ML20214T848
| ML20214T848 | |
| Person / Time | |
|---|---|
| Issue date: | 07/08/1986 |
| From: | Knapp M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-86 NUDOCS 8609300422 | |
| Download: ML20214T848 (7) | |
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JUL 8 1986 14lM s/f WMLU r/f h "/00/00/01 NMSS r/f RE Browning MJ Bell J0 Bunting RD Smith, URF0 D Gillen M Knapp D Martin M Haisfield John G. Themelis, Project Manager S Sntykowski B Ford Uranium Mill Tailings Project Office M Fliegel M #4tudjd U.S. Department of Energy Albuquerque Operations Office P.O. Box 5400 Albuquerque, NM 87115
Dear Mr. Themelis:
The Nuclear Regulatory Commission (NRC) has completed its review of the Draft CADSAR for the Slick Rock, Colorado site.
Our review consisted of a broad overview looking for fatal flaws, potential issue areas, and omissions. The Draft CADSAR is a very preliminary document, which is produced before much environmental data has been collected and before detailed engineering data is available. With this in mind, we did not see any fatal flaws with what appears to be the preferred alternative.
However, NRC concurrence that this alternative will meet Environmental Protection Agency standards cannot be provided until the detailed information discussed above has been reviewed.
The enclosed comments, which identify potential issue areas and omissions, would be useful in improving the quality of the Final CADSAR and should be incorporated where possible. These comments also provide requirements which will be necessary when developing remedial action plans.
It is in this spirit that our comments are provided.
If you have any questions regarding these comments, please contact Mark Haisfield at FTS 427-4722.
Sincerely, Malcolm R. Knapp, Branch Chief Low-Level Waste and Uranium Recovery Projects Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards WM Record Eile WM Project
Enclosure:
Docket flo.
As stated PDR #
l LPDR i
Distribut;on:
8609300422 860708 m
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___j WM-86 PDR (Return to WM,623 SS)_ __ _i 0FC :WMLU
- WMLU NAME :MHaisfield :DE rt
- MR Knapp DATE:86/08/'/
- 86/08/0?
- 86/08/g
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REVIEW 0F SLICK ROCK DRAFT CADSAR SITING AND HYDROGE0 LOGIC COMENTS Section 2, Alternate Site Selection, Page 4 and Section 8, Recommendations Page 29 Through a site selection process carried out with-the State of Colorado, 3
l' stabilization of the tailings out of the floodplain, relocation to Burro Canyon, or relocation to Pioneer Uravan sites were selected.
Pioneer Uravan was not characterized (p. 4) and Burro Canyon site will not be further characterized (p. 29) beyond one hole drilled for geotechnical and hydrogeologic purposes.
Based on these decisioni, Stabilization on Site (S0S) is the only alternative which will receive further site characterization.
Therefore, while the purpose of the Final CADSAR is to evaluate and rank all remedial action alternatives, the Draft CADSAR has eliminated data gathering needs for all but one alternative. The justification for this will need to be provided in the Final CADSAR.
Section 2, Alternate Site' Selection, Page 4 The DOE and State site selection processes do not identify stabilization-on-the-floodplain as an alternative.
However, the Draft CADSAR treats stabilization-on-the-floodplain as an alternative.
This apparent ambiguity, should be explained.
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Section 3,' Characterization of Sites, Page 6 i
Section 3 presents insufficient data on the significance of the bedrock aquifers as a source of water and insufficient support for the conclusion that bedrock aquifers will not be affected by any of the disposal alternatives.
The i
effect of the tailings on bedrock aquifers.could be a significant issue in determining compliance with the EPA standard.
Section 3.1.2, Contaminant Distribution, Page 6 This section of the Slick Rock Draft CADSAR describes the location of existing contamination at the Slick Rock site.
Contamination is described as being present at (1) the tailings piles, (2) windblown materials off the piles, and (3) concrete foundations at the Union Carbide site.
No mention, however, is made of ground-water contamination present in alluvial gravels at the site (Page 12)..This section of the Draft CADSAR should state that contamination is probably present in ground water and that more detailed analysis will be done I
later to describe the location and areal extent of this contamination.
Section 3, Tables 3.2 and 3.3, Pages 12-13
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The report states in Table 3.2 that the design earthquake is 0.2 g, while in Table 3.3 it states the bedrock acceleration is 0.2 g.
More information is needed on how these values were determined and the rationale for using 0.2.g rather than another value. The report should also clarify if the bedrock l
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' acceleration (Table 3.3) is meant to be equivalent to the design earth quake acceleration (Table 3.2).
