LINCOLN SQUARE — Expect some unusual blasts and booms in the vicinity of River Park on Thursday, when crews detonate the first test explosion related to construction of the Albany Park Storm Water Diversion Tunnel.
Ald. Pat O'Connor notified constituents of the test, which is set for sometime between 11 a.m. and 3 p.m. and will last no more than one minute.
A second test is scheduled for Nov. 7 and a third for Nov. 9.
Pedestrian and auto traffic will be stopped briefly to the east and west of the blast site, situated at the southwest juncture of Foster Avenue and the Chicago River.
A series of warning horn signals will alert people in the area that a blast is about to occur.
The series is: a 10-second signal five minutes before a blast, two five-second signals one minute before a blast, three two-second signals 10 seconds before a blast, and four two-second signals to indicate an "all clear."
Daily blasts are needed to create the tunnel's shafts — an outlet in River Park and an inlet near Foster and Pulaski. The shafts will drop 150 feet underground, the last 80 feet of which will cut through stubborn limestone.
Blasting and excavation at the outlet shaft is expected to last through January. The same work at the inlet shaft is expected to last from December through February.
There will only be one blast per day, permitted between 8 a.m and 6 p.m., but the target timing is between 10 a.m. and 1 p.m., according to project engineers.
The decibel levels are quieter than a jet airplane but slightly louder than a motorcycle, engineers said.
Once the shafts have been excavated, a tunnel boring machine will be brought on site in January and assembled underground.
The borer will chew its way north from the outlet shaft to the inlet, from February through May.
The entire project will wrap up in spring 2018, including landscaping and restoration of the areas around the inlet and outlet shafts.
The diversion tunnel is designed to prevent flooding caused by overflow from the Chicago River in the Albany Park and North Park communities.
During overflow conditions, water from the river will enter the tunnel at the inlet shaft and exit at the outlet into the North Shore Channel, bypassing homes in the neighborhoods upstream.
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