Toronto, ON, Canada: Rio Tinto Alcan, Sterling Road Site

Toronto, ON, Canada: Rio Tinto Alcan, Sterling Road Site

Project Description

services-permeable-reactive-barriers-zero-valent-iron-toronto1-onProject 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


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.

services-permeable-reactive-barriers-zero-valent-iron-toronto-onDescription 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.

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