This story has been updated to include additional comments from the Tennessee Valley Authority.

The Tennessee Valley Authority released a report Friday of ongoing groundwater monitoring at the inactive Allen Fossil plant, acknowledging there is an area between the shallow aquifer and the Memphis Sand aquifer without a protective clay barrier.

It's unknown how wide the breach in the clay layer is.

The report states: “Based on deep exploratory drilling in the vicinity of ALF-202, the upper Claiborne confining unit is absent and the Alluvial aquifer directly overlies the Memphis Sand.”

Scott Brooks, a spokesperson for TVA, said that, "The potential for connectivity does not change the fact that the plume is not moving downward. Repeated testing of wells in the Memphis Sand aquifer shows no arsenic."

Recent testing by Memphis Light, Gas & Water has not found evidence of unsafe levels of these pollutants, either.

Clay layer status 'very concerning'

This is the first time TVA has publicly said that a clay layer between the monitoring well and the aquifer is absent, according to the Southern Environmental Law Center. It's not an acknowledgment to brush off, said Amanda Garcia, an attorney for the center.

"It's very concerning that TVA is saying that the clay layer right along the ash pond is not there," Garcia said.

TVA is currently in the process of exploring remedial options for the coal ash pits that were used by the Old Allen. The plant stopped burning coal in 2018, but concern remained among environmental groups that the coal ash pits have been leaking contaminants into groundwater.

TVA says that there is a likelihood that the high levels of arsenic and pollutants found in the groundwater could have originated at a site other than the Allen plant.

The Allen plant is in close proximity to President's Island, an area of Memphis that is largely industrial.

According to Brooks, TVA placed a priority on finding the best method with which to close off the coal ash pit before figuring out where else the arsenic could be coming from.

TVA acknowledged there are high levels of contaminants in the groundwater, but said those contaminants are in the shallow aquifer, not in the much deeper sand aquifer from which the City of Memphis draws its drinking water.

The center has pointed to a layer of clay that has served as a buffer between the two water sources as an area in need of much more research and understanding.

If any breaches are found in the clay layer, it could mean that the contaminants are being pulled from the shallow aquifer into the deeper one, according to the center.

"This highlights the vulnerability of the drinking water that's coming from the sand aquifer," Garcia said. "This is indicative of an ongoing risk."