U.S. Department of the Interior 

U.S. Geological Survey

SIMULATED GROUND-WATER FLOW, NAVAL AIR WARFARE 

CENTER, WEST TRENTON, NEW JERSEY

Water-Resources Investigations Report 02-4019

Prepared in cooperation with the 

U.S. DEPARTMENT OF THE NAVY

science 

uses

for a changing world
' ' . ....'. ".; '.". ."..'' ' " ;' : '../' ;

Cases the are not the

' . ; ' . ';. ' ;.. '

.Page 17,- table-2,

* 26-50' ft (not;

113 in the ' ...' '. .' ';''.-.

* For the 51-100 ft, - ."." 

(not 4.0 ft/d) was used in the model. .' .. ' " ;.

19, last in "Vertical .';.' .

should read; ' . . ' '.; .' '.' 

* The-best the . '; .' . : - o f the of the set- ;at ' the :'.' .

of the of all set ; 

-of the set at 1 ft, the

tributaries was set at 0.1 ft. ;:'' - ' '.- '.' . 

. ' . . .,'' 

» 24, 4, the at well: 36S is ft (not 151,10 -

ft). - -...- ". : ;- -

 Page 34 Table 10: . .''. '. '"

o ' In 2 (recovery-well 2), a at * *

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o In 1 no at the NAWC), at51BR to the of the''

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SIMULATED GROUND-WATER FLOW, NAVAL AIR WARFARE 

CENTER, WEST TRENTON, NEW JERSEY

By Jean C. Lewis-Brown and Donald E. Rice

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4019

Prepared in cooperation with the 

U.S. DEPARTMENT OF THE NAVY

West Trenton, New Jersey 

2002

science 

USGS

fora chan !L i world
U.S. DEPARTMENT OF THE INTERIOR 

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY 

Charles G. Groat, Director

The use of firm, trade, and brand names in the report is for identification 

purposes only and does not constitute endorsement by the U.S. Government.

For additional information Copies of this report can be

write to: purchased from:

District Chief

U.S. Geological Survey U.S. Geological Survey

Mountain View Office Park Branch of Information Services

810 Bear Tavern Road Box 25286

West Trenton, NJ 08628 Denver, CO 80225-028f
CONTENTS

Prge

Abstract.......................................................................................................................................................... 1

Introduction..................................................... 1

Purpose and scope ............................................................................................................................4

Hydrogeologic framework................................................................................................................ 4

Acknowledgments ............................................................................................................................6

Description of ground-water-flow model...................................................................................................... 6

Grid and boundary conditions ..........................................................................................................6

Hydrologic parameters ................................................................................................................... 11

Horizontal hydraulic conductivity..................................................................................... 11

Vertical hydraulic conductivity.......................................................................................... 19

Arealrecharge ................................................................................................................... 19

Specific yield and storage coefficient............................................................................... 19

Simulation of discharge features ....................................................................................................22

Streams..............................................................................................................................22

Pumped wells..................................................................................................................... 23

Calibration......................................................................................................................................23

Static ground-water levels.................................................................................................23

Base flow to streams.......................................................................................................... 28

Drawdown during short-term pumping............................................................................. 28

Sensitivity analysis .........................................................................................................................31

Simulated water budget..................................................................................................................31

Model limitations............................................................................................................................ 33

Simulated ground-water flowpaths.................................................................................................34

Simulation l--Nopumping................................................................................................34

Simulation 2 Recovery-well network I............................................................................ 38

Simulation 3--Recovery-well network II........................................................................... 38

Summary and conclusions...........................................................................................................................41

References.................................................................................................................................................... 43

ILLUSTRATIONS

Figure 1. Map showing location of the Naval Air Warfare Center and vicinity, Ewing Township, New 

Jersey, and extent of model grid....................................................................................... 2

2. Map showing well locations and line of section A-A' at the Naval Air Warfare Center, West 

Trenton, New Jersey.........................................................................................................3

3 Geologic section A-A' showing bedding units and fault zone at the Naval Air Warfare

Center, West Trenton, New Jersey ...................................................................................5

4 Map showing finite-difference grid for the ground-water-flow model, Naval Air Warfare

Center, West Trenton, New Jersey, and vicinity............................................................... 7

5 Map showing part of the ground-water-flow model grid showing cells used to simulate

Gold Run and the fault in the area of the Naval Air Warfare Center, West Trenton, New 

Jersey................................................................................................................................ 8

6. Section showing vertical discretization of ground-water-flow model along geologic section 

A-A at the Naval Air Warfare Center, West Trenton, New Jersey................................ 10

in
ILLUSTRATIONS-Continued

Page

Figure 7. Graphs showing sensitivity of simulated ground-water levels, base flow, drawdown, and 

capture of contaminated water by recovery wells to variations in the values of model 

parameters, Naval Air Warfare Center, West Trenton, New Jersey............................... 32

8. Map showing simulated discharge locations of ground water at and near contaminated wells 

at the Naval Air Warfare Center, West Trenton, New Jersey (no recovery wells 

simulated as pumping)................................................................................................... 37

9. Schematic section showing generalized ground-water-flow path........................................ 39

10. Map showing simulated discharge locations of ground water at and near contaminated wells 

at the Naval Air Warfare Center, West Trenton, New Jersey (Recovery-Well Network 

I or II in operation).........................................................................................................40

TABLES

Table 1. Horizontal hydraulic conductivity at, and well construction data for, wells at and near tire

Naval Air Warfare Center, West Trenton, New Jersey...................................................... 13

2. Horizontal hydraulic conductivity as a function of depth below land surface, Naval Air

Warfare Center, West Trenton, New Jersey....................................................................... 17

3. Base flow and ground-water runoff in streams at or near the Naval Air Warfare Center, West 

Trenton, New Jersey.......................................................................................................... 20

4. Measured and simulated water levels in wells at and near the Naval Air Warfare Center, West 

Trenton, New Jersey, May 18 and 26, 2000...................................................................... 24

5. Measured and simulated base flow to streams at and near the Naval Air Warfare Center, West 

Trenton, New Jersey .........................................................................................................28

6. Measured and simulated drawdown in wells at the Naval Air Warfare Center, West Trenton, 

New Jersey, after well 15BR had been pumped at 25 gallons per minute for 72 hour? .... 29

7. Measured and simulated drawdown in wells at the Naval Air Warfare Center, West Trenton, 

New Jersey, after well BRP1 had been pumped at 12.5 gallons per minute for 48 hours. 30

8. Measured and simulated drawdown in wells at the Naval Air Warfare Center, West Trenton,

New Jersey, after well 5BR had been pumped at 25 gallons per minute for 42 hours...... 30

9. Simulated water budget at and near the Naval Air Warfare Center, West Trenton, New

Jersey................................................................................................................................. 33

10. Simulated discharge points of ground water at and near contaminated wells at the Naval Air 

Warfare Center, West Trenton, New Jersey....................................................................... 35

IV
CONVERSION FACTORS, AND VERTICAL DATUM

Multiply By To obtain

inch (in.)

inch (in.)

foot (ft)

mile (mi)

square foot (ft2) 

square foot (ft2)

gallon (gal) 

gallon (gal) 

gallon (gal)

gallon per minute (gal/min)

inch per year (in/yr)

cubic fet per day (ft3/d)

gallon per minute per foot [(gal/min)/ft)]

foot per day (ft/d)

foot squared per day (ft2/d)

Length

2.54

25.4

0.3048

1.609

Area

929.0

0.09290

Volume

3.785

0.003785

3.785

Flow rate

0.06309

25.4

0.02832

Specific capacity

0.2070 

Hydraulic conductivity

0.3048

Transmissivity* 

0.09290

centimeter 

millimeter 

meter 

kilometer

square centimeter 

square meter

liter

cubic meter 

cubic decimeter

liter per second 

millimeter per year 

cubic meters per day

liter per second per meter

meter per day

meter squared per day

Sea Levej: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 

(NGVD of 1929) a geodetic datum derived from a general adjustment of the first-order 

level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

Altitude: In this report, "altitude" refers to distance above or below the National Geodetic 

Vertical datum of 1929 (NGVD of 1929)

Latitude. Longitude: In this report, latitude and longitude are referenced to North American Datum of 1927 (NAD of 1927)

*Transmissivitv; The standard unit for transmissivity is cubic foot per day per square foot 

times foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced 

form, foot squared per day (ft2/d), is used for convenience.
Simulated Ground-Water Flow, Naval Air Warfare Center,

West Trenton, New Jersey

by Jean C. Lewis-Brown and Donald E. Rice

ABSTRACT

The effectiveness of ground-water pumping by the use of recovery wells in preventing contaminated ground water 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 ground-water flow. The finite-difference, three-dimensional, porous-medium model 

uses the MODFLOW code to solve the groundwater-flow equation. Ground-water flowpaths from 

areas at and near contaminated well sites for a nopumping 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/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 

ground-water 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-wellpumping 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 

ground water that would otherwise discharge to 

Gold Run.

INTRODUCTION

Volatile organic compounds, predominantly trichloroethylene (TCE) and its degradation 

products cw-l,2-dichloroethylene (cis-DCE) and 

vinyl chloride (VC), have been detected in ground 

water at the Naval Air Warfare Center (NAWC), 

West Trenton, N.J. (International Technology Corporation, 1994). The U.S. Geological Survey 

(USGS) provided technical oversight and assistance to the U.S. Department of the Navy to conduct a hydrogeologic investigation of the NAWC. 

In an earlier phase of the investigation, Lacombe 

(2000, 2001) determined the hydrogeologic framework at the NAWC. The location of the NAWC 

and surrounding area is shown in figure 1. A more 

detailed picture of the NAWC site, including the 

location of buildings and wells, is shown in 

figure 2.
74°51'00" 74°50'00" 74°49'00" 74°48'00" 74°47'00" 74°46'00"

MW101

Area shown in figures 2, 

8, and 10

+ 

5

NJM1H

0 10 20 MILES 

0 10 20 KILOMETERS ST1 

ST2 

ST3

EXPLANATION

Naval Air Warfare Center (NAWC) 

Drainage-basin boundary 

Stream 

Road

Fault trace at land surface 

Extent of model grid 

Corporate boundary 

Base flow measurement station; 

number is station number 

Well outside of NAWC used in model 

calibration and identifier 

Unnamed stream 1 

Unnamed stream 2 

Unnamed stream 3

4,000 FEET

1,000 METERS

Figure 1. Location of the Naval Air Warfare Center and vicinity, Ewing Township, New Jersey, and extent 

of the model grid.
40°16'00" 40°16'15"

EXPLANATION

Contaminant source area ^m

Swamp A __ ., A A Line of section and identifier

Building 11BR. vVell open to bedrock and identifier

Fault zone - shows the fault contact at an altitude 

of 150 feet (approximately land surface)

0 100 200 300 FEET

I.I I I

50 METERS

17S» we|| open to unconsolidated material and identifier

Figure 2. Well locations and line of section A-A'ai the Naval Air Warfare Center, West Trenton, New Jersey.
The phase of the investigation reported 

herein concerns the simulated advective pathways 

of these contaminants and the effectiveness of two 

different recovery-well networks in containing the 

contamination on the NAWC property. The first 

network (hereinafter referred to as "recovery-well 

Network I") was in use from January 1998 through 

November 2000. The recovery wells and pumping 

rates used in this network were well 15BR at 15 

gal/min, well 20BR at 8.5 gal/min, well 22BR at 

4.4 gal/min, well 41BR at 10 gal/min, well 45BR at 

5.1 gal/min, and well 48BR at 13.5 gal/min. Waterlevel data collected in May 2000, after that network was in place for more than 16 months, indicated that some ground water from contaminated 

areas of the NAWC may have been discharging 

into the uppermost 500-ft reach of Gold Run (fig. 

1) (Lacombe, 2001). Consequently, the network 

was modified in December 2000 by replacing well 

41BR with well BRP2. This second network is 

hereinafter referred to as "recovery well network 

II."

Purpose and Scope

The purpose of this report is to illustrate 

simulated ground-water flowpaths from well locations where contaminated ground water has been 

detected at the NAWC. Three scenarios were simulated: no pumping at the NAWC, operation of 

recovery-well network I, and operation of recovery-well network II. The ground-water-flow model 

used to make these simulations is described, as are 

the limitations of using this model to simulate 

movement of water. Results of aquifer testing at 

the NAWC also are included, as are data from 

stream-discharge measurements at and near the 

NAWC.

Hvdrogeologic Framework

The hydrogeologic framework of the rocks 

underlying the NAWC is described by Lacombe 

(2000, 2001) and is summarized here. The NAWC 

is underlain by layers of mudstone, siltstone, and 

sandstone of the Lockatong and Stockton Formations. The Lockatong Formation consists primarily 

of mudstone with smaller amounts of siltstone, 

whereas the Stockton Formation consists primarily

of sandstone with smaller amounts of mudstone. 

The Stockton Formation has some primary porosity in rocks near land surface; the Lockatong Formation, however, has almost no primary porosity, 

so virtually all ground water in the Lockatong Formation is transmitted through fractures and joints 

(Kasabach, 1966).

Lacombe (2000) identified 20 bedding 

units underlying the NAWC. These bedding units 

generally are 20 to 60 ft thick and are differentiated 

primarily on the basis of differences in lithology. 

Each bedding unit is composed of many waterbearing units and semiconfining units. The waterbearing units are areally extensive and have interconnected bedding-plane partings and vertical partings that produce water, whereas the semiconfining 

units have a limited number of partings or poorly 

connected partings that produce little water 

(Lacombe, 2000). The units strike N. 60° E. to N. 

70° E. and dip 15 to 70° NW. The steepest dip 

angles are in rocks near a fault that cuts through the 

layers in the southern part of the NAWC site, and 

the gentlest dip angles are in the rocks most distant 

from the fault. The framework is shown in section 

view in figure 3.

