Although other bridge designs were considered, the team chose to go with the steel plate girder spans because it was the right solution for both construction and long-term maintenance of the bridge, says Jason Fuller, vice president and senior project manager at HDR.

Photo courtesy of HDR

“In a design-build atmosphere, the [steel plate girder] was the economical solution,” he says. “It was also the best solution for the service life of the project and the least complex. In the future, it makes things a lot easier for the owner to maintain. It’s a more typical structure and it gives the owner a better long-term product.”

To create a record-breaking structure with a 100-year service life, the team overcame significant challenges, including crossing a navigable channel; maintaining traffic on both the roadway and railway; mitigating a hazardous material site; blasting rock on a slope near traffic; coordinating agencies, stakeholders and the public; and scope changes during construction.

After choosing the structure type, the team prioritized long-lead items. The haunched design eased fabrication, shipping and erection, while accommodating navigational clearances. Standard K-frames connect the diagonal members to the gusset plates, which eased shipping and lifting.

Photo courtesy of HDR

The project’s non-traditional erection methods required sequencing analysis to verify the girders’ adequateness. The team identified site constraints and erection steps early, including temporary navigation clearance windows, eliminating falsework over the river; the load imposed by the strand-jack on the back spans and their impact on girder plate size; and the railroad and state route’s impacts on falsework and span lengths.

While the bridge uses standard, straight steel I-girders with square supports and standard cross frames, they are scaled up. The American Association of State Highway and Transportation Officials Bridge Design Specifications line girder method for live load distribution on beam-slab bridges was only applicable up to 240 feet, though used for spans greater than 300 feet. The I-64 main span nearly doubles the allowable length — 562 feet, with a span-to-width ratio near 10.

Unique structural analyses and nontraditional construction methods were essential to deliver the one-of-a-kind crossing, which posed unusual marine design and construction issues. While the reuse of existing piers minimized permanent channel changes, the river’s significant barge traffic precluded connecting them with temporary falsework. Collaboration with the U.S. Coast Guard and other agencies set limits for temporary navigational channels and permitted the permanent navigational envelope. Standard K-frames connect diagonal members to the gusset plates, which also eased shipping and lifting.

Photo courtesy of HDR

During construction, an unknown utility line along one side of the project footprint was determined to be part of a hazardous waste site drainage mitigation system. Because the line could not be relocated, the team incorporated an additional “jump span” to the design, helping keep the project on schedule.

To maintain two lanes of traffic in each direction throughout construction, the team shrunk lane widths to 11 feet and utilized shoulders as needed. The team also kept a railway and state road beneath the western backspans open throughout construction. Rock blasting on a slope adjacent to the highway required extensive coordination with emergency responders, area political representatives, and police and fire departments.

Throughout the project, the team reused and recycled materials whenever possible. Repurposing the bridge piers helped avoid the roadway, railroad, riverbanks and approach fill slopes, while maintaining the navigational envelope and eliminating permanent river impacts. The team also recycled roadway and deck concrete as fill material in the bridge approaches. The existing drainage system was reused to the maximum extent possible, verifying its hydraulic capacity and removing corrugated metal pipe to reduce future maintenance.

The team also repurposed all soil on-site and used the USEPA’s green remediation practices to reduce demands on the environment during cleanup actions. The approach avoided collateral environmental damage and built on environmentally conscious practices already in place, such as conserving water, improving water quality, increasing energy efficiency, managing and minimizing toxics and waste, and reducing emissions. The soil management plan, in particular, addressed dioxin impacts to soils managed throughout the project lifespan.

Hazardous materials were a constant concern. On the bridge’s west approach, the team made significant rock cuts into the hillside to allow its northern realignment. To the east, a hazardous material site surrounded both sides of the approach. To minimize impacts in these areas, the team’s design shallowed the river structure’s depth as much as possible, while providing the best geometric profile to connect to approaches. The horizontal alignment provided the most efficient solution and turned to long walls to account for height increases. This approach kept the toe of the fill in the same place. A 30-in underdrain system at the toe minimized impacts to the existing hazardous waste site. These solutions kept the project in the right-of-way and eliminate encroachments into the adjacent hazardous areas.

Within the project limits, the Kanawha riverbed was contaminated, which prevented disturbing or removing bed material. The team implemented a clean rock causeway with a geotextile lining between the riverbed and fill material. The strategy limited fines from lifting through the rock, prevented the rock from settling and eased its removal at construction completion.

Completed at budget and ahead of schedule, the one-time interstate chokepoint now accommodates one of West Virginia’s most heavily traveled highway sections, and provides capacity for continued growth in volume.