Chapter NR 538

NR 538.03(8)(c)3. 3. Slag generated by the production or processing of iron or steel that is managed as an item of value in a controlled manner and not discarded.

NR 538.03(8)(c)4. 4. Material that was previously disposed or landfilled.

NR 538.03 Note Note: Materials excluded from the definition of industrial byproducts may be beneficially reused if approved in writing by the department under s. NR 500.08 (5) (a) and s. 289.43, Stats., except iron or steel foundry slag which is exempted under ss. 289.01(33) and 287.29, Stats.

NR 538.03(9) (9) “Lime kiln dust” means the material recovered from air pollution control systems that capture emissions from lime kilns.

NR 538.03(10) (10) “Productive manner” means the use of an industrial byproduct that meets all of the following criteria:

NR 538.03(10)(a) (a) Provides a functional benefit.

NR 538.03(10)(b) (b) Substitutes for the use of a virgin material that must be otherwise obtained.

NR 538.03(10)(c) (c) Meets relevant product specifications, regulatory standards or design standards when available, and, when such standards are not available, is not used in excess quantities.

NR 538.03(11) (11) “Representative sample” means any sample of industrial byproduct material collected for analysis that reliably exhibits the average properties of the byproduct production stream.

NR 538.03(12) (12) “Residential area” means properties that are in an area zoned as residential, are in an area planned for residential zoning under a master plan approved or adopted by a local municipal authority, or in an area within 100 feet of a human residence.

NR 538.03(12m) (12m) “Select foundry sand” means foundry sand, as defined under sub. (6), that is comprised of either spent green molding sand, resin bonded molding sand, or core sand with primary components consisting of combinations of silica sand, bentonite clay, and carbonaceous additives such as bituminous coal, gilsonite, and cellulose. “Select foundry sand” may include nominal quantities of spent molding aides such as riser sleeves and ceramic filters but may not include uncured chemically bonded sands or debris beyond trace quantities. “Select foundry sand” must also have been determined to contain less than the concentration specified for the parameters listed in ch. NR 538 Appendix, Table 1, Column B to meet this definition.

NR 538.03(13) (13) “Soil or plant additive” means a substance, intended for application to seeds, soil, or plants, that is designed for use or claimed to have value in promoting or sustaining plant growth, improving crop yield or quality, promoting or sustaining the fertility of the soil, or favorably modifying the structural, physical, or biological properties of the soil for agronomic or horticultural purposes and used in accordance with subch. III of ch. ATCP 40 or ch. ATCP 41.

NR 538.03(14) (14) “Subgrade” means the uppermost soil bearing surface upon which base aggregates are placed.

NR 538.03(15) (15) “Subgrade fill” means the layer or layers of industrial byproduct material placed to achieve a subgrade.

NR 538.03(16) (16) “Topsoil” has the meaning given in s. NR 500.03 (236).

NR 538.03 History History: Cr. Register, December, 1997, No. 504, eff. 1-1-98; CR 05-020: renum. (2) to (6) to be (4) and (6) to (9) and am. (4) and (6), cr. (2), (3), (5) and (10) Register January 2006 No. 601, eff. 2-1-06; CR 19-080: r. and recr. Register May 2020 No. 773, eff. 11-1-20; correction in (12m) made under s. 35.17, Stats., Register May 2020 No. 773.

NR 538.04 NR 538.04 Performance standards. No person may store, handle or beneficially use an industrial byproduct in a manner that may cause any of the following:

NR 538.04(1) (1) A significant adverse impact on wetland water quality standards as provided under ch. NR 103.

NR 538.04(2) (2) A take of an endangered or threatened species or other activity prohibited under s. 29.604, Stats.

NR 538.04(3) (3) A detrimental effect on any surface water quality standard as provided in s. NR 102.03 (7).

NR 538.04(4) (4) A detrimental effect on groundwater quality or will cause or exacerbate an attainment or exceedance of any preventive action limit or enforcement standard at a point of standards application as defined in ch. NR 140.

NR 538.04(5) (5) The migration and concentration of explosive gases in any structures, or in the soils or air at or beyond the project property boundary in excess of 25% of the lower explosive limit for the gases at any time.

NR 538.04(6) (6) The emissions of any hazardous air contaminant exceeding the limitations for those substances contained in s. NR 445.03.

