The Honorable Jim Geringer
Governor of Wyoming
State Capitol Building
Cheyenne, Wyoming 82002

SUBJECT: STATE OF WYOMING REPORT ON SEISMIC HAZARDS ASSOCIATED WITH RECLAMATION ACTIVITIES AT URANIUM MILL TAILINGS SITES IN WYOMING

Dear Governor Geringer:

I am responding to your letter dated March 5, 1996, to Mr. Joseph J. Holonich, Chief. Uranium Recovery Branch. In that letter, you provided a report, by the Wyoming State Geologic Survey (WSGS), noting some concerns that the WSGS and others had with the seismic design assumptions the U.S. Nuclear Regulatory Commission has, or may adopt, for determining the acceptability of reclamation designs at uranium mill tailings sites. In particular, the WSGS report addresses concerns that the analytical procedures, used by NRC to determine the seismic stability design basis for uranium mill tailings embankments, may produce overly conservative results.

As you may know, the NRC staff is currently evaluating all uranium mill tailings impoundment designs to ensure that the embankments can withstand the expected seismic load. The staff anticipates completing these seismic stability reviews for mill tailings sites this year. To date, the staff has evaluated six sites, five of which are located in Wyoming. With the exception of one site that is located on a cliff. the staff reevaluation has found that the embankments can withstand the seismic events proposed by Lawrence Livermore National Laboratory (LLNL). The one site where the stability was questionable was the Day Loma heap leach that is located in the Gas Hills Mining District. At present, the NRC staff is reviewing a proposal from the licensee, Western Nuclear, INC. to remove the site from the requirements of long-term care. We have coordinated this effort with Messrs. Stan Barnard and Mark Moxley, Wyoming Department of Environmental Quality. Once the NRC makes a determination on this proposal, the staff will then decide what. if any actions will be required for the Day Loma site.

As the WSGS is aware, NRC review criteria are based on 10 CFR Part 40 Appendix A. Using a 10-4 probability of exceedance in a year, as presented in the LLNL report, meets the 1000-year criterion of Part 40 Appendix A. However, NRC's regulations provide licensees with the leeway to propose alternate design approaches.

The Honorable Jim Geringer 2

NRC appreciates the opportunity to consider input from organizations such as the WSGS. The staff plans to review the WSGS report and consider the . information from the report, along with the results of the NRC reevaluations, to determine if the seismic design basis for uranium mill tailings embankments in the State of Wyoming needs to be changed. After the staff has completed this review, we may need to meet with representatives of the WSGS. Mr. Holonich. NRC. and Mr. Jim Case, WSGS, have tentatively discussed an NRC/WSGS meeting. Once it is determined that a meeting is needed, Mr. Holonich will contact Mr. Case to set up a mutually agreeable date and place.

If you have any questions about this letter or the NRC staff's review, please feel free to contact either me or Mr. Holonich. I can be reached at (301) 415-7800. and Mr. Holonich can be reached at (301) 415-7238.