ML20212D956
| ML20212D956 | |
| Person / Time | |
|---|---|
| Issue date: | 10/29/1986 |
| From: | Martin D NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-54 NUDOCS 8701050184 | |
| Download: ML20212D956 (35) | |
Text
,o
'e OCT 2 9 1986 WM54/MH/10/15/86 WM Rccord Fife Wti Project [
Oacke; no. _/
John G. Themelis, Project Manager pajt Uranium Mill Tailings Project Office LP3 U.S. Department of Energy DN!ribution:
Albuquerque Operations Office P.O. Box 5400 Albuquerque, NM 87115
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(R. e_'_ui. n_.to_WM_, 62_3 S.S._)-
Dear Mr. Themelis:
Enclosed are the NRC comments on the Grand Junction draft remedial action plan. These follow the draft comments sent on September 18, 1986, and reflect discussions held with your staff and the TAC during and after our recent site visit.
Although we have quite a few comments regarding details of the reclamation plan, we believe the Cheney Reservoir Site is a good selection. Meeting the EPA standards at this site will likely require only the use of standard UMTRAP engineering practices and should not require any unusually difficult or expensive design features.
If you have any questions regarding these comments, please contact Mark Haisfield at (FTS) 427 4722.
Sincerely ORIGINAL SIGNED BY Dan E. Martin, Section Leader Uranium Recovery Projects Section Low-Level Waste and Uranium Recovery Projects Branch Division of Waste Management Office of Nuclear Materials Safety and Safeguards
Enclosures:
NRC Comments 8701050184 861029 PDR tJASTE I4M-54 PDR OFC :WMLU g :WMLU gy
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6 CONDENSED DOCUMENTS / MARK H GROUNDWATER COMMENTS ON THE DRAFT REMEDIAL ACTION PLAN GRAND JUNCTION, COLORADO
GENERAL COMMENT
S 1.
Possible Cross-river Contamination The DRAP states that groundwater moves west-southwest and discharges into l
the Colorado River. However, several conditions and statements, l
contained in the DRAP, raise questions on the validity of this statement and the possibility that groundwater may flow south, under the Colorado River and impact water quality in the area south of the river. These conditions include:
1.
From cross-sections presented in Figures D.5.3, D.5.4, and D.5.8, it appears that the alluviam-Mancos Shale contact dips south, toward the Colorado River. This lithologic contact may influence the flow direction, as seen in the southwestern direction of groundwater flow.
2.
Contaminate plumes have been mapped and interpreted as moving west, although there is a clear northern component to the migration. The possibility of southern migration of the plume, similar to that observed north of the site, has not been addressed.
3.
Figure D.5.15 indicates a saturated thickness of alluviam beneath the riverbed of the Colorado River of perhaps ten feet.
This supports the premise that southerly flowing groundwater does not necessarily discharge into the Colorado River. There-fore, it is possible that groundwater flows beneath the river in the alluvial material, and may impact potential groundwater users in the area south of the Colorado River (an occurrence of groundwater ficw such as this has been observed at the Shiprock UMTRA Project site).
DOE has not verified that contaminated groundwater, near the processing site, fully discharges from the groundwater system. Therefore, the possibility exists that groundwater flows beneath the Colorado River and may impact the water quality in the area south of the river. DOE needs to address this possibility by characterizing the quality of groundwater in this area and assessing possible impacts to consumers of potentially conta'minated groundwater.
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a 6 CONDENSED DOCUMENTS / MARK H 2.
Possible Northward Flowing Contaminants According to the DRAP, groundwater flows west-southwest and eventually discharges into the Colorado River, resulting in a finding that public health will not be jeapordized.
However, when interpreting data and information contained in the DRAP, groundwater in the Dakota Sandstone may be impacted by contaminated groundwater emanating from the processing site in the alluvial aquifer. This possibility cannot be confirmed or denied, because data and information on the Dakota Sandstone have not been collected.
The following conditions support the determination that additional information needs to be collected:
1.
On page D-47, the DRAP states that the Mancos Shale thins west of the Rte. 50 bridge (.5 mile), where the Dakota Sandstone subcrops with the alluvium. Therefore westerly flowing ground-water, from beneath the tailings may reach this alluvium-Dakota Sandstone contact, and affect groundwater in the Dakota Sandstone.
Although the direction of groundwater flow in the Dakota Sandstone has not been established in the DRAP or the DEIS, page F-137 in the DEIS states that the Dakota Sandstone dips from south to north, with the recherge zone probably located south of the site.
Using this information, potentially contaminated groundwater in the Dakota Sandstone should flow north, away from the zone of recharge, or at least maintain a component of northern flow.
Therefore, potential groundwater users may be affected by ingesting this water.
2.
Using data available in the DRAP, NRC staff have detennined that downward hydraulic gradients, from the alluvium to the Dakota Sandstone, may exist up to five feet. This potential gradient may be enough to promote downward migration of contaminated groundwater, through the Mancos Shale, before there is actual contact between the alluvium and Dakota Sandstone.
These conditions, when used in combination, lead to a hydrogeologic scenario in which contaminants may impact the groundwater in the Dakota Sandstone either by possible downward migration through the Mancos Shale, caused by downward hydraulic gradients, or by direct contact of the alluvial material with the Dakota Sandstone.
DOE needs to characterize the direction of groundwater flow in the Dakota Sandstone, so that the above scenario, and the scenario described in the DRAP can be confirmed or discounted.
Of particular importance is the area adjacent to and west of the Rte. 50 bridge, where the Mancos Shale allegedly pinches out.
This information should be capable of substantiating the hydrogeologic scenario proposed in
s 6 CONDENSED DOCUMENTS / MARK H the DRAP, and lead to subsequent conclusions pertaining to aquifer restoration or institutional control of groundwater.
t 3.
Waste-water treatment and dewatering Page 59 of the DRAP describes potential waste-water treatment and dewatering activities, and mentions that projected volumes of contaminated water will dictate the method of treatment.
