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 Description of area
 Hydrology
 Conclusions
 References


FGS




STATE OF FLORIDA
STATE BOARD OF CONSERVATION



FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director






REPORT OF INVESTIGATIONS NO. 24

PART I


HYDROLOGIC CONDITIONS IN THE VICINITY
OF LEVEE 30, NORTHERN DADE COUNTY,
FLORIDA


By
Howard Klein and C. B. Sherwood
United States Geological Survey











Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
CENTRAL AND SOUTHERN FLORIDA FLOOD CONTROL DISTRICT


TALLAHASSEE, FLORIDA
1961











FLORIDA STATE BOARD Zainta

OFNSER

CONSERVATION


FARRIS BRYANT
Governor


TOM ADAMS
Secretary of State


J. EDWIN LARSON
Treasurer


THOMAS D. BAILEY
Superintendent Public Instruction


RICHARD ERVIN
Attorney General


RAY E. GREEN
Comptroller


DOYLE CONNER
Commissioner of Agriculture






LETTER OF TRANSMITTAL


Jorkid'a


geoloqical

'Callakassee


June 1, 1961


Honorable Farris Bryant, Chairman
Florida State Board of Conservation
Tallahassee, Florida


Dear Governor Bryant:

The Florida Geological Survey is publishing as Report of
Investigations No. 24, Part I, a report on the hydrologic conditions
in the vicinity of Levee 30, northern Dade County, which was
prepared by Howard Klein and C. B. Sherwood of the U. S.
Geological Survey. This report was prepared in cooperation with
the Central and Southern Florida Flood Control District, and this
department is publishing the report in its regular series of water
resources papers.
The formations that underlie Levee 30 are a part of the very
permeable sediments that underlie the southern tip of Florida.
The opportunity to make this study has provided important data
relative to the transmissibility of the sediments and will assist
in design of control structures and in-the development of the water
resources of southern Florida.
Respectfully yours,
Robert O. Vernon, Director


Survey





















































Completed manuscript received
February 27, 1961
Published by the Florida Geological Survey
E. O. Painter Printing Company
DeLand, Florida

iv






CONTENTS

Abstract ___ ;- 1
Introduction ---- ---- -__ 1
General statement and purpose -___ ____- 1
Previous investigations ___ 3
Acknowledgments ___-.______ 3
Description of area --------------------_ --____-------________-.._____. 4
Geology ..........---------. --. --- -_._-----------------------____. ____ 5
Drainage features __ -------- 7
Hydrology ---------____ 9
Water levels and movement ----- --- __________ 9
Relation between ponded water and ground water 12
Underflow along Levee 30 _-__ 16
Conclusions c_______ 22
References -- _-__ ________ __23


ILLUSTRATIONS

Figure Page

1 Map of northern Dade County showing the area of investigation __ 2
2 Map of area of investigation showing the location of the test area
and the location of selected observation stations _--_- -___ 4
3 Cross section A-A' showing details of the near-surface geology near
the north end of Levee 30 __ 5
4 Map of test area showing locations of observation stations and test
sites------------- ---- -_ ---- 6
5 Contour map of the area investigated showing the altitude and con-
figuration of the water level on January 21, 1960 8
6 Hydrographs of groups of observation stations for 1959 and the
early part of 1960 ___---_----- 11
7 Hydrograph of station G72 for the period 1940-59 and the annual
rainfall at the Miami Airport ---12
8 Profile showing the relation between the ponded water and the
piezometric surface at site A-A', January 21 and February 8, 1960 13
9 Profile showing the relation between the ponded water and the
piezometric surface at site B-B', January 21 and February 8, 1960 14
10 Profile along site C-C' showing lines of equal potential, April
19, 1960 !--_5-------------_ 15
11 Graph showing the relation between the head difference across Levee
30 and the head difference between the pool and the piezometric
surface at the toe of the levee _- 21










HYDROLOGIC CONDITIONS IN THE VICINITY OF LEVEE 30,
NORTHERN DADE COUNTY, FLORIDA

By
Howard Klein and C. B. Sherwood
ABSTRACT
Thin layers of dense limestone of low permeability that occur
near the top of the Biscayne aquifer in the vicinity of the north
end of Levee 30 in Dade County, Florida are of hydrologic im-
portance because they retard the downward infiltration of ponded
water in Conservation Area No. 3. This retarding effect frequently
results in high head differentials across the levee. Tests made in
a small area adjacent to Levee 30 indicate that the coefficient of
transmissibility of the aquifer is 3,600,000 gpd (gallons per day)
per foot, and the coefficient of vertical permeability of the dense
limestones is 13 gpd per square foot. If ground-water flow beneath
the levee is laminar, the total inflow to the Levee 30 Canal from
Conservation Area No. 3 will be about 350 mgd (million gallons per
day), or 540 cfs (cubic feet per second), per mile length of levee
when the head difference across the levee is 10 feet.

INTRODUCTION
GENERAL STATEMENT AND PURPOSE
One of the major responsibilities of the Central and Southern
Florida Flood Control District is to minimize flood damage in urban
and agricultural areas west of the coastal ridge in southeastern
Florida. A second function is to protect areas of potential urban
development. A large area of anticipated growth in Dade County
(shown as Area B in fig. 1). is west of Miami and extends about
10 miles eastward from Levees 30 and 31.
The initial project of the Central and Southern Florida Flood
Control District was the construction of an east-coast protective-
levee system west of the Atlantic Coastal Ridge, extending from
Lake Okeechobee southward into Dade County. Levees 33, 30, and
31 form the southern terminus of this levee system and are shown
in figure 1. Its primary purpose was to alleviate flooding in urban
and agricultural land, along and adjacent to the ridge, by retarding
the overland eastward flow of floodwaters from the Everglades.
When the flood-control system is completed, part of these excess
floodwaters will be impounded in conservation areas west of the





FLORIDA GEOLOGICAL SURVEY


Figure 1. Map of northern Dade County showing the area of investigation.
levee. Regulated releases of water will be conveyed by canals from
conservation areas to coastal areas to replenish ground-water
reservoirs during periods of drought.
This report is one of a series prepared in cooperation with the
Central and Southern Florida Flood Control District. The general
purposes of these investigations are (1) to define the hydrology of
certain areas within the Flood Control District, (2) to determine the
effectiveness of existing flood-control and water-control measures,
and (3) to furnish hydrologic data that will be used in the design
and operation of proposed and existing structures and works.





REPORT OF INVESTIGATIONS No. 24


The purpose of this investigation is to define the hydrologic
characteristics of the water-bearing materials in the vicinity of
Levee 30 in northern Dade County, in order to determine the
feasibility of controlling water levels in Area B for maximum flood
protection. Included is an analysis of the relation between the im-
pounded water west of Levee 30 and the ground water in the area.
From this relationship estimates of ground-water underflow along
Levee 30 can be computed under existing conditions and under
anticipated water-level conditions. Midway in the data-gathering
stage of the investigation, major road construction altered the
canal system in the immediate area and caused changes in water
levels and discharge of canals. This resulted in curtailing of the
field work; therefore the results of this investigation should be
considered preliminary.
The work was done under the general supervision of P. E.
LaMoreaux, chief, Ground Water Branch, Washington, D. C., and
under the immediate supervision of M. I. Rorabaugh, district
engineer, Tallahassee, Florida.

PREVIOUS INVESTIGATIONS

A comprehensive report by Parker and others (1955) presented
fairly complete information on the geology and hydrology of south-
eastern Florida, and Parker (1951) gave estimates of the
availability and adequacy of the ground-water supplies of the
Biscayne aquifer which underlies southeastern Florida. Schroeder
and others (1958) summarized additional data on the Biscayne
aquifer collected since 1950. Stallman (1956) made theoretical
computations on the effect of drainage in the area west of Miami
and gave estimates of the amount of seepage that might occur
beneath Levee 30 under certain assumed conditions. A
mimeographed report by the U. S. Army Corps of Engineers
(1953) described the results of permeability tests along different
levees within the Flood Control District.

ACKNOWLEDGMENTS

The writers are indebted to personnel of the Surface Water
Branch, U.S. Geological Survey, Miami, Florida, for making dis-
charge measurements in the Levee 30 Canal and furnishing water-
level information along the Miami Canal. Gratitude is expressed
also to the Public Works Department of metropolitan Dade County
for the record of water-level stages for several observation stations
in the area. The office of the Central and Southern Florida Flood





FLORIDA GEOLOGICAL SURVEY


Control District furnished complete information on the location,
the construction details, and the layout of the Corps of Engineers
test sites near Levee 30. The writers benefited from technical
discussions with F. A. Kohout of the Miami office, and H. H. Cooper,
Jr, and N. D. Hoy of the Tallahassee office, U. S. Geological Survey.

DESCRIPTION OF AREA

The area described in this report comprises 60 square miles
chiefly in northern Dade County, Florida (fig. 1). Figure 2, which
is a large-scale map of the report area, delineates the test site
within the area, locates certain water-level observation stations,
and shows the drainage features. The western part of the area is
traversed by Levees 30 and 33. These levees separate Conservation
Area No. 3, which normally contains ponded water, from Area B
which is swampy during much of the year. The altitude of the
land surface is about 5 feet above msl (mean sea level).


Figure 2. Map of area of investigation showing the location of the test area
and the location of selected observation stations.





REPORT OF INVESTIGATIONS NO. 24


GEOLOGY

The area of investigation is underlain to a depth of 55 feet by
the Biscayne aquifer, a body of highly permeable limestone. The
Biscayne aquifer is underlain by relatively impermeable silt, marl,
and fine sand which retard downward seepage from the aquifer
or upward seepage from deeper materials.
The cross section in figure 3 gives details of the near-surface
geology near the north end of Levee 30 in Dade County, as
determined from shallow test holes drilled at site A-A' (fig. 4).
The area is blanketed by 3 to 5 feet of muck and marl that is
underlain by a layer of solution-riddled Miami oolite, a part of the
Biscayne aquifer, 1 to 2 feet thick. Figure 3 shows two thin layers
of very hard, dense limestone at depths ranging from 0.5 foot
above msl to 3.0 feet below msl. In contrast to the high permeability
of the underlying limestones, these thin layers appear to be
relatively impermeable; and the vertical flow of water through
them is many times less than the horizontal flow of water through
the deeper, more permeable rocks. By effectively retarding the
downward infiltration of water, the thin layers act as a confining


DISTANCE IN FEET A


Figure 3. Cross section A-A' showing details of the near-surface geology near
the north end of Levee 30.






FLORIDA GEOLOGICAL SURVEY


COUNTY -
COUNTY-


EXPLANATION


CANAL AND CONTROL
A M2
RECORDING GAGE
AND NUMBER
030E
OBSERVATION STATION
AND NUMBER
C--C'
LINE OF PROFILE
<-Q2
STREAM-GAGING STATION
SCALE IN FEET
0 2500 5000


Figure 4. Map of test area showing locations of observation stations and
test sites.


DADE





REPORT OF INVESTIGATIONS No. 24


unit that separates the ponded water in Conservation Area No. 3
from the water contained in the permeable limestone.
Geologic information from test wells and shallow borings, and
reported information obtained in connection with canal excavations,
indicate that the hard layers of dense limestone occur throughout
most of Area B and in southern Dade County, and that they occur
at about the same altitude. Each of the wells prefixedd by letter
G) shown in figure 2 penetrated the impermeable layers approxi-
mately at sea level. Similar layers were noted in wells near the
southern terminus of Levee 31 (fig. 1), and in wells south of the
Tamiami Canal and west of Levee 31. It is reasonable to assume
that the relatively impermeable zones underlie much of Conser-
vation Area No. 3 and that their confining characteristics are
widespread. In places, the dense limestones probably contain
openings through which rainfall can infiltrate rapidly; however,
the overall continuity and the blanketing effect of these layers
in general tend to retard infiltration. In the Miami area to the
east, the Biscayne aquifer thickens and contains much sand. The
thin, dense limestones either thin and disappear or they occur
deeper in the aquifer near the coast.

