1. (1) On slopes less than or equal to 10 percent, the liner system must consist of a double composite liner system which meets the following requirements:

   1. (i) the primary composite liner must be comprised of a nominal 60 mil or thicker high density polyethylene (HDPE) geomembrane placed above and in direct and uniform contact with an appropriately specified GCL. In landfills located within the deep recharge area of Nassau or Suffolk county, the primary geomembrane must be a nominal 80 mil or thicker HDPE geomembrane; and
   2. (ii) the secondary composite liner must be comprised of a nominal 60 mil or thicker HDPE geomembrane placed above and in direct and uniform contact with a minimum two-foot-thick low-permeability soil layer that has a remolded hydraulic conductivity of 1x10^-7 centimeter per second or less.

2. (2) On slopes greater than 10 percent, the liner system must consist of a double liner system which meets the following requirements:

   1. (i) from the toe of the slope to five vertical feet up the side slope, the primary liner must meet the double composite liner requirements of subparagraph (1)(i) of this subdivision. Above five vertical feet up the side slope, the primary liner may be constructed of a nominal 60 mil HDPE or thicker geomembrane. For landfills located within the deep recharge area of Nassau or Suffolk county, the primary geomembrane must be a nominal 80 mil or thicker HDPE geomembrane; and
   2. (ii) the secondary composite liner must meet the requirements of subparagraph (1)(ii) of this subdivision.

3. (3) The liner system must include a primary leachate collection and removal system that is designed to maintain no more than 12 inches of leachate depth (head) above the primary liner, except during 24-hour, 25-year storm events and except in sump areas. The leachate collection and removal system must be designed to function with proper maintenance throughout the active life, post-closure period, and custodial care period of the landfill.

   1. (i) The primary leachate collection and removal system must be a minimum of two feet thick.
   2. (ii) On slopes less than or equal to 10 percent, the 24 inches of primary leachate collection and removal system must have a hydraulic conductivity of 1.0 centimeter per second or greater. Alternatively, the upper 12 inches of primary leachate collection and removal system may have a hydraulic conductivity of 0.1 centimeter per second or greater if the lower 12 inches has a hydraulic conductivity of 1 centimeter per second or greater.
   3. (iii) On slopes greater than 10 percent, the entire 24 inch thickness of the primary leachate collection and removal system must have a hydraulic conductivity of 0.1 centimeter per second or greater.

4. (4) The liner system must include a secondary leachate collection and removal system placed between the primary and secondary liners with a design capacity of at least 1,000 gallons per acre per day and a maximum detection time of 24 hours using steady state flow calculations in a saturated medium.

   1. (i) On slopes less than or equal to 10 percent, the secondary leachate collection and removal system must include a geosynthetic drainage layer and a minimum of 1 foot of soil drainage media with a hydraulic conductivity of 0.1 centimeter per second or greater, and a maximum leachate depth (head) of 1 inch.

   2. (ii) On all slopes greater than 10 percent, the secondary leachate collection system may be constructed of a geosynthetic drainage layer system designed to meet the hydraulic and mechanical needs of the landfill with a head that does not exceed the thickness of the confined drainage layer.

      (b) C&D debris landfills, papermill sludge monofills, and municipal waste combustor ash monofills.

      Except in Nassau or Suffolk county, the minimum liner requirement for landfills used for the disposal of C&D debris, papermill sludge, or municipal waste combustor ash is a single composite liner comprised of a nominal 60 mil or thicker HDPE geomembrane placed above and in direct and uniform contact with a minimum two-foot-thick low permeability soil layer that has a remolded hydraulic conductivity of 1x10^-7 centimeter per second or less.

      Above the composite liner, a leachate collection and removal system is required that meets the requirements of paragraph (a)(3) of this section. The department may require additional liner components or other restrictions depending upon the waste to be disposed, monitorability of the site, or other site conditions.

      (c) Other industrial waste monofills.

      Except in Nassau or Suffolk county, monofills used solely for the disposal of solid waste resulting from industrial operations other than those described above are subject to the double composite liner requirements described in subdivision (a) of this section and section 363-6.7 of this Subpart, unless the applicant demonstrates that an alternative liner system is justified. The department may impose additional or less stringent requirements on these monofills based on the pollution potential of the waste. For those monofills where the applicant demonstrates that an alternative liner system is justified, the need for a formal variance is waived.

5. (1) Liner system designs for industrial waste monofills that do not meet the requirements of this section and section 363-6.7 of this Subpart must be demonstrated to adequately prevent a negative impact on groundwater quality. The demonstration must, at a minimum, address the following factors:

   1. (i) climatological conditions in the vicinity of the proposed site;
   2. (ii) hydrogeologic characteristics of the proposed site;
   3. (iii) anticipated liner system leakage to the subsurface;
   4. (iv) development of an accurate profile of leachate quality and production rates sufficient to be used in evaluating the fate and transport of leachate from the point of release to the first point of environmental monitoring in order to determine whether leachate constituents can be expected to exceed the State's groundwater quality standards;
   5. (v) justification that the industrial wastes' chemical characterization was accurately defined and that there are no reasons to anticipate significant changes in the concentrations of compounds that could increase the wastes' pollution potential in the future;
   6. (vi) presentation of data from chemical compatibility tests performed on the proposed liner and/or leachate collection and removal system materials with representative waste leachate, using an appropriate permeameter test to determine potential changes in the permeability of the proposed liner; and
   7. (vii) modeling of contaminant transport to evaluate the impacts of the characterized leachate on groundwater quality at the closest environmental monitoring point based upon the liner system's calculated leakage rate and the site’s hydrogeologic conditions.

6. (2) A new demonstration must be performed in accordance with paragraph (1) of this subdivision whenever the characteristics of the received waste change.

   (d) Final cover system.

   Except as otherwise described in this Part, all landfills must have at a minimum a final cover system that consists of a composite barrier layer, barrier protection and drainage layer, and topsoil layer meeting the requirements of sections 363-6.15 through 363-6.18 of this Subpart and Subpart 363-10 of this Part. The final cover system must be designed to preclude precipitation from entering the landfill and be capable of preventing landfill gas migration to the atmosphere.

(a) Double composite liner system.

Except as otherwise described in this Part for monofills and C&D debris landfills, all landfills regulated under this Part must have a double composite liner system that consists of a primary leachate collection and removal system, a geocushion, a primary composite liner constructed of a geomembrane liner and a GCL, a secondary leachate collection and removal system, a geocushion, and a secondary composite liner system constructed of a geomembrane liner and two feet of low permeability soil. The landfill must be designed and constructed to meet or exceed the following liner system requirements: