Louis Thompson Tightline

What's happening now

The project plans  are completed (see latest Map in sidebar). Current steps are right-of-way acquisition, environmental permitting, and preparing final plans, specifications, reports, and cost estimates for the installation of a stormwater tightline and non-motorized improvements on approximately 0.61 miles of Louis Thompson Hill Road.

Staff is coordinating with Sammamish Plateau Water on its plans (nearing complete) for replacing the existing water main.

Before construction begins this summer, we will have a public meeting to inform residents of what to expect during construction and how they can remain informed of construction phasing and  upcoming traffic control changes.

Design is proceeding on Council's selected alternative

Alternative 4 was selected to move forward during preliminary design. This alternative includes the upgraded stormwater systems, a sidewalk and bike lane on the north (downhill) side of the road, and minor widening on the south (uphill) side of the road to ensure a minimum standard shoulder width. Lane and shoulder total width will be 16-ft to meet a standard road cross-section width, with travel lane striped 10-ft wide to match current configuration (see Map with cross-section detail). Learn more about the project design below.

Your input informed the chosen alternative

Thank you to everyone that took our Design Alternatives Survey! Your input helped inform City Council’s preferred alternative selection, and their decision to proceed with the full project scope.

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.

The City's project team is designing improvements to Louis Thompson Road from 210th Pl SE to Eastlake Sammamish Parkway NE that will upgrade the existing stormwater conveyance, culvert, and ditch systems in the area and alleviate the flooding, erosion, and landslide issues.

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. In addition to these improvements, we will also be redesigning the corridor to 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-ft 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

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: $400,000
• King County Flood Control District - Sub-Regional Opportunity Grant: $192,942
• Department of Commerce - State and Local Fiscal Recovery Funds: $3,000,000