Weeks after a containment pond at the Tennessee Valley Authority’s Kingston Fossil Plant ruptured and caused a massive coal ash flood, the federal utility is now also working to repair a gypsum pond at its Widows Creek Fossil Plant in Alabama, after gypsum slurry overflowed into the creek Friday.

The event was discovered before 6 a.m. on Jan. 9. Water and gypsum from the gypsum pond drained into an adjacent settling pond after a cap dislodged from a 30-inch standpipe, which had at one time been used to drain water from the gypsum pond into the settling pond. When the cap dislodged, water and gypsum flowed into the settling pond. The pond filled to capacity and then overflowed.

The overflow stopped when the level in the gypsum pond dropped to the level of the standpipe. “Some material overflowed into Widows Creek, although most of the gypsum remained in the settling pond,” the TVA said.

Gypsum ponds hold limestone spray from TVA’s scrubbers, which clean sulfur dioxide from coal-plant emissions. Gypsum contains calcium sulfate, which is commonly
used in drywall, a commercially sold construction material. The slurry that overflowed into the creek contained water, a mixture of predominantly gypsum, and some fly ash, the TVA said.

The TVA immediately notified appropriate federal and state authorities, as well as Stevenson, Scottsboro, and Huntsville utilities, to inform them of the incident. The closest municipal water system is in Stevenson, but the Stevenson system does not withdraw water directly from the Tennessee River, it said.

The TVA is still investigating when the leak started and is determining how much material was released. As part of the repair effort, the utility said it would fill the unused pipe with concrete. It said that Widows Creek is also performing maintenance activities to slope the internal wall of the gypsum pond by bringing in about 3,500 cubic yards of sand.

The Widows Creek Fossil Plant is located on the west bank of the Tennessee River in Jackson County, Alabama. It is named for the nearby creek. The plant has eight generating units with a combined net generating capacity of 1,750 MW.

Groundbreaking occurred on March 28, 1950. The first of the eight turbo-generators went into operation on July 1, 1952, and the last one went into commercial operation on February 7, 1965. Units 7 and 8, the largest at the plant, are outfitted with scrubbers.

Source: TVA