# Evaluation of Current

Stormwater Design

Criteria within the

State of Florida Evaluation of Current

Stormwater Design

Criteria within the

State of Florida

Prepared for: Prepared for:

Harvey H. Harper, Ph.D., P.E.

David M. Baker, P.E. Harvey H. Harper, Ph.D., P.E.

David M. Baker, P.E. Prepared By: Prepared By:

3419 Trentwood Blvd., Suite 102

Orlando, FL 32812 3419 Trentwood Blvd., Suite 102

Orlando, FL 32812 

# June 2007 June 2007 

# FLORIDA DEPARTMENT OF

ENVIRONMENTAL PROTECTION

FDEP Contract No. SO108 FLORIDA DEPARTMENT OF

ENVIRONMENTAL PROTECTION

FDEP Contract No. SO108 

# Final Report Final Report

Environmental Research & Design, Inc. Environmental Research & Design, Inc.

# ACKNOWLEDGEMENTS

The authors wish to thank the Bur eau of Watershed Management/Nonpoint

Source Management of the Florida Departme nt of Environmental Protection for their

assistance in funding and admini stration of this project. A sp ecial thank you is also given

to the FDEP Project Manager, Mr. Eric Li vingston, for his invaluable support throughout

this project. His guidance, technical exper tise, and wisdom contributed heavily to the

success of this project. The authors also wi sh to thank the talented personnel from the

various water management districts who re viewed the Draft Final Report and provided

valuable comments and input.

Funding for this project was provided by a TMDL Water Quality Grant from the

Bureau of Watershed Management, Florida Department of Environmental Protection,

Tallahassee, Florida.

FDEP \ STORMWATER TREATMENT REPORT

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE OF CONTENTS

Section Page

LIST OF TABLES LT-1

LIST OF FIGURES LF-1

1. INTRODUCTION 1-1

1.1 Scope of Work 1-1

2. REGULATION OF STORMWATER IN FLORIDA 2-1

2.1 State Regulations 2-1

2.2 Water Management Districts 2-3

2.3 Local Governments 2-14

3. PRECIPITATION CHARACTERISTICS IN FLORIDA 3-1

3.1 Annual and Regional Precipitation 3-1

3.2 Rainfall Event Characteristics 3-6

3.3 Antecedent Dry Period 3-9

4. STORMWATER RUNOFF - QUALITY AND QUANTITY 4-1

4.1 Water Quality Characteristics 4-1

4.1.1 Data Availability 4-1

4.1.2 Single-Family Residential 4-11

4.1.3 Multi-Family Residential 4-14

4.1.4 Low-Density Residential (Rural) 4-15

4.1.5 Low-Intensity Commercial Areas 4-16

4.1.6 High-Intensity Commercial Areas 4-17

4.1.7 Light Industrial 4-17

4.1.8 Highway/Transportation 4-18

4.1.9 Agricultural Areas 4-19

4.1.9.1 Pasture Land Use 4-20

4.1.9.2 Citrus Land Use 4-21

4.1.9.3 Row Crops Land Use 4-21

4.1.9.4 Comparison of Agricultural Characteristics 4-22

TOC-1

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE OF CONTENTS – CONTINUED

4.1.10 Undeveloped/Rangeland/Forest Land 4-23

4.1.11 Mining/Extractive Land Use 4-24

4.1.12 Wetlands 4-24

4.1.13 Open Water/Lakes 4-25

4.1.14 Recommended Characterization Data 4-25

4.2 Estimation of Runoff Quantities 4-27

4.2.1 Methodology 4-27

4.2.2 Impacts of Rainfall Distributions on Runoff Depth 4-34

4.2.3 Annual Runoff Generation 4-40

5. PERFORMANCE EFFICIENCY OF STORMWATER MANAGEMENT

SYSTEMS 5-1

5.1 Literature-Based Removal Efficiencies for Typical Stormwater

Treatment Systems 5-2

5.1.1 Dry Retention Systems 5-2

5.1.2 Wet Detention Systems 5-6

5.1.3 Dry Detention (With and Without Filtration/Underdrain) 5-10

5.1.4 Off-line Retention/Detention (Dual Pond) Systems 5-13

5.1.5 Comparison of Treatment Effi ciencies for Typical Stormwater

Management Systems 5-15

5.2 Performance Efficiency of Exis ting Stormwater Design Criteria 5-16

5.2.1 Dry Retention 5-16

5.2.1.1 Evaluation Methodology 5-17

5.2.1.2 Design Criteria Based on Runoff Depth 5-18

5.2.1.3 Design Criteria Based on Runoff from a Specified

Rainfall Event 5-26

5.2.2 Wet Detention 5-33

5.2.2.1 SJRWMD Design Criteria 5-35

5.2.2.2 SFWMD Design Criteria 5-35

5.2.3 Dry Detention 5-40

6. RECOMMENDED MODIFICATIONS TO EXISTING STORMWATER

DESIGN CRITERIA 6-1

6.1 Design Criteria to Achieve 80% Removal 6-3

6.1.1 Dry Retention 6-3

6.1.2 Wet Detention 6-14

6.2 Design Criteria to Achieve 95% Removal 6-16

6.2.1 Dry Retention 6-16

6.2.2 Wet Detention 6-16

TOC – 2

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE OF CONTENTS – CONTINUED

6.3 Design Criteria to Achieve Post-Development Less Than or Equal To

Pre-Developing Loadings 6-24

6.3.1 Estimation of Pre-Development Pollutant Loadings 6-24

6.3.2 Estimation of Post-Development Pollutant Loadings 6-26

6.3.3 Estimated Annual Removal Efficiencies 6-29

6.4 Evaluation of Wet Detention Pond Depth 6-35

6.4.1 Theory of Shallow vs. Deep Ponds 6-35

6.4.2 Zonation and Stratification 6-44

7. DESIGN EXAMPLES 7-1

7.1 Design Example #1 7-1

7.2 Design Example #2 7-17

7.3 Design Example #3 7-29

7.4 Conclusions 7-53

7.4.1 Dry Retention 7-53

7.4.2 Wet Detention 7-55

7.5 Summary 7-57

8. REFERENCES 8-1

Appendices

A. Precipitation Data

B. Hydrologic Characteristics from Selected Stormwater Land Use Characterization Studies

C. Calculated Annual Runoff Coefficients fo r the Designated Meteorological Zones as a

Function of Curve Number and DCIA

D. Calculated Performance Efficiency of Dry Retention as a Function of DCIA and non-DCIA

Curve Number

TOC-3

# FDEP \ STORMWATER TREATMENT REPORT 

# LIST OF TABLES

Number Page

2-1 Stormwater System Design Standards Outlined in Chapter 62-25 FAC 2-4

2-2 Comparison of Stormwater Management System Design Criteria for Water

Management Districts in Florida 2-7

3-1 Characteristics of Selected Meteorological Sites in Florida 3-5

3-2 Percentage of Annual Rain Events Occurring in Selected Event Intervals 3-8

3-3 Mean Antecedent Dry Periods for Rain Events at the Designated Regional

Sites 3-10

4-1 General Land Use Categories for Runoff Characterization Data 4-2

4-2 Runoff Characterization Data Availability 4-3

4-3 Summary of Selected Stormwater Ch aracterization Studies Performed in the

State of Florida 4-5

4-4 Summary of Mean Stormwater Characteristics from Single-Family Residential

Stormwater Studies 4-12

4-5 Comparison of Runoff Characteristics for Residential Areas Utilizing Grassed

Swales and Curb/Gutter Drainage Systems 4-14

4-6 Summary of Mean Stormwater Characteristics from Multi-Family Residential

Stormwater Studies 4-15

4-7 Summary of Mean Stormwater Characteristics from Low-Intensity Commercial

Stormwater Studies 4-16

4-8 Summary of Mean Stormwater Characteristics from High-Intensity Commercial

Stormwater Studies 4-17

4-9 Summary of Mean Stormwater Character istics from Light Industrial Stormwater

Studies 4-18

4-10 Summary of Mean Stormwater Char acteristics from Highway/Transportation

Stormwater Studies 4-19

LT-1

# FDEP \ STORMWATER TREATMENT REPORT 

# LIST OF TABLES – CONTINUED

4-11 Summary of Mean Stormwater Characteristics from Pasture Land Use

Stormwater Studies 4-20

4-12 Summary of Mean Stormwater Character istics from Citrus Land Use Stormwater

Studies 4-21

4-13 Summary of Mean Stormwater Char acteristics from Row Crop Stormwater

Studies 4-22

4-14 Comparison of Stormwater Concentrations from Agricultural Activities in

Florida 4-23

4-15 Summary of Mean Stormwater Char acteristics from Undeveloped/Rangeland/

Forest Stormwater Studies 4-23

4-16 Summary of Mean Stormwater Character istics from Mining/Extractive Stormwater

Studies 4-24

4-17 Summary of Literature-Based Runoff Characterization Data for General Land Use

Categories in Florida 4-26

4-18 Characteristics of SCS Hydrol ogic Soil Group Classifications 4-28

4-19 Listing of NCDC Hourly Precipitati on Monitoring Stations in Florida 4-30

4-20 Recommended Seasonal Rainfall Depths for the Three Antecedent Moisture

Conditions (AMC) 4-32

4-21 Recommended Curve Number Adjustments Based on Antecedent Moisture

Contents 4-33

4-22 Summary of Hydrologic Assumptions Us ed for Developed Land Use Categories 4-35

4-23 Counties Included in the Designated Meteorological Zones 4-38

4-24 Summary of Mean Runoff Coefficients for Each Cluster as a Function of Land

Use and Hydrologic Soil Group 4-39

5-1 Treatment Efficiencies for Dry Reten tion Systems Based on Selected Research

Studies in Florida 5-5

5-2 Treatment Efficiencies for Wet Deten tion Systems Based on Selected Research

Studies in Florida 5-8

LT-2

# FDEP \ STORMWATER TREATMENT REPORT 

# LIST OF TABLES – CONTINUED

5-3 Treatment Efficiencies for Dry Detention with Filtration Systems Based on Selected

Research Studies in Florida 5-12

5-4 Treatment Efficiencies for Off-Line Retention/Detention Systems (Dual Pond)

Based on Selected Research Studies in Florida 5-15

5-5 Estimated Pollutant Removal Efficien cies for Common Stormwater Treatment

Facilities 5-15

5-6 Calculated Annual Mass Removal Efficiency of a Dry Retention Pond with a

Treatment Volume Equivalent to 0.5-inch of Runoff 5-19

5-7 Calculated Annual Mass Removal Efficiency of a Dry Retention Pond with a

Treatment Volume Equivalent to the Runoff from 1 inch of Rainfall 5-28

5-8 Estimated Performance Efficiency of Wet Detention Ponds Designed According

to SJRWMD Criteria 5-35

5-9 Summary of Studies Relating Mass Removal of Nitrogen and Phosphorus as a

Function of Detention Time in Wet Ponds 5-37

6-1 Required Retention Depths to Achieve an Annual Removal Efficiency of 80% 6-4

6-2 Recommended Design Criteria for Dry Retention Ponds to Achieve 80% Annual

Removal Efficiency 6-11

6-3 Recommended Design Criteria for Wet Detention Ponds 6-14

6-4 Required Retention Depths to Achieve an Annual Removal Efficiency of 95% 6-17

6-5 Hydrologic Assumptions for Estimation of Runoff and Mass Loadings from

Undeveloped Areas 6-24

6-6 Annual C Values for Undeveloped/Natural Areas 6-25

6-7 Calculated Annual Runoff Depths for Undeveloped/Natural Areas 6-25

6-8 Estimated Annual Mass Loadings of Nitrogen and Phosphorus for Undeveloped/

Natural Areas 6-26

6-9 Summary of Hydrologic Assumptions Us ed for Developed Land Use Categories 6-27

6-10 Summary of Calculated Annual Runoff Coefficients for Typical Developed Land

Use Categories 6-28

LT-3

# FDEP \ STORMWATER TREATMENT REPORT 

# LIST OF TABLES – CONTINUED

6-11 Summary of Annual Runoff Depths for Typical Developed Land Use Categories 6-30

6-12 Calculated Total Nitrogen Loadings for Typi cal Developed Land Use Categories 6-31

6-13 Calculated Total Phosphorus Loadings for Typical Developed Land Use

Categories 6-32

6-14 Required Removal Efficiencies to Achieve Post-Development Less Than or Equal

to Pre-Development Loadings for Total Nitrogen 6-33

6-15 Required Removal Efficiencies to Achieve Post-Development Less Than or Equal

to Pre-Development Loadings for Total Phosphorus 6-34

6-16 Regression Statistics for Anoxic Depth Model 6-49

7-1 Comparison of Existing and Required Dry Retention Stormwater Treatment

Requirements 7-53

7-2 Comparison of Existing and Required Wet Detention Stormwater Treatment

Requirements 7-56

LT-4

# FDEP \ STORMWATER TREATMENT REPORT 

# LIST OF FIGURES

Number Page

2-1 Approximate Boundaries for Water Management Districts in Florida 2-5

3-1 Locations of Meteorological Monitoring Sites 3-2

3-2 Isopleths of Mean Annual Precipitation in Florida from 1971-2000 3-3

3-3 Locations of Selected Meteorological Sites 3-5

3-4 Percentage of Annual Rain Events Les than 1 inch at the Selected Regional

Sites 3-7

3-5 Comparison of the Mean Number of Annual Rainfall Events at the Selected

Regional Sites 3-9

3-6 Comparison of Dry and Wet Season Antecedent Dry Periods at the Regional

Monitoring Sites 3-11

4-1 Locations of Hourly Meteorological Monitoring Sites 4-31

4-2 Percentage of Variance in Annual Runoff Coefficients Explained as a Function of

the Number of Clusters 4-36

4-3 Meteorological Zones Identified Using Cluster Analysis 4-37

4-4 General Relationships Between Percent DCIA, Curve Number, and C Value 4-41

4-5 Distribution of C Values as a Function of DCIA and Curve Number for the

Panhandle Area (Zone 1) 4-42

4-6 Distribution of C Values as a Function of DCIA and Curve Number for the

Florida Keys (Zone 3) 4-44

4-7 State-wide Mean Distribution of C Va lues as a Function of DCIA and Curve

Number 4-45

4-8 Modeled Annual Runoff Coefficients (C Values) for a Hypothetical Development

with a DCIA of 40% and a non-DCIA Curve Number of 70 4-46

4-9 Percentage of Annual Rainfall Volume Generated by Rain Events < 0.1 Inch 4-47

LF-1

# FDEP \ STORMWATER TREATMENT REPORT 

# LIST OF FIGURES – CONTINUED

4-10 Percentage of Annual Rainfall Volume Generated by Rain Events > 1 Inch 4-47

4-11 Percentage of Annual Rainfall Depth Lost to Initial Abstraction on Impervious

Surfaces 4-48

5-1 Schematic of a Dry Retention Facility 5-3

5-2 Schematic of a Wet Detention Facility 5-6

5-3 Schematic of a Dry Detention with Underdrain System 5-10

5-4 Schematic of an Off-line Retention/Detention System 5-14

5-5 Calculated Annual Mass Removal Efficien cies for 0.5-inch of Dry Retention for a

Development with 40% DCIA and a non-DCIA Curve Number of 70 5-24

5-6 State-wide Average Removal Efficien cies for 0.5 inch of Dry Retention for

Various DCIA Percentages and non-DCIA Curve Numbers 5-25

5-7 Calculated Annual Mass Removal Effici encies for Dry Retention of the Runoff

from 1 inch of Rainfall for a Development with 40% DCIA and a non-DCIA

Curve Number of 70 5-27

5-8 Comparison of Annual Mass Removal Efficiencies for Dry Retention Systems

Designed for Treatment of 0.5 inch of Runoff or the Runoff from 1 inch of

Rainfall 5-33

5-9 Removal Efficiency of Total Phosphorus in Wet Detention Ponds as a Function of

Residence Time 5-38

5-10 Removal Efficiency of Total Nitrogen in Wet Detention Ponds as a Function of

Residence Time 5-39

6-1 Theoretical Removal of BOD as a Function of Residence Time in a Wet Detention

Pond 6-2

6-2 State-wide Average Variations in Re quired Dry Retention Depth for 80% Removal

as a Function of DCIA Percentage and non-DCIA Curve Number 6-10

6-3 Variations in Required Dry Retention Depth to Achieve 80% Removal in the

Central Zone Area (Zone 2) 6-12

6-4 Variations in Required Dry Retention Depth to Achieve 80% Removal in the

Panhandle Zone Area (Zone 1) 6-13

LF-2

# FDEP \ STORMWATER TREATMENT REPORT 

# LIST OF FIGURES – CONTINUED

6-5 Variations in Required Dry Retention Depth to Achieve 95% Removal on a

State-wide Basis 6-23

6-6 Comparison of Estimated Annual Mass Removal Efficiencies to Achieve Post-

Development # Pre-Development Loadings of Nitrogen and Phosphorus for a

Low-Density Residential Development 6-36

6-7 Comparison of Estimated Annual Mass Removal Efficiencies to Achieve Post-

Development # Pre-Development Loadings of Nitrogen and Phosphorus for a

Single-Family (25% Impervious) Residential Development 6-37

6-8 Comparison of Estimated Annual Mass Removal Efficiencies to Achieve Post-

Development # Pre-Development Loadings of Nitrogen and Phosphorus for a

Single-Family (40% Impervious) Residential Development 6-38

6-9 Comparison of Estimated Annual Mass Removal Efficiencies to Achieve Post-

Development # Pre-Development Loadings of Nitrogen and Phosphorus for a

Multi-Family Residential Development 6-39

6-10 Comparison of Estimated Annual Mass Removal Efficiencies to Achieve Post-

Development # Pre-Development Loadings of Nitrogen and Phosphorus for a

Commercial Development 6-40

6-11 Comparison of Estimated Annual Mass Removal Efficiencies to Achieve Post-

Development # Pre-Development Loadings of Nitrogen and Phosphorus for a

Highway (50% Impervious) Development 6-41

6-12 Comparison of Estimated Annual Mass Removal Efficiencies to Achieve Post-

Development # Pre-Development Loadings of Nitrogen and Phosphorus for a

Highway (75% Impervious) Development 6-42

6-13 Typical Zonation in a Lake or Pond 6-44

6-14 Relationship Between Secchi Disk Depth and Chlorophyll-a for Florida Lakes 6-47

LF-3

# FDEP \ STORMWATER TREATMENT REPORT 

# SECTION 1

INTRODUCTION

The discharge of stormwater within the Stat e of Florida has been subject to regulation

since the early 1980s to prevent pollution of Wate rs of the State and to protect the designated

beneficial uses of surface waters. Currently, st ormwater management is regulated at the State

level by the Florida Department of Environmen tal Protection (FDEP), at the regional level by

water management districts, and at the local level by local governments.

The goals for stormwater management within the State of Florida are outlined in Chapter

62-40 of the Florida Administrative Code (FAC), titled “Water Resource Implementation Rule”.

This rule establishes that stormwater design criteria adopted by FDEP and the water

management districts shall achieve at least 80% reduction of the average annual load of

pollutants that cause or contribute to violations of State Water Quality Standards. When the

stormwater system discharges to an Outs tanding Florida Water (OFW), the design and

performance criteria increases to 95% reduction.

A wide range of stormwater design criteria have been implemented within the State of

Florida to achieve these minimum stormwater treatment performance standards. However,

recent research on the performance efficiency of current stormwater management systems

indicates a high degree of variability in the pollu tant removal effectiveness of commonly used

systems. In addition, stormwater design criteria for the same type of stormwater management

system vary widely throughout the State of Florid a, which can impact the performance efficiency

of stormwater management systems designed in one area compared to another.

1.1 Scope of Work

This report provides a discussion of work efforts performed by Environmental Research

& Design, Inc. (ERD) for the Florida Department of Environmental Protection (FDEP) as part of

Agreement SO108, titled “Evaluation of Current Stor mwater Design Criteria within the State of

Florida”. The primary objective of this project is to evaluate current stormwater design criteria

within the State of Florida and determine if these criteria meet the treatment requirements

specified in Chapter 62-40 FAC. If elements of existing stormwater design criteria fail to meet

the requirements of Chapter 62-40 FAC, then ch anges will be recommended to the current rules

to improve stormwater management so that the minimum treatment requirements can be

achieved. This analysis was also conducted to ev aluate existing design criteria for discharges to

OFWs which have the goal of 95% pollutant re moval. In addition, an evaluation was also

performed to quantify stormwater design criteri a necessary to achieve a condition of no net

increase in loadings for a project site under post- development conditions compared with loadings

discharging from the site under pre-development conditions.

1-1

# FDEP \ STORMWATER TREATMENT REPORT 

# 1-2

The analyses summarized in this report are based primarily upon mass loadings of

nitrogen and phosphorus. Although other constituen ts are commonly present in stormwater

runoff, such as suspended solids, BOD, and h eavy metals, nutrients are the most significant

parameters linked to water quality impairment within the State of Florida today. Other

significant pollutants can often be removed from st ormwater more easily than nutrients, and as a

result, design criteria which provide the desired removal efficiencies for nutrients will likely

achieve equal or better removal efficiencies for other constituents.

The specific objectives of this project are to:

1. Collect and review current stormwater quality design criteria within the State of

Florida developed by FDEP and the various water management districts

2. Collect and review stormwater characterization data to update existing databases

3. Identify significant meteorological regions within the State of Florida and develop

regionally-specific rainfall and runoff characteristics and relationships

4. Estimate pre-development hydrologic and pollutant loading characteristics for

natural areas

5. Collect and review stormwater treat ment system performance efficiency

information based on previous research performed within the State of Florida

6. Perform model simulations of the anticipated treatment system performance

efficiency of common stormwater manage ment systems utilized within the State

of Florida based on regional meteorological and hydrologic conditions

7. Evaluate changes to current stormwater regulations, if necessary, to meet the

requirements of Chapter 62-40 FAC (80% and 95% pollutant removal

efficiencies) and to achieve a condition of no net increase in pollutant loadings

following development

This report is divided into eight separate sections for presentation and discussion of the

analyses and results of this project. The first section provides an introduction to the report, along

with a summary of work efforts performed by ER D. A discussion of stormwater regulations

within the State of Florida is given in Section 2. Annual and regional precipitation

characteristics in Florida are discussed in Sec tion 3. Section 4 contains an analysis and

discussion of the quantity and quality of stormwater runoff generated from various land use

categories within the State of Florida. A disc ussion of the performance efficiency of existing

stormwater management practices is given in Section 5. Proposed modifications to existing

stormwater management design criteria are gi ven in Section 6. Design examples, which

illustrate the proposed design changes, are given in Section 7. Cited references are included in

Section 8. Appendices are also attached which contain supporting data and calculations utilized

to generate the results and conclusions presented in this report.

# FDEP \ STORMWATER TREATMENT REPORT 

# SECTION 2

REGULATION OF

STORMWATER IN FLORIDA

Since the early 1980s, the discharge of stormw ater within the State of Florida has been

subject to regulation to prevent pollution of Wate rs of the State and to protect the designated

beneficial uses of surface waters. Currently, the design, permitting, construction, and operation of

stormwater management systems within the State of Florida are governed by laws and regulations of

the State of Florida, regional water management di stricts, and local governments. A discussion of

existing regulations governing stormwater discharge within Florida is given in the following

sections.

2.1 State Regulations

The goals for stormwater management within the State of Florida are outlined in Chapter 62-

40 of the Florida Administrative Code (FAC), titled “Water Resource Implementation Rule”. This

rule provides general guidelines related to water us e and reuse, water transfer, water quality, surface

water management, flood protection, and minimum fl ows and levels. Specific goals related to

stormwater management are outlined in Section 62-40.431, titled “Stormwater Management

Program”. Paragraph 2a establishes the prim ary goals of the State Stormwater Management

Program:

"The primary goals of the State Stormwater Management Program are to maintain, to the

maximum extent practicable, during and afte r construction and development, the predevelopment stormwater characteristics of the site; to reduce stream channel erosion,

pollution, siltation, sedimentation, and flooding; to reduce stormwater pollutant loadings

discharged to waters to preserve or restore d esignated uses; to reduce the loss of fresh water

resources by encouraging the recycling of stormwater; to enhance groundwater recharge by

promoting infiltration of stormwater in areas w ith appropriate soils and geology; to maintain

the appropriate salinity regimes in estuaries need ed to support the natural flora and fauna; and

to address stormwater management on a watershed basis to provide cost-effective water

quality and water quantity solutions to specific watershed problems."



# Paragraph 3a establishes that the Florida Depart ment of Environmental Protection (Department or

FDEP) “shall be the lead agency responsible for coordinating the state-wide stormwater

management program and is responsible for establishing goals, objectives, and guidance for

development and implementation of the stormwat er management program by water management

districts and local governments”. This section fu rther provides for delegation of administration of

the State Stormwater Management Program to wate r management districts which have implemented

a comprehensive surface water management program.

2-1

# FDEP \ STORMWATER TREATMENT REPORT 

# 2-2

Chapter 62-40.432, titled “Surface Water Manageme nt Regulation”, establishes guidelines

for regulation of surface water management system s. Paragraph 2 of this section establishes

minimum stormwater treatment performance standards as follows:

"When a stormwater management system complies with rules establishing the design and

performance criteria for such systems, there shall be a rebuttable presumption that the

discharge from such systems will comply w ith State water quality standards. The

Department and the Districts, pursuant to Section 373.418, F.S., shall, when adopting rules

pertaining to stormwater management systems, specify design and performance criteria for

new stormwater management systems which:

1. Achieve at least 80% reduction of the average annual load of pollutants that would

cause or contribute to violations of State water quality standards

2. Achieve at least 95% reduction of the average annual load of pollutants that would

cause or contribute to violations of State water quality standards in Outstanding

Florida Waters."



# Based upon the language outlined above, all stormwat er management systems designed within the

State of Florida must “achieve at least 80% reducti on of the annual average lo ad of pollutants that

would cause or contribute to viola tions of state water quality standards”. This statement forms the

minimum basis for all stormwater design criteria within the State of Florida.

If stormwater management systems are designed according to the goals and guidelines

established in Chapter 62-40, there is a rebutta ble presumption that the discharge from the

stormwater system will comply with state water quality standards. Specific numerical criteria for

regulated water quality constituents are outlined in Chapter 62-302 FAC, titled “Surface Water

Quality Standards”. This chapter establishes th e minimum water quality levels which are necessary

to protect the designated uses of a water body. Chapter 62-302.400 outlines five surface water

classifications, according to designated uses, as follows: (1) Class I - Potable Water Supplies;

(2) Class II - Shellfish Propagation or Harves ting; (3) Class III – Recreation, Propagation and

Maintenance of a Healthy Well-Balanced Population of Fish and Wildlife; (4) Class IV- Agricultural

Water Supplies; and (5) Class V -Navigati on, Utility and Industrial Use. Water quality

classifications are arranged in order of the degr ee of protection required, with Class I water having

generally the most stringent water quality criteria and Class V the least. In general, all surface

waters of the State of Florida are classified as Class III unless otherwise specified. A listing of

waterbodies classified as Class I, Class II, or Class IV is given in Ch. 62-302.400(12).

Chapter 62-302.700, titled “Special Protection – Outstanding Florida Waters, Outstanding

Natural Resource Waters”, establishes a list of waters within the State of Florida to be afforded a

higher level of protection. No degradation of wate r quality is to be permitted in Outstanding Florida

Waters (OFW). To achieve this goal, Chapter 62-40 establishes that stormwater management

systems discharging to Outstanding Florida Waters be designed to achieve at least a 95% reduction

of the average annual load of pollu tants that would cause or contribute to violations of state water

quality standards.

# FDEP \ STORMWATER TREATMENT REPORT 

# 2-3

Criteria for stormwater management system s permitted within the State of Florida are

outlined in Chapter 62-25, titled “Regulations of Stormwater Discharge”. Minimum design and

performance standards for stormwater management systems are listed in Chapter 62-25.025, titled

“Design and Performance Standards”. Stormwater management systems designed according to the

criteria outlined in this section are assumed to be in compliance with water quality standards set

forth in Chapter 62-302 and with the primary goals of the State Stormwater Management Program

outlined in Chapter 62-40, specifically that the sy stems are designed to achieve at least an 80%

reduction of the average annual load of pollutants that would cause or contribute to violations of

state water quality standards.

Stormwater system design standards outlin ed in Chapter 62-25 FAC are summarized in

Table 2-1. Detention and retention systems are the only types of stormwater systems referenced in

this chapter. In general, both detention and rete ntion systems must provide treatment for the runoff

generated from the first 1 inch of rainfall, or as an option, for projects less than 100 acres in

size, treatment for 0.5-inch of runoff. Recovery of the specified treatment volume must be achieved

within 72 hours following a storm event. Specifi c design criteria are included for filter systems

which includes guidelines on permeability, percent or ganic matter and silt, uniformity coefficient,

and effective grain size for the filter media.

Exemptions from permitting and construction of stormwater management facilities are

provided for five types of stormwater discharges , summarized at the bottom of Table 2-1. These

exemptions primarily address relatively minor deve lopments such as single-family units, duplexes,

triplexes, or quadruplexes which ar e not part of a larger common plan of development. Exemptions

are also provided for stormwater which discharges into a regional treatment facility with sufficient

capacity and discharges from agricultural and silvicultural activities.

2.2 Water Management Districts

The State of Florida has been divided into fi ve independent water management districts to

address water resources and water supply issues on a regional basis within the state. Approximate

boundaries for the water management districts in Florida are illustrated on Figure 2-1. The

Northwest Florida Water Management District regulates water resources in the Florida Panhandle.

Watersheds in this area typically drain to tributar ies and rivers which ultimately discharge into the

Gulf of Mexico. The Suwannee River Water Mana gement District encompasses watershed areas

which are tributary to the Suwannee River. Si milarly, the St. Johns River Water Management

District includes watershed areas which ultimatel y discharge into the St. Johns River. The

Southwest Florida Water Management District incl udes watersheds which discharge to tributaries

and rivers which ultimately reach the west coas t of Florida at numerous locations. The South

Florida Water Management District primarily includes areas which are tributary to Lake

Okeechobee and the Florida Everglades.

# FDEP \ STORMWATER TREATMENT REPORT 

# 2-4

TABLE 2-1

STORMWATER SYSTEM DESIGN STANDARDS

OUTLINED IN CHAPTER 62-25 FAC

STORMWATER

SYSTEM TYPE DESIGN

PARAMETER CRITERIA

Retention Treatment Volume Runoff from the first 1" of rainfall; or as an option, for projects

< 100 ac, 0.5" of runoff

Volume Recovery < 72 hours following storm using percolation, evaporation, or

evapotranspiration

Swales Treatment Volume Percolate 80% of the runoff from a 3-year/1-hour storm within

72 hours following storm

Volume Recovery < 72 hours following storm using percolation, evaporation, or

evapotranspiration

Dry Detention Treatment Volume Runoff from the first 1" of rainfall; or as an option, for projects

< 100 ac, 0.5" of runoff

Volume Recovery < 72 hours following storm

Filter Systems

(if applicable) Filter Design Permeability $ surrounding soil

Media washed with <1% silt, clay, and organic matter

Media uniformity coefficient > 1.5

Effective grain size from 0.20-0.55 mm

Designed with safety factor of 2

Wet Detention 1 

# Treatment Volume 1.00” of runoff

Volume Recovery <50% in 60 hours following storm

Detention Time Minimum 14 days

Littoral Zone Minimum 30% of pond area

Pond Depth Maximum 8-10 ft below control elevation

Fencing Required for wet ponds unless side slopes are less than 4:1

Exemptions Facilities designed to accommodate only one single-family dwelling un it, duplex, triplex, or

quadruplex, provided the single unit, duplex, triplex, or quadruplex is not part of a larger

common plan of development or sale

Facilities which are designed to serve single-fa mily residential proj ects, including duplexes,

triplexes, and quadruplexes, of less than 10 acres total land area and which have less than 2

acres impervious surface

Stormwater discharge facilities whose functi oning treatment components consist entirely of

swales

Facilities which discharge into a regional stormwater discharge facility

Facilities for agricultural lands, provided those facilities are part of an approved Conservation

Plan

Facilities for silvicultural lands, provided that the facilities are constructed and operated in

accordance with the Silviculture Best Management Practices Manual (1979)

1. Requirements outlined in “Guidelines for Using Structural Stormwater Controls” from FDEP’s The Florida

Development Manual – A Guide to Sound Land and Wate r Management – Stormwater Management Practices

, Chapter 6.

# FDEP \ STORMWATER TREATMENT REPORT 

# 2-5

Figure 2-1. Approximate Boundaries for Wa ter Management Districts in Florida.

(Source: FDEP Web Site)

The authority to delegate implementation of the Stormwater Management Program within

the State of Florida from FDEP to the various water management districts is provided in Chapter 62-

40.431. This section provides that water manage ment districts which have implemented a

Comprehensive Surface Water Management Progr am under Part IV of Chapter 373 (Florida

Statutes) shall be the chief administrators of the State Stormwater Management Program within their

districts. Using this authority, FDEP has de legated responsibility for the Stormwater

Management Program to the Suwannee River, St. Johns River, Southwest Florida, and the South

Florida Water Management Districts. Each of th ese water management districts has developed a

unique set of stormwater design criteria, modeled after the minimum design criteria outlined in

Chapter 62-25 FAC, and designed to achieve the mi nimum stormwater treatment standards specified

in Chapter 62-40 FAC (Water Resource Implementation Rule).

# FDEP \ STORMWATER TREATMENT REPORT 

# 2-6

FDEP has not delegated authority for regulati on of stormwater discharges to the Northwest

Florida Water Management District since this di strict does not have the economic and technical

resources to implement a Comprehensive Surface Wa ter Management Program at this time. As

such, FDEP has retained implementation of the Stat e Stormwater Management Program in this area

and provides permitting services for all new developm ent within the Northwest Florida district based

upon the stormwater system design standards outlined in Chapter 62-25 FAC.

A comparison of existing stormwater manage ment design system criteria within the St.

Johns River, Suwannee River, Southwest Florid a, and the South Florida Water Management

Districts is given in Table 2- 2. Design criteria are summarized for each type of stormwater

management system referenced w ithin each of the four districts, including treatment volume, volume

recovery, vegetation requirements, residence time, depth, and system configuration. Criteria which

do not directly impact the performance efficiency of the stormwater system (such as side slopes,

minimum pipe sizes, vegetative planting success rates, etc.) are not listed in Table 2-2.

Each of the four water management districts provides design criteria for dry retention basins.

In general, retention requirements are typically equivalent to the runoff volume generated by the

first 0.5-inch of runoff or 1 inch of rainfall. Distinctions between off-line and on-line systems are

provided in the design criteria by the St. Johns River and the Southwest Florida Water Management

Districts, with increases in retention volume required for on-line systems. Volume recovery

requirements for retention basins vary, ranging fr om full volume recovery in less than 72 hours in

the St. Johns River, Suwannee River, and Southw est Florida Water Management Districts, to

recovery of 50% of the treatment volume in 24 hours in the South Florida Water Management

District. The St. Johns River Water Management Dist rict requires the retention basin to be stabilized

with pervious material or vegetative cover, while vegetative cover is not referenced by the remaining

districts.

Specifications for underdrain systems ar e provided by the St. Johns River Water

Management District only, with treatment volume requirements similar to those specified for dry

retention. Underdrain systems are not referenced by the remaining water management districts.

Underground exfiltration is specifically refe renced by the St. Johns River, Southwest

Florida, and South Florida Water Management Di stricts. In general, the treatment volume

requirements for underground exfiltration systems are identical to those required for dry retention by

the districts. However, volume recovery require ments vary substantially, with volume recovery

required within 1 hour by the South Florida Water Management District and within 72 hours by the

St. Johns River and Southwest Florida Water Management Districts.

The use of swales for stormwater treatment is referenced by both the St. Johns River and the

Suwannee River Water Management Districts. Each of these districts requires percolation of 80% of

the runoff generated from a 3-year /1-hour storm within the swale system, with recovery of the

treatment volume in less than 72 hours. The use of swales for stormwater treatment is not

specifically referenced by either the Southwes t Florida or South Florida Water Management

Districts.FDEP \ STORMWATER TREATMENT REPORTTABLE 2-2COMPARISON OF STORMWATERMANAGEMENT SYSTEM DESIGNCRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDASTORMWATERSYSTEM TYPEDESIGNPARAMETERCRITERIASt. Johns River WaterManagement District1Suwannee River WaterManagement District2Southwest Florida WaterManagement District3South Florida WaterManagement District4Retention TreatmentVolumeOff-line retention of the first 0.5"of runoff or 1.25" of runoff fromthe impervious area; whichever isgreaterRetention of the runoff from thefirst 1" of rainfallOn-line retention of the runofffrom 1" of rainfallRetention of the first 0.5" of runoffor 1.25" times the percentage ofimperviousness; whichever isgreaterOn-line retention of the first 1" ofrunoff; or 1.25" of runoff from theimpervious area plus 0.5” ofrunoff from entire basin;whichever is greaterIf project discharges to sink, thenoff-line or on-line retention of therunoff from the first 2" of rainfallIf project < 100 ac, on-lineretention of 0.5" of runoffOn-line retention that percolatesthe runoff from the 3-year/1-hourstormOff-line retention of runoff from1" of rainfallFor projects with <40%impervious and only HSG A soils,on-line retention from 1" ofrainfall or 1.25" of runoff fromimpervious areasIf project < 100 ac, off-lineretention of 0.5" of runoffVolumeRecoveryProvide design capacity in 72hours using percolation,evaporation, or evapotranspirationProvide design capacity in 72hours using percolation,evaporation, or evapotranspirationTreatment volume recovered in <72 hoursNo more than half of treatmentvolume in 24 hoursVegetation Stabilized with pervious materialor permanent vegetative coverNot Referenced Not Referenced Not ReferencedReferences: 1. Chapter 40C-42 FAC - Environmental ResourcePermits: Regulation of Stormwater Management Systems2. Chapter 40B-4 - Regulations3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

# 2-7FDEP \ STORMWATER TREATMENT REPORTTABLE 2-2 -- CONTINUEDCOMPARISON OF STORMWATERMANAGEMENT SYSTEM DESIGNCRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDASTORMWATERSYSTEM TYPEDESIGNPARAMETERCRITERIASt. Johns River WaterManagement District1Suwannee River WaterManagement District2Southwest Florida WaterManagement District3South Florida WaterManagement District4UnderdrainSystemTreatmentVolumeOff-line storage of the first 0.5" ofrunoff or 1.25" of runoff fromimpervious area; whichever isgreaterNot Referenced Not Referenced Not ReferencedOn-line retention of the first 1" ofrunoff; or 1.25" of runoff from theimpervious area plus 0.5” ofrunoff from entire basin;whichever is greaterRecoveryVolumeProvide design capacity in 72hours using percolation,evaporation, or evapotranspirationNot Referenced Not Referenced Not ReferencedProvide at least 2 ft of indigenoussoil between pond bottom andunderdrainDesigned with a safety factor of 2VegetationStabilized with permanentvegetative coverNot Referenced Not Referenced Not ReferencedReferences: 1. Chapter 40C-42 FAC - Environmental ResourcePermits: Regulation of Stormwater Management Systems2. Chapter 40B-4 - Regulations3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

# 2-8FDEP \ STORMWATER TREATMENT REPORTTABLE 2-2 -- CONTINUEDCOMPARISON OF STORMWATERMANAGEMENT SYSTEM DESIGNCRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDASTORMWATERSYSTEM TYPEDESIGNPARAMETERCRITERIASt. Johns River WaterManagement District1Suwannee River WaterManagement District2Southwest Florida WaterManagement District3South Florida WaterManagement District4UndergroundExfiltrationTreatmentVolumeOff-line storage of the first 0.5" ofrunoff or 1.25" of runoff from theimpervious area; whichever isgreaterNot Referenced Storage of the runoff from the first1” of rainfallRetention of the first 0.5" of runoffor 1.25" times the percentage ofimperviousness; whichever isgreaterOn-line retention of the first 1" ofrunoff; or 1.25" of runoff from theimpervious area plus 0.5” ofrunoff from entire basin;whichever is greaterIf project < 100 acres, storage of0.5” of runoffDesigned with a safety factor of 2VolumeRecoveryRecover design capacity within 72hours by percolation onlyNot Referenced Recover design capacity within 72hours by percolation onlyRecover design capacity in 1 hourInvert elevation of trench must be> 2 ft above SHWTReferences: 1. Chapter 40C-42 FAC - Environmental ResourcePermits: Regulation of Stormwater Management Systems2. Chapter 40B-4 - Regulations3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

# 2-9FDEP \ STORMWATER TREATMENT REPORTTABLE 2-2 -- CONTINUEDCOMPARISON OF STORMWATERMANAGEMENT SYSTEM DESIGNCRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDASTORMWATERSYSTEM TYPEDESIGNPARAMETERCRITERIASt. Johns River WaterManagement District1Suwannee River WaterManagement District2Southwest Florida WaterManagement District3South Florida WaterManagement District4Wet Detention TreatmentVolumeFirst 1" of runoff or 2.5" of runofffrom impervious area; whicheveris greaterDetention of the runoff from thefirst 1” of rainfallFirst 1" of runoff from watershed First 1" of runoff or 2.5" of runofffrom impervious area; whicheveris greaterIf project discharges to sink, thenoff-line or on-line detention of therunoff from the first 2” of rainfallVolumeRecoveryBleed-down 50% of treatmentvolume in 24-30 hoursRecover design capacity in < 72hours50% in 60 hours; 100% in 120hours50% of treatment volume in 24hoursResidenceTimeMinimum 14-day wet season(June-October)Not Referenced Not Referenced Not ReferencedLittoral Zone30% of pond area at NWL Not Referenced Minimum of 35% of pond area,concentrated at outfall20% of pond area or 2.5% of thepond plus basin areaAs an alternative to littoral zone:(a) 50% additional permanent poolvolume; or (b) 0.5" retention pretreatmentPond Depth Mean depth between 2-8 ft Not Referenced Not Referenced Recommended that 25-50% ofpond area be > 12 ftMaximum depth <12 ftConfiguration Length:Width >2:1 Not Referenced Not Referenced > 0.5 acre in size100 ft minimum widthReferences: 1. Chapter 40C-42 FAC - Environmental ResourcePermits: Regulation of Stormwater Management Systems2. Chapter 40B-4 - Regulations3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

# 2-10FDEP \ STORMWATER TREATMENT REPORTTABLE 2-2 -- CONTINUEDCOMPARISON OF STORMWATERMANAGEMENT SYSTEM DESIGNCRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDASTORMWATERSYSTEM TYPEDESIGNPARAMETERCRITERIASt. Johns River WaterManagement District1Suwannee River WaterManagement District2Southwest Florida WaterManagement District3South Florida WaterManagement District4Swales TreatmentVolumePercolate 80% of runoff from 3-hour/1-hour stormPercolate 80% of runoff from 3-hour/1-hour stormNot Referenced Not ReferencedVolumeRecoveryRegain treatment volume in < 72hoursRegain treatment volume in < 72hoursNot Referenced Not ReferencedDry Detention Use Restriction a. Where HGWT or soilconditions limit use of otherBMPsb. Drainage basin areas < 5 acresNone Not Referenced NoneTreatmentVolumeOff-line detention ofthe first 1" ofrunoff or 2.5" of runoff fromimpervious areasDetention of the runoff from thefirst 1" of rainfallNot Referenced On-line or off-line detention of thefirst 0.75" of runoff or 1.88" timesthe percentage of imperviousness;whichever is greaterIf project discharges to sink, thenoff-line or on-line detention of therunoff from the first 2" of rainfallVolumeRecoveryDischarge of 50% of treatmentvolume in 24-30 hoursRecover design capacity in < 72hoursNot Referenced Recover 50% of treatment volumein 24 hoursAreas of standing water for nomore than 3 daysReferences: 1. Chapter 40C-42 FAC - Environmental ResourcePermits: Regulation of Stormwater Management Systems2. Chapter 40B-4 - Regulations3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

# 2-11FDEP \ STORMWATER TREATMENT REPORTTABLE 2-2 -- CONTINUEDCOMPARISON OF STORMWATERMANAGEMENT SYSTEM DESIGNCRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDASTORMWATERSYSTEM TYPEDESIGNPARAMETERCRITERIASt. Johns River WaterManagement District1Suwannee River WaterManagement District2Southwest Florida WaterManagement District3South Florida WaterManagement District4Detentionwith FiltrationTreatmentVolumeOffline: first 1” of runoff or 2.5”of runoff from impervious area,whichever is greaterDetention of the runoff from thefirst 1" of rainfallOn-line detention of the runofffrom 1" of rainfallNot ReferencedOn-line: additional 0.5” of runofffrom drainage basin above off-linevolumeIf project discharges to sink, thenoff-line or on-line detention of therunoff from the first 2" of rainfallIf project < 100 ac, on-linedetention of 0.5" of runoffOff-line detention of runoff from1" of rainfallIf project < 100 ac, off-linedetention of 0.5" of runoffFilter System Media washed with <1% silt, clay,and organic matterPermeability$surrounding soil Permeability$surrounding soil Not ReferencedMedia uniformity coefficient > 1.5 Media washed with <1% silt, clay,and organic matterMedia washed with <1% silt, clay,and organic matterEffective grain size from 0.20-0.55 mmMedia uniformity coefficient > 1.5 Media uniformity coefficient > 1.5Designed with safety factor of 2 Effective grain size from 0.20-0.55 mmEffective grain size from 0.20-0.55 mmSeasonal HGWT below invert ofperforated pipeDesigned with safety factor of 2 Designed with safety factor of 2Seasonal HGWT >1 ft belowcenterline of perforated pipeVolumeRecoveryRecover treatment volume in <72hoursRegain treatment volume in < 72hoursTreatment volume available in <36 hoursNot ReferencedDischarges toOFW, Class I or IIWatersTreatmentVolumeIn general, 50% additionaltreatment volume above standardcriteria plus 50% additional PPVfor wet detentionIn general, 50% additional volumeabove standard criteriaIn general, 50% additional volumeabove standard criteriaIn general, 50% additional volumeabove standard criteria; plusadditional measures such as pretreatmentReferences: 1. Chapter 40C-42 FAC - Environmental ResourcePermits: Regulation of Stormwater Management Systems2. Chapter 40B-4 - Regulations3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

# 2-12

# FDEP \ STORMWATER TREATMENT REPORT 

# 2-13

Wet detention stormwater treatment is specifi cally referenced by all the water management

districts except the Suwannee River Water Manageme nt District. However, the Suwannee River

Water Management District provides general detenti on criteria which could be interpreted as either

wet or dry systems. In the three districts that provide references for wet detention, the required

treatment volume is equivalent to 1 inch of runo ff from the watershed or 2.5 inches of runoff from

the impervious area, whichever is greater. Volume recovery requirements are variable, with

recovery of 50% of the treatment volume in 24- 30 hours in the St. Johns River Water Management

District, 50% in 60 hours and 100% in 120 hours in the Southwest Florida Water Management

District, and 50% recovery in 24 hours in the Sout h Florida Water Management District. Residence

time, perhaps the most significant factor in determ ining the overall performance efficiency of a wet

detention system, is referenced only by the St. Johns River Water Management District which

requires a minimum 14-day wet season residence time during the months from June-October.

Littoral zone plantings are required by each of the three water management districts, ranging from

20% in the South Florida Water Management Dist rict to 35% in the Southwest Florida Water

Management District. Require ments for pond depth, also an important design parameter, are

provided by the St. Johns River a nd South Florida Water Management Districts. The St. Johns

River Water Management District specifies sha llow ponds, with a mean depth ranging from 2-8 ft

and a maximum depth of 12 ft. In contrast, the South Florida Water Management District

recommends that 25-50% of the pond area be greater than 12 ft to provide storage for accumulated

solids.

Specific references to design criteria for dry detention (without filtration) are provided by the

St. Johns River and South Florida Water Manage ment Districts. The Suwannee River Water

Management District mentions “detention” whic h could be inferred to mean dry detention.

Treatment volume requirements are somewhat variab le, with 1 inch of runoff (or 2.5 inches from

impervious areas) in an off-line system in the St . Johns River Water Management District, the runoff

from 1 inch of rainfall in the Suwannee River Wate r Management District, and 0.5 inch of runoff (or

1.88 inches x impervious area) in the South Florid a Water Management District. Volume recovery

is also highly variable, with recovery of 50% of the treatment volume in 24 hours by the St. Johns

River and South Florida Water Management District s, and complete recovery in 72 hours within the

Suwannee River Water Management District.

Detention with filtration systems are referen ced by the St. Johns River, Suwannee River, and

Southwest Florida Water Management Districts. In general, the treatment volume requirements for

detention with filtration systems are identical to those required for dry retention systems.

Specifications are also provided for the filter system which are virtually identical to the filter system

criteria outlined in Chapter 62-25. Treatment volume recovery ranges from 36 hours in the

Southwest Florida Water Management District to 72 hours in the St. Johns River and Suwannee

River Water Management Districts.

Each of the four water management distri cts provides additional supplemental criteria for

stormwater management systems which discharge to OFW, Class I or II waterbodies, or sensitive

areas. In general, an additional 50% treatment volume is required by the St. Johns River, Suwannee

River, South Florida, and Southwest Florida Wate r Management Districts for discharges to these

waterbodies. In addition to the enhanced treatme nt volume, the St. Johns River Water Management

District also requires an additional 50% perman ent pool volume for wet detention ponds. The South

Florida Water Management District also requires additional assurances in the form of pre-treatment

or other listed options.

# FDEP \ STORMWATER TREATMENT REPORT 

# 2-14

Basin-specific criteria have been developed by the St. Johns River and South Florida Water

Management Districts to address flooding and water qua lity concerns in sensitive basins. In general,

these basin-specific criteria require additional water quality treatment and/or water quantity

protection within designated basins to achieve specific water quantity or water quality goals.

Each of the water management districts also provides design criteria which regulate the rate

of discharge of stormwater fromdeveloped properties to prevent flooding. In general, the postdevelopment rate of discharge for most projects is limited to values equal to or less than those which

occur from the project site under pre-development conditions, generally for a 25-year design storm.

However, since these criteria do not directly rela te to the water quality aspects of stormwater

management systems, they are not included in the discussion presented in this section.

2.3 Local Governments

In addition to the design criteria summarized in previous sections, local governments may

also develop stormwater design criteria, includi ng alternative design criteria, provided that the

design criteria meet the overall objectives and wa ter quality goals achieved by the design criteria

provided by each of the water management dist ricts. Local governments typically include

supplemental design criteria related to maintenance, safety, and aesthetic aspects of stormwater

management systems such as maintenance berms, fencing, and design criteria for outfall structures

to minimize transport of trash and other debris to downstream waterbodies.

Several governmental entities, such as Ma rtin County and Leon County, have developed

alternative stormwater design criteria designed to reduce post-development loadings from developed

areas to levels equal to or less than pre-developmen t loadings in areas within their jurisdiction. In

Martin County, this strategy was implemented on a county-wide basis, while in Leon County this

strategy was developed only for the Bradfordville area. In general, the design criteria developed for

these areas to achieve no net increase in lo adings under post-development conditions are

substantially greater with respect to treatment vol ume than existing design criteria currently utilized

within the State of Florida.

# FDEP \ STORMWATER TREATMENT REPORT 

# SECTION 3

PRECIPITATION

CHARACTERISTICS IN FLORIDA

The need for stormwater treatment in Florid a is fueled by the abundance of rainfall which

occurs throughout the State. The close proximity of Florida to the Atlan tic Ocean and Gulf of

Mexico, along with the State’s many inland lake s and waterways, combine to generate high

humidity and generally abundant and frequent rainfall. However, although precipitation is

generally abundant in Florida, annual precipitati on amounts can vary greatly from year to year,

and serious droughts have occurred periodically within the State. Rainfall is unevenly

distributed throughout the year in Florida, with more than half of the total annual rainfall

occurring during the period from June-September when periods of extremely heavy rainfall are

common. The highest 24-hour rainfall ever record ed in the United States, 38.7 inches, occurred

in Yankeetown, Florida on September 5-6, 1950.

3.1 Annual and Regional Precipitation

In addition to variability in seasonal rainfall characteristics, a significant regional variability

in annual precipitation has been observed throughout th e State of Florida. A ccording to the National

Climatic Data Center (NCDC), 111 meteorological stations are maintained throughout the State of

Florida. During February 2002, the NCDC released a summary of monthly and annual temperature

and precipitation measurements at each of the 111 stations over the 30-year period from 1971-2000.

A summary of this information, including a loca tion map for each of the 111 monitoring sites, is

given in Appendix A.1.

A contour isopleth map of mean annual preci pitation within the State of Florida was

generated by ERD based upon the mean annual preci pitation values for the 111 monitoring sites

summarized in Appendix A.1. Data from additiona l meteorological monitoring sites in Alabama,

Georgia, and Louisiana (generally within 100 mile s of Florida) were also obtained to provide a

smoother transition for the contour lines in the vici nity of the State boundary. The mean rainfall data

obtained from these adjacent stations was also provided by the NCDC as summaries of data

collected over the period 1971-2000. An additional 49 meteorological monitoring locations were

included in this supplemental data set, for a total of 160 meteorological monitoring sites used for

generation of rainfall contour isopleths. A comple te listing of geographical coordinates and mean

annual rainfall from 1971-2000 is given in Appendix A.2 for each of the 160 monitoring sites, and

locations of these monitoring sites are shown on Figure 3-1.

3-1

# FDEP \ STORMWATER TREATMENT REPORT 

# 3-2

#

# # # # #

# #

# # #

# #

#

# # #

#

# #

#

#

#

# # #

# # #

# # # #

# # # #

#

# #

#

# # # # #

# # #

# # #

# # #

# # #

# # #

#

#

# # #

#

# #

#

# #

# #

# # # #

# # #

# #

#

# # #

# #

#

# # #

#

# #

# # #

# # #

# # #

# #

# # #

# # #

#

# #

# #

# # #

# #

# # # # #

# # # #

# #

# #

# #

# # #

#

# #

# #

#

# # # #

# #

# #

# #

#

# #



# Figure 3-1. Locations of Meteorological Monitoring Sites.

An isopleth map of annual precipitation within the State of Florida during the 30-year period

from 1971-2000, generated using the process outlined prev iously, is given in Figure 3-2. In general,

average rainfall within the State ranges from approximately 38-66 inches/year, depending upon

location within the State. The greatest annual pr ecipitation within the State occurs in western

portions of the Florida Panhandle. In addition to the summer time convective storms which affect

most of the State, this area is also impacted by precipitation from frontal boundaries which often

dissipate before reaching more southern portions of the State. The lowest annual precipitation was

recorded in the Florida Keys. Expanded regional ve rsions of the rainfall isopleths map are given in

Appendix A.3.Figure 3-2. Isoplethsof Mean Annual Precipitation in Florida from1971-2000. 

# 3-3FDEP \ STORMWATER TREATMENT REPORT

# FDEP \ STORMWATER TREATMENT REPORT 

# 3-4

Additional regions of elevated rainfall, with annual precipitation ranging from approximately

58-62 inches/year, are apparent in the Big Bend Coastal and the Southeast Coastal regions of the

State. The Big Bend Coastal area is impacted by many of the same precipitation processes that

occur within the Panhandle region, while the Sout heast Coastal region is impacted heavily by

summer time convective thunderstorm activity. The remaining portions of the State, excluding the

Florida Keys, have annual precipitation ranging from approximately 45-55 inches/year, with lower

precipitation in central portions of the State and higher precipitation in coastal areas.

In addition to the regional variability in m ean annual precipitation illustrated on Figure 3-2, a

significant variability also exists w ith respect to the frequency and types of individual rain events

which occur throughout the state. For example, coasta l areas (particularly in southern portions of the

State) often have small convective rainfall events due to the proximity of open water. A large

number of the rain events which o ccurred in these areas are less than 0.2 inches. In contrast, areas

within the Panhandle receive a large portion of th eir annual rainfall from periodic frontal boundaries

which typically dissipate before reaching other parts of the State.

The National Climatic Data Center (NCDC) has collected long-term rainfall data at

numerous precipitation recording stations within the St ate of Florida. This database was reviewed to

identify rainfall recording stations which would be representative of rainfall conditions in various

areas of the State. Eleven separate meteorologi cal stations were selected, scattered from the

Panhandle to the Florida Keys, to examine variability in the characteristics of individual rain events

across the State. Locations of the selected me teorological sites are indicated on Figure 3-3. In

general, it was desired that the monitoring stati ons contain a maximum period of record with a

minimum amount of missing data. Years within th e period of record which contain one or more

months of missing data were generally excluded from the database, providing a data set with

continuous rainfall data for each year included within the set.

Characteristics of the selected meteorological sites in Florida are summarized in Table 3-1.

This table includes a descriptive name to identif y the general location of the monitoring site, the

mean annual rainfall measured at the monitoring site, and the period of record included in the

meteorological data. Continuous rainfall records were initiated in 1942 at seven of the 11 sites

included in Table 3-1. Records at four add itional sites were begun between 1946 and 1949. The

period of rainfall records included in data sets fo r each of the 11 sites is summarized in the final

column of Table 3-1. Each entry includes the peri od of record as well as the number of years of

complete data available for evaluation of rain event characteristics.

# FDEP \ STORMWATER TREATMENT REPORT 

# 3-5

Figure 3-3. Locations of Selected Meteorological Sites.

TABLE 3-1

CHARACTERISTICS OF SELECTED

METEOROLOGICAL SITES IN FLORIDA

GENERAL

LOCATION MONITORING

SITE MEAN ANNUAL

RAINFALL

(in/yr) PERIOD

OF RECORD

Panhandle Pensacola

Tallahassee 62.17

64.55 Pensacola: 33 years (1942-2005)

Tallahassee: 45 years (1959-2005)

Big Bend Coastal Cross City 55.14 47 years (1942-2000)

Northeast Coastal Jacksonville 52.96 64 years (1942-2005)

North Florida Branford 52.27 53 years (1945-2004)

Central Orlando 50.03 62 years (1942-2005)

East Central Coastal Melbourne 47.52 47 years (1942-2005)

West Central Coastal Tampa 46.07 47 years (1949-2005)

Southwest Coastal Ft. Myers 53.13 28 years (1960-2003)

Southeast Coastal Miami 56.92 64 years (1942-2005)

Florida Keys Key West 39.07 63 years (1942-2005)

# FDEP \ STORMWATER TREATMENT REPORT 

# 3-6

3.2 Rainfall Event Characteristics

A probability distribution of individual rain ev ents occurring during the period of record for

each of the selected meteorological sites was de veloped by evaluating common rain events occurring

at each of the sites during an average year. H ourly meteorological data was obtained from the

NCDC for each of the selected me teorological sites. The continuous hourly rainfall record for each

site was scanned to determine the total rainfall dept h for individual rain events which occurred at the

monitoring site over the period of record.

For purposes of this analysis, a rain event is defined as a period of continuous rainfall. The

US EPA typically uses a 6-hour separation for defi ning individual rain events. Using this criterion,

rain episodes separated by less than six hours of dr y conditions are considered to be one continuous

event, while rain events separated by six hours or mo re of dry conditions are assumed to be separate

events. The six-hour separation period is thought to be the minimum period of no rainfall required to

restore the hydrologic characteristics of the site to pre-rain event conditions. Although this

definition may work well in the temperate climat es present throughout much of the U.S., this

definition fails to consider the small convective ev ents which occur frequently within the State of

Florida, particularly during the summer months. For rain events in the range of 0.25 inches or more,

an inter-event separation period of approximately six hours seems adequate to restore hydrologic

characteristics for a Florida watershed. Howeve r, for events less than 0.25 inches, hydrologic

characteristics can be restored rapidly, often within several hours. Therefore, for purposes of this

evaluation, a variable inter-event dry period is utili zed. When the cumulative hourly rainfall is equal

to 0.25 inches or more, an inter-event dry period of six hours is required to initiate the start of a new

rain event. Rainfall which occurs less than six hour s from the termination of the previous rainfall is

assumed to be part of the original rainfall event. However, for rain events less than 0.25 inches, an

inter-event dry period of three hours is used to indi cate the start of a new independent runoff event.

The available data sets for each of the 11 mete orological sites were scanned and divided into

individual rain events based upon the criteria outlined previously. Individual rainfall events at each

of the 11 monitoring sites were divided into 19 rainfall event ranges which include 0.00-0.10

inches, 0.11-0.20 inches, 0.21-0.30 inches , 0.31-0.40 inches, 0.41-0.50 inches, 0.51-1.00 inch,

1.01-1.50 inches, 1.51-2.00 inches, 2.01-2.50 inches, 2.51-3.00 inches, 3.01-3.50 inches, 3.51-

4.00 inches, 4.01-4.50 inches, 4.51-5.00 inches , 5.01-6.00 inches, 6.01-7.00 inches, 7.01-8.00

inches, 8.01-9.00 inches, and greater than 9 inches. For each rainfall event range, the mean depth

of rain events within the interval was calcula ted. A probability distribution was performed on all

rainfall events within each rainfa ll event range to determine the average number of rain events,

the mean rainfall duration, the mean anteceden t dry period, the annual rainfall depth

contributed by each interval, the cumu lative annual event volume, and cumulative

percentage of annual rainfall for each rainfall event range. Frequency distributions of rain

events in each of the 11 meteorological sites are given in Appendix A.4.

# FDEP \ STORMWATER TREATMENT REPORT 

# 3-7

A comparison of the percentage of annual rain events occurring within the selected event

intervals at the regional sites is given in Table 3- 2. In general, it appears that the Key West and

Miami monitoring sites have a higher percentage of relatively small events, which generate

relatively little measurable runoff, and a lower perc entage of larger rain events, compared with

the remaining monitoring sites. For example, approximately 83.7% of the rain events occurring

at the Key West monitoring site and 80.6% of the events occurring at the Miami monitoring sites

are equal to 0.5 inch or less compared with a st ate-wide average of 75.1%. Conversely, the Ft.

Myers and Cross City monitoring sites appear to ha ve a lower percentage of small rain events,

with 72.6% of the events at the Ft. Myers site and 70.8% of the events at the Cross City site

having rainfall depths equivalent to 0.5 inches or less. The Pensacola, Tallahassee, and Ft.

Myers monitoring sites appear to have a higher percen tage of large rain events, with 5.3% of

the Pensacola and Tallahassee and 3.9% of the Ft. My ers rain events equivalent to 2 inches or

greater compared with a state-wide average of 3.6% for this interval. A graphical comparison of

the percentage of annual rainfall events less than 1 inch in depth at each of the designated

regional sites is given in Figure 3-4.BranfordCross CityFt. MyersJacksonvilleKey WestMelbourneMiamiOrlandoPensacolaTallahasseeTampaPercent of Annual Rainfall EventsLess Than 1 inch (%)



# 80 82 84 86 88 90 92 94



# Figure 3-4. Percentage of Annual Rain Events Less than 1 inch at the

Selected Regional Sites.TABLE 3-2PERCENTAGE OF ANNUAL RAIN EVENTSOCCURRING IN SELECTED EVENT INTERVALSRAINFALLSTATIONAVERAGENUMBEROFRAINEVENTSPERCENTAGE OF THE NUMBER OF RAINEVENTS FOR VARIOUS RAINFALL EVENT INTERVALS

0.00-0.10 0.11-0.20 0.21-0.30 0.31-0.40 0.41-0.50 0.51-1.00 1.01-1.50 1.51-2.00 2.01-2.50 2.51-3.00 3.01-3.50 3.51-4.00 4.01-4.50 4.51-5.00 5.01-6.00 6.01-7.00 7.01-8.00 8.01-9.00 9.01-15.00 15.01-20.00Branford 105.85 39.8 13.2 8.2 6.0 4.4 14.6 6.4 3.6 1.7 0.8 0.4 0.2 0.2 0.1 0.1 0.1 0.0 0.0 0.1 0.0Cross City 104.23 36.8 14.0 8.6 6.6 4.8 14.5 6.8 3.3 1.9 1.1 0.6 0.3 0.2 0.1 0.2 0.1 0.0 0.1 0.0 0.0Ft. Myers 108.96 39.2 14.7 9.0 5.2 4.5 13.8 6.4 3.3 1.7 0.8 0.5 0.2 0.1 0.2 0.2 0.0 0.1 0.1 0.0 0.0Jacksonville 127.23 43.8 14.5 7.7 6.2 3.8 12.5 5.3 2.7 1.4 0.9 0.3 0.3 0.2 0.2 0.1 0.1 0.0 0.1 0.1 0.0Key West 127.51 53.7 14.6 6.7 5.5 3.2 9.4 3.2 1.6 0.6 0.4 0.3 0.1 0.1 0.0 0.1 0.1 0.0 0.0 0.0 0.0Melbourne 107.38 41.8 15.8 7.8 6.0 4.0 12.9 5.9 2.7 1.2 0.7 0.4 0.2 0.2 0.1 0.1 0.0 0.1 0.0 0.0 0.0Miami 158.03 50.2 14.6 7.0 5.3 3.5 9.9 4.2 2.2 1.2 0.8 0.3 0.2 0.2 0.1 0.1 0.1 0.0 0.0 0.0 0.0Orlando 126.53 43.3 15.6 7.2 5.7 4.2 12.9 5.5 2.6 1.2 0.7 0.3 0.2 0.1 0.1 0.2 0.0 0.0 0.0 0.0 0.0Pensacola 126.09 45.6 12.9 5.9 4.9 3.4 12.2 6.4 3.4 1.9 1.1 0.6 0.3 0.4 0.2 0.3 0.1 0.2 0.0 0.1 0.0Tallahassee 123.78 40.4 12.6 7.0 6.1 4.3 13.8 7.1 3.4 1.9 1.1 0.9 0.4 0.2 0.2 0.2 0.2 0.1 0.1 0.1 0.0Tampa 111.74 43.4 14.0 7.8 6.1 4.4 12.6 5.7 2.7 1.4 0.6 0.5 0.3 0.2 0.1 0.1 0.0 0.0 0.0 0.1 0.0Minimum 104.23 36.8 12.6 5.9 4.9 3.2 9.4 3.2 1.6 0.6 0.4 0.3 0.1 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.0Maximum 158.03 53.7 15.8 9.0 6.6 4.8 14.6 7.1 3.6 1.9 1.1 0.9 0.4 0.4 0.2 0.3 0.2 0.2 0.1 0.1 0.0Mean 120.67 43.5 14.2 7.5 5.8 4.1 12.7 5.7 2.9 1.5 0.8 0.5 0.3 0.2 0.1 0.2 0.1 0.1 0.0 0.1 0.0 

# 3-8FDEP \ STORMWATER TREATMENT REPORT

# FDEP \ STORMWATER TREATMENT REPORT 

# 3-9

A comparison of the mean number of annual rainfall events at each of the designated

regional sites is given in Figure 3-5. The highest number of annual events occurs at the Miami

monitoring site, with approximately 158 events measured each year. The smallest number of

annual rain events occurs at the Cross City mon itoring site, with a mean of 104 events measured

per year.BranfordCross CityFt. MyersJacksonvilleKey WestMelbourneMiamiOrlandoPensacolaTallahasseeTampaNumber of Annual Rainfall Events



# 100 110 120 130 140 150 160



# Figure 3-5. Comparison of the Mean Number of Annual Rainfall Events at the

Selected Regional Sites.

3.3 Antecedent Dry Period

An evaluation of mean antecedent dry peri od was also conducted for the individual rain

events measured at each of the selected regional monitoring sites. This information was evaluated

on both a dry season (October-May) and wet seas on (June-September) basis. Information on

antecedent dry period is useful in evaluating recovery times for stormwater management systems

which must recover stored treatment volumes prior to the next significant rain event.

# FDEP \ STORMWATER TREATMENT REPORT 

# 3-10

A comparison of mean antecedent dry periods fo r rain events at the selected regional sites

during dry and wet season conditions is given in Table 3-3 and Figure 3-6. Mean antecedent dry

periods between rain events range from 3.03-5.63 days under dry season conditions, with an overall

average of 4.12 days. Under wet season conditions, mean antecedent dry periods range from 1.42-

2.27 days with an overall mean of 1.89 days.

TABLE 3-3

MEAN ANTECEDENT DRY PERIODS FOR RAIN

EVENTS AT THE DESIGNATED REGIONAL SITES

STATION ANTECEDENT DRY PERIOD (days)

DRY SEASON WET SEASON

Branford 4.40 2.14

Cross City 4.87 2.01

Ft. Myers 5.63 1.75

Jacksonville 3.59 1.84

Key West 3.92 1.80

Melbourne 4.14 2.27

Miami 3.03 1.42

Orlando 3.96 1.73

Pensacola 3.36 1.99

Tallahassee 3.73 1.87

Tampa 4.65 1.93

Minimum 3.03 1.42

Maximum 5.63 2.27

Mean 4.12 1.89

# FDEP \ STORMWATER TREATMENT REPORT 

# 3-11BranfordCross CityFort MyersJacksonvilleKey WestMelbourneMiamiOrlandoPensacolaTallahasseeTampaMean Antecedant Dry Period (days)



# 0 1 2 3 4 5 6

Dry Season

Wet Season



# Figure 3-6. Comparison of Dry and Wet Season Antecedent Dry Periods at the

Regional Monitoring Sites.

# FDEP \ STORMWATER TREATMENT REPORT 

# SECTION 4

STORMWATER RUNOFF –

QUALITY AND QUANTITY

The performance efficiency and effectiven ess of stormwater treatment systems are

closely linked to the quantity and quality of the ge nerated stormwater stream. Issues related to

the quantity and quality of stormwater runoff form the basis of existing stormwater treatment

design criteria. A discussion of the quality a nd quantity of stormwater runoff generated by

various land use categories is given in the following sections.

4.1 Water Quality Characteristics

4.1.1 Data Availability

A multitude of stormwater characterization studi es have been conducted within the State of

Florida as part of research projects, permit m onitoring requirements, retrofit projects, and NPDES

permitting. Land use categories included in runoff ch aracterization studies can typically be grouped

into one of 12 general land use designations wh ich are commonly used in pollutant loading

evaluations. A summary of these general land use categories is given in Table 4-1.

When performing pollutant loading studies for large watershed areas, land use information is

often obtained as FLUCCS codes (Florida Land Use Code and Classification System). This system

typically provides multiple sub-categories for each of the 12 general land use categories summarized

in Table 4-1 based upon differences in percen tage imperviousness, vegetative cover, and

development density. Unfortunately, detailed runoff characterization data are not available for most

of these sub-categories. As a result, when pe rforming pollutant loading studies, detailed land use

categories represented by FLUCCS codes must ofte n be assigned to one of the 12 general land use

categories summarized in Table 4-1 for estimation of pollutant loadings. This assignment is

typically performed based upon anticipated sim ilarities in hydrologic and pollutant loading

characteristics between the detailed FLUCCS code designations and the general land use categories.

