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EPA's Region 6 Office

Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations

Guidance for Design and Installation of Final Covers

Notice

The purpose of this document is to address the technical aspects of Closure and Post-Closure Plan for each Open Dumps in Indian Country. This document points out what technically can be done, how to comply with the Federal Regulations, and how to close all open dumps in Indian Country. This document is not a regulation and should not be used as such. Any comments related to this document should be addressed to:

Willie Kelley
Tribal Solid Waste Programs

1445 Ross Avenue (6PD-U)
Dallas, Texas 75202-2733
Phone: (214) 665-8195
Fax: (214) 665-7263
E-Mail: kelley.willie@epa.gov


DEFINITIONS

(40 CFR §258.2 and Indian Lands Open Dump Cleanup Act of 1994))

Unless otherwise noted, all terms contained in this part are defined by their plain meaning. This section contains definitions for terms that appear throughout this document; additional definitions appear in the specific sections to which they apply.

Active life: means the period of operation beginning with the initial receipt of solid waste and ending at completion of closure activities in accordance with Sec. 258.60 of this part.

Active portion: means that part of a facility or unit that has received or is receiving wastes and that has not been closed in accordance with Sec. 258.60 of this part.

Alaska Native Entity (Under Indian Lands Open Dump Cleanup Act of 1994): "Alaska Native entity" includes native corporations established pursuant to the Alaska Native Claims Settlement Act (43 U.S.C. 1600 et seq.) And any Alaska native Village or municipal entity which owns Alaska Native land.

Aquifer: means a geological formation, group of formations, or portion of a formation capable of yielding significant quantities of ground water to wells or springs.

Commercial solid waste: means all types of solid waste generated by stores, offices, restaurants, warehouses, and other nonmanufacturing activities, excluding residential and industrial wastes.

Closure or Close (Under Indian Lands Open Dump Cleanup Act of 1994): means the termination of operations at open dumps on Indian land or Alaska Native land and bringing such dumps into compliance with applicable Federal standards and regulations, or standards promulgated by an Indian tribal government or Alaska Native entity, if such standards are more stringent than the Federal standards and regulations.

Existing MSWLF unit: means any municipal solid waste landfill unit that is receiving solid waste as of the appropriate dates specified in Sec. 258.1(e). Waste placement in existing units must be consistent with past operating practices or modified practices to ensure good management.

Facility: means all contiguous land and structures, other appurtenances, and improvements on the land used for the disposal of solid waste.

Ground water: means water below the land surface in a zone of saturation.

Household waste: means any solid waste (including garbage, trash, and sanitary waste in septic tanks) derived from households (including single and multiple residences, hotels and motels, bunkhouses, ranger stations, crew quarters, campgrounds, picnic grounds, and day-use recreation areas).

Indian lands or Indian country means ((Under Indian Lands Open Dump Cleanup Act of 1994):

    (1) All land within the limits of any Indian reservation under the jurisdiction of the United States Government, notwithstanding the issuance of any patent, and including rights-of-way running throughout the reservation;

    (2) All dependent Indian communities within the borders of the United States whether within the original or subsequently acquired territory thereof, and whether within or without the limits of the State; and

    (3) All Indian allotments, the Indian titles to which have not been extinguished, including rights of way running through the same.

Indian Tribe or Tribe: means any Indian tribe, band, nation, or community recognized by the Secretary of the Interior and exercising substantial governmental duties and powers on Indian lands.

Indian Tribal Government (Under Indian Lands Open Dump Cleanup Act of 1994): means the governing body of any Indian tribe, band, nation, pueblo, or other organized group or community which is recognized as eligible for the special programs and services provided by the United States to Indians because or their status as Indians.

Industrial solid waste: means solid waste generated by manufacturing or industrial processes that is not a hazardous waste regulated under subtitle C of RCRA. Such waste may include, but is not limited to, waste resulting from the following manufacturing processes: Electric power generation; fertilizer/agricultural chemicals; food and related products/by-products; inorganic chemicals; iron and steel manufacturing; leather and leather products; nonferrous metals manufacturing/foundries; organic chemicals; plastics and resins manufacturing; pulp and paper industry; rubber and miscellaneous plastic products; stone, glass, clay, and concrete products; textile manufacturing; transportation equipment; and water treatment. This term does not include mining waste or oil and gas waste.

Lateral expansion: means a horizontal expansion of the waste boundaries of an existing MSWLF unit.

