Chapter NR 504

NR 504.06(5) (5) Leachate collection systems. All leachate collection systems shall incorporate the following design features:

NR 504.06(5)(a) (a) A leachate collection system shall be included in each horizontal phase of the landfill. This system shall be designed to route leachate to the perimeter of the landfill in the most direct manner possible and limit the leachate head level on the liner to one foot or less. The piping layout shall be such that leachate flows no more than 130 feet across the base of the liner before encountering a perforated leachate collection pipe. The department will consider greater flow distances for composite-lined landfills that have a slope of the liner surface greater than the minimum slope required under sub. (2) (d).

NR 504.06(5)(b) (b) The minimum slope on all leachate collection pipes at the base of the landfill shall be a constant 0.5%. The department recommends that greater pipe slopes be utilized whenever possible.

NR 504.06(5)(c) (c) The minimum inside diameter of all leachate collection or transfer pipes shall be 6 inches. Unless otherwise approved by the department in writing, schedule 80 PVC pipe or HDPE pipe shall be used.

NR 504.06(5)(cm) (cm) Pipe fittings selected for use with PVC and HDPE pipe shall be secured to the leachate collection pipe. PVC fittings and pipe shall be solvent-welded. HDPE fittings and pipe shall be fusion welded.

NR 504.06(5)(d) (d) Leachate collection trenches for clay liners shall be designed as rectangular trenches. Leachate collection trenches for composite liners shall be designed as vee-trenches, with a minimum depth of 18 inches and with sideslopes no steeper than 3 horizontal to one vertical. The clay component of vee-trenches shall be smooth-drum rolled such that the clay in the trenches is smooth prior to placement of the membrane.

NR 504.06(5)(dm) (dm) A geotextile shall be used to line the base and sidewalls of all leachate collection trenches and shall be placed directly over the geomembrane component of a composite liner or the clay component of a clay liner. Unless otherwise approved by the department in writing, the geotextile shall have a minimum weight of 16 oz/yd2, and may not be overlapped over the top of the trench. The geotextile specifications, including manufacturer’s data for grab and puncture strength, shall be used to demonstrate that the geotextile can resist damage due to impact and puncture when aggregate is placed over the geotextile.

NR 504.06(5)(e) (e) The bedding material utilized in backfilling the leachate collection pipe trenches shall have a uniformity coefficient of less than 4, a maximum particle diameter of 1.5 inches, and a maximum of 5 percent of the material that passes the number 4 sieve, and shall consist of rounded to subangular gravel. A minimum depth of 4 inches of gravel shall be placed in the trenches prior to installation of the leachate pipes. The backfill shall also be placed such that a minimum of 6 inches of material exists above the top of the pipe and within the trenches. An additional 12 inches of material shall be mounded above the trench. In cases when the particle size of the drainage blanket is significantly less than the collection trench bedding, a properly designed graded soil filter or geotextile shall be utilized to minimize the migration of the drainage blanket material into the collection trenches. Limestone and dolomite may not be used in the leachate collection system unless no other suitable material is reasonably available.

NR 504.06(5)(f) (f) The sizing of sand, gravel, geotextiles and pipe openings shall be analyzed for control of piping of soil materials. The gradation of sand and gravel, the apparent opening size of geotextiles, and the pipe opening sizes shall be selected to achieve a stable and self-filtering structure under all conditions of leachate flow.

NR 504.06(5)(g) (g) All leachate collection lines shall have cleanout access points installed on both ends of each line and may not exceed 1,200 feet from the end of one cleanout to the toe of the opposite slope.

NR 504.06(5)(h) (h) Leachate lines, manholes and other engineering structures may not penetrate the liner in the vertical direction. For clay lined landfills, leachate transfer lines may penetrate the liner in the horizontal direction only. The number of liner penetrations shall be kept to a minimum. Composite lined landfills shall be designed without any perforations in the liner and in accordance with par. (j).

