NR 151.12(5)(b)2.a.a. A post-construction site where the change in hydrology due to development does not increase the existing surface water elevation at any point within the downstream receiving water by more than 0.01 of a foot for the 2-year, 24-hour storm event. NR 151.12 NoteNote: Hydraulic models such as HEC-RAS or another methodology may be used to determine the change in surface water elevations.
NR 151.12 NoteNote: The intent of par. (b) is to minimize streambank erosion under bank full conditions.
NR 151.12(5)(c)(c) Infiltration. BMPs shall be designed, installed and maintained to infiltrate runoff to the maximum extent practicable in accordance with the following, except as provided in subds. 5. to 8.: NR 151.12(5)(c)1.a.a. Infiltrate sufficient runoff volume so that the post-development infiltration volume shall be at least 90% of the pre-development infiltration volume, based on an average annual rainfall. However, when designing appropriate infiltration systems to meet this requirement, no more than 1% of the project site is required as an effective infiltration area. NR 151.12(5)(c)1.b.b. Infiltrate 25% of the post-development runoff volume from the 2–year, 24-hour design storm with a type II distribution. Separate curve numbers for pervious and impervious surfaces shall be used to calculate runoff volumes and not composite curve numbers as defined in TR-55. However, when designing appropriate infiltration systems to meet this requirement, no more than 1% of the project site is required as an effective infiltration area. NR 151.12(5)(c)2.2. For non-residential development, including commercial, industrial and institutional development, one of the following shall be met: NR 151.12(5)(c)2.a.a. For this subdivision only, the “project site” means the rooftop and parking lot areas. NR 151.12(5)(c)2.b.b. Infiltrate sufficient runoff volume so that the post-development infiltration volume shall be at least 60% of the pre-development infiltration volume, based on an average annual rainfall. However, when designing appropriate infiltration systems to meet this requirement, no more than 2% of the project site is required as an effective infiltration area. NR 151.12(5)(c)2.c.c. Infiltrate 10% of the post-development runoff volume from the 2-year, 24-hour design storm with a type II distribution. Separate curve numbers for pervious and impervious surfaces shall be used to calculate runoff volumes and not composite curve numbers as defined in TR-55. However, when designing appropriate infiltration systems to meet this requirement, no more than 2% of the project site is required as an effective infiltration area. NR 151.12 NoteNote: A model that calculates runoff volume, such as SLAMM, P8 or an equivalent methodology may be used. Information on how to access SLAMM and P8 is available from the storm water coordinator in the runoff management section of the bureau of watershed management at dnr.wi.gov.
NR 151.12(5)(c)4.4. Before infiltrating runoff, pretreatment shall be required for parking lot runoff and for runoff from new road construction in commercial, industrial and institutional areas that will enter an infiltration system. The pretreatment shall be designed to protect the infiltration system from clogging prior to scheduled maintenance and to protect groundwater quality in accordance with subd. 8. Pretreatment options may include, but are not limited to, oil/grease separation, sedimentation, biofiltration, filtration, swales or filter strips. NR 151.12 NoteNote: To achieve the infiltration requirement for the parking lots or roads, maximum extent practicable should not be interpreted to require significant topography changes that create an excessive financial burden. To minimize potential groundwater impacts it is desirable to infiltrate the cleanest runoff. To achieve this, a design may propose greater infiltration of runoff from low pollutant sources such as roofs, and less from higher pollutant source areas such as parking lots.
NR 151.12(5)(c)5.5. Exclusions. The runoff from the following areas are prohibited from meeting the requirements of this paragraph: NR 151.12 NoteNote: Runoff from tier 2 parking and rooftop areas may be infiltrated but may require pretreatment.
