Road crews for the Minnesota Department of Transportation (MnDOT), working under a tight deadline and rapid construction schedule, completed a 9 in. (23 cm) un-bonded concrete overlay to bring new life to a 7.5 mi. (12 km) section of I-94, a busy commuter and weekend vacation route in central Minnesota.
Located approximately 55 mi. (88 km) northwest of the Twin Cities, MnDOT and its prime contractor, Knife River Corporation, hit its goal to open this stretch of freeway between Clearwater and St. Cloud, Minn., to four lanes in time for the busy Fourth of July holiday and with two months to spare during the prime Minnesota vacation season.
Tipping panels and a ride surface badly deteriorating sparked the overlay on this section of freeway that was constructed in the early 1970’s and now carries a much heavier traffic load and more trucks according to the MnDOT Web site for this project.
For the motoring public, the benefits of the work include a smoother ride, improved drainage and improved safety with new guardrails and cable median barriers on this stretch of freeway.
For MnDOT and the tax-paying public, the un-bonded overlay method of construction is not only cheaper than a full blown reconstruction; it extends the road surface life to 30 years and reduces short term maintenance costs. It is also much faster to place; significantly reducing the duration of construction related traffic delays.
Knife River Corporation, headquartered in Bismark, N.D., took the contract with a bid of $16.5 million.
The stretch of I-94 that runs northwest out of the Twin Cities is not only a busy commuter route, it is a heavily used weekend vacation escape route for Twin Cities residents driving back and forth to vacation lake country in west central and northwestern Minnesota.
Through the stretch of I-94 running between Clearwater and St. Cloud, the week day ADT is 42,000. However, traffic can swell to 53,000 vehicles during the summer months when Twin Cities residents hit the road to drive northwest to prime lake country in this part of the state.
With a very tight construction schedule and July 4th completion goal, MnDOT closed the eastbound lanes to begin the paving work on the project on April 1, despite a heavy cover of snow on the ground and a long range forecast of more cold weather.
And with warnings to the public of possible 20 mi. (32 km) traffic back-ups, sign crews necked down the freeway to one lane each direction on the westbound lanes.
Though crews worked through more snow and cold through April and heavy rains in May, they hit their first goal to complete the over lay on the eastbound lanes in time for the Memorial Day holiday with just minutes to spare, said Dan Labo, MnDOT project engineer.
“We made it by ten minutes, but we made it. We had some last minute rain; otherwise we would have been done two or three days earlier,” Labo said.
Road crews hit their second and last target date of July 4 several days in advance of the big, summer holiday and re-opened all four lanes of the freeway to traffic, Labo added.
At the same time, MnDOT public information staff was pleasantly surprised that the projected travel delay time and back-ups were not as long and time consuming as expected.
“One of our biggest concerns was westbound traffic heading out of the Twin Cities on Friday afternoons. Our modeling showed we could easily get 20 mi. back-ups,” said JP Gillach, MnDOT public information officer. However, “the longest back-up we have seen is about 7 mi. and now most of the time it is 5 mi. or less.”
Gillach credits, in part, an active and on-going publicity campaign that began last year and targeted the Twin Cities and others to keep the traffic back-ups shorter than expected and more manageable.
“This was a team effort,” Gillach said. “Our traffic engineers, planners and construction team worked together to put together a great project. Without the personal care and professionalism of this team, even the best communications plan could not have produced these kind of results.
v“We have had very few complaints. People are getting to where they need to be,” Gillach added. “The delay time during the week on westbound was about 10 minutes. You get stuck in that back-up and it seems pretty long but traffic funneled through fairly well.”
Drivers familiar with the area also have two other highways and local roads that serve as good alternate routes that head west and northwest out of the cities and many of them are most likely using them, Gillach noted.
Preliminary work on the project started last fall after the summer peak vacation season. Knife River crews completed most of the dirt work, and constructed temporary crossovers in preparation of the more intense paving schedule, which began this spring Labo said.
Crews brought in a Cat paver, Terex milling equipment and Ingersoll Rand rollers for the road work. At the concrete batch plant near the north end of the project, a pair of Cat backhoes worked the site.
Estimated quantities for this project include 154,000 cu. yd. (117,800 cu m) of excavation, 75,000 cu. yd. (57,400 cu m) of granular borrow, 78,000 cu. yd. (59,700 cu m) of concrete and 29,000 ton (26,100 t) of asphalt for the shoulders.
With a six day, sunrise to sunset work schedule, when road crews started work this April, they already had the weather against them with a climate that resembled winter more than spring.
“We battled 26 in. of snow the first two weeks of April. Trying to build a road with a thick snow layer and trying to get it cleared were part of one of the bigger issues we had. Fortunately, the snow fell when we were doing concrete removals, so we only experienced two to three days of delay. However, cold temperatures pushed back concrete paving operations nearly two weeks,” Labo said.
Working for them, though, was the fact that this project is “just a dirt and concrete job,” Labo said. He added that most of the soil in the area is sand so that the frost thawed quickly, which allowed the paving work to begin around April 21, just three weeks after crews rolled onto the site.
On an un-bonded overlay project, after surface cracks and holes are patched, new concrete is poured on top of the existing road surface with an inter layer in between to serve as a bond breaking material. Many times asphalt is placed on top of the existing surface as a bond breaker. However, on this project, a geo textile material was used.
“Due to the schedule, we wanted to get away from using an asphalt inter layer because it takes longer to place than other methods. What we did on this project is actually use a geo textile material as a bond breaker,” Labo said. “We just rolled it down the road in front of the paver and held it in place with concrete nails.”
Under two bridges and at each end of the project, a full reconstruction was done to maintain standard freeway clearances and to tie into the existing road pavement.
Road crews watched the weather radar and forecast information closely and they were able to work in and around the showers to keep the paving work moving forward while the portable concrete batch plan on the north end the project eliminated long travel times for concrete pours.
There also were very little travel conflicts between the motoring public and drivers arriving and leaving the work zone for deliveries or removals, said Labo.
“In reality, there was very little impact to the traveling public as far as actually getting in and out of the work zone. We’re pretty well cordoned off and we generally stayed within our work area,” Labo said.
MnDOT also is backing up its media campaign during the project with real time information available at the touch of a key board and traffic alerts while driving the highway.
“We have real time cameras and real time information on line with 511 so we’re really promoting that option as a way to check the current traffic conditions,” Gillach said. “People can jump on line before leaving home to see if they want to try I-94 or find another route.”
On the freeway, MnDOT has set electronic message boards as far out as 20 mi. in each direction of the project to keep drivers informed of traffic conditions and in time to give drivers other route options. It has a tow truck available at peak travel times to move disabled vehicles off the road and built pull outs about every mile for drivers having mechanical problems, Gillach said.
Throughout the remaining part of the project, Knife River crews will utilize temporary lane closures during off peak travel times to complete the guard rail work and remove the cross-overs and pull outs.
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