iii

CONTENTS

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

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

Background ...................................................................................................................................................................2

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

Study area .....................................................................................................................................................................2

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

Acknowledgments ........................................................................................................................................................5

Hydrogeologic framework .....................................................................................................................................................5

Surficial aquifer and the upper confining unit ..............................................................................................................5

Piney Point-Nanjemoy aquifer ......................................................................................................................................5

Middle confining unit .................................................................................................................................................13

Aquia aquifer ..............................................................................................................................................................13

Ground-water withdrawal and water levels .........................................................................................................................16

Piney Point-Nanjemoy aquifer ....................................................................................................................................16

Aquia aquifer ...............................................................................................................................................................18

Ground-water quality ..........................................................................................................................................................23

Water quality of the Piney Point-Nanjemoy aquifer ...................................................................................................31

Water quality of the Aquia aquifer at Naval Air Station Patuxent River ....................................................................37

Water quality of the Aquia aquifer at Webster Outlying Field ...................................................................................38

Comparison of water types in the Piney Point-Nanjemoy and Aquia aquifers ..........................................................38

Saltwater intrusion ......................................................................................................................................................39

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

References cited ..................................................................................................................................................................41

Appendixes ..........................................................................................................................................................................43

A. Selected geophysical logs with generalized hydrologic units for:

A1. Well SM Df 93 ...........................................................................................................................................44

A2. Well SM Df 96 ...........................................................................................................................................45

A3. Well SM Dg 9 ............................................................................................................................................46

A4. Well SM Ff 21............................................................................................................................................47

A5. Well SM Ff 35............................................................................................................................................48

A6. Well SM Ff 64............................................................................................................................................49

B. Laboratory-analyzed constituents and methods ......................................................................................................50

C. Microorganisms and analytical methods for sample analyses from wells SM Df 61 and SM Df 98 .....................51

FIGURES

1-5. Maps showing:

1. Location of Naval Air Station Patuxent River and Webster Outlying Field study areas,

and outcrop areas of the Piney Point-Nanjemoy and Aquia aquifers, southern Maryland ..........................3

2. Well locations at Naval Air Station Patuxent River and Webster Outlying Field ...........................................4

3. Altitude of the top of the Piney Point-Nanjemoy aquifer, Naval Air Station Patuxent River, Maryland ........9

4. Thickness of the Piney Point-Nanjemoy aquifer ............................................................................................10

5. Location of hydrogeologic sections A-A′and B-B′ ........................................................................................11
iv

FIGURES—Continued

6-6. Hydrogeologic sections A-A′ and B-B′ ...................................................................................................................12

7-8. Maps showing:

7. Altitude of the top of the Aquia aquifer..........................................................................................................14

8. Thickness of the Aquia aquifer at selected locations ......................................................................................15

9-9. Plot showing ground-water withdrawal from the Piney Point-Nanjemoy and Aquia aquifers at

Naval Air Station Patuxent River, ground-water withdrawal from the Aquia aquifer at

Webster Outlying Field, and personnel at Naval Air Station Patuxent River, 1946–99........................................18

10. Map showing altitude of the potentiometric levels of the Piney Point-Nanjemoy aquifer on April 20, 2000..........19

11. Hydrographs for selected wells screened in the Piney Point-Nanjemoy aquifer, 1996–2000...................................20

12. Map showing altitude of the potentiometric surface of the Aquia aquifer on January 12, 2000...............................21

13. Hydrographs for selected wells screened in the Aquia aquifer at 

Naval Air Station Patuxent River, and Webster Outlying Field, 1950–2000 ........................................................22

14. Graph showing average daily ground-water withdrawal from the Aquia aquifer for

large users in parts of Calvert and St. Marys Counties, Maryland, 1980–99 ........................................................22

15. Piper diagram showing the chemistry of water from selected wells at

Naval Air Station Patuxent River, and Webster Outlying Field ............................................................................36

TABLES

1. Records for selected wells at Naval Air Station Patuxent River and Webster Outlying Field, Maryland................6

2. Hydrogeologic units and corresponding geologic units at Naval Air Station Patuxent River...................................8

3. Ground-water withdrawal from the Piney Point-Nanjemoy and Aquia aquifers at

Naval Air Station Patuxent River and the Aquia aquifer at

Webster Outlying Field, 1946–2000 ..................................................................................................................17

4. Concentrations of the major inorganic constituents, selected minor constituents,

and radionuclides of ground water from selected wells in the Piney Point-Nanjemoy

and Aquia aquifers at Naval Air Station Patuxent River and Webster Outlying Field, 1999............................24

5. Historical comparison of major inorganic constituents, and selected minor constituents

in ground water from selected wells in the Piney Point-Nanjemoy and Aquia aquifers,

Naval Air Station Patuxent River, 1943–62.......................................................................................................32

6. Select national primary drinking-water regulations: contaminants and their respective

maximum contaminant level goals (MCLGs), and maximum contaminant levels (MCLs)

as regulated by the U.S. Environmental Protection Agency ..............................................................................37

7. Select secondary drinking-water regulations ..........................................................................................................37

8. Comparison of average sea water and average connate water to ground-water samples collected in 1999

from the Piney Point-Nanjemoy aquifer, the Aquia aquifer at Naval Air Station Patuxent River,

and the Aquia aquifer at Webster Outlying Field ..............................................................................................40
v

CONVERSION FACTORS, ABBREVIATIONS, AND VERTICAL DATUM

_____________________________________________________________________________________________________________________________________

Multiply By To obtain

_____________________________________________________________________________________________________________________________________

inch (in.) 2.54 centimeter

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

acre 4,047 square meter

acre 0.4047 hectare

acre 0.4047 square hectometer

acre 0.004047 square kilometer

square mi (mi2) 259.0 hectare

square mi (mi2

) 2.590 square kilometer

gallon per day (gal/d) 0.003785 cubic meter per day

picocurie per liter (pCi/L) 0.037 becquerel per liter

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

foot squared per day (ft2

/d) 0.09290 meter squared per day

_____________________________________________________________________________________________________________________________________

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 x °C) + 32

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic 

datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called 

Sea Level Datum of 1929.

Altitude, as used in this report, refers to distance above or below sea level.

Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times foot of aquifer thickness 

[(ft3/d)/ft2

]ft. In this report, the mathematically reduced form, foot squared per day (ft2/d), is used for convenience.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter 

(μg/L).

Abstract 1

Hydrogeology and Ground-Water Quality of the Piney PointNanjemoy and Aquia Aquifers, Naval Air Station Patuxent River and 

Webster Outlying Field, St. Marys County, Maryland

By Cheryl A. Klohe and C. Erin Feehley

Abstract

Rapid population growth in southern Maryland has brought ground-water quality and groundwater quantity issues to the forefront. Historical and current water-quality data, ground-water 

withdrawal data, and water-level data were compiled to help water managers at the Naval Air Station 

Patuxent River understand how water-management practices affect regional ground-water resources, 

in particular the Piney Point-Nanjemoy and the Aquia aquifers.

Lithologic and borehole geophysical data were interpreted to create a local hydrogeologic 

framework of the Piney Point-Nanjemoy and Aquia aquifers. Ground-water withdrawal data and 

personnel data were compared to ground-water levels in both aquifers. Water samples were collected 

and analyzed to determine basic ground-water quality of both aquifers, and to compare these data 

with data collected from the 1940’s through the early 1960’s. The data were analyzed to determine 

changes in water quality over the past 50 years, and to investigate indications of saltwater intrusion.

The Piney Point-Nanjemoy aquifer is 50 to 70 feet thick, with a top altitude of 220 to 255 feet 

below sea level and a hydraulic conductivity of 2 feet per day at Naval Air Station Patuxent River. 

This aquifer is 65 feet thick, with a top altitude of 260 feet below sea level and a hydraulic 

conductivity of 2 feet per day at Webster Outlying Field. Ground-water withdrawal from the Piney 

Point-Nanjemoy aquifer has decreased and water levels have remained constant since the 1950’s. 

The water is calcium-magnesium-sodium-bicarbonate rich, and shows no evidence of saltwater 

intrusion.

The Aquia aquifer is 100 to 145 feet thick, with a top altitude of 450 feet below sea level and a 

hydraulic conductivity of 6 to 10 feet per day at Naval Air Station Patuxent River. This aquifer is 

50 feet thick, with a top altitude of 470 feet below sea level and a hydraulic conductivity of 6 to 

10 feet per day at Webster Outlying Field. Although ground-water withdrawal in the Aquia aquifer 

has decreased, water levels continue to decline at Naval Air Station Patuxent River and Webster 

Outlying Field due to increased municipal withdrawal near the air station. The water is sodiumbicarbonate rich at Naval Air Station Patuxent River and at Webster Outlying Field; at Webster 

Outlying Field, however, the specific conductance, acid-neutralizing capacity, and concentrations of 

sodium, sulfate, boron, and iodide are noticeably different from the water at the main facilities. 

There is no evidence of saltwater intrusion at either site, although the specific conductance and the 

concentrations of some constituents are higher at Webster Outlying Field, which could indicate early 

stages of saltwater intrusion.
2 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

Introduction

Development at the Naval Air Station Patuxent River and 

in the suburban Washington, D.C. area (approximately 

50 miles northwest of the air station) (fig. 1) has resulted in 

rapid population growth in southern Maryland, especially in 

St. Marys, Charles, and Calvert Counties. Because of the 

population increase, many County and State water managers, 

private citizens, and air station officials have become 

concerned with water-supply issues in the region. In 1998, 

the U.S. Geological Survey (USGS), in cooperation with the 

Naval Air Station (NAS) Patuxent River, began investigating 

the water resources of the Piney Point-Nanjemoy and Aquia 

aquifers at the air station to understand the effects of the air 

station’s water-use practices on regional water resources.

Published potentiometric surface maps of major aquifers 

in southern Maryland show recent expansion of large, deep 

cones of depression in areas served by high-capacity wells. 

For instance, in the Lexington Park area, the potentiometric 

surface of the Aquia aquifer in 1997 was approximately 90 ft 

(feet) lower than in 1982 (Curtin and others, 1999). Achmad 

and Hansen (1997) simulated ground-water flow for the 

Piney Point-Nanjemoy and Aquia aquifers in southern 

Maryland until the year 2020 with ground-water withdrawal 

values based on projected population growth statistics. The 

simulations show that water levels in the Lexington Park, 

Maryland, area could be as low as -95 ft m.s.l. (mean sea 

level) in the Piney Point-Nanjemoy aquifer, and -235 ft m.s.l. 

in the Aquia aquifer. These levels are about 100 ft lower 

than pre-pumping conditions in the Piney Point-Nanjemoy 

aquifer and about 250 ft lower than pre-pumping conditions 

in the Aquia aquifer. These levels are 75 ft lower than the 

Piney Point-Nanjemoy aquifer in April 2000 (-20 ft 

m.s.l.) and 100 ft lower than the Aquia aquifer in January 

2000 (-150 ft m.s.l.).

Background

Naval Air Station Patuxent River was commissioned in 

1943 as part of an effort to centralize U.S. Navy facilities. 

Webster Outlying Field (WOLF), near St. Inigoes, 

Maryland, serves as an auxiliary landing field for NAS 

Patuxent River. Testing and development of aircraft and 

weaponry at NAS Patuxent River and WOLF increased 

during the Korean and Vietnam Wars and continues today. 

In the 1990’s, the Navy began consolidating their technical 

resources and NAS Patuxent River became a receiver station 

as a result of Base Realignment and Closure of other 

facilities (Naval Air Station Patuxent River, 2000). With this 

consolidation, the facilities and personnel at NAS Patuxent 

River and WOLF grew from 10,000 employees in 1981 to 

13,000 in 1996, and to 18,000 by 1998 (James Darcy, Public 

Affairs Office, Naval Air Station Patuxent River, written 

commun., 2000).

Purpose and Scope

The purpose of this report is to (1) describe the 

hydrogeologic framework at the air station and its relation to 

the regional hydrogeologic framework, (2) analyze the 

relation between the water levels in the Piney PointNanjemoy and Aquia aquifers, ground-water withdrawal, 

and personnel growth at the air station, and (3) characterize 

the quality of water in the Piney Point-Nanjemoy and Aquia 

aquifers. The hydrogeology of the area is described on the 

basis of information from previous reports, State of 

Maryland Drilling Permits, State of Maryland Well 

Completion Reports, and USGS historical well files that 

include water levels, geophysical logs, and well-construction 

data. The water-level data (for the 1940’s to the present) are 

from the USGS National Water Information System (NWIS) 

data base. Ground-water-withdrawal records for NAS 

Patuxent River were obtained from correspondence between 

the USGS and the air station in the 1940’s, 1950’s, and 

1970’s, and continuous records kept by the air station from 

1989 to the present. Ground-water-withdrawal data for 

southern Maryland were obtained from the USGS State 

Water-Use Data System (SWUDS) data base and the 

Maryland Department of the Environment (MDE) 

Regulatory Analysis Management System (RAMS) data 

base. Water-quality analysis is based on ground-water 

samples collected in September 1999, and data published in 

previous reports by Chapelle and Drummond (1983) and 

Bennett (1944).

Study Area

The NAS Patuxent River is in southern Maryland in 

St. Marys County, southwest of the convergence of the 

mouth of the Patuxent River and Chesapeake Bay (fig. 1). 

WOLF is southwest of the air station, on the St. Marys River 

near St. Inigoes, Maryland (fig. 1). Together, the total 

facilities include approximately 7,800 acres of land and five 

runways, with the longest runway measuring 11,800 ft. The 

air operations consist of 50,000 mi2

 (square miles) available 

for operations, 5,000 mi2

 of controlled airspace, and 780 mi2

of restricted airspace. There are 935 buildings, 10 double 

bay hangers, more than 140 aircraft representing all Navy 

types and models, and 21 tenant aircraft (Naval Air Station 

Patuxent River, 2000).

The locations of the ground-water wells discussed in this 

report are shown in figure 2. Most of the wells are 

production wells, or were production wells in the past but 

have since been sealed and replaced by new wells. In this 

report, wells are listed by their USGS identification number. 

