Hydrogeology, ground-water availability, and water quality in the Titicus River valley, Ridgefield, Connecticut

Projected needs for additional water supplies, coupled with limited alternative sources, have prompted an evaluation of the availability and quality of water in the stratified-drift aquifer within the Titicus River valley in Ridgefield, Connecticut.Previous studies indicated that this aquifer may be capable of yielding moderate to large quantities of water to wells.Hydrologic data from test drilling, seismic-refraction profiling, streamflow measurements, and water-quality analyses, coupled with groundwater model simulations, indicate that the aquifer is capable of yielding 1 million gallons per day of potable water.Stratified drift underlies 1.26 square miles of the Titicus River valley, and in places is more than 90 feet thick.Although much of the stratified drift is fine grained, poorly sorted sand and gravel layers are common, and some areas within the valley have dominantly coarse-grained sediments.Transmissivity values estimated from grain-size analyses and logs of test borings range from less than 500 to more than 5,000 feet squared per day.A mathematical model of drawdowns and yields from hypothetical wells in the most hydrologically favorable locations within the upper and lower sections of the Titicus River valley predicts maximum withdrawal rates of 0.9 and 0.4 million gallons per day, respectively.Estimates of the water available from natural and induced recharge in the upper valley area, based on empirical equations for ground-water outflow and the 30-day, 2-year low flow of streams, indicate that 0.6 million gallons per day could be sustained without causing undesirable hydrologic consequences.The total sustained long-term yield for the complete stratified-drift aquifer in the Titicus River valley is estimated to be 1.0 million gallons per day.Water quality in the aquifer generally is suitable for human consumption and most other uses, with the exception of locally elevated levels of hardness and manganese, which may limit use.Hardness is attributed to the solution of carbonate minerals in the aquifer and underlying bedrock; manganese probably is derived from decaying vegetation in swamps.Water quality of the Titicus River is similar to that of ground water but contains elevated concentrations of bacteria that are indicative of livestock sources.