These two terms can be interpreted differently.
Consistency in the terminology should be used through out the report.
Section 4.3, Stabilization at the Burro Canyon Site, Page 19 The Draft CADSAR provides detailed maps of the SIP and the SOS alternatives, but does not contain any detailed map of the Burro Canyon site. A map should be included, since this is the second choice from a cost standpoint, and because it would be very helpful in understanding statements such as, "The surrounding terrain would be graded to direct flow away from the pile" and "The impact on the Burro Canyon site of the PMF in Nicholas Wash must also be evaluated" (page 21).
Also, provide any available information relating to flood studies and erosion protection since erosion protection would likely result in significant design features.
Section 4.2, Stabilization on Site, Page 19 and Figure 4.2 Figure 4.2 indicates that for the SOS alternative, the slopes are steep, uneven, and consist of several arroyos and bedrock spurs.
This alternative may require considerable changes in natural slopes to accommodate the. moved tailings.
Carefully planned drainage controls and diversions will probably be required to maintain the geomorphic stability of the tailings after site closure.
Section 5, Significant Issues, Page 21 The Draft CADSAR does not identify several significant ground-water issues which could affect the selection of an appropriate alternative. These issues should be considered in determining whether any of the sites will be able to meet EPA standards.
The questions to be considered include:
1.
To what extent will the tailings be a potential source of future ground-water contamination?
2.
Will location at the SIP and SOS sites cause ground-water pollution, because the tailings will be exposed to more water either from flooding, increased runoff from surrounding hill sides, or higher ground water levels?
3.
Will any of the sites require a liner underneath the pile to prevent future ground-water contamination?
4.
Will any of the sites present a ground water contamination threat to regional ground-water aquifers?
5.
Will any of the alternatives present a local threat to the public from ground-water contamination?
Specifically, what are the sources of water for the gas sweetener plant and the trailer park immediately adjacent to the SIP and SOS alternatives?
6.
Will there be a need for ground-water restoration?
, Section 5.3, Surface Drainage Impacts, Page 21 The Draft CADSAR mentions that potential surface drainage impacts (depending on the alternative chosen) may exist for the drainage basins of Summit Canyon, Corral Draw, and Nicholas Wash. These basins are not shown on any of the Draft CADSAR figures.
The staff was therefore not able to provide comments on the potential surface water impacts on these basins from various alternatives.
Section 5, Significant Issues, Page 21 The report cites information on faults within five miles of the Slick Rock Site without citing the source for this information.
Without knowing the basis, it is impossible to verify the validity of the information and how the faulting may impact the engineering design.
Section 6, Cost Estimates, Page 22 The SIP alternative appears to underestimate restoration costs, because (1) probable maximum flood (PMF) river velocities of 29 ft/sec will probably require a rock cover on the pile of greater than 24" diameter rock, (2) upstream velocities of 8-9 ft/sec are dependent on stabilizing the downstream constricted section, which may. result in costly and extensive engineering design measures and (3) erosion protection measures in the small arroyos were not addressed in the Draft CADSAR and will likely require somewhat elaborate diversion structures.
Provide any available information to better assess the costs of erosion protection for this option.
Section 6, Cost Estimates, Page 22 Cost estimates for the SOS and the Burro Canyon Site alternatives appear to be underestimated.
Costs that may not have been considered are (1) erosion protection in the arroyos, (2) slope stabilization below the embankment toe, (3) river meander protection, and (4) slope stabilization and diversion ditches.
This information should be provided in enough detail for comparison purposes.
Section 6, Cost Estimates, Page 22 The Draft CADSAR provides information relating to the costs of protection for 50% of a PMF.
The NRC staff does not consider it appropriate at this stage to assess costs for a flood less than a PMF since (1) sufficient information has not been developed to reasonably assess the costs of protecting for a full PMF, and (2) the SOS option will meet a PMF at lower cost.
Section 6, Cost Estimates, Page 22 The Draf t CADSAR is weak in the preparation of preliminary reclamation cost estimates. While the Draft CADSAR is a document that is to be prepared using mostly literature and preliminary data, initial estimates of peak flow rates, elevations, and flow velocities for all streams and diversion channels should be provided.
In addition, preliminary rock durability information should be
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. based on more than visual observation, because costs may be dependent on the
. selection of rock with acceptable durability.
Section 7,- Table 7.1, Page 26 Conditions of sediment deposition are identified in the Draft CADSAR as a positive technical factor for the Burro Canyon site alternative.