Lacombe (2000) also described fractures 

that are parallel to the strike of the bedding units 

and two sets of near-vertical fractures. The more 

predominant of the vertical sets strikes N. 50° E.; 

the other strikes N. 20° W. Fractures parallel to the 

strike of bedding units (bedding-plane fractures) 

are much more continuous than the vertical fractures. Bedding-plane fractures typically extend the 

full length of any given outcrop. Vertical fractures 

typically extend 100 to 200 ft laterally but only 1 to 

10 ft vertically. Vertical fractures generally are less 

than 5 ft high. The density of vertical fractures is 

about one fracture per 2 ft in sandstone and five 

fractures per 1 ft in mudstone and siltstone 

(Lacombe, 2000).

The fault that cuts through the NAWC 

property is at or near the contact between the 

Stockton and Lockatong Formations. The location 

of the fault initially was described by Lacombe 

(2000). On the basis of additional data, the interpreted location of the eastern part of the fault was 

moved slightly to the south (Lacombe, 2001). The
A 1

180 r

150

STOCKTON FO

CKATONGLFOR

EXPLANATION

Land surface

 - Base of overburden

Top of competent bedrock

Bedding-unit contactLimit of fault zone

Center of fault zone 

L-18 Bedding-unit number as defined by Lacombe (2000) 

20 Model layer number

-250 - -300

200 400

DATUM IS SEA LEVEL

600

DISTANCE, IN FEET 

VERTICAL EXAGGERATION x 1.56

800 1,000 1,125

Figure 3. Geologic section A-A1 showing bedding units and fault zone at the Naval Air Warfare Center, West Trenton, New Jersey. (Line of section in 

figs. 2 and 5. Modified from Lacombe, 2000, section H-H1, fig. 17).
fault strikes about N. 70° E. and dips about 40° SE. 

In rock cores collected from the fault zone, the 

rocks are weathered extensively and fractured, and 

the fractures are completely filled with clay. Dry 

clay as much as 60 ft thick was found in rock cores 

from some parts of the fault zone. Abundant clay in 

the fault zone and the absence of drawdown in 

wells on the south side of the fault when wells on 

the north side were pumped indicate that the fault 

is a boundary for ground-water flow (Lacombe, 

2000).

Near land surface, the rocks are weathered. 

At depths up to about 10 ft below land surface, the 

rocks have weathered completely into unconsolidated clay, silt, and sand. Beneath the unconsolidated deposits, the rocks are highly weathered and 

fractured, and many of the fractures are filled with 

clay and silt derived from the weathering process. 

This weathered zone extends about 15 to 60 ft 

below land surface. Beneath these weathered rocks 

are rocks that appear to be nearly unweathered. 

These unweathered rocks are less fractured than 

the overlying rocks. Fractures in the unweathered 

zone are not filled with weathering products, but 

some are filled with precipitates.

Acknowledgments

We thank Jeff Dale, Ed Boyle, and Kenneth Smith of the U.S. Department of the Navy for 

providing information on wells and culverts, as 

well as historical information regarding the NAWC 

site. We also thank Steven Feldmann and Joel 

Dadepogu of EA Engineering, Science, and Technology, Inc., for providing water-quality data and 

water-level data. The assistance of Nicholas Smith, 

Timothy Oden, and Robert Rosman of the U.S. 

Geological Survey in collecting field data also is 

appreciated.

DESCRIPTION OF 

GROUND-WATER-FLOW 

MODEL

A three-dimensional, finite-difference 

ground-water-flow model was used to simulate 

ground-water flow in and near the NAWC. The 

model used the MODFLOW (McDonald and Harbaugh, 1988) code for the simulation. A particletracking post-processor-MODPATH (Pollock, 

1989) was used to compute flowpaths for nopumping and recovery-well-pumping scenarios.

Simulations of steady-state and transient 

ground-water conditions were made. In steadystate conditions, water levels are static and the 

amount of water stored in the ground-water system 

remains constant. Steady state is approximated 

during periods of average precipitation and when 

other stresses, such as ground-water withdrawals, 

have remained steady over a long period. Three 

steady-state simulations were used in this study. 

One simulation represents a scenario before any 

recovery-well network was installed and no wells 

were pumped at the NAWC. The other two steadystate simulations represent scenarios when a recovery-well network has been operating steadily for at 

least a month. All three simulations include steady 

pumping at the Roller Bearing Corporation (RBC, 

fig. 1) of 3,850 ft3/d.

Transient models are appropriate when the 

amount of water stored in aquifers is changing, as 

happens when precipitation or pumping rates are 

changing. Three transient models were used this 

study for calibration only. Each of these models 

represented aquifer tests at the NAWC in which 

single wells were pumped for 3 days or less.

Grid and Boundary Conditions

The finite-difference model used in this 

study is discretized into interconnected rectangular 

cells, each having its own hydrologic characteristics. The cells form a grid comprising 154 rows, 

160 columns, and 71 layers. The large number of 

layers are needed to simulate the effects of the 

anisotropy caused by the steeply dipping, heterogeneous layers of the ground-water system. Cells 

within the NAWC property are 25 to 50 ft wide and 

25 to 50 ft long. Elsewhere, the cells are larger, 

with a maximum size of 500 by 650 ft near the 

model boundaries. The horizontal discretization of 

the entire model area is shown in figure 4. The horizontal discretization of the model in the vicinity of 

the NAWC showing locations of wells and streams 

is shown in figure 5. The model grid is oriented 

along the approximate strike of the bedding units.
ROW NUMBERS

s a I JHfggss s 8

- 160

	EXPLANATION

 Stream cell

EH] Fault cells at land surface

 Inactive model cells (all layers)

 Stream or river

 Canal

 = Road

 NAWC property boundary

 Boundary of model-grid area 

	shown on subsequent figures 

"- No-flow boundary

ST1 Unnamed stream 1

ST2 Unnamed stream 2

ST3 Unnamed stream 3

0 1,000 2,000 3,000 4,000 FEET

1,000 METERS

Figure 4. Finite-difference grid for the ground-water-flow model, Naval Air Warfare Center (NAWC), West Trenton, 

New Jersey, and vicinity.
70 50

COLUMN NUMBERS 

40 30 20

100

32

100 200 300 400 FEET

i I i i

I |

EXPLANATION 

Stream cell

Cell used to simulate the fault in one or 

more model layer 

Building

Fence and approximate property boundary of the 

Naval Air Warfare Center 

Gold Run (West Branch) 

Line of section 

Well open to bedrock

Well screened in unconsolidated material and /or 

weathered bedrock

100 METERS

Figure 5. Part of the ground-water-flow model grid showing cells used to simulate Gold Run and the fault 

in the area of the Naval Air Warfare Center, West Trenton, New Jersey.

8
The size of cells in the NAWC area was set 

at 25 to 50 ft for two reasons. First, cell spacing in 

the area of interest should be small enough to simulate the shape of cones of depression around 

pumped wells. During the three short-term pumping periods used in calibrating this model, the 

smallest cone of depression was about 300 ft wide. 

Cell spacing of 25 ft is adequate to simulate the 

changes in head over that 300-ft interval. The other 

reason for choosing the 25-ft spacing relates to the 

hydrogeologic framework of the site. When fractured-rock aquifers are simulated as a porous 

medium, the model simulates the net effect of 

many fractures rather than the effect of each individual fracture. Instead of simulating the contorted 

path water actually takes through all the fractures 

within an individual cell, the model simulates only 

a straight-line path from the point where water 

enters a cell to the point where it leaves the cell. 

Consequently, each model cell must contain 

enough fractures so that the net cell-to-cell flow is 

correctly simulated. This model represents rocks in 

which there are at least 12 fractures across each 25- 

ft cell. This large number of fractures per cell helps 

to insure that the net effect of all of the fractures in 

a cell is simulated.

The strata described by Lacombe (2000) as 

bedding units LI3 to L23 are represented in the 

model as layers 19 to 29; strata described by 

Lacombe (2000) as bedding units Sll to S15 are 

represented in the model as continuations of layers 

27 to 31. To avoid confusion for readers familiar 

with Lacombe's (2000) bedding-unit numbers, his 

bedding-unit numbers as well as the model layer 

numbers representing those units will be used for 

the remainder of this report. Because the model 

extends beyond the NAWC area, additional layers 

were needed updip and downdip of the layers 

described by Lacombe (2000). These additional 

model layers are numbers 2 to 18 and 32 to 71. 

Thicknesses of these additional layers range from 

30 to 60 ft, similar to the thicknesses of the bedding units at the NAWC.

Model layer 1 represents the highly 

weathered zone near land surface. The weathered 

zone actually is the shallow part of each bedding 

unit. It is modeled as one continuous layer that is 

parallel to land surface rather than as part of each

bedding unit because its hydrologic properties are 

different from those of the less weathered material 

below it. The top of model layer 1 was set at 8.5 ft 

below land surface on the basis of the mean depth 

to water in shallow wells. Although the transition 

between weathered and unweathered rocks is gradational, the bottom of model layer 1 was set at 25 

ft below land surface on the basis of aquifer-test 

data (discussed in the "Horizontal hydraulic conductivity" section later on). Consequently, model 

layer 1 was assigned a constant thickness of 16.5 ft. 

Although the weathered zone is unconfined, it is 

represented in the model as a confined layer. In the 

model code, the difference between an unconfined 

and confined layer is that, in unconfined layers, 

transmissivity varies with the computed thickness 

of the saturated zone, whereas in confined layers 

transmissivity is constant. On the basis of measured water levels, the mean thickness of the 

weathered zone is 16.5 ft and the standard deviation is 3.3 ft. This small variation in actual saturated thickness does not appreciably affect 

computed flowpaths.

The vertical structure of the model is 

shown in figure 6. The section shown in this figure 

is the part of the model that represents the geologic 

section shown in figure 3.

Each model layer represents a bedding unit 

that is composed of numerous water-bearing units 

and semiconfining units. The impedance to vertical 

flow caused by the semiconfining units is 

represented in the model by assigning low vertical 

hydraulic conductivity to each layer, as described in 

the later section "Vertical hydraulic conductivity".

Representation of bedding units as model 

layers is complicated by the dip of the units. Each 

model layer must be present over the full area of the 

model even though the bedding units may not be. 

Each bedding unit terminates updip at the bottom of 

the weathered zone. Although each bedding unit 

probably extends thousands of feet downdip, 

ground-water flow was assumed to be negligible at 

depths greater than 500 ft below land surface, as 

explained in the later section "Horizontal hydraulic 

conductivity." In order to represent these changes in 

the character of each bedding unit, each model layer 

is made up of three zones. The most downdip of
A 1

WEATHERED ZONE (MdDEL LAYER 1) '

L22 20

PSEUDO-ACTIVE ZONE

1.21 21

ABOVE LAND L20 22

SURFACE L19 23

L18 24

L17 25

L16 26

L15 27

S14 L14 28

S13 *y L13 29

L12 30

L11 31

S10 L10 32

S9 L9 33

L8 34

L7 35

L6 36

L5 37

L4 38

200 400

EXPLANATION

L15 Bedding unit number as 22 Model layer number 

defined by Lacombe (2000)

600 

DISTANCE, IN FEET

800 1,000 1,125

Figure 6. Section showing vertical discretization of ground-water-flow model along geologic section A-A' at the Naval Air Warfare Center, 

West Trenton, New Jersey. (Location of section shown on figs. 2 and 5).
these zones is inactive, representing the part of the 

bedding unit deeper than 500 ft. The next zone is 

active, representing the part of the bedding unit 

between the weathered zone and 500 ft below land 

surface. The next zone is pseudoactive and 

represents the extension of the bedding unit beyond 

the outcrop area and above land surface. This zone 

is composed of pass-through nodes that allow water 

to flow vertically from the weathered zone (model 

layer 1) to the bedding unit that actually lies directly 

under the weathered zone (figs. 3 and 6).

The model extends as far as 1.8 mi beyond 

the NAWC property. In areas outside of the NAWC, 

the hydrogeologic framework was assumed to be 

the same as at the NAWC. No hydrogeologic data 

outside NAWC were collected by Lacombe; 

however, Vecchioli and Palmer (1962), in their 

description of the geology of Mercer County, did 

not note any variation in the framework.

The model boundaries were chosen to 

ensure that the entire flowpath of any water that 

passes through the NAWC property is included in 

the model. Most of the model boundaries represent 

natural hydrologic boundaries.The western model 

boundary is the Delaware River. The north-central, 

northeastern, eastern, and southern boundaries are 

defined by the boundaries of the drainage basins of 

Villa Victoria Brook, West Branch Shabakunk 

Creek, and Gold Run (fig. 1). The northwestern 

model boundary is a line extending along strike 

from the northernmost point of the Villa Victoria 

Brook drainage basin to the Delaware River. It 

passes through the drainage basins of the two 

relatively small streams referred to as unnamed 

streams 1 and 2 (fig. 1). This line represents the 

hypothetical flowpath of water that recharges at the 

northernmost point of the Villa Victoria drainage 

basin and flows west-southwest to the unnamed 

streams or the Delaware River.

Hvdrologic Parameters

Hydrologic parameters used in the digital 

model were based on field measurements made in 

the model area. Parameters that cannot be measured 

directly initially were estimated on the basis of 

values used in digital models of similar areas. 

During model calibration (discussed later in the

"Calibration" section), all of the parameters were 

adjusted within reasonable ranges.

Horizontal Hydraulic Conductivity

Horizontal hydraulic conductivity was 

measured at 72 well sites at the NAWC between 

March 15 and July 15, 1997, by means of slug 

testing. The testing was done by instantaneous!]' 

placing a solid-body slug into the well to raise the 

water level and by observing the rate of recover)' of 

the water level. The slug then was instantaneously 

removed from the well to lower the water level, and 

the rate of recovery was again observed. The 

change in water levels was measured with a 

pressure transducer in the well and recorded with a 

data logger.

