DANVILLE, Va.— Plant operator Steven Johns never counted himself a big sports fan, so he didn’t mind working a 6 p.m. to 6 a.m. shift on Super Bowl Sunday last year at the city’s water treatment plant.

But Johns did mind it when he arrived that cold Feb. 2 to find the water plant’s computer system on the fritz. He called his supervisor to help get it back online and learned something else that concerned him.

Daniel Michaelson, biologist, with Virginia Department of Game and Inland Fisheries launch a boat into the Dan River at Abreu-Grogan Park landing on Wednesday, Feb. 5, 2014, in Danville, VA. He will take U.S. Fish and Wildlife Service, Dept. of Interior biologist out onto the rive to gather water and river bottom sediment samples from the coal ash spill at the Dan River Steam Station operated by Duke Energy upriver in Eden, N.C.

“He told me they’d called from Eden and informed him that they had a coal ash spill,” Johns said. “Right then, I started paying closer attention to my turbidity and my chlorine.”

Turbidity is a measure of the amount of tiny particles clouding the water, usually an indicator of dirt likely containing bacteria and other disease carriers. Municipal water plants use chlorine as a disinfectant.

Johns didn’t know it then, but he faced a night-long battle of wits with the river flowing just 100 yards from his lab. A blue-gray plume of coal ash from the North Carolina plant, traveling a few miles an hour, had started its journey sometime earlier that day and already had crossed the state line.

“The first two checks, everything looked normal — 7:30, then 8:30 — all pretty good,” he said of the reading on his lab’s turbidity meter, positioned next to a tub with about a dozen spigots that each tapped water from a different stage in the purification process.

Checking samples of untreated water early that evening, the machine showed an “8” on a scale that went well into the hundreds. When the reading hits the “40” range, the water is visibly dingy.

“At 9:30, it went from an 8 to maybe 15, up some, but still not bad. After that, it really started taking off.”

Maximum concentrations of toxic minerals

Johns, who only a month earlier had been promoted to lead plant operator, followed standard protocol as the turbidity reading soared past 100, 200, 300, 400 and into the 420s.

Working at the computer, he kept increasing the dosage of aluminum sulfate going into the water. Better known as “alum,” it increases the tendency for the small dirt particles to form clumps that are much easier to screen out.

Then he also increased alkaline lime going into the water to neutralize the other additives.

The result should have been clear water, but the readings on his turbidity meter kept climbing.

Johns kept doing tests on the water all night. What puzzled him most, the water at the end of the treatment process was coming out fine — with little turbidity, even though samples of raw water from the river and samples of water in earlier stages of treatment continued to register high turbidity.

Finally, he did a series of “jar tests” in which he drew samples of raw water, then fed different levels of alum into each to find the right amount to add.

The tests showed that despite the water’s cloudy appearance, Johns had been feeding way too much alum and other additives into the water.

“That’s what really threw me off. I was looking at the turbidity and asking, ‘How in the world is it that I’m overfeeding?’ ” Johns said.

The coal ash wasn’t dirt, and the alum simply had no effect on it.

“Once I cut the alum back, it began to stabilize. So I knew I was on the right track,” he said.

Now Johns really was puzzled. Despite the uncontrolled turbidity as water laced with coal ash came in from the river and as it moved through the early stages of treatment, that same water was coming out the other end of the plant clean, clear and drinkable.

Later, he and other water-plant personnel would figure it out. The coal ash was making the water cloudy and undrinkable right up to the last phase of filtration. That’s where it had been screened out and collected neatly atop the plant’s filter beds that were made, ironically enough, partly of anthracite coal.

“So it just gave us an extra bed on the filters to help them do their job,” said Mike Anglin, another plant operator.

Even so, Danville officials did not want to accept that verdict until it was confirmed by an independent laboratory.

Barry Dunkley, the director of Danville’s water and sewage treatment, remembers the uncertainty he felt those first few days after the spill. It nudged him every time he drove across the bridge on his way to work and saw the Dan River running dark with coal ash.

Barry Dunkley, the director of water and sewage treatment for Danville, Va., explains how two 24-inch pipes draw raw water from the Dan River into the treatment plant for the city’s water supply.

“It was noticeably gray,” Dunkley said. “It scared me: Are we really removing that?”

Fortunately, the city had a two-day supply of stored water, treated before the spill. That gave Dunkley time to await the verdict from an outside testing lab, which found no evidence of contamination in any of the post-spill samples, Dunkley said.

So the coal ash came to rest atop the filters of coal, the substance it used to be before it was pulverized and burned to produce electricity in the now-closed steam station about 25 miles upstream. And its only effect on the water plant was to boost the filters’ efficiencies.

Still, coal ash wasn’t supposed to be there, and Duke Energy contractors ultimately removed it from the plant and buried it in a landfill, back across the state line in Person County.

The spill did have one negative effect on Danville’s water system, Dunkley said: a lingering fear among some of its customers.

Immediately after the spill, sales of bottled water spiked citywide. And some residents still won’t drink city water, refusing to accept a continuing series of test results showing it to be problem-free, Dunkley said.

“I think some of our customers still doubt that,” he said. “I can’t convince them that it’s perfectly safe and that bottled water doesn’t have to meet the same testing as our tap water.”

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Contact Taft Wireback at (336) 373-7100, and follow @TaftWirebackNR on Twitter.

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