Does my facility need an industrial stormwater permit?

This image shows a flowchart to decide if facility needs an ISW permit
Flowchart used to decide if facility needs an Industrial Stormwater permit


This fact sheet addresses how to determine a facility’s primary Standard Industrial Classification code (SIC code) or narrative activity and related common questions.

The questions and answers in this fact sheet are based on Minnesota’s Questions and Answers, developed with the U.S. Environmental Protection Agency (EPA) to clarify EPA document “National Pollutant Discharge Elimination System (NPDES) Storm Water Program Questions and Answers, Vol. 1 and Vol. 2.”

Q1 How do I know if my facility needs an industrial stormwater permit?

The MPCA’s industrial stormwater permit lists the industries that need a permit. They are listed by SIC code or are explained in a narrative in Appendix D (page 148) of the permit. Listed industries must get a permit or certify that nothing is exposed to stormwater.

For convenience, the regulated primary SIC codes and descriptions of narrative activities are reprinted at the end of this fact sheet starting on page 10.

Q2 What is a SIC code?

SIC codes are a way of classifying industries by 4-digit codes. It is a descriptor of the kind of work being done at a facility, not a number specifically assigned to the facility like a tax ID. Facilities can have several SIC codes but only one Primary SIC code.

The IRS uses SIC codes, so your tax paperwork or accountant may already have the facility’s SIC code. Look on these federal tax forms:

  • Schedule C or C-EZ for Sole Proprietors
  • Form 1065 for Partners
  • Form 1120 for C Corporations
  • Form 1120-S for S Corporations

A searchable database of the SIC Codes is available here

Example: A company manufactures metal washers and hinges. Searching for the word “washers” on the linked OSHA website returns a few options. One of them – SIC 3452: Bolts, Nuts, Screws, Rivets and Washers – covers the washers, but not the hinges. Searching for “hinges” returns SIC 3429: Hardware Not Elsewhere Classified. Although hinges aren’t mentioned in the title for SIC 3429, they are specifically listed in the description. Be sure to read the descriptions because they frequently offer the SIC codes for related activities.

Q3 What is a Primary SIC code?

If a facility has more than one SIC code, the activity that generates the greatest revenue is the Primary SIC code. If revenue information is unavailable, use the SIC code for the activity with the most employees. If employee information is also unavailable, use the SIC code for the activity with the greatest production.

Q4 Does a facility need more than one stormwater permit if it has more than one SIC code?

No, only one permit or No Exposure certification is required; it will address all the operations at the facility.

Q5 My facility’s Primary SIC code isn’t listed. Do I need a permit?

If the facility fits one of the listed narrative activities, a permit or No Exposure certification is required regardless of whether or not the facility’s Primary SIC code is listed. But if the facility isn’t described by a listed narrative activity and its Primary SIC code isn’t listed, a permit isn’t required even if a Secondary SIC code is listed. See Table 1.

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