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iii iiiiiiiuiiiiii STATE OF COLORADO MINED LAND RECLAMATION DIVISION Department of Natural Resources 137 3 Sherman St., Room 2 t 5 Denver, CO 80203 303 866-3567 FA%: 303 832 8106 DATE: January 26, 1990 T0: Berhan Keffelew FROM: Jim Pendleton RE: Animas/Hel ine a Pile `~~ Revision (Permit #C-82-055) OF COO tik, ' R ie~~ ~ /8~6 ~ Roy Romer, Governor Fretl R. Banta, Division D:recior I have reviewed the Energy Fuels Mining Company's submittal, which you forwarded to my attention. This information responds to Stipulations No. 2 and 3, placed upon their approved permit, proposing a revision to their approved coal waste pile at the Animas/Helen Mine. Stipulation No. 2 required the operator to analyze the shear strength of the waste material and revise the stability analysis, if appropriate. Stipulation No. 3 required the operator to analyze what the potential impact of subsidence of old underground mine workings might be upon the pile, if the operator was allowed to expand the pile above these workings. The waste pile stipulations were imposed when the previous operator requested approval of a revision to significantly expand the capacity of the waste pile. The stability analysis included in that revision application relied upon literature derived representative material shear strength information. The Division found the assumed material shear strength information to be conservative, but required verification through testing of actual waste material. The required materials testing has been canpleted. The current operator has amended the waste pile design, reducing the maximum waste capacity from 4.0 million cubic yards to 1.3 million cubic yards. The facial slopes are being reduced in grade from 2(h ):1 (v) to 3(h ):1(v). The smaller revised waste pile will not infringe upon any previously undermined ground. In my opinion the operator's submittal has demonstrated that the waste pile will achieve a factor of safety (F OS) in excess of 2.5, well above the required minimum FOS of 1.5. In addition, they have deleted the proposed area of deposition overlying the underground workings. Therefore, the Division's concerns, as expressed in Stipulations No. 2 and 3, have been satisfied. I recommend, therefore, the the Division find that Stipulations No. 2 and 3 have been satisfied. Further, I recommend acceptance of the geotechnical slope stability and construction specification aspects of the amended coal waste pile design.