New Interstate Aims to Unweave Minn.’s Traffic

Mon November 20, 2006 - Midwest Edition
Dick Rohland

By Dick Rohland


A critical and heavily used junction of two Minnesota interstate freeways is completing its first full year of major reconstruction to make some long awaited improvements for the motoring public. When the construction is completed, motorists will see a much wider road that will reduce congestion, eliminate most lane changes, improve safety and add capacity to meet future traffic volume increases.

Though work started in 2004 with the reconstruction of one of nine bridges, construction did not kick into high gear until a year ago because of delay by the U.S. Congress in passing the most recent federal highway bill.

The Minnesota Department of Transportation (Mn/DOT) teamed with the local design firms of URS Corporation, Minneapolis and TKDA, St. Paul, to complete the design and planning stages of the project.

The suburbs of Vadnais Heights and Little Canada, Minn., just a few miles north of St. Paul, is the location of this junction, which separates east and westbound I-694 traffic from north and southbound I-35E traffic. I-35E brings mainline I-35 traffic into and out of the heart of St. Paul while I-694 carries east and westbound traffic from mainline I-94 through the northern suburbs of the Twin Cities.

The I-694/I-35E junction splits traffic at two separate interchanges approximately 1 mi. (1.6 m) apart. A six-lane section of common roadway carrying both I-694 and I-35E traffic connects the two freeway interchanges at the east and west ends of this roadway.

The east interchange loops southbound I-35E traffic heading into the city of St. Paul onto the commons road section where it shares traffic lanes with westbound I-694. At the west interchange, I-35E drivers are looped again onto the mainline pavement of southbound I-35E. The reverse movements occur for northbound I-35E traffic.

Currently, east and westbound I-694 drivers share six lanes of road pavement with north and southbound I-35E drivers through the commons road section. Traffic movement through this shared section of road forces drivers to jockey back and forth between lanes to reach their desired entrance and exit ramps at each interchange.

Current traffic volumes are 136,000 vehicles per day (vpd) through the I-35E/I-694 junction with a projected vpd of 201,000 by 2028.

During peak traffic times, traffic slows to a crawl because of the traffic weaving and under-capacity problems of the common roadway. During non-rush hour times, at posted freeway speed, the weaving becomes a safety issue, according to Mn/DOT.

Dubbed “Unweave the Weave” by Mn/DOT, the $110-million three-year project will add three lanes of traffic in each direction of the commons section and realign connections. These improvements will increase capacity and eliminate most of the weaving maneuvers occurring through the commons section.

Bridge and road crews will build nine bridges and eight ramps to improve the connections between the two interstates, according to Mn/DOT.

Shafer Contracting, Shafer, Min., is the primary contractor for the state.

Shafer brought on Lunda Construction, Black River Falls, Wis., to build the bridges and retaining walls of the project.

Both companies are well established in the Midwest. Shafer is primarily an excavation, road and concrete paving contractor while Lunda primarily builds structures. Another 17 subcontractors will eventually be on site to help complete the project.

Each company has mobilized an impressive line-up of heavy equipment to get the job done. Lunda will have 11 American, Terex, Grove and Link-Belt cranes on site to build the nine bridges and nine retaining walls. Lunda also will have Samsung, Volvo and Cat excavating equipment on the project site.

Shafer crews will have over three dozen pieces of heavy equipment including nine Cat and Komatsu backhoes and a couple of Grove cranes on the site.

Crews from Shafer and Lunda have accomplished a lot of work and covered a lot of territory on this 4 mi. (6.4 km) road project since work started last December.

At the west interchange, a key entrance ramp at Little Canada Road carrying traffic from two, St. Paul suburban communities onto southbound I-35E is complete. The work here added one lane for southbound traffic at this location along with a realigned entrance ramp and a noise barrier.

Over on the northern end of the road project, a busy entrance ramp and an interchange hub at County Road East for a busy shopping center has been completed.

And at the northbound I-35E ramp from Little Canada Road, crews recently completed a mammoth retaining wall topped by a noise barrier. Grading and paving work has kicked into high gear at this entrance to add an additional lane and rebuild the ramp.

This construction will force a 35-day traffic restriction which the contractor and Mn/DOT engineers expect to be one of the more difficult traffic restrictions for the project, said Frank Weiss, Shafer vice president and project manager.

“We’ll be necking vehicles down from three to two northbound lanes at this location to expedite the construction in that area so that traffic during the winter months can resume to a normal pattern,” Weiss explained. “There’s just a tremendous amount of work that has to be done in that particular area.”

Mn/DOT officials expect some traffic back ups during the lane restriction. However, they are confident that the daily commuting public will eventually adjust their daily schedules or find alternate routes to ease some of the pain caused by the 35-day construction.

Signs will be posted throughout the Twin Cities metro area to alert the traveling public to the lane restrictions.

Shafer crews also have been pouring concrete for the new highway. To date, nearly $2 million of the $13.1-million contract amount for concrete paving work has been completed, according to Weiss.

And it is pavement that is designed to last. According to Weiss, “the design life of the new concrete pavement is 60 years.”

The new concrete road surface will be made up of 309,000 sq. yds. (260,000 sq m) of concrete pavement 9 to 12.5 in. (23 to 32 cm) thick, 106,000 cu. yds. (80,000 cu m) of structural concrete and 175,000 lbs. (79,000 kg) of stainless steel dowel bars.

This project for its size and lane additions is somewhat unique because no new right of way to accommodate the wider width was acquired, said Tom Krier, Mn/DOT project supervisor of the grading portion of the project. Therefore, working conditions are extremely tight and in the midst of the 136,000 vpd driving through the construction zone.

