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Mountain Permit area and in close proximity to site operations, it is uncertain whether the manganese concentrations detected in site ground water are elevated above natural background levels. See Table 3 for a summary of hazardous substance detections in onsite ground water. Process related ponds onsite possess intact, maintained containment features. The tailings pond has a double liner with a leachate collection system. The leachate and dewatering ponds also have liners. The higher grade ore pile onsite is situated on a pad with a maximum capacity of 150,000 tons and dimensions of 400' by 800' (BMG, 1994). The City of San Luis extracts water from one main (300' depth) and one backup (90' depth) well that draw from unconsolidated alluvial deposits, specifically from a pea gravel deposit occurring at a depth of 110 to 290 feet. The two wells are located within San Luis approximately 2.8 miles from the southwestern comer of the permit boundary. Ground water from the public supply wells serving the residents of San Luis and from a well on the nearby Dos Hemtanos Ranch is analyzed by Battle Mountain Golo biannually for cyanide content. The San Luis Water and Sanitation district submits samples for cyanide and metals analyses to an independent laboratory in addition to analyses performed by Battle Mountain Gold. Cyanide has not been detected in the water collected from these public supply and domestic wells (URS, 1993; SLWSD, 1994). 7.0 SUMMARY The Battle Mountain Gold site, located 5 miles rwrtheast of San Luis, Colorado, is the site of historical and current preaous metal mining operations. Aqueous and sediment samples were collected from the Rito Seto River and sediment was cogected from an unnamed drainage to assess the potential for an ongoing hazardous substance release from the Battle Mountain Gold-San Luis Project precious metal mine. Surface and ground water quality monitoring conducted previously by the mine personnel had indicated the possibility of an uncontrolled release taking plate. Aqueous samples collected from the Rito Seco River during SI field activities contained elevated concentrations of aluminum, iron and manganese as compared to water quality upgradient of the site. No elevated concentrations of cyanide or metals were detected in sediment samples collected from the Rito Seto or the unnamed drainage below the mill/tailings facility. Iron and manganese concenmations were documented to be elevated in Rito Seco River water at ~amo~.oermmrrt - a - R+~ 4 o~/+aoa