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R &V Cripple Creek & Vlctor Gold Mlning Company A Joint Venture -Pikes Peak Mining Company, Manager Operations Office P. O. Box 191 100 North 3rd Street Victor, Colorado 60660 (719) 689-2977 Fax (7197 689-3254 HAND DELIVERED August 5, 1999 Mr. Berhan Keffelew Reclamation Specialist Colorado Department of Natural Resources Division of Minerals and Geology Office of Mined Land Reclamation 1313 Sherman Sueet, Room 215 Denver, Colorado 80203 iiiiiiiiiiiiiiuiii sss !?ECEIVEd AUG 0 6 1999 Division of Minerab 6 Geology Re: Response to Division /nspection Report Dared July /7 /999 -Leak Detection Sump 4 Dear Mr. Keffelew: Cripple Creek & Victor Gold Mining Company ("CC&V") received the above referenced inspection report from the Division of Minerals and Geology ("Division") on July 28, 1999. As we have discussed on several occasions, the excessive precipitation that the Cresson Project (Permit No. M-80-244) has received since March of this yeaz is responsible for the (lows observed ta Leak Detection Sump ("LDS") 4. Attached Table 1 provides a summary of the monthly precipitation for 1995 through July 1999. As noted on Table I, the site has received between 16.2 and 16.8 inches of precipitation during April, May, June, and July, which faz exceeds the average for these months. As such, Flows have been observed throughout the District in locations that previously have been dry during all seasons. The diversion along the northwest side of the Valley Leach Facility ("VLF') is one example o(an area where Flows were previously absent, but have been consistently observed since May o(this year. CC& V believes that the diversion ditch was the principal source of ground water recharge for LDS 4. The close proximity of LDS 4 to the unlined diversion and the fact that the bottom elevation of LDS 4 is below the depth of the diversion channel supports this premise. The LDS is comprised of a free draining granular material, installed below the low penneabilily Soil Liner Fill ("SLF'). The LDSs are intended to intercept seepage below the SLF. The inflow o(water being observed into the LDS, therefore, demonstrates that the LDS is functioning pursuant to the design albeit the Flows are higher than historically documented due to the higher precipitation. All of the LDSs approved and installed in connection with conswction of Phase 1 and Phase B of the VLF are open at the bottom. This allows the leak detection trenches, as well as adjacent areas outside the VLFvnmediately adjacent to the sumps, to contribute Flows [o the LDSs. CC&V and Golder Associates ("Golder") recognized this during the preparation of Amendment No. 7 and modified the design. A sealed bottom has been included in the design approved by the Division in connection with Amendment No. 7 (Volume q Drawing 13 -Phase IB Leak Detection System Details) for the LDS 4 and LDS 5 extensions and new LDS 6. This is intended to minimize the potential for areas ouLSide the VLF to contribute flows to these LDSs. N addition, the new diversion ditch to be instilled along the margins of the Phase IB extension of the VLF combined with the secondary and tertiary underdrain system are designed to intercept surface and shallow ground water flows, respectively. These design elements and the increased distance of the extended leak detection trenches from the margins of the VLF will further limit the volume of water from areas outside the VLF from entering the extended and new LDSs. The location o(the extended and new leak detection trenches are shown in Volume q hawing 5 of the Amendment No. 7 permit application document. Please do not hesitate to contact me at 719<i89-0041, i(you have any questions or comments. Sincerely. ~~~.~.~ Manager, Environmental Affairs Enclosures