Missouri DOT Makes Progress on Three-Year Effort to Replace I-44 Meramec River Bridges
Modernization Over Meramec River: Missouri DOT is Making Headway on Replacing I-44 Meramec River Bridges in St. Louis County
Just over a year ago, the Missouri Department of Transportation (MoDOT) began working on its Meramec River bridge project in Fenton, Missouri. In addition to improving the ramps between Interstate 44 and Interstate 270, crews led by KCI Construction are replacing four aging bridge structures: the westbound and eastbound Interstate 44 bridges over the Meramec River, and the westbound and eastbound bridges connecting I-44 to Watson Road.
Currently, the area between I-44 and I-270 has an average daily traffic count of 120,000, which is expected to increase to 145,000 by 2040. Hence, future regional traffic demands necessitate infrastructure improvements that bolster traveling safety and mobility.
“The existing I-44 bridges are reaching the end of their design life and have required frequent maintenance and repair work over the past several years,” says John Grana, PE, a Resident Engineer at MoDOT. “As a part of the project, MoDOT is adding capacity to the bridges and the adjacent interchange with I-270, which will in turn improve traffic flow through the area. This project is adjacent to a significant industrial area in the southwest region of St. Louis County, so these capacity improvements will be beneficial to freight movement in the region.”
A combination of federal (80 percent) and state (20 percent) funds are being used for this $51.1 million project, which also calls for the construction of a shared-use path across the Meramec River.
“Through the community engagement process, MoDOT received a number of requests to include bicycle and pedestrian accommodations in the project. MoDOT partnered with the Great Rivers Greenway, a local public agency focused on building a trail network in the St. Louis region, to include a multi-use bridge in the project,” Grana says.
The 12-foot-wide pedestrian pathway will share the same substructure as the new westbound I-44 bridge, but will be located on a separate superstructure. This design will help to protect those accessing areas such as the existing Meramec Greenway, Emmenegger Nature Park, Powder Valley Conservation Nature Center, and Possum Woods Conservation Area.
Grana adds, “There will be a 10-foot gap between the two superstructures to accommodate future inspections of the structures as well as provide a buffer between the interstate traffic and bicyclists and pedestrians. MoDOT is continuing to work with Great Rivers Greenway and other municipalities in developing plans for the connections from the multi-use bridge to adjacent trails and local streets.”
Upgrading the I-44 Meramec River Bridges
Project activities kicked off in June 2018 with crews working to construct the new westbound I-44 bridge, located between the existing westbound and eastbound Meramec River crossings. After completion of the replacement structure this summer, eastbound traffic will be shifted onto it, allowing for workers to begin demolishing the old eastbound I-44 bridge.
Beginning this September, the contractor will turn its attention to the replacement eastbound bridge, which will be erected in the same location as its predecessor. It will take approximately one year to build, after which crews will shift eastbound traffic onto it and move westbound traffic onto the new westbound bridge.
During these traffic shifts, drivers will still be able to access I-44 from Watson Road (Highway 366), as well as from northbound and southbound I-270. Drivers also will be able to access the Soccer Park exit from westbound I-44 during construction activities.
Project plans call for the demolition of both existing I-44 bridges, which were originally constructed between the 1950s and 1970s. These aging composite steel-plate girder structures suffer from deteriorating conditions ranging from cracked steel connections and rusting girders to crumbling concrete foundations.
The 1,108-foot-long replacement bridges will each contain nine spans and feature a more resilient composite prestressed concrete design. MoDOT elected to use NU-type girders weighing over 96,000 pounds each. These 112-foot-long girders are designed with 4-foot-wide flanges and 4.5-foot-high webs. The project team is installing land piers supported by 12-foot-by-53-foot H-piles and drilling 5.5-foot-diameter shafts for river piers ranging in length from 13 to 57 feet.
Crews will also slightly raise the bridges and I-44 to just west of the Soccer Park exit. According to MoDOT officials, the profile grade is being raised approximately 4 feet higher than the previous structures to comply with the U.S. Army Corps of Engineers’ 100-year flood elevation standards. The Meramec River – a key tributary to the mighty Mississippi River – is one of the Midwest’s top-ranked watersheds. Since 2015, the Meramec River Basin has experienced several record-breaking flood events that have significantly impacted communities in Jefferson, Franklin and St. Louis counties.
Interchange Improvements Boost Operational Efficiency
The Meramec River bridges are positioned half a mile from I-270, with existing ramp terminals located just 150 feet away. Due to rising traffic volumes on I-44, in 2015, MoDOT converted the shoulders of the westbound I-44 bridge into driving lanes – a temporary solution to alleviate congestion during peak times of traffic. To increase capacity at this juncture, a collector-distributor road is being added between the ramps from northbound/southbound I-270 and westbound I-44.
“The collector-distributor road will also include exiting traffic from westbound I-44 to the Soccer Park exit that is just west of the river,” Grana adds. “This will move the merge point of the I-270 ramps to west of the river and the Soccer Park exit, thus improving capacity and safety.”
On eastbound I-44, a new auxiliary lane will be added for traffic exiting to I-270, increasing interchange capacity even further. MoDOT is also improving the ramps between eastbound I-44 and I-270 to make the curves a little easier to navigate.
Both of the existing Watson Road bridges were built in 1962. Last month, crews began erecting the new two-span westbound structure, which will be 302 feet long and feature a composite steel-plate girder design. With its 56-degree skew, it will have a clearance of 16.5 feet (as opposed to the previous 14.6 feet) to accommodate I-44 traffic. Work on this bridge will continue through October.
The eastbound bridge – a composite prestressed concrete NU-girder design – will be constructed next year, between May and August. The single-span structure will extend 148 feet and have a 60-degree skew and 16.7-foot clearance – a 2-foot increase compared to its predecessor.
Obstacles and Solutions
This three-year project will achieve substantial completion in late 2021. This is several years ahead of the original construction schedule, as project funding became available earlier than anticipated. Consequently, one of the biggest obstacles on this design-bid-build effort involved an accelerated design time frame.
To meet the letting schedule, designers from both MoDOT and Jacobs Engineering Group collaborated biweekly to fast track their decision-making processes – a major benefit on pressing issues such as roadway design and environmental clearances.
Another project hurdle involves traffic control and construction staging. According to Grana, various creative solutions have been devised thanks to the seasoned experience and proactive teamwork demonstrated by both MoDOT and KCI Construction. For example, the new roadway is designed to eliminate temporary pavement, which minimizes the need for staged construction and decreases the overall time schedule.
Furthermore, along both I-44 and I-270, the project team has deployed a series of changeable message boards that deliver real-time status updates on traffic flow and construction events. This type of intelligent transportation system (ITS) uses sensors and other components in the field to collect vital data such as traffic volumes and speeds. In addition to providing alternative routes to travelers, transportation agencies like MoDOT can use this intel to better monitor and manage traffic flow, reduce congestion, improve transit operations, enhance construction productivity – and even save lives.