Snohomish County’s free PDS Map Portal shows the wetlands and streams the county has mapped on or near your property. You can check a parcel yourself in a few minutes. The catch is that the county says its own map is not the final word, so treat it as a first screen and not as an answer.
This guide walks through the check step by step, explains what the map can and can’t tell you, and covers what to do if something shows up.
How to check your property on the Snohomish County wetland map
You need a street address or the Assessor’s parcel number. A computer works better than a phone for this.
- Open the PDS Map Portal. Go to the PDS Map Portal. The county shows its terms and conditions first; accept them to reach the map.
- Find your parcel. Click the Search tab at the top. Choose Search by Address and start typing, then pick your address from the list. If the land has no address yet, use Search by Parcel and enter the parcel ID number. The map zooms to the property.
- Turn on the critical areas layers. Click the Layers tab at the bottom left. Most layers are switched off when the map loads. Click the > arrow beside a group to open it, then tick the boxes for the wetland and stream layers.
- Read the legend. Click the Legend tab to see what each colour and line means. Some layers only appear once you zoom in, so zoom to the parcel before deciding nothing is there.
- Measure the distance. Open the Measure tab, choose Measure Line, and click from the mapped wetland or stream to the spot where you plan to build. Double-click to finish.
- Save what you found. Click the parcel, then the three dots beside its parcel ID in the Result List, and choose Property Report for a PDF. Map Tools > Print Map gives you a printable map of the current view.
The county also publishes a PDS Map Portal User Guide that covers every tool.
What the map is showing you
Three things on the map matter most for a building project.
- Mapped wetlands. These are areas the county or a federal inventory has flagged as likely wetland. They are approximate shapes, not surveyed boundaries.
- Mapped streams. Streams carry their own buffers, and a stream that crosses a neighbour’s land can still affect yours.
- Recorded Critical Area Site Plans (CASPs). A CASP is the recorded drawing that shows the protected critical areas on a parcel. The county has required them to be recorded since April 1995, so if a previous owner pulled a permit, one may already exist for your lot. The Map Portal links to recorded CASPs, and you can also search the County Auditor’s records by parcel number.
A recorded CASP is good news. It means someone has already studied the site, and it tells you where the protected areas are.
Look past your property line: the 500-foot rule
A wetland does not have to be on your land to affect your permit. For residential projects, Snohomish County requires the site plan to identify critical areas within 500 feet of the development, buffers included. For geologic hazard areas such as steep slopes, the distance is 400 feet.
The reason is the buffer. A wetland on the lot next door can have a buffer that reaches across the line onto yours. So when you check the map, zoom out and look at the neighbouring parcels too. Then use the Measure tool to see how far each mapped feature is from your building site.
Why a clean map does not mean a clean property
The county’s wetland map is a starting point, and the county says so. Snohomish County Code states that its maps of wetlands and habitat areas are for informational purposes only and may not accurately represent all such areas.
That cuts both ways:
- Wetlands the map misses. Inventory maps are drawn largely from aerial imagery. Wetlands under tree canopy, small wetlands, and seasonal wetlands that dry out by summer are easy to miss from the air.
- Wetlands the map invents. A mapped shape can turn out to be dry upland once someone looks at the soil and plants on the ground.
What counts for your permit is what is on the ground. A wetland is defined by its soils, its plants and its water, and only a site visit can confirm those.
City or county: whose rules apply?
The PDS Map Portal is built for unincorporated Snohomish County, and so are the county’s critical area rules. If your property is inside city limits, the city reviews your permit under its own critical areas code, with its own buffer widths.
That applies in Everett, Marysville, Lake Stevens, Arlington, Monroe, Mill Creek, Mukilteo, the City of Snohomish and the other incorporated cities. The county map is still a useful first look at what has been mapped nearby, but the distances and requirements in this guide are the county’s. Check with your city’s planning department before relying on them.
What to do with what you found
Your next step depends on what the map shows and where you are in the project.
- You are buying land. Get a wetland reconnaissance before you close. It is a short site visit that tells you whether wetlands or streams are likely present and roughly where, so you know how much of the lot is buildable.
- Something is mapped within 500 feet and you plan to build. Expect the county to ask for a study. Depending on the site, that can be a wetland delineation, a critical area study, an ordinary high water mark determination, a mitigation plan, or a habitat management plan.
- Nothing is mapped nearby. You may be clear, but the map can miss wetlands. If the ground is soggy in winter, has standing water, or grows rushes and skunk cabbage, have it looked at before you design around it.
A wetland delineation marks the actual wetland boundary on the ground and rates the wetland, which is what sets the buffer. Our guide to wetland delineation cost covers pricing and timing. For the permit steps that follow, see Snohomish County’s residential permit process when critical areas are present.
Frequently asked questions
Can you build on wetlands in Snohomish County?
Usually not in the wetland itself. County rules protect both wetlands and their buffers, and a project is expected to avoid them. On a tightly constrained lot, the code has tools such as buffer averaging and buffer reduction, usually paired with a mitigation plan. Whether they apply depends on your site.
How close to a wetland can you build?
It depends on the wetland’s category and habitat score. Under Snohomish County Code 30.62A.320, standard wetland buffers run from 40 feet for the lowest-rated wetlands to 225 feet for wetlands with high habitat value. High-intensity land uses get wider buffers. Standard stream buffers are 50 or 150 feet, depending on the stream type. You need a wetland rating to know which number applies to you.
Is the Snohomish County wetland map legally binding?
No. County code says the maps are for informational purposes only. The county decides your permit on what a qualified professional documents on the ground.
Does the map show every wetland?
No. It can miss wetlands, especially small, forested or seasonal ones, and it can show wetlands that are not there.
What is a CASP?
A Critical Area Site Plan. It is the drawing recorded with the County Auditor that shows the protected critical areas on a parcel and the approved development.
How much does a wetland delineation cost?
See our wetland delineation cost guide for price ranges and what drives them.
Not sure what you are looking at?
Send us the parcel number and what you plan to build. We will tell you which study, if any, your project is likely to need, and what it takes to get a definite answer.
Call Eastside Environmental Pros at (425) 864-6025 or reach us through the Contact page. We work throughout Snohomish County, including Everett, Marysville, Lake Stevens, Arlington, Monroe and Snohomish.
