Post-construction performance standard for new development and redevelopment

Post-construction performance standard for new development and redevelopment. (1) General. In this section: (a) “Post-construction site” means a construction site subject to regulation under this subchapter, after construction is completed and final stabilization has occurred. (b) Average annual rainfall is determined by the following years and locations: Madison, 1981 (Mar. 12-Dec. 2); Green Bay, 1969 (Mar. 29-Nov. 25); Milwaukee, 1969 (Mar. 28-Dec. 6); Minneapolis, 1959 (Mar. 13-Nov. 4); Duluth, 1975 (Mar. 24-Nov. 19). Of the 5 locations listed, the location closest to a project site best represents the average annual rainfall for that site. (2) Applicability. This section applies 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: (a) A post-construction site where the department has received a notice of intent for the construction project, in accordance with subch. III of ch. NR 216 , within 2 years after October 1, 2002. (b) A post-construction site where the department of commerce has received a notice of intent, in accordance with s. Comm 61.115 , within 2 years after October 1, 2002. (bm) A post-construction site for which the department received a notice of intent for the construction project, in accordance with subch. III of ch. NR 216 , on or after January 1, 2011. Post-construction sites for which the department received a notice of intent for the construction project, in accordance with subch. III of ch. NR 216 , on or after January 1, 2011, shall meet the performance standards of ss. NR 151.122 to 151.128 . (c) A redevelopment post-construction site with no increase in exposed parking lots or roads. (d) A post-construction site with less than 10% connected imperviousness based on complete development of the post-construction site, provided the cumulative area of all parking lots and rooftops is less than one acre. (e) Agricultural facilities and practices. (f) An action for which a final environmental impact statement was approved before October 1, 2002. (g) An action for which a finding of no significant impact is made under ch. NR 150 before October 1, 2002. (h) Underground utility construction such as water, sewer and fiberoptic lines, but not including the construction of any above ground structures associated with utility construction. (3) Responsible party. The landowner of the post-construction site or other person contracted or obligated by other agreement to implement and maintain post-construction storm water BMPs shall comply with this section. (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 this subsection. (5) Requirements. The plan required under sub. (4) shall include: (a) Total suspended solids. Best management practices shall be designed, installed and maintained to control total suspended solids carried in runoff from the post-construction site as follows: 1. For new development, by design, reduce to the maximum extent practicable, the total suspended solids load by 80%, based on an average annual rainfall, as compared to no runoff management controls. No person shall be required to exceed an 80% total suspended solids reduction to meet the requirements of this subdivision. 2. For redevelopment, by design, reduce to the maximum extent practicable, the total suspended solids load by 40%, based on an average annual rainfall, as compared to no runoff management controls. No person shall be required to exceed a 40% total suspended solids reduction to meet the requirements of this subdivision. 3. For in-fill development under 5 acres that occurs within 10 years after October 1, 2002, by design, reduce to the maximum extent practicable, the total suspended solids load by 40%, based on an average annual rainfall, as compared to no runoff management controls. No person shall be required to exceed a 40% total suspended solids reduction to meet the requirements of this subdivision. 4. For in-fill development that occurs 10 or more years after October 1, 2002, by design, reduce to the maximum extent practicable, the total suspended solids load by 80%, based on an average annual rainfall, as compared to no runoff management controls. No person shall be required to exceed an 80% total suspended solids reduction to meet the requirements of this subdivision. 5. Notwithstanding subds. 1. to 4. , if the design cannot achieve the applicable total suspended solids reduction specified, the storm water management plan shall include a written and site-specific explanation why that level of reduction is not attained and the total suspended solids load shall be reduced to the maximum extent practicable. (b) Peak discharge. 1. By design, BMPs shall be employed to maintain or reduce the peak runoff discharge rates, to the maximum extent practicable, as compared to pre-development conditions for the 2-year, 24-hour design storm applicable to the post-construction site. Pre-development conditions shall assume “good hydrologic conditions” for appropriate land covers as identified in TR-55 or an equivalent methodology. The meaning of “hydrologic soil group” and “runoff curve number” are as determined in TR-55. However, when pre-development land cover is cropland, rather than using TR-55 values for cropland, the runoff curve numbers in Table 2 shall be used. 2. This paragraph does not apply to: 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. b. A redevelopment post-construction site. c. An in-fill development area less than 5 acres. (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. : 1. For residential developments one of the following shall be met: 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. 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. 2. For non-residential development, including commercial, industrial and institutional development, one of the following shall be met: a. For this subdivision only, the “project site” means the rooftop and parking lot areas. 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. 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. 3. Pre-development condition shall be the same as specified in par. (b) . 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. 5. Exclusions. The runoff from the following areas are prohibited from meeting the requirements of this paragraph: a. Areas associated with tier 1 industrial facilities identified in s. NR 216.21 (2) (a) , including storage, loading, rooftop and parking. b. Storage and loading areas of tier 2 industrial facilities identified in s. NR 216.21 (2) (b) . c. Fueling and vehicle maintenance areas. d. Areas within 1000 feet upgradient or within 100 feet downgradient of karst features. 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. 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. 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. h. Areas where contaminants of concern, as defined in s. NR 720.03 (2) , are present in the soil through which infiltration will occur. 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.