ML20140B427
| ML20140B427 | |
| Person / Time | |
|---|---|
| Issue date: | 01/13/1986 |
| From: | Higginbotham L NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-58 NUDOCS 8601240409 | |
| Download: ML20140B427 (6) | |
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JAN 131986 Distribution
<Gu e Tr3 WM58/ rC/0C/Cl W-WMLU r/f NMSS s/f Mr. John G. Themelis, Project Manager JO Bunting UMTRA Project Office MJ Bell U.S. Department of Energy RE Browning P. O. Box 5400 DM Gillen Albuquerque, New Mexico 87115 DE Martin B Jagannath
Dear Mr. Themelis:
T Johnson We have reviewed the following Shiprock project documents which we recently received from you:
- 1., Modifications to the Remedial Action Plan and Site Conceptual Design for Stabilization of the Inactive Uranium Mill Tailings Site at Shiprock, New Mexico; October 1985.
2.
UMTRA Project - Shiprock Phase II Design Revisions; December, 1985.
Comments on these documents are provided in the attached enclosures.
As indicated by the comments of Enclosure 1 on the October, 1985 document, a complete review of this document was hampered by the knowledge that the design was to be further revised to accommodate previous NRC erosion protection concerns. However, comments and qualified conclusions have been provided pertinent to those modifications related to the NRC's review.
The December 1985 document provides the further aesign revisions discussed above. However, NRC's comments on the document (Enclosure 2) indicate that additional modifics;1ons would likely be necessary prior to NRC concurrence in i
the design. A draft of these comments has been telecopied to Mr. Thiers of the RAC. We expect that the remaining erosion protection design concerns can be resolved through minor des gn revisions by the RAC. Once these are made, we i
will review the RAP modification that you will be submitting based on the final revised design.
g If you have any questions oncerning these reviews, please contact me or Dan Gillen of my staff.
Sincerely, WM Record File WM Project-Q PDRl LPDR_
Leo B. Higginbotham, Chief
_ Distribution-Low-Level Waste and Uranium
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Recovery Projects Branch Division of Waste Management
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(Return to_FJf,6ffTS[~
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Enclosures:
As stated
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o JAN 131985 ENCLOSURE 1 Review of Attachment No. 1, Modifications to the Remedial Action Plan and Site Conceotual Design for Stabilization of the Inactive Uranium Mill Tailings Site at Shiprock, New Mexico The Remedial Action Plan (RAP) and Site Conceptual Design for Stabili ation of the Inactive Uranium Mill Tailings Site at Shiprock, New Mexico was concurred on by NRC (U.S. 00F Agreement No. DE-FC04-83All6258, Appendix B) on April 11, 1985. The DOE has submitted rrco1fications to the above document (RAP). These propnsed modifications have been reviewed for compliance with the requirements in 40 CFR Part 192.
Peview comments on the proposed changes are as follows.
1.
Chacge No. 1:
Construct a single tailings embankment with a single crest and a too slope of 2 to 4 percent instead of two adjoining embankments of different heights separated by a' swale.
The NRC agrees in principle with the proposed change. However, it is our understancing that the design of the ditches surrounding the proposed single pile of the tailings is being revised; this may result in changes to the geometry of the tailings pile. The NRC would like to review the final configuration of the tailings pile and surrcunding ditches prior to granting concurrence to this change.
2.
Change No. 2:
Cut the escarpment face to a 2(H): 1(v) slope from a bench at elevatien 4,930. Place an erosion protection layer over the cut slope.
i The NRC agriees in principle with the proposed change. However, it is ouruncers*fandingthatthematerialproposedinDwgSHP-PS-10-0021,Rev0, for protecjien of the escarptrent sicpe against erosion is being revised.
This firelirevisier to the RAP should be concurred in by the NPC.
3.
Change No; 4:
Charge material to be placed as radon barrier from silty sand to sandy silt, and change erosion protection overlying the radon barrier from pit-run rock to select rock and select beccing material.
The NRC agrees in principle to use sandy silt as raden barrier material, and to u n select rock and select bedding material instead of pit-run rcck for ercsion prctection. Powever, the thickness of the raden barrier and details of the erosien protectior, have not been finalized, and these items should be concurred by the NRC.
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. Changing the radon barrier material from silty sand to sandy silt in the RAP document has been left out in the following places, o
Table E.6.2, Page E Pile cover material is indicated to be silty sand.
Page 13 of Attachment A to Appendix E, Section 111,A, Paragraph 2 -
o The cover material is described to be a silty sandy soil.
The description of the soil is inconsistent with the proposed change.
