u.s. Department of the Interior 

U.S. Geological Survey 

SIMULATION OF GROUND-WATER FLOW AND MOVEMENT 

OF THE FRESHWATER-SALTWATER INTERFACE IN THE 

NEW JERSEY COASTAL PLAIN 

Water-Resources Investigations Report 98-4216 

Prepared in cooperation with the 

NEW JERSEY DEPARTMENT OF ENVIRONMENTAL PROTECTION 
SIMULATION OF GROUND-WATER FLOW AND MOVEMENT 

OF THE FRESHWATER-SALTWATER INTERFACE IN THE NEW 

JERSEY COASTAL PLAIN 

By Dary// A. Pope and Alison D. Gordon 

u.s. GEOLOGICAL SURVEY 

Water-Resources Investigations Report 98-4216 

Prepared in cooperation with the 

NEW JERSEY DEPARTMENT OF ENVIRONMENTAL PROTECTION 

West Trenton, New Jersey 

1999 

_USGS 

science for a changing world 
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITr, Secretary 

u.s. GEOLOGICAL SURVEY 

CHARLES G. GROAT, Director 

For additional information Copies of this report can be 

write to: purchased from: 

District Chief U.S. Geological Survey 

U.S. Geological Survey Branch of Information Services 

Mountain View Office Park Box 25286 

810 Bear Tavern Road, Suite 206 Denver, CO 80225-0286 

West Trenton, NJ 08628 
CONTENTS 

Page 

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

Introduction ...................................................................................................................................... 2 

Purpose and scope ................................................................................................................ 2 

Approach .............................................................................................................................. 3 

Location and extent of study area ....................................................................................... .3 

Previous investigations ........................................................................................................ 5 

Description of hydrogeologic units used in the model .................................................................... 6 

Lower Potomac-Raritan-Magothy aquifer ......................................................................... 10 

Confining unit between the Lower and Middle Potomac-Raritah-Magothy aquifers ........ 11 

Middle Potomac-Raritan-Magothy aquifer ........................................................................ 11 

Confining unit between the Middle and Upper Potomac-Raritan-Magothy aquifers ....... .12 

Upper Potomac-Raritan-Magothy aquifer ......................................................................... 12 

Merchantville-Woodbury confining unit. ........................................................................... 12 

Englishtown aquifer ........................................................................................................... 13 

Marshalltown-Wenonah confining unit .............................................................................. 13 

Wenonah-Mount Laurel aquifer ......................................................................................... 13 

Navesink-Homerstown confining unit ............................................................................... 14 

Vincentown aquifer ............................................................................................................ 14 

Vincentown-Manasquan confining unit ............................................................................. 14 

Piney Point aquifer ............................................................................................................. 15 

Basal Kirkwood confining unit .......................................................................................... 15 

Lower Kirkwood-Cohansey and confined Kirkwood aquifers .......................................... 15 

Confining unit overlying the Rio Grande water-bearing zone .......................................... .16 

Upper Kirkwood-Cohansey aquifer ................................................................................... 1 7 

Estuarine clay confining unit ............................................................................................. 17 

Description of ground-water-flow modeL ..................................................................................... 17 

Sharp-interface approach ................................................................................................... 17 

Limitations ......................................................................................................................... 20 

Model grid .......................................................................................................................... 20 

Boundary conditions .......................................................................................................... 22 

Input data ........................................................................................................................... 25 

Calibration .......................................................................................................................... 28 

Simulation of ground-water flow and freshwater-saltwater interface movement through 1896 ... 29 

Simulation of steady-state conditions from 110,000 to 84,000 years ago ......................... 31 

Simulation of sea-level changes ........................................................................................ .35 

Movement of the freshwater-saltwater interface ............................................................... 36 

Ground-water flow system in 1896 ................................................................................... .38 

Simulation of ground-water flow and freshwater-saltwater interface movement, 1896-1988 ...... 44 

Description of ground-water flow system, 1983-88 .......................................................... 48 

Potomac-Raritan-Magothy aquifer system ............................................................ 48 

Lower Potomac-Raritan-Magothy aquifer ................................................. 53 

Middle Potomac-Raritan-Magothy aquifer ................................................ 55 

Upper Potomac-Raritan-Magothy aquifer ................................................. 60 

111 
CONTENTS--Continued 

Page 

Englishtown aquifer ............................................................................................... 63 

Wenonah Mount-Laurel aquifer ............................................................................. 66 

Vincentown aquifer ................................................................................................ 69 

Piney Point aquifer ................................................................................................. 70 

Lower Kirkwood-Cohansey and confined Kirkwood aquifers .............................. 76 

Freshwater-saltwater interface location and movement, 1896-1988 ................................. 79 

Potomac-Raritan-Magothy aquifer system ............................................................ 80 

Lower Potomac-Raritan-Magothy aquifer ......................................... ~ ....... 80 

Middle Potomac-Raritan-Magothy aquifer ................................................ 81 

Upper Potomac-Raritan-Magothy aquifer ................................................. 83 

Englishtown aquifer ............................................................................................... 84 

Wenonah-Mount Laurel aquifer ............................................................................. 84 

Vincentown aquifer ................................................................................................ 84 

Piney Point aquifer ................................................................................................. 85 

Lower Kirkwood-Cohansey and confined Kirkwood aquifers .............................. 85 

Predictive simulation of ground-water flow and freshwater-saltwater interface movement, 

1988-2040 ................................................................................................................................ 85 

Summary and conclusions ............................................................................................................. 86 

References cited ............................................................................................................................. 98 

Appendixes 

1-8. Figures showing hydrogeologic properties, simulated heads, observation-well 

locations, and chloride concentrations in the: 

1. Lower Potomac-Raritan-Magothy aquifer (model unit AI) 

2. Middle Potomac-Raritan-Magothy aquifer (model unit A2) . 

3. Upper Potomac-Raritan-Magothy aquifer (model unit A3) 

4. Englishtown aquifer (model unit A4) 

5. Wenonah-Mount Laurel aquifer (model unit A5) 

6. Vincentown aquifer (model unit A6) 

7. Piney Point aquifer (model unit A7) 

8. Lower Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8) 

ILLUSTRATIONS 

Figure 1. Map showing location of study area, New Jersey Coastal Plain ............................... .4 

2. Generalized hydrogeologic section through the onshore part of the New Jersey 

Coastal Plain ......................................................................................................... 8 

3. Generalized hydrogeologic section showing model representation of aquifers 

and confining units from the Fall Line to the Continental Shelf, New Jersey 

Coastal Plain ......................................................................................................... 9 

4. Schematic representation of aquifers, confining units, and boundary 

conditions used in the New Jersey Coastal Plain flow model. .......................... .18 

5. Map showing model grid and generalized lateral boundaries of the New Jersey 

Coastal Plain flow model .................................................................................... 21 

iv 
ILLUSTRATIONS--Continued 

Page 

Figure 6. Map showing generalized stream elevations in the New Jersey Coastal Plain ......... 24 

7. Graph showing sea-level curve ................................................................................ .30 

8. Map showing simulated potentiometric surface in the confined Kirkwood aquifer, 

and locations of the simulated freshwater-saltwater interface tip and toe in 

lower Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8) 

in the New Jersey Coastal Plain 84,000 years ago .............................................. 33 

9. Map showing simulated potentiometric surface and locations of the simulated 

freshwater-saltwater interface tip and toe in the upper Kirkwood-Cohansey 

aquifer (model unit A9) in the New Jersey Coastal Plain 84,000 years ago ..... .34 

1{\ 

IV. Hydrogeologic section showing simulated locations of the freshwater-saltwater 

interface in the New Jersey Coastal Plain 84,000 years ago and in 1896 

(predevelopment) ................................................................................................ 37 

11. Schematic representation of budget terms used to describe flow budgets in each 

aquifer in the New Jersey Coastal Plain flow model .......................................... 40 

12. Graph showing annual ground-water withdrawals in the New Jersey Coastal 

Plain from 1917 to 1988 and during model pumping periods ........................... .4 7 

13-15. Hydrographs of simulated and measured water levels in the: 

13. Lower and Middle Potomac-Raritan-Magothy aquifers, New Jersey 

Coastal Plain, 1896-1989 ........................................................................... 49 

14. Upper Potomac-Raritan-Magothy and Englishtown aquifers, New Jersey 

Coastal Plain, 1896-1989 ........................................................................... 50 

15. Wenonah-Mount Laurel aquifer and the lower Kirkwood-Cohansey and 

confined Kirkwood aquifers, New Jersey Coastal Plain, 1896-1989 ......... 51 

16-40. Maps showing: 

16. Observed potentiometric surface and locations of selected wells in the 

Lower Potomac-Raritan-Magothy aquifer (model unit AI) with longterm hydrographs, New Jersey Coastal Plain, 1988 .................................. 54 

17. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and 

measured \vater levels at observation wells, and area of upward flow 

in the Lower Potomac-Raritan-Magothy aquifer (model unit AI), 

New Jersey Coastal Plain, 1988 ................................................................. 56 

18. Observed potentiometric surface and locations of selected wells in the 

Middle Potomac-Raritan-Magothy aquifer (model unit A2) with longterm hydrographs, New Jersey Coastal Plain, 1988 .................................. 57 

19. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and 

measured water levels at observation wells, and area of upward flow 

in the Middle Potomac-Raritan-Magothy aquifer (model unit A2), 

New Jersey Coastal Plain, 1988 ................................................................. 59 

20. Observed potentiometric surface and locations of selected wells in the 

Upper Potomac-Raritan-Magothy aquifer (model unit A3) with longterm hydrographs, New Jersey Coastal Plain, 1988 .................................. 61 

v 
ILLUSTRATIONS--Continued 

Page 

Figure 21. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and 

measured water levels at observation wells, and area of upward flow 

in the Upper Potomac-Raritan-Magothy aquifer (model unit A3), 

New Jersey Coastal Plain, 1988 ................................................................. 62 

22. Observed potentiometric surface and locations of selected wells in the 

Englishtown aquifer (model unit A4) with long-term hydrographs, 

Ne\v Jersey Coastal Plain, 1988 ................................................................. 64 

23. Simulated potentiometric surface, difference between simulated and 

measllred water levels at observation wells, and area of upward flow 

in the Englishtown aquifer (model unit A4), New Jersey Coastal Plain, 

1988 ............................................................................................................ 65 

24. Observed potentiometric surface and locations of selected wells in the 

Wenonah-Mount Laurel aquifer (model unit A5) with long-term 

hydrographs, New Jersey Coastal Plain, 1988 ........................................... 67 

25. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and 

measured water levels at observation wells, and area of upward flow 

in the Wenonah-Mount Laurel aquifer (model unit AS), New Jersey 

Coastal Plain, 1988 .................................................................................... 68 

26. Observed potentiometric surface and locations of selected wells in the 

Vincentown aquifer (model unit A6) with long-term hydrographs, 

New Jersey Coastal Plain, 1988 ................................................................. 71 

27. Simulated potentiometric surface, difference between simulated and 

measured water levels at observation wells, and area of upward flow 

in the Vincentown aquifer (model unit A6), New Jersey Coastal Plain, 

1988 ............................................................................................................ 72 

28. Observed potentiometric surface and locations of selected wells in the 

Piney Point aquifer (model unit A 7) with long-term hydrographs, 

New Jersey Coastal Plain, 1988 ................................................................. 73 

29. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and 

measured water levels at observation wells, and area of upward flow 

in the Piney Point aquifer (model unit A 7), New Jersey Coastal Plain, 

1988 ............................................................................................................ 75 

30. Observed potentiometric surface in the confined Kirkwood aquifer and 

locations of selected wells in the lower Kirkwood-Cohansey and 

confined Kirkwood aquifers (model unit A8) with long-term 

hydrographs, New Jersey Coastal Plain, 1988 ........................................... 77 

vi 
ILLUSTRATIONS--Continued 

Page 

Figure 31. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and 

measured water levels at observation wells, and area of upward flow 

in the lower Kirkwood-Cohansey and confined Kirkwood aquifers 

(model unit A8), New Jersey Coastal Plain, 1988 ..................................... 78 

32. Location of various freshwater-saltwater interface positions in the 

Delaware Estuary ....................................................................................... 82 

33. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow resulting from 

a 30-percent increase in withdrawals at all wells, Lower PotomacRaritan-Magothy aquifer (model unit AI), New Jersey Coastal Plain, 

2040 ............................................................................................................ 87 

34. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow resulting from 

a 30-percent increase in withdrawals at all wells, Middle PotomacRaritan-Magothy aquifer (model unit A2), New Jersey Coastal Plain, 

2040 ............................................................................................................ 88 

3S. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow resulting from 

a 30-percent increase in withdrawals at all wells, Upper PotomacRaritan-Magothy aquifer (model unit A3), New Jersey Coastal Plain, 

2040 ............................................................................................................ 89 

36. Simulated potentiometric surface and area of upward flow resulting from 

a 30-percent increase in withdrawals at all wells, Englishtown aquifer 

(model unit A4), New Jersey Coastal Plain, 2040 ..................................... 90 

37. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow resulting from 

a 30-percent increase in withdrawals at all wells, Wenonah-Mount 

Laurel aquifer (model unit AS), New Jersey Coastal Plain, 2040 ............. 91 

38. Simulated potentiometric surface and area of upward flow resulting from 

a 30-percent increase in withdrawals at all wells, Vincentown aquifer 

(model unit A6), New Jersey Coastal Plain, 2040 ..................................... 92 

39. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow resulting from 

a 30-percent increase in withdrawals at all wells, Piney Point aquifer 

(model unit A 7), New Jersey Coastal Plain, 2040 ..................................... 93 

40. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow resulting from 

a 30-percent increase in withdrawals at all wells, lower KirkwoodCohansey and confined Kirkwood aquifers (model unit A8), New Jersey 

Coastal Plain, 2040 .................................................................................... 94 

VB 
TABLES 

Page 

Table 1. Geologic and hydrogeologic units of the New Jersey Coastal Plain and model 

units used in this study ............................................................................................. 7 

2. Simulated predevelopment flow budgets of confined aquifers in the New Jersey 

Coastal Plain, 1896 ................................................................................................ 39 

3. Ground-water withdrawals from each aquifer and lateral boundary flows by 

pumping period, New Jersey Coastal Plain, 1896-1988 ....................................... .45 

4. Simulated water-level altitudes for 1988, average measured water-level altitudes 

for 1983-88, and the difference between simulated and measured water-level 

altitudes for selected wells, New Jersey Coastal Plain ....................................... .1 0 1 

5. Simulated flow budgets of confined aquifers in the New Jersey Coastal Plain, 

1983-88 .................................................................................................................. 52 

6. Concentrations of chloride at various depths in deep wells and boreholes in 

onshore and offshore areas, New Jersey Coastal Plain, 1888-1974 .................... 104 

7. Concentrations of chloride in selected samples from wells in the New Jersey 

Coastal Plain, 1971-90 ......................................................................................... 1 07 

8. Simulated flow budgets of confined aquifers in the New Jersey Coastal Plain, 

2040 ........................................................................................................................ 95 

Vlll 
CONVERSION FACTORS AND VERTICAL DATUM 

Multiply By To obtain 

Length 

inch (in.) 2.54 centimeter 

inch (in.) 25.4 millimeter 

foot (ft) 0.3048 meter 

mile (mi) 1.609 kilometer 

Volume 

gallon (gal) 3.785 liter 

gallon (gal) 0.003785 cubic meter 

million gallons (Mgal) 3,785 cubic meters 

million gallons per day (Mgal/d) 0.04381 cubic meters per second 

gallons per minute (gal/min) 0.06308 liters per second 

inch per year (in/yr) 25.4 millimeter per year 

Hydraulic conductivity 

foot per day (ft/d) 0.3048 meter per day 

Transmissivity 

foot squared per day (ft2/d)1 0.09290 meter squared per day 

Density 

grams per cubic centimeter (g/cm3) 62.43 pounds per cubic foot 

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

geodetic datum derived from a general adjustment of the first-order level nets of the United 

States and Canada, formerly called Sea Level Datum of 1929. 

This unit is used to express transmissivity, the capacity of an aquifer to transmit water. 

Conceptually, transmissivity is cubic feet (of water) per day per square foot ( of aquifer area) times 

feet (of aquifer thickness), or (ft3/d)/ft2 x ft. In this report, this expression is reduced to its simplest 

form, ft2/d. 

IX 
SIMULATION OF GROUND-WATER FLOW AND MOVEMENT OF THE 

FRESHWATER-SALTWATER INTERFACE IN THE 

NEW JERSEY COASTAL PLAIN 

by Daryll A. Pope and Alison D. Gordon 

ABSTRACT 

The confined aquifers of the New Jersey Coastal Plain are sands that range in thickness 

from 50 to 600 feet and are separated by confining units. The confiningunits are composed of silts 

and clays that range in thickness from 50 to 1,000 feet. The aquifers are recharged by precipitation 

on their outcrop areas. This water then flows laterally downdip and vertically to the deeper 

confined aquifers. The confined aquifers ultimately discharge to the Raritan and Delaware Bays 

and to the Atlantic Ocean. 

In 1988, ground-water withdrawals from confined and unconfined New Jersey Coastal 

Plain aquifers were approximately 345 million gallons per day, more than 75 percent of which was 

pumped from the confined aquifers. These withdrawals have created large cones of depression in 

several Coastal Plain aquifers near populated areas, particularly in Camden and Monmouth 

Counties. The continued decline of water levels in confined aquifers can cause saltwater intrusion, 

reduce stream discharge near the outcrop areas, and threaten the quality of the ground-water 

supply. 

SHARP, a quasi-three-dimensional finite-difference computer model that can simulate 

freshwater and saltwater flow, was used to simulate the ground-water flow system in the New 

Jersey Coastal Plain, including the location and movement of the freshwater-saltwater interface in 

nine aquifers and eight interyening confining units. The freshwater-saltwater interface is defined 

as the hypothetical line seaward of which the chloride concentration is equal to or greater than 

10,000 milligrams per liter. Model simulations were used to estimate the location and movement 

of the freshwater-saltwater interface resulting from (1) eustatic sea-level changes over the past 

84,000 years, (2) ground-water withdrawals from 1896 through 1988, (3) and future ground-water 

withdrawals from 1988 to 2040 from Coastal Plain aquifers. Simulation results showed that the 

location and movement of the freshwater-saltwater interface are more dependent on the historical 

sea level than on the stresses imposed on the flow system by ground-water withdrawals from the 

Coastal Plain aquifers from 1896 to 1988. 

Results of a predictive simulation in which pumpage from existing wells was increased by 

30 percent indicate that additional withdrawals from each of the eight confined aquifers in the 

Coastal Plain would broaden and deepen the existing cones of depression and result in significant 

drawdowns from the 1988 potentiometric surfaces. Drawdowns of 30 feet were simulated at the 

center of the cone of depression in the Upper, Middle, and Lower Potomac-Raritan-Magothy 

aquifers in Camden and Ocean Counties. Simulated drawdowns exceeded 80 feet at the center of 

the cone of depression in the Wenonah-Mount Laurel and Englishtown aquifers in Monmouth 

County. Drawdowns of 30 feet were simulated in the lower Kirkwood-Cohansey and confined 

1 
Kirkwood aquifers in Cape May County. Simulation results showed that the increase in groundwater withdrawals would result in only minimal movement of the freshwater-saltwater interface 

by 2040, despite large drawdowns. 

INTRODUCTION 

In 1988, withdrawals from confined and unconfined aquifers in the New Jersey Coastal 

Plain were approximately 345 Mgal/d, of which more than 75 percent was from the confined 

aquifers. The development of ground-water resources has occurred primarily near large population 

centers, creating large cones of depression in several of the Coastal Plain aquifers. Continued 

decline of water levels in confined aquifers poses the threat of serious adverse effects, including 

saltwater intrusion and reduction of stream discharge near the aquifer outcrop areas. 

Effective management of the ground-water resources in the Coastal Plain requires identification of specific areas where ground-water supplies may be threatened. Threatened areas are 

currently defined as areas where water levels are more than 30 ft below sea level (Battaglin and 

Hill, 1989, p. 8). Mandated reductions in withdrawals of 35 to 50 percent have been considered or 

imposed in these areas (CH2M Hill and others, 1992, p. 4-32). This water-level criterion, however, 

may not always identify the most severely threatened areas. Local hydrogeologic conditions and 

proximity of saltwater may enhance the potential for saltwater intrusion in areas where water levels 

are higher than 30 ft below sea level. Alternatively, areas in which water levels are lower than 30 

ft below sea level may not be threatened by saltwater intrusion if no nearby source of saltwater 

exists or if the hydrogeologic properties of the aquifer limit the movement of saltwater from source 

areas. Factors such as water-transmitting properties of the aquifer, sources of recharge to and 

discharge from the aquifer, and the location and movement of the freshwater-saltwater interface in 

the aquifer also may need to be considered to identify areas where ground-water supplies may be 

threatened and those where ground water may be safely withdrawn without adverse consequences. 

In order to better identify areas in which ground-water supplies may be threatened by 

saltwater intrusion, the U.S. Geological Survey (USGS), in cooperation with the New Jersey 

Department of Environmental Protection, conducted a study of ground-water flow and the 

movement of the freshwater-saltwater interface in the New Jersey Coastal Plain. The objectives of 

the study were to (1) describe the hydrogeology of each aquifer and confining unit in the New 

Jersey Coastal Plain, (2) develop a ground-water flow model of the Coastal Plain that includes the 

parts of the aquifers that contain saltwater, and (3) use the results of the simulations and available 

hydrogeologic data to describe the flow system in the New Jersey Coastal Plain. 

Purpose and Scope 

This report describes the hydrogeology of, ground-water flow system in, and freshwatersaltwater interface movement in the New Jersey Coastal Plain sediments. The SHARP computer 

model (Essaid, 1990) is used to simulate the ground-water flow system, including the location and 

movement of the freshwater-saltwater interface in nine aquifers and eight intervening confining 

units in the Coastal Plain. SHARP is a quasi-three-dimensional finite-difference ground-water 

flow model that simulates both freshwater and saltwater flow separated by a sharp interface. The 

flow model is based on the USGS New Jersey Regional Aquifer-System Analysis (RASA) model 

2 
(Martin, 1998) but has been modified to simulate flow to the seaward limit of the Continental Shelf 

and to include the saltwater part of the flow system. Model design, boundary conditions, input data, 

calibration, and assumptions used in the simulations are described. The results of the simulations 

are used to estimate the location and movement of the freshwater-saltwater interface resulting from 

(1) eustatic sea-level changes over the past 84,000 years, (2) ground-water withdrawals from 

Coastal Plain aquifers from 1896 through 1988, and (3) hypothetical ground-water withdrawals 

from 1988 to 2040. 

ApprQach 

The freshwater-saltwater interface in the New Jersey Coastal Plain is still moving landward 

in response to past (lower) sea levels. Because the current location of the interface is not in equilibrium with the current sea level (Meisler and others; 1985), the past 84,000 years of sea-level 

fluctuations were simulated to obtain initial conditions for the simulation of the flow system during 

development (1896-1988). The resulting saltwater-freshwater interface and simulated heads 

represent the ground-water flow system resulting from eustatic sea-level fluctuations. Water 

budgets representing the flow system in 1896 were developed. 

The stressed ground-water flow system from 1896 through 1988 was simulated by using 

available ground-water withdrawal data. The model was calibrated by using synoptic water-level 

data collected during fall 1988 and continuous water-level data recorded at wells during 1984-88. 

The flow system in 1988, including observed and simulated water levels, the simulated position of 

the freshwater-saltwater interface, and available chloride data, is described by means of water 

budgets representing the flow system in each confined aquifer. 

Pumpage was increased by 30 percent at existing withdrawal sites to simulate changes in 

ground-water flow conditions through 2040. The flow model was used to simulate water levels and 

movement of the saltwater-freshwater interface in response to the increase in withdrawals. Flow 

budgets are used to describe changes in the flow system and the source of water to wells in the 

predictive simulation. 

Location and Extent of Study Area 

The New Jersey Coastal Plain is located in the northern part of the Coastal Plain physiographic province. The Coastal Plain sediments in the study area extend from the Fall Line in the 

northwest to the edge of the Continental Shelf in the southeast, and from the Delaware Bay in the 

southwest to Raritan Bay in the northeast. The study area (fig. 1) extends from the Fall Line to the 

Continental Shelf, about 80 mi offshore from Atlantic City. It includes all of Atlantic, Burlington, 

Camden, Cape May, Cumberland, Gloucester, Monmouth, and Ocean Counties, and parts of 

Middlesex and Mercer Counties in New Jersey, parts of New Castle County in Delaware, and Philadelphia and Bucks Counties in Pennsylvania. The extent of the model area is the same as that of 

the study area. 

3 
'1700 

( GLOUCESTER r' SALEM ( .J '\ )l CA 

: \ \ ) 

wl>- l/~ ~- 1/1 CUMBERLAN~ r - ) WI,?}: ;.. \ ~ 

Q,!;# I 7~ t ! ~ -(~ I 

I DELAWARE ~ / l l ATLANTIC 

;

1 BAY ~ (j, 

CAPE MAY ~ 

EXPLANATION 

LOCATION OF WELL AND NUMBER--

• i 1 Chloride concentrations shown in 

table 6 

e LOCATION OF CONTINENTAL 

COSTB3 OFFSHORE STRATIGRAPHIC 

TEST BOREHOLE AND NUMBER 

A-A' LOCATION OF HYDROGEOLOGIC 

SECTION--Section shown in figures 

3 and 10 

o 

I 

o 

9 MILES i I 

9 KILOMETERS 

DEN} 

/ 

( BURLINGTON 

'I NEW JERSEY 

-) 

~iver 

",1.0 

i§ 

I 

A' 

L......._--- UM\I of CONTINENTAL SHI2L.f: ______ -

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

i FALL LINE 

\ MERCER \ MIDDLESEX 

/~~~---...r----

MONMOUTH 

-~, 4:r<$>o? 

<$>\l' 

Pc. 

/ ~-' 

e 

COSTB3 

COSTB2 

e 

'100 

Figure 1. Map showing location of study area, New Jersey Coastal Plain. 

4 
Previous Inyesti2ations 

Many reports have described the hydrogeology of the Coastal Plain sediments in New 

Jersey. Martin (1998) briefly describes these reports, several of which have been used extensively 

in this report. These reports are listed below along with a brief description of how each report has 

been used in this study. 

Zapecza (1989) describes the hydrogeologic framework of the New Jersey Coastal Plain 

aquifers in onshore areas. The freshwater flow system in the New Jersey Coastal Plain was 

described by Martin (1998) by using a numerical ground-water flow model as part of the USGS 

RASA program. Martin describes the numerical ground-water flow model and uses the results of 

the simulation to describe the predevelopment and 1978 flow systems. Available data on aquifer 

and confining-unit properties in the New Jersey Coastal Plain are presented and discussed. The 

hydrogeologic framework used to develop the model is based on that in Zapecza (1989). The 

conceptual model of the flow system and the modeling approach used in this report are based 

strongly on Martin's work. The conceptual model in this study was modified from Martin (1998) 

to include the saltwater flow system in downdip areas. 

Hathaway and others (1976, 1979), Scholle (1977, 1980), and Mattick and Hennessy 

(1980) describe the geology offshore. Results of these studies were used to extend the hydrogeologic framework in several aquifers to the limit of the Continental Shelf in order to simulate the 

saltwater part of the flow system. 

Freshwater-saltwater relations in the New Jersey Coastal Plain are described in two reports. 

11eisler (1989) used chloride-concentration data from wens and boreholes to describe the iocation 

of salty ground water in both onshore and offshore areas in the Northern Atlantic Coastal Plain. A 

map showing the depth to the 10,000-mgIL chloride concentration in Meisler's (1989) report was 

used in this study to approximate the location of the freshwater-saltwater interface in each aquifer. 

The effects of eustatic sea-level changes on freshwater-saltwater relations are discussed in 

Meisler and others (1985). A cross-sectional flow model through Atlantic City is used to simulate 

the location of the freshwater-saltwater interface. Meisler (1989) concluded that the observed 

freshwater-saltwater interface is not in equilibrium with present sea level but is still influenced by 

lower sea levels that have occurred in the past. He attributes the observed broad freshwatersaltwater transition zone to saltwater circulation caused by eustatic sea-level fluctuations. 

Walker (1983), Eckel and Walker (1986), and Rosman and others (1995) present potentiometric-surface maps of the confined parts of most of the Coastal Plain aquifers for fall 1978, 1983, 

and 1988, respectively. Synoptic water levels in these reports were used to describe the groundwater flow system and calibrate the flow model. 

Results of several more recent modeling studies (Pucci and others, 1994; Spitz and 

Barringer, 1992; and Navoy, 1994) were examined and used to modify the current flow model as 

needed. 

5 
DESCRIPTION OF HYDROGEOLOGIC UNITS USED IN THE MODEL 

The Coastal Plain aquifer system in New Jersey is composed of seaward-dipping layers of 

sand, silt, and clay overlying crystalline bedrock. The sediments generally strike northeastsouthwest and dip 10 to 60 ft/mi to the southeast. Detailed descriptions of the hydrogeology of the 

New Jersey Coastal Plain aquifers and confining units are given in Zapecza (1989) and Martin 

(1998). 

The conceptual model used to represent the aquifer system is based on that used by Martin 

(1998) to simulate the freshwater flow system in the Coastal Plain. Aquifers in the New Jersey 

Coastal Plain are composed predominantly of sand, but also may include interbedded silts and 

clays. The confining units are clay and silt with minor amounts of sand (Martin, 1998, p. 6). In the 

current study, Martin's (1998) conceptual model was modified and extended downdip to include 

the flow system in the saltwater parts of the aquifers and confining units. The aquifer and 

confining-unit designations are the same as those used in the RASA model. The Coastal Plain 

sediments were simulated as ten major aquifers and nine intervening confining units. The Holly 

Beach water-bearing zone (model layer Al 0) and the underlying Cape May confining unit (model 

layer C9) were included in the model, but they are minor units that are present only in the Cape 

May County area. Aquifers in the New Jersey Coastal Plain and their corresponding geologic units 

are shown in table 1. A generalized hydrogeologic section through the Coastal Plain (fig. 2) shows 

the conceptual model of the aquifers and confining units in onshore areas. 

The saltwater part of the flow system was modeled by extending the hydrogeologic framework to the edge of the Continental Shelf. Because little is known of the stratigraphy of the Continental Shelf sediments and even less is known of the hydrogeology offshore, the offshore aquifer 

system was assumed to form a fairly uniform wedge of units correlating to the onshore system and 

striking northeast-southwest. The altitudes of the top and bottom of each aquifer and confining unit 

were estimated by extending the trends observed in the RASA model framework, and by using 

available data from well logs and lithologic descriptions of two deep boreholes near the edge of the 

Continental Shelf. These boreholes, shown in figure 1, were drilled during the 1970's as part of the 

Continental Offshore Stratigraphic Test (COST) program (Scholle, 1977; Scholle, 1980). It was 

not possible to completely correlate the aquifers onshore to the data from these boreholes. Ages of 

sediments and sequences of major sand and clay units were used to estimate the altitude and 

thickness of each aquifer and confining unit at the Continental Shelf, enabling the interpolation of 

the hydrogeologic framework between the known st~cture onshore and the inferred structure at 

the edge of the shelf. Estimates of the framework characteristics of the Potomac-Raritan-Magothy 

aquifer system onshore in'Cumberland, Cape May, and Atlantic Counties and the eastern parts of 

Burlington and Ocean Counties are based on those in O.S. Zapecza (U.S. Geological Survey, 

wri~n commun., 1990). A generalized section showing the model representation of the aquifers 

and confining units to the limit of the Continental Shelf is shown in figure 3. 

In the RASA model, the downdip limits of the Lower, Middle, and Upper PotomacRaritan-Magothy aquifers, the lower Kirkwood-Cohansey and confined Kirkwood aquifers, and 

the upper Kirkwood-Cohansey aquifer were based on the estimated limit of freshwater in each 

aquifer. In this study, the ground-water flow in the saltwater part of each aquifer also is included. 

These aquifers are assumed to be present and to consist of permeable sands to the limit of the Conti6 
Table 1. Geologic and hydrogeologic units of the New Jersey Coastal Plain and model units used in this 

study 

[Modified from Zapecza (1989, table 2) and Seaber (1965, table 3); shading indicates adjacent geologic or hydrogeologic unit is not present] 

MODEL UNITS HYDROGEOLOGIC SYSTEM SERIES GEOLOGIC UNIT UNIT Updip Downdip 

I·U>::>: 

Holocene Undifferentiated Upper Kirkwood-Cohansey aquifer (A9) 

Beach sand Holly Beach water-bearing zone (A 10) Quaternary and gravel 

~------~~---------------+------~ Cape May Kirkwood- Pleistocene Formation Cohanseyl 

l'PellnsauJ(enl'rorm:atlcm 

ntsnaJ,",~et()fl I"vuHauvu 

Beacon Hill Gravel 

Cohansey Sand 

KirkwoodCohansey 

aquifer 

system Lower Kirkwood-Cohansey aquifer (A8) 

Miocene 

Kirkwood FOIDlation 

Tet1iary 

I--_c-:-:;-:-onfiln::;-iin~g:--_k:«<>« ••• ·.·> .......... !;/) ••••..•.••. <»: Confined Kirkwood aquifer (A8) I Atlantic City ••••••• •••••• ••••.•• ••.•••.•••••.•.•••.• ..... ...... :>< •••• 

800-foot sand /nt .•••.•••••••••• ••••••• / •.•.•.•. • ••••••••• 

BasaIK'irkwI:)od confining unit (C7) 

Piney Point Piney Point Formation Piney Point aquifer (A 7) aquifer 

Eocene Vincentown-Manasquan confining unit (A6) • < :"'F"o,l .. rm""iltL"i,Ci",n" 

Vincentown Vincentown Formation Vincentown aquifer (A6) aquifer Paleocene 

TH"'oml~rst()wn Sand 

Tinton 

Red Bank Navesink-Hornerstown confining unit (CS) Red Bank Sand sand 

Mount Laurel Sand Wenonah-Mount Laurel 

aquifer Wenonah-Mount Laurel aquifer (AS) Wenonah :"'Forma·tJon 

~--------1 Marshalltown-Wenonah Marshall town-Wenonah confining unit 

Marshalltown r,bO]rIrultlonl confining unit 

Englishtown aquifer Englishtown Formation Englishtown aquifer (A4) Upper system 

Cretaceous TT " ~1~, Cretaceous IVuuu~y ~'"] MerChantville-Woodbury 

• ." i"F"O',I"nnu"f,ltul"vo"n,I confining unit Merchantville-WoodbUl)' confining unit (C3) 

Upper Magothy FOIDlation Upper Potomac-Raritan-Magothy aquifer (A3) aquifer 

Confining Confining unit between the Middle and Upper Potomac-Raritan-Magothy aquifers (C2) unit 

Raritan Formation 

Middle Middle Potomac-Raritan-Magothy aquifer (A2) aquifer 

Confining Confining unit between the Lower and Middle Potomac-Raritan-Magothy aquifers (Cl) unit 

Potomac Group Lower Lower Lower Potomac-Raritan-Magothy aquifer (AI) Cretaceous aquifer 

Bedrock Bedrock confining unit 

1 Kirkwood-Cohansey aquifer system 

2 Rio Grande water-bearing zone 

7 
NORTHWEST SOUTHEAST ENGLISHTOWN AQUIFER (A4) 

MARSHALLTOWN-WENONAH CONFINING UNIT (C4) 

FALL LINE NAVESINK-HORNERSTOWN CONFINING UNIT (C5) 

VINCENTOWN AQUIFER (A6) 

EXPLANATION 

'/ .::::::- II '\ Model units are described in table 1 

~ \\ ~ // 

Not to scale '; .::::::- II 

Figure 2. Generalized hydrogeologic section through the onshore part of the New Jersey 

Coastal Plain. (From Martin, 1998, fig. 2) 

8 
0 

-500 

-1,000 

-1,500 

Iw -2,000 w 

LL 

Z 

-2,500 

w 

0 

:::> 

r- -3,000 

~ « 

-3,500 

-4,000 

-4,500 

-5,000 

0 

Fall Line 

EXPLANATION 

AQUIFER 

LOW-PERMEABILITY 

AQUIFER 

• CONFINING UNIT 

VERTICAL SCALE GREATLY EXAGGERATED 

20 40 

Coast 

60 80 

MILES 

Upper Kirkwood_C Ohansey 

100 120 140 

Figure 3. Generalized hydrogeologic section showing model representation of aquifers and 

confining units from the Fall Line to the Continental Shelf, New Jersey Coastal Plain. 

