration of the depth to water, and the interest in ensuring limitedconnectivity to Diablo Creek, the sanitary seal was constructed to 230 ft deep. PerforatedPVC casing was installed from 230-500 ft. By the time the total depth of drilling wasreached, the well was naturally producing approximately 40 gpm, as evidenced by theflow resulting from the air injection employed as part of the air-hammer drilling method.2.2.3 Well LoggingSediments encountered during drilling included abundant clay, shale and siltstone withinterspersed layers of sandstone (see State Well Drillers Report, Attachment A). Evidenceof fracturing increased below 240 feet and correlates with increased water production ofthe well during drilling. This observation is particularly relevant because in fracturedbedrock aquifers, essentially all the groundwater that is available to enter the well will bederived from fractures within the rock, rather than from the pore spaces between the sandgrains. Geophysical logs run in the hole included electrical log (resistivity andspontaneous potential [SP]), gamma, sonic velocity and temperature. These logs illustratethe stratified nature of the formation and an increase in the proportion of sandstone-richbeds in the lower 60 feet of the well. The indications provided by the e-logs are largelycorroborated with the lithologic monitoring conducted by ENTRIX during well drilling.Initial stabilized water levels in the well were measured at 219 ft deep. Confined aquiferconditions are evident based upon this static water level in relation to the 230 ft depth ofthe sanitary seal and top of slotted casing at 250 ft deep.DCPP Water Resources Report PgPage 2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008ioto of Monitoring Well #42.2.4 Well Development and TestingWell #4 was developed for a full day following well construction, including severaliterations of surging and bailing at deep, medial and shallow portions of the well.Development was continued until the produced water was clear. Next, in an effort toestablish potential well yield, Well #4 was pumped for two hours at a rate of 30 gallonsper minute, which results in a drawdown of approximately 21 ft. Based on these data, thespecific capacity of the well is approximately 1.4 gpm/ft of drawdown. Given that thereare at least 200 feet of additional available drawdown, flow rates of 80 gpm are attainableif needed at a future date; although the pumping lift would be substantially greater thanthat needed at either Well #2 or Well #5 for this production rate.As indicated in Table 3 below, by the end of the test, the turbidity in the water was greatlyreduced and the pumping water level had nearly stabilized (Table 3, Figure 4). A waterquality sample was collected at Well #4 at the end of the test, on November 8, 2007.Water quality results are provided below in Section 4.DCPP Water Resources ReportPage 3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008If it is determined in the future that production from this well is needed, we suggestconducting, depth-specific water quality sampling to determine if a portion of the well'sproduced water is of the poorer quality than from other depths. If it is determined that aspecific zone (i.e. the deepest zone, for example) is of particularly poor water quality,changes in well construction parameters may aid in controlling water quality from thiswell, although production rates will likely be reduced. Also, although this well still has alower specific capacity than Well #5, it is sufficiently distant from Well #2 so as to reducethe potential for interfering cones of depression from multiple pumping wells, and isworthy of consideration to meet future production needs.Table 3. Development of Well #4 on November 8, 2007.Elapsed Depth Electrical Trity VolumeTime Time to Conductivity Triiy Pumped_______Water___ (mai) (ft bgcs) (NTU) (gallons)12:49 0 217 _ ____ 012:50 1 221.85 1635 53 I13:10 21 234.44 1488 271 60013:30 41 237.03 1463 10.9 120013:50 61 237.05 1483 0 180014:10 81 237.69 1464 0 240014:30 101 238.05 1465 0.7 300014:50 121 238.3 1478 0 3600Well 4 Development and Testing215220"Z 225*9°2302352400 20 40 60 80 100 120 140Elapsed Time (min)Figure 4. Drawdown at Well #4 during development and testing.DCPP Water Resources Report PgPage 4 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Figure 3. Schematic diagram showing Well #4 construction and lithology.DCPP Water Resources Report PgPage 5 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082.3 Well #52.3.1 Site DescriptionWell #5 (Figure 5) is located in the northeast corner of the Man Camp yard. Based uponthe structural geologic work conducted in the Phase I study, this site is located southeastof a throughgoing N75°E structure which may represent a hydrologic barrier, andtherefore the well likely encountered favorable aquifer materials with groundwaterproduction characteristics similar to Well #2. Also, because this monitoring well isrelatively close to Well #2, drawdown during the Well #2 pumping will be evident andthereby helpful in the aquifer analysis efforts.2.3.2 Well ConstructionWell #5 was drilled from October 28 to November 2, 2007 to a total depth of 409 ftbeneath ground surface. Unstable downhole conditions between 50 and 250 ft requiredconversion from air rotary drilling methods to bentonite mud-based drilling methods.Using drilling mud is a common solution to bedrock wells having unstable sections thatwon't stay open with the viscosity of water only. Water was first encountered at 45 fi, andstabilized to a static level of 40 ft. In consideration of the depth to water, and the interestin ensuring limited connectivity to Diablo Creek, the sanitary seal was constructed to 75 ftdeep. Blank PVC casing was installed from 75 to 100 ft; perforated PVC casing wasinstalled from 100-400 ft. By the time the total depth of drilling was reached, the wellwas naturally producing over 100 gpm, as evidenced by the flow resulting from the airinjection employed as part of the air-hammer drilling method.2.3.3 Well LoggingNear surface sediments encountered during drilling of Well #5 included both siltstonewith clay and/or sandy components as present at Well #4 and also a larger proportion ofpoorly-lithified sandstone beds (see State Well Drillers Report, Attachment B). Overall,the sediments in the upper 100 ft+ in this well were poorly consolidated which resulted inunstable hole conditions as mentioned above. Evidence of fracturing was present fromapproximately 50 feet and throughout the depth of the hole, and likely corresponds withthe structural geologic evidence from analysis of aerial photographs that this site is withina northeast-trending fracture system.DCPP Water Resources Report Page 6DCPP Water Resources ReportPage 6 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008gure 5. Photograph of Well #5.Geophysical logs run in the hole included electrical log (resistivity and spontaneouspotential), gamma, sonic velocity and temperature. Collectively, these logs illustrate thestratified nature of the formation and an increase in the proportion of sandstone-rich bedsin the upper and lower portions of the well. The indications provided by the e-logs arelargely corroborated with the lithologic monitoring conducted by ENTRIX during welldrilling.Initial stabilized water levels in the well were measured at approximately 80 ft deep.Confined aquifer conditions are evident based upon this static water level in relation to the250 ft depth to the top of slotted casing.DCPP Water Resources Report PgPage 7 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082.3.4 Well Development and TestingWell #5 was developed for 7.5 hours following well construction, including severaliterations of surging and bailing at deep, medial and shallow portions of the well.Development was continued until the produced water was clear. Next, in an effort toestablish potential well yield, Well #5 was pumped for over two hours at a rate of 49gallons per minute, which resulted in a drawdown of approximately 9 ft (Figure 7). Basedon these data, the specific capacity of the well is approximately 5.9 gpm/ft of drawdown,which represents a higher specific capacity than that measured at Well #4. Based uponthis, albeit limited, production test, this well likely has a production capacity equal to orgreater than that of Well #2. Given that there are at least 300 feet of additional availabledrawdown, flow rates of 150 gpm may be possible if needed at a future date. Note thatthe initial recovery of the well's water level is illustrated in the graph to show the rapidwater level response when pumping stopped.For the second half of the test, the measured turbidity in the water was "0" (see Table 4)indicating that the well development was successful to remove turbid material from boththe drilling process and from the use of drilling mud.A water quality sample was also collected at Well #5 on November 10, 2007. Waterquality results are provided in Section 4 below.Based on this pumping test and water quality data, Well #5 has a higher specific capacityand better water quality than Well #4, and represents a more viable alternative if at afuture date conversion to a production well is needed. However, because Well #5 islocated near the existing Well #2, and approximately 9 feet of drawdown was observed atWell #5 during the pump test of Well #2, consideration and planning of the combineddrawdown effects is needed to adequately forecast the combined yield of the two wellsoperating together.DCPPWate Reourcs ReortPage 8 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Figure 6. Schematic diagram showing Well #5 construction and lithology.DCPP Water Resources Report Page 9DCPP Water Resources Report ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 4. Development of Well #5 (November 10, 2007).Easd Depth Electrical Triiy VlmTime Time to Conductivity Triiy Pumped_______Water(mini) (ft bgs) (NTU) (gallons)7:25 80_____7:30 0 80 ____7:50 20 85.3 1020 3.31 10008:10 40 86.35 962 1.65 20008:30 60 87.12 948 1.3 30008:50 80 88.31 943 1.2 40009:10 100 88.4 941 0 50009:30 120 88.41 935 0 60009:52 142 83.55 930 0 7000Well 5 Development and TestingI-79808182838485868788890 20 40 60 80 100 120 140 160Elapsed Time (min)Figure 7. Drawdown at Well #5 during development2007.and testing on November 10,DCPP Water Resources ReportPae1Page 10 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083. Well #2 Rehabilitation and Testing3.1 Well RehabilitationWell #2 was rehabilitated to provide a series of benefits such as increased reliability,potential for increased yield, and increased operating efficiency of the well. Withcessation of Diablo Creek diversions, the increased dependence upon groundwater can besupported by ensuring Well #2 is mechanically and physically sound.Well #2 was originally installed in 1985 to a total depth of 350 feet by Floyd V. Wells, Incof Santa Maria, California. The 10-inch diameter Schedule 200 PVC casing is perforatedfrom 90 ft bgs to total depth, with 0.040 full-flow horizontal-slot well screen.3.1.1 Results of Pump, Motor, and Column Pipe InspectionThe existing pump and motor on Well #2 were removed by Fisher Pump of Santa Maria,CA, under contract to Woodward Drilling Co. of Rio Vista, CA. The motor, pump andpump column although marginally operational all exhibited signs of wear and debilitationtypical of 20-year old equipment. It was determined that replacement of thesecomponents was in the best interest of DCPP and a greater reliability of the groundwatersupply produced by this facility.3.1.2 Video Log ResultsFollowing pump removal, a video logging tool was used to visually inspect the downholeconditions of Well #2. This video file provided evidence of the presence of encrustationof the well casing, mainly below 238 ft, and the existence of an approximately 20 ft thickpile of debris at the bottom of the well (Attachment C). Using these data, wellrehabilitation was recommended to include swabbing, brushing, air jetting and bailing.3.1.3 Description of Well Rehabilitation Tasks PerformedBased upon results of the video investigation, described above, the following steps wereperformed:* Bail out most of accumulated sediment from bottom of well.* Brush well with plastic-bristle brush to remove major areas of encrustation.* Additional sediment removed by bailing followed by air lifting.* Swab well with dispersant and detergent to clean casing encrustation andre-open clogged perforations.* Re-develop well with swab tool and conduct additional air lifting toremove all dispersant and suspended material.DCPP Water Resources ReportPage 11 ENTRIX, Inc.- Environmental and Natural Resource Management ConsultantsAugust 22, 20083.2 Spinner TestUpon completion of well rehabilitation work, velocity logging of the well was conductedby Pacific Surveys of Claremont, CA to determine the depth-distribution of groundwaterinflow into the well. This involves lowering a flow-metering logging tool into the welland pulling it up past the productive zones during active pumping. The relative inflowrates at the various depths of the well are evident from this effort and can provide valuableinformation if certain zones exhibit dominant flow rates and/or associated water qualityissues. The actual logs provided by the contractor are included as Attachment C.For the spinner test, the well was pumped at a rate of 90 gpm for 2.5 hours prior to andduring the survey. During the test; the pumping water level was 149 ft bgs. The results ofthe velocity logging, summarized in Table 5, indicate that there are two primaryproductive zones that produce over 90% of the flow into the well. The top loggedinterval, from the top of the perforations at 100 ft bgs to 158 ft bgs, producesapproximately 30% of the flow. This zone is underlain by an approximately 30-foot thicklow productivity zone. The most productive zone is located from 190-275 ft bgs.Water quality samples were collected at 158 ft bgs, 190 ft bgs, and 275 ft bgs. The pumpwas set at a depth of 160 ft bgs during this test, which is a fundamental considerationbecause the pump set-depth influences flow direction within the well, and this is animportant consideration for assessing the representativeness of depth-specific waterquality samples. Given the direction of flow within the well, the water quality samplecollected at 158 feet represents water from the 100-158 foot interval; the sample collectedat 190 feet represents water from the 190-275 foot flow zone; and water collected at 275 ftbgs represents the lowest flow zone sampled (275-3 50). Discussion of the water qualitysample analytical results is provided in section 4 below.Table 5. Well #2 Spinner Log Analysis[Flow Rate = 90 gpm1Zone Depths Production % of Flow Zones gpm/ft Thickness(ft bgs) (gpm) (t100-158 20 26% 0.34 58158-190 4 4% 0.13 32190-275 63 67% 0.74 85275-350 3 3% 0.04 75DCPP Water Resources ReportPae1Page 12 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083.3 Pump Tests for Evaluating Well YieldA series of diagnostic pumping tests were conducted to evaluate the Well #2 yield, as wellas its water quality. Results for these tests were used to establish the well's sustainableyield, specify a new submersible well pump and motor, evaluate if groundwater pumpingeffects flows in Diablo Creek, and assess groundwater water quality.A step drawdown test and a constant rate test were performed at Well #2 betweenNovember 20 and December 6, 2008 using a temporary test pump, installed at a depth of300 ft bgs. For over 4 weeks prior to this test, monitoring of water levels was conductedat Well #1, #2, and at the Diablo Creek facilities. Monitoring data was also collected atthe newly constructed Wells #4 and #5 soon after their respective completion dates.These data provide a trend and variation history of water levels at these various locationswhich is useful to establish the natural variability of these water resources in comparisonwith the stresses imposed by the pumping tests.A final pumping test was run in June and July, 2008 to provide specific data to evaluate ifgroundwater pumping affects water levels in Diablo Creek and also to comparegroundwater water quality between these two water bodies.3.3.1 Step Drawdown TestA step drawdown test was conducted to assess the Well #2 optimal and maximumpotential sustainable yields. This test involved pumping the well at a series of four (4)increasingly higher pumping rates for 60 minutes each. The graph of the drawdown andproduction data was used to determine the well's highest sustainable yield and also todetermine the optimal pumping rate for the multi-day constant rate test.On November 20, 2007, a step-rate test was conducted at the rehabilitated Well #2. Thepump set depth was 300 ft bgs. A total of 36,300 gallons were pumped during the courseof the test. The rates used in the test are provided below in Table 6.A graph of the results of the step drawdown test is provided in Figure 8. Drawdownstabilized during the two lower flow rate portions of the test, but not at the two higherflow rate portions. As is relatively common for wells producing from fracture systems ofa bedrock aquifer, extended time is needed at moderate to high flow rates to achievestabilized pumping water levels.In this well, during the 175 gpm pumping of Step 3, water levels continued to declinefrom 208.2 ft bgs after 5 minutes of pumping to 216 ft bgs after 58 minutes of pumping.It is possible, but not assured that the well could have stabilized its drawdown over alonger duration. Additionally, the well was unable to sustain the 215 gpm pumping ratefor Step 4, which is useful information to understand the upper limit of the well's potentialyield. The well recovered quickly after the pump was shut down. At the end of the step-rate test, the water level in the well was 268 ft bgs. The well achieved 90% recoveryDCPP Water Resources ReportPae1Page 13 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008within 10 minutes after pumping ceased and water levels in the well fully recovered inapproximately four (4) hours. Based upon these data, it was determined that a rate of 150gpm would be sustainable for the duration of the planned constant rate pump test.Table 6. DCPP Well #2 -Step Rate TestPumpingDate Start Time Rate_______ _______ (gpm)Step 1 11/20/2007 10:00 75Step 2 11:00 125Step 3 12:00 175Step 4 13:00 21513:03 21513:05 20513:10 20013:20 19513:40 195______________ 13:55 195Diablo Canyon Power Plant -Well 2 Step Drawdown Test4J00.100120140160180200220240260280300Start of Test:November 20, 2007 10:00 AM120 180 240 300360Elapsed Time (min)Figure 8. Graph of Step Drawdown Test at Well #2.DCPP Water Resources Report Page 14DCPP Water Resources ReportPage 14 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083.3.2 Constant Rate TestsA constant rate pumping test was conducted at Well #2 starting at 14:30 on November 26,2007 and ending at noon on December 6, 2007. The static water level at Well #2 at thestart of the test was 112.7 ft bgs and the water level just before the pump was stopped was238.6 ft bgs. A total of 2,321,000 gallons were pumped during the 10-day constant ratetest at a relatively constant rate of 150 gpm. Based on these data, the specific capacity ofthe well is 1.2 gpm/ft of drawdown.As illustrated in Figure 9, the pumping water level at the well dropped steadily andstabilized at approximately 223 ft bgs by the second day of the test. Two additional,discrete steps in the drawdown occur at approximately 48 hours and at approximately 214hours. These are related to minor adjustments of the gate valve on the discharge pipe inan effort to re-establish the target pumping rate of 150 gpm. The well achieved 80%recovery within three (3) hours of the end of the constant rate test, and 94% recovery onweek later.Diablo Canyon Power PlantWell 2 Constant Rate Test100120140*} 160a- 180220S2402602803000 24 48 72 96 120 144 168 192 216 240 264 288 312Start of Test: Elapsed Time (hours)November 26, 200? 2:30 PMFigure 9. Water levels at Well #2 during the constant rate pumping test.336 360 384 408DCPP Water Resources ReportPae1Page 15 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008In addition to recording pumping water levels at Well #2, several other wells on theproperty and two surface water monitoring stations on Diablo Creek were monitoredbefore and during the constant rate test. A further discussion of water level monitoringresults at these monitoring stations is provided in Section 4.Water quality sampling was conducted during the test at the middle and just before shut-down. Results are provided and analyzed in Section 5.Collectively, these data indicate the firm reliability of Well #2 to produce 150 gpm on along-term basis under normal operating conditions. Currently, normal well operationsrequire the well to be operated at intervals of several hours per day. With the futuredecommissioning of the Diablo Creek diversion, an increased demand may be establishedon Well #2 for water supply. Based upon the results of these tests, Well #2 could beoperated at its design flow rate of 150 gpm for significantly longer periods per day whilestill maintaining acceptable margins of safety with respect to pumping water levels.Importantly, because of the limited rainfall in the years preceding this test, drought-typeconditions exist and the results of this testing can be considered representative of limitedwater availability conditions. Although not necessarily worst-case conditions, the yield ofthe well and response of the aquifer will not be any worse than that exhibited during thistest except during periods of even more extreme drought conditions. In a multi-yeardrought, if a greater amount of groundwater is needed than is produced from the wellunder its typical operating patterns, the well could be (a) run for more hours per dayand/or (b) retrofitted with a higher capacity pump set at a deeper level. Finally, duringperiods of higher rainfall and therefore more "average" water supply within the aquifer,the yield of the well as currently equipped will likely be greater and the associateddrawdown effects on the aquifer will be less.3.5 Pump SpecificationsUpon inspection, the condition of the pump, motor and column pipe were determined tobe sufficiently degraded to warrant replacement. A replacement pump, motor and columnpipe was specified, as described below. Installation and operability testing of thesecomponents was conducted on April 18, 2008 by Fisher Pump of Santa Maria, CA.Pump: Grundfos Submersible model # 150S 150-7Pump Serial Number: 07L 19-06-6129Motor: 15 hp FranklinMotor Protector: Franklin SubMonitorControl Panel: Siemens, Class 87Column Pipe: 300 ft of 4-inchProbe access tube: 1-inch PVC (300 ft)DCPP Water Resources ReportPae1Page 16 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084. Aquifer Response to Pumping TestThe response of the aquifer to pumping at Well #2 was evaluated using water level datacollected from Wells # 1, #4, and #5 during the constant rate pumping test conducted in2007. In addition, a second constant rate pumping test was conducted from June 25 toJuly 2, 2008 to evaluate the response of water levels in Diablo Creek to pumping waterfrom Well #2. As part of this analysis, groundwater and creek water level data werecollected before, during and after a test with contemporaneous measurements from thepumping well. Data collected during the 2008 pumping test were also compared with datafrom the 2007 pump test to further evaluate the aquifer response to pumping at Well #2.4.1 Monitoring LocationsWater levels at several wells and two surface water monitoring sites on Diablo Creek weremonitored before and during the constant rate tests at Well #2 (Figures 10 and 11). Inaddition, meteorological conditions were noted at the site and were also reviewed asavailable from the nearest gauging station, the Nipomo CIMIS station. The Nipomostation provides comprehensive data, but its inland setting records different climatologicconditions than the coastal conditions at DCPP.4.1.1 2007 Constant Rate Pumping TestDuring the first constant rate test water levels were monitored in Well #1, near DiabloCreek; Well #4, up the hill from Well #2; and Well #5, near the Man Camp. These wellswere outfitted with pressure transducer devices that automatically collected water leveldata at a programmed frequency of one measurement every 30 minutes.Data was also collected at two locations in Diablo Creek during this test. However, DCPPwater diversions from the creek during the pumping test created water level variations thatprevented determination of any relationship between pumping at Well #2 and creek flow.4.1.2 2008 Constant Rate Pumping TestWater levels at wells #1, #2, #4, and #5, and two surface monitoring sites on Diablo Creekwere monitored before and during the 2008 constant rate test. Wells #2 and #5 as well asthe two creek locations were monitored with pressure transducers that automaticallycollect and record water level data at programmed frequencies. Water levels in Well #1and Well #4 were measured manually with a water level meter just prior to the start of thetest and periodically during the pump test. For the duration of the pumping test,diversions from the Lower Weir pond were stopped.Diablo Creek water levels were monitored throughout the test at the Lower Weir andapproximately 1,000 feet downstream of the Lower Weir, before the creek enters aDCPP Water Resources ReportPage 17 ENTRIX, Inc. -Environ men tal and Natural Resource Management ConsultantsAugust 22, 2008drainage culvert. Where the stream enters the drainage culvert a notched wooden plankestablishes a small pool which flows into the drainage culvert.4.1.3 Effect of