West Virginia Code of State Rules › Agency 38 - Mining And Reclamation › Title 38 - LEGISLATIVE RULE DEPARTMENT OF ENVIRONMENTAL PROTECTION MINING AND RECLAMATION › Series 38-04 - Rules For Quarrying And Reclamation › Section 38-4-8 - Subsidence Evaluation

Current through Register Vol. XLI, No. 28, July 12, 2024
8.1. A
				subsidence evaluation of the site and the dam and its storage area will be
				required considering past and proposed mining. No dams shall be constructed
				over underground workings or other voids unless those underground workings or
				other voids have been stabilized or it has been demonstrated that the coal
				pillars, roofs and floor are strong enough to withstand the superincumbent
				weight of the strata above the workings or are otherwise capable of preventing
				significant subsidence impacts in accordance with 8.2 and 8.3 of this
				rule.
8.2. No plan shall be
				approved unless there is a minimum safe cover to be determined by the
				Secretary, based on test holes drilled by the applicant in a manner to be
				prescribed by the Secretary. Such permits shall require in accordance with a
				plan to be approved by the Secretary, a safety zone be established beneath and
				adjacent to the impoundment storage area.
8.2.a. Basin. There shall be no underground
				mining in a safety zone that extends horizontally 200 feet from the high water
				mark of an impoundment and vertically to a depth that provides for a minimum
				thickness of 100 feet of solid strata between the bottom of the pool and any
				mining. The presence of any mine workings within this safety zone is prohibited
				unless the potential subsidence effects are mitigated by injection grouting or
				otherwise filling the mine related voids completely. Alternately, such risk can
				be mitigated by providing a combination of constructed barriers and grouting to
				establish equivalent distances that will comply with the safety zone
				dimensions. Coal extraction of 80 percent or more is prohibited unless at a
				depth greater than 60 times the coal extraction thickness or at a depth where
				the maximum tensile strain at original ground is less than 5.0 mm/m (0.5%),
				whichever is greater. The Secretary may impose other limitations as specified
				by BM IC 8741, barrier analysis, other pertinent analysis or due to conditions
				such as fracturing, which may require a larger safety zone or further
				limitations in coal extraction.
8.2.b. Embankment. There shall be no mining
				in a safety zone under the structural embankment measured outward 200 feet in
				all directions, downward 350 feet and then outward at a dip of 650 from the
				horizontal, unless acceptable pillar stability and/or strain effects are
				confirmed by a design evaluation to be certified by an RPE. Also, the related
				AHCF must clearly demonstrate that the facility will have a low risk of impact
				to the public and the environment. Existing mine workings within this safety
				zone having the potential to cause significant subsidence impacts are
				prohibited unless those effects are mitigated by grouting, filling the mine
				related voids or providing comparable protection. Additional underground mining
				may be subsequently approved in the embankment safety zone only if a design
				evaluation, certified by an RPE, demonstrates that no significant impacts from
				subsidence can result.
8.2.c.
				Existing Impoundments. Existing impoundments that currently have mining within
				the safety zones must be evaluated in accordance with this section and 3.4.c.
				of this rule. Remedial measures shall be implemented as necessary to eliminate
				or reduce the potentialimpact on the public and/or the environment. Remedial
				measures may include, but are not limited to, constructed barriers, grouting of
				underground works and back stowing of mines.