How to Use an Excavator to Dig a Trench

How to Use an Excavator to Dig a Trench

There are many different types of digging projects that can be performed on commercial and residential properties. From installing fence posts, removing broken water pipes or placing in septic systems, you need the right equipment based on the size of the project and the type of digging that will be performed.
Small projects such as installing irrigation systems or placing in posts for fences can be performed using handheld equipment such as shovels, post hole diggers and augers. Trenches used for underground pipes for gas, water or sewer systems, or when installing electrical cables, will require larger heavy equipment such as backhoes, mini excavators, track loaders, and track hoes.

Before the Dig

You need to plan all the details before one shovel attachment lifts up off the ground. If you are excavating already existing pipes and electrical cables, or placing in new lines, you have to know what is under the ground before you dig. You can contact your local utility companies or get in touch with your provincial (Ontario or BC One Call) service to figure out where gas, water, sewage and electrical lines are located.
Once you know there will be no pipes or lines in your way, you can begin the planning phase for the trench. Decide on how deep and wide the trench will need to be as well as the length. Then you can figure out the types of equipment and shoring materials will be required.

Inspect the Worksite

Perform an inspection of the entire worksite. If the trench will be a small part of a larger development project, decide on the route that the excavator will take when digging a trench to avoid other worksite traffic if dump trucks, skid loaders and workers will be doing other work at the same time.
Ensure that other equipment and materials are moved from the trench worksite. Also determine if any damage will occur to nearby structures, sidewalks or driveways as well as trees, shrubs and other landscape elements. Create a pathway through the worksite to move the excavator to the digging site if you are renting the equipment from a heavy equipment rental company. Leave room for the rental excavator to be unloaded and loaded on the trailer before and after the trenching project.

Perform an Excavator Inspection

Before using any excavator or heavy equipment, perform a full inspection of the machinery. Fill up engine coolant and engine oil levels. Check hydraulic hoses for loose connections or split lines. Also, lubricate pivot points. Familiarize yourself with the excavator controls so you can efficiently operate the machine.
For residential homeowners who have never operated an excavator before, consider hiring a professional who can perform the work safely. An experienced excavator can work the controls in the appropriate manner. You can hire operators from heavy equipment rental companies based on an hourly rate for a minimum of 4 to 6 hours.

Excavating Trenches

Topsoil Layer Removal

Carefully remove the topsoil layer, up to a depth of 4 inches to 8 inches, as it can be returned to the area after you backfill the trench. Keep it away from the rest of the earthen materials that will be excavated so it doesn’t become contaminated. You can over-seed the topsoil layer if you plan to store it for long periods of time do to the length of the excavation project.

Dig to Desired Depth for First Cut

The first cut into the earth should go down to the full desired depth of the trench. Dig into the soil and remove it in layers until reaching the required depth point. If the trench will have to go at a deeper depth, then you will need to bench the excavation.
Benching involves digging in tiers and removing twice as much soil — widthwise —  as the actual trench. This technique is done to take the load pressure of the soil off the walls of the trench. Normally, a wider shovel bucket is used on the excavator machine to create the bench at intervals of 2 feet to 3 feet in space. Then the excavator with the narrower bucket will continue down to dig the trench to the desired depth. If you are using only one excavator for the job, you will have to dig out the trench walls on the left and right side.

Move Soil to Safe Location

Soil that is removed from the trench should be deposited in a location away from the trench so the soil doesn’t collapse the walls or fall back into the trench. Once your work in the trench is completed, you can move the soil back into the trench to backfill it.

Check Soil Conditions

Soil conditions can impact how long it will take to dig the trench and whether the trench walls will be able to support the weight of the soil. You can also see whether you will have to deal with excessive surface water entering the trench and making the trench walls unstable. Consider these trench wall techniques to keep workers safe and to prevent the trench from caving in.
· Trench Deeper than 3 Feet: Shore trench walls using plywood sheets and posts.
· Loose Soil: Perform benching along the sides of the trench
· Large Trenches more than 3 Feet Deep:  Place in sheet pilings and steel trench boxes
· Excess water: Install a diaphragm pump and sock pipe to divert water away and remove water from the trench

Check Trench Depth

A laser level can be used to check the depth of the ditch. You can also use a builder’s level. You should do this before walking the excavator forward to dig out another section of the trench so you don’t have the walk the excavator back and risk the chance that the machine’s heavy weight will cause the trench walls to cave in.
This step is also very important if you plan to place in gravity-assisted sewage lines. One end of the trench will be deeper than the other so that water and sewage can travel through the installed pipes. Having the trench graded at the right level will ensure the pipe system is installed correctly.
Once the trench is completed and the depth has been checked, examine the embankments to ensure that they will be stable during the installation process of the materials that will go into the ditch. Shore up any unstable areas and work on smoothing and grading the bottom of the trench manually with shovels if necessary.

Finishing the Project

The final part of the trench excavation involves installing the wiring or pipework for the project. Then you can remove the plywood or steel trench boxes used to shore up the trench walls and backfill the trench using the removed soil. If it is a deep trench, you should refill it in layers and then tamp it down. So you can fill in 8 inches to 10 inches of soil into the trench and then compact it before adding in the next layer. After the trench is filled, you can replace the topsoil and perform landscaping.
Now you know how to excavate a trench for residential and commercial projects. If you have any questions regarding the type of excavator you need, or require an experienced operator to handle the excavation process, contact equipment rental company Rent1.