Moultrie Creek -- Moses Creek watershed basin management project

[From the U.S. Government Printing Office, www.gpo.gov]

MOULTRIE CREEK - MOSES CREEK WATERSHED

BASIN MANAGEMENT PROJECT

Prepared By

St. Johns County Engineering Department
4020 Lewis Speedway Drive
St. Augustine, Florida 32085

Supported Through

Florida Department of Environmental Regulation
(DER Contract No. CM-217)

(Funds for this project were provided by the Department of
Environmental Regulation, Office of Coastal Management using
funds made available through the National oceanic and Atmo-
sphere Administration under the Coastal Zone Management Act
of 1972, as amended.)

With the Technical Assistance from

U. S. Army Corps of Engineers
Jacksonville District
Through
U. S- Army Corps of Engineers
State Planning Assistance (Section 22) Program

January 1990

GB
990,
S76
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1990

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CONTENTS

PAGE
LIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . . v

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . v!

LIST OF ABBREVIATIONS . . . . . . . . . . . . . . . . vii

FOREWORD . . . . . . . . . . . . . . . . . . . . . . . viii

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . xii

CHAPTER
1 AREA ORIENTATION . . . . . . . . . . . . . . . 1
STUDY AREA . . . . . . . . . . . . . . . . . . 1
WATERSHED LOCATIONAL SIGNIFICANCE . . . . . . . 1 - 7

2 CLIMATE AND RAINFALL . . . . . . . . . . . . . 2 - 1
INTRODUCTION . . . . . . . . . . . . . . . . . 2 - 1
CLIMATIC FACTORS . . . . . . . . . . . . . . . 2 - 3
PRECIPITATION . . . . . . . . . . . . . . . . . 2 - 8

3 GEOLOGY AND LANDFORMS . . . . . . . . . . . . . 3 - 1
GEOLOGY . . * * * * * , , * * * * * * * * * * , 3 - 1
LIMESTONE FORMATIONS . . . . . . . . . . . . . 3 - 3
LANDFORMS . . . . . . . . . . . . . . . . . . . 3 - 9

4 SOILS AND WATER TABLE CONDITIONS . . . . . . . 4 - 1
SOILS . . . . . . . . . . . . . . . . . . . . . 4 - I
RAINFALL CONTRIBUTIONS TO GROUND WATER . . . . 4 - 13

5 STORM WATER STORAGE . . . . . . . . . . . . . . 5 - 1
WATER CONTAINMENT . . . . . . . . . . . . . . . 5 - I

6 WATER LOSSES . . . . . . . . . . . . . . . . . 6 - 1
EVAPOTRANSPIRATION . . . . . . . . . . . . . . 6 - 1
RUNOFF . * * , * * * , * * , * * * * * * * * * 6 - 5
WATER LOSS IMPACTS . . . . . . . . . . . . . . 6 - 12

7 FLOOD PRONE AREAS . . . . . . . . . . . . . . . 7 - 1
NATIONAL FLOOD INSURANCE PROGRAM DATA . . . . . 7 - 1
EVALUATION CRITERIA . . . . . . . . . . . . . . 7 - 3

8 ATLANTIC COASTAL RIDGE . . . . . . . . . . . . 8 - 1
WATER RESOURCE STUDY CRITERIA . . . . . . . . . 8 - 1

9 SIGNIFICANT NATURAL RESOURCE AREA
MANAGEMENT . . . . . . . . . . . . . . . . . . 9 - 1

iii

GENERAL . . . . . . . . . . . . . . . . . . . . 9 - 1
SIGNIFICANT NATURAL RESOURCE AREAS . . . . . . 9 - 1
WETLANDS REGULATION PROBLEMS . * * ' * ' * * * 9 - 14
A FUNCTIONAL BASIS FOR NATURAL RESOURCE AREA
MANAGEMENT . . . . . . . . . . . . . . . . . . 9 - 15
CREATING NATURAL RESOURCE AREAS . . . . . . . 9 - 16
MANAGEMENT CONCEPTS . . . . . . . . . . . . . . 9 - 21

10 WATER MANAGEMENT PROGRAM . . . . . . . . . . . 10 - 1
BASIC PROBLEMS . . . . . . . . . . . . . . . . 10 - 1
ST. JOHNS COUNTY WATER MANAGEMENT
PURPOSES . . . . . . . . . . . . . . . . . . . 10 - 2
COUNTY ENGINEERING DEPARTMENT FUNCTIONS . . . . 10 - 7
ST. JOHNS COUNTY DEVELOPMENT PERMIT
APPLICATION PROCEDURES 10 - 16
ENGINEERING DEPARTMENT FI'EL*D*IN*SP*EC*TI*ON*S* 10 - 22
ENGINEERING DEPARTMENT ORGANIZATION . . . . . . 10 - 24
PROJECTED ENGINEERING DEPARTMENT PROGRAM . . . 10 - 24

11 WATER MANAGEMENT FINDINGS . . . . . . . . . . . 11 - 1
INTRODUCTION . . . . . . . . . . . . . . . . . 11 - 1
EXAMPLE ORDINANCES . . . . . . . . . . . . . . 11 - 2
GENERAL FINDINGS . . . . . . . . . . . . . . . 11 - 4
OBJECTIVES . . . . . . . . . . . . . . . . . . 11 - 6
DEFINITIONS . . . . . . . . . . . . . . . . . . 11 - 8
WATER MANAGEMENT PLAN APPLICATION . . . . . . . 11 - 8
WATER MANAGEMENT PLAN CONTENTS . . . 11 - 10
CATEGORIES OF WATER MANAGEMENT PLANS 11 - 12
DESIGN STANDARDS FOR WATER MANAGEMENT
PLANS . . . . . . . . . . . . . . . . . . . . . 11 - 13
FEES . . ' * * * * * * * ' *11 - 17
ENFORCEME T AND' @IO'LA*TIiON*S* . . . . . 11 - 18
N
LOCAL GOVERNMENTS PROVIDING ORDINANCES FO*R
THIS STUDY . . . . . . . . . . . . . . . . . . 11 - 20
GLOSSARY . . . . . . . . . . . . . . . . . . .. . . . . G - 1

APPENDIX - PHASE 2 STUDY PROCESS . . . . . . . . . . . A - 1
PROJECT PURPOSE . . . . . . . . . . . . . . . . A - 1
INSTITUTIONAL CONSTRAINTS . . . . . . . . . . . A - 2
SOCIAL CONCERNS . . . . . . . . . . . . . . . . A - 2
THE STUDY PROCESS . . . . . . . . . . . . . . . A - 3
ST. JOHNS COUNTY DEVELOPMENT MANAGEMENT
ACTIONS A - 3
PHASE 1 S@u'DY*P*RO*CE*SS*O*BJ*EC'TI*VE'S A - 4
PHASE 2 STUDY PROCESS OBJECTIVES . . . . . . . . A - 5
PHASE 2 TASK SUMMARIES . . . . . . . . . . . . . A - 5

BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . B - 1

FOREWORD

In October 1987 the Florida Department of Environmental Reg-
ulation (DER) provided a grant to St. Johns County to un-
dertake this study of the Lower Matanzas River-Moultrie
Creek-Moses Creek Watersheds out of concern for the water
quality degradation previously observed in the Matanzas
River (DER contract No. CM-207). A previous report pro-
duced under the Florida Coastal Management Program (1979)
had identified septic tank effluent discharges and non-point
source pollution (including storm drainage) as major threats
to shellfish growing areas in the Matanzas River. The first
phase of the study was completed in May 1989. The Phase 1
activities consisted of data collection, development of
evaluation methods and techniques, initial Geographic Infor-
mation system development, and presentation of general condi-
tions found within the Moultrie Creek-Moses Creek watersheds.

The St. Johns County Commission responded to the estuarine
water quality problem identified in the original DER 1979
study through the adoption of a County-wide drainage ordi-
nance in 1986. In spite of these actions, the shellfish
growing areas and the general quality of estuarine waters
within the St. Augustine area continue to be threatened.

In Augu st 1988 St. Johns County requested, through DER, U. S.
Army Corps of Engineers (Corps) technical assistance in evalu-
ating water resource conditions related to the St. Johns
County stormwater management concerns already under study
through the DER grant. The Corps can participate in water
related planning investigations under the authority of Sec-
tion 22, Water Resources Development Act of 1974 (Public Law
93-251). This law provides authority for cooperating with any
state in the preparation of comprehensive plans for water
resources development, utilization, and conservation. The
Corps of Engineers produced partial report materials for
local review in September and October 1989. A draft docu-
ment completing the Corps of Engineers participation in this
study was submitted for finalization by the St. Johns County
Engineering Department in November 1989.

This Phase 2 report in response to DER contract CM-217 pro-
vides an overview of the water resource management problems
in St. Johns County using the Moultrie Creek and Moses

viii

Creek watershed as an example area. The report responds to
the DER grant purpose of developing a basis for County-wide
improvements in stormwater management, flood protection,
and protection of natural resources. The report incorpo-
rates the findings of the Phase 1 efforts of the study acti-
vities and subsequent information development undertaken
through this second phase of the study. The report also pro-
vides information for use by St. Johns County in the de-
velopment of a comprehensive plan in response to State of
Florida growth management requirements.

Finally, the primary focus of this report must be oriented
towards the satisfaction of the DER contract requirements.
The content of the Study Process for DER contract CM-217 ap-
pears in the Appendix. Emphasis has been given in the or-
ganization and content of this report to address contract
required topics.

A component of this study, of interest to the Florida Depart-
ment of Environmental Regulation, is the St. Johns County En-
gineering Department's progress in developing a geographical
information system. This system has great potential for use
as a basis for evaluating existing stormwater related problems
and potential impacts resulting from proposed new develop-
ments. The study identifies some of the technical constraints
accompanying the establishment of such a program.

In support of the report findings and recommendations, the
County has initiated a computerized Geographic Information
system (GIS) to most efficiently manage local government oper-
ations, including evaluation of proposed developments and im-
provements to existing facilities. The GIS is being designed
as a product of this basin management program to address sev-
eral of the tasks within the contractual scope of work. The
GIS has many practical applications including near instanta-
neous updating of graphical information layers illustrating
land use and cover, approved development layouts, soil types,
topography, ownership boundaries, easements for drainage, sep-
tic facility location, wetland boundaries, significant ar-
cheological features, zoning, access, utility location, and
other characteristics. All of these layers can be used singu-
larly or in combination to evaluate new development proposals
and rezonings, modify major utility lines, upgrade existing
facilities, identify significant natural and cultural resource
areas, and evaluate new transportation corridors. The GIS has
tremendous potential for local and regional applications. The
GIS is a highlight of this study because it serves as the
mechanism to incorporate the objectives of the study within
daily local government operations.

In an effort to enhance the capabilities of the GIS system,
the County requested, and was granted permission by DER to ac-
quire a Computer Aided Drafting and Design work station to de-
velop the priority components of the initial stormwater man-
agement plan. The CAD system will be used to input new de-
velopment plans such as Plats, rezonings, DRI's, stormwater
management system plans, utility location and other in-
formation directly into the GIS system as well as assist the
County in inputting existing basin information to be consid-
ered in the review of new development proposals into the GIS.

The report is also intended as a document through which the
Florida Department of Environmental Regulation can provide
guidance to other local governments on problems to be antici-
pated in establishing technologically advanced stormwater man-
agement procedures. The development of local government pro-
cedures for approaching stormwater management from a regional
or watershed perspective is still evolving. The study brings
together information on aspects of stormwater related problems
in the Moultrie Creek and Moses Creek watershed and identi-
fies management procedures for addressing these problems.

To identify parallel management methods used by other
local governments, this study included the review of applica-
ble stormwater management related ordinances used by a vari-
ety of other local governments in Florida. Guidance from some
of these ordinances has been incorporated in this study. In
general, large metropolitan governments in Florida have, in
varying degrees, recognized and addressed watershed management
needs. Acceptable mechanisms by which smaller governmental
bodies can resolve the regional aspects of stormwater man-
agement still remain to be developed.

The study also provides information on changes of manage-
ment processes within St. Johns County that may improve the
effectiveness of local water management procedures. Local
procedures for undertaking management changes is an in-
ternal County matter constrained by existing practices,
public perception of need, available technical capabili-
ties, and the County's financial resources or budget limita-
tions. In practice, changes in local governmental operations
generally evolve slowly. Each small change in procedure may
result in unforeseen problems, and each problem must be re-
solved in a manner acceptable to all affected activities or
departments.

Finally, each local government is a management entity dif-
ferent from any other government. The St. Johns County
governmental structure is unique, and the manner in which
changes can be accomplished in St. Johns County will be
different than procedures adopted by any other government in

Florida. A significant management problem resolution process
within the St. Johns County government extending over a pe-
riod of time should be expected.

EXECUTIVE SUNMARY

This report focuses upon the stormwater management needs of
St. Johns County using the Moultrie Creek and Moses Creek
watersheds as an example area. Stormwater management, as
used in this report, encompasses a range of interrelated water
resource management problems of concern to local governments.
Effective stormwater management within St. Johns County re-
quires coordinated efforts between St. Johns County and mu-
nicipal governments, between St. Johns County and the St.
Johns River Water Management District, and among the several
agencies within the County and municipal governments with spe-
cial responsibilities for specific governmental functions
identified in this report. While the St. Johns County Engi-
neering Department is primarily responsible for enforcing
the St. Johns County Paving and Drainage Ordinance 86-4, ef-
fective stormwater management requires an understanding of
potential impacts of enforcement measures upon the complex
factors that reflect upon the adequacy and quality of the
County's water resources.

Stormwater management in the Florida environment must con-
sider much more than the need to remove excess surface
water from developed areas. The Florida Department of Envi-
ronmental Regulation initiated this study as a means of as-
sisting the County to establish practices that would protect
the water quality of local area estuaries. While water qual-
ity concerns are important, this study also illustrates hy-
drology principles that must be applied to stormwater man-
agement and general water practices in order to preserve St.
Johns County's ground water supplies and significant natural
resource areas.

The State of Florida has determined that wetlands are impor-
tant natural resources that must be protected by local
and state governmental actions. This study identifies sig-
nificant natural resource areas within the Moultrie Creek and
Moses Creek watersheds and establishes some simplified cri-
teria for determining, delineating, and protecting these
areas. However, the study focuses primarily upon the engi-
neering practices that can be used to permit development and
still protect significant natural resource areas along stream
courses and within uplands of watersheds.

xii

As noted above, an important component of this report is the
presentation of the relationship between stormwater man-
agement practices and the need to protect the ground water re-
sources used by all residents living within the County. The
inherent problems associated with the long-term practice of
uncontrolled positive drainage consisting of the ditching,
draining, and dropping of the local area ground water tables
has been given emphasis.

This report has been organized to provide nontechnical read-
ers with a general understanding of interrelated factors
influencing surface and ground water resources within the
County and to assist the reader in understanding the reasoning
behind the need for improved forms of water resource manage-
ment practices. At the same time, the report provides infor-
mation intended for use by the St. Johns County Engineering
Department. The information presented provides a framework
for a long term program that will permit the Engineering De-
partment to provide practical guidance to individuals inter-
ested in undertaking development efforts anywhere within the
County.

As the pressure of urban growth of metropolitan Jacksonville
continues to expand into St. Johns County, governmental pro-
cedures for reviewing proposed property improvements must
become more efficient. Informal methods of permit processing
and decision making acceptable in a slower paced govern-
mental process cannot meet current nor expected future
property development requirements. Property owners need
clear, easily understood, and reasonable requirements that
permit them to evaluate and undertake development actions.
This report presents some criteria oriented towards the pro-
vision of necessary governmental services with objectives and
procedures that are intended as clear and simplified guid-
ance to property owners who desire to improve their prop-
erties.

BASIN MANAGEMENT FEATURES

Basin Management issues addressed in this report primarily in-
clude control of stormwater runoff, protection of natural re-
source areas, recharge and protection of the surficial aqui-
fer, improvement and protection of surface water quality, and
prevention of flooding due to rainfall events. Findings and
recommendations are primarily addressed in chapters 9 and 11
of this report. The findings, criteria and recommendations
discussed in this summary are not inclusive of all the find-
ings and recommendations of this report. Also, the basin man-

xiii

agement problems identified in this report are interrelated
and the long-term impact of these issues going uncorrected is
tremendous.

Control of Stormwater Runoff

Erosion along the banks of the steep stream channels of Moult-
rie Creek occurs following heavy rainfalls. Unless stormwater
is retained or detained on lands improved for development, ac-
celerated eroded materials and contaminants from developed
lands will be discharged into the Matanzas River in increasing
quantities over time. As stormwater is diverted from re-
charge, the base flow of Moultrie Creek is being eliminated.
The reduction in base flow of Moultrie Creek will contribute
towards a decline in the ground water table, and an increase
in salt water intrusion in the areas around Moultrie Creek.

Once stormwater from normal annual rainfall is retained, the
overflow water from the infrequent and heavier rainfalls must
be detained and safely discharged at controlled rates to avoid
significant erosion and sedimentation and damages to receiving
water areas.

Control of stormwater runoff can be accomplished through de-
tention or retention storage in any land area capable of hol-
ding water without causing flooding of structure or roadways.
outlets can be raised to provide some areas for extended
detention storage.

Protection of Natural Resource Areas

Development within or adjacent to the natural resource areas
including the drainageway fringe will require consideration
for the annual rise of the water table in these areas. Any
effort to drain these lands will have long-term impacts on
these areas and potential decline of the surficial aquifer
supplies, potential decline of the natural resource area and
potential of increased salt water intrusion. If the ground
water table is lowered through either overdrainage or through
deficient recharge, new growth of young plants and regenera-
tion of new growth will be eliminated. As this occurs the
natural area will begin a transitional process where vegeta-
tion that can sustain itself with less water will begin to re-
place the original species. Protection of significant natural
areas in uplands can be accomplished through control of water
table conditions.

The environmental health of the natural resource areas is de-
pendent upon continual ground water seepage from adjacent high-

xiv

er water table areas and fresh water discharges from Moultrie
Creek and tributary streams. Thus, ground water recharge in
areas upland from natural resource areas is important for the
continued prosperity of these areas. The prevention of polu-
tion discharge into natural resource areas and areas dis-
charging to Moultrie Creek is also recommended for the future
well being of the natural resource areas.

Recharge and Protection of the Surficial Aquifer

The unpredictable nature of precipitation makes control of
ground water recharge both more difficult and important. Un-
less the stormwater systems are designed to detain or retain
the routine daily rainfall amounts expected on an annual ba-
sis, overdrainage of the surficial aquifer will occur. Re-
charge to the surficial aquifer can only occur when rain water
from normal rainfalls expected on an annual basis is retained
long enough to infiltrate the surface and allowed to slowly
percolate downward through the water table. Currently, with-
drawals from the surficial aquifer for public water supplies
are exceeding the natural rain water recharge in the areas of
the well fields. From this, further declines in the local wa-
ter table can be expected.

Uncontrolled drainage directed to Moultrie Creek removes
stormwater before it can infiltrate to provide recharge to the
surficial aquifer. Detention/retention storage or containment
for ground water supply recharge through infiltration must be
emphasized in the vicinity of the land surface areas beneath
which surficial aquifer water is withdrawn. Increasing stor-
age of stormwater and the diversion of stormwater towards
cones of depressions are essential to avoid water table de-
clines in the vicinity of the well fields.

Septic tank effluents are significant sources of water re-
charge to the surficial aquifer. Maximizing rainfall reten-
tion in these areas would serve to increase recharge and pro-
vide a means for diluting septic tank effluents. As the cone
of depression from a well approaches the ground surface, sep-
tic tank effluents will be drawn downward which may introduce
pathogens into the well water.

Recharge of the surficial aquifer is all important due to the
extreme difficulty in rehabilitating wetlands following over-
drainage. Overdrainage of ground water and uncontrolled
drainage of stormwater contribute to the permanent and even-
tual lowering of the water table and should therefore be
avoided.

Improvement and Protection of Surface Water Quality

Stormwater detention/retention facilities can help reduce pol-
lutant loads characteristically found in urban runoff. Reten-
tion facilities designed to store the first one inch of every
rainfall would more adequately serve water pollution control,
water supply recharge, and significant natural resource area
requirements. A number of small retention facilities provide
a distributed and more effective system for ground water re-
charge than a single large retention facility.

The entrapment of contaminants from roadway traffic in reten-
tion storage catchment facilities along Moultrie Creek and the
Matanzas River is vital for the preservation of the surface
water quality of the Matanzas River. Surface water quality
is also a victim of septic tank effluent which often contains
materials toxic to the natural biological processes in the
estuary. In addition, as development increases, the release of
nutrients as septic tank effluents will also increase and
will eventually overload those natural processes responsible
for handling the effluent.

Prevention of Flooding Due to Rainfall Events

The actual frequency, duration and volume of rainfall events
are unpredictable in St. Johns County, therefore it is impor-
tant that an acceptable design be developed and adhered to on
the County level. The 10-year 24 hour storm shall be used for
design of stormwater infrastructure. Under recommendations of
this st 'ormwater management plan, construction of major roads
and inhabited buildings will be located above the 100-year
flood elevation. In addition, the controlled flow of storm-
water has many advantages including prevention of the
following: erosion of stormwater conveyance systems, sedimen-
tation to downstream areas, accelerated eutrophication of do-
wnstream water bodies, and toxic materials entering receiving
waters and degrading surface water quality.

Other Developmental Concerns

The annual high water table should be of great concern. The
water table naturally fluctuates greatly. As the water table
approaches within six inches of the subbase of a roadway the
subbase can become saturated and cause deterioration of the
subbase and eventual decay of the roadway. Also, as the water
table approaches the bottom of retention facilities used for
recharge, they cease to drain, can become flooded with ground
water, and can cause flooding in the area contributing to the
pond. It is for this reason that developments should be built

xvi

above the annual high water table. In the past this was
accomplished through drainage of the ground water. This has
become an increasingly unacceptable practice as the longterm
effects have become known.

This study serves as the basis for formulation of a County
wide program for improvements in stormwater management, flood
protection, and protection of natural resources. This report
has identified problems, offered recommendations for improve-
ment, and presented alternatives in use by other local gov-
ernments to meet the challenges proposed by the ever in-
creasing demands from growth upon County governments through-
out Florida.

xvii

LIST OF ILLUSTRATIONS

FIGURE PAGE

1-1. Orientation Map . . . . . . . . . . . . . . . 1 - 2

1-2. St. Augustine Harbor, FL . . . . . . . . . . . 1 - 4

3-1. USGS Well SJ 112E Tillman Ridge . . . . . . . 3 - 7

4-1. Localities With Water Tables Rising Above
Land Level Part of Each Year . . . . . . . . . 4 - 6

4-2. Annually Flooded Soils and Drainageway
Soils . . . . . . . . . . . . . . . . . . . . 4 - 8

4-3. Annually Flooded/Drainageway Soils and
Naturally Saturated Soils . . . . . . . . . . 4 - 10

4-4. Well To Excessively Drained Soils . . . . . . 4 - 11

7-1. Flood Hazard Areas Subject To 100-Year
Flooding . . . . . . . . . . . . . . . . . . . 7 - 2

10-1. Current Organization of the Engineering
Department St. Johns County/ Fiscal
Year 1990 . . . . . . . . . . . . . . . . . . 10 - 25

10-2. Proposed Organization of the Engineering
Department St. Johns County/ Fiscal
Year 1991 . . . . . . . . . . . . . . . . . . 10 - 26

LIST OF TABLES

TABLE PAGE

2-1. ANNUAL RAINFALL EXTREMES/ ST. AUGUSTINE,
FLORIDA . . . . . . . . . . . .. . . . . . . . 2 - 9
2-2. DAYS WITH RAINFALL/ HASTINGS, FLORIDA . . . . 2 - 11

2-3. AVERAGES OF DAILY RAINFALL AMOUNTS/
HASTINGS, FLORIDA . . . . . . . . . . . . . . 2 - 12

2-4. PROBABLE RETURN FREQUENCIES OF
PRECIPITATION AMOUNTS/ ST. JOHNS COUNTY,
FLORIDA . . . . . . . . . . . . . . . . . . . 2 - 14

6-1. MOULTRIE CREEK WATERSHED POTENTIAL
EVAPOTRANSPIRATION . . . . . . . . . . . . . . 6 - 3

6-2. ST. AUGUSTINE RAINFALL AND MOULTRIE CREEK
DISCHARGE . . . . . . . . . . . . . . . . . . 6 11

8-1. GUIDELINE HYDROLOGICAL CRITERIA FOR THE
ATLANTIC COASTAL RIDGE/ ST. JOHNS COUNTY,
FLORIDA . . . . . . . . . . . . . . . . . . . 8 2

LIST OF ABBREVIATIONS

B.C.C. - St. Johns County Board of County Commissioners

CAD/GIS - Computer Aided Design/Geographic Information System

Corps - U. S. Army Corps of Engineers

cfs cubic feet per second

DER Florida Department of Environmental Regulation

EPA Environmental Protection Agency

ET Evapotranspiration

FEMA - Federal Emergency Management Agency

FIRM - Flood Insurance Rate Maps

gpcd - gallon per capita day

IFAS - Florida Institute for Food and Agricultural Sciences

mg/l - milligrams per liter

NGVD - National Geodetic Vertical Datum

NOAA - National Oceanic and Atmospheric Administration

NRC - National Research Council

NWS - National Weather Service

ppm - parts per million

SCS - U. S. Soil Conservation Service

SFWMD - South Florida Water Management District

SJRWMD - St. Johns River Water Management District

U.S.D.A. - United States Department of Agriculture

USGS - United States Geological Survey

vii

AREA ORIENTATION

STUDY AREA

General

St. Johns County is located in northeast Florida with about
42 miles of coastline bordering the Atlantic Ocean (Figure
1-1. Orientation Map). The County is bounded on the north
by Duval County and on the south by Flagler County. On the
west and from the County's southwest corner to Deep Creek,
St. Johns County abuts Putnam County. From Deep Creek
northward, the western boundary of the County abutting
Putnam and Clay counties is within the St. Johns River.

The study area is in the southeastern part of the County, with
the boundaries of the study area being State Road No. 207 to
the north, Interstate No. 95 to the west, State Road No. 206
to the south, and the Sebastian and Matanzas Rivers to the
east.

The County has a total area of approximately 673 square
miles, including about 60 square miles of open water. About
14 square miles of open water exists along the eastern side
of the County in association with the Intracoastal Waterway.
About 5 square miles are lakes, borrow pits, and streams.
Another 41 square miles of open water occurs along the
western side of the County within the St. Johns River.

About 362 square miles of the County drains westward towards
the St. Johns River. Drainage from the roughly 16 square
miles of land area in the general area of Palm Valley flows
northward via the Intracoastal waterway and Pablo Creek to
the St. Johns River. An estimated eight square miles of
shoreline area, including 3.2 square miles in the Salt Run
area (largely St. Augustine Beach), drains to the St. Au-
gustine Inlet or the ocean, and about 231 square miles drain
to the Tolomato or Matanzas rivers. of the area draining to
the Matanzas River, it is estimated that 15.8 square miles
drains via Moses Creek and 41.7 square miles drains via Moult-
rie Creek.

Figure 1-1. Orientation Map

DUVAL COUNTY

CLAY COUNTY

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

PUTNAki COUNTY

------------------
FLAGLER COUNTY

SCALE: 140,000

MAJOR DRAINAGE AREAS

PROJECT S - ST. JOHNS RIVER
LOCATION
4POR 0 M - MATANZAS RIVER
M-M - MOULTRIE CREEK
D.E.R. CONTRACT NO. 7CM21171.1 T - TOLOMATO RIVER
ST. JOHNS COUNTY ENCINEERINC DEPARTMENT - GEOCRAPHIC INFORMATION SYSTEM

The Tolomato and Matanzas Rivers have been canalized to a
maintained depth of 12 feet and width of 125 feet as part of
the Intracoastal Waterway Federal project. The combined water
area, marsh area, and associated minor drainageways directly
associated with these two rivers within St. Johns County is
estimated at about 71 square miles.

Essentially all of the 84 square miles of the Tolomato
River drainage area and about 97 square miles of the 161
square mile drainage area of the Matanzas River discharge
fresh water to the ocean through the St. Augustine Inlet.
About 64 square miles of the Matanzas River watershed, essen-
tially the area between Moses Creek and Pellicer Creek, can
be expected to discharge to the Atlantic Ocean through the
Matanzas Inlet. The mouth of Moses Creek is almost 6 miles
from the Matanzas Inlet and about 11 miles from the St. Au-
gustine Inlet. Fresh water discharges from Moses Creek can
be expected to provide a greater influence to water quality
conditions in the vicinity of the Matanzas Inlet.

Moultrie Creek drains into the Matanzas River at a point about
5.8 miles south of the St. Augustine Inlet. Moultrie Creek
is tidally influenced for a distance of about 5 miles upstream
of its mouth and 3.4 miles upstream of the U.S. Highway *1
bridge. The southerly extent of reversing tidal influence and
water exchange in the Matanzas River from the St. Augustine
Inlet is unknown.

St. Augustine Harbor and Inlet

The St. Augustine Harbor was developed as a Federal project
(Figure 1-2. St. Augustine Harbor, FL). The harbor consists
of a stabilized channel 16 feet deep and 200 feet wide across
the St. Augustine Inlet bar, then 12 feet deep to the In-
tracoastal Waterway, and a channel ten feet deep and 100 feet
wide in the San Sebastian River from the Intracoastal Wa-
terway to the Kings Street bridge. The St. Augustine Inlet
was dredged across North Point (Vilano Beach) in 1940. It
was initially known as the north entrance or new inlet.
The original inlet was located at the' southerly extent of
Bird Island (now Conch Island) in what is now Anastasia State
Park. Salt Run is the residual channelway to the original in-
let.

Boat anchorages occur both to north and south of the Bridge
of Lions in the Matanzas River. Salt Run also provides
protected anchorages for boats. The mouth of the San Sebas-
tian River is about 1.8 miles south of the Bridge of Lions.
Most of the commercial terminals in St. Augustine are lo-

1 - 3

Figure 1-2. St. Augustine Harbor, FL.

VILANO
BEACH

S"R- 16

ANASTASIA
KING ST. bRIDCE STATE

PARK
0 LIO

C.R. 214

SCALE: 1 5.000

PRoirrr
LOrMON
Lo
D.E.R. CO-NTRACT NO. 7CH217 11,
ST. JOHNS COUNTY ENGINEERING DEPARTMENT GEOGRAPHIC INFORMATION SYSTEM

cated along the lower 2.5 miles of the San Sebastian River.

Freshwater discharges from urban areas and activities associ-
ated with St. Augustine, St. Augustine Harbor, San Sebastian
Creek, the lower Matanzas River and the Tolomato River are
well mixed by the reversing tides moving through St. Augustine
Inlet. Detailed studies would have to be conducted to esti-
mate the extent of fresh water flushing that occurs through
the inlet with each ebb or outgoing tide. Correspondingly,
ocean water entering the harbor during flood or incoming
tides can be expected to mix with the fresher waters within
the harbor area and distribute these mixed waters upstream
into the lower courses of the tributary streams, including
Moultrie Creek.

The mixing process and redistribution of waters from the
ocean and the several fresh water sources is ongoing with
each tide reversal. The estuarine water quality throughout
the area of influence of the tide reversal mixing pro-
cess reflects the contributions of all sources of water
within the system.

The water carried to the ocean through the St. Augustine Inlet
is picked up and mixed with the ocean alongshore or littoral
current. During the winter months of the year, this cur-
rent or southerly drift moves water southward along the
coastline. This movement is caused by wind generated swells
produced by prevailing winds from the northeast. During the
summer months, prevailing winds are from the southeast, and
water from the St. Augustine Inlet becomes part of a north-
ward littoral current. These alongshore currents are repre-
sentative of the quality of ocean waters reaching St. Johns
County shores.

Tide Ranges

The mean tide range through the St. Augustine Inlet is about
4.5 feet, and the mean spring tide range is about 5.3 feet.
At the Bridge of Lions connecting the City of St. Augustine
with Anastasia Island about two miles from the inlet, the
mean tide range is about 4.2 feet.

The 1989 mean tide level at the Bridge of Lions was 0.38 feet
above the National Geodetic Vertical Datum of 1929 (NGVD).
NGVD is the national land leveling network upon which all land
elevations in the United States are based. Based upon the
tide range of 4.2 feet at the Bridge of Lions, the tide
range at the mouth of Moultrie Creek is estimated at slight-
ly less than four feet, and the elevation of mean high tide is
about 2.3 feet above NGVD.

I - 5

The highest tide on record at St. Augustine occurred during
Hurricane Dora, September 10 and 11, 1964, when a high water
elevation of twelve feet was recorded at the St. Augustine
waterfront. An October 1944 hurricane that originated in the
Caribbean, entered Florida near Sarasota on the west coast
and crossed into the Atlantic Ocean near Jacksonville.
This storm produced a hurricane tide of 7.9 feet NGVD at
St. Augustine. The following return frequencies of storm
surge related flood elevations have been established by the
Federal Emergency Management Agency (FEMA) for national flood
insurance purposes on the Matanzas River at the mouth of
the San Sebastian River: 10 yr.-4.8 feet; 50 yr.-7.3 feet;
100 yr.-8.5 feet; and, 500 yr.-10.9 feet.

Federal Emergency Management Agency Flood Insurance Rate Map
(FIRM) information for St. Johns County (Community No.
125147) (dated September 1985) established a 100 year re-
turn period flood elevation at the mouth of Moultrie Creek at
8 feet NGVD and the ten year return period flood elevation
at about 4.5 feet. These flood elevations would be caused by
storm tides.

Sea Level Rise

Throughout geologic history, global sea level variations
(both rise and fall) have occurred. Some authorities have
found evidence to indicate that we may be entering a new pe-
riod of glacial advance with a resultant future drop in sea
level. others argue that increasing atmospheric concentra-
tions of carbon dioxide and other gases are causing the earth
to accelerate the warming trend of the current interglacial
period. Accelerated warming would lead to further retreat
of continental glaciers and a more rapid rise in sea level.

The national agency responsible for measuring sea level
changes is the National Ocean Survey, a part of the Na-
tional Geodetic Survey. From this agency's publication, sea
Level Variations for the United States 1855-1980 the trend of
relative sea level change is on the order of-a 1.9 mm rise
in sea level per year. The National Research Council (NRC),
whose members are drawn from the Councils of the National
Academy of Sciences, the National Academy of Engineering,
and the Institute of Medicine, has recommended that federal
agencies should consider the high probability of future sea
level rise. It may be some time before precise estimates of
future sea level rise are possible. In the meantime, the
risks associated with a substantial rise should not be disre-
garded.

1 - 6

The U. S. Army Corps of Engineers considers that at least
twenty-five years of additional records will be needed to es-
timate local effective sea level rise rates with reasonable
certainty and to reach some consensus on which of the var-
ious sea level rise scenarios is most likely. For now
planning should consider what impact a higher relative sea
level rise rate scenario would have on the design of projects
based on the historical rate. The rate of change in sea
level along the eastern Florida coast in the 1940 to 1980
time frame has been on the order of 2.4 mm per year. This
rate of apparent sea level rise has been used for recent
Corps of Engineers projects.

A rate of 1.9 mm per year would produce an apparent sea level
rise of 3.7 inches in 50 years. A rate of 2.4 mm per
year would produce a sea level rise of 4.7 inches in 50
years. The net effect of these conditions in the Moultrie
Creek watershed would be the gradual movement of tidal
conditions further upstream within the creek and its tribu-
taries that discharge to tidewater. Ground water conditions
also would be affected with an increased tendency for salt
water intrusion to penetrate further inland from the Matan-
zas River and the tidewater part of Moultrie Creek.

WATERSHED LOCATIONAL SIGNIFICANCE

The Matanzas River, St. Augustine Harbor, and the St.
Johns County shorelines immediately to the north and south of
the St. Augustine Inlet are impacted by the volumes and qual-
ities of the water discharged from the Moultrie Creek wa-
tershed. Moultrie Creek is one of numerous stormwater dis-
charge sources to the area's estuarine receiving waters,
and stormwater management practices would have to be applied
to all discharge sources to significantly improve water
quality conditions within these coastal receiving water ar-
eas.

1 7

CLIMATE AND RAINFALL

INTRODUCTION

An analysis of climate and rainfall serve as the basis for
sound management of the watershed. The effect of frequent
storm events, the associated periods of flooding, and protec-
tion of the surficial aquifer can be predicted with a greater
understanding of climate and rainfall characteristics within
the basin.

Hydrology deals with the properties, distribution, and circu-
lation of water in the atmosphere, on the surface of the land,
and in the soils and underlying rocks. The movement of water
onto the land as rainfall, into the soils as infiltration,
back to the atmosphere as direct evaporation and transpiration
from plants, and as surface water runoff in streams is a pro-
cess known as the hydrological cycle.

Current climatic conditions of northern Florida are heavily
influenced by the large scale weather systems that move across
the region. St. Johns County climate is also influenced by
marine conditions and related weather events. The informa-
tion provided in this report illustrates the dominant sources
of rainfall to be expected within the County, general charac-
teristics of rainfalls, and criteria for managing the result-
ing stormwater.

The source of water replenishing the Floridan aquifer under-
lying St. Johns County is the rainfall received in upland
areas of north central Florida. Governmental actions taken
by St. Johns County cannot control the replenishment of the
Floridan aquifer.

Rainfall received in St. Johns County is the source of water
that replenishes the surficial aquifer underlying the
County. The primary source of potable water in St. Johns
County, water used for human consumption, is the surficial
aquifer. Protection of the surficial aquifer through man-
agement procedures assuring adequate recharge for public wa-
ter supplies and private uses can be controlled by St. Johns

2 - 1

County. Similarly, actions of County government can reduce
the effects of flooding due to rainfall events and provide
protection for some significant natural resources within ju-
risdictional limits.

