ML20137C775
| ML20137C775 | |
| Person / Time | |
|---|---|
| Issue date: | 11/12/1985 |
| From: | Rich Smith NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-64 NUDOCS 8511260603 | |
| Download: ML20137C775 (14) | |
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DISTRIBUTION yf gg . 6, y Docket File 40-181 PDR/DCS DBangart, RIV 40-181/SLW/85/11/05/0 Swastler URF0 r/f KHargis, RCPD, NM NOV 121985 URF0:SLW 0400181301E 0400181201E Mr. John Themelis U.S. Department of Energy Albuquerque Operations Office P.O. Box 5400 Albuquerque, New Mexico 87115 Dear Mr. Themelis; We have reviewed the final Remedial Action Plan (RAP) and Disposal Site Characterization Report (DSCR) for the mill tailings site at Lakeview, Oregon. Our specific comments are provided in the enclosure to this letter. Our review of the final Processing Site Characterization Report (PSCR) has been delayed to allow our staff sufficient time to complete review of the disposal site documents. Our comments on the PSCR will be transmitted to your office by November 30, 1985.
These comments are intended to provide the additional information we need to determine if EPA standards will be met by the proposed RAP. However, based on our recent discussions, we understand that you may not seek NRC concurrence until the final designs are completed and reviewed. In any case, the requested information will be required prior to NRC concurrence.
In many cases our comments were previously made on the draft Environmental Assessment (EA), RAP, PSCR and DSCR but not responded to, or were not responded to adequately. Where applicable, these comments have been restated and we have attempted to note in the enclosure where the responses were inadequate. To preclude any further misunderstandings, we encourage your staff to contact the individual NRC commentors directly should there be any question.
As you are aware, the U.S. Tenth Circuit Court of Appeals set aside EPA's Title I ground-water standards on Septemt er 3,1985. In order to proceed with the remedial action program schedule without significant delays, the 00E, the State of Oregon, and the NRC jointly agreed during the November 1, OFC :
NAME : : : : : : :
DATE :85/11/08 :
8511260603 851112 PDR WASTE WM-64 PDR
40-181/SLW/85/11/05/0 NOV 121985 1985 meeting to consider Title II ground-water standards as a replacement for the design of the disposal site. The consensus was that their use would probably not impose a severe penalty on the Lakeview disposal site design and would likely be at least as conservative as the final EPA standards for Title I sites.
As soon as we receive the information identified in the enclosure, we will expedite our review. If you have any questions regarding our review or the items discussed in this letter, please contact me or Edward F. Hawkins.
Sincerely, Original ?t ro' '-* ,
FAryrd F. Er.vkhs #
/
P, Dale Smith, Director Uranium Recovery Field Office Region IV
Enclosure:
As stated 0 F t.
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DATE :85/11/08 :jl f rg : //kg3 : : : :
URANIUM REC 0VERY FIELD OFFICE
/ Comments on the Renedial Action Plan (RAP) and Disposal Site Characterization Report (DSCR)
Surface Water Hydrology and Erosion Protection
- 1. Flow Concentration on Top and Sides of Pile.
Our review of the information presented in the RAP indicates that flow concentration has not been considered in the design of the erosion The protection to be placed on the top and sides of the remediated pile.
NRC staff concludes that flow concentration will occur on the top of the pile, where the rock voids will be' filled with soil. This will cause the formation of preferential flow paths as the soil is eroded, resulting in rills and gullies which will enlarge as time goes on. The rock on the 20 percent side slopes will also be affected (even though no soil will be used in the rock voids), because the flow from the top slopes will emerge onto the side slopes from these concentrated paths, rather than uniformly over the slope.
Previous agreements reached between NDC and DOE have indicated that flow concentration does not have to be separately considered if the analysis technique used incorporates its effects. However, among other
2 considerations, this applies only when flood runoff is able to flow through the rock voids. In this particular case however, the Safety
+ Factor Method was used for flow over, not through the rock layer, and there will be soil in the rock voids. Therefore, flow concentration must i be separately considered in the analyses, An acceptable method for resolving our concerns is to consider flow t
concentration in the analyses of peak flow using methods similar to those j used in the Canonsburg, PA, design, where the rock voids were also filled ;
with soil, and flow concentration was considered in designing the erosion protectfon.
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~The erosion protection designs for the top and sides of the pile should be resized, as necessary, and the analyses and computations should be I
submitted for NRC review and approval.
Additionally, flow concentrations due to differential settlement should be considered in the analyses for rock protection. If differential l
settlement will not occur, the analyses which document that conclusion should be provided (or cross-referenced). If differential settlement will be mitigated by engineering measures such as overbuilding or surcharge loading, the RAP should provide a commitment to implement such further measures.
