SURPRISES AND CHALLENGES ENCOUNTERED DURING CHARACTERIZATION OF A PARTIALLY CONFINED AQUIFER FOR A NEW MUNICIPAL SUPPLY WELL, IPSWICH, MASSACHUSETTS

Spurred by a need for a new, drought-resistant groundwater source for the growing town of Ipswich, MA, we undertook a comprehensive groundwater exploration program. Over a three year period, we conducted three phases of subsurface drilling to identify a location for a new groundwater source and a 15-day pumping test was conducted at the most viable site. Previously, a confined gravel aquifer was thought to underlie the entire area of investigation. However, the drilling program revealed a convoluted stratigraphy, with water-producing gravel present only in certain locations, not all of which are hydrologically connected. Pumping test drawdown data revealed a previously unknown hydrologic connection between the wells at the site and a local farm pond. Elevated nitrate, sodium, and chloride values in site groundwater indicate an additional connection between the surficial sand unit and the deep gravel unit, which we previously thought were completely isolated from each other by a thick layer of marine clay. Our work highlights the difficulties of working in Massachusetts’ shallow, geologically complex, glacial sand-and-gravel aquifers and yields some intriguing paths for future work at the site.