The effect of urbanization on water quality is an important issue to many water-resource managers and is a major focus of the NECB study. The USGS installed and sampled 29 monitoring wells in unconsolidated surficial aquifers in suburban parts of the Boston, Mass. metropolitan area, including southeastern New Hampshire.

Analyses of water samples collected from the monitoring wells indicate that shallow ground water in recently urbanized settings often contains trace amounts of nutrients, fuel, and industrial-based organic compounds. Most of the samples that contained detectable amounts of organic compounds also had elevated levels of iron and total dissolved solids. Nitrate was detected in 83 percent of the samples, but the USEPA drinking-water standard of 10 milligrams per liter was exceeded in just one sample. Low levels of volatile organic compounds (VOCs) were detected in 76 percent of the samples, with as many as 13 different VOCs detected in a single sample. The concentration of methyl-tert-butyl ether (MTBE) in one sample was 267 micrograms per liter, which exceeds the Massachusetts Department of Environmental Protection drinking-water guideline (70 micrograms per liter). Chloroform and MTBE were the two most frequently detected VOCs. MTBE was detected at the same frequency in ground water in the Boston metropolitan area as in other urban areas of New England. Chloroform was detected at higher frequency in old, densely populated areas in New England than in more recently developed, less densely populated areas. Pesticide detections were few, only at trace concentrations, and none of the concentrations exceeded any drinking-water standard.

--Sarah Flanagan (603) 226-7811 or sflanga@usgs.gov

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