Md. Code Regs. 26.21.04.08

Current through Register Vol. 51, No. 22, November 1, 2024

Section 26.21.04.08 - Closure

A. Minimum Design Features.

(1) As each section of the mine reclamation using coal combustion byproducts is completed, the section shall be closed using the minimum design features specified in this regulation, unless otherwise approved by the Department.

(2) Low Permeability Layer. A low permeability cap shall be emplaced over the filled area. The cap material shall consist of synthetic material with a minimum thickness of 20 mil and a maximum permeability of 1 x 10^-10 centimeters/second, or a minimum of 1 foot of clay or other natural fine-grained material having an in-place permeability less than or equal to 1 x 10^-7 centimeters/second. The cap shall be installed with a minimum slope of 4 percent to facilitate drainage of percolate. The cap shall be placed on a bedding that is free of rocks, roots, and other injurious materials.

(3) Drainage Layer. A drainage layer with a minimum thickness of 6 inches shall be emplaced immediately above the low permeability cap. Acceptable drainage layer material shall include clean sand or other natural coarse grained material with an in-place permeability greater than 1 x 10^-3 centimeters/second adequate to remove water from above the low permeability layer sufficiently quickly that the overlying protective layers remain stable. The drainage layer shall be free of materials which may puncture or otherwise jeopardize the integrity of the low permeability cap. Commercially available filter fabrics, when used in conjunction with synthetic drainage blankets, may serve instead of the fine material, provided that the Department reviews and approves the selected materials and design configuration.

(4) Soil Cover. A final earthen cover shall be placed over the drainage layer. The minimum cover thickness shall be 2 feet. The minimum cover slope shall be 4 percent to facilitate surface drainage from the site. The cover material shall contain sufficient organic material and nutrients to sustain a vegetative cover over time. Topsoil, or topsoil created using sewage sludge, and less select soils as authorized by COMAR 26.04.06, shall constitute acceptable final cover.

(5) Vegetative Stabilization. Within 30 days after the final earthen cover has been installed, the area shall be vegetatively stabilized using a perennial cover species as specified in the mining and reclamation plan.

B. Based on site conditions, the size and design of the project, and other considerations as determined by the Department, the Department may require other closure requirements it considers necessary to protect public health and the environment.

Md. Code Regs. 26.21.04.08