Bridge Project Sails Smoothly

Story by Mike Larson, Editor | September 28, 2010

Zenith Tech, Inc., Waukesha, WI, is the general contractor constructing two parallel bridges, each 2,545 feet long, over the Wisconsin River for the Wisconsin Dept. of Transportation (WisDOT) just north of Stevens Point, WI.

Each bridge will each carry two lanes of U.S. Hwy. 10 over the river.

In addition to constructing those long bridges, the project also includes building two parallel 415-foot-long bridges that will each carry two lanes of U.S. 10 across wetlands near the river. All four of the bridges are constructed of concrete.

The project also encompasses construction of a boat landing on the western shore of the river under the long bridges and the grading of 1.8 miles for the four-lane, divided highway near the bridge site.

New Bridges Are Part Of Larger Project

Started in September 2006 and scheduled for completion by the end of this August, the $23.5-million bridge job is the second project of nine in an overall program to relocate and replace 31 miles of U.S. Hwy. 10 connecting Stevens Point and Marshfield.

The entire nine-project program represents an investment of $234 million and is scheduled for completion in 2012.

The modifications to U.S. 10 will improve traffic flow and safety by changing the highway from a two-lane undivided road into a four-lane divided highway with limited access, by replacing some current intersections with free-flow ramp interchanges, and by changing its route to bypass downtown Stevens Point and four villages.

From-Scratch Construction

As part a brand-new bypass that carries the highway north around Stevens Point, the from-scratch construction on the bridge project began with cutting and grading the new route through woods and fields.

Mashuda Contractors, Inc. did the excavating and grading using global positioning system (GPS) guidance, which enabled the work to be completed with less physical staking. In all, they moved about 12,000 cubic yards of common excavation and 800,000 cubic yards of borrow excavation.

Shorter Wetlands Bridges Completed First

The two shorter, 415-foot bridges over the wetlands were completed first so they could be used to reach the east end of the construction site for the two nearly half-mile-long larger bridges spanning the Wisconsin River.

Each of the shorter bridges has three spans, each containing six 139-foot-long pre-cast concrete girders. Each shorter bridge contains about 1,020 cubic yards of concrete.

Larger Bridges Reach Nearly A Half-Mile Long And Cover 2.2 Acres

Each of the longer bridges is supported by 15 concrete piers ranging in height from 15 feet to 30 feet. Constructing the piers required excavating in the bed of the Wisconsin River, as well as driving between 34 and 37 piles to support each pier.

In all, Zenith Tech drove 48,700 total linear feet (9.2 miles) of piling in diameters ranging from 10 inches to 14 inches to support the piers for the two large bridges. Work on the piers, including concrete pouring, continued right through the frigid winter.

Spanning each set of piers is a set of six massive pre-stressed pre-cast concrete girders set side-by-side to support the roadbed. These wide-flanged girders each measure 160 feet long, stand 82 inches deep, and weigh about 88 tons each. They were placed by two 200-ton-capacity cranes working together from barges. WisDOT regional management believes these are the first wide-flanged pre-cast girders ever used in the state.

The deck for each bridge is 42-1/2 feet wide, including the parapet walls. It carries two 12-foot-wide driving lanes flanked by a 6-foot shoulder on one side and an 8-foot emergency stopping lane on the other. The deck of each bridge covers about 2.5 acres.

Because of the length of the larger bridges, Zenith Tech poured the western two-thirds of each larger bridge first and allowed them to cure so they could be used as a staging area for forming and pouring the eastern one-third, which spans the river. That remaining eastern third was poured in one 1,050-cubic-yard pour that took more than 15 hours to complete.

In all, each larger bridge contains 6,300 cubic yards of concrete, including 3,000 yards of deck concrete, 1,000 cubic yards of parapet concrete, and 2,300 cubic yards of substructure concrete.

Many Challenges, All Met

WisDOT's project manager for construction of the bridges, Kevin Garrigan, said, "This project has presented some interesting challenges. The length of the bridges, the logistics of getting 160-foot-long girders to the site over narrow and wooded rural roads, and making concrete pours of more than 1,000 cubic yards all made things interesting. But the project team has successfully met every one of them."

Girder Length Requires Special Arrangements

One of the challenges was just getting the 160-foot-long, nearly-7-foot-high, 88-ton girders from the factory where County Materials cast them to the job site. Not only were special hauling permits required, but maneuvering them through wooded areas and on rural roads required planning. In some cases, the intersection of county or township roads had to be widened to permit the nearly 180-foot-long trucks to make the turns.

Causeway And Barges Answer On-Site Needs

On the site, Zenith Tech constructed causeways into the river in order to more efficiently make use of their cranes and equipment. Being able to work from ground enabled faster completion that more than made up for the time required to construct and remove the causeways.

Said WisDOT's Garrigan, "By building the causeway into the river and driving temporary sheet piling at the end, Zenith Tech was able to reach further with their cranes, and was also able to dock a long barge that acted as a dock extension for even more reach into the river. That extra working area even permitted us to use a concrete pump for more of the pours, which helped speed up that process, too."

The causeway and dock also provided an ideal place to launch the large girders onto barges so they could be floated into the river for cranes to place when building the mid-river spans.

All in all, Garrigan estimates using the causeways saved several weeks of construction time, versus working more extensively from barges.

Long Pours Pose A Challenge

The six long deck pours of more than 1,000 cubic yards each also provided a challenge. Just deciding when it was likely there would be 15 to 20 rain-free hours at the right temperature required extensive checking of weather reports, making estimates, and coordinating with the concrete supplier and pumping company.

To get concrete to the mid-river span of deck, Zenith Tech used a pumping truck working from the end of the causeway as long as it could reach the work area, then completed the farther areas using 450 feet of belt conveyors.

Explains Garrigan, "The pump can place about 95 cubic yards of concrete per hour, whereas the conveyor can place only about 50 yards. So we use the pump as long as we can in order to get the higher production."

As the concrete was placed and finished and its surface became firm enough, it was covered with two layers of burlap and kept wet for a seven-day water cure that would prevent shrinking and cracking while it cured.

Said Garrigan, "Once the concrete reaches initial firmness, is covered with burlap, and has been wetted, the rain doesn't affect it. But if rain comes before that, you need to keep the extra water from getting into the fresh concrete. There were times on the 15-hour pours when we had to protect the new concrete from rain with plastic sheeting until it was cured enough."

Electronics Simplify Concrete Monitoring

One new technology employed during construction of the bridges was embedding electronic chips into the concrete to simplify monitoring of the curing rate. The microchips provided a continuous record of the concrete's temperature. They were especially useful during the winter because they could be read by a scanner without having to remove the curing blanket and exposing the concrete's surface to the frigid winter air.

The Project Team

The team building the Hwy. 10 bridges near Stevens Point includes: WisDOT (owner); Gremmer & Associates (on-site engineering and inspection); Zenith Tech, Inc. (general contractor, cement work, pile driving, girder erection); Mashuda Contractors, Inc. (excavation and grading); County Materials (concrete).

WisDOT project supervisor David Larson summed up the project: "The construction of these bridges has been an interesting challenge that has turned out very well. The two-year project is on schedule with just a couple of months left to go, and all the major structural work completed. The team has worked well together to meet the project's unique challenges. It is a pleasure to be a part of this."

To view pictures of this project, please visit our photo gallery.