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WA DOSH

Trenching & Excavation - Washington (DOSH)

This talk follows Washington (WAC) rules · See the federal OSHA version →

Updated 2026-09-30

In this bundle Jobsite Fundamentals & Compliance

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A trench in Washington needs cave-in protection a foot sooner than federal OSHA requires, and since June 1, 2026 it needs something federal OSHA never asks for: a written trench excavation work plan, completed by a competent person, before anyone enters a trench that needs a protective system. The state's dig law adds its own steps before the first bucket goes in: white-line the area, then call the one-number locator service at least two full business days ahead. This Washington Trenching & Excavation Toolbox Talk covers the Washington numbers, the new plan, and the locate rules.

Where the boundary of this talk sits#

This talk covers what Washington adds to trench and excavation safety: the 4-foot protection depth, the written trench excavation work plan, the competent person on site, and the dig-law locate steps. How cave-ins happen, soil classification, and how to use a trench box belong to their own talks.

The anchor#

Here is the distinction that carries this whole talk: in Washington the trench is planned on paper before anyone steps in — cave-in protection is required from 4 feet, not 5; any trench an employee may enter that needs a protective system also needs a written trench excavation work plan completed by a competent person, kept on site, with the crew trained on it before entry; a competent person must stay on the job site whenever trench work is going on; and before any digging, the excavator white-lines the area and gives notice through the one-number locator service two to 10 full business days ahead — so "it's only 4 and a half feet" and "the locate should be fine" are both answers Washington has already ruled out.

Protection starts at 4 feet#

WAC 296-155-657(1)(a) requires each employee in an excavation to be protected from cave-ins by an adequate protective system, except when the excavation is entirely in stable rock, or is less than 4 feet (1.22 m) deep and a competent person's examination of the ground shows no indication of a potential cave-in. Federal 29 CFR 1926.652(a)(1) sets that same exception at less than 5 feet. A trench between 4 and 5 feet deep can be legal federally without protection and a violation in Washington.

Protective systems must resist without failure all loads that are intended or could reasonably be expected. Designs that rely on tabulated data or on an engineer must be in writing, and where a registered professional engineer's design or approval is required, it must be kept at the job site.

A competent person on site#

WAC 296-155-655(13)(a) says a competent person must remain on the job site any time trench excavation work is being performed. The competent person also makes daily inspections of the excavation, the adjacent areas, and protective systems before work starts, as needed during the shift, and after every rainstorm or other hazard-increasing event.

The written trench excavation work plan#

L&I adopted its trench excavation work plan rule on April 21, 2026, effective June 1, 2026. Under WAC 296-155-655(13)(b), the employer must have a competent person complete a written trench excavation work plan for any trench an employee may enter where a protective system is required. A plan is not required when the trench is 4 feet or less and no protective system is required, or when the trench is sloped no steeper than 1½ horizontal to 1 vertical (34 degrees from the horizontal).

The employer may use the plan on the department's website or write its own. Either way, the plan must at a minimum:

  • identify every trench needing a protective system;
  • identify the soil and rock classification;
  • identify underground installations and how they will be protected while the trench is open;
  • describe protection from surface encumbrances and how adjacent structures will be stabilized;
  • identify and assess potentially hazardous atmospheres;
  • describe the protective system and how it will be installed and removed;
  • describe the frequency of inspections;
  • describe protection when entering or exiting areas protected by shields;
  • describe protection from falling soil, rock, or equipment, and from water accumulation;
  • describe the means of egress; and
  • be available on the job site for inspection by the department.

Under subsection (13)(d), before employees enter any trench where a protective system is required, the employer must train and instruct them on the requirements of the plan.

Other Washington requirements at 4 feet and 2 feet#

  • Egress: a stairway, ladder, ramp, or other safe means of egress in trenches 4 feet (1.22 m) or more deep, with no more than 25 feet (7.62 m) of lateral travel.
  • Atmosphere: where oxygen below 19.5 percent or a hazardous atmosphere exists or could reasonably be expected, the atmosphere must be tested before employees enter excavations deeper than 4 feet.
  • Spoil and equipment: kept at least 2 feet (0.61 m) from the edge, or held back by retaining devices, or both.

