ML20214J937

Forwards NRC Draft Comments on Grand Junction Draft Remedial Action Plan.Nrc Will Forward Final Comments Following Site Visit During Wk of 860929,per Agreement

ML20214J937
Person / Time
Issue date:	09/18/1986
From:	Martin D NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Themelis J ENERGY, DEPT. OF
Shared Package
ML20214J940	List: ML20214J937 ML20214J945
References
REF-WM-1, REF-WM-54, RTR-NUREG-CR-4271 NUDOCS 8612020062
Download: ML20214J937 (32)

Text

&

l WM Record File 75; ,,, gg~~

SEP 18 gg; Dociet pg -no[7--__._

54/MH/86/9/86 M fiM: -

~

_ J - - -

-(Rejura to Wl.1,621SS)

DISTRIBI)fl0N

. John G. Themelis, Project Manager WM s/fv MKnapp' Uranium Mill Tailings Project Office WMLU r/f DGillen U.S. Department of Energy NMSS r/f DMartin Albuquerque Operations Office RBrowning ' MFliegel P.O. Box 5400 MBell MNataraja Albuquerque, NM 87115 JBunting SSmykowski BFord MHaisfield

Dear Mr. Themelis:

RDSmith, URF0 MYoung JGrimm -TJohnson Enclosed are NRC's draft comments on the Grand Junction draft Remedial Action Plan. As agreed with your staff, we will send our final comments after our site visit scheduled for the week of September 29. We hope by providing these comments now your staff will better understand our concerns, and thus allow for more meaningful discussions during the site visit. If you have any questions regarding these coments, please contact Mark Haisfield at FTS 427-4722. j Sincerely, origiha.( Sthed by 3A rd Adik Dan E. Martin, Section. Leader Low-Level Waste and Uranium Recovery Projects Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards

Enclosure:

NRC Draft Coments 861202o062 86091s PDR WASTE WM-54 PDR l

OFC :WMLU c s/ :WMLU  :  :  :

...__:..__ ..'11850_:_. $___.::____________:..______..:.._________:---_____....:__.._______

NAME-:MHaisfield 6  :  :  :  :  : :

DATE:09/g'/86 :09/ /8 /86

)

r. - -

s *

.i <

i W54/MY/86/9/17 CRAFT GF0l'ND WATER COMMENTS ON THE DRAFT PEMEDIAL ACTION PLAN GRAND JUNCTION, COLORADO '

PART 1 0F 2

GENERAL COMMENT

S

,Po_ssible Cross-river Contamination The DRAP states that groundwater ccvcs vest-southwest and discharges into the Colorado River. Ecwever, several conditions erd statements, contained in the DRAP, raise questions er the validity of this statement and the possibility that groundwater may ficw scuth, under the Colorado Piver and impact water quality in the area south of the river. These conditions include:

1. From cross-sections presented in Figures 0.5.3, 0.5.4, and D.5.8, it appears 1. hat the alluvium-Mancos Shale contact dips south, toward the Colorado River. This lithologic contact may frfluence the flow direction, as seen in the scutFwestern direction of groundwater flow.

2. Contaminate plumes have been rapped and interpreted as moving west, although there is a clear rertbe.rn. component to the migration. The pessibility of southern micratier of tFe plume, similar to that cbserved north of the site, has rot teer addressed.

3. Figure D.E.15 indicates a saturated thickness of alluvium beneath the riverbed of the Colorado River of perhaps ten feet. This supports the prerise that southerly flowing groundwater dces rot recessarily discharge into the Colorado River. Therefore, it is possible that orrurdwater flows beneath the river in the alluvial material, and may imcact potential groundwater users in the area south of the Colorade

' liver (an occurrence of groundwater flow such as this has beer observed at acother UMTRA Project site (00E, 1985)).

00E has made-no effort to verify that contaminated groundwater, near the processing site, fully discharges from the groundwater system. Therefore, the possibility exists that grcundwater flows beneath the Colorado River and may impact tFe veter quality in the area south of the river. DOE needs to address

+Fis possibility by characterizing the quality of groundwater in this area ard essessing possible impacts to consumers of potentially contantrated groundwater.

r

'e M S.Q hI'u 51 I WM54/MY/86/9/17 Possible Northward Flowing Contaminants According tc the DPAP, groundwater flows west-scuthwest and eventually '

discharges into the Colorado River, resulting in a finding that pctlic health will ret be jeapordized. However, when interpreting data and informaticr certained in the DRAP, groundwater in the Dakota Sandstone may he impacted by contaminated groundwater eminating from the processing site in the ellevial aquifer. This pessibility cannot be confirmed or denied, because data and information on the Dakota Sandstone have not been co!1ected. The following conditions support the deternination that additional informaticn needs tn be collected:

1. On page D-47, the DRAP states thet the Mancos Shale thins west of the F.te. 50 bridge (.5 mile), where the Dakota Sandstone subcrops with the alluvium. Therefore westerly rwing groundwater, from beneath the tailings may reach this alluvium-Dakota Sandstone contact, and affect ' groundwater in the Dakota Sandstere. Although the-direction '

of groundwater flow in the Dakota Sandstone has not been established in the DRAP or the EIS, page F-137 in the DEIS states that the Dakota Sandstone dips frcn south to north, with the recharge zcne probably located snuth of the site. Using this information, potentially certarirated groundwater in the Dakota Sandstone should flow north, away from the zone of recharge, or at least maintain a component cf northern flow. Therefore, putential groundwater users may be affected by irgesting this water.

2. Using data availe.ble in the DRAP, NRC staff have determined that downward hydraulic gradients, from the alluviem te the Dakota Sandstere, ray exist up to five feet. This potential gradient may be enough to promote downward migration of contaminated greurdwater, thrcugh the Mancos Shale, before there is actual contact between the alluvium and Dakota Sandstone.

These conditions, when used in ccrbination, lead to a hydrngeoicgic scenario in which contaminants may impact the groundwater in the Deketc Sandstone either by possible downward migration through the Vancos Shale, caused by downward with the hydraulic gradients, or by direct contact of the alluvial material Cakota Sandstone. DOE needs to characterize the direction of groundwater firw in the Dakota Sandstone, so that the above scenario, and the scenario described in the DRAP can be ccnfirmed or discounted. Of particular inpertance is the area adiacert to cod west of the Rte. 50 bridge, where the Marcos Shale allegedly pirches cut. This information should be capable cf substantiating the hydrogeclegic scenario proposed in the DRAP, and lead te subsequent

.4 WM54/MY/36/9/17 conclusio.ns pertaining to aquifer restoratien er institutional control of groundwater. .

DETAILED COPPENTS Section 4.3.7.. Page 50, Paragraph 3 In defending their decision that aquifer restoraticr is unnecessary, DOE states the hydrogeologic setting (i.e., rechcrge from the nearby Colorado River) would complicate the effort. Fron this statement, DOE implies that recharge of relatively fresh waters into the acuifer system would either hinder the restoration of the poor quality groundwater, or increase the cost of restoration by pumping diluted groundwater. It vculd appear logical, however, that a nearby source nf recharge would improve the efficiency of the restoration if extraction wells were properly placed the fresh water recharge ~

could improve the cuality of the groundwater faster, and allow the restoration proc'ess to continue without the threat of the aquifer system dryfrp cut. The success of the restoration, therefore, will be dependent on the design end'

~

purrpirg scheme of the well system. 00E shculd cualify the statement that the hydrogeology of the site wil' complicate the restoration effort, with examples and .iustifications on how the option of restoration is infeasible.

