ML12128A161
| ML12128A161 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/12/2012 |
| From: | Macmanus R Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 12-212 | |
| Download: ML12128A161 (14) | |
Text
Dominion Nuclear Connecticut, Inc.
Millstone Power Station 9iDominion-Rope Ferry Road Waterford, CT 06385 APR 12 2012 U.S. Nuclear Regulatory Commission Serial No.12-212 Attention: Document Control Desk MPS Lic/GJC RO Washington, DC 20555-0001 Docket No. 50-423 License No. NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 3 2011 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT In accordance with Section 5.4.1 of the Environmental Protection Plan (EPP), Appendix B to the Millstone Power Station Unit 3 Operating License, Dominion Nuclear Connecticut, Inc. hereby submits the Annual Environmental Protection Plan Operating Report (AEPPOR), describing implementation of the EPP for the previous year. transmits information for the period of January 1, 2011 to December 31, 2011.
Should you have any questions regarding this report, please contact Mr. William Bartron, at (860) 444-4301.
Sincerely, R. K. MacManus Director, Nuclear Station Safety and Licensing C-
Serial No.12-212 2011 Annual Environmental Protection Plan Operating Report Page 2 of 2
Enclosures:
1 Commitments made in this letter: None.
cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 J. S. Kim NRC Project Manager - Millstone Power Station Units 2 and 3 U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 C2A Rockville, Maryland 20852-2738 NRC Senior Resident Inspector Millstone Power Station
Serial No. 12-21 2 Docket No. 50-42 3 License No. NPF-,19 Enclosure 1 MILLSTONE POWER STATION UNIT 3 2011 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT JANUARY 1 - DECEMBER 31. 2011 MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)
2011 Annual Environmental Protection Plan Operating Report (AEPPOR) 1.
Introduction:
This report covers the period January 1, 2011 through December 31, 2011. During 2011, Millstone Power Station Unit 3 (MPS3) completed refueling outage 3R14 (October 8 - November 23). Since the refueling outage (through December 31, 2011), MPS3 has operated at a capacity factor of 97.6%; overall capacity for 2011 was 87.6%.
As required by the MPS3 Environmental Protection Plan (EPP), Appendix B to the MPS3 Operating License, this AEPPOR includes:
" summaries and analyses of the results of environmental protection activities,
- a list of EPP noncompliances,
- a list of all changes in station design or operation which involved a potentially significant unreviewed environmental question, and
- a list of non-routine reports, describing events that could have resulted in significant environmental impact.
- 2. Environmental Protection Activities:
2.1 Annual National Pollutant Discharge Elimination System (NPDES) Report of Ecological Monitoring (EPP Section 4.2).
Section 10(A) of Millstone Power Station's (MPS) NPDES permit, as issued to Dominion Nuclear Connecticut, Inc. (DNC) by the Connecticut Department of Environmental Protection (now the Department of Energy and Environmental Protection, or DEEP) on September 1,2010 (the Permit),
requires continuation of biological studies of supplying and receiving waters, entrainment, and intake impingement monitoring. These studies include analyses of intertidal and subtidal benthic communities, finfish communities, entrained plankton, lobster populations, and winter flounder populations.
Section 10(A)(2) of the Permit requires an annual report of these studies to be sent to the DEEP Commissioner on or before July 3 1st of each year. The latest report that fulfills these requirements, "Annual Report 2010 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut" (Annual Report), presents results from studies performed during construction and operation of MPS, emphasizing those of the latest sampling year. Changes to the biological communities noted in these studies are summarized in the Executive Summary section of the Annual Report, which is attached as part of this report.
2.2 Effluent Water Quality Monitoring:
Sections 1 and 5 of the Permit require monitoring and recording of various water quality parameters at MPS intakes and at multiple monitoring points within the plant, including outfalls of each unit to the effluent quarry, and outfall of the quarry to Long Island Sound. Section 8 of the Permit requires that a monthly report of this monitoring be submitted to the DEEP. The report that fulfills these requirements, the "Monthly Discharge Monitoring Report" (DMR), includes discharge data from all MPS units. Consistent with prior 2011 AEPPOR Page 1 of 4
annual AEPPOR submissions, water flow, temperature, pH, and chlorine data pertaining to MPS3 are summarized in Table 1.
