Underwater Concrete (Tremie)

Tremie concrete is placed underwater through a sealed pipe to form piles, diaphragm walls, and cofferdam bases.
The tremie pipe must remain embedded in fresh concrete throughout the pour to prevent water contamination.
Concrete mix design for tremie pours requires high workability and cohesion to resist washout.
A continuous and uninterrupted concrete supply is essential — breaks in the pour can compromise integrity.
Tremie operations often take place near open water, creating drowning and falling hazards.
Heavy tremie pipes and hoppers require lifting operations with adequate crane capacity.
Concrete deliveries must be coordinated carefully to avoid delays that allow concrete to stiffen.
Workers near the tremie hopper are exposed to wet concrete splash and potential skin burns.
Vibration is not used in tremie pours — concrete flows under its own weight and head pressure.
Quality control relies on monitoring concrete volume placed against theoretical fill volume.

Structural integrity	Breaks in the tremie pour or water ingress create weak zones that can lead to structural failure.
Drowning risk	Work is conducted adjacent to water-filled excavations and open water with constant drowning hazards.
Concrete burns	Prolonged skin contact with wet concrete causes serious alkaline burns requiring medical treatment.

Do

Don't

Ensure the tremie pipe seal is intact before lowering it into position
Keep the pipe tip embedded in fresh concrete throughout the entire pour
Coordinate concrete deliveries to maintain a continuous uninterrupted supply
Wear waterproof PPE including gloves, boots, and eye protection throughout
Install edge protection and rescue equipment around all water-filled excavations
Monitor the volume of concrete placed against the design requirement
Brief the team on the pour sequence, duration, and emergency procedures
Use a crane with adequate capacity to handle tremie pipes and hoppers safely
Wash any concrete splash from skin immediately with clean water
Record all pour data including start time, volumes, and any interruptions

DON'T allow the tremie pipe to lose its seal during the concrete pour
DON'T interrupt the pour unless there is no alternative — continuity is critical
DON'T stand directly over the tremie hopper during concrete discharge
DON'T work near water-filled excavations without personal flotation devices available
DON'T use concrete that has exceeded its specified workability time
DON'T withdraw the tremie pipe above the surface of the fresh concrete
DON'T ignore rising water levels or unexpected inflows during the operation
DON'T attempt to vibrate tremie concrete — it is designed to flow freely
DON'T leave skin exposed to wet concrete without washing it off promptly
DON'T proceed with the pour if the concrete supply cannot be guaranteed

See also: Concrete Pour Safety | Concrete Burns Prevention

Presenter		Project
Location		Date

Toolbox Talk Record