DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Summary

Workers are at risk of death from 

cave-ins during trenching and excavation activities. NIOSH recommends engineering controls, protective equipment, and safe work 

practices to minimize hazards for 

workers.

Preventing Worker Deaths from 

Trench Cave-ins

Description of

Exposure

Workers who dig or excavate trenches are at risk of death if they enter an 

unprotected trench and the walls collapse. However, hazards associated with 

trench work and excavation are well 

defined and preventable. The OSHA 

standard for excavation and trenching, 

known as 29 CFR* 1926 Subpart P, describes the precautions needed for safe 

excavation work. 

There is no reliable warning when a 

trench fails. The walls can collapse suddenly, and workers will not have time 

to move out of the way. Even though 

small amounts of dirt may not seem 

*Code of Federal Regulations. See CFR in References

treacherous, a single cubic yard of dirt 

can weigh more than 3,000 pounds, 

which can fatally crush or suffocate 

workers [Deatherage et al. 2004]. Even 

small, solid pieces of dirt can cause serious injuries. 

From 2000−2009, 350 workers died in 

trenching or excavation cave-ins—an average of 35 fatalities per year [BLS 2010]. 

Most incidents involve excavation work 

or “water, sewer, pipeline, and communications and power-line construction” 

[CDC 2004]. An analysis of OSHA data 

from 1997−2001 showed that 64% of fatalities in trenches occurred at depths of 

less than 10 feet [Arboleda and Abraham 2004].

Lack of a protective system was the 

leading cause of trench-related fatalities in a review of OSHA inspections 

[Deatherage et al. 2004]. OSHA requires 

that all excavations 5 feet deep or greater make use of one of the following protective system options (see Figure 1): 

(1) sloping the ground; (2) benching 

the ground;† (3) shoring the trench with 

supports such as planking or hydraulic 

jacks, or (4) shielding the trench (using a 

trench box). Workers should never enter 

a trench that does not have a protective 

system in place designed and installed 

by a competent person.‡ 

Factors such as type of soil, water content of soil, environmental conditions, 

proximity to previously backfilled excavations, weight of heavy equipment 

or tools, and vibrations from machines 

and motor vehicles can greatly affect soil 

†Not all protective systems can be used in all types 

of soil. Benching cannot be used in Type C soil. ‡A competent person is one who understands OSHA 

regulations, can recognize hazards, and is authorized to correct them.

Figure 1. Work crew installing water 

pipes. Aluminum hydraulic shoring is 

being used as a protective system for 

the trench. Photo courtesy of George 

Kennedy, NUCA.
stability and the hazards that workers face. When the sides of 

trenches are shored, the type of soil and width and depth of 

the trench affect how far apart the supports should be spaced. 

Different OSHA regulations apply to the different types of 

supports used for shoring. Consult 29 CFR 1926 Subpart P 

Appendices C and D for more information. Appendix F provides a flow diagram for making decisions. Section V, Chapter 2 of the OSHA Technical Manual provides a guide on recognizing and preventing trenching and shoring hazards.

The following case studies, from the NIOSH Fatality Assessment and Control Evaluation Program, describe two fatalities in which workers suffocated during trench collapses. 

Case Studies

Case 1: Male Hispanic Laborer Dies 

When 9-Foot-Deep Trench Collapses

On February 1, 2006, a 29-year-old male Hispanic laborer with 5 years of experience died when the 2-foot-wide, 

16-foot-long, and 9-foot-deep unprotected trench he was 

working in collapsed and covered him with soil during waterproofing work. The victim and four other laborers, all of 

whom spoke primarily Spanish and very little English, had 

been hand digging the trench over a 2-day period at a private residence. The victim was kneeling to inspect a broken 

drain pipe at the bottom of the east end of the trench. The 

victim’s brother saw the soil strike the victim and knock his 

head against the home’s basement wall. The trench wall collapsed and the victim was completely covered with soil in 

seconds. The victim was pronounced dead at the scene by 

emergency response personnel. The company did not have a 

written safety and health program, competent person on site, 

or safety committee [NIOSH 2006].

Case 2: Construction Laborer Dies 

when Trench Walls Collapse

On November 3, 2003, a 38-year-old male construction laborer died when the unprotected, 8-foot-high walls of the 

trench he was working in collapsed only a few minutes after he had entered. The victim was removing an old gas line 

that was a 6-inch diameter high pressure line (300–320 psi) 

in 10-inch steel casing. Five workers were at the job site excavating the gas line: a foreman who was a competent person, 

a lab technician who was a competent person, and 3 laborers (including the victim). The foreman had dug an 8-foot 

deep trench with a track hoe to expose the abandoned gas 

line. After the gas line was extracted from its casing, the victim climbed into the trench with a saw to free the casing, a 

job that the report indicated would only take a few minutes. 

Sloping, benching, or shoring methods were not used to 

support the trench. As the laborer began sawing, the sides of 

the trench collapsed, burying him. He was declared dead at 

the scene [NIOSH 2003].

Recommendations

[Mulhern and Lentz 2008, 2009]

Employers 

Pre-job Planning Before the Job Begins

 Train and designate a competent person to ensure safety 

measures are in place.

 Call 811 before digging so that utility lines can be marked, 

then “pot-hole” utilities to determine the exact location 

and depth before digging.

 Have a competent person evaluate the soil to determine 

its stability. Because soil conditions can vary dramatically over just a few days, Appendix A of Subpart P provides 

techniques (roll test and thumb penetration) for evaluating the condition of the soil. 

 Plan the job layout to identify safe locations (away from 

the trench) for spoil piles and heavy equipment routes. 

 Have a competent person determine what type of protective system will be used for the job and schedule the steps 

needed to have the system complete and in place before 

workers enter.

