Zero-Valent Iron Media
Rochester, MI: Permeable Reactive Barrier Installation By The Bio-Polymer Slurry Trench Method, Former Itt Avon Site
This project included the construction of two permeable reactive barrier (PRB) walls down to an aquiclude to a maximum depth of 34 feet. The walls were designed to intercept a contaminated plume from discharging offsite. The primary contaminants were chlorinated hydrocarbons from solvents leaking into the ground after years of industrial use of the site.
The reactive backfill was a mixture of zero-valent iron filing sand emplaced across the path of the contaminated plume. The wall was designed to have a permeability greater than the surrounding soils, allowing the natural groundwater to passively flow through the wall while the iron filings reduce the contaminants to harmless end products.
Geo-Con installed the wall using the Bio-Polymer (BP) slurry trench method. This method includes excavating a deep, narrow trench supported by biodegradable slurry during excavation and prior to backfilling. This method has been used extensively for installation of PRBs since Geo-Con installed the first BP trench PRB in 1999. The backfill mix was prepared on-site by mixing granular iron and locally available sand in a mobile concrete mixer. Following backfill installation, the degradable slurry was broken and reverted back to water leaving a permeable wall.
Other primary project tasks included; demolition of an existing Air Sparge / Soil Vapor Extraction system, demolition of a concrete building slab, installation of monitoring wells, off-site disposal of all excavated soils, installation of six inches of soil cover over the entire site, and revegetation.