Should I Slope That Trench?

Trench Chart

If you do excavation work you know how much a trench box costs to buy or rent. But do you know how much the alternative costs?

The OSHA trenching and excavation regulations require trench boxes or other shoring to be used if the sides of the trench cannot be properly sloped. The slope depends on the kind of soil. From an excavation safety perspective there are three soil types including Type A, Type B and Type C. In almost every case the soil in Florida is Type C because of the high sand and water content.

This means that your trench or excavation must be sloped at a 34 degree angle (one and a half feet back for every foot deep). This may not seem so bad but consider this. A 5 foot deep and 3 foot wide trench would have to be sloped so that the opening would be 18 feet wide! An excavation that size takes a tremendous amount of time and energy and as a result is often done improperly.

Aside from the safety concern you might also be surprised that sloping often costs more than using trench boxes or other shoring equipment. The cost of removing soil and moving it away from the edges of a trench can be very expensive and will typically exceed the cost of boxes or shoring. This is particularly the case in long, narrow trenches (such as pipelines) where shoring and boxes can be used over and over as the trench is dug and filled but sloping requires extensive soil moving along the entire length of the trench.

For instance, the chart below compares soil removal quantities and costs for a two-mile trench that is 5 feet wide and 15 feet deep.

Trench Chart

If you want more information on trenching and excavation contact Randy Free at 407-353-8165 or email him at rfree(at)safetylinks.net

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