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ID-75: Four Mile Bridge Replacement

This project involves replacement of the Four Mile Bridge that spans the Big Wood River along Idaho Highway 75 in Blaine County.

Approximately 20 miles north of Ketchum.
Traffic will be reduced to a single lane. Temporary signals will be in place with expected average wait times of 15 min.
Anticipated completion is Fall, 2020.
Questions or Comments?

Project Information

The current bridge was built in 1953 and has exceeded its life expectancy. In the coming months, ITD will replace the existing three-span bridge with a new single-span structure. 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 new structure will also be wider in order to accommodate 12-foot lanes with 3-foot shoulders in each direction. This will provide for more separation between vehicles and bicycles on the roadway and improve safety in the area.

Temporary traffic signals, as well as a push button for bicyclists, will be in place at the work zone. Drivers and cyclists alike are advised to adhere to signals and watch for crews and heavy equipment during working hours.

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