Acreage, Net: That portion of gross acreage exclusive of public streets, rights-of-way, and dedications of land for public.

Adaptive Use/Reuse: The process of converting a building to a use other than that for which it was originally designed and/or built. Such a conversion may be accomplished with varying alterations to the building.

Aerobic: A situation in which molecular oxygen is a part of the environment. (Environmental Laboratory 1987)

Affordable Housing: Under state and federal statutes, housing that costs no more than 30 percent of gross household income. Housing costs include rent or mortgage payments, utilities, taxes, insurance, homeowner association fees, and other related costs.

Air Basin: A geographical area in California defined as a distinct air basin for the purpose of managing the air resources of the state on a regional basis. An air basin generally has similar meteorological and geographic conditions. Unless otherwise specified, “air basin” refers to the San Francisco Bay Area Air Basin.

Air Pollutants: Amounts of foreign and/or natural substances occurring in the atmosphere that may result in adverse effects on humans, animals, vegetation, and/or materials.

Air Quality Standards: The prescribed (by the Environmental Protection Agency and the California Air Resources Board) level of pollutants in the outside air that cannot be exceeded legally during a specified time in a specified geographical area.

Airport Influence Area A: The area that is flown by an aircraft at an altitude of 10,000 feet or less above mean sea level a minimum of once weekly.

Ambient: Refers to the overall conditions surrounding a place or thing. For example, ambient monitoring refers to comprehensive monitoring of water quality, biota, sediments, etc. (SFEP 2007)

Ambient Air Quality: The air occurring at a particular time and place outside of structures. Often used interchangeably with “outdoor air.”     

Ambient Air Quality Standards: Health and welfare based standards for clean outdoor air that identify the maximum acceptable average concentrations of air pollutants during a specified period of time.

Ambient Noise Level: The level of noise that is all-encompassing within a given environment for which a single source cannot be determined. It is usually a composite of sounds from many and varied sources near to and far from the receiver.

Anadromous: Fish that live some or all of their adult lives in saltwater but migrate to freshwater to spawn (reproduce).