Annual Well Sampling Report

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The Pesticide Contamination Prevention Act (PCPA) requires DPR to maintain a statewide database of wells sampled for pesticides. Public agencies that sample wells for pesticides must submit these results to DPR in a timely manner. DPR's Well Inventory Database, established in 1983, includes the well number, well type, well location, chemical analyses performed, sample date, sample type (initial or confirmation), analysis date, sample concentration and minimum detection limit (in parts per billion), and laboratory information. Agencies also may send information about well construction or the source of the potential contamination. DPR uses these data to evaluate and guide our groundwater protection monitoring and research activities. These data are used by academic institutions, governmental agencies, and the public.

The following fact sheet contains information about pesticides or degradates that the Groundwater Protection Program actively samples for or has sampled for in the past, including pesticide use and available human health advisory information related to drinking water standards. Not all information is available for all pesticides.

As required by law, DPR posts an annual report that includes statewide well sampling results collected by public agencies and describes the actions taken by DPR and the State Water Resources Control Board to prevent pesticides from migrating to the groundwaters of the state.

These files are in PDF format and download times may vary with the speed of your connection. (If you cannot open these files, you can download a free Acrobat reader).

Electronic versions of previous reports are available upon request at

Annual Well Sampling Report
Report Year Sampling Period
37th Annual Well Sampling Report, 2022 Update, PDF
2021 Update, PDF
2020 and additional data from 2019
2020 Update, PDF 2019 and additional data from 2018
2019 Update, PDF 2018 and additional data from 2017
2018 Update, PDF
Appendix A, PDF
Appendix B, PDF
Appendix C, PDF
Appendix D
Glossary of Terms, PDF
2017 and additional data from 2011-2016
2017 Update, PDF
Appendix A
Appendix B
Appendix C
Appendix D
Glossary of Terms
2016 and additional data from 2015
2016 Update, PDF 2015
2015 Update 2014 and additional data from 2013
2014 Update 2013
2013 Update 2012
2012 Update 2011 and additional data from 2004-2011
2011 Update July 1, 2010 - December 31, 2010
2010 Update July 1, 2009 - June 30, 2010
2009 Update January 1, 2008 - June 30, 2009
2008 Update July 1, 2007 - June 30, 2008
2007 Update July 1, 2006 - June 30, 2007
2006 Update July 1, 2005 - June 30, 2006
2005 Update July 1, 2004 - June 30, 2005
2004 Update July 1, 2003 - June 30, 2004
2003 Cumulative Report 1986-2003 November 1, 1983 - June 30, 2003

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