Slug testing is an expeditious method of 

measuring horizontal hydraulic conductivity in 

contaminated areas. The minimal disturbance to the 

flow system in the aquifer minimizes the potential 

for moving contaminated water into 

uncontaminated areas. Also, because no water is 

removed from the well, disposal of contaminated 

water is unnecessary. Because slug testing displa~.es 

only a small amount of water (less than 1 gallon 

during the tests at NAWC), however, the area of 

influence of the test is limited to the area 

immediately surrounding the well screen or open 

interval probably less than a 5-ft radius and tl ?. 

value of hydraulic conductivity derived from 

analyzing the results of a slug test applies only to 

that small area. Consequently, the purpose of slug 

testing at the NAWC site was to gain information of 

the variability of hydraulic conductivity at the site 

and to determine whether any spatial trends in 

hydraulic conductivity are present.

The slug tests in the shallow wells (less 

than 25 ft deep) were analyzed with the method 

presented by Hvorslev (1951). In this method, it is 

assumed that the aquifer is unconfined, 

homogeneous, and infinite in extent. The 

assumption that the aquifer is unconfined probably 

is valid for these shallow wells. The assumptions 

that the aquifer is homogeneous and infinite 

probably are valid over the small area influenced by 

the slug test.

11
The analytical method of Cooper and 

others (1967) was used to calculate horizontal 

hydraulic conductivity for wells 25 ft deep or 

deeper. The Cooper method is based on three 

assumptions: (1) the aquifer is confined and has an 

infinite areal extent, (2) the aquifer is 

homogeneous, isotropic, and of uniform thickness 

over the area influenced by the slug test, and (3) the 

tested well completely penetrates the aquifer. These 

assumptions probably are met to an acceptable 

degree. It is probable that most of the wells greater 

than 25 ft deep are in parts of the aquifer confined 

by either the overlying weathered zone or an 

overlying semiconflning unit. The assumptions that 

the aquifer has an infinite areal extent and that it is 

homogeneous, isotropic, and of uniform thickness 

probably are valid over the small area influenced by 

each slug test.

The assumption that the well opening fully 

penetrates the aquifer is probably met for the wells 

25 ft deep or deeper. The reason for this 

requirement in the Cooper method is to minimize 

the influence of parts of the aquifer that are above 

or below the well opening. The Lockatong and 

Stockton Formations consist of many thin waterbearing units alternating with thin semiconflning 

units. In wells 25 ft deep or deeper, where the rocks 

are less fractured and less weathered than shallower 

rocks, is it likely that one of the thin semiconfining 

units is at or near the top and bottom of each well 

opening and that the full-penetration assumption is 

adequately met.

At six wells tested at the NAWC, water 

levels changed very slowly after the slug was 

inserted or removed from the well. The water level 

in these wells changed much more slowly than in 

the well where the lowest hydraulic conductivity, 

0.13 ft/d, was measured. Consequently, the 

hydraulic conductivity at the six slower-responding 

wells was probably 0.01 ft/d or lower; therefore, a 

value of O.OOlft/d for hydraulic conductivity is 

estimated for these wells.

Two deep wells, well 43BR and well 44BR, 

were not slug tested. The water level in these wells 

had not recovered to reasonable static levels during 

the 2-month period after the wells had been 

installed and developed. Because of the slow

recovery rates in these wells, a hydraulic 

conductivity of 0.001 ft/d is estimated forthe?e 

wells for purposes of determining trends in 

hydraulic conductivity over the NAWC area. Six 

wells at the NAWC site were not slug tested 

because they were inaccessible, and 12 wells were 

not tested because they were installed after shig 

testing was completed. Results of the slug tests and 

the wells arbitrarily assigned a hydraulic 

conductivity of 0.001 ft/d are listed in table 1.

The slug-test data indicate that hydraulic 

conductivity is a function of depth below land 

surface, as is evident from table 2. The medieri 

hydraulic conductivity of all wells at depths l~.ss 

than 26 ft is 2.6 ft/d, whereas the median hydraulic 

conductivity at depths from 26 to 50 ft below land 

surface is 11.3 ft/d. The lower hydraulic 

conductivities in the weathered zone probably 

result from the presence of clay and silt in fractures.

The median hydraulic conductivity a* 

depths between 51 and 100 ft below land surface is 

lower than in the 26- to 50-ft range. Althougl only 

six wells are deeper than 100 ft, the data from those 

wells indicate that hydraulic conductivity continues 

to decrease at depths greater than 100 ft. A previous 

study (Lewis-Brown and Jacobsen, 1995) of 

specific-capacity data from wells throughout the 

southern part of the Newark Basin in New Jersey 

reported similar results. In the 348 wells open to the 

Lockatong Formation, specific capacity per foot of 

open hole decreases by two orders of magnitude 

(from 0.012 to 0.00011 [(gal/mm)/ft]/ft) as well 

depth increases from 75 ft to greater than 300 ft. In 

271 wells open to the Stockton Formation, specific 

capacity per foot of open hole decreases by about 

one order of magnitude (from 0.032 to 0.00393 

[(gal/min)/ft]/ft) as well depth increases frorr 75 ft 

to over 300 ft. This decrease in hydraulic 

conductivity may indicate the presence of fever 

fractures and fewer interconnected fractures with 

depth. Knopman (1990) suggests the alternatVe 

explanation that deep wells may be complete'l in 

areas where the yield at shallow depths is poor, and 

holes were drilled deeper in search of better 3'ields. 

Although Knopman's explanation may be 

applicable to water-supply wells, it does not explain 

the decrease in hydraulic conductivity found in 

observation wells at the NAWC. Therefore,

12
Table 1 . Horizontal hydraulic conductivity at, and well construction data for, wells at and near the Naval Air Warfare Center, West 

Trenton, New Jersey

Latitude and longitude are referenced to the North American Datum of 1927; nm, hydraulic conductivity was not measured or estimated at this well site; 

est .001, hydraulic conductivity estimated to be 0.001 feet per day at this well site; na, not applicable; --, data not available; WZ, weathered zone; 

L. Lockatong Formation; S. Stockton Formation; USGS, U.S. Geological Survey]

Well 

name

USGS 

well 

number

New 

Jersey 

permit 

number

Latitude Longitude

Altitude of 

land 

surface 

(feet 

above 

sea

level)

Depth of open 

interval (feet 

below land 

surface)

Top

Bottom

Primary 

bedding 

unit 

(Lacombe, 

2000)

Model 

layer 

number

Formation

Horizontal 

hydraulic 

conductivity 

(feet per 

day)

WELLS AT THE NAVAL AIR WARFARE CENTER

IS

2S

4S

6S

us

12S

13S

14S

15S

16S

17S

18S

19S

20S

24S

25S

26S

27S

28S

29S

SOS

31S

32S

33S

34S

35S

36S

37S

38S

39S

210492

210493

210494

210495

210496

210497

210498

210499

210500

210501

210502

210503

210504

210505

210507

210508

210509

210510

210511

210512

210513

210601

210418

210419

210420

210421

210549

210528

210600

210529

27-09892-3

27-09895-8

27-09894-0

27-09893-1

27-09888-5

27-09889-3

27-09890-7

27-09891-5

27-09918-1

27-09919-9

27-09920-2

27-09921-1

27-09922-9

27-09923-7

27-09927-0

27-09925-3

27-09926-1

27-10960-7

27-10962

27-10982-8

27-10964

27-10963

27-12423

27-12424

27-12425

27-12426

27-12680

27-12681

27-12682

27-12683

401611

401607

401605

401604

401612

401612

401613

401614

401608

401611

401609

401616

401615

401615

401615

401614

401614

401612

401611

401609

401609

401609.06

401606

401600

401603

401609

401613

401605

401610

401605

744849

744849

744851

744847

744835

744833

744832

744831

744848

744844

744843

744848

744847

744848

744850

744849

744850

744836

744834

744834

744835

744836.38

744853

744846

744838

744833

744844

744837

744834

744846

150.87

149.82

150.21

147.88

159.82

158.82

159.35

163.89

149.72

150.25

149.99

169.74

169.88

169.13

169.38

168.80

169.13

162.26

157.30

156.95

158.68

150.72

153.55

155.15

144.82

156.15

170.61

148.34

150

150.05

3

3

3

4

8

10.5

10

14.5

3

2

3

6

7

4

5.5

3.5

6.3

11.2

10

10

7.5

10

5

6

8

5

3

6

2

3

13

8

7

10

23

20.5

20

24.5

13

12

8

16

17

19

15.5

18.5

16.3

21.2

25

20

17.5

20

15

16

18

15

13

16

7

13

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

L

L

L

S

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

S

S

L

L

S

S

S

S

S

L

S

0.2

3.5

nm

10.2

1.7

3.6

35.6

2.6

3.7

5.9

1.6

8.1

11.1

est .001

2.5

.21

1.4

1.5

11.8

13.9

34.3

1.6

3.8

.3

.13

7.9

nm

.22

1.8

.6

13
Table 1 . Horizontal hydraulic conductivity at, and well construction data for, wells at and near the Naval Air Warfare Center, West 

Trenton, New Jersey-Continued

Latitude and longitude are referenced to the North American Datum of 1927; nm, hydraulic conductivity was not measured or estimated at this we'? site; 

est .001, hydraulic conductivity estimated to be 0.001 feet per day at this well site; na, not applicable; --, data not available; WZ, weathered zone; 

L. Lockatong Formation; S. Stockton Formation; USGS, U.S. Geological Survey]

Well 

name

40S

41S

42S

BRP1

BRP2

BRP3

2BR

3BR

4BR

5BR

6BR

7BR

8BR

9BR

10BR

11BR

12BR

13BR

14BR

15BR

16BR

17BR

18BR

19BR

20BR

21 BR

22BR

23BR

24BR

25BR

USGS 

well 

number

210532

210531

210539

210537

210422

210423

210545

210535

210530

210424

210425

210514

210515

210516

210426

210427

210517

210518

210519

210520

210521

210522

210523

210524

210525

210526

210527

210428

210429

210430

New 

Jersey 

permit 

number

27-12684

27-12685

27-12686

27-09937-7

27-12419

27-12420

27-10961-5

27-10965

27-11938

27-11939

27-11940

27-11941

27-11942

27-11948

27-11949

27-11950

27-11951

27-11952

27-11953

27-11943

27-11954

27-11944

27-11955

27-11956

27-11945

27-11957

27-11946

27-11947

27-12408

27-12409

Latitude

401606

401606

401610

401609

401605

401607

401612

401609

401606

401605

401603

401606

401610

401612

401619

401614

401614

401614

401614

401607

401609

401608

401625

401621

401605

401614

401604

401606

401606

401607

Longitude

744851

744850

744834

744845

744850

744851

744834

744834

744845

744849

744839

744848

744849

744849

744848

744831

744834

744845

744837

744850

744843

744844

744840

744845

744851

744850

744845

744845

744848

744850

Altitude of 

land 

surface 

(feet 

above 

sea

level)

150.00

150.48

157.88

150.72

150.36

150.52

158.23

156.88

150.%

149.83

143.72

149.64

151.97

153.12

168.80

164.60

162.77

170.25

167.13

149.72

150.41

150.63

176.68

171.55

150.76

168.93

148.36

150.89

150.17

149.60

Depth of open 

interval (feet 

below land 

surface)

Top

3

3

3.6

20

25

25

40

35

24

69

52

38

32

19

63

55

56.5

48

42

26

40

19

27

43

28

50

24

65

80

75

Bottom

13

13

13.6

60

45

40

60

45

39

84

77

53

57

44

88

75

71.5

63

67

41

65

44

52

58

43

65

49

90

95

100

Primary 

bedding 

unit 

(Lacombe, 

2000)

WZ

WZ

WZ

L20

L17

L19

L20

S15

L17

L15

Sll

L18

L22

L23

--

L21

L22

L23

L22

L19

L19

L19

--

~

L17

L23

S13

L16

L16

LI 8

Model 

layer 

number

1

1

1

22

25

23

22

27

25

27

31

24

20

19

18

21

20

19

20

23

23

23

15

16

25

19

29

26

26

24

Formation

L

L

S

L

L

L

L

S

L

L

S

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

S

L

L

L

Horizontal 

hydraulic 

conductivity 

(feet per 

day)

0.9

.5

12.3

11.3

3.3

140

1.36

13

7.4

9.5

2.6

nm

3.1

.22

1.8

190

4.3

1.1

.37

nm

2.4

18

est .001

3.6

49

18

13

est .002

nm

est .002

14
Table 1. Horizontal hydraulic conductivity at, and well construction data for, wells at and near the Naval Air Warfare Conter, West 

Trenton, New Jersey-Continued

Latitude and longitude are referenced to the North American Datum of 1927; nm, hydraulic conductivity was not measured or estimated at this well site; 

est .001, hydraulic conductivity estimated to be 0.001 feet per day at this well site; na, not applicable; --, data not available; WZ, weathered zone; 

L, Lockatong Formation; S, Stockton Formation; USGS, U.S. Geological Survey]

Well 

name

26BR

27BR

28BR

29BR

30BR

31BR

32BR

33BR

34BR

35BR

36BR

37BR

38BR

39BR

40BR

41BR

42BR

43BR

44BR

45BR

46BR

47BR

48BR

49BR

50BR

51BR

52BR

53BR

54BR

55BR

USGS 

well 

number

210431

210432

210433

210417

210434

210435

210436

210437

210438

210439

210440

210441

210442

210534

210533

210541

210551

210546

210547

210542

210543

210538

210540

210536

210544

210548

210576

210581

210575

210582

New 

Jersey 

permit 

number

27-12410

27-12412

27-12413

27-12427

27-12428

27-12429

27-12430

27-12414

27-12415

27-12416

27-12417

27-12418

27-12411

27-13976

27-13977

27-13978

27-13979

27-13980

27-13981

27-13982

27-13983

27-14146

27-14149

27-14148

27-14147

27-14150

27-15277

27-15279

27-15278

27-15275

Latitude

401605

401604

401604

401609

401608

401609

401609

401607

401603

401600

401608

401605

401609

401607

401606

401610

401607

401613

401613

401610

401611

401609

401610

401609

401612

401613

401604.02

401609.92

401607.74

401613.10

Longitude

744851

744847

744844

744849

744845

744836

744833

744853

744853

744846

744851

744834

744846

744842

744853

744843

744842

744841

744841

744851

744847

744845

744836

744839

744830

744833

744845.07

744840.96

744835.87

744850.09

Altitude of 

land 

surface 

(feet 

above 

sea

level)

150.7

147.90

148.20

150.80

150.40

151.65

156.60

153.72

151.22

155.50

155.33

143.75

150.60

150.05

154.04

150.29

159.81

169.02

168.38

159.50

150.72

150.84

160.83

150.15

158.27

159.47

148.30

148.42

153.94

164.02

Depth of open 

interval (feet 

below land 

surface)

Top

80

65

76

85

85

35

40

30

35

31

102

60

100

68

95

85

120

385

305

185

196

3

82

42

60

86

155

95

175

135

Bottom

95

80

91

100

110

45

55

45

48

47

125

75

115

88

120

110

140

410

330

210

221

18

100

60

80

96

180

120

200

160

Primary 

bedding 

unit 

(Lacombe, 

2000)

L15

L13

S12

L21

L18

L15

S14

L21

L15

S10

L19

Sll

L19

L15

L18

L19

L13

L13

L15

L19

L19

WZ

L17

L17

L17

L20

~

L19

~

L21

Model 

layer 

number

27

29

30

21

24

27

28

21

27

32

23

31

23

27

24

23

29

29

27

23

23

1

25

25

25

22

32

23

30

21

Formation

L

L

S

L

L

L

S

L

L

S

L

S

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

Horizontal 

hydraulic 

conductivity 

(feet per 

day)

.27

e*t 0.001

.13

11

.22

65.