Constant Rate Pumping Test at Monitoring Wells4.1.3.1 2007 Constant Rate Pump TestWater levels in Monitoring Wells #1 and 4 did not show drawdown effects related topumping at Well #2 during the course of the constant rate pumping test (Figure 10). Thegreatest observed effect was approximately 9 feet of drawdown at Well #5, which is theclosest monitoring well to the pumping well, at a distance of approximately 250 feet.Water levels in Well #4 remained unchanged throughout the test. This is indicative ofboth the source of the Well #2 water being largely from aquifer zones that may not bephysically connected to Well #4, and also because the upgradient position and distance ofWell #4 relative to #2 minimizes the influence of the Well #2 drawdown.Water levels in Well #1 show a slight and very gradual rise that corresponds in timingwith the pumping at Well #2. This is likely related to the discharge point of the pumpedwater which occurred approximately 200 feet southwest of Well #1, and thereforeprobably induced recharge to the shallow, unconfined sediments in which Well #1 iscompleted.4.1.3.2 2008 Constant Rate Pump TestWater levels in Monitoring Wells #1 and #4 dropped from approximately 27.4 ft bgs and223 ft bgs, respectively, just before the test down to 31.8 ft bgs and 232.4 at the end of thetest (Figure 11). During the second constant rate test the discharge point of the pumpedwater was relocated to a point inside a drainage culvert which is downstream of allsampling locations. This a distinct difference in the response of Well #1 water levelsbetween the two constant rate tests.The water level in Well #5 dropped from approximately 80 ft bgs before the test toapproximately 98 feet just before the test was halted. This is greater drawdown ascompared with the 2007 test is a result of the higher Well #2 pumping rate maintainedduring the 2008 test which resulted in approximately :20 ft more drawdown in that well ascompared with the 2007 test.DCPP Water Resources ReportPae1Page 18 ENTRIX, Inc, -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels at Monitoring Wells During Well 2 Constant Rate Test10356085a. 110160185210235-24 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408Start of Test."November 26, 2007 2.30 PMElapsed Time (hours)Figure 10. Water levels in DCPP Wells during November 2007 constant rate test.4.1.4 Effect of Constant Rate Pumping Test at Surface WaterMonitoring LocationsA pumping test was conducted from 13:30 on June 25, 2008 to 13:45 July 2, 2008 toinvestigate any existing relationships betwveen water levels in Diablo Creek and pumpingwater from Well #2.Data were collected in both creek locations using pressure transducers automaticallyprogrammed to collect water level data. Data collection began on April 18, 2008 and wasterminated on July 3, 2008. An overall saw-tooth trend of declining water levels can beseen in the data set, consistent with a baseline-recession trend of a stream in transitionfrom the wet to dry season (Figure 1 2a).DCPP Water Resources ReportPae1Page 19 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008The data collected before the pumping test show correlations between water levels at theLower Weir and the culvert with frequent drops in water levels at the lower weir,presumably resulting from diverting water from the Lower Weir to the holding tanks on-Site. For the duration of the pumping test, diversions from the Lower Weir pond werestopped. The characteristic drop in water levels at the Lower Weir is not present and thewater levels at both creek sampling points follow the same trend (Figure 1 2b).Creek water level variability during the pump test is within the normal range captured inthe dataset. Approximately 26 hours into the pumping test, a water level drop ofapproximately 0.16 feet occurred. Because fluctuations of this magnitude over similartimescales are present in the non-pumping background data extending back to April 18,2008, this water level change is not related to the groundwater pumping. Additionally,when the pump test was terminated at 13:45 on July 2, 2008, water levels in the creekcontinue in a downward trend for approximately 5 hours without a significant rebound orchange in water levels compared to levels seen over the duration of the test (Figure 12b).Based upon these test data, there is no evidence that creek water levels are affected bypumping at Well #2.DCPPWate Reourcs ReortPage 20 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels in Nearby Wells During 2008 Well#2 Constant Rate Test300250200S150,,0"10050024 48 72 96 120 144 168Elapsed Time (hours) --Well 2 --Well 5Well 4 -Well 1Figure 11. Water Levels in DCPP wells during June 2008 Constant Rate Test.DCPP Water Resources Report Page 21DCPP Water Resources ReportPage 21 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels at Diablo Creek During Well 2 Constant Rate Test1O00120140S1601802402260-70 60 50 40 30Elapsed Time (Days)Start Time: June 25, 2008 13.302.51.50.5-0.5-1CA0).000-25 15 5 0 5 10-Well 2 -----Well 5Well 2 PreTest Data Lower WeirFigure 12a. Water levels at pumping well and Diablo Creek locations (0 hour represents Test start on 6/25/08).DCPP Water Resources ReportPae2Page 22 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diabio Canyon Power PlantWater Levels in Diablo Creek during Well #2 Constant Rate Test1001201401802020.2603.52.0"1.51 £0.500-0.5-1-3 1 0 1 2 3 4 5 6 7 8Start Time: June 25, 2008 13:30Elapsed Time (Days)-Well 2 --Lower Weir-CulvertFigure 1 2b. Water levels at pumping well and Diablo Creek locations focused on time period of test (0 hourrepresents Test start on 6/25/08).DCPP Water Resources ReportPae2Page 23 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2 Water QualityWater quality samples were collected at several intervals throughout the study period.Samples were collected at wells #4 and #5 during development and pumping tests.Multiple samples were collected at Well #2, as follows:* Three sets of paired discrete depth-specific and surface (composite)samples were collected during the spinner test;* Four samples were collected during the step test, near the end of eachpumping step;* Two paired samples from Well #2 and Diablo Creek Upper Weir werecollected at the mid-point and at the end of the first constant rate pumpingtest (December 3 and December 6, 2007); and,* Samples were collected at Well #2 and at Diablo Creek Lower Weir duringthe second constant rate pumping test (June 30, 2008).The water quality data were then reviewed to evaluate:* Similarity of the groundwater extracted from Well #2, Well #4 and Well #5to assist in future water resources planning decisions;* Water quality as a function of depth at Well #2; and,* Similarity of surface water and groundwater composition.A comprehensive series of tables listing all water quality data collected in this phase of theproject are provided in Attachment D of this report.4.2.1 Relative Water Quality of Wells #2, #4 and #5In general, constituent concentrations in the water extracted from Well #5 are similar tothose of the water extracted from Well #2 (Table 7). For most constituents,concentrations are lower at Well #5 than at Well #2. Water chemistry of Well #4 differssignificantly from that of Wells #2 and #5 for many of the constituents sampled. Waterfrom Well #4 is harder (it has a higher specific conductivity, and higher concentrations oftotal dissolved solids, alkalinity, bicarbonate, total hardness, calcium, chloride,magnesium, potassium, sodium, and sulfate) than Well #2. Water from Well #5 has alower concentration than Well #2 for all of these constituents.There are a few other notable differences in the water quality signature of the Well #4water. Water from Well #4 was the only groundwater sample that was found to have adetectable odor. Nitrate was detected in all groundwater samples except for the Well #4sample. The concentration of chromium at Well #4 was more than double the nexthighest concentration detected, as found at Well #2.DCPP Water Resources ReportPae2Page 24 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well #2 was the only well with detectable arsenic concentrations and Well #2 also hadsignificantly higher (by a factor of 4) nickel concentrations than Well #4 or #5, althoughboth nickel and arsenic were below detection limits in the samples collected on June 30,2008.Iron and aluminum concentrations are quite variable (by an order of magnitude) from wellto well, and among the various samples collected at Well #2. A more detailed review ofconcentrations of these constituents with regard to aquifer depth is provided in thefollowing section.Well #2 had the highest silica concentration of any of the wells (at 27 mag/I). Well #2 andWell #4 had concentrations ranging from 19-27 mg/I.DCPP Water Resources Report Page 25DCPP Water Resources ReportPage 25 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 7. Comparison of Well #4, Well #5 and Well #2 Composite SamplesWell #2 Well #2 Well #2 Well #2 Well #2 Well #2 Well #4 Well #5Composite 1 Composite 2 Composite 3Analyte Units PQL (Surface) (Surface) (Surface)11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 11/8/07 11/10/07___________15:40 15:50 16:05pH S.U. -6.6 6.7 6.7 6.9 6.5 7.3 6.6 6.9Color Color Unit 5 <5 <5 <5 <5 <5 <5 <5 <5MBAS Surfactants mg/L 0.1 BQL BQL BQL BQL BQL BQL BQL BQLOdor T.O.N. 1 ND ND ND ND ND ND 2 NDSpec. Conductivity umhos/cm 1 1300 1300 1290 1280 1270 1200 1610 1050T.D.S. mg/L 10 790 790 790 760 780 810 1020 640Turbidity N.T.U. 0.1 4.5 0.69 1.4 0.39 0.4 0.1 1.4 1.8Nitrate (as N) mg/L 0.1 0.2 0.2 0.2 0.3 0.5 0.1 BQL 0.2Alkalinity (CaCO3) mg/L 10 410 400 410 390 390 400 520 380Bicarbonate(CaCO3) mg/L 10 410 400 410 390 390 400 520 380Carbonate (CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQLHardness (as CaCO3) mg/L 10 520 510 520 580 560 590 710 440Hydroxide (as CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQLAluminum ug/L 5 170 46 100 5.8 BQL 52 120Antimony ug/L I BQL BQL BQL BQL BQL BQL BQLArsenic ug/L 0.5 2.2 1.8 2 0.66 BQL BQL BQLBarium ug/L 0.5 30 27 28 38 BQL 33 30Beryllium ug/L 0.5 BQL BQL BQL BQL BQL BQ BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQLCalcium mg/L 0.1 97 94 95 120 110 120 150 90Chloride mg/b 0.2 100 100 100 94 95 91 120 69Chromium ug/L 1 2.8 1.7 1.9 1.3 BQL 6.1 2.2Copper mg/b 0.02 BQL BQL BQL 0.024 BQL BQL BQ BQLFluoride mg/b 0.1 0.4 0.4 0.4 0.5 0.5 0.7 0.3 0.4DCPP Water Resources ReportPae2Page 26 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 7. Comnarisnn nf Well #4. Well #.5 and Well #2 (ennt'd.AWell #2 Well #2 Well #2 Well #2 Well #2 Well #2 Well #4 Well #5Composite 1 Composite 2 Composite 3Analyte Units PQL (Surface) (Surface) (Surface)11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 11/8/07 11/10/07______________15:40 15:50 16:05______ ____Iron mg/L 0.1 0.71 0.12 22 BQL BQL BQL 0.13 0.11Lead ug/L 0.5 1.5 0.63 0.62 BQL BQL 0.65 BQLMagnesium mg/b 0.1 61 60 60 70 68 69 91 57Manganese mg/b 0.005 0.041 0.017 0.018 0.028 0.026 0.02 0.015 0.021Mercury ug/L 0.5 BQL BQL BQL BQL BQL BQ BQLNickel ug/b 1 9.5 8.2 8.5 7.8 BQL 1.5 2.6Potassium mg/b 0.2 2.7 2.7 2.7 2.9 2.8 3.1 8.2 2.3Selenium ug/b 1 2.7 2.1 2.4 3.2 BLQL15Silica mg/L 20 20 19 _ ___ ____ 27 20 25Silver ugiL 0.5 BQL BQL BQL BQL BQL BQ BQLSodium mg/b 0.5 70 69 68 53 50 63 83 51Sulfate mg/b 0.5 140 150 150 160 170 150 210 87Thallium ug/L 0.5 BQL BQL BQL BQL BQ BQ BQLZinc mg/b 0.05 0.15 0.11 0.11 0.43 0.32 0.32 0.2 0.34DCPP Water Resources Report Page 27DCPP Water Resources ReportPage 27 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2.2 Well #2 -Water Quality vs. DepthThree pairs of depth-specific and composite water quality samples were collected at Well#2 during the velocity logging of the well conducted on November 15, 2007. Thesediscrete depth samples provide an opportunity to evaluate water quality from specificdepths within the aquifer and to determine whether changes in pumping practices and/orchanges to well construction parameters may be appropriate for improving the quality ofthe pumped water.Water quality samples were collected at 158 ft bgs, 190 ft bgs, and 275 ft bgs. The pumpwas set at a depth of 160 ft bgs during this test. Because the pump set depth influencesflow direction within the well, this is an important consideration for assessing therepresentativeness of depth-specific water quality samples. Given the direction of flowwithin the well, the water quality sample collected at 158 feet represents water from the100-158 foot interval (which represents approximately 26% of the flow into the well); thesample collected at 190 feet represents water from the 190-275 foot interval (whichproduces approximately 66% of the flow into the well); and water collected at 275 ft bgsrepresents the deepest zone in the well from 275-350 ft bgs (which representsapproximately 3% of the flow in the well).Based upon these data (Table 8), the shallow productive zone (from 100-158 feet bgs) hassubstantially higher turbidity and higher concentrations of silica, total dissolved solids,nickel, aluminum and iron than the deeper productive zone (190-275 ft bgs). Figures 12aand 12b below illustrate these values. Arsenic and bicarbonate concentrations are slightlylower in the shallow productive zone as compared to the deeper productive zone. Forother constituents sampled, concentrations do not differ significantly between these twoproduction zones.Considering these water quality differences between the uppermost zone and the lowerzones, economic analysis may be needed to determine the costs and benefits of specificwell construction modifications to isolate zones. If in the future one or more of theseconstituents adversely affects the water treatment operations, well modificationapproaches can be considered. First, a temporary packer could be installed to prevent theshallowest zone of poor water quality groundwater from entering the well. This device isan elongated, thick-rubber balloon that is attached to a section of column pipe and can beinflated or deflated using an air value at the wellhead. Materials and installation for thisdevice would cost approximately $10,000. Second, the well screen adjacent to theshallowest zone of poor water quality groundwater could be permanently sealed withcement. This is a more complex operation than installation of the packer but is stillviable. This approach has a similar cost to the packer option, but has an advantage ofbeing a permanent solution, whereas the packer may need to be rehabilitated or replacedevery 5 to 10 years.DCPPWate Reourcs ReortPage 28 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008In both cases, the well's produced water quality would improve and its drawdown wouldincrease to maintain the target flow rate of 150 gpm. Because the pump operates at afixed rate, the well would operate at a flow rate approximately 10-20 gpm less and from apumping water level of approximately 5 to 10 feet deeper.Well 2 -Concentration vs. Depth100120140'" 160180G'2005220240260280300Conce ntrationFigure 1 3a. Constituent concentrations as a function of depth at Well #2.DCPP Water Resources Report Page 29DCPP Water Resources ReportPage 29 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well 2 -Concentration vs. Depth100120140'~160.01804-* 200.=2200.240 -*--- Alkalinity (CaCO3)260 Bicarbonate (CaCt-0-Alurninum (ugi)260 -Chloride (rngl)3000 100 200 300 400 500 600 700 800 900 1000ConcentrationFigure 1 3b. Constituent concentrations as a function of depth at Well #2.DCPP Water Resources Report Page 30DCPP Water Resources ReportPage 30 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Tahle 8. Well #~2 Denth-Sneeifie Water Ouialitv Cornposite 1 Discrete 1 Composite 2 Discrete 2 Composite 3 Discrete 3(Surface) (275 Ft.) (Surface) (190 Ft.) (Surface) (158 Ft.)nayeUis PL 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07________________15:40 _______ 15:50 16:05Depth (or Pumping Water Level) _____275 190 158-pH S.U. -6.6 6.9 6.7 6.8 6.7 6.7Color Color Unit S <5 <5 <5 <5 <5 <5MBAS Surfactants mg/L 0.1 BQL BQL BQL BQL BQL BQLOdor T.O.N. 1 ND ND ND ND ND NDSpec. Conductivity umhos/cm 1 1300 1420 1300 1340 1290 1300T.D.S. mg/L 10 790 860 790 800 790 810Turbidity N.T.U. 0.1 4.5 4.7 0.69 3.6 1.4 7Alkalinity (CaCO3) mg/L 10 410 440 400 420 410 400Bicarbonate(CaCO3) mg/L 10 410 440 400 420 410 400Carbonate (CaCO3) mg/b 10 BQL BQL BQL BQL BQL BQLHardness (as CaCO3) mg/L 10 520 530 510 520 520 530Hydroxide (as CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQLAluminum ug/L 5 170 240 46 110 100 300Antimony ug!L I BQL BQL BQL BQL BQL BQLArsenic ug/L 0.5 2.2 4 1.8 2.5 2 1.4Barium ug/L 0.5 30 26 27 27 28 35Beryllium ug/L 0.5 BQL BQL BQL BQL BQL BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQLCalcium mg/L 0.1 97 95 94 96 95 100Chloride mg/L 0.2 100 120 100 110 100 110Chromium ug/L 1 2.8 6.4 1.7 4.3 1.9 4.3Copper mg/b 0.02 BQL 0.037 BQL BQL BQL BQLFluoride mg/b 0.1 0.4 0.5 0.4 0.4 0.4 0.5DCPP Water Resources Report Page 31DCPP Water Resources ReportPage 31 TbeNT.RWel #2 Det-SEvionentalc anWaturQalit Resource MangemntCnsltntTable 8. Well #2 Depth-Specific Water Quality Results (cont'd.)Well 2 Well 2 Well 2 Well 2 Well 2 Well 2Composite 1 Discrete 1 Composite 2 Discrete 2 Composite 3 Discrete 3Analyte Units PQL (Surface) (275 Ft.) (Surface) (190 Ft.) (Surface) (158 Ft.)11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07_______________15:40 15:50 ______ 16:05Depth (or Pumping Water Level) _____________ 275 190 158Iron mgiL 0.1 0.71 0.73 0.12 0.43 22 62Lead ug/L 0.5 1.5 0.78 0.63 0.99 0.62 1Magnesium mg/L 0.1 61 64 60 62 60 69Manganese mg/L 0.005 0.041 0.056 0.017 0.03 0.018 0.0087Mercury ug/L 0.5 BQL BQL BQL BQL BQL BQLNickel ug/L 1 9.5 16 8.2 8.9 8.5 11Potassium mg/L 0.2 2.7 3.2 2.7 3.1 2.7 2.1Selenium ug/L 1 2.7 3.2 2.1 2.2 2.4 6Silica mg/L ___ 20 22 19 20 19 24Silver ug/L 0.5 BQL BQL BQL BQL BQL BQLSodium mg/b 0.5 70 100 69 80 68 59Sulfate mg/L 0.5 140 150 150 150 150 160Thallium ug/L 0.5 BQL BQL BQL BQL BQL BQLZinc mg/L 0.05 0.15 0.07 0.11 0.069 0.11 0.099Total Sulfide mg/L __Ammonia (as N) mg/b 0.1 _____Nitrate (as N) mg/L 0.1 0.2 BQL 0.2 BQL 0.2 0.9Nitrate (as NO3) mg/b 1_________________________________________o-Phosphate-P mg/b 0.05 _______T.K.N. mg/b 1 _________DCPP Water Resources Report Page 32DCPP Water Resources ReportPage32 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2.3 Comparison of Surface Water and GroundwaterCornpositionA significant aspect of this study is to determine if a connection exists betweengroundwater from the existing DCPP production well and surface water in Diablo Creek.In addition to reviewing water level data during the pumping tests in an effort to detecttrends that might indicate a significant connectivity between the extracted groundwaterand the Creek, water quality data were reviewed to assess if any connectivity existsbetween the surface water and the shallow groundwater production zone.Two methods are used to review the water quality data that were collected from Well #2and the creek. The first is the comparison of paired water quality samples collected at thepumping well and at the creek on December 3, 2007, December 6, 2007 and June 30,2008 (Table 9). For these sampling dates which occurred during the constant ratepumping tests at Well #2, samples were collected contemporaneously, so as to provide aninstantaneous snapshot of water quality at both locations for comparison purposes.The second method used to examine the water quality data for trends that indicate thedegree of connectivity between extracted groundwater at Well #2 and the Creek was tocompare the depth-specific water quality samples collected at Well #2 with water qualitysamples collected at the Upper Creek sampling site (Figure 14a and Figure 14b, below).If there is a significant degree of connectivity between water in the upper productive zoneof Well #2 and surface water, it would be expected that the shallowest water qualitysample collected from the well could have a geochemical composition similar to that ofthe surface water sample for a number of constituents (or more similar to the surface waterthan that of the deeper groundwater).The most definitive result of this water quality comparison is the considerable variation inseveral key constituents, such as TDS, Chloride, Sodium, Iron, which are all substantiallylower in concentration in the creek water than in groundwater. The difference is evidentin comparison to both the various composite well samples as well as the depth-specificsamples. The water quality difference evident in these constituents, most of which aregenerally considered "conservative" (i.e., they do not tend to vary with time or reactionsin the subsurface), is diagnostic of largely if not entirely different water source. As oneline of evidence, these data indicate limited, if any, connection between the groundwaterpumping at Well #2 and creek flows.Also, the presence of bacteria (Total Coliform and E Coli) in the creek water and itsabsence in well #2 water (although the Total Coliform results from the December 6, 2007well sample was "present" but this could be a contaminated sample and thereforeanomalous), is additional corroboration that groundwater pumping at Well #2 is notdirectly extracting water from the creek.DCPP Water Resources Report Page 33DCPP Water Resources ReportPage 33 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 9. Water Quality in Diablo Creek Compared to Groundwater ___Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Upper Upper CulvertWeir WeirDiscrete 1 Composite Discrete 2 Discrete 3Analyte Units PQL Composite 1 (7Ft) 2(9F.) Composite 3 (158 Ft.)11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 12/3/07 12/6/07 6/30/0815:40 15:50 16:05pH S.U. -6.6 6.9 6.7 6.8 6.7 6.7 6.9 6.5 7.3 8.2 7.9 8.2Color Color Unit 5 <5 <5 <5 <5 <5 <5 <5 <5 <5 10 10 30Spec. Conductivity umhos/cm 1 1300 1420 1300 1340 1290 1300 1280 1270 1200 870 870 860T.D.S. mgfL 10 790 860 790 800 790 810 760 780 810 530 540 540Turbidity N.T.U, 0.1 4.5 4.7 0.69 3,6 1.4 7 0.39 0.4 0.1 2.1 2 9.5Alkalinity (CaCO3) mg/L 1 0 410 440 400 420 410 400 390 390 400 350 340 370Bicarbonate(CaCO3) mg/L 10 410 440 400 420 410 400 390 390 400 350 340 360Carbonate (CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL 10Hardness (as mg/L 10 520 530 510 520 520 530 580 560 BQL 430 430 420CaCO3)Hydroxide (as mg/'L 10 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLCaCO3) ____Aluminum ug/L 5 170 240 46 110 100 300 5.8 BQL 63 0.25Arsenic ug/L 0.5 2.2 4 1.8 2.5 2 1.4 0.66 BQL 2.1 BQLBarium ug/L 0.5 30 26 27 27 28 35 38 BQL 57 BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL 0.61 0.001Calcium mg/L 0.1 97 95 94 96 95 100 120 110 120 99 89 90Chloride mg/L 0.2 100 120 1 00 110 100 110 94 95 91 33 33 33Chromium ug/L 1 2.8 6.4 1,7 4.3 1.9 4.3 1.3 BQL 1.7 BQLCopper mg/L 0.02 BQL 0.037 BQL BQL BQL BQL 0.024 BQL BQL BQL BQL BQLFluoride mg/L 0.1 0.4 0.5 0.4 0.4 0.4 0.5 0.5 0.5 0.7 0.3 0.3 0.4Iron mg/L 0.1 0.71 0.73 0.12 0,43 0.22 0.62 BQL BQL BQL BQL 0.00011 0.27Lead ug/L 0.5 1.5 0.78 0.63 0.99 0.62 1 BQL BQL BQL BQLMagnesium mg/L 0.1 61 64 60 62 60 69 70 68 69 54 50 47Manganese mg/L 0.005 0.041 0.056 0.017 0.03 0.018 0.0087 0.028 0.026 0.02 BQL BQL BQLDCPP Water Resources ReportPage 34 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 9. Water Quality in Diablo Creek Compared to Groundwater (cont'd.)Nickel ug/L 1 9.5 16 8.2 8.9 8.5 11 7.8 BQL 11 0.01Potassium mg/L 0.2 2.7 3.2 2.7 3.1 2.7 2.1 2.9 2.8 3.1 2.9 2.6 2.5Selenium ug/L 1 2.7 3.2 2.1 2.2 2.4 6 3.2 BQL 1.2 BQLSilica mgIL 20 22 19 20 19 24 24 23 27 31l 29 33Silver ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLSodium mg/L 0.5 70 100 69 80 68 59 53 50 63 22 19 23Sulfate mg/L 0.5 140 150 150 150 150 160 160 170 150 88 89 82Thallium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLZinc mg/L. 0.05 0.15 0.07 0.11 0.069 0.11 0.099 0.43 0.32 0.32 0.13 0.065 BQLNitrate (as N) mg/IL 0.1 0.2 BQL 0.2 BQL 0.2 0.9 0.3 0.5 0.1 BQL BQL BQLE. Coli _____ absent absent present presentTotal Coliform present absent present presentDCPP Water Resources Report Page 35DCPP Water Resources ReportPage 35 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsMay 23, 2008Well 2 -Depth-Specific Samples and Creek Samples-101540I6590115140165190215240265;290ConcentrationFigure 1 4a. Constituent concentrations as a function of depth at Well #2 and Diablo Creek.Well 2 -Depth-Specific Samples and Creek Samples--Alkalinity (CaC;O3) (mgl)140 -NE Bicarbonate (CaCO3) (nrigl)--Aluminum (ugi)165 -a-Chloride (ngl)(6 -Creek-TDS215 A Creek-Alkalinity:: Creek-Bicarbonate* Creek-Alurrinum265 A Creek -Chloride*Cr'ee k-k-on0 100o 200 300 400 500 600 700 800 900 1000Conce ntra tionFigure 14b. Constituent concentrations as a function of depth at Well #2 and Diablo Creek.DCPP Water Resources Report Page 36DCPP Water Resources ReportPage 36 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsMay 23, 20084.2.4 Summary of Water Quality ResultsDepth-specific water quality testing indicates that the water extracted from the deepproduction zone is higher quality (i.e., generally lower in constituent concentrationsimportant to plant operations) than water extracted from the shallow production zone. Inorder to reduce concentrations of certain constituents in extracted groundwater, such assilica, the upper screened portion of Well #2 could be temporarily or permanently sealed.Doing so would improve the quality of pumped groundwater from Well #2. However,this upper productive zone represents approximately 20% of the flow in the well and ifthis portion of the well is sealed, DCPP can expect a 10-20 gpm reduction in groundwaterproduction.The presence of a series of diagnostic constituents with significantly differentconcentrations in Diablo Creek compared with Well #2 groundwater represents a strongline of evidence that groundwater pumping does not draw from Diablo creek.DCPP Water Resources Report Page 37DCPP Water Resources ReportPage 37}} | |||
