WATERLOO -- Black Hawk County's first rural "roundabout" intersection will cost less than originally expected.

Members of the county Board of Supervisors voted unanimously Tuesday to accept the lowest construction bid of $831,500 from Peterson Contractors Inc., of Reinbeck, to build the interchange -- a circle that forces approaching traffic to slow down and merge into their direction of travel -- at the intersection of Independence Avenue and Raymond Road.

The county has $500,000 from the state's Traffic Safety Improvement Program and $300,000 in federal safety funds, while county dollars must pick up the remainder. The original construction cost, when the supervisors approved the design last March, was $1.2 million.

"The net cost to the county will be about $35,000, which is a bargain," said County Engineer Richard King.

PCI was one of six bidders on the project when the Iowa Department of Transportation opened bids Dec. 18.

About 2/3-mile of road approach paving is included in the project, which is expected to begin April 1 and take 90 working days for completion.

The intersection, between Waterloo and Dunkerton, has been ranked in the top 5 percent of the state's most-dangerous intersections in terms of death and property damage from collisions, which prompted the IDOT to approve the grants. While some adjoining property owners opposed the roundabout, arguing additional lights and warning devices would be less costly and more effective, county and state officials noted those improvements would not eliminate potentially deadly T-bone accidents the roundabout prevents.

A new roundabout intersection at Cedar Heights Drive and Viking Road in Cedar Falls opened late last year and has given area residents a taste of how they operate.

"The opening of the roundabout in Cedar Falls has helped ease some of the concerns" about the rural project, King said.

Board chairman John Miller added, "There was some concern from the people in the area about whether farm equipment could get through there. We've got the design so that's OK."

Roundabouts were introduced to U.S. roadways in the 1990s and have been growing in popularity. Since all traffic must yield to vehicles driving around the center island, it lessens the severity of any crashes that may occur.

Contact Tim Jamison at (319) 291-1577 or tim.jamison@wcfcourier.com.