Joint Groundwater Wells Study

As part of Zone 7 Water Agency’s continuing effort to supply the Tri-Valley region with safe, reliable water, Zone 7 and the City of Pleasanton are working together to evaluate the feasibility of installing additional municipal supply wells in the Bernal Subbasin of the Livermore Valley Groundwater Basin, located within Pleasanton.

Increased drought frequency and severity due to climate change, emerging contaminant concerns, including per- and polyfluoroalkyl substances (PFAS), and future projected population growth have prompted efforts to ensure continued clean groundwater production reliability and drought resiliency. This project will explore the feasibility of groundwater development by drilling and constructing up to three planned test wells at different locations in the City of Pleasanton. 

The wells will be analyzed to determine groundwater quality, well capacity, and aquifer sustainability. Test results in conjunction with groundwater modeling will be used to assess the feasibility, siting, and design of up to three new municipal supply wells. This feasibility study will be the basis for future phases of work including full scale design and construction of the production wells and associated infrastructure and construction.

Proposed Well Locations

Zone 7 and the City of Pleasanton have agreed upon the following project sites:

• Site A: Pleasanton Tennis and Community Park
• Site B: Del Prado Park 
• Site C: Hansen Park

Schedule

June 18, 2024

• Pleasanton City Council Approved Project Phase I

July 17, 2024

• Zone 7 Board of Directors Approved Project Phase I

October 16, 2024

• Zone 7 Board of Directors authorized the General Manager to enter into agreement with Nor-Cal Pump & Well Drilling, Inc to perform test well construction and Luhdorff & Scalmanini Consulting Engineers (LSCE) to perform the feasibility study

Fall 2024

• Phase I (Test Well Drilling & Feasibility Study Begins)

Spring 2025

• Feasibility Study Complete

Fall 2025

• Phase II – Design and Construction Begins

Fall 2028

• New Wells Operational

Existing Groundwater Supply Challenges

PFAS

The Livermore Valley Groundwater Basin has been impacted by per- and polyfluoroalkyl substances (PFAS). The City of Pleasanton and Zone 7 both have supply wells impacted by PFAS above regulatory levels. As a result, several wells are currently out of operation, resulting in a loss of groundwater production and delivery to residents. At this time, this area of the Bernal Subbasin is currently outside of the known per- and polyfluoroalkyl substances (PFAS) plume based on terms of the current proposed EPA regulation for six PFAS compounds (PFOA, PFOS, PFHxS, PFBS, PBNA, and GenX). This project will utilize groundwater modeling to assess the feasibility of new groundwater production wells and their potential impact on PFAS migration.

Increased Groundwater Demand

As the population of the Tri-Valley continues to grow, so does the demand for water. Zone 7 relies on imported surface water from the State Water Project, and the local groundwater basin. Unlike population growth, the long-term average water supply is declining. Zone 7 plans for future demand from projected population growth and other challenges with a variety of long-term solutions. This project to construct additional municipal water supply wells will ensure continued groundwater production reliability as the community continues to grow. 

Climate Change

Zone 7 carefully manages the groundwater basin, storing excess imported surface water there during the wet years. Recent droughts have emphasized the importance of groundwater and its ability to supply the community when surface water is scarce. On average, approximately 20% of water delivered by Zone 7 is produced from the Groundwater Basin, however this can increase to over 40% in drought years. Additional municipal supply wells ensure increased drought resiliency.

For more information, see the City of Pleasanton’s project information page here: https://www.cityofpleasantonca.gov/our-government/public-works/regional-groundwater-facilities-project/