NR 504.06(5)(i) (i) Any leachate line that penetrates a clay liner shall have a 4 foot by 4 foot anti-seep collar placed around it. A minimum of 5 feet of compacted clay, as measured from the pipe, shall be placed around the collar in all directions.

NR 504.06(5)(j) (j) All composite lined landfills shall be designed and constructed with sumps and sideslope risers as part of their leachate removal system rather than utilizing systems which penetrate the composite liner sidewall. The leachate removal system shall meet the following requirements:

NR 504.06(5)(j)1. 1. The volume of the sump and the capacity of the pump shall be sized so that accumulation of leachate outside the sump does not occur based on an assumed annual leachate collection rate of 6 inches. The volume of the sump shall take into account the potential buildup of solids over time.

NR 504.06(5)(j)2. 2. The base of the leachate collection sumps shall be protected by the use of a thick polyethylene plate or other means acceptable to the department which is placed prior to the installation of the sideslope riser and backfill.

NR 504.06(5)(j)3. 3. The leachate discharge pipes between the sideslope risers and collection tank shall be equipped with valves to prevent backflow into the waste disposal area.

NR 504.06(5)(j)4. 4. The minimum diameter of the sideslope riser shall be 18 inches. The geometry of the sideslope riser at the junction of the sump and sidewall shall be selected to assure passage of the pump and associated hardware and to assure correct positioning of the intake of the pump.

NR 504.06(5)(j)5. 5. The area of the sump and depth of gravel fill shall be sized to allow remedial installation of access and hardware for removal of leachate in the event of failure of the sideslope riser and pump system. The base of the sump shall be protected by polyethylene plate.

NR 504.06(5)(k) (k) All leachate lines transporting leachate out of the landfill by gravity shall be constructed with valves so the flow of leachate can be controlled. The valves shall be compatible with the leachate and be capable of being operated from the ground surface.

NR 504.06(5)(L) (L) All leachate transfer lines located outside of the composite lined or clay lined area shall be designed to assure groundwater protection through the use of double-cased pipe or by using another approved secondary containment method. All leachate transfer line piping shall be pressure tested prior to use. Unless otherwise approved by the department, the upslope end of the secondary pipe shall be sealed and the downslope end shall be open to allow any collected liquid to flow into the manhole.

NR 504.06(5)(m) (m) All leachate transfer lines, manholes, lift stations and other structures which transfer or store leachate outside the limits of waste shall be designed as shallow as practical and located far enough from the limits of filling so that excavations associated with repair of these devices would not infringe on the landfill cover system or sidewall liner. Each of these devices shall be constructed above the seasonal high groundwater table unless it is not technically feasible to do so and the design meets the requirements of par. (L).

NR 504.06(5)(n) (n) Leachate collection tanks and manholes shall be designed with a secondary containment system to prevent the discharge of leachate to ground and surface waters in the event of a leak or spill. Means shall be provided to monitor the tank and manholes within the secondary containment system unless other means for leak detection are approved by the department.

NR 504.06(5)(o) (o) All leachate collection tanks shall be designed to contain the volume of leachate which is generated by the landfill over a 4 day period and to withstand the soil and liquid loads that will be encountered during installation and use. The installation of the tanks shall follow the recommendations of the consultant and manufacturer.

NR 504.06(5)(p) (p) Measures shall be proposed to prevent accidental discharges at the leachate loadout station from entering groundwater or surface water. Unless an alternate method is approved by the department, the leachate loading station shall be paved with a concrete or asphalt pad and sloped to a catch basin to direct all spills back into the leachate holding tank.

NR 504.06(5)(q) (q) All manholes and enclosed structures for leachate and gas control systems shall be designed to allow for proper venting and access control. For landfills designed with active gas extraction systems, these devices shall be designed to minimize air intrusion into the landfill.

NR 504.06(5)(r) (r) All control systems such as pumps, valves and meters shall be designed to be operated from the ground surface.

