Most residential drainage projects in Portland don’t require a permit. A French drain across a soggy lawn, a catch basin at the bottom of a driveway, or regrading to direct water away from a foundation can typically proceed without filing anything with the city. But there are situations where a permit is required, and starting work without one can create problems that cost more to fix than the permit itself.
Here’s what triggers a permit for drainage work in Portland and how the process works.
When a Permit Is NOT Required
Standard residential drainage improvements that stay within your property and don’t connect to public infrastructure generally don’t need a permit. This includes:
French drains and E-Z Flow drains that collect subsurface water and discharge it to a dry well, pop-up emitter, or daylight outlet within your property. These are private drainage systems that don’t interact with the city’s stormwater network.
Catch basins that collect surface water from lawn low spots, patio edges, or driveway runoff and route it to an on-site discharge point. As long as the water stays on your property or exits to a legal discharge location, no permit is needed.
Yard regrading that reshapes the ground surface to direct water away from your foundation or other structures. Minor grading adjustments are routine landscaping work and don’t trigger permit requirements.
Downspout rerouting that extends or redirects roof runoff into underground pipe within your property. This is maintenance-level work in most cases.
When a Permit IS Required
Permit requirements kick in when the drainage project interacts with public infrastructure, affects neighboring properties, or falls within environmentally sensitive areas.
Connecting to the City Storm System
If your drainage system needs to discharge into a city storm drain, combined sewer, or public right-of-way, you’ll need approval from the Portland Bureau of Environmental Services (BES). This involves a plumbing permit and, in some cases, a stormwater management review. The city needs to verify that your discharge won’t overload the system or introduce pollutants.
Work in Environmental Overlay Zones
Properties near streams, wetlands, or designated drainageways may fall within environmental conservation or protection overlay zones. Drainage work in these areas can trigger a land use review because the city restricts grading, excavation, and water routing near sensitive natural features. Properties along Johnson Creek in Milwaukie, Tryon Creek in Lake Oswego, and Fanno Creek in Tigard and Beaverton are common examples.
Drainage Reserves
Some Portland properties have a recorded drainage reserve, which is an easement that protects a natural drainageway running through or along the property. You can’t build, excavate, or install drainage systems within a drainage reserve without written approval from BES. These reserves are documented in the property’s deed records and show up on a title search.
Large-Scale Grading or Earthwork
If your drainage project involves significant grading that changes the drainage pattern of the property, especially on sloped lots, it may require a grading permit or erosion control plan. This is more common on hillside properties in West Linn, the West Hills, Happy Valley, and Damascus where moving soil on a slope can affect neighboring properties below.
New Impervious Surface
Portland’s stormwater management manual requires that development or redevelopment adding impervious area (like a new patio or driveway) must manage stormwater through retention, infiltration, or treatment. If your drainage project is part of a larger project that adds impervious surface, the stormwater requirements apply to the whole project.
How to Find Out If Your Property Has Restrictions
Before starting any drainage project, it’s worth checking two things:
Portland Maps (portlandmaps.com) shows environmental overlay zones, flood hazard areas, and other land use designations for any address in Portland. Search your property and look for “e” zones (environmental conservation or protection) on the zoning map.
Your title report or property deed will show any recorded drainage reserves or easements. If you bought the property recently, this information is in your closing documents.
For properties outside Portland city limits, Clackamas County, Washington County, and individual cities like Lake Oswego, West Linn, and Happy Valley have their own permit thresholds. We check the applicable requirements for every project we quote, regardless of jurisdiction.
Who Handles the Permit?
We do. When a drainage project requires a permit, we handle the application, documentation, and coordination with the permitting authority. You don’t need to visit the Bureau of Development Services or figure out which forms to file. Permit fees (when applicable) are included in the project estimate so there are no surprises.
For projects that don’t require a permit, we still follow the same installation standards. The absence of a permit doesn’t mean the absence of standards. Every French drain, catch basin, and grading correction we install is designed and built to perform for decades, regardless of whether the city reviews it.
The Short Answer
If your drainage project stays on your property and doesn’t connect to the city’s storm system, you probably don’t need a permit. If it connects to public infrastructure, falls near a waterway, or involves significant earthwork on a hillside, you probably do. We verify this for every project during the planning phase and handle the paperwork when it’s needed.
Call (503) 847-9110 or request your free estimate online. We’ll assess your property, determine whether permits apply, and include everything in the written proposal.
Learn More About Drainage
How Much Does a French Drain Cost in Portland? — 2026 pricing by project type and what drives cost.
5 Signs Your Portland Yard Has a Drainage Problem — How to spot drainage issues before they cause serious damage.
French Drain vs. Catch Basin vs. E-Z Flow — Which drainage system is right for your property.
Can You Install a French Drain Yourself? — What’s involved, what goes wrong, and when to hire a pro.
Backyard Drainage and Grading Guide — How to evaluate your yard and understand your options.
