The shallow-aquifer system in Duval County, Florida ( FGS: Report of investigations 59 )

STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Randolph Hodges, Executive Director

DIVISION OF INTERIOR RESOURCES
Robert 0. Vernon, Director

BUREAU OF GEOLOGY
C. W. Hendry, Jr., Chief

Report of Investigations No. 59

THE SHALLOW-AQUIFER SYSTEM
IN
DUVAL COUNTY, FLORIDA

By
Roy W. Fairchild

Prepared by the
U.S. GEOLOGICAL SURVEY
in cooperation with the
CITY OF JACKSONVILLE
DUVAL COUNTY
and the
FLORIDA DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY

TALLAHASSEE, FLORIDA
1972

DEPARTMENT
OF
NATURAL RESOURCES

REUBIN O'D. ASKEW
Governor

RICHARD (DICK) STONE
Secretary of State

THOMAS D. O'MALLEY
Treasurer

FLOYD T. CHRISTIAN
Commissioner of Education

ROBERT L. SHEVIN
Attorney General

FRED 0. DICKINSON, JR.
Comptroller

DOYLE CONNER
Commissioner of Agriculture

W. RANDOLPH HODGES
Executive Director

LETTER OF TRANSMITTAL

Bureau of Geology
Tallahassee
November 23, 1971

Honorable Reubin O'D. Askew, Chairman
Department of Natural Resources
Tallahassee, Florida

Dear Governor Askew:

The Bureau of Geology is publishing Report of Investigations No. 59, entitled
"The Shallow Aquifer System in Duval County, Florida," by Roy W. Fairchild,
U.S. Geological Survey hydrologist. This report presents specific data pertaining
to the shallow-aquifer system in Duval County.

One of the most important resources of the Jacksonville-Duval area is a large
supply of potable ground water, derived mainly from the deep Floridan aquifer.
However, due to increased water demands, the shallow-aquifer system has gained
recognition as a potential source of fresh water.

The shallow-aquifer system, recharged by local rainfall, yields 10 to 25 million
gallons per day. This water is used mainly for domestic purposes.

Sincerely yours,

C. W. Hendry, Jr., Chief

Completed manuscript received
November 23, 1971
Printed for the Florida Department of Natural Resources
Division of Interior Resources
Bureau of Geology
by St. Petersburg Printing Company
St. Petersburg, Florida

Tallahassee
1972

iv

CONTENTS

Abstract .......................

Introduction ....................
Purpose and scope ..............

Location and extent of area ........

Previous work .................
Climate .....................

Topography and drainage .........

Well-numbering system ...........
Acknowledgments ..............

Shallow-aquifer system .............

Geology .....................
Hawthorn Formation ..........

Upper Miocene or Pliocene deposits
Pleistocene and Holocene deposits .
Hydrologic characteristics .........
Water levels and water-level fluctuati
Area of flow .............
Recharge ..................

Discharge ..................
Springs ................
Evapotranspiration .........

Pumpage ................
Downward percolation ......

Quality of water ...............
Hardness ..................
Dissolved solids ..............
Chloride ..................
Iron .....................
Hydrogen sulfide .............
Water use ....................
Well-construction practices ..........
Additional studies needed ...........

Conclusions ....................
References .....................

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ons

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ILLUSTRATIONS

Figure

1. Map of Duval County showing the location of the study area,
principal features, and the location of the wells used in

this study ....................................
2. Bar graph showing annual rainfall at Jacksonville (Imeson

Airport) 1938-68 ...............................
3. Bar graph showing monthly rainfall at Jacksonville (Imeson
Airport) 1967-68 ................................
4. Explanation of well-numbering system .................

5. Map of Duval County showing the thickness of the sediments
overlying the Ocala Limestone of the Floridan aquifer ......

Page

............. 3

.............. 6

.............. 7

. . . .. 10

. . . .. 19

Figure
6. Lithologic and gamma logs of a typical shallow well in
Duval County (well 302915N0814215.1) .............

Page

................ 23

7. Generalized geologic sections of the shallow-aquifer system
in Duval County ............................................. 25
8. Map of Dural County showing the potentiometric surface of
the shallow-aquifer system and the area of flow in May 1969 ................ 27
9. Graphs showing the relation of ground-water levels in wells
in northeast Duval County and the rainfall at Jacksonville
Weather Bureau, Imeson Airport ................................... 28
10. Graphs of rainfall and ground-water levels at Naval Air
Station, Jacksonville ........................................... 29
11. Graph showing the relation of hardness, dissolved solids,
and iron content to depth of water from the shallow-aquifer
system .................................................... 40
12. Generalized distribution of hardness of water in wells that
tap the shallow-aquifer system in Duval County ......................... 41
13. Generalized distribution of dissolved solids in water from
wells that tap the shallow-aquifer system in Duval County .................. 42
14. Map of Duval County showing the distribution of chloride in
water from the shallow-aquifer system ............................... 43
15. Map of Duval County showing the approximate areal distribution
of iron in water from the shallow-aquifer system ........................ 45

TABLES

Table
1. Estimated number of wells and daily withdrawal from the
shallow-aquifer system and the Floridan aquifer in Duval
County .....................................
2. Monthly rainfall records for 9 stations in and around the
Duval County area ..............................
3- List of recognized Pleistocene marine terraces in northeast
Florida .....................................
4. Record of wells used in study of shallow-aquifer system .....
5. Stratigraphic units making up the shallow-aquifer system in
Duval County .................................
6. Hawthorn and post-Hawthorn stratigraphy in northeast
Florida .....................................
7. Chemical analyses of water from the shallow aquifer in
Duval County, Florida ...........................
8. Iron content in water from shallow wells in Duval County .
9. Water-quality characteristics and their effects ............
10. U. S. Public Health Service drinking-water standards ........

Page

2

5

8
.12-17

............ 20

............ 24

............ 34-35
. . . .. 36
. . . .. 37
. . . .. 38

THE SHALLOW-AQUIFER SYSTEM
IN
DUVAL COUNTY, FLORIDA

ABSTRACT

One of the most important natural resources of the Jacksonville-Duval area
in northeast Florida is a large supply of potable ground water. This water is
derived mainly from deep wells that tap the Floridan aquifer. However, because
of increased growth of population and industry in the area in the past 30 years,
the shallow-aquifer system has gained recognition as a potential source of fresh
water supply to supplement that from the deeper Floridan aquifer.
The shallow-aquifer system consists of permeable beds of sand, shell, and
limestone within the following stratigraphic units; the upper part of the
Hawthorn Formation (middle Miocene age), the upper Miocene or Pliocene
deposits, and the Pleistocene and Holocene deposits.
The aquifer is recharged by local rainfall. The amount of recharge from
rainfall is estimated to be from 10 to 16 inches per year and varies from place to
place within the area. Discharge is by pumpage, outflow from springs, downward
percolation, and by evapotranspiration. From 40,000 to 50,000 wells penetrate
the shallow aquifer in Duval County and discharge 10 to 25 million gallons per
day. These wells range in depth from 20 to 200 feet and are 1% to 6 inches in
diameter; the most common diameter is 2 inches.
In the west central part of Duval County the potentiometric surface of the
shallow-aquifer system is above land surface all or part of the year and shallow
wells will flow.
With only a few exceptions, wells that penetrate the shallow-aquifer
system yield water of good quality. The hardness of the water averages 185
milligrams per liter and ranges from 10 to 1,900 milligrams per liter. The iron
content ranges from 0 to 2.8 milligrams per liter and in places causes staining of
clothing and plumbing fixtures.
Water from the shallow-aquifer system is used primarily for domestic
purposes, particularly in the rural areas and areas not served by private or public
utilities. Other uses for the water consist of refrigerator cooling, industrial,
agricultural, and schools.

BUREAU OF GEOLOGY

INTRODUCTION
PURPOSE AND SCOPE

The deep artesian wells that penetrate the Floridan aquifer constitute the
major source of fresh water in Duval County. However, a substantial quantity of
water is also obtained from shallow wells (20 to 200 feet deep) that penetrate
the shallow-aquifer system (see table 1). Because of increased growth in
population and industry in the Jacksonville area, the demands for fresh water
have increased. As a result, the shallow aquifer is becoming more and more
important as an additional source of potable water.
The purpose of this report is to describe the geologic and hydrologic
characteristics of the shallow-aquifer system, its thickness and extent, the
amount of recharge to and discharge from the aquifer, and the quality of the
water and how it is used. The study was made in an effort to determine the
potential of the shallow aquifer as a primary or supplemental source of water
and to supply background information for future studies to appraise the total
water resources in the area.

LOCATION AND EXTENT OF AREA

Duval County is in northeastern Florida, lies between 300 06' and 300 35'
north latitudes and extends eastward from 820 03' west longitude to the
Atlantic Ocean, and occupies about 840 square miles (figure 1). Most of Duval
County is within the corporate limits of the Consolidated City of Jacksonville.

Table 1. Estimated number of wells and daily withdrawal
from the shallow-aquifer system and the
Floridan aquifer in Duval County.1

Range in Estimated
diameter withdrawal
No. of wells of wells (1960)
Shallow-water 40,000- 1-6 inches 10-25 mgd
aquifer 50,000

Deeper
Floridan 2,500-4,000 2-20 inches 175-190 mgd
aquifer
Leve and Goolsby, 1969

abUo m = ah w I I
STf tM ri eiboloII Tum 23 M to 70g 0

Pl Wbuim"amTO toI1t00lf \ll
\ y\ W "no^ 100 to 170 11M
aboa imm Ms hed I
0tol00M
S aundlln gnsaubu I0 oIoh

ST. JOHNS CO. I -L

8- *10' e20oo 45' 30 61-20
Figure 1. Map of Duval County showing the location of principal features in the area and the location of the wells used in
this study.

BUREAU OF GEOLOGY

PREVIOUS WORK

Reports of previous investigations of the ground-water resources of the
area generally are confined to discussions of the Floridan aquifer. Reports by
Derragon (1955) and Leve (1961 and 1966) include brief descriptions and
discussions of the shallow aquifers in northeastern Florida. Leve and Goolsby
(1969) present quantitative information regarding the use of water from shallow
wells.
The geology of the shallow formations underlying northeastern Florida is
discussed by Cooke (1945), Vernon (1951), Puri and Vernon (1964), and Leve
(1966). The reports by Leve (1966) and Puri and Vernon (1964) include
generalized cross sections showing the formations which make up the
shallow-aquifer system.

CLIMATE

Duval County has a humid, semitropical climate. The average annual
rainfall is about 54 inches, most of which occurs in the late spring and early
summer. Winters are mild and dry, with occasional frost from November through
February.
The amount of rainfall varies from place to place within the county;
thunderstorms may yield several inches of rain in one part of the county and
only a trace in other parts. Table 2 shows the monthly rainfall totals in 1968 for
nine rainfall stations in and around the Duval County area. As shown in table 2,
rainfall for the year ranged from nearly 43 inches at Mayport Naval Air Station
to more than 57 inches at Cecil Field Naval Air Station. Figure 2 shows the
variations in yearly rainfall at Jacksonville's Imeson Airport, 1938-68. The total
annual rainfall at Jacksonville for the period 1938-68 ranged from 36.83 inches
in 1954 to 7737 inches in 1947, and averaged 53.50 inches. Rainfall was
approximately 4 inches below average in 1967 and was about average in 1968.
Figure 3 shows the monthly rainfall at Jacksonville's Imeson Airport,
1967-68; the greatest rainfall occurred during June, July, and August of both
years.

Table 2. Monthly rainfall records for 9 stations in and around the Duval County area.

Monthly Rainfall Totals, Inches, 1968
Station J F M A M J J A S O N D Total

1 0.60 2.03 0.73 1.02 2.77 8.81 5.57 11.28 1.58 5.30 2.08 0.73 42.50
2 .56 3.08 .91 1.58 6.52 10.47 6.64 16.54 2.31 5.54 1.79 1.30 57.24
3 .65 1.07 .98 1.20 3.88 12.29 5.00 17.65 1.14 7.78 2.42 1.14 55.20
4 .82 3.05 1.20 .99 2.17 12.25 6.84 16.24 2.68 5.09 1.30 1.09 53.72
5 .86 1.76 .94 2.08 6.06 8.58 5.20 16.48 2.09 8.95 2.58 .92 56.50
6 .16 1.66 1.96 .31 4.45 7.96 3.86 10.93 1.99 7.56 1.98 1.39 44.21
7 1.05 1.55 .69 1.35 4.06 8.43 8.20 13.91 3.15 4.63 2.50 2.32 51.84
8 .98 2.82 1.37 .81 4.73 8.75 7.73 15.60 7.17 1.96 2.08 1.56 55.56
9 .76 2.01 .1.64 .49 5.53 5.08 11.29 17.21 1.46 3.80 1.99 1.15 52.41

Station Locations
1. Naval Air Station, Mayport
2. Naval Air Station, Cecil Field, Jacksonville
3. Naval Air Station, Jacksonville
4. U.S. Weather Bureau, Imeson Airport, Jacksonville
5. U.S. Weather Bureau, Jacksonville Beach
6. U.S. Weather Bureau, St. Augustine
7. U.S. Weather Bureau, Fernandinra Beach
8. U.S. Weather Bureau, Glen St. Mary
9. U.S. Weather Bureau, Starke

BUREAU OF GEOLOGY

Figure 2. Bar graph showing annual rainfall at Jacksonville (Imeson Airport),
1938-68.

REPORT OF INVESTIGATIONS NO. 59

I

k

0 rl' ~l l r A rcj''W lfZ r 196
J F M A M J J A S O N D
1967

Figure 3. Bar graph showing monthly rainfall at Jacksonville (Imeson
Airport), 1967-68.

IRS

Ibl

101

J F M A M J J A S O N D
1968

12

BUREAU OF GEOLOGY

TOPOGRAPHY AND DRAINAGE

The topography in Duval County is mostly low, gentle to flat, and
composed of a series of ancient marine terraces. The highest altitude is about
190 feet above msl (mean sea level) in the extreme southwest corner of the
county, along the eastern slope of a prominent topographic feature known as
'Trail Ridge." Trail Ridge is a remnant of the highest ancient marine terrace
(Coharie) in Duval County. The terraces trend parallel to the present Atlantic
shoreline and become progressively higher from east to west.
These terraces have been studied in considerable detail by Cooke (1945),
MacNeil (1950), Leve (1966), and Stringfield (1966). Table 3 lists the name,
characteristic altitude, and presumed age of each of the terraces, as recognized
by the above authors. Of those terraces listed, MacNeil (1950) recognized only
four; the Okefenokee at 150 feet, the Wicomico at 100 feet, the Pamlico at
25-35 feet, and the Silver Bluff at 8-10 feet. MacNeil's Okefenokee terrace
falls within the altitude range of Cooke's Sunderland terrace, but MacNeil
believes that the terrace is most prominent at the 150-foot level in Florida
and Georgia.

Table 3. List of Pleistocene marine terraces in northeast Florida
(after Cooke, 1945, MacNeil, 1950, Leve, 1966, Stringfield, 1966).

Characteristic
Name of Terrace elevation (feet) Presumed age
Hazlehurst 270 Aftonian inter-
(Not present in Duval Co.) glaciation
Coharie 215 Yarmouth inter-
Sunderland 170 glaciation

Wicomico 100 Sangamon inter-
Penholoway 70 glaciation
Talbot 42
Pamlico 25 Mid-Wisconsin
Silver Bluff 5 recession

The terraces play a significant role in determining the configuration of
the potentiometric surface of the shallow-aquifer system. The potentiometric
surface based on water levels in wells that penetrate the shallow-aquifer
system roughly follows the contour of the land surface. As a result, the
potentiometric surface is highest where the terraces are highest and lowest
where they are lowest. Also, the areas of flowing shallow wells roughly
follow, but are not confined to, the eastern edges of the Talbot and higher
terraces (fig. 1).

REPORT OF INVESTIGATIONS NO. 59

Surface drainage in the area is through the St. Johns and Nassau rivers
and their tributaries. The St. Johns River is tidal throughout its length in
Duval County, and the tributaries are tidal in their lower reaches. Drainage
is primarily controlled by the ancient marine terraces. Each terrace is
bounded along its east (seaward) edge by remnants of a beach ridge parallel
to the ancient shoreline. These ndges direct runoff so that the streams flow
parallel to the ancient shorelines. In the flat marshy areas of the
northeastern part of the county, drainage is sluggish and the streams form a
dendritic pattern. Because of the low relief over much of the area, drainage
divides are often difficult or impossible to define.

WELL-NUMBERING SYSTEM

The well-numbering system used to catalog wells in this report is that of
the Water Resources Division of the U. S. Geological Survey. It is based on
the location of wells within a 1-second grid of parallels of latitude and
meridians of longitude.
The number used to catalog wells is a 16-character number that defines
the latitude and longitude of the southeast corner of a 1-second quadrangle in
which the well is located. The first six characters of the well number include
the digits of the degrees, minutes, and seconds of latitude, in that order. The
six digits defining the latitude are followed by the letter N, which indicates
north latitude. The seven digits following the letter N give the degrees,
minutes, and seconds of longitude. The last digit, set off by a period from the
rest of the number, is assigned sequentially to identify wells inventoried
within a 1-second quadrangle.
An example of the well number is illustrated in figure 4. The
designation 275134N0815220.1 indicates the first well inventoried in the
1-second quadrangle bounded by latitude 27051'34" on the south and
longitude 081052'20'" on the east.
Table 4 is a list, with descriptions, of all wells used in the study of the
shallow-aquifer system in Duval County.

BUREAU OF GEOLOGY

S7* u** n* *4* 1* 8* 01*. o00
-- -

Figure 4. Explanation of well-numbering system.

Table 4. Record of wells used In study of shallow-squifer system.
Use or water: H. domestic: 1. Irrigation: N, Industrial: P, public supply; S, stock; T. Institutional: U. unused; Z, other. Major aquifer: IF.
FIdrldan: IH Hawthorn limestone: 2H. Hawthorn clayey sand and gravel; IN, non-artesian sand. Remarks: Florida Dureau of Geology
well.lug identification number.
CASING ALTI- DATE
LOCAL WELL CASING DIAM- USE TUDE- MAJOR WATER WATER
LOCATION WELL DEPTH DEPTH ETIR OF CF LSD AQUIFER LEVEL LEVEL
NUMBER (FT.I IFT.)I IN.I WATER IFT.I IFT.I fEAS. REMARKS
DUVAL COUNTY
......._ 1 1

30CE01N0813410.1 I
3CCE06N0813435.1
300815N0813S27.
3CCe25N0813C4C. .1
3CCe88NO8133C5.1
3CCe46N0813q15.1
3CC.851NOB13049. I
3CCes7NOeSI34A.4...
30C6!8N0803C56. I
3CCq23NO813524.1
3COS33NOS13725.
3CCS36N0813721.1
3CC;43N08133C4.1
3CC445NC813307.1
3CCS45NGO8133C7.2
3CC548N0813259.1
3004171NOe1374. i
3CICC3NOEL3645.1
301C53NOR1371C.l
301C NO0813622.1
J01ON0920115.1
3CII1ONOe2GIlS.2
30110N08014151. 1
301135N0814213.1
!01144NCq14138.1
301145N0813727.1
301154NCE 13458. I
3C1154NCe14521.1
301155C e1461C. I
3Cll!ShCE14125. 1
3011!9NCE14615.l
3C12ClhCE14654. 1
301213NCP14723.1
3C1213NCe14723.2
3C1214Ne084448. 1
3CI216NC.13541. 1
301216NCE15545.1
3C1217N9152CC.I1
301220NC8141C7.1
3C122PNC814620.1

CS 146
05 155
05-66
CS 17
CS L31
CS 147
CS 207
OS 16
CS 156

OS I
CS 24
CS 21
CS 230
CS 19
CS 148
C-5T
CS 130
CS 129
CS 76
CS 76A
OS-lq3
CS 27
C 126
OS 89
CS 124
0S 47
OS-12
CS 190
CS-48
CS 157
CS 25
CS 91
DS-164
CS 149
OS 15
CS-194
C-789
CS-195

12-68
3-6B
12-31
12-67
C1-68

12-67
12-68

12-67
12-67
12-67
12-67

3-55
10-69
1C-68

5-69
1C-67
8-40

1C-68
2-68
1-68

2-66
12-66
10-67
6-68

6-68
5-69
11-42
5-69

160

U

0

3464

02
0

\0

Tibir 4.- Meourd uf wel* u*wd iI iludy ur ltalluw uiulftr *ynIin. Culiinued

CASING ALTI- DATE
LOCAL WELL CASING PHIM- USE TUOE- MAJOR WATER WATER
LOCATION WELL DEPTH DEPTH ENTER OF OF LSD AQUIFER LOVEL LEVEL
NUMBER (FT.I IFTeI IINI WATER (FT.eI IFT. I EAS. REMARKS

DUVAL COUNTY
]O1230C081|46151 OS-BO 19 169 2 H 25 IN 3 6-68
301255NOO13710*2 O S 909 H 8
301306N0813221.1 0-406 1060 510 12 1< 45 IF *6 4-69
3013C0N01a4107, 0 161 1015 316 12 P 24 IF *46 7-50 W 514
301324NO0155006.l OS 142 125 2 70TO IN
301326N0814754.1 05 138 H 42 IN #6 12-68
301327N0813630.1 DS 123 -- *- 2 U 10 IN 5 10-60
301i33N0814043.1 OS 26 108 -* 6 U IS -- 4 IC-67
301334NO814452.1 05 79 IS5 -- 2 P 23 IN *S 6-6a
301338h0814828.1 05 29 72 2 I S4 IN 1 10-67
301331N08a1482.2 05 30 67 -* 2 U 54 -- 2 10-67
301340N0814754.1 05-202 60 -- 2 H s0 IN .- -.
301340N0815310. 0-222 960 431 10 P 80 IF 16 5-41
3C1342N08149001 S05 139 72 60 2 H 60 IN *4 12-68
301342NOB1531C.1 0 113 1303 48S 12 P 65 IF 28 11-56 M 4111
301345N0815310.1 0 328 950 572 12 P 75 IF 22 6-53 j
301347N0814218.1 0-65 987 400 12 P 5 IF 4 9-42 W 661
3D1347N0ol5SOs0. OS 94 64 -- 1 U 70 IN *1 6-68 0
301348N0814455.1 OS 76 150 -- H 22 IN *14 6-68
301346N0814621.o OS 206 160 e6 6 H 70 IN -.
3C1354N0815320.1 OS 143 136 -- 4 U 80 IN 7 11-68
301358N0013237.1 0-361 800 575 -- P 39 IF C 4-64
301400N0014450es 05 77 120 -- 2 N 22 IN *9 6-68
301401N0814626.1 05 86 51 -- 2 U 83 IN 16 7-66
3014CEN08156301. 05-172 120 -- 2 H 80 IN .
301435NO147CS.o 0-79 1082 500 8 P 75 IF 29 8-63
30144300814244. 05 88 165 -- H 7 IN -. .
3C140SN0814749. OS 107 100 -- 2 U 30 IN 2 7-68
30145ONO814802.1 S0-110 .. 40 IN -. .
301452N0814110.1 0-428 669 286 8 P -- IF *62 6-22
301454N0814754. 05S-72 68 -- 2 U 40 IN *19 4-68
301454N0814754.2 05 73 64 -- 2 U 40 !IN +1l 4-68
301455N0814720.1 OS C6 108 -- 2 H 80 IN 6 10-67
3C1455N0815355.2 0-66 780 502 8 1 80 IF -- W 731
301456NC813654.l 0 344 706 .. P 26 IF *13 5-66
3C145E8N015818.1 0-426 708 444 6 U 85 IF 31 4-69
301501N0814431.1 US 55 175 170 2 H 25 IN *6 3-68
301508N0014125.1 0-60 705 120 8 P 5 IF -- -- 159
301514N0815658.1 OS 96 107 -- 2 H 60 IN 4 6-68
301516N01235C.1 S0-189 112 -- 2 U 10 IN 13 5-69

Table 4.- Record of wells used In study of shallow aquifer system. Continued

CASING ALTI- DATE
LOCAL WELL CASING CI A- USE TUDE- MAJOR WATER WATER
LOCATION WELL DEPTH DEPTH ETFR OF OF LSO AQUIFER LEVEL LEVEL
NUMBER IFTel (FTIe (IN., WATER I(T.I (PIT. MEANS. REMARKS
DUVAL COUNTY

3C15270814512.1 0 286 1000 460 12 P 30 IF +7 5-62
301529NC813826.e 0 304 1187 757 10 P -- LF +31 3-65
301534NCe13656.1 C-62 739 538 8 N 25 IF *20 -25 H 161
301535MCE13453e. 05-69 57 57 2 h 15 IN 5 4-68
301535NC81379.1 05-64 84 73 -- N 25 IN 6 --
3C1!37NCE144L9.I 0-75 1302 488 8 P 10 IF +30 9-68
3C1540NC613713.1 05-62 37 -- 2 U 25 IN 3 3-68
3C154CNC813713.2 OS 62A 36 *- 1 U 25 IK 3 3-68
301551NC814157.I 129 (00 47C 4 H 9 IF +40 7-4C
301554NC814410.l CS-192 78 -- 2 H 10 IN +5 5-69

301555NC813641.1 OS-52 75 *- 2 U 25 IN 4 2-68
301555NC8137C3.1 DS 23 54 -- 2 U 25 IN 3 12-67
301602NC815C54.1 CS 5 146 -- 2 U 90 IH 10 IC-67
3C16C2NC815054.2 CS SA 140 -- 2 H 90 IH -- -
301612NO 14545.. DS 08 78 -- 2 U 65 LN 23 10-67
3C1632N0813348.1 OS-68 84 64 2 H 30 IN 5 4-68
301725N013921. 0-48 -- -- H 15 IF 416 5-66
301725N0815G45.1 254 750 433 10 N 85 IF 25 1-61
301726NO813715.l OS 28 58 -- I U 20 IN 14 12-67
3C113ChC820CCO.L CS 93 97 -- 2 S 85 IN 5 6-68
3C1737NC813437.1 0 281 1004 487 15 P 13 IF -- -
301737NC813447.1 0-88 675 4 H 27 IF +30 6-39
301738NC8136C8.1 05-1 245 -- 2 U IN 5 2-61 Z
301740NCe13629.1 DS 151 65 -- 2 H 10 IN -- -
301741hC812629.1 CS 75 144 105 2 H 10 IN 1 5-68
3G1743MC813625.I CS-2 68 -- 2 H -- IN 10 2-61
301745NC812623.1 DS 74 21 19 1 U -- IN 4 5-68
301745NC813630.1 053 s5 -- I U -- IN 13 2-61 r
301747NC813624.1 CS 203 55 -- 2 U 20 1h -- 11-66
301801NCE1242C.1 CS-208 168 100 2 H 18 2H -- -
3018CINC813e43.1 C34 1071 505 10 H 20 LF +30 3-39
3018CINC813843.2 C-54A C-34 1348 505 10 P 20 IF +30 3-39
3C18C3N0814426.1 CS 136 76 -- 2 U 25 IN 15 10-68
3C1EC4NC815C10.1 CS 98 -- S 70 IN +3 7-68
3018C7NC815654.1 DS 92 78 -- 2 U 80 IN 3 6-68
3018CeNC815825.1 C 413 716 460 E H 85 IF -- -- W 4202
301812NC815552.1 OS-197 100 -- 6 S 85 IN 5 5-69
301812N0815932.1 OS 137 135 TC 2 H 80 IN -- -
301O17NC813212.* CS-190 39 -- 2 U 42 IN 2 5-69
3C1817NC813749.1 0 425 2486 752 8 U -- IF -- 5-66

LOCATION

iTabl 4.- HI4 urd ufl well Ubwd In bludy of bililuw iluifolyf bini. L'uli| nud

CASING AL.TI- PATE
LOCAL WELL CASING 0IAM- USE IUDE- MAJOR MATER WATER
WELL OEPTH DFPl ETER OF OF LS0D AQUIFER LEVEL LEVEL
NUMBER IF T. I IFT.I L N,I WATER iFT.I (FT. N.45. REMARKS
DUVAL COUNTY

30111?NOe13749.2 CS 90
3018OBNOS610C7.1 OS ICI
30Le20NOBI900Tlo 05-99
3C1I2CNOelC07.2 CS 100c
301634NOa1393l 7.15 111

3Ci836NO813233.1 CS-37
3C1839NO813924.1 D-347 C-27
ICL839NO613924.2 0-347A C-27
301640NOe13915.I D-53 C-35
301840N0813935.2 D-53A C-35

30140ONOeI4449.1
301842N0814220.2
301643NOE14735.
301844N0814239.1
301844NO814235.2

301845N08 12404.1
3CI84BN081J7C4.1
301848h0813925.I
3C1 49N0O14740.1
301055N0813340.1

3CL857NO813429.1
3C1900N0814642. 1
3CSCIN00615115.1
301905N0I5111.l
301907N0813230.1

3C1907N0814821.1
3C1909N0813430.1
3CL910N0813348.1
3C1910N0813436.1
301912NCeiSQ C.1

301912N0815040.2
301913N0815346. 1
3CL915NO813515.1
301918N0613839.L
301921NOe1262e.1

3CL922NO812634.1
301922N0815023.1
301925N0613309.1
301925N0O13309.2
3C1926N0814552.1

05-163
0-50A C-IS
C-80
0-59 C-22
0-59A C-22

0-20
0-55
0-244
DS 07
OS L4

CS 65
DS 121
DS 102
OS-201
CS-182

05-204
DS-53
OS 22
OS-205
CS 108

OS 109
0-4
OS 20C
D-64
05-117

CS 84
DS-162
D 359
D-73
OS-159

140
d0
37

125
1048A
1307
1037
1265

110

1260
1260

622
600
793
132
100

70
100
118

102

286
92
9e
100
21

159
700
20C
1074
137

40
219
75C
1016
165

5C6
SC6

510
SI5

A4C
530

382

516
108

60

75

96

466

;515

40

60
600

I
U

U

U
P
P
P
P

H

S
U
U

H
H
H

U
H
u
H
U
H
U

U

N
U

H
H
U

PS

H

H

t14

4

tC1
#33
*+33
f48
#48

+2

40

+12
11
I I
L4

6
*4
+6

*1

20
13

21
45

+42
7

12

-m

7-68

8-68

1-69
6-56
6-56
3-39
3-39

4-65

12-38

10-61
10-67
9-67

3-68
4-68
7-68
5-66
1-69

1-68
12-67

7-68

7-66
4-6R

7-42

1-66
1:;

Table 4,- Record of wells used in study of shallow aquifer system. Continued

CASING ALT1- DATE
LOCAL WELL CASING CIAM- USE TUDE- MAJoR WATER WATER
LOCATION H LL DEPTH CEPTH PETER OF CF LSO AQUIFER LEV6L LEVEL
NUMBER (FT.) tFT.) (IN.I WATER (FT.*I I(FT.I MEAS. REMARKS

___________DLVAL CEUNTY_______ _________

3C1926NO815329.
3C1931Ne0814554 .1
3Cl93hl06147C.L

3C1S38NOR13333.1

301940K0813546.1
3Cq942NC412825.1
3C1559NCE14C29. L
302CCENCeI421.1
302CL7NC815228.1

302CIeNCEI5715.
302C1lNC8152C7. l
3C2C20hCE15216. I
3C2C22NC813928.1
302C22NCE13928.2

!C2C41NC8138C5S.
302C43NCE14856.1
3C2C49NCE1331. I
3C21CONC8127C7.1
3C21CCNCOL4840.1

302123N0812742.1
302136NCF14256.2
3C2143N08144LC.1l
302143N0E14413.1
3C2145NP013942.

302146NCe14157.1
302147KC0133i3.l1
2C214FPNC133C7.1
30215CNOei355C.1
3021!1NCE14826.1

3021hCS6133LC. L
3021!7NCE1345C. I
3C22CCNCe8124A4.1
3022C3NCE12455.1
302203NCe12455.2

3C2217NCE1434C. l
302219NCE136C5.1
3023CONC815C25.1
3023C7NCE12939.1
3C23CSNC812951.1

CS-170
DS 140
0-67
CS 97
0 41L4

CS-36
CS-183
C-70C
C-307
OS-56

05-196
OS 115
CS 160
0-63 C-29
0-63A C-29

CS199
CS 106
CS-1B5
CS 13
CS-167

CS-184
CS 87
OS IC
CS 09
C-43

CS Lt
CS 15
C21133C2
DS-35
CS 112

C211132
C-415
CS-145
CS LL9
OS- LL9A

C 181
D-356
CS- 166
C-424'
CS-153

150
39
1060
116
LC5C

73
100CO
974
1300
IPC

135
115
185
1244
1264

28

275
22
125

ICC
BC
57
67
67

64
61
38
q1L
75

39
1104
t1C
98
162

69C
1016
15C
700
200CC

11-48
7-29
7-68

1-68

5-69
9-68

9-36
8-36

6-41
7-68

9-67

0-6?
10-67
10-67
IC-67

1R-67
9-67

1-68
9-68

12-68

9-68

11-40
7-65

12-66
--

W 5925

W 103
W 303

0

I

z

1SO

Imd 4. HRecuird u| llb uwd in lud uf dbaillluw 2aqui4r 01lWnI (011inued 9

LEASING A01t. Ga
LQCAL WiLL CASING DIAN- LiS ME J UE- kJil tAl~ik T I
LOCATION 9LL. DEPTH I CEPTh TE F CF LS51 Ag40Jil LEVEL LEVEL
NUM iff oF.l (FI[l UN4 WATER (F(,I (Fll NE45, 'RF IlS
] _______k___,_________'_u4A, CINT_ ______.____..I______.._... __
IC2313NO1531)C1I 0-74 326 Sf6 1C sF IF 14 5*-
3C20INC141l4791 CS-50 SC &a 7 0 $? tN I1 1-66
Ic9oINce0tIe.i5 cs-& 65 -& H 10 H to IN
!0t23NO1I4 01el 0-269 70C -* s S 20 IF JP !-Sb
IC2641N8OSOs5.1 05 lOS M5 -- 2 U S? IN 11 7-64
C02MINO1l5OSi.2 05-1l9'A 9 93 2 k 52 IN -
3C2644NO137O5.1 CS 1i6b 86 -- I / H 1 IN
3C21CI 01N12SC. CS-1lTT -an 2 S 5 IN .
3C27C)N041381 aI cs-eL lac icc 2 H 27 IN .
3C?705NGO13C4I. CS-t75 IC -- ? 1 0 IN -* -*
30270I 0128o00.1 CS-lAS 78 -- 2 H 13 IN 4 5.-6
302711j0814C4 .l OS 104a -- H 12 IN +1 t1oa-
3027tSNOFI46350. CS-165 IC 2 H 2 tIN -. -
30213bNOP133556. CS61 132 116 2 H 21 IN 4 -"da
30273i)6051333e.l CS-40 0 -- 2 U 25 IN 6 1-o0
3C2740NCll3751.1 5C-161 129 -- 2 H 30 IN --
3C2743O0813743.l CS-4j 1oS -- 2 U 24 IN 4 1-66 0
3C27O5NCE1336.1 OS 135 04 -- 2 U 10 IN 4 t1-66
3C8OONO8149'C.t CS lb 59 -- 2 U 15 IN 2 9-6d
3C280tOCei.35169.l 0-187 iC -- 2 H 25 IN --
3C28C4N0813733.L CS-I98 IO -- 2 U 29 IN 9 5-69 .
102E14NC81391t2. CS-54 i8 4d 2 U 21 IN 5 1-68
3C2829NC8141208. OS-61 15C -- 2 H 24 IN -. --
3C2155 C8129tl. 0S-51 59 -- 2 u 5 ItN 2-6b
3C25CSC81i43C3.1 CS-171 t45 -- 2 H 20 IN -. --
302ISCOC14214. CS 125 133 -- 2 U I2 IN b I- 4
30291CNC3142l6.1 C-362 1105 590 12 7 27 IF *1? 1F-67
30215N0814215.1 OS 4 142 126 2 U 23 I0 7 10-67
302S2CNC61375.1l C-427 915 576 6 P 2o IF .14 11-61
302122NCE13C41.1 CS-46 26 -- I U -- IN 4 1-68
302923hClI3CS3.1 CS-33 97 P7 2 1 IC IN -. --
302435NCE13214.1 05-158 110 -- 2 U 23 IN --
1C2946NC814021.1 CS 31 90 -- 2 U -- IN 7 2-4
3C2q5eNCeI3234i. CS-41 75 -- 2 U 22 IN 9 l-.6
3C3CC7TCB13315.l CS-178 9' -- 2 m 30 IN -- -
30305NhC813433.1 0-77 7C6 446 6 P IS IF *25 4-19
303017NCaIZ821.1 CS 4* 9C -- 2 U 7 IN *11 2-61
303017NC1lZ821.2 CS-50 54 -- 1 U 7 IN 1 2-t4
30302CAC813455.1 CS 124 ?t -- 2 u 25 IN 6 9-6e
303022NC813937.1 OS-44 S9 -- 2 u 26 IN 6 1-0,9

