How to dig a trench

Call the local or government utility location service. Before you begin any digging project, call a utility location service. This will locate underground gas, electric, water, and communications pipes and cables in the area, to protect you from injury or liability in the event they are damaged.

Plan a route that causes minimal damage. Take your time in the planning phase to find a layout that meets your needs, avoids utility lines, and minimizes damage to valuable property. With careful planning, the materials you purchase should be sufficient to complete the trench, and you won’t have to change your plan after you start digging.

  • Trees, shrubs and other plants may suffer injury or die if their roots are damaged in excavation. Driveways, sidewalks, and structures can collapse if they are undermined.
  • Small plants, even turf grasses, can be removed and stored for replanting with proper care.

Call your local council during the planning process to ensure your safety moving forward.

Determine the depth your project requires. The trench’s depth requirements (for example, the required depth of a utility line) is a factor in choosing excavation equipment and other materials.

  • Some plumbing systems are gravity operated, and require a slope so the waste or water will flow unaided to the discharge location. In this situation, you may find the trench will be deeper on one end than the other.

Determine the type of soil you will be digging in. Sandy soils, loose stony soils, and wet, mucky material will make excavating a straight, deep ditch difficult and dangerous. In these scenarios, you may have to plan additional measures to complete your project successfully:

  • Shoring: This process uses a support structure for your ditch sides so they do not cave in and injure anyone, or undo the digging you have done before the project is complete. For example, a small excavation could use sheets of plywood supported by posts. Large excavations could use steel trench boxes or sheet piling. Anything deeper than 3 feet (0.91 m) should be shored up. Never enter a trench deeper than your waist if it is not shored up.
  • De-watering: This removes the excess water from the soil to help stabilize it while working. This can be accomplished either with a well point system, or a sock pipe and mud-hog type diaphragm pump to remove the water as it seeps into the excavation.
  • Benching the excavation: If you are digging in loose soil, a deep vertical trench wall is at risk of collapse. Benching involves digging the trench in steps or tiers instead, so the banks do not have to support more material than they are capable of. These benches are usually at intervals (0.76–0.91 m) deep and twice as wide. They do take quite a bit of sidewall digging, which can require extensive area to complete. Keep in mind that it can still collapse the deeper the trench goes.

Get the excavation equipment. Shovels, pickaxes, and other hand tools will suffice for minor excavations, but renting a mini excavator can save a lot of work on large jobs. Backhoes and even trackhoes may be needed if the project requires a very deep and/or long trench.

  • Unless you are already experienced with these types of equipment, it may be cheaper and safer in the long run to hire a professional excavator.

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