Do you have a back-up plan??????

During the wet weather you need an alternate plan when trenching. 
Why do you ask?

Because water can turn an “A” type soil into a “C” type soil very quickly,
(read our previous post on soil types)

What is your back-up plan?




Use a Trench Box!

How do I use a Trench Box you ask!

Here are the instructions….

·       Make sure your trench box is 2 ft. or less from the bottom of your trench.

·       Make sure you have 18 inches of freeboard from the top of the trench to the top of your trench box.

·       Calculate your slope by measuring from the bottom of the freeboard of your trench box.

·       The slope will need to be 34 degrees from horizontal.

What are the signs that my soil type is changing?

·       The soil wall starts oozing water out of the vertical wall of the trench.

·       There is water in the bottom of the trench.

·       There are chunks of soil breaking away from the vertical wall.

Remember: Most soils will change to a type “C” soil very quickly once water is introduced.

The most important safety tip I can share with you is this:

When working with type “C” soil sloping begins at the bottom of the trench. There is no vertical wall.

Do not measure for slope any other way!

The importance of knowing the different Soil Types before you dig your trench is paramount to properly measuring them for slope, shoring and bracing. Having the knowledge of the different soil types will help you determine the appropriate slope and will keep the trench stable. The importance of this knowledge becomes crystal clear when you realize that a single cubic yard of soil can weigh up to 3000 pounds. Think about the danger on a job site if you have human beings working inside this trench and it collapses. The other factor that supports the importance of knowing your soil types is that a single trench can have several different soil types along its length. So you would need to know each different type of soil along the length and determine all the different measurements for the slope and then build your shoring and bracing to accommodate them.

There are 4 basic degrees of soil types that have lessening degrees of stability:

Stable Rock

Type A

Type B

Type C 

The definitions of these different soil types are as follows:

Stable Rock: Is the naturally solid mineral matter that occurs in nature and can be excavated with the vertical sides remaining intact while exposed.

Type A: Is the naturally occurring Cohesive Soils such as clay, silty clay, sandy clay, clay loam, also cemented soils such as caliche and hardpan. This classification of soil cannot have any type of fissures, been disturbed in anyway, or have been exposed to any type of vibration such as heavy traffic, or pile driving. It will also be carry a different classification type if there are any other factors that make it less stable.

Type B: Is the naturally occurring Granular Cohesionless Soils such as angular gravel, silt, silty loam, sandy clay loam, previously disturbed soils, soils that have been subject to vibrations, soils that have fissures. Dry rock that is not stable also falls under this classification.

Type C: Is the naturally occurring Granular Soils such as sand, loamy sand, non-angular gravel, submerged soils or soil where water freely seeps, and submerged rock that is not stable.

It is very important to survey your jobsite for all types of conditions to help you visually determine what soil types you may encounter. It is also extremely important to take several soil samples to help with the classification determination. Remember that as construction continues it is essential to continue to take soil samples. A soil classification can change with the depth of your trench, the width of your trench, and the length of your trench. Remember that properly classifying your soil type will help calculating your slope, your shoring and bracing. It will help keep your costs from running over and more importantly keep your job site safe and free of injuries.

For more detailed and in depth information you may visit the OSHA website.