Figures D.5.1.-D.5.4., Page D D-54 The DRAP provides cross-sections of the tailings pile and a base map for locating these cross-sections. However, tFe bering locationsThese from control which these points figures were developed, are not included en the base map.

are necessary to deternine the accuracy of the cross-sections and their locations. Forecver, the lithology logs of the Fcrings are not contained in the DRAP, or the E:S. 'hese steuld be included in the DPAP since remedial action plans are based, in part, on these logs.

Figure 0.5.11, Page D-61 .

Figure 0.5.11 represents the monitoring well locations at the Frerd Junction orocessing site. Pcwever, there are discrepencies associated with this figure and Table D.5.6.

1. The figure does not include the locations of all the monitor wells.

The wells not shown are upprediert, alluvial wells 711 and 712 and downgracient, alluvial well 738, fer which the water quality information is absent in Table D.5.6. Figure D.5.11 should he

N

'!M54/MY/86/9/17 modified to include the !ccation of all the wells used in the monitoring system. If the present scale of the ficure cannot support

'inclusien of these wells, then an additional figure with an appropriate scale should be provided.

2. The figure represents the location of meritor wells 591 and 596, but no information on well construction, water levels, or water quality is present in Table D.5.6. Therefore it is impossible to determine which strata _is being monitored, er from which strata water samples were retrieved. Therefore, irferration associated with these wells should be included, or the figure shculd be redified to remove then.

Figures D.5.16-0.5.20, Page D 0-67 Figures D.5.16 - D.5.T0 in the DRAP represent water quality maps for several contaminants found in the grcundwater. However, the ficures do not include the location cf tre wells used in construction of these figures, making validation cf proper contour line placement very difficult. The figures shculd be ,

r:cdified to include the well locations used to construct the map. Also, in Figures D.5.16 and D.5.17, the iso-concentration lines do not extend over the full study area, but taper off up-gradient of the site. Since the water ouality results are available for wells up-gradient cf the processing site, the iso-contration lines should be extended to reflect conteminant levels in groundwater in these wells.

Table D.5.5, Page D-75 During the monitoring period..both water level information and water quality results were retrieved from the rcritor well network. However, in several chses, water samples were collected, but ro water levels were recorded.

Interpreting the relationships between water quality and the water table elevation, from information collected usino this groundwater monitoring method, is not defensible because correlating the two conditions in the sane time frame cannot be achieved. Therefore, any comparisons or conclusions that utilized these data in combination may not be valid. If available, these water leve!

data should be included in the DRAP. If the information is not available 00E should assess possible effects on the interpretation of the flow regime and the proposed contaminant migration patterns. Future monitcriro activities should include recording water levels frem wells whenever water samples are collected.

Section 0.5.5., Page D-80 During the monitoring period from approximately Perch-September,1985, two dcwngradient shale wells exhibited enormous water level changes. The rarges of water levels, for wells 729 and 735 are 33.90 and 21.99 feet; during this time

it T12 WM54/MY/86/9/17 LlIllk period, water quality also varied considerably. Nearby wells, however, did not experience changes in water levels or contaminant levels to this degree. These -

anomolous readings may indicate either external influence on the groundwater system by humans, or lack of accuracy and quality control en the part of the technician' collecting the samples. DOE should explain the cause of these perturbations.

Section D.6.6., Page D-154, Paracraph 3 4 The DRAP states that comparisons of water cuality results from samples taken at Cerec ard Fruita indicate no effect of the Grand Junction tailings on the Cn!crado River. However, the CF.AP ard the EIS (DOE, 1986) contain no d6ta te confirm this. Also, there was no mention of where Grand Junction rencves water from the Colorado River for their municipal water supply. A withdrawal point

' downstream of the tailings could result in possible exposure to the public to contaminated groundwater. TFe CPAP should indicate where Grand Junction removes water for their municipal water supply and should provide the information that '

confirms the claim that the Colorado River is unaffected by the tailings.

+

9 G

o WM54/WHF/86/9/11 ORAFT GROUND WATER GRAND JUNCTION, COLORADO COMMENTS ON THE OR ,

PART 2 0F 2

GENERAL COMMENT

Section 3.5, GROUND WATER, Page 34 ite, but does The ORAP describes ground water pollution at theprocessing left at the Grand Junction d is a s

not site.

indicate what will happen to ground ate by water pollutionSin discussion consequence of moving the tailings, the ORAP should incorporThe DRAP sh or reference a description of the effects of such act.ding ion.between the justify, according to agreements in the Memorandum of Understan .

NRC and DOE, why ground water restoration is or is not needed.

DETAILED COMMENTS Section 3.5, GROUND WATER, page 34 i ite, but The ORAP describes the ground water pollution dat water the Grand Junc does not evaluate the consequences of abandoning d the 00E. However, the the existing grou pollution after reclamation activities, as require i does contain and the Memorandum of Understanding between the NRC an draft Environmental Impact Statement for the Grand Junction information on this subject.

l appropriate sections of the draft Environmental Impactt the Grand Junctio the effects of residual ground water contamination a processing site.

1.

OEIS, Section F.3.2.2, Water-ouality impacts, F-147 ter When' the tailings are relocated to the Cheney idual Site, impacts ecipitated quality near the processing site Inwould be due to using this contaminants in the alluvium. evaluate the persistence length of of resid model a number of assumptions were made. indicate time it would take the aquifer to restore itself

~

DRAFT WM54/WHF/86/9/11 -g-I The text should clarify whether this model is providing conservative or realistic results and justify the conclusion.

2. DEIS, Section F.3.2.2, Water-quality impacts, F-147 Since the tailings will have to be dewatered prior to excavation and the pumped water may have to be treated prior to discharge to the Colorado River, significant clean up of the tailings may occur as a result. In estimating the impacts of leaving residual ground water contamination at the Grand Junction site, the effects of dewatering the tailings on the ground water contamination should be included in the discussion or analysis.

3. DEIS, Section F.3.8, AQUIFER RESTORATION, F-168

+

In discussing the possibility of ground water restoration at the Grand Junction processing site the text states that " plume capture near the Grand Junction tailings is complicated by both physical and .

cultural features." As one example, the text states that pumping the shallow aquifer would induce flow from the Colorado River that would dilute the contaminated ground water. Therefore, an increased volume of water would be captured and treated, thus increasing the costs for each activity would be increased. The problem with this statement is i

that it is too generic, since the conclusion is too dependent on the specific design of a particular ground water restoration scheme. For example, if ground water extraction points are located at a distance from the river and more towards the center of contamination, the river could provide a source of clean water to more quickly effect restoration rather than adding to the cost. The text should better explain its conclusion (for example, by defining the contaminate plume te be cleaned up and its relation to the proposed restoration method) or not assume that the river will necessarily increase restoration costs.

1

4. DEIS, Section F.-3.8.5. Degree of human exposure likely to occur, F-174 In discussing the health effects that could occur from residual

' contamination at the Grand Junction processing site, no discussion is included of what measures, if any, are needed to protect the populace from using ground water under the tailings site once it is released to unrestricted use and until it has been naturally restored in the next 100 years.

