DERIVING SPATIAL HYDROGEOLOGIC DATASETS FROM DIGITALIZED LEGACY WELL RECORDS

Many health and environmental agencies rely on domestic well data as a tool for water resource management, environmental risk assessment, and other spatial analyses. Connecticut has recently implemented a data management system for new well completion reports, but it will take many years before there are enough digitalized records to be useful as a GIS tool for producing hydrogeologic models given that only new well records will be included. Historic well records dating back to the 1970s contain the same information as new records, though they cannot be readily integrated into a modern database because the current storage format is in scanned images of each analog report. In this study, over 1,700 legacy well records in a Connecticut township were digitalized into a Microsoft Access database. Data fields found in the majority of the records were queried and used to develop a geodatabase in ArcGIS. Street addresses and parcel lot numbers were geolocated to approximate coordinates for each well. Depth to rock and depth to water were cross referenced with LIDAR surface elevation data to calculate the bedrock elevation, groundwater elevation, and the overburden thickness at each well location. Raster files were generated to contour the bedrock topography, potentiometric surface, and overburden thickness by interpolating the values across all well points. The ArcGIS hydrology toolset was used to determine the groundwater flow direction and flow boundaries. Yield values from each well were used to estimate recharge rates and transmissivities within groundwater flow boundaries. The results of this study demonstrate how legacy well records can be used as a tool for environmental assessments relating to water supply, contaminant releases, and public health risk analyses. If these effective digitalization and data management practices were applied to historic records statewide, the resulting database would be an invaluable resource for the many agencies and parties working to preserve drinking water sources and human health.