During a site visit to the processing site on.0ct.1,1986, nembers of the TAC mentioned that ground-water in the zone of the tailings will probably be pumped to an unlined evaporation pond located on-site, north of the tailings pile; this removal of groundwater is designed to de-water the tailings. Discharge of the tailings water into these unlined ponds may further degrade groundwater quality at the site and. vicinity. The following factors provide the technical basis for this conclusion:
1.
The influx of wa'ter to a surface impoundment will promote infiltration and percolation to the water table by creating a source of high hydraulic head. This induced infiltration may produce a groundwater mound, resulting in radial flow of contaminated groundwater away from the pile.
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2.
Groundwater pumped either from sumps or wells located in or near the zone of tailings will create a cone of depression around the wells and lead to capture of additional groundwater, greater than that originally found in the pores of the tailings. This cone of depression may capture groundwater percolating away from the surface ponds, causing the water to c'Jain migrate through the tailings, leach out additional contamination and further degrade water quality. Thus, groundwater may be recycled through the tailings material several times with ever-increasing concentrations of contaminants.
J l
This type of problem has been observed at the Shiprock, New Mexico UMTRA site, where leaching fluid, disposed in unlined raffinate ponds, contaminated upgradient monitor wells and generally increased groundwater contamination over a larger area. The magnitude of this potential problem, however, is not known because dimensions of the pond, pumping scenarios i
and design of the flow barriers have not been finalized. Therefore, adequate construction of an evaporation pond (if a water treatment facility is not used), with a liner, should be considered since proper construction may ultimately improve groundwater quality in the site and vicinity by permanently removing contaminated groundwater.
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4 6 CONDENSED DOCUMENTS / MARK H 4.
Groundwater Flow Regime at Cheney Reservoir In general, the groundwater flow regime at Cheney Reservoir has not been described in such a way that independent analyses of the conclusions can be performed.
Several pieces of information that would make these analyses possible, include:
1.
Water levels in Figure E.7.4 " Geologic Cross-section B-B'".
2.
A consolidation of water level elevations in tabular form, so that seasonal fluctuations can be quantified.
3.
Lithologic logs for monitor wells 507, 508, 509, and all the boring / monitor wells, as plotted in Figure E.7.2.
4.
Cross-gradient information, south-east of the site towards Cheney Reservoir, such as water level and water quality.
5.
More definitive conclusions on the groundwater discharge location, potential for groundwater flow towards Cheney Reservoir and seasonal fluctuations of the water table, location of actual water table and potential for high elevation perched aquifers.
The first three points can be addressed by including the information appropriately in the DRAP.
The fourth and fifth can be addressed by constructing additional monitor wells in strategic locations. During the site visit on Oct.1,1986, the TAC produced a map of potential locations for five additional wells to be constructed near the embankment, southwest of the alternative site.
However, NRC staff conclude that information may also be effectively collected by drilling a well south-southeast of the site, across Indian Creek, in the direction of Cheney Reservoir. This will provide additional information on regional water levels, flow directions and water quality near a significant source of water, and when used in combination with the other proposed wells, will greatly increase current knowledge of the regional flow regime at the Cheney Reservoir site.
5.
Objectives of Low Permeability Layer at Cheney Reservoir DOE is proposing to employ a liner at the Cheney Reservoir citernative disposal site.
The purpose of this liner, as inferred from the DRAP, is to provide a low-permeability layer that is more permeable than the cover, and to improve the alternative capabilities of the foundation soils. NRC agrees with DOE that groundwater, though not a major
6 CONDENSED DOCUMENTS / MARK H resource at this site, needs to be protected from potential effects from the tailings.
However, several pieces of information have not been included in the DRAP that would demonstrate the adequacy of the low-permeability liner. These include:
1.
Permeability results of representative material samples, tested at the design compaction specifications.
2.
Quantitative projections of leachate concentrations after interactions with the liner material.
These data should provide adequate assurance that the permeability of the liner is high enough to avoid a " bathtub effect," and low enough to prevent upward and/or lateral movement of groundwater into the waste, caused by saturated conditions in the foundation soils (it may be necessary to employ a capillary break beneath the liner to prevent groundwater movement into the tailings). The information should also demonstrate that leachate passing through the liner material will not have contaminate concentrations high enough to significantly affect groundwater quality.
DETAILED COMMENTS 6.
Section 3.5, Page 34, Residual Groundwater Coatamination Although the DRAP describes the ground water pollution at the Grand Junction site, it does not evaluate the consequences of abandoning the existing ground water pollution after reclamation activities, as required by the Title I standards and the Memorandum _of Understanding between the NRC and the D0E. However, the Draft Environmental Impact Statement for the Grand Junction site does contain information on this subject.
There-fore, the following comments refer to the appropriate sections of the Draft Environmental Impact Statement that deal with the effects of residual ground water contamination at the Grand Junction processing site.
1.
DEIS, Section F.3.2.2, Page F-147, Water-quality Impacts After the tailings are relocated to the Cheney Site, impacts to water quality near the processing site would be due to residual contamination in the ground water and possibly sorbed or precipitated contaminants in the alluvium.
To evaluate the persistance of residual contamination in groundwater, a mixing
e 4
6 CONDENSED DOCUMENTS / MARK H model, using a number of assumptions, was employed. However, the text does not indicate if the model overestimates or underestimates the length of time it would take the aquifer to restore itself by natural methods. The text should clarify whether this model is providing conservative or realistic results and justify the conclusion.
2.
DEIS, Section F.3.2.2, Page F-147, Water-quality Impacts 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 and groundwater 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.3.2.2, Page F-147, Water-quality Impacts The contaminated material excavated from the Grand Junction processing site will be replaced with material excavated at the Cheney site. This means that 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/or 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 o'n the ground water quality, positive or negative, from the fill material that will be placed at the Grand Junction processing site.
4.
DEIS, Section F.3.8.5, Page F-174, Likely Degree of Human Exposure Likely To Occur In discussing the health effects that coulo 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.
6 CONDENSED DOCUMENTS / MARK H <
l 7.
