DTIC ADA447018: Geohydrology and Potential for Upward Movement of Saline Water in the Cocoa Well Field, East Orange County, Florida

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Geohydrology and Potential for Upward
Movement of Saline Water in the Cocoa Well
Field, East Orange County, Florida
By G.G. Phelps and Donna M. Schiffer
U.S. GEOLOGICAL SURVEY
Open-File Report 95-736
Prepared in cooperation with
St. Johns River Water Management District
South Florida Water Management District
City of Cocoa, Florida
Tallahassee, Florida
1996
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1. REPORT DATE 2. REPORT TYPE 3. DATES COVERED
1996 N/A -
4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
Geohydrology and Potential for Upward Movement of Saline Water in
5b. GRANT NUMBER
the Cocoa Well Field, East Orange County, Florida
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S) 5d. PROJECT NUMBER
5e. TASK NUMBER
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
U.S. Department of the Interior 1849 C Street, NW Washington, DC REPORT NUMBER
20240
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)
11. SPONSOR/MONITOR’S REPORT
NUMBER(S)
12. DISTRIBUTION/AVAILABILITY STATEMENT
Approved for public release, distribution unlimited
13. SUPPLEMENTARY NOTES
14. ABSTRACT
15. SUBJECT TERMS
16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF
ABSTRACT OF PAGES RESPONSIBLE PERSON

a. REPORT b. ABSTRACT c. THIS PAGE SAR 44
unclassified unclassified unclassified
Standard Form 298 (Rev. 8-98)
Prescribed by ANSI Std Z39-18
U.S. DEPARTMENT OF THE INTERIOR
BRUCE BABBITT, Secretary
U.S. GEOLOGICAL SURVEY
Gordon P. Eaton, Director
For additional information Copies of this report can be
write to: purchased from:
U.S. Geological Survey
District Chief Branch of Information Services
U.S. Geological Survey, WRD Federal Center
227 N. Bronough Street, Suite 3015 Box 25286
Tallahassee, FL 32301 Denver, CO 80225-0286
CONTENTS
Abstract.................................................................................................................................................................................. 1
Introduction .......................................................................................................................................................................... 2
Purpose and Scope....................................................................................................................................................... 3
Previous Investigations................................................................................................................................................ 3
Description of Study Area........................................................................................................................................... 5
Acknowledgments....................................................................................................................................................... 5
Geohydrologic Framework.................................................................................................................................................... 6
Chloride Concentrations in Ground Water ...........................................................................................................................12
Water Levels15......................................................................................................................................................................15
Factors Affecting Water Levels...................................................................................................................................15
Barometric Pressure and Tidal Effects..............................................................................................................15
Density Differences...........................................................................................................................................15
Trends in Long-Term Water Levels.............................................................................................................................19
Aquifer Tests..........................................................................................................................................................................21
Slug Tests.....................................................................................................................................................................21
Aquifer Test 1..............................................................................................................................................................23
Aquifer Test 2..............................................................................................................................................................24
Aquifer Test 3..............................................................................................................................................................27
Factors Affecting Vertical Movement of Saline Water..........................................................................................................30
Vertical Hydraulic Conductivity..................................................................................................................................30
Vertical Hydraulic Gradient.........................................................................................................................................31
Potential for Upward Movement of Saline Water.................................................................................................................32
Summary and Conclusions....................................................................................................................................................35
Selected References...............................................................................................................................................................37
FIGURES
1. Map showing selected wells in the Cocoa well field...................................................................................................... 2
2. Graph showing chloride concentration in water from zone 1 of Cocoa C, 1966-94...................................................... 5
3. Graph showing average monthly rainfall at Orlando, Fla., based on 30 years of record (1961-90).............................. 6
4. Generalized geohydrologic section in the Cocoa well field........................................................................................... 7
5. Geophysical logs for well R........................................................................................................................................... 8
6. Geohydrologic section showing well-completion information for wells C and R.........................................................10
7. Map showing the potentiometric surface of the Upper Floridan aquifer in the vicinity of the
Cocoa well field, September 1993.........................................................................................................................................11