DRAINAGE FEATURES

During the past 10 years the improved canal system that pro-
vides gravity drainage to Biscayne Bay, as shown in figure 1, has
effectively reduced flooding in Area A, the urbanized part of eastern
Dade County. The system, as designed, can remove large quantities
of excess runoff during rainy seasons and can lower ground-water
levels in order to furnish storage in the aquifer to accommodate
anticipated heavy recharge by rainfall. The controlled discharge of
the canals has furnished good flood protection in Area A and at
the same time has maintained adequate water levels in most coastal
areas to retard the inland movement of salt water.
Area A must be at least partially drained before any depletion
in storage can be effected in Area B; consequently, Area B normally
remains inundated or swampy during long periods. Also, the
eastward seepage beneath Levee 30 tends to maintain high water
levels in the western part of Area B. Area B is drained chiefly by
the Miami and Tamiami canals and to a lesser extent by the Snake
Creek and Snapper Creek canals. Their capacities are not adequate
to drain Area B by gravity during the rainy seasons.
Figure 2 shows the drainage features of the report area and
indicates the normal directions of flow in the major canals. The





FLORIDA GEOLOGICAL SURVEY


discharge of the Miami Canal is regulated by a control located at
36th Street, Miami, 6 miles inland from Biscayne Bay (fig. 1). The
control normally is opened a few weeks before the rainy season and
remains open throughout the rainy season to facilitate the discharge
of excess water. During open periods the effect of tides extends
upstream to a point beyond the Pennsuco Canal (fig. 2). After the
rainy season the control is closed in order to conserve water for
heavy municipal and irrigation use during the following dry months
and to maintain high water levels along the coast as a protective
measure against salt-water encroachment.
The main tributaries of the Miami Canal in northern Dade
County are the Levee 30 and 33 canals, the Pennsuco Canal, and
the Russian Colony Canal. Flow in some canals is controlled by
use of earth dams or manually operated sluice gates as located
in figure 2. The Levee 30 Canal is controlled at the Dade-Broward
Levee and its flow to the Miami Canal is maintained by seepage to
the northeast around the control and by ground-water inflow
between the control and the Miami Canal. The control in the
Levee 30 Canal usually remains closed. The flow in the reach of
the Levee 30 Canal upstream from the control is so small that

X -X rL 7,TiON R39EE R40E
--C.. 5 CONtRSCL e $iRnt ON D AN
A e
REZORDING GAGE I9
: I. ^ ^5.32
OCSERVATICN STATION i it
G372 STATION UMBER
5.7fTER LEVE T X E
4.60
LINE SHOWING ALTITUDE 4
aF WATER LEVEL.IN FEET GOLDEN GLIDES C,41va
ABOVE MEAN SEA LEVEL 5 1 -
SCAL-E 11 F-F-T A# \ \



Si. 0 0 0



/ G usi y1 CANAL



/ GG973
:o 9 o 4 b
P39E R40E
Figure 5. Contour map of the area investigated showing the altitude and
configuration of the water level on January 21, 1960.





REPORT OF INVESTIGATIONS NO. 24


ordinarily it cannot be measured. Probably there is a very low water
divide along the north-south reach of the canal from which there
is a slight southward gradient toward the Tamiami Canal and
northward gradient toward the Miami Canal.
The southward flow in the Levee 33 Canal is controlled at the
Miami Canal. Operation of this control depends upon the ability
to maintain water stages of 3.0 to 3.5 feet above msl at station
M3, in the Miami Canal where it is joined by the Pennsuco Canal.
When the stage is below this level, the control is opened and water
is released into the Miami Canal to replenish supplies in the down-
stream reaches.
The southern part of the area is drained by the Pennsuco
Canal, which extends westward to the Dade-Broward Levee, and by
the Russian Colony Canal; however, effective drainage by the
Russian Colony Canal extends only about 31/ miles west of its
confluence with the Miami Canal. The westward extension of this
canal is shallow and unimproved and therefore is effective only
during flood periods. Partly effective drainage probably takes place
along the shallow diagonal canal north of the Pennsuco Canal.

HYDROLOGY

WATER LEVELS AND MOVEMENT

Widespread fluctuations of water levels in Dade County are due
to recharge by rainfall, to discharge into drainage canals and Bis-
cayne Bay, and to evapotranspiration. Water levels in this part
of northern Dade County are regulated also by the operation of
the control in the Miami Canal at 36th Street, Miami, and by
operation of controls in the Levee 30 and Levee 33 canals.
Figure 5 is a contour map of water levels in the area on January
21, 1960. The contours are based on water-level measurements
obtained from observation points in canals that cut through the
dense limestones and from observation wells. Water levels in the
area were relatively high at that time and the control at 36th
Street was open. The configuration shows that the drainage effect
extended along the entire uncontrolled reach of the Miami Canal
and its main tributaries and along the short reach of the Levee 30
Canal downstream from the Dade-Broward Levee. The pattern
of the contours indicates the effectiveness of drainage by deep
canals (Miami, Levee 30, and Pennsuco canals, and the lower
reach of the Russian Colony Canal) and the lack of effective drain-
age by the shallow canals. High heads are maintained above the





FLORIDA GEOLOGICAL SURVEY


control in the Levee 33 Canal and the control in the Levee 30
Canal; however, the close spacing of the contours at these controls
indicates that there is considerable seepage through the aquifer
around the controls.
It is important to compare the pattern of the contours east
of the Dade-Broward Levee with that adjacent to Levee 30 be-
tween the Dade-Broward Levee and the Miami Canal. The
distribution of the heads east of the Dade-Broward Levee indicates
that the shallow diagonal canal and the Dade-Broward Levee
borrow canals do not have an appreciable drainage effect. In
contrast, the steep gradient on the northwest side of Levee 30 and
the low gradient on the southeast side indicate that the Levee 30
Canal is intercepting nearly all the underflow along Levee 30.
High water levels prevailed throughout this part of northern
Dade County during 1958-59 and the early part of 1960. On May
8, 1958, the 36th Street control was opened and drainage of the
area proceeded until January 5, 1959, when the control was closed.
The control again was opened on June 23, 1959, and remained opened
throughout the first half of 1960. During the entire period the
eastern part of Conservation Area No. 3 was inundated to depths
ranging from 1 foot to more than 4 feet. The area between Levee
30 and the Dade-Broward Levee also was flooded during the period,
but the depth of the water was less than that in Conservation Area
No. 3. Flooding east of the Dade-Broward Levee probably was
intermittent and corresponded with periods of heavy rainfall.
Figure 6 shows hydrographs of groups of observation stations
in the area for 1959 and the early part of 1960. The locations of
these stations are shown in figures 2 and 4. The hydrographs show
the relation between canal stages and ponded-water stages in the
area adjacent to the Levee 30 and 33 canals and the Miami Canal.
The hydrographs of stations 30TW and 30TE show the variation
in head differential between the pool in Conservation Area No. 3
(30TW) and the stage in the Levee 30 Canal south of the Dade-
Broward Levee. During dry periods, such as March-May 1959,
the head differential across Levee 30 at this point was very small
and a temporary reversal of gradient (east to west) occurred at
the end of April and in early May. During the dry months, the
eastward underflow of water from Conservation Area No. 3 probably
was negligible as compared to that during periods of high water
stages (July 1959-January 1960).
The persistent high head differential represented by the hydro-
graphs of stations 30W and 30E show the effectiveness of the
control in the Levee 30 Canal at the Dade-Broward Levee. This





REPORT OF INVESTIGATIONS NO. 24


--T ..'z S-- t i I


0 [ J ,

8,-,-_ 5 .____ "'---_







I 30 TPONDED)o-_ -3E i I I


I -----~t--- ------------ --?o"---
s | I I I = i "-.L
7 _

09 ___


II-









6 -. .. "-. .






Figure 6. Hydrographs of groups of observation stations for 1959 and the
early part of 1960.

differential in head suggests continuous leakage by underflow
around the control which tends to maintain, in part, the flow in the
lower reach of the Levee 30 Canal.
An outstanding feature of the hydrographs in figure 6 is the
-j


-LJ






















high head differential between stations M9 pounded ) and M8
Levee 30 al)this differentialranged from 2.2 feet during


a relatively dry period to more than 4.5 feet during high water
lowe rec7fteLee 0Cnl
An outstandin fetreo.hehdo.ahsi.igr..ih
hihhaifrnilbten ttosMjpne)adM
(Leve3 aa) hs ifrnia agdfo etdrn
a>eaieydypro omr, hn45fe uighg ae





FLORIDA GEOLOGICAL SURVEY


stages. Also shown in figure 6 are the heads maintained behind the
control in the Levee 33 Canal (station 33) and the control in the
Miami Canal at the Dade-Broward Levee (station Mil). A
comparison of the hydrographs of stations 30E and M8 shows the
low gradient through the downstream reach of the Levee 30 Canal.
A continuous record of water-level fluctuations has been obtained
from station G72 since 1940. A hydrograph of this station and
the annual rainfall at the Miami Airport are shown in figure 7.
The highest water level of record at station G72 was 9.4 feet above
msl in October 1947, and the lowest of record was 1.1 feet above
msl in June 1945. The hydrograph for the long period of record
gives a comparison between water levels before the levee system
and water-control practices were in effect (before 1952), and water
levels after the water-control measures were in operation (1952-
59). It can be seen that water levels during the drought period of
1955-56 did not decline as much as they did during the comparable
drought periods of 1944-45 and 1950-52. Also, it is apparent that
the unusually heavy rainfall of 1957-59 did not produce water levels
as high as those during the wet years 1947-48. These facts demon-
strate that the proper placement and operation of the existing
controls in canals can decrease flood damage during rainy seasons
and can maintain relatively high water levels during droughts.

RELATION BETWEEN PONDED WATER AND GROUND WATER
Three test sites were established adjacent to the Levee 30 Canal
downstream from the Dade-Broward Levee (fig. 4). The purpose

19391940.1941.19421943 1944194519461947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957.19581 I f
z MIAMI AIRPORT



N--
10- PRIOR TO WATER CONTROL WATER CONTROL--->
S G72. 1 IN EFFECT
Ut


W +TV I LAND SURFACE
I-Z

0 SEA LEVEL
193919401941 19421943 194441945 1946 194719481949 19501951 1952195319541955 19561957 19581959
Figure 7. Hydrograph of station G72 for the period 1940-59 and the annual
rainfall at the Miami Airport.






