A third round of in-reservoir turbidity treatment started Wednesday at the North Fork Reservoir, as a crucial measurement on the path toward potable water continues to drop.

Water Resources Department spokesperson Clay Chandler said at Wednesday’s daily Helene briefing that the turbidity measurement, Nephelometric Turbidity Units (NTUs), stood at 14.8 in the morning. A week ago it stood at 18.

“So it’s still falling,” Chandler said.

The city is now filtering about 20 million gallons of water a day through North Fork, which provides 80 percent of Asheville’s drinking water, and another 3 million gallons daily through its Mills River treatment plant. That leaves the water department just 4 million gallons a day short of being able to pressurize the entire system. That’s the threshold for again providing potable water, which the city has not delivered since Sept. 27 when Helene washed out the main transmission lines and a backup line, and essentially turned North Fork upside down.

Besides the turbidity treatment, which involves an application of aluminum sulfate and caustic soda in the reservoir to foster coagulation and sinking of clay particles, the city is also moving forward on a partnership with the U.S. Army Corps of Engineers to provide a portable filtration system that can handle high-turbidity water. While ideally the city needs the NTU level to hit 1.5 to 2.0 for optimum water production, the Corps’ system can handle higher NTU.

Regarding the Corps of Engineers “interim pretreatment system,” Chandler said, “the private contractor who will perform the work conducted a site visit Monday afternoon, and equipment and materials started arriving yesterday.”

The timeline for completion of that project remains the same — late November or early December. That depends on the weather, though.

The city has a two-pronged approach to returning to potable water service: continue reducing turbidity while increasing the amount of water that can be filtered, and installing the Army Corps technology to filter more turbid water.

Chandler has said previously that once the city is pushing enough potable water, it will have to flush the entire system and then repressurize it, which could take two and a half to three weeks. Asked if the city currently being able to push through more water than expected, the 20 million gallons per day, could shorten that flushing timetable, Chandler said, “Theoretically, that’s possible.

“But you know, that’s all going to depend on the back-end bacterial testing that we’ll do once that process starts,” Chandler said. “But theoretically, yes, it could speed it up, but that’s no guarantee.”

Potable water’s return still will likely come in early to mid-December. The water continues to clear, and Chandler said Wednesday that is in part because workers are now seeing much finer silt particles instead of the heavy, muddy material they encountered right after the storm, when North Fork turned completely brown.

The city remains under a boil water notice for all residents. The tap water the city is providing is acceptable for showering, flushing toilets and doing laundry, but residents should use bottled water for consumption. If you must use tap water for consumption, it has to be boiled for at least one minute.

Asheville Watchdog is a nonprofit news team producing stories that matter to Asheville and Buncombe County. John Boyle has been covering Asheville and surrounding communities since the 20th century. You can reach him at (828) 337-0941, or via email at jboyle@avlwatchdog.org. The Watchdog’s local reporting during this crisis is made possible by donations from the community. To show your support for this vital public service go to avlwatchdog.org/support-our-publication/.

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