250 R.I. Code R. 250-RICR-140-05-2.2

Current through October 15, 2024
Section 250-RICR-140-05-2.2 - Solid Waste Landfill Construction Standards
2.2.1General

Construction of sanitary landfill facilities shall meet all Regulations set forth in this Rule and shall also comply with all applicable Federal Rules, Laws, Regulations or other Federal requirements.

2.2.2Horizontal and Vertical Control
A. One (1) permanent survey benchmark of known elevation measured from the National Geodetic Vertical Datum of 1929 must be established and maintained for each twenty-five (25) acres of developed landfill, or part thereof, at the site. This benchmark must be the reference point for establishing vertical elevation control.
B. North American Datum of 1983 Coordinates must be established. Horizontal control must be established and one (1) of its points must be the benchmark of known NAD 1983 Coordinates.
2.2.3Liner System
A. The minimum liner requirements for all landfills accepting solid waste must consist of the following:
1. On all bottom areas where the landfill slope is less than or equal to twenty-five percent (25%), the liner system must consist of a double composite liner separated by a secondary leachate collection and removal system.
2. On all side slope areas where the landfill slope is greater than twenty-five percent (25%), the liner system need only consist of an upper geomembrane liner and a secondary (lower) composite liner separated by a secondary leachate collection and removal system.
3. A composite liner must consist of two (2) components; an upper geomembrane liner placed directly above a low permeability soil layer meeting the requirements specified in §§ 2.2.7 and 2.2.6 of this Part respectively. Each composite liner is considered a single liner.
4. The double composite liner system must include a primary leachate collection and removal system consisting of a twenty-four inch (24") granular soil layer with a leachate collection pipe network. The primary leachate collection and removal system lies above the primary (upper) composite liner. The primary composite liner consists of a geomembrane that directly overlays an eighteen inch (18") low permeability soil layer. The primary composite liner lies above the secondary leachate collection and removal system. The secondary leachate collection and removal system consists of either a leachate collection pipe network with a twelve inch (12") granular soil layer, or an effective layer of geosynthetic material. The secondary leachate collection and removal system lies above the secondary (lower) composite liner, which consists of a geomembrane that directly overlays a twenty-four inch (24") low permeability soil layer.
5. The Department shall not allow any variance from the requirement to include a secondary (lower) composite liner, as part of the liner system.
2.2.4Leachate Collection and Removal System
A. The leachate collection and removal system must be designed to effectively remove leachate from the landfill. A means of assessing leachate flows in both the primary and secondary leachate collection and removal system must be detailed on plans and discussed in the engineering report.
B. The primary and secondary leachate collection and removal systems must conform to the following requirements:
1. A primary leachate collection and removal system, located over the upper composite liner, must be hydraulically designed to remove leachate from the landfill and ensure that the leachate head over the primary composite liner does not exceed one foot (1') at expected flow capacity, except during storm events. This collection and removal system must be designed and constructed, at a minimum, in accordance with the requirements of §§ 2.2.8 and 2.2.9 of this Part.
2. A secondary leachate collection and removal system must be located between the upper and lower liner systems to effectively collect and rapidly remove leachate from the lower liner system. This collection system must be designed and constructed, at a minimum, in accordance with the requirements of §§ 2.2.8, 2.2.9 and 2.2.10 of this Part.
3. The primary and secondary leachate collection and removal systems must be designed and built to allow for representative sampling of leachate, and to operate without clogging during the effective site life and post-closure maintenance period. All pipes located in the primary leachate collection and removal system must be designed to allow for accessibility of equipment for routine cleaning and maintenance. All leachate conveyance lines outside the double composite liner system of the landfill must be designed to have double containment, and must be constructed to provide for leak detection and collection. Double containment and leak detection provisions shall be maintained along the entire length of conveyance line(s) handling only leachate or other liquid wastes associated with the design of the landfill.
2.2.5Landfill Subgrade
A. The landfill subgrade is the uppermost in situ soil layer or select fill that must be graded and prepared for landfill construction. A foundation analysis must be performed to determine the structural integrity of the subgrade to support the loads and stresses imposed by the weight of the landfill and to support overlying facility components. For lateral expansions adjacent to existing landfills, the Department may approve encroachment upon the existing landfill's side slope if a leachate barrier system is designed and constructed to minimize leachate migration into the existing landfill.
