WSDOT SALT PILOT PROJECT
Frequently Asked Questions
What is the salt pilot project?
The salt pilot project is an evaluation by the Washington State Department of Transportation (WSDOT) of the performance of rock salt or salt brine on highways in comparison to other anti-icing chemicals that are used to control snow and ice on roadways. Salt use is being evaluated to determine:
- The effect on driving conditions
- The corrosive effect on various types of metal
- Impacts to the roadside environment
- Costs to control snow and ice
Why is WSDOT testing salt
on our roadways?
- One of the main reasons is cost. Rock salt is approximately half the
cost of other anti-icers. Liquid salt brine costs between
three to five times less money than alternative liquid chemicals.
- Another reason is the increasing number of complaints about
corrosion to aluminum from other chemicals.
- This
evaluation also serves as a field verification of the standard laboratory
corrosion test for these chemicals. In other words, does the lab test
accurately simulate corrosion in the roadway environment?
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Isn't salt use taking a step
backwards? What's changed?
It’s true that the WSDOT stopped using salt in the late 1980’s
due to concerns about the corrosiveness of salt. The decision was based
on concerns about corrosion, potential adverse effects on the environment,
and encouragement from the public and the legislature.
Even though we’ve switched to alternative chemicals, such as liquid
anti-icers, we continue to notice corrosion on maintenance trucks and
hear complaints from highway users. We want to answer the question, “How
much corrosion reduction is actually occurring on the roadway by using
more expensive alternatives chemicals when compared to the less expensive
salt?”
Didn't the Department of Transportation
do this last year? Why is the pilot project being extended?
The winter of 2002-2003 proved to be unusually mild, with less need for snow
and ice control. This limited the amount of data that we collected for evaluation.
We want to make sure that we have sufficient data as the basis for our decision.
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Where is salt being used?
The 2003-04 Salt Pilot Project is being tested in the same areas that were
established a year ago for this evaluation:
- I-90 from I-82 Interchange to Vantage
- I-90 from east of Moses Lake to Lincoln/Spokane county line
- SR 6 from Chehalis to Raymond
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Why were these locations selected?
- I-90 gets a lot of winter weather and, due to the volume of traffic it
carries, is WSDOT’s highest priority highway in terms of snow and ice control
in eastern Washington.
- Logistically it is easier to isolate maintenance trucks that will
be working just on I-90 for comparison purposes. If we selected more rural
highways, trucks would be operating on several highways, including some not
in the test area, and mixing the chemicals they are exposed to.
- On these sections of I-90 there is little to no surface water in
the area, groundwater is deep, and there are few trees in the area, so there
is lower risk regarding environmental issues.
- SR 6 is winding and has lots of shaded areas that produce icing
problems. WSDOT felt this would be a good place to try and improve driving
conditions through the use of salt brine.
What about the impacts on the
environment?
Our past monitoring of streams, rivers, groundwater, and ponds has shown very
low levels of chlorides from our routine roadway applications of salt or other
chemicals. Levels found have been well below applicable standards or guidelines.
We continue to monitor these applications to determine what, if any, impact
they may have on the environment.
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Isn't salt corrosive to vehicles?
Yes. All ice-inhibiting products – salt and chemical anti-icers alike – have
some corrosive properties. The question boils down to, “Is the extra
cost of the anti-icers worth paying if they still cause corrosion?”
It’s worth noting that vehicle manufacturing techniques have changed.
Many of the newer vehicles have components made of plastic, fiberglass,
stainless steel and other materials, that are less prone to corrosion
than is steel. In any case, it’s advisable to wash your car periodically
through the winter to remove any chemical residue.
What did you learn from last year's
study?
Some of the key findings were:
- Costs for snow and ice control were generally less for maintenance
crews using salt than for crews using anti-icing chemicals, when comparing
labor, materials and equipment.
- Results of laboratory corrosion testing for anti-icers and the
results seen in the field were significantly different. Field tests indicated
a higher
level of corrosion was occurring than the level that was produced in laboratory
tests.
- Anti-icing chemicals generally (it wasn’t clear cut in
all comparison scenarios) appear to be more corrosive on sheet and cast
aluminum alloys than salt.
- Our results varied and there was no clear-cut evidence that
a single alternative is best in all cases.
- In some scenarios, use of corrosion-inhibited chemicals resulted
in less corrosion than the use of salt, and more in others.
Is there any difference between rock salt and salt brine?
Rock salt is sodium chloride in granular form. Salt brine is a liquid solution
made by mixing water and rock salt until we get a 23% salt solution. This
is the concentration at which salt brine is most effective at controlling
roadway snow and ice.
I've heard a lot of liquid anti-icers referred to by different names. Do they all work the same way?
Yes. In general, they all work the same by lowering the freeze point of liquid
on the surface of the roadway. This prevents snow and ice from bonding to
the roadway surface making it easier for removal with snowplows. Some chemicals
work better than others at different temperature ranges.
Some of the anti-icer chemicals used by WSDOT include:
- Magnesium Chloride
- Calcium Chloride
- Sodium Chloride
- Calcium Magnesium Acetate
Why don't you just use sand on the roads?
Sand is still used by WSDOT for improved traction under certain conditions,
however it too has drawbacks:
-
Sand gets picked up in tires and ends up on the side of the road, rather
in the driving area of the roadway. In heavy traffic conditions, it’s
only effective for a very short time.
- Sand can clog roadway drains and ditches. Sand in streams may
have an adverse impact on marine life.
- Maintenance costs for sand are higher at the end of the season
than for salt or anti-icer chemicals due to the need for cleanup.
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