Leachate: means a liquid that has passed through or emerged from solid waste and contains soluble, suspended, or miscible materials removed from such waste.

Municipal Solid Waste Landfill Unit (MSWLF): means a discrete area of land or an excavation that receives household waste, and that is not a land application unit, surface impoundment, injection well, or waste pile, as those terms are defined under Sec. 257.2. A MSWLF unit also may receive other types of RCRA subtitle D wastes, such as commercial solid waste, nonhazardous sludge, conditionally exempt small quantity generator waste and industrial solid waste. Such a landfill may be publicly or privately owned. A MSWLF unit may be a new MSWLF unit, an existing MSWLF unit or a lateral expansion.

New MSWLF unit: means any municipal solid waste landfill unit that has not received waste prior to October 9, 1993, or prior to October 9, 1997 if the MSWLF unit meets the conditions of Sec. 258.1(f)(1).

Open burning: means the combustion of solid waste without:

    (1) Control of combustion air to maintain adequate temperature for efficient combustion,

    (2) Containment of the combustion reaction in an enclosed device to provide sufficient residence time and mixing for complete combustion, and

    (3) Control of the emission of the combustion products.

Open Dump (Under Indian Lands Open Dump Cleanup Act of 1994): means any facility or site where solid waste is disposed of, which is not a sanitary landfill which meets the criteria promulgated under section 6944 of the Solid Waste Disposal Act (42 U.S.C. 6941 et seq.) and which is not a facility for disposal of hazardous waste.

Operator: means the person(s) responsible for the overall operation of a facility or part of a facility.

Owner: means the person(s) who owns a facility or part of a facility.

Postclosure Maintenance (Under Indian Lands Open Dump Cleanup Act of 1994): means any activity undertaken at a closed solid waste management facility on Indian land or on Alaska Native land to maintain the integrity of containment features, monitor compliance with applicable performance standards, or remedy any situation or occurrence that violates regulations promulgated pursuant to Subtitle D of the Solid Waste Disposal Act (42 U.S.C. 6941 et seq.)

Run-off: means any rainwater, leachate, or other liquid that drains over land from any part of a facility.

Run-on: means any rainwater, leachate, or other liquid that drains over land onto any part of a facility.

Saturated zone: means that part of the earth's crust in which all voids are filled with water.

Sludge: means any solid, semi-solid, or liquid waste generated from a municipal, commercial, or industrial wastewater treatment plant, water supply treatment plant, or air pollution control facility exclusive of the treated effluent from a wastewater treatment plant.

Solid waste: means any garbage, or refuse, sludge from a wastewater treatment plant, water supply treatment plant, or air pollution control facility and other discarded material, including solid, liquid, semi-solid, or contained gaseous material resulting from industrial, commercial, mining, and agricultural operations, and from community activities, but does not include solid or dissolved materials in domestic sewage, or solid or dissolved materials in irrigation return flows or industrial discharges that are point sources subject to permit under 33 U.S.C. 1342, or source, special nuclear, or by-product material as defined by the Atomic Energy Act of 1954, as amended (68 Stat. 923).

Solid Waste (Under Indian Lands Open Dump Cleanup Act of 1994): The term "solid waste" has the meaning provided that term by section 1004(27) of the Solid Waste Disposal Act (42 U.S.C. 6903) and any regulations promulgated thereunder.

Uppermost aquifer: means the geologic formation nearest the natural ground surface that is an aquifer, as well as, lower aquifers that are hydraulically interconnected with this aquifer within the facility's property boundary.

Waste management unit boundary: means a vertical surface located at the hydraulically downgradient limit of the unit. This vertical surface extends down into the uppermost aquifer.


Guidance
for
Design and Installation of Final Covers

I.&nbsp&nbsp&nbsp INTRODUCTION

Final Cover is an essential part of all municipal solid waste landfill facilities (MSWLF's). A well designed final cover controls moisture infiltration from the surface into the closed facilities, limits the formation of leachate, and vertical and lateral migration of leachate to the surface and/or ground water. The Completion Plan for the open dump will consist of final cover contours and surface drainage features for the completed landfill.

The United States Environmental Protection Agency (EPA) Region 6, Mutimedia Planning and Permitting Division, UST/Solid Waste Section has developed a Generic Final Closure Plan to be used as a guidance document for the closure of open dumps on Indian Lands.

