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ACID MINE DRAINAGE MITIGATION <br /> The three percent grade, coupled with the layer of lake sediments <br /> and overburden at the top of the fill will control most of the <br /> surface water encountering the fill . As discussed earlier , one <br /> of the ABP tests run on the Sunnyside Pit overburden was -59 . 9 . <br /> Because of the consistency of the rest of the overburden tests , <br /> we feel that this test is not representative of the entire <br /> stockpile. If this number is omitted , the average ABP of the <br /> stockpiled overburden is -5. 00. The average ABP of the in-place <br /> overburden southwest of the lake hole is -1 . 88 , and the average <br /> ABP of the lake sediments is -0. 13 . Therefore, surface water <br /> will come in contact with only material that is relatively <br /> neutral or material that is more or less consistent with the <br /> natural surroundings . <br /> It is not possible to stop subsurface water from entering the <br /> lake hole, but any subsurface water encountering the perimeter of <br /> the fill will enter the French Drain, therefore being diverted <br /> away from the upper waste storage area. Shot rock is a <br /> free-draining, material , and in addition to this , the trench rock <br /> has a net neutralization potential . After flowing through the <br /> French Drain, the water will encounter the buffer zone. Any <br /> water that permeates the lake sediments and waste above will also <br /> flow through the buffer zone . The remaining underground workings <br /> will be filled with a mixture of waste and trench rock . Water <br /> flowing into this area will have contact with both the waste and <br /> the trench rock. Because of underground mining activity, a large <br /> - 11 - <br />