A summary of the availability of runoff charact erization data for various pollutant categories

and land use types is given in Table 4-2. Good runo ff characterization data is generally available for

suspended solids in each of the land use categorie s summarized in Table 4-1. A similar level of

characterization data availability is present for total nitrogen and total phosphorus in virtually all

land use categories. However, information on dissolved species of nitrogen and phosphorus is

relatively limited in the existing literature.

4-1

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-2

TABLE 4-1

GENERAL LAND USE CATEGORIES

FOR RUNOFF CHARACTERIZATION DATA

GENERAL

CATEGORY DESCRIPTION

Low-Density

Residential Rural areas with lot sizes greater than 1 acre or less than one dwelling unit per acre; internal

roadways associated with the homes are also included

Single-Family

Residential Typical detached home community with lot si zes generally less than 1 acre and dwelling

densities greater than one dwelling unit per acr e; duplexes constructe d on one-third to onehalf acre lots are also included in this category; internal road ways associated with the homes

are also included

Multi-Family

Residential Residential land use consisting primarily of apartments, condominiums, and cluster-homes;

internal roadways associated w ith the homes are also included

Low-Intensity

Commercial Areas which receive only a moderate amount of traffic volume where cars are parked during

the day for extended periods of time; these ar eas include universities, schools, professional

office sites, and small shopping centers; internal roadways associated with the development

are also included

High-Intensity

Commercial Land use consisting of commercial areas with high levels of traffic volume and constant

traffic moving in and out of the area; includes downtown areas, commercial sites, regional

malls, and associated parking lots; internal ro adways associated with the development are

also included

Industrial Land uses include manufacturing, shippi ng and transportation services, sewage treatment

facilities, water supply plants, and solid waste dis posal; internal roadways associated with the

development are also included

Highway Includes major road systems, such as interstate highways and major arteries and

thoroughfares; roadway areas associated with residential, commercial, and industrial land use

categories are already included in loading rates for these categories

Agriculture Includes cattle, grazing, row crops, citrus, and related activities

Open/

Undeveloped Includes open space, barren la nd, undeveloped land which ma y be occupied by native

vegetation, rangeland, and power lines; this la nd does not include golf course areas which are

heavily fertilized and managed; golf course areas have runoff ch aracteristics most similar to

single-family residential areas

Mining/

Extractive Includes a wide variety of mining activities fo r resources such as phosphate, sand, gravel,

clay, shell, etc.

Wetlands Include a wide range of diverse wetland ty pes, such as hardwood wetlands, cypress stands,

grassed wetlands, freshwater marsh, and mixed wetland associations

Open Water/

Lakes Land use consists of open water and lakes, ri vers, reservoirs, and other open waterbodies

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-3

TABLE 4-2

RUNOFF CHARACTERIZATION DATA AVAILABILITY

PARAMETE R

GROUP SPECIES DATA

AVAILABILITY LAND USES

Suspended Solids TSS Goo d All

N utrients Total N

Total P Goo d All

N H 3



# NO

x 

# TKN

Ortho-P Limite d Limite d

Metals Zinc

Lead

Coppe r Fair to Goo d Commercial, Residential,

and Highway

Cadmiu m

Nickel

Diss. Metals Poor to Fai r Commercial, Residential,

and Highway

Oxygen Demanding

Substances BOD Fair to Goo d Commercial, Residential,

and Hi g hwa y

COD Poor to Fai r Commercial, Residential,

and Hi g hwa y

Oils, Greases, and

H y drocarbons Oil and Grease

TRPH Poo r Commercial, Residential,

and Hi g hwa y

Specific Compounds Extremely Poo r Commercial, Residential,

and Hi g hwa y

Pathogens Total Colifor m

Fecal Colifor m Poo r Commercial, Residential,

and Hi g hwa y

E. Coli Extremely Poo r Commercial, Residential,

and Hi g hwa y



# Runoff characterization data for zinc, lea d, and copper are most commonly available for

commercial, residential, and highway land uses. Ho wever, even in these categories, the availability

of the data is only considered to be fair to good. Information on other heavy metals, such as

cadmium, chromium, and nickel, as well as dissolved metal species, is poor in virtually all land use

categories. The only studies which include these latter parameters appear to be research-related

projects.

Runoff characterization data for biochemi cal oxygen demand (BOD) is fair to good in

commercial, residential, and highway land use cate gories. A limited amount of information for this

parameter is also present in agricultural studi es. However, chemical oxygen demand (COD) is

measured relatively infrequently, and the data ava ilability for this parameter is considered poor to

fair.

Oils, greases, and hydrocarbons are measured on an infrequent basis in stormwater

characterization studies. Most of the studies incl uding these parameters are research projects, many

of which are designed specifically to address th ese compounds. Oils, greases, and hydrocarbons are

generally evaluated through the generic oil and grease or TRPH (total recoverable petroleum

hydrocarbon) lab tests. Testing for specific compounds is extremely rare within the literature.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-4

Information on pathogens, such as total and fecal coliform, is poor in the available literature,

with the majority of information addressing co mmercial, residential, and highway land uses.

Information on more specific pathogens, such as E. coli, is extremely poor for virtually all land use

categories.

A literature review was conducted by Ha rper during 1992-93 to identify significant

stormwater characterization studies performed with in the State of Florida. Basic information for

many of the evaluated land uses was obtaine d from the document by Harper (1994) titled

“Stormwater Loading Rate Parameters for Central and South Florida”. This report presents the

results of an extensive literature search and analysis of runoff characteristics for selected

parameters and land use types within Central and South Florida. The runoff characteristics

provided in this document include publications and studies conducted specifically within the

State of Florida by a variety of state, fede ral, and local governments, along with private

consultants.

Each study was reviewed for adequacy of the database, with special attention to factors

such as length of study, number of runoff events monitored, monitoring methodology, as well as

completeness and accuracy of the work. In general, it is preferred that selected studies present at

least a one-year period of data collection represen ting a wide range of rainfall and antecedent dry

period conditions. Unfortunately, in a number of cas es, the only available data base for a given land

use category or loading parameter represented a relatively small and limited data collection process.

These studies were carefully examined on a case-by-case basis and a decision was made as to

whether or not to include the data in loading rate estimates. No studies with less than five storm

sample events were used. An important requirement for inclusion of stormwater monitoring data is

that the study measures only a homogeneous watershe d area. This requirement is necessary since

input into most loading rate models is based upon homogeneous land use types. Unfortunately, this

requirement limited the usefulness of several thorough stormwater studi es by the USGS which

evaluated mixed land use areas.

Approximately 120 reports and publications of stormwater research conducted within the

State of Florida were initially reviewed as a part of the literature search process. During the initial

review process, studies which contain an insuffi cient number of sample events or address mixed

land use areas were removed from further consid eration, leaving approximately 40 reports with

potential pollutant loading information.

The Harper (1994) report includes all signi ficant stormwater characterization studies

performed in Florida prior to the early 1990s. However, a limited number of additional runoff

characterization studies have been performed since the publication date for this report.

Therefore, a supplemental literature search was performed by ERD to identify additional

resources for characterization data. Additional land use characterization studies were obtained

for single-family residential areas, low-inte nsity commercial, highway/transportation land use,

agriculture-citrus, agriculture-row crop, and ope n space/undeveloped/rangeland/forest areas.

The supplemental characterization data were comb ined with the data provided by Harper (1994)

to generate a database reflecting all significant ch aracterization studies performed in Florida. A

brief summary of information contained within selected characterization studies from the

combined database is given in Table 4-3. A lis ting of hydrologic and general characteristics for

studies included in the combined database is given in Appendix B.FDEP \ STORMWATER TREATMENT REPORTTABLE 4-3SUMMARY OF SELECTED STORMWATER CHARACTERIZATIONSTUDIES PERFORMED IN THE STATE OF FLORIDAREFERENCELOCATIONOF STUDYAREALAND USETYPEPARAMETERSMEASUREDCOMMENTSFederico(1977)Taylor CreekDrainage Basin,FL1. Pasture2. Dairy3. CitrusGeneral Parameters,NutrientsAn average of 43 daily composite samples collected in drainage ditchesfrom July to September 1975. Data presented as concentration onlywith no hydrologic data for direct conversionto loadingrates.East CentralFloridaRegionalPlanningCouncil(ECFRPC)(1978)Central FloridaArea1. Residential2. Commercial3. Pasture4. Well-drained5. Flatwoods6. Range7. Lake8. SwampNutrients, BOD,SolidsPresents summaries of studies conducted in Central Florida with resultsexpressed in concentration and loading rate forms.Gaggiani,et al.(1978)Maitland, FL Primarily residentialNutrients, Major Ions,Heavy MetalsBulk precipitation and runoff samples were collected from 3 adjacentwatersheds from April 1971 to June 1974. A total of 46 storm eventswere monitored. Data includesevent mean concentration and massloadingfor storm events.Miller(1979)Southeast FloridaCoastal Area1. 17.9 acres low-densityresidential2. 58.3 acres highway basin3. 20.4 acres commercial4. 14.7 acres high-densityresidentialNone Report gives detailed hydrologic information on the four drainagebasins. Results of runoff sampling programs are given in otherpublications by the author.Weinberg,et al. (1980)Broward County,FL26 acres of high-densityresidentialGeneral Parameters,NutrientsGrab samples and timed samples collected from 2 rain events during1975. Insufficient data base.Mattraw, et al.(1981)Broward County3 separate areas:1. 40.8-acre single-familyresidential (43.9% imp.)2. 58.3-acre 6-lane highway(36.2% imp.)3. 28.4-acre commercial(regionalshoppingmall, 98% imp.)General Parameters,Nutrients, Metals,BacteriaMore than 30 flow-weighted samples collected from 1974-1977. Datapresented as concentration and loadings. Detailed hydrology providedfor each basin. 

# 4-5FDEP \ STORMWATER TREATMENT REPORTTABLE 4-3 -- CONTINUEDSUMMARY OF SELECTED STORMWATER CHARACTERIZATIONSTUDIES PERFORMED IN THE STATE OF FLORIDAREFERENCELOCATIONOF STUDYAREALAND USETYPEPARAMETERSMEASUREDCOMMENTSHarper, et al.(1982)Orlando, FL 160 acres of high-densitycommercial and residentialGeneral Parameters,Solids, BOD, Metals,NutrientsRunoff collected from mixed residential and commercial watershedsduring 1978 using manual and automatic techniques. Data presentedin both concentration and loading rate forms but represents mixedland use.Waller(1982)Dade County, FL 1. Commercial2. State Park3. Residential4. Row Crops5. AgriculturalGeneral Parameters,Nutrients, HeavyMetalsRunoff samples collected from June to October 1978 only for stormsof intensity equal to or exceeding 1.0 inch/hour. Data cannot be usedfor loading rate estimation since typical less intense storm eventswere not monitored.Wanielista,et al.(1982)Orlando, FL 1. Residential2. CommercialGeneral Parameters,Nutrients, MetalsFour runoff events were collected from separate residential andcommercial watersheds from July to November 1978 using manualflow-weighted collection techniques. Data presented in bothconcentration and loading rate forms. However, the data base issmall and covers only a portion of the year. Residential area receivesheavytraffic volume from adjacent downtown area.Yousef, et al.(1982)Orlando, FL Interstate Highway (I-4) General Parameters,Nutrients, MetalsRunoff from highway bridges was collected from 11 storm eventsduring August 1975. Data presented in concentration form only.Sampling program and hydrologic information sufficient to generateannual loadings, but data is specific to bridge or highway runoffonly.German(1983)Maitland, FL 2 Sub-basins:Residential and HighwayGeneral Parameters,Nutrients, Metals39 runoff events sampled in residential areas and 17 samples inhighwayareas from 1975-1979.McKenzie,et al.(1983)Miami, FL 1.43 acre Interstate Highway(I-95)General Parameters,Nutrients, MetalsRunoff collected during 5 storm events from November 1979 to May1981 using automated instrumentation. Data presented as bothconcentration and loading rates, but is specific only to highwaysystems.Cullum (1984)Greg(1984)Boca Raton, FL 122 acres single-familyresidentialGeneral Parameters,NutrientsDetailed hydrologic concentration and mass loading data. However,onlyrain events in excess of 1 inch were sampled.ECFRPC(1984)Central Florida 11 land use typesNutrients, BOD,SolidsPresents concentration and loading rate information for expandedland use categories not presented in earlier 1978 publication. Datagenerated from Central Florida studies funded by ECFRPC.Hydrologic information is also provided. 

# 4-6FDEP \ STORMWATER TREATMENT REPORTTABLE 4-3 -- CONTINUEDSUMMARY OF SELECTED STORMWATER CHARACTERIZATIONSTUDIES PERFORMED IN THE STATE OF FLORIDAREFERENCELOCATIONOF STUDYAREALAND USETYPEPARAMETERSMEASUREDCOMMENTSLopez, et al.(1984)Tampa Bay, FL A mixed-use urban watershedGeneral Parameters,Nutrients, HeavyMetalsDetailed study from 1975-1980 including streamflow, climate,physiographic and water quality data. Extremely detailed discussionof watershed characteristics. Data presented in both concentrationand loading rate formats. Although land use is mixed, 3 of the 9 sitesare approximately 70% residential which may be useful for singleland use estimates.Waller, et al.(1984)Coral Gables, FL 1. Commercial, Residential,Highway2. ResidentialNutrients, Metals Sampled 3 runoff events during March and April 1982 using pondedwater collected in a low area. Insufficient data for estimation ofloadingrates. Datagiven as concentrations only.Miller(1985)Broward/DadeCounties, FL1. Residential2. Highway3. Commercial4. ApartmentNutrients, SuspendedSolids, LeadGives percent entrainment curves for various rain events. No actualconcentration data or loading rate information supplied.Yousef, et al.(1985)Orlando, FL Interstate Highway (I-4) General Parameters,Nutrients, MetalsRunoff collected from roadside swales during 17 storm events from1982-1983 using automatic collection equipment. Data presented asboth concentration and loading rates. Limited to highway land useonly. Presents data on pollutant removal efficiencies of swales.Harper, et al.(1985)Sanford, FL 54 acres low-densityresidential areaGeneral Parameters,Nutrients, MetalsFlow-weighted composite runoff samples collected for 22 stormevents during 1984. Grass swales with raised inlets used forconveyance and treatment. Data presented as both concentration andloading rates. Detailed hydrologic and watershed information.Presence of swale drainage/treatment system limits usefulness forcharacterization data.Harper (1985) Orlando, FL Highway runoff (ADT = 16,000)4.0-acre watershedHeavy Metals Flow-weighted runoff samples collected at inlet to wet detentionpond during 16 storm events from April 1983-May 1984 with a widerange of total rainfall and antecedent rainfall conditions. No pretreatment. Data presented as concentration only. Detailed hydrologicand rain event characteristics provided.Data used to evaluate fate ofheavymetals.Martin, et al.(1985)Orange County,FLMixed use basin:33% forest, 27% urban roadway,27% high-density residential, and13% low-densityresidentialGeneral Parameters,Nutrients, MetalsStudy provides evaluation of performance efficiency of a detentionpond-wetlands system. No actual characterization data provided. 

# 4-7FDEP \ STORMWATER TREATMENT REPORTTABLE 4-3 -- CONTINUEDSUMMARY OF SELECTED STORMWATER CHARACTERIZATIONSTUDIES PERFORMED IN THE STATE OF FLORIDAREFERENCELOCATIONOF STUDYAREALAND USETYPEPARAMETERSMEASUREDCOMMENTSHowie, et al.(1986)Broward County,FLHighwayNutrients, Metals A total of 12 storm events were sampled from May to November1983. Samples were collected from swale flow and do not reflectdirect runoff. Surficialaquifer also sampled.Yousef, et al.(1986)Orlando, FL Interstate Highway (I-4) General Parameters,Nutrients, MetalsFlow-weighted composite runoff samples collected over 13-monthperiod in 1982-1983 using automatic equipment. Event meanconcentrations given for measured parameters. Hydrologic dataprovided could be used to generate loading rates. Study limited tohighwayuse only.Fall(1987)Upper St. JohnsRiver Basin222,486 acres ofprimarily agriculture(70% pasture, 5% row crops)General Parameters,Nutrients, MetalsCollection of 58 pumped discharge samples from 9 pumps from1982-1987. Pumped discharges werenot necessarily related to stormevents. Data summarized by concentration only. No hydrologic datagiven for direct conversion to loadingrates.Fall, et al.(1987)Indian RiverCounty, FL27,720 acres agricultural basin(22,000 acres of citrus, remainderin pasture and drainage works)General Parameters,Nutrients, PesticidesSamples of pumped agricultural discharge collected monthly fromNovember 1984 to November 1985. Results given in terms ofconcentration only. No hydrologic data provided.Hendrickson(1987)Brevard County,FL5681 acres agricultural area, rowcrops and rangelandGeneral Parameters,Nutrients, PesticidesA total of 87 samples of pumped agricultural discharge werecollected during August to December 1986. Data given asconcentration only. Loading rates may be determined usinghydrologic datagiven. This represents a ditched agricultural area.Harper(1988)Central FloridaArea1. Interstate Highway2. Residential3. CommercialGeneral Parameters,Nutrients, BOD,Solids, MetalsRunoff collected from 5 watersheds during 8-12 storm events perwatershed in 1987. Data presented in concentration form withhydrologic information on each watershed. Also gives removalefficiencies for stormwater management systems associated witheach watershed alongwithgroundwater effects.Whalen, et al.(1988)VariousLocationsAround U.S.All General Types General Parameters,Nutrients, BOD,Heavy Metals,OrganicsExcellent summary report of runoff studies conducted primarily inFlorida. Also presents dataon effectiveness of stormwatermanagement systems for pollutant removal.Greg, et al.(1989)Boca Raton, FL Medium-density, residential (32.4acres with 37% impervious)Nutrients, SuspendedSolidsSix runoff events were collected from 1985 to January 1986 usingautomatic equipment. Study includes detailed hydrologicinformation. Data given as concentration only, but could beconverted to loadingrate with information provided. 

# 4-8FDEP \ STORMWATER TREATMENT REPORTTABLE 4-3 -- CONTINUEDSUMMARY OF SELECTED STORMWATER CHARACTERIZATIONSTUDIES PERFORMED IN THE STATE OF FLORIDAREFERENCELOCATIONOF STUDYAREALAND USETYPEPARAMETERSMEASUREDCOMMENTSHarper and Herr(1993)DeBary, FL Low-intensity commercial,50.7-acre watershedGeneral Parameters,Nutrients, MetalsHarper and Herr(1994)Orange County,FLSingle-family homeson one-acre lotsGeneral Parameters,Nutrients, BOD,Suspended Solids,MetalsFour runoff events were collected from October 1993 to February1994. Study includes hydrologic information. Data given as bothconcentration and areal loading rates.Bahk (1997) Ruskin, FL Agriculture–row crops210-acre watershedGeneral Parameters,Nutrients, MetalsTotal of 18 grab samples collected from drainage ditch from Feb.1992-Sept. 1995. Data as concentration only. Even though collectedas grab samples, large sample size gives data usefulness. Nohydrologic data provided.Rushton, et al.(1997)Tampa, FL Mixed land use; 30% rooftops andasphalt parking; 6% limestonestorage; and 64%grassed storageGeneral Parameters,Nutrients, MetalsFlow-weighted samples of pond inflow collected during 1993-1994.ERD (2000) Bradfordville–Tallahassee, FLLow-intensity commercial;asphalt parking areas; inlets andstormsewers; 8-acre drainagebasinGeneral Parameters,Nutrients, DemandParametersFlow-weighted composite samples collected during 12 storm eventsfrom Feb.-May 1999. Detailed hydrologic evaluation.ERD (2000) Bradfordville–Tallahassee, FLEvaluated 3 separate areas:1. 1.0-acre highway site on 6-lanedivided highway2. 16.8-acre single-familyresidential3. 7.5-acre rural residentialGeneral Parameters,Nutrients, DemandParametersFlow-weighted composite samplescollected during 11 events athighway site, 5 events at rural residential site, and 7 events at singlefamily residential site. Good hydrologic data provided.City ofTallahassee andERD (2002)Tallahassee, FL 1. High-intensity commercial2. Light industrial3. Recreation/open space4. Multi-family residential5. Low-density residential6. Single-familyresidentialNutrients, DemandParameters, MetalsFlow-weighted composite samples collected at six land usecharacterization sites during 73 events from May 1999-March 2002.Data used to develop and calibrate area-wide pollutant loading model.Rushton (2002) Cockroach Bay -Tampa, FL210-acre row crop area General Parameters,Nutrients, MetalsTotal of 85 runoff samples collected from 1998-2001 using automaticrefrigerated samplers. Also contains extensive rainfall quality data. 

# 4-9FDEP \ STORMWATER TREATMENT REPORTTABLE 4-3 -- CONTINUEDSUMMARY OF SELECTED STORMWATER CHARACTERIZATIONSTUDIES PERFORMED IN THE STATE OF FLORIDAREFERENCELOCATIONOF STUDYAREALAND USETYPEPARAMETERSMEASUREDCOMMENTSERD (2004) Orlando, FL Single-family residential; 2separate sub-basins: 52.9-acreand 19.4 acreGeneral Parameters,Nutrients, DemandParametersFlow-weighted composite samples collected during 25 storm events atone site and 8 events at the other site from June-Sept. 2003.Rushton (2004) Temple Terrace,FL132.4-acre mixed use basinincluding high-intensitycommercial, multi-familyresidential, and golf courseGeneral Parameters,Nutrients, Metals,BacteriaData collected as part of performance evaluation for a CDS unit.Excellent hydrologic data. Extensive water quality data for bothinflow and outflow.Teague, et al.(2005)FloridaAquarium –Tampa, FL11.25-acre parking lot;combination of asphalt, cement,and pervious pavementNutrients, Metals Flow-weighted samples collected during 56 storm events usingrefrigerated auto-sampler from 2000-2003.ERD (2005)UnpublishedDataOrlando, FL 6.5-acre watershed centered alongU.S. 441, 6-8 lane asphalthighwayGeneral Parameters,Nutrients, MetalsFlow-weighted samples collected during 23 storm events usingrefrigerated auto-sampler from April-August 2004.ERD (2007) Winter Haven 43.9-acre basin with lightindustrial and warehouse land useGeneral Parameters,NutrientsFlow-weighted samples collected during 10 storm events using autosampler from October 2005-March 2006.ERD (2007) Windermere 95.4-acre basin, single-family, dirtroads with grassed swalesGeneral Parameters,NutrientsFlow-weighted samples collected during 14 storm events using autosampler from October 2005-March 2006. 

# 4-10

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-11

A large number of stormwater monitoring studi es have been conducted within the State of

Florida as part of the NPDES Program. Stormwater samples collected as part of this program are

restricted to a well defined range of rainfall de pths and antecedent dry period conditions. Although

this information may be useful in comparing runoff characteristics between major metropolitan

areas, the sampling protocols required by this progr am do not necessarily provide accurate estimates

of the average annual runoff concentrations for a given pollutant discharging from various land use

categories. These values can only be estimated by monitoring a wide range of rainfall depths and

antecedent dry period conditions. As a result, data collected as part of th e NPDES Program are not

utilized to estimate runoff characteristics for the purposes of this evaluation.

Studies included in development of stormwater characterization data cover the period from

1977-2005. Runoff concentrations of many parameters appear to be relatively consistent for a

particular land use over this period with the excepti on of lead. Concentrations of lead in studies

conducted prior to 1980-1990 are generally much greater than post 1980-1990 studies, presumably

due to reductions of lead content in gasoline over this same period. Recent research conducted by

ERD indicates that concentrations of total l ead in stormwater runoff measured since 1990 are

substantially lower than values measured prio r to 1990. Therefore, it is assumed that lead

concentrations presented in pre-1990 studies are not representative of current conditions and are not

included in estimation of mean runoff characteristics of lead.

In general, the objective of the literature re view is to provide estimates of event mean

concentrations (emc) for each study included in th e stormwater characterization database. When

applied on an annual basis, the event mean concentration is defined as follows:

In essence, this value reflects a flow-weighted average concentration for a given parameter over

an annual cycle. When the emc is multiplied by the estimated total annual runoff volume, it

provides an estimate of the annual mass loadi ng discharging from the evaluated land use

category for a given pollutant.

4.1.2 Single-Family Residential

Single-family residential land use is define d as a typical detached home with lot sizes

generally less than 1 acre and dwelling densities gr eater than 1 dwelling unit per acre. Duplexes

constructed on one-third to one-half acre lots are al so included in this category. This type of

land use is characterized by a moderate degree of impervious area, generally ranging from

approximately 20-40%. Hydrologic characteristics for the identified single-family residential

stormwater characterization studies are given in Table B.1 (Appendix B). Watershed areas for

the identified characterization studies range fr om 7.39-897 acres, with impervious percentages

ranging from 6.1-65.0%. volume runoff annual total parameter given a for load pollutant annual total

= emc

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-12

A summary of mean stormwater characteristic s from single-family residential stormwater

studies is given in Table 4-4. Each of the studi es included in Table 4-4 provide characterization

data for total nitrogen and total phosphorus. However, nutrient concentrations measured at the

Orlando Duplex site by Harper (1988) appear to be substantially elevated, particularly when

compared with total phosphorus values measured at the remaining sites. The measured emc of

1.69 mg/l for total phosphorus at this site is a clear outlier in the data set and is not included in

estimation of the mean emc values for total phosphorus. The total nitrogen emc of 4.62 mg/l at

this site also appears to be elevated but is not a clear outlier value. Therefore, this value is

retained for estimation of the mean emc for tota l nitrogen. Total nitrogen emc values range from

1.02-4.62 mg/l, with an overall mean of 2.07 mg/l. Total phosphorus emc values range from

0.102-0.510 mg/l, with an overall mean of 0.327 mg/l. All but one of the listed studies provides

characterization data for BOD, with 13 of the 17 studies including information for TSS.

TABLE 4-4

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM SINGLE-FAMILY RESIDENTIAL STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Pompano Beach Mattraw, et al.

(1981) 2.00 0.310 7.9 26.0 -- -- 0.008 0.298 -- 0.167 1 

# 0.086

Tampa - Charter Street U.S. EPA

(1983) 2.31 0.400 13.0 33.0 -- -- -- -- -- 0.49 1 

# 0.053

Maitland (3 basins) German (1983) 2. 20 0.340 7.1 43.0 -- -- 0.014 0.350 0.008 0.230 1 

# 0.016

St. Pete - Bear Creek Lopez, et al.

(1984) 1.50 0.200 4.7 -- -- -- 0.009 -- -- 0.128 1 

# 0.083

Tampa - Kirby Street Lopez, et al.

(1984) 2.20 0.250 4.5 -- -- -- -- -- -- 0.050 1



# --

Tampa - St. Louis

Street Ditch Lopez, et al.

(1984) 3.00 0.450 6.1 -- -- -- 0.016 -- -- 0.213 1 

# 0.133

Orlando Duplex Harper (1988) 4.62 1.69 1 

# 9.5 63.2 0.005 0.015 0.033 0.464 0.020 0.058 1 

# 0.089

Orlando - Essex Pointe Harper (1988) 1.85 0.20 6.5 30.1 0.002 0.017 0.027 0.420 0.029 0.132 1 

# 0.045

Springhill Subdivision,

Palm Beach Greg, et al.

(1989) 1.18 0.307 -- 3.5 -- -- -- -- -- -- --

Tampa - 102 nd 

# Avenue Holtkamp

(1998) 2.62 0.510 13.4 36.8 -- -- 0.019 -- -- 0.005 0.060

Bradfordville, FL ERD (2000) 1. 30 0.280 2.7 57.1 -- -- -- -- -- -- --

Key Colony, Florida

Keys ERD (2002) 1.20 0.281 2.0 26.9 0.0015 0.0025 0.010 0.067 -- 0.001 0.020

Tallahassee -

Woodgate Subdivision COT and ERD

(2002) 1.29 0.505 15.0 76.0 -- -- 0.007 -- -- 0.007 0.039

Sarasota County ERD (2004) 1.17 0.506 4.4 10.1 -- -- -- -- -- -- --

Orlando - Krueger St. ERD (2004) 3.99 0.182 17.1 41.8 -- -- -- -- -- -- --

Orlando - Paseo Street ERD (2004) 1.02 0.102 4.0 12.0 -- -- -- -- -- -- --

Windermere ERD (2007) 1.69 0.402 -- 65.0 -- -- -- -- -- -- --

Overall Mean Value 2.07 0.327 7.9 37.5 0.003 0.012 0.016 0.320 0.019 0.004 0.062



# 1. Data not included in calculation of mean value

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-13

Heavy metal characterization data from the residential land use studies is relatively

limited, with the greatest amount of data availabl e for copper, lead, and zinc. However, as

discussed in Section 4.1.1, lead concentrations measured prior to 1990 are excluded from

estimation of overall mean concentrations, substantially reducing the available data set for this

parameter.

As seen in Table B.1, five of the 17 stor mwater characterization sites utilize grassed

swales exclusively for conveyance of stormwat er runoff, while seven of the stormwater

characterization sites use curb and gutter systems exclusively. The remaining sites use a

combination of swale and curb and gutter system s. A comparison of runoff characteristics for

residential sites utilizing grassed swales and curb/ gutter drainage systems is given in Table 4-5.

With the exception of total phosphorus, runoff char acteristics collected from residential areas

utilizing grassed swales appear to be subs tantially lower in value than observed for

characterization sites utilizing curb and gutter syst ems. Overall, runoff collected from grassed

swale drainage systems was approximately 38% lo wer for concentrations of total nitrogen, 48%

lower for BOD, 46% lower for TSS, 47% lower fo r copper, and 23% lower for zinc than mean

values measured at monitoring sites which utilized curb and gutter systems.

An analysis of variance comparison was conducted between the two data sets to

determine if the observed differences in runo ff concentrations between grassed swales and

curb/gutter sites are statistically significant. This analysis was conducted only for total nitrogen,

total phosphorus, BOD, TSS, copper, and zinc due to the limited data sets available for the other

parameters. None of the differences in concen trations were found to be significant at a 95%

probability level. However, the observed differen ces in total nitrogen concentrations were found

to be statistically different at a 91% probability level, with a 77% probability level for significant

differences in BOD concentrations, a 86% proba bility level for significant differences in TSS

concentrations, and a 75% probability level for si gnificant differences in copper concentrations.

However, the overall number of data points available for this analysis is limited which makes

detection of significant differences between the data sets more difficult.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-14

TABLE 4-5

COMPARISON OF RUNOFF CHARACTERISTICS FOR

RESIDENTIAL AREAS UTILIZING GRASSED SWALES AND

CURB / GUTTER DRAINAGE SYSTEMS

a. Grassed Swales

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Pompano Beach Mattraw, et al.

(1981) 2.00 0.310 7.9 26.0 -- -- 0.008 0.298 -- 0.167 1 

# 0.086

Palm Beach -Springhill

Subdivision Greg, et al.

(1989) 1.18 0.307 -- 3.5 -- -- -- -- -- -- --

Florida KeysKey Colony ERD (2002) 1.20 0.281 2.0 26.9 0.002 0.003 0.010 0.067 -- 0.001 0.020

Sarasota County ERD (2004) 1.17 0.506 4.4 10.1 -- -- -- -- -- -- --

Windermere ERD (2007) 1.69 0.402 -- 65.0 -- -- -- -- -- -- --

Overall Mean Value 1.45 0.361 4.8 26.3 0.002 0.003 0.009 0.183 -- 0.001 0.053



# b. Curb and Gutter

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Tampa - Kirby Street Lopez, et al.

(1984) 2.20 0.250 4.5 -- -- -- -- -- -- 0.050 1



# --

Tampa - St. Louis

Street Ditch Lopez, et al.

(1984) 3.00 0.450 6.1 -- -- -- 0.016 -- -- 0.213 1 

# 0.133

Orlando - Essex Pointe Harper (1988) 1.85 0.200 6.5 30.1 0.002 0.017 0.027 0.420 0.029 0.132 1 

# 0.045

Tampa - 102 nd 

# Avenue Holtkamp

(1998) 2.62 0.510 13.4 36.8 -- -- 0.019 -- -- 0.005 0.060

Bradfordville, FL ERD (2000) 1. 30 0.280 2.7 57.1 -- -- -- -- -- -- --

Tallahassee -

Woodgate Subdivision COT and ERD

(2002) 1.29 0.505 15.0 76.0 -- -- 0.007 -- -- 0.007 0.039

Orlando - Krueger St. ERD (2004) 3.99 0.182 17.1 41.8 -- -- -- -- -- -- --

Overall Mean Value 2.32 0.340 9.3 48.4 0.002 0.017 0.017 0.420 0.029 0.006 0.069



# 1. Value not included in calculation of mean value



# 4.1.3 Multi-Family Residential

Multi-family residential land use consists primarily of apartments, condominiums, and

cluster homes. In general, this land use contai ns a large degree of impervious surface, with

impervious percentages often in excess of 50%. A summary of hydrologic parameters from the six

identified multi-family residential stormwater ch aracterization studies is given in Table B.2.

Watershed areas for the selected studies range from 8.7-73.3 acres, with impervious percentages

ranging from 61-74%. Each of these monitoring sites utilizes underground stormsewer systems.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-15

A summary of mean stormwater emc values from multi-family residential stormwater

studies is given in Table 4-6. E ach of the six listed studies provides characterization data for total

nitrogen and total phosphorus, with five of the studies also providing information on BOD and

TSS. Information on heavy metals is extremel y limited for this land use category, with mean

values provided only for copper, lead, and zinc. Studies performed prio r to 1990 are not included

in estimation of mean values for lead concentrations.

In general, mean concentrations for tota l nitrogen, total phosphorus, BOD, and TSS from

the multi-family studies are higher in concentra tion than mean values obtained from the singlefamily residential studies. The increases in runoff characteristics observed in multi-family

residential areas are expected due to the larger degree of impervious area and the higher level of

activity.

TABLE 4-6

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM MULTI-FAMILY RESIDENTIAL STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Orlando - Shoals

Apartments ECFRPC

(1978) 1.91 0.51 7.8 143 -- -- -- -- -- 0.341 1



# --

Miami - Kings Creek

Apartments Miller (1979) 2. 57 0.45 14.5 36.8 -- -- -- -- -- 0.054 1 

# 0.059

Loch Lomond Weinburg, et al.

(1980) 1.91 0.73 -- -- -- -- -- -- -- -- --

Orlando - Downtown Wanielista, et al.

(1982) 4.68 0.72 10.1 95.6 -- -- -- -- -- -- --

Tampa - Young

Apartments U.S. EPA

(1983) 1.61 0.33 16.0 53.0 -- -- -- -- -- 0.076 1 

# 0.060

Tallahassee - Royal

Pavilion Apartments COT and ERD

(2002) 1.22 0.380 8.0 61.0 -- -- 0.009 -- -- 0.006 0.138

Overall Mean Value 2.32 0.52 11.3 77.8 -- -- 0.009 -- -- 0.006 0.086

1. Data not included in calculation of mean value



# 4.1.4 Low-Density Residential (Rural)

Low-density residential land use is defined as a rural type community with lot sizes

generally greater than one acre and less than one dwelling unit per acre. These areas are typically

characterized by low traffic volum es and runoff coefficients along with relatively low pollutant

loading rates. The majority of these land areas are pervious surfaces covered by grass or wooded

areas with only a small percentage of impervious area.

Low-density rural residential land use is the only general land use category for which

specific loading rate studies were not found during th e literature search. However, this type of land

use is basically a mixture of the categories of single-family residential and open space since

vegetated areas in the low-density category are of ten left in a natural condition typical of open

spaces. Therefore, for purposes of this evaluati on, runoff characteristics for low-density residential

areas are estimated as the arithmetic mean of the m ean values for single family residential (Table 4-4

and open space (Table 4-12).

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-16

4.1.5 Low-Intensity Commercial Areas

For the purposes of this evaluation, the term intensity refers to the level of use of the

commercial area rather than an indication of the type of business or density of development. Lowintensity commercial areas are defined as areas which receive only a moderate amount of traffic

volume and where cars may be parked during the day for extended periods of time. Since most

commercial activities themselves generate relatively little pollutant loading, the majority of pollutant

deposition occurs as a result of automobiles and trucks operating within the commercial area. Lowintensity commercial areas include schools, church es, professional office sites, and small shopping

centers. High-intensity commercial areas include downtown business districts and large regional

shopping areas.

A summary of hydrologic characteristics fr om low-intensity commercial stormwater

characterization studies is given in Table B.3. Nine separate studies were identified in the available

literature, with watershed areas ranging from 2.17- 50.70 acres. Percentage imperviousness for the

commercial sites range from 60% to approximately 100%. Eight of the nine studies utilize curb and

gutter stormsewer systems, with swales utilized for drainage conveyance at the Florida Aquarium

site.

A summary of mean stormwater emc values from low-intensity commercial stormwater

studies is given in Table 4-7. Characterization data for total nitrogen, total phosphorus, and TSS are

provided for each of the nine studi es, with eight of the nine studies providing characterization data

for BOD. As observed in previous land use categories, characterization data for heavy metals is

somewhat limited. In general, low-intensity co mmercial areas are characterized by relatively low

levels of total nitrogen, total phosphorus, and B OD, although TSS concentrations are somewhat

elevated. Runoff characteristics reported by Harper and Herr (1993) are not included in calculation

of the mean value since the runoff in this study r eceived pre-treatment in a vegetated swale prior to

collection.

TABLE 4-7

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM LOW-INTENSITY COMMERCIAL STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Orlando Areawide

Stud y 1 

# ECFRPC (1978) 0.89 0.16 3.6 146 -- -- -- -- -- 0.068 2



# --

Ft. Lauderdale - Coral

Ridge Mall Miller (1979) 1.10 0.10 5. 4 45.0 -- -- 0.015 -- -- 0.387 2 

# 0.128

Tampa - Norma Park U.S. EPA

(1983) 1.19 0.15 12.0 22.0 -- -- -- -- -- 0.046 2 

# 0.037

Orlando - International

Market Place Harper (1988) 1.53 0.19 11.6 111 0.008 0.013 0.031 1.10 0.028 0.136 2 

# 0.168

DeBary 3 

# Harper and Herr

(1993) 0.761 0.260 6.9 79.1 0.0005 0.003 0.010 0.582 -- 0.009 0.028

Bradfordville ERD (2000) 2.14 0.160 9.0 38.3 -- -- -- -- -- -- --

Tallahassee - Cross

Creek Shopping Cente r COT and ERD

(2002) 0.925 0.15 8.0 15.0 -- -- 0.008 -- -- 0.002 0.045

Sarasota Count y ERD (2004) 0.88 0.31 4.3 39.9 -- -- -- -- -- -- --

Florida Aquarium -

Tampa Teague, et al.

(2005) 0.761 0.215 -- 42.4 0.003 -- 0.019 1.17 -- 0.008 0.090

Overall Mean Value 1.18 0.179 7.7 57.5 0.006 0.013 0.018 1.14 0.028 0.005 0.094

1. Average of studies performed on a parking lot, motel complex, and commercial strip development

2. Data not included in calculation of mean value

3. Values excluded from means due to swale pre-treatment

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-17

4.1.6 High-Intensity Commercial Areas

High-intensity commercial land use consists of commercial areas with high traffic volume

and relatively constant traffic moving into and out of the area. For purposes of this evaluation, highintensity commercial areas include downtown busine ss districts and large regional shopping areas.

This land use category is typically characterized by a high degree of imperviousness, with values

often in excess of 90%.

A summary of hydrologic characteristics from high-intensity commercial stormwater studies

in Florida is given in Table B.4. Watershed sizes for the characterization studies range from 28-83

acres, with impervious percentages ranging from 96.4-98%. Four separate studies were obtained

from the literature search which includes a re gional shopping mall, a downtown commercial area,

and commercial areas with heavy traffic volume.

A summary of mean stormwater emc values from high-intensity commercial stormwater

studies is given in Table 4-8. Each of the four studies provides characterization data for total

nitrogen and total phosphorus, while only half of th e studies provide characterization data for BOD

and TSS. Each of the studies also provides char acterization information for lead and zinc, although

all of the studies which provide data for lead were performed prior to 1990 and not useful for

estimating current lead characteristics in runoff. As seen in Table 4-8, runoff characteristics from

high-intensity commercial areas are substantially hi gher for virtually all evaluated parameters than

observed in the low-density commercial studies.

TABLE 4-8

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM HIGH-INTENSITY COMMERCIAL STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Broward County Mattraw, et al.

(1981) 1.10 0.10 5.4 45.0 0.009 -- 0.015 0.334 -- 0.387 1 

# 0.128

Orlando - Downtown Area Wanielista

(1982) 2.81 0.31 17.2 94.3 -- -- -- -- -- 0.560 1 

# 0.165

Dade County Waller (1984) 3.53 0.82 -- -- -- -- -- -- -- 0.187 1 

# 0.183

Broward County Howie, et al.

(1986) 2.15 0.15 -- -- -- -- -- -- -- 0.241 1 

# 0.162

Overall Mean Value 2.40 0.345 11.3 69.7 0.009 -- 0.015 0.334 -- -- 0.160

1. Data not included in the calculation of mean value



# 4.1.7 Light Industrial

Information concerning stormwater characteriza tion data from light industrial areas is very

limited in the existing literature. Only three studi es could be identified which specified industrial

park land use. Two of these studies were performed during the 1980s, with the final study

performed during 2002.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-18

A summary of hydrologic characteristics from th e industrial stormwater studies is given in

Table B.5. Watershed area and percent impervious area are not available for two of the three

studies, with only impervious percentage provided for the final study.

A summary of emc values from industrial land us e areas is given in Table 4-9. In general,

industrial areas are characterized by relatively low concentrations of total nitrogen and BOD, with

more elevated concentrations of total phosphorus and TSS.

TABLE 4-9

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM LIGHT INDUSTRIAL STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Orlando Areawide

Study ECFRPC

(1985) 1.42 0.31 9.1 102 -- -- -- -- -- -- --

Manatee County

Southeast Area Study CDM

(1985) 1.18 0.15 -- -- -- -- -- -- -- -- --

Tallahassee COT and ERD

(2002) 1.09 0.090 6.0 18.0 -- -- 0.003 -- -- 0.002 0.057

Winter Haven ERD (2007) 1.10 0.488 5.3 75.7 -- -- -- -- -- -- --

Overall Mean Value 1.20 0.260 6.8 65.2 -- -- 0.003 -- -- 0.002 0.057

1. Data not included in the calculation of mean value



# 4.1.8 Highway/Transportation

Highway/transportation land use consists prim arily of major highway systems, such as

interstate highways, expressways, and major stat e and federal highway systems. In general,

highway systems included under this category are cons idered to be heavily traveled, with constant

traffic movement throughout the day. This land us e category is typically characterized by a high

degree of imperviousness.

A summary of hydrologic information fr om highway/transportation stormwater

characterization studies is given in Table B.6. Elev en runoff characterization studies were identified

in the literature review, with watershed areas ranging from 1.3-58.3 acres and impervious

percentages ranging from 36-100%. Approximately half of the studies represent interstate highway

systems, with the remaining studies reflecting majo r 4- or 6-lane highways. All of the systems

provide drainage by curb and gutter systems.

A summary of emc values from highway/transpor tation stormwater studies is given in Table

4-10. Each of the 11 studies provides information for total nitrogen and total phosphorus, with five

studies providing information for BOD and eight studies providing information for TSS. A

relatively large number of the studies also in cluded measurements of heavy metals, including

cadmium, chromium, copper, iron, nickel, lead, a nd zinc. In general, highway/ transportation

stormwater appears to have moderate levels of total nitrogen, total phosphorus, and TSS, with a

relatively low level for BOD. Stormwater concentra tions of copper and zinc appear to be somewhat

elevated compared with concentrations measured in other land use categories.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-19

TABLE 4-10

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM HIGHWAY / TRANSPORTATION STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Broward County

(6-lane) Mattraw, et al.

(1981) 0.96 0.08 9.0 15.0 0.007 -- 0.007 0.207 -- 0.282 1 

# 0.090

I-95 Miami

(Bridge) McKenzie, et al.

(1983) 3.20 0.16 -- 42.0 0.001 0.010 0.040 -- -- 0.590 1 

# 0.330

Maitland German (1983) 1.30 0.240 -- 27.0 -- -- 0.012 0.350 0.009 0.092 1 

# 0.055

I-4 Maitland

Interchange Harper (1985) 1.40 0.17 -- -- 0.0025 0.004 0.038 0.341 0.003 0.163 1 

# 0.071

Maitland Blvd. Yousef, et al.

(1986) 1.40 0.17 -- -- 0.0022 0.004 0.039 0.354 0.004 0.181 1 

# 0.074

I-4 EPCOT

Interchange Yousef, et al.

(1986) 3.16 0.42 -- -- 0.0016 0.003 0.024 0.205 0.003 0.026 1 

# 0.024

Winter Park I-4 Harper (1988) 1.60 0.23 6.9 34.0 0.008 0.013 0.050 1.120 0.046 0.224 1 

# 0.170

Orlando I-4 Harper (1988) 2.15 0.550 4.2 66.5 0.008 0.014 0.067 1.450 0.020 0.343 1 

# 0.272

Bayside Bridge -

Tampa Stoker (1996) 1.10 0.10 -- 20.0 0.0001 0.003 0.008 0.530 0.003 0.011 0.050

Tallahassee ERD (2000) 1.10 0.166 1.9 70.6 -- -- -- -- -- -- --

Orlando - U.S. 441 ERD (2005) -

unpublished data 0.683 0.085 4.2 23.1 -- -- -- -- -- -- --

Overall Mean Value 1.64 0.22 5.2 37.3 0.004 0.007 0.032 0.570 0.013 0.011 0.126

1. Data not included in calculation of mean value



# The mean stormwater characteristics summari zed in Table 4-10 are intended for use only

where highway/transportation is the dominant land use category in a particular area. As indicated

previously, stormwater characteristics summarized in this table are most appropriate for

expressways, interstate highway systems, and heavily traveled roadways. Roadways associated with

other land use categories, such as residential, commercial, industrial, agriculture, open space, and

mining/extractive, are included in the stormwat er characteristics presented for each of these

categories. Therefore, roadway areas for these land use types should not be evaluated separately

since runoff generated on the roadway surfaces is mixed with runoff generated from the dominant

land use category.

4.1.9 Agricultural Areas

Agricultural land use within Florida is extr emely varied, both in terms of agricultural

activities and soil types. Agricultural activities su ch as cattle grazing and row crops are commonly

conducted on poorly drained soils which are charact erized by a relatively high runoff potential.

Citrus, however, requires well drained soils with a much lower runoff potential than those typically

associated with grazing or row crop activities. For these reasons, a wide range of agricultural uses

and characteristics must be considered to obtain re presentative emc values appropriate for specific

agricultural activities. For purposes of this analysis , agricultural activities in Florida are divided into

three primary categories, including pasture land, c itrus, and row crops. Su fficient characterization

data currently exists within the literature to provi de separate runoff characteristics for each of these

three categories.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-20

4.1.9.1 Pasture Land Use

Three separate studies were identified in the literature review which provide runoff

characterization data for pasture land use. A summary of hydrologic characteristics from these

pasture land use studies is given in Table B.7. Wa tershed sizes for the evaluated areas range from

21.6-155,741 acres. Each of the three study sites occurred on relatively poorly drained soils.

A summary of emc values from pasture land use studies is given in Table 4-11. Runoff

characterization data is provided in each of the three studies for total nitrogen and total phosphorus,

with BOD and TSS provided in two of the th ree studies. Measurement of heavy metal

concentrations was not conducted in any of the studies . In general, pasture land use appears to have

runoff concentrations for total nitrogen, total phosphorus, and TSS which are substantially greater

than concentrations observed in residential or commercial areas.

TABLE 4-11

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM PASTURE LAND USE STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS

St. Cloud CH2M Hill ( 1977) 5.57 0.88 7.0 180

St. Johns River Basin Fall (1987) 2.48 0.27 3.2 8.6

Ash Slough Hendrickson (1987) 2.37 0.697 -- --

Overall Mean Values 3.47 0.616 5.1 94.3



# A relatively large degree of variability appears to exist between runoff concentrations from

the three pasture land use areas. These differences are particularly apparent in the measured runoff

concentrations for total nitrogen, total phosphorus , and TSS in the St. Cloud study. The studies

performed in the St. Johns River Basin and in Ash Slough present hydrologic and water quality data

at the farm boundaries after transport through conveyance systems to the point of discharge from the

farm. These measured values reflect the effect s of pollutant uptake and attenuation during travel

through conveyance systems such as canals or on-site detention ponds. This type of value is more

representative of runoff characteristics which actually discharge from large farm basin areas.

However, the St. Cloud study represents water qua lity data measured directly as runoff from

the field area prior to entering adjacent canals and d itches and, as a result, does not include pollutant

uptake and deposition of suspended solids and nutrien ts within conveyance systems located within

the farm. As a result, the total nitrogen, total phos phorus, and TSS values obtained at this site are

substantially greater than those obtained at the other sites. Nevertheless, this value is included in

estimation of mean values for pasture land use to account for pasture areas that discharge rapidly

into off-site drainage systems.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-21

4.1.9.2 Citrus Land Use

Seven runoff characterization st udies involving citrus land use were identified during the

literature review. Soil types represented in th ese studies are generally poorly drained soils,

consisting of fine grain sands, peat, or muck. The wa ter table elevations in most of these studies was

controlled by furrows and lateral ditches to keep th e root zone of the plants dry. A summary of

hydrologic characteristics from the citrus land use studies is given in Table B.8. Watershed sizes

included in the land use characterization studies range from 184-56,868 acres. Studies included in

this category were conducted from 1987-1997.

A summary of emc values from the citrus land use studies is given in Table 4-12. Each of

the seven studies provides characterization data for total nitrogen and total phosphorus, with two

studies providing data for BOD, a nd five studies providing studies for TSS. Information on heavy

metal characteristics from citrus land uses is extremely limited. In general, citrus land use appears

to have moderate concentrations for total nitrogen and total phosphorus, with relatively low

concentrations for BOD, TSS, and heavy metals.

TABLE 4-12

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM CITRUS LAND USE STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Pb Zn

St. Johns River Basin

(Citrus/Row) Fall (1987) 3.26 0.24 3.0 28.0 -- -- -- -- --

St. Johns Water Control

District (Citrus/Pasture) Fall, et al. (1987) 1.33 0.09 2.1 4.6 -- -- -- -- --

Armstrong Slough

(Citrus/Pasture) Hendrickson

(1987) 1.57 0.09 -- -- -- -- -- -- --

Upper St. Johns River

Basin Fall (1990) 2.72 0.16 -- 23.3 -- -- 0.004 -- --

Gator Slough

(Hendry/Collier

Counties) Sawka and Black

(1993) 3.32 0.170 -- -- -- -- 0.002 -- --

Upper St. Johns River

Basin Fall (1995) 2.31 0.45 -- 20.1 -- -- -- -- --

Charlotte/DeSoto

Counties (4 sites) Bahk and Kehoe

(1997) 1.15 0.08 -- 1.69 0.0004 0.001 -- 0.001 0.012

Overall Mean Values 2.24 0.183 2.55 15.5 0.0004 0.001 0.003 0.001 0.012



# 4.1.9.3 Row Crops Land Use

Eight separate studies were identified in the literature which provide stormwater

characterization data for row crop activities. A summary of hydrologic characteristics from row

crop stormwater studies in Florida is given in Table B.9. Watershed areas included in these

studies range from 12-5680 acres, although half of the sites did not include information on the

watershed area. Soil types included in the areas are a combination of sand and muck soils.

Studies included for characterization of row crops were performed from 1987-2002.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-22

A summary of emc values from row crop st ormwater studies is given in Table 4-13.

Each of the eight studies provide characteriza tion data for total nitrogen and total phosphorus,

with five of the studies providing informati on for TSS, and none of the studies providing

information for BOD. Information on heavy metal characteristics is included in three of the

eight studies. In general, nutrient concentrations measured in row crop areas appear to be similar

to those observed in pasture land use areas, a lthough measured TSS concentrations in row crop

areas appear to be substantially lower than those observed in pasture areas.

TABLE 4-13

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM ROW CROP STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cd Cr Cu Fe Ni Pb Zn

Willowbrook Farms Hendrickson

(1987) 2.68 0.562 -- -- -- -- -- -- -- -- --

Upper St. Johns

River Basin Fall (1987) 3.26 0.24 -- -- -- -- -- -- -- -- --

Upper St. Johns

River Basin Fall (1990) 4.73 0.43 -- 37.4 -- -- -- -- -- -- --

Upper St. Johns

River Basin Fall (1995) 3.36 1.07 -- 32.4 -- -- -- -- --

Manatee County

(5 sites) Bahk, et al.

(1997) 1.45 0.500 -- 7.0 0.0001 0.001 0.011 -- -- 0.0008 0.017

Cockroach Bay

(Ruskin, FL) Bahk (1997) 1.57 0.51 -- -- 0.0003 0.004 0.035 0.160 BDL 0.008 0.052

Upper St. Johns River

Basin (3 sites) Hendrickson

(unpublished

data) 2.26 0.163 -- 4.9 -- -- -- -- -- -- --

Cockroach Bay

(Ruskin, FL) Rushton (2002) 1.85 1.265 -- 17.4 0.0003 -- 0.019 0.934 -- 0.002 0.020

Overall Mean Values 2.65 0.593 -- 19.8 0.0002 0.003 0.022 0.547 BDL 0.004 0.030



# 4.1.9.4 Comparison of Agricultural Characteristics

A comparison of emc values from pasture, citrus, and row crop agricultural activities is

given in Table 4-14. Pasture land use appears to have the largest mean concentration for total

nitrogen, total phosphorus, and TSS. The lowest concen trations for these parameters occur for citrus

land use.

A category of general agriculture is also included in the final row of Table 4-14. This

category simply reflects the arithmetic mean of the listed characteristics for pasture, citrus, and row

crop activities and is intended as a generic represen tation of agricultural activities for use in studies

where information on specific agricultural activities is not known.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-23

TABLE 4-14

COMPARISON OF STORMWATER CONCENTRATIONS

FROM AGRICULTURAL ACTIVITIES IN FLORIDA

LAND USE MEAN emc VALUE (mg/l)

TN TP BOD TSS

Pasture 3.47 0.616 5.1 94.3

Citrus 2.24 0.183 2.55 15.5

Row Crops 2.65 0.593 -- 19.8

General Agriculture 1 

# 2.79 0.431 3.8 43.2

1. Mean of pasture, citrus, and row crop land uses



# 4.1.10 Undeveloped/Rangeland/Forest Land Use

The category of undeveloped/rangeland/fo rest land use includes open spaces and

undeveloped land occupied by native vegetation, forests, and rangeland. These areas are typically

characterized by little or no impervious area and a relatively low runoff potential throughout most

of the year.

Five separate runoff characterization studies were identified which measured undeveloped,

rangeland, or forest land use areas. A summary of hydrologic characteristics from these studies is

given in Table B.10. The evaluated studies ra nge from Tallahassee to Miami. However,

information on watershed area is not provided for a ny of the studies since delineation of watersheds

for natural areas is often difficult. Land use in the evaluated studies includes flatwood, rangeland,

open spaces, and forests, and studies were conducted over the years from 1977-2004.

A summary of emc values from the undevel oped, rangeland, and forest stormwater studies

is given in Table 4-15. Each of the five studies provides characterization data for total nitrogen and

total phosphorus, with three studies providing data for BOD, and four studi es providing data for

TSS. Heavy metal characteristics for copper, l ead, and zinc are included in only one study. In

general, undeveloped, rangeland, and forest la nd uses are characterized by relatively low

concentrations for each of the available parameters summarized in Table 4-15.

TABLE 4-15

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM UNDEVELOPED / RANGELAND / FOREST STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cu Pb Zn

Orlando ECFRPC CH2M Hill ( 1977) 1.52 0.10 1.7 18.5 -- -- --

Miami Waller (1982) 0.90 0.02 -- 4.8 -- -- --

Boggy Creek Study ECFRPC (1988) 1.47 0.07 -- -- -- -- --

Sarasota/Charlotte Counties ERD (2004) 0.703 0.031 1.0 1.9 -- -- --

Overall Mean Value 1.15 0.055 1.4 8.4 -- -- --

1. Data not included in calculation of mean value

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-24

4.1.11 Mining/Extractive Land Use

The category of mining/extractive land use in cludes a wide variety of mining activities for

resources such as phosphate, sand, gravel, clay, and sh ell. Very little informa tion is available in the

current literature concerning the runoff characteristics of this land use type with the exception of

site-specific studies generated as a result of wate r quality violations and enforcement actions. The

only reference which provides runoff characteriza tion data for mining/extractive land use is the

Boggy Creek Study by the East Central Florida Regional Planning Council (ECFRPC) in 1988.

This study assumes that very little pollution is generated from the actual mining operation, and

runoff characteristics primarily reflect contributions from access roads, parking areas, and office

sites. This assumption appears reasonable for many types of mining activities which generally

extract materials from isolated pit areas. A su mmary of hydrologic data from the ECFRPC study is

given in Table B.11. Although the wa tershed size is not presented in the study, the percentage of

impervious area is estimated to be 23%.

A summary of stormwater emc values from mining/extractive land use studies is given in

Table 4-16. Information is provided in the B oggy Creek study only for total nitrogen and total

phosphorus, with a mean total nitrogen concentr ation of 1.18 mg/l and a mean total phosphorus

concentration of 0.15 mg/l.

TABLE 4-16

SUMMARY OF MEAN STORMWATER CHARACTERISTICS

FROM MINING / EXTRACTIVE STORMWATER STUDIES

LOCATION REFERENCE MEAN emc VALUE (mg/l)

TN TP BOD TSS Cu Pb Zn

Boggy Creek Study ECFRPC (1988) 1.18 0.15 -- -- -- -- --

Overall Mean Value 1.18 0.15 -- -- -- -- --

1. Data not included in calculation of mean value



# 4.1.12 Wetlands

Land uses assigned to the category of wetla nds include a wide range of diverse wetland

types, such as hardwood wetlands, cypress stands, grassed wetlands, and mixed wetland

associations. Wetland systems are routinely in cluded in ongoing monitoring efforts, and wetland

characterization data is available throughout the St ate of Florida for a variety of wetland types.

When wetland characterization data is required, it is best to obtain regionally-specific data

for the type of wetland system being evaluate d. Wetland characterization is available through

STORET, water management districts, FDEP, and local governmental monitoring agencies.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-25

The hydrology of wetlands can be extremely complex, varying from flow-through wetlands

which discharge throughout much of the year , to depressional wetlands which discharge

infrequently. When including wetlands in pollu tant loading evaluations, the site-specific

hydrologic characteristics of the wetlands under evalua tion must be considered. As a result of the

complexities of wetland systems, guidelines c oncerning representative concentrations and

hydrologic characteristics of wetlands are not included in this analysis.

4.1.13 Open Water/Lakes

The final land use category, open water/lakes, c onsists of open waterbodies such as lakes,

reservoirs, streams, and rivers. Pollutant con centrations from these sources are a result of

discharges from the waterbody during and follo wing rain events. The discharge from the

waterbody is a mixture of runoff contributed from the surrounding watershed and the ambient

water quality characteristics of the waterbody. Wate rbodies often provide pollutant attenuation for

watershed areas which are tributary to the waterbody.

Characterization data is currently availabl e for a large number of waterbodies located

within the State of Florida. These data ar e easily available through STORET, the LAKEWATCH

Program at the University of Florida, water ma nagement districts, FDEP, and local governmental

agencies. In many cases, specific water quality data may be available for larger waterbodies which

may be included in a pollutant loading analysis. Due to the abundant availability of site-specific

data, recommendations on representative water quality characteristics for open water/lake land uses

are not provided in this analysis.

4.1.14 Recommended Characterization Data

A summary of literature-based runoff character ization data for general land use categories

in Florida is given in Table 4-17 based upon the info rmation provided in the previous sections. The

values summarized in this table represent the m ean emc values for each of the general land use

categories discussed previously.

In general, the data summarized in Tabl e 4-17 reflect a pattern of increasing runoff

concentrations with increasing land use intensity. Of the three types of residential land uses

summarized in Table 4-17, the lowest emc values ar e associated with low-density residential.

Increases in emc values occur when the land use inte nsity is increased to single-family residential,

and further increases occur as the intensity is increased to multi-family. A similar pattern is

apparent between low- and high-intensity commerc ial areas, with higher emc values reflected for

high-intensity commercial areas for each of the listed parameters. Land use categories which are

not expected to be a significant source of nitroge n or phosphorus loadings, such as industrial and

highway areas, are characterized by relatively low con centrations for these parameters. In contrast,

agricultural areas, which would be expected to ha ve elevated concentrations of nutrients, are

characterized by higher concentrations of nutrients, particularly for total phosphorus.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-26

TABLE 4-17

SUMMARY OF LITERATURE-BASED RUNOFF

CHARACTERIZATION DATA FOR GENERAL LAND

USE CATEGORIES IN FLORIDA

LAND USE

CATEGORY TYPICAL RUNOFF CONCENTRATION (mg/l)

TOTAL N TOTAL P BOD TSS COPPER LEAD ZINC



# Low-Density Residential 1 

# 1.61 0.191 4.7 23.0 0.008 4 

# 0.002 4 

# 0.031 4



# Single-Family 2.07 0.327 7.9 37.5 0.016 0.004 0.062

Multi-Family 2.32 0.520 11.3 77.8 0.009 0.006 0.086

Low-Intensity Commercial 1. 18 0.179 7.7 57.5 0.018 0.005 0.094

High-Intensity Commercial 2. 40 0.345 11.3 69.7 0.015 -- 0.160

Light Industrial 1.20 0. 260 7.6 60.0 0.003 0.002 0.057

Highway 1.64 0.220 5. 2 37.3 0.032 0.011 0.126

Agricultural

Pasture

Citrus

Row Crops

General Agriculture 2 

# 3.47

2.24

2.65

2.79 0.616

0.183

0.593

0.431 5.1

2.55

--

3.8 94.3

15.5

19.8

43.2 --

0.003

0.022

0.013 --

0.001

0.004

0.003 --

0.012

0.030

0.021

Undeveloped / Rangeland / Fore st 1.15 0.055 1.4 8.4 -- -- --

Mining / Extractive 1.18 0.15 7.6 3 

# 60.0 3 

# 0.003 3 

# 0.002 3 

# 0.057 3



# 1. Average of single-family and undeveloped loading rates

2. Mean of pasture, citrus, and row crop land uses

3. Runoff concentrations assumed equal to industrial values for these parameters

4. Value assumed to be equal to 50% of single-family concentration



# The mean runoff characteristics summarized in Table 4-17 are recommended for use in

general runoff characterization and loading studies w ithin the State of Florida. However, in areas

where more site-specific runoff characterization in formation is available, the site-specific data

should be used instead of the generalized data summarized in Table 4-17.

Several assumptions were made in assigni ng runoff concentrations to provide a more

complete database for the general land use categorie s. First, runoff characterization data was not

available for copper, lead, or zinc in low-density residential land uses in the literature. Therefore,

to provide estimates of runoff characteristics for th ese parameters, typical concentrations of copper,

lead, and zinc in low-density residential areas are assumed to be equal to 50% of the mean values

listed for single-family residential. Heavy metal c oncentrations were also not available for copper,

lead, or zinc for mining/extractive land uses. As a result, runoff concentrations for these

parameters in mining/extractive areas are assumed to be similar to concentrations observed in

industrial areas. Pollutant contributions from mining activities are generated primarily from the

movement of trucks and automobiles along access roads into and out of the site, as well as parking

lots and garages. These activities are very similar to those occurring in industrial areas.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-27

4.2 Estimation of Runoff Quantities

Estimates of annual and event-based runoff volum es were calculated to evaluate variability

in regional runoff generation and the performance e fficiencies of dry retention systems. These

calculations were performed using the SCS (Soil Conservation Service) Curve Number

Methodology and the historical rainfa ll data sets for meteorological sites discussed in Section 4.1.

A discussion of the methodology and results of this modeling is given in the following sections.

4.2.1 Methodology

The SCS curve number methodology utilizes se parate calculations for the runoff volume

generated from directly connected impervious ar eas (DCIA) and non-DCIA areas. An impervious

area is considered to be directly connected if r unoff from the area flows dir ectly into the drainage

conveyance system, such as a gutter or stormsewer . Areas are also considered to be directly

connected if runoff from the area occurs as a con centrated shallow flow that is conveyed through a

pervious area, such as a roadside swale, and th en into a drainage system. The SCS curve number

method assumes that after allotting for initial abstraction, all rainfall which occurs on directly

connected impervious areas becomes stormwater runoff.

Non-directly connected impervious areas (non-DCIA) include all pervious areas and

portions of impervious areas which are not consid ered to be directly connected. The SCS model

assumes that runoff generated in these areas has th e opportunity to infiltrate into the soil, depending

upon the soil types and land cover characteristics, be fore significant runoff volumes begin to be

generated within the area. The runoff generati ng characteristics of non-DCIA areas are quantified

through the use of a curve number (CN). A curve number is a hydrologic factor which is used to

reflect the runoff potential of a particular land us e and soil type. Theoretical values for curve

numbers range from 0-100, with low values refl ecting a low runoff potential and higher values

reflecting a high runoff potential. Representative cu rve numbers can be obtained from a variety of

sources, although the original source of these data was published by the Natural Resources

Conservation Service (NRCS) as Technical Release 55 titled “Urban Hydrology for Small

Watersheds” dated June 1986. This reference provi des an extensive listing of curve numbers for

different hydrologic soil groups and land use covers.

The TR 55 document divides soil groups with in the United States into Hydrologic Soil

Groups (HSG) which groups general soil types with respect to runoff-producing characteristics. A

summary of the characteristics of the designated hydrologic soil groups, identified as A, B, C, and

D, is given in Table 4-18. The primary consid eration in assigning soils to the general soil group

types is the inherent capacity of the bare soil to permit infiltration. Soils classified in HSG A

consist primarily of deep sandy soils, with a high infiltration rate and a low runoff potential. The

vast majority of rainfall which occurs in these ar eas is absorbed by infiltration and does not become

stormwater runoff. Soils classified in HSG D c onsist of clayey-type soils or soils with a high

organic content which exhibit a low infiltration ra te and a high runoff potential. A large portion of

the rainfall which occurs on soils in this classification ultimately becomes stormwater runoff.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-28

TABLE 4-18

CHARACTERISTICS OF SCS HYDROLOGIC

SOIL GROUP CLASSIFICATIONS

SOIL

GROUP DESCRIPTION RUNOFF

POTENTIAL MINIMUM

INFILTRATION RATE

(inches/hour)

A Deep sandy soils very low 0.30-0.45

B Shallow sandy soils low 0.15-0.30

C Sandy soil with high clay

or organic content medium to high 0.05-0.15

D Clayey soils very high 0.00-0.05



# The SCS method calculates the runoff volum e for a given rainfall event by adding the

rainfall excess (runoff) from the non-DCIA portion to the rainfall excess created from the DCIA

portion of the land use. Rainfall excess from the non-DCIA areas is calculated using the

following set of equations:

where:

CN = curve number for pervious area

Imp = percent impervious area

DCIA = percent directly connected impervious area

nDCIA CN = curve number for non-DCIA area

P i



# = event rainfall

Q nDCIAi 

# = rainfall excess for non-DCIA for rainfall event 

# ⎟ ⎠ ⎞ ⎜ ⎝ ⎛

10

- CN nDCIA 1000

= S

, Storage Soil DCIA)

- (100 DCIA)

- (Imp 98 + Imp)

- 100 * CN

= CN nDCIA (



# 0.8S) + P ( ) 0.2S

- P (

= Q

i 2

i

nDCIA i

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-29

For the DCIA portion, rainfall excess is calculated using the following equation:

When P i 

# is less than 0.1, Q DCIAi 

# is equal to zero. This factor reflects the initial abstraction for the

impervious areas which assumes that the first 0.1 inch of rainfall is stored w ithin the irregularities in

the impervious surfaces and does not become stormwat er runoff. After these surfaces become filled

with the initial 0.1 inch of rainfall, additional rain fall begins to generate runoff on these surfaces.

One of the primary objectives of the hydrol ogic modeling efforts conducted by ERD is to

evaluate the impact of the variability in probability distributions of individual rain events throughout

the State of Florida, as discussed in Section 3.2, on rainfall/runoff relationships, as characterized by

variabilities in modeled runoff coefficients. The imp acts of variability in the sizes of individual rain

events can best be evaluated using a conti nuous simulation hydrologic model which evaluates

rainfall/runoff relationships over an extended period of time. However, this type of continuous

modeling cannot be adequately conducted using ra infall data summarized on a daily basis. A

portion of the 111 NCDC meteorological stations within the State of Florida also provide

precipitation records which are summarized on an hourly basis. A listing of NCDC hourly

precipitation monitoring stations in Florida is gi ven in Table 4-19. Hourly precipitation data is

available from 45 separate monitoring stations, w ith a period of hourly rainfall data ranging from 13-

64 years.

All available hourly precipitation data was obt ained for each of the 45 monitoring stations

listed in Table 4-19. For each site, a conti nuous simulation was conducted of rainfall/runoff

relationships using the entire record of hourly precipitation data for each site based on the SCS curve

number method. This modeling included a mean of approximately 4685 individual rain events for

each of the 45 monitoring stations. A location map for the 45 hourly precipitation monitoring sites is

given on Figure 4-1.