NR 151.12(5)(c)5.d.d. Areas within 1000 feet upgradient or within 100 feet downgradient of karst features. NR 151.12(5)(c)5.e.e. Areas with less than 3 feet separation distance from the bottom of the infiltration system to the elevation of seasonal high groundwater or the top of bedrock, except this subd. 5. e. does not prohibit infiltration of roof runoff. NR 151.12(5)(c)5.f.f. Areas with runoff from industrial, commercial and institutional parking lots and roads and residential arterial roads with less than 5 feet separation distance from the bottom of the infiltration system to the elevation of seasonal high groundwater or the top of bedrock. NR 151.12(5)(c)5.g.g. Areas within 400 feet of a community water system well as specified in s. NR 811.16 (4) or within 100 feet of a private well as specified in s. NR 812.08 (4) for runoff infiltrated from commercial, industrial and institutional land uses or regional devices for residential development. NR 151.12(5)(c)5.i.i. Any area where the soil does not exhibit one of the following characteristics between the bottom of the infiltration system and the seasonal high groundwater and top of bedrock: at least a 3-foot soil layer with 20% fines or greater; or at least a 5-foot soil layer with 10% fines or greater. This subd. 5. i. does not apply where the soil medium within the infiltration system provides an equivalent level of protection. Subdivision 5. i. does not prohibit infiltration of roof runoff. NR 151.12 NoteNote: The areas listed in subd. 5. are prohibited from infiltrating runoff due to the potential for groundwater contamination.
NR 151.12(5)(c)6.6. Exemptions. The following are not required to meet the requirements of this paragraph: NR 151.12(5)(c)6.a.a. Areas where the infiltration rate of the soil is less than 0.6 inches/hour measured at the bottom of the infiltration system. NR 151.12(5)(c)6.b.b. Parking areas and access roads less than 5,000 square feet for commercial and industrial development. NR 151.12(5)(c)6.f.f. Roads in commercial, industrial and institutional land uses, and arterial residential roads. NR 151.12(5)(c)7.7. Where alternate uses of runoff are employed, such as for toilet flushing, laundry or irrigation, such alternate use shall be given equal credit toward the infiltration volume required by this paragraph. NR 151.12(5)(c)8.a.a. Infiltration systems designed in accordance with this paragraph shall, to the extent technically and economically feasible, minimize the level of pollutants infiltrating to groundwater and shall maintain compliance with the preventive action limit at a point of standards application in accordance with ch. NR 140. However, if site specific information indicates that compliance with a preventive action limit is not achievable, the infiltration BMP may not be installed or shall be modified to prevent infiltration to the maximum extent practicable. NR 151.12(5)(c)8.b.b. Notwithstanding subd. 8. a., the discharge from BMPs shall remain below the enforcement standard at the point of standards application. NR 151.12(5)(d)1.1. In this paragraph, “protective area” means an area of land that commences at the top of the channel of lakes, streams and rivers, or at the delineated boundary of wetlands, and that is the greatest of the following widths, as measured horizontally from the top of the channel or delineated wetland boundary to the closest impervious surface. However, in this paragraph, “protective area” does not include any area of land adjacent to any stream enclosed within a pipe or culvert, such that runoff cannot enter the enclosure at this location. NR 151.12(5)(d)1.a.a. For outstanding resource waters and exceptional resource waters, and for wetlands in areas of special natural resource interest as specified in s. NR 103.04, 75 feet. NR 151.12(5)(d)1.b.b. For perennial and intermittent streams identified on a United States geological survey 7.5-minute series topographic map, or a county soil survey map, whichever is more current, 50 feet. NR 151.12(5)(d)1.d.d. For highly susceptible wetlands, 50 feet. Highly susceptible wetlands include the following types: fens, sedge meadows, bogs, low prairies, conifer swamps, shrub swamps, other forested wetlands, fresh wet meadows, shallow marshes, deep