The Pennsylvania Department of Transportation announced Friday it has launched a study to investigate why mayflies are attracted to the lighting fixtures on the Veterans Memorial Bridge, which carries Route 462 across the Susquehanna River from Columbia in Lancaster County to Wrightsville in York County.
The goal of the study is to identify potential changes to the lighting that could be made in conjunction with a future bridge rehabilitation project, PennDOT said.
The bridge lighting was replaced in 2014 with historic reproduction lanterns. This had the unforeseen effect of attracting swarms of mayflies to the top of the bridge, PennDOT said.
As a result, bridge lighting is turned off during the annual mayfly season to avoid the swarming and the problems that have arisen from it.
This study, in partnership with the Columbia and Wrightsville municipalities, aims to determine why mayflies are attracted to the bridge’s lights with the ultimate goal of devising a solution that may reduce the number of mayflies on the bridge, according to PennDOT.
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Potential solutions may include making minor changes to the lighting and/or adding lighting under the bridge, PennDOT said.
The City of Harrisburg is also a cooperative partner in the study by allowing the Market Street Bridge’s under bridge lighting colors to be varied as part of the testing to determine its attractiveness or deterrence on mayflies, according to PennDOT.
Tests involve leaving the majority of lights turned off on the bridge, while three evenly-spaced groupings of lights, each consisting of four light fixtures, will remain on. The illuminated fixtures will have different colors or shades of light; and for part of the testing may be shielded to partially block the light in certain directions, PennDOT said.
Additionally, floodlight fixtures will be suspended from the edge of the bridge at select locations, to shine light underneath the bridge. Independent researchers, as part of the broader team, will analyze the collected data and develop recommendations, according to PennDOT.
PennDOT said the testing is scheduled for the following timeline, depending on weather:
- Contractor to temporarily modify light fixtures: June 8-9, 2020
- Data collection of lighting and mayfly interaction: June 10-24, 2020
- Contractor to return light fixtures to original set up: June 25-26, 2020
An electrical contractor will perform the lighting modifications during the day-time hours, PennDOT said. Motorists may experience minor delays while the work is being performed.
Pedestrians should use caution along the sidewalk when passing the contractor’s vehicle, PennDOT added.
Message boards placed on each end of the bridge on the nights of testing will also alert motorists and pedestrians, according to PennDOT.
Depending on weather and the level of mayfly activity, testing is anticipated to last up to three nights during the two-week data collection period. Workers will be on site at various times during these night-time tests to observe mayfly interaction with the lights, record light level readings, and take photographs, PennDOT said.
Motorists are advised to slow down and use extra caution during the testing events for their own safety and for that of PennDOT’s workers.
