Md. Code Regs. 26.04.07.21

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

Section 26.04.07.21 - Sanitary Landfill - Closure

A. General. A landfill whose design capacity has been exhausted or which has been ordered by the Department to cease accepting wastes and to initiate closure activities after the effective date of this regulation shall close the landfill in accordance with the provisions of this regulation.

B. Closure Cap. The closure cap shall be designed to minimize infiltration into the landfill and shall be developed through an engineering analysis of the site. The closure cap may be constructed of natural materials found either on the site or imported from an off-site location. Elements of the closure cap may also be constructed of a synthetic or manufactured membrane material.

C. Closure Schedule. Unless the Department approves an alternate schedule for closure of a landfill, closure activities shall begin not later than 24 months from the date of completion of the final lift of the landfill, and shall be completed not later than 36 months from the date of completion of the final lift of the landfill.

D. Alternatives. The Department shall consider alternative proposals for landfill closure based upon an engineering analysis of the site. Proposals may involve surcharging the final cover to induce settlement, liquid addition, or other techniques intended to better stabilize the site before installation of the landfill cap.

E. Municipal Landfills. Municipal landfills shall install a closure cap which includes the following minimum design features:

(1) A low permeability cap shall be emplaced over the final cover. The cap material may consist of synthetic material with a minimum thickness of 20 mil and a maximum permeability of 1 x 10^-10th 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^-5th centimeters/second. The cap shall be installed with a minimum slope of 4 percent to facilitate drainage of percolate.

(2) 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^-3rd centimeters/second. 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.

(3) Final earthen cover shall be placed over the drainage layer. Minimum cover thickness shall be 2 feet. 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.

(4) 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 recommended by the county soil conservation district. Sufficient lime and commercial fertilizer, or sewage sludge as authorized by a permit issued under COMAR 26.04.06, shall be applied to the site to sustain vegetative growth. If the final cover is installed at a time which precludes seeding, the site shall be tacked and mulched in accordance with accepted sediment and erosion control specifications until the next available seeding window, at which time the site shall be vegetatively stabilized.

(5) Gas Venting. The closure cap on the municipal landfill shall include provision for venting of any gases which may form during the landfill stabilization process. Gas shall be vented to the atmosphere or collected for flaring or reuse. The concentration of methane (CH₄) may not exceed:

(a) 25 percent of the lower explosive limit for the gases in facility structures, excluding gas control or recovery system components; and

(b) The lower explosive limit for the gases at the property boundary.

F. Land Clearing Debris Landfills. Land clearing debris landfills as specified in Regulation .11 of this chapter, shall satisfy the following closure cap requirements:

(1) Final earthen cover as specified in §E(3) of this regulation; and

(2) Vegetative stabilization as specified in §E(4) of this regulation.

G. Rubble Landfills. Rubble landfills as specified in Regulation .13 of this chapter, shall satisfy the following closure cap requirements:

(1) A low permeability cap as specified in §E(1) of this regulation;

(2) A drainage layer as specified in §E(2) of this regulation;

(3) Final earthen cover as specified in §E(3) of this regulation; and

(4) Vegetative stabilization as specified in §E(4) of this regulation.

H. Industrial Waste Landfills. Industrial waste landfills as specified in Regulation .19 of this chapter, shall satisfy the following closure cap requirements:

(1) A low permeability cap as specified in §E(1) of this regulation;

(2) A drainage layer as specified in §E(2) of this regulation;

(3) Final earthen cover as specified in §E(3) of this regulation; and

(4) Vegetative stabilization as specified in §E(4) of this regulation.

Md. Code Regs. 26.04.07.21

Regulations .21, Solid Waste Management, adopted effective March 7, 1988 (15:5 Md. R. 618)