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The city’s joint project with the Zone 7 Water Agency to test viable locations in West Pleasanton for two potentially new groundwater wells outside of a PFAS plume is going as planned, with the test drilling coming to an end soon at Del Prado Park in Pleasanton this month, according to officials with both agencies.
However, members of the Pleasanton Public Works Department told the Weekly they still have two parks to study as part of the “Regional Groundwater Facilities Project” before determining whether the city can drill the new wells in order to address the city’s PFAS issues — which might leave residents wondering: what happens if none these sites are viable?
Well, according to public works director Siew-Chin Yeong, all they can do is wait, analyze the data from these next few months of testing and go from there because anything else is simply speculation.
“In the past council (meetings) we did talk about ‘what if this is not the solution, what is Plan B?'” Yeong said. “I understand the community really has a lot of ‘what if’ questions, but … I think the best thing is for us to collect the data, like we’re doing right now … and then we make decisions based on engineering data instead of making assumptions.”
But Yeong said there still is always a chance of encountering PFAS during their test drilling, which as Zone 7 communications specialist Alexandra Bradley noted, could be a strong possibility.
“Our monitoring has shown a PFAS concentration in West Pleasanton, which is in the upper aquifer,” Bradley told the Weekly.
She said while the agency’s monitoring “has not shown a PFAS concentration in the lower aquifer which is what we are studying for the regional groundwater project,” the project will continue to keep an eye on the two aquifers.
“The feasibility study and test wells will help us to understand any potential interaction,” Bradley said.
PFAS, otherwise known as forever chemicals, is an acronym that many Pleasanton residents have come to know and familiar themselves with over the past few years.
The city first discovered the synthetic chemicals in its groundwater Well 8 back in 2019. After shutting it down, the city then discovered similar chemicals in Well 5 and 6, which were later shut down and then allowed for use only if necessary during peak demand.
Even though both Zone 7 and Pleasanton staff continue to assure the public that the synthetic chemicals are not in their drinking water, the city’s groundwater wells contribute up to 3,500 acre-feet per year of water — approximately 20 to 25% — of the city’s total water supply needs.
That’s why the previous council greenlit the Regional Groundwater Facilities Project.
The overall goal of the project is to construct new water wells within the Bernal subbasin, which according to the city’s website is “believed to be outside the existing PFAS plume based on Zone 7 testing and groundwater modeling”.
The city has been funding these recent efforts through its water enterprise fund, but Yeong also said the city is working with the state to finalize securing a $1 million grant to continue funding future costs. Communications manager Heather Tiernan also told the Weekly that the water rate increases that the previous council approved are also helping fund these efforts.
Back in June 2024, the council entered into an agreement with Zone 7 to evaluate the possibility of jointly building and operating these new groundwater wells, which is what the two agencies have been doing over the past few months.
According to Bradley, they are currently in the “exploratory drilling phase” which involves installing test wells at the three sites the agencies deemed viable locations: Del Prado Park, Pleasanton Tennis and Community Park, and Hansen Park.
“These are small wells that will run for a short period of time,” Bradley said. “We will run pumping tests to estimate the potential production capacity at the location and take water quality samples.”
That information will also be used to evaluate potential impacts to nearby Zone 7 wells; find out if there is any PFAS footprint; and run groundwater model scenarios which will analyze even more potential impacts these new wells could have in the area.
“If PFAS and/or any water quality issues are detected at any of the test well sites, staff will inform both the Zone 7 Board and the Pleasanton City Council of the findings along with recommendations based on model results,” Bradley said.
Separately, the water agency has also been monitoring PFAS levels in the city through separate monitoring wells at Ken Mercer Sports Park that it constructed in early 2024.
Utilities planning manager Todd Yamello told the Weekly the next steps, should the sites be deemed viable, would be to draw up infrastructure designs for the new wells and then actually construct them, which the city aims to complete by early 2029.
He said just like the two agencies are sharing costs, both will continue to separately analyze the data from the upcoming test wells. After finishing up at Del Prado this month, Yamello said they plan to go to Pleasanton Tennis and Community Park either at the end of the month or in February.
Hansen Park will be the last stop as the two agencies plan to wrap things up by August in order to present their respective findings to each governing body.
And while Yamello said everything has been going well at Del Prado Park, he and Yeong said there is always the possibility of finding the forever chemicals at either one of the three park sites.
However, Yeong said they believe those locations are the best and have the highest probability of being successful.
“A lot of the things that I think the community is worried about, we take it to heart and we take it very, very seriously,” she said. “But we do need to collect the data … that tells us which way we are heading before we make the decision.”
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