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Coal Creek Bridge.
Coal Creek Bridge No. 3035A located southeast of Black Diamond in unincorporated King County.

Status update

May 13, 2022

Starting on Monday, May 16: The project contractor will be on site on a regular basis, Monday through Friday during daytime hours. The first order of work is to make the temporary bridge approaches wider. This change will make it easier for longer vehicles and trailers to get across the bridge. The project team is also working on a plan to improve one-way traffic over the bridge. They are considering adding either stop signs or a temporary traffic signal.

The temporary bridge has one single lane, and no weight limit restrictions on the temporary bridge. Learn more on Facebook.


Project area.
Coal Creek Bridge No. 3035A project location.

Map showing temporary road and bridge.
The existing bridge will close and traffic will shift to a temporary access road in early spring 2022. This configuration will remain in place until the new Coal Creek bridge opens in fall 2022. Enlarged view JPG 185KB

Project overview

The existing 64-year-old timber support structure is decaying, the 109-year-old steel floor beams are rusted, the paint is peeling, and the bridge has weight restrictions for heavy trucks. All traffic will use a temporary bypass bridge throughout construction until fall 2022, when the new bridge is open. The temporary bridge does not have any weight restrictions.

Work to remove and replace the existing Coal Creek Bridge on SE Lake Walker Road was originally planned for summer 2021, but was delayed one year to spring/summer 2022. The one-year delay was needed because crews are only permitted to do in-water work during late spring and summer. The new, replacement bridge, scheduled for completion in fall 2022, will carry no weight restrictions, and is expected to last for decades.

Getting through the construction zone

Travelers will always have local access in both directions over Coal Creek. King County built a temporary one-lane bridge to carry traffic over Coal Creek just downstream of the current bridge in spring 2022. There are no weight restrictions on the temporary bridge. The temporary bridge will be removed once the new, permanent bridge is built and open to traffic in fall 2022.

Construction timeline

  • Pre-construction utility relocation: Summer 2021
  • Construction of temporary bridge and traffic shift: Winter/early spring 2022
  • Old bridge removed and new bridge built: Spring/summer 2022 through fall 2022
  • Project complete: Fall 2022

Bridge history

  • Built in 1958 with timber creosote substructure
  • Used recycled superstructure from a different bridge
  • Is sole access bridge - serves single family and mobile homes
  • Is two-lane single span bridge, 41 feet long and 18 feet wide
  • Has 310 vehicles per day including about 5 trucks per day

Construction photos

Existing and temporary bridge, looking west.
Travelers will now use the single-lane temporary bridge (left side of photo). Crews will return in late May or June to remove the existing bridge (right side of photo). We can only do work over and in the creek during the warmer months when there is less impact to fish.
(Photo taken on March 29, 2022)

Finishing touches to the new, temporary bridge.
Crews add the finishing touches to the new, temporary bridge (right side of photo). The existing Coal Creek bridge (left side of photo) will be closed to traffic once traffic is shifted onto the temporary bridge.
(Photo taken on March 18, 2022)

Installing bridge deck on temporary bridge.
Crews work to install the bridge deck on the temporary Coal Creek Bridge. This temporary bridge will be in place throughout construction of the new, replacement bridge.
(Photo taken on March 10, 2022; looking west)

Tractor smooths out approach ramp.
A tractor smooths out the top of the approach ramp crews use to access the bridge decking that is under construction on the temporary Coal Creek Bridge.
(Photo taken on March 10, 2022; looking east)

Why King County is replacing this bridge

Losing steel.
We are losing sections of steel.
Severely rusting.
The super-structure is 109 years old and severely rusting.
Timber issues.
The 64-year-old creosote timbers are rotting.
Paint issues.
Paint peeling.

Frequently asked questions

The existing bridge is deteriorating and needs to be replaced. The 64-year-old timber support structure is decaying, the 109-year-old steel floor beams are severely rusting, the paint is peeling, and the curve in the road and bridge do not provide adequate visibility to oncoming traffic.

The bridge has been categorized as structurally deficient and functionally obsolete.

Structurally deficient means there are significant load carrying elements of the bridge that are in poor condition due to deterioration and/or damage or the waterway opening provided by the bridge is insufficient causing water overtopping with significant traffic delays. The fact that a bridge is “structurally deficient” does not imply that it is likely to collapse or that it is unsafe. It means that the bridge must be frequently monitored, inspected and maintained.

A functionally obsolete bridge is one that was built to standards that are not used today. Functionally obsolete bridges are those that do not have adequate load carrying capacity, lane widths, shoulder widths, approach roadway alignment, horizontal and vertical clearances to serve current traffic demand, or those that may be occasionally flooded.

As of September, 2021, the Roads Services Division bridge inspection team reports the existing bridge could only remain open if additional weight restrictions (more than there are today) were in place by winter 2022. For this reason, we will build a temporary bypass bridge and permanently close the old, existing bridge in winter 2022. Crews will return in spring or summer 2022 to remove the old bridge and build a permanent replacement. The temporary bypass bridge will not have any weight restriction.

The county has shifted all traffic onto the temporary bridge. The temporary bridge has one single lane, and there are no weight limit restrictions on the temporary bridge.
Noise levels will be typical for high- impact construction, including excavation, jack hammering, and saw-cutting.
Construction crews will typically work Monday through Friday during the day but there may be occasional weekend and/or nightwork.
Construction barriers will surround the construction area to contain construction-related materials from polluting the water. Also, the creek will be routed through a temporary bypass pipe to further protect fish and wildlife.
The projected bridge replacement cost is $4.7 million.

Project documents

Contact us

24/7 Road Helpline: 206-477-8100 or 1-800-527-6237

TTY Relay: 711

Twitter: @KCRoads