NR 504.06(5)(s) (s) All leachate and groundwater collection systems shall be designed to accurately monitor the volume of liquid removed by the system.

NR 504.06(5)(t) (t) A minimum one-foot thick granular drainage blanket shall be placed on top of the geomembrane component of a composite liner and on top of the clay component of a clay liner. For composite-lined landfills, if the drainage blanket contains gravel greater than 0.25 inch, then a nonwoven geotextile shall be installed below the drainage blanket. Unless otherwise approved by the department in writing, the geotextile shall have a minimum weight of 16 oz/yd2 and shall be certified to be needle-free. The granular drainage blanket shall contain no more than 5 percent material by weight that passes the number 200 sieve.

NR 504.06(5)(tm) (tm) Leachate collection blankets shall have a minimum hydraulic conductivity of 1 cm/sec for any site that accepts any amount of municipal solid waste and 1x10-2 cm/sec for landfills which do not accept municipal solid waste. The gradation of the granular drainage blanket and associated hydraulic conductivity shall be selected to maintain the maximum head in the drain within the drain thickness.

NR 504.06(5)(u) (u) All major horizontal clay lined phases above the saturated zone shall be designed with a collection basin lysimeter to monitor the unsaturated zone except for composite lined landfills.

NR 504.06(6) (6) Additional requirements for landfills with extended collection lines.

NR 504.06(6)(a) (a) Landfills shall meet the requirements of pars. (b) to (f) where they will accept municipal solid waste and contain leachate collection lines that exceed 1,200 feet from the end of each cleanout to the toe of the opposite slope. Where the requirements of this subsection differ from other requirements of this chapter, these requirements shall take precedence.

NR 504.06(6)(b) (b) The maximum length of leachate collection lines from the access point at one end to the toe of the opposite slope may not exceed 2,000 feet.

NR 504.06(6)(c) (c) The minimum slope on all leachate collection pipes and associated pipe trenches at the base of the landfill shall be designed and constructed to be 0.5% after accounting for primary and secondary settlement of the subgrade. The minimum design slope shall be selected following computation of 100% of the primary consolidation settlement and the secondary consolidation settlement of the compressible materials beneath the facility, which includes, as applicable, in-situ soil, added geologic material, structural fill material, and compacted clay liner. Secondary settlement shall be calculated using a 100-year time frame.

NR 504.06(6)(d) (d) Pipe bedding material shall be composed of coarse, uniform gravel with a hydraulic conductivity that is greater than or equal to the hydraulic conductivity of the leachate collection blanket specified in s. NR 504.06 (5) (tm), in addition to meeting the other requirements of s. NR 504.06 (5) (e).

NR 504.06(6)(e) (e) The maximum anticipated construction, operation and post-closure overburden loads over the leachate collection piping shall be calculated and utilized in selecting the pipe material and wall thickness, based on 6-inch pipe diameter and an appropriate in-field consolidated density.

NR 504.06(6)(f) (f) All components of the leachate collection system shall incorporate all of the following design features:

NR 504.06(6)(f)1. 1. Sweep bends at all changes of alignment, using a minimum radius of 10 pipe diameters, consisting of prefabricated PVC sweep bends or smooth pipe bends or prefabricated sweep bends for HDPE or other pipe materials.

NR 504.06(6)(f)2. 2. Pipe alignments that minimize horizontal and vertical alignment changes for the entire leachate collection pipe length.

NR 504.06(6)(f)3. 3. Elimination or minimization of obstructions or artifacts of construction which impose drag on pipe cleaning jetter hose or nozzles.

NR 504.06(7) (7) Composite-lined landfills using GCLs. Use of GCLs in construction of a composite liner may not be used except in landfills which do not accept municipal solid waste, unless the GCL is used as a pad for the upper surface of the 4 foot clay component of a composite liner for a municipal solid waste landfill. The GCL and soil barrier layer components of a barrier system shall meet all of the following requirements:

NR 504.06(7)(a) (a) The hydraulic performance of the GCL shall be assessed by the use of compatibility testing. The testing protocol shall be provided to the department for review and concurrence prior to the initiation of compatibility testing. The compatibility testing shall utilize percolation fluids that simulate the leachate that will be produced by the landfill.

