Potential Environmental Impacts of Full-development of the Marcellus Shale in Pennsylvania

A long-range picture:  Gas development and environmental impacts in Pennsylvania’s Marcellus


Since 2007, Pennsylvania has witnessed a rapid expansion in natural gas production due to development of the Marcellus Shale with hydraulic fracturing. This ‘unconventional’ natural gas development can have a range of environmental impacts, including land disturbance and forest loss, air emissions, water withdrawals, wastewater generation, and potential human health risks, among others. Determining the importance of these impacts - individually or collectively and especially in the future - is extremely difficult because there is great uncertainty around their potential magnitude and spatial distribution.

Regulation and industry practice can have an effect on the magnitude of these impacts at individual well sites, and the relative risk of accidental or uncontrolled impacts (such as spills or well failures).  Many impacts, though, cannot be completely mitigated as they are associated with activities necessary for development (e.g, well pad construction, water acquisition, running equipment), and mostly scale in proportion to the amount of development. These types of impacts can straightforwardly be computed if the amount and locations of well development can be determined. So, gaining an  understanding of how much potential development may yet occur, and where, can enable assessment of a wide range of potential impacts. Finally, it is difficult to predict exactly how much development will occur and when, so to understand the impacts, it makes sense to start with an estimate of how much development could potentially occur.

What would be the potential environmental impacts from natural gas development activities in Pennsylvania if the Interior Marcellus Shale resources were fully developed?

In this study, we use geospatial analysis and Energy Information Administration (EIA) estimates of remaining technically recoverable resources to project most-likely potential locations of additional natural gas wells across the Marcellus shale in Pennsylvania through full-development of those resources. Then, using these well locations combined with additional geospatial data and information from government data sources and peer-reviewed literature, we project the magnitude and locations of potential environmental impacts across several categories. The primary outputs of this work are a report explaining the methodology and summary results at the state level, and a set of maps that displays the magnitude of the potential impacts geographically.

Read the Full Report

Read the Executive Summary

Read the Press Release

Map Sets

The following map sets show the geographic character of the impacts calculated in this study. The report explains in greater detail the methodology used for calculating these impacts.

Map Set 1 – Development Projections

Map Set 2 – Impacts to Land and Forests

Map Set 3 – Impacts to Population

Map Set 4 – Air Emissions

Map Set 5 – Water and Wastewater Impacts

View the Projections

Use the following map viewer to view the projections by county and watershed. Use the “Layer List” button at top right to open a tab where you can turn the layers on or off by clicking the check box. Click on the individual watershed or counties to see the actual projection.

Caveats and Use of the Report

Note that these are projections based on a set of assumptions and are not predictions. Changing the assumptions on which the projections are based may change the projections. For instance, technically recoverable resources is only one measure of the total amount of gas that may be recovered, and it can change in response to technological changes, and understanding of the geology of the shale. Actual development will depend on many factors including gas prices, costs of development, ability to sign leases, regulations, and others.

These projections are not for commercial use, and should not be used to make investment decisions. CNA disclaims responsibility for any damage and/or liability that may arise from the use of these data.