Item 11 DrainageMonroe County Comprehensive Plan Update
DRAINAGE
Table of Contents
Item
Page
11.0. DRAINAGE ELEMENT..............................................................................................................................1
11.1
Introduction..................................................................................................................................1
11.2
Terms and Concepts..................................................................................................................1
11.2.1 Stormwater Runoff......................................................................................................1
11.2.2 Infiltration....................................................................................................................... 2
11.2.3 Impervious Surface...................................................................................................... 2
11.2.4 Stormwater Management System.......................................................................... 2
11.2.5 Best Management Practices..................................................................................... 2
11.2.6 Design Storm..................................................................................................................
2
11.3
Climate and Rainfall...................................................................................................................
3
11.4
Regulatory Framework............................................................................................................
7
11.4.1 Federal Regulations.....................................................................................................
7
11.4.2 State Regulations..........................................................................................................7
11.4.3 Local Regulations..........................................................................................................8
11.4.4 Work Programs and Floirda Keys Carrying Capacity Study ........................
9
11.5
Existing Facilities......................................................................................................................10
11.5.1 The Keys.........................................................................................................................10
11.5.2 The Mainland...............................................................................................................11
11.5.3 Performance Assessment........................................................................................12
11.6
Surface Water Management.................................................................................................13
11.6.1 SFWMD Permitting Practices.................................................................................13
11.6.2 Needs Assessment......................................................................................................16
11.7
Adoption and Implementation of a Stormwater Management Ordinance .........
18
11.8
Stormwater Management Master Plan.............................................................................19
11.9
Level of Service Standards....................................................................................................20
11.9.1 Water Quantity Level of Service Standards......................................................20
11.9.2 Water Quality Level of Service Standards.........................................................21
11.9.3 Retention/Detention Criteria................................................................................21
11.9.4 Present and Projected Future Ability to Meet
Level of Service Standards......................................................................................22
Bibliography..........................................................................................................................................................23
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TABLE OF CONTENTS
Monroe County Comprehensive Plan Update
List of Figures
Eiv.,ure
Pate
Figure 11.1: 10 Year, 24 Hour Return Frequency Storm....................................................................... 4
Figure 11.2: 25 Year, 24 Hour Return Frequency Storm............................................................ Figure 11.3: IDF Curves 5
List of Tables
Table
Page
Table 11.1: Sampling of Monroe County SFWMD Permits ..............
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TABLE OF CONTENTS
Monroe County Comprehensive Plan Update
11.0 DRAINAGE ELEMENT
The Drainage Element of the Monroe County (County) Comprehensive Plan addresses the
data inventory requirements of Rule 9J-5.005(2) and Rule 9J-5.011 of the Florida
Administrative Code (F.A.C.). The data inventory requirements will support the
development of goals, objectives, policies, and implementation programs for the Drainage
Element.
The purpose of the Drainage Element of the Comprehensive Plan is to describe the issues,
needs and general facilities providing for existing and future drainage conditions.
11.1 Introduction
Development and urbanization affect hydrologic cycles, natural systems and drainage
patterns. The natural biologic and geologic systems are adapted to, and altered by, the
climatic and hydrogeologic regimes of a locale. As human activity disturbs this balance by
removing vegetation, altering topography and increasing imperviousness, the intensity and
frequency of damaging storm water runoff increases, as does the resulting erosion and
flooding. Urbanization also alters the chemical composition of runoff. As rainfall washes
over buildings, lawns, roadways, and parking lots, it carries away the detritus of human
activity and absorbs anthropogenic compounds from pesticides, fertilizers, metals and
petrochemicals.
These consequences of human habitation and activity require that stormwater be controlled
and managed to mitigate the adverse effects on the natural environment and to safeguard life
and property. This element provides an analysis of stormwater management system
practices in the County. Based upon this analysis, the subsequent Goals, Objectives and
Policies contained within the Comprehensive Plan policy document outline the growth
management strategies necessary to correct existing deficiencies and accommodate future
development.
11.2 Terms and Concepts
11.2.1 Stormwater Runoff
A certain amount of rainfall is converted to water flowing over land during and immediately
following a storm event. Under the effects of gravity, the runoff flows toward sea level
through depressions and channels which comprise the drainage system of an area. The
drainage system may consist of natural features, artificial features or a combination of both.
The occurrence of stormwater runoff is highly variable, depending upon the amount of rain
falling during each storm event and on the conditions within the drainage basin. Since most
storm events are relatively moderate, natural drainage features typically evolve to
accommodate moderate quantities of stormwater runoff. Severe storm events create runoff
volumes in excess of what these features can handle, resulting in temporary flooding of
adjacent land.
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Monroe County Comprehensive Plan Update
11.2.2 Infiltration
As rain falls to the ground it is initially absorbed by the topsoil and percolates downward
through the soil matrix until the ground is saturated and runoff begins at the surface. This
process is referred to as infiltration.
11.2.3 Impervious Surface
Urbanization increases the imperviousness of a watershed by covering the ground with hard
surfaces such as buildings, roads and parking lots, and thereby increases the quantity and
frequency of runoff, also degrading the water quality.
The existing definition of "impervious surface" in Section 1.7.20 of the South Florida Water
Management District (SFWMD) Environmental Resource Permitting Information Manual is,
"Land surfaces which do not allow, or minimally allow, the penetration of water;
examples are buildings, non -porous concrete and asphalt pavements, and some fine
grained soils such as clays."
