Case Studies

Hunter River: Installation of Deepest Continuous Soil Bentonite Barrier

Project Summary

Soil Bentonite Wall Underground Construction in Mayfield, NSW Australia

This project consisted of a Soil-Bentonite (SB) slurry cutoff wall installed to isolate a plume of contaminated groundwater from migrating into the Hunter River. The project was performed at the former, WWII-vintage, BHP Steelworks site in Mayfield, New South Wales, Australia. This groundwater barrier was, at the time of construction, the deepest continuous SB barrier wall in the world.

The slurry wall was a designed with three sides bounded on the fourth side by the Hunter River . The wall ranged in depth from 35 to 49 m (160+ ft) at the deepest section. The excavation was completed with Geo-Solution's long stick excavator attachment on 125 ton excavator capable of digging 25 m deep. A clamshell bucket mounted on a 100 ton crawler crane was utilized to complete the excavation to full depth. The project also included the successful installation of a 7 meter long soil-cement-bentonite panel section installed 42 meters deep under an active overhead pipeline.

Use of Specialty Exacavation Equipment to Construct SB Wall

Geo-Solutions partnered with a local Australian contractor to install the slurry wall. For the construction effort, Geo-Solutions provided supervision, specialty equipment, and technical assistance services to the contractor. Geo-Solution's specialty equipment included the long stick and long boom for the excavator, bentonite slurry mixing plant, and quality control field laboratory equipment. Geo-Solutions lead the effort to formulate a low permeability SB mixture using the available soils and bentonite to produce a barrier wall material with a low, long term permeability of less than 1 x 10 -7 cm/sec. Geo-Solutions also was responsible for quality control of the work and the operation of key specialty equipment.

The project was completed within the allowed scheduled of 7 months. To meet the schedule, portions of the excavation operations were performed 24 hours a day, 6 day per week.

The successful completion of this project produced a groundwater barrier with a permeability of less than 1 x 10 -7 cm/sec that is compatible with the metals and waste chemicals found in the site groundwater and thereby helps protect the environment from hazardous waste materials stored in the landfill. After the installation of a permanent cap, the site was deemed to be suitable for brown-field redevelopment.

Slurry Wall Dimensions

SB wall: 48,000 sm, 910mm wide, maximum depth of 49 m.

Geo-Solutions Can Help

To download, read, and learn more about the various slurry wall sample specs and technical papers we offer online here at Geo-Solutions.com, click on the links below or to your left:

• Slurry Wall Sample Specs– Geo-Solutions provides slurry wall sample specs which can be modified for real world use on your project. Download sample specification for Slurry Wall Construction.

• Slurry Wall Technical Papers – Browse our library of Slurry Wall Technical Papers.

Call Us Today