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1 <br />Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation <br />1. INTRODUCTION <br />The Schwartzwalder Mine is an underground uranium mine located in Jefferson County near Golden <br />Colorado, in the steep canyon of Ralston Creek (Figure 1). The mine was operated by Cotter Corporation <br />(Cotter) from 1966 until May 2000, when mining operations ceased, dewatering pumps were shut off, and <br />the mine was allowed to flood. <br />Significant quantities of hydrologic and hydrogeologic data were collected prior to mine shutdown and in <br />the seven years that the mine has been refilling. Monitoring wells and surface water stations onsite (Figure <br />2) and offsite (Figure 1) have been monitored, many for more than 20 years. Data have been collected on <br />mine refilling rates, mine water quality, Ralston Creek flow rates, and Ralston Creek water quality. Cotter <br />has reclaimed several waste rock piles in Ralston Creek Canyon, decommissioned numerous buildings, and <br />has conducted bench scale and pilot scale studies of water treatment options. <br />Hydrologic issues related to mine closure include the flooding of the underground workings, effects of <br />waste rock dumps on water quality, and the interaction of surface water in Ralston Creek with alluvium and <br />fill at the site. <br />The purpose of this hydrologic evaluation report is to: <br />• Summarize the available hydrologic and hydrogeologic data; <br />• Analyze the mine filling rates and predict the timing and final water level elevation in the mine; <br />• Evaluate trends in water quality in Ralston Creek and in the underground workings; <br />• Develop and present a geochemical model of the system; and <br />• Develop a list of potential strategies and recommendations for mine closure and mitigation. <br />2. SITE DESCRIPTION <br />2.1 Location <br />The Schwartzwalder Mine is located in Ralston Creek Canyon, in northern Jefferson County, Colorado. <br />The mine occupies the southeast quarter of Section 25, T2S, R71 W (Figure 1). Cotter owns approximately <br />87% (558 acres) of Section 25. Fifty-seven (57) acres were permitted for mining under Colorado mining <br />permit number 77-300. <br />The northeast corner of Section 25, along with adjacent sections to the north, northeast, and northwest, are <br />rural residential properties associated with Blue Mountain Estates. The section west of the mine is used for <br />summer cattle grazing, while the property south and east of the mine is owned by Jefferson County Open <br />Space Parks. This area of Open Space is named White Ranch Park, in honor of Paul and Anna White who <br />were the owners of vast holdings in the area, including Section 25 which their heirs sold to Commonwealth <br />Edison Co. in 1982. <br />From Colorado State Highway 93, north of Golden Colorado, the site can be accessed by either Pine Ridge <br />Road or West 56~' Avenue. Where these roads intersect (one mile west of highway 93) a paved road enters <br />the private properly of 19 exclusive 35-acre home sites called Bear Tooth Ranch. The access road becomes <br />bladed dirt, north of Bear Tooth Ranch, and the road enters Ralston Canyon and turns northwest upstream <br />toward the mine. Approximately one-half mile of land along the road near Ralston Reservoir is owned by <br />the Denver Water Board, and the next two miles of land are owned by Jefferson County Open Space Parks. <br />The road then enters the mine property through a gate on the eastern boundary of mine property. <br />Whetstone Associates <br />4109B.071116 <br />