After 150,000 gallons of wastewater spilled into a creek because of two malfunctions in two months, the Trion, Ga., town council will vote at a special called meeting Thursday on whether to buy a new generator for the treatment plant.
The first spill of about 57,000 gallons occurred on Oct. 2, when the power failed on a system that controls pumps for water intake. The second spill of about 96,000 gallons occurred on Nov. 18, when a power outage swept through Chattooga County and a generator failed to kick in.
In the second case, the generator's batteries were zapped at the critical moment. Plant Superintendent Andy Melton said that was the result of a malfunctioning part that has been at the plant since 1973.
After it was too late, the plant's maintenance team discovered the contact of the solenoid inside the generator was connected to the contact of the two 12-volt batteries. The solenoid is a coil of wire that passes an electrical current from the battery to another function - in this case, the generator's starter.
The contact, meanwhile, opens and closes the electrical circuit, depending on whether the switch is on. But in this case, the contacts for the solenoid and the battery were connected even when the switch was off, draining the battery of its juice even though nobody was using it.
The plant's staff tests the generator every Friday, including the day before the power outage. Melton said it worked during that particular test, leading him to believe the contacts got connected that particular day, throwing off the whole machine.
Melton said the old part must have gotten so hot, the contacts basically welded together.
"You have a 44-year-old piece of equipment," he said. "It's going to fail for some reason. ... We need that piece of equipment to be 100 percent reliable all the time."
Without power - and without the generator - the plant's influent pumps could not handle the wastewater rushing into the plant. Normally, all of that incoming water from town residents and Mount Vernon Mills goes into the plant's wet well. The well has monitors. When too much water enters, a pump automatically starts moving water into another part of the plant. There are three pumps in total, launching at different points as more water comes in.
But when the influent pumps don't work, the backflow valve spits water into Chappel Creek. On Nov. 18, 96,000 gallons rushed out in 45 minutes, before the generator began to work again. To prevent that problem again, Melton said, the council needs to buy a new generator that doesn't have malfunctioning parts.
He has received five bids, which run from about $50,000-$60,000. The Georgia Environmental Protection Division, meanwhile, is still investigating the spill, said James Cooley, manager of the agency's Mountain District.
The October spill was the result of a different malfunction. The power source for the programmable logic controller failed, Melton said. That is the part that is supposed to automatically monitor the wet well, signaling for the pumps to start working as more water enters.
Again, the water level got too high in the well. And this time, 57,000 gallons of untreated water poured into Chappel Creek.
The week before that failure, the town council already had voted to replace the programmable logic controller, knowing it was old. While still waiting for the new part, workers at the plant had to monitor the wet well for 144 straight hours, manually turning the pumps on and off.
When untreated wastewater pours out of the plant, it brings fecal coliform bacteria into the creek. As long as the geometric mean for the bacteria is less than 200 colonies per 100 milliliters, the water is generally safe for swimming or other recreational activities, said Uttam Saha, program coordinator for the agricultural and environmental services lab at the University of Georgia.
In the seven days after the October spill, the level of fecal coliform bacteria in Chappel Creek was above that mark on one day, measuring in at 318 colonies above the spill and 270 colonies below the spill. In the Chattooga River, according to the EPD, the bacteria content was never measured above the safety threshold.
The EPD did not provide measurements for the more recent spill, though Melton wrote to the agency there were some minnows dead around the area where the water flowed out.
Contact staff writer Tyler Jett at 423-757-6476 or tjett@timesfreepress.com. Follow him on Twitter @LetsJett.