2004-08-02_REVISION - M2000158 (3)

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ENVIRONMENT, INC. au~usr z, zooa Rule 6.4.4-Exhibit D - Mining Plan PAGE 2 3. So noted. As the mine develops, minor changes due to irregu- larities in the land, and how an area has developed would be noted in the annual report. PS&G realizes, that if additional lakes are lined the change may need to be addressed as an amendment to the permit prior to lining new areas. 4. The construction of the liners covered in this amendment should be looked at as a two phased plan, the first is to design, install the liner and excavated the material from Longhorn Lake. The second will be do the samething for Sharkey's Lake. Attached is an excerpt titled WORK PLAN NARRATIVE prepared by Envirocon explaining what steps will be taken to design the liner around Longhorn Lake. The liner around Sharkey's Lake will take place at a later date but the same methodology will be used. The table below addresses the dimensional information on each reservoir area. The following information is common to each liner. Asoil-bentonite backfilled slurry wall will be in- stalled around the reservoir perimeter. The exact composition of the mix will be designed from data collected by the design engineers so it is site specific. A track-hoe is used to excavate a narrow trench (36 inches wide) that will be backfilled with a dry 10-' bentonite-soil mixture. During excavations the walls will be supported by filling the exca- vated trench with a 38 bentonite/water mix. This slurry acts as a bulkhead to keep the trench wall from sloughing until it can be backfilled. It also hydrates the dry mix as it is placed. In this project it is estimated that approximately I50 feet of wall will be constructed a day. Backfilling begins as soon as the excavator has removed enough material (30 to 50 feet) of trench so that the backfill will not over- lap the excavation. At the end of the day approximately 25 feet of trench will be unfilled. This is so that when excava- tion begins the next day, the operator is not digging into filled area. As the dry material is pushed into the trench the fill creates a slope to the bottom, so that if filling gets to close to the excavation it will pile up against the face being excavated. Dimension Longhorn Sharkey's Lake Lake LENGTH OF WALL (FT) 9,860.00 10,270.00 AVERAGE DEPTH OF WALL 2H.O0 33.00 INCLUDING KEY WAY (FT) While the liner around Longhorn Lake will be one continuous trench, the Sharkey's Lake liner will be around the west, south and east sides and will need to be tied at two points with the Longhorn liner. Envirocon has said that to tie.the two walls together one simply excavates into the existing wall approxi- mately half way and then begin installation of the new wall. This will create a seal between join the two walls completing the enclosure.