marshes and seasonally flooded basins. Wetland boundary delineation shall be made in accordance with s. NR 103.08 (1m). This paragraph does not apply to wetlands that have been completely filled in accordance with all applicable state and federal regulations. The protective area for wetlands that have been partially filled in accordance with all applicable state and federal regulations shall be measured from the wetland boundary delineation after fill has been placed. NR 151.12(5)(d)1.e.e. For less susceptible wetlands, 10% of the average wetland width, but no less than 10 feet nor more than 30 feet. Less susceptible wetlands include degraded wetlands dominated by invasive species such as reed canary grass. NR 151.12(5)(d)1.f.f. In subd. 1. a., d. and e., determinations of the extent of the protective area adjacent to wetlands shall be made on the basis of the sensitivity and runoff susceptibility of the wetland in accordance with the standards and criteria in s. NR 103.03. NR 151.12(5)(d)1.g.g. For concentrated flow channels with drainage areas greater than 130 acres, 10 feet. NR 151.12(5)(d)2.2. This paragraph applies to post-construction sites located within a protective area, except those areas exempted pursuant to subd. 4. NR 151.12(5)(d)3.a.a. Impervious surfaces shall be kept out of the protective area to the maximum extent practicable. The storm water management plan shall contain a written site-specific explanation for any parts of the protective area that are disturbed during construction. NR 151.12(5)(d)3.b.b. Where land disturbing construction activity occurs within a protective area, and where no impervious surface is present, adequate sod or self-sustaining vegetative cover of 70% or greater shall be established and maintained. The adequate sod or self-sustaining vegetative cover shall be sufficient to provide for bank stability, maintenance of fish habitat and filtering of pollutants from upslope overland flow areas under sheet flow conditions. Non-vegetative materials, such as rock riprap, may be employed on the bank as necessary to prevent erosion such as on steep slopes or where high velocity flows occur. NR 151.12 NoteNote: It is recommended that seeding of non-aggressive vegetative cover be used in the protective areas. Vegetation that is flood and drought tolerant and can provide long-term bank stability because of an extensive root system is preferable. Vegetative cover may be measured using the line transect method described in the university of Wisconsin extension publication number A3533, titled “Estimating Residue Using the Line Transect Method”.
NR 151.12(5)(d)3.c.c. Best management practices such as filter strips, swales or wet detention basins, that are designed to control pollutants from non-point sources may be located in the protective area. NR 151.12 NoteNote: Other regulations, such as ch. 30, Stats., and chs. NR 103, 115, 116 and 117 and their associated review and approval process may apply in the protective area. NR 151.12(5)(d)4.c.c. Structures that cross or access surface waters such as boat landings, bridges and culverts. NR 151.12(5)(d)4.e.e. Post-construction sites from which runoff does not enter the surface water, except to the extent that vegetative ground cover is necessary to maintain bank stability. NR 151.12 NoteNote: A vegetated protective area to filter runoff pollutants from post-construction sites described in subd. 4. e. is not necessary since runoff is not entering the surface water at that location. Other practices necessary to meet the requirements of this section, such as a swale or basin, will need to be designed and implemented to reduce runoff pollutants prior to runoff entering a surface water of the state.
NR 151.12(5)(e)(e) Fueling and vehicle maintenance areas. Fueling and vehicle maintenance areas shall, to the maximum extent practicable, have BMPs designed, installed and maintained to reduce petroleum within runoff, such that the runoff that enters waters of the state contains no visible petroleum sheen. NR 151.12 NoteNote: A combination of the following BMPs may be used: oil and grease separators, canopies, petroleum spill cleanup materials, or any other structural or non-structural method of preventing or treating petroleum in runoff.
