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Groundwater Quality

Most wells in Santa Clara County produce high-quality water that meets drinking water standards without the need for treatment. The primary exception is nitrate, which is elevated in a number of South County wells and continues to be a groundwater quality challenge. Cleanup is ongoing at a number of groundwater contamination sites and elevated levels of perchlorate are still observed in some South County wells. The district is working with other agencies, basin stakeholders, and the public to address these issues and ensure groundwater quality remains high.

The district monitors water quality at wells throughout the county and also evaluates data from local water suppliers to assess regional groundwater quality and identify potential threats so they can be appropriately addressed. The district also monitors the quality of water used for groundwater recharge to ensure groundwater resources are protected. The district's recent groundwater quality and recharge water quality information can be found in the reports below. 

If your water comes from a public water supply, such a city or water company, it is tested regularly to make sure it meets state and federal drinking water standards. If your water comes from a private well, the district encourages you to have your well water tested annually by a certified laboratory to protect your health, even though your water may taste and look fine. More frequent testing is recommended if you notice a change in color, odor, or taste. The district's Guide for the Private Well Owner [PDF] offers helpful information on water quality testing, well maintenance and protection. The district is currently offering basic water quality testing for eligible private domestic wells and rebates for well owners exposed to high nitrate. For more information, please see the domestic well testing page or the nitrate treatment system rebate program page.

Leaking underground fuel tanks, industrial spills, storm runoff, septic systems, inefficient agricultural operations, and other sources can pollute groundwater, making it costly to treat or even unusable. Since the restoration of contaminated groundwater can take decades or longer, preventing contamination is critical. The district oversees well construction and destruction since improperly constructed or destroyed wells can allow contaminants to reach water supply aquifers. Other district efforts to prevent or mitigate contamination include technical studies, coordination with land use and regulatory agencies, and efforts to increase public awareness of the importance of protecting groundwater resources.