Citation
Ground-water resources of the Lower Hillsboro Canal area, southeastern Florida ( FGS: Report of investigations 55 )

Material Information

Title:
Ground-water resources of the Lower Hillsboro Canal area, southeastern Florida ( FGS: Report of investigations 55 )
Series Title:
( FGS: Report of investigations 55 )
Creator:
McCoy, H. J ( Henry Jack )
Hardee, Jack ( joint author )
Geological Survey (U.S.)
Place of Publication:
Tallahassee
Publisher:
[s.n.]
Publication Date:
Language:
English
Physical Description:
vii, 44 p. : illus. ; 23 cm.

Subjects

Subjects / Keywords:
Groundwater -- Florida -- Palm Beach County ( lcsh )
Groundwater -- Florida -- Broward County ( lcsh )
City of Boca Raton ( local )
City of Deerfield Beach ( local )
Broward County ( local )
City of Tallahassee ( local )
City of Lake Worth ( local )
Atlantic Ocean ( local )
Canals ( jstor )
Aquifers ( jstor )
Groundwater ( jstor )
Rain ( jstor )
Pumping ( jstor )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Bibliography: p. 44.
Statement of Responsibility:
by H. J. McCoy and Jack Hardee. Prepared by the U.S. Geological Survey in cooperation with the Bureau of Geology, Division of Interior Resources, Florida Department of Natural Resources and the cities of Boca Raton and Deerfield Beach.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
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:
029051489 ( aleph )
AED9231 ( notis )
73633651 ( lccn )

Downloads

This item has the following downloads:


Full Text
STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY
Robert O. Vernon, Chief
REPORT OF INVESTIGATION NO. 55
GROUND-WATER RESOURCES OF THE LOWER HILLSBORO
CANAL AREA, SOUTHEASTERN FLORIDA
By
H.J. McCoy andJack Hardee U. S. Geological Survey
Prepared by the U. S. GEOLOGICAL SURVEY in cooperation with the BUREAU OF GEOLOGY
DIVISION OF INTERIOR RESOURCES
FLORIDA DEPARTMENT OF NATURAL RESOURCES and the cities of BOCA RATON and DEERFIELD BEACH
Tallahassee, Florida 1970
1




DEPARTMENT OF
NATURAL RESOURCES
CLAUDE R. KIRK, JR.
Governor
TOM ADAMS EARL FAIRCLOTH
Secretary of State Attorney General
BROWARD WILLIAMS FRED O. DICKINSON, JR.
Treasurer Comptroller
FLOYD T. CHRISTIAN DOYLE CONNER Commissioner of Education Commissioner ofAgriculture
W. RANDOLPH HODGES Executive Director
ii




LETTER OF TRANSMITTAL
Bureau of Geology
Tallahassee
April 14, 1970
The Honorable Claude R. Kirk Governor of Florida
Tallahassee, Florida
Dear Governor Kirk:
The Bureau of Geology of the Department of Natural Resources is publishing as its Report of Investigation No. 55 a report on the "Ground Water Resources of the Lower Hillsboro Canal Area, Southeastern Florida". The report was prepared as part of the cooperative program between the Bureau of Geology, the U. S. Geological Survey and the cities of Boca Raton and Deerfield Beach. It is written by Messrs. H. J. McCoy and Jack Hardee of the U. S. Geological Survey and was undertaken to determine the amount and kinds of water being produced from the lower Hillsboro Canal Area in Palm Beach and Broward counties.
All of the potable ground water being produced from the Biscayne aquifer is developed from the canal through infiltration. Rainfall in the area is the ultimate source for all of the water.
Careful control and management will allow the development of large quantities of water from the canal toward Lake Okeechobee, but a fresh water head must be maintained along the contact of fresh water with sea water to prevent salt water intrusion.
Respectfully yours,
R. O. Vernon, Chief
Bureau of Geology
ROV:ebl
iii




Completed manuscript received
April 14,1970
Printed for the Bureau of Geology
Division of Interior Resources
Florida Department of Natural Resources
Designers Press of Orlando, Inc.
Orlando, Florida
iv




CONTENTS
Page
Abstract .... ..................... .. .. ..... .. 1
Introduction ......................................1
Purpose and scope .................................2
Previous investigations ..............................2
Acknowledgments ......................................2
General features ....................................3
Clim ate ........................ ................ 3
Population and industry .......... .. ................... 5
Hydrologic setting ........ .............................. 6
Biscayne aquifer ..................................7
Floridan aquifer ............. ....................9
Surface flow system ...............................11
Ground water ....................................12
Recharge and discharge .............................12
Water-level fluctuations .............................13
Hydraulic properties ...............................24
Water quality ...................................26
Sea-water intrusion ................. ...............33
Water use and potential supply . . . . . . . . . . . . . 38
Summary ..... ............. ........ .............. 42
Well numbers ....................................43
References ......... .. .... .........................44




LIST OF ILLUSTRATIONS
Figure Page
1 Location of lower Hillsboro Canal area, Florida,
showing physiographic subdivisions . . . . . . . . . 4
2 Parts of Broward and Palm Beach Counties showing
canals and levees of the Central and Southern
Florida Flood Control Project and the Lake Worth
Drainage District .............................. 6
3 Map of lower Hillsboro Canal area showing location
of wells and lines of geologic sections . . . . . . . . . 8
4 Geologic section of the Biscayne aquifer in the
lower Hillsboro Canal area along line A-A' in
figure 3 ................................... 9
5 Geologic section of the Biscayne aquifer in the
lower Hillsboro Canal area along line B-B' in
figure 3 .................................. 10
6 Hydrographs of wells PB 470 and PB 488 and monthly
rainfall at Boca Raton, 1963-1967 . . . . . . . . . 14
7 Hydrographs of wells G 1214 and G 1260 at Deerfield
Beach and monthly rainfall at Boca Raton, 1963-1967 . . . 15
8 Water-table contour map of the lower Hillsboro Canal
area, May 7, 1965, during low-water conditions . . . . .... 16
9 Graph showing monthly municipal pumpage and rainfall
at Boca Raton, 1963-1967 ....................... 18
10 Graph showing monthly municipal pumpage at Deerfield
Beach and monthly rainfall at Boca Raton, 1963-1967 . . . . 19
11 Water-table contour map of the lower Hillsboro Canal
area, November 1, 1965, during high-water conditions. . . . 20
12 Contour map showing rise in water levels from May 7 to
November 1, 1965 in the lower Hillsboro Canal area . . . . 21
13 Water-table contour map of the lower Hillsboro Canal
area, October 27, 1966, during high-water conditions . . . . 22
14 Water-table contour map of the lower Hillsboro Canal
area, April 12, 1967, during low-water conditions . . . . . 23
15 An example of the preparation of a water-quality diagram
using the percentage figures in Table 3 . . . . . . . . 31
16 Relative concentrations of chemical constituents in
ground water of the Biscayne aquifer in the lower
Hillsboro Canal area ........................... 32
17 Chloride content of water at nine points in the El Rio
Canal between the Hillsboro Canal and Street . . . . . . 34
18 Chloride content of water at nine points in the
Hillsboro Canal upstream from the Intracoastal
Waterway, September 20, 1966 ..................... 35
19 Section along line A-A' (figure 17) showing lines of
equal chloride content (isochlors) of ground water . . . . 37
vi




20 Approximate daily maximum and minimum chloride content
of water-in the El Rio Canal at 7th Street, Boca Raton,
Florida, for the period March 1964 through August 1965 ..... 39
21 Graph showing the discharge of the Hillsboro Canal at
the control near Deerfield Beach, 1965. . . . . . . . 41
TABLES
Table Page
1. Monthly rainfall at Boca Raton, Florida, 1961-1967 ........ 15
2. Chemical analyses of water from selected wells in the
lower Hillsboro Canal area ....................... 28
3. Selected constituents in water from well PB-487 . . . . . 30
vii




GROUND WATER RESOURCES OF THE
LOWER HILLSBORO CANAL AREA
By
H.J. McCoy andJack Hardee
ABSTRACT
The lower Hillsboro Canal area of this report occupies about 60 square miles of Palm Beach and Broward counties in southeastern Florida. All potable ground water in the lower Hillsboro Canal area is obtained from the Biscayne aquifer. The aquifer extends from the land surface to a depth of about 400 feet and is composed of sand, sandy limestone, shells, and indurated calcareous sand. Municipal well fields of Deerfield Beach and Boca Raton and most of the domestic, irrigation, and industrial wells obtain adequate water supplies from permeable limestone 90 to 130 feet below land surface. Rainfall in the area and induced infiltration from controlled canals provide the recharge to the aquifer.
Sea-water intrusion, although a constant threat, has not advanced inland enough to contaminate either municipal well field. Intrusion from the El Rio Canal toward the Boca Raton well field appears to be stabilized, though further intrusion is a distinct possibility if fresh water levels are further lowered in the area. Data collection stations are maintained to monitor changes of the salt-water front in the aquifer.
Large quantities of water can be withdrawn from the interior part of the area without the attendant threat of salt-water intrusion. Hydraulic characteristics of the aquifer are similar throughout the area and high year-round water levels in the interior afford a potential source of immediate and long-term recharge to the aquifer underlying the coastal ridge.
The lower Hillsboro Canal area is still experiencing rapid growth with resultant demands for larger quantities of potable water. Although potable water is abundant, continuous observation and evaluation of changes in the hydrology of the area should be maintained to protect and efficiently manage the water resources of the area.
INTRODUCTION
Water problems facing the cities of Boca Raton and Deerfield Beach are similar to those experienced by other coastal communities in southeastern Florida with rapid growth and increasing water needs.
.1




2 BUREAU OF GEOLOGY
Water supplies for Boca Raton and Deerfield Beach are obtained from well fields located adjacent to the Intracoastal Waterway and to tidal reaches of the Hillsboro and El Rio Canals, all of which are normally salty. Recognizing that rapid population growth would mean large water demands and that increased well field pumping could cause sea-water intrusion, in 1963 officials of both cities requested the U.S. Geological Survey to study water resources of the area to provide information for the future development of water supplies.
PURPOSE AND SCOPE
The purpose of this report is to present an evaluation of the ground-water resources of the lower Hillsboro Canal area and pertinent supporting data to the officials of Boca Raton and Deerfield Beach, Fla. The evaluation is the result of determining the following: (1) the location, availability, and quality of potable ground water in the Biscayne aquifer; (2) the occurrence and extent of sea-water intrusion into the aquifer in the vicinity of the well fields; (3) the hydraulic characteristics of the aquifer; and (4) the degree of interconnection between the canals and the aquifer.
This report was prepared by the U.S. Geological Survey in cooperation with the cities of Boca Raton and Deerfield Beach, and as part of the statewide program with the Bureau of Geology, Florida Department of Natural Resources. The field work and report preparation were under the immediate supervision of C. B. Sherwood, Projects Engineer, and H. Klein, Subdistrict Chief, Miami, Fla., and under the general supervision of C. S. Conover, District Chief, Tallahassee, Fla., all of the U.S. Geological Survey.
PREVIOUS INVESTIGATIONS
This report results from the first detailed ground-water resources study of the lower Hillsboro Canal area. General information on the hydrology and geology of the area has been published by the Florida Geological Survey in reports by Cooke (1945), Black and Brown (1951), and Schroeder and others (1958). Some additional information on the area is included in a report resulting from a comprehensive investigation of the water resources of southeastern Florida by Parker and others (1955).
ACKNOWLEDGMENTS
Well-field and water-supply information given by William Eddinger, Water Superintendent of Boca Raton, and Arthur Strock, former City Engineer of Deerfield Beach is appreciated. Special acknowledg-




REPORT OF INVESTIGATION NO. 55 3
ment is expressed to Drs. F. A. Eidsness, J. I. Garcia-Bengochea and Mr. Emmett Waite, of Black, Crow and Eidsness, Inc., Gainesville, Fla., consulting engineers for the cities of Boca Raton and Deerfield Beach.
GENERAL FEATURES
The area of study comprises about 60 square miles of Palm Beach and Broward counties in southeastern Florida as shown in figure 1. The area is bounded on the east by the Atlantic Ocean and on the west by an extensive agricultural area and the Everglades; it extends about 6 miles north and 4 miles south of the Hillsboro Canal. The county lines and the city limits of Boca Raton and Deefield Beach coincide with the Hillsboro Canal except near the mouth of the canal. The area is divided into three physiographic sub-areas (Fig. 1): (1) coastal lowlands-barrier island; (2) coastal ridge; and (3) interior flatlands and the Everglades.
The barrier islands parallel the mainland and are separated from it by the Intracoastal Waterway. Barrier islands extend intermittently along most of Florida's east coast. Relic sand dunes form the island in the study area and reach heights of more than 25 feet above msl (mean sea level) in some locations. The white, sandy beach on the ocean side of the island is one of the main tourist attractions in the area. The coastal lowland on the mainland is characterized by mangrove swamps adjacent to the Intracoastal Waterway and is generally less than 5 feet above msl except where dredging and filling has taken place for housing developments.
Paralleling the coastal lowland is the coastal ridge. In Deerfield Beach the ridge is relatively wide and flat, reaching a maximum elevation of about 25 feet above msl. However, in Boca Raton it is narrower, dissected, relatively steep-sided, and reaches a maximum elevation of nearly 40 feet above msl. The ridge is composed of white sand containing varying amounts of shelly material. Westward from the crest of the ridge the land surface slopes to the interior flatlands; in Deerfield Beach the slope is gentle but in Boca Raton it is steep, especially in the vicinity of the El Rio Canal along the west flank of the ridge.
The interior flatland extends westward from the coastal ridge to the Everglades. It is characterized by a relatively flat surface and supports a natural growth of palmettos, pine trees, and a variety of palm trees. The average elevation of the interior flatland is about 15 feet above msl.
CLIMATE
The climate of the lower Hillsboro Canal area is humid subtropical. The nearness of the Atlantic Ocean accounts for the high humidity




4 BUREAU OF GEOLOGY
I' 10, 09* OS1 07' 06 Os'_ 05
I i
CAIA L38 A I
k
_25
CovEREDB THIS REPORT > U.I
EXPLANATION
2j - 20 Z HIGHWAY
CANL O CAAL
~o
1
z
NILL50- CANL.. -j -".
DEERFIELD
BEACH
0 1 MILE
0 07' 0 5 04" 03"
Figure 1. Location of lower Hillsboro Canal area, Florida showing physiographic
subdivisions.
but the Gulf Stream moderates the temperature. The average monthly temperatures for January and August during the period 1946 through 1967 were 68 F. and 820 F. The average annual temperature for that
period was 750 F. (U.S. Weather Bureau).
Rainfall in the area is unevenly distributed with time and location.
The average annual rainfall for the long-term period 1951-1967 is nearly 60 inches. During this period five years were above average, five years were below average, three years were approximately average, and
four years were not totaled because of incomplete data.




REPORT OF INVESTIGATION NO. 55 5
TABLE 1- MONTHLY RAINFALL AT BOCA RATON, FLA.1
(inches)
1961 1962 1963 1964 1965 1966 1967
January 8.56 0.47 2.93 1.85 0.73 3.27 2.41 February .85 .69 6.18 3.82 5.25 5.79 2.34 March 1.09 3.41 4.73 3.20 .97 1.85 3.57 April .67 6.51 .93 4.36 .71 1.66 0.00 May 6.47 1.91 13.01 6.20 1.22 4.93 2.07 June 2.80 5.20 7.47 7.93 10.91 16.51 11.86 July 1.22 10.42 2.02 5.31 11.01 7.63 3.71 August 5.06 6.08 5.43 7.89 3.44 6.18 6.83 September 4.50 7.59 12.51 6.31 4.24 8.32 7.41 October 6.93 1.98 7.11 11.13 29.64 6.95 5.42 November 1.09 1.63 2.42 .63 3.94 1.06 3.71 December .16 .88 3.74 1.93 1.01 1.00 1.72
TOTALS 39.40 46.77 68.48 60.56 73.07 65.15 51.05
SRecord from U.S. Weather Bureau's Climatological Data.
Table 1 shows the monthly rainfall recorded at Boca Raton for the period 1961 through 1967. This period was chosen for presentation because it includes the two dry years preceding the beginning of the study. The average for this periodis 58 inches, or two inches below the long-term average. Abnormally heavy rainfall was recorded during October 1965. Most of the rain occurred during the middle and at the end of the month. At Pompano Beach, shown in figure 2, 24 inches of rainfall was recorded in 24 hours on October 31 and November 1.
POPULATION AND INDUSTRY
The lower Hillsboro Canal area has been strongly affected by the population boom of southeastern Florida. The area has grown in population from about 3,000 in 1950 to more than 36,000 in 1966. The predicted population for 1970 exceeds 50,000.
Although Boca Raton and Deerfield Beach are primarily tourist and retirement communities, both cities have planned for the expansion of light, clean industries. The largest employers are the private and chain sales and service stores. Agriculture contributes significantly to the economy of the area. Several private and state-owned educational institutions also play a part in the overall economic structure.




6 BUREAU OF GEOLOGY
CONSERVATION o .I ,z
AREA N0. I
PALU BEACH COUNTY BOCA RATON CONSERVATIO -- (D~~ EERFIELD
BROWARD COUNTY L-. BEACH
f/EACH
AREA NO.2 c14 POMPANOCH
CONSERVATION A --- AKLAND FORT
sLAUDERDALE
AREA NO..
II EXPLANATION CANAL
LEVEE
BROWARD COUNTY
DADE COUNTY 0 5 MILES
MIAMI
Figure 2. Parts of Broward and Palm Beach counties showing canals and levees of
the Central and Southern Florida Flood Control Project and the Lake
Worth Drainage District.
HYDROLOGIC SETTING
The lower Hillsboro Canal area abounds in water: the Atlantic Ocean is to the east and the vast water control works of the Central and Southern Florida Flood Control District (FCD) is to the far west and south (Fig. 2). A latticework of controlled canals of the Lake Worth Drainage District (LWDD) is immediately adjacent to the north and west sides of Boca Raton; the canals of the FCD and the LWDD were constructed primarily to improve drainage during periods of high rainfall. The canals cut across the top of permeable shallow sediments called the Biscayne aquifer. During periods of low rainfall, the canals convey water from inland areas and replenish the aquifer by induced infiltration. Because rainfall is the primary source of replenishment to




REPORT OF INVESTIGATION NO. 55 7
the Biscayne aquifer, water levels are highest during the wet part of the year and lowest during the dry.
BISCAYNE AQUIFER
All fresh ground-water supplies in the lower Hillsboro Canal area are obtained from the Biscayne aquifer. The aquifer extends from land surface to a depth of about 400 feet (Tarver, 1964). Eight test wells were drilled in the area to augment available data in determining the lithologic composition of the upper part of the aquifer. Figure 3 shows locations. The wells ranged in depth from 127 to 208 feet below the land surface. Data from these wells were used in preparing the geologic sections in Figures 4 and 5.
The Pamlico Sand of Pleistocene age blankets most of the lower Hillsboro Canal area and is the uppermost unit of the Biscayne aquifer. It is composed of very fine to coarse quartz sand, white to black or red, depending upon the staining materials. The Anastasia Formation of Pleistocene age underlies the Pamlico Sand and is composed of coquina, sand, indurated calcarcous sand, and sandy limestone. The Anastasia Formation is the principal source of water from the Biscayne aquifer in the lower Hillsboro Canal area.
The Tamiami Formation of late Miocene age underlies the Anastasia Formation. Permeable limestone beds in the upper part of the Tamiami Formation constitute the basal part of the Biscayne aquifer. The formation is tapped by few wells in the lower Hillsboro Canal area because equally good water and comparable yields can be obtained from wells that are bottomed in shallower limestones in the Anastasia Formation.
Rock materials penetrated by the test wells are shown by Figure 4. Test-well data plus data from a few existing wells were used to draw Figure 5. Both Figures show that sand covers the lower Hillsboro Canal area to depths as much as 60 feet below the land surface. The Pamlico Sand accounts for about 20 feet of this section in the Deerfield Beach area and as much as 50 feet in the Boca Raton area. The geologic sections show that the limestone beds are discontinuous vertically and horizontally. Additional information from drillers in the area indicates that limestone beds are more persistent in the Deerfield Beach area than in the Boca Raton area.
Beds of indurated calcareous sand, or sandy limestone are widespread enough through the lower Hillsboro Canal area that wells can usually be finished with open holes below the casing. However, irrigation and municipal wells subject to heavy withdrawals are usually screened and gravel packed. In the western part of the area private




