Excavation
Curtain Drain Cost in Oregon: Hillside Water Interception
Cojo
April 18, 2026
10 min read
Curtain drains are the right tool for one specific, expensive problem: subsurface water flowing downhill into your property. If you live in the Portland West Hills, Eugene's South Hills, Corvallis' Witham Hill, Lake Oswego's slopes, or any of the thousands of other Oregon hillside lots, there is a good chance the water showing up in your basement, your retaining wall, or the low corner of your yard is not falling from the sky above your property — it is moving through the ground from above it.
A curtain drain (also called an interceptor drain) cuts across the hillside upslope of the problem area, intercepts subsurface water before it reaches the structure or yard, and redirects it to a safe outlet. It looks similar to a French drain but it is doing a very different job: cutting off uphill flow rather than dewatering a localized area. In the context of the broader yard drainage menu, curtain drains are the specialist tool reserved for uphill subsurface water.
This guide walks through what curtain drains typically cost in Oregon, why depth is the variable that drives the price, and how to tell whether a curtain drain is actually what you need.
Curtain drain pricing is mostly about depth. A shallow interceptor (3 – 4 ft) in sandy loam is a very different job than a deep interceptor (6 – 8 ft) through Willamette Valley clay.
Industry Baseline Range
| Scope | Unit | Industry Baseline |
|---|---|---|
| Shallow curtain drain (3 – 4 ft depth) | per lf | $20 – $70+ |
| Standard curtain drain (4 – 6 ft depth) | per lf | $30 – $100+ |
| Deep curtain drain (6 – 8+ ft depth) | per lf | $50 – $180+ |
| Typical residential project (50 – 100 lf) | each | $2,000 – $18,000+ |
| Large residential / light commercial (100 – 300 lf) | each | $5,000 – $45,000+ |
| Outlet to daylight (included in per-lf) | — | — |
| Dry well termination (added cost) | each | $1,500 – $8,000+ |
| Storm sewer tie-in (permit + plumber) | each | $1,500 – $6,000+ |
| Engineered plan (steep slope permit) | each | $500 – $3,000+ |
The industry baseline ranges above represent ideal conditions — easy access, workable soil, shallow depth, and minimal haul-off. In practice, actual project costs frequently exceed published averages by 2 to 3 times when complications arise. Oregon's clay soils, rocky terrain, unmarked utilities, permit requirements, and disposal fees can all push costs well above baseline figures. Because curtain drains are deeper than most drainage work, the variables covered in our excavation cost factors in Oregon guide have an outsized effect on the final number. The only reliable way to know your actual cost is through an on-site assessment.
Even small curtain drain jobs typically exceed the standard $500 – $1,500+ minimum job callout because curtain drains by definition involve serious depth, haul-off, and usually a permitted outlet.
Curtain drain work happens deep enough that the unknowns are significant:
A standard 50 – 100 foot residential curtain drain typically runs 3 to 7 days. Longer runs, deep installs through rock, or projects requiring engineered drawings can extend to 1 to 3 weeks. Wet-season curtain drain work is slower than dry-season work on almost every site.
Plan for 1 to 2 business days of lead time for 811 utility locates. Steep-slope jobs in Portland or Lake Oswego may require additional permit processing time.
The trench runs across the hillside upslope of the structure or area being protected. The bottom of the trench sits below the subsurface flow path — typically 4 to 8 feet down, depending on how deep the water table or flow zone is. A perforated pipe at the bottom collects intercepted water, clean drainage rock surrounds the pipe, and filter fabric wraps the whole assembly to keep clay particles from clogging the system.
The key design decision is depth. A curtain drain that does not reach the subsurface flow zone intercepts only surface water and misses the actual problem. A well-designed curtain drain places the pipe invert below the saturated zone and extends the drainage rock up high enough to capture flow at its seasonal peak.
Willamette Valley clay. Clay pushes subsurface water laterally along layers, which is exactly why curtain drains work so well here. It also means the trench has to be wider and deeper, and most spoils must be hauled off rather than reused.
Hillside lots in the Portland metro. West Hills, West Linn, Lake Oswego, and Hillsboro foothills sites frequently require engineered drawings because of steep slope regulations. Design and permit costs add $500 – $3,000+ on top of the excavation.
