Citation
Report on geographical and television explorations in City of Jacksonville water wells ( FGS: Information circular 64 )

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Title:
Report on geographical and television explorations in City of Jacksonville water wells ( FGS: Information circular 64 )
Series Title:
FGS: Information circular
Creator:
Leve, Gilbert W ( Gilbert Warren ), 1928-
Geological Survey (U.S.)
Place of Publication:
Tallahassee
Publisher:
State of Florida, Dept. of Natural Resources
Publication Date:
Language:
English
Physical Description:
iii, 15 p. : illus. ; 23 cm.

Subjects

Subjects / Keywords:
Aquifers -- Florida -- Jacksonville ( lcsh )
Wells -- Florida -- Jacksonville ( lcsh )
Geophysical well logging ( lcsh )
City of Jacksonville ( local )
Rocks ( jstor )
Surface water ( jstor )
Aquifers ( jstor )
Calipers ( jstor )
Geology ( jstor )
Genre:
non-fiction ( marcgt )

Notes

General Note:
"Prepared by U.S. Geological Survey in cooperation with the Bureau of Geology, Division of Interior Resources, Florida Department of Natural Resources, and the City of Jacksonville, Florida, Duval County."
Funding:
Digitized as a collaborative project with the Florida Geological Survey, Florida Department of Environmental Protection.
Statement of Responsibility:
by G. W. Leve.

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:
022159676 ( aleph )
01287477 ( oclc )
AFD1784 ( notis )
70633653 //r872 ( lccn )

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Full Text
STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY
Robert 0. Vernon,Chief
INFORMATION CIRCULAR NO. 64
REPORT ON GEOPHYSICAL
AND TELEVISION EXPLORATIONS IN CITY OF JACKSONVILLE WATER WELLS
By
G.W. Leve
Prepared by
U.S. GEOLOGICAL SURVEY
in cooperation with the BUREAU OF GEOLOGY
DIVISION OF INTERIOR RESOURCES
FLORIDA DEPARTMENT OF NATURAL RESOURCES and the
CITY OF JACKSONVILLE, FLORIDA, DUVAL COUNTY
rallahassee
1970




Completed manuscript received
March 21, 1969 Printed by the
lorida Department of Natural Resources
Division of Interior Resources
Bureau of Geology
Tallahassee




CONTENTS
Page
Introduction ........ ....................................... I
Description of data obtained ....... ............................. 1
Electric logs ....... ..................................... 1
Gamma logs ....... ..................................... 3
Caliper logs and current meter traverses ..... ...................... 3
Television traverses. ............................. 3
Results .......... ........................................ 3
General ......... ....................................... 3
Analyses of data from individual wells ..... ....................... 4
Main Street well field ....... .............................. 4
Well number 5 ...... ................................. 4
Well number 7 ...... ................................. 4
Well number 13 ....... ................................ 4
Well number 28 ....... ................................ 9
Well number 44 ....... ................................ 9
McDuff well field ....... ................................ 9
Well number 39 ....... ................................ 9
Hendricks Ave. well field ...... ............................. 12
Well number 35 ........ ................................ 12
River Oaks well field ....... ............................... 14
Well number 34 ....... ................................ 14
ILLUSTRATIONS
Figure Page 1. Map showing the location of the wells described in this report .............. 2
2. Photograph of television image showing caved-in zone at 440 feet in city v ell 5. View
looking vertically down into the hole when the television camera was about 3 feet above the caved-in material. A, back of light source; B, smooth side of well bore; C, material which has collapsed into the open hole ..... .................. 6
3. Geophysical data obtained in well no. 7 ..... ...................... 7
4. Geophysical data obtained in well no. 13 .......................... 8
5. Geophysical data obtained in well no. 28 ........................... 10
6. Geophysical data obtained in well no. 44 ........................... 11
7. Geophysical data obtained in well no. 39 ........................... 12
8. Geophysical data obtained in well no. 35 ........................... 13
9. Geophysical data obtained in well no. 34 ........................... 15
TABLES
Table Page 1. Tabulation of data obtained from wells ............................ 5
)l