Revision as of 22:22, 28 May 2018
| ML16050A291 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/22/2008 |
| From: | Thompson T Entrix |
| To: | Squyres D Office of Nuclear Reactor Regulation, Pacific Gas & Electric Co |
| Shared Package | |
| ML16048A230 | List:
|
| References | |
| DCL-15-142, CAC MF4019, CAC MF4020 | |
| Download: ML16050A291 (49) | |
Text
C)I0N)
Environmental and Natural Resource Management Consultantsvia emailAugust 22, 2008Mr. Drew SquyresSenior Project ManagerPacific Gas and Electric Company, Environmental Services4325 South Higuera StreetSan Luis Obispo, CA 93401RE: Pacific Gas & Electric (PG&E) Company, Diablo Canyon Power Plant(DCPP) Water Resources Evaluation: Well Installation and Aquifer Testing
Dear Drew:
Please find enclosed the revised Water Resources Evaluation Phase II report forDiablo Canyon Power Plant. We are providing this to you in accordance withPG&E Contract #46000 16684 and Contract Work Authorization #35007983 13.This draft includes results from additional aquifer testing conducted in June, 2008which improve and expand upon the assessment of any connectivity betweengroundwater pumping and flows within Diablo Creek.We have enjoyed working with you on the important project, and look forward toproviding additional support in the future.Sincerely,Timothy ThompsonVice President -Water Resource Sciencescc: Mr. Mark Coleman, Diablo Canyon Power PlantMr. John Giambastiani, ENTRIX, Concord DIABLO CANYON POWER PLANTWATER RESOURCES EVALUATIONPHASE II REPORT:WELL REHABILITATION,MONITORING WELL INSTALLATION,AND AQUIFER TESTINGPrepared by:Environmental and Natural Resource Management consultantsAugust 22, 2008 ENTRIX, Inc, -Environmental and Natural Resource Management ConsultantsAugust 22, 2008TABLE OF CONTENTSEXECUTIVE SUMMARY ........................................................................................ 11. INTRODUCTION ............................................................................................... 11.1 BACKGROUND......................................................................................................... 11.2 HYDROGEOLOGY .................................................................................................... 21.3 WELL SITE SELECTION.............................................................................................. 32. MONITORING WELL INSTALLATION (WELL #4 AND WELL #5) ................................ 12.1 DRILLER AND DRILLING METHODS................................................................................ 12.2 WELL #4........................................................................................................ 22.2.1 Site Description ........................................................................................ 22.2.2 Well Construction ...................................................................................... 22.2.3 Well Logging............................................................................................ 22.2.4 Well Development and Testing .................................................................... 32.3 WELL#5 .............................................................................................................. 62.3.1 Site Description ........................................................................................ 62.3.2 Well Construction ...................................................................................... 62.3.3 Well Logging............................................................................................ 62.3.4 Well Development and Testing........................................................................ 83. WELL #2 REHABILITATION AND TESTING .......................................................... 113.1 WELL REHABILITATION....................................................................... :.................... 113.1.1 Results of Pump, Motor, and Column Pipe Inspection............................................. 113.1.2 Video Log Results .................................................................:.................... 113.1.3 Description of Well Rehabilitation Tasks Performed .............................................. 113.2 SPINNER TEST........................................................................................................ 123.3 PUMP TESTS FOR EVALUATING WELL YIELD................................................................... 133.3.1 Step Drawdown Test.................................................................................. 133.3.2 Constant Rate Tests................................................................................... 153.5 PUMP SPECIFICATIONS............................................................................................. 164. AQUIFER RESPONSE TO PUMPING TEST......................................................... 174.1 MONITORING LOCATIONS ......................................................................... 2............ 174.1.1 2007 Constant Rate Pumping Test............................................................... 174.1.2 2008 Constant Rate Pumping Test............................................................... 174.1.3 Effect of Constant Rate Pumping Test at Monitoring Wells ................................... 184.1.4 Effect of Constant Rate Pumping Test at Surface Water Monitoring Locations.....'......... 194.2 WATER QUALITY ................................................................................................... 244.2.1 Relative Water Quality of Wells #2, #4 and #5...................................................... 244.2.2 Well #2 -Water Quality vs. Depth.................................................................... 284.2.3 Comparison of Suiface Water and Groundwater Composition .................................... 334.2.4 Summary of Water Quality Results................................................................... 375. SUMMARY AND CONCLUSIONS......................................................................... 385.1 WELL #2 REHABILITATION ....................................................................................... 385.2 EFFECTS OF GROUNDWATER PUMPING ON DIABLO CREEK .................................................. 385.3 RECOMMENDATIONS FOR GROUNDWATER USE............................................................... 385.3.1 Well #2 Construction, Operations and Maintenance............................................... 385.3.2 Monitoring Wells .................................................................................. 395.4 MONITORING PROGRAM RECOMMENDATIONS ................................................................. 39DCPP Water Resources Report Page TOC- 1 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008FIGURESFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.Figure 7.Figure 8.Figure 9.Figure 10.Figure 11.Figure 12a.Figure 12b.Figure 13a.Figure 13b.Figure 14a.Figure 14b.Table 1.Table 2.Table 3.Table 4.Table 5.Table 6.Table 7.Table 8.Table 9.Map of project site showing location of wells.Photograph of Well #4.Schematic diagram showing Well #4 construction and lithology.Drawdown at Well #4 during development and testing.Photograph of Well #5.Schematic diagram showing Well #5 construction and lithology.Drawdown at Well #5 during development and testing.Graph of Step Drawdown Test at Well #2.Water levels at Well #2 during the constant rate pumping test.Water levels in DCPP Wells during November 2007 constant ratetest.Water levels in DCPP Wells during June 2008 constant rate test)Water levels at Pumping Well and Diablo Creek Locations (June/July 2008Pump Test).Water levels at pumping well and Diablo Creek locations focused ontime period of test.Constituent concentrations as a function of depth at Well #2.Constituent concentrations as a function of depth at Well #2.Constituent concentrations as a function of depth at Well #2 andDiablo Creek.Constituent concentrations as a function of depth at Well #2 andDiablo Creek.TABLESDCPP Well Locations.Construction Parameters for Well #4 and Well #5.Development of Well #4 (November 8, 2007).Development of Well #5 (November 10, 2007).Well #2 Spinner Log Analysis.DCPP Well #2 -Step Rate Test.Comparison of Well #4, Well #5 and Well #2 Composite Samples.Well #2 Depth-Specific Water Quality Results.Water quality in Diablo Creek compared to groundwater.DCPP Water Resources Report Page TOC-2DCPP Water Resources ReportPage TOC-2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Attachment A:Attachment B:Attachment C:Attachment D:Attachment E:ATTACHMENTSWell 4 DocumentationWell 5 DocumentationWell 2 DocumentationWater Quality Data TablesDCPP Water Resources Monitoring PlanDCPP Water Resources Report Page TOC-3DCPP Water Resources ReportPage TOC-3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Executive SummaryThe PG&E Diablo Canyon Power Plant ("DCPP") has historically utilized threeindependent water supplies for plant water needs, listed in order of volumetric priority:(a) seawater, treated by a large reverse osmosis system ("SWRO"), (b) diversions fromDiablo Creek, and (c) groundwater produced by a single on-site well ("Well #2"). As aresult of a directive by the California Coastal Commission, diversions from Diablo Creekwill be ceased. This change in supply options increases the dependence upongroundwater and therefore generates a need for the groundwater to be both more reliableand pumped at a slightly greater rate than historically. Given this context, the purpose ofthis Water Resources Evaluation is to develop a better understanding of on-sitegroundwater resources in terms of potential yield, water quality and relationship betweengroundwater pumping and flows in Diablo Creek. This work is based in part on a 2007study ("Phase I: Evaluation of Groundwater and Surface Water Data") that was preparedto identify appropriate steps for refurbishing and testing existing groundwater productionfacilities, evaluating groundwater water quality issues, and installing monitoring wells.The Phase II scope-of-services included: (1) installation of two monitoring wells (Well #4and Well #5), (2) evaluation and rehabilitation Of Well #2, (3) aquifer testing at Well #2,and (4) water quality sampling and analysis. The proposed new monitoring wells willprovide valuable information needed for (a) understanding current groundwater basinconditions, (b) assessing future groundwater production potential and water quality at theproposed locations, and (c) comparing groundwater water levels with flow levels inDiablo Creek to demonstrate if any hydraulic connection is apparent.The two monitoring wells, known as Wells #4 and #5, were drilled and completed to 500ft and 400 ft, respectively. The wells were logged, tested and evaluated for water quality.Well #4 was pumped for two hours at a rate of 30 gallons per minute, had 21 ft ofdrawdown and has a potential yield of 80 gallons per minute (gpm) or more. Waterquality at Well #4 was satisfactory, but poorer than the other wells. Well #5 was pumpedfor over two hours at a rate of 49 gallons per minute, had a drawdown of approximately 8ft and has a potential yield of 150 gpm or more. Water quality at Well #5 was better thanthat at Well #2 in many, but not all, respects.The pre-existing and historically productive Well #2 was rehabilitated, including cleaningof the casing, and replacement of the pump, motor, column pipe and surface controls. Thewell was tested and sampled to determine if the well's inflow rates and water qualitydiffered at different depths. Based upon the results of this work, it is evident thatsignificant inflow rates occur at different depths within the well and that the water qualityat these various depths is also different in certain respects. The majority of the well'swater enters in the 190-275 ft zone, and is of reasonably good water quality. A shallowerzone was identified as contributing approximately 20% of the well's flow and containingelevated concentrations of total dissolved solids, chloride, iron and silica.DCPP Water Resources ReportPaeE-Page EC- I ENTRIX, Inc.- Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well #2 was initially tested from November 26 through December 7, 2007, a 10-dayconstant rate pumping test that included monitoring at Well #2, three monitoring wellsand in Diablo Creek. The test was run at 150 gpm which proved to be an acceptable long-term, sustainable pumping rate for the well, even with the preceding years of limitedrainfall and associated lowered water levels. During wetter climatic periods, the well hasa capacity to produce at a greater flow rate.A second constant rate pump test was conducted at Well #2 from June 25 to July 2, 2008to evaluate the relationship between groundwater pumping and creek water levels. Well#2 was pumped at a rate between 150 and 200 gpm for seven days. Changes in waterlevels were monitored in Wells #2 and #5 as well as at two locations in Diablo Creek.Just before the end of the test, water quality samples were collected from Well #2 and thecreek. The data collected do not show a correlative water level response between waterlevels in Diablo Creek and pumping water levels in Well #2. During the course of thepumping test, water levels in the Creek did not exhibit a drawdown or rebound signaturecorresponding to the start and end of the pump test, respectively. If the creek and wellwere connected, measurable changes in the creek water levels would likely occur. Theabsence of these trends supports the conclusion that there is no discernable connectionbetween creek water levels and pumping at Well #2.Water quality comparisons were also conducted to determine if a relationship existsbetween groundwater pumping at Well #2 and flows within Diablo Creek. Concentrationsof several key constituents from samples collected contemporaneously during the multipletests were markedly different indicating distinct water sources.Finally, a water resource monitoring program was initiated to collect and track hydrologicdata in an effort to ensure adequate understanding of this valuable resource is developedand maintained.Recommendations of this work include continuance of the water resources monitoringprogram, evaluating factors associated with future production use of Wells #4 or #5, andevaluate implementation of downhole well modifications to improve water quality in Well#2.DCPP Water Resources ReportPaeE-Page EC-2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20081. IntroductionThis report provides a summary of well rehabilitation, monitoring well installation,aquifer testing, and water quality analyses conducted at the PG&E Diablo Canyon PowerPlant ("DCPP") from October 2007 through July, 2008. The services were conducted aspart of the Phase II and Phase III Water Resources Evaluation scope of work which, inturn, is based upon the June 30, 2007 technical report entitled: "Phase I: Evaluation ofGroundwater and Surface Water Data". The work provides data and recommendations tosupport increased reliability of groundwater production and an evaluation of whether aconnection exists between groundwater pumping from the existing Well #2 and flowsassociated with Diablo Creek. Also included is a section of the report that summarizesrecommendations for groundwater use and facilities management and provides elementsof a long-term groundwater resource monitoring program.This work is part of a larger effort by DCPP staff to increase reliability of available watersupplies, which also includes modifications to the DCPP seawater reverse osmosis("SWRO") treatment plant system. Properly managed and monitored development oflocal groundwater resources can provide a highly reliable water supply that will continueto supplement the SWRO supply. As part of this ongoing groundwater developmentactivity, groundwater monitoring data will be collected to establish a body of informationto better understand the water resources of the area. Appropriate work to follow the taskssummarized in this document includes implementation of a groundwater monitoringprogram to initiate the collection of water related data that will increase the understandingand forecasting of this valuable resource. Additional phases of work may also include theconversion of one or both of the new monitoring wells to production wells dependingupon future determination of DCPP groundwater supply needs.1.1 BackgroundWater supply for DCPP steam generation is currently acquired from three sources: reverseosmosis treatment of seawater ("SWRO"), surface diversions from Diablo Creek, andpumped groundwater. SWRO is the primary water supply source, with the surface waterand groundwater resources used in supporting roles for augmentation during normalSWRO operations or for temporary backup supply during SWRO outages. Because of aregulatory mandate to cease Diablo Creek diversions, groundwater will be elevated in itsrelative importance to meet the water supply needs of DCPP and it is therefore appropriateto increase groundwater production capability and reliability.Given that context, a study was prepared ("Phase I: Evaluation of Groundwater andSurface Water Data") to identify appropriate steps for refurbishing and testing existingDCPP Water Resources Report PgPage 1 ENTRIX, Inc. -Environmental and Natural Resource Management Cons~ultantsAugust 22, 2008groundwater production facilities, evaluating groundwater water quality issues, andinstalling monitoring wells.The monitoring wells were recommended to gain a broader understanding of thegroundwater conditions present at the DCPP site and to develop information on futureproduction well locations. These wells will provide information needed for (a)understanding current groundwater basin conditions, (b) assessing future groundwaterproduction potential and water quality at the proposed locations, and (c) comparinggroundwater water levels with flow levels in Diablo Creek to demonstrate if any hydraulicconnection is apparent. If replacement of the existing Well #2 or augmentation of theexisting DCPP groundwater pumping capacity is needed at a future date, one or both ofthese monitoring wells could be converted to production wells.In order to comply with the aforementioned regulatory mandate to cease Diablo Creekdiversions, increased groundwater production will be needed. The cessation of creekdiversions generates two considerations:1. Increased dependence upon Well #2 to provide all the water needed toaugment the SWRO system; and,2. The technical concept of demonstrating that both existing and futuregroundwater pumping does not extract subsurface water associatedwith Diablo Creek flows.For these considerations, a series of diagnostic aquifer tests were conducted. These testsinvolved pumping at Well #2 at similar rates to historical and planned usage andcontemporaneous water level monitoring at other wells and at locations within DiabloCreek.1.2 HydrogeologyThe primary aquifer established by existing groundwater extractions is the fracturedsandstone (possibly dolomitic) of the lower to middle Miocene-aged Obispo Formation.This unit also contains siltstones and finer grained beds that are less productive than thefractured sandstones. The brittle nature of the sandstones produces discrete fracture setsthat can form a prolific bedrock aquifer. Because the aquifer material in this region isrelatively hard and locally brittle bedrock, essentially all groundwater production will bederived from fractures within the rock, not from the pore spaces between the sand grainsas occurs in an alluvial (i.e., uncemented, unlithified) aquifer.DCPP Water Resources Report PgPage 2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20081.3 Well Site SelectionSite selection in bedrock aquifers is highly dependent upon the existence of fracturedzones that allow groundwater collection and conveyance from upgradient source areas.For the purpose of monitoring well site selection, a local and regional scale fracture studywas conducted, as described in the Phase I report. This study combined with site accessand other considerations resulted in the identification of three (3) favorable drillinglocations, two (2) of which (site "4" and site "5 b") were selected by PG&E staff for themonitoring wells installed as part of this Phase II work. (see Table 1, Figure 1). Site "5b"of the Phase I report will be referenced as site "5" in this report and all future references.As a historical note, Well #3 was drilled contemporaneously with wells 1 and 2, yetbecause of insufficient yield was abandoned before well completion. It is located in thesmall turn-around circle near the current Diablo Creek diversion and pumping facilities*(see Figure 1). The wellhead is no longer visible in the field, and its elevation in Table 1is approximate.Table 1. DCPP Well LocationsNorth East EeainWell No. Descriptive Location Coordinate* Coordinate* lvainfIt mslWell #1 Near Diablo Creek 2277056.86 5711903.64 251.36Well #2 On Deer Trail Rd. 2276517.11 5712241.45 333.3Well #3 On Turnaround near SempSemp ~ ~ 8Well #3 Lower Weir SempSemp-8On Deer Trail Rd. atWell #4 troftwaetnk 2276209.20 5712999.92 452.35Well 115 Near Man Camp area 2276658.80 5712413.70 303.93*Coordinates and Elevations were surveyed by GraniteConstruction staff. Coordinates are consistent with other DCPPsurveying data. Elevations represent the top of the concrete padat each well.DCPP Water Resources Report PgPage 3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008-~ IrTh~r~ ~ FIgure______________________________________ 6 v~AI L~23t~ofl~ w~-~H lt~oi~ M~,pN A C). k -~ C)r),~, 42~ 1CC)t pidIIo (2afl~o~ Vowe, ~3fltUXD~Figure 1. Map of project site showing location of monitoring stations.DCPP Water Resources Report Pg ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082. Monitoring Well Installation (Well #4 and Well #5)The initial task conducted during this phase of the project involved the installation of two(2) monitoring wells. The design and installation approach for the wells included theprovision that each monitoring well could be converted to a production well at a futuredate. Therefore, careful monitoring was conducted during drilling of the monitoring wellsto assess the potential well yield and water quality. Additionally, upon completion of eachwell, a short-term pumping test was conducted to provide an estimate of yield and allowfor collection of a water sample for water quality analysis.Both wells were drilled to relatively deep depths (506 ft and 409 ft, respectively) to allowfor penetration of a significant depth of bedrock, which greatly increases the potential tointersect fracture zones that have regional connectivity and hence increased yield anddrought-period tolerance. Also, deep sanitary seals were installed at the wells to provideincreased assurance that shallow groundwater that could potentially be tributary to DiabloCreek is not captured by the wells. Additional details of well construction are provided inTable 2 and Figures 3 and 6, below.Table 2. Construction Parameters for Well #4 and Well #5.Well Construction Parameter Well #4 Well #5Drilled Depth 506 ft 409 ftBorehole Diameter 10.5 inches 10.5 inchesDirect Air Rotary/Drilling Method Direct Air Rotary Mud RotarySanitary Seal 230 ft 75 ftCasing Size (OD) 5 inch 5 inchCasing Material PVC (Sch. 80) PVC (Sch. 80)Screen Interval 250 -500 ft 100 -400 ftSlot size 0.050 in 0.050 inGravel Pack #8 mesh sand #8 mesh sandInitial Water Level (below ground) 219 ft 40 ftWellhead Elevation (ft MSL) 452.35 ft 303.93 ftGeophysical Logs SP, Resistivity, Sonic SP, Resistivity, Sonic2.1 Driller and Drilling MethodsCascade Drilling of La Habra, CA was contracted to conduct the monitoring wellinstallation based upon previous experience, qualifications, safety record and familiaritywith PG&E projects. Cascade was directed to employ rotary air-hammer drilling methodswhich are appropriate for hard, fractured bedrock aquifer materials as present at the site.Cascade provided a crew of 3, an auxiliary air compressor and other ancillary drillingequipment for the installation of the two (2) monitoring wells. Geophysical well loggingat Wells #4 and #5 was conducted by Welenco of Bakersfield, CA.DCPP Water Resources Report PgPage 1 ENTRIX, Inc. -Environmnental and Natural Resource Management ConsultantsAugust 22, 20082.2 Well#42.2.1 Site DescriptionWell #4 (Figure 2) is located 0.2 miles up Sky View Road from its intersection with DeerRun Road near the Man Camp, and is at the junction of Sky View Road and the water tankroad. This site was selected because it represents a high potential for sufficient flow ratesto provide supplemental water production, it will likely have at most a limited effect onthe existing Well #2, and its effect on Diablo Creek will likely be very limited. It is alsoat a sufficient distance from Well #2 and Diablo Creek to allow monitoring of up-gradientaquifer conditions that can support development of a broader understanding of aquiferwater levels and possible variability in aquifer water quality.2.2.2 Well ConstructionWell #4 was drilled from October 24 to October 26, 2007 to a total depth of 506 ft beneathground surface. Water was first encountered at 245 ft, and stabilized to a static level of219 ft. In consideration of the depth to water, and the interest in ensuring limitedconnectivity to Diablo Creek, the sanitary seal was constructed to 230 ft deep. PerforatedPVC casing was installed from 230-500 ft. By the time the total depth of drilling wasreached, the well was