Water samples collected earlier this year on the south and east ends of the city's regional water system exceeded federal limits for a chemical compound linked to increased risks of liver and kidney cancer, violations the city said justify its decision to build a 15 million-gallon a day treatment plant near Amity Road.
Samples the Arkansas Department of Health collected during the first quarter of the year contained trihalomethane concentrations in excess of the 80 parts per billion limit the Environmental Protection Agency has set for the disinfectant byproduct.
The interaction of chlorine used in the treatment process with naturally occurring organic and inorganic matter in water forms THMs, the Health Department said, noting that the EPA has done research linking increased risks of liver and kidney cancer with long term exposure to high THM levels.
The Health Department said the elevated levels pose no immediate health risks, and that the city's water is safe to drink.
THMs become more prominent the longer treated water is in the distribution system, increasing exposure for customers farthest away from the Ouachita Plant that treats water from upper Lake Hamilton and the smaller Lakeside Plant that sources water from the city reservoir at Lake Ricks.
The plants are at the west and north ends, respectively, of a 145-square-mile service area. Test samples taken on the south and east ends are prone to exceeding the 80 parts per billion limit. Hot Springs Utility Director Monty Ledbetter said the 87 parts per billion sample reported by the state was collected in the Amity Road area, near the 33-acre site where the city plans to build its first water plant in more than 50 years.
The plant is part of the $100 million project to bring the city's Lake Ouachita allocation online by 2022. The project includes a 17-mile line that will carry raw water from the lake to the Little Mazarn Road plant location. Preliminary estimates for the raw waterline are between $25 million and $30 million, an expense the city has said is justified by the need to rein in persistently high THM levels on the south and east ends.
Putting treated water into the system from the south will reduce water age for outlying customers and distribute water more efficiently, the city said.
"We only have one entry point," Ledbetter, describing how treated water can take up to several days to reach taps at the south and east ends, said. "It all comes from one direction and makes the farthest part of our system have the highest THMs. We don't see any problems downtown or in areas close to the plant. The problems we see are normally at the very ends.
"It's all about hydraulics and turning the system over. That's why we've really been harping on why we needed to locate the new plant where we did. Once we start putting fresh water in from another direction, all future THM problems will be resolved."
The state collected an 84 parts per billion sample earlier this year from Riviera Utilities' service area on the southeast end of the system. Serving the Diamondhead area, Riviera purchases finished water from the city. Several previous samples collected from its service area have also exceeded the limit.
Riviera CEO Jack Plumlee said the utility is considering putting a mixing system in its two storage tanks similar to the one the city added at its Hollywood Avenue tank last year. Mixers inside the tank circulate water, directing older water at the top of the tank to the bottom, where it can be distributed before newer water that enters the tank from the bottom.
Ledbetter said the city plans on putting mixing systems in all of its tanks. The next retrofit is scheduled for the Industrial Park tank on the far east end of the service area.
The city said an automatic flushing function on the Amity Road hydrant near the problematic collection area purges old water once a day during the winter and twice during the summer, when THM levels are more pronounced. Plumlee said Riviera also flushes its lines regularly.
Plant operators began delaying the application of chlorine several years ago, Ledbetter said. Introducing the liquid disinfectant later in the treatment process reduces interaction time with waterborne matter.Local on 05/17/2019
Print Headline: City expects water plant location to curb THMs