Natural topography varies in its ability to absorb rainfall through infiltration; the greater the
degree of imperviousness, the greater the percentage of rainfall that will appear as runoff.
11.2.4 Stormwater Management System
A stormwater management system is the collection of facilities, improvements or natural
systems whereby stormwater runoff is collected, controlled, conveyed, impounded or
obstructed. Stormwater management facilities are designed to ensure that the volume, rate,
timing and pollutant load of runoff after development is similar to that which occurred under
natural conditions.
11.2.5 Best Management Practices
Best Management Practices (BMPs) are the techniques applied to manage stormwater runoff.
These are selected to be the most effective and economical combination of structural,
operational and regulatory practices for local conditions. Stormwater Management practices
are regulated in the County by the SFWMD.
11.2.6 Design Storm
A design storm is a rainfall event of a particular duration and frequency which a stormwater
management system must be designed to accommodate (See section 11.9.1, Water Quality
Level of Service Standards.)
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Monroe County Comprehensive Plan Update
11.3 Climate and Rainfall
[Rule 9J-5.011(1)(f), F.A.CJ
The Florida Keys (the Keys) experience a subtropical savanna -type climate characterized
by warm humid summers and mild dry winters. The mean annual sunshine is 3,300 hours,
10 percent more than the Florida peninsula to the north.
The average temperature in the Keys ranges from a summer high of 89 degrees in July to a
winter low of 63 degrees in February. Temperatures below freezing have not been
recorded in the Keys, primarily due to the moderating effects of the warm marine waters in
the area and the presence of the warm Gulf Stream along the coast.
The typical annual total precipitation in the Keys is 40 inches. Most of the rainfall comes in
the wet season during the months of May through October. Winter rainfall accounts for
less than one-third of the annual precipitation. Thunderstorms are the primary source of
water during the wet season. During hot summer days, moist oceanic air heats up over the
land, becoming unstable as it rises. As the moisture condenses, thunderstorms form.
During the dry winter season, most of the rainfall is due to cold fronts, which pass over the
area on the average of once a week. Day -long dry -season storms are rare.
There is a decrease in precipitation and seasonal differences in precipitation southward
from the Upper Keys to the Lower Keys. This is due to two factors. Winter cold fronts do
not pass into the Lower Keys as often as they pass into the Upper Keys. Further, convective
thunderstorms do not develop as readily over small islands as they do over the mainland.
The SFWMD uses rainfall maps for 24-hour duration storms of various return frequencies.
These maps are used to determine the depth of rainfall in inches for use in the design and
analysis of stormwater management systems. Figures 11.1 and 11.2 present the maps for
the 10-year and 25-year return frequency storms.
The Florida Department of Transportation (FDOT) also uses rainfall data to design and
permit storm drainage along the agency's facilities. Figure 11.3 presents the FDOT Intensity
Duration Frequency (IDF) curves for Zone 11, which includes the Florida Keys.
Prevailing tradewinds from the east and southeast in the Keys are relatively mild,
averaging 11 to 12 knots throughout the year. The strongest winds occur during the
winter months from December through March, when cold fronts move over the area from
the north.
The Keys lie in an area which is susceptible to tropical cyclones and hurricanes. These low
pressure systems vary in intensity and orientation. Tropical depressions or disturbances
are cyclones with winds of less than 38 miles per hour (mph). By comparison, tropical
storms exhibit distinct circulation patterns, with winds exceeding 38 mph. When the
maximum winds exceed 74 mph, the storm is categorized as a hurricane.
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rite, ma vvater ivianagement District, 2010
Figure 11.1- 10 Year, 24 Hour Return Frequency Storm
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Source: South Florida Water Management District, 2010
Figure 11.2 - 25 Year, 24 Hour Return Frequency Storm
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11.4 Regulatory Framework
(Rule 9J-5.011(1)(h), F.A.C.]
11.4.1 Federal Regulations
In 1987 Congress re -authorized the Federal Water Pollution Control Act (the Clean Water
Act") (CWA) 33 United States Code (U.S.C.) §1251 et seq. (1972). Section 208 of the CWA
had been the traditional means of addressing pollution abatement and water quality since
1972. In 1987 Congress also enacted the Water Quality Act (WQA). (Public Law 100-4), Titles
IV & V. The WQA contains three provisions which specifically address stormwater
discharges and sets forth the permitting criteria for municipal and industrial stormwater
discharges. The central provision governing stormwater is Section 405 of the WQA which
adds Section 402(p) to the CWA and establishes the general role and exceptions for
municipal and industrial stormwater discharges. The Environmental Protection Agency
(EPA) has promulgated rules for the application of National Pollution Discharge Elimination
System (NPDES) permit programs for stormwater discharges.
The NPDES is a program under the CWA that regulates the quality of discharges into the
"waters of the United States." The NPDES program initially focused on discrete point source
discharges (e.g., pipe outfalls) and now also has regulatory programs that deal with potential
discharges that might also have been considered non -point sources, such as industrial and
municipal stormwater. Under the NPDES program, the EPA issues permits for operators of
large and small municipal separate storm sewer systems, known as MS4s, and for runoff
associated with industrial operations and construction.
Stormwater NPDES permits issued to industry and construction permit operations require
implementation of stormwater controls to meet narrative and/or numeric effluent limits as
well as documentation of the controls used on -site in a stormwater pollution prevention
plan. Permit recipients must develop and implement a stormwater management plan. At this
writing, based on the EPA's new focus on measurable compliance, the EPA is in the process of
promulgating Water Quality Standards for the State of Florida's Lakes and Flowing Waters
and Marine Systems, 40 Code of Federal Regulations (CFR), part 131, which regulate
discharges that impact surface and groundwater resources.