Table 4.- Record of wells used in study of shallow aquifer system. Continued
CASING ALTI- CATE
LCCAL wELL CASING CIAN- USE TUDE- MAJOR wATER WATER
LOCATION WELL DEPTH DEPTH PETER OF CF LSD AQUIFER LEVEL LEVEL
NUMBER (FT.) (FT.I (IN.I WATER (FT (FT.) MEANS. REMARKS
DUVAL COUNTY
303C3ENCE12e2C.l CS-179 40 -- 2 H 15 IN -- --
3C31C8NC814550.1 CS-174 240 -- 2 H 17 IN -- --
303117NC8141C6.1 CS 141 140 2 U 24 IN e 12-66
303117NC8144C3.1 D5-67 108 C15 2 H 25 IN :2 4-68
303125NCel3524.1 CS-42 67 -- 2 U -- IN. 4 1-68
3C3125NC813715.1 DS-34 100 -- 2 1 39 IN -- -
3C3137NCS14359.1 DS-173 95 -- -- H 21 IN -- -
303237NC813704.1 CS-45 75 -- ,2 U 21 IN 15 1-68
3C3245NCB14356.1 DS 122 -- -- 2 S 4 IN +7 9-68
303356NCeI3645.1 CS 92, 95 -- 2 H 5 IN -- -

CLAY COUNTY
300E31NCE14445.1 C 10 864 358 12 P 27 1F -- --
3CIC58NC820C',49.1 CS 3 57 2 U 83 IN 2 6-6S
3CllC4NCeI4924.l CS-2 117 6 U 6e IN 7 3-66

NASSAU COUNTY

303C2CNCe14735.1 NS 13
3031C5NC614621.1 NS-3
3035!2NC815248.1 N-6

200 -- -- H 10
103 94 2 H 20
770 532 6 S 60

12 4-6B
-- 8-65

I

0
'-TI

0
z
C13
z
P

NO

BUREAU OF GEOLOGY

ACKNOWLEDGMENTS

The author is indebted to many people throughout the area for their
cooperation and helpful assistance. The following companies provided ready
access to their drilling records and permitted on-site collection of rock
samples: Duval Drilling Company, Ricket's Well and Pump Company, 0. E.
Smith's Sons, Harry S. Meir Well Drilling, Williams Nursery, Partridge Well
Drilling Company, Trout Well Drilling Service, Law Engineering Testing
Company, and Jacksonville Engineering and Testing Company.
Especially appreciated is the cooperation extended by the city of
Jacksonville, Water and Sewer Dept. and the many residents who permitted
access to their land and who often assisted in the measuring of water levels in
wells.
The author is particularly indebted to his colleagues for their many
suggestions and assistance throughout the study; especially G. Warren Leve
under whose supervision the fieldwork was conducted.

SHALLOW-AQUIFER SYSTEM
GEOLOGY1

All the formations that overlie the Ocala Limestone of Eocene age
comprise the shallow-aquifer system in Duval County. These rocks range in
age from Miocene to Holocene. The formations that lie above the Hawthorn
Fomation, of Miocene age, have not been given formal names in this report,
and they will be referred to here by their geologic age. In ascending order, the
formations that comprise the shallow-aquifer system are: the Hawthorn
Formation, middle Miocene age; upper Miocene or Pliocene deposits; and
Pleistocene and Holocene deposits. The stratigraphic units making up the
shallow-aquifer system in Duval County are listed and described in table 5. A
map showing the thickness of all the sediments that overlie the Ocala group is
shown in figure 5.

lThe stratigraphic nomenclature in this report follows that of the Bureau of Geology,
Florida Department of Natural Resources.

0

0

5 0

I.S' 1 0 *S / I
BALDWI10N 1 49 495 I

.l 1 0 04

82I 10' e"OO a' 45' 30' 81 0'
Figure 5. Map of DuvalI County showing the thickness of the sediments overlying the Ocala Limestone of the Floridan

aquifer.

Table 5. Stratigraphic units making up the shallow aquifer system in Duval County.

System Series Formation Thickness Lithologic Description

Holocene Pleistocene 0 Sand, tan to yellow, loose, medium to fine quartz, sometimes with shells
H oc and to and/or minor clay content-often has hardpan layer of iron oxide-cemented,
Holocene 90' rusty red to dark brown medium to fine sand in upper part of section-source
Pleistocene Deposits of water to shallow sandpoint wells.

Upper Miocene Upper part-tan to buff, fine to coarse sand and gray to light gray sandy clay,
or 1, clayey sand, and shell beds; clay often contains abundant mollusk shells.
Plocene Pliocene 10 Lower part-limestone, tan to yellow, often highly sandy, porous, and
Deposits 110' cavernous-also few thin beds of brown crystalline, dolomitic,
Slimestone-section is major source of water to shallow wells.

[' Hawthorn 250' Gray to blue-green and olive-green clay, sandy clay, and sandy
Miocene to limestone-usually phosphatic with abundant, well-rounded, polished, granules
Formation 500' and pebbles of phosphate. Formation not usually considered a good source of
water; some wells tap lenses of sand and limestone in the upper part.

REPORT OF INVESTIGATIONS NO. 59

HAWTHORN FORMATION

The name "Hawthorn beds" was originally proposed by Dall and
Harris (1892, p. 107) to include beds exposed at several localities in the
central part of Florida. More recently, Puri and Vernon (1964, p. 146)
designated exposed sections of the Hawthorn Formation at Devils Mill Hopper
and Brooks Sink near Gainesville, Florida, as the "cotype" localities to form
the basis for later correlation.
The Hawthorn Formation, of middle Miocene age, consists mainly of
dark-gray and olive-green sandy to silty clay, clayey sand, clay, and sandy
limestone, all containing moderate to large amounts of black phosphate sand,
granules, and pebbles. In most places the upper surface of the Hawthorn is
marked by the presence of phosphate-rich sediments. In the western part of
the county the upper part of the Hawthorn consists mainly of coarse-grained
sandy phosphatic limestone.
Throughout most of northeast Florida the clay and silty clay within the
Hawthorn Formation serves as a confining layer (aquiclude) that retards
upward movement of water from the underlying artesian Floridan aquifer,
However, in parts of eastern Duval County, from Mayport to Ponte Vedra,
coarse- to very coarse-grained pebbly sand within the Hawthorn Formation is
tapped by wells 140 to 165 feet deep. Wells penetrating this zone will yield at
least 20 gpm (gallons per minute).
The Hawthorn Formation ranges in thickness from about 250 to as
much as 500 feet in Duval County (Leve, 1966, p. 18). Although the
formation thickens generally to the northeast, it varies in thickness from place
to place because of both an irregular upper and lower surface. The Hawthorn
Formation is not exposed in Duval County but occurs at depths ranging from
about 50 to 200 feet below land surface throughout the county.
Sharks' teeth are common in the clay and sandy clay, but the only
other fossils found consist of poorly preserved mollusk shells, usually as
external or internal molds and casts in the sandy limestone.
The sediments of the Hawthorn Formation are considered by Puri and
Vernon (1964) to be deltaic deposits. The delta extended southward from
Florida's northern boundary line, to about the Gainesville area (Alachua
County about 65 mi. southwest of Jacksonville) and possibly farther south.
The sediments were deposited on an irregular surface of the Ocala group
(Eocene) and were later subjected to subaerial erosion.

UPPER MIOCENE OR PLIOCENE DEPOSITS

The upper Miocene or Pliocene deposits consist of sand, shell, sandy
clay, and limestone. The sediments generally can be distinguished from the

BUREAU OF GEOLOGY

Hawthorn Formation by their lack of phosphate and by their lighter colors,
usually tan, buff or light gray. Figure 6 is a lithologic log of a typical shallow
well (well 302915N0814215.1). As shown in the log the upper 55 feet of
sediments penetrated consists of clayey sand and sandy clay. The middle
section (55 to 90 feet) consists of sandy clay and shell, and the lower section
(90 to 140 feet) consists of interbedded sandy clay, clay, and soft porous
bioclastic limestone, which is sandy and cavernous in places.
The limestone section (112 to 140 feet) is the major water-yielding zone
in the shallow-aquifer system. Most shallow wells obtain water from this
limestone section. Where the limestone is missing, lesser amounts of water are
obtained from less permeable sand and shell beds.
The thickness of the upper Miocene or Pliocene deposits ranges from as
little as 10 feet in the extreme southwest part of Duval County to as much as
130 feet in the west-central part of the county. Differences in thickness are
the result of deposition of the upper Miocene or Pliocene deposits on the
irregular Hawthorn Formation. The upper Miocene or Pliocene deposits are
thickest over the lows and thinnest over the highs on the Hawthorn surface,
as shown in figure 7, generalized geologic sections of the shallow-aquifer
system in Duval County. The configuration of the upper surface of the upper
Miocene or Pliocene deposits is similar to the upper surface of the Hawthorn
Formation but with considerably less relief.
There are no known exposures of the upper Miocene or Pliocene
deposits in Duval County. However, dredge spoil indicates that the river may
be incised into the deposits, particularly in the reach east of Jacksonville.
Several small streams west of Jacksonville may also be eroded into the upper
Miocene or Pliocene deposits where the overlying sediments are relatively thin.
No attempt has been made to correlate the sediments making up the
upper Miocene or Pliocene deposits in Duval County with other post-Haw-
thorn sediments in the surrounding areas. Table 6 lists the Hawthorn and
younger formations as mapped in the surrounding areas by various authors. As
indicated in the table, the stratigraphic nomenclature used in this report
follows that of Leve (1966 and 1968). The table also serves to indicate that
the shallow-aquifer system is continuous beyond Duval County.

REPORT OF INVESTIGATIONS NO. 59

EXPLANATION
SAND SANDY CLAY

-D CLAY f17 SHELL

I LIMESTONE
Figure 6. Lithologic and gamma logs of a typical shallow well in Duval
County (well 302915N0814215.1).

Table 6. Hawthorn and post.Hawthorn stratigraphy in northeast Florida,

Bermes, and others
Bermes, and others (1963)
(1963) Leve, (1966) Purl and Vernon,
Clark and others (Western Putnam Leve, ( 1968) (1964)
System Series (1964) County) This report Plate 2B

Younger marine
and estuarine
terrace deposits

Older Pleistocene
terrace deposits

Unnamed coarse
plastics

Choctawhatchee
Formation

--?_

Hawthorn
Formation

Post-Hawthorn
deposits

Hawthorn
Formation

Pleistocene
and
Holocene
deposits

Late Miocene
or
Pliocene
deposits

Hawthorn
Formation

Several lower
marine and
estuarine terrace
deposits

Anastasia
Formation

i
81 Citronelle
u0 Formation

Charlton
Formation
(Pliocenel
Jackson Bluff
Formation

Fort Preston
Formation

Hawthorn
Formation

Quaternary

Tertiary

Holocene

Pleistocene

Pliocene

Miocene

r ----------------- --

000

zoo'

C..

0~
~Ow~m*4low zUb

Figure 7. Generalized geologic sections of the shallow-aquifer system in Duval County.

BUREAU OF GEOLOGY

PLEISTOCENE AND HOLOCENE DEPOSITS

Sediments of Pleistocene and Holocene age were deposited during the
formation of marine terraces and beach ridges and the sediments blanket all of
Duval County. They overlie the upper Miocene or Pliocene deposits and were
deposited on a slightly irregular, undulating surface.