The pervious area curve number values listed in engineering texts and reference manuals,

used to estimate the amount of runoff lost due to inf iltration into the soil during a rain event, reflect

a “normal” antecedent moisture condition at the time of the rain event. These curve number values

are commonly used for modeling design storm events (25- or 100-year storms) for developed areas

where soil infiltration is a relatively insignifican t loss in comparison with the overall volume of

runoff generated during these design storm even ts. However, when performing continuous

simulation modeling, the soil moisture condition at th e time of the rain event can have a significant

impact on the runoff volume generated from pervi ous areas. The Soil Conservation Service (SCS)

has developed three antecedent soil moisture c onditions to account for variability in runoff

generation as a function of antecedent rainfall c onditions. These three antecedent soil moisture

conditions are labeled I, II, and III and are identified as follows:

Condition I: Little significant rainfall during previous 5-day period; soils are dry

Condition II: Average conditions

Condition III: Heavy rainfall, or light rainfall and low temperatures have occurred within the past

5 days; soils are saturated 

# 0.1)

- P (

= Q

i

DCIA i

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-30

TABLE 4-19

LISTING OF NCDC HOURLY PRECIPITATION

MONITORING STATIONS IN FLORIDA

STATION NUMBER

OF YEARS NUMBER

OF EVENTS MEAN ANNUAL

RAINFALL

(inches) MAXIMUM

EVENT

(inches) MEAN

EVENT

(inches)

Apalachicola Municipal Airport (211) 49 5630 55.79 10.06 0.49

Crestview Radio WJSB (1984) 21 2700 64.16 11.20 0.50

Niceville (6240) 20 2112 62.74 12.00 0.59

Panacea 3 S (6828) 32 3137 58.62 12.19 0.60

Panama City 5 NE (6842) 35 3607 58.72 11.10 0.57

Pensacola Regional Airport (6997) 33 4165 62.17 13.93 0.49

Tallahassee Municipal Airport (8758) 45 5570 64.55 13.41 0.52

Avon Park 2 W (369) 27 2985 48.71 9.73 0.44

Branford (3543) 53 5644 52.27 11.89 0.49

Clewiston (1649) 35 3679 46.26 9.60 0.44

Deland 1 SSE (2229) 13 1527 53.95 11.30 0.46

Dowling Park 1 W (2391) 35 3468 51.42 9.00 0.52

Gainesville-Univ. of Florida (3316) 49 5162 50.04 8.69 0.48

Graceville 1 SW (3538) 32 3250 55.31 10.30 0.54

Kissimmee 2 (4625) 25 2747 45.85 15.62 0.42

Lakeland (4797) 53 6413 49.92 10.80 0.41

Leesburg (4980) 48 5071 48.03 8.77 0.45

Lynne (5237) 28 2936 48.97 7.80 0.47

Marineland (5391) 52 5336 47.04 10.85 0.46

Melbourne Regional Airpor t (5612) 47 5073 47.52 9.89 0.44

Moore Haven Lock 1 (5895) 43 4885 45.89 9.60 0.40

Orlando International Airpor t (6628) 62 7855 50.03 13.75 0.39

Raiford State Prison (7440) 30 3076 48.94 10.10 0.48

Tamiami Trail 40 mi (8780) 26 2968 52.13 9.20 0.46

Venus (9184) 39 4260 47.26 11.75 0.43

Woodruff Dam (9795) 27 2794 52.63 9.50 0.51

Key West WB City (4575) 63 8035 39.07 24.39 0.31

Lignumvitae Key (5035) 26 2521 40.92 8.30 0.42

Brooksville Chin Hil (1046) 50 5211 54.03 12.90 0.52

Cross City (2006) 47 4965 55.14 11.10 0.52

Daytona Beach Regional Airport

(2158) 63 8019 49.61 11.46 0.39

Fort Myers-Page Field (3186) 28 3051 53.13 10.15 0.49

Inglis 3 E (4273) 48 4698 51.05 11.43 0.52

Jacksonville (4371) 64 8148 52.96 15.05 0.42

Lamont 6 WNW (4892) 45 4523 54.05 9.73 0.54

Parrish (6880) 44 4349 52.06 10.60 0.53

St. Leo (7851) 54 5619 52.90 11.84 0.51

St. Petersburg Whittd (7886) 45 4607 50.68 11.84 0.50

Tampa International Airport (8788) 47 5253 46.07 13.96 0.41

Vernon (9206) 16 1716 59.89 6.90 0.56

Boca Raton (845) 40 5527 60.10 14.00 0.43

Homestead Exp Stn (4091) 27 3687 58.39 18.00 0.43

Miami WSO City (5668) 64 10119 56.92 15.30 0.36

St. Lucie New Lock 1 (7859) 35 4688 54.82 10.66 0.41

West Palm Beach Intl Airport (9525) 64 10040 60.61 15.23 0.39

Mean: 40.6 4685 52.70 11.66 0.47

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-31

#

# #

# #

#

# #

#

#

# #

# # #

# # #

# #

# #

#

# # #

#

# # #

# # #

# #

#

#

# # #

# #

# # #

#

# #

APALACHICOLA

AVON PARK BLACKMAN

BOCA RATON BRANFORD

BROOKSVILLE

CLEWISTON CRESTVIEW

CROSS CITY

DAYTONA BEACH

DELAND DOWLING PARK

FORT MYERS GAINESVILLE GRACEVILLE

HOMESTEAD EXP STN INGLIS JACKSONVILLE

KEY WEST KISSIMMEE

LAKELAND LAMONT

LEESBURG

LIGNUMVITAE KEY LYNNE MARINELAND

MELBOURNE

MIAMI MOORE HAVEN LOCK 1 NICEVILLE

ORLANDO PANACEA PANAMA CITY

PARRISH PENSACOLA

RAIFORD

ST LEO

ST LUCIE NEW LOCK 1 ST PETERSBURG TALLAHASSEE

TAMIAMI TRAIL 40 MI TAMPA

VENICE VENUS VERNON

VERO BEACH

W PALM BEACH WOODRUFF DAM



# Figure 4-1. Locations of Hourly Meteorological Monitoring Sites.

The antecedent rainfall necessary to trigger AM C I or III conditions is based upon the rate at

which the soil storage is recovered following a rain ev ent. Loss of soil moisture occurs as a result of

several processes, one of which is evapotrans piration. Evapotranspiration increases during the

“growing” season and decreases during the “dormant” season. For Florida, the growing season is

commonly assumed to be from March-September, and the dormant season from October-February.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-32

Recommended rainfall depths corresponding to the three antecedent moisture conditions

(AMC) are summarized in Table 4-20 (USDA, 1986) for both dormant and growing season

conditions. Antecedent moisture conditions are determined by evaluating the total cumulative

rainfall in the 5-day period prior to a selected rainfall event. During dormant season conditions,

occurring from October-February, a cumulative ant ecedent 5-day rainfall less than 0.5 inches would

indicate a shift to antecedent mois ture Condition I for the new rain event. During growing season

conditions, this value increases to 1.4 inches. Howe ver, if the total antecedent 5-day rainfall exceeds

1.1 inches during dormant season conditions, an antecedent moisture Condition III is assigned to the

next rain event. Under growing season conditi ons, this value increases to 2.1 inches. When

performing continuous simulations, the SCS reco mmends that the standard curve number value

assumed for modeling purposes be modified to consider antecedent rainfall conditions.

TABLE 4-20

RECOMMENDED SEASONAL RAINFALL

DEPTHS FOR THE THREE ANTECEDENT

MOISTURE CONDITIONS (AMC)

AMC TOTAL ANTECEDENT 5-DAY RAINFALL (inches)

DORMANT SEASON

(October-February) GROWING SEASON

(March-September)

I < 0.5 < 1.4

II 0.5-1.1 1.4-2.1

III > 1.1 > 2.1



# The tabular curve number values presente d in textbooks and handbooks generally reflect

antecedent moisture Condition II. These values can be modified to reflect either antecedent moisture

Condition I or III, based upon the antecedent cumu lative 5-day rainfall using the relationships

summarized in Table 4-21 (McCuen, 1982). Mathemati cal expressions for these relationships have

been developed by Chow, et al. (1988) as follows:



# CN (I) = 4.2 CN (II)

10 – 0.058 CN (II)

and



# CN (III) = 23 CN (II)

10 + 0.13 CN (II)

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-33

TABLE 4-21

RECOMMENDED CURVE NUMBER ADJUSTMENTS

BASED ON ANTECEDENT MOISTURE CONTENTS

CN FOR

CONDITION II CORRESPONDING CN FOR CONDITION

I III

100 100 100

95 87 99

90 78 98

85 70 97

80 63 94

75 57 91

70 51 87

65 45 83

60 40 79

55 35 75

50 31 70

45 27 65

40 23 60

35 19 55

30 15 50

25 12 45

20 9 39

15 7 33

10 4 26

5 2 17

0 0 0



# Estimates of runoff depths were generated fo r each of the 45 hourly meteorological sites for

a wide variety of directly connected impervious area (DCIA) and non-DCIA curve numbers. Runoff

calculations were performed for combinations of DCIA values ranging from 0-100%, in 5%

increments, and for non-DCIA curve numbers ranging from 30-95, in 5-unit increments, along with

a non-DCIA curve number of 98. The calculated r unoff depth for each combination of DCIA and

non-DCIA curve number represents the total runoff generated for the assumed hydrologic

characteristics over the entire period of record for a gi ven site. The total runoff depth is then divided

by the total rainfall depth which occurred over the entire period of record to generate a runoff C

value for each combination of DCIA and curve number.

The runoff coefficient ranges from 0-1 and represents the ratio of runoff depth to the

precipitation depth. The rated C Value is calculated using the following equation:



# C Value = Generated Runoff (depth or volume)

Total Rainfall (depth or volume)

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-34

Runoff C values can be calculated on either an even t basis or for an annual period. The calculated C

value for each combination of DCIA and curve numbe r reflects the average runoff/rainfall ratio for a

given meteorological monitoring site over the entir e available period of record. The calculated

runoff C value does not represent anticipated rain fall/runoff relationships for any given year, but

does reflect anticipated runoff/rainfall relationships over an extended period of time for each site.

4.2.2 Impacts of Rainfall Distributions on Runoff Depth

The variability in frequency distributions of i ndividual rain events, discussed in the previous

section, has the potential to impact rainfall/runoff rela tionships for individual rain events as well as

on an annual basis. Areas which have a large num ber of small rain events which generate little

measurable runoff may have a lower annual runoff coefficient than a similar area in a different

portion of the State which is char acterized by a high frequency of large rain events which generate

significant runoff.

The potential impacts of rainfall frequency di stributions on runoff volumes were evaluated

by conducting simulations of the annual runoff depth generated by typical residential and

commercial developments constructed at various locations throughout the State. Eight separate

undeveloped and developed land use categories were assumed to evaluate the impacts of rainfall

distributions on annual runoff coe fficients. A summary of hydrologic assumptions used for the

developed land use categories is given in Table 4- 22. The low-density residential areas are assumed

to have approximately 15% impervious area, with 5% of the area as DCIA. Hydrologic

characteristics are provided for single-family residential developments based on 25% impervious

and 40% impervious conditions. High-density reside ntial areas are assumed to be 65% impervious,

with 80% impervious assumed for commercial activitie s. Curve numbers for pervious areas are also

included based on soil types and assumptions rega rding landscaped conditions. Highway land use

categories are also included, based upon 50% and 75% impervious assumptions. Curve number

values for pervious areas are provided for each of the four major hydrologic soil groups.

Estimates of the annual runoff depths genera ted by the land use categories summarized in

Table 4-22 were calculated using the continuous simulation methodology outlined in Section 4.2.1

and the hydrologic characteristics summarized in Tabl e 4-22. These estimates were calculated for

each of the 45 NCDC hourly precipitation monitori ng stations summarized in Table 4-19. This

process resulted in a total of 1440 separate l ong-term continuous simulations by modeling annual

long-term runoff coefficients for each of the eight land use types, four individual soil groups, and 45

monitoring stations. The calculated runoff coeffici ents for each combination of monitoring site, land

use, and curve number reflect the average annual r unoff coefficient for the modeled monitoring sites

over the entire available period of record.

The runoff C values generated as a result of th e process outlined above were evaluated using

a K-means clustering algorithm to identify similaritie s and differences in a nnual runoff coefficients

for each of the eight land use types and four soil gr oups across the State of Florida. The clustering

algorithm attempts to minimize the squared erro r objective function, representing the distance

measured between a data point and the center of a c hosen cluster. Clustering is simply a method of

partitioning a data set into sub-sets (clusters) so that the data in each sub-set are statistically similar

for the evaluated common trait.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-35

TABLE 4-22

SUMMARY OF HYDROLOGIC ASSUMPTIONS

USED FOR DEVELOPED LAND USE CATEGORIES

TYPICAL

LAND USE PERCENT

TOTAL

IMPERVIOUS

AREA %

DCIA 1 

# CURVE NUMBER (CN)

FOR PERVIOUS AREAS

HSG A HSG B HSG C HSG D

Low-Density Residential 15 5 49 2 

# 69 2 

# 79 2 

# 84 2



# Single-Family Residential

a. 25% impervious

b. 40% impervious 25

40 15

25 39 3



# 39 3 

# 61 3



# 61 3 

# 74 3



# 74 3 

# 80 3



# 80 3



# High-Density Residential 65 50 39 3 

# 61 3 

# 74 3 

# 80 3



# Commercial 80 75 39 3 

# 61 3 

# 74 3 

# 80 3



# Highway 4



# a. 50% impervious

b. 75% impervious 50

75 50

75 49 2



# 49 2 

# 69 2



# 69 2 

# 79 2



# 79 2 

# 84 2



# 84 2



# 1. Percentage of total project area

2. Assumes open space, lawns, or landscaping in fair condition

3. Assumes open space, lawns, or landscaping in good condition

4. Includes area within right-of-way



# For this evaluation, cluster analysis was c onducted for 2, 3, 4, 5, 6, 7, and 8 clusters. There

is no standard technique to determine the optimum number of clusters which should be chosen to

represent a particular data set. However, the elbow criterion is a common rule of thumb which is

often used to determine the appropriate number of clusters to be selected. The elbow criterion

indicates that you should select a number of clusters so that adding an additional cluster does not

provide a significant amount of additional informati on in the model. This criterion is typically

evaluated using the percentage of variance expl ained for each cluster model. A graph of the

percentage of variance and annual runoff coeffici ents explained as a function of the number of

clusters is given in Figure 4-2. As the curve begi ns to approach the 4- or 5-cluster models, the

additional variance explained by adding an additiona l cluster to the model becomes incrementally

small. Therefore, an appropriate number of cluste rs for the annual runoff coefficients model appears

to be approximately 4 or 5. The 5-cluster analys is was selected as the final model because this

model identified the Florida Keys as unique in te rms of annual runoff coefficients compared with

other areas throughout the State of Florida. ERD has conducted stormwater and meteorological

monitoring throughout the State of Florida, includi ng the Florida Keys, and has firsthand knowledge

of the substantially different meteorological processes which occur within the Florida Keys

compared with other areas within the State of Florid a. As a result of this firsthand experience, the 5-

cluster model was selected.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-36

60 65 70 75 80 85 90 95

0 2 4 6 8 10



# Number of ClustersPercent of Variance Explained



# Figure 4-2. Percentage of Variance in Annual Runoff Coefficients Explained

as a Function of the Number of Clusters.

A graphical summary of the results of the cluster analysis is given in Figure 4-3.

Meteorological monitoring sites with similar runo ff generating characteristics are grouped together

by color on this figure. Approximate areas repr esented by the clustered meteorological monitoring

sites are shaded in similar colors, generally on a County-wide basis. The majority of the indicated

zones appear to be intuitive with respect to va riability in rainfall events throughout the State.

Portions of the Panhandle have been clustered t ogether in an area which is impacted by a high

number of large frontal events. Portions of the St ate along the Gulf Coast also appear to be similar

runoff generating characteristics. Central and Cent ral-Coastal portions of Florida also appear to

have similar runoff characteristics. Runoff patterns in Southeast Florida appear to be dissimilar to

rainfall patterns in other areas of the State. The Florida Keys are also identified on Figure 4-3 as a

unique meteorological zone. The meteorological zones indicated on Figure 4-3 are utilized

throughout the remainder of this report for eval uating runoff generation, pollutant loadings, and

stormwater management system performance.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-37

#

#

# #

#

# #

#

#

# #

# # #

# # #

# #

# #

#

# # #

#

# # #

# # #

# #

#

#

# # #

# #

# #

# #

#

#

# #

#

# #

#

#

# #

# # #

# # #

# #

# #

#

# # #

#

# # #

# # #

# #

#

#

# # #

# #

# #

# #

APALACHICOLA

AVON PARK

BOCA RATON BRANFORD

BROOKSVILLE

CLEWISTON CRESTVIEW

CROSS CITY

DAYTONA BEACH

DELAND DOWLING PARK

FORT MYERS GAINESVILLE GRACEVILLE

HOMESTEAD EXP STN INGLIS JACKSONVILLE

KEY WEST KISSIMMEE

LAKELAND LAMONT

LEESBURG

LIGNUMVITAE KEY LYNNE MARINELAND

MELBOURNE

MIAMI MOORE HAVEN LOCK 1 NICEVILLE

ORLANDO PANACEA PANAMA CITY

PARRISH PENSACOLA

RAIFORD

ST LEO

ST LUCIE NEW LOCK 1 ST PETERSBURG TALLAHASSEE

TAMIAMI TRAIL 40 MI TAMPA

VENUS VERNON

W PALM BEACH WOODRUFF DAM



# 50 0 50 100 Miles 

# N

E W

S

Clusters

1

2

3

4

5



# Figure 4-3. Meteorological Zones Identified Using Cluster Analysis.

Unfortunately, not all counties in Florida have long-term meteorological monitoring sites

with hourly data. For purposes of designating me teorological zones, counties without a monitoring

site were grouped according to the meteorologi cal characteristics of adjacent counties with

monitoring sites. The resulting zones appear to be relatively intuitive with respect to meteorological

processes. The cluster groupings only have tw o apparent outliers, Daytona Beach and Tamiami

Trail, which appear out of place. However, in a data set containing 45 points, an analysis conducted

at a 95% probability level would be expected to ha ve approximately 2-3 outlier values. A listing of

counties included in each meteorological zone is given in Table 4-23.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-38

TABLE 4-23

COUNTIES INCLUDED IN THE

DESIGNATED METEORLOGICAL ZONES

ZONE

1 2 3 4 5

Okaloosa

Liberty

Bay

Wakulla

Leon

Santarosa

Gulf

Franklin

Escambia

Walton St. Lucie

Columbia

DeSoto

St. Johns

Seminole

Sumter

Flagler

Suwannee

Gadsden

Gilchrist

Glades

Calhoun

Hamilton

Hardee

Hendry

Union

Highlands

Putnam

Holmes

Indian River

Jackson

Volusia

Lafayette

Lake

Polk

Brevard

Bradford

Baker

Madison

Osceola

Marion

Orange

Clay

Okeechobee

Alachua Monroe Washington

Manatee

Levy

Pasco

Pinellas

Lee

Hillsborough

Hernando

Sarasota

Duval

Dixie

Collier

Citrus

Charlotte

Taylor

Nassau

Jefferson

Monroe Martin

Broward

Miami-Dade

Palm Beach



# A summary of mean runoff coefficients for each cluster as a function of land use and

hydrologic soil group is given in Tabl e 4-24. The values summarized in this table reflect the mean

runoff coefficients for each land use and hydrol ogic soil group and each meteorological monitoring

site included in each of the five clusters. The va lues summarized in Table 4-24 reflect differences in

runoff coefficients as a result of frequency distributions of common rain events only. This analysis

does not include variability in rainfall depth throughout the State which must be multiplied times the

mean runoff coefficients to obtain an estimate of annual runoff volume.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-39

TABLE 4-24

SUMMARY OF MEAN RUNOFF COEFFICIENTS

FOR EACH CLUSTER AS A FUNCTION OF LAND

USE AND HYDROLOGIC SOIL GROUP

LAND USE HYDROLOGI

C

SOIL GROUP CLUSTER

1 2 3 4 5

Undeveloped Land A 0.015 0.007 0.013 0.011 0.018

B 0.064 0.039 0.052 0.050 0.067

C 0.126 0.087 0.103 0.105 0.127

D 0.176 0.128 0.143 0.149 0.173

Low-Density

Residential Areas A 0.092 0.069 0.081 0.079 0.093

B 0.166 0.126 0.140 0.144 0.164

C 0.238 0.187 0.200 0.210 0.232

D 0.294 0.237 0.248 0.262 0.284

Single-Family

Residential Areas

(25% Impervious) A 0.155 0.136 0.143 0.144 0.151

B 0.206 0.173 0.184 0.188 0.202

C 0.268 0.223 0.235 0.243 0.260

D 0.313 0.262 0.272 0.285 0.302

Single-Family

Residential Areas

(40% Impervious) A 0.245 0.220 0.227 0.231 0.237

B 0.294 0.257 0.266 0.273 0.284

C 0.350 0.303 0.312 0.324 0.337

D 0.391 0.339 0.347 0.362 0.375

High-Density

Residential Areas A 0.455 0.423 0.424 0.436 0.435

B 0.490 0.450 0.453 0.467 0.469

C 0.529 0.483 0.485 0.503 0.506

D 0.556 0.508 0.509 0.529 0.531

Commercial Areas A 0.648 0.613 0.609 0.628 0.618

B 0.664 0.625 0.622 0.642 0.633

C 0.683 0.641 0.637 0.658 0.651

D 0.697 0.653 0.649 0.671 0.664

Highway Areas

(50% Impervious) A 0.444 0.415 0.416 0.427 0.425

B 0.481 0.442 0.445 0.459 0.460

C 0.517 0.473 0.476 0.492 0.495

D 0.546 0.498 0.500 0.519 0.522

Highway Areas

(75% Impervious) A 0.647 0.612 0.608 0.627 0.616

B 0.665 0.626 0.623 0.642 0.634

C 0.683 0.641 0.638 0.659 0.651

D 0.698 0.654 0.650 0.672 0.665

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-40

4.2.3 Annual Runoff Generation

A summary of calculated mean annual runoff coefficients as a function of curve number and

DCIA is given in Appendix C for each of the five designated meteorological zones. The values

presented in these tables reflect the proportion of annual rainfall which becomes stormwater runoff

in each meteorological zone for 315 DCIA and non- DCIA curve number combinations. Continuous

simulations of runoff generation were conducted over the period of record for each of the 45 hourly

meteorological monitoring stations in Florida. R unoff calculations were performed for combinations

of DCIA values ranging from 0-100%, in 5% in crements, and for non-DCIA curve numbers ranging

from 30-95, in 5 unit increments. A non-DCIA curve number of 98 was also included in this

analysis. The mean runoff C value for each co mbination of DCIA and curve number value was

calculated using values from each of the meteorol ogical monitoring sites within a given zone. The

values summarized in Appendix C reflect the averag e long-term runoff coefficients for each of the

five designated zones over a wide range of DC IA and curve number combinations. The data

summarized in Appendix C reflect a total of 14,175 separate long-term continuous simulations of

runoff coefficients based upon the 21 DCIA intervals, 15 curve number intervals, and 45

meteorological monitoring sites. This information is used in subsequent sections for evaluation of

existing stormwater design criteria and to evaluate the performance efficiency of proposed

alternative regulations.

The information contained in Appendix C can be used to estimate the annual runoff volume

for a given parcel under either pre- or post-de velopment conditions by multiplying the mean annual

rainfall depth for the given area, obtained from th e Figures in Appendix A.3, times the appropriate

runoff coefficient based upon the DCIA and curv e number characteristics for the meteorological

zone in which the parcel is located, listed in Appendix C. This estimate is calculated as follows:



# Annual Runoff Volume (ac-ft) =

Linear interpolation can be used to estimate annua l runoff coefficients for combinations of DCIA

and curve number which fall between the values included in Appendix C.

As seen in Appendix C, a wide degree of va riability is present in calculated annual runoff

coefficients for various combinations of DCIA and non-DCIA curve numbers between the five

meteorological zones in Florida. Increases in DCIA as well as increases in the non-DCIA curve

number both result in significant increases in th e calculated annual runoff coefficients. To

illustrate the general relative relationships between DCIA, curve number, and annual runoff

volumes, a set of average annual runoff coeffi cients was generated by calculating the mean

runoff coefficient for each combination of DC IA and non-DCIA curve number for the five

meteorological zones in Florida. A graphical su mmary of this relationship is given in Figure 4-

4. This graph indicates a linear relationship between runoff coefficients and percent DCIA, with

an exponential relationship between runoff coeffi cient and curve number. Increases in curve

numbers, particularly at curve number values in excess of 80, result in substantial increases in

the estimated annual runoff coefficient and corresponding annual runoff volume. 

# in 12 ft 1

x Value C x (inches) Rainfall Annual Mean x (acres) Area

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-41

0.0 0.2 0.4 0.6 0.8

0 20 40 60 80 100

30 40 50 60 70 80 90 " C " V a l u e



# P e

r c

e

n

t

D

C

I A ( % )



# C

u

r v

e N u

m b

e

r

Figure 4-4. General Relationships Between Percent DCIA, Curve Number, and C Value.

A graphical illustration of the distribution of runoff coefficients as a function of DCIA

and curve number for the Panhandle (Zone 1) rainfall distribution is given in Figure 4-5. In this

meteorological region, DCIA appears to have a re latively small impact on runoff coefficient at

DCIA percentages of 40 or less. However, at percentages above 40, the runoff coefficient

appears to increase rapidly. Changes in curve number appear to have a minimal impact on

runoff coefficients until the curve number begins to exceed approximately 85. Above this value,

subsequent increases in curve number result in large increases in runoff coefficient.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-42



# Panhandle

(Zone 1)

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1



# Curve Number (CN) 30 40 50 60 70 80 90Percent DCIA (%)



# 0 20 40 60 80 100

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 C Value



# Figure 4-5. Distribution of C Values as a Function of DCIA and Curve Number

for the Panhandle Area (Zone 1).

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-43

A graphical representation of the distribution of runoff coefficients as a function of DCIA

and curve number for the Florida Keys meteorologi cal zone is given in Figure 4-6. For this

rainfall distribution, DCIA appears to have a re latively minimal impact on runoff coefficients

until the DCIA begins to exceed a value of approximately 70. Above this value, subsequent

increases in DCIA result in rela tively large increases in runoff coefficients. Changes in curve

number appear to have a relatively small imp act on runoff coefficient until the curve number

begins to exceed a value of approximately 95. A bove this value, runoff coefficients begin to

increase rapidly. The data presented in Figure 4-6 suggest that, for a given combination of

DCIA and curve number, the runoff coefficient for the Florida Keys zone is substantially lower

than the runoff coefficient which would occur in the Panhandle region.

A graphical representation of the state-wide m ean distribution of runoff coefficients as a

function of DCIA and curve number is given in Figure 4-7. This diagram represents the average

of the five designated meteorological zones within the State. On a state-wide basis, significant

changes in runoff volume do not occur until th e DCIA value exceeds approximately 45-50 and

the curve number exceeds 90.

For comparison purposes, modeled annual runoff coefficients for a hypothetical

development with a DCIA of 40% and a non-DCIA curve number of 70 are given in Figure 4-8.

If this development were to be constructed in the Florida Keys (Zone 3) or Central (Zone 2)

portions of the State, approximately 36% of the annual rainfall would become stormwater runoff.

However, if this development were to be c onstructed in the Panhandle area, approximately 39-

40% of the annual rainfall would become stormw ater runoff. On a state-wide average,

approximately 37.5% of the rainfall which o ccurs on the hypothetical development would

become stormwater runoff. Lower than average annual runoff coefficients would be observed in

the Florida Keys (Zone 3), Central Area (Zone 2), and Gulf Coast Area (Zone 4), with higher

runoff coefficients observed in the Panhandle (Zone 1) and Southeast Coastal (Zone 5).

The differences in annual runoff coeffici ents between the meteorological regions

summarized in Figure 4-8 are due primarily to di fferences in the distribution of rain events

which occur at each of these sites. For exampl e, the Key West and Melbourne regional sites are

characterized by a high percentage of annual even ts with a relatively low rainfall depth which

generate little or no measurable runoff volume. Since a large portion of the annual rainfall in

these areas is generated by small events, the net effect is to substantially decrease the annual

runoff coefficient associated with these areas. On the other hand, the Pensacola and Tallahassee

areas are characterized by a high percentage of larger storm events, commonly associated with

frontal boundaries which move through the area. Si nce larger rain events typically generate a

larger proportion of stormwater runoff than sma ller events, the annual runoff coefficients for

these areas tend to be more elevated.

The results summarized in Figure 4-8 have si gnificant implications with respect to the

performance efficiency of stormwater manageme nt systems, particularly systems that have

design criteria based on providing tr eatment for the runoff generated by a stated rainfall event.

Based on the information summarized in Figure 4-8, a 1-inch rain event in the Panhandle area

will generate more runoff than a 1-inch rain even t which occurs in the Florida Keys or Central

areas. This would create a substantial difference, not only in the required treatment volume, but

also in the performance efficiency of a stor mwater system designed for the same hypothetical

development in the Panhandle and Florida Keys.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-44



# Florida Keys

(Zone 3)

0.7

0.6

0.5

0.4

0.3

0.2

0.1



# Curve Number (CN) 30 40 50 60 70 80 90Percent DCIA (%)



# 0 20 40 60 80 100

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 C Value



# Figure 4-6. Distribution of C Values as a Function of DCIA and Curve Number

for the Florida Keys (Zone 3).

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-45



# Statewide Average

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1



# Curve Number (CN) 30 40 50 60 70 80 90Percent DCIA (%)



# 0 20 40 60 80 100

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 C Value



# Figure 4-7. State-wide Mean Distributi on of C Values as a Function of DCIA

and Curve Number.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-46Zone 1Zone 2Zone 3Zone 4Zone 5Annual C Values



# 0.30 0.32 0.34 0.36 0.38 0.40

Mean



# Figure 4-8. Modeled Annual Runoff Coefficients (C Values) for a Hypothetical

Development with a DCIA of 40% and a non-DCIA Curve Number of 70.

The phenomenon illustrated in Figure 4-8 is explained primarily by the relative number

of small and large rain events associated with the different meteorological regions within the

State. For example, a comparison of the percen tage of annual rainfall volume generated by rain

events less than 0.1 inch at the designated meteor ological regions is given in Figure 4-9. For the

Florida Keys (Zone 3) sites, approximately 5-8% of the annual rainfall volume is contributed by

rain events less than 0.1 inch in depth. Ba sed upon the assumption that impervious surfaces

provide an initial abstraction of approximate ly 0.1 inch, no measurable runoff would be

measured by rain events of this size. In cont rast, only approximately 3-6% of the annual rainfall

volume in the Panhandle zone is contributed by rain events less than 0.1 inch in depth.

A comparison of the percentage of annual rainfall volume generated by rain events

greater than 1 inch is given in Figure 4-10. Only approximately 49% of the annual rainfall

volume which occurs in the Florida Keys (Zone 3) is generated by rain events greater than 1

inch. However, at the Panhandle sites (Zone 1), approximately 62% of the annual rainfall volume

occurs as a result of events greater than 1 inch. Since larger rain events generate a

proportionately larger runoff volume due to the lessening impact of initial abstraction, areas

which have a higher proportion of large rain even ts can be expected to have a larger annual

runoff coefficient.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-47Zone 1Zone 2Zone 3Zone 4Zone 5Annual Abstraction Lossas Percent of Rainfall (%)



# 10 12 14 16 18 20 22

Mean



# Figure 4-9. Percentage of Annual Rainfall Volume Generated by Rain Events < 0.1 Inch.Zone 1Zone 2Zone 3Zone 4Zone 5Percent of Annual Rainfall VolumeLess Than 0.1 Inch (%)



# 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5

Mean



# Figure 4-10. Percentage of Annual Rainfall Volume Generated by Rain Events >1 Inch.

# FDEP \ STORMWATER TREATMENT REPORT 

# 4-48

A comparison of the percentage of annual rain fall depth lost to abstraction on impervious

surfaces for each of the meteorological zones is gi ven in Figure 4-11. In the Florida Keys (Zone

3) area, approximately 21% of the total annual ra infall which occurs on impervious surfaces is

lost as a result of initial abstraction. This rainfall, which is stored on the surface of the

impervious areas, is removed by evaporation pro cesses between storm events. However, in the

Panhandle (Zone 1) area, only 15% of the annual ra infall depth is lost to initial abstraction on

impervious surfaces due to the higher percentage of large rain events in this portion of the State.Zone 1Zone 2Zone 3Zone 4Zone 5Percent of Annual Rainfall VolumeGreater Than 1.0 Inch (%)



# 40 45 50 55 60 65

Mean



# Figure 4-11. Percentage of Annual Rainfall Depth Lost to Initial Abstraction on

Impervious Surfaces.

# FDEP \ STORMWATER TREATMENT REPORT 

# SECTION 5

PERFORMANCE EFFICIENCY OF

STORMWATER MANAGEMENT SYSTEMS

A substantial amount of research has been conducted over the past 20-25 years which

demonstrates that some commonly used stormw ater management techniques are much more

efficient in removing and retaining pollutant loadi ngs than others. However, in spite of this

research, many stormwater management facilities are selected or designed based upon the ability

of the system to function hydraulically rather than with regards to pollutant removal

effectiveness. One of the primary objectives of this project is to evaluate stormwater

management systems from a pollutant removal perspective and to make recommendations

concerning the types of stormwater manageme nt facilities which should be emphasized to

maximize pollutant removal effectiveness while maintaining proper hydraulic function of the

system.

This section provides an overview of the anticipated pollutant removal effectiveness of

common stormwater management systems used within the State of Florida. First, a literature

review of previous research performed on t ypical stormwater management systems within

Florida is presented along with a summary of th e pollutant removal effectiveness achieved by the

evaluated studies. Next, estimates of the polluta nt removal effectiveness of common stormwater

management systems are provided based upon curre nt stormwater management design criteria

within the State. These estimates are based upon a combination of computer modeling and linear

regression evaluations of relationships between performance efficiency and significant design

parameters based on previous research.

The terms "detention" and "retention" are of ten used interchangeably by engineers, even

those who have been designing stormwater manage ment facilities for many years. For purposes of

this evaluation, the following definitions shall apply:

Detention : The collection and temporary storage of stormwater, generally for a period

of time ranging from 24-72 hours, in such a manner as to provide for

treatment through physical, biological or chemical processes with

subsequent gradual release of stormwater to downstream receiving waters.

Retention : On-site storage of stormwater with subsequent disposal by infiltration into

the ground or evaporation in such a manner as to prevent direct discharge of

stormwater runoff into receiving waters.



# 5-1

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-2

5.1 Literature-Based Removal Efficiencies

for Typical Stormwater Treatment Systems

A literature review was conducted of previous research performed in the State of Florida

which quantifies pollutant removal efficiencies associated with various stormwater management

systems used throughout the State. Each study which was obtained was evaluated for adequacy

of the database, with special attention to factor s such as length of study, number of runoff events

monitored, monitoring methodology, as well as comp leteness and accuracy of the work. It was

preferred that selected studies contain at least a 3-month period of data collection, representing a

wide range of rainfall and antecedent dry period conditions.

Unfortunately, for a number of studies, the only available database for a particular

stormwater management facility represented a relatively small and limited data collection

process. In other cases, the study evaluated only the outflow from the system and did not present

sufficient information to estimate system performa nce efficiency. Some studies were identified

which evaluated hybrid or experimental system s which cannot be classified into a common

stormwater system type associated with an existing design criteria. All evaluated studies were

carefully examined on a case-by-case basis and a decision was made on whether or not to

include the data in the removal efficiency estimat es. In general, studies with less than five

monitored storm events and studies which could not be classified into a common stormwater

management practice were excluded. Only stormw ater management facilities constructed within

the State of Florida were included in this eval uation. The resulting database contains pollutant

removal efficiencies for the following types of common stormwater management facilities:

1. Dry retention 3. Dry detention with filtration

2. Wet detention 4. Off-line retention/detention (dual pond)

A discussion of removal efficiencies for typical stormwater treatment systems is provided in the

following sections.

5.1.1 Dry Retention Systems

Dry retention systems consist primarily of in filtration basins which are used to retain

stormwater runoff on-site, thus reducing discha rge to downstream waterbodies. Disposal of

stormwater runoff occurs by infiltration into th e groundwater and, to a lesser degree, evaporation

from the water surface during periods of standing water. Because these systems rely primarily

on infiltration of stormwater into the ground to re gain the available pond storage, construction of

these systems is limited to areas with low groundw ater tables and permeable soils. The soil and

water table conditions must be such that the system can provide for a new volume of storage

through percolation or evaporation within a specified period, generally 72 hours following the

stormwater event.

A schematic diagram of a typical dry reten tion system is given in Figure 5-1. This

system is constructed as a dry basin with the pond bottom a minimum of 1-3 ft above the

seasonal high groundwater table elevation, dependi ng on applicable design criteria. The pond is

typically designed to hold a volume of stormwat er, called the "treatment volume", which is

equivalent to either the runoff generated by a sp ecified rain event or a certain depth of runoff

over the contributing watershed area.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-3

Figure 5-1. Schematic of a Dry Retention Facility.

Dry retention ponds may be constructed as e ither on-line or off-line systems. Off-line

systems typically provide storage for the treatme nt volume only. These systems typically utilize

a weir structure to divert runoff into the re tention pond until the treatment volume is reached.

Runoff discharges in excess of the volume bypa ss the pond and discharge into the detention

portion of the system or directly off-site. In an on-line system, the entire runoff volume

discharges into the pond. Runoff in excess of the treatment volume may discharge through an

outfall structure. For on-line systems, an additi onal volume may be provided above the treatment

volume for peak attenuation of on-site discharg es during major (10-year, 25-year, or 100-year)

storm events. The bottom of the pond is designed to be dry at all times except within 72 hours of

the design storm event.

Although retention ponds are most commonly cons tructed as basins similar to Figure 5-1,

retention pond designs can be highly variable as long as the system performs the desired

infiltration function. Retention ponds can be c onstructed as linear pond areas along road rightof-way, within recreational sites such as pl aygrounds or athletic fields, within natural

depressional areas, in open land, as part of the la ndscaping for a commercial site, or as a shallow

swale. Dual use of facilities provides a met hod for conserving valuable land resources while

incorporating stormwater management systems into the on-site landscaping.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-4

As the stormwater runoff percolates thr ough the soil, migrating toward the underlying

groundwater, a variety of physical, chemical, a nd biological processes occur which retain a

majority of the stormwater pollutants in the uppe r layers of the soil with in the retention basin

(Harper, 1985; Harper, 1988). Previous re search conducted by Harper (1985, 1988) has

indicated that stormwater pollutants are trapped in relatively stable associations in the upper 4-6

inches of soil within retention basins. Con centrations of nutrients and heavy metals in

groundwater beneath dry retention basins are t ypically lower in value than measured in

stormwater runoff entering the retention system.

Even though dry retention systems prevent di rect discharge of stormwater runoff to

receiving waterbodies, care must be taken in the design of retention facilities to ensure that

significant underground migration of pollutants does not occur to adjacent surface waters.

Pollutant loadings removed by the system may still reach adjacent receiving waters when

retention basins are constructed immediately ad jacent to the shoreline. Lateral distances

between retention ponds and surface water should be maintained as large as possible, at least 100

ft or more, depending on the site conditions (FDEP, 1988).

The side slopes and bottoms of dry retention basins should be fully vegetated with sod

cover grown in sandy permeable soils. Vegetation plays a crucial role in the removal of

contaminants from stormwater and in stabilization of the soil. The roots from vegetation assist

in maintaining the permeability of the basin soils. Bahia grass is typically used for sod cover

since it is drought resistant and can withstand periods of inundation.

In spite of the fact that on-line dry retention systems are used extensively throughout the

State of Florida, relatively little research has b een conducted to evaluate the pollutant removal

effectiveness of these systems. Only two references on dry retention systems were identified

during the literature search, both of which were conducted as part of the Orlando Areawide 208

Assessment during the late 1970s. A summary of the treatment efficiencies for dry retention

systems, based on available research studies in Florida, is given in Ta ble 5-1. The first study,

published in 1978 by the East Central Flor ida Regional Planning Council (ECFRPC) was

conducted on a commercial watershed in Orlando. Removal efficiencies for the dry retention

system reported in this study ranged from approxi mately 61% for total phosphorus to more than

90% for species of nitrogen. Info rmation on the amount of retention storage available within this

system was not provided so the removal efficiencies could not be related to a particular treatment

volume.

The second study, conducted by Wanielista (1978), was also part of the Orlando

Areawide 208 Assessment. This study presented estimated removal efficiencies for dry retention

systems based upon simulations of yearly rain fall/runoff events. Removal efficiencies are

presented as a function of retention volume, with increasing removal efficiencies associated with

increasing runoff volumes retained. This simu lation assumes that the retention pond drains

completely between rain events so that the design retention volume is available for the next

storm event. Removal efficienci es of approximately 80% are associated with retention of 0.25

inches of runoff, 90% for 0.5 inches of runoff, and 95% for a retention volume of 0.75 inches of

runoff. These values have been used extensivel y throughout the State of Florida as estimates of

the performance efficiency of dry retention systems.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-5

TABLE 5-1

TREATMENT EFFICIENCIES FOR DRY

RETENTION SYSTEMS BASED ON SELECTED

RESEARCH STUDIES IN FLORIDA

REFERENCE STUDY

SITE/

LAND USE TYPE OF

EFFICIENCIES

REPORTED MEAN REMOVAL EFFICIENCIES (%)

Total

N Ortho

-P Total

P TSS BOD Total

Cu Total

Pb Total

Zn

ECFRPC

(1978) Orlando/

Commercial Surface Water 91 -- 61 85 92 -- -- --

Wanielista

(1978) Orlando/

Urban Calculated

a. 0.25" ret.

b. 0.50" ret.

c. 0.75" ret.

d. 1.00" ret.

e. 1.25" ret. 80

90

95

99

99.9 80

90

95

99

99.9 80

90

95

99

99.9 80

90

95

99

99.9 80

90

95

99

99.9 80

90

95

99

99.9 80

90

95

99

99.9 80

90

95

99

99.9



# It is obvious that removal efficiencies ach ieved in retention systems are regulated

primarily by the amount of runoff volume retaine d. In general, the annual pollutant removal

effectiveness of a retention system should increas e as the retention volume increases. Since dry

retention systems do not always recover the en tire pollution abatement volume before the next

storm event, the actual observed pollutant removal efficiencies for dry retention systems are less

than the theoretical values presented by Wani elista. The removal efficiencies proposed by

Wanielista incorporate a first-flush effect whic h assumes that a large portion of the pollutant

loading occurs in the initial por tion of the runoff volume, increasing the theoretical removal

efficiencies achieved by retention of a specified runoff depth. However, in many watersheds,

significant first-flush effects do not occur, and ther efore, removal efficiencies will not be as high

as reported in the Wanielista study. Subsequent research has suggested that first-flush effects

occur primarily on relatively small watersheds (< 10 acres) with a high percentage of DCIA. In

large watersheds with a low or moderate DCIA percentage, significant first-flush effects may not

occur.

As development intensity increases, so doe s the volume of runoff from a given storm

event. For example, a 1-inch storm event on a rural residential development may produce 0.2

inches of runoff while the same storm event at a commercial site may produce 0.6 inches of

runoff. To achieve similar pollutant removal e fficiencies, a larger retention treatment volume

would be required for the commercial site than the rural residential site. Therefore, the treatment

volume alone cannot be directly correlated to the pollutant removal efficiency of the stormwater

treatment system. Instead, the achievable pollutant removal efficiencies are directly related to

the development intensity and the specified treatme nt volume. This concept will be discussed in

detail in Section 5.2. With dry retention treatment systems, the mass pollutant removal

efficiencies are directly related to the volume of runoff retained as a percent of the total runoff

volume produced.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-6

5.1.2 Wet Detention Systems

Wet detention systems are currently a very popular stormwater management technique

throughout the State of Florida, particularly in areas with high groundw ater tables. A wet

detention pond is simply a modified detention f acility which is designed to include a permanent

pool of water. These permanently wet ponds ar e designed to slowly release collected runoff

through an outlet structure. A schematic diagra m of a wet detention system is given in Figure

5-2.

Figure 5-2. Schematic of a Wet Detention System.

Pollutant removal processes in wet dete ntion systems occur through a variety of

mechanisms, including physical processes such as sedimentation, chemical processes such as

precipitation and adsorption, and biological uptake fr om algae, bacteria, and rooted vegetation.

In essence, these systems operate similar to a natural lake system.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-7

The water level in a wet detention system is controlled by an orifice located in the outfall

structure from the pond. A treatme nt volume above the orifice invert elevation is calculated for

each facility based upon a specified depth of runo ff over the contributing drainage basin area.

Inputs of stormwater runoff equa l to or less than the treatment volume leave the facility through

an orifice in the outfall structure, percola tion into the surrounding groundwater table, or by

evaporation. Stormwater inputs into the facility in excess of the treatment volume can exit from

the facility directly over a weir included in the pond outfall structure. The weir is designed to

provide attenuation for peak storm events so that the post-development rate of discharge from

the facility does not exceed the pre-development ra te of discharge for a specified design storm,

typically a 25-year storm event. A littoral zone may be planted around the perimeter of a wet

detention facility to provide additional biological uptake and enhanced biological communities.

Upon entering a wet detention facility, stormwater inputs mix with existing water

contained in the permanent pool. Physical, chem ical, and biological pro cesses begin to rapidly

remove pollutant inputs from the water column. Water which leaves through the orifice in the

outfall structure is a combination of the mixture of stormwater and the water contained within

the permanent pool. In general, the concentra tion of constituents in the permanent pool are

typically much less than input concentrations in stormwater runoff, resulting in discharges from

the facility which are substantially lower in con centration than found in raw stormwater. As a

result, good removal efficiencies are achieved within a wet detention facility for most

stormwater constituents. Although the littoral zone provides a small amount of enhanced

biological uptake, previous research has indicated that a vast majority of removal processes

occurring in wet detention facilities occur within the permanent pool volume rather than in the

littoral zone vegetation for the treatment volume (Harper, 1985; Harper 1988; Harper and Herr,

1993).

Wet detention systems offer several advantag es over some other stormwater management

systems. First, wet detention systems provide relatively good removal of stormwater

constituents since physical, chemical, and biological mechanisms are all available for pollutant

attenuation. Other stormwater management fac ilities provide only one or two of these basic

removal methods for stormwater. A second adva ntage of wet detention systems is that the

systems are not complex and can be relatively eas ily maintained. Wet detention systems do not

have underdrain systems which can become cl ogged and need periodic maintenance. Wet

detention systems can be viewed as amenities in development projects.

Of the stormwater facilities investigated during this evaluation, probably the most

amount of research within the State of Florida has been conducted on wet detention systems.

Unfortunately, much of the existing research was conducted on wet detention systems which

were not constructed to current design st andards regarding mean detention time, pond

configuration, and depth. The majority of th e available studies do not present information

regarding the treatment volume or residence time within the wet detention system. However,

based on the relative pond area and volume for the various studies, it appears that the typical

residence time provided in the evaluated ponds is approximately 15 days or less.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-8

A summary of treatment efficiencies for wet detention systems based on selected

research studies in Florida is given in Ta ble 5-2. Measured removal efficiencies for

orthophosphorus, total phosphorus, TSS, and heavy me tals are relatively consistent between the

studies presented within the table. In contrast , a high degree of variability in measured removal

efficiencies is present for total nitrogen. Rem oval efficiencies for total nitrogen range from 12-

63% for the studies presented in Table 5-2. Wet detention systems provide mean removal

efficiencies of approximately 60-65% for to tal phosphorus, BOD, and copper, while removal

efficiencies for orthophosphorus, TSS, lea d, and zinc approach or exceed 75-85%.

TABLE 5-2

TREATMENT EFFICIENCIES FOR WET

DETENTION SYSTEMS BASED ON SELECTED

RESEARCH STUDIES IN FLORIDA

REFERENCE STUDY

SITE/

LAND USE TYPE OF

EFFICIENCIES

REPORTED MEAN REMOVAL EFFICIENCIES (%)

Total

N OrthoP Total

P TSS BOD Total

Cu Total

Pb Total

Zn

PBS&J

(1982) Brevard

County/

Commercial Surface Water -- -- 69 94 -- -- 96 --

Cullum

(1984) Boca Raton/

Residential Surface Water

Overall 12

15 93

82 55

60 68

64 --

-- --

-- --

-- --

--

Yousef, et al.

(1986) Maitland/

Highway Surface Water 35 94 81 -- -- 56 88 92

Yousef, et al.

(1986) EPCOT/

Highway Surface Water 44 92 62 -- -- -- -- 88

Martin & Miller

(1987) Orlando/

Urban Surface Water -- 57 38 66 -- -- 40 --

Harper

(1988) Orlando/

Residential Surface Water -- -- 91 82 90 90 90 96

Harper & Herr

(1993) DeBary/

Commercial

& Residential Overall

a. t d 

# =7 days

b. t d 

# =14 days 20

30 40

60 60

70 85

85 50

60 40

50 60

85 85

95

Rushton & Dye

(1993) Tampa/Light

Commercial Surface Water -- 67 65 55 -- -- -- 51

Rushton, et al.

(1995) Tampa/

Commercial Overall

a. t d 

# =2 days

b. t d 

# =5 days

c. t d 

# =14 days 33

16

63 69

39

92 62

57

90 71

67

94 --

--

-- ND

1

55 ND

ND

92 56

32

87

DB

Environmental

(2005) Melbourne a. t d 

# =1 day

b. t d 

# =7 days

c. t d 

# =14 days 4

33

36 56

73

88 20

56

65 --

--

-- --

--

-- 32

81

92 41

88

96 --

--

--

MEAN VALUES 1 

# 37 79 69 77 75 69 84 85



# 1. Based on 14-day residence time, if applicable

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-9

In many of the studies, the ability of the sy stem to remove total nitrogen was heavily

dependent upon the proportion of total nitrogen pres ent as organic nitrogen. Organic nitrogen is

not readily available, either biologically or ch emically, and there are relatively few mechanisms

for removal of this species in a wet detention system. In contrast, both NO

x 

# and NH 3 

# are readily

taken up in biological processes which accounts for the relatively good removal efficiencies

achieved for these species in wet detention ponds. In systems where organic nitrogen represents

the dominant portion of the total nitrogen in the incoming stormwater flow, removal of total

nitrogen can be expected to be relativ ely poor. If inorganic species of NO

x 

# and NH 3 

# represent

the dominant nitrogen species found, then removal efficiencies for total nitrogen can be expected

to increase. On an average basis, wet detenti on systems with a detention time of 14 days can be

expected to provide a net removal of approxima tely 20-40% for total nitrogen; 60-70% for total

phosphorus and copper; and 75-85% or more for TSS, total lead and total zinc.

The report by Harper and Herr (1993) presents separate removal efficiencies for pond

residence times of approximately 7 days, along with detention times of 14 days or more. With

the exception of TSS, increasing the pond detenti on time results in a slight improvement in

removal efficiencies for the listed parameters. At a detention time of 7 days, removal of total

nitrogen, total phosphorus and TSS is estimated to be approximately 20%, 50%, and 85%,

respectively. At a detention time of 14 days , removal of total nitrogen, total phosphorus and

TSS increase slightly to approximately 30%, 70%, and 85%, respectively. Little additional

improvement in removal efficiencies was observe d for most parameters at detention times in

excess of 14 days up to the maximum detention time of 41 days included in the study.

The report by Ruston, et al. (1995) summarizes pollutant removal efficiencies achieved

within a wet detention pond in Tampa which recei ves stormwater runoff from a light commercial

area. Pollutant removal efficiencies are provi ded for pond detention times of 2, 5, and 14 days.

In general, pollutant removal efficiencies obtaine d at a detention time of 2 days are lower than

removal efficiencies obtained at a detention tim e of 14 days for all evaluated parameters.

However, the lowest removal efficiencies in th e study were obtained at the 5-day detention time.

Rushton, et al. reports that the lower efficien cies observed during the 5-day detention time study

period were highly influenced by one extreme st orm event where almost 6 inches of rain

occurred during a single week.

The most recent study to evaluate impacts of residence time on performance efficiency

was conducted by DB Environmental (2005). Th is study was performed on a wet detention pond

in Melbourne where portions of the pond were is olated to create microcosms to simulate

residence times of 1, 7, and 14 days. In general, removal efficiencies for all of the evaluated

parameters increased with increases in deten tion time within the microcosms. The removal

efficiencies achieved at the 14-day residence tim e are similar to values reported by Harper and

Herr (1993), also for a 14-day residence time.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-10

5.1.3 Dry Detention (With and

Without Filtration/Underdrains)

Historically, dry detention facilities have been one of the most common stormwater

management techniques used throughout the State of Florida, particularly in South Florida.

These systems are typically utilized in hi gh groundwater table areas where the normal

groundwater level makes the use of a retention type facility less feasible. Dry detention systems

are intended to be dry basins which are designed to hold a specific quantity of stormwater runoff

(treatment volume). Recovery of the design treatme nt volume occurs as a result of migration

of the stormwater runoff through the pond bottom, discharge through an outfall orifice structure,

or into an underdrain system or side bank filter constructed around the perimeter or bottom of the

pond.

A schematic diagram of a dry detention sy stem (with underdrain) is provided in Figure

5-3. The underdrain system is typically used to control the existing groundwater table elevation

in the vicinity of the pond and to improve the r ecovery rate of the pollution abatement volume.

Dry detention ponds are also constructed with side bank filters which perform a similar function.

Figure 5-3. Schematic of a Dry Detention with Underdrain System.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-11

Dry detention systems (without filtration) ha ve been used commonly within the South

Florida Water Management District (SFWMD) and the Southwest Florida Water Management

District (SWFWMD). In the St. Johns Rive r Water Management District (SJRWMD), dry

detention is limited to projects less than 5 acres in size or where the ground water table or soil

conditions limit the feasibility of other BMPs. Dry detention systems utilize an orifice or Vnotch to slowly discharge the specified treatment volume following a storm event.

Physical processes such as sedimentation, a nd chemical processes such as precipitation

and adsorption, are the primary mechanisms respons ible for pollutant removal in dry detention

with underdrain systems. Stormwater inputs into these systems are typically evacuated within

24-72 hours, and as a result, biological processes such as uptake of nutrients by plant surfaces

and roots, are severely limited and do not play a significant role in the removal of stormwater

pollutants. Removal of particulate pollutant s by sedimentation within the pond, as well as

entrapment of particles within the filter system or soils during migration toward the underdrain

system, are the primary physical removal processe s in dry detention with filtration systems.

Removal of particulate forms of phosphorus and heavy metals may also occur due to

sedimentation through the pond. These systems have an extremely limited ability to remove

dissolved constituents, most of which are best removed through biological processes.

Many dry detention systems which utilize underdrains are constructed in a manner which

requires the stormwater to migrate through on-site soil prior to entering the underdrain system.

This design technique probably enhances the rem oval efficiencies achieved by these systems due

to the natural adsorption capacity of soils. Other designs pass the runoff through sand filer

media prior to discharge. However, the ability of common silica sand filter systems to remove

dissolved constituents is severely limited (Harper and Herr, 1993).

As seen in Figure 5-3, the underdrain and f ilter systems associated with dry detention

facilities are sometimes constructed to intercept and control the existing groundwater elevations

in the vicinity of the basin to maintain a dr y pond bottom. This causes an influx of on-site

groundwater into the underdrain system, resulting in a continuous flow from the system which is

unrelated to rain events. This continuous fl ow of groundwater may actually create a system

where substantially more mass leaves the stormwat er facility on an annual basis than enters the

system through stormwater runoff.

However, it is possible for dry detention syst ems to provide good removal efficiencies for

total nitrogen, total phosphorus, TSS, and BOD. This can be accomplished by ensuring that the

seasonal high groundwater table is one or mo re feet below the proposed pond bottom and

underdrain elevation. The separation between pond bottom and seasonal high groundwater table

elevation allows the pond to function as a dry re tention pond system for some rain events. Onehundred percent removal is achieved for all r unoff infiltrated through the pond bottom which is

not intercepted by the underdrain system. Pollu tant removal efficiencies for dry detention

systems can also be improved by removing the underdrain filter system, and replacing the filter

system with a drawdown V-notch or orifice similar to a wet detention system.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-12

As previously discussed, the pollutant remova l effectiveness of dry detention systems are

largely affected by the elevation of the underd rain system and pond bottom in relation to the

seasonal high groundwater table. This is evident in the literature-based treatment efficiencies for

the dry detention systems, provide d in Table 5-3, based on selected research studies performed in

Florida. Each of these systems is constructed with a side bank filter sy stem for drawdown of the

treatment volume. The first entry in Table 5-3 contains removal efficiencies from research

conducted at the Publix shopping center dry detention pond in Bradfordville, north of

Tallahassee. Overall mass removal efficiencies greater than 80% were achieved for total

nitrogen, total phosphorus, TSS, and BOD. These high mass removal efficiencies were observed

since 66% of the runoff entering the pond infiltrat ed through the pond bottom. Only 34% of the

runoff which entered the pond discharged through the underdrain system or the overflow

structure. This pond functioned much differently than typical dry detention with filtration

systems in other areas of Florida.

TABLE 5-3

TREATMENT EFFICIENCIES FOR DRY

DETENTION WITH FILTRATION SYSTEMS BASED

ON SELECTED RESEARCH STUDIES IN FLORIDA

REFERENCE STUDY

SITE/

LAND USE FILTER

SYSTEM

TYPE MEAN REMOVAL EFFICIENCIES (%)

Total

N OrthoP Total

P TSS BOD Total

Cu Total

Pb Total

Zn

Bradfordville

Study 1 

# Leon County/

Commercial Side Bank 80 -- 92 98 93 -- -- --

Harper

& Herr 2



# (1995) Orange

County/

Commercial

& Residential Side Bank -136 -229 -86 77 -49 68 93 25

MEAN VALUES -28 -- 3 88 22 -- -- --



# 1. 66% of runoff infiltrated through pond bottom

2. Underdrain installed be low surface groundwater elevation



# Conversely, the second entry in Table 5-3 summarizes a study conducted on a dry

detention pond in Orange County, FL. The underdra in for this pond was constructed several feet

below the average groundwater table elev ation surrounding the pond. For this reason,

groundwater continually flowed from the su rrounding area into the underdrain system and

directly into the adjacent receiving waterbody. The excess groundwater discharge resulted in a

net export of total nitrogen, orthophosphorus, to tal phosphorus, and BOD for this treatment

facility.

Based on the research performed on dry dete ntion with filtration and dry detention

systems, it is apparent that a majority of the mass removal efficiencies are due to infiltration

through the pond bottom and not due to removal processes occurring within the treatment

facilities. Ponds with bottoms constructed a bove the seasonal high groundwater table elevation

will exhibit higher mass pollutant removal efficien cies than ponds constructed into the seasonal

high groundwater table.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-13

Maximum removal efficiencies for a dry detention system could be achieved using a

design which incorporates infiltration through the pond bottom and forces the remaining inputs

into the underdrain system to pass through the filter media, while maintaining an underdrain

elevation at least 1 ft above the seasonal high groundwater table. This system would utilize

infiltration and filtration as the primary removal mechanisms.

It appears that annual mass removal efficienci es for dry detention with filtration systems

are highly variable. However, in order to provide comparative pollutant removal efficiencies for

common stormwater management systems, theo retical pollutant removal efficiencies are

assumed for dry detention with filtration syst ems based upon the assumption that 25% of the

annual runoff volume which enters the pond infiltr ates through the pond bottom. The estimated

mass removal efficiencies for a dry detention w ith filtration system, based upon this assumption,

is estimated to be approximately 30% for tota l nitrogen, 40% for total phosphorus, 90% for TSS,

and 50% for BOD. These removal efficiencies ma y improve slightly if the treatment volume is

increased beyond the standard design. Since th e primary removal mechanism is the physical

process of sedimentation of particles, the in creased detention time provided by the additional

treatment volume has the potential to increase sy stem efficiency. However, most of the

settleable solids should be removed very quickly and little additional removal may occur at the

extended detention time.

5.1.4 Off-line Retention/Detention

(Dual Pond) Systems

Off-line retention/detention systems provide an off-line retention pond for the treatment

volume and an on-line detention pond for flood cont rol and attenuation of peak discharges. A

diversion device, often called a "smart box", is used to divert first-flush stormwater runoff into

the retention pond. When the retention pond fills, the remaining stormwater runoff is diverted

directly to a detention pond for flow attenuation purposes.

A schematic diagram of an off-line retention/ detention system is given in Figure 5-4.

Volume recovery in the retention portion of the system occurs primarily through groundwater

infiltration and evaporation. Drawdown in the detention pond occurs through an outlet structure

designed to match pre- and post-development di scharge rates. Off-line retention/detention

systems have been used sporadically throughout Florida, although these systems are required

within the City of Orlando. Even though this type of system requires two ponds rather than one,

the required ponds are typically much smaller in size than a single pond, and can be placed into a

development landscape more easily than a singl e large system, minimizing potential impacts on

space requirements.

Off-line retention/detention systems provide pollutant removal mechanisms in both the

retention system as well as the detention portion of the pond. Stormwater runoff retained in the

retention system infiltrates through the gr ound with 100% removal efficiency. Removal

processes such as settling, adsorption, and precipita tion reactions occur in the detention facility

during the drawdown period and al so provide similar mass removal efficiencies to the dry

detention system.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-14

Figure 5-4. Schematic of an Off- Line Retention/Detention System.

A summary of treatment efficiencies for o ff-line retention/detention systems based on

studies conducted within the State of Florida is gi ven in Table 5-4. Only two studies have been

conducted in the State of Florida which provide pollutant removal efficiencies for off-line

retention/detention systems. Each of thes e studies was conducted by Harper (1988) in the

Orlando area on residential and commercial watershe ds, constructed within the City of Orlando,

which provided a treatment volume of 0.5 inches over the contributing watershed area.

Excellent removal efficiencies were achieve d in the study reported by Harper (1988) in

the Orlando residential watershed. Measured removal efficiencies for total nitrogen, total

phosphorus, TSS, BOD, total copper, and total zinc were equal to 85% or more. Removal

efficiencies measured in the commercial wate rshed studies are somewhat lower than those

reported in the residential watershed. Removal efficiencies for total nitrogen, total phosphorus,

TSS, and BOD measured in this study were 30%, 76%, 89%, and 64%, respectively.

Mean values for the two studies are reported at the bottom of Table 5-4. On an average

basis, off-line retention/detention facilities provi de excellent removal efficiencies for total

nitrogen, total phosphorus, TSS, BOD, and heavy metals. Annual removal efficiencies for this

type of system can be expected to be approximately 60-65% for total nitrogen and total copper;

75-85% for total phosphorus and total lead; and 80-90% for TSS, BOD, and total zinc.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-15

TABLE 5-4

TREATMENT EFFICIENCIES FOR OFF-LINE

RETENTION/DETENTION SYSTEMS (DUAL POND) BASED

ON SELECTED RESEARCH STUDIES IN FLORIDA

REFERENCE STUDY

SITE/

LAND USE TYPE OF

EFFICIENCIES

REPORTED MEAN REMOVAL EFFICIENCIES (%)

Total

N Ortho

-P Total

P TSS BOD Total

Cu Total

Pb Total

Zn

Harper

(1988) Orlando/

Residential Overall 85 96 92 95 90 85 71 91

Harper

(1988) Orlando/

Commercial Surface

Water 30 61 76 89 64 47 80 81

MEAN VALUES 58 79 84 92 77 66 76 86



# 5.1.5 Comparison of Treatment Efficiencies

for Typical Stormwater Management Systems

A comparison of treatment efficiencies for t ypical stormwater management systems used

in the State of Florida is gi ven in Table 5-5 based upon information provided in the literature

review. Comparative removal efficiencies are provided for dry retention, wet detention, and dry

detention. For the purposes of the evaluation, rete ntion is considered any method of infiltrating

water into the ground. This includes traditional re tention ponds, stormwater reuse, swales, or the

use of exfiltration trenches.

TABLE 5-5

ESTIMATED POLLUTANT REMOVAL EFFICIENCIES

FOR COMMON STORMWATER TREATMENT FACILITIES

TYPE OF SYSTEM ESTIMATED REMOVAL EFFICIENCIES (%)

Total N Total P TSS BOD

Retention, Reuse,

Source Reduction, Swales 100% for Retained Volume

Wet Detention

a. 7-day detention time

b. 14-day detention time 20

30 60

70 85

85 50

60

Dry Detention 0-30 0-40 90 0-50

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-16

Of the three basic stormwater treatment syst ems, retention provides the highest level of

treatment possible. All stormwater runoff retain ed or infiltrated into the ground is assumed to

have a 100% mass pollutant removal efficiency for th e retained volume. This is the best possible

stormwater treatment system to use in terms of pollutant removal efficiency. Mass removal

efficiencies for wet detention have been divi ded into 7-day and 14-day detention times, with

mass removal efficiencies ranging from 20-30% for total nitrogen, 60-70% for total phosphorus,

85% for TSS, and 50-60% for BOD. Estimated mass removal efficiencies for dry detention

systems are 0-30% for total nitrogen, 0-40% fo r total phosphorus, 90% for TSS, and 0-50% for

BOD, depending on the relationship between the pond bottom or underdrain and the

groundwater table elevation. These removal effi ciencies are based upon anticipated settling of

TSS within the pond and the range of listed polluta nts present in a particulate form. Based on

the information provided in Table 5-5, the most effective stormwater management system in

terms of retaining stormwater pollutants is dry retention, followed by wet detention, and dry

detention systems.

5.2 Performance Efficiency of Existing

Stormwater Design Criteria

The literature review presented in the previous section provides estimates of the performance

efficiency of stormwater management systems wh ich have been evaluated within the State of

Florida. However, each of these studies reflects relatively site-specific performance efficiency data

based upon the specific design of the stormwat er management facility and the regional

meteorological characteristics in the vicinity of th e study site. Since meteorological characteristics

and design criteria for stormwater management syst ems vary widely throughout the State of Florida,

performance efficiency data for a stormwater mana gement system constructed in one part of the

state may not be applicable to similar stormwater management systems constructed in other parts of

the State.

Evaluations were conducted as part of this ev aluation to provide estimates of the anticipated

performance efficiencies of stormwater management systems within the State of Florida considering

variations in design criteria and meteorological ch aracteristics throughout the State. These analyses

are then used to compare the anticipated performa nce efficiency of stormwater management systems

constructed according to current design criteria w ith the overall performance efficiency objectives

outlined in the Water Resource Implementation Rule (Chapter 62-40 FAC).

5.2.1 Dry Retention

As discussed in Section 2, design criteria for dry retention systems within the State of Florida

are based upon providing treatment for a volume equivale nt to a certain depth of runoff, typically 0.5

inch, over the project area, or the runoff generated fr om a specified rain event, typically 1 inch.

Estimates of the annual mass removal efficiencies a ssociated with these design criteria are discussed

in the following sections.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-17

5.2.1.1 Evaluation Methodology

The anticipated annual mass removal efficiencies achieved by dry retention systems were

valuated for each of the five meteorological z ones over a wide range of DCIA percentages and

non-DCIA curve numbers. These evaluations we re conducted using a continuous simulation of

runoff volumes generated on a hypothe tical 1 acre site using the historical rainfall data sets for

meteorological sites in each of the five zone s. This analysis was performed for DCIA

percentages ranging from 0-100 in 5-unit inte rvals and for non-DCIA curve numbers ranging

from 30-95 in 5-unit intervals, along with a non-DCIA curve number of 98, comprising 315

combinations of DCIA percentages and non-DCIA curve numbers.

The runoff generated by individual rain ev ents was calculated using the continuous

simulation methodology outlined in Section 4.2.1. This methodology was used to estimate the

runoff volume generated by individual rain events within the historical rainfall records. The

runoff generated by the rain event was instantane ously routed into a theoretical dry retention

pond with a treatment volume equivalent to a sp ecified depth of runoff or the runoff from a

specified rain event. A hypothetical drawdow n curve was established for the retention pond

based upon typical drawdown design criteria which require recovery of 50% of the treatment

volume in 24 hours and 100% of the treatment volume in 72 hours. If the runoff volume

exceeded the capacity of the retention pond, th e remaining volume was assumed to bypass the

pond directly with a treatment efficiency of 0. Each storm within the historical record was

routed through the theoretical retention pond with excess runoff assumed to bypass the system.

The evaluation methodology used to estimate th e performance efficiency of dry retention

systems is based upon the following assumption:

Watershed areas contributing to each stormwater management facility do not exhibit

first-flush effects with respect to runo ff concentrations. Although small, highly

impervious watershed areas, typically less than 5-10 acres in size, may exhibit first- flush

effects under certain conditions, there is no scien tific evidence to indicate that larger subbasin areas exhibit a first-flush effect on a continuous basis. Therefore, the analyses

presented in this report may be somewhat c onservative for small basins which exhibit a

first-flush effect.

For this analysis, it is assumed that the calculated performance efficiency of a dry

retention stormwater management system is base d entirely upon the percentage of water retained

during each storm event. For a dry retention system, it is assumed that a pollutant removal

efficiency of 100% is achieved for the entire treatme nt volume retained within the system. As a

result, removal efficiencies of 100% are achieve d for all rainfall events which generate runoff

volumes less than or equal to the available tr eatment volume within the pond. Rainfall events

which generate runoff in excess of the ava ilable volume are assumed to have a removal

efficiency of 100% for all generated runoff up to the available treatment volume, with a removal

efficiency of 0% for runoff inputs in excess of the treatment volume.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-18

Pollutant removal efficiencies were calculated for selected dry retention treatment

volumes for each meteorological zone and each of the 315 combinations of DCIA and non-DCIA

curve number listed previously based upon the assumptions outlined in the previous paragraphs.

Removal efficiencies were calculated for re tention treatment volumes ranging from 0.25

inch to 4.0 inches of runoff in 0.25-inch increments. Removal efficiencies were also calculated

for retention volumes based on the runoff from a specified rainfall depth ranging from 0.25-4.0

inches in 0.25-inch increments.

5.2.1.2 Design Criteria Based on Runoff Depth

Estimates of annual mass removal efficiencies for dry retention as a function of selected

runoff depths, DCIA percentages, and non-DCIA curve numbers are given in Appendix D for

each of the five meteorological zones. In genera l, the annual removal efficiency of a retention

pond increases as the retention depth increases. Also, treatment efficiency decreases as the

DCIA percentage and non-DCIA curve number incr ease. The removal efficiencies summarized

in these tables are valid for all stormwater constituents since the efficiencies are based upon

retention of a specific runoff volume within the retention pond. As a result, the stated removal

efficiencies are assumed to be valid for all st ormwater constituents, including total nitrogen, total

phosphorus, TSS, and BOD.

A common design requirement for dry retention systems is a retention treatment volume

of 0.5 inch of runoff or 1.25 inches of runoff from the impervious area, whichever is greater.

Based on this criteria, projects with 40% imperv ious area or less will be required to provide

retention for 0.5 inch of runoff, while projects with impervious percentages in excess of 40%

will be regulated by 1.25 inch of runoff from the impervious area.

A summary of calculated annual mass removal efficiencies for a dry retention pond with

a treatment volume equivalent to 0.5-inch of runo ff is given in Table 5-6 for each of the five

meteorological zones over a wide range of DCIA percentages and non-DCIA curve numbers. In

general, annual mass removal efficiencies of 80% or more, as required the Water Resource

Implementation Rule (Chapter 62-40 FAC), are obtained with a treatment volume equivalent to

0.5 inches of runoff only for projects with lo w percentage DCIA and low non-DCIA curve

number values. On a state-wide average, a rem oval efficiency of 80% can only be achieved at

DCIA percentages of 25-35% or less and non-DC IA curve numbers of approximately 45-55 or

less. An example of a development which woul d meet these characteristics is a single-family

residential community constructed on HSG A soils with grass cover in fair to good condition.

All developments with DCIA percentages a nd non-DCIA curve numbers in excess of these

values will fail to meet the 80% removal criteri on with a retention treatment volume equivalent

to 0.5 inch of runoff.