DRAFT WM54/WHF/86/9/11

5. DEIS, Section F.3.2.2, Water-quality impacts. F-147 The contaminated material excavated from the Grand Junction processing site will be replaced with material excavated at the Cheney site. This means that a different geologic material will occupy the Grand Junction processing site after the completion of reclamation activities. This material will have different hydrologic and geochemical properties than the previous materials.

Accordingly this new material may have positive and negative effects on the ground water quality under the site and may effect the ground water contamination left behind after reclamation activities. The DRAP should include a brief discussion of the effect on the ground water quality, positive or negative, from the fill material that will be placed at the Grand Junction processing site.

Section 0.5.2, FLOW REGIME. page D-48 Wells 711 and 712 were used to establish background water quality for the alluvial aquifer at the Grand Junction mill tailings site. However, no figure is provided to locate these wells with respect to the site and other land uses or sterface water bodies. Since these wells are very important in determining the effects of any ground water impacts, a location map should be provided.

Tables 0.5.6, Ground Water Quality Data by Location, Pages 0-83 to 0-150 Cation / anion balances are a part of DOE's water quality assurance program.

However, NRC staff spot checks for some of the samples in Table 0.:i.6 yielded mcceptable balances, which implies an inaccurate analysis for the major ions.

Therefore, cation / anion balances for each sample should be included in Table 0.5.6 and the text should describe the validity of the chemical data if there has been a lapse in the DOE quality assurance sampling and analysis program.

TABLE D.5.6, Ground Water Quality Data by Location, Page 0-110 An analysis for uranium collected on 3/22/85 from well 739 has a value of 8324 pCi/L. This~seems very high and suggests significant uranium contamination off site. The ORAP should explain the occurrence of this high value and describe the environmental effects and any ground water remedial actions that will be required.

DRAFT WM54/AI/86/9/17 DRAFT SLISMIC COMMENTS ON TPE PRAFT REf4EDIAL ACTION PLAN GRAND JUNCTION, COLORADO .

CEfiERAL COPf4ENT The PAP does not discuss any gecphysical survey which may have been used to suppert the site investigation findings. Discuss the type of geophysical surveys conducted. If no surveys are conducted explain the reasers.

DETAILED COMMENT 5 Section E. 3.6, Seismotectonic Setting, Page E-42 In the RAP it is stated that "the stress fields oriented differently than the riedern stress field in the interior of the Plateau". Provide a map showing the stress field orientations in the Colorado Plateau as compared to the surroundinc provinces, and discuss if the stress fields are used in delineating the different seismotectonic provinces.

Section E.3.6, Westerr Fruntain Province, Page E-48 In the RAP it is stated that, " faults associated with evaporation flowage er solution which cut Neogene rocks are not considered to be capable of generating earthquakes of magnitude greater than 4 or 5". Provide justifications for this statement. Identify the closest fault of this type to the site and provide the estimated magnitude ard compare to the design earthquake.

Sectier F.3.7.4, Analysis-of Seismic Risk, Page E-53 Campbell (1981) attenuation relationship is based rrost!y er earthouake data from California. Provide the rationale for using this relationship for Grand Junction.

Section E.3.7.4, Determination of Ficatino Earthouake Paonitude, Page E-57 n the RAP it is stated that "the FE magnitude should never be creater than the f:E" . Previde the rationale for this staterrent.

DRAFT WM54/AI/86/9/17 Section E.3.7.4. Determination of Floating Earthquake Magnitude, Page E-59 In the RAP it is stated that "In accordance with seisnic desion procedures commonly used in the siting of nuclear power plants, this event is assumed to occur at a radial distance of nine miles (15 km) frem tFe site". The distance of 15 km has been based on tFe average of ensemble of earthquake records, "having similar physical properties to the site. used to generate site specific spectra for unclear power plant sites ard this distance may vary from one site to the other.

Provide the rationale for choosing nine miles (15 km) as the distance from the site to the floating earthquake to calculate the acceleratinn in the Grand Jur.ctier CPAP. .

Section E.3.7.4, Faults ar.d Epicenteral Compilation, Page E-63 Kirkham er.d Pogers (Colorado Geological Survey, Bulletin 43, Plate 3, 1981) identified faults 1,3,4,7,8,9 and 17 as potentially active faults. In the RAP it is stated. that these faults are not proven to be capable. Provide supporting field evidences and aerial photos to support that these faults are ret cepable.

Section 3.7.4, Cheney Reservoir Site Lineament, Page E-65 In the RAP it is stated that this lineament is not the result of faulting.

Provide the field evidences and aerial photos which vicoid support this statement.

Secticn 3.7.4, Epicentral Compilation, Page E-67

n the RAP it is stated that the earthouake of November, 1871 appears to be related to Fault 6. If this is the case it should be considered capable.

Section E.3.7.4, Recommended Seismic Design Parameters, Page E-67 Identify the references and the formulae used to estimate the magnitude ard tFe acceleration from fault 8 and the rationale for chcocing these formulae.

Indicate if the fault type is considered in estimating the macritude and, the exact distance of the fault from the site.

. , - . . t

/

I *

• DRAFT i

WM54/AI/86/9/17 Sectier E.3.8.4, Recommended Seismic Design Parameters, Page E-67 ,

In the Draft Environmental Impact Statement (EIS) (DOE /EIS-0126-D, Vol.II, P.

E-41, March 1986) it is stated that "High accelerations may result from the

-occurrence of earthquakes of magnitude as higher as 6.6 on previously unkncvin

'aults within less than five miles of the sites". Based on this statement should the design earthquake be located et a distance less than 5 miles from the site. If not, discuss with rationale.

Table E.3.5, Earthouakes cf l' 4.0, Page E-89 This table lists earthquakes up to 1081. Update this table to cover recent seismic activities in the area ar.d previve a map showing the locations of these earthquakes.

l i

l 1

g- - , , ~ . - - - - - . - . , , , . , , .,n. , -

,--pr

BRUT WM54/JG/86/9/17/1 .

DRAFT GEOMORPHOLOGY GRAND JUNCTION, COLORADO COMMENTS ON DRAFT* ,

1.

Section E.3.2, Regional Geomorphology,i Page E-25, f rence to paragrap Glacial moraines located near Ridgway, dCO, are mentioned w t the glacial fluvial terraces in regional drainage basins.

to a map in the RAP indicating the location of Ridgway an deposits.

figures.

In all cases, geographic locations referre should be located on a figure within the report.

h2 2.

Section E.3.2, Regional Geomorphology, Page d aE-25, Pliocene paragrap age.

i This age ,

A potassium-argon date of 9.7 m.y. is incorrectl should be reported as Miocene (see Palmer, 1983).

2 3.

Section E.3.2, Regional Geomorphology, Pagei E-25, rate paragraph ,

Based on radiometric age data for Grand Mesa,only an " average The calculation nt level makes has been calculated for the Colorado River valley.This assumption an assumption that the valley has lowered to its prese '

recently and is zero years old relative to the mesa age.An average ll as the mesa.

is not necessarily valid. inimum unless a constraining age is known for the valley rather than an average.

h3 4.

Section E.3.2,_ Reg onal Geomorphology, it i

PaceTherefore, E-28, paragrap t at Citation of' Hunt (1969) is missing from the re i f

calculations at Book Cliffs.

h3 5.

