City starting to repressurize water system in eastern Buncombe, but full systemwide restoration could still take weeks • Asheville Watchdog

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While the City of Asheville crossed a milestone this week by reconnecting a major bypass valve at North Fork Reservoir that can feed the entire system, officials cautioned that full restoration is still weeks away.

Contractors continue to repair the distribution system, which includes miles of pipes often left in disarray by Helene’s floodwaters on Sept. 27, and the city is still wrestling with a turbidity, or sediment, issue at the reservoir. The raging flood waters deposited a huge amount of silt-laden water into the normally pristine North Fork Reservoir, and the facility’s filters cannot handle the clay particles without causing lasting damage.

At the Friday, Oct. 11 briefing, Assistant City Manager Ben Woody said the city was able to fill up and pressurize the 36-inch bypass line that contractors finished repairing in the early morning hours of Thursday. Still, Woody said they’re dealing with two “limiting factors” for returning the North Fork Reservoir service area to full service.

“The first continues to be our ability to use the North Fork water treatment plant to filter and treat water, and our challenge remains the turbidity, or the murkiness, of the reservoir,” Woody said. “The second challenge we’re going to talk about today is the complex process that’s necessary to pressurize and fill the pipes in the water distribution system.”

In consultation with the Environmental Protection Agency, the city’s water department “is hiring a private contractor to source and install curtains in the area of the reservoir closest to the treatment plant,” Woody said, noting these curtains help with filtering out sediment. The curtains will create a 500-foot perimeter around the reservoir’s intake structure, helping the sediment to coagulate and then sink to the bottom.

The city, after consulting with the EPA, has decided “to go ahead and begin pressurizing the distribution system directly with reservoir water,” Woody said. That means it’s not going through the water treatment plant at North Fork, which in turn means the water will not be potable and likely will contain sediment.

“So while this water may contain sediment, it will be highly chlorinated to provide as much disinfection as possible under the circumstances,” Woody said. “So what that means for the North Fork Reservoir treatment area or distribution area is, if you begin to get water …there will be a mandatory boil water notice that will be in effect until our sampling demonstrates that the water is safe to drink.”

The city recommends customers continue to use bottled water for drinking, cooking or brushing teeth, or that you boil the water for at least one minute if you’re using it for any of those purposes.

“So if you’re in the North Fork area or Swannanoa and you start to get water, please, please remember that you are under a boil water advisory,” Woody said. “It is going to contain sediment, but if you take those steps, it will be safe to use that water for basic needs.”

The city also recommends that if you begin to get water restored and it has sediment in it, you should close the valve to your hot water heater, and to your whole house filter if you have one, to prevent sediment from accumulating.

The city began pressuring the North Fork and Lake Eden areas, both in eastern Buncombe County, on Friday. The closer they get to Asheville, the more distribution pipes the system has, so that means getting the water flowing will slow down, Woody said.

Woody also noted that the system usually utilizes two main distribution lines, 24 and 36 inches, respectively, to distribute water from the reservoir, but those lines have not been repaired yet. Utilizing just the one 36-inch bypass valve means water flow will be reduced somewhat.

The city will have to flush the system to remove sediment and air pockets, so residents are likely to see workers opening hydrants to release water and air in the coming days.

“The other thing that happens is, as we begin to pressurize the section, we are going to find new waterline breaks that we previously were not aware of,” Woody said. “We have to repair those before we can move to the next area. We have our crews and our utility partners from across the state on standby to make these repairs as they’re discovered.”

Once they complete one area, they’ll repeat the process in the next. The approach will be very intentional, and incremental, moving in a general westward direction from North Fork toward Asheville. Areas closest to North Fork will receive water first, the areas farthest away last.

Woody said he still did not have a timeline on full restoration. The big challenge this weekend and into early next week, Woody said, is this first stage where they’re filling the system’s distribution lines, removing air and making repairs.

That’s going to be in the hard-hit Swannanoa area.

“So the first place we have to get back online is what I would call basically ground zero for the destruction of the water system,” Woody said. “We believe that once we can get past Swannanoa, it’ll become easier and faster to pressurize the system, but we’ve got a big weekend this weekend to try to pressurize the area around Swannanoa.”

Asked if the encouraging news meant water may return in a matter of days rather than weeks, Water Resources spokesperson Clay Chandler said it’s still a matter of weeks. Once pressurization occurs, he said, they’ll be playing a game of “whack-a-mole” with distribution leaks, which could involve water shooting skyward through breaks.

Chandler said the city on Monday will provide a map of tentative restoration areas in the coming days and weeks.

Regarding the sedimentation curtain process, Chandler said it has been used elsewhere, but Asheville has never employed this system, so they can’t put an expectation on how quickly it will make the clay particles clump together and sink.

“I think it’s a fair assessment to say that the timeline right now is fewer weeks than it was when we started,” Chandler said. “We don’t want to put a number in front of ‘weeks,’ as badly as people want us to, and as badly as we wish we could, because we don’t want people to make plans around that number and then we don’t meet it. And they’re even more frustrated than they are now, rightfully.”

Congressman Chuck Edwards said he was initially told “it might take five weeks.”

“I’ve had two specific briefings since that number was given to me,” the Hendersonville Republican told The Watchdog. “They seem to be backing off of that number now, and they are uncertain when water would be restored back to normal.”

Edwards said, “There are some very competent people working on getting water restored … There’s a good, solid plan in place to phase water service back to Asheville, initially, in the non-potable way. But no one right now can say how long that’s going to take.”

