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Impact Assessment of Natural Gas Production in the NYC Watershed

In recognition of increased natural gas development activity in New York State and its potential to impact New York City’s water supply, the New York City Department of Environmental Protection (DEP) commissioned Hazen and Sawyer in joint venture to prepare an assessment of potential impacts to the NYC water supply from natural gas development utilizing hydraulic fracturing technology. The process required to extract gas from shale formations (such as the Marcellus Shale formation underlying much of WV, MD, PA, and NY), termed hydraulic fracturing, entails injecting large volumes of water, sand, and chemicals at high pressures into the formation, resulting in fractures that increase permeability, allowing the gas to be collected and delivered to the surface.

Hydraulic fracturing can only capture natural gas resources across a relatively small area of a formation. Thousands of wells are needed, as shown here for the Barnett Shale in Texas, to fully exploit the resource.
At the time of the study, geologic information indicated that the NYC watershed could be a high priority area for drilling natural gas in New York.

Natural gas development from shale formations is an intensive industrial activity that has the potential to result in multiple impacts to a water supply watershed:

  • Land use changes from drill pad construction, access roads, and other support infrastructure Water withdrawals for hydraulic fracturing operations (2 to 4 million gallons per well).
  • Use of large volumes of potentially toxic chemicals (100 to 300 tons per well).
  • Potential for disturbance of existing hydrogeologic flow regimes resulting in contamination of groundwater or surface water supplies.
  • Generation and disposal of significant quantities of industrial wastewater containing TDS, bromides, radionuclides, metals, and benzene compounds.

The project team’s analysis included collecting data from developed shale formations on rates and densities of well development, spill/contamination incidents, volumes/quantities of land disturbance, water, chemicals, and wastewater. The project team provided DEP with a conceptual hydrogeologic model based on historical water supply and quality data, a database of endocrine-disrupting and other toxic constituents present in fracking fluids, and estimates of cumulative development in the watershed and the resulting risk potential. The project team also provided DEP with recommendations for appropriate monitoring protocols for both groundwater and surface water resources in order to monitor for changes to water quality related to natural gas development.

Benjamen Wright, PE
Regime disruption

Conceptual process showing how hydraulic fracturing could disrupt subsurface flow regimes leading to surface water and shallow groundwater resources.

Project Outcomes and Benefits

  • DEP, supported by the project team’s data and analyses, successfully obtained additional regulations and restrictions on hydraulic fracturing in unfiltered water supply watersheds in New York State.
  • Project won a NY ACEC Diamond Award.