REPORT ON GEOPHYSICAL
AND TELEVISION EXPLORATIONS IN
CITY OF JACKSONVILLE WATER WELLS by
G. W. Leve
INTRODUCTION
During November 1968 the U.S. Geological Survey conducted geophysical and television explorations in eight City of Jacksonville water production wells. The purpose of this investigation was to aid the City and the City's consulting engineers (Reynolds, Smith, and Hills) in appraising the physical condition of each well and to gain more information on the hydrologic properties of the aquifer.
The explorations in these wells were made as a part of a comprehensive investigation to fully appraise the water resources in the Jacksonville area. The investigation is being conducted by the U.S. Geological Survey in cooperation with the Division of Geology, Florida Board of Conservation, the City of Jacksonville, and Duval County.
This report describes the findings of the well explorations and includes the basic data obtained from these explorations. The locations of the wells explored are shown on figure 1.
DESCRIPTION OF DATA OBTAINED
Conventional well-logging techniques combined with measurements of flow velocity in the borehole can provide valuable information on the geology and water-bearing characteristics of the subsurface rocks penetrated by a well. In addition, the logs and flow velocity traverses obtained from each well can be used to correlate the regional relationship of the rocks. However, the purpose of this report is to present the hydrologic data that was collected during the well explorations and to briefly describe these data to help the City determine the physical condition of the wells. Therefore, a detailed analysis of the data and regional correlations is beyond the scope of this report.
ELECTRIC LOGS
The different rocks adjacent to a well bore will have varying effects on an artificial electrical current that passes through them. An electric log is a graphic portrayal of the electric current as it passes through the rock. Resistivity logs are graphs of the resistivity of the fluid-saturated rocks expressed in ohmmeters. Spontaneous potential (SP) logs, expressed in millivolts, show the electro-chemical effect of media of different nature (i.e., rocks of different lithology or different texture, or two different types of liquid) and the electrokinctic effect of fluids moving through permeable rock in a well. Both the




2 BUREAU OF GEOLOGY
EXPLANATION
Fo ll Direcion of seaword
I 0 Z 4 ILES
Figure 1. Map showing the location of the wells described in this report.
resistivity logs and spontaneous potential logs can be used to determine the depth of casing in a well, to interpret lithology and permeability of the rocks in a well and to estimate the chemical character of fluid in the pore spaces of the rocks. Correlations of the hydrologic and geologic properties of the rocks can be made throughout the area by comparing the electric logs of each well. The electric log is useful only in the uncased part of the well (open-hole).




INFORMATION CIRCULAR NO. 64 3
GAMMA LOGS
The gamma log is a graph of the relative natural gamma radiation of rocks penetrated by the well. Natural gamma radiation is due to the presence of unstable isotopes of uranium, thorium, and potassium and their various decay products within the rocks. The radioactivity is measured by a slowly moving instrument probe which houses a gamma detector, usually a scintillation counter. The gamma log indicates the depth, thickness and lithology of the various types of rocks similar to the electric logs, but it is valuable in determining these characteristics in the cased part of the well which is not possible with an electric log. In general, carbonaceous shales will have a high gamma activity whereas limestone, dolomite and evaporites tend to have low activities.
CALIPER LOGS AND CURRENT METER TRAVERSES
A caliper log is a continuous graph of the diameter of the well bore at different depths (cased and uncased parts) and the current meter traverse measures the relative velocity of flow of water at various depths in the well bore. The quantity of water flowing at different depths in the well bore may be calculated by comparing the velocity of flow from the current meter data and the cross-sectional area from the caliper log at that depth. From this information the location, thickness, and yield of the water-bearing zones in tile aquifer penetrated by a well may be determined.
TELEVISION TRAVERSES
An underwater television camera lowered into a well bore affords direct visual observation of physical conditions in the well. The depth and condition of the casing seat can be determined and-any incrustation, cracks and perforations in the casing can be seen and located. Obstructions, cavities or any other irregularities in the open-hole portion of the well can be observed and located. Video tapes of the television traverses can be played back and the video picture compared to electric, gamma, and caliper logs and to current meter data to obtain additional knowledge of the structure and texture of the rocks penetrated by the wells.
RESULTS
GENERAL
Electric and gamma logs of the wells show that relatively hard beds of rock are present in the aquifer between about 700 and 950 feet below the surface. Relatively soft porous rock is present in the aquifer above and below these hard beds of rock although there are relatively thin beds of hard rock below about 950 feet. Current meter data indicate that little or no water enters the wells




