Chapter NR 504

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.

NR 504.07(4)(a)11. 11. Soil cover placement over the geosynthetics shall be completed in the same construction season as the geosynthetic construction.

NR 504.07(4)(a)12. 12. The soil barrier layer shall consist of fine-grained soil or a well graded sandy soil with fines, meeting the USCS soil types ML, CL, CH, SM, or SC or dual-symbol classifications of these soils, with at least 25% by weight passing the P200 sieve size. The upper one foot shall have a maximum particle size of 2 inches or less. The lower one foot shall have a maximum particle size of 4 inches or less.

NR 504.07(4)(a)13. 13. The soil barrier layer shall be compacted in lift heights of no greater than 12 inches after compaction using footed compaction equipment with feet at least 6 inches long. Each lift shall be disked or otherwise mechanically processed prior to compaction to break up clods and allow for moisture content adjustment. Clod size shall be no greater than 4 inches.

NR 504.07(4)(a)14. 14. A sufficient number of passes of the compaction equipment shall be made over each lift to ensure complete remolding of the soil. All compaction equipment utilized shall have a minimum static weight of 30,000 pounds. Compaction equipment with static weight that exceeds 15,000 pounds may be utilized when it utilizes vibration to achieve dynamic compaction that exceeds 30,000 pounds of compaction energy. Lighter equipment may be used in small areas where it is not possible to use full size equipment. Alternative procedures or equipment may be proposed for written approval by the department.

NR 504.07(4)(a)15. 15. All soil shall be compacted to 90% modified or 95% standard Proctor density or greater at a moisture content at or wet of optimum. As soil placement proceeds, the minimum density and moisture content targets shall be adjusted as necessary.

NR 504.07(4)(a)16. 16. Each lift shall be keyed into clay or soil barrier layer soils in adjacent phases to form a continuous seal. This shall be accomplished by excavating steps with a minimum width of 2 feet along the edge of the existing phase and overlapping them with lifts being placed for the new phase. A minimum of 2 steps shall be included.

NR 504.07(4)(a)17. 17. The surface of the top lift shall be graded or compacted to be smooth and firm and shall be inspected for removal of coarse gravel, cobbles and debris prior to placement of a GCL.

NR 504.07(4)(b) (b) For industrial solid waste landfills that predominantly accept compressible wastes or wastes with high water contents and low strength, the clay layer may be replaced by a GCL overlying a minimum of a one foot sand layer. The gradation of the sand layer shall be a uniform sand selected to vent gas, drain leachate and provide hydration water to the GCL.

NR 504.07(4)(c) (c) For industrial solid waste landfills that predominantly accept ash, the clay layer may be replaced by a GCL overlying a minimum of 2 feet of soil barrier layer. The soil barrier layer shall meet the requirements of par. (a) 13. to 17. The upper foot of soil barrier layer shall also meet the requirements of par. (a) 12. The lower foot shall be designed to provide a capillary break between the ash and the upper one foot of soil barrier layer.

NR 504.07(4)(d) (d) The lower one foot of the clay layer may be replaced with a minimum of one foot of foundry green sand system sand with a bentonite content of greater than 6%, a liquid limit of greater than 20, a plasticity index of greater than 6, and a hydraulic conductivity of less than 1x10-7 cm/sec. The green sand system sand shall be compacted to 90% modified or 95% standard Proctor density or greater at a moisture content at or wet of optimum.

NR 504.07(5) (5) Geomembrane layer. A geomembrane layer shall be designed to provide a low hydraulic conductivity barrier to percolation. The design and construction of the geomembrane component of the final cover system shall meet the requirements of s. NR 504.06 (3) (c) to (j) and the following:

NR 504.07(5)(a) (a) The nominal geomembrane thickness shall be 40 mils or greater, with no thickness measurements falling below industry accepted manufacturing tolerances.

NR 504.07(5)(b) (b) The geomembrane shall be installed in direct contact with the clay capping layer.

NR 504.07(5)(c) (c) Penetrations of the geomembrane, such as gas extraction wells, shall be fitted with prefabricated collars of pipe and membrane or plate and welded at the same angles which the penetrations make with the final cover slope. Methods of fixing membrane boots to vertical pipes extending above the geomembrane shall allow for differential settlement of the waste with respect to the piping without damage to the membrane seal.

NR 504.07(6) (6) Drainage and rooting zone layer. A minimum 2.5 foot thick drainage and rooting zone layer shall be designed above the geomembrane layer or clay capping layer. This layer shall include a rooting zone to provide additional rooting depth for vegetation and to protect the geomembrane layer or the clay capping layer from freeze-thaw damage and other environmental effects. It shall also include a drainage layer to allow for the drainage of liquid infiltrating through the cap. Soils available on or near the proposed landfill property may be proposed for the rooting zone portion of this layer. This layer may not be densely compacted.

NR 504.07(6)(a) (a) For all landfills, a drainage layer shall be designed immediately above the capping layer. The drainage layer shall consist of a minimum of one foot of sand with a minimum hydraulic conductivity of 1x10-3 cm/sec or a geosynthetic drain layer of equivalent or greater flow capacity. The design shall include an analysis which demonstrates whether the maximum head in the drain layer will be confined within the thickness of the drain. Drain calculations shall include infiltration rates based on saturated characteristics of the topsoil and rooting zone and a hydraulic gradient of one through the topsoil and rooting zone.

NR 504.07(6)(b) (b) A perimeter drain pipe shall be placed at the low end of all final cover sideslopes. The drain pipe shall be surrounded by a minimum of 6 inches of gravel or sand with a minimum hydraulic conductivity of 1x10-2 cm/sec. The drain pipe shall be sloped to a series of outlets at spacings no further than every 200 feet. Modeling may be submitted to the department which supports the proposal of a different spacing.

