Many Robeson County residents have drinking water that is more acidic than strong black coffee, while a smaller number of private wells water contained higher than recommended levels of Chromium 6 or lead.
After Hurricane Florence, UNC and Virginia Tech scientists sampled 62 private drinking water wells in Robeson County, one of the areas hardest-hit by the historic storm. Andy George of the UNC Institute of the Environment and Kelsey Pieper, a research scientist at Virginia Tech, revealed a summary of sampling results last week at a public meeting in Pembroke, in Robeson County. The individual well owners had already been notified; that data is confidential for privacy reasons.
For contaminants with health-based standards — meaning exceedances can make some people sick — total coliform was detected in more than a quarter of the wells. While total coliform is a generally harmless bacteria, it usually indicates other contaminants from surface water — like flood waters — might have entered the drinking water well. No E. Coli, a harmful bacteria, was detected. Three wells had lead levels above the EPA standard of 15 parts per billion, and more than dozen tested high for Chromium 6.
The sources of contamination are varied, and in many cases unknown, George said. Some contaminants, like arsenic and Chromium 6 can naturally occur in groundwater, although there might be industrial sources, as well. Duke Energy operated the Weatherspoon coal-fired power plant in Robeson County, retiring it in 2011 and demolishing it in 2013. When the plant operated, Duke Energy had a federal discharge permit allowing it to discharge certain amounts of wastewater into the Lumber River.
However, George said that researchers could not trace the source of the Chromium 6 in the sampled Robeson County wells.
Acidity and iron are considered a nuisance-based contaminants because they usually don’t harm public health. However, acidic water can corrode copper piping, which in turn leaches the metal into the tap water. (If lead pipes corrode, though, the chemical can enter into drinking water; there is no safe level of lead.)
Some wells in Robeson County are shallow — as low as 30 feet deep — and that can reduce the distance and time the water flows to the tap, allowing for less natural filtration.
Pieper also presented solutions for residents concerned about their well water. For example, capping and chlorinating wells or exposing the water to ultraviolet light can reduce bacterial contamination. Wells with acidic water can be treated with acid neutralizers, which can not only help with taste, but also stave off damage to plumbing and appliances. Water softeners, filtration and distillation can remove iron that can stain sinks and clothing.
George and Pieper distributed a brand of filtration pitchers that can sharply reduce the amount of contaminants in tap water. According to researches’ tests, levels of Chromium 6 fell to well below the state health screen levels after the tap water was filtered. The same held true for arsenic and lead.
Number of wells sampled — 62
Percentage that contained levels of Chromium 6 above the state health screening level — 23
State health screening level — 0.07 parts per billion
Highest level recorded in sampled Robeson County wells — .24 ppb
Amount that level exceeds the state recommendation — 3.4 times
Percentage that contained levels of Total Coliform above EPA standard — 27
EPA standard for Total Coliform, in colony-forming units — 0
Highest level recorded in sampled Robeson County wells: 2,419.6
Percentage that recorded acidity levels above EPA guidelines — 94
EPA standard for pH — 6.5 to 8.5
pH of most acidic water sampled — 3.68
pH of vinegar — 3
pH of coffee — 5
Percentage that contained levels of iron above EPA guidelines — 44
EPA standard for iron — 300 parts per billion
Highest level recorded in sampled Robeson County wells: 4,355 ppb