What is the cost of safety? In the case of a 7-mi. (11.3 km) portion of Interstate in North Dakota it is about $20 million.
Two hills coming in to the valley at Valley City, ND, along Interstate 94 are being lowered between 5 and 7 ft. (1.5 and 2 m) by North Dakota Department of Transportation (NDDOT) to try and reduce some of the problems with ice, explained Mike Flaagan, project engineer with NDDOT. “Lowering the road is done for safety because we had problems in the winter with ice on these roads. What we’re trying to do is take some of that away,” he said.
The ice also has caused problems for trucks on the steep road. “With the lower road it is easier for trucks to go up and down the hills. Our sanding crews have had to go up the slopes backwards when it was really icy. That is a safety hazard,” Flaagan added.
Though the hills were reduced, their 4 percent grade will remain the same. Flaagan noted that the length of the grade will actually be reduced from 4,000 to 3,000 ft. (1,219 m to 914 m). “When we cut the hills the constant steady grade was reduced, making the transition easier,” he said.
The first phase of the project included the westbound lanes, most of which was completed last fall by the prime contractor, Progressive Contractors Inc., of St. Michael, MN. Some work, though, remains on interchange lighting.
Work will begin this spring on the eastbound lanes, which will be constructed in the same procedure as the westbound lanes. The asphalt and the existing concrete will be removed, crushed and recycled and then used in the salvage base for the new road.
To breakup the existing concrete, a breaker is used. The broken concrete is then removed with an excavator and hauled away to a gravel pit where it is crushed to a smaller aggregate and a dust, which is placed into the salvage layer, Flaagan explained. The majority of the aggregate that is crushed is used in the permeable drain layer, to drain any water that may enter the pavement.
“Finding aggregate is not a problem but it is a cost saving to reuse what is there,” he said. “This way we don’t have to use a virgin resource, we can reuse something we already have.”
Some on and off ramps were widened to give traffic more time to build up speed while going up hill, thus merging into traffic more safely, he added. The inslope was widened so some of the guardrail could be removed, which also was a safety issue.
A lot of pipe work is included in this project, as the previous pipe was quite a bit smaller and had been deteriorating. Flaagan explained that a 60-in. (152 cm) pipe was placed under the road at the most western exit, which is a new procedure for NDDOT.
“Instead of removing all that soil to get to the pipes, we jacked,” he said. He explained that jacking is the process of using auger bores to bore through the soil, thus removing the soil. Then, the piping can be put in place right behind the boring.
“We saved a lot of money doing it that way,” he said, adding that working that close to traffic can also be a safety issue, so being able to do two procedures in one operation is a plus.
Last summer one new bridge was constructed at the westernmost interchange into the city, and a second bridge at the same location will be constructed as part of this year’s project, Flaagan said.
The bridge includes a stainless steel clad bar for the deck. “We usually use an epoxy coated bar,” he noted, but this is a part of a new research project for North Dakota. “This is the first time the stainless steel clad bar is used in North Dakota,” Flaagan said. “There is always a problem with corrosion and so we’re trying something new.”
The bar, which is rebar coated with stainless steel, was brought in from England, he added.
So far the project has gone very well, Flaagan said, and has created a nice, smooth road for motorists, though some problems were encountered while getting to that point. “We have had some trouble with the subgrade with the poor soils. We ran into some high water tables that were creating poor soil conditions. So then we had to make additional subcuts and remove some of the material and replace it with aggregate,” he said.
Though no problems are expected for this construction season, some of the project won’t be completed until next year, such as inlaid pavement marking, Flaagan said. Landscaping, which is actually a separate project, also will be done in 2002.
