CHICAGO (CBS) — The heavy rain from Sunday’s storms overwhelmed a stormwater system in south suburban Calumet City, causing an explosion in a sewer that’s part of the Deep Tunnel system, and leaving a massive crater.
The storms also caused flooding on many streets, knocked out power to thousands of ComEd customers, and forced airlines to cancel more than 100 flights.
Severe thunderstorms swept through the Chicago area Sunday afternoon and evening. At one point, the storms dumped more than an inch of rain in only 20 minutes.
The heavy rainfall proved too much for a part of the massive Deep Tunnel stormwater system in Calumet City. Rain falling at a rate of up to 2 inches per hour built up so much pressure in a sewer tunnel, it caused a “hydraulic explosion” that blew off a concrete slab and manhole cover buried underground at 1560 Burnham Av., according to Metropolitan Water Reclamation District executive director David St. Pierre.
“Water is coming in at tremendous pace. That water builds up that air pressure,” he said. “Water is displacing air, so you have a combination of hydraulic water pressure and air pressure, and that force is extremely powerful.”
Neighbors said they heard the explosion, and when they looked out of their windows, they saw a geyser gushing from the massive hole in the ground.
“I heard this big roaring sound. It got louder and louder like a jet. Then I looked out patio window and suddenly it exploded over telephone wire, water gushing, unreal,” Debbie Pawlak said.
Other neighbors said the water gushed higher than the telephone wires.
“It sounded like a bomb. And then all this water just came flying at you, and it was carrying everything heavy out of its way,” Sharon Krueger said.
Large rocks and debris sprayed everywhere; initially floating in standing water. However, no homes were damaged, and no one was injured.
Residents said it’s the third time something like this has happened in the past four years. Last year, debris from the explosion damaged cars in a nearby parking lot.
St. Pierre said engineers thought they fixed the problem. The district installed vents after a similar, but less intense, problem last year.
“We put in some restrictors in the past that help restrict that pressure, so that it bleeds off. We put in some vents so that air can escape,” he said. “Obviously, we’re going to have to do some more investigation and calculations and see what we can do this time.”
Monday morning, crews were working to fill the hole, and trying to figure out why the tunnel has not been venting properly. Next year, the MWRD will open a new reservoir that should stabilize the pressure and solve the problem.
After the storms swept through the area, nearly 9,000 ComEd customers in the west, southwest and south suburbs were left without power, according to ComEd. The majority of outages were reported near Harvey in Blue Island, where more than 6,300 customers were without power Sunday night.
Airlines at O’Hare International Airport canceled more than 130 flights Sunday afternoon and evening as a result of the storms. Airlines at Midway International Airport also canceled a “minor” number of flights, according to the city’s Aviation Department.
The heavy rain also left many streets flooded in the Chicago area.
In southwest suburban Bridgeview, pumps worked throughout the night to clear flooded streets. Rain fell so quickly, storm drains simply could not keep up.
In Palos Heights, a pickup truck got stuck in muddy water near 135th and Harlem. The front wheels and most of the engine became completely submerged after the truck apparently drove off the side of the road.
In Hammond, Ind., firefighters rescued a family from a Jeep SUV that got stuck in floodwater. Emergency crews used a raft to bring the children and parents to safety.
A Joliet motel also was damaged during the storms. The roof collapsed at the Best Budget Inn of Joliet, and crews were tearing down what was left of the building.
One motel guest was struck by flying debris, but did not need to go to the hospital.