Each monthly DMR identifies NPDES permit exceedances (i.e., events where a parameter value was beyond permitted limits) or exceptions (i.e., events where Permit conditions were not met) for the month. During 2011, there were no MPS3 events that were reported as NPDES exceedances. However, one event, although originating at Millstone Power Station Unit 2 (MPS2),
involved a discharge point that is shared by MPS3, and is included for information; the description below is summarized from the monthly DMR for May.
a) MPS2 and MPS3 Non-ContaminatedFloorDrains (DischargeSerial Number (DSN) 006)
On May 4, 2011 at 1904 hours0.022 days <br />0.529 hours <br />0.00315 weeks <br />7.24472e-4 months <br />, the MPS3 Control Room received a computer priority alarm from the continuous pH monitor associated with DSN 006. The pH reading recorded at the time was 8.52 standard units (su). The alarm set point is 8.5 su. DSN 006 is an outfall at MPS, discharging both process water from the plant, and surface water runoff from the yard drain system. Station Chemistry was dispatched to the monitoring point and verified through the grab sample analysis at 1912 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.27516e-4 months <br /> that the pH had exceeded the Permit limit of 6.0 to 9.0 su. The grab sample result was 9.15 su. At no time during the entire event did the continuous pH monitor associated with DSN 006 exceed the Permit limit, with a highest recorded pH of 8.96 su.
Subsequent pH samples obtained at key inputs to DSN 006 discharge traced the source of the high pH back to the MPS2 East Turbine Building (TB) Sump. During this time, MPS2 was in the process of returning to 100% power after a scheduled refueling outage that ended on May 2, 2011. Earlier in the day, to further enhance condenser vacuum, MPS2 had shifted from the mechanical vacuum pump system to the steam jet air ejector system ("A" train). Initially, the steam trap drain line for the steam jet air ejector (which was later to be discovered to have a faulty steam trap) was aligned to the East TB sump instead of the condenser, as permitted by procedure. An initial pH reading in the East TB sump yielded result of 10.33 su, and at 1948 hours0.0225 days <br />0.541 hours <br />0.00322 weeks <br />7.41214e-4 months <br />, the associated sump pump was removed from service. To make room in the isolated sump, Operations personnel commenced pumping the East TB sump to totes, with a total of eight totes (approximately 275 gallons each) filled. At 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br />, Operations removed from service the "A" steam jet air ejector and placed into service "B" steam jet air ejector. The apparent leakage to the East TB sump was reduced substantially.
After removing the East TB sump from discharging to DSN 006, and allowing for accumulated waters in the yard drain system to slowly drain to DSN 006, the pH gradually returned to its normal range of approximately 7.0 - 7.2 su by 2300 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.7515e-4 months <br />. On May 5, 2011, based on updated pH results of the East TB sump, the East TB sump was placed back into service for discharge to DSN 006. Additionally, after testing each of the 2011 AEPPOR Page 2 of 4
totes for pH, a determination was made to drain four of the totes back to the MPS2 East TB sump and to process the other four totes for offsite disposal.
The root cause evaluation of this event determined that "system design" does not prevent high pH system water from draining to DSN 006, given that the steam trap associated with the steam jet air ejector had failed during startup of the system, leading to excessive amount of elevated pH (greater than 9.0 su) water to be directed to the East TB sump, and ultimately to DSN 006. Corrective actions for this event include enhancing procedures when starting up the steam jet air ejectors to check for excessive leakage and, if found, to remove the MPS2 East TB sump from discharging to DSN 006; additionally, the MPS3 priority alarm procedure is to be enhanced to ensure all priority alarm notifications are made to the responsible departments in a timely manner.
- 3. Environmental Protection Plan (EPP) Noncompliances:
No EPP noncompliances were identified for MPS3 in 2011.
- 4. Environmentally Significant Changes to Station Design or Operation:
No MPS3 design change records or system operating procedure changes met the criteria for inclusion in this report, i.e.,
- No changes were initiated during the report year, or
" No changes included a determination that a significant unreviewed environmental impact could occur.
- 5. Non-Routine Reports of Environmentally Significant Events:
No MPS3 events met the criteria for inclusion in this year's report, i.e.,
" No events required the submittal of a Licensee Event Report (LER), or
" No events involved a situation that could result in a significant environmental impact.
Only three licensee events that constituted a reportable occurrence at MPS3 occurred in 2011; none were determined to cause a significant environmental impact.
2011 AEPPOR Page 3 of 4
Table 1.
