What’s the Difference Between an NPDES Permit and a Stormwater Permit?

NPDES Permits vs. Stormwater Permits, Explained (and Which One You Need)!

If you’ve ever tried to make sense of the difference between an NPDES permit and a stormwater permit, you’re not alone. We hear this question all the time from facility owners, EHS managers, and operators who are just trying to stay compliant without drowning in red tape.

The confusion usually starts when someone realizes their facility might need “an NPDES permit”... but then they also hear people talk about “stormwater permits,” “individual permits,” and a jumble of acronyms like "MSGPs". Yeah, confusing.

So let’s clear this up once and for all. We’ll walk through what each of these really means, how they’re related, and - most importantly - which one you actually need. And if you’re still unsure by the end, don’t guess. Reach out to us here at RMA. We’ve helped hundreds of facilities figure this out quickly and confidently.

Table of Contents

• The Big Picture: NPDES Is the Umbrella
• The Two Big “Groups” of NPDES Permits
• Stormwater Permits: What Most Facilities Need
• When You Need an Individual NPDES Permit
• What If I Discharge Neither? Non-Exposure Certifications Explained
• How Much Does an NPDES Permit Cost?
• Local Stormwater Rules vs. NPDES Permits
• Putting It All Together: Quick NPDES Summary
• How to Get an NPDES Permit
• Additional NPDES Permitting Information

The Big Picture: NPDES Is the Umbrella

Let’s start at the top.

NPDES stands for the National Pollutant Discharge Elimination System, which is a Federal program created under the Clean Water Act. It regulates any discharge of pollutants to U.S. waters, whether that’s a creek, ditch, storm drain, pond, or wetland.

In other words, if water leaves your property and isn’t perfectly clean, it probably falls under NPDES regulations.

Now, while the NPDES program is Federal, most states have been authorized by the EPA to run their own versions. That’s why the name sometimes changes depending on where you are:

• NJPDES in New Jersey
• SPDES in New York (the S stands for "State")
• VPDES in Virginia
• NPDES in North Carolina (they run their own program, but they still call it NPDES)
• NPDES in Massachusetts (they don't have their own program, so they use the EPA's)

And so on. Kinda confusing, often different names, same basic idea. Every one of these is part of the same NPDES framework - the same goal, the same requirements, but most are managed at the state level.

The Two Big “Groups” of NPDES Permits

Okay, so now under that big NPDES umbrella, there are two main groups of permits your facility might fall under:

• Stormwater Permits - these cover discharges of rain (and snowmelt, sleet, hail, etc. runoff).
• Individual NPDES Permits - these cover discharges of process water, wastewater, a mixture of stormwater and process water, or unique discharges and situations.

Within that first group, known as "stormwater permits", you might also find two main types of "general permits":

• Multi-Sector General Permits (MSGPs) - these apply to a wide variety of operations.
• Industry-Specific General Permits - these are for specific types of operations only.

Here's a simple visual guide that shows how everything fits together:

So, both "stormwater permits" and "individual permits" are technically NPDES permits (or NJPDES, SPDES, or whatever your state calls them). Every stormwater (and individual) permit is an NPDES permit. But not every NPDES permit is a stormwater permit (because it might be an individual permit!). 

Make sense? Now, the difference in which one you'll need usually comes down to the type of water you discharge. Let's take a look at each permit type and who they usually apply to.

Stormwater Permits: What Most Facilities Need

Let’s start with the most common type: the stormwater permit.

A stormwater permit applies to rain (or melted snow, sleet, hail, etc.) that runs off your site and picks up pollutants along the way. Think about it - water falls on your roof, parking lot, storage piles, or equipment. It collects oil, dirt, chemicals, and debris, and then drains into a storm drain, ditch, or nearby stream. That runoff can impact water quality, so it’s regulated.

Unless your facility is fully enclosed with ALL equipment and activities indoors, you have stormwater runoff. Sometimes, even just having an exposed parking lot is enough to trigger the need for a permit. That means that regardless of your operation, you probably need some form of stormwater permit coverage at a minimum.

