Skip to content

Industrial Stormwater Site Inspection Basics

Site inspections are a critical part of your industrial stormwater general permit (ISGP). Inspections are an important tool to catch issues before they cause major stormwater pollution issues, as well as a way to find sources that let to benchmark exceedances. These inspections should be performed monthly by a qualified person at your facility who is familiar with both stormwater and your facility and its processes.  This article is an introductory guide to performing stormwater inspections at your facility.


What To Inspect For:

Use the Printable Site Inspection Template to guide you through inspections of the following:

Stormwater BMPs

You should inspect the condition and effectiveness of all of the stormwater BMPs on your site. You will want to make sure your BMPs are free from clogging and debris, that they are in their proper place, and are working as intended. Your catch basins should also be inspected to ensure sediment buildup is less than 60% of the sump depth or 6″ from the outlet pipe.

Make note of the condition of your treatment and structural BMPs. Are these in need of maintenance or repair? Work to make those fixes promptly to ensure your stormwater discharge is clean.

Stormwater Discharge/ Discharge areas

If possible, perform your inspection when it is raining so you can get a good idea of how stormwater interacts with your site. You should go inspect all areas where stormwater discharges your site. You are looking for obvious signs of pollution. Look out for oil sheen, floating foam or debris, strange odors, or any other signs of contamination.

Illicit Discharge

You also want to inspect for illicit discharge. An illicit discharge is simply a non-stormwater discharge that you are not permitted for. In many cases, it is easier to identify an illicit discharge on a dry day. If water is leaving your site and it is otherwise dry outside, you may likely have an illicit discharge. One common source to look out for is washing operations for vehicles and equipment as well as power washing areas of your property. Other sources may include cooling water or other process wastewater associated with your facility operations.

There are a handful of conditionally allowed non-stormwater discharges that are listed below:

Conditionally authorized non-stormwater discharges include:
a. Discharges from emergency firefighting activities.

b. Fire protection system flushing, testing, and maintenance.

c. Discharges of potable water including water line flushing, provided that water line flushing must be de-chlorinated prior to discharge.

d. Uncontaminated air conditioning or compressor condensate.

e. Landscape watering and irrigation drainage.

f. Uncontaminated groundwater or spring water.

g. Discharges associated with dewatering of foundations, footing drains, or utility vaults where flows are not contaminated with process materials such as solvents. h. Incidental windblown mist from cooling towers that collects on rooftops or areas adjacent to the cooling tower. This does not include intentional discharges from cooling towers such as piped cooling tower blow downs or drains.

Potential Pollutant Sources

The bulk of your inspection will be focused on identifying and eliminating potential pollutant sources. Numerous areas within an industrial site could contribute pollutants to your stormwater. Although all sites are different, some common areas to pay extra attention to include:

Maintenance and Fueling Areas: There are a lot of fluids and other pollutant-generating materials that are associated with vehicle and equipment maintenance. You should be on the lookout for drips, leaks, and spills in these areas. Make sure that maintenance activity is occurring indoors or under cover,  and that these areas have spill kits that are well-stocked and easy to find. Make sure that your fluids are in secondary containment and are stored under cover so that rain won’t interact with them.

Dumpsters: Dumpsters can host several pollutants. Inspect that your dumpsters are not leaking and remain covered when not in use.

Storage Areas: Inspect your storage areas including vehicle and equipment storage. Keep an eye out for leaks and spills. Look at raw materials storage, and look out for accumulated sediment and debris. Look for materials that can be stored under cover or need secondary containment.

Paved Surfaces: Inspect your paved surfaces for accumulated sediment and debris. Is it time to call a sweeping vendor? Accumulated sediment on paved surfaces can lead to elevated values of TSS as well as metals like copper and zinc.


During your inspection, you should be referencing your SWPPP and site maps. Note any changes or variances from these documents that you encounter, and update them as needed. Mark problem areas on your site map that you encounter throughout your site inspection and use that map to remedy the issues.


While site inspections are an important component of ISGP compliance, it is important to remember that it is just one part of a 2 part process. Identifying issues on your site is important, but it is equally as important to take action to ensure that those issues don’t lead to larger problems.

For more video content covering a wide range of stormwater topics, please visit our YouTube page!