4 BUREAU OF GEOLOGY from the hard zones between 700 and 950 feet. Most of the water enters the wells from soft porous zones between about 500 to 700 feet or between about 950 to 1,200 feet.
Television traverses in the wells showed badly corroded casing in one well and casing not firmly seated and cemented in the aquifer in two wells. An obstruction in one well was shown to be caused by a cave-in of clay above the aquifer. Table I lists the wells examined during the investigation, shows the kinds of data collected, and lists the diameter and depth of the well.
ANALYSES OF DATA FROM INDIVIDUAL WELLS MAIN STREET WELL FIELD
WELL NO. 5
(Corner 1st and Laura Streets). This well is reported to be 1,270 feet deep, but instrument probes could not be lowered below 442 feet because of an obstruction in the well bore. The television camera showed that the well is cased to 420 feet, which is about 100 feet above the top of the Floridan aquifer, and that poorly consolidated silty clay below the casing has collapsed and partially blocked the well bore. When the well is discharging, water from the underlying aquifer flows through the restricted opening below the casing at relatively high velocities and carries some silt and clay to the surface in suspension. Figure 2 is a photo of the television screen showing the caved-in zone at a depth of 440 feet in city Well Number 5.
WELL NO. 7.
(Hubbard Street and Confederate Park). Electric and caliper logs were run in this well to about 1,229 feet; however, because of technical difficulties the current meter traverse was made to a depth of only 925 feet. The data obtained indicates that about 70 percent of the water flowing from the well at the surface enters the well bore below 925 feet. The data also indicates that no water enters the well between about 750 feet and the bottom of the casing, and in fact some water is lost back into permeable zones in the aquifer between about 700 feet and the bottom of the casing, which is 485 feet below land surface. The caliper log also shows a probable break in the casing between 90 and 120 feet.
The geophysical logs and a bar graph indicating the percentage of the total natural flow that enters the well at different depth intervals are shown on figure
3.
WELL NO. 13.
(8th Street and Hogans Creek). This well drilled in 1918 is one of the oldest water wells owned by the City. Water has been leaking around the outside of the casing for a number of years, indicating that either the casing is perforated below land surface or the casing is not properly seated in the aquifer and water is leaking upwards around the bottom of the casing. Electric logs were made to locate the bottom of the casing and to obtain geologic and hydrologic information on the rocks penetrated by the well. A television camera traverse was made to inspect the casing seat and to locate any perforations in the casing.




Table I. Data obtained from wells.
City Total
Well Location Diarn Depth Electric Gamma Caliper Current Television' No. (in.) (ft.) Log Log Log Meter '-Traverse
Main Street Well Field
5 1st & Laura Sts. 10 1,270 X
7 Hubbard and
Confederate Park 10 1,250 X X X
13 8th & Hogan Creek 10 1,071 X XI 28 4th & Pearl Sts. 10 1,242 X X X0 v 44 Union & Ionia Sts. 12 1,063 X X X X
McDuff Well Field z.
P
39 Gilmore St. east
of McDuff 12 992 X X X X
Hendricks Avenue Well Field
35 LaRue St. & Playground 10 1,286 X X X x
River Oaks Well Field
34 Pumping Station Yd, 10 1,335 X X X




6 BUREAU OF GEOLOGY
Fioure 7 Photograph of television image showing caved-in zone at 440 feet in city well 5. View looking vertically down into the hole when the television camera was about 3 feet above the caved-in material. A, back of light source; B, smooth side of well bore; C, material which has collapsed into the open hole.
The electric logs and television camera show that the well is cased to about 443 feet below land surface, and that the casing is seated in clay about 60 feet above the aquifer. The television camera shows that the entire casing is badly pitted and corroded and that large longitudinal cracks occur in the casing below about 300 feet below land surface. Water is probably leaking from the casing at many depths below the surface. Although only a small amount of water leaking from the casing reaches the surface, much greater amounts are probably leaking through perforations and cracks in the casing into the surrounding rocks below land surface. Geophysical logs of Well No. 13 are shown on figure 4.




INFORMATION CIRCULAR NO. 64 7
CALIPER LOG WELL DIAMETER o tO" 20" 30" 0
100
200
CITY WELL 7 300
ELECTRIC LOGS
SP RESISTIVITY
25MV 100 COMPUTED
'I ohms FLOW METER LOG
400 1 1
Bottom of I0" (Well flowing at surface
casing
500
Loss of flow
IL,
(n
o 700
z
U,
GO 800 ,I-
-

00
1 200
1229 -20 0 20 40 60 80 PERCENT OF FLOW
Figure 3. Geophysical data obtained in well no. 7.




BUREAU OF GEOLOGY
CITY WELL 13
ELECTRIC LOGS
SP RESISTIVITY
I0 MV 100
I ohms I
Bottom of' KO" casng 400 MO _f_~sn
w
ILX
z
0700cc
.
800t
0
Xb
-900
0
1000
1060
Figure 4. Geophysical data obtianed in well no. 13.




