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Henderson Mine SPCC/MCP May 1999 <br />Seepage from the Lower Tailing Impoundment is collected in a small pond at th'~ base of <br />the impoundment. The Lower Urad Pumphouse contains three electrically powered <br />pumps that pump the water in this pond to Pond No. I via two available pipelines. <br />Typically one to two pumps aze operated at any one time with the others kept av~iilable as <br />spazes. Afresh water buffer pond is located between the collection Pond and the Lower <br />Urad Reservoir. Water levels in the buffer pond aze maintained at higher levels than <br />either the collection pond or reservoir thus maintaining a hydraulic barrier to seepage in <br />this azea. <br />Untreated mine water and treated sewage effluent from the Henderson Mine are piped to <br />Pond No. 1 at the Urad facility utilizing one or two buried HDPE pipes (one 12-inch and <br />one 14-inch diameter pipe). These buried pipes, for the most part, are located a.lungside <br />the main access roads to the Henderson Mine and Urad site. <br />The water treatment ponds at Urad (Figure 4) include Pond No. 1, Pond No. 2, J Well, <br />and the Clear Water Well. Untreated water from Urad and Henderson is directed into <br />Pond No. 1 where it is stored until pumped to the Water Treatment Plant. Pond No. 2 <br />provides additional storage capacity in the event of high water flows or tempor;iry plant <br />shutdown. Runoff water from the plant site and water collected in the north and :south toe <br />drains of the treatment ponds aze routed to the J Well, then transferred back to No. 1 Pond <br />for treatment. In the event that the Water Treatment Plant is down for a period of time, <br />water treatment can be performed dvectly in Ponds No. 1 and No. 2 with the Clear Water <br />Pond serving as the final settlement basin prior to discharge (Outfall 004). <br />Sludge Ponds 1 and 2 aze located next to the treatment ponds and contain sludge pumped <br />from the treatment plant clarifier. The sludge in these ponds is consolidated to the extent <br />practicable, removed, and transported off-site for appropriate disposal. Testing of the <br />sludge shows it to be non-hazardous, as determined by TCLP and other tests (pH and <br />flash point); therefore, it meets requirements for disposal in BFI's sanitary landfill. Pond <br />No. 5 is located downstream from the treatment ponds on the reclaimed Lower Tailing <br />Impoundment and provides additional containment of untreated water in the event of <br />treatment pond overflow. Pond No. 5 drains to the south into the toe drain collection <br />system. <br />The Water Treatment Plant uses a high density sludge process to remove metals. This <br />process includes an aerated reactor, a clarifier with sludge recycle/removal, and ancillary <br />lime, flocculent, and sulfuric acid addition systems. A process flowsheet for the plan is <br />provided on Figure 5. The Old Mill Building, located immediately north of the treatment <br />plant, is used to store chemical reagents (i.e., caustic and sulfuric acid) that may be used <br />to treat the water directly in the ponds in an emergency situation. Secondary containment <br />for the Water Treatment Plant, Old Mill Building, and surrounding azeas is provided by <br />the Surface Interceptor Ditch (Figure 4) which drains into the J Well. <br />C J <br />4 <br />