French Drain Installation in Gresham, Oregon: Cost & Process

French Drains in Gresham's Clay Soil

Gresham gets the full force of the Pacific Northwest wet season, and the ground here makes it worse. Sitting in the eastern Portland metro at the foot of the Cascade foothills, Gresham's soils are heavy with clay and silt — the kind of dense, slow-draining ground that holds water like a sponge and refuses to let it go. When the rain runs from October through May, water that should soak away instead sits in the soil, pools on the surface, and seeps into anything below grade.

A French drain is one of the most effective answers to clay-soil drainage. It is a gravel-filled trench with a perforated pipe that collects subsurface water and routes it to a safe outlet, giving water a fast path out of ground that would otherwise hold it for months. This guide walks through how French drains are installed in Gresham, what affects the cost, and why Multnomah County's clay makes them so valuable.

For the full drainage picture, start with our guide to property and site drainage in Oregon. For statewide pricing detail, see French drain cost in Oregon.

When a Gresham Property Needs a French Drain

• A chronically wet or soggy yard — Clay holds water at the surface, leaving lawns spongy for weeks after the rain.
• A wet basement or crawlspace — Saturated clay against the foundation pushes moisture into below-grade spaces through the wet season.
• Standing water that will not drain — Where the ground is flat and the clay is dense, surface water simply has nowhere to go.
• Runoff from a slope or neighbor — Gresham's foothill terrain sends uphill water toward lower lots, where it has to be intercepted.

How a French Drain Is Installed in Gresham

1. Site Assessment and Outlet Planning

The job begins with where the water will go. The installer evaluates the slope, finds the water source, identifies a safe outlet — a daylight point downhill, a dry well, or a storm connection — and checks the soil. In Gresham's clay, the outlet matters enormously, because the surrounding ground will not absorb overflow on its own.

2. Trench Excavation

The trench is dug to a steady depth with a consistent downhill slope, typically 1 percent or more. Clay digs differently than rock or sand: it is dense and heavy, it can smear and seal the trench walls, and it holds water that has to be managed during the dig. Proper excavation keeps the trench draining toward the outlet the whole way.

3. Fabric, Gravel, and Pipe

Filter fabric lines the trench — essential in Gresham, where fine clay and silt will clog an unprotected drain quickly. A bed of clean drain rock goes down, then the perforated pipe (holes down), then more rock, then the fabric folds over the top to seal out sediment.

4. Backfill and Restoration

The trench is backfilled, compacted, and restored to grade. Done right, the finished drain disappears into the landscape within a season while quietly moving water for decades.

Our excavation services cover the trenching and grading these installations require.

What French Drain Installation Costs in Gresham

French drains are priced per linear foot, with the total driven by length, depth, soil, and outlet. Industry baseline ranges commonly referenced include:

Factor	Industry Baseline Range
French drain (per linear foot)	$25–$60
Typical residential run (50–100 ft)	$1,500–$6,000+
Dry well outlet (each)	$1,500–$4,000

In Gresham, cost drivers include the length of the run, how deep it must go, the distance to a viable outlet, and access for equipment. Heavy clay can slow excavation and may require a more robust outlet because the surrounding soil will not help drain overflow. A shorter run to a nearby daylight point sits at the low end; a long run to a dry well runs higher. Only a site assessment gives an accurate number. See French drain cost in Oregon for the broader breakdown.

Why Gresham's Clay Makes a Local Eye Matter

In clay soil, the outlet is everything. You can build a perfect trench, but if the water has nowhere to go, the system backs up the first wet week. A contractor who works Multnomah County understands that clay will not absorb overflow, plans the outlet accordingly, and uses filter fabric correctly so the fine silt that clay sheds does not clog the pipe. Skipping that local knowledge is how a French drain ends up holding water instead of moving it.

Get Your Gresham French Drain Quote

Cojo Excavation & Asphalt installs French drains throughout Gresham and Multnomah County, designed for the heavy clay that makes east-metro drainage a real challenge. We assess your soil and slope, plan the right outlet, and give you a real number based on your property.

Request a free drainage assessment and we will respond within 24 hours. Explore our full range of excavation services for Gresham-area homes and businesses.