In this investigation, available hydrological information
has been reviewed from the perspective of the need to pro-
vide for recharge to the surficial aquifer, reduce the ef-
fects of flooding, and provide protection to some significant
natural resources through basin-wide stormwater management
practices. Drainage of lands, as practiced in Florida until
very recently, usually ignored the need to retain stormwater
for aquifer recharge and natural resource area protection
purposes. The protection of these resources requires some
modification of local government infrastructural development
and maintenance practices, changes in local governmental de-
velopment review practices, and multiple purpose hydrologi-
cal analyses and hydraulic designs for projects.

Hydrological information provide the basis of engineering de-
sign of all types of water control works. As a part of this
project, a review was conducted of the ways in which hydrolo-
gical information is conventionally used in local government
development decisions. Some hydrological analysis criteria
not generally considered in drainage design have been in-
cluded in this report to provide preliminary guidance for
protecting the aquifer and natural resources have those ar-
eas. Hydrological analyses methods and engineering evaluation
procedures specifically oriented towards the design of
water control facilities are referenced below.

A water management handbook will be prepared by the County
as additional development guidance for property owners. Sev-
eral publications are used for water management guidelines
(see bibliography); however these documents do not adequately
address aquifer and natural resource protection needs of St.
Johns County. This deficiency frequently results in delays of
local development approvals while County staff and permit ap-
plicants attempt to determine effective plans and practices in
the absence of clear criteria and review procedures. In addi-
tion to County guidelines, the Handbook will incorporate or
adapt pertinent engineering criteria for evaluations and meth-
odologies developed by the St. Johns River Water Manage-
ment District. The Applicant's Handbook forManagement and
Storage of Surface Waters, containing Water Management Dis-
trict guidance can be obtained directly from that agency.
However, St. Johns County criteria, notably those criteria
necessary for establishing stormwater retention facilities,
will prevail in any development proposal review. other
useful sources of engineering design information are pre-
sented in the bibliography.

2 - 2

CLIMATIC FACTORS

Temperature Influences

Area temperature characteristics and seasonal changes in tem-
perature reflect climatic conditions of the Floridan penin-
sula that contribute to an understanding of hydrological pro-
cess dynamics. St. Johns County has a borderline subtropi-
cal climate with rare, short-duration freezing events affect-
ing the area during the late December through February winter
season.

Historical records for St. Augustine for the period
1902 through 1938 indicated an average January temperature of
58 degrees Fahrenheit with a lowest recorded temperature of
13 degrees. The July average temperature for that period
was approximately 81 degrees with a maximum recorded tem-
perature of 104 degrees. Temperature norms for the 1951 to
1980 period are 51.8 degrees for January and 79.9 degrees for
July.

The study area generally is not subject to severe, long-dura-
tion freezes sufficient to affect road bases and building
foundations, but exposed water pipes may freeze under occa-
sional one to two day freezes during the movement of a se-
vere winter frontal system through the area. The westerly
part of the study area is subject to slightly cooler winter
temperatures than typically occur within the areas close to
the Matanzas River.

As normal winter conditions within the study area, ice
occasionally has been found on standing shallow water ar-
eas near Tillman Ridge, but this occurrence is rare near
the Matanzas River. Some damage to vegetation has oc-
curred during severe freeze events, with more significant
damage in the interior parts of the watershed. Similarly,
frosts can occur on roofs during December through February
period.

winter temperatures are cool enough to give a pronounced sea-
sonal character to plant growth. Winter cool weather is suf-
ficient to terminate growth cycles of some plants, while
many others become dormant. As a result, the removal of
water from the surface soils by plant transpiration to the
atmosphere decreases significantly during the winter months.

The eastern fringe of the Moultrie Creek watershed is influ-
enced by microclimatic daily sea breeze conditions. Daily air
exchange between the land and the ocean is noticeable inland
to areas immediately west of Matanzas River. The effect

2 - 3

diminishes in importance generally within one half mile in-
land from Matanzas River. Ocean influenced areas are cooled
daily by air moving off the ocean during summer months and
warmed daily by the ocean effect during winter months.

Storms

The daily sea breeze effect can be expected to result in very
slightly reduced summer rainfall totals in St. Augustine
and along the eastern edge of the watershed. St. Augustine
rainfall is recorded at Radio Station WFOY located about one
mile north of the U. S. Post Office and near the St. Au-
gustine Inlet. This rainfall station is within the area
influenced by the daily sea breeze effects. Sea breeze re-
lated storms providing rainfalls to land areas along the
coast occur occasionally. During these stormsi rainfall
typically is more intense within one or two miles of the
coast and diminishes in intensity towards the interior of the
land area.

The familiar summer shower rainfall resulting from heated
land surfaces and cooler air (differential heating and
cooling and corresponding thunderstorms) occurs more fre-
quently over inland parts of the County. This source of
rainfall is typically provided by isolated storms passing
along narrow bands or tracks with short-duration effects.
These storms move with prevailing air currents as cells of
thunderstorms typically one to three miles across. The
highly localized rainfall can be intense, on the order of
one to two inches during five to thirty minute periods.
Part of the rainfall evaporates quickly due to summer temper-
ature conditions. Sometimes, an intense rainfall from such
storms produces short-duration ponded water on properties.
If allowed to drain from the land, the water provided from
these storms can be lost as runoff. While producing heavy,
localized, and short-duration rainfall on small parts of the
watershed. The common summer differential heating and cool-
ing thunderstorms contribute only part of the area's warm
season rainfall.

Rainfall occurs repeatedly on the watershed from midsummer
through the winter months when high pressure systems with as-
sociated cold or cool fronts pass from west to east across the
country and sometimes penetrate into Florida. In the summer
months, most frontal systems move to the north of Florida,
but these systems can penetrate southward into north Flor-
ida almost any month of the year. Strong high pressure
systems passing to the north of Florida can generate persis-
tent clockwise air movements resulting in winds from the
northeast that move off the Atlantic Ocean and onto the

2 - 4

eastern coastline of Florida. These are the northeasterly
storms with winds of 20 or more miles per hour and with
cloudy, drizzly weather lasting for several days. They can
provide long-duration, low-intensity rainfalls across large
areas. Several inches of rainfall over a two or three day
period can be expected from northeasterly storms.

Heavy localized rainfall can occur when frontal systems
move slowly across north Florida from north to south or
northwest to southeast. The effects can become severe when
the system stalls for an extended period over a part of the
peninsula. As the cooler frontal system air comes into
contact with the warmer, moister air over the Floridan
peninsula, gentle, persistent rainfall occurs on the warm
side of the front. Occasionally, a significant low-pressure
trough develops across the peninsula on the southerly and
warm side of the frontal system. As the frontal system
stagnates or moves very slowly southward, very moist air can
flow from the Gulf of Mexico and move across the peninsula
providing rainfall along the low-pressure trough. The inten-
sity of the low- pressure trough and its duration cannot be
forecast easily, but these factors essentially determine the
intensity of the rainfall associated with the event.

The above type of system was responsible for very heavy rain-
fall in parts of Jacksonville in August 1989 and again in late
September 1989. Recorded rainfall in the second event in
Jacksonville reached the expected 100-year return frequency
rainfall of over 11 inches in twenty-four hours in the
downtown and northwest parts of the city. Much of the city
(Duval County) received in excess of 4 and 5 inches of
rainfall. Comparable conditions have been responsible for
major flooding events across much of the state of Florida over
the years.

The September 1989 system that affected northeast Florida
provides a useful example of the character of the rainfall in-
cidence to be expected under this weather condition. The
warm, moist air channeled towards the northeast from the
Gulf of Mexico was concentrated in a series of cells with
thunderstorm characteristics moving in bands across the penin-
sula. The rainfall from specific cells was intense, and the
cells deposited differing amounts of rainfall on the areas
over which they passed. At the same time, only a rela-
tively small part of Jacksonville experienced an extremely
heavy rainfall that might be expected on an average of once
in one hundred years.

2 - 5

The trough also produced the heaviest rainfall in a relatively
narrow band. In northeast Florida, Baker, Duval, and Nas-
sau counties received very heavy rainfall, while Clay County
received a lesser amount of total rain, and St. Johns and Put-
nam counties received rainfall amounts that could be ex-
pected annually from frontal weather systems.

Another more typical frontal system moved southward through
St. Johns County on October 8, 1989. The day started with
clear skies, but clouds became dominant by midday. The rain-
fall began in early afternoon and ended in the early even-
ing hours. On that day, radio station WFOY in St. Augus-
tine recorded a rainfall of 1.09 inches. Conditions became
atypical when the front stalled over central Florida set-
ting up unstable atmospheric conditions. A low pressure
trough formed above the unstable frontal system setting up
a movement of moist Gulf air from the southwest. At the same
time, frontal systems passing to the east and north of Florida
set up a northeasterly air movement from the Atlantic Ocean.
The air moving from the northeast and the cooler Atlantic
Ocean and the warm, moist air moving from the southwest and
the Gulf of Mexico set up bands of rainfall that became
intense along the coastline between St. Augustine and Mel-
borne. The combination of moisture laden warm and cool air
resulted in the 11.28 inch daily rainfall recorded at radio
station WFOY on October 10, 1989. However, a rainfall of 16
inches was recorded at the Emergency Management Center in St.
Augustine on October 10. The official National Weather Ser-
vice (NWS) four day rainfall recorded at radio station WFOY
in St. Augustine between October 8 and 11 was 12.45 inches.

A significant part of the late summer, fall, winter, and
spring rainfall in northeast Florida is provided by, or in
association with, cold fronts passing southward along the Flo-
ridan peninsula. Review of storm data records suggest that
frontal system rainfall, including northeasterly storms,
produce the more significant part of the total annual rain-
fall received on most of the Floridan peninsula.

Another important source of rainfall is associated with
the passage of tropical low-pressure systems across the
peninsula. Beginning in the 1980's, the National Hurricane
Center in Coral Gables, Florida, has been reporting the move-
ment of tropical low-pressure systems that move from east to
west across the Atlantic Ocean and pass over the Floridan pen-
insula.

On the order of 50 or more of tropical or easterly waves
form each year and move to the west across the Atlantic
Ocean at latitudes of between 10 to 20 degrees. Some form
into low-pressure depressions or troughs that can produce

2 - 6

significant rainfall, typically across the southeast part of
the peninsula. Some of these systems extend northward far
enough to produce heavy rainfall along the northeast Florida
coastline.

When the tropical system becomes organized enough to generate
a circulating wind pattern with sustained wind speeds of more
than 39 miles per hour, it is classified as a tropical storm.
Tropical storms can produce significant rainfall over thou-
sands of square miles of the earth's surface in their paths.
In August 1981 Tropical Storm Dennis deposited over 20
inches of rainfall in a twenty-four hour period near Home-
stead, Florida, and relatively widespread rainfall across
much of southeastern Florida. The storm took a track north-
ward through southeastern Florida and back into the Atlantic
Ocean near Fort Pierce. On August 19, Tropical Storm Den-
nis passed to the east of St. Augustine and northern Flor-
ida. Over the 6 day period from August 16 to August 21, St.
Augustine received 2.35 inches of rainfall from the dis-
turbed atmospheric conditions associated with this tropical
storm.

When the circulating wind speeds of tropical storms reach
sustained velocities of 74 miles per hour, they are reclassi-
fied as hurricanes. These storms are very rare, and only
a few have produced damaging effects in northeast Florida.
However, northeast Florida can receive rainfall from the
bands of circulating winds and associated cells of thun-
derstorms moving around a hurricane hundreds of miles from
its center. In 1985 Hurricane Elena moved from the Carib-
bean Ocean into the Gulf of Mexico and stagnated for almost
two days about 75 miles southwest of Cedar Key on Florida's
west coast. For several days, outer bands of that storm
passed across northeast Florida producing significant rain-
fall amounts. During the two days of August 31 and September
1, when Elena was offshore of Cedar Key, St. Augustine re-
corded rainfalls totaling 4.09 inches. Any hurricane pass-
ing within roughly two hundred miles of northeast Florida
can be expected to provide some rainfall for local areas.

The rainfall received in northeast Florida and the study area
is largely dependent upon weather conditions that cannot be
predicted on any long-term basis. Much of the annual
rainfall received occurs as a result of large storm systems
that move across the Floridan peninsula. The amount of
rainfall that is produced by any specific weather system
is also essentially unpredictable. Presently, it is not
possible to know with any degree of certainty how much rain-
fall is going to fall daily, weekly, monthly, or annually on
the Moultrie Creek watershed or any other ground water re-
charge area in Florida.

2 7

PRECIPITATION

Rainfall Records

St. Johns County rainfall is recorded by the National
Weather Service as part of the north Florida Climatic Division
comprised of 20 counties. The normal annual rainfall for
the Division based upon the 1951-1980 period is 53.61
inches. The normal annual rainfall for the Division based
upon the 1931-1960 period was 52.65 inches. Normal annual
rainfalls based upon the 1951-1980 period were available for
Federal Point, in St. Johns County near the mouth of Deep
Creek, (52.84 inches), St. Augustine (52.6 inches), and
Jacksonville Beach (50.35 inches). From these data, an ex-
pected annual rainfall of 53 inches would be generally
representative of conditions in the Moultrie Creek watershed.

Monthly rainfall records for several stations in the vicinity
of St. Augustine dating from 1877 to 1984 were available for
this study. The National Weather Service has compiled
composite information for these stations useful for esti-
mating general rainfall conditions for the St. Augustine lo-
cality. These data are also generally representative of the
rainfall to be expected on the easterly portions of the Moul-
trie Creek watershed.

The composite rainfall records for St. Augustine show a varia-
tion in the annual rainfall ranging between 29.2 (1956)
and 79.5 (1953) inches, with a long-term (1917-1984) average
annual rainfall of 50.7 inches. No real pattern exists
to establish a trend in annual rainfall variation. In il-
lustration, the five years with the highest annual rainfall
and the five years in the record with lowest annual rainfall
are presented in TABLE 2-1. ANNUAL RAINFALL EXTREMES ST. AU-
GUSTINE, FLORIDA.

The National Weather Service has produced an atlas of
monthly Palmer hydrological drought indices for the contig-
uous United States. The Palmer drought index data for the
North Florida Climatic Division was reviewed to determine
the , duration of periods in the rainfall record with below
average rainfall and those periods with above average rain-
fall. Drought Index information was available for the 1,032
month period between 1898 and 1984.

The data indicated that about 5.2 percent of the record pe-
riod (54 months) had extended drought conditions, with evapo-
transpiration exceeding rainfall on an average for three or

2 - 8

TABLE 2-1

ANNUAL RAINFALL EXTREMES
ST. AUGUSTINE, FLORIDA
(Record Period 1877 to 1984)

5 Years With Greatest 5 Years With Least
Total Annual Rainfall Total Annual Rainfall

Amount Amount
Rank Year (Inches) Rank Year (Inches)

1 1953 79.91 1 1956 29.20
2 1964 79.50 2 1911 31.59
3 1972 73.61 3 1954 34.14
4 1942 71.84 4 1927 34.41
5 1880 67.34 5 1917 34.79

more months. The most significant drought period affecting
the Moultrie Creek watershed extended for 16 months between
November 1955 and February 1957. Recorded monthly rainfall
for this period at St. Augustine was 32.69 inches, or 54.7
percent of the normal rainfall.

Extended wet periods represented 3.1 percent of the record
time frame. The longest extended wet period for the North
Florida Climatic Division extended for 8 months between Octo-
ber 1947 and May 1948. In the time frame between September
1947 and March 1948, monthly rainfall at St. Augustine ex-
ceeded the normal of 29.23 inches for those months by 37
percent.

The above data were presented to illustrate the likely range
of extended period rainfall variability which should be ex-
pected in the Moultrie Creek watershed. Extended periods of
drought and above normal rainfalls can be expected at any
time in the future. Lack of rainfall for extended periods
is particularly significant in St. Johns County where the
surficial aquifer is used heavily for* potable water sup-
plies.

The extended wet periods also provide information useful
for stormwater management planning. The large areas of
flatwood soils within the Moultrie Creek watershed have normal
high water tables during the winter months of the year. Ex-
tended wet periods can be expected to result in saturated
soils and shallow flooding within high natural water table
areas during these prolonged wet periods. Consideration of

2 - 9

wet season water table conditions should be incorporated into
revisions of water management framework. of special concern
are the public health and safety needs of people living in
developments permitted in areas where water tables are nat-
urally higher and where shallow flooding is a highly
probable natural occurrence.

Average Daily Rainfall

The available hourly and daily data for rainfall stations in
St. Johns County were reviewed to develop basic information
on the number of rainfall events to expect annually and the
amounts of average daily rainfall to expect during in-
dividual events. Hourly precipitation data were not avail-
able for any station that might be representative of the
Moultrie Creek watershed. All stations reviewed had miss-
ing data, but the Hastings rainfall station had a continuous
record of daily rainfall amounts for the period from January
1978 to December 1986, a 9 year period. The Hastings
rainfall gage is located at the Agricultural Center about
10.5 miles southwest of 1-95 and State Road 207 and the
southwesterly part of the Moultrie Creek watershed.

The total rainfall record period reviewed for Hastings con-
sisted of 3287 days. During the record period, some rain
fell on 1041 days, or 30.7 percent of the days in the period.
However, 388 of the days with rainfall had total amounts of
less than 0.1 inches, and this rainfall represented only 3.1
percent of the total received at Hastings during the 9 year
period. Daily rainfalls of 0.1 inches approximate the amount
of water lost each day to evapotranspiration and do not ef-
fectively contribute to ground water recharge.

No intense nor prolonged periods of extreme rainfall were re-
corded. The maximum daily rainfall recorded for the period
was 4.68 inches. All of the maximum daily rainfalls can be
accounted for in the context of normal events to be expected
annually or on a two year expected return frequency basis.
No attempt was made to separate the data into rainfall
events. Daily records do not permit the identification of
storms that begin on one day and end one or more days later.

Review of the daily data identified numerous periods during
fall, winter, and spring months when no rainfall was recorded
for ten and more days. one time frame of 26 days with no
rainfall occurred during the record period. Some rainfall
occurred on about 31 percent of the total days in the period,
but daily rainfalls of more than 0.1 inches occurred on
only 653 days, about 20 percent of the total days in the 9
year period. Distributing the 653 rainfalls evenly through-

2 - 10

out the total period would reflect one day with rainfall of
more than 0.1 inches on an average of about once every five
days.

The daily rainfall recorded at Hastings during the 9 year pe-
riod is summarized in TABLE 2-2. DAYS WITH RAINFALL HASTINGS,
FLORIDA, and TABLE 2-3. AVERAGES OF DAILY RAINFALL AMOUNTS
HASTINGS, FLORIDA. Table 2-2 describes the general distribu-
tion of days with rainfall grouped by categories of rainfall
amounts recorded. This table illustrates the rare condition
of daily rainfalls with more than two inches. The data
identified only 32 days in the nine year period with daily
rainfalls of more than two inches; a frequency of 3.5 days per
year with rainfalls exceeding two inches.

Table 2-3 summarizes the average rainfall received each year
by categories of rainfall amounts. The average annual rain-
fall at Hastings is 53.9 inches. The first 0.5 inches of ev-
ery rainfall amounts to an average annual total of 29.5
inches. If the first 0.5 inches of all rainfalls are re-
tained or stored and allowed to infiltrate into the ground
as water table recharge, about 55 percent of the annual
rainfall would become available for this purpose. Retention
of the first 1.0 inch of every rainfall would mean that no
runoff would be allowed for rainfalls of less than 1.0
inches. Under this condition, almost 78 percent of the
average annual rainfall would become available for re-
charge. Retention of the first 2.0 inches of every rainfall
would represent the potential storage of almost 92 percent
of all normal annual rainfall amounts.

TABLE 2-2

DAYS WITH RAINFALL
HASTINGS, FLORIDA (station No. 3874)
January 1978 to December 1986

Daily Number of Percent of Percent of
Rainfall Rainfall Total 3287 Days
(Inches) Days Rainfall in Period
Days

0.0 - 0.1 388 37.3 11.8
0.1 - 0.49 353 33.9 10.7
0.5 - 0.99 155 14.9 4.7
1.0 - 1.99 113 10.8 3.4
2.0> 32 3.1 0.1
Total 1041 100.0 30.7

2 11

TABLE 2-3

AVERAGES OF DAILY RAINFALL AMOUNTS
HASTINGS, FLORIDA (Station No. 3874)
January 1978 to December 1986

Daily Average Annual Annual Annual
Rainfall Rainfall Average of Average of Average of
(Inches) Per Year First 0.5 First 1.0 First 2.0
Inches Inches Inches Inches

0.0 - 0.1 1.7 1.7 1.7 1.7
0.1 - 0.49 10.5 10.5 10.5 10.5
0.5 - 0.99 13.6 8.6 13.6 13.6
1.0 - 1.99 16.6 6.3 12.6 16.6
2.0> 11.5 2.4 3.6 7.1
Annual 53.9 29.5 42.0 49.5

Daily rainfalls greater than 2.0 inches represented 4.4
inches of the annual average rainfall.

Until further studies of rainfall characteristics are under-
taken for a larger number of stations, the above data can be
used to estimate annual rainfall characteristics to be
expected in interior St. Johns County. Standard urban area
drainage systems are sized to provide for the removal of ex-
cess stormwater from rainfall events with total amounts
greater than reflected in the above data. Runoff from a 25
year 24 hour rainfall is sometimes used to establish the
maximum capacity of a drainage system. Unless the storm-
water systems are also designed to detain or retain the
routine daily rainfall amounts expected on an annual basis,
overdrainage and associated long-term local ground water de-
ficiency problems can occur.

Expected Rainfall Return Periods

Economic and engineering evaluations of water management mea-
sures and facilities requires information on the, expected
likelihood (return period) of rainfalls of some frequency
and duration. Cooperation between the U. S. Weather Bureau
and the U. S. Department of Agriculture, Soil Conservation
Service, began in 1955 for the purpose of defining the depth-
area-duration frequencies of rainfall in the United States.
These efforts resulted in the Rainfall Frequency Atlas of
the United States, Technical Paper No. 40, published in May
1961. This document provided generalized information for

2 - 12

rainfall with durations from 30 minutes to 24 hours and re-
turn periods from 1 to 100 years.

A second technical paper was produced by the Weather Bureau
in 1964 (Technical Paper No. 49). This document provided
generalized information for two- to ten-day precipitation
for return periods of 2 to 100 years in the contiguous United
States. This document was an extension of the work pub-
lished in Technical Paper No. 40. A final document was
published in June 1977 that provided five- to 60-minute pre-
cipitation frequency information for the eastern and Cen-
tral United States( NWS HYDRO-35). The latest document pro-
vides guidance specifically for the hydrological planning and
design for small area drainage areas.

The map and technical information from the above three docu-
ments has been assembled to represent probable rainfall re-
turn conditions in St. Johns County. The data derived
from the above sources is provided in TABLE 2-4. PROBABLE
RETURN FREQUENCIES OF PRECIPITATION AMOUNTS ST. JOHNS COUNTY,
FLORIDA.

As part of the Weather Bureau's initial study effort, a sta-
tistical probability analysis was conducted to establish the
degree that data for a rainfall station represents rainfall
on adjacent areas. Results from this part of the
Weather Bureau's evaluations indicate the following: 95
percent of 24 hour rainfall data recorded at a location
would be applicable to an adjacent 50 square mile water-
shed and about 92 percent of the rainfall data would be
applicable to a 400 square mile watershed. These findings
suggest that the daily rainfall recorded at St. Augustine or
Hastings would be generally representative of rainfall occur-
ring on the Moultrie Creek watershed.

The Weather Bureau's findings also indicate that as the dura-
tion of the rainfall event decreases, the rainfall station
data are applicable to smaller areas. For example, only
about 70 percent of a 30 minute rainfall recorded at a
station would be expected to directly apply to a nearby 50
square mile watershed. This concept reflects the condi-
tion that localized rainfall systems affecting small areas
tend to be associated with short-duration rainfalls. As a
result of these limitations and as an example, it would not
be appropriate to directly apply hourly rainfall data from
the Hastings rainfall station with rainfall and subsequent
conditions occurring on the Moultrie Creek watershed, but
daily rainfall data would generally remain applicable.

2 - 13

TABLE 2-4
PROBABLE RETURN FREQUENCIES OF PRECIPITATION AMOUNTS
ST. JOHNS COUNTY, FLORIDA
(PRECIPITATION IN INCHES)

RAINFALL RETURN PERIOD
DURATION (years)
(Minutes) 2 5 10 25 50 100

5 0.57 0.62 0.66 0.74 0.79 0.85
10 0.97 1.09 1.18 1.33 1.44 1.56
15 1.25 1.41 1.54 1.74 1.89 2.10
30 1.72 2.07 2.33 2.71 3.00 3.30

(Hours)
1 2.2 2.6 3.0 3.4 3.8 4.2
2 2.7 3.5 3.9 4.5 4.8 5.4
3 3.0 3.9 4.2 5.0 5.5 6.0
6 3.6 4.5 5.3 6.0 6.8 7.3
12 4.4 5.5 6.5 7.2 8.2 9.0
24 5.0 6.5 7.6 8.8 10.0 11.0

(Days)
2 5.5 7.3 8.3 10.0 12.0 12.8
4 6.3 8.2 10.0 12.1 13.8 14.6
7 7.5 9.3 10.6 12.7 14.5 16.2
10 8.2 10.4 12.4 14.5 16.2 18.0

Probable maximum 6 hour rainfall (PMP) for 10 square miles
is about 31 inches in northeast Florida. The main purpose
of the PMP value is to provide complete-safety design crite-
ria in cases where a water control structure failure would be
disastrous.

SOURCES: Values for rainfall durations in minutes were de-
rived from: Ralph H. Frederick, et. al., FIVE- TO 60- MINUTE
PRECIPITATION FREQUENCY FOR THE EASTERN AND CENTRAL UNITED
STATES, NOAA Technical Memorandum NWS HYDRO-35, Office of Hy-
drology, National Weather Service (NWS), National Oceanic and
Atmospheric Administration (NOAA), Silver Springs, Md.,
June 1977. Values for rainfall durations in hours were
derived from: David M. Hershfield, RAINFALL FREQUENCY ATLAS
OF THE UNITED STATES For Durations from 30 Minutes to 24
Hours and Return Periods from 1 to 100 Years,Technical Paper
No. 40, Weather Bureau (now the NWS of NOAA), U. S. Depart-
ment of Commerce, Washington, D. C., May 1961. Values for
rainfall durations in days were derived from: John F. Miller,
Two- to Ten-Day Precipitation for Return Periods of 2 to 100
Years in the Contiguous United States, Weather Bureau,
U. S. Department of Commerce, Washington, D. C., 1964.

2 - 14

GEOLOGY AND LANDFORMS

GEOLOGY

Upper Surficial. Sediments

The upper 50 to 60 feet of materials underlying St. Johns
County and the Moultrie Creek watershed is comprised of sands,
shells or coquina, and small amounts of clay. These materi-
als apparently were deposited during the warm interglacial
periods when sea levels were considerably higher than cur-
rent conditions. Following successive depositions, several
periods of erosion and redeposition apparently occurred.
This process gradually shaped the surface materials to pro-
duce the characteristics of landforms currently found within
the County.

Geologists have traced a series of continental glacial ad-
vances and retreats over the past one to two million years
which they identify as the Pleistocene Epoch. Scientists
generally consider that the Pleistocene Epoch ended about
10,000 years ago, and we are living within a geological pe-
riod known as the Recent or Holocene age.

The maximum penetration of the last major glacial advance on
the North American Continent is now considered to have oc-
curred about 18 1000 years ago. Geologists have estimated
that ocean levels were over 100 feet lower than present sea
level during the height of this glacial period.

A gradual worldwide rise of ocean levels has been occurring
since the last retreat of the continental glaciers. The last
continental glacier receded from the United States part of
North America about 7,000 to 9,000 years ago. As a result of
studies conducted near Miami in Biscayne Bay scientists have
concluded that sea level was about six feet below current
ocean levels approximately 6,000 years before the present.
We are now living in a geological age with current climate
and sea level conditions reflecting an interglacial period in
the geological history of the earth.

3 - 1

At least four Pleistocene interglacial ages appear to have
signifiqance relative to surficial sediments in St. Johns
County..@' An interglacial period labeled the Penholoway Age
produced remnant terraces in Florida at an altitude of about
70 feet. During this age, probably all of St. Johns County
was an offshore bar of an ancient ocean shoreline.

The second interglacial period has been termed the Talbot
Age which resulted in sea cut terraces on the Floridan penin-
sula at an altitude of about 40 feet. During this intergla-
cial period, the Tillman Ridge apparently was a shallow shoal
and island area with sand dunes rising at least ten feet
above sea level. The Moultrie Creek watershed area would
have been a gently sloping beach and foreshore area.

The third interglacial period has been named the Pamlico age
when terraces were cut at an elevation of about 25 feet above
current sea level. Recent scientific studies conducted on
coral reef terraces in the Barbados Islands and in New
Guinea have determined that the world's oceans were at an
elevation of about 20 feet above the current level approxi-
mately 125,000 years ago.

Finally, poorly defined Silver Bluff terrace remnants exist
around the Floridan peninsula at elevations of between five
and ten feet above current sea level. The Talbot and Silver
Bluff interglacial periods could be expected to have pro-
duced the final shaping of the lower landforms in St. Johns
County. From these periods to the present, stormwater runoff
gradually cut Moultrie Creek and its tributary streams into
the low plateau that is now the Moultrie Creek watershed.

Lower Sediment Deposits

Beneath the Moultrie Creek watershed, the upper 50 to 60 feet
of sediments are underlain by more dense, less permeable
sand, shells, sandy clay, and clay about 25 to 50 feet in
thickness. These materials rest upon the blue to green clay
materials of the Hawthorn Formation. The Hawthorn Formation
forms an aquiclude (an impermeable layer) or aquitard (an
area of low permeability) that separates the materials iden-
tified with the St. Johns County surficial aquifer from the
limestone formations associated with the Floridan aquifer.

Limestone Formations

The top of the limestone formations beneath the Moultrie
Creek watershed is generally found about 200 feet beneath land
surface. South of the Moultrie Creek watershed the top of

3 - 2

the limestone occurs about 150 feet beneath land surface.
The several rock formations extending to about 350 feet be-
neath land surface are now collectively called the Ocala
Group. These formations are the primary and more produc-
tive artesian water supply sources associated with the Flo-
ridan aquifer.

LIMESTONE FORMATIONS

General

The top of the limestone formations underlying north cen-
tral Florida and St. Johns County slope generally from
southwest to northeast. In central Alachua County and
western Marion County, the top of the Floridan aquifer is
found 50 to 75 feet above mean sea level. The top of the
limestone formations in this central Florida area is di-
rectly overlain by a zone of permeable silica sands. This
sand zone has been identified as a secondary artesian aquifer
in St. Johns County.

The Hawthorn Formation that functions as an aquiclude or
aquitard (preventing or retarding the upward or downward move-
ment of water) is missing from the central Florida uplands
of western Clay and Putnam counties, and most of Alachua and
Marion counties. Additionally, substantial solutioning has
occurred within the limestone formations, resulting in sink-
hole formations where the limestone is near the land surface.
Where sufficient surface material debris has partially plug-
ged the exposed drainage points within sinkholes, surface
water ponding has occurred.

In the Moultrie Creek study area, the top of the Floridan
aquifer is generally found at elevations of 175 to 200 feet
below mean sea level. Along the St. Johns County coast,
the top of the Floridan aquifer in the vicinity of Pellic-
er Creek, at the south boundary of the County, is about 150
feet below mean sea level. In the Ponte Vedra area on the
north, it occurs more than 350 feet below mean sea level.

Water Supply Aquifers

Floridan Aquifer

Rainwater falling on Clay, Alachua, and other interior coun-
ties infiltrates into the surface sands or runs off di-
rectly into sinkholes. These localities are considered as
primary Floridan aquifer recharge areas that establish the

3 - 3

water pressure head for fresh water withdrawn from the lime-
stone formations beneath St. Johns County. Rainwater enters
the limestone aquifer through permeable materials in areas
where local water tables are at elevations higher than the
water pressure head within the aquifer. The rainwater en-
tering the Floridan aquifer moves by gravity through solution
channels in the limestone, along seams between the rock lay-
ers known by geologists as bedding planes, and through the
rock materials. Where the Floridan aquifer is overlain by
impermeable materials, the pressure exerted by the weight of
the water within and above the aquifer causes increased move-
ment of water through the aquifer.

Some of the ground water flow entering the Floridan
aquifer emerges as seepage back to the land surface at ele-
vations below the points where the rainfall infiltrates into
the ground. Part of the flow of streams flowing eastward
from Central Florida (The Oklawaha River, Rice Creek, and
Black Creek) is the result of reemerging Floridan aquifer
water. Ground water that seeps back to the land surface and
becomes part of the flow of streams is known by hydrologists
as base flow.

The Hawthorn Formation overlies the limestone formations west-
ward from the Atlantic coast through western Putnam, Clay,
and Baker counties. This formation traps the ground water in
the Floridan aquifer,forcing it to flow eastward towards the
Atlantic Ocean. As a result, wells penetrating into the Flo-
ridan aquifer in eastern St. Johns County have in the past
been known to rise in the wells to heights approximating 20
feet above sea level. Aquifers with these conditions are
known as artesian aquifers. Because land elevations in the
Moultrie Creek watershed are generally at altitudes higher
than 20 feet above sea level, artesian flow to the land sur-
face does not occur.

The potential height to which artesian water rises in a
tightly contained well is known as the potentiometric head for
that well. The generalized potentiometric levels for wells
within a region are known as the potentiometric surface for
that regional area.

Within the Moultrie Creek watershed, Floridan aquifer wa-
ters occur beneath the Hawthorn Formation. Wells drilled to
depths of 150 or more feet generally will obtain Floridan
aquifer water. Due to the water pressure in the aquifer,
some seepage upward, termed leakance by hydrogeologists,
into, and perhaps through, the Hawthorn Formation can be
expected. The extent of this upward leakance into the
sands above the Hawthorn Formation has not been investigated.

3 - 4

The quantities of Floridan aquifer water available in eastern
St. Johns County is substantial, though not unlimited. De-
clines in the potentiometric levels of the Floridan aqui-
fer throughout northeast Florida have been widely reported
since the 1950's. These declines generally reflect water
withdrawals in excess of the ability of rainfall in recharge
areas to replenish the aquifer.

Investigations of 85 irrigation wells in western St. Johns
County determined that the upper 50 feet of the aquifer pro-
vided most of the water flow zones. About 50 percent of
the wells tested produced water with chloride (salts) con-
tents of less than 210 parts per million (ppm). Wells
penetrating deeper into the aquifer tended to produce water
with higher chloride concentrations. Some wells penetrating
deeper aquifer zones produced water that exceeded 3,000 ppm.
As withdrawal in the upper aquifer zones were increased, wa-
ter with higher chloride contents were drawn upward, con-
taminating the fresher upper water zones.

While the Floridan a quifer is available as a ground water
supply source in eastern St. Johns County, the water is high
in chlorides and other minerals. The U. S. Environmental
Protection Agency (EPA) and the Florida Department of Envi-
ronmental Regulation have established potable water limits for
chlorides at 250 milligrams per liter (mg/1) or 250 parts per
million. Water high in chloride content is very corrosive
to metals, harmful to most cultivated plants, and unpleasant
to drink. A concentration of about 400 ppm can be tasted
by most people.

North of the Moultrie Creek watershed, the Ocala Group of
the Floridan aquifer generally produces water with chloride
concentrations of less than 250 mg/l. Beneath the Moult-
rie Creek watershed, the chloride content of the upper lime-
stone formations of Floridan aquifer water is at or greater
than 250 mg/l. Towards the south, the chloride content of
Floridan aquifer upper water bearing zones increases to
1,000 mg/l near the Flagler County line. Throughout St.
Johns County, the lower limestone formations of the Florida
aquifer typically produce water with chloride concentrations
of 250 mg/l or more.

Surficial Aquifer

The surficial aquifer within the Moultrie Creek watershed is
a composite of confined and unconfined water-bearing zones
comprised of the sands, shells, and coquina occurring
above the Hawthorn Formation. Most wells used for potable wa-
ter supplies in the study area are drilled to depths of the

3 - 5

less than 100 feet below sea level. Some water is obtained
from wells penetrating sand and shell strata within the Haw-
thorn Formation. The water from wells open to the surficial
aquifer generally meets quality standards recommended for
public water supplies, except for concentrations of iron.
The iron content of water from most of the wells tested dur-
ing a study by the United States Geological Survey (USGS)
conducted in east-central St. Johns County was well above the
recommended limit of 0.3 mg/l. High iron contents of water
are undesirable because of the taste it imparts and the
staining effect it has on clothes, faucets and associated fix-
tures, painted walls, and natural stone. Iron from water can
be removed at water treatment plants by aeration or filtra-
tion.

The surficial aquifer in the Moultrie Creek watershed is re-
plenished primarily from direct rain water. Recharge to the
surficial aquifer can only occur when rain water is retained
long enough to infiltrate the surface sands and slowly per-
colate downward to the water table.

The surficial aquifer is widely used by individual prop-
erty owners for potable and other uses. It was formerly used
exclusively by the City of St. Augustine, but current demands
exceed the capacity of the city's surficial aquifer well
field yield capacity.

St. Augustine and St. Johns County have surficial aquifer
well fields located along or near Tillman Ridge on the western
side of the Moultrie Creek watershed. U. S. Geological Sur-
vey records of two monitoring wells in the Tillman Ridge
area have detected a progressive decline in the water table
in the vicinity of these well fields (Figure 3-1. USGS, Well
Si 112E Tillman Ridge.) These data suggest that long term
withdrawals for public water supplies are currently exceeding
the natural rain water recharge in the areas of the well
fields.

The City of St. Augustine has begun the process of aug-
menting surficial aquifer water with the saltier water from
the Floridan aquifer. This is a temporary measure that will
require further surficial aquifer well field expansion as
public demand for potable water provided by St. Augustine
increases.