9 
nental Shelf. Hydraulic conductivities in downdip areas of each aquifer are estimated from values 

for the sediments near the downdip boundary of the RASA model and are assumed to decrease 

offshore. 

Each aquifer and confining unit is described below. The discussion includes a description 

of the hydrogeologic framework, hydrogeologic properties, and areas where the representation of 

the unit is different from that used in the RASA model. Maps of the transmissivity of each aquifer 

and the leakance of each confining unit are presented. The confining-unit leakance maps are 

limited to areas where leakance in the model actually represents the presence of a confining unit 

and do not include areas where leakance in the model is used to represent conductances to 

overlying streams. Additional details on the hydrogeologic framework in the study area can be 

found in Zapecza (1989). Available data on the hydraulic properties of the aquifers and confining 

units (including transmissivities, horizontal hydraulic conductivities, and storage coefficients of 

the aquifers and vertical hydraulic conductivities of the confining units) are available in Martin 

(1998). 

Lower Potomac-Raritan-Ma20thy Aquifer 

The lowermost aquifer simulated is the Lower Potomac-Raritan-Magothy aquifer (model 

unit AI). The aquifer consists of sand and gravel and is underlain everywhere by crystalline 

bedrock. In downdip and offshore areas the model unit generally represents the lower one-third of 

the undifferentiated Potomac-Raritan-Magothy aquifer system. Crystalline bedrock is not penetrated by either of the COST wells (more than 16,000 ft below sea level), and geophysical investigations indicate that the depth to bedrock is between 13,000 and 20,000 ft below sea leveL A thick 

sequence of Jurassic sediments overlies the bedrock in the COST wells. These sediments include 

large percentages of limestone, dolomite, clay, or claystone, all of which are less permeable than 

the overlying Lower Cretaceous sediments (Scholle, 1977, p. 22) and in the model are considered 

to be impermeable. The altitude of the bottom of the Lower Potomac-Raritan-Magothy aquifer 

near the edge of the Continental Shelf is assumed to be the base of the Lower Cretaceous sediments 

in the COST wells (Scholle, 1980, p. 6). The underlying Jurassic sediments are considered to be 

impermeable and serve as the model's lower boundary. 

The altitude of the top of the Lower Potomac-Raritan-Magothy aquifer ranges from sea 

level near the Delaware River to more than 9,600 ft below sea level near the edge of the Continental 

Shelf. The aquifer is 75 ft thick near the Delaware River and thickens downdip to more than 2,000 

ft at the limit of the Continental Shelf. 

The transmissivity of the Lower Potomac-Raritan-Magothy aquifer ranges from 480 to 

18,900 ft2/d, with an average of 6,290 ft2/d (app. 1, fig. la). Transmissivities are lowest updip 

where the aquifer thins near and under the Delaware River; they are highest downdip, offshore 

from northern Ocean County. Results of aquifer tests indicate that transmissivities range from 

2,300 to 16,600 ft2/d (Martin, 1998). Transmissivity in the Lower Potomac-Raritan-Magothy 

aquifer is generally controlled more by variations in hydraulic conductivity than by thickness. 

Hydraulic conductivities from 2 to 10 ft/d were estimated for the downdip areas where the aquifer 

was extended past the boundaries of the RASA model. The aquifer is assumed to be present and 

permeable down dip to the limit of the Continental Shelf. 

10 
Confinin2 Unit between the LOwer and Middle Potomac-Raritan-Ma20tby Aquifers 

The confining unit between the Lower and Middle Potomac-Raritan-Magothy aquifers 

(model unit C 1) overlies the entire extent of the Lower Potomac-Raritan-Magothy aquifer. The 

confining unit has the same areal extent as model unit A 1 and is overlain everywhere by model unit 

A2. Thickness ranges from less than 50 ft near the Delaware River to more than 1,100 ft southeast 

of Cape May. Along the coast, thickness increases to the south, from less than 50 ft at the updip 

limit of the confining unit near the Manasquan River to the maximum thickness near Cape May. 

At the COST wells, the confining unit is estimated to be about 700 ft thick. 

In downdip areas, the Lower and Middle Potomac-Raritan-Magothy aquifers are largely 

interbedded sands, silts, and clays and cannot be distinguished from one another (Zapecza, 1989, 

p. 12). The high leakance of the yonfining unit (app. 1, fig. Ib) causes the Lower and Middle 

aquifers to respond to stresses as one hydrologic unit. Therefore, this confining unit is more 

permeable than most of the other confining units in the New Jersey Coastal Plain. Leakance varies 

from a maximum of 2.5 x 10-4 ft/d/ft in updip areas to less than 5 x 10-7 ft/d/ft in downdip areas. 

Leakance values updip in Salem, Gloucester, Camden, and southern Burlington Counties are about 

50 percent lower than those reported in Martin (1998). Estimates of leakance down dip are based 

on vertical hydraulic conductivities calculated from RASA model input data. Variations in 

leakance of the unit are primarily the result of differences in the thickness of the confining unit. 

Middle Potomac-Raritan-Ma2othy AQuifer 

The Middle Potomac-Raritan-Magothy aquifer (model unit A2) is equivalent to the 

Farrington aquifer (the Farrington Sand Member of the Magothy Formation) in the northeastern 

part of the New Jersey Coastal Plain. Where the Lower Potomac-Raritan-Magothy aquifer and the 

confining unit between the Lower and Middle Potomac-Raritan-Magothy aquifers are absent, the 

aquifer overlies bedrock, weathered bedrock, or clays (Martin, 1998). In downdip areas the aquifer 

generally represents the sandiest part of the middle one-third of the undifferentiated PotomacRaritan-Magothy aquifer system. In downdip areas onshore the aquifer framework was based on 

data from O.S. Zapecza (written commun., 1992). The altitude of the top of the aquifer ranges from 

100 ft above sea level to 8,000 ft below sea level offshore at the limit of the Continental Shelf. The 

aquifer thickens from 50 ft thick near the Delaware River to more than 800 ft thick at the COST 

wells. Along the coast the thickness varies from 100 ft near Monmouth County to more than 600 

ft east of Ocean County, and decreases to 250 ft in northern Cape May County. 

Transmissivity of the Middle Potomac-Raritan-Magothy aquifer (app. 2, fig. 2a) ranges 

from less than 1,000 ft2/d in up dip areas to more than 16,000 ft2/d in Ocean County, with an 

average value of 2,400 2 ft /d. Estimates of transmissivity from available aquifer tests range from 

42 ft2/d to 68,600 ft2/d (Martin, 1998). Lateral variations in transmissivity are the result of variations in hydraulic conductivity rather than differences in aquifer thickness. Hydraulic conductivities of 2 to 6 ftl d were estimated downdip from the RASA model boundary. The aquifer is assumed 

to extend to the limit of the Continental Shelf. 

11 
Confining Unit Between the Middle and UDDer Potomac-Raritan-Magothy Aquifers 

The confining unit between the Middle and Upper Potomac-Raritan-Magothy aquifers 

(model unit C2) overlies the entire extent of the Middle Potomac-Raritan-Magothy aquifer. The 

confining unit thickens down dip from less than 50 ft thick near the outcrop to 400 ft thick at the 

coast and to more than 750 ft thick at the limit of the Continental Shelf. The confining unit is 

estimated to be between 700 and 800 ft thick at the COST wells. 

The leakance of the confining unit between the Middle and Upper Potomac-RaritanMagothy aquifers (app. 2, fig. 2b) varies from about 2 x 10-4 ft/d/ft in updipareas to less than 

7 5 x 10- ft/d/ft in downdip areas and in parts of Middlesex and Monmouth Counties. Variations in 

leakance are primarily the result of differences in the thickness of the confining unit. Leakance in 

downdip areas is estimated from vertical-hydraulic-conductivity values calculated from RASA 

model input data. 

Uuuer Potomac-Raritan-Magothy AQuifer 

The Upper Potomac-Raritan-Magothy aquifer (model unit A3) consists primarily of the 

Magothy Formation in New Jersey, but is the Old Bridge aquifer (the Old Bridge Sand Member of 

the Magothy Formation) in the northeastern part of the New Jersey Coastal Plain. The altitude of 

the top of the aquifer ranges from 100 ft in the outcrop area to 6,400 ft below sea level at the limit 

of the Continental Shelf. Onshore, the aquifer thickens down dip from a featheredge at the outcrop 

to 1,500 ft thick near the coast in Monmouth County and to about 250 ft thick at Cape May. 

Offshore, the aquifer is approximately 850 ft thick at the limit of the Continental Shelf and about 

900 ft thick at the COST wells. 

Transmissivi~ of the Upper Potomac-Raritan-Magothy aquifer (app. 3, fig. 3a) ranges 

from less than 500 ft Id in updip areas in Salem County to more than 10,000 ft2/d in Gloucester, 

Camden, and Monmouth Counties. The average transmissivity of this unit in the model area is 

2 2,800 ft2/d. Transmissivity determined from aquifer tests ranges from 500 ft /d to 16,600 ft2/d 

(Martin, 1998). Estimates of hydraulic conductivity downdip range from 2 to 10 ftld. The aquifer 

is assumed to extend to the limit of the Continental Shelf. 

Merchantyille-Woodbury Confining Unit 

The Merchantville-Woodbury confining unit (model unit C3) overlies the entire extent of 

the Upper Potomac-Raritan-Magothy aquifer. The confining unit thickens from a featheredge to 

200 ft thick downdip at the coast and to more than 450 ft thick at the downdip boundary of the 

model. At the COST wells the unit is estimated to be between 500 and 600 ft thick. 

Leakance of the Merchantville-Woodbury confining unit (app. 3, fig. 3b) varies from 

2 1 x 10- ftJd/ft updip near the Delaware River in Gloucester, Camden, and Burlington Counties to 

9 2 x 10- ft/d/ft along the coast in Ocean and Monmouth Counties. The Merchantville-Woodbury 

confining unit is one of the least permeable confining units in the New Jersey Coastal Plain. The 

12 
high leakance shown in updip areas in appendix 3 (fig. 3b) represents an extension of the confining 

unit used to simulate the outcrop of the Upper Potomac-Raritan-Magothy aquifer near the 

Delaware River (Martin, 1998). 

En~lishtown Aquifer 

The Englishtown aquifer (model unit A4) in this report includes both the upper and lower 

sand units of the Englishtown aquifer system as described by Zapecza (1989). A facies change 

from sand to silt and clay occurs in northwestern Cumberland, northwestern Atlantic, southwestern 

Burlington, and southwestern Ocean Counties and represents the down dip limit of the simulated 

aquifer. The limit of permeable sediments in the Englishtown aquifer is shown in appendix 4 

(fig. 4a). The penneable part of the aquifer contains only freshwater. 

The altitude of the top of the Englishtown aquifer ranges from 150 ft in the outcrop area to 

more than 1,600 ft below sea level downdip in Ocean County. The aquifer is generally less than 

100 ft thick except in southern Monmouth County and northeastern Ocean County, where it is as 

much as 200 ft thick. 

The transmissivity of the Englishtown aquifer (app. 4, fig. 4a) is generally less than 

500 ft2/d in the southern, penneable part of the aquifer. Transmissivity is highest in parts of Burlington and Ocean Counties and in Monmouth County, where it reaches a maximum of 1,200 ft2/d. 

Estimates of transmissivity from available aquifer tests range from 1,000 to 2,100 ft2/d (Martin, 

1998). Hydraulic conductivity of the aquifer ranges from 4 to 10 ftld. Variations in transmissivity 

generally are the result of differences in aquifer thickness. 

Marshalltown-Wenonah Confinin2 Unit 

The Marshalltown-Wenonah confining unit (model unit C4) overlies the Englishtown 

aquifer in updip areas (where the Englishtown aquifer is present). In downdip areas, the confining 

unit directly overlies the Merchantville-Woodbury confining unit (model unit C3). The confining 

unit is relatively thin; its thickness onshore ranges from 20 to 80 f1. Offshore the unit thickens 

gradually to 180 ft at the limit of the Continental Shelf in the southeastern comer of the study area. 

The leakance of the Marshalltown-Wenonah confining unit (app. 4, fig. 4b) ranges from a 

6 maximum o~ 3 x 10-3 ft/d/ft where the confining unit is thinnest to a minimum of 1 x 10- to 

6 x 10-8 ft/dlft where it is thickest (40-80+ ft thick) in northern Burlington County, parts of Ocean 

County, and southern Monmouth County. The leakance of the Marshalltown-Wenonah confining 

unit is higher than that of the other confining units in the New Jersey Coastal Plain. 

Wenonah-Mount Laurel Aquifer 

The Wenonah-Mount Laurel aquifer (model unit A5), where present, overlies the Marshalltown-Wenonah confining unit. The aquifer extends from its outcrop downdip approximately 50 to 

60 mi where a facies change from sand to silt and clay occurs. This facies change defines the 

13 
downdip, permeable part of the aquifer. The downdip limit of the simulated aquifer is shown in 

appendix 5 (fig. Sa). The altitude of the top of the Wenonah-Mount Laurel aquifer ranges from 200 

ft in the outcrop to 2,600 ft below sea level offshore. The aquifer is generally less than 100 ft thick. 

The transmissivity of the Wenonah-Mount Laurel aquifer (app. 5, fig. 5a) ranges from 3 to 

1,600 ft2/d, with an average value of620 ft2/d. Transmissivity greater than 1,000 ft2/d is limited to 

parts of northern Salem and Cumberland Counties, eastern Gloucester and Camden Counties, 

southern Burlington County, and northwestern Atlantic County. Transmissivity values determined 

from aquifer tests range from 360 to 1,430 ft2/d (Martin, 1998). Lateral variations in transmissivity 

generally are the result of differences in aquifer thickness. 

Nayesink-HQrnerstown Confinine Unit 

The Navesink-Hornerstown confining unit (model unit C5) overlies the entire extent of the 

Wenonah-Mount Laurel aquifer. The confining unit is generally less than 100 ft thick onshore 

except in southern Atlantic County and in Monmouth and northern Ocean Counties. The thickness 

of the confining unit is approximately 60 ft along the coast and increases to 140 to 180 ft at the 

limit of the Continental Shelf. 

The leakance of the Navesink-Hornerstown confining unit (app. 5, fig. 5b) ranges from 

1 x 10-3 ft/d/ft in updip areas to 2 x 10-8 ft/d/ft in north-central Burlington County. Leakance in 

updip areas is among the highest in the Coastal Plain and represents areas of strong vertical connection between the Wenonah-Mount Laurel aquifer and the Vincentown aquifer. 

vincentown Aquifer 

The Vincentown aquifer (model unit A6) extends from its outcrop area approximately 8 to 

10 mi downdip, where a facies change from sand to silt and clay occurs. The permeable part of the 

aquifer is shown in appendix 6 (fig. 6a). The altitude of the top of the aquifer ranges from 200 ft in 

the outcrop area to 400 ft below sea level downdip. Thickness increases from about 25 ft in the 

outcrop area to a maximum of 140 ft in Monmouth County, although the aquifer is generally less 

than 100 ft thick. 

The transmissivity of the Vincentown aquifer (app. 6, fig. 6a) ranges from 500 ft2/d to 

3,500 ft2/d, with an average value of 1,500 ft2/d. Transmissivity determined from a single laboratory test in the outcrop area in Burlington County was reported as 530 rt2/d (Martin, 1998). Transmissivity is greatest in local areas in Salem and Monmouth Counties where the aquifer is thickest. 

Variations in transmissivity are the result of differences in aquifer thickness. 

vincentown-ManasQuan Confinin2 Unit 

The Vincentown-Manasquan confining unit (model unit C6) overlies the Vincentown 

aquifer in updip areas, where the Vincentown aquifer is present. Downdip from the limit of the 

Vincentown aquifer, the confining unit directly overlies the Navesink-Hornerstown confining unit. 

14 
The confining unit thickens from a featheredge in the outcrop area of the overlying lower 

Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8) to more than 900 ft thick at 

the limit of the Continental Shelf. 

The leakance of the Vincentown-Manasquan confining unit (app. 6, fig 6b) ranges from 

2 3.5 x 10- ft/d/ft in updip areas to less than 1 x 10-8 ftldlft downdip. 

Piney Point AQuifer 

The Piney Point aquifer (model unit A 7) is completely overlain by the clay of the basal 

Kirkwood confining unit and does not crop out. The updip limit of the Piney Point aquifer is 

generally at the downdip limit of the Vincentown aquifer. The Piney Point aquifer thins and is 

probably absent several miles downdip from the coast. The altitude of the top of the aquifer ranges 

from less than 100 ft below sea level to 1,300 ft below sea level at its downdip limit. The thickness 

of the aquifer ranges from about 40 ft in Atlantic County to more than 500 ft in western Cumberland County. The Piney Point aquifer is continuous south into Delaware. 

The transmissivity of the Piney Point aquifer (app. 7, fig. 7a) ranges from 150 to 2,700 ft2/d. 

Transmissivity is highest where the aquifer is thickest in Burlington, Ocean, Cumberland, and 

Cape May Counties. Areas where transmissivity is less than 1,000 ft2/d are Atlantic, southern 

Camden, and southern Gloucester Counties'. Transmissivity reported from the only available 

aquifer test in this aquifer is 1,400 ft2/d (Martin, 1998). 

Basal Kirkwood Confinin2 Unit 

The basal Kirkwood confining unit (model unit C7) represents the basal clay of the 

Kirkwood Formation and silty parts of the Piney Point Formation. The basal Kirkwood confining 

unit overlies the Piney Point aquifer where the Piney Point is present, and overlies the VincentownManasquan confining unit both updip and downdip from the limit of the Piney Point aquifer. The 

confining unit thickens gradually down dip to about 140 ft thick at the coast, and to more than 500 ft 

thick at the limit of the Continental Shelf. 

Leakance of the basal Kirkwood confining unit (app. 7, fig. 7b) is low and ranges from 

1 x 10-4 to 5 x 10-8 ft/dlft. Leakance is highest updip in Burlington and Ocean Counties. 

Lower Kirkwood-Cohansey and Confined Kirkwood AQuifers 

The lower Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8) represent 

the confined Atlantic City 800-foot sand and the overlying, relatively minor Rio Grande waterbearing zone in down dip areas. In this report the Atlantic City 800-foot sand and Rio Grande waterbearing zone are together referred to as the confined Kirkwood aquifer. This aquifer is assumed to 

be present and permeable downdip to the limit of the Continental Shelf. In updip areas this unit 

represents the lower part (approximately the lower one-third) of the unconfined KirkwoodCohansey aquifer system and is referred to as the lower Kirkwood Cohansey aquifer. The trans15 
missivity of the lower Kirkwood-Cohansey and confined Kirkwood aquifers and the approximate 

updip limit of the confined Kirkwood aquifer (which is also the updip limit of the overlying 

confining unit) are shown in appendix 8 (fig. 8a). 

The Kirkwood-Cohansey aquifer system was subdivided into an upper and lower aquifer 

in updip areas to better represent the vertical head distributions in the unconfined aquifer system 

and to provide a lateral connection between the confined Kirkwood aquifer and the lower 

Kirkwood-Cohansey aquifer (Martin, 1998). Where the overlying confining unit is present, the 

altitude of the top of the modeled aquifer represents the top of the Rio Grande water-bearing zone 

and ranges from 200 ft below sea level to 1,600 ft below sea level at the limit of the Continental 

Shelf. The thickness of the confined Kirkwood aquifer ranges from about 200 ft to about 1,000 ft 

at the limit of the Continental Shelf and represents the combined thickness of the Atlantic City 

800-foot sand, the Rio Grande water-bearing zone, and the intervening confining unit. 

The altitude of the top of the lower Kirkwood-Cohansey aquifer ranges from 170 ft in the 

outcrop area to 200 ft below sea level in Cumberland County near the updip limit of the overlying 

confining unit. The lower Kirkwood-Cohansey aquifer is generally less than 200 ft thick. 

Transmissivity of the lower Kirkwood-Cohansey and confined Kirkwood aquifers (app. 8, 

fig. 8a) ranges from less than 1,000 ft2/d near the outcrop area to 12,800 ft2/d in Atlantic County, 

with an average value of4,000 ft2/d. Transmissivity determined from available aquifer tests ranges 

from 1,500 to 12,500 ft2/d (Martin, 1998). 

CQnfinio2 Unit Overlyio2 the Rio Grande 'Vater-Bearing Zone 

The confining unit overlying the Rio Grande water-bearing zone (model unit C8) 

completely overlies the confined Kirkwood aquifer. The unit thickens downdip from less than 

150 ft over most of its onshore extent to slightly more than 200 ft thick at the limit of the Continental Shelf. The confining unit offshore has a relatively uniform thickness in the model. 

Southwest of Cape May County in the Delaware Bay, the location of the updip limit of the 

confining unit has been modified from that used in the RASA model. Recent investigations of the 

Cape May County area including the Delaware Bay indicate that the confining unit may be thin or 

absent there (L.M. Voronin, U.S. Geological Survey, oral commun., 1992). The confining unit in 

the Delaware Bay may have been eroded by the Delaware River; in this case, the lower KirkwoodCohansey and confined Kirkwood aquifers would be in direct connection with the saltwater in the 

bay or with overlying recent sediments, which also contain saltwater, in this area. Therefore, 

saltwater is more likely to be moving toward Cape May from the direction of the Delaware Bay 

than from the offshore areas downdip. 

The leakance of the confining unit overlying the Rio Grande water-bearing zone (app. 8, 

fig. 8b) is relatively low and ranges from 5 x 10-5 to 2.4 x 10-8 ft/d/ft. 

16 
Upper Kirkwood-Cohansey Aquifer 

The upper Kirkwood-Cohansey aquifer (model unit A9) overlies the confining unit 

overlying the Rio Grande water-bearing zone, as well as the lower Kirkwood-Cohansey aquifer 

where the confining unit is absent. The upper Kirkwood-Cohansey aquifer is simulated as unconfined, overlain only by the estuarine clay confining unit (model unit C9) in offshore areas, except 

in Cape May County where the Holly Beach aquifer exists. The altitude of the top of the aquifer 

ranges from 180 ft in the outcrop area to about 300 ft below sea level at the limit of the Continental 

Shelf, and the thickness increases gradually from a featheredge in the outcrop to more than 1,100 ft 

at the limit of the Continental Shelf. Transmissivity of the upper Kirkwood-Cohansey aquifer 

ranges from 200 to more than 20,000 ft2

/d in offshore areas. 

Estuarine Clay CQnfinin&: Unit 

The estuarine clay confining unit (model unit C9) overlies the upper Kirkwood-Cohansey 

aquifer, but is present only in peninsular Cape May County and offshore. Its thickness is identical 

to that in the RASA model, but in this report the top of the confining unit offshore corresponds to 

the bathymetry. The confining unit was extended downdip to the limit of the Continental Shelf by 

estimating a uniform thickness of 50 ft. Leakance offshore was determined during model 

calibration. 

DESCRIPTION OF GROUND-WATER-FLOW MODEL 

Freshwater and saltwater heads and freshwater-saltwater interface locations in 10 aquifers 

in the New Jersey Coastal Plain were simulated by using the SHARP model (Essaid, 1990). A 

schematic representation of the model units used to represent the hydrogeologic units is shown in 

figure 4. 

Freshwater and saltwater heads and the location of the freshwater-saltwater interface were 

simulated (1) for an assumed steady-state condition in which sea level was relatively constant for 

20,000 to 30,000 years (from 110,000 to 84,000 years ago); (2) for the past 84,000 years, by 

including the effects of changes in sea level (based on the initial conditions in simulation 1); and 

(3) for 1896 through 1988, by including ground-water withdrawals from the New Jersey Coastal 

Plain (based on the results of simulation 2). 

Sharp-Interface Approach 

The SHARP model is a quasi-three-dimensional, finite-difference model that simulates 

coupled freshwater and saltwater flow separated by a sharp interface (Essaid, 1990). The SHARP 

model can be used to simulate regional ground-water flow more efficiently than a more numerically demanding solute-transport model, which typically is practical only for simulation of flow in 

a two-dimensional section. 

17 
NORTHWEST 

FALL LINE 

EXPLANATION 

Constant head 

Confining unit 

Recharge to aquifer node 

Aquifer 

No-flow boundary 

Vertical hydraulic connection 

between confining units 

Flux boundary 

Streambed 

Low-permeability unit 

- Constant saltwater head equals zero 

Note: Aquifer and confining-unit numbers 

refer to model units listed in table 1 

SOUTHEAST 

Figure 4. Schematic representation of aquifers, confining units, and boundary conditions 

used in the New Jersey Coastal Plain flow model. 

18 
Compared to the RASA model (Martin, 1998), the SHARP model refines the simulation of 

ground-water flow in the New Jersey Coastal Plain in several ways. First, it allows the location of 

the freshwater-saltwater interface in each of the 10 aquifers to be simulated rather than estimated 

on the basis of the sparse data on chloride concentrations that are available for offshore areas. The 

SHARP model determines the location of the interface from the simulated freshwater and saltwater 

heads in the aquifers. Also, heads in the vicinity of the interface represent the actual gradient of the 

freshwater in the aquifer rather than being strongly influenced by an adjacent no-flow boundary. 

The sharp-interface approach is assumed to be valid when the width of the transition zone 

is small relative to the thickness of the aquifer. Although in some areas in the New Jersey Coastal 

Plain the zone of diffusion is wide and this assumption is false, the sharp-interface approach still 

represents a significant improvement over a simulation of the freshwater system only. Errors associated with violating this assumption occur in the downdip, freshwater parts of the aquifers, near 

the freshwater-saltwater interface. Even though the simulation of the interface in these areas may 

not be ideal, the ability to simulate the movement of the interface and more accurately simulate the 

gradients near it make the sharp interface approach more accurate than representing the interface 

as a stationary no-flow boundary. 

In the SHARP model, freshwater and saltwater heads are simulated simultaneously. These 

heads are then used to solve for the elevation of the saltwater interface at each cell. The vertically 

integrated freshwater and saltwater flow equations are described in Essaid (1990). In cells that 

contain the interface, the interface elevation is given by: 

where ~ 1 is the elevation of the interface, 

<l> s is the saltwater head, 

<l> f is the freshwater head, and 

where Y f and y s are the freshwater and saltwater specific weights, respectively. 

From this equation, the value of 6 is 40 when the freshwater and saltwater densities are 

3 1.0 g/cm and 1.025 g/cm3, respectively. Heads in model cells in which only freshwater or 

saltwater are present are simulated by using the appropriate equation for either freshwater or 

saltwater flow. 

19 
The SHARP model code was changed to allow recharge and streams to be simulated in 

aquifers other than the uppermost aquifer. This allows the simulation of recharge and overlying 

freshwater constant heads (representing streams) in the outcrop areas of dipping model units. An 

additional array is used to designate the layer to which recharge is to be applied for each model cell. 

Limitations 

The SHARP model simulates horizontal movement of saltwater but does not directly 

simulate vertical movement of saltwater. Because vertical flow between aquifers in some areas can 

be very large, vertical leakage in the SHARP model is simulated by using the restricted-mixing 

option (Essaid, 1990, p. 27). Use of this option prevents large volumes of water from being 

"converted" from one type to another without the user's knowledge. Because the vertical 

movement of saltwater into either underlying or overlying freshwater aquifers is not simulated, the 

location of the freshwater-saltwater interface tip and toe simulated by the model represents only 

horizontal movement of saltwater. Areas in which saltwater may be moving vertically into freshwater areas are identified by analyzing vertical flow rates from the model output and are considered 

to be possible sources of saltwater. 

Horizontal movement of the interface in confining units or low-permeability sediments is 

much smaller than horizontal movement in aquifers. In these low-permeability areas, vertical 

movement of saltwater probably is much more important than horizontal movement from updip 

aquifers or sources of saltwater. Use of the restricted-mixing option prevents saltwater from 

flowing into either overlying or underlying freshwater aquifers. Because of this limitation, the 

movement of the freshwater-saltwater interface movelnent in confining units and low-permeability 

sediments cannot be reliably simulated. 

In downdip parts of the model units representing the Englishtown (A4), Wenonah-Mount 

Laurel (AS), Vincentown (A6), and Piney Point (A7) aquifers (where the downdip aquifer-limit 

lines shown in appendixes 4 (fig. 4a), 5 (fig. 5a), 6 (fig. 6a), and 7 (fig. 7a) show a facies change 

to silt or clay or an aquifer pinchout), ground-water flow was simulated by using a very low 

hydraulic conductivity (0.001 ft/d). This allowed the position of the interface and freshwater and 

saltwater heads to be simulated in these areas, even though horizontal movement of water 

(including the freshwater-saltwater interface) is very small. These areas are not considered to be 

part of the aquifers as described previously, and are more representative of low-permeability 

confining-unit material. In general, however, movement of saltwater in confining units cannot be 

simulated by using the SHARP model. 

Model Grid 

The block-centered finite-difference model grid used is shown in figure 5. The model 

dimensions are 50 rows by 49 columns. The outside row and column on each side are not active 

cells, but are used to establish the lateral model boundaries. Onshore and in the updip part of the 

model (to 25 mi offshore from the coast at Cape May), the grid spacing is constant at 13,200 ft 

(2.5 mi) on each side. Farther offshore, the row spacing increases to a maximum of 19,800 ft 

(3.75 mi), whereas the column spacing remains constant at 13,200 ft. 

20 
5 

10 

15 

20 90 

5 

v) 

3 0 

3 5 

4 0 

4 5 

5 0 

COLUMN 

5 10 15 20 25 0 30 35 40 45 "Co '\ 

~~ ~ pi NI s LV NJ.t. ;: ~ ~ ...... r- '" k';.: ffii'J~ ~ ""'" ~ i k ~~ ~ t--~ V' t;2 p~ ~ -t-" -.,., /- ( FP LL LIN I~ ~ l-:P I~ t--;: y 

J ( \V '-::: 'C h )irc !V ~ ") iJE W."ORK 

V \ I~ '> ~ ,-, ,~ 

~ ) ~I[ DL SE X t-- r-

~1:6 "- pL U( ES EF ( 1 /\ I "'- !--fJ'- tJ~ - ~ e--- '- - 'sA.! r::. /\--

~ r-~ II"l \ )~ C M ~f\l / ". I", .L I ( 

I ! \-./" -~ 1\ \ I 1 \) \ \ \ , 

I ~. ~6'<9 \ -( I v 1~5)L. /j / 

I ll>-! .~ 

1\/ \ ) 

l- -If ~I~ Ll', r.u MB RL )A.NI r \ ~Itti 1,-> ( ) 

I-:JJ~ ~ ( .ld 

Pi ~ ; if ~, 

I .l(/J \ / .. lr 

II "'h] ~j'./ / ~1 

~ / \ ~r [ El AI fVA RE 1\ l (~ p. [p. ,... I If.' 

/ ti}IY r Il. 

I / l;At-' Fr-J lAY :\ ~ 

~ V /~ ~ .-,,"" -'" ~~ V- b V g::: i'r' V f-/ r----.... t--fJ'-- " I( \ I\.J'. ~ h /?' V k) "- r~ ~ l-J I~ 

/. 

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ 

/ 

o 10 MILES 

Ii! I ) 

o 10 KILOMETERS 

/3U Llf G PN 

, .-' '., , .... ..... ,r1 IlL.. Y ''- ..... 

\ ,liAr / 

M ~~ yV / 

~ II l 

{L / 

JJ 

~( ~ a: t\ // V 

.~~ V ~ Ptli/ 

'j h. ~ ~ r" Yc r-r 

r-'~ ~ " ld_ ~() c °0 ~ 

~~ 

£ r/' 

'" 

·Ie::-

j--- V 

"" ..... . 

II ;-

"- ~-: I\~ in IRiL o~ ?J 

/ -" "'. -% ~ r\0lY 

\ V loon ~v 

\ ( <: V <1l 

Ii; \ /' 

ii1 P'-" 

O(EA f) \\ \f'Y. 

1 ~ I~ ~v t~ 

'\ ~ .r~1 

V P Y !I)'" 

~ r /,v r 

lJ f\"--(V tsl

'" 

,'0' ,iY ,,\ ~ 

0 y t~ 

I[ l'" 

Lo? U\ .\ 

EXPLANATION 

NO-FLOW BOUNDARY--Bottom boundary 

(not shown) is also a no-flow 

boundary 

SPECIFIED-FLUX BOUNDARY 

I "Cia 

~ 

Figure 5. Model grid and generalized lateral boundaries of the New Jersey Coastal Plain 

flow model. 

21 
The grid is aligned approximately parallel to the Fall Line and the strike of the Coastal Plain 

hydrogeologic units. The grid is aligned with the RASA model grid and, in updip areas, the model 

cells are the same as in the RASA model. In downdip onshore and offshore areas, the grid spacing 

is finer than that used in the RASA model. Movement of the interface is simulated more accurately 

if grid spacing in the vicinity of the interface is small. The location of the freshwater-saltwater 

interface ranges from the Delaware Bay to more than 50 mi offshore in the upper KirkwoodCohansey aquifer (model unit A9), and from Salem and Cumberland Counties in the south to 

offshore from Ocean County in the north in the Lower Potomac-Raritan Magothy aquifer (model 

unit AI). Because of the wide area in which the interface is found in different aquifers, the grid was 

constructed to be finer than the RASA model grid in most downdip onshore and offshore areas. 

Roundarv Conditions 

The modeling approach and boundary conditions in aquifer and confining-unit outcrops 

onshore and offshore are the same as those used in the New Jersey RASA model (Martin, 1998). 

Generalized lateral model boundaries are shown in figure 5. The boundary conditions are 

slightly different in some aquifers than in others. The northwestern updip limit of all model layers 

is the limit of Coastal Plain sediments at the Fall Line. This represents the northwestern boundary 

in model unit A 1. In all other model units the northwestern boundary is the updip limit of the 

aquifer. These updip limits are represented as no-flow boundaries in the model. 

The northeastern boundary of the model approximates a flow line in a ground-water 

discharge area in Raritan Bay. The southwestern model boundary approximates a flow line along 

a ground-water divide near the Delaware Bay. These boundaries are simulated as specified-flux 

boundaries in the transient simulation for 1896-1988 by using flows from the Northern Atlantic 

Coastal Plain (NACP) model (Leahy and Martin, 1993), as they were in the New Jersey RASA 

model. The fluxes from the NACP model are the same as those used in the RASA model. Because 

the fluxes generally were small along these boundaries and the hydrogeologic properties of most 

of the aquifers were not changed substantially during calibration, these fluxes are assumed to be 

reasonable. The fluxes were modified for use in the seven stress periods used in this model by 

linear interpolation. In downdip areas, where the aquifers have been extended past the boundary of 

the RASA model, the boundaries are represented as no-flow boundaries. This approximation is 

valid because the gradients along these areas are small, and several of the aquifers are represented 

as low-permeability units with little ground-water flow. 

Boundary flow's were simulated by using injection or recharge wells along the edge of the 

model. In the SHARP model, the flow to or from a well is assumed to be an appropriate percentage 

of the type of water (fresh or salty) that is present in that cell over the screened interval. The ratio 

of freshwater flow to saltwater flow is determined by the percentage of the aquifer that contains 

fresh or salty water. No boundary flows were used in the initial steady-state flow model 

(sea level = -27 ft) or in the simulation of changes in sea level because these fluxes are unknown 

and are assumed to be small because the boundaries are near flow divides. 

22 
The downdip boundaries in this model are considerably different from those in the RASA 

model because the current model was extended to the limit of the Continental Shelf. In the RASA 

model, the downdip boundaries were simulated as a combination of no-flow boundaries (model 

units AI-A 7) and specified-flux boundaries (A8, A9). In the Potomac-Raritan-Magothy aquifer 

system (model units AI-A3), the downdip limit of the aquifers in the RASA model was the 

presumed location of the freshwater-saltwater interface. In this model, these units were extended 

down dip to the limit of the Continental Shelf, where they are represented by a no-flow boundary. 

