Citation
Ground-water resources of the Oakland Park area of eastern Broward County, Florida ( FGS: Report of investigations 20 )

Material Information

Title:
Ground-water resources of the Oakland Park area of eastern Broward County, Florida ( FGS: Report of investigations 20 )
Series Title:
( FGS: Report of investigations 20 )
Creator:
Sherwood, C. B
Place of Publication:
Tallahassee
Publisher:
[s.n.]
Publication Date:
Language:
English
Physical Description:
vii, 40 p. : illus., maps (part fold.) ; 23 cm.

Subjects

Subjects / Keywords:
Groundwater -- Florida -- Broward County ( lcsh )
City of Oakland Park ( local )
City of Fort Lauderdale ( local )
Middle River ( local )
Broward County ( local )
City of Pompano Beach ( local )
Cypress Creek ( local )
Aquifers ( jstor )
Water wells ( jstor )
Canals ( jstor )
Water tables ( jstor )
Pumping ( jstor )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Bibliography: p. 40.
General Note:
"Prepared by the United States Geological Survey in cooperation with the city of Fort Lauderdale and the Florida Geological Survey."

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University of Florida
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University of Florida
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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier:
022574473 ( aleph )
01726052 ( oclc )
AES1343 ( notis )
a 60009306 ( lccn )

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STATE OF FLORIDA

STATE BOARD OF CONSERVATION
Ernest Mitts, Director
FLORIDA GEOLOGICAL SURVEY
Robert 0. Vernon, Director




REPORT OF INVESTIGATIONS NO. 20




GROUND-WATER RESOURCES OF THE OAKLAND PARK
AREA OF EASTERN BROWARD COUNTY, FLORIDA




By
C. B. Sherwood
U. S. Geological Survey




Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
CITY OF FORT LAUDERDALE
and the
FLORIDA GEOLOGICAL SURVEY




TALLAHASSEE, FLORIDA
1959












CULTURAL
LIBRARY
FLORIDA STATE BOARD

OF

CONSERVATION


LEROY COLLINS
Governor


R. A. GRAY
Secretary of State


J. EDWIN LARSON
Treasurer



THOMAS D. BAILEY
Superintendent of Public Instruction


RICHARD ERVIN
Attorney General


RAY E. GREEN
Comptroller



NATHAN MAYO
Commissioner of Agriculture


ERNEST MITTS
Director of Conservation






LETTER OF TRANSMITTAL


'TJY1orlc g eo/ofr(ic(I S urvey

TALLAHASSEE

September 15, 1959

Mr. Ernest Mitts, Director
Florida State Board of Conservation
Tallahassee, Florida

Dear Mr. Mitts:

Florida Geological Survey Report of Investigations No. 20 is a
paper entitled, GROUND-WATER RESOURCES OF THE OAK-
LAND PARK AREA OF EASTERN BROWARD COUNTY, FLOR-
IDA, which was prepared by Mr. C. B. Sherwood, Hydraulic Engineer
with the U. S. Geological Survey, in cooperation with the Florida Geo-
logical Survey and the City of Fort Lauderdale.

The Oakland Park area obtains its water from the Biscayne aquifer,
composed of very permeable and porous, sandy limestones. The per-
meability of the aquifer increases with depth, and wells in the area
generally obtain water at depths ranging from 60 to 80 feet, or between
100 and 200 feet, depending on the quantity of water desired. The
data presented in this paper can be used for further development of
water and wise management of resources in the area. Large quantities
of ground water are still available at Oakland Park, if salt-water en-
croachment can be controlled. The data in this study provide the nec-
essary information to begin an effective water management program.

Respectfully yours,

Robert 0. Vernon, Director


























Completed manuscript received
April 9, 1959
Published by the Florida Geological Survey
Rose Printing Company, Inc.
Tallahassee, Florida
September 1959






TABLE OF CONTENTS


Page

Letter of transmittal __ iii

Abstract 1

Introduction 1

Purpose and scope 1

Previous investigations 2

Acknowledgments ______ -- 3

Geography 3

Location and general features of the area 3

Climate _--________-__ ------- 3

Topography and drainage 3

Geologic formations and their water-bearing characteristics 7

Ground water 12

Recharge and discharge 13

Water-level fluctuations 13

Salt-water encroachment 22

Quality of water 29

Quantitative studies 32

Ground-water use 38

Conclusions 38

References 40






ILLUSTRATIONS

Figure Page'

1 Map of Florida showing location of area investigated 4


2 Map of parts of Broward and Palm Beach counties showing canals and
levees of the Central and Southern Florida Flood Control District 5


3 Map of Oakland Park area showing locations of wells Between 5 & 6


4 Log of well G-563 8


5 Log of well G-820 9


6 Log of well S-998 10


7 Log of well S-999 -___ 11


8 Monthly pumpage from the Prospect well field and monthly rainfall
at Fort Lauderdale 14


9 Map showing contours on the water table in the Biscayne aquifer, in
eastern Broward County, on February 15, 1941 16


10 Hydrographs of wells G-127 and G-128 and weekly rainfall at Fort
Lauderdale during 1940-41 _- 17


11 Map showing contours on the water table in the Biscayne aquifer in
the Oakland Park area, August 7, 1956 18


12 Map showing contours on the water table in the Biscayne aquifer in the
Oakland Park area, September 21, 1956 __- -- 19


13 Map showing contours on the water table in the Biscayne aquifer in the
Oakland Park area, October 19, 1956 __________- 20


14 Hydrographs of wells G-768 and G-820, average daily pumpage from
the Prospect well field, and daily rainfall at Fort Lauderdale, June-
December 1956 21







15 Hydrographs of Middle River Canal above and below dam, August
7-12, 1956 -- 22


16 Hydrographs of Middle River Canal above and below dam during
1956 ________ 23


17 Hydrographs of Pompano Canal above Market and City dams, 1956 24


18 Map of eastern Broward County showing maximum chloride content
recorded in water samples from wells and streams, 1941-57 27


19 Chloride content of water from wells S-330 and S-830, at junction of
South New River and Dania Cutoff Canals, 1941-57 28


20 Map of Prospect well field showing layout of municipal supply wells
and observation wells __ 32


21 Hydrograph of well G-768, in the Prospect well field, during pumping
test, August 7-8, 1956 -.- _____. 34


22 Idealized sketch showing flow in a leaky aquifer 35


23 Hydrograph of well G-768, in the Prospect well field, showing effect
of pumping in the well field 37



Table Page

1 Average monthly temperature, in degrees, at Fort Lauderdale, and av-
erage monthly rainfall, in inches, at Fort Lauderdale and Pompano
Beach -5--


2 Chemical analyses of water from selected wells _----- 30








GROUND-WATER RESOURCES OF THE OAKLAND PARK
AREA OF EASTERN BROWARD COUNTY, FLORIDA

ABSTRACT

The Biscayne aquifer is the source of all fresh ground water in the
Oakland Park area of eastern Broward County, Florida. This aquifer ex-
tends from the land surface to more than 215 feet below mean sea level
and is composed chiefly of sandy marine limestone, calcareous sandstone,
and beds of fine to medium quartz sand. The aquifer differs from place
to place, but, in general, most of the layers of limestone and sandstone
occur at depths below 60 feet. The permeability of the aquifer increases
with depth.
Wells for small supplies generally obtain water at depths ranging
from 60 to 80 feet, whereas wells for large supplies usually obtain water
from the interval between 100 and 200 feet. Large-diameter wells obtain
as much as 1,000 gpm (gallons per minute) from the lower part of the
aquifer.
Chemical analyses of ground-water samples indicate a hard limestone
water that is suitable, naturally or with treatment, for most ordinary uses.
Periodic determinations of chloride content of the ground water show that
some salt-water encroachment has occurred in areas near the coast and
in the Middle River basin.
Pumping-test data for deep wells in the Prospect well field area in-
dicate approximate aquifer coefficients of transmissibility and storage of
2,000,000 gpd per foot and 0.015, respectively. However, the data indicate
also that the hydraulic characteristics of the aquifer are complicated
by the presence of beds of sand, silt, and clay in the upper 100 feet of
the aquifer and by recharge from surface-water sources. Quantitative data
and areawide water-level and salinity data indicate that large quanti-
ties of ground water are available for future development if salt-water
encroachment can be effectively controlled.

INTRODUCTION
PURPOSE AND SCOPE
The rapid growth of population and industries in eastern Broward
County has introduced the problem of preserving existing ground-water
supplies and has caused a growing need for additional supplies. As in
many coastal areas, this problem involves not only finding and devel-
oping a satisfactory source of water but also protecting this source






FLORIDA GEOLOGICAL SURVEY


against salt-water encroachment from the sea. Recognizing the need
for data in solving their problems, officials of the city of Fort Lauderdale
requested that an investigation be made of the ground-water resources
of eastern Broward County, in the vicinity of Oakland Park. The inves-
tigation was made by the U. S. Geological Survey in cooperation with
the Florida Geological Survey and the city of Fort Lauderdale.
The purpose of the investigation was to determine, insofar as pos-
sible, the following things:
1. The ground-water potential of the area.
2. The extent of salt-water encroachment into the Biscayne aquifer.
3. The hydraulic coefficients of the aquifer and the safe rate of with-
drawal for the development of large supplies.
4. The effect of water-control works of the Central and Southern
Florida Flood Control District on the ground-water resources of
the area.
Field studies, begun in December 1955, consisted of the following:
1. A partial inventory of wells in the area.
2. The installation of shallow wells to be used for water-level studies
and one deep test well to be used for geologic and salinity studies.
3. Pumping tests to obtain data on the water-transmitting and storing
properties of the aquifer.
4. A leveling program to determine the altitudes of measuring points
for water-level measurements.
5. The determination of the chloride content of water from selected
wells and sampling points in streams, and comprehensive analyses
of water from selected wells.
6. The installation of two automatic water-stage recorders and the
areawide measurements of water level at selected times.
The investigation was made under the general supervision of A. N.
Sayre, Chief, Ground Water Branch, and under the immediate supervi-
sion of Howard Klein, Geologist, and M. I. Rorabaugh, District Engineer,
all of the U. S. Geological Survey.

PREVIOUS INVESTIGATIONS
No detailed investigation of the ground-water resources of the Oak-
land Park area had been made prior to this investigation. Considerable
information pertinent to the area is available, however, in publications
or unpublished open-file reports of the Florida Geological Survey and
the U. S. Geological Survey. Data from these reports have been used
freely in the preparation of this report. Frequent references to the geology
of the area and the occurrence and quality of the ground water in eastern







REPORT OF INVESTIGATIONS No. 20


Broward County are contained in reports by Vorhis (1948), Parker and
others (1955), and Schroeder and others (1958).

ACKNOWLEDGMENTS
Grateful acknowledgment is hereby made for the cooperation and
assistance given by officials of the city of Fort Lauderdale and the engi-
neering firm of Philpott, Ross and Saarinen. The wholehearted coopera-
tion of the personnel of the Fort Lauderdale water-treatment plants while
field work was in progress, was especially helpful. Data pertaining to
flood-control works in the area were supplied by officials of the Central
and Southern Florida Flood Control District.

GEOGRAPHY
LOCATION AND GENERAL FEATURES OF THE AREA
The Oakland Park area is on the lower east coast of Florida between
the cities of Pompano Beach and Fort Lauderdale (fig. 1). It is bounded
on the north by the Pompano Canal, on the east by the Intracoastal
Waterway, on the south by the south fork of the Middle River, and on
the west by Conservation Area No. 2.
The city of Oakland Park is north of the north fork of the Middle
River, about two miles west of the Intracoastal Waterway (fig. 2). The
Prospect well field, which is one source of water supply for Fort Lauder-
dale, lies between the upper reaches of Cypress Creek and the Middle
River, about two miles northwest of Oakland Park (fig. 3).

CLIMATE
The climate of Fort Lauderdale is subtropical and the humidity is
usually high. The average monthly temperatures, as shown by U. S.
Weather Bureau records, range from 68.83F. to 82.60F. As of the end
of 1956, the mean annual temperature was 74.20F. and the mean yearly
rainfall was 59.88 inches, for 48 years of record. The heaviest rains occur
during the period from June through October. Table 1 shows monthly
and yearly averages of temperature and rainfall at the Fort Lauderdale
station for the period 1940-56, and average rainfall at the Pompano Beach
station, about seven miles north of Fort Lauderdale, for the period
1941-56.

TOPOGRAPHY AND DRAINAGE
The Oakland Park area is on the coastal ridge that separates. the
Atlantic Ocean from the Everglades. The ridge in this area is about six






FLORIDA GEOLOGICAL SURVEY


Figure 1. Map of the peninsula of Florida showing location of area investigated.







REPORT OF INVESTIGATIONS NO. 20


Figure 2. Map of parts of Broward and Palm Beach counties showing canals and
levees of the Central and Southern Florida Flood Control District.

TABLE 1. Average Monthly Temperature, in Degrees, at Fort Lauderdale, and
Average Monthly Rainfall, in Inches, at Fort Lauderdale and Pompano
Beach
Temperature Rainfall
Month Fort Lauderdale Fort Lauderdale1 Pompano Beach'
Jan. 68.3 2.18 2.22
Feb. 68.3 1.96 1.51
Mar. 70.9 2.81 2.17
Apr. 74.2 4.06 3.86
May 77.4 4.93 3.60
June 80.3 7.55 6.01
July 81.7 6.03 7.39
Aug. 82.6 6.74 6.68
Sept. 81.5 8.82 9.32
Oct. 77.8 8.83 9.58
Nov. 72.3 3.05 3.09
Dec. 69.2 2.37 2.08
Yearly average 74.2 59.83 57.51
'Discontinuous record 1940-56, U. S. Weather Bureau.
'Discontinuous record 1941-56, U. S. Weather Bureau.


SC AL IN MILE
5 o 6 0





FLORIDA GEOLOGICAL SURVEY


miles wide and is very low and nearly flat, except where it is cut by the
main streams Cypress Creek near Pompano Beach and the Middle
River south of Oakland Park (fig. 3).
The land surface ranges in altitude from about four feet above mean
sea level in areas adjacent to stream channels to about 15 feet above
mean sea level in the vicinity of the Prospect Air Field and in the area
which parallels U. S. Highway 1, west of the Intracoastal Waterway.
Most of the area, however, is about nine feet above mean sea level.
The area is drained chiefly by underground flow toward the ocean
and into the canals and streams that flow generally eastward to the
Intracoastal Waterway. The permeable quartz sand and oolitic limestone
that form the shallow subsurface materials allow rainwater to infiltrate
rapidly to the water table, and there is very little surface runoff to the
canals and streams. The underground flow pattern is considerably influ-
enced by continuous pumping in Fort Lauderdale's Prospect well field
and by water-control structures in canals.
The Pompano Canal and Cypress Creek traverse the northern part
of the area from west to east, through the ridge, to the Intracoastal
Waterway. Cypress Creek drains the slough area north of Prospect field,
and the Pompano Canal drains the area west of Pompano Beach and is
a part of the overall flood-control system in southern Florida. The tribu-
taries of the Middle River traverse the southern part of the area and
drain the low areas south of Prospect field. Local farm drainage is
effected by intricate systems of shallow ditches which connect to
major drainage channels. The drainage and flood-control works are part
of a cooperative state and federal program designed to alleviate the
effects of both flood and drought conditions in central and southern
Florida.
The Oakland Park area lies east of one of a series of water conserva-
ton areas (Conservation Area No. 2) that are bounded by a levee system
extending from Lake Okeechobee to southern Dade County (fig. 2).
The Pompano Canal and the Middle River Canal connect with a canal
on the east side of Conservation Area No. 2. The Pompano Canal is
controlled by dams near its confluence with Cypress Creek, and the
Middle River Canal is controlled by a dam about 5% miles inland from
the Intracoastal Waterway. The tidal reach of Cypress Creek extends
inland about two miles, and the various branches of the Middle River
are tidal as far upstream as the flood-control dam. In the tidal reaches
of these streams salt water is free to advance upstream as far as tides
and fresh-water flow permit.













M.iL. _


OP
SW 15


ORT


SSl321 EXPLANATION
e 0
1120 oP WELL
S49 PUBLIC-SUPPLY WELL
s OI WATER-LEVEL RECORDING GAGE
0I -ITS CHLORIDE-CONTENT DATA AVAILABLE
0
SURFACE-WATER OBSERVATION POINT
CHEMICAL ANALYSIS AVAILABLE
LAUDER LE 0

S. fCALP iN FEET

Y ^ }j0 L^/ \#31F zf2 4R1"'1f


Figure 8. Map of Oakland Park area showing locations of wells,


fill -


041 42


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m ........


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i
. I _


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I


OMPANO BEACH-




-372 .. L011ITS






\-- 0 DAM **------
0P 57





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F







REPORT OF INVESTIGATIONS No. 20


GEOLOGIC FORMATIONS AND THEIR WATER-BEARING
CHARACTERISTICS
The name Biscayne aquifer was used by Parker (1951, p. 820-823) for
the hydrologicc unit of water-bearing rocks that carries unconfined
ground water in southeastern Florida." This aquifer is the only source
of fresh ground water in Dade and Broward counties. Limestone strata
at depths of 900 to 1,000 feet yield large quantities of water under arte-
sian pressure, but the water is highly mineralized and unsuitable for
general use. The artesian aquifer is not discussed in this report.
In the Oakland Park area the Biscayne aquifer includes marine de-
posits ranging in age (oldest to youngest) from late Miocene through
Pleistocene, in the following sequence (Schroeder, 1958): Tamiami for-
mation (upper part), Anastasia formation, Miami oolite, and Pamlico
sand. In Dade County and southern Broward County the aquifer is
underlain by a relatively impermeable greenish marl at or near the top
of the Tamiami formation, but in northeastern Broward County the
aquifer thickens and its base is considerably below the top of the Tami-
ami formation. Some of the geologic information included in this report
was obtained from shallow observation wells in the Oakland Park area
and some was obtained from four deep wells, namely, test well G-563
in the northern part of Fort Lauderdale, test well G-820 in the Prospect
well field, and supply wells S-998 and S-999 in the Pompano Beach well
field. Logs of these wells are shown in figures 4 through 7.
The log of well G-820 in the Prospect well field shows highly per-
meable limestone at a depth of 224 feet below the land surface, and local
drillers report that similar limestones occur at greater depths. In each of
the deep wells the marine deposits of the Tamiami formation of late
Miocene age are overlain by very similar deposits of the Anastasia for-
mation of the Pleistocene age. Well cuttings from both formations show
that they are composed chiefly of alternating beds or lenses of sandy
limestone or calcareous sandstone, sand, shells, and sandy clay or marl.
Because of the lack of distinctive fossils in the samples and the absence
of good stratigraphic correlation, no line of demarcation was drawn
between the Tamiami and Anastasia formations. In general, the part
of the aquifer underlying the Oakland Park area contains more uncon-
solidated sandy and clayey material than the part underlying areas south
of Broward County; thus, the overall permeability of the aquifer in this
area is lower than the permeability of the aquifer underlying areas to
the south.
Wells developed in the limestones and sands of the Tamiami and An-
astasia formations supply all the public water systems in eastern Broward






8 FLOmDA GEOLOGICAL SURVEY


WELL G563 4TH AVE.8 IOTH ST., N.W. FORT LAUDERDALE, FLA.

WELL LOG
0 10 Sand, quartz, brown.
10 14 Sand, quartz, with tan clay included in a
shelly, oolitic solution-riddled limestone.
2'0- 14 34 Sand, quartz, white; some fine grains of
.:; epidota.


34 40 Sand, quartz, gray-white; many small tan
40 pelecypod shells.
40 45 Limestone, hard at top, soft and shelly
at base.
45 68 Sandstone, calcareous, light-gray, scattered
cellophane and some llmonite, loosely to
60- tightly cemented with somo blue-green clay
below 60 feet.
68 84 Sand, quartz, very fine grained, peppered
with cellophane and ilmenite; some sand-
*0 stone nodules.

,. 84 90 Marl, sandy, clayey, pale-blue-green;
permeability low.
90 107 Sandstone, quartz sand, and shell fragments.
100 Sand is very fine grained and is peppered
k with cellophane and ilmenito.
." t107 112 Sandstone, calcareous, white; quartz sand,
very fine to coarse.
120 112 151 Sand, quartz, shelly, fine to coarse, white,
^ peppered with cellophane and ilmenito;
a few thin layers of sandstone.
I-.-.
%l 140 ':

151 153 Limestone, sandy, very dense, white.
153 155 Sandstone and sand, calcareous, fossilif-
kI0 earous.
155 175 Sand, calcareous, gray-brown to gray;
some nodules or thin sandstone layers.
w 175 177 Limestone, sandy, white.
180 177 179 Sandstone, calareous.



zoo


Figure 4. Log of well G-563.







REPORT OF INVESTIGATIONS No. 20


WELL G 820 PROSPECT WELL FIELD

WELL LOG
0 8 Sand, quartz, white, medium.
8 11 "Hlardpan", sand, quartz, medium; brown
organic material.
20- 11 43 Sand, quartz, tan.



40
43 54 Sand, quartz, tan, fine to medium.


60 54 76 Sand, quartz, white, very fine to medium;
interbodded blue-green clay.


U 80 76 87 Sand, very fine to medium; contains somu blue-
green clay and thin layers or nodules of soft
white sandstone.
87 99 Sand, quartz, gray, medium to coarse,
peppered with ilmanite and phospnate.
-,100 99 110 Sand, can, medium to very coarse; a few
Sthin layers of gray limestone.
11U 131 Same as above but less limestone.

^ 120

131 137 Limestone. sandy, gray; contains a large percentage
of medium to coarse sand.
t4 140 137 142 Same as above but sand very fine to medium.
W4j 142 158 Limestone, sandy, can and gray; contains a large
percentage of very fine to medium sand.

160 158 159 Limestone, gray, very hard.
k 159 171 Limestone, sandy, gray; contains a large
percentage of very fine to medium sand.
171 175 Limestone, gray, very hard.
180 175 189 Limestone, sandy, white,

189 205 Limestone, sandy, gray.

200 -

205 224 Limestone, sandy, white.

220



240



Figure 5. Log of well G-820.






FLORIDA GEOLOGICAL SURVEY


WELL S998 POMPANO BEACH WELL FIELD
__ ._.._WELL LOG
0 o 10 Sand, quart, buff, coarse, calcareous.
10 12 Sand, quarts, white to buff, fine to medium,
calcareous; a few rounded shell fragments,
12 25 Limestone, shelly, very sandy, gray, porous
20 and hard.
S2 2- 30 Sand, quarts, poorly sorted, some shell
fragments.
30 40 Same as above, but fewer shell fragments,
*40 409 67 Sand, quarts, poorly sorted, light gray,
very few shell fragments.

60
67 76 Coquina, very sandy, porous, grayish-buff.
MA 76 80 Sand, quartz, medium to coarse, buff to gray,
. 8 calcareous.
4 5 80 89 Limestone, very sandy, silty and phosphatic,
4 >hard, greenish-gray.
S89 103 Sandstone, very calcareous, gray, hard, fair
100 -porosity; shell fragments and a few
S-- phosphate grains.
h" 103 Sand, quartz, medium to fine, white; very
Sfine-grained phosphate.
120



Figure 6. Log of well S-998.


County. Higher yields can be obtained from wells in the limestone
parts of the aquifer than can be obtained from wells in the sandy parts.
Individual 10-inch wells in the Prospect well field yield 820 gpm with
approximately six feet of drawdown. These wells are screened in soft
sandy limestone or calcareous sandstone, and the bottoms of the screens
are set at depths ranging from 114 to 140 feet. The screens are 10 inches
in diameter and average 20 feet in length. Wells for small individual sup-
plies generally tap thin, local sandstones at depths ranging from 60 to
80 feet.
The Miami oolite of Pleistocene age, which occurs in the upper part of
several test wells, is the surface rock that blankets much of southeastern
Florida. In the Oakland Park area it is generally a white to yellowish
thinly laminated, crossbedded oolitic limestone containing large amounts
of sand and shells. The oolite is mined in shallow excavations south and
west of the Prospect well field, but it is either very thin or missing in
much of the Oakland Park area. The Miami oolite is very permeable,
and it is tapped by domestic supply wells wherever it is thick enough to
supply appreciable amounts of water.







REPORT OF INVESTIGATIONS No. 20 11


WELL S 999 POMPANO BEACH WELL FIELD

____WELL LOG




20-

0 69 No samples'.

40



60-

,'* 6 09 97 Sand, quartz, fine to medium, marly; specks
t 8: of cellophane and a few fragments of
o so calcareous sandstone.


$. W 97 108 Sand, quartz, white, coarser than above,
S100 ''calcareous; some collophane.
108 118 Sand, similar to above, marly, phosphatic.


