Lateral collection grid for landfill gas and method

A gas collection system for use at landfills and the like of the type having a gas-producing waste pile, the gas collection grid comprising:

• a lower geocomposite positioned over the gas-producing waste pile;
• a protective layer of soil positioned over the lower geocomposite, with a grid pattern of vertical openings formed in the protective layer of soil spaced apart from one another;
• an upper geocomposite positioned over the protective layer of soil such that the protective layer of soil is positioned between the lower and upper geocomposites;
• an impermeable geomembrane positioned over the upper geocomposite;
• and
• a cruciform gas collector conduit grid extending laterally beneath the impermeable membrane and positioned within or atop the protective layer of soil and having a plurality of collection orifices formed adjacent the vertical openings formed in the protective layer of soil, and wherein the impermeable geomembrane is non-perforated adjacent the collection orifices and the cruciform gas collector conduit grid is adapted for delivering collected gas laterally from beneath the geomembrane rather than vertically through the geomembrane.

A method of installing a gas collection grid for use at landfills and the like of the type having a gas-producing waste pile, the method comprising the steps of:

• covering the waste pile with a protective layer of soil;
• creating vertical openings in the protective layer of soil spaced apart from one another in a grid pattern;
• creating a cruciform grid of gas collector conduits having a series of gas collection orifices space apart from one another to generally match the spacing of the grid pattern of vertical openings in the protective soil layer and positioning the grid of gas collector conduits such that the orifices generally are aligned with the vertical openings in the protective soil layer;
• covering the grid of gas collector conduits with an upper layer of soil;
• placing a gas-impermeable membrane over the upper layer of soil;
• and
• connecting the grid of gas collector conduits with an external gas extraction apparatus.