The freshwater-saltwater interface was simulated directly in the current model and the freshwater 

flow system near the interface is simulated more realistically than if the interface were a no-flow 

boundary. In model units A4 to A7, the limit of the permeable part of the aquifer is the same as in 

the RASA model; however, the facies change in these units is now represented by low-permeability sediments downdip. The down dip boundaries of model units AS'and A9, which were represented as specified-flux boundaries in the RASi\. model, are now simulated as constant salv.vater 

heads where these units subcrop at the Continental Slope. The saltwater head used is equal to the 

depth of saltwater above the midpoint of the aquifer (bathymetry + 112 aquifer thickness) and the 

depth of the saltwater interface is assumed to be 25 ft above the top of the aquifer. This approach 

allows the freshwater-saltwater interface location to be simulated and improves the accuracy of the 

simulation of the freshwater flow system in these aquifers. 

The lower boundary of the model represents the top of the underlying crystalline bedrock 

in the onshore areas that were simulated as part of the RASA model. The crystalline rocks are 

simulated as a no-flow boundary and underlie the Lower Potomac-Raritan-Magothy aquifer 

(model unit AI), except in the northern part of the New Jersey Coastal Plain onshore where the 

Lower aquifer is absent and the c!),staHine rock underlies the Middle Potomac-Raritan-Magothy 

aquifer (A2). Because the crystalline bedrock was not penetrated by either of the offshore COST 

wells, the lower boundary of the model in offshore areas is a no-flow boundary that represents the 

contact with the thick sequence of low-permeability Jurassic sediments that contain high percentages of limestone, dolomite, and clay or claystone observed at the COST wells. 

The upper boundary of the model in onshore areas represents the water table and streams 

in the outcrop areas of the Coastal Plain aquifers and is the same as that used in the New Jersey 

RASA model (Martin, 1998). Cells in the outcrop areas of the unconfined aquifers receive 

recharge, and water-table altitudes respond to ground-water withdrawals. Streams in these cells are 

represented by a constant head in the overlying layer. The head represents the average long-term 

stream stage for the outcrop cell. (Each outcrop cell is assumed to have at least one stream in it.) 

The average elevations of these streams are shown in figure 6. The effective streambed leakances 

and average stream stages documented in the RASA model were used. This approach is a reasonable way to include the effects of the water table in a regional model, but it has limitations. The 

large cells used limit the resolution of the water table and it is not possible to include many of the 

local features that can be important in the aquifer recharge areas. Because the aquifer outcrops as 

modeled can supply an unlimited amount of water to the deeper confined aquifers, analysis of the 

flow budgets of the aquifers is necessary to confirm that the amount of water supplied is 

reasonable. . 

23 
EXPLANATION 

-- 20 -- STREAM-STAGE CONTOUR--Shows elevation of 

/ / 

o 10 MILES I I i I 

o 10 KILOMETERS 

Base from U,S, Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

stream stage. Contour interval 25 feet. Datum is 

sea leve! 

~.-- "\/> 

(.',~-~'--;.' / 

Figure 6. Generalized stream elevations in the New Jersey Coastal Plain. 

(From Martin, 1998) 

24 
The outcrop areas in offshore areas are represented as constant-head nodes. Recharge is not 

applied in these areas. Most of these cells are in the Holly Beach water-bearing zone. The constanthead values used are equivalent freshwater heads determined from the depth of saltwater above the 

node, which was calculated by using the bathymetry values described in the next section. 

The upper boundary of the model is affected during the simulation of sea-level changes. 

The SHARP model was modified to update the boundary conditions when sea level rises or falls. 

In each time step, the elevation of the top of every cell that is designated as an offshore outcrop cell 

is compared to sea level calculated for that time step to determine whether the cell should be treated 

as an onshore cell or an offshore cell. Cells that are converted to onshore outcrop cells as a result 

of changes in sea level are simulated in a similar way to other onshore outcrop cells. Recharge is 

applied to the cells and overlying leakance values are changed to an average leakance value for 

stre~rn cells in that layer. Stream stage was approximated by using the values of bathymetry for 

these cells, to which recharge is applied at a rate of 10 in/yr. When sea level falls below the bathymetry at a cell, it reverts to an offshore cell and model parameters revert to their original values. 

Saltwater heads are updated at each time step as sea level changes at constant heads overlying 

offshore outcrop cells and at cells in model units A8 and A9, which represent the constant saltwater 

heads in the subcrop areas of these units. 

Because the model was designed primarily to study the confined aquifers in the New Jersey 

Coastal Plain, unconfined aquifers, where they were modeled (updip parts of the confined aquifers 

and the upper Kirkwood-Cohansey aquifer), were included to serve primarily as boundary conditions so that flow to and from these areas to the underlying or adjacent confined aquifers could be 

simulated. Results of simulations for these areas are discussed only in terms of their effect on the 

confined parts of other aquifers. Because the transition zone of the freshwater-saltwater interface 

in the upper Kirkwood-Cohansey aquifer is very wide, the simulated interface position and 

movement are not given with confidence. 

Input Data 

Initial estimates of aquifer and confining-unit properties were taken directly from the 

RASA model. In this section, modifications made to the RASA model input data are described. 

Changes were required to extend model units past the boundary of the RASA model to the limit of 

the Continental Shelf. New data arrays that were necessary for the SHARP model include porosity, 

initial location of the saltwater interface, and the freshwater heads in equilibrium with this initial 

interface. 

Horizontal hydraulic conductivities in the updip areas for each aquifer were calculated by 

using the calibrated transmissivity from the RASA model and the thickness of the aquifer in the 

hydrogeologic framework described earlier. Two methods were used to estimate horizontal 

conductivity downdip from the extent of the RASA model. In the downdip part of model units AI, 

A2, A3, A8, and A9, conductivity was estimated on the basis of trends in the RASA model conductivity values in onshore areas and by assuming a' gradual decrease in conductivity with depth to a 

minimum value of 2 ftld at the edge of the Continental Shelf. This minimum value is consistent 

with the hydraulic-conductivity value of 2.5 ftld used in regions farthest downdip in the model of 

Meisler and others (1985). For the remaining model layers (A4, A5, A6, and Pl.7), in the area in 

25 
which tbe model was extended downdip from the RASA model boundary the layers are simulated 

as low-permeability sediments. Because the downdip parts of these aquifers function more as 

confining units than as aquifers, the horizontal conductivity was assumed to be 30,000 times the 

vertical conductivity of the overlying and underlying confining units on the basis of the anisotropy 

described in Meisler and others (1985). The mean vertical hydraulic conductivity of model units 

C4, C5, C6, and C7, calculated as described below, was multiplied by 30,000 to provide a single 

horizontal-conductivity value for the low-permeability parts of the aquifers. 

Leakance values for this model were taken from the RASA model input data. In down dip 

areas, the RASA leakances were first converted to vertical-hydraulic-conductivity values, and 

trends in conductivity were used to extend the model downdip from the RASA model boundary. 

Vertical hydraulic conductivity is more easily estimated from observed trends than leakance 

because the variable thickness of the unit does not need to be considered. The RASA model calibrated leakance values 'were transformed into vertical conductivities by using the thickness from 

the current framework. Downdip values for model units C1, C2, C7, C8, and C9 were estimated 

from updip trends. In most cases the lowest value at the downdip limit of available data was used 

for the entire downdip area; however, because unit C7 showed considerable variability across 

strike, two zones ofvertical conductivity were used. The vertical-hydraulic-conductivity values do 

not vary with distance downdip because the values used in updip areas range from 1 x 10-8 to 

1 x 10-10 fi/d and are reasonable values. 

The vertical conductivities of model units C3, C4, C5, and C6 in areas where the overlying 

aquifer was not simulated (as a result of a facies change) in the RASA model were calculated by 

using the RASA calibrated leakance values for those units. For each confining unit, a mean vertical 

hydraulic conductivity was calculated from the leakance values for the five rows farthest 

"downdip" in the RASA model. The four values were then averaged to yield a single mean vertical 

conductivity, which was assigned to the downdip parts of the confining units. In model units C3, 

C4, and C5, this value of 3.3 x 10-8 ft/d is slightly to moderately higber than the values at the 

RASA model layer limits. In unit C6, however, the averaged value was more than two orders of 

magnitude greater than the value at the downdip limit of the RASA model. The sharp boundary 

between the two zones caused stability problems in the simulations. Therefore, the average vertical 

10 conductivity at the downdip limit of the RASA model, 2.5 x 10- ft/d, was used for the entire 

downdip part of model unit C6. 

Storage terms used in the current model were modified from those used in the RASA 

model. In the RASA model, a constant storage coefficient was used throughout the modeled area 

(except for the downdip parts of model units AI-A3). In the current mode, a constant value for 

specific storage was used and a storage coefficient was calculated for each cell on the basis of the 

specific storage and the aquifer thickness. This allows more reasonable estimates of the storage 

term in the thicker, downdip part of the aquifers than those used in the RASA model. Specificstorage values of 5 x 10-7 and 1 x 10-6 were used for model units A 1 through A5, as detennined 

during model calibration, and a value of 1 x 10-6 was used for units A6 through Al O. Storage 

values used in the unconfined parts of each aquifer are equal to 0.15, a typical value for specific 

yield. 

26 
Recharge rates used in the model are the same as those used in the calibrated RASA model. 

A uniform rate of 20 in/yr was applied to the outcrop area of each aquifer. This rate was adjusted 

during model calibration and had little effect on model results; streamflow changed but net flow to 

the confined aquifers did not. 

Estimates of porosity in the Coastal Plain aquifers are required for the SHARP model. A 

review of the literature and available data from the area were used to estimate the porosity. Freeze 

and Cherry (1979) list representative porosity values for unconsolidated sediments as follows: 

sand, 25 to 50 percent; silt, 35 to 50 percent; and clay, 40 to 70 percent. Gill (1962) reports porosities for the Cohansey Sand in Cape May County that range from 27.2 percent to 40.8 percent and 

average about 30 percent. 

Scholle (1977, 1980) reports offshore porosities from the COST wells. Porosities were 

determined from ° density and sonic logs in the COST -B2 well and decrease with depth. Sandstone 

porosities from to 4,000 ft beiovi sea level range from 40 to 60 percent, from 4,000 to 9,000 ft 

below sea level range from 20 to 30 percent, and from 9,000 to 16,000 ft below sea level range 

from 5 to 20 percent. At depths below 7,000 ft, virtually all porosity values are less than 25 percent. 

Porosities reported for the COST -B3 well were determined from conventional and sidewall core 

samples beginning at depths of7,000 ft. Porosities at the COST-B3 well are less variable with 

depth; most values are between 15 and 25 percent. On the basis of these values, a reasonable 

estimate of porosity for the New Jersey Coastal Plain aquifers was considered to be between 25 

and 40 percent. For this model, a porosity of 30 percent was used for all aquifers. Porosity was 

varied during model calibration and affects the rate and movement of the freshwater-saltwater 

interface. 

Because the simulation of sea-level rise and fall was a critical aspect of this model, bathymetric data were needed to delineate the onshore areas (areas that receive recharge) during simulation of sea-level changes. Contours at 10- to 20-meter (32.8- to 65.6-ft) intervals from the 

1:750,000 bathymetric map ofUchupi (1970) were digitized. The bathymetry at the edge of the 

Continental Shelf also was modified slightly so that at least one row of cells was always present at 

the offshore limit of the model, even at the lowest sea level simulated. The bathymetry ranges from 

sea level at the present coastline to about 250 ft below sea level at the edge of the Continental Shelf. 

The northeastern corner of the model also includes a small area of the Continental Slope, where 

the bathymetry drops steeply to more than 450 ft below sea level at the edge of the model. 

Initial estimates of freshwater heads and freshwater-saltwater interface locations were used 

as initial conditions for the steady-state run, in which the flow system resulting from a sea level set 

27 ft below present-day sea level was simulated. The results of this simulation were used as a 

starting point for simulation of sea-level rise and fall. 

Initial elevations of the freshwater-saltwater interface were estimated by using the depth to 

the 1 O,OOO-mgIL chloride concentration in Meisler (1989, pI. 5). After the interface elevations were 

fixed, the freshwater heads were calculated so that the freshwater heads and interface elevations 

were consistent. The freshwater heads were calculated from the interface elevation and the 

saltwater heads (which were set to 27 ft below present sea level for the initial simulation) in order 

27 
to fulfill the condition required by the SHARP model that initial saltwater heads be near sea level 

(Essaid, 1990). The freshwater heads were calculated by using the following equation from Essaid 

(1990, p. 52): 

~1+8<pf 

CPs = (1 + 8) , 

\vhere <Ps and <l>f are the saltwater and freshwater heads, respectively; ~l is the interface elevation; 

and 8 = yfl (Ys -y f) ,where Yf and Ys are freshwater and saltwater specific weight, respectively. 

The model was initialized and then stopped so that the interface could be examined for "pockets," 

cells of one type (fresh, salty, or mixed) completely surrounded by cells of a different type. These 

pockets were removed by adjusting the interface elevation and recalculating the freshwater head 

before continuing the model simulation. 

Calibration 

Heads in tbe model were calibrated primarily to potentiometric-surface maps for 1988 and 

long-term water-level hydrographs, but water-level data for 1978 also were used. Interpreted 

potentiometric-surface maps of water-level data collected in fall 1988 (Rosman and others, 1995, 

figs. 1-8) were used for all aquifers. The simulated water levels for 1988 were expected to 

reproduce regional flow patterns, hydraulic gradients, and locations of cones of depression. 

Centers of cones of depression may not be closely simulated because the water level at each cell is 

averaged over the cell area, which is 2-1/2 mi by 2-1/2 mi. Also, tbe synoptic water-level data 

(from which the 1988 potentiometric-surface maps were produced) may reflect local cones of 

depression that cannot be reproduced at tbe scale ofthismodel. Water levels measured in fall 1983 

and fall 1988 were averaged and compared to simulated water levels for the last stress period in 

the model (November 1983 through October 1988). Model calibration was considered acceptable 

when the difference between the average measured water level and the simulated water level (for 

the last stress period) at most observation wells was within 15 ft. Hydrographs of water levels in 

141 observation wells (unpublished data on file at the U.S. Geological Survey office in West 

Trenton, N.J.) also were used to calibrate long-term trends in water levels. Simulated bydrographs 

also were required to match these measured water levels within 15 ft at the end of the pumping 

period 1983-88. 

Although comparing the average water level over the last stress period to the simulated 

head is a good calibration tool, sources of error need to be considered. Average measured water 

levels in 1983 and 1998 could differ from simulated water levels if ground-water withdrawals 

changed sharply over the last stress period. Ground-water withdrawals were relatively steady over 

this period, however, so this concern can be disregarded. In addition, the measured water levels 

represent a specific point in space (the well), whereas tbe simulated water level at a grid cell is a 

representative value for the entire cell. The two values can differ in areas of steep gradients or 

where cones of depression around pumped wells are smaller than can be represented by the model 

28 
grid. Additionally, simulated and observed water-level-altitude maps may differ because the 

simulated water level represents the average water level for 1983-88, whereas the observed water 

level represents conditions in fall 1988. 

The calibration of the location of the freshwater-saltwater interface was accomplished by 

using available chloride-concentration data from Meisler (1989), other chloride-concentration data 

collected by the USGS (computerized data base available at the U.S. Geological Survey office 

West Trenton, N.J.), and interface locations based on the depth to the 10,000-mgIL chloride 

concentration in Meisler (1989). Meisler's map was used to approximate the location of the freshwater-saltwater interface. High concentrations of chloride were used to verify the location of the 

interface; however, because most measured chloride concentrations were less than 10,000 mg/L, 

the chloride-concentration data were used mainiy to deiineate the extreme updip location of the 

interface. 

SIMULATION OF GROUND-WATER FLOW AND FRESHWATERSALTWATER INTERFACE MOVEMENT THROUGH 1896 

The position of the freshwater-saltwater interface in the New Jersey Coastal Plain aquifers 

in modern times is more closely related to the predevelopment flow system than to current conditions. The current flow system is not in equilibrium with the present-day sea level; if it were, the 

interface would be much farther onshore than its current location. The current location of the freshwater-saltwater interface in the New Jersey Coastal Plain and the width of the freshwater-saltwater 

interface are the result of past sea-level conditions (Meisler and others, 1985). Sea level during the 

past 900,000 years has generaliy been iower than current sea level, ha$ fluctuated severai times, 

and has been as much as 300 ft below current sea level (Meisler and others, 1985, p. 6-7). The sealevel curve for the past 300,000 years (Meisler and others, 1985) is shown in figure 7. This curve 

was developed on the basis of work by Zeimer (1979). 

The initial conditions for the simulation offlow from 1896 through 1988 were derived from 

the simulation of the ground-water flow system and freshwater-saltwater interface movement over 

the last 110,000 years. Simulated water levels and interface locations in 1896 were needed as initial 

conditions for a simulation of current conditions (1896-1988). If the current sea level were used, 

the freshwater-saltwater interface would be too far onshore and would be static; the effects of the 

latest rise in sea level, to which the flow system is still responding, would be unaccounted for. Use 

of a sea level that is 75 ft below present sea level would result in a more realistic location of the 

freshwater-saltwater interface, but the interface would again be static and its landward movement 

as a result of the recent sea-level rise would be omitted. Therefore, a simulation of the flow system 

that incorporates the effects of past sea-level conditions was needed. 

Simulation of the flow system and freshwater-saltwater interface movement during the 

time of significant sea-level changes and interface movement requires two major assumptions: 

(1) The geologic and hydrogeologic characteristics of the aquifers and confining units is assumed 

to have been the same during the past 100,000 years. Any recent deposits or reworking of these 

sediments probably had little overall effect on the aquifers at the regional scale of this study. (2) 

Precipitation is assumed to have been constant over the past 100,000 years and equal to the precipitation observed today. 

29 
FEET 

100 

CURRENT SEA ~------------------------~~-------------fTLEVEL 

-100 

-200 

-300 

-400~~------------~------------~------------~ 

300 200 100 o 

TIME, IN THOUSANDS OF YEARS BEFORE PRESENT 

Figure 7. Sea-level curve. (Modified from Meisler and others, 1985, fig. 48) 

30 
Simulation of Steady-State Conditions from 110,000 to 84,000 Years AeQ 

A steady-state simulation in which sea level was -27 ft (27 ft below current sea level) 

provided the initial conditions for a transient simulation that included the changing sea level as part 

of the boundary conditions for the period from 84,000 years ago to 1896. The sea-level curve in 

ZeImer (1979, fig. 7) shows several cyclic rises and falls of sea level with amplitudes of more than 

200 ft over the past 900,000 years. The steady-state simulation represents a period of relatively 

constant sea level from about 110,000 to 84,000 years ago. This is the period during which the flow 

system was most likely to have reached equilibrium. Sea level during this period was about 27 ft 

below current sea level and was fairly stable for about 26,000 years. 

The steady-state model with sea level at -27 ft was initialized by using simulated heads 

from the J"-~evv Jersey RASA flow model (Martin, 1998) as initial heads and initial interlace 

locations derived from the current observed location of the 10,000-mg/L chloride-concentration 

line in Meisler (1989, pI. 5). Initial estimates of the locations of the interface tip and toe in each 

aquifer were determined by using the depth to the 10,OOO-mg/L chloride concentration in Meisler 

and others (1985) and the altitude of the top and bottom of each aquifer used in the current model. 

In several aquifers the initial location of the freshwater-saltwater interface was moved toward the 

updip limit of the aquifer because the interface moved more easily downdip than updip as a result 

of onshore recharge, which "drives" the flow. Although the resulting location of the freshwatersaltwater interface would have been the same, the solution was reached more quickly and with 

fewer numerical problems. 

Because the SH.ARP model does not directly simulate a steady-state condition, a transient 

simulation with a time step of 500 years was used. The porosity was set to an extremely low value 

(0.005) so that little water is displaced as the interface moves. This maximizes the simulated rate 

of movement of the interface. Although the model-output simulation times are no longer accurate, 

this does not affect the steady-state results. The storage coefficient was set equal to 0.0 for the 

steady-state simulation. Any freshwater-storage terms in the model budget are the result of water 

entering or leaving the freshwater system as a result of the movement of the interface. The steadystate simulation was continued until the volume of water contributed from storage was very small, 

indicating that the freshwater-saltwater interface was no longer moving. The flow system is not 

presented and discussed in this section; however, the initial location of the interface in aquifers in 

which the permeability decreases downdip (the Englishtown (A4), Wenonah-Mount Laurel (AS), 

Vincentown (A6), and Piney Point (A 7) aquifers) is discussed. 

In the Englishtown (A4) and Vincentown (A6) aquifers, the interfaces were initialized 

downdip from the permeable part of the aquifer (within the low-permeability areas) and did not 

move significantly during the steady-state simulation. The low-permeability sediments limit the 

movement of the interface. When the interface is initially located within the low-penneability 

zone, or moves downdip to the boundary between the permeable aquifer and the low-permeability 

zone during the steady-state simulation, the exact location of the interface cannot be simulated. The 

interface is somewhere downdip from the change to a low-permeability zone but downdip 

movement has been controlled by the low horizontal hydraulic conductivities. Movement of the 

31 
interface in low-permeability materials (clays, silts, and silty sands) is controlled more by vertical 

movement of saltwater through overlying and underlying sediments than by horizontal movement 

saltwater. 

In the Wenonah Mount-Laurel aquifer (AS), the interface was initialized near the downdip 

limit of the permeable part of the aquifer, and the tip and toe of the interface moved offshore during 

the steady-state simulation (sea level = -27 ft). In northern areas (north of a line extending due east 

from the Great Egg Harbor River at the coast), the interface moved offshore during the steady-state 

simulation until it reached the low-permeability zone and did not move significantly within the 

low-permeability area. This result implies that north of this line the interface is located within the 

low-permeabilirj sediments farther offshore than is simulated. South of this line the steady-state 

interface moved as much as 3.5 mi farther offshore than the initial estimates within the permeable 

limits of the aquifer during the steady-state simulation; however, the movement of the interface in 

this area also may have been affected by proximity to the low-permeability boundary, but to a 

smaller degree. Therefore, this is probably a good approximation of the location of the interface. 

In the Piney Point aquifer (A 7), the interface was initialized just downdip from the 

boundary between the permeable part of the aquifer and the low-permeability sediments in areas 

south of Absecon Island (in Atlantic County north of the mouth of the Great Egg Harbor River). 

Therefore, the location of the freshwater-saltwater interface in this part of the aquifer cannot be 

simulated with confidence. In areas north of Absecon Island, where the interface was initialized 

within the permeable aquifer sediments, both the tip and toe of the interface moved updip from the 

estimated initial position during the steady-state simulation. These estimated positions were 

adjusted during previous steady-state runs and were from 15 to 35 mi farther onshore than the 

locations estimated from data in Meisler and others (1985). 

The lower Kirkwood-Cohansey and confined Kirkwood aquifers (A8) and the upper 

Kirkwood-Cohansey aquifer (A9) are in closer contact with overlying saltwater than the deeper 

aquifers and are assumed to be in connection with saltwater at the downdip subcrop; therefore, the 

freshwater-saltwater interface moves farther in these aquifers than in the deeper aquifers during 

simulation of sea-level changes. The simulated steady-state intetface (representing a sea level of 

27 ft below current sea level) is similar to the static condition that the interfaces in the two aquifers 

would eventually reach under current conditions if no stresses were imposed. The simulated heads 

and interfaces in these aquifers are shown in figures 8 and 9, respectively. 

The confining unit overlying the Rio Grande water-bearing zone (C8) affects the steadystate interface in the 10werKirkwood-Cohansey and confined Kirkwood aquifers (A8). North of 

Island Beach State Park, the confining unit is absent and the simulated steady-state tip and toe of 

the freshwater-saltwater interface in the lower Kirkwood-Cohansey and confined Kirkwood 

aquifers are located just offshore from the barrier islands. Where the confining unit is present, 

however, heads offshore are higher than they are where the confining unit is absent. The interface 

is farther offshore in these areas because the heads are higher. 

Southwest of Cape May County in the Delaware Bay, where the overlying confining unit 

(C8) is absent, the lower Kirkwood-Cohansey and confined Kirkwood aquifers are in direct contact 

with the overlying, saltwater-containing sediments of the upper Kirkwood-Cohansey aquifer (A9). 

32 
"'00 

~.L_ ......... _...;;f~ __ """",, ___ \,,~, arita" <~_/--'.' " FALL LINE ~~~;::;::~X;P /~_~~:-::: 

)v>NEWYORK MERCER ~\ .~-~ '~'''''-'-'''''';;:.- ...... . MIDDLESEX 

-'\--, RARITAN r..,.(J. 

\'/\ BAY 

-----

CUMBERLAND 

--. .. .................................. --_ .... .. 

.... , 

" .... -------- ---~-~-~-~-~---------------~-------~~~ 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE LOWER 

KIRKWOOD-COHANSEY AND CONFINED 

KIRKWOOD AQUIFERS 

-10- SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude of simulated potentiometric surface 

84,000 years ago. Contour interval 10 feet. National 

Geodetic Vertical Datum of 1929 

SIMULATED UPDIP LIMIT OF OVERLYING 

CONFINING UNIT 

Base from U,S, Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

o 

I 

o 

'\ ,1$ \\ /J ""'&Sink R,' \ I 

\\'-''--Y~~=~r;/ "\./' .. ,// 

10 MILES !) I 

10 KILOMETERS 

TIP OF THE SIMULATED FRESHWATERSALTWATER INTERFACE 

TOE OF THE SIMULATED FRESHWATERSALTWATER INTERFACE 

'100 

Figure 8. Simulated potentiometric surface in the confined Kirkwood aquifer, and 

locations of the simulated freshwater-saltwater interface tip and toe in the lower 

Kirkwood-Cohansey and confined Kirkwood aquifers (model unit AS) in the 

New Jersey Coastal Plain 84,000 years ago. 

33 
) i 

\ 

( 

/ / 

o 10 MILES I i I I I 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data. 1 :2,000.000. 1972. 

Universal Transverse Mercator projection. Zone 18 

'I FALL LINE 

MERCER MIDDLESEX 

MONMOUTH 

/ 

SIMULATED LIMIT OF AQUIFER 

EXPLANATION 

- 40 - SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude of simulated potentiometric suriace 

84,000 years ago. Contour interval 20 feet. National 

Geodetic Vertical Datum of 1929 

TIP OF THE SIMULATED FRESHWATERSALTWATER INTERFACE 

TOE OF THE SIMULATED FRESHWATERSALTWATER INTERFACE 

9'00 

Figure 9. Simulated potentiometric surface and locations of the simulated freshwatersaltwater interface tip and toe in the upper Kirkwood-Cohansey aquifer (model unit A9) 

in the New Jersey Coastal Piain 84,000 years ago. 

34 
The simulated steady-state toe of the freshwater-saltwater interface in model unit A8 gradually 

curves toward the west around the southern end of Cape May County. The interface is farther 

onshore near Cape May than farther north because heads near the updip limit of the confining unit 

overlying the Rio Grande water-bearing zone (C8) are low. 

In the upper Kirkwood-Cohansey aquifer, the simulated steady-state interface is narrow, is 

just offshore, and curves toward the tip of Cape May County. The simulated steady-state interface 

positions in the lower and upper Kirkwood-Cohansey aquifers (model units A8 and A9) represent 

the equilibrium condition toward which the flow system is moving. 

Simulation of Sea-Level Cban2"es 

Changes in sea level affect the flo\XJ system and lTIOVement of the freshwater-saltwater 

interface in the New Jersey Coastal Plain in several ways. The depth of overlying saltwater in 

offshore areas decreases when sea level drops, resulting in lower saltwater heads both in the 

constant-head cells overlying the uppennost aquifer (representing overlying saltwater in the ocean) 

and in the constant heads at the subcrop of model units A8 and A9 at the Continental Shelf. 

Saltwater heads offshore have decreased while the freshwater heads remained constant, causing the 

freshwater-saltwater interface to move seaward. Decreasing sea level also exposes sediments that 

had been covered by saltwater; they become part of the onshore freshwater flow system, with freshwater streams and freshwater recharge. The size of the area of freshwater recharge increases, and 

this additional freshwater in the uppermost aquifer (A9) moves the saltwater farther offshore. 

Higher heads resulting from increased freshwater recharge cause the interface to move seaward 

quickly. When sea level rises again, however, no strong force exists to reverse the flow. Therefore, 

the freshwater-saltwater interface moves seaward in response to a sea-level drop much faster than 

it moves landward after a sea-level rise. For these reasons, the freshwater-saltwater interface has 

not yet reached equilibrium with current sea level. 

Sea-level changes during the past 84,000 years were simulated by using the heads and interfaces resulting from the steady-state simulation as initial conditions. Storage coefficients and 

porosity values used were set to reasonable values for a transient simulation. Rates and magnitudes 

of sea-level changes were estimated from the sea-level curve shown in figure 7 and are as follows: 

Time (years Rate Sea level at end of period 

before present) (feet per year) (feet below land surface) 

110,000 - 84,000 0 27 

84,000 - 71,000 -0.015615 230 

71 ,000 - 61,000 .0092 138 

61,000 - 50,000 0 138 

50,000 - 18,000 -.0031875 240 

18,000 - 100 .0133 0 

35 
Calibration of the location of the freshwater-saltwater interface during sea-level changes 

was based primarily on the positions of the interface in the upper Kirkwood-Cohansey aquifer (A9) 

and the lower Kirkwood-Cohansey and confined Kirkwood aquifers (A8) because the interface 

moved farthest and was most sensitive to changes in hydraulic parameters in these aquifers. Most 

of the changes made during calibration were made in model unit A9. For this reason, the simulated 

heads and interface in this aquifer are less reliable than those in the deeper aquifers, and this unit 

was included in the simulation only as a boundary condition so that the heads and interfaces in the 

deeper units (especially A8) could be more accurately simulated. Changes made during calibration 

include (1) reducing the leakance of confining unit C9 overlying the upper Kirkwood-Cohansey 

aquifer (A9), which represents sediments on the ocean floor; (2) adjusting the streambed conductances used when converting offshore cells to onshore cells; and (3) reducing the recharge applied 

to offshore areas to 10 in/yr when sea level falls. These changes were made to simulate the interface 

in model unit A9 so that the general shape (slope and width) and position of the interface were 

reasonable. The model was sensitive to changes in the leakance of model unit C9 and the streambed 

conductances offshore and was not sensitive to changes in recharge. 

The hydrogeologic section in figure 10 shows the simulated interface locations in the 

steady-state simulation (in which sea level is 27 ft below current sea level) and the simulation of 

sea-level changes through 1896. (The location of this section, shown in figure 1, is the same as that 

used for the sections in figures 2 and 3.) 

Simulation of changes in sea level generally resulted in downdip movement of the freshwater-saltwater interface from the simulated steady-state interface position. Most of the downdip 

movement was the result of the drop in sea level from 27 ft below present sea level 84,000 years 

ago to 230 ft below sea level 71,000 years ago. The freshwater-saltwater interface did not reach 

equilibrium with the lowest sea level, but was still moving downdip when sea level began to rise 

again. At the end of the simulation (1896), the freshwater-saltwater interface was moving updip in 

response to the rise in sea level from 240 ft below sea level 18,000 years ago to present sea level 

in 1896. 

Moyement of the Freshwater-Saltwater Interface 

The movement of the freshwater-saltwater interface from 84,000 years ago to 1896 was 

greatest in the upper Kirkwood-Cohansey aquifer and the lower Kirkwood-Cohansey and confined 

Kirkwood aquifers (model units A8 and A9) and in the three Potomac-Raritan-Magothy aquifers 

(model units AI, A2, and A3). The interface moved downdip in the Potomac-Raritan Magothy 

aquifers as much as 3.5 mi as a result of the fluctuations in sea level. The tip and toe of the interface 

in each aquifer moved seaward about 1.75 to 2 mi. Because these aquifers are permeable downdip 

to the Continental Shelf, the movement of the interface is not restricted. The smallest amount of 

movement was observed in the toe of the freshwater-saltwater interface in the Lower PotomacRaritan-Magothy aquifer in Ocean County. In some areas, the tip and toe of the interface in both 

the Middle and Upper Potomac-Raritan-Magothy aquifers moved as much as 2.5 mi downdip. At 

the end of the simulation (1896), the interface was moving landward in all three aquifers in 

response to the most recent sea-level rise. 

36 
° 

-500 

-1,000 

-1,500 

ft±} -2,000 

lJ.. 

~ -2,500 

uJ 

o 

~ -3,000 

~ ~ -3,500 

-4,000 

-4,500 

Fall Line 

-'~ 

~' 

~ 0, 

C}, "- / I -' 

EXPLANATION 

AQUIFER 

LOW-PERMEABILITY 

AQUIFER 

• CONFINING UNIT 

SIMULATED FRESHWATER- ' 

SALTWATER-INTERFACE--

Shows location of simulated 

interface: 

-- 84,000 years ago 

- - - - - In 1896 (predevelopment) 

Coast 

VERTICAL SCALE GREATLY EXAGGERATED -5,000 '---____ -1-_____ -'---___ --'--'--'.>..1-__ ---' 

o 20 40 60 

MILES 

, 

Upper KirkvV()O~j':c·· .. ' .......... Ohansey 

80 100 120 140 

Figure 10. Hydrogeologic section showing simulated locations of the freshwater-saltwater 

interface in the New Jersey Coastal Plain 84,000 years ago and in 1896 (predevelopment). 

37 
During this simulation, the interface in the Wenonah-Mount Laurel aquifer (model unit AS) 

was relatively static. The freshwater-saltwater interface movement can be simulated only in the 

south, where the interface is in the permeable part of the aquifer. During the simulation the toe of 

interface moved downdip as much as 0.5 mi while the tip of the interface was in the lowpermeability sediments; therefore, this result is questionable. 

Movement of the interface in the Piney Point aquifer (model unit A 7) can be simulated only 

where the interface is the permeable part of the aquifer, offshore from northern Atlantic County 

and most of Ocean County. Interface movement in this aquifer is complex and probably is influenced by the proximity of the simulated interface to the low-permeability part of the aquifer. The 

interface tends to move do\~vndip in the northern part of the aquifer as a result of the sea-level 

decline. In the area downdip from Long Beach Island, south of the mouth of the Mullica River in 

Ocean County, the toe of the interface is stationary while the tip moves inland, narrowing the 

interface in this area. 

The tip of the interface in the lower Kirkwood-Cohansey and confined Kirkwood aquifers 

(A8) moved 10 to IS mi downdip during this simulation. Movement was greatest in the southern 

part of the study area, near the model boundary. The interface generally moved less than 12 mi 

seaward in areas north of a line extending due east from Atlantic City. 

The position of the freshwater-saltwater interface in the upper Kirkwood-Cohansey aquifer 

(A9) was most affected by changes in sea level. The interface changed from a narrow (generally 

less than 2-mi-wide), steep interface just off the coast in the steady-state simulation to a much 

wider (about 12-30 mi wide) interface in 1896. Movement was greatest directly offshore from 

northern Cape May County, Atlantic County, and southern Ocean County, where the heads in the 

aquifer were highest and the toe of the interface moved downdip about IS mi. In areas to the north 

and south, where simulated heads in 1896 were less than lOft above sea level, downdip movement 

of the toe was much smaller because heads were lower. Heads were lower offshore because the 

overlying confining unit is absent and the aquifer is unconfined and in connection with the 

overlying aquifer. 

Ground-Water Flow System in 1896 

The results of the simulation of the flow system in the New Jersey Coastal Plain ending in 

1896 represent predevelopment conditions in the system. The simulated location of the freshwatersaltwater interface, simulated heads in 1896, and overall flow budgets for each aquifer derived 

from simulation results are described below. 

Freshwater flow budgets for the confined part of each aquifer are shown in table 2. A 

schematic representation of an aquifer showing each of the terms used in the flow budgets in this 

report is shown in figure 11. Storage in the pre development flow system represents movement of 

the freshwater-saltwater interface; as the interface moves landward, seawater displaces freshwater. 