MPS3 NPDES data summary, Jan 1-Dec 31, 2011. Selected water quality parameters for MPS3(1 ).
Discharge Discharge Discharge Discharge Avg Max Max Max Flow pH Temp. Temp. AT FAC TRC SwS (max) Range Range (avg) (OF) (ppm) (ppm) FAC (OF) (ppm)
(106 gpd) (OF)
Jan. 1360.6 7.8 - 8.1 54.5 - 64.2 58.5 21.2 0.10 0.04 0.20 Feb. 1362.4 7.9 - 8.1 52.6 - 67.7 56.8 21.1 0.11 0.02 0.17 Mar. 1362.5 7.5-8.1 53.5 - 64.1 57.9 18.9 0.08 0.02 0.18 Apr. 1360.4 7.6 - 8.1 56.9 - 77.2 69.3 25.5 0.08 0.03 0.22 May 1360.0 7.8 - 8.1 69.4 - 85.3 74.0 21.9 0.10 0.03 0.20 June 1361.1 7.3-8.5 60.3 - 85.1 78.9 17.6 0.07 0.03 0.18 July 1361.9 7.8 - 8.1 80.6 - 89.0 84.9 16.9 0.06 < 0.02 0.20 Aug. 1361.4 7.7-8.1 81.1 -92.7 87.1 17.2 0.08 0.02 0.22 Sep. 1359.9 7.8 - 8.7 84.4 - 89.8 86.8 18.4 0.07 0.03 0.22 Oct. 1360.4 6.7-8.1 54.3 - 86.9 69.0 6.5 0.09 < 0.02 0.17 Nov. 1350.7 7.6 - 8.1 53.4 - 75.5 60.0 5.5 0.07 0.02 0.19 Dec. 1352.3 7.9 - 8.1 65.9 - 79.0 70.5 18.9 0.08 < 0.02 0.19 Notes:
(1) Parameters are measured at MPS3 discharge (DSN 001C), except for TRC (total residual chlorine), which is measured at MPS discharge (quarry cuts; DSN 001-1),
and SWS FAC (service water system free available chlorine; DSN 001C-5).
Abbreviations Used:
Temp. = Water Temperature AT = Delta-T (difference between discharge and intake water temperature)
FAC = Free Available Chlorine TRC = Total Residual Chlorine SWS = Service Water System 2011 AEPPOR Page 4 of 4
Attachment to the 2011 Annual Environmental Protection Plan Operating Report January 1 - December 31, 2011 Executive Summary Section of "Annual Report 2010 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut" dated July 2011
Executive Summary - 2010 Environmental Monitoring Annual Report Winter Flounder Studies In 2010, overall abundance of winter flounder larvae in the Niantic River was Various life history stages of winter the fifth lowest since 1983 and the Niantic flounder have been monitored since 1976 Bay abundance index was the third lowest to determine what effect, if any, Millstone for the same time series. In most years Power Station (MPS) may have on the since 1995, more Stage 1 larvae were local Niantic River population, particularly found than expected from low adult through the entrainment of larvae. During spawner abundance, suggesting a the past 29 years, annual Niantic River density-dependent compensatory adult winter flounder abundance mechanism during the egg stage that represented an estimated 0.4 to 3.3% of enhanced survival. Density-dependent the total LIS winter flounder resource mortality occurs throughout the larval (mean = 1.34%). Over the past 16 years, period of life. An analysis suggested that low winter flounder abundance levels have mortality decreases with decreasing egg been found throughout Long Island Sound production (a measure of early larval (LIS) by the Connecticut Department of abundance). Larval mortality is also Environmental Protection (CTDEP). influenced by prevailing water During the same time period, adult winter temperatures, with warmer springs flounder abundance in the Niantic River allowing for faster development and lower has remained low. Reflecting these mortality. In 2010, Stage 2 larval trends, catch-per-unit-effort (CPUE) in abundance was particularly low, indicating 2010 was 0.3 fish per trawl tow, tied with high mortality in that stage. In each of the 2009 as the smallest value of the time- past 3 years, both egg production and series. Stage 1 larval abundance were low as An absolute abundance estimate of the were the numbers of metamorphosing 2009 spawning population (the latest year larvae. However, relative to the Niantic for which an estimate could be made) River, larval abundance in Niantic Bay has using the Jolly model was not calculated increased in recent years, suggesting due to a lack of recaptures of previously higher production in LIS rather than in marked fish. Similarly, a lack of estuaries such as the Niantic River.
