Patterson’s water is more than just ‘hard,’ it’s contaminated
The story was originally published by The Modesto Bee with support from our 2025 California Health Equity Fellowship.
Patterson stopped efforts to address a drinking water contaminant not because it was no longer an issue but because the city couldn’t afford remediation. Now residents say Patterson needs to do more to address their growing concerns.
Yolanda Magaña moved to Patterson four years ago. After buying her house but before moving in, she wanted to get to know her new neighborhood so she looked at community pages on Facebook. She came across a group that blamed the city’s water for an increase in cancer in the area.
“That’s when I learned about the water issues and I was like, ‘Oh no,’” Magaña said. She began to have second thoughts about moving to the area, but settled on installing a reverse osmosis system in her home to filter out hexavalent chromium (CR6) .
Patterson has high levels of CR6, a carcinogen most associated with the biopic “Erin Brockovich,” which centered around the small community of Hinkley, California, where high levels of CR6 tied to PG&E’s cooling towers. The town had illnesses its residents attributed to the water, including brain cancer, liver and kidney damage, heart issues, respiratory problems, reproductive harm and Hodgkin’s disease.
Unlike Hinkley, according to a Stanislaus County report, it’s likely heavy metal that seeped into Patterson groundwater naturally, originating in ancient sediments from a Diablo mountain range west of the city.
In 2014, Patterson was found to violate the state’s maximum contaminant level for CR6. The state’s limit of 10 parts per billion (ppb) — a limit established after years of advocacy by environmental health groups — was 500 times the public health goal set by the Office of Environmental Health Hazard Assessment of 0.02 ppb.
In 2017, the state’s CR6 limit was scrapped by a Sacramento Superior Court judge who ruled that the State Water Control Board had not done enough to consider what it would cost for water systems to get below the maximum contaminant level.
Since the limit was no longer in place, the city took a wait-and-see approach, holding back on selecting a way forward until the new level was set.
After the state reviewed the limit and reset it right where it began effective October 2024, Patterson’s water continues to be over the maximum contaminant level, with some wells testing much higher.
In March, one of the city’s seven ground wells exceeded the newly reinstated standard after testing close to 40ppb, tipping the average of all wells in the system to 13ppb. Patterson water resources program manager Maria Encinas gave a presentation in early June as required by the state water control board.
“The exceedance letter only references one well site, but we know historically that we’re going to have issues with all the sites,” Encinas said. “It’s trending that way, but we can’t confirm it until we take one more sampling event.”
Patterson gets its drinking water entirely from the seven wells, all of which routinely test over the state standard for CR6, with only one currently testing below, at 6ppb as of May.
Patterson is growing quickly
Patterson is a rapidly growing city of over 25,000 residents on the West Side of Stanislaus County. Since 2001, the city has doubled in size.
Marco Ahumada, 29, moved into the area in 2019 and earlier this year bought a house in the newly developed Baldwin Ranch neighborhood. He said he knew the water was hard, but didn’t know about the contamination until after he moved into town and received a TikTok message from a longtime resident.
“No way was it brought to our attention that there were any concerns about the water,” he said.
Marco Ahumada outside City Hall in Patterson on Monday, Aug. 11, 2025. Ahumada bought a home in the new Baldwin Ranch subdivision, unaware of the city’s water issues.
Andy Alfaro aalfaro@modbee.com
Two community Facebook groups were created to share concerns about the levels of chromium 6 in the water. The first is “Patterson, CA. Cancer Cluster.” The other, created in 2022 by Magaña, is “Concerned Patterson Citizens: Chromium 6 Water.”
Kayla Lavender, a mother of two, moved to Crows Landing area in 2011 and then to Patterson a year later. The first thing she was told in both places was not to drink the water.
“So, literally, the minute I moved into Crows Landing, my sister said, ‘Don’t drink the water,’” Lavender said.
How did we get here?
