Church, P.E., Armstrong, D.S., Granato, G.E., Stone, V.J., Smith, K.P., and Provencher, P.L., 1996, Effectiveness of highway-drainage systems in preventing contamination of groundwater by road salt, Route 25, southeastern Massachusetts--description of study area, data collection programs, and methodology, U.S. Geological Survey Open-File Report 96-317, 72 pp.

Four test sites along a 7-mile section of Route 25 in southeastern Massachusetts, each representing a specific highway-drainage system, were instrumented to determine the effectiveness of the drainage systems in preventing contamination of groundwater by road salt. One of the systems discharges highway runoff onsite through local drainpipes. The other systems use trunkline drainpipes through which runoff from highway surfaces, shoulders, and median strips is diverted and discharged into either a local stream or a coastal waterway. Route 25 was completed and opened to traffic in the summer of 1987. Road salt was first applied to the highway in the winter of 1987-88.

The study area is on a thick outwash plain composed primarily of sand and gravel. Watertable depths range from 15 to 60 ft. below land surface at the four test sites. Groundwater flow is in a general southerly direction, approximately perpendicular to the highway. Streamflow in the study area is controlled primarily by groundwater discharge. Background concentrations of dissolved chloride, sodium, and calcium-the primary constituents of road salt-are similar in groundwater and surface water and range from 5 to 20, 5 to 10, an 1 to 5 milligrams per liter, respectively.

Data-collection programs were developed for monitoring the application of road salt to the highway, the quantity of road-salt water entering the groundwater, diverted through the highway-drainage systems, and entering a local stream. The Massachusetts Highway Department monitored road salt applied to the highway and reported these data to the U.S. Geological Survey. The U.S. Geological Survey designed and operated the groundwater, highway-drainage, and surface-water data collection programs. A road-salt budget will be calculated for each test site so that the effectiveness of the different highway-drainage systems in preventing contamination of groundwater by road salt can be determined.

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