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Svstem Descriotion The mine water handling system consists of the following major components: • No. 5 Mine Sump • Boreholes and Overland Pipes • Chemical Treatment System • Settling Ponds • Discharge Ditch All major components of the system are shown on the Structures and Renewable Resources map (Map 25). No. 5 Mine Sump. The No. 5 Mine sump is located in the structurally lowest portion of the No. 5 Mine. All water encountered in the No. 5 Mine is routed to the sump. Boreholes were drilled from the No. 5 Mine to the No. 6 Mine to allow the pumping of water encountered in the No. 6 Mine to the No. 5 Mine Sump. The locations of these holes depend upon water volumes encountered. Boreholes and Overland Pipes. Water from the No. 5 Mine sump is pumped to the surface via two (2) 20 inch boreholes. The boreholes were drilled vertically from the Williams Fork River valley approximately 520 feet to the No. 5 Mine sump. It was anticipated that a chemical treatment system would be needed to treat the mine water discharge but experience has shown [his system is not required. Chemical Treatment System Presently, there is no chemical treatment system but if conditions change, one may be brought into service. • Settling Ponds. A series of three (3) ponds have been constructed on the Williams Fork River floodplain to settle out suspended solids from the raw mine water. Each pond has a capacity of 60,000 cu-ft, which translates into a three (3) hour retention time per pond at design capacity. Based on the system design, only two (2) of the three (3) ponds are in 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 - IS00 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. However, experience has shown that they are not required and they may or may not be retained in a pond. 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 (PS) ,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 PS 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 MidTerm Response (Map 26). ~~2 2.05-11 ~~~~ Revised 12/05/01