In Fairfax County, Va., a bridge replacement that might have required months of road closures was transformed by Accelerated Bridge Construction (ABC) methods. By modularizing the bridge and building all the components offsite, the project team limited the road closure for local residents to just 14 days—setting a new standard for rapid, resilient bridge replacement in constrained environments while minimizing disruption to the community.

The Walker Road Bridge over Piney Run, originally built in 1932 as a single-lane timber structure, served the once rural landscape of Fairfax County for decades. Over time, the bridge has faced frequent flooding and weight restrictions, impacting emergency vehicle access and daily connectivity — making its replacement a priority for the Virginia Department of Transportation (VDOT).

As a trusted partner to VDOT, HNTB collaborated closely to develop and deliver an innovative modular design solution tailored to the unique needs of the project.

Why Accelerated Bridge Construction?

Rapid replacement of the Walker Road Bridge was essential due to several key considerations. The existing structure served as a vital link for the local community, supporting daily travel and emergency services. However, limited site access, a short construction window and the need to minimize right-of-way impacts made traditional construction methods impractical. Additionally, frequent flooding and restricted access underscored the urgency for a resilient solution that could be delivered quickly.

An ABC delivery approach provided distinct advantages:

• Minimized disruption: Offsite fabrication of modular substructure and superstructure elements reduced road closure time and limited impacts on residents and emergency services.
• Adaptability to site constraints: With constrained site access, compact precast elements were ideal for installation with standard equipment.
• Enhanced resilience: Reinforced approaches and riprap armoring improved the bridge’s ability to withstand overtopping events, ensuring long-term durability.

To address these unique site constraints and project requirements, HNTB developed a modular design for VDOT using prefabricated concrete elements for both the bridge substructure and superstructure. The new bridge is nearly 52 feet long and 40 feet wide — substantially larger than the former, single-lane timber bridge. By providing a much larger opening while raising the roadway profile only slightly, the design increases water flow capacity while limiting impacts to the surrounding right-of-way.

Compact precast components were optimized for transport and installation using standard equipment, demonstrating constructability-focused engineering. The integration of precast substructure panels with embedded steel piles and ultra-high-performance concrete joints created a continuous, scour-resistant system.

An Improved Approach for Bridge Replacements

The new Walker Road Bridge stands as a benchmark for rapid bridge replacement in constrained environments, prioritizing community needs and setting a new standard for future projects in Fairfax County and beyond.