Sediment Assessment of Stormwater Retention Ponds within the Urban Environment of Calgary, Canada

The treatment of urban stormwater by retention ponds is known to be effective for water quality improvement as well as storm flow management and, in the past two decades, has become widely implemented. However, limited research has been conducted on the quality of sediment deposited in ponds. Therefore this study focuses on contaminant concentrations within the sediment from stormwater ponds built in Calgary, Canada. Electrical conductivity and the sodium adsorption ratio consistently exceeded the Canadian Council of Ministers of the Environment (CCME) agricultural soil quality guidelines, indicating a city-wide salt contamination issue. F3 hydrocarbon fractions, cadmium, chromium, copper, lead, selenium, and zinc were also identified as parameters of concern. In particular, the 61 Avenue SE duck pond displayed the greatest diversity and severity of contaminants due to the industrial catchment area. Removal and disposal options were limited due to the characteristics of the sediment. The examination of the solids content illustrated that all retention ponds will require the sediment to be dewatered prior to disposal. Disposal options were subsequently restricted to landfill disposal due to salt, metal, and/or hydrocarbon parameters exceeding CCME soil guidelines. One exception was the Deerfoot Trail and Highway 22X pond which could be directly disposed of in areas designated as commercial and industrial land use.