Hydrogeology and water quality of the unconsolidated aquifer system in the Lower Fall Creek Valley, Tompkins County, New York

The U.S. Geological Survey, in cooperation with Tompkins County and the Town of Dryden, conducted a hydrogeologic investigation of the lower Fall Creek unconsolidated aquifer system in Tompkins County, New York. This study is part of an ongoing effort to characterize major valley-fill aquifers in the region to support sustainable groundwater management. The lower Fall Creek valley, encompassing the Village of Freeville, the unincorporated communities of Etna, and the hamlets of McLean and Varna, has experienced moderate development and relies heavily on groundwater for residential, agricultural, and commercial use.

The study area spans approximately 51 square miles along the boundary of the Allegheny Plateau and North Rim of the Allegheny Plateau physiographic provinces. The aquifer system, composed primarily of glacially derived sand and gravel deposits, includes both unconfined and confined aquifer units. For the approximately 2,300 people who live over the aquifers, groundwater is the sole source of drinking water. In some areas, such as the Village of Freeville, artesian conditions exist, with potentiometric heads exceeding 25 feet above land surface.

This report describes the hydrogeologic framework, aquifer distribution, groundwater-flow dynamics, and water quality of the lower Fall Creek aquifer system. Groundwater is generally hard and contains elevated concentrations of redox-sensitive constituents, such as iron and manganese relative to U.S. Environmental Protection Agency secondary maximum contaminant levels. Arsenic was not detected above the U.S. Environmental Protection Agency maximum contaminant level during this study but remains a regional concern due to past detections in the study area and nearby aquifers. The findings provide data for local planners and resource managers to use in understanding and protecting this water resource.