1. Materials Required: The landfill subgrade must be free of organic material and consist of on-site soils, or any select fill if approved by the Department.
2. Construction Requirements: The landfill subgrade must be graded in accordance with the requirements of the approved engineering plans, report, and specifications. The material must be sufficiently dry and structurally sound to ensure that the first (1st) lift and all succeeding lifts of soil placed over the landfill subgrade can be adequately compacted to the design requirements.
3. Certification Requirements: At a minimum, the subgrade surface must be inspected in accordance with the following requirements:
a. Before placing any material over the subgrade, the project engineer must visually inspect the exposed surface to evaluate the suitability of the subgrade and ensure that the surface is properly compacted, smooth, and uniform, and that elevations are consistent with the Department approved plans.
b. The subgrade must be proof-rolled using procedures and equipment acceptable to the Department.
c. The subgrade must be tested for density and moisture content at a minimum frequency of five (5) tests per acre.
2.2.6Soil Component of the Liner System
A. The soil component of the liner system must be a continuous layer of low permeability soil constructed to control fluid migration.
1. Materials Required
a. Primary composite liner: The soil component of the primary composite liner must be a minimum compacted thickness of eighteen inches (18"). The top six inches (6") directly below and in contact with the upper geomembrane liner must have a maximum remolded coefficient of permeability of 1 x 10-7 centimeters per second. The lower twelve inches (12") of soil must be compacted to achieve a maximum remolded coefficient of permeability of 1 x 10-5 centimeters per second and be placed without damaging any geosynthetic or secondary leachate collection and removal system components below the primary composite liner. The soil material must be free of particles greater than three inches (3") in any dimension.
b. Secondary composite liner: The soil component of the secondary composite liner must be at least twenty-four inches (24") in compacted thickness, and must have a maximum remolded coefficient of permeability of 1 x 10-7 centimeters per second throughout its thickness. The soil material must be free of particles greater than three inches (3") in any dimension.
2. Construction Requirements: The project engineer must ensure that the soil component of the liner system installation conforms with the following minimum requirements:
a. The soil component of the liner system must be placed on a slope of no less than two percent to promote positive drainage across the liner surface and at a maximum slope not greater than thirty-three percent (33%) to minimize erosion and facilitate construction.
b. Compaction must be performed by properly controlling the moisture content, lift thickness, and other necessary details to obtain satisfactory results. The maximum final compacted thickness of each lift of soil material must be six inches (6"). When placing the first (1st) lift of the soil component of the liner system, the thickness may be increased to ensure adequate compaction and attain the desired permeability depending upon the type and size of compaction equipment used and whether or not the liner and subgrade are of dissimilar materials. Any succeeding lifts of the soil component of the lining system may be reduced in thickness, depending upon the compaction equipment used.
c. The moisture content of the soil component of the liner system must be maintained within the range identified in accordance with §2.2.6(C) of this Part before and during compaction of the soil lift to ensure that the remolded lift attains a maximum in situ permeability as required. The density after compaction must be within the range identified in accordance with §2.2.6(C) of this Part to ensure that the remolded lift attains a maximum in situ permeability, as required.
3. Certification Requirements: The project engineer must include in the construction certification report a discussion of all quality assurance and quality control testing required in §2.2.6(A)(3) of this Part. The testing procedures and protocols must be submitted in accordance with § 2.1.6 of this Part and approved by the Department. The results of all testing must be included in the construction certification report including documentation of any failed test results, descriptions of the procedures used to correct the improperly installed material, and statements of all retesting performed in accordance with the following requirements:
a. The project engineer must certify the quality control testing of any soil liner materials to ensure that the specified material meets the permeability requirements of §2.2.6(A) of this Part and the approved engineering plans, reports, and specifications. Before and during construction of the soil component of the liner system, the following information must be approved by the project engineer: one (1) analysis of soil particle size for every two thousand five hundred (2,500) cubic yards of soil liner materials placed; one (1) Atterberg limits analysis of plastic and liquid limit and plasticity index for every one thousand five hundred (1,500) cubic yards of soil liner material placed; one (1) laboratory permeability test using a triaxial cell with back pressure for every five thousand (5,000) cubic yards of material placed; one (1) moisture content test for every one thousand (1,000) cubic yards of material placed; and a minimum of one (1) comparison of the moisture-density-permeability relation for every five thousand (5,000) cubic yards of material placed, and one (1) comparison each time soil material changes are noted.
