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Plan Map. The sediment fence is designed to safely pass the peak discharge £rom a 10-year, <br />24-hour event. The design demonstration is presented in Appendix 12-2, Small Area Exemption . <br />Demonstrations. Given the limited size of the disturbance area and the demonstration that a <br />sediment fence provides adequate control, HGTI requested, and received CDL~Y, approval to <br />permit this area as a small azea exemption. <br />Office/Parking Lot/Leach Field: There is an office/change building, parking lot, and leach <br />field on the west side of the facilities area as shown on Exhibit 12-2, Surface Water <br />Control Plan Map. Total disturbance associated with the office and parking area is <br />approximately 0.3 acres. The disturbance associated with the existing leach field (0.45 <br />acres) has been successfully revegetated. Runoff from these areas does not drain to the <br />Truck Loop Pond and is controlled using a sediment fence. The location of the sediment fence <br />is shown on Exhibit 12-2, Surface Water Control Plan Map. The sediment fence is designed to <br />safely pass the peak discharge £rom a 10-year, 24-hour event. The design demonstration is <br />presented in Appendix 12-2, Small Area Exemption Demonstrations. Given the limited size of <br />the disturbance area and the demonstration that a sediment fence provides adequate control, <br />HGTI requested, and received CDMG approval to permit this area as a small azea exemption. <br />Railroad Loop: The railroad loop was constructed in 1980. A11 disturbance associated with <br />the construction of the loop has been topsoiled and successfully revegetated. Total <br />reclaimed area associated with the railroad loop is approximately 70.8 acres. The reclaimed <br />area is shown on Exhibit 12-1, Facilities Map. Runoff for a majority of the railroad loop <br />does not drain to either of the sedimentation structures. In order to demonstrate that the <br />railroad loop meets the intention of the CDMG Rule 4.05.2(3), SEDCAD+ analysis was conducted <br />on the entire reclaimed section of the railroad loop. <br />The SEDCAD+ analysis and all associated inputs aze presented in Appendix 12-2, Small Area <br />Exemption Demonstrations. As shown in the analysis, due to the successful revegetation <br />efforts the peak settleable solid concentration is below the water quality effluent standard <br />of 0.5 ml/1. Given these results HGTI requested, and received CDb~ approval to permit this <br />area as a small area exemption. <br />Areas 1 and 2: There are two small areas (Areas 1 and 2) which were disturbed during <br />construction of the loadout area. The location of Areas 1 and 2 are shown on Exhibit 12-2, <br />Surface Water Control Plan Map. After construction of the loadout, the areas were topsoiled <br />and successful revegetated. Total reclaimed area associated witY, the Areas 1 and 2 is <br />approximately 0.6 and 0.4 acres, respectively. Runoff from these areas do not drain to <br />either the Truck Loop Pond or the Rail Loop Pond. In order to demonstrate that the areas <br />meet the intention of the CDMG Rule 4.05.2(3), SEDCAD+ analyses were conducted on both <br />reclaimed sections. <br />TR-06 9 Revised OS/OS <br />