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Hydraulic Isolation of Lagoons or Holding Ponds

Chicago, IL: Soil-Bentonite Slurry Cutoff Wall, South Detention Basin


Geo-Con was contracted to install a soil-bentonite cutoff wall at O'Hare Airport around the South Detention Basin. The detention basin is being rebuilt as part of the Mass Grading project for the south airfield. The project was located within FAA airspace along runway 10C-28C East. The basin will serve as an active retention structure for storm-water runoff management.

The wall extended through several highly permeable zones into a key clay layer, creating an impermeable barrier seal for the basin. The slurry wall is 6,790 linear feet (284,635 vertical square feet) installed to a maximum depth of 53 feet and an average depth of 43 feet below ground surface. The wall was excavated using a Komatsu PC1250-LC excavator with Geo-Con's long reach boom and stick.

Geo-Con met or exceeded the strict quality control and design standards set by the O'Hare Modernization Project and their design engineers. Permeability of the soil-bentonite slurry wall backfill exceeded the specified value of 1x10-7 cm/sec by an order of magnitude on average.

Geo-Con completed a challenging section of the wall at a utility crossing without incident. This section required digging around a 12-foot diameter cement drainage pipe that will feed one of 4 pump stations for the South Detention Basin. The top of the pipe was 5 feet below ground surface.

This project was completed in the security controlled section of the airfield. This required coordination with the General Contractor and the Airport authorities to facilitate normally routine activities such as material deliveries and other visitors to the site.

Geo-Con completed this project with combination of craft labor from our pool of company employees and operators from the Local 150 Operating Engineers Union.


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