b. Quality assurance testing included in this Rule must be compared to and evaluated against the quality control testing of §2.2.6(C)(1) of this Part, where applicable. Quality assurance testing must include: at least five (5) density tests must be performed per acre per lift of soil material placed; a minimum of five (5) moisture content tests per acre per lift of soil material placed; and one (1) shelby tube sample for laboratory permeability testing must be taken per acre per lift. Any tests resulting in penetration of the soil liner must be repaired using bentonite or other means acceptable to the Department.
2.2.7Geomembrane Liners
A. Geomembrane liners are low permeability geosynthetics having a maximum coefficient of permeability of 1 x 10-12 centimeters per second, and are used to control fluid migration from landfills.
1. Materials Required: The geomembrane liner material must have a demonstrated hydraulic conductivity less than 1 x 10-12 centimeters per second, and chemical and physical resistance not adversely affected by waste placement or generated leachate. Documentation must be submitted to ensure chemical compatibility of the geomembrane liner material chosen or, in absence of the appropriate documentation, chemical compatibility testing must be performed using a test method acceptable to the Department.
2. Construction Requirements: Geomembranes must be installed in accordance with the requirements of the approved engineering plans, reports and specifications, and manufacturer's recommendations. The project engineer must ensure that the geomembrane installation, at a minimum, must conform with the following:
a. The geomembrane must have a minimum thickness of forty-five (45) mils in the primary composite liner and thirty-six (36) mils in the secondary composite liner. Geomembranes consisting of high density polyethylene (HDPE) shall be at least eighty (80) mils thick in the primary composite liner and sixty (60) mils thick in the secondary composite liner.
b. All geosynthetic materials must be installed on a subgrade that has a minimum two percent (2%) slope to promote positive drainage.
c. Any geosynthetic materials installed on slopes greater than twenty-five percent (25%) must be designed to withstand the calculated tensile forces acting upon the geosynthetic materials. The design must consider the maximum friction angle of the geosynthetic with regard to any soil-geosynthetic or geosynthetic-geosynthetic interface, and must ensure that overall slope stability is maintained.
d. The surface of the supporting soil below which the geosynthetic material will be installed must be reasonably free of stones, organic matter, irregularities, protrusions, loose soil, and any abrupt changes in grade that could damage the geosynthetic. The supporting soil must conform to the requirements of § 2.2.5 of this Part.
e. The anchor trench must be excavated to the length and width prescribed on the approved design drawings.
f. Field seams should be oriented parallel to the line of maximum slope, i.e., oriented along, not across the slope. In corners and irregularly-shaped locations, the number of field seams should be minimized. No horizontal seam should be less than five feet (5') from the toe of slope toward the upslope direction of the landfill.
g. The materials must be seamed using an appropriate method acceptable to the Department. Seam testing must be in accordance with the requirements of § 2.2.7(C) of this Part.
h. The seam area must be free of moisture, dust, dirt, debris, and foreign material of any kind before seaming.
i. Field seaming is prohibited when ambient air temperatures, precipitation and wind conditions prevent construction of the liner seams in accordance with all quality assurance and quality control requirements.
j. The field crew foreman of the liner installer must have a documented minimum qualification of successful installation experience of at least fifty (50) acres of previous landfill or comparable geosynthetic systems on a minimum of five (5) different projects.
3. Certification Requirements: The project engineer must include in the construction certification report a discussion of the approved data resulting from the quality assurance and quality control testing required in §2.2.7(A)(3) of this Part. The results of all testing must be included in the construction certification report including documentation of any failed test results, descriptions of the procedures used to correct the failed material, and statements of all retesting performed.
a. The project engineer must certify the quality control testing of any geosynthetic materials ensuring that the material and workmanship meet the requirements of the approved engineering plans, reports, and specifications. Before installing any geosynthetic material, the following information must be available to the project engineer for approval:
(1) Origin and identification of the raw materials used to manufacture the geosynthetic material;
(2) Copies of quality control certificates issued by the producer of the raw materials used to manufacture the geosynthetic material; and
(3) Reports of tests conducted to verify the quality of raw materials used to manufacture the geosynthetics. Tests for specific gravity, melt flow index, and percent carbon black must be performed using a method acceptable to the Department.
b. The project engineer must verify through appropriate documentation that the quality control testing of any geosynthetic rolls fabricated into blankets at the factory took place in accordance with the following requirements:
(1) The geomembrane was continuously inspected for uniformity, damage, imperfections, holes, cracks, thin spots, and foreign materials. Additionally, the geomembrane liner must be inspected for tears, punctures, and blisters. Any imperfections must be immediately repaired and re-inspected.
