Army engineers searched for new pumping sites Thursday to drain deeper tunnels on the outskirts of Chicago`s flooded underground system.
Several pumps ran dry Thursday afternoon as the Loop`s higher-level tunnels were emptied, said Lt. Col. Randall Inouye of the Army Corps of Engineers, the Chicago district commander directing pumping operations.
Inouye said he believes much of the remaining water in the tunnels lies along the perimeter of the Loop, where the system is as much as 50 feet below ground level.
Tunnels in the central Loop run about 26 feet below the surface. The deepest of the three original pumping sites is 32 feet deep, Inouye said.
Engineers had hoped to begin pumping Thursday night from a deeper access shaft at Wells Street and Carroll Avenue. Pumping may begin at Jackson Boulevard and Canal Streets and Taylor and Canal Streets this weekend if other sites run dry.
Water levels dropped Thursday at a rate of about 1 1/2 inches per hour, Inouye said. Pumping averaged 13,000 gallons per minute, and about 30 feet of the original 50 feet of floodwater remains in the tunnel system.
The corps hopes to finish pumping by May 1, although Inouye said engineers may be ”chasing water” through some of the system`s deeper tunnels longer than expected.
”What we`re not sure of is all the bulkheads or temporary walls that may have been put in through all the ages, and what the conditions are,” Inouye said.
Divers at the Kinzie Street bridge cleaned silt from the tunnel Thursday in preparation for bulkheads that will permanently seal the system on both sides of the leak in the Chicago River.
Engineers have not determined what type of bulkheads will fill the shafts.
Workers hope to have the leak permanently sealed by Monday.