REPORT OF INVESTIGATIONS NO. 24


of studies at these sites was to determine the relation between
the impounded water in Conservation Area No. 3 and ground water
in the area. When this relationship is known, the amount of
underflow occurring beneath Levee 30 can be calculated for the
existing water-level conditions, and estimates of underflow can be
made for various assumed water-level conditions.
Each of the test sites consists of a line or lines of. test wells
perpendicular to Levee 30; these sites are shown in the profile
sections in figures 8, 9, and 10. The wells at site A-A' (fig. 8) are
the shallowest, but they penetrate the entire thickness of the dense
limestones and terminate in the upper section of the highly
permeable part of the aquifer. Site B-B' (fig. 9) was drilled by
the Corps of Engineers and consists of a line of nine wells extending
northwestward from Levee 30 and one well on the berm between
Levee 30 and the Levee 30 Canal. These wells range in depth from
17 to 40 feet.
The wells at site C-C' (fig. 10) also were drilled by the Corps
of Engineers and were used as observation wells during a pumping
test to determine the permeability of the aquifer. The site consists
of groups of multiple-depth wells extending northwestward into
Conservation Area No. 3. Figure 10 shows the layout of the lines


AD0 20 DISTANCE IN FEET A'
A 300 200 100 0 t00

Pon d level Jn"b.2i 960 LEVEE








S.lI .
4 piezometric 0urfac 60sur
LEVEE
CANAL














piezometric surface at site A-A', January 21 and February 8, 1960.
-4 -ANAL
\a:---
-6 0

-1U ____ -- 1 ------ 1 ------ 1 ------ --- --- ------ 2 ______

2iue8 rfl hwn h eainbtentepne ae n h
pizmti ufaea ieAA, aur 1adFeray8 90




14 FLORIDA GEOLOGICAL SURVEY

DISTANCE IN FEET t 3'
200 300 -





S'.; I CANAL




II I i
4 30











Figure 9. Profile showing the relation between the ponded water and the
piezometric surface at site B-B', January 21 and February 8, 1960.

of wells with reference to Levee 30 and the Levee 30 Canal and
indicates the altitude of the bottom of each well.
Water-level measurements were made at A-A' and B-B' on
January 21 and February 8, 1960. Figures 8 and 9 show the water-
level profiles at the two sites on the dates the measurements were
made. At site A-A' (fig. 8) the gradient of the piezometric surface
on the northwest side of the levee toward the Levee 30 Canal
was 1.1 feet in 270 feet, or 0.0041 foot per foot. Within the 270-
/L EVE




it








foot distance ole sh ead differential between the ponded water and the
the piezometric surface at increased towB-B, January 21 and the levee and ranged, 19
from 3.1 feet at the end well of the profile to 3.6 feet at the Levee 30 Canal andevee.
The gradie the altitude piezom the bottomprofile in figure 9





was 3.17 feet in 650 feet, or 0.049 foot per foot. The head
differential measurements were made at A-A' and B-Bthe piezometric surface
January 21 and February 8, 1960. Figures 8 and 9 show.the water-





ranged frolesm 1.2 feet at the two sites on the dates the profile to 3.5 feet atwere
the levee. The avera (fig. 8) the gradient of the piezometric surface during
on the northwest side of the levee toward the Levee 30 Canal





wthe 3-week test period was 0.0045 foot per foot toward the Levee270-
30ot distance. The aquifer was being replenishe pounded water and
the piezometric surface increased toward the levee and ranged
from 3.1 feet at the end well of the profile to 3.6 feet at the levee'




Tleakage of pounded water, at a rate depealong the profile in figurthe head
was 3.17 feet in 650 feet, or 0.049 foot per foot. The head



differential, and no depletionded level aquifer storage was occurfacering
ranged from 1.2 feet at the end well of the profile to 3.5 feet: at
the levee. The average gradient of the piezometric surface. during
the 3-week test period was 0.0045 foot per foot toward the Levee
30 Chial. The aquifer was being replenished by the downward
leakage of ponded water, at a rate dependent-upon-the. head
differential, and no depletion of aquifer storage was occurring
northwest of Levee 30.
Water-level measurements made during the drilling atsite A-A'











1ISTANCETANC I N FEE T


+10



U
-J
0Q

LU
'
U




UJIQ
LU

U.




wU-30





140


EXPLANATION
BOTTOM OF CASED WELL
,G ,74 5,$6
WATER LEVEL .6
LINE OF EQUAL POTENTIAL
i__I d' ..r, -._.I.... L......,.... _.. .........


. O Lo 9 O


04


,(.s ,.55 54 ,, / ,J,5
.S.9,S9.S.... .... 4 .


Figure 10. Profile along site C-C' showing lines of equal potential, April 1b,
1960.


.40
PIEZOMETRI R P,
LAND SURFACE












Sr .6.34 ,9S .55? 5.1 S.1 .5.5


), ', ',







.,.






I-

02

lz
0 *


Or


I





FLORIDA GEOLOGICAL SURVEY


showed that there was no head difference between the ponded
level and the water level of wells bottomed in the Miami oolite.
This indicates that the confining characteristics of the marl and
muck blanket are of much less significance than those of the dense
limestones.
No appreciable ponding occurred in the area immediately south-
east of the Levee 30 Canal. Figure 8 shows also that the north-
westward gradient of the piezometric surface on the southeast side
toward the Levee 30 Canal was 0.40 foot in 250 feet, or 0.0016
foot per foot. Therefore, the quantity of inflow from the southeast
was equivalent to approximately 40 percent of the inflow occurring
from the northwest at the A-A' site during the period January 21-
February 8, 1960. The profile in figure 8 indicates a slight de-
pletion of ground-water storage immediately southeast of the Levee
30 Canal. It is important to recognize that the contribution of
water from the area southeast of the Levee 30 Canal to the canal
was diminishing as shown on the contour map (fig. 5) by the
decrease in ground-water gradient along the lower reach of the
canal. It is estimated that the average gradient of the piezometric
surface on the southeast side along the uncontrolled reach of the
canal was 0.0010 foot per foot. Therefore, the total inflow to the
Levee 30 Canal from the southeast was equivalent to approximately
20 to 25 percent of the total from the northwest.
UNDERFLOW ALONG LEVEE 30
During periods when the control in the Levee 30 Canal is closed,
discharge along the downstream reach of the Levee 30 Canal
represents a composite of the following: (1) leakage by underflow
around the control, (2) ground-water inflow from the thick
permeable section of the aquifer, and (3) seepage of ponded water
through the levee fill and through the thin layer of permeable
Miami oolite that occurs between the fill and the dense limestone
layers. At high water stages, such as those which prevailed from
July through November 1959, the water level of the downstream
reach of the canal was above the canal bank and sheet flow
occurred toward the Miami Canal. Most of the discharge of the
Levee 30 Canal was maintained by ground-water inflow from the
northwest.
By January 21, 1960, water stages had lowered and discharge
measurements were made at points 1 mile apart in the Levee 30
Canal (Q, and Q2 in fig. 4), downstream from the control. Following
is a tabulation of the discharge and water-level data obtained
during the January 21 test:





REPORT OF INVESTIGATIONS No. 24


A. Discharge measurements in Levee 30 Canal
At Q1 __- ..__ -__...--- __ _____ ---_ 76 cfs (49 mgd)
At Q2 -..-----.----- --------------- --------- 252 cfs (163 mgd)
Q2-Q ----, ---------- ---------- 176 cfs (114 mgd)
Estimated seepage (visible) through the levee
fill, across the berm to the canal (Q) -- 10 cfs (7 mgd)
Net pickup by ground-water inflow (Q,)
Qg=Q2-Q-Qs ------------------------------ 166 cfs (107 mgd)

B. Gradients (I) of piezometric surface toward
Levee 30 Canal (fig. 8, 9).
Northwest of canal
A-A' site ------------- ------- 0.0041 foot per foot
B-B' site---- ------ .0049 foot per foot
Southeast of canal
A-A' site----------- .0016 foot per foot
Estimated average for area
southeast of canal----- ------ .0010 foot per foot

By Darcy's law the rate of flow of a fluid through a porous
medium is directly proportional to the hydraulic gradient and can
be written as follows (Wenzel, 1942, p. 3-7):

Q=PIA

where Q is the discharge rate, P is the coefficient of permeability of
the material being tested, I is the hydraulic gradient, and A is the
area of the cross section through which the fluid moves. If it is
assumed that the permeable section of the aquifer beneath the
dense limestone layers is isotropic and that underflow through this
section is laminar, then the quantity of ground water discharging
into the Levee 30 Canal is directly proportional to the gradient of
the piezometric surface; therefore, about 80 percent of Qg or 86
mgd, represents underflow from the northwest along the 1-mile
reach of the canal. (See tabulation above.)
In order to make computations that involve the entire thickness
of an aquifer as a unit, Darcy's law may be written:

Q=TIL

in which Q is the quantity of water, in gpd (gallons per day), T
is the coefficient of transmissibility, in gallons per day, for each
vertical strip of the aquifer 1 foot wide; I is the hydraulic gradient,





FLORIDA GEOLOGICAL SURVEY


in feet per foot; and L is the length of section, in feet, through
which the quantity (Q) flows. By substituting in the above
equation the hydrologic data obtained during the January 21 test,
a determination of the coefficient of transmissibility of the aquifer
can be made as follows:

Q=TIL
Q (gpd)
T (gpd per foot)= (g
I (foot per foot) x L (feet)

T 86,000,000
0.0045 x 5,280

T = 3,600,000 gpd per foot, or 5.6 square feet
per second
This computed coefficient of transmissibility compares very closely
with the value of 5.76 square feet per second determined by the
Corps of Engineers for the highly permeable part of the aquifer
adjacent to Levee 30 (U.S. Army Corps of Engineers, 1953, p. D-6).
Dry weather prevailed during the spring of 1960, and by the
middle of April the water stage in Conservation Area No. 3 had
declined so that the multiple-depth wells along site C-C' were
accessible. On April 19, 1960, water-level measurements were made
in all wells in this test site. The profile in figure 10 shows the
relation between the pool in Conservation Area No. 3 and the
piezometric surface on that day and shows also, by equipotential
lines, the approximate head distribution in the aquifer along the
profile. The gradient of the piezometric surface within 1,000 feet
of the Levee 30 Canal was 0.0017 foot per foot, but for the
remaining 800 feet of the section the gradient decreased to 0.0011
foot per foot. The head differential between the ponded water and
the piezometric surface ranged from 0.32 foot at the northwestern
end of the profile to 1.57 feet near the toe of the levee.
The equipotential lines, shown in figure 10, indicate that flow
through the highly permeable part of the aquifer (depths more
than 5.0 feet below msl) toward the Levee 30 Canal is virtually
horizontal, except for the section adjacent to and beneath the canal
where the flow direction has an upward component. The distribution
and pattern of the lines suggest that about 75 percent of the loss
in head occurs within 1,000 feet of the levee. The horizontality and
the close spacing of the lines at depths between 0.5 foot above and
3.0 feet below msl indicate a large vertical head loss caused by






REPORT OF INVESTIGATIONS NO. 24


vertical flow through the dense limestone of low permeability at
that interval (fig. 3). The flow through the shallow materials
immediately beneath the levee is virtually horizontal and probably
occurs chiefly through a thin layer of the permeable Miami oolite
beneath the fill.
Detailed information on head distribution through a part of
the aquifer, as shown in figure 10, makes it possible to estimate
the amount of surface water that was seeping downward through
the confining layers to the thick permeable part of the aquifer.
The amount of ground water moving toward the canal in 1 day,
across a section of the aquifer 1 mile long at a distance of 800 feet
from the edge of the canal, may be computed as follows:

Q=-TIL

0.4 foot x 5,280 feet
Q=3,600,000 x400 f
400 feet
Q=19 mgd per mile, or 29 cfs per mile
A similar computation for a distance 400 feet from the canal is as
follows:
0.59 foot x 5,280 feet
Q=3,600,000 x
400 feet
Q=28 mgd per mile, or 43 cfs per mile.

