The detour signs on Mille Lacs County Road 12 between Princeton and Milaca could remain up as much as seven days longer than originally planned due to a change in the design of the new bridge being constructed on that road.
The contractor, Schroeder Construction, of Glenwood, was originally given a deadline of Nov. 4 to complete the $800,000 project of replacing the 1970s-era, two-pier bridge over the Rum River with a one-pier bridge.
Heavy rain in late June swelled the river to where it slowed the work, but what caused the need recently for more time to complete the project was an unforeseen problem in the stream bed – namely big rocks. The original design of the pier for the new bridge required building a temporary coffer dam to hold back the water to construct it.
The original soil borings for the project only suggested smaller size rocks known as cobble in the river bottom. But when the contractor tried hammering the sheets of metal into the stream bed to form the coffer dam, the sheets found resistance from rocks, Mille Lacs County Public Works Director Bruce Cochran and Ron Bray with the project’s engineering firm, WSB & Associates, said last week.
Bray said that further investigation found rocks with two feet diameter and realized that a different kind of pier had to be built that didn’t require a coffer dam. WSB chose a new pier design that has eight extended metal pilings. Bray explained that the pilings, or supports, would extend above the water. Normally pilings are pounded into the ground and then cut off below the surface of the water and concrete is poured around and on top of the pilings.
The new design adds $18,031 to the project and results in the need for extending the completion deadline seven days to Nov. 11.
Cochran told the County Board during an update on the bridge project on Sept. 3 that the extra cost is “negligible.” He explained that it represents only about 2.5 percent of the bid amount. Cochran said the extra cost will be funded by state aid.
Cochran said that he believed the contractor would complete the bridge some days before the deadline but the extra time was given to provide a little more leeway in case other problems arise. Bray said that he had talked to the contractor and learned that he was within one day of being on schedule.
Since the late June precipitation, the area has had consistently dry days through July and August into September, which, while being tough on crops, has been good for bridge construction.