Geohydrology of the Valley-Fill Aquifer in the West Branch Cayuga Inlet and Fish Kill Valleys, Town of Newfield, Tompkins County, New York

PROBLEM

The valley-fill aquifers in the West Branch Cayuga Inlet and Fish Kill valleys (designated as aquifer 15, fig.1), within the Town of Newfield, were mapped by Miller (2000) and identified as one of 17 unconsolidated aquifers in Tompkins County that need to be studied in more detail. The valley-fill in the West Branch Cayuga Inlet and Fish Kill valleys contain a heterogeneous mix of glacial deposits and recent alluvium under mostly unconfined conditions, but may they be under confined conditions in some places. The valley-fill deposits are sources of water for the Village of Newfield, homeowners, farms, and small businesses in these valleys. The Village of Newfield has recently been searching for another location to install a municipal well that will be used to supplement their existing water supply. The need to understand how development may affect the groundwater resource in an area will increase as the population in Tompkins County increases and spreads out from metropolitan areas into these rural areas. The Town of Newfield, 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 valley-fill deposits in Towns of Newfield and Enfield. 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 confined (artesian) or unconfined, (3) extent of ground water/surface-water interaction, (4) groundwater use (type and amount of groundwater withdrawal), (5) water levels in geohydrologic units, and (6) 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. The information that will be provided will better enable Tompkins County and the Town of Newfield to develop a more comprehensive approach to water-resources management. The data will provide local government, water managers, businesses, and homeowners with water information needed to ensure that there will be (1) safe-drinking water supply, (2) water available for economic development, and (3) healthy aquatic environment. The study will build upon the USGS data collection efforts in the state and on the interpretation of the Nation’s water availability. 

APPROACH

The purpose of this study and associated report are to describe the geohydrology and water quality of the stratified-drift aquifers in the West Branch Cayuga Inlet and Fish Kill valleys in Newfield, Tompkins County, New York. The report also describes and illustrates (1) the surficial geology of the study area including the geologic framework of the aquifer system and geohydrologic sections; (2) the groundwater-flow system, including information about groundwater levels, groundwater to surface-water interaction, and recharge and discharge conditions; and (3) groundwater and surface-water quality, including  information about concentrations of common inorganic ions (such as chloride and sodium), species of nitrogen and phosphorus compounds (collectively, nutrients), and trace elements.

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- Groundwater Site Inventory (GWSI). Groundwater use from the aquifer will be estimated from inventorying metered pumping data from large pumping wells and by estimating the groundwater use by homeowners that tap the aquifer.

3) Conduct four seismic-refraction surveys to determine the thickness of the valley-fill deposits and the configuration of the bedrock floor that underlies the valley.

4) Install 4 test wells to (a) gather subsurface data where there is little or no data, (b) serve as control points (ground-truthing) for interpreting seismic-refraction data, and (c) collect water-level and water-quality data that will determine variations between the confined and unconfined system. Tompkins Co. and/or the Towns of Newfield and Enfield will be responsible for the cost of the drilling separate from this project to save costs. USGS will help Tompkins Co. and/or the towns of Newfield and 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. 

Groundwater level/temperature

7) Install water-level recorders in drilled wells. Seasonal water-level fluctuations will be represented by hydrographs. 

Groundwater/surface-water interaction

8) Conduct stream gain/loss measurements in major tributaries, Cayuga Inlet, and Fish Kill to determine whether groundwater discharges into the stream (gaining reaches) or the streams recharge the aquifer (losing reaches). 

Hydraulic properties

9) 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

10) Collect and compile available chemical data from private and non-community supply wells (trailer parks).

11) Collect five groundwater samples to determine the water quality in the aquifer. Water samples will be analyzed for pH, specific conductance, alkalinity, common ions, and nutrients.

12) Collect water samples in 2 streams during base flow conditions to determine the general chemical characteristics of the groundwater contribution of streamflow. Water samples will be analyzed for pH, specific conductance, alkalinity, common ions, and nutrients.