8. Map showing chloride concentration in water from the Upper Floridan aquifer, Orange County, Fla.,
and vicinity.................................................................................................................................................................12
9-14. Graphs showing:
9. Chloride concentrations in water from selected wells in the Cocoa well field, 1960-94.........................................13
10. Chloride concentrations in water from zones of well C, 1966-94............................................................................14
11. Relation of chloride concentration and depth in selected wells...............................................................................16
12. Relation of chloride concentration and depth in parts of wells C, R and S..............................................................17
13. Water levels in well 1 at Bithlo, Fla., and Cocoa R, November 12-19, 1993...........................................................18
14. Water levels in well R and barometric pressure, January 20-February 15, 1994.....................................................19
15. Diagram showing definitions of point-water, freshwater, and environmental-water heads in ground water
with variable density...................................................................................................................................................20
16. Graphs showing point-water heads in zones 1 and 3 of well C, equivalent freshwater head in zone 1,
and monthly rainfall at Orlando, Fla., 1966-94..............................................................................................................21
Contents III
17. Graphs showing water levels in zones 3, 4, and 5 of well C, 1966-94, and in well Bithlo 1, 1974-94.........................22
18. Graphs showing water-level response of zones 1, 3, and 4 in well C to slug tests........................................................24
19. Geohydrologic section showing well-completion data near well C..............................................................................25
20 Graphs showing water levels in wells B and C, August 19-27, 1993............................................................................26
21. Graph showing relation of residual drawdown (s) and ratios of time divided by distance squared (t/r2)
for well B and zone 5 of well C, August 27, 1993.....................................................................................................27
22. Geohydrologic section showing well-completion data for well R and supply well 21.................................................28
23. Graph showing water levels in well R and supply well 22, November 15, 1993..........................................................29
24. Graph showing water levels in zones 1 and 5 of well C, February 9, 1994...................................................................30
25. Geohydrologic section identifying variables for calculating hydrostatic head in ground water with
variable density..........................................................................................................................................................32
26. Graph showing difference between head in zone 3 of well C and calculated hydrostatic head at the
freshwater-mixed water interface, 1965-94................................................................................................................33
27. Graphs showing water levels in the Lake Ivanhoe well, Orlando, Fla., 1989-94..........................................................34
28. Graph showing total monthly pumpage from wells 14 and 15 and chloride concentration in water
from zones of well C, 1967-94...................................................................................................................................35
TABLES
1. Selected wells in the Cocoa well field............................................................................................................................. 4
2. Well information for August 25-27, 1993, aquifer test....................................................................................................25
3. Pumping rates for February 9, 1994, aquifer test.............................................................................................................29
CONVERSION FACTORS, VERTICAL DATUM, ABBREVIATIONS, AND WELL-NUMBERING SYSTEM
____________________________________________________________________________________________________________________________
Multiply By To obtain
_________________
Length
foot (ft) 0.3048 meter
inch (in.) 25.4 millimeter
mile (mi) 1.609 kilometer
Volume
gallon (gal) 0.003785 cubic meter
Flow
gallon per minute (gal/min) 0.06309 liter per second
million gallons per day (Mgal/d) 0.04381 cubic meter per second
Hydraulic conductivity
foot per day (ft/d) 0.3048 meter per day
Transmissivity
foot squared per day (ft2/d) 0.0929 meter squared per day
Acceleration
foot per second, squared (ft/s2) 0.3048 meter per second, squared
___________________________________________________________________________________________________________
Sea level: In this report “sea level” refers to the National Geodetic Vertical Datum of 1929—a geodetic datum derived from a
general adjustment of the first-order level nets of the United States and Canada, formerly called Sea Level Datum of 1929.
Altitude, as used in this report, refers to distance above or below sea level.
Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times foot of aquifer thickness [(ft3/d)/ft2]ft.
In this report, the mathematically reduced form, foot squared per day (ft2/d), is used for convenience.
Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (m S/cm at 25 ˚C).
Concentrations of chemical constituents in water are given in milligrams per liter (mg/L).
IV Contents
ABBREVIATIONS
NOAA National Oceanic and Atmospheric Administration
mg/L milligrams per liter
min minute
SFWMD South Florida Water Management District
SJRWMD St. Johns River Water Management District
USGS U.S. Geological Survey
WATSTORE U.S. Geological Survey’s NationalWater DataStorage andRetrieval System
Well-Numbering System
The supply well numbers in this report were assigned by the city of Cocoa. Supply-well numbers were assigned in the
general order in which the wells were drilled. Observation wells were assigned letters in the general order in which the wells
were incorporated into the monitoring-well network. A second well-numbering system used in this report, a 15-digit number
based on latitude and longitude, identifies wells in the U.S. Geological Survey’s NationalWater DataStorage andRetrieval
System (WATSTORE). The first 6 digits denote the degrees, minutes, and seconds of latitude; the next 7 digits denote degrees,
minutes, and seconds of longitude; and the last 2 digits denote a sequential number of a well site within a 1-second grid. For
example, well 282532081075601 (Cocoa B) is the first well inventoried at latitude 28˚25'32" N, longitude 081˚07'56" W.