Ila 118 128 Sand, quartz, white to tan, fine to medium,
Sntarly, angular to subrounded, phosphatic.
(. 128 134 Sand, quartz, white, subrounded to well-
rounded; fragments of calcareous sandstone,
reworked shells and phosphate,
4j 140- 134 140 Sand, quartz, white, very fine to fine,
"'-' silty, phosphatic.
S';. 140 145 Sand, quartz, white to gray, fine, clean;
rounded shell fragments and cellophane.
145 150 Sand, quartz, similar to above; a few
160 fragments of calcareous sandstone.
S*" 150 155 Sand, qudrtZ, white to gray, fine to coarse;
many rounded shell fragments and much
S5 reworked material,
|180 155 165 Sand, quartz, white to tan, very fine to
medium, marly, phosphatic.
165 170 Sand, quartz, white to gray, fine, clean;
Scllophane.
170 180 Sand, quartz, gray, phosphatic, fine; sand-
200 stone, calcareous, hard; a few shell fragments.
180 195 Sand, quartz, gray to tan, very fine to
medium, very silty, marly, phosphatic.
195 .- 203 Sandstone, calcareous, permeable, hard.
220 -


Figure .7 Log of well S-999.






FLORIDA GEOLOGICAL SURVEY


The Pamlico sand, which was found near the surface in the test and
observation wells, is a late Pleistocene marine terrace deposit (Parker
and Cooke, 1944, p. 75). In the Oakland Park area it overlies and fills
erosion channels and solution cavities in the Miami oolite and the
Anastasia formation. The Pamlico sand is composed chiefly of fine to
coarse quartz sand ranging in color from white to rust or gray-black,
according to the amount of admixed iron oxide or carbonaceous material.
Properly developed sandpoint wells in the Pamlico sand generally
yield enough fresh water for domestic purposes, but the water often
has an objectionable color or odor caused by organic matter.


GROUND WATER

Ground water is the subsurface water in the zone of saturation, the
zone in which all the interstices of the soil or rocks are completely filled
with water under greater than atmospheric pressure. Ground water may
occur under either artesian or nonartesian conditions. Where its upper
surface is free to rise or fall in a permeable stratum it is said to be under
nonartesian conditions, and the surface is called the water table. Where
the water is confined in a permeable bed that is overlain by a less per-
meable bed, its surface is not free to rise and fall. Water thus confined
under pressure is said to be under artesian conditions. The height to
which water will rise in tightly cased wells that penetrate an artesian
aquifer defines the pressure, or piezometric, surface of the aquifer.
In the Oakland Park area the only potable ground water is the rain-
fall that infiltrates downward into the materials of the Biscayne aquifer.
This water is said to be under nonartesian conditions, as its upper sur-
face, the water table, is unconfined and under normal atmospheric pres-
sure. It is recognized, however, that artesian conditions exist to some
extent in parts of the aquifer. (See section on quantitative studies.)
The water table fluctuates in response to recharge or discharge, and
ground water flows under gravitational forces from points of re-
charge, where water levels are high, to points of discharge, where water
levels are low. The direction of flow coincides with the maximum slope
of the water table. The water table may be mapped by determining the
altitude of the water level in a network of wells. Systemic areawide
observations of the shape, slope, and fluctuations of the water table are
an important part of ground-water investigations, as they show the
direction of ground-water movement and changes in the amount of
ground-water storage.







REPORT OF INVESTIGATIONS No. 20


RECHARGE AND DISCHARGE
Rainfall is the source of all fresh-water recharge to the Biscayne
aquifer. Not all of the rainfall infiltrates to the water table, however,
as a large part is lost by evapotranspiration and a small part is lost by
direct runoff into streams or the ocean. Parker (Parker and others, 1955,
p. 221) estimates that about two-thirds of the annual rainfall reaches the
water table in areas underlain by oolite and about half the annual rain-
fall reaches the water table in areas underlain by sand.
In the Oakland Park area, some surface water is introduced into the
aquifer when water levels in the Middle River and Pompano canals are
higher than the water table. This occurs chiefly in upstream areas, above
the closed water-control structures.
Discharge from the aquifer takes place by evapotranspiration, by
ground-water outflow into streams, canals, and the ocean, and by pump-
ing. Discharge by ground-water outflow and evapotranspiration are
greatest when the water table is highest, during and after periods of heavy
rainfall, whereas discharge by pumping is greatest in the drier periods,
which correspond with the peak tourist season. In general, the discharge
by the two natural processes greatly exceeds the quantity of water with-
drawn by pumping from wells. However, the operation of the Prospect
well field makes pumping a significant factor. Figure 8 shows the monthly
pumpage from the Prospect well field and. the monthly rainfall at Fort
Lauderdale during 1955 and 1956.
When water is pumped from a well in a nonartesian aquifer, the de-
watering of the materials adjacent to the well causes the water table to
slope downward toward the well, thus forming a cone of depression.
The slope or hydraulic gradient of this cone causes ground water to flow
from the surrounding area to the well. As pumping continues, the cone of
depression increases in depth and areal extent until it reaches an area
where ground-water discharge is salvaged and/or recharge is increased
in an amount equal to the withdrawal. Studies in other areas indicate
that pumping in a well field near a stream can cause large quantities of
water to be drawn from the stream into the aquifer.
WATER-LEVEL FLUCTUATIONS
Water levels in the Biscayne aquifer fluctuate considerably in re-
sponse to recharge and discharge, and, to a lesser extent, they are affected
by other factors such as tides (in areas adjacent to the coast and tidal
canals), earthquakes, and changes in atmospheric pressure. The greatest
short-term fluctuations are caused by recharge by rainfall and discharge
by pumping, but gradual changes in water levels caused by evapotrans-
piration and normal ground-water outflow have an equally important








1955
I A A U i I.


A U


i LA A U I .1 A


* A LA


S------- ------



- ---- -- --




S.. .. -
Ai i i M i9 a

U U l~ il l lU


s i i n i n i u i i i i i 1 i m i m I I i I i i I i i i,i I i I i mR I am I I n_ I




i M I ------ -t .







Figure 8. Monthly pumpage from the Prospect well feld and monthly rainfall at Fort Lauderdale.


n u n






REPORT oF INVESTIGATIONS No. 20


effect on the amount of water in storage in the aquifer. Parker and
Stringfield (1950, p. 441-460) discussed the effects of earthquakes, winds,
tides, and atmospheric-pressure changes on ground-water levels in south-
ern Florida. Water-level fluctuations in the Oakland Park area are greatly
influenced by pumping in the Prospect well field and by the flood-control
works of the Central and Southern Florida Flood Control District.
Figure 9 is a contour map of eastern Broward County, showing the
approximate altitude and configuration of the water table in the Bis-
cayne aquifer on February 15, 1941. This map was made by using some
of the earliest water-level data available for the area, and it represents
the water table at a time when there was no drawdown due to pumping
in the Prospect well field area or to extensive water-control works. The
Pompano Canal (Cypress Creek Canal) was the only major drainage
canal in the immediate area. Bogart and Ferguson (Parker and others,
1955, p. 505) indicated that the canal was controlled in two pools by
small dams, in much the same manner as it is at present. Parker (Parker
and others, 1955, fig. 148) shows that the water level above the controls
in Pompano Canal ranged from about 1.0 foot to 5.4 feet above mean
sea level during the period 1940-43. The contours in figure 9 were drawn
from water-stage readings in streams and canals and from water-level
measurements in widely scattered wells. In the Oakland Park area, the
contours show, generally, the altitude and configuration of the water
table under relatively natural conditions and indicate a fairly uniform
gradient toward the coast.
The graphs in figure 10 show a correlation between periodic water-
level measurements made in wells G-127 and G-128 (see fig. 9 for
locations) and weekly rainfall at Fort Lauderdale during 1940-41.
Well G-127 was on the present site of the Prospect well field, and well
G-128 was on U. S. Highway 1, 2.7 miles east of well G-127. The hydro-
graphs indicate also the differential in head between wells G-127 and
G-128 during the latter part of 1940 and all of 1941.
Ground-water levels in Broward County during 1955 and 1956 were
generally below the average for the period of record, owing to a defi-
ciency in rainfall. This condition tends to accent the effects of drainage
canals, dams, and pumping on the water table.

During 1956 an areawide program of water-level observations was
established and contour maps of the water table in the Biscayne aquifer
were prepared. Figures 11 through 18 show contours on the water table
on August 7, September 21, and October 19, during periods of low, inter-
mediate, and high water levels, respectively. The most striking feature of





16 FLORIDA GEOLOGICAL SURVEY

PA LM BEACH COUNTY
R4OE R41ER4tE R42E
.... ... < HILLSBOROUGH CANAL


EXPLANATION DEERFIEL
o
WELL

SURFACE WATER
OBSERVATION POINT

WATER LEVEL, IN FEET, REFERRED
TO MEAN SEA LEVEL
0 I 2 3 4 5 6 miles

POMPANO CANAL -





G 2 7 G 1






-- -- .0 b0

R


Gro r


-io A IE las Cut OHff



IDonia DOvie Rd. DANIA






REPORT oF INVESTIGATION No, 20


1 40
JAN.tak. MAK Aft. MAY JUN. JUL AU6.


7,0 -

8.0 --- .... -

4.0 ;-- ---- -- -- .----- -- -r--- -
.0 ... ... ... ...... .- ..- -
5.0

3.0


Figure 10. Hydrographs of wells G-127 and G-128 and weekly rainfall at
Fort Lauderdale during 1940-41.


each contour map is the deep cone of depression caused by pumping
in the Prospect well field. Significant features are the high ground-water
levels and steep gradient maintained as a result of recharge by surface
water in areas upstream from control structures in the Middle River and
Pompano canals. The extremely low water levels and flat gradient in
areas southeast of the cone of depression are caused by the large losses


Ch.

t





FLORIDA GEOLOGICAL SURVEY


L .W ..... ... 11 *- -. ..

---- I I l \ ;


Figure 11. Map showing contours on the water table in the Biscayne aquifer in
the Oakland Park area, August 7, 1956.

of ground water through drainage into the uncontrolled reaches of streams
and canals and by discharge from the Prospect well field. Figure 11 shows
the configuration of the water table at a time when water levels were
near record lows and pumping from the well field was near maximum.
The direction of ground-water flow is perpendicular to contour lines and
in general it is toward the coast. The steep water-level gradient north
and west of the well field indicates that most of the water pumped from
the well field comes from that direction.
Figure 14 shows the fluctuation of water levels in wells G-768 and
G-820 in the Prospect well field, monthly pumpage from the well field,
and daily rainfall at Fort Lauderdale during June-December, 1956. The
hydrographs show the difference between the water levels in well G-768,
near the center of the cone of depression, and well G-820, near the outer
edge of the cone. A comparison of the altitude of the water level of
well G-768, in 1956, with that of well G-127 (same approximate loca-





REPORT OF INVESTIGATIONS No. 20


Figure 12. Map showing contours on the water table in the Biscayne aquifer in
the Oakland Park area, September 21, 1956.

tion) in 1940-41 (fig. 10), shows the marked effect of heavy pumping
in the area.
During extended dry periods, when there is little recharge, the rate
of the natural decline in water levels decreases as the water-level gradient
toward the coast diminishes. However, water levels in the well field
area drop at an increased rate until the cone of depression reaches a new
source of recharge or enough natural discharge is salvaged to balance
the discharge due to pumping. The contours in figure 11 indicate that
the water table in the area between the well field and uncontrolled
reaches of the Middle River Canal was approaching the mean water level
in the canal in August 1956. If the water table in the area declined to
an altitude below that of the water level of the canal, some salty water
would enter the aquifer from the canal. The flow of water from the canal
into the aquifer would be impeded, however, by silt in the canal bed and
by the relatively low permeability of the materials cut by the canal. It





FLOtIDA GEOLOGICAL SURVEY


~t.ti .~ -


I \ ... F.-"' t 4/
ti "ATO LF / I j


I-4 t
-' -^ ipt'1" J--?f- --L '-ll-9a.-- l t~xc -wltltBT -wiif


Figlnrr 13. Map showing contours on the water table in the Bisenayne aquifer In
the Oakland Park area, October 19, 1956.

is possible that during a prolonged drought the cone of depression may
extend outward and cause a relatively steep gradient from the salty canal
to the aquifer, thus resulting in accelerated salt-water intrusion south of
the well field.
Water-level recording gages are maintained above and below the
dam on the Middle River Canal. Weekly readings are recorded from staff
gages above and below the dams on the Pornipano Canal (fig. 8). Figure
15 shows a typical water-level record obtained from gages above and
below the Middle River dam on August 7-12, 1956, and figure 16 shows
daily mean water levels above the dam and mean daily high and low
tide levels below the dam during 1956. The 1956 average water levels
above and below the dam were 4.40 and 0.60 feet above mean sea level,
respectively, and the average tidal fluctuation below the dam was about
2.20 feet. Weekly water-level stages above the dam in the Pompano
Canal, from April 6 to December 81, 1956, are shown in figure 17. The






1bEtPOt OIF 1NVbrT1oAt O6N8 NO, 20


WELL0 010
1-0 p_







I! C b_-












2,0







Figure 14. Hydrographs of wells -768 and 0-820, average daily pumpage from the
Prospect well field, and daily rainfall at Fort Lauderdale, June-
December, 1956.




FLORIDA GEOLOGICAL SURVEY


4


AUIUT I1t


i__ _____ I~i i _____


11


-- _Is


tI


10.
~4~V_ ___
J _____ ____ ____ ____________ ____-V


Figure 15. Hydrographs of Middle River Canal above and below dam,
August 7-12, 1956.
average water levels above the east (City) and west (Market) dams
during this period were 3.89 and 7.16 feet above mean sea level, re-
spectively. No record of the tidal fluctuations in the lower reach of the
canal is available, but the fluctuations are assumed to be similar to those
;n the Middle River Canal.
No data are available to show the beneficial effects of the flood-
control works in this area during flood periods. This is unfortunate
because the system was designed for both high-water and low-water
conditions and its effectiveness is not fully demonstrated unless both
conditions are presented.
SALT-WATER ENCROACHMENT
Salt-water encroachment is the chief factor limiting the use of ground
water from the Biscayne aquifer. The salt water in this aquifer may come
from two general sources, as follows: (1) direct movement inland from
the ocean and from tidal canals and streams, and (2) sea water which


liPi


r-i







1956


Figure 16. Hydrographs of Middle River Canal above and below dam during 1956.






























AB________ AOVE CITY DAMi- ________________












Figure 17. Hydrographs of Pompano Canal above Market and City dams, 1956.






IARu'onT or, NV1mnT1ATioN5, No. 20


entered the aquifer when the sea covered parts of southern Florida dur-
ing various interglacial stages of the Pleistocene and is still present in
parts of it. Parker (Parker and others, 1955, p, 819-821) discussed the
effects of residual sea water in the Everglades area and indicated that
this source of salt water caused little or no contamination of ground water
in the Oakland Park area; however, ground water in the Everglades
area west of Oakland Park has chloride concentrations greater than
30 ppm, the concentrations increasing in a westerly direction and with
depth.
Salt-water encroachment from the ocean into the Biscayne aquifer
is governed by the relationship of ground-water levels to mean sea level.
In coastal areas the depth to salt water is related to the height of the
fresh water above sea level. Under static conditions this relationship is
that of a U-tube whose limbs contain liquids of different density, and
it is expressed by the Ghyben-Herzberg principle (Brown, 1925, p.
16-17), as follows:
t
g -1
where h is the depth of fresh water below sea level, in feet; t is the
height of the fresh-water surface above sea level, in feet; and g is the
specific gravity of sea water. If a specific gravity of 1.025 is assumed for
sea water, then each foot of fresh water above sea level should indicate
40 feet of fresh water below sea level. In the field, this relationship is
modified by mixing of fresh and salt water by dynamic hydraulic condi-
tions, and by geologic conditions, but the relationship holds sufficiently
well to be considered valid for most purposes.
Salt-water encroachment in Broward County has occurred chiefly
in areas adjacent to major streams and uncontrolled parts of drainage
canals that empty into the ocean. These waterways enhance the possi-
bility of salt-water encroachment in two ways, as follows: (1) they
lower ground-water levels, thereby reducing the fresh-water head that
normally would oppose the inland movement of salt water, and (2) they
provide a path for sea water to move inland during dry periods.
The extent of the encroachment at depth in the aquifer, in the Middle
River and Cypress Creek basins, has not been determined because of the
lack of deep wells in these areas. In order to determine accurately the ex-
tent of encroachment, several deep test wells would be required in the
general area between U. S. Highway 1 and the Florida East Coast Rail-
road and in the area adjacent to the downstream parts of the Middle
River. These wells would serve as outpost wells from which water





FLORIDA GEOLOGICAL SURVEY


samples could be taken for periodic determinations of the chloride con-
tent of the ground water.
Considerable data are available in a similar area adjacent to the
North New River in Fort Lauderdale. These data may illustrate some
of the characteristics of salt-water encroachment in the area. Figure 18
shows the maximum chloride content recorded in surface-water and
ground-water samples in eastern Broward County north of Dania. The
ground-water samples were pumped from wells which are cased to
within a few feet of their total depth; therefore, the depth of the sam-
pling point is assumed to be approximately equal to the depth of the
well. The data shown in the Oakland Park area represent samples taken
during 1956-57 and those shown on the southern part of the map repre-
sent samples taken during the past 15 years (expanded from fig. 187
in Parker and others. 1955).
Along the north and south forks of the New River, salt water has
migrated inland, at depth in the aquifer, as much as 38 miles from the
coast. The extent of salt-water encroachment at depth near the river
is indicated by salinity data from well G-514 (fig. 18). The chloride
content in samples taken at a depth of 177 feet in this well has ranged
from 2,700 ppm to 4,900 ppm during the past 10 years. It can be seen,
therefore, that salt water has encroached at depth, in this area, beyond
the junction of the forks of the Middle River. Figure 19 shows the varia-
tion of chloride content in wells S-330 and S-880 caused by salt-water
encroachment from the south fork of the New River during the period
1941-57 (adapted from Vorhis, 1948). These wells were sampled at
depths of 35 feet and 118 feet, respectively, and are near the river, about
53 miles inland from the coast. The data indicate that large and rapid
changes in the chloride content of ground water are caused by salt-water
encroachment from the New River.
In the Oakland Park area appreciable contamination by salt water
was found in samples from wells S-1379 and S-1380, near the dam on
the Middle River Canal, and in well S-1381, near the Fiveash water plant.
Analyses of samples from wells S-1379 and S-1380 show chloride contents
of 600 ppm and 820 ppm, respectively, and indicate contamination from
the Middle River Canal during the prolonged dry period of 1955-56. A
water sample collected at a depth of 240 feet in well S-1881 contained
*2,640 ppm of chloride. The high chloride content in this sample indicates
that salt-water encroachment has been occurring at depth in the aquifer
as a result of lowered ground-water levels in the vicinity of the Middle
River. These are the only data available that indicate extensive salt-
water contamination in the Middle River basin. However, the high







REPORT OF INVESTIGATIONS No. 20 27


Figure 18. Map of eastern Broward County showing maximum chloride content
recorded in water samples from wells and streams, 1941-57.











,1o00


1941 192I 1843 1944 1948 1946 1947 1948 1i949 16i 0 1961 19B. IB6 198i4 19i 6 1i868 1981


I. I ... A I


L..


0,400---- -- ---- -
,, .... ---,-- .- WELL. ^ -- -- -- -- -- -- -- -

DEPTH OF SAMPLE 116 FEET
,10o0 --0
2,800 0

2,600 5 0 -




1,400
2,200










800
1,600 WF-^- S -33
11000- --------- -- \ --

300<--------T- "----- -\---- ---


600--


400 -OEPTH OF SAMPLE 3S5 FEET

400


Figure 19. Chloride content of water from wells S-330 and S-830, at junction of
South New River and Dania cutoff canals, 1941-57.


-


- .- .- ..


- .-. T


! I w w


-------------






REPORT OF INVESTIGATIONS NO. 20


chloride content of the canal water (fig. 18) and the low ground-water
levels shown on the contour map for August 7 (fig. 11) indicate that
there might be considerable salt-water encroachment in this area.
In the area north of the Middle River basin, the available data indi-
cate that salt-water encroachment has been limited to areas close to the
Intracoastal Waterway or Cypress Creek. This limitation is partially due
to the high ground-water levels maintained by the control near the
mouth of Pompano Canal and to the fact that Cypress Creek is not an
improved drainage channel such as the Middle River and the south fork
of the New River.

QUALITY OF WATER
The suitability of ground water for general use depends largely on
the degree to which it fulfills the following requirements: (1) it must be
safe to drink that is, free from disease-causing bacteria and from
excessive quantities of harmful minerals; (2) it should be clear and
free from unpleasant taste or odor; (3) it should be relatively soft; and
(4) it should not be corrosive or excessively damaging to metal surfaces.
The first two requirements are most important for domestic or public
supplies and the last two are most important for industrial supplies.
As ground water must seep through more than 100 feet of sand and
rock to reach the producing zone of the Biscayne aquifer, it is generally
free of dangerous bacteria and suspended material. However, it is
affected by the composition and solubility of the rocks and sediments
with which it has been in contact. As rainwater infiltrates into the aquifer
it exerts. a solvent action upon the rocks through which it passes. This
action is aided by the presence of carbon dioxide, absorbed from the
atmosphere and from organic material in the soil.
To determine the mineral constituents of ground water at different
depths and locations in the area, chemical analyses were made of water
samples from selected wells. The results of these analyses are shown
in table 2. (See fig. 3 for well locations.)
The analyses of the water from these wells show the characteristics
of a hard to very hard limestone water, suitable (naturally or with fairly
simple treatment) for all ordinary uses. Using the amount of dissolved
solids as an indication of the mineralization of the water, the samples
from wells S-340, S-341 and S-1869 in the Pompano Beach area showed
less mineralization than the samples from well G-820 in the Prospect
well field and wells S-336 and S-337 in the Middle River basin. The test-
well logs (figs. 4-7) show that the amount of limestone penetrated
in wells S-998 and S-999 in Pompano Beach was much less than that









Table 2. Chemical Analyses of Water from Selected Well8
(Chemical constituents in parts per million)

City Well City Well Well Well Well Well Well Well Well
No. No.6 0 820 8136001 8336' S3371 S340 8 341' 8372'
Silica (SiO0 ) ................ 9.4 9.3 42 18 ..... .......... ............. ... .. .. ........
Iron (Fe) I ............... .24 .02 .04 .01 .......
Celclum (Ca) ............... 70 75 68 47 89 113 47 56 74
Magnesium (Mg) ........... 1,8 1,2 9.8 1.1 3.1 3.1 2.3 2.5 2.7
Sodium and potassium
(Na+K)................. 7.5 6.9 10.0 10.6 7.6 18 8.5 5.8 5.4
Bicarbonate (HCO ) ......... 217 204 258 140 265 297 136 173 226
Sulfate (80 )............... 1.0 6.0 1.8 14 5.8 1 1 1 1
Chloride (Cl) ............... 14 12 14 16 20 64 15 14 15
Fluoride (F) .......... ..... .3 .2 .2 .1 .. ....... .. ..........
N itrate (N O a) ......... .... 1 .2 .5 .4 .... ...... ......... ... .......
Dissolved solids
Residue on evaporation at
1800C.. .............. 221 234 287 182 256 3454 1654 164 2094
Total hardness as CaCOa ..... 182 192 210 122 235 295 127 150 196
Noncarbonate............. 4 25 0 8
Color ..................... 15 10 5 5 130 50 20 20 40
Temperature (F.)........... ............ ...... ..................... 77 76
pH ... .. ................ 7 .5 7.9 7 .9 7.8 .. .......... .......... .......... .....
Specific conductance
(micromhos at 25*C.) ...... 372 378 420 291 468 643 268 307 389
Date of collection........... Mar. 29 Nov. 11 July 9 Sept. 10 Nov. 19 Oct. 18 Nov. 29 Oct. 18 Oct. 18
1957 1956 1956 1956 1940 1940 1941 1941 1941
Depth of sample (feet below
land surface) .............. 130 130 224 190 60.9 72 170 189 120
Aquifer ................. Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne


1 City of Pompano Beach supply well 3.
2 Iron in solution at time of analysis.


3 Parker and others (1955, p. 798).
* Sum of determined constituents.






REPORT OF INVESTIGATIONS No. 20


in well G-820 in the Prospect well field and well G-563 near the south
fork of the Middle River. Thus, the difference in the mineralization of
the samples is probably related to the amount of limestone contacted
by the water as it infiltrated down from the surface.
Hardness of water is generally recognized because it increases the
consumption of soap. Also, hard water causes the formation of scale in
steam boilers or other vessels in which the water is heated. Water having
a hardness of less than 60 ppm is considered soft; 60 to 120 ppm, mod-
erately hard; 121 to 200 ppm, hard; and more than 200 ppm, very hard
and unsatisfactory for most uses unless treated. Generally, the ground
water in the Oakland Park area ranges in hardness from about 120 to
200 ppm and may be used with or without treatment, according to the
use.
Iron is one of the most noticeable constituents found in ground water
in the Oakland Park area. In quantities of more than 0.5 to 1.0 ppm it
will give the water a disagreeable taste, and in concentrations greater
than 0.8 ppm will cause reddish-brown stain on clothing and fixtures.
The iron content of the water differs from place to place and with depth,
but it is not predictable. Iron may be removed easily by aeration and
filtration from water that is to be used for large public supplies or indus-
tries, but it is more difficult to remove economically from water that is
to be used for small domestic supplies. The analyses show iron in solu-
tion and do not include iron that may have precipitated between the
time the sample was collected and the time of analysis.
Color in water is caused almost entirely by organic matter extracted
from peat, vegetation, and similar organic materials and is often accom-
panied by tastes and odors from the same sources. These characteristics
may not be harmful to persons using the water, but their psychological
effects on the consumer make them undesirable in drinking water. The
analyses showing a color higher than 20 (the concentration at which
color is considered to become objectionable) were of water from rela-
tively shallow wells or wells near to streams.
The pH indicates the degree of acidity or alkalinity of a water and
is an important indication of its corrosive tendencies. A pH of 7.0 indi-
cates neutrality, which means that the water is neither acid nor alkaline.
Values below 7.0 denote increasing acidity; values above 7.0 indicate
increasing alkalinity. The corrosiveness of water usually increases as the
pH decreases. The pH of the samples ranged from 7.5 to 7.9, indicating
that ground water in the area is moderately alkaline and should not be
corrosive.
As the amount of chloride in ground water is used to indicate the





FLORIDA GEOLOGICAL SURVEY


extent of salt-water encroachment from the ocean, samples were col-
lected from several wells in the Oakland Park area and analyzed for
chloride content. The data from the analysis of these samples are shown
in figure 18.
QUANTITATIVE STUDIES
Knowledge of the hydraulic properties of the aquifers of an area is
essential to the evaluation of the ground-water resources. The principal
hydraulic properties of an aquifer are its capacities to transmit and store
water. These properties are generally expressed as the coefficients of
transmissibility and storage.
The coefficient of transmissibility is a measure of the capacity of an
aquifer to transmit water. In customary units it is the quantity of water,
in gallons per day (gpd), that will flow through a vertical section of the
aquifer 1 foot wide and extending the full saturated height, under a
unit hydraulic gradient, at the prevailing temperature of the water (Theis,


Figure 20. Map of Prospect well field showing layout of municipal supply wells
and observation wells.