INFORMATION CIRCULAR NO. 64 9
WELL NO. 28.
(Corner of 4th and Pearl Streets). This well flows about 900 gallons per minute at land surface. Geophysical data indicates that more than 50 percent of this water comes from soft, porous zones in the aquifer between the bottom of the casing at 498 feet below land surface and about 700 feet below land surface.
Although this well is 1,242 feet deep the data indicates that no water enters the well bore below 1,120 feet. Geophysical and flow meter logs are shown on figure
5.
WELL NO. 44.
(Corner of Union and Ionia Streets). This well flows about 1,070 gpm at land surface. Current meter data indicates that most of this water enters the well bore from two major water-bearing zones, between about 550 and 700 feet below land surface and below about 900 feet. The zones above 550 feet and between 700 and 900 feet yield only small quantities of water.
Electric logs indicate numerous alternating soft, porous and hard, nonporous zones occur in the aquifer between 780 and 940 feet below land surface. The caliper log and the television camera indicate that there are many small cavities or fractures in the rock between these depths. Geophysical and flow meter logs are shown on figure 6.
MeDUFF WELL FIELD
WELL NO. 39.
(On Gilmore Street east of McDuff Avenue). The water from this well contains large quantities of green clay and sand. Geophysical and television explorations were made in the well to locate the source of this sediment. The logs and television data show that the casing of this well is seated in limestone at the top of the Floridan Aquifer about 500 feet below land surface. About 1 to 2 feet below the bottom of the casing there is a cavity about 8 feet in height and at least 14 inches larger in diameter than the diameter of the casing. This cavity is the probable source of the sand and clay. Water entering the well bore through this cavity is probably carrying in poorly consolidated material from above the top of the limestone. The television camera showed that while the well was flowing, large quantities of sand were being held in suspension in the well bore below the cavity. When this sand enters the well bore through the cavity, the lighter particles are carried to the surface when the well is flowing and the heavier particles either drop to the bottom of the well or are held in suspension in the bore. When the well is pumped the water moves up the well bore at faster velocities and carries these heavier particles to the surface in suspension. Current meter data indicates that 70 percent of the water discharged at the surface by gravity flow enters the well from this cavity, and that no water enters the bore between 810 feet and the bottom of the well at 992 feet (the last 180 feet). Geophysical logs and current meter data are shown in figure 7.




10 BUREAU OF GEOLOGY
CALIPER LOG
WELL DIAMETER
0
200
CITY WELL 28
30
ELECTRIC LOGS SP RESISTMTY 25 Mv 100 COMPUTED 4L_ 1 Ohm.. u FLOW METER LOG E "cosng (Well f lowing 0 surface) up .___'.___600
b. .
fl
~700
4!
-,J
Uj
-
9I00
1100
0 0 10 20 30 PERCENT OF FLOW Figure 5. Geophysical data obtained in well no. 28 .




INFORMATION CIRCULAR NO.64 11
CITY WELL 44 ELECTRIC LOGS CALIPER LOG
SP RESISTIVITY WELL DIAMETER
25 MV 50 ohms 0 lo" COMPUTED
I .. I ..I FLOW METER LOG
Bottom of 12"cosi
500 II____(Well flowing at surface
I 600z
-J
- 7000
La.
1040 M
0I0 20 30 PERCENT OF FLOW
Figure 6. Geophysical data obtained in well no. 44.




12 BUREAU OF GEOLOGY
CITY WELL 39
ELECTRIC LOGS
CALIPER LOG
SP RES'WTY WELL OAMETER COMPUTED
asV 100 o Ir 248
L... L FLOW METER LOG
4040 *foul "
(Well f awing 'at surface
ilLil 1
mam
L
IA.
60 __
0
X
0 20 40 60 s0
PERCENT OF FLOW
Figure 7. Geophysical data obtianed in well no. 39.
HENDRICKS AVENUE WELL FIELD
WELL NO. 35.
(On LaRue Street between Nira and Cedar Streets).This well flows 1,200 gpm and current meter data indicates that more than 80 percent of this water enters the well from two major water-producing zones in the aquifer: between the bottom of the casing at 508 feet and about 750 feet below the surface and between about 1,150 feet and 1,250 feet below the surface. Only a relatively small amount of water enters the well in the intervals between about 750 and 950 feet and between 1,050 feet and 1,150 feet below the surface. The electric logs show relatively large increases in resistivity in these non-producing zones, which indicates that the rocks in these zones are relatively hard and impermeable. Geophysical logs and flow meter data are shown in figure 8.




INFORhMATION CIRCULAR NO, .64 13
CITY WELL 35 ELECTRIC LOGS
CALIPER LOG SP RESISTIVITY WELL DIAMETER
50 MV 100 0 lo' COMPUTED
I ohms I FLOW METER LOG 400 1
Well flowing of surface) Bottom of tO"cosng 500
600
w
I 700
z
I
oo
w
w
IL
900
Uj
ZIP
IL
0
3: 1000 __I-
w
' N
1100
1200
1265 ____ '
0 10 20 30 PERCENT OF FLOW
Figure 8. Geophysical data obtained in well no. 35 .




14 BUREAU OF GEOLOGY
RIVER OAKS WELL FIELD
WELL NO. 34.
(In River Oaks Pumping Station yard). Current meter data shows that while the well is flowing at the surface all of the water enters the well from below 900 feet beneath land surface. These data also indicate that there is internal circulation of water in the well bere and some of the water that enters the well below 900 feet is lost back into the aquifer between about 800 feet and the bottom of the casing at 508 feet. Although the loss of water is slight while the well is flowing at the surface a current meter traverse made while the well was closed at the surface shows that a comparatively large quantity of water from below 900 feet is lost back into the aquifer above 800 feet. Current meter data in fig. 9 also shows that no water enters the well bore below about 1,240 feet and the bottom of the well at 1,335 feet (the last 95 feet). Geophysical logs and current meter data are shown on figure 9.