For example, well SM Df 14 is a well located in St. Marys 

county indicated by the first two letters “SM,” in the 

5-minute quadrangle “Df,” indicated by the second two 

letters, and is the 14th well mapped in the 5-minute quad, 

indicated by the last two numbers “14.” The 5-minute 

quadrangles are designated by uppercase letters from north 

to south, and lowercase letters from west to east. The USGS 

well numbers can be cross-referenced to air station well 

names and building numbers listed in table 1.
Introduction 3
4 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Hydrogeologic Framework 5

Previous Investigations

In 1944, the Commanding Officer of NAS Patuxent River 

asked the USGS to collect information on the availability of 

ground water at the Naval establishments in the Solomons–

Patuxent River area, Maryland (Bennett, 1944). Bennett 

compiled available records of the wells, ran brief aquifer 

tests, and measured static and pumping water levels of some 

of the wells at the new facilities. Bennett noted that 

interpretation of the data was difficult because information 

on the subsurface geology in the area was sparse, and the 

aquifer tests were of short duration. Nonetheless, his study 

provides some insight into the properties of the Piney PointNanjemoy aquifer and Aquia aquifer, the number of wells 

screened in each aquifer, and the quantity of water pumped 

from the wells at the NAS Patuxent River in the early 1940’s.

Since 1982, the USGS has published maps of the 

potentiometric surfaces of the Aquia aquifer in southern 

Maryland. Each year, the maps show an increase in the size 

and depth of the cone of depression in the potentiometric 

surface of the Aquia aquifer near Lexington Park, Maryland. 

Chappelle and Drummond (1983) described the Piney PointNanjemoy and Aquia aquifers in southern Maryland, but 

detailed information on the Lexington Park, Maryland, the 

NAS Patuxent River, and WOLF areas was not included. 

Chapelle and Drummond (1983) included results of groundwater-flow simulations and described the chemical evolution 

of water in the Aquia and Piney Point-Nanjemoy aquifers in 

southern Maryland. A more recent publication, by Achmad 

and Hansen (1997), also describes ground-water flow 

simulations of the Piney Point-Nanjemoy and Aquia 

aquifers. Assuming the amount of water pumped from the 

aquifers each year is equal to the 1995 maximum GroundWater Appropriation Permits (GAP) rates, Achmad and 

Hansen’s simulations predict that in the NAS Patuxent River/

Lexington Park area, water levels in the year 2020 will 

average -235 ft m.s.l. in the Aquia aquifer. At that pumping 

rate, the simulated cell average water level, for the model 

cell near the center of the cone of depression, comes to 

within 122 ft of the 80-percent available drawdown 

management level of -357 ft m.s.l. In well SM Df 42, in 

Lexington Park, the simulated water level was about -330 ft 

m.s.l., which is within 27 ft of the 80-percent available 

drawdown management level of -357 ft m.s.l.

Acknowledgments

The authors would like to thank the personnel at NAS 

Patuxent River who assisted the project, especially those in 

the Public Works Department, the Environmental Support 

Group, and the Public Affairs Office. In addition, the 

authors thank the many reviewers of this report for their 

helpful comments, and the USGS employees who assisted in 

field data collection.

Hydrogeologic Framework

The Coastal Plain of southern Maryland is underlain by a 

gently dipping wedge of sediments composed mainly of 

unconsolidated clay, silt, sand, and gravel. These sediments 

range in age from Holocene to Lower Cretaceous (Chapelle 

and Drummond, 1983), and crop out subparallel to the 

Fall Line (fig. 1), which is the approximate boundary 

between the Coastal Plain and the Piedmont Physiographic 

Provinces. The hydrogeologic units discussed in this report, 

from youngest to oldest are: the surficial aquifer, the upper 

confining unit, the Piney Point-Nanjemoy aquifer, the 

middle confining unit, and the Aquia aquifer (table 2). The 

Piney Point-Nanjemoy aquifer and the Aquia aquifer are 

relatively deep, confined aquifers in the Coastal Plain 

Physiographic Province of Maryland. In this report, 

hydraulic conductivity values have been calculated from 

transmissivity values given in Chapelle and Drummond 

(1983), divided by thickness of the aquifer determined from 

geophysical and lithologic logs.

Surficial Aquifer and the Upper Confining Unit

The surficial aquifer contains Holocene to Pliocene 

sediments that range from clays and silts to sands and 

gravels. The sediments are undifferentiated in the study 

area, ranging in thickness from 10 to 100 ft. In the past, 

when dug or driven wells were common, the unconfined 

surficial aquifer was used as a source of water for domestic 

and agricultural use (Achmad and Hansen, 1997).

The upper confining unit comprises the Chesapeake 

Group (undivided) clays and silts of Miocene age. The 

upper confining unit lies below the surficial aquifer and 

above the unnamed beds of Oligocene (?) or Miocene (?) 

age. The upper confining unit is approximately 210 to 

250 ft thick at the air station.

Piney Point-Nanjemoy Aquifer

The Piney Point-Nanjemoy aquifer is composed of the 

basal beds of the Chesapeake Group (the Calvert Formation), 

unnamed Oligocene (?) or Miocene (?) beds, the Piney Point 

Formation, and the upper sands of the Nanjemoy Formation 

(Achmad and Hansen, 1997). The Calvert Formation is 

early Miocene and consists of fine- to medium- grained, 

yellowish-green to greenish-light gray quartz sand, and is 

slightly glauconitic with some shell fragments, phosphate 

pebbles, and fine gravel (Achmad and Hansen, 1997). The 

unnamed Oligocene (?) Miocene (?) beds consist of clayey 

sands that are brown to olive green, slightly glauconitic, and 

fossiliferous (Achmad and Hansen, 1997). The Piney Point 

Formation is middle Eocene and consists of medium- to 

coarse-grained, quartz sands that are grayish-green to 

grayish-white in color, glauconitic with calcite cemented 

beds (Chapelle and Drummond, 1983). The upper sands of 

the Nanjemoy Formation are sometimes indiscernible from 

the lower sands of the Piney Point Formation, based on 

routinely collected drill cuttings and drillers’ logs. The 

sands from these four formations are hydraulically 

connected and are collectively referred to as
6 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

Table 1. Records for selected wells at Naval Air Station Patuxent River and 

Webster Outlying Field, Maryland—Continued

USGS

well

no.

State of

Maryland 

well permit

no.

Naval Air Station

well 

no.

Building

no.

Latitude

( °

 ' " )

Longitude

( ° ' " )

Altitude of

land surface

(feet)

Depth of well

(feet below

 land surface)

Casing

diameter

upper-lower

(inches)

SM Df 1 – 1A 522 38 15 53 76 26 50 93 587 8

SM Df 10 – 3B 531 38 17 12 76 26 18 45 534 8–6

SM Df 14 – 1P 532 38 17 20 76 26 48 17 262 8

SM Df 43 A – – – 38 16 47 76 25 24 39 553 8

SM Df 61 55823 2A 524 38 16 05 76 27 13 110 600 8

SM Df 93 SM–92–0358 1B 529 38 16 37 76 26 04 41 567 8–6

SM Df 94 SM–92–0357 3A 574 38 16 14 76 26 59 99 612 8–6

SM Df 95 SM–92–0369 4A 584 38 16 17 76 26 30 79 582 8–6

SM Df 96 SM–93–0036 5B 590 38 17 24 76 25 40 8 539 8

SM Df 97 SM–94–0925 2B 530 38 16 58 76 26 01 47 568 8–6

SM Df 98 SM–94–0410 5A 587 38 16 34 76 27 05 74 575 8–6

SM Df 99 SM–92–0642 4B 2276 38 17 10 76 25 57 44 600 16–8

SM Dg 1 A – – – 38 16 08 76 24 24 18 480 8

SM Dg 4 SM–00–3978 – 966 38 17 27 76 23 47 19 295 2

SM Dg 5 – 2Q 651 38 18 02 76 22 58 21 494 8

SM Dg 9 A, B SM–73–0095 – – 38 18 05 76 23 30 19 586 n/a

SM Dg 11 A – – – 38 17 25 76 23 05 9 290 6

SM Dg 14 SM–92–0370 1Q 617 38 18 11 76 23 27 19 542 8–6

SM Dg 15 SM–92–0570 1C 523 38 16 17 76 24 29 20 500 8–6

SM–92–0245

SM Dg 16 SM–94–0411 3C 583 38 16 20 76 23 56 10 520 8

SM Dg 17 SM–92–0643 – 2275 38 16 17 76 24 42 19 591 12–8

SM Dg 18 SM–94–0926 2C 575 38 16 10 76 24 11 17 553 8–6

SM Dg 19 SM–81–3345 CTR 2136 38 17 46 76 22 36 9 532 8

SM Dg 20 SM–88–0946 – 2100 38 17 20 76 23 42 11 335 4–2

SM Dg 21 SM–94–0074 1H 1633 38 18 10 76 24 44 9 315 4

SM Dg 22 – Weapons 253 38 17 31 76 24 24 11 670 2

SM Ff 21 – – – 38 05 54 76 26 12 9 486 8

SM Ff 35 SM–73–1496 Coast Guard (well 5) 8130 38 09 15 76 25 40 4 537 8–4

SM Ff 62 SM–94–1128 New Well 8195 38 08 21 76 25 59 9 539 8–6

SM Ff 63 – New Well 8195 38 08 22 76 25 57 9 545 8–4

SM Ff 64 B – – – 38 08 21 76 25 55 9 534 –

 A. Well no longer exists.

 B.

 Test hole.

Table 1. Records for selected wells at Naval Air Station Patuxent River and 

Webster Outlying Field, Maryland

[USGS, U.S. Geological Survey; no., number; (° ' " ), degree, minute, second; –, no data available; n/a, not applicable; 

geophyscial log types—G, Gamma; SP, Spontaneous Potential; R, Resistance; SN, Short Normal; LN, Long Normal]
Hydrogeologic Framework 7

 

TTable 1. Records for selected wells at Naval Air Station,Patuxent River and 

Webster Outlying Field, Maryland—Continued

Screen

position

(feet below

land surface)

Screen

length

(feet)

Geophysical

logs Driller

Date of 

construction Aquifer

USGS

well

no.

567–587 20 G Washington Pump and Well Co. 1943 Aquia SM Df 1

514–534 20 – Washington Pump and Well Co. 1943 Aquia SM Df 10

247–262 20 G Washington Pump and Well Co. 1943 Piney Point-Nanjemoy SM Df 14

514–534 20 G Sydnor Pump and Well Co. 1955 Aquia SM Df 43 A

580–600 20 G Patuxent Pump and Well Co. 1964 Aquia SM Df 61

515–565 50 G, SP, R A.C. Schultes of Maryland, Inc. 1994 Aquia SM Df 93

560–610 50 G, SP, R A.C. Schultes of Maryland, Inc. 1994 Aquia SM Df 94

530–580 50 G, SP, R A.C. Schultes of Maryland, Inc. 1994 Aquia SM Df 95

489–539 50 G, SP, R A.C. Schultes of Maryland, Inc. 1994 Aquia SM Df 96

515–565 50 – A.C. Schultes of Maryland, Inc. 1997 Aquia SM Df 97

525–575 50 – A.C. Schultes of Maryland, Inc. 1996 Aquia SM Df 98

490–600 110 – Vans Construction Co., Inc. 1994 Aquia SM Df 99

460–480 20 G Washington Pump and Well Co. 1943 Aquia SM Dg 1 A

275–295 20 – J.J. Payne 1949 Piney Point-Nanjemoy SM Dg 4

475–494 19 – Washington Pump and Well Co. 1950 Aquia SM Dg 5

n/a n/a G, SP, R Shannahan Artesian Well Co. 1972 Aquia SM Dg 9 A, B

– – G, SP, R, SN, LN Calvert Well Drilling Co. 1980 Piney Point-Nanjemoy SM Dg 11 A

490–540 50 G A.C. Schultes of Maryland, Inc. 1994 Aquia SM Dg 14

450–500 50 G Patuxent Pump and Well Co. 1993 Aquia SM Dg 15

470–520 50 – A.C. Schultes of Maryland, Inc. 1996 Aquia SM Dg 16

481–591 110 – Vans Construction Co., Inc. 1995 Aquia SM Dg 17

500–550 50 – A.C. Schultes of Maryland, Inc. 1997 Aquia SM Dg 18

480–510 30 – Sydnor Pump and Well Co. – Aquia SM Dg 19

325–335 10 – Watson and Johnson Well Drilling, Inc. 1991 Piney Point-Nanjemoy SM Dg 20

295–315 20 G Southern Well and Recovery Corp. 1996 Piney Point-Nanjemoy SM Dg 21

640–670 30 – – 1990 Aquia SM Dg 22

464–486 22 G Washington Pump and Well Co. 1945 Aquia SM Ff 21

487–537 50 G, SP, R A.C. Schultes of Maryland, Inc. 1975 Aquia SM Ff 35

486–536 50 G, SP, R, SN, LN A.C. Schultes of Maryland, Inc. 1997 Aquia SM Ff 62

– – – – 1987 Aquia SM Ff 63

– – G – – Aquia SM Ff 64 B
8 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

the Piney Point-Nanjemoy aquifer. Hydraulic conductivity 

(based on transmissivity from Chapelle and Drummond, 

1983) for the Piney Point-Nanjemoy aquifer at NAS 

Patuxent River is approximately 2 ft/d (feet per day). The 

top of the Piney Point-Nanjemoy aquifer ranges from 

-220 to -255 ft m.s.l. (fig. 3). The thickness of the aquifer 

varies slightly, but is approximately 50 to 70 ft thick 

(fig. 4).

The Piney Point-Nanjemoy aquifer is not exposed at the 

surface; therefore, recharge occurs in the subsurface where 

the aquifer is in hydraulic connection with water that 

percolates through the surficial units and other formations 

above the aquifer. The approximate updip extent of the 

aquifer in the subsurface is shown in figure 1, along the 

northern boundaries of Calvert County, and St. Marys 

County, Maryland. The downdip extent of the aquifer runs 

through southeast Sussex County, Delaware, then southwest 

through central Wicomico County, Maryland, and then south 

through the west side of Somerset County, Maryland 

(Vroblesky and Fleck, 1991).

