The foam will be injected through gaps to fill voids under the concrete to prevent future cracking and breaking, said Grand Island Public Works Director John Collins.
“This is the first time Grand Island has done this,” he told the Grand Island City Council Tuesday night.
Both the northbound and southbound lanes of South Locust Street from Lake Street south to the bridge have an uneven surface. Measurements taken on that stretch of road show 1.5- to 2-inch drops between concrete panels.
The uneven surface causes additional vibration along the street that has been pegged as one reason the traffic light at the south Wal-Mart has gone out more and needed more repairs than other traffic lights in the city, Collins said.
The city could take out sections of concrete and replace those at a cost of about $600,000 with several weeks of work, but it won’t necessarily mean a smoother ride because the concrete may not settle out smoothly.
Instead, Collins said the foam can be injected under the existing concrete and help “lift and stabilize it” because the foam does settle out smoothly.
“Polyurethane dries very consistently,” he said.
The existing concrete is in good enough condition that it can be used without replacement, said Grand Island Street Superintendent Shannon Callahan.
The polyurethane foam should save both time and money, Callahan said.
The polyurethane foam can be injected to lift and stabilize the concrete for $250,000. That’s $166,000 worth of repair work on the northbound lanes and $84,000 for the southbound lanes.
Work time is estimated to be one week.
“Just curing concrete is a minimum of a week — not counting all the time to bust it up and pouring new concrete in there,” Collins said of the traditional repair methods.
Councilman Mitch Nickerson said this type of road repair is “very fascinating.” He has heard of polyurethane foam injections used to lift and stabilize sidewalks and driveways, but never for major street usage.
Thrasher Inc. of LaVista was awarded the $250,000 contract. Work is to be completed by Aug. 19, which is one week before the Aug. 26 opening of the Nebraska State Fair.
Collins said if this type of repair goes well on South Locust Street, it may be used on other streets in Grand Island to smooth out the driving surface in areas where concrete hasn’t yet cracked.
“This actually is a miracle material,” he said.