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Information submitted in the permit renewal application demonstrates the <br />pond is an efficient sediment control structure although less than <br />24 hours of detention is provided given the principal spillway design. <br />The pond receives inflow from upslope spoils aquifers which have <br />developed in the old Wadge spoils. Surface runoff detained in the pond <br />is considered to dilute the concentrations of total dissolved solids <br />(TDS) in spoils inflow and may serve to improve water quality in <br />general. This pond is in compliance with the requirements of Rule 4.05. <br />and continues to meet National Pollution Discharge Elimination System <br />(NPDES) effluent limitations. Since the pond does not provide at least <br />24 hours detention time, the following finding is in order: <br />Alternative design criteria have been approved for use in sediment pond <br />design and/or construction. This decision is based on a thorough <br />analytical demonstration by a qualified professional engineer that the <br />resulting pond will be as environmentally sound and structurally stable <br />taking into consideration physical, climatological and other <br />characteristics of the site. (4.05.6(11)). <br />A second pond is located in the Grassy Creek basin and serves to control <br />runoff and sediment from the shop and office area. The Northwest <br />Impoundment (NPDES 003) drains an area of 30.5 acres and has a permanent <br />pool of 5.1 acre-feet. This pond also receives discharge from a truck <br />washing facility after the water has been treated. An increase of total <br />dissolved solids on the order of 1500 mg/1 (from 1500 to 3000) was <br />observed between 1983 and 1991 in the effluent from this pond. This <br />increase is attributable to the truck-wash facility. A review of the <br />pond performance indicated a reduction in the size of the principal <br />spillway to a 6 inch orifice was necessary to provide sufficient <br />detention time to increase sedimentation within the pond and produce <br />effluent within NPDES limitations. The orifice was reconstructed in <br />1987. With this revised design, the pond was in compliance with the <br />design standards of Rule 4.05.6 and should continue to meet NPDES permit <br />requirements. <br />Fish Creek <br />Two ponds are situated in separate drainage basins tributary to <br />Fish Creek. One pond, Pond 004, was constructed in 1982 when mining <br />progressed into the Fish Creek basin in the southeast part of the permit <br />area. Pond 004 is located on Cow Camp Creek and drains an area of <br />393 areas. The pond has a permanent pool of 10 acre-feet. <br />A second pond, Pond 008, has been constructed in the Fish Creek drainage <br />basin in a tributary referred to as Bond Creek. Pond 008 drains an area <br />of 247 acres of which 226 acres will be disturbed. The pond is designed <br />to provide storage for a 10 year, 24 hour precipitation event with <br />2.1 acre-feet of runoff and has a capacity of 16.4 acre-feet. <br />The operation is in compliance with the requirements of this section. <br />Ground Water Hydrology <br />Ground water hydrology information can be found in Volumes 4, 5, and 6, <br />Tab 7 of the permit application, and in the Annual Hydrology Reports <br />submitted by Peabody Coal Company. <br />-14- <br />