GROUNDWATER AND PUBLIC HEALTH: A NOVEL SHALLOW WELL TECHNOLOGY TO PROVIDE SAFE DRINKING WATER FOR PRIVATE DOMESTIC WELLS

In northern New England, about 40 percent of the population uses private domestic groundwater wells. These wells draw primarily from bedrock aquifers where high concentrations of naturally-occurring arsenic are common. In contrast, water in shallow glacial deposits that commonly overlie bedrock typically produce water with little or no naturally occurring arsenic. They exhibit groundwater geochemical conditions that inhibit arsenic solubility. However, these glacial aquifers have been under-utilized in the last few decades due to outdated and unsanitary dug well technology. A shallow well design recently patented by the USGS could eliminate many of the concerns associated with the use of shallow, low-permeability aquifers and could provide safe drinking water to a large fraction of the New England population that would otherwise rely on arsenic-contaminated bedrock wells. The well also is drought resistant, owing to the combined effects of a large inflow area and in-well storage. The USGS well design comprises a single vertical riser with a sanitary well cap and pitless adapter. It also includes horizontal collectors that extend outward from the bottom of the riser within a trench that is backfilled with crushed stone. A geotextile fabric and native fill material overlie the crushed stone in the trench to prevent surface contaminants from reaching the well. In 2018, the U.S. Geological Survey, the U.S. Environmental Protection Agency, the University of New Hampshire, and the Maine Geological Survey completed a project to install and test the well design at two pilot sites in northern New England. Both wells were monitored continuously for water level and sampled bi-monthly for water quality, including chemistry, nutrients, and bacteria. During a year of sampling, none of the samples from the shallow wells had detectable concentrations of arsenic, at a reporting limit of 0.5 µg/L. The project also included two samplings of a bedrock well, proximal to the shallow well locations, both of which resulted in elevated arsenic concentrations. This talk will include discussion of yield, chemical, and bacteriological results.