NR 504.06(7)(b) (b) The GCL shall meet the specifications of s. NR 504.07 (4) (a) 1. to 11.

NR 504.06(7)(c) (c) The GCL shall be underlain by a soil barrier layer that is a minimum of 2 feet thick and that meets the specifications of s. NR 504.07 (4) (a) 12. to 17.

NR 504.06 History History: Cr. Register, January, 1988, No. 385, eff. 2-6-88; r. and recr., Register, June, 1996, No. 486, eff. 7-1-96; am. (5) (e) and (t), Register, August, 1997, No. 500; CR 04-077: cr. (5) (cm), (dm), (j) 4., 5., (tm) and (6), am. (5) (d), (e), and (t) Register November 2005 No. 599, eff. 12-1-05; CR 05-020: cr. (7) Register January 2006 No. 601, eff. 2-1-06; correction made under s. 13.93 (2m) (b) 1., Stats., Register January 2006 No. 601; CR 06-026: am. (5) (dm) and (e), Register December 2006 No. 612, eff. 1-1-07; CR 24-063: am. (1) (a), r. (2) (b), (c), am. (2) (f) 1., cr. (2m), am. (3) (e), (5) (a), (c), (dm), (e), (q), (t) Register September 2025 No. 837, eff. 10-1-25; correction in (1) (a), (2m) (a), (5) (a) made under s. 35.17, Stats., Register September 2025 No. 837.

NR 504.065 NR 504.065 Alternative composite landfill liner design.

NR 504.065(1) (1) An applicant may propose an alternative to the liner design requirements under s. NR 504.06 (2) if the landfill meets the requirements of s. NR 504.06 (2m) and either s. NR 504.06 (3) or (4).

NR 504.065(2) (2) The proposed alternative liner shall consist of, from bottom to top, a prepared soil sub-base component, a clay layer component, and a nominal 60 mil or thicker geomembrane liner component. The design of the proposed alternative shall meet all of the following requirements:

NR 504.065(2)(a) (a) The prepared soil sub-base component of the liner shall meet all of the following requirements:

NR 504.065(2)(a)1. 1. Maintain a minimum thickness of one foot at all locations.

NR 504.065(2)(a)2. 2. Consist of a soil having a hydraulic conductivity of 1x10-6 cm/sec or less with a maximum particle size of 4 inches.

NR 504.065(2)(a)3. 3. A sufficient number of passes of the compaction equipment shall be made over each lift during construction to ensure complete remolding of the soil. All compaction equipment used to construct the prepared soil sub-base shall have a minimum static weight of 30,000 pounds. The prepared sub-base soil shall be constructed to prevent mixing the soil with other in-situ sub-base soil or with underdrain system soil and may be constructed in a single one-foot lift.

NR 504.065(2)(a)4. 4. All sub-base soil shall be compacted to 90 percent modified or 95 percent standard Proctor density at a moisture content at least 2 percent wet of optimum if using the modified Proctor method and wet of optimum if using the standard Proctor method, based on the characteristics of the appropriate Proctor curve for the soil being placed. As soil placement proceeds, the minimum density and moisture content targets shall be adjusted as necessary.

NR 504.065(2)(a)5. 5. If the native in-situ soils meet the requirements of subds. 1. and 2., and the design does not include an underdrain system, the native in-situ soils may be used as the prepared sub-base component in the alternative liner design.

NR 504.065(2)(b) (b) The clay component of the alternative liner shall meet all of the following requirements:

NR 504.065(2)(b)1. 1. All clay used in liner construction shall meet the specifications of s. NR 504.06 (2) (a).

