Regional Groundwater Facilities Project

Background

Zone 7 Water Agency (Zone 7) is a water wholesaler who procures water from the California Department of Water Resources (DWR) and produces water from its regional groundwater wells to sell to the City of Pleasanton (City) and other Tri-Valley water retailers for distribution to its customers. In addition to buying water from Zone 7, the City also has local groundwater wells that supply up to 3,500 acre-feet per year of water (known as City’s groundwater production quota or GPQ), which represents approximately 20 to 25 percent of the City’s total water supply needs.

Per- and polyfluoroalkyl substances (PFAS) have recently been detected above regulatory requirements in portions of the Livermore-Amador Valley Groundwater Basin. This detection has impacted some of Zone 7’s regional groundwater wells (see Zone 7 PFAS Information for details) and all of the City’s groundwater wells (see Pleasanton Water for details). On October 17, 2023, the City Council approved proceeding with the planning of new groundwater wells within the Bernal subbasin (which is believed to be outside the existing PFAS plume based on Zone 7 testing and groundwater modeling) to recover the use of its GPQ. As part of the planning efforts, the City Council placed an emphasis on evaluating the feasibility of collaboration with Zone 7. In February 2024, Zone 7 and City staff completed a process that outlined the terms of collaboration for a joint project titled the Regional Groundwater Facilities Project (Project).

Overview

The Project is envisioned to include the following elements:

Construction of new groundwater well(s) in the Bernal subbasin with the goal to increase Zone 7’s groundwater production capacity and drought resiliency for the overall Tri-Valley region, recover the City’s GPQ, and produce water supply that meets and exceeds all State and federal water quality standards.
Connection of the new groundwater well(s) to Zone 7’s water supply system and upgrade of the existing Zone 7 Hopyard Treatment Facility to treat the water.
Delivery of the City’s GPQ via the Zone 7 water supply system (as opposed to the current configuration of direct delivery from dedicated City wells).

Zone 7 will serve as the lead agency in the evaluation, permitting, design, construction, operation, and maintenance of the project. The City will support Zone 7 by providing necessary land rights and paying its fair share of costs proportional to the City’s GPQ. The Project will be implemented in the following phases:

Phase I – Feasibility: This phase will evaluate the feasibility of the Project and has a target completion date of spring 2025.
Phase II – Design and Construction: If the City and Zone 7 find the Project to be feasible, this phase will include the design and construction of improvements in accordance with Phase I recommendations. The target completion date for this phase is the end of 2028.
Phase III – Operation and Maintenance: This phase would start after completion of Phase II and when required permits to operate are in place.

Upcoming Activities

The Project is currently in Phase I. Current and upcoming activities include the following:

City and Zone 7 Agreement for Phase I: The City and Zone 7 are currently preparing an agreement to perform Phase I of the Project. The anticipated schedule for governing body consideration and approval of the agreement is the June 18, 2024, City Council meeting and the July 17, 2024, Zone 7 Board Meeting.
Well Siting Evaluation: The purpose of this evaluation is to identify potential locations for the installation of new groundwater wells based on factors such as historical information on anticipated yield and water quality, proximity to the PFAS plume, proximity to the Zone 7 water supply system, land rights, and suitability for operation and maintenance activities. Preliminary activities to date have identified the potential locations shown in the figure below. Additional evaluation is ongoing, with a target completion date of summer 2024.
Exploratory Test Drilling: Upon completion of the well siting evaluation, exploratory test drilling will be performed at select locations. Exploratory test drilling includes the use of drill rigs and supporting equipment (such as that pictured below) to install monitoring wells that allows for the collection of information such as water yield and quality. This information is critical in determining the overall feasibility of the Project. Upon completion of exploratory test drilling, the belowground monitoring well remains with only a well box visible at the surface. Exploratory test drilling is anticipated to occur during the summer and fall of 2024. Additional information will be provided once specific locations are selected