Two hydrogeologic sections (A–A′ and B–B′ ; locations 

shown in figure 5) were developed from lithologic logs, 

well-completion reports, and geophysical logs of boreholes. 

Hydrogeologic sections, A–A′ and B–B′, shown in figure 6, 

show the thickness and continuous extent of the Piney PointNanjemoy aquifer. The geophysical logs (natural gammaray and single-point resistance) are plotted on the hydrogeologic sections to show the characteristic peaks that define 

the contacts between the aquifers and confining units. The 

thickness and altitude of the Piney Point-Nanjemoy aquifer 

at the air station is consistent with previously published 

information on regional hydrogeologic sections (Achmad 

and Hansen, 1997, Plates 1 and 2). 

Natural gamma-ray logs are available for most wells at 

the air station, but single-point resistance and spontaneous 

potential (SP) logs are available only for selected wells. 

Gamma, resistance, and SP logs for wells SM Df 93, 

SM Df 96, and SM Dg 9, along with gamma logs for wells 

SM Ff 21, SM Ff 35, and SM Ff 64 are included in 

Appendix A.

Natural gamma-ray logs are graphical plots of the 

emission of gamma rays from natural or artificial 

radioisotopes in the formations penetrated by the borehole. 

In general, silt and clay have much higher natural gamma 

activity than clean quartz sand and carbonates. Gamma 

radiation increases to the right on the gamma-ray log. 

Therefore, permeable sediments such as sand and gravel, 

which generally have low radioactivity, are indicated by log 

deflections toward the left, whereas silt and clay, which 

generally contain radioisotopes, are indicated by log 

deflections toward the right.

The single-point resistance curve is a record of electrical 

resistance of the formation, the formation fluid, and the 

borehole fluid. Most freshwater sands and gravels are 

indicated by sharp deflections to the right.

The SP log is a record of potentials or voltages due to 

electrochemical processes that are caused by salinity 

differences in borehole and interstitial fluids. The salinity 

differences usually occur at formation contacts, and reverse 

the potential, which is then represented as an inflection point 

on the log.

At WOLF, the top of the Piney Point-Nanjemoy aquifer 

is -260 ft m.s.l. and is approximately 65 ft thick. The altitude 

of the top of the aquifer is deeper than the top of the aquifer 

at NAS Patuxent River, but the thickness is the same. 

Although there are no production wells screened in the

Table 2. Hydrogeologic units and corresponding geologic units at Naval Air Station Patuxent River

 [Modified from Achmad and Hansen, 1997] NOT TO SCALE

System Series Geologic Unit Hydrogeologic Unit

Quaternary Holocene to Pleistocene

Surficial units (undifferentiated) Surficial aquifer

Tertiary

Pliocene

Miocene Chesapeake Group (undivided)

Upper confining unit

Oligocene (?) unnamed Oligocene (?) Miocene (?) beds Piney Point-Nanjemoy aquifer

Eocene

Piney Point Formation

Nanjemoy Formation

Paleocene

Marlboro Clay Middle confining unit

Aquia Formation Aquia aquifer

Brightseat Formation

Lower confining unit Cretaceous Upper and Lower Cretaceous Units
Hydrogeologic Framework 9
10 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Hydrogeologic Framework 11
12 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Hydrogeologic Framework 13

Piney Point-Nanjemoy aquifer at WOLF, the horizontal 

hydraulic conductivity is estimated to be 2 ft/d on the basis 

of thickness data from nearby wells, and transmissivity data 

from Chapelle and Drummond, 1983.

Middle Confining Unit

Beneath the Piney Point-Nanjemoy aquifer is a confining 

unit that includes the lower part of the Nanjemoy Formation 

(Eocene) and the Marlboro Clay (Paleocene). The lower part 

of the Nanjemoy Formation consists largely of greenishblack to olive-black silts and clays. The Marlboro clay 

consists of pale red or gray plastic clay (Achmad and 

Hansen, 1997). The thickness of the middle confining unit 

ranges from 130 to 150 ft (fig. 6).

Aquia Aquifer

Below the middle confining unit is the Aquia Formation 

of Paleocene age. The Aquia contains greenish-black, quartz 

sand, glauconite, and lenses of silty clay and shell beds. 

Calcite precipitation is also common (Chapelle and 

Drummond, 1983). Most of the Aquia is water-bearing, and 

thus is known as the Aquia aquifer.

The top of the Aquia aquifer is approximately 

-450 ft m.s.l. (fig. 7), and the aquifer ranges in thickness 

from 100 to 145 ft (fig. 8). Most of the wells screened in the 

Aquia aquifer at the air station are production wells that do 

not penetrate the full thickness of the aquifer. The thickness 

of the aquifer was determined from data for wells that 

penetrate the entire aquifer. Geophysical logs from wells 

outside the air station boundary were used in addition to logs 

from the few fully penetrating wells within the air station

boundaries. The thickness and extent of the aquifer was 

determined from lithologic logs, completion reports, and 

geophysical logs of boreholes, which are plotted on the 

hydrogeologic sections. Low gamma radiation and high 

resistance on the geophysical logs indicate the location of the 

Aquia aquifer, and are shown in the hydrogeologic sections 

(fig. 6). Geophysical logs for wells SM Df 93, SM Df 96, 

SM Dg 9, SM Ff 21, SM Ff 35, and SM Ff 64 are provided in 

Appendix A. The altitude and thickness of the Aquia aquifer 

at the air station are consistent with regional hydrogeologic 

sections (Achmad and Hansen, 1997, Plate 2). The Aquia 

aquifer is recharged primarily along its outcrop (fig. 1). In 

Maryland, the aquifer crops out in central Anne Arundel 

County, central Prince Georges County, and in northwest 

Charles County near the Potomac River. The horizontal 

hydraulic conductivity of the Aquia aquifer ranges from 6 to 

10 ft/d.

At WOLF, the altitude of the top of the Aquia aquifer is 

approximately -470 ft m.s.l. The thickness of the aquifer is 

only 50 ft, less than half its thickness at NAS Patuxent River. 

This thickness corresponds to regional hydrogeologic 

sections that show the Aquia aquifer is approximately 

40 ft thick at nearby Kitts Point (Achmad and Hansen, 1997, 

Plate 2). The horizontal hydraulic conductivity is approximately 6 to 10 ft/d. At WOLF, the aquifer sands are nearing 

their southeasternmost lateral extent (fig. 1), and although 

the Aquia Formation continues southeastward, it becomes 

thinner, finer-grained, and clayey (Achmad and Hansen, 

1997).
14 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Hydrogeologic Framework 15
16 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

Ground-Water Withdrawal and Water Levels

Significant ground-water withdrawal in the Cedar Point 

and St. Inigoes areas began in 1942, when the U.S. Navy 

built NAS Patuxent River and WOLF. Before 1942, 

relatively little ground water was pumped in the area, except 

for domestic use in the town of Solomons, Maryland 

(Bennett, 1944, p. 2). Yearly withdrawal records obtained 

for this report date back to 1946, but are intermittent prior to 

1989 (table 3). For each well, monthly withdrawal values 

(in gallons) were summed for a calendar year and then 

divided by the number of days in that year to calculate an 

average daily withdrawal value in gallons per day. The 

monthly withdrawal values were either measured with a flow 

meter or estimated. Data reported since 1989 are considered 

to be more comprehensive because complete withdrawal 

records were collected and furnished by NAS Patuxent River 

employees, whereas prior records may not include all 

withdrawal data.

Personnel data, furnished by the air station’s Public 

Affairs Office, include the number of military, civilian, 

contractor, and other employees who worked at NAS 

Patuxent River and used its resources. For this report, 

military personnel data records cover the period from 

1962–99, and total personnel data cover the period from 

1981–99. Personnel data for WOLF were unavailable. The 

total number of personnel at the NAS Patuxent River has 

increased from 1981–99, with the greatest number of people 

working at the station between 1995–98 (fig. 9). The NAS 

Patuxent River has had the largest number of personnel on 

record in the latter half of the 1990’s, yet overall groundwater withdrawal at NAS Patuxent River decreased during 

the same period. This decrease is due to water-use changes 

over the past few years. Old buildings with leaky water 

delivery systems have been demolished, and old water lines 

have been replaced. Industrial applications that use large 

amounts of water, such as jet engine testing, are declining. 

The steam generating plant that was used for heating 

buildings and water has been demolished recently and 

replaced by local high efficiency boilers, reducing water and 

energy loss (Don Shaver, Naval Air Station Patuxent River, 

oral commun., 2000). Overall, withdrawals from the Piney 

Point-Nanjemoy aquifer have decreased, declining from 

approximately 48,000 gal/d (gallons per day) in 1946 to 

approximately 500 gal/d in 2000 (table 3). According to 

records dating back to 1989, no water has been withdrawn 

from the Piney Point-Nanjemoy aquifer at WOLF. At NAS 

Patuxent River, withdrawals from the Aquia have decreased 

by approximately 386,000 gal/d, from an average of more 

than 1,128,000 gal/d in 1946 to an average of approximately 

742,000 gal/d in 2000. At WOLF, withdrawals from the 

Aquia aquifer have decreased from approximately 

74,000 gal/d in 1989 to approximately 28,000 gal/d in 1999.

Piney Point-Nanjemoy Aquifer

According to Chapelle and Drummond (1983, p. 23), 

development of the Piney Point-Nanjemoy aquifer in the 

late 1800’s and early 1900’s readily occurred as it is 

relatively shallow and many of the early wells flowed 

without pumping. Darton (1896, p. 128) reported 4 flowing 

Piney Point-Nanjemoy aquifer wells on Solomons Island, 1 

in Leonardtown, and 10 in St. Inigoes that flowed 2 to 20 ft 

above land surface. Significant ground-water withdrawal 

from the Piney Point-Nanjemoy aquifer began during 

World War II when the U.S. Navy built several training 

facilities in the Lexington Park and Solomons areas. The 

wells stopped flowing when pumping caused the groundwater levels to decline. The Navy reduced its withdrawals 

from the Piney Point-Nanjemoy aquifer in the late 1940’s in 

response to community complaints of declining water levels. 

Nevertheless, withdrawal from the aquifer continued to 

increase outside of the air station to support increasing 

domestic and municipal demands (Chapelle and Drummond 

1983, p. 18). Limited withdrawal data from the 1960’s 

through the late 1980’s are available. Thus, discussion of 

water use prior to 1980 is not possible. The NAS Patuxent 

River data records indicate modest usage exclusively from 

one well in the Piney Point-Nanjemoy aquifer from 

1989–93. In 1993, an additional well was pumped for part of 

the year, and in 1994, several more wells contributed to a 

large increase in withdrawal that decreased the following 

year. According to available records that date back to 1989, 

no water has been withdrawn from the Piney PointNanjemoy aquifer at WOLF.

Withdrawals from the Piney Point-Nanjemoy aquifer 

caused water levels in the NAS Patuxent River and 

Lexington Park area to decline. Otton (1955, Plate 10) 

reported the center of a cone of depression in the Piney 

Point-Nanjemoy aquifer at approximately -20 ft m.s.l. 

around the NAS Patuxent River by 1951, with the deepest 

recorded value of -32 ft m.s.l. northwest of well SM Df 43. 

Williams (1979, Plate 3) reported a 1976 water level in the 

Piney Point-Nanjemoy aquifer of -21 ft m.s.l. near well 

SM Df 1. A 1980 potentiometric surface map of the Piney 

Point-Nanjemoy aquifer (Chapelle and Drummond, 1983, 

Plate 8) shows a cone of depression around well fields at the 

NAS Patuxent River and Solomons Island. The lowest 

potentiometric levels reported for the Piney Point-Nanjemoy 

aquifer were -23 and -22 ft m.s.l., near the southwest border 

of the main facilities of the NAS Patuxent River and 

Solomons areas, respectively. Current potentiometric levels 

in wells in the Piney Point-Nanjemoy aquifer are shown in 

figure 10. Although the potentiometric surface of the 

Piney Point-Nanjemoy aquifer at WOLF has not been 

mapped, figures included in previous reports describing the 

area indicate that pumping in the surrounding areas has not 

caused the formation of an extensive cone of depression.
Ground-Water Withdrawal and Water Levels 17

Table 3. Ground-water withdrawal from the Piney Point-Nanjemoy and Aquia aquifers

at Naval Air Station Patuxent River and the Aquia aquifer 

at Webster Outlying Field, Maryland, 1946–2000

[WOLF, Webster Outlying Field; –, no data collected; <, less than; >, greater than]

Year

 NAVAL AIR STATION PATUXENT RIVER WOLF

Average 

daily withdrawal,

in gallons per day

Total daily

withdrawal, in

 gallons per day

Percentage of 

total withdrawal

Average

daily withdrawal,

in gallons per day

Piney Point-

 Nanjemoy

aquifer

 Aquia

 aquifer

Piney PointNanjemoy

aquifer

Aquia

aquifer

Aquia

aquifer

1946 47,761 1,128,458 1,176,218 4 96 –

1947 91,635 1,206,427 1,298,062 7 93 –

1948 99,895 1,313,130 1,413,025 7 93 –

1949 67,874 1,438,823 1,506,697 5 95 –

1953 84,000 1,559,000 1,643,000 5 95 –

1954 74,000 1,414,000 1,488,000 5 95 –

1955 73,780 1,354,143 1,427,923 5 95 –

1956 103,000 1,343,340 1,446,340 7 93 –

1970 107,868 1,249,720 1,357,588 8 92 14,479

1971 133,910 1,153,838 1,287,748 10 90 16,945

1974 75,916 1,152,264 1,228,180 6 94 –

1975 82,231 844,676 926,907 9 91 –

1989 93 1,038,654 1,038,748 <1 >99 73,705

1990 99 938,988 984,087 <1 >99 59,225

1991 99 1,118,700 1,118,799 <1 >99 78,390

1992 99 797,223 797,321 <1 >99 78,489

1993 55,689 808,236 863,925 6 94 55,774

1994 178,150 812,360 990,510 18 82 47,799

1995 43,156 748,439 791,595 5 95 42,627

1996 45,730 697,497 743,227 6 94 40,245

1997 58,984 754,685 813,669 7 93 26,498

1998 1,605 831,382 832,988 <1 >99 26,498

1999 24,061 832,636 856,697 3 97 29,536

2000 A 460 742,090 742,697 <1 >99 28,326

A. Values for 2000 are based on withdrawal values from January 1, 2000 through July 31, 2000.
18 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

It is difficult to make comparisons between the potentiometric surface maps for 1951, 1976, 1980, and recent levels 

of the potentiometric surface because of changes in the 

observation-well network. USGS water-level records for 

existing wells at NAS Patuxent River that are screened in the 

Piney Point-Nanjemoy aquifer date back only to the mid–

1990’s, with water levels measured in wells SM Df 14,

SM Dg 20, and SM Dg 21 averaging -20 ft m.s.l. (fig. 11). 

