Abstract

The timely development of the Etobicoke Exfiltration System (EES) occurred at a period when engineers, biologists and scientists were actively investigating infiltration as a technique to manage stormwater. In most areas which can be significantly impacted by urbanization, infiltration is a major component of the hydrologic cycle. Consequently, the reduction in pervious land cover due to urbanization has a direct and detrimental impact on fluvial geomorphology, erosion, water temperature, chemistry, aquatic environment (fisheries) and adjacent terrestrial environments. Traditionally, stormwater management techniques were concerned with transport, detention and reduction of peak flows with end-of pipe solutions. Infiltration technology offers the opportunity to address two major stormwater management components: volume control and baseflow augmentation. These components reduce the volume of runoff, the duration of flooding and increase duration of baseflow during dry periods.

The Etobicoke Exfiltration System was developed as a new stormwater management approach to eliminate the discharge of storm runoff for frequent rainfall events while maintaining or improving the level of "convenience" of traditional municipal storm sewer systems. This system was designed to complement traditional stormwater management concepts by introducing a "micro" system, which increases the functionality of traditional systems while addressing stormwater quality and environmental concerns.

The City of Etobicoke has adopted a new stormwater manage concept which promotes three levels of control:

1.Major systems (i.e. overland system) designed to transport runoff from large and infrequent storms such as the 100 year storm.

2. Minor systems (i.e. convenience systems) designed to transport the smaller and more frequent storm such as the 2-year and 5-year storm.

3. Micro systems designed to eliminate runoff from the very frequent storms producing rainfal I accumulation in the range of 10 to 15 mm.

Although the Etobicoke Exfiltration System was originally developed for implementation in existing urban areas, it can be successfully implemented in new developments.

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