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| When PCB contamination was discovered in the lagoon area in 1985, the Ontario Ministry of the Environment (MOE) began a site decommissioning and remediation program. |
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| When PCB contamination was discovered in the lagoon area in 1985, the Ontario Ministry of the Environment (MOE) began a site decommissioning and remediation program. |
PCB contamination of a site in Smithville, Ontario, occurred between 1979 and 1985. Originally an industrial waste transfer facility, the site became a storage facility for wastes such as transformer fluids containing polychlorinated biphenyls (PCBs), chlorobenzenes and mineral spirits. When PCB contamination was discovered in the lagoon area in 1985, the Ontario Ministry of the Environment (MOE) began a site decommissioning and remediation program. Since 1998, a team of Acres & Associated Environmental Limited/Acres International Limited (A&A/Acres) and specialist subconsultants have been involved in feasibility studies for the clean-up.
Phases I and II of the four-phase program were completed between 1985 and 1987. These phases secured the wastes from the environment and provided a secure on-site storage facility. From 1991 to 1992, PCB wastes and contaminated soil beneath the lagoon area were incinerated in Phase III.
When contamination was discovered in the bedrock groundwater in 1987, the Ontario government installed a pump and treat system to contain the dissolved phase plume. The system has worked effectively since it was installed in 1989; however, the rate of Dense Non-Aqueous Phase Liquid (DNAPL) removal from the bedrock is very low.
A recent detailed assessment of the PCB DNAPL extent in the bedrock has indicated that the DNAPL source zone is within an area approximately 200 metres wide in an east-west direction, and 250 metres long, north-south, along the direction of groundwater flow. The DNAPL extends to at least 11 metres below the ground surface and possibly as deep as 23 metres.
The fourth and continuing phase is focused on the remediation of contaminants in the bedrock beneath the site. The objective of the Smithville Phase IV Bedrock Remediation Program, begun in 1993, is to recommend to the MOE cost-effective, long-term alternatives for containment and remediation of the remaining DNAPL in the bedrock and groundwater beneath the site. In 1997, the Program Board of Directors selected nine remediation alternatives including:
In a two-stage approach, the engineering team prepared a Common Design Basis Report, then Design Descriptions. The first task facing the engineering team was to consider the site conceptual model developed by scientists and other consultants and ensure that it was sufficient for engineering purposes. The primary focus of the Common Design Basis was to present information on the geology, hydrogeology, free-phase DNAPL contamination, aqueous-phase contamination and potential receptors, sufficient for engineering feasibility studies. The purpose of the Design Descriptions was to provide technical and financial information to allow a comparison of the various alternatives. For each alternative, unit operation diagrams illustrating implementation steps, an implementation schedule, technology experience, operational life of the system, monitoring requirements and costs were prepared.
Optimization studies were carried out by A&A/Acres for three of the alternatives (MNA, permeation grouting and extraction wells), which included comparison of integrated engineering, contaminant transport modelling and site-specific risk assessment data for the alternatives. Critical items with respect to contaminant concentrations at receptor locations, technical confidence and potential modifications to the alternatives were identified. The purpose of the optimization process was to increase the technical confidence and/or reduce the cost for an alternative.
The Board will prepare a report on their findings and recommendations on preferred alternatives for the future management of the Smithville site in the Fall of 2001.
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