A graphical comparison of estimated annua l pollutant removal efficiencies obtained

using 0.5 inch of dry retention in a hypothetical development with a DCIA percentage of 40%

and a non-DCIA curve number of 70 is given in Figure 5-5. Annual removal efficiencies range

from approximately 58-69% between the five mete orological zones. The lowest annual removal

efficiencies would be obtained in the Panhandle area, with the highest annual removal pollutant

efficiencies achieved in the Central areas.FDEP \ STORMWATER TREATMENT REPORTTABLE 5-6CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFFPanhandle (Zone 1)NONDCIACNPERCENT DCIA51015202530354045505560657075808590951003091.891.588.384.079.575.070.766.662.959.656.553.651.148.746.644.642.841.139.638.13588.289.186.682.878.674.370.166.262.659.356.353.551.048.746.544.642.841.139.638.14084.086.384.481.277.473.469.465.762.259.056.053.350.848.546.444.542.741.139.638.14579.682.981.979.375.972.268.565.061.758.655.753.050.648.446.344.442.741.039.538.15074.879.179.077.074.170.867.464.161.058.055.352.750.448.246.244.342.641.039.538.15570.174.975.674.271.969.166.163.060.157.354.752.350.047.946.044.242.540.939.538.16065.570.471.771.169.467.064.461.759.156.554.151.849.647.645.844.042.440.939.538.16561.065.867.567.666.464.762.560.257.855.553.351.149.147.245.543.842.340.839.438.17056.761.163.163.663.161.960.258.356.354.352.350.348.546.845.143.542.140.739.438.17552.756.658.659.359.358.657.556.054.452.751.049.347.746.144.643.241.840.539.338.18049.152.254.155.055.254.954.253.252.150.849.448.046.645.344.042.741.540.339.238.18546.148.349.750.550.850.850.549.949.248.347.346.345.244.243.142.141.040.039.138.19043.544.845.646.146.446.546.446.145.745.244.644.043.342.641.941.140.439.638.938.19541.141.541.841.942.042.142.041.941.841.641.341.140.840.440.139.739.338.938.538.19839.839.839.839.839.839.739.739.639.539.439.339.239.139.038.938.738.638.438.338.1 

# 5-19FDEP \ STORMWATER TREATMENT REPORTTABLE 5-6 -- CONTINUEDCALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFFCentral (Zone 2)NONDCIACNPERCENT DCIA51015202530354045505560657075808590951003097.096.794.891.787.983.879.775.771.968.465.262.159.456.954.552.350.348.446.745.13595.295.593.890.987.383.479.375.471.768.365.062.159.356.854.452.350.348.446.745.14092.994.092.589.986.582.778.975.171.468.064.961.959.256.754.452.250.248.446.745.14590.291.990.988.685.581.978.274.671.167.764.661.759.156.654.352.250.248.446.745.15086.789.288.987.084.280.977.473.970.567.364.361.558.956.554.252.150.248.346.645.15582.786.186.484.982.679.676.473.169.966.863.961.258.656.354.152.050.148.346.645.16078.582.683.482.580.678.075.172.169.166.163.460.858.356.053.951.950.048.246.645.16574.278.679.879.578.176.073.570.768.065.362.760.257.955.753.651.749.948.246.645.17069.874.275.876.075.273.571.469.166.664.261.859.557.355.353.351.449.748.146.545.17565.469.671.471.971.570.468.866.964.962.760.658.656.654.752.851.149.547.946.545.18061.464.966.667.367.266.565.564.162.560.859.057.355.553.952.250.749.247.746.445.18557.660.161.662.262.362.061.360.459.358.156.855.454.052.751.350.048.747.446.245.19054.155.456.256.756.856.756.455.955.254.553.652.851.850.949.948.947.946.946.045.19550.150.550.750.850.850.850.650.450.249.949.549.148.748.247.747.246.746.145.645.19847.847.747.747.647.647.547.447.247.146.946.846.646.546.346.145.945.745.545.345.1 

# 5-20FDEP \ STORMWATER TREATMENT REPORTTABLE 5-6 -- CONTINUEDCALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFFFlorida Keys (Zone 3)NONDCIACNPERCENT DCIA51015202530354045505560657075808590951003087.689.187.684.881.577.874.370.967.864.962.159.657.255.052.951.049.247.646.044.53583.586.585.683.480.477.073.670.467.464.561.959.457.054.952.851.049.247.546.044.54079.383.583.481.779.176.072.969.866.964.261.659.156.954.752.750.949.147.546.044.54574.980.380.979.777.674.972.069.166.463.761.258.956.654.652.650.849.147.545.944.55070.576.778.177.675.973.570.968.365.763.260.858.556.454.452.550.749.047.445.944.55566.372.975.075.173.971.969.667.364.962.660.358.156.154.152.350.648.947.445.944.56062.168.971.772.471.670.168.266.164.061.859.757.755.753.852.150.448.847.345.944.56558.064.968.169.369.168.066.564.762.860.959.057.155.253.551.850.248.747.245.844.57054.460.964.265.866.265.664.563.061.559.858.156.354.653.051.449.948.547.145.844.57551.157.060.462.262.962.762.161.059.858.456.955.453.952.451.049.648.347.045.744.58048.553.556.558.359.159.359.158.557.656.655.454.252.951.650.449.247.946.845.644.58546.750.352.754.255.155.555.655.354.954.253.452.651.650.649.648.547.546.545.544.59045.447.649.150.251.051.451.751.751.551.250.850.349.749.048.347.646.846.145.344.59544.845.646.246.747.147.347.547.647.647.547.447.247.046.746.446.145.745.344.944.59845.245.345.445.445.545.545.545.645.545.545.545.445.345.345.245.044.944.844.744.5 

# 5-21FDEP \ STORMWATER TREATMENT REPORTTABLE 5-6 -- CONTINUEDCALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFFCoastal (Zone 4)NONDCIACNPERCENT DCIA51015202530354045505560657075808590951003094.094.292.188.884.880.576.372.468.665.262.059.156.453.951.749.547.645.844.142.63591.192.390.787.784.079.975.972.068.465.061.959.056.353.951.649.547.645.844.142.64087.890.088.986.482.979.175.371.568.064.761.658.856.253.851.549.447.545.744.142.64584.087.286.884.781.678.174.570.967.564.361.358.656.053.651.449.447.545.744.142.65079.984.084.382.780.176.973.570.266.963.961.058.355.853.551.349.347.445.744.142.65575.680.481.480.478.275.472.369.266.263.360.557.955.553.251.149.247.345.644.042.66071.376.578.177.675.973.670.968.065.262.559.957.455.153.050.949.047.245.644.042.66567.172.474.474.573.371.469.166.664.161.659.256.954.752.650.648.847.145.544.042.67063.068.170.370.870.268.967.064.962.760.558.356.154.152.150.348.646.945.443.942.67559.263.765.966.766.665.764.462.760.959.057.155.253.351.549.848.246.745.243.842.68055.859.461.462.362.461.961.159.958.657.155.553.952.350.749.247.846.445.043.842.68552.755.256.757.557.757.657.156.455.554.553.352.150.849.648.347.145.944.743.642.69049.751.152.052.552.852.852.652.251.751.150.349.648.747.947.046.145.244.343.442.69546.747.147.447.547.647.647.547.347.146.846.546.245.845.444.944.544.043.543.042.69844.944.944.844.844.744.744.644.544.344.244.144.043.843.643.543.343.142.942.742.6 

# 5-22FDEP \ STORMWATER TREATMENT REPORTTABLE 5-6 -- CONTINUEDCALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFFSoutheast Coastal (Zone 5)NONDCIACNPERCENT DCIA51015202530354045505560657075808590951003088.689.987.984.580.576.472.368.565.161.958.956.253.751.449.347.345.543.842.240.83584.186.885.682.879.375.471.668.064.661.558.756.053.651.349.247.345.543.842.240.84079.383.382.980.877.874.370.767.364.161.158.355.853.451.149.147.245.443.842.240.84574.479.580.078.576.072.969.666.563.460.657.955.453.151.048.947.145.343.742.240.85069.775.576.876.073.971.368.465.562.660.057.455.052.850.748.847.045.343.742.240.85565.271.473.473.171.769.566.964.361.759.256.954.652.550.448.646.845.243.642.140.86061.067.269.770.169.267.465.363.060.658.456.254.052.050.148.346.645.043.542.140.86557.163.165.966.866.465.163.361.459.457.355.353.451.549.748.046.444.943.442.140.87053.659.262.063.263.362.561.259.657.956.154.352.650.949.247.646.144.743.342.040.87550.755.558.159.559.859.458.657.456.154.653.151.650.148.647.145.844.443.241.940.88048.352.054.355.556.056.055.654.853.952.851.650.349.047.846.545.344.143.041.840.88546.248.750.551.552.052.252.151.751.150.449.648.647.646.745.644.643.742.741.740.89044.245.646.747.447.948.148.248.147.847.446.946.445.745.144.443.743.042.241.540.89542.543.043.443.743.944.044.144.144.043.943.743.543.243.042.742.342.041.641.240.89842.142.242.242.242.242.242.242.142.142.041.941.841.741.641.541.441.241.140.940.8 

# 5-23

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-24Zone 1Zone 2Zone 3Zone 4Zone 5Treatment Efficiency (%)



# 50 55 60 65 70 75

Mean



# Figure 5-5. Calculated Annual Mass Removal E fficiencies for 0.5 inch of Dry Retention for

a Development with 40% DCIA and a non-DCIA Curve Number of 70.

Isopleths for state-wide average removal effi ciencies using 0.5 inch of dry retention for

various DCIA percentages and non-DCIA curve numbers are illustrated on Figure 5-6 based on

the combined data set for the 45 meteorological st ations with hourly precipitation data. At low

values for DCIA and non-DCIA curve numbers, rem oval efficiencies approach or exceed 80%.

However, as the DCIA percentage and non-DCIA curve number increase, the removal efficiency

for 0.5 inch of dry retention decreases rapidly.

For projects with impervious percentages in excess of 40%, the retention design criterion

within the St., Johns River (for off-line system) and South Florida Water Management Districts

becomes 1.25 inch of runoff from the impervious area. For a project with an impervious

percentage of 80%, which is near the upper e nd of impervious coverage allowed under most

zoning regulations, the required retention depth would be:

Retention Depth = 1.25 inches x 0.8 = 1.00 inch

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-25

50

60

70

80

90



# Curve Number (CN) 30 40 50 60 70 80 90Percent DCIA (%)



# 10 20 30 40 50 60 70 80 90 100

40

50

60

70

80

90

100 Percent

Removal



# Figure 5-6. State-wide Average Removal Effi ciencies for 0.5 inch of Dry Retention

for Various DCIA Percentages and non-DCIA Curve Numbers.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-26

Calculated annual mass removal efficiencies for a dry retention pond with a treatment

volume equivalent to 1 inch of runoff are al so listed in Appendix D. Assuming that the

impervious area is 100% directly connected, the estimated annual mass removal efficiencies for

this system are provided for each of the five meteorological zones in the column designated 80%

DCIA. In general, the highest estimated annual mass removal efficiencies would occur on a

project site with a low non-DCIA curve numbe r, while the lowest anticipated annual mass

removal efficiencies would occur in a system constructed with a high non-DCIA curve number.

Estimated annual mass removal efficiencies for a tr eatment system with 1 inch of retention range

from approximately 67.2-75.9% depending upon the pa rticular meteorological region within the

State. The highest estimated annual removal effi ciencies appear to occur in the central and

coastal areas, with the lowest annual mass removal efficiencies occurring in the southeast coastal

and panhandle areas of the State.

In summary, with the exception of projects constructed on highly permeable soils with

low impervious percentages, current design crite ria based on retention of the first 0.5-inch of

runoff or 1.25 inches from the impervious area fail to meet the target annual mass pollutant

removal efficiency of 80% for stormwater mana gement systems outlined in the Water Resource

Implementation Rule (Chapter 62-40 FAC). A nnual mass removal efficiencies for retention

systems vary substantially within the State of Florida between the designated meteorological

zones.

The SJRWMD requires additional dry reten tion treatment volume when the retention

pond is constructed as an on-line system. Fo r on-line systems, the SJRWMD design criteria

become either (1) 1-inch of runoff over the entir e site; or (2) 1.25-inch over the impervious area

plus 0.5-inch over the entire site, whichever is greater. Estimated removal efficiencies for

projects utilizing 1 inch of dry retention are su mmarized in Appendix D.1. Virtually all of the

SJRWMD is located in the central zone (Zone 2) . As seen in Appendix D.1., an annual removal

efficiency of 80% can be achieved using 1 inch of dry retention for most projects with a DCIA

percentage of approximately 60-65% or less and a non-DCIA curve number of 80 or less. If the

site contains an impervious percentage in excess of 40%, the SJRWMD design criteria become

1.25-inch over the impervious area plus 0.5-inch over the entire site. Assuming a worst case

impervious percentage of approximately 80%, th is design criterion is equal to approximately 1.5

inch of dry retention. As seen in Appendix D.1, 1.5- inch of dry retention in Zone 2 is capable of

providing the required 80% annual mass removal effi ciency for all combinations of DCIA and

non-DCIA curve number. This design criterion is the only current water management district

dry retention design which meets the 80% annual load reduction goal for all possible

combinations of DCIA and CN values.

5.2.1.3 Design Criteria Based on Runoff

from a Specified Rainfall Event

Design criteria for retention basins in th e Suwannee River and Southwest Florida Water

Management Districts are referenced in terms of the runoff generated by a specific rainfall event,

typically a 1-inch event. An evaluation of the an ticipated annual performance efficiency of retention

basins which are designed to provide treatment of runoff from a 1-inch rain event was performed

using the continuous simulation methodology discussed previously.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-27

A summary of calculated annual mass removal efficiencies of dry retention ponds with a

treatment volume equivalent to the runoff from 1 inch of rainfall is given in Table 5-7. In general,

the performance efficiency of retention ponds desi gned to this criterion appear to be relatively

constant for each of the evaluated combinations of DCIA and curve number, compared with the

trend of decreasing performance efficiency with increases in DCIA percentage and non-DCIA curve

numbers observed for treatment systems designed acco rding to a specified runoff volume. It is

interesting to note that the anticipated removal effici ency of the dry retention system increases as the

impervious percentage increases. This phenom enon occurs because the generated runoff volume

from 1 inch of rainfall, which dictates the desi gn treatment volume, increases as the percentage

DCIA increases. As a result, removal efficiencies remain relatively constant, since the treatment

volume changes in response to changes in project characteristics. The maximum anticipated

removal efficiencies which can be achieved using a dry retention system with a treatment volume

equivalent to 1 inch of rainfall are approximately 54-61%.

A graphical comparison of calculated annual ma ss removal efficiencies for dry retention of

the runoff from 1 inch of rainfall for a hypotheti cal development with 40% DCIA and a non-DCIA

curve number of 70 is given in Figure 5-7 for each of the five zones. Estimated annual mass

removal efficiencies for this design range from approximately 50-57%, with the lowest removal

efficiencies obtained in the Panhandle zone and the higher removal efficiencies obtained in the

Central zone. This design criterion also falls short of the 80% pollutant removal efficiency specified

by the Water Resource Implementation Rule (Chapter 62-40).Zone 1Zone 2Zone 3Zone 4Zone 5Treatment Efficiency (%)



# 40 45 50 55 60 65

Mean



# Figure 5-7. Calculated Annual Mass Removal Effi ciencies for Dry Retention of the Runoff

from 1 inch of Rainfall for a Development with 40% DCIA and a non-DCIA

Curve Number of 70.FDEP \ STORMWATER TREATMENT REPORTTABLE 5-7CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUMEEQUIVALENT TO THERUNOFF FROM 1 INCH OF RAINFALLPanhandle (Zone 1)NONDCIACNPERCENT DCIA05101520253035404550556065707580859095100300.916.629.438.845.850.953.852.852.652.853.353.954.354.053.953.954.154.354.454.354.2351.416.829.438.845.850.953.552.752.552.753.253.954.253.953.853.954.154.354.454.354.2402.017.129.538.945.850.953.152.452.352.653.153.854.153.953.853.954.054.354.454.354.2452.917.529.638.945.850.952.652.152.152.453.053.754.053.853.753.854.054.354.454.354.2504.018.029.839.045.851.052.051.751.852.252.953.653.853.653.653.854.054.254.354.354.2555.218.630.139.145.851.051.351.251.452.052.753.553.653.553.553.753.954.254.354.254.2606.819.530.539.345.950.850.450.651.051.752.553.353.453.353.453.653.854.254.354.254.2658.720.531.039.546.049.449.549.950.551.352.253.153.053.153.253.553.854.154.254.254.27011.021.931.739.946.347.748.349.150.050.951.952.752.752.853.053.353.754.054.254.254.27513.923.832.840.544.746.047.148.249.350.551.652.152.252.552.853.153.554.054.154.154.28018.026.734.540.042.544.345.847.248.649.951.051.351.752.052.552.953.453.954.054.154.28523.830.935.138.340.943.044.846.448.049.349.950.551.051.552.152.653.253.753.854.054.29030.033.536.438.941.042.944.746.447.348.249.049.750.451.151.752.453.053.453.753.954.29539.240.942.243.344.345.346.247.047.848.649.350.050.751.352.052.552.853.253.653.954.29847.247.748.248.749.149.650.050.450.851.251.651.952.252.452.753.053.253.553.754.054.2 

# 5-28FDEP \ STORMWATER TREATMENT REPORTTABLE 5-7 -- CONTINUEDCALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUMEEQUIVALENT TO THERUNOFF FROM 1 INCH OF RAINFALLCentral (Zone 2)NONDCIACNPERCENT DCIA05101520253035404550556065707580859095100300.516.130.041.049.255.560.559.859.259.259.660.260.960.960.660.560.660.861.161.161.0350.916.330.141.049.255.560.559.759.159.159.560.160.960.860.660.560.660.861.161.161.0401.416.630.141.049.255.560.559.559.059.059.560.160.960.860.660.560.660.861.161.161.0452.016.930.341.049.255.560.559.258.858.959.460.060.860.760.560.460.560.861.061.161.0502.817.430.541.149.255.559.958.958.558.759.259.960.860.660.460.460.560.761.061.161.0553.817.930.741.249.355.659.358.458.258.559.159.860.760.560.360.360.560.761.061.161.0605.018.731.141.449.455.658.457.957.858.258.959.760.660.360.260.260.460.761.061.161.0656.719.731.741.749.555.757.457.257.457.958.659.560.360.160.060.160.360.661.061.161.0708.921.232.442.149.855.856.256.356.857.558.359.360.059.859.860.060.260.560.961.061.07511.823.233.642.750.154.454.755.356.056.957.959.059.559.559.659.860.160.560.961.061.08016.126.235.543.750.651.952.954.055.156.257.458.658.859.059.259.559.960.360.860.961.08522.531.038.845.047.549.551.152.654.155.556.857.658.058.358.759.259.760.260.760.961.09032.537.541.043.846.248.350.251.953.555.055.756.457.057.658.258.859.460.060.660.861.09542.544.546.448.149.751.152.053.053.854.655.456.156.857.558.158.859.460.060.460.761.09852.753.353.854.354.855.355.856.356.757.257.758.158.559.059.459.760.060.260.560.761.0 

# 5-29FDEP \ STORMWATER TREATMENT REPORTTABLE 5-7 -- CONTINUEDCALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUMEEQUIVALENT TO THERUNOFF FROM 1 INCH OF RAINFALLFlorida Keys (Zone 3)NONDCIACNPERCENT DCIA05101520253035404550556065707580859095100301.315.628.138.045.852.157.256.956.456.356.757.257.958.157.957.857.858.058.258.558.3351.715.828.138.045.852.157.256.656.256.256.557.157.958.057.857.757.858.058.258.558.3402.116.128.238.045.852.157.256.255.956.056.457.057.857.957.757.757.857.958.258.458.3452.616.328.338.145.852.156.655.855.655.856.256.957.757.857.657.657.757.958.258.458.3503.316.628.438.145.852.155.955.355.255.556.156.857.657.757.557.557.757.958.258.458.3554.117.028.638.245.852.155.154.754.855.255.856.657.557.557.457.457.657.858.158.458.3605.117.528.838.345.952.154.154.054.354.955.656.457.357.357.257.357.557.858.158.458.3656.418.229.238.546.052.253.053.353.754.455.256.257.157.057.057.257.457.758.158.458.3708.019.329.738.846.251.351.852.353.153.954.955.956.756.756.857.057.357.658.058.358.37510.320.930.639.246.449.350.351.352.353.354.455.656.256.356.556.857.157.558.058.358.38013.823.332.140.045.247.248.750.051.352.653.955.155.555.856.156.556.957.457.958.258.38518.927.234.839.842.845.147.048.750.351.853.254.254.655.155.656.156.757.257.858.158.39027.632.336.139.241.844.146.147.949.651.352.253.053.754.455.055.756.457.057.658.058.39537.539.741.743.545.346.948.149.150.151.051.952.753.454.254.955.656.357.057.657.958.39848.649.249.850.451.051.652.152.753.253.754.354.855.255.756.256.757.157.457.758.058.3 

# 5-30FDEP \ STORMWATER TREATMENT REPORTTABLE 5-7 -- CONTINUEDCALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUMEEQUIVALENT TO THERUNOFF FROM 1 INCH OF RAINFALLCoastal (Zone 4)NONDCIACNPERCENT DCIA05101520253035404550556065707580859095100300.716.329.940.348.054.058.657.356.856.957.358.058.758.458.258.258.358.558.858.758.6351.116.529.940.348.054.058.357.156.756.857.257.958.758.458.258.258.358.558.858.758.6401.716.830.040.348.054.057.956.856.556.757.257.858.658.358.158.158.258.558.858.758.6452.417.130.140.348.054.057.556.556.356.557.157.858.658.258.158.158.258.558.858.758.6503.317.630.340.448.154.056.956.156.056.356.957.758.458.158.058.058.258.458.858.758.6554.418.230.640.548.154.056.155.655.756.156.757.558.257.957.957.958.158.458.758.758.6605.719.031.040.748.254.055.355.055.255.856.557.458.057.857.757.858.158.458.758.658.6657.420.031.540.948.354.154.354.354.855.456.357.257.757.557.657.758.058.358.758.658.6709.521.432.241.348.652.953.153.554.255.056.057.057.357.357.457.657.958.258.658.658.67512.423.433.341.948.951.051.752.553.554.555.656.756.856.957.157.457.758.258.658.658.68016.626.335.142.847.248.950.151.452.653.955.156.056.256.456.857.257.658.058.558.558.68522.830.938.342.244.846.948.650.251.853.254.655.055.455.856.356.857.457.958.358.458.69031.635.839.141.844.146.248.149.851.452.553.253.954.655.255.956.557.157.758.158.358.69541.343.244.946.547.948.949.950.851.652.453.253.954.655.355.956.657.257.657.958.358.69850.751.351.852.352.853.353.754.254.655.155.556.056.456.857.157.357.657.858.158.358.6 

# 5-31FDEP \ STORMWATER TREATMENT REPORTTABLE 5-7 – CONTINUEDCALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION PONDWITH A TREATMENT VOLUMEEQUIVALENT TO THERUNOFF FROM 1 INCH OF RAINFALLSoutheast Coastal (Zone 5)NONDCIACNPERCENT DCIA05101520253035404550556065707580859095100301.115.928.437.945.050.554.954.053.653.654.054.555.255.254.954.955.055.155.455.555.3351.616.128.437.945.050.554.753.753.453.453.954.455.255.154.954.854.955.155.455.555.3402.316.428.537.945.050.554.253.353.153.353.754.455.155.054.854.854.955.155.455.555.3453.116.828.637.945.050.553.652.952.853.153.654.255.054.954.754.754.955.155.455.455.3504.017.228.838.045.050.552.852.452.452.853.454.154.954.754.654.654.855.055.355.455.3555.217.829.138.145.050.552.051.852.052.553.253.954.754.554.554.554.755.055.355.455.3606.418.629.438.245.150.551.051.151.552.152.953.754.454.354.354.454.754.955.355.455.3658.019.629.938.545.249.750.050.451.051.752.653.554.154.054.154.354.654.955.255.455.37010.220.930.738.945.548.148.849.550.451.352.353.353.753.753.954.154.454.855.255.355.37513.022.931.839.545.046.447.548.649.750.851.953.053.253.353.653.954.354.755.155.355.38016.925.733.540.042.744.646.147.548.950.251.552.352.652.953.353.754.154.655.155.255.38522.529.734.938.341.043.145.046.648.149.650.851.351.852.352.853.453.954.555.055.255.39029.132.936.038.640.942.944.746.447.948.949.750.451.151.852.453.153.754.354.855.155.39538.440.141.843.444.545.546.547.448.249.049.850.551.251.952.553.253.854.354.755.055.39847.447.948.448.949.449.950.450.851.351.752.152.653.053.453.854.154.354.654.855.155.3 

# 5-32

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-33

A comparison of annual mass removal efficien cies for dry retention systems designed for

treatment of 0.5 inch of runoff or the runoff from 1 inch of rainfall, based upon a hypothetical

development with 40% DCIA and a non-DCIA curve number of 70, is given in Figure 5-8. For each

of the five meteorological zones, dry retention treatment for 0.5 inch of runoff provides a higher

level of annual mass removal than criteria designed to treat the runoff from 1 inch of rainfall on the

developed site.Zone 1Zone 2Zone 3Zone 4Zone 5Treatment Efficiency (%)



# 40 45 50 55 60 65 70 75

Treatment for Runoff from 1.0-Inch of Rainfall

Treatment for 0.5-Inches of Runoff



# Figure 5-8. Comparison of Annual Mass Removal Efficiencies for Dry Retention Systems

Designed for Treatment of 0.5 inch of Runoff or the Runoff from 1 inch of Rainfall.

5.2.2 Wet Detention

Wet detention stormwater treatment system s are referenced by the St. Johns River,

Suwannee River, Southwest Florida, and South Fl orida Water Management Districts. However,

detailed design criteria which references residence time and pond depth are provided by only the St.

Johns River and South Florida Water Management Di stricts. The design criteria established by the

St. Johns River Water Management District provi des for wet detention ponds with relatively short

residence times, typically ranging from 14-21 days , during wet season conditions. Ponds designed

in the St. Johns River Water Management District are also relatively shallow, with a maximum

depth of 12 ft. The South Florida Water Management District does not reference a specific criterion

for residence time. However, the District reco mmends that 25-50% of the pond area be greater than

12 ft in depth which tends to create ponds with substantially longer residence times than those

designed within the St. Johns River Water Management District.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-34

Each of the four water management district s mentioned previously provides calculations for

a treatment volume associated with the wet dete ntion system. This treatment volume is often

referred to as the “water quality volume” since the criteria are similar to the water quality treatment

criteria for dry retention or dry detention. Ho wever, research on wet detention ponds clearly

indicates that the most significant factor impacti ng the performance efficiency of a wet detention

pond is the residence time within the system - sp ecifically, the volume of the permanent pool with

respect to the volume of runoff entering the pond (Toet, et al., 1990; Harper and Herr, 1993;

Rushton, et al., 1995; and DB Environmental, 2005). Since the specified treatment volumes are

negligible in comparison to the permanent pool volume contained within the wet detention pond, the

treatment volume criteria primarily regulates the drawdown characteristics of the wet detention pond

and has little impact on the overall water quality performance efficiency of the system.

Residence time within a wet detention pond is determined by the relationship between

the permanent pool volume and the annual runoff inputs, as follows:

where:

PPV = permanent pool volume (ac-ft)

RO = annual runoff inputs (ac-ft/yr)

For purposes of this calculation, the permanent pool volume is considered to include the total

volume of water within the pond below the control elevation.

Criteria related to residence time and pond dept h are not included in specific design criteria

outlined by the Suwannee River or Southwest Florida Water Management Districts. Wet detention

ponds designed in these districts could conceivabl y have a wide range of detention times and

associated performance efficiencies, with some ponds approaching design criteria similar to that

used in the St. Johns River Water Management Di strict and other ponds approaching design criteria

utilized in the South Florida Water Management District. As a result, estimates of the anticipated

performance efficiency of wet detention systems designed in the St. Johns River and South Florida

Water Management Districts will be presented in this section, with the anticipated efficiency of wet

detention systems designed in the Suwannee River and Southwest Florida Water Management

Districts likely to fall somewhere in between. year days 365

x RO PPV

= (days) t Time, Detention

d

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-35

5.2.2.1 SJRWMD Design Criteria

Wet detention ponds designed according to St . Johns River Water Management District

(SJRWMD) criteria are characterized by relatively short residence times, ranging from

approximately 14-21 days under wet season conditions . Virtually all existing research studies on

wet detention systems, as summarized in Table 5-2, have been performed on shallow ponds with

relatively short residence times. Six of the eight studies summarized in Table 5-2 are located in the

St. Johns River Water Management District, although designs for some of the earlier studies may be

different from current design criteria.

A summary of estimated performance effi ciencies of wet detention ponds designed

according to SJRWMD criteria is given in Table 5-8. The values summarized in this table reflect the

overall mean treatment efficiencies for wet deten tion systems summarized in Table 5-2. The values

summarized in Table 5-8 correspond closely to perf ormance efficiencies measured by Harper and

Herr (1993) for a wet detention pond constructed according to SJRWMD criteria. Based upon the

estimated performance efficiency summarized in Ta ble 5-8, with the possibl e exception of TSS, wet

detention ponds designed according to SJRWMD criteria fail to meet the 80% removal criteria

outlined in Chapter 62-40.

TABLE 5-8

ESTIMATED PERFORMANCE EFFICIENCY

OF WET DETENTION PONDS DESIGNED

ACCORDING TO SJRWMD CRITERIA

PARAMETER ANNUAL MASS REMOVAL

(%)

Total N 25

Total P 65

TSS 75-85

BOD 65-70



# 5.2.2.2 SFWMD Design Criteria

As discussed in a previous section, wet dete ntion systems designed within the South Florida

Water Management District (SFWMD) are often excav ated to water depths of 20 ft or more. The

SFWMD does not have any specific limitation on pond depth, and developers often dig deep wet

detention ponds to provide additional fill for low ar eas within a development. This technique can

result in ponds with substantially extended detention times, often in excess of 200 days.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-36

Although more research has been performed on wet detention systems than other stormwater

management systems used within the State of Florid a, relatively few of these studies have evaluated

the relationship between detention time and performan ce efficiency of the system. Only three of the

studies summarized in Table 5-2 provide measurem ents of performance efficiency at designated

detention times within the pond. The remaining studi es lack either basic bathymetric information on

the pond or estimates of annual r unoff inputs, both of which are necessary to estimate pond detention

time. Studies summarized in Table 5-2 which provide information on pond detention time are

generally limited to a maximum residence time of 14 days. Virtually no si gnificant research has

been conducted specifically on wet detention ponds with extended residence times in excess of 100-

200 days similar to those constructed in the South Florida Water Management District.

A number of urban lakes which serve as regiona l wet detention facilities have been evaluated

by ERD as part of water quality improvement or stormwater management projects. Detailed

hydrologic and nutrient budgets were performed on each of these waterbodies which typically

included direct measurements of hydrologic inputs, characterization of stormwater inputs, evaluation

of inputs from groundwater seepag e and bulk precipitation, and evaluation of the fate of nitrogen

and phosphorus inputs into these systems. Each of these studies included an estimate of the mean

annual residence time within the waterbody, along w ith an estimate of annual mass removal for both

nitrogen and phosphorus. Estimated detention times for the waterbodies evaluated in these studies

range from 49-769 days. Since the evaluated wa terbodies function as regional wet detention

facilities, these studies provide useful information on the anticipated performance efficiency of wet

ponds under extended detention time conditions.

A summary of studies relating mass removal of nitrogen and phosphorus as a function of

detention time in wet detention pond is given in Ta ble 5-9. The studies summarized in Table 5-2

include research performed by Rushton, et al. (1995) and DB Environmental (2005), along with

additional studies performed by ERD or Harper, et al. on regional wet detention facilities with

extended residence times. Nineteen studies are av ailable which provide simultaneous estimates of

detention time and phosphorus removal, with some of the studies providing data for more than one

detention time. Thirteen studies provide estimates of nitrogen removal as a function of detention

time.

The information contained in Table 5-9 was en tered into a statistical database, and a linear

regression analysis was conducted to evaluate relationships between removal of nitrogen and

phosphorus as a function of residence time within wet ponds. Removal efficiencies for both total

nitrogen and total phosphorus as a function of resi dence time were observed to exhibit curvilinear

relationships, with a relatively rapid initial rem oval for both nutrients, followed by a slow gradual

increase in removal efficiency over an extended pe riod of time. Various curvilinear models were

evaluated to determine the model which provided the best-fit for the relationship between removal

efficiency and residence time based upon the data set summarized in Table 5-9.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-37

TABLE 5-9

SUMMARY OF STUDIES RELATING MASS

REMOVAL OF NITROGEN AND PHOSPHORUS AS A

FUNCTION OF DETENTION TIME IN WET PONDS

DESCRIPTION DETENTION

TIME

(days) ANNUAL MASS REMOVAL

(%) SOURCE

Total N Total P

Lake Lucerne 105 53 80 ERD (1991)

Tampa Detention Pond 2

5

14 33 1



# 16

63 1 

# 62

57

90 1 

# Rushton, et al. (1997)

Lake Virginia 220 44 85 ERD (2000)

Lake Osceola 102 35 71 ERD (2000)

Lake Maitland 197 35 79 ERD (2000)

Lake Arrowhead 49 52 71 Harper, et al. (2000)

Lake McBride 168 54 76 Harper, et al. (2000)

Lake Tom John 114 34 68 Harper, et al. (2000)

Lake Morton 328 43 83 Harper, et al. (2002)

Lake Holden 427 38 87 ERD (2004)

Melbourne Detention Pond 1

7

14 4

33

36 20

56

65 DB Environmental

(2005)

Lake May 204 39 68 ERD (2007)

Lake Shipp 544 47 87 ERD (2007)

Lake Lulu 464 -- 92 ERD (2007)

Lake Butler 551 -- 91 ERD (2007)

Lake Down 769 -- 97 ERD (2007)

Wauseon Bay 183 -- 77 ERD (2007)

Lake Tibet 298 -- 80 ERD (2007)

Lake Sheen 79 -- 74 ERD (2007)

1. Data outlier, not included in regression analyses



# The relationship between removal efficiency of total phosphorus in wet detention ponds as a

function of residence time is given in Figure 5-9. The removal efficiency of 90% for total

phosphorus with a 14-day residence time, provided by Rushton, et al. (1995), was removed from the

data set as an outlier due to substantially elevated values for the Student T and Cook’s D parameters.

The best-fit relationship for the remaining data was obtained using a second-order relationship

involving the natural log of the detention time. The best-fit equation is provided on Figure 5-9 for

the relationship between removal efficiency and residence time. This equation provides an

extremely good fit between the two variables, with an R 2 

# of 0.897. This value indicates that

residence time explains approximately 90% of the observed variability in removal efficiencies for

total phosphorus in wet detention ponds. The re maining variability is probably explained by

experimental errors involved in the various studies and differences in the chemical composition of

phosphorus species entering the various ponds. In ge neral, phosphorus species such as particulate

phosphorus and soluble reactive phosphorus (SRP) are removed relatively rapidly in wet detention

ponds, while organic phosphorus is removed at a substantially lower rate.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-38



# Detention Time, t

d 

# (days) 0 100 200 300 400 500Removal Efficiency (%)



# 0 20 40 60 80 100



# R 2 = 0.897 2 

# )) (ln( 213

. 0 ) ln( 372

. 6 13

. 40 Removal Percent

d d 

# t t • + • + =

Figure 5-9. Removal Efficiency of Total Phosphorus in Wet Detention Ponds as a

Function of Residence Time.

The relationship indicated on Figure 5-9 s uggests that removal of phosphorus in wet

detention ponds continues to occur, although at a progressively slower rate, with increases in

residence time within the system. A removal effici ency of 80% can be achieved at a detention time

of about 200 days. The upper limit for removal effi ciencies in wet detention ponds appears to be

approximately 90%, although removal efficiencies in excess of 90% were achieved at extended

detention times in three of the 20 studies. At this point, total phosphorus concentrations within wet

detention ponds appear to approach irreducible concentrations which reflect natural background

phosphorus levels in surface waterbodies.

Relationships between detention time and removal efficiencies for total nitrogen in wet

detention ponds are illustrated on Figure 5-10. The data points presented on this figure are based

upon the referenced studies summarized in Table 5- 9. The annual mass removal efficiency of 63%

reported by Rushton, et al. (1995) for a wet pond with a detention time of 14 days and the removal

efficiency of 33% for a 2-day detention time were eliminated from the data set as outliers due to

elevated values for the Student T and Cook’s D parameters.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-39



# Detention Time, t

d 

# (days) 0 100 200 300 400 500 600Removal Efficiency (%)



# 0 20 40 60 80 100

R 2 

# = 0.800 

# ) 38

. 4 ( 75

. 43 Removal Percent

d d



# t t

+ •

=



# Figure 5-10. Removal Efficiency of Total Nitrogen in Wet Detention Ponds as a

Function of Residence Time.

The best-fit for the relationship between rem oval efficiency and detention time for total

nitrogen was obtained using a hyperbolic equation. Th e final version of this equation is summarized

on Figure 5-10. The R 2 

# value of 0.800 suggests that detention time explains approximately 80% of

the observed variability in removal efficiencies for total nitrogen in wet detention ponds. The

remaining variability in removal efficiencies for to tal nitrogen is likely due to variability in methods

of analysis between the listed studies as well as variability in the dominant nitrogen form present in

the stormwater inflows. In general, inorganic forms of nitrogen (ammonia and NO

x 

# ) and particulate

nitrogen are removed relatively rapidly in wet dete ntion ponds. The initial rapid removal of nitrogen

within the first 10-20 days, indicated on Figure 5- 10, is probably a result of the rapid uptake of

inorganic nitrogen and the settling of particulate sp ecies. Other forms of nitrogen, such as organic

nitrogen, are removed at a substantially slower rate and are likely responsible for the dramatic

slowdown in removal efficiency observed for total nitrogen after approximately 20-30 days.

The hyperbolic relationship summarized on Figur e 5-10 indicates that a removal efficiency

of approximately 40% can be achieved for total n itrogen in 50 days, with a maximum efficiency of

approximately 45% at extended detention periods. The lack of additional removal efficiencies for

total nitrogen observed at extended detention times is probably a reflection of either phosphorus

limitation or that irreducible concentrations of total nitrogen have been achieved within the pond.

# FDEP \ STORMWATER TREATMENT REPORT 

# 5-40

The relationships summarized in Figures 5- 9 and 5-10 suggest that wet detention ponds

designed in the South Florida Water Management Di strict with extended detention times in excess

of 200 days are likely to achieve approximately 80-85% removal for total phosphorus and 40-45%

removal for total nitrogen on an annual basis. A lthough the estimated removal efficiencies for total

phosphorus meet the goal of 80% removal for stor mwater management systems outlined in the

Water Resource Implementation Rule (Chapter 62-40 FAC), removal of total nitrogen in wet

detention ponds, even at extended detention periods, still fails to meet the 80% goal.

5.2.3 Dry Detention

As discussed in Section 5.1.3, dry detention syst ems, constructed with or without filtration/

underdrain systems, exhibit highly variable remova l efficiencies which are influenced to a large

extent by the relationships between the seas onal high groundwater table elevation and the pond

bottom. Detention systems which provide infiltra tion for a large portion of the runoff inputs have

exhibited substantially higher removal efficiencies than detention systems which are constructed at

or below the groundwater table elevation. Because of the high degree of variability in removal

efficiencies observed for dry detention systems, th ere is no presumption that these systems will meet

the outlined goals of the Water Resource Implementation Rule for stormwater management systems.

This fact has been recognized by the St. Johns Ri ver and South Florida Water Management Districts

which now discourage the use of dry detention syst ems (with or without filtration/underdrains) in

new development. Since other stormwater manageme nt options are available, such as dry retention

or wet detention, which provide reliable and predicta ble pollutant removal efficiencies, dry detention

systems should be eliminated as a common stormwat er management technique within the State of

Florida.

# FDEP \ STORMWATER TREATMENT REPORT 

# SECTION 6

RECOMMENDED MODIFICATIONS

TO EXISTING STORMWATER

DESIGN CRITERIA

This section provides an analysis of potentia l modifications to existing stormwater design

criteria within the State of Florida to meet the performance objectives outlined in the Water

Resource Implementation Rule (Chapter 62-40 FA C). This rule requires that stormwater

management systems achieve at least an 80% re duction of the average annual load of pollutants

that would cause or contribute to violations of State water quality standards. If the stormwater

management system discharges to a desi gnated OFW or other protected waterbody, the

performance criteria increases to a 95% reduction. Based on the analyses presented in Section

5.2, with the exception of the SMRWMD design criteria for on-line dry retention, existing

stormwater design criteria fail to consistently m eet either the 80% or 95% target goals outlined

in Chapter 62-40.

In addition to modifications required to achieve the 80% and 95% pollutant load

reduction goals, an analysis is also provided in this section of the design criteria necessary to

achieve a condition of no net increase in pollutant loadings for a developed site compared with

loadings which would have reasonably been thought to discharge from the site under predevelopment conditions. Implementation of these criteria would ensure that land developments

do not cause a net degradation of water resources w ithin the State. This objective is supported in

Chapter 62-40.341 in the section titled “Stormwater Management Program”, which states that

“the primary goals of the State’s Stormwater Management Program are to maintain, to the

maximum extent practical, during and after cons truction and development, the pre-development

stormwater characteristics of a site; ...”.

The analyses presented in the subsequent sections are provided for total nitrogen and

total phosphorus which are two of the most common pollutants in urban runoff. Although total

suspended solids (TSS) is also a significant constitu ent in stormwater runoff, the removal of TSS

within stormwater management systems occurs at a much more rapid rate than is commonly

observed for either total nitrogen or total phosphor us. Therefore, if a stormwater management

system provides the required removal efficiency for both total nitrogen and total phosphorus, the

system will easily provide the same pollutant removal efficiency for TSS.

Another common constituent in stormwat er runoff is biochemical oxygen demand

(BOD). Inputs of BOD into surface water can cau se oxygen depletion, resulting in fish kills and

changes in aquatic diversity. Upon entering an aquatic environment, organic matter is rapidly

degraded by a variety of microorganisms within the water. The degradation and removal

processes for BOD in surface waters have b een well documented, and removal of BOD as a

function of time has been shown to observe the following first-order equation:

6-1

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-2

BOD i 

# = BOD

o 

# x exp (-K x t)

where:

BOD

t 

# = BOD at time, t (mg/l)

BOD

o 

# = initial BOD (mg/l)

t = time (days)

K = decomposition constant (time -1 

# )

BOD decomposition constants (K) in surface waters are temperature-dependent but are

typically on the order of 0.1/day. A graphical re presentation of the theoretical removal of BOD

as a function of time, based upon a decomposition constant of 0.1/day, is given in Figure 6-1.

This relationship can be used to estimate the time required to achieve a certain BOD removal

efficiency within a wet detention pond. A removal efficiency of approximately 80% is achieved

for BOD after a residence time of approximately 15 days, with removal efficiencies in excess of

95% after approximately 30-35 days. As a result, the removal of BOD in aquatic systems occurs

at a much more rapid rate than removal of to tal nitrogen or total phosphorus, as indicated in

Figures 5-10 and 5-11. Therefore, if a stormw ater management system provides the required

removal efficiency for both total nitrogen and total phosphorus, the system will also easily

provide the same pollutant removal efficiency for BOD.



# BOD Removal

0 10 20 30 40 50 60 70 80 90 100

0 5 10 15 20 25 30 35

Residence Time (days)Percent Removal



# Figure 6-1. Theoretical Removal of BOD as a Function of Residence Time in a

Wet Detention Pond.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-3

The recommended design criteria discussed in this section include only dry retention and

wet detention as potential stormwater manageme nt options. Based on the discussion presented

in Section 5, these systems provide predictable a nd consistent pollutant removal efficiencies for

a wide range of stormwater pollutants. For purposes of this analysis, the term “retention” can be

used to mean a dry pond, swales, underground exf iltration, or any other practice which provides

for recovery of a specified stormwater treatment volume by infiltration into the soil or

evaporation. Dry detention stormwater management systems, either with or without filtration/

underdrains, are not included as a viable stormwater management alternative in this section. As

discussed previously, dry detention systems are characterized by highly variable removal

efficiencies which depend heavily upon construc tion of the system with respect to the

groundwater table elevation. Dry detention sy stems which have performed well in field

evaluations have performed similar to dry reten tion basins, while poor removal efficiencies have

been achieved in dry detention systems with little or no infiltration.

6.1 Design Criteria to Achieve 80% Removal

6.1.1 Dry Retention Systems

Since a first-flush effect is not assumed for this analysis, removal of 80% of the pollutant

mass is achieved by retention of 80% of the annua l runoff volume. Estimates of the retention

volume required to achieve 80% removal of the annual stormwater runoff volume was calculated

for each of the five meteorological zones and a variety of DCIA percentages and non-DCIA

curve numbers. This information was extracted fr om the performance efficiency tables for dry

retention provided in Appendix D which were u tilized to find the required retention depth to

achieve an annual treatment efficiency of 80% or more for each combination of DCIA

percentage and non-DCIA curve numbe r. If the treatment efficiency for a given combination of

retention depth, DCIA percentage, and non-DC IA curve number exceeded 80%, the retention

depth was interpolated using the next lower re tention depth to achieve an estimated annual

treatment efficiency of exactly 80% for each combination of DCIA percentage and non-DCIA

curve number.

A summary of required retention depths to achieve an annual mass removal efficiency of

80% for dry retention systems is given in Table 6-1 for each of the five meteorological zones.

The state-wide average is provided at the top of Table 6-1. On a state-wi de average, retention

depths necessary to achieve an annual removal efficiency of 80% range from 0.22-1.92 inches of

runoff, depending upon the combination of DCIA percentage and non-DCIA curve number. The

retention depths necessary to achieve 80% remova l efficiency are lowest in the Central zone

areas, with the highest retention depths required in the Panhandle areas.

A graphical illustration of state-wide averag e retention depths required to achieve an

80% annual removal efficiency as a function of DCIA percentage and non-DCIA curve number

is given in Figure 6-2. Increases in the DCIA percentage and non-DCIA curve number clearly

result in increases in the required retention depth necessary to achieve an 80% annual mass

removal efficiency.FDEP \ STORMWATER TREATMENT REPORTTABLE 6-1REQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 80%State-Wide AverageNDCIACNPercent DCIA101520253035404550556065707580859095100300.240.280.370.450.510.590.670.750.820.900.981.051.131.211.291.371.441.521.60350.260.300.390.460.530.600.680.750.830.910.981.061.141.211.291.371.451.521.60400.290.330.410.480.540.620.690.770.840.920.991.071.141.221.301.371.451.521.60450.340.370.440.500.560.640.710.780.850.931.001.081.151.231.301.381.451.531.60500.430.440.480.530.590.670.740.800.870.951.021.091.161.241.311.381.451.531.60550.540.520.540.580.640.700.770.830.900.971.041.111.181.251.321.391.461.531.60600.680.620.620.640.690.750.810.860.930.991.061.131.191.261.331.401.461.531.60650.820.740.720.730.770.810.860.910.971.031.091.151.211.281.341.411.471.541.60700.980.880.850.840.860.890.930.971.021.071.131.181.241.301.361.421.481.541.60751.121.040.990.970.970.991.021.051.091.131.181.231.281.331.381.431.491.551.60801.261.191.141.121.111.111.131.151.181.211.241.281.321.371.411.461.501.551.60851.391.331.291.261.251.251.251.261.281.301.331.351.381.421.451.491.521.561.60901.501.461.431.411.401.391.391.391.401.411.421.441.461.481.501.521.551.571.60951.581.561.551.541.531.531.531.531.531.531.531.541.541.551.561.571.581.591.60981.591.591.581.581.581.581.581.581.581.581.581.581.591.591.591.591.601.601.60 

# 6-4FDEP \ STORMWATER TREATMENT REPORTTABLE 6-1 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 80%Panhandle (Zone 1)NDCIACNPercent DCIA101520253035404550556065707580859095100300.250.360.450.520.630.710.800.900.991.081.171.271.361.451.551.641.731.831.92350.290.390.460.540.640.720.820.911.001.091.181.271.371.461.551.641.741.831.92400.350.430.490.580.670.750.840.931.021.111.201.291.381.471.561.651.741.831.92450.440.470.540.620.700.780.870.951.041.131.211.301.391.481.571.661.741.831.92500.560.550.600.670.740.820.900.981.061.151.231.321.411.491.581.661.751.831.92550.710.670.690.740.800.870.951.021.101.181.261.341.431.511.591.671.751.841.92600.890.810.810.830.880.941.011.071.151.221.301.371.451.531.601.681.761.841.92651.070.980.950.960.991.031.081.141.211.271.341.411.481.551.621.701.771.851.92701.241.151.111.101.111.141.181.231.281.341.401.461.521.581.651.721.781.851.92751.421.331.291.271.271.281.301.331.371.421.471.521.571.621.681.741.801.861.92801.581.501.461.431.421.431.441.461.491.521.551.591.631.681.721.771.821.871.92851.731.671.631.601.591.581.591.591.611.631.651.681.711.741.771.801.841.881.92901.851.821.791.771.751.741.741.741.741.751.761.771.791.811.831.851.871.901.92951.941.921.911.901.891.881.881.871.871.871.871.881.881.881.891.901.901.911.92981.941.931.931.931.921.921.921.921.921.921.921.911.921.921.921.921.921.921.92 

# 6-5FDEP \ STORMWATER TREATMENT REPORTTABLE 6-1 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 80%Central (Zone 2)NDCIACNPercent DCIA101520253035404550556065707580859095100300.220.240.320.400.460.510.600.670.730.800.870.941.011.081.151.221.291.361.43350.230.240.330.410.460.520.600.670.730.800.880.941.011.081.151.221.291.361.43400.230.260.350.420.470.530.610.680.740.810.880.951.011.091.161.221.291.361.43450.240.280.370.430.480.550.620.690.740.820.890.951.021.091.161.221.291.361.43500.270.320.390.450.490.570.640.700.760.830.900.961.031.101.161.231.301.371.43550.350.380.420.470.520.590.660.710.770.840.910.971.041.111.171.231.301.371.43600.450.440.460.500.560.620.680.730.800.860.930.981.051.111.181.241.301.371.43650.570.520.530.560.610.660.710.760.830.890.951.001.061.131.191.251.311.371.43700.700.650.630.650.680.720.760.810.870.920.971.031.091.141.201.251.311.371.43750.840.780.760.750.770.800.830.880.920.961.011.061.111.171.221.271.321.381.43800.980.920.900.890.890.910.930.960.991.021.071.111.151.201.241.291.341.381.43851.121.071.041.031.021.031.041.061.081.111.141.171.201.241.271.311.351.391.43901.241.211.191.181.171.171.181.191.201.211.231.251.271.301.321.351.381.401.43951.351.341.331.331.321.321.321.331.331.341.341.351.361.371.381.391.411.421.43981.391.391.391.391.391.391.391.401.401.401.401.411.411.411.421.421.421.431.43 

# 6-6FDEP \ STORMWATER TREATMENT REPORTTABLE 6-1 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 80%Florida Keys (Zone 3)NDCIACNPercent DCIA101520253035404550556065707580859095100300.310.350.430.490.570.650.720.810.890.961.051.131.211.291.371.451.531.621.70350.370.390.450.520.600.670.740.820.910.981.061.141.221.301.381.461.541.621.70400.490.460.500.560.630.700.770.850.920.991.071.151.221.311.391.461.541.621.70450.680.560.560.600.660.730.800.870.941.011.091.171.241.321.391.471.541.621.70500.870.690.640.660.720.780.830.900.971.041.111.181.251.331.401.471.551.631.70551.060.840.760.760.790.830.880.941.011.071.141.201.271.351.421.481.551.631.70601.261.020.910.870.860.890.941.001.051.111.171.231.291.361.431.491.561.631.70651.451.201.071.000.981.001.021.061.101.151.211.261.321.391.441.501.571.641.70701.621.371.251.161.121.101.111.141.171.211.261.301.361.411.461.521.581.641.70751.771.551.421.331.271.241.241.251.261.291.321.361.401.451.491.541.601.651.70801.901.711.591.491.421.381.361.361.361.381.401.431.461.491.531.571.611.651.70851.981.841.721.641.581.541.511.491.491.491.501.511.521.551.571.601.631.661.70902.001.911.831.761.711.671.641.621.611.601.601.601.611.621.631.641.661.681.70951.921.881.841.811.791.771.751.731.711.701.701.691.691.681.681.691.691.691.70981.791.781.771.761.751.741.741.731.721.721.711.711.711.701.701.701.701.701.70 

# 6-7FDEP \ STORMWATER TREATMENT REPORTTABLE 6-1 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 80%Coastal (Zone 4)NDCIACNPercent DCIA101520253035404550556065707580859095100300.230.270.370.440.500.590.670.730.810.890.961.041.121.201.271.351.431.511.59350.240.290.390.450.510.600.670.740.820.900.971.051.131.201.281.361.431.511.59400.260.330.410.460.520.610.690.750.830.910.981.051.131.211.281.361.431.511.59450.310.370.430.480.550.630.700.760.850.920.991.061.141.211.291.361.441.511.59500.400.420.460.510.590.660.720.790.870.931.001.081.151.221.291.371.441.511.59550.510.480.510.560.630.690.750.820.890.951.021.091.161.231.301.371.441.511.59600.650.580.590.630.680.730.780.850.920.981.041.111.181.241.311.381.451.511.59650.800.720.700.710.740.780.840.900.951.011.071.141.201.261.331.391.451.521.59700.960.860.820.810.830.870.910.951.001.051.111.171.221.281.341.401.461.521.59751.101.010.970.950.950.970.991.021.071.111.161.211.261.311.371.421.471.531.59801.241.161.111.091.081.081.101.121.151.191.221.261.301.351.391.441.491.531.59851.361.301.261.231.221.221.231.241.251.281.301.331.361.401.431.471.501.541.59901.471.431.401.381.371.361.361.371.381.391.401.421.441.461.481.501.531.561.59951.541.531.521.511.511.501.501.501.501.511.511.521.521.531.541.551.561.571.59981.561.561.561.561.561.561.561.561.561.561.561.561.571.571.571.581.581.581.59 

# 6-8FDEP \ STORMWATER TREATMENT REPORTTABLE 6-1 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 80%Southeast Coastal (Zone 5)NDCIACNPercent DCIA101520253035404550556065707580859095100300.260.360.440.500.590.680.760.850.931.021.101.191.281.361.451.541.621.711.80350.330.400.460.530.620.700.780.870.951.031.121.201.291.371.461.541.621.711.80400.410.450.500.570.650.730.810.890.971.051.131.221.301.381.461.551.631.711.80450.550.520.560.630.690.760.840.920.991.071.151.231.311.391.471.551.631.721.80500.710.630.650.690.750.810.880.951.031.101.181.251.331.411.481.561.641.721.80550.890.780.760.780.820.870.931.001.061.131.211.281.351.421.501.571.641.721.80601.070.940.890.880.910.951.001.051.111.171.241.311.371.441.511.581.651.731.80651.251.111.041.021.021.041.071.121.171.231.281.341.401.471.531.601.661.731.80701.411.281.201.161.151.151.171.201.241.291.331.391.441.501.561.611.671.741.80751.571.441.361.311.291.281.291.301.331.361.401.441.491.541.581.631.691.741.80801.701.591.521.471.431.411.411.421.431.451.481.511.541.581.621.661.711.751.80851.801.721.661.611.571.551.541.541.541.551.571.591.611.631.661.691.731.761.80901.871.811.771.731.711.691.671.661.661.661.671.671.691.701.721.731.751.771.80951.881.851.841.821.811.791.791.781.771.771.771.771.771.771.771.781.781.791.80981.831.821.821.811.811.811.801.801.801.801.801.791.791.791.791.791.801.801.80 

# 6-9

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-10



# Statewide Mean Retention Depth Needed to Achieve

80% Annual Mass Removal

1.6

1.4

1.2

1.0

0.8

0.6

0.4



# Curve Number (CN) 30 40 50 60 70 80 90Percent DCIA (%)



# 20 40 60 80 100

Retention Depth (inches)



# Figure 6-2. State-wide Average Variati ons in Required Dry Retention Depth for

80% Removal as a Function of DCIA Percentage and non-DCIA

Curve Number.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-11

Variations in required dry retention depth to achieve 80% removal in the Central zone are

illustrated on Figure 6-3 as an example of an area with lower than average retention depth

requirements. Required dry retention depths in the Central zone area range from approximately

0.22-1.43 inches depending upon the combination of DCIA percentage and non-DCIA curve

number. Variations in required dry retention depth to achieve 80% removal in the Panhandle

area are illustrated on Figure 6-4 as an example of an area with higher than average retention

depth requirements. At high values for DCIA percentage and non-DCIA curve number, the

retention depth required to achieve 80% removal is substantially greater in the Panhandle region

than in the Central region. As discussed previ ously, these variations are primarily due to the

differences in the distribution of typical rain events.

A summary of recommended design criteria fo r dry retention ponds to achieve an annual

removal efficiency of 80% is given in Table 6-2. Recovery of the required treatment volume

must be achieved within 72 hours or less, equiva lent to the volume recovery period utilized for

generation of the performance efficiency tables summarized in Appendix D. Ability of the pond

to achieve this recovery rate must be certified by a registered geotechnical engineer. All side

slopes and bottom areas of the pond must be seeded or sodded with water-tolerant grass species

grown on sandy soils. If sod is used as the vegetative cover on the bottom of the pond, changes

in permeability of the basin resulting from the sod must be included in evaluation of the recovery

period for the pond. Inlets and outlets must be lo cated as far apart as possible to prevent shortcircuiting. Oil and grease skimmers must be provided at all outfall structures. Other

requirements related to side slopes, fencing, maintenance berms, and access will adhere to

applicable local agency criteria.

TABLE 6-2

RECOMMENDED DESIGN CRITERIA FOR

DRY RETENTION PONDS TO ACHIEVE 80%

ANNUAL REMOVAL EFFICIENCY

PARAMETER DESIGN CRITERIA

Treatment Volume Selected using Ta ble 6-1 according to meteorological

zone, DCIA percentage, and non-DCIA curve number

Recovery of Treatment Volume 72 hours (certified by registered professional engineer)

Side Slopes and Bottom Seeded or sodded with water-tolerant grass species; if sod

is used, changes in infiltration resulting from the sod must

be considered

Inlet and Outlet Located as far apart as possible to prevent short-circuiting

Oil and Grease Skimmers Provided at outlet structure

Requirements Related to Side Slopes, Fencing,

Maintenance Berms, and Access According to applicable local or regulatory agency criteria

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-12



# Retention Depth Needed to Achieve

80% Annual Mass Removal for Central Areas (Zone 2)

1.4

1.2

1.0

0.8

0.6

0.4



# Curve Number (CN) 30 40 50 60 70 80 90Percent DCIA (%)



# 20 40 60 80 100

Retention Depth (inches)



# Figure 6-3. Variations in Required Dry Retention Depth to Achieve 80% Removal

in the Central Zone Area (Zone 2).

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-13



# Retention Depth Needed to Achieve

80% Annual Mass Removal fo r Panhandle Areas (Zone 1)

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4



# Curve Number (CN) 30 40 50 60 70 80 90Percent DCIA (%)



# 20 40 60 80 100

Retention Depth (inches)



# Figure 6-4. Variations in Required Dry Retention Depth to Achieve 80% Removal

in the Panhandle Zone Area (Zone 1).

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-14

6.1.2 Wet Detention

Wet detention systems provide reliable and pr edictable pollutant removal efficiencies and

can play a significant part in stormwater manage ment for virtually any type of development.

However, as discussed in Section 5.2, wet dete ntion ponds with short detention times (14-21

days) fail to achieve the 80% pollutant removal efficiency for either total nitrogen or total

phosphorus. Wet detention ponds designed with extended detention periods can achieve the

80% removal criteria for total phosphorus, but will fail to achieve this efficiency for total

nitrogen. Therefore, if 80% removal is necessary for total nitrogen, wet detention ponds must be

used as part of a treatment train approach to achieve the target removal efficiency for both

nitrogen and phosphorus.

A summary of recommended design criteria for we t detention ponds is given in Table 6-3.

Based upon the information presented previously, the most important factor in regulating the

performance efficiency of a wet detention pond is the residence time for runoff inputs within the

system. Assuming that short circuiting does not occu r, residence time is determined primarily by the

permanent pool volume, and this volume becomes the single most important design parameter for

wet detention ponds. The required volume of the permanent pool can be calculated based upon the

removal relationships presented previously in Figures 5-9 (total phosphorus) and 5-10 (total

nitrogen). Design criteria are also listed for the treatment volume, which represents the water

volume stored on top of the permanent pool during an individual rain event. Pond requirements for

treatment volume and recovery time for the treatment volume are based upon current water

management district criteria.

Design criteria for pond depth are based upon the an ticipated depth of the anoxic zone within

the pond based on the anticipated productivity of th e pond. This concept is discussed further in

Section 6.4. No restrictions are placed on the conf iguration of the pond, provided that the inlet and

outlet from the system are located as far apart as possible to maximize travel path. In addition, it is

recommended that at least 20% of the pond surface be planted with a littoral zone consisting of a

combination of submergent and emergent aquatic ve getation. Creation of a littoral zone will create a

more diverse environment and will probably enhance the overall performance efficiency of the wet

detention system.

TABLE 6-3

RECOMMENDED DESIGN CRITERIA

FOR WET DETENTION PONDS

PARAMETER DESIGN CRITERIA

Treatment

Volume 1-inch runoff or 2.5 inch x impervious percent, whichever is greater (current SJRWMD and SFWMD

criteria)

Recovery Time Recover design capacity in 48-72 hours

Permanent Pool Volume based on desired removal efficiency

Pond Depth/

Configuration/

Side Slopes Depth : maximum depth cannot ex ceed anticipated depth of anoxia based on pond productivity

Configuration: no restriction provided that the inlet and outlet are located as far apart as possible

Side Slopes : 4:1 minimum

Littoral Zone At least 20% of the pond surface

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-15

As indicated previously, wet detention system s must be utilized as part of a treatment

train to achieve the required 80% removal efficiency specified under the Water Resource

Implementation Rule (Chapter 62-40). When treatme nt systems are used in series as part of a

treatment train, the efficiency of the overall treat ment train can be calculated using the following

equation:

Overall Treatment Train Efficiency (decimal) = Eff 1 

# + (1 – Eff 1 

# ) x Eff 2 

# (Eq. 1)

where:

Eff 1 

# = efficiency of initial treatment system (decimal)

Eff 2 

# = efficiency of second treatment system (decimal)

After treatment in the initial system, a load reduc tion has occurred which is a function of the type

of treatment provided. After migrating through th e initial treatment system, the remaining load

consists of mass which was not removed in the initial system. This mass is then acted upon by

the second treatment system with an efficiency a ssociated with the particular type of system

used. The overall efficiency can then be calculated according to the above equation.

To achieve an overall annual mass load reduction of 80% using wet detention, a pretreatment system must first be used to provi de a significant portion of the desired pollutant

removal effectiveness. For example, assume that a wet detention pond is designed with a

detention period of approximately 50 days which is sufficient to achieve a removal efficiency of

approximately 40% for total nitrogen. Utilizing the relationship summarized as Eq. 1, and

assuming that the efficiency of the wet detention system for total nitrogen (40%) is represented

by Eff 2 

# , the efficiency of the initial treatment system (Eff 1 

# ) would need to be 67% to achieve an

overall treatment efficiency of 80%.

Depending upon the characteristics of the de velopment and the meteorological region,

achieving an initial 67% annual mass load reduc tion using retention will require between 0.25-

0.75 inch of dry retention as pre-treatment. Wh en pre-treatment is provided and the remaining

stormwater is discharged into the wet deten tion pond, the overall treatment system will achieve a

mass removal efficiency of 80% for total nitr ogen. The mass removal efficiency for total

phosphorus and other significant pollutants will be substantially in excess of 80%.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-16

6.2 Design Criteria to Achieve 95% Removal

6.2.1 Dry Retention

An evaluation of required retention depths to achieve an annual removal efficiency of 95%,

corresponding to the OFW criteria outlined in the Water Resource Implementation Rule (Chapter

62-40), was performed using the same methodology ou tlined previously for evaluation of retention

criteria based upon an 80% annual mass load reducti on. To achieve an annual mass load reduction

of 95%, it is assumed that 95% of the annual runoff volume must be removed by the retention

system. A summary of required retention depths to achieve an annual removal efficiency of 95% for

each of the five zones is given in Table 6-4. Treatment depths necessary to achieve 95% annual

pollutant mass removal range from 2.99-3.98 inches of retention over the project area, based upon

location and variations in DCIA percentage and non-DCIA curve number.

Variations in required dry retention depth to achieve 95% removal on a state-wide average

basis are illustrated on Figure 6-5. The lowest retention depths necessary to achieve 95% annual

mass removal occur at low values for DCIA percen tage and non-DCIA curve number. However, as

DCIA percentages and non-DCIA curve numbers in crease, retention treatment requirements also

increase, approaching values ranging from 3.2-3.4 in ches of retention. Similar to the trends

observed with the analysis for 80% removal, a higher than average retention depth is necessary in

the Panhandle and Florida Keys to achieve a 95% removal, while a lower than average retention

depth would be necessary in Central areas.

6.2.2 Wet Detention

As indicated in previous sections, wet deten tion systems are not capable of providing a 95%

pollutant removal efficiency for either total nitr ogen or total phosphorus, even at extended detention

periods. Therefore, to achieve the 95% removal obj ective for discharges to OFWs, a treatment train

approach must be used with wet detention used in series with a high efficiency pre-treatment

management technique.

To achieve an overall annual mass load re duction of 95% using wet detention, a pretreatment system must be used to provide a significant portion of the desired pollutant removal

efficiency. As an example, assumed that a wet detention pond is designed with a detention period of

approximately 50 days which is sufficient to achieve a removal efficiency of approximately 40% for

total nitrogen. Using the relationship summarized as Eq. 1, and assuming that the efficiency of the

wet detention system for total nitrogen (40%) is represented by Eff 2 

# , the efficiency of the initial

treatment system (Eff 1 

# ) would need to be 92% to achieve an overall treatment efficiency of 95%.

When pre-treatment is provided and the remaining st ormwater is discharged into the wet detention

pond, the overall treatment system will achieve a mass removal efficiency of 95% for total nitrogen.

