Within the past decade, energy companies have increasingly employed hydraulic fracturing techniques to extract methane from deep shale deposits. Because the process involves the injection of toxic compounds underground, many residents worry about contamination of groundwater and surface waters. To assess impacts to surface waters in the Marcellus shale region of northeastern Pennsylvania, we have developed a conceptual model of environmental impact. Study sites include those impacted by gas wells and/or gas related infrastructure. Our analysis relies heavily on historical and ongoing monitoring conducted by the Pennsylvania Department of Environmental Protection, the Susquehanna River Basin Commission and other organizations. We then developed a surface water quality monitoring program that measures parameters that may respond to the impacts, including sampling for chemical analysis, continuous monitoring with sensors, and macroinvertebrate sampling for species presence/absence and diversity. Data collection is synchronized with gas development related construction activities.
Baseline monitoring indicated less than pristine conditions at most of the sites. Nitrogen and phosphorous levels indicate contributions from agriculture and other land uses. Pollution tolerant macroinvertebrates such as black flies and aquatic worms were dominant at sites with elevated nutrients. Continuous monitoring data indicates much of the response is meteorological event-driven or temporary in nature. Responses vary from site to site and from event to event. Short term increases in turbidity and conductance at the beginning of rainfall events were interpreted as indicators of pollutant washoff. Larger rainfalls resulted in short term decreases in conductance due to the diluting effect of runoff. Correlations between continuous measurements of chlorophyll a and blue-green algae with nutrients and macroinvertebrate communities were investigated. Ongoing work will develop tools to integrate continuous monitoring data with conventional grab sampling leading to the development of guidance for the design of monitoring programs.