Conductivity and Chloride Monitoring

While salting roads in winter makes travel much easier in New England’s snow, it has adverse impacts on life in our rivers and streams. High amounts of salt in rivers and streams can be toxic to freshwater life, and the EPA has established a concentration threshold for chloride (a major component of road salt) to protect fresh water aquatic life. Road salt can also adversely affect groundwater, and both public and private wells in Massachusetts have been contaminated by road salt runoff. Because it is associated with adverse effects in our rivers, OARS has been monitoring salt levels in the watershed for a number of years. We have monitored chloride in water samples to get a direct measure of salt concentrations, and we also monitor in-situ conductivity, which is an inexpensive surrogate for chloride.

Our studies have shown that chloride pollution in the SuAsCo rivers is not uniform everywhere. There are many river sections where chloride levels are low enough to be safe for aquatic life. Still, our monitoring has also documented many locations where chloride levels are too high for aquatic life. Roadways, parking lots, and developed areas often result in concentrated chloride pollution that degrades segments of the rivers. Identifying these locations can help us find and address the sources of pollution. OARS has been leveraging the fact that chloride is closely correlated with conductivity, which is very easy to measure with handheld meters. Likewise, it is very easy to conduct a stream survey of conductivity levels from the source of a stream to its mouth. Such a survey can be used to identify conductivity hotspots, which can be inferred to be chloride hot spots. OARS has been recruiting members of our water quality volunteer community to conduct these surveys in a stream or brook that they are familiar with. So far, we have had three volunteer groups step forward to conduct surveys. Please see the attached document for a report about the conductivity surveys that have been conducted so far. Maps of the surveys are included below.

Download OARS Conductivity Surveys Report