Investigation of innovative systems for stormwater management within roadways

As stormwater management in urban areas becomes increasingly more complex, due to densification, more stringent regulations, high costs and low availability of land, innovative solutions have continually been developed to meet these challenges. This paper documents the investigation carried out on several such solutions, including: 1) Etobicoke Exfiltration System (EES), which has been in operation for more than two decades in the City of Toronto, 2) EES combined with Inline Flow Restrictors (IFR) and 3) a proprietary Dome Concrete Forming System (DCFS). All three of these systems aim to increase the capture and infiltration of stormwater runoff from roadways and adjacent drainage areas through modifications of the traditional road and drainage infrastructures, without the requirement for any additional land. A calibrated, dual-drainage Storm Water Management Model (SWMM) model (v 5.2) of a 10.4 ha (25.7 ac) residential development is first used to investigate the runoff control provided by the existing system that features a stormwater management pond. Separate models are then developed to model the three alternative systems (EES, EES-IFR, DCFS) and compare the performance of these solutions to that provided by the existing system, in terms of average annual water balance (continuous simulation), peak flow control and the extent of street flooding (design events). Preliminary findings indicate that all three systems provide significant reduction of both the stormwater runoff and peak flows, while maintaining satisfactory ponding depths on road surfaces. The innovative concepts investigated in this study provide potential direction for alternative solutions that drastically reduce the need for traditional stormwater management ponds for retention and detention in a cost-effective way, while promoting the infiltration and restoration of pre-development flows. Practical experiences with construction, maintenance and monitoring of some of the investigated systems are also discussed.