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• Water Control Measures <br />The subdrainage systems contemplated by Rule 4.09.2(2)(d) are considered to <br />be excessive in size considering there was no water encountered in the test <br />borings performed by Lambert and Associates. Rule 4.10.3(5) allows the DMG <br />to approve an alternative subdrainage system upon a thorough analytical <br />demonstration that such an alternative will ensure the applicable static safety <br />factor, stability of the fill and protection of the surface and groundwater. <br />The purpose of the subdrainage system is to; 1) Intercept all ground water <br />sources; 2) be protected by an adequate filter; and 3) be covered so as to <br />protect against the entrance of surface water or leachate from the coal <br />processing waste. <br />Considering the apparent lack of ground water, the Operator will install an <br />isolated rock drain that is 10-feet wide by 4-feet high. Darcy= Law (Q=Kia) is <br />used to calculate the flow capacity of a 40 square foot rock drain as follows: <br />Q = 45,000 gallons per day where; <br />K = Coefficient of Permeability = 3,000 feet per day for well graded gravel <br />i = gradient or head loss over a given flow distance = 5% minimum <br />a = gross cross-sectional area of soil through which flow takes place = 40SF <br />Clearly a 40 square foot rock drain will handle any anticipated flow rate from <br />ground water sources. The isolated rock drain system will be installed in both <br />Gulch D and the ravine immediately to the west to assure it intercepts all ground <br />water sources. <br />The rock drain will be covered by a geotextile fabric and 12 inches of common fill <br />so as to protect the entrance of leachate from the coal processing waste. Where <br />the rock drain is exposed above the waste disposal area, it shall be temporarily <br />buried with the geotextile fabric and common fill to protect against the entrance <br />of surface water. No more than 10 percent of the rock in the drains will be less <br />than 12 inches in size and no single rock will be larger than 25 percent of the <br />width of the drain. See Figure 2 for the layout of the rock under-drains. <br />• <br />TR-61 -5- 04/09 <br />/?PPRovF.?