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Environment: County rivers remain on state list for ‘impaired’ water quality

By Charles Swenson
Coastal Observer

Each of Georgetown County’s five rivers is included in a new list of waterways that don’t meet state water quality standards. And they all rank low in the state’s priority list for improvement. The result is that people who want to emulate the top anglers who competed in the recent Bassmaster Elite tournament should avoid or limit eating their catch.

The state Department of Health and Environmental Control is taking public comment on the proposed list of “impaired waters” through May 2. In addition to the rivers, the list includes saltwater creeks and estuaries that don’t meet standards for fecal coliform bacteria. It is updated every two years. In creating the proposed list, named for section 303(d) of the Clean Water Act, the state was mandated by the federal Environmental Protection Agency to coordinate its pollution control programs between federal and state agencies, develop a priority list for improvements and set priorities for protecting healthy water bodies.

“It looks like the state has adopted a new strategy that was recommended by the EPA for how to handle the development of Total Maximum Daily Loads, which is the next step when you get on the 303(d) list,” said Susan Libes, a professor of marine chemistry at Coastal Carolina University and director of the Waccamaw Watershed Academy. Total Maximum Daily Loads or TMDLs are plans that specify the amount of pollutant a waterbody can receive and still meet water quality standards. They specify how the current level of pollutants will be reduced.

“They’ve stepped away to a different strategy because everyone’s struggling to meet the deadlines nationwide,” Libes said. “They’ve now developed a system of prioritizing which sites should have TMDLs developed first.” For rivers in Georgetown County, those plans are a long-range priority listed for adoption sometime after 2022.

The most common cause of poor water quality in the county’s rivers is mercury. Those levels have led DHEC to issue advisories to limit or restrict consumption of fish from some rivers and creeks. In the Waccamaw, Black and Little Pee Dee rivers, people are advised not to eat largemouth bass. Other species are recommended for eating once a week or once a month.

Consumption of fish is one of the two main ways mercury poses a risk to humans. Not all species pose a risk, DHEC notes.

“Mercury doesn’t degrade over time. It continues to accumulate,” said Dennis Allen, director of the University of South Carolina’s Baruch Marine Lab at North Inlet. So mercury levels in some fish can be thousands of times higher than the level in the surrounding water. The impaired waters don’t affect the water quality in North Inlet, where data has been recorded for 40 years. “North Inlet is so strongly influenced by the coastal ocean,” Allen said.

A 2010 study of mercury by DHEC identifies the burning of fossil fuels as the primary source of mercury. “Mercury can travel very long distances before it returns to the ground,” Libes said. “Because we’re on the East Coast and the way the winds blow, the potential is there for transport across the ocean.”

Conditions here make “a perfect storm” for the accumulation of mercury, Libes said. Thunderstorms in the summer scrub pollutants from the atmosphere. They fall into a broad watershed with a high water table and slow moving water that is rich in organic material. “That situation sets up for low oxygen conditions which sets up the biomethylation of mercury, and that’s the form of mercury that’s the big health risk and moves up the food chain,” she said.

“This has been an ongoing and perhaps unsolvable set of problems,” Allen said.

The place to start, Libes said, is with the collection of data. Even without human sources, the area was prone to high levels of naturally-occurring mercury. “Because we don’t have any measurement levels prior to the 1970s, who’s to know what natural was,” Libes said. “It’s quite a puzzle about where to point the finger.”

She’s more optimistic about another aspect of the 303(d) list and the new strategy: the waters affected by stormwater runoff, primarily through bacteria. This has resulted in the closure of shellfish beds in Pawleys Island, Litchfield and parts of Murrells Inlet.

“What has been proposed by DHEC by EPA is: let’s all hustle hard to try to do all the things we know how to do to improve water quality so that we don’t have to go to the extra work and expense of developing a TMDL,” Libes said. “Let’s just do the things to get the water quality straightened up right quick.”

Those are things like owners picking up their pet’s waste and rain gardens or rain barrels to slow runoff from paved surfaces. “All these decentralized approaches that each of us needs to be instituting on our property are very amenable to ‘let’s all jump in and get it done,’ ” Libes said. The stormwater management plans adopted by Georgetown and Horry counties nearly a decade ago are a large part of that, she added.

North Inlet remains the standard by which developed estuaries can be measured, Allen said. “Our own long-term ecological research has allowed us to observe changes beyond a few seasons,” he said.

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