NR 504.065(2)(b)2. 2. The minimum thickness of the clay component at the base of the landfill shall be at least 3 feet, except as provided under subds. 3. and 4.

NR 504.065(2)(b)3. 3. The minimum thickness of the clay component of the sloped interior sidewalls of the landfill shall be at least 2 feet.

NR 504.065(2)(b)4. 4. The minimum thickness of the clay component of the leachate collection sump required by s. NR 504.06 (5) (j) shall be at least 4 feet at the bottom and all sides of the sump up to the top of the sump.

NR 504.065(2)(b)5. 5. The clay component of the liner shall be constructed as required by s. NR 504.06 (2) (d) and (f).

NR 504.065(2)(c) (c) The geomembrane component shall meet the requirements of s. NR 504.06 (3).

NR 504.065(2)(d) (d) The leachate collection system shall be designed as required by s. NR 504.06 (5), except that all leachate collection or transfer pipes shall have a minimum 6-inch inside diameter.

NR 504.065(2)(e) (e) In addition to the leachate collection system required in par. (d), a minimum 6-inch inside diameter perforated leachate collection pipe shall be placed at the toe of the 3 horizontal to one vertical interior sidewalls of the landfill with cleanout access as required by s. NR 504.06 (5) (g).

NR 504.065(3) (3) An owner or operator of a landfill proposing an alternative liner design that uses native in-situ soils as the prepared sub-base component and does not include an underdrain system shall investigate subsoils on a 100-foot grid to a minimum depth of 2 feet below the sub-base grades of the liner to determine the degree and extent of sand seams, peat, or other unsuitable soils. All sand seams, peat, or other unsuitable soils found as a result of the investigation or encountered during construction shall be removed and replaced with compacted soil meeting the requirements of sub. (2) (a) 2., 3., and 4., provided the landfill is not a zone-of-saturation design. If the proposed landfill is a zone-of-saturation design, then the owner or operator shall investigate subsoils and replacement as specified in s. NR 504.06 (4) (d) with the replacement of soil in the upper 2 feet also meeting the requirements of sub. (2) (a) 2., 3., and 4.

NR 504.065(4) (4) In accordance with this section, the owner or operator of a landfill may propose an alternative liner system design in the feasibility report required under ch. NR 512 or as a modification to an existing plan of operation. This plan modification request may not increase the approved design capacity of the landfill or change the limits of filling. Plan modification submittals shall adhere to the following schedule:

NR 504.065(4)(a) (a) An owner or operator intending to construct a liner in 2026 may submit a plan modification in 2025.

NR 504.065(4)(b) (b) An owner or operator intending to construct a liner in 2027 may submit a plan modification in 2026.

NR 504.065(4)(c) (c) An owner or operator intending to construct a liner during or after 2028 may submit a plan modification during or after 2027.

NR 504.065 History History: CR 24-063: cr. Register September 2025 No. 837, eff. 10-1-25; correction in (1), (2) (intro.), (a) (intro.), (b) (intro.) made under s. 35.17, Stats., Register September 2025 No. 837.

NR 504.07 NR 504.07 Minimum design and construction criteria for final cover systems.

NR 504.07(1) (1) General.

NR 504.07(1)(a) (a) All final cover systems shall be designed to minimize leachate generation by limiting the amount of percolation through the cap system, reduce landfill maintenance by stabilizing the final surface through design of compatible slopes and establishment of vegetation, account for differential settlement and other stresses on the capping layer, minimize the climatic effects of freeze-thaw and desiccation on the clay capping layer of the final cover system, and provide removal of leachate and venting of gas from those landfills which accept wastes with a high moisture content or which readily biodegrade.

NR 504.07(1)(b) (b) All new landfills and expansions of existing landfills shall be designed with a final cover system meeting the requirements in subs. (2) to (9) unless it is established to the satisfaction of the department that portions of the final cover system are not needed based on the proposed waste types and the proposed design or if the final cover system is for a municipal solid waste landfill and meets all requirements under s. NR 504.073. The geomembrane component in sub. (5) does not apply to landfills designed exclusively for the disposal of high-volume industrial waste, or to other landfills that are not designed to accept municipal solid waste unless the landfill is composite-lined.

