Pleasanton plans to drill new groundwater wells to address contamination

PLEASANTON — Pleasanton is moving forward with a plan to build two new drinking-water wells to replace its wells found to be contaminated.

The new wells would be drilled away from the ones contaminated with the potentially harmful per- and polyfluoroalkyl substances — known as PFAS  — that caused the city to stop using the three wells it currently operates.

The City Council this month approved moving forward with the project, which will take about four years to complete and cost an estimated $23 million to $43 million, according to city figures.

However, city officials have not decided how to pay for the entire project. The City Council only committed $500,000 from the city’s water fund to cover planning and development costs.

Council members are expected to learn more about the project’s cost and viability in the fall of 2024. In the meantime, city officials say a water rate study needs to be completed to determine the effects the project could have on the city’s ratepayers.

“None of this will be easy, and none of this is inexpensive,” Vice Mayor Jack Balch said at the council’s Oct. 17 meeting. “I look forward to a full and frank rate study where we are very transparent with our public as to what needs to go in and how we will be looking to finance this.”

Balch noted the possibility of the city working with Zone 7 Water Agency — a water wholesaler that serves eastern Alameda County — to share the cost of building two wells. And he urged staff to look into possible grants and other funding sources to help pay for the project.

Pleasanton delivers water to 22,000 customers, according to the city. Normally, Pleasanton buys 80% of its potable water from Zone 7. The remaining 20% is supplied by the city’s groundwater wells. But the detection of PFAS — chemicals the U.S. Environmental Protection Agency says may be linked to harmful health effects in humans — in the city’s groundwater supply has caused Pleasanton to stop using its wells.

In June 2019, the city discontinued using one of its wells because PFAS levels were detected above the “response level.” In November 2022, the city stopped using two more wells — instead placing them on standby for potential use if needed — because PFAS were detected at the “notification level.”

Notification levels represent a concentration level of a contaminant in drinking water that “does not pose a significant health risk” but warrants notification to users, according to the state. When contaminants reach the response level, the state recommends the water source be treated or taken out of service.

The wells have not been used since. Zone 7 has agreed to supply Pleasanton with more water in the interim, according to the city.

PFAS are human-made chemicals that have been used in products such as firefighting foam and nonstick cookware for more than 80 years. Because they have been used so broadly, the chemicals are found in low levels in a variety of food products, the environment and even people’s blood.

The city has been studying long-term options to address PFAS in its water supply. It was moving forward with a well upgrading and PFAS treatment plan until the City Council paused the project in September 2022 because of escalating estimated project costs. At the time, the project was estimated to cost about $46 million, according to the city.

Since then, the city has been studying alternatives to that project. The plan to drill two groundwater wells is one of the alternatives evaluated by city staff.

Other options included purchasing 100% of the city’s water from Zone 7 and a smaller well upgrading and PFAS treatment project, according to city staff. The two-wells project was picked as the preferred option.

“This provides the highest reliability at the lowest cost,” said Jenny Gain of Brown and Caldwell, the project consultant contracted by the city, about the option to construct two new wells. “The operational complexity is low. Groundwater pumping is something that city staff are already doing, have done in the past, and it is within the city’s wheelhouse, whereas treatment is not. Also, it is something that will yield high-quality drinking water drawn in a manner unaffected by — and not disturbing — the PFAS plume.”

The City Council unanimously voted to allow the staff to begin the planning work for the two new wells.

“The main thing is we want to provide clean and safe water to our residents, and that’s what we are trying to address here,” Councilmember Valerie Arkin said. “I’m glad we’re moving forward with a plan, and we do need to address this.”

Staff writer Will McCarthy contributed to this report.