11.4.2 State Regulations
While the EPA generally regulates water quality, water quality standards are developed by
Florida Department of Environmental Protection (FDEP) and adopted by the Environmental
Regulatory Commission. FDEP is charged with enforcing the standards, although it may
delegate some of its authority to the regional water management district or other
governmental units. Other regulatory authority, such as the land use/zoning powers of local
government, directly impact water quality, and the SFWMD has established a program to
address water resource concerns related to land use and other comprehensive plan issues.
Currently, FDEP is working with the EPA to establish Water Quality Standards for the State
of Florida's Lakes and Flowing Waters and Marine Systems, 40 CFR, part 131, for Florida.
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The SFWMD regulates surface waters within the district that includes the entire County.
Under Part IV of Chapter 373, F.S., and Rules Chapter 40E-4, F.A.C., and 40E-40, F.A.C., the
SFWMD is responsible for permitting the construction and operation of surface water
management systems. Additionally, the SFWMD has been delegated stormwater quality and
quantity responsibility by the FDEP under Chapter 62-25, F.A.C.
The SFWMD is comprised of 16 counties and has a nine member Governing Board which sets
policy for the agency. The SFWMD is divided into two separate watershed basins: the Big
Cypress Basin and the Okeechobee Basin. The Big Cypress Basin has a Basin Board which
sets policy for the Big Cypress Basin. A portion of mainland Monroe County lies within the
Big Cypress Basin, but the majority of the County is in the Okeechobee Basin.
The FDEP is the primary environmental regulatory agency in the State of Florida and has the
authority under Chapter 403, F.S. to classify water bodies and to regulate discharges to
ensure that they are appropriate to the water body's designation. The FDEP has classified
much of Florida Bay and the reef track as "Outstanding Florida Waters" (OFW) affording
these areas State protection. Rule amendments adopted by the FDEP provide a new water
quality classification: "Outstanding National Resource Waters." The proposed rules impose
an anti -degradation standard for designated water bodies. The Everglades National Park
(including a large portion of Florida Bay) is among those water bodies included in the rule's
designations of Outstanding National Resource Waters.
In addition to the above regulations, the FDOT independently permits stormwater discharges
and connections to FDOT rights -of -way under Chapter 14-86, F.A.C.
11.4.3 Local Regulations
In the past, the only controls on stormwater imposed by the County were those involving
flood protection and floodplain encroachment in Section 122 of the Monroe County Land
Development Code (MCLDC). Subsequently, the MCLDC has been revised, based on
recommendations provided in the County's Stormwater Management Master Plan (SMMP),
2001, to not only provide stormwater controls for flood protection and floodplain
encroachment, but also to include water quality controls in Section 114-3 of the MCLDC. This
new MCLDC also includes water quality controls for existing and proposed residential
development and addresses retrofitting of existing facilities and redevelopment activities.
This meets the intent of Section 114-3(a) of the MCLDC, to protect the vital water resources
of the County.
In conjunction with Section 114-3 of the MCLDC, the County has prepared a Manual of
Stormwater Management Practices which provides information on acceptable forms of
BMPs. This document was prepared with the assistance of the South Florida Regional
Planning Council (SFRPC) and the SFWMD and includes BMPs consisting of rate control
structures, catch basins with skimmers and baffles, and wet and dry detention/retention
facilities.
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Monroe County Comprehensive Plan Update
11.4.4 Work Program and Florida Keys Carrying Capacity Study
In December 12, 1995, the State of Florida Administrative Commission found the 2010
Monroe County Comprehensive Plan not in compliance and it noticed a proposed rule (Rule
28-20.100, F.A.C.) and ordered facilitated rulemaking/mediation to address outstanding
issues. The disputed provisions of the Rule required further action. Mediation was
conducted resulting in subsequent rule changes and challenges. The Administration
Commission eventually adopted Rule 28-20.100, F.A.C. in July 1997. This rule introduced
the concept of the "Five Year Work Program" (Work Program). The Work Program
required, among other things, the implementation of several stormwater improvement
projects and the Florida Keys Carrying Capacity Study (FKCCS).
Reports began to be issued to the Governor and Cabinet in March 1998. In January 1999,
the second report to the Governor and Cabinet was issued stating a lack of substantial
compliance. Subsequent rule amendments extended the program's deadline to
accommodate the tasks that had not been completed and today tasks remain incomplete
beyond the extended horizon of the Work Program. No Work Program task has been
ignored or not acted upon and all tasks may be considered either complete or in progress.
While the number of remaining tasks is limited, these tasks are costly and time consuming
to complete.
The Final Order in 1995 also initiated the FKCCS. In 1996 the Work Program required the
development of a carrying capacity analysis study which was completed in July 2002. The
US Army Corps of Engineers and the Florida Department of Community Affairs (DCA)
formed a partnership to jointly fund and complete the study and the Carrying Capacity
Impact Analysis Model (CCIAM). The goal of the FKCCS, excerpted from Rule 28-20.100,
F.A.C. was as follows:
"The carrying capacity analysis shall be designed to determine the ability of the Florida
Keys ecosystem and the various segments thereof, to withstand all impacts of additional
land development activities."
