Check the National Electric Code for specifics for your trench. The code dictates the depth of the trench depending on what type of wiring you are placing inside the conduit. Check with your building commerce department for assistance with the NEC.
Use spray paint to draw the proposed conduit route on the ground. Keep the path as straight as possible. Limit the number of 90 degree turns to three.
Begin to dig following the paint marks on the ground. Use the tape measure to measure the depth of the trench. Adjust the depth of the trench as needed. Continue digging until the end point is reached. Larger conduit trenches require heavy machinery and shoring. Shoring is the process of placing a metal box inside the trench to keep the sides from caving in. This can happen when the trench is 6 feet or deeper. Many workers have lost their lives or been injured due to failure to follow correct shoring procedures.