Typical Facilities That Need Stormwater Permits

• Warehouses or distribution centers
• Concrete and asphalt plants
• Marinas and boatyards
• Scrap yards and recycling facilities
• Trucking or maintenance operations
• Industrial manufacturing plants with outdoor storage or loading

The bottom line is that even if you don’t use water in your operations, rain happens - and it’s your responsibility to manage what that rainwater carries off your property. You can reach out here if you think you might need help getting a stormwater permit.

How Stormwater Permitting Works: General vs. Industry-Specific

Within the world of stormwater permitting, there are a few paths depending on your state and industry.

Multi-Sector General Permits (MSGPs)

A MSGP covers multiple industries under one general permit - so whether you’re a marina, a recycling center, or a manufacturing plant, you can all operate under the same statewide stormwater permit as long as you only discharge stormwater (provided that particular MSGP allows all of those industries).

The permit sets broad, standardized requirements (like monitoring, inspections, and best management practices) that apply to everyone it covers. One permit, one set of rules, applicable to lots of facilities.

Example: In South Carolina, the MSGP covers dozens of industrial sectors. So a concrete batch plant, a marina, and a machine shop could all be regulated under that same permit.

Industry-Specific General Permits

Some states take a more customized approach. Instead of one big MSGP, they create separate general permits for specific industries. For example, in North Carolina, there are multiple stormwater general permits, such as:

• NCG14 – for concrete and ready-mix facilities
• NCG16 – for asphalt plants
• NCG19 – for marinas and boatyards

This approach lets the state tailor requirements to different sectors while keeping the permitting process streamlined. You're really at the mercy of whatever your particular state offers.

What If Neither Applies?

In some cases, your operation might not fit neatly into any of the general permits. Maybe your discharges are unusual, or your industry isn’t included.

In that case, you’d need an individual stormwater permit - you might still only discharge stormwater, but need something written specifically for your facility. These are less common but sometimes unavoidable. More on this type of permit next.

When You Need an Individual NPDES Permit

Now let’s talk about the other side of the fence - individual NPDES permits.

Here’s the simplest way to think about it:

• If you discharge only stormwater, you can usually stick with a general stormwater permit.
• If you discharge process water (or if you don't qualify for a general permit), you’re stepping into individual permit territory.

Process water - sometimes called "process wastewater" or just "wastewater" (or any other name) - is any water used in your operations. That might mean water used for cooling, washing, as an ingredient in the production of something, etc. The second you turn on a hose, you’re no longer dealing with stormwater. That’s process water, and it’s usually not going to be covered by a "standard stormwater permit".

Now, if you have some sort of closed-loop system and that water never leaves your property as a discharge, you might still be able to stick with a regular stormwater permit. But any time you're using water and then getting rid of it, you're probably looking at some sort of individual NPDES permit.

How Individual NPDES Permitting Works

When a facility discharges stormwater (which basically everyone does) AND process water, regulators don’t typically separate them - they regulate the entire discharge under the stricter category.

Individual permits are site-specific and usually much more detailed. You’ll likely need to submit a detailed application package with sampling data, process descriptions, outfall maps, and more. There might also be a public comment period where your community can voice any concerns with your proposed discharge.

If your application is ultimately approved, a permit writer will need to develop a custom permit for you with discharge limits, testing requirements, and reporting schedules unique to your operation.

Facilities That Typically Need Individual NPDES Permits

• Mining and quarrying operations
• Theme parks, golf courses, resorts
• Pharmaceutical and chemical manufacturers
• Food or beverage manufacturers
• Large-scale farms or aquaculture facilities
• Power plants and data centers (cooling water)
• Landfills (leachate)
• Industrial laundries or car washes

They’re harder to get, more expensive to maintain, and take longer to process - but if you discharge anything beyond clean stormwater, they’re often unavoidable. If you think you might need an individual permit, reach out to us for a quick gut-check.

What If I Discharge Neither? Non-Exposure Certifications Explained

If your facility doesn't discharge process water and has NO outdoor exposure to industrial materials or processes - meaning everything is handled indoors or under cover - you might qualify for a Non-Exposure Certification (NEC) instead of getting an NPDES permit.

