Chicago’s seeing fewer bridge lifts. Here’s why.

It’s bridge-lifting season in Chicago — time for one of the few downtown traffic holdups that can inspire a little wonder, instead of aggravation.

Every spring and fall, bridges along the Chicago River downtown are raised to allow sailboats to pass. In the autumn, the boats head to winter storage along the river’s South Branch; in the spring, they go back toward Lake Michigan.

In decades past, the Chicago River was a regular passageway for commercial shipping, and bridges needed to be lifted often to accommodate the traffic. But declining use of the river by industry, a change in federal regulations and the migration of more sailboats to yards along the Calumet River mean the need for raising downtown bridges has decreased.

So if you want to increase your chances of seeing bridges go up and down, or viewing bridge machinery from beneath the street, you need to plan.

“It is an event. … People do stop and watch because it is pretty amazing when the bridges open,” said Patrick McBriarty, author of the illustrated history “Chicago River Bridges.”

Autumn lifts happen most Saturdays and Wednesdays through mid-November, starting around 9 a.m., with 27 bridges being raised one at a time, going west from Lake Shore Drive to Ashland Avenue. In the spring, the procession of opening bridges goes east.

To see the machinery working up close, there is limited availability to view a lift from under the street this Wednesday morning and on the morning of Nov. 3 at the McCormick Bridgehouse and Chicago River Museum at Michigan Avenue and the river. You can make a reservation for $15 by calling 312-977-0227 or emailing jcoles@chicagoriver.org.

If you do not get a spot during a lift, the museum is still a fun way to learn about the river and the bridge system. The museum is open through Oct. 31.

“Getting Around” recently got to go into the bridge house and watch a lift, and it was like being inside a giant’s pocket watch. The process starts with the humming of a small, gray motor with the horsepower of a 1950s Volkswagen Beetle. The bridge, built in 1920, is so well-balanced that it does not need a lot of power to work, said Joshua Coles, director of the Chicago River Museum.

Big, yellow-toothed wheels begin to turn, and Michigan Avenue’s bascule bridge tilts up by means of a counterweight and a rack-and-pinion system that pulls up the street to clear the way for tall boats. The term “bascule” is French for seesaw, so it helps to visualize a playground seesaw to understand the way the bridge works. The 12,000-ton counterweight goes down 40 feet as the roadway lifts.

There are a total of 60 moveable bridges in Chicago, more than any place else in North America, though not all are active, McBriarty said. Of Chicago’s moveable bridges, 48 are bascule, while the rest are lift or swing bridges, he said.

Under federal law, the city has to maintain the Chicago River as a navigable waterway. Before 1995, the city’s Transportation Department had to have enough staff to be able to open 32 of the 37 movable bridges with advance notice of 30 minutes at all times. Sailboats could request bridge lifts at any time.

Beginning in 1995, the U.S. Coast Guard’s regulations were revised and the city worked with local boatyards to create the current schedule of lifts, Chicago Department of Transportation spokesman Michael Claffey said. Each Wednesday boat run costs the city about $11,000, while each Saturday run costs about $14,000 due to weekend overtime costs. It takes a crew of about 30 workers to conduct the runs.

If no boat owners make arrangements to move their boats on a scheduled day, the bridges will not be lifted.

The city is about to lose two of its bascule bridges since it plans to replace the deteriorating spans at Chicago Avenue and Division Street with less expensive fixed bridges. Federal law no longer requires moveable bridges on the North Branch of the river, McBriarty said.

“It used to have to be navigable all the way up to Belmont Avenue,” he said.

Along with fewer lifts, there are fewer sailboats on the main stem of the Chicago River because Crowley’s Yacht Yard moved from the South Branch to a spot on East 95th Street on the Calumet River in 2005. Owner Grant Crowley said boats destined for his yard had represented up to two-thirds of the traffic along the main branch of the Chicago River.

Crowley said it is just as well that there are fewer sailboats on the Chicago River, since there is much more recreational traffic than there used to be with tour boats, motorboats and kayaks. He noted that the river is much less polluted than when his yard started in 1978 and more suited for recreation.

“There are all these new uses, which are doing great things for Chicago,” said Crowley, who is on the Friends of the Chicago River board.