The Tacoma landfill, located in western Pierce County, Washington, has been used for the disposal of waste since about 1960. Disposal operations are planned to continue at this site until at least 1990. Data were compiled and interpreted to help understand the possible effects of the landfill on water quality in the surrounding area. Data were collected from published and unpublished reports of the U.S. Geological Survey, and from predominantly unpublished data in the files of other government agencies. The Tacoma landfill is underlain by unconsolidated, glacially derived deposits that consist of a wide variety of mixtures of clay to boulder-sized materials. Ground water is mostly the result of rainfall on the land surface, and moves through artesian aquifers (under the landfill) that are tapped for both domestic and municipal use. Hazardous liquid and dissolved wastes are probably present in the landfill, and potential flow paths for waste migration exist. An undetermined number of single-family domestic wells and 18 public-supply wells are within 3 miles of the landfill, three as close as 0.2 miles. There is only limited evidence indicating ground- and surface-water contamination. Further investigations of the geology, hydrology and water quality are needed to characterize the impact the landfill has on ground- and surface-water of the surrounding area.