Patterson’s stance is that the water quality hasn’t changed, just the laws around it. “It’s been in the water as long as we’ve been here,” Encinas said.
Magaña said that when she started looking into the water issues, she reached out to city staff, who told her it was at a standstill due to the removal of the state limit.
“I was like, ‘Well, this has been going on for a while, right?’ To me, it just seems interesting that more hadn’t been done, more investigating,” Magaña said. “It kind of rubbed me the wrong way.”
Patterson continues to monitor for the carcinogen, but stopped developing plans while they waited to see what the new limit was.
“We never got to the point where we actually selected a technology and started doing the design,” Encinas said.
Darrin Polhemus, deputy director of the drinking water division at the state water control board, said the state purposefully didn’t remove grant funding during the gap and by halting progress, the future project will cost more.
“These delays always end up in more costly systems in the end just because of the inflationary aspect of it,” he said.
The Baldwin Ranch housing development is bordered on the west side by the Delta-Mendota Canal and the California Aqueduct in Patterson, Calif., Monday, Jan. 27, 2025.
Andy Alfaro aalfaro@modbee.com
What is the actual risk?
CR6 exposure over the long term has been linked to increased risk of cancer and reproductive harm.
The state’s current 10ppb limit for CR6 is based on a cancer risk level of one in every 2,000 people over a 70-year period.
Tasha Stoiber, a researcher at the Environmental Working Group, a nonprofit environmental advocacy group based in D.C., pushed for an even lower state limit for CR6, which has been in consideration since the early 2000s. “We commented time and time again that 10[ppb] is too high to protect public health, and we advocated for getting as low as possible to the public health goal,” Stoiber said.
Some water wells in Patterson tested two or three times over the state’s standard between 2014 and 2025. One well tested at almost 40ppb in March this year.
Polhemus said there is some reason for concern, maybe not about drinking the glass in front of you, but drinking the water over a longer period if it takes a while for the water system to address the issue.
According to Patterson, the county and state the city has had high CR6 levels for as long as samples have been taken.
Stanislaus County has a slightly higher cancer rate for both men and women across all age groups, according to the county’s latest health assessment when compared to the state of California. But determining a direct link between a particular carcinogen and cancer rates in the real world can be difficult due to multiple environmental factors within a small population size.
Encinas said the numbers seen in Hinkley were much higher – citing readings from the cooling towers a half mile out in Hinkley. She’s skeptical about claims of cancer in the area.
“We all know, you know, you have one neighbor who tells another, and then they tell somebody else, and it’s kind of like you can’t put the fire out,” she said.
Ahumada said his family hasn’t seen any issues in the six years he’s lived in Patterson, but after creating a TikTok and Instagram post about the water situation, he’s received messages from several long-standing members of the community who said their families had cancer or miscarriages related to the water.
Lavender said her daughter, now 14, used to have terrible nose bleeds – something she attributes in part to CR6 in the water.
“My daughter, my oldest, had severe nosebleeds for years of her life,” Lavender said. “They have been mostly under control within the last five years after we started doing more mitigation at home for chromium 6 specifically.”Lavender now gets her drinking water delivered or drives to nearby Del Puerto Canyon.
Kayla Lavender reads through Patterson’s 2024 Consumer Confidence Report.
Kathleen Quinn kquinn@modbee.com
Where does the CR6 come from?
Many of the communities on the West Side of the county report high levels of CR6, following the Interstate 5 corridor.
Polhemus said the majority of the pockets of chromium 6 contamination in the state are naturally occurring.
“The western side of the valley is one of them that seems to be derived from ancient seabed minerals, so it’s probably always been there as a result of that,” Polhemus said.
Grayson, which is served by the city of Modesto, tested over the limit in two wells and exceeded the contaminant level for nitrate in those same wells.
Crows Landing, south of Patterson, is also impacted. Drinking water is run by a small water system with two active wells, one of which has tested over the state’s threshold twice this year.
