What the 5G2 Requires Instead, Which New Jersey Permits Do Require Stormwater Sampling, and Why Some Facilities Sample Anyway
If you've been told your New Jersey facility needs a 5G2 permit, one of the first things you probably want to know is whether you'll be standing in the rain with sample bottles. The short answer is no. The 5G2 is NJDEP's Basic Industrial Stormwater General Permit, and it doesn't require stormwater sampling. The catch is that New Jersey has a whole family of industrial stormwater permits, and some of the others, the scrap metal SM2 permit being the clearest example, do require sampling. So the real question is whether you're on the 5G2 or on something else.
This article covers what the 5G2 asks you to do in place of sampling, how it compares to the industry-specific and individual permits, how to confirm which permit's rules apply to your site, and why some 5G2 facilities collect samples anyway. If you'd rather talk through your own situation, you can reach out to RMA at any point.
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TL;DR
No, the 5G2 doesn't require stormwater sampling. It's built for facilities that keep everything industrial covered or indoors, so it relies on a stormwater plan, regular inspections, training, and an annual certification instead. Some industry-specific permits do require sampling (the scrap metal SM2 permit calls for quarterly samples), and individual permits typically carry more monitoring, so check which permit you're under. Some 5G2 facilities sample voluntarily to confirm their controls are working.
What Is the 5G2 Basic Industrial Stormwater Permit?
New Jersey treats rain that runs off certain industrial sites as a regulated discharge. NJDEP (the New Jersey Department of Environmental Protection) handles that through NJPDES, the New Jersey Pollutant Discharge Elimination System, and one of the permits it issues is the Basic Industrial Stormwater General Permit, known by its category code, 5G2. A general permit is one permit NJDEP wrote once for a whole group of facilities. You apply for coverage under it instead of getting a permit written for your site.
NJDEP describes the 5G2 as available to regulated industrial facilities that have eliminated, or can eliminate within six months of authorization, all exposure of industrial materials and activities to rainfall and snowmelt. You eliminate exposure by covering materials and activities or moving them indoors. NJDEP's industrial stormwater program page says most regulated facilities in the state are authorized under this permit, and the current master general permit took effect February 1, 2023. Think of a manufacturer that keeps everything inside except the parking lot and a covered dumpster. Our guide to the 5G2 permit in New Jersey walks through eligibility and the rest of the permit in more detail.
Does the 5G2 Require Stormwater Sampling?
No. In an NJDEP presentation on its industrial stormwater program, the agency describes the 5G2 as built around best management practices (BMPs) that eliminate stormwater contact with source materials, with no monitoring. The logic holds together. Sampling exists to measure pollutants leaving your site in runoff. The 5G2 is for facilities that have already removed the source of those pollutants from the rain, so there's nothing to sample for.
Skipping sampling doesn't mean skipping work. In our experience with the permit, the ongoing pieces are a stormwater pollution prevention plan (NJDEP calls it an SPPP, and you'll hear it called an SP3 or just a stormwater plan, but we'll call it a SWPPP), monthly inspections, an annual comprehensive inspection, annual training, and an annual certification. The permit text and NJDEP's certification form spell out the details, so read the version in effect. Our explainer on what a SWPPP is covers what goes into the plan.
Less sampling also doesn't mean NJDEP never shows up. NJDEP has described its inspection cycle for 5G2 facilities as roughly every five years, compared with every one to three years for industry-specific permit holders, though in practice it varies, and some 5G2 facilities get inspected more often than that. When an inspector does come, the question is whether your materials are really covered or indoors, because that's the promise the permit rests on.
Which New Jersey Industrial Stormwater Permits Require Sampling?
New Jersey doesn't have one industrial stormwater permit. It has the 5G2, a set of industry-specific general permits, individual permits, and an exclusion for facilities with no exposure at all. The industry-specific general permits are Concrete Products Manufacturing (CPM), Hot Mix Asphalt (R4), Mining and Quarrying (R13), Sand and Gravel (RSG), Scrap Metal (SM2), Vehicle Recycling (RVR), and Wood Waste Recycling and Leaf Composting (WRC). NJDEP says these industry-specific permits may include monitoring, benchmarks, or effluent limits, which is where the sampling requirements come from.
| Permit |
Who it's for |
Stormwater sampling |
| 5G2 Basic Industrial Stormwater General Permit |
Regulated facilities that have eliminated, or can eliminate within six months, all exposure to rain and snowmelt |
None. Built around keeping materials out of the rain. |
| SM2 Scrap Metal General Permit |
Scrap metal processing and recycling facilities |
Quarterly sampling, with results submitted to NJDEP, according to NJDEP's October 2025 compliance advisory. |
| CPM, R4, R13, RSG, RVR, and WRC industry permits |
Concrete products, hot mix asphalt, mining and quarrying, sand and gravel, vehicle recycling, and wood waste recycling and leaf composting |
Each permit sets its own monitoring terms and may include sampling, benchmarks, or limits. Read yours. |
| Individual NJPDES permit |
Facilities that can't eliminate exposure and don't fit a general permit |
Typically more extensive sampling and monitoring, written for the site. |
| No exposure exclusion |
Facilities that qualify by keeping everything industrial permanently indoors or under cover |
No permit, so no sampling. |
We haven't listed sampling parameters and frequencies for every industry permit here because they differ from permit to permit and from one version to the next. NJDEP has reissued several recently. The sand and gravel master general permit, for example, took effect January 1, 2026, so pull the current version from NJDEP's website instead of relying on an old copy or a neighbor's advice. If your permit has benchmarks or effluent limits, our piece on benchmark values versus effluent limits explains why the difference changes what a bad result means.
