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Close Call For The MSA Chlorine Overflow Led To Long Hours For Workers
A recent over-chlorination incident at the Maury Service Authority water treatment plant highlighted the need for upgrades to many aspects of the water treatment system, many of which are already being planned as long-term projects.
It began on the morning of Tuesday, June 4, when the MSA received a shipment of sodium hypochlorite, or hypo, a chemical that contains chlorine that’s used to disinfect water at the plant before it goes into the distribution system.
The Virginia Department of Health requires that chlorine levels in water that gets sent out for distribution contain at least 0.2 parts per million of chlorine and no more than 4.0 parts per million in order to prevent regrowth of bacteria between the treatment plant and the customers.
MSA Executive Director Jordan Combs told The News-Gazette that water that leaves the MSA plant typically has between 1.5 and 2.0 parts per million of chlorine.
The tanks that hold the hypo are usually kept between 20 and 90 percent full and are refilled “about every month and a half or so,” Combs said.
“You can’t drain [the tank] down to zero because then you can be out if they’re late [with the delivery], and you don’t ever fill it up to 100 percent because it expands and contracts,” he explained.
A typical order for the MSA is 1,400 gallons, which is what was supposed to be delivered on June 4.
Instead, 2,800 gallons was pumped into the tanks, causing an overflow, which got into the water at the plant. Combs said that an estimated 1,100 gallons of hypo is what overflowed out of the tanks and into the sedimentation basin and influent channel.
Combs said that there were several different factors that led to the overflow. The time it took to pump the 2,800 gallons, he said was “about the same time or less” than it takes for a normal delivery of 1,400 gallons. He also noted that the tanks and storage system are 20 years old and don’t contain a lot of the safety parameters that are in more modern systems, such as containment pads, overflow pipes, pressure indicators and “other instrumentation that helps you understand how it’s being filled up and what’s going on.” Those parameters are designed to prevent spills, and to allow for containment in the event that a spill does occur.
After the spill was detected, the plant was shut down and cleanup and containment efforts began. The water in the Enfield Clearwell, which feeds into the distribution system, was tested and found to be at normal chlorine levels, which meant that the water that was in it was safe to go out into the distribution system that feeds the city of Lexington and Rockbridge County water systems.
It was a different story for the water still at the plant. Tests of the water in one of the sedimentation basins showed 50 parts per million of chlorine, and when the clearwell at the plant was backwashed, the tests started showing results of over 100 parts per million.
The water was pumped into the lagoons that where the process of dechlorinating the water began, using dechorlination tablets to help lower the levels, while also filtering it back through the MSA system.
The dechlorination tablets that the MSA uses come in 5-gallon buckets, and the plant typically uses between 15 and 20 buckets per year. Dechlorinating the water from this overspill took more than 200 buckets of tablets.
The Lexington Department of Public Works and the Rockbridge County Public Service Authority donated tablets and equipment to help with the dechlorination process, and extra buckets were purchased from “Staunton, Roanoke and everywhere else close by,” Combs said. The MSA also got assistance from Randy Hostetter, who not only donated a pump to help with the dechlorination process at the plant, but also drove to Newport News to pick up 100 buckets of dechlorination tablets.
Throughout that first day, Tuesday, the system brought the chlorine levels down, with the hope of reaching the maximum allowed levels of chlorine by 8 a.m. on Wednesday. By 5 Wednesday morning the levels had been brought down to 10 parts per million, but Combs realized that it wasn’t going to get to 4 parts per million in the next three hours.
“My concern at that point wasn’t just putting out unsuitable water,” he said, “but that customers’ water service would get interrupted and they would start losing pressure in the system and would start losing pressure at the customers, whether that’s a business, or a home-owner, or at the hospital, they would start to lose pressure and start to lose water.”
The two pumps were put to two different tasks at that point. One was pulling water out of the clearwell and dechlorinating it before discharging it into the drainage system and back into the river. Testing on the water showed that chlorine levels were at 0 parts per million for the water going back into the river. Combs estimates that between 750,000 and 1 million gallons of water was discharged out of the system.
The second pump was pulling the water out of the lagoons to run through the dechlorination system to finish getting the chlorine levels to below 4.0 parts per million.
At 8 Wednesday night, the pump at the Enfield Clearwell had to be shut off, because the water level in the clearwell had gotten so low that the pump was starting to pull air. The distribution system was now being supplied by the Grassy Ridge Tank and by what was already in the systems. Three hours later, at around 11 p.m., the water from the plant had been reached Health Department standard levels and water began being pumped into the Enfield Clearwell, and by 3 Thursday morning, the pump at the Enfield Clearwell was turned back on, feeding the water into the distribution system.
“We didn’t have any bad water get sent out, we didn’t have any DEQ permit violations that were a risk to the environment, we didn’t have any risk to the public health, and … nobody in the system lost pressure or lost service, but we were getting mighty close to it,” Combs said. “I don’t know that I’d categorize it as a catastrophic event, but I do think we did get very close to the point that people were going to lose water pressure and water services, which is a very big deal. We didn’t get into any of that. We were able to manage it, and I think due to the training and the quick reaction and the effort by the MSA staff, but also the city and the PSA – and Randy Hostetter, who was also a big help – we were able to avoid that and mitigate it to the point where we didn’t have any of those [issues].”
Since the incident, Combs says that the MSA has been working with the chemical company to put in a better training system for their drivers, and several extra checks have been put in place at the plant for all chemical deliveries to prevent another spill from happening in the future. The long-term solution is to update the system to include safety measures like automatic stopping and spill containment.
“That kind of stuff that would mitigate this, so that even if it happens, it’s got a place to go that’s in a way for us to manage it and we don’t have to worry about it, one, being a risk to public health and safety and, two, getting into the environment,” Combs said. “So we’ve got to get that long-term, but we’re working on short-term [solutions].”
Some of those solutions include getting new pumping equipment, which Combs says the MSA has already received bids for, and to update a lot of the plumbing “in house.”
“That doesn’t necessarily alleviate the risks that happen, but it is going to help us from a chemical injection perspective, so we’re taking steps to make that system as a whole better,” he said.
On June 4 and 5, staff at the MSA worked anywhere from 24 to over 30 hours straight to address the issue, and then worked 15-20-hour days over the rest of the week to help get the plant back up to normal operations. Combs said that MSA water superintendent Josh Fore put in 38 hours on June 4 and 5. He also expressed gratitude for the support from the Lexington Department of Public Works and PSA.
“I can’t say enough about the support we got from our two customers in getting us through this,” Combs said.