The 9-mgd difference in flow represents approximately the amount
of surface water picked up by leakage through the confining beds
to the permeable flow section within the rectangular area 1 mile
long between 400 and 800 feet from the levee.
Inasmuch as the approximate amount of downward infiltration
in a given area has been determined, a computation of the coefficient
of vertical permeability of the confining layers can be made. The
coefficient of permeability is defined as the rate, of flow through
a cross section of 1 square foot, under a gradient of 1 foot per foot.
The computation of the coefficient of vertical permeability of the
dense limestone is as follows:
Rectangular area used in computation __-5,280 feet x 400 feet,
or 2.1 million square
feet
Downward leakage ----- --9 nigd, or 4.3 gpd per
square foot





FLORIDA GEOLOGICAL SURVEY


Altitude of piezometric surface 600
feet from levee 5.93 feet above msl
Altitude of ponded level __6.91 feet above msl
Head differential 600 feet from levee
(assumed average for area 400 to
800 feet from levee) ___ 0.98 foot
Thickness of confining layers _3.0 feet
Gradient across confining layers -----. 0.33 foot per foot

Q
P=
IA
4.3 gpd
0.33 foot per foot x 1 square foot

P= 13 gpd square foot, or 2.0 x 10-5 foot per second

A proposed method of flood control in Area B is to reduce
ground-water storage by means of a network of canals and a
series of large pumping stations. The pumps would be placed at
selected locations along Levees 30 and 31 and would pump water
from the interconnected canal system of Area B westward into
Conservation Area No. 3. Initially, it was proposed that the water
stage in Area B be maintained at mean sea level in order to give
maximum protection during all major storms. It is probable that
water levels along the levee side of Area B will be lowered tempo-
rarily below mean sea level in order to provide adequate gradients
toward the pumping stations.
Reducing the water stage in Area B would result in gradients
across Levee 30 that would greatly exceed those shown in the
profiles of figure 9. There might be times when the head differential
between the pool in Conservation Area No. 3 and the stage in the
Levee 30 Canal would be as much as 10 feet. It is extremely im-
portant, therefore, to determine the amount of water that would
move from Conservation Area No. 3 to the adjacent canals in order
that adequate pumping stations be provided.
To make a determination of the anticipated underseepage it is
necessary to determine the relation between the head across the
levee and the head differential at the toe of the levee at different
water stages. Figure 11 is a graph showing this relationship; and
the plotted points are based on the water-level profiles of figures






REPORT OF INVESTIGATIONS NO. 24


HEAD DIFFERENCE,IN FEET, BETWEEN POOL AND LEVEE 30 CANAL
I 2 3 4 5 6 7 8 10
o8
I-I






0>
a--
UJ w
0 /



o>

Uw0 /

^m JAN.21,1960 -DEC.17 1959
0o FEB. 8,1960
zU-


LL-
wcn

I ^ PAPRIL 19,1960






Figure 11. Graph showing the relation between the head difference across
Levee 30 and the head difference between the pool and the piezometric surface
at the toe of the levee.

9 and 10 and on a series of measurements made on December 17,
1959. The projection of the graph indicates that, if a 10-foot head
were held across the levee, the head difference between the pool and
the piezometric surface at the toe of the levee would be 7.8 feet;
thus the gradient of the piezometric surface across the 150-foot
width of the levee would be 2.2 feet.
Following is a computation of the amount of underflow that
would be intercepted along a 1-mile reach of the canal (Q1 to Q2 in
fig. 4) when the head differential across the levee was 10 feet:

Q=TIL


Q=3,600,000 gpd per foot x 2.2 feet x 5,280 feet
150 feet
Q=279 mgd per mile, or 432 cfs per mile

In order to determine the total quantity of water that would be
intercepted :by the Levee 30. Canal along the 1-mile reach,





FLORIDA GEOLOGICAL SURVEY


consideration must be given to the seepage that would occur
through the levee materials and through the thin permeable layer
of Miami oolite that underlies the levee fill. This approximate
determination is shown by the following tabulation:

Composite estimate of coefficient of
permeability of levee fill and
Miami oolite _20,000 gpd per square foot
Length of flow section 5,280 feet
Thickness of flow section
(10-foot head differential) _. 10 feet
Q=PIA

10 feet
Q=20,000 gpd per square foot x -150 x 5,280 feet x 10 feet
150 feet
Q=70 mgd per mile, or 108 cfs per mile

The estimated coefficient of permeability used in the above
computation probably is high and compares with a well sorted
gravel that contains only small quantities of fine material (Wenzel,
1942, p. 13). However, the estimate was made in consideration of
the probable high permeability of the layer of Miami oolite through
which much of the direct seepage may occur.
The total quantity of water that would be intercepted along the
1-mile reach of Levee 30 Canal when the head difference across
the levee was 10 feet is computed to be 349 mgd, or 540 cfs. These
results were obtained by assuming that water movement beneath
Levee 30 occurs by laminar flow. If there is turbulence through
the large openings in the aquifer beneath the levee, the underflow
would be less. For laminar flow the underflow to the canal would
be directly proportional to the head difference across the levee, and
for turbulent flow the underflow would be directly proportional to
the square root of the head difference; in the transitional zone
underflow would vary exponentially between the first and one-half
powers of the head difference.

CONCLUSIONS

Water-level measurements and geologic data obtained from test
wells indicate that the upper part of the Biscayne aquifer in the
vicinity of Levee 30 in northern Dade County contains dense layers
of limestone of relatively low permeability that retard downward






REPORT OF INVESTIGATIONS No. 24


infiltration to the thick permeable parts of the aquifer. The
coefficient of transmissibility of 3,600,000 gpd per foot, or 5.6 square
feet per second, as determined from water-level profiles taken
normal to Levee 30 and from discharge measurements made in
the Levee 30 Canal, compares closely with the coefficient determined
by the Corps of Engineers by pumping-test methods. The computed
coefficient of permeability of 13 gpd per square foot, or 2.0 x 10-5
foot per second, for the thin dense layers indicates that these layers
form a fairly effective confining unit which separates the ponded
water in Conservation Area No. 3 from the ground water. Geologic
information obtained from the surrounding areas suggests that
the thin, dense limestones probably are widespread, and therefore
that the blanketing effect occurs throughout a large area.
Conservation Area No. 3 generally is flooded for several months
'of each year, the result being high head differentials across Levee
30. When the plan for the development of Area B is in effect,
there may be times when the differential of head across the levee
will be as much as 10 feet. When this condition occurs, it is
estimated that the inflow to the Levee 30 Canal from Conservation
Area No. 3 will be about 350 mgd per mile, or 540 cfs per mile.
This estimate was made by computing separately (1) the underflow
through the main permeable section at the aquifer and (2) the
seepage through the levee fill and the thin layer of permeable
limestone that immediately underlies the levee fill.
When the road construction is completed in the area it would be
desirable to obtain additional data to define more accurately the
relation between head difference across the levee and discharge in
the Levee 30 Canal.
The coefficient of transmissibility of the aquifer, the coefficient
of vertical permeability of the confining layers, and the estimated
rates of inflow from Conservation Area No. 3, as determined from
this study, may be valid only for the north end of Levee 30. It is
probable that hydrologic conditions vary along the entire length
of Levee 30, and therefore similar studies will be required for the
southern reaches in order to' determine total leakage along the
levee system.

REFERENCES
Ferguson, G. E. (see Parker, G. G.)
Love, S. K. (see Parker, G. G.)
Parker, G. G.
1951 Geologic and hydrologic factors in the perennial yield of the
Biscayne aquifer: Am. Water Works Assoc. Jour., v. 43, p. 817-
834.





FLORIDA GEOLOGICAL SURVEY


1955 (and Ferguson, G. E., Love, S. K., and others) Water resources
of southeastern Florida, with special reference to the -geology
and ground water of the Miami area: U. S. Geol. Survey Water-
Supply Paper 1255, 965 p.
Schroeder, M. C.
1958 (and others) Biscayne aquifer of Dade and Broward counties,
Florida: Florida Geol. Survey Rept. Inv. 17, 56 p.
Stallman, R. W.
1956 Preliminary findings on ground-water conditions relative to Area
B flood-control plans, Miami, Florida: U. S. Geol. Survey Open-
File Rept., Tallahassee, Florida, 42 p.
U-S. Army Corps of Engineers
1952 Test levee investigations: Partial Definite Project Report, Central
and Southern Florida Project, pt. 1, supp. 5, mimeograph
Rept., March 28.
1953 Agricultural and conservation areas, design memorandum, per-
meability investigations by well-pumping tests: Partial Definite
Project Report, Central and Southern Florida Project, pt. 1,
supp. 7, Mimeograph Rept., February 16.
1954 Design memorandum, Hydrology and hydraulic design canals in
Greater Miami area (C-2 through C-9) (revised) ; Partial Definite
Project Report, Central and Southern Florida Project, pt. 5, supp.
12, mimeograph Rept., March 23.
Wenzel, L. K.
1942 Methods for determining permeability of water-bearing materials,
with special reference to discharging-well methods, with a section
on direct laboratory methods and bibliography on permeability
and laminar flow, by V. C. Fishel: U. S. Geol. Survey Water-
Supply Paper 887, 192 p.



























































































































.




Hydrologic conditions in the vicinity of Levee 30,
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 Material Information
Title: Hydrologic conditions in the vicinity of Levee 30, northern Dade County, Florida ( FGS: Report of investigations 24, pt.1 )
Series Title: ( FGS: Report of investigations 24, pt.1 )
Physical Description: v, 24 p. : map. diagrs. ; 24 cm.
Language: English
Creator: Klein, Howard
Sherwood, C. B. ( joint author )
Publisher: s.n.
Place of Publication: Tallahassee Fla
Publication Date: 1961
 Subjects
Subjects / Keywords: Groundwater -- Florida -- Miami-Dade County   ( lcsh )
Genre: non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Howard Klein and C. B. Sherwood.
General Note: "Prepared by the United States Geological Survey in cooperation with the Central and Southern Florida Flood Control District."
General Note: "References" : p. 23-24.
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Table of Contents
    Front Cover
        Page i
    Florida State Board of Conservation
        Page ii
    Transmittal letter
        Page iii
        Page iv
    Contents
        Page v
        Page vi
    Abstract and introduction
        Page 1
        Page 2
        Page 3
        Page 4
    Description of area
        Page 5
        Page 6
        Page 4
        Page 7
        Page 8
        Page 9
    Hydrology
        Page 10
        Page 11
        Page 12
        Page 13
        Page 9
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
    Conclusions
        Page 23
        Page 22
    References
        Page 23
        Page 24
        Copyright
            Copyright
Full Text

STATE OF FLORIDA
STATE BOARD OF CONSERVATION



FLORIDA GEOLOGICAL SURVEY
Robert 0. Vernon, Director






REPORT OF INVESTIGATIONS NO. 24

PART I


HYDROLOGIC CONDITIONS IN THE VICINITY
OF LEVEE 30, NORTHERN DADE COUNTY,
FLORIDA


By
Howard Klein and C. B. Sherwood
United States Geological Survey











Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
CENTRAL AND SOUTHERN FLORIDA FLOOD CONTROL DISTRICT


TALLAHASSEE, FLORIDA
1961











FLORIDA STATE BOARD Zatna

OFNSERVATION

CONSERVATION


FARRIS BRYANT
Governor


TOM ADAMS
Secretary of State


J. EDWIN LARSON
Treasurer


THOMAS D. BAILEY
Superintendent Public Instruction


RICHARD ERVIN
Attorney General


RAY E. GREEN
Comptroller


DOYLE CONNER
Commissioner of Agriculture






LETTER OF TRANSMITTAL


Ji1orida


geological

'(ailakassee


June 1, 1961


Honorable Farris Bryant, Chairman
Florida State Board of Conservation
Tallahassee, Florida


Dear Governor Bryant:

The Florida Geological Survey is publishing as Report of
Investigations No. 24, Part I, a report on the hydrologic conditions
in the vicinity of Levee 30, northern Dade County, which was
prepared by Howard Klein and C. B. Sherwood of the U. S.
Geological Survey. This report was prepared in cooperation with
the Central and Southern Florida Flood Control District, and this
department is publishing the report in its regular series of water
resources papers.
The formations that underlie Levee 30 are a part of the very
permeable sediments that underlie the southern tip of Florida.
The opportunity to make this study has provided important data
relative to the transmissibility of the sediments and will assist
in design of control structures and in-the development of the water
resources of southern Florida.
Respectfully yours,
Robert 0. Vernon, Director


