TVA suspects arsenic came from other sources

 Just a curved pipe protruding from the ground, monitoring well No. 203 lies at the edge of a harbor and at the center of a mystery.

It was mainly from this well situated between a coal-ash pond and McKellar Lake that the Tennessee Valley Authority recently discovered astronomical and unprecedented levels of arsenic, along with lead and other contaminants, in shallow groundwater.

The finding has prompted a major, two-pronged environmental investigation at TVA's 58-year-old Allen Fossil Plant in Southwest Memphis, site of the coal-ash pond.

TVA is installing a network of wells to identify the source and the extent of the contamination. The agency also has contracted with experts at the University of Memphis and U.S. Geological Survey to map the geology of the area and determine if there's any connection between the shallow water layer containing the contaminants and the deep Memphis Sand aquifer, the source of local drinking water.

While the investigation is under way, TVA will restrict its use of five wells the agency recently drilled into the Memphis Sand to provide cooling water for a nearby $975 million natural gas-fired power plant being built to replace the coal-burning fossil facility next year.

But while arsenic naturally occurs in coal, and therefore its ash, TVA officials said the levels found in well 203 are so high they likely point to other sources. If it didn't all originate in the ash pond, the arsenic could have come from a variety of places in the highly industrialized area along McKellar, which serves as a slack-water harbor on the Mississippi River, they say.

"We're looking at our entire site, plus other possible contributors," said Scott Turnbow, TVA's general manager of strategy for coal-combustion residuals.

TVA for years has checked for arsenic and other pollutants beneath its coal-ash ponds, with state regulators requiring an intensified effort now that Allen and several other fossil plants are being retired.

In older wells tested at the Allen plant in past years, arsenic levels measured as high as 43 parts per billion, or more than four times the federal drinking water maximum of 10 parts per billion. 

But the arsenic concentrations at well 203, which was installed within the past year or so, ranged from 2,890 to 4,140 parts per billion - more than 400 times the federal standard. In another new well, No. 202, levels of up to 298 parts were measured. Three other wells also showed arsenic above the federal standard, at levels of 12 to about 57 parts per billion.

A known carcinogen, arsenic is associated with an increased risk of bladder, kidney, liver, lung and skin cancers among those who ingest it. Well 203 also yielded concentrations of lead - a toxin that can damage the brain, central nervous system and kidneys - that were more than four times the federal action limit. 

The arsenic concentrations in well 203 also are suspicious because they're an order of magnitude higher than any found at other TVA plants with ash ponds.

A 2013 report by a non-profit group known as the Environmental Integrity Project documented what it called TVA's "toxic legacy" - the contamination of groundwater beneath coal-ash ponds. But while arsenic levels at more than a half-dozen other TVA coal plants exceeded the drinking-water standard, most of the measurements were below 100 parts per billion.

The highest level found at any other plant was still less than one-seventh the maximum concentration measured at Allen.

"We've never seen these kind of high levels," Turnbow said.

TVA officials also checked with an electric-industry group to see if other utilities have found arsenic levels as high as those in well 203 beneath their ash ponds. None had, Turnbow said.

The high arsenic levels could have come from a number of sources in the factory-heavy area near Allen, which includes President's Island and the Frank Pidgeon Industrial Area, he said.

During a recent tour of the wells and the coal-ash pond, Turnbow pointed out a city of Memphis sewer force main that carries wastewater from President's Island underneath McKellar Lake, continuing beneath the coal-ash pond before connecting with an interceptor leading to the Maxson South Treatment Plant. That force main on occasion has leaked, he said, spewing industrial wastes into the area of the ash pond.

But Robert Knecht, the city's Public Works director, said the only leak he's aware of occurred in 2010 when a TVA contractor accidentally ruptured the force main. "That was because of the negligence of their contractor," he said.

Knecht added that the spilled wastewater couldn't have been a significant source of arsenic. As part of their permit requirements, industrial wastewater customers must report the compounds in their releases.

"None of them have anywhere near those levels of arsenic," Knecht said.

The Commercial Appeal reviewed hazardous-waste releases reported to the U.S. Environmental Protection Agency by three dozen existing and former plants along McKellar Lake and in Southwest Memphis. They showed none had discharged arsenic to sewers or to land or surface water in recent years.

There are other potential sources of arsenic. In past decades, before the practice was banned, the substance was used as an agricultural pesticide.

Also, the shallow groundwater at the Allen plant ebbs and flows with the rise and fall of the Mississippi and McKellar Lake. That means contaminants carried in the water from places upriver theoretically could seep into the ground near TVA site, officials have said.

"That's a very old site, and it's next to McKellar Lake, and that's not the cleanest lake in the world," said Brian Waldron, director of the Center for Applied Earth Science and Engineering Research at the University of Memphis. 

"To point the finger at TVA and not look for other sources would be irresponsible."

Still, Waldron says the extremely high arsenic levels appear to be very "localized" to the TVA plant.

Well 203 and others near it were drilled only 30-50 feet deep. TVA now is installing additional wells in the 90-110-foot-deep range and still more at about 150 feet deep. They will tell the agency if the arsenic has seeped to near the top of a dense clay layer protecting the Memphis Sand, which lies more than 500 feet beneath the surface.

So far, researchers say there's no indication that the arsenic has reached the drinking-water aquifer. But they want to make sure there are no pathways, such as nearby gaps in the clay.

"Our goal is to to let science tell us what the problem is and what to do about it," Turnbow said.

Reach Tom Charlier at thomas.charlier@commercialappeal.com or 901-529-2572 and on Twitter at @thomasrcharlier.