7/30/2019 Lecture 1 Flood Protection Efforts

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David Wach 998834846

Optional Assignment: Summary of Industrial Presentations

Lecture 1 Flood Protection EffortsMr. Haley

Mr. Haley started out by explaining Conservation Authorities in Ontario. These agencies deliver

services and programs that manage water and other natural resources. The agencies areorganized on a watershed basis. One watershed is the Don River watershed. The largest risk for

flooding in this watershed was identified as the Lower Don.

Part of the Lower Don is an area known as the West Don Lands that had been an industrial area.The West Don Lands was to be revitalized as part of a project called Waterfront Toronto. As

such land-use would have to be changed from industrial to residential. However, because theWest Don Lands was subject to a very high risk of flooding should another Hurricane Hazel

Event occur. Thus in order to change the land-use the risk of flooding in the West Don Landshad to be eliminated. The solution was a Flood Protection Landform, which was constructed

with fill taken from construction sites around the Greater Toronto Area, and by widening the

channel of the Don River so that it could handle more volume.

Due to the fact that the West Don Lands had been an industrial area for some time the site was

considered Brownfield and thus was subject to substantial soil contamination issues presentingmajor challenges. The area also consisted of organic soils which constitute a poor base. When

fill for the area was brought in it sank 1.3 metres. Other challenges included those resulting fromexisting infrastructure in the area. Due to underground infrastructure it would have to be ensured

that any construction would not sink which would break underground utilities. Another examplewas the necessity to keep rail operating when widening a bridge as it impossible to close such

and important and busy railway.

Central to protecting the West Don Lands area from flooding so that it could be revitalized andits land-use designation changed from industrial to residential is the concept of return period and

design storms. Generally 100-year storms (a storm that has a 100 year return period) are usedfor important infrastructure design but Toronto uses Hurricane Hazel as its base for flooding

volume. According to Mr. Haley, because this storm was so large in magnitude this project wasmore challenging than if a smaller reference storm had been used.

Another hydrologic concept that was considered for the design was that of the urban hydrologic

cycle. A combination of runoff from natural surroundings and man-made drainage systemscome together at a single outlet (1). The West Don Lands area is located adjacent to the outlet

for the whole Don Lands watershed. This is why there was such a flooding risk during such a

large storm, because all the water would drain to Lake Ontario in this area. Therefore thedesigners had to understand the concept of runoff in an urban area to design adequate runoffsystems (widening of the Don River channel) and barriers (Flood Protection Landform) toprotect against flooding in the area.

1. Bedient, Huber, Vieux. Hydrology and Floodplain Analysis

7/30/2019 Lecture 1 Flood Protection Efforts

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David Wach 998834846

Optional Assignment: Summary of Industrial Presentations

Lecture 2 Stormwater Facility and OutfallMr. Langan

Mr. Langdon focused on the stormwater treatment infrastructure that had to be created in the

West Donlands area as part of the urban revitalization of which Mr. Haley described in the firstlecture. Toronto had recently released stringent stormwater treatment requirements that were

designed to protect the environment. This created challenges for the engineers working on theWaterfront Toronto project and it was decided to build a new stormwater management facility

that would discharge into the Keating Channel.

Mr. Langdon explained how the stormwater treatment system would work with a large focus onthe outfall which would discharge into the channel. First the stormwater would go through a

large oil grit separator which was actually the largest in Canada. This would trap and removegrit and solids from the stormwater. Next the stormwater would head to balancing tanks which

act as a clarifier. Then it goes through UV disinfection before being pumped through the outfall

tunnel to the Keating Shaft at which point it is discharged.

There were challenges during the construction for this project. The outfall shaft had to be

properly aligned in order to reverse runoff direction to the channel. The decision had to be madeas to whether this channel would be excavated with a tunnel or an open cut. An open cut is less

expensive but due to the amount of existing infrastructure in the area a tunnel was chosen.

In order to use smaller and less expensive equipment at the stormwater treatment facility avertical standpipe was created at the Keating Shaft. It has a funnel-like weir structure reducing

the intensity of flows allowing for the smaller equipment size. This uses the hydraulic principleof continuity in which the velocity of a continuous flow can be controlled using various

geometries of flow shafts, tunnels and channels. In this particular case the flow into thestandpipe was constricted increasing the velocity, which then spiraled into the shaft reducing the

overall intensity of the discharge.

A flushing shaft was constructed in order to clear out debris from the system after a large stormthat may have settled. This was a new technology. It employed hydraulic principals of pressure

and head. Like a drinking straw a vacuum would be created in a shaft. Due to the lowerpressure the water would rise up the shaft. When the vacuum was released the water would flow

out of the shaft due to gravity. A weir was employed to create a wave called a flushing wavethat would wash away settled debris.