The saltwater flow term includes flow from the aquifer outcrop or overlying-confining-unit 

outcrop in the Delaware or Raritan Bay. This flow term represents freshwater flow from areas that 

are known to contain saltwater. The model does not simulate inflow of saltwater, but these areas 

38 
Table 2. Simulated predevelopment flow budgets of confined aquifers in the New Jersey Coastal 

1896 

[Values are in million gallons per day] 

Inflow 

Flow 

downdip Leakage Leakage Leakage 

from from from from 

unconfined overlying overlying underlying 

aquifer or unconfined confined confined 

Model unit Storage outcrop Saltwater aquifer aquifer aquifer Total 

Lower Potomac-Raritan- 0 0 0 0 3.4 0 

Magothy aquifer (A 1) 

Middle Potomac-Raritan- 0 3.1 0 5 5.3 2.3 

Magothy aquifer (A2) 

Upper Potomac-Raritan- 0 1.4 0 6 7.4 .4 

Magothy aquifer (A3) 

Englishtown aquifer (A4) 0 0 0 5.2 6.6 .6 

Wenonah-Mount Laurel 0 .5 0 3.8 7.3 1.6 

aquifer (A5) 

Vincentown aquifer (A6) 0 2.1 0 9.2 0 .9 

Piney Point aquifer (A 7) 0 0 0 5.3 0 .3 

Lower Kirkwood- 1.2 3.2 .1 .1 0 1.4 

Cohansey and confined 

Kirkwood aquifers (AS) 

3.4 

15.7 

15.2 

12.4 

13.2 

12.2 

5.6 

6.0 

Model unit 

Outflow 

Storage 

Flow 

downdip to 

unconfined 

aquifer Saltwater 

Leakage to 

overlying 

unconfined 

aquifer 

Leakage to 

overlying 

' confined 

aquifer 

Leakage to 

underlying 

confined 

aquifer Total 

Lower Potomac-RaritanMagothy aquifer (AI) 

Middle Potomac-RaritanMagothy aquifer (A2) 

Upper Potomac-RaritanMagothy aqui fer (A3) 

Englishtown aquifer (A4) 

Wenonah-Mount Laurel 

aquifer (AS) 

Vincentown aquifer (A6) 

Piney Point aquifer (A 7) 

Lower KirkwoodCohansey and confined 

Kirkwood aquifers 

0 

0 

0 

0 

0 

0 

0 

.1 

0.2 

3 

8.2 

2.8 

1.9 

2.5 

0 

2.6 

0 

.1 

.5 

.5 

.1 

0 

.4 

2.9 

0.9 

8.8 

.6 

.4 

3.0 

3.4 

3.6 

.4 

2.3 

.4 

.6 

1.6 

1.3 

0 

1.4 

0 

0 

3.4 

5.3 

7.1 

6.9 

6.3 

.2 

0 

3.4 

15.7 

15.2 

12.4 

13.2 

12.2 

5.6 

6.0 

39 
Horizontal flow downdip 

to/from unconfined aquifer 

Horizontal flow downdip to/from 

outside model area 

Flow to/from storage 

as interface moves 

Leakage to/from overlying unconfined aquifer 

Leakage to/from 

overlying confined 

_ aquifer 

Flow from saltwater 

sources in Delaware 

........ 11'+ ... - or Raritan Bay 

Downdip extent of 

freshwater flow system 

Leakage to/from underlying confined aquifer 

11. Schematic representation of budget terms used to describe flow budgets 

in each aquifer in the New Jersey Coastal Plain flow model. 

40 
represent potential or real sources of saltwater to the system--for example, the Delaware Bay. The 

overlying-unconfined-aquifer term includes flow from the outcrop of the overlying unconfined 

aquifer as well as from the outcrop of an overlying confining unit. 

Simulated heads in 1896 in the three Potomac-Raritan-Magothy aquifers are within lOft of 

each other in all areas, indicating that the aquifers behaved as a single hydrologic unit before development. Flow in the Potomac-Raritan-Magothy aquifers is driven by recharge from the outcrop 

areas of the Middle and Upper aquifers in Middlesex and Mercer Counties. Discharge is to Raritan 

Bay and the Raritan River to the north and to the Delaware River in the south. 

In all three Potomac-Raritan-Magothy aquifers the interface is farther downdip in northern 

areas and closer to the updip lin-tits of the aquifers in the south. This is especially true in the Lower 

(AI) and Middle (A2) Potomac-Raritan-Magothy aquifers. High heads near the recharge areas in 

the north in the Middle and Upper aquifers (A2 and A3) cause the interface in these areas to be 

located farther downdip than in the southern part of the study area. Because the downdip part of 

the Potomac-Raritan-Magothy aquifer system functions as a single unit, the interface locations in 

the three aquifers are related. In the section in figure 8, the interface positions in the Lower, Middle, 

and Upper aquifers are nearly horizontal, with altitudes between -2,100 and -2,500 ft. In downdip 

parts of the Middle and Upper Potomac-Raritan-Magothy aquifers, saltwater probably is present 

in either the underlying aquifer or the underlying confining unit. 

The simulated heads and positions of the tip and toe of the freshwater-saltwater interface 

in the Lower Potomac-Raritan-Magothy aquifer (AI) in 1896 are shown in appendix 1 (fig. Ic). 

Simulated heads in this aquifer generally are within a few feet of the simulated heads in the Middle 

Potomac-Raritan-Magothy aquifer. Flow in the Lower aquifer is from the ground-water high in and 

offshore from Ocean County southeast toward the Delaware River. The flow budget for the Lower 

Potomac-Raritan-Magothy aquifer in 1896 is shown in table 2. In the predevelopment flow system, 

this aquifer receives all of its inflow from the overlying Middle Potomac-Raritan-Magothy aquifer 

in downdip areas. Discharge is to the Middle aquifer offshore from Ocean County, in parts of Burlington County, and updip near the Delaware River and the outcrop. 

The freshwater-saltwater interface in the Lower Potomac-Raritan-Magothy aquifer is 

farthest updip in the southern part of the aquifer, down dip from the discharge area to the Delaware 

River, where heads in the aquifer are lowest, and is farthest downdip in Ocean County, where heads 

are highest. Irregularities in the shape of the toe of the interface in the Lower Potomac-RaritanMagothy aquifer in eastern Burlington and Ocean Counties result from the shape of the bedrock 

surface (which represents the bottom of the Lower Potomac-Raritan-Magothy aquifer) in this area 

(Zapecza, 1989, pI 1). The freshwater-saltwater interface narrows offshore from Ocean County, 

where the aquifer thins. 

The simulated heads and the position of the freshwater-saltwater interface in the Ivliddle 

Potomac-Raritan-Magothy aquifer (A2) in 1896 are shown in appendix 2 (fig. 2c). Predevelopment 

heads in the Middle aquifer are 40 to 70 ft above sea level in the recharge area in Middlesex and 

Mercer Counties. Heads downdip from the recharge area are higher than those simulated in the 

RASA model. Most of the recharge to the Middle Potomac-Raritan-Magothy aquifer (table 2) is 

vertical flow from the confined and unconfined Upper Potomac-Raritan-Magothy aquifer and 

41 
horizontal flow from the unconfined part of the Middle aquifer in Middlesex County. Recharge 

from the underlying Lower Potomac-Raritan-Magothy aquifer occurs in the northeastern part of 

the study area, near the freshwater-saltwater interface in the Lower aquifer, and updip near the 

discharge area in the southwestern part. Discharge is to the unconfined part of the Middle PotomacRaritan-Magothy aquifer, the overlying Upper aquifer near the Delaware River in the southwest, 

and the overlying Upper aquifer near Raritan Bay. 

The interface in the Middle Potomac-Raritan-Magothy aquifer is widest in northern 

Atlantic, southeastern Gloucester, and eastern Ocean Counties where the aquifer is more than 350 

ft thick, and is narrower to the north and south where the aquifer thins. The interface is farthest 

offshore downdip from the recharge area in the northwestern part of the stl-ldy area because heads 

are high in this area. 

Simulated heads and the position of the freshwater-saltwater interface in the Upper 

Potomac-Raritan-Magothy aquifer (A3) in 1896 are shown in appendix 3 (fig. 3c). Heads in the 

Upper aquifer are 60 to more than 70 ft above sea level in the recharge area in Mercer and 

Middlesex Counties, and are less than 20 ft below sea level near Raritan Bay and updip near the 

Delaware River. Most of the recharge to the Upper Potomac-Raritan-Magothy aquifer (table 2) is 

from overlying areas in the northwestern part of the study area. Slightly more than half (55 percent) 

of this recharge is from the confined Englishtown aquifer; the remainder is from the unconfined 

Englishtown aquifer and the simulated outcrop of the Merchantville-Woodbury confining unit. 

More than half (54 percent) the discharge from the Upper Potomac-Raritan-Magothy aquifer is 

horizontal flow to the unconfined part of the aquifer near the Delaware River. About one-third of 

the discharge is flow to the underlying Middle aquifer. 

As in the Lower and Middle Potomac-Raritan-Magothy aquifers, the freshwater-saltwater 

interface in the Upper Potomac-Raritan-Magothy aquifer is farthest offshore downdip from the 

area of high heads in the recharge area in Middlesex and Monmouth Counties. The interface is 

farthest offshore in the southern part of the simulated area. The width of the interface ranges from 

3 to 5.5 mi in most areas. 

The simulated predevelopment flow systems in the Englishtown (A4) and Wenonah-Mount 

Laurel (AS) aquifers are similar as a result of the high vertical conductivity of the intervening 

MarshaUtown-Wenonah confining unit (the conductance of confining unit is more than an order of 

magnitude larger than in the Merchantville-Woodbury confining unit (C3». Heads in the Englishtown and Wenonah-Mount Laurel aquifers are within 1 0 ft of one another except in updip areas in 

southern Monmouth, western Ocean, and northern Burlington Counties, where heads in both 

aquifers are relatively high. Both aquifers are recharged primarily from overlying units. Recharge 

areas for the aquifers are in Camden and Gloucester Counties in the southern part of the study area 

and in southern Monmouth County in the northern part, where the heads are more than 120 ft above 

sea level in both aquifers. 

The simulated heads in the Englishtown aquifer (A4) in 1896 are shown in appendix 4 

(fig. 4c). Discharge from the aquifer (table 2) is primarily to the underlying Upper PotomacRaritan-Magothy aquifer (A3) with smaller amounts of lateral flow to the unconfined part of the 

42 
aquifer and vertical flow to the overlying aquifer. Upward discharge to the Wenonah-Mount Laurel 

aquifer occurs in updip areas and offshore from western Monmouth County. The Englishtown 

aquifer contains freshwater throughout its extent. 

Simulated heads and the position of the freshwater-saltwater interface in the WenonahMount Laurel aquifer (A5) in 1896 are shown in appendix 5 (fig. 5c). Recharge from the overlying 

unconfined Vincentown aquifer represents about 29 percent of the total recharge to the WenonahMount Laurel aquifer (table 2). Flow from the overlying confined aquifers includes flow from the 

overlying confined parts of the Vincentown (A6), Piney Point (A 7), and lower KirkwoodCohansey and confined Kirkwood aquifers (A8). About half of the discharge from the aquifer is 

flow to the underlying Englishtown aquifer. Twenty-five percent of the discharge is upward flow 

to the unconfined Vincento\vn aquifer. The remainder of the discharge is horizontal flow to the 

outcrop area and vertical flow to the overlying confined aquifers. The Wenonah-Mount Laurel 

aquifer contains freshwater throughout most of its extent. The freshwater-saltwater interface is 

simulated within the Wenonah-Mount Laurel aquifer only in extreme downdip areas in the southeastern part of the study area, near Cape May County. 

The simulated heads in the Vincentown aquifer (A6) in 1896, shown in appendix 6 (fig. 6c), 

are similar to the simulated heads in the underlying Wenonah-Mount Laurel aquifer. Heads in the 

two aquifers are within 5 ft of each other except near the coast in Monmouth County. Simulated 

heads in the Vincentown aquifer are highest in Camden and western Ocean Counties, and are 

lowest in the areas of discharge to the Delaware River in the south and the outcrop of the Vincentown aquifer offshore from the coast of Monmouth County. About 75 percent of the recharge to 

the Vincentown aquifer is vertical flow from the overlying unconfined Kirkwood-Cohansey 

aquifer (table 2). Horizontal flow from the outcrop and vertical flow from the underlying 

Wenonah-Mount Laurel aquifer provides the rest of the recharge. Discharge is primarily down dip 

flow to the Wenonah-Mount Laurel aquifer (52 percent of discharge), but also includes flow to the 

overlying Kirkwood-Cohansey aquifer and horizontal discharge to the outcrop. The Vincentown 

aquifer contains freshwater throughout its extent. 

Simulated heads and the position of the freshwater-saltwater interface in the Piney Point 

aquifer in 1896 are shown in appendix 7 (fig. 7c). Heads are highest, more than 120 ft above sea 

level, along the border between Burlington and Ocean Counties where the overlying KirkwoodCohansey aquifer recharges the aquifer. Flow is toward the Delaware Bay and the coast in Ocean 

County, where the water discharges to overlying aquifers. Almost all of the recharge (95 percent) 

to the Piney Point aquifer is from the overlying lower Kirkwood .. Cohansey and confined Kirkwood 

aquifers. Discharge is primarily (64 percent) to the overlying lower Kirkwood-Cohansey and 

confined Kirkwood aquifers (model unit A8). Also, 25 percent of the discharge is flow to the 

overlying confined Kirkwood aquifer (A8) in downdip areas. 

The freshwater-saltwater interface in the Piney Point aquifer is from 2 to 4.25 mi wide. The 

interface is simulated within the permeable part of the Piney Point aquifer only in areas offshore 

from Ocean County and northern Atlantic County. 

43 
Simulated heads and the position of the freshwater-saltwater interface in the lower 

Kirkwood-Cohansey and confined Kirkwood aquifers (A8) in 1896 are shown in appendix 8 

(fig. 8c). Heads are highest near the updip limit of the confining unit overlying the Rio Grande 

water-bearing zone (C8), where the confined part of the aquifer receives recharge from the unconfined lower Kirkwood-Cohansey aquifer (53 percent of inflow). Flow from the underlying Piney 

Point aquifer accounts for about 23 percent of inflow to the confined part of the aquifer (table 2). 

The remaining source of freshwater recharge to the aquifer is water released from storage. In the 

sharp-interface approach, as the freshwater-saltwater interface moves inland, freshwater is 

displaced by encroaching saltwater (the total volume of freshwater has not changed but the area 

occupied by freshwater in the aquifer is smaller). The storage term in the budget in table 2 represents the freshwater displaced from pores by the encroaching saltwater. Ground-water flow is from 

the high areas in Atiantic County toward the Delaware Bay where the overlying confining unit is 

absent offshore. In the predevelopment simulation, about half the outflow from the aquifer is freshwater discharge to lateral or overlying salty parts of the aquifer offshore. Most of the remaining 

discharge from the confined part of the aquifer is lateral flow to the unconfined part of the aquifer. 

Where the overlying confining unit (C9) is present, the freshwater-saltwater interface 

roughly follows the shape of the coast 30 to 40 mi offshore. The interface is 10 to 15 mi wide in 

this area. 

Near the updip limit of the overlying confining unit (C8) and in areas where the overlying 

confining unit is not present, south and west of Cape May in the Delaware Bay, and offshore from 

Ocean County, the toe of the interface is farther onshore than in the rest of the aquifer. As described 

previously, heads updip from these areas were too low to completely flush the saltwater out of the 

aquifer as the interface moved downdip. The aquifer in these areas generally contains freshwater 

with only a small layer of saltwater underlying the freshwater. ° The thickness of the saltwater layer 

in these areas is less than 25 ft and represents less than 1 percent of the thickness of the aquifer. 

SIMULATION OF GROUND-WATER FLOW AND FRESHW ATERSALTWATER INTERFACE MOVEMENT, 1896-1988 

The ground-water flow model was used to simulate the ground-water flow system in the 

New Jersey Coastal Plain for the period 1896-1988. Initial conditions for the simulation were the 

results of the 84,OOO-year simulation of sea-level change described in the previous section. Starting 

freshwater and saltwater heads and location and altitude of the saltwater interface in each active 

cell were taken from the'simulation of the flow-system response to sea-level changes ending in 

1896. 

The period from November 1, 1896, through October 31, 1988, was simulated by using 

seven stress periods ranging in length from 5 to 25 years. Stress periods were selected on the basis 

of withdrawal data and to coincide with the synoptic water-level data collected every 5 years. The 

ending dates of the stress periods were changed slightly from those used in the RASA model to 

coincide more closely with the synoptic measurements collected in the fall of 1978, 1983, and 

1988. The lengths of the stress periods and the total boundary flows for each stress period are 

shown in table 3. 

44 
Table 3. Ground-water withdrawals from each aquifer and lateral boundary flows by pumping period, New Jersey Coastal Plain, 

1896-1988 

[Pump age is in minion gallons per day] 

Model Aquifer unit 1 

11/0111896-

2 

1110111921-

3 

11/0111946-

Pumping period 

4 

11/0111958-

5 

11101/1968-

6 

11/01/1978-

7 

11/0111983-

Potomac Raritan-Magothy aquifer system: 

1013111921 10/31/1946 10/3111958 10/3111968 1013111978 10/31/1983 10/3111988 

Al Lower Potomac-Raritan-Magothy aquifer 8.9 27.1 40.7 54.4 64.2 64.7 63.7 

A2 Middle Potomac-Raritan-Magothy aquifer 3.1 15.7 27.4 45.9 69.8 70.3 64.5 

A3 Upper Potomac-Raritan-Magothy aquifer 1.6 8.6 16.9 37 51.7 51.2 52.3 

A4 Englishtown aquifer 1.7 3.4 5.7 7.7 10.9 9.7 9.1 

A5 Wenonah-Mount Laurel aquifer .5 1..0 1.8 3.6 4.5 4.5 4.9 

A6 Vincentown aquifer 0 0 0 .1 .6 1.0 .6 

A7 Piney Point aquifer .1 .3 .6 .9 1.8 1.8 1.8 

A8 Lower Kirkwood-Cohansey and confined 1.5 8.7 13.3 21.1 34 37.6 39 

Kirkwood aquifers 

A9 Upper Kirkwood Cohansey aquifer 2.3 10.8 12.2 27 42.1 47 50.4 

A10 Holly Beach water-bearing zone 

Boundary flow 

0 

4.6 

0 

3.9 

.1 

3.9 

.1 

4.5 

.1 

4.3 

.2 

2.5 

0 

4.3 

..J::;.. 

t.Il 
Total annual ground-water withdrawals from the New Jersey Coastal Plain aquifers are 

shown in figure 12 for the seven stress periods. Withdrawal data for 1918"-80 (from Zapecza and 

others, 1987) were used as input for the New Jersey RASA model (Martin, 1998). In this model, 

these data were supplemented with additional data for 1981-88 from the USGS, New Jersey 

District, water-use data base (unpublished data available at the U.S. Geological Survey office in 

West Trenton, N.J.). Average ground-water withdrawals for each stress period by aquifer are 

shown in table 3. 

The withdrawal data generally are limited to wells from which withdrawals were greater 

than 10,000 gaVd,but also include some lower capacity wells. Although many domestic and irrigation wells were not included, they account for only a small percentage of the total withdrawals 

and tend to be concentrated in and near the aquifer outcrop areas, where the effects of withdrawals 

are smallest. 

In this section, the ground-water flow system in each aquifer in the New Jersey Coastal 

Plain and locations of ground-water withdrawals during 1983-88 are described. Observed-potentiometric-surface maps for fall 1988 are used to describe cones of depression, ground-water flow 

directions, and ground-water gradients. Simulated heads in observation wells are compared with 

measured heads in 1988 and with average water levels for 1983-88 (table 4, at end of report). 

Simulated and observed water levels were used together to describe the ground-water flow system. 

Changes in hydrogeologic properties made during model calibration also are discussed. 

Simulated heads at the end of the last stress period represent the period from October 1983 

through September 1988. Average pumpage for each well during this period was used during the 

simulation. Water levels in areas near wells from which ground-water withdrawals changed significantly during this period did not closely match the observed 1988 water levels (Eckel and Walker, 

1986). In areas where pumpage was relatively constant during the stress period the simulated heads 

are compared to heads measured in 1988. In order to quantify average flow conditions, monthly 

water levels at 91 observation wells were used to determine an average measured water level for 

1983-88. Most of these observation wells are not near large withdrawal wells; therefore, water 

levels in these wells are likely to reflect regional water levels more closely than water levels 

measured near withdrawal wells. These average measured water levels were compared to 

simulated water levels. Maps showing the locations of the observation wells for which residuals 

(the difference between the simulated head at the well and the average measured head at the well 

during 1983-88 (table 4» were calculated and locations of selected wells in which chloride concen .. 

tration was determined are shown by aquifer. 

Simulated heads near large cones of depression may not match observed water levels for 

several reasons. Simulation of cones of depression with very steep gradients is difficult because 

the grid cells used in the model are large. The withdrawals in the model are distributed over the 

entire area of the model cell rather than at a single point. Water flows into this cell across all six 

faces; this combined surface is much larger than the flow surface that exists around a well field. In 

addition, some of the 1988 synoptic water-level measurements were made at pumped wells (in 

which water levels may not have recovered fully before the measurements were made) and may 

reflect local draw down due to withdrawals rather than regional water levels. Measurements made 

in observation wells a small distance from the pumping centers provide the best estimates of 

regional water levels. 

46 
400 l'iii""'!""""'I""""'!""""'I"""'i'j'i'iii'i'j""'i"'j"",""'j""""'j""'i"'1 

350 

~ 0 

a: 300 

ill 

Q.. Total annual withdrawals 

~ C/) 

Z 

0 

..J 250 ..J 

<{ 

CJ 

z 

Q 

..J 200 ..J 

::2! 

z 

uS 

..J 150 

« Average withdrawals for 

~ each pumping periO\ 

a: 

0 

I 100 I-

~ Estimated 

withdrawals 

50 \-- o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

1890 1900 1910 1920 1930 1940 1950 1960 1 970 1980 1990 

YEAR 

Figure 12. Annual ground-water withdrawals in the New Jersey Coastal Plain 

from 1917 to 1988 and during model pumping periods. 

47 
Description Qf GrQund-Water Flow System, 1983-88 

Simulated and measured hydrographs for selected wells completed in the Lower and 

Middle Potomac-Raritan-Magothy aquifers (AI and A2), the Upper Potomac-Raritan-Magothy 

aquifer and the Englishtown aquifer (A3 and A4), and the Wenonah-Mount Laurel aquifer and the 

confined Kirkwood aquifer (A5 and A8) are shown in figures 13 through 15, respectively. Because 

of the length of the stress periods and the use of average annual withdrawal data, seasonal variations observed in the measured hydrographs for some wells are not represented in the simulated 

hydrographs. Both simulated and measured water levels in well 7-412 in the Lower PotomacRaritan-Magothy aquifer (fig. 13) and in well 7-477 in the Upper Potomac-Raritan-Magothy 

aquifer (fig. 14) declined approximately 50 ft fron11965 to 1988. \Vater levels in \ve1l23-194 in 

the Middle Potomac-Raritan-Magothy aquifer (fig. 13) declined approximately 25 ft from 1965 to 

1988. Simulated water levels in well 29-138 in the Englishtown aquifer (fig. 14) are about 10 ft 

lower than measured water levels. Water levels in this well declined approximately 35 ft from 

about 1965 to 1988. Simulated water levels in well 7-478 in the Wenonah-Mount Laurel aquifer 

(fig. 15) are about 5 ft higher than measured water levels. The simulated hydrograph for 

wenl-l80 in the confined Kirkwood aquifer (fig. 15) matched measured water levels from 1975 

to 1988, but simulated water levels were higher than measured water levels from 1960 to 1975. 

Flow budgets for the confined part of each aquifer were calculated for the period 1983-88 

(table 5). Storage is important during the simulation of the stressed ground-water flow system from 

1896 to 1988 because, as the freshwater-saltwater interface begins to move inland in response to 

steepening gradients caused by withdrawals, the encroaching saltwater displaces the freshwater in 

downdip parts of the aquifer near the interface. This freshwater released from storage is particularly important in the flow budgets for the Potomac-Raritan-Magothy aquifer system. 

PotQmac-Raritan-Magothy Aquifer System 

Heads in the three Potomac-Raritan-Magothy aquifers were similar in 1988, especially near 

the large regional cone of depression in Camden, Gloucester, and southwestern Burlington 

Counties. Simulated heads in the Lower and Middle aquifers were within 5 ft of each other except 

in updip areas and at the centers of cones of depression, where heads generally were within 10ft 

of each other. Vertical gradients between the Middle and Upper aquifers were smallest in the 

southern part of the study area and largest in Ocean, Monmouth, and Middlesex Counties to the 

north. The flow system in each aquifer is described first by means of simulated and observed water 

levels. Changes made to hydrogeologic properties in all of the Potomac-Raritan-Magothy aquifers 

during model calibration are discussed together because similar changes were made to all three 

aquifers. Withdrawals from the three Potomac-Raritan-Magothy aquifers represent 67 percent of 

aU withdrawals simulated in the model. 

Of the three aquifers, the change in the representation of the downdip boundary from a noflow boundary to a sharp freshwater-saltwater interface most greatly affected the flow system in 

the Lower Potomac-Raritan-Magothy aquifer. This is because the large cones of depression in the 

Lower aquifer are near the freshwater-saltwater interface. 

48 
...J 

UJ 

> UJ 

...J 

« 0 UJ 

(/J 

5 

g 

UJ ·20 cD 

a: 

o 

UJ 

> o ·40 cD 

<C 

tu 

ill 

LL. -60 

~ 

..i 

ill 

> ill 

...J -80 

a: 

UJ 

I-

<C 

5 

...J 

ill 

> ill 

...J 

<C 

ill 

(j) 

~ 

o 

...J 

ill 

cD 

a: 

20 

o 

o -20 ill 

> 

o 

cD 

<C 

I- -40 ill 

ill 

LL. 

Z 

...J- -60 

ill 

> 

ill 

...J 

ffi -80 

le::( 

~ 

------------------------\ \ ------------------------\ 

Simulated 

Measured 

Lower Potomac-Raritan-Magothy aquifer (model unit A 1) 

Well 7-412 

Node 21,8 

\ 

' ...... _---------, I 

I 

I 

I 

\ 

\ 

'------

1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 

------------------------, \ 

\ 

\ 

~-----------------------I 

Simulated 

Measured 

Middle Potomac-Raritan-Magothy aquifer (model unit A2) 

Well 23-194 

Node 41,4 

I 

I 

I 

I 

1 

I 

1 

.... _-- ------1 1 

I 

I 

I 

~ 

1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 

YEAR 

Figure 13. Simulated and measured water levels in the Lower and Middle Potomac-RaritanMagothy aquifers, New Jersey Coastal Plain, 1896-1989. (Well locations shown in figs.16 

and 18, respectively) 

49 
...J 

W 

> W 

...J 

« 20 W 

(/) 

s: 

o 

...J 

W 0 

CO 

a:. 

o 

W 

> o -20 CO 

« 

fW 

W 

LL 

Z -40 

..i 

W 

> W 

...J -60 

a:. 

W 

f-

« 

s: 

...J 

W 

> W 

...J 

« 100 W 

(/) 

s: 

o 

...J 

~ 90 

a:. 

o 

W 

> o 

CO 

« 

fW 

W 

LL 

Z 

..i 

W 

> W 

...J 

a:. 

W 

~ 

80 

70 

60 

'------------------------~ 

\ 

\ 

\ .... -----------------------, \ 

\ 

' .... _---------\ 

Simulated 

Measured 

Upper Potomac-Raritan-Magothy aquifer (model unit A3) 

Well 7-477 

Node 19, 11 

\"~ \ 

I 

I 

I 

\ 

\ 

' .... -

1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955' 1960 1965 1970 1975 1980 1985 1990 

\ 

.... .... _--- ------------------~ , '-----------------------~ 

Simulated 

Measured 

Englishtown aquifer ( model unit A4) 

Well 29-138 

Node 33,10 

\ 

\ 

" .... _-

1900 1905 1910 1915· 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 

YEAR 

Figure 14. Simulated and measured water levels in the Upper Potomac-Raritan-Magothy and 

Englishtown aquifers, New Jersey Coastal Plain, 1896-1989. (Well locations shown in figs. 20 

22, respectively) 

50 
-1 

ill 

> ill 

-1 

« 

ill 

(f) 

3 

g 

ill 

OJ 

a:: 

o 

ill 

> o 

OJ 

« 

fw 

ill 

LL 

~ 

....i 

ill 

> ill 

-1 

a: 

ill 

~ 

3 

-1 

ill 

> 

70 

60 

50 

40 

30 

20 

:::1 20 

« 

w 

(f) 

~ 10 

o 

-l 

W 

OJ 

a: 

o 

w 

> o -10 OJ 

« 

IW 

w -20 LL 

z 

-lw -30 

> 

w 

-l 

ffi -40 I-

« 

~ 

~------------------------~-­

----------------------, 

Simulated 

Measured 

Wenonah-Mount Laurel aquifer (model unit AS) 

Weil7-478 

Node 19, 11 

.... _----------, , 

, 

I 

\ 

...... _-------, , 

I (----1 I I I 

\ I \. 

' ...... _------_: '---. 

~ 

\ 

1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 

\ 

\. 

-----------------------, 

\ 

\ 

Simulated 

Measured 

, 

\ 

, 

........... _- -------------------~ 

Lower Kirkwood-Cohansey and confined 

Kirkwood aquifers (model unit A8) 

Well 1-180 

Node 22, 22 

, 

..... _---------, , 

, 

I 

\ 

\ 

19001905 1910 1915 1920 1925 1930 1935194019451950 1955 1960 19651970 1975 1980 1985 1990 

YEAR 

Figure 15. Simulated and measured water levels in the Wenonah-Mount Laurel aquifer and 

the lower Kirkwood-Cohansey and confined Kirkwood aquifers, New Jersey Coastal Plain, 

1896-1989. (Well locations shown in figs. 24 and 30, respectively) 

51 
Table 5. Simulated flow budgets of confined aquifers in the New Jersey Coastal Plain, 1983-88 

[Values are in million gallons per day] 

Inflow 

Flow Leakage Leakage Leakage 

downdip from from from Flow 

from overlying overlying underlying across 

unconfined unconfined confined confined model 

Model unit Storage aquifer Saltwater aquifer aquifer aquifer boundary Total 

Lower Potomac-Raritan- 5.2 2 0 2.6 62 0 0.4 

Magothy aquifer (A 1) 

Middle Potomac-Raritan- 2.0 15.9 .1 93 16.9 3.4 2.7 

Magothy aquifer CA2) 

Upper Potomac-Raritan- 1.4 25.3 .5 18.6 18.1 3.6 2.7 

Magothy aquifer (A3) 

Englishtown aquifer (A4) 0 .1 .2 9.1 18.9 .3 .4 

Wenonah-Mount Laurel .1 .6 .2 7.4 IS.2 .2 .1 

aquifer (AS) 

Vincentown aquifer (A6) 0 3.0 .1 16.3 0 .1 0 

Piney Point aquifer (A 7) .4 0 1.0 7.9 0 .S 0 

Lower Kirkwood- 2.2 U.S 2.3 1.6 .1 2.7 .S 

Cohansey and confined 

Kirkwood aquifers (AS) 

72.2 

134 

70.2 

29 

26.S 

19.5 

10.1 

23.5 

Model unit 

Outflow 

Storage 

Flow 

downdipto 

unconfined 

aquifer Saltwater 

Leakage to 

overlying 

unconfined 

aquifer 

Leakage 

to 

overlying 

confined 

aquifer 

Leakage 

to 

underlying 

confined 

aquifer 

Flow 

across 

model 

boundary Pump age Total 

Lower Potomac-RaritanMagothy aquifer (AI) 

Middle Potomac-RaritanMagothy aquifer (A2) 

Upper Potomac-RaritanMagothy aquifer (A3) 

Englishtown aquifer (A4) 

Wenonah-Mount Laurel 

aquifer (AS) 

Vincentown aquifer (A6) 

Piney Point aquifer (A 7) 

Lower KirkwoodCohansey and confined 

Kirkwood aquifers (A8) 

0 

0 

0 

0 

0 

0 

.1 

.1 

0 

.1 

J 

1.9 

1.4 

1.3 

0 

.2 

0 

0 

0 

.2 

0 

.1 

0 

.4 

0 

.3 

0 

0 

.6 

1.5 

1.3 

0 

3.4 

3.6 

.3 

.1 

.7 

0 

2.7 

0 

0 

62 

16.9 

17.7 

19.1 

16.1 

.6 

0 

5.1 

3.5 

.4 

0 

.1 

0 

3.6 

.5 

63.7 

64.5 

52.3 

9.1 

4.9 

.6 

1.8 

22.3 

72.2 

134 

70.2 

29 

26.8 

19.5 

10.1 

23.5 

52 
Inflow from storage near the freshwater-saltwater interface accounted for 7 percent of the 

water coming into the Lower Potomac-Raritan-Magothy aquifer. Most of this water was released 

from storage down dip from the two cones of depression. Rates of flow from storage were largest 

downdip from the cone of depression in Ocean County. This additional source of water initially 

resulted in simulated heads in the Lower Potomac-Raritan-Magothy aquifer that were 5 to 10ft 

above the simulated heads in the RASA model. In the RASA model, this water was supplied to the 

withdrawal wells as flow from the overlying Middle Potomac-Raritan-Magothy aquifer. During 

model calibration, leakance values for the confining units overlying the Lower and Middle 

Potomac-Raritan-Magothy aquifers (model units C1 and C2) near the large cone of depression in 

Camden County were reduced by as-much as 50 percent from leakances used in the RASA modeL 

Because of the interconnection of the three Potomac-Raritan-Magothy aquifers, this additional 

'Nater supplied from storage as a result of the movement of the interface-in the Lower PotomacRaritan-Magothy aquifer affected heads over large areas in the overlying Middle and Upper 

Potomac-Raritan-Magothy aquifers (model units A2 and A3) as well. 

Inflows from storage to the Middle and Upper Potomac-Raritan-Magothy aquifers were 

similar, but less significant. Because changes in storage due to the movement of the freshwatersaltwater interface in the Potomac-Raritan-Magothy aquifer system (primarily from the Lower 

Potomac-Raritan-Magothy aquifer) were important, flow from overlying aquifers was reduced. In 

general, leakances over large areas of the confining units overlying the aquifers of the PotomacRaritan-Magothy aquifer system were reduced (about 75 percent) during model calibration. 

Leakances of the Merchantville-Woodbury confining unit (model unit C3) in downdip 

areas were reduced significantly during model calibration to supply less water to the PotomacRaritan-Magothy aquifer system in general. The isolation between the Potomac-Raritan-Magothy 

aquifer system and the overlying Englishtown and Wenonah-Mount Laurel aquifers is consistent 

with Zapecza's (1989, pI. 12) description of the Merchantville-Woodbury confining unit. 

Transmissivities in the Lower Potomac-Raritan-Magothy aquifer were reduced near the 

cone of depression in Camden County during model calibration so that hydraulic conductivities 

were consistent with values in adjacent areas. Similar reductions in transmissivity were made in 

the same area in the Middle Potomac-Raritan-Magothy aquifer. 

Lower Potomac-Raritan-Ma2othy aquifer 

Locations of withdrawal wells in the Lower Potomac-Raritan-Magothy aquifer used in the 

model for the period 1983-88 are shown in appendix 1 (fig. 1 d). Wells with average annual 

pump age greater than 5 Mgal/d (347 gal/min) represent the largest purveyors. Withdrawals are 

primarily from updip areas near the Delaware River in Camden (73 percent), northwestern 

Gloucester (12 percent), and southwestern Burlington Counties (9 percent). 

The observed potentiometric surface and the ground-water flow direction in the Lower 

Potomac-Raritan-Magothy aquifer in fall 1988 are shown in figure 16. Ground water in this aquifer 

flows toward the large cone of depression centered in Camden County and toward a less areally 

extensive cone along the Delaware River in Salem County. Water levels in large areas of Camden 

County are 40 to more than 90 ft below sea level. Flow directions have reversed from the pre de53 
/ / 

o 10 MILES I ! j j 

o 10 KILOMETERS 

'i FALL LINE 

MIDDLESEX 

MONMOUTH 

EXPLANATION 

---20 - - POTENTIOMETRIC CONTOUR--Shows altitude at 

which water level would have stood in tightly cased 

wells. Contours modified from Rosman and others 

(1995, pI. 8) and are based on water levels measured 

October-December 1988. Contour interval 20 feet. 

Dashed where approximately located. 

Datum is sea level 

UPDIP LIMIT OF AQUIFER 

7-4120 OBSERVATION WELL AND WELL NUMBER--

Hydrograph shown in figure 13 

• OBSERVATION WELL--Location of well with 

long-term hydrograph 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

'li"Oo 

Figure 16. Observed potentiometric suriace and locations of selected wells in the Lower 

Potomac-Raritan-Magothy aquifer (model unit A 1) with long-term hydrographs, New 

Jersey Coastal Plain, 1988. 

