Why Would You Need a NPDES Stormwater Permit and When do You Submit a Stormwater Permit Renewal?

Stormwater pollution and permit renewals

Why Would You Need a NPDES Stormwater Permit and When do You Submit a Stormwater Permit Renewal?

What are stormwater permits and when do you need to complete a stormwater permit renewal? When stormwater runoff is generated in developed areas after precipitation, it inevitably picks up “non-point source” pollutants. These pollutants are low in quantity and therefore impossible to trace their origins. The longer stormwater runs over impervious surfaces, where it can’t be absorbed and naturally cleaned by soil, the higher the chance it will be integrated with “point-source pollutants” before it empties into water bodies like rivers and lakes. Anyone who owns these developed areas, streets, facilities (buildings), and/or parking lots, etc., are responsible for obtaining a stormwater permit to ensure that the runoff generated in their area is not integrated with point-source pollutants. 

Stormwater permits detail out the Best Management Practices (BMPs) that attempt to either remove pollutants at their source or respond to them by filtering them out before the runoff leaves the property. They typically specify an acceptable level or concentration of pollutant in a property’s stormwater discharge.

There are different types of stormwater permits. The Federal permit, published by the Environmental Protection Agency (EPA), is used by a handful of states, all territories and Indian lands. The National Pollutant Discharge Elimination System (NPDES) regulates stormwater discharges from Municipal Separate Storm Sewer Systems (MS4s) as well as construction and industrial activities. MS4s are owned by governmental entities specifically, i.e. cities or counties. Sometimes these are called “MS4 permits”. MS4s collect and discharge stormwater to local water bodies through a system of storm drain inlets, gutters, and sewers. 

Most states have issued their own NPDES stormwater general permits, based off the Federal permit and under delegated authority from the EPA. If a property doesn’t fall under the NPDES permit requirements and conditions, they must apply to be under an individual permit that reflects site-specific conditions and has generally stricter guidelines.


What counts as construction or industrial activities? Heavy manufacturing facilities like chemical plants, coal and oil processing plants, hazardous waste treatment, landfills, junkyards, power plants, and transportation facilities are all examples of industrial activities. Any clearing, excavating, or grading of land counts as a construction activity. A NPDES stormwater permit is required for any construction activity that disturbs more than 1 acre of land. High amounts of sediment in stormwater from construction or erosion can be just as harmful as chemicals leaked into stormwater.

Common permit requirements can include but are not limited to: routine inspections, stormwater sample examinations, that represent the onsite stormwater discharge, and stormwater pollution prevention training. For example, employees need to be trained once a year on how to immediately prevent an observed spill or leak from entering into stormwater. There are often specific requirements with stormwater sample examinations such as submitting samples to a lab and having it analyzed to ensure it falls under the acceptable limits of the permit.


Notice of Intents (NOI) are the application forms that are submitted to the state in order to be covered under a general NPDES or state permit. A submitted NOI certifies that a property meets all of the conditions outlined in the general permit. The Clean Water Act limits the length of state and NPDES permits to five years. Because stormwater permit renewals can occur at any time, state stormwater permit renewal schedules vary greatly. If adjustments are made to the permit requirements during a renewal, these new changes will need to be followed by the permittees. For example, the most recent renewal permit in Colorado added several new requirements for control measures at construction sites. Control measures describe in the permit the range of pollutant reduction practices a permittee may implement. This often includes required “booms” around stormwater drain inlets that filter out the dirt in stormwater (suspended solids).

Notice of Terminations (NOT) only occur when a permittee does not meet condition(s) listed under the permit. Like NOIs, NOTs are submitted by the facility. Submitting a Notice of Termination can either mean that permit coverage is no longer necessary or that the facility needs to apply for a different type of permit. For example, if the stormwater discharge changes from MS4 to Combined Sewer system, it no longer needs to be under a stormwater permit and it will have to provide notice of termination

Combined Sewer systems treat both sanitary and stormwater runoff through treatment plants therefore coverage under a state permit is not required.  Check your local regulations, however, as you may have other city regulations to follow. 

Another common example of when an NOT needs to be submitted is when construction is no longer occurring and the site has been stabilized under a construction permit. 

Individual permits are often more intensive when compared to a general permit. For example, required facility inspection frequency can change from quarterly to monthly or a facility may be required to perform laboratory analysis on multiple parameters. A facility may also have to apply for an individual permit if the state’s general permit is expired and a new permit has not been issued yet. During the permit renewal process, no NEW NOI’s can typically be processed by the state or EPA if the current permit is expired. Existing dischargers, already under the permit, would continue to have coverage under an administrative extension.

While permits are varied and use exceedingly technical legalese language, they are basically just guidelines for how to minimize or eliminate pollution to your closest waterways and therefore protect yourself from the legal consequences of doing so. If your facility needs assistance with submitting a Notice of Intent or Notice of Termination, or interpreting a permit and consulting on its requirements, Stormwater Compliance Solutions, LLC can help! Please CONTACT US to find out more or visit our Compliance Services page to learn more about our stormwater permit compliance services.

Lisa Cratty has over 20 years of experience in management. Previously, Lisa worked for an international law firm as the Department Head of both IT and Accounting. She managed the staff, spearheaded various committees and was responsible for strategic planning and the implementation of multiple projects. In 2012, Lisa transitioned into the environmental world where she began the work of interpreting industrial stormwater permits and keeping clients in compliance with regulations in multiple states. In late 2015 she began working with Stormwater Compliance Solutions where she now manages the Stormwater Compliance Division, the Colorado office and team and over 1,400 facilities across the United States under industrial, construction and municipal stormwater permits.  Lisa is an expert at project management and keeps our clients in regulatory compliance with their permits so they are free to focus on their business.