The 350-acre North Fork reservoir, located outside of Black Mountain in eastern Buncombe County, provides 80 percent of the water for Asheville. The city’s Mills River plant, located in northern Henderson County, currently is working fully, providing water to about 20 percent of the system’s customers, mostly in southern Buncombe.

While turbidity is no issue at Mills River, which draws from the French Broad River, it remains problematic at North Fork.

Turbidity is a measure of solid materials in water. To determine the level of turbidity, workers use an instrument to measure the amount of light that’s scattered by particles in the water sample. Asheville uses one of the most common methods, called Nephelometric Turbidity Units.

The EPA requires filter water to be less than .30 NTU for consumption, Chandler said, noting that normal filtered water from North Fork is between .03 and .05 NTU, meaning it’s “typically exponentially cleaner than required.”

Typical raw water coming into the treatment plant from North Fork has a NTU of 1 or less. As of Oct. 11, it stood at 30 NTU, Chandler said. He said they don’t know what level of NTU the system could theoretically handle, as that would just be an assumption.

North Fork has a maximum depth of 120 feet, Chandler said, although the average depth is 40 feet. The treatment plant there has water intakes at 21 feet, 50 feet and 80 feet, so the city does have the option of taking in water from a higher level of the lake, where the water should be clearer.

While some residents have expressed frustration with the city for not providing a more specific restoration timeline, or at least a “best case/worst case” scenario, Desmond Lawler, a professor in the Civil Engineering Department at the University of Texas, said that’s actually understandable.

“I can easily see they’d be hard pressed to put a timeline on the repairs, because they probably don’t know until they start pressurizing parts of the system to see if they have more problems than they knew of before,” Lawler said. “I don’t blame them for saying, ‘We don’t know.’ They’d probably rather put up with people being angry with the uncertainty than saying ‘12 days’ and then it turns out to be 20.”

In short, they can’t be specific until they fully know the extent of the problems, Lawler said. From what he’s read about the system and the issues, Lawler said, he would be cautiously optimistic that the outage would not be painfully extended, say in 8 to 12 weeks.

“I would imagine they’re talking two weeks but that could pull up to three and a half weeks,” Lawler said Oct. 10, referring to full restoration of potable water.

North Fork’s filtration system is a “direct filtration” system designed for cleaner water, Lawler noted. Chandler said North Fork uses “dual-media filters” that are made up of 12 inches of gravel, 12 inches of sand, and 23 inches of anthracite. It uses an “air scour backwash system.”

“Direct filtration plants are only used for systems which have a normally quite low turbidity in the influent water,” Lawler said, noting that’s normally the case for North Fork, which is surrounded by 22,000 acres of protected forest. “But unfortunately, that is not the case now.”

“Plants that often or normally have a much higher turbidity in the influent water have an additional sedimentation step prior to the filtration,” Lawler said. “So, basically, this plant can’t handle high influent turbidity at the normal flow rates because you would have to be backwashing the filters very often.”

The city has to hope the turbidity at the highest intake level gets low enough pretty soon, he said, noting this adds to the uncertainty in the timing of when water service will be restored.

“My guess is that they will operate this plant at a flow rate much lower than usual when they bring it back online, and they will have to use a substantial fraction of the water they produce to backwash the filters much more frequently than normal,” Lawler added.

North Fork is rated to produce 31 million gallons a day, although under normal conditions it produces about 21.5 million gallons. Chandler confirmed they would have to run the plant at a lower flow rate during early restoration because of the turbidity issue.

John Shaw, a professional engineer who has worked in the water industry for 37 years, previously lived in Asheville for five years and still owns a home here that is without water.

Shaw agreed that Asheville has to conquer both distribution and treatment of the reservoir water before it can distribute potable water to its 63,000 customers.

“It sounds to me like the biggest problem is distribution,” Shaw said, noting that if the 25-foot deep main distribution lines coming out of North Fork washed out, that’s an indication of potentially similar issues with other, smaller lines.

Shaw suggested the city might want to look at an “interim system” for water delivery in some places, such as high-density polyethylene temporary water lines that are flexible and can be laid on the ground while excavation, removal and replacement of permanent piping is ongoing. That could get water into the city faster, he noted.

Asked what he thinks the best case/worst case scenario would be for full restoration of potable water to the entire system, Shaw offered a sobering assessment.

“They’re at least a couple of months out,” Shaw said. “I can’t imagine getting this thing up and running in less time than that.”

The city has multiple contractors already on the job, and they have been installing new pipes, but Shaw said doing such a job right, as the city has pledged to do, just takes time. You have to bring in or reuse an enormous amount of fill material, and it’s got to be compacted and tested to make sure it has the proper stability, he said.

So he understands why the city is not giving any specific timetable for restoration.

“You can’t make unreasonable or unfounded predictions,” Shaw said. “What my suggestion would be is to be very forthcoming in what the conditions are, what they’re doing to remediate the conditions, and what elements are going to be at play that delay or speed the process, then let the cards fall where they may. Don’t hide things. Just be forthcoming as much as you can.”

The city has provided regular updates on the water system at the daily briefings, with photos and videos of ongoing work.

Shaw said that down the line, the city may want to consider installing a filtration system that can handle higher turbidity, as these types of heavy rainfall events are becoming more common.

For now, he said, he’s glad to hear the city is “focused on getting the system wet rather than drinkable.”

Potability, Shaw said, will be the big hurdle.

“Once they get everything wet they’ll have to purge the entire system and introduce a water with a high concentration of chlorine in order to disinfect, purge that water, then follow it with potable,” Shaw said. “That has to happen for every single distribution system line. That’s going to take time and a lot of production capability at the treatment plants. In short, it’s still a long slog.”

Watchdog investigative reporter Sally Kestin contributed to this report.

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