Section 4.3.7., Page 50, Groundwater Restoration Alternatives In defending their decision that a states the hydrogeologic setting (quifer restoration is unnecessary, DOE i.e., proximity to the nearby Colorado River) would complicate the effort by implying that' recharge of relatively fresh waters into the aquifer system would either hinder the restoration of the poor quality groundwater, or increase the cost of restoration by pumping diluted groundwater.
It would appear logical, however, that a nearoy source of recharge would improve the efficiency of the restoration if extraction wells were properly placed; the fresh water recharge could i
improve the quality of the groundwater faster, and allow the restoration process to continue without the threat of the aquifer system drying out.
The success of the restoration, therefore, will be dependent on the design and pumping scheme of the well system. DOE should qualify the statement that the hydrogeology of the site will complicate the restoration effort, with examples and explanations (i.e. cost-benefit analysis) on how the option of restoration is infeasible.
- 8.
Section D.5.2, Table D.5.6, Page D-110, Water Quality Data 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 DRAP should explain the occurrence of this high value and describe the environmental effects and any ground water renedial actions that will be required.
9.
Section D.5.2, Tables D.5.6, Pages D-83 to D-150, Water Quality Data 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 D.5.6 yielded unacceptable balances, which implies an inaccurate analysis for the major ions.
Therefore, cation / anion balances for each sample should be included in Table D.5.6 and the text should describe the validity of the chemical data if there has bee a lapse in the DOE quality assurance sampling and analysis program.
- 10. Section D.5.2, Figures D.5.1.-D.5.4., Page D D-54, Cross-section of i
Processing Site
[
The DRAP provides cross-sections of the ta: lings pile and a base map for locating these cross-sections.
However, tt Doring locations from which these figures were developed, are not included on the base map. These control points are necessary to determine the accuracy of the cross-i i
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6 CONDENSED DOCUMENTS / MARK H sections and their locations.
Furthermore, the lithology logs of the borings are not contained in the DRAP, or the DEIS. These should be included in the DRAP since remedial action plans are based, in part, on these logs.
- 11. Section D.5.2, Figure D.5.11, Page D-61, Monitoring Well Locations Figure D.5.11 represents the monitoring well locations at the Grand Junction processing site. However, 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 upgradient, alluvial wells 711 and 712, and downgradient, alluvial well 738, for which the water quality information is absent in Table D.5.6.
Figure D.5.11 should be modified to include the location of all the wells used in the monitoring system.
If the present scale of the figure cannot support inclusion of these wells, then an additional figure with an appropriate scale should be provided.
2.
The figure represents the location of monitor 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, or from which strata water samples were retrieved. Therefore, information associated with these wells should be included, or the figure should be modified to remove them.
- 12. Section D.5.2, Table D.5.5, Page D-80, Groundwater Level Fluctuations During the monitoring period from approximately March-September,1985, two downgradient shale wells exhibited enormous water level changes. The ranges of water levels, for wells-729 and 735 are 33.90 and 21.99 feet, respectively; during this time 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 on the part of the technician collecting the samples. 00E should explain the cause of these perturbations.
13.
Section D.5.3, Table D.5.5, Page D-75, Static Groundwater Levels and Water Quality During the monitoring period, both water level information and water quality results were retrieved from the monitor well network. However, in l
several cases, water samples were collected, but no water levels were l
6 CONDENSED DOCUMENTS / MARK H
-9 recorded. Interpretation of the relationships between water quality and the water table elevation, from information collected using this ground-water monitoring method, is not defensible because correlating the two conditions in the same time frame cannot be achieved. Therefore, any comparisons or conclusions that utilized these data in combination may not be valid.
If available, these water level data should be included in the DRAP.
If the information is not available, DOE should assess possible effects on the interpretation of the flow regime and the proposed contaminant migration patterns. Future monitoring activities should include recording water levels from wells whenever water samples are collected.
- 14. Section D.5.3, Figures D.5.16-D.5.20, Page D D-70, Iso-concentration Maps Figures D.5.16 - D.5.20 in the DRAP represent water quality maps for several contaminants found in the groundwater. However, the figures do not include the location of the wells used in construction of these figures, making validation of proper contour line placement very difficult.
The figures should be modified to include the well locations used to construct the map.
Furthermore, 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 quality results are available for wells up-gradient of the processing site, the iso-concentration lines should be extended to reflect contaminant levels in groundwater in these wells.
- 15. Section D.6.6., Page 0-154, Withdrawal Point at Colorado River The DRAP states that comparisons of water quality results from samples taken at Cameo and Fruita indicate no effect of the Grand Junction tailings I
on the Colorado River.
dowever, the DRAP and the DEIS (DOE, 1986) contain i
no data to confirm this. Also, there was no mention of where Grand Junction l
removes 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. The DRAP 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.
- 16. Table E-5.4, Page E-129, Hydraulic Conductivity Values for Radon Barrier Table E.5.4 lists hydraulic conductivity results for the radon barrier material. However, only one actual sample of material was tested. The results from this sole sample do not provide representative hydraulic conductivity values for all the material proposed for the radon barrier. This assertion is defended by statements made in the DRAP (Page E-36) l I
o 6 CONDENSED DOCUMENTS / MARK H where the surficial deposits are stated to be subject to " extreme variability" and " sudden and unpredictable changes in lithology..." that "... can be expected to vary over short distances". The DRAP provides no reasonable assurance that sample,#614-001 is representative of the material to be used in the radon barrier.
Furthermore, the 98% compaction used in one of the tests is not appropriate because design specifications require 95%
compaction. Although this degree of compaction may be observed in the field, it cannot be used in assessing the adequacy of the remedial action.
Therefore, NRC staff conclude that additional samples be tested for hydraulic conductivity values, under realistic and conservative compaction specifications, using material shown to be representative of the proposed radon barrier material. This material should be available since 13 TAC tests pits were excavated during site characterization.
- 17. Section E.7.3, Water Quality and Containment Migration, Page E-177.
Although the DRAP states that the results of a water quality analysis for a surface water sample from Whiting's Ditch are presented in Table E.7.5, they are missing.
It is therefore difficult to evaluate the interpretations reached in this section regarding the relationship' between the ditch as a recharge source and the downgradient wells.