naturally producing approximately 40 gpm, as evidenced by theflow resulting from the air injection employed as part of the air-hammer drilling method.2.2.3 Well LoggingSediments encountered during drilling included abundant clay, shale and siltstone withinterspersed layers of sandstone (see State Well Drillers Report, Attachment A). Evidenceof fracturing increased below 240 feet and correlates with increased water production ofthe well during drilling. This observation is particularly relevant because in fracturedbedrock aquifers, essentially all the groundwater that is available to enter the well will bederived from fractures within the rock, rather than from the pore spaces between the sandgrains. Geophysical logs run in the hole included electrical log (resistivity andspontaneous potential [SP]), gamma, sonic velocity and temperature. These logs illustratethe stratified nature of the formation and an increase in the proportion of sandstone-richbeds in the lower 60 feet of the well. The indications provided by the e-logs are largelycorroborated with the lithologic monitoring conducted by ENTRIX during well drilling.Initial stabilized water levels in the well were measured at 219 ft deep. Confined aquiferconditions are evident based upon this static water level in relation to the 230 ft depth ofthe sanitary seal and top of slotted casing at 250 ft deep.DCPP Water Resources Report PgPage 2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008ioto of Monitoring Well #42.2.4 Well Development and TestingWell #4 was developed for a full day following well construction, including severaliterations of surging and bailing at deep, medial and shallow portions of the well.Development was continued until the produced water was clear. Next, in an effort toestablish potential well yield, Well #4 was pumped for two hours at a rate of 30 gallonsper minute, which results in a drawdown of approximately 21 ft. Based on these data, thespecific capacity of the well is approximately 1.4 gpm/ft of drawdown. Given that thereare at least 200 feet of additional available drawdown, flow rates of 80 gpm are attainableif needed at a future date; although the pumping lift would be substantially greater thanthat needed at either Well #2 or Well #5 for this production rate.As indicated in Table 3 below, by the end of the test, the turbidity in the water was greatlyreduced and the pumping water level had nearly stabilized (Table 3, Figure 4). A waterquality sample was collected at Well #4 at the end of the test, on November 8, 2007.Water quality results are provided below in Section 4.DCPP Water Resources ReportPage 3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008If it is determined in the future that production from this well is needed, we suggestconducting, depth-specific water quality sampling to determine if a portion of the well'sproduced water is of the poorer quality than from other depths. If it is determined that aspecific zone (i.e. the deepest zone, for example) is of particularly poor water quality,changes in well construction parameters may aid in controlling water quality from thiswell, although production rates will likely be reduced. Also, although this well still has alower specific capacity than Well #5, it is sufficiently distant from Well #2 so as to reducethe potential for interfering cones of depression from multiple pumping wells, and isworthy of consideration to meet future production needs.Table 3. Development of Well #4 on November 8, 2007.Elapsed Depth Electrical Trity VolumeTime Time to Conductivity Triiy Pumped_______Water___ (mai) (ft bgcs) (NTU) (gallons)12:49 0 217 _ ____ 012:50 1 221.85 1635 53 I13:10 21 234.44 1488 271 60013:30 41 237.03 1463 10.9 120013:50 61 237.05 1483 0 180014:10 81 237.69 1464 0 240014:30 101 238.05 1465 0.7 300014:50 121 238.3 1478 0 3600Well 4 Development and Testing215220"Z 225*9°2302352400 20 40 60 80 100 120 140Elapsed Time (min)Figure 4. Drawdown at Well #4 during development and testing.DCPP Water Resources Report PgPage 4 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Figure 3. Schematic diagram showing Well #4 construction and lithology.DCPP Water Resources Report PgPage 5 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082.3 Well #52.3.1 Site DescriptionWell #5 (Figure 5) is located in the northeast corner of the Man Camp yard. Based uponthe structural geologic work conducted in the Phase I study, this site is located southeastof a throughgoing N75°E structure which may represent a hydrologic barrier, andtherefore the well likely encountered favorable aquifer materials with groundwaterproduction characteristics similar to Well #2. Also, because this monitoring well isrelatively close to Well #2, drawdown during the Well #2 pumping will be evident andthereby helpful in the aquifer analysis efforts.2.3.2 Well ConstructionWell #5 was drilled from October 28 to November 2, 2007 to a total depth of 409 ftbeneath ground surface. Unstable downhole conditions between 50 and 250 ft requiredconversion from air rotary drilling methods to bentonite mud-based drilling methods.Using drilling mud is a common solution to bedrock wells having unstable sections thatwon't stay open with the viscosity of water only. Water was first encountered at 45 fi, andstabilized to a static level of 40 ft. In consideration of the depth to water, and the interestin ensuring limited connectivity to Diablo Creek, the sanitary seal was constructed to 75 ftdeep. Blank PVC casing was installed from 75 to 100 ft; perforated PVC casing wasinstalled from 100-400 ft. By the time the total depth of drilling was reached, the wellwas naturally producing over 100 gpm, as evidenced by the flow resulting from the airinjection employed as part of the air-hammer drilling method.2.3.3 Well LoggingNear surface sediments encountered during drilling of Well #5 included both siltstonewith clay and/or sandy components as present at Well #4 and also a larger proportion ofpoorly-lithified sandstone beds (see State Well Drillers Report, Attachment B). Overall,the sediments in the upper 100 ft+ in this well were poorly consolidated which resulted inunstable hole conditions as mentioned above. Evidence of fracturing was present fromapproximately 50 feet and throughout the depth of the hole, and likely corresponds withthe structural geologic evidence from analysis of aerial photographs that this site is withina northeast-trending fracture system.DCPP Water Resources Report Page 6DCPP Water Resources ReportPage 6 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008gure 5. Photograph of Well #5.Geophysical logs run in the hole included electrical log (resistivity and spontaneouspotential), gamma, sonic velocity and temperature. Collectively, these logs illustrate thestratified nature of the formation and an increase in the proportion of sandstone-rich bedsin the upper and lower portions of the well. The indications provided by the e-logs arelargely corroborated with the lithologic monitoring conducted by ENTRIX during welldrilling.Initial stabilized water levels in the well were measured at approximately 80 ft deep.Confined aquifer conditions are evident based upon this static water level in relation to the250 ft depth to the top of slotted casing.DCPP Water Resources Report PgPage 7 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082.3.4 Well Development and TestingWell #5 was developed for 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> following well construction, including severaliterations of surging and bailing at deep, medial and shallow portions of the well.Development was continued until the produced water was clear. Next, in an effort toestablish potential well yield, Well #5 was pumped for over two hours at a rate of 49gallons per minute, which resulted in a drawdown of approximately 9 ft (Figure 7). Basedon these data, the specific capacity of the well is approximately 5.9 gpm/ft of drawdown,which represents a higher specific capacity than that measured at Well #4. Based uponthis, albeit limited, production test, this well likely has a production capacity equal to orgreater than that of Well #2. Given that there are at least 300 feet of additional availabledrawdown, flow rates of 150 gpm may be possible if needed at a future date. Note thatthe initial recovery of the well's water level is illustrated in the graph to show the rapidwater level response when pumping stopped.For the second half of the test, the measured turbidity in the water was "0" (see Table 4)indicating that the well development was successful to remove turbid material from boththe drilling process and from the use of drilling mud.A water quality sample was also collected at Well #5 on November 10, 2007. Waterquality results are provided in Section 4 below.Based on this pumping test and water quality data, Well #5 has a higher specific capacityand better water quality than Well #4, and represents a more viable alternative if at afuture date conversion to a production well is needed. However, because Well #5 islocated near the existing Well #2, and approximately 9 feet of drawdown was observed atWell #5 during the pump test of Well #2, consideration and planning of the combineddrawdown effects is needed to adequately forecast the combined yield of the two wellsoperating together.DCPPWate Reourcs ReortPage 8 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Figure 6. Schematic diagram showing Well #5 construction and lithology.DCPP Water Resources Report Page 9DCPP Water Resources Report ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 4. Development of Well #5 (November 10, 2007).Easd Depth Electrical Triiy VlmTime Time to Conductivity Triiy Pumped_______Water(mini) (ft bgs) (NTU) (gallons)7:25 80_____7:30 0 80 ____7:50 20 85.3 1020 3.31 10008:10 40 86.35 962 1.65 20008:30 60 87.12 948 1.3 30008:50 80 88.31 943 1.2 40009:10 100 88.4 941 0 50009:30 120 88.41 935 0 60009:52 142 83.55 930 0 7000Well 5 Development and TestingI-79808182838485868788890 20 40 60 80 100 120 140 160Elapsed Time (min)Figure 7. Drawdown at Well #5 during development2007.and testing on November 10,DCPP Water Resources ReportPae1Page 10 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083. Well #2 Rehabilitation and Testing3.1 Well RehabilitationWell #2 was rehabilitated to provide a series of benefits such as increased reliability,potential for increased yield, and increased operating efficiency of the well. Withcessation of Diablo Creek diversions, the increased dependence upon groundwater can besupported by ensuring Well #2 is mechanically and physically sound.Well #2 was originally installed in 1985 to a total depth of 350 feet by Floyd V. Wells, Incof Santa Maria, California. The 10-inch diameter Schedule 200 PVC casing is perforatedfrom 90 ft bgs to total depth, with 0.040 full-flow horizontal-slot well screen.3.1.1 Results of Pump, Motor, and Column Pipe InspectionThe existing pump and motor on Well #2 were removed by Fisher Pump of Santa Maria,CA, under contract to Woodward Drilling Co. of Rio Vista, CA. The motor, pump andpump column although marginally operational all exhibited signs of wear and debilitationtypical of 20-year old equipment. It was determined that replacement of thesecomponents was in the best interest of DCPP and a greater reliability of the groundwatersupply produced by this facility.3.1.2 Video Log ResultsFollowing pump removal, a video logging tool was used to visually inspect the downholeconditions of Well #2. This video file provided evidence of the presence of encrustationof the well casing, mainly below 238 ft, and the existence of an approximately 20 ft thickpile of debris at the bottom of the well (Attachment C). Using these data, wellrehabilitation was recommended to include swabbing, brushing, air jetting and bailing.3.1.3 Description of Well Rehabilitation Tasks PerformedBased upon results of the video investigation, described above, the following steps wereperformed:* Bail out most of accumulated sediment from bottom of well.* Brush well with plastic-bristle brush to remove major areas of encrustation.* Additional sediment removed by bailing followed by air lifting.* Swab well with dispersant and detergent to clean casing encrustation andre-open clogged perforations.* Re-develop well with swab tool and conduct additional air lifting toremove all dispersant and suspended material.DCPP Water Resources ReportPage 11 ENTRIX, Inc.- Environmental and Natural Resource Management ConsultantsAugust 22, 20083.2 Spinner TestUpon completion of well rehabilitation work, velocity logging of the well was conductedby Pacific Surveys of Claremont, CA to determine the depth-distribution of groundwaterinflow into the well. This involves lowering a flow-metering logging tool into the welland pulling it up past the productive zones during active pumping. The relative inflowrates at the various depths of the well are evident from this effort and can provide valuableinformation if certain zones exhibit dominant flow rates and/or associated water qualityissues. The actual logs provided by the contractor are included as Attachment C.For the spinner test, the well was pumped at a rate of 90 gpm for 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> prior to andduring the survey. During the test; the pumping water level was 149 ft bgs. The results ofthe velocity logging, summarized in Table 5, indicate that there are two primaryproductive zones that produce over 90% of the flow into the well. The top loggedinterval, from the top of the perforations at 100 ft bgs to 158 ft bgs, producesapproximately 30% of the flow. This zone is underlain by an approximately 30-foot thicklow productivity zone. The most productive zone is located from 190-275 ft bgs.Water quality samples were collected at 158 ft bgs, 190 ft bgs, and 275 ft bgs. The pumpwas set at a depth of 160 ft bgs during this test, which is a fundamental considerationbecause the pump set-depth influences flow direction within the well, and this is animportant consideration for assessing the representativeness of depth-specific waterquality samples. Given the direction of flow within the well, the water quality samplecollected at 158 feet represents water from the 100-158 foot interval; the sample collectedat 190 feet represents water from the 190-275 foot flow zone; and water collected at 275 ftbgs represents the lowest flow zone sampled (275-3 50). Discussion of the water qualitysample analytical results is provided in section 4 below.Table 5. Well #2 Spinner Log Analysis[Flow Rate = 90 gpm1Zone Depths Production % of Flow Zones gpm/ft Thickness(ft bgs) (gpm) (t100-158 20 26% 0.34 58158-190 4 4% 0.13 32190-275 63 67% 0.74 85275-350 3 3% 0.04 75DCPP Water Resources ReportPae1Page 12 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083.3 Pump Tests for Evaluating Well YieldA series of diagnostic pumping tests were conducted to evaluate the Well #2 yield, as wellas its water quality. Results for these tests were used to establish the well's sustainableyield, specify a new submersible well pump and motor, evaluate if groundwater pumpingeffects flows in Diablo Creek, and assess groundwater water quality.A step drawdown test and a constant rate test were performed at Well #2 betweenNovember 20 and December 6, 2008 using a temporary test pump, installed at a depth of300 ft bgs. For over 4 weeks prior to this test, monitoring of water levels was conductedat Well #1, #2, and at the Diablo Creek facilities. Monitoring data was also collected atthe newly constructed Wells #4 and #5 soon after their respective completion dates.These data provide a trend and variation history of water levels at these various locationswhich is useful to establish the natural variability of these water resources in comparisonwith the stresses imposed by the pumping tests.A final pumping test was run in June and July, 2008 to provide specific data to evaluate ifgroundwater pumping affects water levels in Diablo Creek and also to comparegroundwater water quality between these two water bodies.3.3.1 Step Drawdown TestA step drawdown test was conducted to assess the Well #2 optimal and maximumpotential sustainable yields. This test involved pumping the well at a series of four (4)increasingly higher pumping rates for 60 minutes each. The graph of the drawdown andproduction data was used to determine the well's highest sustainable yield and also todetermine the optimal pumping rate for the multi-day constant rate test.On November 20, 2007, a step-rate test was conducted at the rehabilitated Well #2. Thepump set depth was 300 ft bgs. A total of 36,300 gallons were pumped during the courseof the test. The rates used in the test are provided below in Table 6.A graph of the results of the step drawdown test is provided in Figure 8. Drawdownstabilized during the two lower flow rate portions of the test, but not at the two higherflow rate portions. As is relatively common for wells producing from fracture systems ofa bedrock aquifer, extended time is needed at moderate to high flow rates to achievestabilized pumping water levels.In this well, during the 175 gpm pumping of Step 3, water levels continued to declinefrom 208.2 ft bgs after 5 minutes of pumping to 216 ft bgs after 58 minutes of pumping.It is possible, but not assured that the well could have stabilized its drawdown over alonger duration. Additionally, the well was unable to sustain the 215 gpm pumping ratefor Step 4, which is useful information to understand the upper limit of the well's potentialyield. The well recovered quickly after the pump was shut down. At the end of the step-rate test, the water level in the well was 268 ft bgs. The well achieved 90% recoveryDCPP Water Resources ReportPae1Page 13 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008within 10 minutes after pumping ceased and water levels in the well fully recovered inapproximately four (4) hours. Based upon these data, it was determined that a rate of 150gpm would be sustainable for the duration of the planned constant rate pump test.Table 6. DCPP Well #2 -Step Rate TestPumpingDate Start Time Rate_______ _______ (gpm)Step 1 11/20/2007 10:00 75Step 2 11:00 125Step 3 12:00 175Step 4 13:00 21513:03 21513:05 20513:10 20013:20 19513:40 195______________ 13:55 195Diablo Canyon Power Plant -Well 2 Step Drawdown Test4J00.100120140160180200220240260280300Start of Test:November 20, 2007 10:00 AM120 180 240 300360Elapsed Time (min)Figure 8. Graph of Step Drawdown Test at Well #2.DCPP Water Resources Report Page 14DCPP Water Resources ReportPage 14 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083.3.2 Constant Rate TestsA constant rate pumping test was conducted at Well #2 starting at 14:30 on November 26,2007 and ending at noon on December 6, 2007. The static water level at Well #2 at thestart of the test was 112.7 ft bgs and the water level just before the pump was stopped was238.6 ft bgs. A total of 2,321,000 gallons were pumped during the 10-day constant ratetest at a relatively constant rate of 150 gpm. Based on these data, the specific capacity ofthe well is 1.2 gpm/ft of drawdown.As illustrated in Figure 9, the pumping water level at the well dropped steadily andstabilized at approximately 223 ft bgs by the second day of the test. Two additional,discrete steps in the drawdown occur at approximately 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> and at approximately 214hours. These are related to minor adjustments of the gate valve on the discharge pipe inan effort to re-establish the target pumping rate of 150 gpm. The well achieved 80%recovery within three (3) hours of the end of the constant rate test, and 94% recovery onweek later.Diablo Canyon Power PlantWell 2 Constant Rate Test100120140*} 160a- 180220S2402602803000 24 48 72 96 120 144 168 192 216 240 264 288 312Start of Test: Elapsed Time (hours)November 26, 200? 2:30 PMFigure 9. Water levels at Well #2 during the constant rate pumping test.336 360 384 408DCPP Water Resources ReportPae1Page 15 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008In addition to recording pumping water levels at Well #2, several other wells on theproperty and two surface water monitoring stations on Diablo Creek were monitoredbefore and during the constant rate test. A further discussion of water level monitoringresults at these monitoring stations is provided in Section 4.Water quality sampling was conducted during the test at the middle and just before shut-down. Results are provided and analyzed in Section 5.Collectively, these data indicate the firm reliability of Well #2 to produce 150 gpm on along-term basis under normal operating conditions. Currently, normal well operationsrequire the well to be operated at intervals of several hours per day. With the futuredecommissioning of the Diablo Creek diversion, an increased demand may be establishedon Well #2 for water supply. Based upon the results of these tests, Well #2 could beoperated at its design flow rate of 150 gpm for significantly longer periods per day whilestill maintaining acceptable margins of safety with respect to pumping water levels.Importantly, because of the limited rainfall in the years preceding this test, drought-typeconditions exist and the results of this testing can be considered representative of limitedwater availability conditions. Although not necessarily worst-case conditions, the yield ofthe well and response of the aquifer will not be any worse than that exhibited during thistest except during periods of even more extreme drought conditions. In a multi-yeardrought, if a greater amount of groundwater is needed than is produced from the wellunder its typical operating patterns, the well could be (a) run for more hours per dayand/or (b) retrofitted with a higher capacity pump set at a deeper level. Finally, duringperiods of higher rainfall and therefore more "average" water supply within the aquifer,the yield of the well as currently equipped will likely be greater and the associateddrawdown effects on the aquifer will be less.3.5 Pump SpecificationsUpon inspection, the condition of the pump, motor and column pipe were determined tobe sufficiently degraded to warrant replacement. A replacement pump, motor and columnpipe was specified, as described below. Installation and operability testing of thesecomponents was conducted on April 18, 2008 by Fisher Pump of Santa Maria, CA.Pump: Grundfos Submersible model # 150S 150-7Pump Serial Number: 07L 19-06-6129Motor: 15 hp FranklinMotor Protector: Franklin SubMonitorControl Panel: Siemens, Class 87Column Pipe: 300 ft of 4-inchProbe access tube: 1-inch PVC (300 ft)DCPP Water Resources ReportPae1Page 16 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084. Aquifer Response to Pumping TestThe response of the aquifer to pumping at Well #2 was evaluated using water level datacollected from Wells # 1, #4, and #5 during the constant rate pumping test conducted in2007. In addition, a second constant rate pumping test was conducted from June 25 toJuly 2, 2008 to evaluate the response of water levels in Diablo Creek to pumping waterfrom Well #2. As part of this analysis, groundwater and creek water level data werecollected before, during and after a test with contemporaneous measurements from thepumping well. Data collected during the 2008 pumping test were also compared with datafrom the 2007 pump test to further evaluate the aquifer response to pumping at Well #2.4.1 Monitoring LocationsWater levels at several wells and two surface water monitoring sites on Diablo Creek weremonitored before and during the constant rate tests at Well #2 (Figures 10 and 11). Inaddition, meteorological conditions were noted at the site and were also reviewed asavailable from the nearest gauging station, the Nipomo CIMIS station. The Nipomostation provides comprehensive data, but its inland setting records different climatologicconditions than the coastal conditions at DCPP.4.1.1 2007 Constant Rate Pumping TestDuring the first constant rate test water levels were monitored in Well #1, near DiabloCreek; Well #4, up the hill from Well #2; and Well #5, near the Man Camp. These wellswere outfitted with pressure transducer devices that automatically collected water leveldata at a programmed frequency of one measurement every 30 minutes.Data was also collected at two locations in Diablo Creek during this test. However, DCPPwater diversions from the creek during the pumping test created water level variations thatprevented determination of any relationship between pumping at Well #2 and creek flow.4.1.2 2008 Constant Rate Pumping TestWater levels at wells #1, #2, #4, and #5, and two surface monitoring sites on Diablo Creekwere monitored before and during the 2008 constant rate test. Wells #2 and #5 as well asthe two creek locations were monitored with pressure transducers that automaticallycollect and record water level data at programmed frequencies. Water levels in Well #1and Well #4 were measured manually with a water level meter just prior to the start of thetest and periodically during the pump test. For the duration of the pumping test,diversions from the Lower Weir pond were stopped.Diablo Creek water levels were monitored throughout the test at the Lower Weir andapproximately 1,000 feet downstream of the Lower Weir, before the creek enters aDCPP Water Resources ReportPage 17 ENTRIX, Inc. -Environ men tal and Natural Resource Management ConsultantsAugust 22, 2008drainage culvert. Where the stream enters the drainage culvert a notched wooden plankestablishes a small pool which flows into the drainage culvert.4.1.3 Effect of Constant Rate Pumping Test at Monitoring Wells4.1.3.1 2007 Constant Rate Pump TestWater levels in Monitoring Wells #1 and 4 did not