Glacial stratified-drift deposits composed primarily of sand and gravel form the major aquifers in the Taunton River basin. In the northern half of the basin, the aquifers are long, narrow, and thin, and saturated thicknesses range from about 20 feet to slightly more than 100 feet. Aquifer widths range from about 0.1 mile to 1.5 miles, and lengths range from about 1 mile to 5 miles.

Aquifer yield from storage, representative of short-term yield during severe drought conditions, were estimated for 26 selected aquifers in the basin. For a 30-day pumping period, 14 aquifers have yields less than 5 ft³/s (cubic feet per second), 7 have yields of from 5 to 10 ft³/s; and 5 have yields of from 10 to 15 ft³/s. Aquifer yields under normal climatic conditions were estimated for the 26 aquifers by considering the cumulative yield from intercepted ground-water discharge, induced infiltration, and storage. These yield estimates are related to the estimated duration of flow of the stream that drains the aquifer. The two highest aquifer yields equal or exceed 11.9 and 11.3 ft³/s 90 percent of the time, respectively, if minimum stream discharge is maintained at 99.5 percent flow duration. Water for public supply was pumped in 18 of the 26 aquifers during 1983, and all the developed aquifers were pumped at a rate either equal to or greater than 70 percent of the estimated rate of aquifer yield determined in this study.

The pH of the ground water ranges from 5.4 to 7.0, which categorizes the water as mildly corrosive. Hardness of the ground water ranges from 9 to 112 mg/L (milligrams per liter). No concentrations of sulfate or chloride exceeded EPA recommended limits for drinking water. However, concentrations of sodium exceeded the Massachusetts recommended limit for drinking water for those individuals on a sodium-restricted diet of 20 mg/L in 19 of the samples. Natural concentrations of iron and manganese commonly exceed the limits of 0.3 mg/L and 0.05 mg/L recommended for drinking water.

Of 51 analyses for trace metals, including arsenic, barium, cadmium, chromium, copper, cyanide, lead, mercury, selenium, silver, zinc, and nickel, only lead, with a concentration of 60 ug/L (micrograms per liter) exceeded the recommended limit of 50 ug/L at one site. In 13 of 74 analyses for selected organic compounds, one or more of the following compounds were detected: Chloroform; carbon tetrachloride; 1,1 dichloroethane; 1,2 transdichloroethylene; tetrachloroethylene; toluene; 1,1,1 trichloroethane; and trichloroethylene. The U.S. Environmental Protection Agency has set Maximum Contaminant Levels (MCLs) for three of these compounds. These three compounds and their MCLs are: Trichloroethylene, 5 ug/L; carbon tetrachloride, 5 ug/L; and 1,1,1-trichloroethane, 200 ug/L. Trichloroethylene was detected in five samples. The concentration of trichloroethylene in one of these five samples exceeded the limit of 5 ug/L. A concentration of carbon tetrachloride of 0.8 ug/L was detected in one sample, which is below the limit of 5 ug/L. Concentrations of 1,1,1 trichloroethane were detected in ten samples, but none exceeded the limit for that compound.