A mayfly study conducted last year on a Susquehanna River bridge connecting the boroughs of Columbia in Lancaster County and Wrightsville in York County has resulted in something rare in highway and bridge construction – a scientific research paper.
Last year's study on the 1.26-mile Route 462 Veterans Memorial Bridge (Columbia-Wrightsville Bridge) was initiated to help designers of a major bridge rehabilitation project pinpoint potential solutions to eliminate or reduce swarms of mayflies on the bridge. Mayfly swarms have been so intense in recent years local municipalities have been forced to turn off the bridge lights during the summer when mayflies were hatching on the river.
"It was like a blizzard effect," said District 8 Senior Design Project Manager Mark Malhenzie. "It was nature at its weirdest."
Even without the mayfly swarms, the bridge and the proposed improvements to it are unique. Opened September 30, 1930, the multiple span, reinforced concrete arch bridge is an engineering landmark listed on the National Register of Historic Places. The proposed rehab project includes intersection improvements at both ends of the bridge and enhanced pedestrian and bicycle connectivity to local parks and trails.
"Both the bridge and the project are unique. The bridge is the world's largest concrete arch span bridge, which is amazing in itself," Mark said. "It connects two historic towns, the bike and pedestrian stuff – it just has a lot of interesting pieces. The mayflies are just one more thing that makes it unusual."
The mayfly issue came to the fore during the summer of 2015 after replica period lighting was installed on the bridge. Mayflies attracted to the lighting swarmed the bridge like an ancient plague, resulting in slippery conditions and poor visibility.This resulted in several vehicle crashes and the temporary closing of the bridge to traffic. Mayflies lay in piles on the bridge and locals said they smelled like rotting fish.
Shutting off the bridge lights during mayfly season helped reduce swarms, but also limited visibility for motorists and pedestrians on the bridge. It clearly was not an ideal solution.
"When they shut off the lights, it's dark," said Mark Malhenzie. "You can't even see your hand in front of your face. It is pitch black."
"Pedestrians were literally walking across the bridge in shear darkness," said Brad Burford, a member of the district Environmental Unit who served on the study team due to his expertise with aquatic insects.
Fast forward to the summer of 2020. District 8 launched the study with the idea of identifying mitigation measures that could be incorporated into the rehabilitation project. This included the potential use of shielding, different colors or intensities of lights and installing lights under the bridge to keep the mayflies where they were supposed to be (under the bridge).
"This was a unique opportunity because we'd be working on the bridge and under the bridge," Mark said. "If we were going to put lights under the bridge, that would be the time to do it."
PennDOT staff discovered the firm previously involved with the period bridge lighting – Brinjac Lighting Studio – and brought them on board as a subcontractor to consulting firm RK&K due to their familiarity with the bridge lighting. It was soon discovered during discussions that Shawn Good of Brinjac was an adjunct faculty at Penn State University. It was Shawn who suggested a research team from the university analyze data collected from the study for a scientific paper. The PennDOT team agreed with the caveat that the paper made no recommendations – those would be laid out in the department's internal documents.
The team was comprised of Mark Malhenzie, Brad Burford, Jeremy Ammerman from the district Environmental Unit, and design consultant engineering firm RK&K of Philadelphia.
"The whole scientific research paper connection fell into our lap by accident," Brad said. "It just came up in discussions. Shawn (Good) suggested doing a bridge lighting scientific paper. It was an extra bonus."
The field work was performed by Brinjac with assistance from the PennDOT team. The Penn State researchers developed a scientific paper that presented the results of the field work. The team reviewed the paper and offered some tweaks to it before it was published in the university's online scientific journal "Energies".
Titled "The Effect of Electric Bridge Lighting at Night on Mayfly Activity," the paper goes where no researcher has gone before in analyzing how mayflies are attracted to bridge lighting.
According to Brad Burford, this research could set the bar for how bridge lighting designers approach their work in the future. And while the mayfly swarms created a hazard on the bridge, the presence of them is indicative of good water quality and a healthy ecosystem, he said.
The project is currently is heading to final design, and work is anticipated to take place between the 2023 and 2027 construction seasons.