recaptures in 2007 precluded an absolute Densities of age-0 young in the Niantic abundance estimate in 2008. The last River following larval metamorphosis and three absolute abundance estimates from settlement were linearly related to Stage 4 2004 to 2007 were imprecise, having large larval abundance at low to moderate 95% confidence intervals, and are not levels. However, at higher larval considered reliable. abundance juvenile densities apparently Using another methodology termed reached an asymptote of about 250 young standardized catch, female spawner per 100 m 2 of bottom, which could abundance in 2010 was estimated at only represent the carrying capacity of the river 801 fish that produced about 428 million habitat. As expected from low larval eggs. Previous annual standardized catch abundance in 2010, initial settled juvenile estimates ranged from approximately 323 abundance was very low.
females in 2009 to 77 thousand in 1982 The number of larvae entrained at MPS and corresponding total egg production is a measure of potential impact to winter estimates were 0.2 to 44.8 billion. flounder. In most years, Stage 3 larvae dominated entrainment collections. Annual
estimates of entrainment are related to young fish in several recent years, both larval densities in Niantic Bay and probably from population compensatory MPS cooling-water volume. With Unit 3 in mechanisms and possibly greater a spring refueling outage in 2010, the contributions from spawners outside of the 2010 entrainment estimate of 56.1 million Niantic River. Relatively good abundance reflected low Niantic Bay larval densities. of age-0 winter flounder (a life stage not Annual entrainment density (abundance entrained) occurred in some recent years, index divided by total seawater volume) yet significant recruitment to the adult has varied without trend since 1976, spawning population did not occur.
indicating that larval production and Processes that are unrelated to MPS availability in Niantic Bay remained operation and which occur after juvenile relatively stable despite increased water winter flounder leave shallow nursery use during the 1986-95 period of three- waters during the fall of their first year of unit operation and reduced cooling-water life seem to be operating to account for demand in 1995-97. Correlations fewer adults. A bottleneck appears to be between entrainment estimates and occurring during the late juvenile life stage abundance indices of post-entrainment (ages-1 and 2), probably from predation.
age-0 juveniles were positive. This Environmental effects, including changes implies no entrainment effect, as the more to the Niantic River habitat (e.g., increased larvae that were available for entrainment, eelgrass abundance), a warming trend in the more larvae metamorphosed and regional seawater temperature, and settled in Niantic River and Bay. This was interactions with other species (e.g.,
also demonstrated by a comparison of predation), especially during early life annual entrainment and juvenile year- history, are also important processes class abundance, which suggested that affecting winter flounder population entrainment estimates were simply a dynamics. Weak year-classes produced measure of emerging year-class strength. in 2006-10 are indications of likely Thus, entrainment is not an important continued low recruitment to the Niantic factor in determining juvenile abundance. River spawning population in forthcoming The potential impact of larval years.
entrainment on the Niantic River stock Results from winter flounder studies depends upon the fraction of the annual through 2010 suggest that MPS winter flounder reproduction entrained operations have had minimal effects on each year (termed production loss in this winter flounder biomass in the Niantic report), which was calculated as River. Declines in stock size have been equivalent eggs removed by entrainment. greatly evident on a regional basis, Previous empirical mass-balance model including Long Island Sound, Rhode calculations showed that a large number Island and all other Southern New of entrained larvae came from a number of England waters. Entrainment during the sources in LIS besides the Niantic River. larval life stages of winter flounder occurs, These estimates attributed anywhere from however there has been large variation in 7 - 61% of entrained larvae to the Niantic the amount of larval mortality and River stock. recruitment in recent years, both occurring Despite a small adult spawning stock in independently of MPS operations.
the river, there have nonetheless been relatively large numbers of larvae and
Fish Ecology Studies individual taxa were attributed to changes in habitat, range extensions or Monitoring during 2010 indicated that no contractions, and a warming trend in long-term abundance trends in various life ambient seawater temperature that has stages of seven selected taxa could be occurred over the past three decades.
