Description: The California Air Basins layer is a polygon shapefile coverage representing the 15 California air basins, as defined in state statute and regulation. See the California Health and Safety Code, Section 39606 et seq. and California Code of Regulations, Title 17, Section 60100 et seq. Shapefile coverage. This data layer shows the air basin boundaries and their names, as of October 2014. The file has been updated using as main source the: California Environmental Protection Agency Air Resources Board maps (http://www.arb.ca.gov/knowzone/basin/basin.htm)