5.4

227

34.0

.45

.71

.32

est .001

23

.84

47

1.3

est .001

est .001

12.6

nm

15

73

9.5

14

140

nm

nm

nm

nm

15
Table 1. Horizontal hydraulic conductivity at, and well construction data for, wells at and near the Naval Air Warfare Center, West 

Trenton, New Jersey-Continued

Latitude and longitude are referenced to the North American Datum of 1927; nm, hydraulic conductivity was not measured or estimated at this w^ll site; 

est .001, hydraulic conductivity estimated to be 0.001 feet per day at this well site; na, not applicable; --, data not available; WZ, weathered zone; 

L, Lockatong Formation; S, Stockton Formation; USGS, U.S. Geological Survey]

Well 

name

56BR

57BR

58BR

59BR

11MW1

12MW1

35MW1

35MW2

USGS 

well 

number

210579

210577

210578

210573

210570

210580

210572

210571

New 

Jersey 

permit 

number

27-15276

27-15269

27-15270

~

27-14458

27-15414

27-14459

27-14460

Latitude

401607.66

401605.98

401606.24

401605.74

401606.89

401608.60

401615.89

401615.48

Longitude

744849.93

744854.68

744857.81

744855.84

744835.78

744834.65

744848.97

744849.50

Altitude of 

land 

surface 

(feet 

above 

sea

level)

150.36

151.42

154.89

152.54

153.15

156.52

169.91

157.31

Depth of open 

interval (feet 

below land 

surface)

Top

140

12

85

56

8

5

7

6.5

Bottom

165

27

110

80

22

15

25

22.5

Primary 

bedding 

unit 

(Lacombe, 

2000)

L17

WZ

L18

L19

WZ

WZ

WZ

WZ

Model 

layer 

number

25

1

24

23

1

1

1

1

Formation

L

L

L

L

S

S

L

L

Horizontal 

hydraulic 

conductivity 

(feet per 

day)

nm

nm

nm

nm

nm

nm

nm

nm

WELLS OUTSIDE NAVAL AIR WARFARE CENTER PROPERTY

MW101

MW3

MW4

MJM5

NJM6

NJM7

NJM11

Civil Defense

MW7-17

MW7-80

MW7-250

MW32-25

MW32-57

MW35-25

MW35-57

MW44-30

MW44-80

MW48-25

MW48-63

210470

210586

210583

210584

210587

210588

210585

210028

210595

210594

210593

210592

210591

210589

210590

210598

210599

210596

210597

27-13573

27-09331-0

24-09332-8

-

~

..

~

27-04214

27-11594

27-14055

27-11484

27-11612

27-11659

27-11614

-

~

--

-

27-11705

401658

401458

401448

401455

401501

401504

401457

401553

401532

401532

401532

401526

401526

401523

401523

401540

401540

401534

401534

744843

744925

744929

744855

744905

744902

744903

745012

744851

744851

744851

744841

744841

744856

744856

744835

744835

744834

744834

201.80

91.0

51.5

73.42

96.59

95.78

90.16

122.99

126.8

126.5

127.0

109.9

110.0

118.8

118.7

118.2

118.2

112.5

112.5

2.17

44

9

-

-

..

-

33.0

7

60

240

13

37

8

37

10

65

10

38.0

22.2

80

19

24.8

29.7

30

25.4

300.0

17

80

250

25

57

25

57

30

80

25

63.0

-

-

-

--

--

-

--

-

--

..

-

-

~

-

--

--

-

..

1

54

1

1

1

1

1

18-23

1

45

49

1

48

1

48

1

44

1

46

L

S

S

S

S

S

S

L

S

S

S

S

S

S

S

S

S

S

S

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

nm

16
Table 2. Horizontal hydraulic conductivity as a function of depth below land surface, Naval Air Warfare Center, 

West Trenton, New Jersey

[na, not applicable]

Depth of center of screen or 

open interval 

(feet below land 

surface)

0 - 25 (weathered zone)

26-50

51- 100

101 - 300

301 - 500

0 - 25(weathered zone)

26-50

51- 100

101- 300

301 - 500

Numbc 

of well

32

17

24

5

2

23

13

21

5

2

Horizontal hydraulic

jr .. . . . Horizontal h (feet per day)

Range

0.001

.001-

.001-

.001-

.001-

.001-

.001-

.001-

.001-

.001-

-35.6

227

190

126

.001

35.6

227

190

12.6

.001

Median

ALL WELLS

2.6

11.3

3.1

.40

.001

LOCKATONG FORMATION

2.5

11.3

4.3

.84

.001

ydraulic conductivity used in model 

(feet per day)

na

na

na

na

na

2.5

11.3

4.0

.4

.001

All Lockatong 64 

All fault cells 0

.001 - 227 3.2

na na

FAULT ZONE

.001

STOCKTON FORMATION

North Central (columns 111- 

(columns 28-79) (columns 80-1 10) * "ifiQ^

0 - 25 (weathered 

zone)

26-50

51-100

101 - 300

301 - 500

All Stockton

9

4

3

0

0

16

.13-34.3

.45 - 13

.13-2.6

~

-

.13-34.3

7.9

9.2

.32

-

-

4.0

1.25

1.13

.375

.0375

.001

1.75

1.75

.625

.0625

.001

5.0

5.0

1.75

.175

.001

17
for purposes of the ground-water-flow model used 

in this study, it was assumed that hydraulic 

conductivity does decrease with depth and that, at 

depths below 500 ft, hydraulic conductivity 

virtually is zero.

The hydraulic conductivity at depths less 

than 26 ft is more uniform than in deeper wells. This 

greater uniformity in the weathered zone probably 

is a result of more homogeneous conditions because 

fractures are filled with silt and clay. The higher 

variability below the weathered zone, where 

fractures are open, is not surprising, given the 

nature of the fractured-rock aquifer. Wells in which 

high hydraulic conductivities (greater than 25 ft/d) 

were measured probably are completed where one 

or more vertical fractures intersect bedding-plane 

fractures, whereas wells with low hydraulic 

conductivities (less than 0.01 ft/d) probably are 

between vertical fractures. This high degree of 

variability is not represented in the model. Rather, 

the rock units were modeled as porous media, with 

fractures being the pores and each cell containing 

many fractures. The hydraulic conductivity of a 

given cell is a function of the net effect of all 

interconnected fractures in the cell.

On the basis of the hydraulic conductivity 

data, the bottom of the weathered zone was set in 

the model at 25 ft below land surface. In the model, 

hydraulic conductivity was initially set at the 

median values obtained from slug testing. On the 

basis of calibration, the hydraulic conductivities 

were adjusted slightly to achieve the optimum 

match between measured and simulated groundwater levels and base flow in streams. The final 

values used in simulations and flow-path analyses 

are listed in table 2. A complete description of the 

model-calibration process is given later in the 

"Calibration" section.

Hydraulic conductivity data are sparse for 

the model area beyond the NAWC. Various regional 

investigations have reported that, in general, the 

Stockton Formation is more transmissive than the 

Lockatong Formation (Vecchioli and Palmer, 1962; 

Kasabach, 1966; Houghton, 1990). Data from an 

aquifer test at the General Motors Corporation (now 

Delphi, fig. 1) indicate that the hydraulic 

conductivity of the weathered zone in that area

ranges from 8.0 to 31.0 ft/d (Roy F. Weston, Inc., 

1989). Data from an aquifer test at the Roller 

Bearing Corporation (RBC, fig. 1) indicate thrt the 

median hydraulic conductivity in that area is about 

41.0 ft/d in the weathered zone and about 20 fi/d in 

the 60- to 80-ft-depth range (Rare Earth 

Envirosciences, Inc., 1992). During each of these 

aquifer tests, less than 10 gal/min of water was 

pumped, so only a small area around the screen of 

the pumped well was influenced by the pump;ng. 

Therefore, the hydraulic conductivity at each of the 

aquifer-test sites could be estimated by dividing the 

reported transmissivity by the length of the screen 

of the pumped well.

The data for the Stockton Formation 

indicate that the hydraulic conductivity of the 

formation is higher in the southern part of the study 

area than it is in the northern part of the area, near 

the contact with the Lockatong Formation. The 

contact between the Stockton and Lockatong 

Formations is gradational, so a gradual change in 

hydraulic properties with distance from the contact 

is not surprising.

The horizontal hydraulic conductivity of 

the fault zone was assumed to be extremely low on 

the basis of evidence that only a small amount of 

ground water moves across the fault, as described in 

the earlier section "Hydrogeologic framework." 

During model calibration, the best match between 

measured and simulated heads and base flow was 

achieved when the horizontal hydraulic 

conductivity of the fault zone was set to 0.001 ft/d.

During model calibration, the best match 

between measured and simulated heads and tose 

flow was achieved when the Stockton formation 

was divided into three zones. The northern zone 

includes the NAWC area and comprises mode1 

columns 28-79, the central zone includes the 

General Motors area and comprises model columns 

80 to 110, and the southern zone includes the B oiler 

Bearing Corporation area and comprises model 

columns 111 to 160. The horizontal hydraulic 

conductivities used in the final calibrated model in 

the Stockton Formation are listed in table 2.

Cells in the pseudoactive zone described in 

the earlier section "Grid and boundary conditions"

18
were assigned a horizontal hydraulic conductivity 

of zero. Only vertical movement of water is 

represented in this zone because the purpose of this 

zone is to allow water to move directly from the 

weathered zone down to whatever model layer 

represents the bedding unit directly below the 

weathered zone.

Vertical Hydraulic Conductivity

Vertical hydraulic conductivity cannot be 

readily measured in the field, especially in fractured 

rock. Vertical hydraulic conductivity is assumed to 

be lower than horizontal hydraulic conductivity 

because horizontal fractures are more numerous 

than vertical fractures per unit volume of aquifer, 

and the horizontal fractures are more continuous. 

The vertical hydraulic conductivity of each model 

cell initially was set at one-tenth the horizontal 

hydraulic conductivity of the cell. Although the 

fraction was adjusted during model calibration, the 

best match between measured and simulated 

ground-water levels and stream discharge was 

achieved when the vertical hydraulic conductivity 

was set at one-tenth the horizontal hydraulic 

conductivity. Vertical conductance, the parameter 

actually used in the model, was calculated in a 

computer program (not part of the model) by 

dividing the vertical hydraulic conductivity at each 

cell by the thickness of the bedrock unit represented 

by the cell.

Cells in the pseudoactive zone were 

assigned a vertical conductance of 100 ft/d to insure 

instantaneous movement of water through the 

pseudoactive zone from the weathered zone to the 

model layer that represents the bedding unit directly 

beneath the weathered zone.

The rate of flow between a stream and the 

aquifer is affected primarily by the vertical 

hydraulic conductivity and thickness of the 

streambed material. Because the vertical hydraulic 

conductivity of a streambed is difficult to measure 

in the field, this parameter was estimated on the 

basis of reasonable hydraulic conductivity values of 

the streambed material. Streambed material in the 

study area consists of silty sand and fractured 

bedrock with silty sand filling the fractures. Heath

(1983) estimated the horizontal hydraulic 

conductivity of silty sand to range from about 0.1 to 

30 ft/d. The bed of the Delaware River consists of 

about 6 in. of silty sand overlying fractured 

bedrock. The beds of the tributaries to the Delaware 

River in the study area typically have no sedirrents 

overlying the bedrock. Consequently, the bed 

thickness is greater and the streambed conductance 

(the product of the vertical hydraulic conductivity 

of the streambed and the area of the stream within a 

model cell divided by the thickness of the 

streambed) is lower in the river than in the 

tributaries. The best model calibration was 

achieved when the vertical hydraulic conductivity 

of all streambed material was set at 0.5 ft/d, th~. 

thickness of the riverbed was set at 1 ft, and the 

thickness of the beds of the tributaries was set at 

0.1 ft.

Areal Recharge

Effective areal recharge rates were 

estimated from stream base-flow data collected in 

the model area. These data are summarized in table 

3. Areal recharge is affected by land use. 

Agricultural, residential, commercial, and 

industrial areas may all receive different amour ts of 

recharge because each has different proportiors of 

impermeable cover and is subject to different 

irrigation practices. The predominant land use in 

each model cell and in each drainage basin was 

determined by means of data in a geographic 

information system (GIS) coverage. By comparing 

predominant land use and measured base flow in 

each drainage basin, recharge rates were estimated 

to be 11 in/yr in agricultural and undeveloped rreas 

and 5 in/yr in residential, commercial, and 

industrial areas. As a comparison, average animal 

precipitation measured at Trenton, New Jersey, is 

42 inches.

