Problem - The Village of Pulaski in Oswego County, N.Y., obtains its water supply from groundwater that drains under gravity from an unconfined aquifer into three shallow dug wells. The well field is in an area where groundwater discharges to springs along the west edge of the Tug Hill Aquifer, which is comprised of beach and kame deposits of sand and gravel. A numerical groundwater model was constructed previously to simulate groundwater conditions in part of the Tug Hill Aquifer near the Pulaski well field. The modeling work was part of a wellhead protection study to develop a plan to protect the groundwater resources of the Village of Pulaski's public water-supply system. In addition, the USGS, in cooperation with Oswego County of Health, began a 2-year study in 1999 using the concentrations of environmental tracers, such as chlorofluorocarbons (CFCs), tritium, and other chemicals and isotopes in groundwater to estimate the recharge age of groundwater that is tapped by 28 community wells in Oswego County. For the Pulaski water supply, there were significant discrepancies between groundwater recharge ages determined by chemical data (CFC groundwater age of 24 years) and those determined by simulation of groundwater flow (approximately 8 years for the longest flow path from the east edge of the aquifer to the wells). Groundwater samples taken from a collection cistern, which all three wells drain into, had bacteriological contamination for several consecutive months during the spring and summer of 2002 indicating short travel times from recharge areas. This contamination highlighted the need for the Oswego County Department of Health to determine: (1) the factors that resulted in the discrepancies between the time-of-travel of groundwater as determined by a numerical groundwater-flow model and as determined by a geochemical age dating, and (2) the source(s) of bacteriological contamination.
Objectives - The objective of the study is to refine the conceptual understanding of the groundwater-flow system in the shallow sand-and-gravel aquifer near Pulaski, Oswego County, N.Y., by reconciling differences in recharge ages and groundwater-flow rates obtained through the geochemical age-dating and numerical groundwater-flow modeling approaches.
Benefits - The integrated application of age dating of groundwater and numerical groundwater-flow simulation will be used to improve the understanding of hydrologic processes in the shallow unconsolidated glacial aquifers in central New York. Information about the aquifer and groundwater travel times gained from this study will be applicable to other water-supply systems in Oswego County and in similar glaciated areas of the northeastern United States where hydraulic and geochemical approaches have yielded inconsistent recharge results. This information will provide valuable data to local, state, and federal agencies that are responsible for developing source water delineation and protection strategies for public-water supply systems.
Approach - Fieldwork will include a well inventory and installation of wells for measurement of water levels and temperature. A groundwater-head map will be constructed showing the local groundwater flow directions near the well field. A subset of the well network will be used to collect water samples for recharge-age and common-ion determinations. The temperature and water-quality data will be used to develop a conceptual model of recharge, water movement, and interactions of ground and surface water that affect the Village well field.
Project
Location by County
Oswego County, NY