Complete water quality analyses results should be presented in the final RAP. Calculations should also be presented that demonstrate the recharge capabilities of Whiting's Ditch are substantial enough to saturate the observed thickness of the alluvial perched aquifer.
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l 6 CONDENSED DOCUMENTS / MARK H.
SURFACE WATER HYDROLOGY AND EROSION PROTECTION COMMENTS ON THE DRAFT REMEDIAL ACTION PLAN GRAND JUNCTION, COLORADO 1.
Section 3.6.2, Cheney Reservoir Site, Page 38.
This section and section E.8.3 incorrectly state the upstream drainage area of the site as 240 acres, the maximum flow length as 8000', and the locations of the two ephemeral washes as 800' N and 1700' S of the site.
These sections should be corrected in the final RAP to correspond with the upstream drainage area, maximum flow length, and location of ephemeral washes, as stated in other Sections of the RAP.
2.
Section 4.3.8, Surface Water, Page 51; and Appendix B.
j The proposed RAP design includes a rock apron which will be provided to prevent erosion of the toe of the reclaimed pile. We note that this apron will be designed to resist erosive velocities created by sheet flow past the site from the small (310 acres) watershed tributary to the site. Our i
review of the proposed design and supporting calculations indicates that several additional factors need to be evaluated.
l 1.
Examination of the topography upstream of the site and in the site vicinity indicates that the assumption of sheet flow past the site may not be realistic. Because gullies already exist, it appears that there is a potential for the fornulation of preferred flow paths; such paths (gullies, e.g.) would likely be created at random under the present design and could be created immediately adjacent to the rock apron.
Therefore, we conclude that the rock apron should be designed assuming that a gully or preferred flow path exists at the apron and the erosion protection should be redesigned, as necessary. Additional i
hydraulic analyses should be provided in support of the design selected.
2.
Examination of the site topography also indicates that there is a possibility that the ephemeral drainage channels flanking the site and/or Indian Creek, could contribute flow to the 310 acre drainage area past the site by overflowing their banks upstream of the site.
In fact, a diversion (irrigation) ditch already exists which intercepts flow and conveys it to another drainage basin. Therefore, the rock apron may need to be designed for a I
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6 CONDENSED DOCUMENTS / MARK H.
peak flow greater than assumed, in addition to the flow concentration problem identified in (1) above. Additional flood studies should be provided to document that the peak flow past the site will not be greater than assumed, that the apron erosion protection provided is capable of resisting the larger peak flow, or that the design will prevent the formation of preferred flow paths at the apron.
3.
Section B.1.4, Design Considerations, Pace B-5.
This section does not address those design considerations associated with the subtle topographic and vegetational lineament which crosses the lower part of the disposal site. Sections 3.3.4 and E.3.7.1 describe the lineament, and both sections suggest that the final design of the tailings pile should compensate for the accelerated erosion observed along this trend.
It is unclear whether or not the proposed tailings pile design considers accelerated erosion along the lineament because such considerations are not discussed in this nor any other section. The final RAP should discuss how the proposed design of the tailings pile compensates for accelerated erosion along the lineament.
4.
Section B.9.5, Material Properties (Durability), Page B-63.
Erosion protection material will apparently be obtained from the disposal site area, will consist of basalt clasts of questionable durability (Section E.5.2), and will likely require oversizing to account for long-term degradation. Since no other sources of rock have been identified, it is not clear whether rock of better quality is readily available at a reasonable cost.
i In general, oversizing of poor quality rock is not appropriate if rock of better quality is available at approximately the same cost, or if other designs could be implemented to utilize the better quality rock at approximately the same cost.
i DOE should make every effort to obtain high quality erosion material and utilize poorer quality rock only if it is shown that it is clearly impractical (costs are clearly excessive) to obtain good quality rock.
The final RAP should justify the selection of erosion protection material that will be used. This justification should consist of the following:
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6 CONDENSED DOCUMENTS / MARK H '
1.
Identification of several sources of erosion protection, several remedial action designs to accomodate the sizes and durability of erosion protection available from those sources and the costs associated with placement of erosion protection. The rock costs should be broken down by unit cost and total cost for the following portions of the design:
(a) top of pile (b) sides of pile (c
aprons / toes (d
drainage and diversion channels (e
adjacent streams (f
other erosion protection features 2.
Comparisons which indicate that the minimum cost of providing good quality rock greatly exceeds the cost of providing over-sized poor quality rock.
3.
Documentation, calculations, drawings, and design bases used in the above determinations. Oversizing calculations may be performed in accordance with NUREG/CR-4620 (Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Mill Tailings Impoundments), if it is determined that oversizing is necessary and cost effective.
5.
Section E.8.6, Surface Water Quality, Page E-200.
This section states that no surface water quality data exist for the ephemeral streams near the Cheney Reservoir site and gives no ' indication that any will be collected.
The water quality of Indian Creek downstream of the proposed tailings site should be characterized to establish back-ground levels against which subsequent water quality monitoring results can be compared. Such characterization data may also provide insight into the groundwater discharge problem discussed in Section E.7.2.1.
6 CONDENSED DOCUMENTS / MARK H 4 GE0 TECHNICAL ENGINEERING COMMENTS ON THE DRAFT REMEDIAL ACTION PLAN GRAND JUNCTION, COLORADO 1.
Section B.4, Slope Stability, Pages B-11 to B-21:
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A review of the stability analysis and the shear strength parameter values which were used in the analysis raises several questions pertaining to the estimated minimum factor of safety against slope failure. First, the appropriateness of the test procedure, which uses multiple stage triaxial testing to estimate shear strength values for the radon barrier. low-permeability layer, and tailings materials, is questionable and not a typical engineering practice which conforms to a standard ASTM procedure.
It is questionable, based on the unexpectedly high strength values obtained for this case, whether results obtained from this test procedure are conservative and representative of actual field conditions.
In addition, the basis for utilizing a test procedure which varies from normal engineering laboratory testing procedures described in ASTM D-2850 (Ref.
l
- 1) and the manuals of the Corps of Engineers (Ref. 2) and NAVFAC (Ref. 3),
has not been presented by D0E.
