ML20154L621
| ML20154L621 | |
| Person / Time | |
|---|---|
| Issue date: | 04/14/1988 |
| From: | Hawkins E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Arthur W ENERGY, DEPT. OF |
| References | |
| REF-WM-63 NUDOCS 8805310366 | |
| Download: ML20154L621 (7) | |
Text
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l DISTRIBUTION Docket File WM-63 i
SPOR /DCS +
DBangart, RIV WM-63/SRG/88/04/13/0 SGrace LLO Branch, LLWM URF0 r/f RCPD, NM DJacoby AFM L 4 000 RGonzales URF0:SRG Oocket No. WM-63 040WM063700E W. John Arthur, III, Project Manager U.S. Department of Energy Albuquerque Operations Office P.O. Box 5400 Albuquerque, New Mexico 87115
Dear Mr. Arthur:
We have received and reviewed the following submittals pertaining to the Mexican Hat site; (1) the preliminary final Remedial Action Plan (pfRAP) submitted January 24,1988,(2) the final design for review documents submitted August 18, 1987, and (3) your March 24, 1988 submittal, responding to our March 2, 1988 comments.
In our review to date, we have found the following areas to be in accordance with the NRC Standard Review Plan and therefore acceptable:
(1) site geology and seismology, (2) erosion protection design (rock size) of the pile top, outslopes, gullies and diversion ditches (assuming that oversizing of the rock is not required), (3) the design events (Probable Maximum Precipitation and Probable Maximum Flood), and (4) the liquefaction analysis. These items are detailed in Enclosure 1.
Areas reviewed that were found to be incomplete and/or unable to be reviewed to date include; (1) water resources information pertaining to compliance with the proposed EPA standards, including evaluation of cover infiltration and justification for supplemental standards for the uppermost aquifer, (2) specific information on proposed rock source, including sizing evaluation and a discussion on why the diversion ditch does not require a flared outlet, and (3) radon barrier design, slope stability, construction specifications and settlement calculations.
These items are also detailed in Enclosure 1.
We understand that it is your intention to classify the ground water in the vicinity of the site as Class III ground water. As discussed in the enclosed comments, we are skeptical that the uppermost hydrostratigraphic 0FC : : '
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1 WM-63/SRG/88/04/13/0 APR l 41988 unit can meet the definition of Class III ground water as used in 40 CFR Part 192.11(e). Additionally, the information presented in the submittals indicates that this upper unit is an aquifer as described.in l our March 28, 1988 Draft Technical Position. You will also note that we I feel it important to establish a ground-water monitoring program at the site in the near future in order to determine a representative background water quality and designate location (s) for point of compliance well(s).
These items are also discussed in the attached comments.
Please keep us informed on when additional information can be submitted.
Our review of the proposed remedial action cannot continue until we receive the specified information.
We are aware that DOE is considering the possibility of relocating the tailings from the Monument Valley site to Mexican Hat. Please keep us informed on the developments of this possibility as it will affect much of our review and conclusions.
If you have any questions, please contact Scott Grace of my staff at FTS 776-2805.
Sincerely,
/5 Edward F. Hawkins, Chief Licensing Branch 1 Uranium Recovery Field Office '
Region IV
Enclosure:
As stated
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l ENCLOSURE 1 COMMENTS ON MEXICAN HAT !
PRELIMINARY FINAL REMEDIAL ACTION PLAN (JANUARY 1988)
AND FINAL DESIGN FOR REVIEW 00CUMENTS (AUGUST 1987) 1.0 SITE GE0 LOGY AND SEISM 0 LOGY 1.1 A review of the geologic conditions existing at the site preclude the likelihood of poor foundation materials, ground settlement, and hazard due to slope instability or creep. A review of the site seismicity data in the final design for review documents (Volume III, Section 9-238-01) indicates little or low probability that ground accelerations at the Mexican Hat site could exceed the design earthquake. Therefore, the section on site seismicity was found to be in accordance with the acceptance criteria set forth in the SRP (Reference 1) and therefore acceptable.
