Timing the city's fall comprehensive street sweep and leaf cleanup is something of an inexact science. Start too early, and the trucks go through before many of the leaves have fallen -- as many have complained is happening this year. Start too late, and the snow and ice hit before workers can clean all the streets, leaving a frozen, slippery mess.
"Go back 30 years when this was a city of elms, the leaves all dropped at the same time," said Mike Kennedy, director of field services for Public Works. "As we have dealt with the Dutch Elm Disease, and reforested by planting a wide variety of trees, they drop their leaves at different times and different rates. It has definitely stretched out the leaf drop for us."
The city's leaf sweep started Oct. 24 and had an estimated cost of $1 million, he said. The city had five crews, roughly a dozen workers each, driving flushers, front-end loaders, dump trucks and sweepers. With those resources, it takes 17 days to make one pass through each street, avenue and boulevard, covering roughly 1,000 miles of roadways.
"We always seem to get accused -- or get second-guessed -- at the beginning of the sweep, [people say] 'you're starting too early and the leaves are falling behind you,'" Kennedy said. "We kind of know that. If we get a snow storm before we can finish, then people second-guess and say, 'Gee, you didn't start soon enough and my street didn't get swept.' It's a dicey call."
Mike Zins, an extension horticulturalist at the University of Minnesota's landscape arboretum, said the leaf drop this year was not unusually late. A number of species like silver maple, Siberian elms, oaks and buckthorn tend to keep their leaves late.
Some "will freeze and fall off in December," he said.
The city tries to move the sweeping routes around annually, so the same streets are not always first, and the same ones are not always last, Kennedy said.
Leaves left in the street cause problems, he said. They degrade water quality by adding algae-blooming nutrients to storm- water runoff. They make the streets slick for drivers. They wash into gutters and may plug storm drains.
Kennedy said anything residents can do to help remove and bag leaves from the street is greatly appreciated. "We can use all the help we can get," he said.