Wastes that exhibit certain characteristics may be regulated by RCRA. A waste may be considered hazardous if it is ignitable (i.e., burns readily), corrosive, or reactive (e.g., explosive). Waste may also be considered hazardous if it contains certain amounts of toxic chemicals. In addition to these characteristic wastes, EPA has also developed a list of over 500 specific hazardous wastes. Hazardous waste takes many physical forms and may be solid, semi-solid, or even liquid. A hazardous waste landfill is built to specific regulations to allow for the disposal of waste designated by regulatory agencies as being hazardous. These regulations are far more stringent that for an MSW landfill. WM has 5 secure hazardous waste landfills permitted under RCRA. These sites all operate under the name "chemical waste management" (CWM).