Louis Thompson Tightline
What's happening now
***Update***
Two Tamarack residential streets intersecting with Louis Thompson Road have scheduled road closures for water main connections:
- April 15, 2025 - 210th Avenue NE will be closed at the intersection with Louis Thompson Road for one day during water main connection. A detour will direct motorists to access Tamarack via 210 PL SE.
- April 16-18, 2025 - The short section of the private street Thompson Hill Road (aka E. Main Street) serving three homes right off of Louis Thompson Road will have a road closure between the hours of 8 AM - 3:30 PM. From April 21-29, this same section of street will experience intermittent delays accessing their homes while water testing is in progress.
On May 12, 2025, excavation for the stormwater detention system opposite NE 3rd Street will begin.
Current Phase - Water Main Replacement
Portable Temporary Traffic signals will be used to alternative 2-way traffic between NE 2nd and NE 3rd. Water main materials and construction equipment will be stored in the closed lane during construction.
As part of the City of Sammamish's Louis Thompson Tightline project, Sammamish Plateau Water and Sewer District (SPWater) is having to relocate its existing 8” Asbestos Concrete and Ductile Iron water mains. This necessary work will result in temporary water service interruptions.
For planned water shutdowns, SPWater customers will be notified at least 72 hours in advance via a door hanger, which will include the date and estimated duration of the interruption. Typically, water shutdowns will occur on Tuesdays, Wednesdays, and Thursdays between 9:00 AM and 3:00 PM.
Project Background
Louis Thompson Road is a vital connection route serving residents of Sammamish and surrounding communities. Historically, the corridor has been impacted by uncontrolled stormwater runoff. This construction phase will improve Louis Thompson Road from 210th Place Southeast to Eastlake Sammamish Parkway Northeast.
Following community feedback and preferences expressed previously, the City of Sammamish City Council approved the implementation of proposed alternative #4 in September 2022. Planned improvements include:
- Upgrades to existing stormwater conveyance, culvert, and ditch systems in the area to alleviate flooding, erosion, and landslide issues.
- A new sidewalk and bike lane on the north (downhill) side of the road to improve safety and connectivity to adjacent neighborhoods.
- A 6-inch paint line and widened 6-foot shoulder on the south (uphill) side to improve safety along the road.
Project Area Today
Project Needs and Goals
Controlling stormwater runoff and erosion
Uncontrolled stormwater runoff from the existing roadway and surrounding private properties results in erosion of the existing ditches and at culvert outfalls. Upgrades in the stormwater collection and conveyance system will be implemented to improve conditions and reduce the frequency of flooding events, erosion, and possibility of landslides.
Adding a sidewalk and bike lane
The corridor does not currently include any sidewalks, bike lanes, or other non-motorized improvements. While the project’s primary goal is to address the stormwater runoff issues, the City will also be adding non-motorized improvements, including a sidewalk and bike lane to connect adjacent neighborhoods with Lake Sammamish.
Protecting streams and wetlands
These improvements will be coupled with the City’s commitment to protecting environmentally sensitive areas, such as stream crossings and wetlands. The City will work with the community and appropriate agencies to ensure that roadway improvements are made without negatively impacting natural areas and areas which serve as important habitat for fish and wildlife.
Project Design
This project will upgrade the existing stormwater conveyance, culvert, and ditch systems in the area and alleviate the flooding, erosion, and landslide issues. New sidewalk and bike lane will improve safety.
Selected alternative
The preferred alternative - selected by City Council in September 2022 and informed by community input earlier this year – will include a sidewalk and bike lane on the north (downhill) side of the road, as well as a 6-in paint line on the south (uphill) side of the road. The south (uphill) side of the road will also be locally widened to provide a five-foot wide shoulder throughout the project area.
Project location
These improvements will be built from 210th Pl SE to Eastlake Sammamish Parkway NE. See the cross-section and map below for more details.
Outreach and Community Engagement
August 2024 - Virtual Public Meeting #3
Thanks to everyone who attended our Virtual Open House on Wednesday, August 7. A recording of the presentation and Q&A is available below.
October 2022 - Virtual Open House
Thanks to everyone who attended our Virtual Open House on Thursday, October 27. A recording of the presentation and Q&A is available below. You can also view the slideshow.
May 2022 - Virtual Public Meeting
Thank you to everyone who attended our May 5 Virtual Public Meeting. If you were not able to make it, you can view a recording of the presentation and Q&A below. You can also view the slideshow.
- The City is planning to engage the public throughout the design process to gather community input on proposed improvements and build trusting relationships with stakeholders.
- The City is committed to a clear and transparent design process to ensure the final design reflects the preferences of the community and meets their current and future needs.
- The City's project team is available to meet virtually with interested community organizations, schools, businesses, property owners, and residents to share more about the project and better understand concerns, priorities for design, and how they would like to communicate with the City and share input throughout the project.
The health and safety of the greater Sammamish community will be the forefront priority when planning and executing outreach related to this project. The project team expects to prioritize virtual and digital engagement opportunities for the foreseeable future.
Grant funding partners
- King County Flood Control District - Flood Reduction Grant: $700,000 (2022 and 2023 Awards)
- King County Flood Control District - Sub-Regional Opportunity Grant: $192,942
- Department of Commerce - State and Local Fiscal Recovery Funds: $3,000,000