In 2001, the FKCCS was peer reviewed by the National Research Council (NRC). The NRC
found that the CCIAM was not ready to determine the ability of the Florida Keys ecosystem
to withstand all impacts of additional development activities as required by Rule 28-
20.100, F.A.C. Based on subsequent FKCCS revisions, it was later concluded that the CCIAM
may be a useful tool in some circumstances, but it had limitations, particularly the inability
to determine the impact to near shore water quality. The NRC did agree with several
recommendations of the study including the implementation of the Stormwater
Management Master Plan (SMMP) (See Section 11.6.2.1, Stormwater Management Master
Plan.)
In November 2010, DCA proposed amendments to Rule 28-20 F.A.C. which includes specific
stormwater tasks and their associated timelines:
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• By July 1, 2011, Monroe County shall evaluate and allocate funding for stormwater
implementation. Monroe County shall identify any funding in the annual update to the
Capital Improvements Element of the Comprehensive Plan;
• By July 1, 2011, Monroe County shall apply for stormwater grants from the South
Florida Water Management District; and
• By July 1, 2011, Monroe County shall complete Card Sound Road stormwater
improvements.
11.5 Existing Facilities
[Rule 9J-5.011(1)(1), F.A.C.J
11.5.1 The Keys
Over the last 50 years, the County has witnessed rapid growth as development has spread
beyond the confines of Key West and Key Largo. Over this period, the unincorporated
sections of the County have been transformed from very isolated and rural to increasingly
urbanized.
Because of the combination of the proximity of the ocean, dense vegetation and permeable
soil, many citizens of the County have traditionally given little concern to stormwater runoff.
Most rainfall readily infiltrates the undifferentiated sands that comprise the soil of the
Florida Keys. (See Chapter 12.0, Natural Ground Water and Aquifer Recharge Element.)
Historically, drainage works in the County primarily consisted of improvements addressing
low areas, mosquito ditches cut to drain native wetlands, and boat canals used as primary
drainage facilities with building sites draining directly into them by sheet flow, minor ditches
or through percolation. On a number of projects, the County has also included the
installation of stormwater seepage trenches as part of many of the County Road resurfacing
projects. Further, a number of injection wells have been installed as part of drainage
improvements within County Roads when possible and funding allowed.
The dredging of navigable canals and borrow pits has also had an effect on the hydrologic
regime of the Florida Keys. Besides the obvious impact to the landscape, such activities can
have widespread off -site effects. Because canal cuts open new interfaces between the ocean
and groundwater, they can have dramatic hydrogeologic consequences.
Ditches along U.S. 1 have served as primary drainage systems on several Keys, transporting
stormwater along the axis of the highway to the ocean. The highway was originally
constructed on an old railroad with little improvement other than pavement installation.
Key Largo, Islamorada and other urbanized segments of U.S. 1 have limited storm drainage
systems. As part of a major roadway projects, the FDOT installs storm sewer and retention
basins adjacent to U.S. 1 as required to meet current attenuation and water quality
requirements.
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The overriding stormwater concern for residents of the County has always been the low-
lying topography with the threat of inundation by hurricane -driven storm surges. In some
areas, particularly in Key West and Marathon, significant localized flooding occurs from
longer duration storms which occur almost annually. Virtually the entire landmass of the
Florida Keys lies within the 100-year flood plain designated by the Federal Emergency
Management Agency (FEMA) and is classified as an area of special flood hazard. (See Chapter
3.0, Conservation and Coastal Management Element.)
11.5.2 The Mainland
The mainland segment of the County has been largely ignored by development interests
because it consists solely of the vast system of marshes, sloughs, tree islands and cypress
forests known as the Everglades. This indifference has not, however, protected this
wilderness from the effects of human activity. Much of mainland Monroe County was
incorporated into the Everglades National Park which was created in 1947. Also in 1947, the
U.S. Army Corps of Engineers undertook the Central and Southern Florida Flood Control
Project (C&SFP). This extensive network of canals and control structures was intended to
meet the needs of flood protection, drainage and irrigation of farmland, and water supply to
the urban areas along the coast. Although none of the C&SFP improvements are within
Monroe County, the project modified the hydrology of the Shark River Slough, Rocky Glades,
Taylor Slough and Broad River which serve as headwaters to the Everglades National Park.
Completed in the 1960s, the C&SFP had unfortunate consequences for the Everglades,
including Everglades National Park. This management system altered the hydro period of
the Everglades, exacerbating droughts and extending inundations. The C&SFP also altered
the quantity of fresh water and transported an increased quantity of nutrients and
agrichemicals from the Everglades Agricultural Area through the Everglades National Park
and into Florida Bay.
Currently planned improvements to restore the Everglades are underway under the
Comprehensive Everglades Restoration Plan (CERP). This plan is one of the largest
ecosystem restoration programs in United States. CERP was authorized by the Water
Resources Development Act of 2000. The goal of CERP is to restore the South Florida
ecosystem, including the Everglades, while providing for other water supply and flood
protection needs of South Florida.
The restoration focuses on several major problems affecting Florida Bay and the Florida
Keys. These issues include water quantity, flow, increased salinity, water quality, fish and
wildlife resource management, water supply and public access. Examples of projects
designed to improve the water resources of Monroe County include:
• Water Conservation Areas: Protect and improve the natural resources of the Water
Conservation Areas (WCA) as an integral part of the Everglades system while maintaining
the multiple functions of the WCA.
