Section 90.113. Hydrologic balance: coal processing waste dams and embankments

(a) In addition to the requirements of § 90.112 (relating to hydrologic balance: dams, ponds, embankments and impoundments—design, construction and maintenance), each dam and embankment constructed of coal processing waste or intended to impound coal processing waste shall meet the requirement of this section.

(b) Waste may be used in the construction of dams and embankments if it has been demonstrated to, and approved by, the Department that the stability of such a structure conforms with the requirements of this section and the use of the waste material may not have a detrimental effect on downstream water quality or the environment.

(c) The design freeboard between the lowest point on the embankment crest and the maximum water elevation shall be at least 3 feet. The maximum water elevation shall be that determined by the freeboard hydrograph criteria contained in the United States Soil Conservation Service’s Technical Release No. 60, ‘‘Earth Dams and Reservoirs.’’ The standards contained therein are hereby incorporated by reference.

(d) The dam and embankment shall have a minimum safety factor of 1.5 for the partial pool with steady seepage saturation conditions, and the seismic safety factor shall be at least 1.2.

(e) The dam or embankment foundation and abutment shall be designed to be stable under all conditions of construction and operation of the impoundment. Sufficient foundation investigations and laboratory testing shall be performed to determine the safety factors of the dam and embankment for all loading conditions appearing in subsection (d) and for all increments of construction.

(f) Spillways and outlet works shall be designed to provide adequate protection against erosion and corrosion. Inlets shall be protected against blockage.

(g) Dams and embankments constructed of or impounding waste materials shall be designed so that at least 90% of the water stored during the design precipitation event shall be removed within a 10-day period.

(h) Before coal processing waste is placed at a dam or embankment site:

(1) Trees, shrubs, grasses and other organic material shall be cleared and grubbed for a distance of 50 feet from the coal refuse disposal pile, bank or dam within the site, and combustibles shall be removed and stockpiled in accordance with this subchapter.

(2) Surface drainage that may cause erosion to the embankment area or the embankment features, whether during construction or after completion, shall be diverted away from the embankment by diversion ditches that comply with the requirements of § 90.104 and 90.105 (relating to hydrologic balance: diversions; and stream channel diversions). Diversions that are designed to divert drainage from the upstream area away from the impoundment areas shall be designed to carry the peak runoff from a 100-year, 24-hour precipitation event. The diversion shall be maintained to prevent blockage, and the discharge shall be in accordance with § 90.109 (relating to hydrologic balance: discharge structures). Sediment control measures shall be provided at the discharge of each diversion ditch before entry into natural watercourses in accordance with § § 90.105 and 90.108 (relating to stream channel diversions; and hydrologic balance: sedimentation ponds).

(i) Impoundments constructed of coal processing wastes or used to impound coal processing wastes may not be retained permanently as part of the approved postmining land use, unless these structures are developed into fills meeting the construction requirements of § 90.122 (relating to coal refuse disposal).

The provisions of this § 90.113 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 15, 1990, 20 Pa.B. 3383, effective July 27, 1991, 21 Pa.B. 3316; amended December 11, 1992, effective December 12, 1992, 22 Pa.B. 5945; amended December 15, 1995, effective December 16, 1995, 25 Pa.B. 5821. Immediately preceding text appears at serial pages (180941) to (180942).

Notation

Authority

The provisions of this § 90.113 amended under the Surface Mining Conservation and Reclamation Act (52 P. S. § § 1396.1—1396.19a); The Clean Streams Law (35 P. S. § § 691.1—691.1001); and section 1920-A of The Administrative Code of 1929 (71 P. S. § 510-20).

Cross References

This section cited in 25 Pa. Code § 90.39 (relating to ponds, impoundments, banks, dams, embankments, piles and fills); and 25 Pa. Code § 90.130 (relating to coal refuse dams).