S BUREAU OF GEOLOGY
1s o o09 a 07 06 os
. ..- II I,
I I Cditis L-38
489+
SCAMLS CONTI OLo
*OnSERVATION WELL
TEST WELL
* MUNICIPAL SUPPLY WELL
s WATE-LEVEL RECORDER
7 SLINFtCIE- a MEASURING POINT
A--A LINE OF GEOLOGIC SECTION
CAAL L 43 P 5
''9
n ?
aB 9 o_ O55a PS 549
49 09 0 06 0 0d0 SALIN oaP4
A BARRIER p INRAC TAt 22 WATER SY
PG484 o 47 CANAL 47 *
a BOCA RATON ,"
a0 o
a
geologicseoions.
AMMADM COUNTY
o* 1214 DEERFIELD o a0 BEACH
supply wells penetrate perm eable material at depths ranging from 60 to 90 feet. This perm eable material could be the same limestone as that penetrated at 70 feet in well PB488 or the shelly, friable limestone
Figure 3. Map of lower Hilsboro Canal area showing location of wells PB-556, 557, and 558 (see Fig. 3 for
locations).geologic sections.
supply wells penetrate permeable material at depths ranging from 60 to 90 feet. This permeable material could be the same limestone as that penetrated at 70 feet in well PB488 or the shelly, friable-limestone penetrated at 89 feet in wells PB-556, 557, and 558 (see Fig. 3 for locations). .
The Boca Raton well field obtains water from the limestone shown by well PB 548 in Figure 5. The limestone is discontinuous and becomes increasingly sandy to the north. This is indicated by the




REPORT OF INVESTIGATION NO. 55 9
.J
z
A o0 A
D EALEVEL
40'- 40
so' a. a a
I20'r- -3I~ 12 .. ... 0. O r
SEA i il ii il ii i SEA
... .. . 8 0.. .
200--20
EXPLANATION
CALCAREOUS SHELL SAND SANDYLEVEL
SAND LIMESTONE
.. . ........................ .................... ............
:: .....: = :: .....:. :::. :...:..:.:::::: .. .. .. .. .
.. . .. ..........:: : :: : :: : : :: : . ..... .. . . . .. ... . .
.. . .... ... .......... ..............:.
0 .. IMILE0'
Figure 4. Geologic section of the Biscayne aquifer in the lower Hillsboro Canal
area along line A-A' in figure 3.
absence of dense limestone in wells PB489, PB549 and PB550. Wells in the original Deerfield Beach well field and the southern extension are obtaining water from the limestone shown in wells G-1228 and G-1272 in Figure 5.FLORIDAN AQUIFER
The Floridan aquifer is a thick sequence of highly permeable
. limestone underlying most of Florida. In the central and western parts
of the Florida peninsula the aquifer is exposed or covered by relatively thin layers of sand, but ini the southeastern part of the state the aquifer
;r .. .. .. .. .. ....... ... .....
: : ,+.. . . . . . . . . .. . . . .
4 !:: E ;ii.- i ii i~ - : -!'. ..'.'. .. 8
.... i........ .... .... .F. .... I .. i i .,i
16 0 '- .. .... ....... :: : : i iii i : 1 0
:' .. .... ....: : : : : : : :: : : ...
12 0 .. ... .;.L ,. .......- 2
00'. 200'.
....L....I..
CALCAREOUS. SHELL .... SND
SAND_ L 200ON
0 MILE
Figure 4. Geologic section of the Biscayne aquifer in the lower Hillsboro Canal
area along line A-A' in figure 3.
absence of dense limestone in wells PB489, PB549 and PB550. Wells in the original Deerfield Beach well field and the southern extension are obtaining water from the limestone shown in wells G-1 228 and G- 1272 in Figure 5.0 .
FLORIDAN AQUIFER,The Floridan aquifer- is a thick sequence of highly permeable limestone underlying most of Florida. In the central- and westernparts of the Florida peninsula the aquifer is exposed or covered by relatively thin layers of *sand, bu-tinthe southeaste part of thie.state the aquife




W
0
o
a. B
B 0 B
S40 40 40- In 04 1
---
8 0 19 *:: : :::::::: : ::::::.. *:: ..: ..
40 c -4
80o 8 rD AE A 0 ATI
L..E .... .J1.4i.i. . "" "
I-SOAND".4:::'. to 120- -120- P.A M L. -,.:!!i I C i 0 : : :: .... ........ 1 0
5,7 40 5
. ......:: : ..-...:':' mm:::'::::, ," :.'" :';::'
160 ....1 6... .
: ;~ ~~~~~ .:. .' : ;. ............ ...... .... .,W :: a d" :
20.. ...... ...EXPLANATION -200'
CALCAREOUS SHELL LIMESTONE SAND SANDY
SAND LIMESTONE
0 MILE
Figure 5. Geologic section of the Biscayne aquifer in the lower Hillsboro Canal area along line B-B' in
figure 8.




REPORT OF INVESTIGATION NO. 55 11
is about 1,000 feet below the land surface and the water is under greater than atmospheric pressure. The water level in a well penetrating this aquifer in the lower Hillsboro Canal area will rise more than 25 feet above msl. Such a well may yield as much as 2,000 gpm (gallons per minute) by natural flow. However, in the study area, as in most of south Florida, water from the Floridan aquifer is too mineralized for most uses. Because of the tremendous quantities of water available, the upper, less mineralized part of the aquifer, may be considered as a potential source of supplemental water. However, the deeper, more mineralized part of the aquifer is already being used as a reservoir for discharge of chemical wastes near Lake Okeechobee, and sewage wastes for a municipality near Pompano Beach.
SURFACE FLOW SYSTEM
The Hillsboro Canal is one of the primary canals of the controlled network of the regional Central and Southern Florida Flood Control District (FCD) as shown in Figure 2. The Hillsboro Canal extends eastward from Lake Okeechobee between water Conservation Areas 1 and 2, where excess water is stored, to the Intracoastal Waterway. The canal not only provides gravity drainage for flood control, but also conveys water from the conservation areas eastward for replenishment of the aquifer near the coast during droughts. This is accomplished by keeping the control structure near the coast closed during the dry season, thereby maintaining water levels in the canal higher than the adjacent ground-water levels. During wet periods when ground-water levels begin to rise higher than the canal levels the control structure is opened to prevent flooding and the canal level and ground-water levels are lowered.
Water levels in Boca Raton are affected more by operations of the Lake Worth Drainage District than by the Hillsboro Canal. The Lake Worth Drainage District is immediately west of Boca Raton (Fig. 2) and consists of a system of controlled canals. The primary (equalizing) canals flow southward bringing water during wet periods from areas north of Boca Raton and discharge excess waters into the Hillsboro Canal several hundred feet east of the control structure. The secondary (lateral) canals are oriented east-west and connect to primary canals.
In September 1965 a salinity barrier was constructed on the El Rio Canal about 1,600 feet north of State Road 808 bridge to prevent sea-water intrusion into the Boca Raton well field. The barrier was placed as far downstream as economically feasible.




12 BUREAU OF GEOLOGY
GROUND WATER
Ground water occurs beneath the land surface in the zone of saturation where it fills the interstices, joints, crevices, fissures, solution holes, and any or all other voids and is the supply for springs and wells (Meinzer, 1923, p. 38-39). The subsurface formations containing ground water, and from which this water is collectible for use, are called aquifers.
The upper surface of the zone of saturation, which is under atmospheric pressure and free to rise and fall, is called thewater table. Where ground water is confined in a permeable bed overlain by a relatively impermeable bed its surface is not free to rise and fall and the water is under greater than atmospheric pressure. Water thus confined under pressure is called artesian. Direction of ground-water movement is from areas of high water levels to areas of low water levels.
The Biscayne aquifer is essentially a nonartesian (or water-table) aquifer, but in most locations in the lower Hillsboro Canal area the permeable limestone beds are partly confined by discontinuous overlying layers or lenses of less permeable materials.
RECHARGE AND DISCHARGE
The amount of fresh water potentially available in the lower Hillsboro Canal area is determined by the recharge to and discharge from the Biscayne aquifer and the quantity available from storage in the aquifer. Infiltration of rainfall through surface materials and seepage from controlled canals are the means of recharge. Recharge by rainfall is greatest, naturally, during the rainy season of June to November. Recharge from canals is greatest during the dry season, December to May, when canal levels are higher than adjacent water levels in the aquifer.
Discharge from the aquifer is by evapotranspiration, by groundwater flow to canals and by pumping from wells. Discharge by groundwater and surface-water flow and losses by evapotranspiration are greatest during and after periods of rainfall when water levels are high; discharge by pumping from wells is greatest during the dry periods, at the peak of the tourist season. Discharge by wells constitutes only a small part of the total discharge from the area.
The average annual rainfall of 60 inches evenly distributed over the lower Hillsboro Canal area would be equivalent to about 170 mgd (million gallons per day). Probably as much as 100 mgd would be lost by evapotranspiration and discharge to the ocean. The remaining 70 mgd would be available to recharge the aquifer.




REPORT OF INVESTIGATION NO. 55 13
WATER-LEVEL FLUCTATIONS
Ground water in the Biscayne aquifer moves from areas where water levels are high to areas where water levels are low. Water levels are highest in recharge areas or in areas that are the greatest distance from points of discharge; water levels are lowest in discharge areas along the coast, along uncontrolled drainage canals, or in the vicinity of heavy pumping.
Fluctuations of the water levels reflect the effects of recharge to and discharge from the aquifer. Water levels in the lower Hillsboro Canal area fluctuate in response to rainfall in the immediate area; therefore water levels generally are high during the rainy season (JuneNovember) and low during the dry season (December-May). A rise in water levels does not register the total replenishment to the aquifer, but the rise is an indication of the excess of the recharge over the discharge. Fluctuations are determined by water-level measurements in a network of observation stations in canals and on wells; some stations are equipped with automatic recording instruments which provide continuous, detailed records. The network is shown in Figure 3.
Water level changes in selected wells in Boca Raton and Deerfield Beach for the period 1963-67 are shown by hydrographs on Figures 6 and 7. Monthly rainfall at Boca Raton is shown for the purpose of correlation. The hydrographs show both the day-to-day changes and the long-term trends. Well PB 470 (Fig. 6) is on the coastal ridge about a half mile east of the Boca Raton municipal well field, and the water level in the well is mildly influenced by well-field withdrawals. During extended dry periods, such as the spring of 1964 and 1965, water levels there approached one foot above msl. On the other hand, water levels in the vicinity of well PB 488 (Fig. 6) about 2 miles west of the well field are not affected by well-field withdrawals and remain high throughout most of the year. During 1967, levels near well PB 488 were 5 feet or more higher than levels east of the well field. Also, the magnitude of fluctuations at well PB 470 is greater than it is at well PB 488 because well PB 470 is influenced by well field pumping and is located near the coast where ground water is being discharged into the Intracoastal Waterway.
The hydrographs of both wells show that the response to rainfall is rapid, indicating that infiltration to the water table takes place quickly.
The hydrograph of well G-1260 (Fig, 7) in Deerfield Beach, 1500 feet west of the municipal well field, is similar to that of well PB-470 in Boca Raton. Levels in the Deerfield Beach well are generally higher than those in the Boca Raton well because the Deerfield Beach well is




14 P
2 w32
-j
, PS-488 Mo ,,. -to
Z -24
6* o RNo to -RO PS-470 .,
i 'N, RECOR, 24
-W
Ea.
- Ne .i 12
HI
0 hi HIM111111I
Fi iig Hdoa owellsnd rton, 1963 -19 67.
1963 1964 1965 1966 197
Figure 6. Hydrographs of wells PB 470 and PB 488 and monthly rainfall at Boca Raton, 1963-1967.




14 5
I2 -52 .J
10 -28
_1
w
w ,
U, 0 Sa- -24 LL, no RECORD 1-1260 No RcoRD
-- -1214- \0=20
Fiur 7 ~. Hyd h o 21 16 EC D
R a
H!: 11 11S.
: i 111 ...... I IN .
". .i.... ...., 4
-- t il iiiii!
RatoI 1968-1967.
III~~~~~iti~~~~i.. .iiil ...............: : ..... .... ..
IIell, 1964 1965 1966 1967 3
Figure 7. Hydrographs of wells G 1214 and G 1260 at Deerfield Beach and monthly rainfall at Boca
Raton, 1963-1967.




16 BUREAU OF GEOLOGY
1n 09 0 07 6 05
EXPCNL AML25'
-IGWAY
CANALS CONTROL OBSERVATION WELL
+ TEST WELL
* MUNICIPAL SUPPLY WELL A WIRM-LEVEL RECORDER
02
7 .SURFACE-WATER MEAURING POINT0V R-AII. cONTOR ,DASHED WHERE
MAY 7 19~O
CANALi L22'
ae ul o
sina oniurtonofte aersrfc focopcfi ie iure 8
CANAL L-47
a. BOCA RATON_ -2
20 0 20
MIL.LSBORO CANAVL ..
DERFCIELD
0 MILE
Figure 8. Water-table contour nap of the lower Hillsboro Canal area, May 7,
1965, durng low-water conditions.
farther from an area of natural discharge (Hillsboro Canal), and because the significantly lower pumping rate at the Deerfield Beach well field causes less drawdown of water level.
Water-level contour maps are representations of the three-dimensional configuration of the water surface for a specific time. Figure 8 shows the configuration of the water table on May 7, 1965 the record low-water levels for the period 1963-1967. For the time this




REPORT OF INVESTIGATION NO. 55 17
map was made, rainfall had been deficient for about seven months, and pumpage from the two municipal well fields was record high as shown in figures 9 and 10. The irrigation system west of Deerfield Beach was continuously pumping water from the Hillsboro Canal into a network of irrigation canals (not shown in Fig. 8) thus maintaining relatively high water levels in the west during the drought.
The configuration of the contours north of the Boca Raton well field shows that ground water was discharging into the El Rio Canal, but adjacent to and for some distance southward of the well field, water from the El Rio Canal was recharging the well field by induced infiltration. This was because heavy withdrawals of water had lowered the water table to four feet below msl in the well field. In addition, these withdrawals lowered the water-table mound between the well field and the Intracoastal Waterway to one foot above msl. Water levels north of Boca Raton remained relatively high due to very little pumping and the fact that less permeable sandy materials retarded the lateral movement of the ground water.
In the Deerfield Beach area, hydrologic conditions contrast rather sharply with those in Boca Raton. Water from the recharge area west of the. well field, and outseepage of water from the controlled reach of the Hillsboro Canal maintained relatively high water levels in the vicinity of the well field. Pumping lowered water levels in the Deerfield Beach well field only to about one foot above msl, which was considerably higher than the pumping levels in the Boca Raton field. However, the watertable mound between the Deerfield Beach well field and the tidal reach of the Hillsboro Canal was still only one foot above msl.
Figure 11 represents the configuration of the water table on November 1, 1965 the highest water levels for the period 1963-67. The absence of depression contour lines in the well fields indicates that municipal pumping was not significantly affecting the configuration of the water table at that time.
A salinity barrier was constructed in the El Rio Canal in September 1965 about one-half mile north of the State Road 808 bridge. The top of the barrier is two feet above msl and is designed to limit tidal flow in the canal and to impound fresh water upstream of the barrier for recharge to the well field. The water level in the canal was above the top of the salinity barrier at the time the map in figure 11 was compiled; therefore the effect of the barrier can not be seen.
The coastal ridge is delineated by the high water-level contours paralleling the coast. The saddle in the contour lines east of the Boca Raton well field corresponds to a natural depression in the land surface. The distorted contour lines in and northeast of the Deerfield Beach well field conform to a natural drainageway.




300 36
275- EXPLANATION -32
E PUMPAGE
RAINFALL
250. '26
225- .24 ..j
z
0
9 j
2 0- Nd lei
,,, Iiji t.MIMI! 0
/ 9*:1:64J965196 167~
F 9 p w1ma p d a B.6
I H11 21' ill* 1
2. Ii1 .' I Ml
1963 964 165 196il 96
Figur 9. Gahsoig4nhymncplpmaeadrifl tBc ao,16-




160 '32 EXPLANATION
14(> 28 PUMPAGE
- RAINFALL
120 -24
!H0
-J80 .16J .. M- ... ... x
601 J.... ........{
E N{{ :i1..i ...... ..... .. ........
I 2"'" 8iii!iiiiiiiiiii!!iii!ii ,,,,!iiiiiiiii~ i~ I' ' .'" ' '
... .. ) .. ... . ....... ...... .. ...Hii!{! i ii i o
0. .......... 0
1963 1964 1965 1966 1967
Figure 10. Graph showing monthly municipal purnpage at Deerfield Beach and monthly rainfall at Boca
Raton, 1963 67




20 BUREAU OF GEOLOGY
0ao as7 06 0s .
I CANAL L-38
EXPLANATION 25
CAnALS CONTROL
* OSERTION WELL
+ TEST WILL
* MNICIPAL SUPPLY WELL A WiER-LEVIL RECORDER
7 SURFACE-WATER MEASURING POINT
---- ATER-TABLE OITOUR (FET.M SL)
S NOV. 1 .1965
~o iro o/
CANAL L-43 o ~0
0 0
AWRAcoAsrL 2
t""-_ BOCA RATON-,,(2
HILLSBRO CANAL
I :i; -1-110101 COUNTY DEERFIELD
BEACH
0 MILE
a IB::{
1I 15 141312ttl 0 IMILE o 09" 0 07 00 004
Figure 11. Water-table contour map of the lower Hillsboro Canal area, November 1, 1965, during high-water conditions.
The net increase in storage in the aquifer from May 7 to November 1, 1965, is shown by the rise in water level on Figure 12. The average rise in water levels from the low period to the high period was about six feet for the area contoured, and the average estimated rise in the remainder of the area was about two feet. If an average porosity of 25 percent is assumed for the Biscayne aquifer in the area, then the rise in levels during the period represents an increase in storage of about 10.2




REPORT OF INVESTIGATION NO. 55 21
tO* 09 OR 07 0"
EXPLANATION
-HIGHWAY
CANALS I CONTROL
o OBSERVATION WELL
+ TEST WELL I
* MUNICIPAL SUPPLY WELL
A WATER-LEVEL RECORDER
v SURFACE-WATER MEASURING POINT
-5- CONTOUR LINE SHOWING RISE IN
WATER LEVELS,FFET, FROM MAY 7
TO NOV. 1.1965
CANAL L-43 o 0
0U
goe 0a
b0 o iRAcoAsT urn INTEMAY
tisi- th CANAL o- 47rl 00 inhe Vfi uigOtbr(
0U
2i 'BOCA RATON-,2,
26I
.HILLSBORO CANAL
o 0 PALM BEACN COUNTY 31 CZ BRWR COUNT
0 IL
19 E R I L
0B 1 1 to
sT 10' 09 os or o0 05 eo
Figure 12. Contour map showing rise in water levels from May 7 to November 1,
1965, in the lower Hillsboro Canal area.
billion gallons or 60 mngd. This large increase in net storage was possible because over 60 inches of rainfall was recorded at Boca Raton during this six-month period nearly 30 inches of it during October (see Table 1), resulting in this substantial recharging of the aquifer.
Figures 13 and 14 reflect high and low water level conditions on October 27, 1966 and April 12, 1967. Additional shallow observation wells were installed in the inland area between the El Rio Canal and




22 BUREAU OF GEOLOGY
: 09 o 07 6 03 oi ~o.
a I
CAMAL L -38 M 2.
2 X ATION25
*CANALS CONTROL
SOSUM0ON WELL
+ TEST WELL
MUNICIPAL SUPPLY WELL
2 ,.-- n WTER-LEVEL RECORDER POIN_ .=
SSUIRFACE-WATER MEASURING POINT
'5-WATER-TABLE CONTOUR ( FEET M.SL
OCT 27,1966 S C
CANAL L-43I
3 o
23 or- 3
72 072
CANAL L-47
*DOCA RATON 21
-20
HILLSBORO CANAL .3
b DEERFIELD $EACH
oo
0 1 MILE
07- 06 0S Jd21
Figure 13. Water-table contour map of the lower Hillsboro Canal area, October 27, 1966, during high-water conditions.
Canal E-3 in the Boca Raton area and around the Deerfield Beach well field to allow monitoring of the effects of the salinity barrier on the El Rio Canal, the extension of the configuration of the water table west of the El Rio Canal, and more accurate delineation of the pumpinglevels in the Deerfield Beach well field.
The top of the control structure on Canal E-3 just north of L-43 is about 16 feet above msl, and the top of the structure near the Hillsboro




