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<br />Mr. Steven Self <br />Page 9 <br />February 7, 1980 <br />into pond S!!-Pl, which has a calculated contributing area of 9.53 acres. <br />Although the pond's conservative design may be able to accomodate <br />the discrepancy, calculations should be submitted to account For all <br />of the area (approximately 14 acres) bounded by S!lD1, the road, and <br />the ditch-pond system (SH-D3, S40P2, S(f-D2, SH-P1). <br />b. On the SH-P2 blueprint, there is evidently a typographical error <br />that reverses storage volumes (actual and required). <br />4. Area 9 - previously passed, with the agreement that four questions <br />were to be answered. One of these, the K and LS factors used in the <br />USLE, has been addressed; the following still require clarification. <br />a. Wi11 there be any diversion ditches built to divert overland <br />flow away from ponds 9-PZ, -P2, and P3? If so, location and design <br />information is necessary. <br />If not, explanation of why ditches are not necessary must be <br />included. <br />b. Dewatering provisions and location of principal and emergency <br />spillways for ponds-P9 and PS have been addressed; however, the pipes <br />seem to be located in the middle of the 10-year flood storage. This <br />means that a 10 year event above dead storage would outflow through <br />the emergency spillway - the pipes should be lowered to the top of ~° <br />calculated sediment storage level, or other provisions made. <br />c. There is no sediment control plan for the Eagle b9 rock <br />dust tank. <br />d. The amount and rate of water discharged from the b9 mine <br />should be specified so that a determination can be made as to the <br />adequacy cppond sizing relative to the requirements of 817.50 and <br />817.42(a). This is especially important since ditches 9-07,9-08 <br />9-09 will intercept water from undisturbed areas, according to the <br />current plan. <br />5. Area 9A <br />a. Peak flows for all 9A ponds were based on moderate slopes - <br />3e - 7~, according to the SCS method used - but in the area drained <br />into 9A-Pl,~the contours seem to indicate that most slopes are <br />steeper. This peak flow should be recalculated, and the spillway <br />demonstrated capable of handling it (as well as the ditches). <br />(cont'd) <br />