Zone 7 Water Agency (Zone 7) is a water wholesale agency that provides high-quality treated drinking water to four water retailers serving over a quarter million residents and businesses. Water is delivered to the City of Livermore, City of Pleasanton, Dublin-San Ramon Services District and the California Water Service Company, along with some direct customers. Zone 7 also manages the Livermore-Amador Valley groundwater basin.
Zone 7 is implementing the design of a per- and polyfluoroalkyl substances (PFAS) treatment system to address the PFAS compounds found in the Chain of Lakes wellfield. The facility will be designed to treat to the state’s Consumer Confidence Report Detection Limits of PFAS compounds that have regulations.
The treatment process to be employed at the COL PFAS Treatment Facility includes media filled pressure vessels for adsorption of PFAS; the project consists of several key components: production well pumps, desanders, cartridge filters, and media pressure vessels.
This project will include construction of concrete pads, piping modifications, installation of new valving and installation of new pressure vessels containing specialized media for the adsorption of PFAS compounds. Water from the three COL wells (1, 2, and 5) will be routed through these pressure vessels. Once the water passes through the vessels, the water will be PFAS free and will have small amounts of disinfectant injected back in before being sent out to Zone 7’s distribution system for delivery. More detailed work of the project includes:
• Wells 2 and 5 (located nearby) would combine with Well 1 for chemical additions and distribution. Existing chemical addition and distribution lines would remain in Well No. 1 building. New raw water transmission lines would be added to reroute the raw water into the centralized PFAS treatment facility prior to chemical addition.
• Two bypass systems; the first would be in an underground vault allowing for a complete bypass of the PFAS treatment facility, and the second would be a bypass valve prior to the treatment vessels.
• A new concrete pad for the pressure vessels to accommodate six media contactor trains filled with Ion Exchange (IX) media with additional space to add six more at a later date if the treatment facility is expanded.
• Cartridge filters with one additional filter for future facility expansion, if required to meet Zone 7’s future planned commitments.
• New driveways.
• New pavement on the east side of the Project site to allow chemical deliveries and PFAS treatment maintenance vehicles. The existing driveway would provide access until the new one is constructed.
Work is contained within Zone 7’s existing wellsite property. Once constructed, the facility will generally look and operate much as it does today. The facility will remain an unstaffed facility, with operators onsite approximately daily to ensure it is functioning correctly and respond to any maintenance needs. No new deliveries as this facility would not introduce new chemicals, though it would introduce a new shipment of media approximately once a year which would be delivered by semi-truck.
Project construction is anticipated to begin in February, 2023, and be completed in mid-March, 2024 — a period of approximately 13 months. Project construction will occur year-round, with the exception of inclement weather conditions.