Comparison of water levels from 1951 through 1980, 

reported by Otton (1955), Williams (1979), and Chapelle and 

Drummond (1983), to water levels from 1996 through 2000 

(fig. 11) indicates that the Piney Point-Nanjemoy water 

levels in the NAS Patuxent River area have remained 

relatively stable for the past 50 years.

Aquia Aquifer

Withdrawal records indicate that the Aquia aquifer has 

historically provided most of the ground water used by NAS 

Patuxent River, WOLF, and surrounding areas. At least 

90 percent of the withdrawal at NAS Patuxent River has 

consistently been from the Aquia aquifer, and all withdrawal 

at WOLF has been from the Aquia aquifer (table 3). The 

use of the Aquia aquifer in southern Maryland increased, 

just as it did for the Piney Point-Nanjemoy aquifer during 

World War II (Chapelle and Drummond 1983, p. 18). In the 

early 1950’s, the Korean War necessitated an increase in 

development and improvement of aircraft, thereby elevating 

water use (Marcoa Publishing Inc., 1998). Water use 

fluctuated during the 1990’s, but withdrawal from the 

Aquia aquifer generally decreased at the NAS 

Patuxent River, from approximately 1,000,000 gal/d in 1989 

to approximately 742,000 gal/d in 2000 (table 3; fig. 9). 

Aquia aquifer withdrawal data for WOLF from 1989–2000 

show a decrease in withdrawal, except for a slight increase in 

1999. Overall, withdrawal decreased from approximately 

74,000 gal/d in 1989 to approximately 28,000 gal/d in 2000.

Potentiometric surface maps of the Aquia aquifer in 

southern Maryland from 1951–97 show a dynamic cone of 

depression in the Lexington Park-Solomons-NAS Patuxent 

River areas. This cone formed in an oblong shape around the 

Lexington Park area, expanding deeper and wider over time 

during the period of record (Weigle and Webb, 1970); 

Chapelle and others, 1981; Chapelle and Drummond, 1983; 

Mack and others, 1983; Mack and others, 1985, 1987; Mack 

and others, 1987, 1989, 1990; Mack and others, 1991, 1992; 

Curtin and others, 1993, 1996, 1997, 1999; Curtin and 

others, 1994, 1995). Otton (1955, Plate 9) prepared the first 

potentiometric-surface map of the Aquia aquifer in southern 

Maryland (Chapelle and Drummond, 1983, p. 17). This map 

shows a large cone of depression in the Lexington Park area 

in 1951. A similar cone of depression was described by 

Weigle and Webb (1970), but water levels had declined 

approximately 20 ft near Leonardtown as a result of 

increased municipal withdrawal. A potentiometric surface 

map created by Chapelle and Drummond (1983) delineates a 

cone of depression in the NAS Patuxent River-Lexington 

Park area with levels reported as low as -63 ft m.s.l. along the 

western boundary of the NAS Patuxent River and 
Ground-Water Withdrawal and Water Levels 19
20 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

-83 ft m.s.l. just outside the NAS Patuxent River in 

Lexington Park in 1981. Curtin, Andreasen, and Mack 

(1999, p. 1) show an extensive cone of depression in the 

Aquia aquifer around well fields at Lexington Park and 

Solomons Island during September 1997. Ground-water 

levels were more than -80 ft m.s.l. in a 60-mi2 area 

surrounding the deepest part of the cone of depression, 

with measured values at the NAS Patuxent River approximately -120 ft m.s.l. The lowest measurement was 

-143 ft m.s.l. in one well in Lexington Park, Maryland. 

Ground-water-level measurements recorded at the NAS 

Patuxent River in January 2000 ranged from about 

-116 ft m.s.l. (well SM Dg 19) on the eastern side to 

-154 ft m.s.l. (well SM Df 98) on the western side (fig. 12). 

None of the potentiometric surface maps of the Aquia 

aquifer specifically include water levels recorded at WOLF; 

however, a water level collected by USGS personnel on 

December 30, 1999, for well SM Ff 64 was -80 ft m.s.l. 

Curtin, Andreasen, and Mack (1999, p. 1) show the change 

in the potentiometric surface of the Aquia aquifer between 

September 1982 and September 1997. This map shows a 

decline of the potentiometric surface during the 15-year 

period of 60 to 80 ft at the NAS Patuxent River, a decline 

of 95 ft at Lexington Park, and a decline of 42 ft near 

St. Marys City, just north of WOLF. 

Water-level records for wells measured by the USGS at 

the NAS Patuxent River and WOLF date as far back as the 

early 1940’s, but were not measured on a regular basis until 

the 1980’s. Hydrographs of water levels for which 15 or 

more years of record exist show a declining trend in Aquia 

water levels, decreasing 60 to 80 ft in the last 15 years, with 

faster rates of decline after 1987 (fig. 13). For wells where 

monthly water-level data are available, seasonal trends show 

that water levels are higher in the spring and lower in the fall. 

Records for water levels at WOLF are not as extensive. The 

longest water-level record for WOLF is for well SM Ff 

21; however, this well was removed in 1991. It appears that 

the declining water levels occurring at NAS Patuxent River 

are also occurring at WOLF (fig. 13).

The potentiometric surface maps in previous reports and 

the hydrographs in this report (fig. 13) show substantial 

declines in the hydraulic head in the Aquia aquifer, caused 

by withdrawal of water from the aquifer. In Maryland, large 

users permitted to withdraw more than 10,000 gal/d are 

required to report monthly withdrawal values to State 

permitting agencies. These reported data are then transferred and stored in the USGS SWUDS data base. Withdrawal values for large users of the Aquia aquifer within a 

13-mi radius of the NAS Patuxent River in parts of both 

St. Marys and Calvert Counties (east of Leonardtown, north 

of St. Marys City, and south of Calvert Cliffs Nuclear Power 

Plant) were pulled from the SWUDS data base. Figure 14 

shows that from 1989–99, withdrawal from the Aquia 

aquifer by large users within the 20-mi radius of the NAS 

Patuxent River increased from approximately 2 Mgal/d 

(million gallons per day) to approximately 4 Mgal/d. During 

this period, withdrawal from the Aquia aquifer at the NAS 

Patuxent River decreased from 1 Mgal/d to approximately 

0.75 Mgal/d.
Ground-Water Withdrawal and Water Levels 21
22 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Ground-Water Quality 23

Ground-Water Quality

This section describes procedures used in the collection 

of water samples, laboratory methods used to analyze 

different chemical constituents, and data-analysis methods. 

Results of the ground-water and quality-control sample 

analyses can be found in table 4, and are discussed later in 

this section.

In August 1999, USGS field personnel collected water 

samples from one well screened in the Piney PointNanjemoy aquifer at the NAS Patuxent River, six wells 

screened in the Aquia aquifer at the NAS Patuxent River, and 

two wells screened in the Aquia aquifer at WOLF. At 

production wells, most of which had some type of chlorine 

treatment, samples were taken from spigots before the water 

was treated. The samples for laboratory analysis were 

collected after the wells were purged and water temperature, 

pH, and specific conductance had stabilized. USGS 

personnel (1) measured field parameters such as air 

temperature, water temperature, pH, specific conductance, 

dissolved oxygen, and acid-neutralizing capacity (ANC) 

(unfiltered, digital-titration method); (2) collected the raw 

(unfiltered and unacidified) water samples; (3) filtered the 

water for selected laboratory samples with a 0.45-micron 

capsule filter and a peristaltic pump; (4) preserved all 

laboratory samples as required with appropriate acid, and 

(5) shipped the samples overnight to the analyzing 

laboratory. The USGS National Field Manual for the 

Collection of Water-Quality Data (Wilde and others, 1998) 

documents the methods used in the collection of the groundwater samples.

The USGS National Water-Quality Laboratory (NWQL) 

in Denver, Colorado, analyzed water samples for iron, 

potassium, silica, magnesium, bromide, sodium, fluoride, 

manganese, chloride, calcium, sulfate, nitrite plus nitrate, 

boron, barium, iodide, and Radon-222. Robert Michel 

(USGS, Menlo Park, California) analyzed water samples for 

tritium. The Quanterra-Richland Laboratory (Richland, 

Washington) analyzed water samples for selected radiochemicals (Radium-226, Radium-228, alpha, gross beta, and 

Uranium). Laboratory methods are documented in Fishman 

and Friedman (1989) and are verified for bias, accuracy, and 

precision with standard-reference materials and by 

participation in the USGS Office of Water Quality sampletesting program (Maloney and others, 1994; Pritt and Raese, 

1995). Appendix B lists all constituents for which water 

samples were analyzed and provides a brief description of 

methods that were used by the analyzing laboratory. All 

water-quality data are stored in the USGS NWIS data base.

At two Aquia aquifer wells, SM Df 61 and SM Df 98, 

water samples were collected and sent to the Wisconsin State 

Hygiene Laboratory for analysis of human pathogens. All 

results were negative for the presence of human pathogens 

(see Appendix C for list of viral contaminants analyzed).

In addition to the "environmental" water samples 

mentioned above, quality-control samples were collected to 

estimate the magnitude of the bias and variability introduced 

into sampling and analyzing procedures. First, a field blank 

was collected from well SM Ff 63 and analyzed to determine 

the bias in the nitrite-plus-nitrate data. Inorganic blank water 

certified by the USGS National Laboratory in Ocala, Florida, 

was used to collect a field blank to test for possible nitrate 

contamination during the collection, shipping, or laboratory 

analysis of samples. Second, a duplicate sample was 

collected to check for variability in the water-quality data. 

The duplicate sample was collected at well SM Ff 63 by use 

of a sequential method, in which a large churn was filled 

with ground water from a spigot; as the water was filtered, 

one Radium-226 sample bottle was filled, then a second 

(duplicate) Radium-226 sample bottle was filled, then one 

Radium-228 sample bottle was filled, then a second 

(duplicate) Radium-228 sample bottle was filled, and so on. 

Third, the pH, specific conductance, and ANC of the water 

samples were determined by the laboratory to verify the 

field-measured values. The percent relative standard 

deviation (%RSD) was calculated from the duplicate data 

using the followng equation:

 ,

where:

%RSD = the percent relative standard deviation,

 x1 = the concentration of the ground-water 

sample, and

 x2 = is the concentration of the duplicate 

sample.

The %RSD was less than 5.7 percent for all laboratorymeasured constituents except barium (%RSD = 14.6), and 

bromide (%RSD = 23.0), and the median of the %RSDs for 

all laboratory-measured constituents was 0.0 percent. The 

%RSD for all laboratory-measured constituents (less than 

5.7%) indicates that the variability introduced by fieldcollection methods, shipping, and analyzing methods is 

minimal for all constituents except barium and bromide. The 

%RSD between field-measured values and laboratorymeasured values for pH was less than 1.0 percent, except for 

well SM Dg 18 (%RSD = 8.7); specific conductance was less 

than 10 percent, and ANC was less than 1 percent except for 

well SM Ff 35 (%RSD = 2.7), and well SM Df 61 (%RSD = 

6.0).

Cation-anion balances were calculated, as the percent 

difference between total anions to total cations in milliequivalents per liter, to ensure that all major ions dissolved in 

solution were accurately accounted for during analysis. A 

cation-anion balance of less than 2 percent is considered 

acceptable (Hem, 1992). The cation-anion balances for all 

water samples collected from the Piney Point-Nanjemoy

%RSD = 100 x1 – x2 ( )2 ⁄ 2

x1 + x2 ( ) ⁄ 2 ---------------------------------    
24 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland Table 4. Concentrations of the major inorganic constituents, selected minor constituents, and radionuclides of ground water from selected wells in the Piney Point-Nanjemoy and Aquia aquifers at Naval Air Station Patuxent River and Webster Outlying Field,Patuxent River, Maryland, 1999—Continued Well identification no. Building no. Aquifer Date Specific conductance (field)

(μS/cm)

 pH  (field) (standard units)

Airtemperature(°C)

Watertemperature(°C)

Dissolvedoxygen(mg/L)

Calcium(dissolved,mg/L as Ca)

SM Df 14 532 Piney Point-Nanjemoy 08/05/1999 257 8.0 32.0 17.5 <0.1 22SM Df 61 524 Aquia 08/03/1999 273 7.9 30.5 17.0 2.5 24SM Df 98 587 Aquia 08/04/1999 301 8.9 28.5 19.0 2.9 3.4SM Df 99 2276 Aquia 08/05/1999 309 8.9 29.0 18.5 1.3 2.4 SM Dg 5 651 Aquia 08/04/1999 291 8.7 27.5 19.5 – 3.0SM Dg 15 523 Aquia 08/04/1999 307 8.9 29.0 19.0 2.9 3.0SM Dg 18 575 Aquia 08/05/1999 315 8.6 29.0 18.5 4.5 6.7SM Ff 35 8130 Aquia 08/30/1999 562 8.7 21.5 19.0 <.1 3.5SM Ff 63 8195 Aquia 08/31/1999 645 8.5 20.5 19.0 <.1 2.6SM Ff 63 

A 8195 Aquia 08/31/1999 – – – – – 2.5

SM Ff 63

B 8195 Aquia 08/31/1999 – – – – – –

A. DUPLICATE

B. NITRATE BLANK

Table 4. Concentrations of the major inorganic constituents, selected minor constituents, and radionuclides of ground water

 from selected wells in the Piney Point-Nanjemoy and Aquia aquifers at Naval Air Station Patuxent River and

Webster Outlying Field, Maryland, 1999

 [no., number; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; pCi/L, picocuries per liter; <, less than; E, estimated; 

–, no data available]
Ground-Water Quality 25

Table 4. Concentrations of the major inorganic constituents, selected minor constituents, and radionuclides of ground water

 from selected wells in the Piney Point-Nanjemoy and Aquia aquifers at Naval Air Station Patuxent River and

Webster Outlying Field, Maryland, 1999--Continued

Wellidentificationno.