NR 504.07(1)(c) (c) Any phases of an existing landfill that have been designed and constructed with a composite liner shall be designed and constructed with a final cover system meeting the requirements under subs. (2) to (9).

NR 504.07(1)(d) (d) Landfills which accept papermill sludges or other industrial solid wastes with high water contents and low strength may propose alternate final cover systems if the strength of the waste mass will not allow for the construction of the cover system required in this section.

NR 504.07(2) (2) Grading layer. A minimum 6 inch thick grading layer shall be designed over the final waste elevation of landfills proposing to accept municipal solid waste to attain the required slope and provide for a stable base for subsequent system components. Daily and intermediate cover may be used for this purpose.

NR 504.07(3) (3) Support layer for low-strength wastes. A support layer shall be designed for stabilization, reinforcement and removal of leachate and gas over the final waste elevations for landfills which accept industrial solid wastes with high water contents and low strength.

NR 504.07(4) (4) Clay capping layer. A minimum 2 foot thick clay cap shall be designed to provide a low hydraulic conductivity barrier to percolation. Clay used for this layer shall meet the specifications in s. NR 504.06 (2) (a). The clay capping layer shall be constructed according to s. NR 504.06 (2) (f). Final cover systems that are required to include a geomembrane layer may be designed with the following alternatives to the clay component of the composite capping layer:

NR 504.07(4)(a) (a) The clay component of the capping layer may be replaced by a GCL overlying a minimum of 2 feet of soil barrier layer. This GCL layer and the soil barrier layer shall meet the following material and construction specifications:

NR 504.07(4)(a)1. 1. The GCL shall consist of a layer of sodium bentonite clay encapsulated between 2 geotextiles.

NR 504.07(4)(a)2. 2. The GCL shall be covered with a geomembrane the same day that it is unpacked and placed in position. The GCL may not be installed in standing water or during rain. The GCL shall be dry when installed and covered. A GCL exhibiting unconfined swelling shall be removed and replaced.

NR 504.07(4)(a)3. 3. The GCL shall be installed in a relaxed condition and shall be free of tension or stress upon completion of the installation. The GCL may not be stretched to fit.

NR 504.07(4)(a)4. 4. Adjoining panels of a GCL shall be laid with a minimum of 6 inches of overlap on the longitudinal seams and a minimum 20 inches of overlap on the panel end seams.

NR 504.07(4)(a)5. 5. Irregular shapes, cuts or tears in the installed GCL shall be covered with a GCL patch that provides a minimum 12 inch overlap onto adjacent GCL surfaces.

NR 504.07(4)(a)6. 6. A seal of loose bentonite granules shall be placed in seam overlaps at a minimum rate of one quarter pound per linear foot of seam for all panel end seams and longitudinal seams. The seal of loose bentonite may be deleted, with concurrence by the department, for longitudinal seams where the manufacturer has processed the overlap area to enhance sealing. The seal may not be deleted for any longitudinal seams that are transitions between construction phases.

NR 504.07(4)(a)7. 7. Loose bentonite or bentonite amended soil shall be placed at all patches and penetrations.

NR 504.07(4)(a)8. 8. GCL panels shall be certified needle-free through magnetic and metal detection tests.

NR 504.07(4)(a)9. 9. The GCL shall be placed in direct contact with a soil barrier layer.

NR 504.07(4)(a)10. 10. Vehicle traffic on the subgrade of the GCL and on the GCL shall be restricted to the minimum weight and number of machines needed to deploy the GCL and geomembrane. Vehicles shall be operated to minimize the formation of ruts and surface deformations and to prevent damage to the GCL and geomembrane. Deployment methods shall be selected to prevent any tearing or combing out of fibers of the GCL.