(2) Non-destructive seam testing was performed on all fabricated seams over their full length using a test method acceptable to the Department.
(3) Destructive seam testing was performed on a minimum of two (2) samples per blanket. The samples must be taken from extra material at the beginning or end of blanket seams such that the blanket is not damaged and the blanket geometry is not altered. The size of the sample taken must be large enough to perform the required testing. An independent laboratory acceptable to the Department must have performed the required testing on the samples taken. If a sample fails a destructive test, the entire seam length must be reconstructed or repaired using a method acceptable to the Department and retested using non-destructive seam testing over their full length using a method acceptable to the Department.
c. Quality assurance testing performed in the field under the supervision of the project engineer must assure conformity of the geosynthetic installation with the engineering plans, reports, and specifications submitted in accordance with the following requirements:
(1) During the construction phase, the geosynthetic must be inspected for uniformity, damage, and imperfections. The liner must be inspected for tears, punctures, or blisters. Any imperfections must be immediately repaired and re-inspected.
(2) All field seams must be non-destructively tested in accordance with the procedures listed in this clause using a test method acceptable to the Department. The project engineer must: Supervise all non-destructive testing; Record the location, date, test unit number, name of tester, and results of all testing; Inform the installer of any required repairs; and overlay all seams which cannot be non-destructively tested with the same geomembrane. The seaming and patching operation must be inspected by the project engineer for uniformity and completeness.
(3) Destructive testing must be performed on the geomembrane liner seam sections in accordance with the requirements listed in this Rule and using test methods acceptable to the Department.
(4) Seam samples for testing must be taken as follows: a minimum of one (1) test per every five hundred feet (500') of seam length unless a more frequent testing protocol is agreed upon by the installer and project engineer; additional test locations may be determined during seaming at the project engineer's discretion; all test locations must be appropriately documented.
(5) The project engineer must approve the sample size to be taken. The sample size must be predetermined as being large enough to perform the required testing.
(6) An independent laboratory acceptable to the Department must perform the required testing, which must include, at a minimum, testing for seam strength and peel adhesion using testing procedures acceptable to the Department.
(7) If a sample fails destructive testing the project engineer must ensure that: the seam is reconstructed between the location of the sample which failed and the location of the next acceptable sample; or the welding path is retraced to an intermediate location at least ten feet (10') from the location of the sample which failed the test, and a second (2nd) sample is taken for an additional field test. If this second (2nd) test sample passes, the seam must be then reconstructed between the location of the second (2nd) test and the original sampled location. If the second (2nd) sample fails, this process must be repeated.
(8) All acceptable seams must lie between two (2) locations where samples passed the test procedures found in §2.2.7(C)(3)(c) ((4)) of this Part, and include one (1) test location along the reconstructed seam.
(9) Non-destructive testing of the geomembrane liner must be performed in accordance with §2.2.7(C)(3)(b) of this Part.
2.2.8Soil Drainage Layers
A. All soil material used in the primary and secondary leachate collection and removal systems of the landfill must conform to the following requirements:
1. Materials Required: Soil materials used to construct a drainage layer must be designed to ensure that the hydraulic leachate head on the primary liner system does not exceed one foot (1') at the expected flow capacity from the drainage area, except during storm events. The soil drainage layer must be free of any organic material and have less than five percent (5%) of the material by weight pass the No. 200 sieve. Soil material testing must be performed in accordance with §2.2.8(A)(2)(c) of this Part.