Two of those permits have their own write-ups from us. Scrap yards can read about the SM2 scrap metal permit, and concrete producers can start with our guide to concrete plants and stormwater permits. For a broader look at how New Jersey's requirements fit together, see our overview of NJPDES stormwater permit requirements.
When Is the 5G2 the Wrong Stormwater Permit for Your Facility?
The 5G2 only fits if exposure is eliminated, or will be within six months of authorization. If you have uncovered stockpiles, open bins, scrap, equipment stored outside, or vehicles being serviced in the yard, you can't truthfully say you've removed exposure. That puts you on a different permit, and a different permit can change your sampling answer completely.
We see this situation fairly often. A facility ends up on the 5G2 because it looked like the simplest option, then keeps material outside year after year. On paper the site has no exposure. In the yard, it does. There are two honest fixes. You can cover or move the materials so the 5G2 is accurate, or you can get on the permit that matches what you really do, whether that's an industry-specific permit or an individual permit. Our guide to which NPDES permit you need lays out how general, individual, and no-exposure coverage differ, and our article on common NPDES permit problems covers mismatches like this one.
If you're not sure whether you qualify for no exposure instead of a permit, our explanation of what no exposure means is a good place to start. The bar is high, and a site that qualifies has to stay that way.
Why Do Some 5G2 Facilities Sample Stormwater Anyway?
The permit doesn't ask for samples, but plenty of 5G2 facilities collect them. The most common reason is that a sample is the quickest way to find out whether your controls are really working. A plan that says everything is covered doesn't tell you what's in the water leaving the property, and a pH reading or a lab result can catch a problem before an inspector or a neighbor does. Others sample because a customer, lender, insurer, or corporate environmental program asks for data. Some do it after a spill or a change in operations, and some do it because they suspect they might be heading toward a different permit and want a baseline first.
If you decide to sample voluntarily, treat it like real data. The 5G2 doesn't set parameters or limits for you, so a lab or consultant can help you pick what makes sense for what's on your site. If you want results to hold up with anyone else, use a New Jersey-certified lab and follow standard sampling methods. Our tips on how to take a good stormwater sample and our article on taking your own stormwater samples cover the practical side, and we've explained why more monitoring than your permit requires can be a smart move for some facilities.
Before you start, decide what you'll do with a bad result. A result is a record, and a high reading usually means going back to look at your covers, your housekeeping, or your assumptions about what's outside. Our article on whether you have to report bad stormwater results is worth reading before you collect your first bottle.
How Do You Confirm Which Stormwater Sampling Rules Apply to You?
Start with the paperwork NJDEP issued when it authorized your facility. It identifies the permit category, such as 5G2, CPM, or SM2. If you can't find it, track it down first, because everything else depends on knowing which permit you're under. Then pull the current version of that permit from NJDEP's industrial stormwater general permits page and read the monitoring section, if it has one. A permit with no monitoring section is telling you something, too.
Next, compare the permit to what happens on your site. A facility with a 5G2 but open piles of material needs to fix the mismatch. A facility in a regulated industry, such as concrete, asphalt, mining, scrap metal, vehicle recycling, or wood and leaf recycling, should confirm it's under that industry's permit instead of the basic one. Permit coverage also depends on where your water goes and on the industrial activity at your site, so details vary, and we'd rather you confirm than assume. It's also the kind of mismatch inspectors notice.
How Does RMA Help With 5G2 and Stormwater Sampling Questions?
If you're on the 5G2 and everything really is covered or indoors, you may not need much help from us. There's no sampling to manage, and plenty of 5G2 facilities handle their own plan and annual paperwork. Our article on writing your own SWPPP is a fair starting point if you'd rather go that route.
Where we help is figuring out which permit your facility belongs on, building the SWPPP, training your team through our online training library, and supporting you after you're permitted, with reminders, help interpreting results, annual updates, and inspection prep. We're based in New Jersey and know how NJDEP sorts these permits. If your permit requires sampling, we don't collect your samples. You know your site, and storm windows are too short for us to get there in time, so we train your team to sample correctly instead. If what you need is a treatment system designed, that's engineering work, and we're not the right firm for it.
If you'd like a second set of eyes on which permit you're under, or what it requires, you can call, email, or fill out the form on our website. There's no pressure and no obligation. Just contact RMA and tell us a bit about your facility.
