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University Study Seeks Perfect Plow
Civil engineering professor, students contract with MnDOT on de-icing study.
Dan Linehan, Mankato Free Press, 1-28-2015
(Photos courtesy of Stephen Druschel. In the top photo, experimenters pour water from 5-gallon buckets to create an icy driving surface. In the bottom photo, Druschel uses a hose to create ice in a Shakopee parking lot.)
Plow drivers know their business. They know what works, and what doesn’t.
“It’s one thing to intuitively say, ‘We’ve seen it. We know it,’” said Tom Peters, maintenance research engineer for the Minnesota Department of Transportation.
But without hard data, their observations are unlikely to change the practice of plowing.
That’s where Minnesota State University, Mankato civil engineering professor Stephen Druschel and his team of undergrads come in. In a series of experiments last winter, they measured the effectiveness of deicing and plowing methods on contract with MnDOT at a cost of $116,144.
Their task, broadly speaking, was to evaluate the methods and materials MnDOT uses to clear roads of ice and snow, and see if they could be improved, Peters said.
The work followed a 2010 Minnesota State Mankato project that examined the effectiveness of 25 types of road salt. Though that earlier work was done in a lab, the second phase moved into the field during what happened to be the coldest Minnesota winter in 35 years.
One of the three outdoor sites was the North Star Bridge on Highway 169, where the researchers had set up large plastic bins to catch water runoff. Instruments detected the rate at which the salty, dirty water flowed off the bridge from slots and into pipes and down into the bins.
They discovered something curious.
At most, the bins caught about 250 pounds of deicer per lane mile in a given week. This is a low amount for a single pass, and a typical week may have seen 10 or more passes.
This means that a significant amount of the deicer is unaccounted for. That might mean that most of it was thrown off as water, after it did its job. Or it may have been wasted, perhaps tossed off the bridge entirely.
Peters said the bridge, which is in a wide-open area raised high above the ground, is too unusual a testing site to draw wide conclusions.
“I would be cautious to say this would be definite for every situation,” he said. A clue to how the researchers intend to explore that question sits in Minnesota State Mankato’s civil engineering lab. Several dozen clues, actually, in the form of rubber bins that, when placed on the ground, can measure how much deicer is being thrown from the bridge.
That would be part of Phase 3, which MnDOT has agreed in principle to fund. The estimated cost is $148,732.
Druschel said MnDOT and the department’s other clients tend to appreciate how students gain experience carrying out the work.
One of the most involved students in this project, Amy Nguyen, is just beginning her fourth semester at Minnesota State Mankato. She started out her college career as a business student in Alaska but said she hated it.
After only a few semesters in the civil engineering program, she’s gotten dirty working with drainage ditches and frozen on windswept parking lots. Nguyen is the type of student Druschel is looking for. Grades are important, but not as essential as diligence and a willingness to work hard.
Like other students, Nguyen received a stipend to do some of this research but as of now is working more or less as a volunteer.
Evaluating how well different snowplowing techniques and materials work, it turns out, is quite complicated.
Case in point: What’s the most effective way to apply a chemical deicer?
To answer that, the researchers received permission from Valleyfair and Canterbury Park to turn their huge vacant parking lots into 1,000-foot-long snowplow test runs.
As in virtually all experiments, the researchers picked one variable at a time to test — from alternative plow configurations to temperature to (simulated) traffic conditions — while keeping everything else the same.
Unsurprisingly, the deicer was more effective in warmer temperatures, but even a nine-degree drop made the deicer all but worthless.
A deicer used at 13 degrees created some bare patches after 10 minutes and connected clear patches after an hour. At 4 degrees, the bare spots of pavement created by the deicer had only increased slightly after an hour. In other words, it just didn’t work.
But there’s a small exception: At the highest doses, 800 pounds per lane mile, the treatment was partly effective even at 4 degrees.
Even so, drawing conclusions about cause and effect, especially ones that can be applied to roads around the state, can be tricky. Might the angle of the sun have had an effect? The type of snow? The type of pavement?
Drivers had reported that another factor, heavy traffic and especially truck traffic, could improve deicing. They appear to be right. During testing at the Canterbury Park lanes, car traffic that followed the deicer truck led to a modest improvement in deicer effectiveness, especially between 30 and 60 minutes. The truck traffic, though, led to substantial melting only 10 and 20 minutes later.
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