However, the mass removal for total phosphorus and other significant pollutants will be in excess of

95%.FDEP \ STORMWATER TREATMENT REPORTTABLE 6-4REQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 95%State-Wide AverageNDCIACNPercent DCIA101520253035404550556065707580859095100300.700.770.901.041.191.351.511.671.842.002.162.332.492.662.822.983.133.273.40350.880.911.011.131.271.421.571.721.882.042.202.362.522.682.842.993.143.273.40401.111.081.151.251.371.501.641.791.942.092.242.402.552.702.863.013.153.283.40451.371.291.321.391.491.611.731.872.012.152.292.442.592.732.883.023.153.283.40501.651.531.521.561.641.741.851.962.092.222.352.492.632.772.913.043.163.283.40551.921.781.741.761.811.891.982.082.192.312.432.552.682.812.943.063.183.293.40602.192.041.981.982.002.062.132.212.312.412.512.632.742.862.973.083.193.303.40652.462.302.232.202.212.252.302.362.442.522.612.712.812.913.013.113.213.313.40702.702.562.482.442.442.452.482.532.592.662.732.812.892.983.063.153.233.323.40752.932.812.732.682.662.672.682.712.752.802.862.922.983.053.123.193.263.333.40803.123.032.972.922.892.882.882.902.922.952.993.033.083.123.183.233.293.343.40853.273.213.163.133.103.083.083.083.093.103.123.153.183.213.243.283.323.363.40903.393.353.323.303.283.263.253.253.253.253.263.273.283.293.313.333.353.373.40953.463.443.433.413.403.393.393.383.383.383.373.373.373.383.383.383.393.393.40983.443.443.433.433.423.423.423.423.413.413.413.413.403.403.403.403.403.403.40 

# 6-17FDEP \ STORMWATER TREATMENT REPORTTABLE 6-4 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 95%Panhandle (Zone 1)NDCIACNPercent DCIA101520253035404550556065707580859095100300.820.921.091.281.461.661.862.062.262.462.662.863.063.263.473.653.793.903.95351.111.081.211.371.561.741.932.122.312.512.702.903.093.293.493.663.793.903.95401.431.321.381.511.671.842.022.202.382.572.752.943.133.323.513.683.803.903.95451.751.601.611.701.821.972.132.302.472.642.823.003.183.363.543.693.813.903.95502.061.891.871.932.022.142.282.422.582.742.903.063.233.413.573.713.823.913.95552.362.192.142.182.242.342.452.582.712.853.003.153.303.463.613.733.833.913.95602.642.482.432.442.492.562.652.752.872.993.123.253.393.533.653.763.843.913.95652.912.782.722.722.752.802.862.953.043.153.263.373.493.603.703.783.863.923.95703.183.073.023.013.023.053.103.163.243.323.403.503.593.673.753.813.883.923.95753.463.373.323.303.303.313.343.383.443.503.563.623.683.743.793.843.903.933.95803.723.653.603.583.573.573.583.603.633.673.703.733.773.803.843.883.913.933.95853.833.813.793.783.773.773.773.773.783.793.813.823.843.863.893.913.923.943.95903.923.903.893.893.883.883.883.883.883.893.893.903.903.913.923.933.933.943.95953.963.953.953.953.943.943.943.943.943.943.943.943.943.943.943.953.953.953.95983.963.963.963.963.963.963.953.953.953.953.953.953.953.953.953.953.953.953.95 

# 6-18FDEP \ STORMWATER TREATMENT REPORTTABLE 6-4 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 95%Central (Zone 2)NDCIACNPercent DCIA101520253035404550556065707580859095100300.440.550.690.820.961.111.251.401.541.691.831.982.122.262.412.552.702.842.99350.540.610.740.871.001.141.281.421.561.711.851.992.132.282.422.562.712.852.99400.690.710.810.931.061.191.321.461.601.741.872.012.152.292.432.572.712.852.99450.880.860.911.011.131.251.381.511.641.771.902.042.172.312.452.582.722.852.99501.111.041.061.131.221.331.451.571.691.821.952.072.202.332.462.592.732.862.99551.361.251.231.271.351.431.541.641.761.872.002.122.242.362.492.612.742.862.99601.611.481.441.451.501.571.651.751.841.952.062.172.282.402.522.632.752.872.99651.861.721.661.661.681.731.791.871.952.052.142.242.342.452.552.662.772.882.99702.101.961.891.871.881.911.962.012.082.152.242.322.412.502.602.692.792.892.99752.332.202.132.102.092.112.142.182.232.292.352.422.492.572.652.732.822.902.99802.542.442.372.332.322.322.332.362.392.432.482.532.592.652.712.782.852.922.99852.732.652.602.572.552.542.542.552.572.592.622.662.702.742.792.832.882.942.99902.882.842.812.782.772.762.752.752.762.772.782.802.822.842.872.902.932.962.99953.002.982.972.962.952.942.942.942.942.942.942.942.942.952.952.962.972.982.99983.023.013.013.013.013.003.003.002.992.992.992.992.992.992.992.992.992.992.99 

# 6-19FDEP \ STORMWATER TREATMENT REPORTTABLE 6-4 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 95%Florida Keys (Zone 3)NDCIACNPercent DCIA101520253035404550556065707580859095100302.251.961.711.721.821.962.132.302.482.672.863.053.243.433.593.693.793.883.98352.322.402.102.052.072.152.282.442.602.762.943.123.303.483.603.703.793.883.98402.422.472.552.382.362.382.462.582.732.873.033.193.363.523.613.703.793.893.98452.552.582.622.702.652.642.672.752.873.003.133.283.433.543.623.713.803.893.98502.692.702.732.792.852.902.892.943.033.143.253.383.473.563.643.723.813.893.98552.832.842.862.892.953.003.073.143.213.283.353.433.503.583.663.743.823.903.98602.982.982.993.013.063.103.153.213.283.343.413.473.543.613.683.753.833.903.98653.133.133.123.143.173.213.253.303.353.413.473.523.593.653.713.783.843.913.98703.293.283.263.283.303.333.363.403.443.493.543.593.643.693.743.803.863.923.98753.443.423.413.423.443.453.473.503.543.583.613.653.693.743.783.833.883.933.98803.593.573.573.573.583.593.603.623.653.673.703.733.763.793.823.863.903.943.98853.753.743.733.733.723.723.733.743.763.773.793.813.833.853.873.893.923.953.98903.913.893.883.873.873.873.873.873.873.883.883.893.903.913.923.933.953.963.98953.993.993.993.994.003.993.983.983.983.973.973.973.973.973.973.973.973.973.98984.004.004.004.004.004.004.004.004.003.993.993.993.993.993.983.983.983.983.98 

# 6-20FDEP \ STORMWATER TREATMENT REPORTTABLE 6-4 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 95%Coastal (Zone 4)NDCIACNPercent DCIA101520253035404550556065707580859095100300.620.730.851.001.151.311.471.631.791.952.112.282.442.602.762.933.093.253.41350.830.850.961.091.231.371.521.681.831.992.152.302.462.622.782.943.103.263.41401.091.041.101.211.321.461.601.741.892.042.192.342.492.652.802.953.113.263.41451.381.271.281.351.451.561.691.821.952.102.242.382.532.682.822.973.123.273.41501.681.531.501.531.601.701.801.912.042.172.302.432.572.712.852.993.133.273.41551.981.811.751.741.791.861.942.042.142.252.372.502.622.752.883.013.153.283.41602.272.082.001.981.992.042.102.182.262.362.462.572.692.802.923.043.173.293.41652.552.362.262.222.212.232.282.342.402.482.572.662.762.862.973.083.193.303.41702.822.632.522.472.452.452.472.512.562.622.692.762.852.933.023.123.223.313.41753.062.892.792.722.682.672.682.702.732.772.822.882.943.013.093.163.253.333.41803.253.133.042.972.922.902.892.892.912.932.963.003.053.103.163.223.283.353.41853.423.323.253.203.153.123.103.093.093.103.113.143.163.203.243.283.323.373.41903.533.473.423.383.353.323.293.283.273.263.273.273.293.303.323.343.363.393.41953.563.533.513.493.473.453.443.433.423.413.403.403.403.403.403.403.403.413.41983.493.483.483.473.463.463.453.453.443.443.433.433.433.423.423.423.423.423.41 

# 6-21FDEP \ STORMWATER TREATMENT REPORTTABLE 6-4 -- CONTINUEDREQUIRED RETENTION DEPTHS TO ACHIEVE ANANNUAL REMOVAL EFFICIENCY OF 95%Southeast Coastal (Zone 5)NDCIACNPercent DCIA101520253035404550556065707580859095100301.051.081.191.341.511.681.862.042.222.412.592.782.973.153.343.523.693.803.91351.431.371.421.521.651.811.972.142.312.492.662.833.013.193.373.553.703.803.91401.821.711.701.751.841.962.112.262.412.572.742.903.073.243.403.573.713.813.91452.222.052.012.012.072.152.272.392.532.682.822.983.133.293.443.603.723.813.91502.592.402.322.302.322.372.452.552.672.792.933.063.203.343.493.633.743.823.91552.952.742.642.592.582.602.652.732.822.933.043.163.283.413.543.653.753.833.91603.283.072.952.882.852.852.872.922.993.073.173.273.373.493.593.693.763.843.91653.583.383.253.163.113.093.093.123.163.233.303.393.473.563.643.723.783.843.91703.773.663.533.443.373.333.313.323.353.393.453.513.573.633.703.753.803.853.91753.923.863.753.663.593.553.523.523.533.553.583.623.663.713.753.783.823.863.91803.973.953.923.853.783.723.693.683.683.693.703.733.753.773.793.823.843.883.91854.003.983.973.953.893.863.843.823.813.813.813.813.823.833.843.853.873.893.91904.004.004.003.993.973.953.933.923.913.903.893.893.893.883.883.893.893.903.91954.004.003.993.993.983.973.973.963.953.953.943.933.933.923.923.923.913.913.91983.973.963.963.963.953.953.953.943.943.933.933.933.933.923.923.923.913.913.91 

# 6-22

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-23



# Statewide Mean Retention Depth Needed to Achieve

95% Annual Mass Removal

3.4 3.2

3.0

2.8

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8



# Curve Number (CN) 30 40 50 60 70 80 90Percent DCIA (%)



# 20 40 60 80 100

Retention Depth (inches)



# Figure 6-5. Variations in Required Dry Re tention Depth to Achieve 95% Removal

on a State-wide Basis.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-24

6.3 Design Criteria to Achieve Post-Development

Less Than or Equal to Pre-Development Loadings

An analysis was also performed to provide estimates of the annual mass pollutant removal

efficiencies necessary to achieve no net increa se in pollutant loadings following development

compared with loadings which discharge from the site under pre-development conditions. This

analysis is conducted primarily for nitrogen a nd phosphorus, since systems which achieve post < pre

pollutant loadings for nitrogen and phosphorus will automatically provide this condition for TSS,

BOD, and other significant runoff pollutants.

6.3.1 Estimation of Pre-Development Pollutant Loadings

This analysis assumes that the undeveloped condition consists of brush (brush-weed-grass

mixture), woods, or a mixture of the two. A summary of hydrologic assumptions for this predevelopment condition is given in Table 6-5. For estimation of annual runoff volumes, the

hydrologic condition is assumed to be fair, w ith 50-75% ground cover and litter covering much of

the soil. SCS curve numbers for use in hydrol ogic modeling are assumed for hydrologic soil groups

(HSG) A, B, C, and D using the average curve num bers for brush and wooded areas provided in the

TR-55 publication.

TABLE 6-5

HYDROLOGIC ASSUMPTIONS FOR ESTIMATION OF

RUNOFF AND MASS LOADINGS FROM UNDEVELOPED AREAS

PARAMETER ASSUMED CONDITION / VALUE

Land Use Brush / woods

Hydrologic Condition Fair: 50-75% ground cover, woods not burned, forest litter covers the soil

Curve Number 1 

# HSG A: 35.5 HSG B: 58 HSG C: 71.5 HSG D: 78

1. Average of brush and woods categories



# Calculated annual C values for undeveloped/na tural areas are summarized in Table 6-6 for

each of the regional meteorological zones. Th ese values are calculated using the continuous

simulation technique discussed in Section 4.2 and the hydrologic characteristics listed in Table 6-5.

The mean values summarized at the bottom of Table 6-6 reflect the state-wide mean rather than the

arithmetic mean of the values for each zone. In general, approximately 1.5% or less of the annual

rainfall which occurs on undeveloped/natural ar eas under HSG A conditions becomes stormwater

runoff. Under HSG B conditions, this percentage increases to approximately 4-7%, with 9-13%

under HSG C conditions and 13-18% under HSG D conditions.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-25

TABLE 6-6

ANNUAL C VALUES FOR

UNDEVELOPED / NATURAL AREAS

METEOROLOGICA

L

ZONE ANNUAL C VALUE

HSG A HSG B HSG C HSG D

1 0.015 0.064 0.126 0.176

2 0.006 0.038 0.087 0.128

3 0.015 0.053 0.103 0.142

4 0.010 0.050 0.104 0.149

5 0.018 0.067 0.127 0.173

Mean 1 

# 0.011 0.049 0.103 0.147

1. Reflects state-wide average value



# Estimates of annual runoff depths for undevel oped/natural areas were calculated using the

methodology outlined in Section 4.2.1 for each of the five meteorological zones and four hydrologic

soil groups. A summary of calculated runoff depths for undeveloped/natural areas is given in Table

6-7 for each of the five meteorological zones. Th e runoff depth presented for each zone is calculated

by multiplying the annual C value for each hydrologic soil group (summarized in Table 6-6) times

the mean annual rainfall for each zone. The values summarized in Table 6-7 reflect estimates of the

long-term mean annual runoff depth for undeveloped/na tural areas in each of the five zones based

upon available rainfall data. A relatively high degree of variability is apparent in calculated annual

runoff depths for undeveloped/natural areas in each of the five zones. The degree of variability

appears to be greatest for soils in HSG A, with decreases in variability observed for less permeable

soil types.

TABLE 6-7

CALCULATED ANNUAL RUNOFF DEPTHS

FOR UNDEVELOPED / NATURAL AREAS

METEOROLOGICA

L

ZONE ANNUAL RUNOFF DEPTH (inches) MEAN

RAINFAL

L

(in/yr) HSG A HSG B HSG C HSG D

1 0.91 3.90 7.68 10.73 60.96

2 0.30 1.89 4.33 6.36 49.72

3 0.65 2.30 4.47 6.16 43.41

4 0.52 2.62 5.45 7.81 52.42

5 1.05 3.90 7.39 10.06 58.17

Mean 0.69 2.92 5.86 8.23 52.94

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-26

Estimates of annual mass loadings of nitrogen and phosphorus discharging from

undeveloped/natural areas were generated for each of the hydrologic soil groups and meteorological

zones included in Tables 6-6 and 6-7. The annua l runoff volume generated by each combination of

meteorological zone and hydrologic soil group was cal culated, assuming a theoretical area of 1 acre,

using the annual runoff coefficients summarize d in Table 6-6 and the annual rainfall depth

represented by each meteorological site. The estimated annual runoff volumes were then multiplied

by the assumed runoff characteristics for undevelope d/natural areas summarized in Table 4-17. For

purposes of this analysis, total nitrogen concentr ations in runoff discharging from undeveloped/

natural areas is assumed to be 1.15 mg/l, with a total phosphorus concentration of 0.055 mg/l.

Estimates of the annual mass loadings of n itrogen and phosphorus generated by stormwater

runoff in undeveloped/natural areas are summarized in Table 6-8. Annual mass loads are calculated

for each hydrologic soil group and meteorological z one in terms of kg/acre-year for both total

nitrogen and total phosphorus. The values summarized in this table represent the pre-development

loadings generated by undeveloped/na tural areas for each hydrologic soil group and

meteorological zone. To achieve the goal of no net increase in loadings following development,

discharges of total nitrogen and total phosphorus from the land parcel following development cannot

exceed the pre-development values listed in Table 6-8.

TABLE 6-8

ESTIMATED ANNUAL MASS LOADINGS OF NITROGEN

AND PHOSPHORUS FOR UNDEVELOPED / NATURAL AREAS

METEOROLOGICAL

ZONE ANNUAL TN MASS LOAD

(kg/ac-yr) ANNUAL TP MASS LOAD

(kg/ac-yr)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D



# 1 0.11 0.46 0.91 1.27 0.005 0.022 0.043 0.061

2 0.04 0.22 0.51 0.75 0.002 0.011 0.024 0.036

3 0.08 0.27 0.53 0.73 0.004 0.013 0.025 0.035

4 0.06 0.31 0.64 0.92 0.003 0.015 0.031 0.044

5 0.12 0.46 0.87 1.19 0.006 0.022 0.042 0.057

Mean 0.08 0.35 0.69 0.97 0.004 0.017 0.033 0.046



# 6.3.2 Estimation of Post-Development Pollutant Loadings

When a stormwater management system is designed to provide sufficient treatment so that

the post-development loadings from a parcel are e qual to or less than the pre-development loadings

from the parcel, the post-development loadings would be calculated based upon the specific

hydrologic and land use characteristics of the site, combined with the anticipated pollutant removal

effectiveness of the proposed stormwater treatment option. However, for purposes of this analysis

and to provide estimates of the magnitude of pollu tant removal efficiencies necessary to achieve no

net increase in pollutant loadings following deve lopment, calculations of estimated annual mass

loadings for nitrogen and phosphorus were perfor med for “typical” residential and commercial

developments, including low-density residential, singl e-family residential, high-density residential,

and commercial land use categories.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-27

A summary of hydrologic assumptions used for th e developed land use categories is given in

Table 6-9. The low-density residential areas are assumed to have approximately 15% impervious

area, with 5% of the area as DCIA. Hydrologic characteristics are provided for single-family

residential developments based on 25% impervious and 40% impervious conditions. High-density

residential areas are assumed to be 65% impervi ous, with 80% impervious assumed for commercial

activities. Highway land use categories are al so included, based upon 50% and 75% impervious

assumptions. Curve numbers for pervious areas ar e based on soil types and assumptions regarding

landscaped conditions.

TABLE 6-9

SUMMARY OF HYDROLOGIC ASSUMPTIONS

USED FOR DEVELOPED LAND USE CATEGORIES

TYPICAL

LAND USE PERCENT

TOTAL

IMPERVIOUS

AREA %

DCIA 1 

# CURVE NUMBER (CN)

FOR PERVIOUS AREAS

HSG A HSG B HSG C HSG D

Low-Density Residential 15 5 49 2 

# 69 2 

# 79 2 

# 84 2



# Single-Family Residential

a. 25% impervious

b. 40% impervious 25

40 15

25 39 3



# 39 3 

# 61 3



# 61 3 

# 74 3



# 74 3 

# 80 3



# 80 3



# High-Density Residential 65 50 39 3 

# 61 3 

# 74 3 

# 80 3



# Commercial 80 75 39 3 

# 61 3 

# 74 3 

# 80 3



# Highway 4



# a. 50% impervious

b. 75% impervious 50

75 50

75 49 2



# 49 2 

# 69 2



# 69 2 

# 79 2



# 79 2 

# 84 2



# 84 2



# 1. Percentage of total project area

2. Assumes open space, lawns, or landscaping in fair condition

3. Assumes open space, lawns, or landscaping in good condition

4. Includes area within right-of-way



# Estimates of the annual runoff coefficients for each of the developed land use categories

were generated using the methodology outlined in Section 4.2.1 and the hydrologic characteristics

summarized in Table 6-9. Separate calculations were performed for each of the five meteorological

zones and four hydrologic soil groups for each iden tified land use category. Separate calculations

were performed for each of the hourly meteorological monitoring sites contained within each of the

five zones, and the mean runoff coefficient wa s calculated for each combination of development

category, soil type, and zone. A summary of calcu lated annual runoff coefficients for typical

developed land use categories is given in Table 6- 10. The values summarized in Table 6-10 reflect

long-term average runoff coefficients based upon the available period of record for hourly

meteorological sites within each of the five zones. In general, estimated annual runoff coefficients

increase with changes in hydrologic soil group and increases in land use intensity.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-28

TABLE 6-10

SUMMARY OF CALCULATED ANNUAL RUNOFF

COEFFICIENTS FOR TYPICAL DEVELOPED LAND USE CATEGORIES

METEOROLOGICAL

ZONE LOW-DENSITY

RESIDENTIAL AREAS SINGLE-FAMILY RESIDENTIAL

AREAS (25% Impervious)

ANNUAL C VALUE ANNUAL C VALUE

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 0.092 0.166 0.238 0.294 0.155 0.206 0.268 0.313

2 0.069 0.126 0.187 0.237 0.136 0.173 0.223 0.262

3 0.084 0.141 0.198 0.243 0.145 0.186 0.233 0.269

4 0.080 0.143 0.209 0.232 0.144 0.187 0.242 0.283

5 0.093 0.164 0.232 0.284 0.151 0.202 0.260 0.302

Mean 0.084 0.148 0.213 0.258 0.146 0.191 0.245 0.286

METEOROLOGICAL

ZONE SINGLE-FAMILY RESIDENTIAL

AREAS (40% Impervious) MULTI-FAMILY RESIDENTIAL

ANNUAL C VALUE ANNUAL C VALUE

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 0.245 0.294 0.350 0.391 0.455 0.490 0.529 0.556

2 0.220 0.257 0.303 0.339 0.423 0.450 0.483 0.508

3 0.228 0.266 0.310 0.343 0.424 0.451 0.482 0.504

4 0.231 0.272 0.322 0.360 0.435 0.465 0.501 0.527

5 0.237 0.284 0.337 0.375 0.435 0.469 0.506 0.531

Mean 0.232 0.275 0.324 0.362 0.434 0.465 0.500 0.525

METEOROLOGICAL

ZONE COMMERCIAL AREAS HIGHWAY AREAS (50% Impervious)

ANNUAL C VALUE ANNUAL C VALUE

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 0.648 0.664 0.683 0.697 0.444 0.481 0.517 0.546

2 0.613 0.625 0.641 0.653 0.415 0.442 0.473 0.498

3 0.606 0.619 0.633 0.644 0.415 0.444 0.472 0.496

4 0.626 0.639 0.656 0.669 0.426 0.457 0.490 0.517

5 0.618 0.633 0.651 0.664 0.425 0.460 0.495 0.522

Mean 0.622 0.636 0.653 0.665 0.425 0.457 0.489 0.516

METEOROLOGICAL

ZONE HIGHWAY AREAS (75% Impervious)

ANNUAL C VALUE

HSG A HSG B HSG C HSG D

1 0.647 0.665 0.683 0.698

2 0.612 0.626 0.641 0.654

3 0.605 0.619 0.634 0.645

4 0.625 0.640 0.657 0.670

5 0.616 0.634 0.651 0.665

Mean 0.621 0.637 0.653 0.666

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-29

Estimates of annual runoff depths for typical developed land use categories and hydrologic

soil groups are summarized in Table 6-11. These values are calculated by multiplying the annual

runoff coefficients (summarized in Table 6-10) by the annual average rainfall for each of the

designated meteorological zones.

Estimates of annual mass loadings of total n itrogen and total phosphorus for typical land use

categories were calculated by multiplying the es timated annual runoff volume generated by each

developed land use category and soil type times the recommended runoff characterization data for

total nitrogen and total phosphorus summarized in Table 4-17. Annual runoff volumes were

estimated for a theoretical 1 acre parcel by multiplying the annual runoff coefficients (summarized in

Table 6-10) times the mean annual rainfall for each meteorological zone. This value was then

multiplied by the typical concentrations summarized in Table 4-17 for total nitrogen and total

phosphorus to obtain estimates of annual mass loadi ngs for a wide variety of developed land use

categories and hydrologic soil group types.

Calculated annual total nitrogen loadings for typical land use categories are summarized in

Table 6-12. The values summarized in these tables reflect the estimated annual total nitrogen load

discharging from each evaluated land use category and soil group type. In general, total nitrogen

loadings increase as the intensity of developm ent increases and soil permeability decreases.

Calculated annual total phosphorus loadings for t ypical land use categories are summarized in Table

6-13. The values summarized in this table are cal culated in the same manner as that previously

described for total nitrogen. In general, estimated annual total phosphorus loadings also increase as

the intensity of land development increases and soil permeability decreases.

6.3.3 Estimated Annual Removal Efficiencies

Required annual removal efficiencies were calculated to reduce the estimated annual

loadings of total nitrogen (summarized in Table 6-12) and total phosphorus (summarized in Table 6-

13) to values equal to or less than the estimated annual mass loadings of nitrogen and phosphorus for

undeveloped/natural areas summarized in Table 6-8. This analysis was conducted for each

evaluated land use category, soil type, and meteorological zone.

A summary of required removal efficien cies to achieve post-development < predevelopment loadings for total nitrogen is given in Table 6-14. In general, required removal

efficiencies for total nitrogen range from a pproximately 54-99%, depending upon the particular

combination of land use category and soil type. The largest required removal efficiencies are

required for multi-family and commercial areas.

Required removal efficiencies to achieve post-development < pre-development loadings for

total phosphorus are summarized in Table 6-15. Re quired removals for total phosphorus range from

approximately 82-99%, depending upon the specific combination of land use type, hydrologic soil

group, and meteorological location.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-30

TABLE 6-11

SUMMARY OF ANNUAL RUNOFF DEPTHS

FOR TYPICAL DEVELOPED LAND USE CATEGORIES

METEOROLOGICAL

ZONE LOW-DENSITY

RESIDENTIAL AREAS SINGLE-FAMILY RESIDENTIAL

AREAS (25% Impervious)

ANNUAL RUNOFF DEPTH (inches) ANNUAL RUNOFF DEPTH (inches)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 5.61 10.12 14.51 17.92 9.45 12.56 16.34 19.08

2 3.43 6.26 9.30 11.78 6.76 8.60 11.09 13.03

3 3.65 6.12 8.60 10.55 6.29 8.07 10.11 11.68

4 4.19 7.50 10.96 12.16 7.55 9.80 12.69 14.83

5 5.41 9.54 13.50 16.52 8.78 11.75 15.12 17.57

Mean 4.46 7.91 11.37 13.79 7.77 10.16 13.07 15.24

METEOROLOGICAL

ZONE SINGLE-FAMILY RESIDENTIAL

AREAS (40% Impervious) MULTI-FAMILY RESIDENTIAL

ANNUAL RUNOFF DEPTH (inches) ANNUAL RUNOFF DEPTH (inches)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 14.94 17.92 21.34 23.84 27.74 29.87 32.25 33.89

2 10.94 12.78 15.07 16.86 21.03 22.37 24.01 25.26

3 9.90 11.55 13.46 14.89 18.41 19.58 20.92 21.88

4 12.11 14.26 16.88 18.87 22.80 24.38 26.26 27.63

5 13.79 16.52 19.60 21.81 25.30 27.28 29.43 30.89

Mean 12.33 14.61 17.27 19.25 23.06 24.70 26.58 27.91

METEOROLOGICAL

ZONE COMMERCIAL AREAS HIGHWAY AREAS (50% Impervious)

ANNUAL RUNOFF DEPTH (inches) ANNUAL RUNOFF DEPTH (inches)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 39.50 40.48 41.64 42.49 27.07 29.32 31.52 33.28

2 30.48 31.08 31.87 32.47 20.63 21.98 23.52 24.76

3 26.31 26.87 27.48 27.96 18.02 19.27 20.49 21.53

4 32.81 33.50 34.39 35.07 22.33 23.96 25.69 27.10

5 35.95 36.82 37.87 38.62 24.72 26.76 28.79 30.36

Mean 33.01 33.75 34.65 35.32 22.55 24.26 26.00 27.41

METEOROLOGICAL

ZONE HIGHWAY AREAS (75% Impervious)

ANNUAL RUNOFF DEPTH (inches)

HSG A HSG B HSG C HSG D

1 39.44 40.54 41.64 42.55

2 30.43 31.12 31.87 32.52

3 26.26 26.87 27.52 28.00

4 32.76 33.55 34.44 35.12

5 35.83 36.88 37.87 38.68

Mean 32.95 33.79 34.67 35.37

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-31

TABLE 6-12

CALCULATED TOTAL NITROGEN LOADINGS

FOR TYPICAL DEVELOPED LAND USE CATEGORIES

METEOROLOGICAL

ZONE LOW-DENSITY

RESIDENTIAL AREAS SINGLE-FAMILY RESIDENTIAL

AREAS (25% Impervious)

ANNUAL TN MASS LOAD (kg/ac-yr) ANNUAL TN MASS LOAD (kg/ac-yr)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 0.93 1.67 2.40 2.97 2.01 2.67 3.48 4.06

2 0.57 1.04 1.54 1.95 1.44 1.83 2.36 2.77

3 0.60 1.01 1.42 1.75 1.34 1.72 2.15 2.48

4 0.69 1.24 1.81 2.01 1.61 2.09 2.70 3.16

5 0.90 1.58 2.23 2.73 1.87 2.50 3.22 3.74

Mean 0.74 1.31 1.88 2.28 1.65 2.16 2.78 3.24

METEOROLOGICAL

ZONE SINGLE-FAMILY RESIDENTIAL

AREAS (40% Impervious) MULTI-FAMILY RESIDENTIAL

ANNUAL TN MASS LOAD (kg/ac-yr) ANNUAL TN MASS LOAD (kg/ac-yr)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 3.18 3.81 4.54 5.07 6.61 7.12 7.69 8.08

2 2.33 2.72 3.20 3.59 5.01 5.33 5.73 6.02

3 2.11 2.46 2.86 3.17 4.39 4.67 4.99 5.22

4 2.58 3.03 3.59 4.01 5.44 5.81 6.26 6.59

5 2.93 3.51 4.17 4.64 6.03 6.50 7.02 7.36

Mean 2.62 3.11 3.67 4.10 5.50 5.89 6.34 6.65

METEOROLOGICAL

ZONE COMMERCIAL AREAS HIGHWAY AREAS (50% Impervious)

ANNUAL TN MASS LOAD (kg/ac-yr) ANNUAL TN MASS LOAD (kg/ac-yr)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 9.74 9.98 10.27 10.48 4.56 4.94 5.31 5.61

2 7.52 7.66 7.86 8.01 3.48 3.70 3.96 4.17

3 6.49 6.63 6.78 6.90 3.04 3.25 3.45 3.63

4 8.09 8.26 8.48 8.65 3.76 4.04 4.33 4.57

5 8.87 9.08 9.34 9.53 4.17 4.51 4.85 5.12

Mean 8.14 8.32 8.55 8.71 3.80 4.09 4.38 4.62

METEOROLOGICAL

ZONE HIGHWAY AREAS (75% Impervious)

ANNUAL TN MASS LOAD (kg/ac-yr)

HSG A HSG B HSG C HSG D

1 6.65 6.83 7.02 7.17

2 5.13 5.25 5.37 5.48

3 4.43 4.53 4.64 4.72

4 5.52 5.65 5.80 5.92

5 6.04 6.22 6.38 6.52

Mean 5.55 5.70 5.84 5.96

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-32

TABLE 6-13

CALCULATED TOTAL PHOSPHORUS LOADINGS

FOR TYPICAL DEVELOPED LAND USE CATEGORIES

METEOROLOGICAL

ZONE LOW-DENSITY

RESIDENTIAL AREAS SINGLE-FAMILY RESIDENTIAL

AREAS (25% Impervious)

ANNUAL TP MASS LOAD (kg/ac-yr) ANNUAL TP MASS LOAD (kg/ac-yr)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 0.110 0.199 0.285 0.352 0.318 0.422 0.549 0.641

2 0.067 0.123 0.183 0.231 0.227 0.289 0.373 0.438

3 0.072 0.120 0.169 0.207 0.212 0.271 0.340 0.392

4 0.082 0.147 0.215 0.239 0.254 0.329 0.426 0.499

5 0.106 0.187 0.265 0.324 0.295 0.395 0.508 0.590

Mean 0.088 0.155 0.223 0.271 0.261 0.341 0.439 0.512

METEOROLOGICAL

ZONE SINGLE-FAMILY RESIDENTIAL

AREAS (40% Impervious) MULTI-FAMILY RESIDENTIAL

ANNUAL TP MASS LOAD (kg/ac-yr) ANNUAL TP MASS LOAD (kg/ac-yr)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 0.502 0.602 0.717 0.801 1.482 1.596 1.723 1.811

2 0.368 0.429 0.506 0.566 1.124 1.196 1.283 1.350

3 0.333 0.388 0.452 0.500 0.984 1.046 1.118 1.169

4 0.407 0.479 0.567 0.634 1.219 1.303 1.403 1.476

5 0.463 0.555 0.659 0.733 1.352 1.458 1.573 1.651

Mean 0.414 0.491 0.580 0.647 1.232 1.320 1.420 1.491

METEOROLOGICAL

ZONE COMMERCIAL AREAS HIGHWAY AREAS (50% Impervious)

ANNUAL TP MASS LOAD (kg/ac-yr) ANNUAL TP MASS LOAD (kg/ac-yr)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 1.401 1.435 1.476 1.507 0.612 0.663 0.713 0.753

2 1.081 1.102 1.130 1.151 0.467 0.497 0.532 0.560

3 0.933 0.953 0.974 0.991 0.407 0.436 0.463 0.487

4 1.163 1.188 1.219 1.243 0.505 0.542 0.581 0.613

5 1.275 1.306 1.343 1.369 0.559 0.605 0.651 0.687

Mean 1.170 1.197 1.228 1.252 0.510 0.548 0.588 0.620

METEOROLOGICAL

ZONE HIGHWAY AREAS (75% Impervious)

ANNUAL TP MASS LOAD (kg/ac-yr)

HSG A HSG B HSG C HSG D

1 0.892 0.917 0.941 0.962

2 0.688 0.704 0.721 0.735

3 0.594 0.608 0.622 0.633

4 0.741 0.759 0.779 0.794

5 0.810 0.834 0.856 0.875

Mean 0.745 0.764 0.784 0.800

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-33

TABLE 6-14

REQUIRED REMOVAL EFFICIENCIES TO ACHIEVE

POST-DEVELOPMENT LESS THAN OR EQUAL TO

PRE-DEVELOPMENT LOADINGS FOR TOTAL NITROGEN

METEOROLOGICAL

ZONE LOW-DENSITY

RESIDENTIAL AREAS SINGLE-FAMILY RESIDENTIAL

AREAS (25% Impervious)

Required Removal Efficiency (%) Required Removal Efficiency (%)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 88.4 72.5 62.2 57.2 94.6 82.7 73.9 68.8

2 93.8 78.5 66.8 61.4 97.5 87.8 78.3 72.9

3 87.2 73.2 62.8 58.3 94.3 84.2 75.4 70.7

4 91.1 75.0 64.5 54.1 96.1 85.1 76.1 70.7

5 86.2 70.8 60.9 56.5 93.4 81.6 72.9 68.2

Mean 89.3 74.0 63.4 57.5 95.2 84.3 75.3 70.2

METEOROLOGICAL

ZONE SINGLE-FAMILY RESIDENTIAL

AREAS (40% Impervious) MULTI-FAMILY RESIDENTIAL

Required Removal Efficiency (%) Required Removal Efficiency (%)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 96.6 87.9 80.0 75.0 98.4 93.5 88.2 84.3

2 98.5 91.8 84.0 79.0 99.3 95.8 91.1 87.5

3 96.3 88.9 81.5 77.0 98.2 94.2 89.4 86.0

4 97.6 89.8 82.1 77.0 98.9 94.7 89.7 86.0

5 95.8 86.9 79.1 74.4 97.9 92.9 87.6 83.9

Mean 97.0 89.1 81.3 76.5 98.5 94.2 89.2 85.5

METEOROLOGICAL

ZONE COMMERCIAL AREAS HIGHWAY AREAS (50% Impervious)

Required Removal Efficiency (%) Required Removal Efficiency (%)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 98.9 95.4 91.2 87.9 97.6 90.7 82.9 77.4

2 99.5 97.1 93.5 90.6 99.0 94.0 87.1 82.0

3 98.8 95.9 92.2 89.4 97.5 91.6 84.7 79.9

4 99.2 96.3 92.4 89.3 98.4 92.3 85.1 79.8

5 98.6 94.9 90.7 87.5 97.0 89.8 82.0 76.8

Mean 99.0 95.9 92.0 89.0 97.9 91.7 84.4 79.2

METEOROLOGICAL

ZONE HIGHWAY AREAS (75% Impervious)

Required Removal Efficiency (%)

HSG A HSG B HSG C HSG D

1 98.4 93.3 87.1 82.3

2 99.3 95.7 90.5 86.3

3 98.3 94.0 88.6 84.6

4 98.9 94.5 88.9 84.4

5 98.0 92.6 86.3 81.8

Mean 98.6 94.0 88.3 83.9

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-34

TABLE 6-14

REQUIRED REMOVAL EFFICIENCIES TO ACHIEVE

POST-DEVELOPMENT LESS THAN OR EQUAL TO

PRE-DEVELOPMENT LOADINGS FOR TOTAL PHOSPHORUS

METEOROLOGICAL

ZONE LOW-DENSITY

RESIDENTIAL AREAS SINGLE-FAMILY RESIDENTIAL

AREAS (25% Impervious)

Required Removal Efficiency (%) Required Removal Efficiency (%)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 95.3 88.9 84.8 82.8 98.4 94.8 92.1 90.5

2 97.5 91.3 86.6 84.4 99.3 96.3 93.4 91.8

3 94.9 89.2 85.0 83.2 98.3 95.2 92.6 91.1

4 96.4 89.9 85.7 81.5 98.8 95.5 92.8 91.1

5 94.4 88.2 84.2 82.5 98.0 94.4 91.8 90.4

Mean 95.7 89.5 85.3 82.9 98.5 95.2 92.5 91.0

METEOROLOGICAL

ZONE SINGLE-FAMILY RESIDENTIAL

AREAS (40% Impervious) MULTI-FAMILY RESIDENTIAL

Required Removal Efficiency (%) Required Removal Efficiency (%)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 99.0 96.3 93.9 92.4 99.7 98.6 97.5 96.7

2 99.5 97.5 95.2 93.6 99.8 99.1 98.1 97.3

3 98.9 96.6 94.4 93.0 99.6 98.8 97.7 97.0

4 99.3 96.9 94.6 93.0 99.8 98.9 97.8 97.0

5 98.7 96.0 93.7 92.2 99.6 98.5 97.3 96.6

Mean 99.1 96.7 94.4 92.9 99.7 98.8 97.7 96.9

METEOROLOGICAL

ZONE COMMERCIAL AREAS HIGHWAY AREAS (50% Impervious)

Required Removal Efficiency (%) Required Removal Efficiency (%)

HSG A HSG B HSG C HSG D HSG A HSG B HSG C HSG D

1 99.6 98.5 97.1 96.0 99.2 96.7 93.9 91.9

2 99.8 99.0 97.8 96.9 99.6 97.9 95.4 93.6

3 99.6 98.6 97.4 96.5 99.1 97.0 94.5 92.8

4 99.7 98.8 97.5 96.4 99.4 97.3 94.7 92.8

5 99.5 98.3 96.9 95.8 98.9 96.4 93.6 91.7

Mean 99.7 98.6 97.3 96.3 99.2 97.0 94.4 92.6

METEOROLOGICAL

ZONE HIGHWAY AREAS (75% Impervious)

Required Removal Efficiency (%)

HSG A HSG B HSG C HSG D

1 99.4 97.6 95.4 93.7

2 99.8 98.5 96.6 95.1

3 99.4 97.9 95.9 94.5

4 99.6 98.0 96.0 94.4

5 99.3 97.4 95.1 93.5

Mean 99.5 97.9 95.8 94.2

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-35

Differences between the required removal e fficiencies for nitrogen and phosphorus to

achieve no net increase in loading under post-deve lopment conditions are due primarily to the

differences in runoff characteristics for ge neral land use categor ies between nitrogen and

phosphorus. As seen in Table 4-17, nitrogen concen trations increase by a factor of approximately

1.1-3 under developed conditions, compared with values measured under undeveloped conditions.

However, total phosphorus concentrations increase by a factor of approximately 3-9, suggesting that

removal efficiencies for total phosphorus need to be greater than those which occur for total nitrogen

to reach pre-development loading conditions.

A graphical comparison of required removal effi ciencies to achieve no net increase in postdevelopment loadings is given in Figure 6-6 for low-density residential areas, Figure 6-7 for singlefamily residential (25% impervious), Figure 6-8 for single-family residential (40% impervious),

Figure 6-9 for high-density residential, Figure 6-10 for commercial areas, Figure 6-11 for highway

areas (50% impervious), and Figure 6-12 for highw ay areas with 75% impervious. A stormwater

management system designed according to the goal of the Water Resource Implementation Rule

(Chapter 62-40) of 80% removal will achieve a no ne t increase in nitrogen loadings for low-density

residential areas and single-family residential ( 25% impervious) constructed in HSG B, C, and D

soils, single-family residential (40% impervious), and highway areas (50% impervious) constructed

in HSG D soils. However, these same developments constructed in HSG A soils and other soil types

not listed will fail to meet this criterion and will n eed supplemental stormwater treatment to achieve

the goal of no net increase in nitrogen loadings.

A stormwater management system designed fo r 80% removal will not achieve a condition of

no net increase for total phosphorus for any of the ev aluated land use categories. In some cases,

removal efficiencies as high as 99% must be achieved to obtain the goal of no net increase in

phosphorus loadings, particularly for development constructed in HSG A areas. Even systems

constructed to OFW design criteria, equivalent to a 95% annual mass removal, will fail to meet the

objective of no net increase in total phosphorus load ings for many combinations of land use category

and hydrologic soil group.

6.4 Evaluation of Wet Detention Pond Depth

6.4.1 Theory of Shallow vs. Deep Ponds

One of the most controversial design para meters for stormwater management systems

involves the constructed depth for wet detention ponds. As discussed in Section 5.2.2, wet detention

systems designed in the St. Johns River Water Mana gement District are limited to a maximum of 12

ft in depth, with a mean depth ranging from 2-8 ft , and relatively short detention times ranging from

14-21 days during wet season conditions. In contrast , the South Florida Water Management District

recommends that 25-50% of the pond area be greater than 12 ft in depth which tends to create ponds

with detention times on the order of several hundred days.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-36



# Total Nitrogen

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100

HSG A

HSG B

HSG C

HSG D



# Total Phosphorus

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100



# Figure 6-6. Comparison of Estimated Annual Mass Removal Efficiencies to Achieve PostDevelopment < Pre-Development Loadings of Nitrogen and Phosphorus for a

Low-Density Residential Development.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-37



# Total Nitrogen

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100

HSG A

HSG B

HSG C

HSG D



# Total Phosphorus

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100



# Figure 6-7. Comparison of Estimated Annual Mass Removal Efficiencies to Achieve PostDevelopment < Pre-Development Loadings of Nitrogen and Phosphorus for a

Single-Family (25% Impervious) Residential Development.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-38



# Total Nitrogen

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100

HSG A

HSG B

HSG C

HSG D



# Total Phosphorus

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100



# Figure 6-8. Comparison of Estimated Annual Mass Removal Efficiencies to Achieve PostDevelopment < Pre-Development Loadings of Nitrogen and Phosphorus for a

Single-Family (40% Impervious) Residential Development.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-39



# Total Nitrogen

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100

HSG A

HSG B

HSG C

HSG D



# Total Phosphorus

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100



# Figure 6-9. Comparison of Estimated Annual Mass Removal Efficiencies to Achieve PostDevelopment < Pre-Development Loadings of Nitrogen and Phosphorus for a

Multi-Family Residential Development.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-40



# Total Nitrogen

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100

HSG A

HSG B

HSG C

HSG D



# Total Phosphorus

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100



# Figure 6-10. Comparison of Estimated Annual Mass Removal Efficiencies to Achieve PostDevelopment < Pre-Development Loadings of Nitrogen and Phosphorus for a

Commercial Development.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-41



# Total Nitrogen

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100

HSG A

HSG B

HSG C

HSG D



# Total Phosphorus

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100



# Figure 6-11. Comparison of Estimated Annual Mass Removal Efficiencies to Achieve PostDevelopment < Pre-Development Loadings of Nitrogen and Phosphorus for a

Highway (50% Impervious) Development.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-42



# Total Nitrogen

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100

HSG A

HSG B

HSG C

HSG D



# Total Phosphorus

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5Required Percent Removal (%)



# 50 60 70 80 90 100



# Figure 6-12. Comparison of Estimated Annual Mass Removal Efficiencies to Achieve PostDevelopment < Pre-Development Loadings of Nitrogen and Phosphorus for a

Highway (75% Impervious) Development.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-43

Neither of the design criteria outlined in th e previous paragraph is supported by specific

research projects designed to address allowabl e depths for wet detention ponds. The depth

limitation of 12 ft for wet detention ponds designe d in the St. Johns River Water Management

District appears to have been influenced by severa l previous research projects designed to evaluate

the effectiveness of a particular wet detention pond design. These ponds, which were coincidentally

designed to a maximum depth of approximately 12 ft, maintained aerobic conditions throughout the

water column of each pond, resulting in the conclu sion that wet detention ponds constructed to a

depth of 12 ft would maintain aerobic conditions.

In order to understand factors which may imp act the allowable depths for wet detention

ponds, it is essential to understand that wet dete ntion ponds are simply man-made lake systems

subject to the same physical, chemical, and biological processes which exist in natural lake systems.

Virtually every lake in Florida, particularly in urbanized environments, acts as a regional wet

detention facility for runoff inputs generated from the surrounding areas. The limnological concepts

of nutrient uptake, chemical and biological transformations, and primary productivity are no

different in waterbodies which have been assigne d permit numbers than in waterbodies which have

been assigned formal names.

The underlying assumption in maximizing the pollutant removal effectiveness of a wet

detention pond is that aerobic conditions must be maintained throughout the water column at all

times. Assuming that aerobic conditions are reflect ed by dissolved oxygen concentrations in excess

of 1 mg/l, this means that dissolved oxygen concentr ations must be in excess of 1 mg/l within the

water column at all times.

The depth of anoxia in a waterbody, defined as the water depth at which dissolved oxygen

concentrations drop below 1 mg/l, is highly corre lated with the algal productivity which exists

within the pond. At low levels of algal productivity, light penetration can extend to deeper layers of

the pond, which increases the portion of the water column in which photosynthetic activities take

place and increases the depth of anoxia. As algal productivity increases, light penetration into the

water column is restricted, and the depth of anoxia begins to approach closer to the surface. This

phenomenon is well documented by limnologists who consistently observe that eutrophic lakes with

high levels of algal productivity often develop anoxi c conditions at a relatively shallow water depth,

while lake systems exhibiting oligotrophic charact eristics and low algal productivity often maintain

aerobic conditions to depths of 30- 40 ft. The fact that a wet detention pond is constructed to a

maximum depth of 12 ft in no way guarantees that aerobic conditions will be maintained within the

pond at all times. In fact, a wet detention pond w ith a deeper depth and larger permanent pool

volume, receiving the same mass loadings as a 12- ft deep pond, would exhibit substantially lower

algal productivity and have a correspondingly deeper depth for the anoxic zone. As a result, the

allowable depth of a wet detention pond should be ev aluated with respect to the anticipated algal

productivity within the pond rather than an arb itrary depth which may or may not achieve the

objective of maintaining aerobic conditions within the water column.

Maximizing the depth of a wet detention pond while still maintaining aerobic conditions

provides several significant water quality benefits. First, deeper ponds generally have a larger

permanent pool volume which decreases the likelihood of water quality violations at the outfall from

runoff inputs entering the pond. When a pond has a detention time of several hundred days,

runoff inputs into the system reflect a very small percentage of the available permanent pool

volume. This permanent pool volume provides signi ficant attenuation and dilution for runoff inputs,

minimizing variability in discharges from the pond and water quality violations. On the other hand,

runoff inputs into a pond with a relatively short detention time comprise a significantly larger

portion of the permanent pool volume, increasing th e likelihood of water quality violations at the

outfall.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-44

Another advantage of deeper ponds is the incr eased storage for suspended solids provided in

these systems. As shallow detention ponds begin to fill in with sediments, aquatic vegetation

(commonly cattails) begins to encroach into the pond, creating significant negative water quality

impacts. In deeper ponds, this phenomenon is substantially postponed. Shallow ponds with a short

residence time also tend to be highly productive and often have aesthetically unpleasing algal

blooms. Homeowners associations often contract with aquatic weed control companies to correct

these visual concerns using herbicides or coppe r-based algicides, both of which decrease the

performance efficiency of the pond and increase th e likelihood of water quality violations at the

pond outfall.

6.4.2 Zonation and Stratification

Typical zonation in a pond or lake is illust rated on Figure 6-13. The upper portions of

the water column in a waterbody are typically well mixed, with a relatively uniform temperature.

This upper layer, often called the epilimnion, is the area in which the majority of algal

production within the lake occurs. In this zone, photosynthesis exceeds respiration, and

adequate levels of dissolved oxygen are typically maintained. Lower layers of a lake are often

isolated from the upper layers as a result of thermal stratification within the waterbody.

Penetration of sunlight into these lower layers is typically poor, and as a result, little algal

productivity occurs in these areas. In this lo wer zone, commonly referred to as the hypolimnion,

respiration exceeds photosynthesis, and the wate r column may become void of dissolved oxygen

during portions of the year.

Figure 6-13. Typical Zonation in a Lake or Pond.

Development of stratification in waterbodies occurs primarily as a result of differential

absorption of solar energy w ithin the water column resulting in relatively large temperature

differences between the upper warm epilimnion wate r and the lower cooler hypolimnion water. In

Florida, temperature differences as high as 8-10 E C can occur during the summer months between

the epilimnion and the hypolimnion in a deep water body. Temperature differences within the water

column result in density gradients which inhibit circulation between surface and deeper portions of

the water column, resulting in stable stratified conditions.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-45

Under stratified conditions, the hypolimni on becomes isolated from oxygen input

mechanisms such as reaeration from the surface and algal production, and anaerobic conditions may

develop in deeper waters. Anaerobic or anoxic c onditions are considered to occur when dissolved

oxygen concentrations in portions of a waterbody decrease to less than 1 mg/l. These conditions

may increase the release of ions such as ammonia and orthophosphorus, along with gases such as

H 2 

# S and CO 2 

# , from the bottom sediments into the hypolimnion water where significant

accumulation of these ions and gases can occur. The accumulated constituents in the hypolimnion

can then be circulated into the epilimnion as a re sult of a destratifying event, such as a prolonged

windy period or strong storm event, theoretically resulting in episodes of reduced water quality.

Circulation may also occur naturally within a waterbody with seasonal changes in temperature.

Stratified conditions commonly develop as a re sult of absorption of solar energy by particles

in the water column, either as a result of turbid ity or by excess algal production near the surface.

Both inorganic particles and organic matter can strongly absorb solar radiation and create a

significant degree of stratification and a sharp decrease in temperature in the water column at depths

below 4-6 feet if large quantities of suspended matte r are present in the water column. However, if

significant suspended matter is not present in the wa ter column, waterbodies as deep as 20 feet or

more may not experience stratification or anaerobic conditions at deeper water depths.

One method of evaluating the potential for st ratification in a waterbody is to perform

estimates of anticipated algal production and corresponding chlorophyll-a values within the

proposed system. If algal production is predicted to be low, generally characterized by chlorophyll-a

concentrations less than 5 mg/m 3 

# , then the potential for stratificati on in a waterbody is low, and if it

develops, it will occur in relatively deep portions of the water column. The stratification potential

increases substantially as chlorophyll-a concentr ations increase above these values. If total

phosphorus concentrations in a waterbody are known or can be estimated, the corresponding

chlorophyll-a concentration can be calculated. Dillon and Rigler (19974) proposed the following

empirical relationship between chlorophyll-a and total phosphorus, based on data collected primarily

from northern temperate lakes:

log (Chyl-a) = 1.449 log TP - 1.136 (Eq. 2)

where:

TP = Mean total phosphorus concentration ( μ g/l)

Once the anticipated algal production and chlor ophyll-a values in the aquatic system have

been determined, corresponding Secchi disk depths can be estimated based upon a second

empirical relationship presented by Dillon and Rigl er (1974), also based on data collected primarily

from northern temperate lakes, which results in an estimated Secchi disk depth in meters, based upon

a chlorophyll-a input in units of mg/m 3 

# according to the following equation:

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-46

where:

SD = Secchi disk depth (m)

Chyl-a = Chlorophyll-a concentration (mg/m 3 

# )

The Secchi disk is a simple device used to estimate water clarity in a lake or pond. It consists of a

weighted circular plate, 20 cm in diameter, with the surface painted with alternating black and white

quarters. The depth to which this disk can be seen in the water column is defined as the Secchi disk

depth. The Secchi disk depth in a body of water is generally assumed to correspond to a water depth

where the available light is approximately 10-15% of the incident light at the water surface.

Although the general relationships referenced previously between total phosphorus,

chlorophyll-a, and Secchi disk were developed prim arily from data generated on northern temperate

lakes, these equations have been utilized extensiv ely within the State of Florida to model water

quality characteristics in lakes. However, for purposes of evaluating wet detention pond design, a

revised evaluation of these relationships was conducted based specifically on water quality data

colleted within the State of Florida. As a sour ce of data, the STORET database was searched for

existing surface water data which includes simultaneous measurements for total phosphorus,

chlorophyll-a, and Secchi disk for waterbodies with in the State of Florida. This data search

generated in excess of 65,000 measurements whic h include the three evaluated parameters.

Unfortunately, this dataset exceeds the input capabilities for most commonly used statistical

programs. As a result, average values were calculated for each monitoring location over the period

of record contained within the STORET database. Th ese mean values were used to form a separate

database which contained approximately 2467 individual data points. This dataset was then used to

perform regression analyses to evaluate relati onships between total phosphorus, chlorophyll-a, and

Secchi disk specifically for Florida conditions.

A regression analysis was conducted to evaluate the most significant functional forms for the

relationships between chlorophyll-a and total phosphor us. This evaluation indicated that a log-log

relationship, similar to that expressed as Eq. 2, provides the best-fit between these parameters. This

regression analysis was evaluated for outliers by ex amination of the Student T residuals and Cook’s

D values. Approximately 327 data points were elimin ated from the data set as outliers during this

process. The remaining data set contained 2140 data points.

The best-fit relationship between chlorophyll-a and total phosphorus is summarized below:

ln (chyl-a) = 1.058 ln (TP) - 0.934 R 2 

# = 0.815 (Eq. 4) SD = 8.7 1

1 + 0.47 Chyl - a ⎛

⎝ ⎜ ⎞

⎠ ⎟ 

# (Eq. 3)

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-47

where:

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total phosphorus concentration ( μ g/l)

The best-fit relationship obtained with Florida data is similar to that originally proposed by Dillon

and Rigler (1974) with different co efficients and intercepts. The R 2 

# value for this relationship is

0.815 which indicates that the value of total phosphorus explains approximately 82% of the

variability in measured chlorophyll-a concentrations . This relationship can be used to estimate

chlorophyll-a concentrations in the a detention pond based upon estimated concentrations of total

phosphorus.

Predictive relationships between Secchi disk depth and chlorophyll-a were also evaluated

based upon the Florida lakes data set. A regression analysis for this relationship was also conducted

to identify the best-fit relationship between the two variables. A plot of the relationship between

Secchi disk depth and chlorophyll-a for Florida lake s is given in Figure 6-14. The best-fit equation

for this relationship is a hyperbolic e quation which is summari zed on Figure 6-14. The R 2



# value of 0.807 for this relationship indicates th at chlorophyll-a explains approximately 81% of the

variability in Secchi disk depth within a waterbody in Florida. This relationship may be used to

estimate the Secchi disk depth in a waterbody based on measured or calculated values of

chlorophyll-a.



# Chlorophyll a (mg/m 3 

# ) 0 100 200 300 400Secchi Depth (m)



# 0 1 2 3 4 5 6



# ) 0632

. 6 ( ) 0.3041 (24.2386 (m) Depth Secchi chyla chyla

+ • +

=



# R 2 =0.807

Figure 6-14. Relationship Between Secchi Disk Depth and Chlorophyll-a for Florida Lakes.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-48

Development of stratification and anoxic c onditions in a non-colored waterbody, such as a

wet detention pond, is directly related to th e amount of algal production and the corresponding

Secchi disk depth within the water column. Although algal production adds oxygen in areas where

active photosynthesis occurs, algal cells also absorb solar radiation and limit the amount of sunlight

and corresponding algal productivity at deeper depths within the water column. Wet detention

ponds are primarily phosphorus-limited systems. Since algal production is limited primarily by

inputs of total phosphorus, phosphorus is also an im portant variable in determining the depth of

anoxia.

A linear regression was developed to predict th e depth of anoxia in a waterbody as a function

of ambient concentrations of ch lorophyll-a, total phosphorus, and Secchi disk depth. The depth of

anoxia was obtained from field measured dissolved oxygen profiles collected in a waterbody at the

time of sample collection for laboratory analyses. A data set was develope d containing 426 sets of

measurements of Secchi disk depth, chlorophyll-a, total phosphorus, and depth of anoxia, defined as

dissolved oxygen concentrations less than 1 mg/l, for waterbodies in Central and South Florida. The

data were generated from field monitoring and laboratory analyses conducted by ERD over the past

20 years. The data set was evaluated for outliers by examination of the Student T residuals and

Cook’s D values. A total of 54 data points was eliminated as outliers. Both linear and log

transformations were performed on the variables to obtain the “best-fit” model which maximizes R 2



# while minimizing the mean square error (MSE). This modeling exercise is designed to maximize

the predictability of the model rather than to examine functional forms. The resulting linear

regression relationship for the variables indicates th at the depth of anoxia is regulated primarily by

Secchi disk depth according to the following relationship:

Anoxic Depth = 3.035 x Secchi Disk Depth (m) – 0.004979

(Eq. 5)

x Total P ( μ

g/l) + 0.02164 x chyl-a (mg/m 3 

# )

R 2 

# = 0.951

where:

Anoxic Depth = depth of anoxia (m)

The above equation is valid for: 0.25 m < anoxic depth < 9.0 m

0.09 m < Secchi disk depth < 3.49 m

1 μ g/l < Total P < 498 μ g/l

1 mg/m 3 

# < chyl-a < 332 mg/m 3



# Regression statistics for the anoxic depth model are given in Table 6-16.

# FDEP \ STORMWATER TREATMENT REPORT 

# 6-49

TABLE 6-16

REGRESSION STATISTICS FOR

ANOXIC DEPTH MODEL

VARIABLE PARAMETER

ESTIMATES LEVEL OF

SIGNIFICANCE

(%) STANDARIZED

ESTIMATE

Total P -0.004979 > 99.99 - 0.070

Secchi Disk 3.035 > 99.99 0.217

Chlorophyll-a 0.02164 > 99.99 0.911



# The R 2 

# value for this relationship is 0.951 which indicates that the regression model explains

95.1% of the variability in estimated anoxic depth. If the Secchi disk depth, total phosphorus, and

chlorophyll-a for a proposed wet detention pond can be estimated based upon the relationships

summarized previously, then the depth of anoxia can be estimated using Eq. 5. This depth of anoxia

would be an estimate of the maximum depth to which the wet detention pond could be constructed

without generating anoxic conditions in lower portions of the water column.

# FDEP \ STORMWATER TREATMENT REPORT 

# SECTION 7

DESIGN EXAMPLES

Several design examples were developed to illustrate the basic methodology which would

be utilized by a design engineer to develop an appropriate stor mwater management system to meet the proposed modifications to existing stormw ater design criteria summarized in Section 6.

Design examples are provided based upon stormwater criteria intended to meet both the 80% and

95% pollutant reduction target go als outlined in Chapter 62-40. These design examples are also

intended to illustrate differences in required water quality treatment volumes for different

meteorological zones within the St ate of Florida based on differen ces in total annual rainfall and

the frequency distribution for individual rain ev ents. In addition, design examples are also

provided to illustrate treatment requirements nece ssary to achieve a condition of no net increase

in pollutant loadings for a developed site under post-development conditions.

7.1 Design Example #1:

Stormwater Treatment to Meet the 80 % Pollution Reduction Target Goal

Determine the water quality treatment requi rements for a 100-acre proposed single-family

residential site. Perform separa te calculations for identical projects located in Pensacola (Zone

1), Orlando (Zone 2), and Key West (Zone 3). A summary of pre- and post-development

conditions is given below.

Calculate Pre- and Post-Development Conditions

Pre-Development Conditions

1. Land Use : 90 acres - mixture of rangel and/forest (fair condition)

10 acres – isolated wetlands

2. Ground Cover/Soil Types : Rangeland/Forest – Hydr ologic Soil Group (HSG) D

Wetland – hydric soils

3. Impervious Areas : 0% impervious, 0% Directly Connected Impervious Area (DCIA)

Post Development Conditions

1. Land Use : 90 acres of single-family residential

5 acres of stormwater management systems

5 acres of preserved wetlands

7-1

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-2

2. Ground Cover/Soil Types

A. Residential areas will be cove red with lawns in good condition

B. Soil types will remain HSG D

3. Impervious/DCIA Areas

A. Residential areas wi ll be 25% impervi ous, 75% of which will be DCIA

Impervious Area = 25% of residentia l area = 90 ac x 0.25 = 22.50 acres

DCIA Area = 22.50 acres x 0.75 = 16.88 acres

DCIA Percentage = (16.88 ac/90.0 ac) x 100 = 18.7% of developed area

4. Calculate composite non-DCIA curve number from TR-55 :

Curve number for la wns in good condition in HSG D = 80

Areas of lawns = 90 acres to tal – 22.50 ac imperv ious area = 67.50 acres pervious area

Impervious area which is not DCIA = 22.50 ac – 1 6.88 ac = 5.62 ac

Assume a curve nu mber of 98 for impervious areas

Non-DCIA curve number =

Calculate Treatment Requirements for 80% Removal

Estimation of treatment requirements assumes th at only dry retention and wet detention are

capable of approaching the 80% pollutant reduction goal.

1. Dry Retention

A. Pensacola Project (Zone 1)

The required retention depth to achieve an annual removal efficiency of 80% in

the Pensacola (Zone 1) area is determined from Table 6-1 (Zone 1) based on

DCIA percentage and the non-DCIA CN value. For this project:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4 

# 4

. 81

62 50

. 67 62 50

. 67

=

ac 5. + ac (98) ac 5. + (80) ac

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-3

The required dry retention depth is obtained by iterat ing between DCIA

percentages of 10 and 20, and for non-DCIA CN values between 80 and 90. The

required dry retention depth = 1. 52 inches over the developed area.

B. Orlando Project (Zone 2)



# If the project was located in Orlando (Centr al Zone), the required dry retention depth

would be slightly different due to differences in the distribution of rain events. The

required retention depth would be obtained from Table 6-1 (Zon e 2) by iterating

between DCIA percentages of 10 and 20, an d for non-DCIA CN values between 80

and 90. The required dry re tention depth = 0.96 inches over the developed area.

C. Key West Project (Zone 3)



# If the project was located in Key West (Zone 3), the required dry retention depth

would be slightly different due to differences in the distribution of rain events. The

required retention depth would be obtained from Table 6-1 (Zon e 3) by iterating

between DCIA percentages of 10 and 20, an d for non-DCIA CN values between 80

and 90. The required dry re tention depth = 1.66 inches over the developed area.

2. Wet Detention

Treatment Train Approach



# Calculation of design criteria for a wet deten tion pond is based on determining the detention

time required to achieve the desired pollutant removal efficiency of 80%. For practical

purposes, this efficiency is assumed to apply to nitrogen and phosphoru s since other

pollutants such as BOD and TSS ar e typically removed at a faster rate than nutrients. As

discussed in Section 5.2.2, wet detention syst ems are capable of prov iding annual mass load

reduction for phosphorus in excess of 80% at extended detention times (> 200 days).

However, wet detention ponds ar e not capable of providing 80% removal for total nitrogen

since removal efficiency for total nitrogen in wet detention ponds appears to peak at

approximately 40-45%.

Therefore, when wet detention is desired as a treatment option, pr e-treatment must be

provided to enhance the total system performance efficiency to a minimum of 80% for total

nitrogen. Since dry retention provides the best pre-treatment in a minimal space, dry

retention appears to be the pre-treatment system of choice for this application. There are

many combinations of dry rete ntion and wet detention which can provide the desired 80%

removal.

Assume that a wet detention pond is designed with a residence time of 200 days.

Anticipated TN removal (Figure 5-10) =

% 4

= 200 + 5.46 200 x 44.72

= ) t + ( ) t x (4 Eff

d d 

# 8

. 2

38

. 4 75

. 3

=

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-4

Anticipated TP removal (Figure 5-9) =

Eff = 40.13 + 6.372 ln (t d 

# ) + 0.213 (ln t d 

# ) 2 

# = 40.13 + 6.372 ln (200) + 0.213 (ln 200) 2 

# = 79.9%



# Although the wet detention po nd approaches the 80% remova l criteria for TP, the removal

for TN is only 42.8%. Therefor e, the remaining efficiency is achieved using dry detention.

The required efficiency for the dry rete ntion is calculated by Eq. 1 below:

Treatment Train Efficiency = Eff 1 

# + (1 – Eff 1 

# ) x Eff 2 

# (Eq. 1)

where: Eff 1 

# = required efficiency of dry retention

Eff 2 

# = efficiency of wet detention

0.8 = Eff 1 

# + (1 – Eff 1 

# ) x 0.428

Eff 1 

# = 0.650 = 65.0%

2A. PENSACOLA (ZONE 1) PROJECT



# The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

1. Required Dry Retention Depth



# From Appendix D (Zone 1), the required removal ef ficiency of 65.0% is achieved with a dry

retention depth between 0.75 and 1.00 inch.

For a dry retention depth of 0.75 inch, the treat ment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 63.4%

.

For a dry retention depth of 1.00 inch, the treat ment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 70.5%

.

By iterating between 0.75 inch (63.4%) and 1.00 inch (70.5%), the dry retention depth required to

achieve 65.0% remova l is 0.81 inch.

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-5

Therefore, the required treat ment train will consist of:

a. 0.81 inch dry retention, followed by

b. Wet detention pond with a 2 00-day mean residence time

Based on the relationships given in Figures 5-9 an d 5-10, the removal effici encies for TN and TP

increase very little at detention times in excess of 200 days. Although the pond size may be

increased (if desired) for fill or other purposes, the required dry re tention pre-treatment depth will

not be significantly reduced. Ho wever, if the pond residence ti me is decreased below 200 days,

then the dry retention pre-treatment depth will increas e correspondingly.

2. Wet Detention Pond Characteristics



# The required physical characteristic s of the wet detention pond are determined based on the desired

residence time and the impacts of the proposed dry retention pre-treatment.

a. Calculate annual ru noff inputs to pond



# The annual runoff coefficient for the development can be estimate d using the tables included

in Appendix C (Zone 1).

For: DCIA = 18.75% an d non-DCIA CN = 81.4

The estimated “C” value is obtained by iteration as discussed previously.

Annual C Value = 0.304

The annual rainfall for the Pensacol a area = 65.5 inches (Appendix A.3)

Annual generated runoff volume =

90 acres x 65.5 inches/year x 1 ft/1 2 inches x 0.304 = 149.34 ac-ft/yr

The calculated efficiency of 65.0% for the dr y retention pre-treatment means that 65.0% of

the annual runoff volume w ill be infiltrated into the ground and will not disc harge directly

into the wet detention pond. The annual runo ff volume which reaches the pond is calculated

as:

Annual Inputs to Pond = 149.34 ac-ft/yr x (1 - 0.650) = 52.27 ac-ft/yr

For a 200-day residence time, the pond volume will be:

52.27 ac-ft/yr x 1 year/365 days x 200 days = 28.64 ac-ft

Assuming a mean pond depth of 8 ft, the required pond area =

Pond Area = 28.64 ac- ft x 1/8 ft = 3.58 ac = 4% of project area

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-6

b. Estimate maximum allowable pond depth



# The maximum allowable pond depth is directly re lated to the anticipated algal productivity

within the pond. Assuming that wet dete ntion ponds are primarily phosphorus-limited

ecosystems, the productivity can be estimated based on the mean TP concentration.

1. Estimate runoff characteristics



# For a single-family residentia l land use, the event mean concentration (emc) for TP

in runoff can be obtain ed from Table 4-17:

TP = 0.327 mg/l (singl e-family residential)

2. Calculate TP loading to wet detention pond



# After the dry retention pre-treatment, th e annual runoff input to the pond = 52.27

ac-ft/yr

TP load to pond =

3. Calculate TP concentration in pond



# At the proposed 200-day residence time, the TP removal was pr eviously estimated

as 79.9%.

Annual mass of TP remaining =

21.08 kg TP/yr x (1 – 0.799) = 4.24 kg TP/yr

The mass will be distributed within the pond permanent pool volume (28.64 ac-ft)

and the pond outflow. Assu ming that inflow and outflo w are approximately equal,

the outflow will be 52.27 ac-ft.

Mean pond c oncentration =

4.24 kg TP

x 1 yr

x 1 ac

x 1 ft 3



# yr (52.27 + 28.64 ac-ft) 43,560 ft 2 

# 7.48 gal

x 1 gal

x 10 6 

# mg = 0.042 mg TP/ liter = 42 μ g TP/liter 3.785 liter kg TP/yr kg 21.

=

mg 10 kg

1

x liter mg 0.3

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x ft/yr

- ac 5

6 3 2



# 08 27 27

. 2

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-7

4. Calculate mean chloroph yll-a concentration in pond



# The relationship between TP and chlorophy ll-a in a Florida waterbody is expressed

by the following relationship:

ln (chyl-a) = 1.058 ln (TP) - 0.934 (Eq. 4)

where: chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total P concentration ( μ 

# g/l)

ln (chyl-a) = 1.058 ln (42) - 0.934

chyl-a = e 3.02 

# = 20.5 mg/m 3



# 5. Calculate mean Secchi disk depth



# The relationship between chlorophyll- a and Secchi disk depth in a Florida

waterbody is expressed by the following relationship:

where: SD = Secchi disk depth (m)

chyl-a = chlorophyll-a (mg/m 3 

# )

6. Calculate depth of an oxic conditions in pond



# Using the relationship expres sed in Eq. 5, the depth of anoxic conditions within the

pond can be estimated as follows:

Depth of DO < 1 = 3.035 x Secchi + 0.02164 x (chyl- a) – 0.004979 x Total P 

# a)

- chyl + (6.0632 a)

- chyl 0.3041 + 24.2386

= SD ] )( [(

ft 3.

= m = ) 2 + (6.0632 ) (2 0.3041 + 24.2386

= SD 76 15

. 1

5

. 0 ] 5

. 0 ) [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-8

where:

Depth of DO < 1 = anoxic depth (m)

Secchi = Secchi disk depth (m)

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

Total P = total phosphorus concentration ( μ 

# g/l)

Depth of DO < 1 = 3.035 (1.15) + 0.02164 (20.5) - 0.004979 (42) = 3.73 m = 12.2 ft

If the proposed pond depth exceeds the es timated anoxic zone depth of 12.2 ft,

aeration or other mixing will be required for areas deeper than 12.2 ft to maintain a

well mixed water column. The aeration or mixing must be sufficient to mix the

water column to the maximum pond dept h. The specific design of the required

system should be selected by a qualified aeration specialist.

As an alternative to providing aeration or mixing within the pond, the required

permanent pool volume could be considered as only the volume above the anoxic

zone and not the entire volume of the pond. Areas below the anoxic depth would be

considered as dead storage, although thes e areas would provide a significant storage

volume for collect ed solids.

If the pond is modified, based on the results of the calcula ted anoxic zone depth, the

calculations would need to be redone to estimate new values for total phosphorus,

Secchi disk depth, chlorophyll-a, and dept h of anoxia to demo nstrate that the new

design meets the required permanent pool volume above the zone of anoxia.

7. Estimate pond dimensions



# For the estimation of pond dimensions, assume that the mean depth (pond

volume/pond area) is 2/3 of the maximum depth.

Mean pond depth = 12 .2 ft x 2/3 = 8.13 ft

Pond surface area = pond volume/mean depth = 28.64 ac-ft/8.13 ft = 3.52 ac

2B. ORLANDO (ZONE 2) PROJECT



# The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-9

1. Required Dry Retention Depth



# From Appendix D (Zone 2), the required removal ef ficiency of 65.0% is achieved with a dry

retention depth between 0.25 and 0.50 inch.

For a dry retention depth of 0.50 inch, the treat ment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 65.7%

.

For a dry retention depth of 0.25 inch, the treat ment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 49.0%

.

By iterating between 0.25 inch (49.0%) and 0.50 inch (65.7%), the dry retention depth required to

achieve 65.0% remova l is 0.49 inch.

Therefore, the required treat ment train will consist of:

a. 0.49 inch dry retention, followed by

b. Wet detention pond with a 2 00-day mean residence time

2. Wet Detention Pond Characteristics



# The required physical characteristic s of the wet detention pond are determined based on the desired

residence time and the impacts of the proposed dry retention pre-treatment.

A. Calculate annual ru noff inputs to pond



# The annual runoff coefficient for the development can be estimate d using the tables included

in Appendix C (Zone 2).

For: DCIA = 18.75% an d non-DCIA CN = 81.4

The estimated “C” value is obtained by iteration as discussed previously.

Annual C Value = 0.253

The annual rainfall fo r the Orlando area = 50.0 inches (Appendix A.3)

Annual generated runoff volume =

90 acres x 50.0 inches/year x 1 ft/1 2 inches x 0.253 = 94.92 ac-ft/yr

The calculated efficiency of 65.0% for the dr y retention pre-treatment means that 65.0% of

the annual runoff volume w ill be infiltrated into the ground and will not disc harge directly

into the wet detention pond. The annual runo ff volume which reaches the pond is calculated

as:

Annual Inputs to Pond = 94.92 ac-ft/yr x (1 - 0.650) = 33.22 ac-ft/yr

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-10

For a 200-day residence time, the pond volume will be:

33.22 ac-ft/yr x 1 year/365 days x 200 days = 18.21 ac-ft

B. Estimate maximum allowable pond depth



# The maximum allowable pond depth is directly re lated to the anticipated algal productivity

within the pond. Assuming that wet dete ntion ponds are primarily phosphorus-limited

ecosystems, the productivity can be estimated based on the mean TP concentration.

1. Estimate runoff characteristics



# For a single-family residential land use, th e emc for TP in runoff can be obtained

from Table 4-17:

TP = 0.327 mg/l (singl e-family residential)

2. Calculate TP loading to wet detention pond



# After the dry retention pre-treatment, th e annual runoff input to the pond = 33.22

ac-ft/yr

TP load to pond =

3. Calculate TP concentration in pond



# At the proposed 200-day residence time, the TP removal was pr eviously estimated

as 79.9%.