The RCRA subtitle D final cover requirements vary according to the characteristics of the underlying liner. Since no specific liner or liner parameters were established for any of the open dumps on Indian Lands, the final cover requirements under RCRA Subtitle D [40 CFR §258.1(d)] state that " . . . MSWLF units that meet the conditions of §258.1(f)(1) and receive waste after October 9, 1991, but stop receiving waste before October 9, 1997, are exempt from all the requirements of part §258, except the final cover requirement specified in §258.60(a)." These facilities must install the final cover by October 9, 1998. Owners or operators of MSWLF units that fail to complete cover installation by October 9, 1998 will be subject to all requirements of part 40 CFR §258.

II. &nbsp&nbsp&nbspREGULATIONS REQUIREMENTS:

1. Small Landfill and Arid Exemptions

Under 40 CFR Part 258.1(f) " Owners or operators of new MSWLF units, existing MSWLF units and lateral expansions that dispose of less than twenty (20) tons of municipal solid waste daily, based on an annual average, are exempt from the design criteria (Subpart D) and the ground water monitoring requirements (Subpart E) of the regulations, as long as there is no evidence of existing ground-water contamination from the MSWLF unit and the MSWLF unit serves:

    (i) A community that experiences an annual interruption of at least three consecutive months of surface transportation that prevents access to a regional waste management facility, or

    (ii) A community that has no practical waste management alternative and the landfill unit is located in an area that annually receives less than or equal to 25 inches of precipitation.

The determination of "practicable waste management alternative" includes considerations of technical, economic, and social factors. The use of no practicable waste management alternative is generally reserved for small rural communities which are located great distances from alternative waste management units making regionalization of waste management difficult".

If the owner or operator of a landfill unit has knowledge of ground-water contamination resulting from the unit and has asserted the small, arid exemption described above, the owner or operator should notify the Tribal Director of such contamination and, thereafter, comply with the design criteria (Subpart D and E) of the regulations pursuant to 40 CFR Part 258.f(3). The Tribal Director may request technical assistant from EPA, IHS and BIA.

2. Final Cover Closure Design

All MSWLF units must install a final cover system designed to minimize infiltration and erosion. The final cover system pursuant to RCRA Subtitle D, 40 CFR § 258.60(a), must be designed and constructed to:

    (a) Have permeability less than or equal to the permeability of any bottom liner system or natural subsoil present, or a permeability no greater than 1 x 10-5 cm/sec, whichever is less, and

    (b) Minimize infiltration through the closed MSWLF unit by an infiltration layer that contains a minimum of 18-inches of an earthen soil material, and

    (c) Minimize erosion of the final cover by an erosion layer that contains a minimum of 6-inches of earthen material that could sustain native plant growth.

3. Closure Plan Requirements

Under 40 CFR Part 258.60 (c & d), the Owner/Operator of any landfill facility must:

(a) Prepare a written closure plan that describes the steps necessary to close all MSWLF units using the cover design requirements in 40 CFR § 258.60(a). The closure plan at a minimum must include the following information:

    (1) A description of the final cover, designed according to 40 CFR § 258.60(a) and the methods and procedures to be used to install the cover;

    (2) An estimate of the largest area of the MSWLF unit ever requiring a final cover as required under 40 CFR § 258.60(a);

    (3) An estimate of the maximum inventory of wastes ever on-site over the active life of the landfill facility; and

    (4) A schedule for completing all activities necessary to satisfy the closure criteria in 40 CFR § 258.60.

(b) The EPA recommendation to all Tribes is to notify IHS, and BIA Director that a closure plan has been prepared and placed in the operating record.

4. Closure Schedule

A schedule for completing all activities necessary to satisfy the closure criteria should be addressed within the closure plan. Under the Closure Criteria of Subtitle D, the site will be closed in an orderly fashion, carrying out the following steps per 40 CFR §258.60(e)-(j):

    (1) Before beginning closure of each MSWLF unit, the tribe should notify the EPA, IHS, and BIA, in writing, that a notice of intent to close the unit has been placed in the operating record.

    (2) The owner or operator of all MSWLF units must begin closure activities within30 days of notifying the EPA, IHS and BIA.

    (3) The Owner/Operator must complete closure activities of each MSWLF unit according to the closure plan within 180 days following the beginning of the closure, but no later than, October 9, 1998.

    (4) Following closure of each MSWLF unit, the owner or operator should notify, in writing, the EPA, IHS, and BIA that a certification signed by an independent registered professional engineer verifying that closure has been completed according to the closure plan, has been placed in the operating record.

