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! ~ TZA TED ZORICH & ASSOCIATES, INC. CONSUL 7ING ENGINEERS IN WATER RESOVRC ES 1221 sou11+ C:LAN91(S~LJN. +cc~ DEM7ER. COLORADO 80210 (303)777-058A September 26, 1985 ®1~~~®s ~161J Mr. Mark Steen Gold Hill Ventures Limited SEP 26 198: Partnership Post office Box 1523 MINED LAND Longmont, Colorado 80501 RECLAMATION DIVISION Re: Capacity of Interim Ditches and Freeboard for the Tailings Pond Dear Mr. Steen: As you requested, Ted Zorich and Associates, Inc. (TZA) has estimated the required carrying capacity of_ the interim ditches associated with the tailings pond, and the freeboard required for the tailings pond dikes. The purpose of these precautions is to insure that low quality water does not enter the surrounding environment. As you discussed, the tailings pond to be constructed will have a 400 foot long dike and will extend 260 feet up slope from the dike. Permanent ditches will be installed initially to divert surface runoff around the 260 by 400 foot area. The portion of the 260 by 400 foot area that is used will increase with time. The 400 foot dike will be constructed initially and the initial active area of the tailings pond will extend up slope 50 feet. The interim ditch will be located just over 50 feet up slope from the dike and will collect surface water rl7noff that occurs below the permanent drainage ditches and within the 400 by 260 foot area, and carry this water off the tailings pond area. As you stated, the distance up slope from the dike will increase from 50 feet to 100 feet, then to 200 feet before being extended to 260 feet. Interim ditches are planned to be constructed each time the pond is expanded except when it is expanded to the full 260 feet. The estimated drainage areas and maximum runoff rates are given on the attached table. TZA's recommended freeboard distance for the tailings pond dikes is 0.5 feet. The 100 year, 24 hour storm is 4.6 inches