Annual mass of TP remaining in water column =

13.40 kg TP/yr x (1 – 0.799) = 2.69 kg TP/yr

Remaining TP mass will be distributed between the po nd volume and the annual

outflow:

= 18.21 ac-ft + 33 .22 ac-ft = 51.43 ac-ft TP/yr kg

=

mg 10 kg

1

x liter mg 0.3

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x ft/yr

- ac

6 3 2



# 40

. 13 27 22

. 33

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-11

Mean pond c oncentration =

2.69 kg TP

x 1 yr

x 1 ac

x 1 ft 3



# yr 51.43 ac-ft 43,560 ft 2 

# 7.48 gal

x 1 gal

x 10 6 

# mg = 0.042 mg TP/ liter = 42 μ 

# g TP/liter 3.785 liter kg

4. Calculate mean chloroph yll-a concentration in pond



# The relationship between TP and chlorophy ll-a in a Florida waterbody is expressed

by the following relationship:

ln (chyl-a) = 1.058 ln (TP) - 0.934 (Eq. 4)

where: chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total P concentration ( μ 

# g/l)

ln (chyl-a) = 1.058 ln (42) - 0.934

chyl-a = e 3.02 

# = 20.5 mg/m 3



# 5. Calculate mean Secchi disk depth



# The relationship between chlorophyll- a and Secchi disk depth in a Florida

waterbody is expressed by the following relationship:

where: SD = Secchi disk depth (m)

chyl-a = chlorophyll-a (mg/m 3 

# ) a)

- chyl + (6.0632 a)

- chyl 0.3041 + 24.2386

= SD ] ( ) [(

ft 3.

= m = ) 2 + (6.0632 ) (2 0.3041) + 24.2386

= SD 76 15

. 1

5

. 0 ] 5

. 0 [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-12

6. Calculate depth of an oxic conditions in pond



# Using the relationship expres sed in Eq. 5, the depth of anoxic conditions within the

pond can be estimated as follows:

Depth of DO < 1 = 3.035 x Secchi + 0.02 164 (chyl-a) – 0. 004979 x Total P

where:

Depth of DO < 1 = anoxic depth (m)

Secchi = Secchi disk depth (m)

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

Total P = total phosphorus concentration ( μ 

# g/l)

Depth of DO < 1 = 3.035 (1.15) + 0.02164 (20.5) - 0.004979 (42) = 3.73 m = 12.2 ft

If the proposed pond depth exceeds the estimated photic zone depth of 12.2 ft,

aeration or other mixing will be required for areas deeper than 12.2 ft to maintain a

well mixed water column. The aeration or mixing must be sufficient to mix the

water column to the maximum pond dept h. The specific design of the required

system should be selected by a qualified aeration specialist.

As an alternative to providing aeration or mixing within the pond, the required

permanent pool volume could be considered as only the volume above the anoxic

zone and not the entire volume of the pond. Areas below the anoxic depth would be

considered as dead storage, although thes e areas would provide a significant storage

volume for collect ed solids.

If the pond is modified, based on the results of the calcula ted anoxic zone depth, the

calculations would need to be redone to estimate new values for total phosphorus,

Secchi disk depth, chlorophyll-a, and dept h of anoxia to demo nstrate that the new

design meets the required permanent pool volume above the zone of anoxia.

7. Estimate pond dimensions



# For the estimation of pond dimensions, assume that the mean depth (pond

volume/pond area) is 2/3 of the maximum depth.

Mean pond depth = 12 .2 ft x 2/3 = 8.13 ft

Pond surface area = pond volume/mean depth = 18.21 ac-ft/8.13 ft = 2.24 ac

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-13

2C. KEY WEST (ZONE 3) PROJECT



# The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

1. Required Dry Retention Depth



# From Appendix D (Zone 3), the required removal ef ficiency of 65.0% is achieved with a dry

retention depth between 0.75 and 1.00 inch.

For a dry retention depth of 0.75 inch, the treat ment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project conditions is 65.0% . There is no need to conduc t further iterations since a dry

retention depth of 0.75 inch will provide the required removal efficiency of 65.0%.

The dry retention depth required to achieve 65.0% removal is 0.75 inch.

Therefore, the required treat ment train will consist of:

a. 0.75 inch dry retention, followed by

b. Wet detention pond with a 2 00-day mean residence time

2. Wet Detention Pond Characteristics



# The required physical characteristic s of the wet detention pond are determined based on the desired

residence time and the impacts of the proposed dry retention pre-treatment.

A. Calculate annual ru noff inputs to pond



# The annual runoff coefficient for the development can be estimate d using the tables included

in Appendix C (Zone 3).

For: DCIA = 18.75%and non-DCIA CN = 81.4

The estimated “C” value is obtained by iteration as discussed previously.

Annual C Value = 0.266

The annual rainfall for the Key West area = 40.0 inches (Appendix A.3)

Annual generated runoff volume =

90 acres x 40.0 inches/year x 1 ft/1 2 inches x 0.266 = 79.80 ac-ft/yr

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-14

The calculated efficiency of 65.0% for the dr y retention pre-treatment means that 65.0% of

the annual runoff volume w ill be infiltrated into the ground and will not disc harge directly

into the wet detention pond. The annual runo ff volume which reaches the pond is calculated

as:

Annual Inputs to Pond = 79.80 ac-ft/yr x (1 - 0.650) = 27.93 ac-ft/yr

For a 200-day residence time, the pond volume will be:

27.93 ac-ft/yr x 1 year/365 days x 200 days = 15.30 ac-ft

B. Estimate maximum allowable pond depth



# The maximum allowable pond depth is directly re lated to the anticipated algal productivity

within the pond. Assuming that wet dete ntion ponds are primarily phosphorus-limited

ecosystems, the productivity can be estimated based on the mean TP concentration.

1. Estimate runoff characteristics



# For a single-family residential land use, th e emc for TP in runoff can be obtained

from Table 4-16:

TP = 0.327 mg/l (singl e-family residential)

2. Calculate TP loading to wet detention pond



# After the dry retention pre-treatment, th e annual runoff input to the pond = 27.93

ac-ft/yr

TP load to pond =

3. Calculate TP concentration in pond



# At the proposed 200-day residence time, the TP removal was pr eviously estimated

as 79.9%.

Annual mass of TP remaining in water column =

11.26 kg TP/yr x (1 – 0.799) = 2.26 kg TP/yr TP/yr kg

=

mg 10 kg

1

x liter mg 0.3

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x ft/yr

- ac

6 3 2



# 26

. 11 27 93

. 27

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-15

The remaining TP mass will be distributed between the po nd volume and the annual

outflow:

= 15.30 ac-ft + 27 .93 ac-ft = 43.23 ac-ft

Mean pond c oncentration =

2.26 kg TP

x 1 yr

x 1 ac

x 1 ft 3



# yr 43.23 ac-ft 43,560 ft 2 

# 7.48 gal

x 1 gal

x 10 6 

# mg = 0.042 mg TP/ liter = 42 μ 

# g TP/liter 3.785 liter kg

4. Calculate mean chloroph yll-a concentration in pond



# The relationship between TP and chlorophy ll-a in a Florida waterbody is expressed

by the following relationship:

ln (chyl-a) = 1.058 ln (TP) - 0.934 (Eq. 4)

where: chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total P concentration ( μ 

# g/l)

ln (chyl-a) = 1.058 ln (42) - 0.934

chyl-a = e 3.02 

# = 20.5 mg/m 3



# 5. Calculate mean Secchi disk depth



# The relationship between chlorophyll- a and Secchi disk depth in a Florida

waterbody is expressed by the following relationship:

where: SD = Secchi disk depth (m)

chyl-a = chlorophyll-a (mg/m 3 

# ) a)

- chyl + (6.0632 a)

- chyl 0.3041 + 24.2386

= SD ] )( [(

ft 3.

= m = ) 2 + (6.0632 ) (2 0.3041) + 24.2386

= SD 76 15

. 1

5

. 0 ] 5

. 0 [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-16

6. Calculate depth of an oxic conditions in pond



# Using the relationship expres sed in Eq. 5, the depth of anoxic conditions within the

pond can be estimated as follows:

Depth of DO < 1 = 3.035 x Secchi + 0.02 164 (chyl-a) – 0. 004979 x Total P

where:

Depth of DO < 1 = anoxic depth (m)

Secchi = Secchi disk depth (m)

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

Total P = total phosphorus concentration ( μ 

# g/l)

Depth of DO < 1 = 3.035 (1.15) + 0.02164 (20.5) - 0.004979 (42) = 3.73 m = 12.2 ft

If the proposed pond depth exceeds the estimated photic zone depth of 12.2 ft,

aeration or other mixing will be required for areas deeper than 12.2 ft to maintain a

well mixed water column. The aeration or mixing must be sufficient to mix the

water column to the maximum pond dept h. The specific design of the required

system should be selected by a qualified aeration specialist.

As an alternative to providing aeration or mixing within the pond, the required

permanent pool volume could be considered as only the volume above the anoxic

zone and not the entire volume of the pond. Areas below the anoxic depth would be

considered as dead storage, although thes e areas would provide a significant storage

volume for collect ed solids.

If the pond is modified, based on the results of the calcula ted anoxic zone depth, the

calculations would need to be redone to estimate new values for total phosphorus,

Secchi disk depth, chlorophyll-a, and dept h of anoxia to demo nstrate that the new

design meets the required permanent pool volume above the zone of anoxia.

7. Estimate pond dimensions



# For the estimation of pond dimensions, assume that the mean depth (pond

volume/pond area) is 2/3 of the maximum depth.

Mean pond depth = 12 .2 ft x 2/3 = 8.13 ft

Pond surface area = pond volume/mean depth = 15.30 ac-ft/8.13 ft = 1.88 ac

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-17

7.2 Design Example #2:

Stormwater Treatment to Meet the 95% (OFW)

Pollution Reduction Target Goal



# Determine the water quality treatment requi rements for a 100-acre proposed single-family

residential site. Perform separate calculations for identical projects located in Pensacola (Zone

1), Orlando (Zone 2), and Key West (Zone 3). A summary of pre- and post-development

conditions is given below.

Calculate Pre- and Post-Development Conditions

Pre-Development Conditions

1. Land Use 

# : 90 acres - mixture of rangel and/forest (fair condition)

10 acres – isolated wetlands

2. Ground Cover/Soil Types 

# : Rangeland/Forest – Hydr ologic Soil Group (HSG) D

Wetland – hydric soils

3. Impervious Areas : 

# 0% impervious, 0% Directly Connected Impervious Area (DCIA)

Post Development Conditions

1. Land Use 

# : 90 acres of single-family residential

5 acres of stormwater management systems

5 acres of preserved wetlands

2. Ground Cover/Soil Types



# A. Residential areas will be cove red with lawns in good condition

B. Soil types will remain HSG D

3. Impervious/DCIA Areas



# A. Residential areas wi ll be 25% impervi ous, 75% of which will be DCIA

Impervious Area = 25% of site = 90 ac x 0.25 = 22.50 acres

DCIA Area = 22.50 acres x 0.75 = 16.88 acres

DCIA Percentage = (16.88 ac/90.0 ac) x 100 = 18.7% of developed area

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-18

4. Calculate composite non-DCIA curve number from TR-55 

# :

Curve number for lawns in go od condition in HSG D = 80

Areas of lawns = 90 acres to tal – 22.50 ac imperv ious area = 67.50 acres pervious area

Impervious area which is not DCIA = 22.50 ac – 16.88 ac = 5.62 ac

Assume a curve nu mber of 98 for impervious areas

Non-DCIA curve number =

Calculate Treatment Requirements for 95% Removal (OFW Criteria)



# Estimation of treatment requirements assumes th at only dry retention and wet detention are

capable of approaching the 95% pollutant reduction goal.

1. Dry Retention

A. Pensacola Project (Zone 1)



# The required retention depth to achieve an annual removal efficiency of 95% in

Zone 1 is determined from Table 6-4 (Z one 1) based on DCIA percentage and the

non-DCIA CN value. For this project:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

The required dry retention depth is obtained by iterat ing between DCIA

percentages of 10 and 20, and for non-DCIA CN values between 80 and 90. The

required dry retention depth = 3. 66 inches over the developed area.

B. Orlando Project (Zone 2)



# If the project was located in Orlando, th e required dry retention depth would be

slightly different due to diffe rences in the distribution of rain events. The required

retention depth would be obtained from Table 6-4 (Zone 2) by iterating between

DCIA percentages of 10 and 20, and for non-DCIA CN values between 80 and 90.

The required dry retention depth = 2. 45 inches over the developed area. 4

. 81

62 50

. 67 62 50

. 67

=

ac 5. + ac (98) ac 5. + (80) ac

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-19

C. Key West Project (Zone 3)



# If the project was located in Key West, the required dry reten tion depth would be

slightly different due to diffe rences in the distribution of rain events. The required

retention depth would be obtained from Table 6-4 (Zone 3) by iterating between

DCIA percentages of 10 and 20, and for non-DCIA CN values between 80 and 90.

The required dry retention depth = 3. 62 inches over the developed area.

2. Wet Detention

Treatment Train Approach



# Calculation of design criteria for a wet deten tion pond is based on determining the detention

time required to achieve the desired pollutant removal efficiency of 95%. For practical

purposes, this efficiency is assumed to apply to nitrogen and phosphoru s since other

pollutants such as BOD and TSS are typically re moved at a faster rate than nutrients.

However, as discussed in Section 5.2.2, wet detention systems are incapable of providing

95% annual mass load reduction for either nitrogen or phosphorus, even at extended

detention times (> 200 days).

Therefore, when wet detention is desired as a treatment option, pr e-treatment must be

provided to enhance the total system performance efficiency to a minimum of 95% for both

total nitrogen and total p hosphorus. Since dry retention prov ides the best pr e-treatment in a

minimal space, dry retention ap pears to be the pre-treatment system of choice for this

application. There are many combinations of dry retentio n and wet detention which can

provide the desired 95% removal.

Assume that a wet detention pond is designed with a residence time of 100 days.

Anticipated TN removal (Figure 5-11) =

Anticipated TP removal (Figure 5-10) =

Eff = 40.13 + 6.372 ln (t d 

# ) + 0.213 (ln t d 

# ) 2 

# = 40.13 + 6.372 ln (100) + 0.213 (ln 100) 2 

# = 70.5%

Based on the estimated performance efficiency of the wet detention po nd, the pond fails to

meet the 95% removal criteria for either TN or TP. Therefore, the remaining efficiency is

achieved using dry detention. The required effici ency for the dry reten tion is calculated by

Eq. 1 below:

Treatment Train Efficiency = Eff 1 

# + (1 – Eff 1 

# ) x Eff 2 

# (Eq. 1)

where: Eff 1 

# = required efficiency of dry retention

Eff 2 

# = efficiency of wet detention %

. 4

= 00 + 4 00 x 4

= ) t + ( ) t x (4 Eff

d d 

# 9 1

1 38

. 1

75

. 3

38

. 4 75

. 3

=

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-20

For total nitrogen: 0.95 = Eff 1 

# + (1 – Eff 1 

# ) x 0.419

Eff 1 

# = 0.947 = 94.7%

For total phosphorus: 0.95 = Eff 1 

# + (1 – Eff 1 

# ) x 0.705

Eff 1 

# = 0.831 = 83.1%

The largest removal efficiency of 94.7% is required for total nitrogen. Therefore, this

efficiency will dictate the require d design for the treatment train.

2A. PENSACOLA (ZONE 1) PROJECT



# The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

1. Required Dry Retention Depth



# From Appendix D (Zone 1), the required removal ef ficiency of 94.7% is achieved with a dry

retention depth between 3.50 and 3.75 inches.

For a dry retention depth of 3.50 inches, the treatment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 94.3%

.

For a dry retention depth of 3.75 inches, the treatment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 95.1%

.

By iterating between 3.50 inches (94.3%) and 3.75 inches (95.1%), the dry retention depth required

to achieve 94.7% rem oval is 3.72 inches.

Therefore, the required treat ment train will consist of:

a. 3.72 inches dry rete ntion, followed by

b. Wet detention pond with a 1 00-day mean residence time

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-21

2. Wet Detention Pond Characteristics



# The required physical characteristic s of the wet detention pond are determined based on the desired

residence time and the impacts of the proposed dry retention pre-treatment.

a. Calculate annual ru noff inputs to pond



# The annual runoff coefficient for the development can be estimate d using the tables included

in Appendix C (Zone 1).

For: DCIA = 18.75% an d non-DCIA CN = 81.4

The estimated “C” value is obtained by iteration as discussed previously.

Annual C Value = 0.304

The annual rainfall for the Pensacol a area = 65.5 inches (Appendix A.3)

Annual generated runoff volume =

90 acres x 65.5 inches/year x 1 ft/1 2 inches x 0.304 = 149.34 ac-ft/yr

The calculated efficiency of 94.7% for the dr y retention pre-treatment means that 94.7% of

the annual runoff volume w ill be infiltrated into the ground and will not disc harge directly

into the wet detention pond. The annual runo ff volume which reaches the pond is calculated

as:

Annual Inputs to Pond = 149.34 ac-ft/yr x (1 - 0.947) = 7.92 ac-ft/yr

For a 100-day residence time, the pond volume will be:

7.92 ac-ft/yr x 1 year/365 days x 10 0 days = 2.17 ac-ft

b. Estimate maximum allowable pond depth



# The maximum allowable pond depth is directly re lated to the anticipated algal productivity

within the pond. Assuming that wet dete ntion ponds are primarily phosphorus-limited

ecosystems, the productivity can be estimated based on the mean TP concentration.

1. Estimate runoff characteristics



# For a single-family residentia l land use, the event mean concentration (emc) for TP

in runoff can be obtain ed from Table 4-17:

TP = 0.327 mg/l (singl e-family residential)

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-22

2. Calculate TP loading to wet detention pond



# After the dry retention pre-treatment, th e annual runoff input to the pond = 7.92

ac-ft/yr

TP load to pond =

3. Calculate TP concentration in pond



# At the proposed 100-day residence time, the TP removal was pr eviously estimated

as 70.5%.

Annual mass of TP remaining in water column =

3.19 kg TP/yr x (1 – 0.705) = 0.94 kg TP/yr

The remaining TP mass will be distributed between the po nd volume and the annual

outflow:

= 2.17 ac-fat + 7. 92 ac-ft = 10.09 ac-ft

Mean pond c oncentration =

0.94 kg TP

x 1 yr

x 1 ac

x 1 ft 3



# yr 10.09 ac-ft 43,560 ft 2 

# 7.48 gal

x 1 gal

x 10 6 

# mg = 0.076 mg TP/ liter = 76 μ 

# g TP/liter 3.785 liter kg

4. Calculate mean chloroph yll-a concentration in pond



# The relationship between TP and chlorophy ll-a in a Florida waterbody is expressed

by the following relationship:

ln (chyl-a) = 1.058 ln (TP) - 0.934 (Eq. 4)

where: chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total P concentration ( μ 

# g/l)

ln (chyl-a) = 1.058 ln (76) - 0.934

chyl-a = e 3.648 

# = 38.4 mg/m 3 

# TP/yr kg

=

mg 10 kg

1

x liter mg 0.3

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x ft/yr

- ac

6 3 2



# 19

. 3 27 92

. 7

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-23

5. Calculate mean Secchi disk depth



# The relationship between chlorophyll- a and Secchi disk depth in a Florida

waterbody is expressed by the following relationship:

where: SD = Secchi disk depth (m)

chyl-a = chlorophyll-a (mg/m 3 

# )

6. Calculate depth of an oxic conditions in pond



# Using the relationship expres sed in Eq. 5, the depth of anoxic conditions within the

pond can be estimated as follows:

Depth of DO < 1 = 3.035 x S ecchi + 0.02164 x (chyl-a) – 0.004979 x Total P

where:

Depth of DO < 1 = anoxic depth (m)

Secchi = Secchi disk depth (m)

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

Total P = total phosphorus concentration ( μ 

# g/l)

Depth of DO < 1 = 3.035 (0.81) + 0.02164 (38.4) - 0.004979 (72) = 2.93 m = 9.6 ft

If the proposed pond depth exceeds the estimated photic zone depth of 9.6 ft,

aeration or other mixing will be required fo r areas deeper than 9. 6 ft to maintain a

well mixed water column. The aeration or mixing must be sufficient to mix the

water column to the maximum pond dept h. The specific design of the required

system should be selected by a qualified aeration specialist. a)

- chyl + (6.0632 a)

- chyl 0.3041 + 24.2386

= SD ] )( [(

ft

= m 0.

= ) + (6.0632 ) ( 0.3041) + 24.2386

= SD 65

. 2 81

4

. 38 ] 4

. 38 [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-24

As an alternative to providing aeration or mixing within the pond, the required

permanent pool volume could be considered as only the volume above the anoxic

zone and not the entire volume of the pond. Areas below the anoxic depth would be

considered as dead storage, although thes e areas would provide a significant storage

volume for collect ed solids.

If the pond is modified, based on the results of the calcula ted anoxic zone depth, the

calculations would need to be redone to estimate new values for total phosphorus,

Secchi disk depth, chlorophyll-a, and dept h of anoxia to demo nstrate that the new

design meets the required permanent pool volume above the zone of anoxia.

7. Estimate pond dimensions



# For the estimation of pond dimensions, assume that the mean depth (pond

volume/pond area) is 2/3 of the maximum depth.

Mean pond depth = 9.6 ft x 2/3 = 6.40 ft

Pond surface area = pond volume/mean depth = 2.17 ac-ft/6.40 ft = 0.34 ac

2B. ORLANDO (ZONE 2) PROJECT



# The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

1. Required Dry Retention Depth



# From Appendix D (Zone 2), the required removal ef ficiency of 94.7% is achieved with a dry

retention depth between 2.25 and 2.00 inches.

For a dry retention depth of 2.25 inches, the treatment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project conditions is 94.8

.

For a dry retention depth of 2.00 inches, the treatment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project conditions is 92.4

.

By iterating between 2.00 inches (92.4%) and 2.25 inches (94.8%), the dry retention depth required

to achieve 94.7% rem oval is 2.24 inches.

Therefore, the required treat ment train will consist of:

a. 2.24 inches dry rete ntion, followed by

b. Wet detention pond with a 1 00-day mean residence time

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-25

2. Wet Detention Pond Characteristics



# The required physical characteristic s of the wet detention pond are determined based on the desired

residence time and the impacts of the proposed dry retention pre-treatment.

A. Calculate annual ru noff inputs to pond



# The annual runoff coefficient for the development can be estimate d using the tables included

in Appendix C (Orlando).

For: DCIA = 18.75% an d non-DCIA CN = 81.4

The estimated “C” value is obtained by iteration as discussed previously.

Annual C Value = 0.253

The annual rainfall fo r the Orlando area = 50.0 inches (Appendix A.3)

Annual generated runoff volume =

90 acres x 50.0 inches/year x 1 ft/1 2 inches x 0.253 = 94.88 ac-ft/yr

The calculated efficiency of 94.7% for the dr y retention pre-treatment means that 94.7% of

the annual runoff volume w ill be infiltrated into the ground and will not disc harge directly

into the wet detention pond. The annual runo ff volume which reaches the pond is calculated

as:

Annual Inputs to Pond = 94.88 ac-ft/yr x (1 - 0.947) = 5.03 ac-ft/yr

For a 100-day residence time, the pond volume will be:

5.03 ac-ft/yr x 1 year/365 days x 10 0 days = 1.38 ac-ft

B. Estimate maximum allowable pond depth



# The maximum allowable pond depth is directly re lated to the anticipated algal productivity

within the pond. Assuming that wet dete ntion ponds are primarily phosphorus-limited

ecosystems, the productivity can be estimated based on the mean TP concentration.

1. Estimate runoff characteristics



# For a single-family residential land use, th e emc for TP in runoff can be obtained

from Table 4-17:

TP = 0.327 mg/l (singl e-family residential)

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-26

2. Calculate TP loading to wet detention pond



# After the dry retention pre- treatment, the annual runoff input to the pond = 5.03 acft/yr

TP load to pond =

3. Calculate TP concentration in pond



# At the proposed 100-day residence time, the TP removal was pr eviously estimated

as 70.5%.

Annual mass of TP remaining in water column =

2.03 kg TP/yr x (1 – 0.705) = 0.60 kg TP/yr

The remaining TP mass will be distributed between the po nd volume and the annual

outflow:

= 1.38 ac-ft + 5. 03 ac-ft = 6.41 ac-ft

Mean pond conc entration =

0.60 kg TP

x 1 yr

x 1 ac

x 1 ft 3



# yr 6.41 ac-ft 43,560 ft 2 

# 7.48 gal

x 1 gal

x 10 6 

# mg = 0.076 mg TP/ liter = 76 μ 

# g TP/liter 3.785 liter kg

4. Calculate mean chloroph yll-a concentration in pond



# The relationship between TP and chlorophy ll-a in a Florida waterbody is expressed

by the following relationship:

ln (chyl-a) = 1.058 ln (TP) - 0.934 (Eq. 4)

where: chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total P concentration ( μ 

# g/l)

ln (chyl-a) = 1.058 ln (76) - 0.934

chyl-a = e 3.65 

# = 38.4 mg/m 3 

# TP/yr kg

=

mg 10 kg

1

x liter mg 0.3

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x ft/yr

- ac

6 3 2



# 03

. 2 27 03

. 5

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-27

5. Calculate mean Secchi disk depth



# The relationship between chlorophyll- a and Secchi disk depth in a Florida

waterbody is expressed by the following relationship:

where: SD = Secchi disk depth (m)

chyl-a = chlorophyll-a (mg/m 3 

# )

6. Calculate depth of an oxic conditions in pond



# Using the relationship expres sed in Eq. 5, the depth of anoxic conditions within the

pond can be estimated as follows:

Depth of DO < 1 = 3.035 x S ecchi + 0.02164 x (chyl- a) – 0.004979 x Total P

where:

Depth of DO < 1 = anoxic depth (m)

Secchi = Secchi disk depth (m)

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

Total P = total phosphorus concentration ( μ 

# g/l)

Depth of DO < 1 = 3.035 (0.81) + 0.02164 (38.4) - 0.004979 (76) = 2.91 m = 9.5 ft

If the proposed pond depth exceeds the estimated photic zone depth of 9.5 ft,

aeration or other mixing will be required fo r areas deeper than 9. 5 ft to maintain a

well mixed water column. The aeration or mixing must be sufficient to mix the

water column to the maximum pond dept h. The specific design of the required

system should be selected by a qualified aeration specialist. a)

- chyl + (6.0632 a)

- chyl 0.3041 + 24.2386

= SD ] )( [(

ft

= m 0.

= ) + (6.0632 ) ( 0.3041) + 24.2386

= SD 65

. 2 81

4

. 38 ] 4

. 38 [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-28

As an alternative to providing aeration or mixing within the pond, the required

permanent pool volume could be considered as only the volume above the anoxic

zone and not the entire volume of the pond. Areas below the anoxic depth would be

considered as dead storage, although thes e areas would provide a significant storage

volume for collected solids.

If the pond is modified, based on the results of the calcula ted anoxic zone depth, the

calculations would need to be redone to estimate new values for total phosphorus,

Secchi disk depth, chlorophyll-a, and dept h of anoxia to demo nstrate that the new

design meets the required permanent pool volume above the zone of anoxia.

7. Estimate pond dimensions



# For the estimation of pond dimensions, assume that the mean depth (pond

volume/pond area) is 2/3 of the maximum depth.

Mean pond depth = 9.5 ft x 2/3 = 6.36 ft

Pond surface area = pond volume/mean depth = 1.38 ac-ft/6.36 ft = 0.22 ac

2C. KEY WEST (ZONE 3) PROJECT



# The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

1. Required Dry Retention Depth



# From Appendix D (Zone 3), the required removal ef ficiency of 94.7% is achieved with a dry

retention depth in ex cess of 4 inches.

For a dry retention depth of 4.00 inches, the treatment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 93.8%

.

The maximum retention depth of 4 inches listed in Appendix D fail s to reach the required removal

efficiency of 94.7% for the retention portion of the treatment train. Since increasing the detention

time of the wet detention pond will not significantly enhance the efficiency of the system, it is not

possible to achieve the goal of 95% pollutant remo val for both total nitrogen and total phosphorus

for Zone 3 conditio ns without involving unreasonable dry rete ntion requirements.

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-29

7.3 Design Example #3:

Stormwater Treatment to Mee t the Post- Less Than or

Equal to Pre-Pollution Reduction Target Goal



# Determine the water quality treatment requi rements for a 100-acre proposed single-family

residential site. Perform separate calculations for identical projects located in Pensacola (Zone

1), Orlando (Zone 2), and Key West (Zone 3). A summary of pre- and post-development

conditions is given below.

Calculate Pre- and Post-Development Conditions

Pre-Development Conditions

1. Land Use 

# : 90 acres - mixture of rangel and/forest (fair condition)

10 acres – isolated hardwood wetlands

2. Ground Cover/Soil Types 

# : Rangeland/Forest – Hydr ologic Soil Group (HSG) D

Wetland – hydric soils

3. Impervious Areas : 

# 0% impervious, 0% Directly Connected Impervious Area (DCIA)

4. Estimation of Pre-Development Loadings 

# : The total project site covers 100 acres,

including 90 acres of rangeland/ forest and 10 acres of wetlands . Five acres of the on-site

wetlands will be preserved and 5 acres will be incorporated into the project.

A. Pre-Development Runoff Volume

(1) Rangeland/Forest 

# : From TR-55, the CN for rangeland (fair condition) in

HSG D soils is 84 and the CN for fore st areas (woods) is 82. Assuming a

50-50 mixture of rangeland and forest, the composite CN is:

Composite CN = 84 (rangeland) x 0.5 + 82 (forest) x 0.5 = 83

From Appendix C, the annual runoff co efficient for DCIA = 0 and CN =

83 can be estimated by interpolation:

Pensacola (Zone 1) = 0.197

Orlando (Zone 2) = 0.140

Key West (Zone 3) = 0.159

From Appendix A.3, the annual rainfall depths for the 3 sites are:

Pensacola = 65.5 in/yr

Orlando = 50.0 in/yr

Key West = 40.0 in/yr

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-30

Annual runoff volumes for the 3 sites are:

Pensacola:

90 acres x 65.5 in/yr x 1 ft/12 in x 0.197 = 96.78 ac-ft/yr

Orlando:

90 acres x 50.0 in/yr x 1 ft/12 in x 0.140 = 52.5 ac-ft/yr

Key West:

90 acres x 40.0 in/yr x 1 ft/12 in x 0.159 = 47.7 ac-ft/yr

(2) Isolated Hardwood Wetland : 

# From TR-55, the CN for wooded areas

(fair condition) in hydric soils (HSG D) is 82.

From Appendix C, the annual runoff coefficient for DCIA = 0 and CN =

82 can be estimated by interpolation:

Pensacola (Zone 1) = 0.185

Orlando (Zone 2) = 0.142

Key West (Zone 3) = 0.159

Based on a review of the site cond itions (including wetland indicators and

water level data) by the project biologi st and engineer, it was determined

that approximately 75% of the genera ted runoff volume is retained in the

wetland and 25% leaves the wetland as runoff. Of the 10 acres of on-site

wetlands, 5 acres will be preserved and 5 acres will be incorporated into

the development. Calculations are conducted only for the 5 acres to be

altered, since the remaining 5 acr es will have the same loading

characteristics under pre- and post-conditions.

Annual runoff export from the 5-acre wetland areas are:

Pensacola:

5 acres x 65.5 in/yr x 1 ft/12 in x 0.185 x 0.25 = 1.26 ac-ft

Orlando:

5 acres x 50.0 in/yr x 1 ft/12 in x 0.131 x 0.25 = 0.68 ac-ft

Key West:

5 acres x 40.0 in/yr x 1 ft/12 in x 0.149 x 0.25 = 0.62 ac-ft

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-31

B. Total Nitrogen

(1) Rangeland/Forest 

# : The typical TN concen tration for undeveloped land

(rangeland-forest) = 1.15 mg/l (Table 4-17)

Pensacola: Annual TN Load =

96.78 ac-ft

x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 1.15 mg TN

x 1 kg = 137.3 kg TN/yr yr ac ft 3 

# gal liter 10 6 

# mg

Orlando: Annual TN Load =

52.5 ac-ft

x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 1.15 mg TN

x 1 kg = 74.5 kg TN/yr yr ac ft 3 

# gal liter 10 6 

# mg

Key West: Annual TN Load =

47.7 ac-ft

x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 1.15 mg TN

x 1 kg = 67.7 kg TN/yr yr ac ft 3 

# gal liter 10 6 

# mg

(2) Hardwood Wetland 

# : Water quality monitoring was conducted in the

hardwood wetland to establish ambient wa ter quality characte ristics. This

monitoring resulted in a mean TN concentration of 2.0 mg/l for TN.

Pensacola: Annual TN Load =

1.26 ac-ft x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 2.00 mg TN

x 1 kg = 3.11 kg TN/yr ac ft 3 

# gal liter 10 6 

# mg

Orlando: Annual TN Load =

0.68 ac-ft x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 2.00 mg TN

x 1 kg = 1.68 kg TN/yr ac ft 3 

# gal liter 10 6 

# mg

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-32

Key West: Annual TN Load =

0.62 ac-ft x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 2.00 mg TN

x 1 kg = 1.53 kg TN/yr ac ft 3 

# gal liter 10 6 

# mg

(3) Total TN Loadings 

# : The total pre-development TN loadings are equal to

the sum of the loadings from the rangeland/forests and hardwood wetland

areas:

Pensacola: 137.3 kg TN/yr + 3.11 kg TN/yr = 140.41 kg TN/yr

Orlando: 74.5 kg TN/yr + 1.68 kg TN/yr = 76.18 kg TN/yr

Key West: 67.7 kg TN/yr + 1.53 kg TN/yr = 69.23 kg TN/yr

C. Total Phosphorus: 

# For HSG D conditions, the natural/undeveloped areal

phosphorus loadings vary by meteor ological area within the State

( 1) Rangeland/Forest : 

# The typical TP concentration for undeveloped land =

0.055 mg/l

Pensacola: Annual TP Load =

96.78 ac-ft

x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 0.055mg TP

x 1 kg = 6.57 kg TP/yr yr ac ft 3 

# gal Liter 10 6 

# mg

Orlando: Annual TP Load =

52.5 ac-ft

x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 0.055 mg TP

x 1 kg = 3.56 kg TP/yr yr ac ft 3 

# gal Liter 10 6 

# mg

Key West: Annual TP Load =

47.7 ac-ft

x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 0.055 mg TP

x 1 kg = 3.24 kg TP/yr yr ac ft 3 

# gal liter 10 6 

# mg

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-33

(2) Hardwood Wetland 

# : Water quality monitoring was conducted in the

hardwood wetland to establish ambient wa ter quality characte ristics. This

monitoring resulted in a mean TP concentration of 0.066 mg/l.

Pensacola: Annual TP Load =

1.26 ac-ft x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 0.066 mg TP

x 1 kg = 0.10 kg TP/yr ac ft 3 

# gal Liter 10 6 

# mg

Orlando: Annual TP Load =

0.68 ac-ft x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 0.066 mg TP

x 1 kg = 0.055 kg TP/yr ac ft 3 

# gal Liter 10 6 

# mg

Key West: Annual TP Load =

0.62 ac-ft x 43,560 ft 2



# x 7.48 gal

x 3.785 liter

x 0.066 mg TP

x 1 kg = 0.05 kg TP/yr ac ft 3 

# gal liter 10 6 

# mg

(3) Total TP Loadings 

# : The total pre-development TP loadings are equal to

the sum of the loadings from the rangeland/forests and hardwood wetland

areas:

Pensacola: 6.57 kg TP/yr + 0.066 kg TP/yr = 6.64 kg TP/yr

Orlando: 3.56 kg TP/yr + 0.055 kg TP/yr = 3.62 kg TP/yr

Key West: 3.24 kg TP/yr + 0.05 kg TP/yr = 3.29 kg TP/yr

Post Development Conditions

1. Land Use 

# : 90 acres of single-family residential

5 acres of stormwater management systems

5 acres of preserved wetlands

2. Ground Cover/Soil Types



# A. Residential areas will be cove red with lawns in good condition

B. Soil types will remain HSG D

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-34

3. Impervious/DCIA Areas



# A. Residential areas wi ll be 25% impervi ous, 75% of which will be DCIA

Impervious Area = 25% of site = 90 ac x 0.25 = 22.50 acres

DCIA Area = 22.50 acres x 0.75 = 16.88 acres

DCIA Percentage = (16.88 ac/90.0 ac) x 100 = 18.7% of developed area

4. Calculate composite non-DCIA curve number from TR-55 

# :

Curve number for lawns in go od condition in HSG D = 80

Areas of lawns = 90 acres to tal – 22.50 ac imperv ious area = 67.50 acres pervious area

Impervious area which is not DCIA = 22.50 ac – 16.88 ac = 5.62 ac

Assume a curve nu mber of 98 for impervious areas

Non-DCIA curve number =

5. Calculate annual runoff volume for developed area 

# : The proposed developed area for

the project is 90 ac. Estimation of runoff vol umes is not included fo r the 5-acre stormwater

management area since runoff generated in thes e areas is incorporated into the performance

efficiency estimates for the stormwater system . Also, runoff volumes are not calculated for

the 5-acre wetland tract wh ich is to be preserved.

a. Pensacola (Zone 1) Project 

# : From the tables included in Appendix C (Zone 1), the

annual runoff coefficient is estimated for a project site with 18.75% DCIA and nonDCIA CN = 81.4

Annual C value = 0.304

The annual rainfall for the Pensac ola area = 65.5 inch es (Appendix A.3)

Annual generated runoff volume = 90 ac x 65.5 in/yr x 1 ft/12 in x

0.304 = 149.3 ac-ft/yr

b. Orlando (Zone 2) Project 

# : From the tables included in Appendix C (Zone 2), the

annual runoff coefficient is estimated for a project site with 18.75% DCIA and nonDCIA CN = 81.4 4

. 81

62 50

. 67 62 50

. 67

=

ac 5. + ac (98) ac 5. + (80) ac

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-35

Annual C value = 0.253

The annual rainfall for the Orlando area = 50.0 inches (Appendix A.3)

Annual generated runoff volume = 90 ac x 50.0 in/yr x 1 ft/12 in x

0.253 = 94.8 ac-ft/yr

c. Key West (Zone 3) Project 

# : From the tables included in Appendix C (Zone 3), the

annual runoff coefficient is estimated for a project site with 18.75% DCIA and nonDCIA CN = 81.4

Annual C value = 0.234

The annual rainfall for the Key We st area = 40.0 inch es (Appendix A.3)

Annual generated runoff volume = 90 ac x 40.0 in/yr x 1 ft/12 in x

0.234 = 70.2 ac-ft/yr

6. Calculate post-development loading prior to stormwater treatment 

# : Under postdevelopment conditions, nutrient loadings will be generated from the 90-acre developed

single-family area. The 5-acre preserved wetland area is not included since the area has the

same loadings under pre- and post-conditions.

Stormwater management systems are not in cluded in estimates of post-development

loadings since incidental mass inputs of pollu tants to these systems are included in the

estimation of remo val effectiveness.

From Table 4-17, mean emc values for total n itrogen and total phosphorus in single-family

residential runoff are:

TN = 2.07 mg/l TP = 0.327 mg/l

a. Pensacola (Zone 1) Project

(1) TN load from single-family area:



# TN/yr kg

=

mg 10 kg

1

x liter mg 2.0

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x

yr ft

- ac

6 3 2



# 381 7 3

. 149

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-36

(2) TP load from single-family area

b. Orlando (Zone 2) Project

(1) TN load from single-family area

(2) TP load from single-family area

c. Key West (Zone 3) Project

(1) TN load from single-family area

(2) TP load from single-family area 

# TP/yr kg

=

mg 10 kg

1

x liter mg

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x

yr ft

- ac

6 3 2



# 2

. 60 327

. 0 3

. 149

TN/yr kg

=

mg 10 kg

1

x liter mg 2.0

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x

yr ft

- ac

6 3 2



# 0

. 242 7 8

. 94

TP/yr kg

=

mg 10 kg

1

x liter mg

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x

yr ft

- ac

6 3 2



# 2

. 38 327

. 0 8

. 94

TN/yr kg

=

mg 10 kg

1

x liter mg 2.0

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x

yr ft

- ac

6 3 2



# 2

. 179 7 2

. 70

TP/yr kg

=

mg 10 kg

1

x liter mg

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x

yr ft

- ac

6 3 2



# 3

. 28 327

. 0 2

. 70

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-37

7. Calculate required removal efficiencies to achieve post- less th an or equal to preloadings for TN and TP : 

# A summary of pre- and post -loadings and required removal

efficiencies is given in the following table:

PROJECT

LOCATION TOTAL NITROGEN TOTAL PHOSPHORUS

Pre-Load

(kg/yr) Post-Load

(kg/yr) Required

Removal

(%) Pre-Load

(kg/yr) Post-Load

(kg/yr) Required

Removal

(%)

Pensacola (Zone 1) 140.4 381 63.2 6.64 60.2 89.0

Orlando (Zone 2) 76.2 242 68.5 3.62 38.2 90.5

Key West (Zone 3) 69.2 179.2 61.4 3.29 28.3 88.4



# Calculate Treatment Requirements for Post - Less Than or Equal to Pre-Loadings



# Estimation of treatment requirements assumes th at only dry retention and wet detention are

capable of approaching the desi red pollutant reduction goal.

1. Dry Retention: 

# For dry retention, the removal effi ciencies for TN and TP are identical

since the removal efficiency is based on th e portion of the annual runoff volume which is

infiltrated. The required removal is the larg er of the calculated removal efficiencies for

TN and TP.

A. Pensacola Project: 

# For the Pensacola area, the annual load reduction is 63.2%

for total nitrogen and 89.0% for total phos phorus. The design criteria is based on

the largest required removal which is 89. 0%. The required retention depth to

achieve an annual removal efficiency of 89.0% in the Pensacola area is

determined from Appendix D (Zone 1) based on DCIA percentage and the nonDCIA CN value. For this project:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

From Appendix D (Zone 1), th e required removal efficiency of 89.0% is achieved

with a dry retention depth between 2.50 and 2.75 inches.

For a dry retention depth of 2.50 inches, the treatment efficiency is obtained by

iterating between DCIA percentages of 10 and 20, and for non-DCIA CN values

between 80 and 90. The efficiency for the proj ect conditions is 88.9%

.

For a dry retention depth of 2.75 inches, the treatment efficiency is obtained by

iterating between DCIA percentages of 10 and 20, and for non-DCIA CN values

between 80 and 90. The efficiency for the proj ect conditions is 91.0%

.

By iterating between 2.50 inches (88.9%) an d 2.75 inches (91.0% ), the dry retention

depth required to achieve 89 .0% removal is 2.51 inches.

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-38

B. Orlando Project : 

# For the Orlando area, the annual load reduction is 68.5% for

total nitrogen and 90.5% for total phosphorus . The design criteria is based on the

largest required removal which is 90.5%. If the project was lo cated in Orlando, the

required dry retention depth would be sligh tly different due to differences in the

distribution of rain events. The required retention depth would be obtained from

Appendix D (Zone 2) by iterating between DCIA percentages of 10 and 20, and for

non-DCIA CN values between 80 and 90.

From Appendix D (Zone 2), th e required removal efficiency of 86.8% is achieved

with a dry retention depth between 1.50 and 1.75 inches.

For a dry retention depth of 1.75 inches, the treatment efficiency is obtained by

iterating between DCIA percentages of 10 and 20, and for non-DCIA CN values

between 80 and 90. The efficiency for the proj ect conditions is 91.25%

.

For a dry retention depth of 1.50 inch, the treatment efficiency is obtained by

iterating between DCIA percentages of 10 and 20, and for non-DCIA CN values

between 80 and 90. The efficiency for the proj ect conditions is 88.9%

.

By iterating between 1.50 in ch (88.9%) and 1.75 inches (91.25%), the dry retention

depth required to achieve 91 .0% removal is 1.72 inches.

C. Key West Project: 

# For the Key West area, th e annual load reduction is 61.4%

for total nitrogen and 88.4% for total phos phorus. The design criteria is based on

the largest required removal which is 88.4%. If the project was located in Key

West, the required dry retention depth would be slightly different due to differences

in the distribution of rain events. The required retention depth would be obtained

from Appendix D (Zone 3) by iterating be tween DCIA percentages of 10 and 20,

and for non-DCIA CN values between 80 and 90.

From Appendix D (Zone 3), th e required removal efficiency of 88.4% is achieved

with a dry retention depth between 2.50 and 2.75 inches.

For a dry retention depth of 2.75 inches, the treatment efficiency is obtained by

iterating between DCIA percentages of 10 and 20, and for non-DCIA CN values

between 80 and 90. The efficiency for the proj ect conditions is 88.55%

.

For a dry retention depth of 2.50 inches, the treatment efficiency is obtained by

iterating between DCIA percentages of 10 and 20, and for non-DCIA CN values

between 80 and 90. The efficiency for the proj ect conditions is 87.61%

.

By iterating between 2.50 inches (87.6%) and 2.75 inches (88.55%), the dry

retention depth required to achieve 88.4% removal is 2.71 inches.

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-39

2. Wet Detention

Treatment Train Approach



# Calculation of design criteria for a wet deten tion pond is based on determining the detention

time required to achieve the post- < pre-pollutant removal effici encies for TN and TP listed

previously. For practical purposes, this effi ciency is assumed to apply to nitrogen and

phosphorus since other pollutant s such as BOD and TSS are t ypically removed at a faster

rate than nutrients. As disc ussed in Section 5.2.2, wet de tention systems are capable of

providing annual mass load reductions for phosphorus in excess of 80% at extended

detention times (> 200 days), but the removal efficiency for to tal nitrogen in wet detention

ponds appears to peak at approximately 45%. As a result, wet detentio n alone is not capable

of achieving the requir ed efficiencies of 88.4-90.5% for TP and 61.4 -68.5% for TN.

Therefore, when wet detention is desired as a treatment option, pr e-treatment must be

provided to enhance th e total system performance efficien cy to the minimum efficiencies

necessary to achieve post- < pre-loadings for TN and TP. Since dry retention provides the

best pre-treatment in a minimal space, dry rete ntion appears to be the pre-treatment system

of choice for this application. There are many combinations of dry retention and wet

detention which can provid e the desired removals.

Assume that the primary compon ent in the treatment train will be a wet detention pond with

a residence time of 150 days.

Anticipated TN removal (Figure 5-10) =

Anticipated TP removal (Figure 5-9) =

Eff = 40.13 + 6.372 ln (t d 

# ) + 0.213 (ln t d 

# ) 2 

# = 40.13 + 6.372 ln (150) + 0.213 (ln 150) 2 

# = 77.4%

2A. PENSACOLA (ZONE 1) PROJECT



# Since a wet detention p ond cannot meet both the 89.0% remo val criteria for TP and the 63.2%

removal for TN, the remaining effici ency is achieved using dry rete ntion. The design of the dry

retention pond is dictated by the required removal for TN since this is where the largest deficit exists

between the required removal and the removal provided by the wet detention pond. The required

efficiency for the dry retention is calculated by Eq. 1 below:

Treatment Train Efficiency = Eff 1 

# + (1 – Eff 1 

# ) x Eff 2 

# (Eq. 1) %

= 0 + 5.46 0 x 44.72

= ) t + ( ) t x (4 Eff

d d 

# 5

. 42

15 15

38

. 4 75

. 3

=

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-40

where: Eff 1 

# = required efficiency of dry retention

Eff 2 

# = efficiency of wet de tention (42.5% for TN)

Overall Eff. = 0.632 = Eff 1 

# + (1 – Eff 1 

# ) x 0.425

Eff 1 

# = 0.360 = 36.0%

The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

1. Required Dry Retention Depth



# From Appendix D (Zone 1), the required removal ef ficiency of 36.0% is achieved with a dry

retention depth between 0.00 and 0.25 inch.

For a dry retention depth of 0.25 inch, the treat ment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 38.0%

.

By iterating between 0.25 inch (38.0%) and 0.00 inch (0.00%), the dry retention depth required to

achieve 36.0% remova l is 0.24 inch.

Therefore, the required treat ment train will consist of:

a. 0.24 inch dry retention, followed by

b. Wet detention pond with a 1 50-day mean residence time

Based on the relationships given in Figures 5-9 an d 5-10, the removal effici encies for TN and TP

increase little at dete ntion times in excess of 100-150 days . Although the pond size may be

increased (if desired) for fill or other purposes, the required dry re tention pre-treatment depth will

not be significantly reduced. Ho wever, if the pond residence ti me is decreased below 150 days,

then the dry retention pre-treatment depth will increas e correspondingly.

2. Wet Detention Pond Characteristics



# The required physical characteristic s of the wet detention pond are determined based on the desired

residence time and the impacts of the proposed dry retention pre-treatment.

a. Calculate annual ru noff inputs to pond



# The annual runoff coefficient for the development can be estimate d using the tables included

in Appendix C (Zone 1).

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-41

For: DCIA = 18.75% an d non-DCIA CN = 81.4

The estimated “C” value is obtained by iteration as discussed previously.

Annual C Value = 0.304

The annual rainfall for the Pensacol a area = 65.5 inches (Appendix A.3)

Annual generated runoff volume =

90 acres x 65.5 inches/year x 1 ft/1 2 inches x 0.304 = 149.3 ac-ft/yr

The calculated efficiency of 36.0% for the dr y retention pre-treatment means that 36.0% of

the annual runoff volume w ill be infiltrated into the ground and will not disc harge directly

into the wet detention pond. The annual runo ff volume which reaches the pond is calculated

as:

Annual Inputs to Pond = 149.3 ac-ft/yr x (1 - 0.360) = 95.55 ac-ft/yr

For a 150-day residence time, the pond volume will be:

95.55 ac-ft/yr x 1 year/365 days x 150 days = 39.27 ac-ft

b. Estimate maximum allowable pond depth



# The maximum allowable pond depth is directly re lated to the anticipated algal productivity

within the pond. Assuming that wet dete ntion ponds are primarily phosphorus-limited

ecosystems, the productivity can be estimated based on the mean TP concentration.

1. Estimate runoff characteristics



# For a single-family residentia l land use, the event mean concentration (emc) for TP

in runoff can be obtain ed from Table 4-16:

TP = 0.327 mg/l (singl e-family residential)

2. Calculate TP loading to wet detention pond



# After the dry retention pre-treatment, th e annual runoff input to the pond = 95.55

ac-ft/yr

TP load to pond =

TP/yr kg

=

mg 10 kg

1

x liter mg 0.3

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x ft/yr

- ac

6 3 2



# 53

. 38 27 55

. 95

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-42

3. Calculate TP concentration in pond



# At the proposed 150-day residence time, the TP removal was pr eviously estimated

as 77.4%.

Annual mass of TP remaining in water column =

38.53 kg TP/yr x (1 – 0.774) = 8.71 kg TP/yr

This mass will be distribute d within the pond permanent pool volume (39.27 ac-ft)

and the pond outflow. Assu ming that inflow and outflo w are approximately equal,

the outflow volume is 95.55 ac-ft.

Mean pond conc entration =

8.71 kg TP

x 1 yr

x 1 ac

x 1 ft 3



# yr 95.55 + 39.27 ac-ft 43,560 ft 2 

# 7.48 gal

x 1 gal

x 10 6 

# mg = 0.052 mg TP/ liter = 52 μ 

# g TP/liter 3.785 liter kg

4. Calculate mean chloroph yll-a concentration in pond



# The relationship between TP and chlorophy ll-a in a Florida waterbody is expressed

by the following relationship:

ln (chyl-a) = 1.058 ln (TP) - 0.934 (Eq. 4)

where: chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total P concentration ( μ 

# g/l)

ln (chyl-a) = 1.058 ln (52) - 0.934

chyl-a = e 3.25 

# = 25.7 mg/m 3



# 5. Calculate mean Secchi disk depth



# The relationship between chlorophyll- a and Secchi disk depth in a Florida

waterbody is expressed by the following relationship:

a)

- chyl + (6.0632 a)

- chyl 0.3041 + 24.2386

= SD ] )( [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-43

where: SD = Secchi disk depth (m)

chyl-a = chlorophyll-a (mg/m 3 

# )

6. Calculate depth of an oxic conditions in pond



# Using the relationship expres sed in Eq. 5, the depth of anoxic conditions within the

pond can be estimated as follows:

Depth of DO < 1 = 3.035 x Secchi + 0.0216 4 x (chyl-a) – 0.004979 x Total P

where:

Depth of DO < 1 = anoxic depth (m)

Secchi = Secchi disk depth (m)

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

Total P = total phosphorus concentration ( μ 

# g/l)

Depth of DO < 1 = 3.035 (1.01) + 0.02164 (25.7) - 0.004979 (52) = 3.37 m = 11.1 ft

If the proposed pond depth exceeds the es timated anoxic zone depth of 11.1 ft,

aeration or other mixing will be required for areas deeper than 11.1 ft to maintain a

well mixed water column. The aeration or mixing must be sufficient to mix the

water column to the maximum pond dept h. The specific design of the required

system should be selected by a qualified aeration specialist.

As an alternative to providing aeration or mixing within the pond, the required

permanent pool volume could be considered as only the volume above the anoxic

zone and not the entire volume of the pond. Areas below the anoxic depth would be

considered as dead storage, although thes e areas would provide a significant storage

volume for collect ed solids.

If the pond is modified, based on the results of the calcula ted anoxic zone depth, the

calculations would need to be redone to estimate new values for total phosphorus,

Secchi disk depth, chlorophyll-a, and dept h of anoxia to demo nstrate that the new

design meets the required permanent pool volume above the zone of anoxia. ft

. = m = ) 2 + (6.0632 ) (2 0.3041 + 24.2386

= SD 31 3 01

. 1

7

. 5 ] 7

. 5 ) [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-44

7. Estimate pond dimensions



# For the estimation of pond dimensions, assume that the mean depth (pond

volume/pond area) is 2/3 of the maximum depth.

Mean pond depth = 11 .1 ft x 2/3 = 7.4 ft

Pond surface area = pond volume/mean depth = 39.27 ac-ft/7.4 ft = 5.31 ac

2B. ORLANDO (ZONE 2) PROJECT



# Since a wet detention p ond cannot meet both the 90.5% remo val criteria for TP and the 68.5%

removal for TN, the remaining effici ency is achieved using dry rete ntion. The design of the dry

retention pond is dictated by the required removal for TN since this is where the largest deficit exists

between the required removal and the removal provided by the wet detention pond. The required

efficiency for the dry retention is calculated by Eq. 1 below:

Treatment Train Efficiency = Eff 1 

# + (1 – Eff 1 

# ) x Eff 2 

# (Eq. 1)

where: Eff 1 

# = required efficiency of dry retention

Eff 2 

# = efficiency of wet de tention (42.5% for TN)

Overall Eff. = 0.685 = Eff 1 

# + (1 – Eff 1 

# ) x 0.425

Eff 1 

# = 0.452 = 45.2%

The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

1. Required Dry Retention Depth



# From Appendix D (Zone 2, the re quired removal efficiency of 45.2% is achieved with a dry

retention depth between 0.00 and 0.25 inch.

For a dry retention depth of 0.25 inch, the treat ment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project conditions is 48.97%

.

By iterating between 0.25 inch (48.97%) and 0.00 inch (0.0%), the dry retention depth required to

achieve 45.2% remova l is 0.23 inch.

Therefore, the required treat ment train will consist of:

a. 0.23 inch dry retention, followed by

b. Wet detention pond with a 1 50-day mean residence time

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-45

2. Wet Detention Pond Characteristics



# The required physical characteristic s of the wet detention pond are determined based on the desired

residence time and the impacts of the proposed dry retention pre-treatment.

A. Calculate annual ru noff inputs to pond



# The annual runoff coefficient for the development can be estimate d using the tables included

in Appendix C (Zone 2).

For: DCIA = 18.75% an d non-DCIA CN = 81.4

The estimated “C” value is obtained by iteration as discussed previously.

Annual C Value = 0.253

The annual rainfall fo r the Orlando area = 50.0 inches (Appendix A.3)

Annual generated runoff volume =

90 acres x 50.0 inches/year x 1 ft/1 2 inches x 0.253 = 94.88 ac-ft/yr

The calculated efficiency of 45.2% for the dr y retention pre-treatment means that 45.2% of

the annual runoff volume w ill be infiltrated into the ground and will not disc harge directly

into the wet detention pond. The annual runo ff volume which reaches the pond is calculated

as:

Annual Inputs to Pond = 94.88 ac-ft/yr x (1 - 0.452) = 51.99 ac-ft/yr

For a 150-day residence time, the pond volume will be:

51.99 ac-ft/yr x 1 year/365 days x 150 days = 21.37 ac-ft

B. Estimate maximum allowable pond depth



# The maximum allowable pond depth is directly re lated to the anticipated algal productivity

within the pond. Assuming that wet dete ntion ponds are primarily phosphorus-limited

ecosystems, the productivity can be estimated based on the mean TP concentration.

1. Estimate runoff characteristics



# For a single-family residential land use, th e emc for TP in runoff can be obtained

from Table 4-17:

TP = 0.327 mg/l (singl e-family residential)

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-46

2. Calculate TP loading to wet detention pond



# After the dry retention pre-treatment, th e annual runoff input to the pond = 51.99

ac-ft/yr

TP load to pond =

3. Calculate TP concentration in pond



# At the proposed 150-day residence time, the TP removal was pr eviously estimated

as 77.4%.

Annual mass of TP remaining in water column =

20.97 kg TP/yr x (1 – 0.774) = 4.74 kg TP/yr

This phosphorus mass w ill be distributed within the pond permanent pool (21.37

ac-ft) and the pond outflow. Assuming that inflow and outflow are approximately

equal, the outflow w ill be 51.99 ac-ft.

Mean pond conc entration =

4.74 kg TP

x 1 yr

x 1 ac

x 1 ft 3



# yr 21.37 + 51.99 ac-ft 43,560 ft 2 

# 7.48 gal

x 1 gal

x 10 6 

# mg = 0.052 mg TP/ liter = 52 μ 

# g TP/liter 3.785 liter kg

4. Calculate mean chloroph yll-a concentration in pond



# The relationship between TP and chlorophy ll-a in a Florida waterbody is expressed

by the following relationship:

ln (chyl-a) = 1.058 ln (TP) - 0.934 (Eq. 4)

where: chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total P concentration ( μ 

# g/l)

ln (chyl-a) = 1.058 ln (52) - 0.934

chyl-a = e 3.25 

# = 25.7 mg/m 3 

# TP/yr kg

=

mg 10 kg

1

x liter mg 0.3

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x ft/yr

- ac

6 3 2



# 97

. 20 27 99

. 51

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-47

5. Calculate mean Secchi disk depth



# The relationship between chlorophyll- a and Secchi disk depth in a Florida

waterbody is expressed by the following relationship:

where: SD = Secchi disk depth (m)

chyl-a = chlorophyll-a (mg/m 3 

# )

6. Calculate depth of an oxic conditions in pond



# Using the relationship expres sed in Eq. 5, the depth of anoxic conditions within the

pond can be estimated as follows:

Depth of DO < 1 = 3.035 x Secchi + 0.0216 4 x (chyl-a) – 0. 004979 x Total P

where:

Depth of DO < 1 = anoxic depth (m)

Secchi = Secchi disk depth (m)

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

Total P = total phosphorus concentration ( μ 

# g/l)

Depth of DO < 1 = 3.035 (1.01) + 0.02164 (25.7) - 0.004979 (52) = 3.36 m = 11.0 ft

If the proposed pond depth exceeds the estimated photic zone depth of 11.0 ft,

aeration or other mixing will be required for areas deeper than 11.0 ft to maintain a

well mixed water column. The aeration or mixing must be sufficient to mix the

water column to the maximum pond dept h. The specific design of the required

system should be selected by a qualified aeration specialist. a)

- chyl + (6.0632 a)

- chyl 0.3041 + 24.2386

= SD ] ( ) [(

ft

= m = 2 + (6.0632 ) (2 0.3041) + 24.2386

= SD 31

. 3 01

. 1 ) 7

. 5 ] 7

. 5 [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-48

As an alternative to providing aeration or mixing within the pond, the required

permanent pool volume could be considered as only the volume above the anoxic

zone and not the entire volume of the pond. Areas below the anoxic depth would be

considered as dead storage, although thes e areas would provide a significant storage

volume for collect ed solids.

If the pond is modified, based on the results of the calcula ted anoxic zone depth, the

calculations would need to be redone to estimate new values for total phosphorus,

Secchi disk depth, chlorophyll-a, and dept h of anoxia to demo nstrate that the new

design meets the required permanent pool volume above the zone of anoxia.

7. Estimate pond dimensions



# For the estimation of pond dimensions, assume that the mean depth (pond

volume/pond area) is 2/3 of the maximum depth.

Mean pond depth = 11 .0 ft x 2/3 = 7.3 ft

Pond surface area = pond volume/mean depth = 21.37 ac-ft/7.3 ft = 2.91 ac

2C. KEY WEST (ZONE 3) PROJECT



# Since the wet detention p ond fails to meet the 88 .4% removal criteria for TP and the 61.4% removal

for TN, the remaining efficiency is achieved usin g dry retention. The design of the dry retention

pond is dictated by the required removal for TN sin ce this is where the larges t deficit exists between

the required removal and the removal provided by th e wet detention pond. Th e required efficiency

for the dry retention is calculated by Eq. 1 below:

Treatment Train Efficiency = Eff 1 

# + (1 – Eff 1 

# ) x Eff 2 

# (Eq. 1)

where: Eff 1 

# = required efficiency of dry retention

Eff 2 

# = efficiency of wet de tention (42.5% for TN)

0.614 = Eff 1 

# + (1 – Eff 1 

# ) x 0.425

Eff 1 

# = 0.329 = 32.9%

The required dry retention volume is estimated from the tables given in Appendix D using the

development characteristics:

DCIA Percentage = 18.75% of developed area

Non-DCIA CN = 81.4

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-49

1. Required Dry Retention Depth



# From Appendix D (Zone 3), the required removal ef ficiency of 32.9% is achieved with a dry

retention depth between 0.00 and 0.25 inch.

For a dry retention depth of 0.25 inch, the treat ment efficiency is obtained by iterating between

DCIA percentages of 10 and 20, an d for non-DCIA CN values betwee n 80 and 90. The efficiency

for the project co nditions is 42.9%

.

By iterating between 0.00 inch (0.0%) and 0.25 inch (42.9%), the dry retent ion depth required to

achieve 32.9% remova l is 0.19 inch.

Therefore, the required treat ment train will consist of:

a. 0.19 inch dry retention, followed by

b. detention pond with a 150- day mean residence time

2. Wet Detention Pond Characteristics



# The required physical characteristic s of the wet detention pond are determined based on the desired

residence time and the impacts of the proposed dry retention pre-treatment.

A. Calculate annual ru noff inputs to pond



# The annual runoff coefficient for the development can be estimate d using the tables included

in Appendix C (Zone 3).

For: DCIA = 18.75% an d non-DCIA CN = 81.4

The estimated “C” value is obtained by iteration as discussed previously.

Annual C Value = 0.266

The annual rainfall for the Key West area = 40.0 inches (Appendix A.3)

Annual generated runoff volume =

90 acres x 40.0 inches/year x 1 ft/1 2 inches x 0.266 = 79.8 ac-ft/yr

The calculated efficiency of 32.9% for the dr y retention pre-treatment means that 32.9% of

the annual runoff volume w ill be infiltrated into the ground and will not disc harge directly

into the wet detention pond. The annual runo ff volume which reaches the pond is calculated

as:

Annual Inputs to Pond = 79.8 ac-ft/yr x (1 - 0.329) = 53.55 ac-ft/yr

For a 150-day residence time, the pond volume will be:

53.55 ac-ft/yr x 1 year/365 days x 150 days = 22.01 ac-ft

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-50

B. Estimate maximum allowable pond depth



# The maximum allowable pond depth is directly re lated to the anticipated algal productivity

within the pond. Assuming that wet dete ntion ponds are primarily phosphorus-limited

ecosystems, the productivity can be estimated based on the mean TP concentration.

1. Estimate runoff characteristics



# For a single-family residential land use, th e emc for TP in runoff can be obtained

from Table 4-17:

TP = 0.327 mg/l (singl e-family residential)

2. Calculate TP loading to wet detention pond



# After the dry retention pre-treatment, th e annual runoff input to the pond = 53.55

ac-ft/yr

TP load to pond =

3. Calculate TP concentration in pond



# At the proposed 150-day residence time, the TP removal was pr eviously estimated

as 77.4%.

Annual mass of TP remaining in water column =

21.60 kg TP/yr x (1 – 0.774) = 4.88 kg TP/yr

This mass will be distribute d within the pond permanent pool volume (22.01 ac-ft)

and the pond outflow. Assu ming that inflow and outflo w are approximately equal,

the outflow volume is 53.55 ac-ft.

Mean pond conc entration =

4.88 kg TP

x 1 yr

x 1 ac

x 1 ft 3



# yr 22.01 + 53.55 ac-ft 43,560 ft 2 

# 7.48 gal

x 1 gal

x 10 6 

# mg = 0.052 mg TP/ liter = 52 μ 

# g TP/liter 3.785 liter kg TP/yr kg

=

mg 10 kg

1

x liter mg 0.3

x gal liter 3.785

x ft gal 7.48

x

ac ft 43,560

x ft/yr

- ac

6 3 2



# 60

. 21 27 55

. 53

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-51

4. Calculate mean chloroph yll-a concentration in pond



# The relationship between TP and chlorophy ll-a in a Florida waterbody is expressed

by the following relationship:

ln (chyl-a) = 1.058 ln (TP) - 0.934 (Eq. 4)

where: chyl-a = chlorophyll-a concentration (mg/m 3 

# )

TP = total P concentration ( μ 

# g/l)

ln (chyl-a) = 1.058 ln (52) - 0.934

chyl-a = e 3.25 

# = 25.7 mg/m 3



# 5. Calculate mean Secchi disk depth



# The relationship between chlorophyll- a and Secchi disk depth in a Florida

waterbody is expressed by the following relationship:

where: SD = Secchi disk depth (m)

chyl-a = chlorophyll-a (mg/m 3 

# )

6. Calculate depth of an oxic conditions in pond



# Using the relationship expres sed in Eq. 5, the depth of anoxic conditions within the

pond can be estimated as follows:

Depth of DO < 1 = 3.035 x Se cchi + 0.02164 x (chyl-a) – 0.0049 79 x Total P a)

- chyl + (6.0632 a)

- chyl 0.3041 + 24.2386

= SD ] )( [(

ft

= m = ) 2 + (6.0632 ) (2 0.3041) + 24.2386

= SD 31

. 3 01

. 1

7

. 5 ] 7

. 5 [(

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-52

where:

Depth of DO < 1 = anoxic depth (m)

Secchi = Secchi disk depth (m)

chyl-a = chlorophyll-a concentration (mg/m 3 

# )

Total P = total phosphorus concentration ( μ 

# g/l)

Depth of DO < 1 = 3.035 (1.01) + 0.02164 (25.7) - 0.004979 (52) = 3.36 m = 11.0 ft

If the proposed pond depth exceeds the estimated photic zone depth of 11.0 ft,

aeration or other mixing will be required for areas deeper than 11.0 ft to maintain a

well mixed water column. The aeration or mixing must be sufficient to mix the

water column to the maximum pond dept h. The specific design of the required

system should be selected by a qualified aeration specialist.

As an alternative to providing aeration or mixing within the pond, the required

permanent pool volume could be considered as only the volume above the anoxic

zone and not the entire volume of the pond. Areas below the anoxic depth would be

considered as dead storage, although thes e areas would provide a significant storage

volume for collect ed solids.

If the pond is modified, based on the results of the calcula ted anoxic zone depth, the

calculations would need to be redone to estimate new values for total phosphorus,

Secchi disk depth, chlorophyll-a, and dept h of anoxia to demo nstrate that the new

design meets the required permanent pool volume above the zone of anoxia.

7. Estimate pond dimensions



# For the estimation of pond dimensions, assume that the mean depth (pond

volume/pond area) is 2/3 of the maximum depth.

Mean pond depth = 11 .0 ft x 2/3 = 7.3 ft

Pond surface area = pond volume/mean depth = 22.01 ac-ft/7.3 ft = 3.02 ac

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-53

7.4 Conclusions

7.4.1 Dry Retention



# The design examples illustrated in the previous sections are intended to present alternative

stormwater designs whic h will meet both the 80% and 95% pollutant reduction goals outlined in

Chapter 62-40 FAC as well as a condition of no net increase in pollutant loadings for a developed

site under post-development cond itions. The design examples pr ovide calculations for treatment

systems comprised exclusively of dry retention as well as a combination of wet detention with dry

retention pre-treatment. The hypothetical site cons ists of a 100-acre rangeland/forest parcel which

is converted into a single-family residential co mmunity with a DCIA percentage of 18.7% and a

non-DCIA curve num ber of 81.4.

A comparison of existing and proposed dry re tention stormwater tr eatment requirements,

based upon the hypothetical 100-acre parcel, is give n in Table 7-1 for developments in Pensacola,

Orlando, and Key West. Existing requirements fo r dry retention stormwater treatment at the

Pensacola site are based upon the FDEP criteria outlined in Chapter 62-25 FAC. Dry retention

stormwater treatment requirements for the Orlando site are base d upon SJRWMD design criteria,

while dry retention treatment re quirements for the Key West s ite are based upon SFWMD design

criteria.

TABLE 7-1

COMPARISON OF EXISTING AND REQUIRED DRY

RETENTION STORMWATER TREATMENT REQUIREMENTS

DESIGN

OBJECTIVE RETENTION REQUIREMENT BY REGION

PENSACOLA –

ZONE 1

(FDEP) O RLANDO-

ZONE 2

(SJRWMD) KEY WEST-

ZONE 3

(SFWMD)

80% Pollutant Removal

a. Existing 0.50" 0.50" off-line or 1.00" on-line 0.50"

b. Required 1.52” 0.94” 1.66”

95% Pollutant Removal (OFW)

a. Existing 0.75" 0.75" off-line or 1.50" on-line 0.75"

b. Required 3.66” 2.45” 3.62”

Post ≤ Pre Loadings

a. Required Removals (%) TN: 63.2%

TP: 89.0% TN: 68.5%

TP: 90.5% TN: 61.4%

TP: 88.4%

b. Required Retention 2.42” 1.67” 2.63”



# Under existing conditions, the dry retention treatment requirement for the hypothetical

development, assuming that the development does not discharge to an OFW, would be 0.5 inch of

retention for the Pensacola and Key West sites. At the Orlando s ite, the dry retention requirement

would be 0.5 inch for an off-line system and 1.00 inch for an on-line sy stem. Retention

requirements necessary to achieve an 80% reduction in the annual runoff volume, assumed to be

equivalent to an 80% pollutant removal efficiency , are indicated under the column designated as

“required”. To achieve an 80% pollutant removal in the Pensacola area, th e dry retention system

would have to provide a treatment volume of 1.52 inches of runoff. Inthe Orlando area, the

required dry retention treatment volume would be 0.94 inch, with a dry retention requirement of

1.66 inches in th e Key West area.