Specific Yield and Storage 

Coefficient

Specific yield is used to define the storage 

capacity of model layer 1, the weathered zone, 

which is assumed to be unconfined. Specific yield 

is defined as the ratio of the volume of water that

19
Table 3. Base flow and ground-water runoff in streams at or near the Naval Air Warfare Center, West Trentcn, New Jersey 

[mi2, square miles; ft3/s, cubic feet per second; in/yr, inches per year; nm, not measured]

Station Location of station 

number (see fig. 1)

1 Mouth of unnamed tributary to the Delaware and 

Raritan Feeder Canal at

Wilburtha, NJ. (unnamed

stream 3)

2 Villa Victoria Brook, near

mouth, at Villa Victoria 

Academy

3 West Branch of Gold Run,

just west of Naval Air 

Warfare Center

4 Gold Run below culverts

containing west and east 

branches of Gold Run just

east of Naval Air Warfare

Center

5 Gold Run upstream from

Tributary 1

6 Tributary 1 to Gold Run at

mouth

Predominant 

land use(s)

Agricultural

Residential

Agricultural

Residential

Industrial

Industrial

Industrial

Residential

Industrial

Drainage 

area 

(mi2)

0.29

1.10

.21

.50

.93

.11

Date of 

measurement

08/20/96

05/16/97

09/04/97

09/29/98

05/17/00

08/20/96

05/16/97

09/04/97

09/29/98

05/17/00

08/20/96

05/16/97

09/04/97

09/29/98

05/17/00

08/20/96

05/16/97

09/04/97

09/29/98

05/17/00

08/20/96

05/16/97

09/04/97

09/30/98

05/17/00

08/20/96

05/16/97

09/04/97

09/30/98

05/17/00

Base 

flow 

(ft3/s)

0.383

.0027

.00004

0

.25

.492

.829

.313

.160

.489

0

0

0

0

0

.09

nm

.203

nm

nm

.53

.457

.177

.082

.52

.117

.16

.117

.009

nm

Mean 

groundwater 

runoff at 

station 

(in/yr)

10

5.6

0

4.0

5.2

12

20
Table 3. Base flow and ground-water runoff in streams at or near the Naval Air Warfare Center, West Trenton, New JerseyContinued

[mi2, square miles; ft3/s, cubic feet per second; in/yr, inches per year; nm, not measured]

Station Location of station 

number (see fig. 1)

7 Gold Run upstream from 

Tributary 2

8 Tributary 2 to Gold Run at 

mouth

9 Gold Run just upstream 

from Delaware and Raritan Feeder Canal

10 West Branch of Shabakunk Creek at Olden 

Avenue

Predominant 

land use(s)

Industrial 

Commercial

Commercial

Commercial 

Undeveloped 

Residential

Residential

Commercial

Drainage Date of 

area measure- 

(mi2) ment

1.36 08/20/96 

05/16/97

09/04/97

09/30/98

05/17/00

.39 08/20/96 

05/16/97

09/04/97

09/04/98

05/17/00

1.98 08/20/96 

05/16/97

09/04/97

09/04/98

05/17/00

2.74 08/20/97

05/16/97

09/04/97

09/29/98

05/17/00

Base 

flow 

(ft3/s)

0.740 

.918

.348

.105

nm

.176 

.112

.088

0

nm

1.44 

1.51

.668

.227

1.30

nm

2.04

1.28

.153

.978

Mean 

groundwater 

runoff at 

station 

(in/yr)

5.3

3.3

7.1

5.5

21
can be drained from a rock to the volume of the 

rock. In the calibrated model, the specific yield of 

the weathered zone was estimated to be 0.15.

The storage term used in the model for 

layers below the weathered zone is storage 

coefficient, which is specific storage of the aquifer 

multiplied by the thickness of the aquifer. Specific 

storage is the amount of water released from or 

taken into storage per unit volume of aquifer per 

unit change in head. Rima and others (1962) found 

that the storage coefficient of the upper part of the 

Stockton Formation in southeastern Pennsylvania is 

about 1.37xlO"4 . Because the water-bearing 

properties of the Lockatong Formation are lower 

than that of the Stockton Formation, the storage 

coefficient of the Lockatong Formation was 

assumed to be less than 10~4 . During model 

calibration, specific storage was set at 4.0x10"5 in 

all units below the weathered zone. Specific storage 

was multiplied by the thickness of each model cell 

to determine the storage coefficient of each cell.

Simulation of Discharge Features

Features in the model area that allow water 

to leave the ground-water system include streams 

and pumped wells. These features were included in 

the model by use of the "River" and "Wells" 

modules of MODFLOW.

Streams

Streams in the model area include the 

Delaware River, Villa Victoria Brook, Gold Run, 

unnamed streams 1, 2, and 3, and West Branch 

Shabakunk Creek (fig. 1). The position of these 

streams relative to the model grid was determined 

by overlaying the model grid on topographic maps 

by means of a GIS. Field inspection of all streams 

except Gold Run indicate that the start of flow of 

each stream during base flow actually is about 

1,500 ft upstream from the mapped start of flow. 

The start of visible flow of Gold Run is at a point 

east of and across Parkway Avenue from the 

NAWC property at base-flow measurement site 4 

(fig. 1). Historical maps (New Jersey Department of 

Environmental Protection, 1913) show that before 

the NAWC began operations in the mid- 1950's, the

start of flow of Gold Run was approximately 2CO ft 

upstream from base-flow measurement site 3 (fig. 

1). Since the early 1940's, a culvert under Parkway 

Avenue accepts ground-water discharge between 

base-flow measurement sites 3 and 4 (Lacombe, 

2000). In the model, stream cells represent the 

culvert and the 200-ft reach above measurement site 

3.

The streams were simulated with the 

"River" module of MODFLOW. This module treats 

the streams as head-dependent boundaries. 

McDonald and Harbaugh (1988) define the flow 

between a stream and the aquifer in a given model 

cell according to the equation

Q KSLW,, . , , = £ (hnv-haq),

ms

where

Q is the flow between the stream and the 

aquifer, taken as positive if it is directed 

into the aquifer, in cubic feet per day;

Ks is the vertical hydraulic conductivity 

of the streambed material, in feet per 

day;

L is the length of the reach within tH 

given model cell, in feet;

W is the width of the stream, in feet;

ms is the thickness of the streambed, in 

feet;

hriv is the head in the stream, in feet; and 

haq is the head in the aquifer, in feet.

The length and width of the Delaware River 

and the length of the smaller streams within each 

model cell were estimated by intersecting GIS 

stream coverages with model-grid coverages. The 

width of the smaller streams was estimated at 2 ft on 

the basis of measurements at a few representative 

sites. The thickness of the streambeds of the river 

and its tributaries was set at 1.0 ft and 0.1 ft, 

respectively.

22
The head in the stream at each model cell 

containing a stream was determined by (1) using 

topographic maps to determine the altitude of 

streams at points where topographic contours cross 

streams and then (2) interpolating between those 

points.

Pumped Wells

Most of the model simulations made as a 

part of this study included pumpage at one or more 

well. All of these wells are open to only one 

bedding unit except for well BRP1, which is open to 

the bottom 4 ft of the weathered zone (model layer 

1; see fig. 6), all 21 ft of bedding unit 20 (model 

layer 22), and 15 of the 60 ft of bedding unit 19 

(model layer 23). In the model run in which well 

BRP1 was pumped, all of the pumpage was applied 

to bedding unit 20 because the well is open to only 

small parts of the adjacent bedding units.

Calibration

Measured ground-water levels and base 

flow in Villa Victoria Brook, unnamed stream 3, 

Gold Run, and West Branch Shabakunk Creek were 

used in calibrating the steady-state model. 

Measured drawdown was used to calibrate the 

transient model. The initial estimates of hydrologic 

parameters described in previous sections were 

adjusted within reasonable limits until 65 percent of 

simulated water levels were within 5 ft of measured 

water levels; simulated base flow at each 

measurement site was within 17 percent of the 

mean measured base flow at the site; and 70 percent 

of simulated drawdowns were within 1 ft of 

measured drawdown.

Static Ground-Water Levels

Ground-water levels measured at the 

NAWC on May 18, 2000, and at other wells in the 

model area on May 26, 2000, were used in 

calibrating the steady-state model. When the 

measurements at the NAWC were made on May 18, 

the six wells in recovery-well network I had been 

pumped almost continuously at about constant rates 

for at least 1 month preceding the measurements. 

No rainfall was recorded at a precipitationmeasurement site 9 mi north of the NAWC from

May 15 through 18, 2000 (National Oceanic and 

Atmospheric Administration, 2000). Althougl 0.88 

in. of precipitation was recorded on May 14, waterlevel data from continuous recorders at the NAWC 

indicate that water levels had returned to static 

levels. Therefore, water levels were static or rearly 

so when they were measured on May 18, 2000. In 

contrast, water levels measured at locations outside 

of the NAWC on May 26 probably were not static. 

Rainfall totaled 3.35 in. during May 19 through 25. 

At eight wells where water levels were measured on 

May 18 and again on May 26, the water level rose 

between 1.21 and 9.99 ft during the 8-day period 

between the two measurements. In order to use the 

water-level data measured on the later date fcr 

model calibration, the water levels measured on 

May 26 were decreased by 2.48 ft (the median 

change in water levels at the eight wells measured 

both days). The measured and simulated water 

levels are listed in table 4. Of the 89 simulated water 

levels in wells at the NAWC, 86 are within 10 ft of 

the measured water levels, and 63 are within 5 ft. 

The average absolute difference between simulated 

and measured water levels at the NAWC is 4.32 ft.

At the 19 wells outside the NAWC 

property, 15 of the simulated water levels are vithin 

10 ft of the adjusted measured water levels, and 7 

are within 5 ft. Most of the hydrogeologicframework data and hydraulic-conductivity data 

used to determine hydraulic parameters for the 

entire model area were collected at the NAWC site. 

If the estimated hydraulic parameters for arer s 

outside of the NAWC differ greatly from actual 

values, the result could be poorer agreement 

between measured and simulated water levels in 

wells outside of the NAWC, as opposed to wells at 

the NAWC.

Some of the wells used for calibration are 

open to more than one bedding unit. In this care, the 

following guidelines were used to arrive at the 

simulated head in the well. If the well opening 

straddles two or more bedding units, then the 

average water level in all units that are at least half 

included by the well opening was used as the 

simulated water level. If the well opening straddles 

two units but does not include more than half the 

thickness of either one, then the well was ass; gned 

to the layer containing the greater part of the open 

interval of the well.

23
Table 4. Measured and simulated water levels in wells at and near the Naval Air Warfare Center, West Trenton, New Jersey, 

May 18 and 26, 2000

{Water levels are referenced to the National Geodetic Vertical Datum of 1929; --, no data; WZ, Weathered Zone; L, Lockatong; S, StockDn; R, water level 

recorded by continuous water-level recorder on 5/26/00 at 1200 noon; P, pumped well; adj, adjusted to approximate 5/18/00 conditions by subtracting 2.48 feet 

from water level measured on 5/26/00]

Water level (feet above sea level)

Well name

Date of 

water-level 

measurement

Primary 

bedding unit 

number 

(Lacombe, 

2000)

Model 

layer 

number

Bedrock 

formation

Measured Simulated

Difference 

(simulated - 

measured)

Note

WELLS AT THE NAVAL AIR WARFARE CENTER

IS

4S

6S

us

12S

14S

16S

17S

18S

19S

20S

24S

25S

26S

27S

28S

29S

30S

31S

32S

33S

34S

35S

36S

37S

38S

39S

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/1 8/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00 

5/26/00

5/18/00

5/1 8/00

5/18/00 

5/26/00

5/18/00

5/18/00

5/18/00

5/18/00

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

L

L

S

L

L

L

L

L

L

L

L

L

L

L

L

L

S

S

L

L

S

S

S

S

S

L

S

146.79

144.14

140.48

148.46

148.00

148.40

146.78

144.91

156.86

156.37

156.31

157.15

156.15

155.85

148.72

148.08

147.23

146.44

144.55

143.84 

145.99

142.90

136.10

145.27 

149.69

157.29

139.91

145.32

138.95

149.38

143.89

142.88

152.14

152.43

154.45

150.83

147.20

154.62

153.83

154.10

153.41

152.75

152.63

151.48

150.81

150.57

149.26

147.89

146.01

142.60

142.38

153.01

151.10

145.52

151.07

142.21

2.59

-.25

2.40

3.68

4.43

6.05

4.05

2.29

-2.24

-2.54

-2.21

-3.74

-3.40

-3.22

2.76

2.73

3.34

2.82

3.34

2.17

-.30

6.28

7.74

-6.19

5.61

5.75

3.26

. 

-

-

--

--

~

-

-

-

-

__

~

-

-

-

_

-

--

P.

..

R

-

-

__

24
Table 4. Measured and simulated water levels in wells at and near the Naval Air Warfare Center, West Trenton, New Jersey, 

May 18 and 26, 2000-Continued

{Water levels are referenced to the National Geodetic Vertical Datum of 1929; --, no data; WZ, Weathered Zone; L, Lockatong; S, Stockton; R, water level 

recorded by continuous water-level recorder on 5/26/00 at 1200 noon; P, pumped well; adj, adjusted to approximate 5/18/00 conditions by subtracting 2.48 feet 

from water level measured on 5/26/00]

Water level (feet above sea level)

Well name

40S

42S

11MW1

12MW1

35MW1

35MW2

BRP1

BRP2

BRP3

2BR

3BR

4BR

5BR

6BR

7BR

8BR

9BR

10BR

11BR

12BR

13BR

14BR

15BR

16BR

17BR

18BR

20BR

21BR

Date of 

water-level 

measurement

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00 

5/26/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00 

5/26/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

Primary 

bedding unit 

number 

(Lacombe, 

2000)

WZ

WZ

WZ

WZ

WZ

WZ

L20

L17

L19

L20

S15

L17

L15

S11

L18

L22

L23

--

L21

L22

L23

L22

L19

L19

L19

..