Buildingno. Aquifer Date

Magnesium(dissolved,mg/L as Mg)

Sodium(dissolved,mg/L as Na)

Potassium(dissolved,mg/L as K)

ANC(field)(mg/L asCaCO3)

Carbonate(field)(mg/L as CO3)

Bicarbonate(field)(mg/L as HCO3)

SM Df 14 532 Piney Point-Nanjemoy 08/05/1999 11 17 12 140 – –SM Df 61 524 Aquia 08/03/1999 12 13 1.0 146 – –SM Df 98 587 Aquia 08/04/1999 1.5 62 6.8 155 9 171SM Df 99 2276 Aquia 08/05/1999 0.97 67 6.0 160 8 179 SM Dg 5 651 Aquia 08/04/1999 1.4 68 6.4 160 6 183SM Dg 15 523 Aquia 08/04/1999 1.3 72 6.5 168 7 190SM Dg 18 575 Aquia 08/05/1999 3.0 59 8.9 164 5 189SM Ff 35 8130 Aquia 08/30/1999 1.6 130 7.8 288 10 332SM Ff 63 8195 Aquia 08/31/1999 1.5 152 7.8 342 9 398SM Ff 63 A 8195 Aquia 08/31/1999 1.5 152 8.3 – – –

SM Ff 63 B 8195 Aquia 08/31/1999 – – – – – –
26 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland Table 4. Concentrations of the major inorganic constituents, selected minor constituents, and radionuclides of ground water from selected wells in the Piney Point-Nanjemoy and Aquia aquifers at Naval Air Station Patuxent River and Webster Outlying Field, Maryland, 1999--Continued Well identification no. Building no. Aquifer Date Bicarbonate (calculated) (mg/L as HCO3) Sulfate (dissolved, mg/L as SO4) Chloride (dissolved, mg/L as Cl) Fluoride (dissolved, mg/L as F) Silica (dissolved, mg/L as SiO2) Dissolved solids sum (mg/L) SM Df 14 532 Piney Point-Nanjemoy 08/05/1999 171 7.7 3.8 0.38 53 211 SM Df 61 524 Aquia 08/03/1999 178 5.9 3.0 .37 54 208 SM Df 98 587 Aquia 08/04/1999 – 6.3 1.6 .57 13 193 SM Df 99 2276 Aquia 08/05/1999 – 5.7 1.8 .53 11 191 SM Dg 5 651 Aquia 08/04/1999 – 3.8 2.2 .53 11 193 SM Dg 15 523 Aquia 08/04/1999 – 4.1 2.2 .53 11 202 SM Dg 18 575 Aquia 08/05/1999 – <0.1 1.5 .41 16 190

SM Ff 35 8130 Aquia 08/30/1999 – 11 1.7 1.3 13 343SM Ff 63 8195 Aquia 08/31/1999 – 11 1.8 1.8 11 395SM Ff 63 

A 8195 Aquia 08/31/1999 – 11 1.8 1.8 11 395

SM Ff 63

B 8195 Aquia 08/31/1999 – – – – – –
Ground-Water Quality 27

Table 4. Concentrations of the major inorganic constituents, selected minor constituents, and radionuclides of ground water

 from selected wells in the Piney Point-Nanjemoy and Aquia aquifers at Naval Air Station Patuxent River and

Webster Outlying Field, Maryland, 1999--Continued

Wellidentificationno.

Buildingno. Aquifer Date

Hardness(calculated)(mg/L as CaCO3)

Nitrite +nitrate(dissolved,mg/L as N)

Barium(dissolved,

μg/L as Ba)

Boron(dissolved,

μg/L as B) 

Bromidedissolved,mg/L as Br)

Iodide(dissolved,mg/L as I)

SM Df 14 532 Piney Point-Nanjemoy 08/05/1999 100 <0.05 E 0.5 100 0.016 0.006SM Df 61 524 Aquia 08/03/1999 110 <.05 1.2 80 .021 .006SM Df 98 587 Aquia 08/04/1999 15 <.05 E 0.47 190 .014 .008SM Df 99 2276 Aquia 08/05/1999 10 <.05 1.0 200 .015 .007 SM Dg 5 651 Aquia 08/04/1999 13 .082 E 0.94 190 <.01 .005SM Dg 15 523 Aquia 08/04/1999 13 <.05 E 0.51 190 .011 .006SM Dg 18 575 Aquia 08/05/1999 29 <.05 1.3 200 <.01 .005SM Ff 35 8130 Aquia 08/30/1999 15 <.05 2.1 300 .014 .01SM Ff 63 8195 Aquia 08/31/1999 12 <.05 1.6 400 .018 .013SM Ff 63 A 8195 Aquia 08/31/1999 12 <.05 1.3 390 .025 .012

SM Ff 63 B 8195 Aquia 08/31/1999 – <.05 – – – –
28 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland Table 4. Concentrations of the major inorganic constituents, selected minor constituents, and radionuclides of ground water from selected wells in the Piney Point-Nanjemoy and Aquia aquifers at Naval Air Station Patuxent River and Webster Outlying Field, Maryland, 1999--Continued Well identification no. Building no. Aquifer Date Iron (dissolved,

μg/L as Fe)

Manganese(dissolved,μg/L as Mn)

Alpharadioactive water,(dissolved, pCi/L as TH-230)

Alpha count,2 sigma,(water, dissolved,pCi/L as TH-230)

Gross beta(dissolved,pCi/L as CS-137)

SM Df 14 532 Piney Point-Nanjemoy 08/05/1999 <10 <3 <3.0 2.4 13SM Df 61 524 Aquia 08/03/1999 51 <3 <3.0 2.0 16SM Df 98 587 Aquia 08/04/1999 E 5.1 <3 <3.0 2.7 11.0SM Df 99 2276 Aquia 08/05/1999 16 <3 <3.0 2.7 7.0 SM Dg 5 651 Aquia 08/04/1999 <10 <3 <3.0 2.3 8.1SM Dg 15 523 Aquia 08/04/1999 <10 <3 <3.0 1.9 9.2SM Dg 18 575 Aquia 08/05/1999 E 9.2 <3 <3.0 2.5 10.0SM Ff 35 8130 Aquia 08/30/1999 E 8 E 1.9 <3.0 2.1 5.2SM Ff 63 8195 Aquia 08/31/1999 <10 E 1.2 <3.0 2.4 5.6SM Ff 63 

A 8195 Aquia 08/31/1999 10 1.4 <3.0 2.7 5.1

SM Ff 63

B 8195 Aquia 08/31/1999 – – – – –
Ground-Water Quality 29

Table 4. Concentrations of the major inorganic constituents, selected minor constituents, and radionuclides of ground water

 from selected wells in the Piney Point-Nanjemoy and Aquia aquifers at Naval Air Station Patuxent River and

Webster Outlying Field, Maryland, 1999--Continued

Wellidentificationno.

Buildingno. Aquifer Date

Beta, 2 sigma,(water, dissolved,pCi/L as CS-137)

Radium-226(dissolved,planchet count)(pCi/L)

Radium-226,2 sigma(water, dissolved)(pCi/L)

Radium-228,(dissolved,pCi/L asRa-228)

Radium-228,2 sigma,(pCi/L)

SM Df 14 532 Piney Point-Nanjemoy 08/05/1999 4.5 <0.1 0.054 0.821 0.32SM Df 61 524 Aquia 08/03/1999 1.7 <.1 .037 .540 .31SM Df 98 587 Aquia 08/04/1999 1.5 <.1 .052 .498 .29SM Df 99 2276 Aquia 08/05/1999 1.4 <.1 .037 <1.0 .20 SM Dg 5 651 Aquia 08/04/1999 1.4 <.1 .032 .113 .19SM Dg 15 523 Aquia 08/04/1999 1.4 <.1 .038 .442 .23SM Dg 18 575 Aquia 08/05/1999 1.6 <.1 .059 .616 .26SM Ff 35 8130 Aquia 08/30/1999 4.7 <.1 .034 .359 .30SM Ff 63 8195 Aquia 08/31/1999 4.8 <.1 .063 .421 .30SM Ff 63 A 8195 Aquia 08/31/1999 4.7 <.1 .051 .901 .35

SM Ff 63 B 8195 Aquia 08/31/1999 – – – – –
30 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland Table 4. Concentrations of the major inorganic constituents, selected minor constituents, and radionuclides of ground water from selected wells in the Piney Point-Nanjemoy and Aquia aquifers at Naval Air Station Patuxent River and Webster Outlying Field, Maryland, 1999--Continued Well identification no. Building no. Aquifer Date Radon-222 (total) (pCi/L) Radon-222, 2 sigma, (water whole, total) (pCi/L) Tritium (pCi/L) Tritium, 2 sigma (water, whole, total) (pCi/L) Uranium (natural, dissolved,

μg/L as U)

Uranium,natural, 2 sigma,(water, dissolved)(pCi/L)

SM Df 14 532 Piney Point-Nanjemoy 08/05/1999 378 22 4.2 1.0 <1.0 0.2

SM Df 61 524 Aquia 08/03/1999 323 19 <2.5 1.9 <1.0 .1SM Df 98 587 Aquia 08/04/1999 404 21 <2.5 1.9 <1.0 .1SM Df 99 2276 Aquia 08/05/1999 415 23 <2.5 1.9 <1.0 .1 SM Dg 5 651 Aquia 08/04/1999 302 19 <2.5 1.9 <1.0 .1SM Dg 15 523 Aquia 08/04/1999 415 21 <2.5 1.9 <1.0 .1SM Dg 18 575 Aquia 08/05/1999 331 21 <2.5 1.9 <1.0 .1SM Ff 35 8130 Aquia 08/30/1999 506 24 <2.5 1.9 <.40 0.0SM Ff 63 8195 Aquia 08/31/1999 434 22 <2.5 1.9 <.40 0.0SM Ff 63 

A 8195 Aquia 08/31/1999 445 22 <2.5 1.9 <.40 0.0

SM Ff 63 B 8195 Aquia 08/31/1999 – – – – – –

A. DUPLICATE

B. NITRATE BLANK
Ground-Water Quality 31

and Aquia aquifers in 1999 agreed within 1 percent, except 

those for samples from well SM Df 98 (-2 percent) and well 

SM Df 61 (-7 percent). The percent difference for well 

SM Df 61 is most likely due to error in accounting for all the 

potassium dissolved in the water sample.

The ground-water chemistry of both the Piney PointNanjemoy and Aquia aquifers is described on the basis of 

cations or anions that account for the majority of ions in the 

samples. In the Aquia aquifer, sodium and bicarbonate 

account for the majority of dissolved ions in solution. 

Samples collected recently were compared to values 

reported in the literature (table 5) to determine if there are 

any temporal differences in water chemistry. This 

comparison was especially important for the Piney PointNanjemoy sample discussion because only one well 

screened in the Piney Point-Nanjemoy aquifer was sampled 

in 1999. Constituent concentrations in the samples collected 

in 1999 also were compared to average constituent 

concentrations in saltwater to see if saltwater intrusion is 

occurring in these aquifers.

Piper diagrams were used as a tool to analyze the 

similarities and/or differences in the water between the two 

aquifers, between current and historical values, and between 

current and average seawater values. Piper diagrams are 

trilinear diagrams that show concentrations of major cations 

and anions as percentages of total cations or anions. Water 

samples that have the same percentage of cations and anions 

will plot in the same area on the Piper diagram. Samples 

with different percentages will plot in different areas. In 

figure 15, the analysis of the water sample from well 

SM Df 14 (Piney Point-Nanjemoy aquifer sampled in 1999) 

is plotted as a red triangle. The concentrations of major 

cations (magnesium, calcium, sodium, and potassium) were 

summed, and then the percentage of each cation based on the 

total cations was calculated. The cations are plotted in the 

left triangle and show that the water sample from well SM 

Df 14 contains 34 percent sodium plus potassium, 36 percent 

calcium, and 30 percent magnesium (100 percent total). The 

same process was used to plot the major anions in the right 

triangle. The cation and anion percentages were then 

projected to the diamond part of the plot, which shows the 

combined percentages of the ions. The sample from the 

Piney Point-Nanjemoy aquifer (red triangle) had different 

percentages of ions than all but one of the Aquia aquifer 

samples (yellow circles) and therefore plotted in a different 

area of the diagram.

Results of these analyses were also compared to the 

U.S. Environmental Protection Agency (USEPA) national 

primary drinking water regulations (table 6) to see if the 

concentrations of any of the constituents were greater than 

the maximum contaminant levels (MCLs), the maximum 

permissible level of a contaminant in water to protect human 

health, or maximum contaminant level goals (MCLGs), 

health standards based on the amount of a contaminant in 

drinking water that will not endanger human health over a 

lifetime of exposure (U.S. Environmental Protection Agency, 

1999a). Results were also compared to the USEPA national 

secondary drinking water regulations (table 7). These 

regulations cover contaminants that are considered to be 

esthetically unpleasant (i.e. causing odor or bad taste) but are 

not considered to pose health problems (U.S. Environ-mental 

Protection Agency, 1999b).

