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~'' ~~ • • III IIIIIIIIIIIillll /_L\ 899 TR9PPER 1~INING INC. - ~, t. CERTIFIED ttP568142109 Ms. Sandi Marek Colorado Dept. of Health Water Quality Control Division 4210 East 11th Ave. Denver, CO 80220 Dear Sandi: ~•,,.._ . . 1,4 C:. ... ..... May 3, 1990 -~ This correspondence is to inform the Water Quality Control Division of pro- posed activities at Trapper Mine during the 1990 field season. Specifically, these activities are de-watering of Ashmore pit to acco~muodate mining, the use of Magnesium Chloride "DusTop" for dust control, the establishment of a new ash monitoring well in Middle Pyeatt Culch, and the establishment of a Par- shall Flume in Ute (NPDES 008) and Elk (NPDES 010) Gulches. In February, 1990, the "Baby Doe" dragline opened a boxcut at the lower reaches of East Pyeatt drainage. A result of this boxcut is the accumulation of a small amount of water at the north end of [he pit. To date, pit pumping has not been necessary, however, if additional water begins to build up, de- watering will be necessary to accommodate the draglines activity. The dragline is currently moving in a westerly direction toward Middle Pyeatt drainage and will eventually excavate a boxcut at the north end of this drainage as well, approximately mid-summer. The amount of water to be pumped from both drainage boxcuts, if necessary, is uncertain at this tune. Both drainages have adequate sediment control structures in place downstream of the proposed dewatering pits. East Pyeatt drainage contains two sediment control structures, one being NPDES location 011. Middle Pyeatt has three sediment control structures, the last in the system is NPDES site 009. In 1989, both the WQCD and CM1RD approved the use of Magnesium Chloride for dust suppression on haul roads and within the heavy equipment yard at Trapper Mine. The treatment was so successful in reducing dust emissions that Trapper proposed to apply MgC12 on all haulroads (approx 11 miles) within Trapper's permit area in 1990. An application rate of .5 gal/sq yd (recommended rate) is proposed for the target area. As suggested by WQCD, Trapper has monitored the levels of magnesium and chloride in the two previously impacted drainages prior co and after MgC12 application in 1989. The results of this sampling indicate no elevated levels of either magnesium or chloride following applica- tion. Trapper will continue to evaluate these two parameters for possible impacts. As previously mentioned, Middle Pyeatt Culch will be disturbed by the Ashmore pit mining advance. Further, the pit cuts in Ashmore pit will be elongated in a North-South direction within this drainage. As has been the case througl~ouc P 0. Box 187 Craig, Colorado 81626 (303) 824 4401