Chattanooga and the Moccasin Bend Sewage Treatment Plant are facing state sanctions for the spill Thursday and Friday of more than 100,000 gallons of raw sewage.
The spill, caused by an undetected outage at the plant after a lightning strike, killed at least 3,600 fish and forced live-aboard residents at Browns Ferry Marina from their floating homes.
"We will be issuing a notice of violation," said Dr. Richard Urban, head of the Chattanooga water pollution field office for the Tennessee Department of Environment and Conservation.
A first lightning strike on Thursday completely disabled the entire sewage treatment plant for about an hour and a half, then knocked it out again briefly on Friday, officials said.
Jerry Stewart, who oversees the plant for Chattanooga, said workers were so busy getting the main plant back online, they failed to notice the Tiftonia pump station also was knocked out on Thursday.
With the pump station offline, about 100,000 gallons of raw sewage ran into the Browns Ferry Marina bay for 12 to 14 hours, Stewart said.
The sewage became trapped in the stagnant, bottlenecked bay, which is tucked away from the normally diluting current of the Tennessee River. Stewing in the heat, nitrites and microbes in the sewage consumed all the oxygen in the water, suffocating the fish, Urban said.
Normal water oxygen levels needed to sustain fish and other aquatic life is 5.0 milligrams per liter, but water in the marina tested on Monday morning tallied less than 1 milligrams per liter at all water depths.
"This (Monday's measure) is almost like a septic tank," Urban said.
The spill marks the second major environmental problem for the Moccasin Bend sewage treatment plant this year. In January, an electrical arc after a rainstorm fried circuits on a sewage substation downtown, resulting in a 130 million gallon spill into the main stem of the Tennessee River near Coolidge Park.
On Monday, Browns Ferry Marina overseer, Terry Schrimpsher, said he called the city and state offices all weekend for help, but received only recordings. In the meantime, he said, the bay and boat slips became "completely coated with an oily scum and dead fish."
"That's a 100 pound manhole cover," he said pointing to site of the overflow. "The stuff pouring out it was lifting it this high," he said, holding his fingers to measure six or eight inches.
Schrimpsher said the Tennessee Wildlife Resources Agency finally came to look at the situation on Sunday afternoon.
By that time, city workers had gotten the Tiftonia substation running again and the overflow stopped. But dead fish already were floating - and smelling, said David Schrimpsher, Terry Schrimpsher's son as well as the marina mechanic who lives onboard a boat at the marina.
Early Monday morning, regulators with the Tennessee Department of Environment and Conservation - along with city officials and a city contractor, Marion Environmental Inc. - began cleanup.
Marion workers scooped thousands of fish one-by-one from the water and sprayed a microbiological dispersant into the water to get rid of the oil sheen.
Marion supervisor William Seavey said the dispersant "eats hydrocarbons" and is a completely benign substance.
Both Stewart and Urban said their offices reported no weekend calls about the problem at the marina.
Stewart said a Moccasin Bend worker, making routine checks, found the overflow malfunction on Friday morning and got it stopped.
"We first thought it had been running only on a short time, but apparently that wasn't the case," Stewart said. "That (Thursday and Friday) is probably the two most intense storms we've had downtown in years."
He said the he estimates Marion Environmental's work will cost the city about $10,000.
Stewart and Chattanooga spokesman Richard Beeland said officials with the U.S. Environmental Protection Agency have been looking at the January spill as well the Moccasin Bend Sewage Treatment Plant's history of combined sewer overflow problems.
The city hasn't yet heard from EPA about the weekend mishap, Beeland said.
"But we expect to," he added.
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