54 
velopment flow system. In this simulation, water flows from the Delaware River to withdrawal 

wells instead of discharging to the Delaware River. The location of the tip and toe of the freshwater-saltwater interface in the Lower Potomac~Raritan-Magothy aquifer and residuals at eight 

observation wells are shown in figure 17. Simulated heads are within 10ft of the measured heads 

except at the center of the cone of depression in Camden County, where the simulated heads are 

more than 10ft higher than measured heads, and in Salem County near the Delaware River, where 

the small cone of depression observed in the potentiometric-surface map is not simulated. 

Residuals at the observation wells are less than 12 ft except at two wells updip near the Delaware 

River. Gradients near the river are not well simulated because the grid cells in this area are large. 

A cone of depression was simulated down dip in northeastern Ocean County, where head 

measurements for 1988 are not available. Simulated freshwater heads between the tip and toe of 

the freshwater-saltwater interface are more than 30 ft below sea level except in most of Cumberland and Salem Counties in the south. Low freshwater heads near the interface allow the freshwater-saltwater interface to move landward. 

In the flow budget for the confined part of the Lower Potomac-Raritan-Magothy aquifer 

(table 5), most of the recharge to the updip part of the aquifer occurs as flow from the overlying 

Middle Potomac-Raritan-Magothy aquifer in Camden County and, to a lesser degree, in Burlington 

and Gloucester Counties. This vertical flow represents 86 percent of the recharge to the Lower 

Potomac-Raritan-Magothy aquifer. Inflow from storage occurs downdip as a result of movement 

of the freshwater-saltwater interface. Discharge from the aquifer is primarily through withdrawal 

wells. Vertical flow to the overlying aquifer occurs in Gloucester County near the cone of depression and downdip near the freshwater-saltwater interface. 

Middle Potomac-Raritan-Ma2othy aquifer 

Ground-water flow in the Middle Potomac-Raritan-Magothy aquifer (model unit A2) also 

has been altered significantly as a result of ground-water withdrawals. Locations of withdrawal 

wells for 1983-88 are shown in appendix 2 (fig. 2d). Withdrawals are primarily from updip areas 

along the Delaware River in Burlington (30 percent), Gloucester (9 percent), and Camden 

(9 percent) Counties. 

The observed-potentiometric-surface map of the Middle Potomac-Raritan-Magothy 

aquifer (fig. 18) shows that areas along the Delaware River in the southern part of the study area 

and Raritan Bay in the northern part that were discharge areas in the R;fedevelopment flow system 

are now recharge areas. Several cones of depression have developed; some are deep regional cones 

that affect the entire Potomac-Raritan-Magothy aquifer system and others are smaller cones due to 

local ground-water withdrawals. The large cone of depression centered in Camden County is 

present in all three Potomac-Raritan-Magothy aquifers. Gradients are much steeper updip from the 

cone, toward the Delaware River, than downdip. The cone of depression in eastern Middlesex and 

western Monmouth Counties is also present in the Upper Potomac-Raritan-Magothy aquifer, 

although water levels in the Middle Potomac-Raritan-Magothy aquifer are much lower. Water 

levels in the local cone in northeastern Ocean County declined from 30 to 40 ft below sea level in 

1983 to more than 70 ft below sea level in 1988. 

55 
-... ! o'fl1!lJ)~"'-... I 

ff·/\··L....··;-~. ' ..................... , \ / (-'\ .•. ~ ~\ ...... 

, t.' 

L CUMBERLAND ,/ 

i 

/ 

J) 

~( 

,~ { 

, MalJ~./ '~) .~f \t~"'" 

". DELAWARE \, . BAY \! '1., , 

i.~@}!i;;;::;]~j{~~~?~5(~L/;:)}' .' 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

LOWER POTOMAC-RARITAN-MAGOTHY 

AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

- -20 - SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude at which water level would have stood 

in tightly cased wells, October 31, 1988, Contour 

interval 1 o feet. Datum is sea level 

o 

I I 

o 

------ TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

• -2 

TOE OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED LIMIT OF AQUIFER 

OBSERVATION WELL--Number is difference between simulated head 

and measured water level at the well during 1983-88 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

10 MILES I i I 

10 KILOMETERS 

'100 

Figure 17. Simulated potentiometric surface, location of the simulated freshwatersaltwater interlace tip and toe, difference between simulated and measured water 

levels at observation wells, and area of upward flow in the Lower Potomac-RaritanMagothy aquifer (model unit A 1), New Jersey Coastal Plain, 1988. 

56 
/ / 

o 10 MILES I j ! I ! 

o 10 KILOMETERS 

EXPLANATION 

OUTCROP AREA OFTHE MIDDLE POTOMACRARITAN-MAGOTHY AQUIFER 

---20 - - POTENTIOMETRIC CONTOUR--Shows altitude at 

which water level would have stood in tightly cased 

wells. Contours modified from Rosman and others 

(1995, pI. 7) and are based on water levels measured 

October-December 1988. Contour interval 20 feet. ,\,g 

Dashed where approximately located. 

Datum is sea level 

UPDIP LIMIT OF AQUIFER 

o OBSERVATION WELL AND WELL NUMBER--

23-194 Hydrograph shown in figure 13 

• OBSERVATION WELL--Location of well with 

long-term hydrograph 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Figure 18. Observed potentiometric surface and locations of selected wells in the Middle 

Potomac-Raritan-Magothy aquifer (model unit A2) with long-term hydrographs, New 

Jersey Coastal Plain, 1988. 

57 
Simulated heads and the freshwater-saltwater interface tip and toe in the Middle PotomacRaritan-Magothy aquifer in 1988 are shown in figure 19. Residuals between simulated heads in 

1988 and the average measured heads for 1983-88 at 17 selected wells also are shown. Simulated 

heads at observation wells are within 10ft of average measured heads except in some wells near 

the cone of depression in Camden County and in downdip areas. Simulated water levels are similar 

to observed water levels in 1988 in most areas. The simulated centers of the large regional cones 

of depression are 10 to 15 ft above the observed water levels. Water levels in observation wells 

downdip near the interface are not well simulated. Also, local cones of depression in the observed 

potentiometric surface were not simulated as a result of the scale of the model; however, the 

general flow directions and gradients in the Middle Potomac-Raritan-Magothy aquifer are well 

simulated. The deepest part of the cone of depression in northv/estem Ivfonmouth County near the 

coast could not be simulated by using reasonable values of hydrogeologic properties. Because 

water levels at the center of the cone were measured in a withdrawal well and may not have 

recovered completely, the measured water level may represent local conditions rather than the 

regional flow system. The simulated cone of depression along the coast in northern Ocean County 

is 10 to 20 ft higher than the observed water levels in 1988, but observed water levels in 1983 were 

only 30 to 40 ft below sea level in this area. The simulated heads are high in this area because 

ground-water withdrawals in the early part of the stress period were less than withdrawals at the 

end of the stress period. The simulated heads at observation well 33-251 west of the cone are within 

about 5 ft of the average water levels at the well. Simulated heads in the recharge area in Mercer 

and Middlesex Counties are about 10ft higher than measured water levels. 

The major recharge areas in the Middle Potomac-Raritan-Mago~hy aquifer are the groundwater high in Mercer County and southern Middlesex County and parts of the aquifer along the 

Delaware River in the southern part of the study area. Ground-water flow directions near the 

Delaware River in this area have reversed from those in tbe predevelopment flow system. 

The flow budget for the confined part of the Middle Potomac-Raritan-Magothy aquifer 

(table 5) shows that recharge occurs primarily by vertical flow from the outcrop of the Upper 

Potomac-Raritan-Magothy aquifer and the confining unit overlying the Middle Potomac-RaritanMagothy aquifer (69 percent). Most of this flow is near the Delaware River in the southern part of 

the study area, and two-thirds of this water flows downward to the Lower Potomac-RaritanMagothy aquifer. This inflow represents water contributed from the Delaware River. Horizontal 

flow from the outcrop represents about 12 percent of inflow to the Middle Potomac-RaritanMagotby aquifer and occurs in updip areas. Flow from the overlying Upper Potomac-RaritanMagothy aquifer represents 1,3 percent of inflow and is greatest in updip areas in Gloucester, 

Camden, and Burlington Counties. Ground-water withdrawals account for 48 percent of the 

outflow from the aquifer and vertical flow to the underlying LowerPotomac-Raritan-Magothy 

aquifer accounts for 46 percent of the outflow. Discharge to the overlying confined aquifer occurs 

near the cone of depression in the Upper Potomac-Raritan-Magothy aquifer in Camden County and 

downdip offshore from Ocean and Monmouth Counties. 

58 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

MIDDLE POTOMAC-RARITAN-MAGOTHY 

AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

- -20 - SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude at which water level would have stood 

in tightly cased wells, October 31, 1988. Contour 

interval 10 feet. Datum is sea level 

------ TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED LIMIT OF AQUIFER 

-2- OBSERVATION WELL--Number is difference between simulated head 

and measured water level at the well during 1983-88 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ 

/ 

o 10 MILES hi .-'-T-I--,-I l---ll 

o 10 KILOMETERS 

Figure 19. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and measured water 

levels at observation wells, and area of upward flow in the Middle Potomac-RaritanMagothy aquifer (model unit A2), New Jersey Coastal Plain, 1988. 

59 
llpper Potomac-Raritan-Ma2othy aQuifer 

Locations of withdrawal wells in the Upper Potomac-Raritan-Magothy aquifer during 

1983-88 are shown in appendix 3 (fig. 3d). Withdrawals from this aquifer represent 25 percent of 

the withdrawals from Coastal Plain aquifers. More than half (53 percent) of the ground-water 

withdrawals for the period are from wells in Middlesex and Monmouth Counties. 

Observed water levels in the Upper Potomac-Raritan-Magothy aquifer in fall 1988 (fig. 20) 

generally are lower than those in fall 1983 (Eckel and Walker, 1986) at the beginning of the stress 

period. Water levels are more than 100 ft below sea level at the center of the cone of depression in 

Camden and Gloucester Counties, and in southwestern Burlington County. The second regional 

cone of depression occupies most of Monmouth County and parts of northern Ocean County. 

Water levels generally are 20 to 40 ft below sea level in this area. 

Simulated 1983-88 heads in the Upper Potomac-Raritan-Magothy aquifer are shown in 

figure 21. The simulated location of the tip and toe of the freshwater-saltwater interface and 

residuals at eight observation wells also are shown. The major observed cones of depression are 

well simulated and flow directions and gradients generally are consistent with heads in fall 1988. 

Differences between simulated and observed heads are largest near the centers of the cones of 

depression in Camden, Burlington, and Gloucester Counties, and near the pumping center in northeastern Monmouth County. Simulated gradients in the recharge area in Mercer and Middlesex 

Counties are similar to measured gradients in 1988; however, simulated heads are more than 10ft 

above the 1988 measured water levels. Observed water levels in this area were higher in 1983 than 

in 1988; therefore, average conditions for the period are higher than shown in the 1988 water-level 

map. Heads in this area generally are within 10 ft of the observed water levels in 1983. 

Average observed water levels for 1983-88 were within 13 ft of the simulated heads at all 

eight observation wells. The best matches were in updip areas and in northern Middlesex and 

Monmouth Counties. Differences were largest near the cone of depression in Camden County and 

in southern Salem County. 

Simulated heads in the Upper Potomac-Raritan-Magothy aquifer generally are lower than 

heads in the overlying Englishtown and W enonah-Mount Laurel aquifers except downdip in 

Monmouth and Ocean Counties, where water discharges from the Upper Potomac-RaritanMagothy aquifer to the Englishtown aquifer. This area coincides with the location of a large cone 

of depression in the Englishtown aquifer. 

In the flow budget for the confined part of the Upper Potomac-Raritan-Magothy aquifer for 

1983-88 (table 5), about 36 percent of the recharge t() the aquifer is horizontal flow from the unconfined part of the aquifer. Vertical flow from the overlying unconfined Englishtown aquifer and the 

outcrop of the Merchantville-Woodbury confining unit and vertical flow from the confined 

Englishtown aquifer (primarily in updip areas) each provide 26 percent of the inflow to the Upper 

Potomac-Raritan-Magothy aquifer. Vertical flow from the underlying Middle Potomac-RaritanMagothy aquifer is greatest near the center of the cone of depression in Camden County. 

60 
/ / 

o 10 MILES I j'l 1 j I 

o 10 KILOMETERS 

-

/OCEAN 

/ 

-- -- EXPLANATION 

OUTCROP AREA OF THE UPPER POTOMACRARITAN-MAGOTHY AQUIFER 

---20 - ~ POTENTIOMETRIC CONTOUR--Shows altitude at 

which water level would have stood in tightly cased 

wells. Contours modified from Rosman and others 

(1995, pI. 6) and are based on water levels measured 

October-December 1988. Contour interval 20 and 

40 feet Dashed where approximately located. 

Datum is sea level 

UPDIP LIMIT OFAQUIFER . 

o OBSERVATION WELL AND WELL NUMBER--

7-477 Hydrograph shown in figure 14 

• OBSERVATION WELL--Location of well with 

long-term hydrograph 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

'\tao 

Figure 20. Observed potentiometric surface and locations of selected wells in the Upper 

Potomac-Raritan-Magothy aquifer (model unit A3) with long-term hydrographs, New 

Jersey Coastal Plain, 1988. 

61 
" 

'-..,. ..... _---- ....... . --, 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

UPPER POTOMAC·RARITAN-MAGOTHY 

AQUIFER 

"-

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

...... -----

- .20 - SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude at which water level would have stood 

in tightly cased wells, October 31, 1988. Contour 

interval 10 feet. Datum is sea level 

------ TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

TOE OFTHE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED LIMIT OF AQUIFER 

• OBSERVATION WELL--Number is difference between simulated head 

13 and measured water level at the well during 1983-88 

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ / 

o 10 MILES I, ! I ! 

o 10 KILOMETERS 

""00 

Figure 21. Simulated potentiometric suriace, location of the simulated freshwatersaltwater interiace tip and toe, difference between simulated and measured water 

levels at observation wells, and area of upward flow in the Upper Potomac-RaritanMagothy aquifer (model unit A3), New Jersey Coastal Plain, 1988. 

62 
Discharge from the aquifer is primarily ground-water withdrawals (75 percent). The 

remaining 25 percent of discharge is downward flow to the Middle Potomac-Raritan-Magothy 

aquifer, which is greatest in updip areas in northern Gloucester, Camden, Burlington, Mercer, and 

southern Middlesex Counties. 

Englishtown Aquifer 

Locations of withdrawal wells in the Englishtown aquifer are shown in appendix 4 (fig. 4d). 

Almost all of the pump age from the Englishtown aquifer is in Ocean and Monmouth Counties. The 

largest withdrawals are near the coast at the border between Ocean and Monmouth Counties. 

Observed water levels in the Englishtown aquifer are shown in figure 22. The major feature 

of the flow system is the large, deep cone of depression in southern Monmouth and northeastern 

Ocean Counties where measured water levels are more than 220 ft below sea level. The cone of 

depression is composed of several distinct pumping centers; the deepest part is near the coast. 

Observed water levels in the Englishtown aquifer in 1988 are similar to water levels in fall 1983. 

The shape of the cone of depression is the same but water levels inland, west of the Manasquan 

Inlet, were lower in 1983 (more than 200 ft below sea level) than in 1988. 

Simulated water levels in the Englishtown aquifer for 1983-88 and residuals at six observation wells are shown in figure 23. Simulated heads match the observed water levels wen, especially updip in Monmouth County and northern Burlington County. Measured water levels are 

within 10ft of simulated values updip and near the center of the cone (downdip). Simulated heads 

are 1 ft above average measured water levels near the center of the cone. Simulated heads along 

the edges of the steep cone of depression are 20 to 30 ft above the average observed heads. The 

steep gradients and large grid cells make simulation of the cone of depression difficult. Flow directions and gradients near the cone, however, are reasonable. 

Simulated heads in Camden and Gloucester Counties are higher than observed water levels. 

The gradient in observed heads is much steeper than the simulated gradient in updip areas, but 

observed water levels in this area are sparse. Simulated gradients between the local ground-water 

high in Camden and Gloucester Counties and the large cone of depressioQ were steeper than the 

observed water levels indicate. 

Water-level differences between the Englishtown aquifer and the overlying WenonahMount Laurel aquifer are less than 10ft throughout most of the aquifer except up dip in the recharge 

areas and near the cone of depression in the northern half of Ocean County and southern 

Monmouth County. Vertical head differences between the aquifers near the cone exceed 100 ft in 

some areas. 

In the ground-water flow budget for the confined part of the Englishtown aquifer (table 5), 

most of the recharge to the Englishtown aquifer is from the overlying Wenonah-Mount Laurel 

aquifer near ground-water highs in Camden and Gloucester Counties and western Monmouth 

County. Almost one-third of the inflow occurs where the Wenonah-Mount Laurel aquifer crops 

out. Flow from the confined part of the Wenonah-Mount Laurel aquifer is more than 0.5 in/yr in 

Gloucester and Camden Counties, near the ground-water high. Downdip flow from the unconfined 

63 
EXPLANATION 

OUTCROP AREA OF THE ENGLISHTOWN 

AQUIFER 

---20 - - POTENTIOMETRIC CONTOUR--Shows altitude at 

whichwater level would have stood in tightly cased 

"100 

wells. Contours modified from Rosman and others '\~ 

/ / 

o 10 MILES 

I i I I I ! 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

(1995, pI. 5) and are based on water levels measured 

October-December 1988. Contour interval 20 feet. 

Dashed where approximately located. 

Datum is sea level 

UPDIP LIMIT OF AQUIFER 

DOWNDIP LIMIT OF AQUIFER 

o OBSERVATION WELL AND WELL NUMBER--

29-138 Hydrograph shown in figure 14 

• OBSERVATION WELL--Location of well with 

long-term hydrog~aph. 

Figure 22. Observed potentiometric surface and locations of selected wells in the 

Englishtown aquifer (model unit A4) with long-term hydrographs, New Jersey 

Coastal Plain, 1988. 

64 
CUMBERLAND / 

.p/ 

~( 

~\8'j ",.!~f.,~! .. , 

''', DELAWARE "\ (' 

BAY Y 

) 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

ENGLISHTOWN AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OFTHE AQUIFER 

- -20 - SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude at which water level would have stood 

in tightly cased wells, October 31 J 1988. Contour 

interval 20 and 40 feet. Datum is sea level 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

/ / 

o 10 MILES If--.r'-.--'-r-I ----,I 

o 10 KILOMETERS 

10. OBSERVATION WELL--Number is difference between simulated head 

and measured water level at the well during 1983-88 

Base from U,S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

<)1'00 

Figure 23. Simulated potentiometric surface, difference between simulated and measured 

water levels at observation wells, and area of upward flow in the Englishtown aquifer 

(model unit A4), New Jersey Coastal Plain, 1988. 

65 
part of the Englishtown aquifer accounts for very little of the recharge. Much of the recharge to the 

outcrop of the Englishtown aquifer flows downward to recharge the underlying Upper PotomacRaritan-Magothy aquifer. Discharge from the confined part of the Englishtown aquifer is to 

ground-water withdrawals, the Upper Potomac-Raritan-Magothy aquifer, and the outcrop oftbe 

Englishtown aquifer. Vertical flow to the underlying Upper Potomac-Raritan-Magothy aquifer 

represents 61 percent of outflow. Most of this flow occurs in updip areas, where the MerchantvilleWoodbury confining unit is thinnest. 

Several changes were made to hydrogeologic properties of the Englishtown aquifer and the 

overlying Marshalltown-Wenonah confining unit during model calibration. The hydraulic conductivity used for the Englishtown aquifer (6 to 8 ft/d) was more uniform than that used in the RASA 

model. This resulted in reduced transmissivity in updip areas and increased the gradient toward the 

major cone of depression. Transmissivities down dip are larger than those used in the RASA model. 

As discussed earlier, the leakance of the underlying Merchantville-Woodbury confining unit was 

decreased to reduce flow to the Potomac-Raritan-Magothy aquifers. The leakance of the overlying 

Marshalltown-Wenonah confining unit also was decreased (about 75 percent) during calibration. 

Reductions were largest along the coast in the northern part of the study area near the cone of 

depression. 

Wenonah Mount-Laurel Aquifer 

Locations of ground-water withdrawals from the Wenonah-Mount Laurel aquifer during 

1983-88 are shown in appendix 5 (fig. 5d). Withdrawals from updip areas were made in Salem, 

Gloucester, Camden, and Burlington Counties. Withdrawals from the deeper parts of the aquifer 

were made downdip in Monmouth and Ocean Counties. Many of the simulated wells are small; 

only a few of those shown have average withdrawals for the period of more than 0.5 Mgal/d. Withdrawals were largest in Burlington (41 percent), Camden (25 percent), and Monmouth (21 percent) 

Counties. 

The observed water levels in the Wenonah Mount-Laurel aquifer in 1988 are shown in 

figure 24. The flow system in the Wenonah-Mount Laurel aquifer is similar to that in the underlying Englishtown aquifer. Water levels are more than 140 ft above sea level in southwestern 

Monmouth and western Ocean Counties, where the aquifer receives recharge. Water levels are 

lowest in southern Monmouth and northern Ocean Counties near the coast, where water levels in 

the center of the large cone of depression are more than 200 ft below sea level. Large draw downs 

in this area are primarily the r~sult of withdrawals from the underlying Englishtown aquifer. 

Ground-water flow in the Wenonah-Mount Laurel aquifer is from recharge areas in southern 

Monmouth, western Ocean, and northwestern Burlington Counties toward the cone of depression 

near the coast. Water from the recharge area at the ground-water high in Camden and Gloucester 

Counties flows both downdip toward the cone and toward the Delaware Bay, and updip toward the 

aquifer outcrop in Gloucester County. 

Simulated heads, the location of the tip and toe of the freshwater-saltwater interface, and 

residuals at eight observation wells in the Wenonah-Mount Laurel aquifer (model unit AS) for 

1983-88 are shown in figure 25. Simulated heads are within 13 ft of the average measured water 

level at all eight wells. Heads updip from the cone of depression in Monmouth and Ocean Counties 

66 
\,/ ~ CUMBERLAND ,/ \ 

C" / 

tf 

'vlb i , Ma0~./ .... ~.! .. f\,.·~· .. · 

'\, 

DELAWARE \;;,," 

BAY V 

( 

/ 

" 

) CAPE MAY 

EXPLANATION 

OUTCROP AREA OF THE WENONAH MOUNT· 

LAUREL AQUIFER 

---20 - - POTENTIOMETRIC CONTOUR--Shows altitude at 

'100 

which water level would have stood in tightly cased ,\0 

wells. Contours modified from Rosman and others 

o 

I 

o 

/ / 

10 MILES t I I 

10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1:2,000,000,1972, 

Universal Transverse Mercator projection, Zone 18 

(1995, pI. 4) and are based on water levels measured 

October-December 1988. Contour interval 20 feet. 

Dashed where approximately located. 

Datum is sea level 

UPDIP LIMIT OF AQUIFER 

DOWNDIP LIMIT OF AQUIFER 

o OBSERVATION WELL AND WELL NUMBER--

7 -4 78 Hydrograph shown in figure 15 

• OBSERVATION WELL--Location of well with 

long-term hydrograph 

Figure 24. Observed potentiometric surface and locations of selected wells in the 

Wenonah-Mount Laurel aquifer (model unit AS) with long-term hydrographs, New 

Jersey Coastal Plain, 1988. 

67 
<100 

/ 

EXPLANATION / 

DISCRETIZED AREA OF OUTCROP OF THE o 10 MILES WENONAH-MOUNT LAUREL AQUIFER I 

o ! I ! 

10 KILOMETERS 

AREA OF UPWARD FLOW THROUGH THE TOP 

OFTHE AQUIFE.R 

- -20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows altitude at which water level would have 

stood in tightly cased wells, October 31, 1988. Contour interval 10 feet. Datum is sea level 

------ TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

.11 OBSERVATION WELL--Number is difference between simulated head 

and measured water level at the well during 1983-88 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Figure 25. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and measured water 

levels at observation wells, and area of upward flow in the Wenonah-Mount Laurel 

aquifer (model unit A5), New Jersey Coastal Plain, 1988. 

68 
and near the Delaware Bay in Salem and Cumberland Counties match the observed water levels 

well. The simulated water level at well 25-486 near the center of the cone is only 12 ft higher than 

the average observed water level. Simulated heads in Camden and Gloucester Counties are from 

10 to 15 ft above the observed water le,:,eis near the recharge area. The simulated water levels are 

more similar to the 1983 water levels than the 1988 water levels. Downdip from the recharge area, 

simulated heads are higher and gradients are less steep than measured water levels and observed 

gradients. In general, simulated flow directions and gradients in the Wenonah-Mount Laurel 

aquifer are similar to those in the observed flow system. 

In the flow budget for the confined part of the Wenonah-Mount Laurel aquifer (table 5), 

95 percent of inflow comes from the overlying aquifers and discharges downward to the underlying Englishtown and Upper Potomac-Raritan-Magothy aquifers. Horizontal flow from the 

outcrop of the Wenonah-Mount Laurel aquifer supplies only 2 percent of inflow. Vertical flow 

from the overlying unconfined aquifer and confining-unit outcrop supplies almost 28 percent of 

inflow, and vertical flow from the overlying confined Vincentown, Piney Point, and lower 

Kirkwood-Cohansey and confined Kirkwood aquifers supply 68 percent of inflow. Flow from the 

overlying confined aquifers occurs primarily in updip areas. Areas in which vertical flow is 0.5 to 

more than 7 in/yr coincide with the ground-water highs in western Monmouth County and parts of 

Gloucester, Burlington, and Salem Counties. 

Flow from the Wenonah-Mount Laurel aquifer to the underlying Englishtown aquifer 

represents 71 percent of aquifer discharge. Most of the vertical flow occurs in updip areas and near 

the cone of depression in the Englishtown aquifer. Water also discharges from the WenonahMount Laurel aquifer to the overlying aquifer in southern and down dip areas in Cumberland and 

Cape May Counties and parts of Salem and Atlantic Counties. Ground-water withdrawals from the 

confined W enonah-Mount Laurel aquifer account for 18 percent of outflow. As in the Englishtown 

aquifer, ground-water discharges horizontally to the aquifer outcrop in Gloucester, Camden, and 

northern Salem Counties. 

Both the transmissivity of the Wenonah-Mount Laurel aquifer and the leakance of the 

overlying Navesink-Hornerstown confining unit (model unit C5) were adjusted during model calibration. Transmissivity was decreased in northern Ocean and southern Monmouth Counties to 

better simulate gradients updip from the cone of depression. Hydraulic conductivities in this area 

are 6to 85 ftld and are similar to conductivities in the Englishtown aquifer. Leakance of the 

overlying confining unit was decreased during calibration to reduce heads in the Wenonah-Mount 

Laurel aquifer. 

Vincentown Aquifer 

Ground-water withdrawals from the Vincentown aquifer (model unit A6) generally are less 

than 1 Mgal/d. Locations of withdrawal wells in this aquifer during 1983-88 are shown in appendix 

6 (fig. 6d). Withdrawal wells are present only in the northern part of the Coastal Plain in Monmouth 

and Ocean Counties. 

69 
The observed water levels in the Vincentown aquifer in 1988 are shown in figure 26. 

Water-level data are sufficient to draw an observed-potentiometric-surface map only in Monmouth 

and Ocean Counties. Ground-water flow is from the topographic high in northwestern Ocean 

County and southern Monmouth County toward the Atlantic Coast. 

The simulated potentiometric surface of the Vincentown aquifer during October 1983-

October 1988 is shown in figure 27. Measured water levels are available for this period at only one 

observation well. The simulated head at this well is 8 ft below the average measured water level 

for the period. In general, the simulated heads match the measured water levels in 1988 closely in 

the northern part of the aquifer where measured water levels are available. 

Simulated flow is from the ground-water highs in Camden, Burlington, Ocean, and 

Monmouth Counties toward the Delaware Bay to the south and the Atlantic Ocean to the north. 

Between the two ground-water highs, water flows downward to the Wenonah-Mount Laurel 

aquifer. In the southern part of the aquifer in Salem, Gloucester, and Camden Counties, water 

levels in the Vincentown aquifer and underlying Wenonah-Mount Laurel aquifer are very similar. 

In the northern part of the aquifer, water levels in the Vincentown aquifer generally are higher than 

in the southern part, and water near the topographic highs flows downward to recharge the 

Wenonah-Mount Laurel aquifer. 

In the flow budget for the confined part of the Vincentown aquifer (table 5), recharge is by 

vertical flow from the overlying lower Kirkwood-Cohansey and confined Kirkwood aquifers 

(model unit A8) and by horizontal flow from its outcrop areas. Recharge from the outcrop occurs 

in Burlington, Ocean, and southern Monmouth Counties, near the topographic highs. Vertical flow 

from the overlying aquifer occurs everywhere except in northern Burlington County and parts of 

Monmouth County. In Monmouth County, near the Manasquan River, water flows downdip 

toward the downdip limit of the aquifer and discharges to both the underlying Wenonah-Mount 

Laurel aquifer and the overlying lower Kirkwood-Cohansey and confined Kirkwood aquifers. 

Discharge from the aquifer is primarily vertical flow to the underlying aquifer. Water also 

discharges horizontally to the outcrop near Raritan Bay in the south and near the Atlantic Coast in 

Monmouth County. 

The transmissivity of the Vincentown aquifer was not changed during model calibration. 

The leakance of the overlying Vincentown-Manasquan confining unit (model unit C6) was 

decreased about 70 percent. 

Piney Point Aquifer 

Ground-water withdrawals from the Piney Point aquifer (model unit A 7) are relatively 

minor; locations of withdrawal wells in this aquifer are shown in appendix 7 (fig. 7d). Wells in 

Ocean County are near the coast and 'account for 84 percent of the withdrawals. 

The observed water levels in the Piney Point aquifer in fall 1988 are shown in figure 28. 

Ground water flows from updip areas in eastern Burlington and southern Ocean Counties southeast 

toward the Atlantic Coast and south toward the Delaware Bay. Water levels in Cumberland County 

70 
"-, 

DELAWARE '\ ,/ 

BAY 'y; 

) 

/ / 

o 10 MILES I ! I ! 

o 10 KILOMETERS 

EXPLANATION 

~ OUTCROP AREA OF THE VINCENTOWN AQUIFER 

--100 -- POTENTIOMETRIC CONTOUR··Shows altitude at 

which water level would have stood in tightly cased 

wells. Contours modified from Rosman and others 

(1995, pI. 3) and are based on water levels 

measured October-December 1988. Contour interval 

20 feet. Dashed where approximately located. 

Datum is sea level 

UPDIP LIMIT OF AQUIFER 

DOWNDIP LIMIT OF AQUIFER 

• OBSERVATION WELL--Locati(;:m of well with long-term 

hydrograph 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Figure 26. Observed potentiometric surface and locations of selected wells in the 

Vincentown aquifer (model unit A6) with long-term hydrographs, New Jersey 

Coatal Plain, 1988. 

71 
DELAWARE 

BAY 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

VINCENTOWN AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OFTHE AQUIFER 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude at which water level would have stood 

in tightly cased wells, October 31, 1988. Contour 

interval 20 feet. Datum is sea level 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

/ / 

o 10 MILES f-I ,--'-, -,--L"'-I ---,I 

o 10 KILOMETERS 

--8 OBSERVATION WELL--Number is difference between simulated head 

and measured water level at the well during 1983-88 

Base from U.S. Geological Survey digital data, 1:2,000.000. 1972, 

Universal Transverse Mercator projection. Zone 18 

Figure 27. Simulated potentiometric surface, difference between simulated and 

measured water levels at observation wells, and area of upward flow in the 

Vincentown aquifer (model unit A6), New Jersey Coastal Plain, 1988. 

72 
/;:y/ SALEM 

MIDDLESEX ,/:'\ 

.. _._ .......... ./ '.~ .. , RARITAN "'.;. 

MONMOUTH v'\ BAY 

BURLINGTON 

/ 

'100 

EXPLANATION 

---20 - - POTENTIOMETRIC CONTOUR--Shows altitude at ",rb 

which water level would have stood in tightly cased 

/ 

/ 

o 10 MILES I I I I 

o 10 KILOMETERS 

Base from U,S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

wells. Contours modified from Rosman and others 

(1995, pI. 2) and are based on water levels 

measured October-December 1988. Contour interval 

20 feet. Dashed where approximately located. 

Datum is sea level 

UPDIP LIMIT OF AQUIFER 

• OBSERVATION WELL--Location of well with long-term 

hydrograph 

Figure 28. Observed potentiometric surface and locations of selected wells in the Piney 

Point aquifer (model unit A7) with long-term hydrographs, New Jersey Coastal Plain, 1988. 

73 
are affected by withdrawals in Delaware (where water levels are more than 120 ftbelow sea level). 

Ground-water withdrawals from the barrier islands off the coast of Ocean County have resulted in 

two smal1 cones of depression where water levels are more than 20 ft below sea level. 

Simulated heads and the location of the tip and toe of the freshwater-saltwater interface in 

the Piney Point aquifer for 1983-88 are shown in figure 29. Water levels at the seven observation 

wells are all within 11 ft of the average measured water levels and only one well had a residual 

greater than ±6 ft. The configuration of the simulated potentiometric surface and flow directions 

match those in the observed flow system. Water levels in Burlington and Ocean Counties are 

within 10 ft of the measured water levels. One of the small cones of depression on the barrier 

islands (north of the mouth of the Mullica River) is not well simulated because of the large grid 

cells. 

Simulated water levels in the southern part of the study area in Cumberland and Cape May 

Counties and parts of Gloucester, Camden, and Atlantic Counties are as much as 20 ft higher than 

measured water levels in 1988. Simulated water levels, however, are very similar to measured 

water levels in 1983 (Eckel and Walker, 1986, pI. 6), and simulated water levels at three observation wells in the area are within 6 ft of the average water level during 1983-88. Differences between 

simulated and measured heads are the result of changes in the flow system that occurred during the 

last model stress period (1983-88): 

In the flow budget for the confined part of the Piney Point aquifer (table 5), recharge is 

primarily flow from the overlying unconfined lower Kirkwood-Cohansey and confined Kirkwood 

aquifers (model unit A8). Most of this recharge occurs updip along the border between Burlington 

and Ocean Counties, where the confining unit is thin and water levels in the overlying aquifer are 

greater than 120 ft above sea level (as a result of a topographic high). Other sources of water to the 

aquifer are upward flow from the Wenonah-Mount Laurel aquifer and downward flow from the 

overlying lower Kirkwood-Cohansey and confined Kirkwood aquifers in the Delaware Bay 

(included in the saltwater-flow tenn). Flow in the Piney Point aquifer differs from that in the other 

aquifers because less of the water that recharges the aquifer updip flows downward to underlying 

aquifers. The largest discharge from the aquifer is flow across the model boundary near the 

Delaware Bay. Because these flows were such an important part of the budget of the aquifer, they 

were adjusted by using fluxes estimated from 1983 and 1988 heads near the Delaware Bay and 

estimates of transmissivity in order to calibrate the model. Water discharges to the overlying 

af(Uifer only in small areas where the overlying aquifer is unconfined, but discharges over most of 

the area where the aquifer is confined. 

The leakance of the overlying basal Kirkwood confining unit (model unit C7) was 

decreased 75 percent over much of the extent of the confining unit during model calibration. Transmissivity was reduced in a small area in Cumberland County to obtain a more unifonn transmissivity distribution in the area. 

74 
MIDDLESEX \ 

.. _._ ...• ···•· .. /·····\~ •• I RARITAN ~-;. 

MONMOUTH"\ BAY 

(~t-. \, /) 

',c>sink R.' \ /; 

BURLINGTON " ....... (,;~~;/I 

EXPLANATION 

/ / 

/ 

o 10 MILES '-I .-'-, .,.-...J.-"'-i ----.Ji 

/ 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

o 10 KILOMETERS 

- -20 - SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude at which water level would have stood 

in tightly cased wells, October 31, 1988. Contour 

interval 1 0 feet. Datum is sea level 

------ TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

.•••••••••• TOE OF THE SIMULATED FRESHWATER·SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

• • • • • •• SIMULATED LATERAL LIMIT OF AQUIFER 

OBSERVATION WELL--Number is difference between simulated head 

-5 and measured water level at the well during 1983-88 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

'11'00 

Figure 29. Simulated potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, difference between simulated and measured water 

levels at observation wells, and area of upward flow in the Piney Point aquifer 

(model unit A7), New Jersey Coastal Plain, 1988. 