NR 538.04 Note Note: The emissions of particulates and volatile organic compounds are regulated under s. NR 415.03 and chs. NR 419 to 424.

NR 538.04(7) (7) A discharge of pollutants carried by storm water exceeding any applicable permit requirements or standards under ch. NR 216.

NR 538.04 Note Note: The placement of materials in a floodplain where an obstruction to flood flows or an increase in regional flood event or an adverse affect upon a drainage course is regulated under ch. NR 116.

NR 538.04 History History: Cr. Register, December, 1997, No. 504, eff. 1-1-98; CR 05-020: am. (2) Register January 2006 No. 601, eff. 2-1-06; CR 19-080: am. (1), (3), cr. (7) Register May 2020 No. 773, eff. 11-1-20.

NR 538.05 NR 538.05 Solid waste rules exemption.

NR 538.05(1) (1) General. Persons who generate, use, transport, or store industrial byproducts that are characterized and beneficially used in compliance with this chapter are exempt from licensing under s. 289.31, Stats., and the regulatory requirements in chs. NR 500 to 528.

NR 538.05(2) (2) Existing exemptions. This chapter does not abrogate, rescind or terminate an approval or grant of exemption that was issued under s. 289.43 (7) or (8), Stats. Nothing in this subsection limits the authority of the department to modify, terminate or rescind any approval or grant of exemption as provided by law.

NR 538.05 History History: Cr. Register, December, 1997, No. 504, eff. 1-1-98; correction in (1) made under s. 13.92 (4) (b) 7., Stats., Register February 2010 No. 650; CR 19-080: am. Register May 2020 No. 773, eff. 11-1-20.

NR 538.06 NR 538.06 Industrial byproduct characterization.

NR 538.06(1) (1) General.

NR 538.06(1)(a) (a) Industrial byproducts that are beneficially used under this chapter shall be characterized, as specified in this section, to determine their eligible uses under s. NR 538.10. A generator, or the generator’s designee, shall report the results of this characterization to the department as specified in s. NR 538.14 (1). The department shall reply with a written concurrence within 10 business days provided the applicant meets the applicable criteria of this chapter. The department has the option of concurring with the characterization, requesting additional information or analysis, determining that a case-specific approval under s. NR 538.09 is required, or issuing a non-concurrence decision. If the department does not respond to a certification request within 10 business days, the certification is deemed complete and concurrence is considered granted. The department may approve eligible uses for industrial byproducts that do not meet the listed characterization criteria on a case-specific basis in accordance with s. NR 538.09.

NR 538.06(1)(b) (b) For those materials not explicitly listed in, and which are subject to the requirements of the “Other” materials column of ch. NR 538 Appendix Tables 1 and 2, the department may do any of the following:

NR 538.06(1)(b)1. 1. Exempt the requirement to analyze for certain parameters on a material-specific basis.

NR 538.06(1)(b)2. 2. Require analysis for additional parameters on a material-specific basis in order to demonstrate compliance with performance standards identified at s. NR 538.04.

NR 538.06(1)(b)3. 3. Require the applicant submit a testing program plan, which the department must approve in writing prior to commencement of characterization.

NR 538.06(2) (2) Initial characterization. A representative sample of each industrial byproduct shall be properly characterized prior to beneficial use to determine its eligible uses under s. NR 538.10. Samples shall be obtained at the point of accumulation nearest to where the byproduct is generated. A case-specific approval under s. NR 538.09 may be required by the department if the byproduct is subject to any deliberate post-accumulation processing, excluding mechanical size reduction or sorting and the application of water to improve handling or as dust suppression.

NR 538.06(3) (3) Characterization methods.

NR 538.06(3)(a) (a) General. The limits of detection used in the characterization shall be at or below the concentrations listed in ch. NR 538 Appendix, Tables 1 to 3 for each parameter. When a limit of detection at or below a standard is not achievable, the method that will achieve the lowest detection limit shall be used. All material sampling, total elemental analyses, and analyses of elutriate from leach testing shall be performed using EPA SW-846 methods, unless alternate methods are otherwise approved by the department in writing. The generator shall report the limit of detection and the limit of quantitation with the sample results. If a substance is detected below the limit of quantitation, the detected value with the appropriate qualifier shall be reported.

