Nationally, HomeGuide's 2026 trenching page shows $5 to $12 a linear foot, which makes 100 feet cost $500 to $1,200. Around Vancouver, the soil and the season decide how fast a trench goes: sandy gravel is quick, wet clay slumps.
We did not set the dollar figures on this page: they are national ranges from HomeGuide. In Clark County, wet-season clay, trees, slope, groundwater and haul distance are what push a real job up or down. Figures checked October 2026.
What is the trenching cost for a 100-foot trench?
A 100-foot trench costs $500 to $1,200 at HomeGuide's $5 to $12 per foot, with the machine about $2 to $3 of that and labor $3 to $9. Depth, roots, wet ground that needs shoring and crossings of other lines push the price up.
| Trench length | National range, HomeGuide |
|---|---|
| 50 ft | $250 to $600 |
| 100 ft | $500 to $1,200 |
| 200 ft | $1,000 to $2,400 |
Who do I call for a water line trench, and what does it cost?
For a water line, use a plumbing contractor registered with L&I, with a certified plumber doing the pipe work, and an excavator for the trench unless the plumber digs too. HomeGuide puts main water line replacement at $2,000 to $5,000 on average, or $50 to $200 a foot trenched and $70 to $250 trenchless.
How deep should a water line be buried so it won't freeze?
Your plumbing code and the plumber's plans set the burial depth, which keeps the pipe below the frost line. Hard freezes come with east wind storms off the Gorge, and exposed pipe at the house or a shallow line to a barn can split. Insulate anything above ground.
What does it cost to replace a sewer line?
On HomeGuide's sewer page, replacement runs $50 to $250 a linear foot, or $2,000 to $10,000 for 40 feet, with pipe bursting at $60 to $200 and lining at $90 to $250 a foot. Older laterals in Hazel Dell, Orchards and Portland often get a camera inspection first, at $125 to $500.
What does an electric line trench to a shop, ADU or garage cost?
The trench itself costs the same $5 to $12 a foot. In Washington, electrical work is done by an electrical contractor holding an L&I licence, with certified electricians, and they set the conduit depth. Shops, ADUs, EV chargers and barns are the common reasons here.
What does it cost to run a gas or propane line underground?
HomeGuide's trenching page lists a trenched gas line at $12 to $25 a foot, about $350 to $1,000 or more in total. The pipe must be installed and tested by a qualified gas contractor. Where a rural home runs on propane, the supplier sets where the tank and line may go.
Can you trench under a driveway without tearing it up?
Yes: a bore passes the line under the slab or asphalt. HomeGuide prices directional boring at $10 to $30 a foot, or about $1,000 to $3,000 for 100 feet. It also works for running a line under a lawn, a creek buffer or tree roots that should not be cut.
Can water and sewer go in the same trench?
At times, yes. The plumbing code keeps drinking water apart from sewer by distance or height, and the plumber sets how that works in one trench. Only a layout that meets code lets both use the same trench.
Can you trench near tree roots or close to the house?
Yes, with care. Near big firs and maples we route around the main roots, dig by hand or bore under them, and follow any tree rules in your city or the county. Close to the house we stay off the footing and backfill quickly before rain fills the trench.
Which trades need a state licence or registration in Washington?
Washington requires all construction contractors to register with the Department of Labor and Industries, which checks a surety bond ($30,000 for general contractors and $15,000 for specialty contractors) and liability insurance. Plumbing and electrical work also need L&I licences or certificates for the contractor and the workers. You can check any contractor with L&I's Verify a Contractor tool.
Tell us about your project and we will come look at the ground, then send the scope and the price in writing. Call or text (360) 276-9112.