“It makes construction staging a key to completing the work on time,” Krier said. “This is a highly complex plan. Shafer Contracting is working in so many different areas of this job at the same time. It’s so fragmented and yet at the same time we’re pulling it all together. This is usually not typical of interstate reconstruction.”

Weiss added that the crew was working in eight different locations along with the current ramp and road work. “We have noise walls being constructed, reinforced soil slopes being built, and large diameter, long run pipe jackings,” Weiss said. “Maintaining traffic is a big issue and it’s an aggressive schedule so staging is a big factor on this project.”

He maintained that Mn/DOT and the contractor have made efforts to minimize the impact to traffic and still get the work done.

“There are compromises that are made, some of the compromises favor the traffic and some of them favor the contractor,”

Weiss said. “It’s a balancing act to get the project done.”

Along with the tight working conditions, 52 temporary bypasses will be built to maintain traffic flow around paving and bridge construction zones.

Though construction under traffic can be very frustrating to the motoring public, daily motorists along this stretch of the highway had a chance to experience one of the many benefits the new highway will bring to them.

“We had a temporary bypass earlier from southbound I-35E coming into the commons area that separated westbound I-694 and southbound I-35E traffic at the east side of the commons, which eliminated one of the weaving movements,” Jennie Read, PE and Mn/DOT project engineer of bridge and retaining wall construction, explained. “That’s where we have received the positive feedback so far.”

Though crews temporarily abandoned this bypass recently to complete some permanent road construction further east of the commons section, it will come back on line once this construction is completed, Read added.

This road project is notable just for the excavation work alone, said Weiss.

“It’s a big project,” Weiss said. “There are large quantities of excavation and embankment. There is a lot of trucking going on.”

Over all, Weiss estimated that on the average, 60 to 70 trucks per day have been hauling 1,000 loads per shift out of or into the construction zone sharing the same road way as the 136,000 motorists.

According to estimated quantities supplied by Mn/DOT staff, more than 2 million cu. yds. (1,520,000 cu m) of material will be excavated, with 600,000 cu. yds. (460,000 cu m) hauled off the project. The maneuvering of these huge trucks, which include belly dumps, tandems and side dumps into and out of the daily traffic has been going well, Weiss added.

Construction of stormwater retention ponds scattered throughout the work zone and laying pipe is a project in itself. With an increase of concrete surface, from 35 lane mi. (56 km) to 50 lane mi. (80 km) to be built along this corridor, 70,000 ft. (21,000 m) or nearly 14 mi. (24 km) of sewer pipe will be laid to take away stormwater runoff, Krier said.

“This initially was a rural design; water just sheeted off the road,” Krier explained. “With the additional lanes, it’s going to a more urban design with curbs and gutters.”

According to construction managers, some of the sewer pipe will be laid 40 ft. (12 m) underground, which requires double stacking the trench boxes. At the same time, pile hammers have been punching bridge pilings 80 ft. (24 m) deep in some areas.

Along with tight right of way limits, the geography of the project made retaining wall construction a critical feature to this project. Expanding the interstate width, especially at the locations of the entrance and exit ramps forced engineers to design mammoth retaining walls at these locations.

One of the largest cantilever retaining walls is located at the eastbound connection of I-694 from northbound I-35E. Here, Lunda workers will build a 6,800 sq. ft. (632 sq m) wall. More than 630,000 lb (285,000 kg) of reinforcement steel will be placed and approximately 860 cu. yds. (650 cu m) of concrete will be poured to complete the wall.

The largest retaining wall, somewhat unique in its construction style because crews constructed it using the ’top down’ construction method is the soldier pile wall located at the southern limits of the project along the Little Canada Road ramp onto northbound I-35E.

“This was a new experience for our resident construction office,” Read remarked. “There were challenges due to the lack of right of way, which affected the anchor design and installation. The determination during the design phase was to go with the soldier pile wall which uses soldier piles and soil anchors. Usually, the anchors go in about 15 degrees below horizontal. On this wall, we had some going in about 30 to 45 degrees to stay within the right of way we had.”

Crews drilled approximately 500 tieback anchors into the existing slope, placed 572,000 lbs. (260,000 kg) of structural steel and 180,000 lbs. (82,000 kg) of epoxy steel to build the wall.

At the completion of the project, Lunda crews will have constructed more than 250,000 sq. ft. (23,225 sq m) of retaining walls. They will eventually pour 4175 cu. yds. (3,200 cu m) of concrete to construct all nine walls.

Weiss explained that the noise wall construction is significant because the highway cuts through well populated residential areas of the northern suburbs of the Twin Cities. According to Weiss, 570,000 sq. ft. (53,000 sq m) of noise walls will be constructed using 108,000 ft (32,500 m) of concrete posts.

Bridge construction also is quickly moving forward. According to Bruce Reihl, Lunda project superintendent, bridge crews have started building seven of the nine permanent bridges to carry vehicles over highway lanes at the east and west interchanges.

The longest bridge that Lunda crews will build is a 1,928-ft. (580 m) steel beam bridge that will ramp northbound I-35E traffic onto the westbound lanes of I-694. Once completed, it will make an easy loop over one of the larger storm water retention ponds that will be dug as well as two ramps and three lanes of mainline traffic.

To date, crews have completed the substructure and are now raising the steel beams. Lunda officials expect to begin decking operations in the spring and open it to traffic in July 2007.

Work will continue for another two years before the entire project is completed in the fall of 2008. CEG

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