PROBLEM
The unconsolidated aquifer in Enfield Creek Valley (fig. 1) was mapped by Miller (2000) and identified as one of 17 unconsolidated aquifers in Tompkins County that needs to be studied in more detail. Well records in Enfield Creek valley indicate that the northern part of Enfield Creek valley contains sand and gravel deposits which may be under unconfined conditions in some areas, confined in others, or both; and the southern part of the valley contains mostly sand and gravel under unconfined conditions. The valley will probably undergo increased development as the population in Tompkins County increases and spreads out from metropolitan areas. However, there is little geohydrologic data in the valley. The Town of Enfield, Tompkins County, and the New York State Departments of Health and Environmental Conservation are in need of geohydrologic information to help planners develop a more comprehensive approach to water-resources management in Tompkins County.
OBJECTIVE
The objective of the proposed study is to improve the understanding of the geohydrology of the sand and gravel aquifer in the Enfield Creek Valley. Specifically, the study will provide the following information: (1) extent and thickness of geohydrologic units, (2) hydraulic conditions in the aquifers— whether the units are under confined (artesian) or unconfined conditions, (3) extent of ground water/surface-water interaction, (4) ground-water use (type and amount of ground-water withdrawal), (5) general water quality of the aquifers.
BENEFITS
The study will benefit federal, state, and county governments and the residents in the study area by (1) advancing knowledge of the regional geohydrologic framework of these types of valley-fill systems, (2) increasing the understanding of hydrologic processes in sand-and-gravel aquifer systems in the glaciated northeast, and (3) contributing data to national data bases that will be used to advance the understanding of regional and temporal variations in hydrologic systems. This study will provide additional information to help Tompkins County and the Town of Enfield develop a more comprehensive approach to water-resources management. Additionally, the information will provide local government, water managers, businesses, and homeowners with ground-water information to help ensure that there will be (1) safe drinking-water supply, (2) water available for economic development, and (3) healthy aquatic environments. The study will build upon the USGS data collection efforts in the state and on the interpretation of the Nation’s water availability.
APPROACH
Geohydrologic data will be collected, compiled, and analyzed to determine (1) geohydrologic framework and aquifer geometry, (2) ground-water/surface-water interaction, (3) hydraulic properties (if existing aquifer test data is available), and (4) general water quality of ground water.
Individual work elements
Geohydrologic framework
1) Construct base map- Arc/Info topographic map coverage.
2) Inventory wells in the valley and enter data into the USGS national well database- Ground-Water Site Inventory (GWSI). Ground-water use from the aquifer will be estimated by inventorying metered pumping data from large pumping wells and by estimating the ground-water use by homeowners that tap the aquifer.
3) Conduct horizontal-to-vertical seismic ratio (HVSR) surveys, to determine the thickness of the valley-fill deposits and the configuration of the bedrock floor that underlies the valley.
4) Test drilling- install four pairs of wells Test drilling will (a) gather stratigraphic data where there is little or no data, (b) serve as control points (ground-truthing) for interpreting seismic-refraction data, and (c) provide access to collect water-level and water-quality data. Drilling costs will be paid separately by the cooperator (Tompkins Co. and/or by the Town of Enfield). USGS will help Tompkins County and/or the Town of Enfield in writing the drilling contract, drilling oversight, and sample collection.
5) Construct geohydrologic sections showing the glacial stratigraphy and aquifer boundaries.
6) Compile a surficial geology map using the maps made by the New York State Geological Survey and, if needed, modify them based on subsurface data collected during this study.
Ground-water/surface-water interaction
7) Conduct streamflow measurements in several major tributaries and in Enfield Creek to determine whether ground-water discharges into the stream (gaining reaches) or the streams recharge the aquifer (losing reaches).
Hydraulic properties
8) Collect and analyze available aquifer-test data (if any) from drillers’ records to determine specific capacity of wells and estimate aquifer transmissivity and hydraulic conductivity (permeability of aquifer materials).
Water quality
9) Collect water samples from wells that tap the aquifer and confined parts of the aquifer and analyze for pH, specific conductance, alkalinity, common ions, and nutrients.
10) Collect water samples from tributary streams where streamflow measurements are to be made during baseflow conditions (when flow in the stream is mostly from ground water) and one from the main stream (Enfield Creek) and analyze for pH, specific conductance, alkalinity, common ions, and nutrients.
PUBLICATIONS
Fisher, B.N., Heisig, P.M., and Kappel, W.M., 2019, Geohydrology and water quality of the unconsolidated aquifers in the Enfield Creek Valley, town of Enfield, Tompkins County, New York: U.S. Geological Survey Scientific Investigations Report 2019–5136, 52 p., https://doi.org/10.3133/sir20195136
REFERENCES
Miller, T.S., 2000, Unconsolidated aquifers in Tompkins County, New York: U.S. Geological Survey Water-Resources Investigations Report 00-4211, 1 sheet
Project Location by County
Tompkins County, NY
