Twenty-year Performance Evaluation of Grass Swale and Perforated Pipe Drainage Systems

Three sewersheds in Ottawa, Canada, consisting of two grass swale and perforated pipe (GSPP) drainage systems and one conventional curb and gutter drainage system were studied to compare the performance of GSPP systems to the conventional drainage systems. The research was conducted by J.F. Sabourin in 1991/92, with follow-up studies in 1998 and 2006 by J.F. Sabourin and Associates Inc. (JFSA). The evaluation included precipitation monitoring, flow monitoring, water quality analyses, video inspections, surface infiltration tests, system exfiltration test, and soil and vegetation analyses. Winter monitoring was included in the 2006 assessment. GSPP drainage systems were shown to provide many stormwater management benefits in comparison to conventional storm sewer systems. Low installation cost, low maintenance cost, combined with a proven performance, makes the GSPP systems a viable drainage solution in low-density residential areas. Perforated pipe/grass swale systems continue to function beneficially after more than twenty years of service.