1995-08-11_REVISION - M1977493 (9)

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. storage tanks for combination with other source waters requiring treatment. Water is collected and treated with lime (at an average monthly rate of 1317 tons) at the TDH and delivered by gravity to the Mayflower tailing impoundment where the alkaline,water pool (pH:10.5-11.5) acts to precipitate metals. A lime slaking facility is under construction and is scheduled to be completed east of and adjacent to the Ten Mile impoundment in late 1995 (after which the TDH facility will become a treatment backup system). This facility includes a fresh water supply well. Feasibility studies indicated that the installation of such a slaking facility with storage bins and a fresh water source would increase the effectiveness of the lime for the water treatment system by up to 15 percent. The location of the facility will allow treated water to be gravity fed to any of the tailing impoundments, thus, reducing pumping costs. A brief summary of the operation of the new lime plant is presented in Appendix I. Presently, following the addition of lime at the TDH, water is gravity transported to the Mayflower tailing impoundment. This pool water is maintained at approximately pH:10.5-11.5 to allow metal hydroxides to precipitate and settle. Clear water then is decanted from the west side of the pool for discharge. Just prior to discharge, sulfuric acid is added to the water flow through a drip feed system to regulate the pH at between 6.5 and 9.0. iSeep waters from the Ten Mile tailing impoundment are combined with other source water for treatment in the Mayflower impoundment pool. Seepage from the toe of No.3 Dam at the upstream Ten Mile impoundment runs directly into the Mayflower pool. Seepage from No.5 Dam is captured through a system of engineered subdrains constructed beneath the toe of the dam and upstream for a distance of 1500 feet. Seepage is routed by gravity flow directly into either of the two concrete seep water ponds located at the toe of the dam just above the clear water pond(Figure 1). These collection ponds are designed to allow all seepage to be collected in one pond when the other is being serviced. Seep water thus collected is pumped back to the Mayflower impoundment pool for mixing and treatment with other waters. In addition to treating the aforementioned source waters, acidic drainages from several major historic mines in the Ten Mile Mining District are routed to the Mayflower impoundment water pool for mixing and treatment. This AMD/ARD originates primarily in Searle Gulch and Kokomo Gulch and includes waters from the Kimberly-Wilfley Mines group (the Wilfley Mine being the largest contributer),the White Quail/Colonel Sellers complex,the Delaware Tunnel, and others. In addition, non-point run-off from historic waste rock dumps and mill sites in the Searle Gulch area is captured and treated in the Mayflower impoundment as part of the active Climax water treatment and discharge system. These historic mines and mills reached their peak of activity and operations in the 1880s during the silver boom period which saw development of the towns of Recen, Kokomo, Carbonateville, and Robinson Camp. A second activity peak, not 22