Maintaining Compliance with Your Industrial Storm Water Permit

Industrial storm water permits are designed to protect the quality of surface waters, wetlands, and groundwater. Here’s what you need to know to ensure your company complies with state and federal laws under the Tier 1 or Tier 2 General Permit for Storm Water Associated with Industrial Activity.

What Inspections Should I Be Doing?

The Tier 1 and 2 industrial storm water permits require the following:

  • Quarterly visual wet weather inspections of all outfalls for runoff quality
  • Semiannual dry weather inspection of the facility’s outfalls for the presence of illicit discharges
  • Annual facility site compliance inspection (AFSCI)
  • For Tier 1 permits, annual chemical sampling of the discharge from outfalls for the first two years, after which the Wisconsin Department of Natural Resources (WDNR) may allow you to stop sampling
  • By February 15 of each year, perform a review to determine if your facility discharges to an impaired water or a water with an approved Total Maximum Daily Load (TMDL)

The WDNR has quarterly wet weather and AFSCI inspection form templates on their website. Perform regular site inspections to ensure that you implement and maintain best management practices (BMPs) specified in the plan. This will help you minimize the potential for contaminating storm water runoff, thereby making your quarterly wet weather inspections easy and uneventful. Consider a customized site inspection form that addresses your source areas and the specified BMPs.

What if I Notice Contamination During an Inspection?

If you find signs of contamination during your quarterly wet weather inspection (e.g., color, odor, or clarity issues):

  • Inspect the source areas in the outfall drainage area, which should be shown on the site map in your Storm Water Pollution Prevention Plan (SWPPP). Address noted areas of concern.
  • If off-site runon discharges through this outfall, inspect the condition of the run-on entering your property to determine if this could be the source of the contamination.
  • Document operational changes made (e.g., covering open dumpsters), repairs/ maintenance performed (e.g., repairing leaking equipment), and/or issues with runon entering the property.

Recordkeeping Requirements

Maintain records of all facility inspections/ monitoring, sampling, spills, and SWPPP training. Keep the records on site or in an easily accessible electronic format available for the WDNR to review upon request. The WDNR requires you submit the following (refer to the permits for timing of submittals):

  • If you are unable to evaluate an outfall for non-storm water discharges, you must send a statement to the WDNR certifying that you could not meet the inspection requirement.
  • For Tier 1 permittees, send the AFSCI and chemical sampling and analysis results for the first two years. Additional submissions are required if the WDNR requires additional chemical sampling beyond the first two years.

If discharge from your facility enters a municipal separate storm sewer system covered under a chapter NR 216, Wisconsin Administrative Code, storm water permit, additional reporting requirements are outlined in Part 5.3 of both the Tier 1 and Tier 2 permits.

When Do I Need to Update My SWPPP?

Review and appropriately update your SWPPP when any of the following occur:

  • Changes at the site will result in significant increases in the exposure of pollutants to waters of the state or to storm water treatment devices
  • Inspections/monitoring reveal that the provisions of the SWPPP are ineffective
  • WDNR provides written notice that the SWPPP is ineffectiv
  • The site discharges to an impaired water
  • When the Tier 1 or 2 general permits are reissued (current Tier 1 and 2 general permits expire May 31, 2021) 

Submitted by Betsy Powers, PE (Wisconsin),, 608-216-7347

For a copy of the Tier 1 or Tier 2 Industrial Storm Water General Permits:

WPDES Tier 1 General Permit for Storm Water Associated with Industrial Activity:

WPDES Tier 2 General Permit for Storm Water Associated with Industrial Activity:

Standard WDNR Inspection Templates: