2004-08-02_REVISION - M2000158 (3)

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ENVIRONMENT. INC. A UdU8T 2. 2004 PAdE 3 Longhorn Lake has two wells that lie within the lake perimeter that have 2 inch steel feeder lines that will have to pass thru the liner. Envirocon has provided the attached UTILITY PROTECTION AND CROSSINGS guide that explains how they plan to handle cross any gaslines. We believe this will provide the necessary protection for the gaslines. 5. The GEI report was a preliminary report and we will have more detail once the slurry wall design is complete. Initially we believe a ditch will be needed, but once the area south of Sharkey's lake is mined then that lake would absorb the ground- water height and an outlet from that lake would have to be planned to divert the water to the river. I have added the temporary ditch location and design cross section to map Exhibit C-lb. The ditch will divert the water to the west so to carry overflow back to the river. It is a fairly simple design and is intended to keep the ground water elevation along this side, 2 feet below the existing ground surface. The natural drainage along the west side of Bluff Lake will regulate the height of the ground water along the eastern sides of Longhorn and Sharkey's lake since its bottom is 2.5 to 4 feet lower that the top of the slurry wall. Rule 6.4.7 Exhibit G • Water information. 6. The amount of water loss due to evaporation will be reduced by 438 with the lining of the two lakes. The amount used for dust control and lost with the gravel will not be reduced. We still estimate that 15.0 of-ft per year will be needed for dust control, processing and washing activities. The flow rates associated with this use will vary with the dryness of the climate and other uncontrollable variable. The estimated amount of water lost with finished product is 4~ by weight so it is consistent with Office of the State Engineer's (OSE) guidelines and at 238,000 tpy this amounts to 7.0 ac-ft and is included in the 15 ac-ft estimate above. The tables below outlines the differences between the existing plan and the proposed lining of the two lakes. TOTAL LAKE AREA (ACRES) EVAPORATIVE LOSS (AC-FT) OPERATIONAL USES (AC-FT) Pre lining 768.32 2,274.23 15.00 Post lining 437.14 1,293.93 15.00 NET CHANGE -331.18 -980.30 0.00 The average net annual evaporation is calculated to be 2.96 ac-ft/surface acre of unlined lake area. This is for an aver- age year and may be higher or lower depending on actual condi- tion's encounter in the future. PS&G has an approved Well Permit and Temporary Substitute Supply Plan for this mine. Once the liners are complete the water trapped in the reser- voir areas will be pumped to the river. We estimate that 11,000 gpm pumps will be used to removed the trapped water.