2. Construction Requirements: The soil drainage layer must be constructed and graded in accordance with the requirements of the approved engineering plans, reports, and specifications along with the following requirements:
a. The minimum thickness of the soil drainage layer in the primary leachate collection and removal system must be twenty-four inches (24") and provide adequate protection to all liner materials and piping placed within the primary leachate collection system, and have a minimum coefficient of permeability of 1 x 10-2 centimeters per second.
b. The minimum thickness of the secondary leachate collection and removal system layer must be twelve inches (12") and have a minimum coefficient of permeability of 1 x 10-1 centimeters per second.
c. The soil drainage layer must be designed and placed on a minimum slope of two percent (2%) to promote efficient positive drainage to the nearest leachate collection pipe and prevent ponding above the liner.
3. Certification Requirements: The project engineer must include in the construction certification report the results of an analysis of the approved data resulting from quality assurance and quality control testing required in §2.2.8(A)(3) of this Part. The results of all testing must be included in the construction certification report including any failed test results, descriptions of the procedures used to correct the failed material, and any retesting performed.
a. The project engineer must certify the quality control testing of any soil drainage materials, and ensure that the material meets the requirements of §2.2.8(A)(1) of this Part and the approved engineering plans, reports, and specifications. A particle size analysis of the soil drainage layer material must be submitted to the project engineer for approval before installation of the soil drainage layer and during installation at a frequency of at least one (1) test for every one thousand five hundred (1,500) cubic yards of material placed.
b. Quality assurance testing performed by the project engineer must ensure that the material is placed in accordance with the requirements of the engineering plans, reports, and specifications.
2.2.9 Leachate Collection Pipes
A. Leachate collection pipes that are located in any soil or geosynthetic drainage layer must be hydraulically designed to remove leachate from the landfill, provide conveyance to an appropriately designed and sized storage or treatment facility, and must comply with the following:
B. Materials Required: The leachate collection pipe must have a minimum diameter of four inches (4") and meet the following:
1. The physical and chemical properties must not be adversely affected by waste placement or leachate generated by the landfill. Documentation must be submitted which demonstrates the chemical compatibility of the leachate collection pipe material or, in absence of the appropriate documentation, chemical compatibility testing must be performed using a method acceptable to the Department.
2. Piping must have adequate structural strength to support the maximum static and dynamic loads and stresses that will be imposed by the overlying material, including the drainage layer, liners, waste material, and any equipment used in constructing and operation of the landfill. Specifications for the proposed leachate collection pipe network must be submitted in the engineering report.
C. Construction Requirement: Leachate collection pipes must be installed in accordance with the requirements of the approved engineering plans, reports, and specifications. The leachate collection pipe size, spacing and slope of at least one percent (1%) must be designed to ensure that the leachate head on the primary liner does not exceed one foot (1') at the expected flows from the drainage area, except during storm events.
D. Certification Requirements: The project engineer must include in the construction certification report a discussion of all quality assurance and quality control testing to ensure that the material is placed in accordance with requirements of the approved engineering plans, reports, and specifications. The testing procedures and protocols must be acceptable to the Department and submitted in accordance with § 2.1.6 of this Part. The results of all testing must be included in the construction certification report, including documentation of any failed test results, a description of the procedures used to correct the failed material, and any retesting performed.
2.2.10Geosynthetic Drainage Layers
A. Any geosynthetic drainage layers used in the secondary leachate collection and removal system of a landfill must be designed and constructed to have an equivalent hydraulic transmissivity to that of a one foot (1') sand layer with a minimum coefficient of permeability of 1 x 10-1 centimeters per second, and must comply with the following:
1. Materials Required: The hydraulic conductivity, transmissivity, and chemical and physical resistance of the geosynthetic material must not be adversely affected by waste placement or leachate generated by the landfill. Documentation must be submitted which demonstrates the chemical compatibility of the geosynthetic drainage layer material and the waste to be deposited, or chemical compatibility testing must be performed using a method acceptable to the Department. Documentation must also be submitted to ensure effective liquid removal throughout the active life of the facility, and that the maximum compressive load of the materials to be placed above the geosynthetic drainage layer does not impede transmissivity during the post-closure period.
2. Construction Requirements: The project engineer must ensure that the geosynthetic drainage layers are installed in accordance with the requirements of the approved engineering plans, reports, and specifications, and conform with the following requirements:
a. The geosynthetic drainage layer must be designed and constructed to effectively remove leachate from the landfill's secondary leachate collection and removal system.
b. The geosynthetic drainage layer must be installed in accordance with the procedure set forth in §§2.2.7(B)(2) through (6) and 2.2.7(B)(10) of this Part.
