Remediation projects can range from large, expensive projects, on which a great deal of effort is spent to clean up contaminated sites, to smaller, less costly projects, such as cleaning up a highway accident in which oil is spilled. In some cases, a site is so contaminated that it can only be fenced off and isolated as much as possible from the rest of the environment. Remediation projects usually begin with a site assessment to determine the costs of the project, as well as the technology that would be the most appropriate for the particular site.
Environmental remediation is carried out on various environmental media, including soil, sediment, groundwater, and surface water. This article classifies remediation according to whether it is done on water or soil. Water remediation includes both groundwater and surface water, whereas soil remediation includes topsoil, subsoil, and sediment. Soil and water remediation may be conducted separately or together, depending on the type and extent of the pollution.