REPORT OF INVESTIGATION NO. 55 23
2 0 30 09' o 07 0 05' 04
CANAL L -38
25 EXPLANATION s
- H IGGWAY +
- CANALS I CONTROL cP
o -OBSERVATION WELL
TEST WELL
* MUNICIPAL SUPPLY WELL
24 A WATER-LEVEL RECORDER I
v SURFACE-WATER MEASURING POINT
-5- WATER-TABLE CONTOUR DASHED WHERE
INFERRED FEET MSL) 0
APRIL 12,1967 i 0
CANAL L-4 /
0 0
0
0 '6
2i e 9D
VATWAMNWAY
21 0 0arac0sra
CANAL L-47o -o.
o1 1oo O A AT N
HILLSBORO CANAL
toPALM BEACH COUNTY
-- W RROIIWARD COUNTY
" DEERFIELD ~BEACH
0 I MILE
1011 '- 0 09 8 7 06r 05" 01f 0~e1
Figure 14. Water-table contour map of the lower Hillsboro Canal area, April 12,
1967, during low-water conditions.
Canal is set at about 12 feet above msl. Thus when canal levels in the northern reach of Canal E-3 exceed 16 feet msl, the excess water is discharged southward where it is impounded until it reaches, a level about 12 feet msl. When levels exceed 12 feet at the lower structure, water is discharged into the uncontrolled reach of the Hillsboro Canal.
The contours in Figure 13 represent high water levels of October 27, 1966, and show that the water table west of the El Rio Canal was




24 BUREAU OF GEOLOGY
approximately the same level as the water table west of Deerfield Beach. The similar water table levels are due primarily to Canal E-3 replenishing :he aquifer west of the El Rio in the same manner as the irrigation district west of Deerfield Beach replenishes the aquifer there. Small drainage canals have reduced water levels in the highly urbanized area adjacent to the west side of the El Rio Canal. The drawdown in the Boca Raton well field is small because of the reduction in pumping (see Fig. 9). The depression contours have extended west of the Deerfield Beach well field, probably as a result of large withdrawals for irrigation at the municipal golf course. The control structure on the Hillsboro Canal was closed and was maintaining a canal level more than seven feet above msl on the upstream side. The level in Canal E-2 upstream of the control at the Hillsboro Canal was more than 10 feet above msl.
Figure 14 depicts the low water conditions of April 12, 1967 and shows the effects of the pumping in the well-field extensions of the two cities. Although withdrawals from each well field are at record high, the pumping levels do not exceed the record low levels in either well field (Fig. 8). Instead, the pumping level in the Boca Raton well field was two feet higher than on May 7, 1965 (Fig. 8). This higher level is due in part to the recharge contributed to the Boca Raton well field extension from the controlled reach of the El Rio Canal. The position of the zero contour line in figure 14 is more than a quarter of a mile farther from the canal than it was in Figure 8. The additional pumping in the well field extension in Deerfield Beach made the pumping level depression more circular and displaced it farther inland from the tidal reach of the Hillsboro Canal.
HYDRAULIC PROPERTIES
The hydraulic properties of the Biscayne aquifer must be known in order to determine the ground-water potential of the area and to plan properly for large-scale withdrawals of ground water. The principal properties of an aquifer are its capacities to transmit and store water, which are generally expressed as transmissivity and the storage coefficient. Transmissivity (T) is the quantity of water in gallons per day that will flow through a vertical section of the aquifer one foot wide and extending the full saturated height, under unit hydraulic gradient, at the prevailing temperature of water (Theis, 1938, p. 892). The storage coefficient (S) is defined as the volume of water released from or taken int6 storage per itffit surface area of the-aquifer per unit change in the component of head normal to that surface. The most commonly used method for determining these properties is by an aquifer test, whereby a well penetrating the aquifer is pumped and the




REPORT OF INVESTIGATION NO. 55 25
resultant lowering of the water table in nearby nonpumped wells is observed to relate the lowering of the water level to distance and time.
Aquifer tests were made on wells in the Deerfield Beach well field in August 1961 and on test wells west of Boca Raton (Fig. 3) in August 1967. In both areas the water is pumped from permeable limestone that is overlain by thick sections of less permeable sand, silt, shells, and marl. In the test west of Boca Raton, well PB-556 was pumped and water levels were observed in well PB-558 200 feet to the east. Both wells are 92 feet deep with 89 feet of casing. In Deerfield Beach, municipal well number 9, which is 90 feet deep with 80 feet of casing was pumped and water levels were recorded in an observation well 95 feet deep with 80 feet of casing and 100 feet to the east.
The data collected from the aquifer tests were analyzed by the leaky-aquifer method described by Hantush (1956, p. 702) which assumes, among other things, that the aquifer is artesian, is overlain by a leaky confining bed, and that the pumped well is open to the full thickness of the aquifer. None of these assumptions were completely satisfied in either of the two tests. Although under long-term conditions water levels in the Biscayne aquifer respond as if the aquifer were a water-table aquifer, the presence of less permeable sands overlying the highly permeable pumped zone causes the aquifer to react as a leaky artesian system when subjected to short-term conditions such as heavy pumping. Also, none of the wells in the lower Hillsboro Canal area are open to the full thickness of the Biscayne aquifer.
The water level drawdowns, in feet, were plotted (on logarithmic paper) against the quantity t/r2, where t is time, in minutes, since pumping started, and r is the distance, in feet, between the pumping well and the observation well. The resulting curve was matched to a family of leaky-aquifer type curves (Cooper, 1963 p. C-48-55). By superposition, match points were established for the best fit of the observed data to the type curves, and the T and S were calculated from the match points. For the test west of Boca Raton the T was 380,000 gpd/ft (gallons per day per foot) and at the test in Deerfield Beach, the T was 400,000 gpd/ft. The value for S at the test site west of Boca Raton was 0.04. At the Deerfield Beach test site the value for S was
0.0004.
Values obtained from specific capacity tests of wells indicate to some extent the hydraulic properties of the aquifer and in some cases are of more immediate benefit than T and S values. The specific capacity is the amount of water in gpm discharged from a pumping well per foot of drawdown in the pumping well.
Specific capacity tests were made on several wells in the north extension of the Boca Raton well field. Well PB 550 had a drawdown of




26 BUREAU OF GEOLOGY
about three feet after being pumped for 8 hours at 1130 gpm or a specific capacity of 377 gpm per foot. This figure conforms with the data from the test wells west of Boca Raton and is similar to figures furnished by Dr. J. I. Garcia-Bengochea (personal communication) for wells in the Boca Raton and Deerfield Beach well fields. This indicates that the hydraulic properties of the aquifer in both well fields and the test area west of Boca Raton are similar.
The wells in the Boca Raton field range in depth from 115 to 120 feet with about 25 to 35 feet of open hole. The fact that the aquifer yields about the same amount of water to wells with 10-15 feet of open hole in the Deerfield Beach well field and 3 feet in the test area west of Boca Raton, and 25-35 feet in the Boca Raton well field, indicates that the aquifer is somewhat less permeable in the Boca Raton well field area than it is in the other areas.
WATER QUALITY
Major influences on the quality of fresh ground water in the lower Hillsboro Canal area are the quality of precipitation that reaches the water table and the infiltration, from canals draining inland areas, of highly colored water that is moderately mineralized. The chemical characteristics of the ground water also depend upon composition of the earth material through which the water moves and length of time the water is in contact with the materials.
Ground-water samples for chemical analyses were collected throughout the area from 26 private wells and 8 test wells. Depth of the wells ranged from 40 to 206 feet below land surface; samples were collected at different depths during drilling of each test well. Chemical analyses of water samples are shown in Table 2. The concentration of dissolved constituents is expressed as mg/l (milligrams per liter).
Iron, the most objectionable constituent found in solution in the ground water of this area, is derived from iron-bearing minerals within the aquifer. In samples analyzed, iron ranged from 0.03 to 1.83 mg/l and the average was about 0.45 mg/l. For public supply iron concentrations in excess of 0.3 mg/fl are objectionable and impart a noticeable taste if the concentration exceeds 0.5 mg/1. When used for lawn irrigation, water containing iron in excess of 0.3 mg/1 may cause staining on houses, sidewalks, and vegetation. The concentration of dissolved iron in ground water in thelower Hillsboro Canal area cannot be accurately predicted with reference to location or depth. Removal of iron from large volumes of water can be accomplished economically by aeration and filtration.




REPORT OF INVESTIGATION NO. 55 27
Hardness of water results from the solution of alkaline-earth minerals (such as the carbonate compounds) from soil and rocks, or from direct pollution by wastes. Calcium carbonate (limestone) is prevalent in the Hillsboro Canal area but is only sparingly soluble in pure water. Water that contains carbon dioxide or other acidic constituents will dissolve carbonate minerals readily; in the presence of carbon dioxide the carbonates are converted to the more soluble bicarbonates:
CaCO3 + CO2 + H20 ~ Ca(HCO3)2
Hard water is generally believed to be harmless to man although urinary concretions may result from the consistent drinking of hard water (Rainwater, 1960, p. 173). Water having CaCO3 concentration in excess of 120 mg/1 is considered hard. The CaCO3 concentration of water sampled in the study area ranged from 126 to 368 mg/1 and averaged about 235 mg/1. Hardness increases with depth and with distance inland.
Acidity or alkalinity of water is measured by the hydrogen ion concentration (pH). Water that is neither acid nor alkaline has a pH value of 7.0. Values smaller than 7.0 denote acidity and usually indicate a corrosive water; values greater than 7.0 denote alkalinity. The pH values of the water analyzed ranged from 7.4 to 8.2 and averaged about 7.7, which is slightly alkaline and would be expected to be noncorrosive.
Color in water is expressed in terms of platinum-cobalt or Hazen units starting at zero and increasing with added color. Visible coloration of drinking water is aesthetically undesirable and concentrations in excess of 15 units is considered by U.S. Public Health Service (1962) to be unsuitable for use on interstate carriers. The range of concentration in the Hillsboro Canal area is from 0 to 50 units, the higher concentrations occurring in the western areas. Color in water is usually caused by decomposition of organic matter such as peat and muck which are common in the western part of the area and in buried mangrove swamps along the coast. Discoloration of water in the study area is also due partially to iron in solution. Material that causes high coloration in water can sometimes be recognized by its odor.
The odor of hydrogen sulfide gas (H2 S) was noted in water samples from some wells. This gas is derived from decomposition of organic matter, and it imparts an undesirable "sulphur water" odor which is easily removed by aeration. Hydrogen sulfide is not usually shown in standard complete analyses because of special techniques involved in obtaining samples.




28 BUREAU OF GEOLOGY TABLE 2 CHEMICALS ANALYSES OF WATER FROM SELECTED WELLS
IN THE LOWER HILLSBORO CANAL AREA (chemical constituents are expressed in milligrams per liter).
- 0
E -a .0 C13
E 0 0 0L u- .
Well Dateof .=
00 CL I :5 cc number' Collectlon I 3 I t C M o
61228 120-63 22 22 22 79 3.2 0.48 50 0.2 2.6 0.2 146 G-1228 01-06-64 185 195 195 79 9.8 .03 61 1.5 8.5 .6 176 G-1239 11-19-63 56 56 56 -- 3.3 .07 30 29 15 1.0 206 G-1239 11-25-63 102 102 102 73 14 .07 96 20 210 7.2 310 G-1272 02-01-65 62 61 62 71 6.0 -- 64 1.1 7.1 .6 204 6-1272 02403-65 173 168 173 - 8.9 - 62 1.3 8.0 .7 198 61298 03-12-64 165 -- 165 74 11 .12 138 5.7 22 1.2 293 6-1299 04-14-64 145 -- 145 75 15 1.38 138 5.7 23 1.0 388 G-1300 03-12-64 106 - 106 77 13 .42 123 1.6 17 1.3 384 G-1301 04-14-64 62 - 62 77 7.3 1.03 98 3.8 8.4 .4 288 -1302 03-12-64 100 -- 100 77 16 .82 135 3.6 29 1.1 364 G-1303 04-14-64 104- 104 75 19 .10 175 23 298 8.0 522 G-1304 04-05-62 83 -- 83 78 6.9 .70 68 .9 8.7 .5 194 -1314 03-12-64 - - 82 13 .98 139 4.1 15 1.0 422
PB-220 03-11-64 174 174 77 7.3 .78 86 2.8 12 .6 220 P-251 04-14-64 150 150 75 17 .30 82 3.3 13 1.4 250 PB472 01-24-64 97 -- 97 76 11 1.83 104 4.0 22 1.2 312 P-473 01-24-64 105 -- 105 76 12 .27 136 3.5 14 .6 404 PB474 03-10-64 56 54 56 78 7.4 .20 59 3.2 15 1.2 178 PB475 03-10-84-- - - 78 9.1 .25 66 2.8 12 .6 204
PB476 03-13-64 95-- 95 76 18 .31 84 1.6 13 1.2 250 PS-477 03-11-64 120 -- 120 78 5.5 .33 50 2.2 8.3 1.6 140 P-478 03-11-64 97 -- 97 77 8.9 .85 106 3.8 17 .5 236 PB479 03-11-64 121 -- 121 77 13 .32 78 2.8 12 1.1 240 P8480 03-11-64 40 -- 40 77 7.1 .39 104 15 115 3.9 200 P-481 03-13-64 112 -- 112 76 13 .32 133 1.9 16 1.1 396 PB482 03-13-64 75 -- 75 76 5.5 .11 110 3.8 22 1.4 328 P483 04-14-64 100 -- 100 77 14 .18 83 4.6 21 1.2 264 P-484 04-1464 120 -- 120 78 15 .05 90 3.3 14 1.0 274 P8-485 12-02-64 40 -- 40 - 5.9 1.30 94 1.3 10 1.4 260
PS486 12-02-64 30 -- 30 78 6.2 1.20 76 .6 8.3 1.3 228 P-487 12-03-64 80 -- 80 73 6.1 .12 100 4.5 65 3.0 194 P8-488 01-18 5 83 82 83 68 20 - 69 1.0 6.8 1.0 210 P8488 01-20-65 163 158 163 69 10 - 64 2.1 5.3 .6 194 P489 01-21-65 60 55 60 69 10 - 48 2.4 7.0 .8 140 P-489 01-25-65 208 204 208 69 11 - 125 1.9 21 1.6 356 P8490 01-26-65 65 61 65 72 7.6 - 75 3.2 22 .8 220 PB49 01-27-65 135 131 135 70 16 -- 220 81 700 7.0 282 P8491 01-28-65 66 61 66 71 5.5 -- 82 4.7 17 3.4 218 P84ST 01-30-65 205 202 205 68 9.6 - 1420 148 4850 30 261 PB492 02-04-65 81 79 81 71 7.8 -- 72 .1 18 1.0 212 P8-492 02-05-65 163 161 163 70 11 - 78 1.3 12 .8 248
1 2
G wellsare in Broward County 2 Sampled while drilling PBweilsare in Palm Beach County 3 Dissolved solids (Sum)




REPORT OF INVESTIGATION NO. 55 29
Hardness
as D
CaCO3 P
_- _. o
4.8 5.0- 0.5 0.0 144 126 6 232 .9 70 2
3.6 16 .3 .3 180 158 14 312 8.0 20 2
15 28 .1 .4 262 194 25 429 7.8 20 2 C32 340 .4 .1 872 320 6 1520 7.6 20 2 .0 8.0 .2 .1 187 164 0 317 7.9 10 2
CD a, .a E
- C C C L 00
U- z M cE z W C. Remarks
4.8 5.0- 0.5 0.0 144 126 6 232 -7.9 70 2
3.6 13 .1 .0 19180 15860 014 322 7.8 520 2 15 28 .1 .4 262 194 25 429 7.8 20 2 32 340 .4 .1 872 320 66 1520 7.6 20 2
.0 8.0 .2 .1 187 3 164 0 317 1.9 10 2 .0 13 .1 .0 1913 160 0, 322 7.8 5 2
32 36 .2 .1 494 368 47 740 7.6 25 Pumping 31 36 .2 .2 482 368 50 741 7.6 15 Pumping
.0 25 .3 .1 386 326 12 650 7.5 15
4.4 14 .3 .0 336 280 24 485 7.7 90 Pumped sample 17 63 .3 .0 492 352 54 755 7.7 20 120 518 .4 .6 1458 530 102 2700 7.7 10 7.2 15 .0 .0 204 168 9 360 7.9 25 .0 24 .3 .3 420 364 18 690 7.6 15 33 19 .2 .0 264 226 46 460 7.8 5
2.4 18 .3 1.3 294 218 13 435 7.6 20 Pumped sample
2.4 39 .3 .0 346 276 20 585 7.5 25 4.0 28 .4 .0 406 354 23 659 7.9 40 5.6 22 .1 .0 208 160 14 361 7.9 5 1.6 18 .1 .0 200 176 9 370 7.5 5 2.4 21 .3 .0 264 216 11 440 7.5 20
16 12 .2 .0 160 134 20 290 7.5 5 Pumped 68 30 .1 .0 406 280 86 585 7.4 25 .0 18 .1 .1 270 206 10 415 7.4 5 48 232 .1 16 748 320 156 1100 7.5 5
3.2 26 .7 .0 408 340 16 645 7.6 50 1.6 38 .3 .0 358 290 21 600 7.6 40 2.4 26 .2 .4 310 226 10 485 7.5 25
.0 24 .2 .1 310 238 14 491 7:4 15 20 17 .2 .1 2783 240 27 468 8.0 40 10 11 .3 .2 2293 192 2 390 8.2 50 Pumping 44 141 .1 16 4753 268 109 840 7.9 0 Golf Course .0 12 .1 .0 2133 176 4 339 8.1 3 2 .0 7.0 .2 .1 1853 168 9 315 8.0 15 2 2.0 9.0 .3 .0 1483 130 16 248 7.6 120 2 16 32 .2 11 3953 320 28 632 7.9 45 2 8.0 34 .1 .1 2593 200 20 440 8.0 20 2 136 1290 .2 1.4 25703 800 569 4400 8.0 20 2 41 25 .1 1.5 2873 224 46 478 7.9 5 2 974 9410 .2 4.0 170003 4150 3940 23900 7.6 15 2 17 22 .2 .1 2423 180 6 400 7.7 5 2 .8 19 .1 .0 2453 200 0 408 8.1 10 2




30 BUREAU OF GEOLOGY
Dissolved solids content of water represents the degree of mineralization of water and is determined by either of two methods: (1) evaporation of a measured amount of sample to dryness and weighing the residue; and (2) the sum of amounts of individually determined cations and anions. Cations are constituents which have positive electrical charges whereas anions have negative charges.
Chemical analyses in Table 2 are expressed in mg/l by weight of the constituent. However, most of the chemical characteristics of water can be better understood and more accurately represented from analyses expressed in epm (equivalents per million). Equivalents per million takes into account not only the weight of each constituent, but also the chemical reacting properties of the constituents. Therefore an analyses expressed in epm can be used more effectively in comparison of waters.
Chemical type of water is commonly classified according to the concentration of seven principal chemical constituents or ions. Difficulty in comparing seven constituents simultaneously can be overcome by using geometric figures or polygons (Stiff, 1951) to represent the type of water.
The preparation of a polygon that represents a specific chemical analysis can be shown with the analysis of water from well PB-487, in Table 2. The principal constituents are converted from mg/1 to epm by using conversion factors found in most chemical handbooks. Equivalents per million of each constituent is then converted to a percentage of the total cation of anion. The results of the conversions are shown in Table 3. Percentage values are then used to construct the polygon, figure 15.
TABLE 3- SELECTED CONSTITUENTS IN WATER FROM WELL PB-487.
Constituent mg/I epm Percent
Calcium (Ca) 100 4.99 60 Magnesium (Mg) 4.5 .37 5 Sodium (Na) and Potassium (K) 68 2.91 35 Total cations - 8.27 100 Bicarbonate (HCO3) 194 3.18 38 Sulfate (SO4) 44 .92 11 Chloride (Ci) 141 3.98 48
Fluoride (F) 0.1 .01
Nitrate (N03) 16 .26 3 Totalanions 8.35 100
Dissolved solids 475 mg/1




REPORT OF INVESTIGATION NO. 55 31
Points show percent concentration of dissolved constituents in water from well PB487
Ca HCO3
Mg SO4
Na andK C l
100% 50% 50% 100%
cations anions
Equivalents per million
a. Details and scale for preparing a polygon. b. Polygon showing the general chemical type of water in well
number PB-487.
Figure 15. An example of the preparation of a water-quality diagram using the
percentage figures in table 3.
Figure 15a shows the basic scale with seven constituents plotted on the graph. Joining the six points by straight lines gives the polygon shown in Figure 15b. The shape of the polygon and the relative length of the "spears" show the water to be somewhat equally strong in both calcium bicarbonate type and sodium chloride type. The relatively small amounts of magnesium and sulphate are typical of shallow ground water in southeastern Florida.
Polygons showing the general type of the water from several wells distributed throughout the lower Hillsboro Canal area are shown in Figure 16. The diagrams also show the depth of the sample on the left side and the dissolved solids content on the right side. The relatively uniform shape of the polygons show that, except for a few samples, the water in the area to a depth of 200 feet is the same type (calcium bicarbonate type) containing dissolved solids generally less than 400 mg/1.
Ground water in the narrow coastal ridge area is of exceptionally good quality, but ground water of good quality in larger quantities is available for future development farther inland.
Well G-1239, located 4 miles west of State Road 7, is not in the immediate study area, figure 17, but should be considered in the overall water picture. At a depth of 56 feet the dissolved solids concentration of 226 mg/1 is normal, but the concentrations of magnesium and calcium ions are almost equal. The increase in magnesium is caused by the presence of dolomite, a carbonate rock and equal amounts of calcium and magnesium. Dissolved solids increased to 872 mg/1 at a




32 BUREAU OF GEOLOGY
X P LA NA 1 90
Ir-I
PS--4-2 +

i lr[L.. z ~ 1 ees
Figure 16. Map showing relative concentrations of chemical constituents in ground
water of the lower Hillsboro Canal area.
depth of 102 feet, caused by the increase in sodium chloride. Saline water in shallow aquifers in inland areas of southern Florida may be residual from invasions of the sea during Pleistocene time (Sherwood and Klein, 1963).
In general the data show water in the area to be good in quality except in areas adjacent to the coast and the uncontrolled reaches of the Hillsboro and El Rio Canals where sea-water intrusion has occurred.