Correspondingly, St. Johns County can be expected to be re-
quired to supply potable water to increasing numbers of
County residents in the near future. The rural practice
of using individual surficial aquifer wells for potable water
in the same locations where septic tank waste disposal is per-

3 6

Figure 3-1. USGS Well SJ 112E Tillman Ridge

E-
Lx- 0

-10 -

-15
1981 1982 1983 19B4 1985 1986 1987 1988 1989

MINIMUM DAILY DEPTH BELOW LAND SURFACE (FT)

PROlrrr
Worm

D. F. R. CONTRACT NO. CM2171
ST. JOHNS COUNTY ENGINEERING DEPARTMENT GEOGRAPHIC INFORVATION SYSTEM

mitted can be expected to lead to increased County public
health problems as County areas urbanize.

Stormwater Management Implications

As increased amounts of surficial aquifer water beneath
the Moultrie Creek watershed becomes used by St. Augustine
and St. Johns County for public water supplies, further de-
clines in local water table conditions can be expected.
Trestle Swamp, Cowan Swamp, and other upland natural areas
will have longer and longer periods when the water table will
be below the land surface. The weight of the water re-
tained in the surficial aquifer acts against the upward
leakance potential of the Floridan aquifer. As the water
table declines, corresponding upward movement of Floridan
aquifer waters into and, to some extent, through parts of the
Hawthorn Formation could be expected to occur.

In areas of the watershed where septic tanks are used for
sewage disposal, septic tank effluents are significant sources
of water recharge to the surficial aquifer. Maximizing rain-
fall retention in these areas, as opposed to primary depen-
dence upon uncontrolled stormwater drainage, would serve to
increase recharge to the surficial aquifer and provide a
means for diluting septic tank effluents introduced into the
surficial aquifer.

A perspective of the ground water recharge significance of
septic tank effluents can be obtained by the following example
analysis. Assume a family of four living in a home on a one
quarter acre lot. Each person uses an average of 100 gallons
of water per day which is discharged to the septic tank.
This is an approximate average water usage for urban popula-
tions using public water supplies. The total family daily
water usage is then 400 gallons, or about 53.4 cubic feet
per day. The family's property, at one fourth acre, is
10,890 square feet. If the 53.4 cubic feet per day were dis-
charged to a septic tank and the resultant effluent was dis-
tributed across the 10,890 square foot lot, the effluent
would be roughly equivalent to rainfall infiltration into
the soil approximating 0.06 inches every day, 365 days of
the year. In the event that the above amount of water was
discharged into a septic tank, the effluent could be equiva-
lent to the infiltration into the ground of about 20 inches
per year from rainfall.

Later information in this study shows that the Moultrie
Creek watershed, on the average, receives about 53 inches per
year from rainfall, and about 30 percent of any significant
rainfall is directly discharged to streams as runoff within 4

3 - 8

days following the rainfall event. At best, about 37
inches of the area's rainfall may infiltrate into the
ground, but roughly 20 percent of that amount reemerges as
base flow within three weeks following a rain event.

LANDFORMS

The Moultrie Creek watershed is a nearly flat to gradu-
ally sloping plateau generally raised 30 to 45 feet above
existing sea level. The easterly side of the plateau at
the Matanzas River generally has land elevations exceeding
20 feet. Land elevations exceeding 40 feet still exist at
isolated locations along U.S. Highway #1 north of Moultrie
Creek. The westerly side of the Moultrie Creek watershed
forms a surface water drainage divide between runoff drain-
ing to the Matanzas River and runoff draining westward to
the St. Johns River. The Tillman Ridge, which forms the
drainage divide, is paralleled by Interstate Highway #95
located about 1 mile to the east as shown in Figure 1-1. The
Tillman Ridge is a gradually sloping upland with general land
elevations of 40 to 48 feet.

The landforms of the Moultrie Creek watershed and all of
St. Johns County were formed in association with shore-
lines to ancient seas. Geologists consider the study ar-
eas's landforms as a terrace system formed during previous
interglacial times when ocean levels were 25 to 40 feet
above present sea level. The Tillman Ridge is geologically
associated with the Atlantic Coastal Ridge that extends for
most of the length of the Floridan peninsula. What is now
the Moultrie Creek watershed was once a very gradually slop-
ing shoreline related formation, possibly an offshore bar.

Wave action along shorelines produces slight wave cut
troughs just offshore of beach fronts, with the disturbed
sands redeposited as low ridges or bars some distance off-
shore. As ocean water elevations become lowered, the
former beach sand dunes become sand ridges and the former
offshore bars become slightly lower ridge line areas.

Immediately east of the Tillman Ridge is a large, par-
allel depressional area known as the Trestle Bay Swamp.
The bottom elevation of this swamp is at or above 35 feet.
About one mile to the east is another parallel depressional
area known locally as the Cowan Swamp. Between State Roads
16 and 214, the bottom of the Cowan Swamp is above 30 feet
in elevation. Near State Road 214 the beginning of the
Moultrie Creek channel begins with a channel flow direction
towards the south and generally aligned according to the an-
cient shoreline trough to tidewater.

3 - 9

The fall of Moultrie Creek from State Road 16 to tidewater is
on the order of one foot per thousand feet, or a slope of
slightly less than 0.1 percent. This slope represents a rela-
tive balance between slope stability of the area's sandy
soils and stormwater runoff from the plateau in recent geo-
logical times.

Heavy rainfalls and subsequent runoff from the 30 to 40 foot
high plateau gradually cut deep stream channels in the
fine ocean deposited sand mantle materials. Continual cut-
ting or erosion of the sides of the steep stream channels typ-
ical of Moultrie Creek and its tributaries can be expected to
occur within the watershed following heavy rainfalls. As
development occurs and unless stormwater is retained or
stored on lands improved for development, accelerated erod-
ed materials and contaminants from developed lands will
be discharged into the Matanzas River in increasing quanti-
ties over time.

on the plateau of the watershed, numerous large and small
shallow depressional areas currently maintain wetland veg-
etation. Many of these depressions are isolated or have no
natural drainage channel to established stream courses. Nor-
mal rainfalls are retained within these depressions, with
some of the rainfall infiltrating and percolating water
to the ground water table. Very heavy rainfalls often fill
depressions and allow sheet water flow to move across normally
drier areas to other depressions or to stream courses.

3 - 10

SOILS AND WATER TABLE CONDITIONS

SOILS

General

The term, Soil is typically applied to the weathered surface
layer of sediment materials. The science of soils has been
highly developed by the U.S. Soil Conservation Service (SCS)
in support of the nation's agricultural needs. The materials
used in this investigation are heavily dependent upon in-
formation provided by the Soil Conservation Service through
the Soil Survey of St. Johns County, Florida. The Soil Con-
servation Service classified the soils in the study area ac-
cording to a variety of characteristics such as soil color,
texture, size and shape of soil aggregates, kind and amount
of rock fragments, distribution of plant roots, acidity, and
other features that would identify the soils. This informa-
tion is highly valuable for general identification of ar-
eas with unique surface sediment characteristics. The in-
formation is suitable for preliminary engineering determina-
tion of potential problems to expect within given areas,
and the soil survey information has been used for this pur-
pose in this study.

soil survey information does not replace the need for site
specific field and laboratory analyses required to insure that
load bearing and other construction design parameters are ade-
quate for an engineered project.

Engineering Factors

The soils underlying the Moultrie Creek watershed are essen-
tially comprised of silica sands deposited as marine sedi-
ments. All upland soils in the study area, not subject to
prolonged flooding, are classified as fine sands with more
than 50 percent of the material passing a #40 sieve and less
than 50 percent passing a #200 sieve. Typically, at least 75
percent of the materials pass the #40 sieve and less than 20
percent pass the #200 sieve.. Being primarily silica sands,

4 - 1

the surface materials generally are not subject to liquid lim-
its and are not plastic. The very fine silts and clay com-
ponents and organic matter are typically low within those
soils not subject to periodic and prolonged flooding. Corre-
spondingly, soils with low clay and organic matter content
in the study area tend to be highly permeable and typically
have low available water and low water holding capacities.

Soils with low available water also are less affected by
capillary rise of water in soils. Capillary rise results
from the direct suction of the atmosphere due to differences
in pressure between the air and the soil water. Capillary
rise is more pronounced in soils with higher contents of
clays, silts, and organic materials. A capillary rise of
as much as 18 inches can be expected to occur in clay and
clay loam soils.

In the fine sands typical of the Moultrie Creek watershed,
a capillary rise of less than six inches would be expected.
This phenomenon is an important consideration in roadway
design. Roadway load bearing capability decreases when
the subgrade supporting the road surface becomes saturated.
The result is the familiar cracking of pavements into an alli-
gator hide look. When the surface pavements protecting the
load- bearing subgrade becomes broken through cracking pro-
cesses, the roadway quickly deteriorates.

The alligator cracking roadway deterioration process can be
alleviated by insuring that the bottom of the road subgrade
is built above local high water table conditions. The road
subgrade bottom should be further elevated in fine sandy
soils another 6 or more inches to reduce the soil saturating
effect of capillary rise of water above the height of the an-
nual high local water table.

Roadway construction and repair is a major tax dollar expendi-
ture 'of the St. Johns County government. Review of water ta-
ble conditions, subsoils, subgrade materials, roadway con-
struction procedures, and local area drainage are essential
before the County agrees to accept a privately constructed
roadway system.

The following information provides general guidance on the
natural soils and normal water table conditions found
within the Moultrie Creek watershed. This information also
provides useful guidance for determining the stormwater man-
agement needs within the watershed.

4 - 2

Soil Porosity and Water Storage Capabilities

The ratio of openings or voids between soil particles and
the total volume of the soil matrix is referred to as soil
porosity. Porosity is normally presented as a ratio or per-
centage of void area per total area of the soil matrix. For
sandy soils, total porosity is normally considered as 25
percent of the total soil matrix. Within this 25 percent of
the soil matrix, part of the void space is occupied by
air. The trapped air reduces the potential for water stor-
age in the surface soil materials. Part of the void area
is also occupied by capillary water that is specifically
retained or bound to the soil particles.

In sandy soils, specific retention losses may be estimated
at about 15 percent of the total porosity. For saturated
soils, a generalized estimate of the specific yield of a
sandy soil matrix, or the part of water stored in a soil
that will drain under the influence of gravity, may be esti-
mated at 22 percent of the unit area volume. This percent-
age also provides an approximate estimate of the accessi-
ble water in saturated fine sands. (Center for Environ-
mental Research 1985, Frevert 1955, Resource Control Depart-
ment, SFWMD 1983).

The U. S. Soil Conservation Service provided the following
estimates of soil water storage capability for the normal
sandy soils found within the South Florida Water Management
District. Until different information is established for St.
Johns County, these values provide preliminary guidance
for estimating potential water infiltration volumes into
local fine sand soil matrix areas.

Depth to Water Table Cumulative Water Storage

11 0.611
21 2.511
31 6.611
41 10.91,

The above values are applicable to soils in their natural
state. The cumulative water storage capabilities of sandy
soils that have been compacted intentionally or through
usage, typically those associated with urban activities,
should be reduced by 25 percent. This reduction factor
would be applied to any proposed use of an open area. Con-
sideration of the use of soils occurring under impervious
areas, when calculating an area's water storage potential,
requires still further adjusted estimates. Water can be
introduced beneath impervious areas at reduced percent-

4 - 3

ages, as compared with a natural land area, but only when
sufficient air bleed mechanisms are installed to prevent
trapped air from further reducing the soil water storage po-
tential.

Soil Permeability

soil permeability is the quality of a soil that allows it
to transmit water or air. Permeability refers to the rate at
which water moves through the soil. The term should not be
confused with the perviousness or water storage capabilities
of soil which determines the amount of water that can be
withdrawn from, or stored within, a soil matrix. The perme-
ability of soils is referred to as the percolation rate
when applied to septic tank drain field requirements. Per-
meability is measured by engineers and soil scientists in
terms of the number of inches per hour water will seep or
flow (usually downward by gravity) through a cross section
of soil.

Soil survey data indicate that the surface layers of the
fine sands within the Moultrie Creek watershed would be clas-
sified as having rapid permeabilities (5.00 to 10.00 inches
per hour). The excessively drained soils typical of upland
sand dunes have very rapid permeability rates (over ten
inches per hour). At varying depths below the surface materi-
als, soil permeability data show zones with moderately slow
permeability rates (0.20 to 0.80 inches per hour) in many
of the area's soils.

The upper one or two feet of most soils in the Moultrie
Creek watershed have rapid permeability ratings. At vary-
ing lower depths, permeability becomes moderately slow. The
lower permeability rates may result from confining layers or
saturated soil conditions. In many localities of the Moult-
rie Creek watershed, the surface soils are fully capable of
accepting more than the first one inch of every rainfall
within relatively short periods of time.

The surface soils with zones of lower permeability typically
are associated with depressions, floodplains, and flat-
woods, all areas with naturally high water tables. Zones of
lower soil permeability within these areas often are associ-
ated with the top of local water tables. As water percolates
downward, it carries organic and inorganic sediment fines
largely developed from decomposed and reduced plant materi-
als. Downward percolation of these materials is stopped by
the density of water near the top of the water table. Con-
tinued percolation carrying sediment fines to the vicinity
of the water table gradually clog the pore spaces between the

4 - 4

silica sand materials, reducing permeability. A wide variety
of biological actions and chemical reactions occur to produce
these zones of lower permeability, but the available informa-
tion can be used to generally determine the normal depth to
water table in localities within the watershed.

Once zones of reduced permeability are developed within
sandy soils by the above process, increased soil permeability
in the affected zones can only be increased by perma-
nently reducing water table levels in these areas and by
fracturing or otherwise disturbing the confining zones to re-
establish permeability. Both of these practices have been
widely used in Florida to improve lands for agricultural and
urban development purposes.

Watershed Soils Distribution

Within the numerous shallow depressional areas occurring
throughout the watershed plateau, decomposition of detrital
materials and the transport of these materials with runoff
from locally higher areas to the depressions has resulted
in localized and often isolated accumulations of silts,
clays, and organic materials. Those depressional areas with
significant clay and organic materials accumulations typi-
cally have high water table conditions with ground water
emerging and flooding the depressional areas for extended
periods. Those watershed localities identified in the soil
survey as having water tables rising above, or flooding, land
surfaces part of each year are generally displayed on Figure
4-1. Localities With Water Tables Rising Above Land Level Part
of Each Year.

The areas identified in Figure 4-1 include some of the same
areas described later in this study as significant natural
resource areas. The areas displayed on Figure 4-1 include as
a grouping the following soils series found in St. Johns
County: (A) freshwater depressional areas with muck soils in-
cluding the following soil series: Samsula muck (26), Hon-
toon muck (35), Tomoka muck (41), Bluff sandy clay loam,
frequently flooded (42), and Bakersfield muck (69); and, (B)
freshwater depressional areas with mineral (silica sand) soils
including: Myakka fine sand, depressional (4), St. Johns fine
sand, depressional (5), and Riviera fine sand, depressional
(61). Some of these soils series are not found in the Moult-
rie Creek watershed but are important on a County-wide basis.

soils subject to extended periods of flooding annually can
be identified by accumulations of dark colored organic mat-
ter as peat or muck, a predominance of mottling with dark
brown and grey colors staining the normally light colored

4 - 5

Figure 4-1. Localities With Water Tables
Rising Above Land Level Part of Each Year

a 1E
D R 16

ST G

'g; -r rJA -LJ
smo E;S

R)
C1

SCALE: 110,000

LEGEND:

PROJECT UPLAND DEPRESSIONS (MUCK SOILS)
LOCATION
p R'0
UPLAND DEPRESSIONS (SANDY SOILS)
D.E.R. CONTRACT NO. 7CM 2117]-,,4 TIDAL AREA SOILS
ST. JOHNS COUNTY ENGINEERING DEPARTMENT - GEOGRAPHIC INFORNATION SYSTEM

natural sands, or the characteristic dark grey color of iron
accumulating under anaerobic conditions characteristic of
saturated or flooded soils. Red stained soils are charac-
teristic of iron accumulations after oxidation of the iron
has taken place. The generalized soil characteristics of
soils subject to periodic flooding also can be used to iden-
tify soils that serve as shallow drainageways connecting
larger depressions to more clearly defined stream channels.

Also included in Figure 4-1 are tidal area soils. These soils
are flooded periodically due to tide conditions. Tidal area
soils and immediately adjacent areas are subject to accas-
sional storm tides reaching elevations of 8 and 9 feet above
mean sea level in Moultrie Creek. Soils found in tidal areas
are: Pellicer silty clay loam, frequently flooded (24), Moult-
rie fine sand, frequently flooded (49), Durbin muck, fre-
quently flooded (52), and Tisonia mucky peat, frequently
flooded (67).

The Moultrie Creek watershed has a poorly defined natural
drainage system. Figure 4-1, above, displayed those
fresh water areas normally flooded for parts of each year.
Many of the soil series that identify shallow drainageways
carry surface water as runoff only following rare, very
heavy rainfalls. In character with poorly drained flatwoods
soils, the shallow drainageway soils tend to become fully
saturated during part of each year as a result of high water
table conditions. Some of these soils are also found on the
floodplains of established streams.

Figure 4-2. Annually Flooded Soils and Drainageway Soils,
displays the relationship of annually flooded soils with
natural drainageway soils. The soils displayed in Figure 4-1
appear in Figure 4-2 grouped as upland annually flooded
soils. Also displayed in Figure 4-2 as a second group are
the soil series classified as shallow drainageway soils in
St. Johns County including: Floridana fine sand, frequently
flooded (18), Pompano fine sand (19), Manatee fine sandy loam,
frequently flooded (22), Parkwood fine sandy loam, frequently
flooded (25), Wesconnett fine sand, frequently flooded (30),
Riviera fine sand, frequently flooded (36),Tomoka muck (41),
Bluff sandy clay loam, frequently flooded (42) (a muck soil of
drainageways and floodplains), Holopaw fine sand, frequently
flooded (47), winder fine sand, frequently flooded (48), and,
Terra Ceia muck, frequently flooded (66) (a deep muck found on
the floodplains of rivers and streams). Some of these soil
series are not found in the Moultrie Creek watershed but are
important on a County-wide basis.

Figure 4-2 provides a generalized display of the natural sur-
face water storage and drainageway system in the Moultrie

4 - 7

F
Tyure 4-2. Annually Flooded
Soils and Drainageway Soils

C) v
ST A

ST A
so u: 7r
cl

CRY.

t
AU C; INE
0
u,

SCALE: 110,000

LECEND:

UPLAND ANNUALLY FLOODED SOILS
iocmu

DRAINAGEWAY SOILS
Dl-R. CONTRACT NO. CAf 2717
ST. JOHNS COUNTY ENGI.IVEER[NC DEPARTMENT - GEOGRAPHIC INFORMATION SYSTEM

Creek watershed. Adjacent to this system are poorly drain-
ed drainageway fringe and flatwoods soils. Figure 4-3.
Floodprone/Drainageway Soils and Naturally Saturated Soils,
displays the relationship of the natural surface water stor-
age and drainageway system with the drainageway fringe and
flatwoods soils. These soils typically become saturated dur-
ing a part of each year or have water table waters rising to,
or within one foot below, the land surface. Naturally satu-
rated soils identified in the soil survey include: Myakka fine
sand (3), Immokalee fine sand (7), Pomona fine sand (9),
Smyrna fine sand (11), Ona fine sand (12), St. Johns fine sand
(13), Floridana fine sand, frequently flooded (18), Pompano
fine sand (19), Wabasso fine sand (21), Manatee fine sandy
loam, frequently flooded (22), Parkwood fine sandy loam, fre-
quently flooded (25), Wesconnett fine sand, frequently flooded
(30), Tocoi fine sand (34), Riviera fine sand, frequently
flooded (36),Pottsburg fine sand (40), Bluff sandy clay loam,
frequently flooded (42), Holopaw fine sand (46), Holopaw fine
sand, frequently flooded (47), Winder fine sand, frequently
flooded (48), Immokalee-Urban land complex (53), Eau Gallie
fine sand (58), Floridana fine sand (62), Placid fine sand
(63), Ellzey fine sand (64), Riviera fine sand (65), Terra
Ceia muck, frequently flooded (66), and Winder fine sand (68).

Any developed use (including roadways, buildings and other fa-
cilities or structures) on the drainageway fringe and
flatwoods soils will require control of, or consideration for,
the annual rise of the water table. Any effort to drain
these lands should be undertaken with a full understanding of
the long range impact of total area development drainage upon
local ground water table conditions, the potential decline
of surficial aquifer water supplies, and the resulting
potential of increased salt water intrusion from the Flori-
dan aquifer and sea water into the surficial aquifer.

Under significant rainfall events, flatwoods areas also
are affected by extensive, shallow flooding. Historical de-
velopment practices have simply resorted to ditching and
draining. Some draining combined with adequate deten-
tion/retention storage systems, controlled drainage systems,
and a variety of development control measures can provide
for development in flatwoods areas of the Moultrie Creek
watershed and still protect the area's ground water re-
sources and significant natural areas.

Based upon soil survey information, significant parts of the
Moultrie Creek watershed are free of potential flooding or can
be developed with minimum negative impact upon ground water
table conditions. Figure 4-4. Well To Excessively Drained
Soils displays those soil series within the watershed with
well to excessively drained soils and local water table con-

4 - 9

Figure 4-3. Annually Flooded/Drainageway
Soils And Naturally Saturated Soils

9 1E

SR 16 SD 0

-Sr

g-b"-A C;

Ogg

SCALE: f 10,000

LEGEND:

PROarr UPLAND ANNUALLY FLOOD EDID RAINAGEffAY SOILS
LOCATION NATURALLY SATURATED SOILS

*(ANNUAL WATER TABLE RISES TO WITHIN
D.E.R. CONTRACT NO. CM2171 I FOOT OF LAND SURFACE)
ST. JOHNS COUNTY ENGINEERING DEPARTMENT - GEOGRAPHIC INFORMATION SYSTEM

Figure 4-4. Well To Ercessively Drained Soils

SR Is

(7ST A.

tip

STIT*J

R 2

SCALE@ 1 10,000

LECEND:

SOILS WITH WATER TABLES 1.5 TO 6 FEET
I.OrArl
BELOW LAND SURFACE

SOILS WITH WATER TABLES MORE THAN
D.E.R. CONTRACT NO. CM2f7 6 FEET BELOW LAND SURFACE

ST. JOHNS COUNTY ENCINEERING DEPARTMENT GEOGRAPHIC INFORMATION SYSTEM

ditions where ground water does not reach the land surface.
The group of soils identified as having ground water tables
more than six feet below ground surface include: Astatula
fine sand, 0 to 8 percent slopes (2), Paola fine sand, 0 to 8
percent slopes (23), Fripp-Satellite complex (31), Palm Beach
sand, 0 to 5 percent slopes (32), and, Astatula Urban land
complex (54). These soils occur along the plateau edge and the
tidal portions of Moultrie Creek and the Matanzas River.
The plateau in this locality is 20 or more feet above sea
level. The water table is well below ground level because the
ground water is flowing by gravity to sea level and emerges as
seepage where the land merges with the tidal flats.

Further inland along Moultrie Creek and upstream of tidal in-
fluence, the incised stream course occurs at elevations rang-
ing from sea level at tidewater to less than 15 feet at
State Road 207. The average plateau land surface throughout
this area is at an elevation of nearly 30 feet. The gravity
flow of ground water in this part of the watershed would be
towards the lower land elevation of the stream bed with a re-
sultant effect of a significantly lowered ground water ta-
ble in areas adjacent to the stream course.

Inland and upstream along Moultrie Creek from the localities
with water tables at least six feet below the land surface
are soils with intermediate depth water tables. Figure 4-4
displays as a second group the soils with water tables at
least 1.5 feet below land surface. In St. Johns County, these
soils include: Adamsville fine sand (1), Tavares fine sand, 0
to 5 percent slopes (6), Zolofo fine sand (8), Cassia fine
sand (14), Pomello fine sand, 0 to 5 percent slopes (15), Ors-
ino fine sand, 0 to 5 percent slopes (16), St. Augustine fine
sand (27), Satellite fine sand (29), Jonathan fine sand (33),
Sparr fine sand, 0 to 5 percent slopes (44), St. Augustine
fine sand, clayey substratum (45), Narcoossee fine sand,
shelly substratum (50), St. Augustine-Urban land complex (51),
and Adamsville Variant fine sand (57). Some of these soils
may not occur within the Moultrie Creek watershed, but are
important for County-wide application.

The soils having intermediate height water tables occur be-
tween the more poorly drained flatwoods soils and the exces-
sively drained soils. The water table heights probably are
controlled by the natural slope of the water table as the
ground water flows by gravity from the highly saturated in-
terior soils of the plateau towards lower land surface eleva-
tions along Moultrie Creek and finally to tidewater and sea
level.

4 - 12

RAINFALL CONTRIBUTIONS TO GROUND WATER

Infiltration and Percolation

As rainfall occurs, part of the rainwater infiltrates or
seeps into the soil. once in the soil, it moves by gravity
or percolates downward to the water table. The rate at which
the water is able to move through the soil matrix is referred
to as the soil permeability. The terms soil permeability and
soil hydraulic conductivity are essentially the same.

The rate at which rainfall infiltrates into the soil varies
with soil structure, soil compactness, and the degree of
wetness of the surface soil particles. Water can move more
rapidly into course sands than into fine sands because of
the larger void areas between the particles in the course
sands. Water infiltrates very slowly into soils high in
very fine silt and clay particles. Recently disturbed or
broken soil surfaces permit more rapid water infiltration
than well compacted or undisturbed soils. When soil sur-
faces are completely dry, water tends to bead on the soil
particles until the weak electromagnetic bond between the
soil and air molecules is broken. The time required for
this process to take place varies with different types of
soils, temperature conditions, and with the degree of dryness
of the soil.

Percolation within the soil matrix is also dependent upon
soil wetness. Water moves more rapidly through wet soils. If
soil is allowed to dry out to significant depths, percola-
tion will be slowed until the soil matrix becomes thoroughly
wet.

Urban area soils tend to be compacted, and when overdrained,
the soil surface and upper several inches of soil can become
extremely dry, with temporarily reduced permeability. In
Florida's sandy soils, a vegetation cover retards the soil
drying process by shading the soil surface and by lifting wa-
ter from lower elevations through the plants' root system.
The vegetation mat of detrital material and the decomposed or-
ganic matter in the upper soil horizon provide the means for
sandy soils to hold water. The water, in turn, slows down the
oxidation rate of the organic fraction of the surface soil ma-
trix.

Unshaded sands can become dry to depths of six or more
inches during the spring and summer months within a week or so
following a rainfall. When these conditions are allowed to
occur, rainfall that does not pond for a sufficient time for
the infiltration process to occur must runoff. Under these

4 - 13

conditions, the typically short-duration, relatively intense,
annually occurring summer showers contribution to ground
water recharge requirements can become very limited.

Water Table Conditions

General Concepts

Water that percolates downward continues to move to a point
where gravity forces and forces associated with 6apillary wa-
ter movement, or suction forces, become balanced. If enough
water enters the soil, it eventually percolates to the water
table, the natural level within the soil mantle or matrix be-
low which all voids between soil particles contain water. In
most parts of St. Johns County, the water table is also the
effective top of the surficial aquifer.

The water table beneath the Moultrie Creek watershed is not a
flat surface. Under every knoll or ridge, the water table
is higher than under swales or depressions. Rainfall on
knolls and ridges percolates to the soil matrix saturation
zone directly beneath the knoll or ridge land surface. These
localities, being at higher elevations, are the primary ground
water recharge areas within the County. From the saturated
soil zones under knolls and ridges, the ground water moves
by gravity along a hydraulic gradient to the saturated soil
zones of land surfaces with lower land elevations. The lower
land surfaces may be natural swales, or larger depressions.

When depressions have standing water, the elevations of that
standing water generally reflect the height of the local wa-
ter table. The wet edges of the depressions identify the
seepage points from which ground water is slowly moving down-
ward along a hydraulic gradient from beneath adjacent knolls
and ridges and is emerging as surface water in the depression.

The movement of ground water and seepage is generally imper-
ceptible, except during periods immediately following heavy
rainfalls on the adjacent uplands. Whenever wet perimeters
or seepage zones are observable along edges of depressions,
the water table under adjacent uplands is higher than the ob-
served seepage zone.

The hydraulic gradient or slope created by the water under up-
land areas flowing to depressions is steepest immediately fol-
lowing periods of high infiltration rainfalls. Gradually, the
mounded ground water decreases in height as it is lost to
seepage and other factors. As the height of the water be-
comes reduced and the slope to the seepage point is lowered,
the movement or flow of the ground water also diminishes.

4 - 14

As a result of the above process, the ground water table is in
a continual state of fluctuation. Every major rainfall allows
some water to infiltrate. Repeated moderate rainfalls of in-
tensities low enough to allow infiltration to take place can
provide significant recharge to the water table. Because
soils accept water slowly, intense rainfalls result in high
runoff from the land and the water is largely lost relative
to ground water recharge needs.

At the opposite extreme, prolonged drought periods typi-
cally result in a progressive decline in the height of
the water table. Based upon St. Johns County Soil Survey
information, natural water table fluctuations on the order of
three or more feet are normal each year beneath flatwoods
soils. The ground water is always moving along some hydrau-
lic gradient to points of lower land elevation.

Moultrie Creek Effects

The stream bed of Moultrie Creek is the most significant low
land surface point within the interior part of the basin.
Unless repeated recharge occurs at land elevations adjacent to
and extending from Moultrie Creek, prolonged drought condi-
tions can result in significantly lowered ground water ta-
bles extending outward on either side of the incised por-
tions of the Moultrie Creek stream course. The lowered
ground water table and excessively drained soil conditions
in the watershed noted in the Soil Survey are directly
related to the affected soils' close proximity to the lowest
land elevations along Moultrie Creek and the Matanzas River.

Uncontrolled drainage directed to Moultrie Creek removes
stormwater before it can infiltrate and provide recharge to
the ground water. Because this water has been diverted, the
source of water that permits extended base flow in Moultrie
Creek is being eliminated. As this base flow and the general
ground water table is allowed to decline in the vicinity of
Moultrie Creek, salt water can be expected to move slowly into
those areas previously supplied by the gradual movement of
ground water from areas of higher elevation.

During normal seasonal low elevation periods of the water ta-
ble, surface water in the fresh water natural resource areas
(depressions and natural drainageways) become lowered or dis-
appear. As long as the bottom materials of these areas remain
moistf the natural regeneration of vegetation in these areas
can continue. If, however, extended drought conditions oc-
cur, new growth and young plants with shallow roots can be
lost. An uncontrolled drainage program that permanently

4 - 15

lowers the water table beneath these areas will also pre-
vent any regeneration of new growth. The natural area
will then begin a transitional process where vegetation that
can sustain itself with less water will begin to replace the
original species.

Perched Water Tables

The extent of perched water table conditions within the water-
shed is unknown. A perched water table usually occurs in a
depressional area where local conditions prevent downward
percolation of ground water to the area-wide water table.
When the general area water table permanently falls below the
bottom elevation of a depressional area and wet soils in the
depression persist, the condition is representative of a
perched, and highly localized, water table. These areas typ-
ically reflect former natural water table conditions.

Upland depressional areas tend to accumulate detrital mate-
rials and sediment fines that are transported with runoff from
adjacent lands of higher elevations. Chemical and bacterial
action within the depressional environments act to convert
organic materials into fine organic and inorganic compounds
and combine the compounds into stable, often denser materials.

As a result of the above processes, dense and relatively im-
pervious clays tend to underlay depressions with continually
saturated soils. Where this phenomenon occurs, a periodic
water table decline below the bottom of the depression may
have a delayed impact on the vegetation growth cycle in the
depression. To the degree that thick water holding materials
can be maintained in such depressions, existing vegetation
characteristics can be maintained for long periods of time.
Maintenance or restoration of perched water table areas re-
quires the application of sufficient water to reestablish
near natural hydroperiod conditions.

Water Table Management

Initial Considerations

For development purposes, the height of the water table in
local areas must be known, and the height to which the water
table is to be maintained must be determined. The Soil
Survey information provides general information on the natu-
ral height of water table conditions for specific series of
soils. Correlation of this information with one foot con-
tour information will provide guidance for determining natu-
ral water table heights and seasonal variations , of these

4 - 16

heights. Once governmental policy determines the area fea-
tures and ground water conditions essential for residents'
health and welfare, engineering analysis can establish the
criteria and methods for accomplishing the policy decisions.

Development Alternatives

Unless specifically designed for high water table conditions,
all load bearing foundations of structures and subbases of
roadways must remain above normal water table heights to re-
tain structural integrity. As noted previously, normal cap-
illary rise of water in sands with some fines will normally
be less than six inches. Therefore, as a minimum engineering
requirement, the bases of roadways and foundations should be
at least six inches above expected annual heights of local
water tables. Under those conditions where road bases are
close to the annual high water table, road base and foundation
designs would have to accommodate the reduced load bearing
capabilities of periodically saturated soil conditions.

Four courses of action are open for development on high water
table soils. Traditional practices consist of permanent low-
ering the water table by positive and uncontrolled drainage.
This practice results in the total drying of surface soils
during seasonal and extended drought periods.

The second course of action consists of the recontouring
and raising of the land beneath all load bearing facili-
ties. The bases of both roadways and structure foundations
can be raised. In both cases, the practice of constructing
roads and structure foundations on compacted non-plastic
fill materials is now common in Florida. Monolithic home
slabs constructed on three and four feet of compacted fill
have become routine construction practice in some Florida
communities. Raising roads above 100-year flood elevations
ensures user safety during flooding emergencies and provides
for emergency vehicle access to and from flood prone areas.

A third option consists of the specific design of road bases
and foundations for high water table conditions. Under heavy
loads, saturated fine sands can move very rapidly from a
nonplastic material to a liquid state with greatly reduced
load bearing capability. Hydrated lime mixtures with added
fines have been successfully used to stabilize saturated
fine sand soils in Florida. Soil cement mixtures are
also usable when the water content of the soil can be
carefully controlled during the curing process. As with
hydrated lime stabilization, soil cement requires the addi-
tion of some fines to achieve sufficient load bearing
strength. Spread footings of soil cement or hydrated lime

4 - 17

also can be used as bases for structure foundations in wet
areas.

A fourth option consists of mixtures of the first three ap-
proaches. In upper flatwood soils areas, some lowering of
the ground water table may be possible without signifi-
cantly impacting overall water table conditions. In lower
flatwoods and drainageway soils areas, however, positive
drainage could be expected to negatively impact the water
table, and compacted fill practices would be necessary.
For example, the placement of two feet of compacted fill to
raise roadways and two feet of compacted fill for house pads
(an elevated base upon which concrete house slabs are plac-
ed) would eliminate most property flooding potentials, pro-
vide for safe road access to properties, and provide for
temporary water storage in remaining open areas during the in-
frequent heavy rainfalls characteristic to Florida. Where de-
velopment is essential and fill practices cannot provide sat-
isfactory results, design practices for high water table
conditions may become necessary.

Public and Private Property Owner Concerns

Because of generally lower initial costs, positive and un-
controlled drainage to permanently lower water tables is a
preferred action by developers, while designing for building
and roadway structural integrity, safe use of roadways and
access to properties during infrequently heavy rainfalls,
and storage of stormwater in areas of high water table or
saturated soil conditions have higher associated development
costs. The County's concern is the integrity of the con-
struction practices for the long-term health and welfare of
citizens. It remains for private entrepreneurs to determine
whether the costs of proposed developments achieve required
short term profitability. The County is also concerned
about the costs of infrastructural repair and maintenance.
For example, a roadway constructed as a private venture can
only be accepted as a public facility when the County can be
assured that sound engineering practices are followed by
the constructor of that road.

Management Criteria

The natural annual fluctuation of localized area water
table heights provides the best general guidance available
for establishing criteria for the design of stormwater
management systems in high water table areas. The annual low
elevation of the water table in high water table locali-
ties reflects the maximum safe depths for constructing

4 - 18

drainageways and channels. The annual high elevation of the
water table in high water table localities reflects the low-
est elevation at which water storage containment facilities
can be assured of functioning at complete capacity throughout
the year. Design of stormwater management facilities to
these criteria will assure the maximum possible protection
to the surficial aquifer and significant natural resource
areas.

simplifying the above and providing for a standardized proce-
dure for the entire County is necessary. Any parcel pro-
posed for development in the County should have the maximum
and minimum land elevation of that parcel and immediately
adjacent parcels established. The points of maximum and min-
imum should be identified and clearly marked on the develop-
ment drainage plan. Large parcels and parcels with signifi-
cant land contour changes would need determinations by seg-
ments with common characteristics. Using this information,
the localities on the parcel representing the mean land ele-
vation should be presented. This process will establish the
natural sheet flow, infiltration, water table, and ground wa-
ter hydraulic gradient tendencies of a parcel.

The annual high water table will be assumed to extend to
within one foot of the land surface at the parcel's mean land
elevation unless Soil Survey data or documentation by a regis-
tered engineer are provided to establish a different natural
annual high water table elevation for critical segments of
parcels. An approved annual high water table condition for
the parcel or delineated segments will be used as the base
elevation for the design of stormwater containment facilities.

4 19

STORMWATER STORAGE

WATER CONTAINMENT

General Considerations

Depressional areas represent natural rain water storage loca-
tions within a watershed. As these areas become filled,
the water begins to move via a drainageway to some nearby de-
pression or to a stream course. A primary focus of drainage
engineering is the estimation of the amount of water likely
to runoff from a watershed under some given rainfall condi-
tion and the design of some water control works to safely
move the runoff from one place to another.

Stormwater management oriented towards the most useful reten-
tion of water for ground water recharge and significant natu-
ral area protection has a different engineering focus.
These purposes require the design of storage facilities to
retain runoff from normal rainfalls expected on an annual
basis. once this requirement is met, the overflow water from
the infrequent and heavier rainfalls must be detained and
safely removed at controlled rates to avoid significant ero-
sion and sedimentation damages to receiving water areas.

In hydrological analyses of potential runoff from a water-
shed, estimates are made of the amount of rainfall received by
a watershed that is retained or lost before runoff begins.
This initial retained or lost amount is referred to as the
initial abstraction, a best initial estimate of water losses
due to water storage and other factors to be subtracted from
the calculated runoff. For normal or non-compacted soils,
the U. S. Soil Conservation uses an estimate of 0.2 inches as
an initial abstraction estimate. The drainage engineer's
efforts then focus upon the additional rainfall amount that
produces runoff water and how to design water control struc-
tures to accommodate such flows.

