Groundwater discharge from an aquifer test at the Tennessee Valley Authority Allen Combined Cycle Plant in October.
A contaminated aquifer is linked to the Memphis Sand aquifer, the source of the Memphis’ drinking water, but the mingling of the waters does not yet pose an immediate threat to that drinking water.
That’s according to the latest findings from the United States Geological Survey (USGS) and the University of Memphis. The agencies issued a final report last week from their investigation into whether or not Tennessee Valley Authority (TVA) wells drilled in the Memphis Sand aquifer posed a threat to Memphis’ drinking water.
TVA drilled five wells into the aquifer, the source of the city’s famously pure drinking water. Those wells were drilled a half of a mile away from a TVA coal ash pond, where the power provider stores the remains of burnt coal.
It was found that high levels of arsenic and lead were found in groundwater close to that pond. After that finding, TVA officials decided against using the wells to cool its nearly $1 billion natural gas energy plant built close to Presidents Island. TVA will instead cool the plant with waste water from Memphis Light, Gas, & Water (MLGW).
“The study did confirm a likely connection between the aquifers, and TVA has committed to not using the production wells at the gas plant,” said spokesman Scott Brooks. “In fact, we recently completed two 2.5 million gallon tanks to hold MLGW water for cooling the gas plant. As you know, that water also comes from the Memphis Aquifer.”
Scott Schoefernacker, a senior research scientist at the University of Memphis' Herff College of Engineering, co-authored the aquifer report. He said it was unclear if running TVA’s wells would have brought contaminants from the shallower well into the Memphis Sand. But the report said those two aquifers were linked (and linked before TVA drilled wells).
“Results of the study collectively confirm that the Mississippi River Valley alluvial and Memphis aquifers are hydraulically connected near the TVA plants area,” reads the report.
Amanda Garcia, senior attorney with the Southern Environmental Law Center (SELC), said her group is “deeply troubled” by the report’s findings, especially that ground water is leaking into the Memphis Sand near the contaminated TVA coal ash pit. But what troubles Garcia more are the unanswered questions.
“Arguably the most troubling aspects of the report are the facts we still don't know,” Garcia said. “How big is the breach in the clay layer? How much polluted water is getting into the city’s drinking water source, even without TVA running its new wells at the Allen gas plant?
“And what about the effect of other nearby industrial wells on the movement of contaminated shallow groundwater? The bottom line is that leaving coal ash in a leaking, unlined pit near this breach is irresponsible.”
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Waters from the two aquifers are mingling, Schoefernacker said, but contaminants from the shallower Mississippi River Valley alluvial have not yet leaked into the Memphis Sand.
”From what we saw at the test, the concentrations in the shallow (aquifer) were at at the highest 5.44 micrograms per liter,” Schoefernacker said. “The (maximum contaminant level) set by the (U.S. Environmental Protection Agency) is 10. They’re half of that. And in the (Memphis Sand) it was even lower than that, an order of magnitude lower than that.”
The connection between the two aquifers needs further study, said Schoefernacker. But the city’s water is not in immediate danger, he said, as TVA has chosen to use MLGW water to cool the plant.
However, Garcia said TVA still has a responsibility here.
“Memphians deserve clean drinking water,” she said. “TDEC, our state’s environmental agency, should require TVA to take all necessary steps to protect the Memphis Sand aquifer from coal ash pollution at the Allen Plant.”