It would be about 1,000 feet from the river. Before construction can begin, Gregory Canyon Ltd. must obtain operating permits from several agencies, including the county's Department of Environmental Health and the San Diego Regional Water Quality Control Board. The agencies will focus on how the landfill's designers propose to keep 30 million to 33 million tons of refuse from contaminating ground water that underlies the canyon and flows into the San Luis Rey. Toxins that can leak from a landfill are produced primarily when rainwater seeps into decomposing refuse and picks up chemicals as it flows downward. Modern landfills are designed to keep garbage as dry as possible to prevent creation of this toxic liquid, called leachate.
Operators cover newly dumped garbage with soil each day.
Once the landfill closes, they cap the entire site with a plastic liner, soil and vegetation. Modern landfills also have a liner system below the refuse, consisting of layers of plastic sheeting, gravel, soil and drainage pipes. This system is intended to collect leachate and prevent it from coming in contact with underlying ground water. The engineering challenge is formidable, but Southern California landfills have the advantage of a relatively dry climate. Landfills here do not present the same problems as those in wetter parts of the country, such as the Southeast, where rainfall is heavy and water tables high.