Part of the water lost to runoff through storage on the
land infiltrates into the soil matrix and is gained by the
ground water storage system. Revisions in drainage system de-

5 - 1

sign criteria are required to give greater emphasis to the
retention of normal annual rainfalls while still providing
for removal of unusual or infrequent rainfall events. Engi-
neering analysis to determine the greatest beneficial uses
of stormwater prior to runoff has now become the area of
concern in the design of stormwater management systems.

Stormwater Containment Purposes

Detention/retention storage or containment for ground water
supply recharge through infiltration must be emphasized in
the vicinity of the land surface areas beneath which surficial
aquifer water is withdrawn. As water is withdrawn from the
surficial aquifer at depths of 90 or 100 feet below land
surface, water moves slowly towards the well head from all
directions. The pumpage effects cause a lower water pres-
sure to develop at the well head. As more water is with-
drawn, a decreased pressure zone forms from the well head as
the apex, the area of decreased pressure, extends outward and
upward towards the land surface with an expanding circumfer-
ence creating the general form of a cone. This is called the
cone of depression for that well, and ground water moves from
all points with greater amounts of water at higher pres-
sures towards the apex of the cone. As the cone of de-
pression extends to the land surface, the water table within
that cone of depression declines, and the overlying surface
soils begin to dry out.

The size of the cone of depression depends upon the well size
and withdrawal rates. Major agricultural and municipal system
wells may be expected to measurably influence water tables
in sandy soils for distances of 1,000 or more feet from the
well. Without adequate recharge, the water table declines
can become progressively extended over larger areas. In-
creasing storage of stormwater and the diversion of storm-
water towards cones of depressions are essential if the lo-
cally severe water table declines in the vicinities of large
well fields are to be avoided.

Protection of significant natural areas in uplands can be
accomplished through control of water table conditions. Main-
tenance of high water tables requires retention and detention
storage and control of runoff. Increased use of stormwater
storage facilities designed to retain most of the expected
annual rainfall can provide long-term protection of natural
water table conditions. continuation of positive drainage pro-
grams in the interior flatwood soil areas of the Moultrie
Creek watershed will result in the gradual drying of nearby
depressional areas.

5 - 2

In areas with excessively drained soils and where septic
tanks are used, detention/retention storage and subsequent
infiltration can be expected to augment the diffusion of
septic tank effluents that can percolate towards the water
table. Most of these areas occur along the tidal portions
of Moultrie Creek and the Matanzas River. Numerous indi-
viduals within these areas also use private wells, some
which may serve as sources of potable water. Two ground wa-
ter problems are apparent in this part of the watershed. As
development increases and more people utilize individual
wells, water withdrawals can be expected to exceed natural
recharge capabilities in local areas. As this occurs, as it
has in communities all around coastal Florida, saline ocean
water will move into the composite cones of depression
formed by the close groupings of the withdrawal wells.

The second problem is public health related. Water wells in
the surficial aquifer are typically drilled to depths of
less than 100 feet. As the cone of depression formed by a
single well or a close grouping of wells approaches the land
surface, septic tank effluents will be drawn downward.
Septic tank drain fields function by distributing efflu-
ents into the upper 18 inches of the soil matrix where
aerobic bacteria can render pathogens harmless. The pro-
cess requires that the effluents remain in the upper soil
zones for some extended period of time for the soil bacteria
to render them harmless.

Numerous studies have been conducted around the country il-
lustrating that some pathogens can remain viable for many
days and weeks under anaerobic conditions characteristic of
saturated soil matrix materials in the surficial aquifer.
Excessive water withdrawals can lead to the introduction
of these pathogenic materials into the well water withdrawn
from the aquifer.

Finally, numerous studies nationwide have determined that
stormwater detention/retention facilities can help reduce pol-
lutant loads characteristically found in urban runoff. The
Florida Department of Environmental Regulation has es-
tablished a state policy for the retention of the first one
half inch of runoff from storms.

Stormwater Containment Criteria

In an effort to reduce the water pollution impacts of storm-
water runoff upon lower property owners, public stormwater
conveyance facilities, and as a water pollution reduction mea-
sure, St. Johns County has adopted the following stormwater
containment measures. Any parcel proposed for commercial or

5 3

industrial use and any parcel proposed for use as a resi-
dential subdivision is required to provide retention fa-
cilities for stormwater. A single containment facility or
the composite capacity of several facilities will be sized to
accept a volume of water equivalent to the greater volume
of either one half inch of runoff water distributed across
the entire parcel or one inch of runoff water distributed
across the total impervious area within the parcel.

Under primarily rural development conditions, the above con-
tainment measures would provide some protection for water el-
evations in the surficial aquifer where extensive posi-
tive surface water drainage had not been practiced. Under
the population increases occurring within the County and pro-
jected populations in the immediate future, the above crite-
ria can be expected to result in a continued decline in water
tables and long term water supply potentials of the surficial
aquifer.

As an immediate measure, retention facilities designed to
store the first one inch of every rainfall from the drainage
area of that facility would more adequately serve water
pollution control, water supply recharge, and significant
natural resource area requirements. on larger land par-
cels, a number of small retention facilities would provide a
distributed and more effective system for ground water re-
charge than a single large retention facility. The poten-
tial benefits of storing the first one inch of rainfall appear
in Table 2-2.

Storing the first one inch of every rainfall on developed
properties should be considered as an interim and minimum wa-
ter resource protection measure. The preliminary informa-
tion presented in this report suggests that more stringent
measures actually may be necessary to assure the long-term
viability of the County's water resources. More detailed
studies of the County's total water resource needs will be
needed to make that determination.

Preliminary Design Concepts

In recent years, stormwater detention and retention facili-
ties have been incorporated into the stormwater control design
process. As definitions for use in this study, a detention
facility is designed for the collection and temporary storage
of stormwater to provide for treatment with subsequent gradual
release of the stormwater. A retention facility is designed
to prevent the discharge of a given volume of stormwater run-
off by complete on-site storage. These definitions are now

5 - 4

being used with increased frequency by urban hydrology spe-
cialists in Florida.

A detention facility will have an outlet designed to re-
lease stormwater at controlled rates from some defined rain-
fall for the design drainage area until full draw down occurs
near the end of the design period. A retention facility
has no controlled outlet but extends the draw down period by
percolating stormwater runoff into the soil. In both cases,
the effective stormwater containment capacity of each facility
is based upon an available containment area above the
height of the seasonal high water table conditions for the es-
ign drainage area.

The focus of most research on urban stormwater detention/re-
tention facilities has been oriented towards their effective-
ness in reducing the impacts of pollutants in stormwater run-
off. Reducing the impacts of pollutants in stormwater run-
off through detention/retention is an important consideration
for justifying the use of these types of facilities. This
purpose applies to the entire Moultrie Creek watershed.

Stormwater detention and retention facilities can be built in
a wide variety of forms. They can be built to replicate
natural depressions characteristic of an area. In devel-
opments near significant upland natural areas, it may be
possible to divert some stormwater into natural depres-
sions. Depressional areas can be constructed adjacent to
natural drainageways or depressions to augment the vegeta-
tive environment of the natural areas. Overflow channels in
developments can be built to simulate the characteristics of
natural drainageways. They can be part of golf courses,
parks, and constructed semi-natural woodlands. They can be
slightly depressed areas of lawns, or gardens on individual
properties. They can be designed as extensions to existing
ponds or lakes with controlled release structures. Stormwa-
ter storage areas can be well landscaped earthen areas of al-
most any description or they can be concrete boxes simply
built to hold rainwater. Stormwater can be retained or de-
tained on the roofs of buildings, in containers constructed
alongside buildings, or in galleried or entrenched areas un-
der parking lots and driveways. All of these practices are
technically possible.

The design of stormwater detention/retention facilities re-
quires engineering evaluations of probable impacts upon col-
lector drainage systems and receiving streams. The Engi-
neering Department must have a reasonably clear understanding
of the water carrying capacities of the larger systems into
which storage facilities gradually release stormwater. Col-
lector systems in low water table areas will be designed to

5 - 5

provide for ground water recharge while accepting controlled
release stormwater from a system of smaller storage facili-
ties. In high water table areas, collector systems will drain
to larger storage facilities before releasing stormwater to
receiving streams, natural drainageways, or natural depres-
sion areas.

Maintenance Considerations

Surface water containment facilities require maintenance in
order to retain the effectiveness of their intended func-
tions. Stormwater detention/retention facilities need to be
cleaned periodically. Numerous examples are now apparent
of facilities constructed below seepage zones permitting
extensive growths of cattails and related vegetation. Cat-
tails grow prodigiously in saturated soils, and their detri-
tal materials quickly accumulate. Where allowed to become
established, expanses of cattails quickly reduce the effec-
tive storage capacities of open containment facilities.

Vegetation growth in constructed detention/retention facili-
ties is to be expected, and the facilities must be sized on
the basis of the expected reduction in capacity due to de-
trital and sediment materials buildup over a projected time-
frame between clean out periods. Additionally, the entities
responsible for maintenance of these facilities must be de-
termined prior to establishment. Access and adequate right-
of-way for maintenance and inspection equipment also must
be part of facility design. Finally, measures for assuring
that maintenance actually will be performed are needed.

Various types of exfiltration procedures have been used
for distributing stormwater. Exfiltration techniques include
buried perforated storm drains surrounded by highly permeable
material that would allow rapid water percolation. Experience
shows that the silts and clays associated with the fine
sands typically found in St. Johns County are easily
eroded and are carried with high velocity flows of stormwater.
These materials quickly plug storm sewer drain perforation lo-
cations and the surrounding exfiltration material. Because
storm sewers are buried, inspection is usually not possi-
ble and maintenance of perforation locations in the sewer
lines is not practical. When these facilities cease to func-
tion effectively, lower property owners can be subjected to
unwarranted discharges of stormwater from higher property
owners.

Exfiltration facilities include French drains and all sim-
ilar techniques. Use of these methods require periodic
maintenance, and their design must accommodate these rou-

5 - 6

tine needs. Wide variety in the design of containment
systems is possible, and their use is practical when de-
signed to permit easy and periodic maintenance. Buried
storm sewers intended for exfiltration purposes cannot be
inspected easily, cannot be effectively maintained as an ex-
filtration system, and will not be permitted.

Example Design Concepts

� one acre parcel of land is an area with 43,560 square feet.
� one fourth acre parcel contains 10,890 square feet. one
inch of water distributed across a one fourth acre parcel is
equivalent to 907.5 cubic feet of water. This volume of wa-
ter can be contained in a shallow depression one foot deep,
10 feet wide, and 100 feet long. one side of a typical one
fourth acre lot is often about 100 feet long, and a typical
drainage easement on a parcel is 20 feet wide. A one inch
storage requirement can be provided for by property owners
with little modification to existing subdivision regula-
tions. The one inch containment requirement can be met
through a single shallow swale or it can be met through
very shallow depression contoured areas within lawn ex-
panses. It also can be met by constructed containers.of any
configuration.

In subdivisions, road rights-of-way, sidewalks, and normal
stormwater systems typically use between one fourth and one
third of the total pre-subdivided parcel. On the basis of
a one acre parcel subdivided into three building lots, the
developer would have to provide for the one inch containment
equivalent to one fourth acre as part of the total infra-
structural system. Numerous techniques can be devised at
moderate costs for accomplishing this containment criteria.
For larger subdivisions, numerous widely dispersed contain-
ment areas designed as part of the landscape provide the
greatest benefits for ground water recharge. Much of the cost
for constructed open space areas (recreation areas, parks,
woodlands, lawn expanses, flower gardens, and entranceways)
can be designed so that the composite of all areas are equiva-
lent to the one inch stormwater volume criteria for the total
parcel.

Natural Depressional Areas

Potential Uses for Stormwater Containment

Natural depressional areas may be useful for stormwater stor-
age under specific and controlled conditions. When these ar-
eas contain wetland vegetation and are classified as sig-

5 - 7

nificant natural resource areas, acceptable stormwater loading
rates will have to be determined. Existing wetland vege-
tation exists in specific areas due to present climatic con-
ditions and the resulting natural hydroperiod regime. The
hydroperiod regime consists of a natural rise and fall of
water on a periodic basis within the locality with desirable
wetland vegetation.

The natural hydroperiod of specific depressional areas
with desirable wetland vegetation is difficult to determine
with any degree of precision. Depressional areas in the
Moultrie Creek watershed typically have poorly defined bound-
ary conditions; the land surface slopes towards adjacent up-
lands very gradually from low points within depressional ar-
eas.

Technical determination of boundary areas can be made when
an acceptable high water elevation for desired wetland
vegetation protection for a specific area is determined.
The acceptable high water elevation determination is a judg-
mental decision. A typical practice is to look for evi-
dence of annual high water marks and vestiges of higher
water marks on woody vegetation. Once the field evidence
establishes preferred high and low water heights, a survey
can establish the controlling water elevation and range of
acceptable elevations for that depression.

Survey procedures then can establish the land elevation
of acceptable high water conditions and the cross sectional
character of the depressional area containing the desired
wetland vegetation. Available aerial photogrammetry and spa-
tial analysis techniques (geographic information system pro-
cedures) then can be used to delineate the area encom-
passed within the specified elevations of the high water
condition area.

The next step requires the determination of the areal extent
of the natural watershed draining to the depression of con-
cern. For smaller depressions a volumetric analysis can pro-
vide an estimate of the volume of runoff water supplied to
the depression from storms of specific return frequencies.
This analysis will establish the height of water rise (water
stage) to expect in the depression from some design rainfall
and the resultant approximate expansion of water surface
area of the depression.

Using available evapotranspirational data and infiltration
rates for the soil conditions characteristic of the de-
pression, an average surface water recession rate can be es-
tablished for the design rainfall condition. The recession
rate data establishes time durations expected for the sur-

5 - 8

face water to remain at specific water stages and the total
length of time required for the water surface to fall to
some specified elevation.

Once these data are available, a judgment decision must be
made to estimate the maximum height and duration of flood-
ing that would be acceptable without causing significant
injury to the desirable vegetation. The comparison of this
judgmental decision and the natural runoff water estimates
will determine the volume of additional water under given
storm conditions that could be supplied to the depressional
area.

Legal Considerations

Some of the major depressional areas in the Moultrie Creek
watershed (examples are Cowan Swamp and Trestle Swamp), have
been parceled and are now in multiple private ownership. A
number of residences have been constructed on platted
parcels within some natural depressional areas. Care must
be taken when considering the discharge of stormwater into
depressional areas to guard against injuring other land-
owners. The legal implications of modifying the natural
flow of water to large natural depressional areas in multiple
ownership are complex. The lower infiltration rates to be
expected in depressional areas due to natural soil matrix
characteristics and naturally high water table conditions
contribute to prolonged periods of natural flooding in
these areas. The use of depressional areas held in multiple
ownership cannot be recommended as receiving areas for in-
creased stormwater discharges until all property owners are
in agreement with the proposed action (As an initial refer-
ence on legal ramifications, see Maloney, 1980).

5 9

WATER LOSSES

EVAPOTRANSPIRATION

Evapotranspiration (ET) is the collective term applied to the
combined effect of direct evaporation of water from land and
water surfaces to the atmosphere and the transpiration of
water from plants through their respiration processes.
The concept of evapotranspiration is well understood, but
estimation of the amount of water returned to the atmosphere
by this process can only be roughly approximated. Too many
highly variable factors influence evaporation and transpi-
ration rates, and the unique characteristics of every wa-
tershed prevent easy analysis of actual evapotranspiration
conditions at any given locality.

The evapotranspiration process requires energy, and the rate
at which the net process can function varies daily and season-
ally at any location according to net solar radiation re-
ceived by soil, water, and plants. Direct evaporation from
soil surfaces also varies according the wetness of the
soil surface. Saturated soils will permit more evapora-
tion than dry soils, and soils totally dry to depths ex-
ceeding their capillary rise ability will permit essentially
no evaporation. Unshaded shallow water areas permit the max-
imum evaporation. Transpiration from plants varies according
to plant species throughout the annual growth cycle of each
species. Plants adapted to dry or xeric conditions can
conserve water and transpire less than plants adapted to wet
or hydric envir9nments.

within the Moultrie Creek watershed, less evapotranspiration
can be expected to occur in those localities with excessively
drained soils, low water tables, and coverings of sand pine,
scrub oaks, and similar vegetation adapted to dry condi-
tions. Increased evapotranspiration can be expected in the
flatwoods and drainageway soil areas within the watershed. The
maximum evapotranspiration can be expected to occur within
shallow water bodies and upland depressions during the periods
when inundation extends to the edges of these areas.

6 - 1

Evapotranspiration is maximized during the summer daytime pe-
riods immediately following rainfalls. The sun heated
soils permit rapid evaporation to occur. The higher summer
air temperatures also permit the atmosphere to absorb and
hold more moisture in vapor form before releasing it again
as rainfall.

The National Weather Service has conducted studies to de-
velop criteria for estimating potential evapotranspiration for
any locality within the United States. An Evaporation Atlas
for the Contiguous United States has been prepared based upon
the national network of pan evaporation stations. The Na-
tional Weather Service methods are used in this study to ex-
press the approximate potential evaporation from a shallow wa-
ter surface and the potential evapotranspiration to be ex-
pected to occur from a vegetated surface with an unlimited
supply of water.

Previous research had established that net radiation received
on the earth's surface is dominantly influenced by lati-
tude and altitude. Evaporation summary data for Gainesville
(altitude 100 feet) and Lake City (altitude 200 feet) were
used to establish an estimate for the Moultrie Creek water-
shed (altitude 30 feet). The mean of the summary data for
Gainesville and Lake City was used to approximate daily and
monthly potential evapotranspiration conditions in the Moult-
rie Creek watershed. These daily and monthly potential evap-
otranspiration estimates appear in TABLE 6-1. MOULTRIE CREEK
WATERSHED POTENTIAL EVAPOTRANSPIRATION. St. Augustine is lo-
cated at a latitude 12 minutes to the north of Gainesville
and 22 minutes to the south of Lake City. Due to the minor
pan evaporation data differences between the two stations,
developing a weighted average would not have meaningfully im-
proved the estimate for St. Augustine.

The potential evapotranspiration estimates shown in Table
6-1 would apply primarily to areas with shallow surface wa-
ter conditions and to vegetation adapted to saturated
soil conditions. Vegetation adapted to saturated and
flooded soil conditions is now generally classified as wetland
vegetation. Wetland vegetated areas remove significantly more
water to the atmosphere through evapotranspiration than up-
land vegetated areas.

Numerous theoretical methods have been devised over the years
to provide useful potential evapotranspiration estimates for
commercially important vegetation species. These methods
have been developed largely to estimate potential evapo-
transpiration from land areas and transpiration from plants
to identify the optimum amount of water to be applied or that

6 - 2

would be needed for maximum production. The Florida Insti-
tute for Food and Agricultural Sciences (IFAS) has under-

TABLE 6-1

MOULTRIE CREEK WATERSHED
POTENTIAL EVAPOTRANSPIRATION

MONTH AVERAGE DAILY AVERAGE MONTHLY PERCENT OF
(Inches) (Inches) TOTAL

JANUARY 0.08 2.48 4.9
FEBRUARY 0.10 2.80 5.5
MARCH 0.14 4.34 8.5
APRIL 0.17 5.10 10.0
MAY 0.20 6.20 12.2
JUNE 0.19 5.70 11.2
JULY 0.18 5.58 11.0
AUGUST 0.17 5.27 10.3
SEPTEMBER 0.15 4.65 9.1
OCTOBER 0.12 3.60 7.1
NOVEMBER 0.09 2.70 5.3
DECEMBER 0.08 2.48 4.9
TOTAL 50.90 100.0

Source: Derived from criteria in Evaporation Atlas for the
Contiguous 48 United States, NOAA Technical Report NwS 33, Na-
tional Weather Service, National Oceanic and Atmospheric Ad-
ministration, June 1982, based upon evaporation data for
Gainesville and Lake City, Florida.

taken a series of studies for these purposes. These studies
provide useful guidance for understanding potential evapo-
transpiration as the amount of water lost to the atmosphere by
evaporation and transpired by plants in given localities when
the water necessary for the plants is supplied. By comparing
these estimates with average monthly rainfall data or ob-
served rainfall, agriculturalists can estimate the net irriga-
tion requirements for maximizing crop production.

Field studies oriented towards the measurement of poten-
tial evapotranspiration also have been undertaken for many
crops. one study with useful guidance for this analysis
(Stewart, 1967) measured the monthly evapotranspiration of
St. Augustine grass over a five year period at the Planta-
tion Field Laboratory near Fort Lauderdale. The plantings
were observed under normal local rainfall conditions but with
saturated soils maintained at depths of 12 inches, 24 inches

6 - 3

and 36 inches. The average annual evapotranspiration (ET)
amounts resulting from this study were: 12 inch water ta-
ble 43.68 inches ET; 24 inch water table = 42.77 inches
ET; 36 inch water table = 42.05 inches ET. The mean
evapotranspiration was 42.84 inches with ET amounts
varying monthly from 1.92 inches in December to 4.81 inches in
July. The findings of this study illustrate perennial up-
land vegetation requirements in the Fort Lauderdale area and
the more general effects of lowered water tables on evapo-
transpiration rates.

While the monthly ET rate for St. Augustine grass in St.
Johns County may be slightly less than in Ft. Lauder-
dale due to cooler winter temperatures in north Florida, the
summer-to-winter difference in ET rates (about 1.9 inches in
December and 4.8 inches in July) is significant to water
management in the Moultrie Creek watershed. High water ta-
bles occur in St. Johns County during the winter months. This
condition can be accounted for, in large part, by cooler
temperatures and the dormancy and slower growth of perennial
vegetation during the winter months. These factors result in
lower ET water losses to the atmosphere during the winter
months.

Potential evapotranspiration is a measure of evaporation
and transpiration from vegetated areas when all the necessary
water is provided from maximum plant growth. Potential evapo-
transpiration estimates do not reflect the actual evapo-
transpiration conditions to be expected in watersheds. The
highest land areas in a watershed may have very dry surface
soils, deep water tables, and xerophytic vegetation.
These locations would have very low actual evapotranspi-
ration water losses. Natural upland depressions with ponds,
swamps, and marshes; hydric soils; and hydrophytic vegetation
have high evapotranspiration rates. High evapotranspiration
rates also occur along stream flood plains and around shallow
water bodies. As the antecedent period between rainfalls be-
comes extended, evapotranspiration water losses are highest
immediately following a rainfall and gradually diminish until
the next rainfall. For water management purposes, it is im-
portant to have an understanding of the actual evapotranspi-
ration characteristics of each watershed.

Some efforts have been taken by the United States Geolog-
ical Survey to establish general information on actual evapo-
transpiration for large drainage basin areas by comparing
estimates of rainfall with measured runoff. The term ap-
plied to these estimates is areal evapotranspiration. From
the United States Geological Survey information (Hughes,
1976) and a conceptual modeling effort (Morton, 1976),
areal annual evapotranspiration at the north Florida border

6 - 4

was estimated at 37.4 inches and in central Florida at 42
inches. From these data, a general areal evapotranspiration
estimate of 38 inches annually for the Moultrie Creek water-
shed and St. Johns County may be assumed. Disaggregation of
the above annual areal evapotranspiration estimate to
monthly values for use in hydrological analyses can use the
"Percent of Total" column data presented in Table 6-1 applied
to 38 inches to establish areal average monthly and areal av-
erage daily evapotranspiration rates.

RUNOFF

Concept

Runoff is rain water moving as surface water flow from one
location to another following a rainfall after the immediate
localized demands of soils, vegetation, and the process of
evaporation are met. Runoff can be increased by positive
drainage programs, compaction of soils by urban land uses
and the construction of impervious areas, removal of natu-
ral water storage areas, disturbances of surface soils con-
taining long-term accumulations of detrital materials, and re-
moval of high water utilization vegetation. Reduction in
runoff can be accomplished through controlled drainage
programs, maintenance of natural vegetated areas and man-
agement practices to maintain soil in permeable condi-
tions, creation of additional water containment areas, and
by constructing natural wetlands. Public policy deter-
mines which of the above actions are acceptable practice.
Engineering design of works to provide for development
needs within the public policy framework then can be applied.

Drainageways

Throughout the upland areas of the Moultrie Creek water-
shed, broad, flat areas serve as sheet flow drainageways when
unusually large rainfalls fill adjacent depressional ar-
eas. The Soil Survey information in Figure 4-2 generally
identifies natural drainageway localities. Over time, re-
peated stormwater runoffs from adjacent higher lands have
carried sediments and detrital materials into the drainageways
giving the soils a different color and slightly changed
constituent characteristics. In many cases, only a few
feet in land elevation mark the difference between sheet
flow drainageways and adjacent knolls. Under natural condi-
tions, these areas provide some level of control of runoff
flow from one depressional area to another.

6 - 5

Development within the Moultrie Creek watershed is ongoing,
and property owners have ditched and drained the lands
through and across natural drainageways. Parcels have been
platted over the years in gridiron fashion with essentially
no consideration -for natural drainageways or depressional
area conditions. scattered lots subsequently have been de-
veloped within natural drainageways with associated property
perimeter ditching and draining efforts practiced. Property
owners in these areas, understandably, generally desire
improved drainage programs.

The gridiron platting and resulting development process
has altered the natural runoff to depressional areas that
public policy normally would now consider as significant
natural resource areas. The long-term maintenance of sig-
nificant natural resource areas can only be assured when they
are able to receive runoff waters periodically in the vol-
umes necessary for their sustenance.

Drainageway Management

once significant natural resource areas are identified and
their runoff water supply needs are estimated, engineering
works can provide for designed systems that either supple-
ment or replace original natural drainageways. Within this
stormwater management system framework and other conditions
essential for protecting the health and welfare of citi-
zens, property owners can undertake development actions.

Following development of public policy and general runoff
system design criteria, private property owners will be able
to construct systems in any configuration that meet govern-
mental criteria and are not detrimental to the rights of ad-
jacent property owners. Where private drainage projects
already exist, some remedial action by government may be
necessary with attending legal ramifications. Where lands
have been platted but remain undeveloped, other governmen-
tal actions may become necessary- The greatest flexibility
for preserving, supplementing, or replicating natural drain-
ageways are in those areas not yet platted. In these areas,
the essential functions of natural drainageways can be de-
termined by government or as a private development re-
quirement. The necessary system can be designed to pre-
serve the effectiveness of significant natural resource areas
likely to be impacted by development actions within the
proximity of the natural drainageway.

6 - 6

Controlled Drainage Criteria

A controlled drainage system will provide for the maximum ex-
filtration from the system and infiltration into the ground
water table. It will be designed to retard the effects of
erosion and the transport of the silts and clays associated
with the sandy soils found throughout St. Johns County.
Also, by controlling fine organic materials the system con-
fines pollutants and protects water quality. It will also
provide for the rare rainfall from major storms. A system
channel with a controlled flow capacity will be designed to
provide for stormwater from rainfalls expected on the 25
year 24 hour return frequency basis, or a total of about 8.8
inches for the rainfall event. Finally, any system consid-
ered for operation and maintenance by the County, will be
designed with overflow areas to accept the 50 year, 24 hour
rainfall event runoff, or 10 inches of rainfall, with all
structures designed to maintain structural integrity under
the same event condition.

Silts, clays, detritus, and very fine sandy soils become sus-
pended in water flowing at rates in excess of 1.5 cubic
feet per second. Broad channels, distributed flow channels,
and the use of low flow water control structures providing
effective flat bottoms or near zero profile slopes between
structures for low and intermediate flows can reduce flow
rates and eliminate erosion from annual and higher rainfall
condition storms. Construction of downstream weir crests and
inverts of culverts at raised elevations to create an ef-
fectively flat channel will provide sediment control to
trap initial construction disturbed very fine sands, silts,
and clays to weir crest levels.

Exfiltration estimates of open channel bottoms will be based
upon potential infiltration rates of the sediment fines trap-
ped within the drainage channel and the height of the channel
bottom above average annual high water 'table conditions for
the parcel proposed for development. Drop boxes, inverts
of culverts, and sills of weirs will be designed to maintain
required flow rates.

While channel depths constructed to the lower point of an-
nual natural water table conditions may become necessary,
maximum exfiltration will occur when the channel is con-
structed at an elevation above the annual natural high water
table conditions. Where the lower depth channels are nec-
essary, outflow points from the system will be controlled
by raised culverts and weirs to elevations determined by
the Engineering Department to assure that overdrainage will
not occur.

6 - 7

Channels will have outfall structures at final discharge
points to control discharge flows. All systems will be
designed for zero discharge from the first one inch of
runoff expected from the drainage area (see Tables 2-1 and
2-2). After retaining the first one inch of rainfall, a
maximum discharge equivalent to about two inches of con-
trolled runoff per day from rainfalls of up to three inches
per day would provide for normal rainfalls expected annually
(see Table 2-3). An additional discharge capacity of three
inches per day of controlled runoff from the still larger
and the extremely rare rainfall events will accommodate flood
protection needs while providing controlled flow protection to
the County infrastructure and the natural environment.

The Engineering Department will further evaluate the possibil-
ity of using simple volumetric analyses of expected runoff for
smaller areas. The use of the above controlled flow concepts
will permit the use of simpler calculation methods for
achieving acceptable water detention/retention for recharge
and controlled discharge purposes. For example, the Ratio-
nal Method for estimating runoff peak flows and the Ratio-
nal Mass Curve Method for estimating required storage vol-
umes can be simply calculated. These methods provide rea-
sonable approximations useful for small area analysis. As the
size of the area becomes larger, these calculation methods
progressively overestimate runoff and storage volume re-
quirements. From the County's management perspective, the
use of these methods to determine detention/retention facil-
ities, controlled flow conveyance systems, and runoff con-
trol structures results in increased system capacities.
The use of these simpler techniques benefits the public due
to the conservativeness of the resulting controlled flow
systems and the simplified permit application review pro-
cess. The use of these simpler computation methods can-
not be recommended for the design of large area
uncontrolled-flow discharge systems. From a developer's
perspective, these simpler methods reduce the costs of anal-
yses as compared with more complex evaluation procedures,
but their use for large areas results in increased con-
struction costs due to system over design.

Natural Streams

The riverine (above tidewater) part of Moultrie Creek and
its tributary stream courses receive and discharge the runoff
waters to tidewater. This fresh water mixes with ocean water
to form estuarine waters of progressively increasing sa-
linity in the lower course of the Moultrie Creek to its
mouth at the Matanzas River.

6 - 8

A significant part of riverine flow is derived from ground
water seepage. Rain water infiltrating into the ground flows
from high water table areas and emerges as seepage along
stream courses. Stream flow derived from seepage is termed
base flow. Rain water infiltrating the ground can provide
seepage or base flow water to the riverine part of Moultrie
Creek for several weeks following a heavy rainfall. The
length of time that base flow contributes to stream flow is
dependent upon the replenished or maintained height of
the water table in adjacent upland areas.

During extended drought periods, base flow in Moultrie Creek
can cease. Review of The United States Geological Survey
maintained stream discharge gage at State Road 207 (ID
02246900) indicates an increasing number of days with lit-
tle or no flow in recent years. This condition reflects
decreased rainfall amounts and the effects of development
with uncontrolled storm drainage in the watershed above the
gage.

Documented Stream Flows

The stream gage at State Road 207 (ID 02246900) measures
flow from a 19.8 square mile area of Moultrie Creek water-
shed (49 percent of the watershed) above the gage. The datum
of the gage is 14.24 feet above the National Geodetic Verti-
cal Datum of 1929 (about mean sea level), an elevation fif-
teen or more feet lower than the elevation of the average
land surface in the vicinity of the gage. The information
referenced below is based upon the time period from October
1961 through September 1988.

The minimum water surface elevation in the record was 1.84
feet above the datum on July 15, 1981. Zero stream flow oc-
curs when the gage height (water surface) is less than
about 2.2 feet above the datum. The highest gage height
recorded for the 27 year record period was 9.16 feet above
the datum on September 21, 1969, when the maximum discharge
of 860 cubic feet per second (cfs) occurred.

During the October 1987 through September 1988 period or the
1988 water year, 60 percent of the days recorded flows of less
than 1 cfs and numerous days in the months of October and
November 1987 and June and August 1988 recorded zero flows.
Low flows of 0.06 and 0.05 cfs were recorded during the months
of July and September 1988. The discharge data for the 1988
water year reflected an average daily flow rate at the gage
of 15.2 cfs. This average value represents a 1988 water
year runoff from the watershed above the gage equivalent to
10.4 inches of watershed rainfall. The 27 year average

6 - 9

daily flow at the gage is 17.7 cfs, equivalent to 12.14
inches of rainfall.

Provisional data for a second stream gage (ID02247012) on
the Moultrie Creek tributary (Tributary No. 4 in the Federal
Emergency Management Agency Flood Insurance Study) at State
Road 207 were also reviewed. This gaging station was estab-
lished in March 1988. The provisional data showed zero flow
periods during the 1988 water year similar to Moultrie Creek.
The maximum discharge recorded was 41 cfs in November 1988.
only three days indicated flows in excess of 10 cfs. Dis-
cussions with a United States Geological Survey represen-
tative revealed that water diversions may be occurring up-
stream of the gage as a result of private development ac-
tions.

Stream Discharge Characteristics

The stream discharge characteristics of Moultrie Creek
were reviewed. Data were assembled from daily stream flow
records to establish the runoff characteristics from a vari-
ety of storms. The available data indicated that stream
flow at the State Road 207 gage typically peaked approxi-
mately twenty" four hours following a rainfall event, Ini-
tial runoff discharges are considered to reflect a three to
four day period following rainfalls. The stream gage data
indicates that discharge volumes recorded prior to an
event typically return to the pre-event volumes within
about four weeks following the event. These findings
suggest that initial runoff ends within roughly four days
following an event, and a gradually declining and delayed
runoff and base flow continues for several weeks following
an event.

TA13LE 6-2. ST. AUGUSTINE RAINFALL AND MOULTRIE CREEK DISCHARGE
MARCH 1 THROUGH MARCH 26, 1980 presents data for a March 1980
rainfall for St. Augustine and March 1980 stream discharge
data ( Station ID 02246900) for the 19.8 square mile drainage
area of Moultrie Creek upstream of State Road 207. The pri-
mary rainfall occurred on March 9 and 10, amounting to 4.12
inches. This was a minor annual rainfall, not even equiva-
lent to the two year, two day expected rainfall. The period
preceding the rainfall was six days, including March 3 with
a trace of rainfall recorded. During the event period
from March 3 to March 27, when a new rainfall event occurred,
three rainfalls events occurred. The average antecedent pe-
riod between the rainfall events was five days.

The stream gage data shows a progressive decline from March
2 through March 8. A slight increase occurred on March 9,

6 - 10

with a major increase in discharge on March 10. The dis-
charge peaked on March 11, with a rapid decline through
March 13, indicating completion of the initial storm run-

TABLE 6-2

ST. AUGUSTINE RAINFALL AND MOULTRIE CREEK DISCHARGE
MARCH 1 THROUGH MARCH 26, 1980

Day Daily Rainfall Discharge
(Inches) Cubic Feet Per Second

1 0 8.7
2 0.15 8.9
3 Trace 8.1
4 0 7.4
5 0 7.0
6 0 6.6
7 0 6.2
8 0 5.8
9 0.65 7.7
10 3.47 157.0
11 0 269.0
12 0 166.0
13 0.18 120.0
14 0 93.0
15 0 71.0
16 0 59.0
17 0 52.0
18 0 45.0
19 0 39.0
20 0 35.0
21 0.3 32.0
22 0 28.0
23 0 24.0
24 0 21.0
25 0 19.0
26 0 16.0
Total 1246.0
27 Beginning of New Rain Event

off. Of the total volume of water discharged between March
10 and March 26, the four day period of March 10 through
March 13 accounted for 57.1 percent of the total. The remain-
ing 42.9 percent of the stream flow would be representative of
delayed runoff and seepage flows.

6 - 11

WATER LOSS IMPACTS

A perspective of the significance of water loss'factors is
provided by the following example analysis. The volume of
water represented by the 4.6 inch rainfall occurring between
March 9 and March 26, 1980, an the 19.8 square mile Moultrie
Creek watershed approximates 4857.6 acre feet. The total
discharges noted in Table 6-2 for the March 9 to March 26 pe-
riod are equivalent to about 2471.3 acre feet of water or
about 50.9 percent (2.34 inches) of the total 4.6 inches of
rainfall received by the 19.8 square mile watershed. Areal
evapotranspiration at 0.105 inches per day for that same
period represents about 1.785 inches of rainfall. Runoff
and evapotranspiration can account for all but 7 percent of
the rainfall during the 17 day period.

Had another storm not occurred on March 27, the daily
stream discharges would have continued to recede slowly each
day for about 10 more days before declining to 5.8 cubic feet
per second, the discharge recorded on March 8 and the day be-
fore the March 9 rainfall. Estimated discharges for the ad-
ditional 10 days would approximate about 196 acre feet of
water discharged to the stream essentially as seepage. The
total runoff, including base flow for a 27 day period could
account for about 55 percent or 2.53 inches of the rainfall
received on the watershed during this example event. Areal
evapotranspiration for a 27 day period in March would be ap-
proximately equivalent to another 2.84 inches of the rainfall.
Without another rainfall, the entire 4.6 inches of example
rainfall can be accounted for in evapotranspiration and run-
off, and the continued water losses would result in a defi-
ciency of 0.77 inches of rainfall. The process of rainfall,
continual evapotranspiration, runoff, and a three to four
week period of delayed runoff and slow seepage providing base
flow to the stream, as exemplified in Table 6-2, is ongoing.

Evapotranspiration is a highly variable and an essentially un-
controllable process. Vegetated areas with saturated soils
evapotranspire water at a rate of about 50.9 inches per year
in St. Johns County. An average, estimated actual, or areal
evapotranspiration rate of 38 inches per year is more repre-
sentative of the varied conditions on the watershed. The
United States Geological Survey estimates that runoff ac-
counts for about 12 inches of annual rainfall. For an aver-
age rainfall year of 53 inches, only 3 inches of rainfall
remain for ground water recharge or water use if a balance
between rainfall and water use is to be maintained.