L17

L23

Model 

layer 

number

1

1

1

1

1

1

22

25

23

22

27

25

27

31

24

20

19

18

21

20

19

20

23

23

23

15

25

19

Bedrock 

formation

L

S

S

S

L

L

L

L

L

L

S

L

L

S

L

L

L

L

L

L

L

L

L

L

L

L

L

L

Measured

142.81

142.89

145.26

145.95

157.33

156.79

144.57

141.51

143.90 

146.28

147.69

145.18

142.28

142.20

140.33

141.74

146.41

149.43

158.21

147.78

147.43 

148.64

149.84

149.29

131.26

140.32

142.77

160.29

137.18

155.87

Simulated

144.06

150.24

148.38

151.20

154.33

153.93

147.34

143.09

143.57

152.17

150.24

145.73

144.18

141.22

144.68

148.95

150.92

155.98

154.23

154.53

152.85

153.74

138.07

146.61

146.62

161.72

139.68

152.27

Difference 

(simulated - 

measured)

1.25

7.35

3.12

5.25

-3.00

-2.86

2.77

1.58

-.33

4.48

5.05

3.45

1.98

.89

2.94

2.54

1.49

-2.23

6.45

7.10

3.01

4.45

6.81

6.29

3.85

1.43

2.50

-3.60

Note

-

-

--

--

-

__

--

-

R

--

_

~

--

-

-

_

~

~

--

R

_

P

-

_

P

_.

25
Table 4. Measured and simulated water levels in wells at and near the Naval Air Warfare Center, West Trentcn, New Jersey, 

May 18 and 26, 2000-Continued

{Water levels are referenced to the National Geodetic Vertical Datum of 1929; , no data; WZ, Weathered Zone; L, Lockatong; S, Stockton; R, water level 

recorded by continuous water-level recorder on 5/26/00 at 1200 noon; P, pumped well; adj, adjusted to approximate 5/18/00 conditions by subtracting 2.48 feet 

from water level measured on 5/26/00]

Water level (feet above sea level)

Well name

22BR

23BR

24BR

26BR

27BR

28BR

29BR

30BR

31BR

32BR

33BR

34BR

35BR

36BR

37BR

38BR

39BR

40BR

41BR

42BR

45BR

47BR

48BR

49BR

50BR

51BR

52BR

Date of 

water-level 

measurement

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00 

5/26/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00 

5/26/00

5/18/00

5/18/00 

5/26/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00 

5/26/00

5/18/00

Primary 

bedding unit 

number 

(Lacombe, 

2000)

S13

L16

L16

L15

L13

S12

L21

L18

L15

S14

L21

L15

-

L19

S11

L19

L15

L18

L19

L13

L19

WZ

L17

L17

L17

L20

-

Model 

layer 

number

29

26

26

27

29

30

21

24

27

28

21

27

32

23

31

23

27

24

23

29

23

1

25

25

25

22

32

Bedrock 

formation

S

L

L

L

L

S

L

L

L

S

L

L

S

L

S

L

L

L

L

L

L

L

L

L

L

L

L

Measured

136.80

142.01

141.98

143.36

140.65

141.10

144.55

139.49

141.32

145.08

144.32 

146.57

143.09

143.25

141.26

137.84

134.59 

144.58

142.06

142.41 

145.00

135.00

142.07

111.98

144.45

103.30

139.09

146.88

146.00 

148.93

141.51

Simulated

116.97

145.64

144.97

143.90

144.46

137.61

147.93

146.36

147.25

151.92

146.16

144.80

142.43

144.63

144.90

147.00

146.45

144.34

144.51

146.24

119.44

147.21

137.31

147.34

151.78

152.37

139.44

Difference 

(simulated - 

measured)

-19.83

3.63

2.99

.54

3.81

-3.49

3.38

6.87

5.93

6.84

1.84

1.71

-.82

3.37

7.06

12.41

4.39

1.93

9.51

4.17

7.46

2.76

-34.01

8.25

4.90

6.37

-2.07

Notes

P

-

-

--

--

..

--

--

--

-

R

-

-

-

-

R

R

P

-

P

-

P

--

-

R

_.

26
Table 4. Measured and simulated water levels in wells at and near the Naval Air Warfare Center, West Trenton, New Jersey, 

May 18 and 26, 2000-Continued

{Water levels are referenced to the National Geodetic Vertical Datum of 1929; -, no data; WZ, Weathered Zone; L, Lockatong; S, Steel ton; R, water level 

recorded by continuous water-level recorder on 5/26/00 at 1200 noon; P, pumped well; adj, adjusted to approximate 5/18/00 conditions by subtracting 2.48 feet 

from water level measured on 5/26/00]

Water level (feet above sea level)

Well name

53BR

54BR

55BR

56BR

57BR

58BR

59BR

Date of 

water-level 

measurement

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

5/18/00

Primary .. 

bedding unit "odel

number ' *» /i _ num- (Lacombe,

2000) oe

L19 23

30

L21 21

L17 25

WZ 1

L18 24

L19 23

Bedrock 

formation

L

L

L

L

L

L

L

Measured Simulated

140.91

140.65

149.93

143.03

144.06

143.78

143.10

147.80

147.80

150.20

144.15

145.85

145.42

145.25

Difference 

(simulated - 

measured)

6.89

7.15

.27

1.12

1.79

1.64

2.15

Not^

-

-

~

-

-

WELLS OUTSIDE NAVAL AIR WARFARE CENTER PROPERTY

MW101

Civil Defense

MW3

MW4

NJM5

NJM6

NJM7

NJM11

MW7-17

MW7-80

MW7-250

MW32-25

MW32-57

MW35-25

MW35-57

MW44-30

MW44-80

MW48-25

MW48-63

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

5/26/00

1

18-24

54

1

1

1

1

--

1

45

49

1

48

1

48

1

44

1

49

L

L

S

S

S

S

S

S

S

S

S

S

S

S

S

S

S

S

S

193.25

104.32

43.85

38.87

61.57

67.28

73.72

67.12

117.86

115.00

103.76

93.10

92.57

102.07

101.96

108.52

104.31

94.48

94.18

197.91

70.09

77.71

51.56

51.03

76.31

75.42

63.93

114.50

113.87

111.03

98.56

98.23

104.21

103.24

114.41

113.79

103.18

104.02

4.66

-34.23

33.86

12.69

-10.54

9.03

1.70

-3.19

-3.36

-1.13

7.27

5.46

5.66

2.14

1.28

5.89

9.48

8.70

9.84

adj

adj

adj

aij

adj

adi

adj

adi

adi

adj

adi

adj

adj

adj

adj

adj

adj

sdj

£dj

27
Base Flow to Streams

The steady-state model simulating the 

scenario when recovery-well network I was 

operating also was calibrated to mean measured 

base flow in streams in the model area. Simulated 

base flow to streams was calculated by use of the 

computer program Zonebudget (Harbaugh, 1990). 

The measured and simulated base flow at the mouth 

of each stream is listed in table 5. All simulated base 

flows are within 17 percent of the mean measured 

base flow. Given the measurement error inherent in 

base-flow measurements, the model calibration is 

considered to be acceptable with regard to its 

simulation of ground-water discharge to streams.

Drawdown During Short-Term 

Pumping

The transient model was calibrated to 

drawdown that resulted from pumping three 

different wells for short periods of time. Well If BR 

was pumped at a rate of 25 gal/min for 72 hour;? on 

April 8-11, 1993 (International Technology 

Corporation, 1994); well BRP1 was pumped at a 

rate of 12.5 gal/min for 48 hours on August 9-11, 

1995; and well 5BR was pumped at a rate of 25 gal/ 

min for 42 hours on August 15-17, 1995 (EA 

Engineering, Science, and Technology, Inc., 19%). 

Measured drawdown in wells near these pumped 

wells ranges from 0 to 11.50 ft. Simulated 

drawdown at 70 percent of the wells are within 1 ft 

of the measured drawdown. The difference between 

measured and simulated drawdown ranges from 

0.01 to 3.26 ft. The measured and simulated 

drawdowns for each well are listed in tables 6, 7, 

and 8.

Table 5. Measured and simulated base flow to streams at and near the Naval Air Warfare 

Center, West Trenton, New Jersey

[ft /s, cubic feet per second; frVd. cubic feet per day]

Station 

number 

(shown on 

figure 1)

1

2

9

10

Mean measured base flow

Location of 

station ft3/s n3/d

Mouth of 0.103 8,900

unnamed tributary to the Delaware and

Raritan Feeder

Canal at Wilburtha,NJ. (unnamed stream 3)

Villa Victoria .457 39,490

Brook, near

mouth, at Villa

Victoria Academy

Gold Run 20 1.029 88,910

feet upstream

from Delaware

and Raritan

Feeder Canal

West Branch of 1.113 96, 160

Shabakunk

Creek at Olden

Avenue

Simulated base flow

Percent 

ft3/d of measured

9,010 101

33,400 85

73,500 83

97,590 101

28
Table 6. Measured and simulated drawdown in wells at the Naval Air Warfare Center, West Trenton, 

New Jersey, after well 15BR had been pumped at 25 gallons per minute for 72 hours

Well 

name

BRP1

BRP2

BRP3

4BR

5BR

6BR

7BR

8BR

15BR

16BR

17BR

20BR

22BR

23BR

24BR

25BR

26BR

27BR

28BR

29BR

30BR

33BR

34BR

36BR

38BR

Bedding 

unit number 

(Lacombe, 

2001)

L20

L17

L19

L17

L15

S11

L18

L22

L19

L19

L19

L17

S13

L16

L16

L18

L15

L13

S12

L21

L18

L21

L15

L19

19

Model layer 

number

22

25

23

25

27

31

24

20

23

23

23

25

29

26

26

24

27

29

30

21

24

21

27

23

23

Bedrock 

formation

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Stockton

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Stockton

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Stockton

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Measured 

drawdown 

(feet)

1.50

.87

2.56

.74

.45

.00

1.48

.82

11.50

1.52

1.12

.97

.00

.63

.72

1.69

.51

.12

.00

1.99

1.19

2.31

.49

2.95

3.87

Simulated 

drawdown 

(feet)

0.45

1.12

3.50

.64

.78

.08

1.80

.36

12.80

.37

.52

.96

.05

.64

1.04

3.31

.76

.59

.05

.57

.59

.59

.41

2.54

.61

Difference 

between measured and 

simulated 

drawdown 

(simulated - 

measured, in 

feet)

-1.05

.25

.94

-.10

.33

.08

.32

-.48

1.30

-1.15

-.60

-.01

.05

.01

.32

1.62

.25

.47

.05

-1.42

-.60

-1.72

-.08

-.41

-3.26

29
Table 7.

Trenton,

Well 

name

17S

4BR

8BR

16BR

17BR

23BR

29BR

30BR

38BR

Table 8.

Trenton,

Well 

name

32S

41S

4BR

7BR

20BR

22BR

23BR

24BR

25BR

26BR

27BR

33BR

Measured and simulated drawdown in wells at the Naval Air Warfare Center, West 

New Jersey, after well BRP1 had been pumped at 12.5 gallons per minute for 48 hours

Bedding 

unit number 

(Lacombe, 

2001)

Weathered 

Zone

L17

L22

L19

L19

L16

L21

L18

L19

Model layer 

number

1

25

20

23

23

26

21

24

23

Bedrock 

formation

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Measured 

drawdown 

(feet)

0.67

.40

.91

1.83

1.56

.15

1.82

.40

1.07

Simulated 

drawdown 

(feet)

0.56

.62

.35

1.94

2.48

.56

.52

1.56

3.17

Difference

between 

measured 

and simulated drawdown

(feet)

-0.11

.22

-.56

.11

.92

.41

-1.30

1.16

2.10

Measured and simulated drawdown in wells at the Naval Air Warfare Center, West 

New Jersey, after well 5BR had been pumped at 25 gallons per minute for 42 hours

Bedding 

unit number 

(Lacombe, 

2001

Weathered 

Zone

Weathered 

Zone

L17

L18

17

S13

L16

L16

18

L15

L13

21

Model layer 

number

1

1

25

24

25

29

26

26

24

27

29

21

Bedrock 

formation

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Stockton

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Lockatong

Measured 

drawdown 

(feet)

0.00

.00

1.09

.73

.91

.09

2.03

4.03

.00

7.05

.27

.00

Simulated 

drawdown 

(feet)

0.09

.23

.80

.93

1.95

.03

1.22

1.66

.92

4.22

2.87

.25

Difference

between 

measured 

and simulated drawdown

(feet)

0.09

.23

-.29

.20

1.04

-.06

-.81

-2.37

.92

-2.83

2.60

.25

30
Sensitivity Analysis

The purpose of a sensitivity analysis is to 

quantify the uncertainty in the calibrated model. In 

the model used in this study, uncertainty is created 

by estimation of the horizontal and vertical 

hydraulic conductivity, storage coefficient, and 

recharge rates. A sensitivity analysis was performed 

by systematically changing the values of these 

parameters within hydrologically reasonable 

ranges. Although the model results also may be 

sensitive to boundary conditions, grid 

discretization, and spatial and temporal variations 

of parameters, sensitivity testing of these factors is 

impractical. Results of the sensitivity analysis are 

reported as the effects of the parameter changes on 

the simulated water levels, drawdown, and base 

flow to streams. Because an important use of the 

model is to test the effectiveness of recovery-well 

networks in capturing contaminated water 

(discussed in the section "Simulated ground-water 

flowpaths" later on), the effects of parameter 

changes on the number of contaminated well 

locations captured by recovery wells also were 

computed.

Results of the sensitivity analysis are 

shown in figure 7. Changes in hydraulic properties 

were applied equally to all model cells, and changes 

in recharge were applied equally to all active cells 

in layer 1 (fig. 4). These parameters were varied 

over the range from one-half to two times the 

calibrated value. The steady-state model was most 

sensitive to recharge and least sensitive to vertical 

hydraulic conductivity. The transient model was 

most sensitive to horizontal hydraulic conductivity 

and least sensitive to storage coefficient.

