2004-08-11_REVISION - M2000156 (2)

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Coulson Excavating Company, Inc. -Bonser Gravel Pit Exhibit E -Reclamation Plan Fines (as measured) and Hydraulic 2.9x10" to 2.9x10 Conductivity Clay Content (20-40%) and Hydraulic 2.9x10 to 5.7x10" Conductivity In the same paper, Benson et al. also correlated plasticity index with clay content. With a plasticity index of 24, clay content can vary between 20-40%. This content is sufficient enough to facilitate a low hydraulic conductivity after compaction. Daniel (1990) recommends a plasticity index of at least 10 for a material to be suitable for lining. In addition, Daniel and Koerner (1993) suggest a minimum of 50% fines for a suitable liner material, and with 95.6% fines, the soil sample material exceeds this criterion. Liner Design/Specifications The liner is to be constructed with weathered Pierre shale from the Bonser pit. The moisture content during construction will be 15% to 18% (1 % dry of optimum or 2% wet of optimum). This moisture content is slightly above the plastic limit, and will allow the soil to remold to a homogenous, low-conductivity material. Liner material will be placed in two 1-foot lifts. A 35,000 Ib Caterpillar 316 sheep's-foot roller will compact each lift of soil. Each foot on the roller measures 12 inches in length. The roller covers 20% of the ground with each pass, requiring four passes over each lift to ensure complete compaction. Full penetration of the sheep's-foot will ensure bonding of the lifts. The native water table surrounding the proposed pit boundaries is approximately 4-9 feet below existing ground surface. The liner will be designed to withstand the hydrostatic pressure exerted against the liner wall due to groundwater, even with the absence of water in the pond. Constructing the liner with the correct thickness and compaction will accomplish this objective. Depression of the surrounding water table will be accomplished through drain the/horizontal pumping and will allow the pond liner to be constructed on a completely dry substrate. This depression of the surrounding water table will continue until the pond has been filled. The liner will be constructed to meet the following specifications: a) The liner soil will contain a minimum of 50 percent material passing the No. 200 sieve on a dry weight basis; b) The liner soil will have a plasticity index between 10 and 35; c) The percentage of gravel, defined as material retained on the No. 4 sieve, will not exceed 10 percent; d) The liner soil will be compacted to a minimum of 95 percent maximum dry density as determined by the Standard Proctor (ASTM D698);