DHHS (NIOSH) Publication Number 85-110
Thefts during excavations cause serious and often fatal injuries to workers in the United States. A National Institute for Occupational Safety and Health (NIOSH) analysis of workers' compensation claims from 1976 to 1981 in the Bureau of Labor Statistics Supplemental Data System suggests that thefts during excavations caused about than 1,000 work-related injuries each year. Of these, some 140 lead to permanent disability and 75 to death. Therefore, this type of incident is one of the leading causes of deaths related to excavation work, accounting for almost 1% of all annual work-related deaths in the country.
NIOSH's Fatal Accident Circumstances and Epidemiology (FACE) Project recently investigated four deaths caused by excavation thefts. Summaries of these cases are as follows:
A 53-year-old worker employed by a city sewer agency entered an 11 1/2-foot deep unsupported vertical wall manhole excavation to lower and level the area where the manhole foundation would be placed. . When he emerged from the excavation after completing this task, a wall collapsed, completely burying him and killing him.
Fall n. two:
A 22-year-old worker hand-dug an 8-foot-deep dry hole and trench to connect a drainage pipe. None of the walls in the excavation areas were supported or sloped to a safe angle of repose; h the largest angle above the horizontal plane at which a material will rest without slipping. As the worker was digging the trench, a wall collapsed, covering him with 6 feet of earth and killing him.
Fall n. 3:
A 45-year-old construction manager removed loose soil from the bottom of a 21-foot unreinforced vertical wall excavation to make room for a precast trench shield. The dirt began to fall from a side wall; When the worker tried to leave the site, the ground "gave in", covering him completely and killing him.
Fall n. 4:
A 32-year-old construction manager was in an unpatched excavation with vertical walls at a depth of approximately 7 feet. A wall collapsed, throwing the foreman to the ground, covering him completely in dirt and killing him.
Appropriate Standards and Recommended Work Practices
Standards published by the Occupational Safety and Health Administration (OSHA) establish specific requirements to protect workers in excavations and trenches (29 CFR 1926.651 and .652, respectively). In general, these standards require that the walls and walls of all excavations in which workers are exposed to a potential hazard from moving soil must be protected by a shoring system, safe soil slope, or means of restraint. equivalent protection, such as trench protectors or boxes. However, the standards only apply to trenches that are 5 feet deep or greater.
A table published in 29 CFR 1926.652 provides the required horizontal-to-vertical ratio for the slope of the sides of excavations in relation to specific soil types. These requirements are intended to approximate the safe angle of repose for each type of soil. The standards also define the minimum trench shoring requirements for different soil classifications. Standards require additional methods of shoring and bracing when excavations or trenches are adjacent to previously filled excavations, or when excavations are subject to vibration from highway or rail traffic, machine operation, or other sources.
A major problem associated with existing OSHA standards for excavation, trenching, and shoring is the classification of soil. Soil classification provides an empirical estimate of soil stability. When the possibility of collapse or other dangerous ground movement is suspected, appropriate decisions must be made to ensure adequate protection. However, when it comes to land classification, critics have described existing standards as vague and confusing, and dangerously open to different interpretations .
Recently, the National Bureau of Standards (NBS) and NIOSH jointly publishedPreparation of draft construction safety standards for excavations,DHHS (NIOSH) Publication No. 83-103 . This document recommends establishing a protection requirement for excavations 5 feet deep or greater, regardless of soil type. It also presents a simplified soil classification system for use in determining appropriate side slope requirements and calculating lateral soil pressures exerted on shoring systems.
Application of existing standards and recommended work practices
In the fatal incidents described above, none of the excavations were found to include the safeguards specified in the applicable OSHA standards or the NBS/NIOSH joint publication. Table 1 suggests that compliance with existing regulations or compliance with recommended work practices may have prevented important causal factors in each of the four fatal incidents.
Status of compliance with standards (or BSS/NIOSH recommended work practices) in the operations that led to the four fatal excavation collapses
* Subjective, vague or unclear as to its applicability.[Back to top of table]
** Hydraulic bench was used in a crossing ditch.[Back to top of table]
*** Excavations include trenches; as in current OSHA standards, no distinction is made between them.[Back to the main part of the table]
**** For all excavations deeper than 24 feet, except excavations in intact rock, shoring, protection, or slope requirements must be determined by an engineer (qualified person).[Back to the main part of the table]
NA = Not applicable.
The primary goal of research conducted by NIOSH as part of its Fatal Accidents and Epidemiology (FACE) project is to determine what factors made the fatality possible. The goal is to learn how these deaths can be prevented. In this context, whether or not an operation was "according" to established standards is only one of many variables that may or may not have contributed to death. However, in the course of the investigation reported here, it became apparent that full compliance with the relevant OSHA standards or adoption of NBS/NIOSH recommended work practices would likely have prevented each fatality.
As an obvious first step to prevent such deaths in the future, we conclude that all of these surgeries should only be performed in full compliance with existing OSHA standards.
The consistent lack of evidence of compliance in the four incidents described above suggests that employers are either (1) unaware of the existence of OSHA standards or (2) failing to meet the requirements of the standards regarding exemptions from the features of the OSHA standards. standards misinterpret soil.
NIOSH recommends the following:
- Shoring systems or sloped walls are used in all excavations 5 to 24 feet deepanySoil type other than solid, stable rock.
- Appropriate shoring, screening, or slope requirements for any excavation deeper than 24 feet (excluding excavations in intact rock) must be determined by an engineer qualified to make such determinations.
- all employers involved in excavation work familiarize themselves with the provisions of the NBS/NIOSH document(Preparation of construction safety standards projects for excavations)and implement them as safe work practices in addition to complying with existing OSHA standards.
We urge trade and safety associations, underground utilities, municipalities and other local governments responsible for underground utilities, and state OSHA advisory services to report these recommendations to employers involved in excavation.
Suggestions, requests for additional information on safe work practices, or questions about this announcement should be directed to Mr. John Moran, Director, Division of Safety Research, 944 Chestnut Ridge Road, Morgantown, WV 26505, phone (304) 291-4595.
Thank you for your help in protecting the lives and health of America's workers.
J. Donald Millar, MD, DTPH (Londres)
Assistant Surgeons General
Director, National Institute of Safety and Health at Work
Centers for Disease Control
- Injury and fatality data for 1976-1981. [Unpublished data from US Department of Labor, Bureau of Labor Statistics, Supplemental Data System].
- Hinze J. A Study of Labor Practices to Protect Trench Workers, NBSIR No. 79-1942. National Bureau of Standards, December 1979; NTIS PB 80-167-497.
- Preparation of draft construction safety standards for excavations. National Institute for Occupational Safety and Health/National Bureau of Standards, NBSIR 83-2693, DHHS (NIOSH) publication no. 83-103, Volumes 1 and 2. NTIS PB 84-100-569 (Vol. I) and NTIS PB 83-233-353 (Vol. II).
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