Santa Clara's Groundwater: Pollutants And Their Impact

The safety of groundwater in Santa Clara is affected by a variety of pollutants, which can be attributed to diverse human activities. These pollutants include nitrate and perchlorate, which have been found in some wells in the county. Other sources of groundwater pollution include leaking underground tanks, industrial spills, septic systems, inefficient agriculture, and illegal discharges and dumping of solid or liquid waste. To address these issues, organizations such as Valley Water are working to protect groundwater quality, advocate for effective remediation, and educate the community about water safety.

Elevated nitrate and perchlorate in South County wells

While most wells in Santa Clara County produce high-quality water that meets drinking water standards without any treatment, some South County wells have been found to contain elevated levels of nitrate and perchlorate. Nitrate is formed in the soil when nitrogen and oxygen combine, and it is easily transported through the soil, finding its way into groundwater supplies. Shallow wells, wells near a source, wells in sandy soil, or those that are improperly constructed or maintained are more likely to be affected by nitrate contamination.

The presence of elevated nitrate levels in South County wells is a particular concern due to the area's long history of agricultural production and continued use of septic systems in some areas. Sources of nitrate include fertilizers, septic systems, and livestock waste, making it a common issue in rural and agricultural areas. Nitrate contamination can interfere with the blood's ability to transport oxygen, leading to a condition called methemoglobinemia, which is especially dangerous for infants and pregnant women.

Perchlorate, on the other hand, has been detected in water wells in Morgan Hill, San Martin, and Gilroy, with the Central Coast Regional Water Quality Control Board overseeing the cleanup of the resulting groundwater plume.

To address these issues, Valley Water has implemented various programs and collaborated with stakeholders and agencies to define the extent and sources of nitrate contamination, reduce nitrate loading to groundwater, and minimize exposure to elevated nitrate levels. They also continue to monitor and protect groundwater from pollutants, including nitrate and perchlorate, through regular testing and by providing resources and guidance to well owners.

Leaking underground tanks

In Santa Clara, the oversight responsibility for investigations and clean-up of releases from underground storage tanks falls under the Santa Clara County Department of Environmental Health. This department works in partnership with Local Oversight Programs (LOPs) to oversee the cleanup of UST cases, with the Regional Water Board serving as the lead oversight agency when necessary.

The cleanup process for leaking underground tanks involves several steps, including free product removal, vapor extraction, enhanced bioremediation, bioventing, and monitored natural attenuation. In some cases, soil excavation and disposal are also required. The assessment and cleanup of UST leaks are governed by the Porter Cologne Water Quality Control Act and the Underground Storage Tank Regulations.

To prevent contamination from leaking underground tanks, the Santa Clara Valley Water District takes several measures. These include overseeing well construction and destruction, as improperly constructed or destroyed wells can allow contaminants to reach water supply aquifers. The district also conducts technical studies, coordinates with land use and regulatory agencies, and works to increase public awareness about groundwater protection.

In addition to leaking underground tanks, other sources of groundwater pollution in Santa Clara include industrial spills, septic systems, inefficient agriculture, and fuel leaks. Remediation of contaminated groundwater can take decades or longer, highlighting the importance of preventing contamination in the first place.

Industrial spills

Nonpoint source pollution, including industrial spills, poses a severe threat to the groundwater in Santa Clara County. These pollutants can infiltrate the groundwater basin, which provides about half of the county's water supply. The contamination of groundwater can have significant consequences for the residents who rely on it for their daily needs.

To address the issue of industrial spills and their impact on groundwater safety in Santa Clara, prevention is critical. Regulatory agencies and local authorities must implement measures to minimize the risk of spills and control their impact on the environment. This includes enforcing strict guidelines for industrial operations, ensuring proper waste management, and promoting best practices to prevent spills from occurring.

Additionally, regular monitoring and assessment of groundwater quality are essential. By detecting contaminants early, authorities can implement timely remediation efforts and mitigate the potential health risks associated with polluted groundwater. Collaboration between government agencies, industries, and the community is vital to ensuring the safety and sustainability of Santa Clara's groundwater resources.

Inefficient agriculture

• Nitrate Pollution: Nitrate is a common contaminant found in Santa Clara's groundwater, especially in South County wells. It is formed in the soil when nitrogen and oxygen combine, and its presence is of great concern for infants and pregnant women as it interferes with the blood's ability to transport oxygen, causing "blue baby syndrome." The use of fertilizers, septic systems, and livestock waste in agricultural practices contributes to elevated nitrate levels. Santa Clara Valley, with its history of agricultural production and continued use of septic systems, faces ongoing challenges in protecting groundwater from nitrate contamination.
• Water Hardness: While hard water does not pose direct health risks, it can cause aesthetic issues such as affecting the taste of water and creating nuisances for cleaning and plumbing. The high mineral content in hard water, particularly calcium and magnesium, can lead to scale buildup in pipes and fixtures, reducing water pressure and the efficiency of water heaters. This affects both agricultural irrigation systems and mechanical equipment in food processing plants, highlighting the importance of efficient water management in the region's agricultural sector.
• Perchlorate Contamination: Perchlorate has been detected in water wells in Morgan Hill, San Martin, and Gilroy, posing risks to the local water supply. While the Santa Clara Valley Water District is working to address this issue, it underscores the need for efficient agricultural practices to prevent further contamination.
• Saltwater Intrusion: While saltwater intrusion has stabilized in recent years, historical over-extraction of groundwater in Santa Clara Valley led to seawater intrusion. This problem was primarily addressed by importing surface water and implementing groundwater recharge techniques. However, efficient water management in agriculture is crucial to prevent future saltwater intrusion and protect groundwater resources.
• Leaking Underground Tanks and Spills: While not directly related to agriculture, leaking underground storage tanks and industrial spills can also impact groundwater quality. Santa Clara Valley has faced issues with leaking underground storage tanks, which can contaminate groundwater with chemicals and pollutants.

To address these issues, Santa Clara Valley Water promotes efficient agricultural practices and provides resources for residents, such as the "Guide for the Private Well Owner," which offers guidance on water quality testing, well maintenance, and groundwater protection. Efficient agriculture plays a vital role in preventing groundwater contamination, protecting public health, and ensuring a sustainable water supply for the region.

Septic systems

The Santa Clara Valley has a history of agricultural production, and septic systems are still in use in certain areas, making nitrate contamination an ongoing challenge for groundwater protection, particularly in South County. To address this issue, Valley Water has implemented several programs and collaborated with stakeholders and agencies to define the extent and sources of nitrate contamination, reduce nitrate loading to groundwater, and minimize exposure to elevated nitrate levels.

To prevent nitrate contamination from septic systems, it is crucial to ensure proper well location, construction, and maintenance. Wells should be located uphill and at a safe distance from septic tanks and leach fields. Regular maintenance of septic systems is also essential to avoid system failure and subsequent contamination. This includes not driving or parking heavy equipment over the septic tank, avoiding planting trees or shrubs near drain pipes, properly disposing of hazardous chemicals, and having the septic tank inspected and pumped regularly.

By following these guidelines and working together with local communities, Valley Water strives to protect the safety of Santa Clara's groundwater and reduce the impact of pollutants like nitrate from septic systems.

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