directly related to the operation of MPS. Cooling-water use at MPS was reduced No long-term trend was identified in larval 23% because of the shutdown of Unit 1 in abundance of American sand lance. No November 1995, resulting in less significant long-term trends were detected entrainment and impingement. Fish return in populations of juvenile or adult systems at Units 2 (2000) and 3 (1986) silversides collected by trawl or seine. further reduce impingement mortality at Similarly, no long-term trends were found MPS. Further reductions in cooling-water for cunner eggs and larvae, and for tautog flows have been implemented at MPS eggs. Tautog larval abundance has during the peak period of winter flounder significantly increased over the past 35 annual spawning in accordance with the years. Juvenile tautog are increasing in NPDES permit issued on September 1, abundance at the Niantic River trawl 2010. Increasing trends in abundance or station, decreasing at the Intake trawl the lack of decreasing trends suggests station, and adults are increasing in that MPS has had minimal, if any, effect Jordan Cove lobster pot catches. Juvenile on local fish and shellfish assemblages.
and adult cunner have significantly decreased at the Intake trawl station, but Lobster Studies the decline was attributed to the 1983 removal of the Unit 3 intake cofferdam, a Impacts associated with recent MPS preferred reef-like habitat for this species. operations on the local lobster population Since that time, no significant abundance were assessed by comparing results of the trend was found from 1984 through 2010. 2010 study year to data collected from Gunner abundance significantly increased 1978 through 2009. Emphasis has been at the Niantic River trawl station and placed on assessing long-term trends in continued to fluctuate without trend in the abundance and population Jordan Cove trawls, but decreased in characteristics of lobsters collected in the Jordan Cove lobster pots. Grubby larval Millstone Point area.
abundance is increasing and no long-term Throughout LIS, the lobster population trend was exhibited in the grubby trawl was stable or increasing from 1978 through data. Atlantic menhaden larvae showed a 1999. The abundance of lobsters in LIS significantly increasing trend in was lower from 2000 to 2010, but unrelated abundance, as did juveniles taken by to MPS operations. Rather, the lobster seine and trawl. Since the late 1970s the abundance declines were attributed to a densities of anchovy eggs and larvae significant mortality event in western LIS collected in entrainment samples showed and to an outbreak of shell disease significant negative trends. affecting lobster populations from eastern Changes in the species composition and LIS to the Gulf of Maine. In the MPS area, temporal and spatial abundance of fishes no significant long-term trends were and shellfishes collected by trawl over the identified in the annual CPUE of lobsters past 35 years were unrelated to MPS (combined over all sizes and stations) operation. Shifts in the dominance of collected either in pots or by trawl. The
total pot-CPUE of lobsters at the three the east side of the power station monitoring stations has varied without discharge to LIS.
trend since 1978. However, annual CPUE Seasonal shifts in occurrence of annual of legal-size lobster has exhibited a algal species were noted at Fox Island-significant declining trend at the Jordan Exposed (FE) during 2010. These shifts Cove and Twotree stations, but not at the included abbreviated season for cold-Intake station located nearby MPS. water species (e.g., Monostroma grevillei, Significant declines in the abundance of Spongomorpha arcta, and Dumontia legal-size lobsters were attributed in part to contorta) and extended season for warm-shell disease and to a 4.7 mm increase in water species (e.g., Grinnellia americana, the minimum legal size since 1978. Dasya baillouviana, and Bryopsis Long-term trends observed in lobster hypnoides). Similar shifts have been population characteristics over the past observed in most years since Unit 3 began three decades (growth, female maturity operation (1986), with the exception of the and egg-bearing lobsters) appear related extended shutdown of all MPS reactors to warmer ambient seawater temperatures from March 1996 to June 1998 when and/or the recent outbreak of shell seasonality of these species at FE during disease, and not MPS operation. the recent shutdown period was more Increased ambient water temperature may typical of other sites.
be responsible for the increased Thermal effects on dominant species susceptibility and transmission of diseases abundance and distribution patterns were affecting lobsters in LIS, which are near also evident at FE in 2010 and most their southern range of distribution in apparent in the low intertidal zone.
nearshore waters. Seasonally high abundance of Hypnea The number of lobster larvae entrained musciformis, a species observed for the through the MPS cooling water systems first time in 2001, and expanded was highly variable and has not resulted in populations of Sargassum filipendula, a decrease in local lobster abundance. Corallina officinalis, and Gelidium pusillum Impacts associated with entrainment and now characterize the lower shore impingement of lobsters at MPS have been community at FE. Neosiphonia (formerly greatly reduced by the shutdown of Unit 1, Polysiphonia) harveyi maintained a which eliminated 23% of the cooling water perennial population at FE in 2010, but used, and the installation of aquatic occurred mainly as a summer annual at organism return systems at Units 2 and 3, sites unaffected by MPS.
