With tight budgets and increases in salt prices, county road commissions across Michigan should consider ways to reduce salt usage. That was a message delivered at the Association of County Road Superintendents of Michigan's 34th Annual Superintendents' Seminar at Crystal Mountain in Thompsonville, MI, in October 2008.
Mark Cornwell, of Schmidt North America, explained that there are hidden costs to salt usage. He discussed a study that was recently done.
"I've been tracking studies and I've been trying to follow studies that talk about the hidden cost of salt. The most recent one that I've been able to get was done at the Western Transportation Institute in Montana. The report says that corrosion and the environmental cost of road salt add up to at least an average of $469 per ton. These costs are often ignored in formulating highway winter maintenance strategies," Cornwell said. He explained that road salt is causing damage to the roads and putting additional strains on tight road agency budgets.
The report looked at the deleterious chemical effects of concentrated deicing solutions on concrete. "They first wanted to look at magnesium chloride because they thought it was causing concrete to deteriorate in the Western United States. What they found in this five-year study is that calcium and magnesium chloride are potentially reducing the surface life of our concrete pavements. The report talks about sodium chloride deicers being the least deleterious to concrete; however, we know that they attack structural steel," Cornwell said.
"The suggested mitigation strategies were pretty straightforward — use less chemicals, use sodium chloride brines, and perhaps enhance those brines with some other additives in order to lower the temperature ranges if possible and to use sealants in order to minimize the literal chloride penetration into the concrete."
Cornwell explained that a 30-to-70 ratio of liquid and salt amounts to approximately 60 to 80 gallons of liquid per ton of salt.
"As an example, if we have an application rate of 400 pounds per lane mile, 120 pounds of that is in the form of a liquid, and typically we'll use 23 pounds of salt if we're talking about salt brine and then 280 pounds of solids. If sodium chloride brine is used as a pre-wetting agent, it weighs approximately 10 pounds per gallon, so we're adding another 23 pounds of liquid to the 280 pounds of salt, which then comes to approximately 303 pounds of salt, approximately 97 pounds less than the operator sees on the controller. The important thing is, is 303 pounds going to get the job done that 400 pounds would've? You're realizing a 97-pound savings in salt," Cornwell said.
"From a cost standpoint, if salt is $40 per ton, we're talking about an $8 per lane-mile road salt application cost. If the same cost and application rates apply in the 30-to-70 ratio, salt will cost $5.60 per lane-mile for dry salt, and if we make the assumption that salt brine is being produced for 10 cents per gallon, we're adding $1.20 for the salt brine, for a total of $6.80 per lane-mile. This results in a potential savings of $1.20 per lane-mile.
"You still have to prove that this is effective and that's going to be your task. You must compare one system against another and you need to watch it closely. Also, these numbers don't reflect the potential savings from bounce and scatter that we're going to see from a highly pre-wetted salt."
Cornwell said that the 30-to-70 ratio is used extensively in Europe. Canada, Maine, New Hampshire, and Vermont are also using it. Michigan has a number of different practices that are advancing a higher liquid-to-solid ratio.
Robert Mykitiak, of the Road Commission of Macomb County, said that the agency has been actively using anti-icing for approximately five to 10 years.
"We purchased our own brine makers. We feel that this is very effective. The foremen like to use the liquid products with the salt, and we use the 30-to-70 ratio," Mykitiak said.
Gerald C. Peterson, manager at the Manistee County Road Commission, said that his agency has been using a beet juice product for the last two years.
"In 2007, we pre-treated our salt piles. We did that approximately 1-1/2 months before winter arrived, so that it had an opportunity to soak into the granules. That made a huge difference. What we actually ended up seeing was a 30-percent decrease in salt usage in 2007 compared to 2006. We also decreased our overtime," Peterson said. Peterson said that the Manistee County Road Commission realized a savings of approximately $50,000 to $60,000 in 2007, compared to 2006.
"I have 29 truck drivers and a lot of them have been with us 10 years to 30 years. Twenty-eight of the 29 agreed that it was a huge savings in salt usage. It's proven good for us." Peterson said that the Manistee County Road Commission was looking at adding 21-percent calcium chloride instead of water this winter season to dilute the beet juice in order to provide an extra boost.
Mike TerHorst, of the Ottawa County Road Commission, said that in 2004, his agency looked at the amount of salt it used and decided it was too much. The agency implemented a plan with the goal of reducing salt usage by 25 percent.
"First we evaluated the level of service we wanted to provide to the roads; whether we wanted a road to be bare pavement or partial bare pavement. Once we did that, we had to get the word to the drivers and provide them with information through maps. They responded very well. We also did more calibration, pre-wetting, anti-icing, and we updated some of our equipment. It went very well. It was a team effort. We exceeded the 25 percent in some areas. We reduced our salt usage by 25 percent to 30 percent. We are going to continue this," TerHorst said.