A landfill is a site for the disposal of waste materials, where waste is buried in the ground. Landfills are designed, operated, and regulated to minimize the risk of pollution and negative impacts to people and the environment. Modern landfills are well-engineered and managed facilities that meet stringent design, operation, and closure requirements established under the Resource Conservation and Recovery Act (RCRA). Landfills are classified into different types, including municipal solid waste landfills (MSWLFs), bioreactor landfills, industrial waste landfills, coal combustion residual (CCR) landfills, and hazardous waste landfills. MSWLFs are designed to receive household waste, as well as other types of nonhazardous wastes, such as commercial solid waste, nonhazardous sludge, conditionally exempt small quantity generator waste, and industrial nonhazardous solid waste. Landfill operators must monitor their facilities to detect any contamination, report monitoring data to the regulatory agency, and respond quickly to any problems.