Survey




















































Completed manuscript received
February 27, 1961
Published by the Florida Geological Survey
E. 0. Painter Printing Company
DeLand, Florida

iv






CONTENTS

Abstract 1
Introduction 1
General statement and purpose 1
Previous investigations : 3
Acknowledgments 3
Description of area -------- .------_............ 4
Geology ..........-------.-- --.--- --- ------------------- 5
Drainage features _--- 7
Hydrology ---- --- ___ 9
Water levels and movement ----------_ ____ 9
Relation between ponded water and ground water 12
Underflow along Levee 30 16
Conclusions 22
References -- 23


ILLUSTRATIONS

Figure Page

1 Map of northern Dade County showing the area of investigation __ 2
2 Map of area of investigation showing the location of the test area
and the location of selected observation stations ------ 4
3 Cross section A-A' showing details of the near-surface geology near
the north end of Levee 30 ____ 5
4 Map of test area showing locations of observation stations and test
sites 6-------- --- -- 6
5 Contour map of the area investigated showing the altitude and con-
figuration of the water level on January 21, 1960 8
6 Hydrographs of groups of observation stations for 1959 and the
early part of 1960 ___- ---- 11
7 Hydrograph of station G72 for the period 1940-59 and the annual
rainfall at the Miami Airport 12
8 Profile showing the relation between the ponded water and the
piezometric surface at site A-A', January 21 and February 8, 1960 13
9 Profile showing the relation between the ponded water and the
piezometric surface at site B-B', January 21 and February 8, 1960 14
10 Profile along site C-C' showing lines of equal potential, April
19, 1960 ----------------- 15
11 Graph showing the relation between the head difference across Levee
30 and the head difference between the pool and the piezometric
surface at the toe of the levee ___---------------------_ 21










HYDROLOGIC CONDITIONS IN THE VICINITY OF LEVEE 30,
NORTHERN DADE COUNTY, FLORIDA

By
Howard Klein and C. B. Sherwood
ABSTRACT
Thin layers of dense limestone of low permeability that occur
near the top of the Biscayne aquifer in the vicinity of the north
end of Levee 30 in Dade County, Florida are of hydrologic im-
portance because they retard the downward infiltration of ponded
water in Conservation Area No. 3. This retarding effect frequently
results in high head differentials across the levee. Tests made in
a small area adjacent to Levee 30 indicate that the coefficient of
transmissibility of the aquifer is 3,600,000 gpd (gallons per day)
per foot, and the coefficient of vertical permeability of the dense
limestones is 13 gpd per square foot. If ground-water flow beneath
the levee is laminar, the total inflow to the Levee 30 Canal from
Conservation Area No. 3 will be about 350 mgd (million gallons per
day), or 540 cfs (cubic feet per second), per mile length of levee
when the head difference across the levee is 10 feet.
INTRODUCTION
GENERAL STATEMENT AND PURPOSE
One of the major responsibilities of the Central and Southern
Florida Flood Control District is to minimize flood damage in urban
and agricultural areas west of the coastal ridge in southeastern
Florida. A second function is to protect areas of potential urban
development. A large area of anticipated growth in Dade County
(shown as Area B in fig. 1). is west of Miami and extends about
10 miles eastward from Levees 30 and 31.
The initial project of the Central and Southern Florida Flood
Control District was the construction of an east-coast protective-
levee system west of the Atlantic Coastal Ridge, extending from
Lake Okeechobee southward into Dade County. Levees 33, 30, and
31 form the southern terminus of this levee system and are shown
in figure 1. Its primary purpose was to alleviate flooding in urban
and agricultural land, along and adjacent to the ridge, by retarding
the overland eastward flow of floodwaters from the Everglades.
When the flood-control system is completed, part of these excess
floodwaters will be impounded in conservation areas west of the





FLORIDA GEOLOGICAL SURVEY


Figure 1. Map of northern Dade County showing the area of investigation.
levee. Regulated releases of water will be conveyed by canals from
conservation areas to coastal areas to replenish ground-water
reservoirs during periods of drought.
This report is one of a series prepared in cooperation with the
Central and Southern Florida Flood Control District. The general
purposes of these investigations are (1) to define the hydrology of
certain areas within the Flood Control District, (2) to determine the
effectiveness of existing flood-control and water-control measures,
and (3) to furnish hydrologic data that will be used in the design
and operation of proposed and existing structures and works.





REPORT OF INVESTIGATIONS No. 24


The purpose of this investigation is to define the hydrologic
characteristics of the water-bearing materials in the vicinity of
Levee 30 in northern Dade County, in order to determine the
feasibility of controlling water levels in Area B for maximum flood
protection. Included is an analysis of the relation between the im-
pounded water west of Levee 30 and the ground water in the area.
From this relationship estimates of ground-water underflow along
Levee 30 can be computed under existing conditions and under
anticipated water-level conditions. Midway in the data-gathering
stage of the investigation, major road construction altered the
canal system in the immediate area and caused changes in water
levels and discharge of canals. This resulted in curtailing of the
field work; therefore the results of this investigation should be
considered preliminary.
The work was done under the general supervision of P. E.
LaMoreaux, chief, Ground Water Branch, Washington, D. C., and
under the immediate supervision of M. I. Rorabaugh, district
engineer, Tallahassee, Florida.

PREVIOUS INVESTIGATIONS

A comprehensive report by Parker and others (1955) presented
fairly complete information on the geology and hydrology of south-
eastern Florida, and Parker (1951) gave estimates of the
availability and adequacy of the ground-water supplies of the
Biscayne aquifer which underlies southeastern Florida. Schroeder
and others (1958) summarized additional data on the Biscayne
aquifer collected since 1950. Stallman (1956) made theoretical
computations on the effect of drainage in the area west of Miami
and gave estimates of the amount of seepage that might occur
beneath Levee 30 under certain assumed conditions. A
mimeographed report by the U. S. Army Corps of Engineers
(1953) described the results of permeability tests along different
levees within the Flood Control District.

ACKNOWLEDGMENTS

The writers are indebted to personnel of the Surface Water
Branch, U.S. Geological Survey, Miami, Florida, for making dis-
charge measurements in the Levee 30 Canal and furnishing water-
level information along the Miami Canal. Gratitude is expressed
also to the Public Works Department of metropolitan Dade County
for the record of water-level stages for several observation stations
in the area. The office of the Central and Southern Florida Flood





FLORIDA GEOLOGICAL SURVEY


Control District furnished complete information on the location,
the construction details, and the layout of the Corps of Engineers
test sites near Levee 30. The writers benefited from technical
discussions with F. A. Kohout of the Miami office, and H. H. Cooper,
Jr, and N. D. Hoy of the Tallahassee office, U. S. Geological Survey.

DESCRIPTION OF AREA

The area described in this report comprises 60 square miles
chiefly in northern Dade County, Florida (fig. 1). Figure 2, which
is a large-scale map of the report area, delineates the test site
within the area, locates certain water-level observation stations,
and shows the drainage features. The western part of the area is
traversed by Levees 30 and 33. These levees separate Conservation
Area No. 3, which normally contains ponded water, from Area B
which is swampy during much of the year. The altitude of the
land surface is about 5 feet above msl (mean sea level).


Figure 2. Map of area of investigation showing the location of the test area
and the location of selected observation stations.





REPORT OF INVESTIGATIONS NO. 24


GEOLOGY

The area of investigation is underlain to a depth of 55 feet by
the Biscayne aquifer, a body of highly permeable limestone. The
Biscayne aquifer is underlain by relatively impermeable silt, marl,
and fine sand which retard downward seepage from the aquifer
or upward seepage from deeper materials.
The cross section in figure 3 gives details of the near-surface
geology near the north end of Levee 30 in Dade County, as
determined from shallow test holes drilled at site A-A' (fig. 4).
The area is blanketed by 3 to 5 feet of muck and marl that is
underlain by a layer of solution-riddled Miami oolite, a part of the
Biscayne aquifer, 1 to 2 feet thick. Figure 3 shows two thin layers
of very hard, dense limestone at depths ranging from 0.5 foot
above msl to 3.0 feet below msl. In contrast to the high permeability
of the underlying limestones, these thin layers appear to be
relatively impermeable; and the vertical flow of water through
them is many times less than the horizontal flow of water through
the deeper, more permeable rocks. By effectively retarding the
downward infiltration of water, the thin layers act as a confining


DISTANCE IN FEET A


Figure 3. Cross section A-A' showing details of the near-surface geology near
the north end of Levee 30.






FLORIDA GEOLOGICAL SURVEY


COUNTY -
----COUNTY---


EXPLANATION


CANAL AND CONTROL
A M2
RECORDING GAGE
AND NUMBER
030E
OBSERVATION STATION
AND NUMBER
C--C'
LINE OF PROFILE
+<-Q2
STREAM-GAGING STATION
SCALE IN FEET
0 2500 5000


Figure 4. Map of test area showing locations of observation stations and
test sites.


DADE





FLORIDA GEOLOGICAL SURVEY


Control District furnished complete information on the location,
the construction details, and the layout of the Corps of Engineers
test sites near Levee 30. The writers benefited from technical
discussions with F. A. Kohout of the Miami office, and H. H. Cooper,
Jr, and N. D. Hoy of the Tallahassee office, U. S. Geological Survey.

DESCRIPTION OF AREA

The area described in this report comprises 60 square miles
chiefly in northern Dade County, Florida (fig. 1). Figure 2, which
is a large-scale map of the report area, delineates the test site
within the area, locates certain water-level observation stations,
and shows the drainage features. The western part of the area is
traversed by Levees 30 and 33. These levees separate Conservation
Area No. 3, which normally contains ponded water, from Area B
which is swampy during much of the year. The altitude of the
land surface is about 5 feet above msl (mean sea level).


Figure 2. Map of area of investigation showing the location of the test area
and the location of selected observation stations.





REPORT OF INVESTIGATIONS No. 24


unit that separates the ponded water in Conservation Area No. 3
from the water contained in the permeable limestone.
Geologic information from test wells and shallow borings, and
reported information obtained in connection with canal excavations,
indicate that the hard layers of dense limestone occur throughout
most of Area B and in southern Dade County, and that they occur
at about the same altitude. Each of the wells prefixedd by letter
G) shown in figure 2 penetrated the impermeable layers approxi-
mately at sea level. Similar layers were noted in wells near the
southern terminus of Levee 31 (fig. 1), and in wells south of the
Tamiami Canal and west of Levee 31. It is reasonable to assume
that the relatively impermeable zones underlie much of Conser-
vation Area No. 3 and that their confining characteristics are
widespread. In places, the dense limestones probably contain
openings through which rainfall can infiltrate rapidly; however,
the overall continuity and the blanketing effect of these layers
in general tend to retard infiltration. In the Miami area to the
east, the Biscayne aquifer thickens and contains much sand. The
thin, dense limestones either thin and disappear or they occur
deeper in the aquifer near the coast.