The practical significance of the need to retain more water
on the land for recharge can be illustrated through the

6 - 12

following example. If a family of four uses 400 gallons of
water per day, they will, in one year, use 146,000 gallons
of water. One acre inch of water is equivalent to 27,155
gallons, and one inch of water per square mile is equivalent
to 17,380,000 gallons of water. Therefore, 119 families,
each with four people, would use one inch of rain water that
has managed to infiltrate into a one square mile land area
and recharge the surficial aquifer.

As another example, assume 20,000 people, at an average
per capita use of 100 gallons of water per day, are supplied
from a well field withdrawing water from the surficial aqui-
fer. Assume also that three inches of rain water could in-
filtrate into the soil and recharge the aquifer. The 3
inches of recharge would be required from a land area of
about 14 square miles for the recharge to balance the wa-
ter use. This simple example assumes that three inches of
rainfall could be saved and allowed to infiltrate and re-
charge the surficial aquifer with no additional losses of
evapotranspiration, runoff, or agricultural or industrial
withdrawals from that same supply. The example also assumes
that the average annual 53 inches of rainfall will occur. Fi-
nally, the 100 gallons per capita per day water use estimate
is used here for simplification. Urban area estimates of per
capita daily water uses are typically higher; an estimate of
133 gallons per capita per day (gpcd) is widely used for St.
Johns County.

6 - 13

FLOOD PRONE AREAS

NATIONAL FLOOD INSURANCE PROGRAM DATA

The Federal Emergency Management Agency completed a flood in-
surance study for the unincorporated areas of St. Johns
County (Community Number 125147), dated September 18, 1985.
This study includes peak discharges, floodway, and base flood
elevations for Moultrie Creek and three tributaries. The
three tributaries studied drain from the north in the devel-
oping parts of the Moultrie watershed between Moultrie Creek
and the Matanzas River. This study and companion Flood In-
surance Rate Maps establish a 100-year flood elevation (base
flood elevation) along the studied stream courses.
Figure 7-1. Flood Hazard Areas Subject To 100-Year Flooding,
depicts the special flood hazard areas subject to 100-year
flood conditions as determined by the Federal Emergency Man-
agement Agency.

Tributary #1 drains a small 1.5 square mile area located east
of State Road 5A. The mouth of this small stream is located
immediately west of Shore Drive. The 100-year flood eleva-
tions along this stream range from 8 feet NGVD at the stream
mouth to 25 feet NGVD at Lewis Point Road. Upstream of Lewis
Point Road, a generalized area is depicted on the Flood Insur-
ance Rate Maps identifying a Zone A, a special flood hazard
area with no base flood elevation determined.

In those cases where the Federal Emergency Management Agency
does not establish base flood elevation, the interagency
agreement with the local government requires that the lo-
cal government establish an interim base flood elevation
applicable to local development actions. Zone A locations
in the Moultrie Creek watershed are typically upland de-
pressions, natural drainageways, and some flatwoods soils
area that would be subject to shallow flooding under a
storm of an intensity capable of producing a 100-year return
frequency flood.

Tributary #2 drains a small area on the south side of Moul-
trie Creek that was not studied. Tributary #3 drains a

7 - 1

Figure 7-1. Flood Hazard Areas
Subject To 100-Year Floodi-
-,V@\j x

R 16

C05

0
0

ST
sou

Sao 2=DS

SCALE: 1 10,000

LEGEND:

PROJICT
10CITION AREAS OF fOO-YEAR FLOODING
P'
11)1A
D.E.R. CONTRACT NO. CM7217
ST. JOHNS COUNTY ENGINEERING DEPARTMENT - GEOGRAPHIC INFORMATION SYSTEM

small 0.7 square mile area on the north of Moultrie Creek
between ..: the Florida East Coast Railroad and State Road 5A.
Base flood elevations ranging from 9 feet NGVD at tidewater
to 21 feet NGVD at a point 5800 feet upstream of the tribu-
tary's mouth. A generalized area upstream of 5800 feet along
the tributary's stream course is delineated as a Zone A.

Tributary #4 drains a 4.1 square mile area located immediately
to the west of Tributary #3. Delineated base flood elevations
range from 9 feet NGVD at tidewater to 35 feet at State
Road 207. Upstream of that location, a generalized Zone A
area is delineated.

On Moultrie Creek, flood elevations are provided from tide-
water to State Road 214. The following are base flood ele-
vations in feet above NGVD obtained from stream profile data:
Osceola Trail, 10.7; State Road 207, 25.8; Lightsey Road,
30.2, Florida East Coast Railway, 32; and State Road 214,
34.2. An extended area upstream of State Road 214 is delin-
eated as a Zone A.

EVALUATION CRITERIA

Construc tion of roads and inhabited buildings above the 100--
year flood elevation will be required. The National Flood
Insurance Program has established the 100-year return
frequency flood condition as the base elevation for insured
habitable structures. The need for emergency access to prop-
erties, the protection of the public from injury resulting
from flooding of roads, and the obligation of local govern-
ment to provide for the safe movement of people on public
roads dictates the need to establish the 100-year return
frequency flood as the elevation above which roads should
be constructed.

In those parts of the watershed where National Flood Insur-
ance flood information is available, the elevations es-
tablished through that program will be used. In those areas
where the base flood elevation must be estimated, the follow-
ing procedure will be used.

The 100-year return frequency 24-hour rainfall (12.8 inches)
will be used. The normal annual high water table condition
and the SCS Runoff Curve Number applicable to the area in-
cluded in the proposed development will be used to estab-
lish a soil infiltration runoff reduction estimate. Large
developments encompassing many different water table and soil
conditions will be segmented into representative soil charac-
teristic subareas.

7 - 3

The planned stormwater containment facilities for the pro-
posed development will be used to estimate initial abstrac-
tion land storage and retention requirements. The proposed
channels and other components of the development stormwater
management system will be used to establish rainfall depth
reductions to be expected from runoff during and immedi-
ately following the rainfall event. Open land areas of the
parcel or surface water storage areas sufficient to detain
or retain the remaining rainfall will be estimated.

All parcel land elevations above the maximum water eleva-
tion required to contain or otherwise manage the 100-year
rainfall will be considered as above the base flood elevation.
All public roads will be constructed with road surfaces above
the base flood elevations. Access to public facilities, and
all structures used as residences and as established locations
of employment will be constructed with habitable or occu-
pied first floors above the base flood elevation.

7 4

ATLANTIC COASTAL RIDGE

WATER RESOURCE STUDY CRITERIA

The information assembled provides guidance for evaluating
hydrological analyses conducted in the Moultrie Creek water-
shed : In addition to the review of existing information
previously presented, TABLE 8-1. GUIDELINE HYDROLOGICAL CRITE-
RIA FOR THE ATLANTIC COASTAL RIDGE ST. JOHNS COUNTY, FLORIDA
has been prepared as initial guidance for application to the
Tillman Ridge part of the Moultrie Creek watershed. Until
rainfall gage data becomes available for the interior part of
St. Johns County, these data provide information that may be
applied to all of the Atlantic Coastal Ridge portions of the
County.

The monthly rainfall estimates presented in Table 8-1 are
composites of mofithly averages obtained from the unedited
or non-normalized data available for Hastings and St. August-
ine. Hastings data are based upon the 1978 to 1986 record
period and St. Augustine data are based upon the 1973 to
1986 record period. The reduced average monthly rainfall
for July reflects decreased rainfall for that month at St.
Augustine during the record period.

Because rain gaging stations are not available for the west-
erly parts of St. Johns County from Switzerland northward,
the data presented in Table 8-1 may be applied to analyses
conducted in northwestern St. Johns County. Hastings data
provides guidance for the southwestern part of the County,
Marineland for the southeast, St. Augustine for the central
coastal area, and Jacksonville Beach for the north coastal
areas. The data for these stations are generally available
from the United States Weather Service. Later studies may
find that a single composite set of data may be appropriate
for the entire coastal portion of the County.

The average daily evapotranspiration data presented in Table
8-1 were derived from the annual estimate of 38 inches used to
represent areal evapotranspiration in this study. This an-
nual estimate was then disaggregated based upon the average

8 - 1

TABLE 8-1

GUIDELINE HYDROLOGICAL CRITERIA
FOR THE ATLANTIC COASTAL RIDGE
ST JOHNS COUNTY, FLORIDA

MONTH AVERAGE AVERAGE AVERAGE EVAPOTRANSPIRATION
RAINFALL NUMBER OF NUMBER OF MONTHLY DAILY
(Inches) RAINFALL ANTECEDENT (Inches) (Inches)
DAYS DAYS

January 3.2 4.8 6 1.86 0.06
February 3.4 5.0 6 2.09 0.07
March 3.9 5.6 5 3.23 0.11
April 3.4 3.8 5 3.80 0.13
May 3.5 3.9 5 4.64 0.15
June 6.7 7.9 4 4.26 0.14
July 5.8 9.3 3 4.18 0.13
August 6.8 9.3 3 3.91 0.13
September 7.3 8.5 3 3.46 0.12
October 3.6 4.8 6 2.70 0.09
November 2.3 4.6 6 2.01 0.07
December 3.1 4.9 6 1.86 0.06

Note: Slight anomalistic characteristics appearing in
the average rainfall data are believed to be due
to the short time frame of the database.

monthly potential evapotranspiration values as percents of to-
tal potential annual evapotranspiration noted in Table 6-1.

The average number of rainfalls per month and the average
number of antecedent days between rainfalls were developed
from an evaluation of the available Hastings record (TABLE
2-2 and TABLE 2-3). These values are intended as guidance un-
til further studies are conducted for more stations in north
Florida with longer periods of records.

Additional studies are also needed using hourly rainfall
data. Average Daily rainfall data do not reflect rainfall
events adequately for some design purposes. Review of sta-
tions that may be representative of conditions in St. Johns
County is needed, and procedures for incrementally pro-
gressing rainfall through a system of characteristic, but
hypothetical, storms would provide improved criteria for
evaluating storm effects. Generalized procedures are avail-
able for this purpose, but no standardized procedure is yet

8 - 2

available that can provide reasonable assurance that the re-
presentations used are applicable to St. Johns County con-
ditions.

Finally, studies are needed to correlate observational surfi-
cial aquifer water well log data with rainfall to estab-
lish well recovery extents following rainfalls of varying
intensities and durations under existing conditions. Wells
withdrawing water from different depths can be expected to
recover differently. Similarly, wells penetrating differ-
ing soils matrix materials also will react differently to
rainfall events. Information from this type of analysis will
have to be spatially correlated with land use and natural
resource areas within the theoretical recharge localities
of the observational wells to establish the extent and de-
pendability of natural recharge capabilities. The final re-
sults of these analyses will provide fundamental information
on the effectiveness of differing engineered water management
facility configurations. These study efforts will provide
necessary information for establishing cost-effective measures
and final Engineering Department criteria for basin-wide man-
agement of stormwater.

8 3

SIGNIFICANT NATURAL RESOURCE AREA MANAGEMENT

GENERAL

Those natural areas within the County that require special
governmental management procedures have been identified as
"Significant Natural Resource Areas." These areas include
important wetlands of state and national concern and other
natural environmental areas of importance to the well being
of residents of St. Johns County. Significant natural re-
source areas include surficial aquifer recharge areas, riv-
erfront areas, shorelines, water bodies, wetlands, wood-
lands, wildlife sanctuaries, and archaeologically important
locations.

Developments permitted adjacent and near to these areas re-
quire special pre-project review. Natural conditions re-
quired to preserve these areas are to be maintained if the
natural area is to remain viable and not move into a grad-
ual process of decline. Cultural developments that may im-
pact upon these areas also must be reviewed to determine
the significance of negative impacts resulting from the
development. Where possible, government guidance can be
provided to property owners to assist them to undertake de-
velopment efforts that could lead to the enhancement of
significant natural resource areas. To be encouraged, are
those private efforts to create new natural resource areas
and efforts to augment or extend existing significant nat-
ural resource areas.

SIGNIFICANT NATURAL RESOURCE AREAS

Tidal Wetlands (Moultrie Creek Estuary)

General Protection Needs

The Moultrie Creek estuary and associated tidal wetlands
extend for approximately five miles upstream of the river's
confluence with the Matanzas River. The natural vegetation

9 - 1

consists of seashore saltgrass, bushy sea-oxeye, glasswort,
and needlegrass rush. This is an important wildlife area.
The native vegetation and fauna are important links in the
food chain for many sport and commercial finfish and shell-
fish.

The environmental health of the natural area is dependent
upon continual ground water seepage from adjacent higher wa-
ter table areas and fresh water discharges from Moultrie
Creek and tributary streams. A primary hazard to this
natural area is the introduction of pollutants and exces-
sive sediments with stormwater discharges from roadway
drainage systems and urban developments in the watershed.
Excessive nutrients introduced with effluents from septic
tanks and waste water treatment plants are also potential
hazards affecting the balance of biological processes within
the estuary.

Contamination From Roadways

A primary source of pollutants occurs with runoff from road-
ways. As roadway traffic loads increase with development, the
practice of positive uncontrolled drainage from these road-
ways is introducing increasing loads of oils, greases, tars,
rubber and other tire composition materials, oxides from au-
tomobile exhausts, and a host of other types of particu-
late matter associated with modern vehicular traffic into
the estuary. The entrapment of these contaminants in reten-
tion storage facilities constructed as roadway drainage facil-
ities is essential for preservation of the biological pro-
cesses in the Matanzas River and St. Augustine Harbor es-
tuary.

Roadway Retention Storage Catchment, Benefits

No technical reason exists for avoiding the use of roadway re-
tention storage catchments along Moultrie Creek and the
Matanzas River. The natural water tables in these areas are
found generally at six or more feet below ground eleva-
tion. The water holding capacity of the first four feet
of soils immediately adjacent to the estuarine parts of
Moultrie Creek are on the order of ten inches or more of
equivalent rainfall. The permeability or rate at which the wa-
ter percolates through these soils is very high. Retention
basins constructed in these low or deep water table, highly
permeable soils would remain dry except for short periods
following the most intense rainfalls. Materials entrapped
in these basins would be reduced by aerobic organisms and
conservative materials (heavy metals) would electro-chemically

9 - 2

bind to fine silts and clays washed into, or formed by reduc-
tion processes, within the catchments. When constructed
above the natural high water table, catchments constructed
in these areas would require very infrequent maintenance.

The extensive use of retention storage catchments throughout
the low or deep water table localities also provides for the
continued base flow essential for maintaining fresh water
flows into the Moultrie Creek estuary. The fresh water head
created by the infiltration of trapped rainfall also serves
to reduce the potential of salt water intrusion into the surf-
icial aquifer adjacent to the tidal parts of the Matanzas
River and Moultrie Creek.

Contamination From Septic Tanks

St. Johns County has permitted urban development with septic
tank effluent disposal along the Matanzas River and Moultrie
Creek estuaries. When properly operating, septic tank drain-
age releases nutrient rich effluents that move with ground-
water seepage into the estuaries. As long as population
densities remained low, these enriched septic tank effluents
with high levels of nitrogen, phosphorous, and other nu-
trients could be accommodated by biological processes
within the estuary.

As development increases throughout the St. Augustine metro-
politan area, the increasing release of nutrients from septic
tanks, waste treatment plants, and natural vegetative sources
can overload the natural biological nutrient processing ca-
pacity of the estuarine system. The result will become no-
ticeable by increased vegetation growth, increased quantities
and accumulations of detritus (plant remains) in shallow
waters, increased buildup of resulting organic materials
filling in shallow waters, increased biochemical reduction
of these organic materials through anaerobic processes with
resulting increases in hydrogen sulfide, methane, and similar
anaerobic process gas releases; and subsequent decline in the
suitability of extended areas of the estuary as food produc-
tion and protection areas for juvenile finfish and shellfish.

Septic tank effluent releases pose still other problems
for protection of the estuarine waters. Modern urban living
has come to depend upon a host of highly toxic cleaning and
other materials. Many homeowners have little concern for
the biological processes that make a septic tank reduce hu-
man waste into relatively harmless sediments and a liquid,
nutrient rich effluent that is released through a drain
field. Household cleaners, paint products, pesticides,
etc., can easily reduce the' effectiveness of the system

9 - 3

and permit the release of human waste pathogenic materials and
the toxic materials in the septic tank effluents. No known
process exists for readily determining the extent of misuse
of septic tanks.

Septic tanks also require cleanout periodically in order
to continue to function properly. As the sediments (sludges)
gradually build up within the tank, the efficiency of the
system declines. -Eventually, very poorly treated effluents
are released into the environment. No County program exists
to certify to the proper operation of septic tanks.

Dredge and Fill Problems

The environmental health of tidal portions of the Moultrie
Creek watershed requires the preservation of wetlands vegeta-
tion in the estuary and the biological processes associated
with those vegetated areas. Construction activities in
estuarine wetlands remove some vegetation. When construction
actions are not extensive, reestablishment of the original
vegetation can occur within three to five years following the
construction activity.

construction activities also disturb wetlands bottom mate-
rials and/or upland soils matrix materials. In the process,
runoff from the land carries increased loads of silts and
clays. Tidal exchange waters then carry the silts and clays
from uplands and from the disturbed bottom materials to other
locations within the Matanzas River and into the greater St.
Augustine Harbor area. The construction related increases
in suspended sediments creates turbid waters that reduce the
normal biological processes within the greater estuary. In
sufficient quantities, the introduced silts and clays can
smother benthic organisms and destroy significant areas of
sessile vegetation within the estuary.

For the continued and normal environmental health of the
greater St. Augustine Harbor estuary, all construction activi-
ties likely to cause high levels of water turbidity or oth-
erwise affect the quality of the water in the estuary must be
managed to assure the minimum of short- and long-term damage
from the activity occurs. Federal and State of Florida pro-
grams exist to provide protection from direct disturbances
of wetlands from urban development actions.

9 - 4

U. S. Army Corps of Engineers Regulatory Program

The U. S. Army Corps of Engineers regulates activities in
open waters and wetlands under the following four separate but
related laws:

1. The Rivers and Harbors Act of 1899 which requires
authorization for activities such as constructing piers,
bulkheads, subaqueous pipe- lines, filling, dredging,
stream channelization, and similar works in navigable
waters of the United States. In response to 1968
court rulings, permit application reviews now include
protection of fish and wildlife, conservation, pol-
lution, esthetic, ecology, and general public interest;

2. The Federal Water Pollution Control Act of 1972 re-
quiring the restoration and maintenance of the chemical,
physical, and biological integrity of the nation's
waters. Section 404 of the Act established the permit
program to regulate discharges of dredged or filled ma-
terial into waters of the United States;

3. The Clean Water Act of 1977 expanded the'Corps Sec-
tion 404 authority to include, but not be limited to,
all coastal and inland waters, lakes, tributaries to
navigable waters, wetlands adjacent to navigable waters,
and certain isolated wetlands and water bodies;

4. The Marine Protection Research and Sanctuaries Act
of 1972 authorizes the Corps of Engineers, under Section
103, to issue permits for the transportation of dredged
material for ocean disposal.

In general, Corps of Engineer permits are required for any
construction in all tidal areas channelward of mean high water
lines in the Moultrie Creek estuary. Complete information on
Corps of Engineers regulatory requirements can be obtained
from: Regulatory Division, P. 0. Box 4970, Jacksonville, Flor-
ida, 32232-0019. Telephone: 904/791-1676.

Florida Department of Environmental Regulation Permits

The Florida Department of Environmental Regulation exercises
regulatory jurisdiction over dredge and fill activities in wa-
ters of the State to their landward extent. Landward extent
is determined by the dominance of certain wetland indicator
vegetation species defined in Chapter 17-4 of the Florida
Administrative Code. The State Wetlands Protection Act of
1984 (Chapter 403, Florida Statutes) authorizes regulation
of wetlands to protect and preserve water quality and pre-

9 - 5

serve fish and wildlife habitat. Determination of regula-
tory jurisdiction is based upon an area's regular and peri-
odic inundation, physical waterbody connections to "waters of
the State," and dominance by the specified wetland indicator
species. Waters of the State are rivers, streams and
their tributaries, bayous, sounds, estuaries and bays and
their natural tributaries, most natural lakes and the Atlan-
tic ocean and Gulf of Mexico to the seaward limit of the
state's territorial boundaries.

The Florida Department of Environmental Regulation develop-
ment action review evaluates the potential impact of a
proposed project on the waters of the State. This review
process is intended to assure that the project will not:

1. Obstruct or alter the natural flow of navigable wa-
ters;

2. Induce harmful or increased erosion, shoaling of
channels, or create stagnant areas of water;

3. Interfere with the conservation of fish, marine
resources and wildlife, or other natural resources;

4. Induce destruction of oyster beds, clam beds, or ma-
rine productivity including, but not limited to, de-
struction of natural marine habitats and grass flats
suitable as nursery or feeding grounds for marine life.

More complete information on the Department of Environ-
mental Regulation rules may be obtained from: Office of Pub-
lic Information, Florida Department of Environmental Regula-
tion, 2600 Blair Stone Road, Tallahassee, Florida 32301.

Florida Department of Natural Resources Review

Under the authorization of Chapter 253, Florida Statutes and
in accordance with Rule 16 of the Florida Administrative
Code, the Florida Department of Natural Resources (DNR) con-
ducts the following evaluations of development actions rela-
tive to,tidal portions of Moultrie Creek:

1. The water dependency of the project;

2. The setback of the project from the applicant's
riparian lines;

3. The project's consistency with other policies, stan-
dards, and criteria set forth in the Florida Adminis-
trative Code Rule 16Q-21.04.

9 - 6

More complete information on the above regulatory procedures
may be obtained from the Bureau of Beaches and Shores and the
Bureau of State Lands, Florida Department of Natural Re-
sources, 3900 Commonwealth Boulevard, Tallahassee, Florida
32303.

St. Johns County Tidal Wetland Criteria

In order to avoid duplication of regulatory measures dealing
with dredge and filling ot waters impacting national navigable
waterways, St. Johns County shall develop review procedures
incorporating the process established by the U. S. Army Corps
of Engineers. Similarly, the Florida Department of Environ-
mental Regulation's wetland protection criteria and the Flor-
ida Department of Natural Resources criteria shall be incor-
porated into the County review process. The primary envi-
ronmental criteria of concern in the dredge and fill permit-
ting process include:

1. The potential impact of the action on the essential
and sustainable quality of waters in the County;

2. The potential effect of the action of the propaga-
tion and sustenance of wildlife, fish and aquatic
plants and animals important to the food chain of com-
mercial and sport fish and wildlife;

3. The potential impact of the action on the health
and welfare of property owners fronting the impacted
water body, users of that water body and the general
public of the County;

4. Other reasonable, practical, and implementable envi-
ronmental concerns of regional, state, and federal gov-
ernmental agencies and professional bodies.

St. Johns County Tidal Wetland Management Alternatives

The maintenance of water quality conditions suitable for fin-
fish and shellfish within the Moultrie Creek/Matanzas Riv-
er/St. Augustine Harbor estuary will require coordinated man-
agement efforts between St. Johns County and the municipali-
ties of St. Augustine and St. Augustine Beach. Actions to
alleviate existing and projected problems by any single gov-
ernmental entity in the area would have limited effective-
ness. Effective protection of the estuarine environment

9 - 7

will require common and consistent procedures adopted by all
of the governmental bodies regarding stormwater runoff and
waste management.

The problems identified in this report regarding the tidal
portions of the Moultrie Creek watershed also apply to every
watershed that discharges stormwater runoff and waste efflu-
ents into the Matanzas and Tolomota River systems. Stormwa-
ter management practices by the County and without cooperation
from St. Augustine and St. Augustine Beach can only provide
partial protection for the greater St. Augustine Harbor estu-
ary.

An effective estuary resource management program would re-
quire participation from the three local governments whose
practices determine the environmental health of the total
St. Augustine estuary. Coordination of stormwater manage-
ment practices among the three governments at policy levels
and at governmental operational levels would be a major focus
of such a program. Parallel functions in each governmental
body impacting upon environmental conditions within the es-
tuary would be identified. Information on problems and po-
tential solutions to specific problems would be exchanged
among the three governments. Technical assistance procedures
among the three governments would be established, and coordi-
nated means for dealing with emergency situations that
impact upon the estuary conditions would be developed. Inter-
governmentally coordinated procedures for obtaining state and
federal assistance to resolve St. Augustine metropolitan area
problems associated with the estuary will gradually evolve
from the process.

Fresh Water Wetlands

Basic Processes

Wetlands exist in upland depressions, along flood plains
of streams, and along the edges of base receiving water
areas (upland depressions, lakes, and ponds). All wetlands
have one primary characteristic. All wetlands are receiving
or transition locations of runoff of surface waters and
seepage of ground waters. They function as nutrient sinks
or temporary storage areas for surface water runoff. In
that capacity, all wetlands function to delay the movement of
water. The time delay of water movement through wetlands al-
lows biological and chemical actions to reduce detrital ma-
terials and provides time for the chemical bonding of con-
servative materials to sediment fines in the wetland. The
sediment fines are introduced into the wetland through runoff

9 - 8

or are created within the wetland through biological or
chemical-detrital reduction actions.

As water moves through and out of wetlands, minerals and nu-
trients are introduced from the wetland into adjacent water
bodies. Under low or controlled water flow conditions, the
transported minerals and nutrients from wetlands provide es-
sential materials for sustenance of biological processes in
adjacent water areas. Under high water runoff conditions
through wetlands, large amounts of detrital materials and
sediment fines with chemically bound contaminants can be
washed out of the wetlands and into the adjacent waters.

Factors Affecting Upland Wetland Function Declines

Wetlands can persist only when they are able to receive regu-
lar and controlled amounts of surface water runoff and
ground water seepage from the adjacent upland watershed sup-
plying the depressional area. once drainage programs alter
the natural movement of water from the adjacent uplands or
drain water to other locations, the original wetland begins
a slow process of change.

Forested wetlands or swamps, bayheads, and hydric hammocks
are primary sources of cypress and a variety of hardwoods
used for commerce in Florida. As the uplands that formerly
supplied the surface water runoff and ground water that
seeped into these areas are converted to agricultural and
urban land uses and the natural movement of water is al-
tered, these areas also begin a gradual conversion to
mixed mesic woodland or pine flatwood communities.

Without the regular supply of water from adjacent higher land
areas, upland wetlands and their associated vegetation will
gradually' convert to areas with different soil characteris-
tics and with different vegetation characteristics. The
preservation of any upland wetland requires the hydrologi-
cal determination of the regime of water flow or movement to
the depression essential for sustaining a depressional area
as a wetland with some desired vegetation characteristics.

In areas where the water table has been lowered through
water withdrawals and overdrainage of surface waters, tempo-
rary sustenance of wetlands occurs due to the compacted
bottoms. of wet depressions that prevent or retard the infil-
tration and percolation of surface water. In these areas of
perched water tables, the perched condition will persist for
some time. As the available water declines, vegetation
roots will penetrate the impervious clay layers in their
search for water. Gradually, through the culmination of

9 - 9

life cycles of this vegetation, progressive generations of
this pr 'ocess, and subsequent root reconversion to natural
elements, percolation through the clay bottom slowly in-
creases.

Much of Florida was formerly in wet meadow vegetation. Prai-
ries, meadows, or grassy wetlands all over Florida have been
converted to agricultural and urban uses. High water tables
due to lack of drainage prevailed wherever extensive flat-
land areas existed. soils in these areas were soggy
through much of the year, and progressive generations of
grasses had produced accumulations of organic materials in
the upper horizons of the soils. As the detritus broke
down and released nutrients and sediment fines, percolation
carried these materials to the water table and formed imper-
vious layers. These impervious layers helped to per-
petuate the natural wet meadow conditions.

When these areas were drained, usually for agriculture, the
hot Florida sun caused oxidation of the organic materials
that had collected on and in the surface soil materials.
Agricultural practices broke up the upper soil matrix layers
and the sun's actions caused further oxidation of organic
fractions within the soils. As water tables were dropped and
impervious soils layers were altered, water percolated down-
ward and away from the soil surface.

When water tables are dropped more than roughly two feet
below the land surface, the ability of grasses to obtain
sufficient water without irrigation results in their reduced
productivity. As vegetation functions decline, evapotrans-
piration also declines, and stormwater runoff has to in-
crease. To compensate, agriculturalists have constructed
larger and more efficient drainage systems. Similar prac-
tices have been followed by urban developers. The final
result is the inability of the land to hold enough water
to provide essential natural resource functions. In many
parts of Florida where the surface soils have been drained,
the water holding capacity of the sandy surface soils and
the essential high water table conditions needed to sustain
former wetlands no longer exists.

Long-Term Effects of overdrainage

The following is an extreme example of the difficulty of at-
tempting to rehabilitate wetlands following urban develop-
ment and agricultural overdrainage practices. The water
table aquifers along the Orlando Ridge, the Lake Wales
Ridge, and the Osceola Plain in Central Florida formerly
provided ground water seepage flows to sustain extended flood

9 - 10

plain marshes along the Kissimmee River. The water levels in
the Floridan aquifer along the Orlando Ridge at the head of
the Kissimmee River have dropped largely through agricultural
and urban development actions on the order of 35 feet over
the last fifty years. Formerly high water tables and near
saturated surface soils existed from Orlando southward on
uplands of the basin through the 19601s. The formerly
soggy surface soils typical of the basin's upland areas now
are dry sands.

The formerly high water tables on the uplands surrounding
the Kissimmee River flood plain will have to be recreated to
provide ground water that can move as gravity flow and
gradually seep onto the river flood plains. This cannot
occur today because the potentiometric elevation of the
Floridan aquifer throughout the area is very low, and in-
filtrating rain water percolates by gravity downward to the
lower potentiometric levels of the Floridan aquifer. To
redirect the movement of water table aquifer waters hor-
izontally to the Kissimmee River flood plain will require the
entrapment of enough rain water to recharge the Floridan
aquifer to something near former potentiometric levels.

Assume, as an example of the difficulty of restabilizing
former floodplain conditions, the Floridan aquifer can store
an average of 3 inches of water per foot of elevation, and 3
inches of annual rainfall could be trapped and allowed to
infiltrate into the aquifer on all of the upland areas
around the Kissimmee River. Under this condition, it would
take at least 35 years, assuming no incidents of prolonged
droughts were to occur, to reestablish the ground water
seepage flows necessary to sustain the former wetland
flood plains of the Kissimmee River. The Orlando area,
Lake Wales ridge area, and Osceola County are developing
rapidly, and water demands are increasing commensurately.
The technical likelihood of reestablishing the Kissimmee
River flood plain wetlands is not promising. The above
example is an extreme simplification of the overall re-
gional problem of the Kissimmee River watershed. Solu-
tion of the Kissimmee River ground water recharge part of the
watershed problem would require the coordinated efforts of
Orange, Osceola? Polk, Highlands, and Okeechobee counties
and numerous municipal governments.

St. Johns County Upland Natural Resource Concerns

The St. Augustine metropolitan area partially depends upon
the surficial aquifer beneath the Tillman Ridge for public
water supplies. On a average, every 1,000 new people will
require at least 100,000 gallons of water per day or 35 mil-

9 - 11

lion gallons of water per year. The existing withdrawals are
already resulting in water drawdowns and less ground water
seepage to Trestle Swamp and the headwaters area of the
Moultrie Creek watershed. Unless rainfall water storage
practices are initiated in St. Johns County, neither the
surficial aquifer water supplies nor the existing Trestle
Swamp wetlands can be preserved. It is far simpler and
more cost effective to begin the process of protecting the
County's water resources for various purposes early in the
area growth process than to attempt to restore the resource
at some later date.

The Cowan Swamp at the head of the Moultrie Creek channel is
also in jeopardy. old gridiron plats and scattered residen-
tial development now exist within the depression storage
area of Cowan Swamp. Ditching and draining is now occur-
ring. As more people purchase properties in this area they
will demand drainage improvements. Because the County per-
mitted this type of development, the County is now obligated
to provide for a healthy living environment for these resi-
dents. The preservation of the wetlands environment in
Cowan Swamp is essential for continued base flow in Moultrie
Creek and for the sustenance of the environment in the tidal
estuary part of Moultrie Creek. The incompatibility of past
governmental actions, the health of the area's environment,
and the public health needs of residents will require re-
medial governmental actions that will be costly to County
taxpayers. The County need only look at the multi-million
dollar drainage programs now being demanded by Jacksonville
residents to see the future of the existing conditions in the
Cowan Swamp area.

The difficulty of preserving the Cowan Swamp is further com-
pounded by the extensive uncontrolled positive drainage oc-
curring to the east of Moultrie Creek. The water table re-
duction required for the coquina mining operations can be
expected to gradually result in a long-term decline in the
water table beneath Cowan Swamp and much of the land area
south of State Road 16. As the dewatering of the area con-
tinues, Moultrie Creek can be expected to experience more
days of zero flow and longer extended periods of zero flow.
The dewatering effect on the general area also can be ex-
pected to gradually affect water levels in Five Mile Swamp
and Four Mile Swamp.

Finally, as the demand for potable water from the surfi-
cial aquifer increases, and positive uncontrolled drainage

9 - 12

continues, the inevitable declines in water table conditions
can be expected to result in the following:

1. Increasing residential demands for lawn watering
to support landscape vegetation;

2. Progressive salt water intrusion into surficial
aquifer areas adjacent to Moultrie Creek and the Matan-
zas River;

3. Progressive incidents of upwelling saline water
from the Floridan aquifer as the weight of the fresh
water in the surficial aquifer is removed;

4. Progressive deterioration of wetland conditions in
the 'tidal parts of Moultrie Creek as fresh water
discharges change from the former steady base flow rates
to pulses of heavy runoff following rainfalls;

5. Increasing loads of sediments carried into the
tidal part of Moultrie Creek along with increasing
runoff from rainfall;

6. A gradual extension of the deteriorated estuarine
conditions from Moultrie Creek throughout the greater
St. Augustine Harbor estuary.

Federal Fresh Water Wetland Permits

The U. S. Army Corps of Engineers regulatory program considers
as waters of the United States all tributary streams to
navigable waters to a point where flows are less than five
cubic feet per second. In general, this criterion is being
interpreted as the uppermost five square miles of all water-
sheds, but actual determination is made on a case-by-case
basis. The determination of federal jurisdiction of a pro-
posed project will be made by the Corps of Engineers. All
proposed development actions by private individuals or public
agencies are subject to Corps of Engineers regulatory review.

Florid a Department of Environmental Regulation Permits

Previously cited Florida Department of Environmental Regula-
tion evaluation criteria for tidal wetlands also are appli-
cable to fresh water wetlands.

9 - 13

St. Johns River Water Management District Criteria

The St. Johns River Water Management District (SJRWMD) consid-
ers wetlands as hydrologically sensitive areas and conduct
regulatory review of proposed developments in these areas in
accordance with Section 373.016, Florida Statutes (Section
40C-4.021(5), Florida Administrative Code). Information on
the St. Johns River Water Management District's wetland reg-
ulatory procedures may be obtained from: office of Rules
and Policy Development, St. Johns River Water Management
District, P. 0. Box 1429, Palatka, Florida 32078-12429.

WETLANDS REGULATION PROBLEMS

The enforcement powers of the federal and state government
are being applied to all proposed development actions that
directly disturb tidal and fresh water wetlands. Govern-
mental actions to evaluate the effects of upland areas devel-
opment that can functionally deprive existing wetlands of
the surface and ground water essential for their mainte-
nance is normally given limited consideration.

Primary governmental efforts directly focus upon existing wet-
land conditions and areas. Field inspections typically give
limited review to the long-term functional condition of ob-
served hydric soils, the vegetation indications of an expand-
ing or contracting wetland condition, and the hydrological
regime necessary for sustaining wetland conditions for a
given depressional area of some determined size.

The differing jurisdictional reviews of upland wetlands are
based upon different criteria used by the reviewing agencies.
Private property owners still do not have clear non-conflict-
ing criteria to follow that may be acceptable to all permit-
ting agencies.

Field interpretation procedures used by the differing regula-
tory agencies are not consistently determined among differ-
ing field inspection personnel in any of the regulatory
agencies. The three primary field inspection criteria (hy-
dric soils, indicator vegetation, and actual hydrological
conditions) require cross training and significant field ex-
perience before consistency in judgmental decisions is
achievable.

Finally, the emphasis given by all regulatory agencies is fo-
cused upon the ability of the agency's enforcement power to
regulate. The desire to provide practical and useful guid-
ance to improve the proposed development action in a manner

9 - 14

that could achieve the practical purposes of environmental
management in an expanding urban environment is generally
lacking. As a result, advocacy, confrontational, and avoid-
ance positions are often resorted to by private property
owners.

A FUNCTIONAL BASIS FOR NATURAL RESOURCE AREA MANAGEMENT

Natural resource areas have functional utility beneficial to
the well being of St. Johns County residents. These areas
perform a number of functions that enhance the County's
natural environment. These functions include:

1. Retarding stormwater runoff by serving as tempo-
rary water storage areas;

2. Serving as drainageways and flow-ways that re-
lieve flooding in urban areas while also slowing
stormwater runoff;

3. Serving as sediment and nutrient sinks where mate-
rials are slowly reduced and nutrient and mineral
components essential for other biological processes are
slowly released to streams and estuaries;

4. Serving as wildlife retreats or protected areas in
uplands and as nursery and feeding areas for wild-
life, fin fish, and shellfish in estuaries;

5. Serving as protected corridors for migrating wild-
life;

6. Providing commercially useful wood and other vegeta-
tion based materials;

7. Functioning as natural green space areas within de-
velopments separating urban land use functions;

8. Functioning as a resource for local nature study
of climax and transitional natural vegetation;

As St. Johns County continues to evolve from a predomi-
nately rural to a highly urbanized County, the need to protect
existing natural resources and support the creation of new
natural resource areas will become increasingly apparent. A
balance between subdivisions and natural areas is highly de-
sired by Florida residents. A County management program to
encourage the protection and enhancement of existing natural
areas and the construction of new wetlands and woodlands as

9 - 15

stormwater storage and drainageways would serve many County
resident's desires.

