Last updated May 16, 2017

Landfill gas is a natural byproduct of waste decomposition from waste placed in a landfill such as wood and paper.  The principal components of landfill gas are methane and carbon dioxide.  Methane becomes potentially dangerous when it migrates into confined spaces in these concentrations. Confined spaces can range from trenches or cavities in the soil to buildings and structures. Methane can be flammable or explosive at concentrations between 5 to 15 percent by volume.  In addition to the risk of explosion, higher concentrations of methane in confined spaces can displace the oxygen and may lead to suffocation. To protect public health and safety, the regulatory limit for methane found in the soil at a landfill property boundary is 2.5 percent (by volume).  

Most modern landfills have gas monitoring wells in place near the property boundary of their facility. They are required to test these wells and report their findings to the Missouri Department of Natural Resources. Regulations enforced by the department prohibit methane gas concentrations, as measured in wells, from exceeding 2.5 percent by volume in soil at the landfill property boundary.

Most older landfills, however, are not required to have gas monitoring wells in place. In the case of these older landfills without gas wells, department staff look for any signs of methane migration during routine inspections, (e.g., dead or distressed vegetation off the fill boundary, gas bubbles in standing puddles of water, odors). If homes are nearby and there is a concern that methane may be leaving the site, the department may require the landfill to install gas monitoring wells and investigate for potential gas problems. Protecting Missouri citizens is the department’s highest priority.

For more information about methane issues, contact:

Missouri Department of Natural Resources
Solid Waste Management Program
P.O. Box 176
Jefferson City, MO 65102
800-361-4827 or 573-751-5401