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Excavation Hazard Recognition - OSHA Standards

John Poullain, P.E.

Course Outline

This two-hour online course provides general guidelines for recognizing the potential hazards of excavation and trenching operations and measures to prevent or reduce exposure to the hazards. Topics include the OSHA standards for safety in excavation, the importance of excavation preplanning and the kinds of excavation that do not apply. The text discusses selection of systems used to protect against cave-ins and other hazards of excavation such as falling debris, open excavation falls and hazardous atmospheres. Safe installation and removal of protective systems, access and egress requirements and site inspections are presented. Other factors such as water table, weather conditions, soil types and site safety requirements are considered.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will:

Intended Audience

This course is intended for engineers, construction managers, safety inspectors and building owners.

Benefit to Attendees

The student will become familiar with OSHA safety standards for excavation and trenching and understand some potential excavation hazards such as cave-ins; water accumulation and the importance of providing access and egress from excavations. OSHA standards cover protective systems used to prevent cave-ins, shield workers and the selection of the most appropriate systems and their safe installation and removal. Primary soil types, basic soil mechanics and other contributing factors such as the water table and its effect on excavation stability are discussed. The importance of excavation preplanning, site inspections, site safety and safety equipment are also discussed.

Course Introduction

The course us based on OSHA excavation publications, which cover standards written to provide for safe excavation and trenching operations. Excavations are recognized as one of the most hazardous of construction operations. They are inherently unstable and pose several serious hazards to workers, which include mainly excavation failures such as cave-ins, slides, toppling, subsidence and bottom heaving of excavations. Other excavation hazards include falls, falling debris and materials or construction equipment and unhealthful atmospheric conditions.

Existing soils at the site may be unstable due to excess clay, expansive clays, silts, fine sands, gravels, voids, or high watertables. Problem soils may be encountered such as loess, hydraulic fills and tailings which have collapsing or low-density structures, and when saturated from ground water have large decreases in volume and loss of strength.

Planning excavation work must be given careful attention. Hazards such as vehicular traffic, vibration from moving construction equipment near to the excavation, any nearby buildings, surface drainage, water tables, utilities, inhalation of toxic fumes and changes in the weather have to considered and planned for to prevent costly delays or contract changes later for remediation of problems. Control of traffic may have to be planned for and the excavation site may have to be tested for low oxygen, hazardous or toxic gases. Motors or construction equipment may be running or storage tanks or pipes may have leaked, saturating the soil. Surface water should be controlled by sloping drainage away from the excavation.

Factors, which affect stability of excavations, are the types of soil, depth of cut, slope of cut, subsidence of soil and surcharges. Using maximum allowable slopes and/or benching and shoring or shielding systems provides protection from cave-ins and other open excavation hazards. OSHA categorizes soils according to their overall composition, appearance and the presence of any cracks, fissures or seepage water. Spoil material from an excavation must be properly placed in order to maintain excavation stability. The weight of spoil material can cause cave-ins or fall onto workers in an excavation. Spoils may have to be hauled somewhere else temporarily if there is insufficient space or ROW at the excavation.


Course Content

This course is based primarily on Chapter 2, Section V, of OSHA's Technical Manual 29 CFR 1926 "Excavations" (2002 Edition, 11 pages), PDF file.
The course is also based on the Aurora OSHA's Construction News issue, "Trenching Still a Concern", (2002 Edition, 6 pages), PDF file and the course paragraph "Course Introduction".

The links to the course materials are:

Chapter 2, Section V, of OSHA's Technical Manual 29 CFR 1926 "Excavations"

Aurora OSHA's Construction News issue, "Trenching Still a Concern"

You need to open or download above documents to study this course.

Course Summary

In order to keep an excavation safe and free from accidents it is vital to recognize potential hazards of excavations and trenching. Their causes and selection of protection systems are discussed along with general guidelines considering the types of soil, problems caused by groundwater, spoil placement and the effects of weather changes. The importance of pre-job planning for excavations, the minimum amount of site inspections and having safety equipment available at the work site is discussed.

Related Links

For additional technical information related to this subject, please refer to:
National Institute for Occupational Safety and Health (NIOSH) information and guideline publications for web training, case studies for actual accidents and their prevention.
Information and resources for excavation safety and hazards, accident analysis and alerts from NIOSH, Construction Safety Council and the construction industry.


Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.