RECON, as a geotechnical company, is at the forefront of these advances. Our slurry wall construction fleet includes a hydraulic excavator capable of digging over 100 feet in depth and our dedicated slurry wall personnel have experience using a highly chemically resistant slurry made with Attapulgite clay and soil.

A partial list of slurry wall systems that RECON installs includes:

• Soil-Cement-Bentonite Slurry Wall
• Cement-Bentonite Slurry Wall
• Soil-Bentonite Slurry Wall
• Soil-Attapulgite Slurry Wall
• Cement-Attapulgite Slurry Wall
• Blast Furnace Slag Cement-Attapulgite Slurry Wall

Geomembranes can be used in conjunction with any of these technologies to meet site-specific requirements. In fact, any of these technologies can be coupled with other technologies such as sheet piles or jet grouting to form a complete containment system to assist with groundwater remediation and environmental remediation projects. RECON, as a geotechnical company, also uses these technologies with permeable reactive barrier walls to build "funnel and gate" systems.

RECON, as a geotechnical company, has constructed over 6,000,000 square feet of slurry walls with depths ranging from 30 to 120 feet. These slurry walls have been through soils ranging from soft clays to sands, and to hard rock.

Additional technical information on the construction of slurry walls can be found at www.slurrywall.com.

Slurry Wall Case Studies

SLURRY WALL CONSTRUCTION
Palestine, Texas

As part of a remedial action, related to an unleaded gasoline pipeline release, Remedial Construction Services, L.P. (RECON) installed a soil-bentonite slurry wall in Anderson County, Texas. Assessment data indicated that a release had impacted two intermittent creeks that converged at the site.

Voluntary action was taken by the pipeline company to contain and properly remediate the resulting groundwater contamination. The slurry wall prevented migration of the gasoline downstream and provided a central contained location to treat the impacted water.

Installation
The location of the slurry wall provided a challenge for the RECON crew. The wall was placed in the shape of a "V" and installed adjacent to the conveyance of the two intermittent creeks. The 3-foot wide wall was installed to an average depth of 25 feet below grade.

A working platform was constructed, following a minor amount of clearing and grubbing. Excavation operations were completed in late summer taking advantage of the lower groundwater elevation.

RECON´s slurry wall crew utilized a RECON-owned Liebherr hydraulic excavator to remove the trench soils and key into the designated confining clay layer. Bentonite slurry was mixed remotely at the site and pumped approximately 1,000 feet to the trench. The slurry provided trench integrity, as well as, aided in the mixture of the soils within the trench. The bentonite slurry and clay soils were blended together, resulting in a low permeability (1 x 10-7 cm/sec) subsurface barrier that was compliant with the project specifications.

Subsequent to trenching and installation of the slurry and soil backfill, the trench was topped with soil and graded to promote positive drainage into the adjacent creeks.

An independent, third party completed project oversight. They performed permeability testing at numerous locations along the wall.

SLURRY WALL
SUBSURFACE CONTAINMENT SYSTEM
Riverview, Florida

Remedial Construction Services, L.P. (RECON) constructed a soil-bentonite slurry trench cut-off wall for Cargill Fertilizer at their facility in Riverview, Florida. The cut-off wall was designed to prevent the migration of acidic process water to the Tampa Bay. Cargill hired RECON, because they considered the project to be "high" profile, and required the contractor to maintain a "positive image" throughout construction.

The scope of work included the installation of a 300,000 square feet barrier wall that was approximately 9,000 feet long, with a maximum depth of 40 feet. RECON constructed the wall with a Link Belt 7400 hydraulic excavator. The 200,000-pound excavator is owned and operated by RECON and has digging capability of 65 feet. In addition to the barrier wall construction, RECON performed all ancillary tasks including work platform construction, storm water management, utility relocation, and site restoration.

Special construction techniques were required to overcome difficulties during the performance of this project, including:

• Numerous "solution" channels created by acid water over the years provided potential conduits for slurry to enter the Tampa Bay.
• The work area around most of the site was very limited.
• The excavated materials required supplemental fines and dry bentonite to produce the soil-bentonite backfill