R4 vs. 5G2: Which NJPDES Stormwater Permit Covers a Hot Mix Asphalt Plant?
If you run a hot mix asphalt plant in New Jersey, someone has probably told you that you need a stormwater permit, and then handed you two permit names that sound like they could both apply: the R4 and the 5G2. The New Jersey Department of Environmental Protection (NJDEP) regulates rain that runs across industrial sites, and it sorts facilities into general permits, which are single permits written for a whole category of facilities. For most asphalt plants, the answer is the R4, the Hot Mix Asphalt Producers general permit. The 5G2 is a different kind of permit, and it rarely works for an operating plant.
Below, we walk through why the R4 is the usual fit, how it differs from the 5G2, what can complicate things when an asphalt plant shares a site with recycling or other operations, and how to confirm which permit you're under. If you'd rather talk it through with someone, you can reach out to RMA anytime.
Table of Contents
TL;DR
Most New Jersey hot mix asphalt plants are covered by the R4, NJDEP's industry-specific general permit for facilities in SIC code 2951 and NAICS code 324121. The 5G2 Basic Industrial Stormwater Permit is a catch-all for facilities no industry permit covers, and in practice it expects materials and activities to stay indoors or under cover, which a working asphalt plant can't do. Recycling, aggregate, or concrete operations on the same site can change the answer, so confirm your codes, your current NJDEP authorization, and every activity on your site before assuming the R4 covers it all.
Why Do Most New Jersey Asphalt Plants Use the R4 General Permit?
New Jersey handles industrial stormwater differently than most states. Instead of one general permit for everyone, NJDEP has the Basic Industrial Stormwater General Permit (5G2), plus industry-specific general permits for Concrete Products Manufacturing (CPM), Hot Mix Asphalt (R4), Mining and Quarrying (R13), Sand and Gravel (RSG), Scrap Metal (SM and SM2), Vehicle Recycling (RVR), and Wood Waste Recycling and Leaf Composting (WRC). If your industry has its own permit, that's normally where you belong.
The R4 authorizes stormwater discharges to surface water and groundwater for facilities that manufacture hot mix asphalt, which NJDEP defines by SIC code 2951 and NAICS code 324121. Those are the classification codes that describe what a business does, and a hot mix plant fits them squarely. Because the permit was written for this one industry, it was built around how a plant really operates, with stockpiles, silos, loadout, and truck traffic. It also comes with its own required contents for your stormwater pollution prevention plan, which NJDEP calls an SPPP and which you'll also hear called an SP3 or just a stormwater plan. We call it a SWPPP, and under the R4 it has to follow the contents the permit lays out.
Sampling and monitoring requirements are set in each permit's own text and differ from one permit to the next, so read the current R4 document itself instead of relying on what another plant told you.
How Does the R4 Differ From the 5G2 Basic Industrial Stormwater Permit?
The 5G2 is New Jersey's catch-all. It's meant for industrial facilities that no industry-specific permit covers, and it's the simplest of the New Jersey industrial stormwater permits. The catch is what it asks of you. In practice, the 5G2 expects industrial materials and activities to be kept indoors or under cover, and facilities get a window after authorization to eliminate exposure to rain. We cover that requirement in detail in our 5G2 permit explainer. An asphalt plant has aggregate piles, hot mix loadout, and trucks moving all day, and none of that goes inside a building.
| Question |
R4 (Hot Mix Asphalt) |
5G2 (Basic Industrial) |
| Who is it written for? |
Facilities manufacturing hot mix asphalt (SIC 2951, NAICS 324121) |
Industrial facilities that no industry-specific permit covers |
| Can materials and activities be outdoors? |
It's written for a working plant, so yes, managed under your SWPPP |
In practice, no. Materials and activities need to be indoors or under cover |
| What does the plan look like? |
A SWPPP built to the contents the R4 specifies |
A SWPPP, with an NJDEP template available |
| Does it fit a typical operating asphalt plant? |
Yes, it's the intended permit |
Rarely workable |
A facility that fits neither a general permit nor the no exposure exclusion can end up needing an individual permit written just for it. That's a slower, tougher path, and our guide on individual NJPDES industrial permits explains why most facilities want to avoid it. For an asphalt plant, the R4 usually keeps you out of that situation entirely.
What Edge Cases Change the Stormwater Permit for an Asphalt Plant?
Hot mix plants rarely sit alone on a site. Plenty of them also crush and process reclaimed asphalt pavement or recycled concrete, run a concrete batch plant, screen or stockpile aggregate, or maintain a fleet. The R4 is tied to manufacturing hot mix asphalt, so an activity that belongs to a different category, such as concrete products, mining, or sand and gravel, gets looked at on its own terms. Which permit or permits end up covering a mixed site depends on the activities present, how the site drains, and how NJDEP classifies each operation. We wouldn't reduce that to a rule of thumb, and you shouldn't either.
Recycling adds a second layer. New Jersey regulates recycling operations separately from stormwater, so processing asphalt or concrete material may carry its own approval requirements on top of any stormwater permit. We handle New Jersey recycling approvals, so we see these overlaps regularly, and it's worth sorting out both pieces together rather than discovering the second one during an inspection.
Two other situations come up. If you bought or leased an existing plant, the permit coverage you inherited may not match what you actually do on the site today. And a site that stores or sells asphalt without manufacturing it, like a paving contractor's yard, may not carry the hot mix classification at all and could land in a different category or none. In both cases, the codes and activities on paper are what NJDEP will compare against your permit.
How Can You Confirm Which Stormwater Permit Covers Your Asphalt Plant?
Start with the paperwork you already have. Your NJDEP authorization names the permit category you're covered under, so if it says R4 and your operations haven't changed, you're probably in good shape and may not need anyone's help. Next, check how your business is classified. If your SIC and NAICS codes line up with 2951 and 324121, the R4 is the right home for the asphalt production side of the site.
Then list every activity that happens outdoors on the property, from asphalt production to recycling, crushing, concrete, fueling, and vehicle maintenance, and compare each one against the industry-specific permit categories above. NJDEP's R4 page posts the final permit, the fact sheet, and the attachment describing what the SPPP has to contain, and reading those will answer most coverage questions. Our overview of which NPDES permit you need and our walkthrough of NJPDES stormwater permit requirements help with the bigger picture.
If your site mixes activities and you still can't tell where the lines fall, ask NJDEP or a consultant before you file anything. A wrong filing can leave part of your site uncovered, and you'd rather learn that from a conversation than from an inspector.
How Can RMA Help With Your New Jersey Asphalt Plant Stormwater Permit?
We're a family-run firm based in New Jersey, and our senior staff does the work themselves. For asphalt plants, that usually means confirming which permit or permits your site really needs, preparing a SWPPP that follows the permit, and training your team to run inspections and take their own samples. We don't take your samples for you, because storm timing makes that impractical, and we believe taking your own stormwater samples works better anyway. We also don't do engineering design or treatment system construction, and if that's what your site needs, you'll want an engineering firm for that piece.
If your plant is under the R4 already and nothing has changed, you may not need us at all. If you're unsure, or your site has recycling, concrete, or aggregate operations layered in, we're glad to look at it with you. You can call us at 888-RMA-0230, email info@rmagreen.com, or fill out the form on our website, and you can contact RMA here. There's no pressure and no obligation, and if we're not the right fit, we'll tell you.
