2009-05-22_PERMIT FILE - C1981044A (6)

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service at a given time. The total retention time is six (6) hours. Operating experience and testing by Nalco indicates this to be a conservative design. A retention time of approximately twenty minutes is adequate for settling. The ponds are designed to adequately retain and settle suspended solids for a maximum inflow of 2,500 gpm. It has been estimated that the total combine pumping requirements from the No. 5 and No. 6 Mines will be 1300 - 1800 gpm. To date, this volume of water has not been encountered in this mine. Therefore, the ponds are designed to handle all mine water from both the No. 5 and the No. 6 Mines. In addition to the conservative design of the ponds, each pond has two (2) internal baffles. The purpose of the baffles, which are constructed of snow fence, is to broaden the flow through the pond. The baffles have been constructed perpendicular to the direction of flow. The baffles increase the settling efficiency of each pond by providing a barrier to the total transport of the suspended solids. The general flow through the system is as follows: mine water enters on the eastern end of the system, water flows in a westerly direction through the first pond (P5) , water enters a pipe on the western end of pond (P5) and enters the eastern end of the second pond (P6) (in this description, ponds P5 and P6 are the two functional ponds), water then flows in an easterly direction towards the discharge pipe. Both the inter-pond linkage and the discharge pipe are six (6) feet above the pond bottom. The manipulation of the valves on the inlet, outlets, and inter-pond linkage will allow the water to be directed and discharged from any pond at any time. The general flow schematic for the pond system is presented on Figure 53, Pond Flow Schematic. The general pond system designed is shown on Figure 54, Settling Ponds - Plan View. Presented on Figure 55, Pond Cross-Section A-A' and Figure 56, Pond Cross-Section B-B', are north-south and east-west pond cross-sections. The location of these section lines can be found on the Drainage and Sediment Control Map (Map 26). In order to prevent water from seeping out of the ponds, they have been lined with bentonite. The bentonite was applied to the pond bottom and embankments and mixed in the surface soil layer. The heterogeneous mass of • bentonite and soil was wetted and then rolled to form a good seal. The embankments are sloped at 3H:1 V and should not present any operational problems. Each of the ponds has a dewatering device located in its bottom. Once a pond is filled with settled solids, it will be taken out of service and solids removed. The water that is drained from the pond will flow into a sump and then pumped from the sump into the first functioning pond of the system. This will prevent any discharge of water, high in suspended solids, into the Williams Fork River. Two ramps as shown on Map 27, will be installed up the embankments of the ponds to provide access for sediment cleaning equipment. A contractor will be utilized in the maintenance operation. The solids will be hauled to the waste disposal site or placed into an approved landfill. However, the material may be subjected to soil and overburden testing, and depending on the test results, the material may be used as a plant growth media. It is understood by RAG EC that the DMG and OSM must approve this alternate use of material before the material is used as a plant growth media. A discharge ditch has been constructed to allow water discharged from the ponds to enter the Williams Fork River. All discharge is in compliance with the terms of the NPDES Permit. In order to supply additional water to the mine for dust suppression, longwall emulsion, and other mining related uses, RAG EC proposed to use water from the #5 Mine Discharge Well. To accomplish this, approximately 400' of 4" pipe was installed between pond 5P-6 and the waterline that comes up from the Wise Hill #4 Well. The waterline was buried 5' to 6' deep, and extended south approximately 275' (from the west end of pond 5P-6) and, from there, west approximately 125'. A transformer will sit on the west bank of pond 5-P6 or on a pole adjacent to the pond. The pump will be put in a small pump house adjacent to the transformer to supply water. There is a small area exemption for the pump house disturbance (see Exhibit 18, page 373). After the line was buried, the disturbed area (2' x 350' _ 700 ft2) was seeded with pastureland seed mix. The remaining 100' is part of the haul road and railroad so no seeding was required. Permit Renewal RN08-05 2.05-13 01/15/09