NR 538.06(3)(b) (b) Hazardous waste determination. All industrial byproducts that are to be beneficially used under this chapter shall first be determined not to be a hazardous waste, as defined under s. NR 660.10 (52), using a method specified under ch. NR 662.011. The generator shall provide supporting documentation of the waste determination along with the initial certification submitted to the department as specified in sub. (1).

NR 538.06 Note Note: Supporting documentation may include representative sampling and analysis, safety data sheets, published information, process flow diagrams, profiles developed from the prior handling of industrial byproducts, or supported process knowledge.

NR 538.06(3)(c) (c) Water leach test. All industrial byproducts, except byproducts to be used as a soil or plant additive in accordance with s. NR 538.10 (5), shall be analyzed using ASTM D3987-12 water leach test as specified in ch. NR 538 Appendix, Table 1.

NR 538.06(3)(d) (d) Bulk analysis. All industrial byproducts, except byproducts to be used as a soil or plant additive in accordance with s. NR 538.10 (5), shall be analyzed using a bulk analysis for the parameters in ch. NR 538 Appendix, Table 2, unless another analytical method is approved by the department in writing.

NR 538.06(3)(e) (e) Flue gas desulfurization analysis. All flue gas desulfurization materials to be marketed and used as soil or plant additives in accordance with s. NR 538.10 (5) shall be analyzed using a total elemental analysis for the parameters in ch. NR 538 Appendix, Table 3, unless another analytical method or parameters are approved by the department in writing.

NR 538.06(3)(f) (f) Select foundry sand. Generators may request that the department designate their foundry industrial byproducts as select foundry sand with their initial certification notification under sub. (1) (a) or recharacterization under sub. (5) provided they submit supporting documentation to the department demonstrating that the foundry byproducts meet the definition under s. NR 538.03 (12m) and have been determined to contain less than the concentration specified for the parameters listed in ch. NR 538 Appendix, Table 1, Column B. Supporting documentation shall include evidence of segregation which may include process flow diagrams, written material handling and segregation procedures, or byproduct management summaries. If the department determines that the foundry byproduct meets the definition, the department shall reply with a written concurrence of the designation within 10 business days provided the applicant meets the applicable criteria of this chapter. If the department does not respond to a notification within 10 business days, the notification is deemed complete and concurrence is considered granted.

NR 538.06(4) (4) Mixing of industrial byproducts. If separate industrial byproducts will be mixed together, each of the byproducts must be individually eligible for the specific intended final use of the resulting mixture unless otherwise approved by the department in writing under s. NR 538.09.

NR 538.06 Note Note: Copies of EPA SW-846 test methods are available directly from the U.S. environmental protection agency at https://www.epa.gov/hw-sw846. Copies of the test methods are available for inspection at the offices of the department of natural resources and the legislative reference bureau. See also the definition for SW-846 at s. NR 500.03 (231), Wis. Admin. Code.

NR 538.06 Note Note: ASTM D3987-12 is the American society for testing and materials “Test Method for Shake Extraction of Solid Wastes with Water.” Copies of the ASTM standard may be obtained from ASTM International at https://www.astm.org/Standards/D3987.htm. Copies of the standard are available for inspection at the offices of the department of natural resources and the legislative reference bureau.

NR 538.06(5) (5) Recharacterization.

NR 538.06(5)(a) (a) Industrial byproducts that are beneficially used under this chapter shall be recharacterized after the initial characterization in accordance with this section, unless the department approves, in writing, an alternative recharacterization method.

NR 538.06(5)(b) (b) Industrial byproducts shall be recharacterized as follows:

NR 538.06(5)(b)1. 1. A representative sample of each industrial byproduct shall be recharacterized whenever there is a change in the process that produces the industrial byproduct that could potentially result in a change in the eligible uses of the industrial byproduct.

NR 538.06(5)(b)2. 2. A representative sample of each industrial byproduct shall be recharacterized in accordance with ch. NR 538 Appendix, Tables 1 and 2, at a minimum of once every 4 years from the date of the initial certification or the last recharacterization, except that recharacterization is not required under this subsection for any industrial byproduct of which less than 1000 cubic yards were beneficially used or stored for beneficial use in any calendar year during the previous 4-year period.

NR 538.06(5)(c) (c) The generator shall submit documentation of any recharacterization test results required under this section to the department in accordance with s. NR 538.14 (2). The department shall reply with a written concurrence within 10 business days, provided the submittal meets the applicable criteria of this chapter. If the department does not respond to a recertification request within 10 business days, the recertification is deemed complete and concurrence with the recharacterization is considered granted.

