The trench only needs to be 1 foot wide, and even a trench just 6 inches wide can suffice. If you need to use a digging machine, you may end up with a trench 16 or 24 inches wide.

The estimate assumed a 76,000-pound machine would dig a foot of trench every minute and 41 seconds, at a cost of $2.26 per foot. A minor improvement in digging methods that trimmed just 5 seconds from ...