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> Alternately, discussion and documentation should be provided to demonstrate that flow concentrations either will not occur or will be safely accomodated due to the conservativeness of the design of the proposed rock.
- 2. Peak Shear Stresses in Ditches.
3 i Our review of the revised erosion protection analyses (dated 8/27/85) indicates that calculated peak shear stresses were used to design the riprap in the East dit: , but that average shear stresses were used in the design of the West and South ditches. This results in riprap which is undersized by about a factor of 2. It is the position of the NRC staff that peak, rather than average, shear stresses should be used to
- design erosion protection, particularly in ditches where there will be a large variation in shear stress across the section. The erosion l
protection designs should be revised to reflect peak shear stresses in the West and South ditches accordingly,'and the revised calculations should be provided for NRC review and approval.
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' Additionally, the calculational procedure should be iterated, as necessary, to verify that proper Manning's 'n' values are being used to compute the flow velocity, hydraulic radius, and flow depth, which are in turn, used to compute riprap size. Methods for verifying that the i
assumed 'n' values are very close to the computed 'n' values may be found i
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in EM1110-2-1601, Plate 4 (This is also applicable to design of rock on the top and sides of the pile. See Comment 1, above.)
- 3. Peak Flow in Ditches.
Based on an examination of the most recent calculations (dated 8/27/85),
it appears that the peak flows in the diversion ditches may be underestimated. If the rainfall-intensity curve developed in the revised calculations is used, it appears that rainfall intensities and amounts will be greater than assumed in previous calculations, with a corresponding increase in peak flows in the ditches. However, the peak flows in the ditches are unchanged from previous estimates. These discrepancies should be further analyzed and revisions should be made to the peak flows in the ditches, as necessary.
4 Channel Transitions and Junctions.
We note from our review of the RAP that the final details of the designs for channel transitions, junctions, and bends will be developed in the near future by the RAC. While we recognize that such final details may be postponed, the design criteria for these details should be provided in the RAP. The RAP should go into some detail on the criteria and concepts that will be used (1) to transition the. man-made channels into the existing channels at the site, (2) to design the erosion protection associated with channel junctions, bends, or transitions where flow
5 direction may abruptly change, and (3) to determine the locations where erosion protection should be terminated at the downstream end of the natural channel to prevent headcutting and/or lateral erosion.
In addition, drawings and cross-sections should be submitted to provide
! preliminary information on the designs that are being considered, especially in those cases where it appears that extensive rock protection
-may be necessary to prevent erosion.
Geology and Seismology
- 5. In order to develop a Remedial Action Plan and Site Conceptual Design for Stabilization at the Collins Ranch alternative site that adequately addresses long term stability, additional geologic, seismic, and geothermal information must be provided. While the preliminary DSCR provided a very thorough analysis of the site specific and regional geologic, seismologic and geothermal conditions at the Lakeview site, only the regional portion of this study has any bearing on the Collins Ranch site. For example, nowhere in Appendix C of the DSCR is there a discussion of the Collins Ranch alternative site and its location with respect to regional or site specific faulting, how the MCE was determined for site design purposes, or its relationship to the KGRA. The evaluation completed for the Lakeview site is inadequate for evaluating the effects of site specific geologic, seismologic and geothermal conditions on the Collins Ranch site and therefore cannot support tne
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6 statements made in Section 3.3 of the RAP which indicate that surface rupture or geothermal activity does not exist at this site. As stated on j
page C-44 of Appendix C to the DSCR, the possible alternative disposal areas have been identified but not visited or fully studied and therefore other fatal flaws or negative consequences may.be associated with these locales.
Therefore, the RAP should provide a discussion of the site specific geology, seismology and geothermal acitivity for the Collins Ranch site which includes but is _not limited to the following:
The relationship between the regional tectonics and the site specific structural geology, eThe relationship between the regional and site specific seismicity and the determination of the MCE and the resulting horizontal ground acceleration.
- The relationship between the regional geothermal activity and potential site specific geothermal activity, and
'An assessment of the potential for liquefaction at the Collins Ranch site.
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- 6. Page 15 of Section 3.3 of the RAP describes the maximum horizontal bedrock acceleration of 52% of gravity at the Collins Ranch site. The EA on page 60 describes the horizontal ground acceleration for the MCE to be 489 Which value is correct, and where is the detailed seismic analysis to support the determination of the horizontal ground acceleration and
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the MCE? The determination of the acceleration value should be based on a site specific analysis as requested in Comment 5 above.
Ground-water Hydrology
- 7. The RAP states that electronagnetic and resistivity surveys were conducted at the mill site, with regard to contaminant plume definition.
However, no supporting documentation is presented to verify results.