Management practices are needed that serve to encourage pri-
vate property owners to incorporate new natural resource
management concepts into their projects. The present emphasis
upon protection of wetlands by governmental powers at
state and federal levels without commensurate emphasis upon
assistance to property owners to provide functionally effec-
tive natural areas achieves little more than submission
without empathy. The continued loss of essential natural
resource areas can be expected from the existing governmen-
tal divisiveness in wetlands regulation.

A County program that provides clear development criteria can
be established to meet the stated intents of all state and
federal wetlands legislation. Such a County program will
include improved policy level and technical level coordina-
tion with regional and state development review agencies. As
the County program evolves, the need for intensive state
and federal review will become more perfunctory.

CREATING NATURAL RESOURCE AREAS

Retention Storage Areas

Retention storage requirements to accommodate the first one
inch of all rainfalls can be constructed in a wide variety
of forms depending upon the natural storage capacity of local
soils. The basic storage capacity of soils can be deter-
mined from available Soil Conservation Service runoff curve
number information. All types of minor depressions can be
created at elevations above local area annual high water ta-
ble conditions. Swales, or elongated depressions without
outlets or with controlled overflow outlets, are the most
common type of retention facility now in use in Florida,
but all slightly lower land areas between raised resi-
dence pads and raised roadways can be used. On essen-
tially flat lands with normally high water tables, raising
residential house pads and roadways by two or more feet
can effectively provide the necessary detention/retention
storage while preventing flooding of structures and flood-
ing related transportation hazards.

Created sloping topography with low berms along contours
can serve to retain low intensity rainfalls. On slightly
sloping land, flat benches also can be created along contours
to retard the sheet flow runoff. The extensive use of
broad, low elevation recontouring of subdivision, commer-

9 - 16

cial, and industrial open space areas can provide the re-
quired retention storage requirement while effectively re-
ducing sediment transport potentials. Where extensive re-
working of the land surface occurs during the project con-
struction phase, the construction of sediment basins may be-
come necessary until a new vegetation cover is established.
Care in the design of the construction sediment basins
permit their continued use as a permanent detention/retention
areas.

Retention areas should be designed with overflow locations
capable of passing the very infrequent and heavier rainfalls.
overflow should be directed into detention storage basins,
drainageways, flow-ways, or controlled flow discharge chan-
nels.

Detention Storage Areas

Detention storage areas are intended as temporary storage
areas built to accommodate water depths from heavier rain-
falls that must be stored for a short time within a develop-
ment while discharge channels release stormwater at a con-
trolled rate. Any land area capable of holding water with-
out causing flooding of structures and roadways can serve
as detention storage areas. These areas may be extensions
of retention areas where the first one inch from a subwa-
tershed area is not released, but water runoff accumula-
tions to depths in excess of the one inch retention require-
ment are released through saddles or limited capacity drain
pipes to the major storm sewer or surface drainage system.
Playgrounds, general recreation areas, golf courses, wood-
lands, created wetlands, etc., can serve as detention storage
locations. Where shallow drainage channels are constructed,
tieback areas from the discharge location weir, flume, drop-
box, etc., can be raised sufficiently and extended as low
levees or broad berms connected to higher ground to form an
extended detention storage area.

Drainageways and Flow-ways

Constructed drainageways are intended as very low profile
slope systems extending across broad areas that allow storm-
water to flow slowly. Natural systems may be wooded or
wet meadows. When constructed within the annual elevation
range of a local water table, the drainageway will evolve into
a natural wetland typical of a slough. A natural slough
may have a width of several hundred feet, very gradual

9 - 17

side slopes, and maximum cross sectional depths of three or
four feet. Created drainageways will be similarly con-
structed.

Within developments, black willow and cattails tend to become
the first opportunistic vegetation to occupy these areas.
A wide variety of other vegetation natural to north Flor-
ida can be planted to accelerate the establishment of natu-
ral woodland or meadowland conditions. As the vegetation
becomes established, the hydraulic roughness of the drain-
ageway will increase. The design of the system will be
based upon the flow roughness expected from the mature sys-
tem. Again, by weiring or other means these areas can be
designed to provide some detention storage from the infre-
quent periods of heavy rainfall.

Flow-ways are vegetated areas designed to accommodate the
overflow from drainageways and carry runoff from heavy
rainfalls around drainageways or water storage facilities. As
with drainageways, flow-ways will restrict discharges to a
rate of 1.5 cubic feet per second to prevent sediment trans-
port and land erosion. Flow-way design permitting a short
term 2.3 cubic feet per second discharge velocity for runoff
equivalent to the amount expected from the five year, one
hour rainfall occurring on saturated soils will be accepted.
This higher discharge velocity will be used to estimate po-
tential runoff expected only as peak discharge from those
infrequent 24 hour storms expected on a return frequency ba-
sis of 25 years and less frequent storms with still great-
er rainfall depths. Routine distribution of runoff from
the 25 year, 24 hour, rainfall anticipates a short period of
more intense rainfall.

Flow-ways associated with drainageways have bottom elevations
at or slightly above the normal high water table elevation
for the local area. A constructed flow-way can be flat
bottomed or slope slightly away from the drainageway towards
higher ground. The profile slope of the flow-way will par-
allel the similar slope of the drainageway. The width of the
flow-way will be determined by hydrological analysis to, as a
minimum, carry the remainder of the 25 year, 24 hour, runoff
from the local watershed that is beyond the carrying capacity
of the drainageway.

Flow-ways may be designed as a separate major stormwater
runoff collectors of a total system. These facilities will
have bottom elevations above normal high water table condi-
tions for a local area and will remain dry except during pe-
riods of heavy rainfall. A flow-way will be constructed with
broad and shallow cross sections and with gradual sloping
sides on the order of 1:4 (one foot rise per four feet hor-

9 - 18

izontal) or less. Any considered use of steeper side
slopes will require periodic placement of egress means to
permit safe exit by children and animals.

If vegetated side slopes and flow-way bottoms are to be part
of the design, the bottom will be sufficiently broad to
permit vehicular access within the flow-way for maintenance.
Vegetation within the flow-way system will be limited to
grasses and sedges.

Broad flow-ways also will be designed with maintenance
accessways on each side of the flow-way. Open woodland
vegetation planted outside of grassed accessways on either
side of a flow-way would improve the aesthetic acceptability
of system within urban areas. The integration of the
flow-way system with other open space functions such nature
trails or walkways and parks is encouraged.

All storm sewer feeders lines and secondary surface
drains providing runoff to the flow-way will have controlled
flow outlets and sufficient armoring of tailwater areas to
assure that discharge water velocities will not erode the
flow-way's bottom or sidewalls. Where trails and walkways
are designed as part of the system, outlet structures can be
modified for use as pedestrian bridges or viewing locations.

Outlet localities of flow-ways will be at locations where
flow velocities must be increased due to designed system
changes of profile slope. These locations will be armored
to prevent erosion. A wide variety of system designs can be
used. Gunnited or simulated rock garden spillway and water
velocity absorbing areas can be constructed and incorporated
into a development's landscaping plan. Where such ef-
forts are undertaken, hydraulic design to accommodate the
50 year or 100 year stormwater runoff conditions will assure
a longer life for the outlet locality of the flow-way.

Ponds and Lakes

Constructed ponds and lakes have long been used in Florida
to augment subdivisions. Most are actually borrow areas from
which fill has been obtained to provide a desirable contoured
landscape for the development. The use of ponds and lakes in
new developments is an attractive amenity when properly
constructed. Grassed side slopes should be at least 1:4 (one
foot vertical to 4 feet horizontal), for resident safety and
erosion prevention. Gradual slopes should extend into the
pond or lake for a distance of at least 10 feet from the nor-
mal water elevation shoreline. The area above the normal

9 - 19

high water table elevation of ponds and lakes can be used for
water detention storage.

Where constructed in close proximity to residential units,
the need for lakes and ponds to be able to accept runoff from
heavy rainfalls may preclude their consideration as reten-
tion/detention storage facilities. Lakes and ponds con-
structed as an urban area amenity must retain water. Many
such facilities have impervious bottoms to retain surface wa-
ters, and, therefore, have limited retention potential.
Capacity, outlet facility capability, and discharge channel
capability calculations will have to demonstrate the abil-
ity of these facilities to function effectively for both
purposes.

Borrow Pits

Borrow pits are considered as material extraction areas with
no further end use anticipated. The need for sand and
coquina extraction for various development purposes in St.
Johns County is expected to expand with urban development
and the construction of new roadways. A finish design that
will reduce the hazard potential of these areas is neces-
sary. Borrow pits normally are deep excavations with steep
side slopes. Because the excavation extends below the
normal water table, borrow pits fill with ground water
seepage.

To reduce the hazard potential to humans and livestock,
these areas will be constructed with a minimum 10 foot
wide access roadway at normal ground elevation around the en-
tire perimeter of the pit. Outside of this accessway, a
swale type parallel depression at least 15 feet wide and
extending to a depth of at least three feet will be con-
structed around the pit. one 10 foot wide entranceway will
permit access to the edge of the pit. Upon completion of
use, the entranceway will be blocked by fencing or other
means.

The above criteria will provide a created depression sur-
rounding the borrow pit that will evolve into an wetland
populated with opportunistic vegetation. Any sheet flow
moving towards the excavated area will first pass through
the created wetland environment. Similarly, any overflow
from the excavated area will again first pass through the
created wetland depression. The system normally will not
have an overflow outlet, but a constructed drainageway to a
nearby natural drainage system will be permitted.

9 - 20

Greenbelt Woodlands

Larger developments have the opportunity to preserve or
create extended greenbelt woodlands. These areas may be
transitional zones extending from wetlands. They may be
created extensions of existing upland woodlands. Greenbelt
woodlands perform the a variety of functions in urbanizing
areas. As extensions to drainageways, they provide pro-
tected corridors for the migration of wildlife. In an urban
environment, woodlands serve as recreation areas for observing
wildlife and other nature related experiences.. Woodlands
serve as visual natural area breaks between urbanized areas.
Such areas also serve to alter wind flow patterns.

Even small developments can improve the amenity value of
properties by preserving patches of natural woodland. These
areas can be extended by lineal plantings of native vegeta-
tion within and adjacent to drainage easements and con-
structed flow-ways.

Created woodlands can be planted with a variety of trees na-
tive to north Florida that provide food for desired wildlife.
Along the fringes of created woodlands, a variety of food
bearing vines and grasses also can be planted to support
desired wildlife. North Florida has a rich variety of
natural vegetation that provide sources of food and shelter
for wildlife and are adaptable to urban environments.
Guidelines for use by property owners for this purpose can
be prepared and distributed by the County within the context
of its development management program. These guidelines
could be developed as extensions to the St. Johns County
Landscape (Green Law) ordinance No. 79-19.

MANAGEMENT CONCEPTS

Data and Information Needs

Large land areas of St. Johns County are undergoing conver-
sion from open space and agriculture to urban uses. The
current conversion is expected to continue through the fore-
seeable future. More effective methods are needed for eval-
uating the impacts of proposed developments. Improved meth-
ods for evaluating potential impacts of development are need-
ed before land parcels are committed for development if es-
sential County resources and existing natural areas are to be
protected.

This report has identified the need to review proposed de-
velopment actions with recognition of potential long-term im-

9 - 21

pacts upon natural resource conditions in the County important
to the majority of residents. A first step has been taken
to begin the process of developing basic and objective in-
formation on conditions within the Moultrie Creek watershed.
This information is now being incorporated into a computer
geographical information system. This system and its associ-
ated database will permit spatial analyses that will more
clearly pinpoint potential problems within watersheds. With
this information, means for alleviating existing urban area
problems and avoiding future problems associated with proposed
development actions can be more clearly identified. The
continued extension of the process started in the Moultrie
Creek watershed provides the most cost-effective means for
avoiding future problems associated with expected urban devel-
opment within the County.

The County could benefit from revisions in the -development
permit application process that provide for permit application
information to be routinely entered into the geographic
information system and other departmental databases. Much of
the information presently prepared is procedural in nature and
is readily adaptable to entry and recall as computer proce-
dures are expanded.

As the County moves to greater dependence upon computer sys-
tems, procedures can be modified to reduce the departmental
work loads related to the permit application review process.
Changes in the review process also would benefit applicants
as procedures are clarified and simplified for data entry
and recovery purposes.

Additionally, most property owners are unaware of the details
of the County's need to permit economic development while,
at the same time, providing for the health and welfare of all
citizens. It is incumbent upon the County to provide clear
information on the purposes of essential restrictions, as
well as the dictates of those restrictions.

The process of revising development related ordinances and
preparing public information on the purposes and essential
conditions of such ordinances will require substantial
inter-agency coordination within the County government.
This is an internal governmental process that can be ex-
pected to require a significant and long-term effort.

Natural Resource Diversity Needs

A need also exists to maintain a diversity of natural re-
source areas within the County. This can be accomplished
through the protection of existing areas, where practical,

9 - 22

and the creation of new areas to perform essential functions
of natural resource areas as integral parts of new develop-
ments within the County. The following outline lists the
steps required to establish County-level management proce-
dures for protecting and enhancing significant natural re-
source areas.

1. Define the conditions that identify significant nat-
ural resources.

2. Identify subtypes of each category of area that
would require different governmental review and action
procedures.

Develop technically supportable, and legally bind-
ing procedures for delineating these areas.

4. Provide clear statements of the significance of
each area.

5. Develop internal review procedures for proposed de-
velopment actions.

6. Develop database and geographic information sys-
tem analysis procedures for evaluating development ac-
tions and for maintaining records of the character of
each area, its condition, and requirements for mainte-
nance.

7. Prepare urban and agricultural development compati-
bility guidance to assist adjacent and nearby property
owners to undertake property improvements that will
not detract from, and may improve, adjacent signifi-
cant natural resource areas.

8. Prepare performance standards applicable to fu-
ture adjacent and nearby property improvements.

9. Prepare a clear and simplified application and a
one-stop development approval process to be fol-
lowed by property owners.

10. Provide, as available and where applicable, tech-
nical guidance, assistance, and support to property
owners when parallel development approvals must be ob-
tained from regional, state, and federal offices.

11. Develop and consistently implement, reasonable, le-
gally unambiguous, and cost effective enforcement
mechanisms applicable and applied evenly to all pro-
posed development actions to assure that the County's

9 - 23

natural resources and conditions that protect the pub-
lic health and welfare are preserved or enhanced by
each proposed development action.

General and Public Information Needs

Additional general information on the area's resource manage-
ment problems is needed. Information that would permit gov-
ernmental operations personnel to recognize the need for
changes in operations practices would be highly beneficial.
Information that would permit policy-level bodies to respond
to, and apply, the most cost-effective measures for the
benefit of all residents also should be prepared. Fi-
nally, property owners who wish to invest in the area
should be able to obtain clear guidance on County management
purposes, as well as the letter, of development restrictions.

The general public also needs improved information on the
meaning of regional water management and how changes in
policies and practices will affect their lives and the cost
of living within the area. The process of regional water
management will require improved educational Anformation
for use in County schools. Information is needed on real
problems in St. Johns County and how individuals make a
difference in solving problems and in creating a more de-
sirable living environment for everyone. The above actions
provide a means for developing the support and the consent
from St. Johns County residents for improved County re-
source management practices.

9 24

WATER MANAGEMENT PROGRAM

BASIC PROBLEMS

This study has identified a broad range of water related prob-
lems that are interrelated. The general public has a very
limited perspective of County water management needs. Gen-
eral County government concepts focus primarily upon the need
to drain areas and prevent flooding. The public tends to
become concerned with a government's water management pro-
gram for short periods following rare and extremely heavy
rainfalls or storms that cause catastrophic conditions.
Many years may elapse between natural events that cause se-
rious problems. The governmental related problems result-
ing from each event are remembered by too few people.

As St. Johns County continues to develop, the individuals
who witnessed previous heavy rainfalls, flooding events, and
the host of problems associated with such natural occurrences
will become smaller proportions of the County's total popula-
tion. The newer population will be unaware of potential wa-
ter related problems and will be less tolerant of resulting
conditions.

For example, earlier residents of Florida living in a more
relaxed environment were much more tolerant of street flooding
than current populations. St. Johns County is rapidly be-
coming a residential County for people working in the greater
Jacksonville metropolitan area. These newer residents will
be less tolerant of periodically flooded streets that hinder
daily activities or make living conditions more hazardous.

All residents are concerned about the increasing cost of gov-
ernmental functions. The water management program outlined in
this report will result in some increased governmental imple-
mentation costs. Either the increased costs are levied
against new developments by initially requiring the use of
higher levels of technology, or the costs are transferred
to the general population at a later time through higher lev-
els of governmental facility repair and future remedial ac-
tions.

10 - 1

Sound engineering practices exist to prevent or reduce
water related infrastructural problems and natural resource
deterioration. The following information is provided as sug-
gested guidance for a County-wide water management program.
The information is intended only for use as a base for
internal discussions within St. Johns County during the de-
velopment of a scope and structure of a program acceptable
within the County.

ST. JOHNS COUNTY WATER MANAGEMENT PURPOSES

Basic Concepts

1. St. Johns County is a highly desirable place to
live, but experience shows that haphazard development
can be detrimental to the interests and concerns of
the majority of the area's residents.

2. Development will continue to occur throughout the
County and it must be accommodated.

3. The County can absorb all prospective growth with-
out resorting to progressive destruction of the region's
water and other natural resources.

4. County water and other development management ac-
tions can provide for sound economic growth while
continually improving the living amenities of the area.

5. Careful review of proposed development actions and
pre-development resolution of potential problems are
more cost effective actions benefiting the majority of
St. Johns County residents than future remedial ac-
tions that may become necessary to correct development
related problems.

6. County governmental review of proposed develop-
ments must focus upon the potential long-range costs
to County residents of a proposed development and the
manner in which a proposed development will impact upon
.area environmental amenities and the social and eco-
nomic well being of the majority of County residents.

7. Private property owners and developers must recog-
nize that the potential profitability of a proposed de-
velopment action is a private concern to be evaluated
within the framework of County development constraints
considered by the majority of residents as essential for

10 - 2

the maintenance of their health, social and economic
well being, and the area's natural resources.

8. The majority of individual property owners, develop-
ers, and associated legal and technical representatives
do care about the local area and are willing to ensure
the long-term contribution of their development to the
area's well being through careful actions and adherence
to County water and natural resource management con-
cerns.

9. The County government is obligated to develop and
maintain a comprehensive understanding of the social
and economic concerns of residents, general growth man-
agement needs, and criteria essential for designing and
developing projects that will not damage and can im-
prove the infrastructure, water, and other natural re-
sources within basins or other regions in the County.

10. The County government is further obligated to pro-
vide essential guidance and assistance to individual
residents and property owners to assure that proposed
development actions are undertaken within the framework
of County water and natural resource management goals,
objectives, and development constraints.

11. Strong and effectively implemented county pro-
project, construction period, and post-project enforce-
ment measures are necessary and essential to protect
the County's resources, the public health, and the
social and economic well being of 'Majority of the County
residents.

Moultrie Creek Watershed

Concepts

1. The water supply and environmental resources of
the entire St. Augustine metropolitan area are af-
fected by County water management decisions made re-
garding proposed developments in the Moultrie Creek wa-
tershed.

2. The region's economic growth potential, individual's
costs of living, and the St. Augustine metropolitan
area's social, economic, and environmental amenities
will be detrimentally affected by continuation of hap-
hazard development and uncoordinated proposed develop-
ment review procedures in the Moultrie Creek watershed.

10 3

3. Basic information being prepared for the Moultrie
Creek watershed is still incomplete, but newly assembled
materials identify problems sufficiently to provide di-
rection for County actions needed to further improve
the County's ability to provide for the health and so-
cial and economic well being of Moultrie Creek water-
shed residents.

4. Coordinated development review procedures will be
required among County government agencies with re-
sponsibilities for protecting the public health, social
and economic well being of residents, and the County's
infrastructural base (rcads, drainage, and utilities).

5. Coordinated programs, with direct and continual par-
ticipation among all local governments, will be re-
quired to assure the adequacy in quality and quantity
of the regional water supplies and the protection of
the region's environmental attributes.

6. An expanded program is needed immediately within
the County Engineering Department to prepare and
distribute improved development related guidance for use
by individual property owners and large land developers
based upon sound and current engineering principles
that reflect the total water management needs of the
County within the Moultrie Creek watershed.

Subbasin Stormwater Management

Engineering Department capabilities currently are being
fully utilized for permit application reviews, pre-
application site inspections, and emergency field inspec-
tions. Further formalization of these current activities to
provide information suitable for identifying subbasin loca-
tions of inspected sites can provide much of the required da-
tabase information necessary for subbasin analyses. As
capabilities within the Engineering Department increase and
fuller data are entered into the geographical information
system, further development of information on existing
stormwater management systems essential for subbasin evalua-
tions can be assembled.

Subbasin stormwater management procedures consist of analyses
of existing systems in platted areas to determine operational
functions and improvement needs. The analyses provide a
means for the Engineering Department to determine potential
effects of new developments which propose to connect to old-
er conveyance systems. This process will be applied to all
problem areas where new subdivisions have been constructed

10 - 4

in recent years and still additional new development is pro-
posed within a subbasin. The process is specifically needed
to establish the potential, long-term impacts of continued
and total development upon natural stream courses and final
receiving water bodies.

Eventually, the County will have to undertake the rehabilita-
tion of older systems within some platted areas. Master plan
preparation and the construction of systems within exist-
ing platted areas also will have to be undertaken by the
County. Subbasin analyses of these areas by the Engineering
Department will provide necessary information on the reha-
bilitation needs of older drainage systems accepted by the
County.

The following information outlines stormwater management an-
alysis procedures useful for subbasin level evaluations of
potential impacts from new development and for remedial
stormwater system rehabilitation and reconstruction. Primary
evaluation considerations for the above purposes would in-
clude the following:

1. Segmentation of watersheds and delineation of sub-
basin hydrological units or areas with similar types
of Water conveyance. Wetland preservation analyses
would require such delineations to include the proba-
ble ground water contribution areas and surface water
drainage area supplying water for the wetland's suste-
nance.

2. Field inspection of all conveyance units (natur-
al streams and drainageways, channels, and struc-
tures) to establish existing conditions and need for
improvement of each unit identified. The condition and
capacity of each conveyance segment and each structure
must be established. This process requires a standard-
ized evaluation process based upon previously accepted
engineering criteria. The conveyance capabilities of
natural and constructed segments must be determined.
The field inspection process also will identify those
natural systems that can be improved and those sys-
tems that must be preserved in existing conditions.

3. Subbasin hydrology will establish expected run-
off conditions, retention storage requirements, and the
hydraulic adequacy of the existing natural and con-
structed conveyance systems. For new subdivisions, the
developer is required to prepare a hydrological
analysis. Once the County accepts plats and con-
structed drainage systems, maintenance and rehabilita-

10 5

tion normally become County or homeowner association re-
sponsibilities.

4 The hydraulic analysis of existing conveyances
will include identification of utilities, roadway
segments, private ingress points to roadways, and other
factors that are affecting the overall system's per-
formance. A rating system for determining the signifi-
cance of each constraining factor will be developed
as a basis for determining necessary improvement and
for scheduling such improvements.

5. The above rating system will include means for eval-
uating impacts upon natural areas and constructed con-
veyance system components. Included in the rating system
will be an estimate of direct costs for improvements
and cost estimates for subsequent improvements re-
quired at downstream locations.

6. The above information will provide estimates of
costs to the County resulting from continued develop-
ment within subbasins. This information will permit
the County to establish potential impacts on existing
systems resulting from new subdivisions. The informa-
tion also provides a basis for determining County costs
for improving stormwater management systems in older
platted areas.

7. once basic subbasin hydrological and hydraulic
data have been developed, the probable effectiveness of
detention and retention storage procedures can be as-
sessed more completely. These assessments are partic-
ularly important for maintaining significant natural
resource areas. In upland areas, the assessments
will establish the water regime provided to wetlands.
In tidal areas, the concern is oriented towards a re-
duction of strong pulses of stormwater immediately fol-
lowing rainfalls and the need to increaselin base flow
from ground water seepage.

8. A program to address the ongoing and existing prob-
lems in watersheds and subbasins of each watershed pro-
vides the basis for watershed stormwater management.
The effort requires the development of hydrological
and hydraulic data, evaluation of existing conditions,
determination of impacts from new developments, esti-
mates of costs for necessary improvements undertaken
by the County, and a schedule for undertaking the re-
quired improvements.

10 - 6

The above process will require the County Engineering Depart-
ment to allocate some part of its routine operations to the
identification of primary stormwater management problem areas
within the County. Field inspections have already been con-
ducted to determine the conditions of major structures in
the Moultrie Creek watershed. The conveyance unit condition
and capacity determinations remain to be undertaken. These
data are being placed in the geographical information sys-
tem database as non-priority entry items.

The Engineering Department has the technical capabilities
for undertaking the subbasin analysis process, and necessary
analyses can be undertaken as sufficient staff engineers
and engineering technicians are trained to conduct other re-
view and inspection functions. Subbasin analyses and master
plan type system rehabilitation analyses are normally un-
dertaken by internal staffs of large municipalities and coun-
ties.

Effective stormwater management coupled with broader water
management needs of St. Johns County require the development
of an active program for subbasin analyses within the Engi-
neering Department. Computer technology for undertaking nec-
essary evaluations are now readily available and inexpensive.
Microcomputers sufficient for these analyses are being used
within the Engineering Department. The geographical infor-
mation system database information is being assembled. A
program for the gradual development of the subbasin analysis
process can be accomplished as departmental staffing needs
are met.

COUNTY ENGINEERING DEPARTMENT FUNCTIONS

Program Development Efforts

The St. Johns County Commission recognizes the need for an
improved operational program within the County Engineering
Department. Changing long standing practices is a complex
and difficult process. Sound engineering decisions require a
staff of trained professionals. Modern water management
practices in Florida require that professional engineers and
technicians in the County Engineering Department have compe-
tent backgrounds in current techniques for evaluating exist-
ing and potential effects of ground water and surface water.
The County Engineering Department must be able to provide
current technology guidance to County officials and the public
on: (1) flood potentials, (2) reducing flood hazards,(3) pro-
tecting ground water resources, (4) providing water control
measures to protect and enhance significant natural re-

10 - 7

sources within the County, (5) assuring that private water
control measures do not pose a future hazard that may result
in damages to public and private properties or harm to resi-
dents, (6) and assuring that sound, up-to-date engineering
principles are used in the construction and maintenance of
the County's very high cost infrastructure (roads, drainage
systems, and utilities).

Over the past several years, the County Commission has pro-
vided for the gradual transition of the County Engineering
Department operations to provide for the ongoing and future
growth within the County. As part of this transition pro-
cess, the study of the Matanzas River - Moses/Moultrie Creek
watersheds was initiated to identify water related develop-
ment problems and a means for resolving existing and pre-
venting future water management problems within these wa-
tersheds. This initial study effort was oriented towards
the assembly of base level information needed for water man-
agement purposes.

The second phase of the study effort has focused on the Moul-
trie Creek watershed. A concentrated effort has been un-
derway to finalize the assembly of basic technical infor-
mation on the watershed, while, at the same time, pre-
liminary departmental procedures for using the newly avail-
able information were identified and initiated. Part of this
process has included improved inter-departmental coordina-
tion and immediate use of newly developed data and informa-
tion. A final part of this study effort has been oriented
towards the identification of changes needed in the Engineer-
ing Department's water management procedures and operations.
While the focus of the study has been on the Moultrie Creek
watershed, the watershed has served primarily as a model for
improving the Engineering Department's response to development
problems throughout the County.

Basic Data and Information Development

Purpose

The County Engineering Department has been faced with the
problem of reviewing development requests while technical
information needed to determine the regional water, other
natural resource, and infrastructural effects of proposed
development actions have been lacking. Under conditions of
slow growth, small population centers, and primarily distrib-
uted rural land use patterns, pressures on County water re-
lated resources were limited. This condition has changed,
and urban development pressures exist and are expanding
throughout much of the County.

10 - 8

Without adequate data and information and a development re-
view program applicable to, and evenly applied to, all
proposed development projects, little potential exists to
maintain or enhance the County's water and other natural re-
sources. Failure to implement a fair and effective pro-
gram applicable to all potential development actions will
result in: (1) the continued deterioration of the County's
natural resources, (2). the ultimate spread of the deterio-
rated urban blight conditions in those developments which do
not provide suitable living conditions required by future
residents, and (3) extremely high future costs to long term
County taxpayers for remedies to solve problems created by
permissive governmental actions. A number of very large
scale developments are currently in planning stages in St.
Johns County. Numerous other smaller satellite projects
also are already underway or are being planned. The quality
of future water and other natural resource conditions and
the general quality and cost of living in St. Johns County
will be heavily impacted by the combined effects of these
current and planned development projects.

Geographical Information System

In recognition of the need to begin the process of devel-
oping improved base data, The County Commission authorized the
purchase and development of a computer-based geographic
information system. Initial development of this system
also was supported by the Florida Department of Environ-
mental Regulation as part of the Moultrie Creek watershed
study.

A computer-based geographical information system permits
the development, maintenance, and evaluation of data in more
effective formats than were previously possible. The process
requires the digital coding of specific types of data keyed
to a location. Wide varieties of data can be entered and
recalled for evaluation. Any combination of data can be
recalled for a single location or locality for visual
review. This aspect of the system is now in use by the
Engineering Department for those locations and localities
with data entered into the system.

Basic information being coded into the system includes Soil
Survey Data, topographic data, natural drainage system data,
property plat data, roadway data, water and sewer utilities
data, constructed drainage facilities data, floodway and
flood prone area data, and natural resource areas data. Zon-
ing data remain to be entered into the system. Various types
of socioeconomic and land use information being developed by

10 - 9

consultants will be entered into the system as the data be-
come available. Plans are underway to expand soil survey
data to include more engineering criteria available for
soils conditions and data on natural water table conditions.
A wide variety of other specialized types of information are
being considered for entry into the system by other County
agencies. System expansion and networking procedures for
these purposes are underway. Also being studied, are
data exchange programs with regional, state, and federal agen-
cies. A variety of data on St. Johns County are being
collected and maintained on other database systems. Proce-
dures and arrangements for obtaining data useful for County
management purposes need to be developed.

As the above information is entered into the system, it is be-
coming practical for the County to provide property owners
with improved data essential for designing projects and for
meeting County development constraints. Much of the infor-
mation being incorporated into the system was previously
unavailable to property owners and small developers in under-
standable forms and at a reasonable cost. A program is
planned to develop procedures to make basic information
available at a reasonable cost and to permit controlled ac-
cess to the system by technical professionals who are will-
ing to obtain training in the use of the system.

A geographic information system represents a level of tech-
nology that requires care in development and operations.
Personnel entering data into the system require training in
the system operations and an understanding of the signifi-
cance of the data being entered. Academic and commercial
training programs for these purposes are not available,
and on-the-job training in County Engineering Department op-
erational, requirements is needed and must be developed.
Effective use of the system will be dependent upon the
quality of the people employed by the County to operate and
maintain the system.

A geographic information system is not viable as a pur-
chased service. Engineering Department review personnel must
be trained in data entry and access procedures to be able to
perform their normal functions. Two levels of data entry
are required. Initial digitizing or scanning can be accom-
plished by individuals with limited training. Some Engi-
neering Department technical review personnel are already
trained to undertake the first step of digitizing incoming
data. A second step consists of editing the digitized in-
formation before final entry into the system.

Editing and finalizing data require a more complete under-
standing of the performance levels required by users of

10 - 10

the system. Complete documentation procedures for train-
ing personnel and monitoring both levels of data entry
need to be developed for each type of data being incorpo-
rated into the system. This process has been started but
must be fully developed and applied to each new type of en-
tered data.

The start-up of the system also identified the need for stan-
dardizing database system management. Initial data has been
entered for the Moultrie Creek and Moses Creek watershed
studies. As data for other parts of the County or for use
by other County departments are entered into the system,
standardized procedures for entering and accessing data for
the entire County will have to be fully documented. As
the information is assembled in standardized forms, it will
become practical to array and display various types of infor-
mation for any small or large geographical area in the
County. Similarly, numerical data representing any desired
area in the County will become easily accessible, and mea-
surements of area-wide conditions or attributes at some
location will become available for evaluating proposed
developments.

Geographical information system management decisions will have
to be made for every new system user within the St. Johns
County government. Decisions will be needed to deter-
mine whether information suggested for incorporation into the
system is critical or not essential information. Every type
of data to be entered has a cost. Data must be developed,
entered into the system, and stored as part of the system.
Costs are associated with each of these functions. If de-
sired data are not to be used widely or regularly, a decision
will have to be made on whether the costs of assembly and en-
try are worthwhile.

As data are entered into the system, the database storage
requirements for each attribute or overlay must be determined.
If stored off the system, procedures must be developed for
loading and unloading the data for some use. Management
decisions to control access to the system also must be de-
veloped. Complete documentation of the geographical informa-
tion management process and a priority schedule for system
development within available County budget constraints also
must be developed.

The development of the system management process is un-
derway within the Engineering Department. A framework for
the management process and a schedule for the long term de-
velopment of critical database information for other areas
within the County and other user departments within the
County will be prepared during the current fiscal year.

10 - 11

Guidelines

The Engineering Department recognizes the need to provide
improved guidance to individual property owners and large de-
velopers desiring to undertake developments within the
County. This report provides outlined information on many of
the water management related types of information that must
be developed. Individual property owners and small devel-
pers do not have access to the full range of professional
engineering services available to large developers.
0

Additionally, many small engineering firms do not have
ready access to adequate technical information for evaluat-
ing the inter-relationships of ground and surface water
management. Similarly, it is difficult, confusing, and
costly for individuals to be responsive to the varied
environmental rules of local, regional, state, and federal
enforcement agencies.

The Engineering Department has begun the process of devel-
oping fundamental information for use by private individuals
reguesting applications for developments. The initial guide-
lines will consist of hydrological and hydraulic analysis
procedures that will be acceptable to the Department. Much
of the information outlined in this report gradually will
be expanded upon and restructured as guideline information
to be provided for use by individuals interested in some
form of development action. The Engineering Department will
coordinate'the guideline preparation efforts with other local
and regional agencies in an effort to incorporate simpler
and more consistent procedures for individuals to follow dur-
ing a development action.

Technical Investigations

This study of the Moultrie Creek watershed identified prob-
lems and conditions which require further investigation.
The study has raised questions concerning an apparent need
to improve water recharge to the surficial aquifer lying be-
neath the watershed. Questions have been raised about cur-
rent drainage practices and potential impacts upon signifi-
cant natural resource areas. The need to develop clear means
to delineate areas considered as significant natural resource
areas also was noted. Concerns have been raised by the
Department of Environmental Regulation about potential pol-
lution of the greater St. Augustine estuary from roadway
drainage and other urban activities. Potential hazards from
septic tank effluents draining into estuarine waters or con-
taminating ground water supplies have been raised.

10 - 12

The above issues represent potential problems within the Moul-
trie Creek watershed that require further evaluations. A need
exists to determine the significance of identified potential
problems to establish which of these concerns require immedi-
ate governmental actions and the degree of action needed to
resolve each problem. In some cases, early governmental
action can be adopted and effectively administered to
reduce potential hazards to the health, and socioeconomic
welfare of residents, and water and, other natural resources.
In other cases, further evaluations to establish the
most cost effective measures to be undertaken by the County
would be the more prudent governmental action. A number
of the problems identified require further discussions with
residents of the County to determine the extent of local
concerns. This process of public discussion of potential
problems is highly recommended. Residents' concerns and
their willingness to support measures that require higher
levels of technical information and greater governmental con-
straints on development actions must, in effect, guide the
decisions of the County Commission.

As development pressure occurs in other parts of St. Johns
County, some problems similar to those identified in the
Moultrie Creek watershed will be identified. The County
does not have sufficient funds to undertake detailed in-
vestigations of all potential problem areas. A priority
schedule of topics and locations where detailed technical
studies are needed must be developed. This effort is being
undertaken by the Engineering Department. A schedule of
needed investigations will be developed during the 1990
fiscal year.

Every effort will be made by the Engineering Department to ob-
tain supporting assistance for needed studies from other
sources. This report was prepared with technical assistance
from the U. S. Army Corps of Engineers through the Corps of
Engineers State Planning Assistance (Section 22) Program.
The Moultrie Creek study was initiated through a Coastal
Zone Management Grant from the Florida Department of Envi-
ronmental Regulation. St. Johns County is now initiating
a shared effort with the St. Johns River Water Management Dis-
trict to develop basic topographic and soils information
for that portion of the lower St. Johns River basin located
within St. Johns County which is currently under heavy devel-
opment pressure. Soils data for the Moultrie Creek and
Moses Creek watershed were digitized for inclusion in the
County database through an agreement with the U. S. Soil
Conservation Service. Similar data for the lower St.
Johns River basin will become available within the next year.
Additional studies are needed to determine stream flow char-
acteristics in watersheds under development pressure. The

10 - 13

Engineering Department is investigating current needs and the
ability of the County to obtain assistance from the United
States Geological Survey for necessary information. Efforts
by the Engineering Department to extend essential technical
information needed for effective water management through
cooperative efforts and various forms of interagency as-
sistance will continue.

Finally, the findings of studies will be prepared for
distribution and will be provided to County residents. In
some cases, complete reports will be reproduced for dis-
tribution at nominal costs. In other cases, summary data
and information will be prepared for general distribution.
Much of the technical data gradually will be incorporated
into the County database system for use by County agencies
and the public. Findings of investigations also will be dis-
tributed to other governments on a reciprocating basis.

Public and Educational Information

The primary functions of the County Engineering Department
can only be accomplished when the majority of residents un-
derstand and accept the County's resource management needs.
Highly technical information must be summarized and pre-
sented in terms readily understandable by residents. The
previously noted guidelines represent one type of such infor-
mation. However, a need exists to prepare general infor-
mation on technical aspects of water and other natural
resource management as a service to County residents.

The County's water and other natural resource management
needs are appropriate topics for study and discussion in local
schools. The County will cooperate with school system rep-
resentatives in the development of resource materials for lo-
cal educational purposes.

