ABSTRACT
At least 528 of a total of 2226 groundwater areas in Finland important for water supply are traversed by roads on which NaCl is used for deicing. One aim of the risk assessment was to collect water quality data, especially on those parameters indicating contamination of groundwater caused by road salt. The database includes risk assessment data on approximately 1100 groundwater areas, including 5400 chloride observations from more than 400 monitoring wells. In the risk assessment, factors characterizing the potential for groundwater pollution are assigned numerical values. According to results of the risk assessment, there are about 400 water intake areas in which more detailed studies should be carried out. Protective actions are essential in 129 areas to prevent the groundwater from becoming polluted by de-icing salt. The mean chloride concentrations in groundwater were compared between 3 different periods. Variation in the amount of salt used for deicing during these 3 periods could be detected to some extent in groundwater quality. During the last period the use of salt was somewhat reduced, but the restoration of chloride concentrations in groundwater will require a lengthy period and needs more substantial reduction in salt amounts.
