I need to channel an electricity (and network) cable under the lawn to an outbuilding.
I understand it would be best to shield the cable to stop anyone from danger when digging in the future, but what is the best way to excavate the small channel required for the cables and shielding? I'm guessing there's some kind of tool that makes the job easier with the least amount of damage to the grass?
Depending where you are, you often have a minimum burial depth, which in my area depends on how you protect the cable. Pouring concrete around/over it reduces the depth it needs to be buried to.
As for the digging, it depends on the amount of trench and you.
Step zero - contact the local "call before you dig", "dig-safe", "blue stake" or whatever the service is called in your area to have existing underground services marked before you dig. If you call them and dig through a fiber optic cable that isn't where they said it was, that's their problem. If you don't call them and dig through one, it's your, very expensive, problem. While this may well be unlikely between your house and an outbuilding, it's better to get in the habit of ALWAYS having the area marked, even if what actually happens is a lot of flags saying "No FO" "No Gas" "No Phone."
At the low, cost, high manual labor end, you take an edger and cut the sod on both sides, then remove it with a spade, then spade and mattock your way down to the appropriate depth. Given you are concerned with lawn damage you might want to place plywood to dump the dirt on.
At the high-cost, low labor end, you rent a sod cutter (since you are concerned with lawn damage - a more typical "contractor approach" is to dig up the sod and reseed the trench, but you have a higher class job in mind, evidently) then dig the trench with a ditcher (sort of a dirt chainsaw) or an excavator (those deal better with large rocks, if you have them.)
Having gone to the bother (and expense) of digging the trench, do yourself two favors and place conduit in the trench, [in my area, two separate conduits are required for network (low voltage) and electricity (high voltage)] so you don't have to dig the trench again, and place "buried electric line below" tape in the top 6" of dirt as you refill the trench (it comes in a huge roll, typically, so I place it there, and also 6" above the conduit in the bottom of the trench - but if it's only one place, the top one is most important, so that anyone digging in the future finds it BEFORE they find the wires/conduits.)
I personally prefer to add an extra, empty (and capped off) conduit, so that if something else comes along later that I might want to run between the two buildings, I have a place to put it - conduit is very inexpensive compared to the cost (however you count it) of digging the trench to put it in.
