#906:Ground currents force closure of pedestrian bridge
The following article I find particularly interesting as a local Hobart school, located near transmission lines and with a substation in the basement had to close down its swimming pool because people were receiving shocks when entering the water.
Don
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From Joanne Mueller:
Elm Creek Park bike-pedestrian bridge closed due to close proximity to high voltage powerlines
STAR TRIBUNE.COM – MINNEAPOLIS/ST. PAUL, MINNESOTA
Medicine Lake trail bridge is, uh, shocking
Literally. Bicyclists have reported electrical shocks crossing the Maple Grove bridge. MnDOT says no one is in danger.
By RODRIGO ZAMITH, Star Tribune
Last update: July 3, 2008 – 11:35 PM
Shocked by the new bridge on the Medicine Lake Regional Trail?
Some bikers were, causing the Minnesota Department of Transportation to shut down the bridge leading into Elm Creek Park Reserve over County Road 81 in Maple Grove.
The bridge, which opened last fall, is expected to re-open next week with additional grounding support to prevent shocks. It was closed on June 16 after a handful of complaints.
“It felt like insects fluffed my bicycle shorts,” said Kris Siejko, a cyclist who has experienced the shock numerous times.
According to MnDOT spokesman Kent Barnard, nobody on the biker and pedestrian bridge was in danger at any point and that the shocks only caused discomfort.
Barnard said the shocks appear to be connected with nearby power lines, although both the bridge and the power lines were all built within specifications.
“We are operating under the assumption that part of what is happening is that people themselves are getting charged as they are traveling underneath [the power lines] and they are discharging to the bike and rail,” Xcel Energy engineer Benjamin Gallay said. “There’s nothing significant we can do to stop that other than telling people, ‘No, you can’t walk there.’ ”
Gallay said that even with additional grounding, riders may still feel a bit of the sensation.
Siejko, an electrical engineer at Boston Scientific, said it felt like a current ran through his bicycle seat every time he went underneath the power lines on the bridge. “Eventually I just started riding standing up,” he said.
Barnard said the department has dealt with similar issues before, and that if additional work on the bridge is necessary, they will look into it.
He also said MnDOT will pick up the tab for the project, and though no cost figures are available, “we are not looking at it costing much money.”
Three Rivers Park District spokesman Tom Knisely said his office has received three complaints about people getting shocked. The first complaint came in early April, another came in mid-May and by Siejko’s complaint in early June, the park system sent a specialist to have a look.
After complaints were confirmed on June 13, the park notified MnDOT and re-routed traffic to a nearby crossing. MnDOT officially closed the bridge three days later.
One complainant said he felt “a zap in his left leg.” Another said “a current tingles my fingers” every time he crossed under the high lines on the south side of the bridge.
Barnard said work was done via a partnership among MnDOT, Three Rivers Park District and Xcel Energy.
Detour signs are now in place advising trail users to cross at the controlled intersection at Fernbrook Lane.
Rodrigo Zamith “¢ 612-673-4895
http://www.startribune.com/local/west/22923059.html?page=1&c=y
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