Section 1817.84  Coal Mine Waste: Impounding Structures

New and existing impounding structures constructed of coal mine waste or intended to impound coal mine waste shall meet the requirements of Section 1817.81.

a)         Coal mine waste shall not be used for construction of impounding structures unless it has been demonstrated to the Department that the stability of such a structure conforms to the requirements of this Part and the use of coal mine waste will not have a detrimental effect on downstream water quality or the environment due to acid seepage through the impounding structure.  The stability of the structure and the potential impact of acid mine seepage through the impounding structure shall be discussed in detail in the design plan submitted to the Department in accordance with 62 Ill. Adm. Code 1780.25.

b)         Construction Requirements

1)         Each impounding structure constructed of coal mine waste or intended to impound coal mine waste shall be designed, constructed and maintained in accordance with Section 1817.49(a) and (c).  Such structures may not be retained permanently as part of the approved post-mining land use.

2)         Each impounding structure constructed of coal mine waste or intended to impound coal mine waste that meets the criteria of 30 CFR 77.216(a) shall have sufficient spillway capacity to safely pass, adequate storage capacity to safely contain, or a combination of storage capacity and spillway capacity to safely control the probable maximum precipitation of a 6-hour precipitation event or greater event as specified by the Department after consideration of factors such as watershed size and characteristics necessary to ensure design in accordance with prudent engineering practices.

c)         Spillways and outlet works shall be designed to provide adequate protection against erosion and corrosion in accordance with Section 1817.47.  Inlets shall be protected against blockage.

d)         Drainage control.  Runoff from areas above the disposal facility or runoff from the surface of the facility that causes instability or erosion of the impounding structure shall be diverted into stabilized diversion channels designed to meet the requirements of Section 1817.43 and designed to safely pass the runoff from a one hundred (100) year, six (6) hour design precipitation event.

e)         Impounding structures constructed of or impounding coal mine waste shall be designed so that at least ninety (90) percent of the water stored during the design precipitation event can be removed within a ten (10) day period.

f)         For an impounding structure constructed of or impounding coal mine waste, at least ninety (90) percent of the water stored during the design precipitation event shall be removed within the 10-day period following the design precipitation event.

(Source:  Amended at 17 Ill. Reg. 11031, effective July 1, 1993)