Second, the staff questions whether the sand-slime laboratory sample (#17-M), that was tested to establish shear strength, is a conservative representation of the proposed relocated Grand Junction tailings. Laboratory sample 17-M contains 32 percent material passing the No. 200 sieve. However, the RAP indicates that the tailings will be uniformly blended to form a sand / slime mixture that may contain from 30 to 70 percent passing the No. 200 sieve.
In pursuit of resolution of these concerns, the staff has discussed details of the stability analysis with the TAC staff. As stated previously, the strength values appear unusually high for this material 4
type, and the reason for such high strengths has not been resolved through these discussions. As a result, the TAC has agreed to submit ~to the staff j
a revised stability analysis-using the more conservative strength values, which have been determined to be acceptable for this site, identified in Table 1. These values are based on the staff's engineering judgement and experience with other uranium mill tailings sites.
If this revised analysis indicates that minimum stability criteria are still met, the staff's concerns will be satisfied.
The TAC has also agreed to provide a copy of the test procedure for multiple stage triaxial testing for staff revies. An evaluation as to the appropriateness of this procedure is requestec. Resolution of this issue i
is important in reccgnition of the TAC's expressed intention of using this test procedure in the design of other UMTRAP sites.
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6 CONDENSED DOCUMENTS / MARK H TABLE 1 LAYER Q-STRENGTHS S-STRENGTHS PHI C0HESION PHI C0HESION ANGLE (psf)
ANGLE (psf)
Erosion 40 0
40 0
Barrier (1)~
Radon Barrier
- 0 900 27 0
Low-k layer **
0 700 22-25 0
(layer 2)
Tailings (3) 0 700 24-27 0
Surface Soil 0
1000 30 0
(layer 4)
Foundation 0
1000 30 0
Soil (5)
Weathered 0
1300 30 0
Bedrock (6)
Bedrock (7) 0 10000 0
10000
- Compacted to 95% standard proctor maximum dry density
- Compacted to 90% standard proctor maximum dry density i
2.
Section B.7, Ground Settlement, Pages B-53/B-54:
A review of the settlement analysis raises several staff concerns related to the reasonableness of the DOE estimated settlement.
First, very limited laboratory data exists to support the study that estimates the amount of settlement.
The estimate appears to be based on one Colorado State University laboratory consolidation test performed on a remolded sand / slime sample (#17-M) at the proposed design density. Second, based on telephone conversations with the TAC, the staff understands that no
6 CONDENSED DOCUMENTS / MARK H laboratory data is presently available on which to base conclusions regarding the estimated time of primary settlement.
Therefore, the staff concludes that the analyses to determine the magnitude of the estimated imediate and primary settlement for the relocated tailings and the time required for this settlement to occur appears to be inadequate.
A telephone conversation between Steve Smykowski (NRC), Eric Banks (TAC) and Jack Caldwell (TAC) was held on October 15, 1986 to discuss these concerns. The TAC has agreed to submit to the staff a best estimate of the magnitude and time rate of settlement. Since the best estimate will lack supporting laboratory data and the time period required to generate and assess this data could be lengthy, it was agreed that laboratory testing during construction should be performed to verify these estimates of settlement. The staff envisions that verification would require performing representative consolidation testing 'sn samples of the blended tailings material as it is actually.placed at the disposal site. The results from this testing will be used to confirm the estimated settlements. This commitment should be clearly defined in DOE's response to this coment.
3.
Section B.7, Ground Settlement, Pages B-53/B-54:
Thestaffisconcernedwiththeadverseimpactofanticiphtedsettlements on the relatively thin radon barrier cover (1.5 feet).
It appears that the cover thickness was determined based on the radiological assessment of the remediated pile.
It is recommended that the proposed cover thickness be further assessed to determine whether differential settlements could result in cracking and reduction in the performance of the radon barrier to comply with the EPA radon flux standard. Because of the importance to limit settlement and avoid cover cracking, DOE may want to consider the use of field instrumentation to monitor settlement prior to placing the radon barrier. This would permit recognition of when primary settlement is complete and cover construction could begin.
4.
Section E.6.5, Compaction Test, Section E.6.6, Consolidation Test, Pages E-134/135:
For design purposes, the DRAP 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 specific parameter values are representative of the Grand Junction tailings.
If the pile material censists of a high percentage of slimes, then using a value that may be appropriate for a sand-slime mixture to
o 6 CONDENSED DOCUMENTS / MARK H assess design performance (settlement, stability, etc.) would not be appropriate. The percentage of slimes, sand-slimes, and sands that comprise the tailings material should be identified and the staff recommends that discussion be provided which would justify the use of sand-slime parameter values as being representative of the tailings material.
5.
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 low 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 recommended 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.
6.
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 content is 19.2%. Tables E.2.3 and B.6.4 report this value as 18.0%, and 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.
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6 CONDENSED DOCUMENTS / MARK H 5 7.
Section B.6.7, Moisture Content, Page B-33:
The staff considers the -15 bar moisture content as a conservative estimate of the long-term moisture content of the tailings. Since the DOE is using a less conservative value (-2 bar moisture content) for this specific site, the staff is currently investigating the use of the -2 bar moisture content as the selection of the design long-term moisture content of the Grand Junction tailings.
8.
Section B.6.8, Radon Emanation, p. B-37:
1 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.S.5 were determined for 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.
9.
Section B.9.3, Perimeter Apron, Page B-60:
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 apron serves to provide toe protection from surface water erosion. The shear strengths of the foundation soils were based on high blow counts i
from standard penetration test results where the natural foundation soils have low moisture contents. Since the foundation soi.ls 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. As a result of discussions with the TAC, it has been indicated that the rock apron will be graded to allow drainage of the apron which would prevent the foundation soils from becoming saturated.
It is recommended that the DRAP identify this aspect of the design.
- 10. Tables B.6.2, B.6.3, B.6.4, E.2.3, Radon Diffusion Coefficients:
The methods which were used to obtain the as-tested dry density and moisture content should be identified.
