Abstracts

estimates of road salt loading to the water table were made by repeating the earlier field
program from 2008 to 2010. The data indicate that the average pore water Cl concentration
had reduced by approximately 65% and the average cumulative stored chloride mass in
the vadose zone had reduced by approximately 30%. The average mass loading to the water
table was estimated to have reduced by over 40% following the reduction in the road salt
application rates. Water table monitoring wells installed at each of the field locations confirmed
a progressive reduction in chloride concentration over time. To our knowledge, this
is the first study of its kind to quantitatively assess the effects of best management practices
to reduce the impacts of road salt to ground water by directly comparing pre-BMP and
post-BMP chloride levels. The results suggest that the road salt management practices
involving the reduction in the application rate of the deicers implemented by the RMOW
can significantly reduce the loading to the water table and subsequently result in a progressive
decrease in groundwater chloride concentrations ultimately leading to improved water
quality in the public supply wells.
122 - Assessment of Road Salt Impacts to Four Priority Well Fields
in the Region of Waterloo
Michael L. Duchene, Tiffany Svensson & Ian Macdonald
BluMetric Environmental Inc., Kitchener, Ontario, Canada
Rachel Vaillancourt & Geoff Moroz
Hydrogeology and Source Water, Regional Municipality of Waterloo, Kitchener, Ontario,
Canada
The Regional Municipality of Waterloo obtains approximately 75% of its drinking water
supply from 122 groundwater supply wells. The on-going assessment of the water quality
has shown that sodium and chloride concentrations are close to or have exceeded the
drinking water objectives at four priority well fields, William Street, Greenbrook, Parkway
and Middleton Street. Assessments on the issue of elevated chloride and sodium levels in
these well fields have been ongoing since the 1990s. This assessment was an update and
expansion of previous assessments.
The primary assessment tool used was a mass balance model developed by the Region.
The model predicts the mass loading in the extracted groundwater by integrating the chloride
loading (portion of road salt that infiltrates to the groundwater) and factoring in the
advective travel time to the production well based on the capture zone delineation. Salt
application on both roadways and parking lots was input into the model. The mass of salt
applied to roads was reported by the cities. The mass of road salt applied to parking lots
was estimated by determining the total area of parking lots in each wellhead protection
area and estimating the application rate.
Currently there are no guidelines and little published data for the application of salt on
parking lots. Two surveys completed by others were obtained and a survey was completed
as part of this assessment to quantify the salt applications used on parking lots. The results
indicate that the general range of salt application on parking lots is between 50 g/m 2 and
75 g/m 2 .
40 IAH-CNC 2015 WATERLOO CONFERENCE