75 
Lower Kirkwood~Cohansey and confined Kirkwood Aquifers 

Withdrawals from the lower Kirkwood-Cohansey and confined Kirkwood aquifers (model 

unit A8) total about 22 Mgal/d and are primarily from wells along the Atlantic Coast. :rhis aquifer 

is a major source of water supply in the New Jersey Coastal Plain. Locations of withdrawal wells 

in the lower Kirkwood-Cohansey and confined Kirkwood aquifers for 1983-88 are shown in 

appendix 8 (fig. 8d). Withdrawals in Atlantic, Cape May, and southern Ocean Counties account 

for 48 percent, 30 percent, and 22 percent, respectively, of the total withdrawals from the confined 

aquifer. 

The observed water levels in the lower Kirkwood-Cohansey and confined Kirkwood 

aquifers (model unit A8) in fall 1988 are shown in figure 30. Only water levels for the confined 

part of layer A8 (the confined Kirkwood aquifer) are shown. A large cone of depression is centered 

around Atlantic City and water levels have fallen 30 to 50 ft from predevelopment levels over most 

of the aquifer. Water levels at the center of the cone are more than 80 ft below sea level. The . 

ground-water flow direction in Cape May County, near the Delaware Bay, has reversed since 

predevelopment; water now flows from the Delaware Bay (where the aquifer is unconfined) 

toward Cape May and Atlantic Counties rather than discharging to the Delaware Bay. 

Simulated heads and the location of the tip and toe of the freshwater-saltwater interface in 

the confined Kirkwood aquifer during 1983-88 are shown in figure 31. Simulated heads closely 

match the heads observed in 1988 except near the center of the cone of depression, where simulated 

heads are higher than observed heads as a result of the large model cells. Differences between 

simulated heads and average measured water levels are less than 11 ft at all six wells and are less 

than ± 7 ft at five of the six wells. Where the aquifer is unconfined (and model unit A8 represents 

the lower Kirkwood-Cohansey aquifer), residuals at observation wells are reasonable and the 

simulated water levels closely match the water levels observed in 1988. 

Simulated water levels west of Cape May in the Delaware Bay are 10 to 20 ft below sea 

level near the updip limit of the overlying confining unit. Where the confining unit is absent, the 

aquifer is in contact with overlying saltwater in the upper Kirkwood-Cohansey aquifer (model unit 

A9); however, saltwater in unit A9 was not simulated in this area. Water flows from the overlying 

upper Kirkwood-Cohansey aquifer into the confined Kirkwood aquifer over most of the aquifer. 

Freshwater discharges to the overlying aquifer downdip, near the freshwater-saltwater interface. 

In the flow budget for the confined Kirkwood aquifer (model unit A8) (table 5), recharge 

to the aquifer is primarily by, horizontal flow from the unconfined part of the lower KirkwoodCohansey aquifer (59 percent of inflow). The underlying Piney Point aquifer (model unit A 7) 

contributes more inflow (11 percent) than do the overlying unconfined parts of the upper 

Kirkwood-Cohansey aquifer (model unit A9). Flow from saltwater areas, unconfined areas in the 

lower Kirkwood-Cohansey aquifer (model unit A8) in the Delaware Bay, and offshore areas in the 

upper Kirkwood-Cohansey aquifer (model unit A9) is significant and accounts for 10 percent of 

the inflow to the aquifer. Water displaced by updip movement of the freshwater-saltwater interface 

is represented as inflow from storage and accounts for about 9 percent of inflow. This occurs 

76 
) \ 

• \ 

\~ 

) 

.I 

i 

! OCEAN 

/' 

/' 

---20--

) 

/ 

/ 

J 

/ 

( 

/ 

/' 

../ 

.......... ------EXPLANATION 

OUTCROP AREA OF THE LOWER KIRKWOODCOHANSEY AND CONFINED KIRKWOOD 

AQUIFERS 

POTENTIOMETRIC CONTOUR--Shows altitude at 

which water level would have stood in tightly cased 

wells. Contours modified from Rosman and others 

(1995, pI. 1) and are based on water levels 

measured October-December 1988. Contour interval 

20 feet. Dashed where approximately located. 

Datum is sea level 

UPDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ 

/ 

/ 

/ / 

/ 

o 10 MILES 1-1 ,...-'-..-.L.,! i-J 

o 10 KILOMETERS 

UPDIP LIMIT OF CONFINING UNIT 

1-180 OBSERVATION WELL AND WELL 

o NUMBER--Hydrograph shown in 

figure lp 

• OBSERVATION WELL--Location 

of well with long-term hydrograph 

Figure 30. Observed potentiometric surface in the confined Kirkwood aquifer and 

locations of selected wells in the lower Kirkwood-Cohansey and confined Kirkwood 

aquifers (model unit AS) with long-term hydrographs, New Jersey Coastal Plain, 1988. 

77 
Base from U.S. Geological Survey digital data, 1:2,000,000,1972, 

Universal Transverse Mercator projection, Zone 18 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

LOWER KIRKWOOD-COHANSEY AND 

CONFINED KIRKWOOD AQUIFERS 

AREA OF UPWARD FLOW THROUGH THE TOP 

OFTHE AQUIFER 

- -20 - SIMULATED POTENTIOMETRIC CONTOUR--

Shows altitude at which water level would have stood 

in tightly cased wells, October 31, 1988. Contour 

interval 10 feet. Datum is sea level 

------ TIP OF THE SIMULATED FRESHWATER-SALTWATER 

INTERFACE 

o 10 MILES 

I I! 

o 10 KILOMETERS 

TOE OF THE SIMULATED FRESHWATERSALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED UPDIP LIMIT OF OVERLYING 

CONFINING UNIT 

<100 

7- OBSERVATION WELL--Number is difference 

between simulated head and measured water 

level at the well during 1983-88 

Figure 31. Simulated potentiometric surface, location of the simulated freshwater-saltwater 

interlace tip and toe, difference between simulated and measured water levels at 

observation wells, and area of upward flow in the lower Kirkwood-Cohansey and confined 

Kirkwood aquifers (model unit A8), New Jersey Coastal Plain, 1988. 

78 
offshore between the tip and toe of the interface, east of Atlantic and Ocean Counties. Groundwater withdrawals from the aquifer represent 95 percent of the outflow from the confined 

Kirkwood aquifer. Other outflows are relatively minor. 

The hydrogeologic properties of the lower Kirkwood-Cohansey and confined Kirkwood 

aquifers and the confining unit overlying the Rio Grande water-bearing zone (model unit C8) were 

adjusted slightly during model calibration. Leakance of the confining unit was decreased 

75 percent, a reduction similar to those made in other confining units. Transmissivity was 

increased in a small area updip from the cone of depression in order to match observed gradients 

near the cone of depression. 

Freshwater-Saltwater Interface Location and Moyement, 1896-1988 

Available chloride-concentration data in downdip and offshore parts of the aquifers were 

used to simulate the location of the freshwater-saltwater interface and to describe the zone of 

diffusion in each aquifer. Because chloride-concentration data near the interface are limited, it was 

not always possible to determine whether the interface was well or poorly simulated or whether the 

zone of diffusion was narrower or wider than expected. 

Meisler (1989) provides chloride measurements made at 11 onshore and offshore locations 

(fig. 1). In most cases chloride concentrations were measured at various depths in each well. These 

measurements are shown in table 6 (at end of report). For this study, the sample depths were 

compared to the hydrogeologic framework and each sample was assigned to the appropriate model 

unit. Where the aquifer contains only freshwater, chloride values at both the top and bottom of the 

aquifer are likely to be low (much less than 10,000 mg/L). Where the aquifer contains both freshwater and saltwater (contains the interface), chloride values at the top of the aquifer are likely to 

be less than 10,000 mg/L, and values from near the bottom of the aquifer are likely to be greater 

than 10,000 mg/L. Where the aquifer contains only saltwater, chloride values at all depths are 

expected to be significantly greater than 10,000 mg/L (that is, similar to concentrations in pure 

seawater). These guidelines were used to determine, where possible, where the location of the 

interface may not be well simulated and where the zone of diffusion near the interface may be 

wider than the sharp-interface assumptions in the model indicates. The chloride concentrations of 

some brines in the study area are greater than those of seawater (18,000 mglL) (table 6). Meisler 

and others (1985) conclude that the transition zones probably were produced by the mixing of fresh 

and salty ground water of either brine or salty ground-water origin. The chloride concentration of 

brine is several times that of seawater (Trapp and Meisler, 1992). 

All chloride measurements of samples from the 106 wells were made by the U.S. Geological Survey National Water Quality Laboratory (table 7, at end of report). Most of these data were 

collected during 1983-88. Where data were not available for this period, a sample collected on 

another date was substituted. Seventeen samples, therefore, were collected during 1989-90, 

generally in Ocean and Salem Counties. These samples were collected as part of the New Jersey 

Coastal Plain saltwater monitoring network (Bauersfeld and others, 1989, 1990a, 1990b). These 

wells are 9-067, 9-302,11-061,11-691,15-194,25-001,25-320, 29-004, 29-454,29-626,29-807, 

29-815, 33-035, 33-108, 33-346, 33-364, and 33-459. Eighteen samples collected from wells 

79 
during 1971-82 were used when more recent data were not available. These wells are 9-153, 

11-063,11-066,11-133,11-137, 15-231,15-324, 15-349,25-009,25-142,25-243,25-321,33-074, 

33-106,33-251,33-253,33-368, and 33-426. 

Most of the chloride concentrations were determined in samples collected from production 

wells. Some data from observation and test wells also were available. The wells were selected on 

the basis of proximity to an area of documented saltwater intrusion or to an area in which simulation results indicated that ground water may be moving vertically from an area of saltwater to an 

area of freshwater. Chloride concentrations were compared to the simulated position of the tip and 

toe of the freshwater-saltwater interface. 

Potomac-Raritan-Magothy Aquifer System 

The simulated freshwater-saltwater interface in the Potomac-Raritan-Magothy aquifer 

system is fairly consistent among the aquifers because the sediments down dip are well connected. 

The depth to the interface is between 2,000 and 2,500 ft below sea level in all three aquifers. The 

interface is deepest in the Upper Potomac-Raritan-Magothy aquifer and shallowest in the Lower 

Potomac-Raritan-Magothy aquifer. This means that freshwater in down dip parts of the Middle and 

Upper Potomac-Raritan-Magothy aquifers overlies saltwater in the underlying Lower and Middle 

Potomac-Raritan-Magothy aquifers, respectively, creating areas where saltwater could potentially 

flow upward into freshwater in overlying aquifers. 

Lower PQtQwac-Rarit~n-M~ 2"Qthy ~ Q llifer 

The position and shape of the freshwater-saltwater interface in the Lower Potomac-RaritanMagothy aquifer (app. 1, fig. If) are basically unchanged from those in 1896. The interface moved 

less than O.l mi in all areas; however, large amounts of water (5.2 Mgal/d, or 7 percent of inflow) 

have been released from storage near the interface as a result of the landward movement of 

saltwater and the displacement of freshwater. This release from storage occurs prirnarily in 

Burlington and Ocean Counties between the tip and toe of the freshwater-saltwater interface. 

The simulated location of the interface in the southern part of the New Jersey Coastal Plain 

matches the observed data fairly well. Minimum and maximum chloride concentrations in a 

borehole in Cape May County and two wells on the northern boundary of Cumberland County 

(table 6) are 11,600 and 38,100 mg/L. Chloride values from the Anchor Gas Dickinson 1 well 

(number 9, fig. 1) in Cape ,May County show that the aquifer contains saltwater. At the Anchor Gas 

Ragovin well (number 7, fig. 1) in Cumberland County, concentrations range from 11,600 mg/L 

near the top of the aquifer to 27,400 mgIL near the bottom. This indicates that the water in the 

aquifer is primarily salty but becomes less salty near the top, an interpretation that matches the 

simulated location of the interface closely. Chloride concentrations in the Island Beach Test well 

(number 6, fig. 1) near the coast in Ocean County, about 6 mi downdip from the tip of the interface, 

range from 5,400 to 11,300 mgIL. The presence of fresher water near the top of the aquifer than 

near the bottom may indicate that the interface is farther offshore than is simulated in the model or 

that the width of the zone of transition may be greater than that of the sharp interface between fresh80 
water and saltwater used in the model. Because the highest concentrations at this well are only 

slightly greater than 10,000 mg/L, the interface location in this area probably is farther offshore 

than the simulated interface location. 

High chloride concentrations measured in updip areas in Salem and Gloucester Counties 

-(170 to more than 800 mgIL) are the result of the movement of salty water from the southeast 

(Schaefer, 1983, p. 46-47). The only wells that withdraw water from the Lower Potomac-RaritanMagothy aquifer in this area tap a pocket of relatively fresh water near the Delaware River in Salem 

County. This indicates that the zone of transition in this aquifer in the southwestern part of the 

study area probably is wide. Water in the updip part of the aquifer near the Delaware River is relatively fresh; therefore, movement of water from the Delaware River into the aquifer has not 

increased chloride concentrations in these areas. 

The extent of saltwater in the Delaware River under various conditions is shown in figure 

32. The average position of the freshwater-saltwater interface in the estuary is near the Delaware 

Memorial Bridge in Salem County. The average position of the interface under summer (low-flow) 

conditions is south of Philadelphia and the farthest upstream encroachment of saltwater is near the 

Benjamin Franklin Bridge. 

Gradients in the down dip part of the Lower Potomac-Raritan-Magothy aquifer are steepest 

in eastern Camden County. Fresh ground water near the toe of the freshwater-saltwater interface 

moves updip at a rate of 0.002 ftld. 

Middle PotQmac-Raritan-Maeothy aquifer 

The simulated freshwater-saltwater interface tip and toe in the Middle Potomac-RaritanMagothy aquifer in 1988 (app. 2, fig. 2f) continue to move updip in response to past sea-level rise 

and ground-water withdrawals downdip, which have reversed flow gradients. The interface 

location is similar to that in predevelopment and has moved updip less than 0.1 mi; however, 

saltwater has displaced freshwater near the interface and contributes 2 Mgal/d of inflow to the 

aquifer as water released from storage. 

The simulated freshwater-saltwater interface generally matches the available chloride 

concentrations from about 1988. Chloride concentrations at the Anchor Gas Dickinson well in 

Cape May County (number 9, fig. 1) are much greater than 10,000 mg/L, and the aquifer contains 

only saltwater. At the Anchor Gas Ragovin well in Cumberland County (number 7, fig. 1), chloride 

concentrations range from 8,700 to 11,000 mg/L, which means that the freshwater-saltwater 

interface is near the well. The simulated interface is near this location but probably is farther 

offshore than the actual interface. At the Island Beach well at the coast in Ocean County (number 

6, fig. 1) chloride concentrations are lower, and water in the well is fresh. This interpretation corresponds well with the simulated location of the toe of the freshwater-saltwater interface. The 

chloride concentrations slightly less than 10 mi updip from the toe of the interface were between 

210 and 300 mg/L at the Warren Grove well in Ocean County (number 11, fig. 1), indicating that 

the zone of transition in the northern part of the study area is wide. Chloride concentrations as high 

as 100 mgIL in wells within 1.5 mi of the Delaware River in Salem County are a result of induced 

recharge from the river (Schaefer, 1983, p. 44). Flow of salty water from the Delaware River is 

81 
DELAWARE 

BAY 

o 

I 

o 

CAPE MAY 

/ / 

10 MILES I 

I 

10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

I FALL LINE 

Head of tide _ ~\ MERCER \ MIDDLESEX 

Position of maximum I~~~-~----

recorded upstream MONMOUTH 

encroachment of 

freshwater-saltwater - ~ "-

interface (near ~ 

Benia~in Franklin /1 ~ 

BURLINGTON / -

I OCEAN 

NEW JERSEY) 

/ 

/ 

""00 

Figure 32. Location of various freshwater-saltwater interface positions in the 

Delaware Estuary. (From Ayers and Leavesley, 1989, fig. 9) 

82 
limited to areas where withdrawal wells are located near the salty parts of the Delaware River. The 

high chloride concentration at well 33-251 in Salem County (1,900 mgIL) cannot be explained in 

terms of the ground-water flow model. Contamination probably is the result of either updip 

movement of saltwater from the east, upward flow from the underlying Lower Potomac-RaritanMagothy aquifer, or local activities. 

Saltwater contamination in downdip parts of the aquifer may be the result of vertical flow 

from the underlying Lower Potomac-Raritan-Magothy aquifer in areas where it contains salty 

water (see shaded areas in app. 2, fig. 2f). In most of the model cells in this area water flows from 

the Lower Potomac-Raritan-Magothy aquifer, which contains saltwater, into the Middle PotomacRaritan-Magothy aquifer, which contains freshwater. As stated previously, in down dip areas the 

three Potomac-Raritan-.I\.1agothy aquifers behave as a single hydrologic unit and heads in the three 

aquifers are similar. Vertical movement of saltwater from below is more likely than horizontal 

movement of the freshwater-saltwater interface from the east because the vertical conductance of 

the confining unit is high and the distance the saltwater must travel vertically is much smaller than 

the distance it must travel horizontally. 

Upper Potomac-Raritan-rvIaeothy aquifer 

The simulated freshwater-saltwater interface and available chloride concentrations for the 

Upper Potomac-Raritan-Magothy aquifer are shown in appendix 3 (fig. 3f). The interface is 

moving inland as it was during predevelopment conditions, but has moved less than 0.1 mi in all 

areas. As in the Lower and Middle Potomac-Raritan-Magothy aquifers, water is released from 

storage during the simulation as a result of the land\vard movement of saltwater and the displacement of freshwater. The amount of water contributed from storage is smaller than in the Lower and 

Middle Potomac-Raritan-Magothy aquifers but greater than in any of the other aquifers except the 

lower Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8). 

The simulated freshwater-saltwater interface matches the limited available chloride data. 

At the Anchor Gas Dickinson well (number 1, fig. 1) in Cape May County, all chlorides concentrations are greater than 10,000 mg/L, indicating that the aquifer contains saltwater. This well is 

about 10 mi down dip from the simulated interface, and chloride concentrations near 10,000 mglL 

may indicate that the zone of transition downdip from the interface is wide. Updip from the interface, chloride concentrations at the Anchor Gas Ragovin well (number 7, fig. 1) in Cumberland 

County range from 3,300 to 8,000 mglL, even though the well is 10 mi updip from the interface, 

also indicating a wide zone of transition. Chloride concentrations distant from the simulated 

interface both updip and downdip are about 10,000 mg/L, or half of the concentration in seawater, 

which indicates that the simulated position of the interface is accurate and the zone of transition is 

very wide. Chloride concentrations are low (1.0 mg/L) at well 29-577 in Ocean County, which is 

about 20 mi updip from the interface toe; this may indicate that the maximum width of the zone of 

transition updip from the interface is 10 to 20 mi. 

The presence of high chloride concentrations at the coast in Monmouth County has been 

discussed in several reports (Schaefer, 1983, p. 20-23; Schaefer and Walker, 1981; Pucci and 

others, 1994). Pucci and others (1994) concluded that the source of the contamination in the Upper 

Potornac-Raritan-Magothy aquifer is ground water that flows from the area near the freshwater83 
saltwater interface beneath Raritan Bay, where it was located in predevelopment, rather than from 

the submerged outcrop of the Upper Potomac-Raritan-Magothy aquifer or a break in the overlying 

confining unit. The location of the freshwater-saltwater interface was not simulated in Raritan Bay 

with the current model. High chloride concentrations are limited to wells near the coast, and 

encroachment of saltwater stopped when withdrawals from the Upper Potomac-Raritan-Magothy 

aquifer near the coast were discontinued in the 1970' s. 

Chloride concentrations in downdip parts of the aquifer in Salem and Gloucester Counties 

are above 250 mg/L in some areas. The chloride probably is derived from vertical flow from the 

underlying aquifers ratber than lateral movement of saltwater from the interface to the east. 

Simulated flow is from the Lower (where chloride concentrations exceed 250 mg/L (app. 1, 

fig. It) to the tvfiddle Potomac-Raritan-Magothy aquifer and then from the Middle to the Upper 

Potomac-Raritan-1\1agotby aquifer in most of Gloucester County. Vertical movement of saltwater 

through the relatively permeable confining units over a distance of only thousands of feet is more 

likely than horizontal movement of water from the interface miles away. The source of the high 

chloride concentration measured at well 33-253 in Salem County is unknown, but could be 

saltwater moving vertically through permeable underlying confining units. 

Englishtown Aquifer 

Available chloride-concentration data for the Englishtown aquifer are shown in appendix 

4 (fig. 4f). The simulated freshwater-saltwater interface is not present in this aquifer. Chloride 

concentrations within the aquifer boundaries are less than 10 mg/L, although a chloride concentration of 10,300 mg/L was measured in water from the less permeable part of the Englishtown 

aquifer sediments in Cape May County, about 40 mi down dip from the simulated boundary of the 

aquifer. 

Wenonah-Mount Laurel Aquifer 

The simulated freshwater-saltwater interface and the available chloride-concentration data 

for the Wenonah-Mount Laurel aquifer are shown in appendix 5 (fig. Sf). Chloride concentrations 

in a borehole in Cape May County range from 1,500 to 6,400 mg/L downdip from the permeable 

part of the Wenonah-Mount Laurel aquifer. In the southern part of the study area, the freshwatersaltwater interface is relatively near the simulated interface, whereas in the northern part it 

probably is farther offshore than the simulated interface. In general, it is difficult to draw any 

conclusions about the location of the interface other than that it is located within the low-permeability sediments down dip from the limit of the Wenonah-Mount Laurel aquifer. The interface 

probably does not move horizontally over large distances in this aquifer. 

Vincentown Aquifer 

Available chloride-concentration data for the Vincentown aquifer are shown in appendix 6 

(fig. 6f). The simulated freshwater-saltwater interface in the Vincentown aquifer is not present 

within the aquifer boundaries. All observed chloride concentrations within the aquifer are less than 

10 mgIL. Chloride concentrations are greater in the less permeable sediments south of the aquifer's 

downdip limit and are as high as 14,100 mglL offshore from Ocean County. 

84 
Piney Point Aquifer 

The simulated freshwater-saltwater interface and available chloride-concentration data for 

the Piney Point aquifer are shown in appendix 7 (fig. 7f). The simulated freshwater-saltwater 

interface in the Piney Point aquifer is about 10 mi offshore from Ocean County, where a chloride 

-concentration of 8,100 mg/L was measured, to more than 10 mi offshore from Atlantic County. 

Onshore chloride concentrations in this aquifer range from less than 10 mglL in Burlington County 

to 330 mg/L in coastal Atlantic County. 

Lower Kirkwood-Cohansey and Confined Kirkwood Aquifers 

The simulated freshwater-saltwater interface and available chloride-concentration data for 

the lower Kirkwood-Cohansey and confined Kirkwood aquifers for 1983-88 are shown in 

appendix 8 (fig. 8f). As described previously, the interface is many miles offshore except in the 

southern part of the study area in the Delaware Bay and in the northern part near the estimated 

location of the updip limit of the confining unit and aquifer outcrop offshore. In these areas a thin 

layer of saltwater, less than 50 ft thick, remains at the bottom of the aquifer. 

Chloride concentrations in samples collected at multiple depths in the AMCOR 1 well 

(number 1, fig. 1) range from 820 to 8,000 mg/L, indicating that water updip from the simulated 

toe of the interface is fresh. The 8,000-mg/L concentration was measured in one of the shallowest 

samples from the well. Samples from deeper parts of the aquifer contain less chloride (820-

1,800 mg/L); these low values probably are a local phenomenon. Chloride concentrations at this 

well generally indicate that the zone of transition is wide, probably as a result of the cyclic 

landward and seaward movement of the interface in response to changes in sea level. The simulated 

interface in the aquifer moved large distances during simulation of sea-level changes. This wide 

mixing zone may correspond with the "finger" of saltwater that underlies freshwater in the area 

near the AMCOR 1 well. Chloride concentrations in samples from Wildwood Pines wells 1 and 2 

(number 8, fig. 1) in Cape May County range from 90 to 200 mg/L and other measurements at wells 

in this area also indicate high chloride concentrations. 

PREDICTIVE SIMULATION OF GROUND-WATER FLOW AND 

FRESHWATER-SALTWATER INTERFACE MOVEMENT, 1988-2040 

An increase in ground-water. withdrawals of 30 percent by 2040 was simulated to predict 

water levels and approximate the location of the freshwater-saltwater interface in the modeled 

aquifers in 2040. Heads and interface locations from the calibrated transient 1988 model were used 

as initial conditions. Ground-waterwithdrawals were increased from 216.6 Mgal/d in 1983-88 to 

285.9 Mgal/d in 2040 in the confined aquifers. A 30-percent increase in average 1983-88 pumpage 

was applied uniformly to each well by aquifer. Recharge and boundary fluxes remained constant. 

The results of this simulation show the response of each aquifer to an increase in withdrawals from 

existing wells. 

85 
Simulated water levels in all eight confined aquifers are shown in fig~res 33-40. The 

configuration of water-level contours are similar to those simulated for 1988, but the cones of 

depression are broader and deeper. By 2040, water levels are, on average, about 30 ft lower near 

pumping centers than water levels simulated for 1988. A 30-ft decline in water levels was 

simulated in the Lower and Upper Potomac-Raritan-Magothy aquifers (model units Al and A3) at 

a pumping center in northern Camden County; a 20-ft decline was simulated in the Middle 

Potomac-Raritan-Magothy aquifer (model unit A2) in the same area. A 30-ft decline in water levels 

in the Middle Potomac-Raritan-Magothy aquifer was simulated at a pumping center in Middlesex 

County and in the Upper Potomac-Raritan-Magothy aquifer in Monmouth County. Water-level 

declines of more than 100 ft were simulated in the Englishtown aquifer (model unit A4) along the 

border bet-ween Ocean and ~Y1onmouth Counties. In the Wenonah-Mount Laurel aquifer (model 

unit AS) simulated water levels declined 80 ft around a pumping area in Monmouth County. A 

30-ft decline in water levels was simulated for a pumping center in Atlantic County in the lower 

Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8). 

The flow budget for the predictive simulation is shown in table 8. The 55.1-Mga1/d increase 

in withdrawals from the aquifers of the Potomac-Raritan-Magothy aquifer system from those in 

1988 resulted in an increase in downward leakage to the Lower and Middle Potomac-RaritanMagothy aquifers. Vertical flow to the Lower Potomac-Raritan-Magothy aquifer from the 

overlying Middle Potomac-Raritan-Magothy aquifer increased 30 percent from the 1988 simulation; vertical flow from the overlying unconfined aquifers to the Middle Potomac-Raritan Magothy 

aquifer increased 32 percent. Lateral flow from the outcrop or downdip from unconfined aquifers 

to the Upper Potomac-Raritan-Magothy aquifer increased about 41 percent. 

Although a comparison of the interface locations between the maps of simulated results for 

1988 (figs. 17,19,21,25,29, and 31) and the maps of simulated results for 2040 (figs. 33,34,35, 

37, 39, and 40) shows no apparent movement of the freshwater-saltwater interface, water levels 

declined nearthe interface. The water-level declines signify changes in the gradient near the 

interface that may affect the salinity at wells near the interface. A 20-ft decline was simulated near 

the interface in the Lower Raritan-Potomac-Magothy aquifer. A 30-ft decline was simulated in the 

Middle and Upper Potomac-Raritan-Magothy aquifers and the Wenonah-Mount Laurel aquifer. A 

10-ft decline was simulated near the interface in the Piney Point and lower Kirkwood-Cohansey 

and confined Kirkwood aquifers. The interface in the latter two model units is located offshore. 

In general, the simulated freshwater-saltwater interface did not move significantly in any 

aquifer during 1988-2040. Simulated movement was greatest (30 ft) inland in the Lower PotomacRaritan-Magothy aquifer in Ocean County. The interface moved less than 5 ft inland in the other 

confined aquifers. 

SUMMARY AND CONCLUSIONS 

The confined aquifers of the New Jersey Coastal Plain are composed of sand, range from 

50 to 600 ft in thickness, and are separated by confining units. The confining units are composed 

of silt and clay and range in thickness from 50 to 1,000 ft. The aquifers are recharged by precipitation on their outcrop areas that flows laterally downdip. Water in the confined aquifers ultimately 

discharges to the Raritan and the Delaware Bays and to the Atlantic Ocean. 

86 
DELAWARE 

BAY 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE LOWER 

POTOMAC-RARITAN-MAGOTHY AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

/ / 

o 10 MILES 1--1 ,..-'-, '-1 -"-'-1 -JI 

o 10 KILOMETERS 

- -20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows predicted altitude of water level 

in tightly cased wells in 2040. Contour interval 10 feet. Datum is sea level 

------ TIP OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

•......••.. TOE OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

"00 

Figure 33. Simulated potentiometric surface, location of the simulated freshwater-saltwater 

interface tip and toe, and area of upward flow resulting from a 30-percent increase in 

withdrawals at all wells, Lower Potomac-Raritan-Magothy aquifer (model unit A 1), New 

Jersey Coastal Plain, 2040. 

87 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE MIDDLE 

POTOMAC-RARITAN-MAGOTHY AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

o 10 MILES I I I I \ \ 

o 10 KILOMETERS 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows predicted altitude of water level in tightly 

cased wells in 2040. Contour interval 10 feet. Datum is sea level 

TIP OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Figure 34. Simulated potentiometric surface, location of the simulated freshwater-saltwater 

interface tip and toe, and area of upward flow resulting from a 3D-percent increase in 

withdrawals at all wells, Middle Potomac-Raritan-Magothy aquifer (model unit A2), 

Jersey Coastal Plain, 2040. 

88 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE UPPER 

POTOMAC-RARITAN-MAGOTHY AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

o 

Ii 

o 

/ / 

10 MILES ! I I 

10 KILOMETERS 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows predicted altitude of water 

level in tightly cased wells in 2040. Contour interval 10 feet. Datum is sea level 

------ TIP OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Figure 35. Simulated potentiometric suriace, location of the simulated freshwater-saltwater 

interface tip and toe, and area of upward flow resulting from a 3D-percent increase in 

withdrawals at all wells, Upper Potomac-Raritan-Magothy aquifer (model unit A3), 

New Jersey Coastal Plain, 2040. 

89 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

ENGLISHTOWN AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

/ / 

o 10 MILES 1-1 ,-J-, ''-1 --'---;-1 -----11 

o 10 KILOMETERS 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows predicted altitude of water level in 

tightly cased wells in 2040. Contour interval 20 and 40 feet. Datum is sea level 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 1 B 

Figure 36. Simulated potentiometric surface and area of upward flow resulting from a 

3D-percent increase in withdrawals at all wells, Englishtown aquifer, (model unit A4), 

New Jersey Coastal Plain, 2040. 

90 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE WENONAHMOUNT LAUREL AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

o 10 MILES I i I ! I I 

o 10 KILOMETERS 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows predicted altitude of water level 

in tightly cased wells in 2040. Contour interval 20 and 40 feet. Datum is sea level 

------ TIP OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Figure 37. Simulated potentiometric surface, location of the simulated freshwater-saltwater 

interface tip and toe, and area of upward flow resulting from a 3D-percent increase in 

withdrawals at all wells, Wenonah-Mount Laurel aquifer (model unit AS), New Jersey 

Coastal Plain, 2040. 

91 
JERSEY/ 

/ 

/ 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

VINCENTOWN AQUIFER 

I 

AREA OF UPWARD FLOW THROUGH THE TOP 

OFTHE AQUIFER 

OCEAN 

o 

I 

o 

/ / 

10 MILES ! I ! 

10 KILOMETERS 

- -20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows predicted altitude of water level 

in tightly cased wells in 2040. Contour interval 20 feet. Datum is sea level 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

"i1'00 

Figure 38. Simulated potentiometric surface and area of upward flow resulting from a 

3D-percent increase in withdrawals at all wells, Vincentown aquifer (model unit A6), 

New Jersey Coastal Plain, 2040. 

92 
BURLINGTON 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

PINEY POINT AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP OF THE AQUIFER 

:I 

/ 

o 10 MILES 

I, I I 

o 10 KILOMETERS 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows predicted altitude of water level in 

tightly cased well in 2040. Contour interval 10 feet. Datum is sea level 

------ TIP OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

• • • • • •• SIMULATED LATERAL LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

""00 

Figure 39. Simulated potentiometric surface, location of the simulated freshwater-saltwater 

interface tip and toe, and area of upward flow resulting from a 30-percent increase in 

withdrawals at all wells, Piney Point aquifer (model unit A7), New Jersey Coastal Plain, 2040. 

93 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF 

THE LOWER KIRKWOOD-COHANSEY 

AND CONFINED KIRKWOOD AQUIFERS 

AREA OF UPWARD FLOW THROUGH 

THE TOP OF THE AQUIFER 

/ / 

o 10 MILES '-I ...-'-r-...L..,-I ----,I 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1:2,000,000,1972, 

Universal Transverse Mercator projection, Zone 18 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows 

predicted altitude of water level in tightly cased wells 

in 2040. Contour interval 10 feet. Datum is sea level 

------ TIP OF THE PREDICTED FRESHWATERSALTWATER INTERFACE 

..•....••.• TOE OF THE PREDICTED FRESHWATERSALTWATER INTERFACE 

................. - SIMULATED UPDIP LIMIT OF AQUIFER 

Figure 40. Simulated potentiometric surface, location of the simulated freshwater-saltwater 

interface tip and toe, and area of upward flow resulting from a 30-percent increase in 

withdrawals at all wells, lower Kirkwood-Cohansey and confined Kirkwood aquifers (model 

unit AS), New Jersey Coastal Plain, 2040. 

94 
Table 8. Simulated :flow budgets of confined aquifers in the New Jersey Coastal Plain, 2040 

[Values are in million gallons per day] 

Inflow 

Flow Leakage Leakage Leakage 

downdip from from from Flow 

from overlying overlying underlying across 

unconfined unconfined confined confined model 

Model unit Storage aquifer Saltwater aquifer aquifer aquifer boundary 

Lower Potomac-Raritan- 5 2.3 0 3.6 SO.9 0 0.4 

Magothy aquifer (A 1) 

Middle Potomac-Raritan- 1.7 20.9 .2 123.1 21.7 4.0 2.7 

Magothy aquifer (A2) 

Upper Potomac-Raritan- 1.2 35.8 .9 23.1 22.2 4.7 2.7 

Magothy aquifer (A3) 

Englishtown aquifer (A4) 0 .2 .4 10.6 23.4 .3 .4 

Wenonah-Mount Laurel .1 .7 .4 9 22.1 .1 .1 

aquifer (AS) 

Vincentown aquifer (A6) 0 3.4 .2 19 0 .1 0 

Piney Point aquifer (A 7) .2 0 1.1 8.9 .1 .6 0 

Lower Kirkwood- 2.2 17.S 3.9 2.1 .1 3.1 .8 

Cohansey and confined 

Kirkwood aquifers (AS) 

Total 

92.2 

174.3 

90.6 

35.3 

32.5 

22.7 

10.9 

30 

Model unit 

Lower Potomac-RaritanMagothy aquifer (AI) 

Middle Potomac-RaritanMagothy aquifer (A2) 

Upper Potomac-RaritanMagothy aquifer (A3) 

Englishtown aquifer (A4) 

Wenonah-Mount Laurel 

aquifer (AS) 

Vincentown aquifer (A6) 

Piney Point aquifer (A 7) 

Lower KirkwoodCohansey and confined 

Kirkwood aquifers (A8) 

Outflow 

Pump age 

82.7 

84.9 

68 

11.8 

6.4 

.7 

2.3 

29.1 

Total 

92.2 

173.3 

90.6 

35.3 

32.5 

22.7 

10.9 

30 

Storage 

0.4 

0 

0 

0 

0 

0 

.1 

.1 

Flow 

downdipto 

unconfined 

aquifer 

0 

.1 

.3 

1.6 

1.3 

0 

.1 

Saltwater 

0 

0 

0 

.2 

0 

.2 

0 

.1 

Leakage to 

overlying 

unconfined 

aquifer 

0 

.2 

0 

0 

.2 

1.3 

.9 

0 

Leakage 

to 

overlying 

confined 

aquifer 

4.0 

4.7 

.3 

.1 

.6 

0 

3.1 

0 

Leakage 

to 

underlying 

confined 

aquifer 

0 

80.9 

21.6 

21.6 

23.9 

19.5 

.9 

.1 

Flow 

across 

model 

boundary 

5.1 

3.5 

.4 

0 

.1 

0 

3.6 

.5 

95 
In 1988, withdrawals from confined and unconfined aquifers in the New Jersey Coastal 

Plain were approximately 345 Mgal/d, of which more than 7~ percent was from the confined 

aquifers. The development of ground-water resources, primarily near large population centers, has 

created large regional cones of depression in several of the Coastal Plain aquifers. Continued 

decline of water levels in confined aquifers poses the threat of serious adverse effects, including 

saltwater intrusion and reduction of stream discharge near the aquifer outcrop areas. 

