Code of Maryland Regulations › Title 26 - DEPARTMENT OF ENVIRONMENT › Part 1 - SUBTITLES 01-07 › Subtitle 04 - REGULATION OF WATER SUPPLY, SEWAGE DISPOSAL, AND SOLID WASTE › Chapter 26.04.07 - Solid Waste Management › Section 26.04.07.21 - Sanitary Landfill - Closure

Current through Register Vol. 51, No. 14, July 12, 2024
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.