Formatted Title
A CSM and Risk-Based Analysis of Storm Water Management Pond Sediment Chemistry Data to Support Beneficial Reuse
Background/Objectives
Municipalities across Canada, as well as internationally, are investigating the possibility of beneficial reuse of storm water management (SWM) pond sediments. Under usual circumstances, these sediments are normally trucked to landfills, as they may contain environmental contaminants. Recent legislative changes in Canada, however, such as Ontario Regulation 406/19, “On-Site and Excess Soil Management” under the Environmental Protection Act, have focused industry attention on diverting soils and similar materials from landfills and promoting their reuse in a manner protective of human and ecological health.
The objective of the current study is to use an existing database of chemical analyses of sediment samples collected from SWM ponds across Canada, combined with a human health and ecological risk assessment (HHERA) approach, to determine how the characterized sediments could be reused safely, and propose potential reuse scenarios and theoretical risk management measures to allow this to occur.
Approach/Activities
Dr. Francine Kelly-Hooper has previously collected 375 sediment samples from 126 SWM Ponds in British Columbia, Alberta, Saskatchewan, Manitoba, and Ontario. These samples were analyzed for pH, electrical conductivity (EC), sodium adsorption ratio (SAR), cyanide, metals and metalloids, benzene, toluene, ethylbenzene, and xylenes (collectively known as BTEX), petroleum hydrocarbons, and polycyclic aromatic hydrocarbons (PAHs). This database and the corresponding summary statistics will form the foundation for this work.
The HHERA analysis will begin with the construction of generic human and ecological conceptual site models (CSMs) for reuse of SWM pond sediments that will be consistent with standard CSMs used in the Canadian provinces, in which the data originated, as well as with US EPA guidance. Various land use scenarios will be considered for the CSMs, including agricultural, residential, parkland, institutional, industrial, commercial, and community. The CSMs will include typical fate, transport, and exposure pathways for the chemicals in question.
Once the CSMs are developed, default human and ecological receptor assumptions will be taken from the various above jurisdictions to develop risk-based concentrations or measurements of the various analyzed chemicals and other parameters that would not be expected to pose potential health risks to the human and ecological receptors in question. The bioavailability and toxicity of components of these sediments, such as asphalt, as well as previous forensics work discussing potential sources of the various chemicals and other parameters will be considered and integrated with this process.
As a final evaluation, the database of samples will be compared to the risk-based concentrations or measurements, taking into account the overall risk conclusions, and any exceedances that would theoretically require mitigation will be identified. Risk management options, potentially including fill soil or hard capping, land use restrictions, among others, will be recommended for these exceedances to allow for a general strategy for beneficial reuse of sediments to be developed.
Results/Lessons Learned
The final presentation of results will include visual depictions of the human and ecological CSMs, tables of generated risk-based concentrations compared to summary statistics from the SWM pond database, an overall discussion, and general recommendations.