A full closure of SE May Valley Road for the removal and replacement of the Fifteen Mile Creek Bridge #493C will begin at 7 a.m., on Monday, June 15.

SE May Valley Road near Issaquah-Hobart Road SE will close in both directions, and a temporary signed detour route will be in place. The road will be closed to all vehicles, including emergency responders, pedestrians, and bicycles.

Due to freight restrictions on roads in downtown Issaquah, trucks over 15,000-pound gross vehicle weight will need to follow alternate routes.

The road is expected to remain closed through Aug. 23.

A detour will be posted and is available on the project website. Special truck warning signs are placed to inform them about using alternate routes. Crews are expected to work from early morning until evening, Monday through Friday, with occasional work on weekends.

The existing bridge, constructed in 1932, is well beyond its useful life. Built 94 years ago, the timber bridge was treated with creosote, which typically lasts about 50 years. Due to its age and condition, it can no longer be safely repaired or maintained, and a full replacement is required.

Replacing the Fifteen Mile Creek Bridge is essential to keeping our road network safe and reliable for the communities who depend on it every day. This project not only brings the bridge up to modern safety standards but also improves access for people walking, biking, and rolling. We appreciate the public’s patience as we complete this important work. – King County Road Services Division Director Tricia Davis

The new bridge will meet current road standards for weight capacity, lane and shoulder widths, and environmental protection.

The new design includes:

  • Adding standard 8-foot shoulders on each side of the bridge for people walking, biking and rolling
  • New bridge railings will meet current safety standards
  • Increasing span length gives the creek more room to flow during high water, which helps prevent flooding and reduces pressure on the bridge

The goal is to reopen the road before the start of the Issaquah School District’s 2026–27 academic year. Dates may shift due to weather or crew and equipment availability, but this timeline provides the best opportunity to complete the project before the next school year begins.

King County Road Services Division has been working closely with WSDOT, Eastside Fire & Rescue, Bellevue Fire, Puget Sound Regional Fire Authority, and the Renton Regional Fire Authority and all agencies are planning accordingly. Eastside Fire & Rescue deputy chief of operations does not expect any change to emergency response times for nearby communities.

A map of where general vehicle traffic will be detoured during the closure of the Fifteen Mile Creek Bridge.
This is where general vehicle traffic will be detoured during the closure of the Fifteen Mile Creek Bridge along SE May Valley Road near Isssaquah-Hobart Road SE.
A map of where alternative truck traffic will be detoured during the closure of the Fifteen Mile Creek Bridge.
Alternate truck routes Large freight trucks are generally restricted from using local City of Issaquah roads (e.g., Front Street S.) unless making local deliveries, with through-traffic directed to SR 18 or I-90. Heavy, oversized loads (exceeding 8’6″ wide, 14′ high, or 80,000 lbs) require permits, and significant restrictions apply during peak commuter hours.

Learn more about the Fifteen Mile Creek Bridge #493C Replacement Project and detour routes on the project website.

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