NR 538.06(6) (6) Initial applicability. A generator that submitted an initial certification prior to January 1, 2021, may submit a recharacterization and a hazardous waste determination under sub. (3) (b) to the department within 4 years of the date the last recharacterization or initial certification was submitted to the department prior to January 1, 2021, provided there has been no change in the process that produces the industrial byproduct in accordance with sub. (5) (b) 1.

NR 538.06 History History: Cr. Register, December, 1997, No. 504, eff. 1-1-98; CR 05-020: am. (3) (c) Register January 2006 No. 601, eff. 2-1-06; corrections in (3) (b) made under s. 13.92 (4) (b) 7., Stats., Register February 2010 No. 650; CR 19-080: r. and recr. Register May 2020 No. 773, eff. 11-1-20; correction in numbering in (1) (b) made under s. 13.92 (4) (b) 1., Stats., and correction in (1) (a), (b) 3., (3) (b), (5) (c), (6) made under s. 35.17, Stats., Register May 2020 No. 773.

NR 538.08 NR 538.08 Determination of eligible uses. Acceptable beneficial uses for industrial byproducts that have been determined not to be a hazardous waste, as defined in s. NR 660.10 (52), and tested in accordance with s. NR 538.06 shall be determined as follows:

NR 538.08(1) (1) Contained or converted uses. All industrial byproducts, including select foundry sand, are eligible for contained or converted uses in accordance with provisions of s. NR 538.10 (1).

NR 538.08(2) (2) Geotechnical fill. Industrial byproducts, including select foundry sand, that have been determined to contain less than the concentration specified for the parameters listed in ch. NR 538 Appendix, Table 1, Column B, are eligible for use as geotechnical fill in accordance with the provisions of ss. NR 538.10 (2) and 538.12, except nonmetallic mine reclamation uses under s. NR 538.12 (2) (e), which must be designated by the department as a select foundry sand under s. NR 538.06 (3) (f) or determined to contain less than the concentration specified for the parameters listed in ch. NR 538 Appendix, Table 1, Column A.

NR 538.08(3) (3) Construction uses. Industrial byproducts, including select foundry sand, that have been determined to contain less than the concentration specified for the parameters listed in ch. NR 538 Appendix, Table 1, Column B, are eligible for construction uses in accordance with the provisions of s. NR 538.10 (3).

NR 538.08(4) (4) Unconfined uses. Industrial byproducts, including select foundry sand, that have been determined to contain less than the concentration specified for the parameters listed in ch. NR 538 Appendix, Table 1, Column B and Table 2 are eligible for unconfined uses in accordance with the provisions of s. NR 538.10 (4).

NR 538.08(5) (5) Soil or plant additives. Flue gas desulfurization materials that have been determined to contain less than the concentration specified for the parameters listed in ch. NR 538 Appendix, Table 3, are eligible for use as soil and plant additives in accordance with the provisions of s. NR 538.10 (5). Industrial byproducts intended for use as agricultural liming additives that have been determined to contain less than the concentrations specified in Table 3 of s. NR 204.07 (5) (c) are eligible for use as soil or plant additives in accordance with the provisions of s. NR 538.10 (5).

NR 538.08(6) (6) Criteria and process for using eligibility standards.

NR 538.08(6)(a) (a) If a standard for a parameter listed in ch. NR 538 Appendix is above the limit of detection and the limit of quantitation, the standard shall be considered exceeded if the parameter is reported at or above the standard.

NR 538.08(6)(b) (b) If a standard for a parameter listed in ch. NR 538 Appendix is between the limit of detection and the limit of quantitation, inclusive, the standard shall be considered exceeded if the parameter is reported at or above the limit of quantitation.

NR 538.08(6)(c) (c) The following applies when a standard for a parameter listed in ch. NR 538 Appendix is below the lowest achievable limit of detection:

NR 538.08(6)(c)1. 1. If a parameter is not detected in a sample, the standard shall be considered to have been met.

NR 538.08(6)(c)2. 2. If a parameter is reported at or above the limit of detection but below the limit of quantitation, a confirmation analysis shall be conducted. The standard shall be considered exceeded if the presence of that parameter has been confirmed by the use of an appropriate analytical method as determined by the department.