REPORT OF INVESTIGATION NO. 55 33
SEA-WATER INTRUSION
Sea-water intrusion in the Biscayne aquifer usually occurs from:
(1) direct intrusion of sea water into the coastal parts of the aquifer and along uncontrolled canals; and (2) sea water that remained in the sediments after deposition during Pleistocene interglacial, when the ocean inundated most of south Florida. Present day intrusion of sea water is the only source of salt-water contamination in the lower Hillsboro Canal area. Farther west, the chloride content of the water increases with depth, indicating that residual sea water is present in the aquifer. However, part of the salty water comes from materials of lower permeability that lie below the Biscayne aquifer.
Sea-water intrusion in the lower Hillsboro Canal area of the Biscayne aquifer is governed by the relationship of ground-water levels to mean sea level. If a specific gravity of 1.025 is assumed for seawater, each foot of fresh water above mean sea level should indicate 40 feet of fresh water below mean sea level as described by the Ghyben-Herzberg principle (Brown, 1925, p. 16-17). However, in southeast Florida, geologic and hydrologic conditions are such that the depth to salt water is generally more than 40 feet for each foot of fresh water head, but the relationship is sufficiently valid to the extent that intrusion would be expected in areas where ground-water levels were persistently low.
The uncontrolled canals and waterways are connected to the ocean, which facilitates sea-water intrusion in two ways: (1) drainage is allowed which lowers adjacent ground-water levels and reduces freshwater head that normally would oppose the inlaid movement of sea water; and (2) sea water is conveyed inland during dry periods, providing a source of intrusion by infiltration of the sea water into the aquifer.
Because about 91 percent of the dissolved constituents in sea water are chloride salts, analyses of the chloride content of water samples can be used reliably to determine the extent of sea-water intrusion. Figures 17 and 18 show the results of chloride traverses of the uncontrolled reaches of the El Rio and Hillsboro Canals. Water samples taken during these traverses were from the bottom of the canal at each station. Although the chloride content of the canals has a wide range, the figures illustrate that the chloride content decreases with increasing distance inland from the sea-water source. Decreased chloride content in the upper reaches also results from increased groundwater flow to the canals due to higher ground-water levels there than in the area adjacent to the lower reaches of the canals.
The El Rio Canal is relatively shallow throughout most of its reach in the vicinity of Boca Raton the depth decreases northward from




34 BUREAU OF GEOLOGY
s MILE RI CAt4
20poo0
10,000
rt
- \
So i
LdI
Cana covyat wae "oteE i aa;teeoeteclrd
a
dUNL- -66. -- .- -.--50
Figure 17. Chloride content of water at nine points in the El Rio Canal between the
Hhlisboro Canal and 13th Street.
about seven feet at the confluence with the Hillsboro Canal to about two or three feet at the N.W. 7th Street bridge (Fig. 17). The Hilisboro Canal conveys salt water to the El Rio Canal; therefore the chloride content of the water at the confluence of the two canals will determine to some degree the chloride content of the upper reaches of the El Rio Canal. The chloride content at the confluence depends largely on the combination of tidal stage and discharges at the Hillsboro Canal and E-3 Canal control structures. In Figure 17, the sample taken at the;




REPORT OF INVESTIGATION NO. 55 35
HILLSBORO CANAL MIL
topooo '
,tooo / II
20,000
-51,000
w
.z000
OX
0
0 0
-j
10.
Z50
I o
Figure 18. Chloride content of water at nine points in the Hillsboro Canal upstream
from the IntracoastalWaterway, September 20, 1966.
I.
confluence on August 12, 1964 was during high tide. On the-same day discharge at the structure in _the Hillsboro Canal was.3 7 cfs (cubic feet per second) and.had been low- for several days prior to the sampling. The September 20, 1,966 sample: was taken ona falling tide and the




36 BUREAU OF GEOLOGY
discharge was 198 cfs. The June 2, 1966 sample was taken on a falling tide also, but discharge at the control was 485 cfs.
Figure 18 shows that on September 20, 1966, during a falling tide, the chloride content of the Hillsboro Canal from the Intracoastal Waterway to the El Rio Canal was about the same as that of sea water. West of the confluence of the El Rio and Hillsboro Canals discharge through the controls of the Hillsboro and E-3 Canals into the lower Hillsboro Canal have freshened the water in the Hillsboro Canal.
Figure 19 shows isochlors in a subsurface section extending from the barrier islands westward through the Boca Raton well field and into the interior flatlands along line A A' in Figure 16. The dashed lines (isochlors) connect points in the subsurface where the chloride content of the ground water is equal to the value of the line. Examination of Figure 19 indicates that sea water has intruded into the Biscayne aquifer, at depth, from both the Intracoastal Waterway and the El Rio Canal. The continuous pumping and the resultant lowering of water levels in the Boca Raton well field has caused the most intrusion from the El Rio Canal; this is indicated by the more gentle slope of the isochlors on the west side of the ridge area than on the east side of the ridge.
Sea-water intrusion from the Intracoastal Waterway into the Biscayne aquifer in the Boca Raton area is indicated by the high concentrations of sodium and chloride in the polygon diagrams of wells PB 478 and PB 489 (Fig. 16). The wells are used for irrigation of a golf course in south Boca Raton. The Diagrams in Figure 16 show that although well PB 487 is twice as deep as PB 480 the dissolved solids content of its water is only about half that of PB 480. This is probably because well PB 487 is slightly farther from the major source of sea water, Lake Boca Raton, and that well PB 480 has been in use 24 years longer than well PB 487 and has had more time to induce a tongue of sea water to move toward it.
Although some sea water has entered the Biscayne aquifer in the Boca Raton area, fresh water levels have been sufficiently high between the well field and the El Rio Canal to prevent the intrusion of a harmful amount. This is indicated by the low chloride content of water in well PB 492 to a depth of 162 feet below land surface (Fig. 16 and 19). However, several consecutive dry years might change the situation drastically, especially if pumping levels in the well field are lowered and the El Rio Canal is deepened.
Figure 20 shows the fluctuations of the chloride content of the water in the El Rio Canal at the 7th Street bridge. The relatively small volume of water in the El Rio Canal allows the chloride content to




2 25
00
50' 34 /05 A 1 \ 18 22 1 Wz 4.r Q I.- <
S 422 / 5
1 00 7 / C. < 150
200 0 w
EXPJ..ANATION
-- -tso---ISOCHLORS, MILLIGRAMS PER LITER
NUMBERS INDICATE CHLORIDE CONTENT .AT POINT SAMPLED IN WELL
Figure 19. Section along line A-A' (figure 16) showing lines of equal chloride content (isochlors) of ground water.
it I 50 3 [[ 50, 01 0 1% I 2 2 o/1 1 ,, z
100-~ I41010
200 I MLE .... O0 %
EXPO.NATIO N ISOCHLORS, MILLIGRAMS PER LITER
NUMBERS INDICATE CHLORIDE CONTENT AT POINT SAMPLED IN WELL Figure 19. Section along line A-A' (figure 16) showing lines of equal chloride content (isochlors) of ground water.




38 BUREAU OF GEOLOGY
change rapidly. These changes are in response to: (1) tidal action; (2) ground-water inflow from adjacent areas where ground-water levels are sufficiently high; and (3) discharge from the Hillsboro Canal and E-3 Canal. Discharge in excess of 500 cfs from the Hillsboro Canal with attendant discharge from the E-3 Canal and ground-water inflow along the uncontrolled reach of the Hillsboro Canal appears to be sufficient to maintain fresh water in the Hillsboro Canal downstream of the mouth of the El Rio Canal.
Sea-water intrusion into the Biscayne aquifer was not detected in the Deerfield Beach area except in wells adjacent to finger canals off the Intracoastal Waterway. Well G-1228 is located between the Hillsboro Canal and the Deerfield Beach well field (Fig. 3 and 16), in an area that would be most vulnerable to the threat of sea-water intrusion. Water levels in the vicinity of the well G-1228 are affected by continuous drainage to the uncontrolled reach of the Hillsboro Canal and by the pumping in the well field. Therefore, if sea water were to move inland in the aquifer, sampling of well G-1228 would give an early indication of the movement. No indication of movement has been observed in the analysis of samples from this well.
WATER USE AND POTENTIAL SUPPLY
The Biscayne aqifer is the source for all municipal water supplies in the lower Hillsboro Canal area. The rapidly increasing population of the area will require larger quantities of water from the-aquifer to meet future needs. This is substantiated by past pumpage records shown in Figures 9 and 10 for the period 1963-67. The capacities of the water plants of Boca Raton and Deerfield Beach were both doubled in 1965, Boca Raton to 23 mgd and Deerfield Beach to 16 mgd, to meet the increased demands for treated water. The predicted population figure of more than 50,000 for the area by 1970 will require further expansion of the well fields or the establishment of new well fields. This is partly due to the fact that the per capita use of water increases with time: the per capita use in American cities in 1920 was 115 gallons per day; in 1960 the average use had increased to 150 gallons per day, a 30 percent rise in 40 years; in 1966, the average per capita use of water in the lower Hillsboro Canal area was about 180 gallons per day.
The potential supply available from the Biscayne aquifer in the lower Hillsboro Canal area depends upon the factors which balance recharge and discharge in accordance with the following equation: Recharge =Discharge (surface-water discharge +
ground-water discharge + evapotranspiration + pumpage) + change in storage.




*** NO RECORD
6 00. :- .MAXIMUM ~ 500
I 60" MINIMUM
MAR 'eR MAY JUN 'JUL 'AUG 'SEP 'OCT NOV 'DEC JAN' PE 'MAR APR MAY JUN 'JUL AUG 1964 1965
Figure 20. Approximate daily maximum and minimum chloride content of water in the El Rio Canal at
7th Street, Boca Raton, Florida, for the period March 1964 through August 1965.




40 BUREAU OF GEOLOGY
Replenishment by rainfall can be assumed as constant, evapotranspiration and ground-water discharge rates will not change in magnitude, and pumping will increase with time. Water levels have not changed significantly during the period 1964-1967 indicating that the net aquifer storage has remained unchanged. The total potential supply of the area therefore represents the quantity of water discharged through the Hillsboro Canal to the ocean, plus the amounts that can be withdrawn from aquifer storage each year without lowering water levels to the detriment of quality. Lowering of water levels as a result of pumping from storage will not significantly change losses by evapotranspiration in the area.
The most critical periods affecting the water resources of the lower Hillsboro Canal area are the prolonged droughts when water levels are lowest and well field pumping is heaviest. A graph of the discharge of the Hillsboro Canal at the control structure for 1965 is shown in Figure 21. Discharge is greatest during the rainy season, the maximum of more than 3,000 cfs (1,900 mgd) occurring at the end of October.
The minimum discharge during the dry season was 40 cfs (26 mgd) and the average discharge for the year was 373 cfs (240 mgd). A significant part of the flow through the Hillsboro Canal represents water that could be used in the future if facilities were made available for retention in the system water that could be salvaged instead of being lost to the ocean.
In addition, vast quantities of ground water are available from aquifer storage, primarily in the area west of the coastal ridge where water levels are high throughout the year. Water control practices of the Lake Worth Drainage District have maintained water levels in the area west of Canal E-3 near 12 feet above msl. Because a large part moves eastward, surface water in that District can be considered a perennial source of recharge by underseepage to the aquifer between the El Rio Canal and Canal E-3. Also, the aquifer in the inland areas of Deerfield Beach is replenished during the dry season by seepage from the controlled reach of the Hillsboro Canal and by ground water inflow from the irrigation district farther west. These sources can also be depended upon as perennial sources of replenishment to the aquifer. Therefore large withdrawals of ground water can be made from the inland areas between the Sunshine State Parkway on the west and the Seaboard Coast Line Railroad on the east without seriously lowering waterlevels.
Furthermore, additional supplies are yet (1969) available from the coastal ridge north of Boca Raton well field but as indicated, the aquifer there decreases in permeability and well-field expansion in that




30
28
26
24
zo
a
0 22
00 m 820
W
14
0. I
JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC.
Figure 21. Graph showing the discharge of the Hillsboro Canal at the control near
Deerfield Beach, 1965.




42 BUREAU OF GEOLOGY
direction might not be feasible. On the other hand, the area south of the Deerfield Beach well field is underlain by materials of moderate to high permeability and possible expansion in that direction might be considered. However, withdrawals along the coastal ridge should be limited or closely monitored because of the constant threat of seawater intrusion.
As the area continues to urbanize and water demands increase, greater reliance will have to be placed on interior water resources and possibly on importation of water from the inland water conservation system of the Central and Southern Florida Flood Control Project. Expansion of the data collection network will be necessary to monitor changes in the hydrology of the inland area for adequate management and protection of the water resources of the lower Hillsboro Canal area.
SUMMARY
The Biscayne aquifer is the only source of fresh ground water for municipal supplies in the lower Hillsboro Canal area. The aquifer extends from land surface to a depth of about 400 feet near the coast, thins to the west and decreases in permeability to the north.
The primary source of recharge to the aquifer is local rainfall, of which more than one-third reaches the water table. An additional source of recharge is infiltration from the controlled canals of the local irrigation and drainage districts and the Central and Southern Florida Flood Control District, especially the controlled reach of the Hillsboro Canal.
The ground water is of generally good chemical quality except in areas adjacent to the coast and uncontrolled reaches of the Hillsboro and El Rio Canals where sea-water intrusion has occurred.
Data indicate that the greatest potential source of water from the Biscayne aquifer is in the inland areas where water levels are high throughout the year and perennial replenishment to the aquifer is available by infiltration from the controlled canals and underseepage from the conservation areas. Large quantities of fresh ground water can be withdrawn from the Biscayne aquifer in the interior area to meet future demands without the threat of sea-water intrusion. Much of the average flow of 240 mgd through the Hillsboro Canal control represents water that could be used in the future if facilities were made available for retention in the system.
As urbanization expands to the west, the accompanying demands for water and the expansion of drainage systems for development will have a significant effect on the hydrologic system of the area. This will require that the data collection network now in existence be expanded to monitor future changes in the system so the water resources of the lower Hillsboro Canal area can be adequately managed and protected.




REPORT OF INVESTIGATION NO. -55 43
WELL NUMBERS
In order to coordinate data from wells on a nationwide basis, the U.S. Geological Survey has adopted a well numbering system which locates the well by a 16 character number based on latitude and longitude. The consecutive county well numbers used in this report are referenced to the nationwide system, as follows: County Latitude-Longitude County Latitude-Longitude No. No. No. No.
G-1228 261914N0800607.1 PB-479 262218N0800739.1 G-1239 261838N0801513.1 PB-480 262039N0800503.1
G-1272 261334N0800619.1 PB-481 262150N0801148.1 G-1298 261527N0801138.1 PB-482 262211N0801008.1 G-1299 261659N0800859.1 PB-483 262519N0800714.1
G-1300 261704N0801022.1 PB-484 262123N0800738.1 G-1301 261821N0800709.1 PB-485 262444N0800452.1 G-1302 261856N0800842.1 PB-486 262443N0800453.1 G-1303 261840N0801633.1 PB-487 262054N0800501.1 G-1304 261908N0800622.1 PB-488 262205N0800717.1
G-1314 261815N0801115.1 PB-489 262453N0800454.1 PB-220 262256N0800531.1 PB-490 262117N0800550.1 PB-251 262206N0800842.1 PB-491 262114N0800540.1 PB-472 262454N0801236.1 PB-492 262120N0800532.1 PB-473 262133N0801254.1 PB-548 262148N0800525.l PB-474 262306N0800507.1 PB-549 262219N0800538.1
PB-475 262332N0800448.1 PB-550 262311N0800534.1 PB-476 262159N0800844.1 PB-555 262118N0800515.1 PB-477 262138N0800501.1 PB-556 262229N0800934.1 PB-478 262222N0800527.1 PB-557 262229N0800934.2 PB-558 262229N0800935.1




44 BUREAU OF GEOLOGY
REFERENCES
Black, A.P., and Brown, Eugene 1951 Chemical character of Florida's waters: Fla. State Bd. of Cons., Div. Water
Survey and Research, Paper 6. Cooke, C. W.
1945 Geology of Florida, Fla. Geol. Surv. Bull. 29. Cooper, H. H.,Jr.
1963 Type curves for nonsteady radial flow in an infinite leaky artesian aquifer
in shortcuts and special problems in aquifer tests: See WSP 1545-C for
U.S. Geol. Survey Water-Supply Paper 1545-C, p. C48-C55. Cooper, H. H.Jr., andJacob, C. E. 1946 A generalized graphical method for evaluation formation constants and
summarizing well-field history, Am. Geophys. Union Trans., v. 27, no. 4,
p.526-534.
Hantush, M.C.
1956 Analysis of data from pumping tests in leaky aquifers: Am. Geophys.
Union Trans. v. 37, no. 6, p. 702-714. Meinzer, O. E.
1923 The occurrence of water in the United States, with a discussion of
principles: U.S. Geol. Survey Water-Supply Paper 489. Parker, G. G., Ferguson, G. E., and Love, S. K. 1955 Water resources of southeastern Florida, with special reference to the geology and ground water of the Miami area: U.S. Geol. Survey WaterSupply Paper 1255.
Rainwater, F. H. and Thatcher, L. L. 1960 Methods for collection and analysis of water samples: U.S. Geol. Survey Water-Supply Paper 1454.
Schroeder, M. C., Milliken, D. L., and Love, S. K. 1954 Water resources ofPalm Beach County, Fla: Fla. Geol. Survey Bull. 13.
Sherwood, C. B., and Klein, Howard 1963 Saline ground water in southern Florida: Nat. Water Well Assoc. "Ground Water", v. 1, no. 2.
Stiff, H. A.,Jr.
I1951 The interpretation of chemical water analysis by means ofpatterns: Jour.
of Petrol. Tech., p. 15, Oct. Tarver, G. R.
1964 Hydrology of the Biscayne aquifer in the Pompano Beach area, Broward County, Fla.: Fla. Geol. Survey Rept. Inv. no. 36. Theis, C. V.
1938 The significance and nature of the cone of depression in ground-water bodies:Econ. Geology, v. 33, no. 8, p. 889-902. U. S. Public Health Service 1962 U.S. Public Health Service drinking water standards: Public Health Service Pub. 956, 61 p. See Public Health Repts.




