Trenching and Excavation Safety for Workers (Caught-In/Between)

Cave-ins and the 5-foot rule

These rules apply to all open excavations in the earth's surface, including trenches. A trench is a narrow excavation: in general deeper than it is wide, and no more than 15 feet wide at the bottom.

A cave-in is when soil or rock separates from the side of an excavation, or soil is lost from under a trench shield or support system, and moves suddenly into the hole in enough quantity to trap, bury, or otherwise injure and immobilize a person.

The rule

Every worker in an excavation must be protected from cave-ins by an adequate protective system, except when:

• The excavation is made entirely in stable rock, or
• It is less than 5 feet deep and a competent person has examined the ground and found no sign of a possible cave-in.

Reference: 29 CFR 1926.650(a) · 29 CFR 1926.650(b) "Cave-in" · 29 CFR 1926.650(b) "Trench (Trench excavation)" · 29 CFR 1926.652(a)(1)

Protective systems you will see

There are four main types of protective system you will see. Learn to recognize each one.

Reference: 29 CFR 1926.650(b) "Protective system" · 29 CFR 1926.650(b) "Sloping (Sloping system)" · 29 CFR 1926.650(b) "Benching (Benching system)" · 29 CFR 1926.650(b) "Shoring (Shoring system)" · 29 CFR 1926.650(b) "Shield (Shield system)" · 29 CFR 1926.652(b)(1)(i)

Ladders, ramps and trench boxes

A way out within 25 feet

In trenches 4 feet or more deep, there must be a stairway, ladder, ramp or other safe way out located so you never have to travel more than 25 feet sideways to reach it.

Trench boxes

• You must be protected from cave-ins while entering and leaving the area a shield protects.
• Stay out of a shield while it is being installed, removed or moved vertically.

Crossing over

Use a walkway to cross an excavation where crossing is required or permitted. Walkways 6 feet or more above the lower level need guardrails.

Reference: 29 CFR 1926.651(c)(2) · 29 CFR 1926.652(g)(1)(iii) · 29 CFR 1926.652(g)(1)(iv) · 29 CFR 1926.651(l)

At the edge

• Spoil and materials: excavated soil, materials and equipment must be kept at least 2 feet from the edge, or held back by retaining devices, or both, so they cannot fall or roll in.
• Loads: never stand under loads handled by lifting or digging equipment. Stand away from any vehicle being loaded or unloaded so spillage or falling material cannot hit you.
• Traffic: if you are exposed to public traffic, you must be given and must wear a warning vest or other garment made of or marked with reflective or high-visibility material.
• Equipment near the edge: when mobile equipment works next to an excavation or approaches its edge, and the operator cannot clearly see the edge, a warning system such as barricades, hand or mechanical signals, or stop logs must be used.
• Utilities: the estimated location of underground utilities must be determined before the excavation is opened.

Reference: 29 CFR 1926.651(j)(2) · 29 CFR 1926.651(e) · 29 CFR 1926.651(d) · 29 CFR 1926.651(f) · 29 CFR 1926.651(b)(1)

In the hole: water and bad air

Water

Do not work in an excavation where water has collected or is collecting unless adequate precautions have been taken to protect you from the hazards of that water.

Air

Where low oxygen (less than 19.5 percent) or a hazardous atmosphere exists or could reasonably be expected, such as in landfill areas or near stored hazardous substances, the air must be tested before anyone enters an excavation deeper than 4 feet.

Where hazardous air exists or may develop, emergency rescue equipment, such as breathing apparatus, a safety harness and line, or a basket stretcher, must be readily available.

Reference: 29 CFR 1926.651(h)(1) · 29 CFR 1926.651(g)(1)(i) · 29 CFR 1926.651(g)(2)(i)

Inspections, and getting out

A competent person must inspect the excavation, the area around it and the protective systems every day that workers can be expected to be exposed, looking for signs of a possible cave-in, failing protective systems, hazardous air or other hazards.

• Before work starts
• As needed during the shift
• After every rainstorm or other event that increases the hazard

When the competent person finds one of those hazards, exposed workers must be removed from the hazardous area until the needed precautions are in place.

If shoring, a shield or other protective equipment is damaged, a competent person must examine it before it stays in use.

Reference: 29 CFR 1926.651(k)(1) · 29 CFR 1926.651(k)(2) · 29 CFR 1926.652(d)(3)

Common test questions

When is fall protection required at the edge of a trench or excavation?

When it is 6 feet or more deep and hard to see (plants or other visual barriers) - use guardrails, fences or barricades.

Rule: 29 CFR 1926.501(b)(7)(i)

When does a trench need a protective system?

When it is 5 feet deep or more, unless it is made entirely in stable rock.

Rule: 29 CFR 1926.652(a)(1)

How far can workers have to walk to get out of a trench?

No more than 25 feet sideways: trenches 4 feet deep or more need a stairway, ladder, ramp or other safe way out within that distance.

Rule: 29 CFR 1926.651(c)(2)

How far back must dirt piles be kept from a trench edge?

At least 2 feet from the edge.

Rule: 29 CFR 1926.651(j)(2)

When must a competent person inspect a trench?

Daily before work starts, as needed during the shift, and after every rainstorm or other event that increases the hazard.

Rule: 29 CFR 1926.651(k)(1)

Practice these in the course