NR 538.08(6)(c)3. 3. If a parameter is reported at or above the limit of quantitation, the standard shall be considered exceeded.

NR 538.08 History History: Cr. Register, December, 1997, No. 504, eff. 1-1-98; CR 05-020: am. (3) and (7) Register January 2006 No. 601, eff. 2-1-06; corrections in (1) to (5), (6) (a) to (c) made under s. 13.93 (2m) (b) 7., Stats., Register April 2013 No. 688; CR 19-080: r. and recr. Register May 2020 No. 773, eff. 11-1-20; correction in (intro.) made under s. 35.17, Stats., Register May 2020 No. 773.

NR 538.09 NR 538.09 Case-specific approvals. The department may review the characterization results for an industrial byproduct not defined in s. NR 538.03 (8) in response to a request from the generator and may, on a case-specific basis, approve a beneficial use or uses for that material or conditionally approve a beneficial use that does not meet the beneficial uses or standards specified in this chapter. The department may require additional information prior to a case-specific approval. Any exemption or approval granted under this section shall be in accordance with the applicable requirements of s. 289.43 (4), (7) and (8), Stats. If the department determines that the industrial byproduct material falls under the s. NR 538.03 (8) (b) or (c) exclusions or the proposed use does not meet the definition of a beneficial use under s. NR 538.03 (2), approval for use or disposal must be obtained through the applicable provisions under ss. NR 500 to 528.

NR 538.09 History History: CR 19-080: r. and recr. Register May 2020 No. 773, eff. 11-1-20; correction made under s. 35.17, Stats., Register May 2020 No. 773.

NR 538.10 NR 538.10 Eligible beneficial uses. All uses of industrial byproducts shall meet all applicable structural and physical specifications and generally accepted engineering practices for the use. Under this chapter, the eligible beneficial uses of industrial byproducts that may be exempt from licensing under s. 289.31, Stats., and the regulatory requirements under chs. NR 500 to 528 include any of the following:

NR 538.10(1) (1) Contained or converted uses. Uses that are fully contained within a licensed, engineered disposal facility, are encapsulated within a matrix material, are burned for fuel, or are converted into a product, including any of the following:

NR 538.10(1)(a) (a) Encapsulated uses. Products that may meet these criteria include cement, lightweight aggregate, structural or ornamental concrete or ceramic materials, portland cement concrete pavement, asphaltic concrete pavement, slurry seals, roofing materials, plastics, paint, fiberglass, mineral wool, wallboard, plaster and other products approved in writing by the department.

NR 538.10(1)(b) (b) Agents for physical or chemical stabilization, solidification or other treatment of solid waste that is to be disposed of at a licensed, engineered disposal facility or utilized in some other final use approved in writing by the department.

NR 538.10(1)(c) (c) Supplemental material used for fuel or to assist air pollution control during the process of combustion for energy production.

NR 538.10(1)(d) (d) Daily cover or internal structures at licensed, approved landfills having a liner and leachate collection system. The industrial byproducts used for this purpose may not contain free liquids. The industrial byproducts beneficially used at landfills for alternate daily cover in accordance with s. NR 506.055 may contain no more than 15% silt and clay sized materials as determined by their P200 content and may not be placed in layers greater than 6 inches thick. Any uses under this paragraph shall be subject to the conditions of the plan of operation and any other applicable solid waste approvals associated with the landfill.

NR 538.10(2) (2) Geotechnical fill. Geotechnical fill material meeting the project criteria and uses specified in this subsection and s. NR 538.12 where applicable. If more than 5,000 cubic yards are to be used in an individual project, prior written notification in accordance with s. NR 538.14 (5) and concurrence by the department under s. NR 538.14 (6) are required unless the specific concurrence requirements in par. (b) or (f) apply. Industrial byproducts shall be used in accordance with best management practices. The criteria and uses under this subsection are as follows:

NR 538.10(2)(a) (a) Subgrade fill for the construction of commercial, industrial or non-residential institutional buildings. Industrial byproducts used as subgrade fill for the construction of commercial, industrial, or non-residential institutional buildings shall have placement of the concrete floor or frostwalls completed as soon as practical after placement of the fill material in accordance with s. NR 538.12 (4). Any area where industrial byproducts are not directly beneath the building shall be sloped to prevent ponding of water, covered with 2 feet of native soil including a minimum of 4 inches of topsoil, and seeded or otherwise covered as approved by the department in writing. Cover shall be placed over fill material as soon as practical after byproduct placement. Final vegetated slopes may not be steeper than a 3:1 horizontal to vertical incline. The use of industrial byproducts as subgrade fill in the construction of residential buildings is prohibited.

