The most important consideration during trench digging is safety, as construction of such a hole is one of the more dangerous practices in construction. The risk of a cave-in is quite high during trench digging, so for deeper trenches, supports should be used to reduce this likelihood. Smaller trenches around the home can often be built using a shovel, but if the trench needs to be long or deep, a walk-behind trench digging machine should be used. The best methods for digging trenches depend on how deep and wide the trench needs to be, and for what purposes it is being built.
Trench diggers come in a variety of sizes and they make digging trenches exponentially easier than the shovel method. On construction sites, trench digging is usually done with a piece of heavy machinery that takes an expert to operate. Such trenches are usually quite deep and long, so the risk of a cave-in is extremely high. Steel wall supports should be used in this application if possible, and time spent inside the trench should be limited, especially if steel or other types of supports are not being used.
Smaller trench digging projects can be done by hand or with a walk-behind trench digger. The latter is much easier, since the time spent digging the hole will be considerably shorter. The trench digger also requires far less energy to operate; using a shovel can take a long time and the person digging will expend a significant amount of energy. Shovel digging should be reserved for only the smallest trenches, or trenches that require precise digging around corners or through other obstacles. A motorized, walk-behind trench digger may be faster, but it cannot do detail work the way a person with a shovel can.
For detail work, a trench digger and a shovel combined may be the best option. The trench digger can cut the long parts of the trench that do not run near obstacles, while a person with a shovel can dig around obstacles or around corners. Even on larger construction jobs, shoveling by hand may be necessary. If the trench will be open and unattended for any period of time, it should be blocked off sufficiently and signs should be posted to prevent passers-by from falling in. A trench should not be left open for any longer than it needs to be, as it is a safety hazard and flooding is possible during inclement weather.