Yard Drainage in Forest Grove, Oregon: Fixing a Soggy Lawn

Why Forest Grove Lawns Stay Wet

Forest Grove sits where the flat Tualatin Valley floor meets the foothills of the Coast Range, and that location gives local lawns two ways to stay soggy. On the valley-floor side of town, the soil is heavy silty clay with little natural fall, so water that lands simply ponds — the same flat-ground, clay-bound problem that keeps lawns wet across Washington County. On the western and northern edges, where the land starts rising toward the hills, lawns can also take on runoff sheeting down from higher ground and collecting in the first flat or low area. Through Forest Grove's long Pacific Northwest wet season, either pattern can leave a lawn soggy for months.

Clay is the common thread on both sides of town. Once the surface clay saturates, it stops absorbing water, so whatever lands — or arrives from uphill — stays on top. The key to fixing a Forest Grove soggy lawn is knowing which pattern you have: water that won't move on the flat, or water arriving from above. The fix is different for each.

What's Causing the Wet Spot in Forest Grove

Flat grade with nowhere to go. On the valley floor, little natural fall means water just sits. The most common cause in town.

Clay holding water at the surface. Once the top layer of clay saturates, rainfall pools rather than soaking in.

Runoff from the foothills. On the rising western and northern edges, water sheets down from higher ground and collects in the first low area.

Downspouts at the foundation. Roof water concentrated near the house saturates a lot of lawn.

Compacted soil. Construction and foot traffic pack the clay until it sheds water like pavement.

Drainage Solutions That Work in Forest Grove

Regrading and Swales

Because Forest Grove's clay sheds water at the surface, moving water across the top of the ground is often more effective than draining it down. On flat valley lots, a gentle regrade or shallow grassed swale carries water toward a usable outlet or rain garden. On foothill-edge lots, a swale across the slope diverts incoming runoff. Either way, this is frequently the most cost-effective first move.

Interceptor and French Drains

On the rising edges of town, an interceptor drain — a French drain placed across the slope above the wet area — catches downhill runoff before it reaches the lawn. On the valley floor, a French drain collects subsurface water and conveys it to an outlet, working best shallower and combined with grading. For pricing, see our yard drainage cost guide for Oregon.

Catch Basins and Area Drains

For a persistent low spot, a catch basin set at the dip with a buried line to an outlet removes standing water at its source. On flat valley lots these may pair with a pump if gravity can't carry the water far enough.

Downspout Control and Rain Gardens

Carrying roof water away on solid pipe, and directing it to a rain garden where it can soak in, keeps gutter water from adding to the lawn problem. Keep clean roof water on solid pipe, separate from any perforated French drain.

What Yard Drainage Costs in Forest Grove

Pricing depends on length, depth, soil, access, and where the water can exit — which varies between the flat valley floor and the foothill edge. Industry baseline ranges are a reference, not a quote. On the valley floor, a hard-to-reach outlet pushes cost up; on the foothill edge, slope access and erosion control do. A short swale or downspout line sits at the low end; a long interceptor drain or a French drain needing a sump runs higher. Forest Grove's clay digs harder than sandy soil.

Rather than budget from a chart, the reliable path is a site visit. We read where the water comes from, find where it can go, and quote the actual work. Our yard drainage cost guide for Oregon details the cost drivers.

When to Call a Drainage Contractor

Extending a downspout is a weekend job. Establishing slope on flat ground, placing an interceptor drain on a foothill lot, finding a legal outlet, working near a foundation, or regrading is not. If water is reaching your crawlspace, if runoff is arriving from above, if you share a drainage easement, or if the wet area keeps returning after DIY attempts, it's time for a professional look. A good contractor traces the water to its source first — because matching the fix to your pattern is what makes it last. For the bigger picture, see our guide to property & site drainage in Oregon.