Pennsylvania Code › Title 25 - ENVIRONMENTAL PROTECTION › Part I - Department of Environmental Protection › Subpart C - Protection of Natural Resources › Article I - Land Resources › Chapter 90 - COAL REFUSE DISPOSAL › Subchapter D - PERFORMANCE STANDARD FOR COAL REFUSE DISPOSAL › Section 90.113 - Hydrologic balance: coal processing waste dams and embankments

Current through Register Vol. 54, No. 28, July 13, 2024
(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 Natural Resources 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).