Established in 1982, Government Code Section 65570 mandates FMMP to report biennially on even numbered years, the conversion of farmland and grazing land, and to provide maps and data to local government and the public.The Important Farmland survey area is based on Natural Resources Conservation Service (NRCS) modern soil surveys covering most non-governmental lands in California; 51 counties are fully or partially surveyed during the 2020 map update. Soil surveys specific to National Forests or other government land units are not surveyed. Beginning in 2000 SSURGO digital soil information was incorporated into the Contra Costa Important Farmland data and the 2016 data began to incorporate the new NRCS Gridded Soil Survey (gSSURGO). Data subsequent to 2000 may have acreage and soil line differences due to incorporation of newer NRCS-SSURGO or gSSURGO editions.

Prior to the availability of SSURGO or gSSURGO, soil information was hand-transferred from the paper soil surveys. Older versions of the data have not been modified. The land use minimum mapping unit of ten acres has not changed, but digital soil units of less than one acre occur in the gSSURGO-enhanced Important Farmland data. The data between 2000 and 2014 incorporates SSURGO and the interaction of land use and soil components resulted in units of less than ten acres for categories such as Other Land. The 2016 data incorporates gSSURGO and will no longer merge resulting polygons less than one acre for any map category for that and future updates. For more information on gSSURGO, contact the USDA-Natural Resources Conservation Service: https://www.nrcs.usda.gov

USDA NRCS soil survey CA013 (Contra Costa County).

Contra Costa County initial mapping year - 1984.

Geodetic Model:

1984 to 2012 - North American Datum of 1927

2014 to 2020 - North American Datum of 1983

2020 county boundaries: California Department of Forestry and Fire Protection, Fire and Resource Assessment Program (FRAP) 2018 version (cnty 18_2) of California Counties GIS data. https://frap.fire.ca.gov

2020 Imagery source: USDA Farm Service Agency - National Agricultural Imagery Program (NAIP); Summer 2020; True color; 1 meter resolution. https://www.fsa.usda.gov

Google Incorporated; Various dates; True color; Google Maps and Streetview. https://www.google.com/maps