St. Louis County said Thursday that KCI Construction Co. of south St. Louis County was the successful bidder for a design-build contract for the stretch between Olive Boulevard and Page. Jacobs Engineering Group is the company's design partner. KCI's bid for the work was nearly $52 million, about $6 million lower than the county's estimate.

Officials also gave KCI Construction the highest technical score of the three firms seeking the contract. The county rated the bidders' designs for scope, safety, maintenance and schedule, and also rated the companies for the level of personnel they would devote to the work.

At 11 a.m. today, state transportation officials are scheduled to open bids for extending Highway 141 as a six-lane expressway from St. Luke's Hospital to Olive. The new road would be east of the current Highway 141.

When the two projects are complete, motorists will be able to drive on an expressway-type outer belt with few traffic signals from Interstate 55 in Arnold to St. Charles Rock Road in Bridgeton. Through the years, officials have said this outer belt could ease traffic congestion on Interstate 270 and promote economic development.

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"We're talking about a new six-lane road that will benefit our community for the next 50 years," County Executive Charlie Dooley said in a statement. "This project is vitally needed."

The county is using its own money, $5 million each from Chesterfield and Maryland Heights and federal stimulus money to pay for the work. Federal stimulus money will finance most of the state Highway 141 project.

From south to north, the county's project would consist of linking with the state project at Olive, building a six-lane expressway from there to Page Avenue, expanding the interchange at Page and linking the new portion with the Maryland Heights Expressway at River Valley Drive.

Millstone Bangert Construction Co. of St. Charles submitted a bid of more than $54.3 million for the work and Fred Weber Inc. of Maryland Heights, $58 million. County officials gave Millstone Bangert the second-highest technical score and Weber, third.

The state expects work will begin on its part in late spring. County officials were less specific about construction time, saying work would begin this year and be completed in 2012.