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Henderson Mine SPCC/NiCP May 1999 • Materials stored on the surface at the Henderson Minesite are up-slope from the West Fork of Clear Creek but are on flat benches (Figure 2). Most liquid matEtrials aze secondarily protected by earthen or concrete retaining walls. Materials stored underground in the >~tine are protected by retainer walls or sloped floors with sumps. Any substance which mixes with mine water underground ends !lp in the mine water collection system. This water is pumped to a surge tank at the surface and is then piped three miles via gravity feed to the Urad treatment ponds (Figure 3). Floating contaminants, if present, can be contained in these ponds thereby allowing for their physical removal. Building drains and sewage lines aze routed to the mine's sewage treatment plar,.t (Figure 2). Sewage from underground facilities is also collected periodically and transported to the plant for treatment. The treatment plant utilizes an activated sludge system with the treated effluent being discharged to the Henderson Mine settling ponds. "fhe plan discharge is monitored under the terms of CDPS Permit CO-0041467 (Outfall 007). The water from sewage treatment and precipitation events that collects in the Henderson Mine settling ponds is piped directly to the Urad surge pond. From the surge pond water is pumped directly to the Urad treatment plan. This treated water can then be directed to Lower Urad Reservoir where any discharge is covered by CDPS Permit CO-0041467 (Outfall005). 2.2.3 Urad Minesite The Urad Minesite is a reclaimed mine located southeast of the Henderson Mine in Woods Creek Valley. This site consists of two reclaimed tailing impoundments, two plugged portals, water treatment collection ponds, and a water treatment plant (Figure 3). Seepage collected from the two tailing impoundments and the drain pipes in the portal seals are piped to Pond No. 1, from where it is then pumped to the treatment plant. Water from the Henderson Mine is also piped to this pond via buried pipeline. Seepage collection for the Upper Tailing Impoundment consists of both surface and underground collectors. The seepage is collected within channels, pipes and gravel collection trenches located upstream of slow-permeable bentonite barrier. Thi:• seepage is then piped via gravity feed in a buried 12-inch pipe. There is also a backup 8-inch buried pipe available for this system. The two mine portals are located immediately southwest of the treatment plant and aze sealed with concrete barriers approximately 800 feet inside each opening. Drain:. in these portals are connected via a small diameter plastic pipe to Pond No. 1. These portals produce only a small volume of water (1 to 2 gpm). n LJ 3