The mysterious world of underground construction work emerged into daylight Tuesday with two projects intended to speed the recovery of a water- logged downtown Chicago.
A sophisticated and potentially dramatic project, in which divers lowered down in metal cages will seal off the freight tunnel under the Chicago River, got under way at the Kinzie Street site where river water poured into the tunnel Monday.
And officials of the Metropolitan Water Reclamation District said they had found a fast way to connect their Deep Tunnel system with the freight tunnels, using a newly constructed Commonwealth Edison tunnel in the South Loop.
If successful, that would allow the estimated 250 million gallons of murky river water that now fills the obsolete freight-delivery network to drain into the district`s vast pollution- and flood-control system.
At the Kinzie Street site, construction crews used yard-wide augers to bore through the roadway on either side of the river and reach the tunnels 50 feet below ground. Throughout the day and into the evening, they went through a ritual of pouring concrete, waiting for it to harden and then drilling out the center to leave a hollow access shaft.
After six shafts to the tunnels are completed, perhaps as soon as early Wednesday morning, divers were to descend into the frigid, dark water and seal the tunnels, possibly using sandbags. Designers said the effort is dangerous because of the uncertain conditions in the lightless tunnels.
Late Tuesday night, after at least one shaft to the tunnels was completed, a diver descended into the frigid, dark water to launch the process of sealing the tunnels, possibly using sandbags. The diver entered the water twice at about 11 p.m. but ran into complications, first when the metal cage began spinning and then when the current proved too swift.
”It`s very, very dangerous,” said John Kenny, head of Kenny Construction Co., the Wheeling firm that is building the access shafts. ”But this will be a long, slow, safe process.” If there`s any problem with safety, we`re not going to go in.”
Kenny and city officials say the object of the work is to
”encapsulate,” or seal off, the collapsed section of the freight tunnel so that it no longer poses the threat of sending rushing waters into the basements of Loop buildings.
”Everybody`s in agreement with what we`re doing,” said Kenny, whose project has been approved by all the city agencies involved in fighting the flood and by the U.S. Army Corps of Engineers, which is at the scene of the rupture.
A vivid but frightening picture of the procedure emerged during a City Hall briefing Tuesday.
The first step in isolating the damaged portion of tunnel was drilling six holes, each about 6 feet wide, down to the top of the turn-of-the-century freight tunnel.
Two of the shafts are on the east side of the river, but on the west side, where the tunnel forks in two, there are four shafts. As a precaution, each leg of the tunnel will be sealed off in two places.
Next, steel cylinders were lowered into the holes to provide the frame for the access shafts. The cylinders were filled with quick-setting concrete, which hardens in about three hours.
After the concrete set, a special coring machine carved out a 56-inch-wide hole down at least one of the shafts. This paradoxical procedure of pouring concrete and then boring it out leaves a strong cylinder of steel and concrete that, if above ground, would be five stories tall.
Then, either a machine or a diver will be lowered into the hole to punch through the concrete top of the tunnel to expose the dirty, bone-chilling water inside. A flow-measuring device will be lowered into the flooded tunnel to determine if water is still flowing through it from the hole beneath the Chicago River.
Although work continued Tuesday to cap the hole in the river bottom with more quick-setting concrete, reports of rising water in the Chicago Board of Trade building and the Grant Park underground garage fed doubts whether the hole has been plugged.
But Kenny said during the briefing that the worst of the flooding is over. ”We`ve got the river stabilized,” he said.
If the flow meter detects a current in the water, Kenny said, he will not send a diver into the tunnels because of the danger of a person being sucked into the flooded tunnel.
But if the water in the tunnel is motionless, divers from two firms-Lindahl Marine and Brand Inc., a Waste Management subsidiary-will begin the laborious task of sealing the tunnel at each access point.
Working in a metal cage for safety, the divers will be raised and lowered, at a rate of about two or three minutes each way, methodically carrying 40 pound sandbags or other blocking material into the tunnel to seal it off.
Kenny emphasized that the divers will be working without light, without prior knowledge of what they will encounter and with limited space in which to work.
”The shaft is just a steel can,” Kenny said. ”All it will contain is the diver and his hands and 40-pound sandbags.”
Encapsulating work may take several days.
”This is not going to be a quick-fix solution,” said Mayor Richard Daley at the briefing. ”It`s going to take time.”
And time may be one thing that is on the side of a new proposal to drain the freight tunnels once it has been verified that no more river water is entering them.
Just one day after conceding that a connection between the freight system and the Deep Tunnel at Jefferson and Monroe Streets will take more than a week to construct, Water Reclamation District President Nicholas Melas said Tuesday that a new way to connect the systems had been discovered.
A deep Commonwealth Edison tunnel with water is only 25 feet from a Deep Tunnel dropshaft, a 12-foot wide opening that connects local sewer systems with the district`s $2.5 billion project to capture stormwater and prevent backups into Cook County basements.
If district officials get the go-ahead from the city and Edison, six small holes, measuring only 4 to 6 inches in diameter, could be drilled between the dropshaft and the Edison tunnel in only two days, Melas said.
The Edison tunnel, which is 110 feet below ground level at Taylor and Franklin Streets, is itself flooded by water from a freight tunnel above it. It is still under construction, and will eventually carry 345,000-volt power lines under the Chicago River to the utility`s Taylor Street substation, which supplies some of the Loop`s electricity.
When construction workers arrived for work Monday, they found that a construction shaft for the Edison tunnel was flooded. Later, executives of the firm, J.F. Shea Construction Co., realized that the water came from the freight tunnel.
In sinking the construction shaft, Shea workers cut through the freight tunnel and sealed it off, said Shea area manager Larry Christensen. But the floodwater eroded the seal and then filled the Edison tunnel and construction shaft.
Drilling a series of holes between the Edison tunnel and the Deep Tunnel dropshaft would allow an estimated quarter-billion gallons of water to drain out of the freight tunnel in four or five days, said Water Reclamation District General Supt. Frank Dalton.
Officials for both the district and the city have stressed that draining should be done slowly in case the 90-year-old tunnel system has been weakened by the flooding. Using six smaller holes rather than one large hole will allow district workers to control the flow of water.
After entering the dropshaft, the floodwater would fall some 250 feet below ground level to the district`s 30-foot-diameter tunnel system, which is intended to end the periodic flooding of an estimated 550,000 homes in Cook County.
The Deep Tunnel, which is still under construction but can hold about a billion gallons of stormwater, is linked to the district`s Stickney sewage treatment plant. Water from the freight system would be treated at the Stickney plant and discharged into the Sanitary and Ship Canal, which empties into the Des Plaines River at Lockport.
But if the rains that are forecast for the rest of the week materialize, draining the freight system will have to wait. Rainfalls of as little as three-eights of an inch in a day will fill the completed portions of Deep Tunnel.
The Central Weather Service said the Chicago area could receive 2 to 3 inches of rain by the beginning of next week.
While discussions continue over using the Edison tunnel, work will continue at Jefferson and Monroe Streets, where Kenny Construction Co. is digging a trench to connect a Deep Tunnel dropshaft with the freight tunnel. That project is expected to take until next Wednesday because, in addition to digging a trench 50 feet deep and 20 feet long, workers have to reroute a variety of utility lines.
If approved, the Edison tunnel project could work so well that the Loop will be drained dry before the Jefferson Street trench is finished. But work will continue on both projects in case the Edison connection does not work.
”The more places you`ve got to drain, the faster it`ll go,” Melas said.
