Fighting early summer rains that turned to a blistering hot summer, bridge and road crews are making good time during their first, full season of construction on a two-year project to rebuild a series of aging bridges and improve a busy, congestive and geometrically awkward interchange just north of the Twin Cities of St. Paul and Minneapolis.
Located in the Twin Cities suburbs of Arden Hills, Shoreview and Mounds View, Minn., construction started on rehabilitating the I-694, TH-10 and the Snelling Avenue connection in the early fall of 2011.
The majority of the roadwork is taking place on I-694 and a short piece of shared pavement with TH-10. I-694 is part of the interstate beltline that circles the Twin Cities for 70 mi. (112 km). TH-10 is a busy east/west highway that breaks out of I-694 in Arden Hills in a northwesterly direction and runs northwest to Fargo, N.D. Snelling Avenue is actually HWY-51 and serves as a city arterial street running from the south side of St. Paul through northern suburbs to its connection nearly 12 mi. (19 km) north at I-694.
Shafer Contracting, a company specializing in road, sewer and grading work based in Shafer, Minn., came in with a low bid of $46 million to build the project. The company will eventually bring in more than a dozen sub-contractors to complete the project.
Another, separate project from the interchange work is the reconstruction of a pair of bridges carrying TH-10 traffic over I-35W on the west end of the I-694 work.
Lunda Construction, based out of Black River Falls, Wis., with a Minneosta office in Rosemount, is rebuilding these bridges at a bid amount of $8.6 million. Lunda is a Midwest bridge contractor
MnDOT engineers had been planning to improve the long, out-dated geometrics of these highways for more than ten years. However, it was the deteriorating condition of nine bridges along the I-694/ TH-10 corridor that carried funding priority.
As MnDOT set off to replace these bridges, they also began looking into funding to include the geometric improvements and, in the words of MnDOT Public Affairs Coordinator Kent Barnard, improvements that were equally critical as the bridge replacements.
Chief among them was a short piece of four lanes of traffic shared by both highways that caused a less than ideal connection for the two roads.
Along with the traffic chaos created by the shared pavement of I-694 and TH-10, there were “some non-standard left entrances and exits that we wanted to eliminate and we have had a higher than average crash problem along this particular corridor for some time,” said Barnard.
The substandard geometrics that contribute to congestion and crashes include the lack of lane continuity for mainline I-694 eastbound and westbound through the TH-10 commons area, the left side entrance of eastbound TH-10 to I-694, the left side entrance of northbound Snelling Avenue to westbound I-694 and the short distance of 1500 ft. (460 m) between the two intersecting highways, according to MnDOT reports.
The reports state that because of these existing design deficiencies, traffic is forced to weave one lane which is a factor in the congestion and crash problems through this corridor.
This “combination of travel demand and geometric deficiency (traffic weaving) results in safety issues and travel delays on the corridor and has created one of the worst bottlenecks in the Twin Cities Metro area,” according to the Minnesota Department of Transportation (MnDOT) Web site.
Traffic statistics that support these improvements include an Average Daily Traffic (ADT) count of 110,000 vehicles per day along the I-694 and TH-10 corridor with a projected volume of 165,000 vehicles per day by 2030.
At the same time, MnDOT crash studies show a high number of accidents. The majority of them are rear-end crashes which is indicative of “congested conditions” according to the MnDOT traffic reports.
Though the bridge replacements drove the entire project, Barnard said that the geometric improvements had also been on MnDOT’s radar at the same time. The project turned public eight years ago when MnDOT staff presented preliminary designs and studies to the public through a series of open houses.
When completed, the new geometrics will add four through-lanes and two ramps that will loop around to separate I-694 traffic from TH-10 as the two highways merge together through the commons area. Drivers will have a pair of highways with improved traffic flow, more capacity, exits and entrances dedicated to both roads and less accidents according to the MnDOT Web site.
This is the first of four scheduled projects to reach MnDOT’s long term goal to improve I-694 running between I-35E and I-35W for approximately 7 mi. (11 km) across the northern suburbs of the Twin Cities.
A separate project jumpstarted work on the I-694 corridor several years ago when road crews completed the “Unweave the Weave” project. Similar to the current work, the “Unweave the Weave” project was another mammoth reconstruction to separate common lanes shared by I-694 and I-35E on the east end of I-694.
To make the improvements, though, construction crews will close lanes and build bypasses as they rip out thousands of cu. yds. of pavement through the I-694/TH-10 commons area while maintaining four lanes of traffic.
Drivers also will face detours throughout the project area when bridges come down and traffic lanes along with ramps are closed for construction. The good news to all this is that MnDOT and its contractor are on schedule to complete this work in two years.
As the construction season turns into shorter days and cooler weather, both the MnDOT project engineer and Shafer project superintendent agree that the project has been going well while fighting a wet spring after a warm and nearly snow-less winter.
