Brine proves to be an innovative tool for winter road safety
DERRY — What started as an environmental ultimatum has turned into a snow- and ice-fighting innovation for the state Department of Transportation that’s saved money, made roads safer and curbed the use of corrosive road salt.
State and local highway experts said it’s not a fail-proof tool, since conditions on the ground and in the air have to be just right for it to work best.
But who would have thought even a decade ago that this liquid solution for pre-treating roads prior to storms would be the same recipe many use to cook their Thanksgiving turkey or to store their pickles?
We’re talking about salt brine. In 11 years, it has gone from a device used only on a short, southern stretch of Interstate 93 to one deployed for any given storm along more than 4,000 miles of New Hampshire roadway.
“As the years have gone by our crews have developed a really good understanding with it,” said David Rodrigue, director of operations for the Department of Transportation.
‘We are at that right place now where we are comfortable with it. From a management perspective, we had to encourage our crews that we want you to use this and it is safe for our system. Over time they have certainly gained confidence.”
What moved state officials to pursue this was the widening of I-93 from Salem to Manchester.
Federal environmental officials made it crystal clear that they weren’t going to accept New Hampshire dumping that much more road salt onto the federally financed widening of the interstate to at least three lanes in either direction,
“We knew something had to give and brine was the way to go, to introduce it and use it liberally to reduce our use of road salt,” DOT spokesman Bill Boynton said.
Salt brine is a solution of 2.5 pounds of dissolved salt per gallon; the resulting mixture is a 23 percent solution. The exact amount of magnesium chloride and an organic solution is a secret formula revealed only to companies found to be pre-qualified to bid on supplying the product, state officials said.
It sticks to surface
The appeal of using brine is that unlike salt, it can be used to pre-treat roads before a storm’s snow or sleet can adhere to the surface — instead of just bouncing off the road as salt can.
“We are trying to be proactive, we are trying to get out ahead of the storm,” said Caleb Dobbins, a state highway engineer who plays a major role in the deployment of brine.
“It takes us anywhere from an hour-and-a-half to two hours on the interstate to do a complete run. It is a level of service, a safety enhancement, that we are able to do this,” he said.
Jay W Davini, Manchester’s chief of street operations, said his city has been using brine since 2012 when the Department of Public Works moved into its new headquarters.
“Brine is applied and remains directly on the road surface, as opposed to rock salt, which has a tendency to scatter to the gutters. This preemptive approach intuitively improves safety over the reactive approach of spreading salt crystals after snow begins,” Davini said.
There’s a perfect temperature window for this pre-treatment. If the thermometer reads below 20 degrees, they don’t spread the brine because it will freeze and not provide the desired protection.
“We aren’t going to get the benefit of that treatment below 20 degrees and often times we try to keep a cold road because in that case the snow will stay powdery and tend to blow off the roads,” Rodrigue said.
Using salt brine as a pre-treatment cut from 250 pounds per road mile to 125 to 150 pounds the amount of road salt required for later application to the road, state engineer Dobbins said.
State officials said they use the brine pre-treatment when the temperatures are right on the F.E. Everett Turnpike from Nashua all the way to Concord, on Interstate 93 from Salem to Concord and then from Tilton north to Plymouth, as well as the entire length of I-95 and on the Spaulding Turnpike from Portsmouth to Rochester.
“Making brine is cheap. It takes a few backhoe buckets of salt to make enough brine to treat the roads we do,” Davini said.
How much road salt is being saved?
“One would have to consider the hypothetical question as to how much salt we are not putting down because the streets were pre-treated,” Davini said. “We are utilizing less salt per storm than we have in the past.”
Pre-treatment is only part of brine’s appeal. The other, even more wider use is known as pre-wetting, which is to spray the liquid brine into the spinner that’s holding the salt in the trucks.
This is done to reduce what’s known as dry salt’s “bounce and scatter.”
“National studies show that with pre-wetting there is 20 percent more salt kept in the travel lane. The scatter is down to closer to 3 or 4 percent, which is where you want it,” Dobbins said.
“That’s one of the largest salt savings that brine brings to us.”
DOT’s Rodrigue said using brine in this way to make road salt more stationary is done statewide; all highway crews have been trained how to apply it.
“The pre-wetting is a very big bang for our buck and that is around the state,” Rodrigue said.
A recent study from the New York Department of Transportation found anti-icing done with brine to be very effective.
“Anti-icing is currently recognized as a pro-active approach to winter driver safety by most transportation agencies. Pre-wetting (using salt brines) has been shown to increase both the performance of solid chemicals and abrasives, as well as their longevity on the roadway surface, thereby reducing the amount of materials required,” the study said.
Pre-treatment can have added costs. For example it often has to occur during off hours, which means paying state highway crews overtime, Dobbins said.
And while less road salt means there is some savings, this doesn’t prevent state or local highway budgets from getting busted during a heavy storm season, as is the case with 2016-17.
Rodrigue confirmed the Department of Transportation will ask the Legislative Fiscal Committee this spring to approve a transfer of at least $6.3 million to bail out the state’s Highway Fund. Without it, the fund will run out of money well before the budget year ends June 30. [RELATED: Fiscal Committee approves $9 million transfer for NH DOT snow budget]
“It’s important to note that although we request extra funds at times it doesn’t change what we do,” Rodrigue said. “We can’t ever control what Mother Nature decides to do to us.”