Utility Trenching in the Catskills & Hudson Valley

What goes in a utility trench

Most residential trenching is one of a handful of jobs:

• Water service from a well or a municipal main to the house
• Sewer laterals and lines to a septic tank (see sewer and septic excavation)
• Underground electric to a house, garage, barn or generator
• Propane lines, and conduit for internet or low-voltage wiring
• Footing drains and downspout lines

Each has its own depth and bedding requirements, set by the plumber, electrician, utility company and local code, not by guesswork. A water line has to sit below frost depth, which is about 4 feet in most of this area, or it will freeze. Electric conduit has its own required cover. Before digging, Justin gets the existing underground utilities located and marked so a new trench doesn't cut an old line.

How utility trenching gets done

The route comes first. Straight and short is cheapest, but the best route also avoids the septic field, big trees, ledge, and anywhere trucks will drive every day. Then the trench is dug to grade and the bottom is cleaned of rocks. In stony ground, the pipe or conduit gets a bed of sand or fine material under and over it, because a sharp stone pressed against plastic pipe by 4 feet of backfill will eventually wear through. Warning tape goes in above the line, so the next person to dig there finds tape before they find pipe.

Often the line has to be inspected before it's covered, so the trench may sit open until the inspector comes. After that, it's backfilled in lifts and compacted, with the topsoil going back on top. A trench that sinks into a ditch across the lawn a year later is almost always a compaction problem.

What makes a trench slow or expensive?

Length, depth and what's in the ground. A 4-foot trench through sandy loam goes quickly. The same trench through glacial till full of cobbles, or across ledge that has to be broken, can take several times as long. Crossing a driveway or walk, working around a high water table, and tight access all add time too.

In the mountain towns, rock is the big unknown. On some lots bedrock sits a couple of feet under the surface, and a water line can't live in 2 feet of cover. Sometimes the answer is a different route, sometimes it's insulation over the line where the plumber and code allow it, and sometimes it means breaking the rock (see rock and boulder removal). Near the Hudson, clay digs easily but doesn't stand well when it's wet, so trench walls can slump.

Trench safety and mistakes to avoid

A deep trench is one of the most dangerous places on any job. Walls can collapse without warning, especially in wet or sandy soil, and even a small cave-in can trap a person. Deep trenches need to be sloped, benched or shored before anyone climbs in, and kids and pets need to stay well clear of an open trench.

The other common mistakes: running water and sewer lines together without the separation the code requires, leaving out tracer wire or warning tape, and backfilling with the big rocks that came out of the hole. Plan ahead while the ground is open. If you might add a generator, a barn or a detached garage someday, laying an extra empty conduit now costs very little compared with digging a second trench later. If the trench is part of a new build, it's often done alongside the site excavation.