Fish Passage Restoration Program

The Fish Passage Restoration Program removes barriers for salmon to reach miles of historic spawning and rearing habitat and restore healthy populations.

Connecting salmon to their historic habitat

Surveying the elevation of a culvert inlet Many culverts under roads and trails block salmon from reaching upstream habitat. Fish passage projects that remedy these barriers are key to restoring salmon populations. When we travel on roads and trails around the county, we don't notice how many streams we cross. We enjoy movement without barriers to our passage. Fish passage projects remove barriers in streams. This means that salmon can swim upstream to good habitat.

Restoring fish passage is one of the best ways to help salmon and increase their numbers.

This program focuses on restoring fish passage at barriers owned by the county. We’re also working with our partners to coordinate fish passage work on King County streams. Better planning helps link up projects on the same stream to increase total habitat gain.

Since 2019, King County has increased funding for fish passage projects. With this money, we've completed 22 barrier remedies. In 2025, the county proposes $9 million towards fish passage projects. This would support construction of 3 projects that will allow salmon to reach 3 miles of upstream habitat. Another 30 projects are moving through design toward construction in future years.

The county has scored fish passage projects to find out which would have the most benefit for salmon. As a result, the county knows which fish passage projects will help salmon the most. The county plans to fix about 60 high priority barriers by 2032.

We’re also improving our project development process. This will allow the county to get projects built faster. Yet we must speed up our efforts work to recover native salmon before it's too late. Abundant salmon have been important to the way of life here since time immemorial. Restoring fish passage to historic stream habitat is essential to increase salmon numbers. And more salmon will provide endangered Southern Resident Killer Whales with vital food.

Working to fix fish passage barriers

The King County Fish Passage Restoration Program provides a roadmap to success. This requires:

a regional approach driven by data,
strong partnerships,
enough funding, and
a flexible permitting process.

Most fish passage barriers are metal or concrete pipes, known as culverts. Culverts carry streams underneath roads, trails, and railroads. In King County, many culverts are decades old. Older culverts are often too small, too steep, or have a waterfall coming out of them.

Many culverts resemble firehoses, pushing water through at a high speed. This can make the culvert impossible for salmon to swim through. Over time, flows from the culvert can erode a deep hole in the streambed downstream. This prevents fish from being able to jump high enough to enter the culvert. The resulting waterfall out of the culvert creates a fish passage barrier.

Modern culverts look more like arches than pipes. They are big enough to allow the stream in the culvert to simulate natural stream conditions. This means that it's easy for fish and other aquatic life to move upstream or downstream through them.

A before and after illustration. The before side shows salmon unable to complete their migration due to an inaccessible pipe culvert blocking the way. The after side shows a new wide box culvert that allows for the fish to access their historic habitat.

Prioritizing which barriers to remove first to achieve the best results

King County scientists and engineers have identified the best locations to remove barriers. Starting in 2019, King County field crews completed an inventory of about 3,000 locations. The crews evaluated each site to see if it was a fish passage barrier. The surveyed locations are along county-owned roads, trails, and on county property. These barriers prevent many salmon from swimming to high-quality habitat.

The field inventory found more than 900 county-owned fish passage barriers. Using this data, we’ve worked with Tribes, federal and state agencies to develop way to score the barriers. The goal is to find the priority barriers that we can remove first to achieve the best results for salmon.

The scoring formula considers the following factors:

The quality of upstream habitat;
The amount of upstream habitat;
The other barriers on the stream; and
If the stream provides Chinook or kokanee habitat.

The higher the score for a barrier, the higher priority for restoring fish passage there. The scoring allows the county to better plan fish passage projects. We can achieve more habitat gain with fish passage projects at the high scoring barriers. The county has drafted a plan to complete about 60 fish passage projects by 2032. This is less than ten percent of all county barriers. But these projects would restore salmon access to more than half of total habitat gain. This is many times the habitat gain achieved from a less deliberate project sequence.

After 2032, the county plans more fish passage projects at high scoring barriers. Work at 150 of the top scoring county barriers could achieve about 80 percent of total habitat gain.

See reports from 2021 and 2022 for details about the inventory and scoring analysis:
King County Fish Passage Barrier Prioritization Summary Report (743 KB), June 2022
Final Report Regarding Remedies to Existing Fish Passage Barriers for King County (1.9 MB), March 2021

Access the county’s fish passage data:
GIS data for the King County fish passage barrier inventory and prioritization scoring

Early action to produce results sooner

Starting in the 2018, the county has invested more than $30 million on dozens of fish passage projects. Between 2018 and the end of 2023, the county has restored salmon passage at 23 barriers, opening up 42 miles of stream habitat for salmon.

The county has drafted a proposed 10-year work plan for fish passage. This plan will guide work at about 60 barriers through 2019 to 2032. To correct these barriers would cost about $150 million. These projects would open up more than 300 miles of streams to salmon. This represents more than half of the total possible habitat gain.

It's essential to get the most habitat value from investments in fish passage. This includes taking advantage of innovative ways to standardize common tasks and designs.

We’re also exploring options to close the gap between the current funding and the amount of funding we’ll need. Possible funding and financing options include:

Maximizing grant funding;
Flexible regulatory approaches to focus funding on barrier remedies with high habitat gain - this could provide much more habitat benefit than current procedures;
Public-private partnerships; and
Public funding options like future levy proposals and bonds that need voter approval.

The barrier inventory and scoring provide the groundwork for future fish passage work. As a result, King County is very competitive for local, state, and federal grants for fish passage. A key new grant source is the federal Bipartisan Infrastructure Law. This law became effective in 2021. By 2026, it will provide more than $1 billion toward fish passage work.