ASHEVILLE - In bracing for the winter months, and the potential for storms or heavy winds to stir up sediment at the already turbid North Fork reservoir, the U.S. Army Corps of Engineers is bringing its temporary filtration system online. A spokesperson described it as an added layer of protection to ensure the city's water customers do not land back under a boil water notice.
There is an initial $39.2 million six-month contract for the project, Army Corps of Engineers Spokesperson Patrick Moes told the Citizen Times Dec. 5. Asheville Watchdog first reported on the contract.
The contract is issued by the Army Corps and FEMA provided the funding, Moes said. The city did not shoulder any of the cost.
Moes said they started testing the system Dec. 4 and expect to have it online in the next several days.
The city says potable water is back. So why is the system still necessary?
Potable water was restored to the system's 160,000 customers Nov. 18, more than seven weeks after Tropical Storm Helene pummeled Western North Carolina. But turbidity remains higher than pre-storm levels, sitting at about 12.5 Nephelometric Turbidity Units Dec. 5. The goal is less than 2. In the immediate aftermath of the storm, it was pushing 80 and was described as the consistency of "chocolate milk."
While the water is currently treatable at the city's plant, Water Resources Spokesperson Clay Chandler said the Army Corps' filtration system would "provide a critical layer of security" should a weather event cause turbidity to surge.
The storm severely damaged the Asheville water system, which serves Buncombe County and the northern portion of Henderson County. It has interconnections with several towns and municipalities throughout. At the North Fork plant, fed by the Burnette reservoir and serving 80% of the system, the lake was essentially flipped upside down, stirring up sediment and clay.
"It's a long road to recovery," Moes said, and the likelihood of another rain event or largescale snow event is a "real possibility."
"Having this system in place to ensure that the community does not have to go back into a boil water predicament is huge," he said. "It really provides that ability for citizens, i.e.: survivors, to be able to continue their recovery process.”
The filtration system contract was awarded to a joint venture between two firms, Alaska-based Ahtna and CDM Smith.
The hefty $39.2 million price tag includes capital costs and operations and is "holistic" to the entire project. There is the option for two additional six-month contracts, "but clearly we aren't there yet," Moes said, focusing still on getting the system online.
"Having the capacity to remove this turbidity, the sediment, from the reservoir, gives the city (and) Buncombe County a little more time to develop a more maybe holistic option moving forward."
How does the temporary filtration system work?
Chandler said system operation is expected to begin over the weekend and will start slowly, producing about 5 million gallons of water per day, with North Fork providing the rest. Eventually, the Army Corps' filtration system will do most of the "heavy lifting," with North Fork supporting, to meet an average daily demand of 25 million gallons per day.
The technical term, Moes said, is a "turbidity reduction system." Picture a makeshift barge on the reservoir, with six pumps running water to 13 dissolved air flotation units — or DAF units — which cleans it of sediment and sends it into the water intake for the treatment plant.
“To my knowledge, this is the first time we’ve done anything of this magnitude," he said of the system.
More:Asheville's North Fork Water Treatment Plant; What happened to the 'pristine' reservoir?
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Sarah Honosky is the city government reporter for the Asheville Citizen Times, part of the USA TODAY Network. News Tips? Email [email protected] or message on Twitter at @slhonosky. Please support local, daily journalism with a subscription to the Citizen Times.