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Ms Carla Lenkey THIRD QUARTER 1997 DMR December 9, 1997 gage 3 The conditions at Outfall 002A on 7uly 14, 1997 were warm and dry with the only inflow into the pond being that which fell as summer thunder showers. The water in the pond was being released in anticipation of summer maintenance to the pond embankment. The higher than normal pH was verbally reported to Jon Kubic during July, 1997. Excluding the above mentioned higher than normal pH reading at Outfall 002A, all remaining analytical data exceeding permit conditions are related to precipitation events occurring between September 18-22, 1997. Precipitation Station Descriptions There are currently four automated precipitation stations located throughout the Colowyo mine site. Each precipitation station is located in a watershed with sediment control ponds associated with them. It is important to note that a precipitation event can occur within a watershed boundary but not be recorded by the precipitation gauge. Colowyo has carefully chosen the location of the precipitation gauges but, given the vagaries of Colorado storm patterns, it is not a guazantee that the center of the storm event will be directly over a measuring device. A map is enclosed which details the location of the sediment control ponds, the watershed boundaries, and the location of the precipitation stations. The breakdown of these locations and precipitation event standards for Colowyo are as follows: 24 Hour Precipitation Measured t ti Associated Sediment Control Pond a'n a Section 16 Outfa11007A-Prospect, Outfall 004A-Gulch A 2.34" Section 34 Outfall 004A-Gulch A, Outfall OOIA-Streeter, 1.84" Outfall 002A-W orkarea West Station Outfall OOIA-Streeter, Outfall 008A-West Pit, out of Outfall OlOA- East Taylor, Outfa11002A-Workarea service Gossard Outfal1005A-Stoker Siding, Outfall-006A Rail Loop, 1.64" Outfall 003A-Gossard Precipitation Event Standards for Colowvo The 10 year, 24 hour precipitation event is 1.8 inches. The 25 year, 24 hour precipitation event is 2.3 inches. The 100 year, 24 hour precipitation event is 2.8 inches. Thus, for Outfalls 002A and OOSA, the Section 34 and Gossard stations demonstrate a precipitation event, ttitling the discharge to the Alternate Limitations for SS and Fe. For outfalls 004A and 007A, the Section 16