Zapped critters cause 17% of PUD outages
The culprit turned out to be a furry, four-legged creature with sharp teeth, a bushy tail and a taste for seeds and nuts. The apparently curious squirrel, likely an Eastern gray, became an electrical conductor when it squeezed into some equipment. The rodent was zapped into oblivion, likely by 7,200 volts of electricity.
Each year, squirrels, birds and other wildlife account for about 17 percent — or 270 — of the nearly 1,600 power outages reported to the Snohomish County Public Utility District. In comparison, car crashes account for about 4 percent, or roughly 60 outages a year. Downed trees and limbs cause about one-third of the disruptions in service.
Outages caused by wildlife generally don't last as long as when equipment is damaged by downed tree or power poles are knocked over by a car. A wildlife-caused outage may mean just locating the unfortunate animal and removing it from the equipment.
Since 2001, the public utility has spent about $487,000 on wildlife protection, spokesman Neil Neroutsos said.
It's critical to address conflicts with wildlife, obviously to protect the animals and birds but also because the district doesn't want the system vulnerable to outages, said Christoph Enderlein, PUD's manager of environmental affairs.
“Whether it's a squirrel or a bird, it's very unfortunate for the wildlife and an undesired outcome. We absolutely care because it also shows a vulnerability to the reliability of the system,” Enderlein said.
Snohomish County PUD serves 327,000 customers and maintains about 115,000 poles, tens of thousands of transformers and 90 substations.
Back in 2001, the PUD hired a consultant to look for better ways to protect birds from electrical equipment.
Birds fly near charged lines, perch on equipment and even nest on top of structures.
Some birds, particularly those with large wingspans, are not only vulnerable to collisions with power lines but also electrocution.
Significant work has been done in the Silvana and Warm Beach area where there are flocks of trumpeter swans and snow geese, Neroutsos said.
The district has installed longer cross arms on some power poles so perched birds are less likely to make contact between two energized lines — completing a circuit — with their outstretched wings. The PUD also added visual clues to lines to provide birds more advanced warning when they are flying in areas where there are power lines. That is particularly important in areas where large flocks are common and the birds in the back are relying on those in the front to avoid danger.
PUD investigates all bird-related injuries and deaths involving the district equipment, said Rob Larson, distribution services manager. Additionally all the incidents are reported to US Fish and Wildlife Service, he said.
Birds aren't the only creatures that have been on PUD's radar.
The district has tried to cut down on high-voltage encounters between squirrels and PUD equipment. Primarily that has meant installing bushing caps on transformers on power poles. The covers prevent squirrels from touching two lines at once.
Power outages involving squirrels are reported throughout the country, said John L. Koprowski, a wildlife conservation and management professor at the University of Arizona in Tucson. He has been studying tree and ground squirrels for about 30 years.
Squirrels were blamed for power outages that shut down the NASDAQ, twice, according to news reports.
The most common types of squirrels seen in Washington state cities and suburbs are Eastern gray squirrels. They are not native to the area and were brought over from the eastern half of the country in the early 1900s. The larger Western gray squirrel is native to the area and is classified as a threatened species and can't be trapped, hunted or killed.
The Eastern gray is up to two feet long, including the tail.
Squirrels use power lines as a highway. The tree squirrel will see a power pole as a “tree with very few branches that's nice and straight,” Koprowski said.
Tree squirrels prefer to travel above ground to avoid predators. In the cities, those are neighborhood dogs and cats. In the wild, it's bobcats and coyotes. The squirrels also nest in trees and eat out of them.
It's no wonder that they are drawn to power poles and lines, Koprowski said.
“They essentially mimic their habitat,” he said. “They're look for the same kinds of things that they find in trees, insects, seeds, and nest-building material.”
They've been known to nest in the transformers on poles. Their nests are generally the size of basketballs and are usually made from woven pine needles, small branches and leaves.
They'll build a nest anywhere, including inside the walls of houses and the rotting parts of trees. That cavernous environment may be what attracts them to explore transformers.
Substations have their own allure. What looks barren to people may be attractive to the rodents looking for cover and protection provided by the complex metal structure.
Also, the squirrels may be taking advantage of substation cooling fans.
“They're fur-covered rodents with a high metabolic rate,” Koprowski said.
They'll look for shade or a cool breeze and flop down on their bellies, spread-eagle, with the tail curled up toward their backs. A group of blood vessels at the base of their tails helps release heat.
The fans might also attract the squirrels because of the accumulations of bugs. Insects get sucked into the fans and “squirrels will eat protein any way they can get it,” Koprowski said.
A squirrel's natural instinct to gnaw also can get the rodent in trouble. A squirrel's four front teeth continue to grow. Gnawing helps keep the teeth sharp and a manageable length, and of course, it helps the squirrel find food and nest-making materials.
PUD officials say they don't really have a problem with squirrels gnawing on equipment. However, in other parts of the country, squirrels have been electrocuted chewing through insulation on wires.
“We have these conflicts when we move into their habitat and build structures that mimic their habitat,” Koprowski said.
It's a win-win for humans and the wildlife if steps are taken to cut down on the conflict, he said.
Diana Hefley: 425-339-3463, firstname.lastname@example.org. Twitter: @dianahefley
Our new comment system is not supported in IE 7. Please upgrade your browser here.