DRAINAGE FEATURES

During the past 10 years the improved canal system that pro-
vides gravity drainage to Biscayne Bay, as shown in figure 1, has
effectively reduced flooding in Area A, the urbanized part of eastern
Dade County. The system, as designed, can remove large quantities
of excess runoff during rainy seasons and can lower ground-water
levels in order to furnish storage in the aquifer to accommodate
anticipated heavy recharge by rainfall. The controlled discharge of
the canals has furnished good flood protection in Area A and at
the same time has maintained adequate water levels in most coastal
areas to retard the inland movement of salt water.
Area A must be at least partially drained before any depletion
in storage can be effected in Area B; consequently, Area B normally
remains inundated or swampy during long periods. Also, the
eastward seepage beneath Levee 30 tends to maintain high water
levels in the western part of Area B. Area B is drained chiefly by
the Miami and Tamiami canals and to a lesser extent by the Snake
Creek and Snapper Creek canals. Their capacities are not adequate
to drain Area B by gravity during the rainy seasons.
Figure 2 shows the drainage features of the report area and
indicates the normal directions of flow in the major canals. The





FLORIDA GEOLOGICAL SURVEY


discharge of the Miami Canal is regulated by a control located at
36th Street, Miami, 6 miles inland from Biscayne Bay (fig. 1). The
control normally is opened a few weeks before the rainy season and
remains open throughout the rainy season to facilitate the discharge
of excess water. During open periods the effect of tides extends
upstream to a point beyond the Pennsuco Canal (fig. 2). After the
rainy season the control is closed in order to conserve water for
heavy municipal and irrigation use during the following dry months
and to maintain high water levels along the coast as a protective
measure against salt-water encroachment.
The main tributaries of the Miami Canal in northern Dade
County are the Levee 30 and 33 canals, the Pennsuco Canal, and
the Russian Colony Canal. Flow in some canals is controlled by
use of earth dams or manually operated sluice gates as located
in figure 2. The Levee 30 Canal is controlled at the Dade-Broward
Levee and its flow to the Miami Canal is maintained by seepage to
the northeast around the control and by ground-water inflow
between the control and the Miami Canal. The control in the
Levee 30 Canal usually remains closed. The flow in the reach of
the Levee 30 Canal upstream from the control is so small that

-X X L, TiON R 39E R40E
-- 5..., COntorCL .. o. th e" re- i esti7"" s-owig t, e a COUN T-
A e
REZCRDING GAGE
OBSERVATICN STATION i i
G372 STA R ON UMB

-INE SHOWING ALTITUDE 4O/ O
aF WATER LEVEL.IN FEET G__ OLDEN GLADES C41Ma
ABOVE MEAN SEA LEVEL 8 1
SCAL-E 11 F-F-T A# \ \



C. S6 0 C. 0 0 0'



/ G usi y1 CANAL



91 4
P39E R4OE
Figure 5. Contour map of the area investigated showing the altitude and
configuration of the water level on January 21, 1960.





REPORT OF INVESTIGATIONS NO. 24


ordinarily it cannot be measured. Probably there is a very low water
divide along the north-south reach of the canal from which there
is a slight southward gradient toward the Tamiami Canal and
northward gradient toward the Miami Canal.
The southward flow in the Levee 33 Canal is controlled at the
Miami Canal. Operation of this control depends upon the ability
to maintain water stages of 3.0 to 3.5 feet above msl at station
M3, in the Miami Canal where it is joined by the Pennsuco Canal.
When the stage is below this level, the control is opened and water
is released into the Miami Canal to replenish supplies in the down-
stream reaches.
The southern part of the area is drained by the Pennsuco
Canal, which extends westward to the Dade-Broward Levee, and by
the Russian Colony Canal; however, effective drainage by the
Russian Colony Canal extends only about 31/ miles west of its
confluence with the Miami Canal. The westward extension of this
canal is shallow and unimproved and therefore is effective only
during flood periods. Partly effective drainage probably takes place
along the shallow diagonal canal north of the Pennsuco Canal.

HYDROLOGY

WATER LEVELS AND MOVEMENT

Widespread fluctuations of water levels in Dade County are due
to recharge by rainfall, to discharge into drainage canals and Bis-
cayne Bay, and to evapotranspiration. Water levels in this part
of northern Dade County are regulated also by the operation of
the control in the Miami Canal at 36th Street, Miami, and by
operation of controls in the Levee 30 and Levee 33 canals.
Figure 5 is a contour map of water levels in the area on January
21, 1960. The contours are based on water-level measurements
obtained from observation points in canals that cut through the
dense limestones and from observation wells. Water levels in the
area were relatively high at that time and the control at 36th
Street was open. The configuration shows that the drainage effect
extended along the entire uncontrolled reach of the Miami Canal
and its main tributaries and along the short reach of the Levee 30
Canal downstream from the Dade-Broward Levee. The pattern
of the contours indicates the effectiveness of drainage by deep
canals (Miami, Levee 30, and Pennsuco canals, and the lower
reach of the Russian Colony Canal) and the lack of effective drain-
age by the shallow canals. High heads are maintained above the





FLORIDA GEOLOGICAL SURVEY


control in the Levee 33 Canal and the control in the Levee 30
Canal; however, the close spacing of the contours at these controls
indicates that there is considerable seepage through the aquifer
around the controls.
It is important to compare the pattern of the contours east
of the Dade-Broward Levee with that adjacent to Levee 30 be-
tween the Dade-Broward Levee and the Miami Canal. The
distribution of the heads east of the Dade-Broward Levee indicates
that the shallow diagonal canal and the Dade-Broward Levee
borrow canals do not have an appreciable drainage effect. In
contrast, the steep gradient on the northwest side of Levee 30 and
the low gradient on the southeast side indicate that the Levee 30
Canal is intercepting nearly all the underflow along Levee 30.
High water levels prevailed throughout this part of northern
Dade County during 1958-59 and the early part of 1960. On May
8, 1958, the 36th Street control was opened and drainage of the
area proceeded until January 5, 1959, when the control was closed.
The control again was opened on June 23, 1959, and remained opened
throughout the first half of 1960. During the entire period the
eastern part of Conservation Area No. 3 was inundated to depths
ranging from 1 foot to more than 4 feet. The area between Levee
30 and the Dade-Broward Levee also was flooded during the period,
but the depth of the water was less than that in Conservation Area
No. 3. Flooding east of the Dade-Broward Levee probably was
intermittent and corresponded with periods of heavy rainfall.
Figure 6 shows hydrographs of groups of observation stations
in the area for 1959 and the early part of 1960. The locations of
these stations are shown in figures 2 and 4. The hydrographs show
the relation between canal stages and ponded-water stages in the
area adjacent to the Levee 30 and 33 canals and the Miami Canal.
The hydrographs of stations 30TW and 30TE show the variation
in head differential between the pool in Conservation Area No. 3
(30TW) and the stage in the Levee 30 Canal south of the Dade-
Broward Levee. During dry periods, such as March-May 1959,
the head differential across Levee 30 at this point was very small
and a temporary reversal of gradient (east to west) occurred at
the end of April and in early May. During the dry months, the
eastward underflow of water from Conservation Area No. 3 probably
was negligible as compared to that during periods of high water
stages (July 1959-January 1960).
The persistent high head differential represented by the hydro-
graphs of stations 30W and 30E show the effectiveness of the
control in the Levee 30 Canal at the Dade-Broward Levee. This





REPORT OF INVESTIGATIONS NO. 24


S-- ------- !---------- --
10











-7-_ ..I. __________Z!-" 1 1__




30T W(PONDED)~-/ M \ ^-30TEiI





__ -_._ __.. __ I __ "____
09 _T__4



















Figure 6. Hydrographs of groups of observation stations for 1959 and the
early part of 1960.

differential in head suggests continuous leakage by underflow
around the control which tends to maintain, in part, the flow in the
lower reach of the Levee 30 Canal.
An outstanding feature of the hydrographs in figure 6 is the
high head differential between stations M9 (ponded) and M8
(Levee 30 Canal) ; this: differential ranged from 2.2 feet during
a relatively dry period to more. than 4.5 feet during high water
-j


-LJ









Fiue65.rgah fgop fobevto ttosfr15 n h
eal4ato 90

difrnili1ed0ugsscniuu laaeb nefo





FLORIDA GEOLOGICAL SURVEY


stages. Also shown in figure 6 are the heads maintained behind the
control in the Levee 33 Canal (station 33) and the control in the
Miami Canal at the Dade-Broward Levee (station M11). A
comparison of the hydrographs of stations 30E and M8 shows the
low gradient through the downstream reach of the Levee 30 Canal.
A continuous record of water-level fluctuations has been obtained
from station G72 since 1940. A hydrograph of this station and
the annual rainfall at the Miami Airport are shown in figure 7.
The highest water level of record at station G72 was 9.4 feet above
msl in October 1947, and the lowest of record was 1.1 feet above
msl in June 1945. The hydrograph for the long period of record
gives a comparison between water levels before the levee system
and water-control practices were in effect (before 1952), and water
levels after the water-control measures were in operation (1952-
59). It can be seen that water levels during the drought period of
1955-56 did not decline as much as they did during the comparable
drought periods of 1944-45 and 1950-52. Also, it is apparent that
the unusually heavy rainfall of 1957-59 did not produce water levels
as high as those during the wet years 1947-48. These facts demon-
strate that the proper placement and operation of the existing
controls in canals can decrease flood damage during rainy seasons
and can maintain relatively high water levels during droughts.

RELATION BETWEEN PONDED WATER AND GROUND WATER
Three test sites were established adjacent to the Levee 30 Canal
downstream from the Dade-Broward Levee (fig. 4). The purpose

19391940.1941.19421943 1944194519461947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957.19581 I f
T5 MIAMI AIRPORT '


IiN-

10- PRIOR TO WATER CONTROL WATER CONTROL--->
S G72. 1 IN EFFECT

US



0 SEA LEVEL
S19391940 941 19421943 1944 1945 1946 194719481949 19501951 1952195319541955 19561957 1958 1959
Figure 7. Hydrograph of station G72 for the period 1940-59 and the annual
rainfall at the Miami Airport.






REPORT OF INVESTIGATIONS NO. 24


of studies at these sites was to determine the relation between
the impounded water in Conservation Area No. 3 and ground water
in the area. When this relationship is known, the amount of
underflow occurring beneath Levee 30 can be calculated for the
existing water-level conditions, and estimates of underflow can be
made for various assumed water-level conditions.
Each of the test sites consists of a line or lines of. test wells
perpendicular to Levee 30; these sites are shown in the profile
sections in figures 8, 9, and 10. The wells at site A-A' (fig. 8) are
the shallowest, but they penetrate the entire thickness of the dense
limestones and terminate in the upper section of the highly
permeable part of the aquifer. Site B-B' (fig. 9) was drilled by
the Corps of Engineers and consists of a line of nine wells extending
northwestward from Levee 30 and one well on the berm between
Levee 30 and the Levee 30 Canal. These wells range in depth from
17 to 40 feet.
The wells at site C-C' (fig. 10) also were drilled by the Corps
of Engineers and were used as observation wells during a pumping
test to determine the permeability of the aquifer. The site consists
of groups of multiple-depth wells extending northwestward into
Conservation Area No. 3. Figure 10 shows the layout of the lines


00 200 DISTANCE IN FEET A'
A 300 200 100 0 t00

a Pon d level "b l, LEVEE



I4 piezometric surfucac F
LEVEE
2 30
CANAL
1!












piezometric surface at site A-A', January 21 and February 8, 1960.
-4 -ANAL
\a:---
-6 0

-1U ____ -- 1 ------ 1 ------ 1 ------ --- --- ------ 2 ______

2iue8 rfl hwn h eainbtentepne ae n h
pizmti ufaea ieAA, aur 1adFeray8 90





REPORT OF INVESTIGATIONS NO. 24


ordinarily it cannot be measured. Probably there is a very low water
divide along the north-south reach of the canal from which there
is a slight southward gradient toward the Tamiami Canal and
northward gradient toward the Miami Canal.
The southward flow in the Levee 33 Canal is controlled at the
Miami Canal. Operation of this control depends upon the ability
to maintain water stages of 3.0 to 3.5 feet above msl at station
M3, in the Miami Canal where it is joined by the Pennsuco Canal.
When the stage is below this level, the control is opened and water
is released into the Miami Canal to replenish supplies in the down-
stream reaches.
The southern part of the area is drained by the Pennsuco
Canal, which extends westward to the Dade-Broward Levee, and by
the Russian Colony Canal; however, effective drainage by the
Russian Colony Canal extends only about 31/ miles west of its
confluence with the Miami Canal. The westward extension of this
canal is shallow and unimproved and therefore is effective only
during flood periods. Partly effective drainage probably takes place
along the shallow diagonal canal north of the Pennsuco Canal.