Section E.3.2, Regional Geomorphology, Page h BookE-28, paragrap Cliffs Slope retreat rates of 23 m per 1000 yrs are reported by Hunt (1969?).

h WM54/JG/86/9/17/1 seem exceptionally rapid. The DRAP should not simply discount these data without an explaination. Justification for an assumption that the cal'culations are erroneous should be based upon quantitative data which refute the rapid rate. Such quantitative evidence is not cited in the DRAP.

6. Section E.3.2, Regional Geomorphology, Page E-29, paragraph 2 Use of the terminology " detached pediment" is unclear and needs definition or illustration. Even though graphic projection of longitudinal profiles of the pediment surfaces may be approximate and inconclusive, they would be instructive for the reviewers' understanding of the scale of pediment extent and of topographic relations.

7. Section E.3.3, Climate and Vegetation, Pages E-31 to E-36 The DRAP provides conversions of temperature-change data from degrees Celsius to Fahrenheit and elevations from feet to meters. Some of these conversions are erroneous and require revision for accuracy.

8. Section E.3.4, Site Geology, Page E-36, paragraph 2 Appendix E here refers the reader to Figures 3.13, 3.14, and 3.15 in volume 1 of the DRAP. These figure do not exist.

Therefore, the reviewer cannot comment on stratigraphy of surface P3 deposits. The reviewer, however, believes the reference is to Figures 3.6, 3.7, and 3.8. If this is so, the figures are duplicated in Appendix E (Figs. E.7.2, E.7.3 and E.7.4), and reference to another volume is unnecessary.

9. Section E.3.4, Site Geology, Page E-38, paragraphs 2, 3, and 4 The DRAP suggests differentiation of geomorphic surfaces P3a and P3b based upon separate criteria: 1) two separate cycles (ages) of pediment formation, or 2) different types of depositional processes for the associated alluvial deposits. The discussion, however, does conclude which criteria accurately distinguish the two surfaces nor does it indicate which criteria were actually used for the classification.

If the classification is based upon separate ages, use of one number designation, P3, is inconsistent with the method of surface nomenclature.

l l

l

v WriS4/JG/86/9/17/1 Therefore, the final RAP should clarify the age relationships and draw a conclusion regardiro relative age, or it should eliminate the inference of temporal distinction between surfaces P3a and P3b. ,

If the classification is based uper surface morphology, the final PAP should provide evidence that the merphologies are due to original depositional processes and are not related to recent surficia.1 processes.

Varying surface trorphologies related to recent processes would indicate incipient surface erosicn and irstability.

10. Section E.3.4, Site Geo'ogy, Pace E-38, paragraph 3 The text reports on weakly developed and thin textural B horizons in the soil profiles on surfaces P3a and P3b. On page E-36, however, the DRAP cites "strcr.g caliche cementation" at least 1 m thick in the same deposits. Well-deveicped calcic horizons in ar area 'ree of carbonate parent materials rencests long-term surface stability, while lack of well developed B horizons suggests lack of such stability. This centradiction must be further explained to determine that the Cheney Reservoir site will provide geomorphic stability.

11. Section E.3.4, Site Geology, Page E-38, parecraph 3. 4, and 5 In the discussion c# surface morphology, desert pavement, and desert varnish in the Cheney Reservoir site area, references to 00hrenwend (19841 are tenuous or inappropriate for several reasons:

1) The Dohrenwend (1984) reference is a guidebook containing several papers which address the above subjects. General citation cf ar editcr is irappropriate and delays location of the desired in formation. The DRAP should cite specific works within the guidebook.

2) Original bar-anc'-swale depositional morpholcgy was identified on surfaces P3a and P3b from aerial photoaraphy of the Cheney Reservoir site. The DRAP cites OcFrerwend (1984) using relict bar-ar.d-swale morphology as an indicator of relative age. Table E.3.3 gives a comparison of surfaces P3a and P?b but provides no quantitative descripticr r,f the bar and swale morphology.

The specific reference to be cited is Wells and others (1934) regarding alluvial fan deposits at Silver Lake, CA. This paper i

HAFT WM54/JG/86/9/17/1 includes detailed field data indicating latest Holocene deposits exhibit less than 1 m original depositional relief and provides that bar-and-swale relief decreases with age. -

From the above discussion, the DRAP's interpretation of surface morphology seems tenuous. Citing Wells and others (1984), the reviewer maintains that bar-and-swale morphology could be tentatively identified from aerial photographs, but that morphology with less than 1 m relief requires field observation and measurement for verification. The DRAP does not report this.

3) Existence of well developed desert pavements and desert varnish is generally recognized as common in hot arid climates, like the Sonoran and Mojave Deserts. Therefore, discovery of these features in a semiarid area like western Colorado may be problematic.

4) The DRAP draws comparisons between basaltic pediment deposits on surface P3 and " basalt-bearing" . deposits discussed within Dohrenwend .

(1984). The specific paper concerned with fluvial deposits and desert pavement is the Wells and others (1984) study at Silver Lake, CA. The deposits studied are derived from plutonic and metamorphic rocks and Tertiary gravels (Wells and others, 1984, p. 72) and are not composed of basaltic material as suggested in the DRAP.

Processes of desert pavement formation and their rates are not necessarily correlative between the two types of deposits.

5) Depiction of the climate of GraniJunction area as " roughly similar" to the hot arid climate of the eastern Mojave Desert is tenuous, at best. The DRAP should probably attempt to make its geomorphic comparisons with areas of similar, semiarid climate within the Colorado Plateau.

12. Section E.3.4, Site Geology, Page E-39, paragraph 2 The DRAP credits alluvium on pediment surfaces with protection of bedrock against erosion. The fact that channels have not formed on a particular pediment remnant, however, is likely a factor of both basin morphometry and underlying surficial deposits. Furthermore, the concept is discredited because pediment surfaces in the area occur as relatively small remnants and occur at many different levels, indicating that the pediment surfaces are indeed abandonned and degraded over time.

l l

l e

l 1

l 1

i

- 5 DRAFT WM54/JG/86/9/17/1 The concept of pediment deposits being treated as distinct entities, separate from the geomorphic surface itself, and providing geomorphic stability is an untested one. Generally, pediments and their surf-icial ,

deposits are recognized as a result of geomorphic stability, not a cause.

The final RAP should attempt to verify the concept in the geologic literature.

13. Sectio E.3.4, Site Geology, Page E-49, paragraph 2 The DRAP makes a conclusion that length of an incised channel is directly related to the basin area which In it drains. However, no morphometric data are presented to support this. the Piceance basin north of the site, Patton and Schumm (1975) have shown that the mere occurrence of incised channels is a factor not only of drainage area, but also of valley slope.

To predict likelihood of future geomorphic stability at the Cheney Reservoir site, DOE may wish to consider a similar analysis of gullied and -

ungullied charinels in the site area. The analysis may assist a determination that a threshold condition does not exist for channel instability on surface P3.

14. Figure E.3.6, page E-76 The geomorphic map of the Indian Creek area shows-nine geomorphic surfaces and the text (page E-37) explains the techniques employed for identifying the surfaces. Existence of nine sur~ faces suggests very complex geomorphic history at the site. The ORAP, however, has not providedTherefore, or explained the NRC data which resulted in differentiation of the surfaces.

review cannot address the potential impact of past geomorphic history upon stability of the site, especially surface P3. The types of required data include:

1) projec.ted height above local base level (Indian Creek)

2) surface orientation

3) deposit descriptions (stratigraphy, grain size, thickness)

4) soil descriptions (weathered pedogenic profiles)

15. Figure E.3.6, page E-76 The geomorphic map of the Indian Creek area leaves a number of areas near the proposed site unlabeled. Whether these areas are pediment surfaces, hillslopes, or active washes, they need to be so designated.