Accordingly, provide additional data on aspects of the surveys, including methods, location grids or arrays., spacings, depths, calculations, field data and reference.
- 8. The RAP does not provide the bases or the substantiation necessary to support the hydraulic conductivity, storativity, transmissivity and velocity values used at the disposal site. Although we recognize that the values obtained from pump and slug tests are not entirely inappropriate, we also recognize that they probably represent the best efforts available under the circumstances. However, the RAP does not provide sufficient information to determine that the derived values are, at least, conservative for their given purposes. Accordingly, provide
8 additional information to confirm that the values are reasonably conservative estimates.
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- 9. The RAP states that hydraulic conductivity values for the Collins Ranch site are based on seven test wells. Only two of the seven test wells are located near or on the site boundary itself, and these two wells are installed in the South-Central portion of the site.
Accordingly, additional analyses and testing (as necessary) should be conducted to encompass a more representative area (site boundaries proper) of the Collins Ranch site. The analyses and tests should relate hydraulic conductivity to lithologic depth and be representative of not only the site boundary, but site traverse. In addition, the tests should include supporting documentation such as method, calculations, field and/or laboratory data, location map and references.
- 10. The RAP does not provide a site specific workup of the geology (stratigraphy and structurel that lends itself- well to understanding the complex subsurface. This is necessary to understand the ground-water regime of the disposal site. Provide more detailed geological analysis to include a more comprehensive description of the subsurface stratigraphy and structure with regard to site boundaries.
- 11. Based on the RAP review, provide detailed cross-sections and three-dimensional diagrams of the saturated, unsaturated and water table zones beneath the Collins Ranch site, to better relate the existing
9 complex subsurface environment. The scale of the sections and diagrams should be such that the stratigraphy is shown in detail with regard to r
the Collins Ranch site,
- 12. The ground-water gradient descriptions of the disposal site presented in the RAP are not supported by documentation. For all 4 ground-water gradient narratives in the RAP, provide the supporting field data, calculations, methods, locations and references.
Geotechnical Concerns
- 13. It is not clear what assumptions were incorporated into the settlement calculations. Specifically, what assumption was made regarding the percentage of low density, high porosity " ash" material included in the upper tailings (i.e., lesser contaminated) layer?
Discuss what effect this assumption had on the choice of consolidation parameters used in the settlement calculations and substantiate that the assumption was reasonably conservative.
14 In response to NRC connents on the DRAP, it is stated that the freeze-thaw rock durability test will only be performed if the results of the other proposed tests show the rock to be of fair to poor quality. It is also stated that to run 250 freeze-thaw cycles would require 80-90 days.
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10 (a) Due to the high relative cost of the freeze-thaw test, it is
. acceptable to base the need for the test on the results of other tests. However, specific criteria should be established which would dictate the need for the test. In particular, the need for the freeze-thaw test should be based at least partially on the results of absorption tests, as the ability of the rock to absorb water could impact the rock's freeze-thaw resistance.
(b) The Bureau of Reclamation routinely runs 250 freeze-thaw cycles as part of its rock durability testing progran. Eight cycles are run per day, with testing compl'eted in five weeks, as opposed to the 80-90 days specified in the DOE response. The need for 250 cycles is especially warranted in light of the fact that the test will be run only if the results of other tests already indicate the rock to be af fair to poor quality, it is therefore critical that the test provide maximun information regarding the rock's durability over a minimum 200 year period. This would be provided by 250 cycles of the freeze-thaw test. Accordingly, if a freeze-thaw test is required 250 cycles should be used, or until the rock fails (which ever comes first).
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- 15. The determination of the site specific MCE as requested in Comments 5 and 6 above, may result in a need to reverify the pseudo-static stability and liquifaction potential for the proposed plan.
Radon Attenuation and Radiological Safety
- 16. NRC staff review of radon barrier thickness calculations indicates that conservative values were not utilized for various RAEC0ft input parameters for both the cover and upper tailings layer. Values were often based on very limited data. To provide assurance that the EPA radon flux standard will be met, the required cover thickness should be recomputed utilizing either more conservative values or values based on additional testing sufficient to adequately characterize the layers of concern. Specifically, a re-evaluation should be made of the following parameters: ,
(1) long-term moisture content of the cover soil, (2) emanating fraction for the upper tailings layer, (3) diffusion coefficients for both layers, (4) porosity and density of the upper tailings layer.
Provide this re-evaluation to NRC for review and approval. Substantiate all parameters, demonstrating that they are reasonably conservative.
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- 17. In addition to the above information that is needed before we can concur in the proposed RAP, we note that two other documents should be provided; the site specific Health Physics Monitoring Plan (for information) and the Remedial Action Inspection Plan (for concurrence).