Overcoming Nature’s Obstacles: Remote Environment Creates Construction Challenges on US 12 in Idaho

Bridges and a road along U.S. 12 in a recreational area receiving a needed $17 million upgrade have presented some logistical and environmental issues for contractors and the Idaho Transportation Department (ITD).

“It’s in a remote area, and that’s one of the challenges we had to address,” says Janet Zarate, PE, Project Manager of the U.S. 12 project for ITD. “This is a critical route.”

The area offers exquisite scenic views and serves summer and winter recreation areas. The corridor has been designated as wild and scenic. It hugs the Lochsa River.

“At ITD we’ve looked at improving the corridor in its context – its popularity and recreational opportunities make it a challenge to get what needs to be done and still maintain access for users, but we have worked with the U.S. Forest Service to protect the corridor and phased work to reduce impacts where we can,” Zarate says. “It’s a very popular rafting area, and we phased the road work to minimize impacts during rafting season.”

ITD also has worked closely with the U.S. Forest Service and the Montana Department of Transportation to help educate people visiting the area about the construction activity. The Forest Service identified staging areas and restricted other areas, so people still have access to the river.

“We are working with ITD to help keep our forest visitors in the loop about the construction work,” says Jennifer Becar, Spokesperson for the Forest Service in Kamiah, Idaho. “It’s our effort that no one is taken by surprise if the drive is longer than they expected it to be. It’s a very popular corridor for our visitors accessing campgrounds and trails along the Lochsa River.”

The two bridges being replaced were built in the 1950s and late 1940s, and have not had any major repairs over the years. The road was constructed in the 1950s and 1960s and has been repaved several times. The most recent repaving was nearly 20 years ago. As a result, several areas are cracked and rutted, which can be dangerous for drivers. This project will resurface 50 miles between Lowell and the Idaho-Montana state line.

“We are paving as much as we can all at once to improve mobility through the entire corridor and to limit the duration of impacts to our stakeholders along U.S. 12,” Zarate says. “Because the road was deteriorating, this will improve the mobility for the traveling public.”

Planned Road Construction

Fifty miles of winding road will receive resurfacing and updated signage and delineators. Knife River of Boise, Idaho, received both road contracts: the $6 million, 27-mile Tumble Creek to Saddle Camp Road contract and the $7.3 million, 23-mile from the Warm Springs Pack Bridge to the Idaho-Montana border job. The road follows a narrow river canyon. Work was expected to begin this summer and is anticipated to be completed in October. Knife River plans to work six or seven days per week, day and night. Due to the narrow corridor, the work is phased with a lane closure and pilot car operation. ITD placed restrictions in the contract on the length of the work zone to reduce delays.

The contractor will give the millings to the Forest Service to fix its roads.

Fish Creek Bridge

Concrete Placing Co. of Boise, received the $2.1 million contract to replace Fish Creek Bridge, built in 1952, near Bald Mountain. It is currently a three-span bridge, but once the work is complete, Fish Creek Bridge will be a single-span, concrete-girder structure.

“What’s unique about this one is the location, pretty remote and disconnected from everything,” says Zane Reed, Project Manager for Concrete Placing. “This is one of the most beautiful places on earth, with the steep mountains, white water and pine trees. How does it get better than that? We can build a bridge or paved road anywhere. We happen to like the work we do.”

Work began in April and is scheduled to wrap up in October. Crews are working four days per week, during the day. There is only one narrow lane alternated for each direction with traffic signals. Concrete Placing used three pilot cars to move two 140-ton cranes up the narrow corridor to the site with a 130-foot-long transport weighing 200,000 pounds. “Getting it through the narrow lanes took planning,” Reed says.

All of the demolition is from above. Crews saw cut the concrete, lift pieces off using the cranes and break them up for disposal. They have already removed half of the bridge, while traffic progresses on the other half. Once the first half is complete, traffic will move to it, and work will begin on the opposite side.

“We phased it that way to minimize environmental impacts,” Zarate says. “Due to the narrow and environmentally sensitive corridor it is not possible to use a shoo fly or a temporary bridge to complete the demolition and construction in one phase and maintain traffic through the corridor.”

Work will take place from the road while protecting the river. However, removing the piers no longer necessary will require some water work below the high-water mark. Concrete Placing will remove the piers during a six-week window during low-flow season in the river and a fish window. Crews also will remove portions of the old bridge that sits below the new structure.

Concrete Placing will install dual-chamber gabions with a soil fill, which will be seeded with native plants. A gabion basket is a retaining wall with cobble rock contained by a wire cage.

“As you are rafting down the river, you will not see the gabion face; you see native vegetation,” Zarate says.

Maggie Creek Bridge

Braun-Jensen of Payette, Idaho, is working on the $1.5 million Maggie Creek Bridge, built in 1949, near Kooskia. As with the other bridge, work commenced in April and is on track to finish in October 2018. Braun-Jensen is working six days per week, during the day. Work will take place in the right of way to minimize any impact on the environment. Braun-Jensen also will be staying out of the water. The existing bridge is 20 feet long and the new one will be 60 feet long.

This bridge employs a voided slab construction technique, an accelerated bridge construction, due to the short construction schedule.

“You do not have to form up a bridge deck on the project,” says Darin Braun, President of Braun-Jensen. “The voided slab will be poured in Caldwell, Idaho, hauled to the project, set on the abutments, and welded and grouted together.”

Road Closures

One of the biggest challenges for the project is the delays. Drivers can expect to be delayed as much as two hours. Each project can delay traffic for up to 30 minutes during construction activity, plus some 15-minute work zones. Limited passing opportunities exist.

“Folks in the area will need to leave extra time to pass through the corridor, but we hope they’ll see it as just more time to enjoy the views,” Zarate says.

Flaggers and pilot cars will help move traffic through the lane closures, and portable signals will keep traffic moving on the bridges.

ITD has taken steps to maintain mobility through the corridor, such as installing video detection on the Fish Creek Bridge, so officials can log onto the department’s website to check on traffic flow. In addition, the department has a hot spot at Fish Creek to call if a problem exists or emergency personnel needs to get through.

The department suggested drivers take alternate routes if possible. But the closest, Interstate 90, is many miles to the north.

Despite the temporary hassles for drivers this year, the project is expected to enhance access to the area.

“This project is going to improve our visitors’ experience, and we appreciate the work ITD is doing to improve the road,” Becar says.

“It’s going to be a tough season, because there is a lot of work that needs to be done,” Zarate adds. “Be patient and bear with us as we work to ensure that everyone can appreciate these improvements in the corridor for years to come.”

Project Partners