MODFLOW 6 and MODPATH7 used to simulate regional groundwater flow and advective transport of per- and polyfluoroalkyl substances, Joint Base McGuire-Dix-Lakehurst and vicinity, New Jersey, 2018

A three-dimensional groundwater flow model using MODFLOW 6 (version 6.2.2) was developed and calibrated for unconsolidated Coastal Plain aquifers underlying the Joint Base McGuire-Dix-Lakehurst (JBMDL) and vicinity, New Jersey, to evaluate groundwater flow pathways of per- and polyfluoroalkyl substances (PFAS) contamination associated with use of aqueous film forming foam (AFFF). The model was developed and calibrated by the U.S. Geological Survey (USGS) in cooperation with the U.S. Air Force Civil Engineer Center (AFCEC) based on the previously developed hydrogeologic framework (https://doi.org/10.3133/ofr20191134). Steady-state flow in the unconsolidated aquifers was simulated using the MODFLOW 6 which accounts for hydrostratigraphic pinchouts and discontinuities in the Coastal Plain aquifers underlying JBMDL. To account for local patterns of fluid flow driving advective subsurface migration of PFAS, the grid was refined using quadtree meshes spanning areas where historical AFFF use was identified, where PFAS is most likely to pose a potential danger to local drinking water supplies, and along streams that behave as drains in the baseflow-dominated Coastal Plain. The model was calibrated using the parameter-estimation program PEST (version 17.3), which adjusts model parameters to most closely matching 544 water levels and 20 estimated baseflows. The MODPATH7 (version 7.2.001) particle-tracking algorithm was used to estimate advective transport paths of PFAS in the vicinity of JBMDL. Forward tracking was used to determine paths of PFAS away from AFFF source areas to streams, wetlands, pumping wells, and general geographic areas that PFAS may contaminate. Reverse tracking was used to determine particle tracks that intersect off-site PFAS reconnaissance areas to determine PFAS capture zones, or areas within which all sources of PFAS that might be advectively transported into subsurface drinking-water supplies underlying those areas. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/ofr20221112).