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• Everglades National Park: Provide adequate timing, distribution and flow of rainfall -
quality water (phosphorus concentrations equal to or less than 0.03 milligrams per liter
(mg/0) to the Everglades National Park (ENP) which will maintain and perpetuate
natural southern Everglades habitats and functional ecosystems.
• C-111 Basin: Manage the C-111 Basin to protect environmental resources and maintain
existing public uses, and to provide more natural hydroperiod and flow conditions and
adequate water quality to the basin's wetlands, coastal estuaries and the ENP.
• Florida Bay: Protect and improve natural surface water quality,
quantity,
and timing of water flowing into Florida Bay through the ENP, the C-111nddthe rFlorida
Keys so as to maintain the ecosystem integrity and habitat diversity of the receiving
waters.
11.5.3 Performance Assessment
[Rule 9J-5.O11(1)(f), F.A.C]
11.5.3.1 Water Ouantitv
Little documentation about the design or implementation of drainage improvements in the
County existed prior to the creation of the County SMMP. The presence of flooding problems
and inference of inadequate capacity was based upon the personal knowledge of local
residents. This information was collected during the development of the SMMP through
public involvement activities. In the past, the FDOT has used a 3-year frequency event of
critical duration for the design of its facilities within Monroe County. More recently the
FDOT has been using a 25-year frequency for U.S. 1 highway improvements.
The Natural Resources Conservation Service (NRCS) completed a comprehensive soil survey
of the County in 1995. The delineation of soil types compiled in this survey provides an
important tool in the analysis and design of stormwater systems and assists in the
assessment of potential problem areas. Existing soil types in the Florida Keys are illustrated
on the Soils Map series of the Map Atlas.
11.5.3.2 Water Quality
In 1988 the FDEP prepared an assessment of nonpoint source pollution for the entire State in
conjunction with the Federal Clean Water Act, Section 2050) water quality assessment
program. The data collected in the Florida Keys was extremely limited and insufficient to
distinguish potential stormwater problems. The assessment, however, did show degradation
of water quality in urbanized areas.
The County participated in research projects through the Florida Department of
Environmental Protection, and published the document Reasonable Assurance
Documentation (FKRAD -May 2008), which "provides reasonable assurance that the
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stakeholders in the Keys have provided or will implement sufficient control mechanisms to
return the area's near shore waters to the water quality targets". The following elements
were implemented to provide the reasonable assurance: Description of the Impaired
Water, Description of the Water Quality and Aquatic Ecological Goals, Description of the
Proposed Management Actions to Be Undertaken, Description of Procedures for Monitoring
and Reporting Results, and Description of Proposed Corrective Actions. Further the report
introduces the following stormwater program rules. Current stormwater management
enic
programs will limit any significant Halo Zone waters through thefnutrient
following provisions: stormwater discharged to th
authority of FDEP under the delegated Stormwater NPDES program to enforce permit
conditions against communities that are not in compliance with their MS4 Permits; Existing
on -site stormwater management requirements of SFWMD related to new development
activities; Authority for FDEP and SFWMD to undertake enforcement actions for non-
complying stormwater management practices; Local Monroe County land development
regulations governing the development of raw land and the redevelopment of properties
that establish on -site stormwater attenuation and treatment requirements prior to
discharge; and ability of Monroe County to undertake authorized enforcement actions for
non -complying stormwater management practices.
11.6 Surface Water Management
[Rule 9J-5.011(1)(g), F.A.C.]
The major impact of inadequate draining facilities upon surrounding natural resources is
that associated with flooding and stormwater runoff. Rapid runoff of stormwater results in
the loss of valuable freshwater resources, and may have other ecological impacts as well.
Further, potential recharge capabilities of natural water systems have been lost or greatly
diminished, due to the lack of stormwater drainage practices throughout the County.
Development associated with urbanization increases runoff by increasing flow velocity and
flow volume due to the characteristics of impervious surfaces. Flow velocity and volume
increase significantly when the path is changed from rough surfaces, such as woodland,
grassland, or natural channels to smoother surfaces, such as parking lots. The creation of
large expanses of impervious surfaces also prohibits water storage in the soils they cover. In
this manner the problem is compounded since natural water storage capacity is lost while
stormwater runoff is increased.
Urban development covers large areas of land with impervious surfaces which inhibit the
ground's ability to absorb rainfall and increases stormwater runoff. This increased amount
of runoff places greater stress on the natural drainage system, which results in increased
probability of flooding during periods of heavy rainfall.
11.6.1 SFWMD Permitting Practices
The permitting of surface water management systems by the SFWMD is specified in Chapter
373, Part IV, F.S. This section regulates the construction, alteration, maintenance and
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Monroe County Comprehensive Plan Update
operation of most real property improvements designed to control surface waters. An
applicant for a surface water permit must show that the proposed project is consistent with
the goals and policies expressed in Section 373.016, F.S. (Declaration of Policy) and Section
373.016, F.S. (State Water Use Plan), and must demonstrate that construction or alteration of
SFWMD. In addition, the operation and maintenance of the systems
the surface water management systems will not be harmful to the water resources of the
cannot
with the overall objectives of the District or be harmful to the water resourcbe inconsistent
es of the District.
Documentation of existing conditions is limited to General and Individual Surface Water
Management Permits issued by the SFWMD. A general SFWMD surface water management
permit is applicable to development which is less than 40 acres in size and has limited site
activities such as upland clearing, earthwork and lake construction. An individual SFWMD
surface water management permit is generally applied to sites greater than 40 acres. An
individual surface water management permit must be approved by the SFWMD Governing
Board. SFWMD issues exemptions from obtaining a general permit for projects less than 10
acres of total land area and less than two acres of impervious surface. Projects within the
County that have been issued permits by the SFWMD are listed in Appendix A.
