Wisconsin Administrative Code
Department of Natural Resources
NR 100-199 - Environmental Protection General
Chapter NR 151 - Runoff Management
Subchapter III - Non-Agricultural Performance Standards
Section NR 151.122 - Total suspended solids performance standard
Current through August 26, 2024
(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.
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Table 1. TSS Reduction Standards |
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Development Type |
TSS Reduction |
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New Development |
80 percent |
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In-fill >= 5 acres |
80 percent |
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In-fill < 5 acres on or after October 1, 2012 |
80 percent |
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Redevelopment |
40 percent of load from parking areas and roads |
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In-fill < 5 acres and before October 1, 2012 |
40 percent |
(2) REDEVELOPMENT. Except as provided in s. NR 151.121(5), the redevelopment total suspended solids reduction standard of Table 1., applies to redevelopment.
(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.
Note: 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.
(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.