Rocky terrain in Central and Southern Oregon. Slower trenching, harder on equipment, sometimes requires hammer attachments on the excavator. Rocky soils often drain better overall but curtain drains are still used where water is channeled along bedrock.
Wet-season logistics. Curtain drain work is possible year-round but wet-season trenches fill with groundwater during excavation, which slows progress and often requires dewatering pumps on site.
Permit variance. Portland, Lake Oswego, and similar jurisdictions have formal hillside development rules. Any curtain drain on a regulated slope will require a permit and often an engineer's stamp.
CCB licensing. Deep excavation near foundations and on steep slopes is work that homeowners should only hire licensed CCB contractors for. An unlicensed curtain drain install is both a legal and a structural risk.
Curtain drain vs. French drain. A French drain dewaters an area. A curtain drain intercepts flow across an area. Both use perforated pipe wrapped in gravel and fabric, but they are placed in different positions and sized for different jobs. Using one for the other is a common and expensive diagnostic error.
Curtain drain vs. foundation drain. A foundation drain sits directly against the footing and handles water that has already reached the house. A curtain drain sits upslope and keeps water from reaching the house at all. On hillside properties, both are often needed. A sump pump is often the third leg of that stool.
Curtain drain vs. swale. A swale handles surface water along a low channel. A curtain drain handles subsurface water through a deeper trench. Some hillside sites use both — a swale on the surface plus a curtain drain below.
Curtain drains are almost never a DIY job. The depth, slope risk, and sizing calculations all require professional equipment and experience.
DIY may make sense on:
Hire a pro for:
Our guide on how to hire a residential excavation contractor covers the specific screening questions that matter most on deep hillside work.
Hillside curtain drains frequently require permits — Portland, Lake Oswego, West Linn, and most Willamette Valley cities have formal hillside development or erosion-control rules. Engineered drawings are often required on slopes steeper than a certain grade. Permit costs vary widely but typically land at $200 – $800+ for the permit itself, with an additional $500 – $3,000+ for engineered drawings when required.
Hillside water problems are among the most expensive to ignore. Retaining wall failures, foundation shifts, and slope instability are all downstream consequences of uphill water that was never intercepted. A properly designed curtain drain is one of the most consequential small-excavation investments a hillside Oregon property can make. If yours is part of a larger swamped-lawn situation, our backyard standing water fix cost guide walks through how curtain drains fit into multi-fix diagnoses.
Get a free excavation estimate, explore our services, or see past projects. More reading lives in our resources library.
How much does a curtain drain cost in Oregon? Industry baseline pricing runs $20 to $100+ per linear foot for standard installs and up to $180+ per linear foot for deep installs through clay or rock. A typical 50 – 100 foot residential curtain drain lands between $2,000 and $18,000+. Larger projects on steep lots with engineered drawings can exceed $45,000+. Actual quotes depend heavily on depth and outlet.
How long does curtain drain installation take? A standard residential curtain drain runs 3 to 7 days. Longer or deeper projects, jobs through rock, or installs requiring engineered drawings can extend to 1 to 3 weeks. Wet-season work is typically slower than dry-season work on any given site.
What is the difference between a curtain drain and a French drain? A French drain dewaters an area. A curtain drain intercepts subsurface water flowing across an area. The construction looks similar — perforated pipe in gravel wrapped in filter fabric — but they are placed in different positions and sized differently. Using one for the other is a common and expensive mistake.
How deep does a curtain drain need to be in Oregon? Most Oregon curtain drains are installed 4 to 8 feet deep. The pipe invert has to sit below the subsurface flow zone the drain is trying to intercept. On hillside Willamette Valley lots with clay soil, deeper is usually better because subsurface water moves along clay layers at varying depths.
Do I need a permit for a curtain drain in Oregon? On hillside lots in regulated jurisdictions — Portland, Lake Oswego, West Linn, and most incorporated cities — yes, and often with an engineer's stamp. On rural or low-slope properties with straightforward outlets, a permit may not be required. Always check with your local building department before digging.
Plan your French drain installation budget with 2026 Oregon pricing. Covers interior and exterior drains, yard drainage, and foundation waterproofing costs.
Understand land clearing costs per acre in Oregon for residential, commercial, and agricultural projects. Pricing by terrain, vegetation density, and disposal methods.
Compare drainage solutions for standing water. Ranked by effectiveness, cost, and suitability for Oregon's climate. French drains, regrading, dry wells, and more.