Portsmouth residents notified about drinking water contaminant. What to know.

The Portsmouth Water and Fire District has notified residents that the level of a potentially harmful disinfectant byproduct in drinking water called tetrahalomethane (TTHM) has exceeded the EPA standard, but told The Newport Daily News the temporarily elevated level does not pose a danger to Portsmouth residents.

Studies have shown TTHM has potentially carcinogenic effects on the liver, kidneys, and reproductive system of laboratory animals, but studies on humans have produced mixed conclusions, with some but not all reporting similar effects on people, according to a Massachusetts DEM factsheet.

“Consumption of water with high TTHM levels for a limited duration… is not likely to significantly increase adverse effects for people," Jessica Lynch, general manager and chief engineer of the district, said. "This is something you would have to drink at high levels for a very long time, is what studies have shown.”

She explained while the law requires a consumer notice about the violation to be sent via USPS to every consumer in the district, the water is still safe to drink and does not need to be boiled. She said any event causing the drinking water to be unsafe would result in a boil water notice being disseminated to the public within 24 hours.

Violation occurred at one sampling site in Common Fence Point

Lynch explained the district found levels over the EPA standard at only one of its four sampling locations – near the VFW Hall on Common Fence Point – but is required to send out consumer notices to the entire district. This has been the only EPA violation the district has experienced in Lynch’s six-year tenure.

She explained the elevated TTHM levels were the result of a combination of last year’s unseasonably high temperatures and the unavailability of advanced water treatment contactors at Lawton Valley Water Treatment Plant. The advanced treatment contactors have since been fixed, and their main function is to control TTHM levels coming out of the treatment plant.

Why Common Fence Point TTHM levels are higher

Lynch explained the reason the Portsmouth VFW Hall sampling site has higher TTHM levels than all of the other sampling sites in Newport and Portsmouth is because it is at an extremity of the system.

This means the water takes longer to get there and is generally “older” by the time it arrives at Common Fence Point than it is at other locations, giving the chlorine-based disinfectant used by the district more time to bond with organic matter in the water and form the potentially harmful compounds.

Consumers received another violation notice in June 2023, but TTHM levels in the system are down

The district’s most recent notice went out to consumers on June 15, 2023, noting the levels at the VFW site tested above the EPA standard not only for the fourth quarter of 2023 before the advanced treatment contactors were repaired, but also again in both the first and second quarters of 2023.

The notice states the problem has been resolved, and samples taken after the repairs were completed continue to show elevated TTHM levels only because the properly treated water has not fully reached the extremities of the system yet.

“We did violate for quarter one and quarter two of this year,” acknowledged Lynch. “That being said, our levels that we actually saw in the system were under (the EPA standard of) 80. But because we’re looking at the average, our high numbers from last year are pushing us over.”

Portsmouth Water and Fire District serves over 13,000 residents with water purchased from Newport

The Portsmouth Water and Fire District’s system consists of over 132 miles of water main, four storage tanks, two pumping stations, 1,749 valves and 602 hydrants. The majority of Portsmouth’s water is treated at the Lawton Valley Water Treatment Plant, which is in Portsmouth but owned by Newport.

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The district does not own any water supplies, but instead purchases its regular water supply on a wholesale basis from the city of Newport. Newport Water draws its raw water supply from a system of nine surface water reservoirs:

  • Lawton Valley Reservoir, Sisson Pond and St. Mary’s Pond in Portsmouth

  • Nonquit Pond in Tiverton

  • Watson Reservoir in Little Compton

  • North and South Easton Ponds in Middletown and Newport

  • Paradise Pond and Gardner Pond in Middletown

This article originally appeared on Newport Daily News: Portsmouth residents notified about presence of TTHN in drinking water