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Introduction <br />i <br />Sediment Pond 008 was originally constructed in 1987. The pond is located <br />in the NW/4, Section 7, Township 5 North, Range 86 West (see Exhibit 13-2A, <br />Postmining Topography and Permanent Features) in the Bond Creek drainage, <br />which is tributary to Fish Creek. The contributing watershed is <br />approximately 271 acres, of which 229 acres were disturbed by mining <br />activities, and which have since been reclaimed and revegetated. <br />Pond 008 was constructed as an earthen fill embankment pond (see Exhibit 7- <br />17A, Sediment Pond 008 As-Built). The original spillway was a 6-inch <br />diameter orifice cut into a 24-inch diameter drop inlet pipe. In 1992, a <br />trapezoidal emergency spillway channel was cut into the embankment to <br />increase the capacity of the pond. Certified as-built reports for each <br />phase are included as Appendix 7-6f.1, Pond 008 1987 As-Built Report and <br />Appendix 7-6£.2, Pond 008 Emergency Spillway As-Built Report. Certified <br />as-built drawings for each phase are included as Exhibits 7-17A and 7-17C, <br />Sediment Pond 008 As-Built. <br />During the April 2005 inspection following snow and ice melt, Seneca Coal <br />Company {SCC) representatives noted that the "existing" principal spillway <br />was no longer functioning as designed and constructed. The 24-inch CMP <br />riser pipe had significantly deteriorated below the 6-inch inlet orifice <br />and was not retaining the design volume of water. SCC submitted a <br />technical revision (TR-39) which presented the design and replacement plan <br />for a new principal spillway pipe in June 2005. <br />The replacement principal spillway construction was initiated and completed <br />during August 2D05. The new principal spillway is an 8-inch diameter <br />plastic corrugated straight pipe set at an invert elevation o£ 7,015.3 <br />feet. A screened cage is fitted to the inflow end to prevent trash and <br />debris clogging the spillway pipe. <br />The redesign did not affect or include the pond embankment configuration <br />(except to abandon the old pipe and install the new pipe) or the existing <br />emergency spillway channel. The existing 24-inch CMP straight pipe was <br />abandoned as follows: the pipe was uncovered for approximately 15 feet at <br />the downstream end; the exposed pipe was crimped; concrete was pumped into <br />the straight pipe until the barrel through the embankment was filled; and, <br />the exposed pipe was back£illed at both the downstream end and the riser. <br />TR-37 1 Revised 10/OS <br />