    (5) Following closure of all MSWLF units, the owners or operators must record a notation on the deed to the landfill facility property, or another instrument that is normally examined during title searches, and notify the EPA, IHS, and BIA Director that the notation has been recorded and a copy has been place in the operating record. The notation on the deed must in perpetuity notify any potential purchaser of the property that: The land has been used as a landfill facility. Its use is restricted under 40 CFR 40 CFR § 258.61(c)(3).

III. &nbsp&nbsp&nbspPRE-CONSTRUCTION CLOSURE PLAN

(A)&nbsp&nbsp&nbsp Executive Summary

The executive summary to the closure plan outlines the overall scope and the general procedure to be utilized by the Owner/Operator to close and maintain the open dump (landfill) pursuant to 40 CFR § 258. The Owner/Operator should address all requirements for closure as outlined below. The closure plan should address all open dumps and trenches on tribal lands for which a closure plan is required under the regulation (any dumps or landfills improperly closed or in use after October 9, 1991).

(B) Corrective Action Section

If any contamination is encountered during the site investigation (ground water or waste characterization phase of the planning), the owner and/or operator should notify the Tribal Director of such contamination. The Tribal Director may request technical assistant from EPA Solid Waste Section, IHS and BIA.

(3) &nbsp&nbsp&nbsp Recommendations on Final Cover Open Dumps Acreages.

Descriptions Dumps less than or equal to 5 acres Dumps greater than 5 acres and less than 20 acres Dumps greater than 20 acres
Executive Summary
The closure plan should address all open dumps and trenches on tribal lands for which a closure plan is required under the regulation (any dumps or landfills improperly closed or in use after October 9, 1991).
Background on Individual Tribes: For each individual tribe, the closure plan introduction will include tribal details as follows:
The approximate number of tribal residents living in the reservation, X X X
Description of Tribal Industries with waste generated, X X X
Acreage of Tribal Lands with Map of Tribal lands with major structures with dumps locations (Latitude and Longitude) on a USGS topographic map) and the names of each dump, X X X
The number and sizes of all open dumps be addressed by the plan, X X X
Discussion of Tribal Solid Waste Alternatives or Needs (Provide Copy of SW Mgmt Plan as attachment), X X X
The source and dollar amounts of all financial allocations received by the tribe from any governmental agencies to be used for solid waste alternatives and closure of open dumps on tribal lands (1997 and beyond). X X X
The annual precipitation of the area as determined by the National Weather Service serving the area. X X X
Open Dump/Landfill Facility Information: For each open dump/landfill facility covered by the closure plan, the introduction includes:
Year the facility began operation and accepting waste, X X X
Disposal practices, landfill type (trench),cover, burning and management history, X X X
The overall quantity and average depth of solid waste in the open dump, X X X
The average daily tonnage of solid waste received at the dump (landfill), X X X
Sources and types of waste which entered the facility (municipal waste; industrial waste; waste from Adjacent county, non-tribal residents, companies and types of waste), X X X
Special waste items present at the dump site (drums, white goods, tires), X X X
The geologic formation in which waste was buried. X X X
The surface and subsurface hydrology and depth to groundwater. X X X
Open Dump/Landfill Report Content
Year dump opened, date dump ceases to receive waste, X X X
Description of disposal practices (trench, area fill, burned, covered annually), X X X
Approximate quantity and depth of waste (with average daily tonnage received) X X X
Detail of Sources of waste going into the landfill (residential, light industrial) X X X
Waste Characterization and Special Wastes present. (Before Photo) X X X
Detail Site Plan (Latitude and Longitude on a USGS topographic map) (Professional Surveyor from IHS)) X X X
Brief discussion of Surface Hydrology X X X
Discussion on groundwater and surface water testing. Install 1 well minimum to 100 feet test any water encountered Install 2 wells minimum to 100 feet test any water encountered Install 3 wells minimum to 100 feet test any water encountered
Final Cover Recommendations with proposed cross section X X X
Geotechinical Testing Schedule 1 test minimum 4 tests minimum 1 test per 5 acres of area minimum
Methane Vent, if applicable. If depth of waste > 15 feet, install one Passive Vent per acre near population or structures. If depth of waste > 15 feet, install one Passive Vent per acre near population or structures. If depth of waste > 15 feet, install one Passive Vent per acre near population or structures.
Schedule of Closure X X X
Closure Cost Estimate X X X
Pre Closure Notification to the Tribal Director. The Tribal Director may submit the notification to EPA, IHS, and BIA X X X
Final Notification, Engineers Certification and As Built Drawings (x-section with any updates to closure plan) X X X
Post Closure Plan (semi annual inspections and methane monitoring in nearby structures) X X X
Access Restrictions X X X
Posting of Signs (with photo). X X X
Inventory of and domestic wells within 1 mile radius. X X X


