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Lake Wabukayne: Innovation in Storm Water Management Pond Maintenance


Mitigation of the adverse impacts of land development on rivers, creeks, streams and other natural storm drainage systems is a paramount objective in today’s municipal world. Stormwater management works in the form of retention ponds offer effective solutions for the promotion of enhanced storm water quality and are common to the transportation and public works community. Proper maintenance of these ponds, including removal of accumulated sediment, is critical to ensure their continued operation. Such maintenance can prove costly for road authorities and municipalities due to the contaminate levels in sediment associated with road runoff, as well as the land and time requirements needed to de-water the sediment prior to disposal. In addition, there may be negative impacts to the aquatic and terrestrial habitat during these maintenance activities. The City of Mississauga has recently undertaken an innovative method for removing accumulated sediment from a large and aging retention pond with minimal impact on the environment and at a competitive cost. Lake Wabukayne is a 1.8 hectare man-made in-stream storm water retention pond located in Mississauga, Ontario. The lake was constructed in 1976 and continues to serve an important role in controlling the quality and quantity of storm water that enters the downstream river systems. As the lake reaches it sediment containment capacity, its effectiveness in removing suspended sediment and associated environmental toxins is significantly reduced due to the reduction in retention times. In 2004, the City of Mississauga retained Marshall Macklin Monaghan as an engineering consultant and began examining methods for sediment removal and disposal. Hydraulic dredging and the use of large geosynthetic tubes for de-watering were selected as the preferred alternative and is unique in Canada for this type and scale of project. In 2005, McNally Construction Inc. was selected as the general contractor and began suctioning sediment from the lake bottom using a small hydraulic dredge fitted with a mud shield to minimize the release of sediment into the water column. Sediment was pumped in a slurry form to a sediment de-watering area where it was mixed with a polymer to promote flocculation and decrease de-watering times. The mixture was pumped into a series of high strength geosynthetic tubes (each approximately 3.0m wide by 1.7m high by 50 m long ) from which the water was filtered out and drained by gravity back to the lake. As water drained from the sediment mixture in the tubes, additional slurry was pumped in until the tubes were filled with de-watered sediment only. The stored sediment was removed by piercing the tubes, excavating the sediment contained within using standard excavation equipment, and loading the sediment onto trucks for offsite disposal. This initiative removed approximately 5,613 m3 of sediment from Lake Wabukayne at a final cost of $1.3 million and was fully completed in 2007. The majority of the sediment removed was attributable to winter road maintenance and road debris flushing. There are many advantages to using this technology for sediment removal including the minimized impact on the natural environment and the reduction in both land and time requirement for de-watering of the sediment. 

Conference Paper Details

Session title:
Josh Pitushka
Education, Human resources