REPORT OF INVESTIGATIONS NO. 20


1.988, p. 892). The coefficient of storage is a measure of the capacity of
an aquifer to'store water and is defined as the volume of water released
from or taken into storage per unit surface area of the aquifer per unit
change in the component of head normal to that surface.
In this area, the best opportunity for making pumping tests to obtain
these aquifer coefficients was through the use of municipal supply wells
in the Prospect well field. Figure 20 shows the layout of the municipal
supply wells and observation wells in this well field. Two tests were run
in this field by observing the effects on water levels of changes in the
rate of pumping. A 12-hour pumping test was made on August 8, 1956,
using 10 city supply wells, each being pumped at the rate of 820 gpm.
City supply wells 3, 4, and 5 were operated for eight hours prior to the
start of the test, and then pumping was begun in the remaining seven
wells in the field at the beginning of the test. Water-level recorders were
operated on wells G-768 and G-820 beginning June 15, 1956, and August
6, 1956, respectively, and tape measurements of the changes in water
level were made in well G-803 during the test. Well G-820 is a 4-inch
well, drilled to a depth of 224 feet, and the casing was dynamited at a
depth of 215 feet to open it to the aquifer. Well G-768 is a 6-inch well, 91
feet deep, cased to an approximate depth of 80 feet; and well G-803
is a 1h-inch sandpoint well 16 feet deep, cased to 14 feet below the land
surface and screened from 14 to 16 feet below the land surface. A draw-
down of 1.0 foot was recorded in well G-768, whereas no measurable
drawdown occurred in well G-803 during the test. If drawdown affected
the water level in well G-820 it was apparently overshadowed by the
natural decline of the water table and fluctuations caused by changes
in barometric pressure. Figure 21 shows the fluctuation of the water
level in well G-768 before and during the test.
On March 27, 1957, a 36-hour test was made using city wells 11, 12,
and 14 (fig. 20) as observation wells. Supply wells 1, 2, and 3 were
operated for 20 hours preceding this test and then pumping was started
in wells 8, 9, and 10. Each of these wells is pumped at approximately
820 gpm. A water-level recorder was in operation on well G-820 during
the 20-hour period before the test, and recorders were operated on city
wells 11, 12, and 14 during the test. Drawdowns of approximately 0.2
foot and 0.4 foot were recorded in city wells 11 and 12, respectively,
whereas city well 14 and well G-820 showed no appreciable drawdown.
All the city supply wells are finished with well screens 20 feet long which
extend to a depth of approximately 130 feet. The water pumped in both
tests was discharged into the city mains so that no complication was
caused by infiltration of the pumped water near the wells.





FLOIDA GEOLOGICAL SURVEY


Figure 21. Hydrograph of well G-768, in the Prospect well field, during pumping
test, August 7-8, 1956.

Water-level and pumping-test data indicate that under static (non-
pumping) conditions the Biscayne aquifer exhibits different character-
istics than it does under pumping conditions. Under static conditions, the
water level in a shallow well will stand at the same altitude as the water
level in an adjacent deep well, suggesting that the aquifer is under non-
artesian conditions. However, when the deep, highly permeable zones of
the aquifer were pumped, water levels in deep wells as much as 1,000 feet
away showed an immediate rapid decline. Water levels in shallow wells
much closer to the pumping wells showed no immediate change during
the test, but they do show a long-term drawdown of several feet. (See
contour maps, figs. 11, 12 and 13.) Thus, in pumping tests of short
duration the zone in which the supply wells are developed reacts as an
artesian aquifer overlain and partly confined by a leaky roof of less
permeable beds (fig. 5). The fact that the water levels of deep wells






REPORT OF INVESTIGATIONS No. 20


respond readily to changes in barometric pressure is further evidence
of artesian conditions.
Data from the aquifer tests were first analyzed by the Theis non-
equilibrium method (Theis, 1985), which assumes the following condi-
tions: (1) the aquifer is without limit in a lateral direction; (2) the
aquifer is homogeneous throughout and transmits water equally readily
in all directions at all times; (8) the pumped well completely penetrates
the aquifer; (4) the pumped well has an infinitesimal diameter; and
(5) water taken from storage in the aquifer is discharged instantane-
ously with the decline in head. Although not all these assumptions
were fulfilled, this method was useful in that it indicated that the
pumped zone was receiving recharge during the test.
Further analysis was made by means of a leaky-aquifer type curve
developed by H. H. Cooper, Jr., of the U. S. Geological Survey, Talla-
hassee, Florida, (personal communication) and by a method outlined by
Hantush (1956) which is based on the theory of ground-water flow in a
leaky artesian aquifer (Hantush and Jacob, 1955). Figure 22 shows
radial flow in and leakage to an ideal leaky artesian aquifer (Jacob, 1946).
These methods involve the same assumptions of the Theis method, but,
in addition, they assume leakage into the aquifer through a semiconfining
bed and a constant head in the bed supplying the leakage. In treating


WELL
______WATER- TABLE ..
SNONARTESIAN AQUIFER

' ./ //SEMI- PERVIOUS ///
//-| | //I //. /// CONFINING BED/ //

-ARTESIAN AQUIFER

IMPERVIOUS BED



Figure 22. Idealized sketch showing flow in a leaky aquifer
(modified from Jacob, 1946, p. 199).





FLORIDA GEOLOGICAL SURVEY


problems in leaky systems these methods add a third aquifer coefficient,
called the leakage coefficient, which indicates the ability of the semi-
confining bed to transmit water upward from or downward into the aqui-
fer being tested. This coefficient may be defined as the quantity of flow
that crosses a unit area of the interface between the main aquifer and its
semiconfining bed if the difference between the head in the main aquifer
and the bed supplying the leakage is unity. It is obvious that the head
in the bed supplying the leakage in the well field area is not constant
during long periods, but water levels in shallow wells in the well field
were very nearly constant during the pumping tests. The water level in
well G-803 rose 0.02 foot during the 16 hours preceding the first pumping
test and declined 0.03 foot during the first five hours of the test.
Computation of the aquifer coefficients is complicated not only by
vertical leakage in the stratified material but also by the possibility of
inducing recharge from canals and quarries and the limitations on the
accurate measurement of the small drawdowns.
The coefficients of transmissibility obtained ranged from 2,000,000 to
3,000,000 gpd per foot. The storage coefficient was approximately 0.015,
and the leakage coefficient was about one gpd per square foot per foot
of vertical head.
It is apparent from the large cone of depression shown in figures 11,
12, and 13 that long-term pumping has caused considerable unwatering of
the beds overlying the pumped zone in the aquifer. Thus, the drawdown
caused by large-scale pumping from the deep zone is reflected at the
water table, and it is controlled by the coefficients of transmissibility and
storage of both the pumped zone and the overlying beds.
An approximate value for the coefficient of transmissibility, under
equilibrium conditions, may be calculated by substituting the average
hydraulic gradient at points around the cone of depression and the aver-
age pumpage from the well field in the formula Q = TIW (a modified
expression of Darcy's law for ground-water flow) where:
Q =the average pumpage from the well field, in gallons per day
T = the transmissibility of the aquifer, in gallons per day per foot
W=the circumference of a cylinder through the aquifer at a given
radius from the center of pumpage, in feet
I = the average slope of the cone depression around this cylinder,
in feet per foot.
The record of water-level fluctuations in well G-768 during the period
July 12-24 (fig. 23) indicates that water levels in the well field area had
reached approximate equilibrium for the rate of pumping at that time.
A coefficient of transmissibility of about 1,000,000 gpd per foot was















Io '



-3. 0

.. .. .. __..


____- ____-- ____-- --i-- -- -- ___ .-- --____ __ ___ ___ -.


Figure 23. Hydrograph of well G-768, in the Prospect well field, showing effect of pumping in the well field.




co4





FLORIDA GEOLOGICAL SURVEY


obtained from the above formula by using the water-level data from the
contour map of August 7, 1956, and the average pumping rate for the
period July 25-August 7, 1956 (10.0 mgd). This figure is on the low side
because evapotranspiration was not considered. The area within the
contour used (sea level) is about 34,000,000 square feet. Evapotranspira-
tion of ground water is estimated at 6 inches per month or 0.2 inch per
day. Natural water loss for the area is then about 4.2 mgd. By use of the
combined discharge of 10.0 mgd by pumping and 4.2 mgd by evapo-
transpiration, the coefficient of transmissibility is computed to be about
1,500,000 gpd per foot.

GROUND-WATER USE
Wells supply most of the water for public, domestic, irrigation, and
industrial use in the Oakland Park area. Until recent years the area was
relatively undeveloped and ground-water withdrawals were small. Since
about 1950, however, the growth of population and industry in the area
has been extremely rapid, and ground-water use has increased corre-
spondingly.
The largest pumpage is that from the Prospect well field, which
yielded about 10.0 mgd in 1956. When all proposed wells are in opera-
tion, the pumpage from the field will be about 20 mgd. Separate water-
supply systems have been developed for several large housing develop-
ments in the area, and many residents have private wells for domestic
use and lawn sprinkling. In the area west of Oakland Park, several large
farms use ground water for irrigation. Generally, the peak pumping for
municipal supplies and irrigation occurs during December through June,
as these months include both the tourist season and the dry season. The
use of ground water by industries is growing rapidly, especially in areas
adjacent to the two railroads.

CONCLUSIONS
The Biscayne aquifer is the source of all fresh ground water in the
Oakland Park area. The water in the aquifer comes from local rainfall
or from surface water brought into the area by canals. It is generally of
good quality except for hardness and color. The Biscayne aquifer is com-
posed of permeable marine deposits chiefly sandy limestone, calcareous
sandstone, and quartz sand which extend from the land surface to a
depth of more than 215 feet below mean sea level. The components of
the aquifer differ from place to place, but, in general, the amount of sand
decreases with depth and most of the consolidated rocks occur at depths
greater than 60 feet.





REPORT OF INVESTIGATIONS No. 20


Wells used for small water supplies generally tap thin beds of lime-
stone at depths ranging from 60 to 80 feet, whereas most wells used for
large supplies are developed in highly permeable limestones and sand-
stones of the Anastasia and Tamiami formations, at depths greater than
100 feet.
There is a natural seaward water-level gradient in the Oakland Park
area, but it is greatly influenced by pumping in the Prospect well field
and by water-control structures in the Middle River and Pompano
canals. Ground-water levels in areas downgradient (east) from these
canal controls are lowered by pumping and by ground-water drainage
into the canals, whereas water levels in areas upgradient (west) from the
controls remain high owing to ground-water recharge from the canals.
Salt-water encroachment from the ocean is the chief factor affecting
the use of ground water in the Oakland Park area. This encroachment is
governed by the relationship of ground-water levels to mean sea level
and may occur in two ways: (1) direct inland movement of salt water
at depth in the aquifer, and (2) the movement of salt water from tidal
reaches of canals into the aquifer during low-water periods. Determina-
tions of the chloride content of water from the deep wells in the area
indicate that under the conditions in 1956 there is little danger of salt-
water encroachment except in areas adjacent to Cypress Creek and the
Intracoastal Waterway and in the Middle River basin. Direct contamina-
tion from the Middle River Canal has occurred in wells only a mile east
of the dam. Further encroachment could be retarded by placing and
operating controls downstream from the present location of the control
in the Middle River Canal and by reducing drawdowns in the Prospect
well field and vicinity.
Pumping tests in the Prospect well field and areawide water-level data
indicate that large quantities of ground water are available for future
development, especially in areas west of the controls on the two major
canals.





FLORIDA GEOLOGICAL SURVEY


REFERENCES
Brown, J. S.
1925 A study of coastal water, with special reference to Connecticut' U, S.
Geol. Survey Water-Supply Paper 537.
Cooke, C. Wythe (see Parker, G. C.)
Hantush, M. C.
1955 (and Jacob, C. E.) Non-steady radial flow in an infinite leaky aquifer:
Am. Geophys. Union Trans.,j v. 36, p. 95-100.
1956 Analysis of data from pumping tests in leaky aquifers: Am. Geophys.
Union Trans., v, 37, no. 6, p. 702-714.
Hoy, N. D. (see Schroeder, M, C.)
Jacob, C. E. (also see Hantush, M. C.)
1946 Radial flow in a leaky artesian aquifer: Am, Geophys. Union Trans.,
v. 26, no. 11.
Klein, Howard (see Schroeder, M. C.)
Meinzer, 0. E.
1923 Outline of ground-water hydrology, with definitions: U. S. Geol, Survey
Water-Supply Paper 494.
Parker, G. G.
1944 (and Cooke, C. Wythe) Late Cenozoic geology of southern Florida, with
a discussion of the ground water: Florida Geol. Survey Bull, 27.
1950 (and Stringfield, V. T.) Effects of earthquakes, trains, tides, winds, and
atmospheric pressure changes in water in the geologic formations in
southern Florida: Econ. Geology, v. 45, no. 5, p. 441-460.
1951 Geologic and hydrologic factors in the perennial yield of the Biscayne
aquifer: Am. Water Works Assoc. Jour., v. 43, no. 10, p. 820-828,
1955 (and others) Water resources of southeastern Florida, with special refer-
ence to the geology and ground water of the Miami area: U. S. Geol.
Survey Water-Supply Paper 1255.

Schroeder, M. C.
1958 (and Klein, Howard, and Hoy, N. D.) Biscayne aquifer of Dade and
Broward Counties, Florida: Florida Geol. Survey Iept, Inv, 17.
Stringfield, V. T. (see Parker, G, G.)
Theis. C. V.
1935 The relation between the lowering of the piezometric surface and the
rate and duration of discharge of a well using ground-water storage:
Am. Geophys. Union Trans., p. 519-524.
1938 The significance and nature of the cone of depression in ground-water
bodies: Econ. Geology, v. 33, no. 8.
1948 Geology and ground water of the Fort Lauderdale area, Florida: Florida
Geol. Survey Bept. Inv. 6.
Vorhis, R. C.




Full Text

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STATE OF FLORIDA STATE BOARD OF CONSERVATION Ernest Mitts, Director FLORIDA GEOLOGICAL SURVEY Robert 0. Vernon, Director REPORT OF INVESTIGATIONS NO. 20 GROUND-WATER RESOURCES OF THE OAKLAND PARK AREA OF EASTERN BROWARD COUNTY, FLORIDA By C. B. Sherwood U. S. Geological Survey Prepared by the UNITED STATES GEOLOGICAL SURVEY in cooperation with the CITY OF FORT LAUDERDALE and the FLORIDA GEOLOGICAL SURVEY TALLAHASSEE, FLORIDA 1959



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10 FLORIDA GEOLOGICAL SURVEY WELL S998 POMPANO BEACH WELL FIELD WELL LOG 0 -10 Sand, quarta, buff, coarse, calcareous. 10 -12 Sand, quarts, white to buff, fine to medium, calcareous; a few rounded shell fragments, 12 -25 Limestone, shelly, very sandy, gray, porous 20 and hard. 23 -30 Sand, quarts, poorly sorted, some shell fragments. 30 -40 Same as above, but fewer shell fragments, 40 49 -67 Sand, quarts, poorly sorted, light gray, S:very few shell fragments. 'o S60 o 67 -76 Coquina, very sandy, porous, grayish-buff. S 76 -80 Sand, quarts, medium to coarse, buff to gray, a 80 calcareous. .4 80 -89 Limestone, very sandy, silty and phosphatic, 4 hard, greenish-gray. 89 -103 Sandstone, very calcareous, gray, hard, fair 100 -porosity; shell fragments and a few Sphosphate grains. r 103 -Sand, quarts, medium to fine, white; very fine-grained phosphate. 120 Figure 6. Log of well S-998. County. Higher yields can be obtained from wells in the limestone parts of the aquifer than can be obtained from wells in the sandy parts. Individual 10-inch wells in the Prospect well field yield 820 gpm with approximately six feet of drawdown. These wells are screened in soft sandy limestone or calcareous sandstone, and the bottoms of the screens are set at depths ranging from 114 to 140 feet. The screens are 10 inches in diameter and average 20 feet in length. Wells for small individual supplies generally tap thin, local sandstones at depths ranging from 60 to 80 feet. The Miami oolite of Pleistocene age, which occurs in the upper part of several test wells, is the surface rock that blankets much of southeastern Florida. In the Oakland Park area it is generally a white to yellowish thinly laminated, crossbedded oolitic limestone containing large amounts of sand and shells. The oolite is mined in shallow excavations south and west of the Prospect well field, but it is either very thin or missing in much of the Oakland Park area. The Miami oolite is very permeable, and it is tapped by domestic supply wells wherever it is thick enough to supply appreciable amounts of water.



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REPORT OF INVESTIGATIONS No. 20 WELL S 999 POMPANO BEACH WELL FIELD .-WELLLOG 200 -69 No samples'. 40 60' 09 -97 Sand, quartz, fine to medium, marly; specks 80 of cellophane and a few fragments of t 0 s. calcareous sandstone. S 97 -108 Sand, quartz, white, coarser than above, ;,h calcareous; some collophane. S3 108 -118 Sand, similar to above, marly, phosphatic. I I 118 128 Sand, quartz, white to tan, fine to medium, Stamarly, angular to subrounded, phosphatic. (. 128 -134 Sand, quartz, white, subrounded to wellQ rounded; fragments of calcareous sandstone, S"' reourked shells and phosphate. j 140 -134 -140 Sand, quartz, white, very fine to fine, silty, phosphatic. S 140 -145 Sand, quartz, white to gray, fine, clean; rounded shell fragments and collophane. 14 -150 Sand, quartz, similar to above; a few 160 fragments of calcareous sandstone. 150 -155 Sand, qudrtz, white to gray, fine to coarse; many rounded shell fragments and much -15 reworked material, 1o0 -155 -165 Sand, quartz, white to tan, very fine to medium, marly, phosphatic. S 165 -170 Sand, quartz, white to gray, fine, clean; collophane, -170 -180 Sand, quartz, gray, phosphatic, fine; sand200 -.stone, calcareous, hard; a few shell fragments. 180 -195 Sand, quartz, gray to tan, very fine to medium, very silty, marly, phosphatic. 195 .203 Sandstone, calcareous, permeable, hard. 220 Figure 7. Log of well S-999.



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8 FLOMDA GEOLOGICAL SURVEY WELL G563 4TH AVE.8 IOTH ST., N.W. FQRT LAUDERDALE, FLA. WELL LOG 0 -10 Sand, quartz, brown. 10 -14 Sand, quarts, with tan clay included in a shelly, oolitic solution-riddled limestone. 14 --34 Sand, quartz, white; some fine grains of epidote. 34 -40 Sand, quartz, gray-white; many small tan 4 pelecypod shells. 40 -45 Limestone, hard at top, soft and shelly at base. 45 -68 Sandstone, calcareoun, light-gray, scattered collophane and some ilmenite, loosely to 60tightly cemented with some blue-green clay below 60 feet. 68 -84 Sand, quartz, very fine grained, peppered with collophane and ilmenite; some sand*0stone nodules. 84 -90 Marl, sandy, clayey, pale-blue-green; ..permeability low. 90 -107 Sandstone, quartz sand, and shell fragments. 100 Sand is very fine grained and is peppered k with collophane and ilmenito. ." t107 -112 Sandstone, calcareous, white; quartz sand, Svery fine to coarse. 120 112 -151 Sand, quartz, shelly, fine to coarse, white, Speppered with collophane and ilmonito; a few thin layers of sandstone. %L 140151 -153 Limestone, sandy, very dense, white. 153 -155 Sandstone and sand, calcareous, fossilif60 .erous. 155 -175 Sand, calcareous, gray-brown to gray; some nodules or thin sandstone layers. w 175 -177 Limestone, sandy, white. 180 177 -179 Sandstone, calareous. zoo Figure 4. Log of well G-563.



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REPORT OF INVESTIGATIONS NO. 20 13 RECHARGE AND DISCHARGE Rainfall is the source of all fresh-water recharge to the Biscayne aquifer. Not all of the rainfall infiltrates to the water table, however, as a large part is lost by evapotranspiration and a small part is lost by direct runoff into streams or the ocean. Parker (Parker and others, 1955, p. 221) estimates that about two-thirds of the annual rainfall reaches the water table in areas underlain by oolite and about half the annual rainfall reaches the water table in areas underlain by sand. In the Oakland Park area, some surface water is introduced into the aquifer when water levels in the Middle River and Pompano canals are higher than the water table. This occurs chiefly in upstream areas, above the closed water-control structures. Discharge from the aquifer takes place by evapotranspiration, by ground-water outflow into streams, canals, and the ocean, and by pumping. Discharge by ground-water outflow and evapotranspiration are greatest when the water table is highest, during and after periods of heavy rainfall, whereas discharge by pumping is greatest in the drier periods, which correspond with the peak tourist season. In general, the discharge by the two natural processes greatly exceeds the quantity of water withdrawn by pumping from wells. However, the operation of the Prospect well field makes pumping a significant factor. Figure 8 shows the monthly pumpage from the Prospect well field and. the monthly rainfall at Fort Lauderdale during 1955 and 1956. When water is pumped from a well in a nonartesian aquifer, the dewatering of the materials adjacent to the well causes the water table to slope downward toward the well, thus forming a cone of depression. The slope or hydraulic gradient of this cone causes ground water to flow from the surrounding area to the well. As pumping continues, the cone of depression increases in depth and areal extent until it reaches an area where ground-water discharge is salvaged and/or recharge is increased in an amount equal to the withdrawal. Studies in other areas indicate that pumping in a well field near a stream can cause large quantities of water to be drawn from the stream into the aquifer. WATER-LEVEL FLUCTUATIONS Water levels in the Biscayne aquifer fluctuate considerably in response to recharge and discharge, and, to a lesser extent, they are affected by other factors such as tides (in areas adjacent to the coast and tidal canals), earthquakes, and changes in atmospheric pressure. The greatest short-term fluctuations are caused by recharge by rainfall and discharge by pumping, but gradual changes in water levels caused by evapotranspiration and normal ground-water outflow have an equally important



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4 FLORIDA GEOLOGICAL SURVEY G E 0 R G I A i S-.NASSAU --BAKER AK N D -UVAL$ LU lY TAYLOR 0 CITRUS e LAKE BROWARD OAKLAND ./ -1IGHLAND .LUCI 0 miles I o a MonY PeaM nsa MONROE1 DADE DADE Key West el l Figure 1. Map of the peninsula of Florida showing location of area investigated.



