1990-01-18_REVISION - M1988112 (7)

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r III IIIIIIIIIIIIIIII ~ STATE OF COLORADO MINED LAND RECLAMATION DIVISION Department of Natural Resources ~~; ~F~~.py yr? 1313 Sherman SI., Roam 215 ~$ Denver, CO 80203 ~ 4 LL ~ y • ~ ~'"\ . 303 866-3567 • ra'!e FA%.303 832-8106 Roy Ramer, Governor Fred R. Banta. Division D:reclor DATE: January 18, 1990 T0: Steven G. Renner, Senior Reclamation Specialist ~ \ FROM: James A. Pendleton, Ph.D., Supervisory Geologist ~ .~1~1y_~-- RE: Battle Mountain Gold Company's Amendmen - Geotech al Adequacy (File #M-B8-112) I have completed a review of Battle Mountain Gold Company's San Luis Project amendment application and their subsequent responses to your initial adequacy comments. In formulating my opinion, I have considered the comments rendered at my request by Dr. W. Pat Rogers, Supervisory Engineering Geologist with the Colorado Geological Survey. Dr. Rogers is well versed in seismology considerations for structure stability. He was co-author of the 1!481 Colorado Geological Survey publication titled "Earthquake Potential in Colorado" (Bulletin 43). For consistency with your earlier record, I will present my brief comments in the format of your earlier adequacy comments. Topic 5: Mill Facility Seismic Design Dr. Rogers expressed a concern (See attached memo, Item 3.) regarding the seismic design criteria for the Mill facilities. "Given the acknowledged potential seismicity of the site it would seem essential that the facility be designed for at least UBC (Unified Building Code) Seismic Zone 2 (this would be about .15g bedrock acceleration). There was uncertainty on the point by the applicant at our last meeting as to what parameter was used. ~ihe more conservative zonation is needed because of personnel and hazardous materials safety considerations. Clarification is needed on this point." I concur with Dr. Rogers' recommendation. Topic 15: Liquifaction Potential of the Tailings Battle Mountain's consultant, Steffen Robertson & Kirsten (SRK), rtasponded to your request for a liquifaction potential investigation. Based upon the projected material gradation, Mr. Rob Dorey of SRK projects that liquifaction of the tailings would not occur in any critical portions of the tailings structure (Attachment 4, Figure D.6-16 ). Mr. Dorey's conclusions +are appropriate, as long as the tailings' material properties projecteri to result from the proposed tailings placement method are accurate. It will be important, therefore, to verify the material properties of the tailings materials, and to report the results to the Division..