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Northeastern Section - 50th Annual Meeting (23–25 March 2015)

Paper No. 3
Presentation Time: 2:10 PM

ADVANCES IN STUDIES ON THE IMPACT OF WINTER DE-ICING CHEMICALS ON WATER QUALITY IN AQUIFERS IN SOUTHEASTERN MASSACHUSETTS


HON, Rudi1, DILLON, Peter2, BESANCON, James3, BEUTEL, David1 and BELLO, Bianca1, (1)Earth and Environmental Sciences, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA 02467, (2)Norwell Water Department, Town of Norwell, 345 Main Street, Norwell, MA 02061, (3)Department of Geosciences, Wellesley College, 106 Central Street, Wellesley, MA 02481, hon@bc.edu

In this presentation we report on new data from small headwater catchments along Third Herring Brook and Wildcat Brook in Norwell, Southeastern Massachusetts. Both catchments include active drinking water exploration fields for the Towns of Norwell and Hanover. In the Norwell part of the underlying aquifer, 327 meters apart, are two pumping wells with contrasting water quality characteristics. Chemical data on groundwater samples collected from these wells on August 12, 2014 show chloride concentrations of 199 and 103 ppm respectively. Aquatic life standard for chloride is 230 ppm and secondary standard for drinking water is 250 ppm.

A survey of groundwater and surface water samples from the studied aquifer field indicates chloride based deicers constitute between 70 to 90 wt% of total dissolved solids. In addition this proportion has an increasing annual rate suggesting that as early as 2018 these waters will exceed the regulatory limit for secondary drinking water standard. Currently, our research field program includes a set of 6 TDC (temperature, water depth, specific conductance) sensors deployed for long term monitoring at 15 min intervals along a 5.5 km long section of Third Herring Brook. Preliminary data suggests a chloride loosing trend along the stream channel pointing to a chloride retention mechanism within the aquifer.

The underlying aquifer represents up to 120 ft thick layer of glacier deposits formed near the edge of retreating/readvancing continental ice sheet with deep kettle depressions now filled with organic peat, esker deposits, outwash deposits, and till material as documented by sediment cores obtained from 10 separate boring locations. Groundwater flow lines are preferentially channelized through zones avoiding the low transmissivity peat horizons which also modify the preferential pathways of the deicers. Our data indicate a presence of a commercial zone with higher rate of deicer application and the corresponding sharp chloride increase in one of the pumping wells.

Session No. 19

T22. State and Fate of Urban Watersheds in the Northeast
Monday, 23 March 2015: 1:30 PM-5:30 PM
Gifford Room (Omni Mount Washington Resort)
Geological Society of America Abstracts with Programs. Vol. 47, No. 3, p.66
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