- 2. WATER RESOURCES 2.1 The March 24, 1988 submittal contained a brief discussion of how the remedial action at Mexican Hat will be in compliance with the proposed EPA ground-water standards. In this discussion is an evaluation of the factors that make the site suitable for the application of supplemental standards by defining the ground water in the vicinity Subpart B. The of the site as Class III under 40 CFR Part 192, staff agrees that the middle and lower - -
hydrostratigraphic units could probably meet the definition of Class III ground water (as specified in 40 CFR Part 192.11(e))
therefore and However, a,dditional information is required for the staff to make abe determination definition on whether of Class orwater.
III ground not these units are consistent with the The staff is skeptical that the upper hydrostratigraphic can meet the definition of Class III ground water or not be considered an aquifer. As discussed in Section 2.1 of the NRC Draft Technical Position (Reference 2), any saturated zone created by uranium recovery operations should not be considered an aquifer unless the zone is or potentially is (1) hydraulically interconnected to a natural aquifer, (2) capable of discharge to surface water, or (3) reasonably accessible because of migration beyond the vertical projection of the boundary of land transferred for long-term government ownership and care. The staff consider the upper hydrostratigraphic unit to be an aquifer as this unit is capable of discharge ~to surface water. As discussed in your.
submittals, there are discharges of tailings seepage via the upper hydrostrati Juan River. graphic unit to Gypsum Creek, and possibly to the San Therefore, the staff tentatively conclude that the upper hydrostratigraphic unit is part of the uppermost aquifer, not subject to classification as Class III ground water, and accordingly
2 not subject to the supplemental standards of Subpart C. Regardless, additional information on site hydrogeology is necessary to adequately evaluate this aspect of the Mexican Hat site. If DOE wishes to pursue this issue, they should submit additional information to to address the three criterion in Part 192.11(e) as well as information addressing the three criterion in Section 2.1 of the NRC Draft Technical Position (Reference 2).
2.2 As the upper hydrostratigraphic unit will probably not meet the definition of Class III ground water, additional information will be necessary for NRC to evaluate compliance with proposed EPA regulations. Of primary concern for the near term is the implementation of an integrated ground-water monitoring program as required under 40 CFR Part 192.12(c)(1) and discussed in Sections 2.1, 2.4 and 3.3 of the NRC Draft Technical Position (Reference 2).
As part of this monitoring program, a methodology for determination of a background water quality for the uppermost aquifer (upper hydrostratigraphic unit) should be developed soon in order to allow setting of concentration limits for the hazardous constituents. The NRC staff are aware that this aquifer was saturated as a result of seepage be from the impossible tailings and that an upgradient background well may to locate. Regardless, a method to determine a representative background water quality must be developed and proposed.
As part of the monitoring program, point of compliance well(s) also need to be located. The staff also note that only limited ground-water data exists for the Mexican Hat site and that more current site data may be necessary to evaluate proposed-locations of background and point of compliance well s). Therefore, DOE should propose a ground-water monitoring program (that specifies a procedure to determine a representative background water as well as locate appropriate point of compliance well(s). quality 2.3 The pfRAP contains no evaluation of potential infiltration, only a conclusion that the stabilized pile will be covered with very low permeability materials which will present a barrier to infiltration. The staff reviewed the permeability testing on the proposed cover material located in the March 24, 1988 submittal, but note no discussion on which tests tre representative of the material to be used for the cover. When the cover design is finalized and a borrow material selected, DOE should submit a discussion on the hydraulic characteristics of the cover material as well as an evaluation of the potential for infiltration through the cover, tailings and the unsaturated portion of the uppermost aquifer. As part of the evaluation, consideration should be given to a method (s) to confirm the ability to achieve minimum hydraulic conductivity in the cover. This may be necessary for the staff to evaluate whether or not the proposed design will prevent further leakage and contamination at the point of compliance.
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3.0 SURFACE WATER HYDROLOGY AND EROSION PROTECTION 3.1 The staff reviewed the material presented by 00E and concluded that there are no other credible sources of potential flooding that could adversely affect the reclaimed pile. The staff also concluded that the design events (Probable Maximum Precipitation and Probable Maximum Flood; PMP and PMF) meet the criteria outlined in the Standard Review Plan (Reference 1) and are, therefore, acceptable.
3.2 The staff reviewed DOE's calculations and performed independent analyses to verify the adequacy of the riprap. These analyses were performed using procedures discussed in NUREG/CR-4651 (Reference 3).