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REPORT OF INVESTIGATIONS No. 20 7 GEOLOGIC FORMATIONS AND THEIR WATER-BEARING CHARACTERISTICS The name Biscayne aquifer was used by Parker (1951, p. 820-823) for the "hydrologic unit of water-bearing rocks that carries unconfined ground water in southeastern Florida." This aquifer is the only source of fresh ground water in Dade and Broward counties. Limestone strata at depths of 900 to 1,000 feet yield large quantities of water under artesian pressure, but the water is highly mineralized and unsuitable for general use. The artesian aquifer is not discussed in this report. In the Oakland Park area the Biscayne aquifer includes marine deposits ranging in age (oldest to youngest) from late Miocene through Pleistocene, in the following sequence (Schroeder, 1958): Tamiami formation (upper part), Anastasia formation, Miami oolite, and Pamlico sand. In Dade County and southern Broward County the aquifer is underlain by a relatively impermeable greenish marl at or near the top of the Tamiami formation, but in northeastern Broward County the aquifer thickens and its base is considerably below the top of the Tamiami formation. Some of the geologic information included in this report was obtained from shallow observation wells in the Oakland Park area and some was obtained from four deep wells, namely, test well G-563 in the northern part of Fort Lauderdale, test well G-820 in the Prospect well field, and supply wells S-998 and S-999 in the Pompano Beach well field. Logs of these wells are shown in figures 4 through 7. The log of well G-820 in the Prospect well field shows highly permeable limestone at a depth of 224 feet below the land surface, and local drillers report that similar limestones occur at greater depths. In each of the deep wells the marine deposits of the Tamiami formation of late Miocene age are overlain by very similar deposits of the Anastasia formation of the Pleistocene age. Well cuttings from both formations show that they are composed chiefly of alternating beds or lenses of sandy limestone or calcareous sandstone, sand, shells, and sandy clay or marl. Because of the lack of distinctive fossils in the samples and the absence of good stratigraphic correlation, no line of demarcation was drawn between the Tamiami and Anastasia formations. In general, the part of the aquifer underlying the Oakland Park area contains more unconsolidated sandy and clayey material than the part underlying areas south of Broward County; thus, the overall permeability of the aquifer in this area is lower than the permeability of the aquifer underlying areas to the south. Wells developed in the limestones and sands of the Tamiami and Anastasia formations supply all the public water systems in eastern Broward



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2 FLORIDA GEOLOGICAL SURVEY AUtKT I n *1.5 -a---i------------I----U ----------------e---e----------'L ----1 Figure 15. Hydrographs of Middle River Canal above and below dam, August 7-12, 1956. average water levels above the east (City) and west (Market) dams during this period were 3.89 and 7.16 feet above mean sea level, respectively. No record of the tidal fluctuations in the lower reach of the canal is available, but the fluctuations are assumed to be similar to those ;n the Middle River Canal. No data are available to show the beneficial effects of the floodcontrol works in this area during flood periods. This is unfortunate because the system was designed for both high-water and low-water conditions and its effectiveness is not fully demonstrated unless both conditions are presented. SALT-WATER ENCROACHMENT Salt-water encroachment is the chief factor limiting the use of ground water from the Biscayne aquifer. The salt water in this aquifer may come from two general sources, as follows: (1) direct movement inland from the ocean and from tidal canals and streams, and (2) sea water which



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1955 1956 MiAM i A ai 300 Io*n---------------H Ic .. eif 3 I "I Figure 8. d and monthly rainfall at Fort derdae.



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'JULY 1956 uI .... I -a, I I "! 0 S' -.0 Figure 23. Hydrograph of well G-768, in the Prospect well field, showing effect of pumping in the well field. "4



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6 FLORIDA GEOLOGICAL SURVEY miles wide and is very low and nearly flat, except where it is cut by the main streams -Cypress Creek near Pompano Beach and the Middle River south of Oakland Park (fig. 3). The land surface ranges in altitude from about four feet above mean sea level in areas adjacent to stream channels to about 15 feet above mean sea level in the vicinity of the Prospect Air Field and in the area which parallels U. S. Highway 1, west of the Intracoastal Waterway. Most of the area, however, is about nine feet above mean sea level. The area is drained chiefly by underground flow toward the ocean and into the canals and streams that flow generally eastward to the Intracoastal Waterway. The permeable quartz sand and oolitic limestone that form the shallow subsurface materials allow rainwater to infiltrate rapidly to the water table, and there is very little surface runoff to the canals and streams. The underground flow pattern is considerably influenced by continuous pumping in Fort Lauderdale's Prospect well field and by water-control structures in canals. The Pompano Canal and Cypress Creek traverse the northern part of the area from west to east, through the ridge, to the Intracoastal Waterway. Cypress Creek drains the slough area north of Prospect field, and the Pompano Canal drains the area west of Pompano Beach and is a part of the overall flood-control system in southern Florida. The tributaries of the Middle River traverse the southern part of the area and drain the low areas south of Prospect field. Local farm drainage is effected by intricate systems of shallow ditches which connect to major drainage channels. The drainage and flood-control works are part of a cooperative state and federal program designed to alleviate the effects of both flood and drought conditions in central and southern Florida. The Oakland Park area lies east of one of a series of water conservaton areas (Conservation Area No. 2) that are bounded by a levee system extending from Lake Okeechobee to southern Dade County (fig. 2). The Pompano Canal and the Middle River Canal connect with a canal on the east side of Conservation Area No. 2. The Pompano Canal is controlled by dams near its confluence with Cypress Creek, and the Middle River Canal is controlled by a dam about 5% miles inland from the Intracoastal Waterway. The tidal reach of Cypress Creek extends inland about two miles, and the various branches of the Middle River are tidal as far upstream as the flood-control dam. In the tidal reaches of these streams salt water is free to advance upstream as far as tides and fresh-water flow permit.



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15 Hydrographs of Middle River Canal above and below dam, August 7-12, 1956 --_ __ _________ "22 16 Hydrographs of Middle River Canal above and below dam during 1956 __ ___-23 17 Hydrographs of Pompano Canal above Market and City dams, 1956 -24 18 Map of eastern Broward County showing maximum chloride content recorded in water samples from wells and streams, 1941-57 27 19 Chloride content of water from wells S-330 and S-830, at junction of South New River and Dania Cutoff Canals, 1941-57 28 20 Map of Prospect well field showing layout of municipal supply wells and observation wells 32 21 Hydrograph of well G-768, in the Prospect well field, during pumping test, August 7-8, 1956 _--_ 34 22 Idealized sketch showing flow in a leaky aquifer 35 23 Hydrograph of well G-768, in the Prospect well field, showing effect of pumping in the well field 37 Table Page 1 Average monthly temperature, in degrees, at Fort Lauderdale, and average monthly rainfall, in inches, at Fort Lauderdale and Pompano Beach --5 2 Chemical analyses of water from selected wells ---30 vii



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IEuPOnT OF INVESTIGATIONS No. 20 25 entered the aquifer when the sea covered parts of southern Florida during various interglacial stages of the Pleistocene and is still present in parts of it. -Parker (Parker and others, 1955, p, 819-821) discussed the effects of residual sea water in the Everglades area and indicated that this source of salt water caused little or no contamination of ground water in the Oakland Park area; however, ground water in the Everglades area west of Oakland Park has chloride concentrations greater than 30 ppm, the concentrations increasing in a westerly direction and with depth. Salt-water encroachment from the ocean into the Biscayne aquifer is governed by the relationship of ground-water levels to mean sea level. In coastal areas the depth to salt water is related to the height of the fresh water above sea level. Under static conditions this relationship is that of a U-tube whose limbs contain liquids of different density, and it is expressed by the Ghyben-Herzberg principle (Brown, 1925, p. 16-17), as follows: t g -1 where h is the depth of fresh water below sea level, in feet; t is the height of the fresh-water surface above sea level, in feet; and g is the specific gravity of sea water. If a specific gravity of 1.025 is assumed for sea water, then each foot of fresh water above sea level should indicate 40 feet of fresh water below sea level. In the field, this relationship is modified by mixing of fresh and salt water by dynamic hydraulic conditions, and by geologic conditions, but the relationship holds sufficiently well to be considered valid for most purposes. Salt-water encroachment in Broward County has occurred chiefly in areas adjacent to major streams and uncontrolled parts of drainage canals that empty into the ocean. These waterways enhance the possibility of salt-water encroachment in two ways, as follows: (1) they lower ground-water levels, thereby reducing the fresh-water head that normally would oppose the inland movement of salt water, and (2) they provide a path for sea water to move inland during dry periods. The extent of the encroachment at depth in the aquifer, in the Middle River and Cypress Creek basins, has not been determined because of the lack of deep wells in these areas. In order to determine accurately the extent of encroachment, several deep test wells would be required in the general area betwen U. S. Highway 1 and the Florida East Coast Railroad and in the area adjacent to the downstream parts of the Middle River. These wells would serve as outpost wells from which water



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GROUND-WATER RESOURCES OF THE OAKLAND PARK AREA OF EASTERN BROWARD COUNTY, FLORIDA ABSTRACT The Biscayne aquifer is the source of all fresh ground water in the Oakland Park area of eastern Broward County, Florida. This aquifer extends from the land surface to more than 215 feet below mean sea level and is composed chiefly of sandy marine limestone, calcareous sandstone, and beds of fine to medium quartz sand. The aquifer differs from place to place, but, in general, most of the layers of limestone and sandstone occur at depths below 60 feet. The permeability of the aquifer increases with depth. Wells for small supplies generally obtain water at depths ranging from 60 to 80 feet, whereas wells for large supplies usually obtain water from the interval between 100 and 200 feet. Large-diameter wells obtain as much as 1,000 gpm (gallons per minute) from the lower part of the aquifer. Chemical analyses of ground-water samples indicate a hard limestone water that is suitable, naturally or with treatment, for most ordinary uses. Periodic determinations of chloride content of the ground water show that some salt-water encroachment has occurred in areas near the coast and in the Middle River basin. Pumping-test data for deep wells in the Prospect well field area indicate approximate aquifer coefficients of transmissibility and storage of 2,000,000 gpd per foot and 0.015, respectively. However, the data indicate also that the hydraulic characteristics of the aquifer are complicated by the presence of beds of sand, silt, and clay in the upper 100 feet of the aquifer and by recharge from surface-water sources. Quantitative data and areawide water-level and salinity data indicate that large quantities of ground water are available for future development if salt-water encroachment can be effectively controlled. INTRODUCTION PURPOSE AND SCOPE The rapid growth of population and industries in eastern Broward County has introduced the problem of preserving existing ground-water supplies and has caused a growing need for additional supplies. As in many coastal areas, this problem involves not only finding and developing a satisfactory source of water but also protecting this source



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SFLORIDA GEOLOGICAL SURVEY against salt-water encroachment from the sea. Recognizing the need for data in solving their problems, officials of the city of Fort Lauderdale requested that an investigation be made of the ground-water resources of eastern Broward County, in the vicinity of Oakland Park. The investigation was made by the U. S. Geological Survey in cooperation with the Florida Geological Survey and the city of Fort Lauderdale. The purpose of the investigation was to determine, insofar as possible, the following things: 1. The ground-water potential of the area. 2. The extent of salt-water encroachment into the Biscayne aquifer. .3. The hydraulic coefficients of the aquifer and the safe rate of withdrawal for the development of large supplies. 4. The effect of water-control works of the Central and Southern Florida Flood Control District on the ground-water resources of the area. Field studies, begun in December 1955, consisted of the following: 1. A partial inventory of wells in the area. 2. The installation of shallow wells to be used for water-level studies and one deep test well to be used for geologic and salinity studies. 3. Pumping tests to obtain data on the water-transmitting and storing properties of the aquifer. 4. A leveling program to determine the altitudes of measuring points for water-level measurements. I5. The determination of the chloride content of water from selected wells and sampling points in streams, and comprehensive analyses of water from selected wells. 6. The installation of two automatic water-stage recorders and the areawide measurements of water level at selected times. The investigation was made under the general supervision of A. N. SaYre, Chief, Ground Water Branch, and under the immediate supervision of Howard Klein, Geologist, and M. I. Rorabaugh, District Engineer, all of the U. S. Geological Survey. PREVIOUS INVESTIGATIONS No detailed investigation of the ground-water resources of the Oakland Park area had been made prior to this investigation. Considerable information pertinent to the area is available, however, in publications or unpublished open-file reports of the Florida Geological Survey and the U. S. Geological Survey. Data from these reports have been used freely in the preparation of this report. Frequent references to the geology of the area and the occurrence and quality of the ground water in eastern



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26 FLORIDA GEOLOGICAL SURVEY samples could be taken for periodic determinations of the chloride content of the ground water. Considerable data are available in a similar area adjacent to the North New River in Fort Lauderdale. These data may illustrate some of the characteristics of salt-water encroachment in the area. Figure 18 shows the maximum chloride content recorded in surface-water and ground-water samples in eastern Broward County north of Dania. The ground-water samples were pumped from wells which are cased to within a few feet of their total depth; therefore, the depth of the sampling point is assumed to be approximately equal to the depth of the well. The data shown in the Oakland Park area represent samples taken during 1956-57 and those shown on the southern part of the map represent samples taken during the past 15 years (expanded from fig. 187 in Parker and others. 1955). Along the north and south forks of the New River, salt water has migrated inland, at depth in the aquifer, as much as 38 miles from the coast. The extent of salt-water encroachment at depth near the river is indicated by salinity data from well G-514 (fig. 18). The chloride content in samples taken at a depth of 177 feet in this well has ranged from 2,700 ppm to 4,900 ppm during the past 10 years. It can be seen, therefore, that salt water has encroached at depth, in this area, beyond the junction of the forks of the Middle River. Figure 19 shows the variation of chloride content in wells S-330 and S-880 caused by salt-water encroachment from the south fork of the New River during the period 1941-57 (adapted from Vorhis, 1948). These wells were sampled at depths of 35 feet and 118 feet, respectively, and are near the river, about 53 miles inland from the coast. The data indicate that large and rapid changes in the chloride content of ground water are caused by salt-water encroachment from the New River. In the Oakland Park area appreciable contamination by salt water was found in samples from wells S-1379 and S-1380, near the dam on the Middle River Canal, and in well S-1381, near the Fiveash water plant. Analyses of samples from wells S-1379 and S-1380 show chloride contents of 600 ppm and 820 ppm, respectively, and indicate contamination from the Middle River Canal during the prolonged dry period of 1955-56. A water sample collected at a depth of 240 feet in well S-1881 contained *2,640 ppm of chloride. The high chloride content in this sample indicates that salt-water encroachment has been occurring at depth in the aquifer as a result of lowered ground-water levels in the vicinity of the Middle River. These are the only data available that indicate extensive saltwater contamination in the Middle River basin. However, the high



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34 FLORDA GEOLOGICAL SURVEY PROSPEGT FIELO PU MPI M TEST Figure 21. Hydrograph of well G-768, in the Prospect well field, during pumping test, August 7-8, 1956. Water-level and pumping-test data indicate that under static (nonpumping) conditions the Biscayne aquifer exhibits different characteristics than it does under pumping conditions. Under static conditions, the water level in a shallow well will stand at the same altitude as the water level in an adjacent deep well, suggesting that the aquifer is under nonartesian conditions. However, when the deep, highly permeable zones of the aquifer were pumped, water levels in deep wells as much as 1,000 feet away showed an immediate rapid decline. Water levels in shallow wells much closer to the pumping wells showed no immediate change during the test, but they do show a long-term drawdown of several feet. (See contour maps, figs. 11, 12 and 13.) Thus, in pumping tests of short duration the zone in which the supply wells are develped reacts as an artesian aquifer overlain and partly confined by a leaky roof of less permeable beds (fg. 5). The fact that the water levels of deep wells permeable beds (fig. 5). The fact that the water levels of deep wells



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CULTURAL LIBRARY FLORIDA STATE BOARD OF CONSERVATION LEROY COLLINS Governor R. A. GRAY RICHARD ERVIN Secretary of State Attorney General J. EDWIN LARSON RAY E. GREEN Treasurer Comptroller THOMAS D. BAILEY NATHAN MAYO Superintendent of Public Instruction Commissioner of Agriculture ERNEST MITTS Director of Conservation ii



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36 FLORIDA GEOLOGICAL SURVEY problems in leaky systems these methods add a third aquifer coefficient, called the leakage coefficient, which indicates the ability of the semiconfining bed to transmit water upward from or downward into the aquifer being tested. This coefficient may be defined as the quantity of flow that crosses a unit area of the interface between the main aquifer and its semiconfining bed if the difference between the head in the main aquifer and the bed supplying the leakage is unity. It is obvious that the head in the bed supplying the leakage in the well field area is not constant during long periods, but water levels in shallow wells in the well field were very nearly constant during the pumping tests. The water level in well G-803 rose 0.02 foot during the 16 hours preceding the first pumping test and declined 0.03 foot during the first five hours of the test. Computation of the aquifer coefficients is complicated not only by vertical leakage in the stratified material but also by the possibility of inducing recharge from canals and quarries and the limitations on the accurate measurement of the small drawdowns. The coefficients of transmissibility obtained ranged from 2,000,000 to 3,000,000 gpd per foot. The storage coefficient was approximately 0.015, and the leakage coefficient was about one gpd per square foot per foot of vertical head. It is apparent from the large cone of depression shown in figures 11, 12, and 13 that long-term pumping has caused considerable unwatering of the beds overlying the pumped zone in the aquifer. Thus, the drawdown caused by large-scale pumping from the deep zone is reflected at the water table, and it is controlled by the coefficients of transmissibility and storage of both the pumped zone and the overlying beds. An approximate value for the coefficient of transmissibility, under equilibrium conditions, may be calculated by substituting the average hydraulic gradient at points around the cone of depression and the average pumpage from the well field in the formula Q = TIW (a modified expression of Darcy's law for ground-water flow) where: Q= the average pumpage from the well field, in gallons per day T = the transmissibility of the aquifer, in gallons per day per foot W=the circumference of a cylinder through the aquifer at a given radius from the center of pumpage, in feet I = the average slope of the cone depression around this cylinder, in feet per foot. The record of water-level fluctuations in well G-768 during the period July 12-24 (fig. 23) indicates that water levels in the well field area had reached approximate equilibrium for the rate of pumping at that time. A coefficient of transmissibility of about 1,000,000 gpd per foot was



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REPORT OF INVESTIGATIONS No. 20 15 effect on the amount of water in storage in the aquifer. Parker and Stringfield (1950, p. 441-460) discussed the effects of earthquakes, winds, tides, and atmospheric-pressure changes on ground-water levels in southern Florida. Water-level fluctuations in the Oakland Park area are greatly influenced by pumping in the Prospect well field and by the flood-control works of the Central and Southern Florida Flood Control District. Figure 9 is a contour map of eastern Broward County, showing the approximate altitude and configuration of the water table in the Biscayne aquifer on February 15, 1941. This map was made by using some of the earliest water-level data available for the area, and it represents the water table at a time when there was no drawdown due to pumping in the Prospect well field area or to extensive water-control works. The Pompano Canal (Cypress Creek Canal) was the only major drainage canal in the immediate area. Bogart and Ferguson (Parker and others, 1955, p. 505) indicated that the canal was controlled in two pools by small dams, in much the same manner as it is at present. Parker (Parker and others, 1955, fig. 148) shows that the water level above the controls in Pompano Canal ranged from about 1.0 foot to 5.4 feet above mean sea level during the period 1940-43. The contours in figure 9 were drawn from water-stage readings in streams and canals and from water-level measurements in widely scattered wells. In the Oakland Park area, the contours show; generally, the altitude and configuration of the water table under relatively natural conditions and indicate a fairly uniform gradient toward the coast. The graphs in figure 10 show a correlation between periodic waterlevel measurements made in wells G-127 and G-128 (see fig. 9 for locations) and weekly rainfall at Fort Lauderdale during 1940-41. Well G-127 was on the present site of the Prospect well field, and well G-128 was on U. S. Highway 1, 2.7 miles east of well G-127. The hydrographs indicate also the differential in head between wells G-127 and G-128 during the latter part of 1940 and all of 1941. Ground-water levels in Broward County during 1955 and 1956 were generally below the average for the period of record, owing to a deficiency in rainfall. This condition tends to accent the effects of drainage canals, dams, and pumping on the water table. During 1956 an areawide program of water-level observations was established and contour maps of the water table in the Biscayne aquifer were prepared. Figures 11 through 18 show contours on the water table on August 7, September 21, and October 19, during periods of low, intermediate, and high water levels, respectively. The most striking feature of



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32 FLORIDA GEOLOGICAL SURVEY extent of salt-water encroachment from the ocean, samples were collected from several wells in the Oakland Park area and analyzed for chloride content. The data from the analysis of these samples are shown in figure 18. QUANTITATIVE STUDIES Knowledge of the hydraulic properties of the aquifers of an area is essential to the evaluation of the ground-water resources. The principal hydraulic properties of an aquifer are its capacities to transmit and store water. These properties are generally expressed as the coefficients of transmissibility and storage. The coefficient of transmissibility is a measure of the capacity of an aquifer to transmit water. In customary units it is the quantity of water, in gallons per day (gpd), that will flow through a vertical section of the aquifer 1 foot wide and extending the full saturated height, under a unit hydraulic gradient, at the prevailing temperature of the water (Theis, .-------------" ---____________ P42F 15 9 *14 13 0 Oslo OPS20 O0804 62 EXPLANATION 0id T2 ) i I4 I 10 SCALE COMPLETE WELL IOT OPERATING 842 Figure 20. Map of Prospect well field showing layout of municipal supply wells and observation wells.



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38 FLORIDA GEOLOGICA. SURVEY obtained from the above formula by using the water-level data from the contour map of August 7, 1956, and the average pumping rate for the period July 25-August 7, 1956 (10.0 mgd). This figure is on the low side because evapotranspiration was not considered. The area within the contour used (sea level) is about 34,000,000 square feet. Evapotranspiration of ground water is estimated at 6 inches per month or 0.2 inch per day. Natural water loss for the area is then about 4.2 mgd. By use of the combined discharge of 10.0 mgd by pumping and 4.2 mgd by evapotranspiration, the coefficient of transmissibility is computed to be about 1,500,000 gpd per foot. GROUND-WATER USE Wells supply most of the water for public, domestic, irrigation, and industrial use in the Oakland Park area. Until recent years the area was relatively undeveloped and ground-water withdrawals were small. Since about 1950, however, the growth of population and industry in the area has been extremely rapid, and ground-water use has increased correspondingly. The largest pumpage is that from the Prospect well field, which yielded about 10.0 mgd in 1956. When all proposed wells are in operation, the pumpage from the field will be about 20 mgd. Separate watersupply systems have been developed for several large housing developments in the area, and many residents have private wells for domestic use and lawn sprinkling. In the area west of Oakland Park, several large farms use ground water for irrigation. Generally, the peak pumping for municipal supplies and irrigation occurs during December through June, as these months include both the tourist season and the dry season. The use of ground water by industries is growing rapidly, especially in areas adjacent to the two railroads. CONCLUSIONS The Biscayne aquifer is the source of all fresh ground water in the Oakland Park area. The water in the aquifer comes from local rainfall or from surface water brought into the area by canals. It is generally of good quality except for hardness and color. The Biscayne aquifer is composed of permeable marine deposits -chiefly sandy limestone, calcareous sandstone, and quartz sand -which extend from the land surface to a depth of more than 215 feet below mean sea level. The components of the aquifer differ from place to place, but, in general, the amount of sand decreases with depth and most of the consolidated rocks occur at depths greater than 60 feet.



