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drain). If thalweg flows of the inverted triangle are anticipated to be too high, convert the cross <br />section from triangular to trapezoidal. Rules 4.09.1(13) and 4.09.2(2)(a) <br />Rule 4.09.1 (14) The foundation and abutments of the fill shall be stable under all conditions of <br />construction and operation. Sufficient foundation investigation and laboratory testing offoundation <br />materials shall be performed in order to determine the design requirements for stability of the <br />foundation. Analyses of foundation conditions shall include the effect of underground mine <br />workings, if any, upon the stability of the structure. <br />The application is in compliance (one source) with this rule. <br />Rule 4.09.2 Valley Fill. <br />Disposal of excess spoil in valley fills shall meet all the requirements of 4.09.1 and the additional <br />requirements of 4.09.2. <br />Rule 4.09.2(1) The fill shall be designed to attain along-term static safetyfactor of 1.5 based upon <br />data obtained from subsurface exploration, geotechnical testing, foundation design, and accepted <br />engineering analyses. <br />See Rules 4.09.1(7) and 4.09.1(14) above. <br />Rule 4.09.2(2) A subdrainage system for the fill shall be constructed in accordance with the <br />following: <br />Rule 4.09.2(2)(a) Underdrains shall consist ofnon-degradable, non-acid or toxic forming rocksuch <br />as natural sand and gravel, sandstone or limestone. Other durable rock maybe used, if it has been <br />demonstrated not to slake in water or degrade to soil material and will be free of coal, clay and <br />other non-durable material. <br />See Rule 4.09.1(13) above. <br />Rule 4.09.2(2)(6) A system of underdrains shall: <br />Rule 4.09.2(2)(b)(i) Be installed along the natural drainage system; <br />The application is in compliance with this rule. See Figure 5 of Exhibit 21 Item 1. <br />Rule 4.09.2(2)(b)(ii) Extend from the toe to the head of the fill; and <br />The head of hollow is pit backfill. The application is in general compliance with this rule. <br />Rule 4.09.2(2)(6) Contain lateral drains to each area of potential drainage or seepage. <br />The application is in compliance with this rule. See Figure 5 of Exhibit 21 Item 1. <br />6 <br />