Trenching and excavation remain among the most hazardous jobs in the construction industry, so the U.S. Department of Labor’s Occupational Safety and Health Administration, or OSHA, has a specific set of requirements for such work.
Following OSHA guidelines for trenching and excavating can protect workers from cave-ins and other hazards associated with these jobs.
Excavation Versus Trench
An excavation, according to OSHA’s definition, is any man-made cut, trench, cavity or depression in the Earth’s surface formed by Earth removal. OSHA defines a trench as a narrow excavation made below the ground surface. The depth of a trench is greater than its width, but not more than 15 feet.
What are the Dangers?
All workers participating in trenching and excavation work face serious hazards, including cave-ins, which post the greatest risk. They are more likely to result in worker deaths, since one cubic yard of soil can weigh as much as an automobile.
Some refer to unprotected trenches as early graves, so employers must be sure to provide adequate protections before workers enter trenches.
Other hazards associated with trench work includes hazardous atmospheres, falling loads and hazards created by mobile equipment.
How OSHA Standards Protect Workers
OSHA standards for trenching and excavating apply to all openings created on the Earth’s surface. By following the requirements set forth by OSHA, you can greatly reduce or even prevent the risk of cave-ins and other related incidents.
Classifying Soil Categories
The excavation compliance methods require in some instances that a competent person classify soil and rock deposits as:
· Stable rock – This is natural solid mineral matter that workers can excavate with vertical sides and remain intact while exposed.
· Type A Soil – This type is cohesive soils with unconfined compressive strength of 1.5 tons per square foot or greater. This includes sandy clay, silty clay, clay and clay loam. You cannot classify soil in certain conditions as Type A. That includes when it is fissured or was previously disturbed.
· Type B Soil – This category includes cohesive soil with an unconfined compressive strength greater than 0.5 tons per square foot, or tsf, but less than 1.5 tsf. It also includes granular cohesionless soils, including crushed rock, sandy
loam, silty loam, silt loam and sometimes includes silty clay loam and sandy clay loam.
· Type C Soil – This is cohesive soil with an unconfined compressive strength of 0.5 tsf or less, as well as granular soils, including gravel, sand, and loamy sand, submerged soil, submerged rock that is unstable, or soil from which water is freely seeping. It also includes material in a sloped, layered system where the layers are part of the excavation or with a slope of four horizontal to one
vertical or steeper.
Trenching and Excavation Safety
Compression is extremely important when trenching and excavation, since uncompressed strength means the load per unit area will fail.
This can be estimated in the field using a pocket penetrometer, thumb penetration tests or by other means. It can also be determined through laboratory testing.
Determine Who is a Competent Person
In this context, a competent person is someone designated by the employer as the one who will identify existing and predictable hazards in the work area. That includes conditions that are unsanitary, hazardous or pose other danger to workers. This person is authorized to take prompt actions to eliminate threats and hazards.
According to the excavation standards, this competent person will:
· Classify soil types
· Inspect protective systems
* Design structural ramps
* Monitor water removal equipment
* Conduct site inspections
* Conduct preplanning
Why Preplanning Is Important to Excavation Work
Approach each new trenching, backfilling and shoring job with care and preparation, no matter how many you have completed in the past.
Initial planning is so important in avoiding on-the-job accidents. Do not wait until after work has already started to correct mistakes in shoring or sloping. It slows down operations, adds to the cost of the project and makes excavation failures, including cave-ins more likely.
Consider Safety Factors When Bidding
Know as much as possible about the job site and the materials needed before preparing a bid. Know what you will need to have on hand to perform work safely and in compliance with OSHA’s standards.
Consider preparing a safety checklist for new projects. Include:
- Proximity and condition of any nearby structures
- Location of the water table
- Soil classification
- Surface and groundwater
- Overhead and underground utilities
- Weather conditions
- Quantity of protective systems or shoring that you may require
- Fall protection systems
- Number of ladders needed
- Other equipment needed
Gather information through observations, test borings, jobsite studies and soil types. Also, consult with local utility companies and officials.
Disclaimer: The information contained in this article is for general educational information only. This information does not constitute legal advice, is not intended to constitute legal advice, nor should it be relied upon as legal advice for your specific factual pattern or situation.