It’s a great option if you can meet the criteria, but it’s strict. Even one uncovered dumpster, storage area, or maintenance activity outdoors can disqualify you. We've seen denials over paved parking lots before!

If you think you might qualify, talk to us - we’ll confirm whether that’s realistic before you go through the paperwork.

How Much Does an NPDES Permit Cost?

We get this question all the time, and the honest answer is that it depends.

The total cost of getting an NPDES permit varies a lot depending on your state, your industry, and whether you’re dealing with a simple stormwater discharge or a more complex process water situation. In most cases:

• Stormwater general permits are on the lower end, typically ranging from a few hundred to a couple thousand dollars in state fees.
• Individual NPDES permits are more involved and can run anywhere from several thousand to tens of thousands of dollars.

And keep in mind, those are just permit costs paid to your state or regulating agency. They don’t include consultant costs, which cover the technical work it takes to prepare and submit a complete application, conduct site assessments, develop your SWPPP, and help you stay compliant after approval.

Because every facility is different, the best way to get a clear picture of your costs is to use our NPDES permit cost calculator below! It’s quick, free, and built by the same environmental professionals who’ve been navigating these permits since 1992. Just answer a few simple questions about your site, and you’ll get an instant estimate of what your permit project is likely to cost before you start the process.

Local Stormwater Rules vs. NPDES Permits

One quick note: your town or county might also have local stormwater requirements - like drainage plans, impervious surface limits, or required site inspections. Those are absolutely important, but they’re not the same thing as an NPDES permit.

You can be 100% compliant locally and still need NPDES stormwater coverage from your state. They work side by side, not as substitutes.

Construction NPDES Permits

Another quick disclaimer: you might’ve also heard about construction stormwater permits, and yes, those are also part of the NPDES program. But they’re a completely different ballgame.

Construction permits deal with temporary runoff from active building sites (things like grading, excavation, and soil disturbance during development projects). They’re focused on preventing sediment and erosion issues while construction is happening.

Our focus at RMA (and in this article) is on NPDES and stormwater permits for ongoing facility operations, not for building or construction projects.

Putting It All Together: Quick NPDES Summary

Here’s the big picture in plain English:

• The NPDES program is the big umbrella that regulates anything leaving your property.
• Stormwater permits sit under that umbrella and cover rain and runoff from things like snowmelt, and are usually offered as either MSGPs or industry-specific general permits.
• Individual NPDES permits are for anything more - process water, washwater, anything that touches your operations, or a combination of the two.
• Most facilities do discharge stormwater. Some discharge both stormwater and process water - and that’s when you move into individual permit territory.
• If you’re truly fully enclosed, you might qualify for a Non-Exposure Certification.
• And regardless of where you’re located, the principles are the same - rain falls, water flows, and you’re responsible for what happens next.

How to Get an NPDES Permit

All stormwater permits are NPDES permits, but not all NPDES permits are stormwater permits. And because no two facilities are exactly alike, figuring out which one applies to you can get complicated fast. That’s where we come in.

At RMA, we’ve been helping companies navigate NPDES permitting since 1992. Over the past three decades, we’ve helped hundreds of businesses across the country get covered under the right permit - whether that’s a general stormwater permit, a Non-Exposure Certification, or a full individual NPDES permit.

Here's how our process works:

• We start by assessing your site.
  We look at your layout, operations, materials, and drainage patterns to determine exactly what kinds of discharges you have - stormwater, process water, or both.
• We identify which permit you actually need.
  Almost every state runs its own version of NPDES, and each one has different forms, timelines, and technical requirements. We sort through all of that for you.
• We handle the application from start to finish.
  NPDES applications can be complicated (and a single mistake can delay your approval for months). We make sure your application is complete, correct, and submitted to the right agency the first time.
• We stay with you through approval and beyond.
  Once your permit is issued, we help you stay compliant, from monitoring and reporting to annual inspections, training, and renewals.

We’ve been doing this for over 30 years, and we know exactly how to navigate the system efficiently, accurately, and with minimal disruption to your business. Contact us here, and we’ll help you find the right permit, get it approved faster, and stay fully compliant - so when the next inspection (or rainstorm) comes around, you’re covered and confident.