Case Study

Traffic Flows Freely Over the Daniel Boone Bridge Expansion

In 1937, the new two-lane Daniel Boone Bridge over the Missouri River was more than enough to serve travelers coming to and from St. Charles and St. Louis counties. Since then, the once-rural area west of St. Louis has become one of the fastest-growing in the nation; even the 1981 addition of a second bridge couldn’t keep pace. Today, the new and improved Daniel Boone Bridge is open and accommodating traffic of all kinds.


The first two times a bridge was built across the Missouri River into St. Charles County, design and construction was done the old-fashioned way: Each contract was bid separately. When explosive regional growth created demand for an improved Missouri River crossing in the early 2010s, the Missouri Department of Transportation (MoDOT) wanted to think outside the traditional design and construction box.








Hoping to speed construction and maximize the value of its investment, the agency chose a design-build approach this time around, encouraging bidders to suggest ways to enhance the project while working within the budget.


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Hoping to speed construction and maximize the value of its investment, the agency chose a design-build approach this time around, encouraging bidders to suggest ways to enhance the project while working within the budget.

With experience in designing more Missouri River bridges than any other consultant, Burns & McDonnell had some ideas. After teaming with a joint venture led by Walsh/Alberici, we put our engineering experience to work on a winning design-build proposal that offered to do more in less time than MoDOT anticipated.

The design called for a half-mile-long bridge with a navigation span of 510 feet, making it the longest parallel flange, steel-plate girder span to be built on the Missouri River. With drilled shafts up to 11 feet in diameter and socketed into limestone, the deepwater foundations for the new bridge were designed to resist seismic and barge impact loads, even in the event of major flooding or sediment shifts.

In addition to the four 12-footwide traffic lanes, the bridge also includes a separate 10-foot-wide shared-use path designed to protect cyclists and hikers from vehicular traffic. That path, which connects to the popular Katy Trail in St. Charles County and Monarch Levee Trail in St. Louis County, shares space with pedestrian overlooks, providing users with a scenic view of the river below.

In accordance with the plan, the traffic lanes on the new Daniel Boone Bridge are designated for eastbound traffic, while the existing 1980s bridge carries vehicles heading west. The team added value to its proposal with the addition of a fourth westbound lane that runs a total of 1.5 miles. Factored into the original cost estimate, the lane was designed to alleviate congestion for those approaching and leaving the bridge.

The winning design also included plans to raise an existing overpass at Spirit of St. Louis Boulevard to correct a long-standing vertical clearance problem. By raising the bridge’s height 24 inches, the boulevard achieved the standard vertical clearance that is important for traffic safety.


The project team’s experience paid dividends when developing the project’s accelerated design and construction schedule. Design was completed in just nine months, rather than a typical 12, allowing steel orders to be submitted with ample lead time to keep the contractors on track.

Because MoDOT placed high priority on minimizing traffic disruption, construction sequencing was designed so there were no lane reductions during construction. That resulted in a brief but effective game of “musical bridges.”

Once the new bridge was complete, it began carrying eastbound traffic that had previously traveled on the 1980s span. The roughly 30-year-old bridge then underwent rehabilitation, while the 1930s bridge continued to carry westbound traffic. When the 1980s bridge renovation was complete, westbound traffic shifted from the original bridge to the 1980s bridge. And, with its job complete, the 1930s bridge was demolished in early 2016.

Incorporating links to two local nature trails and scenic river views, the new four-lane, $114 million Daniel Boone Bridge accomplished what the design-build team set out to do: provide the people of a booming St. Charles County with a better way to drive, bike and walk across the river into St. Louis County while delivering exceptional value to the taxpayers who funded it.

Project Stats


Missouri Department of Transportation


St. Charles County, Missouri, and St. Louis County, Missouri