Trenching Types & Techniques

All trenches are considered excavations, but not all excavations are considered trenches. Trenching is a specific type of excavation technique and offers a great alternative to install underground pipes and cables when boring isn’t right for the job. Trenches are often a large part of all types of construction projects and the ongoing maintenance of existing infrastructure.

What Is Trenching?

Trenching is a simple excavation technique that involves removing dirt, rock and other organic matter to create a hole in the ground. Trenches are usually dug from aboveground in a path that’s deeper than it is wide. Trenches can vary greatly in depth, but OSHA only considers an excavation to be a trench if it’s less than 15 feet wide at the very bottom of the trench. Anything larger and it’s considered an excavation, which can be any depression or opening in the earth’s surface.

Different Types of Trenches

Trenching may be used to create new ditches for installing drainage, retaining walls, electrical or fiber conduit, sprinkler systems and gas, sewer and water lines. It can also be used to create replacement trenches to replace old sewer, water and drain lines with new materials. There are several different types of trenches, with trench type determined by its shape and the shape determined by the purpose of the trench. Issues that affect the type of trench you can use include:

  • Type of soil being dug in
  • Availability of shoring or shielding
  • Size of pipe or conduit being installed in the trench
  • Location of the trench, i.e., roadway versus open field
  • Proximity to any existing utilities, buildings or other structures

Four commonly used trench types include:

  • Straight Trenches: Have parallel sides that are at right angles to the base. These trenches are usually utilized in areas where there’s limited surface area, such as near buildings or roadways. Shoring or trench boxes are required protective systems.
  • Sloped Trenches: Have angled sides to prevent cave-ins, with the slope’s angle determined by trench depth, soil type and how long the trench must remain open. These trenches are used for placing large culverts or pipes and are also common for new construction sites where there’s a wider path of soil and other protective systems aren’t available. Sloping and shielding are employed as protective systems.
  • Benched Trenches: Have sides that have been cut away to create steps, with the height of the steps determined by soil type and shallower angles required in less stable soils. Single or multiple bench systems may be used to stabilize a trench that needs to be up to 20 feet deep. Shielding or trench boxes are used as protective systems.
  • Bell-Bottom Pier Hole Trenches: Have tops that are usually narrower than the bottom of the hole, giving it a bell shape. These trenches are typically used for installing footings to support a structure’s foundation. Additional protective systems are required because there’s a higher potential for collapse due to the sides sloping inward over the floor of the excavation.

Trenching Safety

Excavation and trenching are among the most hazardous tasks in construction. Potential hazards include slip and fall accidents, electrocution, falling loads, unsafe atmospheres and accidents involving mobile equipment. However, cave-ins pose the greatest risk to worker safety, with a high likelihood for fatalities. Unless the trench is made entirely in stable rock, OSHA generally requires employers to utilize a protective system to protect workers from cave-ins.

Placing a shield between the work area and the sides of the excavation and/or shoring, benching and/or supporting the sides of the excavation are the most common types of protective systems used. Employers are allowed to choose the most practical protective system that provides the necessary protection for workers. Deciding factors for choosing a protective system include weather and climate, soil type and water content, depth of the trench and proximity to other operations.

Contact the Trenching Experts in Kansas City

Whether you’re installing a single utility line for a residential project or the entire infrastructure for a commercial project, the excavation experts at Earthworkz can help you choose the right type of trenching for your construction needs. We use mechanical chain trenchers to cut our ditches and efficiently complete trenching requirements for all types of construction projects, both large and small. Earthworkz is one of the top trenching contractors in the Greater Kansas City area and has been expertly fulfilling our customers’ excavation needs since 2009. Contact us at 816-355-0280 to schedule a consultation on your trenching project today.