show drawdown effects related topumping at Well #2 during the course of the constant rate pumping test (Figure 10). Thegreatest observed effect was approximately 9 feet of drawdown at Well #5, which is theclosest monitoring well to the pumping well, at a distance of approximately 250 feet.Water levels in Well #4 remained unchanged throughout the test. This is indicative ofboth the source of the Well #2 water being largely from aquifer zones that may not bephysically connected to Well #4, and also because the upgradient position and distance ofWell #4 relative to #2 minimizes the influence of the Well #2 drawdown.Water levels in Well #1 show a slight and very gradual rise that corresponds in timingwith the pumping at Well #2. This is likely related to the discharge point of the pumpedwater which occurred approximately 200 feet southwest of Well #1, and thereforeprobably induced recharge to the shallow, unconfined sediments in which Well #1 iscompleted.4.1.3.2 2008 Constant Rate Pump TestWater levels in Monitoring Wells #1 and #4 dropped from approximately 27.4 ft bgs and223 ft bgs, respectively, just before the test down to 31.8 ft bgs and 232.4 at the end of thetest (Figure 11). During the second constant rate test the discharge point of the pumpedwater was relocated to a point inside a drainage culvert which is downstream of allsampling locations. This a distinct difference in the response of Well #1 water levelsbetween the two constant rate tests.The water level in Well #5 dropped from approximately 80 ft bgs before the test toapproximately 98 feet just before the test was halted. This is greater drawdown ascompared with the 2007 test is a result of the higher Well #2 pumping rate maintainedduring the 2008 test which resulted in approximately :20 ft more drawdown in that well ascompared with the 2007 test.DCPP Water Resources ReportPae1Page 18 ENTRIX, Inc, -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels at Monitoring Wells During Well 2 Constant Rate Test10356085a. 110160185210235-24 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408Start of Test."November 26, 2007 2.30 PMElapsed Time (hours)Figure 10. Water levels in DCPP Wells during November 2007 constant rate test.4.1.4 Effect of Constant Rate Pumping Test at Surface WaterMonitoring LocationsA pumping test was conducted from 13:30 on June 25, 2008 to 13:45 July 2, 2008 toinvestigate any existing relationships betwveen water levels in Diablo Creek and pumpingwater from Well #2.Data were collected in both creek locations using pressure transducers automaticallyprogrammed to collect water level data. Data collection began on April 18, 2008 and wasterminated on July 3, 2008. An overall saw-tooth trend of declining water levels can beseen in the data set, consistent with a baseline-recession trend of a stream in transitionfrom the wet to dry season (Figure 1 2a).DCPP Water Resources ReportPae1Page 19 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008The data collected before the pumping test show correlations between water levels at theLower Weir and the culvert with frequent drops in water levels at the lower weir,presumably resulting from diverting water from the Lower Weir to the holding tanks on-Site. For the duration of the pumping test, diversions from the Lower Weir pond werestopped. The characteristic drop in water levels at the Lower Weir is not present and thewater levels at both creek sampling points follow the same trend (Figure 1 2b).Creek water level variability during the pump test is within the normal range captured inthe dataset. Approximately 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> into the pumping test, a water level drop ofapproximately 0.16 feet occurred. Because fluctuations of this magnitude over similartimescales are present in the non-pumping background data extending back to April 18,2008, this water level change is not related to the groundwater pumping. Additionally,when the pump test was terminated at 13:45 on July 2, 2008, water levels in the creekcontinue in a downward trend for approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> without a significant rebound orchange in water levels compared to levels seen over the duration of the test (Figure 12b).Based upon these test data, there is no evidence that creek water levels are affected bypumping at Well #2.DCPPWate Reourcs ReortPage 20 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels in Nearby Wells During 2008 Well#2 Constant Rate Test300250200S150,,0"10050024 48 72 96 120 144 168Elapsed Time (hours) --Well 2 --Well 5Well 4 -Well 1Figure 11. Water Levels in DCPP wells during June 2008 Constant Rate Test.DCPP Water Resources Report Page 21DCPP Water Resources ReportPage 21 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels at Diablo Creek During Well 2 Constant Rate Test1O00120140S1601802402260-70 60 50 40 30Elapsed Time (Days)Start Time: June 25, 2008 13.302.51.50.5-0.5-1CA0).000-25 15 5 0 5 10-Well 2 -----Well 5Well 2 PreTest Data Lower WeirFigure 12a. Water levels at pumping well and Diablo Creek locations (0 hour0 days <br />0 hours <br />0 weeks <br />0 months <br /> represents Test start on 6/25/08).DCPP Water Resources ReportPae2Page 22 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diabio Canyon Power PlantWater Levels in Diablo Creek during Well #2 Constant Rate Test1001201401802020.2603.52.0"1.51 £0.500-0.5-1-3 1 0 1 2 3 4 5 6 7 8Start Time: June 25, 2008 13:30Elapsed Time (Days)-Well 2 --Lower Weir-CulvertFigure 1 2b. Water levels at pumping well and Diablo Creek locations focused on time period of test (0 hourrepresents Test start on 6/25/08).DCPP Water Resources ReportPae2Page 23 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2 Water QualityWater quality samples were collected at several intervals throughout the study period.Samples were collected at wells #4 and #5 during development and pumping tests.Multiple samples were collected at Well #2, as follows:* Three sets of paired discrete depth-specific and surface (composite)samples were collected during the spinner test;* Four samples were collected during the step test, near the end of eachpumping step;* Two paired samples from Well #2 and Diablo Creek Upper Weir werecollected at the mid-point and at the end of the first constant rate pumpingtest (December 3 and December 6, 2007); and,* Samples were collected at Well #2 and at Diablo Creek Lower Weir duringthe second constant rate pumping test (June 30, 2008).The water quality data were then reviewed to evaluate:* Similarity of the groundwater extracted from Well #2, Well #4 and Well #5to assist in future water resources planning decisions;* Water quality as a function of depth at Well #2; and,* Similarity of surface water and groundwater composition.A comprehensive series of tables listing all water quality data collected in this phase of theproject are provided in Attachment D of this report.4.2.1 Relative Water Quality of Wells #2, #4 and #5In general, constituent concentrations in the water extracted from Well #5 are similar tothose of the water extracted from Well #2 (Table 7). For most constituents,concentrations are lower at Well #5 than at Well #2. Water chemistry of Well #4 differssignificantly from that of Wells #2 and #5 for many of the constituents sampled. Waterfrom Well #4 is harder (it has a higher specific conductivity, and higher concentrations oftotal dissolved solids, alkalinity, bicarbonate, total hardness, calcium, chloride,magnesium, potassium, sodium, and sulfate) than Well #2. Water from Well #5 has alower concentration than Well #2 for all of these constituents.There are a few other notable differences in the water quality signature of the Well #4water. Water from Well #4 was the only groundwater sample that was found to have adetectable odor. Nitrate was detected in all groundwater samples except for the Well #4sample. The concentration of chromium at Well #4 was more than double the nexthighest concentration detected, as found at Well #2.DCPP Water Resources ReportPae2Page 24 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well #2 was the only well with detectable arsenic concentrations and Well #2 also hadsignificantly higher (by a factor of 4) nickel concentrations than Well #4 or #5, althoughboth nickel and arsenic were below detection limits in the samples collected on June 30,2008.Iron and aluminum concentrations are quite variable (by an order of magnitude) from wellto well, and among the various samples collected at Well #2. A more detailed review ofconcentrations of these constituents with regard to aquifer depth is provided in thefollowing section.Well #2 had the highest silica concentration of any of the wells (at 27 mag/I). Well #2 andWell #4 had concentrations ranging from 19-27 mg/I.DCPP Water Resources Report Page 25DCPP Water Resources ReportPage 25 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 7. Comparison of Well #4, Well #5 and Well #2 Composite SamplesWell #2 Well #2 Well #2 Well #2 Well #2 Well #2 Well #4 Well #5Composite 1 Composite 2 Composite 3Analyte Units PQL (Surface) (Surface) (Surface)11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 11/8/07 11/10/07___________15:40 15:50 16:05pH S.U. -6.6 6.7 6.7 6.9 6.5 7.3 6.6 6.9Color Color Unit 5 <5 <5 <5 <5 <5 <5 <5 <5MBAS Surfactants mg/L 0.1 BQL BQL BQL BQL BQL BQL BQL BQLOdor T.O.N. 1 ND ND ND ND ND ND 2 NDSpec. Conductivity umhos/cm 1 1300 1300 1290 1280 1270 1200 1610 1050T.D.S. mg/L 10 790 790 790 760 780 810 1020 640Turbidity N.T.U. 0.1 4.5 0.69 1.4 0.39 0.4 0.1 1.4 1.8Nitrate (as N) mg/L 0.1 0.2 0.2 0.2 0.3 0.5 0.1 BQL 0.2Alkalinity (CaCO3) mg/L 10 410 400 410 390 390 400 520 380Bicarbonate(CaCO3) mg/L 10 410 400 410 390 390 400 520 380Carbonate (CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQLHardness (as CaCO3) mg/L 10 520 510 520 580 560 590 710 440Hydroxide (as CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQLAluminum ug/L 5 170 46 100 5.8 BQL 52 120Antimony ug/L I BQL BQL BQL BQL BQL BQL BQLArsenic ug/L 0.5 2.2 1.8 2 0.66 BQL BQL BQLBarium ug/L 0.5 30 27 28 38 BQL 33 30Beryllium ug/L 0.5 BQL BQL BQL BQL BQL BQ BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQLCalcium mg/L 0.1 97 94 95 120 110 120 150 90Chloride mg/b 0.2 100 100 100 94 95 91 120 69Chromium ug/L 1 2.8 1.7 1.9 1.3 BQL 6.1 2.2Copper mg/b 0.02 BQL BQL BQL 0.024 BQL BQL BQ BQLFluoride mg/b 0.1 0.4 0.4 0.4 0.5 0.5 0.7 0.3 0.4DCPP Water Resources ReportPae2Page 26 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 7. Comnarisnn nf Well #4. Well #.5 and Well #2 (ennt'd.AWell #2 Well #2 Well #2 Well #2 Well #2 Well #2 Well #4 Well #5Composite 1 Composite 2 Composite 3Analyte Units PQL (Surface) (Surface) (Surface)11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 11/8/07 11/10/07______________15:40 15:50 16:05______ ____Iron mg/L 0.1 0.71 0.12 22 BQL BQL BQL 0.13 0.11Lead ug/L 0.5 1.5 0.63 0.62 BQL BQL 0.65 BQLMagnesium mg/b 0.1 61 60 60 70 68 69 91 57Manganese mg/b 0.005 0.041 0.017 0.018 0.028 0.026 0.02 0.015 0.021Mercury ug/L 0.5 BQL BQL BQL BQL BQL BQ BQLNickel ug/b 1 9.5 8.2 8.5 7.8 BQL 1.5 2.6Potassium mg/b 0.2 2.7 2.7 2.7 2.9 2.8 3.1 8.2 2.3Selenium ug/b 1 2.7 2.1 2.4 3.2 BLQL15Silica mg/L 20 20 19 _ ___ ____ 27 20 25Silver ugiL 0.5 BQL BQL BQL BQL BQL BQ BQLSodium mg/b 0.5 70 69 68 53 50 63 83 51Sulfate mg/b 0.5 140 150 150 160 170 150 210 87Thallium ug/L 0.5 BQL BQL BQL BQL BQ BQ BQLZinc mg/b 0.05 0.15 0.11 0.11 0.43 0.32 0.32 0.2 0.34DCPP Water Resources Report Page 27DCPP Water Resources ReportPage 27 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2.2 Well #2 -Water Quality vs. DepthThree pairs of depth-specific and composite water quality samples were collected at Well#2 during the velocity logging of the well conducted on November 15, 2007. Thesediscrete depth samples provide an opportunity to evaluate water quality from specificdepths within the aquifer and to determine whether changes in pumping practices and/orchanges to well construction parameters may be appropriate for improving the quality ofthe pumped water.Water quality samples were collected at 158 ft bgs, 190 ft bgs, and 275 ft bgs. The pumpwas set at a depth of 160 ft bgs during this test. Because the pump set depth influencesflow direction within the well, this is an important consideration for assessing therepresentativeness of depth-specific water quality samples. Given the direction of flowwithin the well, the water quality sample collected at 158 feet represents water from the100-158 foot interval (which represents approximately 26% of the flow into the well); thesample collected at 190 feet represents water from the 190-275 foot interval (whichproduces approximately 66% of the flow into the well); and water collected at 275 ft bgsrepresents the deepest zone in the well from 275-350 ft bgs (which representsapproximately 3% of the flow in the well).Based upon these data (Table 8), the shallow productive zone (from 100-158 feet bgs) hassubstantially higher turbidity and higher concentrations of silica, total dissolved solids,nickel, aluminum and iron than the deeper productive zone (190-275 ft bgs). Figures 12aand 12b below illustrate these values. Arsenic and bicarbonate concentrations are slightlylower in the shallow productive zone as compared to the deeper productive zone. Forother constituents sampled, concentrations do not differ significantly between these twoproduction zones.Considering these water quality differences between the uppermost zone and the lowerzones, economic analysis may be needed to determine the costs and benefits of specificwell construction modifications to isolate zones. If in the future one or more of theseconstituents adversely affects the water treatment operations, well modificationapproaches can be considered. First, a temporary packer could be installed to prevent theshallowest zone of poor water quality groundwater from entering the well. This device isan elongated, thick-rubber balloon that is attached to a section of column pipe and can beinflated or deflated using an air value at the wellhead. Materials and installation for thisdevice would cost approximately $10,000. Second, the well screen adjacent to theshallowest zone of poor water quality groundwater could be permanently sealed withcement. This is a more complex operation than installation of the packer but is stillviable. This approach has a similar cost to the packer option, but has an advantage ofbeing a permanent solution, whereas the packer may need to be rehabilitated or replacedevery 5 to 10 years.DCPPWate Reourcs ReortPage 28 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008In both cases, the well's produced water quality would improve and its drawdown wouldincrease to maintain the target flow rate of 150 gpm. Because the pump operates at afixed rate, the well would operate at a flow rate approximately 10-20 gpm less and from apumping water level of approximately 5 to 10 feet deeper.Well 2 -Concentration vs. Depth100120140'" 160180G'2005220240260280300Conce ntrationFigure 1 3a. Constituent concentrations as a function of depth at Well #2.DCPP Water Resources Report Page 29DCPP Water Resources ReportPage 29 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well 2 -Concentration vs. Depth100120140'~160.01804-* 200.=2200.240 -*--- Alkalinity (CaCO3)260 Bicarbonate (CaCt-0-Alurninum (ugi)260 -Chloride (rngl)3000 100 200 300 400 500 600 700 800 900 1000ConcentrationFigure 1 3b. Constituent concentrations as a function of depth at Well #2.DCPP Water Resources Report Page 30DCPP Water Resources ReportPage 30 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Tahle 8. Well #~2 Denth-Sneeifie Water Ouialitv Cornposite 1 Discrete 1 Composite 2 Discrete 2 Composite 3 Discrete 3(Surface) (275 Ft.) (Surface) (190 Ft.) (Surface) (158 Ft.)nayeUis PL 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07________________15:40 _______ 15:50 16:05Depth (or Pumping Water Level) _____275 190 158-pH S.U. -6.6 6.9 6.7 6.8 6.7 6.7Color Color Unit S <5 <5 <5 <5 <5 <5MBAS Surfactants mg/L 0.1 BQL BQL BQL BQL BQL BQLOdor T.O.N. 1 ND ND ND ND ND NDSpec. Conductivity umhos/cm 1 1300 1420 1300 1340 1290 1300T.D.S. mg/L 10 790 860 790 800 790 810Turbidity N.T.U. 0.1 4.5 4.7 0.69 3.6 1.4 7Alkalinity (CaCO3) mg/L 10 410 440 400 420 410 400Bicarbonate(CaCO3) mg/L 10 410 440 400 420 410 400Carbonate (CaCO3) mg/b 10 BQL BQL BQL BQL BQL BQLHardness (as CaCO3) mg/L 10 520 530 510 520 520 530Hydroxide (as CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQLAluminum ug/L 5 170 240 46 110 100 300Antimony ug!L I BQL BQL BQL BQL BQL BQLArsenic ug/L 0.5 2.2 4 1.8 2.5 2 1.4Barium ug/L 0.5 30 26 27 27 28 35Beryllium ug/L 0.5 BQL BQL BQL BQL BQL BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQLCalcium mg/L 0.1 97 95 94 96 95 100Chloride mg/L 0.2 100 120 100 110 100 110Chromium ug/L 1 2.8 6.4 1.7 4.3 1.9 4.3Copper mg/b 0.02 BQL 0.037 BQL BQL BQL BQLFluoride mg/b 0.1 0.4 0.5 0.4 0.4 0.4 0.5DCPP Water Resources Report Page 31DCPP Water Resources ReportPage 31 TbeNT.RWel #2 Det-SEvionentalc anWaturQalit Resource MangemntCnsltntTable 8. Well #2 Depth-Specific Water Quality Results (cont'd.)Well 2 Well 2 Well 2 Well 2 Well 2 Well 2Composite 1 Discrete 1 Composite 2 Discrete 2 Composite 3 Discrete 3Analyte Units PQL (Surface) (275 Ft.) (Surface) (190 Ft.) (Surface) (158 Ft.)11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07_______________15:40 15:50 ______ 16:05Depth (or Pumping Water Level) _____________ 275 190 158Iron mgiL 0.1 0.71 0.73 0.12 0.43 22 62Lead ug/L 0.5 1.5 0.78 0.63 0.99 0.62 1Magnesium mg/L 0.1 61 64 60 62 60 69Manganese mg/L 0.005 0.041 0.056 0.017 0.03 0.018 0.0087Mercury ug/L 0.5 BQL BQL BQL BQL BQL BQLNickel ug/L 1 9.5 16 8.2 8.9 8.5 11Potassium mg/L 0.2 2.7 3.2 2.7 3.1 2.7 2.1Selenium ug/L 1 2.7 3.2 2.1 2.2 2.4 6Silica mg/L ___ 20 22 19 20 19 24Silver ug/L 0.5 BQL BQL BQL BQL BQL BQLSodium mg/b 0.5 70 100 69 80 68 59Sulfate mg/L 0.5 140 150 150 150 150 160Thallium ug/L 0.5 BQL BQL BQL BQL BQL BQLZinc mg/L 0.05 0.15 0.07 0.11 0.069 0.11 0.099Total Sulfide mg/L __Ammonia (as N) mg/b 0.1 _____Nitrate (as N) mg/L 0.1 0.2 BQL 0.2 BQL 0.2 0.9Nitrate (as NO3) mg/b 1_________________________________________o-Phosphate-P mg/b 0.05 _______T.K.N. mg/b 1 _________DCPP Water Resources Report Page 32DCPP Water Resources ReportPage32 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2.3 Comparison of Surface Water and GroundwaterCornpositionA significant aspect of this study is to determine if a connection exists betweengroundwater from the existing DCPP production well and surface water in Diablo Creek.In addition to reviewing water level data during the pumping tests in an effort to detecttrends that might indicate a significant connectivity between the extracted groundwaterand the Creek, water quality data were reviewed to assess if any connectivity existsbetween the surface water and the shallow groundwater production zone.Two methods are used to review the water quality data that were collected from Well #2and the creek. The first is the comparison of paired water quality samples collected at thepumping well and at the creek on December 3, 2007, December 6, 2007 and June 30,2008 (Table 9). For these sampling dates which occurred during the constant ratepumping tests at Well #2, samples were collected contemporaneously, so as to provide aninstantaneous snapshot of water quality at both locations for comparison purposes.The second method used to examine the water quality data for trends that indicate thedegree of connectivity between extracted groundwater at Well #2 and the Creek was tocompare the depth-specific water quality samples collected at Well #2 with water qualitysamples collected at the Upper Creek sampling site (Figure 14a and Figure 14b, below).If there is a significant degree of connectivity between water in the upper productive zoneof Well #2 and surface water, it would be expected that the shallowest water qualitysample collected from the well could have a geochemical composition similar to that ofthe surface water sample for a number of constituents (or more similar to the surface waterthan that of the deeper groundwater).The most definitive result of this water quality comparison is the considerable variation inseveral key constituents, such as TDS, Chloride, Sodium, Iron, which are all substantiallylower in concentration in the creek water than in groundwater. The difference is evidentin comparison to both the various composite well samples as well as the depth-specificsamples. The water quality difference evident in these constituents, most of which aregenerally considered "conservative" (i.e., they do not tend to vary with time or reactionsin the subsurface), is diagnostic of largely if not entirely different water source. As oneline of evidence, these data indicate limited, if any, connection between the groundwaterpumping at Well #2 and creek flows.Also, the presence of bacteria (Total Coliform and E Coli) in the creek water and itsabsence in well #2 water (although the Total Coliform results from the December 6, 2007well sample was "present" but this could be a contaminated sample and thereforeanomalous), is additional corroboration that groundwater pumping at Well #2 is notdirectly extracting water from the creek.DCPP Water Resources Report Page 33DCPP Water Resources ReportPage 33 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 9. Water Quality in Diablo Creek Compared to Groundwater ___Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Upper Upper CulvertWeir WeirDiscrete 1 Composite Discrete 2 Discrete 3Analyte Units PQL Composite 1 (7Ft) 2(9F.) Composite 3 (158 Ft.)11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 12/3/07 12/6/07 6/30/0815:40 15:50 16:05pH S.U. -6.6 6.9 6.7 6.8 6.7 6.7 6.9 6.5 7.3 8.2 7.9 8.2Color Color Unit 5 <5 <5 <5 <5 <5 <5 <5 <5 <5 10 10 30Spec. Conductivity umhos/cm 1 1300 1420 1300 1340 1290 1300 1280 1270 1200 870 870 860T.D.S. mgfL 10 790 860 790 800 790 810 760 780 810 530 540 540Turbidity N.T.U, 0.1 4.5 4.7 0.69 3,6 1.4 7 0.39 0.4 0.1 2.1 2 9.5Alkalinity (CaCO3) mg/L 1 0 410 440 400 420 410 400 390 390 400 350 340 370Bicarbonate(CaCO3) mg/L 10 410 440 400 420 410 400 390 390 400 350 340 360Carbonate (CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL 10Hardness (as mg/L 10 520 530 510 520 520 530 580 560 BQL 430 430 420CaCO3)Hydroxide (as mg/'L 10 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLCaCO3) ____Aluminum ug/L 5 170 240 46 110 100 300 5.8 BQL 63 0.25Arsenic ug/L 0.5 2.2 4 1.8 2.5 2 1.4 0.66 BQL 2.1 BQLBarium ug/L 0.5 30 26 27 27 28 35 38 BQL 57 BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL 0.61 0.001Calcium mg/L 0.1 97 95 94 96 95 100 120 110 120 99 89 90Chloride mg/L 0.2 100 120 1 00 110 100 110 94 95 91 33 33 33Chromium ug/L 1 2.8 6.4 1,7 4.3 1.9 4.3 1.3 BQL 1.7 BQLCopper mg/L 0.02 BQL 0.037 BQL BQL BQL BQL 0.024 BQL BQL BQL BQL BQLFluoride mg/L 0.1 0.4 0.5 0.4 0.4 0.4 0.5 0.5 0.5 0.7 0.3 0.3 0.4Iron mg/L 0.1 0.71 0.73 0.12 0,43 0.22 0.62 BQL BQL BQL BQL 0.00011 0.27Lead ug/L 0.5 1.5 0.78 0.63 0.99 0.62 1 BQL BQL BQL BQLMagnesium mg/L 0.1 61 64 60 62 60 69 70 68 69 54 50 47Manganese mg/L 0.005 0.041 0.056 0.017 0.03 0.018 0.0087 0.028 0.026 0.02 BQL BQL BQLDCPP Water Resources ReportPage 34 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 9. Water Quality in Diablo Creek Compared to Groundwater (cont'd.)Nickel ug/L 1 9.5 16 8.2 8.9 8.5 11 7.8 BQL 11 0.01Potassium mg/L 0.2 2.7 3.2 2.7 3.1 2.7 2.1 2.9 2.8 3.1 2.9 2.6 2.5Selenium ug/L 1 2.7 3.2 2.1 2.2 2.4 6 3.2 BQL 1.2 BQLSilica mgIL 20 22 19 20 19 24 24 23 27 31l 29 33Silver ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLSodium mg/L 0.5 70 100 69 80 68 59 53 50 63 22 19 23Sulfate mg/L 0.5 140 150 150 150 150 160 160 170 150 88 89 82Thallium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLZinc mg/L. 0.05 0.15 0.07 0.11 0.069 0.11 0.099 0.43 0.32 0.32 0.13 0.065 BQLNitrate (as N) mg/IL 0.1 0.2 BQL 0.2 BQL 0.2 0.9 0.3 0.5 0.1 BQL BQL BQLE. Coli _____ absent absent present presentTotal Coliform present absent present presentDCPP Water Resources Report Page 35DCPP Water Resources ReportPage 35 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsMay 23, 2008Well 2 -Depth-Specific Samples and Creek Samples-101540I6590115140165190215240265;290ConcentrationFigure 1 4a. Constituent concentrations as a function of depth at Well #2 and Diablo Creek.Well 2 -Depth-Specific Samples and Creek Samples--Alkalinity (CaC;O3) (mgl)140 -NE Bicarbonate (CaCO3) (nrigl)--Aluminum (ugi)165 -a-Chloride (ngl)(6 -Creek-TDS215 A Creek-Alkalinity:: Creek-Bicarbonate* Creek-Alurrinum265 A Creek -Chloride*Cr'ee k-k-on0 100o 200 300 400 500 600 700 800 900 1000Conce ntra tionFigure 14b. Constituent concentrations as a function of depth at Well #2 and Diablo Creek.DCPP Water Resources Report Page 36DCPP Water Resources ReportPage 36 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsMay 23, 20084.2.4 Summary of Water Quality ResultsDepth-specific water quality testing indicates that the water extracted from the deepproduction zone is higher quality (i.e., generally lower in constituent concentrationsimportant to plant operations) than water extracted from the shallow production zone. Inorder to reduce concentrations of certain constituents in extracted groundwater, such assilica, the upper screened portion of Well #2 could be temporarily or permanently sealed.Doing so would improve the quality of pumped groundwater from Well #2. However,this upper productive zone represents approximately 20% of the flow in the well and ifthis portion of the well is sealed, DCPP can expect a 10-20 gpm reduction in groundwaterproduction.The presence of a series of diagnostic constituents with significantly differentconcentrations in Diablo Creek compared with Well #2 groundwater represents a strongline of evidence that groundwater pumping does not draw from Diablo creek.DCPP Water Resources Report Page 37DCPP Water Resources ReportPage 37 C)I0N)
