Yard Drainage in Hillsboro, Oregon: Fixing a Soggy Lawn

Why a Hillsboro Yard Stays Soggy

A soggy lawn in Hillsboro usually comes down to geography. The city sits on the flat floor of the Tualatin Valley, where the soil is heavy clay, the water table runs high through winter, and the ground is so level that water has nowhere to flow. When the Pacific Northwest wet season delivers months of steady rain, that combination keeps lawns waterlogged from fall through spring.

A perpetually wet yard kills grass, breeds mosquitoes, makes the space unusable for half the year, and — when the water sits near the house — threatens the foundation. The cause is almost always a combination of flat grading and Hillsboro's slow-draining clay, and both have known fixes. This guide explains what is happening beneath your lawn and how to dry it out.

For the full picture of how water moves on a property, start with our guide to property and site drainage in Oregon. For statewide pricing, see the yard drainage cost guide for Oregon.

What Causes Yard Drainage Problems in Hillsboro

Flat Valley Ground

This is the defining issue in Hillsboro. Water needs slope to drain, and the Tualatin Valley floor offers very little. Surface water that should flow to a low point and away instead spreads out and sits, because there is nowhere lower for it to go.

Heavy Clay Soil

Washington County's clay packs tightly and lets water pass slowly, so rain that should soak away instead lingers near the surface. Flat ground plus slow-draining clay is the worst combination for a lawn.

A High Seasonal Water Table

Through the wet months the groundwater in Hillsboro rises close to the surface. When the water table is high, the soil is already full, and any additional rain has nowhere to soak in — it stays on top.

Downspouts and Hardscape Runoff

Roof water dumped at the foundation and runoff from patios and driveways concentrate water onto ground that is already saturated and flat, overwhelming it quickly.

How Yard Drainage Gets Fixed in Hillsboro

The right solution depends on the cause, so an assessment comes first. Common approaches include:

• Regrading — Reshaping the yard to create what slope the flat lot allows, directing water toward an outlet, is the foundation of most fixes.
• French drains — A gravel-filled trench with perforated pipe intercepts subsurface water and carries it away — the workhorse for flat clay where surface slope is scarce.
• Dry wells — Where daylight drainage is not available, a dry well collects water and releases it slowly, sized to account for clay and a high water table.
• Channel and catch-basin drains — Surface inlets capture water from patios, downspouts, and low spots and route it underground.
• Downspout extensions — Carrying roof runoff well away from the foundation solves many soggy-yard complaints on its own.

Our excavation services cover the precise grading and trenching these solutions require.

What Yard Drainage Costs in Hillsboro

Yard drainage is priced by the type and length of system, not a flat rate. Industry baseline ranges commonly referenced include:

Solution	Industry Baseline Range
French drain (per linear foot)	$25–$60
Dry well (each)	$1,500–$4,000
Channel / trench drain (per linear foot)	$50–$150
Yard regrading (per project)	$1,000–$5,000+

In Hillsboro, the flat ground and high water table both influence cost: reaching a workable outlet can mean a longer run, and the clay demands a substantial outlet because the surrounding soil will not absorb overflow. A simple regrade or downspout fix sits at the low end; a French drain to a dry well runs higher. A site assessment is the only way to budget accurately. See the yard drainage cost guide for Oregon for the broader breakdown.

Why a Site Assessment Comes First

On flat Hillsboro lots, finding a path for the water is the whole challenge, and two soggy yards can need very different solutions. One may just need a regrade and downspout extensions; the next may need a full French drain to an engineered outlet because the flat clay and high water table give surface grading nothing to work with. An assessment measures what slope exists, evaluates the soil and water table, and finds a viable outlet — the diagnosis that separates a lasting fix from a patch that floods again next winter.

Get Your Hillsboro Yard Drainage Quote

Cojo Excavation & Asphalt helps Hillsboro and Washington County homeowners dry out soggy lawns for good, with solutions designed for flat Tualatin Valley clay and a high winter water table. We assess your grade, soil, and water table, find the right outlet, and recommend a fix matched to your property.

Request a free drainage assessment and we will respond within 24 hours. Learn more about our excavation services for Hillsboro-area properties.