Farther south, Newman is also over in an inactive well, but Patterson is the largest system in Stanislaus County to have high levels of untreated chromium hexavalent in potable water. Los Banos, south of the Stanislaus County line in Merced County, has even higher levels and recently put forward a bill to prevent them from being sued due to inaction on CR6 that passed in July.
What will it cost?
Patterson estimated the cost to get CR6 levels under control to be $65 million to $128 million, and is working on an updated estimate. It could create a centralized facility with the most effective filtration, but that comes with its own complications.
“We know that [reverse osmosis] is going to take everything out of the water, but it’s also the most expensive technology,” Encinas said.
Also with reverse osmosis, there is often water waste. Though more efficient systems are now available, in a city known as the “apricot capital of the world” and whose ground is sinking as its aquifer depletes, it’s a hard sell.
“Now when you’re faced with that decision and then not knowing what the [maximum contamination level] is going to be when they come back with the new one — for those two reasons, that’s why the city kind of put it off and waited to see until we got further regulatory direction,” Encinas said.
Polhemus said a centralized reverse osmosis system in Patterson wouldn’t be practical due to the cost and the logistics of brine disposal. It’s more likely something much cheaper will be done, he said.
“It does work, but we’re definitely not trying to say we expect most communities to install that, that would be unusual [for them] and just not really practical,” he said.
What can be done now?
Magaña said she understands that addressing the issue will take time and be expensive, but she believes the city could be doing more to help inform the community about the issue and potential health risks. She thinks notices should be written in more layman’s terms.
“They sugarcoat it,” she said.
Lavender recently received the city’s English-only consumer confidence report and said the way Patterson provides information about the contaminant isn’t clear and appears to downplay the issue.
Patterson and its surrounding areas have the highest concentration of Spanish-Speakers in the county according to the 2025 County Health Assessment.
Posted warning about contaminated drinking water at City Hall in Patterson, Monday, Aug. 11, 2025.
Andy Alfaro aalfaro@modbee.com
On Aug. 11, the city had thumbtacked notices next to City Hall in English, letting residents know about the contamination but saying they didn’t need an alternative drinking water source. There is a sentence in Spanish that includes a phone number for interpretation.
Residents received a notice in June that said in part: “This is not an emergency.” But it also said, “However, some people who drink water containing hexavalent chromium over the course of many years have an increased risk of getting cancer.”
Ahumada said he doesn’t remember seeing the notice in the mail about the contamination. “Maybe I did and it ended up in the garbage,” he said. “But if I’m doing that, how many other people did that?”
Magaña said that’s why she created the newer Facebook page, to get that communication started. “I don’t know if it gets brushed under, or if the city just doesn’t do a good enough job of saying in layman’s terms: ‘Water’s bad because of this.’”
Ahumada, the creator of a TikTok and Instagram video on the issue, agreed. “I do think it’s necessary to get with the times, blast it on social media – blast it on TikTok, Instagram, Facebook and whatnot, making it bite-sized and chewable for the community to understand.”
He added that he doesn’t think the city is ignoring the issue. “All the city officials live in the city, too. They, too, want clean water.”
But Lavender said the response she got from the city when she reached out about the issue was condescending. She hopes newfound awareness of the issue will increase the chances that more will get done.
“We’re just building and building and building and bringing more people to town – to poison,” Lavender said. “Community awareness would be a huge step, and maybe it would freaking light a fire under Patterson’s a-- to actually do something about it.”
The way the new regulations are set up, Patterson’s exceedance does not rise to the level of an official violation until it has passed the compliance deadline set for October 2027.
Magaña recommends those who can afford it get a reverse osmosis system like she did, but understands that may not be fiscally possible for many. Whole house reverse osmosis systems can cost several thousand dollars. Many of the residents, even those who didn’t know about the contamination, said they purchased bottled water for themselves and avoided drinking from their tap.
Patterson City Hall in Patterson, Tuesday, July, 29, 2025.
Andy Alfaro aalfaro@modbee.com