Water Quality of the Piney Point-Nanjemoy Aquifer

Water was collected from well SM Df 14, which is 

screened in the Piney Point-Nanjemoy aquifer. Due to 

logistical concerns, well SM Df 14 was the only well 

screened in the Piney Point-Nanjemoy aquifer that could be 

sampled. The authors determined that the constituent 

concentrations in the sample from 1999 matched historical 

values, so the discussion of water quality in the Piney PointNanjemoy aquifer could be based on the single sample from 

well SM Df 14.

The water in the Piney Point-Nanjemoy aquifer is a 

calcium-magnesium-sodium-bicarbonate water. The water 

temperature was about 17.5 °C (degrees Celsius), pH was 

8.0, specific conductance was 285 μS/cm (microsiemens per 

centimeter), hardness was 100 mg/L (milligrams per liter) as 

calcium carbonate, and ANC was 140 mg/L (as calcium 

carbonate). There was no detectable nitrite plus nitrate. The 

water contained 22 mg/L of calcium, 11 mg/L of 

magnesium, 17 mg/L of sodium, 12 mg/L of potassium, 

53 mg/L of silica, 100 μg/L (micrograms per liter) of boron, 

3.8 mg/L of chloride, and 7.7 mg/L of sulfate.

The Radon-222 value was 378 pCi/L (picocuries per 

liter). This value is greater than the USEPA proposed MCL 

of 300 pCi/L, but is less than the alternative maximum 

contaminant level (AMCL) of 4,000 pCi/L (U.S. Environmental Protection Agency, 1999c). The AMCL is used when 

a multimedia mitigation program is followed to address 

radon concentrations in air (U.S. Environmental Protection 

Agency, 1999c). The radon value is also on the same 

order of magnitude as other radon concentrations (502 and 

719 pCi/L) sampled in the Piney Point-Nanjemoy aquifer in 

Queen Annes County, Maryland (Smigaj and others, 1999). 

The tritium concentration was 4.2 pCi/L. The gross beta 

count was 13 pCi/L (as Cesium 137), Radium-228 was 0.821 

± 0.32 pCi/L, and all other radionuclide values were lower 

than the detection limits. In the Piney Point-Nanjemoy 

aquifer, the concentrations of constituents were less than the 

MCLs, MCLGs, and the secondary drinking-water 

standards.

To compare the samples collected in 1999 (table 4) with 

those collected in the 1940’s and 1950’s (Chapelle and 

Drummond, 1983) (table 5), major ions of the samples were 

plotted on a Piper diagram (fig. 15). The samples plot in the 

same location on the Piper diagram (fig. 15), indicating that 

the water chemistry of the Piney Point-Nanjemoy aquifer has 

not changed during the past 56 years. This would be 

expected in deep, confined aquifers such as the Piney PointNanjemoy aquifer. Achmad and Hansen (1997, p. 76) 

estimate that the time of travel for water entering the Aquia 

aquifer is thousands of years, with age dates reported to be 

greater than 8,500 years (Mignery, 1994). Since the Piney 

Point-Nanjemoy aquifer is a deep, confined aquifer similar 
32 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

 

Table 5. Historical comparison of major inorganic constituents, and selected minor constituents in 

ground water from selected wells in the Piney Point-Nanjemoy and Aquia aquifers, 

Naval Air Station Patuxent River, Maryland, 1943–62

Well

identification

no. Aquifer Date

Specific

conductance

(μS/cm)

 

pH

(standard

units)

Water

temperature

(°C)

Calcium

(dissolved,

mg/L as Ca)

1A Aquia 07/22/1943 n/a 8.7 n/a 2.1

1B Aquia 07/22/1943 n/a 8.7 n/a 0.07

1C Aquia 07/22/1943 n/a 8.7 n/a 2.9

2B Piney Point-Nanjemoy 07/22/1943 n/a 7.9 n/a 23

SM Df 1 Aquia 10/29/1951 316 8.5 16.6 2.4

05/18/1954 336 8.8 18.8 3.0

03/13/1956 341 8.8 – 2.5

04/12/1957 342 8.8 – 3.2

06/02/1958 337 8.0 – 1.7

08/13/1959 344 8.1 – 3.7

06/24/1962 344 8.7 – 3.4

SM Df 3 Aquia 10/29/1951 301 8.6 16.6 3.2

05/18/1954 324 8.9 16.1 2.9

03/13/1956 323 8.8 – 2.5

04/09/1957 324 8.9 – 2.7

06/02/1958 331 8.6 – 2.0

08/05/1959 331 8.6 – 2.8

06/24/1962 323 8.4 – 7.5

SM Dg 1 Aquia 11/21/1951 325 8.5 18.8 2.8

05/20/1954 331 8.4 18.3 3.1

03/15/1956 326 8.7 – 3.4

04/09/1957 332 8.7 – 3.5

06/04/1958 334 7.9 – 2.7

08/11/1959 334 8.3 – 3.2

SM Df 14 Piney Point-Nanjemoy 11/27/1951 280 8.0 18.3 22

05/19/1954 279 8.1 17.7 22

03/20/1956 283 7.9 – 22

04/12/1957 290 7.8 – 27

06/09/1958 291 7.7 – 22

06/24/1962 289 7.8 – 22

Table 5. Historical comparison of major inorganic constituents, and selected minor constituents in 

ground water from selected wells in the Piney Point-Nanjemoy and Aquia aquifers,

Naval Air Station Patuxent River, Maryland, 1943–62

[Data taken from Bennett, 1944, for well nos. 1A, 1B, 1C, 2B; data taken from Chapelle and Drummond, 1983, for well nos. SM Df 1, 

SM Df 3, and SM Dg 1 (table 9), and SM Df 14 (table 10), respectively; no., number; μS/cm, microsiemens per centimeter; °

C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; n/a, not applicable; –, no data available]
Ground-Water Quality 33

Table 5. Historical comparison of major inorganic constituents, and selected minor constituents in 

ground water from selected wells in the Piney Point / Nanjemoy and Aquia aquifers, 

Naval Air Station Patuxent River, Maryland, 1943–62—Continued

Magnesium

(dissolved,

mg/L as Mg)

Sodium

(dissolved,

mg/L as Na)

Potassium

(dissolved,

mg/L as K)

Alkalinity

(mg/L as 

CaCO3)

Carbonate

(mg/L as CO3)

Sulfate

(dissolved,

mg/L as SO4)

Well

identification

no.

0.0 n/a n/a n/a 15 6.9 1A

2.4 n/a n/a n/a 13 6.9 1B

0.5 n/a n/a n/a 25 7.1 1C

12 n/a n/a n/a 8.9 7.7 2B

1.0 76 9.0 173 n/a 5.5 SM Df 1

1.2 73 6.1 174 n/a 9.6

0.7 73 7.3 175 n/a 9.4

0.8 73 6.9 171 n/a 5.8

0.3 70 7.8 175 n/a 6.0

1.9 71 6.0 171 n/a 7.6

0.6 76 7.9 173 n/a 6.4

0.7 72 9.0 164 n/a 6.5 SM Df 3

1.0 68 5.6 167 n/a 6.6

0.4 69 6.4 164 n/a 6.6

0.5 69 6.7 164 n/a 6.0

1.6 69 6.1 169 n/a 7.0

0.9 69 9.9 163 n/a 4.3

2.3 63 7.7 161 n/a 7.0

1.6 76 7.0 173 n/a 6.0 SM Dg 1

1.2 71 6.3 169 n/a 6.6

1.0 68 6.7 167 n/a 5.8

0.7 70 6.7 170 n/a 5.6

0.3 70 6.4 178 n/a 6.0

1.2 70 5.7 168 n/a 3.3

12 17 12 143 n/a 6.8 SM Df 14

12 14 12 143 n/a 7.8

11 13 12 137 n/a 7.6

8.7 11 12 139 n/a 6.4

9.6 20 13 140 n/a 7.2

11 17 14 141 n/a 6.6
34 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

Table 5. Historical comparison of major inorganic constituents, and selected minor constituents in 

ground water from selected wells in the Piney Point-Nanjemoy and Aquia aquifers,

Naval Air Station Patuxent River, Maryland, 1943–62--Continued

Well

identification

no. Aquifer Date

Chloride

(dissolved,

mg/L as Cl)

Fluoride

(dissolved,

mg/L as F)

Silica

(dissolved,

mg/L as SiO2)

Dissolved

solids sum

(mg/L)

1A Aquia 07/22/1943 2.9 n/a 16 234

1B Aquia 07/22/1943 3.5 n/a 23 226

1C Aquia 07/22/1943 2.4 n/a 32 194

2B Piney Point-Nanjemoy 07/22/1943 2.6 n/a 50 224

SM Df 1 Aquia 10/29/1951 2.5 0.5 12 213

05/18/1954 2.7 0.6 12 –

03/13/1956 2.5 0.5 13 –

04/12/1957 2.8 0.6 12 –

06/02/1958 3.0 0.5 12 –

08/14/1959 2.5 0.6 12 –

06/24/1962 2.5 0.2 12 213

SM Df 3 Aquia 10/29/1951 2.8 0.4 12 –

05/18/1954 3.6 0.5 11 –

03/13/1956 1.7 0.5 13 –

04/09/1957 3.0 0.5 13 –

06/02/1958 3.0 1.4 11 –

08/05/1959 2.6 1.0 14 –

06/24/1962 3.5 0.7 18 207

SM Dg 1 Aquia 11/21/1951 4.2 0.4 12 214

05/20/1954 2.5 0.5 13 –

03/05/1956 1.8 0.4 12 –

04/09/1957 2.2 0.5 13 205

06/04/1958 3.0 0.7 11 209

08/11/1959 2.2 0.6 12 –

SM Df 14 Piney Point-Nanjemoy 11/27/1951 2.9 0.3 56 215

05/19/1954 3.8 0.4 48 –

03/20/1956 1.6 0.3 56 –

04/12/1957 2.4 0.5 55 –

06/09/1958 3.0 0.6 50 –

06/24/1962 3.4 0.0 56 –
Ground-Water Quality 35

Table 5. Historical comparison of major inorganic constituents, and selected minor constituents in 

ground water from selected wells in the Piney Point / Nanjemoy and Aquia aquifers, 

Naval Air Station Patuxent River, Maryland, 1943–62—Continued

Hardness

(mg/L as CaCO3)

Nitrate

(mg/L as NO3)

Iron,

total recoverable

(μg/L as Fe)

 

Manganese

dissolved 

(μg/L as Mn) 

Well

identification

no.

19 0.26 100 0 1A

45 0.3 80 0 1B

28 0.3 0 0 1C

122 0.2 0 0 2B

10 n/a 0 – SM Df 1

13 n/a 60 0

9 n/a 270 0

11 n/a 30 20

6 n/a 20 0

17 n/a 10 0

11 n/a 100 0

11 n/a 100 – SM Df 3

11 n/a 50 0

8 n/a 20 0

9 n/a 190 20

12 n/a 0 0

11 n/a 20 0

28 n/a 120 0

14 n/a 0 – SM Dg 1

13 n/a 70 0

13 n/a 70 70

12 n/a 20 0

8 n/a 30 0

13 n/a 40 0

104 n/a 80 – SM Df 14

104 n/a 40 0

100 n/a 90 10

103 n/a 50 0

94 n/a 100 0

102 n/a 60 10
36 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Ground-Water Quality 37

to the Aquia aquifer, the age of ground water in the Piney 

Point-Nanjemoy aquifer is probably of similar age to ground 

water in the Aquia aquifer.

Water Quality of the Aquia Aquifer at Naval Air Station 

Patuxent River

USGS personnel collected water samples from six wells 

screened in the Aquia aquifer (SM Df 61, SM Df 98, 

SM Df 99, SM Dg 5, SM Dg 15, and SM Dg 18) at NAS 

Patuxent River, Maryland, on August 4–5, 1999. The 

chemistry of the water in well SM Df 61 is more consistent 

with that of water in the Piney Point-Nanjemoy aquifer than 

water in the Aquia aquifer. For this reason, water samples 

collected from well SM Df 61 are discussed separately at the 

end of this section. The explanation for the non-Aquia 

water type will be discussed in a later section.

The Aquia aquifer contains sodium-bicarbonate water, 

the water temperature is about 19 °C, pH ranges from 8.6 to 

8.9, specific conductance ranges from 291 to 315 μS/cm, 

hardness is 10 to 29 mg/L (as calcium carbonate), and the 

ANC ranges from 155 to 168 mg/L (as calcium carbonate). 

Only well SM Dg 5 had a detectable concentration of nitrite 

plus nitrate with a value of 0.082 mg/L as N. The median 

concentrations were 67 mg/L of sodium, 3 mg/L of calcium, 

1.4 mg/L of magnesium, 6.5 mg/L of potassium, 1.8 mg/L of 

chloride, 11 mg/L of silica, 4.9 mg/L of sulfate, and 

0.53 mg/L of fluoride.

Radon-222 values ranged from 302 to 415 pCi/L, with a 

median value of 404 pCi/L. This value is greater than the 

USEPA proposed MCL of 300 pCi/L, but is less than the 

AMCL of 4,000 pCi/L (U.S. Environmental Protection 

Agency, 1999c). The radon values are on the same order of 

magnitude as other radon concentrations sampled from 

the Aquia aquifer in Anne Arundel and Queen Annes 

Counties, Maryland (Smigaj and others, 1999) that ranged 

from 162 to 989 pCi/L, with a median value of 300 pCi/L. 

Gross Beta values ranged from 8.1 to 11 pCi/L, Radium-228 

values ranged from 0.113 ± 0.19 to 0.616 ± 0.26 pCi/L, with 

a median of 0.442 ± 0.23 pCi/L, and all other radionuclide 

values were lower than the detection limits.

As with the Piney Point-Nanjemoy water samples, the 

Aquia aquifer ground-water samples at the NAS Patuxent 

River were compared to USEPA primary drinking-water 

MCLs, MCLGs, and national secondary drinking water 

regulations (tables 6 and 7). Sample concentrations were not 

greater than the primary drinking-water MCLs or MCLGs. 