NR 504.07(7) (7) Topsoil. A minimum of 6 inches of topsoil shall be designed over the cover layer to support the proposed vegetation. Fertilizer and lime shall be added in accordance with section 629 of the latest edition of the department of transportation standard specifications for highway and structure construction or other appropriate specifications in order to establish a thick vegetative growth.

NR 504.07(8) (8) Revegetation. The landfill owner or operator shall propose the seed type and amount of fertilizer to be applied that is compatible with the type and quality of topsoil, the native vegetation, and the final use. Application rates for fertilizer and mulch shall also be specified. Unless otherwise approved by the department in writing, seed mixtures and sowing rates shall include one of the following:

NR 504.07(8)(a) (a) A grass seed mixture and sowing rates based on those specified for a highway right-of-way according to section 630 of the latest edition of the department of transportation standard specifications for highway and structure construction.

NR 504.07(8)(b) (b) A native seed mixture and sowing rates based on those specified for a highway right-of-way in table 630-2 of section 630 of the latest edition of the department of transportation standard specifications for highway and structure construction. A native seed mixture submittal shall, at a minimum, include all of the following information:

NR 504.07(8)(b)1. 1. The rate of application, method of application, and anticipated timeline for vegetation to become established enough to prevent erosion of the topsoil.

NR 504.07(8)(b)2. 2. The nurse crop, cover crop, and erosion control measures that will be used if the native vegetation is anticipated to take more than one year to become established.

NR 504.07(8)(b)3. 3. A maintenance plan for ensuring the health and viability of the native seed mix, including specific methods for preventing the establishment of woody vegetation and Wisconsin terrestrial invasive species and specifying that mowing for routine maintenance shall occur outside the primary nesting bird season of June 1 through August 31.

NR 504.07(8)(c) (c) An alternative native seed mixture that includes the scientific name of all species within the alternative native seed mixture and the information required under par. (b) 1. to 3. The alternative seed mixture may not include plant species that are considered a Wisconsin terrestrial invasive species or require burning as a maintenance practice.

NR 504.07 Note Note: The department of transportation standard specifications for highway and structure construction and any annual supplemental specifications are available at https://wisconsindot.gov/pages/doing-bus/eng-consultants/cnslt-rsrces/rdwy/stndspec.aspx or can be obtained from the department of natural resources, bureau of waste management, P.O. Box 7921, Madison, WI 53707-7921, [e-mail]. Copies are also available for inspection at the office of the legislative reference bureau.

NR 504.07(9) (9) Final use. The proposed final use shall be compatible with the final cover system. The following activities are prohibited at solid waste disposal landfills which are no longer in operation unless specifically approved by the department in writing.

NR 504.07(9)(a) (a) Use of the waste disposal area for agricultural purposes.

NR 504.07(9)(b) (b) Establishment or construction of any buildings over the waste disposal area.

NR 504.07(9)(c) (c) Excavation or disturbance of the final cover or any waste materials.

NR 504.07 History History: Cr. Register, January, 1988, No. 385, eff. 2-6-88; am. (1) (a), (b), (2), cr. (1) (c), (d), (5), (6) (a), (b), r. and recr. (3), (4), r. (5) (a) to (c), renum. (5) to (8) to be (6) to (9) and am. (6) (intro.), (7), (9) (intro.), (a), (b), Register, June, 1996, No. 486, eff. 7-1-96; CR 04-077: am. (6) (a) Register November 2005 No. 599, eff. 12-1-05; CR 05-020: r. and recr. (4), am. (8) Register January 2006 No. 601, eff. 2-1-06; CR 24-063: am. (1) (b), (c), (4) (a) 14., (7), renum. (8) to (8) (intro.) and am., cr. (8) (a) to (c), am. (9) (c) Register September 2025 No. 837, eff. 10-1-25; correction in (8) (c) made under s. 35.17, Stats., Register September 2025 No. 837.

NR 504.073 NR 504.073 Alternative final cover design for municipal solid waste landfills. All new municipal solid waste landfills and expansions of existing municipal solid waste landfills shall meet all of the requirements under s. NR 504.07 unless the owner demonstrates to the satisfaction of the department that the final cover system is designed to adequately protect public health, welfare, and the environment and meets all of the following criteria:

NR 504.073(1) (1) Design.

NR 504.073(1)(a) (a) The final cover system shall include a grading layer meeting all of the requirements under s. NR 504.07 (2).

NR 504.073(1)(b) (b) The permeability of the final cover system shall be no greater than the permeability of the landfill’s liner system or 1 x 10-7 cm/second, whichever is lower.

NR 504.073(1)(c) (c) The final cover system shall include a layer that achieves an equivalent reduction in infiltration as the layers specified under s. NR 504.07 (4).

NR 504.073(1)(d) (d) The disruption of the integrity of the final cover system shall be minimized through a design that accommodates settling and subsidence.

NR 504.073(1)(e) (e) The final cover system shall include an erosion-prevention layer that provides equivalent protection from wind or water erosion as the topsoil layer and vegetation specified under s. NR 504.07 (7) and (8).

NR 504.073(1)(f) (f) The final cover system shall meet the requirements of s. NR 504.07 (9).

NR 504.073(2) (2) Submittal. The owner or operator of a landfill may propose an alternative final cover design in the feasibility report required under ch. NR 512 or as a modification to an existing plan of operation. Plan modification submittals shall adhere to the following schedule: