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Section 780.21 (b) Continued. <br />• <br />The secondary and final protection method for surface water quality will be <br />the construction and maintenance of properly designed sedimentation ponds <br />and auxiliary features such as spillways, energy dissipating discharge <br />structures, stabilization practices and sideslope protection. <br />The location of all sedimentation ponds is shown on Energy Mines No. 1 and 2 <br />Hydrology (Map 13), Eckman Park Hydrology (Map 14) and Permit Renewal Map 9A <br />Hydrologic FeaturesjSediment Control. These maps also show the locations of <br />watershed boundaries from which, along with other sources, the design <br />criteria were established. Generally, ponds and spillways were sized and <br />placed according to such hydrologic factors as required sediment storage <br />volume, rate of flow and volume of flow for the appropriate storm event. <br />All ponds not within the criteria of 30 CFR 816.43 (q) or 30 CFR 77.216 have <br />been designed with respect to the 10-year, 24-hour precipitation event. Any <br />pond, especially pond A, located in the northeast quarter of Section 7, <br />Township 4 North, Range 86 West, that meets the size or other criteria of 30 <br />• CFR 816.46 (q) or 77.216 has been designed, at a minimum, with respect to <br />the 100-year, 24-hour precipitation event. <br />Pond embankments, slopes, spillways, and construction methods have been <br />designed according to such engineering factors as structural integrity and <br />stability; slope and surface stability; adequacy in height, size, and shape <br />to provide sufficient volume for sediment and detained water; and selection <br />of proper spillways and outlet devices to provide for non-clogging <br />operation, passing of design storm events, and proper outflow rates. All <br />ponds have been designed by one or more registered professional engineers in <br />accordance with the plan set forth under Section 780.25 and in accordance <br />with 30 CFR 816.43 and 816.49. <br />The purpose of the sedimentation ponds is not only to provide a final <br />measure to prevent additional contributions of sediment <br />• <br />89-23 780-157 Revised 02/22/89 <br />