Delineation and Remediation of Soil and Groundwater Impacts - 3100 Mainway, Burlington, Ontario
XCG was retained by Barnes Group Inc. (BGI) to conduct site assessment and remediation activities at a former automotive component manufacturing facility located at 3100 Mainway, Burlington, Ontario. As a result of Phase I and II ESA activities completed by another consultant in 2009, elevated concentrations of chlorinated volatile organic compounds (CVOCs) were identified in both the shallow overburden groundwater and the deep fractured bedrock groundwater in the vicinity of a former chemical storage room.
BGI retained XCG in 2010 to further investigate and delineate the extent of the CVOC-related impacts and to conduct pilot-scale remediation activities using sodium permanganate to assess the effectiveness of in-situ chemical oxidation (ISCO) as a remedial approach. XCG identified the presence of elevated CVOC concentrations in the shallow soil in the vicinity of the former chemical storage room. Based on the vertical extent of the CVOC-related soil impacts, which extended into the water table, XCG reported that the CVOC-impacted soil was likely acting as a significant secondary source of ongoing releases of CVOCs in the shallow groundwater. XCG injected a dilute solution of sodium permanganate into several shallow injection wells and compared pre- and post-injection monitoring data to evaluate the remedial performance of the ISCO process. XCG’s interpretation of key field parameters (i.e. specific conductance and oxidation-reduction potential) and laboratory analytical results identified that the permanganate solution had been successfully distributed within the subsurface and that the concentrations of CVOCs had been significantly reduced at some of the groundwater monitoring locations.
During 2011, XCG completed additional subsurface investigation activities at the site to provide further delineation of the shallow groundwater impacts and to better characterize the deep bedrock groundwater quality. XCG supervised the installation of multiple groundwater monitoring wells, including wells installed within the deep fractured shale bedrock. The deep bedrock wells were installed using advanced telescopic drilling methods which involved steel casings grouted directly into the bedrock to prevent the potential downward migration of CVOC impacted water from the shallow weathered shale to the deeper fractured and competent bedrock water bearing zones. XCG also investigated the potential migration of shallow groundwater impacts along potential preferential flow pathways (e.g. utility trenches) in order to verify that the extent of the shallow groundwater impacts had been adequately delineated prior to proceeding with any full-scale remediation activities.
During 2012, XCG prepared a detailed scope of work and cost estimate to remediate the on-site CVOC-related soil and groundwater impacts over a three-year period. Following approval of the work plan by BGI, XCG proceeded with the remedial activities, including demolition of the former chemical storage room, excavation of a total of 1,800 [TK1] metric tonnes of CVOC-impacted soil, placement of 4,000 kilograms of potassium permanganate along the base of the remedial excavation, installation of an infiltration gallery and shallow injection wells and the completion of two ISCO injection events. The two ISCO injection events completed during 2012 each consisted of injecting 50,000 litres of a dilute sodium permanganate solution into the on-site shallow injection wells and the infiltration gallery. In addition to completing on-site remedial activities, XCG’s involvement with this project also included negotiating site access with neighbouring property owners for off-site drilling, reviewing historical information for neighbouring properties to identify potential contaminating activities, communicating with the local municipality and the Ontario Ministry of the Environment and Climate Change (MOECC) on behalf of BGI, and assisting BGI in negotiations with prospective site purchasers.
Between 2013 and 2017, XCG installed additional monitoring wells to further delineate the extent of on-site impacts, as well as additional shallow and deep injection wells to target localized `hot spots`. During the same period, XCG completed, typically two injection events per year using the infiltration gallery and select injection wells. On average, approximately 120,000 litres of a 5 percent aqueous solution of sodium permanganate was injected on an annual basis into the subsurface. Since the commencement of remedial activities in 2012, the average CVOC concentrations in on-site monitoring wells decreased by between 90 and 100%.
In 2016, BGI retained XCG to conduct a screening level risk assessment (SLRA) in order to develop criteria that can be used to identify risk management options that can be used to mitigate potential impacts associated with any remaining contamination. The SLRA process identified trichloroethylene (TCE) and vinyl chloride as the site-specific COCs, as concentrations of all other CVOCs have been reduced below the site-specific standards. However, based on the SLRA it was determined that the potential impact to human health is low, because the maximum concentrations of TCE and VC were found in deep groundwater wells, (i.e. in wells screened below 7 metres below ground surface), located down-gradient (away) from the on-site building. In addition, shallow groundwater, which meets the site-specific criteria in the vicinity of the building, is overlaying the deep groundwater and is acting as a barrier between the on-site building and the VOC vapours originating from the deep groundwater. Therefore, XCG concluded that the potential impact to human health from vapor intrusion is low.
Based on the size and complexity of this project, XCG implemented several innovative technologies in order to better understand, monitor, and document the remedial activities, including the use of multi-parameter groundwater quality instruments, electrical conductivity data loggers, high-resolution geo-referenced air photos, high-accuracy GPS surveying equipment, and advanced 2D/3D visualization software. The use of multi-parameter groundwater quality instruments allowed XCG to evaluate the changes in groundwater geochemical parameters (e.g. pH, specific conductance, dissolved oxygen, oxidation-reduction potential, etc.) in response to the ISCO remediation activities. The deployment of electrical conductivity data loggers at selected monitoring well locations allowed XCG to track the distribution of the permanganate within the subsurface. By developing accurate site plans using high-resolution geo-referenced air photos and GPS-surveyed site features, XCG was able to accurately target and evaluate the site remediation activities based on real world coordinates and reproducible measurements. Finally, the use of advanced visualization software enabled XCG to quickly and accurately process the field data, analytical data, and GIS data, into meaningful site plans for conveying important information to stakeholders.
Although BGI no longer owns the subject property, (the property was sold in 2015), XCG, on behalf of BGI, continues to monitor and addresses the known groundwater impacts that may have occurred as a result of historical releases of CVOCs on the subject property.