Decommissioning & Decontamination (# 84)
Two Barriers Built at Contaminated Site
By Keely Mundle, Perth, Australia
For complex issues at many industrial locations - which may involve more than one groundwater plume and a range of hydrocarbons and industrial solvents - detailed site investigations to evaluate the extent of the contamination are often necessary to develop the most appropriate clean-up strategies.
At a former liquid waste treatment and recycling plant in Bellevue, an eastern suburb of Perth, Australia, the contamination resulting from both a fire and the facility's historical use extends for about 200 metres (656 feet) underneath several parcels of land southwest of the site and migrating in the direction of a nearby river.
To treat the contaminated groundwater before it would eventually reach the river, Golder has been involved in developing a solution that can be considered at the technological forefront of remedial methods.
The first dual passive barrier system designed in Australia has been installed at the site. This permeable reactive barrier (PRB) is a groundwater treatment design that makes use of the natural groundwater flow to channel contaminants to an engineered in-situ treatment area. As groundwater passes through the PRB, contaminants are treated and clean water flows out the other side.
Each one of the PRBs, 76 metres (249 feet) long by 10 metres (33 feet) deep, is filled with a different reactive material. One contains sawdust to handle the nitrates in the groundwater, and the other has zero valent iron, a nontoxic granular material used to treat chlorinated solvents.
This type of barrier requires no ongoing operation of pumps or other equipment that might be disruptive to local residents or surrounding businesses. As it is not visible above ground, it will not affect future use of the land.
Further remediation options for two source areas in connection with the site, one onsite and the other offsite, are currently being examined by Golder. Due to the distribution and nature of the contaminants present, there is a possibility that more than one remediation method will be used.