 Trenches greater than 20 feet deep can be more complex. 

The competent person may choose a manufactured protective system with the appropriate depth rating, or use a 

registered professional engineer to design a site-specific 

protective system. Refer to 29 CFR 1926 Subpart P for 

requirements.

 Ensure that none of the workers designated for entry into 

the trench are under age 18. 

 Ensure that workers involved in the job are trained about 

hazards and work practices in a language that they understand and at the appropriate literacy level. 

 Develop a trench emergency action plan [NIOSH 2006] 

to describe steps to be taken and to provide contact information in case of an emergency. 

Safe Operations During the Job

 The competent person must inspect the excavation, adjacent areas, and protective systems each day before the 

start of work, as needed throughout the shift, and after every rainstorm. 

 Notify other subcontractors who come on site of the 

trench location and precautions and ensure that vehicles 

are kept a safe distance from the excavation.
 Ensure that ladders and other means of exit from the 

trench are repositioned so that ladders are never more 

than 25 feet away from any worker in the trench. 

 The competent person must remove workers from the excavation upon any evidence of a situation that could cause 

a cave-in, such as accumulation of water in the trench or 

protective system problems. (The competent person must 

also take actions for other types of hazards such as falling 

loads or hazardous atmospheres.)

 Monitor other types of trench–related hazards that can 

occur such as falls from the edge, rigging hazards, or toxic and combustible gases.

 Implement and enforce procedures to ensure that work in 

an unprotected trench is not allowed. 

Workers

 Do not enter an uprotected trench, even for a short task. 

 Inspect the protected trench before entering.

 Exit the trench and call the competent person if you see 

any evidence of problems with a protective system.

 Do not assume there will be a warning sign before a cave 

in or that you will have time to move out of the way.

Owners and Clients

 Insist on trench safety practices when you commission 

work [Thompson and Tannenbaum 1977].

 Put trench safety into bid documents and contractor qualifications. 

Acknowledgments

This document was developed by T.J. Lentz, Susan Afanuh, 

and Matt Gillen, National Institute for Occupational Safety 

and Health.

References

Arboleda CA, Abraham DM [2004]. Fatalities in trenching 

operations analysis using models of accident causation. J 

Const Eng Mgmt 130(2):273−280.

BLS [2010]. Census of fatal occupational injuries (2000−2009). 

Washington, D.C. Bureau of Labor Statistics. 

CDC [2004]. Occupational fatalities during trenching and excavation work United States, 1992–2001. MMWR 53(15):311–

314. http://www.cdc.gov/mmwr/preview/mmwrhtml/

mm5315a2.htm 

CFR. Code of Federal regulations. Washington, DC: U.S. 

Government Printing Office, Office of the Federal Register.

Deatherage JH, Furches LK, Radcliffe M, Schriver WR, Wagner JP [2004]. Neglecting safety precautions may lead to 

trenching fatalities. Am J Ind Med 45:522−527.

Mulhern B, Lentz TJ [2008]. Coming out of the trenches...

safely. Hard Hat News Nov. http://hardhat.com/ME2/Audiences/dirmod.asp?sid=D8F3EF8405924C33B5F670EB0

A95DCE2&nm=Association+News&type=Publishing&m

od=Publications%3A%3AArticle&mid=8F3A7027421841

978F18BE895F87F791&id=474F54A087824914BC785DE

9FFC92DA9&tier=4 

Mulhern B, Lentz TJ [2009]: Trenching, Part 2: Steps for employers. Landscape Management, February 4. 

NIOSH [2003]. 38 year-old construction laborer dies when 

trench walls collapse. http://www.cdc.gov/niosh/face/

stateface/ky/03KY107.html

NIOSH [2006]. 29-year old male Hispanic landscape laborer 

dies when nine foot deep trench collapses. http://www.cdc.

gov/niosh/face/stateface/mi/06mi004.html 

OSHA. Excavations: hazard recognition in trenching and 

shoring. OSHA Technical Manual, Section V, Chapter 2. 

Washington, DC: U.S. Department of Labor, Occupational 

Safety and Health Administration. http://www.osha.gov/

dts/osta/otm/otm_v/otm_v_2.html 

Thompson L, Tannenbaum R [1977]. Responsibility for 

trenching excavation and design. J Geotech Eng Division 

103(4):327−338. http://cedb.asce.org/cgi/wwwdisplay.

cgi?7322
For More Information

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

4676 Columbia Parkway

Cincinnati, OH 45226–1998

Official Business

Penalty for Private Use $300

Safer • Healthier • PeopleTM September 2011

More information about trenching and excavation can be 

found on the NIOSH Web site: 

http://www.cdc.gov/niosh/topics/trenching/

To receive copies of the NIOSH field study reports that 

formed the basis of this document or to obtain information about other occupational safety and health topics, contact NIOSH at

Telephone: 1–800–CDC–INFO (1–800–232–4636)

TTY: 1–888–232–6348 ■ E-mail: cdcinfo@cdc.gov

or visit the NIOSH Web site at www.cdc.gov/niosh.

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endorsement by NIOSH. In addition, citations to Web sites 

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This document is in the public domain and may be 

freely copied or reprinted. NIOSH encourages all 

readers of the Workplace Solutions to make them 

available to all interested employers and workers.

As part of the Centers for Disease Control and Prevention, 

NIOSH is the Federal agency responsible for conducting 

research and making recommendations to prevent workrelated illness and injuries. All Workplace Solutions are 

based on research studies that show how worker exposures 

to hazardous agents or activities can be significantly reduced.

Preventing Worker Deaths from Trench Cave-Ins

DHHS (NIOSH) Publication No. 2011—208

(Supersedes 2011–180)