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Environmental Protection at Vancouver Landfill

[ Leachate Containment and Collection System ]  Leachate Containment and Collection System
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Leachate is produced by water percolating through waste. Leachate is managed by a system of two parallel ditches surrounding the Landfill. The inner ditch collects leachate, and the outer ditch contains clean surface water from outside the Landfill. By keeping the water level in the outer ditch higher than in the inner ditch a hydraulic gradient is formed, preventing the leachate from migrating out of the Landfill. There is a porous demolition layer, consisting primarily of wood, underneath the Landfill that provides a preferential pathway for leachate to move laterally toward the leachate collection ditches. The leachate collected in the inner ditch is then pumped to the Annacis Island Wastewater Treatment Plant. In 2004 approximately 2 million cubic metres of leachate were pumped to Annacis Island for treatment. The program involves sampling from 15 deep and 13 shallow groundwater wells, 10 surface water locations and one leachate location. To ensure the effectiveness of the leachate collection system, water quality is routinely monitored.

The samples are sent to an independent lab and analyzed for up to 40 different parameters.

Landfill gas is produced by decomposing organic material, and can lead to greenhouse gas emissions and odours unless properly managed. Landfill gas is comprised mainly of carbon dioxide and methane with trace amounts of other gases including odorous hydrogen sulfide. The gas is collected by approximately 200 vertical and 10 horizontal extraction wells.

In December 2002, the City of Vancouver and the Corporation of Delta entered into an agreement with Maxim Power Corp and Hot House Growers for the sale of landfill gas for beneficial purposes. Previously, landfill gas collected at the Landfill were flared off to control greenhouse gases and odour emissions, and also used to provide heat and hot water at the Landfill Administration building. The Vancouver Landfill Gas Utilization Project conveys the majority of landfill gases collected at the Landfill to Hot House Growers' greenhouses in Delta, where it is used to produce electricity for sale to BC Hydro. Heat cogenerated by the production of electricity is used in Hot House Growers' greenhouse operations.

Utilization of the landfill gas reduces greenhouse gas emissions by a pproximately 30,000 tonnes per year of carbon dioxide equivalents, or approximately 6,000 automobiles/year, and reduces the consumption of non-renewable energy by approximately 500,000 gigajoules of energy per year, equivalent to providing the annual energy requirements for approximately 3,000 to 4,000 homes.

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