Simulated Water Budget

Simulated water budgets for three steadystate simulations are listed in table 9. One 

simulation represents a scenario when no wells are 

pumped at the NAWC; the other two simulations 

represent a scenario when recovery-well networks I 

and II are in operation. All three simulations include 

steady pumping of 3,850 ft3/d at the Roller Bearing 

Corporation (RBC, fig. 1). The budgets, which were 

calculated with the computer program Zonebudget 

(Harbaugh, 1990), indicate that most of the water

pumped at the NAWC recovery wells represents 

base flow diverted from Gold Run, Villa Victoria 

Brook, and West Branch Shabakunk Creek in nearly 

equal amounts. Small amounts of base flow also are 

diverted from the Delaware River and unnamed 

streams 2 and 3.

The budgets also indicate that the change 

from recovery-well network I to recovery-well 

network II (a change from pumping well 41BR to 

pumping well BRP2) achieved the desired result of 

preventing contaminated ground water in the 

southwestern part of the NAWC property from 

discharging to Gold Run. The simulated water 

budgets indicate that recovery-well network F 

diverts about 290 ft3/d more than network I does 

from Gold Run. Calculations of ground-water 

discharge to discrete reaches of Gold Run indicate 

that this additional diversion of 290 ft3/d represents 

all of the ground water that was flowing from the 

southwestern part of the NAWC property into the 

uppermost 500-ft reach of Gold Run. The change 

from pumping well 41BR to pumping well BPP2 

also causes 290 ft3/d more ground water from the 

NAWC property to discharge to West Branch 

Shabakunk Creek. This additional discharge to 

West Branch Shabakunk Creek probably is not a 

threat to the water quality in the creek for two 

reasons: (1) ground water flowing from the NAWC 

property to the West Branch of Shabakunk Cr^ek 

originates in and flows through the eastern part of 

the NAWC property, which is far less contaminated 

than the southwestern part of the property 

(Lacombe, 2000), and (2) the distance from tire 

NAWC property to the nearest point of the West 

Branch of Shabakunk Creek is approximately 

3,000 ft, whereas Gold Run flows through N/ WC 

property.

Most of the water that enters the weatl ?.red 

zone (model layer 1) as recharge flows downward 

into the competent bedrock layers (model layers 2 

to 71). When no wells at NAWC are pumped, 78 

percent of recharge flows into the competent 

bedrock; when recovery-well network I or II is 

pumped, 80 percent of recharge flows into the 

competent bedrock. Except for water that flows to 

pumped wells, all the water that flows downward 

into competent bedrock eventually flows back into 

the weathered zone and leaves the ground-water 

system as base flow to streams.

31
0.5 1.0 1.5 2.0 

MULTIPLICATION FACTOR FROM CALIBRATED VALUES

0.5 1.0 1.5 2.0 

MULTIPLICATION FACTOR FROM CALIBRATED VALUES

Transient model, simulation of aquifer test 

atwelMSBR .

0.5 1.0 1.5 2.0 

MULTIPLICATION FACTOR FROM CALIBRATED VALUES

0.5 1.0 1.5 2.0 

MULTIPLICATION FACTOR FROM CALIBRATED VALUES

EXPLANATION

[H Aquifer horizontal hydraulic conductivity

A Aquifer vertical hydraulic conductivity

O Recharge

 Storage coefficient

Figure 7. Sensitivity of simulated ground-water levels, base flow, drawdown, and capture of 

contaminated water by recovery wells to variations in the values of model parameters, 

Naval Air Warfare Center, West Trenton, New Jersey.

32
Table 9. Simulated water budget at and near the Naval Air Warfare Center, West Trenton, New Jersey

[ft3/d, cubic feet per day; na, not applicable]

WATER INTO GROUND- WATER

SYSTEM

Recharge

Total into ground- water system

WATER OUT OF GROUNDWATER SYSTEM

Base flow to Delaware River

Base flow to Villa Victoria Brook

Base flow to Gold Run

Base flow to West Branch Shabakunk Creek

Base flow to unnamed stream 1

Base flow to unnamed stream 2

Base flow to unnamed stream 3

Flow to pumped wells (includes 

3,850 fr/d at Roller Bearing Corporation)

Total out of ground- water system

Difference (in - out)

Budget with no

recovery wells 

pumping 

(ftVd)

348,320

348,320

111,340

36,710

76,870

101,500

1,180

7,790

9,040

3,850

348,280

0

Budget with recovery well

network 1 operating

Flow 

(ftVd)

348,320

348,320

111,150

33,400

73,470

97,580

1,180

7,780

9,000

14,730

348,300

20

Base flow to

streams

diverted by 

pumping at 

NAWC

recoverywell network

(tf/d)

na

na

190

3,310

3,400

3,920

0

10

40

na

10,870

na

Budget with recovery-wc'l

network II operating

Flow 

(tf/d)

348,320

348,320

111,160

33,390

73,180

97,870

1,180

7,780

9,000

14,730

348,290

30

Base flow to

streamr

diverted by 

pumping at 

NAWC

recoverywell network

(tf/d)

r*

r*

1FO

3,370

3,6?0

3,6?0

0

10

AO

r*

10,870

r*

Model Limitations

Ground-water flow in fractured rocks is too 

complex to be succinctly simulated in a digital 

model. By making various necessary simplifying 

assumptions, however, one can construct a model 

that is capable of approximating flow through the 

fractured rock units.

The model used in this study is based on the 

assumption that the fault found at the NAWC 

property extends from the western to eastern model 

boundaries and that the fault permeability is very 

low throughout the entire fault zone. No data are 

available that indicate whether the lowpermeability assumption is valid throughout the

entire model area. As a result of this assumption, the 

model simulates little ground-water flow across the 

fault anywhere in the modeled area. It is possible, 

however, that, if the fault is more permeable cr not 

present outside the NAWC area, large amount- of 

water could flow across the fault.

Another important assumption 

incorporated into the model is that ground-wa*er 

flow is negligible at depths below 500 ft. If this 

assumption is flawed, then some of the simukted 

flowpaths especially paths beginning at deep 

wells could be shallower than actual flowpaths, 

and the discharge points of these flowpaths could be 

inaccurately simulated by the model.

33
The primary intended use of this model is 

to simulate ground-water flow and to estimate the 

effectiveness of two recovery-well networks at the 

NAWC. Most of the data used to calibrate the model 

are from the NAWC property. Therefore, the model 

should not be used to obtain detailed simulations of 

ground-water conditions outside of the NAWC 

area.

The model represents a porous medium, 

and the pores in this hydrogeologic setting consist 

of a network of fractures in three orientations that 

are at right angles to and interconnected with each 

other. Each model cell represents a volume of space 

that contains many fractures. The model calculates 

the flowpath from one cell to the next by simulating 

the net effect of all of the fractures in that interval. 

Therefore, the model cannot simulate flowpaths on 

a scale smaller than the cell size. In the NAWC area, 

this limitation means that flowpaths within areas 

smaller than a 25-ft by 25-ft square cannot be 

simulated.

Only advective movement of contaminants 

can be simulated by the model. The model does not 

simulate density-driven movement, dispersion, 

diffusion, dilution, or biological or chemical 

degradation of contaminants.The effects of densitydriven movement, dispersion, diffusion, and 

dilution widen the contaminant flowpaths, whereas 

degradation shortens them.

Simulated Ground-Water 

Flowpaths

The flowpaths of contaminated water at the 

NAWC property under conditions when no 

recovery wells are pumped at the NAWC and when 

recovery-well networks I and II are used were 

estimated by means of the steady-state, groundwater-flow model. The purpose of the no-pumping 

simulation is to estimate the paths of contaminated 

ground water before either recovery-well network 

was installed. The purpose of the pumping 

simulations is to assess the effectiveness of the 

networks. The flowpaths and discharge points 

simulated by the model are approximate because of 

the limitations of modeling flow in fractured rock, 

as described in the preceding section; however,

digital modeling provides a closer approximation to 

actual flowpaths than simpler methods, such a^ 

water-level gradients, because many of the 

complexities caused by the fractured-rock 

hydrogeologic framework are incorporated into the 

digital model.

Simulation l--No Pumping

This simulation depicts ground-water flow 

at times when no wells are pumping and reflects 

conditions before the recovery-well network I was 

installed. The results of this simulation are listed in 

table 10 and shown in figure 8. The discharge point 

of water at and near each contaminated well at the 

NAWC is listed in table 10. For purposes of tl is 

report, a well is contaminated if any sample 

collected from the well contained TCE, DCE, or 

vinyl chloride in concentrations above the Ne^v 

Jersey maximum contaminant level, which is 1,10, 

and 2 micrograms per liter, respectively.

In simulation 1, ground water at and near 

most of the contaminated well sites in the southern 

part of the NAWC flows into the west branch of 

Gold Run. This water does not cross the fault; water 

from wells on the north side of the fault flows westsouthwest or southwest and discharges to the reach 

of Gold Run that is on the north side, whereas water 

at and near the nine wells on the south side of the 

fault remains on the south side and discharger into 

the Gold Run reach carried in the culvert beneath 

Parkway Avenue. Water at and near the three 

easternmost contaminated wells (14S, 11BR and 50 

BR) flows generally east and discharges to West 

Branch Shabakunk Creek, also without crossir g the 

fault. Water at and near five contaminated we?Is in 

the northwesternmost part of the NAWC and one 

relatively deep well (56BR, 165 ft deep) farther 

southwest flows generally southwest to Villa 

Victoria Brook, also remaining on the north side of 

the fault. Water at and near seven contaminated 

wells on the north side of the fault remains or the 

north side and discharges into the Delaware Fiver. 

Two of these wells (45BR and 46BR) are more than 

200 ft deep; their flowpaths remain deep and pass 

under Villa Victoria Brook before discharging into 

the river. The other five wells whose flowpaths 

discharge into the river (US, 2BR, 49BR, 51BR,

34
Table 10. Simulated discharge points of ground water at and near contaminated wells at the Naval Air Warfare 

Center (NAWC), West Trenton, New Jersey

[WZ, weathered zone; gal/min, gallons per minute; L, Lockatong; S, Stockton; -, no data)]

Stream or pumped well where water discharges from ground-water system

Well name

2S

6S

us

12S

13S

14S

15S

24S

25S

28S

31S

37S

39S

41S

11MW1

12MW1

35MW1

BRP1

BRP2

BRP3

2BR

4BR

5BR

7BR

8BR

9BR

11BR

Primary 

bedding 

unit 

(Lacombe, 

2000b)

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

WZ

L20

L17

L19

L20

L17

L15

L18

L22

L23

L21

Model 

layer 

number

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

22

25

23

22

25

27

24

20

19

21

Bedrock 

formation

L

S

L

L

L

L

L

L

L

L

L

S

S

L

S

S

L

L

L

L

L

L

L

L

L

L

L

Simulation 1 

(no pumpage at the 

NAWC)

Gold Run (west branch)

Gold Run (west branch)

Delaware River

Gold Run (main stem)

Gold Run (main stem)

West Branch Shabakunk Creek

Gold Run (west branch)

Villa Victoria Brook

Villa Victoria Brook

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Villa Victoria Brook

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Delaware River

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Villa Victoria Brook

West Branch Shabakunk Creek

Simulation 2, 

recovery-well 

network I 

(well 15BR pumped at 

15 gal/min; 20BR at 8.5 

gal/min; 22BR at 4.4 

gal/min; 41 BR at 10 

gal/min; 45BR at 5.1 

gal/min; 48BR at 13.5 

gal/min)

Well 15BR

Well 22BR

Well 48BR

Well 48BR

Well 48BR

Well 48BR

Well 15BR

Well 15BR

Well 15BR

Well 48BR

Well 48BR

Gold Run (west branch)

Well 22BR

Well 20BR

Gold Run (west branch)

Gold Run (west branch)

Well 15BR

Well 15BR

Well 20BR

Well 15BR

Well 48BR

Well 20BR

Well 20BR

Well 15BR

Well 15BR

Well 15BR

Well 48BR

Simulation 3, 

recovery-welf 

network II 

(well 15BR pumped at 

15 gal/min; 20BRr* 8.5 

gal/min; 22BR at 4.4 

gal/min; 45BR at 5.1 

gal/min; 48BR at 13.5 

gal/min; BRP2 a* 10 

gal/min)

Well 15BR

Well 22BR

Well 48BR

Well 48BR

Well 48BR

Well 48BR

Well 15BR

Well 15BR

Well 15BR

Well 48BR

Well 48BR

Gold Run (west branch)

Well 22BR

Well BRP2

Gold Run (west branch)

Gold Run (west bnnch)

Well 15BR

Well 15BR

Well BRP2

Well 15BR

Well 48BR

Well BRP2

Well BRP2

Well 15BR

Well 15BR

Well 15BR

Well 48BR

35
Table 10. Simulated discharge points of ground water at and near contaminated wells at the Naval Air Warfare 

Center (NAWC), West Trenton, New Jersey-Continued

[WZ, weathered zone; gal/min, gallons per minute; L, Lockatong; S, Stockton; --, no data)]

Stream or pumped well where water discharges from ground-water system

Well name

12BR

15BR

16BR

17BR

20BR

21BR

22BR

23 BR

24BR

25BR

27BR

29BR

30BR

31BR

36BR

37BR

38BR

40BR

41BR

45BR

46BR

47BR

48BR

49BR

50BR

51BR

54BR

56BR

Primary

bedding 

unit 

(Lacombe, 

2000b)

L22

L19

L19

L19

L17

L23

S13

L16

L16

L18

L13

L21

L18

L15

L19

Sll

L19

L18

L19

L19

L19

WZ

L17

L17

L17

L20

--

L17

Model 

layer 

number

20

23

23

23

25

19

29

26

26

24

29

21

24

27

23

31

23

24

23

23

23

1

25

25

25

22

30

25

Bedrock 

formation

L

L

L

L

L

L

S

L

L

L

L

L

L

L

L

S

L

L

L

L

L

L

L

L

L

L

L

L

Simulation 1 

(no pumpage at the 

NAWC)

Delaware River

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Villa Victoria Brook

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Gold Run (west branch)