The thickness of the Pleistocene and Holocene deposits ranges from less
than 10 feet in the St. Johns River valley to about 100 feet in western Duval
County. The deposits are thickest below the ridges and where they overlie
depressions in the upper surface of the upper Miocene or Pliocene deposits.
See figure 7.
The Pleistocene and Holocene deposits consist primarily of tan to yellow
medium- to fine-grained loose quartz sand, locally stained rusty brown and red
from iron oxide. The deposits locally contain thin gray sandy clay beds,
which, in places, contain mollusk shells, particularly near the coast.
Discontinuous layers of rusty brown hardpan, composed of slightly to
well-indurated iron-oxide cemented quartz underlie some of the higher areas.
The hardpan is generally 2 to 3 feet below the surface and ranges in thickness
from 1/2 to 20 feet. In places it is so well indurated that dynamite must be
used to break through its upper surface during road and foundation
construction.
In the east central part of the area Pleistocene and Holocene sand ridges
as much as 90 feet in altitude parallel the present shoreline. The sand,
although made up predominately of medium to fine quartz, also contains
heavy minerals such as rutile, zircon, sphene, and leucoxine. In the past the
heavy minerals were strip mined along the ridges; the mines are no longer in
operation.

HYDROLOGIC CHARACTERISTICS
WATER LEVELS AND WATER-LEVEL FLUCTUATION
During the 1 years of field study, water-level fluctuations were
monitored in a network of 30 wells throughout Duval County. The locations
of the observation wells are shown in figure 1.
Where the water level in a well rises above the top of the aquifer that
yields the water, artesian conditions may exist. The level to which water will
rise in such wells is called the "potentiometric surface." Figure 8 is a map of
the potentiometric surface of the shallow-aquifer system for May 1969. Also
shown in the figure are profiles of the land surface and the potentiometric
surface of the Floridan aquifer. As can be seen in the diagram, the
shallow-aquifer potentiometric surface roughly follows the configuration of
the land surface and in places, where it crosses the stream valleys, it is above
land surface.

REPORT OF INVESTIGATIONS NO. 59

WEST EAST
Pod- WICOMICO TERRACE -Im.
-------------------
SHALLOW AQUIFER
POTENTICIMETRIC SURFACEj LAND SURFACE
Sr JOV06 RIVER
FLORIDAN AQUIFER / "
SEA POTENTIOMETRIC SURFACE SEA
LEVEC" -LEVI

5d- a I LAILKS -5d
NOTE: VERTICAL SCALE EXAGGERATED

Figure 8. Map of Duval County showing the potentiometric surface of the
shallow-aquifer system and the area of flow in May 1969.

Hydrographs showing the relation of rainfall to water levels in wells
302604N0813835.1 and 302456N0813358.1 in the northeast part of the area
are shown in figure 9. As indicated by the graphs, high water levels occur
after periods of heaviest rainfall, and lowest water levels occur after the drier
periods of the year. As can be seen from the hydrograph in figure 10, the
water level in well 301333N0814043.1 rises only a short time after the rain
begins. Rainfall August 27 to 31, 1968, totaling 15.3 inches, resulted in a
1.5-foot rise in water level. The water level then declined slowly during
September, when about one inch of rain fell. The rate of rise and decline of
the water levels is a function of the hydraulic and geologic properties of the
aquifer and the rate of recharge to or discharge from the aquifer.

BUREAU OF GEOLOGY

J F M A M J J A S 0 N OjJ
1968

F M A M J
1969

Figpe 9. Graphs showing the relation of ground-water levels in wells in
northeast Duval County and the rainfall at Jacksonville Weather
Bureau, Imeson Airport.

WELL 302456N0813358.1
DEPTH 57 FT.

WELL 302604N0813835.1
DEPTH 76 FT.

101

JACKSONVILLE WEATHER
BUREAU
(IMESON AIRPORT)

-P -v

11

BE%-

REPORT OF INVESTIGATIONS NO. 59

WELL 301333N0814043.1
NAVAL AIR STATION, JACKSONVILLE
DEPTH 108 FT.

78-

FLEET WEATHER FACILITY
NAVAL AIR STATION, JACKSONVILLE

2 ---------------------------------

25 5 15 25 5
SEPT.

15 25
OCT.
1968

15 25 5 15 25
NOV. DEC.

Figure 10. Graphs of rainfall and ground-water levels in
301333N0814043.1 at Naval Air Station, Jacksonville.

well

Water levels range from as much as 35 feet below land surface to as
much as 22 feet above land surface. Water levels generally are farthest below
land surface in areas of higher altitude, as in western Duval County.
The yearly water-level fluctuation in wells during the period of study
ranged from about 2 to 5 feet.

AREA OF FLOW

In areas where the shallow-aquifer potentiometric surface is above land
surface, wells that tap the shallow limestone aquifer flow. Several such areas
occur in Duval County and are shown in .figure 8. The flowing wells are
mainly in the west-central part of the county in low areas such as stream
valleys.

Artesian heads of the shallow wells range from a few inches to more
than 20 feet above land surface. Some wells stop flowing during the dry

5 15
AUG.

BUREAU OF GEOLOGY

season when the potentiometric surface is below land surface. In the area of
103rd Street and Ortega Creek several 60- to 70-foot-deep wells flow
perennially and yield an adequate supply of water for domestic use.

RECHARGE
Recharge to the shallow-aquifer system is directly from local rainfall.
The relation between local rainfall and water levels in wells that penetrate the
shallow-aquifer system are shown in figures 9 and 10.
An estimate of the amount of recharge to the shallow-aquifer system
from local rainfall can be obtained from rainfall and runoff records and
estimated evapotranspiration. Rainfall in Duval County averages about 54
inches per year, and the average annual runoff from streams is about 20
inches (calculated from U. S. Geological Survey Surface Water Records). Base
flow in the streams is sustained by ground-water inflow from the
shallow-aquifer system and accounts for about 10 to 12 inches of the annual
runoff (20 inches). The remainder of the annual runoff is direct runoff from
overland flow.
Studies by Visher and Hughes (1969) indicate a difference between
rainfall and potential evaporation in this area of approximately 8 inches per
year. Accordingly, potential evaporation for the Duval County area is
approximately 46 inches per year. This value is based on meteorologic factors
such as solar radiation, wind movement, air temperature, and humidity. It is
considered equivalent to the amount of natural evaporation from an extensive
water surface of little thickness and under the prevailing meteorologic
conditions. This value represents maximum annual evaporation and probably is
far in excess of the actual evaporation. Factors such as topography, geology,
vegetal cover, and the permeability of the soil all play a part in reducing
evaporation below the potential rate. Hughes (oral commun., 1970) suggests
that a valid estimate of the evapotranspiration for the Duval County area is
from 36 to 38 inches per year. Subtracting the 20-inch average annual runoff
from the average annual rainfall leaves 34 inches of evapotranspiration per
year, a value that compares favorably with Hughes' estimate.
Hydrographs of water levels in wells indicate that from 10 to 16 inches
of rainfall recharges the shallow-aquifer system annually (based on the amount
of the total annual rise in water level in the aquifer and an estimated effective
porosity of 20 percent for the aquifer material). About this same amount is
discharged from the aquifer as ground-water outflow to streams and by
evapotranspiration from the soil zone.
Average annual runoff varies from place to place. In the upper Yellow
Water Creek basin in southwestern Duval County, runoff averages about 5
inches per year (Clark and others, 1964). Runoff from the Ortega Creek basin

REPORT OF INVESTIGATIONS NO. 59

averages about 24 inches per year. The high runoff rate in the Ortega Creek
basin indicates that little or no recharge to the shallow-aquifer system takes
place within the basin or that the shallow aquifer is full and that ground-water
outflow to Ortega Creek is high in the rainy season. In the upper Yellow
Water Creek basin there may be as much as 11 to 13 inches of recharge to the
aquifer. The area near the head of Yellow Water Creek is flat and swampy.
Rain that falls on the ground stands for long periods and considerable
evaporation, transpiration, and seepage to the water table occurs. If the
average recharge in that area is 12 inches per year, the average
evapotranspiration would be about 37 inches per year.
Throughout most of the eastern two-thirds of Duval County, the
potentiometric surface of either the Floridan aquifer or the shallow-artesian
aquifer is above land surface, and in these areas recharge does not take place.
Also, as much as 50 sq mi in western Duval County is underlain by
fresh-water swamps and has a sparse drainage system. Most of the rain on this
area either seeps downward very slowly to recharge the aquifer or is consumed
by evapotranspiration. Probably less than 200 sq. mi. within the county can
be considered as a potential recharge area.
The areas of greatest recharge to the shallow-aquifer system are usually
those having the highest altitudes, particularly the high sand ridges. However,
some high areas are underlain by a hardpan layer, which retards downward
percolation, and perched water-table conditions exist. In such areas the surface
is often swampy and is marked by groves of cypress trees. In some places,
where construction has taken place and the hardpan has been broken or
removed, the swamp water drains into the underlying permeable sand, drying
the surface and making the area suitable for development.
Another possible source of recharge to the shallow-aquifer system may
be by upward leakage from the deeper Floridan aquifer. Figure 5 is a map
showing the thickness of the sediments overlying Eocene limestones of the
Floridan aquifer. In those places where post-Eocene sediments are thinnest,
and where the potentiometric surface of the Floridan aquifer is above land
surface, upward leakage would most likely be greatest. As can be seen by
comparing figure 5 and figure 8, one of the most likely places for upward
leakage would be south of Jacksonville on the west side of the St. Johns
River. Water entering the shallow sand and limestone layers probably does not
move directly upward but follows lenses of permeable sand, shell, or limestone
along paths of least resistance. Further studies (p. 47, step c) in areas of large
withdrawals from deep wells should lead to a better understanding of the
hydraulic relation between the deep and shallow-aquifer systems.
Some recharge to the shallow-aquifer system may be derived from
ground-water underflow-water that percolates into the ground at higher
altitudes outside the area and moves underground through the aquifer into

BUREAU OF GEOLOGY

Duval County. Such possible recharge areas lie to the west of Duval County in
Baker County and to the southwest in Clay County.

DISCHARGE
Discharge from the shallow-aquifer system is through springs and seeps,
by evapotranspiration, by pumpage from wells, and by downward percolation
into underlying formations.

SPRINGS
Springs discharge an undetermined amount of water from the
shallow-aquifer s stem. These springs are of two types; (1) depression springs
or "seeps" where the water table intercepts the land surface (usually along
stream valleys), and (2) "sand boils" issuing under artesian pressure (Ferris
and others, 1962), generally through an opening in the confining beds that
overlie the shallow aquifer in areas where the potentiometric surface is above
land surface (fig. 1).
The depression springs or "seeps" contribute water to streams in the
area as long as the water table is above the level of the bottom of the stream.
When the water table declines, the seeps dry.
In most areas of artesian flow the potentiometric surface is above land
surface the year around and the artesian springs (sand boils) continue to
contribute to stream flow throughout the year. However, as the artesian flow
diminishes considerably during the dry season, the water discharged into the
stream bed may flow only a short distance downstream and then percolate
into the sand in the stream bed. Thus the stream may have water flowing in
one reach while other reaches are dry.
The specific conductance of water in several of the artesian springs was
determined and found to be similar to that of the water in nearby wells
penetrating the shallow aquifer. The spring water has a moderate hydrogen
sulfide odor, as does the water in the shallow aquifer wells. In most springs
the specific conductance of water is slightly less than that of the well water,
indicating less mineral content. Where springs discharge int6 the bottom of a
stream, they can be easily detected during the summer when the temperature
of the spring water is considerably less than that of the streamflow.
The springs were not studied in detail. However, the similarity of the
spring water to water in the shallow-artesian aquifer shows that the shallow
aquifer leaks and that a considerable amount of groundwater discharge is
contributing to flow in the streams.

REPORT OF INVESTIGATIONS NO. 59

EVAPOTRANSPIRATION
Four to 6 inches of water per year is discharged from the
shallow-aquifer system by evaporation and transpiration. Rain percolates into
the surface sand, where some is held in the soil and some continues downward
to the water table. Water held in the soil is discharged into the atmosphere
either by evaporation directly from the soil or by transpiration of plants.
Water in a saturated zone moves laterally downgradient, where it may come
close enough to the surface to be discharged from the soil as above or may
discharge as seeps into a stream.

