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Seepage Barriers

Gary, IN: Jet Grout Containment Wall


Geo-Con installed a containment wall at the US Steel Gary Works facility in Gary, Indiana. The purpose of this containment wall was to mitigate a plume of LNAPL and DNAPL that was leaking into Lake Michigan. The project was completed using jet grouting technology. The project was designed on a performance basis and the contractor was responsible for selecting the appropriate method to install the barrier wall. Geo-Con proposed and implemented jet grouting in an overlapping "bow-tie" pattern. This method created panels that are of a slight 15 degree "V" shape. With close 3-foot spacing, Geo-Con was able to create a double overlapping criss-cross, or essentially a diamond pattern along the wall alignment.

Geo-Con proposed and used Impermix® grout to create the wall. Impermix® was found to be compatible with groundwater contaminants. It also provides ultra-low permeabilities (1x10-7) along with compressive strength (50-200 psi).

The significant challenge on the project was the tight working conditions. The containment wall was installed immediately adjacent to US Steel's Vessel Slip Turning Basin in Lake Michigan. The jet grout drilling occurred between the older concrete dock and the newer steel sheet piles that act as the head wall to the lake. The maximum clearance for drilling was 7 inches. Geo-Con's "bow-tie" jet grouting method applied virtually no high pressure directly against the sheet piles.

A change of conditions also presented a challenge. Geo-Con encountered the presence of previously unknown subsurface voids along the containment wall alignment during construction. The grouting procedure was modified in the field to inject cement grout under low pressure. This was done to fill the voids so that successful installation of the containment wall could resume.

Additional scope of work on the project included removal and replacement of guardrail and side walk, characterization and disposal of excess grout return, sealing of an underwater steel plate using marine divers, and re-vegetation. Geo-Con completed this project through the winter months.


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