Guidance for Design and Installation of Final Covers

(A) Executive Summary

The executive summary to the closure plan outlines the overall scope and the general procedure to be executed by the Owner/Operator to close and maintain the open dump (landfill) pursuant to 40 CFR § 258. The Owner/Operator should address all requirements for closure as outlined below. The closure plan should address all open dumps and trenches on tribal lands for which a closure plan is required under the regulation (any dumps or landfills improperly closed or in use after October 9, 1991). The final closure plan content list shall include the following subheadings:

(B) Background on Individual tribes

In the background on individual tribes, the Owner/Operator of the open dump will describe the following:

  • The approximate number of tribal residents living on the reservation,
  • Description of Tribal Industries with waste generated,
  • Acreage of Tribal Lands with Map of Tribal lands with major structures with dumps located (Latitude and Longitude) and named,
  • The number and sizes of all open dumps be addressed by the plan,
  • Discussion of Tribal Solid Waste Alternatives or Needs (Provide Copy of SW Mgmt Plan as attachment),
  • The source and dollar amounts of all financial allocations received by the tribe from any governmental agencies to be used for solid waste alternatives and closure of open dumps on tribal lands (1997 and beyond).
  • The annual precipitation of the area as determined by the National Weather Service serving the area,

(C) Open Dump/Landfill Facility Information

For each open dump/landfill facility covered by the closure plan, the introduction will include:

  • Year the facility began operation and accepting waste,
  • Disposal practices, landfill type (trench, area fill, burned, covered annually),cover, burning and management history,
  • The overall quantity and average depth of solid waste in the open dump,
  • The average daily tonnage of solid waste received at the dump (landfill),
  • Sources and types of waste which entered the facility (municipal waste; industrial waste; waste from adjacent county, non-tribal residents, companies and types of waste...),
  • Special waste items present at the dump site (drums, white goods, tires) with "before" photo,

(D) Open Dump/Landfill Report Content:

  1. Site Plan.

    The owner or operator shall prepare a site development plan. In the site plan, the owner/operator of the open dump will describe the location of the open dump, the legal description, provide a plan survey and legal description as noted on the deed (if available). The Owner/Operator will include a topographic field survey of the site. In the Site Plan, the Owner/Operator will address all nearby (within 1 mile) residences, schools, hospitals, water wells, wetlands, and buildings; and will denote the 100-year floodplain, creeks, arroyos, and surface water bodies, if applicable. The field survey will be performed by a Registered Professional Surveyor to assure the legal description and ownership of the site are established. The site plan should be drawn on a 7.5 minute USGS quadrant map. The survey shall provide latitude and longitude of site on a map.

  2. Surface Water Hydrology.

    To determine the design of the final cover, a drainage plan will be drawn and engineered to control run-on to the facility and run-off from the facility into adjacent surface waters. The drainage plan will be designed to include an overall plan view of the facility, a grade profile for any drainage structures, and a typical channel with an appropriate cross section. The plan will be engineered to control the rain fall from a 24 hours/25 years storm event. Erosion control, washout prevention and long term maintenance will be paramount in the design of the final cover. The peak value runoff for the 24 hours/25 years storm event should be calculated using the Rational Formula Method Criteria. Water surface profiles shall be calculated. The hydraulic control structures shall be designed and sized to carry the 25 year/24 hour volume.

  3. Hydrogeological and Hydrology Data.

    The owner/operator of the landfill will include a hydrogeological study of the site including information on the underlying geologic stratum (drillers' logs), the depth to groundwater, the groundwater hydraulic gradient, the groundwater direction and magnitude of the flow, and a description of any nearby water wells (depth, drinking water source, owner). Three wells, minimum to 100 feet, are required to test any water encountered to Table 1 constituents (see attached). If contamination is encountered, see Corrective Action Section for more detailed information.