In order to better identify areas in which ground-water supplies may be threatened by 

saltwater intrusion, the U.S. Geological Survey (USGS), in cooperation with the New Jersey 

Department of Environmental Protection, conducted a study of the ground-water flow and 

freshwater-saltwater interface movement in the New Jersey Coastal Plain. 

Ground-water flow and the saltwater-freshwater interface were simulated by using a sharpinterface flow model that is based on a model previously developed as part of the USGS New 

Jersey Regional Aquifer System Analysis (RASA) program. The lower model boundary is a noflow boundary representing the top of the underlying crystalline bedrock. The upper boundary is a 

constant-head boundary representing streams ( and recharge) in the aquifer outcrop areas onshore 

and ocean levels in aquifer outcrop areas offshore. The downdip boundary of the model was 

changed from a no-flow boundary in the New Jersey RASA model to a direct simulation of the 

saltwater interface in all aquifers. In the uppermost aquifers, a constant saltwater-head boundary 

was used to represent presumed outcrops of the aquifers at the downdip limit of the Continental 

Shelf. A no-flow boundary was applied in the northwestern part of the study area at the updip limit 

of the Coastal Plain sediments (the Fall Line). Specified-flux boundaries applied at the northeastern and southwestern boundaries represent flow to the Raritan and the Delaware Bays, 

respectively. 

Water levels and the location of the freshwater-saltwater interface were simulated (1) under 

steady-state conditions in which sea level was relatively constant from 110,000 to 84,000 years 

ago; (2) from 84,000 years ago to 1896, including the effects of glaciation on the rise and fall of 

sea level; (3) under transient conditions from 1896 to 1988 by including ground-water withdrawals 

from the Coastal Plain aquifers; and (4) in a predictive simulation to the year 2040 with a 

30-percent increase in withdrawals at pumping centers existing in 1988. From 110,000 to 84,000 

years ago, the freshwater-saltwater interface stabilized in equilibrium with a sea level 27 ft below 

current sea level. Sea level fell from -27 ft 84,000 years ago to -230 ft 71,000 years ago, which 

caused the interface to move offshore. As sea level rose beginning 71,000 years ago, the freshwater-saltwater interface began moving landward. The interface has not yet stabilized and is still 

moving landward in respon'se to this rise in sea level. The freshwater-saltwater interface is considered to be the boundary seaward of which chloride concentrations equal or exceed 10,000 mglL. 

The model was then used to simulate conditions from 84,000 years ago to 1896 by 

adjusting areas receiving recharge (onshore areas) and boundary conditions to account for the rise 

and fall of sea level during the glacial periods. The model was calibrated to present-day (1988) 

conditions by simulating water levels measured in fall 1988, by matching simulated water levels 

to bydrographs at 141 observation wells, and by approximating the location of the freshwatersaltwater interface from chloride-concentration measurements. Under pumping conditions, 

regional cones of depression developed in Camden County in the Lower Potomac-Raritan96 
Magothy aquifer; in Camden and Monmouth Counties in the Middle and Upper Potomac-RaritanMagothy aquifers; and in southern Monmouth County in the Englishtown and Wenonah-Mount 

Laurel aquifers. 

The results of the predevelopment simulation from 84,000 years ago to 1896, the transient 

simulation from 1896 to 1988, and the predictive simulation from 1988 to 2040 show minimal 

movement of the interface between freshwater and saltwater in response to increased ground-water 

withdrawals. The position and movement of the freshwater-saltwater interface are more dependent 

on historical sea level than on the stressed flow system resulting from ground-water withdrawals 

from the Coastal Plain aquifers from 1896 to 1988. The freshwater-saltwater interface has not 

reached equilibrium with current sea level because the interface moves seaward in response to a 

fall in sea level faster than it moves landward after a sea-level lise. 

Results of the predictive simulation to 2040 indicate that additional withdrawals from each 

of the eight confined aquifers in the Coastal Plain would broaden and deepen the existing cones of 

depression. Because the withdrawals were increased at current pumping locations (those in use 

during 1983-88), the configurations of the potentiometric surfaces of the aquifers were not significantly different from those in 1988. Compared with the 1988 potentiometric surfaces, a 30-percent 

increase in ground-water withdrawals caused drawdowns of 30 ft at the centers of the cones of 

depression in the Lower, Middle, and Upper Potomac-Raritan-Magothy aquifers in Camden and 

Ocean Counties; caused drawdowns of more than 80 ft at the center of the cone of depression in 

the W enonah-Mount Laurel and Englishtown aquifers in Monmouth County; and caused 

drawdowns of 30 ft in the lower Kirkwood-Cohansey and confined Kirkwood aquifers in Cape 

May County. The simulated interface did not move significantly in any of the confined aquifers. 

97 
REFERENCES CITED 

Ayers, M.A., and Leavesley, G.R., 1989, Assessment of the potential effects of climate change on 

water resources of the Delaware River Basin: Work plan for 1988-90: U.S. Geological 

Survey Open-File Report 88-478, 37 p. 

Battaglin, W.A., and Hill, M.C., 1989, Simulated effects of future withdrawals on water levels in 

the Northeastern Coastal Plain Aquifers of New Jersey: U.S. Geological Survey WaterResources Investigations Report 88-4199, 58 p. 

Bauersfeld, W.R., Moshinsky, E.W., Pustay, E.A., and Jones, W.D., 1990a, Water resources data 

for New Jersey--water year 1989, volume 1, Atlantic Slope basins, Hudson River to Cape 

tviay: U.S. Geological Survey Water-Data Report J'~J-89-1, 345 p. 

__ 1990b, Water resources data for New lersey--water year 1989, volume 2, Delaware River 

basin and tributaries to Delaware Bay: U.S. Geological Survey Water-Data Report 

NJ-89-2, 215 p. 

__ 1991, Water resources data for New Jersey--wateryear 1990, volume 2, ground-water data: 

U.S. Geological Survey Water-Data Report NJ-90-2, 178 p. 

CH2M Hill, Metcalf & Eddy, Inc., and New Jersey First, Inc., 1992, Water supply baseline data 

development and analysis: New Jersey Statewide Water Supply Master Plan Task 2 Report, 

not paginated. 

Eckel, lA., and Walker, R.L., 1986, Water levels in major artesian aquifers of the New Jersey 

Coastal Plain, 1983: U.S. Geological Survey Water-Resources Investigations Report 

86-4028, 62 p. 

Essaid, R.I., 1990, The computer model SHARP, a quasi-three-dimensional finite-difference 

model to simulate freshwater and saltwater flow in layered coastal aquifer systems: 

U.S. Geological Survey Water-Resources Investigations Report 90-4130,181 p. 

Freeze, R.A., and Cherry, lA., 1979, Groundwater: Englewood Cliffs, N.J., Prentice-Hall, Inc., 

604 p. 

Hathaway, lC., and others, eds., 1976, Preliminary summary of the 1976 Atlantics Margin Coring 

Project of the U.S. Geological Survey: U.S. Geological Survey Open-File Report 76-844, 

217 p. 

Hathaway, lC., and others, eds., 1979, U.S. Geological Survey core drilling on the Atlantic shelf: 

Science, v. 206, no. 4418, p. 515-527. 

Gill, H.E., 1962, Ground-water resources of Cape May County, New Jersey: Salt-water invasion 

of principal aquifers: New Jersey Department of Conservation and Economic Development 

Special Report 18, 48 p. 

98 
REFERENCES CITED--Continued 

Leahy, P.P., and Martin, M.M., 1993, Geohydrology and simulation of ground-water flow in the 

Northern Atlantic Coastal Plain aquifer system: U.S. Geological Survey Professional Paper 

1404-K, 81 p. 

Martin, M.M., 1998, Ground-water flow in the New Jersey Coastal Plain: U.S. Geological Survey 

Professional Paper 1404-H, 146 p. 

Mattick, R.E., and Hennessy, J.L., 1980, Structural framework, stratigraphy, and petroleum 

geology of the area of oil and gas lease sale No. 49 on the U.S. Atlantic continental shelf and 

slope: U.S. Geological Survey Circular C812, 101 p. 

Meisler, H.A., Leahy, P.P., and Knobel, L.L., 1985, Effect of eustatic sea-level changes on 

saltwater-freshwater relations in the Northern Atlantic Coastal Plain: U.S. Geological 

Survey Water-Supply Paper 2255,28 p. 

Meisler, B.A., 1989, The occurrence and geochemistry of salty ground water in the Northern 

Atlantic Coastal Plain: U.S. Geological Survey Professional Paper 1404-D, 51 p. 

Navoy, A.S., and Carleton, G.B., 1994, Ground-water flow and future conditions in the PotomacRaritan-Magothy aquifer system, Camden area, l'Jew Jersey: New Jersey Geological Survey 

Bulletin GSR-38, 184 p. 

Pucci, A.A., Jf., Pope, D.A., and Gronberg, lM., 1994, Hydrogeology, simulation of regional 

ground-water flow, and saltwater intrusion, Potomac-Raritan-Magothy aquifer system, 

Northern Coastal Plain of New Jersey: New Jersey Geological Survey Report GSR 36, 

209 p. 

Rosman, Robert, Lacombe, PJ., and Storck, D.A., 1995, Water levels in the major aquifers of the 

New Jersey Coastal Plain, 1988: U.S. Geological Survey Open-FIle Report 95-4060, 74 p. 

Schaefer, F .L., 1983, Distribution of chloride concentrations in the principal ,aquifers of the New 

Jersey Coastal Plain, 1977-81: U.S. Geological Survey Water-Resources Investigations 

Report 83-4061,56 p. 

Schaefer, F .L., and Walker, R.L., 1981, Saltwater intrusion into the Old Bridge aquifer in the 

Keyport-Union Beach area of Monmouth County, New Jersey: U.S. Geological Survey 

Water-Supply Paper 2184,21 p. 

Scholle, P.A., 1977, Geological studies on the COST No. B-2 Well, U.S. Mid-Atlantic Outer 

Continental Shelf Area: U.S. Geological Survey Circular 750, 71 p. 

Scholle, P.A. 1980, Geological studies of the COST No. B-3 Well, United States Mid-Atlantic 

Continental Slope Area: U.S. Geological Survey Circular 833, 132 p. 

99 
REFERENCES CITED--Continued 

Spitz, FJ., and Barringer, T.H., 1992, Ground-water hydrology and simulation of saltwater 

encroachment, shallow aquifer system of Southern Cape May County, New Jersey: 

U.S. Geological Survey Water-Resources Investigations Report 91-4191,87 p. 

Trapp, Henry, Jr., and Meisler, Harold, 1992, The regional aquifer system underlying the Northern 

Atlantic Coastal Plain in parts ofNortb Carolina, Virginia, Maryland, Delaware, New Jersey, 

and New York: U.S. Geological Survey Professional Paper 1404-A, 33 p. 

Uchupi, Elazar, 1970, Atlantic Continental Shelf and Slope of the United States--Shallow 

structure: U.S. Geological Survey Professional Paper 529-1, pI. 1. 

Walker, R.L., 1983, Evaluation of water levels in major aquifers of the New Jersey Coastal Plain, 

1978: U.S. Geological Survey Water-Resources Investigations Report 82-4077, 56 p. 

Zapecza, O.S., 1989, Hydrogeologic framework of the New Jersey Coastal Plain: U.S. Geological 

Survey Professional Paper 1404-B, 49 p., 24 pI. 

Zapecza, O.S., Voronin, L.M., and Martin, M.M., 1987, Ground-water withdrawal and water-level 

data used to simulate regional flow in the major Coastal Plain aquifers of New Jersey: 

U.S. Geological Survey Water-Resources Investigations Report 87-4038, 120 p. 

ZeImer, L.R., 1979, Development and application of a Pleistocene sea level curve to the Coastal 

Plain of southeastern Virginia: Williamsburg, Va., College of William and Mary, School of 

Marine Science, unpublished Master's thesis, 85 p. 

100 
Table 4 .. Simulated water-level altitudes for 1988, average measured water-level altitudes for 

1983-88, and the difference between simulated and measured water-level altitudes for selected 

wells, New Jersey Coastal Plain 

Simulated water-level A verage measured u.s. Geological Difference altitude water-level altitude Survey (simulated-measured) (feet below land (feet below land well number (feet) surface) surface) 

Lower Potomac-Raritan-Magothy 

5-262 -50.39 -54.35 3.96 

5-645 -38.24 -36.35 -1.89 

7-283 -60.44 -72.72 12.29 

7-354 -18.99 1.84 ~20.82 

7-412 -68.41 -73.42 5.01 

15-296 -25.12 -17.52 -7.60 

15-323 -30.93 -46.15 15.22 

33-187 -19.42 -26.3 8 6.96 

Middle Potomac-Raritan-Magothy aquifer (model unit A2) 

5- 63 -20.98 -18.96 -2.02 

5-101 5.95 2.64 3.31 

5-261 -47.53 -54.45 6.93 

5-274 -23.92 -25.84 1.92 

5-440 -17.71 -30.24 12.53 

5-683 -32.11 -34.75 2.64 

7-413 -62.07 -78.50 16.44 

7-476 -50.21 -52.35 2.14 

11-137 -25.68 -44.69 19.01 

15- 97 -2.82 -1.18 -1.64 

23-194 -53.28 -52.76 -0.52 

23-229 45.90 52.80 -6.90 

25-272 -53.55 -59.73 6.18 

29- 19 -24.89 -6.98 -17.92 

29- 85 -38.62 -31.30 -7.32 

33-251 -24.18 -29.33 5.15 

Upper Potomac-Raritan-Magothy aquifer (model unit A3) 

5-258 -53.15 -61.80 8.65 

7- 30 -15.95 -18.00 2.06 

7-117 -74.36 -87.21 12.85 

7-477 -64.61 -71.94 7.34 

15-297 -7.35 -10.72 3.38 

23-182 15.02 16.20 -1.18 

25-206 -14.54 -14.24 -0.29 

33-253 -12.84 -24.67 11.83 

101 
Table 4. Simulated water-level altitudes for 1988, average measured water-level altitudes for 

1983-88, and the difference between simulated and measured water-level altitudes for selected 

wells, New Jersey Coastal Plain--Continued 

Simulated water-level A verage measured U.S. Geological Difference altitude water-level altitude Survey (simulated-measured) (feet below land (feet below land well number (feet) surface) surface) 

Englishtown aquifer (model unit A4) 

5-259 30.87 20.95 9.92 

25-250 ., ,...'" 97.18 iOO.43 -_l.LJ 

25-429 -159.75 -140.74 -19'(ll 

29-138 57.72 62.41 -4.69 

29-503 -192.51 -193.70 1.20 

29-534 -57.86 -85.36 27.49 

Wenonah-Mount Laurel aquifer (model unit A5) 

7-118 81.42 69.33 12.09 

7-478 48.38 35.42 12.95 

11- 72 1.90 9.02 -7.12 

25-353 -9.13 -11.14 2.01 

25-486 -163.71 -176.18 

11 A oc 29-140 11~.O.J 113.63 

12.47 

1.22 

33- 20 43.87 32.76 11.12 

33-252 7.42 1.19 6.23 

Vincentown aquifer (model unit A6) 

29-139 121.78 130.04 -8.27 

Piney Point aquifer (model unit A 7) 

5-407 55.91 51.34 

5-676 108.10 118.69 

11- 44 14.65 11.31 

11- 96 -16.36 -22.23 

11-163 11.31 12.75 

29- 18 5.54 0.44 

29-425 114.38 118.94 

4.56 

-10.59 

3.34 

5.88 

-1.44 

5.10 

-4.57 

102 
Table 4. Simulated water-level altitudes for 1988, average measured water-level altitudes for 

1983-88, and the difference between simulated and measured water-level altitudes for selected 

wells, New Jersey Coastal Plain--Continued 

Simulated water-level A verage measured U.S. Geological Difference altitude water-level altitude Survey (simulated-measured) (feet below land (feet below land well number (feet) surface) surface) 

Lower Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8) 

1- 37 -68.45 -75.02 6.57 

1-180 -38.63 -32.73 -5.90 

1-566 -54.66 -43.94 -10.72 

1-578 -52.00 -54.78 2.78 

1-703 -37.62 -38.79 1.18 

1-706 -26.22 -20.37 -5.85 

5- 30 68.60 65.44 3.15 

7-479 113.51 109.94 3.56 

11- 43 70.58 76.97 -6.39 

11- 97 12.31 1.13 11.18 

15-792 119.80 97.28 22.52 

29- 17 0.65 4.38 -3.73 

29-514 37.06 36.43 0.63 

103 
Table 6. Concentrations of chloride at various depths in deep wells and boreholes in onshore and 

offshore areas, New Jersey Coastal Plain, 1888-1974 

[Data from Meisler (1989); mgIL as CI, milligrams per liter as chloride~ 00 in sample date indicates unknown day] 

Chloride Sample depth 

Well number concentration (feet below 

(fig. 1) Local well identifier (mg/L as CI) sea level) Sample date Model unit 

Amcor 6011 16,200 103 8-17-76 A9 

16,200 241 8-17-76 A9 

8,000 306 8-17-76 A8 

820 305 . 8-17-76 A8 

1,800 337 8-17-76 A8 

1,600 460 8-17-76 A8 

1,000 523 8-17-76 A8 

1,160 585 8-17-76 A8 

1,350 648 8-17-76 A7 

2,090 710 8-17-76 A7 

8,100 802 8-17-76 A7 

2,720 895 8-17-76 A7 

1,800 926 8-17-76 A7 

2 Amcor 6020 14,950 154 9-13-76 A9 

12,800 211 9-13-76 A9 

10,900 240 9-13-76 A9 

4,020 272 9-13-76 A9 

3 Amcor 6009, 6009B 17,000 213 8-00-76 A9 

18,200 243 8-00-76 A9 

11,260 273 8-00-76 A9 

6,340 304 8-00-76 A9 

5,140 335 8-00-76 A9 

3,700 335 8-00-76 A9 

3,790 429 8-00-76 A9 

3,520 460 8-00-76 A9 

3,170 460 8-00-76 A9 

3,390 491 8-00-76 A9 

3,530 522 8-00-76 A9 

3,7,70 554 8-00-76 A9 

4,830 616 8-00-76 A9 

4,960 647 8-00-76 A9 

5,640 709 8-00-76 A9 

7,330 771 8-00-76 A9 

6,190 832 8-00-76 A9 

9,070 926 8-00-76 A9 

7,210 1,018 8-00-76 A9 

10,970 1,081 8-00-76 A9 

14,270 1,112 8-00-76 A8 

104 
Table 6. Concentrations of chloride at various depths in deep wells and boreholes in onshore and 

offshore areas, New Jersey Coastal Plain, 1888-1974--Continued 

Chloride Sample depth 

Well number concentration (feet below 

(fig. 1) Local well identifier (mg/L as Cl) sea level) Sample date Model unit 

4 Amcor 6010 17,600 276 8-15-76 A9 

15,800 335 8-15-76 A9 

14,000 397 8-15-76 A9 

15,500 522 .8-15-76 A9 

14,600 585 8-15-76 A9 

13,900 772 8-15-76 A9 

13,400 832 8-15-76 A9 

13,200 957 8-15-76 A9 

13,500 1,019 8-15-76 A9 

13,400 1,081 8-15-76 A9 

14,100 1,144 8-15-76 A6 

18,000 1,237 8-15-76 A8 

5 Amcor 6021 17,600 1,001 9-16-76 A9 

18,000 1,013 9-16-76 A9 

18,400 1,028 9-16-76 A9 

18,100 1,072 9-16-76 A9 

18,000 1,196 9-16-76 A9 

18,000 1,258 9-16-76 A9 

18,200 1,414 9-16-76 A9 

18,000 1,502 9-16-76 A9 

18,000 1,634 9-16-76 A9 

18,000 1,728 9-16-76 A9 

18,200 1,821 9-16-76 A9 

6 u.s. Geological Survey 6 390 11-17-77 A7 

Island Beach Test Well 780 2,730 5-24-67 A2 

1.100 2,740 5-07-62 A2 

2,700 2,860 5-07-62 A2 

5,400 3,030 5-07-62 Al 

7,000 3,090 5-07-62 Al 

7,000 3,170 5-07-62 Al 

11,300 3,370 5-07-62 Al 

11,300 3,480 5-07-62 Al 

105 
Table 6. Concentrations of chloride at various depths in deep wells and boreholes in onshore and 

offshore areas, New Jersey Coastal Plain, 1888-1974--Continued 

Chloride Sample depth 

Well number concentration (feet below 

(fig. 1) Local well identifier (mg/L as Cl) sea level) Sample date Model unit 

7 Anchor Gas, Ragovin 11,000 1,980 10-22-74 A2 

12,000 2,490 10-15-74 Al 

18,000 3,010 10-08-74 Al 

22,000 3,180 iO-OI-74 . , 1\.1 

27,000 3,310 9-24-74 Al 

600 860 10-31-64 A6 

3,300 1,230 10-31-64 A3 

8,000 1,480 10-31-64 A3 

8,700 1,840 10-31-64 A2 

11,600 2,410 10-31-64 Al 

12,400 2,660 10-31-64 Al 

16,700 2,940 10-31-64 Al 

25,900 3,030 10-31-64 Al 

27,400 3,110 10-31-64 Al 

27,400 3,240 10-31-64 Al 

8 Wildwood Pines 2 90 350 4-21-66 A8 

Wildwood Pines 1 200 880 8-22-61 A8 

9 Anchor Gas, Dickinson 1 1,300 1,840 7-14-63 A6 

1,500 2,100 7-14-63 AS 

6,400 2,210 7-14-63 AS 

10,300 2,420 7-14-63 A4 

10,300 2,580 7-14-63 A3 

11,600 2,690 7-14-63 A3 

21,000 3,010 7-14-63 A2 

28,800 3,110 7-14-63 A2 

28,000 3,680 7-14-63 A2 

32,200 3,910 7-14-63 Al 

38,100 4,360 7-14-63 Al 

22,100 5,200 7-14-63 Al 

22,100 5,380 7-14-63 Al 

10 Atlantic City 330 1,020 00-00-1888 A7 

11 Warren Grove 210 1,515 11-00-82 A2 

300 1,785 11-00-82 A2 

106 
Table 7. Concentrations of chloride in selected samples from wells in the New Jersey Coastal 

Plain, 1971-90 

[mgIL, milligrams per liter; --, missing data] 

Geological New Jersey Chloride 

Survey well permit Sample concentration 

number number Latitude Longitude Well depth date (mglL) 

Lower Potornac-Raritan-Magothy aquifer (model unit AI) 

11-133 392512 745212 3,410 09/2411974 27,000 

15-139 30-01223 394608 752135 345 1111011986 820 

15-308 395044 751242 271 09126/1985 79 

15-312 51-00063 395107 750946 372 1211711986 42 

15-324 31-00036 395236 750821 224 11119/1982 21 

15-349 394650 752316 220 10/0111980 110 

15-398 30·02016 394935 751938 60 1111711986 140 

15-671 394957 750530 670 06/03/1986 10 

15-680 30-03602 395038 751605 196 09/2211986 73 

15-712 30-04347 394808 751724 295 03/19/1987 660 

33-137 50-00003 394112 753028 361 0811711988 76 

33-187 394037 751914 672 10/0711985 170 

33-346 30-00563 394256 752718 357 08/22/1989 220 

Middle Potornac-Raritan-Magothy aquifer (model unit A2) 

5-683 395122 743017 2,120 0112811988 3,5 

11-137 392514 745217 2,090 10/2211974 11,000 

15- 72 30-00037 394936 751747 101 1110811984 87 

15-140 30-01248 394608 752135 184 11/20/1985 33 

15-166 30-00410 394755 752108 88 06/16/1986 14 

15-374 31-13385 394843 750728 489 0711211985 15 

15-780 31-26244 395223 751117 90 08/2711987 34 

25-153 29-05942 402444 741010 690 09/19/1985 2.3 

25-320 402705 735959 878 0811111989 5,0 

29- 19 394829 740535 2,760 1211211984 850 

29-626 33-10224 395721 741230 1,870 08/18/1989 .9 

33-106 393514 752917 366 1011011980 460 

33-108 30-00052 393641 753322 319 08/15/1989 100 

33-127 30-00698 394100 753030 188 09/2511986 69 

33-251 393348 752755 709 11/2211982 1,900 

33-364 34-01031 392743 753158 840 08/23/1990 26 

33-459 30-03336 393928 752147 457 08/15/1989 16 

107 
Table 7. Concentrations of chloride in selected samples from wells in the New Jersey Coastal 

Plain, 1971-90--Continued 

U.S. 

Geological New Jersey Chloride 

Survey well permit Sample concentration 

number number Latitude Longitude Well depth date (mg/L) 

Upper Potomac-Raritan-Magothy aquifer (model unit A3) 

15- 03 31-06676 394015 750559 740 0811811987 110 

15- 60 31-02358 394206 750758 612 09/25/1984 69 

15-129 50-00049 394409 751330 263 09/26/1984 170 

15-194 31-05309 394732 751037 265 08/28/1989 34 

15-231 394147 751651 358 10/20/1980 22 

15-253 31-04741 394437 750249 652 07/2411985 22 

15-332 51-00100 395009 750922 188 10/29/1986 31 

15-353 394649 752316 17.50 04/18/1985 67 

15-519 30-01788 394649 751738 87 1111811986 15 

15-626 30-33900 394729 752101 19 12/0511986 14 

25- 13 29-07461 401137 740121 1,160 09/21/1983 2.1 

25- 34 401558 740908 836 05/0611985 2.5 

25-119 29-06480 402403 735923 779 0711511988 1.1 

25-294 49-00042 402428 741345 252 10/06/1986 2.0 

25-321 402706 735952 486 09/0i!1977 42 

25-419 29-03786 402632 741049 285 04/25/1986 1,300 

25-462 29-05558 402717 740816 260 08/0711985 45 

25-560 28-11985 401904 742102 306 06/2611985 2.0 

29-577 33-05553 395741 740437 1,500 08/09/1988 1.0 

33- 74 30-01151 394241 752201 206 10/03/1980 1.7 

33-117 30-00451 393954 753013 102 09/19/1985 19.0 

33-253 393348 752755 340 1112211982 670.0 

33-360 28-10466 393750 753131 125 07/2511986 7.2 

33-370 30-01800 394449 752554 52 0711711986 8.7 

Englishtown aquifer (model unit A4) 

25- OJ 29-00116 401401 740025 570 08/25/1989 1.3 

25- 09 49-00050 402441 740234 200 08/20/1980 5.6 

25- 30 29-00069 400645 740345 750 09/0111987 .8 

25-386 29-04721 400952 740149 670 09/0111987 .6 

25-563 28-07643 401703 742304 49 05/30/1985 6.6 

25-638 29-18401-1 401105 741202 499 10/06/1987 2.8 

29-138 400414 742702 427 05/19/1983 1.9 

29-454 53-00002 395808 740421 1,140 0811711989 1.9 

108 
Table 7. Concentrations of chloride in selected samples from wells in the New Jersey Coastal 

Plain, 1971-90--Continued 

Geological New Jersey Chloride 

Survey well permit Sample concentration 

number number Latitude Longitude Well depth date (mgIL) 

Wenonah-Mount Laurel aquifer (model unit A5) 

11- 66 392124 751904 310 0311711972 227 

25- 11 19-00018 401136 740120 501 09/0211987 2.1 

25-142 29-01935 402255 741010 121 08/02/1971 41 on 25-243 401854 741325 ov 08/02/1971 3.9 

33- 33 392751 752441 340 1110711984 42 

33- 35 34-00757 392744 753206 281 08/22/1989 390 

33-279 393622 751531 425 03/1311985 1.9 

33-426 393451 752718 127 09/2911981 17 

25-636 29-18404-5 401105 741202 100 1011511987 9.0 

29-139 28-04784 400414 742702 171 05/23/1983 1.9 

33-368 393253 752425 133 10/04/1974 6.5 

Piney Point aquifer (model unit A 7) 

1-701 35-03992 393148 745617 460 02/18/1986 27 

1-713 35-04656 392902 745051 535 1011011985 110 

5-407 394422 744309 260 0212011986 1.2 

5-676 394914 742546 540 09/2311985 4.8 

11-44 35-01197 392732 750929 376 06/26/1984 45 

11- 61 34-01191 391926 751921 354 08/28/1989 66 

11- 92 391746 751510 417 0910111988 82 

11- 96 391829 751208 375 09/2211986 4 

11-364 34-02333 391617 751355 420 09105/1986 174 

29- 04 33-00364 394524 740632 646 08/2211989 2.6 

29-541 53-00022 395451 740455 525 07/30/1985 2.5 

Lower Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8) 

1- 42 56-00010 392456 742121 788 08/16/1988 2.4 

1-710 391726 742221 1.020 09/13/1985 77 

1-711 391955 742507 871 08/14/1985 15 

5-451 394536 743542 170 0911111987 8.3 

9- 67 37-00271 390135 745352 592 09/0111989 75 

9-153 385932 744851 931 03/16/1972 114 

9-161 390704 744750 654 03/20/1985 40 

109 
Table 7. Concentrations of chloride in selected samples from wells in the New Jersey Coastal 

Plain, 1971-90--Continued 

U.S. 

Geological New Jersey Chloride 

Survey well permit Sample concentration 

number number Latitude Longitude Well depth date (mglL) 

Lower Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8)--Continued 

9-173 37-00579 390314 744532 862 08/2711987 20 

9-302 37-03628-9 385709 745128 903 09/06/1990 570 

11- 52 35-01299 391420 751023 303 08/3111988 5.5 

11- 63 34-00846 391959 752152 72 06/0811978 3,600 

11-100 34-00460 391840 751336 74 0811111987 42 

11-309 392247 751313 130 12/13/1988 2.6 

11-691 35-09802-3 391116 745705 160 09/04/1990 15 

15-730 393154 745811 98 07/30/1987 33 

15-785 31-20754 393917 750149 56 0911911988 9.9 

25- 29 49-00013 400644 740344 150 09/0111987 2.5 

25-512 29-10880 400802 740230 124 09/0111987 9.8 

29-508 33-00896 395528 740826 i53 08/30/1984 6.3 

29-544 33-00219 393839 741052 578 08/13/1987 2.9 

29-807 29-12178 400536 740251 132 0811711989 410 

29-815 33-18281 395643 740443 i54 08/08/1989 150 

110 
APPENDIXES 

III 
FALL LINE 

MIDDLESEX 

1 0, 000 --::;::::. 

