Underwater Placed Concrete AHA (Activity Hazard Analysis / Job Hazard Analysis)

Updated 2026-06-23

A Underwater Placed Concrete AHA (Activity Hazard Analysis / Job Hazard Analysis) is the plan that keeps the crew placing concrete underwater safe during the diving and underwater work, through the tremie and placement equipment, and around the drowning and over-water hazards. Underwater placed concrete places concrete beneath the water using tremie and pumped methods — combining the diving and underwater-work hazard, the tremie and placement- equipment hazard, and the drowning and over-water hazard. This guide walks through building a Underwater Placed Concrete AHA that names the diving/underwater-work, tremie/placement-equipment, and drowning/over-water hazards and assigns the diving, tremie, and drowning controls that hold up in the field.

Why underwater placed concrete needs its own AHA

Underwater placed concrete is the placement of concrete beneath the water surface — for foundations, seals, piers, and marine structures — using tremie pipes (a pipe delivering concrete below the water so it displaces water without washing out) or pumped underwater placement, often supported by commercial divers. The defining feature is the underwater environment: the work may involve commercial diving (a high-hazard, specialized activity), the tremie/pumped placement equipment, and the drowning and over-water hazards for the surface crew. The hazards combine the diving and underwater-work (underwater concrete placement often involves commercial divers positioning/managing the tremie and work underwater — the commercial-diving hazards (a highly specialized, high-hazard activity — drowning, decompression, entrapment, requiring the diving standards)), the tremie and placement-equipment (the tremie pipe and placement equipment — the handling of the heavy tremie, the placement-equipment hazards, and maintaining the tremie seal/placement), the drowning and over-water (the surface crew working over/near the water (from barges, platforms) — the drowning and over-water hazards), and the wet-concrete/marine. The diving/underwater-work and the drowning/over-water justify a dedicated AHA.

Breaking underwater placed concrete into steps

The steps for a Underwater Placed Concrete AHA follow the placement:

• Plan the underwater placement (tremie/pump, diving if needed)
• Establish the diving operation (if divers used — dive plan)
• Establish drowning prevention for the surface crew
• Set up and position the tremie/placement equipment
• Place the concrete underwater (maintaining the tremie seal)
• Manage the diving, tremie, and drowning hazards
• Monitor and complete the placement
• Complete

Each step carries a hazard, and the diving/underwater-work, the tremie/placement-equipment, and the drowning/ over-water are where the most significant risks concentrate.

The hazards step by step

Diving and underwater-work

Underwater concrete placement often involves commercial divers positioning/managing the tremie and work underwater — the commercial-diving hazards (a highly specialized, high-hazard activity — drowning, decompression, entrapment, requiring the diving standards). The controls are commercial diving conducted under the commercial- diving standards (qualified/certified commercial divers, a dive plan, dive tables/decompression, dive team with standby diver and tender, dive supervisor — commercial diving is a specialized high-hazard activity governed by its own standards, not general construction diving), coordinating the diving with the concrete placement, and the diving controls. The diving/underwater-work is the primary defining hazard — commercial diving is a specialized high-hazard activity. (These follow the commercial-diving fundamentals.)

Tremie and placement-equipment

The tremie pipe and placement equipment — the handling of the heavy tremie, the placement-equipment hazards, and maintaining the tremie seal/placement. The controls are safe handling of the tremie pipe (heavy, positioned over/ in water — rigging, handling), safe placement-equipment operation (pumps, the placement system), maintaining the tremie seal (the tremie must stay embedded in the concrete to prevent washout — a placement-quality point), and the tremie/equipment controls. The tremie/placement-equipment is a defining hazard — the heavy tremie and placement equipment carry handling and operation hazards. (These follow the tremie-placement fundamentals.)

Drowning and over-water

The surface crew working over/near the water (from barges, platforms) — the drowning and over-water hazards. The controls are the drowning-prevention program for the surface crew (PFDs, water rescue, edge protection — the same marine drowning controls), safe over-water work, coordination with any divers (never endangering divers with surface operations), and the drowning/over-water controls. The drowning/over-water is a defining hazard — the surface crew works over water. (These follow the working-over-water fundamentals.)

Wet-concrete/marine

The wet concrete and marine conditions (caustic concrete, marine/weather) carries the contact/conditions hazard. The controls are wet-concrete contact protection, marine-conditions management, and the contact/conditions controls. (These follow the cement-contact fundamentals.)

A simple Underwater Placed Concrete AHA structure

Commercial-diving safety and drowning/tremie management

A Underwater Placed Concrete AHA centers on commercial-diving safety and drowning/tremie management. The commercial-diving safety addresses the specialized underwater work — controlled by commercial diving conducted under the commercial-diving standards (qualified divers, dive plan, decompression, dive team with standby diver and tender, dive supervisor) and coordinating the diving with the placement. The drowning/tremie management addresses the surface crew and the tremie — controlled by the drowning-prevention program for the surface crew (PFDs, water rescue, edge protection) and safe handling/operation of the tremie and placement equipment. And the wet concrete and marine conditions get contact controls. An AHA built on commercial-diving safety and drowning/ tremie management, with contact controls, addresses the hazards that define underwater placed concrete.