    • For dumps less than 1 acre in size, the study requires the drilling of at least one well to the water table (or 100 feet, whichever is more shallow).
    • For dumps between 1 and 5 acres in size, the study requires the drilling of at least two wells to the water table (or 100 feet, whichever is more shallow).
    • For dumps larger than 5 acres in size, an appropriate Hydrogeological Study will be required, but no less than 2 wells drilled to a depth of 100 feet or to the water table. The owner shall submit any and all existing well drilling logs. If contamination is encountered, see Corrective Action Section.
  4. Final Cover Recommendations with proposed Cross section:

    The owner or operator of a landfill should describe the multi-layer final cover system as described under RCRA Subtitle D that will provide a low maintenance cover, reduce rainfall percolation through the cover system, and minimize leachate generation within the landfill. In the case of a side slope 4H:1V, a drainage system must be in place to control storm-water surface water run-off and to minimize erosion of the final cover. The top of the landfill must be regraded and reshaped as needed to provide the proper slope for positive drainage. The regulatory design criteria for the final closure requirements are:

    • A minimum of 6-inches vegetation and erosion top cover layer capable of sustaining plant growth. Special techniques, including mulching, hydro seeding, installation of erosion control mats, or sodding may be considered in areas with a higher potential for erosion (e.g., ditches, runoff control berms, landfill side slopes, terraces, flumes, etc.). Anticipated erosion due to surface water run off for given design criteria may be approximated using the US Department of Agriculture (USDA) Modified Universal Soil Loss Equation (MUSLE). By evaluating erosion loss, the design may be optimized to reduce maintenance through selection of the best available soil materials or by initially adding excess soil to increase the time required before maintenance is needed. Values for the Universal Soil Loss Equation parameters may be obtained from the US Soil Conservation Service (SCS) technical guidance.

    The vegetation layer should perform the following functions: stabilize the soil against erosion by water and wind; minimize percolation down to the waste; maximize evapotranspiration of moisture from the soil material cover; enhance the natural beauty (aesthetics) of the site; develop basic recreational and related resources at the site; and create self-sustaining ecosystems of low maintenance. (See Figure 1, Minimum Final Cover Requirements, 40 CFR § 258.60(a))

    • An 18-inch thick clay infiltration layer. The infiltration layer will be installed to minimize infiltration of surface water into the underlying waste material. The infiltration layer should be free of rocks, clods, debris, cobbles, rubbish, and roots that may increase the hydraulic conductivity by promoting preferential flow paths. To facilitate run-off while minimizing erosion, the surface of the compacted soil should have a minimum slope of 3 percent and a maximum slope of 5 percent after allowance for settlement. It is critical that sides slope, which are frequently greater that 5 percent, be evaluated for erosion potential.

    The material used in the infiltration layer will be described in the closure plan (clay, sandy loam...)

    Minimum Final Cover Requirements Diagram

  5. Design Criteria to be considered for the Final Cover

    • Installation of some run-off control berms or terraces along the top of the landfill will be required, in areas with a higher potential for erosion. These berms will minimize long-term maintenance requirements.
    • Installation of terraces on the side slopes of the landfill, if applicable, to minimize erosion and divert surface water runoff to the drainage ditches. The terraces must be designed and sloped to drain the storm water.
    • Consideration must be given to the geotechnical stability of the final cover system to prevent failures, such as sliding. Conduct slope stability analysis, if applicable.
    • Installation of storm water ditches to convey concentrated flows from the landfill top slope to the perimeter ditch system, if applicable.
    • Control landfill gas migration using passive vent systems, if applicable.
    • Consideration must be given to selecting plant species that are not deeply rooted prevent damage of the underlying infiltration layer.
  6. Alternative Final Cover Closure Design
    • An alternative material and/or alternative thickness may be used for an infiltration layer as long as the infiltration layer requirements specified in 40 CFR § 258.60(a)(1) and (a)(2) are met. The final cover alternative options depend mainly on the site specific conditions, and soil-climate situations. Additional layers incorporated into the final cover design may be used to promote lateral drainage of infiltration and to provide a zone under the cover for gas movement. If an alternative cover is recommended by the Owner/Operator, the following information must be provided:
    • Characterize the site to identify major site constraints. Every open dump in Indian lands requires a site-specific design. The designers need to accommodate site constraints or site related limitations and take advantage of favorable site conditions. From the site's specific characteristics, the designer will establish the need to impose various layers of the cover system, thus emphasizing the need for a complete site characterization. If the natural materials suitable for some or all cover system layer components are not locally available, then the design may have to incorporate imported and/or synthetic materials.
    • The designer should identify the site-specific cover system after the initial site characterization is fully identified. First, he identifies appropriate layers for each site including a surface erosion/vegetation layer, drainage layer, synthetic geomembrane layer and infiltration layer along with the need for any alternate layers (e.g., a rock-armored erosion layer, biotic layer or geotextile layer), to fulfill intended functions, as appropriate.
    • A crushed rock (3 to 5 inches in diameter) may be spread over the landfill final cover in areas where weather conditions such as a wind, heavy rains, or temperature may cause deterioration of vegetative covers.
    • Alternative components such as a drainage layer and an overall surface water management plan should be considered.
    • Alternative components such as a gas vent layer, and a biotic barrier layer may be used.
    • Flexible Membrane Liner (FML) or Geosynthetic Clay Liner (GCL) material may be used for the infiltration layer to replace the 18-inch thick clay infiltration layer.
    Diagram of Minimum Final Cover Requirements

