Fixing the Road, From the Concrete Up
Mackinac Bridge Work Is on Schedule
By Karen Gould

With the bituminous layer removed from the deck of the Mackinac Bridge, Bob Sweeney, executive secretary of the Mackinac Bridge Authority, examines spauling areas early Thursday morning, April 24. As part of the resurfacing project, the sections will be cleaned out, repaired, and finished in preparation for the application of the new road surface.

The sounds of a milling machine, mechanical broom, dragging chains, and multiple jackhammers mix with engines of cars and semi trucks on the Mackinac Bridge, during part of a two-year resurfacing project.

This year, the two east side lanes of the bridge will remain closed until mid-June as the road surface is removed and replaced. The same work is planned for the two west lanes next spring. The $3.2 million project includes replacing deteriorated sections of the concrete curb and repairs to steel expansion joints.

The seven-minute trip across the bridge has now stretched to about 20 minutes as traffic is reduced to one lane in each direction and no passing is allowed.

On the two northbound lanes, Payne and Dolan of Gladstone and Gaylord is milling off between 0.75 inches and 1.5 inches of the bituminous road surface, exposing grates filled with concrete. The milling machine must skip over joint sections, which run the width of each lane and are in place every 80 feet along the five-mile stretch. Hand chipping is required to remove the old road surface near the joints. Concrete curb sections also require hand chipping. Both jobs are accomplished with jackhammers by crews from Anlaan Corporation of Spring Lake.

Walt Loveless of Whitehall uses a jackhammer to clean away areas of spauling concrete. A new concrete curb will be poured over the steel reinforcing bars.

In some areas, water has seeped through the old roadway, and freezing and thawing have caused the concrete to flake or separate, referred to as "spaul," in the parlance of highway engineers. On most bridges, spauling can be spotted from underneath the deck. On the Mackinac Bridge, the original construction forms remain below the deck, blocking the view of its underside. So while the concrete is exposed, a chain is dragged across its surface, producing a ringing sound. This becomes a dull ring when the chain snakes across a spauled section.

Kim Mikula of Petoskey listens to the ringing sound created by the chain she pulls back and forth over the bridge deck. The ringing dulls when the chain passes over spauling concrete. She then marks the area with pink fluorescent paint. Crews will repair the section in preparation for the new roadway.

When spauling is located, the sections are marked with pink fluorescent paint, and these areas will be chipped out and repaired before the bridge is resurfaced.

Kim Mikula, an inspector with Northwest Design Group of Petoskey, the construction inspection contractor, said trucks crossing the bridge make it hard to listen for spauling, so the chain work is intermittent. She also uses a hammer to pinpoint spauling areas, listening for the sound to change.

Two years ago, the Michigan Department of Transportation performed ground penetrating radar tests on the bridge to estimate spauling on the deck. The radar is most often used on highways to detect the thickness of layers that remain on a road surface, and only recently has been used on bridges.

According to Bob Sweeney, executive secretary of the Mackinac Bridge Authority, "the amount of concrete spauling that we have identified so far is about what we had estimated for this portion of the project."

A slight increase in the amount of shallow concrete repairs is being offset by a smaller amount of full depth concrete repairs than estimated, he noted. To complete the work by June 18, in time for the St. Ignace Antique Auto Show, Payne and Dolan has two shifts working on the project six days a week, depending on weather. With less than eight weeks remaining on the project, Mr. Sweeney said, the resurfacing work is progressing on schedule.

Construction will be suspended over the Memorial Day weekend, and may even be completed by then, he noted.