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Introduction <br />The following report presents the results of a hydrogeologic evaluation and opinions of the <br />author (Joby Adams) regarding the existing gravel quarry operations operated by Varra <br />Companies in Platteville, Colorado in association with CDRMS Permit # M1999 -006. <br />Specifically the evaluation was performed to assess possible impacts to wetlands <br />downgradient of Tract B — a 13.75 acre parcel. Site conditions are depicted on Plate 1. <br />Background Information <br />Information provided by current mining operation data and water resource evaluation <br />reports document local and regional hydrogeology. Soil conditions generally consist of two <br />to five feet of top soil underlain by sand and gravel deposits, which in turn are underlain by <br />shale. Over the entire area the average saturated thickness of the sand and gravel <br />deposits (prior to mining) is estimated at 20 feet. The natural hydraulic gradient as <br />documented by past water resource investigation reports is on the order of 0.002 feet per <br />feet, with the depth to water varying between 6 and 15 feet below ground surface. The <br />natural groundwater flow direction is to the north — northeast. Seasonal water table <br />fluctuations of between one and three feet are common for this area; however, fluctuations <br />of greater than ten feet have been documented during drought conditions (Schneider, <br />1983). <br />The water table in the vicinity of Tract B will be drawn down to bedrock over an estimated <br />13 acres. The mine is dewatered by allowing groundwater to flow from the side walls of the <br />excavation into ditches excavated into the shale bedrock at the toe of the excavation walls. <br />The ditches are sloped so water drains to the north toward St. Vrain Creek. The water is <br />then pumped from the excavation into a settling pond located just to the east of an area <br />identified as wetlands. The water then outfalls to Last Chance Ditch, which flows to the <br />north. <br />Project Assumptions <br />The following are assumptions made in estimating affects of mine dewatering operations. <br />> The aquifer within the model boundary is homogeneous and isotropic. <br />