Sweeping arches rising from the river until they nearly touch at a towering height above a wide four-lane deck characterize the preferred design of a new I-74 bridge across the Mississippi River, the Quad-City Times reported.
When asked in public meetings what mattered most in a new bridge, Quad-City residents said aesthetics and having a unique landmark. Bridge planners believe they hit both with a proposed basket handle twin arch bridge design.
"What we heard is they wanted a signature bridge, and we think this will accomplish that," said Cathy Cutler, an Iowa Department of Transportation (DOT) field services coordinator.
If built, the proposed I-74 bridge would be the only true arch bridge across the Mississippi River.
Typically, true arch bridges span smaller gaps, such as canyons and mountain passes, Cutler said. However, there is sufficient bedrock under the Mississippi here to anchor a nearly half-mile-long arch, she said.
The unanimous decision from a bridge project team was announced during a news conference in Rock Island, Ill.
The team includes officials from both the Illinois and Iowa DOTs, bridge consultant CH2M Hill, an architect and an engineer, the Quad-City Times reported.
The project team said it found several advantages to the true arch, including twin decks, which would allow for efficient deck replacement, greater flexibility in terms of traffic construction and a higher level of security.
Lidia Pilecky of CH2M Hill said this is one of the first bridge project designs to be examined by Department of Homeland Security officials. They believe a single-span bridge would be an easier target for potential sabotage than a two-span bridge.
The three other designs considered were modified basket handle tied arch twin bridges, a basket handle tied arch with a vertical pier and vertical hangers and a single deck cable-stayed bridge, according to the newspaper.
Input from Quad-City residents was sought at several public hearings, including a meeting held in May in which an informal survey revealed the majority of area drivers preferred the cable-stayed option. The true arch was a close second with 42% in favor of that compared with 46.5% for the cable-stayed option.
The current I-74 span is a steel suspension bridge with towers, a design not suited for the wider span proposed as a replacement. The existing bridge with two lanes on each of two spans was not designed to handle the large volume of traffic it carries on a daily basis, the Quad-City Times reported.
If federal and state funding is available, construction on the new bridge could begin by 2010, with approach work and configurations in downtown Bettendorf and Moline beginning as early as 2007.
The bridge itself is expected to cost between $170 million and $190 million, Pilecky said.
Despite the fact that nearly $90 million in design and property acquisition money already has been earmarked for the project, there is no guarantee it will receive federal funding. The current estimated cost for the entire corridor project--stretching from 53rd Street in Davenport to the Avenue of the Cities in Moline--is $671 million.
The design finalists all were within about 5% of each other in terms of estimated cost, Iowa DOT officials said. The four types offered the best mix of aesthetics, cost and engineering suitability for the Bettendorf-Moline span, officials added.
The next phase of the bridge project is preliminary design, Pilecky said. That work is expected to finish by the middle of 2007.
Cutler said DOT financing for the next five-year transportation program will be put together by the end of 2006, when DOT commissioners decide which projects will be funded. The I-74 bridge corridor project will be considered at that time.
"Due to funding cycles, we'll know more at the end of 2006 about moving forward to the final design phase," she said.