S.C. Code Regs. § § 61-107.19.V.D.258.40

Current through Register Vol. 48, 12, December 27, 2024

Section 61-107.19.V.D.258.40 - Design Criteria

a. Class Three landfills shall be constructed:

(1) In accordance with a design approved by the Department. The design shall ensure that the maximum contaminant level (MCL) as specified in the South Carolina State Primary Drinking Water Standards, R.61-68 will not be exceeded in the uppermost aquifer at the relevant point of compliance, as specified by the Department in Section258.40.i. below; or,

(2) With a composite liner, as defined in Item b. below of this section and a leachate collection system that is designed and constructed to maintain less than a one (1) foot depth of leachate over the liner, except in sumps.

(3) Monofills that accept coal combustion byproducts that test greater than ten (>10) times the maximum contaminant level (MCL), may be constructed with a clay liner system consisting of a minimum of a two (2) foot layer of compacted soil with a hydraulic conductivity of no more than 1 x 10-7 cm/sec, and an appropriate leachate collection system. These facilities shall comply with all other requirements for a Class III landfill.

b. Liner. A composite liner system shall consist of two components: the upper component shall consist of a minimum 30-mil flexible membrane liner (FML); and, the lower component shall consist of at least a two foot layer of compacted soil with a hydraulic conductivity of no more than 1 x 10-7 cm/sec. FML components consisting of High Density Polyethylene (HDPE) shall be at least 60-mil thick. The FML component shall be installed in direct and uniform contact with the compacted soil component.

c. The leachate collection and removal system shall be designed and built to operate without clogging during the operational life of the site and post-closure maintenance period. The system shall be designed to allow for routine maintenance and cleaning of the system.

d. Filter layers shall be designed to prevent the migration of fine soil particles into a coarser grained material, and allow water or gases to freely enter a drainage medium (pipe or drainage blanket) without clogging.

e. The total thickness of the drainage and protective layers above the liner material shall be a minimum of two feet thick, and shall be composed of material with a minimum hydraulic conductivity of 1 x 10-4 cm/sec.

f. All material used in the leachate collection and removal system of the landfill shall be designed to ensure that the hydraulic leachate head on the liner system does not exceed one foot as a result of a 24-hour, 25-year storm event during the active life and post-closure care period of the landfill.

g. A foundation analysis shall be performed to determine the structural integrity of the subgrade to support the horizontal and vertical stresses and overlying facility components.

(1) The constructed landfill subgrade material shall consist of on-site soils or select fill with minimal organic material, as approved by the Department.

(2) The landfill subgrade shall be graded in accordance with the requirements of the approved engineering plans, reports and specifications. The material shall be sufficiently dry and structurally sound to ensure that the first lift and all succeeding lifts of soil placed over the landfill subgrade can adequately be compacted to the design requirements.

h. When approving a design that complies with the requirements of this Part, the Department shall consider at least the following factors:

(1) The hydrogeologic characteristics of the facility and surrounding land;

(2) The climatic factors of the area; and,

(3) The volume and physical and chemical characteristics of the leachate.

i. The relevant point of compliance specified by the Department shall be no more than 150 feet from the waste management unit boundary and shall be located on land owned by the owner of the Class Three landfill. In determining the relevant point of compliance, the Department shall consider at least the following factors:

(1) The hydrogeologic characteristics of the facility and surrounding land;

(2) The volume and physical and chemical characteristics of the leachate;

(3) The quantity, quality, and direction of flow of groundwater;

(4) The proximity and withdrawal rate of the groundwater users;

(5) The availability of alternative drinking water supplies;

(6) The existing quality of the groundwater, including other sources of contamination and their cumulative impacts on the groundwater and whether groundwater is currently used or reasonably expected to be used for drinking water;

(7) Public health, safety, and welfare effects; and,

(8) Practicable capability of the permittee.

j. One permanent survey benchmark of known elevation measured from a U.S. Geological Survey benchmark shall be established and maintained at the site. This benchmark shall be the reference point for establishing horizontal and vertical elevation control.

k. A minimum separation of three feet shall be maintained between the base of the constructed liner system and the high water table. Settlement of the landfill base grade shall be factored into the minimum separation requirement.

l. The soil component of the liner system shall conform with the following:

(1) The soil component of the liner system shall be placed on a slope of no less than 2% to promote positive drainage across the liner surface and at a maximum slope not greater than 33% to facilitate construction; and,

(2) Compaction shall be performed by properly controlling the moisture content, lift thickness and other necessary details to obtain satisfactory results.

m. The flexible membrane liner material shall demonstrate a chemical and physical resistance to waste placement or leachate generated by the landfill. Documentation shall be submitted to ensure chemical compatibility of the geomembrane liner material chosen, or in absence of the appropriate documentation, chemical compatibility testing shall be performed using a test method acceptable to the Department. Flexible membrane liners shall be installed in accordance with the requirements of the approved engineering plans, report, specifications and manufacturer's recommendations.

n. All storm water ditches should have a minimum slope of 0.5% or a minimum permissible non-silting velocity of two feet per second. When it is not possible to achieve minimum slopes and/or velocities, alternative system design and maintenance, which ensures proper run-on and run-off control, may be approved by the Department.

o. For landfill expansions adjacent to existing Class Three landfills, the Department may approve encroachment upon the existing landfill's side slopes only if a leachate barrier system is designed and constructed to eliminate leachate migration into the existing landfill. The expansion area shall be constructed in compliance with all applicable sections of this regulation. The subsurface conditions of the underlying area shall be capable of supporting the expansion.

p. A construction certification report shall be submitted to the Department for approval after the completion of landfill construction by a S.C. licensed engineer other than the design engineer. This report shall include at a minimum, the information prepared in accordance with the application requirements. In addition, the construction certification report shall contain as-built drawings prepared and sealed by a land surveyor registered in South Carolina noting any deviations from the approved engineering plans. The construction certification report shall include a comprehensive narrative by the engineer. Upon approval of the construction certification report and a satisfactory Department inspection, the Department will grant approval for disposal of waste.

q. The Department may, on a case-by-case basis, approve other landfill designs, provided there is adequate information to demonstrate that the proposed design meets or exceeds the environmental and public health protection standards outlined in this regulation.

r. Class Three landfills shall have a minimum 1.7 factor safety against failure, where the soil conditions are complex and when available strength data does not provide a consistent, complete, or logical picture of the strength characteristics. Where the soil conditions are uniform and high quality strength data provides a consistent, complete, and logical picture of the strength characteristics, a minimum 1.2 factor safety against failure may be used. The determination of the maximum horizontal acceleration of the lithified earth material for the site shall be based on the seismic 250-year interval maps in U.S. Geological Survey Open-File Report 82-1033 [FN1]. The permittee shall place the demonstration in the operating record and submit a copy to the Department.

[FN1] Entitled "Probabilistic Estimates of Maximum Acceleration and Velocity in Rock in the Contiguous United States," (Algermissen and Perkins, 1982).

S.C. Code Regs. § 61-107.19.V.D.258.40