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' Mule Creek Gravel Pit ~ironmental Assessment • Page 27 t exposed cut banks up to 150-feet high as a result ofmining operations, no seeps or other signs of groundwater were observed during a visit to the site in July, 1999. ' The tributary, which starts as a wet meadow and becomes a defined channel, is located entirely on private property the entire length of the proposed permit azea. The drainage area of the entire tributary above its confluence with Fourmile Creek is 2 square miles, ' and the azea of the drainage above the gravel pit is 1.2 squaze miles. Elevations across the tributary range from 9,120 feet at the confluence with Fourmile Creek to 9,720 feet, ' with elevations of the proposed operation ranging from 9,200 to 9,480 feet. The mine faces west and receives approximately 16 inches ofmoisture annually (Colo Climate Center, "Colorado Annual Average Precipitation, 1951-1980," Ft. Collins, CO). The nearest U.S.G.S. stream gage is located on Fourmile Creek below Cripple Creek, near Victor, Colorado. The gage has a published period of record from October 1992, through the present. The maximum runoff is 1.4 cfs per square mile, while the minimum runoff is ' 0.01 cfs per square mile. The average daily runoff for the entire-period of record is 0.08 cfs per square mile. Translating this yield to the Mule Creek gravel pit, the unnamed tributary could have an average annual flow in the vicinity of the mine of around 0.1 cfs, ' which seems a reasonable number, given the size and stability of the existing stream channel. ' The wet meadow in the upper reaches of the tributary extends for approximately half a mile upstream and varies between 50 and 150 feet across. An access road has been constructed from the highway across the wet meadow to the mine just upstream from the ' entrance to Mueller Slate Park. The access road was made by laying a culvert in the meadow and putting approximately £tve feet of cover over it. On the upstream side, meadow grass grows right up to the embankment and there is no defined channel. On the ' downstream side, outfall from the culvert has created a live channel, which has incised so that the bottom of the channel is approximately 15 feet below the access road. Consequently, the access road and associated culverts have come to serve as a hydraulic ' control for this section of the stream. ' 3.1.1.4 Water Quality No water quality data was found for the unnamed tributary which drains the basin the t gravel pit is located in. There are several possible sources of contaminants to the tributary. First, there is runoff' from Highway 67, which could contain salts, oil, grease, gasoline and diesel fuel and antifreeze. However, unless there is a major accident ' involving a vehicle carrying a large amount of one of these materials, the shoulder of the road is likely to be a sufficient filter strip to stop these materials from reaching the stream. Second, there could be bacteriological contamination from individual septic systems or from livestock waste. Residences in the drainage aze assumed to be on septic systems, and horses are kept both upstream and downstream of the mine. While there is - some possibility of this sort of contamination, the distance between these sources and the stream would require a large-scale failure of a septic system or an extreme runoff event ' from a corral to move a meaningful amount of waste into the stream. Third and lastly, there is the mine itself. The primary source of pollution from the mine is likely to be ' Hydrosphere Resource Consulian¢, 1002 Walnut Suire 200, Boulder, CO 80302