INFORMATION CIRCULAR NO. 64 15
.GAMMA RAY LOG
S areose in radiation
100
200" 300
CITY WELL 34 400
ELECTRIC LOGS S RESISTIVITY COMPUTED 10 MV 100 FLOW METER LOG x500 U) ( Well flowing at surface)
m
z
600 __Loss of flow
-j
W 7o00.
LL.
o 800 (
900
1000
1100
1200
1300
135-10 0 10 20 30 PERCENT OF FLOW
Figure 9. Geophysical data obtained in well no. 34.




Full Text

PAGE 1

STATE OF FLORIDA DEPARTMENT OF NATURAL RESOURCES BUREAU OF GEOLOGY Robert O. Vernon,Chief INFORMATION CIRCULAR NO. 64 REPORT ON GEOPHYSICAL AND TELEVISION EXPLORATIONS IN CITY OF JACKSONVILLE WATER WELLS By G.W. Leve Prepared by U.S. GEOLOGICAL SURVEY in cooperation with the BUREAU OF GEOLOGY DIVISION OF INTERIOR RESOURCES FLORIDA DEPARTMENT OF NATURAL RESOURCES and the CITY OF JACKSONVILLE, FLORIDA, DUVAL COUNTY Tallahassee 1970

PAGE 2

Completed manuscript receoved March 21, 1969 Printed by the Florida Department of Natural Resources Division of Interior Resources Bureau of Geology Tallahassee

PAGE 3

CONTENTS Page Introduction ................. ......... ...... .... .1 Description of data obtained ....................... ...... .. 1 Electric logs ........................... .......... ... 1 Gamma logs ............... ..................... 3 Caliper logs and current meter traverses ....................3 Television traverses .. ............... .......... ...... 3 Results .. ................ .......................3 G eneral .......................................3 Analyses of data from individual wells .....................4 Main Street well field .............................. 4 Well number 5 ................................ .4 Well number 7 ................... .............. 4 Well number 13 ............................... .4 Well number 28 ............................... .9 Well number 44 ............................... .9 McDuff well field ................................ 9 Well number 39 ................................ 9 Hendricks Ave. well field ....... ... ................... .12 Well number 35 ................................ 12 River Oaks well field ............................... 14 Well number 34 ................... ............. 14 ILLUSTRATIONS Figure Page 1. Map showing the location of the wells described in this report ...........2 2. Photograph of television image showing caved-in zone at 440 feet in city v ell 5. View looking vertically down into the hole when the television camera was about 3 feet above the caved-in material. A, back of light source; B, smooth side of well bore; C, material which has collapsed into the open hole ..................6 3. Geophysical data obtained in well no. 7 ......................7 4. Geophysical data obtained in well no. 13 ......................8 5. Geophysical data obtained in well no. 28 ...................... 10 6. Geophysical data obtained in well no. 44 ...................... 11 7. Geophysical data obtained in well no. 39 ...................... 12 8. Geophysical data obtained in well no. 35 ...................... 13 9. Geophysical data obtained in well no. 34 ...................... 15 TABLES Table Page 1. Tabulation of data obtained from wells ................... ...... 5 1l1

PAGE 5

REPORT ON GEOPHYSICAL AND TELEVISION EXPLORATIONS IN CITY OF JACKSONVILLE WATER WELLS by G. W. Leve INTRODUCTION During November 1968 the U.S. Geological Survey conducted geophysical and television explorations in eight City of Jacksonville water production wells. The purpose of this investigation was to aid the City and the City's consulting engineers (Reynolds, Smith, and Hills) in appraising the physical condition of each well and to gain more information on the hydrologic properties of the aquifer. The explorations in these wells were made as a part of a comprehensive investigation to fully appraise the water resources in the Jacksonville area. The investigation is being conducted by the U.S. Geological Survey in cooperation with the Division of Geology, Florida Board of Conservation, the City of Jacksonville, and Duval County. This report describes the findings of the well explorations and includes the basic data obtained from these explorations. The locations of the wells explored are shown on figure 1. DESCRIPTION OF DATA OBTAINED Conventional well-logging techniques combined with measurements of flow velocity in the borehole can provide valuable information on the geology and water-bearing characteristics of the subsurface rocks penetrated by a well. In addition, the logs and flow velocity traverses obtained from each well can be used to correlate the regional relationship of the rocks. However, the purpose of this report is to present the hydrologic data that was collected during the well explorations and to briefly describe these data to help the City determine the physical condition of the wells. Therefore, a detailed analysis of the data and regional correlations is beyond the scope of this report. ELECTRIC LOGS The different rocks adjacent to a well bore will have varying effects on an artificial electrical current that passes through them. An electric log is a graphic portrayal of the electric current as it passes through the rock. Resistivity logs are graphs of the resistivity of the fluid-saturated rocks expressed in ohmmeters. Spontaneous potential (SP) logs, expressed in millivolts, show the electro-chemical effect of media of different nature (i.e., rocks of different lithology or different texture, or two different types of liquid) and the elcctrokinctic effect of fluids moving through permeable rock in a well. Both the

