They found the flaw in the beet-flavored brine in December, while testing the saltwater blends designed to help melt Lincoln’s icy streets in the coldest conditions.
The salt that was supposed to stay dissolved was returning to solid form, threatening to clog the city’s truck-mounted tanks and sprayer nozzles.
“The pumps won’t push liquid when it’s crystallized,” said Ty Barger, the city’s public works maintenance manager. “We realized this would be catastrophic if we had this problem in the middle of a storm.”
It wouldn’t be an issue in most winter weather. Before the city embraced the switch to brine last winter -- as an alternative to dumping dry salt -- Barger and his crew had come up with seven blends, each designed for a different temperature range.
In every recipe, they started with water and 10 percent beet juice, a byproduct of sugar refining, to help the brine stick to the streets. And after a series of tests, they chose the levels of the melting agents -- sodium chloride and calcium chloride -- to match the conditions and forecast.
They built a massive mixing and storage station, retrofitted trucks with more tanks and sprayers and got ready for winter.
But then, during the December testing, Barger discovered crystallization in the four blends designed to work in temperatures that fell beyond 6 degrees below zero. Not an everyday concern in Lincoln, where the average winter temperature is typically in the 20s, but it could keep streets slick in the worst weather.
“You'd see a layer of crystals at the bottom,” he said. “I didn't realize this was going to be a problem.”
It wasn’t as if Barger and his crew hadn’t done their homework. He'd spent last summer filling and freezing plastic Star Wars cups at home and packing them in a cooler to the shop, where they used a chest freezer and micro-brewing equipment to measure each blend's ice-melting ability.
But now he knew he needed to discover what was causing the problem -- and how to fix it.
First, he talked to a scientist for Cargill, which supplies de-icing salt. He was told to dilute the strength of the sodium chloride.
And then Barger emailed just about every science department at the University of Nebraska-Lincoln, asking for help on the city's behalf.
“I knew I needed a really cold freezer. But beyond that, I didn't know what I needed.”
In January, he met with faculty and staff of the Department of Chemical and Biomolecular Engineering.
“And they were pretty excited to be able to help me. They opened up their doors and gave me 24-7 access to their lab and made their staff available to me.”
He had months of testing ahead of him. But the snow, and the temperatures, were already falling. Without new cold-weather recipes, he was forced to wing it: He told his brine-makers to dilute the sodium chloride.
“But that was all guesswork,” he said. “We were kind of flying blind.”
Over the course of the winter, the city would spray nearly 550,000 gallons of brine on 1,200 lane miles of key city streets. They would cut their use of granular road salt by 27 percent per snow event, compared to the 10-year average. Barger would give high marks to the brine's inaugural year, despite the unexpected low-temp troubles.
“I'd give it a good, solid A,” he said.
Still, they fielded a few complaints and concerns.
That the brine stained vehicles: Absolutely not, Barger said. It washes right off.
That the water-based brine penetrated cracked streets and led to potholes: No again, he said. The amount of liquid they apply is less than a half-teaspoon per square foot.
“There are always going to be people who aren't satisfied, but we got lots of compliments, too.”
And through all of this, Barger was spending hundreds of hours on the second floor of Othmer Hall, trying to make the saltwater more effective. He estimated he, and some of his staff, were in the lab several hours each day, every day, for four months.
Their task was two-fold: Develop brine recipes that wouldn't crystallize in low temperatures, and then test each blend's ability to melt ice in similar conditions.
They started with 12 variations of five formulas, or 60 total recipes, testing each at every temperature between 6 degrees below zero and 18 below. Barger would fill a cardboard tray of cuvettes -- small, square cups -- with 14 milliliters of each and put them in a freeze-dryer, set to chill at a specific temperature.
He'd pull them out after an hour, hold them up to a light, search for the telltale salt crystals.
As he narrowed down the blends, he'd pour the brine in beakers, dip ice blocks in them and put those in the freezer, too, to measure how effectively the mixture could melt the cubes in extreme temperatures.
It was exacting work, monotonous, and when they were done, they did it all over again, to make sure they could replicate the first set of results. In the end, Barger estimated they made nearly 1,000 observations, and now have eight brine blends ready for winter.
Hunter Flodman, an assistant professor of practice, was tapped to help Barger. The lab work was important, he said: More controlled than Barger's research last summer, more precise than computer modeling.
“Because of the consistency of his samples and what’s at stake -- community safety -- I think experimental testing was by far the best way to do it,” Flodman said.
The scientist praised the maintenance manager's lab skills. Barger was thorough, Flodman said. He even fixed a broken sensor in the freeze-dryer.
“I was extremely impressed. How innovative he was, how dedicated he was to the project. He pretty much took it on all by himself.”
But Barger, working alongside grad students and faculty, was learning skills he hadn't mastered as a natural resources major.
“I just barely survived chemistry by the skin of my teeth.”