Environmental and Natural Resource Management Consultantsvia emailAugust 22, 2008Mr. Drew SquyresSenior Project ManagerPacific Gas and Electric Company, Environmental Services4325 South Higuera StreetSan Luis Obispo, CA 93401RE: Pacific Gas & Electric (PG&E) Company, Diablo Canyon Power Plant(DCPP) Water Resources Evaluation: Well Installation and Aquifer Testing
Dear Drew:
Please find enclosed the revised Water Resources Evaluation Phase II report forDiablo Canyon Power Plant. We are providing this to you in accordance withPG&E Contract #46000 16684 and Contract Work Authorization #35007983 13.This draft includes results from additional aquifer testing conducted in June, 2008which improve and expand upon the assessment of any connectivity betweengroundwater pumping and flows within Diablo Creek.We have enjoyed working with you on the important project, and look forward toproviding additional support in the future.Sincerely,Timothy ThompsonVice President -Water Resource Sciencescc: Mr. Mark Coleman, Diablo Canyon Power PlantMr. John Giambastiani, ENTRIX, Concord DIABLO CANYON POWER PLANTWATER RESOURCES EVALUATIONPHASE II REPORT:WELL REHABILITATION,MONITORING WELL INSTALLATION,AND AQUIFER TESTINGPrepared by:Environmental and Natural Resource Management consultantsAugust 22, 2008 ENTRIX, Inc, -Environmental and Natural Resource Management ConsultantsAugust 22, 2008TABLE OF CONTENTSEXECUTIVE SUMMARY ........................................................................................ 11. INTRODUCTION ............................................................................................... 11.1 BACKGROUND......................................................................................................... 11.2 HYDROGEOLOGY .................................................................................................... 21.3 WELL SITE SELECTION.............................................................................................. 32. MONITORING WELL INSTALLATION (WELL #4 AND WELL #5) ................................ 12.1 DRILLER AND DRILLING METHODS................................................................................ 12.2 WELL #4........................................................................................................ 22.2.1 Site Description ........................................................................................ 22.2.2 Well Construction ...................................................................................... 22.2.3 Well Logging............................................................................................ 22.2.4 Well Development and Testing .................................................................... 32.3 WELL#5 .............................................................................................................. 62.3.1 Site Description ........................................................................................ 62.3.2 Well Construction ...................................................................................... 62.3.3 Well Logging............................................................................................ 62.3.4 Well Development and Testing........................................................................ 83. WELL #2 REHABILITATION AND TESTING .......................................................... 113.1 WELL REHABILITATION....................................................................... :.................... 113.1.1 Results of Pump, Motor, and Column Pipe Inspection............................................. 113.1.2 Video Log Results .................................................................:.................... 113.1.3 Description of Well Rehabilitation Tasks Performed .............................................. 113.2 SPINNER TEST........................................................................................................ 123.3 PUMP TESTS FOR EVALUATING WELL YIELD................................................................... 133.3.1 Step Drawdown Test.................................................................................. 133.3.2 Constant Rate Tests................................................................................... 153.5 PUMP SPECIFICATIONS............................................................................................. 164. AQUIFER RESPONSE TO PUMPING TEST......................................................... 174.1 MONITORING LOCATIONS ......................................................................... 2............ 174.1.1 2007 Constant Rate Pumping Test............................................................... 174.1.2 2008 Constant Rate Pumping Test............................................................... 174.1.3 Effect of Constant Rate Pumping Test at Monitoring Wells ................................... 184.1.4 Effect of Constant Rate Pumping Test at Surface Water Monitoring Locations.....'......... 194.2 WATER QUALITY ................................................................................................... 244.2.1 Relative Water Quality of Wells #2, #4 and #5...................................................... 244.2.2 Well #2 -Water Quality vs. Depth.................................................................... 284.2.3 Comparison of Suiface Water and Groundwater Composition .................................... 334.2.4 Summary of Water Quality Results................................................................... 375. SUMMARY AND CONCLUSIONS......................................................................... 385.1 WELL #2 REHABILITATION ....................................................................................... 385.2 EFFECTS OF GROUNDWATER PUMPING ON DIABLO CREEK .................................................. 385.3 RECOMMENDATIONS FOR GROUNDWATER USE............................................................... 385.3.1 Well #2 Construction, Operations and Maintenance............................................... 385.3.2 Monitoring Wells .................................................................................. 395.4 MONITORING PROGRAM RECOMMENDATIONS ................................................................. 39DCPP Water Resources Report Page TOC- 1 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008FIGURESFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.Figure 7.Figure 8.Figure 9.Figure 10.Figure 11.Figure 12a.Figure 12b.Figure 13a.Figure 13b.Figure 14a.Figure 14b.Table 1.Table 2.Table 3.Table 4.Table 5.Table 6.Table 7.Table 8.Table 9.Map of project site showing location of wells.Photograph of Well #4.Schematic diagram showing Well #4 construction and lithology.Drawdown at Well #4 during development and testing.Photograph of Well #5.Schematic diagram showing Well #5 construction and lithology.Drawdown at Well #5 during development and testing.Graph of Step Drawdown Test at Well #2.Water levels at Well #2 during the constant rate pumping test.Water levels in DCPP Wells during November 2007 constant ratetest.Water levels in DCPP Wells during June 2008 constant rate test)Water levels at Pumping Well and Diablo Creek Locations (June/July 2008Pump Test).Water levels at pumping well and Diablo Creek locations focused ontime period of test.Constituent concentrations as a function of depth at Well #2.Constituent concentrations as a function of depth at Well #2.Constituent concentrations as a function of depth at Well #2 andDiablo Creek.Constituent concentrations as a function of depth at Well #2 andDiablo Creek.TABLESDCPP Well Locations.Construction Parameters for Well #4 and Well #5.Development of Well #4 (November 8, 2007).Development of Well #5 (November 10, 2007).Well #2 Spinner Log Analysis.DCPP Well #2 -Step Rate Test.Comparison of Well #4, Well #5 and Well #2 Composite Samples.Well #2 Depth-Specific Water Quality Results.Water quality in Diablo Creek compared to groundwater.DCPP Water Resources Report Page TOC-2DCPP Water Resources ReportPage TOC-2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Attachment A:Attachment B:Attachment C:Attachment D:Attachment E:ATTACHMENTSWell 4 DocumentationWell 5 DocumentationWell 2 DocumentationWater Quality Data TablesDCPP Water Resources Monitoring PlanDCPP Water Resources Report Page TOC-3DCPP Water Resources ReportPage TOC-3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Executive SummaryThe PG&E Diablo Canyon Power Plant ("DCPP") has historically utilized threeindependent water supplies for plant water needs, listed in order of volumetric priority:(a) seawater, treated by a large reverse osmosis system ("SWRO"), (b) diversions fromDiablo Creek, and (c) groundwater produced by a single on-site well ("Well #2"). As aresult of a directive by the California Coastal Commission, diversions from Diablo Creekwill be ceased. This change in supply options increases the dependence upongroundwater and therefore generates a need for the groundwater to be both more reliableand pumped at a slightly greater rate than historically. Given this context, the purpose ofthis Water Resources Evaluation is to develop a better understanding of on-sitegroundwater resources in terms of potential yield, water quality and relationship betweengroundwater pumping and flows in Diablo Creek. This work is based in part on a 2007study ("Phase I: Evaluation of Groundwater and Surface Water Data") that was preparedto identify appropriate steps for refurbishing and testing existing groundwater productionfacilities, evaluating groundwater water quality issues, and installing monitoring wells.The Phase II scope-of-services included: (1) installation of two monitoring wells (Well #4and Well #5), (2) evaluation and rehabilitation Of Well #2, (3) aquifer testing at Well #2,and (4) water quality sampling and analysis. The proposed new monitoring wells willprovide valuable information needed for (a) understanding current groundwater basinconditions, (b) assessing future groundwater production potential and water quality at theproposed locations, and (c) comparing groundwater water levels with flow levels inDiablo Creek to demonstrate if any hydraulic connection is apparent.The two monitoring wells, known as Wells #4 and #5, were drilled and completed to 500ft and 400 ft, respectively. The wells were logged, tested and evaluated for water quality.Well #4 was pumped for two hours at a rate of 30 gallons per minute, had 21 ft ofdrawdown and has a potential yield of 80 gallons per minute (gpm) or more. Waterquality at Well #4 was satisfactory, but poorer than the other wells. Well #5 was pumpedfor over two hours at a rate of 49 gallons per minute, had a drawdown of approximately 8ft and has a potential yield of 150 gpm or more. Water quality at Well #5 was better thanthat at Well #2 in many, but not all, respects.The pre-existing and historically productive Well #2 was rehabilitated, including cleaningof the casing, and replacement of the pump, motor, column pipe and surface controls. Thewell was tested and sampled to determine if the well's inflow rates and water qualitydiffered at different depths. Based upon the results of this work, it is evident thatsignificant inflow rates occur at different depths within the well and that the water qualityat these various depths is also different in certain respects. The majority of the well'swater enters in the 190-275 ft zone, and is of reasonably good water quality. A shallowerzone was identified as contributing approximately 20% of the well's flow and containingelevated concentrations of total dissolved solids, chloride, iron and silica.DCPP Water Resources ReportPaeE-Page EC- I ENTRIX, Inc.- Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well #2 was initially tested from November 26 through December 7, 2007, a 10-dayconstant rate pumping test that included monitoring at Well #2, three monitoring wellsand in Diablo Creek. The test was run at 150 gpm which proved to be an acceptable long-term, sustainable pumping rate for the well, even with the preceding years of limitedrainfall and associated lowered water levels. During wetter climatic periods, the well hasa capacity to produce at a greater flow rate.A second constant rate pump test was conducted at Well #2 from June 25 to July 2, 2008to evaluate the relationship between groundwater pumping and creek water levels. Well#2 was pumped at a rate between 150 and 200 gpm for seven days. Changes in waterlevels were monitored in Wells #2 and #5 as well as at two locations in Diablo Creek.Just before the end of the test, water quality samples were collected from Well #2 and thecreek. The data collected do not show a correlative water level response between waterlevels in Diablo Creek and pumping water levels in Well #2. During the course of thepumping test, water levels in the Creek did not exhibit a drawdown or rebound signaturecorresponding to the start and end of the pump test, respectively. If the creek and wellwere connected, measurable changes in the creek water levels would likely occur. Theabsence of these trends supports the conclusion that there is no discernable connectionbetween creek water levels and pumping at Well #2.Water quality comparisons were also conducted to determine if a relationship existsbetween groundwater pumping at Well #2 and flows within Diablo Creek. Concentrationsof several key constituents from samples collected contemporaneously during the multipletests were markedly different indicating distinct water sources.Finally, a water resource monitoring program was initiated to collect and track hydrologicdata in an effort to ensure adequate understanding of this valuable resource is developedand maintained.Recommendations of this work include continuance of the water resources monitoringprogram, evaluating factors associated with future production use of Wells #4 or #5, andevaluate implementation of downhole well modifications to improve water quality in Well#2.DCPP Water Resources ReportPaeE-Page EC-2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20081. IntroductionThis report provides a summary of well rehabilitation, monitoring well installation,aquifer testing, and water quality analyses conducted at the PG&E Diablo Canyon PowerPlant ("DCPP") from October 2007 through July, 2008. The services were conducted aspart of the Phase II and Phase III Water Resources Evaluation scope of work which, inturn, is based upon the June 30, 2007 technical report entitled: "Phase I: Evaluation ofGroundwater and Surface Water Data". The work provides data and recommendations tosupport increased reliability of groundwater production and an evaluation of whether aconnection exists between groundwater pumping from the existing Well #2 and flowsassociated with Diablo Creek. Also included is a section of the report that summarizesrecommendations for groundwater use and facilities management and provides elementsof a long-term groundwater resource monitoring program.This work is part of a larger effort by DCPP staff to increase reliability of available watersupplies, which also includes modifications to the DCPP seawater reverse osmosis("SWRO") treatment plant system. Properly managed and monitored development oflocal groundwater resources can provide a highly reliable water supply that will continueto supplement the SWRO supply. As part of this ongoing groundwater developmentactivity, groundwater monitoring data will be collected to establish a body of informationto better understand the water resources of the area. Appropriate work to follow the taskssummarized in this document includes implementation of a groundwater monitoringprogram to initiate the collection of water related data that will increase the understandingand forecasting of this valuable resource. Additional phases of work may also include theconversion of one or both of the new monitoring wells to production wells dependingupon future determination of DCPP groundwater supply needs.1.1 BackgroundWater supply for DCPP steam generation is currently acquired from three sources: reverseosmosis treatment of seawater ("SWRO"), surface diversions from Diablo Creek, andpumped groundwater. SWRO is the primary water supply source, with the surface waterand groundwater resources used in supporting roles for augmentation during normalSWRO operations or for temporary backup supply during SWRO outages. Because of aregulatory mandate to cease Diablo Creek diversions, groundwater will be elevated in itsrelative importance to meet the water supply needs of DCPP and it is therefore appropriateto increase groundwater production capability and reliability.Given that context, a study was prepared ("Phase I: Evaluation of Groundwater andSurface Water Data") to identify appropriate steps for refurbishing and testing existingDCPP Water Resources Report PgPage 1 ENTRIX, Inc. -Environmental and Natural Resource Management Cons~ultantsAugust 22, 2008groundwater production facilities, evaluating groundwater water quality issues, andinstalling monitoring wells.The monitoring wells were recommended to gain a broader understanding of thegroundwater conditions present at the DCPP site and to develop information on futureproduction well locations. These wells will provide information needed for (a)understanding current groundwater basin conditions, (b) assessing future groundwaterproduction potential and water quality at the proposed locations, and (c) comparinggroundwater water levels with flow levels in Diablo Creek to demonstrate if any hydraulicconnection is apparent. If replacement of the existing Well #2 or augmentation of theexisting DCPP groundwater pumping capacity is needed at a future date, one or both ofthese monitoring wells could be converted to production wells.In order to comply with the aforementioned regulatory mandate to cease Diablo Creekdiversions, increased groundwater production will be needed. The cessation of creekdiversions generates two considerations:1. Increased dependence upon Well #2 to provide all the water needed toaugment the SWRO system; and,2. The technical concept of demonstrating that both existing and futuregroundwater pumping does not extract subsurface water associatedwith Diablo Creek flows.For these considerations, a series of diagnostic aquifer tests were conducted. These testsinvolved pumping at Well #2 at similar rates to historical and planned usage andcontemporaneous water level monitoring at other wells and at locations within DiabloCreek.1.2 HydrogeologyThe primary aquifer established by existing groundwater extractions is the fracturedsandstone (possibly dolomitic) of the lower to middle Miocene-aged Obispo Formation.This unit also contains siltstones and finer grained beds that are less productive than thefractured sandstones. The brittle nature of the sandstones produces discrete fracture setsthat can form a prolific bedrock aquifer. Because the aquifer material in this region isrelatively hard and locally brittle bedrock, essentially all groundwater production will bederived from fractures within the rock, not from the pore spaces between the sand grainsas occurs in an alluvial (i.e., uncemented, unlithified) aquifer.DCPP Water Resources Report PgPage 2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20081.3 Well Site SelectionSite selection in bedrock aquifers is highly dependent upon the existence of fracturedzones that allow groundwater collection and conveyance from upgradient source areas.For the purpose of monitoring well site selection, a local and regional scale fracture studywas conducted, as described in the Phase I report. This study combined with site accessand other considerations resulted in the identification of three (3) favorable drillinglocations, two (2) of which (site "4" and site "5 b") were selected by PG&E staff for themonitoring wells installed as part of this Phase II work. (see Table 1, Figure 1). Site "5b"of the Phase I report will be referenced as site "5" in this report and all future references.As a historical note, Well #3 was drilled contemporaneously with wells 1 and 2, yetbecause of insufficient yield was abandoned before well completion. It is located in thesmall turn-around circle near the current Diablo Creek diversion and pumping facilities*(see Figure 1). The wellhead is no longer visible in the field, and its elevation in Table 1is approximate.Table 1. DCPP Well LocationsNorth East EeainWell No. Descriptive Location Coordinate* Coordinate* lvainfIt mslWell #1 Near Diablo Creek 2277056.86 5711903.64 251.36Well #2 On Deer Trail Rd. 2276517.11 5712241.45 333.3Well #3 On Turnaround near SempSemp ~ ~ 8Well #3 Lower Weir SempSemp-8On Deer Trail Rd. atWell #4 troftwaetnk 2276209.20 5712999.92 452.35Well 115 Near Man Camp area 2276658.80 5712413.70 303.93*Coordinates and Elevations were surveyed by GraniteConstruction staff. Coordinates are consistent with other DCPPsurveying data. Elevations represent the top of the concrete padat each well.DCPP Water Resources Report PgPage 3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008-~ IrTh~r~ ~ FIgure______________________________________ 6 v~AI L~23t~ofl~ w~-~H lt~oi~ M~,pN A C). k -~ C)r),~, 42~ 1CC)t pidIIo (2afl~o~ Vowe, ~3fltUXD~Figure 1. Map of project site showing location of monitoring stations.DCPP Water Resources Report Pg ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082. Monitoring Well Installation (Well #4 and Well #5)The initial task conducted during this phase of the project involved the installation of two(2) monitoring wells. The design and installation approach for the wells included theprovision that each monitoring well could be converted to a production well at a futuredate. Therefore, careful monitoring was conducted during drilling of the monitoring wellsto assess the potential well yield and water quality. Additionally, upon completion of eachwell, a short-term pumping test was conducted to provide an estimate of yield and allowfor collection of a water sample for water quality analysis.Both wells were drilled to relatively deep depths (506 ft and 409 ft, respectively) to allowfor penetration of a significant depth of bedrock, which greatly increases the potential tointersect fracture zones that have regional connectivity and hence increased yield anddrought-period tolerance. Also, deep sanitary seals were installed at the wells to provideincreased assurance that shallow groundwater that could potentially be tributary to DiabloCreek is not captured by the wells. Additional details of well construction are provided inTable 2 and Figures 3 and 6, below.Table 2. Construction Parameters for Well #4 and Well #5.Well Construction Parameter Well #4 Well #5Drilled Depth 506 ft 409 ftBorehole Diameter 10.5 inches 10.5 inchesDirect Air Rotary/Drilling Method Direct Air Rotary Mud RotarySanitary Seal 230 ft 75 ftCasing Size (OD) 5 inch 5 inchCasing Material PVC (Sch. 80) PVC (Sch. 80)Screen Interval 250 -500 ft 100 -400 ftSlot size 0.050 in 0.050 inGravel Pack #8 mesh sand #8 mesh sandInitial Water Level (below ground) 219 ft 40 ftWellhead Elevation (ft MSL) 452.35 ft 303.93 ftGeophysical Logs SP, Resistivity, Sonic SP, Resistivity, Sonic2.1 Driller and Drilling MethodsCascade Drilling of La Habra, CA was contracted to conduct the monitoring wellinstallation based upon previous experience, qualifications, safety record and familiaritywith PG&E projects. Cascade was directed to employ rotary air-hammer drilling methodswhich are appropriate for hard, fractured bedrock aquifer materials as present at the site.Cascade provided a crew of 3, an auxiliary air compressor and other ancillary drillingequipment for the installation of the two (2) monitoring wells. Geophysical well loggingat Wells #4 and #5 was conducted by Welenco of Bakersfield, CA.DCPP Water Resources Report PgPage 1 ENTRIX, Inc. -Environmnental and Natural Resource Management ConsultantsAugust 22, 20082.2 Well#42.2.1 Site DescriptionWell #4 (Figure 2) is located 0.2 miles up Sky View Road from its intersection with DeerRun Road near the Man Camp, and is at the junction of Sky View Road and the water tankroad. This site was selected because it represents a high potential for sufficient flow ratesto provide supplemental water production, it will likely have at most a limited effect onthe existing Well #2, and its effect on Diablo Creek will likely be very limited. It is alsoat a sufficient distance from Well #2 and Diablo Creek to allow monitoring of up-gradientaquifer conditions that can support development of a broader understanding of aquiferwater levels and possible variability in aquifer water quality.2.2.2 Well ConstructionWell #4 was drilled from October 24 to October 26, 2007 to a total depth of 506 ft beneathground surface. Water was first encountered at 245 ft, and stabilized to a static level of219 ft. In consideration of the depth to water, and the interest in ensuring limitedconnectivity to Diablo Creek, the sanitary seal was constructed to 230 ft deep. PerforatedPVC casing was installed from 230-500 ft. By the time the total depth of drilling wasreached, the well was naturally producing approximately 40 gpm, as evidenced by theflow resulting from the air injection employed as part of the air-hammer drilling method.2.2.3 Well LoggingSediments encountered during drilling included abundant clay, shale and siltstone withinterspersed layers of sandstone (see State Well Drillers Report, Attachment A). Evidenceof fracturing increased