Except for impoundments with concrete walls that are approved in the permit, the inside slopes of an impoundment shall be designed, constructed, operated and maintained as follows:
25 Pa. Code § 289.272
This section cited in 25 Pa. Code § 287.114 (relating to interim operational requirements for unpermitted processing or disposal facilities); 25 Pa. Code § 287.115 (relating to filing by permitted facilities); 25 Pa. Code § 287.116 (relating to interim operational requirements); 25 Pa. Code § 289.161 (relating to impoundment plan); and 25 Pa. Code § 299.144 (relating to operating requirements).