Chapter 40E-4, F.A.C. describes the permit requirements for construction, alteration or
operation of surface water management systems. To satisfy the permit requirements an
applicant must either receive an individual permit or qualify for a general permit. Individual
permits are issued by the Governing Board upon application and compliance with Part IV of
Chapter 363, F.S. and Chapter 40E, F.A.C. with the specific permitting criteria found in Rule
40E-4.091, F.A.C. General permits are issued by Rule for most small projects and certain
types of highway construction. To qualify for a general permit, an applicant needs to file the
notice specified in the rules, a copy of the project construction plans and basic technical data
about the project such as proposed minimum road and floor elevations, proposed discharge
rate, and retention/detention volume and facilities.
Upon receipt of this information, the District determines whether the project qualifies for a
general permit and/or if any additional information is needed. Once the District has
indicated that the general permit is in effect for the project, no further application is
required. Both individual and general permits are subject to revocation, suspension or
modification in accordance with the provision of Chapter 40E, F.A.C. and Chapter 373, F.S.
SFWMD regulates stormwater discharge and water treatment quality through the provisions
contained in Chapter 62-25, F.A.C. which are the State stormwater discharge regulations.
In 2005, the SFWMD initiated the implementation of their "ePermitting" program, making it
possible to apply for a permit online, in addition to providing the public with convenient
access to its existing permit files. In 2009, the online public access to existing permit portion
of the project was completed, providing online access to more than 9.1 million records.
Table 11.1 is a sampling of the permits issued by the SFWMD within the County. (See
Appendix A for the complete list.)
Drainage 14
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Monroe County Comprehensive Plan Update
Prior to the 1990's, given the location and configuration of the Keys and the unlimited
outfall capacity of the surrounding water bodies, relatively little consideration had
been given to stormwater runoff. There is concern that this history of unregulated
stormwater runoff contributes to a portion of the nearshore water nutrient and
sediment loading. Subsequent regulatory developments have increased focus on
stormwater management practices related to water quality and quantity. Designation
of the Keys as an Area of Critical State Concern (ACSC) (Section 380.0552 F.S.) in 1974
and designation of the surrounding waters as Outstanding Florida Waters (OFW)
(Chapter 62-3, F.A.C.) in 1985 required that a county -wide comprehensive water
quality monitoring program be established. In 2001, the County Stormwater
Management Master Plan was created, and a portion of its recommendations have
been implemented, though not yet complete.
11.6.2 Needs Assessmen t
[Rule 9J-5.011(1)(f), F.A.C.]
11.6.2.1 Stormwater Management Master Plan
At the present time, only project specific surface water management systems exist in
the County that are capable of servicing existing land use or mitigating associated
impacts. A facility -specific land use inventory has not been completed to ascertain the
drainage system needed to serve a combination of residential, commercial, industrial,
extractive, institutional and agricultural land uses as well as public facilities,
conservation/preservation areas and vacant lands.
Similarly, a comprehensive analysis of current demand and projected needs for
stormwater management facilities, which would include future facility capacity
analysis based on development permitted by the County, projected population, and
land use distributions based on the "Future Land Use Map," has not been completed.
Recognizing the inadequacy regarding surface water management in the County, a
SMMP was completed in 2001 to assess the need for design of drainage systems in the
developed portions of the County. The objectives of the SMMP included:
• assessing the adequacy of existing stormwater conveyance systems in developed
or developing basins;
• prioritizing stormwater management needs of each island within a framework of
the needs of the entire County; and
• developing a plan of identifying options available to the County on how to finance
the cost of construction, operation, and maintenance of required stormwater
management facilities.
Drainage 16 Technical Document: May 2011
Monroe County Comprehensive Plan Update
Monroe County's present stormwater management practices have been revised,
partially as a result of information and recommendations provided in the SMMP.
However, these revised practices have not been adequate to solve all of the problems
associated with stormwater management. The SMMP did identify a significant
number of stand alone improvements, some of which have been implemented, that
have had positive water quantity and quality impacts in localized areas. A number of
SMMP referenced projects are in various stages of completion with yet other
needing funding Projects identified that have been completed or are in process
include: El Prado Circle on Big Coppitt Key, Card Sound Road (SR905A), Marathon
Government Center, Burton Drive at U.S. 1 in Tavernier, Jo -Jean Way in Tavernier
and Veterans Park in Little Duck Key. It should be further noted, projects associated
with U.S. 1 right-of-way are the responsibility of FDOT. The County has partnered
with the FDOT on numerous occasions and look forward to maintain this
partnership.
Additionally, the focus of the SMMP was on public facilities, and did not address the
needs of many of the private stormwater management systems throughout the
County.
To this end, in an effort to provide increased control of water quantity, enhance water
quality, and effectively manage stormwater, the feasibility of creating a county -wide
Stormwater Utility entity can be examined. Under the Utility, developed parcels of
property could be assessed a fair and equitable user fee based upon that property's
amount of impervious surface or other criteria. This user fee could then be used by
the utility to correct existing deficiencies and provide for future facilities in the
stormwater management system. The utility fee could also provide ongoing revenues
for operation and maintenance of the public system.