Contents V
VI Contents
Geohydrology And Potential For Upward Movement Of
Saline Water In The Cocoa Well Field, East Orange
County, Florida
By G. G. Phelps and Donna M. Schiffer
ABSTRACT with depth and to monitor changes with time,
including a multi-zone well drilled in 1965 (well
The Floridan aquifer system, an approxi- C) and two wells drilled in the 1990’s
mately 2,000-foot thick sequence of Eocene-age (wells R and S). Chloride concentrations have
limestone and dolomite, is the main source of increased in the zone pumped by the supply wells
water supply in central Florida. Hydraulic con- (the upper 500 feet of the aquifer) and in the
ductivity is different in strata of different lithol- 1,351-1,357-foot deep zone of well C, but not in
ogy and is the basis for separating the aquifer the two intervening zones. This indicates that the
system into the Upper Floridan aquifer, a middle source of saline water is located laterally, rather
semi-confining unit, and the Lower Floridan aqui- than vertically, from the pumped zone in the area
of well C.
fer. The coastal city of Cocoa withdraws about
The potential for upward movement of
26 million gallons of water per day from the
saline water depends on the direction of the verti-
Upper Floridan aquifer from a well field in east
cal hydraulic gradient and on the vertical hydrau-
Orange County, about 25 miles inland. About
lic conductivity of the aquifer. A series of aquifer
60 million gallons per day are withdrawn from the
tests was run in 1993-94 and existing water-level
Upper Floridan aquifer and 56 million gallons per
and water-quality data were analyzed to evaluate
day from the Lower Floridan aquifer in the
the potential for upward movement of saline
Orlando area, about 15 miles west of the Cocoa
water in the well field. The transmissivity of the
well field.
upper 500 feet of the aquifer is about 100,000 feet
Wells drilled in the Cocoa well field from squared per day (the horizontal hydraulic conduc-
1955-61 yielded water with chloride concentra- tivity is about 200 feet per day) and the storage
tions ranging from 25-55 milligrams per liter. coefficient is about 2x10-4. Horizontal hydraulic
Soon after the wells were put in service, chloride conductivities determined from slug tests of the
concentrations increased; therefore, new wells three deepest zones of well C ranged from
were drilled further inland. Chloride concentra- 20-50 feet per day. Vertical hydraulic conductivi-
tions in water from many of the new wells also ties probably do not exceed 0.05 feet per day.
have increased. Possible sources of saline water The vertical hydraulic gradient is deter-
are lateral movement of relict seawater in the mined by comparing water levels in the various
Upper Floridan aquifer from the east, regional zones, but because of density differences, unad-
upconing of saline water from the Lower Floridan justed water levels in the deepest zone investi-
aquifer or underlying older rocks, or localized gated cannot be directly compared to water levels
upward movement of saline water through frac- in the overlying freshwater zones. The difference
tures. Several test wells were drilled to provide between environmental-water heads (adjusted for
information about chloride concentration changes density differences) in the saline-water zone of
Abstract 1
well C and the overlying freshwater zone were Lower Floridan aquifer if the low conductivity
calculated from measured water levels for the zone is thin or breached by fractures, or by a com-
period 1966 to 1994. During most of this time bination of both lateral and vertical movement.
period, the gradient was downward, indicating
that saline water did not move upward.
INTRODUCTION
Upconing of saline water probably is not
taking place in the center and western part of the The city of Cocoa in Brevard County, Florida,
well field, based on the low vertical hydraulic has withdrawn water from the Floridan aquifer system
conductivity values estimated for the middle in East Orange County, Florida, since 1955 when the
semi-confining unit, the generally downward ver- Cocoa well field (fig. 1) was constructed. The city of
tical hydraulic gradient, and the constant chloride Cocoa supplies water for much of central Brevard
concentrations in the intermediate zones of well C. County. The well field is located 25 mi inland because
However, there is no information about the extent of the saline water which underlies most of Brevard
of the zone of low vertical hydraulic conductivity County and the extreme eastern part of Orange
or about the direction of the vertical hydraulic County. The term saline water, as used in this report, is
gradient in the eastern part of the well field. Thus, defined as water with a chloride concentration greater
increased chloride concentrations in supply wells than 250 mg/L.
in the eastern part of the well field could be The original 13 wells in the Cocoa well field
caused either by lateral movement of saline water (numbers 1-11 and 12A and 12B, fig. 1) were drilled
from the east, or by upward movement from the from 1956 to 1961 and collectively have a capacity to
811(cid:176) 5¢ 10¢ 810(cid:176) 5¢
EXPLANATION 50 JACKSONVILLE
COCOAMONITOR WELL BITHLO1
COCOA
COCOAMONITOR WELLEQUIPPED
WITH WATER LEVELRECORDER
COCOASUPPLY WELL
ORANGE
COUNTY
0 1 2 3 MILES ORLANDO
COCOA
WELLFIELD
0 1 2 3 KILOMETERS AREA
283(cid:176) 0¢ 520
15A Ec
o
nlo
ck
h
atc H
h
e
e
15 Rive 10F
528 r 528
TOORLANDO 9
AIRPORT P
3MILESFROM 8
INTERSECTION 2
3
C B 7A
282(cid:176) 5¢ Lake BLaukcek WEEWAHOOTEEROAD D 1178 16 15 14 13 S 15 76(DESTROYED)
Nona 19
LRaekde LBaakrteon Lake R 221022 44A1 12B12A WAEEWAHOCOOTECEOWAAWTEERLLPLFANIETLDROAD
MLaukde Lake MaryJane 11
Hart
Figure 1. Location of selected wells in the Cocoa well field.
