|Client:||Leggett & Platt Inc.|
XCG was retained by Leggett & Platt Inc. (LPI) in 2006 to provide engineering services in relation to the investigation of soil and groundwater quality and subsequent remediation of a former industrial facility, located at 66 Jutland Road, Etobicoke, Ontario. Phase I and II Environmental Site Assessment (ESA) activities completed by XCG between 2006 and 2007, identified the presence of elevated concentrations of chlorinated volatile organic compounds (CVOCs) within the shallow overburden soil and groundwater at the site. Based on information obtained from the site investigation and delineation activities, XCG developed a remedial action plan (RAP) in 2008 to address the elevated CVOC concentrations present in the soil and groundwater on-site.
The RAP included the demolition of the on-site buildings and remediation of the soil and groundwater based on an in-situ chemical oxidation (ISCO) approach, using potassium/sodium permanganate. ISCO using permanganate was selected due to its high persistency, effectiveness for treating CVOCs and the favourable oxidizing groundwater conditions identified at the site.
The demolition of the on-site buildings was completed between 2008 and 2009. To prepare for the demolition of the on-site buildings, XCG completed a Designated Substances and Hazardous Materials Survey (DSHMS) to identify hazardous materials that required special handling/disposal and supervised the decommissioning of on-site monitoring wells. In 2008, in response to a transformer oil release caused by an act of vandalism, XCG provided engineering services to decommission and remove the transformer from the site, and subsequently coordinated remediation of the released polychlorinated biphenyl (PCB)-containing transformer oil and removal/disposal of impacted soil.
In 2009, as per the RAP, site remediation activities were completed to address the CVOC ‘source area’ located in the center portion of the site, as identified from the investigation and delineation activities previously completed by XCG. The soil within the ‘source area’ was mixed with potassium permanganate using a hydraulic excavator (soil mixing) and a permanganate-based permeable reactive barrier (PRB) was constructed around the perimeter of the ‘source area’ to treat shallow groundwater discharging from this area. Overall, a total of 5,500 kilograms of potassium permanganate was mixed within the ‘source area’ and used to construct the PRB. To address and prevent the migration of CVOC-impacted groundwater from the site, XCG designed and supervised the installation of a groundwater re-circulation system comprising a groundwater extraction trench along the down-gradient property boundary and a groundwater infiltration gallery within the ‘source area’. To enhance the treatment of CVOC-impacted groundwater, XCG completed manual addition of potassium/sodium permanganate into the recirculation system at regular intervals since 2009.
In 2010, XCG completed targeted ISCO injections using RegenOx, a proprietary chemical oxidant, to address concentrations of chlorinated ethanes, specifically 1,1,1-trichloroehtane (1,1,1-TCA), identified at the site. The injections were completed using direct-push technology and a total of 8,000 litres of a RegenOx solution was injected into the subsurface at 40 locations. In addition, LPI retained XCG to conduct a preliminary screen level risk assessment (SLRA) to develop criteria identifying risk management options to mitigate potential impacts associated with any remaining contamination. The overall conclusion of the preliminary SLRA was that the current site maximum concentrations of CVOCs in the groundwater exceed the SLRA-derived standards, which were more restrictive than the currently applicable generic Ministry of the Environment and Climate Change (MOECC) standards due to the shallow groundwater condition at the site. XCG concluded that additional contaminant mass reduction would be required to meet these standards.
Between 2010 and 2015, XCG completed groundwater monitoring and ongoing remediation activities using the groundwater recirculation system. The groundwater conditions as identified during the monitoring activities indicated that the groundwater chemistry was becoming more suitable to facilitate reduction reactions. As such, XCG prepared a revised RAP in 2015 which included the replacement of the extraction trench along the down-gradient property boundary of the site with a zero-valent iron (ZVI)-based PRB.
In 2015, prior to the construction of the PRB, pre-treatment in-situ chemical reduction (ISCR) injections were completed up-gradient of the proposed PRB to reduce the CVOC concentrations and to enhance reducing and anaerobic groundwater conditions. Overall, a total of 12,000 litres of a proprietary chemical reductant called EHC-L was delivered to the subsurface up-gradient of the PRB using direct-push technology. XCG completed pre- and post-injection groundwater monitoring which indicated that the ISCR injections were successful in enhancing reducing and anaerobic groundwater conditions and reduced the overall concentrations of CVOCs, based on key field parameters (i.e. dissolved oxygen, pH and oxidation-reduction potential) and laboratory analytical results.
The PRB was constructed in 2016 using a total of 13,000 kilograms of Daramend mixed with imported coarse sand at a concentration between 2 and 8-percent (by volume). In order to monitor the performance of the PRB, monitoring wells were installed up-gradient, within and down-gradient of the PRB. XCG continues to complete groundwater monitoring activities to evaluate the performance of the PRB and the results have indicated that overall CVOC concentrations down-gradient of the PRB have decreased between 90 and 100%.
In addition to completing on-site remedial activities, XCG’s involvement with this project also included negotiating site access with neighbouring property owner for off-site investigation/delineation, reviewing historical information for neighbouring properties to identify potential contaminating activities and assisting LPI in negotiations with prospective site purchasers.
Although LPI no longer owns the subject property, (the property was sold in 2016), XCG, on behalf of LPI, continues to monitor and address the known groundwater impacts on the site. The anticipated completion date for this project is September 2018.
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