~B'O~_-- 1'00 

~OQ 

V~ 

~~~ '~--------6,000------------

EXPLANATION 

--4,000 -- LINE OF EQUAL TRANSMISSIVITY--

Interval is 2,000 square feet per day 

SIMULATED UPDIP LIMIT OF AQUIFER 

Base from U,S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ 

/ 

o 10 MILES f-I -r-'-r--'-r-I _I 

o 10 KILOMETERS 

1 a. Transmissivity of the Lower Potomac-Raritan-Magothy aquifer (model unit A 1) 

used in the ground-water flow model of the New Jersey Coastal Plain. 

112 
EXPLANATION 

--5 X 10-6 -- LINE OF EQUAL LEAKANCE--Interval, 

in feet per day per foot, is variable 

SIMULATED UPDIP LIMIT OF 

CONFINING UNIT 

Base from U,S, Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

( FALL LINE 

\,,~~~~ l' /'::.:::-1"';'::':' 

MIDDLESEX )/?NEWYORK 

" .' .... ~- ... -.,'::-...... " 

'-------.- '--'/--\''-'" RARITAN /\..~ "'\ BAY 

/ 

/ 

o 10 MILES 

I I I 

/ 

o 10 KILOMETERS 

1 b. Vertical leakance of the confining unit between the Lower and Middle 

Potomac-Raritan-Magothy aquifers (model unit C1) used in the ground-water 

flow model of the New Jersey Coastal Plain. 

113 
" /.\ .. ./ 'vI RARITAN ~~ 

v'\ BAY 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE LOWER 

POTOMAC-RARITAN-MAGOTHY AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OFTHE AQUIFER 

MONMOUTH 

o 

! 

o 

/ / 

10 MILES !! I 

10 KILOMETERS 

_ -20 _ SIMULATED POTENTIOMETRIC CONTOUR--Shows altitude of simulated predevelopment 

potentiometric surface. Contour interval 10 feet. Datum is sea level 

------ TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

••••••••• _- TOE OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

'\tOo 

1 c. Simulated predevelopment potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow, Lower Potomac-RaritanMagothy aquifer (model unit A 1), New Jersey Coastal Plain, 

114 
DELAWARE 

BAY 

/ / 

o 10 MILES I I ! i I 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

'700 

./ 

EXPLANATION 

- UPDIP LIMIT OF AQUIFER 

LOCATION OF GROUND-WATER WITHDRAWAL--

Greater than 0.5 million gallons per day 

o Less than 0.5 million gallons per day 

1 d. Locations of ground-water withdrawal sites in the Lower Potomac-Raritan-Magothy 

aquifer (model unit A 1), New Jersey Coastal Plain, 1983-88. 

115 
J 

J 

i 

DELAWARE '''' \,;:' 

BAY 'r" 

o 

I I 

o 

I 

I CAPE MAY 

/ / 

10 MILES t I I 

10 KILOMETERS 

Base from U.S, Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

eVDI 1\ II.II\TIr'lII.1 L.A! 1-1"\1'111"\1 IVI'! 

- UPDIP LIMIT OF AQUIFER 

o 7-412 

11-133 

• 

33-187 Ii 

OBSERVATION WELL AND WELL NUMBER--

Difference between simulated and average measured 

water levels (1983-88) is shown in figure 17. Simulated 

and average measured water levels are shown in table 4 

SAMPLED WELL AND WELL NUMBER--Chloride 

concentrations shown in table 7 and appendix 1 (fig. 1 f) 

SAMPLED OBSERVATION WELL AND WELL 

NUMBER--Difference between simulated and 

average measured water levels (1983-88) shown in 

table 4 and figure 17. Chloride concentrations shown 

in table 7 and appendix 1 (fig. 1 f) 

<100 

1 e. Locations of observation wells for which water-level residuals are available and 

selected wells for which measured chloride concentrations are available, Lower 

Potomac-Raritan-Magothy aquifer (model unit A 1), New Jersey Coastai Plain. 

116 
" FALL LINE \~~~~) ~ %:::::j<:-'::'::' 

MIDDLESEX j.riNEWYORK 

\ ~ ........ --.-.--... ~.-

._. __ .. _jr\\ ..... , RARI;'~ ... ",>!J. 

''-'\ BAY 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE LOWER 

POTOMAC-RARITAN-MAGOTHY AQUIFER 

------ TIP OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

.. 79 SAMPLED WELL--Number is chloride concentration, rounded to nearest integer, 

in milligrams per liter. Concentrations and sample dates shown in table 7 

22,100 SAMPLED WELL--Top number is minimum chloride concentration; bottom 

038,100 number is maximum chloride concentration; all values in milligrams per liter 

(Meisler, 1989). Samples collected at various depths. Concentrations and 

sample dates are shown in table 6 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ / 

/ 

o 10 MILES Iii i I 

o 10 KILOMETERS 

'il'Oo 

1 f. Measured chloride concentrations and location of simulated freshwater-saltwater 

interface tip and toe, Lower Potomac-Raritan-Magothy aquifer (model unit A 1), 

New Jersey Coastal Plain, 1983-88. 

117 
EXPLANATION 

--4,000 -- LINE OF EQUAL TRANSMISSIVITY--

Interval is 2,000 square feet per day 

SIMULATED UPDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

( FALL LINE 

/ / 

10 MILES !! ! 

() 

4,000 

o 

I 

o 10 KILOMETERS 

2a. Transmissivity of the Middle Potomac-Raritan-Magothy aquifer (model unit A2) 

used in the ground-water flow model of the New Jersey Coastal Plain. 

118 
EXPLANATION 

--5 X 10-6 -- LINE OF EQUAL LEAKANCE--Interval, 

in feet per day per foot, is variable 

SIMULATED UPDIP LIMIT OF 

CONFINING UNIT 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ 

/' 

o 10 MILES I t 1 ! 

o 10 KILOMETERS 

2b. Vertical leakance of the confining unit between the Middle and Upper 

Potomac-Raritan-Magothy aquifers (model unit C2) used in the ground-water 

flow model of the New Jersey Coastal Plain. 

119 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE MIDDLE 

POTOMAC-RARITAN-MAGOTHY AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

o 10 MILES 

[f---r--'-,-L-'-i --.-J! 

o 10 KILOMETERS 

_ 20 _ SIMULATED POTENTIOMETRIC CONTOUR--Shows altitude of simulated predevelopment 

potentiometric surface. Contour interval 10 feet. Datum is sea level 

TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

2c. Simulated predevelopment potentiometric surtace, location of the simulated freshwatersaltwater interlace tip and toe, and area of upward flow, Middle Potomac-RaritanMagothy aquifer (model unit A2), New Jersey Coastal Plain. 

120 
Base from U.S. 

o 

Ii 

o 

/ 

/ 

10 MILES ! 

I 

10 KILOMETERS 

i 

) 

Survey digital data, 1 :2,000,000, 1972, 

projection, Zone 18 

· ~ CAMDEN,:' 

BURLINGTON 

NEW JERSEY 

EXPLANATION 

OUTCROP AREA OF THE MIDDLE POTOMACRARITAN-MAGOTHY AQUIFER 

- UPDIP LIMIT OF AQUIFER 

LOCATION OF GROUND-WATER WITHDRAWAL--

Greater than 0.5 million gallons per day 

Less than 0.5 million gallons per day 

"00 

2d. Locations of ground-water withdrawal sites in the Middle Potomac-Raritan-Magothy 

aquifer (model unit A2), New Jersey Coastal Plain, 1983-88. 

121 
33-45~\ 15-374. 

SALEM 

/ / 

,'GLOUCESTER 

\_.- _. 

o 10 MILES I tit 

o 10 KILOMETERS 

.I 

CAMDEN 

o 7-413 ( 

\07-476 

! 

j 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

05-440 o 5-261 

BURLINGTON 

-

·33-364 

5-683 ;' 

" / / OCEAN 

EXPLANATION 

OUTCROP AREA OF THE MIDDLE POTOMACRARITAN-MAGOTHY AQUIFER 

UPDIP LIMIT OF AQUIFER 

/ 

OBSERVATION WELL AND WELL NUMBER--

Difference between simulated and average measured 

water levels (1983-88) is shown in figure 19. Simulated 

and average measured water levels are shown in table 4 

SAMPLED WELL AND WELL NUMBER--Chloride 

concentrations shown in table 7 and appendix 2 (fig. 2f) 

SAMPLED OBSERVATION WELL AND WELL 

"29-19 NUMBER--Difference between simulated and 

average measured water levels (1983-88) shown in 

table 4 and figure 19. Chloride concentrations shown 

in table 7 and appendix 2 (fig. 2f) 

'S1'Oo 

2e. Locations of observation wells for which water-level residuals are available and 

selected wells for which measured chloride concentrations are available, Middle 

Potomac-Raritan-Magothy aquifer (model unit A2), New Jersey Coastal Plain. 

122 
BURLINGTON 

NEW JERSEY 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE MIDDLE 

POTOMAC-RARITAN-MAGOTHY AQUIFER 

AREA WHERE UNDERLYING AQUIFER CONTAINS 

HIGH CHLORIDE CONCENTRATIONS 

/ 

AREA WHERE WATER FLOWS INTO AQUIFER FROM UNDERLYING 

AQUIFER WITH HIGH CHLORIDE CONCENTRATIONS 

\ 

• AREA WHERE FLOW IS INTO AQUIFER FROM OVERLYING AQUIFER 

WITH HIGH CHLORIDE CONCENTRATIONS 

------ TIP OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

\, 

o 

I 

o 

.4 SAMPLED WELL-- Number is chloride concentration, rounded to nearest integer, 

in milligrams per liter. Concentrations and sample dates shown in table 7 

21,000 SAMPLED WELL--Top number is minimum chloride concentration; bottom number is 

028,800 maximum chloride concentration; all values in milligrams per liter (Meisler, 1989). 

Samples collected at various depths. Concentrations and sample dates are shown in 

table 6 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

10 MILES ! i I 

10 KILOMETERS 

<100 

2f. Measured chloride concentrations, location of simulated freshwater-saltwater 

interface tip and toe, and areas of saltwater flow from overlying and underlying aquifers, 

Middle Potomac-Raritan-Magothy aquifer (model unit A2), New Jersey Coastal Plain, 

1983-88. 

123 
EXPLANATION 

--4,000 -- LINE OF EQUAL TRANSMISSIVITY--

Interval, in square feet per day, is variable 

SIMULATED UPDIP LIMIT OF AQUIFER 

/ 

/ 

o 10 MILES I I i I 

o ,10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

3a. Transmissivity of the Upper Potomac-Raritan-Magothy aquifer (model unit A3) 

used in the ground-water flow model of the New Jersey Coastal Plain. 

124 
/ 

EXPLANATION 

--5 x 10-6 -- LINE OF EQUAL LEAKANCE--Interval, 

in feet per day per foot, is variable 

SIMULATED UPDIP LIMIT OF 

CONFINING UNIT 

Base tram U,S, Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ 

/ 

~\G ~ ~'v'r ~ 

~~~ 0° 

o 

I 

o 

/ / 

10 MILES 

I I 

10 KILOMETERS 

</00 

3b. Vertical leakance of the Merchantville-Woodbury confining unit (model unit C3) 

used in the ground-water flow model of the New Jersey Coastal Plain. 

125 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE UPPER 

POTOMAC-RARITAN-MAGOTHY AQU I FER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

o 

I 

o 

/ / 

10 MILES I 

I 

10 KILOMETERS 

_ 20 _ SIMULATED POTENTIOMETRIC CONTOUR--Shows altitude of simulated predevelopment 

potentiometric surface. Contour interval 10 feet. Datum is sea level 

------ TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Se. Simulated predevelopment potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow, Upper Potomac-RaritanMagothy aquifer (model unit A3), New Jersey Coastal Plain. 

126 
o 

I 'I 

o 

/ / 

10 MILES I I 

10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

EXPLANATION 

OUTCROP AREA OF THE UPPER POTOMACRARITAN-MAGOTHY AQUIFER 

- UPDIP LIMIT OF AQUIFER 

LOCATION OF GROUND-WATER WITHDRAWAL--

Greater than 0.5 million gallons per day 

Less than 0.5 million gallons per day 

'il'Oo 

3d. Locations of ground-water withdrawal sites in the Upper Potomac-Raritan-Magothy 

aquifer (model unit A3), New Jersey Coastal Plain, 1983-88. 

127 
'I • 0 

33-7l\ 15-519 15-297815_?32 

<15-231 &15-194) 

#33-253 ,,~ &15-129 ( 7-1 

SALEM i~LOUCESTER .') CAMDEN 

/ / 

\ 15-60& 15-25~\ , .. I 15-3 

\ 

i 

o 10 MILES 

I I I 

o 10 KILOMETER.S 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

BURLINGTON 

NEW JERSEY 

-

EXPLANATION 

OUTCROP AREA OF THE UPPER POTOMACRARITAN-MAGOTHY AQUIFER 

UPDIP LIMIT OF AQUIFER 

OBSERVATION WELL AND WELL NUMBER--

Difference between simulated and average measured 

water levels (1983-88) is shown in figure 21. Simulated 

and average measured water levels are shown in table 4 

SAMPLED WELL AND WELL NUMBER--Chloride 

concentrations shown in table 7 and appendix 3 (fig. 3f) 

SAMPLED OBSERVATION WELL AND WELL 

"33-253 NUMBER--Difference between simulated and 

average measured water levels (1983-88) shown in 

table 4 and figure 21. Chloride concentrations shown 

in table 7 and appendix 3 (fig. 3f) 

~Oo 

3e. Locations of observation wells for which water-level residuals are available and 

selected wells for which measured chloride concentrations are available, Upper 

Potomac-Raritan-Magothy aquifer (model unit A3), New Jersey Coastal Plain. 

128 
i • 

Ii 110 

\ 

BURLINGTON 

/ 

NEW JERSEY 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE UPPER 

POTOMAC-RARITAN-MAGOTHY AQUIFER 

AREA WHERE UNDERLYING AQUIFER CONTAINS 

HIGH CHLORIDE CONCENTRATIONS 

OCEAN 

AREA WHERE WATER FLOWS INTO AQUIFER FROM UNDERLYING 

AQUIFER WITH HIGH CHLORIDE CONCENTRATIONS 

• AREA WHERE WATER FLOWS INTO AQUIFER FROM OVERLYING 

AQUIFER WITH HIGH CHLORIDE CONCENTRATIONS 

------ TIP OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE PREDICTED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

o 10 MILES I, ! I I 

o 10 KILOMETERS 

.2 SAMPLED WELL--Number is chloride concentration, rounded to nearest integer, in milligrams per liter. 

Concentrations and sample dates shown in table 7 

10,300 SAMPLED WELL--Top number is minimum chloride concentration; bottom number is maximum chloride 

011,600 concentration; all values in milligrams per liter (Meisler, 1989). Samples collected at various depths. 

Concentration and sample dates are shown in table 6 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone j 8 

'100 

31. Measured chloride concentrations, location of simulated freshwater-saltwater 

interface tip and toe, and areas of saltwater flow from overlying and underlying aquifers, 

Upper Potomac-Raritan-Magothy aquifer (model unit A3), New Jersey Coastal Plain, 

1983-88. 

129 
i.··'-// 

1,QOg:;) r / 

~ o 

\1 

EXPLANATION 

--500 -- LINE OF EQUAL TRANSMISSIVITY--

Interval is 500 square feet per day 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

o 

Ii 

o 

/ 

/ 

10 MILES I 

i 

10 KILOMETERS 

I 

4a. Transmissivity of the Englishtown aquifer (model unit A4) used in the ground-water 

flow model of the New Jersey Coastal Plain. 

130 
EXPLANATION 

--5 x 10-6 -- LINE OF EQUAL LEAKANCE--Interval, 

in feet per day per foot, is variable 

SIMULATED UPDIP LIMIT OF 

CONFINING UNIT 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

----1 X 10-6 

/ 

/ 

o 10 MILES 

I I I 

o 10 KILOMETERS 

4b. Vertical leakance of the Marshalltown-Wenonah confining unit (model unit C4) used 

in the ground-water flow model of the New Jersey Coastal Plain. 

131 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

ENGLISHTOWN AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

/ 

/ 

o 10 MILES 1---1 r, ~~I ----11 

o 10 KILOMETERS 

_ 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows altitude of simulated predevelopment 

potentiometric surface. Contour interval 20 feet. Datum is sea level 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

4c. Simulated predevelopment potentiometric surface and area of upward flow, 

Englishtown aquifer (model unit A4), New Jersey Coastal Plain. 

132 
\ J 

/ / 

o 10 MILES 1--1 r-'-r---'--r-I ----,I 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

-

/ FALL LINE 

EXPLANATION 

OUTCROP AREA OF THE ENGLISHTOWN 

AQUIFER 

UPDIP LIMIT OF AQUIFER 

DOWNDIP LIMIT OF AQUIFER 

LOCATION OF GROUND-WATER WITHDRAWAL--

Greater than 0.5 million gallons per day 

Less than 0.5 million gallons per day 

4d. Locations of ground-water withdrawal sites in the Englishtown aquifer 

(model unit A4), New Jersey Coastal Plain, 1983-88. 

133 
1 (\ 

! i ........... "-L.L~ ) \ 

I 

) wiG; I 

cr;'C/) t_. 

~icr: Ii 

5/yt 

UJ/:S: 

C'UJ !Z 

\. GLOUCESTER 

SALEM 

/ 

/ 

o 10 MILES I I I I I 

o 10 KILOMETERS 

( 

\CAMDEN 

I 

) 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

~ 

-

0 

5-259 

·25-454 

29·138 

Ii 

( FALL LINE 

29-138 

Ii 

! ,-I 

~I 

OCEAN i:[:,' 

1/),1 J) 

Of 

29-534 ' 

EXPLANATION 

OUTCROP AREA OF THE ENGLISHTOWN 

AQUIFER 

UPDIP LIMIT OF AQUIFER 

DOWNDIP LIMIT OF AQUIFER 

OBSERVATION WELL AND WELL NUMBER--

Difference between simulated and average measured 

water levels (1983-88) is shown in figure 23. Simulated 

and average measured water levels are shown in table 4 

SAMPLED WELL AND WELL NUMBER--Chloride 

concentrations shown in table 7 and appendix 4 (fig. 4f) 

SAMPLED OBSERVATION WELL AND WELL 

NUMBER--Difference between simulated and 

average measured water levels (1983-88) shown in 

table 4 and figure 23. Chloride concentrations shown 

in table 7 and appendix 4 (fig. 4f) 

"'00 

,\0 

4e. Locations of observation wells for which water-level residuals are available and 

selected wells for which measured chloride concentrations are available, Englishtown 

aquifer (model unit A4), New Jersey Coastal Plain. 

134 
BURLINGTON 

NEW JERSEY 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

ENGLISHTOWN AQUIFER 

AREA WHERE WATER FLOWS INTO AQUIFER FROM UNDERLYING 

AQUIFER WITH HIGH CHLORIDE CONCENTRATIONS 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

,i SAMPLED WELLe-Number is chloride concentration, 

rounded to nearest integer, in milligrams per liter. 

Concentrations and sample dates shown in table 7 

/ / 

o 10 MILES ~I ,..-L, .,.--.L~I ----ll 

o 10 KILOMETERS 

10,300 SAMPLED WELLe-Number is chloride concentration, in milligrams per liter 

o (Meisler, 1989). Concentrations and sample dates are shown in table 6 

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

4f. Measured chloride concentrations and areas of saltwater flow from underlying aquifers, 

Englishtown aquifer (model unit A4), New Jersey Coastal Plain, 1983-88. 

135 
EXPLANATION 

--500 -- LINE OF EQUAL TRANSMISSIVITY--

Interval is 500 square feet per day 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ / 

o 10 MILES f.-I ,.--', ,--l-~I -----,I 

o 10 KILOMETERS 

5a. Transmissivity of the Wenonah-Mount Laurel aquifer (model unit AS) used in the 

ground-water flow model of the New Jersey Coastal Plain. 

136 
EXPLANATION 

--5 X 10-6 -- LINE OF EQUAL LEAKANCE--Interval, 

in feet per day per foot, is variable 

SIMULATED UPDIP LIMIT OF 

CONFINING UNIT 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ / 

o 10 MILES 

IiI ! 

o 10 KILOMETERS 

5b. Vertical leakance of the Navesink-Hornerstown confining unit (model unit C5) used 

in the ground-water flow model of the New Jersey Coastal Plain. 

137 
EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE WENONAHMOUNT LAUREL AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

o 

I, ') 

o 

10 MILES ) ) 

10 KILOMETERS 

_ 20- SIMULATED POTENTIOMETRIC CONTOUR--Shows altitude of simulated predevelopment 

potentiometric surface. Contour interval 20 feet. Datum is sea level 

TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U,S, Geological Survey digital data. 1 :2.000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Se. Simulated predevelopment potentiometric surface, location of the simulated freshwatersaltwater interface tip and toe, and area of upward flow, Wenonah-Mount Laurel aquifer 

(model unit A5), New Jersey Coastal Plain. 

138 
SALEM 

DELAWARE 

BAY 

/ 

/ 

o 10 MILES 1-1 r-'-,.-....!..-,-I_I 

o 10 KILOMETERS 

J 

"~\ 

t 0 / o I 0 I 

\ 0 0 0 a / 

o gl, 

! CAMDEN 

j 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

o 

o 

( FALL LINE 

BURLINGTON 

JERSEY! 

/ 

OCEAN 

/ 

EXPLANATION 

OUTCROP AREA OF THE WENONAH-MOUNT 

LAUREL AQUIFER 

- UPDIP LIMIT OF AQUIFER 

DOWNDIP LIMIT OF AQUIFER 

LOCATION OF GROUND-WATER WITHDRAWAL--

Greater than 0.5 million gallons per day 

Less than 0.5 million gallons per day 

<700 

5d. Locations of ground-water withdrawal sites in the Wenonah-Mount Laurel aquifer 

(model unit AS), New Jersey Coastal Plain, 1983-88. 

139 
/ / 

o 10 MILES I, ! f I 

o 10 KILOMETERS 

\CAMDEN/ 

\ \ 

" F7-478 

,/ 

Base from U,S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

29-140 

o BURLINGTON 

OCEAN 

/ 

/ 

EXPLANATION 

OUTCROP AREA OF THE WENONAH-MOUNT 

LAUREL AQUIFER 

-- UPDIP LIMIT OF AQUIFER 

o 

7-478 

DOWNDIP LIMIT OF AQUIFER 

OBSERVATION WELL AND WELL NUMBER--

Difference between simulated and average measured 

water levels (1983-88) is shown in figure 25, Simulated 

and average measured water levels are shown in table 4 

SAMPLED WELL AND WELL NUMBER--

-33-279 Chloride concentrations shown in table 7 and 

appendix 5 (fig. 5f) 

"'00 

Se. Locations of observation wells for which water-level residuals are available and 

selected wells for which measured chloride concentrations are available, WenonahMount Laurel aquifer (model unit AS), New Jersey Coastal Plain. 

140 
')7'00 

\ 390 SALEM .2 / I' .42 I / \ ... __ /, ... _,. ""_"'_"", 

! 

DELAWARE 

BAY 

/ 

/ 

BURLINGTON 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE WENONAHMOUNT LAUREL AQUIFER 

AREA WHERE UNDERLYING AQUIFER CONTAINS 

HIGH CHLORIDE CONCENTRATIONS 

AREA WHERE WATER FLOWS INTO AQUIFER FROM 

UNDERLYING AQUIFER WITH HIGH CHLORIDE CONCENTRATION 

II AREA WHERE WATER FLOWS INTO AQUIFER FROM 

OVERLYING AQUIFER WITH HIGH CHLORIDE CONCENTRATION 

• • 

... 

10 MILES I I I o 

I 

o 10 KILOMETERS 

.2 SAMPLED WELL--Number is chloride 

concentration, rounded to nearest 

integer, in milligrams per liter. 

Concentrations and sample 

dates shown in table 7 

TIP OF THE PREDICTED FRESHWATER-SALTWATER 

INTERFACE 

1,500 

06,400 

SAMPLED WELL--Top number is 

minimum chloride concentration; 

bottom number is maximum chloride 

concentration; all values in milligrams 

per liter (Meisler, 1989). Samples 

collected at various depths. 

Concentrations and sample dates are 

shown in table 6 

TOE OF THE PREDICTED FRESHWATER-SALTWATER 

INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

5f. Measured chloride concentrations, location of simulated freshwater-saltwater 

interface tip and toe, and areas of flow from overlying and underlying aquifers, 

Wenonah-Mount Laurel aquifer (model unit A5), New Jersey Coastal Plain, 1983-88. 

141 
: FALL LINE 

MIDDLESEX ) \ 

' .. '_ .. _~'_' ._. __ '- ._.J.'i\,-.\~A:~~AN ~.;. 

/ 

/ 

'-~\-'I"-..........;il' --1,000---

i 

j CAMDEN 

JERSEY/ 

EXPLANATION 

--2,000 -- LINE OF EQUAL TRANSMISSIVITY--

Interval is 1,000 square feet per day 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Sase from U,S. Geological Survey digital data, 1:2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

MONMOUTH 

/ / 

o 10 MILES If-r'-i ,-'--'1 ---,I 

o 10 KILOMETERS 

Jl 

)/ 

$'00 

6a. Transmissivity of the Vincentown aquifer (model unit A6) used in the ground-water 

flow model of the New Jersey Coastal Plain. 

142 
"--'~r--\-;----r---f---_--"".~ ~,.o?-~~.eL· 

\~tj/ NEW JERSEy 

EXPLANATION 

II 

1/ 

--5 X 10-6 -- LINE OF EQUAL LEAKANCE--Interval, 

in feet per day per foot, is variable 

SIMULATED UPDIP LIMIT OF 

CONFINING UNIT 

Base from U.S. Geological Survey digital data. 1:2,000.000, 1972. 

Universal Transverse Mercator projection. Zone 18 

FALL LINE 

MIDDLESEX 

/ / 

o 10 MILES I, j ! 

o 10 KILOMETERS 

6b. Verticalleakance of the Vincentown-Manasquan confining unit (model unit C6) used 

in the ground-water flow model of the New Jersey Coastal Plain. 

143 
CUMBERLAND JERSEY/ 

/ 

/ 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

VINCENTOWN AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

OCEAN 

o 

I 

o 

/ / 

10 MILES I I 

10 KILOMETERS 

- -20 -- SIMULATED POTENTIOMETRIC CONTOUR--Shows altitude of simulated predevelopment 

potentimetric surface. Contour interval 10 feet. Datum is sea level 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

<;700 

6e. Simulated predevelopment potentiometric surface and area of upward flow, 

Vincentown aquifer (model unit A6), New Jersey Coastal Plain. 

144 
': FALL LINE 

'ilOo 

EXPLANATION 

OUTCROP AREA OF THE VINCENTOWN AQUIFER 

-- UPDIP LIMIT OF AQUIFER 

DOWNDIP LIMIT OF AQUIFER 

LOCATION OF GROUND-WATER WITHDRAWAL-- "rb 

/ / 

o 10 MILES 1-1 r-'-, .,--L~I _I 

o 10 KILOMETERS 

Base from U,S, Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

Greater than 0.5 million gallons per day 

Less than 0.5 million gallons per day 

6d. Locations of ground-water withdrawal sites in the Vincentown aquifer (model unit 

A6), New Jersey Coastal Plain, 1983-88. 

145 
/ 

/ 

o 10 MILES I i I I 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

EXPLANATION 

~ OUTCROP AREA OF THE VINCENTOWN AQUIFER 

- UPDIP LIMIT OF AQUIFER 

DOWNDIP LIMIT OF AQUIFER 

-25-636 SAMPLED WELL AND WELL NUMBER--Chloride 

concentrations shown in table 7 and appendix 6 

(fig.6f) 

29-139 

" 

SAMPLED OBSERVATION WELL AND WELL NUMBER--

Difference between simulated and average measured 

water levels (1983-88) shown in table 4 and figure 27. 

Chloride concentrations shown in table 7 and appendix 6 

(fig.6f) 

6e. Locations of observation wells for which water-level residuals are available and 

selected wells for which measured chloride concentrations are available, Vincentown 

aquifer (model unit A6), New Jersey Coastal Plain. 

146 
MIDDLESEX 

) \ 

" __ .",._,-,-.-'-'-"/'\\_'\~A:'~~ "". ~~ 

JERSEY/ 

/ 

/ 

/ 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

VINCENTOWN AQUIFER 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

.2 SAMPLED WELL--Number is chloride concentration, 

rounded to nearest integer, in milligrams per liter. 

Concentrations and sample dates shown in table 7 

°14,100 

SAMPLED WELL--Number is chloride concentration, in milligrams 

0

1,300 per liter (Meisler, 1989). Concentrations and sample dates are 

shown in table 6 

Base from U,S, Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ / 

o 10 MILES 

Ii') )) ! 

o 10 KILOMETERS 

(, 

II 

)/ 

'I 

'1100 

6f. Measured chloride concentrations, Vincentown aquifer (model unit A6), New Jersey 

Coastal Plain, 1983-88. 

147 
EXPLANATION 

--2,000 -- LINE OF EQUAL TRANSMISSIVITY--

Interval, in square feet per day, is variable 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

••••••• SIMULATED LATERAL LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ / 

o 10 MILES f-I r-'-T--'--,-i-I 

o 10 KILOMETERS 

'100 

7a. Transmissivity of the Piney Point aquifer (model unit A7) used in the ground-water 

flow model of the New Jersey Coastal Plain. 

148 
/ 

/ 

o 10 MILES I, ! I I 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

MIDDLESEX 

EXPLANATION 

--5 X 10-6 -- LINE OF EQUAL LEAKANCE--

Interval, in feet per day per foot, 

is variable 

SIMULATED UPDIP LIMIT OF 

CONFINING UNiT 

7b. Vertical leakance of the basal Kirkwood confining unit (model unit C7) used in the 

ground-water flow model of the New Jersey Coastal Plain. 

149 
BURLINGTON 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE 

PINEY POINT AQUIFER 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

o 

I 

o 

/ / 

10 MILES ! I ! 

10 KILOMETERS 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows altitude of simulated predevelopment 

potentiometric surface. Contour interval 10 feet. Datum is sea level 

TIP OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

TOE OF THE SIMULATED FRESHWATER-SALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

• • • • • • • SIMULATED LATERAL LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

7e. Simulated predevelopment potentiometric suriace, location of the simulated freshwatersaltwater interiace tip and toe, and area of upward flow, Piney Point aquifer (model unit A7), 

New Jersey Coastal Plain. 

150 
'; FALL LINE 

MERCER MIDDLESEX 'i .-•••.••• 

SALEM 

···/'\'-"i RARITAN A.,e. 

,."\ BAY 

I 

) 2#/~ CUMBERLAND 

~.cr: 

«!!:!:j 

iIJis 

Q'lJ.) !~ 

DELAWARE 

BAY 

o 

I, 

o 

/ 

/ 

10 MILES I I 

10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

BURLINGTON 

NEW JERSEY 

EXPLANATION 

LlMIT OF AQUIFER 

o LOCATION OF GROUND-WATER WITHDRAWAL--

Withdrawalless than 0.5 million gallons per day 

9'00 

7d. Locations of ground-water withdrawal sites in the Piney Point aquifer (model unit A7), 

New Jersey Coastal Plain, 1983-88. 

151 
FALL LINE 

MIDDLESEX 

BURLINGTON 

RARITAN I~';" 

BAY 1 ((.t"' \. 

~ o\'B/].s-2UMBERLAND \ 

f\AL_)~ ~~ 11-4~ i\ 

\11 11 -61 ~ -

L. 1-92 

" 11-96 1-364 

/ / 

o 10 MILES I j I I t 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

EXPLANATION 

LIMIT OF AQUIFER 

011-163 OBSERVATION WELL AND WELL NUMBER--

Difference between simulated and average measured 

water levels (1983-88) is shown in figure 29. Simulated 

and average measured water levels are shown in table 4 

8

11 -

364 SAMPLED WELL AND WELL NUMBER--Chloride 

concentrations shown in table 7 and appendix 7 (fig. 7f) 

11-44 SAMPLED OBSERVATION WELL AND WELL NUMBER--

" Difference between simulated and average measured water 

levels (1983-88) shown in table 4 and figure 29. Chloride 

concentrations shown in table 7 and appendix 7 (fig. 7f) 

'1100 

7e. Locations of observation wells for which water-level residuals are available and 

selected wells for which measured chloride concentrations are available, Piney Point 

aquifer (model unit A7), New Jersey Coastal Plain. 

152 
BURLINGTON 

.' 

......... /:::::.::.:.~r-----

-,; / 

EXPLANATION 

AREA WHERE WATER FLOWS INTO AQUIFER FROM 

UNDERLYING AQUIFER WITH HIGH CHLORIDE 

CONCENTRATIONS 

AREA OF UPWARD FLOW THROUGH THE TOP 

OFTHE AQUIFER 

AREA WHERE WATER FLOWS INTO AQUIFER FROM 

OVERLYING AQUIFER WITH HIGH CHLORIDE 

CONCENTRATIONS 

TIP OF THE PREDICTED FRESHWATER· 

SALTWATER INTERFACE 

TOE OF THE PREDICTED FRESHWATERSALTWATER INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

SIMULATED DOWNDIP LIMIT OF AQUIFER 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ 

/ 

o 10 MILES 

I 1'1 II 1 

o 10 KILOMETERS 

SIMULATED LATERAL LIMIT OF AQUIFER 

-3 SAMPLED WELL··Number is chloride 

concentration, rounded to nearest integer, 

in milligrams per liter. Concentrations and 

sample dates shown in table 7 

1,350 

08,100 

SAMPLED WELL--Top number is minimum 

chloride concentration; bottom number is 

maximum chloride concentration; all values 

in milligrams per liter (Meisler, 1989). Samples 

collected at various depths. Concentrations 

and sample dates are shown in table 6 

<100 

71. Measured chloride concentrations, location of simulated freshwater-saltwater 

interface tip and toe, and areas of saltwater flow from overlying and underlying aquifers, 

Piney Point aquifer (model unit A7), New Jersey Coastal Plain, 1983-88. 

153 
i \ NEW JERSEY 

j CAMDEN ! 

, p,iv_~L, ) 

- - -! -- '-'-"-'-"\<t:;rf;'$}r-

\ 

I 

I 

QjJ 

if/ ATLANTIC ;.{ 

\ ! 

4,000 ------

2,000-__ _ 

'2.,000-

__ --------------------J 

EXPLANATION 

--2,000-- LINE OF EQUAL TRANSMISSIVITY--

Interval is 2,000 square feet per day 

SIMULATED UPDIP LIMIT OF OVERLYING 

CONFINING UNIT 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

o 

I 

o 

10 MILES 

I I 

10 KILOMETERS 

8a. Transmissivity of the lower Kirkwood-Cohansey and confined Kirkwood aquifers 

(model unit AS) used in the ground-water flow model of the New Jersey Coastal Plain. 

154 
700 1) "\ 

) \ SALEM 

CAMDEN 

NEW JERSEY 

i 

) 

/ 

EXPLANATION 

--5 X 10-7 -- LINE OF EQUAL LEAKANCE--Interval, 

in feet per day per foot, is variable 

SIMULATED UPDIP LIMIT OF 

CONFINING UNIT 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

/ 

OCEAN 

( FALL LINE 

MIDDLESEX 

MONMOUTH 

~\G ""~ ~\_:r' 

~ 

/ 

/ 

~~~ 0° 

o 10 MILES 

I I 

o \ I \ 10 KILOMETERS 

'\tJ. 

"'00 

ab. Verticalleakance of the confining unit overlying the Rio Grande water-bearing zone 

(model unit C8) used in the ground-water flow model of the New Jersey Coastal Plain. 

155 
! 

CUMBERLAND ! 

EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF 

THE LOWER KIRKWOOD-COHANSEY 

AND CONFINED KIRKWOOD AQUIFERS 

AREA OF UPWARD FLOW THROUGH 

THE TOP OFTHE AQUIFER 

/ / 

o 10 MILES Ii! i i 

o 10 KILOMETERS 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

- 20 - SIMULATED POTENTIOMETRIC CONTOUR--Shows 

altitude of simulated predevelopment potentiometric 

surface. Contour interval 10 feet. Datum is sea level 

------ TIP OF THE SIMULATED FRESHWATERSALTWATER INTERFACE 

.••.••.•••. TOE OF THE SIMULATED FRESHWATERSALTWATER INTERFACE 

--- SIMULATED UPDIP LIMIT OF CONFINING UNIT 

'100 

Be. Simulated predevelopment potentiometric suriace of the confined Kirkwood aquifer, 

location of the simulated freshwater-saltwater interiace tip and toe, and area of upward 

flow, lower Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8), 

New Jersey Coastal Plain. 

156 
, ;~:';- ,:::.-::~~~:;J c.:~'~::;'::'~5~:'~::;:::;::;'::~'<':;'.:c"=/~:;::JL·,~--M-E .... A-C-EA.....-

F

-

A

-

L

-

L 

-~ .... : ..... : .... LE.,.S .... E .... Xr:''.\'?;~~)';~~~t~:K 

," _ .,. _ --- • ./ \. 'I RARITAN ....,r7"'!IIII_~"7.,..//,//,'L/j/",,/·:/7, ___ r.\ ................ JlIL. I, VI BAY 

I 

! 

OCEAN 

Q) 

/ e 

EXPLANATION 

OUTCROP AREA OF THE LOWER KIRKWOOD-COHANSEY 

AND CONFINED KIRKWOOD AQUIFERS 

- UPDIP LIMIT OF AQUIFER 

UPDIP LIMIT OF CONFINING UNIT 

LOCATION OF GROUND-WATER WITHDRAWAL--

Greater than 0.5 million gallons per day 

Less than 0.5 million gallons per day 

Base from U,S, Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

o 

I 

o 

/ / 

/ 

10 MILES 

I 

10 KILOMETERS 

'700 

ad. Locations of ground-water withdrawal sites in the lower Kirkwood-Cohansey and 

confined Kirkwood aquifers (model unit A8), New Jersey Coastal Plain, 1983-88. 

157 
'I FALL LINE 

. p.i"~L, ._ .. __ . .J\ tt;-c,"3 r " 

'fl/ .5-451 '\ 

) // OCEAN 

.s,' ~J 

1-710 • 

EXPLANATION 

,/ 

5-30 

o / 

/ 

OUTCROP AREA OFTHE LOWER KIRKWOOD 

COHANSEY AND CONFINED KIRKWOOD AQUIFERS 

-- UPDIP LIMIT OF AQUIFER 

UPDIP LIMIT OF CONFINING UNIT 

OBSERVATION WELL AND WELL NUMBER--

Difference between simulated and average measured 

water levels (1983-88) shown in figure 31. Simulated 

and average measured water levels shown in table 4 

SAMPLED WELL AND WELL NUMBER--Chloride 

concentrations shown in table 7 and appendix 8 (fig. 8f) 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 

29508 ;y!'\;L: 029-514" / ~29-815 / 

/ 

/ / 

o 10 MILES 1-1 -,',--L.-,-t _I 

o 10 KILOMETERS 

Se. Locations of observation wells for which water-level residuals are available and 

selected wells for which measured chloride concentrations are available, lower 

Kirkwood-Cohansey and confined Kirkwood aquifers (model unit A8), New Jersey 

Coastal Plain. 

158 
o 

I 

o 

10 MILES !! I 

10 KILOMETERS 

/ / 

014,270 

018,000 

Base from U.S. Geological Survey digital data, 1 :2,000,000, 1972, 

Universal Transverse Mercator projection, Zone 18 EXPLANATION 

DISCRETIZED AREA OF OUTCROP OF THE LOWER 

KIRKWOOD-COHANSEY AND CONFINED 

KIRKWOOD AQUIFERS 

AREA WHERE UNDERLYING AQUIFER CONTAINS 

HIGH CHLORIDE CONCENTRATIONS 

AREA WHERE WATER FLOWS INTO AQUIFER FROM 

UNDERLYING AQUIFER WITH HIGH CHLORIDE 

CONCENTRATIONS 

AREA OF UPWARD FLOW THROUGH THE TOP 

OF THE AQUIFER 

AREA WHERE WATER FLOWS INTO AQUIFER FROM 

OVERLYING AQUIFER WITH HIGH CHLORIDE 

CONCENTRATIONS 

------ TIP OF THE PREDICTED FRESHWATER-SALTWATER 

INTERFACE 

TOE OF THE PREDICTED FRESHWATER-SALTWATER 

INTERFACE 

SIMULATED UPDIP LIMIT OF AQUIFER 

.. SAMPLED WELL--Number is chloride concentration, 

3 rounded to nearest integer, in milligrams per liter. 

Concentrations and sample dates shown in table 7 

1,350 SAMPLED WELL--Top number is minimum chloride 

8 100 concentration; bottom number is maximum chloride 

o , concentration; all values in milligrams per liter (Meisler, 

1989). Samples collected at various depths. 

Concentrations and sample dates are shown in table 6 

8f. Measured chloride concentrations, location of simulated freshwater-saltwater interface 

tip and toe, and areas of saltwater flow from overlying and underlying aquifers, lower KirkwoodCohansey and confined Kirkwood aquifers (model unit A8), New Jersey Coastal Plain, 1983-88. 

159