WDNR MS4 Suspended Solids Reduction Guidance

The Wisconsin Department of Natural Resources (WDNR) has recently published guidance to be used by municipalities to demonstrate compliance with total suspend solids reduction requirements. Under Wisconsin Rules NR 151.13 (2), municipalities subject to the municipal WPDES stormwater permit requirements must, to the maximum extent practicable, implement a 20% and a 40% reduction in total suspended solids in runoff that enters waters of the state as compared to no controls, by March 10, 2008 and March 10, 2013, respectively.

The updated guidance assists affected municipalities to understand what areas under the municipalities' jurisdictions will be included in this requirement, what is meant by "no controls" and "with controls", and what methods are acceptable for making these calculations.
To comply with the code, the developed urban area must be modeled under a "no control" condition and a "with controls" condition. The 20% and 40% TSS reductions are assessed against the "no control" condition for the entire area served by the MS4.

Caltha LLP provides expert consulting services to public and private sector clients nationwide to address Stormwater Permitting & Regulatory Support, Stormwater Pollution Prevention Plans (SWPPP), Stormwater Monitoring and Stormwater Training.

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