  7. Infiltration Layer Geotechnical Testing Schedule: (1 test minimum):

    The owner or operator of a landfill should provide final cover testing procedures for the final cover components. The 18 inches of compacted infiltration material must be tested for coefficient of permeability at a frequency of at least one test per surface acre of final cover. The infiltration layer shall be constructed in three lifts that are 6 inches thick. Each 6-inch lift shall be compacted to achieve a permeability 1 x 10 -5 cm/sec. Other testing shall be considered, as appropriate such as Atterberg Limits, Moisture Content and Standard Proctor Density to provide control and verification during construction of the final cover. If an FML is required in the final cover, construction quality control for the FML shall be performed according to methods approved by the engineer. Recommendations from the manufacture, installer, and owner shall be incorporated. A slope stability analysis must be conducted in the FML/Soil interface. Prior to construction of any soil infiltration layer, representative samples of the materials to be used should be tested in a geotechnical laboratory to ensure that they meet the minimum requirements set forth in the regulations for the final cover infiltration layer soils. The minimum soil and laboratory testing parameters and procedures considered necessary for constructing infiltration layer soils are as follows:

    • Sieve Analysis: ASTM D 422 or ASTM D 1140 - At least 30% should pass the #200 mesh sieve if the infiltration layer is to be at least as impermeable as the landfill bottom. The permeability of the infiltration layer soil must not exceed 1 x 10 -5 cm/sec. A lesser percentage passing the #200 mesh may be acceptable.
    • Atterberg Limits: ASTM D 4318 - Liquid Limit (LL) of not less than 30 and a plasticity index (PI) of not less than 15 are required, if the infiltration layer is to be at least as impermeable as the liner. The permeability of the infiltration layer soil must not exceed 1 x 10 -5 cm/sec.
    • Moisture/Density Testing: There are two standard proctors density test methods used: (a) ASTM D 698 (Standard Proctor) - 12,400 ft-Ibf/ft3 (for light-weighted equipment), or (b) ASTM D 1557 (Modified Proctor) - 56,000 ft-Ibf/ft3 (for heavy equipment)
    • Coefficient of Permeability: The two acceptable laboratory test methods for determining the coefficient of permeability are: (a) Falling head (as described in the Corps of Engineers Manual EM 1110-2 1906 or ASTM D 5084), and (b) Constant head (as described in the Corps of Engineers Manual EM 1110-2 1906 or ASTM D 5084). Once moisture-content/density relationship has been determined for one or more compactive efforts, a soil sample should be compacted to approximately 95% of the maximum dry density at the optimum moisture content using ASTM D 698 to approximately 90% of maximum dry density at a moisture content 1% drier than optimum using ASTM D 1557. Once a permeability less than 1 x 10-5 cm/sec is demonstrated through testing, the percent compaction, moisture content, liquid limit, plasticity index, and percentage passing the #200 mesh of the demonstration sample become the minimum standards for use in field control.
    • For Slopes that are greater than 5%, a slope stability analysis shall be conducted.
  8. Methane Venting Recommendations (if applicable, depth of waste > 15 feet) (minimum 1 Passive Vent per acre near population or structures).
  9. The number and location of gas probes is a site-specific and highly dependent on subsurface conditions, land use, and location and design of facility structures. Monitoring of gas migration should be within the more permeable strata. Multiple or nested probes are useful in defining the vertical configuration of the migration pathway. Structures with basements or crawl spaces are more susceptible to landfill gas. For any methane venting, EPA recommendations are, if applicable at a depth of solid waste greater than 15 feet, minimum of one Passive Vent per acre near population or structures.

