Siting of waste-disposal facilities in Cortland County poses a potential threat to local ground-water resources. An especially sensitive waste-disposal siting issue arose in 1988, when the New York State Low-Level Radioactive Waste Siting Commission (NYSLLWSC) identified 15 sites in six towns (Towns of Solon, Taylor, Freetown, Cincinnatus, Marathon, and Willet) in the eastern part of the county for possible disposal of low-level radioactive waste (New York State Low-Level Radioactive Waste Siting Commission, 1988). Eventually, two sites in the Town of Taylor became finalist sites; one was selected from the list of 15 potential sites, and the other was offered by a private landowner. Little information was available on geohydrologic conditions in eastern Cortland County, such as the extent of aquifers and the thickness of unconsolidated deposits of low permeability (such as clay and till), even though these two criteria were among those used by NYSLLWSC for selection of potential disposal sites. The source of information on thickness of drift over bedrock was the surficial geologic map of New York (Muller and Cadwell, 1986). The siting effort was terminated before a final selection was made, but the issue had made county managers aware that detailed information on the extent and thickness of unconsolidated deposits (particularly till, which typically has low permeability and can limit the migration of contaminants) is needed before sound decisions on waste-disposal siting can be made.

Glaciers deposited till nearly everywhere over bedrock in the uplands of central New York, but the thickness of the till varies greatly from place to place. An analysis by Coates (1966) of 400 drillers' logs of wells in a 2,000-mi² area in the uplands of south-central New York (south of the Cortland County) indicated that (1) till is thin or absent on hilltops and is thickest on the lower parts of hills, (2) overall till thickness averages 60 ft, and (3) till thickness on the south, east, west, and north slopes averages 92, 52, 62, and 22 ft, respectively. Hills that have thick till on their south slopes have been referred to as till-shadowed hills by Coates (1974), who attributes this characteristic to glaciers that deposited thick amounts of till on the downflow side of a hill (analogous to flowing streams or wind that deposit sediment on the lee side of an object). Because the till on the south slopes is relatively thick and typically has low permeability, these slopes have been considered as potential areas for waste-disposal sites.

In 1997, the U.S. Geological Survey (USGS), in cooperation with the Cortland County Department of Planning, began a 1-year study to map the thickness of unconsolidated deposits and the extent of valley-fill aquifers in the Towns of Solon and Taylor (an area of 60 mi²) in eastern Cortland County.

This report (1) depicts the thickness of unconsolidated deposits and the extent of valley-fill aquifers in the Towns of Solon and taylor in eastern Cortland County, (2) examines whether the "till-shadowed hill" concept developed by Coates (1966) is applicable in this area, and (3) provides three schematic geologic sections showing the thickness of unconsolidated deposits in the uplands in the northwestern part of the study area.