below 240 feet and correlates with increased water production ofthe well during drilling. This observation is particularly relevant because in fracturedbedrock aquifers, essentially all the groundwater that is available to enter the well will bederived from fractures within the rock, rather than from the pore spaces between the sandgrains. Geophysical logs run in the hole included electrical log (resistivity andspontaneous potential [SP]), gamma, sonic velocity and temperature. These logs illustratethe stratified nature of the formation and an increase in the proportion of sandstone-richbeds in the lower 60 feet of the well. The indications provided by the e-logs are largelycorroborated with the lithologic monitoring conducted by ENTRIX during well drilling.Initial stabilized water levels in the well were measured at 219 ft deep. Confined aquiferconditions are evident based upon this static water level in relation to the 230 ft depth ofthe sanitary seal and top of slotted casing at 250 ft deep.DCPP Water Resources Report PgPage 2 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008ioto of Monitoring Well #42.2.4 Well Development and TestingWell #4 was developed for a full day following well construction, including severaliterations of surging and bailing at deep, medial and shallow portions of the well.Development was continued until the produced water was clear. Next, in an effort toestablish potential well yield, Well #4 was pumped for two hours at a rate of 30 gallonsper minute, which results in a drawdown of approximately 21 ft. Based on these data, thespecific capacity of the well is approximately 1.4 gpm/ft of drawdown. Given that thereare at least 200 feet of additional available drawdown, flow rates of 80 gpm are attainableif needed at a future date; although the pumping lift would be substantially greater thanthat needed at either Well #2 or Well #5 for this production rate.As indicated in Table 3 below, by the end of the test, the turbidity in the water was greatlyreduced and the pumping water level had nearly stabilized (Table 3, Figure 4). A waterquality sample was collected at Well #4 at the end of the test, on November 8, 2007.Water quality results are provided below in Section 4.DCPP Water Resources ReportPage 3 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008If it is determined in the future that production from this well is needed, we suggestconducting, depth-specific water quality sampling to determine if a portion of the well'sproduced water is of the poorer quality than from other depths. If it is determined that aspecific zone (i.e. the deepest zone, for example) is of particularly poor water quality,changes in well construction parameters may aid in controlling water quality from thiswell, although production rates will likely be reduced. Also, although this well still has alower specific capacity than Well #5, it is sufficiently distant from Well #2 so as to reducethe potential for interfering cones of depression from multiple pumping wells, and isworthy of consideration to meet future production needs.Table 3. Development of Well #4 on November 8, 2007.Elapsed Depth Electrical Trity VolumeTime Time to Conductivity Triiy Pumped_______Water___ (mai) (ft bgcs) (NTU) (gallons)12:49 0 217 _ ____ 012:50 1 221.85 1635 53 I13:10 21 234.44 1488 271 60013:30 41 237.03 1463 10.9 120013:50 61 237.05 1483 0 180014:10 81 237.69 1464 0 240014:30 101 238.05 1465 0.7 300014:50 121 238.3 1478 0 3600Well 4 Development and Testing215220"Z 225*9°2302352400 20 40 60 80 100 120 140Elapsed Time (min)Figure 4. Drawdown at Well #4 during development and testing.DCPP Water Resources Report PgPage 4 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Figure 3. Schematic diagram showing Well #4 construction and lithology.DCPP Water Resources Report PgPage 5 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082.3 Well #52.3.1 Site DescriptionWell #5 (Figure 5) is located in the northeast corner of the Man Camp yard. Based uponthe structural geologic work conducted in the Phase I study, this site is located southeastof a throughgoing N75°E structure which may represent a hydrologic barrier, andtherefore the well likely encountered favorable aquifer materials with groundwaterproduction characteristics similar to Well #2. Also, because this monitoring well isrelatively close to Well #2, drawdown during the Well #2 pumping will be evident andthereby helpful in the aquifer analysis efforts.2.3.2 Well ConstructionWell #5 was drilled from October 28 to November 2, 2007 to a total depth of 409 ftbeneath ground surface. Unstable downhole conditions between 50 and 250 ft requiredconversion from air rotary drilling methods to bentonite mud-based drilling methods.Using drilling mud is a common solution to bedrock wells having unstable sections thatwon't stay open with the viscosity of water only. Water was first encountered at 45 fi, andstabilized to a static level of 40 ft. In consideration of the depth to water, and the interestin ensuring limited connectivity to Diablo Creek, the sanitary seal was constructed to 75 ftdeep. Blank PVC casing was installed from 75 to 100 ft; perforated PVC casing wasinstalled from 100-400 ft. By the time the total depth of drilling was reached, the wellwas naturally producing over 100 gpm, as evidenced by the flow resulting from the airinjection employed as part of the air-hammer drilling method.2.3.3 Well LoggingNear surface sediments encountered during drilling of Well #5 included both siltstonewith clay and/or sandy components as present at Well #4 and also a larger proportion ofpoorly-lithified sandstone beds (see State Well Drillers Report, Attachment B). Overall,the sediments in the upper 100 ft+ in this well were poorly consolidated which resulted inunstable hole conditions as mentioned above. Evidence of fracturing was present fromapproximately 50 feet and throughout the depth of the hole, and likely corresponds withthe structural geologic evidence from analysis of aerial photographs that this site is withina northeast-trending fracture system.DCPP Water Resources Report Page 6DCPP Water Resources ReportPage 6 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008gure 5. Photograph of Well #5.Geophysical logs run in the hole included electrical log (resistivity and spontaneouspotential), gamma, sonic velocity and temperature. Collectively, these logs illustrate thestratified nature of the formation and an increase in the proportion of sandstone-rich bedsin the upper and lower portions of the well. The indications provided by the e-logs arelargely corroborated with the lithologic monitoring conducted by ENTRIX during welldrilling.Initial stabilized water levels in the well were measured at approximately 80 ft deep.Confined aquifer conditions are evident based upon this static water level in relation to the250 ft depth to the top of slotted casing.DCPP Water Resources Report PgPage 7 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20082.3.4 Well Development and TestingWell #5 was developed for 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> following well construction, including severaliterations of surging and bailing at deep, medial and shallow portions of the well.Development was continued until the produced water was clear. Next, in an effort toestablish potential well yield, Well #5 was pumped for over two hours at a rate of 49gallons per minute, which resulted in a drawdown of approximately 9 ft (Figure 7). Basedon these data, the specific capacity of the well is approximately 5.9 gpm/ft of drawdown,which represents a higher specific capacity than that measured at Well #4. Based uponthis, albeit limited, production test, this well likely has a production capacity equal to orgreater than that of Well #2. Given that there are at least 300 feet of additional availabledrawdown, flow rates of 150 gpm may be possible if needed at a future date. Note thatthe initial recovery of the well's water level is illustrated in the graph to show the rapidwater level response when pumping stopped.For the second half of the test, the measured turbidity in the water was "0" (see Table 4)indicating that the well development was successful to remove turbid material from boththe drilling process and from the use of drilling mud.A water quality sample was also collected at Well #5 on November 10, 2007. Waterquality results are provided in Section 4 below.Based on this pumping test and water quality data, Well #5 has a higher specific capacityand better water quality than Well #4, and represents a more viable alternative if at afuture date conversion to a production well is needed. However, because Well #5 islocated near the existing Well #2, and approximately 9 feet of drawdown was observed atWell #5 during the pump test of Well #2, consideration and planning of the combineddrawdown effects is needed to adequately forecast the combined yield of the two wellsoperating together.DCPPWate Reourcs ReortPage 8 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Figure 6. Schematic diagram showing Well #5 construction and lithology.DCPP Water Resources Report Page 9DCPP Water Resources Report ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 4. Development of Well #5 (November 10, 2007).Easd Depth Electrical Triiy VlmTime Time to Conductivity Triiy Pumped_______Water(mini) (ft bgs) (NTU) (gallons)7:25 80_____7:30 0 80 ____7:50 20 85.3 1020 3.31 10008:10 40 86.35 962 1.65 20008:30 60 87.12 948 1.3 30008:50 80 88.31 943 1.2 40009:10 100 88.4 941 0 50009:30 120 88.41 935 0 60009:52 142 83.55 930 0 7000Well 5 Development and TestingI-79808182838485868788890 20 40 60 80 100 120 140 160Elapsed Time (min)Figure 7. Drawdown at Well #5 during development2007.and testing on November 10,DCPP Water Resources ReportPae1Page 10 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083. Well #2 Rehabilitation and Testing3.1 Well RehabilitationWell #2 was rehabilitated to provide a series of benefits such as increased reliability,potential for increased yield, and increased operating efficiency of the well. Withcessation of Diablo Creek diversions, the increased dependence upon groundwater can besupported by ensuring Well #2 is mechanically and physically sound.Well #2 was originally installed in 1985 to a total depth of 350 feet by Floyd V. Wells, Incof Santa Maria, California. The 10-inch diameter Schedule 200 PVC casing is perforatedfrom 90 ft bgs to total depth, with 0.040 full-flow horizontal-slot well screen.3.1.1 Results of Pump, Motor, and Column Pipe InspectionThe existing pump and motor on Well #2 were removed by Fisher Pump of Santa Maria,CA, under contract to Woodward Drilling Co. of Rio Vista, CA. The motor, pump andpump column although marginally operational all exhibited signs of wear and debilitationtypical of 20-year old equipment. It was determined that replacement of thesecomponents was in the best interest of DCPP and a greater reliability of the groundwatersupply produced by this facility.3.1.2 Video Log ResultsFollowing pump removal, a video logging tool was used to visually inspect the downholeconditions of Well #2. This video file provided evidence of the presence of encrustationof the well casing, mainly below 238 ft, and the existence of an approximately 20 ft thickpile of debris at the bottom of the well (Attachment C). Using these data, wellrehabilitation was recommended to include swabbing, brushing, air jetting and bailing.3.1.3 Description of Well Rehabilitation Tasks PerformedBased upon results of the video investigation, described above, the following steps wereperformed:* Bail out most of accumulated sediment from bottom of well.* Brush well with plastic-bristle brush to remove major areas of encrustation.* Additional sediment removed by bailing followed by air lifting.* Swab well with dispersant and detergent to clean casing encrustation andre-open clogged perforations.* Re-develop well with swab tool and conduct additional air lifting toremove all dispersant and suspended material.DCPP Water Resources ReportPage 11 ENTRIX, Inc.- Environmental and Natural Resource Management ConsultantsAugust 22, 20083.2 Spinner TestUpon completion of well rehabilitation work, velocity logging of the well was conductedby Pacific Surveys of Claremont, CA to determine the depth-distribution of groundwaterinflow into the well. This involves lowering a flow-metering logging tool into the welland pulling it up past the productive zones during active pumping. The relative inflowrates at the various depths of the well are evident from this effort and can provide valuableinformation if certain zones exhibit dominant flow rates and/or associated water qualityissues. The actual logs provided by the contractor are included as Attachment C.For the spinner test, the well was pumped at a rate of 90 gpm for 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> prior to andduring the survey. During the test; the pumping water level was 149 ft bgs. The results ofthe velocity logging, summarized in Table 5, indicate that there are two primaryproductive zones that produce over 90% of the flow into the well. The top loggedinterval, from the top of the perforations at 100 ft bgs to 158 ft bgs, producesapproximately 30% of the flow. This zone is underlain by an approximately 30-foot thicklow productivity zone. The most productive zone is located from 190-275 ft bgs.Water quality samples were collected at 158 ft bgs, 190 ft bgs, and 275 ft bgs. The pumpwas set at a depth of 160 ft bgs during this test, which is a fundamental considerationbecause the pump set-depth influences flow direction within the well, and this is animportant consideration for assessing the representativeness of depth-specific waterquality samples. Given the direction of flow within the well, the water quality samplecollected at 158 feet represents water from the 100-158 foot interval; the sample collectedat 190 feet represents water from the 190-275 foot flow zone; and water collected at 275 ftbgs represents the lowest flow zone sampled (275-3 50). Discussion of the water qualitysample analytical results is provided in section 4 below.Table 5. Well #2 Spinner Log Analysis[Flow Rate = 90 gpm1Zone Depths Production % of Flow Zones gpm/ft Thickness(ft bgs) (gpm) (t100-158 20 26% 0.34 58158-190 4 4% 0.13 32190-275 63 67% 0.74 85275-350 3 3% 0.04 75DCPP Water Resources ReportPae1Page 12 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083.3 Pump Tests for Evaluating Well YieldA series of diagnostic pumping tests were conducted to evaluate the Well #2 yield, as wellas its water quality. Results for these tests were used to establish the well's sustainableyield, specify a new submersible well pump and motor, evaluate if groundwater pumpingeffects flows in Diablo Creek, and assess groundwater water quality.A step drawdown test and a constant rate test were performed at Well #2 betweenNovember 20 and December 6, 2008 using a temporary test pump, installed at a depth of300 ft bgs. For over 4 weeks prior to this test, monitoring of water levels was conductedat Well #1, #2, and at the Diablo Creek facilities. Monitoring data was also collected atthe newly constructed Wells #4 and #5 soon after their respective completion dates.These data provide a trend and variation history of water levels at these various locationswhich is useful to establish the natural variability of these water resources in comparisonwith the stresses imposed by the pumping tests.A final pumping test was run in June and July, 2008 to provide specific data to evaluate ifgroundwater pumping affects water levels in Diablo Creek and also to comparegroundwater water quality between these two water bodies.3.3.1 Step Drawdown TestA step drawdown test was conducted to assess the Well #2 optimal and maximumpotential sustainable yields. This test involved pumping the well at a series of four (4)increasingly higher pumping rates for 60 minutes each. The graph of the drawdown andproduction data was used to determine the well's highest sustainable yield and also todetermine the optimal pumping rate for the multi-day constant rate test.On November 20, 2007, a step-rate test was conducted at the rehabilitated Well #2. Thepump set depth was 300 ft bgs. A total of 36,300 gallons were pumped during the courseof the test. The rates used in the test are provided below in Table 6.A graph of the results of the step drawdown test is provided in Figure 8. Drawdownstabilized during the two lower flow rate portions of the test, but not at the two higherflow rate portions. As is relatively common for wells producing from fracture systems ofa bedrock aquifer, extended time is needed at moderate to high flow rates to achievestabilized pumping water levels.In this well, during the 175 gpm pumping of Step 3, water levels continued to declinefrom 208.2 ft bgs after 5 minutes of pumping to 216 ft bgs after 58 minutes of pumping.It is possible, but not assured that the well could have stabilized its drawdown over alonger duration. Additionally, the well was unable to sustain the 215 gpm pumping ratefor Step 4, which is useful information to understand the upper limit of the well's potentialyield. The well recovered quickly after the pump was shut down. At the end of the step-rate test, the water level in the well was 268 ft bgs. The well achieved 90% recoveryDCPP Water Resources ReportPae1Page 13 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008within 10 minutes after pumping ceased and water levels in the well fully recovered inapproximately four (4) hours. Based upon these data, it was determined that a rate of 150gpm would be sustainable for the duration of the planned constant rate pump test.Table 6. DCPP Well #2 -Step Rate TestPumpingDate Start Time Rate_______ _______ (gpm)Step 1 11/20/2007 10:00 75Step 2 11:00 125Step 3 12:00 175Step 4 13:00 21513:03 21513:05 20513:10 20013:20 19513:40 195______________ 13:55 195Diablo Canyon Power Plant -Well 2 Step Drawdown Test4J00.100120140160180200220240260280300Start of Test:November 20, 2007 10:00 AM120 180 240 300360Elapsed Time (min)Figure 8. Graph of Step Drawdown Test at Well #2.DCPP Water Resources Report Page 14DCPP Water Resources ReportPage 14 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20083.3.2 Constant Rate TestsA constant rate pumping test was conducted at Well #2 starting at 14:30 on November 26,2007 and ending at noon on December 6, 2007. The static water level at Well #2 at thestart of the test was 112.7 ft bgs and the water level just before the pump was stopped was238.6 ft bgs. A total of 2,321,000 gallons were pumped during the 10-day constant ratetest at a relatively constant rate of 150 gpm. Based on these data, the specific capacity ofthe well is 1.2 gpm/ft of drawdown.As illustrated in Figure 9, the pumping water level at the well dropped steadily andstabilized at approximately 223 ft bgs by the second day of the test. Two additional,discrete steps in the drawdown occur at approximately 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> and at approximately 214hours. These are related to minor adjustments of the gate valve on the discharge pipe inan effort to re-establish the target pumping rate of 150 gpm. The well achieved 80%recovery within three (3) hours of the end of the constant rate test, and 94% recovery onweek later.Diablo Canyon Power PlantWell 2 Constant Rate Test100120140*} 160a- 180220S2402602803000 24 48 72 96 120 144 168 192 216 240 264 288 312Start of Test: Elapsed Time (hours)November 26, 200? 2:30 PMFigure 9. Water levels at Well #2 during the constant rate pumping test.336 360 384 408DCPP Water Resources ReportPae1Page 15 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008In addition to recording pumping water levels at Well #2, several other wells on theproperty and two surface water monitoring stations on Diablo Creek were monitoredbefore and during the constant rate test. A further discussion of water level monitoringresults at these monitoring stations is provided in Section 4.Water quality sampling was conducted during the test at the middle and just before shut-down. Results are provided and analyzed in Section 5.Collectively, these data indicate the firm reliability of Well #2 to produce 150 gpm on along-term basis under normal operating conditions. Currently, normal well operationsrequire the well to be operated at intervals of several hours per day. With the futuredecommissioning of the Diablo Creek diversion, an increased demand may be establishedon Well #2 for water supply. Based upon the results of these tests, Well #2 could beoperated at its design flow rate of 150 gpm for significantly longer periods per day whilestill maintaining acceptable margins of safety with respect to pumping water levels.Importantly, because of the limited rainfall in the years preceding this test, drought-typeconditions exist and the results of this testing can be considered representative of limitedwater availability conditions. Although not necessarily worst-case conditions, the yield ofthe well and response of the aquifer will not be any worse than that exhibited during thistest except during periods of even more extreme drought conditions. In a multi-yeardrought, if a greater amount of groundwater is needed than is produced from the wellunder its typical operating patterns, the well could be (a) run for more hours per dayand/or (b) retrofitted with a higher capacity pump set at a deeper level. Finally, duringperiods of higher rainfall and therefore more "average" water supply within the aquifer,the yield of the well as currently equipped will likely be greater and the associateddrawdown effects on the aquifer will be less.3.5 Pump SpecificationsUpon inspection, the condition of the pump, motor and column pipe were determined tobe sufficiently degraded to warrant replacement. A replacement pump, motor and columnpipe was specified, as described below. Installation and operability testing of thesecomponents was conducted on April 18, 2008 by Fisher Pump of Santa Maria, CA.Pump: Grundfos Submersible model # 150S 150-7Pump Serial Number: 07L 19-06-6129Motor: 15 hp FranklinMotor Protector: Franklin SubMonitorControl Panel: Siemens, Class 87Column Pipe: 300 ft of 4-inchProbe access tube: 1-inch PVC (300 ft)DCPP Water Resources ReportPae1Page 16 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084. Aquifer Response to Pumping TestThe response of the aquifer to pumping at Well #2 was evaluated using water level datacollected from Wells # 1, #4, and #5 during the constant rate pumping test conducted in2007. In addition, a second constant rate pumping test was conducted from June 25 toJuly 2, 2008 to evaluate the response of water levels in Diablo Creek to pumping waterfrom Well #2. As part of this analysis, groundwater and creek water level data werecollected before, during and after a test with contemporaneous measurements from thepumping well. Data collected during the 2008 pumping test were also compared with datafrom the 2007 pump test to further evaluate the aquifer response to pumping at Well #2.4.1 Monitoring LocationsWater levels at several wells and two surface water monitoring sites on Diablo Creek weremonitored before and during the constant rate tests at Well #2 (Figures 10 and 11). Inaddition, meteorological conditions were noted at the site and were also reviewed asavailable from the nearest gauging station, the Nipomo CIMIS station. The Nipomostation provides comprehensive data, but its inland setting records different climatologicconditions than the coastal conditions at DCPP.4.1.1 2007 Constant Rate Pumping TestDuring the first constant rate test water levels were monitored in Well #1, near DiabloCreek; Well #4, up the hill from Well #2; and Well #5, near the Man Camp. These wellswere outfitted with pressure transducer devices that automatically collected water leveldata at a programmed frequency of one measurement every 30 minutes.Data was also collected at two locations in Diablo Creek during this test. However, DCPPwater diversions from the creek during the pumping test created water level variations thatprevented determination of any relationship between pumping at Well #2 and creek flow.4.1.2 2008 Constant Rate Pumping TestWater levels at wells #1, #2, #4, and #5, and two surface monitoring sites on Diablo Creekwere monitored before and during the 2008 constant rate test. Wells #2 and #5 as well asthe two creek locations were monitored with pressure transducers that automaticallycollect and record water level data at programmed frequencies. Water levels in Well #1and Well #4 were measured manually with a water level meter just prior to the start of thetest and periodically during the pump test. For the duration of the pumping test,diversions from the Lower Weir pond were stopped.Diablo Creek water levels were monitored throughout the test at the Lower Weir andapproximately 1,000 feet downstream of the Lower Weir, before the creek enters aDCPP Water Resources ReportPage 17 ENTRIX, Inc. -Environ men tal and Natural Resource Management ConsultantsAugust 22, 2008drainage culvert. Where the stream enters the drainage culvert a notched wooden plankestablishes a small pool which flows into the drainage culvert.4.1.3 Effect of Constant Rate Pumping Test at Monitoring Wells4.1.3.1 2007 Constant Rate Pump TestWater levels in Monitoring Wells #1 and 4 did not show drawdown effects related topumping at Well #2 during the course of the constant rate pumping test (Figure 10). Thegreatest observed effect was approximately 9 feet of drawdown at Well #5, which is theclosest monitoring well to the pumping well, at a distance of approximately 250 feet.Water levels in Well #4 remained unchanged throughout the test. This