Ouachita Plant gets upgrade
The newest improvements the Hot Springs Board of Directors approved last week for the Ouachita Plant will outfit the 50-year-old facility with the latest water-treatment technology, city officials said.
The $3.89 million project will replace the chlorine gas-disinfection system with sodium hypochlorite, a disinfectant city officials have said eliminates the possibility of a public safety hazard caused by a chlorine gas leak. Monty Ledbetter, director of utilities for the city, said sodium hypochlorite also creates lower levels of trihalomethanes.
A disinfectant byproduct, THMs have been identified by the Environmental Protection Agency as possible contributors to liver and kidney cancer. Increased levels are a function of the amount of time the disinfectant has to commingle with organic matter in the water, making levels bump up against the EPA mandated
80-parts-per-billion limit by the time treated water reaches the outer parts of the system.
Riviera Utilities, a wholesale customer of the city serving the Diamondhead community, reported THM levels at 83 parts per billion last year.
“(Sodium hypochlorite) is like the wrapper around a loaf of bread,” Ledbetter said. “It keeps the water safe and does help with THMs.”
The construction of the $622,000 sodium hypochlorite facility is part of the $3.37 million contract awarded to Van Horn Construction. The Russellville company was contracted for the previous round of plant improvements, which included upgrades to some of the sedimentation basins.
City Engineer Gary Carnahan told the board Van Horn will also rehab and replace all nine filters at the plant. According to bid information, the $2.29 million for the filter improvements accounts for most of Van Horn’s contract, which was the lowest of the nine companies that submitted bids.
“In some cases, the structural or mechanical parts have to be replaced, not just the sand and other media,” Carnahan said. “They’ll put covers over the filters that will keep the algae down during the summer, making it easier for year-round operations.”
The project also includes $129,000 of improvements to the pumps that push treated water from the plant into the distribution system.
“They’re going to replace the valves that function there, so we can regulate how much water we’re sending to the city in a better way,” Carnahan said.
The board adopted an ordinance designating Brown Engineers of Little Rock as the solesource provider of electrical engineering services for the city’s water and wastewater systems. It’s been contracted for $524,750 to integrate Van Horn’s improvements into the plant’s control system.
“(Van Horn) will bring wires and conduits to the main control panels,” Carnahan said. “At that point, we want Brown Engineers to install the computers, do all the integration and put the software in to make it operate like it’s supposed to operate.
“We set up the bid package so that it was clear that the contractor could stop at this point, and Brown Engineers would take it from there. We believe that’s one reason our water plant bids came in under budget.”
Carnahan said 2014 and 2015 revenue bonds secured by water rates will pay for the improvements. Ledbetter said construction will begin in the fall, when demand for water is low and parts of the plant can be taken off line.
The Arkansas Department of Health’s 2016 Sanitary Survey said the plant can treat 22.33 million gallons a day, but Ledbetter said 20 mgd is the plant’s limit. Capacity drops to about 19 mgd when turbid water collects near the plant intake on upper Lake Hamilton, he said.
Runoff from the Lake Hamilton watershed backs up near the intake during significant rain events, creating a turbid raw water supply if the backwash isn’t pushed downstream by Entergy Arkansas Inc. releasing Lake Ouachita water through Blakely Mountain Dam.
Ledbetter said new chemicals added to the flocculation process have improved the plant’s ability to treat turbid water. The improved flocculant binds raw water particles together faster than the previous system, allowing floc to accumulate faster and fall to the bottom of sedimentation basins.