Table 2.3, Page 14 of Attachment A to Appendix E,Section III A -
o radon barrier material is described as silty sand. The description of the soil is inconsistert with the proposed change, Page 15 of Attachment A to Appendix E,Section IV, Paragraph 1, o
Line 2 - Radon barrier material is described as silty sandy soil.
The descripticns of the soil is inconsistent with the proposed change.
o Table 10.1, Page 75 of Attachment A to Appendix E.
Icentification of the cover material (gravelly sand, silty sand) is inconsistent with the proposed change.
o Figure 10.2, Page 73 of Attachment A to Appendix E - Description of radon barrier (soil No. 6) is inconsistent with the proposed change.
4 Change No. 5:
Require that rock to be used for erosion protection meet specific gravity and absor ption requirements.
The NRC concurs with the proposed change.
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ENCLOSURE 2 SHIPROCK PHASE II DESIGN REVISIONS SURFACE WATER HYDROLOGY AND EROSION PROTECTION QUESTIONS AND COMMENTS 1.
Based on a review of the calculations provided, it is not clear if the channel riprap design includes an allowance for increased shear stresses in the' areas of channel bends. While it appears that the alignment, configuration, and sizing of the ditches have been adequately addressed (in accordance with appropriate Corps of Engineers references), additional calculations should be provided to document that the erosion protection at channel bends has been oroperly designed. Corps of Engineers EM 1110-2-1601 provides acceptable guidance for determining shear stress increases and for designing erosion orotection at channel bends.
2.
We note that statistical extrapolation of data was used to determine the "1,000-year" storm. However, there is no basis to support such extrapolations, especially for small uiqaged watersheds with limited flooding and precipitation data bases.
We further note that several of the drainage ditches will be designed to accomodate only this "1,000-year storm", which is also 18'; of the PMP.
The benefits to be gained by labeling the storm a 1,000-year storm are cuestionable. We suggest that any reference to a 1000-year storm he deleted.
It should be simply called 18" of the PMP.
3.
The elimination of ditches D-3 and 0-4 has resulted in a design where runoff is directed over an apron directiv over unprotected slopes into the excavated borrow area east of the embankment. While this design concept may be acceptable, it is not immediately evident how erosion of the borrow area slopes will be prevented.
Slopes of 5% in silty soils and 10% in gravelly soils (Reference Drawing SHP-PS-10-0022) may not be sufficiently flat to prevent erosion and gullying of the slopes over long time periods. This is particularly true if concentrated, rather than sheet, flow occurs on the slopes.
Based on the design presented, it appears that concentrated flow could occur, gullies could form, and the gullies could eventually enlarge and headcut toward the protected embankments. In order to resolve this potential erosion problem, the NRC staff sugcests that one or more of the following be performed:
Provide calculations which document that the unprotected 5-10" a.
slooes will not be gullied and eroded.
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b.
Provide ditches which orevent discharges from flowing over the borrow area side slopes. (Depending on the configuration, there will likely always be some discharges down the slopes due to direct rainfall and runoff).
c.
Provide erosion protection for the borrow area side slooes so that gullyinq and erosion will not occur.
d.
Flatten the slopes (possibly by filling) in the borrow area.
Recardless of the design selected, the final grading plan and design for the borrow area slopes should be provided for NRC review and approval.
4.
The redesign of ditches D-1 and D-2 has resulted in a design where only 18% o# the PMP will be carried in the ditches and the remainder of the flood peak will overflow the ditches. While this design concept is acceptable, it is not clear if the site grading is such that ditch overflow ard off-site floods could possibly enter the ditches further downstream.
Examination of the topography in the immediate area of the ditches indicates that ditch overflow will not be directed away from the ditches and that off-site floods could actually overflow into the ditches.
Accordingly, documentation and drawings should be provided to demonstrate that:
a.
overflow from the ditches will either not reenter the ditches further downstrean or that the ditches are designed to safely convey this volume of flow; b.
off-site floods wither will not enter the ditches or will be safely conveyed by the proposed ditch design. (Note that floods entering ditches D-1 and D-? may also affect either ditches further downstream); or C.
the apron and erosion protection to be provided on the outside portions o' the ditche are capabla of resisting (1) PMF velocities produced by overflow out of the ditches and (?)
velocities produced by an off-site PMF flowine along the outside toe of the ditch where it meets existing ground.
Additionally, if credit is taken for the diversion ditch to be placed around the perimeter of the M-K borrow area, the ditch should be
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designed for a PMF and resulting velocities. Calculations and documentation should be provided to demonstrate that the ditch has been adequately designed.
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