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12 FLORIDA GEOLOGICAL SURVEY The Pamlico sand, which was found near the surface in the test and observation wells, is a late Pleistocene marine terrace deposit (Parker and Cooke, 1944, p. 75). In the Oakland Park area it overlies and fills erosion channels and solution cavities in the Miami oolite and the Anastasia formation. The Pamlico sand is composed chiefly of fine to coarse quartz sand ranging in color from white to rust or gray-black, according to the amount of admixed iron oxide or carbonaceous material. Properly developed sandpoint wells in the Pamlico sand generally yield enough fresh water for domestic purposes, but the water often has an objectionable color or odor caused by organic matter. GROUND WATER Ground water is the subsurface water in the zone of saturation, the zone in which all the interstices of the soil or rocks are completely filled with water under greater than atmospheric pressure. Ground water may occur under either artesian or nonartesian conditions. Where its upper surface is free to rise or fall in a permeable stratum it is said to be under nonartesian conditions, and the surface is called the water table. Where the water is confined in a permeable bed that is overlain by a less perrmeable bed, its surface is not free to rise and fall. Water thus confined under pressure is said to be under artesian conditions. The height to which water will rise in tightly cased wells that penetrate an artesian aquifer defines the pressure, or piezometric, surface of the aquifer. In the Oakland Park area the only potable ground water is the rainfall that infiltrates downward into the materials of the Biscayne aquifer. This water is said to be under nonartesian conditions, as its upper surface, the water table, is unconfined and under normal atmospheric pressure. It is recognized, however, that artesian conditions exist to some extent in parts of the aquifer. (See section on quantitative studies.) The water table fluctuates in response to recharge or discharge, and ground water flows -under gravitational forces -from points of recharge, where water levels are high, to points of discharge, where water levels are low. The direction of flow coincides with the maximum slope of the water table. The water table may be mapped by determining the altitude of the water level in a network of wells. Systemic areawide observations of the shape, slope, and fluctuations of the water table are an important part of ground-water investigations, as they show the direction of ground-water movement and changes in the amount of ground-water storage.



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REPORT OF INVESTIGATIONS No. 20 19 ,lA I.ill .w .......' I i f .. .. Figure 12. Map showing contours on the water table in the Biscayne aquifer in the Oakland Park area, September 21, 1956. tion) in 1940-41 (fig. 10), shows the marked effect of heavy pumping -j 6944"-7;T-,in the area. During extended dry periods, when there is little recharge, the rate of the natural decline in water levels decreases as the water-level gradient toward the coast diminishes. However, water levels in the well field area drop at an increased rate until the cone of depression reaches a new source of recharge or enogh natural discharge is salvaged to balance Fthe 12. Mscharge due to pumpp showing. The contours on the water tablefigure 11 in the Biscayne aquife inthat the Oakland Park area, September 21, 1956. tion) in 1940-41 (fig. 10), shows the marked effect of heavy pumping the ater table in the area between the well field and uncontrolled During extended dry periods, when there is little recharge, the rate reaches of the natural ddle River Canal was approaching the mean water level gradient towardin the canal in August 195diminishes. If thever, water levels in the area declined to area drop at an increased rate until the cone of depression reaches a new source of recharge or enough natural discharge is salvaged to balance the discharge due to pumping. The contours in figure 11 indicate that the water table in the area between the well field and uncontrolled reaches of the Middle River Canal was approaching the mean water level in the canal in August 1956. If the water table in the area declined to an altitude below that of the water level of the canal, some salty water would enter the aquifer from the canal. The flow of water from the canal into the aquifer would be impeded, however, by silt in the canal bed and by the relatively low permeability of the materials cut by the canal. It



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REPORT OF INVESTIGATIONS No. 20 29 chloride content of the canal water (fig. 18) and the low ground-water levels shown on the contour map for August 7 (fig. 11) indicate that there might be considerable salt-water encroachment in this area. In the area north of the Middle River basin, the available data indicate that salt-water encroachment has been limited to areas close to the Intracoastal Waterway or Cypress Creek. This limitation is partially due to the high ground-water levels maintained by the control near the mouth of Pompano Canal and to the fact that Cypress Creek is not an improved drainage channel such as the Middle River and the south fork of the New River. QUALITY OF WATER The suitability of ground water for general use depends largely on the degree to which it fulfills the following requirements: (1) it must be safe to drink -that is, free from disease-causing bacteria and from excessive quantities of harmful minerals; (2) it should be clear and free from unpleasant taste or odor; (3) it should be relatively soft; and (4) it should not be corrosive or excessively damaging to metal surfaces. The first two requirements are most important for domestic or public supplies and the last two are most important for industrial supplies. As ground water must seep through more than 100 feet of sand and rock to reach the producing zone of the Biscayne aquifer, it is generally free of dangerous bacteria and suspended material. However, it is affected by the composition and solubility of the rocks and sediments with which it has been in contact. As rainwater infiltrates into the aquifer it exerts a solvent action upon the rocks through which it passes. This action is aided by the presence of carbon dioxide, absorbed from the atmosphere and from organic material in the soil. To determine the mineral constituents of ground water at different depths and locations in the area, chemical analyses were made of water samples from selected wells. The results of these analyses are shown in table 2. (See fig. 3 for well locations.) The analyses of the water from these wells show the characteristics of a hard to very hard limestone water, suitable (naturally or with fairly simple treatment) for all ordinary uses. Using the amount of dissolved solids as an indication of the mineralization of the water, the samples from wells S-340, S-341 and S-1869 in the Pompano Beach area showed less mineralization than the samples from well G-820 in the Prospect well field and wells S-336 and S-337 in the Middle River basin. The testwell logs (figs. 4-7) show that the amount of limestone penetrated in wells S-998 and S-999 in Pompano Beach was much less than that



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1941 1942 1943 1944 1946 1946 1947 1948 1949 I980 1961 195B I9S3 1984 16 19 06 J9 7 '00 --------------_-,. 400 .-, .WELL I B 1,200 z DEPTH OF SAMPLE 116 FEET ..J Ic 2,600--------a. t,400 --g__ II-_ 2,,|00 I V Iloo CC 1,400---o 6000 -E 1 V-I -___ --OEPTH OF SAMPLE 35 FEET < 400 -, 200-K4..ZI.Z Figure 19. Chloride content of water from wells S-330 and S-830, at junction of South New River and Dania cutoff canals, 1941-57.



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REPORT OF INVESTIGATIONS No. 20 9 WELL G 820 PROSPECT WELL FIELD WELL LOG 0 -8 Sand, quartz, white, medium. 8 -11 "Hlardpan", sand, quartz, medium; brown organic material. ~20 11 -43 Sand, quartz, tan. 40 43 -54 Sand, quartz, tan, fine to medium. 60 54 -76 Sand, quartz, white, very fine to medium; interbodded blue-green clay. U 80 76 -87 Sand, very fine to medium; contains some bluegreen clay and thin layers or nodules of soft 87 .99 Sand, quartz, gray, medium to coarse, peppered with ilmanite and phospnate. -100 99 -110 Sand, tan, medium to very coarse; a few Sthin layers of gray limestone. S11 -131 Same as above but less limestone. 120 131 -137 Limestone. sandy, gray; contains a large percentage of medium to coarse sand. t 140 137 -142 Same as above but sand very fine to medium. W 142 -158 Limestone, sandy, can and gray; contains a large percentage of very fine to medium sand. 160 158 -159 Limestone, gray, very hard. k .: 159 -171 Limestone, sandy, gray; contains a large percentage of very fine to medium sand. .171 -175 Limestone, gray, very hard. 180 175 -189 Limestone, sandy, white. 189 -205 Limestone, sandy, gray. 200205 -224 Limestone, sandy, white. 220 240 Figure 5. Log of well G-820.



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40 FLORIDA GEOLOGICAL StmVEY REFERENCES Brown, J. S. 1925 A study of coastal water, with special reference to Connecticut: U, S. Geol. Survey Water-Supply Paper 537. Cooke, C. Wythe (see Parker, G. C.) Hantush, M. C. 1955 (and Jacob, C. E.) Non-steady radial flow in an infinite leaky aquifer: Am. Geophys. Union Trans, v, 36, p. 95-100. 1956 Analysis of data from pumping tests in leaky aquifers: Am. Geophys. Union Trans., v, 37, no. 6, p. 702-714. Hoy, N. D. (see Schroeder, M, C,) Jacob, C. E. (also see Hantush, M. C.) 1946 Radial flow in a leaky artesian aquifer: Am, Geophys, Union Trans., v. 26, no. 11. Klein, Howard (see Schroeder, M. C.) Meinzer, O. E. 1923 Outline of ground-water hydrology, with definitions: U. S. Geol, Survey Water-Supply Paper 494. Parker, G. G. 1944 (and Cooke, C. Wythe) Late Cenozoic geology of southern Florida, with a discussion of the ground water: Florida Geol. Survey Bull, 27. 1950 (and Stringfield, V. T.) Effects of earthquakes, trains, tides, winds, and atmospheric pressure changes in water in the geologic formations in southern Florida; Econ. Geology, v. 45, no. 5, p. 441-460. 1951 Geologic and hydrologic factors in the perennial yield of the Biscayne aquifer: Am. Water Works Assoc. Jour., v. 43, no. 10, p. 820-828, 1955 (and others) Water resources of southeastern Florida, with special reference to the geology and ground water of the Miami area: U. S. Geol. Survey Water-Supply Paper 1255. Schroeder, M. C. 1958 (and Klein, Howard, and Hoy, N. D.) Biscayne aquifer of Dade and Broward Counties, Florida: Florida Geol. Survey Rept, Inv, 17. Stringfield, V. T. (see Parker, G, G,) Theis. C. V. 1935 The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using ground-water storage: Am. Geophys. Union Trans., p. 519-524. 1938 The significance and nature of the cone of depression in ground-water bodies: Econ. Geology, v. 33, no. 8. 1948 Geology and ground water of the Fort Lauderdale area, lid Florida Flor Geol. Survey Rept. Inv. 6. Vorhis, R. C. .-I.



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Table 2. Chemical Analyses of Water from Selected Wells (Chemnical constituents in parts per million) City Well City Well Well Well Well Well Well Well Well o. 1 No. 6 0 820 813001 8336 S 337 S 340 1 8 341 8372' Silica (SiO ) ................ 9.4 9.3 42 18 ..... ....... ... .... ........... Iron (Fe) ... e.... ...... .24 .02 .04 ,01 ...... .. Celclum (Ca) .............. 70 75 68 47 89 113 47 56 74 Magnesium (Mg)............. 1,8 1,2 908 1,1 3.1 3.1 2,3 2.5 2.7 Sodium and potassium (Na+K) ................ 7.5 6.9 10.0 10.6 7.6 18 8,5 5.8 5.4 Bicarbonate (HCO ) ........ 217 204 258 140 265 297 136 173 226 Sulfate (SO 4)............... 1.0 6.0 1.8 14 5.8 1 1 1 1 Chloride (C)............... 14 12 14 16 20 64 15 14 15 Fluoride (F) ......... ...... .3 .2 .2 .1 .... ...... .. ..... .. .......... N itrate (N O ) .............. .1 .2 .5 .4 .... ........ ........ .......... ......... Dissolved solids Residue on evaporation at 1800C.. .............. 221 234 287 182 256 3454 1654 164 2094 Total hardness as CaCO a..... 182 192 210 122 235 295 127 150 196 Noncarbonate............. 4 25 0 8 ...... ... ..... .. Color ..................... 15 10 5 5 130 50 20 20 40 Temperature ("F.)........... ..... ... ....... .77 ......... 76 ....... ...... H ... .. ...... .......... 7.5 7.9 7.9 7.8 .......... .......... ...... ... .......... ..... Specific conductance (micromhos at 25*C.)...... 372 378 420 291 468 643 268 307 389 Date of collection.......... Mar. 29 Nov. 11 July 9 Sept. 10 Nov. 19 Oct. 18 Nov. 29 Oct. 18 Oct. 18 1957 1956 1956 1956 1940 1940 1941 1941 1941 Depth of sample (feet below land surface) .............. 130 130 224 190 60.9 72 170 189 120 Aquifer .................. .Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne SCity of Pompano Beach supply well 3. Parker and others (1955, p. 798). SIron in solution at time of analysis. 4 Sum of determined constituents.



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1f.ot.T o.P 1NV•rT1GAti6N8 NO, 20 2 1981 50llll IWELL 8 010 h -----........ -. -._._.. __ PR4M oI .0____ Figure 14. Hydrographs of wells 0-768 and 0-820, average daily pumpage from the Prospect well field, and daily rainfall at Fort Lauderdale, JuneDecember, 1956.



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ILLUSTRATIONS Figure Page" I Map of Florida showing location of area investigated 4 2 NMap of parts of Broward and Palm Beach counties showing canals and levees of the Central and Southern Florida Flood Control District 5 3 Map of Oakland Park area showing locations of wells Between 5 & 6 4 Log of well G-563 8 53 Log of well G-820 9 6 Log of well S-998 10 7 Lo of well S-999 11 8 Monthly pumpage from the Prospect well field and monthly rainfall at Fort Lauderdale 14 9 NMap showing contours on the water table in the Biscayne aquifer, in eastern Broward County, on February 15, 1941 16 10 Hydrographs of wells G-127 and G-128 and weekly rainfall at Fort Lauderdale during 1940-41 -17 11 Mvlap showing contours on the water table in the Biscayne aquifer in the Oakland Park area, August 7, 1956 18 12 Map showing contours on the water table in the Biscayne aquifer in the Oakland Park area, September 21, 1956 19 13 Map showing contours on the water table in the Biscayne aquifer in the Oakland Park area, October 19, 1956 _________20 14 Hydrographs of wells G-768 and G-820, average daily pumpage from the Prospect well field, and daily rainfall at Fort Lauderdale, JuneDecember 1956 21 vi



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Completed manuscript received April 9, 1959 Published by the Florida Geological Survey Rose Printing Company, Inc. Tallahassee, Florida September 1959 iv



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"20 FLOMtDA GEOLOGICAL SutWVEY Figure 18. Map showing contours on the water table in the Btsenyne aquifer in the Oakland Park area, Otobr 1, 195. is possible that during a prolonged drought the cone of depression may extend outward and cause a relatively steep gradient from the salty canal to the aquifer, thus resulting in accelerated salt-water intrusion south of the well field. Water-level recording gages are maintained above and below the cam on the Middle River Canal. Weekly readings are recorded from staff gages above and below the dams on the Pornipano Canal (fig. 8). Figure 15 shows a typical water-level record obtained from gages above and below the Middle River dam on August 7-12, 1956, and figure 16 shows daily mean water levels above the dam and mean daily high and low tide levels below the dam during 1956. The 1956 average water levels aboxve and below the dam were 4.40 and 0.60 feet above mean sea level, respectively, and the average tidal fluctuation below the dam was about 2.20 feet. Weekly water-level stages above the dam in the Pompano Canal, from April 6 to December 81, 1956, are shown in figure 17. The daily mean waer levels abve (lie dam nd mendiyigadlo tie evl blo teda drng196.Te 95 veag wtr evl abov andbelw th da wer 4.4 an 0.6 fet abve man ea lvel respecivelyand th averae tida fluctation elwtheda asabu 2.20feet Wekly aterlevl stges aboeteda nte opn Canal frmArl6t eebr3.156 r hw nfgr 7 h



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REPORT OF INVESTIGATIONS No. 20 27 "<41E IRrr S4 RIttE 84SC T49$ S3171 2o EXPLANATION 0 / 5o 1174 Surfoce water Tampling stolIon .Top number is chloride Botlom number is opproximote OSIS Er .deplh from which eomple S 1371 .13 I was taoken o.a 2.eoT 0 T490 0 3 i .I PoV54 11 9 R 1 90 $• rs1s 't op' 3 14 D 154 S o e T|S I? MAN /L Figure 18. Map of eastern Broward County showing maximum chloride content recorded in water samples from wells and streams, 1941-57.



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S",'51369 I OMPANO BEACHs 13 7 -eaR -1-9 0R0|T 6A // I S PROSPECT LMT G j43 e044 0 P 157 0 616F, 0 I9 .. 9156 S80C 0LO S06308 WATER LV*ER PROSPECT08_ 0 'C15810 D13A I 0.o s 1 42 e3. Mp O akan Pk ae shn s o .0 2 0075a C 19Y M A 13 0 010 0815 1 /014 i \ sol I321 k / s is Il EXPLANATION 0s 1320 0 Al ~WELL i 149' PUBLIC-SUPPLY WELL ,i, WATER-LEVEL RECORDING GAGE 1--3v-10 I T -lY LIMITS -CHLORIDE-CONTENT DATA AVAILABLE SURFACE-WATER OBSERVATION POINT CHEMICAL ANALYSIS AVAILABLE FORT LAUDER LE 0 .SCALP IN FE ETr Figure 8. Map of Oakland Park area showing locations of wells.



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90g AS WE AR T DAMA ...' sW AV l U -A, CI DA _0 -------------------_>I ^ f P*M>. £-_ ---, -____ --^ ___ -J w u /, \ / 0 0 Fiure 17. Hydrorahs of Pomano Canal above arket and City ams 195.. w 4 ^--I Figure 17. Hydrographs of Pompano Canal above Market and City damrns, 1956.



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REPORT OF INVESTIGATIONS No. 20 31 in well G-820 in the Prospect well field and well G-563 near the south fork of the Middle River. Thus, the difference in the mineralization of the samples is probably related to the amount of limestone contacted by the water as it infiltrated down from the surface. Hardness of water is generally recognized because it increases the consumption of soap. Also, hard water causes the formation of scale in steam boilers or other vessels in which the water is heated. Water having a hardness of less than 60 ppm is considered soft; 60 to 120 ppm, moderately hard; 121 to 200 ppm, hard; and more than 200 ppm, very hard and unsatisfactory for most uses unless treated. Generally, the ground water in the Oakland Park area ranges in hardness from about 120 to 200 ppm and may be used with or without treatment, according to the use. Iron is one of the most noticeable constituents found in ground water in the Oakland Park area. In quantities of more than 0.5 to 1.0 ppm it will give the water a disagreeable taste, and in concentrations greater than 0.3 ppm will cause reddish-brown stain on clothing and fixtures. The iron content of the water differs from place to place and with depth, but it is not predictable. Iron may be removed easily by aeration and filtration from water that is to be used for large public supplies or industries, but it is more difficult to remove economically from water that is to be used for small domestic supplies. The analyses show iron in solution and do not include iron that may have precipitated between the time the sample was collected and the time of analysis. Color in water is caused almost entirely by organic matter extracted from peat, vegetation, and similar organic materials and is often accompanied by tastes and odors from the same sources. These characteristics may not be harmful to persons using the water, but their psychological effects on the consumer make them undesirable in drinking water. The analyses showing a color higher than 20 (the concentration at which color is considered to become objectionable) were of water from relatively shallow wells or wells near to streams. The pH indicates the degree of acidity or alkalinity of a water and is an important indication of its corrosive tendencies. A pH of 7.0 indicates neutrality, which means that the water is neither acid nor alkaline. Values below 7.0 denote increasing acidity; values above 7.0 indicate increasing alkalinity. The corrosiveness of water usually increases as the pH decreases. The pH of the samples ranged from 7.5 to 7.9, indicating that ground water in the area is moderately alkaline and should not be corrosive. As the amount of chloride in ground water is used to indicate the



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REPORT OF INVESTIGATIONS NO. 20 33 1.938, p. 892). The coefficient of storage is a measure of the capacity of an aquifer to'store water and is defined as the volume of water released from or taken into storage per unit surface area of the aquifer per unit change in the component of head normal to that surface. In this area, the best opportunity for making pumping tests to obtain these aquifer coefficients was through the use of municipal supply wells in the Prospect well field. Figure 20 shows the layout of the municipal supply wells and observation wells in this well field. Two tests were run in this field by observing the effects on water levels of changes in the rate of pumping. A 12-hour pumping test was made on August 8, 1956, using 10 city supply wells, each being pumped at the rate of 820 gpm. City supply wells 3, 4, and 5 were operated for eight hours prior to the start of the test, and then pumping was begun in the remaining seven wells in the field at the beginning of the test. Water-level recorders were operated on wells G-768 and G-820 beginning June 15, 1956, and August 6, 1956, respectively, and tape measurements of the changes in water level were made in well G-803 during the test. Well G-820 is a 4-inch well, drilled to a depth of 224 feet, and the casing was dynamited at a depth of 215 feet to open it to the aquifer. Well G-768 is a 6-inch well, 91 feet deep, cased to an approximate depth of 80 feet; and well G-803 is a 1,-inch sandpoint well 16 feet deep, cased to 14 feet below the land surface and screened from 14 to 16 feet below the land surface. A drawdown of 1.0 foot was recorded in well G-768, whereas no measurable drawdown occurred in well G-803 during the test. If drawdown affected the water level in well G-820 it was apparently overshadowed by the natural decline of the water table and fluctuations caused by changes in barometric pressure. Figure 21 shows the fluctuation of the water level in well G-768 before and during the test. On March 27, 1957, a 36-hour test was made using city wells 11, 12, and 14 (fig. 20) as observation wells. Supply wells 1, 2, and 3 were operated for 20 hours preceding this test and then pumping was started in wells 8, 9, and 10. Each of these wells is pumped at approximately 820 gpm. A water-level recorder was in operation on well G-820 during the 20-hour period before the test, and recorders were operated on city wells 11, 12, and 14 during the test. Drawdowns of approximately 0.2 foot and 0.4 foot were recorded in city wells 11 and 12, respectively, whereas city well 14 and well G-820 showed no appreciable drawdown. All the city supply wells are finished with well screens 20 feet long which extend to a depth of approximately 130 feet. The water pumped in both tests was discharged into the city mains so that no complication was caused by infiltration of the pumped water near the wells.


