Author: Laura Oleniacz
A water quality sampling effort launched in the aftermath of Hurricane Helene helped NCDEQ Division of Water Resources staff identify potential sources of contamination.
DWR staff in the Asheville Regional Office (ARO) began sampling for E. coli in select streams in Buncombe County after the hurricane. The data is uploaded into an online GIS mapping tool: Helene E. coli Sampling Dashboard.
While testing creeks and rivers for E. coli alone does not provide a complete assessment of water quality conditions, the presence of E. coli at elevated levels can indicate potential fecal contamination, which has been shown to co-occur with gastrointestinal illness.
“Sampling for E. coli is a cost-effective sampling method that has a faster turnaround time in the laboratory, compared to other tests,” said Andrew Moore, supervisor of Asheville Regional Office Water Quality Regional Operations. “It gives us a general indication for what’s going on in terms of potential contamination sources from domestic wastewater collection systems or other sources.”
Moore said the program allowed ARO staff to identify a discharge of wastewater from a privately-owned sewer line, which was addressed by the collection system, the Metropolitan Sewerage District (MSD) in Asheville.
“After we identified elevated numbers at a sampling location in Town Branch, staff from our office went out and collected additional samples, and identified a discharge from a private sewer line,” Moore said. “While MSD doesn’t own the wastewater line connecting to their collection system, they went above and beyond to address it quickly.”
The program began with a focus on Buncombe County, but has expanded to an additional location – Richland Creek in Haywood County - by request, as staffing has allowed.
The sampling of waterways after Hurricane Helene builds off a recreational monitoring program launched by staff in the Asheville Regional Office. The WNC Recreational Water Quality program was developed to monitor water quality in heavily recreated waterbodies in western North Carolina, through a partnership between DWR and nonprofits.
Moore said staff have seen, through that program, that data trends can be impacted by factors including precipitation.
“If we have a rainstorm, and nonpoint source inputs of potential pollution, that could drive up the numbers we’re seeing,” Moore said. “The dataset has limitations."
For the sampling effort, DWR employs a laboratory methodology for E. coli analysis with results reported as Most Probable Number (MPN). MPN values have been found to be comparable to colony forming units, or CFU. The samples have been compared with the United States Environmental Protection Agency’s (EPA’s) 2012 Recreational Water Quality Criteria (RWQC) for E. coli, based on a recommendation from the NC Department of Health and Human Services (DHHS) for the Asheville region.
This freshwater recreational guidance states that E. coli values greater than 126 CFU/100 mL represent an increased exposure risk for primary recreation, which includes activities such as swimming and snorkeling.
DHHS also used recently updated EPA guidance to calculate a non-primary contact recreational (i.e. secondary recreation) guidance value of 886 CFU/100 mL for E. coli. Secondary recreation activities are those where there is lower or limited potential of full immersion and ingestion of water such as tubing and kayaking. E. coli values greater than 886 CFU/100 mL represent an increased exposure risk for secondary recreation.
Water quality is subject to change rapidly in flowing natural waters especially those impacted by severe storm events. DHHS advises the public to use caution during recreational water activities after Hurricane Helene.
More about DWR’s long-term water quality monitoring program, known as AMS/RAMS, or the Ambient Monitoring System and Random Ambient Monitoring System, can be found online: Life Cycle of a Water Sample.
In addition, the public can track sanitary sewer overflows online: Sanitary Sewer Overflow Tracking Map.