HYDROLOGY

WATER LEVELS AND MOVEMENT

Widespread fluctuations of water levels in Dade County are due
to recharge by rainfall, to discharge into drainage canals and Bis-
cayne Bay, and to evapotranspiration. Water levels in this part
of northern Dade County are regulated also by the operation of
the control in the Miami Canal at 36th Street, Miami, and by
operation of controls in the Levee 30 and Levee 33 canals.
Figure 5 is a contour map of water levels in the area on January
21, 1960. The contours are based on water-level measurements
obtained from observation points in canals that cut through the
dense limestones and from observation wells. Water levels in the
area were relatively high at that time and the control at 36th
Street was open. The configuration shows that the drainage effect
extended along the entire uncontrolled reach of the Miami Canal
and its main tributaries and along the short reach of the Levee 30
Canal downstream from the Dade-Broward Levee. The pattern
of the contours indicates the effectiveness of drainage by deep
canals (Miami, Levee 30, and Pennsuco canals, and the lower
reach of the Russian Colony Canal) and the lack of effective drain-
age by the shallow canals. High heads are maintained above the




14 FLORIDA GEOLOGICAL SURVEY

DISTANCE IN FEET t 13
200 300 -







e .I 8, CANAL



IH 'I 1
4 30
> 1 b I








Figure 9. Profile showing the relation between the ponded water and the
piezometric surface at site B-B', January 21 and February 8, 1960.

of wells with reference to Levee 30 and the Levee 30 Canal and
indicates the altitude of the bottom of each well.
Water-level measurements were made at A-A' and B-B' on
January 21 and February 8, 1960. Figures 8 and 9 show the water-
level profiles at the two sites on the dates the measurements were
made. At site A-A' (fig. 8) the gradient of the piezometric surface
on the northwest side of the levee toward the Levee 30 Canal
was 1.1 feet in 270 feet, or 0.0041 foot per foot. Within the 270-
foot distance the head differential between the ponded water and
the piezometric surface increased toward the levee and ranged
from 3.1 feet at the end well of the profile to 3.6 feet at the levee.
The gradient of the piezometric surface along the profile in figure 9
was 3.17 feet in 650 feet, or 0.049 foot per foot. The head
differential between the ponded level and the piezometric surface
ranged from 1.2 feet at the end well of the profile to 3.5 feet at
the levee. The average gradient of the piezometric surface during
the 3-week test period was 0.0045 foot per foot toward the Levee
30 Canal. The aquifer was being replenished by the downward
leakage of ponded water, at a rate dependent upon the head
differential, and no depletion of aquifer storage was occurring
northwest of Levee 30.
Water-level measurements made during the drilling at site A-A'









1)ISTANCE C E IN FEET


+10


Uj
-j


LU

JI-
10
'UJ

LU

U.
LU


wU-30




140


EXPLANATION
BOTTOM OF CASED WELL
WTER4 LEVEL ..
LINE OF EQUAL POTENTIAL


/ Ii I 1 s 1
04

(S.9 .5..9 S. / 54aj
.4'


Figure 10. Profile along site C-C' showing lines of equal potential, April 1b,
1960.


63
PQ&0 C.- ..5.93 S. 5,f ,J L 30
PE.ZOMETRI uRFAg
'-LAND SURFACE-'





,,.si ,~t > ~ a5 s.s o s y. s-- v-

. yl ,6, $4sss

7 t .6.34 ,S.55 S.t S1 a S'


), ', ',












I-
02

z
0)*


O


I





FLORIDA GEOLOGICAL SURVEY


showed that there was no head difference between the ponded
level and the water level of wells bottomed in the Miami oolite.
This indicates that the confining characteristics of the marl and
muck blanket are of much less significance than those of the dense
limestones.
No appreciable ponding occurred in the area immediately south-
east of the Levee 30 Canal. Figure 8 shows also that the north-
westward gradient of the piezometric surface on the southeast side
toward the Levee 30 Canal was 0.40 foot in 250 feet, or 0.0016
foot per foot. Therefore, the quantity of inflow from the southeast
was equivalent to approximately 40 percent of the inflow occurring
from the northwest at the A-A' site during the period January 21-
February 8, 1960. The profile in figure 8 indicates a slight de-
pletion of ground-water storage immediately southeast of the Levee
30 Canal. It is important to recognize that the contribution of
water from the area southeast of the Levee 30 Canal to the canal
was diminishing as shown on the contour map (fig. 5) by the
decrease in ground-water gradient along the lower reach of the
canal. It is estimated that the average gradient of the piezometric
surface on the southeast side along the uncontrolled reach of the
canal was 0.0010 foot per foot. Therefore, the total inflow to the
Levee 30 Canal from the southeast was equivalent to approximately
20 to 25 percent of the total from the northwest.
UNDERFLOW ALONG LEVEE 30
During periods when the control in the Levee 30 Canal is closed,
discharge along the downstream reach of the Levee 30 Canal
represents a composite of the following: (1) leakage by underflow
around the control, (2) ground-water inflow from the thick
permeable section of the aquifer, and (3) seepage of ponded water
through the levee fill and through the thin layer of permeable
Miami oolite that occurs between the fill and the dense limestone
layers. At high water stages, such as those which prevailed from
July through November 1959, the water level of the downstream
reach of the canal was above the canal bank and sheet flow
occurred toward the Miami Canal. Most of the discharge of the
Levee 30 Canal was maintained by ground-water inflow from the
northwest.
By January 21, 1960, water stages had lowered and discharge
measurements were made at points 1 mile apart in the Levee 30
Canal (Q, and Q2 in fig. 4), downstream from the control. Following
is a tabulation of the discharge and water-level data obtained
during the January 21 test:





REPORT OF INVESTIGATIONS No. 24


A. Discharge measurements in Levee 30 Canal
At Q1 .-. ---- _--- _---_-- 76 cfs (49 mgd)
At Q2 -..--------- -------------------- 252 cfs (163 mgd)
Q2 ---------------------------------- 176 cfs (114 mgd)
Estimated seepage (visible) through the levee
fill, across the berm to the canal (Q) -- 10 cfs (7 mgd)
Net pickup by ground-water inflow (Qg)
Qg=Q2-Q-Qs ------------------------------ 166 cfs (107 mgd)

B. Gradients (I) of piezometric surface toward
Levee 30 Canal (fig. 8, 9).
Northwest of canal
A-A' site ---------------------0.0041 foot per foot
B-B' site .0049 foot per foot
Southeast of canal
A-A' site .-------------------- 0016 foot per foot
Estimated average for area
southeast of canal .0010 foot per foot

By Darcy's law the rate of flow of a fluid through a porous
medium is directly proportional to the hydraulic gradient and can
be written as follows (Wenzel, 1942, p. 3-7):

Q=PIA

where Q is the discharge rate, P is the coefficient of permeability of
the material being tested, I is the hydraulic gradient, and A is the
area of the cross section through which the fluid moves. If it is
assumed that the permeable section of the aquifer beneath the
dense limestone layers is isotropic and that underflow through this
section is laminar, then the quantity of ground water discharging
into the Levee 30 Canal is directly proportional to the gradient of
the piezometric surface; therefore, about 80 percent of Qg or 86
mgd, represents underflow from the northwest along the 1-mile
reach of the canal. (See tabulation above.)
In order to make computations that involve the entire thickness
of an aquifer as a unit, Darcy's law may be written:

Q=-TIL

in which Q is the quantity of water, in gpd (gallons per day), T
is the coefficient of transmissibility, in gallons per day, for each
vertical strip of the aquifer 1 foot wide; I is the hydraulic gradient,





FLORIDA GEOLOGICAL SURVEY


in feet per foot; and L is the length of section, in feet, through
which the quantity (Q) flows. By substituting in the above
equation the hydrologic data obtained during the January 21 test,
a determination of the coefficient of transmissibility of the aquifer
can be made as follows:

Q=TIL
Q (gpd)
T (gpd per foot)= (gpd)
I (foot per foot) x L (feet)

T 86,000,000
0.0045 x 5,280

T = 3,600,000 gpd per foot, or 5.6 square feet
per second
This computed coefficient of transmissibility compares very closely
with the value of 5.76 square feet per second determined by the
Corps of Engineers for the highly permeable part of the aquifer
adjacent to Levee 30 (U.S. Army Corps of Engineers, 1953, p. D-6).
Dry weather prevailed during the spring of 1960, and by the
middle of April the water stage in Conservation Area No. 3 had
declined so that the multiple-depth wells along site C-C' were
accessible. On April 19, 1960, water-level measurements were made
in all wells in this test site. The profile in figure 10 shows the
relation between the pool in Conservation Area No. 3 and the
piezometric surface on that day and shows also, by equipotential
lines, the approximate head distribution in the aquifer along the
profile. The gradient of the piezometric surface within 1,000 feet
of the Levee 30 Canal was 0.0017 foot per foot, but for the
remaining 800 feet of the section the gradient decreased to 0.0011
foot per foot. The head differential between the ponded water and
the piezometric surface ranged from 0.32 foot at the northwestern
end of the profile to 1.57 feet near the toe of the levee.
The equipotential lines, shown in figure 10, indicate that flow
through the highly permeable part of the aquifer (depths more
than 5.0 feet below msl) toward the Levee 30 Canal is virtually
horizontal, except for the section adjacent to and beneath the canal
where the flow direction has an upward component. The distribution
and pattern of the lines suggest that about 75 percent of the loss
in head occurs within 1,000 feet of the levee. The horizontality and
the close spacing of the lines at depths between 0.5 foot above and
3.0 feet below msl indicate a large vertical head loss caused by






REPORT OF INVESTIGATIONS NO. 24


vertical flow through the dense limestone of low permeability at
that interval (fig. 3). The flow through the shallow materials
immediately beneath the levee is virtually horizontal and probably
occurs chiefly through a thin layer of the permeable Miami oolite
beneath the fill.
Detailed information on head distribution through a part of
the aquifer, as shown in figure 10, makes it possible to estimate
the amount of surface water that was seeping downward through
the confining layers to the thick permeable part of the aquifer.
The amount of ground water moving toward the canal in 1 day,
across a section of the aquifer 1 mile long at a distance of 800 feet
from the edge of the canal, may be computed as follows:

Q=-TIL

0.4 foot x 5,280 feet
Q=3,600,000 x400 feet
400 feet
Q=19 mgd per mile, or 29 cfs per mile
A similar computation for a distance 400 feet from the canal is as
follows:
0.59 foot x 5,280 feet
Q=3,600,000 x 0 ee
400 feet
Q=28 mgd per mile, or 43 cfs per mile.

