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Southwestern Landfill Environmental Assessment

Water Protection

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picture of water

Today's landfills must be fully protective of water. It's our top priority.


Landfill Liner

landfill liner diagram

Today's landfills must be constructed to fully protect the surrounding groundwater and all nearby water bodies. Landfills use durable liners with multiple layers to protect the environment, and surrounding water is monitored during and after operations.

Walker is proposing to use a generic double composite liner for the Southwestern Landfill. This is the same liner Walker uses at our South Landfill in Niagara Falls, Ontario. Our South Landfill is also constructed in a mined-out limestone quarry and the liner has been performing as designed.

A landfill liner serves two important purposes:

  1. Provide a barrier between the waste inside the landfill and the outside environment, including groundwater.
  2. Collect leachate so it can be removed from the landfill and treated.

The landfill liner must work for a long time - longer than the "contaminating lifespan" of the landfill, which is the length of time it takes for the waste to stabilize. Environmental engineers and scientists who specialize in materials designed the generic double composite liner to be fully protective of the environment in a wide variety of hydrogeologic settings (different environments of rocks, soil, and water).

To be approved, landfill liners must be fully protective of the environment and meet the strict requirements of the Environmental Protection Act, Ontario Landfill Standards, and other regulations.

Click here to learn more about the landfill liner




Landfills safely manage two types of water

There are two types of water that need to be managed at a landfill - leachate and stormwater. Both leachate and stormwater are managed while the landfill is open and after it is capped and closed.



Leachate is rain or snow that comes into contact with the waste, usually by filtering down through the landfill. It is collected in pipes in the landfill liner system, then is pumped to a treatment plant. The treated water must meet strict water quality guidelines before being released back into the environment. 


Diagram of leachate management and treatment




Stormwater is rain or snow that does not come into contact with waste, for example in buffer areas around the landfill or on finished areas that are capped. Stormwater is collected in a pond and it is tested. If it meets Provincial requirements, the clean stormwater is released to the environment. 


Diagram of stormwater management



Frequently Asked Water Questions

How is water monitored?

Landfills are required to monitor water at many different places, even after the landfill is closed. Some typical water monitoring requirements include:

  • Quality of treated leachate water
  • Local groundwater quality and quantity
  • Surface water quality and quantity, upstream and downstream
  • Secondary leachate collection system (to detect issues with the primary liner)

Monitoring reports are submitted each year to the Ministry of the Environment, Conservation and Parks for review and to confirm that the landfill and its operations meet the requirements of environmental approvals.


What can be done if a leak in the liner ever occurred?

  • In the generic double composite liner design, there is a secondary liner as a backup beneath the primary liner.
  • Landfills require a contingency plan (i.e. groundwater collection systems) for the unlikely event of a leak.
  • The contingency plan outlines the tools and procedures ready and available to deal with issues.
  • Laws require a landfill owner to notify the Ministry of the Environment, Conservation and Parks if a leak or spill occurs.


What happens if a landfill is abandoned by its owner?

  • Since businesses cannot guarantee that they will be around in the future (ie. bankruptcy), the Ministry of the Environment Conservation and Parks requires all private landfills to provide Financial Assurance. 
  • Financial Assurance is money provided by the company to the Province that would be used to pay for monitoring, maintenance and contingencies in case the owner cannot.
  • The amount of Financial Assurance is calculated by the MOECC, using the F-15: Financial Assurance Guideline