"The deck pour consists of about 1,100 cubic yards of concrete which is being using pumps," Chicago Department of Transporation engineer John Sadler told ABC7.
A caravan of some 130 concrete-mixing trucks are at Wacker Drive and Lake Street for the pour, which will likely continue until 1 p.m. Motorists should take into account some added congestion in the area.
"We have a very specific time that we have to get these trucks in at, so anybody who doesn't really need to go through this intersection should avoid it. However, all of the access to all of the buildings will be maintained throughout the process," said Sadler.
Since the re-construction project began last year, crews have removed Upper and Lower Wacker from Randolph to just South of Washington. Workers have installed new columns and placed the foundations to support the concrete pours.
"This is a major pour for us. This will be one of three pours during the first stage. So this is essentially pouring the concrete that will eventually be the Randolph-Wacker intersection on Upper Wacker Drive," Sadler said.
Randolph is expected to reopen sometime in June. Crews will then begin work on Madison Street. In 2012 work will progress on the Monroe to Van Buren stretch of Wacker Drive.