Dardenne Prairie officials plan to lobby vigorously for construction of a roundabout interchange with Highway 364 when it is extended through the city.

City officials consider such an interchange a key factor in Dardenne Prairie's future growth.

Mayor Pam Fogarty told the city’s Planning and Zoning Commission Oct. 10 that she plans to contact the four design teams vying for a contract with the state to build the third phase of Highway 364, the final leg of the 21-mile Page Avenue extension.

The first two phases extended the highway from Bennington Place in St. Louis County, across the Missouri River on the Veterans Memorial Bridge to Highway 94 and then to Mid Rivers Mall Drive. Phase three will take it from Cottleville through southern O'Fallon and Dardenne Prairie to Interstate 64 near Lake Saint Louis.

Fogarty said earlier discussions with the Missouri Department of Transportation (MoDOT) indicated Hanley Road, a major thoroughfare in Dardenne Prairie, could end in a cul-de-sac south of the proposed extension's route. Immaculate Conception Church and City Hall are on Hanley.

“That’s not going to be a cul-de-sac,” Fogarty said. Ending Hanley without an exit could cut the city in half, she said.

Fogarty and City Engineer Luke Kehoe said a roundabout exit could be cheaper than building an interchange. Much of the projected $100 million cost of phase three will go toward building several interchanges, particularly at Highway K in O’Fallon.

A roundabout is a circular road where traffic flows in a circle and can exit at various points. Fogarty said the roundabout exits on the Kansas City Parkway could be a model for creating a roundabout in Dardenne Prairie.

A roundabout could enhance development along Hanley in what is considered to be Dardenne Prairie's downtown area. The city has had a downtown plan in place since 2007 that includes maps suggesting the roundabout.

MoDOT announced in September that it had identified four design teams to compete for a design-build contract for phase three of Highway 364. They are expected to submit proposals by Jan. 1. A construction contract could be awarded by February, with construction beginning in the spring. Completion is expected by Dec. 1, 2014.

Meanwhile, Dardenne Prairie is in the process of updating its comprehensive plan for the first time since 2002. The downtown plan would be incorporated into the comprehensive plan, which could be completed next year.

Kehoe said the comprehensive plan will serve as a guide. “The plan lays out future development in the city, making an accounting of aspects of the city that would be of interest to future developers, residents and anyone who has a stake in the city — the way it is currently and in the future,” he said.

The plan's zoning maps show about 175 acres north of the Highway 364 route zoned for mixed use. Property north of the extension right of way is shown as commercial.

The city's Planning and Zoning Commission and the Board of Aldermen are expected to review the plan during the next few months.