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Sunnyside Basin M-77-378 <br /> Page 3 <br /> General Specifications - Cont <br /> Cross-Section- The side slopes will be 2: 1 where excavated in <br /> overburden with transitions (steeper or flatter) to <br /> natural rock contour where exposed or approximately <br /> 3/4 : 1 where blasted. <br /> The finished ditch bottom will be approximately 5 <br /> feet wide. It will be overexcavated initially and <br /> the downhill sideslope will be rebuilt with lake <br /> sediments (ie. clay material ) to maximize <br /> groundwater flow interception. The depth will vary <br /> with surface and bedrock topography. <br /> Excavated Material - Overburden material excavated will be; <br /> 1) blended into the surrounding disturbed hillside. <br /> 2) used to reduce a portion of the nighwall in the <br /> Sunnyside pit. <br /> 3) used to backfill ditch excavations where <br /> groundwater interception does not warrant ditch <br /> or drainpipe installation. <br /> 4) used to backf i ll ditch excavations where the <br /> drainpipe installation is selected because of <br /> depth or surface runoff interception potential . <br /> Drainpipe - See Figure 2 for typical section <br /> Slope - The profile will be the same as for open ditch <br /> construction. <br /> Pipe - The pipe size will vary with the intercepted flow. <br /> It is anticipated that it will vary from 8 " to 12" . <br /> The pipe will be either HDPE or concrete with a <br /> clean aggregate cover. The aggregate will be <br /> covered with filter cloth to prevent fine material <br /> from infiltrating. The HDPE will have slot <br /> perforations and the concrete pipe will be laid <br /> with 1" - 1 1/2" spacing every joint (approximately <br /> 5 ' ) . Perforations/joint spaces will be wrapped <br /> with filter cloth to prevent aggregate <br /> infiltration. <br />