The reviewer assumes these conditior.3 involve fluvial and/or eolian deposition.
These conditions cannot be considered a positive technical factor without an evaluation of their effects.
Depositional conditions may result in aggradation and blockage of engineered drainage systems, which could require specific designs to reduce or eliminate sedimentation.
Section 7, Table 7.1, Page 26 The negative technical factor of habitat disturbance at the Burro Canyon alternate site is not addressed in the table of alternatives comparison.
Section 7, Table 7.2, Page 28 Table 7.2 contains a tabulation of risks associated with each restoration alternative. 'However, the-table does not explain or reference how the risks-were determined.
The report should clarify how these probabilities were determined.
Section 8, Recommendations, Page 29 According to the draft UMTRA Project Site Management Manual (DOE, 1986) the Draft CADSAR should (among other things) provide the basis for DOE, NRC, and affected states and tribes to " agree on site characterization data requirements." The Draft CADSAR states that it presents a description of the field characterization program "needed to prepare the final CADSAR and to select the preferred alternative." The description of the characterization program given in the Draft CADSAR, however, consists only of the number of geotechnical'and hydrological borings to be performed and the number of test pits to be dug to characterize the 505 and SIP alternatives (no characterization is planned at the Burro Canyon site at this time).
Since few l
details of the site characterization plans or planned data gathering are included in the Draft CADSAR, the NRC staff could not assess whether such plans are adequate to assure that the sites will be properly characterized.
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l ENGINEERING COMENTS' 1
Section 3, Characterization of Sites The' Draft CADSAR indicates that the foundation soils at the stabilization-in place (SIP) site are permeable silty sands and gravels.
The foundation soils for the stabilization-on-site (SOS) alternative are identified l
as " alluvial gravel, cobbles, and an occasional boulder in a matrix of silty i
sand" (page 19). The foundation soils.at Burro Canyon are silty sands overlying bedrock (page 13).
These specific soils at each site, if saturated, may be susceptible to liquefaction or significant loss in shear strength under the vibratory motion of the specified design earthquake (0.2 g, page 12) and special design considerations may be required.
Has the potential for i
liquefaction been addressed for each of the alternative sites and has this potential been factored into the cost comarative evaluation shown in Table 6.1?
Section 3, Characterization of Sites Table 3.2, page.12, indicates that the~ foundations soils are a concern for.the Slick Rock site wh-ich may impact the costs for meeting the EPA standards.
However, the Draft CADSAR does not discuss the basis for the concern nor does l
it indicate how this concern is. reflected in the cost comparative evaluation in Table 6.1.
Supporting information should be provided which would indicate 1
whether these concerns for foundation stability would adversely impact the design necessary to meet the EPA standards.
The foundation soils at the Burro Canyon site are indicated not to be a concern (Table 3.3), however, information has not been provided which would support this conclusion and should be included.
Section 4, Site Conceptual Design The Draft CADSAR does not provide a discussion on slope stability which would allow the staff to conclude that the EPA standards will be met for each alternative site.
It would likely be possible to provide an engineered slope design which would ensure the necessary stability in order to meet the EPA standards.
However, specific but different design considerations may be required which would significantly impact the construction costs for each i
alternative site. Were any specific design considerations for slepe stability assumed for the alternative sites and were these specific design considerations factored into the comparative evaluation shown in Table 6.1?
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I Section 4, Site Conceptual Design According-to the Draft CADSAR, the SIP alternative will require an estimated 190,000 cubic yards of radon barrier material.
The 505 and Burro Canyon alternatives, however, will require an estimated 90,000 and 100,000 cubic yards of radon barrier material, respectively.
The CADSAR should explain why the SIP alternative requires almost twice the volume of radon barrier material to cover the same volume of tailings with the same five foot thickness.
Does this reflect the need for special design conditions? In addition, if SOS or relocation to Burro Canyon are selected for remedial action, segregated 4
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" layering of tailings would be possible and could reduce the required cover thickness. This could significantly affect the costs and accordingly, it should be factored into the Draft CADSAR.
Section 4, Site Conceptual Design The effects of total and differential settlements for each alternative to meet the EPA standards have not been discussed.
If the SIP alternative is chosen for remedial action, the tailings may be susceptible to larger differential settlements if zones of soft material exist.
If placement of the tailings is controlled, as would be the case.with the SOS and relocation alternative, differential settlements may not be a problem and would likely be less than those expected with the SIP alternative. Were any special designs considered to reduce the amount of differential settlement at each site and have these effects-been factored into the comparative analysis shown in Table 6.1?.
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