- Pennsylvania Department of Transportation
- Clearwater Construction, Dawood Engineering, CHRS Inc.
- Chester County, Pennsylvania
- Our Role
- Preliminary Engineering, Final Design.
- 315-foot bridge, 1,700-foot roadway
- Construction Cost
- $8.8 million
- New Construction
- 5 years
- Mobility maintained during heavy storms for 13,200 daily motorists
- Occurrences of bridge flooding reduced by an estimated 95 percent
- Duration of bridge floods decreased by an estimated 80 percent
- Road realignment protects nearby historic buildings from traffic impacts.
The Route 926 bridge spans the Brandywine Creek northwest of Chadds Ford, Pennsylvania. Since its construction in 1937, the crossing flooded up to nine times each year because of low approaches. As a result, drivers converged onto the nearby substandard Route 52 bridge, where traffic narrowed to gridlock, adding as much as three hours to a trip. The congestion severely restricted emergency access to the area’s only hospital and made transporting approximately 2,000 students across the creek to attend school nearly impossible.
To improve mobility during heavy storms and divert traffic from bottlenecked Route 52, the Pennsylvania Department of Transportation (PennDOT) replaced the deficient Route 926 bridge. Gannett Fleming provided preliminary engineering and final design for the replacement. Our firm’s work included rebuilding and raising 1,700 feet of the roadway approaches to make them less susceptible to flooding, replacing the undersized culvert over Radley Run with twin 48-foot-span culverts, and realigning 800 feet of Creek Road to connect with Route 926. The completed project presents a new reality for 13,200 drivers every day, eliminating flooding and maintaining mobility in the region.
The team’s complex solution is designed to withstand a 100-year-storm event and was built without impacting historic properties that flank the structure, including the Brandywine Battlefield National Historic Landmark. The project spans two Federal Emergency Management Agency (FEMA) flood zones, which demanded separate, complex requirements to perform the hydraulic analysis. The Route 926 crossing and the culverts over Radley Run feature stone form liners covering the piers to integrate seamlessly into the community.
The team implemented a financial incentive/disincentive contract provision to complete construction a full year ahead of the original 18-month schedule. Working six-day work weeks, 10 hours a day, the contractor completed construction within six months. The contracting provision is rarely used in PennDOT, District 6-0 because of the demands it can place on a project team. This project sets a positive example of its use to rehabilitate a flood-prone structure quickly and improve safety and mobility.
- Route 926 bridge replacement widens the creek crossing by 12 feet, increasing traffic mobility
- Approaches to bridge rebuilt and raised 8 feet to prevent recurring flooding
- 4-by-6-foot culvert over Radley Run replaced with two 48-foot culverts to handle 25-year-storm events.
- Higher bridge parapets enable use by pedestrians and cyclists, encouraging sustainable forms of transportation
- New quarter-acre mitigation wetland with native plantings alleviates environmental impacts of construction
- Standard slopes with seeding around the wetland instead of retaining walls and split rail fences enhance natural surroundings.
- Outstanding Medium Span Bridge, 2019, Association for Bridge Construction and Design (ABCD) Susquehanna Chapter
- Outstanding Project Award, 2019, Delaware County Chapter of the Pennsylvania Society of Professional Engineers (Delco PSPE)
- Project of the Year, 2017, American Society of Highway Engineers (ASHE) Delaware Valley Section