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Bacteria levels up in some private CT wells following summer of extreme rain

A glass pouring out drinking water.
AFP via Getty Images
According to the state Department of Public Health, about one in four Connecticut residents rely on private wells. Currently, the EPA does not regulate private wells or provide recommended standards – and the state doesn’t require Connecticut homeowners to test their wells annually.

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Torrential rains caused widespread problems across the region this summer, ruining crops, washing out roads and flooding homes.

But there’s another, often unnoticed, consequence of all that rainwater pouring onto the ground — private wells are getting contaminated.

A UConn extension testing program established in September 2022 saw more wells contaminated with coliform bacteria this summer, according to Mike Dietz, an extension educator, and director of the Connecticut Institute of Water Resources.

Half of the water samples at the lab were positive for total coliform this summer, up from 30% in months prior, Dietz said. It’s a concern, because Connecticut’s thousands of private wells are less regulated than city water.

“Any public water supplier is required to test that water frequently, and have to meet all the EPA Safe Drinking Water Act requirements,” Dietz said. “Private well owners are only required to do that when the well goes in. The responsibility is on every person that owns that well.”

Coliform itself isn’t dangerous, but can indicate the presence ofother bacteria from shallow groundwater leaking into residential wells, like E. coli,which negatively impacts health.

According to the state Department of Public Health, aboutone in four Connecticut residents rely on private wells. Currently, the EPA does not regulate private wells or provide recommended standards — and the state doesn’t require Connecticut homeowners to test their wells annually. Because of this, testing doesn’t happen enough.

Dietz said residents should test every one or two years, and the U.S. Environmental Protection Agency recommends testing if there is local flooding.

Wells with positive coliform samples are typically disinfected with bleach, a process which takes at least a week to complete. Then the lab tests the water again to ensure it’s safe. Health experts recommend bottled water for drinking and cooking until the issue is corrected.

This newer testing program at UConn doesn’t have a long-term record to compare data, Dietz said. According to state Department of Health spokesperson Christopher Boyle, before Oct. 1, 2022, DPH was not receiving water quality test results from private commercial laboratories that test private wells for contamination. Now, Connecticut law requires that all private well test results submitted to the DPH be kept confidential.

Boyle added that the department can’t easily draw conclusions on well-related health issues – individuals with gastrointestinal symptoms that may have been impacted by such bacterial contamination aren’t required to report their illness to the DPH.

As larger, more powerful storms are predicted to continue with climate change, excess rain poses more of a risk to water quality in rural areas.

“When we have a lot of rainfall — like we have this past summer — that excess rain gets down into the shallow groundwater, and can change the way that shallow groundwater moves and gets into the well itself,” Dietz said.

He added that his team is looking to continue the grant-funded program to expand the contaminants they can test for, and continue offering testing to residents at a low cost.

Information on certified labs and water testing is published online through local and state health departments.

This story has been updated.

Updated: November 13, 2023 at 5:29 PM EST
Updated to reflect added comments from the state Department of Health.
As Connecticut Public's state government reporter, Michayla focuses on how policy decisions directly impact the state’s communities and livelihoods. She has been with Connecticut Public since February 2022, and before that was a producer and host for audio news outlets around New York state. When not on deadline, Michayla is probably outside with her rescue dog, Elphie. Thoughts? Jokes? Tips? Email
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