Construction of three roundabouts in Ann Harbor, Mich., is expected to relieve congestion and improve geometrics on Interstate 23 that runs north and south in an area that sees heavy traffic due to adjacent colleges and hospitals.
The city of Ann Harbor is home to about 114,000, of which almost 37,000 are college students.
The $5.3 million improvement project is being facilitated by the Michigan Department of Transportation with the assistance of prime contractor Fonson Inc., of Brighton, Mich.
The improvement project, which was started last fall by widening the express way for the traffic shift, runs along the Geddes Road Corridor that runs east and west from Earhart Road to the west and Dixboro Road to the east.
A major component of this project involves work on the Geddes Road/U.S.-23 interchange that includes replacing the signaled intersections at the northbound and southbound exit/entrance ramps with roundabouts. A third roundabout was constructed at the Geddes Road and Earhart Road intersection.
Also included in the project is a bike/pedestrian asphalt path that includes a pedestrian bridge spanning U.S.-23, which is being added along the south side of Geddes Road.
Concrete sidewalks, LED lighting and landscaping also are part of the project, which is expected to be completed by the end of this month.
“The pedestrian bridge ties into the bike path that ties into the adjacent Concordia College off of Dixboro Road. That bridge work went fine,” said James Daavettila, project engineer with MDOT.
The bridge portion of the project consists of about $1 million of the project’s cost.
Managing traffic on Geddes Road to the east in order to access the University of Michigan and St. Joe’s Hospital proved to be one of the biggest challenges of the project.
“The motorists adapted well; there were no real backups on the ramps, even though the city of Ann Harbor was conducting a construction project west of this project and had created one-way traffic,” Daavettila said.
Balancing the five phases of the project proved challenging as crews worked to ensure traffic to flowed smoothly.
“The project is running smoothly with only those couple of minor issues to contend with,” Daavettila said. “Bronson has done and excellent job coordinating the project and maintaining traffic.”
Constructing the new roundabouts required about the same amount of space as a traditional 4-way stop. However, to create the new roundabouts the existing ramps needed to be realigned with the interstate. The southbound entrance ramp that was previously straight is now a circle, so more acceleration is needed to enter the expressway where U.S. 23 meets the Huron River. The entrance ramp to travel north was turned, creating a longer acceleration lane, Johnston said.
Cats, dozers, dump trucks, excavators and scrapers worked to move 100,000 cu. yds. (76,455 cu m) of soil on a 15-acre (6 ha) spot, creating tight working conditions. A temporary bypass road was built so traffic could access Concordia College and the University of Michigan and St. Joseph Mercy Hospital the Veterans Hospital.
“Once work is completed that bypass road will be removed and the materials will be recycled and donated to the University to resurface some of their gravel parking lots,” Johnston said. “It’s a good use of those materials.”
Not a lot of new materials were hauled in for use on the project; crews instead had to balance materials from one phase to another. Johnston explained that as the freeway ramps were redone, the soil from the existing ramps was moved for use as other ramps were constructed.
“We had to keep swapping soil from one ramp to another to build the ramps,” he said.
About 72,000 cu. yds. (55,048 cu m) of earth was moved during excavation, while about 70,000 cu. yds. (53,519 cu m) of embankment soil was needed, which almost balanced out the material needs.
“On this job the numbers kind of balanced out like that,” Daavettila explained.
Also used on the project were about 23,000 cu. yds. (17,584 cu m) of sand sub-base and about 11 tons (10 t) of top mix asphalt.
For the roundabouts, crews placed 18 in. (45.7 cm) of sand along with 6 in. (15.2 cm) of crushed concrete/recycled concrete, which was topped with 6 in. of asphalt, Johnston added.
During the course of construction, crews ended up closing a couple of ramps for safety and differential, Daavettila said.
“We always maintained the southbound 23 Geddes off ramp for access to the hospitals. We did close the northbound Geddes 23 off ramp and the northbound 23 onramp for a short time to facilitate the construction of them.”
Norm Johnston, project manager with Fonson Inc., added that roadways are often closed in order to complete roundabouts but that was not the case on this project since it is important to allow traffic to flow through the area because of the nearby colleges and hospitals.
“We wanted to keep access to those as well as we could,” Johnston said.
The express way was closed during the course of the project to allow crews to set bridge beams, which was done at night to help relieve congestion. Concrete pours for the bridge decks also were done at night on the 14-ft. (4.3 m) wide bridge that consists of two lanes. Johnston said.
The Earhart Road intersection was closed for 14 days during August while work continued on that roundabout. Crews encountered some soil and utility issues at the Earhart Road intersection.
“The soil was unstable due to silt so we’re going to undercut that; because of the utilities the DOT chose to use geogrid,” Daavettila said.
As of the middle of August, basically everything on east side of the interchange was completed except for the top wearing course of hot mix asphalt and some restoration work.
“That part of Geddes is going great,” Daavettila said.
A temporary road was paved and traffic was shifted onto that road on west side of the project.
“Hopefully we will have Geddes paved soon and traffic shifted to that new road so we can close Earhard Road and pave the 300 feet that ties into the new roundabout and the new southbound onramp.”
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