Full Text
xml version 1.0 encoding UTF-8
REPORT xmlns http:www.fcla.edudlsmddaitss xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.fcla.edudlsmddaitssdaitssReport.xsd
INGEST IEID EM4UU3NYG_98LD60 INGEST_TIME 2017-05-08T19:29:30Z PACKAGE UF00001242_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC
FILES



PAGE 1

STATE OF FLORIDA DEPARTMENT OF NATURAL RESOURCES BUREAU OF GEOLOGY Robert O. Vernon, Chief REPORT OF INVESTIGATION NO. 55 GROUND-WATER RESOURCES OF THE LOWER HILLSBORO CANAL AREA, SOUTHEASTERN FLORIDA By H.J. McCoy andJack Hardee U. S. Geological Survey Prepared by the U. S. GEOLOGICAL SURVEY in cooperation with the BUREAU OF GEOLOGY DIVISION OF INTERIOR RESOURCES FLORIDA DEPARTMENT OF NATURAL RESOURCES and the cities of BOCA RATON and DEERIELD BEACH Tallahassee, Florida 1970 i

PAGE 2

DEPARTMENT OF NATURAL RESOURCES CLAUDE R. KIRK, JR. Governor TOM ADAMS EARL FAIRCLOTH Secretary of State Attorney General BROWARD WILLIAMS FRED O. DICKINSON, JR. Treasurer Comptroller FLOYD T. CHRISTIAN DOYLE CONNER Commissioner of Education Commissioner ofAgriculture W. RANDOLPH HODGES Executive Director ii

PAGE 3

LETTER OF TRANSMITTAL Bureau of Geology Tallahassee April 14, 1970 The Honorable Claude R. Kirk Governor of Florida Tallahassee, Florida Dear Governor Kirk: The Bureau of Geology of the Department of Natural Resources is publishing as its Report of Investigation No. 55 a report on the "Ground Water Resources of the Lower Hillsboro Canal Area, Southeastern Florida". The report was prepared as part of the cooperative program between the Bureau of Geology, the U. S. Geological Survey and the cities of Boca Raton and Deerfield Beach. It is written by Messrs. H. J. McCoy and Jack Hardee of the U. S. Geological Survey and was undertaken to determine the amount and kinds of water being produced from the lower Hillsboro Canal Area in Palm Beach and Broward counties. All of the potable ground water being produced from the Biscayne aquifer is developed from the canal through infiltration. Rainfall in the area is the ultimate source for all of the water. Careful control and management will allow the development of large quantities of water from the canal toward Lake Okeechobee, but a fresh water head must be maintained along the contact of fresh water with sea water to prevent salt water intrusion. Respectfully yours, R. O. Vernon, Chief Bureau of Geology ROV:ebl iii

PAGE 4

Completed manuscript received April 14,1970 Printed for the Bureau of Geology Division of Interior Resources Florida Department of Natural Resources Designers Press of Orlando, Inc. Orlando, Florida iv

PAGE 5

CONTENTS Page Abstract .... ............... ...... .. .. ..... .. ....1 Introduction ................... ........... ... ...... Purpose and scope .................................. 2 Previous investigations .............................. 2 Acknowledgments ........... ............. ........ ..... 2 General features ... .......... .... ................... 3 Climate ....................... .. ... ......... .....3 Population and industry ........... ........... ... ........ 5 Hydrologic setting .................... .................. 6 Biscayne aquifer ................................... 7 Floridan aquifer ............. ...... ... ......... .9 Surface flow system ....................... .. ............. 11 Ground water .............. ............. .. .... ...12 Recharge and discharge ............................. 12 Water-level fluctuations ............................. 13 Hydraulic properties ....... ..................... ...24 Water quality .................... .... ........... .26 Sea-water intrusion .......... ... .............. 33 Water use and potential supply ........................... 38 Summary .... .............. ............. ............ 42 Well numbers .......... ....... ....................... 43 References ............. .... .... .................... 44 ;'. ;-; .-.-' ' -.-: ' :.' ^ "' .. \ .. .. .'.. * -*

PAGE 6

LIST OF ILLUSTRATIONS Figure Page 1 Location of lower Hillsboro Canal area, Florida, showing physiographic subdivisions ...................4 2 Parts of Broward and Palm Beach Counties showing canals and levees of the Central and Southern Florida Flood Control Project and the Lake Worth Drainage District. .............................6 3 Map of lower Hillsboro Canal area showing location of wells and lines of geologic sections. ..................8 4 Geologic section of the Biscayne aquifer in the lower Hillsboro Canal area along line A-A' in figure 3.............................................9 5 Geologic section of the Biscayne aquifer in the lower Hillsboro Canal area along line B-B' in figure 3. ......... ... .... ...... .... ..... .10 6 Hydrographs of wells PB 470 and PB 488 and monthly rainfall at Boca Raton, 1963-1967. ................. ..14 7 Hydrographs of wells G 1214 and G 1260 at Deerfield Beach and monthly rainfall at Boca Raton, 1963-1967. ...... ...15 8 Water-table contour map of the lower Hillsboro Canal area, May 7, 1965, during low-water conditions ......... ...16 9 Graph showing monthly municipal pumpage and rainfall at Boca Raton, 1963-1967. ............. .......... 18 10 Graph showing monthly municipal pumpage at Deerfield Beach and monthly rainfall at Boca Raton, 1963-1967. ....... .19 11 Water-table contour map of the lower Hillsboro Canal area, November 1, 1965, during high-water conditions. ...... 20 12 Contour map showing rise in water levels from May 7 to November 1, 1965 in the lower Hillsboro Canal area. ........ 21 13 Water-table contour map of the lower Hillsboro Canal area, October 27, 1966, during high-water conditions. ......... 22 14 Water-table contour map of the lower Hillsboro Canal area, April 12, 1967, during low-water conditions. ......... .23 15 An example of the preparation of a water-quality diagram using the percentage figures in Table 3 ................ .31 16 Relative concentrations of chemical constituents in ground water of the Biscayne aquifer in the lower Hillsboro Canal area. ... ........................ 32 17 Chloride content of water at nine points in the El Rio Canal between the Hillsboro Canal and Street. ............ 34 18 Chloride content of water at nine points in the Hillsboro Canal upstream from the Intracoastal Waterway, September 20, 1966. ..................... 35 19 Section along line A-A' (figure 17) showing lines of equal chloride content (isochlors) of ground water .........37 vi

PAGE 7

20 Approximate daiy maximum and minimum chloride content of water-in the El Rio Canal at 7th Street, Boca Raton, Florida, for the period March 1964 through August 1965. ..... 39 21 Graph showing the discharge of the Hillsboro Canal at the control near Deerfield Beach, 1965 ..............41 TABLES Table Page 1. Monthly rainfall at Boca Raton, Florida, 1961-1967. ........ 15 2. Chemical analyses of water from selected wells in the lower Hillsboro Canal area. ....................... 28 3. Selected constituents in water from well PB-487. ........... 30 vii

PAGE 8

GROUND WATER RESOURCES OF THE LOWER HILLSBORO CANAL AREA By H.J. McCoy and Jack Hardee ABSTRACT The lower Hillsboro Canal area of this report occupies about 60 square miles of Palm Beach and Broward counties in southeastern Florida. All potable ground water in the lower Hillsboro Canal area is obtained from the Biscayne aquifer. The aquifer extends from the land surface to a depth of about 400 feet and is composed of sand, sandy limestone, shells, and indurated calcareous sand. Municipal well fields of Deerfield Beach and Boca Raton and most of the domestic, irrigation, and industrial wells obtain adequate water supplies from permeable limestone 90 to 130 feet below land surface. Rainfall in the area and induced infiltration from controlled canals provide the recharge to the aquifer. Sea-water intrusion, although a constant threat, has not advanced inland enough to contaminate either municipal well field. Intrusion from the El Rio Canal toward the Boca Raton well field appears to be stabilized, though further intrusion is a distinct possibility if fresh water levels are further lowered in the area. Data collection stations are maintained to monitor changes of the salt-water front in the aquifer. Large quantities of water can be withdrawn from the interior part of the area without the attendant threat of salt-water intrusion. Hydraulic characteristics of the aquifer are similar throughout the area and high year-round water levels in the interior afford a potential source of immediate and long-term recharge to the aquifer underlying the coastal ridge. The lower Hillsboro Canal area is still experiencing rapid growth with resultant demands for larger quantities of potable water. Although potable water is abundant, continuous observation and evaluation of changes in the hydrology of the area should be maintained to protect and efficiently manage the water resources of the area. INTRODUCTION Water problems facing the cities of Boca Raton and Deerfield Beach are similar to those experienced by other coastal communities in southeastern Florida with rapid growth and increasing water needs. 1

PAGE 9

2 BUREAU OF GEOLOGY Water supplies for Boca Raton and Deerfield Beach are obtained from well fields located adjacent to the Intracoastal Waterway and to tidal reaches of the Hillsboro and El Rio Canals, all of which are normally salty. Recognizing that rapid population growth would mean large water demands and that increased well field pumping could cause sea-water intrusion, in 1963 officials of both cities requested the U.S. Geological Survey to study water resources of the area to provide information for the future development of water supplies. PURPOSE AND SCOPE The purpose of this report is to present an evaluation of the ground-water resources of the lower Hillsboro Canal area and pertinent supporting data to the officials of Boca Raton and Deerfield Beach, Fla. The evaluation is the result of determining the following: (1) the location, availability, and quality of potable ground water in the Biscayne aquifer; (2) the occurrence and extent of sea-water intrusion into the aquifer in the vicinity of the well fields; (3) the hydraulic characteristics of the aquifer; and (4) the degree of interconnection between the canals and the aquifer. This report was prepared by the U.S. Geological Survey in cooperation with the cities of Boca Raton and Deerfield Beach, and as part of the statewide program with the Bureau of Geology, Florida Department of Natural Resources. The field work and report preparation were under the immediate supervision of C. B. Sherwood, Projects Engineer, and H. Klein, Subdistrict Chief, Miami, Fla., and under the general supervision of C. S. Conover, District Chief, Tallahassee, Fla., all of the U.S. Geological Survey. PREVIOUS INVESTIGATIONS This report results from the first detailed ground-water resources study of the lower Hillsboro Canal area. General information on the hydrology and geology of the area has been published by the Florida Geological Survey in reports by Cooke (1945), Black and Brown (1951), and Schroeder and others (1958). Some additional information on the area is included in a report resulting from a comprehensive investigation of the water resources of southeastern Florida by Parker and others (1955). ACKNOWLEDGMENTS Well-field and water-supply information given by William Eddinger, Water Superintendent of Boca Raton, and Arthur Strock, former City Engineer of Deerfield Beach is appreciated. Special acknowledg-

PAGE 10

REPORT OF INVESTIGATION NO. 55 3 ment is expressed to Drs. F. A. Eidsness, J. I. Garcia-Bengochea and Mr. Emmett Waite, of Black, Crow and Eidsness, Inc., Gainesville, Fla., consulting engineers for the cities of Boca Raton and Deerfield Beach. GENERAL FEATURES The area of study comprises about 60 square miles of Palm Beach and Broward counties in southeastern Florida as shown in figure 1. The area is bounded on the east by the Atlantic Ocean and on the west by an extensive agricultural area and the Everglades; it extends about 6 miles north and 4 miles south of the Hillsboro Canal. The county lines and the city limits of Boca Raton and Deefield Beach coincide with the Hillsboro Canal except near the mouth of the canal. The area is divided into three physiographic sub-areas (Fig. 1): (1) coastal lowlands-barrier island; (2) coastal ridge;-and (3) interior flatlands and the Everglades. The barrier islands parallel the mainland and are separated from it by the Intracoastal Waterway. Barrier islands extend intermittently along most of Florida's east coast. Relic sand dunes form the island in the study area and reach heights of more than 25 feet above msl (mean sea level) in some locations. The white, sandy beach on the ocean side of the island is one of the main tourist attractions in the area. The coastal lowland on the mainland is characterized by mangrove swamps adjacent to the Intracoastal Waterway and is generally less than 5 feet above msl except where dredging and filling has taken place for housing developments. Paralleling the coastal lowland is the coastal ridge. In Deerfield Beach the ridge is relatively wide and flat, reaching a maximum elevation of about 25 feet above msl. However, in Boca Raton it is narrower, dissected, relatively steep-sided, and reaches a maximum elevation of nearly 40 feet above msl. The ridge is composed of white sand containing varying amounts of shelly material. Westward from the crest of the ridge the land surface slopes to the interior flatlands; in Deerfield Beach the slope is gentle but in Boca Raton it is steep, especially in the vicinity of the El Rio Canal along the west flank of the ridge. The interior flatland extends westward from the coastal ridge to the Everglades. It is characterized by a relatively flat surface and supports a natural growth of palmettos, pine trees, and a variety of palm trees. The average elevation of the interior flatland is about 15 feet above msl. CLIMATE The climate of the lower Hillsboro Canal area is humid subtropical. The nearness of the Atlantic Ocean accounts for the high humidity

PAGE 11

4 BUREAU OF GEOLOGY -s-o o -on ot* oo .I CAN& 1-38 EXPLANATION ---I 20 C:1 x~ ftA 7 T R > C IL ALAO COTROL MU temperatures for January and August during the period 1946 through Iperiod was 75 F. (U.. W r CLL-47 Q The average annual rainfall for the long-term period 1951-1967 is zi BOC 5 \KA RATON,, C1 nearly 60 inches. During this period five years were above average, five fr yas w n tad ba f aa «f D5ERFIELD SIACH 0 I MILE • n; 09, 07' O " 04" 03" Figure 1. Location of lower Hillsboro Canal area, Florida showing physiographic subdivisions. but the Gulf Stream moderates the temperature. The average monthly temperatures for January and August during the period 1946 through 1967 were 68° F. and 82° F. The average annual temperature for that period was 75° F. (U.S. Weather Bureau). Rainfall in the area is unevenly distributed with time and location. The average annual rainfall for the long-term period 1951-1967 is nearly 60 inches. During this period five years were above average, five years were below average, three years were approximately average, and four years were not totaled because of incomplete data.

PAGE 12

REPORT OF INVESTIGATION NO. 55 5 TABLE 1 -MONTHLY RAINFALL AT BOCA RATON, FLA.1 (inches) 1961 1962 1963 1964 1965 1966 1967 January 8.56 0.47 2.93 1.85 0.73 3.27 2.41 February .85 .69 6.18 3.82 5.25 5.79 2.34 March 1.09 3.41 4.73 3.20 .97 1.85 3.57 April .67 6.51 .93 4.36 .71 1.66 0.00 May 6.47 1.91 13.01 6.20 1.22 4.93 2.07 June 2.80 5.20 7.47 7.93 10.91 16.51 11.86 July 1.22 10.42 2.02 5.31 11.01 7.63 3.71 August 5.06 6.08 5.43 7.89 3.44 6.18 6.83 September 4.50 7.59 12.51 6.31 4.24 8.32 7.41 October 6.93 1.98 7.11 11.13 29.64 6.95 5.42 November 1.09 1.63 2.42 .63 3.94 1.06 3.71 December .16 .88 3.74 1.93 1.01 1.00 1.72 TOTALS 39.40 46.77 68.48 60.56 73.07 65.15 51.05 SRecord from U.S. Weather Bureau's Climatological Data. Table 1 shows the monthly rainfall recorded at Boca Raton for the period 1961 through 1967. This period was chosen for presentation because it includes the two dry years preceding the beginning of the study. The average for this periodis 58 inches, or two inches below the long-term average. Abnormally heavy rainfall was recorded during October 1965. Most of the rain occurred during the middle and at the end of the month. At Pompano Beach, shown in figure 2, 24 inches of rainfall was recorded in 24 hours on October 31 and November 1. POPULATION AND INDUSTRY The lower Hillsboro Canal area has been strongly affected by the population boom of southeastern Florida. The area has grown in population from about 3,000 in 1950 to more than 36,000 in 1966. The predicted population for 1970 exceeds 50,000. Although Boca Raton and Deerfield Beach are primarily tourist and retirement communities, both cities have planned for the expansion of light, clean industries. The largest employers are the private and chain sales and service stores. Agriculture contributes significantly to the economy of the area. Several private and state-owned educational institutions also play a part in the overall economic structure.

PAGE 13

6 BUREAU OF GEOLOGY CONSERVATION I AREA N0. Ij PALU BEACH COUNTY BOCARATON CONSERVATIO -( f DEERFIELD BROWARD COUNTY L-. BEACH AREA NO.2 c4 PMBEACH OAKLAND CONSERVATION /3 -PARKND FORT p LAUDERDALE AREA NO.3 c| . S|EXPLANATION CANAL LEVEE BROWARD COUNTY DADE COUNTY 0 SMILES MIAMI Figure 2. Parts of Broward and Palm Beach counties showing canals and levees of the Central and Southern Florida Flood Control Project and the Lake Worth Drainage District. HYDROLOGIC SETTING The lower Hillsboro Canal area abounds in water: the Atlantic Ocean is to the east and the vast water control works of the Central and Southern Florida Flood Control District (FCD) is to the far west and south (Fig. 2). A latticework of controlled canals of the Lake Worth Drainage District (LWDD) is immediately adjacent to the north and west sides of Boca Raton; the canals of the FCD and the LWDD were constructed primarily to improve drainage during periods of high rainfall. The canals cut across the top of permeable shallow sediments called the Biscayne aquifer. During periods of low rainfall, the canals convey water from inland areas and replenish the aquifer by induced infiltration. Because rainfall is the primary source of replenishment to

PAGE 14

REPORT OF INVESTIGATION NO. 55 7 the Biscayne aquifer, water levels are highest during the wet part of the year and lowest during the dry. BISCAYNE AQUIFER All fresh ground-water supplies in the lower Hillsboro Canal area are obtained from the Biscayne aquifer. The aquifer extends from land surface to a depth of about 400 feet (Tarver, 1964). Eight test wells were drilled in the area to augment available data in determining the lithologic composition of the upper part of the aquifer. Figure 3 shows locations. The wells ranged in depth from 127 to 208 feet below the land surface. Data from these wells were used in preparing the geologic sections in Figures 4 and 5. The Pamlico Sand of Pleistocene age blankets most of the lower Hillsboro Canal area and is the uppermost unit of the Biscayne aquifer. It is composed of very fine to coarse quartz sand, white to black or red, depending upon the staining materials. The Anastasia Formation of Pleistocene age underlies the Pamlico Sand and is composed of coquina, sand, indurated calcarcous sand, and sandy limestone. The Anastasia Formation is the principal source of water from the Biscayne aquifer in the lower Hillsboro Canal area. The Tamiami Formation of late Miocene age underlies the Anastasia Formation. Permeable limestone beds in the upper part of the Tamiami Formation constitute the basal part of the Biscayne aquifer. The formation is tapped by few wells in the lower Hillsboro Canal area because equally good water and comparable yields can be obtained from wells that are bottomed in shallower limestones in the Anastasia Formation. Rock materials penetrated by the test wells are shown by Figure 4. Test-well data plus data from a few existing wells were used to draw Figure 5. Both Figures show that sand covers the lower Hillsboro Canal area to depths as much as 60 feet below the land surface. The Pamlico Sand accounts for about 20 feet of this section in the Deerfield Beach area and as much as 50 feet in the Boca Raton area. The geologic sections show that the limestone beds are discontinuous vertically and horizontally. Additional information from drillers in the area indicates that limestone beds are more persistent in the Deerfield Beach area than in the Boca Raton area. Beds of indurated calcareous sand, or sandy limestone are widespread enough through the lower Hillsboro Canal area that wells can usually be finished with open holes below the casing. However, irrigation and municipal wells subject to heavy withdrawals are usually screened and gravel packed. In the western part of the area private

