For the love of trees

Published 27/6, 2014

In 1916 the Municipal Pier in Chicago, Illinois, was the first pier in the US to combine shipping with entertainment. The pier was re-named Navy Pier in 1927 as a tribute to the US Navy personnel that served in WWI and is considered one of Chicago’s most historical and popular landmarks.

In June 2011, Navy Pier Inc. was established as a not-for-profit corporation to maintain the structure as a historic public landmark and oversee its redevelopment. They issued The Centennial Vision, which advised the redevelopment of the pier into a bolder, greener, and more contemporary urban space to elevate it as a world-class attraction.
The redevelopment project involved cutting out and removing 56 sections of structural concrete slabs and beams directly over Lake Michigan. The concrete openings were created for the installation of new recessed steel and concrete tree pits that range in size between 5.19m X 4.9m up to 5.19m X 8.54m. Alliance Concrete Sawing and Drilling located in East Dundee, Illinois was called upon by Madison Evans joint venture because of its over 50 years of experience in demolition, concrete sawing and robotic demolition.

Cutting and removal
The cutting and removal sequences were planned in a step-by-step process of cutting procedures and methods. All pre-cutting was completed to full depth between existing structural beams prior to installing anchors to insure smooth working surface for slab saws. After precuts had been made drilling and setting Hilti epoxy anchors for rigging points were completed. Alliance’s 50t mobile crane was used to lift the concrete pieces that weighed an excess of 16t. Four different Alliance wire saws and a Diamond Products CC110 deep cut slab saw with a 1.83m blade were used to cut through the 790mm railroad track embedded slabs and 864mm concrete beams.

Protection
To work above Lake Michigan in the fluctuating water levels and tides Alliance built three pontoons to catch any chips of concrete and slurry from getting into the water. Positioning the pontoons during the cold months was difficult because of the large amount of ice that formed on the lake. Six Kasco de-icers were strategically placed in the water and ran non-stop to keep ice from forming and allow the pontoons to be moved to the work areas. Diteq gelling agent was spread out and dispersed on the pontoons to turn the falling concrete slurry into a gel substance that could be shovelled up for easy clean up and preventing contamination of the lake.

Timeline, weather and safety
Completing a concrete saw cutting project of this nature is complicated, but when you factor in The Chicago winter of 2013/2014 was the third snowiest on record and the coldest winter in 30 years. To combat this abnormal weather Alliance came up with ingenious ways to keep on schedule for the three months they were on site. Electrically heated water hose was used to keep the water from freezing for the saw cutting. In addition the company fabricated and erected two heated working enclosures to work inside during the snow, cold and rain. The enclosures had a vinyl retractable roof system that could be pulled back quickly for lifting by crane and closed quickly to maintain heat. Alliance cut out over 1,316t of structural concrete that was trucked away and recycled and completed its Navy Pier project ahead of schedule.
By: Don Collier

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