Even as a construction team provided hope that the flow of river water filling the city`s underground freight system could be sealed this weekend, Mayor Richard Daley delivered a message of caution and uncertainty Friday.
”While we have made steady progress, we still have a ways to go,” Daley said. ”I don`t want to create false expectations. None of us can say when this will be over.”
One of the lessons of the week-that the unprecedented engineering project to stop the underground flooding was as unpredictable as a raging river-seemed to have sunk in, tempering any optimism.
The construction effort near the site of the tunnel breach progressed as planned Friday. In the morning, cement trucks arrived with a screaming police escort to begin filling a shaft east of the Kinzie Street bridge, a process completed in a few hours.
Similar work on two branches of the tunnel west of the bridge was begun in the afternoon. Cement would be poured there Saturday at the earliest.
Describing the effort, Jerry Kenny, president of Kenny Construction Co., said that workers are essentially placing ”three corks in a three-ended bottle.” Once that is done, the flow of water through the tunnel should essentially be blocked.
But Daley cautioned that simply sealing the leak from the Chicago River into the 60-mile tunnel system was just one step in a multifaceted solution.
Even after the leak is stopped, Daley said, the pumping to rid the tunnels of water will be a ”delicate” process, one that the Army Corps of Engineers has said may take two weeks.
”This is an extremely complex and dangerous situation,” Daley said.
”My first priority is safety, both for the workers and the city of Chicago.”
The pumping of millions of gallons of water, which have spread through tunnels and into basements, shutting down large portions of the Loop since Monday, requires preparation of a different sort.
City officials have expressed fear that removing the water too quickly could cause a change in pressure that would damage the tunnel and building foundations near it.
The ”long-term stability” of old downtown buildings with eight or fewer stories could be compromised when water finally is drained, said Marshall Silver, professor of foundation engineering at the University of Illinois at Chicago.
Water saturating the soil could weaken shallow foundations, he said.
”These buildings have been there for 100 years and were stable and reached equilibrium,” he said. ”We`re now changing the conditions around their foundations. It could be a real problem.”
Chuck Askren, Midwest regional service manager for Flygt Corp., said city officials should ensure that once the decision is made to begin pumping, private businesses draining basements and city contractors working at the tunnel should pump at the same rate. Otherwise, he said, basement walls in a number of buildings could collapse.
”Everything should go down at the same time so that all pressures are equalized,” said Askren, whose company is one of the nation`s top
distributors of submersible high-powered water pumps and is supplying equipment to many businesses in the Loop.
”Water is very powerful, as we`ve seen already,” he said.
As an example of the problems facing the city, Askren described the experiences of homeowners near Rock Island, Ill., during a minor flood a couple years ago. He said residents began pumping water out of their basements before the flood waters had receded, and as a result some basements caved in. The city, while acknowledging the potential for structural damage, has not revealed its plan.
John Derbyshire, spokesman for the Army Corps of Engineers, said the corps doesn`t know exactly how or when the Loop would be drained.
Part of the uncertainty, he said, is the lack of a formal agreement authorizing the corps to take control of the flood project. The corps was waiting for the Federal Emergency Management Agency to give orders, he said.
Once pumping begins, he said, the corps will follow tight guidelines:
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– Pumps would be placed at 10 to 20 sites, both in the tunnel and in basements, he said. He said no decision has been made on whether dropshafts will be needed or how the pump sites will be determined. ”It`s not the size of the pump that`s critical, it`s the number of pumps,” Derbyshire said.
”We`ve got to put pumps in a lot of different locations.”
– Each pump could churn out 3,000 to 5,000 gallons of water per minute, although Derbyshire did not rule out use of larger pumps, which can move 15,000 gallons of water a minute.
– Once pumping starts, he said, it is important for all businesses to coordinate draining of basements with any pumping directly from the tunnel.
In addition to protecting buildings and infrastructure, officials are extremely sensitive to the safety of workers seeking to seal the breached tunnel and the divers who have descended into the shafts.
At the Kinzie site, a makeshift helipad has been cleared so that injured workers can be flown away immediately. Whenever divers enter a shaft, an ambulance and stretcher are nearby.
”Since we started this last Monday, we haven`t had a first aid injury,” said John Kenny Jr., vice president of operations of Kenny Construction.
”This is a miracle, in my opinion.”
Daley also said he was proud of the safety record, singling out Monday`s evacuation of the Loop for praise while criticizing the news media.
”Monday, over a million people left the Loop area. No one was injured or killed. That`s never been done before,” Daley said. ”You don`t give people the credit for doing their job.
”Sometimes when people are injured or killed, that makes your business much easier,” he said before cutting off questions at an afternoon news briefing.
In the Loop, about 35 buildings still had flooded basements on Friday, while at Union Station, Amtrak officials were keeping an eye on water percolating into the station`s south baggage tunnel, apparently from an old streetcar tube that has flooded. The city started pumping water out of the tube on Friday.
The CTA, meanwhile, said that water leaks in the State Street subway of the Howard-Englewood-Jackson Park line extend along almost the entire length of the downtown platform, from Washington Street to Jackson Boulevard.
A transit spokesman described it as ”some seepage” but said there was no accumulation of water.