TVA faces high costs for cooling water in Memphis
Rising 77 feet above the bustle of Frank C. Pidgeon Industrial Park, the two newly built 2.5 million-gallon storage tanks at the Allen Combined Cycle Plant stand as shiny symbols of a massive and costly change in plans.
The Tennessee Valley Authority spent $15 million completing the twin structures even though they were not included in the original plans for the $975 million natural gas-fired power plant. The tanks became necessary after environmental concerns forced TVA to change, at least temporarily, its method of obtaining cooling water for the facility.
Although it had planned to use 650foot-deep wells drilled into the Memphis Sand aquifer, the federally owned utility for the foreseeable future will purchase the cooling water it needs — an average of 3.5 million gallons daily — from the Memphis Light, Gas and Water Division.
The two 86-foot-diameter tanks, which were put into service June 29, are used when the plant is operating at or near capacity for extended periods, especially during hot summer weather. They also would provide a backup supply in the event of a disruption in water service.
Contamination forced change
The plant in Southwest Memphis began operating this spring, generating up to 1,150 megawatts of power, enough to
serve more than a half-million homes.
TVA turned to MLGW for its cooling water after exorbitantly high levels of arsenic and other toxins were found in a shallow aquifer beneath coal ash ponds at the nearby Allen Fossil Plant, which was replaced by the gas-fired facility. Subsequent tests showed that the pumping wells at the new plant could pull water from the contaminated shallow aquifer into the Memphis Sand, which supplies drinking water for Memphis and other municipalities.
TVA spokesman Scott Brooks said the agency remains committed to purchasing cooling water from MLGW at least until the contamination is fully investigated and remedied. The Tennessee Department of Environment and Conservation is reviewing TVA’s plans to study the problem.
The tanks wouldn’t have been needed had the wells been used. TVA had been planning to get its regular coolingwater supply from four of the 650-footdeep wells, with a fifth well serving as a backup source.
During an August 2016 meeting, TVA President and CEO Bill Johnson told members of the agency’s board that the prospect of building large, costly storage tanks was among the reasons officials favored the use of well water. TVA is required by law to generate power at the lowest feasible cost.
“We could not get sufficient water from MLGW at peak operating levels, and to do that would require significant upgrades to their system and require the additional construction of multimilliongallon, large storage tanks at Allen for supplemental cooling water,” Johnson told the board.
After the discovery of the high levels of arsenic last year, however, TVA announced it would refrain from using the wells, which had been authorized in permits issued by the Shelby County Groundwater Quality Control Board in 2016.
‘Gray water’ studied as option
Environmentalists, many of whom opposed the wells even before the discovery of the arsenic contamination, said the need for costly storage tanks shows that TVA should have used effluent, or “gray water,” from a nearby sewage treatment plant to cool the Allen facility.
TVA initially considered using gray water from the T.E. Maxson Wastewater Treatment Facility but eventually opted for wells after determining it would cost too much to adequately treat the effluent. Officials also were reluctant to rely solely on the Maxson facility for cooling water.
“I think it’s really a shame that TVA did not listen to the concerns of local citizens who were trying to help them make the right decision to begin with,” said Scott Banbury, conservation programs coordinator for the Sierra Club’s Tennessee chapter.
In addition to avoiding the need for costly storage tanks, the use of gray water “would’ve shown TVA’s commitment to environmental stewardship,” he said.
But Brooks said the gray water option remains unfeasible. TVA estimates it would cost between $9 million and $23 million to construct a treatment plant to sufficiently purify the effluent for use in the highly efficient plant. The agency would spend an additional $6 million a year operating and maintaining the treatment facility.
In addition to the costs of the tanks, TVA is spending extra money buying utility water instead of pumping its own. MLGW is projecting water revenues of $1.7 million a year from sales to the plant, Gale Jones Carson, director of corporate communications for the utility, said in an email.
Water to the TVA plant comes from MLGW’s Davis Pumping Station, which taps the Memphis Sand and is about 3 miles away, near West Shelby Drive. To better serve the Allen plant and other facilities in the industrial park, MLGW is installing a water main extension from the pumping station to an existing main on Paul R. Lowry Road.
Reach Tom Charlier at thomas. charlier@commercialappeal.com.