PAGE 15

8 BUREAU OF GEOLOGY 1s o o09 " 07 06c os0 ....-II I )-----IWMGMWur »489 -CAMLS I CONTWR OOL TEST WL L * MUNICIPML SUPPLY WELL SWAE-M-LEVEL RECOORDER A--A" LINE OF GEOLOGIC SECTION CA°AL L -43 P 550 n -? e P5496 _55a PO549 0A BARRIE _ NRAmC TAt 22 WATER SY CANAL -47 0 a0 o o °0 BEACH I 0 I MILE i Figure 3 Map of lower Hillsboro Canal area showing location of wells and lines of geologic sections. supply wells penetrate permeable material at depths ranging from 60 to 90 feet. This permeable material could be the same limestone as that penetrated at 70 feet in well PB488 or the shelly, friable limestone penetrated at 89 feet in wells PB-556, 557, and 558 (see Fig. 3 for locations). The Boca Raton well field obtains water from the limestone shown by well PB 548 in Figure 5. The limestone is discontinuous and becomes increasingly sandy to the north. This is indicated by the

PAGE 16

REPORT OF INVESTIGATION NO. 55 9 .-J z AS oo A 40? -2 r -40C -Im m C a aC 40'40 So a. a. -a. SEALCAREOUS SHELL SANDiij SEA LEVEL pAI O LEVEL PALIO SAIMILE area along line A-A' in figure 3. absence of dense limestone in wells PB489, PB549 and PB5.0. Wells in 40 -" ::::::::::l^-:::::::::: :::::::::: :::,:: ::::: : -0 ::::x::::: :::::::-:: :::: : :: ::::::::::::::::::: .::::::::::. ..:: ::::.::: :.. ..::::: : : :: : ...... ... .... .... ::... .::::.:: :::::::::;:.::: : :.:::.:::. :: :' : : ::. :::::::: :::::::: :::* * *:: -::: -::: -_ S.: ..: : : ::. :.: : : ... ..; ....1 of the Florida peninsula the aquifer is exposed or covered by relatively thin layers of sand, but in the southeastern part of the state the aquifer ............. ............. ... ::::'4 Eo; -ýi-.',ii j:i!iiji i ... ..' 'o8 0 .. ..'.. .. .... ... ..... ..j .. ..... .-: ..,i: :'7 -..i .... 1::....j:: ::: ::. . 12 0 ,.... ... .......... ...:1 20 200'. 004.' EXPLANATION Figure 4. Geologic section of the Biscayne aquifer in the lower Hillsboro Canal absence of dense limestone in wells PB489, PB549 andPB550. Wells in in Figure 5.. •of the Florida peninsula the aquifer is exposed or covered by relatively thin layers of sand, but inthesoutheastern part of the state the aquifer

PAGE 17

0 w go "® j 0 B' 4PAMLC s a I D S40' g40i.-.-. .. .. ..L... it Q : IM L V L N' ........ ....1...... : . ::" .i , ,E L .E ..... , A. .: ...... L .A ND ....... 1 ....... ..... ". " 4"i ...",..:...'.:. :.. .:'.".'"i. ... : .... .. ." a i i,:::::: ,::::,,::,,, ,, :,, :.. ..... .. :, '",: ..... ....... ;: U MILEM !-l l " I : '-_ .I *........ ... : .-, " "» ... .. : ...._.... .. .. .. ... .::.. .. ... ; ii ·ii!;; i :, ..« *:: : .:! Cg, -'"-'Tllll *..^ -J ^ .i '.m-M :: .......... ;.^!:: !:!!, ',,:. ::f,,,.,.1 ; I r0 . ' i::,..::::.^^ fi .: '::.-l. t'.l:'::: ';.l : i ;;;';^ -fc; ^'*i E-i. I',S:^:,i ... ............; ^> .., :'"S -*: *i.|<.i-L. j^ y ^ 11 8 I , I ..la g, ::|:::::::::::::::::::::::: (]j' , i:i::::::&:,; .."P. ':E ; :,.; ::.,i , :, ; :; ':::..,:; ': :::LL'.^ ^' l4;: ...: i20 0 'J.. ' ...: : l:.i.. ...::.;: EX PLA NAT IO N -20d CALCAREOUS SHELL LIMESTONE SAND SANDY SAND LIMESTONE 0 I MILE Figure 5. Geologic section of the Biscayne aquifer in the lower Hillsboro Canal area along line B-B' in figure 3.

PAGE 18

REPORT OF INVESTIGATION NO. 55 11 is about 1,000 feet below the land surface and the water is under greater than atmospheric pressure. The water level in a well penetrating this aquifer in the lower Hillsboro Canal area will rise more than 25 feet above msl. Such a well may yield as much as 2,000 gpm (gallons per minute) by natural flow. However, in the study area, as in most of south Florida, water from the Floridan aquifer is too mineralized for most uses. Because of the tremendous quantities of water available, the upper, less mineralized part of the aquifer, may be considered as a potential source of supplemental water. However, the deeper, more mineralized part of the aquifer is already being used as a reservoir for discharge of chemical wastes near Lake Okeechobee, and sewage wastes for a municipality near Pompano Beach. SURFACE FLOW SYSTEM The Hillsboro Canal is one of the primary canals of the controlled network of the regional Central and Southern Florida Flood Control District (FCD) as shown in Figure 2. The Hillsboro Canal extends eastward from Lake Okeechobee between water Conservation Areas 1 and 2, where excess water is stored, to the Intracoastal Waterway. The canal not only provides gravity drainage for flood control, but also conveys water from the conservation areas eastward for replenishment of the aquifer near the coast during droughts. This is accomplished by keeping the control structure near the coast closed during the dry season, thereby maintaining water levels in the canal higher than the adjacent ground-water levels. During wet periods when ground-water levels begin to rise higher than the canal levels the control structure is opened to prevent flooding and the canal level and ground-water levels are lowered. Water levels in Boca Raton are affected more by operations of the Lake Worth Drainage District than by the Hillsboro Canal. The Lake Worth Drainage District is immediately west of Boca Raton (Fig. 2) and consists of a system of controlled canals. The primary (equalizing) canals flow southward bringing water during wet periods from areas north of Boca Raton and discharge excess waters into the Hillsboro Canal several hundred feet east of the control structure. The secondary (lateral) canals are oriented east-west and connect to primary canals. In September 1965 a salinity barrier was constructed on the El Rio Canal about 1,600 feet north of State Road 808 bridge to prevent sea-water intrusion into the Boca Raton well field. The barrier was placed as far downstream as economically feasible.

PAGE 19

12 BUREAU OF GEOLOGY GROUND WATER Ground water occurs beneath the land surface in the zone of saturation where it fills the interstices, joints, crevices, fissures, solution holes, and any or all other voids and is the supply for springs and wells (Meinzer, 1923, p. 38-39). The subsurface formations containing ground water, and from which this water is collectible for use, are called aquifers. The upper surface of the zone of saturation, which is under atmospheric pressure and free to rise and fall, is called the-water table. Where ground water is confined in a permeable bed overlain by a relatively impermeable bed its surface is not free to rise and fall and the water is under greater than atmospheric pressure. Water thus confined under pressure is called artesian. Direction of ground-water movement is from areas of high water levels to areas of low water levels. The Biscayne aquifer is essentially a nonartesian (or water-table) aquifer, but in most locations in the lower Hillsboro Canal area the permeable limestone beds are partly confined by discontinuous overlying layers or lenses of less permeable materials. RECHARGE AND DISCHARGE The amount of fresh water potentially available in the lower Hillsboro Canal area is determined by the recharge to and discharge from the Biscayne aquifer and the quantity available from storage in the aquifer. Infiltration of rainfall through surface materials and seepage from controlled canals are the means of recharge. Recharge by rainfall is greatest, naturally, during the rainy season of June to November. Recharge from canals is greatest during the dry season, December to May, when canal levels are higher than adjacent water levels in the aquifer. Discharge from the aquifer is by evapotranspiration, by groundwater flow to canals and by pumping from wells. Discharge by groundwater and surface-water flow and losses by evapotranspiration are greatest during and after periods of rainfall when water levels are high; discharge by pumping from wells is greatest during the dry periods, at the peak of the tourist season. Discharge by wells constitutes only a small part of the total discharge from the area. The average annual rainfall of 60 inches evenly distributed over the lower Hillsboro Canal area would be equivalent to about 170 mgd (million gallons per day). Probably as much as 100 mgd would be lost by evapotranspiration and discharge to the ocean. The remaining 70 mgd would be available to recharge the aquifer.

PAGE 20

REPORT OF INVESTIGATION NO. 55 13 WATER-LEVEL FLUCTATIONS Ground water in the Biscayne aquifer moves from areas where water levels are high to areas where water levels are low. Water levels are highest in recharge areas or in areas that are the greatest distance from points of discharge; water levels are lowest in discharge areas along the coast, along uncontrolled drainage canals, or in the vicinity of heavy pumping. Fluctuations of the water levels reflect the effects of recharge to and discharge from the aquifer. Water levels in the lower Hillsboro Canal area fluctuate in response to rainfall in the immediate area; therefore water levels generally are high during the rainy season (JuneNovember) and low during the dry season (December-May). A rise in water levels does not register the total replenishment to the aquifer, but the rise is an indication of the excess of the recharge over the discharge. Fluctuations are determined by water-level measurements in a network of observation stations in canals and on wells; some stations are equipped with automatic recording instruments which provide continuous, detailed records. The network is shown in Figure 3. Water level changes in selected wells in Boca Raton and Deerfield Beach for the period 1963-67 are shown by hydrographs on Figures 6 and 7. Monthly rainfall at Boca Raton is shown for the purpose of correlation. The hydrographs show both the day-to-day changes and the long-term trends. Well PB 470 (Fig. 6) is on the coastal ridge about a half mile east of the Boca Raton municipal well field, and the water level in the well is mildly influenced by well-field withdrawals. During extended dry periods, such as the spring of 1964 and 1965, water levels there approached one foot above msl. On the other hand, water levels in the vicinity of well PB 488 (Fig. 6) about 2 miles west of the well field are not affected by well-field withdrawals and remain high throughout most of the year. During 1967, levels near well PB 488 were 5 feet or more higher than levels east of the well field. Also, the magnitude of fluctuations at well PB 470 is greater than it is at well PB 488 because well PB 470 is influenced by well field pumping and is located near the coast where ground water is being discharged into the Intracoastal Waterway. The hydrographs of both wells show that the response to rainfall is rapid, indicating that infiltration to the water table takes place quickly. The hydrograph of well G-1260 (Fig, 7) in Deerfield Beach, 1500 feet west of the municipal well field, is similar to that of well PB-470 in Boca Raton. Levels in the Deerfield Beach well are generally higher than those in the Boca Raton well because the Deerfield Beach well is

PAGE 21

14P 12 "32 -j i , P-8488S-24A i "NO RECORD 4 S \P8-470 | C 19 2198 1985 1916 1992 i i gllu I6 h la ow lls0 ndPm lyfal l a B lc i ji IR .. 13,,1 1963 1964 1965 1966 1967 Figure 6. Hydrographs of wells PB 470 and PB 488 and monthly rainfall at Boca Raton, 1963-1967.

PAGE 22

242 -32 .J _1 w w I u, NO RECORD O , S8 \ -24 --12140i=iii 2 ii , !1 S n 12 , .oc. ......... ..... IIH IIIt : .i ii i i i ! iii::i.4it 1 i!!!I i!!i: iii !1 l :LllIillIIW lllllllllllll l U ii Illl j f :2 i lL 1969 1964 1965 1966 1967 Figure 7. Hydrographs of wells G 1214 and G 1260 at Deerfield Beach and monthly rainfall at Boca Raton, 1963-1967.

PAGE 23

16 BUREAU OF GEOLOGY 10, 090, 07' -05" EXPLNAMION -HIGHWAY SCANALS * CONTROL * OBSERVATION WELL + TEST WELL * MUNICIPAL SUPPLY WELL A WTrM-LEVEL RECORDER 7 SURIFACE-WATER MEASURING POINT INFEIRED (FEET.MSL) MAY 7 1965 CANAL L-43 rce o, 0 CANAL L-47 NCOUNTY SBO CA RATO N -2 1 DEERFIELD S0 -0 0 MILE 0 io 090o? 07 o os o" 20 Figure 8. Water-table contour map of the lower Hillsboro Canal area, May 7, 1965, during low-water conditions. farther from an area of natural discharge (Hillsboro Canal), and because the significantly lower pumping rate at the Deerfield Beach well field causes less drawdown of water level. Water-level contour maps are representations of the three-dimensional configuration of the water surface for a specific time. Figure 8 shows the configuration of the water table on May 7, 1965 -the record low-water levels for the period 1963-1967. For the time this

PAGE 24

REPORT OF INVESTIGATION NO. 55 17 map was made, rainfall had been deficient for about seven months, and pumpage from the two municipal well fields was record high as shown in figures 9 and 10. The irrigation system west of Deerfield Beach was continuously pumping water from the Hillsboro Canal into a network of irrigation canals (not shown in Fig. 8) thus maintaining relatively high water levels in the west during the drought. The configuration of the contours north of the Boca Raton well field shows that ground water was discharging into the El Rio Canal, but adjacent to and for some distance southward of the well field, water from the El Rio Canal was recharging the well field by induced infiltration. This was because heavy withdrawals of water had lowered the water table to four feet below msl in the well field. In addition, these withdrawals lowered the water-table mound between the well field and the Intracoastal Waterway to one foot above msl. Water levels north of Boca Raton remained relatively high due to very little pumping and the fact that less permeable sandy materials retarded the lateral movement of the ground water. In the Deerfield Beach area, hydrologic conditions contrast rather sharply with those in Boca Raton. Water from the recharge area west of the well field, and outseepage of water from the controlled reach of the Hillsboro Canal maintained relatively high water levels in the vicinity of the well field. Pumping lowered water levels in the Deerfield Beach well field only to about one foot above msl, which was considerably higher than the pumping levels in the Boca Raton field. However, the watertable mound between the Deerfield Beach well field and the tidal reach of the Hillsboro Canal was still only one foot above msl. Figure 11 represents the configuration of the water table on November 1, 1965 -the highest water levels for the period 1963-67. The absence of depression contour lines in the well fields indicates that municipal pumping was not significantly affecting the configuration of the water table at that time. A salinity barrier was constructed in the El Rio Canal in September 1965 about one-half mile north of the State Road 808 bridge. The top of the barrier is two feet above msl and is designed to limit tidal flow in the canal and to impound fresh water upstream of the barrier for recharge to the well field. The water level in the canal was above the top of the salinity barrier at the time the map in figure 11 was compiled; therefore the effect of the barrier can not be seen. The coastal ridge is delineated by the high water-level contours paralleling the coast. The saddle in the contour lines east of the Boca Raton well field corresponds to a natural depression in the land surface. The distorted contour lines in and northeast of the Deerfield Beach well field conform to a natural drainageway.

PAGE 25

300 36 -275. EXPLANATION -32 EM PUMPAGE -RAINFALL 250'26 225I 24 ..j |zoo~ I ni 20o z S175N 7111 IIjI t MII 0§ 150M: .6 !iii j 11 I m A I1 I 1W i 1f 75.1, I H1l illlI1 1963 1964 1965 1966 1967 Figure 9. Graph showing monthly municipal pumpage and rainfall at Boca Raton, 1963-67

PAGE 26

160 '32 EXPLANATION ~140 28 in PUMPAGE -RAINFALL 120 -24 ! 0 MJ 80 16J ..x g °°ii 'n::{ ii:. iiIIF.I {II M l lifli'i iil i IIML, * E N 11.ii ...... :. .....:. ... .... V" i ii i "iii ii! _ ii!!ii S Eiiiiiiijj ii i ,. P"i '" iiiiiiiiii ff i, "iii"" "1 " ! ! :!! '1 " ,..! i":: Z ... ..... o 6060 J .......l i !!! .i................i......... ; !'.iiiiiiiiiiiii ...ii :' : ::i: : : 0, i !:: ;:: ![ :i M ii i: i i S Figure 10 Graph showing monthly municipal punpage at Deerfield Beach and monthly rainfall at Boca Raton, 1963-67 ii ii~iii jii ::::::: !iiii: iii iiiiiriii i.:iiii iii::::::: :::: iii::::iii :>::: :::::iiiiiiii~i,,l,,::::::illiii :::: iiiliiiiiio

PAGE 27

20 BUREAU OF GEOLOGY 0a" '. 07 ° 06* 0S" a .To o o' as o"' c' oI EXPLANATION 25 A WIEM-LiEVL RECORDER 7 SUPRACE-WTEII MEASURING POINT S NOV. 1.1965 CANAL L-43 o A--T --wRAcoA srL 2 " -*__ l BOCA RATON. HILLSBOR1 CANAw. , c o n DEERFIELD -\ BEACH S !I/ "15 15 /41312 lD 0 IMILE to 0o " of0 07 05" 00"' 0 Figure 11. Water-table contour map of the lower Hillsboro Canal area, November 1, 1965, during high-water conditions. The net increase in storage in the aquifer from May 7 to November 1, 1965, is shown by the rise in water level on Figure 12. The average rise in water levels from the low period to the high period was about six feet for the area contoured, and the average estimated rise in the remainder of the area was about two feet. If an average porosity of 25 percent is assumed for the Biscayne aquifer in the area, then the rise in levels during the period represents an increase in storage of about 10.2

PAGE 28

REPORT OF INVESTIGATION NO. 55 21 tO* 09 OfR 07 ° 0" EXPLANATION -HIGHWAY -b CANALS I CONTROL o OBSERVATION WELL + TEST WELL I * MUNICIPA SUPPLY WELLI A WATER-LEVEL RECORDER v SURFACE-WATER MEASURING POINT -5CONTOUR LINE SHOWING RISE IN WATER LEVELS,FFET, FROM MAY 7 TO NOV. 1.1965 0 IITENMFY 31 -' BfII OCA ATON2 .HILLSBORO CANAL u ._ _1 SMILE 0 ..^o~oy I PALM_1ACHoCOUNTY ~fw' 10' 09 Os 07or 08 05' 54o Figure 12. Contour map showing rise in water levels from May 7 to November 1, 1965, in the lower Hillsboro Canal area. billion gallons or 60 mgd. This large increase in net storage was possible because over 60 inches of rainfall was recorded at Boca Raton during this six-month period -nearly 30 inches of it during October (see Table 1), resulting in this substantial recharging of the aquifer. Figures 13 and 14 reflect high and low water level conditions on October 27, 1966 and April 12, 1967. Additional shallow observation wells were installed in the inland area between the El Rio Canal and

PAGE 29

22 BUREAU OF GEOLOGY :l0 oe O9 07 060 oo" i . a I CAMAL L -38 M 2. 2 -EXPLANATION25 -*CANALS I CONT"IOL SoasEUTON WELL + TEST WELL * MUNICIPAL SUPPLY WELL S -A WnT-LEVEL RECORDEoaR P O _ 7 SUIRFACE-WATER MEAUIIG M POINT S W-5-ATER-TABLE CONTOUR ( FEET MSL) OCT 27,1966 5 CANAL L-47 A LLSBORO CWNL 3 DEERFIELD -Y BEACH o I 2MILE "-:' I " or or o" o6 oS o R iT O 2" Figure 13. Water-table contour map of the lower Hillsboro Canal area, October 27, 1966, during high-water conditions. Canal E-3 in the Boca Raton area and around the Deerfield Beach well field to allow monitoring of the effects of the salinity barrier on the El Rio Canal, the extension of the configuration of the water table west of the El Rio Canal, and more accurate delineation of the pumpinglevels in the Deerfield Beach well field. The top of the control structure on Canal E-3 just north of L-43 is about 16 feet above msl, and the top of the structure near the Hillsboro

PAGE 30

REPORT OF INVESTIGATION NO. 55 23 62. 0 09" ,o0" 06 o" 0" 05' 042. CANAL L -38 . 25EXPLANATION H IGHWAY I -CANALS I CONTROL cP o -OBSERVATION WELL + TEST WELL * MUNICIPAL SUPPLY WELL 24 -A WATER-LEVEL RECORDER r v SURFACE-WATER MEASURING POINT -5-WATER-TABLE CONTOUR DASHED WHERE INFERRED AFEETMSL) 0 APRIL 12,1967 I 0 0 o. 0' 0 W 1 I 09 0 0 ss050 CANAL L-47 wtc-d o BOCA RATON. // 1 HILLSBORO CANAL to PALM REACH COUINTY --°BROWARD COUNTY DEERFIELD BEACH wr ' 10 ' 0907 06r 05" 01f B01 Figure 14. Water-table contour map of the lower Hillsboro Canal area, April 12, 1967, during low-water conditions. Canal is set at about 12 feet above msl. Thus when canal levels in the northern reach of Canal E-3 exceed 16 feet msl, the excess water is discharged southward where it is impounded until it reaches, a level about 12 feet msl. When levels exceed 12 feet at the lower structure, water is discharged into the uncontrolled reach of the Hillsboro Canal. The contours in Figure 13 represent high water levels of October 27, 1966, and show that the water table west of the El Rio Canal was