DR AFT WM54/JG/86/9/17/1 .

REFERENCES CITED Dohrenwend, J. C., ed., 1984, Surficial geology of the eastern Mojave Desert, California: Geological Society of America 1984 Annual Meeting Field Trip 14 Guidebook, 183 p.

Palmer, A. S., 1983, The Decade of North American Geology 1983 geologic time scale: Geology, v. 11, n. 9, p. 503-504.

Patton, P. C. and Schumm, S. A., 1975, Gully erosion, northwestern Colorado:

a threshold phenomenon: Geology, v. 3, n. 2, p. 88-90.

F., Feilberg, 8.

Wells, S. G., McFadden, L. D., Dohrenwend, J. C., Bullard, T.

F. , Ford, R. L. , Grimm, J. P. , Miller, J. R. , Orbock, S. M. , and Pickle, J. D., 1984, Late Quaternary geomorphic history of Silver Lake, eastern Mojave Desert, California: an example of the influence of climate change on desert piedmonts, in Dohrenwend,'J. C., ed., Surficial geology of the eastern Mojave Desert, California: Geologic Society of America 1984 Annual Meeting Field Trip 14 Guidecook, p. 69-87.

, . - . - - - -- .-----.,..-._,-,-,...-y_ ,-

O DRAFT GE0 CHEMISTRY COMMENTS ON THE DRAFT REMEDIAL ACTION PLAN GRAND JUNCTION, COLORADO -

GENERAL COMMENT

Upon completion of the review of the DOE's DRAP the WGT, Gecchemistry staff found that the DOE has neither taken into consideration nor addressed the potentially adverse short term and long term effects of geochemical processes (due to the intrinsic geochemical disequilibrium of the unconditoned tai 14ros) which could contribute to the physical instability and potential breach of the radon barrier and migration of toxic contaminants ct any cf the UMTRAP sites.

It has recently come to the staff's attention that studies of about twenty inactive uranium mill tailings sites by a CCE centractor (Markos 1979, Markos dnd Eush, 1980, Markos and Bush 1981a ard Markcs and Bush 1981b, 1983) indicate that salts with sulfate and thirride are mainly responsible for the upward migration of contamirants in the tailipps material. Many of these salts are deliquescent or hygresccpic. As such, they are able to absorb moisture from both the interstitial atmcspbere of the tailings and the rearby water table.

This process, ccmbined with the dry conditions on the surface of the tailings, creates an upward flux of salt _ migration, which in turn transports certani-nants. Both radioactive and chemically toxic ions such as U, Ra, Pb, V, Cd, and_Ag move together with the major constituents of the Na,Ca, K, Cl, and 504 salts. Field studies shew that the concentrations of contaminants in the precipitating salts on the surface o' tM1iros are several times to several orders of ragnitude higher than in the underlying tailing material. For example, Markos and Eush '.'.9PO) found the association of Ra with the movement of Nacl and other salts of Cl to the surface of the tailings. This phenomenon is in good agreemert with the experimental studies listed in the Geological Survey Circular 814 (Landa,1980). Further, Markos and Bush (1980) cbserved that the upward movement of salts and centaminants are present in all the tventy tailings they studied during their field investigations. These selts trd contaminants move through the protective covers and dikes of the tailinas.

The observed profound effects of these salts are:

(1) development of osmotic pressure,

(?) liberation of gases within the tailings pile, (3) generation of heat by exothermic reactions, (4) desiccation of areas with lower salt content resultirg in desiccation cracks, (5) blackening (oxidation?) of the surface of some species of vegetation (possibly due to oxidizing gases?i, (6) dissolution of silicate materials in contact with interstitial or soil

2 moisture solutions of high icnic strength and low pH (high acidity), and, (7) growth of crystals or precipitation nodules.

Osmotic pressure is significant for two reasons. It is a mode of transport of contaminants to the surface. It also represents a physical force to disrupt structures such as dikes of non-ore materials around tailings, soils, gravel and asphalt covers on the tailiros by ferning boils and cracks, thereby loosening the material which beccmes highly susceptible for erosion. According to Markos and Bush (1981) the boils on the surface vary in diameter from less than a meter to several tens of meters and in height from a few centimeters to occasionally over a meter. Concentration of contaminants, including radio-nuclides, ere elevated in these boils relative to the adjacent areas of tailings. Salts of different kinds usually precipitate en boils.

Active chemical reactions in the tailings can form various gases. For example, hydrcgen sulfide gas was detected in wells on the tailings in Cannonsburg, Pa. '

Cases are expressed in fortration of various size boils on the surface, especially in slime areas. The escaping gases create flow structures in These teilings materials and may be evidence for considerable physical forces.

flow structures rey act as pathways for the direct emanation of hazardous radon gas towards the surface.

The generation of heat by eyethermic reactions occurring within the tailings pile could accelerate the movement of radon.and other gases towards the surface.

Crysta! grewth or precipitation nodules of salts result in volume changes.

Urder con'ined physical conditions, increased volumes may exert considerable forces. The effect of these forces have been observed on dikes where Fru1ders have been dislocated by growth of crystals and on the experimental asphalt cover on part of the Grand Junction tailings which has beer broken up by growing precipitaticn ocdules of salts.

The rate of upward mcVerent of salts within a tailings pile is relatively rapid. A year-round observation of salt movements in the Vitro tailings pile in Salt Lake City, Utah, and the tailings pile in Grand Junction, Colorado, irdicates that salts removed from the surface by rainfall through dissolution er runoff have been replenished a few months later. Although the distarce of trave' o' salts in their upward movement for a given time has not been presently established, the curve of salt distribution with depth ard the constant recereration uf the salts suggest a continucus process. This process will continue until an equilibrium is established. Lateratory experiments resulted in a movement of salts over a distance of I centimeter within a period of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> at ambient room temperature conditions.

Water soluble salts have a profound effect on growth of vegetation. During the time of seeding and growth of vegetation, sprinkling systems are set up on tailinas. Constant or extr.nded watering of the surface of tailings suppresses

. . -. - - . . - =- - - .... ~

3 l

4 I

the salts and washes them dcwn below the root system. After stopping the sprinkling, salts begin to move upwards. After a few years of movement, the salts reach the root system ard destroy vegetation as has been observed'on. -

several tailings piles.

t Another role of selts is the creation of a chemical environment such as very low pH (1.8-3.5) and the supply of anions, particularly sulfate, to other j geochemical reactions such as dissolution of silicate and clay minerais.

The 1cng-term stability of clay and silicate minerals represents another area of concern. The hydration energy of deliquescent and hygroscopic salts may have a signi'icant influence on dehydration of clay minerals. Chemical l

stability of clay and silicate minerals with respect to time is also relatively unknown. Thermodynamic stability of clay and silicate minerals under the pH conditions in many tailings is very low. Acids may attack and destroy clay minerals. Markos and Bush (108n) alsc found that the various types of clay and

[

j silicate minerals have considerable differences in stability with respect to pH ~

' conditions. This night be of concern in terms of the long-term perfor-mance i and. stability of the radcr Farrier or the impermeable clay liner if one is proposed.

