WCW24

Inner City neighbourhoods are often some of the oldest developments in a large metropolitan area. Due to the vintage of the area, their drainage infrastructure is often limited in it's performance and does not meet modern standards. The often do not contain any defined overland drainage paths. Implementation of drainage upgrades are often difficult due to the retrofit nature of the setting: set underground drainage inverts, utility congestion, poor record information, and mature trees. Stantec was retained to provide engineering consultant services to EPCOR for the design of a flood mitigation project in the mature Parkdale neighbourhood of Edmonton, including sewer separation and a dry pond, and had to over come many of the difficulties with inner City drainage upgrades. The Parkdale Dry Pond and Sewer Separation Project has many components that showcase EPCOR's commitment to providing storm water management services that protect communities long term. The Parkdale neighborhood was identified through EPCOR's Stormwater Integrated Resource Plan (SIRP) as being exposed to significant health and safety, environmental, social and financial risks caused by stormwater impacts. This project aims to reduce the risk posed to this community through separating targeted combined sewers into dedicated sanitary and storm sewers, installing a dry pond supplemented with underground storage, and installing absorbent landscaping and low-impact development in the area to provide stormwater management for varying rainfall conditions. 2D modeling was completed under a variety of storm scenarios to better understand the areas of surface ponding concern and sewer surcharge. This in combination with EPCOR's data on floods reported by residents played a part in selecting the location of the dry pond and the areas targeted for sewer separation. The dry pond will be located within an existing Parkdale school field (constructed in 1912) and the decision was made to incorporate underground storage as this would allow the dry pond bottom to be raised up and create a larger space for community activities and recreation. New storm sewers in the area direct surface runoff first to the underground storage system before surcharging into the dry pond. For the majority of storm events, runoff will be stored in the underground storage system and only in very large events will it surcharge into the dry pond. This combined storage system then outlets to a deep existing storm trunk at a controlled release rate to damped the impacts to the downstream system. It is anticipated that there will be new residential development downstream of this site and by creating this storage opportunity, capacity in the storm trunk will be made available for these future developments. In the vicinity of the dry pond and sewer separation, absorbent landscaping was installed in public boulevards to help manage the road runoff from smaller storm events (approximately the first 17mm of rainfall) and will be planted with shrubs and grasses. Minimal ponding will be allowed in these facilities and a primary function will be the storage of runoff in the soil media and the plants themselves.