Alternative composite landfill liner design

Alternative composite landfill liner design. (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) . (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: (a) The prepared soil sub-base component of the liner shall meet all of the following requirements: 1. Maintain a minimum thickness of one foot at all locations. 2. Consist of a soil having a hydraulic conductivity of 1x10 -6 cm/sec or less with a maximum particle size of 4 inches. 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. 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. 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. (b) The clay component of the alternative liner shall meet all of the following requirements: 1. All clay used in liner construction shall meet the specifications of s. NR 504.06 (2) (a) . 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. 3. The minimum thickness of the clay component of the sloped interior sidewalls of the landfill shall be at least 2 feet. 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. 5. The clay component of the liner shall be constructed as required by s. NR 504.06 (2) (d) and (f) . (c) The geomembrane component shall meet the requirements of s. NR 504.06 (3) . (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. (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) . (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. (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: (a) An owner or operator intending to construct a liner in 2026 may submit a plan modification in 2025. (b) An owner or operator intending to construct a liner in 2027 may submit a plan modification in 2026. (c) An owner or operator intending to construct a liner during or after 2028 may submit a plan modification during or after 2027.