The slug of toxic 1,4-Dioxane coursing down the Haw River from Greensboro arrived in Pittsboro at just the right time.
Pittsboro Town Manager Chris Kennedy announced in a press release today that based on low levels of compound in drinking water, the contamination passed the town’s water intake from the Haw River during “dormant raw water draw hours,” when demand is low, as common in fall and winter.
Levels of 1,4-Dioxane in both treated and untreated water in Pittsboro ranged from less than 1 part per billion to 2.09 ppb. The EPA has set a health advisory goal of 35 ppb in drinking water, which represents a 1-in-10,000 excess lifetime cancer risk.
That is not as protective as the 1-in-1 million cancer risk that the EPA uses for chemicals that have no safe dose. However, research is incomplete on 1,4-Dioxane, and the EPA has yet to set legally enforceable standards for the compound.
1,4-Dioxane is a toxic chemical used in degreasers that the EPA has classified as a likely carcinogen.
Routine sampling showed Greensboro’s TZ Osborne wastewater treatment plant discharged the contamination on Wednesday, Nov. 3, but the city did not receive the lab results until Monday, Nov. 8, at 11:20 a.m.
Kennedy said that Greensboro notified them about three hours later. The amount of 1,4-Dioxane in the original discharge was 767 parts per billion; that’s more than 2,100 times the EPA’s and the state’s health advisory goal for surface water. That level is more stringent — just 0.35 ppb — than in drinking water.
If Pittsboro’s raw water intake had pulled the contamination into the drinking water system, which has happened before, the contamination would have “persisted in our system for weeks,” Kennedy said. “While this news is a relief, it does not discount the fact that an excessive release could have contaminated our drinking water supply. Frankly, the town was simply lucky this time.”
Kennedy said the town will continue to sample both treated and untreated water “until it is abundantly clear that the 1,4-Dioxane has cleared the raw water intake.”
Greensboro has yet to publicly announce the source of the contamination.
The wastewater treatment plant in Greensboro receives discharges from both residential and industrial customers in Guilford County. From there, the plant treats the discharge before sending it into South Buffalo Creek, which feeds the Haw. However, conventional treatment systems don’t remove 1,4-Dioxane.
The discharge violates the terms of a Special Order by Consent between DEQ and the City of Greensboro, which set a maximum daily level of 45 parts per billion of 1,4-Dioxane in wastewater. The Haw River Assembly, represented by the Southern Environmental Law Center, has challenged the terms of the order, saying they are not protective enough.
The recent incident was just one of several illegal discharges from the Greensboro plant. In July 2021, sampling results showed that levels from in wastewater ranged from 543 parts per billion to 687 parts per billion. Greensboro officials said they had not identified the source.
In August 2019, Greensboro’s discharge contained levels of 1,4-Dioxane ranging from 705 ppb to 1,210 ppb. The source of the contamination was Shamrock Environmental, an industrial customer that discharges its wastewater to the Osborne plant. That incident prompted DEQ to enter a Special Order by Consent with the city.
While DEQ regulates discharge from cities and towns, the municipalities are responsible for regulating their dischargers and ensuring wastewater is compliant with state and federal law.
According to Greensboro documents obtained under public records law, roughly two dozen companies discharge their wastewater into the city system. Since 2018, the city has issued 18 violations related to contaminants in the discharge, none of them related to 1,4-Dioxane.
Shamrock Environmental has been cited three times and fined $2,500 for exceedances of a compound called p-cresol, which is used in the manufacture of household products. Shamrock is not a manufacturer, but is a hauler and disposal service for that sector. Vertellus, a specialty chemical company received violations for exceedances of chloroform, toluene and since.