PAGE 6

2 BUREAU OF GEOLOGY EXPLANATION l City well explored and well number S-Direction of seaward C. COUNTY..€ I \I .0 I 4 MILES Figure I. Map showing the location of the wells described in this report. resistivity logs and spontaneous potential logs can be used to determine the depth of casing in a well, to interpret lithology and permeability of the rocks in a well and to estimate the chemical character of fluid in the pore spaces of the rocks. Correlations of the hydrologic and geologic properties of the rocks can be made throughout the area by comparing the electric logs of each well. The electric log is useful only in the uncased part of the well (open-hole).

PAGE 7

INFORMATION CIRCULAR NO. 64 3 GAMMA LOGS The gamma log is a graph of the relative natural gamma radiation of rocks penetrated by the well. Natural gamma radiation is due to the presence of unstable isotopes of uranium, thorium, and potassium and their various decay products within the rocks. The radioactivity is measured by a slowly moving instrument probe which houses a gamma detector, usually a scintillation counter. The gamma log indicates the depth, thickness and lithology of the various types of rocks similar to the electric logs, but it is valuable in determining these characteristics in the cased part of the well which is not possible with an electric log. In general, carbonaceous shales will have a high gamma activity whereas limestone, dolomite and evaporites tend to have low activities. CALIPER LOGS AND CURRENT METER TRAVERSES A caliper log is a continuous graph of the diameter of the well bore at different depths (cased and uncased parts) and the current meter traverse measures the relative velocity of flow of water at various depths in the well bore. The quantity of .water flowing at different depths in the well bore may be calculated by comparing the velocity of flow from the current meter data and the cross-sectional area from the caliper log at that depth. From this information the location, thickness, and yield of the water-bearing zones in tile aquifer penetrated by a well may be determined. TELEVISION TRAVERSES An underwater television camera lowered into a well bore affords direct visual observation of physical conditions in the well. The depth and condition of the casing seat can be determined and-any incrustation, cracks and perforations in the casing can be seen and located. Obstructions, cavities or any other irregularities in the open-hole portion of the well can be observed and located. Video tapes of the television traverses can be played back and the video picture compared to electric, gamma, and caliper logs and to current meter data to obtain additional knowledge of the structure and texture of the rocks penetrated by the wells. RESULTS GENERAL Electric and gamma logs of the wells show that relatively hard beds of rock are present in the aquifer between about 700 and 950 feet below the surface. Relatively soft porous rock is present in the aquifer above and below these hard beds of rock although there are relatively thin beds of hard rock below about 950 feet. Current meter data indicate that little or no water enters the wells

PAGE 8

4 BUREAU OF GEOLOGY from the hard zones between 700 and 950 feet. Most of the water enters the wells from soft porous zones between about 500 to 700 feet or between about 950 to 1,200 feet. Television traverses in the wells showed badly corroded casing in one well and casing not firmly seated and cemented in the aquifer in two wells. An obstruction in one well was shown to be caused by a cave-in of clay above the aquifer. Table I lists the wells examined during the investigation, shows the kinds of data collected, and lists the diameter and depth of the well. ANALYSES OF DATA FROM INDIVIDUAL WELLS MAIN STREET WELL FIELD WELL NO. 5 (Corner Ist and Laura Streets). This well is reported to be 1,270 feet deep, but instrument probes could not be lowered below 442 feet because of an obstruction in the well bore. The television camera showed that the well is cased to 420 feet, which is about 100 feet above the top of the Floridan aquifer, and that poorly consolidated silty clay below the casing has collapsed and partially blocked the well bore. When the well is discharging, water from the underlying aquifer flows through the restricted opening below the casing at relatively high velocities and carries some silt and clay to the surface in suspension. Figure 2 is a photo of the television screen showing the caved-in zone at a depth of 440 feet in city Well Number 5. WELL NO. 7. (Hubbard Street and Confederate Park). Electric and caliper logs were run in this well to about 1,229 feet; however, because of technical difficulties the current meter traverse was made to a depth of only 925 feet. The data obtained indicates that about 70 percent of the water flowing from the well at the surface enters the well bore below 925 feet. The data also indicates that no water enters the well between about 750 feet and the bottom of the casing, and in fact some water is lost back into permeable zones in the aquifer between about 700 feet and the bottom of the casing, which is 485 feet below land surface. The caliper log also shows a probable break in the casing between 90 and 120 feet. The geophysical logs and a bar graph indicating the percentage of the total natural flow that enters the well at different depth intervals are shown on figure 3.. WELL NO. 13. (8th Street and Hogans Creek). This well drilled in 1918 is one of the oldest water wells owned by the City. Water has been leaking around the outside of the casing for a number of years, indicating that either the casing is perforated below land surface or the casing is not properly seated in the aquifer and water is leaking upwards around the bottom of the casing. Electric logs were made to locate the bottom of the casing and to obtain geologic and hydrologic information on the rocks penetrated by the well. A television camera traverse was made to inspect the casing seat and to locate any perforations in the casing.