Dissolution is an important process .in tailings which results in a volume change. Flux of water through the tailings dissolves soluble salts easily.

The dissolved salts move either by diffusion or by water transport. As water i moves tcward the surface with the temperature gradient, evaporation causes eversaturation, and part or all of the solute precipitates. Transpertation in i response to differences in chemical potentials causes a redistribution of i

material and volume within the tailings. Silicate ard/or clay materials in contact with waters of high ionic strength and low pH may also dissolve i creating large solution cavities and subsidence or collapse of the affected parts.of tailings piles.

Both dissolution and loosening of material can result in extensive piping and collapse of dikes protecting tailings. These, in turn, continue in development irto erosional features and/or destruction of cover or protective materials.

All these phenomenon have been observed in all the tailings investigated, but the magnitudes expressed differ from one tailings pile to arother.

I The overall effect of soluble salts in the tailings is very important. They establish a water circulatory system in the opposite direction to gravity.

3 j

They create an envirormert where many metals are highly mobile. The selts tend j

to rove to the surface of the tailings carryirc certaminants which can enter into the surroundings by surface erosional processes such as wind and runoff.

i The salts are corrosive, and they can move through cover materials and tend to

' destroy vegetation or the surface of the tailings.

{

The NRC staff's position is that any containrent technology proposed by DOE in

this DRAP'for Grand Junction and ir future DRAPs should assess and consider the j above results of the geocherica' study of the twenty inactive uranium milling

,- - ,,,, e-- -- - ww--, r.re,-r------- - - = - - -me...w,v,.,-

DPR 4

d Bush,1983,1981a,b, i d to sites conducted Engicecrire by Markosdesigns and Bush forfor l reactions DOE protective in the(Markes actions tailings. an must be des 1980 and 1979). liminate the forces withstand physical forces caused by chemicaContainren preduced b'y the chemical interactions in tai protection of the environment.

f I

.I

. _ _ - . - ~ - . _ _ , , , , _ . - , , _ _ . . - . _ _ _ _. , _ _ _ , _ _ - _ . , _ _ _ , _ _ . . . _ _ . _ , . . . , _ . _ , _ . , , , , - . - - . - . . , - - - - - - . - _ _ _

e-g .

0 VO 5 ia m DETAILED COMMENTS Section B.I.7 Frtanknent Construction, p. B-1 The DRAP states that the stabilized tailings pile will be designed to provide long-tenn stability, and mirir.ize radon emanation and groundwater contamina-tion. It is not clear how the design ob,*ectives of long-term stability, and minimization of radon emanation and arourdwatcr contamination (for periods of 200 to 1000 years after the preposed remedial action 1 will be accomplished.

This is because the design of the Cheney Site and the precess of stabilization of the tailings piles as described in this DRAP did not consider or address the short and long term impacts of the geochemical processes mentiened in our General Ccmments section. These geochemical processes could contribute to the physicel instability and potential breach of the radon and other superimposed minimal covers as illustrated by the results of the extensive POE contractor research study of the gecchemical impacts of about twenty inactive uranium mill '

tailings sites. The revised DRAP should' describe clearly how the tech-nological controls for prctective action will be designed or utilized to withstand the disruptive physical forces ceused by the geochemical reactions in the tailings.

Section B.6 Radcr Parrier, Subsection B.6.1 Sumary p. B-29 The DRAP only considers the barrier (about crly 1.5 foot thickness of clean soil) to attenuate raden emissions and reduce the potential inhalation or direct radiation doses to individuals that may occupy the surface of the site.

The DRAP had ret a #ressed the preventive neasures to control or prevent the migration of other toxic contaminants such as, uranium, radium (which could radioectivPly transform to radon), lead, Vanadium, Cadmium and silver, due to the pecerenical processes described by Markos and Eush (1981a, b). The revised DRAP should consider and address the appropriate eff'ucnt/ certaminant control measures to prevent migration of these toxic contaminants or to mitigate their effects on the environment.

Secticn b.6.2, Conceptual Design, p. C-29 The NRC staff feel that the conceptual design of the radcn barrier and superimposed covers as described or proposed in the DPAP is inadequate to ensure both short tern and long term stability of the site ard prrtection of public health and sa'rty and the environment. The revised CPAP should describe in detail hcw the tailings will be stabilized ar.d Few tFe design of the radon Sarrier and superimoosed ccvers will take into consideration the DOE study results provided by Markos and Bush.

Section P.6.7, Moisture Content, p. B-33 The first sentence of this section states: "The long term meisture content of the cover naterial Fat tren estimated at 17.5 percent and the tailings at 10

,o '. .

6 per cent." Judging from the results of the Markos and Bush studies, the above relative conditions of moisture contents #cr the cover material and the tailings with highly hygresccpic salts will draw moisture from the cover ,

material, cause cracks in the radon ccver, release radon, and allow other contaminants to migrate to the surface of the tailing site. The revised ORAP should describe how the DOE plans to r:iticate these problems.

Section D.3.6 Geologic Hazards, Subsection 0.3.6.1, Geomorphic Ha:ards, Erosion by other prece;ies, p. 0-30 The second paragraph of this subsection described a large sinkhole, about 25 feet wide by 35 feet long and four to five f 4 to 51 feet deep, which has evidently devcirred within the last few years near the north edge of the tailings pile. With regard to this large sinkhole, the ORAP stated: "The sinkhole showed evidence of recent expansinn during on-site reconnaissance in October and November of 1984." Further, within 50 feet to the east of this feature, the third paragraph described several smaller sinkholes, with diameters of three to five feet and from three feet or more in depth. .TFe DPJ1P steres that the cause of these large and small sinkholes is not known and cenjectured that an underground cavity may have existed due to previous construction.

However, it is pcssible that the geochemical processes of dissolution of salts cnd subsequent dissolution of silicate materials by soil moisture solutions of high ionic strength and low pH observed by Markos and Bush (1981) is contributing to the volume chances vithin the tailings piles or cover material to eventually create large solution cavities and subsidence or collapse of the affected parts of the tailirgs cr cover materials.

The DOE should investigate the cause of these sirkholes and describe the remedial and protective acticns that will be taken to prevent the formation of these on-site erosional feature: agair at the proposed Cheney relocation site.

Section D.3.6. Geologic Hazards, Subsection 0.3.6.1, Geomorphic Hazards, Erosion by cther processes Too paracrapF, p. 0-31 This paragraph states: "Burrcwire by prairie dog colonies is widespread, especially near the northwest corner of the site. This causes disruption and dispersion of the clay cap and contributes te ernsion of the area. Wind gusts were observed dispersirc meterials brought to the surface in burrows during the l

an-site investigation." It is very likely that the materiels brought to the surface in Ferrows are contaminated with toxic materials from the mill tailings. The DOE shoule address in the revised DRAP the remedial /pretective r:easures that will be taken at the Cteney relocation site to prevent sini'cr disruptien and dispersion of the clay cap, erosion of the area and atmospheric resuspension or hydrologic dispersion / runoff of the potentially contaminated materials brought to the surface in burrows.

,g . .

. I l

SS 9/11/86 SLOPE STABILITY I , fi3 ;fb$y i

GE0 TECHNICAL ENGINEERING REVIEW 0F THE GRAND JUNCTION, C0.

