How TrapBag Cofferdam Bags Work
A cofferdam is a temporary enclosure that walls off part of a river, lake, or shoreline so the water inside can be pumped out, leaving a dry space to build or repair. TrapBag Cofferdam Bags form that wall as a line of rectangular, rigid-panel bags filled with gravel on site. Each bag sits flush against the next, so the wall holds its shape and resists leaks while your crew works on the dry side.
How to Install TrapBag Cofferdam Materials
Setting up a TrapBag cofferdam takes three moves and standard site equipment.
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Fill: Slide your forklift forks into the sleeves at the top of each bag to hold it open, then fill with gravel or local aggregate on site.
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Lift: Lift each unit by its fork sleeves or lift belts with an excavator or skid steer.
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Place: Set each bag flush against the last to form a continuous wall, and run an HDPE liner along the water-facing side for a watertight seal.
Who We Serve
TrapBags help organizations of all types control water levels wherever they need to work. Some of the industries and organizations we support include:
Construction
Crews use TrapBag cofferdams to hold a dry, safe footprint while working on bridges, culverts, and roadways over water.
Learn More »Civil & Coastal Engineering
Firms get a stable, dewatered work zone for underwater infrastructure, from pier foundations to intake structures.
Learn More »Municipalities & Governments
Cities and agencies rely on TrapBag for bridge work, pier installation, and dam and reservoir repair. TrapBag holds a GSA Multiple Award Schedule contract (47QSMS26D0024) that covers cofferdams, so public buyers can purchase directly off-schedule.
Learn More »Mining
Operations use TrapBag cofferdams to hold back water and open a dry pit for extraction, wherever the deposit sits.
Learn More »Environmental Protection Services
Conservation groups dewater a section of riverbed for cleanup or to reintroduce native aquatic and amphibian species.
Learn More »Projects
How TrapBag Cofferdams Compare
Every method has a place. Here's where each one fits, and where TrapBag is the better call.
Best Fit: Deep water and long-duration work like major bridge foundations.
Limitations: Heavy mobilization, cranes, skilled crews; slow to install and pull.
Cost & Reuse: Highest cost; rarely reused.
Best Fit: Fast, low-height diversion on flat ground.
Limitations: Punctures and leaks under debris or wave action; weak against current.
Cost & Reuse: Moderate cost; limited reuse once damaged.
Best Fit: Small, shallow, low-budget jobs.
Limitations: Labor-heavy; high failure rate if built imperfectly; slow.
Cost & Reuse:Low material cost, high labor cost; single use.
Best Fit: Shallow and transitional water, concrete or uneven ground, fast turnarounds.
Limitations: Not built for the deepest water or permanent installations.
Cost & Reuse: Lower cost than sheet pile; filled on site and reused across projects.
Why Choose Reusable TrapBag Cofferdam Bags?
Standard TrapBags come as a long chain of cells. Cofferdam bags work differently: each is a discrete two-cell unit with rigid Coroplast panels on every side, so it holds a true rectangular shape with no sloped face. Set flush against the next unit, the panels keep the wall straight and resist bulging for a tighter seal. And because each unit lifts in and out with a spreader bar, crews can empty and relocate it, which most cofferdam sites require and which water-filled barriers can’t do.
At a glance:
- Height: 4 ft
- Shape: rectangular, no slope; rigid Coroplast panels in all walls
- Configuration: a single bag built in a two-cell layout, set flush in a continuous row
- Material: heavy-duty, permeable polypropylene geotextile
- Fill: gravel or local aggregate, filled on site
- Handling: top fork sleeves for forklift placement, plus lift belts
- Emptying: bottom discharge chute to release fill for removal and reuse
- Watertight seal: add an HDPE liner on the water-facing side
- Reuse: emptied, removed, and redeployed across projects
TrapBag supports projects worldwide, with crews available 24/7.