11.6.2.2 Other Needs
11.6.2.2.1 Revise as Necessary, Section 114-3 of the Monroe County Land
Development Code Which Regulates Stormwater Management
Section 114-3 of the MCLDC provides stormwater management criteria compliant
with existing federal and State criteria, and Section 114-4 provides for revisions to
114-3 to maintain compliance. Revisions to the MCLDC may soon be necessitated by
impending EPA and FDEP establishment of quantitative nutrient criteria for surface
water, anticipated sea level rise due to global warming and possible deviations from
historically observed storm frequencies, intensities and durations. Additionally,
revisions may also be necessitated to insure compliance and inspectability for
residential permits.
urainage 17 Technical Document: May 2011
Monroe County Comprehensive Plan Update
11.6.2.2.2 Continue and Expand the Assessment of Ground Water and Surface water
uali
As mentioned above, the County participated in the development of the FKRAD
documents that provided control mechanisms in the quest to return near shore
waters to the water quality targets. The results of recent studies clearly demonstrate
that development is adversely affecting water quality in the County. (See Chapter
12.0, Natural Ground Water and Aquifer Recharge Element.)
11.6.2.2.3 Prepare an Inventory of Drainage e Systems and Performance Data for All
Public and Private Systems Within the County
The Monroe County Department of Public Works should undertake the inventory and
evaluation of existing drainage structures and facilities within county rights -of -way,
identifying flooding issues; and, obtain data from the FDOT and municipalities for
their facilities, collaborating efforts to resolve common issues.
11.6.2.2.4 Evaluate the Performance of Systems Constructed Under Monroe County
Stormwater Management Regulation.
The County should periodically sample the discharge from stormwater management
systems to determine compliance with the water quality requirements of the MCLDC
and modify BMP recommendations as appropriate to improve the performance of
future systems.
11.7 Adoption and Implementation of a Stormwater Management
Ordinance
[Rule 9J-5. 011 (1)(h), F.A.C.]
Section 114-4 of the MCLDC, revises the Surface Water Management Criteria of the
adopted Monroe County Land Development Codes and sets forth the following
Monroe County responsibilities related to updating surface water management
criteria:
The County Planning Commission shall consult with the Florida Department of
Environmental Protection and the South Florida Water Management District, and
shall recommend a stormwater management ordinance for adoption by the Board of
County Commissioners that is consistent with Chapter 62-25, F.A.C. The
recommendation shall be provided to the Board of County Commissioners pursuant
to Section 102-158 of the MCLDC within 12 months of its effective date.
The following tasks are recommended for implementing stormwater management
ordinance revisions aimed at controlling the quality and quantity of stormwater
discharges from new and existing duplex and single family home development in the
Drainage 18 Technical Document: May 2011
Monroe County Comprehensive Plan Update
County, and to provide information for distribution to the general public explaining
the County's proposed stormwater management ordinance revisions:
Task 1: Review and assess the stormwater management techniques used in the
development of typical duplex and single family homes in the County in the
past to determine compliance with existing code and to determine the need
for code revision or enforcement.
Task 2: Prioritization of project areas (residential subdivisions) most in need of
implementation of stormwater management criteria.
Task 3: Refine criteria, procedures, and techniques used in the development of
new and the retrofitting of existing duplex and single-family homes using
the information developed in Tasks 1 and 2, and provided in the SMMP to
a) eliminate or alleviate discharge into the public right-of-way from new
duplex and single-family homes and b) retrofitting of existing duplex and
single family homes to accomplish the same. The criteria must
demonstrate the ability to be implemented through effective, practical, and
cost-effective stormwater management improvements and BMP
implementation. Procedures and techniques to control stormwater are to
be implementable within the site planning, construction, and retrofitting
stages of single family and duplex home sites. The code shall also require
that the building official verify the implementation of required stormwater
controls for new and updated construction. The intent of these procedures
is to improve localized flooding conditions and improve the quality of the
nearshore waters of Monroe County.
Task 4: Alternative analysis of all criteria, procedures, and techniques identified in
Task 3.
Task 5: Development of a layman's brochure for distribution to the general public
explaining the implementation of the criteria developed in Task 3 above, in
addition to the refinement of the County's Stormwater Management
Ordinance.
The current surface water management criteria for new development, and the
retrofitting of existing duplexes and single family home sites, is contained in the
MCLDC, Section 114-3.
11.8 Stormwater Management Master Plan
[Rule 9J-5.O11(1)(f), F.A.C.]
Currently, no comprehensive study of drainage systems and stormwater management
systems has been conducted in the County. Many research efforts have been directed
at identifying specific impact areas of flooding or biotic communities in the nearshore
urainage 19 Technical Document: May 2011
Monroe County Comprehensive Plan Update
waters of the County while not being designed specifically to identify the causative
stormwater discharge points which, in most cases, were beyond the scope of these
studies. Although these studies have been reviewed and when applicable have been
incorporated in the SMMP as design and improvement recommendations, it is now
recognized that, in order to properly address the issue of preventing environmental
degradation resulting from stormwater runoff, a comprehensive effort beyond the
magnitude of anything yet undertaken will be required. Implementation of the SMMP
has affected the fiscal, regulatory, and public and private operational characteristics
presently in place related to stormwater systems utilized in the County. Successful
implementation of the SMMP has and continues to require fiscal and political
commitments and coordination at varying levels governmental and regulatory
agencies.
The end result of the SMMP was to provide adequate and equitable means for the
construction of a comprehensive, long-term, surface water management system
which addresses existing as well as new development.
