WELCOME Lake Wabukayne OPEN HOUSE

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1 WELCOME Lake Wabukayne Sediment Removal Project OPEN HOUSE We are here to: Update you, the community, on recent developments and activities at Lake Wabukayne Present the preferred alternative and receive comments Hosts: City of Mississauga Marshall Macklin Monaghan

2 Lake Wabukayne Lake Wabukayne is a constructed stormwater management facility It was developed in 1976 by incorporating several engineering features into an existing pond known as Cook's Pond Modifications made at that time included cleaning the pond, installing a dam, gabion weir and gate and increasing the size and sediment storage capacity The Lake was designed to contain stormwater and control its discharge to Mullet Creek, which drains to the Credit River Lake Wabukayne has an important role in controlling the quality and quantity of stormwater that enters the river system and reducing erosion and sedimentation of receiving streams such as Mullet Creek and the Credit River However, the Lake requires periodic maintenance to ensure efficient control of flow volumes and suspended sediments Lake Wabukayne has operated very effectively It is estimated that it has prevented approximately 3 15,675 m of sediment from entering the Mullet Creek and Credit River systems This sediment has elevated concentrations of salt

3 Why Manage Stormwater? Stormwater runoff has two potentially significant negative impacts: 1 Runoff water entering sewers, lakes, rivers and streams may cause flooding and other quantity-related problems 2 Stormwater often carries pollutants that may adversely effect water quality In urban areas, the stormwater effects are intensified because surfaces such as roads, parking lots, sidewalks, driveways and rooftops do not allow rainfall to seep into the ground, so the water remains on the surface where it can pond or flood In general, the more impervious the surface is, the greater the volume and rate of runoff, and levels of pollutants are Stormwater ponds can be an effective, low-cost means of providing water quality improvement and reduced flooding in a watershed Usually, the longer the stormwater is detained in a pond, the greater the sediment removal efficiency

4 Current Status of Lake Wabukayne Several studies have been carried out to assess the current condition of Lake Wabukayne The quantity of sediment has been estimated and the quality and characteristics of the material have been determined It has been estimated that approximately half of the total storage capacity of the Lake is now consumed by sediment The volume 3 capacity is 32,000 m The quantity of sediment present in the Lake may 3 be as much as 16,000 m Laboratory analysis has indicated that some compounds in the sediment exceed Ministry of Environment and Energy (MOEE) Guidelines for the Protection and Management of Aquatic Sediment in Ontario (PSQE) lowest effect level criteria At these concentrations there is a potential that contaminants may get passed through the food chain by sediment dwelling organisms The City of Mississauga and its consultants, Marshall Macklin Monaghan, have completed an Engineering Design Study to evaluate options and determine the preferred alternative for removing the sediment from the Lake

5 Engineering Design Study Potential sediment removal options were identified and evaluated, considering the unique aspects of the Lake: Bench-scale tests were performed to evaluate potential techniques for dewatering the removed sediment prior to its disposal, recognising the available space: Regulatory agencies and the public were consulted The preferred alternative for sediment removal was determined considering: Demonstrated Effectiveness Site-specific applicability Potential effect on continuing function as a storm-water management facility Community Acceptability Potential Environmental Effects Related to: Surface or groundwater, Noise, Land, Atmosphere, Birds/wildlife, Aquatic habitat, Continuing use of the area by the public, Roads and traffic, Visual impacts Cost

6 Preferred Alternative: Sediment Removal Using a Hydraulic Dredge A hydraulic dredge operates like a large vacuum cleaner, breaking up the sediment with augers or cutting heads and removing it with strong pumps The sediment, in slurry form, is pumped to the shore in a floating pipeline where it is dewatered, following which it may be transferred to a final disposal location It is estimated that 2 months will be required to remove the sediment from Lake Wabukayne Some interference with the walking trails surrounding the Lake and access limitations to Cheega Park are anticipated during this time

7 Preferred Alternative: Sediment Dewatering in Sediment Containment Tubes The sediment will be pumped to a series of high strength fabric sediment containment tubes placed in Cheega Park A dewatering agent will be added to the sediment slurry as it enters the tubes Because the sediment will be pumped under pressure and with the aid of the dewatering agent, it is expected that drainage of the water contained in the sediment slurry will be rapid Once dewatered, the sediment will be loaded onto trucks and shipped offsite via Cheega Court The area will be completely restored upon completion

8 Preferred Alternative: Overview Lake Access (Inlake Court) Pathway blocked during construction Sediment Dewatering Area (Cheega Park) Dredging Operations (Lake Wabukayne) Above ground temporary pipeline from Dredge to Sediment Dewatering Area Truck Access (Cheega Court)

9 Advantages of this Methodology Lake maintains function as stormwater management facility Potential for offsite tracking of mud or spillage is minimised Potential for suspended sediment to be conveyed downstream is limited Potential effects to area residents are limited Considers input from public Overall low potential for environmental effects