Four Mile Bridge

Work has now commenced to replace the Four Mile Bridge on Highway 75 north of Ketchum.

Work began this week to replace the Four Mile Bridge along state Highway 75 near Galena Lodge, according to the Idaho Transportation Department.

Built in 1953, the bridge has “exceeded its life expectancy,” the ITD stated on its website. Its replacement structure—expected to be completed in October—will have 12-foot lanes and 3-foot shoulders to better accommodate recreationalists.

“This will provide for more separation between vehicles and bicycles on the roadway and improve safety in the area,” the ITD stated.

Currently supported by several piers over the Big Wood River, the aging bridge will also be rebuilt as a single-span bridge, meaning it will use two main support structures.

“Unlike the current bridge, the new structure will not have any piers in the water, which will more readily allow for the natural meandering of the river,” the ITD said.

Cannon Builders of Blackfoot, Idaho, has been hired to replace the Four Mile Bridge, 20 miles north of Ketchum. Traffic will be reduced to a single lane with a traffic signal, and drivers should be prepared to stop for up to 15 minutes at the light, the ITD said.

According to ITD project manager Lynn White, the department’s Galena Summit slope-stabilization project is still in its planning phase. The aim of the project is to prevent an active landslide on the southern slope of Galena Summit from impacting Highway 75—an ongoing threat, according to the ITD.

“This landslide is 300 to 400 feet wide and 300 to 400 feet long, it has damaged the highway various times in the past, resulting in costly repairs, shifting of the roadway alignment and other impacts,” the department’s website states. “A large slide could result in a highway closure indefinitely.”

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