NR 538.10(2)(b) (b) Subgrade fill for the construction of portland cement concrete or asphaltic concrete paved infrastructure. Industrial byproducts used for subgrade fill for the construction of portland cement or asphaltic concrete paved infrastructure including parking lots, access roads, and private roadways shall have placement of the pavement completed as soon as practical after placement of the fill material. Any area where industrial byproducts are not directly beneath the pavement structure shall be sloped to prevent ponding of water, covered with 2 feet of native soil including a minimum of 4 inches of topsoil, and seeded as soon after byproduct placement as is practical or otherwise covered as approved by the department in writing. Prior written notification in accordance with s. NR 538.14 (5) and written concurrence by the department under s. NR 538.14 (6) are required for fills that do not meet the criteria in this paragraph. The use of industrial byproducts as paved lot fill is prohibited in residential areas.

NR 538.10(2)(c) (c) Geotechnical fill material with a soil or gravel cover. Industrial byproducts beneficially used as geotechnical fill with a soil or gravel cover for sight, sound, safety and structural berms, public recreation trails, construction of sporting venues, limited use parking areas, access lanes, utility trenches not covered by a paved surface in accordance with sub. (3) (c), or other beneficial uses demonstrated to be acceptable by the department shall be sloped to prevent ponding of water, covered with 2 feet of native soils, including a minimum of 4 inches of topsoil or other cover approved by the department in writing, and seeded as soon as practical after placement of the industrial byproducts. Final vegetated slopes may not be steeper than a 3:1 horizontal to vertical incline. Gravel or other granular material may be substituted for topsoil if necessary for the specified use, provided the total fill cover is at least 2 feet. The beneficial use of industrial byproducts as geotechnical fill with a soil or gravel cover is prohibited in residential areas.

NR 538.10(2)(d) (d) Use of foundry sand at livestock operations. Foundry sand may be beneficially used at livestock operations for any of the following:

NR 538.10(2)(d)1. 1. Liner material in an impoundment or structure used for the storage of livestock manure, livestock feed, or process wastewater. The impoundment or structure shall be designed and constructed in accordance with applicable natural resources conservation service standards and local ordinances, and in accordance with plans and specifications approved under chs. NR 213 and 243, if applicable.

NR 538.10(2)(d)2. 2. Geotechnical fill beneath an area where livestock will be housed or confined. Any areas of foundry sand fill that will be washed or mechanically scraped shall be paved with an asphalt or concrete surface, or a 2 feet thick protective soil layer, over the industrial byproduct. The livestock housing or confinement area design and construction shall be in accordance with applicable natural resources conservation service standards and local ordinances, and in accordance with plans and specifications approved under ch. NR 243, if applicable to any portion of the project.

NR 538.10 Note Note: Under ch. NR 243 Natural Resources Conservation Service (NRCS) conservation practice standard Code 313, dated December 2005 applies to waste storage facilities. Under ch. ATCP 50, NRCS conservation practice standard Code 629 dated January 2014 applies to feed storage runoff control facilities. Copies of these and other conservation practice codes can be obtained online from the NRCS Field Office Technical Guide, www.nrcs.usda.gov/wps/portal/nrcs/site/wi/home. Copies are also available at the Wisconsin NRCS state office or the Wisconsin Land and Water Conservation Association office.

NR 538.10(2)(e) (e) Transportation facility embankments. Industrial byproducts used as geotechnical fill for transportation facility embankments such as linear roadway sound and sight barrier berm embankments, airport embankments, and roadway bridge or overpass embankments constructed under the authority of the Wisconsin department of transportation or a municipality shall meet the criteria in this paragraph. Any area where industrial byproduct is used as an embankment and not covered by pavement or road shoulder material, shall be sloped to prevent ponding of water, covered with 2 feet of native soils including a minimum of 4 inches of topsoil, or other cover approved by the department in writing, and seeded with an approved Wisconsin department of transportation seed mix as soon as practical after placement of the industrial byproducts. Final vegetated slopes may not be steeper than a 3:1 horizontal to vertical incline.