3. Certification Requirements: The project engineer must include in the construction certification report a summary of all quality assurance and quality control testing required in §2.2.10(A)(3) of this Part. The testing procedures and protocols must be acceptable to the Department and submitted in accordance with § 2.1.6 of this Part. The results of all testing must be included in the construction certification report, including documentation of any failed test results, a description of the procedures used to correct the failed material, and any testing performed.
a. The project engineer must certify the quality control testing according to the requirements of §2.2.7(C)(1) of this Part for any geosynthetic drainage materials. The project engineer must also certify that a hydraulic transmissivity test was performed on the geosynthetic drainage material at the maximum design compressive load on the materials to be used in the geosynthetic drainage layers. The test method must consider the physical properties of all the materials above and below the geosynthetic drainage material being tested.
b. Quality assurance testing as performed by the project engineer must adequately demonstrate that the material is placed in accordance with the requirements of the engineering plans, reports, and specifications.
2.2.11Filter Layer Criteria
A. The filter layer must be designed to prevent the migration of the 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.
1. For graded cohesionless soil filters - The granular soil material used as a filter must have not more than five percent (5%) by weight passing the No. 200 sieve and no soil particles larger than three inches (3") in any dimension.
2. Geosynthetic Filters: Geotextiles filter material must demonstrate that the hydraulic conductivity, and chemical and physical resistance, is not adversely affected by waste placement, any overlying material or leachate generated at the landfill. Geotextile filter openings must be sized in accordance with the following criteria which takes into consideration the soil found in layers located adjacent to the geotextile filter:

Click here to view image

a. The d85 is the soil particle size at which eighty-five percent (85%) of the particles are finer, and the d15 is the soil particle size at which fifteen percent (15%) of the particles are finer. The O95 is the apparent opening size of the geotextile at which ninety-five percent (95%) of the soil particles will pass. An apparent opening size test acceptable to the Department must be performed to demonstrate compliance with this criteria.
3. Construction Requirements: Both the soil filters and geotextiles filters must be installed in accordance with the approved engineering plans, reports, and specifications.
4. Certification Requirements: The project engineer must include in the construction certification report the results of all the required quality assurance and quality control testing performed. The testing procedures and protocols must be acceptable to the Department and submitted in accordance with § 2.1.6 of this Part.
2.2.12Final Cover System
A. The final cover must be designed to minimize infiltration of precipitation into the landfill after closure. It must operate with minimum maintenance and promote drainage from its surface while minimizing erosion. It must also be designed so that settling and subsidence are accommodated to minimize the potential for disruption of continuity and function of the final cover.
1. Bedding Layer Criteria: A bedding layer must be located directly below the barrier layer of the final cover system and above the compacted waste layer.
a. Materials required: The bedding layer for the final cover system must be free of organic material and consist of on-site soils or any select fill if approved by the Department. The bedding material must be free of particles greater than three inches (3") in any dimension.
b. Construction requirements: The bedding layer must be constructed and graded in accordance with the requirements of the approved engineering plans, reports, and specifications. The minimum thickness of the bedding layer must be six inches (6").
c. Certification requirements: The project engineer must include in the construction certification report the results of all the required quality assurance and quality control testing performed. The testing procedures and protocols must be acceptable to the Department, and submitted in accordance with § 2.1.6 of this Part.
2. Low Permeability Covers
a. Low permeability barrier soil covers: A low permeability barrier soil cover is a layer of low permeability soil constructed to minimize precipitation migration into the landfill.
(1) Materials required: A low permeability barrier soil cover must consist of materials having the same characteristics as those found in §2.2.6(A)(2) of this Part.
(2) Construction requirements: Low permeability barrier soil covers must be constructed in accordance with the requirements of §2.2.6(B) of this Part. The low permeability barrier soil cover must be placed on a slope of no less than five percent (5%) to promote positive drainage and at a maximum slope of thirty-three percent (33%) to minimize erosion.
(3) Certification requirements: Certification for the installation of barrier soil covers must be conducted in accordance with the requirements in § 2.1.6 of this Part.
b. Geomembrane covers: A geomembrane may be used as an alternative to the low permeability barrier soil cover as a final cover and must be constructed to preclude precipitation migration into the landfill.
