Two miles south of Enumclaw, SE Mud Mountain Road crosses Boise Creek on a bridge King County built in 1956. By its last summer the steel deck and girders were rusting, the creosote-treated timber foundations were rotting, and lead paint was peeling off into the creek. It also had a weight limit low enough to keep heavy fire engines and large commercial trucks off it. For drivers who used it to get past SR 410 congestion, the old Boise X Connection Bridge #3055A worked as a shortcut for cars, and that was about it.
The bridge going in now has no weight or size restrictions. So when the road reopens, any vehicle can use the back way, including the fire engines the old span couldn't carry.
Where the reopening date stands this week
King County closed SE Mud Mountain Road between SR 410 and 248th Avenue SE on Monday, June 1, 2026. Its status update dated October 20 says the road stays closed in both directions, 24 hours a day, to all travelers through November 8, 2026. That includes pedestrians, cyclists and emergency services. The same page warns that machine, crew or equipment availability, or weather, could delay the project.
November 8 falls on a Sunday, so the earliest scheduled reopening is the end of this weekend. The target has moved more than once, though, and the slips are easier to follow in order:
- Summer 2025. This was the original construction plan. A King County spokesperson told the Courier-Herald the work slipped a year because of funding obligations, permitting and the in-water fish window.
- June 1, 2026. The road closed, with reopening expected "near November."
- October 2, 2026. The Courier-Herald reported the bridge was scheduled to open October 28.
- October 20, 2026. The county extended the closure through November 8. Its timeline still listed major work as anticipated for completion by October 30.
As of King County's road alert update on October 28, the segment was still listed as closed. Before you plan the Monday, November 9 commute around it, check the county's MyCommute map or sign up for the county's road alert emails and texts. Both carry schedule changes as they happen.
Why this short stretch of county road carries so much weight
According to the county, about 947 vehicles a day used the bridge, and 2% of them were trucks. That's modest traffic for most roads. This road's value is where it goes. The Courier-Herald described 248th Way and SE Mud Mountain Road as the route locals use to skirt the "Buckley Crawl" in the morning and evening.
The Crawl is the paper's name for the recurring backup on the Enumclaw–Buckley route. Its worst stretch came in 2025. After a vehicle struck the SR 410 White River Bridge, the Courier-Herald's look back at 2025 reported that a drive of about 10 minutes stretched to an hour. WSDOT estimated at the time that its signed detour would add 45 to 60 minutes or more at peak hours. The White River Bridge reopened on October 17, 2025 after repairs. In August 2026, WSDOT installed an over-height vehicle detection system there to warn tall vehicles. The bridge's 14-foot clearance stays the same.
So the main road has one chokepoint with fixed limits, and the side road that relieves it had its own limits until this year. Both of the area's alternate routes, SR 410 over the White River and SE Mud Mountain Road over Boise Creek, have been closed for months at a time within roughly a year of each other. That explains why so many people have been asking when this one reopens.
What the new bridge is, compared with the old one
King County removed the 1956 span and is building the replacement in the same location on SE Mud Mountain Road, east of SR 410.
| Bridge built in 1956 | Replacement opening late fall 2026 | |
|---|---|---|
| Structure | Steel deck and girders on creosote-treated timber foundations | 67-foot-long, 34-foot-wide reinforced concrete |
| Weight limit | Restricted; heavy fire engines and large commercial trucks could not use it | No weight or size restrictions |
| Lanes | Two lanes the county described as too narrow for today's vehicles | Two 11-foot travel lanes with 6-foot shoulders |
| Approaches | Noticeable curve on both ends | Curves eased slightly for longer sight distance |
The new bridge also gets new railings and guardrails on both sides. The first two rows of the table matter most. With the weight restriction gone, fire engines can reach SE Mud Mountain Road straight from the highway again, which the Courier-Herald pointed out the old bridge did not allow. The shoulders count too. Six feet on each side gives a cyclist or a stalled car room the old deck never had.
The project is estimated at $4.7 million, paid for with Federal Highway Administration grants and King County matching funds.
What happens under the deck
King County's project includes this work in and along Boise Creek:
- Decaying creosote timber piles, which leach toxic chemicals into soil and water, are coming out.
- The peeling lead paint that fell into the stream goes away with the old steel.
- The bridge supports sit farther from the stream, so the creek has more room to move.
- Large woody material and new streambed gravel go in to improve fish habitat.
- Invasive plants are being removed, and the banks replanted with native shrubs and trees.
The contractor hauls the creosote-treated piles to an approved disposal facility, and most of the rusted steel and concrete gets recycled. The county says crews will keep working on plantings and site cleanup after traffic returns. If you see work trucks parked near the creek into winter, the road probably hasn't closed again. It's most likely the restoration crew.
The trail is already open
Walkers and riders got their crossing back before drivers did. The Foothills Trail at SE Mud Mountain Road closed fully on October 5 for asphalt paving. King County now lists it as fully open for cyclists and pedestrians. That paving date had already moved once. A county road alert said the closure was rescheduled to October 5 because of weather-related construction delays.
The Courier-Herald reported in June that the closure would not affect access to the Boise Creek Trail or Pinnacle Peak Park. Those two never closed, so a weekend at Pinnacle Peak didn't depend on this project at all.
Until the barricades come down
The detour hasn't changed. To head west on SE Mud Mountain Road, you go by way of 252nd Avenue and 248th Way, following the county's signed detour route. Traffic on SR 410 at the Mud Mountain Road intersection has already been through the heaviest part of construction. According to the Courier-Herald, the new girders were due August 18, with intermittent stops on the highway while they arrived.
The last piece goes on after the road opens
The project includes a public art installation funded through King County's 1 Percent for Art program. The county is working with the Muckleshoot Indian Tribe. Artist Lillianna Ramirez was selected through 4Culture in partnership with the Tribe. Her design is in development and has been approved through that process. The artwork will show images on blades made by the King County Sign Shop, and county crews will install it. The Courier-Herald reported that the art will be created once construction is complete. So the bridge most people drive in November may look plainer than the finished one.
For more on what's changing around town, our Enumclaw neighborhood page and our Buckley page follow both ends of the SR 410 route.
Many of the acreage and farm properties we work with south of town sit on county roads like this one, where a single bridge decides which trucks, trailers and fire engines can get in. If you'd like to know how the reopened Mud Mountain Road route affects access to a particular property, Porterhouse Property Group is glad to drive it with you. Connect with our Enumclaw specialists.