Direct Liquid Applications: A Winter Maintenance Best Practice for Improved Road Salt Efficiency

Focus Area

Water Quality/Wetlands


Natural Resources






1-2 years

Research Idea Scope

As evidenced by the recent
January 2013 EPA Webinar entitled “Road Salt Pollution Prevention” in

which over 1000 people
participated, the concern for road salt, or rock salt, and water resource
concerns continues to grow.  Utilization
of sodium chloride brine (rock salt and water) in winter operations has been in
practice for many years but its use has been primarily limited to anti-icing
(preventative application ahead of the storm to prevent snow and ice bonding to
pavement) in direct pavement applications and use as a pre-wetting liquid to
rock salt via on-board pre-wetting systems. 
Its use in direct application for deicing has seen limited
implementation in field operations across North America but recent research and
additional in-field evaluations have indicated that significant rock salt
reductions could be achieved if the practice were more widely implemented.    This ultimately leads to less chloride,
rock salt, into the environment.


A recent research efforts
by the Clear Roads organization in 2010 entitled “Identifying the
Parameters for Effective Implementation of Liquid only Plow Routes”
(Project Number: Clear Roads 09-02/WisDOT 0092-10-18) appears to indicate that
direct liquid applications (DLA) has great potential as an additional  winter maintenance best practice to combat
snow and ice.  Rock salt must first go
into solution by making brine with available precipitation on the roadway.  By the time this process has occurred,
significant quantities of rock salt are lost due to bounce and scatter, vehicle
movement, or by plowing action.  The use
of sodium chloride brine eliminates this intermediary step and, in addition to
greatly minimizing applied material loss, provides quicker melting action thus
enabling quicker attainment of pavement level of service (LOS) goals.  By incorporating DLA into winter operations
we can enhance public safety while minimizing environmental degradation.

Urgency and Payoff

Sodium chloride rock salt
will continue to be the primary deicing chemical of choice due to the cost
differential with other deicers such as magnesium chloride or non chloride
deicers .  Dry rock salt can be difficult
to retain on pavement often resulting in significant loss into unintended
areas.  Older winter maintenance
equipment can have problems applying consistent applications rates less than
200 pounds per lane mile (LM) (90kg/Lane Kilometer (Lkm) and are significantly
challenged when trying to apply rates under 100 pounds per lane mile
(45kg/Lkm).  Problems with the spreading
equipment can also occur due to variances in salt gradation and moisture
content in the stockpile.  In addition to
potential damage that occurs from deicing materials that end up off the roadway
and into the environment, there is a significant economic loss that accompanies
this waste.  This loss of material and
resulting failure in attaining desired LOS often leads to the perception that
more salt is needed to maintain public safety. 


A gallon (3.74 l) of brine
contains approximately 2.28 pounds (1.03 kg) of dissolved sodium chloride.  Typical dry solid applications may range from
200-300 pounds per lane mile (90-136 kg/ Lkm). 
If DLA ranges of 50-80 gallons/LM (189-302 l/Lkm) provide the desired
LOS for a high percentage of winter storm events.  By using sodium chloride brine in DLA the
potential reduction of sodium chloride in our soil and water, is reduced.   DLA can also provide additional benefits of
improved public safety that results from quicker LOS attainment and potential
operations savings. 


Practitioners need to
fully understand and follow the appropriate protocols for implementing DLA in
their operations.  DLA is a tool that is
best implemented after it has been tested and its practices and procedures
further refined.  We are seeking funding
support to prove that DLA is a cost effective best practice that enhances
public safety while minimizing the impacts to environmental resources through
reduction of total sodium chloride inputs. 


Research needs identified
in this proposal:

•              Further define practices and procedures for utilizing

•              Compare pavement retention of applied solid materials
versus liquids (loss to unintended targets)

•              Conduct field and laboratory analysis to determine
actual effects of short and long-term exposure to various chloride levels in
receiving streams.


This proposal is supported
by the TRB Winter Maintenance Committee, AHD65.

Suggested By

Mark Cornwell Sustainable Salting Solutions, LLC 248/634-0820

[email protected]