| (a) Coal mine waste banks shall be constructed in compliance with §12.531 and §12.532 of this title (relating to Disposal of Underground Development Waste and Excess Spoil: General Requirements, and to Disposal of Underground Development Waste and Excess Spoil: Valley Fills), except to the extent the requirements of those sections are specifically varied in this section. (b) Coal mine waste banks shall have a minimum static factor of safety of 1.5. (c) Compaction requirements during construction or modification of all coal mine waste banks shall meet the requirements of this subsection, instead of those specified in §12.532(d) of this title (relating to Disposal of Underground Development Waste and Excess Spoil: Valley Fills). The coal mine waste shall be: (1) spread in layers no more than 24 inches in thickness; and (2) compacted to attain 90% of the maximum dry density in
order to prevent spontaneous combustion and to provide the strength required for stability of the coal processing waste bank. Dry densities shall be determined in accordance with the American Association of State Highway and Transportation Officials (AASHTO) Specification T99-74 (Twelfth Edition) (July, 1978) or an equivalent method. AASHTO T99-74 is on file and available for inspection at the Commission office, 1701 N. Congress Avenue, Austin, Texas. (d) Following grading of the coal mine waste bank, the site shall be covered with a minimum of 4 feet of the best available non-toxic and non-combustible material, in accordance with §12.505(e) of this title (relating to Topsoil: Removal), and in a manner that does not impede flow from subdrainage systems. The coal mine waste bank shall be revegetated in accordance with §§12.555-12.560 of this title (relating to Revegetation: General Requirements, to Revegetation: Use of Introduced Species, to
Revegetation: Timing, to Revegetation: Mulching and Other Soil Stabilizing Practices, to Revegetation: Grazing, and to Revegetation: Standards for Success). The Commission may allow less than 4 feet of cover material based on physical and chemical analyses which show that the requirements of §§12.555-12.560 of this title (relating to Revegetation: General Requirements, to Revegetation: Use of Introduced Species, to Revegetation: Timing, to Revegetation: Mulching and Other Soil Stabilizing Practices, to Revegetation: Grazing, and to Revegetation: Standards for Success) will be met.
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