Deep Soil Mixing
Cape Canaveral Air Station
Cape Canaveral, Florida

Geo-Con constructed a Permeable Treatment Wall (PTW) using a combination of Deep Soil Mixing (DSM) and vibro-installation techniques at the Launch Complex 34 in Cape Canaveral Air Station, Florida. The project was funded through and designed by the University of Central Florida and NASA. It was a pilot program to determine 1) the feasibility of insitu treatment of local groundwater contamination consisting mostly of chlorinated solvents, 2) a possible alternative installation method for the construction of a PTW. The in-situ use of iron fillings for groundwater remediation is patented by Environmental Technologies, Inc. of Ontario, Canada.

The site is located on Cape Canaveral Air Station. The property owner is the Air Force, however NASA has accepted responsibility for the site's cleanup, as it was formerly used by NASA during the Apollo Space Program. The launch site was abandoned in place after the Apollo 1 accident, and was not used as a launch pad for the Saturn program thereafter. The site is lithologically characterized by medium to fine sand with shell to 40 feet below ground surface (bgs). At approximately 40 feet bgs, a continuous confining unit of at least one foot thickness exists.

Geo-Con used a vibratory hammer to drive four 10-inch steel casings to a depth of 40 feet below ground surface within the radius of each 11 DSM columns. A total of 44 casings were driven. To assure casing penetration during installation and to serve as the bottom plug, a steel drive point was used. Once a set of four casings were installed, the gravel/iron mixture was gravitationally fed into the casings to a level 1-foot above the groundwater table. After gravel/iron installation, the casings were removed, leaving the drive point in place at the bottom of the column.

After completion of the vibrational installation of the iron/gravel mixture, the vibrating hammer was removed from the crane and the soil mixing rig was attached. Geo-Con used a top drive soil mixing rig which moves vertically on a set of leads suspended from the tip of the boom of the crane. Two mixing strokes from the ground surface to 40 feet below ground surface were performed for each of the 11 mixing locations, using air as a drilling fluid. Each column is 4 feet in diameter. These iron/soil columns form a continuous PTW to 40 feet below ground surface. To increase the permeability of the soil in the area just upgradient of the PTW, a row of 10 soil mixed columns were installed. There was no zero-valent iron addition in these columns. It was the intent to simply fluff the soil to increase permeability.

Upon completion of the mixing operation, the University sampled the columns, which was done to verify adequate mixing of the gravel/iron with the native soils and to assure a resultant permeability of 10^-3 cm/sec.

• Start: 2/16/98
• Completion: 3/16/98