Intra-Agency Coordination

Coordination with other agencies of the St. Johns County gov-
ernment occurs at administrative and technical levels. The
County Engineer is responsive to activities of other depart-
ments that require Engineering Department assistance.
Throughout the Moultrie Creek study period, new information
developed as a result of the study has been reviewed to deter-
mine applicability for use by other departments. Meetings
have been held with other departments to exchange pertinent
information and to determine the future course of action
needed.

10 - 14

On technical staff levels, information exchanges between
the Engineering Department and other departments are essen-
tial. The Engineering Department routinely provides,other
departments with a variety of technical information.

Inter-Agency Coordination

The County Engineer regularly meets with counterparts in
other local governments and with representatives of re-
gional, state, and federal agencies. Each major develop-
ment action requires significant coordination efforts to
resolve management level problems evolving from the action.
Differing technical positions among agencies must be under-
stood and resolved in a manner that satisfies County con-
cerns.

Engineering technology is continually advancing and tech-
nical positions of regional, state, and federal agencies pe-
riodically change. The County Engineer is required to attend
meetings with other governmental bodies when proposed rule
changes and technical requirements of those agencies are
likely to impact upon St. Johns County.

Through the above coordination activities, the County Engi-
neer can more effectively convey St. Johns County interests
and concerns to other agencies. Technical discussions of new
engineering advances and other technological changes advanced
during the coordination process permit the County Engineer to
identify new programs and sources of technical assistance
that would benefit the County.

Coordination with other governmental agencies also is under-
taken by the Engineering Department's technical staff. Much
of this process occurs during the exchange of technical in-
formation. The process provides valuable insight into the
technical operations of other agencies. This process
provides guidance on technical procedures that may improve
the Engineering Department's operational practices. Reg-
ular discussions are held between the County Engineer and
internal staff to identify factors that may lead t o improved
inter--governmental coordination results.

10 15

ST. JOHNS COUNTY DEVELOPMENT PERMIT APPLICATION PROCEDURES

Clearance Sheet Procedures

The following is a summary of the current process required by
any individual interested in undertaking a development action
within St. Johns County-

1. A Clearance Sheet must be obtained from the 911 of-
fice.

a. The St. Johns County Clearance Sheet for Build-
ing Permits outlines the entire process required for
all construction and mobile home permits.

b. The 911 office maintains a database of street
addresses for mailing and emergency purposes. This
office requires the applicant to verify the property
owner, legal description of the property, the public
street to which the property driveway is connected,
and the address of the property. The office then re-
cords the real estate tax number and a tax assessor's
map number on the Clearance Sheet.

C. The 911 office is located at 4425 Avenue A,
Building A, located immediately off Lewis Speedway Drive
and across the street from the County Administration
Building.

d. Telephone Number (904) 829-5722.

2. Once the Clearance Sheet process at the 911 office
is complete, the applicant continues the processing
procedure at the Engineering Department. The Engineer-
ing Department assigns a file number to the Clearance
Sheet and performs the following:

a. establishes a census tract location for the
property;

b. determines the National Flood Insurance Program
zone number, Flood Insurance Rate Map Panel Number,
determination of whether the property is subject to
flooding or is in a floodway or velocity zone, the
first floor elevation criteria requirement;

C. determines whether the property is located on
undrained hydric soils. Proposed developments on und-
rained hydric soils normally may require wetland permits
from the St. Johns River Water Management District, the

10 - 16

U. S. Army Corps of Engineers, and/or the Florida De-
partment of Environmental Regulation. The wetlands
permit will establish the jurisdictional line for the
wetland and those development actions that are permit-
ted in the wetland. The Engineering Department notes
the jurisdictional line, and;

d. establishes the types of utilities planned
(well, public water system, septic tank, sewer system)
and written proof of the arrangements undertaken for
these services. An Engineering Department release is
part of the Clearance Sheet process if the applicant
intends to apply to the Health Department for a septic
tank permit. The Engineering Department also;

e. establishes, as applicable, the location of
the proposed development with respect to the County's
coastal building zone;

f. establishes the type of access required for spe-
cific types of developments abutting specific classes
of roads in the County;

9. establishes criteria and adequacy of plans
for, property drainage.

h. The Engineering Department is located in the
County Administration Building at 4020 Lewis Speedway
Drive;

i. Telephone Number (904) 824-8131, extension 207.

3. Following completion of the Engineering Department
review, the next permit processing step requires a re-
view by the Planning and Zoning Department. The Zoning
review:

a. establishes the property zoning category and
zoning district;

b. establishes pertinent physical characteristics
of the property;

C. establishes any other zoning restrictions or
problems associated with the property;

d. determines whether County subdivision require-
ments are met;

C. establishes other significant information to
be noted regarding division of the land, and;

10 - 17

f. for commercial and multifamily properties, de-
termines the applicability of the County Landscaping re-
quirements.

4. Application for an actual building permit from
the Building Department follows the above steps. The
Building Department requires completed Clearance Sheet
information as a basis for a separate application pro-
cess to obtain a building permit, electric permit,
plumbing permit, and mechanical permit. In addition
to Clearance Sheet information, the Building Department
requires the following prior to issuance of a building
permit:

a. Notice of Commencement;

b. Completed arrangement for utilities and/or nec-
essary Health Department permits;

C. Completed and signed building permit applica-
tion;

d. Building Department information sheet;

e. Three sets of structure design plans;

f. Completed energy compliance forms;

9- Flood hazard information and first floor eleva-
tion restrictions, as applicable.

h. The Building Department is also located in the
county Administration Building.

i. Telephone Number (904) 824-9185.

During the above process, the Engineering Department must
pprove final paving and drainage plans and road and
bridge plans for projects requiring site plan review and ap-
a

proval, pursuant to the ordinance 86-4. These approvals are
required prior to issuance of a building permit. Due to man-
power limitations, no further Engineering Department reviews
are normally conducted prior to final issuance of a Certifi-
cate of Occupancy.

10 18

Permit Application Improvement Needs

The above Clearance Sheet process is complex, costly to ap-
plicants, and costly to taxpayers to implement. The diffi-
culties encountered by a first-time applicant proceeding
from initial contact with the 911 office to completion of a
project are substantial. The complexity of the existing
process is not conducive to the development of even greater
development constraints that may be necessary to protect
and enhance County water and other natural resources.

As growth continues, changes in the current development ap-
plication process will be mandated. Confusion in the mind
of an applicant becomes translated into frustration. Appli-
cant views of governmental bureaucracy and inefficiency
tend to emerge. These views often become attitudes that
can lead- to difficult discussions related to the applica-
tion process at each stop the applicant must make. The pro-
cess can lead to substantial difficulties for application re-
view personnel in each department.

The Engineering Department presently does not have enough
trained personnel to perform necessary reviews and inspec-
tions. Increasing levels of water, other natural resource,
and roadway needs require well-trained staff personnel, and
these are difficult to find at salaries the County gov-
ernment can afford to pay. The ability to obtain and retain
well qualified personnel can be expected to become more dif-
ficult.

The additional staff required by the Engineering Department
will dictate the need for more physical space. other permit
application review departments can be expected to experi-
ence similar conditions. The permit application process can
be expected to result in continually increasing cost to St.
Johns County residents. A need exists to clarify and sim-
plify the existing permit application process.

One-Stop Permit Process

Management Premise

A well-managed government conveys to the public an image
of providing a positive and desired service. Each contact a
government representative has with any resident or his rep-
resentative conveys a view to the public of governmental
management effectiveness and efficiency. The following
process outlines some methods by which a positive image of
government can be conveyed and actual efficiencies in the
permit application process can be obtained.

10 19

Clearance Sheet Process

The Clearance Sheet Process can be improved by the fol-
lowing actions.

1. A general guideline document of the' development
permit application process steps is needed. This docu-
ment would serve as an initial training device for
new governmental employees and as a clear guide useful
to all individuals who wish to know more about the
governmental development management processes. The
guideline document would be written to help the public
understand the purposes of governmental imposed con-
straints upon developments. It would be written to
provide clear guidance on the information and materials
that must be supplied to the government by the individ-
ual. Where additional guidance and detailed direction
is necessary, the guideline would provide clear instruc-
tions on where to go and what must be done by the ap-
plicant to satisfy additional governmental procedures.

Satisfying the complex requirements of the develop-
ment permit application process requires significant
technical capabilities. The guideline document would
clearly describe those technical capabilities necessary
for preparing materials for the process. The need for
knowledge of sound engineering methods and construc-
tion methods would be emphasized. Clear outlines of
the technical concerns of the Engineering Department,
Planning and Zoning Department, Health Department, and
Building Department would be presented. Supplemental
guidelines or codes used by each department would be
noted and guidance for obtaining these materials would
be provided.

Finally, the guideline document would detail the steps
of the permit application process. The Clearance Sheet
checkpoint and sign-off requirements would be clearly
documented and examples of all other necessary de-
partmental forms would be displayed in the document.
Included also would be a description of the stages of
the review process and how the permit application
moves through the several departments. Telephone num-
bers of each department would be provided to permit
the individual to check on the progress of the review
process. Every essential aspect of the permit appli-
@ation process would be identified in the document,
including an applicant's waiver and recourse rights
and actions.

10 - 20

The guideline document would be prepared as.an 8 1/2 by
11 inch document printed in one color for ease in re-
production. it would be structured to represent
government effectiveness, without excess. A reasonable
price, including publication and expected distribution
costs, would be established and noted on the document.
The document would be provided without cost to educa-
tional institutions and other governments. First time
Developers normally would obtain, at a cost, the doc-
ument as part of a permit application package. The
permit application package would include other more de-
tailed department guidelines and criteria.

2. With the guideline document, an applicant could
submit an initial application for a 911 review in per-
son or by mail. Instructions in the guideline docu-
ment would be complete enough to permit individuals
familiar with the system to begin the process by
mail. Signature and other required verification re-
quirements could be accomplished by any Notary Public
prior to application submittal.

An internal permit application review flow process would
be established. Each reviewing office or department
would receive the application through an internal mail
or messenger system. A check sheet would be prepared
to note the time and date of receipt and time and
date of process completion. Each office or department
would have a specified time allocated for initial re-
view. If the application could not be processed within
the stated time, the applicant would be notified of the
delay by phone and a time extension would be noted on
the application check sheet.

If a problem is noted, the applicant would be contacted
by phone or in writing, depending upon the number and
extent of problems involved, and an appointment could
be set up for a discussion session. In some cases, a
decision may be made by the applicant to have the en-
tire application package returned by mail. once an ap-
pointment is made with an applicant, that time period
is his and any walk-ins or extended meetings would
be abbreviated to accommodate the individual holding
the appointment time. All phone calls and personal
discussions would be noted on the application check
sheet. This check sheet would be retained with the
permanent file of the application as a reference of
the entire process.

10 21

if a problem is minor and only procedural, resolution
may be possible through a telephone discussion with the
applicant. For minor development permits or permits
applied for by individuals knowledgeable of the process,
it may become possible for most of the process to be
conducted by telephone and by mail, with only a limited
actual appearance of the applicant.

The above process greatly reduces the need for individuals
to appear at governmental offices. Having an applicant func-
tion as his own permit application messenger is not cost
effective to either the individual nor to governmental de-
partments. Fewer direct contacts with departmental review
personnel required by individuals provide more internal
reviewer processing time through the elimination of unnec-
essary and sometimes unproductive discussions with frustrated
applicants.

Much of the Check sheet information is procedural. As
County database information is expanded and the geographical
information system has wider areal application, the time re-
quired in each department for permit application review
will decrease. Where the review process identifies condi-
tions that require additional application constraints, the
applicant would be notified immediately and, as noted
above, a decision would be made with the applicant on nec-
essary follow-up activities.

As the above process is implemented and greater use is made
of computer based data and information management, the num-
ber of review personnel and space required in each depart-
ment can be better controlled. Emphasis then could be
given to obtaining the highly qualified engineering and
other specialists needed to manage complex technical sys-
tems and perform essential technical evaluations.

ENGINEERING DEPARTMENT FIELD INSPECTIONS

General

Field inspections are essential aspects of the Engineering
Department's routine functions. Staff limitations currently
restrict field inspections to critical problems or emergency
situations. Every inspection requires travel time to and
from the inspection site, time spent at the site, and time
spent preparing documentation of the inspection. Many in-
spections require the participation of two people. with the

10 - 22

Department's current developing staff, on-the-job training
is provided during some routine and emergency field inspec-
tions.

As noted previously, each field inspection provides an oppor-
tunity to add pertinent information on existing stormwater
management systems, roadways, and natural areas to the ge-
ographical information system databases. Field inspection
forms designed to permit subsequent data entry into appli-
cable databases will accelerate the department's data devel-
opment process.

Application Inspections

Preapplication inspections are conducted for larger and com-
plex developments. Applicants desiring to undertake de-
velopments in wetland environments often request County
review of project areas.

Current and expected requests for subdivision development per-
mits exceed the manpower capabilities of the Engineering De-
partment. Preapplication field inspections of such de-
velopments would require the full time effort of at least one
trained inspector.

Construction Completion Inspections

Construction completion inspections prior to issuance of Cer-
tificates of occupancy are not conducted for most development
actions due to manpower limitations. only larger commercial
developments with complex road and drainage systems are regu-
larly inspected.

Emergency Inspections

Emergency situations are reported to the Engineering Depart-
ment on the average of several times each week. These
consist of various drainage and roadway problems. Each
such inspection represents several man-hours of effort. An
estimate 1.5 man-days of effort per week are required by the
Engineering Department to respond to the emergency requests.

10 - 23

ENGINEERING DEPARTMENT ORGANIZATION

Current Structure

Figure 10-1. Current organization of the St. Johns County En-
gineering Department depicts the staff positions currently
funded to undertake daily Engineering Department functions
including permitting information management and special pro-
jects.

Projected Requirements

Figure 10-2. Proposed Organization of the St. Johns County En-
gineering Department depicts the immediate staffing needs of
the Engineering Department to be requested for funding in the
next fiscal year.

PROJECTED ENGINEERING DEPARTMENT PROGRAM

Activity Expansion Needs

Additional capabilities are needed to conduct preapplication
and pre-Certificate of occupancy inspections. One new pro-
fesional engineer recently has been added to the Engineering
staff, but an estimated two additional full-time employees are
needed for these activities.

A departmental executive assistant is needed immediatel@r.
This individual must be capable of providing routine adminis-
trative and supervisory functions while the County Engineer
is not present. The individual need not be a registered
engineer but must be fully knowledgeable with reference
to departmental procedures and functions. This individual
must be capable of providing routine operational practice
guidance to the technical staff in the absence of the
County Engineer. Incoming communications, mail and tele-
phone, would be directed through the executive assistant
to the County Engineer.

Additional technical personnel are needed to expand the de-
velopment of database information associated with the geo-
graphical information system. Cost effective operation of the
system would entail weekend and nighttime data entry and ed-
iting of database information.

Dependence upon the geographical information system and
its expansion is expected. A complete management system is
needed to assure the proper use and controlled expansion of

10 - 24

Current Organization of the St. Johns County Engineering Department FIGURE 10-1

DIRECTOR OF ENGINEERINC

3PECIALIST II

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SENIOR ENGINEER GRAPH IC SYSTETJ =R I GHT OF IrAY AGENT
MANAGER

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CONSTRUCTION
OFFI CIALI INSPECTOR
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Proposed Organization of the St. Johns County Engineering Department FICURE 10-2

DIRECTOR OF ENGINEERING

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ICE SPECIALIST II

ARCHITECTURAL GEOGYAPHICAL
GRAPHICS MAPPING
SPECIALIST SPECIALIST
REAL ESTATE
PROFESSIONAL
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CIVIL ENGINFEED

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SPECIALIST

TECH III
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P 3
TE CH I

the technology. The design of the management system should
be developed with a high degree of departmental control.
A technical specialist capable of designing and implementing
a full range of management procedures is needed. The man-
agement system would be developed to assure adequate and
proper use of the technology by all departments within the
County government. The individual also would be expected
to develop management procedures for the inter-governmen-
tal transfer of database data to and from other regional,
state, and federal agencies.

Engineer Technician Training

The department is going to continue to depend upon engi-
neering technicians for application review and field inspec-
tions. These individuals will need progressive on-the-job
training. They also will be cross trained as geographical
information system operators. All engineering technicians
will be expected to access and interpret routine information
available through the geographical information system. They
also will be responsible for entering new data into digi-
tized form for use in the system when data editing is
complete. Those technicians with an interest and demon-
strated capability will be given further training in final
data editing.

Geographical Information System Development

In coming years, the geographical information system will be-
come a 'primary source of information used for routine and
special functions of the Engineering Department. Other
County departments also will become increasingly dependent
upon the technology.

The progressive expansion of County capabilities in the use
of this technology must be carefully developed to assure
continued cost effectiveness. The current equipment must be
maintained. Data storage management will require increasing
levels of control. Operations will require increasing ac-
cess control measures and priority use measures. A schedule
of expected system expansion requirements must be developed.
Cost estimates of equipment, space, and manpower require-
ments and a priority schedule for system expansion within
budget constraints must be developed. Cooperation procedures
and cost contributions by other departments also must be
developed. System networking potentials and limitations
with potential users in other departments must be deter-
mined. The special needs of other departments may dictate
the need for independent systems, and data exchange proce-

10 - 27

dures then would have to be considered. Finally, the techni-
cal decision process regarding the above must be developed
and fully documented.

Public Involvement Procedures

County administration decisions would be required prior to
consideration of changes in the permit application process.
The Engineering Department would be willing to develop the
guideline document necessary for the process. The Engineer-
ing Department also intends to develop technical guideline
information for use by individuals who must prepare drainage
and paving plans.

10 28

WATER MANAGEMENT FINDINGS

INTRODUCTION

This report section presents guideline information on water
management criteria for consideration in revising the St.
Johns County Paving and Drainage Ordinance. The information
included represents requirements for an urbanizing area where
the interrelated problems of water supply, aquifer recharge,
flood control, stormwater management, and significant natu-
ral resource area maintenance must given consideration.

Without consideration of the above multiple purposes, the
long-term effects upon taxpayers of inaction by a governmental
entity can be illustrated by the following extracts from a No-
vember 19, 1989, Florida Times-Union newspaper article found
on pages A-1 and A-16.

By David Hosansky, Staff Writer

The $23 million that Jacksonville is spend-
ing on drainage projects is just a "drop in
the bucket" compared with what needs to be
spent on drainage citywide, officials say.

Jacksonville's long-neglected flooding prob-
lems have become so overwhelming that an
estimated $50 million to $100 million will
be needed to provide drainage to just a few
of the most frequently flooded areas, such
as Hogans and McCoys creeks, officials say.@

At least 137 areas in the city exist where
flooding can become so serious that people
may drown, and evacuation routes and emer-
gency vehicles become blocked, said prelimi-
nary information in the city's master storm-
water management plan....

After September floods killed two peop le
and stranded hundreds of others, Hazouri

(Mayor) promised a "hurry-up offense" to
get proper drainage to aging neighbor-
hoods....

officials don't even know the full extent of
the flooding problems in the city much of
which lie in a natural floodplain. A $2
million study on the situation should be
completed in two years.

Sixteen projects now are under construction
or being designed....

Once the city does get financing for a pro-
ject, three to five years may be needed to
build it, assuming the project is not put on
hold. It usually takes that long for city
employees or consultants to survey the neigh-
borhood, design the project, acquire right
of way, apply for environmental permits and
coordinate construction with utility compa-
nies.

The city has kept drainage projects on the
back burner for decades. Unlike other pub-
lic works projects, drainage is important
only in bad weather.

EXAMPLE ORDINANCES

Ordinances from a number of Florida counties and communities
were reviewed to determine methods used by other jurisdic-
tions that could have applicability in St. Johns County. As
one example, an ordinance structure has been adopted by
Seminole County that incorporates drainage, dredge and
fill permitting, wetlands protection, paving, subdivision
regulations, and zoning regulations into a land development
code. The code presents the individual ordinances in a
standardized format and represents a movement by the
County towards a coordinated process for managing land devel-
opment activities. The separate departmental responsibilities
are clearly identified.

The Seminole County example represents a simplified codifica-
tion process useful for clarifying individual departmental
functions while eliminating overlapping or ambiguous regula-
tory statements that can occur in separate ordinances. The
procedure also permits improved standardization of termi-

11 - 2

nology and a movement towards a more readable and under-
standable ordinance presentation format.

The ordinance used by the City of Ormond Beach establishes
procedures for a city utility to provide stormwater manage-
ment services. This ordinance also stipulates the prepara-
tion of a water management plan for every new development.
Additional useful guidance appears in the fee schedule for
development reviews and enforcement functions noted in this
ordinance.

The Orange County site development ordinance establishes cat-
egories for land development. This procedure provides for
improved flexibility in the review of proposed develop-
ment actions. Design criteria for stormwater management ap-
pears in the Orange County subdivision regulations.

Finally, Hillsborough County has established a development re-
view department to manage development actions. Stormwater
management purposes appear in the County's site development
regulations and subdivision regulations. These ordinances
provide information on purposes, procedures, fees, enforce-
ment, and penalties applicable to stormwater management and
roadways. The County ordinances reference the Hillsborough
County Storitrwater Management Technical Manual, as the source
of design criteria and analysis methods for stormwater manage-
ment applicable within the County. Similarly, a Highway and
Bridge Technical Manual, provides design criteria and analysis
methods for roadway design. The use of these methods frees
the County ordinance from the need to include design crite-
ria that-require periodic modification.

ordinances adopted at different times and for specific pur-
poses essentially reflect orientations, attitudes and in-
terests of individuals involved in preparing the origi-
nal development restrictions. Revisions undertaken at dif-
ferent times tend to be simple amendments to the original
documents. These conditions result in wide variances in
different ordinance structures, presentation forms, and re-
sultant interpretations.

St. Johns County could benefit from a review of existing
land development management ordinances and some form of
unification of separate ordinances. This study has focused
upon water management needs within St. Johns County. The
following water management criteria reflect some of the man-
agement concerns that could be incorporated into a more gen-
eral codification of land development management procedures.

11 - 3

GENERAL FINDINGS

Purpose

Findings statements are normally included in ordinances.
These statements generally reflect the basis of the ordinance.
Governmental bodies normally include in the findings
statement the general public perceptions of the problem be-
ing addressed in an ordinance.

General public attitudes towards stormwater are largely ori-
ented towards drainage, the simpler removal of water.
Developing concern for the effects of overdrainage on water
supplies and natural resources still requires emphasis. Wa-
ter shortages are now occurring in northeast Florida, but
the relationship between drainage practices and the in-
creased need for landscape irrigation, possibly the major
consuming use in urban areas, is not well understood.

Many developers in St. Johns County are following practices
of cutting roadways down to obtain fill for raising resi-
dential units above 100-year flood levels. This practice
has been followed by developers in Jacksonville and
elsewhere. When allowed in floodplains and on flatlands
with high water tables, the roadways flood following heavy
rainfalls. over time, as storm sewers and other compo-
nents of the local drainage system deteriorate, the flood-
ing problems become compounded. The long-term result
of this practice is illustrated in the above newspaper ar-
ticle on Jacksonville's flood problems. This type of devel-
opment action, in effect, transfers a development cost from
the developer to a future governmental body and the general
taxpayers.

Numerous examples of methods and practices exist for prevent-
ing a wide range of future problems requiring solutions which
eventually become high cost burdens of long-term county
residents. Comprehensive stormwater management in St.
Johns County is readily achievable. The costs of implemen-
tation would be largely a developer's immediate cost and
not a general taxpayers future cost.

Findings Statement

Uncontrolled drainage and development of land have a variety
of significant adverse impacts upon the County's long-term
economic development potential; long-term County infrastruc-

11 - 4

tural management costs; and the health, safety, and welfare
of the residents of the County. More specifically:

1. Uncontrolled drainage can reduce water recharge to
the surficial aquifer used as a source of potable water;

2. Uncontrolled drainage lowers water tables, and,
thereby, removes water from the surficial aquifer by
lowering ground water conditions. This action subse-
quently deprives wetlands of essential ground water, re-
duces essential base flow waters necessary to sustain
low flow conditions in streams, and results in the
need for increased water use for landscape irrigation;

3. Impervious and compacted urban development land
surfaces increase the volume and rate of surface water
runoff, allowing less water to percolate into the
soil and thereby decrease ground water recharge;
4. Construction requiring the alteration 'of the natu-
ral topography and removal of vegetation without
compensating water management control measures results
in increased stormwater runoff and an increased erosion
potential;

5. Uncontrolled stormwater runoff can damage, by
floodwaters erosion and sedimentationP public storm-
water conveyance systems, roadways, and other essen-
tial components of the publicly maintained infra-
structure essential to residents and, thereby, results
in increased costs to residents while also placing the
safety and health of residents in jeopardy;

6. Uncontrolled stormwater runoff can damage and cause
the suspension of services provided by public and
private utility systems upon which residents depend,
and, thereby, can create hazards to the safety and
health of residents;

7. Uncontrolled stormwater runoff can cause damages to
lower properties through flooding, erosion, and sedi-
ment deposition, and these actions can create direct
safety hazards resulting in the endangerment to
residents;

8. Uncontrolled stormwater runoff from streets and
land areas carries increased levels of pollutants into
receiving water bodies, degrading water quality and en-
dangering natural biological processes;

11 5

9. The increase in nutrients supplied to receiving wa-
ters through stormwater runoff from all sources accel-
erates eutrophication of receiving waters, adversely af-
fecting flora and fauna;

10. Improperly managed surface water runoff interferes
with the maintenance of optimum salinity in estuarine
receiving waters.

OBJECTIVES

Purpose

The objectives statement in an ordinance establishes the
legal purpose of the ordinance. The objectives statement be-
comes the basis of criteria and specifications to be followed
in the preparation of water management plans and in the
construction of stormwater management systems.

Criteria

The County recognizes the need for, and encourages, land de-
velopment that will be undertaken and constructed with:

1. Full regard of the long-term socioeconomic well be-
ing of the majority of current and future residents of
the County;

2. Full recognition of the development's long term po-
tential impacts upon the area's public and private in-
frastructure and the developer's responsibility to un-
dertake the development in a manner that will not cause
preventable future infrastructure repair, maintenance,
and rehabilitation costs attributable to the develop-
ment to be absorbed by the County and the majority of
residents;

3. Full understanding that the County is obligated to
protect, maintain, and enhance the immediate and
long-term health, safety, and general welfare of all
residents;

4. Full recognition that by affixing ones signature
to an application for a development permit constitutes
a legal and binding agreement between the signer and
the County that establishes the signer's acknowledge-

11 - 6

ment of personal responsibility for accepting and adher-
ing to the following land development objectives:

a. To permit and encourage development actions
that will not attempt, by any means, to transfer
development related costs, that should be borne
by the developer through full compliance with
established land development and water manage-
ment criteria, to other residents of the County
by lack of compliance or other actions to avoid
compliance;

b. To prevent individuals, business organiza-
tions, and governments from causing harm to the
County by activities which adversely affect water
resources;

C. To protect, restore, and maintain the chemi-
cal, physical, and biological integrity of sig-
nificant natural resource areas and water bodies
within and contiguous to the County by requiring
the preparation of water management plans for all
new development actions that:

(1) result in controlled discharge drain-
age systems designed to provide flood and
stormwater control without damaging water
and other natural resources, and which,
where applicable, provide for ground water
recharge;

(2) provide protection of natural systems
and use them in ways which do not impair
their beneficial functioning;

(3) provide designed water control systems
that function to protect and augment the
functions of natural systems;

(4) minimize the transport of excessive
nutrients and pollutants to waters within
and adjacent to the County;

(5) maintain ground water levels at eleva-
tions sufficient to protect water sup-
plies, wetlands, and natural stream base
flow conditions;

(6) protect, maintain, or restore natu-
ral salinity levels in estuaries;

11 - 7

(7) minimize erosion and sedimentation;

(8) maintain, to the most practical de-
gree, natural fluctuations in levels of
ground water and surface water;

(9) protect, restore, and maintain habitats
for fish and wildlife.

DEFINITIONS

Definitions required for clarification of water management de-
velopment criteria appear in the Glossary of this report.
Specific terms applicable to individual ordinances and to
referenced guidelines normally would appear in each document.

WATER MANAGEMENT PLAN APPLICATION

Purpose

The simpler concept of drainage is now included in a
broader purpose of stormwater management. As an example eval-
uation, the Moultrie Creek watershed study served to
identify basin-wide stormwater management concepts. The
concepts identified included the need to consider the ef-
fects of drainage on the surficial aquifer and the need to
maintain water table conditions through increased ground wa-
ter recharge. High water table conditions are also necessary
to protect wetland natural resource areas and to extend base
flow conditions in natural streams. Runoff water to wetlands
must be sufficient to maintain these natural systems, but
runoff to the systems also must be controlled.

Runoff also must be controlled to prevent erosion and sedi-
mentation in natural streams. By retaining and detaining
runoff on properties, the first flush of pollutants is mea-
surably reduced, and recharge of the surficial aquifer is
increased. Detained runoff released to natural systems at
controlled rates carries less toxic materials and nutrients
to receiving waters. Toxic materials in runoff from road-
ways are major pollutants, and all public and private road-
ways should be managed to reduce pollutants from these
sources.

The above and other purposes presented as County objec-
tives should be addressed before any development action is ap-
proved. A water management plan is a means for presenting

11 - 8

an applicant's proposed actions to address all of the
County's stormwater management concerns.

Criteria

A water management plan shall be submitted to the County
Engineering Department and approved before any private or
governmental water management development action is undertaken
including:

1. A plat is recorded or land is subdivided;

2. A building permit is issued;

3. Any existing public or private stormwater manage-
ment system, or attribute thereof, is altered, rerouted,
deepened, widened, enlarged, obstructed, or filled;

A water management plan is not required for the following de-
velopment activities:

1. Agricultural or siviculture activity being con-
structed and operated in a manner consistent with widely
recognized best management practices and not involving
artificial drainage of land;

2. Any maintenance, alteration, use, or improvement to
an existing structure not changing or affecting the
quality, rate, volume, or location of surface water dis-
charge.

A water management plan is not required for any emergency
act necessary to prevent the material harm to, or destruc-
tion of, real or personal property as a result of condi-
tions, including, but not limited to, fire and hazards
resulting from violent storms or hurricanes or when a prop-
erty is in imminent peril and obtaining a permit is imprac-
tical. Following the emergency action by public agencies
or private individuals, a report of the emergency action shall
be provided to the County Engineer by the responsible admin-
istrator of the action agency or by the person responsible
for management of a private property within a reasonable pe-
riod, but not to exceed ten (10) days, following the in-
cident. The County Engineer or his designee shall conduct a
field inspection of the site and determine whether remedial
action may be needed by the County or private property
owner. The County Engineer shall provide to the County

11 - 9

Administrator a cost estimate and recommendations for any
required remedial action.

WATER MANAGEMENT PLAN CONTENTS

Purpose

Explicit presentation of the acceptable contents of a
water management plan clearly establishes those items that
will be emphasized during the County Engineering Department
review. The County Engineering Department has the responsi-
bility for assuring that every proposed development is re-
sponsive to the County's stormwater management objectives.
The types of information required extend far beyond the
simpler discharge computations typically used to determine
how large a ditch is necessary to get rid of water. The
County must provide clear information to applicants, in
part, to assist the applicant to follow and the public to
accept the County's larger water management concerns. The
water management plan content information presented in the
ordinance is complex, and will have to be supplemented with
additional guidance.

Criteria

it is the responsibility of an applicant to prepare a
water management plan with sufficient information to demon-
strate full adherence to County water management objectives.
All information submitted to the County shall conform with
the ordinary professional skill and diligence of accepted
engineering standards. The information shall be sufficient
to permit the County Engineer to evaluate:

1. The proposed development's impacts upon existing
environmental characteristics of potentially affected
areas;

2. The potential and predicted impacts of the pro-
posed activity on waters within and adjacent to the
County, and;

3. The essential performance and effectiveness of mea-
sures proposed by the applicant for accomplishing the
water management objectives of the County.

The water management plan shall contain maps, charts,
graphs, tables, photographs, narrative descriptions, explana-
tions, system component design specifications, and cita-

11 - 10

tions to supporting references based upon the best current
and available technology, data, and information, as appro-
priate for communicating the information required to sat-
isfy St. Johns County water management objectives, including
the following:

1. The names, mailing addresses, and telephone numbers
of the applicant, property owner, developer, and their
agents including, legal and technical representatives.

2. The legal description of the property and its lo-
cation referenced by state plane coordinates or geo-
graphical coordinates and such landmarks as major wa-
ter bodies, adjoining roads, railroads, subdivisions,
and governmental jurisdictional boundaries clearly de-
picted on a map.

3. A map of the watershed in which the property is lo-
cated including, sufficient watercourse information
to support hydrological and hydraulic determinations
of natural and stormwater flows upstream of the proposed
development and development runoff discharge down-
stream of the development to a point where development
discharge impacts are negligible.

4. The existing environmental and hydrological condi-
tions of the site, the site outfall locality, the wa-
tershed area also contributing to flows at the site
outfall locality, and detailed conditions of the re-
ceiving waters at the site outfall locality including:

a. The direction, flow rate, and volume of sur-
face water runoff under existing conditions;

b. The location of detention and retention areas
on the site where surface water collects or per-
colates into the ground, including estimates of
percolation rates;

C. A description of existing conditions of all
watercourses, waterbodies, and natural resource
areas on and within 1,000 feet of the site.

5. Site conditions and proposed site alterations in-
cluding:

a. Seasonal natural water table elevations, the
existing seasonal fluctuation of water table
elevations, and changes in the existing water
table elevations proposed;

b. The delineated locations of flood hazard ar-
eas and determined elevations, as applicable;

C. Natural vegetation areas and proposed plant-
ings;

d. Existing and proposed site topography;

e. Soils as determined from the Soil Survey for
St. Johns County, Florida;

f. Existing and proposed impervious surface
areas;

9. The locations and sizes of buildings and
structures;

h. Plans and specifications for all stormwater
management structures including estimates of oper-
ational system water surface elevations and dis-
charge rates;

i. Plans for control of erosion and sedimentation
which describe in detail the type and location of
control measures, the stage of development at
which they will be put into place or used, and
provisions for their maintenance;

j. other such information which the developer
or the County Engineer believes is reasonable
and necessary for an evaluation of the develop-
ment.

CATEGORIES OF WATER MANAGEMENT PLANS

Purpose

It would be unrealistic to require a small residential prop-
erty owner wanting to build an addition to his home to
produce a complex water management plan. Abbreviated forms
of the basic management plan requirements are needed for
minor development actions. Each of the topics may require
some statement from an applicant, but the expected perfor-
mance and design specifications of stormwater management mea-
sures presented in a submitted water management plan may
be abbreviated. The actual criteria for types of develop-
ments that should be largely exempted from one or more of the
management plan component requirements are subjects for St.

11 - 12

Johns County to determine. For example purposes, criteria
developed for use in Orange County are noted below.

Example Criteria from Orange County

1. Category One - Development that currently contains
mostly impervious area and where additional development,
and/or site modifications, will cause no increase in im-
pervious area.

2. Category Two - Development not covered in Category
one above, and is less than ten (10) acres total.

3. Category Three - Development not covered in Category
one above and is ten (10) acres or more total.

The above criteria require great care in interpretation.
For example: Category One could apply to a shopping center
or it could apply to a residence that, together with a ga-
rage, driveway, patio, and swimming pool, had more than fifty
percent of the property in impervious area.

if the County adopts some form of the above type of proce-
dure, the preparation of criteria to establish a locally
acceptable category system requires careful review. The pos-
sible inclusions and exceptions to each category must be
weighed to determine that the County objectives will be ade-
quately met through the use of the system of categories se-
lected.

DESIGN STANDARDS FOR WATER MANAGF14ENT PLANS

Purpose

The design of water control systems to accomplish St.
Johns County objectives will require a means for informing
applicants of all required evaluation criteria. Technical re-
quirements for undertaking necessary evaluations requires
higher levels of professional competence than.,are required
for simple ditching and draining.

Design requirements appear within the body of ordinances of
many local governments. For example, Hillsborough County uses
Technical manuals to supplement local development ordi-
nances. The Hillsborough County Stormwater Management
Technical Manual provides a useful example for this

11 - 13

study. The purpose of the Hillsborough County technical
manual is stated below:

The purpose of this Manual is to guide engineers,
architects, planners, and developers in the design
of stormwater management systems in Hillsborough
County. The manual integrates recommended method-
ologies, design procedures, standards and County
stormwater criteria into a single-source document.
The intent of the Manual is to (1) standardize cri-
teria and present suggested procedures and design
aides, (2) make it compatible to the Hillsborough
County Capital Improvement Program and Stormwater
Management Element of the Comprehensive Plan. This
manual represents a coordinated effort to bring
water resource managers, developers and designers
up-to-date with the regulations and criteria appli-
cable to stormwater management design in Hillsbor-
ough County. As an integral part of the Hillsbor-
ough County Stormwater Management Master Plan, this
manual will be utilized by Hillsborough County
for permitting, study, review, and design.

The complexity of modern water management technology re-
quires substantial technical definitions and specification de-
tails that can be readily separated from the legal and ad-
ministrative body of an ordinance. Technical criteria and
design standards can be incorporated into separate technical
guideline documents. These guideline documents would be re-
ferred to in the actual ordinance and, by such reference,
become addendum documents to the ordinance with a legal ba-
sis parallel to the ordinance.

Producing technical criteria and design standards in a sepa-
rate guideline document has the following advantages:

1. - The technical guideline document can be expanded
without modifying the basic ordinance as methodologies,
material specifications, and technical criteria change
to meet new needs and changing technology. Revisions
could be handled administratively under the direction of
the County Administrator.

2. The document can be expanded to include examples
of acceptable procedures for meeting County criteria.
These procedures would be presented as suggested
methods and would not be considered as mandatory.

3. The document could also serve as a single source
of criteria, standards, and suggested procedures for
use by the County government, for all stormwater man-

11 - 14

agement works constructed for the County, and for all
stormwater management works constructed by individuals
with the intent of.requesting the County to accept
the works within a public system.

