City of Ottawa Grass Swale and Perforated Pipe Drainage System Study

The City of Ottawa will conduct a field test on Grass Swale and Perforated Pipe (GSPP) drainage systems. It will also develop a manual and supporting software for the design and installation of GSPP systems. The evaluation will include continuous flow monitoring, water quality analysis, video inspections, surface infiltration tests, surface and vegetation analysis, and exfiltration tests. The GSPP Drainage Evaluation Study is intended to move GSPP systems beyond the experimental stage. The City will monitor and analyse the performance of three sewersheds – two serviced by GSPP drainage systems, and one serviced by a conventional system. These sewersheds were initially evaluated in 1991-92 and in 1998. By returning to the same sites, the City will evaluate whether the performance of the GSPPs holds up over time. As of 2006, parts of these GSPP systems had been in place for more than twenty years. The City estimates that increased use of GSPP technology in suburban drainage systems would result in decreased installation and maintenance costs, lower design peak flows and run-off volumes, a 95 percent reduction in pollutants conveyed through drainage systems (compared to conventional systems), and maintenance of potential groundwater recharge and augmentation of baseflow in nearby watercourses.