Specifically, DOE should identify the procedures that were used to compact the samples and the methods for J
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In 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,
- 11. 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 sample. The DRAP indicates that the borrow for the radon cover will be obtained by selective stockpiling of the foundation excavation material (DRAP, p.33). Sinc 2 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 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 borrow 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.
12.
Section B.6.10, Radium Content, p. B-44:
The RAP should identify any radium extraction operations at the Grand Junction processing site that would result in the Ra-226 not being in secular equilibrium with the parent Th-230.
Additionally, the degree to which the Ra-226 is out of equilibrium should also be identified. These operations should be considered in the estimate of the tailings radium concentrations listed in Table B.6.1 which would account for the ingrowth of Ra-226 from the parent Th-230.
13.
Section B.6.2, Conceptual Design, p. B-29, Last Bullet:
The staff requests the meaning of the "30-year floating average".
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^ 14. General Comment:
What provisions are planned for disposing of additional vicinity property material after the radon barrier has been placed on the encapsulation cell?
REFERENCES 1.
Book of ASTM Standards and Special Technical Fublications, American Society for Testing and Materials.
2.
Engineering Manual EM-111-2-1906, " Laboratory Soil Testing," U.S. Army Corps of Engineers, November 1970.
3.
Department of the Navy, " Soil Mechanics," NAVFAC DM-7.1, May 1982
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GE0 MORPHOLOGY COMMENTS ON DRAFT REMEDIAL ACTION PLAN.
GRAND JUNCTION, COLORADO
'i J
o 1.
Section E.3.2, Regional Geomorphology, Page E-25, paragraph 1 s
s Glacial moraines located near Ridgway, CO, are mentionedswith reference to alluvial terraces in regional drainage basins. This statement is unclear because it does not refer to a figure within the DRAP indicating the location of Ridgway and the glacial deposits.. -In the same light, DeBeque, C0 (page E-26), is not found in the figures.
In all cases, geographic locations referred to in a report <should be located on a f,igure within the report.
2.
Section E.3.2, Regional Geomorphology, Page E-25, paragraph 2 Based on radiometric age data for Grand Mesa, an " average" erosion rate has been calculated for the Colorado River valley. The calculation makes an assumption that the valley has lowered to its present level only recently and is zero years old relative to the mesa age. This assumption is not necessarily valid. An average erosion rate can not be calculated unless a constraining age is known for the valley as well as the mesa.
Therefore, the calculated erosion rate should be reported as a minimum rather than an average.
3.
Each of the following addresses geomorphology of the Cheney Reservoir Site i
Section E.3.2, Regional Geomorphology, Page E-29, paragraph 2 Discussion of pediments that are detached is unclear and needs definition or illustration.
Even though graphic projections of longitudinal profiles of the pe'diment surfaces may be approximate and inconclusive, they would add to the clarity of the scale of pediment extent and of topographic j
relations. As it stands now, the DRAP 'is very unclear as to the L
topographic relations between base level (Indian Creek), each of the nine i
pediment surfaces, and the upper portions cf the drainage basins and Grand Mesa.
Section E.3.4, Geomorphology and surficial deposits, pace E-37 The geomorphic map of the Indian Creek area (fig. E.3.6) indicates nine pediment surfaces in the site area.
Even though the text here explains t
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.,.c 6 CONDENSED DOCUMENTS / MARK H the techniques employea for identifying the surfaces, no data are.
presented which support the differentiation of so many surfaces.
For example, the distinctions between surface P3 and P4, and between P5 and P6 are not apparent on the topographic map of the site or in Soil Survey aerial photographs (Spears and Kleven,1978). Additionally, the DRAP has not addressed the significance of the orientation of surface P7, which slopes perpendicular to the slope of all other pediments in the area.
Without data regarding each surface, NRC can not address the accuracy of the geomorphic setting as portrayed in the DRAP.
The variety of quantitative data normally required to differentiate geomorphic surfaces are obtained through inspections of topographic maps, aerial photographs, and observations in the field. They include:
1) heights above local base level (Indian Creek) 2)
surface orientations 3) descriptions of associated deposits (stratigraphy, grain size, thickness), unless they are comparable from one surface to another 4) soil descriptions (weathered pedogenic profiles) which indicate relative age differences The NRC requests that the final RAP include data as in 1) and 2) above, and suggests that data presented in tabular form will readily show distinctions between surfaces. Data types 3) and 4) are not required at this time because they were observed by NRC during the October 1, 1986, site visit, and are unlikely to raise new concerns regarding site suitability of Cheney Reservoir.
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.
4.
Section E.3.4, Site Geology, Page E-38, paragraphs 2, 3, and 4 The DRAP suggests differentiation of geomorphic surfaces P3a and R3b based on more than one criteria:
- 1) two separate cycles (ages) of pediment formation, or 2) different types of depositional processes for the associated alluvial deposits. Each of these criteria is based upon an observation of relic braided bar morphology on surface P3. The discussion, however, does not conclude which. criterion accurately t
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distinguishes the two surfaces nor does it indicate which criterion was actually used for the classification.
Based upon inspectinn of aerial photographs and a site visit on October 1, 1986, the NRC' disagrees with the distinction of P3-surfaces based on bar-and-swale depositional morphology. With particular reference to aerial photographs in the soil survey of the area (Spears and Kleven, 1978), tonal contrasts resembling bar-end-swale topography are closely associated with modern drainage paths which have developed on surface P3.
The NRC maintains that the observed features do not reflect depositiont.1 landforms, but recent erosion resulting from sheetwash and/or incipient channel and gully formation.
Two items in the DRAP support this interprettdion.
First, the deposits associated with surface P3 bdve been interpreted as debris flows (p.
E-37) which would not be expected to display braided bar patterns normally associated with fluvial deposits. Secondly, the " distinct braided bar pattern"'is observed on surface P3a, which lies immediately adjacent to a roderately sloping interpediment scarp grading downward to Indian Creek (surface P1). Therefore, the tonal pattern may be due to new drainage patterns forming atop the steeper edges of the pediment deposits.