PAGE 31

24 BUREAU OF GEOLOGY approximately the same level as the water table west of Deerfield Beach. The similar water table levels are due primarily to Canal E-3 replenishing 'he aquifer west of the El Rio in the same manner as the irrigation district west of Deerfield Beach replenishes the aquifer there. Small drainage canals have reduced water levels in the highly urbanized area adjacent to the west side of the El Rio Canal. The drawdown in the Boca Raton well field is small because of the reduction in pumping (see Fig. 9). The depression contours have extended west of the Deerfield Beach well field, probably as a result of large withdrawals for irrigation at the municipal golf course. The control structure on the Hillsboro Canal was closed and was maintaining a canal level more than seven feet above msl on the upstream side. The level in Canal E-2 upstream of the control at the Hillsboro Canal was more than 10 feet above msl. Figure 14 depicts the low water conditions of April 12, 1967 and shows the effects of the pumping in the well-field extensions of the two cities. Although withdrawals from each well field are at record high, the pumping levels do not exceed the record low levels in either well field (Fig. 8). Instead, the pumping level in the Boca Raton well field was two feet higher than on May 7, 1965 (Fig. 8). This higher level is due in part to the recharge contributed to the Boca Raton well field extension from the controlled reach of the El Rio Canal. The position of the zero contour line in figure 14 is more than a quarter of a mile farther from the canal than it was in Figure 8. The additional pumping in the well field extension in Deerfield Beach made the pumping level depression more circular and displaced it farther inland from the tidal reach of the Hillsboro Canal. HYDRAULIC PROPERTIES The hydraulic properties of the Biscayne aquifer must be known in order to determine the ground-water potential of the area and to plan properly for large-scale withdrawals of ground water. The principal properties of an aquifer are its capacities to transmit and store water, which are generally expressed as transmissivity and the storage coefficient. Transmissivity (T) is the quantity of water in gallons per day that will flow through a vertical section of the aquifer one foot wide and extending the full saturated height, under unit hydraulic gradient, at the prevailing temperature of water (Theis, 1938, p. 892). The storage coefficient (S) is defined as the volume of water released from or taken int6 storage per tffit surfate area of the-aquifer per unit change in the component of head normal to that surface. The most commonly used method for determining these properties is by an aquifer test, whereby a well penetrating the aquifer is pumped and the

PAGE 32

REPORT OF INVESTIGATION NO. 55 25 resultant lowering of the water table in nearby nonpumped wells is observed to relate the lowering of the water level to distance and time. Aquifer tests were made on wells in the Deerfield Beach well field in August 1961 and on test wells west of Boca Raton (Fig. 3) in August 1967. In both areas the water is pumped from permeable limestone that is overlain by thick sections of less permeable sand, silt, shells, and marl. In the test west of Boca Raton, well PB-556 was pumped and water levels were observed in well PB-558 200 feet to the east. Both wells are 92 feet deep with 89 feet of casing. In Deerfield Beach, municipal well number 9, which is 90 feet deep with 80 feet of casing was pumped and water levels were recorded in an observation well 95 feet deep with 80 feet of casing and 100 feet to the east. The data collected from the aquifer tests were analyzed by the leaky-aquifer method described by Hantush (1956, p. 702) which assumes, among other things, that the aquifer is artesian, is overlain by a leaky confining bed, and that the pumped well is open to the full thickness of the aquifer. None of these assumptions were completely satisfied in either of the two tests. Although under long-term conditions water levels in the Biscayne aquifer respond as if the aquifer were a water-table aquifer, the presence of less permeable sands overlying the highly permeable pumped zone causes the aquifer to react as a leaky artesian system when subjected to short-term conditions such as heavy pumping. Also, none of the wells in the lower Hillsboro Canal area are open to the full thickness of the Biscayne aquifer. The water level drawdowns, in feet, were plotted (on logarithmic paper) against the quantity t/r2, where t is time, in minutes, since pumping started, and r is the distance, in feet, between the pumping well and the observation well. The resulting curve was matched to a family of leaky-aquifer type curves (Cooper, 1963 p. C-48-55). By superposition, match points were established for the best fit of the observed data to the type curves, and the T and S were calculated from the match points. For the test west of Boca Raton the T was 380,000 gpd/ft (gallons per day per foot) and at the test in Deerfield Beach, the T was 400,000 gpd/ft. The value for S at the test site west of Boca Raton was 0.04. At the Deerfield Beach test site the value for S was 0.0004. Values obtained from specific capacity tests of wells indicate to some extent the hydraulic properties of the aquifer and in some cases are of more immediate benefit than T and S values. The specific capacity is the amount of water in gpm discharged from a pumping well per foot of drawdown in the pumping well. Specific capacity tests were made on several wells in the north extension of the Boca Raton well field. Well PB 550 had a drawdown of

PAGE 33

26 BUREAU OF GEOLOGY about three feet after being pumped for 8 hours at 1130 gpm or a specific capacity of 377 gpm per foot. This figure conforms with the data from the test wells west of Boca Raton and is similar to figures furnished by Dr. J. I. Garcia-Bengochea (personal communication) for wells in the Boca Raton and Deerfield Beach well fields. This indicates that the hydraulic properties of the aquifer in both well fields and the test area west of Boca Raton are similar. The wells in the Boca Raton field range in depth from 115 to 120 feet with about 25 to 35 feet of open hole. The fact that the aquifer yields about the same amount of water to wells with 10-15 feet of open hole in the Deerfield Beach well field and 3 feet in the test area west of Boca Raton, and 25-35 feet in the Boca Raton well field, indicates that the aquifer is somewhat less permeable in the Boca Raton well field area than it is in the other areas. WATER QUALITY Major influences on the quality of fresh ground water in the lower Hillsboro Canal area are the quality of precipitation that reaches the water table and the infiltration, from canals draining inland areas, of highly colored water that is moderately mineralized. The chemical characteristics of the ground water also depend upon composition of the earth material through which the water moves and length of time the water is in contact with the materials. Ground-water samples for chemical analyses were collected throughout the area from 26 private wells and 8 test wells. Depth of the wells ranged from 40 to 206 feet below land surface; samples were collected at different depths during drilling of each test well. Chemical analyses of water samples are shown in Table 2. The concentration of dissolved constituents is expressed as mg/l (milligrams per liter). Iron, the most objectionable constituent found in solution in the ground water of this area, is derived from iron-bearing minerals within the aquifer. In samples analyzed, iron ranged from 0.03 to 1.83 mg/l and the average was about 0.45 mg/l. For public supply iron concentrations in excess of 0.3 mg/l are objectionable and impart a noticeable taste if the concentration exceeds 0.5 mg/1. When used for lawn irrigation, water containing iron in excess of 0.3 mg/1 may cause staining on houses, sidewalks, and vegetation. The concentration of dissolved iron in ground water in the lower Hillsboro Canal area cannot be accurately predicted with reference to location or depth. Removal of iron from large volumes of water can be accomplished economically by aeration and filtration.

PAGE 34

REPORT OF INVESTIGATION NO. 55 27 Hardness of water results from the solution of alkaline-earth minerals (such as the carbonate compounds) from soil and rocks, or from direct pollution by wastes. Calcium carbonate (limestone) is prevalent in the Hillsboro Canal area but is only sparingly soluble in pure water. Water that contains carbon dioxide or other acidic constituents will dissolve carbonate minerals readily; in the presence of carbon dioxide the carbonates are converted to the more soluble bicarbonates: CaCOa + COa + H20 -Ca(HC03)2 Hard water is generally believed to be harmless to man although urinary concretions may result from the consistent drinking of hard water (Rainwater, 1960, p. 173). Water having CaCOa concentration in excess of 120 mg/1 is considered hard. The CaCOa concentration of water sampled in the study area ranged from 126 to 368 mg/1 and averaged about 235 mg/1. Hardness increases with depth and with distance inland. Acidity or alkalinity of water is measured by the hydrogen ion concentration (pH). Water that is neither acid nor alkaline has a pH value of 7.0. Values smaller than 7.0 denote acidity and usually indicate a corrosive water; values greater than 7.0 denote alkalinity. The pH values of the water analyzed ranged from 7.4 to 8.2 and averaged about 7.7, which is slightly alkaline and would be expected to be noncorrosive. Color in water is expressed in terms of platinum-cobalt or Hazen units starting at zero and increasing with added color. Visible coloration of drinking water is aesthetically undesirable and concentrations in excess of 15 units is considered by U.S. Public Health Service (1962) to be unsuitable for use on interstate carriers. The range of concentration in the Hillsboro Canal area is from 0 to 50 units, the higher concentrations occurring in the western areas. Color in water is usually caused by decomposition of organic matter such as peat and muck which are common in the western part of the area and in buried mangrove swamps along the coast. Discoloration of water in the study area is also due partially to iron in solution. Material that causes high coloration in water can sometimes be recognized by its odor. The odor of hydrogen sulfide gas (H2S) was noted in water samples from some wells. This gas is derived from decomposition of organic matter, and it imparts an undesirable "sulphur water" odor which is easily removed by aeration. Hydrogen sulfide is not usually shown in standard complete analyses because of special techniques involved in obtaining samples.

PAGE 35

28 BUREAU OF GEOLOGY TABLE 2 -CHEMICALS ANALYSES OF WATER FROM SELECTED WELLS IN THE LOWER HILLSBORO CANAL AREA (chemical constituents are expressed in milligrams per liter). 30 E 0-a °E E 00 E 0 Well Dateof | --5 number1 Collectlon I 3 It 2 3 S o -1228 12-0-63 22 22 22 79 3.2 0.48 50 0.2 2.6 0.2 146 G-1228 01-06-64 195 195 195 79 9.8 .03 61 1.5 8.5 .6 176 G-1239 11-19-63 56 56 56 -3.3 .07 30 29 15 1.0 206 -1239 11-25-63 102 102 102 73 14 .07 96 20 210 7.2 310 6-1272 02-01-65 62 61 62 71 6.0 -64 1.1 7.1 .6 204 6-1272 02-03-65 173 168 173 -8.9 --62 1.3 8.0 .7 196 -1298 03-12-64 165 -165 74 11 .12 138 5.7 22 1.2 293 6-1299 04-14-64 145 -145 75 15 1.38 138 5.7 23 1.0 388 6-1300 03-12-64 106 -106 77 13 .42 123 1.6 17 1.3 384 6-1301 04-14-64 62 -62 77 7.3 1.03 98 3.8 8.4 .4 288 6-1302 03-12-64 100 -100 77 16 .82 135 3.6 29 1.1 364 6-1303 04-14-64 104 -104 75 19 .10 175 23 298 8.0 522 G-1304 04-05-62 83 -83 78 6.9 .70 66 .9 8.7 .5 194 -1314 03-12-64 ----82 13 .98 139 4.1 15 1.0 422 PB-220 03-11-64 174 -174 77 7.3 .78 86 2.8 12 .6 220 PB-251 04-14-64 150 -150 75 17 .30 82 3.3 13 1.4 250 PB-472 01-24-64 97 -97 76 11 1.83 104 4.0 22 1.2 312 PB473 01-24-64 105 -105 76 12 .27 136 3.5 14 .6 404 PB-474 03-10-64 56 54 56 78 7.4 .20 59 3.2 15 1.2 178 PB-475 03-10864 ----78 9.1 .25 66 2.8 12 .6 204 PB476 03-13-64 95 -95 76 18 .31 84 1.6 13 1.2 250 P-477 03-11-64 120 -120 78 5.5 .33 50 2.2 8.3 1.6 140 PB478 03-11-64 97 -97 77 8.9 .85 106 3.8 17 .5 236 PB479 03-11-64 121 -121 77 13 .32 78 2.8 12 1.1 240 PB480 03-11-64 40 -40 77 7.1 .39 104 15 115 3.9 200 P-481 03-13-64 112 -112 76 13 .32 133 1.9 16 1.1 396 PB482 03-13-64 75 -75 76 5.5 .11 110 3.8 22 1.4 328 PB483 04-14-64 100 -100 77 14 .18 83 4.6 21 1.2 264 PB-484 04-1464 120 -120 78 15 .05 90 3.3 14 1.0 274 PB-485 12-02-64 40 -40 -5.9 1.30 94 1.3 10 1.4 260 P8486 12-02-64 30 -30 78 6.2 1.20 76 .6 8.3 1.3 228 P&487 12-03-64 80 -80 73 6.1 .12 100 4.5 65 3.0 194 PB488 01-18-65 83 82 83 68 20 -69 1.0 6.8 1.0 210 P8-488 01-20-65 163 158 163 69 10 -64 2.1 5.3 .6 194 P8489 01-21-65 60 55 60 69 10 -48 2.4 7.0 .8 140 PB-489 01-25-65 208 204 208 69 11 -125 1.9 21 1.6 356 PB-490 01-26-65 65 61 65 72 7.6 -75 3.2 22 .8 220 P-490 01-27-65 135 131 135 70 16 -220 61 700 7.0 282 P-491 01-28-65 66 61 66 71 5.5 -82 4.7 17 3.4 218 P8-4S1 01-30-65 205 202 205 68 9.6 -1420 148 4850 30 261 PB492 02-04-65 81 79 81 71 7.8 -72 .1 18 1.0 212 PB492 02-05-65 163 161 163 70 11 -78 1.3 12 .8 248 1 2 G wellsare in Broward County 2Sampled while drilling PBwHelsare in Palm Beach County 3 Dissolved solids (Sum)

PAGE 36

REPORT OF INVESTIGATION NO. 55 29 Hardness as D CaCO P 3.6 3 .3 .3 180 158 14 312 8.0 20 2 15 28 .1 .4 262 194 25 429 7.8 20 2C o 0 .4 .1 8 0 .0 8.0 .2 .1 187 164 0 317 Remarks 4.8 5.0 0.5 0.0 144 126 6 232 7.9 70 2 3.6 16 .3 .3 180 158 14 312 8.0 20 2 15 28 .1 .4 262 194 25 429 7.8 20 2 32 340 .4 .1 872 320 66 1520 7.6 20 2 .0 8.0 .2 .1 1873 164 0 317 7.9 10 2 .0 13 .1 .0 1913 160 0 322 7.8 5 2 32 36 .2 .1 494 368 47 740 7.6 25 Pumping 31 36 .2 .2 482 368 50 741 7.6 15 Pumping .0 25 .3 .1 386 326 12 650 7.5 15 4.4 14 .3 .0 336 260 24 485 7.7 90 Pumped sample 17 63 .3 .0 492 352 54 755 7.7 20 120 518 .4 .6 1458 530 102 2700 7.7 10 7.2 15 .0 .0 204 168 9 360 7.9 25 .0 24 .3 .3 420 364 18 690 7.6 15 33 19 .2 .0 264 226 46 460 7.8 5 2.4 18 .3 1.3 294 218 13 435 7.6 20 Pumped sample 2.4 39 .3 .0 346 276 20 585 7.5 25 4.0 28 .4 .0 406 354 23 659 7.9 40 5.6 22 .1 .0 208 160 14 361 7.9 5 1.6 18 .1 .0 200 176 9 370 7.5 5 2.4 21 .3 .0 264 216 11 440 7.5 20 16 12 .2 .0 160 134 20 290 7.5 5 Pumped 68 30 .1 .0 406 280 86 585 7.4 25 .0 18 .1 .1 270 206 10 415 7.4 5 48 232 .1 16 748 320 156 1100 7.5 5 3.2 26 .7 .0 408 340 16 645 7.6 50 1.6 38 .3 .0 358 290 21 600 7.6 40 2.4 26 .2 .4 310 226 10 485 7.5 25 .0 24 .2 ,.1 310 238 14 491 7.4 15 20 17 .2 .1 2783 240 27 468 8.0 40 10 11 .3 .2 2293 192 2 390 8.2 50 Pumping 44 141 .1 16 4753 268 109 840 7.9 0 Golf Course .0 12 .1 .0 2133 176 4 339 8.1 3 2 .0 7.0 .2 .1 1853 168 9 315 8.0 15 2 2.0 9.0 .3 .0 1483 130 16 248 7.6 120 2 16 32 .2 11 3953 320 28 632 7.9 45 2 8.0 34 .1 .1 2593 200 20 440 8.0 20 2 136 1290 .2 1.4 25703 800 569 4400 8.0 20 2 41 25 .1 1.5 2873 224 46 478 7.9 5 2 974 9410 .2 4.0 170003 4150 3940 23900 7.6 15 2 17 22 .2 .1 2423 180 6 400 7.7 5 2 .8 19 .1 .0 2453 200 0 408 8.1 10 2

PAGE 37

30 BUREAU OF GEOLOGY Dissolved solids content of water represents the degree of mineralization of water and is determined by either of two methods: (1) evaporation of a measured amount of sample to dryness and weighing the residue; and (2) the sum of amounts of individually determined cations and anions. Cations are constituents which have positive electrical charges whereas anions have negative charges. Chemical analyses in Table 2 are expressed in mg/1 by weight of the constituent. However, most of the chemical characteristics of water can be better understood and more accurately represented from analyses expressed in epm (equivalents per million). Equivalents per million takes into account not only the weight of each constituent, but also the chemical reacting properties of the constituents. Therefore an analyses expressed in epm can be used more effectively in comparison of waters. Chemical type of water is commonly classified according to the concentration of seven principal chemical constituents or ions. Difficulty in comparing seven constituents simultaneously can be overcome by using geometric figures or polygons (Stiff, 1951) to represent the type of water. The preparation of a polygon that represents a specific chemical analysis can be shown with the analysis of water from well PB-487, in Table 2. The principal constituents are converted from mg/1 to epm by using conversion factors found in most chemical handbooks. Equivalents per million of each constituent is then converted to a percentage of the total cation of anion. The results of the conversions are shown in Table 3. Percentage values are then used to construct the polygon, figure 15. TABLE 3SELECTED CONSTITUENTS IN WATER FROM WELL PB-487. Constituent mg/I epm Percent Calcium (Ca) 100 4.99 60 Magnesium (Mg) 4.5 .37 5 Sodium (Na) and Potassium (K) 68 2.91 35 Total cations -8.27 100 Bicarbonate (HCO3) 194 3.18 38 Sulfate (SO4) 44 .92 11 Chloride (CI) 141 3.98 48 Fluoride (F) 0.1 .01 Nitrate (N03) 16 .26 3 Total anions -8.35 100 Dissolved solids 475 mg/1

PAGE 38

REPORT OF INVESTIGATION NO. 55 31 Points show percent concentration of dissolved constituents in water from well PB-487 Ca -HCO3 Mg *SO4 Na and K -Cl 100% 50% 50% 100% cations anions Equivalents per million a. Details and scale for preparing a polygon. b. Polygon showing the general chemical type of water in well number PB-487. Figure 15. An example of the preparation of a water-quality diagram using the percentage figures in table 3. Figure 15a shows the basic scale with seven constituents plotted on the graph. Joining the six points by straight lines gives the polygon shown in Figure 15b. The shape of the polygon and the relative length of the "spears" show the water to be somewhat equally strong in both calcium bicarbonate type and sodium chloride type. The relatively small amounts of magnesium and sulphate are typical of shallow ground water in southeastern Florida. Polygons showing the general type of the water from several wells distributed throughout the lower Hillsboro Canal area are shown in Figure 16. The diagrams also show the depth of the sample on the left side and the dissolved solids content on the right side. The relatively uniform shape of the polygons show that, except for a few samples, the water in the area to a depth of 200 feet is the same type (calcium bicarbonate type) containing dissolved solids generally less than 400 mg/1. Ground water in the narrow coastal ridge area is of exceptionally good quality, but ground water of good quality in larger quantities is available for future development farther inland. Well G-1239, located 4 miles west of State Road 7, is not in the immediate study area, figure 17, but should be considered in the overall water picture. At a depth of 56 feet the dissolved solids concentration of 226 mg/1 is normal, but the concentrations of magnesium and calcium ions are almost equal. The increase in magnesium is caused by the presence of dolomite, a carbonate rock and equal amounts of calcium and magnesium. Dissolved solids increased to 872 mg/1 at a

PAGE 39

32 BUREAU OF GEOLOGY IX P L A NAT1O 0 -'rI :.----2r -^^ + { oP-g Figure 16. Map showing relative concentrations of chemical constituents in ground water of the lower Hillsboro Canal area. depth of 102 feet, caused by the increase in sodium chloride. Saline water in shallow aquifers in inland areas of southern Florida may be residual from invasions of the sea during Pleistocene time (Sherwood and Klein, 1963). In general the data show water in the area to be good in quality except in areas adjacent to the coast and the uncontrolled reaches of the Hillsboro and El Rio Canals where sea-water intrusion has occurred.

