Using Unique Modeling Techniques for Groundwater Cleanup Planning

For several decades, the Northrop Grumman Corporation manufactured aircraft for the U.S. Navy in the Town of Oyster Bay, New York. Chemical handling and disposal practices during this time resulted in trichloroethylene contamination in the Long Island Aquifer System, creating a large, approximately 150-billion-gallon plume of groundwater almost 1,000 feet deep and extending over four miles from the former manufacturing facility. 

In partnership with state regulators, we mapped the extent of the groundwater contamination and developed a solution with 20 new wells pumping more than 10,000 gallons per minute, treating the water to remove the trichloroethylene, then returning the water to the aquifer. But there was still a need to optimize the complex system to most effectively capture groundwater contamination while minimizing impacts to nearby water districts and surface water resources. 

We began working with the United States Geological Survey and other team partners to create a probability-based modeling approach, leveraging 1,000 groundwater models adjusted for variations in geologic and hydrologic conditions in the aquifer. The team simultaneously ran the models, evaluating different cleanup parameters, like well pumping, to optimize the groundwater remediation. 

The outcome was a range of results that helped the team select a risk-adverse, a risk-tolerant, or most-likely result, also called the central tendency. We were also able to better understand the uncertainty of the models, called uncertainty quantification.

This one-of-a-kind modeling work is showcased in a scientific investigations report from the USGS, “Analysis of Factors Affecting Plume Remediation in a Sole-Source Aquifer System,” which credits HDR’s Dan St. Germain and Jillian Troyer as co-authors and Shane McDonald as an acknowledgement. The report goes into detail on the background of the plume, the work required to study, build and run the model, and the model’s results.  

Thanks to this research and modeling approach, a comprehensive, multimillion-dollar remediation plan is underway, led by New York’s Department of Environmental Conservation and executed by the U.S. Navy and Northrop Grumman.