Is My Property Near a Nitrate-Impacted Water Well?

Over 95% of Californians receive safe drinking water from their public water system. This interactive tool is intended for private domestic well owners to evaluate if their well is near a nitrate-impacted well.

If your location is not within 2,000 feet of a nitrate-impacted well, the State Water Board still recommends that you test your domestic well annually by a certified drinking water laboratory. Since the availability of groundwater data is limited, and domestic wells are not regulated, domestic well water quality is largely unknown.

Show all sampled wells

To maintain well owner confidentiality, well locations are not displayed at this scale.
Nitrate FAQ Nitrate in Groundwater Frequently Asked Questions

Within 2,000 feet

Nitrate impacted wells are near my location. What do I do now?

The supplied map displays well locations of recent nitrate contamination above the maximum contaminant level (MCL). If you find that one or more wells are within a 2,000 feet radius of your address using the supplied mapping tool, the State Water Board highly recommends that you test your water well as soon as possible.

If your analytical results reflect high levels of nitrate in your drinking water, boiling, softening, and filtering your well water will not reduce or remove nitrate. Besides bottled water, water treatment methods such as reverse osmosis, distillation, purification, and ion exchange are effective at removing nitrate. Various products exist that treat your water at the sink (point of use, POU), or as water enters your household (point of entry, POE).


For the purposes of this interactive tool, a "nitrate-impacted well" means it has at least one detection of nitrate above the maximum contaminant level (MCL) since 2000. To determine if your domestic well has nitrate above the MCL, you need to test your well. Please see the informative links provided and contact a drinking water laboratory to test the water quality in your well.

Data used in this evaluation includes:

  • Environmental monitoring (site cleanup) wells from GeoTracker

And water supply wells from the following agencies' datasets:

  • State Water Board Division of Drinking Water (formerly California Department of Public Health Drinking Water Program)
  • State Water Board GAMA Program (Priority Basin, Domestic Well and Special Studies Projects)
  • Department of Water Resources
  • UC Davis well data
  • U.S. Geological Survey National Water Information System NWIS

All data are available at the GAMA program's online groundwater information system, GeoTracker GAMA (

The datasets used for the map represent both the shallow and deep aquifer resources. The domestic well data included is a direct result of the participation of well owners in domestic well sampling events. The absence of an impacted well does not mean that nitrate contamination is not present.

This map uses a third-party address-locating service (also known as a "geocoding service") which translates addresses to points on a map. This process, which does not match the address to the parcel, is only as accurate as the underlying street data, which varies depending on the area.

This map is intended for general informational purposes only.


Domestic wells are typically shallower in depth, and may be more susceptible to contamination at the land surface. If your well is near a potentially nitrate-contaminating activity (i.e., a dairy, a septic tank, or agricultural nitrogen fertilizers), we recommend that you have your well tested. For all other instances, the State Water Board recommends that you test your domestic well water once per year as part of its regular maintenance. For more information about nitrate in groundwater, please see these Frequently Asked Questions. You can also call your local county environmental management department or the State Water Board Division of Water Quality for any water quality questions.

For more information, please contact Dori Bellan at or (916) 341-5502.

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