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1 <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br />William J. Carter March 12, 1998 <br />Re: Response to Susan Bwgmaier's comments on the 1996 Annual Hydrologic Report <br />A sample was taken on February 21, 1996 at the discharge sample point for Pond A. During <br />the period of February 20 to 22, 1996, the area azound the Sanborn Creek Mine received <br />abnormally warm weather and rain. Information contained in the report entitled "Frequency <br />Analysis of Rain on Snow Event of February 21, 1996" by Wright Water Engineers prepared <br />for Mountain Coal Company, West Elk Mine, indicated the equivalent of a 25-year, 24-hour <br />storm event. The West Elk Mine is located dvectly across the North Fork of the Gunnison <br />River, south of the Sanborn Creek Mine. <br />As a result of the rain and snow-melt runoff, Sanborn Creek Mine dischazged for the first <br />time ever from Pond A, Outfall 009, and Pond B, Outfall 012. However, Hubbard Creek <br />Pond, Outfa11007, East Yazd Pond, Outfall 010, and Substation Number 3 Pond, Outfall <br />013, did not discharge during the storm event of February 20 to 22, 1996. All ponds are <br />designed to contain the 10-yeaz, 24-how event below the emergency spillways, based on <br />assumed runoff curve numbers for the drainage areas. In accordance with Colorado <br />Wastewater Discharge Permit System, Permit No. CO-0000132, July 1, 1992, the effluent <br />parameters, alternate discharge limitations for any discharge or increase in volume of a <br />discharge caused by precipitation within any 24-hour period greater than the 10-year, 24- <br />hour event (or series of storms or snowmelt of equivalent volume), and sample results for the <br />sample taken at Outfall 009 aze <br />Effluent Parameter Dail Sample Result <br />Flow Report 0.06 MGD <br />Total Suspended Solids Report 92 mgJl <br />Total Iron Report 3.29 mg/l <br />Settleable Solids Report <0.1 mUl <br />Total Dissolved Solids Report 230 mg/1 <br />pH (minimum-maximum) 6.5-9.0 s.u. 7.56 s.u. <br />Oil and Grease 10 mg/1 <5 mg/1 <br />Although not required by Colorado Wastewater Discharge Permit System, Permit No. CO- <br />0000132, for the purpose of determining the impact of the discharge on the receiving water, <br />a sample was taken at approximately the same time on February 21, 1996 from the North <br />Fork of the Gunnison River upstream of the discharge. Sample results for the sample taken <br />from the North Fork of the Gunnison River are: <br />Effluent Parameter Samnle Result <br />Flow 142.83 MGD <br />Tota] Suspended Solids 6] mg/1 <br />Total Iron 2.13 mg/l <br />Settleable Solids 0.2 mUl <br />Total Dissolved Solids 130 mg/1 <br />17 <br />1 <br />