PAGE 9

Table 1. Data obtained from wells. City Total Well Location Diam Depth Electric Gamma Caliper Current Television No. (in.) (ft.) Log Log Log Meter Traverse Main Street Well Field 5 1st & Laura Sts. 10 1,270 7 Hubbard and Confederate Park 10 1,250 X X X 13 8th & Hogan Creek 10 1,071 X X 28 4th & Pearl Sts. 10 1,242 X X X g 44 Union & Ionia Sts. 12 1,063 X X X X McDuff Well Field Z P 39 Gilmore St. east of McDuff 12 992 X X X X Hendricks Avenue Well Field 35 LaRue St. & Playground 10 1,286 X X X X River Oaks Well Field 34 Pumping Station Yd. 10 1,335 X X X I

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6 BUREAU OF GEOLOGY Figure I Photograph of television image showing caved-in zone at 440 feet in city well 5. View looking vertically down into the hole when the television camera was about 3 feet above the caved-in material. A, back of light source; B, smooth side of well bore; C, material which has collapsed into the open hole. The electric logs and television camera show that the well is cased to about 443 feet below land surface, and that the casing is seated in clay about 60 feet above the aquifer. The television camera shows that the entire casing is badly pitted and corroded and that large longitudinal cracks occur in the casing below about 300 feet below land surface. Water is probably leaking from the casing at many depths below the surface. Although only a small amount of water leaking from the casing reaches the surface, much greater amounts are probably leaking through perforations and cracks in the casing into the surrounding rocks below land surface. Geophysical logs of Well No. 13 are shown on figure 4.

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INFORMATION CIRCULAR NO. 64 7 CALIPER LOG WELL DIAMETER 0 10" 20" 30" 1 1--0100 200 CITY WELL 7 300 ELECTRIC LOGS SP RESISTIVITY 25MV 100 COMPUTED I ohms I FLOW METER LOG 400 Bottom of 10" (Well flowing at surface) casing 500 Loss of flow -600 Ld 0 700 z G 800 I-L 100 IO800 -----^» -------^ ------1 200-__ 129 -20 0 20 40 60 80 PERCENT OF FLOW Figure 3. Geophysical data obtained in well no. 7.

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8 BUREAU OF GEOLOGY CITY WELL 13 ELECTRIC LOGS SP RESISTIVITY 10 MV 100 1 I I ohms I 400 ---------|i--lBottom of K'"cosing w L. US) 0 z 0700-I00ta 0 1-900 1000 1060 Figure 4. Geophysical data obtianed in well no. 13.

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INFORMATION CIRCULAR NO. 64 9 WELL NO. 28. (Corner of 4th and Pearl Streets). This well flows about 900 gallons per minute at land surface. Geophysical data indicates that more than 50 percent of this water comes from soft, porous zones in the aquifer between the bottom of the casing at 498 feet below land surface and about 700 feet below land surface. Although this well is 1,242 feet deep the data indicates that no water enters the well bore below 1,120 feet. Geophysical and flow meter logs are shown on figure 5. WELL NO. 44. (Corner of Union and Ionia Streets). This well flows about 1,070 gpm at land surface. Current meter data indicates that most of this water enters the well bore from two major water-bearing zones, between about 550 and 700 feet below land surface and below about 900 feet. The zones above 550 feet and between 700 and 900 feet yield only small quantities of water. Electric logs indicate numerous alternating soft, porous and hard, nonporous zones occur in the aquifer between 780 and 940 feet below land surface. The caliper log and the television camera indicate that there are many small cavities or fractures in the rock between these depths. Geophysical and flow meter logs are shown on figure 6. McDUFF WELL FIELD WELL NO. 39. (On Gilmore Street east of McDuff Avenue). The water from this well contains large quantities of green clay and sand. Geophysical and television explorations were made in the well to locate the source of this sediment. The logs and television data show that the casing of this well is seated in limestone at the top of the Floridan Aquifer about 500 feet below land surface. About 1 to 2 feet below the bottom of the casing there is a cavity about 8 feet in height and at least 14 inches larger in diameter than the diameter of the casing. This cavity is the probable source of the sand and clay. Water entering the well bore through this cavity is probably carrying in poorly consolidated material from above the top of the limestone. The television camera showed that while the well was flowing, large quantities of sand were being held in suspension in the well bore below the cavity. When this sand enters the well bore through the cavity, the lighter particles are carried to the surface when the well is flowing and the heavier particles either drop to the bottom of the well or are held in suspension in the bore. When the well is pumped the water moves up the well bore at faster velocities and carries these heavier particles to the surface in suspension. Current meter data indicates that 70 percent of the water discharged at the surface by gravity flow enters the well from this cavity, and that no water enters the bore between 810 feet and the bottom of the well at 992 feet (the last 180 feet). Geophysical logs and current meter data are shown in figure 7.

