New North Fork bridge to be open for traffic by the end of August

The superintendent for the contractor replacing the North Fork bridge and the project manager overseeing the work for the Montana Department of Transportation (MDT) said they believe the new bridge will be completed and open for traffic by the end of August. Planning for the $2.8 million dollar replacement project began about six years ago. Actual work began in March of this year under a contract awarded to COP Construction, a multi-state business doing work throughout Montana and surrounding states. The new bridge replaces a one-lane, steel K-truss bridge that was erected in 1910 per a plaque found when the old bridge was removed. The North Fork bridge crosses the Milk River about four miles south and west of Zurich.

The bridge is one of several paid for with federal highway funds (about 86% of the total cost) and state taxes on fuel. Certain rural bridges, like the North Fork, qualified for replacement through the Non-System Bridge Program if the structure met MDT and federal criterion. Blaine County Commissioners and MDT said as far as they know the North Fork is the last bridge in the Blaine County that was on the program. The current project was moved up a year when additional federal funds became available from states that did not use all their funds.

A visit to the North Fork site

Greg Jergeson, of Chinook, is the District 3 Commissioner for the Montana Transportation Commission which reviews future plans and approves contract awards for MDT. He invited me to accompany him for a visit to the North Fork site. We met MDT Project Manager Beth Doran and COP Construction Superintendent David Burg at the south access to the new bridge.

The new bridge is a steel pony truss design with two spans totaling 227 feet. A pony truss bridge has no beams across the top of the structure to connect the side spans. The northern span is 148 feet in length and work to set it in place began in mid-July. The day we visited the site workers were torqueing the bolts that hold the various girders and beams that make up the longest span.

Each of the two 77,000 pound longer spans arrived at the site by truck in 50 foot lengths. Workers at the site bolted the lengths into the two 148 foot lengths. In mid-July the crew was ready to lift the first long span onto the bridge footings with a special crane. Superintendent Burg described the conditions that day as "wind gusts in the 35-40 mile per hour range. The worse thing that can happen with that kind of load is for it to begin 'helicoptering' from the wind. We had to abandon the lift for that day."

The first span was set in place and tethered by cables attached to steel girders driven into the river bank, much like a tent peg is used to hold a tent. The second span was set in place and stabilized, then girders were put in place between the two spans to tie them together and form what will eventually be part of the roadway across the bridge. MT Project Manager Doran said the 79-foot shorter span, still in four pieces on the ground, would be put together and set in place during the next few days.

Work started in March, 2018

The first work in the spring involved removing the old bridge, which was cut up for scrap, and preparing the site for the new bridge foundations. In April the flooding river stopped the prep work. Burg said, "The river flooded the area where we had dug a 70-foot deep coffer dam to begin pouring foundations below the river level to support the new bridge. When the flood water went away we had about 700 cubic yards of sand and dirt that we had to remove."

When uncontrollable events stop all work MDT can allow the contractor added time on the contract. The North Fork Bridge was a "100 work day contract" meaning once the project started the contractor had to have the work done in 100 work days. Both Superintendent Burg and MDT rep Doran said it's best if the contractor and the state can cooperatively work out the 100-day schedule to assure work is done on time. Doran said, "If work stops because of uncontrollable conditions MDT has to take that into account with the contract."

Once the second shorter span is in place the roadway on the bridge will be added. Burg said, "That will be a single pour so there are no seams in the roadway on either span. We'll start the pour at the north end and have a concrete pumping unit at each end to allow us to reach all areas of the bridge." There is one expansion joint on the roadway where the two spans meet.

The new roadway will be 30 feet wide with a curb and guardrail along the inside of each span, effectively making the roadway 28 feet wide. The bridge runs slightly down hill to the north to help drain water off the bridge and has a slight crown from the center of the roadway toward each edge, again for drainage.

Commenting on the steel pony truss design, Burg said, "It seems perfect for this application. With no connectors across the top, tall equipment can easily pass use the bridge." He pointed out the wider roadway would accommodate wider farm equipment that was never imagined when the old bridge was built a century ago. Burg added, "An open bridge is also cheaper to build." Greg Jergeson added, "The steel for this bridge was bought before the tariff was imposed. That would have increased the cost of steel for the bridge about 25%."

Other thoughts on the project

Asked about some of the challenges on the bridge project Burg said, "Well, there was the flooding in April. Another problem was finding local workers. I hired a couple of locals but at the last minute they decided not to take the jobs." He was very complimentary of the local suppliers and subcontractors used on the job, noting, "we were able to meet MDT specs on the concrete despite a long haul to get it here. The suppliers made a special effort to be sure we had the right materials."

Among work left to complete the project is adding the second span and pouring the roadway on the bridge. Then material will have to be added and moved to build access to the bridge from the gravel road at each end of the bridge. There will be hydro seeding to stabilize the new fill, fencing and signage. The crew of six hourly workers is currently on five, 10-hour shifts. Both Burg and Doran feel the work is moving well and a completion date by the end of August is doable.

A local twist to the

North Fork bridge story

One laborer at the job site does have a local connection. Ian McIntosh is a 2016 Chinook High grad studying construction engineering technology at MSU-Bozeman. When he learned which contractor got the bid McIntosh approached COP Construction to see if the company would hire him as an engineering intern. COP Superintendent Burg said, "The company made a place for Ian as an intern. I really needed more construction helpers on the project so I changed Ian's status to laborer and put him to work helping build the bridge. I'm sure when in school he reads about constructing bridges he'll appreciate it more because he actually helped build a bridge."

Ian agreed with Burg, adding, "I wanted to do some internships before I finish school and started looking for a job. This has really worked out well for me to get this hands on experience." Burg said, "I'll encourage the company to make a place for Ian next year. We might make a bridge engineer out of him yet. Ian wanted to see and learn things, he's been right in the thick of it this summer."