Analysis of Factors Affecting Plume Remediation in a Sole-Source Aquifer System, Nassau County, New York (Northrup Grumman Plume)

Science Center Objects

Problem: Dissolved volatile-organic compounds (VOCs), including trichloroethylene (TCE), have been identified in a sole-source aquifer near the former Northrop Grumman Bethpage facility and Naval Weapons Industrial Reserve Plant (NWIRP) in Nassau County, N.Y. The Northrop Grumman Bethpage facility and NWIRP are listed as Class II inactive hazardous waste disposal sites (Site Nos. HW130003A and...

Problem: Dissolved volatile-organic compounds (VOCs), including trichloroethylene (TCE), have been identified in a sole-source aquifer near the former Northrop Grumman Bethpage facility and Naval Weapons Industrial Reserve Plant (NWIRP) in Nassau County, N.Y.  The Northrop Grumman Bethpage facility and NWIRP are listed as Class II inactive hazardous waste disposal sites (Site Nos. HW130003A and HW130003B respectively) on the New York State registry of Inactive Hazardous Waste Disposal Sites.  Past investigations have documented that the groundwater contamination originated from these two sites and now extends nearly four miles to the south; in the direction of groundwater flow.  During 2019, a groundwater-flow model was developed by the U.S. Geological Survey (USGS), in cooperation with the New York State Department of Environmental Conservation (NYSDEC), to analyze plume movement as part of a feasibility study. Specifically, the analysis simulated contaminant transport, evaluated potential effects of contamination on public-supply wells and nearby hydroecological resources, and studied the feasibility of  hydraulically containing and treating groundwater containing contaminants exceeding applicable standards  (NYSDEC, 2019a)

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The USGS modeling effort helped inform an Amended Record of Decision (AROD) that identified a comprehensive plan to contain and clean up the contamination plume (NYSDEC, 2019b). Detailed groundwater modeling is an essential part of designing a full containment and treatment system that can effectively halt the further spread of contaminants under the remedial program. Moreover, additional data collection, analysis, and modeling is required to effectively manage groundwater resources and mitigate potential adverse effects of plume remediation on drinking-water supplies and on ecosystems. The proposed USGS work will allow the NYSDEC to evaluate design options necessary for the construction, operation, optimization, maintenance, and monitoring of the remedy selected in the December 2019 AROD. 
 
Objective: The primary objective of this investigation is to evaluate the effects of the hydraulic containment and post-treatment water-management system on migration of VOC groundwater contamination originating from the former Northrop Grumman Bethpage facility and NWIRP sites. This modeling will also evaluate the potential hydraulic influences on surface waters, public-water supply wells, existing groundwater-recovery systems, and freshwater-saltwater interfaces under the selected remedial program. 
 
Approach: The groundwater-flow model used in 2019 to evaluate the feasibility of plume containment (Misut and others, in press) will be updated and modified during the study to enhance the analysis of contaminant transport and containment. The updated model will be used to support the ongoing remedial design activities, and will involve routine interaction between the USGS, NYSDEC, and their engineering contractor HDR (based in Omaha, NE). This modeling analysis will provide insight on the optimal number, placement, depths, and pumping rates of extraction wells, and on preferred strategies for managing treated water. These strategies are expected to include the use of recharge basins, surface-water bodies (streams), irrigation, and injection wells. 
 
A sequence of seven interrelated and partially overlapping tasks are proposed as part of this effort. The first task focuses on updating several sources of hydrologic data in the study area to improve confidence in the modeling analysis. The second task involves a series of updates and upgrades to the existing model, which is based on the MODFLOW-NWT software code. The third task involves conversion of the model to a form capable of utilizing the MODFLOW 6 code, with enhancements made possible through use of this new code. The fourth task is to incorporate solute transport, by use of the MT3D-USGS code, into this model to enhance selected analyses presented in Misut and others (in press), including incorporation of updated and current plume delineations and potential refinements to the hydraulic containment system. The fifth task is to develop a version of the model capable of representing density-dependent movement of the freshwater-saltwater interface in response to changing hydraulic stresses. The sixth task involves iterative coordination with the NYSDEC and HDR to apply these newly developed tools to specific remedial design issues and questions. The seventh task involves production of a model documentation report and archive, and maintenance of the models for future use.


References :

Evenson, E.J., Orndorff, R.C., Blome, C.D., Böhlke, J.K., Hershberger, P.K., Langenheim, V.E., McCabe, G.J., Morlock, S.E., Reeves, H.W., Verdin, J.P., Weyers, H.S., and Wood, T.M., 2013, U.S. Geological Survey water science strategy—Observing, understanding, predicting, and delivering water science to the Nation: U.S. Geological Survey Circular 1383–G, 49 p. [Also available at https://pubs.usgs.gov/circ/1383g/circ1383-G.pdf.]

Misut, P.E., 2014, Simulation of zones of contribution to wells at site GM–38, Naval Weapons Industrial Reserve Plant, Bethpage, New York: U.S. Geological Survey Scientific Investigations Report 2014-5036, vii, 58 p. 

Misut, P.E., 2018, Simulation of zones of contribution to wells south of the Naval Weapons Industrial Reserve Plant, Bethpage, New York: U.S. Geological Survey Scientific Investigations Report 2017–5161, 45 p., http://dx.doi.org/10.3133/sir20175161.

Misut, P.E.,Walter, D.A.,Schubert, C.E., and Dressler, S.,  20xx, Analysis of remedial scenarios affecting plume movement through a sole-source aquifer system, Southeastern Nassau County, New York: U.S. Geological Survey Scientific Investigations Report 20xx-xxxx

New York State Department of Environmental Conservation, 2019a, Feasibility Study Report: Northrup Grumman Bethpage Facility (Operable Units 2 and 3) & Naval Weapons Industrial Reserve Plant (Operable Unit 2), work assignment D007625-32, April 2019

New York State Department of Environmental Conservation, 2019b, Fact Sheet - Amended Remedy Proposed for Navy Grumman Groundwater, site no. 130003A & 130003B, May 2019, 4 p., http://www.dec.ny.gov/docs/remediation_hudson_pdf/130003abdraftarodfs.pdf

Project Location by County

Nassau County, NY