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• -6 • A statistical summary of water quality data from the Fish Creek U.S.G.S. gauging station (now operated by the U.S.D.A.-SEA) is tabulated in the mine plan. A complete Ii sting of all data is available at the U.S.D.A., Science and Education Administra- tion in Fort Collins, Colorado. The .concentration of dissolved constituents in Fish Creek increases downstream. Some of the increase can be attributed to an adjacent mining operation Iocated near Fish Creek, but agricultural runoff is responsible for most of the increase. The mean flow in Fish Creek is 12.75 cfs. Peak flows ranging between 51 cfs and 342 cfs have occurred during spring runoff without exception. Water quality data from Crassy Creek, Little Grassy Creek and Seneca mine effluent are listed in the mine plan. The basic chemical properties of the effluent and Grassy Creek are very similar and of the Ca-Mg-So tupe.. During spring, alkalinity is lower than other seasons and acidity is higher9 The concentration of total iron varies with suspended solids which increase during high runoff periods. Manganese exhibits the same seasonal fluctuation as iron and total suspended solids. pH has no apparent seasonal variations. Flow rates in Grassy Creek ranged from 28 gpm to 12,280 gpm downstream from the mine and from no flow to 7800 gpm upstream from the mine for water year 4/80 - 4/81. Flow rates in Little Grassy Creek upstream from the mine ranged from no flow to 1625 gpm during 4/80 - 4/B1. Flow fran Little Crassy Creek downstream from the mine is controlled by the Wadge Impoundment. SEDIMENT PONDS All surface drainage from disturbed areas and areas recently reclaimed will be passed through one of three sediment ponds. The Northwest Impoundment (pond 8003) is located in the northern portion of the permit area and treats runoff from the shop area and nearby previously mined areas, approximately 60 acres total. The Northwest Impoundment has a capacity of 7 acre feet. This pond is in compliance with the design standards of 4.05.6. The South Section 12 pond (H004) will be located at the southeastern end of the permit area and will treat runoff from future mining operations. This pond will be constructed prior to any disturbance in this drainage area. This proposed pond will have a drainage area of 597 acres and a capacity of 19 acre feet. This pond has been designed to meet the standards of 9.05.6 The Wadge Impoundment has a maximum capacity of 303.3 acre feet and has a surface area at high waterline of over 80 acres. The drainage area for the Wadge is approxi- mately 2,382 acres. The Wadge Impoundment was formed in 1976 when a previously mined pit was allowed to fill with water. The entire storage capacity of this reservoir is incised. According to 4.05.6(10), a sedimentation pond with a capacity of more than 1000 acre feet, or with a dam or embankment in excess of 10 feet in vertical height, or with a surface area at high waterline in excess of 20 acres, must meet the requirement of C.R.S. 37-87-105 and 9.05.6(10)(a)(b) and (c). The requirements of 9.05.6(10) were intended to prevent an embankment failure of a Iarge pond, and do not concern a completely incised impoundment. Therefore, the Wadge Impoundment does not have to meet the requirements of 9.05.6(10), even though it has a surface area at high waterline in excess of 20 acres. This sediment pond is in compliance with the requirements of 9.05.6.