『Abstract
North America's fifth most populated municipality - the Great
Toronto Area (GTA) - is undergoing rapid urban development with
serious questions being raised regarding the long-term impacts
of urban growth on the quality and quantity of ground and surface
water. Degradation of groundwater quality by NaCl de-icing salt
is the primary concern since there are no cost effective alternatives
to NaCl de-icing salt and there is little evidence that salt loadings
to the subsurface can be significantly reduced. In 2001, the issue
acquired a new sense of urgency when de-icing chemicals containing
inorganic chloride salts (with or without ferrocyanide de-caking
agents) were designated as toxic under the Canadian Environmental
Protection Act.
To heighten concerns, future growth in the GTA will inevitably
take place in areas where groundwater is regularly used for potable
supply. Studies using groundwater flow and transport models show
that significant deterioration of groundwater quality can be expected
in shallow aquifers as a result of urban development with chloride
concentrations approaching the drinking water quality standard
of 250 mg/l. Results demonstrate that urban planning needs a fresh
approach that explicitly includes groundwater protection and aquifer
management in the decision-making process, clearly defines acceptable
environmental performance standards and makes greater use of groundwater
models to evaluate alternative urban designs.
Keywords: Urban groundwater; Road salt; Models; Urban planning』
1. Introduction
1.1. Documented impacts of de-icing salt on GTA groundwater
1.2. The challenge
1.3. A new sense of urgency
1.4. The goal
2. The Seaton lands study area
2.1. Geology and hydrogeology of the study area
2.2. Background water quality
2.3. Proposed environmental protection measures for the Seaton
lands
3. Model predictions of urban impact
3.1. Methodology and experimental design
3.2. Pre-development simulations
3.3. Post-development predictions
3.4. Model results
4. Discussion - implications for the planning process
5. Conclusion
Acknowledgments
References