DRAFT REMEDIAL ACTION PLAN (RAP) prepared by: Engineering Branch, WM Section B.4, Slope Stability, Pages B-11 to B-21:

A review of the stability analysis and the parameter values which were used in the analysis raises several questions pertaining to the estimated minimum factor of safety. These concerns are discussed below,

a. Are the shear strength values shown in Figures B.4.1 and B.4.2 for the tailin materials)gs material (soil layer 3 that includes fine-grained slime, the foundation soils (soil layer 5) based on consolidated-drained (CD) soil conditions? The adopted strengths for the above soils appear to be unreasonably high and use of.the drained strength when assessing short-term stability is questionable and possibly unconservative. The staff recommends that short-term stability be assessed using the appropriate unconsolidated-undrained (UU) strength values for each of the slow draining soil layers. For the fill materials, the shear strength values should be determined by laboratory testing at placement densities and moisture contents which fall within the range permitted by the compaction control specifications.

b. The long-term stability analysis shown in Figures B.4.3 and B.4.4 use shear strength values for the radon barrier (soil layer 2), and soils 3, 4, and 5 that are based on consolidated-drained (CD) conditions.

These values appear conservative provided the soils do not become wet and saturated during the design life of the project. What monitoring is planned to check that these soils do not become saturated under which conditions lower shear strengths could be reasonably anticipated? For the long-term condition, if monitoring is not planned, the staff recommends a conservative approach which would assess stability using the lower of the strengths from either the consolidated-undrained (CU) or the consolidated-drained (CD) shear test results (see NRC Regulatory Guide 3.11). For the fill soils, these strengths should be determined by testing at the planned placement densities and moisture content range permitted by the specifications,

c. Figures B.4.1 to B.4.4 indicate that the surface soil extending from the toe of the pile is soil 4. Will this soil layer meet the same

, 4 ,

SS 9/11/86 SLOPE STABILITY DRE 9

design requirements as the recompacted low permeability soil layer 4 that will exist under the tailings? If so, what distance will this compacted layer extend from the toe of the pile. Discussion should be provided on the importance of this design feature.

d. Figure E.5.3 reports shear strength values for the radon barrier material and the low-permeability liner material from a triaxial compression test performed on the same soil sample and at three different densities and three different moisture contents. The results of these tests are questionable because the lab samples were tested at densities and moisture contents which are unconservatively different from the planned design placement densities and moisture contents. It is standard engineering practice to perform triaxial compression tests on several samples of the same material and at the same density and same moisture content. The staff recommends that the stability analysis use shear strength values for the radon barrier material and the low-permeability liner material that have been determined by laboratory testing at design densities and moisture contents to .be permitted by the compaction specifications.

e. The staff questions the representativeness of the strength parameter values reported in Table E.6.7 for the tailings material. Based on the staff's experience and typical values reported in the litsrature, the strength values reported in Table E.6.7 are unusually high and may be unconservative for use in a stability analysis. The staff agrees with DOE's reference (Vick, 1983), that typical values for friction angles for drained sands range from 30 to 37 degrees.

However, these are not typical shear strength values for a soft cohesive soil which would include the slime tailings material. A soft cohesive soil could have much lower strengths than what was determined by Colorado State University (CSU) testing. The staff is attempting to obtain and review the CSU document which reports these high strength results. The staff plans to check that the materials are similar and were tested under conditions which are expected to exist at the Grand Junction project site. Additionally, in an attempt to better understand the strength properties of the tailings, the staff requests that the laboratory results from all direct shear and triaxial compression tests performed on Grand Junction tailings material be provided for review.

Section B.7, Ground Settlement, Pages B-53/B-54:

A review of the settlement analysis and the parameter values which were used in the analysis raises several questions related to the i

• I I

gi -

SS 9/11/86 SLOPE STABILITY P

reasonableness of the estimated settlement. These concerns are discussed ,

below.

a. The consolidation test results shown in Figures E.6.23 and EI6.25 indicate that the sand and the sand-slime samples had water added after the test was initiated. This same procedure has not been indicated in Figure E.6.24 which shows the consolidation test results for the slime sample. Was the sample of slime material saturated at the start of the test? Since consolidation tests on saturated slime material would likely reflect greater soil compressibility, the omission of wetting the sample would likely result in unconservative results. The test sample for the slime material was also prepared at a much higher density than the DOE proposed design density and at a moisture content greater than the proposed placement moisture content. Because the laboratory preparation and testing procedures do not duplicate anticipated field conditions, the results become questionable and may be unconservative. .

b. Figure E.6.23 indicates that the sand-slime sample was tested at a moisture content greater than the proposed design moisture content?

What is the reason why the sample was not tested at the design moisture content and discuss the effects of the difference in i

moisture between the lab and actual field placement on the estimates of settlement? Provide discussion that addresses whether the sand-slime material that was tested in the lab is similar (classification, gradation, plas'ticity) to the material that is expected to be placed at the Cheney Reservoir disposal site allowing for the expected construction operations of excavation, transporting and placement.

c. The staff questions the magnitude of the estimated immediate settlement (2.45 feet) for the relocated tailings and the time required for this settlement to occur. Section B.7, Ground Settlements, indicates that the immediate settlement in the compacted tailings was calculated using conventional settlement methods which incorporated laboratory test results of the tailings material. The report also indicates that the construction of the final embankment and subsequent placement of the radon barrier is expected to take three years. The staff has several concerns.

First, the analysis completed assumes that settlement will occur immediately after the tailings have been placed. Immediate settlement for the slime and sand-slimes mixture is not a reasonable

- assumption. Primary consolidation will likely require several years to occur after the fill has been placed. Therefore, it is very

_ . .. - .. - . - . _ ~ . _-

, 4 i ..

SS 9/11/86 SLOPE STABILITY

_4-i unlikely that all of the estimated settlement of 2.45 feet will occur

, prior to placement of the radon barrier. Second, Section E.6.6 indicates that a compression index of 0.13 was used to characterize .

4 the tailings for design purposes and that this value corresponds to the sand-slime mixture. Since the slime material is more compressible than a sand-slime mixture, the use of a compression index of 0.13 may be unconservative in estimates of settlements if actual placement operations of the tailings result in segregated placement of slime and sand materials. Discuss the operations which are planned that will result in a unifonn blending and placement of tailings material.

In recognition of these concerns, the staff recommends that a settlement monitoring program be implemented which would record actual settlements

and permit future settlements to be estimated. This record would indicate where settlements would be within tolerable limits and when placement and compaction of the radon barrier should begin. ,

Section E.6.5, Compaction Test Section E.6.6, Consolidation Test, Pages E-134/135:

) For design purposes, the RAP has adopted parameter values for compaction and consolidation that are representative of a sand-slime mixture. No basis has been provided which would explain why the selection of these i specific parameter values are representative of the Grand Junction tailings. If the pile material consists of a high percentage of slimes,

then using a value that may be appropriate for a sand-slime mixture to assess design performance (settlement, stability, etc.) would not be l

appropriate. The percentage of slimes, sand-slimes, and sands that l

comprise the tailings material should be identified and the staff

! recommends that discussion be provided which would justify the use of *

! sand-s10ne parameter values as being representative of the tailings material.

i General Comment:

Considering the maximum depth of iiost penetration for this area and the i thickness of the erosion barrier, what specific design features are being

planned to prevent frost heave and frost damage to the radon barrier?