If }his interpretation is correct, it may be problematic for assuring site stability at Cheney Reservoir.
The DOE must show that occurence of incipient drainage lines and formation of new channels and gu' lies in the disposal area will not affect tailings stability, or that the, proposed remedial action will include features to retard the.degradational processes.
j j
(See also following comment, and comments in Surface-Water Hydrology) i l
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6 CONDENSED DOCUMENTS / MARK H
} l 5.
Section E.3.4, Site Geology, Page E-38, paragraph 3 i
This comment is closely associated with previous comment No. 4.
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
" strong caliche cementation" at least 1 m thick in the same deposits.
I Well-developed calcic horizons in an area free of carbonate parent materials suggests long-term surface stability, indicating an age perhaps as old as mid-Pleistocene for surface P3. Lack of well developed B horizons, on the other hand, suggests lack of such stability. These opposing conditions might be interpretted as incipient stages of surface instability on P3, with resultant stripping of textural B horizons by sheetwash.
This concern was amplified by field observations during the October 1, 1986, site visit. A southeastward traverse of the proposed disposal area crossed a number of undulating topographic highs and lows. The total relief in this area is perhaps 1 - 2 meters, with different and more dense vegetation occurring upon the topographic highs. The lows appear to be the focus of sheetwash and soil instability. These conditions should be further considered to detennine that the Cheney Reservoir site will provide geomorphic stability.
6.
Section E.3.4, Site Geology, Page E-38, paragraph 3, 4, and 5 In the discussion of surface morphology, desert pavement, and desert varnish in the Cheney Reservoir site area, references to Dohrenwend (1984) are tenuous or inappropriate for several reasons:
1)
Original bar-and-swale depositional morphology was identified on surfaces P3a and P3b from aerial photograrhy of the Cheney Reservoir site.
In light of above comments, bar-and-swale morphology at Cheney Reservoir is probably not a relic of depositional topography.
Therefore, reference to studies of relic bar-and-swale morphology as an indicator of relative age is inappropriate.
2)
Based on a Cheney Reservoir site visit on October 1, 1986, The NRC disagrees with the observation of desert pavements at the site.
Surface P3 lacks a well developed interlocking texture amoung clasts, common in typical desert pavements. The gravelly surficial material observed at the site instead resembles a lag deposit resulting from eolian deflation of fine-grained matrix sediment. Furthermore, existence of well developed desert pavements is generally recognized
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- 6 CONDENSED DOCUMENTS / MARK H,
as common in hot arid climates, such as exist in the Sonoran and Mojave Deserts.
3)
The DRAP draws comparisons between basaltic pediment deposits on surface P3 and " basalt-bearing" deposits discussed within Dohrenwend (1984). The specific paper-in this reference concerned with surficial 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.
4)
Depiction of the climate of Grand Junction 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 geomorphic comparisons with areas of similar, semiarid climate within the Colorado Plateau.
7.
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.
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 surficial 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.
8.
Section E.3.4, Site Geology, Page E-49, paragraph 2 I
The DRAP makes a conclusion that length of an incised channel is directly related to the basin area which it drains.
However, no morphometric data are presented to support this.
In the Piceance basin north of the site,
6 CONDENSED DOCUMENTS / MARK H 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 channels in the site area. The analysis may assist a determination that a threshold condition does not exist for channel instability on surface P3.
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6 CONDENSED DOCUMENTS / MARK H 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.
Spears, C.F. and Kleven, E.V.,1978, Soil survey of Mesa County area, Colorado:
U.S. Deparanent of Agriculture, Soil Conservation Service, 58 p.
Wells, S. G., McFadden, L. D., Dohrenwend, J. C.,
Bullard, T.
F., Feilberg, B.
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 Guidebook, p. 69-87.
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6 CONDENSED DOCUMENTS / MARK H SEISMIC COMMENTS ON THE DRAFT REMEDIAL ACTION PLAN GRAND JUNCTION, COLORADO
GENERAL COMMENT
E The DRAP does not discuss any geophysical survey which may have been used to support the site investigation findings such as identification of unexposed faults. Discuss the type of geophysical surveys conducted.
If no surveys were conducted explain the reasons.
DETAILED COMMENTS i
1.
Section E. 3.6, Seismotectonic Setting, Page E-42 In the DRAP it is stated that the " stress fields oriented differently than the modern stress field in the interior of the Plateau".
Provide a map showing the stress field orientations in the Colorado Plateau as compared to the surrounding provinces, and discuss if the stress fields are used in delineating the different seismotectonic provinces.
2.
Section E.3.6, Western Mountain Province, Page E-48 j
In the DRAP it is stated that, " faults associated with evaporite flowage or solution also cut Neogene rocks.
Faults of this type 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 and compare to the design earthquake.
2 1
3.
Section E.3.7.4, Analysis of Seismic Risk, Page E-53 Campbell (1981) attenuation relationship is based mostly on earthquake data from California.
Provide the rationale for using this relationship for Grand Junction versus other recognized methods as mentioned in the NRC Standard Review Plan.
4.
Section E.3.7.4, Determination of Floating Earthquake Magnitude, Page E-57 r
According to the definition of the maximum earthquake on page E-14, the statement on page E-57, "the FE magnitude should never be greater than the i
r'o 6 CONDENSED DOCUMENTS / MARK H ME" is not necessarily true.
For example, the Charleston earthquake of 1886, M=7, which is not associated so far with a geologic structure is larger than any known maximum earthquake associated with a structure in the eastern seaboard of the U.S.
5.
Section E.3.7.4. Determination of Floating Earthquake Magnitude, Page E-59 In the DRAP it is stated that "In accordance with seismic design 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) from the site". The distance of 15 km has been based on the average of a group of earthquake records having similar physical properties to the site.
It is used to generate ~ site specific spectra for nuclear power plant sites and 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 acceleration in the Grand Junction DRAP.
6.
Section 3.7.4, Epicentral Compilation, Page E-67 In the DRAP it is stated that the earthquake of November, 1871 appears to be related to Fault 6.
If this is the case it should be considered-capable.
7.
