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<br />Susan Mowry <br />Tom Schreiner <br />Page 2 <br />NOV C-86-042 <br />Cleanout of lower waste pile sediment pond, dewater sediment pond <br />Bear Na. 1 Mine area, and maintain adequate drainage control at UTL <br />conveyor bent. <br />Lower Refuse Pile Sediment Pond <br />The lower refuse pile sediment pond is sized to handle the runoff from <br />a 10 year, 24 hour precipitation event fora total disturbed area of <br />23.6 acres (Table 6.6 Mt. Gunnison MdcR Plan, Volume 12 ). The total <br />acreage currently disturbed is 12.1 acres (Table 6.6). This means that <br />under current conditions, the pond is 48.7% larger than required to <br />contain the runoff from a 10 year, 24 hour event. <br />The 100% sediment marker for this pond is the bottom of the <br />dewatering valve on the combination drop inlet spillway/dewatering <br />device. The sediment in the major portion of the pond is not up to the <br />level of the bottom of the valve. There are two areas, one near the <br />southwest corner, and one on the east side where the material is above <br />the level of the valve. These two areas comprise about 15 to 20% of <br />the pond area. <br />The operator had cleaned an approximately 30' x 30' (total pond area is <br />100' x 100') area of the pond in the southeast corner in February and <br />March and April 1986. Cleaning operations were halted on several <br />occassions by inclement weather conditions. Equipment was stuck in <br />the mud in the pond on several occassions, including a D-7 Caterpillar, <br />a 215 Caterpillar hydraulic excavator, and a 988B Caterpillar front- <br />end loader. <br />No problems were being encountered with containment of runoff and <br />NPDES permit effluent Limitations were being met. It was obvious the <br />pond could not be cleaned with conventional equipment at the mine <br />during existing weather conditions and to wait until the weather <br />cleared up appeared to be the most reasonable choice. If the pond had <br />been having trouble containing runoff or meeting effluent limitations <br />and was not almost twice as large as it needed to be for existing <br />conditions, WECC would have opted to take overly expensive <br />operations to insure no damage to the environment or violation of <br />effluent limitations occurred. <br />