Since construction began, road and bridge crews have been busy.
Several key bridges have reopened including the TH-10 and County Rd. 10 bridges that cross I-35W in the west end of the project that also ended a lengthy detour for regular users of these bridges. A couple of associated ramps for the bridges also were recently reopened.
Bridge crews completed several months ahead of schedule another pair of bridges on the east end of the project that carry fast moving, high volume I-694 traffic over the Island Lake channel that connects the two separate bodies of water that form Island Lake; a popular recreational lake in Arden Hills.
Along with the bridge openings, crews have completed a couple of busy intersections along the route and paved the eastbound lanes of I-694. Traffic crews recently shifted traffic to the new alignment to begin work on the new westbound lanes of I-694.
Along with hundreds of workers to move the project forward, at any one time, there are dozens of pieces of road equipment digging, grading and moving dirt around the site. Included in this mix are a half dozen Komatsu, Volvo, Hyundai and John Deere backhoes digging sewer trenches and removing topsoil. Assisting the backhoes in some of the work is more than a half dozen Cat and Volvo dozers and several Bobcats.
On hand for grading work are Cat blades, and Bomag, Ingersoll Rand and Dynapac rollers.
Nearly a dozen cranes rolled in by Lunda crews loomed above the project throughout the summer at several distinct areas for bridge demolition and construction work. Included in this mix were Terex and American cranes for the heavier bridge demolition and construction and smaller Grove cranes for the lighter work.
This huge onsite equipment inventory was put to good use when crews demolished the pair of bridges carrying TH-10 traffic over I-35W earlier this summer.
On an early weekend in June, traffic crews closed both highways from Friday evening to the following Monday morning. With a combined ADT of nearly 185,000 vehicles per day for both highways, detour routes had to be planned and ready to go with advanced notice to the thousands of drivers using these roads.
Time also was very critical. I-35W had to be open by 5 a.m. the following Monday in time for the morning rush hour commute into St. Paul and Minneapolis.
Once traffic crews choked off traffic on each highway, Lunda bridge crews rolled in with a small army of workers with a good representation of cranes, dozers, backhoes and bobcats for the tear down.
Drawing a small crowd of onlookers on a sunny and warm Saturday morning to a frontage road vantage point, they enjoyed watching as much as the operators enjoyed handling the controls of a pair of large, American cranes swinging a wrecking ball while a pair of Volvo backhoes chipped away at a huge piece of highway deck brought down by the wrecking ball that landed tipped up and out.
Of this particular demolition, one of the largest of all demolitions on the project, Steve Barrett, MnDOT resident construction engineer, was pleased with the work and timing.
“It went really well. We had the freeway open on time and we also put in a new culvert crossing I-35W and there was some paving work done also. So, there were three different operations going in a relatively confined work space” Barrett said.
“Crews worked from midnight that Friday to 10 a.m. on Saturday to drop all bridge superstructures,” Barnard added. “Then demolition efforts focused on removing the bridge debris and hauling it away.”
“Bridge demolition of this size and configuration performed in a single weekend is extraordinary but minimizing the closure of I-35W was a priority and the construction crews made it happen!”
Barnard noted that approximately 3,000 cu. yd. (2,295 cu yd) of concrete and steel was trucked from the site, “about the size of an NBA basketball court piled 17 ft (5.1 m) deep.”
About four mi. (6.4 km) east of the TH-10 bridges, crews also tore down and reconstructed the Island Lake bridges through the summer months. Though much smaller in size, they carry more than 100,000 vehicles per day and four lanes of I-694 traffic crossing a narrow channel connecting the two sections of Island Lake.
Here, preparations for the demolition and new construction involved lining each end of the channel with sheet piling to close off the small channel from water.
As Barrett explained, “we received permission from the Minnesota Department of Natural Resources to drive sheet piling and cut off the north side of the lake from the south side so that the work area could be isolated from the lake. So for erosion and environmental reasons we could replace the bridges and not worry about protecting the channel under the bridge.”
MnDOT allowed a six-month window to complete the pair of bridges. Each bridge was removed and rebuilt separately to maintain traffic on bypasses through the construction zone.
Excavation crews also have been busy. Because sections of the highway were lowered more than 12 ft. (19 m), engineer’s estimated that approximately 1 million cu. yd. (765,000 cu m) of excavation will be dug out. Another estimated 800,000 cu. yd. (612,000 cu m) of embankment will be removed.
With the limited right-of-way space, MnDOT added five retaining walls of more than 7,000 sq. ft. (651 sq m) to support areas that lost embankment.
Other features include five new ponds and infiltration areas that will be dug with 30,000 lin. ft. (9,150 lin m) of sewer pipe to be placed.
Road and bridge crews will continue to work through the fall and into the winter with efforts next year to focus on rebuilding TH-10 along with completing the remainder of westbound I-694.
The contractor is expected to have the entire project completed by November of next year.