TVA probe finds ‘connection’ between Memphis Sand and shallow, contaminated aquifer
Although none of the arsenic found beneath a TVA ash pond is currently seeping into drinkingwater supplies, investigators discovered a “connection” between the Memphis Sand aquifer — the source of tap water throughout Shelby County — and a shallower aquifer containing the toxic contaminant, a report submitted to state environmental officials says.
The report found that when water was pumped from wells drilled into the Memphis Sand to provide cooling water for the Tennessee Valley Authority’s Allen Combined Cycle Plant in Memphis, there was a “discernible drawdown” in the upper Alluvial aquifer. The Alluvial is the aquifer in which TVA last year found extremely high levels of arsenic near a coal-ash pond at the nearby Allen Fossil Plant.
The drawdown indicates the two aquifers are connected, probably because of a nearby gap in a protective clay layer, according to the report.
The findings, released by TVA Wednesday, could further stoke a long-running controversy over the five wells the agency installed at the Allen Combined Cycle Plant, which is set to begin operations late this spring.
Environmentalists and some researchers opposed TVA’s plans to pump an average of 3.5 million gallons daily from the Memphis Sand to cool the plant, saying the withdrawals could suck contaminants from the Alluvial aquifer into drinking-water supplies.
Scott Banbury, coordinator of conservation programs for the Sierra Club’s Tennessee chapter, said the findings prove that opponents’ concerns “were valid.”
Amid the remedial investigation, which was conducted with help from the U.S. Geological Survey and the University of Memphis, TVA announced last summer that it would not use the wells until it was shown the pumping would not endanger drinking water.
TVA spokesman Scott Brooks reiterated that commitment Wednesday, saying the agency plans to buy water from MLGW to run the plant, at least for the time being. TVA is installing two 2.5 milliongallon tanks to store water purchased from the Memphis municipal utility.
Brooks emphasized tthe report showed no trace of arsenic in water pumped from the new wells. He added that the movement of groundwater in the Alluvial aquifer is horizontal, not downward.
TVA is preparing to begin operating a new natural gas plant built to replace the coal-fired plant at Allen that TVA first erected in 1956.
TVA said it will construct water tanks and a second redundant water feed to increase reliability of the water supply for the new gas-fired power plant.