PUMPAGE
Estimates of pumpage from the shallow-aquifer system by Leve and
Goolsby (1969) indicate that approximately 45,000 to 50,000 domestic wells
discharge 10 to 25 mgd (million gallons per day). Most wells are 2 inches in
diameter or less, and water is withdrawn from them by small-capacity jet
pumps powered by 1/4 to 1 horsepower motors.

DOWNWARD PERCOLATION
Quantitative studies of the Floridan aquifer presently underway in Duval
County suggest the occurrence of downward percolation (leakage) from the
shallow-aquifer system into the Floridan aquifer (Leve, oral commun., 1970). In
areas such as western Duval County, where the potentiometric surface in the
shallow-aquifer system is above that in the Floridan aquifer, the hydraulic
gradient is downward, and considerable water may be moving from the
shallow-aquifer system into the Floridan aquifer below.
Figure 8 indicates that the potentiometric surface of the aquifer west of
the St. Johns River slopes generally eastward. A considerable amount of water
from the aquifer may be discharging into the St. Johns River, particularly
where dredging has been deep enough to remove less permeable silt and clay,
exposing permeable layers of coarse sand and porous limestone.

QUALITY OF WATER
The water in the shallow-aquifer system is generally of good chemical
quality, well within the limits for water used on interstate carriers
recommended by the U. S. Public Health Service (1962). The chemical quality
was determined by analyzing water from 32 wells throughout Duval County.
The results of the analyses are listed in table 7. In addition to the 32
"standard complete" analyses, water from 45 other wells was analyzed for
iron content and the results are listed in table 8. The significance of the
various chemical constituents normally analyzed for in a sample of water is

BUREAU OF GEOLOGY

ACKNOWLEDGMENTS

The author is indebted to many people throughout the area for their
cooperation and helpful assistance. The following companies provided ready
access to their drilling records and permitted on-site collection of rock
samples: Duval Drilling Company, Ricket's Well and Pump Company, 0. E.
Smith's Sons, Harry S. Meir Well Drilling, Williams Nursery, Partridge Well
Drilling Company, Trout Well Drilling Service, Law Engineering Testing
Company, and Jacksonville Engineering and Testing Company.
Especially appreciated is the cooperation extended by the city of
Jacksonville, Water and Sewer Dept. and the many residents who permitted
access to their land and who often assisted in the measuring of water levels in
wells.
The author is particularly indebted to his colleagues for their many
suggestions and assistance throughout the study; especially G. Warren Leve
under whose supervision the fieldwork was conducted.

SHALLOW-AQUIFER SYSTEM
GEOLOGY1

All the formations that overlie the Ocala Limestone of Eocene age
comprise the shallow-aquifer system in Duval County. These rocks range in
age from Miocene to Holocene. The formations that lie above the Hawthorn
Fomation, of Miocene age, have not been given formal names in this report,
and they will be referred to here by their geologic age. In ascending order, the
formations that comprise the shallow-aquifer system are: the Hawthorn
Formation, middle Miocene age; upper Miocene or Pliocene deposits; and
Pleistocene and Holocene deposits. The stratigraphic units making up the
shallow-aquifer system in Duval County are listed and described in table 5. A
map showing the thickness of all the sediments that overlie the Ocala group is
shown in figure 5.

lThe stratigraphic nomenclature in this report follows that of the Bureau of Geology,
Florida Department of Natural Resources.

34 BUREAU OF GEOLOGY

Table 7. Chemical analyses* of water from the

Mag- Po- Car-
Depth Cal- ne- So- tas- bon-
Date Depth Cased Iron Silica cium sium dium sium ate
Well Number Collected (feet) (feet) (Fe) (SiO2) (Ca) (Mg) (Na) (K) (CO3)

300857N0813444.2 5-20-65 92
301110N0820115.2 11-8-65 135
301145N0813727.1 5-19-65 126
301255N0813710.I 5-20-65 89
301324N0815506.1 11-8-68 125

301340N0814754.1 11-3-66 60
301443N0814244.1 5-27-65 165
301450N0814802.1 8-6-65 -
301454N0814754.1 4-16-68 68
301602N0815054.2 10-11-67 146

301706N0812957.1 11-7-68 85
301718N0812538.1 6-6-66 140
301747N0813624.1 11-1-66 55
301812N0815932.1 11-8-68 135
301817N0813749-2 3-19-65 -

301820N0815007.1 7-2-68 140
301820N0815007.2 7-2-68 60
301905N0815111.1 5-13-6 -
301907N0814821.1 8-02-65 286
301915N0813515.1 5-20-65 200

301922N0812634.1 9-21-66 40
301017N0815228.1 3-25-68 190
302136N0814255.1 5-27-65 80
302148N0813307.1 5-19-65 38
302155N0813310.1 5-19-65 39

302203N0812455.1 9-26-68 162
302424N0815042.1 7-2-68 107
302703N0813819.1 9-22-66 120
302829N0814128.1 4-3-68 150
302915N0814215.1 9-27-67 142

302923N0813053.1 1-19-68 87
303125N0813715.1 1-19-68 100
303356N0813645.1 9-22-66 90

- 2.0 29
- 2.6 19
98 .5 43
- .9 25
- 1.0 26

83 15 14 1.3 0
58 22 7.8 2.2 -
83 14 14 2.9 0
99 5.1 15 2.2 0
58 13 14 2.1 -

- .01 19 43 16 6.6 1.2 -
125 .04 29 57 11 12 2.5 0
- .21 9.0 33 9.5 3.8 .6 0
- 9.7 43 9.1 4.1 .7 -
- .65 22 56 20 6.4 1.9 -

- 2.8 13
92 52
- .02 32
- .1 38
- .31 43

- 32
- 6.8
- .03 33
- .02 26
- 22

61 2.2 8.8 .6 -
63 29 19 5.7 0
39 3.3 9.2 1.2 -
75 13 28 2.9 -
39 16 15 6.1 0

90 5.4 8.7 2.1 -
.2 2.2 7.8 1.1 -
85 52 0 1.5 0
88 2.3 7.4 1.8 0
72 25 14 2.1 0

40 1.6 2.3 1.9 2.0 2.0 .3 0
- 36 596 100 23 8.2 0
- 2.8 18 73 12 13 1.1 0
- .11 11 32 14 5.8 .9 0
- .09 11 34 2.7 6.1 .8 0

- 55 46 16 25 4.7 -
- 15 41 7.5 4.4 .3 -
100 .08 33 32 2.4 7.6 1.3 0
- 31 630 70 20 22 0
126 35 64 9.9 17 4.4 126

87 .68 23 111
- .92 14 55
- 2.7 49 59

6.2 17 .9
28 8.5 1.4
9.0 19 1.8

*Chemical analyses in milligrams per liter except where otherwise indicated.
**Sum of determined constituents.

REPORT OF INVESTIGATIONS NO. 59

shallow aquifer in Duval County, Florida.

Hardness Specific
Cal- Con-
cium duct-
Mag- Non- ance
Bicar- Chlo- Fluo- Ni- Phos- Dis- ne- car- (micro-
bonate Sulfate ride ride trate phate solved sium bon- mhos at
(HCO3) (SO4) (Cl) (Fl) (NO3) (P04) Solids** (CaMg) ate 250C) pH Color

0.0 21 .2 .0
.4 8.0 .2 .1
4.0 15 .2 .0
0.0 16 .1 .0
.8 12 .4 .1

.8 12 .5 .1
4.8 9.0 .3 .0
0.0 6.0 .2 .0
.4 6.0 .2 .6
0.0 14 .3 .2

.8 11
122 16
3.6 12
.8 28
4.0 18

.1 .1
1.4 .1
.2 .0
.2 .3
1.4 .0

328
284
328
344
256

213
236
166
172
270

206
212
138
324
204

304
0
296
286
160

- 326
04 253
- 338
- 331
04 253

56 205
- 242
- 149
- 159
27 254

25 199
) 393
27 165
14 347
- 243

- 301
- 44
.16 289
- 278
- 385

0 48
- 2560
- 289
- 154
- 122

0 299
- 159
.10 140
- 2550
- 272

- 367
- 268
- 344

268
225
264
268
198

174
186
134
145
222

162
288
111
241
162

249
10
234
230
284

12
1910
232
136
96

182
134
90
1870
200

303
252
226

0 533 7.3 0
0 440 7.8 5
0 521 7.5 0
0 542 7.2 0
0 418 7.9 5

0 349 7.8 0
0 395 7.6 5
0 272 7.8 0
4 279 7.5 0
2 548 8.1 10

0 338 7.9 5
114 600 7.9 10
0 270 7.4 10
0 560 7.7 5
0 353 7.8 0

0 440 7.3 0
10 97 4.3 30
0 470 7.9 10
0 450 8.0 10
153 580 7.6 0

6 105 5.5 5
1720 2700 7.5 5
38 472 7.9 10
2 263 7.5 0
1 208 7.6 0

0 442 8.1 5
0 275 7.7 0
0 220 7.4 10
1690 2620 7.3 5
0 440 7.9 5

0 615 7.5 10
6 480 8.0 0
72 535 7.3 0

0.0 12 .3 .2
16 9.8 .1 .0
.8 8.0 .4 .2
.4 10 .2 .3
146 24 .7 .0

0.0 25 .1 .1
1660 12 1.0 .1
38 18 .3 .0
.8 8.0 .1 .0
0.0 10 .1 .0

14 25 .9 .3
0.0 7.0 .2 .0
0.0 8.0 .2 .0
1650 12 .7 .0
0.0 16 .2 .0

.4 25 .3 .0
.4 12 .4 .5
80 23 .5 .0

36 BUREAU OF GEOLOGY

shown in table 9. Table 10 lists the drinking water standards recommended by
the U. S. Public Health Service.

Table 8. Iron content in water from shallow wells in Duval County.

Well number Depth (feet) Date sampled Iron content, mg/1

300801N0813410.1 76 12-17-68 .03
300815N0813927.1 187 12-19-68 .10
300851N0813049.1 60 12-17-68 .16
300933N0813725.1 145 12-19-68 .99
300948N0813259.1 55 12-19-68 .15
301135N0814213.1 160 1-09-69 .10
301155N0814925.1 47 12-16-68 .48
301214N0814448.1 175 1-09-69 .37
301216N0813541.1 75 12-19-68 .66
301408N0815630.1 120 1-09-69 .71
301535N0813453.1 57 12-20-68 .13
301632N0813758.1 120 12-20-68 1.4
301647N0814943.1 148 1-09,69 .41
301740N0813629.1 65 12-20-68 .16
301840N0814449.1 110 1-08-69 .18
301907N0813230.1 102 1-30 69 .07
301922N0815023.1 219 1-09-69 .08
301926N0814552.1 165 1-08-69 2.8
301926N0815329.1 150 1-09-69 .46
301942N0812825.1 100 1-30-69 .28
302019N0815207.1 115 1-09-69 1.2
302049N0813319.1 275 1-31-69 .04
302100N0814840.1 125 1-10-69 .09
302123N0812742.1 100 1-31-69 .05
302200N0812454.1 110 12-12-68 .02
302300N0815025.1 150 1-10-69 .87
302309N0812951.1 200 12-12-68 .22
302309N0813630.1 90 12-11-68 2.2
302446N0814136.1 90 1-16-69 .35
302501N0813358.1 65 2-03-69 .12
302515N0814625.1 85 1-15-69 .29
302641N0815055.2 95 1-09 69 .65
302644N0813705.1 86 1-17-69 .60
302701N0812750.1 88 1-17-69 .46
302705N0813041.1 90 1-17-69 .51
302715N0814635.1 110 1-10-69 .17
302740N0813751.1 129 1-24-69 .15
302801N0813516.1 110 2-03-69 .24
302905N0814303.1 145 1-16 69 .73
303007N0813315.1 99 1-17-69 .11
303038N0812820.1 80 1-17-69 .45
303108N0814550.1 240 1-16-69 .20
303125N0813524.1 67 1-16-69 .22
303137N0814359.1 95 1-16-69 .21
303237N0813704.1 75 1-16-69 .21

REPORT OF INVESTIGATIONS NO. 59 37

Table 9. Water quality characteristics and their effects.*

Constituent Source and/or solubility Effects

Silica (SiO2) Most abundant element in Causes scale in boiler and
earth's crust resistant to deposits on turbine blades.
solution.

Iron (Fe) Very abundant element, readily Stains laundry and porcelain,
precipitates as hydroxide. bad taste.

