By ADRIAN SAINZ ,  Associated Press

MEMPHIS, Tenn. (AP) — Tests on drinking water revealed no detectable traces of arsenic and lead after the toxins were found in groundwater at a coal-fired power plant in Tennessee, a utility company said Thursday.
Memphis, Light, Gas & Water said in a statement that tests conducted by an independent lab on 10 wells that supply water to a pumping station near the Allen Fossil Plant came up below detectable limits for the toxins. Tests conducted on treated drinking water that goes to Memphis' homes and businesses also indicated toxin levels were below detectable limits, the utility said.
The Tennessee Department of Environment & Conservation asked the utility to test water at the pumping station after excessive levels of arsenic and lead were found in wells that monitor pollution from coal ash ponds at the Allen plant, operated by the Tennessee Valley Authority. Coal ash is the dirty byproduct of burning coal.
One well at the Allen plant had arsenic at levels more than 300 times the federal drinking-water standard. The monitoring wells run about 50 feet (15 meters) deep and are about a half-mile (four-fifths of a kilometer) from far deeper wells drilled by the TVA directly into the Memphis Sand aquifer, which provides the city's drinking water.
The TVA plans to pump 3.5 million gallons (13.2 million liters) of fresh water out of the aquifer per day to cool a natural gas power plant that is replacing the coal plant next year. Discovery of the toxins at the coal plant caused alarm among officials and environmental groups who feared contaminants could seep into the treasured aquifer.
A layer of clay lies between the groundwater and the aquifer. The environment and conservation department, through spokesman Eric Ward, said last week it was "confident the contaminants found in TVA wells at the Allen Fossil Plant are not impacting drinking water."
Memphis, Light, Gas & Water said initial test results had some traces of lead in two of the 10 wells at the pumping plant. Results on the second samples from the two wells indicated that lead was below detection limits.
State regulators also have also told the TVA to pinpoint where the contaminants came from. Spokesman Scott Brooks said the TVA, the nation's largest public utility, doesn't know the source of the toxins and is cooperating with state's instructions. Brooks has said finding the toxins' source could take months of investigation.
The Sierra Club demanded for tests to be done after high levels of toxins at the Allen plant were revealed last week. Scott Banbury, the group's conservation program coordinator in Tennessee, said there is still long-term concern about whether there are cracks in the clay barrier that sits between groundwater and the aquifer.
The Sierra Club and U.S. Rep. Steve Cohen, a Memphis Democrat, have expressed concerns about the deep aquifer wells the TVA plans to use to cool the new gas plant. The Sierra Club has said the TVA should get its cooling water from the city utility, not directly from the aquifer.
"The operation of these high-powered wells in such close proximity to these materials that are contaminating our shallow aquifer could lead to contamination of the Memphis Sand, should there be any holes or breaches in the clay in the vicinity, which we just don't know," Banbury said in a phone interview.