Toronto Water manages, operates and maintains 85 stormwater management pond facilities across the city of Toronto. These facilities are designed to collect runoff from rain and melted snow, which is important in large urban cities like Toronto that have a lot of pavement.
Benefits of Stormwater Management Pond Facilities
By collecting runoff from rain and melted snow, stormwater management ponds help:
- reduce localized flooding.
- control erosion by limiting the amount of stormwater that goes to nearby creeks and rivers.
- improve water quality by allowing dirt and other solids in stormwater runoff to settle to the bottom of the pond.
Types of Stormwater Management Pond Facilities
There are two different types of stormwater management pond facilities:
Wet ponds hold water all the time, and are designed to collect and store runoff from rain and melted snow. This allows dirt, sand, silt and other solids in the runoff to settle to the bottom of the pond, which improves the quality of water released back into creeks and rivers downstream.
The City of Toronto also operates two larger wet ponds near Lake Ontario that feature an additional "flow balancing system", which directs the flow of stormwater runoff through different cells. These cells help to support the settlement process and clean the runoff before it is released into Lake Ontario. These ponds can be found in Humber Bay (Etobicoke) and Bluffer's Park (Scarborough).
Dry ponds are dry and often found in wide open spaces. These ponds are equipped with gates that close off access to local storm sewers and direct water to the detention area during periods of heavy rain. Once the storm has stopped and water levels have decreased, the gates open and water is directed into the storm sewers.
Pond Cleaning and Maintenance
Many of the City's stormwater management pond facilities were built in the 80s and 90s, and are aging and accumulating sediment. To help ensure the facilities are working as designed, Toronto Water and the Toronto and Region Conservation Authority (TRCA) have initiated a pilot project to remove sediment and conduct maintenance on seven key ponds.
Six facilities have been cleaned to date with work on the following pond currently underway:
Pond clean out and maintenance occurs in the following four phases:
Site Preparation and Construction Access
In order to gain access to the pond, the first step is to prune, and remove some of the trees and brush around the pond. This is done in consultation with the City of Toronto's Parks, Forestry and Recreation division. An area is then created to stockpile the sediment. In some cases, a platform that extends into the pond is also made out of gravel, so that all areas of the pond can be reached for clean out.
Sediment Dewatering and Dredging
The next phase involves lowering the water level of the pond in order to safely dredge the sediment. This is done gradually to allow for wildlife to be collected and re-located by staff who are licensed by the Ministry of Natural Resources. Sediment from the entire pond is then dredged and moved to a designated area, where it is dried and tested for contaminants. Based on the findings, sediment is then trucked away for either re-use or disposal.
Once sediment has been removed, the pond is fully inspected and repairs to the walls of the pond are conducted, as needed.
The final stage of the project is to restore vegetation surrounding the pond. This will be done in collaboration with the City's Parks, Forestry and Recreation division and consists of site appropriate landscaping and earthworks in accordance with the City's landscaping guidelines.