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STATE OF FLORIDA STATE BOARD OF CONSERVATION Ernest Mitts, Director FLORIDA GEOLOGICAL SURVEY Robert 0. Vernon, Director REPORT OF INVESTIGATIONS NO. 20 GROUND-WATER RESOURCES OF THE OAKLAND PARK AREA OF EASTERN BROWARD COUNTY, FLORIDA By C. B. Sherwood U. S. Geological Survey Prepared by the UNITED STATES GEOLOGICAL SURVEY in cooperation with the CITY OF FORT LAUDERDALE and the FLORIDA GEOLOGICAL SURVEY TALLAHASSEE, FLORIDA 1959

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CULTURAL LIBRARY FLORIDA STATE BOARD OF CONSERVATION LEROY COLLINS Governor R. A. GRAY RICHARD ERVIN Secretary of State Attorney General J. EDWIN LARSON RAY E. GREEN Treasurer Comptroller THOMAS D. BAILEY NATHAN MAYO Superintendent of Public Instruction Commissioner of Agriculture ERNEST MITTS Director of Conservation ii

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LETTER OF TRANSMITTAL @a 7TJYorlcl g eo/ofr(ic(I S urvecy TALLAHASSEE September 15, 1959 x Mr. Ernest Mitts, Director Florida State Board of Conservation 4 Tallahassee, Florida Dear Mr. Mitts: Florida Geological Survey Report of Investigations No. 20 is a S paper entitled, GROUND-WATER RESOURCES OF THE OAKLAND PARK AREA OF EASTERN BROWARD COUNTY, FLORIDA, which was prepared by Mr. C. B. Sherwood, Hydraulic Engineer 1 with the U. S. Geological Survey, in cooperation with the Florida Geological Survey and the City of Fort Lauderdale. The Oakland Park area obtains its water from the Biscayne aquifer, S composed of very permeable and porous, sandy limestones. The per3 meability of the aquifer increases with depth, and wells in the area <\ generally obtain water at depths ranging from 60 to 80 feet, or between S 100 and 200 feet, depending on the quantity of water desired. The data presented in this paper can be used for further development of water and wise management of resources in the area. Large quantities S of ground water are still available at Oakland Park, if salt-water encroachment can be controlled. The data in this study provide the necessary information to begin an effective water management program. Respectfully yours, Robert 0. Vernon, Director iii-

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Completed manuscript received April 9, 1959 Published by the Florida Geological Survey Rose Printing Company, Inc. Tallahassee, Florida September 1959 iv

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TABLE OF CONTENTS Page Letter of transmittal __ iii Abstract 1 Introduction 1 Purpose and scope 1 Previous investigations 2 Acknowledgments ______ -3 Geography 3 Location and general features of the area 3 Climate _--_-_--_ ------3 Topography and drainage 3 Geologic formations and their water-bearing characteristics 7 Ground water 12 Recharge and discharge 13 Water-level fluctuations 13 Salt-water encroachment 22 Quality of water 29 Quantitative studies 32 Ground-water use 38 Conclusions 38 References --40

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ILLUSTRATIONS Figure Page" I Map of Florida showing location of area investigated 4 2 NMap of parts of Broward and Palm Beach counties showing canals and levees of the Central and Southern Florida Flood Control District 5 3 Map of Oakland Park area showing locations of wells Between 5 & 6 4 Log of well G-563 8 53 Log of well G-820 9 6 Log of well S-998 10 7 Lo of well S-999 11 8 Monthly pumpage from the Prospect well field and monthly rainfall at Fort Lauderdale 14 9 NMap showing contours on the water table in the Biscayne aquifer, in eastern Broward County, on February 15, 1941 16 10 Hydrographs of wells G-127 and G-128 and weekly rainfall at Fort Lauderdale during 1940-41 -17 11 Mvlap showing contours on the water table in the Biscayne aquifer in the Oakland Park area, August 7, 1956 18 12 Map showing contours on the water table in the Biscayne aquifer in the Oakland Park area, September 21, 1956 19 13 Map showing contours on the water table in the Biscayne aquifer in the Oakland Park area, October 19, 1956 _________20 14 Hydrographs of wells G-768 and G-820, average daily pumpage from the Prospect well field, and daily rainfall at Fort Lauderdale, JuneDecember 1956 21 vi

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15 Hydrographs of Middle River Canal above and below dam, August 7-12, 1956 --_ __ _________ "22 16 Hydrographs of Middle River Canal above and below dam during 1956 __ ___-23 17 Hydrographs of Pompano Canal above Market and City dams, 1956 -24 18 Map of eastern Broward County showing maximum chloride content recorded in water samples from wells and streams, 1941-57 27 19 Chloride content of water from wells S-330 and S-830, at junction of South New River and Dania Cutoff Canals, 1941-57 28 20 Map of Prospect well field showing layout of municipal supply wells and observation wells 32 21 Hydrograph of well G-768, in the Prospect well field, during pumping test, August 7-8, 1956 _--_ 34 22 Idealized sketch showing flow in a leaky aquifer 35 23 Hydrograph of well G-768, in the Prospect well field, showing effect of pumping in the well field 37 Table Page 1 Average monthly temperature, in degrees, at Fort Lauderdale, and average monthly rainfall, in inches, at Fort Lauderdale and Pompano Beach --5 2 Chemical analyses of water from selected wells ---30 vii

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GROUND-WATER RESOURCES OF THE OAKLAND PARK AREA OF EASTERN BROWARD COUNTY, FLORIDA ABSTRACT The Biscayne aquifer is the source of all fresh ground water in the Oakland Park area of eastern Broward County, Florida. This aquifer extends from the land surface to more than 215 feet below mean sea level and is composed chiefly of sandy marine limestone, calcareous sandstone, and beds of fine to medium quartz sand. The aquifer differs from place to place, but, in general, most of the layers of limestone and sandstone occur at depths below 60 feet. The permeability of the aquifer increases with depth. Wells for small supplies generally obtain water at depths ranging from 60 to 80 feet, whereas wells for large supplies usually obtain water from the interval between 100 and 200 feet. Large-diameter wells obtain as much as 1,000 gpm (gallons per minute) from the lower part of the aquifer. Chemical analyses of ground-water samples indicate a hard limestone water that is suitable, naturally or with treatment, for most ordinary uses. Periodic determinations of chloride content of the ground water show that some salt-water encroachment has occurred in areas near the coast and in the Middle River basin. Pumping-test data for deep wells in the Prospect well field area indicate approximate aquifer coefficients of transmissibility and storage of 2,000,000 gpd per foot and 0.015, respectively. However, the data indicate also that the hydraulic characteristics of the aquifer are complicated by the presence of beds of sand, silt, and clay in the upper 100 feet of the aquifer and by recharge from surface-water sources. Quantitative data and areawide water-level and salinity data indicate that large quantities of ground water are available for future development if salt-water encroachment can be effectively controlled. INTRODUCTION PURPOSE AND SCOPE The rapid growth of population and industries in eastern Broward County has introduced the problem of preserving existing ground-water supplies and has caused a growing need for additional supplies. As in many coastal areas, this problem involves not only finding and developing a satisfactory source of water but also protecting this source

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SFLORIDA GEOLOGICAL SURVEY against salt-water encroachment from the sea. Recognizing the need for data in solving their problems, officials of the city of Fort Lauderdale requested that an investigation be made of the ground-water resources of eastern Broward County, in the vicinity of Oakland Park. The investigation was made by the U. S. Geological Survey in cooperation with the Florida Geological Survey and the city of Fort Lauderdale. The purpose of the investigation was to determine, insofar as possible, the following things: 1. The ground-water potential of the area. 2. The extent of salt-water encroachment into the Biscayne aquifer. .3. The hydraulic coefficients of the aquifer and the safe rate of withdrawal for the development of large supplies. 4. The effect of water-control works of the Central and Southern Florida Flood Control District on the ground-water resources of the area. Field studies, begun in December 1955, consisted of the following: 1. A partial inventory of wells in the area. 2. The installation of shallow wells to be used for water-level studies and one deep test well to be used for geologic and salinity studies. 3. Pumping tests to obtain data on the water-transmitting and storing properties of the aquifer. 4. A leveling program to determine the altitudes of measuring points for water-level measurements. I5. The determination of the chloride content of water from selected wells and sampling points in streams, and comprehensive analyses of water from selected wells. 6. The installation of two automatic water-stage recorders and the areawide measurements of water level at selected times. The investigation was made under the general supervision of A. N. SaYre, Chief, Ground Water Branch, and under the immediate supervision of Howard Klein, Geologist, and M. I. Rorabaugh, District Engineer, all of the U. S. Geological Survey. PREVIOUS INVESTIGATIONS No detailed investigation of the ground-water resources of the Oakland Park area had been made prior to this investigation. Considerable information pertinent to the area is available, however, in publications or unpublished open-file reports of the Florida Geological Survey and the U. S. Geological Survey. Data from these reports have been used freely in the preparation of this report. Frequent references to the geology of the area and the occurrence and quality of the ground water in eastern

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REPORT OF INVESTIGATIONS No. 20 3 Broward County are contained in reports by Vorhis (1948), Parker and others (1955), and Schroeder and others (1958). ACKNOWLEDGMENTS Grateful acknowledgment is hereby made for the cooperation and assistance given by officials of the city of Fort Lauderdale and the engineering firm of Philpott, Ross and Saarinen. The wholehearted cooperation of the personnel of the Fort Lauderdale water-treatment plants while field work was in progress, was especially helpful. Data pertaining to flood-control works in the area were supplied by officials of the Central and Southern Florida Flood Control District. GEOGRAPHY LOCATION AND GENERAL FEATURES OF THE AREA The Oakland Park area is on the lower east coast of Florida between the cities of Pompano Beach and Fort Lauderdale (fig. 1). It is bounded on the north by the Pompano Canal, on the east by the Intracoastal Waterway, on the south by the south fork of the Middle River, and on the west by Conservation Area No. 2. The city of Oakland Park is north of the north fork of the Middle River, about two miles west of the Intracoastal Waterway (fig. 2). The Prospect well field, which is one source of water supply for Fort Lauderdale, lies between the upper reaches of Cypress Creek and the Middle River, about two miles northwest of Oakland Park (fig. 3). CLIMATE The climate of Fort Lauderdale is subtropical and the humidity is usually high. The average monthly temperatures, as shown by U. S. Weather Bureau records, range from 68.83F. to 82.60F. As of the end of 1956, the mean annual temperature was 74.20F. and the mean yearly rainfall was 59.88 inches, for 48 years of record. The heaviest rains occur during the period from June through October. Table 1 shows monthly and yearly averages of temperature and rainfall at the Fort Lauderdale station for the period 1940-56, and average rainfall at the Pompano Beach station, about seven miles north of Fort Lauderdale, for the period 1941-56. TOPOGRAPHY AND DRAINAGE The Oakland Park area is on the coastal ridge that separates. the Atlantic Ocean from the Everglades. The ridge in this area is about six

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4 FLORIDA GEOLOGICAL SURVEY G E 0 R G I A i S-.NASSAU --BAKER AK N D -UVAL$ LU lY TAYLOR 0 CITRUS e LAKE BROWARD OAKLAND ./ -1IGHLAND .LUCI 0 miles I o a MonY PeaM nsa MONROE1 DADE DADE Key West el l Figure 1. Map of the peninsula of Florida showing location of area investigated.

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REPORT OF INVESTIGATIONS NO. 2 5 R3?E R"8 39E R419 R41E R 11 0NSERVATIbN T6s AREA Nb. I ---....i BROWARD COUNTY i I I ---AKLAND SC i IN MILES t----~-T I-t------.-..... .BAC 5 i 10 --PARKAND S AREA MIDDL RPARK FORT mOU -I r CA.A EXPLANATION SALEF IN MILES Figure 2. Map of parts of Broward and Palm Beach counties showing canals and levees of the Central and Southern Florida Flood Control District. TABLE 1. Average Monthly Temperature, in Degrees, at Fort Lauderdale, and Average Monthly Rainfall, in Inches, at Fort Lauderdale and Pompano Beach Temperature Rainfall Month Fort Lauderdale Fort Lauderdale1 Pompano Beach' Jan. 68.3 2.18 2.22 Feb. 68.3 1.96 1.51 Mar. 70.9 2.81 2.17 Apr. 74.2 4.06 3.86 May 77.4 4.93 3.60 June 80.3 7.55 6.01 July 81.7 6.03 7.39 Aug. 82.6 6.74 6.68 Sept. 81.5 8.82 9.32 Oct. 77.8 8.83 9.58 Nov. 72.3 3.05 3.09 Dec. 69.2 2.37 2.08 Yearly average 74.2 59.83 57.51 'Discontinuous record 1940-56, U. S. Weather Bureau. 'Discontinuous record 1941-56, U. S. Weather Bureau.

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6 FLORIDA GEOLOGICAL SURVEY miles wide and is very low and nearly flat, except where it is cut by the main streams -Cypress Creek near Pompano Beach and the Middle River south of Oakland Park (fig. 3). The land surface ranges in altitude from about four feet above mean sea level in areas adjacent to stream channels to about 15 feet above mean sea level in the vicinity of the Prospect Air Field and in the area which parallels U. S. Highway 1, west of the Intracoastal Waterway. Most of the area, however, is about nine feet above mean sea level. The area is drained chiefly by underground flow toward the ocean and into the canals and streams that flow generally eastward to the Intracoastal Waterway. The permeable quartz sand and oolitic limestone that form the shallow subsurface materials allow rainwater to infiltrate rapidly to the water table, and there is very little surface runoff to the canals and streams. The underground flow pattern is considerably influenced by continuous pumping in Fort Lauderdale's Prospect well field and by water-control structures in canals. The Pompano Canal and Cypress Creek traverse the northern part of the area from west to east, through the ridge, to the Intracoastal Waterway. Cypress Creek drains the slough area north of Prospect field, and the Pompano Canal drains the area west of Pompano Beach and is a part of the overall flood-control system in southern Florida. The tributaries of the Middle River traverse the southern part of the area and drain the low areas south of Prospect field. Local farm drainage is effected by intricate systems of shallow ditches which connect to major drainage channels. The drainage and flood-control works are part of a cooperative state and federal program designed to alleviate the effects of both flood and drought conditions in central and southern Florida. The Oakland Park area lies east of one of a series of water conservaton areas (Conservation Area No. 2) that are bounded by a levee system extending from Lake Okeechobee to southern Dade County (fig. 2). The Pompano Canal and the Middle River Canal connect with a canal on the east side of Conservation Area No. 2. The Pompano Canal is controlled by dams near its confluence with Cypress Creek, and the Middle River Canal is controlled by a dam about 5% miles inland from the Intracoastal Waterway. The tidal reach of Cypress Creek extends inland about two miles, and the various branches of the Middle River are tidal as far upstream as the flood-control dam. In the tidal reaches of these streams salt water is free to advance upstream as far as tides and fresh-water flow permit.

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S",'51369 I OMPANO BEACHs 13 7 -eaR -1-9 0R0|T 6A // I S PROSPECT LMT G j43 e044 0 P 157 0 616F, 0 I9 .. 9156 S80C 0LO S06308 WATER LV*ER PROSPECT08_ 0 'C15810 D13A I 0.o s 1 42 e3. Mp O akan Pk ae shn s o .0 2 0075a C 19Y M A 13 0 010 0815 1 /014 i \ sol I321 k / s is Il EXPLANATION 0s 1320 0 Al ~WELL i 149' PUBLIC-SUPPLY WELL ,i, WATER-LEVEL RECORDING GAGE 1--3v-10 I T -lY LIMITS -CHLORIDE-CONTENT DATA AVAILABLE SURFACE-WATER OBSERVATION POINT CHEMICAL ANALYSIS AVAILABLE FORT LAUDER LE 0 .SCALP IN FE ETr Figure 8. Map of Oakland Park area showing locations of wells.

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REPORT OF INVESTIGATIONS No. 20 7 GEOLOGIC FORMATIONS AND THEIR WATER-BEARING CHARACTERISTICS The name Biscayne aquifer was used by Parker (1951, p. 820-823) for the "hydrologic unit of water-bearing rocks that carries unconfined ground water in southeastern Florida." This aquifer is the only source of fresh ground water in Dade and Broward counties. Limestone strata at depths of 900 to 1,000 feet yield large quantities of water under artesian pressure, but the water is highly mineralized and unsuitable for general use. The artesian aquifer is not discussed in this report. In the Oakland Park area the Biscayne aquifer includes marine deposits ranging in age (oldest to youngest) from late Miocene through Pleistocene, in the following sequence (Schroeder, 1958): Tamiami formation (upper part), Anastasia formation, Miami oolite, and Pamlico sand. In Dade County and southern Broward County the aquifer is underlain by a relatively impermeable greenish marl at or near the top of the Tamiami formation, but in northeastern Broward County the aquifer thickens and its base is considerably below the top of the Tamiami formation. Some of the geologic information included in this report was obtained from shallow observation wells in the Oakland Park area and some was obtained from four deep wells, namely, test well G-563 in the northern part of Fort Lauderdale, test well G-820 in the Prospect well field, and supply wells S-998 and S-999 in the Pompano Beach well field. Logs of these wells are shown in figures 4 through 7. The log of well G-820 in the Prospect well field shows highly permeable limestone at a depth of 224 feet below the land surface, and local drillers report that similar limestones occur at greater depths. In each of the deep wells the marine deposits of the Tamiami formation of late Miocene age are overlain by very similar deposits of the Anastasia formation of the Pleistocene age. Well cuttings from both formations show that they are composed chiefly of alternating beds or lenses of sandy limestone or calcareous sandstone, sand, shells, and sandy clay or marl. Because of the lack of distinctive fossils in the samples and the absence of good stratigraphic correlation, no line of demarcation was drawn between the Tamiami and Anastasia formations. In general, the part of the aquifer underlying the Oakland Park area contains more unconsolidated sandy and clayey material than the part underlying areas south of Broward County; thus, the overall permeability of the aquifer in this area is lower than the permeability of the aquifer underlying areas to the south. Wells developed in the limestones and sands of the Tamiami and Anastasia formations supply all the public water systems in eastern Broward

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8 FLOMDA GEOLOGICAL SURVEY WELL G563 4TH AVE.8 IOTH ST., N.W. FQRT LAUDERDALE, FLA. WELL LOG 0 -10 Sand, quartz, brown. 10 -14 Sand, quarts, with tan clay included in a shelly, oolitic solution-riddled limestone. 14 --34 Sand, quartz, white; some fine grains of epidote. 34 -40 Sand, quartz, gray-white; many small tan 4 pelecypod shells. 40 -45 Limestone, hard at top, soft and shelly at base. 45 -68 Sandstone, calcareoun, light-gray, scattered collophane and some ilmenite, loosely to 60tightly cemented with some blue-green clay below 60 feet. 68 -84 Sand, quartz, very fine grained, peppered with collophane and ilmenite; some sand*0stone nodules. 84 -90 Marl, sandy, clayey, pale-blue-green; ..permeability low. 90 -107 Sandstone, quartz sand, and shell fragments. 100 Sand is very fine grained and is peppered k with collophane and ilmenito. ." t107 -112 Sandstone, calcareous, white; quartz sand, Svery fine to coarse. 120 112 -151 Sand, quartz, shelly, fine to coarse, white, Speppered with collophane and ilmonito; a few thin layers of sandstone. %L 140151 -153 Limestone, sandy, very dense, white. 153 -155 Sandstone and sand, calcareous, fossilif60 .erous. 155 -175 Sand, calcareous, gray-brown to gray; some nodules or thin sandstone layers. w 175 -177 Limestone, sandy, white. 180 177 -179 Sandstone, calareous. zoo Figure 4. Log of well G-563.

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REPORT OF INVESTIGATIONS No. 20 9 WELL G 820 PROSPECT WELL FIELD WELL LOG 0 -8 Sand, quartz, white, medium. 8 -11 "Hlardpan", sand, quartz, medium; brown organic material. ~20 11 -43 Sand, quartz, tan. 40 43 -54 Sand, quartz, tan, fine to medium. 60 54 -76 Sand, quartz, white, very fine to medium; interbodded blue-green clay. U 80 76 -87 Sand, very fine to medium; contains some bluegreen clay and thin layers or nodules of soft 87 .99 Sand, quartz, gray, medium to coarse, peppered with ilmanite and phospnate. -100 99 -110 Sand, tan, medium to very coarse; a few Sthin layers of gray limestone. S11 -131 Same as above but less limestone. 120 131 -137 Limestone. sandy, gray; contains a large percentage of medium to coarse sand. t 140 137 -142 Same as above but sand very fine to medium. W 142 -158 Limestone, sandy, can and gray; contains a large percentage of very fine to medium sand. 160 158 -159 Limestone, gray, very hard. k .: 159 -171 Limestone, sandy, gray; contains a large percentage of very fine to medium sand. .171 -175 Limestone, gray, very hard. 180 175 -189 Limestone, sandy, white. 189 -205 Limestone, sandy, gray. 200205 -224 Limestone, sandy, white. 220 240 Figure 5. Log of well G-820.

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10 FLORIDA GEOLOGICAL SURVEY WELL S998 POMPANO BEACH WELL FIELD WELL LOG 0 -10 Sand, quarta, buff, coarse, calcareous. 10 -12 Sand, quarts, white to buff, fine to medium, calcareous; a few rounded shell fragments, 12 -25 Limestone, shelly, very sandy, gray, porous 20 and hard. 23 -30 Sand, quarts, poorly sorted, some shell fragments. 30 -40 Same as above, but fewer shell fragments, 40 49 -67 Sand, quarts, poorly sorted, light gray, S:very few shell fragments. 'o S60 o 67 -76 Coquina, very sandy, porous, grayish-buff. S 76 -80 Sand, quarts, medium to coarse, buff to gray, a 80 calcareous. .4 80 -89 Limestone, very sandy, silty and phosphatic, 4 hard, greenish-gray. 89 -103 Sandstone, very calcareous, gray, hard, fair 100 -porosity; shell fragments and a few Sphosphate grains. r 103 -Sand, quarts, medium to fine, white; very fine-grained phosphate. 120 Figure 6. Log of well S-998. County. Higher yields can be obtained from wells in the limestone parts of the aquifer than can be obtained from wells in the sandy parts. Individual 10-inch wells in the Prospect well field yield 820 gpm with approximately six feet of drawdown. These wells are screened in soft sandy limestone or calcareous sandstone, and the bottoms of the screens are set at depths ranging from 114 to 140 feet. The screens are 10 inches in diameter and average 20 feet in length. Wells for small individual supplies generally tap thin, local sandstones at depths ranging from 60 to 80 feet. The Miami oolite of Pleistocene age, which occurs in the upper part of several test wells, is the surface rock that blankets much of southeastern Florida. In the Oakland Park area it is generally a white to yellowish thinly laminated, crossbedded oolitic limestone containing large amounts of sand and shells. The oolite is mined in shallow excavations south and west of the Prospect well field, but it is either very thin or missing in much of the Oakland Park area. The Miami oolite is very permeable, and it is tapped by domestic supply wells wherever it is thick enough to supply appreciable amounts of water.

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REPORT OF INVESTIGATIONS No. 20 WELL S 999 POMPANO BEACH WELL FIELD .-WELLLOG 200 -69 No samples'. 40 60' 09 -97 Sand, quartz, fine to medium, marly; specks 80 of cellophane and a few fragments of t 0 s. calcareous sandstone. S 97 -108 Sand, quartz, white, coarser than above, ;,h calcareous; some collophane. S3 108 -118 Sand, similar to above, marly, phosphatic. I I 118 128 Sand, quartz, white to tan, fine to medium, Stamarly, angular to subrounded, phosphatic. (. 128 -134 Sand, quartz, white, subrounded to wellQ rounded; fragments of calcareous sandstone, S"' reourked shells and phosphate. j 140 -134 -140 Sand, quartz, white, very fine to fine, silty, phosphatic. S 140 -145 Sand, quartz, white to gray, fine, clean; rounded shell fragments and collophane. 14 -150 Sand, quartz, similar to above; a few 160 fragments of calcareous sandstone. 150 -155 Sand, qudrtz, white to gray, fine to coarse; many rounded shell fragments and much -15 reworked material, 1o0 -155 -165 Sand, quartz, white to tan, very fine to medium, marly, phosphatic. S 165 -170 Sand, quartz, white to gray, fine, clean; collophane, -170 -180 Sand, quartz, gray, phosphatic, fine; sand200 -.stone, calcareous, hard; a few shell fragments. 180 -195 Sand, quartz, gray to tan, very fine to medium, very silty, marly, phosphatic. 195 .203 Sandstone, calcareous, permeable, hard. 220 Figure 7. Log of well S-999.

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12 FLORIDA GEOLOGICAL SURVEY The Pamlico sand, which was found near the surface in the test and observation wells, is a late Pleistocene marine terrace deposit (Parker and Cooke, 1944, p. 75). In the Oakland Park area it overlies and fills erosion channels and solution cavities in the Miami oolite and the Anastasia formation. The Pamlico sand is composed chiefly of fine to coarse quartz sand ranging in color from white to rust or gray-black, according to the amount of admixed iron oxide or carbonaceous material. Properly developed sandpoint wells in the Pamlico sand generally yield enough fresh water for domestic purposes, but the water often has an objectionable color or odor caused by organic matter. GROUND WATER Ground water is the subsurface water in the zone of saturation, the zone in which all the interstices of the soil or rocks are completely filled with water under greater than atmospheric pressure. Ground water may occur under either artesian or nonartesian conditions. Where its upper surface is free to rise or fall in a permeable stratum it is said to be under nonartesian conditions, and the surface is called the water table. Where the water is confined in a permeable bed that is overlain by a less perrmeable bed, its surface is not free to rise and fall. Water thus confined under pressure is said to be under artesian conditions. The height to which water will rise in tightly cased wells that penetrate an artesian aquifer defines the pressure, or piezometric, surface of the aquifer. In the Oakland Park area the only potable ground water is the rainfall that infiltrates downward into the materials of the Biscayne aquifer. This water is said to be under nonartesian conditions, as its upper surface, the water table, is unconfined and under normal atmospheric pressure. It is recognized, however, that artesian conditions exist to some extent in parts of the aquifer. (See section on quantitative studies.) The water table fluctuates in response to recharge or discharge, and ground water flows -under gravitational forces -from points of recharge, where water levels are high, to points of discharge, where water levels are low. The direction of flow coincides with the maximum slope of the water table. The water table may be mapped by determining the altitude of the water level in a network of wells. Systemic areawide observations of the shape, slope, and fluctuations of the water table are an important part of ground-water investigations, as they show the direction of ground-water movement and changes in the amount of ground-water storage.

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REPORT OF INVESTIGATIONS NO. 20 13 RECHARGE AND DISCHARGE Rainfall is the source of all fresh-water recharge to the Biscayne aquifer. Not all of the rainfall infiltrates to the water table, however, as a large part is lost by evapotranspiration and a small part is lost by direct runoff into streams or the ocean. Parker (Parker and others, 1955, p. 221) estimates that about two-thirds of the annual rainfall reaches the water table in areas underlain by oolite and about half the annual rainfall reaches the water table in areas underlain by sand. In the Oakland Park area, some surface water is introduced into the aquifer when water levels in the Middle River and Pompano canals are higher than the water table. This occurs chiefly in upstream areas, above the closed water-control structures. Discharge from the aquifer takes place by evapotranspiration, by ground-water outflow into streams, canals, and the ocean, and by pumping. Discharge by ground-water outflow and evapotranspiration are greatest when the water table is highest, during and after periods of heavy rainfall, whereas discharge by pumping is greatest in the drier periods, which correspond with the peak tourist season. In general, the discharge by the two natural processes greatly exceeds the quantity of water withdrawn by pumping from wells. However, the operation of the Prospect well field makes pumping a significant factor. Figure 8 shows the monthly pumpage from the Prospect well field and. the monthly rainfall at Fort Lauderdale during 1955 and 1956. When water is pumped from a well in a nonartesian aquifer, the dewatering of the materials adjacent to the well causes the water table to slope downward toward the well, thus forming a cone of depression. The slope or hydraulic gradient of this cone causes ground water to flow from the surrounding area to the well. As pumping continues, the cone of depression increases in depth and areal extent until it reaches an area where ground-water discharge is salvaged and/or recharge is increased in an amount equal to the withdrawal. Studies in other areas indicate that pumping in a well field near a stream can cause large quantities of water to be drawn from the stream into the aquifer. WATER-LEVEL FLUCTUATIONS Water levels in the Biscayne aquifer fluctuate considerably in response to recharge and discharge, and, to a lesser extent, they are affected by other factors such as tides (in areas adjacent to the coast and tidal canals), earthquakes, and changes in atmospheric pressure. The greatest short-term fluctuations are caused by recharge by rainfall and discharge by pumping, but gradual changes in water levels caused by evapotranspiration and normal ground-water outflow have an equally important

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1955 1956 MiAM i A ai 300 Io*n---------------H Ic .. eif 3 I "I Figure 8. d and monthly rainfall at Fort derdae.