Manganese (Mn) Less abundant than iron, Stains laundry and porcelain,
present in lower concentra- bad taste.
tions.

Calcium (Ca) Dissolved from most rock,
especially limestone and dolo-
mite. Causes hardness, forms boiler
scale, helps maintain good soil
Magnesium (Mg) Dissolved from rocks, industrial structure and permeability.
wastes.

Sodium (Na) Dissolved from rocks, industrial Injurious to soils and crops,
wastes, and certain physiological condi-
tions in man.

Potassium (K) Abundant, but not very soluble Causes foaming in boilers,
in rocks and soils, stimulates plankton growth.

Bicarbonate (HCO3) Abundant and soluble from Causes foaming in boilers and
Carbonate (CO3) limestone, dolomite, and soils. embrittlement of boiler steel.

Sulfate (SO4) Sedimentary rocks, mine water, Excess: cathartic, taste.
and industrial wastes.

Chloride (Cl) Rocks, soils, industrial wastes, Unpleasant taste, increases cor-
sewage, brines, sea water. rosiveness.

Fluoride (F) Not very abundant, sparingly Over 1.5 mg/l causes mottling
soluble, seldom found in of children's teeth, 0.88 to 1.5
industrial wastes except as mg/1 aid in preventing tooth
spillage, some sewage. decay.

Nitrate (NO3) Rocks, soil, sewage, industrial High indicates pollution, causes
waste, normal decomposition, methemaglobanemia in infants.
bacteria.

Hardness as CaCO3 Excessive soap consumption,
scale in pipes interferes in
industrial processes.
up to 60 mg/1 soft
60 to 120 mg/1 moder. hard
120 to 200 mg/1 hard
over 200 mg/1 very hard

*After Leve and Goolsby, 1969.

BUREAU OF GEOLOGY

Table 10. U.S. Public Health Service drinking-water standards.

Limit not to Cause for
Chemical substance be exceeded rejection

Physical
Color 15 units
Taste Unobjectionable
Threshold odor number 3
Turbidity 15 units

Chemical (mg/1) (mg/1)
Alkyl benzene sulfonate .5
Arsenic .01 .05
Barium 1.0
Cadmium .01
Chloride 250
Chromium hexavalentt) .05
Copper 1.
Carbon chloroform extract* .2
Cyanide .01 .2
Fluoride** .7-1.2 14.24
Iron .3
Lead .05
Manganese .05
Nitrate 45
Phenols .001
Selenium .01
Silver .05
Sulfate 250
Total dissolved solids 500
Zinc 5

*Organic contaminants
**The concentration of fluoride should be between 0.6 and 1.7 mg/1, depending on the
listed and average maximum daily air temperatures.

HARDNESS

The hardness of water is reported by the Geological Survey in terms of
an equivalent quantity of calcium carbonate in a sample of water. Table 7
gives the hardness of water sampled from shallow wells in Duval County.
Hardness ranged from 10 mg/1 (milligrams per liter) to greater than 1,900
mg/L With the exception of water from wells 302829N0814128.1 and
302017N0815228.1, which has anomalously high mineral content, the average
hardness is 187 mg/l. As a comparison, water in the Floridan aquifer in Duval
County has a hardness ranging from 50 to about 350 mg/1 and averaging
about 250 mg/l. In some places waters from both the shallow and the
Floridan aquifer show similarity in hardness, as well as in other mineral
constituents.
The two wells that have anomalously high mineral content of water
(table 7) are apparently isolated occurrences. Chemical analyses indicate that

REPORT OF INVESTIGATIONS NO. 59

the quality of the water is related to aquifer constituents at those two places,
possibly gypsum or anhydrite. Water in wells a few hundred feet away and
the same depth was field tested for specific conductance, and results indicate
a relatively low mineral content.
Figure 11 shows the relation of hardness with depth. In general the
hardness increases with depth down to about 100 feet. Above this level, 13
analyses showed an average hardness of 165 mg/1, whereas, below, 14 analyses
resulted in an average hardness of 213 mg/1. Wells that tap sandy zones
usually yield softer water than those that tap carbonate rocks. As rain
recharges the aquifer, water near the surface is relatively soft but becomes
progressively harder as it passes downward through the aquifer.
The generalized distribution of hardness of water pumped from the
shallow-aquifer system of Duval County is shown on figure 12. Although
hardness varies somewhat with depth, the map on figure 12 shows the
distribution of hardness, as reflected by the predominant well depth in each
area. Most of the wells in a given area are about the same depth and obtain
water from the same zone.

DISSOLVED SOLIDS
The generalized map showing distribution of dissolved solids in water in
the shallow-aquifer system throughout Duval County is shown on figure 13.
Dissolved solids are lowest in the east-central part of the county and
southwest of metropolitan Jacksonville. The area of lowest dissolved solids
generally coincides with an ancient coastal ridge, which roughly parallels the
present shoreline. The ridge is underlain by permeable sand, which readily
accepts recharge from rainfall.
The Geological Survey uses the residue-on-evaporation method and the
calculation method to determine dissolved solids in a water sample. Calculated
values determined from analyses of water from shallow wells are listed in table
7. Dissolved solids range from about 50 mg/1 to 2,560 mg/1. A plot of
dissolved solids versus depth is shown in figure 11 and shows a general
increase with depth to 100 feet.

CHLORIDE
All chloride content of water in the shallow aquifer ranges from 6 mg/1
to less than 30 mg/l, far below the maximum concentration of 250 mg/1
suggested by the U. S. Public Health Service. Figure 14 is a map of Duval
County showing chloride distribution in the shallow-aquifer system. Although
none of the water tested showed excessively high concentrations of chloride,
local well drillers report that water from shallow wells along the St. Johns
River east of Jacksonville and on the north side of the river is relatively salty.

______ .~ .~

.
*
S
0
S
S
S
0
\ S 0
--~ *'e S

I .5

-I

B S *Uj\

2
*
300-- ______(______

I 2 3 0 200 400 600 0 200 400 60
IRON DISSOLVED SOLIDS HARDNESS (os CoCO)
MILLIGRAMS PER LITER

Graph showing the relation of hardness, dissolved solids, and iron content to depth of water from the shallow-aquifer system.

S\

S **

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\ \

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IS I
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-- \- -I

I I

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met
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Figure 11.

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301 1? 7 2 T 14954
9 14 0ye gl5140

ISH
az zI
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3 185

1740
MAYPO

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145
Fi gr4 1t ifA

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iWell 0 240 o
Number Indclalm hardnie of water in mWliramis per user.
HARDNESS

201400
More.theoo 400 ST. JOHNS CO. 0o 5 MILES
80210, 02,00' 45' 30 81 20'
Figure 12. Generalized distribution of hardness of water in wells that tap the shallow-aquifer system in Duval County.

82010' 82100' 45' 30 8102 0'
Figure 13. Generalized distribution of dissolved solids in water from wells that tap the shallow-aquifer system in Duval County.

I2

400

-AL10

040
Oroo

I NATION CLAY COUNTy
NIabe tais ddws megllt of w t inr Ulam p l.s".
CRInIVDE
Il milpas pr lPt" r

1010o20
Moh0 ST JOHNS CO MOsO

6200' 45' 30 Of 20'
Figure 14. Map of Duval County showing the distribution of chloride in water from the shallow-aquifer system.

BUREAU OF GEOLOGY

In that area the river has been dredged to a shallow limestone layer, and it is
possible that salt water is entering the limestone from the river.

IRON
Iron occurs in varying amounts in the water from shallow wells
throughout Duval County. As indicated in table 8 and on figure 11, the iron
content ranges from 0.01 mg/1 to 2.8 mg/1. Many of the waters tested had an
iron content much higher than that recommended by the Public Health
Service standard of 0.3 mg/1l. Such water may stain clothing and plumbing
fixtures, turning them a yellow or rusty color. In some places filters have been
used with moderate success to remove the iron.
Forty-five samples were collected from shallow wells throughout the
county and analyzed for iron content only. All samples were filtered with a
0.45 micron filter at the time of collection to remove any possible
iron-bearing solids from the water.
The iron content of the water in many shallow sandpoint wells often
increases after a few years' use of the wells. This is primarily caused by the
corrosive nature of the water in the aquifer, which corrodes the pipes and
fittings inside the wells and water systems. The iron can be partly removed by
filtering, by aeration, or by softening equipment. The relation of iron content
with depth is shown in the graph in figure 11. Only those samples that had
been filtered at the time of collection are plotted on the graph. As indicated
by the graph, the highest concentrations of iron occur at the depth interval
between 70 and 150 feet.
Figure 15 is a map showing the distribution of iron in the
shallow-aquifer system in Duval County. Throughout much of the area the
iron content is 0.5 mg/l or less. In those areas of highest iron concentration,
much of the land is marshy. Doubtless, the marshy land, with its reducing
environment, insofar as iron is concerned, creates a condition whereby rainfall,
saturated with oxygen as it infiltrates the land surface, can take into solution
a relatively large amount of iron. At least a part of this iron is carried
downward into the aquifer.
The main chemical factors that control the solubility of iron in natural
waters are the hydrogen ion concentration (pH) and the oxidation-reduction
potential (Eh). Hem (1970, p. 114-126) gives a fairly complete description of
the chemical and physical factors that control the occurrence of iron in
ground water.

MIS 0 0024M.
0
00.12
0 0.sI

0
2.1MAYPO
1/ ~~JACKSONVILLE 0
00.02 112WETitOP WIAN 1 0.0
goje .ao o7 c
Si0.16 JACSSONVILEB
BEACH
I' -- .;2l O, r".13a

I D~'AAIN CL AY COUNT N'S
m Numlber hId'igaII iron content or Wlter, in mW smlslpilr ther.,
IRON CONTENT BAYARD
In malptme per Uhe \ 10.o3
Ove 1.0 ST, JOHNSCO
2*10" 6200' 45' 30 0120'
qJI
Figure 15. Map of Duval County showing the approximate areal distribution of iron in the water from the shallow-aquifer
system.

BUREAU OF GEOLOGY

HYDROGEN SULFIDE
Hydrogen sulfide occurs in the water from many of the wells that
penetrate the shallow-aquifer system. Water from wells that are less than
about 50 feet deep usually contains no noticeable hydrogen sulfide; however,
a few wells 60 feet deep yield water having a moderate to strong hydrogen
sulfide odor.
Hydrogen sulfide is corrosive to pipes and fixtures and is undesirable in
drinking water. As hydrogen sulfide is a gas, it can be easily removed by a
simple aeration process.

WATER USE

Water from the shallow-aquifer system is used for domestic, industrial,
commercial, and agricultural purposes. Most of the water withdrawn is used
for washing, toilets, drinking, swimming pools, and lawn irrigation. In many
residential areas served by water utilities, private shallow-aquifer wells supply
supplemental water for swimming pools or to irrigate lawns and small gardens.
The most common industrial use is for heat-exchange units in large
air-conditioning systems. Several small commercial establishments, including
laundries, stores, fishing camps, and service stations, use water from the
shallow aquifer. Several schools in Duval County are supplied water from wells
that penetrate the shallow-aquifer system.
A considerable amount of water is used for irrigation in Duval County.
Besides water for irrigating lawns and small gardens, several small truck farms
and nurseries in the Jacksonville area use water from shallow wells. Shallow
wells also supply water for cattle, hogs, horses, and chickens.

