Groundwater Monitoring In Pennsylvania

Groundwater is extremely important in Pennsylvania. Pennsylvania’s groundwater provides environmental benefits and contributes to the well-being of the citizens and the economic growth potential of the Commonwealth. Groundwater is an important source of the drinking water for our population of nearly 12 million. High quality groundwater also is critical to industry and agriculture. Groundwater is essential to Pennsylvania’s surface streams because it provides the sustaining baseflow to the approximately 83,000 miles of streams and rivers. In times of drought, groundwater flow provides nearly all of the baseflow. The amount of groundwater in the United States at any given moment is 20 to 30 times the amount of water in all of the lakes, streams, and rivers.

Nearly one million private water wells supply water to over 2.5 million people in Pennsylvania. Community water systems supply groundwater to an additional two million people. This indicates that over one-third of the population in Pennsylvania uses groundwater daily for drinking water purposes. When restaurants, churches, schools and parks (of which most rely on groundwater) are factored in, the number of Pennsylvanians who use groundwater is closer to 50 percent. In many areas of the state, groundwater serves as the sole source of water and is the only practical water supply.

Ambient Survey and Fixed Station Network (FSN) Program Overview

Monitoring of groundwater quality in Pennsylvania is usually done near a permitted facility to determine the impacts of the facility on the groundwater or to monitor as a safeguard for a public water supply well. In either case, the monitoring is limited to the immediate area around a permitted facility. DEP’s Bureau of Water Supply Management conducts the only DEP program that monitors the ambient or background groundwater quality on a watershed basis. U.S. Environmental Protection Agency (EPA) groundwater grants support the program.

The Bureau of Water Supply Management uses two combined programs to monitor the general quality of groundwater. The Fixed Station Network (FSN) and Ambient Monitoring program is described in the DEP document Pennsylvania’s Groundwater Quality Monitoring Network: Ambient and Fixed Station Network (FSN) Monitoring Programs (document 383-3200-009 / 6/97). This document is available to the public by calling 717-772-4018.

The FSN program involves the sampling of selected groundwater basins over an extended period of time. Three objectives of the monitoring program are to 1) determine the general baseline quality of the groundwater resources, 2) monitor for changes in the groundwater quality and 3) generate statistical reports and assessments of sample results and trends. FSN sampling can contribute to an understanding of long-term water quality trends, and can be used to assess the impact of land management practices on groundwater quality.

Sampling points have been selected to provide a measure of background at unaffected or minimally affected sampling locations. Ambient Surveys for a groundwater basin are accomplished by collecting two groundwater samples per monitoring point over one year.

The monitoring program has included the sampling of 27 analytes (except for basins in southwestern Pennsylvania, which were sampled for 24 analytes), as shown in Table 1. The monitoring program was established in 1985. As of 1999, 1106 monitoring points had been sampled and their data placed on the EPA STORET system. FSN basin monitoring points that were established in 1985 have been sampled up to 34 times. Monitoring in the southwest part of the state was discontinued in 1989 because of resource constraints. This area accounts for 139 FSN monitoring points and 10 monitoring points that are categorized as ambient.

Based on the initial groundwater basin prioritization, the top 50 ranked basins out of 478 were to be monitored as part of the FSN program (Map 1). Because of resource constraints, this goal has not been realized. To reach more areas of the state, the program was revised in 1997 to emphasize ambient monitoring. If prolonged monitoring is needed, an ambient basin can be converted into FSN monitoring. Of the 27 FSN basins that have been established since 1985, 15 are continuing while additional basins are being designed. The new emphasis on ambient basins is to reach additional areas of the state while allowing DEP regions more flexibility in using the monitoring program. All of the FSN basins in the southeast region (14) are continuing plus one in the northeast region.

A summary of the FSN and ambient data was completed in 1998. The report is entitled Summary of Groundwater Quality Monitoring Data (1985 - 1997) from Pennsylvania’s Ambient and Fixed Station Network (FSN) Monitoring Program — Selected Groundwater Basins in Southwestern, Southcentral and Southeastern Pennsylvania. A companion Geographical Information System point coverage with accompanying data was created for this report. This coverage has been updated to include data through 1998. This coverage is available from the Pennsylvania Spatial Data Access (PASDA) website (http://www.pasda.psu.edu/flash.shtml). The report includes trend analyses and summary data by basin, geology, and land use. Nearly 10,000 sample results have been reviewed and compared to any existing groundwater quality standards such as maximum contaminant levels shown in Table 1.

In 1999, a trend analysis study was completed on monitoring points in the Fixed Station Network for southeastern Pennsylvania. This report is available as a WORD document (177K).

Map 1. Location of ambient and FSN groundwater basins in Pennsylvania.

For more information, contact Stuart Reese at 717-772-4018, or send an e-mail message to streese@state.pa.us