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    Pennsylvania's Legacy Ambient and Fixed Station Network Groundwater Quality Monitoring Program began in 1985 to characterize background conditions and to assess changes in groundwater quality within groundwater basins of Pennsylvania. Under a joint funding agreement with Pennsylvania Department of Environmental Protection (DEP) in 2005, the United States Geological Survey (USGS) compiled electronically available groundwater quality data to help point out data gaps and to guide future monitoring efforts; over 24,000 wells from 14 different agencies/programs were included in the project. For more information on this project, and to access the full report, please visit the USGS reports webpage.

    In 2014, the U.S. Geological Survey (USGS) Water Science Center, in cooperation with the DEP, initiated a project in which select groundwater stations would be sampled on a routine basis, throughout the state. This effort is referred to as the “Expanded” (or “Statewide”) Fixed Station Groundwater Quality Monitoring Network (GWMN) to distinguish it from the original “Legacy” effort. Through this project, 28 wells are currently sampled biannually to monitor ambient groundwater quality conditions throughout Pennsylvania. From this information, DEP has begun to better understand the status of groundwater quality in Pennsylvania.

    Each well is sampled in the spring and fall of every year for major elements, trace metals, nutrients, and organic compounds. First-time wells are sampled for light hydrocarbons, radiological elements, and volatile organic compounds. Project goals include characterizing ambient groundwater quality conditions, monitoring short- and long-term changes in groundwater quality, and generating statistical reports and analyses of sample results.

    In 2022, the USGS published a summary of findings titled “Characterization of ambient groundwater quality within a statewide, fixed-station monitoring network in Pennsylvania, 2015–19.”

    The Pennsylvania Groundwater Quality Monitoring Network Data Exploration Tool provides trend data for ongoing monitoring activities of the fixed-station monitoring network.