Performance Assessment of a Highway Stormwater Quality Retention Pond – Rouge River, Toronto, Ontario
This stormwater pond was constructed in 1994 by the Ontario Ministry of Transportation as part of the Highway 401 widening project to address water quality and fisheries concerns associated with polluted highway runoff. The facility is long and narrow with a length-to-width ratio of 10:1. A submerged berm partitions the pond into a forebay and quiescent treatment/retention zone. Flow exits the facility via a reversed-slope pipe that draws water from below the surface of the pond such that floatables are trapped in the pond and effluent temperatures are cooler than they otherwise would be. The combined permanent pool and extended detention storage meets Ontario Ministry of the Environment’s ‘enhanced level’ guidelines for stormwater quality ponds.
Comprehensive monitoring of the pond was undertaken under the SWAMP program between 1995 and 1997. The major objective was to evaluate the ability of the wet pond to reduce impacts on the receiving stream in terms of water quantity and water quality. To this end, the monitoring program included an assessment of hydrology, water chemistry, water temperature, water toxicity and changes in algae and vegetation communities in the pond. The pond was also the subject of a separate study investigating chloride pathways in stormwater ponds. A summary of data from the chloride study is provided in the final performance assessment report.
For monitoring results on this project, see the report entitled Performance Assessment of a Highway Stormwater Quality Retention Pond – Rouge River, Toronto