4. The document could serve as a training and educa-
tional device for new employees and as educational in-
formation for the public. As an educational device,
the information included could be further expanded to
illustrate County purposes for the required criteria and
standards.

Technical Guideline Outline

The following outline is based upon the Hillsborough
County Stormwater Management Technical Manual. The outline is
intended as an example only. The contents of a guideline
document prepared for use in St. Johns County would present
those criteria, design standards, procedures, and other
materials considered locally applicable.

STORMWATER MANAGEMENT
TECHNICAL MANUAL

TABLE OF CONTENTS

1. Introduction
Purpose
objectives
organization of the Manual

2.1 County Ordinances, Regulations and Policies
Introduction
Subdivision Regulations
Land Alteration and Landscaping Ordinance
Park Site Improvement Ordinance
Flood Damage Control Ordinance
Land Excavation Ordinance
Site Development Ordinance
Zoning Ordinance
Building Code
Comprehensive Plan Land Use Element
Comprehensive Plan Drainage Element
Water Pollution Rules
Wetlands Rules

11 - 15

3. General Drainage Standards/Criteria
Requirements Applicable to all Developments
Requiring Review
Drainage Review
Outfall Conditions
Capital Improvement Program Coordination
Developments in Floodplains
Criteria For Development
Interagency Jurisdiction
Stormwater Management Data Requirements
Drainage Area Maps
Stormwater Design Calculations
Drainage Easement Criteria
General Criteria
Enclosed Stormwater Conveyance Systems
Canals and Ditches
Detention and Retention Ponds
Ingress/Egress

4. Determination of Storm Runoff
General
Rainfall Criteria
Rational and Modified Rational Methods
SCS Synthetic Unit and Santa Barbara Urban
Hydrograph Methods
Time of Concentration
Rational Method
Modified Rational Method Inflow Hydrograph
Approach
SCS Synthetic Unit Hydrograph Method
Santa Barbara Urban Hydrograph Method
Modified Santa Barbara Method Computation Format

5. Culvert and Bridge Design
General
Culvert Design Criteria
Culvert Design Procedures
Materials Specifications for Culverts to be
Maintained by the County
Bridge Design

6. Storm Sewer Design
General
Design Criteria
Design Procedure
Storm Sewer Tabulation Form

11 - 16

7. Detention and Retention Ponds
General Criteria
Detention Ponds
Retention Ponds
Detention/Retention Pond Analysis

8. Roadway Underdrain Design
Roadway Underdrain Criteria

9. Non-roadway Ditch Design
General Design Criteria
Utilities Crossing Ditches

10. Roadway (Pavement) Drainage Design
General
Elevation of Low Edge of Pavement
Minimum Roadway Grades
Minimum Roadway Cross Slope
Design Frequency
Runoff Determination
Concrete, Curb, Gutter, and Sidewalks
Grassing, Mulching, and Sodding
Roadway Ditches
Street Drainage

Many of the topics included above would be appropriate for use
in a St. Johns County Technical Guide. All criteria and
specifications presented in local ordinances applicable to
stormwater management would be included in the technical
guide. St. Johns County review agencies regularly encounter
a variety of difficulties in the application review process.
Prepared information to address many of these problem areas
can be usefully expanded upon in the prepared technical guide.

FEES

Purpose

Significant costs are incurred by St. Johns County during
the review of an application for a development permit. Much
of these costs should be a burden of the applicant.

A pre-application conference is highly desirable. This
meeting probably should be a County cost, but its use would
result in fewer application processing problems and subse-
quent negative applicant actions.

11 - 17

Example Fee Schedule

The following standardized fee schedule used by Ormond
Beach provides some guidance for consideration:

Industrial, Commercial, Subdivisions, and Multi-Family
Residential, Including PUD's

BASE FEE $200.00
Plus $15.00 per acre for each acre or fraction
thereof up to 10 acres
Plus $8.00 per acre for each acre or fraction
thereof over 10 acres up to 40 acres
Plus $5.00 per acre for each acre or fraction
thereof over 40 acres up to 160 acres
Plus $2.00 per acre for each acre of fraction
thereof over 160 acres

Miscellaneous

BASE FEE $100.00
Plus $7.50 per acre for each acre or fraction
thereof up to 10 acres
Plus $4.00 per acre for each acre or fraction
thereof over 10 acres up to 40 acres
Plus $2.50 per acre for each acre or fraction
thereof over 40 acres up to 160 acres
Plus $1.00 per acre for each acre or fraction
thereof over 160 acres

ENFORCEMENT AND VIOLATIONS

Purpose

The purpose of a water management ordinance and the meaning-
fulness of the stated County objectives are determined by the
willingness of the County to undertake enforcement actions.
Enforcement actually begins with the actions of the County
Engineer in approving and disapproving proposed development
actions. Each reversal of a departmental determination by
administrative action sets precedence for development actions
unacceptable to the County. When administratively approved
development actions are outside of the terms of the ordi-
nance criteria and design specifications, the administrative
action constitutes a precedent that can diminish the ef-
fectiveness of the ordinance. Other individuals learning of
an accepted action not in conformity with the ordinance can

11 - 18

legally demand equal or Parallel treatment. The ordinance
can then become essentially void and noneffective.

The ordinance is also reduced in effectiveness when viola-
tions are overlooked or are forgiven. The strictness of
enforcement actions must be acceptable to the public, and,
therefore, the structure of the ordinance and the design of
enforcement mechanisms for stormwater management in St.
Johns County must be developed with the consent of resi-
dents.

Criteria

Enforcement actions should be standardized and documented.
Environmental enforcement procedures in federal and state a-
gencies are moving towards the greater use of administrative
processes for civil actions.

Once a standardized administrative fine system is estab-
lished, the Engineering Department would make the determina-
tion of actions occurring in violation of County criteria
and design specifications. The County Administrator or his
designee would then levee the fine.

The administrative enforcement procedure would be estab-
lished through the local ordinance process as one of a sys-
tem of enforcement mechanisms. Included in the ordinance
could be a parallel system for resolving violations using
the state judicial system. Under the above administrative
process, the judicial process normally would be a recourse
action for an individual.

The ordinance also could include other actions of the County
to insure maximum compliance with established criteria and
specifications. County Engineering Department criteria and
design specifications should be based upon current and appli-
cable professional standards. Registered professionals who
affix their signatures and registration seals to documents
are certifying that the ordinary standards of their profes-
sion have been applied to the information in that document.
Significant deviations from professional standards on the
part of, members of registered professions are matters
that should be directed to state professional registration
agencies. The County's intent to follow such redress ac-
tions should be included in an ordinance, in guideline
documents, and on development permit application forms.

11 - 19

LOCAL GOVERNMENTS PROVIDING ORDINANCES FOR THIS STUDY

Alachua County
Clay County
Duval County (Jacksonville)
Flagler County
Hillsborough County
Orange County
Pinellas County
Seminole County
Volusia County
City of Jacksonville Beach
City of Ormond Beach
City of Port Orange

11 20

GLOSSARY OF TERMS

Adverse Impacts - Any modifications, alterations, or effects
on a feature or characteristic of waters within or adjacent
to the County and significant natural resource areas, in-
cluding their quality, quantity, hydrodynamics, surface
area, species composition, living resources, aesthetics or
usefulness for human or natural purposes which are or may be
potentially harmful or injurious to human health, welfare,
safety, or property; to biological productivity, diversity,
or stability; or which unreasonably interfere with the enjoy-
ment of life or property, including outdoor recreation.

Alligator Cracks - Interconnected cracks forming a series of
small blocks resembling an alligator's skin or chicken-wire.
These cracks are caused by excessive deflection of the surface
over unstable subgrade usually as a result of saturated granu-
lar bases or subgrade.

Applicant - Any property owner or person, partnership, or
corporation, agent, or duly authorized representative who ap-
plies for a development permit.

Aquifer.-- A water bearing stratum of permeable rock, sand or
gravel. A body of saturated rock or sediment through which
water can move readily.

Artesian Water - Water confined under hydrostatic pressure
which will rise in a well when tapped.

Base flood - The flood having a one percent chance of being
equaled or exceeded in any given year, according to FEMA.

Base flood elevation - The elevation measured in feet above
mean sea level, as shown on a Federal Emergency Management
Agency Flood Insurance Rate Map.

Base Flow - Release of water from subsurface storage to a
stream flow.

Benthic Organisms - Those organisms which occur at the bottom
of a body of water or at the depths of the ocean.

G - 1

Bond - A form of surety or guarantee agreement which contains
the promise of a third party to complete or pay for the cost
of remedial action or completion of a construction con-
tract, a subdivider's agreement, a developer's agreement, or
a condition or finding certified by an agent which subse-
quently does not perform as certified.

Borrow Pits - Location of excavation of soil to be used in
another location as fill.

Capillary Rise - The distance above the water table and into
the less saturated soil that water rises by capillary forces.

Commensurately - Corresponding in size, measure, or amount.

Cone Of Depression - Water-table shape resulting from flow to
a well.

Clearing - The removal of trees and brush from the land but
shall not include mowing.

Construction - Any activity including land clearing, earth-
moving or the erection of structures which will result in the
creation of a system.

County - Unincorporated St. Johns County.

Detention - The collection and storage of surface water in a
manner that provides for treatment through physical, chemi-
cal, or biological processes for subsequent discharge at a
rate which is less than the rate of inflow.

Detrital A product of disintegration, destruction or wear-
ing away.

Detritus Loose material (as rock fragments or organic part-
icles) that results directly from disintegration. Product of
disintegration or wearing away.

Developer - Any person who acts on his own behalf or as the
agent of an owner of property and who engages in alteration
of land or vegetation in preparation for construction activ-
ity.

Development - Any man-made change to improved or unimproved
real estate, including, but not limited to, buildings or
?ther structures, mining, dredging, filling, clearing, grad-
ing, paving, excavating, drilling operations, or permanent
storage of materials.

G - 2

Direct Evaporation - Evaporation directly from the surface of
a body of water.

Discharge point - The outf low of water from a project, site,
aquifer, drainage basin, or facility.

Drainage system, natural drainage system - Surface water
streams or wetland natural resource areas which convey water
to natural points of discharge.

Drainageway Soils - Soils occurring in drainageways as re-
ported by the SCS in the soil descriptions of the Soil Survey
of St. Johns County, Florida.

Dropbox - Also called a drop structure. A grade control
structure which provides for a vertical drop in the channel
invert between the upstream and downstream sides.

Enforcement official - The County engineer or his duly ap-
pointed representative responsible for enforcing the provi-
sions of these criteria and insuring plan adherence during
and following construction phases.

Engineer - A professional engineer registered in the State
of Florida, or other person exempted pursuant to the provi-
sions of Chapter 471, Florida Statutes, who is competent in
the field of civil engineering.

Engineer of Record (EOR) - Any individual registered by the
State of Florida as a Professional Engineer. Further, the
individual must be competent to perform engineering assign-
ments in the specific technical field of Civil Engineering
and such engineering practice must not be in conflict of
Rule 21H-19.01 of the Rules of the Department of Profes-
sional Regulation, Board of Professional Engineers.

Estuary A water passage where the tide meets a river cur-
rent.

Eutrophic Rich in dissolved nutrients but often shallow and
seasonally deficient in oxygen.

Eutrophication - The process by which a body of water becomes
either naturally or by pollution rich in dissolved nutrients
(as phosphates) and often shallow with a seasonal deficiency
in dissolved oxygen.

Evapotranspiration - Loss of water from the soil both by
evaporation and by transpiration from the plants growing
thereon.

G - 3

Existing The average condition occurring immediately before
development or redevelopment commences.

Final Discharge Points - Point at which the entire flow being
considered is discharged into another region or larger body of
water, usually a lake or the ocean.

Flatwoods - This type of ecological community occurs on
nearly level land. Water movement is very gradual to the nat-
ural drainageways, swamps, ponds, and marshes associated with
this community. Wet conditions prevail during the rainy sea-
son with the water table at or near the surface. It is easily
identified by the flat topography and characteristic vegeta-
tion. Types of flatwoods include South Florida Flatwoods,
North Florida Flatwoods, and Cabbage Palm Flatwoods.

Flood or flooding - A general and temporary condition of
partial or complete inundation of normally dry land from
the overflow of inland or tidal waters or the unusual and
rapid accumulation of stormwater runoff.

Flood plain or flood prone area - Any land area susceptible
to being inundated by water from any source.

Floodway - The channel of a stream plus any adjacent flood
plain areas that must be kept free of encroachment in a
manner that the 100-year return frequency flood discharge can
be carried without increasing flood heights by more than one
foot. The location and extent of floodway areas are defined
in the Flood Insurance Study for St. Johns County, pub-
lished by the Federal Emergency Management Agency (FEMA),
revised'September 18, 1985, and as may be amended from time to
time.

Flood hazard area - A land area within St. Johns County
determined by the Federal Emergency Management Agency and
displayed on Flood Insurance Rate Maps prepared by that
agency as being subject to flooding from a 100-year return
frequent flood event.

Flume - An open channel constructed of wood, steel, or rein-
forced concrete and used to convey water for various purposest
including grade control.

Hardwoods - Periodic or seasonal flooding is characteristic
of this ecological community. Hardwoods are often associated
with adjacent swamps.

Hydric Characterized by or requiring an abundance of mois-
ture.

G - 4

Hydric Hammocks - Moderately moist regimes without excessive
water or drought conditions characterize this community.

Hydric Soils - Soils that are sufficiently wet under und-
rained conditions to support the growth and regeneration of
hydrophytic vegetation. The list of these soils includes hy-
dric soils that are either drained or undrained; therefore,
not all areas of hydric soils support predominantly hydro-
phytation and thus are not wetlands. Soils designated by the
SJRWMD which have the characteristics of being inundated or
saturated on an average of 30 consecutive days per year.

Hydraulic Gradient - The total head loss divided by the
length of flow in a drainage structure.

Hydrologic Cycle - The movement of water and water vapor from
the sea to the atmosphere, to the land, and back to the sea
and atmosphere again.

Inundation - Completely covered by a flood.

Land - The earth, water, air, above, below, or on the sur-
face, including any vegetation, improvements or structures
customarily regarded as land.

Liquid Limit - The moisture content at which the soil passes
from a plastic to a liquid state.

Lot - A portion of land identified as a single unit in a
subdivision and intended for lease, transfer of ownership,
use, or.. improvements; or a parcel, or a tract. Such land
consisting of sufficient size to meet minimum development
requirements, and such land having an assigned number, let-
ter, or other name through which it may be identified.

Mounded Ground Water - Groundwater which follows the contours
of the land surface through an increase and decrease in eleva-
tion (as in a hill).

Muck - Dark colored, finely divided, well decomposed organic
soil material.

Natural flow - The rate, volume, and direction of the surface
or ground water flow occurring under natural conditions in
any given portion of the County.

100-Year Return Frequency Event - A precipitation event which
can be expected to occur on the average of once every 100
years or which has a 1/100 (1 percent) chance of occurring in
any given year.

G - 5

Parent Material - The unconsolidated organic and mineral ma-
terial in which soil forms.

Peat - Unconsolidated material, largely undecomposed organic
matter, that has accumulated under excess moisture.

Perched Water Table - A surficial aquifer, usually limited in
extent, above an impervious stratum which separates the
perched water table from a larger, more significant aquifer.
A water table separated from the main water table beneath it
by a zone that is not saturated.

Percolation - The downward movement of water through the
soil.

Permeability - The quality of the soil that enables water to
move downward through the soil profile.

Perviousness - The degree of permeability.

Plastic - Capable of being deformed continuously and perma-
nently in any direction without rupture.

Plat - A map or a delineated representation of the subdivi-
sion of lands.

Porosity - The ratio of the volume of intertices of a mate-
rial to the volume of its mass. The percentage of a rock's
volume that is taken up by openings.

Positive Drainage - Drainage of a soil, usually an aquifer,
which removes more water than can naturally or than is artifi-
cially recharged. This type of drainage permanently lowers the
water table below the level at which the water table naturally
occurs.

Potentiometric Surface - The level to which water rises with-
out pumping in a tightly cased well.

Prairies - occur in shallow depressions in pine flatwood and
dry sand pine/scrub oak communities. Inundation is typically
seasonal, ranging from 0.5 to 2 feet. Soils are typically
shallow organics overlying clay or compact sands. Water
reaches prairies either from direct rainfall or runoff from
immediately adjacent uplands. Prairies are typically small,
isolated perched wetland systems in the upper portion of the
watershed.

Private Roads - A cleared or improved street or road located
within a right-of-way or easement owned by a home owners asso-
ciation, private individuals or any entity other than St.

G - 6

Johns County or the State of Florida. ownership of private
roadways shall be vested jointly in all abutting land owners
or in a home owners association whose voting members consist
of such abutting land owners. ownership of the private road-
way by the developer is not permitted after construction of
the private roadway unless he is the sole owner of all abut-
ting properties and agrees that any properties abutting the
private roadway which may be conveyed to others in the future
will include the use of the private roadway by the lot owners,
their guests, invitees, successors and assigns.

Public Roads - A street or road located within a right-of-way
owned by St. Johns County or the Florida Department of
Transportation. The street must have been dedicated or deeded
to, and accepted by, either agency.

Predevelopment conditions - Those conditions which existed
before alteration, resulting from human activity, of the nat-
ural topography; vegetation; and rate, volume, or direction of
surface or ground water flow, as indicated by the best avail-
able technical data and information.

Receiving bodies of water - Any water bodies, water courses,
or wetland natural resource areas into which surface water
flows or ground water seepage reemerges or results in satu-
rated surface soils.

Recharge Capabilities - The ability to annually replace vol-
umes of groundwater.

Retention - The collection and storage of stormwater runoff
without subsequent discharge to surface waters.

Return Frequency - Time interval between storm events which
produce -similar predetermined intensity and runoff volumes
which are used in designing surface and stormwater management
systems.

Right-of-way - Land dedicated, deeded, used, or to be used
for a street, alley, walkway, boulevard, drainage facil-
ity, access for ingress or egress, or other purpose by the
public, certain designated individuals, or governing bodies.

Riparian Lines - Bank of a watercourse.

Runoff - The precipitation discharged into stream channels
from an area. The water that flows over the surface of the
land without percolation into the soil.

G - 7

SCS Curve Number - Values ranging between 1 and 100 that are
used in calculating runoff rates by the SCS method. The more
impervious a surface, the higher the curve number.

Saddles - Drainage structures to limit discharge.

Saturated Soils - Soils in which all the interstices are com-
pletely filled with water.

Sediment - Fine particulate material, whether mineral or or-
ganic, that is in suspension in a water column or has been
transported by flowing water and has settled on land or within
a water body.

Sedimentation facility - Any structure or area which is de-
signed to hold runoff water until suspended sediments have
settled.

Sheetflow - Uniform flow of water in thin layers on a sloping
surface.

Significant Natural Resource Areas - Conservation areas and
preservation areas which include but are not limited to the
following types of wetlands, natural water bodies, and up-
lands: freshwater marshes, shallow grassy ponds, hardwood
swamps, cypress swamps, natural shorelines other than natural
beaches and dunes, Class III Waters, and sand pine-scrub com-
munities. Preservation Areas include the following types of
wetlands, natural water bodies and uplands: coastal marshes,
mangrove swamps, marine grassbeds, natural beaches and dunes,
Class I and II Waters, aquatic preserves, critical habitat for
endangered, threatened or rare species, and State wilderness.

Site - Any tract, lot, or parcel of land or combination of
tracts, lots, or parcels of land which are in one ownership,
or are contiguous and in diverse ownership where development
is to be performed as part of a unit, subdivision, or
project.

Slough - An ecological community which appears as an open ex-
panse of grasses, sedges, and rushes in areas where the soil
is saturated during the rainy season. Most sloughs are rela-
tively long and narrow and slightly lower in elevation than
the surrounding flatwoods or hammocks.

Soil Horizon - A layer of soil approximately parallel to the
surface, having distinct characteristics produced by soil-form-
ing processes.

Soil Matrix - Structure and arrangement of soil particles
within the soil horizon.

G - 8

Soil Mottling - Irregular spots of different colors that vary
in number and size. Mottling generally indicates poor aerea-
tion and impeded drainage.

Soil Profile - A vertical section of the soil extending
through all its horizons and into the parent material.

Species - A class of individuals having common attributes and
designated by a common name.

Stormwater - The flow of water which results from, and which
occurs immediately following, a rainfall event.

Stormwater Management System - The designed collection of fa-
cilities, improvements, or natural systems of the project
which collect, convey, channel, hold, inhibit, detain, retain,
release, or divert the movement of stormwater in a controlled
manner. Includes dams, impoundments, reservoirs, and appurte-
nant works.

Structure - That which is built or constructed, an edifice or
building of any kind, or any piece of work artificially built
up or composed of parts joined together in some definite man-
ner.

Surficial Aquifer - An aquifer that is at atmospheric pres-
sure.

Surveyor of Record (SOR) - An individual registered under
Chapter . 472, Florida Statutes. Further, the individual must
be in good standing with the Florida Board of Professional
Regulation.

Swale - -A man-made trench which:
A) Has a top width-to-depth ratio of the cross-section
equal to or greater than 6:1, or side slopes equal to or
greater than three (3) feet horizontal to one (1) foot vert-
ical: and,
B) Contains contiguous areas of standing or flowing
water only following a rainfall event: and,
C) Is planted with or has stabilized vegetation suit-
able for soil stabilization, stormwater treatment, and nutri-
ent uptake: and,
D) Is designed to take into account the soil erodibil-
ity, soil percolation, slope, length, and drainage area so as
to prevent erosion and reduce pollutant concentration of
any discharge.

Swamps - A poorly drained depression in which water is at or
above the surface periodically throughout the year.

G - 9

Transpiration - The passage of watery vapor from a living
member through a membrane of pores.

Turbid Waters - Stream flow that is thick or opaque with
sediment.

Vegetation - All plant growth, especially trees, shrubs,
vines, ferns, mosses, and grasses.

Water - Any and all water on or beneath the surface of the
ground or in the atmosphere. This includes the water in wa-
ter courses, waterbodies, and natural or constructed drain-
age systems. Water also includes diffused surface water
and water percolating, standing, or flowing beneath the
surface of the ground.

Water Management Plan - The detailed analysis and materials
prepared to display and provide information regarding any and
all development actions that impact water.

Water Quality - Characteristic of the water based on relative
turbidity, temperature, amount of dissolved oxygen, and
amounts and types of contaminants.

Water Table The upper limit of the soil or underlying rock
material that is wholly saturated with water.

Watercourse Any natural or constructed stream, river,
creek, drainageway, flow-way, channel, ditch, canal, con-
duit, culvert, drain, waterway, gully, ravine, slough,
spillway, swale, wash, and similar natural or constructed
area in which water flows in a definite direction, either
continuously or intermittently, and which has a definable
channel, bank, and bed or bottom.

Waterbody - Any natural or artificial pond, lake, reservoir,
borrow pit, or other area which ordinarily or intermit-
tently contains water and which has a discernible shoreline.

Watershed - A region or area bounded peripherally by a water
parting and draining ultimately to a particular watercourse or
body of water.

Weir - A dam in a waterway to raise the water level or divert
its flow. An instrument for measuring or regulating surface
water discharge.

G - 10

Wetlands Those natural resource areas with normally and pe-
riodically saturated soils or with shallow flooded areas
and with dominant plant communities adapted to saturated
soils and shallow flooding conditions.

G 11

APPENDIX

PHASE 2 STUDY PROCESS

PROJECT PURPOSE

A 1979 study was conducted in the Matanzas River under the
Florida Coastal Zone Management Program to determine means for
saving the local shellfish growing areas for human use. Sep-
tic tank drainage and stormwater runoff were identified as the
major sources of decreased water quality and contamination of
shellfish areas within the Matanzas River.

The progressive deterioration of water quality in the estua-
rine water in the Matanzas River gradually can be expected to
extend to all the water bodies served by the St. Augustine In-
let and to the coastlines adjacent to the inlet. Unless im-
proved management practices are adopted and adhered to by St.
Johns County and the City of St. Augustine, the loss of the
local estuary's water quality can be expected to be progres-
sive. Shellfish harvesting is now generally prohibited, with
some remaining areas "conditionally approved," and the water
quality of the estuary now generally falls within a Class III
category or waters suitable for fishing and swimming. Only
the caring application of well-known management practices re-
lated to urban development throughout St. Johns County can
arrest this progressive trend towards further estuarine water
quality deterioration.

Subsequent to the 1979 study, the St. Johns County Commission
adopted a County-wide drainage ordinance and strengthened
regulation of septic tanks. However, progressive deteriora-
tion of water quality in the Matanzas River and adjacent wa-
ters has continued.

The Florida Department of Environmental Regulation has recog-
nized that a local comprehensive basin-wide approach to man-
agement of stormwater and other point and nonpoint sources of
water pollution is necessary to arrest the ongoing water qual-
ity deterioration problem in the St. Augustine area estuary.
DER has noted that project by project review and approval of
developments without consideration of basin-wide conditions

A - 1

and project impacts is resulting in continued deterioration of
estuaries throughout the state.

As a means of assisting St. Johns County and other smaller
governments to develop capabilities to undertake the level of
management necessary to protect the state's waters, DER sup-
ported the County Engineering Department's efforts to under-
take a comprehensive surface water condition and management
analysis of the Moultrie Creek and Moses Creek Basins. The
analysis of surface water conditions was conducted as Phase 1
of the study completed in May 1989. The Phase 2 analysis and
the primary focus of this report, is the development of a
conceptual stormwater management process for the Moultrie
Creek and Moses Creek Watersheds and the development of a com-
puterized information management system that could support wa-
tershed level stormwater management in St. Johns County.

INSTITUTIONAL CONSTRAINTS

The St. Johns County Engineering Department has the technical
capabilities for undertaking an analysis of existing surface
water conditions within the study area. The Department also
can conduct comparative evaluations of technical alternatives
for reducing pollution to estuaries carried with surface water
runoff from roadways and land developments. The existing
County Paving and Drainage Ordinance (No. 86-4) provides very
limited capabilities for Engineering Department control needed
for more comprehensive basin-wide stormwater management pur-
poses.

Effective management of pollutants being discharged to the Ma-
tanzas River and other important natural resource areas re-
quires a comprehensive approach to point and nonpoint source
pollution discharges with positive participation from a number
of local governmental agencies. The effort would require co-
operation between the County government and the City of St.
Augustine. As importantly, the residents of the County and
St. Augustine would have to strongly support governmental ac-
tions to undertake a basin-wide approach to reducing the dis-
charge of contaminants to the County's estuaries

SOCIAL CONCERNS

The need for comprehensive basin-wide management of pollution
sources has been recognized by technical specialists in the
United States for several decades. The ability to develop ef-
fective measures to reduce the effects of pollution have been

A - 2

limited because of the numerous ways that pollutants enter the
environment. All governmental agencies are segmented into
specialized departments, and the responsibilities and abili-
ties of any single department to participate in a comprehen-
sive program to control pollution is very limited. Finally,
most solutions are based upon obscure or technical and costly
premises that are difficult to understand and accept.

Technically sound engineering practices that can reduce pollu-
tion discharges in stormwater can only be applied to the de-
gree that the residents of the County can understand and ac-
cept the usefulness and added costs to projects of these prac-
tices. The County Engineering Department rules must balance
the application of technically based restrictions to proposed
projects and local comprehension and willingness to accept
these restrictions. Therefore, the structure of a conceptual
basin-wide stormwater management process must balance the
technically based constraints of the management process
against the community understanding and acceptance of such
practices.

Moreover, the County Engineering Department's rules and devel-
opment evaluation procedures are responsive to only the storm-
water discharge part of the pollution affecting the Matanzas
River. Technical evaluations of the significance of the vari-
ous sources of pollution presently cannot determine which pol-
lution sources are more significant than others. Therefore,
it is not possible to determine whether more stringent Engi-
neering Department actions, without commensurate actions by
other agencies, will be significantly effective in an immedi-
ate future time frame. Unless public benefits can be clearly
described, public acceptability of a comprehensive basin-wide
stormwater management program cannot be assured.

THE STUDY PROCESS

The study's Master Work Plan identified seven major tasks as
project objectives. Phase 1 of the study focused upon the
completion of tasks I through 5. The primary emphasis of the
Phase 2 study efforts were oriented towards the accomplishment
of tasks 6 and 7.

ST. JOHNS COUNTY DEVELOPMENT MANAGEMENT ACTIONS

St. Johns County is undergoing development pressure that re-
quires expanded capabilities for providing for the citizens of
the County. The need for improved methods for dealing with

A - 3

development actions in fair and technically responsible man-
ners has been recognized by the County Commissioners and the
County Administration. The Moultrie Creek-Moses Creek wa-
tershed Study provided timely assistance to the County by per-
mitting the Engineering Department to focus efforts on the
preparation of improved development evaluation tools.

Under the auspices of the above noted study, the Engineering
Department established a computerized geographic information
system (GIS). The initial system is now being- expanded to
permit wider use of the GIS capabilities for a variety of en-
gineering and other departmental uses through the addition of
a computer aided design (CAD) component which will allow imme-
diate transfer of a floppy disk provided by the developer into
the County GIS.

PHASE 1 STUDY PROCESS OBJECTIVES

Specific Phase 1 work objectives were as follows:

1. Develop a comprehensive inventory of areas within the wa-
tershed that deserve special management consideration. This
inventory will be used as a basis for the following:

a. Improving coordination and regulation consistency be-
tween St. Johns County, the St. Johns River Water Management
District, the U. S. Army Corps of Engineers, and DER;

b. Revising the County's Comprehensive Plan; and

C. Future resource investigations by state and local
agencies.

2. Develop detailed information on topography, soils, flood
prone areas, land use, and other conditions pertinent to
achieving stormwater management, flood prevention, and re-
sources protection objectives for the study area.

3. Evaluate County ordinances, plans procedures, and coordi-
nation requirements regarding development reviews and stormwa-
ter management considerations. Identify needed improvements.

4. Use products developed for special area management in the
project areas as a prototype for improving flood protection
and stormwater controls in critical resource areas throughout
the County.

A - 4

PHASE 2 STUDY PROCESS OBJECTIVES

Specific Phase 2 work objectives are as follows:

1. Development of basin-specific management tools such as de-
tailed future land use map, plan and permit application review
guidelines, etc.

2. Assessment of potential stormwater management, flood pro-
tection, natural resource protection problems, and management
options.

3. Development of recommendations on stormwater performance
criteria and formulation of basin stormwater management plans
which address priority resource protection and growth needs.

4. Improvement of consistency and support between County, wa-
ter management district, and state programs regarding stormwa-
ter management and infrastructure planning.

PHASE 2 TASK SUMMARIES

Task 6: Assessment of Potential Stormwater Management, Flood
Protection, and Natural Resource Protection Problems and Eval-
uation of Management Options.

This task focused on the review of potential stormwater,
flooding, and natural resources problems resulting from pro-
jected basin development patterns, uses, and intensities, as
well as general population growth requirements. During the
evaluation process, regulatory, infrastructure, and other man-
agement considerations in the watershed were evaluated. The
development impacts on wetlands and water quality are reviewed
and evaluated in terms of basin resource protection strategy
alternatives. The evaluations undertaken during this task
provided a focus for describing Engineering Department water
management program concerns.

The assessment process was undertaken within the context of
current local government requirements for comprehensive plan
updates,' growth management planning, development of regional
impacts reviews, Florida Quality Development program reviews,
routine County clearance sheet reviews required for construc-
tion and mobile home permits, and dredge and fill permits.
The local agencies responsible for applicable planning and/or
review functions were identified. The Engineering De-
partment's review processes were described and means for pos-

A - 5

sible improvem@nt to current evaluation practices were identi-
fied.

The Geographic Information System is perceived as a mechanism
to most efficiently manage local government operations, in-
cluding management of growth and development. The GIS has been
designed as a product of this basin management program to ad-
dress several of the tasks within the scope of work. The GIS
has many practical applications including near instantaneous
updating of graphical information layers illustrating land use
and cover, approved development layouts, soil types, topogra-
phy, ownership boundaries, easements for drainage, septic fa-
cility location, wetland boundaries, significant archeological
features, zoning, access, utility location, and other charac-
teristics. All of these layers can be used singularly or in
combination to review new development proposals and re-
zonings, retrofit stormwater management facilities, install
and modify major utility lines, identify significant natural
and cultural resource areas, and evaluate new transportation
corridors. The GIS has tremendous potential for local and re-
gional applications. A result of Phase 1 of this study has
been joint funding between St. Johns County and the St. Johns
River Water Management District for digitized soil coverage
for the entire County. In addition, during Phase 2 of this
study St. Johns County has jointly contracted with the St.
Johns River Water Management District for approximately sixty
square miles of topographic aerials to expand the concepts
developed be this study County-wide.

A major effort of the study was the formulation of a GIS
implementation program to apply the information generated.
The first step was to expand the GIS program beyond the@ Engi-
neering Department to include the County departments with the
most immediate need. The departments selected to use the GIS
during this trial period in cooperation with the Engineering
Department are Planning and Zoning, Emergency 911 (Sheriff's
office), Health Department, and the water and wastewater util-
ity known as Anastasia Sanitary District. Several terminals
have been purchased and are being installed for the inputting
of data and viewing of information by each department. The
reference maps for data entry are the County property owner-
ship maps and the topographic aerials acquired as part of
Phase 1. The property ownership maps are manually prepared by
the Property Appraiser and then digitized by the Engineering
Department for GIS implementation.

The GIS was a highlight of this study because it served as the
mechanism to incorporate the objectives of the study within
daily local government operations. The tasks within the scope
of work were reviewed in light of the specific applications of
the GIS. Some of the tasks have received less effort than

A - 6

others because a more practical use of DER Coastal Zone Man-
agement funds was made through the implementation of the GIS
than could have been made without the GIS data in other non-
funded areas such as the retrofitting of facilities.

The County has a tremendous need for uniform, up to the minute
maps depicting the existence and characteristics of road,
structures, stormwater management facilities, natural re-
sources, etc. The uniformity of these maps is critical for
consistency from County department to department. The County
has had a severe problem with map updating because, as in most
counties, the property appraiser's maps upon which all other
maps have been historically based are only updated once a
year. This means that all new development is undocumented
graphically for up to twelve months after completion. This
delay can seriously misrepresent conditions related to well
and septic tank location, vegetation and wetlands alterations,
new drainage facilities, changes in land use and zoning, and
other vital information. Development of the computerized Geo-
graphic Information System enables the County to update in-
formational maps instantaneously. As new subdivisions and
other types of land use changes are completed, the information
will be submitted by the developers and immediately input into
the system. The maps will be available to those County de-
partments requiring this sort of information for daily op-
erations. A major emphasis of this study was the design and
formulation of a computerized information system which will
meet the County's informational needs.

Some recommended changes to the existing development regula-
tions as they relate to County Engineering Department func-
tions have been identified as a part of this study.
These recommendations include design criteria for stormwater
management system performance,and minimum finished floor ele-
vations for structures and access roads serving new develop-
ment.

Flood control and flood protection measures were applied
within the basin through careful consideration of existing
conditions and regulation of new construction within the ba-
sin. These objectives were accomplished in two ways: iden-
tification of more stringent development regulations, and for-
mulation of a means to update and maintain up to the minute
information on development patterns within the basin through
use of the GIS.

The identification of corrective measures for existing flood-
ing problems received minimal effort due to limitations in
funding. The focus on new construction through revisions to
growth management regulations will enable the county to keep

A - 7

pace with its inevitable growth while searching for funds to
retrofit existing facilities.

Provision for the protection of natural resource areas was
satisfied by recommended changes to the St. Johns County Pav-
ing and Drainage Ordinance No.86-4, utilization of the map
layers depicting soil types, land cover and flood plain infor-
mation within the GIS, and through plans to implement of a
digitized jurisdictional wetlands map to be prepared and pro-
vided by the St. Johns River Water Management District.

Revisions to the existing County Paving and Drainage Ordinance
have been initiated during this study. The County Attorney
has completed reconstruction of the Ordinance framework to fa-
cilitate ordinance implementation and enforcement. one of the
major problems with the administration of the existing ordi-
nance has been the lack of specific and enforceable penalties
for failure to comply. This report presents revised design
criteria for stormwater management system performance. Some
new sections within the ordinance will be written to address
the objectives of this study and the recommendations within
this report. An applicants handbook will also be prepared to
present performance standards and procedures for permitting of
construction activity within the Moultrie/Moses Creek basin
and beyond.

Land Use plans, Zoning and Building Codes will not be ad-
dressed in this revision process. Revisions to these regula-
tions will take years to draft and adopt and therefore are
considered beyond the scope of this study.

Task 7: Development of Priority Components of a Comprehensive
Basin Management Program

During this task, the Engineering Department prepared basic
information on local stormwater management requirements. A
conceptual County program was identified to incorporate habi-
tat/wetland enhancement features for fresh water discharges
into an estuarine environment. The interface factors between
a County prepared stormwater management plan for the study
area, revisions needed in the St. Johns County Drainage Ordi-
nance, and Engineering Department rules and procedures and
suggestions for local actions were addressed.

A Computer Aided Design (CAD) system, has been acquired as
part of Task 7 to input new development plans such as Plats,
rezonings, DRI's, stormwater management system plans, utility
location and other information directly into the GIS system.
The CAD will facilitate immediate? automated transfer of de-
velopment information provided by the developer by floppy disk

A - 8

directly from the floppy disk via CAD into the GIS system, and
eliminate the need to manually digitize all plans, plats, etc.
from print drawings into the GIS. It will also assist the
County in inputting existing basin information to be consid-
ered in the review of new development proposals into the GIS.
The time limitations inherent in the contract study process
prohibited completion of the applicants handbook and adoption
of ordinance revisions within the time allowed by the grant
contract. Therefore, the acquisition of the CAD system will
serve as the first step in developing the primary components
of the stormwater management plan. The CAD will serve as the
mechanism to implement many of the goals and findings of the
study within the daily operation of the County government pro-
cessing of building permits, right of way improvements, storm-
water management system upgrades and development of a County-
wide system of development plan documentation and updating.

A 9

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