From the field: what actually goes wrong

In fourteen years across federal, heavy civil, and industrial projects, underwater placed concrete places concrete beneath the water using tremie and pumped methods, and its defining hazards center on the underwater environment — most significantly, where commercial divers are involved. The diving and underwater-work hazard is the primary defining concern when divers are used — underwater concrete placement often requires commercial divers to position and manage the tremie pipe, inspect the placement, and work underwater, and commercial diving is a highly specialized, high-hazard activity with its own serious hazards (drowning, decompression sickness, entrapment, and the underwater environment) and its own regulatory standards (OSHA's commercial diving standards). Commercial diving is not general construction work that a construction crew improvises — it must be conducted under the commercial-diving standards by qualified and certified commercial divers, with a proper dive plan, dive tables and decompression procedures, a full dive team (including a standby diver and a tender), and a dive supervisor. So the control is that the diving is conducted properly under the commercial-diving standards, and the concrete placement is coordinated with the diving. Commercial diving is a specialized discipline with its own standards, and treating it as anything less is where fatalities happen.

The tremie/placement-equipment and the drowning/over-water are the other defining hazards. On the projects I have run, the tremie pipe (the pipe that delivers concrete below the water surface, kept embedded in the fresh concrete so it displaces water without the concrete washing out) is heavy and positioned over and in the water, so safe handling of the tremie (rigging and handling the heavy pipe), safe placement-equipment operation, and maintaining the tremie seal (keeping the tremie embedded in the concrete — a placement-quality point that also avoids washout) are the controls. And the drowning/over-water hazard applies to the surface crew, who work over and near the water from barges and platforms, so the drowning-prevention program (PFDs, water rescue, edge protection — the same marine drowning controls as the marine concrete AHA) and, critically, coordination with any divers so that surface operations never endanger the divers below are the controls. Protecting the surface crew from drowning and never endangering the divers are both essential. The wet-concrete contact and marine conditions round it out. The AHA built on commercial-diving safety and drowning/tremie management is the one that protects the underwater-placement crew.

The bottom line

A Underwater Placed Concrete AHA names the diving/underwater-work, the tremie/placement-equipment, and the drowning/over-water hazards with specific controls — commercial diving conducted under the commercial-diving standards by qualified divers (a specialized high-hazard activity, not improvised), safe handling of the heavy tremie while maintaining its seal, and drowning prevention for the surface crew coordinated with the divers. The commercial-diving safety and the drowning/tremie management are the defining concerns. The AHA that manages both is the one that protects the crew.

Frequently asked questions

Why must commercial diving be conducted under its own standards?

Underwater concrete placement often requires commercial divers to position and manage the tremie and work underwater, and commercial diving is a highly specialized, high-hazard activity with serious hazards (drowning, decompression sickness, entrapment) and its own regulatory standards — it is not general construction work that a crew improvises, and treating it as less is where fatalities happen. Controls are commercial diving conducted under the commercial-diving standards (qualified/certified commercial divers, a dive plan, dive tables/decompression, a dive team with standby diver and tender, a dive supervisor), coordinating the diving with the placement, and the diving controls.

What tremie hazards apply?

The tremie pipe (delivering concrete below the water surface, kept embedded in the fresh concrete so it displaces water without washout) is heavy and positioned over and in the water. Controls are safe handling of the tremie pipe (rigging, handling), safe placement-equipment operation (pumps, the placement system), maintaining the tremie seal (keeping it embedded in the concrete), and the tremie/equipment controls.

What protects the surface crew?

The surface crew works over and near the water from barges and platforms, facing drowning and over-water hazards. Controls are the drowning-prevention program for the surface crew (PFDs, water rescue, edge protection — the same marine drowning controls), safe over-water work, coordination with any divers (never endangering divers with surface operations), and the drowning/over-water controls.

What is underwater placed concrete?

Underwater placed concrete is the placement of concrete beneath the water surface — for foundations, seals, piers, and marine structures — using tremie pipes or pumped underwater placement, often supported by commercial divers. Because it may involve commercial diving (a specialized high-hazard activity), the tremie/placement equipment, and drowning/over-water hazards for the surface crew, those hazards apply.

Related AHAs and JHAs

• Marine Concrete AHA — the broader marine concrete work
• Cast-in-Place Concrete AHA — the concrete placement fundamentals
• Structural Concrete AHA — the structural concrete fundamentals
• Concrete Placement JHA — the placement fundamentals

Written by Mustafa Tok, CSP, ASP, CHST — OSHA Authorized Outreach Trainer with 14+ years of international construction safety experience across federal, heavy civil, and industrial projects.