Asheville's North Fork Water Treatment facility 6 weeks after Helene

ASHEVILLE - From a vantage point along stretches of the Blue Ridge Parkway, at popular peaks like Craggy Pinnacle, you might glimpse a shimmering 5.8 billion-gallon lake, fed by mountain streams. It is the typically pristine Burnett reservoir, which supplies water to the majority of the Asheville system's 160,000 customers.

But rather than a clear, crystal-blue body of water, on Nov. 11 it was gray-green and choppy. Six weeks after Tropical Storm Helene wreaked havoc on areas of Western North Carolina, the system — which serves Buncombe County and the northern portion of Henderson County — was still without potable water. The entire system remains under a boil water notice.

The 355-acre reservoir feeds the North Fork plant, the largest of the city's three water plants. It serves 80% of the city's customers.

The water's turbidity level was at 15 Nephelometric Turbidity Units Nov. 11, said Water Resources Department spokesperson Clay Chandler. NTUs are the unit of measurement used to quantify the amount of suspended particles in water.

The goal is less than 2. But it was a far cry from the immediate aftermath of the storm when the turbidity level was pushing 80, then described as the consistency of "chocolate milk."

This week, the city is poised to enter its third round of in-lake treatment with a combination of aluminum sulfate and caustic soda, intended to continue reducing sediment, along with recently installed "curtains."

Simultaneously, the city is pursuing a backup plan: The U.S. Army Corps of Engineers will install a temporary water filtration system at the North Fork plant. If the build goes according to plan, the city could see potable water restored by late November to early December.

In mid-November, Chandler led a group of local reporters on a visit to the North Fork plant. For the Citizen Times, it was the first visit since Helene, despite multiple requests after the storm.

Historic flooding and record rainfall severely damaged the system. Primary transmission mains and a key 36-inch bypass line were destroyed. The reservoir was essentially flipped upside down, stirring up sediment and clay. With roads washed out, the water mains and bypass line could not be reached with equipment for days.

The bypass was built to withstand a typical hurricane event after the 2004 floods from tropical storms Frances and Ivan. Though it was buried 25 feet deep, the storm gouged what Chandler has called "an entirely new river channel," eroding several feet of topsoil. It has been buried back even deeper.

The journey to the plant crossed over the North Fork Swannanoa River, a small tributary that feeds the larger river, partly running parallel to the road until it meets the reservoir.

After the storm, the Swannanoa crested at more than 26 feet, roaring from its banks and destroying homes, businesses, livelihoods and human lives. The destruction still evident along U.S. Highway 70. Areas around Black Mountain and Swannanoa were hard hit. Silt and mud lay thickly on riverbanks, punctuated by downed trees. The front half of an 18-wheeler could be seen amid the damage, its cab crunched like a tin can.

On the banks of the reservoir were totes of aluminum sulfate, a coagulating agent used to treat the lake. The yellow turbidity curtains were a stark contrast to the murky water. Craggy Pinnacle was lost in bulky cloud cover. To the east, were the looming peaks of the Seven Sisters.

At the south side of the reservoir, a multimillion dollar concrete auxiliary spillway was "almost certainly" the reason that the North Fork dam did not fail after Helene, Chandler shared in an Oct. 25 briefing. The spillway resulted from the North Fork Dam Improvement Project, operational in 2021.

He had a similar message in an early October interview with the Citizen Times. The intent of the secondary spillway was to create resiliency in the event of large storm events, the city said in a 2021 news release.

“Without that auxiliary dam ... it is not only not out of the question, it is likely that the dam of North Fork would have failed," Chandler told the Citizen Times Oct. 9. "It just simply would not have been able to hold that amount of water back."

If the dam had failed, three catastrophic events would have occurred, he said. First, a tremendous loss of life from the flooding. Second, billions of gallons of water would have been turned loose, hurtling down to areas southwest of the plant. Finally, it would have resulted in the total loss of the water treatment facility and, as a result, 80% of the system's water supply.

“(The improvement project) very likely prevented those things from happening," Chandler said. "For the city to have the forethought they did, and construct that, looking back was absolute genius. Lifesaving genius.”

On Nov. 11, the chute was still littered with debris. Down the sloping ramp of the spillway, one of the eight fusegates — massive concrete blocks or buckets — had tipped and tumbled down. This is the intended design, the city has said.

The spillway activates at 7.5-feet above full pool, Chandler said at the Oct. 25 briefing. When the first bucket fills, it tips.

"This is a mechanical activation based on the weight of water behind a concrete block, and not initiated by human. Water Resources has absolutely no ability to release water from our reservoirs. The only way water is released from our reservoirs is from our primary spillway and, in the event of an emergency, like Hurricane Helene, our auxiliary spillway," Chandler said.

The auxiliary spillway was designed to begin trickling water at a 200-year storm event, the Citizen Times reported in October. The first fusegate was designed to break out at just over a 1,000-year storm event. In order for all fusegates to let go causing a dam failure, a 50,000-year storm event would need to occur.

More:Non-potable water returns to nearly 95% of Asheville's system. What city learned from 2022-23 holiday outage

More:Drinkable water will be restored to Asheville's system by mid-December, officials say

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.