Groundwater in the Great Lakes Basin

far reaching. Road salt can inhibit the absorption of
water and nutrients by plants and can result in the
degradation of ecosystem biodiversity (RiverSides
Stewardship Alliance and Sierra Legal Defence Fund,
2006). Additional ions from road salt deposited into
lakes can result in unnatural stratification. This can
prevent seasonal mixing of lakes, changing nutrient
and oxygen distributions (Environment Canada, 2001).
High salinity levels in waters have likely allowed
for initial invasion and subsequent adaptation and
dispersal of exotic algae species within the Great
Lakes (Jude, Stoermer, Johengen and Perakis, 2002).
Road salts can have harmful effects on soil, changing
physical and chemical properties including structure,
permeability and conductivity as well as resulting
in soil swelling and crusting (Environment Canada,
2001; RiverSides Stewardship Alliance and Sierra
Legal Defence Fund, 2006). These effects can be seen
up to 100 feet from a major highway and 50 feet from
a two-lane road (Schueler, 2005). Road salt can create
an artificial salt lick on roads which attracts animals
and birds, resulting in an increased amount of roadkill
(Schueler, 2005; Environment Canada, 2001).
Chemical Components
Chloride, the main component of road salt, is extremely
soluble in water and once in a watershed becomes nearly
impossible to remove (Schueler, 2005). Increasing use
of road salts has resulted in a rise in chloride levels in
ground and surface waters (Jackson and Jobbágy, 2005;
Kaushal et al., 2005; Godwin, Hafner and Buff, 2003;
Siver, Canavan, Field, Marsicano and Lott, 1996; Peters
and Turk, 1981). A water quality study (see Table 1)
across the Lake Ontario drainage basin from 1980-82 to
1996-98 showed an increasing trend level of chloride in
71% of monitored sites (RiverSides Stewardship Alliance
and Sierra Legal Defence Fund, 2006). While natural
levels of chloride are generally only a few mg/L, chloride
concentrations in runoff from roadways and uncovered
salt piles has been measured in upward of 18,000 mg/L
and 82,000 mg/L, respectively (Environment Canada,
2001). Levels of chloride in groundwater adjacent to
storage yards have been measured as high as 2,800
mg/L (Environment Canada, 2001). It is estimated that
30-45% of all chlorides in the Great Lakes are a result
of winter road salt application (ECO, 2007). Southern
Ontario and Southern Quebec are among the provinces
facing the greatest risk of groundwater contamination
from road salts due to high road density (Environment
Canada, 2001). In Minnesota, water quality standards
for chloride concentrations are exceeded in some fresh
water bodies (Stefan and Mohseni, 2007).
Concentrations of chloride in water strongly correlate
to seasonal use of road salt (Jackson and Jobbágy, 2005;
Kaushal et al., 2005). A water quality monitoring study
by Ehlinger recorded a jump in chloride levels from
900 to 11,000 ppm in Underwood Creek in Milwaukee,
during a rain storm after roads had previously been
salted (Bergquist, 2008). However, Kaushal et al.
demonstrate that when road salt is not being used
chloride does not return to baseline levels due to salt
build-up in surrounding soil and groundwater (Jackson
and Jobbágy, 2005) and reduced water flow during
the summer and ion travel time (Environment Canada,
2001). It can take centuries before groundwater will
return to pre-contaminated levels even after road salt
application is totally eliminated (Jackson and Jobbágy,
2003; Burtt, 2003; Environment Canada, 2001).
A study of 23 springs in Toronto found chloride levels
to be greater than 1,200 mg/L as a result of road salt
contamination (Kaushal et al., 2005). Chloride levels
above 250 mg/L render water non-potable. In 2004 the
city implemented a reduction goal of 25% to take place
over three years (Gray, 2004). To accomplish this, the
city was adding water tanks onto its salt trucks so
that brine could be sprayed on the roads, making the
de-icing process more efficient. In 2004, 45 of the 185
trucks had been altered (Gray, 2004).
Table 1.
Peak Chloride concentrations in Water
Source
Normal Freshwater
Urban Streams in winter
Groundwater
Snow Cleared from Roadways
Highway Runoff
Ocean Water
Salt Storage Area Runoff
Peak Chloride Concentration
20-50 mg/L
Over 1,000 mg/L
2,800 mg/L
3,000-5,000 mg/L
Over 18,000 mg/L
25,000-30,000 mg/L
82,000 mg/L
110
Source: RiverSides Stewardship Alliance and Sierra Legal Defence Fund, 2006.