Md. Code Regs. 26.20.26.03

Current through Register Vol. 51, No. 19, September 20, 2024

Section 26.20.26.03 - Head-of-Hollow Fills

A. Disposal of spoil in a head-of-hollow fill shall meet all standards set forth in Regulations .01 and .02 of this chapter, and the additional requirements of this regulation.

B. The fill shall be designed to completely fill the disposal site to the approximate elevation of the ridgeline. A rock-core chimney drain may be used instead of the subdrain and surface diversion system required for valley fills. If the crest of the fill is not approximately at the same elevation as the low point of the adjacent ridgeline, the fill shall be designed as specified in valley fills, with diversion of runoff around the fill. A fill associated with contour mining and placed at or near the coal seam, and which does not exceed 250,000 cubic yards may use the rock-core chimney drain.

C. The alternative rock-core chimney drain system shall be designed and incorporated into the construction of head-of-hollow fills as follows:

(1) The fill shall have, along the vertical projection of the main stream channel or rill, a vertical core of durable rock at least 16 feet thick which shall extend from the toe of the fill to the head of the fill, and from the base of the fill to the surface of the fill. A system of lateral rock underdrains shall connect this rock core to each area of potential drainage or seepage in the disposal area. Rocks used in the rock core and underdrains shall meet the requirements of valley fills.

(2) A filter system to ensure the proper functioning of the rock core shall be designed and constructed using standard geotechnical engineering methods.

(3) The grading may drain surface water away from the outslope of the fill and toward the rock core. The maximum slope of the top of the fill shall be 33:1. A drainage pocket may be obtained at the head of the fill during and after construction, to intercept surface runoff and discharge the runoff through or over the rock drain, if stability of the fill is not impaired. This pocket or sump may not have a potential for impounding more than 10,000 cubic feet of water. Terraces on the fill shall be graded with a 3 to 5 percent grade toward the fill and 1 percent slope toward the rock core.

D. The drainage control system shall be capable of passing safely the runoff from a 100-year, 24-hour precipitation event.

Md. Code Regs. 26.20.26.03

Regulations .03 were previously codified as COMAR 08.13.09.32 a A_D, respectively. Recodification occurred in April, 1993. For a history of these regulations before April, 1993, see "Administrative History of COMAR 08.13.09 before April, 1993" which follows COMAR 26.20.01.