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Ms. Anne Baldrige <br />Page 2 <br />November S, 1985 <br />the pond bottom. At the same time, the instrument man, setting on a survey control <br />point station, turned an angle and shot the distances to the grid points. Vertical eleva- <br />tion of the bottom was calculated by subtracting the sounding measurements from the <br />water elevation. As stated earlier, these methods will be used in future monitoring <br />surveys. <br />Abatement step 2 requires PCC to "implement (a) pond clean-out schedule for 603'0 <br />sediment level". Based on the results of the sediment pond survey, which included resur- <br />veying of the various pond structures, the following information for present sediment <br />levels, sediment storage capacities, and estimated clean-out levels and years of remain- <br />ing storage (calculated at 60% of storage capacity)is provided. <br />Pond 002 (Wadge Impoundment) calculations are summarized as follows: <br />As-built sediment pond storage <br />volume including water and sediment <br />(based on June 1980 survey) <br />303.6 ac: ft. <br />Calculated annual sedimentation rate )~ y`. - =~ hr• 10.2 ac.-ft./yr. <br />using the Universal Soil Loss Equation (USLE) <br />o- S~or m <br />Estimated sediment volume deposited 54.4 ac: ft. <br />since June 1980 survey (10.2 ac.-ft./yr. x 5.33 yr) <br />Present remaining sediment capacity 249.2 ac.-ft. <br />As shown above, there remains 249.2 ac.-ft. of storage in pond 002 at this time. Using <br />60% of the available storage volume, sediment should be cleaned out when the volume of <br />sediment reaches 182.2 ac: ft. (303.6 ac.-ft. x 0.60). Considerinq the present sediment <br />volume in the pond of 54.4 ac: ft., there remains 127.8 ac: ft. of storage. At an annual <br />sedimentation rate of 10.2 ac.-ft./yr., pond 002 should be cleaned out in 12.5 years (127.8 <br />ac: ft./10.2 ac: ft./yr. = 12.5 yr.). o xa,,,,=r~ <br />r) ~o~ <br />Pond 003 (Shop Area Pond) calculations are as follows: <br />As-built sediment pond storage volume 8.14 ac.-ft. ~ ~ ~ ~ <br />including water and sediment (as corrected by o-~,~~~1 3.3 <br />1985 survey, see discussion below) ~~^`~Q ya <br />e <br />Present remaining pond storage volume considering 5.13 ac.-ft. <br />present sediment levels (from 1985 sediment survey) <br />Present estimated volume of sediment 3.01 ac.-ft. <br />(corrected as-built volume minus remaining <br />surveyed volume) <br />USLE estimoted annual rate of sediment yield 2.13 ac: ft. <br />~I.O <br />3. 3 9 <br />7.6~ <br />3.o I <br />4.X <br />