Northeastern Section–41st Annual Meeting (20–22 March 2006)

Paper No. 5
Presentation Time: 7:00 PM-9:30 PM


COEFER, Joshua, Department of Geology & Geophysics, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA 02467 and HON, Rudolph, Department of Geology & Geophysics, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467,

The chloride ion concentration of local surface water throughout the Greater Boston Area has been rising steadily over the course of the past several decades. This increase coincides with the amount of rock salt applied to the extensive and expanding road system of the area. As traffic increases and public calls for better road surface maintenance are more frequent, more rock salt is used for roadways deicing. This process allows for safer travel and faster recovery from snowfalls. However, the ions present in the crystalline structures of the salts (mostly NaCl with minor CaCl2, KCl, and MgCl2) will readily dissolve, dissociate, and enter our surface water and ground water sources. The amount of testing and observation concerning this process has increased over the course of the past 10 years. An ongoing project on the Saugus River near Boston, Massachusetts, monitors the changing water quality of the surface waters. A similar study was started in June, 2005. Its location is a spring in a park on the outskirts of Boston. This project is still underway. This study compares the results of these 2 projects. The chloride ion concentrations have been shown to fluctuate with rainfall, temperature, and rock salt applications in both cases. Calibrated direct relationships between specific conductance and total dissolved solids, chloride and sodium concentrations allow a reliable monitoring of chloride levels in both systems. Saugus River base flow water contains 100 to 150 ppm chloride reaching up to 400 ppm and peak values in excess of 850 ppm during the winter runoffs. Data for the park spring water during its typical discharge flows have values of 350 to 400 ppm chloride fluctuating with the amount of rain and evapotranspiration. EPA (EPA, 1988) limit for aquatic life chronic exposure to chloride is 230 ppm and for an acute exposure 860 ppm. None of these environments under present conditions is capable to sustain normal aquatic life. The question we face today is what we can do to prevent this problem from escalating in a society that has become so dependant on its roadways.