MODFLOW-2005, MODFLOW-NWT, and SEAWAT models used to simulate variable-density groundwater flow and contaminant transport at Naval Base Kitsap, Keyport, Washington

The U.S. Geological Survey, in cooperation with the U.S. Department of the Navy, 
developed several 3-D groundwater flow models for used with MODFLOW-2005, 
MODFLOW-NWT, and SEAWAT model codes to evaluate variable-density 
groundwater flow and contaminant transport in Operable Unit 1 on Naval Base 
Kitsap in Keyport, Washington.  Chlorinated volatile organic compounds (CVOCs) 
have migrated to groundwater beneath a former 9-acre landfill at Operable Unit 1 
(OU-1). The three predominant ground-water contaminants are the chloroethene 
compounds trichloroethene (TCE), cis-1,2-dichloroethene (cis-DCE), and vinyl 
chloride (VC).  A need for remedial action was identified because some of the 
contaminants present a potential risk to humans primarily through drinking 
contaminated groundwater or through ingesting seafood harvested from 
contaminated surface water.  An ongoing effort with the U.S. Navy and U.S. 
Geological Survey (USGS) began in 1995 by evaluating the effectiveness of 
natural attenuation processes for removing and controlling the migration of CVOCs 
in ground water at OU-1. Additional collection of geochemical and contaminant 
concentration data demonstrated that biodegradation of CVOCs in shallow 
groundwater at OU-1 is substantial and prevents most of the mass of dissolved-phase 
CVOCs in groundwater beneath the landfill from discharging to surface water. However, 
dissolved-phase contaminant concentrations in the hundreds of milligrams per liter 
continue to persist in localized areas of OU-1. Data suggest that residual sources of 
chloroethenes in the form of non-aqueous phase liquid remain at the site, and that 
biodegradation is only partly effective at reducing the dissolved-phase contaminants 
that are generated from these sources.  In 2018 an additional USGS effort was begun 
to simulate variable-density groundwater flow and contaminant transport in the vicinity 
of OU-1 using a revised hydrogeologic model of the site and a refined delineation of 
persistent contaminant sources. MODFLOW-2005 and MODFLOW-NWT model codes 
were used to calibrate a new model.  Then groundwater flow and contaminant transport 
models were developed using SEAWAT-Version 4, a computer program based on 
MODFLOW and MT3DMS, to simulate three-dimensional variable-density groundwater 
flow coupled with multi-species solute transport. These models were used to simulate 
the direction and rate of groundwater flow near OU-1, estimate the CVOC mass in 
groundwater and the rate of mass loading, and assess possible remedial activities at 
OU-1. 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/sir20205066).

Tags: environment, geoscientificinformation, groundwater, groundwater-model, inlandwaters, keyport, modflow-2005, modflow-nwt, naval-base-kitsap, remediation, seawat, solute-transport, ucode, usgs-1e3e81eb-cbd2-4f16-91ee-67db83e77c98, usgsgroundwatermodel, washington
Organization: Department of the Interior