which return impinged lobsters to Niantic Ascophyllum nodosum growth monitoring Bay. during 2009-10 continued to demonstrate no clear relationships among monitoring Rocky Intertidal Studies stations, or correlation with plant operating conditions, indicating that the thermal Rocky intertidal monitoring studies plume from MPS has had little effect on during 2010 continued to document local populations. Natural influences of ecological changes to the shore other factors, such as ambient temperature community near, and associated with, the conditions, storms and wave action, MPS thermal discharge. These changes nutrients and light, play the dominant role are not widespread, and remain restricted in determining Ascophyllum growing to approximately 150 m of shore-line on conditions in the Millstone area.
The rocky intertidal monitoring program prior to 2000. This estuary is located well has also documented regional patterns beyond (> 2 km) the influence of the MPS and modifications to shore communities discharge. Since 2001, eelgrass unrelated to MPS operation. These distribution in the Niantic River has include the introduction to the region of expanded, with a gradual, steady increase three exotic red algae (Antithamnion in shoot density through 2009, followed by pectinatum in 1986, Grateloupia turuturu a moderate decline observed in 2010.
in 2004, and Heterosiphonia japonica in Ongoing extensions of municipal 2010), decreases in barnacle abundance sewerage lines in the Niantic River in recent years, and long-term increases in watershed, possibly coupled with abundance of the common seaweeds depletion of nutrient inputs from old septic Fucus vesiculosus and Chondrus crispus. systems no longer in use, may be contributing to population recovery during Eelgrass the last 9 years.
Eelgrass (Zostera marina L.) populations Benthic Infauna were monitored from 1985 to 2010 at three locations in the vicinity of MPS. Benthic infaunal monitoring documented Data from 2010 surveys indicated that at long-term trends in sediment all three study sites supported healthy and characteristics at all the subtidal sites in expansive eelgrass populations, the vicinity of MPS. At the effluent station consistent with results from the past 7-8 (EF), the sedimentary environment years. These populations have also remains coarse, with low silt/clay which is exhibited variability in population related to discharge of cooling water into parameters (e.g., shoot density, shoot LIS at the Quarry cuts. Sediments at the length, and standing stock biomass) and intake station (IN) were consistent with distribution over the entire 26-year study sediment characteristics prior to dredging period, but this variability was not related during MPS Unit 3 construction.
to MPS operation. Eelgrass populations Sediments at Jordan Cove (JC) continue at two monitoring sites to the east of MPS to show stabilization following an earlier (Jordan Cove - JC and White Point - WP) siltation event when increased water flow near the fringes of the thermal plume (< from the discharge after startup of MPS 1.5 km from the MPS discharge to LIS) Unit 3 scoured fine sediments surrounding have exhibited moderate variability and EF and deposited them at JC.
subtle declines in some population Sedimentary characteristics at the parameters since 1985. However, both reference site at Giants Neck (GN) were predicted and measured thermal input similar to previous years' observations and from the cooling water discharge to these continued to reflect natural variability sites is at most minimal (< 10C above unrelated to MPS.
ambient conditions) and well below levels The 2010 infaunal communities at all considered stressful to eelgrass. sampling sites continued to respond to By comparison, high eelgrass population sedimentary environments. Dominant variability has been observed in the taxa at all sites were reflective of climax Niantic River (NR), where complete and communities that have undergone long-often sudden eelgrass bed losses were term successional development in documented on five separate occasions response to more stable sedimentary
environments. Surface deposit-feeding oligochaetes and polychaetes continued to be dominant organisms at all sites in 2010. Multivariate analyses showed a higher degree of among-station similarity in 2010 than previously observed, but also showed distinct separation of communities when they were affected by construction and initial operation of Unit 3. Changes in community structure and functional group dominance at EF, JC, and IN during the period 1980-2010 reflected a combination of effects related to construction and initial operation of MPS Unit 3 and other regional and/or local biotic and abiotic factors. Community changes at GN during the period 1980-2010 were attributed solely to these latter factors, and not to operation of MPS. The 2010 benthic data corroborate previous conclusions that operation of the Millstone Power Station does not perturb local benthic infaunal communities.