Real-Time Monitoring of Road-Salt Runoff Into a Recharge Basin on Long Island, New York

As the Nation’s premier earth science agency, the U.S. Geological Survey (USGS) applies existing and emerging technologies to develop new methods of assessing geologic and hydrologic conditions and hazards. The USGS New York Water Science Center has continually enhanced its network of real-time hydrologic-monitoring stations to meet the water-data needs of other Federal, State, and local agencies, water managers, stakeholders, and the public.

In recent years, Mill Lane, a production well field located on the North Fork of Long Island, has been adversely affected by increasing chloride contamination. Geophysical surveys completed at the site indicate that a chloride plume is emanating from a recharge basin in close proximity to the well field. Road-salt runoff, entering the aquifer from the recharge basin, may be the source of measured increases in chloride concentrations at the well field. Potential factors influencing plume migration include quantity of salinity and volume of road-salt runoff, rate of recharge from precipitation [ in the context of a changing climate], aquifer transmissivity, proximity to the well field capture zone, and intensity and duration of pumping.

The USGS in cooperation with the Suffolk County Water Authority recently installed a real-time monitoring station within the recharge basin. This continuous-recording station measures water elevation, water temperature, and salinity (calculated from specific conductance) every fifteen minutes. Collected data are transmitted by satellite telemetry to the USGS National Water Information System Web Interface (NWISWeb) at http://waterdata.usgs.gov/ny/nwis every hour, where it is available for public dissemination.

The objective of this monitoring is to accurately assess the correlation between road-salt runoff and seasonal recharge basin salinity concentrations. This information may help delineate a point source of aquifer contamination and empower water managers with the data required to evaluate the potential for future chloride contamination at the well field.