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Water Control Measures <br />The subdrainage systems contemplated by Rule 4.09.2(2)(d) are considered to be <br />excessive in size considering there was no water encountered in the test borings <br />performed by Lambert and Associates. Rule 4.10.3(5) allows the DMG to approve an <br />alternative subdrainage system upon a thorough analytical demonstration that such <br />an alternative will ensure the applicable static safety factor, stability of the fill and <br />protection of the surface and groundwater. <br />The purpose of the subdrainage system is to; 1) Intercept all ground water sources; <br />2) be protected by an adequate filter; and 3) be covered so as to protect against the <br />entrance of surface water or leachate from the coal processing waste. <br />Considering the apparent lack of ground water, the Operator will install an isolated <br />rock drain that is 10 -feet wide by 4 -feet high. Darcy= Law (Q=Kia) is used to <br />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 ground <br />water sources. The isolated rock drain system will be installed in both Gulch D and <br />the ravine immediately to the west to assure it intercepts all ground water sources. <br />The rock drain will be covered by a geotextile fabric and 12 inches of common fill so <br />as to protect the entrance of leachate from the coal processing waste. Where the <br />rock drain is exposed above the waste disposal area, it shall be temporarily buried <br />with the geotextile fabric and common fill to protect against the entrance of surface <br />water. No more than 10 percent of the rock in the drains will be less than 12 inches <br />in size and no single rock will be larger than 25 percent of the width of the drain. See <br />Figure 2 for the layout of the rock under -drains. <br />Lateral drains were constructed as discussed under the Stability Analysis Section in <br />Lambert and Associates report dated November 10, 2003. Lateral drains consist of a <br />toe drain and bench drains as show on Figure 4 of Lambert's report. Bench drains <br />will be constructed on 50 -foot vertical centers or at any damp spots encountered in <br />TR -98 - 9 - 01/15 <br />