The 9-mgd difference in flow represents approximately the amount
of surface water picked up by leakage through the confining beds
to the permeable flow section within the rectangular area 1 mile
long between 400 and 800 feet from the levee.
Inasmuch as the approximate amount of downward infiltration
in a given area has been determined, a computation of the coefficient
of vertical permeability of the confining layers can be made. The
coefficient of permeability is defined as the rate, of flow 'through
a cross section of 1 square foot, under a gradient of 1 foot per foot.
The computation of the coefficient of vertical permeability of the
dense limestone is as follows:
Rectangular area used in computation __-5,280 feet x 400 feet,
or 2.1 million square
feet
Downward leakage ----9 nigd, or 4.3 gpd per
square foot





FLORIDA GEOLOGICAL SURVEY


Altitude of piezometric surface 600
feet from levee 5.93 feet above msl
Altitude of ponded level ____6.91 feet above msl
Head differential 600 feet from levee
(assumed average for area 400 to
800 feet from levee) 0.98 foot
Thickness of confining layers __ 3.0 feet
Gradient across confining layers ----. 0.33 foot per foot

Q
P=
IA
4.3 gpd
0.33 foot per foot x 1 square foot

P= 13 gpd square foot, or 2.0 x 10-5 foot per second

A proposed method of flood control in Area B is to reduce
ground-water storage by means of a network of canals and a
series of large pumping stations. The pumps would be placed at
selected locations along Levees 30 and 31 and would pump water
from the interconnected canal system of Area B westward into
Conservation Area No. 3. Initially, it was proposed that the water
stage in Area B be maintained at mean sea level in order to give
maximum protection during all major storms. It is probable that
water levels along the levee side of Area B will be lowered tempo-
rarily below mean sea level in order to provide adequate gradients
toward the pumping stations.
Reducing the water stage in Area B would result in gradients
across Levee 30 that would greatly exceed those shown in the
profiles of figure 9. There might be times when the head differential
between the pool in Conservation Area No. 3 and the stage in the
Levee 30 Canal would be as much as 10 feet. It is extremely im-
portant, therefore, to determine the amount of water that would
move from Conservation Area No. 3 to the adjacent canals in order
that adequate pumping stations be provided.
To make a determination of the anticipated underseepage it is
necessary to determine the relation between the head across the
levee and the head differential at the toe of the levee at different
water stages. Figure 11 is a graph showing this relationship; and
the plotted points are based on the water-level profiles of figures






REPORT OF INVESTIGATIONS NO. 24


HEAD DIFFERENCE,IN FEET, BETWEEN POOL AND LEVEE 30 CANAL
I 2 3 4 5 6 7 8 10
IIO

0 7---- --- --- --- --- --- --- --- --- ---
N /



UJ wJ
0 /
z 6 ---- --- --- ----- --- ---- ----- ---
L e e 0/
IUJ
o>




9 and0an n JAN.21,1960 e Dem159
oUJ /


F.U.T idcet /0
Uw /









LL-





Figure 11. Graph showing the relation between the head difference across
Levee 30 and the head difference between the pool and the piezometric surface
at the toe of the levee.

9 and 10 and on a series of measurements made on December 17,
1959. The projection of the graph indicates that, if a 10-foot head
were held across the levee, the head difference between the pool and
the piezometric surface at the toe of the levee would be 7.8 feet;
thus the gradient of the piezometric surface across the 150-foot
width of the levee would be 2.2 feet.
Following is a computation of the amount of underflow that
would be intercepted along a 1-mile reach of the canal (Q1 to Q2 in
fig. 4) when the head differential across the levee was 10 feet:

Q=TIL
Q=-3,600,000 gpd per foot x 2.2 feet x 5,280 feet

150 feet
Q--279 mgd per mile, or 432 cfs per mile

In order to determine the total quantity of water that Would be
intercepted, by the Levee 30. :Canal along the 1-mile reach,





FLORIDA GEOLOGICAL SURVEY


consideration must be given to the seepage that would occur
through the levee materials and through the thin permeable layer
of Miami oolite that underlies the levee fill. This approximate
determination is shown by the following tabulation:

Composite estimate of coefficient of
permeability of levee fill and
Miami oolite 20,000 gpd per square foot
Length of flow section 5,280 feet
Thickness of flow section
(10-foot head differential) 10 feet
Q=PIA

10 feet
Q=20,000 gpd per square foot x 150 feet x 5,280 feet x 10 feet
150 feet
Q=70 mgd per mile, or 108 cfs per mile

The estimated coefficient of permeability used in the above
computation probably is high and compares with a well sorted
gravel that contains only small quantities of fine material (Wenzel,
1942, p. 13). However, the estimate was made in consideration of
the probable high permeability of the layer of Miami oolite through
which much of the direct seepage may occur.
The total quantity of water that would be intercepted along the
1-mile reach of Levee 30 Canal when the head difference across
the levee was 10 feet is computed to be 349 mgd, or 540 cfs. These
results were obtained by assuming that water movement beneath
Levee 30 occurs by laminar flow. If there is turbulence through
the large openings in the aquifer beneath the levee, the underflow
would be less. For laminar flow the underflow to the canal would
be directly proportional to the head difference across the levee, and
for turbulent flow the underflow would be directly proportional to
the square root of the head difference; in the transitional zone
underflow would vary exponentially between the first and one-half
powers of the head difference.

CONCLUSIONS

Water-level measurements and geologic data obtained from test
wells indicate that the upper part of the Biscayne aquifer in the
vicinity of Levee 30 in northern Dade County contains dense layers
of limestone of relatively low permeability that retard downward






REPORT OF INVESTIGATIONS No. 24


infiltration to the thick permeable parts of the aquifer. The
coefficient of transmissibility of 3,600,000 gpd per foot, or 5.6 square
feet per second, as determined from water-level profiles taken
normal to Levee 30 and from discharge measurements made in
the Levee 30 Canal, compares closely with the coefficient determined
by the Corps of Engineers by pumping-test methods. The computed
coefficient of permeability of 13 gpd per square foot, or 2.0 x 10-5
foot per second, for the thin dense layers indicates that these layers
form a fairly effective confining unit which separates the ponded
water in Conservation Area No. 3 from the ground water. Geologic
information obtained from the surrounding areas suggests that
the thin, dense limestones probably are widespread, and therefore
that the blanketing effect occurs throughout a large area.
Conservation Area No. 3 generally is flooded for several months
-'of each year, the result being high head differentials across Levee
30. When the plan for the development of Area B is in effect,
there may be times when the differential of head across the levee
will be as much as 10 feet. When this condition occurs, it is
estimated that the inflow to the Levee 30 Canal from Conservation
Area No. 3 will be about 350 mgd per mile, or 540 cfs per mile.
This estimate was made by computing separately (1) the underflow
through the main permeable section at the aquifer and (2) the
seepage through the levee fill and the thin layer of permeable
limestone that immediately underlies the levee fill.
When the road construction is completed in the area it would be
desirable to obtain additional data to define more accurately the
relation between head difference across the levee and discharge in
the Levee 30 Canal.
The coefficient of transmissibility of the aquifer, the coefficient
of vertical permeability of the confining layers, and the estimated
rates of inflow from Conservation Area No. 3, as determined from
this study, may be valid only for the north end of Levee 30. It is
probable that hydrologic conditions vary along the entire length
of Levee 30, and therefore similar studies will be required for the
southern reaches in order to' determine total leakage along the
levee system.

REFERENCES
Ferguson, G. E. (see Parker, G. G.)
Love, S. K. (see Parker, G. G.)
Parker, G. G.
1951 Geologic and hydrologic factors in the perennial yield of the
Biscayne aquifer: Am. Water Works Assoc. Jour., v. 43, p. 817-
834.





FLORIDA GEOLOGICAL SURVEY


consideration must be given to the seepage that would occur
through the levee materials and through the thin permeable layer
of Miami oolite that underlies the levee fill. This approximate
determination is shown by the following tabulation:

Composite estimate of coefficient of
permeability of levee fill and
Miami oolite 20,000 gpd per square foot
Length of flow section 5,280 feet
Thickness of flow section
(10-foot head differential) 10 feet
Q=PIA

10 feet
Q=20,000 gpd per square foot x 150 feet x 5,280 feet x 10 feet
150 feet
Q=70 mgd per mile, or 108 cfs per mile

The estimated coefficient of permeability used in the above
computation probably is high and compares with a well sorted
gravel that contains only small quantities of fine material (Wenzel,
1942, p. 13). However, the estimate was made in consideration of
the probable high permeability of the layer of Miami oolite through
which much of the direct seepage may occur.
The total quantity of water that would be intercepted along the
1-mile reach of Levee 30 Canal when the head difference across
the levee was 10 feet is computed to be 349 mgd, or 540 cfs. These
results were obtained by assuming that water movement beneath
Levee 30 occurs by laminar flow. If there is turbulence through
the large openings in the aquifer beneath the levee, the underflow
would be less. For laminar flow the underflow to the canal would
be directly proportional to the head difference across the levee, and
for turbulent flow the underflow would be directly proportional to
the square root of the head difference; in the transitional zone
underflow would vary exponentially between the first and one-half
powers of the head difference.

CONCLUSIONS

Water-level measurements and geologic data obtained from test
wells indicate that the upper part of the Biscayne aquifer in the
vicinity of Levee 30 in northern Dade County contains dense layers
of limestone of relatively low permeability that retard downward






REPORT OF INVESTIGATIONS No. 24


infiltration to the thick permeable parts of the aquifer. The
coefficient of transmissibility of 3,600,000 gpd per foot, or 5.6 square
feet per second, as determined from water-level profiles taken
normal to Levee 30 and from discharge measurements made in
the Levee 30 Canal, compares closely with the coefficient determined
by the Corps of Engineers by pumping-test methods. The computed
coefficient of permeability of 13 gpd per square foot, or 2.0 x 10-5
foot per second, for the thin dense layers indicates that these layers
form a fairly effective confining unit which separates the ponded
water in Conservation Area No. 3 from the ground water. Geologic
information obtained from the surrounding areas suggests that
the thin, dense limestones probably are widespread, and therefore
that the blanketing effect occurs throughout a large area.
Conservation Area No. 3 generally is flooded for several months
-'of each year, the result being high head differentials across Levee
30. When the plan for the development of Area B is in effect,
there may be times when the differential of head across the levee
will be as much as 10 feet. When this condition occurs, it is
estimated that the inflow to the Levee 30 Canal from Conservation
Area No. 3 will be about 350 mgd per mile, or 540 cfs per mile.
This estimate was made by computing separately (1) the underflow
through the main permeable section at the aquifer and (2) the
seepage through the levee fill and the thin layer of permeable
limestone that immediately underlies the levee fill.
When the road construction is completed in the area it would be
desirable to obtain additional data to define more accurately the
relation between head difference across the levee and discharge in
the Levee 30 Canal.
The coefficient of transmissibility of the aquifer, the coefficient
of vertical permeability of the confining layers, and the estimated
rates of inflow from Conservation Area No. 3, as determined from
this study, may be valid only for the north end of Levee 30. It is
probable that hydrologic conditions vary along the entire length
of Levee 30, and therefore similar studies will be required for the
southern reaches in order to' determine total leakage along the
levee system.

REFERENCES
Ferguson, G. E. (see Parker, G. G.)
Love, S. K. (see Parker, G. G.)
Parker, G. G.
1951 Geologic and hydrologic factors in the perennial yield of the
Biscayne aquifer: Am. Water Works Assoc. Jour., v. 43, p. 817-
834.





FLORIDA GEOLOGICAL SURVEY


1955 (and Ferguson, G. E., Love, S. K., and others) Water resources
of southeastern Florida, with special reference to the -geology
and ground water of the Miami area: U. S. Geol. Survey Water-
Supply Paper 1255, 965 p.
Schroeder, M. C.
1958 (and others) Biscayne aquifer of Dade and Broward counties,
Florida: Florida Geol. Survey Rept. Inv. 17, 56 p.
Stallman, R. W.
1956 Preliminary findings on ground-water conditions relative to Area
B flood-control plans, Miami, Florida: U. S. Geol. Survey Open-
File Rept., Tallahassee, Florida, 42 p.
U-S. Army Corps of Engineers
1952 Test levee investigations: Partial Definite Project Report, Central
and Southern Florida Project, pt. 1, supp. 5, mimeograph
Rept., March 28.
1953 Agricultural and conservation areas, design memorandum, per-
meability investigations by well-pumping tests: Partial Definite
Project Report, Central and Southern Florida Project, pt. 1,
supp. 7, Mimeograph Rept., February 16.
1954 Design memorandum, Hydrology and hydraulic design canals in
Greater Miami area (C-2 through C-9) (revised) ; Partial Definite
Project Report, Central and Southern Florida Project, pt. 5, supp.
12, mimeograph Rept., March 23.
Wenzel, L. K.
1942 Methods for determining permeability of water-bearing materials,
with special reference to discharging-well methods, with a section
on direct laboratory methods and bibliography on permeability
and laminar flow, by V. C. Fishel: U. S. Geol. Survey Water-
Supply Paper 887, 192 p.










FLRD GEOLIOWC( ICA SURflViEWY~


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