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ENVIRONMENTAL CONSTRUCTION AND REMEDIATION Permeable Reactive Wall Installation This project included the construction of 150 linear foot of permeable reactive wall that was designed to intercept a plume contaminated with TCE, 1,2-DCE and vinyl chloride. The permeable reactive wall was designed with a sand and zero-valent iron filing backfill mixture that was equivalent to 0.8 feet of iron placed across the path of the contaminated plume. The wall has a permeability greater than the surrounding soils which allows the natural groundwater to passively flow through the wall while the iron filings reduce the contaminants to harmless end products.
The bid specifications allowed for contractors choice of installation method and Geo-Con proposed the use of a bio-polymer (BP) slurry trench. This method includes excavating a deep narrow trench supported by a bio-degradable slurry during excavation and prior to backfilling. The backfill mix was a mixture of sand and iron filings mixed in concrete ready-mix trucks that was tremie placed into the trench. Following backfill installation, the degradable slurry was broken and reverted back to water leaving a permeable wall.
The BP method offered the most cost efficient method for the PRW installation. It also allowed for easy verification of the excavation depth and width along with testing for the proper backfill proportioning.
The trench was 30 inches wide with a maximum depth of 36 feet. The project was completed on schedule and within budget
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