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-54

As seen in Table 7-1, the existing design crite ria for dry retention in the Pensacola and Key

West areas fall well short of the actual dry retention treatment vol ume required to achieve an 80%

annual pollutant removal effici ency. For a project designed in the Orlando area, based upon

SJRWMD design criteria, the dry re tention requirement for an off-line system would fail to meet the

80% pollutant removal goal, while the pollutant re moval goal would be ex ceeded by an on-line

retention system with 1.00 inch of dry retention.

Existing and proposed dry retention requireme nts are also provided fo r developmen ts which

discharge to OFWs which are assumed to be de signed according to the 95% pollutant reduction

target goal outlined in Ch apter 62-40 FAC. The applicable desi gn criteria for e ach of the three

project areas is 50% additional dry retention tr eatment volume above th e amount necessary to

achieve 80% pollutant removal. For projects de signed in the Pensacola and Key West areas, this

treatment volume requirement become s 0.75 inch. If a development is constructed in the Orlando

area, the current dry retention requirement becomes 0.75 inch for off-line sy stems and 1.50 inch for

on-line systems. However, the actual dry retenti on treatment requirements necessary to achieve a

95% pollutant removal far exceed the existing dry retention treatment requirements. Dry retention

requirements for 95% pollutant removal are 3.66 inch es for the Pensacola area, 2.45 inches for the

Orlando area, and 3.62 inches for the Key West area.

Dry retention requirements necessary to achieve post < pre-development loadings are

summarized at the bottom of Table 7-1. The required removals necessary to achieve no net increase

in loadings for total nitr ogen range from 61.4-68.5%. These va lues indicate that a pollutant removal

efficiency of 80% is not required fo r total nitrogen to achieve no net increase in pollutant loadings.

Required removal efficiencies for total phosphorus to achieve no net increase in pollutant loadings

range from 88.4-90.5%, suggesting that stormwat er management systems designed for an 80%

pollutant removal will fa il to achieve post < pre-development loadings fo r total phosphorus. Based

upon these values, it is apparent that a stormwater management sy stem designed to achieve 80%

pollutant removal will remove more than the required amount of tota l nitrogen, while removing less

than the required amount of total phosphorus. A stormwater management system designed to

achieve a true 95% reduction in po llutant loadings will re move substantially mo re total nitrogen and

total phosphorus than requ ired to achieve post < pre-development loadings.

Based upon the comparative info rmation summarized in Table 7- 1, it appears that designing

stormwater management systems to achieve an arbitrary pollutant removal goal for both total

nitrogen and total ph osphorus is an ineffective method for achieving comp liance with water quality

or anti-degradation criteria. A much more effe ctive method of addressi ng stormwater treatment

requirements appears to be designs based upon post < pre-development loadings. The proposed dry

retention requirements necessary to achieve this goal for the hypot hetical projects range from 1.67

inches in the Orlando area to 2.42 inches in the Pensacola area. These values are greater than the

actual dry retention requirements necessary to achieve an 80% pollutant removal goal, but are

substantially less than the dry retention requireme nts necessary to achieve a 95% pollutant removal

goal. If post < pre-development criteria are utilized, th ere would be no need for supplemental

design criteria for discharges into OFWs since a ll projects would result in no net increase in

pollutant loadings into the recei ving waterbody. However, it should be noted that the post < predevelopment dry retention design criteria liste d at the bottom of Table 7-1 are based upon the

removal efficiencies required for total phosphorus. Since all cons tituents are removed at the same

rate using dry retentio n, an excess removal would still be achieved for total nitrogen.

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-55

7.4.2 Wet Detention



# A comparison of existing a nd proposed wet detention stormwater treatment requirements to

achieve the evaluate d design objectives is given in Tabl e 7-2. Under exis ting conditions, wet

detention systems designed in th e Pensacola area according to FDEP design criteria must have a

treatment volume equivalent to 1.00 inch of runoff over the project area. The FDEP design criteria

do not specify requirements for detention time. The project constructed in the Orlando area would

be designed according to SJRWMD cr iteria. These criteria specify a treatment volume of 1 inch of

runoff, with a minimum 14-day wet season detenti on time and a maximum pond depth of 12 feet.

The project constructed in the Key West area would be designed acco rding to SFWMD design

criteria which specify a treatment volume of 1 inch of runoff, with no specified detention time and

25-50% of the pond depth gr eater than 12 feet.

A summary of proposed wet detention desi gn criteria necessary to achieve the 80%

pollutant removal goal is provided in Table 7-2. For this analysis, the trea tment volume is assumed

to be the same as under existing design criteria. Although this treatment vo lume is often termed the

“water quality” component of the system, it has very little imp act on the overall performance

efficiency of the system and prim arily regulates the drawdown charact eristics of the pond following

a storm event. The design example assumes a we t detention pond with a detention pond of 150

days since this design tends to maximize rem oval efficiencies for ni trogen and phosphorus.

However, lower detention times could also be used, although this would increase treatment

requirements for other portions of the overall treatment train.

Although wet detention ponds can provide a re moval efficiency of 80 % or more for total

phosphorus at extended detention times, wet detention ponds are not capable of providing an 80%

pollutant removal for total nitrogen. As a result, retention pre-treat ment will be required to increase

the overall performance efficiency of the system to 80% for total nitrogen. Based on the analyses

presented in the previous sections , this will require a dry retention pre-treatment of 0.81 inch in the

Pensacola area, 0.49 inch in the Orlando area, a nd 0.75 inch in the Key West area. Under the

alternative design, the maximum depth for each pond is based upon predicted water quality

characteristics and the anticipated depth of anoxia within the pond rather than an arbitrary depth

standard. Ponds which ar e constructed deeper than the anticipated depth of anoxia may require

supplemental aeration or circulation to maintain ae robic conditions. It should be noted that, while

this design will meet the 80% pollu tant removal goal for total nitroge n, the overall pollutant removal

for total phosphorus will substantiall y exceed 80%.

Wet detention design criteria to achieve a 95% pollutant removal are also summarized in

Table 7-2. Under existing design criteria, the treatment volume would be increased by 50% for

each of the three projects, while other components of the wet detention pond woul d remain

unchanged. Under the proposed alternative we t detention design, the treatment volumes are

assumed to be the same as those provided unde r existing conditions since the treatment volumes

have little impact on overall system performan ce. The example summarized in a previous section

utilizes a 100-day detention pond, although other deten tion times could be u tilized as well. The

remaining dry retention pre-treatment necessary to boost the overall performa nce of the system to

95% ranges from 2.42 inches in the Orlando area to greater than 4 inches in the Key West area.

These relatively large dry retent ion requirements are necessary primarily to boost the removal

efficiency for total nitrogen to 95%, while the removal efficien cy for total ph osphorus will

substantiall y exceed 95%.TABLE 7-2COMPARISON OF EXISTINGANDREQUIREDWETDETENTION STORMWATER TREATMENT REQUIREMENTSDESIGNOBJECTIVETREATMENT REQUIREMENT BY REGIONPENSACOLA - ZONE 1(FDEP)ORLANDO - ZONE 2(SJRWMD)KEY WEST - ZONE 3(SFWMD)80% Pollutant Removala. Existing 1. 1" of runoff treatment volume2. no specified detention time3. depth < 12 feet1. 1" of runoff treatment volume2. minimum 14-day detention time3. depth < 12 feet1. 1" of runoff treatment volume2. no specified detention time3. 25-50% > 12 feetb. Proposed 1. 1" of runoff treatment volume2. 200-day detention time3. 0.69" retention pre-treatment4. maximum depth based on water quality1. 1" of runoff treatment volume2. 200-day detention time3. 0.45" retention pre-treatment4. maximum depth based on water quality1. 1" of runoff treatment volume2. 200-day detention time3. 0.66" retention pre-treatment4. maximum depth based on water quality95% Pollutant Removal(OFW)a. Existing 1. 1.5" of runoff treatment volume2. no specified detention time3. depth < 12 feet1. 1.5" of runoff treatment volume2. minimum 14-day detention time3. depth < 12 feet1. 1.5"of runoff treatment volume2. no specified detention time3. 25-50% > 12 feetb. Proposed 1. 1.5" of runoff treatment volume2. 100-day detention time3. 2.45" dry retention pre-treatment1. 1.5" of runoff treatment volume2. 100-day detention time3. 1.63" dry retention pre-treatment1. 1.5" of runoff treatment volume2. 100-day detention time3. >4" dry retention pre-treatmentPost≤Pre Loadingsa. Required Removals (%) TN: 63.2%TP: 89.0%TN: 68.5%TP: 90.5%TN: 61.4%TP: 88.4%b. Proposed Retention 1. 1.5” of runoff treatment volume2. 150-day wet detention3. 0.24" dry retention pre-treatment1. 1.5” of runoff treatment volume2. 150-day wet detention3. 0.23" dry retention pre-treatment1. 1.5” of runoff treatment volume2. 150-day wet detention3. 0.19" dry retention pre-treatment 

# 7-56FDEP \ STORMWATER TREATMENT REPORT

# FDEP \ STORMWATER TREATMENT REPORT 

# 7-57

Proposed wet detention treatment requirements necessary to achieve post < pre-development

loadings are summarized at th e bottom of Table 7-2. These are the same values utilized in Table

7-1. A wet detention treatment train which will achieve post < pre-developmen t loadings is

provided in the bottom ro w of Table 7-2. This can be acco mplished using a wet detention pond

with a 150-day detention time, with dry retention pre-treatment ranging from 0.19-0.24 inch. The

requirements necessary to achieve post < pre-development loadings ar e less than the requirements

necessary to achieve a true 80% pollutant removal goal since the elevated removal efficiencies are

no longer required for total nitrogen . The detention time of the we t detention system listed under

the proposed conditions could be reduced with a proportionate increase in the volume of dry

retention pre-treatment for each of the three options.

7.5 Summary



# Based on the analyses provid ed in the previous sections, it is apparent that the most

appropriate method of developi ng stormwater treatme nt requirements is to utilize a post < predevelopment loading conditions. Developing stormw ater design criteria to achieve an arbitrary

80% pollutant removal goal will pr ovide substantially higher than required removals for total

nitrogen while providing total phosphorus removals in excess of 80%. Requiring stormwater

management systems to be designed to achieve an arbitrary 95% pollutant removal goal will far

exceed the required removals for both total nitrog en and total phosphorus necessary to achieve a

post < pre-development loadin g, while resulting in substantially elevated stormwater treatment

requirements and cost s compared with existing conditions.

# FDEP \ STORMWATER TREATMENT REPORT 

# SECTION 8

REFERENCES

Bahk, B.M. (1997). "An I nvestigation of a Wet Detention Pond Used to Treat Stormwater

and Irrigation Runoff from an Agricultural Basin." Proceedings of the Fifth Biennial Stormwater

Research Conference , November 5-7, 1997.

Bahk, B. and M. Kehoe. (1997). "A Surv ey of Outflow Water Qu ality from Detention

Ponds in Agricultur e." Report submitted to the Southwest Florida Water Management District -

Environmental Section.

Camp, Dresser & McKee. (1984). "Tri butary Streamflow and Pollutant Loading."

Delivered to Tampa Bay for Florida Department of Environmental Regulation, Tallahassee, FL.

Camp, Dresser & McKee. (1985). "Sou theast Area Stormwater Management Study -

Manatee County, Florida." Bradenton, FL.

Carr, D.W. and M.J. Kehoe. (1997). “Outfa ll Water Quality from We t Detention Systems.”

Southwest Florida Water Management District , Environmental Section/Resource Projects

Department, Brooksville, FL.

Chow, V.T.; Maidment, D.R.; an d Mays, L.W. (1988). “App lied Hydrology.” New York:

McGraw-Hill Bo ok Company.

Cullum, M.G. (1984). "Eva luation of the Water Management System at a Single-Family

Residential Site: Water Quality An alysis for Selected St orm Events at Timbercreek S ubdivision in

Boca Raton, Florida." South Flor ida Water Management District , Tech. Pub. 84-11 Volume II,

West Palm Beach, FL.

DB Environmental, Inc. (2005). “Quantifying the Effect of a Vegetated Littoral Zone on

Wet Detention Pond Pollutant Load Reduction”. Final Report prepared for the Florida Department

of Environmental Protection, Tallahassee, FL.

Dillon, P.J., and F.H. Rigler. (1974). “The Phosphorus-Chlor ophyll Relationship in Lakes.”

Limnol. Oceanogr ., Vol. 19, pp. 767-773.

East Central Florida Regional Planning Council. (1978). "208 Area wide Water Quality

Management Plan – Orla ndo Metropolitan 208 Pla nning Area, Volume III: Point/Nonpoint Source

Needs and Recommendations." Prepared for the 208 Areawide Water Quality Management

Planning Program. Winter Park, FL.

East Central Florida Regional Planning Counci l. (1984). "Lake To hopekaliga Drainage

Area Agricultural Runoff Manageme nt Plan." Winter Park, FL.

8-1

# FDEP \ STORMWATER TREATMENT REPORT 

# 8-2

East Central Florida Regional Planning Council. (1985). "Point and Nonpoint Source

Assessment of the Middle St. Johns River - Volume I." Winter Park, FL.

East Central Florida Regional Planning Coun cil and the South Florida Water Management

District. (1988). "Boggy Creek Water Quality Ma nagement Study - Final Report." Winter Park,

FL.

Environmental Research & Desi gn, Inc. (ERD). (2000). “W inter Park Chain-of-Lakes

Groundwater/Sediment Study.” Final Report prepar ed for the City of Wint er Park, Winter Park,

FL.

Environmental Research & Desi gn, Inc. (ERD). (2002). “Lake Morton Water Quality

Diagnostic Evaluation.” Final Report prepared for the City of Lakeland Lakes and Stormwater

Division, Lakeland, FL.

Environmental Research & Design, Inc. (ERD). (2004). “Lak e Holden Revised

Hydrologic/Nutrient Budget and Ma nagement Plan.” Final Report prepared for Professional

Engineering Consultants, Orlando, FL.

Environmental Research & Design, Inc. (ERD). (2004). “Non point Source Model

Development and Basin Management Strategies fo r Lemon Bay.” Final Re port prepared for the

Southwest Florida Water Manageme nt Distri ct, Brooksville, FL.

Fall, C. (1987). "Characterization of Agricu ltural Pump Discharge Qu ality in the Upper St.

Johns River Basin." St. Johns River Water Manage ment District, Contract #WM108, Pa latka, FL.

Fall, C. (1990). "Characterization of Agricu ltural Pump Discharge Qu ality in the Upper St.

Johns River Basin." St. Johns River Wa ter Management District, Palatka, FL.

Fall, C. and J. Hendrickson. (1987). "An In vestigation of the St. Johns River Water Control

District: Reservoir Water Quality and Farm Pr actices." St. Johns Ri ver Water Management

District, Contract #WM108, Palatka, FL.

Fall, C., P. Jennings, and M. Von Canal. (1995). "The Effectiveness of Agricultural

Permitting in the Upper St. Johns River Water." St. Johns Rive r Water Management District,

Palatka, FL.

Federico, A.C. (1977). "Investigations of the Relationship Between Land Use, Rainfall,

and Runoff Quality in th e Taylor Creek Watershed." South Florida Water Mana gement District,

Tech. Pub. 77-3, West Palm Beach, FL.

Florida Department of Environmental (Regul ation) Protection. (1988). "The Florida

Development Manual: A Guide to Sound Land and Water Mana gement." Prepared by the

Nonpoint Source Management De partment. Tallahassee, FL.

Gaggiani, N.G. and A. G. Lamonds. (1 978). "Chemical and Biol ogical Quality of Lakes

Faith, Hope and Charity at Mai tland, Florida, with Em phasis on the Effects on Storm Runoff and

Bulk Precipitation, 1971-74." U. S. Geological survey Open-File Report 77-491, Tallahassee, FL.

# FDEP \ STORMWATER TREATMENT REPORT 

# 8-3

German, E.R. (1983). "Wat er Quality of Lakes Faith, Hope , Charity and Lucien, 1979-79,

in an Area of Residential Deve lopment and Highway C onstruction at Maitland , Florida." U.S.

Geological Survey Water Resources Investigations 82-51, Tallahassee, FL.

Gregg, J.R. (1984). "Evaluation of the Water Management System of a Single-Family

Residential Site: Hydrology and Hydraulics of Timbercreek Subdivi sion in Boca Raton, Florida."

South Florida Water Management District Tech. Pub. 84-11 Volume I, West Palm Beach, FL.

Gregg, J.R. and T.R. Slater. (1989). "Evaluation of the Su rface Water Management System

at a Single-Family Reside ntial Development: Springh ill Subdivision." South Florida Water District

Tech. Pub. 89, West Palm Beach, FL.

Gupta, M.K. (1981). "Cons tituents of Highway Runoff." Executive Summary, Volume VI

- Final Report. Federal Highway Administra tion Report #FHWA/RD-81/ 047, Washington, D.C.

Gupta, M.K., R.W. Agnew, D. Gruber, and W. Kreutzberger. (1981). "Constituents of

Highway Runoff." Characteristic s of Highway Runoff from Op erating Highways - Research

Report; Volume IV - Final Report. Federal Highway Administration Report #FHWA/RD-81/045,

Washington, D.C.

Harper, H.H. (1985). "Fate of Heavy Me tals from Highway Ru noff in Stormwater

Management Systems." Ph.D. Di ssertation for the Univ ersity of Central Florida, Orlando, FL.

Harper, H.H. (1988). "E ffects of Stormwater Manage ment Systems on Groundwater

Quality." FDEP Project #WM190 . Florida Department of Envi ronmental Regulation, Tallahassee,

FL.

Harper, H.H. (1994). "Stormwater Load ing Rate Parameters for Central and South

Florida." Revised October 1994.

Harper, H.H. (1995). "Pollutant Removal Efficiencies for Typical Stormwater Management

Systems in Florida." Proceedings of the 4t h Biennial Stormwater Research Conference , Southwest

Florida Water Management District, Cl earwater, FL, Octo ber 18-20, 1995.

Harper, H.H. and J.L. Herr. (1993). "Treatme nt Efficiencies of De tention with Filtration

Systems." Final Report to the St. Johns River Water Management District for Project No. 90B103,

August 1993.

Harper, H.H., J.L. Herr , and D.M. Baker. (2000). Bradfo rdville Stormwater Study.” Final

Report prepared for the Bo ard of County Commission ers, Leon County, FL.

Harper, H.H., M.P. Wanielis ta, B.M. Fries, and D.M. Baker. (1986). "Stormwater

Treatment by Natural Systems." Star Project # 84-026 - Final Report. Florida Department of

Environmental Regulation, Tallahassee, FL.

Harper, H.H., M.P. Wanielista, D.M. Baker, B.M. Fries, and E.H. Livingston. (1985).

"Treatment Efficiencies of Residential Stormwat er Runoff in a hardwo od Wetland." Lake and

Reservoir Management - Proceeding s of the Fifth Annual Conferen ce and International Symposium

on Applied Lake and Watershed Management , Lake Geneva, WI, No vember 13-16, 1985.

# FDEP \ STORMWATER TREATMENT REPORT 

# 8-4

Harper, H.H., M.P. Wanielista , Y.A. Yousef, and D. Didomenico. (1982). "Lake Eola

Restoration: Water Quality Bac kground and Stormwater Management Practices." University of

Central Florida, Orlando, FL.

Hendrickson, J. (1987). "Effect of the Willowbrook Farms Detentio n Basin on the Quality

of Agricultural Runoff." St. Johns River Water Management District, Co ntract #WM108, Palatka,

FL.

Hendrickson, J. (No date given). Unpub lished data on 3 citrus sites in Florida.

Holler, J.D. (1989). “Water Quality Effi ciency of an Urban Co mmercial Wet Detention

Stormwater Management System at the Boynton Beach Mall in South Palm Beach County,

Florida.” Florida Scientist , Vol. 52, No. 1, pp. 48-57.

Holtkamp, M.L. (1998). "An Assessment of the Effectiveness of Enhancing the Existing

Stormwater Pond Near 102nd Avenue on its Water Quality Functio n." Draft Report for the

Southwest Florida Water Manageme nt District - SWIM Section.

Howie, B. and B.G. Waller. (1986). "Chemical Effects of Hi ghway Runoff on the Surficial

Aquifer, Broward Count y, Florida." U.S. Geological Survey Water Resources Investigations

Report 86-4200, Tallahassee, FL.

Kehoe, M.J., C.W. Dye, and B.T. Rushton. (1994). “A Survey of the Water Quality of

Wetlands-Treatment Stormwater Ponds – Final Re port.” Southwest Florida Water Management

District, Environmental S ection, Brooksville, FL.

Lopez, M.A. and R.F. Giovanne lli. (1984). "Water Quality Characteristics of Urban Runoff

and Estimates of Annual Loads in the Tampa Bay Area, Florida, 1975 -80." U.S. Geological Survey

Water Resources Investigations Report 83-4181, Tallahassee, FL.

Lynard, W.G., E.J. Finnemore, J.A. Loop, an d R.M. Finn. (1980). "Urban Stormwater

Management and Technology: Case Histor ies." EPA 68-03-2617. Cincinnati, OH.

Martin, E.H., and Mille r, R.A. (1987). “Efficiency of an Ur ban Stormwater Detention

System.” Proceedings of the Fourth International Confer ence on Urban Storm Drainage

.

Mattraw, Jr., H.C., and R.A. Miller. (1981). "Stormwate r Quality Processes for Three

Land-Use Areas in Broward Count y, Florida." U.S. Geological Survey Report #USGS/WRI 81-23,

Tallahassee, FL.

Mattraw, Jr., H.C., J. Hardee, a nd R.A. Miller. (19 78). "Urban Stormwat er Runoff Data for

a Residential Area, Pompano Beac h, Florida." U.S. Geological Survey Open-File Report 78-324,

Tallahassee, FL.

McCuen, R.H. (1982). “A Guide to H ydrologic Analysis Using SCS Methods.”

Englewood Cliffs, NJ: Prentice-Hall, Inc.

# FDEP \ STORMWATER TREATMENT REPORT 

# 8-5

McKenzie, D.J. and G.A. Irwin. (1983). "Wat er Quality Assessment of Stormwater Runoff

from a Heavily Used Urban Highwa y Bridge in Miami, Florida." U.S. Geological Survey Water

Resources Investigations Report 83-4153, Tallahassee, FL.

Miller, R.A. (1979). "Char acteristics of Four Ur banized Basins in S outh Florida." U.S.

Department of the Interior Geological Survey Open- File Report 79-694 . Tallahassee, FL.

Miller, R.A. (1985). "Percen tage Entrainment of Constituent Loads in Urba n Runoff, South

Florida." U.S. Geological Survey Water Resources Investigations Report 84-4329. Tallahassee,

FL.

Miller, W.L. (1988). "Description and Evalua tion of the Effects of Urban and Agricultural

Development on the Surficial Aqui fer System, Palm Beach County, Florida." U.S. Geological

Survey Water Resources I nvestigations Report 88-4056, Tallahassee, FL.

Post, Buckley, Schuh & Jernig an, Inc. (1982). “Evaluation of Two Best Management

Practices: A Grassy Swale and a Retention/Detention Pond.” Brevard 208 Continuing Planning

Process. EPA Gran t No. 067-301.00.

Rushton, B.T., and C.W. Dy e. (1993). “An In-depth Analysis of a Wet Detention

Stormwater System.” Southw est Florida Water Management District , Brooksville, FL.

Rushton, B., C. Miller, and C. Hull. (1995). “Residence Time as a Pollutant Removal

Mechanism in Stormwater Detent ion Ponds.” Proceedings of th e Fourth Biennial Stormwater

Research Conference, Clearwater Beach, FL, October 18-20, 1995.

Sawka, G.J., D.W. Bl ack, and M.N. Allhands. (1993). "Evaluation of Wet Detention for

Treatment of Surface Water Runoff from a Citrus Grove in South Florida." Proceedings of the

Third Biennial Stormwater Research Conference , Tampa, FL, October 7-8, 1993.

Southwest Florida Water Management District. (1988). "Archie Creek/Coastal Areas and

Buckhorn Creek Watersheds - Stormwater Management Plan." Final Report.

Toet, C., T. Hvitved-Jacobsen , and Y.A. Yousef. (1990) . “Pollutant Removal and

Eutrophication in Urban Runoff Dete ntion Ponds.” Wat. Sci. Tech. Vol. 22, No. 10/11, pp. 197-

204.

United States Department of Agriculture . (1986). “Urban Hydrology for Small

Watersheds.” Technical Release 55 prepared by the Natural Re sources Conservation Service –

Engineering Division.

United States Environmental Protection Agen cy (U.S. EPA). (1983) . "Results of the

National Urban Runoff Program (NURP)." Executive Summar y; Volume I - Final Report; Volume

II - Appendices; Volume III - Data Appendix. U.S. EPA, Washington, D.C.

United States Geologi cal Survey (USGS). (1985). “C onstituent-Load Ch anges in Urban

Stormwater Runoff Routed Throug h a Detention Pond-Wetlands System in Central Florida.” Water

Resources Investigations Report No. 85-4310.

# FDEP \ STORMWATER TREATMENT REPORT 

# 8-6

United States Geological Survey (USGS). (1 985). "Percentage Entrainment of Constituent

Loads in Urban Runoff, South Florida." Wate r Resources Investigations Report No. 84-4329.

Waller, B.G. (1982). "E ffects of Land Use on Surfac e Water Quality in the East

Everglades, Dade County, Florida." U.S. Geologi cal Survey Water Resour ces Investigation 81-59,

Tallahassee, FL.

Waller, B.G., H. Klein, and L.J. Lefkoff. (1984). "Attenuation of Stormwater

Contaminants from Highw ay Runoff within Unsaturated Limest one, Dade County, Florida." U.S.

Geological Survey Water Resources Invest igations Report 84-4083, Tallahassee, FL.

Wanielista, M.P. (1978). Stormwater Ma nagement: Quantity and Quality. Ann Arbor,

MI: Ann Arbor Sc ience Publishers.

Wanielista, M.P., Y.A. Yousef , and J.S. Taylor. (1982). "Stormwater Management to

Improve Lake Water Quality." EPA Grant 600/82-048.

Weinburg, M., D. Reece, and D. Allman. (1980). "Effect of Urban Stormwater Runoff to a

Man-Made Lake on Groundwater Qu ality." South Florida Water Ma nagement Distri ct Tech. Pub.

80-4, West Palm Beach, FL.

Whalen, P.J. and M.G. Cullum. (1988). "An Asse ssment of Urban Land Use/Stormwater

Runoff Quality Relationships and Treatment Efficiencies of Sel ected Stormwater Management

Systems." South Florida Water Management Di strict Tech. Pub. 88-9, West Palm Beach, FL.

Yousef, Y.A., M.P. Wanielista , H.H. Harper, and J.E. Christ opher. (1982). "Management

of Drainage Systems from Highway Bridges of Pollution Control." Tr ansportation Research

Record 896, Hydrology and Hydrauli cs: Water, Noise and Air Quality . Washington, D.C.

Yousef, Y.A., M.P. Wanielista, H.H. Harper, D. B. Pearce, and R. D. Tolbert. (1985). "Best

Management Practices - Removal of Highway Co ntaminants by Roadside Swales." Florida

Department of Transportation, Publication FL-ER-30-85, Tallahassee, FL.

Yousef, Y.A., M.P. Wanielista, H.H. Harper , and T. Hvitved-Jacobson. (1986). "Best

Management Practices - Effectiven ess of Retention/Deten tion Ponds for Control of Contaminants in

Highway Runoff." Florida Depart ment of Transportation, Publi cation FL-ER-34-86, Tallahassee,

FL.

# FDEP \ STORMWATER TREATMENT REPORT 

# APPENDICES

# FDEP \ STORMWATER TREATMENT REPORT 

# APPENDIX A

PRECIPITATION DATA

A.1 Summary of Monthly and Annual Pr ecipitation at Florida Monitoring

Sites from 1971-2000

A.2 Geographical Coordinates and Mean Annual Rainfall for Florida

Meteorological Monitoring Sites fo r Available Period of Record

A.3 Expanded Views of Rainfall Isopleths by Region

A.4 Frequency Distribution of Rain Even ts in Selected Meteorological Regions

# FDEP \ STORMWATER TREATMENT REPORT 

# A.1 Summary of Monthly and Annual Precipitation at Florida Monitoring

Sites from 1971-2000

# CLIMATOGRAPHY OF THE UN ITED STATES NO. 81



# Monthly Station Normals

of Temperature, Precipitation,

and Heating and Cooling

Degree Days

1971 - 2000



# 08

FLORIDA

NATION A L OC EANIC A ND ATMOS P H ERIC ADMINISTRATI O N

NATION A L E N VIR O NMEN TAL SATELL ITE, DATA

, AND INF O R M ATION S E R VIC E

NATION A L CLIMATIC DATA CENT E R

ASHE VILL E, NC

# CLIMATOGRAPHY OF THE UNITED STATES NO. 81

Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days



# 1971-2000



# FLORIDA Page 2

(This Page Intentionally Left Blank)

# CLIMATOGRAPHY OF THE UNITED STATES NO. 81

Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days



# 1971-2000



# FLORIDA Page 3

NOTES

Product Description:

This Climatography includes 1971-2000 normals of monthly and annual maximum, minimum, and mean temperature (degrees F), monthly and annual

total precipitation (inches), and heati ng and cooling degree days (base 65 degrees F). Normals stations include both National Weather Service

Cooperative Network and Principal Observation (First-Order) locati ons in the 50 states, Puerto Rico, the Virgin Islands, and Pa cific Islands.

A bbreviations:

No. = Station Number in State Map Latitude = Latitude in degrees, minutes, and hemisphere (N=North, S=South)

COOP ID = Cooperative Network ID (1:2=State ID, 3:6=Station Index) Longitude = Longitude in degrees, minutes, and hemisphere (W=West, E=East)

WBAN ID = Weather Bureau Army Navy ID, if assigned Elev = Elevation in feet above mean sea level

Elements = Input Elements (X=Maximum Temperature, Flag 1 = * if a published Local Climatological Data station

N=Minimum Temperature, P=Precipitation) Flag 2 = + if WMO Fully Qualified (see Note below)

Call = 3-Letter Station Call Sign, if assigned

MAX = Normal Maximum Temperature (degrees Fahrenheit) HIGHEST MEAN/YEAR = Maximum Mean Monthly Value/Year, 1971-2000

MEAN = Average of MAX and MIN (degrees Fahrenheit) MEDIAN = Median Mean Monthly Value/Year, 1971-2000

MIN = Normal Minimum Temperature (degrees Fahrenheit) LOWEST MEAN/YEAR = Minimum Mean Monthly Value/Year, 1971-2000

HDD = Total Heating Degree Days (base 65 degrees Fahrenheit) MAX OBS TIME ADJUSTMENT = Add to MAX to Get Midnight Obs. Schedule

CDD = Total Cooling Degree Days (base 65 degrees Fahrenheit) MIN OBS TIME ADJUSTMENT = Add to MIN to Get Midnight Obs. Schedule

Note: In 1989, the World Meteorological Organization (WMO) prescr ibed standards of data completeness for the 1961-1990 WMO Standard Normals.

For full qualification, no more than three consecutive year-mont h values can be missing for a giv en month or no more than five overall values can be

missing for a given month (out of 30 values). Stations meeting these standards are indi cated with a '+' sign in Flag 2. Otherw ise, stations are included in

the normals if they have at least 10 year-month values for each month and have been active sinc e January 1999 or were a previou s normals station.

Map Legend: Numbers correspond to ‘No.’ in Station Inventory; Shaded Circ les indicate Temperature and Prec ipitation Stations, Triangles ( Point Up)

indicate Precipitation-Only Stations, Tri angles (Point Down) indicate Temperature-On ly Stations, and Hexagons indicate stations with Flag 1 = *.

Computational Procedures:

A climate normal is defined, by convention, as the arithmetic mean of a climatological element computed over three consecutive decades

(WMO,1989). Ideally, the data record for such a 30-year period should be free of any inconsistenc ies in observational practices ( e.g ., changes in station

location, instrumentation, time of observation, etc .) and be serially complete ( i.e ., no missing values). When present, in consistencies can lead to a nonclimatic bias in one period of a station’ s record relative to another, yielding an “inhomogeneous” data record. Adjustments a nd estimations can make a

climate record “homogeneous” and serially complete, and allow a clim ate normal to be calculated simply as the average of the 30 monthly values.

The methodology employed to generate the 1971-2000 normals is not the same as in previous nor mals, as it addresses inhomogeneit y and missing

data value problems using several st eps. The technique developed by Karl et al. (1986) is used to adjust monthl y maximum and minimum temperature

observations of conterminous U.S. stations to a consistent midnight-to-midnight sche dule. All monthly temperature averages and precipitation totals are

cross-checked against archived daily observati ons to ensure internal consistency. Ea ch monthly observation is evaluated using a modified quality

control procedure (Peterson et al .,1998), where station observation departures are computed, compared with neighboring stations, and then flagged and

estimated where large differences with nei ghboring values exist. Miss ing or discarded temperature and precipitation observatio ns are replaced using a

weighting function derived from the observ ed relationship between a candidate’s monthly observations and those of up to 20 neig hbo r ing stations whose

observations are most strongly correlated with the candidate site . For temperature estimates, neighboring stations were select ed from the U.S.

Historical Climatology Network (USHCN; Karl et al. 1990). For precipitation estimates, all avail able stations were poten tial neighbors, maximizing

station density for estimating the more s patially variable precipitation values.

Peterson and Easterling (1994) and Easterling and Peterson (1995) outline the method for adjusting temperature inhomogeneities. This technique

involves comparing the record of the candidate station with a reference series generated from neighboring data. The reference s eries is reconstructed

using a weighted average of firs t difference observations (the diffe rence from one year to the next) for neighboring stations w ith the highest correlation

with the candidate. The underlying assumption behind this methodol ogy is that temperatures ov er a region have similar tendencie s in variation. If this

assumption is violated, the potential disc ontinuity is evaluated for statistical signi ficance. Where significant discontinuiti es are detected, the difference in

average annual temperatures before and after the inhomogeneity is applied to adjust the mean of the earlier block with the mean of the latter block of

data. Such an evaluation requires a minimum of five years bet ween discontinuities. Consequently, if multiple changes occur with in five years or if a

change occurs very near the end of the normals period ( e.g., after 1995), the discontinuity may not be detectable using this methodology.

The monthly normals for maximum and minimum temperature and precip itation are computed simply by averaging the appropriate 30 v alues from

the 1971-2000 record. The monthly average temperature normals ar e computed by averaging the corresponding monthly maximum and m inimum

normals. The annual temperature normals are calculated by taki ng the average of the 12 monthly normals. The annual precipitatio n and degree day

normals are the sum of the 12 monthly normals. Trace precipit ation totals are shown as zero. Precipitation totals include ra in and the liquid equivalent

of frozen and freezing precipitation ( e.g ., snow, sleet, freezing rain, and hail). For many NWS loca tions, indicated with an ‘*’ next to ‘HDD’ and ‘CDD’ in

the degree day table, degree day normals are computed directly from daily values for the 1971-2000 period. For all other stati ons, estimated degree day

totals are based on a modification of the rational conversion formula developed by Thom (1966), using daily spline-fit means an d standard deviations of

average temperature as inputs.

References:

Easterling, D.R, and T.C. Peterson, 1995: A new method for de tecting and adjusting for undocumented discontinuities in climatol ogical time series

. Intl. J. Clim

., 15 , 369-377.

Karl, T.R., C.N. Williams, Jr., P.J. Young, and W.M. Wendland,1986: A model to estimate the time of observation bias associated with monthly mean maximum, minimum, and mean

temperatures for the United States

, J. Clim. Appl. Met

., 25 , 145-160.

Peterson, T.C., and D.R. Easterling, 1994: Creation of homogeneous composite climatological reference series

. Intl. J. Clim

., 14 , 671-679.

Peterson,T.C., R. Vose, R. Schmoyer, and V. Razuvaev, 1998: Global Historical Climat ology Network (GHCN) qua lity control of mon thly temperature data

. Intl. J. Clim.

, 18 , 1169-1179.

Thom, H.C.S., 1966: Normal degree days above any base by the universal truncation coefficient

, Month. Wea. Rev

., 94 , 461-465.

World Meteorological Organization, 1989: Calculation of Monthly and Annual 30-Year Standard Normals , WCDP-No. 10, WMO-TD/No. 341, Genev a: World Meteorological Organization.



# Rel e ase Dat e : Revised 02 / 2002 * National Climatic Data Center/NES DIS/NOAA, Ashe v ille, N orth Carolina

# 08 - FLORIDA

86 ° W 84 ° W 82 ° W 80 ° W 26 ° N 28 ° N 30 ° N

50 miles 1

2 3 4 6

7 9 10 11

12 13

14

15 16 17

18 20

21

23

24 25 26

27 28

30 32 33

34 35 37

38

39 40

42 43 44 45 46

47 48 49

50 51 52

53 54 55

56 57 58

59 60 61

62

63

64 65 66

67

68 69

70

71 72

73 74

75 76 77 78

79 80

82 83

84

85 86 87

88 89

90

91 92 93

94

95 96

97 98 99

100 101 102

103 104 105

106 107

108 109 110

111

5 8

22 29 41 **JAX**

**EYW MIA**  **MCO TLH** 

**TPA**

**PBI** 

# 19

DAB

31

FMY 36

GNV PNS 81

# CLIMATOGRAPHY OF THE UNITED STATES NO. 81

Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days



# 1971-2000



# FLORIDA Page 5

1 080211 12832 XNP APALACHICOLA AP AAF 29 44 N 85 01 W 20 +

2 080228 XNP ARCADIA 27 13 N 81 52 W 30 +

3 080236 XNP ARCHBOLD BIO STATION 27 11 N 81 21 W 140 +

4 080369 XNP AVON PARK 2 W 27 36 N 81 32 W 154 +

5 080390 P BABSON PARK 1 ENE 27 51 N 81 31 W 125

6 080478 XNP BARTOW 27 54 N 81 51 W 125 +

7 080611 XNP BELLE GLADE EXP STN 26 39 N 80 38 W 15 +

8 080758 P BITHLO 28 33 N 81 07 W 65

9 080945 XNP BRADENTON 5 ESE 27 27 N 82 29 W 20 +

10 081046 XNP BROOKSVILLE CHIN HILL 28 37 N 82 22 W 240 +

11 081163 XNP BUSHNELL 2 E 28 40 N 82 05 W 75 +

12 081276 XNP CANAL POINT USDA 26 52 N 80 38 W 30 +

13 081544 XNP CHIPLEY 3 E 30 47 N 85 29 W 130 +

14 081641 XNP CLERMONT 7 S 28 27 N 81 45 W 110 +

15 081654 XNP CLEWISTON US ENGINEERS 26 45 N 80 55 W 20 +

16 081978 XNP CRESCENT CITY 29 26 N 81 30 W 55 +

17 081986 13884 XNP CRESTVIEW BOB SIKES AP CEW 30 47 N 86 31 W 190

18 082008 XNP CROSS CITY 2 WNW CTY 29 39 N 83 10 W 42 +

19 082158 12834 XNP DAYTONA BEACH INTL AP DAB 29 11 N 81 03 W 31 * +

20 082220 XNP DE FUNIAK SPRINGS 30 44 N 86 04 W 230 +

21 082229 XNP DELAND 1 SSE 29 01 N 81 19 W 25 +

22 082288 P DESOTO CITY 8 SW 27 22 N 81 31 W 85 +

23 082298 XNP DEVILS GARDEN 26 36 N 81 08 W 20

24 082850 XNP EVERGLADES 25 51 N 81 23 W 5

25 082915 XNP FEDERAL POINT 29 45 N 81 32 W 5 +

26 082944 XNP FERNANDINA BEACH 30 40 N 81 28 W 13 +

27 083020 XNP FLAMINGO RANGER STN 25 09 N 80 55 W 3 +

28 083137 XNP FORT DRUM 5 NW 27 35 N 80 51 W 71 +

29 083153 P FORT GREEN 12 WSW 27 34 N 82 08 W 112 +

30 083163 XNP FORT LAUDERDALE FLL 26 06 N 80 12 W 16 +

31 083186 12835 XNP FORT MYERS (PAGE AP) FMY 26 35 N 81 52 W 15 * +

32 083207 XNP FORT PIERCE 27 28 N 80 21 W 25 +

33 083230 XNP FOUNTAIN 3 SSE 30 26 N 85 25 W 140

34 083321 XNP GAINESVILLE 3 WSW 29 38 N 82 22 W 96

35 083322 XNP GAINESVILLE 11 WNW 29 41 N 82 30 W 95

36 083326 12816 XNP GAINESVILLE RGNL AP GNV 29 42 N 82 17 W 134 *

37 083470 XNP GLEN ST MARY 1 W 30 16 N 82 11 W 128 +

38 083874 XNP HASTINGS ARC 29 43 N 81 30 W 10

39 083909 XNP HIALEAH 25 50 N 80 17 W 12 +

40 083956 XNP HIGH SPRINGS 29 50 N 82 36 W 65 +

41 083986 P HILLSBOROUGH RVR ST PK 28 09 N 82 14 W 53

42 084091 XNP HOMESTEAD EXP STN 25 30 N 80 30 W 11

43 084210 XNP IMMOKALEE 3 NNW 26 28 N 81 26 W 35 +

44 084289 XNP INVERNESS 3 SE 28 48 N 82 19 W 40 +

45 893832 93832 XNP JACKSONVILLE CECIL NAS 30 13 N 81 53 W 89 +

46 084358 13889 XNP JACKSONVILLE INTL AP JAX 30 30 N 81 42 W 26 * +

47 893837 93837 XNP JACKSONVILLE NAS 30 14 N 81 40 W 30 +

48 084366 XNP JACKSONVILLE BEACH 30 17 N 81 24 W 10

49 084394 XNP JASPER 30 31 N 82 57 W 147 +

50 084570 12836 XNP KEY WEST INTL AP EYW 24 33 N 81 45 W 4 * +

51 812850 12850 XNP KEY WEST NAS 24 35 N 81 41 W 23 +

52 084625 XNP KISSIMMEE 2 28 17 N 81 25 W 60 +

53 084662 XNP LA BELLE 26 45 N 81 26 W 16

54 084707 XNP LAKE ALFRED EXP STN 28 06 N 81 43 W 138 +

55 084731 XNP LAKE CITY 2 E 30 11 N 82 36 W 195 +

56 084797 12883 XNP LAKELAND 28 01 N 81 55 W 145

57 085076 XNP LISBON 28 52 N 81 47 W 68 +

58 085099 XNP LIVE OAK 30 17 N 82 58 W 120 +

59 085182 XNP LOXAHATCHEE 26 41 N 80 16 W 14

60 085275 XNP MADISON 30 27 N 83 25 W 120

61 803853 03853 XNP MAYPORT PILOT STN 30 24 N 81 25 W 16

62 085539 XNP MAYO 30 03 N 83 10 W 65 +

63 085612 12838 XNP MELBOURNE WFO MLB 28 06 N 80 39 W 25 +

64 085658 12859 XNP MIAMI BEACH 25 47 N 80 08 W 5 +

65 085663 12839 XNP MIAMI INTL AP MIA 25 49 N 80 18 W 35 * +

66 085793 XNP MILTON EXPERIMENT STN 30 47 N 87 08 W 217 +

67 085879 XNP MONTICELLO 3 W 30 32 N 83 55 W 145 +

68 085895 XNP MOORE HAVEN LOCK 1 26 50 N 81 05 W 35 +

69 085973 XNP MOUNTAIN LAKE 27 56 N 81 36 W 125 +

70 086065 XNP MYAKKA RIVER STATE PARK 27 14 N 82 19 W 20 + STATION INVENTORY

No. COOP ID WBAN ID Elements Station Name Call Latitude Longitu de Elev Flag 1 Flag 2

# CLIMATOGRAPHY OF THE UNITED STATES NO. 81

Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days



# 1971-2000



# FLORIDA Page 6

71 086078 XNP NAPLES 26 10 N 81 47 W 5 +

72 086240 XNP NICEVILLE 30 32 N 86 30 W 60

73 086406 XNP OASIS RANGER STN 25 51 N 81 02 W 8

74 086414 XNP OCALA 29 12 N 82 05 W 75 +

75 086485 XNP OKEECHOBEE 27 12 N 80 50 W 21

76 086628 12815 XNP ORLANDO INTL AP MCO 28 26 N 81 20 W 96 * +

77 086753 XNP PALATKA 29 39 N 81 40 W 70

78 086842 XNP PANAMA CITY 5 NE PFN 30 13 N 85 36 W 32 +

79 086880 XNP PARRISH 27 37 N 82 21 W 60 +

80 803855 03855 XNP PENSACOLA SHERMAN NAS 30 21 N 87 19 W 33 +

81 086997 13899 XNP PENSACOLA RGNL AP PNS 30 29 N 87 11 W 112 * +

82 087020 XNP PERRINE 4 W 25 35 N 80 26 W 10

83 087025 XNP PERRY 30 06 N 83 34 W 45 +

84 087205 XNP PLANT CITY 28 01 N 82 08 W 120 +

85 087254 XNP POMPANO BEACH 26 14 N 80 09 W 15 +

86 087397 XNP PUNTA GORDA 4 ESE 26 55 N 82 00 W 20 +

87 087429 XNP QUINCY 3 SSW 30 36 N 84 33 W 245 +

88 087760 XNP ROYAL PALM RANGER STN 25 23 N 80 36 W 7

89 087826 XNP ST AUGUSTINE WFOY 29 55 N 81 19 W 8 +

90 087851 XNP SAINT LEO 28 20 N 82 16 W 190 +

91 087886 XNP ST PETERSBURG SPG 27 46 N 82 38 W 8 +

92 087982 XNP SANFORD ORLANDO SFB 28 48 N 81 16 W 12 +

93 088527 XNP STARKE 29 56 N 82 06 W 162

94 088565 XNP STEINHATCHEE 6 ENE 29 43 N 83 18 W 35 +

95 088620 XNP STUART 1 S 27 11 N 80 14 W 10 +

96 088758 93805 XNP TALLAHASSEE MUNICIPAL AP TLH 30 24 N 84 21 W 55 * +

97 088780 XNP TAMIAMI TRAIL 40 MI BEND 25 46 N 80 49 W 15 +

98 088788 12842 XNP TAMPA INTL AP TPA 27 58 N 82 32 W 19 * +

99 088824 XNP TARPON SPRINGS SWG PLNT 28 09 N 82 45 W 8 +

100 088841 XNP TAVERNIER 25 00 N 80 31 W 7 +

101 088942 XNP TITUSVILLE 28 38 N 80 50 W 5 +

102 089120 XNP USHER TOWER 29 25 N 82 49 W 33 +

103 089176 XNP VENICE 27 06 N 82 26 W 8

104 089214 12843 XNP VERO BEACH MUNI ARPT 27 39 N 80 25 W 24

105 089219 XNP VERO BEACH 4 W 27 41 N 80 26 W 20 +

106 089401 XNP WAUCHULA 27 33 N 81 48 W 60 +

107 089430 XNP WEEKI WACHEE 28 31 N 82 35 W 20 +

108 089525 12844 XNP WEST PALM BEACH INTL AP PBI 26 41 N 80 06 W 18 * +

109 089566 XNP WEWAHITCHKA 30 07 N 85 12 W 42 +

110 893841 93841 XNP WHITING FIELD NAS 30 43 N 87 01 W 177 +

111 089707 XNP WINTER HAVEN 28 01 N 81 44 W 145 + STATION INVENTORY

No. COOP ID WBAN ID Elements Station Name Call Latitude Longitu de Elev Flag 1 Flag 2

# CLIMATOGRAPHY OF THE UNITED STATES NO. 81

Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days



# 1971-2000



# FLORIDA Page 12

001 APALACHICOLA AP 4.87 3.76 4.95 3.00 2.62 4.30 7.31 7.29 7.10 4.18 3.62 3.51 56.51

002 ARCADIA 2.13 2.43 3.10 1.86 3.87 7.81 7.64 7.02 6.77 2.87 2.08 1.76 49.34

003 ARCHBOLD BIO STATION 2.32 2.38 3.25 2.33 3.98 7.74 7.66 7.42 6.50 3.00 2.07 1.95 50.60

004 AVON PARK 2 W 2.48 2.41 3.02 2.17 3.63 8.25 6.81 7.18 5.98 3.02 2.27 1.87 49.09

005 BABSON PARK 1 ENE 2.06 2.56 3.13 1.95 4.10 6.86 8.23 7.29 5.65 2.29 2.48 1.75 48.35

006 BARTOW 2.51 2.82 3.11 2.53 3.81 6.78 8.56 6.52 6.68 2.71 2.18 2.37 50.58

007 BELLE GLADE EXP STN 2.51 1.88 2.65 2.41 5.04 7.33 7.34 7.16 7.09 3.54 2.79 1.82 51.56

008 BITHLO 2.35 2.69 2.81 1.88 3.47 7.26 6.86 8.06 6.14 3.75 2.14 1.87 49.28

009 BRADENTON 5 ESE 2.94 2.66 3.36 1.83 2.85 7.41 8.71 9.43 7.25 2.88 2.35 2.45 54.12

010 BROOKSVILLE CHIN HILL 3.27 3.24 4.22 2.62 3.40 7.24 7.16 8.24 5.96 2.38 2.39 2.45 52.57

011 BUSHNELL 2 E 3.43 3.02 3.93 2.34 3.79 6.18 6.43 7.24 6.00 2.14 2.18 2.52 49.20

012 CANAL POINT USDA 2.60 2.27 3.44 2.42 4.61 7.64 6.22 6.69 7.28 3.91 2.95 2.07 52.10

013 CHIPLEY 3 E 6.09 4.81 6.11 3.84 4.21 5.24 6.92 5.38 4.76 2.90 4.12 3.86 58.24

014 CLERMONT 7 S 3.11 2.58 3.81 2.18 3.67 7.86 6.78 6.96 5.59 2.40 2.40 2.40 49.74

015 CLEWISTON US ENGINEERS 2.38 2.01 2.68 2.16 4.50 7.15 6.58 6.28 4.99 2.87 2.28 1.52 45.40

016 CRESCENT CITY 3.34 2.83 4.06 2.56 3.52 6.53 6.34 6.28 6.11 3.12 2.55 2.55 49.79

017 CRESTVIEW BOB SIKES AP 6.49 4.91 7.06 4.26 4.94 7.41 6.83 6.34 4.88 3.02 4.20 3.60 63.94

018 CROSS CITY 2 WNW 4.41 3.54 4.42 3.48 3.06 6.34 8.92 9.67 6.10 2.93 2.35 3.27 58.49

019 DAYTONA BEACH INTL AP 3.13 2.74 3.84 2.54 3.26 5.69 5.17 6.09 6.61 4.48 3.03 2.71 49.29

020 DE FUNIAK SPRINGS 5.61 5.39 6.23 3.93 4.95 6.60 7.67 6.77 6.03 3.23 4.76 4.35 65.52

021 DELAND 1 SSE 3.35 2.96 3.84 2.80 4.27 7.60 7.88 7.70 7.17 4.09 2.72 2.65 57.03

022 DESOTO CITY 8 SW 2.31 2.57 3.10 2.20 3.61 8.21 7.00 6.97 6.48 2.64 2.30 1.62 49.01

023 DEVILS GARDEN 2.37 2.09 2.78 2.63 4.33 8.58 7.52 8.10 6.53 3.52 2.58 1.64 52.67

024 EVERGLADES 1.71 1.49 1.92 1.93 3.56 9.89 7.34 8.62 8.23 3.80 1.89 1.72 52.10

025 FEDERAL POINT 3.09 2.89 3.68 2.34 3.55 6.67 6.16 6.57 6.83 3.34 2.70 2.72 50.54

026 FERNANDINA BEACH 3.82 3.17 4.01 2.91 2.87 5.30 5.80 5.34 7.73 4.22 2.49 2.73 50.39

027 FLAMINGO RANGER STN 1.94 1.63 1.87 2.06 5.06 7.25 4.73 7.43 7.20 4.26 2.46 1.57 47.46

028 FORT DRUM 5 NW 2.27 2.47 3.78 2.43 4.47 8.05 7.60 7.27 6.60 3.73 2.30 1.86 52.83

029 FORT GREEN 12 WSW 2.43 2.62 3.31 2.09 3.42 8.18 8.29 7.78 6.86 2.62 2.13 2.23 51.96

030 FORT LAUDERDALE 2.94 2.70 2.80 3.91 6.33 10.01 6.70 6.88 8.26 6.44 4.57 2.65 64.19

031 FORT MYERS (PAGE AP) 2.23 2.10 2.74 1.67 3.42 9.77 8.98 9.54 7.86 2.59 1.71 1.58 54.19

032 FORT PIERCE 2.70 2.99 3.27 2.77 4.38 5.84 5.79 6.35 7.81 5.82 3.50 2.28 53.50

033 FOUNTAIN 3 SSE 5.83 4.69 6.38 3.05 4.39 7.20 8.00 6.50 6.61 2.95 4.01 4.41 64.02

034 GAINESVILLE 3 WSW 4.13 3.90 3.94 3.03 3.70 5.87 5.34 6.69 5.33 1.89 2.58 3.05 49.45

035 GAINESVILLE 11 WNW 3.95 2.34 4.31 2.92 3.34 6.20 7.50 7.89 4.05 2.99 1.87 2.20 49.56

036 GAINESVILLE RGNL AP 3.51 3.39 4.26 2.86 3.23 6.78 6.10 6.63 4.37 2.50 2.17 2.56 48.36

037 GLEN ST MARY 1 W 4.34 3.41 4.52 3.29 3.58 6.53 6.33 7.33 5.36 3.10 2.23 2.92 52.94

038 HASTINGS ARC 3.39 2.69 3.94 2.72 3.47 6.98 5.56 6.37 7.40 3.94 2.88 2.65 51.99

039 HIALEAH 2.34 2.22 3.20 3.90 6.08 10.24 7.00 9.20 8.88 6.56 3.83 2.59 66.04

040 HIGH SPRINGS 4.35 3.69 4.33 3.28 3.63 6.88 7.53 7.92 4.56 2.96 2.28 2.74 54.15

041 HILLSBOROUGH RVR ST PK 3.35 3.12 3.41 2.23 3.21 7.87 7.27 8.16 7.23 2.71 2.72 3.28 54.56

042 HOMESTEAD EXP STN 1.94 1.78 1.88 2.74 5.77 9.51 6.82 9.16 8.90 5.49 2.59 1.61 58.19

043 IMMOKALEE 3 NNW 2.33 2.26 2.97 2.36 4.08 7.78 7.27 7.49 6.61 2.88 2.27 1.77 50.07

044 INVERNESS 3 SE 3.55 2.96 4.17 2.40 3.33 7.40 7.05 7.52 5.93 2.63 2.27 2.56 51.77

045 JACKSONVILLE CECIL NAS 3.50 3.20 4.16 2.91 3.25 6.54 6.39 7.07 6.69 3.24 2.28 2.65 51.88

046 JACKSONVILLE INTL AP 3.69 3.15 3.93 3.14 3.48 5.37 5.97 6.87 7.90 3.86 2.34 2.64 52.34

047 JACKSONVILLE NAS 3.39 2.59 3.97 2.77 3.22 5.78 5.99 5.87 7.28 3.30 2.35 2.45 48.96

048 JACKSONVILLE BEACH 3.56 2.84 3.92 2.87 3.03 5.70 5.21 6.11 7.53 5.04 2.36 2.75 50.92

049 JASPER 4.96 4.13 5.16 3.45 3.33 6.03 5.62 6.27 4.20 2.87 2.79 3.43 52.24

050 KEY WEST INTL AP 2.22 1.51 1.86 2.06 3.48 4.57 3.27 5.40 5.45 4.34 2.64 2.14 38.94

051 KEY WEST NAS 2.50 1.65 1.80 2.12 3.88 5.42 4.11 5.48 6.33 4.58 2.62 2.24 42.73

052 KISSIMMEE 2 2.39 2.72 3.32 2.02 3.83 6.02 6.55 7.32 6.01 3.17 2.42 2.24 48.01

053 LA BELLE 2.31 2.16 2.89 2.29 3.91 8.88 7.69 7.78 6.57 3.35 2.34 1.71 51.88

054 LAKE ALFRED EXP STN 2.52 2.75 3.43 1.99 4.12 6.88 7.11 7.43 6.53 2.96 2.29 2.28 50.29

055 LAKE CITY 2 E 4.52 3.61 4.90 3.15 3.71 6.91 6.74 7.19 4.67 2.82 2.42 2.96 53.60

056 LAKELAND 2.45 2.73 3.38 2.04 3.81 7.00 7.51 7.33 6.33 2.29 2.12 2.14 49.13

057 LISBON 3.32 2.87 4.03 2.80 4.13 6.13 5.67 6.20 5.76 2.54 2.53 2.65 48.63

058 LIVE OAK 4.99 4.01 5.33 3.29 3.23 6.06 6.35 6.13 4.64 3.26 2.43 3.11 52.83

059 LOXAHATCHEE 2.99 2.23 2.97 2.27 5.33 8.84 7.30 5.58 9.25 5.18 4.44 2.06 58.44

060 MADISON 5.50 4.11 5.59 3.22 3.10 5.82 6.18 5.38 3.94 2.96 3.31 4.07 53.18

061 MAYPORT PILOT STN 2.70 2.58 3.23 2.41 2.13 4.06 4.21 4.45 7.15 4.16 1.74 2.20 41.02

062 MAYO 4.88 3.66 4.85 3.07 3.19 5.82 7.60 7.97 5.07 3.01 2.52 3.23 54.87

063 MELBOURNE WFO 2.48 2.49 2.92 2.08 3.94 5.83 5.38 5.78 7.20 4.76 3.12 2.31 48.29

064 MIAMI BEACH 2.44 2.14 2.20 2.81 4.90 6.90 3.63 5.44 6.31 4.53 3.32 1.98 46.60

065 MIAMI INTL AP 1.88 2.07 2.56 3.36 5.52 8.54 5.79 8.63 8.38 6.19 3.43 2.18 58.53

066 MILTON EXPERIMENT STN 6.39 5.04 7.32 4.35 4.83 7.11 8.17 6.62 6.12 3.66 5.47 4.40 69.48

067 MONTICELLO 3 W 5.63 4.64 6.00 3.63 4.03 5.60 6.50 6.73 4.70 3.32 3.63 3.90 58.31

068 MOORE HAVEN LOCK 1 2.04 2.05 2.93 2.35 3.70 6.98 6.67 6.80 6.42 2.95 1.91 1.64 46.44

069 MOUNTAIN LAKE 2.38 2.43 3.12 2.02 3.88 7.12 7.45 6.64 5.83 2.50 2.23 2.10 47.70 PRECIPITATION NORMALS (Total in Inches)

No. Station Name JAN FEB MAR APR MAY JUN JUL AU G SEP OCT NOV DEC ANNUAL

# CLIMATOGRAPHY OF THE UNITED STATES NO. 81

Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days



# 1971-2000



# FLORIDA Page 13

070 MYAKKA RIVER STATE PARK 3.15 2.88 3.49 2.16 3.12 9.10 9.65 9.48 8.12 3.17 2.25 2.34 58.91

071 NAPLES 2.01 2.17 2.08 1.99 4.21 8.18 7.98 8.05 8.11 3.60 1.99 1.53 51.90

072 NICEVILLE 5.80 5.39 6.52 4.26 4.32 6.08 9.40 6.91 6.72 4.53 4.70 4.57 69.20

073 OASIS RANGER STN 2.14 1.70 2.86 2.94 6.40 9.96 7.43 9.15 8.10 4.02 2.39 1.73 58.82

074 OCALA 3.55 3.11 4.02 2.78 3.55 7.20 6.20 5.84 5.60 2.71 2.47 2.65 49.68

075 OKEECHOBEE 2.11 2.09 2.93 2.35 3.93 6.16 5.94 6.43 5.96 3.62 2.36 1.78 45.66

076 ORLANDO INTL AP 2.43 2.35 3.54 2.42 3.74 7.35 7.15 6.25 5.76 2.73 2.32 2.31 48.35

077 PALATKA 3.53 3.46 3.94 2.49 2.87 5.83 6.43 7.21 5.76 2.97 3.02 2.91 50.42

078 PANAMA CITY 5 NE 5.74 4.71 6.22 3.73 3.86 6.01 8.74 7.52 6.14 3.50 4.53 4.06 64.76

079 PARRISH 2.79 3.13 3.02 2.05 2.98 7.09 7.57 8.67 7.45 2.78 2.31 2.25 52.09

080 PENSACOLA SHERMAN NAS 5.72 4.86 6.32 3.97 4.41 5.17 7.09 6.11 6.75 4.26 4.43 4.02 63.11

081 PENSACOLA RGNL AP 5.34 4.68 6.40 3.89 4.40 6.39 8.02 6.85 5.75 4.13 4.46 3.97 64.28

082 PERRINE 4 W 2.57 1.98 2.45 3.60 6.34 11.37 5.75 8.72 8.39 6.40 2.60 1.39 61.56

083 PERRY 4.90 3.90 5.23 3.23 3.51 5.93 8.39 8.31 5.19 3.07 2.71 3.31 57.68

084 PLANT CITY 2.73 3.05 3.39 2.20 3.58 7.35 7.51 7.71 6.62 2.36 2.12 2.55 51.17

085 POMPANO BEACH 2.78 2.76 3.00 3.40 5.73 7.31 5.94 6.91 7.01 5.73 4.24 2.46 57.27

086 PUNTA GORDA 4 ESE 2.21 2.32 2.73 1.70 3.15 8.45 7.78 7.82 6.75 3.12 1.88 1.77 49.68

087 QUINCY 3 SSW 5.63 4.37 6.00 3.68 4.80 5.59 6.68 5.49 3.65 3.31 3.52 3.62 56.34

088 ROYAL PALM RANGER STN 1.83 1.69 1.95 2.94 5.48 8.58 6.64 8.82 8.37 5.13 2.65 1.47 55.55

089 ST AUGUSTINE WFOY 3.16 2.88 3.87 2.63 3.11 5.27 4.50 5.91 6.45 4.56 2.24 2.84 47.42

090 SAINT LEO 3.41 3.38 4.06 2.35 3.89 7.13 7.69 7.47 6.54 2.75 2.52 2.65 53.84

091 ST PETERSBURG 2.76 2.87 3.29 1.92 2.80 6.09 6.72 8.26 7.59 2.64 2.04 2.60 49.58

092 SANFORD ORLANDO 2.88 2.96 3.80 2.55 3.53 6.41 7.02 7.23 5.88 3.56 2.96 2.53 51.31

093 STARKE 3.31 3.32 3.87 2.89 3.76 6.32 6.28 6.76 5.82 1.95 2.58 3.48 50.34

094 STEINHATCHEE 6 ENE 4.80 3.61 4.61 3.37 3.03 6.73 9.30 9.41 5.69 3.51 2.46 3.09 59.61

095 STUART 1 S 3.02 3.24 4.06 2.96 5.30 6.82 6.33 6.41 8.09 6.29 4.23 2.78 59.53

096 TALLAHASSEE MUNICIPAL A 5.36 4.63 6.47 3.59 4.95 6.92 8.04 7.03 5.01 3.25 3.86 4.10 63.21

097 TAMIAMI TRAIL 40 MI BEN 1.83 1.85 2.02 2.59 4.83 8.65 7.81 6.95 6.70 4.29 2.34 1.69 51.55

098 TAMPA INTL AP 2.27 2.67 2.84 1.80 2.85 5.50 6.49 7.60 6.54 2.29 1.62 2.30 44.77

099 TARPON SPRINGS SWG PLNT 3.17 3.14 3.85 1.96 3.02 5.78 7.07 8.47 7.25 3.36 2.37 2.98 52.42

100 TAVERNIER 2.47 1.93 2.14 1.99 3.73 6.90 3.23 5.20 6.72 5.40 3.08 2.03 44.82

101 TITUSVILLE 2.48 2.79 3.60 2.79 3.66 6.09 7.03 7.27 6.82 4.29 3.45 2.52 52.79

102 USHER TOWER 4.51 3.39 4.73 3.47 3.05 6.74 8.55 9.80 6.61 2.94 2.64 3.22 59.65

103 VENICE 2.68 2.16 3.37 1.91 2.20 6.72 6.68 8.12 7.38 3.14 2.08 2.33 48.77

104 VERO BEACH MUNI ARPT 2.89 2.45 4.20 2.88 3.80 6.03 6.53 6.04 6.84 5.04 3.04 2.19 51.93

105 VERO BEACH 4 W 2.72 2.92 3.84 2.55 4.39 6.96 6.36 6.93 7.20 5.60 3.83 2.28 55.58

106 WAUCHULA 2.30 2.63 3.27 2.37 3.83 7.92 7.85 7.37 6.17 2.68 2.05 2.00 50.44

107 WEEKI WACHEE 3.74 3.09 4.10 2.44 2.74 5.99 8.43 7.54 6.55 2.23 2.22 2.49 51.56

108 WEST PALM BEACH INTL AP 3.75 2.55 3.68 3.57 5.39 7.58 5.97 6.65 8.10 5.46 5.55 3.14 61.39

109 WEWAHITCHKA 5.55 4.59 5.97 3.43 3.69 6.45 9.19 8.03 6.08 3.28 3.51 3.89 63.66

110 WHITING FIELD NAS 5.73 5.02 6.74 4.20 5.67 7.18 8.11 6.08 5.64 3.67 5.06 4.22 67.32

111 WINTER HAVEN 2.39 2.57 3.36 2.21 3.68 6.91 8.12 7.52 6.16 2.64 2.43 2.23 50.22 PRECIPITATION NORMALS (Total in Inches)

No. Station Name JAN FEB MAR APR MAY JUN JUL AU G SEP OCT NOV DEC ANNUAL

# FDEP \ STORMWATER TREATMENT REPORT 

# A.2 Geographical Coordinates and Mean Annual Rainfall for Florida

Meteorological Monitoring Sites fo r Available Period of Record

# ID STATION Latitude Longitude Rainfall

( inches )

80211 APALACHICOLA AP 29.73 85.02 56.51

80228 ARCADIA 27.22 81.87 49.34

80236 ARCHBOLD BIO STATION 27.18 81.35 50.60

80369 AVON PARK 2 W 27.60 81.53 49.09

80390 BABSON PARK 1 ENE 27.85 81.52 48.35

80478 BARTOW 27.90 81.85 50.58

80611 BELLE GLADE EXP STN 26.65 80.63 51.56

80758 BITHLO 28.55 81.12 49.28

80945 BRADENTON 5 ESE 27.45 82.48 54.12

81046 BROOKSVILLE CHIN HILL 28.62 82.37 52.57

81163 BUSHNELL 2 E 28.67 82.08 49.20

81276 CANAL POINT USDA 26.87 80.63 52.10

81544 CHIPLEY 3 E 30.78 85.48 58.24

81641 CLERMONT 7 S 28.45 81.75 49.74

81654 CLEWISTON US ENGINEERS 26.75 80.92 45.40

81978 CRESCENT CITY 29.43 81.50 49.79

81986 CRESTVIEW BOB SIKES AP 30.78 86.52 63.94

82008 CROSS CITY 2 WNW 29.65 83.17 58.49

82158 DAYTONA BEACH INTL AP 29.18 81.05 49.29

82220 DE FUNIAK SPRINGS 30.73 86.07 65.52

82229 DELAND 1 SSE 29.02 81.32 57.03

82288 DESOTO CITY 8 SW 27.37 81.52 49.01

82298 DEVILS GARDEN 26.60 81.13 52.67

82850 EVERGLADES 25.85 81.38 52.10

82915 FEDERAL POINT 29.75 81.53 50.54

82944 FERNANDINA BEACH 30.67 81.47 50.39

83020 FLAMINGO RANGER STN 25.15 80.92 47.46

83137 FORT DRUM 5 NW 27.58 80.85 52.83

83153 FORT GREEN 12 WSW 27.57 82.13 51.96

83163 FORT LAUDERDALE 26.10 80.20 64.19

83186 FORT MYERS (PAGE AP) 26.58 81.87 54.19

83207 FORT PIERCE 27.47 80.35 53.50

83230 FOUNTAIN 3 SSE 30.43 85.42 64.02

83321 GAINESVILLE 3 WSW 29.63 82.37 49.45

83322 GAINESVILLE 11 WNW 29.68 82.50 49.56

83326 GAINESVILLE RGNL AP 29.70 82.28 48.36

83470 GLEN ST MARY 1 W 30.27 82.18 52.94

83874 HASTINGS ARC 29.72 81.50 51.99

83909 HIALEAH 25.83 80.28 66.04

83956 HIGH SPRINGS 29.83 82.60 54.15

83986 HILLSBOROUGH RVR ST PK 28.15 82.23 54.56

84091 HOMESTEAD EXP STN 25.50 80.50 58.19

84210 IMMOKALEE 3 NNW 26.47 81.43 50.07

84289 INVERNESS 3 SE 28.80 82.32 51.77

893832 JACKSONVILLE CECIL NAS 30.22 81.88 51.88

84358 JACKSONVILLE INTL AP 30.50 81.70 52.34

893837 JACKSONVILLE NAS 30.23 81.67 48.96

84366 JACKSONVILLE BEACH 30.28 81.40 50.92

84394 JASPER 30.52 82.95 52.24

84570 KEY WEST INTL AP 24.55 81.75 38.94

812850 KEY WEST NAS 24.58 81.68 42.73

84625 KISSIMMEE 2 28.28 81.42 48.01

84662 LA BELLE 26.75 81.43 51.88

84707 LAKE ALFRED EXP STN 28.10 81.72 50.29

# ID STATION Latitude Longitude Rainfall

( inches )