(1) Materials required: The geomembrane material used in a final cover system must have a maximum coefficient of permeability of 1 x 10-12 centimeters per second, chemical, and physical resistance to materials it may come in contact with, and accommodate the expected forces and stresses caused by settlement of waste.
(2) Construction requirements: Geomembrane covers must be constructed in accordance with the same requirements as those found in §2.2.7 of this Part with the following exceptions: The geomembrane must have a minimum thickness of thirty-six (36) mils. Geomembrane consisting of high density polyethylene (HDPE) shall be at least sixty (60) mils thick. The geomembrane must be placed on a five percent (5%) minimum slope to promote gravity drainage and a thirty-three percent (33%) maximum slope to ensure stability of the capping system.
c. Certification requirements: Certification for the installation of a geomembrane cover must be conducted in accordance with the same conditions found in §2.2.7(C) of this Part.
3. Drainage Layer Criteria: All soil material used in the drainage layer of the final cover system must conform to the following requirements.
a. Materials required: Soil materials used to construct the drainage layer must be free of any organic material and have less than five percent (5%) of the material by weight pass the No. 200 sieve. Soil material testing must be performed in accordance with §2.2.8(C) of this Part.
b. Construction requirements: The soil drainage layer must be constructed and graded in accordance with the requirements of the approved engineering plans, report and specifications, along with the following requirements:
(1) The minimum thickness must be twelve inches (12") and have a minimum coefficient of permeability of 1 x 10-3 centimeters per second.
(2) The soil drainage layer must have a final bottom slope of at least five percent (5%) to allow for settling and subsidence.
(3) To prevent clogging, the soil drainage layer must be overlain by a graded granular or synthetic fabric filter that meets the specifications of §§2.2.11(A) through (D) of this Part.
(4) The soil drainage layer must be designed so that discharge flows freely in the lateral direction to minimize head on and flow through the low permeability layer.
c. Certification requirements: The drainage soil layer must be certified in accordance with the same conditions found in §§2.2.8(C)(1) and (2) of this Part.
4. Vegetated Top Cover: A vegetated top cover must be designed and constructed to maintain vegetative growth over the landfill.
a. Materials required: The vegetated layer must be suitable to maintain vegetative growth.
b. Construction requirements: The vegetated top cover must be constructed and graded in accordance with the following requirements:
(1) The vegetated top cover must be at least twelve inches (12") thick.
(2) It must support vegetation that will effectively minimize erosion without need for contingency application of fertilizers, irrigation, or other non-applied materials to ensure viability and persistence. (Fertilizers, water and other materials may be applied during the closure or post-closure period, if necessary, to establish vegetation or to repair damage).
(3) The vegetated top cover must be planted with persistent species that will effectively minimize erosion, and that do not have a root system that will penetrate beyond the vegetative and drainage layer.
(4) The final top slope must be, at a minimum, between three (3%) and five percent (5%) after allowing for settling and subsidence, and at a maximum slope of thirty-three percent (33%). For slopes exceeding five percent (5%), the maximum erosion rate should not exceed two (2) tons/acre/year using the USDA Universal Soil Loss Equation (USLE).
(5) The vegetated top cover must have a surface drainage system capable of conducting run-off across the cap without forming erosion rifts and gullies.
2.2.13 Construction Certification Report

A construction certification report must be submitted to the Department within forty-five (45) days after the completion of landfill construction. This report must include, at a minimum, the information prepared in accordance with the application requirements of § 2.1.6 of this Part containing results of all quality assurance and quality control testing required in this section, including documentation of any failed test results, descriptions of procedures used to correct the improperly installed material, and statements of all retesting performed. In addition, the construction certification report must contain as-built drawings noting any deviation from the approved engineering plans and must also contain a comprehensive analysis including, but not limited to, daily reports from the project engineer and a series of color photographs of major project features. The Department will review the submitted material for approval within thirty (30) days after receipt.

2.2.14 Equivalent Design

The applicant may propose an equivalent design to the individual components of the primary composite liner required in §2.2.3(D) of this Part by the submission in the application of documentation substantiating the alternative component's ability to perform in the same manner as the component specified in this section.

250 R.I. Code R. 250-RICR-140-05-2.2

Amended effective 1/3/2021