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COLORADO DEPARTMENT OF PUBLIC HEALTH AND THE ENVIRONMENT, Water Quality Control Division Rationale -Page 9, Permit No. CO-0045225 Table I/! - 3c Quality of Receiving Water, Sta[ian 0002 -Cripple Creek Below Squaw Gulch (POR 2/96 thru 2/97) >:.... >.... . /con, TR, mg/1 /3 1.187615 1.618592 5.400000 0.132000 0.520 1.862000 Lead, Dissolved, mg/[ 13 0.000231 0.000576 0.002000 0.000000 0. 0.000200 Manganese, Dissolved, mg/i 13 1.013462 1.120658 3.200000 0.000000 0.43 2.440000 Mercury, Total, mg/l !3 0.000000 0.000000 0.000000 0.000000 0. 0.000000 Ntckel, Dissolved, mg/l 13 0.0036!5 0.005664 0.015000 0.000000 0. 0.012200 Se/etium, TR. mx/1 13 0.000000 0.000000 0.000000 0.000000 0. 0.000000 Silver, Dissolved, mg/1 ~ 13~ 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 Zinc, Dissolved, mz/l 13 0.047231 0.035930 0.156000 0.000000 0.037 0.060800 2. Scream ow Information -The flows which are ordinarily used to calculate acute and chronic effluent limitations are the one day in three year low flow (IE3) and the 30 day in three year !ow flow (30E3) respectively. /n this case, however, it was appropriate !o use the mean flow of Cripple Creek regenerative release concentration calculations, as described in Section VI of this rationale. The mean flow for Cripple Creek is listed below, along with law-flows that are provided for purposes of comparison. Table II! - 4 - S[reamflows, cjs .Mean Flow:.: Acute Low.=Flow. :::: Chroieic Low=Flaw; Squaw Gulch 0.0 0.0 0.0 Cripple Creek above Squaw Gulch 0.96° 0.3 b 0.5 b a based upon studirs done by prrmirtrr b bawd upon Ditision studies 3. Dept~jPrecipitation Based upon isopluvial design charts, the /0-yr/24-hr storm depth at the mine site is 2.4". Based upon imerpolation, the 1-in-3 yr/24-hr storm depth is approximately 1.8 ". 4. lmoacts on Downstream Water Supplies or Other Receiving Waterc Provided that the terms and conditions of this permit are complied with, and that the perminee complies with the terms and conditions of its approval from the Stare Division of Minerals and Geology, it is expected that there will be no adverse impac! to downstream water supplies or other receiving waters. IV. FACIL/TYDESCRIPTION A. Industry Description 1. yype ojlndustrv -This facility is a cyanide heap leach gold mining operation. The project features consist of the Cresson Mine Pit, the Valley Leach Facility, the Minerals Benefaction Facility, the ore crusher and overburden stockpile areas. The ore produc[ion rate is planned to be 8 million ions per year, wtth a projected mine excavation period of seven years. The leaching facility will be operated for approximately nine years. This permit addresses only Jhe crusher area, the Ironclad Overburden Storage Area, and the mine haul road leading from the mine pit to that overburden storage area.