Project Features:
- Sand/Zero-Valent Iron Permeable Reactive Barrier
- 280 Linear Feet. 7,006 Square Feet. Maximum of 26 feet deep
- Installed using Slurry Trench method with Guar Gum Biopolymer Slurry
Background:
The Sterling Road project site was originally home to Northern Aluminum, which eventually became Alcan Aluminum and later Tower Automotive. Northern/Alcan/Tower manufactured various aluminum products from 1912 through 2005, when Tower entered into bankruptcy. The original 10-story building, once one of the tallest buildings in Canada and one of the first with an elevator, is now designated as a cultural heritage site. The site has been purchased by Castlepoint Realty, who, along with Rio Tinto Alcan, is remediating the site for a future mixed-use residential development – 45 new townhouses with live-work spaces, new office towers with urban agriculture rooftops, a public square, and revitalization of the heritage Tower Automotive building.
Two primary plumes of chlorinated solvents currently reside in a sub-surface sand layer across the site. The plumes are being remediated through a combination of soil removal/replacement and the installation of a funnel-and-gate system with a permeable reactive barrier.
Project Objectives:
Geo-Solutions’ Canadian Subsidiary was contracted by Tervita Corporation (Tervita) to install a Permeable Reactive Barrier (PRB), to serve as the subsurface groundwater “gate” for passive groundwater treatment.
Description of Work:
The PRB was installed using the slurry trenching method. The 30-inch wide trench totaled 280 lineal feet in length and was installed up to 26-feet below ground surface. Bio-polymer slurry was produced in Geo-Solutions’ colloidal batch plant and pumped to the trench.
The PRB backfill consisted of well-graded sand and zero-valent iron (ZVI) filings and was produced on site in a volumetric mobile mixer which blended the components at a specific ratio into a uniform ZVI-backfill blend. Iron separation testing was performed on ZVI backfill samples by Geo-Solutions to confirm the sand/ZVI ratios were within project tolerances. ZVI backfill was placed into the trench using a custom-made tremie-hopper apparatus to prevent segregation of the ZVI backfill as backfill operations progressed.
Project Challenges:
The PRB was divided into 4 specific gate segments, each requiring a unique sand/ZVI ratio. Leftover biopolymer slurry was pumped to frac tanks where it was circulated and degraded.
