PERFORMANCE STANDARDS
§ 89.111. Large impoundments.
(a) Large impoundments are those where:
(1) The structures are located on a water course, and one of the following applies:
(i) The contributory drainage area exceeds 100 acres.
(ii) The greatest depth of water at maximum storage elevation exceeds 15 feet.
(iii) The impounding capacity at maximum storage elevation exceeds 50 acre-feet.
(2) The structures are not located on a watercourse and have no contributory drainage, but the greatest depth of water at maximum storage elevation exceeds 15 feet and the impounding capacity at maximum storage elevation exceeds 50 acre feet.
(b) Large impoundments shall be designed, constructed and maintained in accordance with the Dam Safety and Encroachment Act (32 P. S. § § 693.1—693.27) and Chapter 105 (relating to dam safety and waterway management).
(c) If the embankment is more than 20 feet in height as measured from the upstream toe of the embankment to the crest of the emergency spillway, or has a storage volume of 20 acre feet or more, is located where failure could cause loss of life or serious property damage or otherwise poses a hazard to miners or the public, it must:
(1) Be stable under all probable conditions of operation and be designed and constructed to achieve a static safety factor of 1.5, or higher if required by the Department and a seismic safety factor of at least 1.2.
(2) Have an appropriate combination of principal and emergency spillway to discharge safely the runoff from a 100-year, 24-hour precipitation event, or larger if required by the Department.
(3) Have a foundation investigation, as well as any necessary laboratory testing of foundation material to determine the design requirements for foundation stability.
Source The provisions of this § 89.111 adopted December 19, 1980, 10 Pa.B. 4789, effective July 31, 1982, 12 Pa.B. 2382; amended July 30, 1982, 12 Pa.B. 2473, effective July 31, 1982, 12 Pa.B. 2382; amended June 25, 1993, effective June 26, 1993, 23 Pa.B. 3075; amended June 17, 2011, effective June 18, 2011, 41 Pa.B. 3084. Immediately preceding text appears at serial pages (207631) to (207632).
Cross References This section cited in 25 Pa. Code § 89.89 (relating to permanent impoundments); and 25 Pa. Code § 89.101 (relating to general requirements).
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