Leave a generator on a job site long enough and there’s usually a dark spot under it. A fuel fitting weeps, oil seeps past a gasket, or someone overfills it at the end of a long shift. A low foam wall berm under the unit catches that before it reaches the gravel or a storm drain. Setting one up is just unfolding it.
Why a foam wall berm works under equipment
- No set-up. Unfold it and the foam walls stand on their own. No frames, pins or inflation.
- Tow it in. Trailer-mounted units can be backed straight in. The walls compress under the tires and stand back up.
- Reusable. When the job moves, fold it and throw it in the truck.
Match the berm to the footprint
Measure the unit’s footprint, then add about a foot on every side. Don’t forget the trailer tongue. A common mistake is buying for the generator body and ending up with the tongue jack sitting on the foam wall. Footprints below are rough ranges; measure your own equipment.
| Equipment | Typical footprint | Berm to look at | Capacity |
|---|---|---|---|
| Small portable generator or pressure washer | under 3′ x 3′ | Mini foam wall 2′ x 2′ or 4′ x 4′ | 15 or 60 gal |
| Skid-mounted generator, pump or welder | up to about 3′ x 5′ | Mini foam wall 4′ x 6′ or 4′ x 6′ PVC foam wall | 75 or 59 gal |
| Towable light tower or small towable compressor | about 5′ x 10′ with tongue | 10′ x 10′ | 249 gal |
| Towable generator or large compressor | about 6′ x 14′ to 7′ x 18′ with tongue | 10′ x 20′ | 498 gal |
| Generator plus fuel cube or several units in a row | varies | 10′ x 30′ and up, or a custom size | 748 gal and up |
For a small skid-mounted unit, we’d start with a mini foam wall berm. They have 6-inch walls and weigh 3 to 9 pounds, so one person carries them in. For anything on a trailer, go to the 4-inch PVC foam wall berms, which come in the longer footprints towable equipment needs.
How much capacity is enough?
Compare the berm’s gallon rating with the largest fuel tank or oil reservoir sitting inside it. A berm that holds more than the full tank covers a total failure, not just drips. If the site has an SPCC plan or a permit with containment requirements, size the berm to what that document says.
Set-up tips
- Pick level ground. A berm on a slope loses capacity on the low side.
- Clear the ground. Rake away rocks, rebar ends and anything sharp before you unfold it.
- Keep the exhaust clear. Position the berm so hot exhaust does not blow onto the liner or the foam walls.
- Line it. A few sorbent pads under the fuel fill and drain points soak up drips so the berm stays clean.
- Watch the rain. An outdoor berm fills with rainwater. Check it after storms and remove the water so the berm keeps its full capacity.
Refueling inside the berm
Refuel with the unit sitting in the berm. If a fuel nozzle overfills or a can tips, the spill lands in the berm instead of on the ground. Keep a small spill kit at the refueling spot for anything that splashes outside the walls.
Frequently asked questions
What size berm do I need for a towable generator? Measure the unit with its tongue and add about a foot on each side. Many towable generators fit a 10′ x 20′ berm; smaller towable light towers and compressors often fit a 10′ x 10′.
Can I back a trailer-mounted generator into a foam wall berm? Yes. The foam walls compress under the tires and stand back up after the wheels pass.
What’s the difference between the mini foam wall and the standard foam wall berm? The mini berms have 6-inch walls, weigh 3 to 9 pounds and come in 2′ x 2′, 4′ x 4′ and 4′ x 6′. The standard PVC foam wall berms have 4-inch walls and run from 4′ x 6′ up to 10′ x 50′ for larger towable equipment.
Do foam wall berms ship free? Yes, to the continental US. Smaller sizes ship UPS Ground; 10′ x 30′ and larger ship LTL freight.
Shop generator containment
Browse the mini foam wall berms for small equipment and the foam wall containment berm collection for towable units. If you also fuel equipment on site, see spill containment for mobile refueling and fuel transfer. Need help matching a berm to your equipment? Call (800) 869-9633.
