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. NR 151.123 NoteNote: Where the pre-development condition is a combination of woodland, grassland, or cropland, the runoff curve number should be pro-rated by area.
NR 151.123(2)(2) Exemptions. This section does not apply to the following: NR 151.123(2)(a)(a) A post-construction site where the discharge is directly into a lake over 5,000 acres or a stream or river segment draining more than 500 square miles.