11.9 Level of Service Standards
[Rule 9J-5.011(1)(e) and (f), F.A.C.J
The level of service (LOS) standards for drainage meets or exceeds the requirements
set forth in Chapter 62-25 F.A.C. The levels of service standards can only be applied to
development having drainage systems permitted after the adoption of Section 9.5-
293 of the MCLDC and, subsequently Section 114-3 of the MCLDC, and cannot be
immediately applied to the vast number of unpermitted drainage systems or
developments not having drainage systems. Stormwater quality and quantity
infractions can only be addressed through vigilance and enforcement of the County's
criteria. The level of service standards are described in Sections 11.9.1, 11.9.2 and
11.9.3 of the MCLDC.
11.9.1 Water Quantity Level of Service Standards
The following protection levels for development are based upon design storm
frequency and duration:
• Residential and commercial building floors - 100 year, 3 day;
• Emergency shelters/service building floors - 100 year, 3 day;
• Evacuation routes and emergency service road - 100 year, 3 day;
• Arterial roads - 100 year, 3 day;
• Collector roads - 25 year, 3 day;
• Neighborhood roads - 5 year, 1 day;
• Urban sites - 5 year, 1 day;
• Rural sites - 3 year, 1 day; and
• Off -site discharge rates are limited to historic, predevelopment conditions or as
previously determined by the SFWMD or the County.
Drainage 20 Technical Document: May 2011
Monroe County Comprehensive Plan Update
11.9.2 Water Quality Level of Service Standards
Projects shall be designed and operated so that off -site discharges meet State water
quality standards, as set forth in Chapter 62-302, F.A.C.
11.9.3 Retention/Detention Criteria (SFWMD Water Quality Criteria, 5.0
and Monroe County Criteria, Section 114-3 of the MCLDC)
• Retention, detention, or both retention and detention in the overall system,
including swales, lakes, canals, greenways, etc., shall be provided for one of the
three following criteria or equivalent combinations thereof (SFWMD Water
Quality Criteria):
- Wet detention volume shall be provided for the first inch of runoff from the
developed project, or the total runoff of 2.5 inches times the percentage of
imperviousness, whichever is greater.
- Dry detention volume shall be provided equal to 75 percent of the above
amounts computed for wet detention. (Note: This reduction is not allowed
per MCLDC, Section 114-3.)
- Retention volume shall be provided equal to 50 percent of the above
amounts computed for wet detention. Retention volume included in flood
protection calculations requires a guarantee of long term operation and
maintenance of system bleed -down ability. (Note: This reduction is not
allowed per MCLDC, Section 114-3.)
• Projects that discharge directly to sensitive receiving waters shall provide the
dry retention or detention volume according to the following formula:
Treatment volume = C x Disturbed area (acres) x 3.2 (inches)/12 (inches/foot)
Where treatment volume (acre feet) is the amount of stormwater treatment
necessary, the disturbed area is the total lot area and C is the rational method
runoff coefficient. The rational method coefficient for the water quality
treatment volume calculations shall be 0.1 for pervious areas and 0.95 for
impervious areas.
• Commercial or industrial projects shall provide at least one -half -inch of dry
detention or retention pretreatment prior to discharge to a disposal structure
such as a well, subsurface drainage basin, or trench, as part of the required
retention/detention.
Drainage 21 Technical Document: May 2011
Monroe County Comprehensive Plan Update
11.9.4 Present and Projected Future Ability to Meet Level of Service
Standards
The established SFWMD water quantity and quality drainage criteria and related
Florida Administrative Code water quality requirements in conjunction with the
implementation of the revisions to the Surface Water Management Criteria in Section
114-3 of the MCLDC, allows for drainage requirement criteria to be imposed on a site
specific basis. Section 114-3 of the MCLDC allows for imposition of stormwater
management criteria on development exempted from SFWMD requirements because
of site characteristic such as size and impervious area, such as residential lots.
Additionally, Section 114-3 of the MCLDC allows for more stringent requirements
than those imposed by SFWMD, not allowing water quality credits for providing
retention or dry detention.
The Remainder of This Page Intentionally Left Blank
urainage 22 Technical Document: May 2011
Monroe County Comprehensive Plan Update
Bibliography
Monroe County, 2010 Comprehensive Plan, 1990.
U.S. Environmental Protection Agency, "Overview of Climate Change Adaptation in
the Southeastern United States with a Focus on Water and Coastal Resources
Draft Discussion Paper," Prepared by Stratus Consulting Inc., January 26,
2010.
Florida Stormwater Association, "General Comments Concerning EPA's Proposed
Numeric Nutrient Criteria (40 CFR Part 131.43)," 2010.
FDEP, "Florida Keys Area Reasonable Assurance Documentation - North, Central,
South -Central and Southern," May 2008
Monroe County, "Monroe County and Incorporated Municipalities Key West,
Marathon, Key Colony Beach, Layton, and Islamorada Village of Islands Local
Mitigation Strategy 2005 Revision," November 2005.
CERP Assessment Team, "Comprehensive Everglades Restoration Plan 2009 System
Status Report Draft," April 2010,
SFWMD, SFWMD News Release "SFWMD Expands Online Public Access to
Permitting Records," January 28, 2009,
Monroe County, Stormwater Management Master Plan, August 2001, Prepared by
Camp Dresser & McKee, Inc.
SFWMD, "Basis of Review for Environmental Resource", November 11, 2009.
Drainage 23 Technical Document: May 2011
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