PITTSBORO — A second round of Pittsboro water analysis released Monday suggests another “slug” of 1,4-Dioxane was illegally released into the Haw River a week after Greensboro representatives announced a substantial onetime discharge from a still-unknown source.
On July 1, the City of Greensboro and the North Carolina Dept. of Environmental Quality reported a discharge of 1,4-Dioxane into South Buffalo Creek — a Haw River tributary — in effluent from Greensboro’s TZ Osborne Wastewater Treatment Plant. The chemical is a suspected carcinogen derived from industrial runoff.
Preliminary samples in Greensboro indicated levels between 543 parts per billion and 687 parts per billion of 1,4-Dioxane in the water there. The U.S. Environmental Protection Agency recommends no more than 35 ppb in healthy drinking water.
After learning of the pollution, Pittsboro staff began testing the town’s water supply, Pittsboro Water Plant Superintendent Adam Pickett told the News + Record, and have taken daily samples since. A first round of results, which was processed at Reidsville’s Meritech Labs, came back last Wednesday.
In the immediate wake of Greensboro’s contamination, 1,4-Dioxane levels at Pittsboro’s raw water intake were non-detectable. Two days later a raw water sample included 76.5 ppb, and later samples showed 38.2 ppb and 43.7 ppb over the next few days — all in excess of the EPA’s guidelines. Finished water at Pittsboro’s water tanks contained much lower concentrations of 1,4-Dioxane, none higher than 5.56 ppb.
On Monday, though, town representatives announced a troubling inference: there appears to have been at least a second discharge of 1,4-Dioxane from Greensboro, they say, although none had been officially reported. A new batch of water samples showed a spike in 1,4-Dioxane levels at Pittsboro’s water intake a week after the initial scare.
Raw water samples from July 6 showed 1,4-Dioxane ranging from 26.5 ppb to 93.6 ppb, a higher ceiling than earlier detected. The chemical’s concentration in treated drinking water was also elevated. At the Chatham Forest water tank, levels were as high as 66.8 ppb. The town’s 1.0M tank showed 21.7 ppb. Treated water from the Horton tank was much lower, just 1.71 ppb.
“Town staff believes that these numbers indicate a delayed or secondary influx of 1,4-Dioxane reaching the Pittsboro raw water intake with what appears to be an additional slug of contamination coming from Greensboro on or immediately before July 6, 2021 ...” Town Manager Chris Kennedy said in a statement.
Upon seeing the test results, town staff flushed the Chatham Forest tank and refilled it with what they “expect to be less contaminated finished water given the raw water contamination diminishment from July 6 (93.6 ppb) to July 7 (26.5 ppb),” the press release said. “From a strategic perspective, the Town is continually turning over the stored water in our water tanks more frequently than usual to continually refresh the water with improved and better quality finished water so that 1,4-Dioxane contaminated water exits our public supply as quickly as possible.”
As of press time Tuesday, two weeks following the initial 1,4-Dioxane contamination, the chemical’s original source remained unknown. Greensboro is obligated to limit 1,4-Dioxane discharge per a Special Order of Consent between the city and NCDEQ signed in February. The SOC stipulates no more than 45 parts per billion of 1,4-Dioxane may be discharged per day.
The agreement was triggered in 2019 after the discovery that Shamrock Environmental — an environmental and industrial waste management services company — was dumping 705 parts per billion to 1,210 parts per billion of 1,4-Dioxane at the TZ Osborne plant. The Shamrock location in Greensboro is a tanker cleaning facility that also manages wastewater and recycles drilling mud.
Water samples of Shamrock’s effluent showed 98.8 ppb of 1,4-Dioxane on July 6 and July 7 and 466 ppb on July 7 in a “flume grab” — water which had not been mixed with other sources at the wastewater treatment pant. But Greensboro spokesperson Elijah Williams, in an interview with N.C. Policy Watch, said Shamrock was not the source of contamination appearing in Pittsboro’s water.
“Accounting for dilution factors,” the report said, “Shamrock’s levels would need to have been much higher for it to be responsible for this spill.”
Other potential sources of the contaminant had not been released as of press time. The only official, public notice from Greensboro is the original announcement from July 1 on the town’s website.
“City staff has notified and is in coordination with the N.C. Department of Environmental Quality (NCDEQ) and downstream utilities and is actively investigating possible sources of the substance,” it reads.
The notice points out “this discharge does not affect Greensboro’s drinking water quality.”
“So that’s what Greensboro is working on,” Pickett, Pittsboro’s water superintendent, said, “trying to figure out where this source is coming from all of a sudden. And we’re working with Greensboro, as well, so hopefully we can get this knocked down pretty quick.”
It’s unclear whether the City of Greensboro or private companies identified as having discharged 1,4-Dioxane into the Haw will be required by NCDEQ to pay financial penalties for the contamination.
Despite the second spike in 1,4-Dioxane levels, and the uncertainty of the chemical’s source location, Pittsboro staff maintain the town’s drinking water is safe for consumption.
“While the numbers are above non-detect based on the latest sample results,” Kennedy said in the release, “we are encouraged by the drop from July 6 to July 7 in our raw water sample and the trends shown in Greensboro’s water grab ... trending towards a non-detection level.”
A third round of water sample results were expected to be released after press time. For the latest on Pittsboro’s water quality, check this story for updates.
Reporter D. Lars Dolder can be reached at dldolder@chathamnr.com and on Twitter @dldolder.