Laserfiche WebLink
the NPDES permit also dictate preventative and mitigation measures for ensuring <br />that all water leaving the mine site meets applicable effluent limits. <br />Disturbed areas, as defined by Rule 1.04(36), are delineated on permit area map <br />Exhibit 12-2. Disturbed areas drain into approved sedimentation ponds, with the <br />exception of certain haul road and access road segments that are located outside <br />approved sedimentation pond collection areas, as allowed by Rule 4.03, and with the <br />further exception of certain small area exemption locations as discussed in the <br />following paragraph. <br />The Division has granted a small area exemption from use of sediment ponds due to <br />the limited size of the area and due to the fact that ponds and treatment facilities are <br />not necessary for the drainage to meet the effluent limitations of Rule 4.05.2 and <br />applicable State and Federal water quality standards for receiving streams, and also <br />due to the fact that no mixing of surface drainage with a discharge from underground <br />workings will occur. The small areas to be exempted are the topsoil stockpiles listed <br />on Table 13-8-1 and shown on Exhibits 13-2 and 13-3. (4.05.2(3)(b)(i)). <br />B. Diversions and Conveyance of Overland Flow <br />All major drainages disturbed by mining were to be reclaimed to approximate the <br />pre -mining configuration and to blend with the undisturbed drainage above and <br />below the area to be reclaimed. The Division has verified compliance with this <br />requirement for all drainages reestablished within the original permit boundary, as <br />discussed in the findings document issued with the approval of SL -2. Table 20-2 <br />provides the pre -and post -mine drainage channel summary. The reclaimed drainages <br />are located on Exhibit 20-2. <br />The average post -mining stream gradients were to have concave longitudinal profiles <br />which approximate the pre -mining slopes. The pre -mining and post -mining drainage <br />areas of the reclaimed channels are similar in acreage and slope. After the watershed <br />was graded and the location of the drainage channels determined, the channels were <br />to be constructed to the required shape. Permanent channel construction including <br />riprap installation (where specified) was completed within one year of completion <br />of the final grading of adjacent backfill slopes, and prior to topsoiling of areas <br />adjacent to the channel. Following construction, the channels left untopsoiled to <br />allow for initial stabilization and inspected for stability according to the rill and gully <br />plan in Tab 22. When the channels stabilized, the non-riprapped segments were <br />topsoiled and vegetated. <br />SP has permitted permanent and temporary stock pond impoundments in both the <br />reclaimed drainage channels at the Seneca II -W Mine and some existing culvert <br />outlets. The stock ponds will slow the peak runoff of precipitation events and help <br />to minimize erosion in the drainage channels. They will also act as additional <br />alternate sediment control measures, minimizing the potential for sediment from <br />roads to be carried off the permit site. These small ponds will benefit both livestock <br />C.l <br />