The dig law: white-line, then call#

RCW 19.122.030(1)(a) says that before starting any excavation, the excavator must mark the boundary of the excavation area with white lining or, when necessary, white pin flags on the ground, then give notice of the scheduled start to all facility operators through a one-number locator service. If boundary marking is infeasible, notice must be given electronically.

Under RCW 19.122.030(2), notice must be given not less than two full business days and not more than 10 full business days before the scheduled work-to-begin date, unless the excavator and facility operators agree otherwise in writing. A business day is any day other than Saturday, Sunday, or a legal holiday. Subsection (5) says the excavator must not excavate until all known facility operators have marked their locatable facilities, and since January 1, 2026, not until the excavator has received a positive response from every operator with facilities in the area identified in the notice.

RCW 19.122.040(2) then requires the excavator to determine the precise location of marked facilities, plan the excavation to avoid damage, support facilities during excavation and backfill, use safe and careful work methods, and, for directional boring, supplement white lining with physical exposure to avoid blind boring.

Where the duty sits#

WAC 296-155-657(1) sets protection at 4 feet. WAC 296-155-655 sets utility locates (2), egress (3), atmospheres (7), spoil setback (10), daily inspections (11), and trench excavations (13): competent person on site, written work plan, contents, and training. RCW 19.122.030 sets white lining, notice two to 10 business days ahead, and no digging before marks and a positive response from every operator. RCW 19.122.040 sets excavator duties near marked facilities. For contrast, federal 29 CFR 1926.652(a)(1).

What can go wrong?#

  • A 4½-foot trench is dug without protection because "federal is 5 feet."
  • The work plan is filled out after the crew is already in the trench.
  • The competent person leaves for another site while the crew keeps working.
  • The locate is called in on Friday for a Monday start.
  • Nobody white-lined the area, so the locators marked the wrong block.

How do we manage this properly?#

  • Protect at 4 feet — unless stable rock, or under 4 feet with a competent person's clean examination.
  • Write the plan first — completed by the competent person, on site, crew trained before entry.
  • Keep the competent person on site — whenever trench work is happening.
  • White-line, then call — two to 10 full business days ahead, and wait for all marks and a positive response from every operator.
  • Ladder within 25 feet, spoil 2 feet back.

Before you start#

Confirm the trench work plan is on site and you've been trained on it. Know who the competent person is today. Check that the locate ticket is valid, every operator has marked, and every operator has sent a positive response.

Talk it over#

  • How deep is this trench, and what protective system does the plan call for?
  • Who is our competent person today, and are they staying on site?
  • When was the locate called, and have all operators marked and sent a positive response?

The bottom line#

Washington requires cave-in protection from 4 feet, a foot shallower than federal OSHA. Since June 1, 2026, any trench an employee may enter that needs a protective system also needs a written trench excavation work plan completed by a competent person, kept on site, with the crew trained on it before entry, and a competent person must stay on site while trench work goes on. Before digging, white-line the area, give notice two to 10 full business days ahead, and wait for all the marks and a positive response from every operator.

Frequently asked questions about Washington trenching rules#

At what depth does Washington require cave-in protection?

At 4 feet. Under WAC 296-155-657(1)(a), a protective system is required unless the excavation is entirely in stable rock, or is less than 4 feet deep and a competent person's examination shows no indication of a potential cave-in. The federal rule uses 5 feet.

Download the Washington trenching and excavation toolbox talk PDF#

Download this Washington Trenching & Excavation Toolbox Talk as a printable PDF in English and Spanish, and review it with the crew with the trench work plan in hand.

Related toolbox talks#

Sources#

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

Hazards covered

cave inunderground utilitiesatmospheric
By Mustafa Tok, CSP, ASP, CHST

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