The discovery of cracks in steel beams along Lake Shore Drive this week raised alarms about other problem bridges.

Two of the worst bridges in the state are along Interstate 80, crossing the Des Plaines River in Joliet, a rapidly developing area in Will County with heavy interstate truck traffic and distribution centers for companies like Amazon and Dollar Tree.

A prolonged shutdown of the bridges would be economically devastating. Joliet Mayor Bob O’Dekirk on Thursday said he is asking the city’s public safety officials to begin working with county, state and federal authorities to establish a specific plan of action in case of a partial or complete failure of the structures.

He is also pressing lawmakers for emergency funding to repair and replace the bridges. O’Dekirk warned that unless the Illinois or U.S. departments of transportation give the city a “definitive plan” for funding and repairing the bridges in the near future, he will order a diversion of vehicles away from it, warn motorists of potential dangers and advise on alternative routes.

“Do I think the bridge is going to fall in the river tomorrow, no, but these (IDOT) reports are pretty alarming,” said John Greuling, president and CEO of the Will County Center for Economic Development. “There are a lot of local folks who are concerned about this.”

IDOT said in a statement that short-term repairs for the bridges are planned for this spring, and that the bridges are safe for travel and do not need to be closed. The bridges are inspected every three months.

The bridges were built in 1965 and reconstructed in 1998. The westbound section has an overall rating of 6 out of 100, the lowest for an interstate in the Chicago area, according to Illinois Department of Transportation records. The eastbound section scores a slightly higher 7.4. Both bridges together carry 85,400 vehicles per day.

The I-80 bridges are among 400 out of 3,460 bridges in the six-county area, or about 12 percent, deemed “structurally deficient,” meaning they are in need of repair or possible replacement.

The trucking industry is concerned that the state might decide to limit weight on I-80 over the Des Plaines River, which authorities sometimes do to relieve stress on aging infrastructure, said Matt Hart, executive of the director of the Illinois Trucking Association.

If truck weights are limited more than they are now, more trucks will be needed. Hart noted this would add to the cost of carrying goods.

There are also serious problems along other I-80 bridges from I-55 to I-294, according to IDOT records. The Briggs Street bridge over I-80, for example, gets a rating of 2 out of 9 for its superstructure. A rating of 1 would result in the bridge being closed.

IDOT is planning maintenance and improvement projects for several I-80 bridges, according to spokesman Guy Tridgell. A project that will start this spring will make structural steel and bearing repairs on the bridges over the Des Plaines River at an estimated cost of $5 million. Tridgell said lane closures for the work will be temporary and overnight.

Repairs for the 54-year-old Briggs Street bridge, which sees about 13,600 vehicles daily, are planned in about five years, at a cost of $3.5 million.

Next year, the department plans to rehabilitate and/or replace eastbound I-80 bridges east of the Des Plaines River at Chicago Street, Gardner Street/BNSF Railroad, Richards Street, Hickory Creek and Rowell Avenue/CN Railroad in Will County, at a cost of $47 million, Tridgell said. Westbound bridges will be scheduled for rehabilitation or replacement within the next couple of years, Tridgell said.

Bridges are not the only problem along I-80. The stretch of interstate, built in the 1960s, is too narrow for the amount of traffic it gets, with two lanes of traffic in each direction, said Mary Craighead, transportation policy analyst at the lllinois Economic Policy Institute, a think tank whose board members represent the construction industry and labor unions. A lot of the roadway does not have shoulders, and sharp curves require slow speeds, Craighead said.

The 16-mile stretch of I-80 near Joliet witnessed 37 fatal crashes between 2001 and 2016, Craighead found.

The Chicago Metropolitan Agency for Planning called I-80 improvements “critical” in its “On to 2050” regional transportation proposal.

IDOT is finishing a multiyear study this year that will come up with a more comprehensive solution to I-80’s needs between Minooka and New Lenox, including a new Des Plaines River bridge, Tridgell said. The total price of the improvements, which would be done in phases, is expected to be more than $1 billion.

IDOT’s plan could take more than a decade to build, and Will County officials want it quicker. The Will County Center for Economic Development has formed the I-80 Coalition of government, business and labor leaders to push for “significant progress” in completing the improvements by 2023, Greuling said.

IDOT has to figure out how to pay for it, along with all the other work it needs to do. The department’s current multiyear program has $2.6 billion in bridge maintenance funding to be spent over the next six years, far less than the estimated $10 billion in present-day needed bridge repairs, according to the American Society of Civil Engineers.

Transportation agency officials and construction companies are hoping for a capital bill out of Springfield for the first time in a decade, to help pay for the backlog of needs for bridges, roads and public transit.

One financing strategy for I-80 could involve tolls, which does not sit well with the trucking association. Hart compared the tolls to a homeowner paying rent on his own house.

“We think it would be absolutely horrible to take a public roadway the public already paid for, and charge rent on it,” he said.

Another way to pay for infrastructure is an increase in the gas tax, which hasn’t been raised in Illinois since 1990. Mayor Rahm Emanuel and some suburban leaders have called for a 20- to 30-cent per gallon hike.

Adding to the problems of aging infrastructure is the changing climate, which can cause temperature extremes and flooding.

Steel beams on the Lake Shore Drive bridge cracked as a result of corrosion exacerbated by a big swing in temperature from -23 degrees to 51 between late January and early February, according to Chicago officials.

Craighead said the state may want to consider more inspections after big weather events. The Chicago Department of Transportation and IDOT are planning checks of bridges with structures similar to the Lake Shore Drive bridge.

“A lot of our roads and ridges are really old and can’t handle what our climate realities are,” Craighead said.

mwisniewski@chicagotribune.com

Twitter @marywizchicago