Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety. MCLGs are set by the EPA.

Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology.

Primary Drinking Water Standard - Maximum levels of contaminants that may have an adverse effect on the health of persons; specific treatment techniques adopted in lieu of maximum contaminant levels; the monitoring and reporting requirements that pertain to maximum contaminant levels.

Secondary Drinking Water Standard - An aesthetic quality standard. May apply to any contaminant in drinking water that may adversely affect the odor or appearance of the water and may cause a substantial number of persons served to discontinue its use.

Public Health Goal - The level of a contaminant in drinking water below which there is no known or expected risk to health. PHGs are set by the California Environmental Protection Agency.

Action Level - The concentration of a contaminant that, if exceeded, triggers a treatment or other requirement that a water system must follow.

Aquifer - A geologic unit that can store and supply significant quantities of water in underground formations composed of rock, sand, fractures and gravel. Water is stored in the small spaces between the grains of sand, rock or in the fractures.

Ground Water - The water that is stored in aquifers. Extracted for use by wells.

Well - A bored hole drilled through a geologic formation into an aquifer. Used to extract water from the aquifer.

Surface Water - Water either flowing in an open channel like a river or creek, or confined in a lake.

Watershed - Large areas of land that drain into a particular river, lake, reservoir or aquifer.

Treatment Technique - A required process intended to reduce the level of a contaminant in drinking water Links to

Other Water Related Web Sites

California-Nevada Section, American Water Works Association - www.ca-nv-awwa.org

American Water Works Association Research Foundation - www.awwarf.com

Association of California Water Agencies - www.acwanet.com

United States Environmental Protection Agency Office of
  Ground Water and Drinking Water - www.epa.gov/OGWDW/

Division of Drinking Water and Environmental Management - www.dhs.cahwnet.gov/ps/ ddwem.