PAGE 40

REPORT OF INVESTIGATION NO. 55 33 SEA-WATER INTRUSION Sea-water intrusion in the Biscayne aquifer usually occurs from: (1) direct intrusion of sea water into the coastal parts of the aquifer and along uncontrolled canals; and (2) sea water that remained in the sediments after deposition during Pleistocene interglacial, when the ocean inundated most of south Florida. Present day intrusion of sea water is the only source of salt-water contamination in the lower Hillsboro Canal area. Farther west, the chloride content of the water increases with depth, indicating that residual sea water is present in the aquifer. However, part of the salty water comes from materials of lower permeability that lie below the Biscayne aquifer. Sea-water intrusion in the lower Hillsboro Canal area of the Biscayne aquifer is governed by the relationship of ground-water levels to mean sea level. If a specific gravity of 1.025 is assumed for seawater, each foot of fresh water above mean sea level should indicate 40 feet of fresh water below mean sea level as described by the Ghyben-Herzberg principle (Brown, 1925, p. 16-17). However, in southeast Florida, geologic and hydrologic conditions are such that the depth to salt water is generally more than 40 feet for each foot of fresh water head, but the relationship is sufficiently valid to the extent that intrusion would be expected in areas where ground-water levels were persistently low. The uncontrolled canals and waterways are connected to the ocean, which facilitates sea-water intrusion in two ways: (1) drainage is allowed which lowers adjacent ground-water levels and reduces freshwater head that normally would oppose the inland movement of sea water; and (2) sea water is conveyed inland during dry periods, providing a source of intrusion by infiltration of the sea water into the aquifer. Because about 91 percent of the dissolved constituents in sea water are chloride salts, analyses of the chloride content of water samples can be used reliably to determine the extent of sea-water intrusion. Figures 17 and 18 show the results of chloride traverses of the uncontrolled reaches of the El Rio and Hillsboro Canals. Water samples taken during these traverses were from the bottom of the canal at each station. Although the chloride content of the canals has a wide range, the figures illustrate that the chloride content decreases with increasing distance inland from the sea-water source. Decreased chloride content in the upper reaches also results from increased groundwater flow to the canals due to higher ground-water levels there than in the area adjacent to the lower reaches of the canals. The El Rio Canal is relatively shallow throughout most of its reach in the vicinity of Boca Raton -the depth decreases northward from

PAGE 41

34 BUREAU OF GEOLOGY 0poo ---_--\ S\ t 5 v \ i t\H 4 I \ al o 50 10 --------Figure 17. Chloride content of water at nine points in the El Rio Canal between the Hillsboro Canal and 13th Street. about seven feet at the confluence with the Hillsboro Canal to about two or three feet at the N.W. 7th Street bridge (Fig. 17). The Hillsboro Canal conveys salt water to the El Rio Canal; therefore the chloride content of the water at the confluence of the two canals will determine to some degree the chloride content of the upper reaches of the El Rio Canal. The chloride content at the confluence depends largely on the combination of tidal stage and discharges at the Hillsboro Canal and E-3 Canal control structures. In Figure 17, the sample taken at the;

PAGE 42

REPORT OF INVESTIGATION NO. 55 35 HILLSBORO CANAL MIL ooo , .J I 20,000 2 -Z o 5 1,000 i 5002 0 5) 0 10 cr 00 -j IId Figure 18. Chloride content of water at nine points in the Hillsboro Canal upstream from the IntracoastalWaterway, September 20,1966. confluence on August 12, 1964 was during high tide. On the same day discharge at the structure in the Hillsboro Canal was.3 7 cfs (cubic feet per second) and had been low for several days prior to the sampling. The September 20, 1966 sample was taken on a falling tide and the The September 20, 1966 samnple was taken on':a falling tide and the

PAGE 43

36 BUREAU OF GEOLOGY discharge was 198 cfs. The June 2, 1966 sample was taken on a falling tide also, but discharge at the control was 485 cfs. Figure 18 shows that on September 20, 1966, during a falling tide, the chloride content of the Hillsboro Canal from the Intracoastal Waterway to the El Rio Canal was about the same as that of sea water. West of the confluence of the El Rio and Hillsboro Canals discharge through the controls of the Hillsboro and E-3 Canals into the lower Hillsboro Canal have freshened the water in the Hillsboro Canal. Figure 19 shows isochlors in a subsurface section extending from the barrier islands westward through the Boca Raton well field and into the interior flatlands along line A -A' in Figure 16. The dashed lines (isochlors) connect points in the subsurface where the chloride content of the ground water is equal to the value of the line. Examination of Figure 19 indicates that sea water has intruded into the Biscayne aquifer, at depth, from both the Intracoastal Waterway and the El Rio Canal. The continuous pumping and the resultant lowering of water levels in the Boca Raton well field has caused the most intrusion from the El Rio Canal; this is indicated by the more gentle slope of the isochlors on the west side of the ridge area than on the east side of the ridge. Sea-water intrusion from the Intracoastal Waterway into the Biscayne aquifer in the Boca Raton area is indicated by the high concentrations of sodium and chloride in the polygon diagrams of wells PB 478 and PB 489 (Fig. 16). The wells are used for irrigation of a golf course in south Boca Raton. The Diagrams in Figure 16 show that although well PB 487 is twice as deep as PB 480 the dissolved solids content of its water is only about half that of PB 480. This is probably because well PB 487 is slightly farther from the major source of sea water, Lake Boca Raton, and that well PB 480 has been in use 24 years longer than well PB 487 and has had more time to induce a tongue of sea water to move toward it. Although some sea water has entered the Biscayne aquifer in the Boca Raton area, fresh water levels have been sufficiently high between the well field and the El Rio Canal to prevent the intrusion of a harmful amount. This is indicated by the low chloride content of water in well PB 492 to a depth of 162 feet below land surface (Fig. 16 and 19). However, several consecutive dry years might change the situation drastically, especially if pumping levels in the well field are lowered and the El Rio Canal is deepened. Figure 20 shows the fluctuations of the chloride content of the water in the El Rio Canal at the 7th Street bridge. The relatively small volume of water in the El Rio Canal allows the chloride content to

PAGE 44

A I " A' W z Q. ,, I. a S0 0 C J c ) < 50 LEVEL LEVEL g 50 28 w .0 50-34 / 50 1 2 28 S 1o 22 o/!1 , 2" 100l7 1/ *1500 ,,,o ( /S , 1 410 EXPJ.ANATION --0-o----1 ISOCHLORS, MILLIGRAMS PER LITER IS NUMBERS INDICATE CHLORIDE CONTENT AT POINT SAMPLED IN WELL Figure 19. Section along line A-A' (figure 16) showing lines of equal chloride content (isochlors) of ground water. ,,4

PAGE 45

38 BUREAU OF GEOLOGY change rapidly. These changes are in response to: (1)i tidal action; (2): ground-water inflow from adjacent areas where ground-water levels are sufficiently high; and (3) discharge from the Hillsboro Canal and E-3 Canal. Discharge in excess of 500 cfs from the Hillsboro Canal with attendant discharge from the E-3 Canal and ground-water inflow along the uncontrolled reach of the Hillsboro Canal appears to be sufficient to maintain fresh water in the Hillsboro Canal downstream of the mouth of the El Rio Canal. Sea-water intrusion into the Biscayne aquifer was not detected in the Deerfield Beach area except in wells adjacent to finger canals off the Intracoastal Waterway. Well G-1228 is located between the Hillsboro Canal and the Deerfield Beach well field (Fig. 3 and 16), in an area that would be most vulnerable to the threat of sea-water intrusion. Water levels in the vicinity of the well G-1228 are affected by continuous drainage to the uncontrolled reach of the Hillsboro Canal and by the pumping in the well field. Therefore, if sea water were to move inland in the aquifer, sampling of well G-1228 would give an early indication of the movement. No indication of movement has been observed in the analysis of samples from this well. WATER USE AND POTENTIAL SUPPLY The Biscayne aquifer is the source for all municipal water supplies in the lower Hillsboro Canal area. The rapidly increasing population of the area will require larger quantities of water from the aquifer to meet future needs. This is substantiated by past pumpage records shown in Figures 9 and 10 for the period 1963-67. The capacities of the water plants of Boca Raton and Deerfield Beach were both doubled in 1965, Boca Raton to 23 mgd and Deerfield Beach to 16 mgd, to meet the increased demands for treated water. The predicted population figure of more than 50,000 for the area by 1970 will require further expansion of the well fields or the establishment of new well fields. This is partly due to the fact that the per capita use of water increases with time: the per capita use in American cities in 1920 was 115 gallons per day; in 1960 the average use had increased to 150 gallons per day, a 30 percent rise in 40 years; in 1966, the average per capita use of water in the lower Hillsboro Canal area was about 180 gallons per day. The potential supply available from the Biscayne aquifer in the lower Hillsboro Canal area depends upon the factors which balance recharge and discharge in accordance with the following equation: Recharge =Discharge (surface-water discharge + ground-water discharge + evapotranspiration + pumpage) + change in storage. + -I -g, ..;

PAGE 46

0-0 ' .* NO RECORD O ' , .: op ,,oo1 -, ° 6 -. :-MAXIMUM " , 0" MINIMUM 10 MAR APR 'MAY JUN 'JUL 'AUG SEP 'OCT ' NOV 'DEC JAN FEB 'MAR APR MAY 'JUN JUL 'AUG 1964 1965 Figure 20. Approximate daily maximum and minimum chloride content of water in the El Rio Canal at 7th Street, Boca Raton, Florida, for the period March 1964 through August 1965. w C.,'

PAGE 47

40 BUREAU OF GEOLOGY Replenishment by rainfall can be assumed as constant, evapotranspiration and ground-water discharge rates will not change in magnitude, and pumping will increase with time. Water levels have not changed significantly during the period 1964-1967 indicating that the net aquifer storage has remained unchanged. The total potential supply of the area therefore represents the quantity of water discharged through the Hillsboro Canal to the ocean, plus the amounts that can be withdrawn from aquifer storage each year without lowering water levels to the detriment of quality. Lowering of water levels as a result of pumping from storage will not significantly change losses by evapotranspiration in the area. The most critical periods affecting the water resources of the lower Hillsboro Canal area are the prolonged droughts when water levels are lowest and well field pumping is heaviest. A graph of the discharge of the Hillsboro Canal at the control structure for 1965 is shown in Figure 21. Discharge is greatest during the rainy season, the maximum of more than 3,000 cfs (1,900 mgd) occurring at the end of October. The minimum discharge during the dry season was 40 cfs (26 mgd) and the average discharge for the year was 373 cfs (240 mgd). A significant part of the flow through the Hillsboro Canal represents water that could be used in the future if facilities were made available for retention in the system -water that could be salvaged instead of being lost to the ocean. In addition, vast quantities of ground water are available from aquifer storage, primarily in the area west of the coastal ridge where water levels are high throughout the year. Water control practices of the Lake Worth Drainage District have maintained water levels in the area west of Canal E-3 near 12 feet above msl. Because a large part moves eastward, surface water in that District can be considered a perennial source of recharge by underseepage to the aquifer between the El Rio Canal and Canal E-3. Also, the aquifer in the inland areas of Deerfield Beach is replenished during the dry season by seepage from the controlled reach of the Hillsboro Canal and by ground water inflow from the irrigation district farther west. These sources can also be depended upon as perennial sources of replenishment to the aquifer. Therefore large withdrawals of ground water can be made from the inland areas between the Sunshine State Parkway on the west and the Seaboard Coast Line Railroad on the east without seriously lowering water levels. Furthermore, additional supplies are yet (1969) available from the coastal ridge north of Boca Raton well field but as indicated, the aquifer there decreases in permeability and well-field expansion in that

PAGE 48

30 28 26 24 zo 0 22 § S0 m 20 a. I 0 IJAN. FEB. MAR. APR, MAY JUNE JULY AUG. SEPT. OCT. *NOV DEC. 12 Figure 21. Graph showing the discharge of the Hillsboro Canal at the control near Deerfield Beach, 1965.

PAGE 49

42 BUREAU OF GEOLOGY direction might not be feasible. On the other hand, the area south of the Deerfield Beach well field is underlain by materials of moderate to high permeability and possible expansion in that direction might be considered. However, withdrawals along the coastal ridge should be limited or closely monitored because of the constant threat of seawater intrusion. As the area continues to urbanize and water demands increase, greater reliance will have to be placed on interior water resources and possibly on importation of water from the inland water conservation system of the Central and Southern Florida Flood Control Project. Expansion of the data collection network will be necessary to monitor changes in the hydrology of the inland area for adequate management and protection of the water resources of the lower Hillsboro Canal area. SUMMARY The Biscayne aquifer is the only source of fresh ground water for municipal supplies in the lower Hillsboro Canal area. The aquifer extends from land surface to a depth of about 400 feet near the coast, thins to the west and decreases in permeability to the north. The primary source of recharge to the aquifer is local rainfall, of which more than one-third reaches the water table. An additional source of recharge is infiltration from the controlled canals of the local irrigation and drainage districts and the Central and Southern Florida Flood Control District, especially the controlled reach of the Hillsboro Canal. The ground water is of generally good chemical quality except in areas adjacent to the coast and uncontrolled reaches of the Hillsboro and El Rio Canals where sea-water intrusion has occurred. Data indicate that the greatest potential source of water from the Biscayne aquifer is in the inland areas where water levels are high throughout the year and perennial replenishment to the aquifer is available by infiltration from the controlled canals and underseepage from the conservation areas. Large quantities of fresh ground water can be withdrawn from the Biscayne aquifer in the interior area to meet future demands without the threat of sea-water intrusion. Much of the average flow of 240 mgd through the Hillsboro Canal control represents water that could be used in the future if facilities were made available for retention in the system. As urbanization expands to the west, the accompanying demands for water and the expansion of drainage systems for development will have a significant effect on the hydrologic system of the area. This will require that the data collection network now in existence be expanded to monitor future changes in the system so the water resources of the lower Hillsboro Canal area can be adequately managed and protected.

PAGE 50

REPORT OF INVESTIGATION NO. 55 43 WELL NUMBERS In order to coordinate data from wells on a nationwide basis, the U.S. Geological Survey has adopted a well numbering system which locates the well by a 16 character number based on latitude and longitude. The consecutive county well numbers used in this report are referenced to the nationwide system, as follows: County Latitude-Longitude County Latitude-Longitude No. No. No. No. G-1228 261914N0800607.1 PB-479 262218N0800739.1 G-1239 261838N0801513.1 PB-480 262039N0800503.1 G-1272 261334N0800619.1 PB-481 262150N0801148.1 G-1298 261527N0801138.1 PB-482 262211N0801008.1 G-1299 261659N0800859.1 PB-483 262519N0800714.1 G-1300 261704N0801022.1 PB-484 262123N0800738.1 G-1301 261821N0800709.1 PB-485 262444N0800452.1 G-1302 261856N0800842.1 PB-486 262443N0800453.1 G-1303 261840N0801633.1 PB-487 262054N0800501.1 G-1304 261908N0800622.1 PB-488 262205N0800717.1 G-1314 261815N0801115.1 PB-489 262453N0800454.1 PB-220 262256N0800531.1 PB-490 262117N0800550.1 PB-251 262206N0800842.1 PB-491 262114N0800540.1 PB-472 262454N0801236.1 PB-492 262120N0800532.1 PB-473 262133N0801254.1 PB-548 262148N0800525.1 PB-474 262306N0800507.1 PB-549 262219N0800538.1 PB-475 262332N0800448.1 PB-550 262311N0800534.1 PB-476 262159N0800844.1 PB-555 262118N0800515.1 PB-477 262138N0800501.1 PB-556 262229N0800934.1 PB-478 262222N0800527.1 PB-557 262229N0800934.2 PB-558 262229N0800935.1

PAGE 51

44 BUREAU OF GEOLOGY REFERENCES Black, A.P., and Brown, Eugene 1951 Chemical character of Florida's waters: Fla. State Bd. of Cons., Div. Water Survey and Research, Paper 6. Cooke, C. W. 1945 Geology of Florida, Fla. Geol. Surv. Bull. 29. Cooper, H. H.,Jr. 1963 Type curves for nonsteady radial flow in an infinite leaky artesian aquifer in shortcuts and special problems in aquifer tests: See WSP 1545-C for U.S. Geol. Survey Water-Supply Paper 1545-C, p. C48-C55. Cooper, H. H.Jr., andJacob, C. E. 1946 A generalized graphical method for evaluation formation constants and summarizing well-field history, Am. Geophys. Union Trans., v. 27, no. 4, p.526-534. Hantush, MC. 1956 Analysis of data from pumping tests in leaky aquifers: Am. Geophys. Union Trans. v. 37, no. 6, p. 702-714. Meinzer, O. E. 1923 The occurrence of water in the United States, with a discussion of principles: U.S. Geol. Survey Water-Supply Paper 489. Parker, G. G., Ferguson, G. E., and Love, S. K. 1955 Water resources of southeastern Florida, with special reference to the geology and ground water of the Miami area: U.S. Geol. Survey WaterSupply Paper 1255. Rainwater, F. H. and Thatcher, L. L. 1960 Methods for collection and analysis of water samples: U.S. Geol. Survey Water-Supply Paper 1454. Schroeder, M. C., Milliken, D. L., and Love, S. K. 1954 Water resources of Palm Beach County, Fla: Fla. Geol. Survey Bull. 13. Sherwood, C. B., and Klein, Howard 1963 Saline ground water in southern Florida: Nat. Water Well Assoc. "Ground Water", v. 1, no. 2. Stiff, H. A.,Jr. 1951 The interpretation of chemical water analysis by means of patterns: Jour. of Petrol. Tech., p. 15, Oct. Tarver, G. R. 1964 Hydrology of the Biscayne aquifer in the Pompano Beach area, Broward County, Fla.: Fla. Geol. Survey Rept. Inv. no. 36. Theis, C. V. 1938 The significance and nature of the cone of depression in ground-water bodies:Econ. Geology, v. 33, no. 8, p. 889-902. U. S. Public Health Service 1962 U.S. Public Health Service drinking water standards: Public Health Service Pub. 956, 61 p. See Public Health Repts.

PAGE 52

-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.


xml record header identifier oai:www.uflib.ufl.edu.ufdc:UF0000124200001datestamp 2008-12-08setSpec [UFDC_OAI_SET]metadata oai_dc:dc xmlns:oai_dc http:www.openarchives.orgOAI2.0oai_dc xmlns:dc http:purl.orgdcelements1.1 xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.openarchives.orgOAI2.0oai_dc.xsd dc:title Ground-water resources of the Lower Hillsboro Canal area, southeastern FloridaReport of investigations - Florida Bureau of Geology ; no. 55dc:creator McCoy, H. J. (Henry Jack)Hardee, Jack.dc:subject Groundwater -- Florida -- Palm Beach County.Groundwater -- Florida -- Broward County.dc:description Cover title.Includes bibliographical references (p. 44).Digitized as a collaborative project with the Florida Geological Survey, Florida Department of Environmental Protection.dc:publisher Bureau of Geology, Florida Department of Natural Resourcesdc:date 1970.dc:type Bookdc:format vii, 44 p. : ill. ; 23 cm.dc:identifier http://www.uflib.ufl.edu/ufdc/?b=UF00001242&v=00001AAA0638 (notis)AED9231 (notis)49977937 (oclc)dc:source University of Floridadc:language Englishdc:coverage 1209912011