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Excavation Safety

Excavation Safety

Excavation SafetyExcavation safety should be of the utmost importance to people who work in the excavation industry. As experts in ore field we know how potentially dangerous and devastating a trench line or excavation collapse could be. In fact excavation work has a 112% higher fatality rate than general construction. This is why trenching & shoring standards must be met for all excavations deeper than 5 ft this is actually a required by law and depending on your location the standard may be 4 ft. Check with local and state regulations.

Pocket penetrometer

It is important to classify your soils before entering any excavation deeper than 4 ft. Classification of soils can only be done by soils engineer or on site certified “Competent Persons”. Soils classification is based on site conditions and soil composition. The three ways of soil classification on site are:

  • Thumb penetration test
  • Plasticity test
  • Pocket penetrometer

There are a four types of soil classifications with the following subsets

Type A-25 Soils

Cohesive soils with an unconfined, comprehensive strength of 1.5 “Pocket Penetrometer” ton per square foot (tsf) or greater. Examples of cohesive soils are: clay, silty clay, sandy clay, clay loam and sandy clay loam. Cemented soils such as caliche and hardpan are also considered type A “stable rock”.

However, no soil is type A if:

  1. The soil is fissured
  2. The soil is subject to vibration from traffic, pile driving, or similar effects
  3. The soil has been previously disturbed
  4. the soil is part of a sloped, layered system where the layers dip into the excavation on a slope of four horizontal to one vertical (4H:1V) or greater
  5. The material is subject to other factors that would require it to be classified as a less stable material

Type B-45 Soil

  1. Cohesive soil with an unconfined compressive strength greater than 0.5 tsf but less than 1.5 tsf
  2. Granular cohesionless soils including: angular gravel (similar to crushed rock), silt, silt loam, sandy loam and, in some cases silty clay loam and sandy clay loam.
  3. Previously disturbed soils except those which would otherwise be classed as type C soils.
  4. Soil that meets the unconfined compressive strength or cementation requirements for type A but is fissured or subject to variation
  5. Dry rock that is not stable
  6. Material that is part of the sloped, layered system where the layers dip into the excavation on a slope less steep than four horizontal to one vertical “4 to 1”, but only if the material would otherwise be classified as type B

Type C-60 Soil

  1. Moist, cohesive soil or a moist dense granular soil which does not fit into type A or B classifications, and is not flowing or submerged.
  2. This material can be cut with near vertical sidewalls and will stand unsupported long enough to allow the vertical shores to be properly installed.
  3. The competent persons must monitor the excavation for signs of deterioration of soils as indicated by, but not limited to, freely seeping water of flowing soils entering the excavation around or below the sheeting
  4. An alternate design for less stable type C soils will be required where there is evidence of deterioration

Type C-80 Soil

  1. Cohesive soil with an unconfined compressive strength of 0.5 tsf or less
  2. Granular soils including gravel, sand, and loamy sand.
  3. Submerged soils or soils from which water is freely seeping.
  4. Submerged rock that is not stable
  5. Material in a sloped, layered system where the layers dip into the excavation or a slope 4 to 1 or steeper

If no certified “Competent Persons” is on site all soils must be treated as class c soils. For more information, review the current OSHA Standards.


Owner and operator of Willhite Grading

This Post Has 7 Comments
  1. I’ve been a part of a few excavation projects in the past. I can see why it has a 112% higher fatality rate than general construction. A lot of times we complain about laws and regulations, but they are most of the time meant for our safety. Thanks for sharing this.

  2. Excavating is definitely dangerous and a good reason to be involved with a company that follows safe practices and standards. 112% higher fatality rate is not something you can cut corners with. I wonder how you can check a companies policies and standards to see how they compare with rules and regulations. Thank you for the post.

    1. Just ask for a copy of the safety program certification. Companies are required to have a safety program in California. We use Safety Services Company.

  3. I appreciated your comment about how excavation can be done safely if trenching and shoring are checked ahead of time. I didn’t know that you should classify your soils to make sure you can dig as deep as you need to. If someone were looking into hiring an excavation company to prepare to build something on their property, I would assume that they would keep these tips in mind.

  4. Thank you for all the excavation safety information. I didn’t know that it was important to classify your soils before they can begin to excavate deeper than 4 ft. I am really curious why you would have to know that.

  5. I do like how you mentioned that excavation is highly risky compared to general construction which is why safety is their utmost priority. That is something I will be sure to keep in mind if I ever would need an excavation service. Honestly, I do appreciate that these excavation companies focus on keeping their workers safe. I might need them for my pool creation soon. Thanks!

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