Zone 7 Celebrates Groundwater Awareness Week with the Upcoming Completion of its Second PFAS Treatment Plant

News Release

LIVERMORE, Calif. (March 7, 2025) – Zone 7 Water Agency (Zone 7) continues to strategically invest in groundwater treatment infrastructure to ensure the Tri-Valley’s drinking water remains safe from per- and polyfluoroalkyl substances (PFAS), commonly known as “forever chemicals.” This month, Zone 7 will celebrate the completion of its second Ion Exchange (IX) PFAS treatment plant at the Chain of Lakes wellfield, which will be operational this month, and is currently planning a third treatment plant at the Mocho Wellfield in Pleasanton. The Livermore Valley Groundwater Basin plays a critical role in providing reliable water for the area, especially during droughts. Investments in PFAS treatment infrastructure will ensure that the basin remains a safe and sustainable source of water, further ensuring long-term water reliability for the Tri-Valley.

“As California faces increasing water challenges, expanding our groundwater treatment infrastructure is a critical step in ensuring long-term reliability for the residents of the Tri-Valley,” said Zone 7 Water Agency General Manager Valerie Pryor. “These investments allow us to treat groundwater using state-of-the-art ion exchange treatment, providing families and businesses with a more secure and sustainable water supply when imported State Water Project water is unavailable, as is typical in periods of drought. Our commitment to proactive groundwater management means we are always looking ahead to protect this vital, local resource for our community.”

Advancing PFAS Treatment to Protect Water Quality

PFAS are synthetic chemicals found in everyday products such as non-stick cookware, food packaging, and firefighting foams. These substances have been detected in air, soil, and water worldwide. Although water agencies do not produce PFAS, they are responsible for removing it from contaminated water sources to ensure safe drinking water.

In 2018, Zone 7 voluntarily initiated proactive monitoring for PFAS and in an abundance of caution, voluntarily reduced production in wells where PFAS was detected as the regulatory bodies worked on drafting new regulations for the contaminants of emerging concern.

In April 2024, the U.S. Environmental Protection Agency (EPA) adopted new regulations for six types of PFAS. Public water systems must complete initial monitoring by 2027 and address any contaminated sources that are over the new compliance requirements by April 2029. In its commitment to safeguarding public health, Zone 7 was an early adopter of PFAS treatment in anticipation of the new regulations:

  • Stoneridge IX PFAS Treatment Plant – Opened in September 2023, this was the first plant of its kind in Northern California. Funded in part by a $16 million grant from the California Department of Water Resources, the plant sets a new standard for PFAS removal.
  • Chain of Lakes IX PFAS Treatment Plant – A larger-scale version of the Stoneridge plant, the Chain of Lakes treatment plant will become operational this month and will be celebrated with a ribbon cutting ceremony at 10am on March 26.
  • Upcoming Mocho Wellfield Treatment Plant – In 2025, Zone 7 will begin designing a third PFAS treatment plant in Pleasanton. This plant will further expand PFAS treatment locally, improve water quality, and restore groundwater pumping capacity when needed.

Decades of Commitment to Groundwater Sustainability

The Livermore Valley Groundwater Basin is the Tri-Valley’s local water savings account, providing a crucial supply that supports the region, especially during dry years. For decades, Zone 7 has proactively managed this resource, implementing sustainable practices to maintain groundwater levels and ensure long-term reliability.

Recognizing the statewide importance of groundwater, the California State Legislature enacted the Sustainable Groundwater Management Act (SGMA) in 2014 to address overuse and protect this critical resource, which provides up to 60% of California’s water supply during droughts. Groundwater overdraft has caused land subsidence, dry wells, and reduced surface water availability, prompting SGMA’s mandate for local agencies to develop plans to balance groundwater use within 20 years.

However, decades ahead of SGMA, Zone 7 recognized many of these same issues and had already been managing the Tri-Valley’s groundwater basin since the 1960’s. As the designated Groundwater Sustainability Agency, Zone 7 submitted its existing plan as an Alternative Groundwater Sustainability Plan (AGSP)—one of only nine accepted statewide in 2019—demonstrating its long-standing commitment to sustainable water management. Continuing its leadership, Zone 7 submitted the Sustainable Groundwater Management Annual Report for Water Year 2023 ahead of the April 1, 2024, statutory deadline. On June 27, 2024, the Department of Water Resources (DWR) reaffirmed Zone 7’s approach by approving its Alternative Groundwater Sustainability Plan (AGSP) submitted in 2021.

Today, groundwater accounts for approximately 10% of the Tri-Valley’s annual water supply, and the agency actively replenishes the basin with water it imports through the Delta from the State Water Project. In fiscal year 2023-24, Zone 7 added 9,600 acre-feet of water, increasing total groundwater storage from 216,800 acre-feet in 2022 to 231,000 acre-feet in 2024—this groundwater is a critical local water supply during times of drought when imported water is limited or unavailable.

During Groundwater Awareness Week, March 9-15, Zone 7 is highlighting these efforts through a special groundwater installment in its Wondrous World of Water video series, which walks viewers through the process of how the local arroyos are utilized to strategically recharge the groundwater basin with imported water to ensure water reliability and the health of the basin.

Learn more at zone7water.com/groundwater.

Image courtesy of Zone 7: PFAS Management Timeline