NR 151.12(5)(f)(f) Location. To comply with the standards required under this subsection, BMPs may be located on-site or off-site as part of a regional storm water device, practice or system, but shall be installed in accordance with s. NR 151.003. NR 151.12(5)(g)(g) Timing. The BMPs that are required under this subsection shall be installed before the construction site has undergone final stabilization. NR 151.121NR 151.121 Post-construction performance standards. NR 151.121(1)(1) General. In ss. NR 151.121 to 151.128, “post-construction site” means a construction site subject to regulation under this subchapter, after construction is completed and final stabilization has occurred. NR 151.121(2)(2) Applicability. Sections NR 151.121 to 151.128 apply to a post-construction site that is or was subject to the construction performance standards of s. NR 151.11, except any of the following: NR 151.121(2)(a)(a) A post-construction site with less than 10 percent connected imperviousness, based on the area of land disturbance, provided the cumulative area of all impervious surfaces is less than one acre. However, the exemption of this paragraph does not include exemption from the protective area standard of s. NR 151.125. NR 151.121 NoteNote: This exemption includes both point and nonpoint discharges from agricultural facilities and practices. Therefore, post-construction structures such as barns, manure storage facilities, sand settling lanes, and barnyard runoff control systems are subject to subch. II and are not subject, under s. NR 216.47 (1), to the post-construction performance standards of this subchapter. NR 151.121(2)(c)(c) Underground utility construction, but not including the construction of any above ground structures associated with utility construction. NR 151.121(3)(3) Responsible party. The landowner of the post-construction site or other person contracted or obligated by other agreement with the landowner to implement and maintain post-construction storm water BMPs is the responsible party and shall comply with ss. NR 151.121 to 151.128. NR 151.121(4)(4) Storm water management plan. A written storm water management plan shall be developed and implemented for each post-construction site and shall incorporate the requirements of ss. NR 151.122 to 151.128. NR 151.121 NoteNote: Examples of storm water management plans that may be used to comply with ss. NR 151.122 to 151.128 may include those specified in s. NR 216.47 or the municipal storm water management program specified in s. NR 216.07 (5). NR 151.121(5)(5) Maintenance of effort. For redevelopment sites where the redevelopment will be replacing older development that was subject to post-construction performance standards of this chapter in effect on or after October 1, 2004, the responsible party shall meet the total suspended solids reduction, peak flow control, infiltration, and protective areas standards applicable to the older development or meet the redevelopment standards of ss. NR 151.122 to 151.125, whichever are more stringent. NR 151.121 HistoryHistory: CR 09-112: cr. Register December 2010 No. 660, eff. 1-1-11. NR 151.122NR 151.122 Total suspended solids performance standard. NR 151.122(1)(1) Requirement. BMPs shall be designed, installed and maintained to control total suspended solids carried in runoff from the post-construction site. BMPs shall be designed in accordance with Table 1., or to the maximum extent practicable as provided in sub. (3). The design shall be based on an average annual rainfall, as compared to no runoff management controls. NR 151.122(2)(2) Redevelopment. Except as provided in s. NR 151.121 (5), the redevelopment total suspended solids reduction standard of Table 1., applies to redevelopment. NR 151.122(3)(3) Maximum extent practicable. If the design cannot meet a total suspended solids reduction performance standard of sub. (1), Table 1., the storm water management plan shall include a written, site-specific explanation of why the total suspended solids reduction performance standard cannot be met and why the total suspended solids load will be reduced only to the maximum extent practicable. The department may not require any person to exceed the applicable total suspended solids reduction performance standard to meet the requirements of maximum extent practicable. NR 151.122 NoteNote: Pollutant loading models such as DETPOND, SLAMM, P8, or equivalent methodology may be used to evaluate the efficiency of the design in reducing total suspended solids. Information on how to access these models is available from the department’s storm water management program at dnr.wi.gov. Use the most recent version of the model and the rainfall files and other parameter files identified for Wisconsin users unless directed otherwise by the regulatory authority.
NR 151.122(4)(4) Off-site drainage. When designing BMPs, runoff draining to the BMP from off-site shall be taken into account in determining the treatment efficiency of the practice. Any impact on the efficiency shall be compensated for by increasing the size of the BMP accordingly. NR 151.122 HistoryHistory: CR 09-112: cr. Register December 2010 No. 660, eff. 1-1-11. NR 151.123NR 151.123 Peak discharge performance standard. NR 151.123(1)(1) Requirement. By design, BMPs shall be employed to maintain or reduce the 1-year, 24-hour and the 2-year, 24-hour post-construction peak runoff discharge rates to the 1-year, 24-hour and the 2-year, 24-hour pre-development peak runoff discharge rates respectively, or to the maximum extent practicable. The runoff curve numbers in Table 2. shall be used to represent the actual pre-development condition.