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10 BUREAU OF GEOLOGY CALIPER LOG WELL DIAMETER 0 0100 -CITY WELL 28 300 ELECTRIC LOGS SP RESISTIITY 25v 100 COMPUTED 4L_._ i hm I FLOW METER LOG i"cosing (Well flowing (o surface) o --6 00 -,J I7200 0 10 20 30 PERCENT OF FLOW Figure 5. Geophysical data obtained in well no. 28 .

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INFORMATION CIRCULAR NO. 64 11 CITY WELL 44 ELECTRIC LOGS CALIPER LOG SP RESISTIVITY WELL DIAMETER 25 MV 50 ohms 0 18" COMPUTED I... I I I LI I I FLOW METER LOG Bottom of 12"cosin 500 _______ SWell flowing at surface S600 z no --J 9700 I'W 1040 0 10 20 30 PERCENT OF FLOW Figure 6. Geophysical data obtained in well no. 44. Figure 6. Geophysical data obtained in well no. 44.

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12 BUREAU OF GEOLOGY CITY WELL 39 ELECTRIC LOGS CALIPER LOG SP RESIST'WTY WILL 01AMETER COMPUTED asM 100 o0 * 248 St l ..i I I I FLOW METER LOG 400 o -1 -" S(Wei flowing at surface ) 500 sZo 1m 20 40 60 so PERCENT OF FLOW Figure 7. Geophysical data obtianed in well no. 39 . HENDRICKS AVENUE WELL FIELD WELL NO. 35. (On LaRue Street between Nira and Cedar Streets).This well flows 1,200 gpm and current meter data indicates that more than 80 percent of this water enters the well from two major water-producing zones in the aquifer: between the bottom of the casing at 508 feet and about 750 feet below the surface and between about 1,150 feet and 1,250 feet below the surface. Only a relatively small amount of water enters the well in the intervals between about 750 and 950 feet and between 1,050 feet and 1,150 feet below the surface. The electric logs show relatively large increases in resistivity in these non-producing zones, which indicates that the rocks in these zones are relatively hard and impermeable. Geophysical logs and flow meter data are shown in figure 8. HEDICSAENEWLL.L 0ELNO 5 impermeable. Geophysical logs and flow meter data are shown in figure 8.

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INFORMATIONCIRCULAR NO, 64 13 CITY WELL 35 ELECTRIC LOGS CALIPER LOG SP RESISTIVITY WELL DIAMETER 50 MV 100 0 10' COMPUTED SI ohms I I_ FLOW METER LOG 400 (Well flowing ot surface) Bottom of 10"cosing 500 600 w | 700 -Seo SL IL 0 Z 1000 110012001265 -_ ' ' 0 10 20 30 PERCENT OF FLOW Figure 8. Geophysical data obtained in well no. 35 .

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14 BUREAU OF GEOLOGY RIVER OAKS WELL FIELD WELL NO. 34. (In River Oaks Pumping Station yard). Current meter data shows that while the well is flowing at the surface all of the water enters the well from below 900 feet beneath land surface. These data also indicate that there is internal circulation of water in the well bere and some of the water that enters the well below 900 feet is lost back into the aquifer between about 800 feet and the bottom of the casing at 508 feet. Although the loss of water is slight while the well is flowing at the surface a current meter traverse made while the well was closed at the surface shows that a comparatively large quantity of water from below 900 feet is lost back into the aquifer above 800 feet. Current meter data in fig. 9 also shows that no water enters the well bore below about 1,240 feet and the bottom of the well at 1,335 feet (the last 95 feet). Geophysical logs and current meter data are shown on figure 9.

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INFORMATION CIRCULAR NO. 64 15 GAMMA RAY LOG 0 crese in radiation 100 200 " 300 CITY WELL 34 400 ELECTRIC LOGS SP RESISTIVITY COMPUTED 5 10 MV 100 FLOW METER LOG SL---hm, , 500 S( 1 Well flowing at surface) 600 Loss of flow O 7_00 _ ___ _ ._ 900 -j S7o00 0 800 (1000 __ 1300 1335 -10 0 10 20 30 PERCENT OF FLOW Figure 9. Geophysical data obtained in well no. 34.

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


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