    Passive Gas Control Venting Diagram
    Diagrams of Extensive Lateral Migration
  10. Closure Schedule.

    The owner or operator of a landfill should provide a schedule for completing all activities necessary to satisfy the closure criteria in 40 CFR § 258.60 within the closure plan. Under the Closure Criteria of RCRA Subtitle D (40 CFR § 258.60(e)-(j)), the site will be closed in orderly fashion, implementing the following steps:

    • Prior to beginning closure of each MSWLF unit, the tribes must notify the EPA, IHS, and BIA Director that a notice of the intent to close the unit has been placed in the operating record. The Owner/Operator of all MSWLF units must complete closure activities of each MSWLF unit in accordance with the closure plan by October 9, 1998 or within 180 days of beginning closure activities, which ever comes first.
    • Following closure of each MSWLF unit, the owner or operator must supply the EPA, IHS, and BIA with a certification signed by an independent registered professional engineer verifying that closure has been completed in accordance with the closure plan. A copy of this certification must be placed in the operating record.
    • Following closure of all MSWLF units, the owners or operators must record a notation on the deed to the landfill facility property, or some other instrument that is normally examined during title searches, and notify the EPA, IHS, and BIA Director that the notation has been recorded and a copy has been placed in the operating record. The notation on the deed must in perpetuity notify any potential purchaser of the property that the land has been used as a landfill facility. Its use is restricted under 40 CFR 40 CFR § 258.61(c)(3).
  11. Closure Cost Estimate
  12. The Owner/Operator of a landfill should provide a closure cost estimate using a standard form developed by the consulting engineer. The closure cost estimate may include usage of tribal or BIA resources (equipment, manpower, etc.) in the closure, but these resources must be assigned an acceptable value.

  13. Pre-Closure Notification of EPA, IHS, & BIA (30 days prior to construction).

    Prior to beginning closure of each MSWLF unit, the tribes must notify the EPA, IHS, and BIA Director that a notice of the intent to close the unit has been placed in the operating record. The Owner/Operator of all MSWLF units must complete the pre-closure notification of each MSWLF unit in accordance with the closure plan by October 9, 1998 or within 30 days of beginning closure activities.

  14. Final Notification, Engineers Certification and As-Built Drawings.

    The Owner/Operator of a landfill will provide a closure certification, signed and sealed by a Professional Registered Engineer, upon completion of the final closure cover. A copy of the recorded deed restriction document will be forwarded to the EPA, IHS, and BIA. The certification should outline the completion of the closure construction, any construction quality assurance plan, record drawing, and final cover grades in their as-built state. The Final Notification, Engineers Certification and As-Built Drawings should include cross-sections with any updates to final closure plan, copies of any testing, ground water plat, and final grading.

  15. Post-Closure Plan.

    The Owner/Operator of the landfill will provide a post-closure care plan describing the maintenance activities that will be required over the post-closure period of the landfill (30 years). The plan shall include the name of a contact person responsible for landfill maintenance and the telephone number. This post closure plan will outline any and all maintenance activities and the inspection criteria to be used to determine the need for maintenance (these criteria typically outline inspecting for cracks in the final cover, erosion, any drainage structures, any ground-water monitoring well maintenance, and vegetation of the final cover on a semiannual basis). Inspections should be occurring after the highest precipitation season and the highest dry weather season. The Post-Closure plan should be inspected semi-annually and methane monitoring in nearby structures. The post closure care period may be reduced if demonstration is provided that a shorter period would be effective. Maintenance on the final cover will consist of replanting vegetation/grass, repairing erosional gullies and settlement depressions.

  16. Access Restrictions.

    The owner or operator of a landfill will control public access and prevent unauthorized vehicular traffic and illegal dumping of wastes by using artificial barriers, natural barriers, or both, as appropriate pursuant to 40 CFR §258.25. Chain link, barbed wire added to chain links, and open farm-type fences are examples of fencing that may be used. Access to facilities should be controlled through gates that can be locked when the site is unsupervised. Gates may be the only additional measure needed at remote facilities.

  17. Posting of Signs.

During the construction of the final cover of the landfill, the owner or operator of a landfill should provide a sign stating that the site is closed to any further dumping (photographs should be included within the report). This sign shall also describe the alternative disposal for the community.

 

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