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REPORT OF INVESTIGATIONS No. 20 15 effect on the amount of water in storage in the aquifer. Parker and Stringfield (1950, p. 441-460) discussed the effects of earthquakes, winds, tides, and atmospheric-pressure changes on ground-water levels in southern Florida. Water-level fluctuations in the Oakland Park area are greatly influenced by pumping in the Prospect well field and by the flood-control works of the Central and Southern Florida Flood Control District. Figure 9 is a contour map of eastern Broward County, showing the approximate altitude and configuration of the water table in the Biscayne aquifer on February 15, 1941. This map was made by using some of the earliest water-level data available for the area, and it represents the water table at a time when there was no drawdown due to pumping in the Prospect well field area or to extensive water-control works. The Pompano Canal (Cypress Creek Canal) was the only major drainage canal in the immediate area. Bogart and Ferguson (Parker and others, 1955, p. 505) indicated that the canal was controlled in two pools by small dams, in much the same manner as it is at present. Parker (Parker and others, 1955, fig. 148) shows that the water level above the controls in Pompano Canal ranged from about 1.0 foot to 5.4 feet above mean sea level during the period 1940-43. The contours in figure 9 were drawn from water-stage readings in streams and canals and from water-level measurements in widely scattered wells. In the Oakland Park area, the contours show; generally, the altitude and configuration of the water table under relatively natural conditions and indicate a fairly uniform gradient toward the coast. The graphs in figure 10 show a correlation between periodic waterlevel measurements made in wells G-127 and G-128 (see fig. 9 for locations) and weekly rainfall at Fort Lauderdale during 1940-41. Well G-127 was on the present site of the Prospect well field, and well G-128 was on U. S. Highway 1, 2.7 miles east of well G-127. The hydrographs indicate also the differential in head between wells G-127 and G-128 during the latter part of 1940 and all of 1941. Ground-water levels in Broward County during 1955 and 1956 were generally below the average for the period of record, owing to a deficiency in rainfall. This condition tends to accent the effects of drainage canals, dams, and pumping on the water table. During 1956 an areawide program of water-level observations was established and contour maps of the water table in the Biscayne aquifer were prepared. Figures 11 through 18 show contours on the water table on August 7, September 21, and October 19, during periods of low, intermediate, and high water levels, respectively. The most striking feature of

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16 FLORIDA GEOLOGICAL SURVEY PALM BEACH COUNTY R4OE R41E R4tE R42E HILLSBOROUGH CANAL EXPLANATION DEERFIELD 0 WELL SURFACE WATER OBSERVATION POINT WATER LEVEL,IN FEET, REFERRED TO MEAN SEA LEVEL 0 1 2 3 4 5 6 miles _'b---:----,m== POMPANO CANAL MPAN i 5,-9 H I 8 oG 12o 7 G 12 4.0 F3 \ ---(-/ 30 eastern Bw Co on February 15, 141 -30 IE ld cut of Lock I "Dania Davie Rd. DANIA SHollywood BlvdHOL WOOD DADE COUNTY 0 F&4ME R41 E Figure 9. Map showing contours on the water table in the Biscayne aquifer, in eastern Broward County, on February 15, 1941.

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RPORT OF INVESTIGATIONS No. 20 17 1940 1941 -i i 14 o -e --RA i ....WE.. ._A_ Oln .. ...... ..... ..... W {L 0 12 1" PROSPECT FIELD b WELL 0 12\ -Ii 3 MILES eAsY Of P SCP'FECf FILD -\I 0, ---O --" -[ .... ... ..... ..... ..... ...... ... ..... ...-----to Figure 10. Hydrographs of wells G-127 and G-128 and weekly rainfall at Fort Lauderdale during 1940-41. each contour map is the deep cone of depression caused by pumping in the Prospect well field. Significant features are the high ground-water levels and steep gradient maintained as a result of recharge by surface water in areas upstream from control structures in the Middle River and Pompano canals. The extremely low water levels and fiat gradient in areas southeast of the cone of depression are caused by the large losses

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18 FLORIDA GEOLOGICAL SURVEY :/ G pEACHS." ."" ...i .A i i /.,, -C't!(.i '.' i / < ,_i ,,J Figure 11. Map showing contours on the water table in the Biscayne aquifer in the Oakland Park area, August 7, 1956. of ground water through drainage into the uncontrolled reaches of streams and canals and by discharge from the Prospect well field. Figure 11 shows the configuration of the water table at a time when water levels were near record lows and pumping from the well field was near maximum. The direction of ground-water flow is perpendicular to contour lines and in general it is toward the coast. The steep water-level gradient north and west of the well field indicates that most of the water pumped from the well field comes from that direction. Figure 14 shows the fluctuation of water levels in wells G-768 and G-820 in the Prospect well field, monthly pumpage from the well field, and daily rainfall at Fort Lauderdale during June-December, 1956. The hydrographs show the difference between the water levels in well G-768, near the center of the cone of depression, and well G-820, near the outer edge of the cone. A comparison of the altitude of the water level of wel G-768, in 1956, with that of well G-127 (same approximate loca-

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REPORT OF INVESTIGATIONS No. 20 19 ,lA I.ill .w .......' I i f .. .. Figure 12. Map showing contours on the water table in the Biscayne aquifer in the Oakland Park area, September 21, 1956. tion) in 1940-41 (fig. 10), shows the marked effect of heavy pumping -j 6944"-7;T-,in the area. During extended dry periods, when there is little recharge, the rate of the natural decline in water levels decreases as the water-level gradient toward the coast diminishes. However, water levels in the well field area drop at an increased rate until the cone of depression reaches a new source of recharge or enogh natural discharge is salvaged to balance Fthe 12. Mscharge due to pumpp showing. The contours on the water tablefigure 11 in the Biscayne aquife inthat the Oakland Park area, September 21, 1956. tion) in 1940-41 (fig. 10), shows the marked effect of heavy pumping the ater table in the area between the well field and uncontrolled During extended dry periods, when there is little recharge, the rate reaches of the natural ddle River Canal was approaching the mean water level gradient towardin the canal in August 195diminishes. If thever, water levels in the area declined to area drop at an increased rate until the cone of depression reaches a new source of recharge or enough natural discharge is salvaged to balance the discharge due to pumping. The contours in figure 11 indicate that the water table in the area between the well field and uncontrolled reaches of the Middle River Canal was approaching the mean water level in the canal in August 1956. If the water table in the area declined to an altitude below that of the water level of the canal, some salty water would enter the aquifer from the canal. The flow of water from the canal into the aquifer would be impeded, however, by silt in the canal bed and by the relatively low permeability of the materials cut by the canal. It

PAGE 28

"20 FLOMtDA GEOLOGICAL SutWVEY Figure 18. Map showing contours on the water table in the Btsenyne aquifer in the Oakland Park area, Otobr 1, 195. is possible that during a prolonged drought the cone of depression may extend outward and cause a relatively steep gradient from the salty canal to the aquifer, thus resulting in accelerated salt-water intrusion south of the well field. Water-level recording gages are maintained above and below the cam on the Middle River Canal. Weekly readings are recorded from staff gages above and below the dams on the Pornipano Canal (fig. 8). Figure 15 shows a typical water-level record obtained from gages above and below the Middle River dam on August 7-12, 1956, and figure 16 shows daily mean water levels above the dam and mean daily high and low tide levels below the dam during 1956. The 1956 average water levels aboxve and below the dam were 4.40 and 0.60 feet above mean sea level, respectively, and the average tidal fluctuation below the dam was about 2.20 feet. Weekly water-level stages above the dam in the Pompano Canal, from April 6 to December 81, 1956, are shown in figure 17. The daily mean waer levels abve (lie dam nd mendiyigadlo tie evl blo teda drng196.Te 95 veag wtr evl abov andbelw th da wer 4.4 an 0.6 fet abve man ea lvel respecivelyand th averae tida fluctation elwtheda asabu 2.20feet Wekly aterlevl stges aboeteda nte opn Canal frmArl6t eebr3.156 r hw nfgr 7 h

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1f.ot.T o.P 1NV•rT1GAti6N8 NO, 20 2 1981 50llll IWELL 8 010 h -----........ -. -._._.. __ PR4M oI .0____ Figure 14. Hydrographs of wells 0-768 and 0-820, average daily pumpage from the Prospect well field, and daily rainfall at Fort Lauderdale, JuneDecember, 1956.

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2 FLORIDA GEOLOGICAL SURVEY AUtKT I n *1.5 -a---i------------I----U ----------------e---e----------'L ----1 Figure 15. Hydrographs of Middle River Canal above and below dam, August 7-12, 1956. average water levels above the east (City) and west (Market) dams during this period were 3.89 and 7.16 feet above mean sea level, respectively. No record of the tidal fluctuations in the lower reach of the canal is available, but the fluctuations are assumed to be similar to those ;n the Middle River Canal. No data are available to show the beneficial effects of the floodcontrol works in this area during flood periods. This is unfortunate because the system was designed for both high-water and low-water conditions and its effectiveness is not fully demonstrated unless both conditions are presented. SALT-WATER ENCROACHMENT Salt-water encroachment is the chief factor limiting the use of ground water from the Biscayne aquifer. The salt water in this aquifer may come from two general sources, as follows: (1) direct movement inland from the ocean and from tidal canals and streams, and (2) sea water which

PAGE 31

1956 At FE. MAR. APR.n MNA PULY. ,EP .1 JECA. B .0 II BELOWB DAMD F 6.0 0 d BELOW DAM 0MEAN DAILY LOW. Figure 16. ydrogphs of Middle River Caal above d below dam durg 196. F-od

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90g AS WE AR T DAMA ...' sW AV l U -A, CI DA _0 -------------------_>I ^ f P*M>. £-_ ---, -____ --^ ___ -J w u /, \ / 0 0 Fiure 17. Hydrorahs of Pomano Canal above arket and City ams 195.. w 4 ^--I Figure 17. Hydrographs of Pompano Canal above Market and City damrns, 1956.

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IEuPOnT OF INVESTIGATIONS No. 20 25 entered the aquifer when the sea covered parts of southern Florida during various interglacial stages of the Pleistocene and is still present in parts of it. -Parker (Parker and others, 1955, p, 819-821) discussed the effects of residual sea water in the Everglades area and indicated that this source of salt water caused little or no contamination of ground water in the Oakland Park area; however, ground water in the Everglades area west of Oakland Park has chloride concentrations greater than 30 ppm, the concentrations increasing in a westerly direction and with depth. Salt-water encroachment from the ocean into the Biscayne aquifer is governed by the relationship of ground-water levels to mean sea level. In coastal areas the depth to salt water is related to the height of the fresh water above sea level. Under static conditions this relationship is that of a U-tube whose limbs contain liquids of different density, and it is expressed by the Ghyben-Herzberg principle (Brown, 1925, p. 16-17), as follows: t g -1 where h is the depth of fresh water below sea level, in feet; t is the height of the fresh-water surface above sea level, in feet; and g is the specific gravity of sea water. If a specific gravity of 1.025 is assumed for sea water, then each foot of fresh water above sea level should indicate 40 feet of fresh water below sea level. In the field, this relationship is modified by mixing of fresh and salt water by dynamic hydraulic conditions, and by geologic conditions, but the relationship holds sufficiently well to be considered valid for most purposes. Salt-water encroachment in Broward County has occurred chiefly in areas adjacent to major streams and uncontrolled parts of drainage canals that empty into the ocean. These waterways enhance the possibility of salt-water encroachment in two ways, as follows: (1) they lower ground-water levels, thereby reducing the fresh-water head that normally would oppose the inland movement of salt water, and (2) they provide a path for sea water to move inland during dry periods. The extent of the encroachment at depth in the aquifer, in the Middle River and Cypress Creek basins, has not been determined because of the lack of deep wells in these areas. In order to determine accurately the extent of encroachment, several deep test wells would be required in the general area betwen U. S. Highway 1 and the Florida East Coast Railroad and in the area adjacent to the downstream parts of the Middle River. These wells would serve as outpost wells from which water

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26 FLORIDA GEOLOGICAL SURVEY samples could be taken for periodic determinations of the chloride content of the ground water. Considerable data are available in a similar area adjacent to the North New River in Fort Lauderdale. These data may illustrate some of the characteristics of salt-water encroachment in the area. Figure 18 shows the maximum chloride content recorded in surface-water and ground-water samples in eastern Broward County north of Dania. The ground-water samples were pumped from wells which are cased to within a few feet of their total depth; therefore, the depth of the sampling point is assumed to be approximately equal to the depth of the well. The data shown in the Oakland Park area represent samples taken during 1956-57 and those shown on the southern part of the map represent samples taken during the past 15 years (expanded from fig. 187 in Parker and others. 1955). Along the north and south forks of the New River, salt water has migrated inland, at depth in the aquifer, as much as 38 miles from the coast. The extent of salt-water encroachment at depth near the river is indicated by salinity data from well G-514 (fig. 18). The chloride content in samples taken at a depth of 177 feet in this well has ranged from 2,700 ppm to 4,900 ppm during the past 10 years. It can be seen, therefore, that salt water has encroached at depth, in this area, beyond the junction of the forks of the Middle River. Figure 19 shows the variation of chloride content in wells S-330 and S-880 caused by salt-water encroachment from the south fork of the New River during the period 1941-57 (adapted from Vorhis, 1948). These wells were sampled at depths of 35 feet and 118 feet, respectively, and are near the river, about 53 miles inland from the coast. The data indicate that large and rapid changes in the chloride content of ground water are caused by salt-water encroachment from the New River. In the Oakland Park area appreciable contamination by salt water was found in samples from wells S-1379 and S-1380, near the dam on the Middle River Canal, and in well S-1381, near the Fiveash water plant. Analyses of samples from wells S-1379 and S-1380 show chloride contents of 600 ppm and 820 ppm, respectively, and indicate contamination from the Middle River Canal during the prolonged dry period of 1955-56. A water sample collected at a depth of 240 feet in well S-1881 contained *2,640 ppm of chloride. The high chloride content in this sample indicates that salt-water encroachment has been occurring at depth in the aquifer as a result of lowered ground-water levels in the vicinity of the Middle River. These are the only data available that indicate extensive saltwater contamination in the Middle River basin. However, the high

PAGE 35

REPORT OF INVESTIGATIONS No. 20 27 "<41E IRrr S4 RIttE 84SC T49$ S3171 2o EXPLANATION 0 / 5o 1174 Surfoce water Tampling stolIon .Top number is chloride Botlom number is opproximote OSIS Er .deplh from which eomple S 1371 .13 I was taoken o.a 2.eoT 0 T490 0 3 i .I PoV54 11 9 R 1 90 $• rs1s 't op' 3 14 D 154 S o e T|S I? MAN /L Figure 18. Map of eastern Broward County showing maximum chloride content recorded in water samples from wells and streams, 1941-57.

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1941 1942 1943 1944 1946 1946 1947 1948 1949 I980 1961 195B I9S3 1984 16 19 06 J9 7 '00 --------------_-,. 400 .-, .WELL I B 1,200 z DEPTH OF SAMPLE 116 FEET ..J Ic 2,600--------a. t,400 --g__ II-_ 2,,|00 I V Iloo CC 1,400---o 6000 -E 1 V-I -___ --OEPTH OF SAMPLE 35 FEET < 400 -, 200-K4..ZI.Z Figure 19. Chloride content of water from wells S-330 and S-830, at junction of South New River and Dania cutoff canals, 1941-57.

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REPORT OF INVESTIGATIONS No. 20 29 chloride content of the canal water (fig. 18) and the low ground-water levels shown on the contour map for August 7 (fig. 11) indicate that there might be considerable salt-water encroachment in this area. In the area north of the Middle River basin, the available data indicate that salt-water encroachment has been limited to areas close to the Intracoastal Waterway or Cypress Creek. This limitation is partially due to the high ground-water levels maintained by the control near the mouth of Pompano Canal and to the fact that Cypress Creek is not an improved drainage channel such as the Middle River and the south fork of the New River. QUALITY OF WATER The suitability of ground water for general use depends largely on the degree to which it fulfills the following requirements: (1) it must be safe to drink -that is, free from disease-causing bacteria and from excessive quantities of harmful minerals; (2) it should be clear and free from unpleasant taste or odor; (3) it should be relatively soft; and (4) it should not be corrosive or excessively damaging to metal surfaces. The first two requirements are most important for domestic or public supplies and the last two are most important for industrial supplies. As ground water must seep through more than 100 feet of sand and rock to reach the producing zone of the Biscayne aquifer, it is generally free of dangerous bacteria and suspended material. However, it is affected by the composition and solubility of the rocks and sediments with which it has been in contact. As rainwater infiltrates into the aquifer it exerts a solvent action upon the rocks through which it passes. This action is aided by the presence of carbon dioxide, absorbed from the atmosphere and from organic material in the soil. To determine the mineral constituents of ground water at different depths and locations in the area, chemical analyses were made of water samples from selected wells. The results of these analyses are shown in table 2. (See fig. 3 for well locations.) The analyses of the water from these wells show the characteristics of a hard to very hard limestone water, suitable (naturally or with fairly simple treatment) for all ordinary uses. Using the amount of dissolved solids as an indication of the mineralization of the water, the samples from wells S-340, S-341 and S-1869 in the Pompano Beach area showed less mineralization than the samples from well G-820 in the Prospect well field and wells S-336 and S-337 in the Middle River basin. The testwell logs (figs. 4-7) show that the amount of limestone penetrated in wells S-998 and S-999 in Pompano Beach was much less than that

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Table 2. Chemical Analyses of Water from Selected Wells (Chemnical constituents in parts per million) City Well City Well Well Well Well Well Well Well Well o. 1 No. 6 0 820 813001 8336 S 337 S 340 1 8 341 8372' Silica (SiO ) ................ 9.4 9.3 42 18 ..... ....... ... .... ........... Iron (Fe) ... e.... ...... .24 .02 .04 ,01 ...... .. Celclum (Ca) .............. 70 75 68 47 89 113 47 56 74 Magnesium (Mg)............. 1,8 1,2 908 1,1 3.1 3.1 2,3 2.5 2.7 Sodium and potassium (Na+K) ................ 7.5 6.9 10.0 10.6 7.6 18 8,5 5.8 5.4 Bicarbonate (HCO ) ........ 217 204 258 140 265 297 136 173 226 Sulfate (SO 4)............... 1.0 6.0 1.8 14 5.8 1 1 1 1 Chloride (C)............... 14 12 14 16 20 64 15 14 15 Fluoride (F) ......... ...... .3 .2 .2 .1 .... ...... .. ..... .. .......... N itrate (N O ) .............. .1 .2 .5 .4 .... ........ ........ .......... ......... Dissolved solids Residue on evaporation at 1800C.. .............. 221 234 287 182 256 3454 1654 164 2094 Total hardness as CaCO a..... 182 192 210 122 235 295 127 150 196 Noncarbonate............. 4 25 0 8 ...... ... ..... .. Color ..................... 15 10 5 5 130 50 20 20 40 Temperature ("F.)........... ..... ... ....... .77 ......... 76 ....... ...... H ... .. ...... .......... 7.5 7.9 7.9 7.8 .......... .......... ...... ... .......... ..... Specific conductance (micromhos at 25*C.)...... 372 378 420 291 468 643 268 307 389 Date of collection.......... Mar. 29 Nov. 11 July 9 Sept. 10 Nov. 19 Oct. 18 Nov. 29 Oct. 18 Oct. 18 1957 1956 1956 1956 1940 1940 1941 1941 1941 Depth of sample (feet below land surface) .............. 130 130 224 190 60.9 72 170 189 120 Aquifer .................. .Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne Biscayne SCity of Pompano Beach supply well 3. Parker and others (1955, p. 798). SIron in solution at time of analysis. 4 Sum of determined constituents.

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REPORT OF INVESTIGATIONS No. 20 31 in well G-820 in the Prospect well field and well G-563 near the south fork of the Middle River. Thus, the difference in the mineralization of the samples is probably related to the amount of limestone contacted by the water as it infiltrated down from the surface. Hardness of water is generally recognized because it increases the consumption of soap. Also, hard water causes the formation of scale in steam boilers or other vessels in which the water is heated. Water having a hardness of less than 60 ppm is considered soft; 60 to 120 ppm, moderately hard; 121 to 200 ppm, hard; and more than 200 ppm, very hard and unsatisfactory for most uses unless treated. Generally, the ground water in the Oakland Park area ranges in hardness from about 120 to 200 ppm and may be used with or without treatment, according to the use. Iron is one of the most noticeable constituents found in ground water in the Oakland Park area. In quantities of more than 0.5 to 1.0 ppm it will give the water a disagreeable taste, and in concentrations greater than 0.3 ppm will cause reddish-brown stain on clothing and fixtures. The iron content of the water differs from place to place and with depth, but it is not predictable. Iron may be removed easily by aeration and filtration from water that is to be used for large public supplies or industries, but it is more difficult to remove economically from water that is to be used for small domestic supplies. The analyses show iron in solution and do not include iron that may have precipitated between the time the sample was collected and the time of analysis. Color in water is caused almost entirely by organic matter extracted from peat, vegetation, and similar organic materials and is often accompanied by tastes and odors from the same sources. These characteristics may not be harmful to persons using the water, but their psychological effects on the consumer make them undesirable in drinking water. The analyses showing a color higher than 20 (the concentration at which color is considered to become objectionable) were of water from relatively shallow wells or wells near to streams. The pH indicates the degree of acidity or alkalinity of a water and is an important indication of its corrosive tendencies. A pH of 7.0 indicates neutrality, which means that the water is neither acid nor alkaline. Values below 7.0 denote increasing acidity; values above 7.0 indicate increasing alkalinity. The corrosiveness of water usually increases as the pH decreases. The pH of the samples ranged from 7.5 to 7.9, indicating that ground water in the area is moderately alkaline and should not be corrosive. As the amount of chloride in ground water is used to indicate the

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32 FLORIDA GEOLOGICAL SURVEY extent of salt-water encroachment from the ocean, samples were collected from several wells in the Oakland Park area and analyzed for chloride content. The data from the analysis of these samples are shown in figure 18. QUANTITATIVE STUDIES Knowledge of the hydraulic properties of the aquifers of an area is essential to the evaluation of the ground-water resources. The principal hydraulic properties of an aquifer are its capacities to transmit and store water. These properties are generally expressed as the coefficients of transmissibility and storage. The coefficient of transmissibility is a measure of the capacity of an aquifer to transmit water. In customary units it is the quantity of water, in gallons per day (gpd), that will flow through a vertical section of the aquifer 1 foot wide and extending the full saturated height, under a unit hydraulic gradient, at the prevailing temperature of the water (Theis, .-------------" ---____________ P42F 15 9 *14 13 0 Oslo OPS20 O0804 62 EXPLANATION 0id T2 ) i I4 I 10 SCALE COMPLETE WELL IOT OPERATING 842 Figure 20. Map of Prospect well field showing layout of municipal supply wells and observation wells.

