One of the most important responsibilities of field and office management is planning for safety. Most on-the-job problems and accidents directly result from improper planning. Correcting mistakes in sloping, shoring and/or shielding after work has started slows down the operation, adds to the cost and increases the possibility of an excavation failure.
Contractors should use OSHA's eTools Guide for Daily Inspection of Trenches and Excavations to make certain there is enough information about the jobsite and all needed items, such as safety equipment, are on hand.
To help ensure safety in trenching and excavation operations before the start of trenching or excavation, the contractor will need to take these specific conditions into account:
These and other conditions can be determined by jobsite studies, observations and consultations with local officials and utility companies.
1. The contractor must always contact the utility companies involved and inform them of the work _____.a. to let them know work has been completed
A stairway, ladder, ramp or other safe means of access and egress must be located in trench excavations that are 4 feet (1.22 m) or more in depth so as to require no more than 25 feet (7.62 m) of lateral travel for employees.
2. Structural ramps that are used solely by employees for access or egress from excavations _____.a. may be designed by employees working in the excavation
Surface crossing of trenches should be discouraged; however, if trenches must be crossed, they are only permitted under the following conditions:
3. What is one of the requirements for trench walkways or bridges?a. They may be fitted with at least one handrail
Employees must be protected from loads or objects falling from lifting or digging equipment.
Here are some procedures to protect your employees:
The following steps should be taken to prevent vehicles from accidentally falling into the trench:
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4. Which of the following practices is NOT allowed while working in a trench?a. Work in a sloped trench with Type C soil
There are important steps the employer should take to minimize the risk of unexpectedly encountering underground utilities such as sewer, telephone, fuel, electric, water lines, or any other underground installations that reasonably may be expected to be encountered during excavation work. Before starting work, the Excavation standards require employers to do the following:
5. If a utility company cannot establish the exact location of an underground utility, what action may the employer take?a. Proceed with caution using an acceptable means of detection
Common hazardous atmospheres might be due to methane, hydrogen sulfide, and carbon monoxide. Precautions include providing workers with proper respiratory protection or forced air ventilation. Do not assume that natural ventilation (natural air movement across and into the excavation) is sufficient to keep an atmosphere safe in the trench.
Employees must not work in hazardous and/or toxic atmospheres including those with:
All operations involving hazardous atmospheres must be conducted in accordance with OSHA requirements for occupational health and environmental controls (see 29 CFR Part 1926 Subpart D) for personal protective equipment and for lifesaving equipment (see 29 CFR Part 1926 Subpart E). Engineering controls (e.g., ventilation) and respiratory protection may be required.
A competent person must test an excavation before employees enter an excavation greater than 4 feet (1.22 m) in depth for where hazardous atmospheres exist or could reasonably be expected to exist, such as in excavations in landfill areas or excavations in areas where hazardous substances are stored nearby.
When testing for atmospheric contaminants within excavations or confined spaces in excavations, the following should be considered:
6. What is a primary control measure if a flammable/combustible atmosphere is detected in a trench?a. Water suppression system
29 CFR Part 1926, Subpart AA applies to non-excavation work within a confined space located in an excavation. These standards are intended to complement the excavation standard and address two distinct hazards:
For example, the Confined Spaces in Construction standard covers entry into a large prefabricated storm drain, other pipe, or manhole large enough for human occupation, even if located at the bottom of an open excavation.
If unhealthful atmospheric conditions exist or develop in an excavation or confined space, workers must exit immediately, and not reenter until testing proves safe levels have been achieved. Under no circumstance may workers enter an excavation when flammable/combustible atmospheres are present.
Emergency rescue equipment is required when a hazardous atmosphere exists or can reasonably be expected to exist. Requirements are as follows:
7. Which of the following is an example of a non-excavation confined space within an excavation?a. A 2 ft wide pipe for electrical wiring
Two employees were installing storm drain pipes in a trench, approximately 20-30 feet long, 12-13 feet deep and 5-6 feet wide. The side walls consisted of unstable soil undermined by sand and water. There was 3-5 feet of water in the north end of the trench and 5-6 inches of water in the south end. At the time of the accident, a backhoe was being used to clear the trench. The west wall of the trench collapsed, and one employee was crushed and killed.
As result of the investigation, OSHA issued citations for one willful, one serious, and one-other-than-serious violation of its construction standards.
OSHA's construction safety standards include several requirements which, if they had been followed here, might have prevented this fatality.
Click on the button to see OSHA recommendations for this accident.
Accident Prevention Recommendations
8. A trench is 12 feet deep and 5 feet wide. The unprotected walls consist of unstable soil with beginning to seep into the trench. You are the competent person. What are your actions?a. Confer with the contractor for instructions
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