is indicative ofboth the source of the Well #2 water being largely from aquifer zones that may not bephysically connected to Well #4, and also because the upgradient position and distance ofWell #4 relative to #2 minimizes the influence of the Well #2 drawdown.Water levels in Well #1 show a slight and very gradual rise that corresponds in timingwith the pumping at Well #2. This is likely related to the discharge point of the pumpedwater which occurred approximately 200 feet southwest of Well #1, and thereforeprobably induced recharge to the shallow, unconfined sediments in which Well #1 iscompleted.4.1.3.2 2008 Constant Rate Pump TestWater levels in Monitoring Wells #1 and #4 dropped from approximately 27.4 ft bgs and223 ft bgs, respectively, just before the test down to 31.8 ft bgs and 232.4 at the end of thetest (Figure 11). During the second constant rate test the discharge point of the pumpedwater was relocated to a point inside a drainage culvert which is downstream of allsampling locations. This a distinct difference in the response of Well #1 water levelsbetween the two constant rate tests.The water level in Well #5 dropped from approximately 80 ft bgs before the test toapproximately 98 feet just before the test was halted. This is greater drawdown ascompared with the 2007 test is a result of the higher Well #2 pumping rate maintainedduring the 2008 test which resulted in approximately :20 ft more drawdown in that well ascompared with the 2007 test.DCPP Water Resources ReportPae1Page 18 ENTRIX, Inc, -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels at Monitoring Wells During Well 2 Constant Rate Test10356085a. 110160185210235-24 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408Start of Test."November 26, 2007 2.30 PMElapsed Time (hours)Figure 10. Water levels in DCPP Wells during November 2007 constant rate test.4.1.4 Effect of Constant Rate Pumping Test at Surface WaterMonitoring LocationsA pumping test was conducted from 13:30 on June 25, 2008 to 13:45 July 2, 2008 toinvestigate any existing relationships betwveen water levels in Diablo Creek and pumpingwater from Well #2.Data were collected in both creek locations using pressure transducers automaticallyprogrammed to collect water level data. Data collection began on April 18, 2008 and wasterminated on July 3, 2008. An overall saw-tooth trend of declining water levels can beseen in the data set, consistent with a baseline-recession trend of a stream in transitionfrom the wet to dry season (Figure 1 2a).DCPP Water Resources ReportPae1Page 19 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008The data collected before the pumping test show correlations between water levels at theLower Weir and the culvert with frequent drops in water levels at the lower weir,presumably resulting from diverting water from the Lower Weir to the holding tanks on-Site. For the duration of the pumping test, diversions from the Lower Weir pond werestopped. The characteristic drop in water levels at the Lower Weir is not present and thewater levels at both creek sampling points follow the same trend (Figure 1 2b).Creek water level variability during the pump test is within the normal range captured inthe dataset. Approximately 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> into the pumping test, a water level drop ofapproximately 0.16 feet occurred. Because fluctuations of this magnitude over similartimescales are present in the non-pumping background data extending back to April 18,2008, this water level change is not related to the groundwater pumping. Additionally,when the pump test was terminated at 13:45 on July 2, 2008, water levels in the creekcontinue in a downward trend for approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> without a significant rebound orchange in water levels compared to levels seen over the duration of the test (Figure 12b).Based upon these test data, there is no evidence that creek water levels are affected bypumping at Well #2.DCPPWate Reourcs ReortPage 20 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels in Nearby Wells During 2008 Well#2 Constant Rate Test300250200S150,,0"10050024 48 72 96 120 144 168Elapsed Time (hours) --Well 2 --Well 5Well 4 -Well 1Figure 11. Water Levels in DCPP wells during June 2008 Constant Rate Test.DCPP Water Resources Report Page 21DCPP Water Resources ReportPage 21 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diablo Canyon Power PlantWater Levels at Diablo Creek During Well 2 Constant Rate Test1O00120140S1601802402260-70 60 50 40 30Elapsed Time (Days)Start Time: June 25, 2008 13.302.51.50.5-0.5-1CA0).000-25 15 5 0 5 10-Well 2 -----Well 5Well 2 PreTest Data Lower WeirFigure 12a. Water levels at pumping well and Diablo Creek locations (0 hour0 days <br />0 hours <br />0 weeks <br />0 months <br /> represents Test start on 6/25/08).DCPP Water Resources ReportPae2Page 22 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Diabio Canyon Power PlantWater Levels in Diablo Creek during Well #2 Constant Rate Test1001201401802020.2603.52.0"1.51 £0.500-0.5-1-3 1 0 1 2 3 4 5 6 7 8Start Time: June 25, 2008 13:30Elapsed Time (Days)-Well 2 --Lower Weir-CulvertFigure 1 2b. Water levels at pumping well and Diablo Creek locations focused on time period of test (0 hourrepresents Test start on 6/25/08).DCPP Water Resources ReportPae2Page 23 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2 Water QualityWater quality samples were collected at several intervals throughout the study period.Samples were collected at wells #4 and #5 during development and pumping tests.Multiple samples were collected at Well #2, as follows:* Three sets of paired discrete depth-specific and surface (composite)samples were collected during the spinner test;* Four samples were collected during the step test, near the end of eachpumping step;* Two paired samples from Well #2 and Diablo Creek Upper Weir werecollected at the mid-point and at the end of the first constant rate pumpingtest (December 3 and December 6, 2007); and,* Samples were collected at Well #2 and at Diablo Creek Lower Weir duringthe second constant rate pumping test (June 30, 2008).The water quality data were then reviewed to evaluate:* Similarity of the groundwater extracted from Well #2, Well #4 and Well #5to assist in future water resources planning decisions;* Water quality as a function of depth at Well #2; and,* Similarity of surface water and groundwater composition.A comprehensive series of tables listing all water quality data collected in this phase of theproject are provided in Attachment D of this report.4.2.1 Relative Water Quality of Wells #2, #4 and #5In general, constituent concentrations in the water extracted from Well #5 are similar tothose of the water extracted from Well #2 (Table 7). For most constituents,concentrations are lower at Well #5 than at Well #2. Water chemistry of Well #4 differssignificantly from that of Wells #2 and #5 for many of the constituents sampled. Waterfrom Well #4 is harder (it has a higher specific conductivity, and higher concentrations oftotal dissolved solids, alkalinity, bicarbonate, total hardness, calcium, chloride,magnesium, potassium, sodium, and sulfate) than Well #2. Water from Well #5 has alower concentration than Well #2 for all of these constituents.There are a few other notable differences in the water quality signature of the Well #4water. Water from Well #4 was the only groundwater sample that was found to have adetectable odor. Nitrate was detected in all groundwater samples except for the Well #4sample. The concentration of chromium at Well #4 was more than double the nexthighest concentration detected, as found at Well #2.DCPP Water Resources ReportPae2Page 24 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well #2 was the only well with detectable arsenic concentrations and Well #2 also hadsignificantly higher (by a factor of 4) nickel concentrations than Well #4 or #5, althoughboth nickel and arsenic were below detection limits in the samples collected on June 30,2008.Iron and aluminum concentrations are quite variable (by an order of magnitude) from wellto well, and among the various samples collected at Well #2. A more detailed review ofconcentrations of these constituents with regard to aquifer depth is provided in thefollowing section.Well #2 had the highest silica concentration of any of the wells (at 27 mag/I). Well #2 andWell #4 had concentrations ranging from 19-27 mg/I.DCPP Water Resources Report Page 25DCPP Water Resources ReportPage 25 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 7. Comparison of Well #4, Well #5 and Well #2 Composite SamplesWell #2 Well #2 Well #2 Well #2 Well #2 Well #2 Well #4 Well #5Composite 1 Composite 2 Composite 3Analyte Units PQL (Surface) (Surface) (Surface)11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 11/8/07 11/10/07___________15:40 15:50 16:05pH S.U. -6.6 6.7 6.7 6.9 6.5 7.3 6.6 6.9Color Color Unit 5 <5 <5 <5 <5 <5 <5 <5 <5MBAS Surfactants mg/L 0.1 BQL BQL BQL BQL BQL BQL BQL BQLOdor T.O.N. 1 ND ND ND ND ND ND 2 NDSpec. Conductivity umhos/cm 1 1300 1300 1290 1280 1270 1200 1610 1050T.D.S. mg/L 10 790 790 790 760 780 810 1020 640Turbidity N.T.U. 0.1 4.5 0.69 1.4 0.39 0.4 0.1 1.4 1.8Nitrate (as N) mg/L 0.1 0.2 0.2 0.2 0.3 0.5 0.1 BQL 0.2Alkalinity (CaCO3) mg/L 10 410 400 410 390 390 400 520 380Bicarbonate(CaCO3) mg/L 10 410 400 410 390 390 400 520 380Carbonate (CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQLHardness (as CaCO3) mg/L 10 520 510 520 580 560 590 710 440Hydroxide (as CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQLAluminum ug/L 5 170 46 100 5.8 BQL 52 120Antimony ug/L I BQL BQL BQL BQL BQL BQL BQLArsenic ug/L 0.5 2.2 1.8 2 0.66 BQL BQL BQLBarium ug/L 0.5 30 27 28 38 BQL 33 30Beryllium ug/L 0.5 BQL BQL BQL BQL BQL BQ BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQLCalcium mg/L 0.1 97 94 95 120 110 120 150 90Chloride mg/b 0.2 100 100 100 94 95 91 120 69Chromium ug/L 1 2.8 1.7 1.9 1.3 BQL 6.1 2.2Copper mg/b 0.02 BQL BQL BQL 0.024 BQL BQL BQ BQLFluoride mg/b 0.1 0.4 0.4 0.4 0.5 0.5 0.7 0.3 0.4DCPP Water Resources ReportPae2Page 26 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 7. Comnarisnn nf Well #4. Well #.5 and Well #2 (ennt'd.AWell #2 Well #2 Well #2 Well #2 Well #2 Well #2 Well #4 Well #5Composite 1 Composite 2 Composite 3Analyte Units PQL (Surface) (Surface) (Surface)11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 11/8/07 11/10/07______________15:40 15:50 16:05______ ____Iron mg/L 0.1 0.71 0.12 22 BQL BQL BQL 0.13 0.11Lead ug/L 0.5 1.5 0.63 0.62 BQL BQL 0.65 BQLMagnesium mg/b 0.1 61 60 60 70 68 69 91 57Manganese mg/b 0.005 0.041 0.017 0.018 0.028 0.026 0.02 0.015 0.021Mercury ug/L 0.5 BQL BQL BQL BQL BQL BQ BQLNickel ug/b 1 9.5 8.2 8.5 7.8 BQL 1.5 2.6Potassium mg/b 0.2 2.7 2.7 2.7 2.9 2.8 3.1 8.2 2.3Selenium ug/b 1 2.7 2.1 2.4 3.2 BLQL15Silica mg/L 20 20 19 _ ___ ____ 27 20 25Silver ugiL 0.5 BQL BQL BQL BQL BQL BQ BQLSodium mg/b 0.5 70 69 68 53 50 63 83 51Sulfate mg/b 0.5 140 150 150 160 170 150 210 87Thallium ug/L 0.5 BQL BQL BQL BQL BQ BQ BQLZinc mg/b 0.05 0.15 0.11 0.11 0.43 0.32 0.32 0.2 0.34DCPP Water Resources Report Page 27DCPP Water Resources ReportPage 27 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2.2 Well #2 -Water Quality vs. DepthThree pairs of depth-specific and composite water quality samples were collected at Well#2 during the velocity logging of the well conducted on November 15, 2007. Thesediscrete depth samples provide an opportunity to evaluate water quality from specificdepths within the aquifer and to determine whether changes in pumping practices and/orchanges to well construction parameters may be appropriate for improving the quality ofthe pumped water.Water quality samples were collected at 158 ft bgs, 190 ft bgs, and 275 ft bgs. The pumpwas set at a depth of 160 ft bgs during this test. Because the pump set depth influencesflow direction within the well, this is an important consideration for assessing therepresentativeness of depth-specific water quality samples. Given the direction of flowwithin the well, the water quality sample collected at 158 feet represents water from the100-158 foot interval (which represents approximately 26% of the flow into the well); thesample collected at 190 feet represents water from the 190-275 foot interval (whichproduces approximately 66% of the flow into the well); and water collected at 275 ft bgsrepresents the deepest zone in the well from 275-350 ft bgs (which representsapproximately 3% of the flow in the well).Based upon these data (Table 8), the shallow productive zone (from 100-158 feet bgs) hassubstantially higher turbidity and higher concentrations of silica, total dissolved solids,nickel, aluminum and iron than the deeper productive zone (190-275 ft bgs). Figures 12aand 12b below illustrate these values. Arsenic and bicarbonate concentrations are slightlylower in the shallow productive zone as compared to the deeper productive zone. Forother constituents sampled, concentrations do not differ significantly between these twoproduction zones.Considering these water quality differences between the uppermost zone and the lowerzones, economic analysis may be needed to determine the costs and benefits of specificwell construction modifications to isolate zones. If in the future one or more of theseconstituents adversely affects the water treatment operations, well modificationapproaches can be considered. First, a temporary packer could be installed to prevent theshallowest zone of poor water quality groundwater from entering the well. This device isan elongated, thick-rubber balloon that is attached to a section of column pipe and can beinflated or deflated using an air value at the wellhead. Materials and installation for thisdevice would cost approximately $10,000. Second, the well screen adjacent to theshallowest zone of poor water quality groundwater could be permanently sealed withcement. This is a more complex operation than installation of the packer but is stillviable. This approach has a similar cost to the packer option, but has an advantage ofbeing a permanent solution, whereas the packer may need to be rehabilitated or replacedevery 5 to 10 years.DCPPWate Reourcs ReortPage 28 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008In both cases, the well's produced water quality would improve and its drawdown wouldincrease to maintain the target flow rate of 150 gpm. Because the pump operates at afixed rate, the well would operate at a flow rate approximately 10-20 gpm less and from apumping water level of approximately 5 to 10 feet deeper.Well 2 -Concentration vs. Depth100120140'" 160180G'2005220240260280300Conce ntrationFigure 1 3a. Constituent concentrations as a function of depth at Well #2.DCPP Water Resources Report Page 29DCPP Water Resources ReportPage 29 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Well 2 -Concentration vs. Depth100120140'~160.01804-* 200.=2200.240 -*--- Alkalinity (CaCO3)260 Bicarbonate (CaCt-0-Alurninum (ugi)260 -Chloride (rngl)3000 100 200 300 400 500 600 700 800 900 1000ConcentrationFigure 1 3b. Constituent concentrations as a function of depth at Well #2.DCPP Water Resources Report Page 30DCPP Water Resources ReportPage 30 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Tahle 8. Well #~2 Denth-Sneeifie Water Ouialitv Cornposite 1 Discrete 1 Composite 2 Discrete 2 Composite 3 Discrete 3(Surface) (275 Ft.) (Surface) (190 Ft.) (Surface) (158 Ft.)nayeUis PL 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07________________15:40 _______ 15:50 16:05Depth (or Pumping Water Level) _____275 190 158-pH S.U. -6.6 6.9 6.7 6.8 6.7 6.7Color Color Unit S <5 <5 <5 <5 <5 <5MBAS Surfactants mg/L 0.1 BQL BQL BQL BQL BQL BQLOdor T.O.N. 1 ND ND ND ND ND NDSpec. Conductivity umhos/cm 1 1300 1420 1300 1340 1290 1300T.D.S. mg/L 10 790 860 790 800 790 810Turbidity N.T.U. 0.1 4.5 4.7 0.69 3.6 1.4 7Alkalinity (CaCO3) mg/L 10 410 440 400 420 410 400Bicarbonate(CaCO3) mg/L 10 410 440 400 420 410 400Carbonate (CaCO3) mg/b 10 BQL BQL BQL BQL BQL BQLHardness (as CaCO3) mg/L 10 520 530 510 520 520 530Hydroxide (as CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQLAluminum ug/L 5 170 240 46 110 100 300Antimony ug!L I BQL BQL BQL BQL BQL BQLArsenic ug/L 0.5 2.2 4 1.8 2.5 2 1.4Barium ug/L 0.5 30 26 27 27 28 35Beryllium ug/L 0.5 BQL BQL BQL BQL BQL BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQLCalcium mg/L 0.1 97 95 94 96 95 100Chloride mg/L 0.2 100 120 100 110 100 110Chromium ug/L 1 2.8 6.4 1.7 4.3 1.9 4.3Copper mg/b 0.02 BQL 0.037 BQL BQL BQL BQLFluoride mg/b 0.1 0.4 0.5 0.4 0.4 0.4 0.5DCPP Water Resources Report Page 31DCPP Water Resources ReportPage 31 TbeNT.RWel #2 Det-SEvionentalc anWaturQalit Resource MangemntCnsltntTable 8. Well #2 Depth-Specific Water Quality Results (cont'd.)Well 2 Well 2 Well 2 Well 2 Well 2 Well 2Composite 1 Discrete 1 Composite 2 Discrete 2 Composite 3 Discrete 3Analyte Units PQL (Surface) (275 Ft.) (Surface) (190 Ft.) (Surface) (158 Ft.)11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07_______________15:40 15:50 ______ 16:05Depth (or Pumping Water Level) _____________ 275 190 158Iron mgiL 0.1 0.71 0.73 0.12 0.43 22 62Lead ug/L 0.5 1.5 0.78 0.63 0.99 0.62 1Magnesium mg/L 0.1 61 64 60 62 60 69Manganese mg/L 0.005 0.041 0.056 0.017 0.03 0.018 0.0087Mercury ug/L 0.5 BQL BQL BQL BQL BQL BQLNickel ug/L 1 9.5 16 8.2 8.9 8.5 11Potassium mg/L 0.2 2.7 3.2 2.7 3.1 2.7 2.1Selenium ug/L 1 2.7 3.2 2.1 2.2 2.4 6Silica mg/L ___ 20 22 19 20 19 24Silver ug/L 0.5 BQL BQL BQL BQL BQL BQLSodium mg/b 0.5 70 100 69 80 68 59Sulfate mg/L 0.5 140 150 150 150 150 160Thallium ug/L 0.5 BQL BQL BQL BQL BQL BQLZinc mg/L 0.05 0.15 0.07 0.11 0.069 0.11 0.099Total Sulfide mg/L __Ammonia (as N) mg/b 0.1 _____Nitrate (as N) mg/L 0.1 0.2 BQL 0.2 BQL 0.2 0.9Nitrate (as NO3) mg/b 1_________________________________________o-Phosphate-P mg/b 0.05 _______T.K.N. mg/b 1 _________DCPP Water Resources Report Page 32DCPP Water Resources ReportPage32 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 20084.2.3 Comparison of Surface Water and GroundwaterCornpositionA significant aspect of this study is to determine if a connection exists betweengroundwater from the existing DCPP production well and surface water in Diablo Creek.In addition to reviewing water level data during the pumping tests in an effort to detecttrends that might indicate a significant connectivity between the extracted groundwaterand the Creek, water quality data were reviewed to assess if any connectivity existsbetween the surface water and the shallow groundwater production zone.Two methods are used to review the water quality data that were collected from Well #2and the creek. The first is the comparison of paired water quality samples collected at thepumping well and at the creek on December 3, 2007, December 6, 2007 and June 30,2008 (Table 9). For these sampling dates which occurred during the constant ratepumping tests at Well #2, samples were collected contemporaneously, so as to provide aninstantaneous snapshot of water quality at both locations for comparison purposes.The second method used to examine the water quality data for trends that indicate thedegree of connectivity between extracted groundwater at Well #2 and the Creek was tocompare the depth-specific water quality samples collected at Well #2 with water qualitysamples collected at the Upper Creek sampling site (Figure 14a and Figure 14b, below).If there is a significant degree of connectivity between water in the upper productive zoneof Well #2 and surface water, it would be expected that the shallowest water qualitysample collected from the well could have a geochemical composition similar to that ofthe surface water sample for a number of constituents (or more similar to the surface waterthan that of the deeper groundwater).The most definitive result of this water quality comparison is the considerable variation inseveral key constituents, such as TDS, Chloride, Sodium, Iron, which are all substantiallylower in concentration in the creek water than in groundwater. The difference is evidentin comparison to both the various composite well samples as well as the depth-specificsamples. The water quality difference evident in these constituents, most of which aregenerally considered "conservative" (i.e., they do not tend to vary with time or reactionsin the subsurface), is diagnostic of largely if not entirely different water source. As oneline of evidence, these data indicate limited, if any, connection between the groundwaterpumping at Well #2 and creek flows.Also, the presence of bacteria (Total Coliform and E Coli) in the creek water and itsabsence in well #2 water (although the Total Coliform results from the December 6, 2007well sample was "present" but this could be a contaminated sample and thereforeanomalous), is additional corroboration that groundwater pumping at Well #2 is notdirectly extracting water from the creek.DCPP Water Resources Report Page 33DCPP Water Resources ReportPage 33 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 9. Water Quality in Diablo Creek Compared to Groundwater ___Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Well 2 Upper Upper CulvertWeir WeirDiscrete 1 Composite Discrete 2 Discrete 3Analyte Units PQL Composite 1 (7Ft) 2(9F.) Composite 3 (158 Ft.)11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 11/15/07 12/3/07 12/6/07 6/30/08 12/3/07 12/6/07 6/30/0815:40 15:50 16:05pH S.U. -6.6 6.9 6.7 6.8 6.7 6.7 6.9 6.5 7.3 8.2 7.9 8.2Color Color Unit 5 <5 <5 <5 <5 <5 <5 <5 <5 <5 10 10 30Spec. Conductivity umhos/cm 1 1300 1420 1300 1340 1290 1300 1280 1270 1200 870 870 860T.D.S. mgfL 10 790 860 790 800 790 810 760 780 810 530 540 540Turbidity N.T.U, 0.1 4.5 4.7 0.69 3,6 1.4 7 0.39 0.4 0.1 2.1 2 9.5Alkalinity (CaCO3) mg/L 1 0 410 440 400 420 410 400 390 390 400 350 340 370Bicarbonate(CaCO3) mg/L 10 410 440 400 420 410 400 390 390 400 350 340 360Carbonate (CaCO3) mg/L 10 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL 10Hardness (as mg/L 10 520 530 510 520 520 530 580 560 BQL 430 430 420CaCO3)Hydroxide (as mg/'L 10 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLCaCO3) ____Aluminum ug/L 5 170 240 46 110 100 300 5.8 BQL 63 0.25Arsenic ug/L 0.5 2.2 4 1.8 2.5 2 1.4 0.66 BQL 2.1 BQLBarium ug/L 0.5 30 26 27 27 28 35 38 BQL 57 BQLCadmium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL 0.61 0.001Calcium mg/L 0.1 97 95 94 96 95 100 120 110 120 99 89 90Chloride mg/L 0.2 100 120 1 00 110 100 110 94 95 91 33 33 33Chromium ug/L 1 2.8 6.4 1,7 4.3 1.9 4.3 1.3 BQL 1.7 BQLCopper mg/L 0.02 BQL 0.037 BQL BQL BQL BQL 0.024 BQL BQL BQL BQL BQLFluoride mg/L 0.1 0.4 0.5 0.4 0.4 0.4 0.5 0.5 0.5 0.7 0.3 0.3 0.4Iron mg/L 0.1 0.71 0.73 0.12 0,43 0.22 0.62 BQL BQL BQL BQL 0.00011 0.27Lead ug/L 0.5 1.5 0.78 0.63 0.99 0.62 1 BQL BQL BQL BQLMagnesium mg/L 0.1 61 64 60 62 60 69 70 68 69 54 50 47Manganese mg/L 0.005 0.041 0.056 0.017 0.03 0.018 0.0087 0.028 0.026 0.02 BQL BQL BQLDCPP Water Resources ReportPage 34 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsAugust 22, 2008Table 9. Water Quality in Diablo Creek Compared to Groundwater (cont'd.)Nickel ug/L 1 9.5 16 8.2 8.9 8.5 11 7.8 BQL 11 0.01Potassium mg/L 0.2 2.7 3.2 2.7 3.1 2.7 2.1 2.9 2.8 3.1 2.9 2.6 2.5Selenium ug/L 1 2.7 3.2 2.1 2.2 2.4 6 3.2 BQL 1.2 BQLSilica mgIL 20 22 19 20 19 24 24 23 27 31l 29 33Silver ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLSodium mg/L 0.5 70 100 69 80 68 59 53 50 63 22 19 23Sulfate mg/L 0.5 140 150 150 150 150 160 160 170 150 88 89 82Thallium ug/L 0.5 BQL BQL BQL BQL BQL BQL BQL BQL BQL BQLZinc mg/L. 0.05 0.15 0.07 0.11 0.069 0.11 0.099 0.43 0.32 0.32 0.13 0.065 BQLNitrate (as N) mg/IL 0.1 0.2 BQL 0.2 BQL 0.2 0.9 0.3 0.5 0.1 BQL BQL BQLE. Coli _____ absent absent present presentTotal Coliform present absent present presentDCPP Water Resources Report Page 35DCPP Water Resources ReportPage 35 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsMay 23, 2008Well 2 -Depth-Specific Samples and Creek Samples-101540I6590115140165190215240265;290ConcentrationFigure 1 4a. Constituent concentrations as a function of depth at Well #2 and Diablo Creek.Well 2 -Depth-Specific Samples and Creek Samples--Alkalinity (CaC;O3) (mgl)140 -NE Bicarbonate (CaCO3) (nrigl)--Aluminum (ugi)165 -a-Chloride (ngl)(6 -Creek-TDS215 A Creek-Alkalinity:: Creek-Bicarbonate* Creek-Alurrinum265 A Creek -Chloride*Cr'ee k-k-on0 100o 200 300 400 500 600 700 800 900 1000Conce ntra tionFigure 14b. Constituent concentrations as a function of depth at Well #2 and Diablo Creek.DCPP Water Resources Report Page 36DCPP Water Resources ReportPage 36 ENTRIX, Inc. -Environmental and Natural Resource Management ConsultantsMay 23, 20084.2.4 Summary of Water Quality ResultsDepth-specific water quality testing indicates that the water extracted from the deepproduction zone is higher quality (i.e., generally lower in constituent concentrationsimportant to plant operations) than water extracted from the shallow production zone. Inorder to reduce concentrations of certain constituents in extracted groundwater, such assilica, the upper screened portion of Well #2 could be temporarily or permanently sealed.Doing so would improve the quality of pumped groundwater from Well #2. However,this upper productive zone represents approximately 20% of the flow in the well and ifthis portion of the well is sealed, DCPP can expect a 10-20 gpm reduction in groundwaterproduction.The presence of a series of diagnostic constituents with significantly differentconcentrations in Diablo Creek compared with Well #2 groundwater represents a strongline of evidence that groundwater pumping does not draw from Diablo creek.DCPP Water Resources Report Page 37DCPP Water Resources ReportPage 37