FOCUSED STUDY ON ROAD SALT CONTAMINATION OF DRINKING WATER SUPPLY AQUIFER, SE MASSACHUSETTS

Monitoring water quality in the water supply aquifer in Southeastern Massachusetts shows the aquifer being progressively impacted by salinization from the winter de-icing chemicals that at the current salinization rates would reach alarming non-compliance levels for chloride in drinking waters well before the year of 2020. For the Towns of Norwell and Hanover the public water supply is entirely from groundwater and the salinization raises concerns for the future availability of drinking water supplies. The aquifer is presently stressed by high de-icing chemical loadings derived from applications of de-icing chemicals along a divided highway, highway interchange, de-icing chemical storage facility, large shopping mall, and from winter maintenance of local roads and from the residential and business properties. Producing drinking water wells are principally located along a drainage stream flowing over a up to 100 ft. thick glacial sequence consisting of outwash with drumlins and eskers, wetlands with kettle ponds and kettle depressions filled with peat materials. Groundwater flow patterns are therefore complex due to a highly variable aquifer structure as revealed by sediment coring to a depth of 60 ft. and further convoluted by the variable density nature of brine solutions.

In cooperation with the Norwell water department a focused monitoring of water quality of GW and SW is developed to track 3D-time water quality variations in the upstream section of the drainage stream, GW monitoring along a 250 ft vertical cross-section defined by 10 screened monitoring wells located slightly upstream from the main production well, and continuous monitoring (15 min intervals) of water quality entering the cone of depression and by continuous monitoring water quality in the public water distribution system. Preliminary data suggests existence of preferential flow paths within the aquifer as well as evidence for the presence of distributed sources (de-icers from impervious surfaces) and for a more saline point source.