In a departure from the conventional "dig and dump" approach to contaminated soil, the City of Kingston, ON, chose an innovative underground filtering and cleaning technology to stop the flow of groundwater contaminants from Emma Martin Park into the Cataraqui River. The park's industrial past had left its soil and groundwater with elevated concentrations of soluble arsenic and other metals, posing a risk to the aquatic environment and Kingston's Inner Harbour.
The city worked closely with stakeholders to find a sustainable solution; taking an integrated approach to consultation, design and procurement. They selected an underground Zero-Valent Iron Permeable Reactive Barrier that captures contaminants as groundwater flows through porous treatment material. New pavement and a geosynthetic clay layer prevent rainwater absorption and slow the release of contaminants into groundwater. The city removed and disposed of some of the park's contaminated surface soil, targeting contamination "hot spots". A sustainable remediation process in other areas resulted in project costs nearly 40 per cent less than preliminary estimates for a conventional approach, and reduced the environmental impact of trucking and landfilling soil. On-site treatment also minimized disruption to park users.
237 tonnes of hazardous soil and non-hazardous contaminated soil removed
99.98% reduction of arsenic in groundwater flowing to the river
75% less soil transported to landfill, reducing GHG emissions and landfill volume
40% reduction in anticipated costs through on-site treatment
Estimated $30,000 saved annually by avoiding a groundwater pump and treatment system
Enhanced waterfront park with new parking, pathway improvements and landscape design
No disruption to rowing and canoe club activities
Reduced risk to human health
There was no standard process for consulting the city's Parks Department early in the planning stage. Additional and earlier consultation may have resulted in a more detailed park redesign, with greater value added to the project.
Council had already approved the project when stakeholder consultation showed that the original dig and dump soil removal concept would be disruptive to park users. While this meant a change in plan, it may also have avoided long-term costs to pump and treat groundwater through a more conventional approach.
Involve relevant city departments early in the planning stages to ensure optimal design and outcomes.
Consider a design-build procurement process that emphasizes project outcomes rather than a specific approach, and ask bidders to propose value-added solutions drawn from their expertise.
Use an integrated project design approach and seek solutions that complement other aspects of municipal service.