Section E.3.7.4, Recommended Seismic Design Parameters, Page E-67 Identify the references and the formulae used to estimate the magnitude and the acceleration from fault 8 and the rationale for choosing these formulae.
Indicate if the fault type is considered in estimating the magnitude.
8.
Section E.3.8.4, Recommended Seismic Design Parameters, Page E-67 In the Draft Environmental Impact Statement (EIS) (00E/EIS-0126-D, Vol.II, P. E4-1, March 1986) it is stated that "High accelerations may result from the occurrence of earthquakes of magnitude as high as 6.6 cn previously unknown faults within less than five miles of the sites". Based on this statement should the design earthquake be located at a distance less than 5 miles from the site?
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6 CONDENSED DOCUMENTS / MARK H '9.
Table E.3.5, Earthquakes of M 4.0, Page E-89 This table lists earthquakes up to 1981. Update this table to cover recent seismic activities in the area and provide a map showing the locations of these earthquakes.
e-6 CONDENSED DOCUMENTS / MARK H GE0 CHEMISTRY COMMENTS ON THE DRAFT REMEDIAL ACTION PLAN 4
GRAND JUNCTION, COLORADO r
GENERAL COMMENT
To the best of our knowledge DOE has not addressed the potentially adverse short term and long term effects of geochemical processes (due to.the intrinsic geochemical disequilibrium of the unconditioned tailings) which could contribute to the physical instability and potential breach of the radon barrier and migration of toxic contaminants at any of the UMTRAP sites.'It has recently come to the staff's attention that studies of about twenty inactive uranium mill tailings sites by a DOE contractor (Markos 1979, Markos and Bush, 1980, Markos and Bush-1981a and Markos and Bush 1981b, 1983) indicate that salts with sulfate and chloride are mainly responsible for the upward migration of contaminants in the tailings material. Many of these salts are deliquescent or hygroscopic. As such, they are able to absorb moisture from both the interstitial atmosphere of the tailings and the nearby water table.
This process, combined with the dry conditions on the surface of the' tailings, creates an upward flux of salt migration, which in turn transports contaminants. 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, C1, and 50, salts.
Field studies show that the concentratiens of contaminants in the 1
prdcipitating salts.on the surface of tailings are several times to several orders of magnitude higher than in the underlying tailing material.
For example, Markos and Bush (1980) 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 agreement with the experimental studies listed in the Geological Survey Circular 814 (Landa, 1980).
Further, Markos and Bush (1980) observed
- that.the upward movement of salts and contaminants are present in all the twenty tailings they studied during their field investigations. These salts and contaminants move through the protective covers and dikes of the tailings.
The observed profound effects af these salts are:
(1) development of osmotic pressure, (2) liberation of gases within the tailings pile, (3) generation of heat by exothermic reactions, (4) desiccation of areas with Icwer salt content resulting in desiccation
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6~ CONDENSED DOCUMENTS / MARK H (5) blackening (oxidation?) of the surface of some species of vegetation (possibly due to oxidizing gases?),
(6) dissolution of silicate materials in contact with. interstitial or soil moisture solutions of high ionic 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
&nd asphalt covers _on the tailings by forming boils and cracks, thereby loosening the material which becones 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, are elevated in these boils relative to the adjacent areas of
_ tailings. Salts of different kinds usually precipitate on boils.
Active chemical reactions in the tailings can form various gases.
For example, hydrogen sulfide gas was detected in wells on the tailings in Cannonsburg, Pa.
Gases are expressed in formation of various size boils on the surface, especially in slime areas.
The escaping gases create flow structures in F
tailings materials and may be evidence for considerable physical forces. These i-flow structures may act as pathways for the direct emanation of hazardous radon gas towards the surface.
The generation of heat by exothermic reactions occurring within the tailings pile could accelerate the movement of radon and other gases towards the surface.
i i-Crystal growth or precipitation nodules of salts result in volume changes.
Under confined physical conditions, increased volumes may exert considerable forces. The effect of these forces have been observed on dikes where boulders have been dislocated by growth of crystals and on the experimental asphalt cover on part of the Grand Junction tailings which has been broken up by growing precipitation ncdules of salts.
The rate of upward movement 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 Jur.ction, Colorado, indicates that salts removed from the surface by rainfall through dissolution or runoff have been replenished a few months later. Although the distance o' travel of salts in their upward movement for a given time has not been i
4 4
oo p 6 CONDENSED DOCUMENTS / MARK H i presently established, the curve of salt distributicn with depth and the constant regeneration of the salts suggest a continuous process.
This process will continue until an equilibrium is e~stablished.
Laboratory 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 tailings. Constant or extended watering of the surface of tailings suppresses the salts and washes them down 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 and destroy vegetation as has been observed on several tailings piles.
i Another role of salts is the creation of a chemical environment such as very 1
low pH (1.8-3.5) and the supply of anions, particularly sulfate, to other geochemical reactions such as dissolution of silicate and clay minerals.
The long-term stability of clay and silicate minerals represents another area of concern. The hydration energy of deliquescent and hygroscopic salts may have a significant influence on dehydration of clay minerals.
Chemical 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 (1980) also found that the various types of clay and silicate minerals have considerable differences in stability with respect to pH conditions. This might be of concern in terms of the long-term perfor-mance and stability of the radon barrier or the impermeable clay liner if one is proposed.
Dissolution is an important process in tailings which resulcs 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 moves toward the surface with the temperature gradient, evaporation causes oversaturation, and part or all of the solute precipitates. Transportation in response to differences in chemical potentials causes a redistribution of material and volume within the tailings. Silicate and/or clay materials in contact with waters of high ionic strength and low pH may also dissolve 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 into 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 another.
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6 CONDENSED DOCUMENTS / MARK H The overall effect of soluble salts in the tailings is very important. They establish a water circulatory system in the opposite direction to gravity, i
They create an environment where many metals are highly mobile. The salts tend to move to the surface of the tailings carrying contaminants which can enter into the surroundings by surface erosional processes such as wind and runoff.
The salts are corrosive, and they can move through cover materials and tend to destroy vegetation on the surface of the tailings.
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