WELL CONSTRUCTION PRACTICES
The shallow-aquifer system is present throughout all of Duval County,
and wells of varying depths obtain dependable supplies of water from it. Most
obtain water from highly permeable, sometimes cavernous, limestone, and in
places a single 2-inch well may supply water to as many as four homes. These
wells are often referred to locally as "rock wells." The shallow limestone is
missing in the Arlington area and along the coastline from Mayport to Ponte
Vedra. In the Arlington area, many wells obtain water from coarse sand and
shell beds 75 to 100 feet below land surface. Along the coastline they obtain
water from coarse sand in the Hawthorn Formation, 140 to 160 feet below
land surface.
Wells that obtain water from the shallow-aquifer system are usually
constructed by either of two methods by jetting or by hydraulic rotary. A

REPORT OF INVESTIGATIONS NO. 59

water-bearing zone is indicated when circulation is lost, that is, when drill
cuttings and drilling fluid no longer return to the surface. The well is then
jetted or drilled a few feet deeper to insure adequate penetration of the
water-yielding zone. The well is then cased with the appropriate diameter
casing which usually is seated into the top of the water-yielding zone, leaving
from 10 to 20 feet of open hole below the end of the casing. When the
water-yielding bed is sand or shell, the wells are usually equipped with a short
well screen to prevent sand from getting into the water system.
After completion, the well is equipped with a jet pump and a / to 1
horsepower electric motor. Where the water level in the well is greater than 10
feet below land surface, a deep-well jet pump is used to insure adequate lifting
power during low water level periods.
During the dry season, when water levels are lowest, wells may yield
sand upon heavy pumping. This may be the result of improper screen
selection or inadequate well construction. In a few places water has been
pumped from wells at velocities sufficient to carry sand out of the wells,
causing the uncased part of the wells to cave in or to yield sand. When
limestone is tapped, the problem of caving or pumping of sand can be avoided
by setting the casing in the top of the limestone, thus preventing the overlying
clay or sandy clay from collapsing or flaking into the well bore.

ADDITIONAL STUDIES NEEDED
To further evaluate the water in the shallow-aquifer system and to
determine its importance in the overall water resources of Duval County,
considerable knowledge is yet to be gained. The following steps should be
taken in an effort to obtain this knowledge:
(a) obtain detailed data on the amount of water withdrawn from the
shallow-aquifer system;
(b) conduct aquifer tests to determine the ability of the aquifer to
transmit water, to define the best producing zones, and to
delineate the areas where greatest yields can be expected;
(c) continue to monitor water levels and quality of water in shallow
wells in an effort to determine the relation between the
shallow-aquifer system and the Floridan aquifer;
(d) investigate those areas where salt water is suspected to enter the
shallow-aquifer system, particularly along the St. Johns River east
of Jacksonville; and,
(e) investigate areas of artesian spring flow to determine the amount of
ground-water discharge to streams in the area. A detailed inventory
of all springs in the area coupled with periodic measurements of
their discharge should lead to valuable information regarding the
relation of spring discharge to surface-water runoff.

47

BUREAU OF GEOLOGY

Information obtained in establishing the hydraulic relation between the
shallow-aquifer system and the Floridan aquifer will be used in conjunction
with an analog model of the Floridan aquifer to determine the future water
supplies for the Jacksonville area.

CONCLUSIONS
Present growth trends indicate that the population of the Jacksonville
area will increase 30 percent from 1966 to 1980 (Leve and Goolsby, 1969).
In addition to this estimated increase in population, present industries will
probably expand, and new industries will probably be established, and more
water will be needed. If total pumpage in the Jacksonville area increases 25 to
40 percent, the shallow-aquifer system, which underlies all of Duval County,
could be further tapped to supplement the supply from the Floridan aquifer.
The water in the shallow-aquifer system is generally of good quality and
meets the U. S. Public Health Service standards for drinking water. In most
places it has less mineral content than water from the Floridan aquifer. In
some places the water in both aquifers is similar in quality, suggesting that
they may be hydraulically connected.
Recharge to the shallow-aquifer system is from local rainfall. Water
levels respond rapidly to rainfall and are highest during the rainy season (June
to October) and lowest during the dry season (November to May). Ten to
sixteen inches of rainfall is estimated to recharge the aquifer, the amount
varying from place to place. The main recharge area is in the western
one-third of the county and along high sand ridges east of Jacksonville.
The shallow-aquifer system is discharged through springs and seeps, by
evapotranspiration, by pumping from wells, and by downward percolation to
the deeper Floridan aquifer. Discharge varies from place to place within the
county, but 10 to 16 inches of water is estimated to discharge from the
aquifer annually, of which 4 to 6 inches is discharged into the atmosphere.
Water is obtained from three principal zones in the shallow-aquifer
system: (1) Surficial sand beds of Pleistocene and Holocene age, (2) a
relatively continuous layer of shell, limestone, and sand of late Miocene or
Pliocene age, and (3) lenses of coarse sand and sandy limestone within the
upper part of the Hawthorn Formation of middle Miocene age.
Because the water in the shallow-aquifer system is easily accessible, is
directly replenished by rainfall, and is of good quality, it represents a reliable
source of fresh water for future use. In some parts of Duval County large
quantities of water are obtained from large-diameter wells that penetrate the
permeable limestone of the shallow-aquifer system. In other areas, where

BUREAU OF GEOLOGY

HYDROGEN SULFIDE
Hydrogen sulfide occurs in the water from many of the wells that
penetrate the shallow-aquifer system. Water from wells that are less than
about 50 feet deep usually contains no noticeable hydrogen sulfide; however,
a few wells 60 feet deep yield water having a moderate to strong hydrogen
sulfide odor.
Hydrogen sulfide is corrosive to pipes and fixtures and is undesirable in
drinking water. As hydrogen sulfide is a gas, it can be easily removed by a
simple aeration process.

WATER USE

Water from the shallow-aquifer system is used for domestic, industrial,
commercial, and agricultural purposes. Most of the water withdrawn is used
for washing, toilets, drinking, swimming pools, and lawn irrigation. In many
residential areas served by water utilities, private shallow-aquifer wells supply
supplemental water for swimming pools or to irrigate lawns and small gardens.
The most common industrial use is for heat-exchange units in large
air-conditioning systems. Several small commercial establishments, including
laundries, stores, fishing camps, and service stations, use water from the
shallow aquifer. Several schools in Duval County are supplied water from wells
that penetrate the shallow-aquifer system.
A considerable amount of water is used for irrigation in Duval County.
Besides water for irrigating lawns and small gardens, several small truck farms
and nurseries in the Jacksonville area use water from shallow wells. Shallow
wells also supply water for cattle, hogs, horses, and chickens.

WELL CONSTRUCTION PRACTICES
The shallow-aquifer system is present throughout all of Duval County,
and wells of varying depths obtain dependable supplies of water from it. Most
obtain water from highly permeable, sometimes cavernous, limestone, and in
places a single 2-inch well may supply water to as many as four homes. These
wells are often referred to locally as "rock wells." The shallow limestone is
missing in the Arlington area and along the coastline from Mayport to Ponte
Vedra. In the Arlington area, many wells obtain water from coarse sand and
shell beds 75 to 100 feet below land surface. Along the coastline they obtain
water from coarse sand in the Hawthorn Formation, 140 to 160 feet below
land surface.
Wells that obtain water from the shallow-aquifer system are usually
constructed by either of two methods by jetting or by hydraulic rotary. A

REPORT OF INVESTIGATIONS NO. 59 49

water is withdrawn from coarse sand and shell beds, large-diameter, properly
constructed gravel-packed or screened wells could yield larger quantities of
water.
Many areas now being supplied with water from individual wells in the
shallow-aquifer system, may, in the future, be supplied by municipal utilities
pumping from the Floridan aquifer; more water from the shallow aquifer,
therefore, could be used for other purposes.
In places where the shallow aquifer yields large quantities of water, the
water may prove to be suitable for some industrial use, if water of better
quality than that in the Floridan aquifer is required. The water is already used
for irrigation and dairy farming in parts of Duval County.

BUREAU OF GEOLOGY

Information obtained in establishing the hydraulic relation between the
shallow-aquifer system and the Floridan aquifer will be used in conjunction
with an analog model of the Floridan aquifer to determine the future water
supplies for the Jacksonville area.

CONCLUSIONS
Present growth trends indicate that the population of the Jacksonville
area will increase 30 percent from 1966 to 1980 (Leve and Goolsby, 1969).
In addition to this estimated increase in population, present industries will
probably expand, and new industries will probably be established, and more
water will be needed. If total pumpage in the Jacksonville area increases 25 to
40 percent, the shallow-aquifer system, which underlies all of Duval County,
could be further tapped to supplement the supply from the Floridan aquifer.
The water in the shallow-aquifer system is generally of good quality and
meets the U. S. Public Health Service standards for drinking water. In most
places it has less mineral content than water from the Floridan aquifer. In
some places the water in both aquifers is similar in quality, suggesting that
they may be hydraulically connected.
Recharge to the shallow-aquifer system is from local rainfall. Water
levels respond rapidly to rainfall and are highest during the rainy season (June
to October) and lowest during the dry season (November to May). Ten to
sixteen inches of rainfall is estimated to recharge the aquifer, the amount
varying from place to place. The main recharge area is in the western
one-third of the county and along high sand ridges east of Jacksonville.
The shallow-aquifer system is discharged through springs and seeps, by
evapotranspiration, by pumping from wells, and by downward percolation to
the deeper Floridan aquifer. Discharge varies from place to place within the
county, but 10 to 16 inches of water is estimated to discharge from the
aquifer annually, of which 4 to 6 inches is discharged into the atmosphere.
Water is obtained from three principal zones in the shallow-aquifer
system: (1) Surficial sand beds of Pleistocene and Holocene age, (2) a
relatively continuous layer of shell, limestone, and sand of late Miocene or
Pliocene age, and (3) lenses of coarse sand and sandy limestone within the
upper part of the Hawthorn Formation of middle Miocene age.
Because the water in the shallow-aquifer system is easily accessible, is
directly replenished by rainfall, and is of good quality, it represents a reliable
source of fresh water for future use. In some parts of Duval County large
quantities of water are obtained from large-diameter wells that penetrate the
permeable limestone of the shallow-aquifer system. In other areas, where

BUREAU OF GEOLOGY

REFERENCES

Bermes, B. J.
1963 (and Leve, G. W., and Tarver. G. R.) Geology and ground-water resources of
Flagler, Putnam, and St. Johns counties, Florida, Florida Geol. Survey Rept. Inv.
32, 97 p.
Clark, W. E.
1964 (and Musgrove, R. H., Menke, C. B., and Cagle, J. W., Jr.) Water resources of
Alachua, Bradford, Clay, and Union counties, Florida, Florida Geol. Survey Rept.
Inv. 35, 170 p.
Cooke, C. W.
1945 Geology of Florida, Florida Geol. Survey Bull 29, 339 p.
Dall, W. H.
1892 (and Harris, G. D.) Correlation paper: Neocene, U. S. Geol. Survey Bull 84,
349 p.
Derragon, Eugene
1955 Basic data of the 1955 study of ground water resources of Duval and Nassau
counties, Florida, U. S. Geol. Survey open-file report.
Ferris, J. G.
1962 (and Knowles, D. B., Brown, R. H., and Stallman, R. W.) Theory of aquifer tests,
U. S. Geol. Survey Water-Supply Paper 1536-E, 174 p.
Hem, J. D.
1970 Study and interpretation of the chemical characteristics of natural water, U. S.
Geol. Survey Water-Supply Paper 1473, 363 p.
Leve, G. W.
1961 Preliminary investigation of the ground-water resources of northeast Florida,
Florida GeoL Survey Inf. Circ. 27, 28 p.
1966 Ground water in Duval and Nassau counties, Florida, Florida Geol. Survey Rept.
Inv. 43, 91 p.
1968 The Floridan aquifer in northeast Florida, Ground Water vol. 6, no. 2, Urbana,
IlL, p. 19-29.
Leve, G. W.
1969 (and Goolsby, D. A.) Production and utilization of water in the metropolitan area
of Jacksonville, Florida, Florida Geol. Survey Inf. Circ. 58, 37 p.
MacNeil, S. F.
1950 Pleistocene shorelines in Florida and Georgia, U. S. Geol. Survey Prof. Paper
221-F.
Puri, H. S.
1964 (and Vernon, R. 0.) Summary of the geology of Florida and a guidebook to the
classic exposures, Florida Geol. Survey Spec. Publication No. 5, 312 p.
S tringfield, V. T.
1966 Artesian water in tertiary limestone in the southeastern states, U. S. Geol. Survey
Prof. Paper 517.
Vernon, R. 0.
1951 Geology of Citrus and Levy counties, Florida, Florida Geol. Survey Bull. 33,
256 p.
Visher, F. N.
1969 (and Hughes, G. H.) The difference between rainfall and potential evaporation in
Florida, Fla. Dept. of Nat Resources, Bureau of Geology, Map Series No. 32.

FLRD GEOLIOWC( ICA SURflViEWY~

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	Title Page
	Transmittal letter
	Contents
	Abstract
	Introduction
	Shallow-aquifer system
	Well construction practices
	Conclusions
	References
	Copyright