The pH values for the Aquia aquifer at NAS Patuxent River 

Table 6. Select national primary drinking-water

regulations: contaminants and their

respective maximum contaminant 

level goals (MCLGs), and maximum

contaminant levels (MCLs) as

regulated by the U.S. Environmental

Protection Agency

 [U.S. Environmental Protection Agency, 1999a; MCLG, 

maximum contaminant level goal; MCL, maximum 

contaminant level; mg/L, milligrams per liter; pCi/L, 

picocuries per liter; n/a, not applicable]

NATIONAL PRIMARY 

DRINKING-WATER REGULATIONS

Contaminant MCLG

(mg/L)

MCL

(mg/L)

Inorganic Chemicals

Barium 2 2

Fluoride 4 4

Nitrate (measured

 as Nitrogen)

10 10

Nitrite (measured 

 as Nitrogen)

1 1

Radionuclides

Gross Beta n/a 04 millirems

 per year

Gross Alpha n/a 15 pCi/L

Radium-226 and 

 -228 combined

n/a 05 pCi/L

Microorganisms

Viruses (enteric) 0 n/a

Table 7. Select secondary drinking-water 

regulations

 [U.S. Environmental Protection Agency, 1999b;

 mg/L, milligrams per liter]

NATIONAL SECONDARY 

DRINKING-WATER REGULATIONS

Contaminant Secondary standard

(mg/L)

Chloride 250

Fluoride 2

Iron 0.3

Manganese 0.05

pH 6.5-8.5

Sulfate 250

Total Dissolved Solids 500
38 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

were greater than the secondary drinking-water regulation 

maximum pH of 8.5.

Comparison of the results of analyses of samples 

collected in 1999 (table 4) to the analyses of samples 

collected in the 1940’s through the early 1960’s (table 5) 

shows that the concentrations of major constituents in the 

aquifer have not changed appreciably during the past 

56 years. This is common in deep, confined aquifers, where 

the water is thousands of years old because of long flow 

paths from areas of recharge to areas of discharge. As noted 

previously, well SM Df 61 was not included in the discussion 

of water quality in the Aquia aquifer at NAS Patuxent River, 

even though the depth and water levels measured in that well 

are comparable to those of other wells screened in the Aquia 

aquifer. The chemistry of water at well SM Df 61 

(supposedly completed in the Aquia aquifer) is similar to 

that of water in wells completed in the Piney PointNanjemoy aquifer, possibly because (1) the well is screened 

in both aquifers, or (2) improper/faulty construction is 

allowing water from the Piney Point-Nanjemoy aquifer to 

move into the well. A mix-up of sample bottles, and/or 

sampling of a different well have been ruled out as possible 

explanations. The screened interval (580 to 600 ft below sea 

level) noted on the State of Maryland Well Completion 

Report is consistent with that of other wells screened in the 

Aquia aquifer. If the well was screened in both aquifers, 

then the water type would be expected to be a mixture of 

both water types. In this case, the water is similar to Piney 

Point-Nanjemoy aquifer water rather than a mixture of both 

aquifers. It is possible that the well was not properly 

constructed—Otton (1955, p. 120) reported that there were 

indications of ground water from the Piney Point-Nanjemoy 

aquifer possibly leaking into the Aquia aquifer. Otton 

suggested that this was due to improper construction of 

Aquia aquifer wells, whereby casing size was reduced 

through the Piney Point-Nanjemoy aquifer, and that this 

resulted in vertical movement of ground water through the 

packers or along the casings of the wells. This would also 

result in a mixing of waters, however. Further investigation 

of construction in this well is necessary to determine why the 

water is not similar to that of the Aquia aquifer. More water 

samples could be collected from the well, and further 

examination of the well with a down-hole video camera and/

or a caliper log might help determine whether there are 

construction problems, screened intervals through both 

aquifers, or a decrease in casing diameter through the Piney 

Point-Nanjemoy aquifer.

Water Quality of the Aquia Aquifer at Webster Outlying Field

USGS personnel collected water samples from two wells 

screened in the Aquia aquifer (SM Ff 35 and SM Ff 63) at 

WOLF on August 30–31, 1999. Although the water in the 

Aquia aquifer at WOLF is sodium-bicarbonate water, like 

the water in the Aquia aquifer at NAS Patuxent River, there 

are observable differences in the chemistry of the water at 

two facilities. These differences are probably due to 

chemical reactions between the water and the aquifer matrix 

that occur as the water moves downgradient from the NAS 

Patuxent River toward WOLF (Chapelle and Drummond, 

1983).

WOLF-Aquia aquifer waters are about 19 °C, the pH is 

8.6, specific conductance ranges from 562 to 645 μS/cm, 

hardness is 12 to 15 mg/L (as calcium carbonate), and the 

ANC ranges from 288 to 342 mg/L (as calcium carbonate). 

Neither sample had a detectable concentration of nitrite plus 

nitrate. The ground water contained about 140 mg/L of 

sodium, 3 mg/L of calcium, 2 mg/L of magnesium, 8 mg/L 

of potassium, 2 mg/L of chloride, 12 mg/L of silica, 11 mg/L 

of sulfate and 1.5 mg/L of fluoride.

The Radon-222 values ranged from 434 to 506 pCi/L. 

Gross Beta values were about 5 pCi/L, Radium-228 was 

about 0.40 ± 0.30 pCi/L, and all other radionuclide values 

were lower than the detection limits.

As with the other water samples collected in 1999, the 

chemistry of the samples from the Aquia aquifer at WOLF 

was compared to USEPA drinking-water MCLs, MCLGs, 

and secondary drinking-water regulations. Concentrations 

of constituents in the samples did not exceed the primary 

MCLs or MCLGs. At well SM Ff 63, the fluoride 

concentration of 1.8 mg/L is close to, but does not exceed, 

the secondary drinking-water regulation concentration of 

2 mg/L. The pH values were greater than the secondary 

drinking-water regulation maximum pH of 8.5.

Comparison of Water Types in the Piney Point-Nanjemoy 

and Aquia Aquifers

The chemistry of the waters in the Piney Point-Nanjemoy 

and Aquia aquifers differs within the study area. Water in 

the Piney Point-Nanjemoy aquifer is primarily a calciummagnesium-sodium-bicarbonate type, and water in the Aquia 

aquifer is a sodium-bicarbonate type. Water in the Aquia 

aquifer at NAS Patuxent River can be distinguished from 

water in the Aquia aquifer at WOLF on the basis of 

significant differences in specific conductance, ANC, and 

concentrations of sodium, sulfate, boron, and iodide. The 

present-day values and the differences in the water types of 

the two aquifers (table 4) are similar to those of historical 

water samples reported by Bennett (1944) and Chapelle and 

Drummond (1983) (table 5). Although not all of the same 

constituents were analyzed in the 1940’s, and some of the 

methods and/or detection limits may have been different, the 

unique water types can be identified.

A qualitative comparison of the data in table 4 show that 

several concentrations of constituents distinguish Piney 

Point-Nanjemoy ground water from Aquia ground water, and 

the Aquia ground water at NAS Patuxent River from the 

Aquia ground water at WOLF. The distinguishable 

characteristics between the Piney Point-Nanjemoy ground 

water and the Aquia ground water at the NAS Patuxent River 

are also supported by the historical data (table 5).
Ground-Water Quality 39

The differences in water chemistry of the aquifers can be 

summarized as follows:

• The pH of the sample from the Piney Point-Nanjemoy 

aquifer is slightly less than the pH of representative 

ground-water samples from the Aquia aquifer 

(8.0 and 8.9, respectively).

• ANC in the Aquia aquifer at WOLF (300 mg/L) is 

about twice that in the Aquia aquifer (160 mg/L) and 

in the Piney Point-Nanjemoy aquifer (140 mg/L) at 

NAS Patuxent River.

• Specific conductance of the water in the Aquia aquifer 

at WOLF (600 μS/cm) is almost double the specific 

conductance in the Piney Point-Nanjemoy aquifer 

(290 μS/cm) and the Aquia aquifer at NAS Patuxent 

River (310 μS/cm).

• The concentration of calcium in the sample from the 

Piney Point-Nanjemoy aquifer (22 mg/L) is about 

eight times higher than the calcium concentration 

representative of the Aquia aquifer samples (3 mg/L).

• The concentration of magnesium in the Piney PointNanjemoy aquifer (11 mg/L) is also notably different 

from the concentration of magnesium in the Aquia 

aquifer, both at NAS Patuxent River and at WOLF 

(1.5 mg/L).

• The concentration of sodium in the Piney PointNanjemoy aquifer (15 mg/L) is one-third lower than 

the concentration of sodium in the Aquia aquifer at 

NAS Patuxent River (65 mg/L). The concentration of 

sodium in the Aquia aquifer at WOLF (140 mg/L) is 

twice that of the concentration of sodium in the Aquia 

aquifer at NAS Patuxent River (65 mg/L).

Saltwater Intrusion

Saltwater intrusion can contaminate an aquifer in coastal 

areas. If the water becomes too brackish, it becomes 

unusable without treatment. The location of the Piney PointNanjemoy and Aquia aquifers puts them at risk for saltwater 

intrusion as ground-water withdrawals continue. One 

possible source of saltwater intrusion is downward leakage 

from the Chesapeake Bay. A second possible source is 

updip migration of the freshwater/saltwater interface. The 

following discussion compares constituents in the ground 

water that indicate the presence of saltwater with concentrations of those constituents in samples collected in 1999.

High total dissolved solids (TDS), high concentrations of 

sulfate, calcium to magnesium (Ca:Mg) ratios equal to 1.0, 

sodium to chloride (Na:Cl) ratios equal to 2 (Piper, 1953), 

and chloride to bromide (Cl:Br) ratios equal to 287.5 can 

indicate seawater intrusion. Freshwater has less than 

1,000 mg/L TDS, brackish waters have 1,000 to 

10,000 mg/L TDS, saline waters have 10,000 to 

100,000 mg/L TDS, and brines have greater than 

100,000 mg/L TDS (Faure, 1991, p. 443). All of the water 

samples collected in 1999 from both the Piney PointNanjemoy and Aquia aquifers were freshwater samples, 

with a median TDS of 240 mg/L and a maximum TDS of 

395 mg/L at well SM Ff 63. Concentrations of sulfate in the 

samples were less than 15 mg/L. Concentrations of sulfate 

in seawater are usually greater than 2,000 mg/L (Hem, 1992, 

p. 205); (Drever, 1988, p. 266). Ratios of Ca:Mg in groundwater samples collected in 1999 were greater than 1.7. For 

the Piney Point-Nanjemoy aquifer at NAS Patuxent River, 

the Na:Cl ratio was 4.0; in the Aquia aquifer at NAS 

Patuxent River, the ratio was 30.0; and at WOLF, the ratio 

was 12.0. The Cl:Br ratios were close to those of seawater 

for wells SM Df 14 (237.5), SM Dg 5 (220.0), and SM Dg 15 

(200) (table 8).

The presence of connate water, water that is trapped 

within the sediments as they are deposited, can make an 

aquifer unsuitable as a source of water supply. In some 

cases, when the sediments are deposited in a marine 

environment, the trapped water can be seawater (Faure, 

1991, p. 354). The Na:Cl ratios of the water samples 

collected in this study are higher than ratios commonly 

found in connate seawater (0.5). Connate water is also 

indicated by a relative abundance of barium and iodide 

(24 to 142 mg/L, and 30 to 80 mg/L, respectively) (Piper, 

1953). The maximum concentrations of these two 

constituents in the samples collected in 1999 were only 

0.002 mg/L of barium and 0.013 mg/L of iodide (table 8).

Therefore, there is no evidence of saltwater intrusion 

either from seawater or from connate water at the NAS 

Patuxent River in either the Piney Point-Nanjemoy aquifer or 

the Aquia aquifer. At WOLF, the concentrations of sulfate 

and sodium are higher than at NAS Patuxent River, but are 

not as high as those typically present in seawater or connate 

water.
40 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland Table 8. Comparison of average sea water and average connate water to ground-water samples collected in 1999 from the Piney Point-Nanjemoy aquifer, the Aquia aquifer at Naval Air Station Patuxent River, and the Aquia aquifer at Webster Outlying Field, Maryland [NAS, Naval Air Station; WOLF, Webster Outlying Field; mg/L, milligrams per liter; <, less than; >, greater than; 

E, estimated; n/a, not applicable]

AQUIFER

Average Sea Water Average Connate Water Piney Point-Nanjemoy (1 sample) Aquia at NAS Patuxent River (Range of 5 samples) 

A

A. Water from well SM Df 61 is not included in “Aquia at NAS Patuxent River” samples because of anomalous chemistry which is discussed in the text.

Aquia at WOLF(2 samples)

Total dissolved solids (mg/L) 1,000 

B

B. Faure, 1991.

n/a 211 190–202 343, 395

Sulfate (mg/L) 2,000 C, D

C. Hem, 1992.

D. Drever, 1988.

n/a 7.7 <0.1–6.3 11, 11

Calcium : Magnesium (mg/L : mg/L) 1 E

E. Piper, 1953.

n/a 2 2.1–2.4 1.7, 2.2

Sodium : Chloride (mg/L : mg/L) 2 

E 0.5 

B 4.5 30.9–39.3 76.5, 84.4

Chloride : Bromide (mg/L : mg/L) 287.5 F

F. Waterloo Hydrologic, 1999.

n/a 237.5 114–220 100, 121

Barium (mg/L) n/a 24–142 

E

E 0.5

E 0.47–1.3 1.6, 2.1

Iodide (mg/L) n/a 30–80 

E 0.006 0.005–0.008 0.010, 0.013
Summary and Conclusions 41

Summary and Conclusions

The Piney Point-Nanjemoy aquifer and the Aquia aquifer 

are sources of water supply for the Naval Air Station 

Patuxent River and Webster Outlying Field in southern 

Maryland. At Naval Air Station Patuxent River, the top of 

the Piney Point-Nanjemoy aquifer is 220 to 255 feet below 

sea level, the thickness is 50 to 70 feet, and the hydraulic 

conductivity is approximately 2 feet per day. At Webster 

Outlying Field, the top of the Piney Point-Nanjemoy aquifer 

is approximately 260 feet below sea level, the thickness is 

65 feet, and the hydraulic conductivity is approximately 

2 feet per day. At Naval Air Station Patuxent River, the top 

of the Aquia aquifer is 450 feet below sea level, the thickness 

is 100 to 145 feet, and the hydraulic conductivity is 6 to 10 

feet per day. At Webster Outlying Field, the top of the Aquia 

aquifer is 470 feet below sea level, the thickness is 50 feet, 

and the hydraulic conductivity ranges from about 6 to 10 

feet per day. Both aquifers are continuous throughout Naval 

Air Station Patuxent River and Webster Outlying Field, 

consistent with the regional hydrogeologic framework.