On th0 basis of these independent calculations, the staff concluded that tre erosion protection design of the pile top, outslopes and gullies meets the acceptance criterion of the SRP (Reference 1) and is therefore acceptable.
3.3 On the basis of review and independent analysis, using procedures discussed in NUREG/CR-4651 (Reference 3) and the design basis events, the staff has concluded that the riprap sizes proposed by DOE for the key trench of the North Ditch and for the entire West Ditch and Diversion Ditch are acceptable. However, if during construction, DOE finds that the area where the North Ditch is being excavated does not contain competent rock as was assumed in designing the ditch or if the surface of the rock is below the PMF level, a new design may be required. 00E should submit information confirming the assumptions or submit a new design for review'and approval. The staff will also require that 00E explain and justify the reason for not providing a flared outlet for the diversion ditch.
3.4 The rock proposed by DOE to be used as a source of riprap is
- imestone from the vicinity of Alhambra Rock. The staff in a letter dated October 16, 1987, provided comments to DOE on their evaluation i Af the proposed rock but no response has been received. Therefore, I
@ proval of a rock source by the staff will be delayed pending aceipt from DOE of a re-evaluation of the acceptability of a rock 1 aurce. If a new rock source is proposed, the riprap designs of the rila top, outslopes, gullies and ditches may have to be evaluated to easure the adequacy of the design. If this evaluation indicates that the rock has to be oversized, the specifications will have to be changed to reflect the increased rock sizes. The staff notes that in designing riprap, DOE used a rock specific gravity of 2.64. l Since the specifications call for a minimum specific gravity of 2.5, this lower value should be used in riprap design.
4.0 GE0 TECHNICAL STABILITY 4.1 The staff reviewed DOE's liquefaction calculation and performed an independent evaluation to determine the potential for liquefaction l
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4 for the reclaimed facility. The independent study of the material presented has resulted in the staff position that the soils at the site will not be susceptible to liquefaction of any consequence.
4.2 The slope stability calculation indicates that the long-term static and pseudo-static stability factors of safety for the reclaimed structure will meet the requirements presented in Regulatory Guide 3.11 (Reference 4). A review of the supporting data indicated that the calculation is representative of site conditions and meets the general requirements of the SRP (Reference 1). DOE must submit a discussion of why a pseudo-static analysis is appropriate for this site before the slope stability analysis will be acceptable.
4.3 The final radon barrier design has not been submitted, and preliminary designs presented are not based on site-specific soils l data from the proposed RB-4 and RB-7 borrow areas. The "Information '
for Reviewers" (MKE Document 5025-HAT-R-01-00769-001 contained in l Appendix E) of the Remedial Action Plan, further indicates the i currently proposed radon barrier thickness may undergo major design changes. Additionally, URF0 has not received a complete soil testing package from the RB-4 and RB-7 borrow areas. l The adequacy j of the selected soil and the radon barrier design will be reviewed when the information is submitted, l 4.4 The construction specifications for the radon barrier materials will also require revision to reflect the new material sources and design. The present material specification is representative of ;
l most soils and therefore cannot be considered supportive of any -
specific design. The construction specifications did not include moisture control during construction for uncontaminated fill materials. This information should also be included in the review. l Additionally, as the stability analysis modeled relocated tailings compacted to 95 percent of the maximum dry density, the j specifications should support this design. ;
I 4.5 The settlement calculation review is not complete at this time. The review, including the void reduction specifications, will be completed and any comments will be forwarded in the near future.
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REFERENCES
- 1. U.S. Nuclear Regulatory Commission, "Standard Review Plan for UMTRCA Title I Tailings Remedial Action Plans," USNRC, Division of Waste Management Report, October 1985.
- 2. U.S. Nuclear Regulatory Commission, "Information Needs to Demonstrate Compliance with EPA's Proposed Ground-Water Protection Standards in 40 CFR Part 192, Subparts A-C," USNRC, Division of Low-level Waste Management and Decommissioning, Draft Technical Position, March 28, 1988.
- 3. Abt, S. R. , et.al. , "Development of Riprap Design Criteria by Riprap Testing in Flumes: Phase I," NUREG/CR-4651.
- 4. U.S. Nuclear Regulatory Commission, Regulatory Guide 3.11, "Design, Construction and Inspection of Embankment Retention Systems for Uranium Mills," December 1977.
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