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• is unlikely due to mine discharge because of the discharge's downgradient location and <br />the dissimilar chemical composition of mine discharge water. The mine discharge water <br />is strongly sodium-bicarbonate water with a conductivity of approximately 1500 mg/I, <br />while AVF-3 water is typically a mixed sodium-magnesium~alcium-bicarbonate-sulfate- <br />chloride water with conductivity averaging approximately 2000 mg/I. The noted <br />increase in conductivity in well AVF-3 does not appear to be related to the wastewater <br />lagoon as the conductivities in the well water have historically exceeded the levels <br />measured in the wastewater (approximately 1500 mg/I) and the water discharged to the <br />lagoon is primarily Trout Creek Sandstone water, typically strongly sodium-bicarbonate <br />water. <br />SURFACE WATER MONITORING <br />R/VERS <br />There are two rivers in the vicinity of the mine site. The Yampa, flows in a southeasterly <br />direction across the mine site. The Yampa River drains most of the northeast corner of <br />Colorado and part of south~entral Wyoming. The second river is the Williams Fork, <br />which is a major tributary of the Yampa River. The Williams Fork River joins the Yampa <br />River on the mine property. Monitoring data is collected for the Williams Fork River. <br />Monitoring data is also collected from one spring, the #1 Strip Pit (NPDES site 022). In <br />1997 there was a discharge from some sediment ponds (NPDES sites 003, 013, and <br />018) for a short duration in response to an unusually rapid melt of the snow pack. <br />• C-81-044 1997AHR Page 9 <br />