Hydraulic and Solute-Transport Properties and Simulated Advective Transport of Contaminated Groundwater in a Fractured-Rock Aquifer at the Naval Air Warfare Center, West Trenton, New Jersey
by Jean C. Lewis-Brown and Donald E. Rice
By Jean C. Lewis-Brown and Donald E. Rice
MODEL VERSION/TYPE: MODFLOW-2000, steady state and transient
AREA STUDIED: West Trenton, Mercer County
AQUIFERS SIMULATED: Lockatong and Stockton Formations
MOST RECENT WITHDRAWALS SIMULATED: 2000
MODEL SIZE:71 layers, 154 rows, 160 columns
MINIMUM GRID SPACING:25 feet x 25 feet
MODEL ARCHIVE AVAILABLE ON REQUEST: gs-nj-model-request@usgs.gov
REPORT ABSTRACT:
The effectiveness of groundwater pumping by the use of recovery wells in preventing contaminated groundwater at the Naval Air Warfare Center (NAWC), West Trenton, N.J., from moving off the NAWC property was evaluated by use of a digital model of groundwater flow. The finite-difference, three-dimensional, porous-medium model uses the MODFLOW code to solve the groundwater-flow equation. Groundwater flowpaths from areas at and near contaminated well sites for a no-pumping and two-recovery-well-pumping scenarios were computed using the post-processor MODPATH.
The NAWC is underlain by the Lockatong and Stockton Formations, which consist of alternating layers of mudstone, siltstone, and sandstone. A fault transects the area and forms the contact between the Lockatong and Stockton Formations. Water flows through these rocks primarily in fractures that are parallel to the strike of the bedding—N. 65° E.—and, to a lesser degree, in fractures that are nearly vertical.
The median horizontal hydraulic conductivity measured at 32 shallow wells (less than 25 ft (feet) deep) at the NAWC is 2.6 ft/d (feet per day). At 17 wells, 26 to 50 ft deep, the median horizontal hydraulic conductivity is 11.3 ft/d. The hydraulic conductivity is lower in the shallow rocks than in the rocks from 26 to 50 ft below land surface because the shallow rocks are weathered, and clay and silt from the weathering process fills many of the fractures. Deeper than 50 ft, the horizontal hydraulic conductivity decreases, probably because the interconnection of fractures decreases with depth. The broad range in measured hydraulic conductivity (0.001 to 227 ft/d) is a result of the heterogeneity of the fractured-rock aquifer. Wells where high hydraulic conductivities were measured probably are completed where one or more vertical fractures intersect horizontal fractures, whereas wells with low hydraulic conductivities probably are between vertical fractures.
Under no-pumping conditions, simulated groundwater flowpaths from the NAWC are primarily in the direction of the strike of the bedding units, with most water from the NAWC flowing west-southwest to discharge at Gold Run on and adjacent to the NAWC. Under recovery-well-pumping conditions, most flowpaths are diverted toward the pumped wells.
Two different recovery-well networks, each comprising six wells pumping a total of 56.5 gallons per minute, have been used at the NAWC. Modeling results indicate that both networks capture water from the area around 51 of the 55 contaminated wells at the NAWC and that the second network captures more potentially contaminated groundwater than would otherwise discharge to Gold Run.
Reports using this model:
Hydraulic and solute-transport properties and simulated advective transport of contaminated ground water in a fractured rock aquifer at the Naval Air Warfare Center, West Trenton, New Jersey, 2003
Simulated ground-water flow, Naval Air Warfare Center, West Trenton, New Jersey
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- Overview
Hydraulic and Solute-Transport Properties and Simulated Advective Transport of Contaminated Groundwater in a Fractured-Rock Aquifer at the Naval Air Warfare Center, West Trenton, New Jersey
by Jean C. Lewis-Brown and Donald E. Rice
By Jean C. Lewis-Brown and Donald E. Rice
Map of the study area covered by the Naval Air Warfare Center Model. MODEL VERSION/TYPE: MODFLOW-2000, steady state and transient
AREA STUDIED: West Trenton, Mercer County
AQUIFERS SIMULATED: Lockatong and Stockton Formations
MOST RECENT WITHDRAWALS SIMULATED: 2000
MODEL SIZE:71 layers, 154 rows, 160 columns
MINIMUM GRID SPACING:25 feet x 25 feet
MODEL ARCHIVE AVAILABLE ON REQUEST: gs-nj-model-request@usgs.gov
REPORT ABSTRACT:
The effectiveness of groundwater pumping by the use of recovery wells in preventing contaminated groundwater at the Naval Air Warfare Center (NAWC), West Trenton, N.J., from moving off the NAWC property was evaluated by use of a digital model of groundwater flow. The finite-difference, three-dimensional, porous-medium model uses the MODFLOW code to solve the groundwater-flow equation. Groundwater flowpaths from areas at and near contaminated well sites for a no-pumping and two-recovery-well-pumping scenarios were computed using the post-processor MODPATH.
The NAWC is underlain by the Lockatong and Stockton Formations, which consist of alternating layers of mudstone, siltstone, and sandstone. A fault transects the area and forms the contact between the Lockatong and Stockton Formations. Water flows through these rocks primarily in fractures that are parallel to the strike of the bedding—N. 65° E.—and, to a lesser degree, in fractures that are nearly vertical.
The median horizontal hydraulic conductivity measured at 32 shallow wells (less than 25 ft (feet) deep) at the NAWC is 2.6 ft/d (feet per day). At 17 wells, 26 to 50 ft deep, the median horizontal hydraulic conductivity is 11.3 ft/d. The hydraulic conductivity is lower in the shallow rocks than in the rocks from 26 to 50 ft below land surface because the shallow rocks are weathered, and clay and silt from the weathering process fills many of the fractures. Deeper than 50 ft, the horizontal hydraulic conductivity decreases, probably because the interconnection of fractures decreases with depth. The broad range in measured hydraulic conductivity (0.001 to 227 ft/d) is a result of the heterogeneity of the fractured-rock aquifer. Wells where high hydraulic conductivities were measured probably are completed where one or more vertical fractures intersect horizontal fractures, whereas wells with low hydraulic conductivities probably are between vertical fractures.
Under no-pumping conditions, simulated groundwater flowpaths from the NAWC are primarily in the direction of the strike of the bedding units, with most water from the NAWC flowing west-southwest to discharge at Gold Run on and adjacent to the NAWC. Under recovery-well-pumping conditions, most flowpaths are diverted toward the pumped wells.
Two different recovery-well networks, each comprising six wells pumping a total of 56.5 gallons per minute, have been used at the NAWC. Modeling results indicate that both networks capture water from the area around 51 of the 55 contaminated wells at the NAWC and that the second network captures more potentially contaminated groundwater than would otherwise discharge to Gold Run.
- Publications
Reports using this model:
Hydraulic and solute-transport properties and simulated advective transport of contaminated ground water in a fractured rock aquifer at the Naval Air Warfare Center, West Trenton, New Jersey, 2003
Volatile organic compounds, predominantly trichloroethylene and its degradation products, have been detected in ground water at the Naval Air Warfare Center (NAWC), West Trenton, New Jersey. An air-stripping pump-and-treat system has been in operation at the NAWC since 1998. An existing ground-water-flow model was used to evaluate the effect of a change in the configuration of the network of recovAuthorsJean C. Lewis-Brown, Glen B. Carleton, Thomas E. ImbrigiottaSimulated ground-water flow, Naval Air Warfare Center, West Trenton, New Jersey
No abstract available.AuthorsJ. C. Lewis-Brown, D.E. Rice - Partners
Below are partners associated with this project.