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January 2026
An update on what we’re hearing and how you can share your comments and questions
Thank you to everyone who has visited the Sammamish Plateau Diversion Project online open house! We appreciate people who have taken the time to fill out a survey and shared thoughts and questions. Your responses help us to see where we can provide more information and clarity.
Please note that the survey was not accessible on January 13, 2026. It is available again as of January 14. You can access the survey and are welcome to fill it out more than once if you think of something later.
If you need accommodations to access this material or would like to share your thoughts with us directly, please contact Monica Van der Vieren at monica.vandervieren@kingcounty.gov or 206-477-5502 or Emily Berry at emberry@kingcounty.gov or 206-848-0698.
For an example of what we are hearing, keep scrolling.
What we’re hearing so far
Since launching our online open house last week, we have received questions on different topics. You are wondering about:
- Temporary traffic and trail impacts during construction
- Protecting trees
- Streams and erosion on the slopes above the project corridor
- How residents currently on septic systems can connect to the sewer system
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How this project connects to existing local sewers
We are gathering your questions as they come in and will share responses soon on the project website. Here is an example.
Question: There is already a sewer pipe in the parkway. How does the new pipe relate to that pipe and connect with houses?
King County’s response: There is an existing pipe along East Lake Sammamish Parkway. This pipe is owned and operated by the Northeast Sammamish Sewer and Water District. It will continue to collect wastewater from area homes and send flows north to the County’s Northeast Lake Sammamish Interceptor.
During design, King County’s project team will consider the location of this existing pipe when deciding where to place the new pipe in the project corridor.
The new King County pipe will collect wastewater flows from the Sammamish Plateau Water and Sewer District that currently travel south to the County’s Issaquah Interceptor pipe. In the future, those flows will travel north in the County’s new pipe.
As a regional wastewater treatment provider, King County’s pipes connect to local sewer districts. Local sewer systems provide service directly to private properties.
You can see how the local and regional systems work together in this graphic:
 The graphic above illustrates the water system. Fresh water comes into drinking water pipes. Wastewater leaves through drains and pipes and goes to a treatment plant. The treated water is discharged or recycled.
We're here for you!
We know that large construction projects can be stressful for communities, and there are a lot of construction projects going on across the Eastside. Our project team is committed to being available and continuing to work with neighbors, businesses, visitors, and commuters every step of the way. We will be here for you all the way through design and construction and into operations. Feel free to contact us at any time!
Contact us
Community Services Project Team
Visit us at kingcounty.gov/SammamishPlateauDiversion
Please note that voicemails and emails are considered records and may be subject to public disclosure. The project phone number is operated by a third-party service called Grasshopper. Recordings on this service are considered records. If you prefer to discuss the project with us rather than commenting in voicemail or email, please leave a message and we'll call you back within one business day.
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