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<br />NPDES POND SEDIMENT SURVEY RESULTS <br />Introduction <br />Annual sediment surveys have been performed at the following ponds in both 7985 and 1986. <br />Design information and calculations presented in the August 27, 1986 Seneca II Permit <br />Renewal Application are based on the 7985 pond survey data. <br />Sedimentation Pond 002 <br />Design information and calculations for this pond were submitted in the Seneca II Permit <br />Renewal Application (August 27, 1986) and subsequently approved by CMLRD. Based on the <br />updrainage watershed characteristics, one 10-year, 24-hour precipitation event would <br />generate 5.07 ac-ft of sediment using M.U.S.L.E. <br />With the principal spillway elevation at 6,611.2, the pond can store approximately 267.36 <br />ac-ft, or the equivalent of the sediment generated from approximately fifty-three 10-year, <br />24-hour precipitation events. This indicates that a considerable amount of sediment <br />storage exists for this sedimentation pond and no remedial sediment clean-out work is <br />scheduled for the five-year permit term at this time. <br /> <br />Sedimentation Pond 003 <br />Design information and calculations for this pond were submitted in the Seneca II Permit <br />Renewal Application (August 27, 1966) and subsequently approved by CMLRD. On September 8, <br />1986, Sedimentation Pond 003 was resurveyed as part of Seneca's 1986 annual sediment <br />survey. The survey information was used to develop a computer-generated contour map. <br />This data was then used to ca leulate the remaining sediment storage beneath the principal <br />spillway. The following table shows a comparison of the 1985 and the September 8, 1986 <br />volume calculations. <br />G-3 <br />