Cal/OSHA Trench and Excavation Protection Rules

In California, every employee in an excavation must be protected from cave-ins by a protective system, with two exceptions: excavations made entirely in stable rock, and excavations under 5 feet deep where a competent person examines the ground and sees no sign of a potential cave-in. (8 CCR §1541.1(a)(1)) That 5-foot line is the one most people remember, but several other depth triggers in Cal/OSHA's excavation article start at 4 feet, 6 feet and beyond. This article walks through the ones printed in 8 CCR 1539 through 1541.1.

What counts as a trench

The excavation article applies to all open excavations in the earth's surface, and the definition of an excavation includes trenches. (8 CCR §1540(a)) A trench is a narrow excavation, usually deeper than it is wide, with a bottom width of no more than 15 feet. (8 CCR §1540(b)) If forms or other structures inside a larger excavation bring the distance to the side down to 15 feet or less, it is treated as a trench too. (8 CCR §1540(b))

Section 1539 handles permits by pointing to a separate Cal/OSHA regulation, Section 341, which is outside the sections covered here. (8 CCR §1539) Check that rule and your local requirements before the work starts.

The competent person and daily inspections

Cal/OSHA defines a competent person as someone able to spot hazards that exist or can be predicted on the job and who has the authority to fix them promptly. (8 CCR §1504) Three things stand out in the excavation rules:

• A competent person makes a daily inspection of the excavation, the adjacent areas and the protective system. (8 CCR §1541(k)(1))
• The inspection happens before work starts and as needed through the shift, and again after every rainstorm or other event that increases the hazard. (8 CCR §1541(k)(1))
• When the competent person finds signs of a possible cave-in, protective system failure or hazardous atmosphere, exposed employees leave the area until the precautions are in place. (8 CCR §1541(k)(2))

The text does not attach a depth to the daily inspection. It applies whenever employee exposure can reasonably be anticipated. (8 CCR §1541(k)(1))

Getting in and out: the 4-foot egress rule

A trench that is 4 feet or more deep needs a way out, whether a stairway, ladder, ramp or other safe exit, placed so that no worker must move more than 25 feet along the trench to reach one. (8 CCR §1541(c)(2)) Ramps built of structural members need to be designed by a competent person, and ramps and runways of several members must be connected so they cannot shift. (8 CCR §1541(c)(1))

Testing the air is also tied to depth. Where oxygen deficiency or another hazardous atmosphere exists or could reasonably be expected, such as near landfill or stored hazardous substances, the atmosphere must be tested before employees enter an excavation deeper than 4 feet. (8 CCR §1541(g)(1)) Oxygen deficiency is defined as an atmosphere below 19.5 percent oxygen. (8 CCR §1541(g)(1))

Spoil piles and equipment

Excavated material and equipment that could fall or roll into the excavation must be kept at least 2 feet from its edge, or held back by retaining devices that stop them, or both. (8 CCR §1541(j)(2)) Measure the setback from the edge of the excavation. For loose rock or soil on the face, protection means scaling it off, barricades on the face, or something equivalent. (8 CCR §1541(j)(1))

When mobile equipment works next to an excavation and the operator cannot see the edge, a warning system such as barricades, signals or stop logs has to be used. (8 CCR §1541(f)) Nobody is permitted under loads handled by lifting or digging equipment. (8 CCR §1541(e))

Crossing, water and utilities

Where people or equipment cross an excavation more than 6 feet deep and more than 30 inches wide, the crossing must be a walkway or bridge with standard guardrails. (8 CCR §1541(l)(1)) Employees may not work in accumulating water unless adequate precautions are taken, which could include special support, water removal or a harness and lifeline. (8 CCR §1541(h)(1))

Utilities come first. Before opening ground, the excavator determines the approximate location of subsurface installations, and digging cannot begin until the area is marked and the excavator has positive responses from known owners. (8 CCR §1541(b)(1)) Notification to regional centers is required at least 2 working days before digging, with an exception for emergency repairs. (8 CCR §1541(b)(2))

Choosing a protective system

Once a trench reaches the point where protection is required, the employer picks a design. Sloping and benching can follow Option 1, which is a slope no steeper than 1 1/2 horizontal to 1 vertical, or 34 degrees from horizontal. (8 CCR §1541.1(b)(1)) Other options use the appendices, other tabulated data or a registered professional engineer's design. (8 CCR §1541.1(b)) Shoring, shields and other systems have their own options, including manufacturer's tabulated data. (8 CCR §1541.1(c))

Some details for specific systems:

• Uprights run up to the top of the trench, and their lower ends stop within 2 feet of the bottom. (8 CCR §1541.1(h))
• Soil may be removed up to 2 feet below the bottom of a support system only if the system was designed for the full trench depth and there are no signs of soil loss from behind or beneath it. (8 CCR §1541.1(e)(2))
• Employees cannot be inside a shield while it is being installed, removed or moved vertically. (8 CCR §1541.1(g)(1))
• Workers are not allowed to work on a sloped or benched face above other employees unless those below are protected from falling or rolling material. (8 CCR §1541.1(f))

Worked example: a 7-foot trench, 90 feet long

A pipe trench is 7 feet deep, 3 feet wide at the bottom and 90 feet long, dug in an area where nothing suggests stable rock.

1. Protection required? Seven feet is not under 5 feet, so a protective system is required. (8 CCR §1541.1(a)(1))
2. Slope option. At 1 1/2 to 1, each side runs out 1.5 x 7 = 10.5 feet. The top width is 3 + 2 x 10.5 = 24 feet. (8 CCR §1541.1(b)(1)) If that is too wide for the site, shoring or a shield is the alternative.
3. Egress. The trench is deeper than 4 feet, so no one may be more than 25 feet of lateral travel from a ladder or other exit. Two ladders placed 25 feet and 75 feet along the trench cover the whole length. (8 CCR §1541(c)(2))
4. Spoil. Keep the pile at least 2 feet back from the edge. (8 CCR §1541(j)(2))
5. Inspection. A competent person looks at the trench before the crew enters and again after any rain. (8 CCR §1541(k)(1))

Where to study this

Trench work is part of plumbing, pipeline and earthwork scopes, so the plumbing contractor exam prep page and the general engineering page are natural places to review these rules. Plumbing contractor license exam prep General engineering contractor license exam prep For a worked sloping calculation by soil type, see the pipeline lesson on sloping a trench. Sloping a pipe trench by soil type