Delaware River

Delaware River

Gold Run (west branch)

Gold Run (west branch)

Delaware River

West Branch Shabakunk Creek

Delaware River

Gold Run (west branch)

Villa Victoria Brook

Simulation 2, 

recovery-well

network I

(well 15BR pumped at 

15 gal/min; 20BR at 8.5 

gal/min; 22BR at 4.4 

gal/min; 41 BR at 10

gal/min; 45BR at 5.1

gal/min; 48BR at 13.5

gal/min)

Well 48BR

Well 15BR

Well 41BR

Well 15BR

Well 20BR

Well 45BR

Well 22BR

Well 20BR

Well 20BR

Well 15BR

Well 22BR

Well 15BR

Well 15BR

Well 48BR

Well 15BR

Gold Run (west branch)

Well 15BR

Well 20BR

Well 41BR

Well 45BR

Well 45BR

Well 15BR

Well 48BR

Well 48BR

Well 48BR

Well 48BR

Well 22BR

Well 15BR

Simulation 3, 

recovery-well

network II

(well 15BR pumpfi at 

15 gal/min; 20BR at 8.5 

gal/min; 22BR at 4.4 

gal/min; 45BR at 5.1

gal/min; 48BR at 13.5

gal/min; BRP2 at 10

gal/min)

Well 48BR

Well 15BR

Well BRP2

Well BRP2

Well 20BR

Well 45BR

Well 22BR

Well BRP2

Well BRP2

Well 15BR

Well 22BR

Well 15BR

Well BRP2

Well 48BR

Well 15BR

Gold Run (west branch)

Well 15BR

Well 20BR

Well BRP2

Well 45BR

Well 45BR

Well BRP2

Well 48BR

Well BRP2

Well 48BR

Well 48BR

Well 22BR

Well 15BR

36
40°16'00" 40°161 15"

?4

Approximate distance to

Villa Victoria Brook 4,000 feet

Approximate distance to

Delaware River 9,000 feet

T5BR -5>««x -^,,

IV *Ya*/Z/:-&B& v / t'">/

\^//M

Contaminant 

source area

EXPLANATION

Fault zone - shows the fault contact at an altitude 

of 150 feet (approximately land surface)

Fence which is the approximate property boundary of 

the Naval Air Warfare Center

[__j Swamp 

^^1 Building

25S'

31 BR' 

12S 1

11S 1

Contaminated well and identifier; flow at and near this site simulated to discharge at Villa Victoria Brook 

Contaminated well and identifier; flow at and near this site simulated to discharge at Gold run (West Branch) 

Contaminated well and idenitifer; flow at and near this site simulated to discharge at Gold run (main stem) 

Contaminated well and identifier; flow at and near this site simulated to discharge at Delaware River

11 BR ° Contaminated well and identifier; flow at and near this site simulated to discharge at West Branch of Shabakunk Creek

Figure 8. Simulated discharge locations of ground water at and near contaminated wells at the 

Naval Air Warfare Center, West Trenton, New Jersey (no recovery wells simulated as pumping).

37
and 12BR) are at the eastern part of the NAWC. 

Water originating at these locations flows toward 

the fault in confined layers below the weathered 

zone, then alongside the fault, and then upward into 

the river. Water that originates at or near two 

contaminated wells (12S and 13S) flows in much 

the same pattern until it reaches the fault, but it then 

crosses the fault and eventually discharges into the 

Gold Run main stem.

Ground-water flowpaths in the no-pumping 

simulation are strongly affected by the 

hydrogeologic framework. When water from 

precipitation recharges the ground-water system, it 

first enters the weathered zone. If the precipitation 

falls near a stream, the water remains in the 

weathered zone and discharges to the stream. 

Precipitation that falls farther from a stream, 

however, flows through the weathered zone and 

then into the underlying bedrock, where the 

fractures are more open and hydraulic conductivity 

is higher than in the weathered zone. In the bedrock, 

water probably flows mostly in bedding-plane 

fractures because these fractures are much more 

continuous than the near-vertical fractures. Water 

does move from one bedding-plane fracture to the 

next, however, through the relatively short vertical 

fractures. Overall movement of ground water, then, 

probably is in an elongated stairstep-like pattern, 

with the near-horizontal (bedding-plane) fractures 

analogous to long steps and the near-vertical 

fractures analogous to short risers. In the absence of 

pumping or other artificial stresses, ground-water 

flows in this stairstep-like path until it reaches a 

stream (fig. 9).

The overall direction of flow is nearly 

parallel to the strike direction of the bedding units 

(west-northwest and east-southeast). This flow 

direction results because (1) numerous thin waterbearing units and confining units are present within 

each bedding unit, and (2) all of the units dip, so that 

the water-bearing units are extensive in the strike 

direction but not in the dip direction. Each waterbearing unit terminates updip at the weathered zone

and downdip at a depth of about 500 ft, where 

fractures are sparse. Consequently, in each waterbearing unit, flow is constrained in both the updip 

direction (south-southeast) and the downdip 

direction (north-northwest), so flow is 

predominantly to the west-southwest or eastnortheast.

Simulation 2--Recovery-Well 

Network I

This simulation represents water levels and 

flowpaths at times when recovery-well Network I 

had been pumping for at least 1 month. Under these 

conditions, ground-water flowpaths near the 

pumped well are diverted from the ambient strike 

direction. Under these conditions, one of the 

recovery wells captures water from areas around 51 

of the 55 contaminated wells. The other four 

contaminated wells (37S, MW11-1, MW12-1, and 

37BR) are all on the south side of the fault and more 

than 650 ft from the only recovery well south of the 

fault (22BR). Details of the results of this scenario 

are shown in figure 10 and listed in table 10.

Simulation 3~Recovery-Well 

Network II

This simulation represents water levels and 

flowpaths at times when recovery-well network II 

had been pumping for at least 1 month. In this 

network, well BRP2 is pumped instead of well 

41BR. In this simulation, water from areas around 

the same 51 contaminated wells captured by 

network I is captured by network II although, in 

many cases, water is captured by a different 

recovery well. As explained in the earlier section on 

simulated water budgets, the primary difference 

between the effects of recovery-well networks I and 

II is that network II prevents any water from the 

southwestern part of the NAWC property from 

flowing into Gold Run. Details of the results of this 

simulation are shown in figure 10 and listed in table 

10.

38
Generalized flow path

Vertical scale 

greatly exaggerated

Model 

Layer 20

Figure 9. Generalized ground-water-flow path. (Section is oriented paralllel to the strike of 

bedding.)

39
40°16'00" 40°16'15"

Approximate distance to 

\ Villa Victoria Brook 4,000 feet

Contaminant 

source area

Swamp 

Building

EXPLANATION

Fault zone - shows the fault contact at an altitude 

of 150 feet (approximately land surface)

Fence which is the approximate property boundary of 

the Naval Air Warfare Center

12MW1, Contaminated well and identifier; flow at and near this site simulated to discharge at Gold Run (West Branch) 

11BR Contaminated well and identifier; flow at and near this site simulated to discharge at recovery well 

22BR * Recovery well and identifier

Figure 10. Simulated discharge locations of ground water at and near contaminated wells at the 

Naval Air Warfare Center, West Trenton, New Jersey (Recovery-well Network I or n in operation).

40
SUMMARY AND 

CONCLUSIONS

Volatile organic compounds, 

predominantly trichloroethylene (TCE) and its 

degradation products m-l,2-dichloroethylene (cisDCE) and vinyl chloride (VC), have been detected 

in ground water at the Naval Air Warfare Center 

(NAWC), West Trenton, N. J. (International 

Technology Corporation, 1994). A study by the 

U.S. Geological Survey, in cooperation with the 

U.S. Department of the Navy, was done to 

determine (1) the directions that contaminated 

water at the NAWC would move when no pumping 

occurs at the NAWC and (2) the efficiency of the 

two alternative recovery-well networks that have 

been used at the NAWC in containing ground-water 

contamination on the NAWC property. The primary 

means of investigation was a digital model of 

ground-water flow at and near the NAWC. The 

model area is bounded by natural hydrologic 

boundaries, including streams, drainage-basin 

boundaries, and ground-water flowlines parallel to 

the boundary that don't cross the boundary.

The Lockatong and Stockton Formations 

form the bedrock in the study area. Both formations 

consist of interlayered mudstone, siltstone, and 

sandstone. The rock layers dip north-northwest. 

Ground water flows mostly through three sets of 

fractures that are nearly perpendicular to each other. 

Bedding-plane fractures extend for much longer 

distances than vertical fractures, and most of the 

water probably flows in bedding-plane fractures. 

Vertical fractures carry water from one beddingplane fracture to the next. Near land surface, the 

rocks are weathered, and fractures are filled with 

clay and silt from the weathering process. A nearly 

impermeable fault cuts through the southern part of 

the NAWC property. The fault is at or near the 

contact of the Stockton Formation to the south and 

the Lockatong Formation to the north.

The model used in this study is a finitedifference, three-dimensional, porous-medium 

representation of the ground-water-flow system. It 

is composed of 154 rows, 160 columns, and 71 

layers. Cells within the NAWC property are 25 to 

50 ft wide and 25 to 50 ft long. Elsewhere, the cells

are larger, with a maximum size of 500 ft by 650 ft 

near the model boundaries. Model layer 1 

represents the highly weathered part of each 

dipping bedding unit near land surface. The otHr 

70 layers represent the deeper, less weathered part 

of each dipping bedding unit.

Horizontal hydraulic conductivity was 

measured using slug testing at 72 wells and 

estimated at 8 wells on the NAWC property. The 

range of hydraulic conductivity at these well sites 

was 0.001 to 227 ft/d. The slug-test data indicate 

that the median hydraulic conductivity in the 

weathered zone is 2.6 ft/d, whereas the median 

hydraulic conductivity in wells 26 to 50 ft belc w 

land surface is 11.3 ft/d. Conductivity in the 

weathered zone is lower probably because the 

fractures are partly filled by clay and silt derived 

from the weathering process. Deeper than 50 f 

below land surface, hydraulic conductivity 

decreases and becomes negligible deeper than 500 

ft below land surface. The decrease in horizontal 

hydraulic conductivity at depths greater than 50 ft 

probably is caused by a decrease in the density of 

interconnected fractures at increasing depths. Ir the 

calibrated model, the hydraulic conductivity of the 

weathered zone was set at values ranging from 1.25 

to 5.0 ft/d, depending on location. The confinei 

bedding units at depths less than 300 ft below land 

surface were assigned depth- and location-based 

horizontal hydraulic conductivity values ranging 

from 0.0375 to 11.3 ft/d. The horizontal hydraulic 

conductivity at all points 300 ft deep or deeper 

below land surface and all points in the fault zone 

was set at 0.001 ft/d.

In the model, the vertical hydraulic 

conductivity of each model cell was set at one-tenth 

the horizontal hydraulic conductivity. The vert; °al 

hydraulic conductivity of all streambeds in the 

study area was set at 0.5 ft/d. Because the bed of the 

Delaware River is thicker than the beds of its 

tributaries, the conductance of the bed of the river is 

lower than that of the tributaries. Effective areal 

recharge rates used in the model are 11 in/yr hi 

agricultural and undeveloped areas and 5 in/yr in 

residential, commercial, and industrial areas. 

Specific yield of the weathered zone was set at C. 15, 

and the specific storage of the confined layers was 

set at 4.0 x 10"5 .

41
The steady-state model was calibrated by 

obtaining acceptably close agreement between 

measured and simulated ground-water levels at and 

near the NAWC property and base flow in nearby 

streams. The transient model was calibrated by 

obtaining an acceptable agreement between 

measured and simulated drawdown in wells during 

three different periods of short-term pumping (72 

hours or less) at the NAWC.

Most of the data used in calibrating the 

model were collected at the NAWC property. 

Consequently, it would not be appropriate to use 

this model to obtain detailed simulations of groundwater flow outside of the NAWC area. Another 

limitation of the model is that only advective 

movement of contaminants is simulated; 

dispersion, diffusion, dilution, and biological and 

chemical degradation of contaminants are not 

simulated.

To test the effectiveness of the two 

alternative recovery-well networks in preventing 

movement of contaminated water to areas beyond 

the NAWC property, the directions of movement of 

contaminated water with and without recovery-well 

networks in operation were estimated by use of the 

ground-water-flow model. Because the model is 

based on various necessary simplifying 

assumptions, the simulated flowpaths and discharge 

points are approximate. For both simulations, the 

discharge point of water from the area around each 

contaminated well at the NAWC was determined. 

Model results indicate that when no wells at NAWC 

were pumped, most of the ground water at the

NAWC flowed west-southwest to the reach of Gold 

Run that is adjacent to and on the NAWC prct>erty. 

Some contaminated water flowed to Villa Victoria 

Brook, West Branch Shabakunk Creek, and the 

Delaware River. In this no-pumping scenario, 

ground water flows primarily in the direction of the 

strike of the bedding units (west-northwest and 

east-southeast) and probably mostly in fractures 

parallel to bedding.

Both recovery-well networks that have 

been used at the NAWC consist of five wells on the 

north (Lockatong) side of the fault pumping a total 

of 52.1 gal/min and one well on the south 

(Stockton) side of the fault pumping 4.4 gal/min. 

Network I was used during January 1998 through 

November 2000. The network was modified in 

December 2000 because static water-level 

measurements indicated that contaminated water 

may have been discharging into the upper 500-ft 

reach of Gold Run. In network II, which beg^n 

operating in December 2000, well BRP2 replaced 

well 41BR because it is closer to Gold Run than 

well 41BR and more likely to capture water flowing 

to Gold Run. Water budgets based on simulations 

representing each of the recovery-well networks 

indicate that network II prevents any ground water 

from flowing to the upper 500 ft of Gold Run. 

Flowpaths computed for each simulation ind^-ate 

that, in both networks, water at and near 51 of the 

55 contaminated well sites at the NAWC is captured 

by a recovery well. The four well sites from which 

contaminated water is not captured by a recovery 

well are on the south side of the fault and more than 

650 ft from the nearest recovery well.

42
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44