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REPORT OF INVESTIGATIONS NO. 20 33 1.938, p. 892). The coefficient of storage is a measure of the capacity of an aquifer to'store water and is defined as the volume of water released from or taken into storage per unit surface area of the aquifer per unit change in the component of head normal to that surface. In this area, the best opportunity for making pumping tests to obtain these aquifer coefficients was through the use of municipal supply wells in the Prospect well field. Figure 20 shows the layout of the municipal supply wells and observation wells in this well field. Two tests were run in this field by observing the effects on water levels of changes in the rate of pumping. A 12-hour pumping test was made on August 8, 1956, using 10 city supply wells, each being pumped at the rate of 820 gpm. City supply wells 3, 4, and 5 were operated for eight hours prior to the start of the test, and then pumping was begun in the remaining seven wells in the field at the beginning of the test. Water-level recorders were operated on wells G-768 and G-820 beginning June 15, 1956, and August 6, 1956, respectively, and tape measurements of the changes in water level were made in well G-803 during the test. Well G-820 is a 4-inch well, drilled to a depth of 224 feet, and the casing was dynamited at a depth of 215 feet to open it to the aquifer. Well G-768 is a 6-inch well, 91 feet deep, cased to an approximate depth of 80 feet; and well G-803 is a 1,-inch sandpoint well 16 feet deep, cased to 14 feet below the land surface and screened from 14 to 16 feet below the land surface. A drawdown of 1.0 foot was recorded in well G-768, whereas no measurable drawdown occurred in well G-803 during the test. If drawdown affected the water level in well G-820 it was apparently overshadowed by the natural decline of the water table and fluctuations caused by changes in barometric pressure. Figure 21 shows the fluctuation of the water level in well G-768 before and during the test. On March 27, 1957, a 36-hour test was made using city wells 11, 12, and 14 (fig. 20) as observation wells. Supply wells 1, 2, and 3 were operated for 20 hours preceding this test and then pumping was started in wells 8, 9, and 10. Each of these wells is pumped at approximately 820 gpm. A water-level recorder was in operation on well G-820 during the 20-hour period before the test, and recorders were operated on city wells 11, 12, and 14 during the test. Drawdowns of approximately 0.2 foot and 0.4 foot were recorded in city wells 11 and 12, respectively, whereas city well 14 and well G-820 showed no appreciable drawdown. All the city supply wells are finished with well screens 20 feet long which extend to a depth of approximately 130 feet. The water pumped in both tests was discharged into the city mains so that no complication was caused by infiltration of the pumped water near the wells.

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34 FLORDA GEOLOGICAL SURVEY PROSPEGT FIELO PU MPI M TEST Figure 21. Hydrograph of well G-768, in the Prospect well field, during pumping test, August 7-8, 1956. Water-level and pumping-test data indicate that under static (nonpumping) conditions the Biscayne aquifer exhibits different characteristics than it does under pumping conditions. Under static conditions, the water level in a shallow well will stand at the same altitude as the water level in an adjacent deep well, suggesting that the aquifer is under nonartesian conditions. However, when the deep, highly permeable zones of the aquifer were pumped, water levels in deep wells as much as 1,000 feet away showed an immediate rapid decline. Water levels in shallow wells much closer to the pumping wells showed no immediate change during the test, but they do show a long-term drawdown of several feet. (See contour maps, figs. 11, 12 and 13.) Thus, in pumping tests of short duration the zone in which the supply wells are develped reacts as an artesian aquifer overlain and partly confined by a leaky roof of less permeable beds (fg. 5). The fact that the water levels of deep wells permeable beds (fig. 5). The fact that the water levels of deep wells

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REPORT OF INVESTIGATIONS No. 20 35 respond readily to changes in barometric pressure is further evidence of artesian conditions. Data from the aquifer tests were first analyzed by the Theis nonequilibrium method (Theis, 1985), which assumes the following conditions: (1) the aquifer is without limit in a lateral direction; (2) the aquifer is homogeneous throughout and transmits water equally readily in all directions at all times; (8) the pumped well completely penetrates the aquifer; (4) the pumped well has an infinitesimal diameter; and (5) water taken from storage in the aquifer is discharged instantaneously with the decline in head. Although not all these assumptions were fulfilled, this method was useful in that it indicated that the pumped zone was receiving recharge during the test. Further analysis was made by means of a leaky-aquifer type curve developed by H. H. Cooper, Jr., of the U. S. Geological Survey, Tallahassee, Florida, (personal communication) and by a method outlined by Hantush (1956) which is based on the theory of ground-water flow in a leaky artesian aquifer (Hantush and Jacob, 1955). Figure 22 shows radial flow in and leakage to an ideal leaky artesian aquifer (Jacob, 1946). These methods involve the same assumptions of the Theis method, but, in addition, they assume leakage into the aquifer through a semiconfining bed and a constant head in the bed supplying the leakage. In treating WELL __ WATER_ TABLE -NONARTESIAN AQUIFER SEMI-PERVIOUS // // // /// CONFINING BED// -ARTESIAN AQUIFER IMPERVIOUS BED Figure 22. Idealized sketch showing flow in a leaky aquifer (modified from Jacob, 1946, p. 199).

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36 FLORIDA GEOLOGICAL SURVEY problems in leaky systems these methods add a third aquifer coefficient, called the leakage coefficient, which indicates the ability of the semiconfining bed to transmit water upward from or downward into the aquifer being tested. This coefficient may be defined as the quantity of flow that crosses a unit area of the interface between the main aquifer and its semiconfining bed if the difference between the head in the main aquifer and the bed supplying the leakage is unity. It is obvious that the head in the bed supplying the leakage in the well field area is not constant during long periods, but water levels in shallow wells in the well field were very nearly constant during the pumping tests. The water level in well G-803 rose 0.02 foot during the 16 hours preceding the first pumping test and declined 0.03 foot during the first five hours of the test. Computation of the aquifer coefficients is complicated not only by vertical leakage in the stratified material but also by the possibility of inducing recharge from canals and quarries and the limitations on the accurate measurement of the small drawdowns. The coefficients of transmissibility obtained ranged from 2,000,000 to 3,000,000 gpd per foot. The storage coefficient was approximately 0.015, and the leakage coefficient was about one gpd per square foot per foot of vertical head. It is apparent from the large cone of depression shown in figures 11, 12, and 13 that long-term pumping has caused considerable unwatering of the beds overlying the pumped zone in the aquifer. Thus, the drawdown caused by large-scale pumping from the deep zone is reflected at the water table, and it is controlled by the coefficients of transmissibility and storage of both the pumped zone and the overlying beds. An approximate value for the coefficient of transmissibility, under equilibrium conditions, may be calculated by substituting the average hydraulic gradient at points around the cone of depression and the average pumpage from the well field in the formula Q = TIW (a modified expression of Darcy's law for ground-water flow) where: Q= the average pumpage from the well field, in gallons per day T = the transmissibility of the aquifer, in gallons per day per foot W=the circumference of a cylinder through the aquifer at a given radius from the center of pumpage, in feet I = the average slope of the cone depression around this cylinder, in feet per foot. The record of water-level fluctuations in well G-768 during the period July 12-24 (fig. 23) indicates that water levels in the well field area had reached approximate equilibrium for the rate of pumping at that time. A coefficient of transmissibility of about 1,000,000 gpd per foot was

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'JULY 1956 uI .... I -a, I I "! 0 S' -.0 Figure 23. Hydrograph of well G-768, in the Prospect well field, showing effect of pumping in the well field. "4

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38 FLORIDA GEOLOGICA. SURVEY obtained from the above formula by using the water-level data from the contour map of August 7, 1956, and the average pumping rate for the period July 25-August 7, 1956 (10.0 mgd). This figure is on the low side because evapotranspiration was not considered. The area within the contour used (sea level) is about 34,000,000 square feet. Evapotranspiration of ground water is estimated at 6 inches per month or 0.2 inch per day. Natural water loss for the area is then about 4.2 mgd. By use of the combined discharge of 10.0 mgd by pumping and 4.2 mgd by evapotranspiration, the coefficient of transmissibility is computed to be about 1,500,000 gpd per foot. GROUND-WATER USE Wells supply most of the water for public, domestic, irrigation, and industrial use in the Oakland Park area. Until recent years the area was relatively undeveloped and ground-water withdrawals were small. Since about 1950, however, the growth of population and industry in the area has been extremely rapid, and ground-water use has increased correspondingly. The largest pumpage is that from the Prospect well field, which yielded about 10.0 mgd in 1956. When all proposed wells are in operation, the pumpage from the field will be about 20 mgd. Separate watersupply systems have been developed for several large housing developments in the area, and many residents have private wells for domestic use and lawn sprinkling. In the area west of Oakland Park, several large farms use ground water for irrigation. Generally, the peak pumping for municipal supplies and irrigation occurs during December through June, as these months include both the tourist season and the dry season. The use of ground water by industries is growing rapidly, especially in areas adjacent to the two railroads. CONCLUSIONS The Biscayne aquifer is the source of all fresh ground water in the Oakland Park area. The water in the aquifer comes from local rainfall or from surface water brought into the area by canals. It is generally of good quality except for hardness and color. The Biscayne aquifer is composed of permeable marine deposits -chiefly sandy limestone, calcareous sandstone, and quartz sand -which extend from the land surface to a depth of more than 215 feet below mean sea level. The components of the aquifer differ from place to place, but, in general, the amount of sand decreases with depth and most of the consolidated rocks occur at depths greater than 60 feet.

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REPORT OF INVESTIGATIONS No. 20 39 Wells used for small water supplies generally tap thin beds of limestone at depths ranging from 60 to 80 feet, whereas most wells used for large supplies are developed in highly permeable limestones and sandstones of the Anastasia and Tamiami formations, at depths greater than 100 feet. There is a natural seaward water-level gradient in the Oakland Park area, but it is greatly influenced by pumping in the Prospect well field and by water-control structures in the Middle River and Pompano canals. Ground-water levels in areas downgradient (east) from these canal controls are lowered by pumping and by ground-water drainage into the canals, whereas water levels in areas upgradient (west) from the controls remain high owing to ground-water recharge from the canals. Salt-water encroachment from the ocean is the chief factor affecting the use of ground water in the Oakland Park area. This encroachment is governed by the relationship of ground-water levels to mean sea level and may occur in two ways: (1) direct inland movement of salt water at depth in the aquifer, and (2) the movement of salt water from tidal reaches of canals into the aquifer during low-water periods. Determinations of the chloride content of water from the deep wells in the area indicate that under the conditions in 1956 there is little danger of saltwater encroachment except in areas adjacent to Cypress Creek and the Intracoastal Waterway and in the Middle River basin. Direct contamination from the Middle River Canal has occurred in wells only a mile east of the dam. Further encroachment could be retarded by placing and operating controls downstream from the present location of the control in the Middle River Canal and by reducing drawdowns in the Prospect well field and vicinity. Pumping tests in the Prospect well field and areawide water-level data indicate that large quantities of ground water are available for future development, especially in areas west of the controls on the two major canals.

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40 FLORIDA GEOLOGICAL StmVEY REFERENCES Brown, J. S. 1925 A study of coastal water, with special reference to Connecticut: U, S. Geol. Survey Water-Supply Paper 537. Cooke, C. Wythe (see Parker, G. C.) Hantush, M. C. 1955 (and Jacob, C. E.) Non-steady radial flow in an infinite leaky aquifer: Am. Geophys. Union Trans, v, 36, p. 95-100. 1956 Analysis of data from pumping tests in leaky aquifers: Am. Geophys. Union Trans., v, 37, no. 6, p. 702-714. Hoy, N. D. (see Schroeder, M, C,) Jacob, C. E. (also see Hantush, M. C.) 1946 Radial flow in a leaky artesian aquifer: Am, Geophys, Union Trans., v. 26, no. 11. Klein, Howard (see Schroeder, M. C.) Meinzer, O. E. 1923 Outline of ground-water hydrology, with definitions: U. S. Geol, Survey Water-Supply Paper 494. Parker, G. G. 1944 (and Cooke, C. Wythe) Late Cenozoic geology of southern Florida, with a discussion of the ground water: Florida Geol. Survey Bull, 27. 1950 (and Stringfield, V. T.) Effects of earthquakes, trains, tides, winds, and atmospheric pressure changes in water in the geologic formations in southern Florida; Econ. Geology, v. 45, no. 5, p. 441-460. 1951 Geologic and hydrologic factors in the perennial yield of the Biscayne aquifer: Am. Water Works Assoc. Jour., v. 43, no. 10, p. 820-828, 1955 (and others) Water resources of southeastern Florida, with special reference to the geology and ground water of the Miami area: U. S. Geol. Survey Water-Supply Paper 1255. Schroeder, M. C. 1958 (and Klein, Howard, and Hoy, N. D.) Biscayne aquifer of Dade and Broward Counties, Florida: Florida Geol. Survey Rept, Inv, 17. Stringfield, V. T. (see Parker, G, G,) Theis. C. V. 1935 The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using ground-water storage: Am. Geophys. Union Trans., p. 519-524. 1938 The significance and nature of the cone of depression in ground-water bodies: Econ. Geology, v. 33, no. 8. 1948 Geology and ground water of the Fort Lauderdale area, lid Florida Flor Geol. Survey Rept. Inv. 6. Vorhis, R. C. .-I.

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-FLORIDA-GEOLOGICAL-SURVEY COPYRIGHT NOTICE [year of publication as printed] Florida Geological Survey [source text] The Florida Geological Survey holds all rights to the source text of this electronic resource on behalf of the State of Florida. The Florida Geological Survey shall be considered the copyright holder for the text of this publication. Under the Statutes of the State of Florida (FS 257.05; 257.105, and 377.075), the Florida Geologic Survey (Tallahassee, FL), publisher of the Florida Geologic Survey, as a division of state government, makes its documents public (i.e., published) and extends to the state's official agencies and libraries, including the University of Florida's Smathers Libraries, rights of reproduction. The Florida Geological Survey has made its publications available to the University of Florida, on behalf of the State University System of Florida, for the purpose of digitization and Internet distribution. The Florida Geological Survey reserves all rights to its publications. All uses, excluding those made under "fair use" provisions of U.S. copyright legislation (U.S. Code, Title 17, Section 107), are restricted. Contact the Florida Geological Survey for additional information and permissions.



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REPORT OF INVESTIGATIONS No. 20 35 respond readily to changes in barometric pressure is further evidence of artesian conditions. Data from the aquifer tests were first analyzed by the Theis nonequilibrium method (Theis, 1985), which assumes the following conditions: (1) the aquifer is without limit in a lateral direction; (2) the aquifer is homogeneous throughout and transmits water equally readily in all directions at all times; (8) the pumped well completely penetrates the aquifer; (4) the pumped well has an infinitesimal diameter; and (5) water taken from storage in the aquifer is discharged instantaneously with the decline in head. Although not all these assumptions were fulfilled, this method was useful in that it indicated that the pumped zone was receiving recharge during the test. Further analysis was made by means of a leaky-aquifer type curve developed by H. H. Cooper, Jr., of the U. S. Geological Survey, Tallahassee, Florida, (personal communication) and by a method outlined by Hantush (1956) which is based on the theory of ground-water flow in a leaky artesian aquifer (Hantush and Jacob, 1955). Figure 22 shows radial flow in and leakage to an ideal leaky artesian aquifer (Jacob, 1946). These methods involve the same assumptions of the Theis method, but, in addition, they assume leakage into the aquifer through a semiconfining bed and a constant head in the bed supplying the leakage. In treating WELL __ WATER_ TABLE -NONARTESIAN AQUIFER SEMI-PERVIOUS // // // /// CONFINING BED// -ARTESIAN AQUIFER IMPERVIOUS BED Figure 22. Idealized sketch showing flow in a leaky aquifer (modified from Jacob, 1946, p. 199).



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18 FLORIDA GEOLOGICAL SURVEY :/ G pEACHS." ."" ...i .A i i /.,, -C't!(.i '.' i / < ,_i ,,J Figure 11. Map showing contours on the water table in the Biscayne aquifer in the Oakland Park area, August 7, 1956. of ground water through drainage into the uncontrolled reaches of streams and canals and by discharge from the Prospect well field. Figure 11 shows the configuration of the water table at a time when water levels were near record lows and pumping from the well field was near maximum. The direction of ground-water flow is perpendicular to contour lines and in general it is toward the coast. The steep water-level gradient north and west of the well field indicates that most of the water pumped from the well field comes from that direction. Figure 14 shows the fluctuation of water levels in wells G-768 and G-820 in the Prospect well field, monthly pumpage from the well field, and daily rainfall at Fort Lauderdale during June-December, 1956. The hydrographs show the difference between the water levels in well G-768, near the center of the cone of depression, and well G-820, near the outer edge of the cone. A comparison of the altitude of the water level of wel G-768, in 1956, with that of well G-127 (same approximate loca-



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REPORT OF INVESTIGATIONS No. 20 3 Broward County are contained in reports by Vorhis (1948), Parker and others (1955), and Schroeder and others (1958). ACKNOWLEDGMENTS Grateful acknowledgment is hereby made for the cooperation and assistance given by officials of the city of Fort Lauderdale and the engineering firm of Philpott, Ross and Saarinen. The wholehearted cooperation of the personnel of the Fort Lauderdale water-treatment plants while field work was in progress, was especially helpful. Data pertaining to flood-control works in the area were supplied by officials of the Central and Southern Florida Flood Control District. GEOGRAPHY LOCATION AND GENERAL FEATURES OF THE AREA The Oakland Park area is on the lower east coast of Florida between the cities of Pompano Beach and Fort Lauderdale (fig. 1). It is bounded on the north by the Pompano Canal, on the east by the Intracoastal Waterway, on the south by the south fork of the Middle River, and on the west by Conservation Area No. 2. The city of Oakland Park is north of the north fork of the Middle River, about two miles west of the Intracoastal Waterway (fig. 2). The Prospect well field, which is one source of water supply for Fort Lauderdale, lies between the upper reaches of Cypress Creek and the Middle River, about two miles northwest of Oakland Park (fig. 3). CLIMATE The climate of Fort Lauderdale is subtropical and the humidity is usually high. The average monthly temperatures, as shown by U. S. Weather Bureau records, range from 68.83F. to 82.60F. As of the end of 1956, the mean annual temperature was 74.20F. and the mean yearly rainfall was 59.88 inches, for 48 years of record. The heaviest rains occur during the period from June through October. Table 1 shows monthly and yearly averages of temperature and rainfall at the Fort Lauderdale station for the period 1940-56, and average rainfall at the Pompano Beach station, about seven miles north of Fort Lauderdale, for the period 1941-56. TOPOGRAPHY AND DRAINAGE The Oakland Park area is on the coastal ridge that separates. the Atlantic Ocean from the Everglades. The ridge in this area is about six



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RPORT OF INVESTIGATIONS No. 20 17 1940 1941 -i i 14 o -e --RA i ....WE.. ._A_ Oln .. ...... ..... ..... W {L 0 12 1" PROSPECT FIELD b WELL 0 12\ -Ii 3 MILES eAsY Of P SCP'FECf FILD -\I 0, ---O --" -[ .... ... ..... ..... ..... ...... ... ..... ...-----to Figure 10. Hydrographs of wells G-127 and G-128 and weekly rainfall at Fort Lauderdale during 1940-41. each contour map is the deep cone of depression caused by pumping in the Prospect well field. Significant features are the high ground-water levels and steep gradient maintained as a result of recharge by surface water in areas upstream from control structures in the Middle River and Pompano canals. The extremely low water levels and fiat gradient in areas southeast of the cone of depression are caused by the large losses



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TABLE OF CONTENTS Page Letter of transmittal __ iii Abstract 1 Introduction 1 Purpose and scope 1 Previous investigations 2 Acknowledgments ______ -3 Geography 3 Location and general features of the area 3 Climate _--_-_--_ ------3 Topography and drainage 3 Geologic formations and their water-bearing characteristics 7 Ground water 12 Recharge and discharge 13 Water-level fluctuations 13 Salt-water encroachment 22 Quality of water 29 Quantitative studies 32 Ground-water use 38 Conclusions 38 References --40



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REPORT OF INVESTIGATIONS NO. 2 5 R3?E R"8 39E R419 R41E R 11 0NSERVATIbN T6s AREA Nb. I ---....i BROWARD COUNTY i I I ---AKLAND SC i IN MILES t----~-T I-t------.-..... .BAC 5 i 10 --PARKAND S AREA MIDDL RPARK FORT mOU -I r CA.A EXPLANATION SALEF IN MILES Figure 2. Map of parts of Broward and Palm Beach counties showing canals and levees of the Central and Southern Florida Flood Control District. TABLE 1. Average Monthly Temperature, in Degrees, at Fort Lauderdale, and Average Monthly Rainfall, in Inches, at Fort Lauderdale and Pompano Beach Temperature Rainfall Month Fort Lauderdale Fort Lauderdale1 Pompano Beach' Jan. 68.3 2.18 2.22 Feb. 68.3 1.96 1.51 Mar. 70.9 2.81 2.17 Apr. 74.2 4.06 3.86 May 77.4 4.93 3.60 June 80.3 7.55 6.01 July 81.7 6.03 7.39 Aug. 82.6 6.74 6.68 Sept. 81.5 8.82 9.32 Oct. 77.8 8.83 9.58 Nov. 72.3 3.05 3.09 Dec. 69.2 2.37 2.08 Yearly average 74.2 59.83 57.51 'Discontinuous record 1940-56, U. S. Weather Bureau. 'Discontinuous record 1941-56, U. S. Weather Bureau.



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REPORT OF INVESTIGATIONS No. 20 39 Wells used for small water supplies generally tap thin beds of limestone at depths ranging from 60 to 80 feet, whereas most wells used for large supplies are developed in highly permeable limestones and sandstones of the Anastasia and Tamiami formations, at depths greater than 100 feet. There is a natural seaward water-level gradient in the Oakland Park area, but it is greatly influenced by pumping in the Prospect well field and by water-control structures in the Middle River and Pompano canals. Ground-water levels in areas downgradient (east) from these canal controls are lowered by pumping and by ground-water drainage into the canals, whereas water levels in areas upgradient (west) from the controls remain high owing to ground-water recharge from the canals. Salt-water encroachment from the ocean is the chief factor affecting the use of ground water in the Oakland Park area. This encroachment is governed by the relationship of ground-water levels to mean sea level and may occur in two ways: (1) direct inland movement of salt water at depth in the aquifer, and (2) the movement of salt water from tidal reaches of canals into the aquifer during low-water periods. Determinations of the chloride content of water from the deep wells in the area indicate that under the conditions in 1956 there is little danger of saltwater encroachment except in areas adjacent to Cypress Creek and the Intracoastal Waterway and in the Middle River basin. Direct contamination from the Middle River Canal has occurred in wells only a mile east of the dam. Further encroachment could be retarded by placing and operating controls downstream from the present location of the control in the Middle River Canal and by reducing drawdowns in the Prospect well field and vicinity. Pumping tests in the Prospect well field and areawide water-level data indicate that large quantities of ground water are available for future development, especially in areas west of the controls on the two major canals.



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LETTER OF TRANSMITTAL @a 7TJYorlcl g eo/ofr(ic(I S urvecy TALLAHASSEE September 15, 1959 x Mr. Ernest Mitts, Director Florida State Board of Conservation 4 Tallahassee, Florida Dear Mr. Mitts: Florida Geological Survey Report of Investigations No. 20 is a S paper entitled, GROUND-WATER RESOURCES OF THE OAKLAND PARK AREA OF EASTERN BROWARD COUNTY, FLORIDA, which was prepared by Mr. C. B. Sherwood, Hydraulic Engineer 1 with the U. S. Geological Survey, in cooperation with the Florida Geological Survey and the City of Fort Lauderdale. The Oakland Park area obtains its water from the Biscayne aquifer, S composed of very permeable and porous, sandy limestones. The per3 meability of the aquifer increases with depth, and wells in the area <\ generally obtain water at depths ranging from 60 to 80 feet, or between S 100 and 200 feet, depending on the quantity of water desired. The data presented in this paper can be used for further development of water and wise management of resources in the area. Large quantities S of ground water are still available at Oakland Park, if salt-water encroachment can be controlled. The data in this study provide the necessary information to begin an effective water management program. Respectfully yours, Robert 0. Vernon, Director iii-



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16 FLORIDA GEOLOGICAL SURVEY PALM BEACH COUNTY R4OE R41E R4tE R42E HILLSBOROUGH CANAL EXPLANATION DEERFIELD 0 WELL SURFACE WATER OBSERVATION POINT WATER LEVEL,IN FEET, REFERRED TO MEAN SEA LEVEL 0 1 2 3 4 5 6 miles _'b---:----,m== POMPANO CANAL MPAN i 5,-9 H I 8 oG 12o 7 G 12 4.0 F3 \ ---(-/ 30 eastern Bw Co on February 15, 141 -30 IE ld cut of Lock I "Dania Davie Rd. DANIA SHollywood BlvdHOL WOOD DADE COUNTY 0 F&4ME R41 E Figure 9. Map showing contours on the water table in the Biscayne aquifer, in eastern Broward County, on February 15, 1941.



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1956 At FE. MAR. APR.n MNA PULY. ,EP .1 JECA. B .0 II BELOWB DAMD F 6.0 0 d BELOW DAM 0MEAN DAILY LOW. Figure 16. ydrogphs of Middle River Caal above d below dam durg 196. F-od