Trench: a cut (usually 2" to 6" wide, but sometimes much larger) is made with a chain blade (generally 2' to 6' deep) pulled through the ground by a tractor. Microtrenching is a method of installing fiber optic cables, HDPE ducts, and Microducts by creating a narrow trench, usually less than an inch wide and up to 12 inches deep. The trench is then filled with a special grout back-fill material that provides stability and support to the cable. Typical trench dimensions range from. 2 mm) and 8 in to 17 in deep (20. It can therefore be used both in and out of town.