WDNR Final Industrial Stormwater Discharge General Permits

The Wisconsin Department of Natural Resources (WDNR) has released its final industrial stormwater general permits for Tier 1 and Tier 2 facilities. These permits cover stormwater discharges from certain types of industrial and “industrial-like” operations that are required to have a WPDES permit to discharge stormwater. The previous general permits expired in 2006.

You can review a Regulatory Briefing on either of the final permits using the following links:

Summary of Tier 1 Industrial Stormwater Discharge Permit
Summary of Tier 2 Industrial Stormwater Discharge Permit


The final permits are effective May 13, 2011; all facilities covered under the previous permit are now subject to the requirements of the new permit. Some of the key changes reflected in WDNR’s revised permit compared to the previous permit include:

Discharges To Outstanding and Exceptional Resource Waters. A facility covered under the permit may not create a new storm water discharge to an Outstanding Resource Water (ORW) or an Exceptional Resource Water (ERW) unless the facility’s storm water pollution prevention plan (SWPPP) is updated to prevent the discharge of pollutants above background levels within the water body.
What are Wisconsin Outstanding Resource Water (ORW) or an Exceptional Resource Water (ERW)?

WDNR defines “new storm water discharge” as a discharge that did not exist before the start date of permit coverage. A new discharge does not include an increase in a storm water discharge to a water body to which the facility discharged on or before permit coverage started.
If a facility has an existing storm water discharge to an ERW, it may not increase the discharge of pollutants that results in a violation of water quality standards. If a facility has an existing storm water discharge to an ORW, it may increase the discharge of pollutants provided that: 1) the pollutant concentration within the receiving water would not increase; and 2) the increased discharge would not result in a violation of any water quality standard.

Discharges To Impaired Water Bodies and Total Maximum Daily Load Requirements: If a facility discharges a pollutant of concern to a listed impaired water body, the pollutant levels in the discharge need to be reduced as much as possible as part of an overall state effort to reduce the pollutant loading to impaired water bodies. The final permit requires that an annual check be conducted to determine if the facility discharges listed impaired water body, and to update their SWPPP to reduce the pollutant of concern.

Federal law prohibits the issuance of a WPDES permit to a new source or new discharger that will contribute to a violation of a water quality standard in a listed impaired water. For a new facility requesting coverage under the general permit, the DNR will evaluate the proposed new pollutant discharge and receiving water to determine if the above requirement can be met.
The final permit also requires that facilities conduct an annual check to determine whether the facility discharges storm water runoff to a water body that has an EPA approved TMDL allocation, and to determine if additional storm water control measures are necessary.

Discharges To Fish and Aquatic Life Waters: Under the general permit, a facility must determine whether its discharges storm water to a fish and aquatic life water as defined in Wisconsin Rules. Most receiving waters in Wisconsin are classified as a fish and aquatic life waters. A facility can not create a new storm water discharge to a fish and aquatic life water unless the storm water pollution prevention plan is designed to prevent the significant lowering of water quality.
What are Wisconsin Fish and Aquatic Life Waters?

Compliance with Runoff Management Performance Standards: Wisconsin Rules specifies post-construction performance standards for new development and redevelopment. A newly constructed or redeveloped industrial facility that is required to meet the post-construction performance standards must describe in its SWPPP the BMPs necessary to maintain compliance with the applicable performance standards.

Discharges To The Great Lakes & Tributaries: Under the final permit, discharge of persistent, bioaccumulating toxic (PBT) substances to the Great Lakes waters or their tributaries, must be limited to the maximum extent practicable.

Caltha LLP provides expert environmental consultant services in Wisconsin to obtain air and wastewater permits, evaluate regulatory requirements, and to develop cost effective compliance programs.

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