! Section B.9.3, Perimeter Aaron, Page B-60:

l The staff has concerns related to the impact that the perimeter rock apron

will have on the engineering properties of the foundation soils as the I

J i._,__________.. _.- . _ _ _ ___

SS 9/11/86 SLOPE STABILITY apron serves to provide toe protection from surface water erosion. The ~

shear strengths of the foundation soils were based on high blow counts from standard penetration test results where the natural foundatiott soils have low moisture contents. Since the foundetion soils have low natural moisture contents and the in-situ dry densities are relatively low (Table E.4.1), a significant reduction in shear strength and an increase in soil compressibility could result if the soils were to become saturated because of water collected in the rock apron. There is a need to verify by laboratory testing that the foundations soils will retain adequate shear strength and exhibit acceptable compressibility characteristics if they were to become saturated, or to demonstrate that these soils will not come sa y aud. p y jggrj p g i h i ] k o,A R ....

M -

""'~";7'"""'""""'""""""""'"

17 . "". 5 2 '!" ; " ' ,

.. ...... v. eom .v o.. .vo avi.a.

Section B.6.7, Moisture Content - Radon Barrier, p. B-37:

It is questionable whether the long-term moisture content of the radon barrier soil (17.5%) has been conservatively estimated for several reasons. First, Table E.5.1 indicates that the in-situ moisture content of the radon barrier soil is 10.1% which is significantly lower than the estimated long-term moisture content. Second, if the radon barrier will be placed and compacted at a moisture content of optimum to 3 percent above optimum (RAP, p.B-37), then based on the results reported in Tables E.2.3 and B.6.4, the placement moisture content could be as high as 18%.

Since the annual precipitation at Grand Junction is 8 to 9 inches and high temperatures can be expected during the summer months (RAP, Section E.3.3), it would be reasonable to expect the long-term moisture content to be much lower than the placement moisture content. Third, high blow counts from standard penetration tests in Cheney Reservoir borrow material (RAP, p.32) and the low in-situ moisture contents and densities reported in Table E.5.1 indicate a material at moisture contents much lower than' the estimated long-term moisture content. As identified in the NRC Standard Review Plan, it is reconnended that values which have been measured for the near surface material existing at the borrow site be correlated to the conditions at the actual disposal site to aid in the selection of a conservative long-term moisture value. (see RAP, p. B-45, paragraph 2). The staff recommends that a more conservative long-term moisture content be estimated because of these staff comments.

Section B.6.7, Moisture Content - Radon Barrier, Page B-37:

It is unclear which value represents the optimum moisture content of the radon barrier soils. Section B.6.7 states that the optimum moisture

i . .-

SS 9/11/86 SLOPE STABILITY i.

content is 19.2%. Tables E.2.3 and B.6.4 report this value as 18.0%, and i

Table E.5.1 identifies this value as 19.6%. Since the placement moisture content is determined from this value and certain aspects of the design ,

are based upon this value, clarification of the correct value should be provided.

Section B.2.1, Design Requirements, p. B-7:

It is unclear whether the materials used to construct the low-permeability layer will be obtained from the foundation materials at the Cheney Reservoir site or whether they will be obtained from another borrow l

source. The RAP indicates that the soil layer will be placed and i compacted to a minimum of 90% of the standard Proctor maximum dry density (ASTM D-698). All rock larger than 6 inches will be removed prior to compaction. If the layer is intended to " reduce the amount and rate of contaminant migration" (RAP, p. B-3), then it becomes questionable whether 4

the required permeability can be achieved when'the soils are placed at this moderately low degree of compaction. Additionally, if the materials j contain a large percentage of coarse material, it would be difficult to

! achieve the low-permeability at the planned density limit. The staff requests that the RAP identify the material type (classification, gradation, plasticity) for the low-permeability soil layer and that the soil be placed and compacted to a minimum of 95% of the standard Proctor i maximum dry density. In order to assure that the required impermeability

' will be achieved, the RAP should identify the specification requirements l

which limit the percentage of coarse grained material and the field j procedures to be used to control the maximum size and to assure the needed gradation. It is recommended that this material require a minimum of 30 4

percent passing the No. 200 mesh sieve to assure impermeability.

i Section B.6.8, Radon Emanation, p. B-37:

As recommended in the NRC Standard Review Plan, the value of the long-term

! moisture content should be factored into the determination of radon emanation, E. The values of E reported in Table B.6.5 were determined for .

l a range of moisture contents and the average value for E was determined.

The DOE should provide justification why this average value reflects the long-term moisture content that can be expected at this site.

Tables B.6.2, B.6.3, B.6.4, E.2.3, Radon Diffusion Coefficients:

What methods were used to obtain the as-tested dry density and moisture content? Specifically, what procedure was used to compact the samples and how were they dried or wetted to obtr.in the test moisture content? In

--,-,-yw-- - - e,-w.-,- en,w--=,-- ---..---=-----e-- *%w----,--='.->---=--e.-e-,me- --. -m...r---. ,v-- - , - - - .------w------'w-s -,,,. . - .

t-SS 9/11/86 SLOPE STABILITY order to assure accurate measurements for diffusion coefficients, it is '

important that the methods for compacting lab samples be similar to the field compaction methods, and the laboratory procedures for wetting and ,

drying the samples simulate conditions that can be expected in the field.

4 Tables B.6.2, B.6.3, B.6.4, E.2.3, Radon Diffusion Coefficients:

The staff agrees that the cover diffusion coefficient is one of the most

' influential parameters used for estimating the cover thickness and the resultant radon flux. The estimate of the Cheney Reservoir cover radon diffusion coefficient is based on the results of tests performed on one j sample. The RAP indicates that the borrow for the radon cover will be

' obtained by selective stockpiling of the foundation excavation material j- (DRAP, p.33). Since the error in the parameter value discussed in Section

' b.6.13 is a function of the number of samples tested, and since the -

material properties of the radon barrier borrow soils can be expected to vary over short distances due to the extreme variability of the surficial l

deposits in the site area (DRAP, p. E.36), it is recommended that the

, estimate for cover diffusion coefficient be based on an evaluation of

results from several samples. Section B.6.13 (page B-47) mentions that additional diffusion coefficient measurements will be made on borr'ow material samples once the final borrow site is selected. In recognition of the need for additional test data, the staff is unable to concur in the design cover thickness at this time. Once the testing has been performed, the additional data should be submitted so that a review of the required cover thickness can be completed.

Section B.6.10, Radium Content, p. B-44:

i Were there any radium extraction operations at the Grand Junction i processing site that would result in the Ra-226 not being in secular equilibrium with the parent Th-2307 If so, to what degree is the Ra-226 out of equilibrium? How have these operations been considered in the

! estimate of the tailings radium concentrations listed in Table B.6.1 which i would account for the ingrowth of Ra-226 from the parent Th-2307

General Coment:

! What provisions are planned for disposing of additional vicinity property material after the radon barrier has been placed on the encapsulation cell?

i

,- - - - - , , , , - , . - - , . . - . . . ,.,. --------,.- w w- m--w

t ** .

SS 9/11/86 SLOPE STABILITY P

Section B.6.2, Conceptual Design, p. B-29. Last Bullet:

What does the "30-year floating average" represent? .

d 4

i i

4 l

l l

l l

l

, . , . _ . . - - - - - _ _ . _ - - . . _ - - - , . _ . . . - , , .-.