Ground-water withdrawal from the Piney PointNanjemoy and Aquia aquifers at the Naval Air Station 

Patuxent River began in 1942. In 2000, an average of 460 

gallons per day was pumped from the Piney Point-Nanjemoy 

aquifer, an average of 742,500 gallons per day was pumped 

from the Aquia aquifer at the main facilities at Patuxent 

River, and an average of 28,000 gallons per day was pumped 

from the Aquia aquifer at Webster Outlying Field. Water 

levels in the Piney Point-Nanjemoy aquifer at Naval Air 

Station Patuxent River have remained relatively constant 

over the past 49 years, at approximately 20 feet below sea 

level. Ground-water levels have decreased approximately 40 

to 80 feet in the Aquia aquifer during the past 15 to 20 years. 

At the Naval Air Station Patuxent River, water levels were 70 

feet below sea level in the Aquia aquifer in 1983, and 115 to 

150 feet below sea level in January 2000. At Webster 

Outlying Field, Aquia aquifer water levels were 37 feet 

below sea level in 1984, and 80 feet below sea level in 

December 1999. The decrease in water levels is most likely 

due to increased withdrawal outside of the air station 

boundaries in response to growing public water-supply needs 

in St. Marys and Calvert Counties, Maryland.

Two main types of ground water are present in the study 

area: calcium-magnesium-sodium-bicarbonate water in the 

Piney Point-Nanjemoy aquifer, and sodium-bicarbonate 

water in the Aquia aquifer. Water in the Aquia aquifer can 

be separated into two sub-types based on significant 

differences in specific conductance, acid-neutralizing 

capacity, sodium concentration, sulfate concentration, boron 

concentration, and iodide concentration observed at Naval 

Air Station Patuxent River and Webster Outlying Field. No 

evidence of saltwater intrusion, either from seawater or 

connate water, was observed in any of the ground-water 

samples collected in either area.

References Cited

Achmad, Grufron, and Hansen, H.J., 1997, 

Hydrogeology, model simulation, and water-supply 

potential of the Aquia and Piney Point-Nanjemoy 

Aquifers in Calvert and St. Mary’s Counties, Maryland: 

Maryland Geological Survey Report of Investigations 

No. 64, 197 p.

Bennett, R.R., 1944, Ground-water resources at the Naval 

establishments in the Solomons-Patuxent River area, 

Maryland: U.S. Geological Survey Open-File Report, 

35 p.

Chapelle, F.H., Drummond, D.D, and Curley, Tracey, 

1981, Map showing the potentiometric surface of the 

Aquia Aquifer, May 19–23, 1980: U.S. Geological 

Survey Open-File Report 81–416, 1 p.

Chapelle, F.H., and Drummond, D.D., 1983, 

Hydrogeology, digital simulation, and geochemistry of 

the Aquia and Piney Point-Nanjemoy Aquifer System in 

Southern Maryland: Maryland Geological Survey 

Report of Investigations No. 38, 100 p.

Curtin, S.E., Andreasen, D.C., and Mack, F.K., 1993, 

Potentiometric surface of the Aquia Aquifer in Southern 

Maryland, September 1991: U.S. Geological Survey 

Open-File Report 93–652, 1 p.

_____ 1996, Potentiometric surface of the Aquia Aquifer in 

Southern Maryland, September 1995: U.S. Geological 

Survey Open-File Report 96–620, 1 p.

_____ 1997, Potentiometric surface of the Aquia Aquifer in 

Southern Maryland, September-October 1996: U.S. 

Geological Survey Open-File Report 97–788, 1 p.

_____ 1999, The difference between the potentiometric 

surfaces of the Aquia Aquifer, September 1982 and 

September 1997 in Southern Maryland: U.S. Geological 

Survey Open-File Report 99–81, 1 p.

_____ 1999, Potentiometric surface of the Aquia Aquifer in 

Southern Maryland, September 1997: U.S. Geological 

Survey Open-File Report 99–82, 1 p.

Curtin, S.E., Mack, F.K., and Andreasen, D.C., 1994, 

Potentiometric surface of the Aquia Aquifer in 

Southern Maryland, September 1993: U.S. Geological 

Survey Open-File Report 94–390, 1 p.

_____ 1995, Potentiometric surface of the Aquia Aquifer in 

Southern Maryland, September 1994: U.S. Geological 

Survey Open-File Report 95–743, 1 p.

Darton, N.H., 1896, Artesian well prospects in the 

Atlantic Coastal Plain region: U.S. Geological Survey 

Bulletin 138, 232 p.

Drever, J.I., 1988, The geochemistry of natural waters 

(2d ed.): Englewood Cliffs, New Jersey, Prentice Hall, 

266 p.

Faure, Gunter, 1991, Principles and applications of 

inorganic geochemistry: New York, New York, 

Macmillan Publishing Company, 626 p.
42 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

Fishman, M.J., and Friedman, L.C., eds., 1989, Methods 

for determination of inorganic substances in water and 

fluvial sediments: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 5, chap A1, 545 p.

Hem, J.D., 1992, Study and interpretation of the chemical 

characteristics of natural water (3rd ed.): U.S. 

Geological Survey Water-Supply Paper 2254, 263 p.

Mack, F.K., Andreasen, D.C., Curtin, S.E., and 

Wheeler, J.C., 1987, Potentiometric surface of the 

Aquia Aquifer in Southern Maryland during the fall of 

1986: U.S. Geological Survey Water-Resources 

Investigations Report 87–4214, 1 p.

_____ 1989, Potentiometric surface of the Aquia Aquifer in 

Southern Maryland during the fall of 1987: U.S. 

Geological Survey Water-Resources Investigations 

Report 89–4012, 1 p.

_____ 1990, Potentiometric surface of the Aquia Aquifer in 

Southern Maryland during September 1998: U.S. 

Geological Survey Water-Resources Investigations 

Report 90–4037, 1 p.

Mack, F.K., Curtin, S.E., Andreasen, D.C., and 

Wheeler, J.C., 1991, Potentiometric surface of the 

Aquia Aquifer in Southern Maryland, September 1989: 

U.S. Geological Survey Water-Resources Investigations 

Report 91–4094, 1 p.

_____ 1992, Potentiometric surface of the Aquia Aquifer in 

Southern Maryland, September 1990: U.S. Geological 

Survey Open-File Report 92–459, 1 p.

Mack, F.K., Wheeler, J.C., and Curtin, S.E., 1983, 

Preliminary map showing the potentiometric surface 

of the Aquia Aquifer in Southern Maryland, 

September 1982: U.S. Geological Survey Open-File 

Report 83–929, 1 p.

Mack, F.K., Wheeler, J.C., Curtin, S.E., and 

Andreasen, D.C., 1985, Preliminary map showing the 

potentiometric surface of the Aquia Aquifer in Southern 

Maryland, September 1984: U.S. Geological Survey 

Water-Resources Investigations Report 85–4338, 1 p.

_____ 1987, The potentiometric surface of the Aquia 

Aquifer in Southern Maryland, September 1985: 

U.S. Geological Survey Water-Resources Investigations 

Report 87–4029, 1 p.

Maloney, T.J., Ludke, A.S., and Krizman, T.L., 1994, 

Quality-assurance results for routine water analysis in 

U.S. Geological Survey laboratories, water year 1991: 

U.S. Geological Survey Water-Resources Investigations 

Report 94–4046, 144 p.

Marcoa Publishing, Inc., 1998, Patuxent River Naval Air 

Station, where the future of naval aviation begins: San 

Diego, California, [variously paged.]

Mignery, A.C., 1994, Organic carbon-14 in coastal plain 

aquifers (synopsis), in Helz, G.R., Fiscal Year 1993 

Annual Report: College Park, Maryland, University of 

Maryland, Water Resources Research Center, p. 17–27.

Naval Air Station Patuxent River, Naval Air Station 

History: accessed December 4, 2000, at URL 

http://nas.nawcad.navy.mil

Otton, E.G., 1955, Ground-water resources of the 

Southern Maryland Coastal Plain: Maryland Department 

of Geology, Mines, and Water Resources Bulletin 15, 

347 p.

Pritt, J.W., and Raese, J.W., eds., 1995, Quality assurance/

quality control manual—National Water-Quality 

Laboratory: U.S. Geological Survey Open-File Report 

95–443, 35 p.

Piper, A.M., and Garrett, A.A., and others, 1953, Native 

and contaminated ground waters in the Long BeachSanta Ana Area, California: U.S. Geological Survey 

Water-Supply Paper 1136, 320 p., 11 pls.

Smigaj, M.J., Starsoneck, R.J., Saffer, R.W., and 

Marchand, E.H., 1999, Water resources data—

Maryland and Delaware, water year 1998, Volume 2, 

Ground-Water Data: U.S. Geological Survey 

WDR-MD–DE–98–2, 562 p.

U.S. Environmental Protection Agency, 1996, EOA 

Information Collection Rule microbial laboratory 

manual: Washington, D.C., EPA/600/R–95/178.

U.S. Environmental Protection Agency, 1999a, Code of 

Federal Regulations 40, Part 141—National Primary 

Drinking Water Regulations: Washington, D.C., 

Office of the Federal Register, [variously paged.]

_____ 1999b, Code of Federal Regulations 40, Part 143—

National Secondary Drinking Water Regulations: 

Washington, D.C., Office of the Federal Register, 

[variously paged.]

_____ 1999c, Proposed radon in drinking water rule: 

Technical Factsheet, EPA 815–F–99–006, 6 p.

Vroblesky, D.A., and Fleck, W.B., 1991, Hydrogeologic 

framework of the Coastal Plain of Maryland, Delaware, 

and the District of Columbia: U.S. Geological Survey 

Professional Paper 1404–E, 45 p.

Waterloo Hydrologic, Inc., 1999, AquaChem version 3.7 

for Windows 95/98/NT, Aqueous geochemical analysis, 

plotting and modeling: Ontario, Canada, Lukas 

Calmbach and Waterloo Hydrogeologic, Inc., 184 p.

Weigle, J.M., and Webb, W.E., 1970, Southern Maryland 

records of selected wells, water levels and chemical 

analyses of water: Maryland Geological Survey 

Basic Data Report No. 4, 48 p.

Wilde, F.D., Radtke, D.B., Gibs, J., and Iwatsubo, R.T., 

eds., 1998, National field manual for the collection of 

water-quality data: U.S. Geological Survey Techniques 

of Water-Resources Investigations, book 9, Handbooks 

for Water-Resources Investigations, [variously paged.] 

Williams, J.F., III, 1979, Simulated changes in water level 

in the Piney Point Aquifer in Maryland: Maryland 

Geological Survey Report of Investigations No. 31, 49 p.
Appendixes 43

APPENDIXES A THROUGH C FOLLOW
44 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Appendixes 45
46 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Appendixes 47
48 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland
Appendixes 49
50 Hydrogeology and Ground-Water Quality, Naval Air Station Patuxent River, Maryland

Appendix B. Laboratory-analyzed constituents and methods

[ICP, inductively coupled plasma; IC, ion chromatography; ASF, automated-segmented flow;

NWQL, National Water-Quality Laboratory; LC, lab code]

Constituent Laboratory Method NWQL Schedule or Lab Code number

Calcium ICP 1011

Potassium Atomic Absorption, flame 1011

Sulfate IC 1011

Chloride IC 1011

Bromide Colorimetry 1011

Magnesium ICP 1011

Silica ICP 1011

Manganese ICP 1011

Fluoride Colorimetry, ion-selective electrode 1011

Iron ICP 1011

Gross Alpha Gross Alpha as Thorium-230, by Residue Procedure 456

Gross Beta Gross Beta as Cesium-137, by Residue Procedure 456

Uranium Direct laser induced phosphorescence 1385

Tritium Electrolytic enrichment and liquid scintillation LC 624

Radium-226 Planchet counting and precipitation LC 799

Radium-228 Radiochemical separation and beta counting LC 1364

Radon-222 Liquid scintillation LC 1369

Nutrients Colorimetry, ASF, cadmium reduction diazotization LC 1975

Barium ICP LC 641

Boron ICP LC 2354

Iodide Colorimetry, ASF, ceric-arsenious LC 1202
Appendixes 51

 

Appendix C. Microorganisms and analytical methods for sample analyses from wells

 SM Df 61 and SM Df 98

[USEPA, U.S. Environmental Protection Agency; mL, milliliters; °C, degrees Celsius]

Microorganism Analytical Method

Most Probable Number (MPN) Assay for culturable viruses USEPA, Information Collection Rule (USEPA 600/R-95/178)

Molecular Assay for virus groups USEPA 600/R-95/178 A

Somatic Coliphage USEPA 600/R-95/178 A

Male-Specific Coliphage USEPA 600/R-95/178 A

Clostridium perfringens Membrane filtration

Enterococci Membrane filtration

Escherichia coli (density per 100 mL) Colilert assay

Fecal Streptococci (density per 100 mL) Membrane filtration at 35 °C for 48 hours

Fecal Coliform (density per 100 mL) Membrane filtration at 44.5 °C for 24 hours

Total Coliform (density per 100 mL) Membrane filtration

A.

 U.S. Environmental Protection Agency, 1996.