2 Geohydrology and Potential for Upward Movement of Saline Water in the Cocoa Well Field, East Orange County, Florida
produce 17.5 Mgal/d. Chloride concentrations in many are regional in scope. More site-specific information is
of these wells began to increase soon after being put needed to estimate the rate of possible upward move-
into service and the regular use of some of the wells ment of saline water, which is a function of the
was discontinued. Some of the original 13 wells were hydraulic properties of the aquifers and confining lay-
placed on standby and some were plugged back to ers between the aquifers and of the magnitude and
shallower depths. These 13 wells are referred to col- direction of the vertical hydraulic gradient. The U.S.
lectively as the “old well field.” Six additional wells Geological Survey (USGS), in cooperation with the
(numbers 7A and 13-17, fig. 1), with a combined St. Johns River Water Management District
capacity of 12Mgal/d, were drilled beginning in 1962 (SJRWMD), the South Florida Water Management
along an east-west line to avoid further increases in District (SFWMD), and the city of Cocoa, began a
chloride concentrations in water from wells in the two-year study in the Cocoa well field in 1993 to
old well field. Well 4A1 was drilled in the 1970’s. determine aquifer properties of the confining zones
Wells 18-22 were drilled between 1984 and 1992. Well between the Lower Floridan aquifer (zone1) and the
7A and all wells to the west are referred to collectively Upper Floridan aquifer zone used for water supply
as the “new well field.” Well locations are shown in (zone 5) using a series of aquifer tests.
figure 1 and well depths are listed in table1.
A multi-zone well (Cocoa C) was constructed in
1965 to monitor the salinity of water in several zones Purpose and Scope
of the Floridan aquifer system. Cocoa C is located
This report presents the results of three slug
about 180 ft from the city of Cocoa’s supply well14.
tests, three aquifer tests, and the analysis of data from
Chloride concentrations in water from the deepest
these tests to evaluate hydraulic properties of the
zones are monitored to detect possible upward move-
zones of the Floridan aquifer system in the Cocoa well
ment of saline water from lower zones.
field. The geohydrology of the Cocoa well-field area is
The deepest zone of well C (zone 1) is com-
described and long-term hydrographs and water-
pleted in the upper part of the Lower Floridan aquifer,
quality data are presented. Factors affecting water
between 1,351-1,357 ft below land surface. Chloride
levels, including barometric pressure and density dif-
concentrations in zone 1 have increased from 625mg/L
ferences resulting from salinity content are discussed.
in 1966 to about 3,000 mg/L in 1994 (fig. 2). A second
Analytical techniques used in this investigation and
salinity monitoring well (Cocoa R), drilled in June
described in this report include a method for aquifer
1991, is open to a zone from 1,098-1,205 ft below land
test analysis described by Neuman and Witherspoon
surface. Chloride concentrations in water samples col-
(1972) and a method for slug-test analysis described
lected during drilling of this well increased from
by Van der Kamp (1976). The potential for upward
70 mg/L at 1,100 ft below land surface to about
movement of saline water in the Cocoa well field is
250 mg/L at 1,200 ft below land surface.
evaluated. Possible reasons for the increasing chloride
The uppermost zone of well C (zone 5) is open
concentrations in zone 1 of the Cocoa C monitoring
from 248-1,004 ft below land surface and is used to
well and other wells in the well field are discussed.
monitor the zone of the Upper Floridan aquifer used
for water supply. Chloride concentrations in zone 5
and in some supply wells in the new well field also
Previous Investigations
have increased. In 1993, increasing chloride concen-
trations in the water in well 15 (from about 50 to about
Ground-water resources in the Cocoa well field
100 mg/L) prompted the reduction of the pumping rate
have been described in several reports. Tibbals and
and the amount of pumping time for that well. A possi-
Frazee (1976) described the general geohydrology of
ble source of the increased chloride in well 15 might
the area, including an analysis of the potential for
be upconing of water from deeper zones of the aquifer
saline-water upconing, based on observed water levels
system near well 15.
and water quality. A report on the drilling in 1991 of
No quantitative data are available to estimate
three new production wells and one monitoring well
the rate at which saline water can move upward from
for the city of Cocoa was prepared by the consulting
the Lower Floridan aquifer to the zone that is used for
firm CH2M Hill and includes a description of geology
water supply. Vertical hydraulic conductivity values
and water quality based on the results of sampling the
generated from calibrated ground-water flow models
Introduction 3