2014-10-20_REPORT - M1990041 - Laserfiche WebLink

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REMEDIAL ACTION COMPLETION REPORT GOLDEN GILPIN MILL SITE CENTRAL CITY/CLEAR CREEK SUPERFUND SITE OPERABLE UNITS 3 AND 4 I. INTRODUCTION The Golden Gilpin Mill Site is one of numerous priority areas within the Central City/Clear Creek Superfund Study Area. Priority areas are those locations scheduled for clean up as part of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) response actions at the Central City/Clear Creek Superfund Site. Remediation of the Golden Gilpin Mill Site occurred from June of 2008 through September of 2008. The Colorado Department of Public Health and the Environment(CDPHE) managed the remediation project in coordination with the United States Environmental Protection Agency (EPA). Clear Creek originates in the high mountains of Colorado's Continental Divide, at 11,000 feet of elevation near Torrey's Peak. The river finds it way from the mountains following glaciated, U- shaped valleys and a steep river canyon until it reaches the City of Golden, Colorado, 60 miles to the east and several thousand feet lower in elevation. The river is a major source of water for industry, agriculture, and recreation. Clear Creek is the drinking water source for nearly 350,000 people living in the northern and western suburbs of Denver, Colorado. Eventually, Clear Creek empties into the South Platte River just north of Denver. Clear Creek passes through the Colorado Mineral Belt which includes several mining districts in Clear Creek and Gilpin Counties. Due to the rich mineralization, these two counties became some of the most heavily mined areas of Colorado, with gold and silver accounting for the vast majority of the mining. Mining activity in the area commenced in 1859 with placer gold being found at the mouth of Chicago Creek, a tributary to Clear Creek. The first lode discovery occurred in Gregory Gulch later that year. Gregory Gulch is a tributary to North Clear Creek which is a tributary to Clear Creek. By the summer of 1860, almost all surface lodes had been claimed. As the extraction of surface ores progressed, the depth of the mines increased, often to a point below the ground water table. To compensate,the miners constructed tunnels which not only drained and dried the mines, but were used for hauling ore out of the mines. Today, acidic metal-rich water from these mine tunnels enters Clear Creek and its tributaries at many locations and has a profoundly harmful effect on the ecology of the river. Mine tailings from inactive or abandoned milling operations and waste rock from the development of the mines dot Clear Creek's river banks. These tailings and waste rock piles also contribute metals such as iron, zinc, copper, cadmium, manganese, lead and arsenic to the river, especially during