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By Laura Jean Whitcomb
When an unexpected snowstorm hit areas of the Upper
Valley just before Hallo-ween, the discussion of
road salt started early. Every year, Mother Nature
inspires a debate on motorist safety versus
environmental protection.
Essential to Public Safety and Commerce
Salt is the fastest, least expensive way of coping
with winter’s ice and snow. According to the Salt
Institute (www.saltinstitute.org), thousands of
municipal, state and provincial transportation
agencies rely on deicing salt to assure wintertime
mobility and safety. Medical emergencies can occur
at any time, and people need to get care — no matter
the weather. So, many transportation departments
rely on salt application rates ranging from 300 to
800 pounds per two-lane mile (the amount depends on
road, storm and temperature conditions) to keep
roads free and clear for motorists.
Dependency on deicing chemicals has increased since
the 1940s. More people moving to the suburbs, higher
travel speeds and a growing reliance on automobiles
increased the need for snow and ice removal — and
safer roadways. In 1960, use of sodium chloride,
common table salt, was widespread. It was readily
available, effective and inexpensive.
Mixing salt with sand has been
a good method to cut back on the amount of salt used
to keep roads clear.
Unfortunately, more is not always better. According
to the Environmental Protection Agency’s Office of
Water, extensive use of salt on roadways resulted in
environmental concerns: Automobile and bridge
corrosion, effect on environment and water supply,
and degraded habitats where salt was accumulating.
In New England, where fall foliage has always been
an attraction, everyone noticed when the roadside
sugar maples, a salt intolerant species, started to
wither and fade.
All materials used in winter maintenance have the
potential to harm the natural environment, including
roadside vegetation, trees and shrubs. According to
the Salt Institute, high concentrations of chloride
can interfere with a plant’s absorption of moisture
from the soil and cause browning or burning of
leaves. It’s not a one-to-one ratio, however, as
many factors are at play. The amount of
environmental harm depends on the amount of salt,
type of soil, total precipitation, distance from the
roadway, wind direction and plant species (different
plants and soils tolerate chloride differently).
Protection Efforts
Environmental concern sparked a number of research
programs and resulted in major initiatives such as
improved operational procedures, alternative deicing
chemicals, pretreatment, mechanical approaches and
road weather information systems.
Local transportation departments developed proper
storage for salt stockpiles, making sure the supply
was covered to reduce runoff. Instead of salt poured
randomly down a pipe off the back of the truck,
calibrated spreaders provided a consistent
application rate and stopped pouring when the truck
stopped. Snowplow designs improved, with better
cutting edges and hydraulics. Fences — made of
lightweight plastic — were positioned in areas to
keep snow from blowing into drifts. Roadways that
need attention are prioritized and local weather
prediction helped improve effectiveness.
The Grantham Highway Department has two full-time
employees who maintain 22 miles of road in the
winter. Joe Newcomb, road agent, and Jeff Hastings,
assistant road agent, use two dump/plow trucks, a
backhoe, a grader, a roller, a tractor, and a
one-ton pickup with plow to ensure that the main
routes through Grantham and the school bus routes
are clear.
“To prepare for a storm we fill the sand pile, check
all the equipment and watch the weather forecast,”
says Newcomb, noting that it takes approximately
2,000 man hours a year to maintain roads during the
winter months. “We use about 200 tons of road salt
(this gets mixed with the sand) and 600 tons of
sand. During a snowstorm we plow and sand all the
roads — and we never use straight salt on the
roads.”
“You have to have a head’s up
on the storm, have time to lay the foundation before
the storm hits and hope that the pretreatment
doesn’t get washed away by rain.”
Mixing salt with sand has been a good method to cut
back on the amount of salt used to keep roads clear.
Over the years, chemical engineers tried their best
to develop an acceptable alternative deicer. Calcium
magnesium acetate — made from limestone treated with
acetic acid — was not as corrosive as the commonly
used sodium chloride and calcium chloride, but
needed to be applied in larger quantities. It was
also expensive to make.
Salt Brine Pretreatment
What would you do if you knew a big snowstorm was
headed your way? Put on the snow tires on the car,
get out the shovels, bring wood in for the woodstove
and stock up on canned food and bottled water.
Transportation departments think the same way, and
have tested road “pretreatments” as a way to limit
salt usage.
In January 2005 New Hampshire state transportation
workers used a new technique for deicing highways —
salt brine. Instead of using granular salt during
and after a storm, four tanker trucks spray a liquid
solution of salt and water on pavement at about 60
gallons per mile. The solution stays on roads and
remains effective for several days, preventing ice
and snow from packing onto the roadway.
“Timing is everything,” says Bill Boynton from the
Public Information Office of the New Hampshire
Department of Transportation (NHDOT). “You have to
have a head’s up on the storm, have time to lay the
foundation before the storm hits and hope that the
pretreatment doesn’t get washed away by rain.”
Salt brine pretreatment has been used with success
in Maine and Iowa. Interstate 93, between Salem and
Manchester, has high chloride levels and was the
perfect test spot for salt brine last winter. “We
were pleased with the results,” says Boynton. “Salt
brine will be part of the mix from now on, and we’ll
continue to refine and improve techniques.” In fact,
it will also be used on New Hampshire Route 101, a
high traffic area between Bedford and Wilton, this
winter.
Carol Murray, transportation department
commissioner, said the use of brine solution over
the course of a winter could reduce the overall
quantity of salt used by as much as 25 percent. Salt
brine only costs 5 cents per gallon to make,
compared to 88 cents per gallon for calcium
chloride, and will save about $300 every time roads
are treated. There is a capital investment up front,
however, as there needs to be a building for mixing
the solution (NHDOT mixes its brine at the
Londonderry Patrol facility off I-93) and trucks
need to be equipped to dispense the salt brine.
Since you can’t always predict the big storms, it
can be difficult to decide how and when to use a
pretreatment. “Our top mission is safety, but we try
to balance that with environmental concern,” says
Boynton. “We continue to review and test new
products, but there’s no magic product yet.”
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