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Patton Bridge.
Patton Bridge No. 3015 over the Green River, southeast of Auburn.

Status update

May 10, 2021

Repair work on Patton Bridge is now complete. All lanes are open.

Project location

Patton Bridge is located on SE Green Valley Road over the Green River, about 1.5 miles southeast of the intersection of SE Auburn-Black Diamond Road. The bridge can be reached from State Route 18 by exiting onto SE Auburn Black Diamond Road and traveling east to SE Green Valley Road.

Project overview

The 70-year old Patton Bridge No. 3015 on SE Green Valley Road southeast of Auburn spans the Green River and is one of a handful of roads connecting SR 18 in an easterly direction to SR 169. It serves several residences in the rural, farming area and is the only bridge over the Green River on SE Green Valley Road.

Between February and May, 2021, the King County Road Services Division installed new steel and concrete reinforcements under and inside the bridge at the ends of the center span to extend the life of this bridge and keep it strong for the many types of vehicles that use it every day.

This safety work did not change the 33T weight limit.

New steel supports and brackets.
These new steel supports and brackets (bright green) reinforce the concrete bridge structure.

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Broch Bender, Roads Communications Manager
Desk 206-263-1189
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Project overview

The 70-year old Patton Bridge No. 3015 on SE Green Valley Road southeast of Auburn spans the Green River and is one of a handful of roads connecting SR 18 in an easterly direction to SR 169. It serves several residences in the rural, farming area and is the only bridge over the Green River on SE Green Valley Road.

The bridge has been repaired several times in the past 70 years and is due for another round of structural repairs to keep the bridge in good working order. If the 430-foot bridge were to fail, easy access to hundreds of residents, local businesses and farms would be cut off. Alternate routes would add approximately 15- to 20 minutes to a typical trip. More than 2500 vehicles cross this bridge every day.

The King County Road Services Division will install new steel and concrete reinforcements under and inside the bridge. To do this, they might close one lane for construction operations. Toward the end of the project, they will close the entire bridge to all vehicles for up to seven days to pour and cure the new concrete reinforcement.

Why King County is repairing this bridge

Inspections found deteriorating concrete in the support structure at the ends of the center span. There are currently weight limits on this bridge. Weight limits will remain in place when the work is complete.

Project schedule

Contractors started work mid-February, have completed two round-the-clock closures to pour new concrete reinforcements. The final round-the-clock closure is scheduled for May 4 to remove all scaffolding.

No traffic will be allowed on the bridge during the full, around-the-clock closures. Drivers must use the signed detour along SE Auburn Black-Diamond Road and 218th Avenue SE when the bridge is closed to vehicle traffic.

We anticipate all construction to be compete by 8 p.m. , May 4.

Project budget and timeline

The estimated construction budget is $450,000.

The work is scheduled to begin mid-February at the earliest with full bridge closures tentatively mid-March though it is weather-dependent. King County will post signs at the bridge site about two weeks prior to the actual full closure.

The bridge has two travel lanes. During most of construction, the contractor will keep one lane open to traffic at all times. The bridge closed at the start, in the middle and will close again at the end, May 4 to remove scaffolding and construction equipment.

Project detour

All trucks, including local delivery trucks, are strongly advised against using Lake Holm Road at Auburn-Black Diamond Road. This is a narrow and windy road. Truck drivers unfamiliar with this area have been known to get stuck and are unable to back down or move forward. Use Auburn-Black Diamond Road and turn right on 148th Avenue SE.

detourmap

Frequently-asked questions

The bridge has two travel lanes. The contractor has one travel lane open with traffic alternating in the single open lane. The entire bridge will completely close May 4, 6 a.m. to 8 p.m. and will reopen with all lanes open to all traffic on May 4 at 8 p.m.
Emergency vehicles will be allowed to use the bridge when it is open to general traffic. However, fire trucks, ambulances and all vehicle traffic will be prohibited from using the bridge during planned full closures. We are coordinating closely with Mountain View Fire and Rescue to ensure emergency response coverage on both sides of the bridge.
No. The contractor will not be allowed to use the waterway for construction access. All work will be conducted from the bridge using platforms or scaffoldings suspended from bridge deck.
No. This project will repair the support structure but will not increase the load capacity.
Yes. Detour is available from SE Auburn Black Diamond Road and 218th Ave SE. Detour signs will be in-place at various locations around the project site. This detour will add up to 15-20 minutes to the trip.

Bridge history

This bridge was built in 1950 and was considered innovative at the time based on the variation of the box girder design.

It was designed by Washington State Consulting Engineer Homer Hadley who later designed the I-90 floating bridge. It was added to the National Register of Historic Places in 1995.

Location map

Patton Bridge, located east of Auburn.
See this location on the My Commute map.

Photos - During repairs

Holes cut into bridge deck.
Holes cut into the deck of Patton Bridge to gain access to the structure are now filled with steel rebar coated in epoxy then sealed with concrete.
Rust-proof epoxy.
Rust-proof epoxy to make it stronger.
Concrete seal.
Concrete seals the access hole.
Old steel bridge rackets.
This is one of four old steel bridge brackets that will be replaced with sturdier steel and concrete beams under the bridge. Working on a narrow bridge with heavy steel parts is a difficult job.

Access to inside of bridge.
Contractor crews must access the inside of the bridge from above and below. On the bridge deck, they cut holes and come in from the top. They also built platforms to access to work zone from below. This hole will be sealed up once the work is complete.
Platform.
These platforms are secured to the bridge. The contractor works underneath installing rebar to stabilize the bridge.

Rebar.
This rebar is installed prior to the first concrete pour on March 17-20. The metal stud in the wall is part of an earlier earthquake retrofit project. It will remain in place.

Photos - Before repairs

Cracked supporting brackets.
Concrete, steel-supporting brackets are cracked.
Missing concrete.
Concrete has fallen away from the load-bearing steel portion of the bridge.

Underside of bridge center span.
Center drop-in span locations where steel box girder support repairs are needed.
Corbel support repairs.
Remove steel brackets and keep steel beam.
Contact us

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

TTY Relay: 711

Twitter: @KCRoads