Sound Transit is moving ahead with a final design contract for the 8.5-mile Lynnwood Link extension.

On Monday, Sound Transit issued a formal notice to proceed on the $73.7-million contract with HNTB Jacobs Trusted Design Partners joint venture.

A trip from Lynnwood to downtown Seattle on the light rail is expected to take 28 minutes. The extension is projected to carry up to 74,000 riders each weekday by 2035.

The step taken on April 11 follows news in February that the project received approval from the Federal Transit Administration to move into final engineering work and is in line for up to a $1.2- billion grant through the FTA New Starts program.

Cost estimates for the Lynnwood Link extension range from $1.5 billion to $1.7 billion. Sound Transit is also requesting federal funding for other elements needed to support the extension, including 34 new light rail vehicles and a portion of a new light rail maintenance facility, bringing the total project cost to approximately $2.3 billion. A final budget will be established in 2017 with construction scheduled to begin in 2018 and the Lynnwood Link opening for service in 2023.

The line will extend north from the Northgate Link extension that is currently under construction and is scheduled to open in 2021.

Last year, the Sound Transit Board selected the final alignment and station locations for Lynnwood Link. Trains will run along the I-5 corridor from Northgate to Lynnwood with four new stations at Northeast 145th Street, Northeast 185th Street, the Mountlake Terrace Transit Center at 236th Street Southwest and at the Lynnwood Transit Center. New parking structures at 145th, 185th and Lynnwood Transit Center will add approximately 1,500 park and ride spaces within the I-5 corridor as part of the project.

For more information on the project, visit the Sound Transit website.

Last year, the board also directed staff to plan for potential future stations at Northeast 130th Street in Seattle and 220th Street Southwest in Mountlake Terrace. The light rail tracks in those areas will be built to accommodate construction of future boarding platforms in a way that would not severely impact service.

Lynnwood Link is the northernmost of the more than 30 miles of Sound Transit 2 light rail extensions approved by voters in 2008.

This June, the Sound Transit Board is expected to adopt a package of potential transit expansion projects to put before voters in November. The current Sound Transit 3 draft expansion package includes a light rail extension from Lynnwood to Everett. For more details on the ST3 draft package and how to comment, see: www.soundtransit3.org.