California Department of Resources Recycling and Recovery (CalRecycle) 

Beyond 2000: California's Continuing Need for Landfills

Protecting Environmental Quality

Cross section of liner system.

Protection of Water Quality

Leachate Collection and Removal System: Leachate is liquid generated from moisture brought in with the waste, from rainfall which percolates into the landfill, and from the waste decomposition process. It contains dissolved and insoluble chemicals. A network of perforated pipes within the landfill collects the leachate, which then is pumped to a treatment plant.

Leachate Treatment Plant: Leachate may be treated on site for reuse (e.g., to control dust) or may be piped to a treatment plant off site for safe disposal.

Composite Liner System: The composite liner extends entirely beneath the landfill, like a bowl, to contain any leachate. It consists of at least 2 feet of compacted clay, on top of which is a heavy sheet of tough, 60-80 mil HDPE plastic and a protective geo-textile cushion. Over this is a two-foot layer of crushed rock or gravel, within which are the perforated leachate collection pipes.

Groundwater Monitoring Wells: These wells are installed around the perimeter of the landfill and are sampled periodically to detect any possible migration of leachate off the site.

Protection of Air Quality

Landfill Gas Removal System: Landfill gas, mostly methane and carbon dioxide, is formed as the waste decomposes. A grid system of perforated pipes connected to vacuum blowers collects and removes the gas.

Flare Station or Electrical Generator: The landfill gas is either burned off in a flare, or used to generate electricity in a gas turbine.

Gas Monitoring Wells: Gas monitoring wells are placed all around the site, and sampled frequently, to make certain that there is no migration of the gas beyond the site boundaries.

Protection Against Off-Site Flooding

Drainage and Erosion Control System: This system consists of carefully graded decks, surface channels, down drains and holding basins to prevent off-site flooding. The system must be able to control flows resulting from a 100-year-frequency, 24-hour storm.

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Last updated: May 28, 2003
Landfills, Perez: (916) 323-0834