84731 LAKE CITY 2 E 30.18 82.60 53.60

84797 LAKELAND 28.02 81.92 49.13

85076 LISBON 28.87 81.78 48.63

85099 LIVE OAK 30.28 82.97 52.83

85182 LOXAHATCHEE 26.68 80.27 58.44

85275 MADISON 30.45 83.42 53.18

803853 MAYPORT PILOT STN 30.40 81.42 41.02

85539 MAYO 30.05 83.17 54.87

85612 MELBOURNE WFO 28.10 80.65 48.29

85658 MIAMI BEACH 25.78 80.13 46.60

85663 MIAMI INTL AP 25.82 80.30 58.53

85793 MILTON EXPERIMENT STN 30.78 87.13 69.48

85879 MONTICELLO 3 W 30.53 83.92 58.31

85895 MOORE HAVEN LOCK 1 26.83 81.08 46.44

85973 MOUNTAIN LAKE 27.93 81.60 47.70

86065 MYAKKA RIVER STATE PARK 27.23 82.32 58.91

86078 NAPLES 26.17 81.78 51.90

86240 NICEVILLE 30.53 86.50 69.20

86406 OASIS RANGER STN 25.85 81.03 58.82

86414 OCALA 29.20 82.08 49.68

86485 OKEECHOBEE 27.20 80.83 45.66

86628 ORLANDO INTL AP 28.43 81.33 48.35

86753 PALATKA 29.65 81.67 50.42

86842 PANAMA CITY 5 NE 30.22 85.60 64.76

86880 PARRISH 27.62 82.35 52.09

803855 PENSACOLA SHERMAN NAS 30.35 87.32 63.11

86997 PENSACOLA RGNL AP 30.48 87.18 64.28

87020 PERRINE 4 W 25.58 80.43 61.56

87025 PERRY 30.10 83.57 57.68

87205 PLANT CITY 28.02 82.13 51.17

87254 POMPANO BEACH 26.23 80.15 57.27

87397 PUNTA GORDA 4 ESE 26.92 82.00 49.68

87429 QUINCY 3 SSW 30.60 84.55 56.34

87760 ROYAL PALM RANGER STN 25.38 80.60 55.55

87826 ST AUGUSTINE WFOY 29.92 81.32 47.42

87851 SAINT LEO 28.33 82.27 53.84

87886 ST PETERSBURG 27.77 82.63 49.58

87982 SANFORD ORLANDO 28.80 81.27 51.31

88527 STARKE 29.93 82.10 50.34

88565 STEINHATCHEE 6 ENE 29.72 83.30 59.61

88620 STUART 1 S 27.18 80.23 59.53

88758 TALLAHASSEE MUNICIPAL A #N/A #N/A 63.21

88780 TAMIAMI TRAIL 40 MI BEN #N/A #N/A 51.55

88788 TAMPA INTL AP 27.97 82.53 44.77

88824 TARPON SPRINGS SWG PLNT 28.15 82.75 52.42

88841 TAVERNIER 25.00 80.52 44.82

88942 TITUSVILLE 28.63 80.83 52.79

89120 USHER TOWER 29.42 82.82 59.65

89176 VENICE 27.10 82.43 48.77

89214 VERO BEACH MUNI ARPT 27.65 80.42 51.93

89219 VERO BEACH 4 W 27.68 80.43 55.58

89401 WAUCHULA 27.55 81.80 50.44

89430 WEEKI WACHEE 28.52 82.58 51.56

89525 WEST PALM BEACH INTL AP 26.68 80.10 61.39

# ID STATION Latitude Longitude Rainfall

( inches )

89566 WEWAHITCHKA 30.12 85.20 63.66

893841 WHITING FIELD NAS 30.72 87.02 67.32

89707 WINTER HAVEN 28.02 81.73 50.22

90140 ALBANY 3 SE 31.53 84.13 53.40

90211 ALMA BACON COUNTY AP 31.53 82.50 49.13

90441 ATKINSON 2 W 31.23 81.87 52.72

90586 BAINBRIDGE INTL PAPER C #N/A #N/A 55.47

90979 BLAKELY 31.37 84.95 54.52

91340 BRUNSWICK 31.17 81.50 49.42

91345 BRUNSWICK MCKINNON AP 31.15 81.38 48.27

91463 CAIRO 2 N 30.90 84.22 49.61

91500 CAMILLA 3 SE 31.18 84.20 52.88

92153 COLQUITT 2 W 31.17 84.77 53.19

92736 DONALSONVILLE 1 S 31.02 84.88 54.73

92783 DOUGLAS 31.52 82.85 52.03

93325 FARGO 17 NE 30.83 82.37 45.07

93460 FOLKSTON 3 SW 30.80 82.02 50.08

93465 FOLKSTON 9 SW 30.73 82.13 52.56

94429 HOMERVILLE 5 N 31.08 82.80 52.84

94676 JESUP 8 S 31.50 81.87 48.70

96087 MOULTRIE 2 ESE 31.17 83.75 50.93

96219 NAHUNTA 3 E 31.22 81.93 51.80

96244 NASHVILLE 4 N 31.25 83.22 44.84

96838 PATTERSON 31.38 82.13 48.89

97276 QUITMAN 2 NW 30.80 83.58 53.06

97808 SAPELO ISLAND 31.40 81.28 51.84

98666 THOMASVILLE 3 NE 30.88 83.93 54.07

98703 TIFTON EXP STA 31.50 83.53 46.99

99186 WAYCROSS 4 NE 31.25 82.32 50.44

99192 WAYCROSS WSMO 31.25 82.40 47.31

161157 BOOTHVILLE 29.35 89.40 59.95

161292 BURAS 29.33 89.52 59.83

10252 ANDALUSIA 3 W 31.30 86.52 61.89

10402 ATMORE STATE NURSERY 31.17 87.43 64.52

10583 BAY MINETTE 30.88 87.78 67.64

11080 BREWTON 3 ENE 31.13 87.05 68.62

11084 BREWTON 3 SSE 31.05 87.05 66.12

11566 CHATOM 31.47 88.25 63.92

11803 CODEN 30.38 88.23 64.14

12172 DAUPHIN ISLAND #2 30.25 88.08 64.25

12577 ELBA 31.42 86.07 59.37

12675 ENTERPRISE 5 NNW 31.38 85.90 56.88

12758 EVERGREEN 31.45 86.95 64.07

12813 FAIRHOPE 2 NE 30.55 87.88 67.71

13105 FRISCO CITY 3 SSW 31.38 87.42 60.78

13251 GENEVA NO 2 31.05 85.88 58.98

13761 HEADLAND 31.35 85.33 56.61

84394 JASPER 30.52 82.95 52.24

14431 KINSTON 31.23 86.18 60.14

15478 MOBILE RGNL AP 30.68 88.25 66.29

16988 ROBERTSDALE 5 NE 30.63 87.65 67.92

18637 WALLACE 2 E 31.22 87.18 65.71

# FDEP \ STORMWATER TREATMENT REPORT 

# A.3 Expanded Views of Rain fall Isopleths by Region	
		
		



#  

	

  	  
		
		
												
	

			 	
	

		
		





	



			
		

	

			



	
	

# 


 

# 		


		
 
	
		

	


			







	

			


    

	




# FDEP \ STORMWATER TREATMENT REPORT 

# A.4 Frequency Distribution of Rain Even ts in Selected Me teorological RegionsRainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 57.67 0.035 1.0 62.2 2.02 2.02 3.240.11-0.20 15.36 0.152 2.0 68.5 2.34 4.36 7.010.21-0.30 8.24 0.250 2.6 62.6 2.06 6.42 10.320.31-0.40 5.61 0.354 3.9 74.2 1.98 8.40 13.510.41-0.50 4.97 0.453 4.2 81.2 2.25 10.65 17.130.51-1.00 15.42 0.711 5.4 71.5 10.96 21.61 34.761.01-1.50 8.06 1.219 8.2 66.1 9.82 31.43 50.561.51-2.00 4.18 1.720 11.2 66.8 7.19 38.63 62.132.01-2.50 2.45 2.215 13.3 59.3 5.44 44.07 70.882.51-3.00 1.36 2.745 14.2 56.0 3.74 47.81 76.903.01-3.50 0.73 3.192 17.2 75.0 2.32 50.13 80.633.51-4.00 0.42 3.757 19.4 61.1 1.59 51.72 83.204.01-4.50 0.55 4.216 18.1 82.5 2.30 54.02 86.894.51-5.00 0.27 4.682 17.8 36.4 1.28 55.30 88.955.01-5.50 0.18 5.308 22.2 66.0 0.97 56.27 90.505.51-6.00 0.15 5.736 25.8 43.8 0.87 57.14 91.906.01-6.50 0.03 6.450 57.0 18.0 0.20 57.33 92.216.51-7.00 0.12 6.745 34.0 109.5 0.82 58.15 93.537.01-7.50 0.15 7.332 22.6 51.2 1.11 59.26 95.327.51-8.00 0.06 7.765 32.5 64.5 0.47 59.73 96.078.01-8.50 0.03 8.450 43.0 6.0 0.26 59.99 96.488.51-9.00 0.03 8.710 52.0 64.0 0.26 60.25 96.91>9.00 0.18 10.572 35.3 76.3 1.92 62.17 100.00126.24 62.17Missing Years:PENSACOLA REGIONL AP (6997)from 1942 to 2005 (n=33)(minimum number of months per year at site =9)1963, 1969, 1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983,Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 49.98 0.039 0.9 64.8 1.96 1.96 3.040.11-0.20 14.49 0.150 1.9 65.6 2.17 4.13 6.400.21-0.30 9.71 0.252 2.3 65.3 2.45 6.58 10.200.31-0.40 6.89 0.353 3.2 72.0 2.44 9.02 13.970.41-0.50 6.04 0.453 3.5 70.0 2.74 11.76 18.210.51-1.00 17.09 0.726 4.7 71.9 12.41 24.17 37.441.01-1.50 8.78 1.219 6.7 64.3 10.70 34.87 54.021.51-2.00 4.27 1.730 7.8 77.5 7.38 42.25 65.452.01-2.50 2.31 2.217 10.7 75.5 5.12 47.37 73.392.51-3.00 1.36 2.714 14.8 71.5 3.68 51.05 79.093.01-3.50 1.07 3.211 17.5 71.1 3.43 54.48 84.393.51-4.00 0.47 3.768 11.6 75.9 1.76 56.24 87.124.01-4.50 0.22 4.240 16.0 68.4 0.94 57.18 88.584.51-5.00 0.29 4.778 26.5 55.3 1.38 58.56 90.715.01-5.50 0.13 5.375 18.5 73.0 0.72 59.27 91.825.51-6.00 0.16 5.689 25.6 87.6 0.88 60.16 93.196.01-6.50 0.09 6.130 36.0 58.5 0.54 60.70 94.046.51-7.00 0.11 6.676 26.8 127.0 0.74 61.45 95.197.01-7.50 0.07 7.117 35.0 32.3 0.47 61.92 95.927.51-8.00 0.07 7.790 28.3 58.0 0.52 62.44 96.738.01-8.50 0.07 8.290 22.7 148.0 0.55 62.99 97.588.51-9.00 0.04 8.875 45.0 20.0 0.39 63.39 98.19>9.00 0.11 10.490 33.8 73.4 1.17 64.55 100.00123.80 64.55Missing Years:TALLAHASSEE MUNI AP (8758)from 1959 to 2005 (n=45)(minimum number of months per year at site =9)1961, 1987Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 42.23 0.077 0.8 73.3 3.26 3.26 6.230.11-0.20 13.55 0.178 1.6 84.6 2.41 5.67 10.850.21-0.30 9.21 0.280 3.9 81.6 2.57 8.24 15.770.31-0.40 6.26 0.380 2.5 74.5 2.38 10.63 20.330.41-0.50 4.96 0.482 3.2 90.3 2.39 13.02 24.900.51-1.00 15.60 0.745 4.3 82.2 11.63 24.64 47.151.01-1.50 6.85 1.238 6.1 79.0 8.48 33.12 63.371.51-2.00 3.83 1.750 8.0 94.4 6.70 39.82 76.192.01-2.50 1.81 2.288 9.6 86.1 4.14 43.97 84.122.51-3.00 0.83 2.743 11.1 48.9 2.28 46.25 88.483.01-3.50 0.45 3.283 17.9 62.9 1.49 47.73 91.323.51-4.00 0.26 3.736 17.4 69.3 0.99 48.72 93.214.01-4.50 0.26 4.208 10.4 56.6 1.11 49.83 95.334.51-5.00 0.08 4.648 18.8 144.8 0.35 50.18 96.005.01-5.50 0.11 5.267 27.5 72.0 0.60 50.78 97.155.51-6.00 0.02 5.800 37.0 7.0 0.11 50.89 97.356.01-6.50 0.02 6.400 33.0 13.0 0.12 51.01 97.596.51-7.00 0.06 6.867 30.0 155.0 0.39 51.40 98.337.01-7.50 0.02 7.100 23.0 386.0 0.13 51.53 98.597.51-8.00 --- --- --- --- --- 51.53 98.598.01-8.50 0.02 8.400 32.0 4.0 0.16 51.69 98.898.51-9.00 --- --- --- --- --- 51.69 98.89>9.00 0.06 10.263 30.0 116.0 0.58 52.27 100.00106.49 52.27Missing Years:BRANFORD (3543)from 1945 to 2004 (n=53)(minimum number of months per year at site =9)1947, 1950, 1951, 1973, 1998, 2001, 2002Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 54.85 0.041 0.9 68.3 2.23 2.23 4.450.11-0.20 18.52 0.152 1.8 67.0 2.82 5.05 10.090.21-0.30 10.37 0.252 2.3 62.5 2.61 7.66 15.310.31-0.40 6.79 0.353 2.8 69.2 2.40 10.06 20.100.41-0.50 5.79 0.456 3.3 70.9 2.64 12.70 25.380.51-1.00 16.39 0.716 4.2 63.7 11.74 24.44 48.851.01-1.50 7.03 1.225 5.6 64.3 8.62 33.05 66.071.51-2.00 3.24 1.725 8.1 61.3 5.59 38.64 77.252.01-2.50 1.65 2.228 9.4 52.8 3.66 42.31 84.572.51-3.00 0.82 2.702 13.5 65.7 2.22 44.53 89.013.01-3.50 0.39 3.271 9.9 37.1 1.27 45.80 91.553.51-4.00 0.31 3.721 19.7 43.1 1.14 46.94 93.824.01-4.50 0.18 4.218 17.9 66.2 0.75 47.69 95.324.51-5.00 0.06 4.703 15.3 48.8 0.30 47.99 95.935.01-5.50 0.10 5.203 25.2 61.0 0.50 48.49 96.935.51-6.00 0.10 5.767 29.0 109.2 0.56 49.05 98.056.01-6.50 0.03 6.255 59.0 7.5 0.20 49.25 98.456.51-7.00 --- --- --- --- --- 49.25 98.457.01-7.50 0.02 7.280 42.0 87.0 0.12 49.37 98.697.51-8.00 0.02 7.900 30.0 40.0 0.13 49.50 98.948.01-8.50 0.02 8.190 3.0 21.0 0.13 49.63 99.218.51-9.00 --- --- --- --- --- 49.63 99.21>9.00 0.03 12.310 66.0 73.0 0.40 50.03 100.00126.69 50.03Missing Years:ORLANDO INTL ARPT (6628)from 1942 to 2005 (n=62)(minimum number of months per year at site =9)1945, 1974Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 45.04 0.075 0.7 78.4 3.38 3.38 7.120.11-0.20 16.74 0.179 1.3 83.9 3.00 6.38 13.430.21-0.30 8.81 0.279 1.7 81.8 2.46 8.84 18.600.31-0.40 6.28 0.378 2.3 78.0 2.37 11.21 23.600.41-0.50 4.51 0.479 2.6 73.3 2.16 13.37 28.140.51-1.00 13.89 0.736 3.7 77.4 10.23 23.60 49.671.01-1.50 6.40 1.252 5.6 65.3 8.02 31.62 66.541.51-2.00 2.96 1.748 7.6 80.4 5.17 36.79 77.432.01-2.50 1.28 2.255 7.8 59.1 2.88 39.67 83.492.51-3.00 0.70 2.717 16.2 98.4 1.91 41.58 87.503.01-3.50 0.40 3.299 10.9 63.9 1.33 42.91 90.313.51-4.00 0.23 3.730 15.6 61.9 0.87 43.78 92.154.01-4.50 0.21 4.219 22.0 115.1 0.90 44.68 94.044.51-5.00 0.15 4.781 19.3 149.6 0.71 45.39 95.535.01-5.50 0.11 5.334 15.4 46.8 0.57 45.96 96.735.51-6.00 0.04 5.650 36.0 14.5 0.24 46.20 97.236.01-6.50 --- --- --- --- --- 46.20 97.236.51-7.00 0.02 6.560 26.0 12.0 0.14 46.34 97.537.01-7.50 0.09 7.260 25.8 44.8 0.62 46.96 98.837.51-8.00 --- --- --- --- --- 46.96 98.838.01-8.50 0.04 8.140 39.0 29.5 0.35 47.31 99.568.51-9.00 --- --- --- --- --- 47.31 99.56>9.00 0.02 9.890 73.0 12.0 0.21 47.52 100.00107.94 47.52Missing Years:MELBOURNE REGIONL AP (5612)from 1942 to 2005 (n=47)(minimum number of months per year at site =9)1954, 1955, 1957, 1958, 1960, 1966, 1967, 1986, 1987, 1995, 1996, 1997, 1998, 1999, 2000, 2003,Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 68.56 0.037 0.8 66.6 2.52 2.52 6.450.11-0.20 17.40 0.149 1.5 71.2 2.59 5.11 13.090.21-0.30 9.70 0.250 2.0 65.6 2.43 7.54 19.300.31-0.40 6.60 0.353 2.4 69.5 2.33 9.87 25.260.41-0.50 4.51 0.453 3.1 62.1 2.04 11.91 30.490.51-1.00 11.97 0.712 4.1 67.0 8.52 20.44 52.301.01-1.50 4.11 1.236 6.2 68.2 5.08 25.52 65.311.51-2.00 2.05 1.730 7.9 59.4 3.54 29.06 74.372.01-2.50 0.86 2.225 9.6 78.0 1.91 30.96 79.252.51-3.00 0.56 2.752 12.8 85.4 1.53 32.49 83.173.01-3.50 0.41 3.255 12.0 78.5 1.34 33.84 86.603.51-4.00 0.17 3.795 20.2 65.9 0.66 34.50 88.304.01-4.50 0.19 4.161 18.5 89.3 0.79 35.29 90.334.51-5.00 0.06 4.728 16.0 35.5 0.30 35.59 91.105.01-5.50 0.05 5.170 16.7 72.3 0.25 35.84 91.735.51-6.00 0.05 5.783 32.7 111.3 0.28 36.11 92.436.01-6.50 0.05 6.227 45.0 30.7 0.30 36.41 93.196.51-7.00 0.06 6.728 32.0 33.8 0.43 36.84 94.287.01-7.50 0.03 7.105 41.0 33.5 0.23 37.06 94.867.51-8.00 0.03 7.735 29.0 93.5 0.25 37.31 95.498.01-8.50 --- --- --- --- --- 37.31 95.498.51-9.00 0.05 8.653 32.7 26.7 0.41 37.72 96.54>9.00 0.10 14.183 35.5 12.5 1.35 39.07 100.00127.56 39.07Missing Years:KEY WEST WB CITY (4575)from 1942 to 2005 (n=63)(minimum number of months per year at site =9)1952Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 42.71 0.069 0.7 82.1 2.93 2.93 5.510.11-0.20 15.39 0.170 1.1 81.8 2.61 5.54 10.430.21-0.30 10.50 0.273 1.7 94.9 2.87 8.41 15.830.31-0.40 5.54 0.380 1.9 74.3 2.10 10.51 19.780.41-0.50 5.00 0.479 2.5 78.2 2.39 12.91 24.290.51-1.00 15.00 0.746 3.0 63.7 11.19 24.10 45.351.01-1.50 6.93 1.259 3.8 59.2 8.72 32.82 61.771.51-2.00 3.64 1.766 4.9 70.8 6.43 39.25 73.872.01-2.50 1.82 2.284 6.8 96.8 4.16 43.41 81.702.51-3.00 0.89 2.757 4.8 62.1 2.46 45.87 86.343.01-3.50 0.50 3.221 9.1 37.1 1.61 47.48 89.373.51-4.00 0.21 3.690 3.8 45.7 0.79 48.28 90.864.01-4.50 0.14 4.128 19.0 77.7 0.59 48.87 91.974.51-5.00 0.21 4.700 17.7 48.2 1.01 49.87 93.865.01-5.50 0.07 5.410 13.0 14.0 0.39 50.26 94.595.51-6.00 0.14 5.715 26.3 33.8 0.82 51.08 96.126.01-6.50 0.04 6.180 37.0 24.0 0.22 51.30 96.546.51-7.00 --- --- --- --- --- 51.30 96.547.01-7.50 --- --- --- --- --- 51.30 96.547.51-8.00 0.07 7.800 14.0 238.0 0.56 51.85 97.598.01-8.50 0.04 8.200 7.0 78.0 0.29 52.15 98.148.51-9.00 0.07 8.765 44.0 44.5 0.63 52.77 99.32>9.00 0.04 10.150 34.0 14.0 0.36 53.13 100.00108.96 53.13Missing Years:FORT MYERS PAGE FLD (3186)from 1960 to 2003 (n=28)(minimum number of months per year at site =9)1967, 1980, 1982, 1983, 1984, 1986, 1987, 1990, 1991, 1992, 1996, 1997, 1998, 1999, 2000, 2001Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 38.66 0.075 0.8 72.8 2.91 2.91 5.270.11-0.20 14.11 0.176 1.6 87.1 2.49 5.40 9.790.21-0.30 9.77 0.277 2.0 81.0 2.71 8.10 14.690.31-0.40 6.91 0.376 2.5 75.2 2.60 10.70 19.400.41-0.50 5.17 0.480 3.0 89.5 2.48 13.18 23.910.51-1.00 15.32 0.737 4.0 83.2 11.29 24.48 44.391.01-1.50 7.26 1.247 5.7 91.3 9.05 33.52 60.791.51-2.00 3.51 1.742 7.5 86.0 6.12 39.64 71.892.01-2.50 2.04 2.247 10.1 77.7 4.59 44.23 80.212.51-3.00 1.17 2.757 12.7 77.6 3.23 47.45 86.063.01-3.50 0.68 3.259 13.0 58.0 2.22 49.67 90.083.51-4.00 0.32 3.769 14.2 103.9 1.20 50.88 92.264.01-4.50 0.17 4.226 23.1 59.7 0.72 51.60 93.574.51-5.00 0.11 4.854 11.4 108.0 0.52 52.11 94.515.01-5.50 0.13 5.335 29.0 29.8 0.68 52.79 95.745.51-6.00 0.06 5.650 25.7 84.7 0.36 53.15 96.396.01-6.50 0.04 6.250 21.5 99.0 0.27 53.42 96.886.51-7.00 0.06 6.667 30.3 72.3 0.43 53.85 97.657.01-7.50 0.04 7.250 20.0 14.0 0.31 54.15 98.217.51-8.00 --- --- --- --- --- 54.15 98.218.01-8.50 0.02 8.150 49.0 9.0 0.17 54.33 98.528.51-9.00 0.04 8.825 30.0 202.5 0.38 54.70 99.20>9.00 0.04 10.320 28.5 31.5 0.44 55.14 100.00105.64 55.14Missing Years:CROSS CITY (2006)from 1942 to 2000 (n=47)(minimum number of months per year at site =9)1959, 1963, 1964, 1965, 1971, 1972, 1975, 1976, 1977, 1981, 1995, 1998Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 48.45 0.038 0.9 76.1 1.86 1.86 4.050.11-0.20 14.77 0.150 1.7 75.3 2.22 4.08 8.860.21-0.30 9.57 0.253 2.2 79.6 2.43 6.51 14.130.31-0.40 6.38 0.352 3.2 82.7 2.24 8.75 19.000.41-0.50 5.34 0.455 3.4 85.4 2.43 11.18 24.270.51-1.00 14.13 0.725 4.2 75.5 10.24 21.43 46.511.01-1.50 6.36 1.230 5.5 68.1 7.82 29.25 63.491.51-2.00 3.02 1.705 8.6 69.4 5.15 34.40 74.672.01-2.50 1.64 2.253 9.9 69.1 3.69 38.09 82.682.51-3.00 0.66 2.767 15.8 52.5 1.83 39.92 86.643.01-3.50 0.60 3.239 15.9 35.6 1.93 41.85 90.833.51-4.00 0.34 3.758 17.4 104.3 1.28 43.13 93.614.01-4.50 0.23 4.311 23.0 36.5 1.01 44.13 95.804.51-5.00 0.06 4.650 25.3 6.3 0.30 44.43 96.445.01-5.50 0.09 5.185 34.0 35.0 0.44 44.87 97.405.51-6.00 0.02 5.700 34.0 20.0 0.12 44.99 97.676.01-6.50 --- --- --- --- --- 44.99 97.676.51-7.00 --- --- --- --- --- 44.99 97.677.01-7.50 0.02 7.370 69.0 7.0 0.16 45.15 98.017.51-8.00 0.02 7.550 70.0 5.0 0.16 45.31 98.358.01-8.50 --- --- --- --- --- 45.31 98.358.51-9.00 --- --- --- --- --- 45.31 98.35>9.00 0.06 11.873 32.7 18.0 0.76 46.07 100.00111.77 46.07Missing Years:TAMPA INTL ARPT (8788)from 1949 to 2005 (n=47)(minimum number of months per year at site =9)1952, 1953, 1954, 1955, 1956, 1957, 1958, 1967, 2001, 2002Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 55.75 0.037 1.0 64.2 2.09 2.09 3.950.11-0.20 17.23 0.150 2.1 69.1 2.59 4.68 8.840.21-0.30 11.08 0.251 2.5 64.0 2.78 7.47 14.100.31-0.40 7.36 0.355 3.4 72.3 2.61 10.07 19.020.41-0.50 5.36 0.456 4.4 64.8 2.44 12.52 23.640.51-1.00 15.92 0.708 5.5 67.7 11.27 23.79 44.921.01-1.50 6.77 1.214 8.6 67.3 8.22 32.01 60.441.51-2.00 3.36 1.740 10.3 60.0 5.84 37.85 71.482.01-2.50 1.75 2.249 13.1 56.4 3.94 41.79 78.912.51-3.00 1.09 2.736 14.8 61.1 2.99 44.78 84.563.01-3.50 0.34 3.245 13.5 47.6 1.12 45.90 86.673.51-4.00 0.33 3.753 15.0 44.8 1.23 47.13 88.994.01-4.50 0.25 4.226 21.3 57.4 1.06 48.18 90.994.51-5.00 0.27 4.739 21.4 28.6 1.26 49.44 93.365.01-5.50 0.06 5.380 21.5 63.8 0.34 49.78 94.005.51-6.00 0.06 5.885 42.3 9.0 0.37 50.15 94.696.01-6.50 0.06 6.268 24.8 31.0 0.39 50.54 95.436.51-7.00 0.05 6.723 48.7 21.3 0.32 50.85 96.037.01-7.50 0.02 7.270 36.0 20.0 0.11 50.97 96.247.51-8.00 0.02 7.720 33.0 136.0 0.12 51.09 96.478.01-8.50 0.05 8.237 33.3 47.7 0.39 51.47 97.208.51-9.00 0.03 8.875 55.5 5.5 0.28 51.75 97.72>9.00 0.11 11.023 49.6 86.6 1.21 52.96 100.00127.31 52.96Missing Years:JACKSONVILLE (4371)from 1942 to 2005 (n=64)(minimum number of months per year at site =9)Rainfall EventRange(in)Number ofAnnual Eventsin RangeMeanRainfallDepth(in)MeanRainfallDuration(hr)AntecedentDry Period(days)AnnualEventVolumeCumulativeAnnual EventVolume(inches)CumulativePercent ofTotal Rainfall0.00-0.10 79.33 0.038 0.8 55.2 3.02 3.02 5.310.11-0.20 21.64 0.150 1.7 51.9 3.24 6.26 11.000.21-0.30 12.53 0.251 2.1 53.4 3.15 9.41 16.530.31-0.40 7.84 0.352 2.5 46.8 2.76 12.17 21.380.41-0.50 6.02 0.455 3.0 59.7 2.73 14.90 26.180.51-1.00 15.70 0.714 4.2 49.5 11.20 26.11 45.871.01-1.50 6.59 1.225 5.9 42.5 8.08 34.18 60.061.51-2.00 3.42 1.748 8.9 49.0 5.98 40.17 70.572.01-2.50 1.88 2.224 11.2 65.6 4.17 44.34 77.892.51-3.00 1.30 2.741 10.6 42.6 3.56 47.89 84.143.01-3.50 0.55 3.226 19.0 40.1 1.76 49.66 87.243.51-4.00 0.36 3.752 17.0 26.3 1.35 51.00 89.614.01-4.50 0.31 4.233 14.3 40.6 1.32 52.33 91.934.51-5.00 0.09 4.787 14.5 52.3 0.45 52.78 92.725.01-5.50 0.14 5.227 23.3 25.4 0.74 53.51 94.015.51-6.00 0.08 5.804 17.2 102.4 0.45 53.96 94.816.01-6.50 0.11 6.184 25.4 14.9 0.68 54.64 95.996.51-7.00 0.05 6.853 24.3 6.3 0.32 54.96 96.567.01-7.50 0.03 7.235 27.5 10.0 0.23 55.19 96.967.51-8.00 0.03 7.805 44.5 8.5 0.24 55.43 97.398.01-8.50 0.03 8.180 27.5 83.0 0.26 55.69 97.838.51-9.00 0.02 8.590 22.0 8.0 0.13 55.82 98.07>9.00 0.09 11.718 35.7 60.3 1.10 56.92 100.00158.14 56.92Missing Years:MIAMI WSO CITY (5668)from 1942 to 2005 (n=64)(minimum number of months per year at site =9)#VALUE!

# FDEP \ STORMWATER TREATMENT REPORT 

# APPENDIX B

HYDROLOGIC CHARACTERISTICS

FROM SELECTED STORMWATER LAND USE

CHARACTERIZATION STUDIES

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE B.1

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM SINGLE-FAMILY RESIDENTIAL STORMWATER

STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) PERCENT

IMPERVIOUS

(%) LAND USE DRAINAGE

SYSTEM

Pompano Beach 40.8 43.9 Single-family residential

(5.3 units/acre) Grass swales Mattraw, et al.

(1981)

Tampa - Charter

Street 42.0 14.0 Single-family residential

(2 units/acre) 12% curb-gutter, 75%

grass swales, 13% ditches

(100% sewered) U.S. EPA

(1983)

Maitland (3 basins) Not provided Not provided Single-family residential

(3 watersheds) Curb and gutter;

grassed swales German (1983)

Tampa - Kirby Street 897 19.0 68% single-family

(2.5 units/acre) Curb and gutter Lopez, et al.

(1984)

Tampa - St. Louis

Street Ditch 326 27.0 69% single-family

(2 units/acre) Curb and gutter Lopez, et al.

(1984)

Orlando Duplex 25.13 34.0 Duplex (4 units/acre) Curb and gutter Harper (1988)

Orlando - Essex Pointe 7.39 65.0 Cluster hom es 100% curb and gutter Harper (1988)

Springhill Subdivision,

Palm Beach 32.4 37.0 Single-family residential

(3 units/acre) Grass swales Greg, et al.

(1989)

Tampa - 102 nd 

# Avenue 70.0 N/A Single-family re sidential Curb and gutter Holtkamp

(1998)

Bradfordville, FL 16.8 35.0 Single-family residential Curb and gutter ERD (2000)

Key Colony,

Florida Keys 24.3 6.1 Single-family residential

with golf course Overland flow to

grassed swales ERD (2002)

Tallahassee - Woodgate

Subdivision 214 Single-family residential Curb and gutter COT and ERD

(2002)

Sarasota County 30.0 25.0 Single-family residential Grass swales ERD (2004)

Orlando - Krueger St. 52.9 37.0 Single-fa mily residential Curb and gutter;

stormsewers ERD (2004)

Orlando - Paseo Street 19.4 53. 0 Single-family residential Curb and gutter; roadside

swales ERD (2004)

Windermere 95.42 29.4 Single-family re sidential Grass swales ERD (2007)

Overall Mean Value -- 33.0 -- -- --

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE B.2

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM MULTI-FAMILY RESIDENTIAL STORMWATER

STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) PERCENT

IMPERVIOUS

(%) LAND USE DRAINAGE

SYSTEM

Orlando - Shoals

Apartments N/A 74.0 Apartments 100% grates and sewers ECFRPC

(1978)

Miami - Kings Creek

Apartments 14.7 70.7 Apartments Drainage along centerline

of roadway Miller

(1979)

Loch Lomond 26.0 65.0 High-density

(18 units/acre) 100% grates and sewers Weinburg, et al.

(1980)

Orlando - Downtown 62.5 66.4 High-density 100% curb and gutter Wanielista, et al.

(1982)

Tampa - Young

Apartments 8.7 61.0 High-density multifamily 100% curb and gutter U.S. EPA (1983)

Tallahassee - Royal

Pavilion Apartments 73.3 65.0 Apartments 100% curb and gutter COT and ERD

(2002)

Overall Mean Value -- 67.0 -- -- --

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE B.3

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM LOW-INTENSITY COMMERCIAL STORMWATER

STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) PERCENT

IMPERVIOUS

(%) LAND USE DRAINAGE

SYSTEM

Orlando Areawide

Study 1 

# -- 75.5 Parking lot, motel,

strip commercial Curb and gutter or

inlets with sewers ECFRPC (1978)

Ft. Lauderdale - Coral

Ridge Mall 20.4 98.0 Shopping center 100% inlets and

stormsewers Miller (1979)

Tampa - Norma Park 46.6 90.3 Co mmercial 21.7% curb/gutter,

72.5% ditch/swale

5.8% grass swale U.S. EPA (1983)

Orlando - International

Market Place 2.17 100 Parking lot, strip mall 100% inlets and

stormsewers Harper (1988)

DeBary 50.7 59.6 Commercial areas along

U.S. 17 41% stormsewer,

59% roadside swale Harper and Herr

(1993)

Bradfordville 8.0 90 Parking lot, rooftop

landscaping 100% inlets and

stormsewers ERD (2000)

Tallahassee - Cross

Creek Shopping Center 46.0 Mixed commercial,

office, and public areas 100% inlets and

stormsewers COT and ERD

(2002)

Sarasota County N/A N/ A Commercial area along

major highway 100% inlets and

stormsewers ERD (2004)

Florida Aquarium -

Tampa 11.25 90 Parking lot (700,000

visitors annually) Swales to inlet

drop boxes Teague, et al.

(2005)

Overall Mean Value -- 91.0 -- -- --

1. Average of studies performed on a parking lot, motel complex, and comme rcial strip development

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE B.4

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM HIGH-INTENSITY COMMERCIAL STORMWATER

STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) PERCENT

IMPERVIOUS

(%) LAND USE DRAINAGE

SYSTEM

Broward County 28.4 98.0 Regional shopping mall Overland flow to

collection system Mattraw, et al.

(1981)

Orlando - Downtown

Area 83.3 96.4 Downtown commercial/

office area, parking lots 100% curb and gutter Wanielista

(1982)

Dade County N/A 98.0 Commercial area with

heavy traffic Overland flow to roadside

swale Waller (1984)

Broward County N/A 98.0 Heavily traveled highway

with adjacent commercial

area Overland flow to roadside

swale Howie, et al.

(1986)

Overall Mean Value -- 97.5 -- -- --



# TABLE B.5

SUMMARY OF HYDROLOGIC CHARACTERISTICS FROM

LIGHT INDUSTRIAL STORMWATER STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) PERCENT

IMPERVIOUS

(%) LAND USE

Orlando Areawide Study N/A N/A Light industrial park ECFRPC (1985)

Manatee County

Southeast Area Study N/A 70 Light industrial CDM (1985)

Tallahassee N/A N/A Light industrial park COT and ERD (2002)

Winter Haven 43.9 62 Light industrial and

warehouse ERD (2007)

Overall Mean Value -- 66 -- --

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE B.6

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM HIGHWAY / TRANSPORTATION STORMWATER

STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) PERCENT

IMPERVIOUS

(%) LAND USE DRAINAGE

SYSTEM

Broward County 58.3 36.4 6-lane divided highway

plus roadside areas Curb and gutter Mattraw, et al.

(1981)

I-95 Miami (Bridge) 1.43 100 Asphalt interstate

highway, 70,000 vpd Curb and gutter; inlets

with sewers McKenzie, et al.

(1983)

Maitland Blvd. 48.9 -- Asphalt highway, 15,000

vpd Curb and gutter; inlets

with sewers Yousef, et al.

(1986)

I-4 EPCOT

Interchange -- -- Asphalt highway Curb and gutter; roadside

swale Yousef, et al.

(1986)

Winter Park I-4 1.17 100 Concrete interstate

highway, 65,000 vpd Curb and gutter; inlets

with sewers Harper (1988)

Orlando I-4 1.30 70 Concrete interstate

highway, 69,000 vpd Concrete swales;

stormsewers Harper (1988)

I-4 Maitland Interchange 4.0 100 Asphalt highway Curb and gutter; inlets

with sewers Harper (1985)

Maitland -- -- 4-lane divided connector

highway Curb and gutter; inlets

with sewers German (1983)

Bayside Bridge - Tampa 12.9 100 4-lane bridge, concrete

surface Bridge drains connected

to stormsewer Stoker (1996)

Tallahassee 1.0 90 6-lane divided asphalt

highway Curb and gutter; inlets

with sewers ERD (2000)

Orlando U.S. 441 12.0 74 6-lane asphalt highway Curb and gutter; inlets

with sewers ERD (2005) -

unpublished data

Overall Mean Value -- 76.6 -- -- --

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE B.7

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM PASTURE LAND USE STORMWATER

STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) SOIL TYPES LAND USE

St. Cloud 21.6 Poorly drained,

HSG D Pasture, cattle

(1.4 acres/cow) CH2M Hill (1977)

St. Johns River Basin 155,741 Muck, fi ne sand, peat Pasture Fall (1987)

Ash Slough 220 Felda, Myakka,

Pompano sands Pasture Hendrickson

(1987)



# TABLE B.8

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM CITRUS LAND USE STORMWATER

STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) SOIL TYPES LAND USE

Upper St. Johns River Basin 56,867 Muck, peat Citrus;

some row crops Fall (1987)

St. Johns Water Control District 27,721 Organic muck, poorly

drained Citrus;

some pasture Fall, et al.

(1987)

Armstrong Slough 10,000 Placi d, Basinger Sands;

Samsula Muck Citrus;

some pasture Hendrickson

(1987)

Upper St. Johns River Basin 27,721 Poorly drained sand Citrus;

some pasture Fall (1990)

Gator Slough

(Hendry/Collier Counties) 1,492 Sand/muck,

poorly drained Citrus Sawka and

Black (1993)

Upper St. Johns River Basin -- Poor ly drained sand Citrus Fall (1995)

Charlotte/DeSoto Counties (4 sites) 184-602 P oorly drained sand Citrus Bahk, et al.

(1997)

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE B.9

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM ROW CROP STORMWATER STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) SOIL TYPES LAND USE

Willowbrook Farms 5680 Felda, Wabasso Sands;

Canova Peat Row crop Hendrickson

(1987)

Upper St. Johns River Basin N/ A Sand/muck Row crops; some

citrus Fall (1987)

Upper St. Johns River Basin N/A Sand/muck Row crops;

some pasture Fall (1990)

Upper St. Johns River Basin N/A Sand/muck Row crops;

some dairy Fall (1995)

Manatee County (5 sites) 5 areas ranging

from 12-20 acres Sand/muck Row crops;

tomatoes Bahk, et al.

(1997)

Cockroach Bay (Ruskin, FL) 210 Sand/muck Row crops Bahk (1997)

Upper St. Johns River Basin

(3 sites) N/A Sand/muck Row crops Hendrickson

(unpublished

data)

Cockroach Bay (Ruskin, FL) 210 Sand/muck Row crops Rushton (2002)



# TABLE B.10

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM UNDEVELOPED / RANGELAND / FOREST

STORMWATER STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) PERCENT

IMPERVIOUS

(%) LAND USE

Orlando ECFRPC N/A 0 Flatwood CH2M Hill

(1977)

Miami N/A 0 Range/park Waller (1982)

Boggy Creek Study N/A 2 Range/park ECFRPC (1988)

Tallahassee - Tom Brown Park N/A 0 Park/open COT and ERD

(2002)

Sarasota/Charlotte Counties (3 s ites) N/A 0 Range/forest ERD (2004)

Overall Mean Value -- 1.5 -- --

# FDEP \ STORMWATER TREATMENT REPORT 

# TABLE B.11

SUMMARY OF HYDROLOGIC CHARACTERISTICS

FROM MINING / EXTRACTIVE STORMWATER

STUDIES IN FLORIDA

LOCATION PARAMETER

REFERENCE WATERSHED

AREA

(acres) PERCENT

IMPERVIOUS

(%) LAND USE

Boggy Creek Study N/A 23 Mixed mining

activities ECFRPC (1988)

Overall Mean Value -- 23 -- --

# FDEP \ STORMWATER TREATMENT REPORT 

# APPENDIX C

CALCULATED ANNUAL RUNOFF

COEFFICIENTS FOR THE DESIGNATED

METEOROLOGICAL ZONES AS A FUNCTION

OF CURVE NUMBER AND DCIA05101520253035404550556065707580859095100300.0060.0480.0900.1320.1750.2170.2590.3010.3430.3860.4280.4700.5120.5540.5960.6390.6810.7230.7650.8070.849350.0090.0510.0930.1350.1770.2190.2610.3030.3450.3870.4290.4710.5130.5550.5970.6390.6810.7230.7650.8070.849400.0140.0560.0980.1390.1810.2230.2650.3070.3480.3900.4320.4740.5150.5570.5990.6410.6820.7240.7660.8080.849450.0200.0620.1030.1450.1860.2280.2690.3110.3520.3940.4350.4760.5180.5590.6010.6420.6840.7250.7670.8080.849500.0290.0700.1110.1520.1930.2340.2750.3160.3570.3980.4390.4800.5210.5620.6030.6440.6850.7260.7670.8080.849550.0390.0790.1200.1610.2010.2420.2820.3230.3630.4040.4440.4850.5250.5660.6060.6470.6870.7280.7680.8090.849600.0520.0920.1320.1720.2120.2520.2910.3310.3710.4110.4510.4910.5310.5700.6100.6500.6900.7300.7700.8100.849650.0690.1080.1470.1860.2250.2640.3030.3420.3810.4200.4590.4980.5370.5760.6150.6540.6930.7320.7710.8100.849700.0920.1300.1670.2050.2430.2810.3190.3570.3950.4330.4710.5080.5460.5840.6220.6600.6980.7360.7740.8120.849750.1210.1580.1940.2300.2670.3030.3400.3760.4120.4490.4850.5220.5580.5950.6310.6670.7040.7400.7770.8130.849800.1620.1960.2300.2650.2990.3340.3680.4020.4370.4710.5060.5400.5740.6090.6430.6780.7120.7460.7810.8150.849850.2200.2520.2830.3150.3460.3780.4090.4410.4720.5030.5350.5660.5980.6290.6610.6920.7240.7550.7870.8180.849900.3120.3390.3660.3930.4190.4460.4730.5000.5270.5540.5810.6080.6340.6610.6880.7150.7420.7690.7960.8230.849950.4780.4960.5150.5330.5520.5710.5890.6080.6260.6450.6640.6820.7010.7190.7380.7570.7750.7940.8120.8310.849980.6560.6660.6760.6850.6950.7050.7140.7240.7340.7430.7530.7630.7720.7820.7920.8010.8110.8210.8300.8400.849Zone 1Mean Annual Runoff Coefficients (C Values) as a Functionof DCIA Percentage and Non-DCIA Curve Number (CN)NDCIACNPercent DCIA05101520253035404550556065707580859095100300.0020.0430.0830.1230.1640.2040.2440.2850.3250.3660.4060.4460.4870.5270.5670.6080.6480.6880.7290.7690.809350.0040.0440.0850.1250.1650.2050.2460.2860.3260.3660.4070.4470.4870.5280.5680.6080.6480.6890.7290.7690.809400.0070.0470.0870.1270.1670.2070.2480.2880.3280.3680.4080.4480.4880.5280.5690.6090.6490.6890.7290.7690.809450.0100.0500.0900.1300.1700.2100.2500.2900.3300.3700.4100.4500.4900.5300.5700.6100.6500.6900.7290.7690.809500.0150.0550.0950.1340.1740.2140.2540.2930.3330.3730.4120.4520.4920.5310.5710.6110.6510.6900.7300.7700.809550.0220.0610.1010.1400.1790.2190.2580.2980.3370.3760.4160.4550.4940.5340.5730.6130.6520.6910.7310.7700.809600.0300.0690.1080.1470.1860.2250.2640.3030.3420.3810.4200.4590.4980.5370.5760.6150.6540.6930.7310.7700.809650.0420.0800.1190.1570.1950.2340.2720.3110.3490.3870.4260.4640.5020.5410.5790.6180.6560.6940.7330.7710.809700.0570.0950.1330.1700.2080.2450.2830.3210.3580.3960.4330.4710.5090.5460.5840.6210.6590.6970.7340.7720.809750.0790.1160.1520.1890.2250.2620.2980.3350.3710.4080.4440.4810.5170.5540.5900.6270.6630.7000.7360.7730.809800.1110.1460.1810.2160.2510.2850.3200.3550.3900.4250.4600.4950.5300.5650.6000.6350.6700.7050.7400.7740.809850.1600.1920.2250.2570.2900.3220.3550.3870.4200.4520.4850.5170.5500.5820.6140.6470.6790.7120.7440.7770.809900.2420.2700.2990.3270.3550.3840.4120.4400.4690.4970.5260.5540.5820.6110.6390.6670.6960.7240.7530.7810.809950.4040.4240.4440.4640.4850.5050.5250.5460.5660.5860.6060.6270.6470.6670.6880.7080.7280.7490.7690.7890.809980.5950.6050.6160.6270.6380.6480.6590.6700.6800.6910.7020.7130.7230.7340.7450.7560.7660.7770.7880.7990.809Zone 2Mean Annual Runoff Coefficients (C Values) as a Functionof DCIA Percentage and Non-DCIA Curve Number (CN)NDCIACNPercent DCIA05101520253035404550556065707580859095100300.0080.0470.0870.1260.1650.2050.2440.2830.3230.3620.4010.4410.4800.5190.5590.5980.6370.6770.7160.7560.795350.0120.0510.0900.1290.1680.2070.2470.2860.3250.3640.4030.4420.4820.5210.5600.5990.6380.6770.7170.7560.795400.0160.0550.0940.1330.1720.2110.2500.2890.3280.3670.4060.4450.4830.5220.5610.6000.6390.6780.7170.7560.795450.0220.0610.0990.1380.1770.2150.2540.2920.3310.3700.4080.4470.4860.5240.5630.6020.6400.6790.7180.7560.795500.0290.0670.1050.1440.1820.2200.2590.2970.3350.3740.4120.4500.4880.5270.5650.6030.6420.6800.7180.7570.795550.0370.0750.1130.1510.1890.2270.2650.3020.3400.3780.4160.4540.4920.5300.5680.6050.6430.6810.7190.7570.795600.0480.0850.1230.1600.1970.2350.2720.3090.3470.3840.4210.4590.4960.5330.5710.6080.6450.6830.7200.7580.795650.0610.0980.1340.1710.2080.2440.2810.3180.3550.3910.4280.4650.5010.5380.5750.6110.6480.6850.7210.7580.795700.0780.1140.1490.1850.2210.2570.2930.3290.3650.4000.4360.4720.5080.5440.5800.6160.6510.6870.7230.7590.795750.1000.1350.1700.2040.2390.2740.3080.3430.3780.4130.4470.4820.5170.5520.5860.6210.6560.6910.7250.7600.795800.1310.1640.1970.2310.2640.2970.3300.3630.3970.4300.4630.4960.5290.5620.5960.6290.6620.6950.7280.7620.795850.1770.2080.2390.2690.3000.3310.3620.3930.4240.4550.4860.5170.5480.5790.6090.6400.6710.7020.7330.7640.795900.2520.2790.3060.3330.3600.3880.4150.4420.4690.4960.5230.5500.5780.6050.6320.6590.6860.7130.7410.7680.795950.3990.4190.4390.4580.4780.4980.5180.5380.5570.5770.5970.6170.6370.6560.6760.6960.7160.7350.7550.7750.795980.5780.5890.6000.6110.6220.6330.6430.6540.6650.6760.6870.6970.7080.7190.7300.7410.7520.7620.7730.7840.795Zone 3Mean Annual Runoff Coefficients (C Values) as a Functionof DCIA Percentage and Non-DCIA Curve Number (CN)NDCIACNPercent DCIA05101520253035404550556065707580859095100300.0040.0450.0860.1270.1680.2090.2500.2910.3320.3730.4140.4550.4960.5360.5770.6180.6590.7000.7410.7820.823350.0070.0480.0890.1290.1700.2110.2520.2930.3330.3740.4150.4560.4970.5370.5780.6190.6600.7010.7410.7820.823400.0110.0510.0920.1330.1730.2140.2540.2950.3360.3760.4170.4580.4980.5390.5790.6200.6610.7010.7420.7820.823450.0160.0560.0960.1370.1770.2170.2580.2980.3390.3790.4190.4600.5000.5400.5810.6210.6620.7020.7420.7830.823500.0220.0620.1020.1420.1820.2220.2620.3020.3420.3820.4230.4630.5030.5430.5830.6230.6630.7030.7430.7830.823550.0300.0700.1090.1490.1890.2280.2680.3080.3470.3870.4270.4660.5060.5460.5850.6250.6640.7040.7440.7830.823600.0400.0800.1190.1580.1970.2360.2750.3140.3530.3930.4320.4710.5100.5490.5880.6270.6670.7060.7450.7840.823650.0540.0920.1310.1690.2080.2460.2850.3230.3620.4000.4380.4770.5150.5540.5920.6310.6690.7080.7460.7850.823700.0710.1090.1470.1840.2220.2590.2970.3350.3720.4100.4470.4850.5220.5600.5980.6350.6730.7100.7480.7850.823750.0960.1320.1680.2050.2410.2770.3140.3500.3870.4230.4590.4960.5320.5680.6050.6410.6780.7140.7500.7870.823800.1300.1650.1990.2340.2680.3030.3380.3720.4070.4420.4760.5110.5460.5800.6150.6500.6840.7190.7540.7880.823850.1820.2140.2460.2780.3100.3420.3740.4060.4380.4700.5020.5340.5660.5990.6310.6630.6950.7270.7590.7910.823900.2660.2940.3220.3500.3780.4060.4330.4610.4890.5170.5450.5730.6000.6280.6560.6840.7120.7400.7670.7950.823950.4290.4490.4690.4880.5080.5280.5470.5670.5870.6060.6260.6460.6650.6850.7050.7250.7440.7640.7840.8030.823980.6160.6260.6360.6470.6570.6670.6780.6880.6990.7090.7190.7300.7400.7500.7610.7710.7820.7920.8020.8130.823Zone 4Mean Annual Runoff Coefficients (C Values) as a Functionof DCIA Percentage and Non-DCIA Curve Number (CN)NDCIACNPercent DCIA05101520253035404550556065707580859095100300.0080.0480.0880.1280.1680.2080.2480.2880.3280.3680.4080.4480.4880.5280.5680.6080.6480.6880.7280.7680.808350.0120.0520.0920.1320.1710.2110.2510.2910.3310.3700.4100.4500.4900.5290.5690.6090.6490.6890.7280.7680.808400.0180.0570.0970.1360.1760.2150.2550.2940.3340.3730.4130.4520.4920.5310.5710.6110.6500.6900.7290.7690.808450.0250.0640.1030.1420.1820.2210.2600.2990.3380.3770.4170.4560.4950.5340.5730.6120.6510.6910.7300.7690.808500.0340.0720.1110.1500.1890.2270.2660.3050.3430.3820.4210.4600.4980.5370.5760.6140.6530.6920.7310.7690.808550.0440.0820.1210.1590.1970.2350.2730.3120.3500.3880.4260.4640.5020.5410.5790.6170.6550.6930.7320.7700.808600.0570.0950.1320.1700.2070.2450.2820.3200.3570.3950.4330.4700.5080.5450.5830.6200.6580.6950.7330.7700.808650.0730.1100.1470.1830.2200.2570.2940.3300.3670.4040.4410.4770.5140.5510.5880.6240.6610.6980.7350.7710.808700.0930.1290.1650.2010.2360.2720.3080.3440.3790.4150.4510.4860.5220.5580.5940.6290.6650.7010.7370.7720.808750.1200.1550.1890.2230.2580.2920.3270.3610.3950.4300.4640.4980.5330.5670.6020.6360.6700.7050.7390.7740.808800.1570.1890.2220.2540.2870.3190.3520.3850.4170.4500.4820.5150.5470.5800.6130.6450.6780.7100.7430.7750.808850.2090.2390.2690.2990.3290.3590.3890.4190.4490.4790.5090.5380.5680.5980.6280.6580.6880.7180.7480.7780.808900.2920.3180.3430.3690.3950.4210.4470.4720.4980.5240.5500.5760.6020.6270.6530.6790.7050.7310.7560.7820.808950.4450.4640.4820.5000.5180.5360.5540.5720.5900.6090.6270.6450.6630.6810.6990.7170.7360.7540.7720.7900.808980.6140.6240.6330.6430.6530.6620.6720.6820.6920.7010.7110.7210.7300.7400.7500.7600.7690.7790.7890.7980.808Zone 5Mean Annual Runoff Coefficients (C Values) as a Functionof DCIA Percentage and Non-DCIA Curve Number (CN)NDCIACNPercent DCIA

# FDEP \ STORMWATER TREATMENT REPORT 

# APPENDIX D

CALCULATED PERFORMANCE EFFICIENCY

OF DRY RETENTION AS A FUNCTION OF

DCIA AND NON-DCIA CURVE NUMBER51015202530354045505560657075808590951003086.281.373.365.558.753.048.344.240.837.935.333.131.129.427.826.425.124.022.921.93581.678.771.764.558.052.547.944.040.637.735.233.031.029.327.826.425.123.922.921.94076.475.569.663.157.151.947.443.640.337.535.032.930.929.227.726.325.123.922.921.94570.771.767.261.455.951.046.843.140.037.234.832.730.829.127.626.325.023.922.921.95064.767.564.259.454.550.046.042.639.536.934.632.530.729.027.526.225.023.922.921.95558.662.860.957.052.748.745.141.839.036.534.232.330.528.927.426.124.923.922.921.96052.857.857.154.250.747.143.940.938.335.933.831.930.228.727.326.024.923.822.821.96547.352.653.051.148.345.342.539.837.435.333.331.529.928.427.125.924.823.822.821.97042.247.348.647.645.643.240.838.536.434.432.631.029.528.126.925.724.723.722.821.97537.842.243.943.742.440.738.836.935.133.431.830.429.027.826.625.524.523.622.721.98034.037.539.139.438.837.736.434.933.532.130.829.528.327.226.225.224.323.522.721.98530.833.134.334.834.734.233.432.531.430.429.428.427.426.525.724.824.123.322.621.99027.929.229.930.330.330.229.829.328.828.227.526.826.225.524.924.223.623.022.521.99525.325.625.825.926.025.925.825.625.425.224.924.624.324.023.623.323.022.622.321.99823.823.823.823.723.723.623.523.423.323.223.123.022.922.822.622.522.422.222.121.951015202530354045505560657075808590951003091.891.588.384.079.575.070.766.662.959.656.553.651.148.746.644.642.841.139.638.13588.289.186.682.878.674.370.166.262.659.356.353.551.048.746.544.642.841.139.638.14084.086.384.481.277.473.469.465.762.259.056.053.350.848.546.444.542.741.139.638.14579.682.981.979.375.972.268.565.061.758.655.753.050.648.446.344.442.741.039.538.15074.879.179.077.074.170.867.464.161.058.055.352.750.448.246.244.342.641.039.538.15570.174.975.674.271.969.166.163.060.157.354.752.350.047.946.044.242.540.939.538.16065.570.471.771.169.467.064.461.759.156.554.151.849.647.645.844.042.440.939.538.16561.065.867.567.666.464.762.560.257.855.553.351.149.147.245.543.842.340.839.438.17056.761.163.163.663.161.960.258.356.354.352.350.348.546.845.143.542.140.739.438.17552.756.658.659.359.358.657.556.054.452.751.049.347.746.144.643.241.840.539.338.18049.152.254.155.055.254.954.253.252.150.849.448.046.645.344.042.741.540.339.238.18546.148.349.750.550.850.850.549.949.248.347.346.345.244.243.142.141.040.039.138.19043.544.845.646.146.446.546.446.145.745.244.644.043.342.641.941.140.439.638.938.19541.141.541.841.942.042.142.041.941.841.641.341.140.840.440.139.739.338.938.538.19839.839.839.839.839.839.739.739.639.539.439.339.239.139.038.938.738.638.438.338.1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.25-inches of Retention for Zone 1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 151015202530354045505560657075808590951003094.094.993.491.088.185.081.878.775.572.669.767.064.562.159.857.755.753.852.150.53591.293.091.989.887.284.281.278.275.272.369.566.864.362.059.757.655.753.852.150.54088.190.590.188.386.083.380.577.674.771.969.266.664.161.859.657.655.653.852.150.54584.587.787.986.584.582.179.576.874.071.468.866.363.961.659.557.555.553.752.050.55080.884.685.284.482.880.778.375.873.370.768.365.963.661.459.357.355.553.752.050.55577.181.182.281.980.779.076.974.672.370.067.665.463.261.159.157.255.353.652.050.56073.277.579.079.178.376.975.273.271.169.066.964.762.760.758.856.955.253.551.950.56569.673.875.475.875.574.573.271.569.767.865.963.962.060.258.456.755.053.451.950.57066.169.971.772.372.371.770.869.568.066.464.763.061.359.657.956.354.853.351.850.57562.766.067.868.668.868.567.967.165.964.763.361.860.358.857.355.954.553.151.750.58059.662.263.864.765.165.164.864.263.462.561.460.359.157.856.655.354.052.851.650.58556.858.760.060.861.261.461.361.060.559.959.158.357.456.555.554.553.552.551.450.59054.555.656.457.057.357.557.557.457.256.856.455.955.454.754.153.452.751.951.250.59552.552.953.253.353.553.653.653.653.553.453.253.052.852.552.251.951.651.250.850.59851.751.751.751.751.751.751.751.651.651.551.451.351.351.251.151.050.850.750.650.551015202530354045505560657075808590951003095.396.595.994.492.590.387.985.583.180.678.275.873.671.469.267.265.363.461.660.03593.194.994.693.391.689.587.385.082.780.377.975.673.471.269.167.165.263.461.660.04090.793.093.092.090.588.686.684.482.179.977.675.473.271.169.067.065.263.361.660.04588.090.791.090.589.287.585.683.681.579.377.275.072.970.968.866.965.163.361.660.05085.088.088.888.687.686.284.582.780.778.776.674.672.670.668.666.865.063.261.660.05581.885.386.486.385.784.683.281.579.877.975.974.072.170.268.466.664.863.161.560.06078.782.383.683.983.582.781.580.178.676.975.173.471.669.868.066.364.763.061.560.06575.679.180.681.281.080.579.678.577.275.774.172.570.969.367.666.064.462.961.460.07072.775.977.578.278.378.077.476.575.574.272.971.570.168.667.165.664.262.761.360.07569.972.774.275.075.375.274.874.273.472.571.470.369.167.866.565.163.862.561.260.08067.269.570.871.772.172.172.071.671.170.469.668.767.866.765.664.563.462.261.160.08564.866.567.668.368.768.968.968.768.468.067.566.866.165.464.563.762.861.860.960.09062.763.764.465.065.365.565.665.665.565.265.064.664.263.763.162.661.961.360.660.09561.161.561.862.062.162.262.362.362.362.262.162.061.861.661.461.260.960.660.360.09860.760.760.760.860.860.860.860.860.760.760.760.660.660.560.460.360.360.260.160.0Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention for Zone 1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 1NDCIACNPercent DCIA51015202530354045505560657075808590951003096.197.397.296.394.993.491.689.787.885.883.881.879.977.976.074.272.470.668.967.33594.596.196.295.494.192.791.089.287.485.583.581.679.777.875.974.172.370.668.967.34092.594.594.894.293.291.990.388.686.985.083.281.379.577.675.874.072.370.668.967.34590.492.793.292.892.090.989.487.986.384.582.881.079.277.475.673.972.270.568.967.35088.090.691.391.290.689.788.487.085.583.982.280.578.877.175.473.772.170.468.967.35585.488.289.289.388.988.287.286.084.683.181.680.078.476.775.173.571.970.368.867.36082.785.786.987.287.086.585.784.783.582.280.879.377.876.374.873.271.770.268.867.36580.183.184.484.984.984.583.983.182.181.079.878.577.175.774.372.971.570.168.767.37077.680.381.782.482.582.481.981.380.679.778.677.576.375.173.872.571.269.968.667.37575.277.679.079.780.079.979.779.378.778.077.276.375.374.273.172.070.969.768.567.38073.074.976.176.877.277.377.377.076.676.175.574.874.073.272.371.470.469.468.467.38570.972.373.373.974.374.574.674.574.373.973.573.172.571.971.270.569.869.068.267.39069.270.070.671.171.471.671.771.771.771.571.371.170.770.470.069.569.068.567.967.39567.868.168.468.668.768.968.969.069.069.068.968.968.768.668.568.368.167.867.667.39867.767.767.767.867.867.867.867.867.867.867.867.867.767.767.667.667.567.567.467.351015202530354045505560657075808590951003096.897.898.097.596.595.394.092.590.989.387.786.084.382.781.079.377.776.174.673.13595.596.997.196.795.894.793.592.190.689.087.485.884.182.580.979.377.776.174.673.14093.995.696.095.795.094.092.891.590.188.687.185.583.982.380.779.277.676.174.673.14592.194.294.794.593.993.192.090.889.588.186.685.183.682.180.679.077.576.074.573.15090.392.593.193.192.792.091.190.088.887.586.184.783.381.880.378.977.475.974.573.15588.290.591.391.491.290.789.989.087.986.885.584.282.881.580.178.677.275.874.473.16085.988.389.389.689.689.288.687.886.985.984.783.582.381.079.778.477.075.774.473.16583.586.087.287.787.787.587.086.485.784.883.882.881.780.579.378.176.875.674.373.17081.483.785.085.585.785.685.384.884.283.582.781.880.979.978.877.776.575.474.273.17579.481.482.583.283.583.583.383.082.682.181.480.779.979.178.177.276.275.274.173.18077.479.180.180.881.181.281.281.080.880.479.979.478.878.177.376.575.774.974.073.18575.776.977.778.378.678.878.978.978.778.578.277.877.476.976.375.875.174.573.873.19074.274.975.475.976.276.476.576.576.576.476.376.175.875.575.274.874.474.073.673.19573.173.373.673.873.974.074.174.274.274.274.274.274.174.073.973.873.673.573.373.19873.173.173.273.273.373.373.373.373.373.373.373.373.373.373.373.273.273.273.173.1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.50-inches of Retention for Zone 1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.25-inches of Retention for Zone 151015202530354045505560657075808590951003097.398.198.498.297.696.695.694.493.291.890.489.087.686.184.783.381.880.479.077.63596.197.497.797.697.096.195.194.092.891.590.288.887.486.084.683.281.880.479.077.64094.996.496.896.796.295.594.593.592.491.189.988.587.285.884.483.181.780.378.977.64593.595.395.895.795.394.693.892.991.890.689.588.286.985.684.282.981.680.278.977.65092.093.994.594.594.293.793.092.191.290.189.087.886.685.384.082.881.580.278.977.65590.392.393.093.192.992.592.091.290.489.488.487.386.185.083.882.681.380.178.877.66088.490.591.391.591.591.290.890.189.488.687.786.785.684.583.482.381.180.078.877.66586.488.489.489.889.989.789.488.988.387.686.886.085.084.083.082.080.979.878.777.67084.486.487.488.088.188.187.987.587.086.485.885.184.383.482.581.680.679.678.677.67582.684.485.486.086.286.386.285.985.685.184.684.083.482.781.981.180.379.478.577.68081.082.483.383.984.284.384.384.284.083.783.382.882.481.881.280.679.979.178.477.68579.480.581.281.782.082.282.382.382.282.081.881.581.280.880.479.979.378.878.277.69078.178.879.379.679.980.180.280.380.380.280.180.079.879.679.379.078.778.478.077.69577.377.577.877.978.178.278.378.378.478.478.478.478.478.378.278.178.077.977.777.69877.477.577.577.677.677.777.777.777.777.777.777.777.777.777.777.777.777.677.677.651015202530354045505560657075808590951003097.998.598.698.698.397.696.795.894.893.792.591.390.088.887.586.285.083.782.481.23596.797.898.198.197.897.196.395.494.493.492.291.189.988.787.486.284.983.782.481.24095.697.097.597.497.196.695.894.994.093.091.990.889.788.587.386.084.883.682.481.24594.596.196.696.696.395.895.294.493.592.691.690.589.488.387.185.984.783.682.481.25093.395.095.595.695.494.994.493.793.092.191.190.189.188.086.985.884.683.582.381.25591.993.794.394.494.293.993.592.992.291.490.689.688.787.786.685.684.583.482.381.26090.492.192.893.093.092.892.491.991.390.689.989.188.287.386.385.384.383.382.281.26588.790.491.291.591.691.591.290.890.389.889.188.487.686.885.985.084.183.182.281.27087.088.689.489.990.190.189.989.689.288.788.287.686.986.285.484.683.883.082.181.27585.386.887.788.288.488.588.488.287.987.687.186.786.185.584.984.283.582.882.081.28083.885.185.886.386.786.886.886.786.586.386.085.685.284.784.283.783.182.581.981.28582.583.484.084.584.885.085.085.084.984.884.684.484.183.883.483.182.682.281.781.29081.481.982.482.782.983.183.283.383.383.383.283.182.982.882.682.382.181.881.581.29580.780.981.181.281.481.581.681.681.781.781.781.781.781.781.681.681.581.481.381.29880.980.981.081.081.181.181.181.281.281.281.281.281.281.281.281.281.281.281.281.2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.75-inches of Retention for Zone 1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.00-inches of Retention for Zone 151015202530354045505560657075808590951003098.498.898.998.998.798.297.696.895.995.094.093.091.990.889.788.687.586.385.284.13597.298.198.498.598.397.997.296.595.694.793.892.891.890.789.688.587.486.385.284.14096.297.497.897.997.897.396.896.195.394.493.592.691.690.589.588.487.386.285.184.14595.396.797.297.397.196.796.295.594.894.093.292.391.390.389.388.387.286.285.184.15094.395.896.396.596.395.995.594.994.393.692.891.991.090.189.188.187.186.185.184.15593.294.895.395.495.395.094.694.293.693.092.391.590.689.888.987.987.086.085.084.16092.093.594.194.394.294.093.793.392.892.391.690.990.289.488.687.786.885.985.084.16590.692.092.792.993.092.992.792.492.091.590.990.389.789.088.287.486.685.884.984.17089.190.491.191.591.691.691.591.391.090.590.189.689.088.487.887.186.485.684.884.17587.688.889.590.090.290.390.290.189.889.589.288.888.387.887.386.786.185.484.784.18086.287.287.988.488.688.888.888.788.688.488.187.887.587.186.786.285.785.284.684.18585.085.886.486.887.087.287.387.387.287.186.986.886.586.386.085.685.384.984.584.19084.084.584.985.285.485.685.785.785.785.785.785.685.585.485.285.084.884.684.384.19583.483.683.884.084.184.284.384.384.484.484.484.484.484.484.484.384.384.284.184.19883.783.783.883.883.983.983.984.084.084.084.084.084.084.184.184.184.184.184.184.151015202530354045505560657075808590951003098.799.199.199.199.098.798.297.696.896.195.294.393.492.591.590.589.588.587.486.43597.798.498.698.798.698.497.997.396.695.895.094.293.392.391.490.489.488.487.486.44096.797.898.298.398.298.097.596.996.395.594.893.993.192.291.390.389.388.487.486.44595.997.297.697.897.797.497.096.495.895.294.493.792.892.091.190.289.388.387.486.45095.196.597.097.197.096.796.395.995.394.794.193.392.691.790.990.089.288.287.386.45594.395.696.196.396.295.995.695.294.794.293.692.992.291.590.789.989.088.287.386.46093.394.695.195.395.295.094.894.494.093.693.092.491.891.190.489.688.988.187.286.46592.293.493.994.194.194.093.893.693.292.992.491.991.390.790.089.488.787.987.286.47090.891.992.592.892.992.992.892.692.492.091.691.290.790.289.689.188.487.887.186.47589.590.591.191.591.691.791.791.691.491.190.890.490.189.689.288.788.187.687.086.48088.289.189.790.190.390.490.490.490.390.189.989.689.389.088.688.287.887.486.986.48587.187.888.388.688.989.089.189.189.089.088.888.788.588.388.087.787.487.186.886.49086.386.787.087.387.587.687.787.887.887.887.787.787.687.587.387.287.086.886.686.49585.885.986.186.286.386.486.586.686.686.686.786.786.786.786.686.686.686.586.586.49886.086.186.186.286.286.286.386.386.386.386.386.386.486.486.486.486.486.486.486.4Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention for Zone 1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.25-inches of Retention for Zone 1NDCIACNPercent DCIA51015202530354045505560657075808590951003098.999.399.399.399.299.098.698.297.596.996.295.494.693.892.992.091.190.289.388.33598.298.798.898.998.998.798.497.997.396.796.095.294.593.692.891.991.190.289.288.34097.298.198.498.598.598.498.097.697.096.495.795.094.393.592.791.891.090.189.288.34596.497.597.998.198.197.997.697.196.696.195.494.894.193.392.591.790.990.189.288.35095.897.097.497.697.697.497.096.696.295.695.194.593.893.192.491.690.890.089.288.35595.196.396.896.996.996.796.496.095.695.194.694.193.592.892.191.490.789.989.188.36094.495.595.996.196.095.995.795.395.094.694.193.693.192.591.991.290.589.889.188.36593.494.594.995.195.195.094.894.694.393.993.693.192.692.191.590.990.389.789.088.37092.393.293.793.994.094.093.993.793.593.292.992.592.191.791.290.790.189.588.988.37591.091.992.492.792.992.992.992.892.692.492.291.991.591.190.790.389.989.488.988.38089.990.691.191.591.791.891.891.891.791.591.391.190.990.690.389.989.689.288.888.38588.989.589.990.290.490.590.690.690.690.590.490.390.189.989.789.589.289.088.788.39088.188.588.889.089.289.389.489.489.589.589.489.489.389.289.189.088.988.788.588.39587.787.888.088.188.288.388.488.488.588.588.588.588.588.588.588.588.588.488.488.39887.988.088.088.188.188.188.288.288.288.288.388.388.388.388.388.388.388.388.388.351015202530354045505560657075808590951003099.199.499.599.499.399.299.098.698.197.596.996.295.594.894.193.392.491.690.889.93598.699.099.199.199.199.098.798.497.997.396.796.195.494.794.093.292.491.690.889.94097.798.498.698.798.798.798.598.197.697.196.595.995.294.693.893.192.391.590.889.94596.997.898.298.498.498.398.197.797.396.896.295.795.094.493.793.092.291.590.789.95096.397.397.898.098.097.997.697.296.996.495.995.494.894.293.592.992.291.490.789.95595.796.897.397.497.497.397.096.796.496.095.595.094.593.993.392.792.091.490.789.96095.296.296.696.896.796.696.496.195.895.495.094.694.193.693.192.591.991.390.689.96594.595.395.895.995.995.895.795.495.294.994.594.193.793.392.892.391.791.190.689.97093.594.394.794.995.094.994.894.794.594.293.993.693.392.992.492.091.591.090.589.97592.493.293.693.893.993.993.993.893.793.593.393.092.792.492.191.791.390.990.489.98091.392.092.492.692.892.992.992.992.892.792.692.492.191.991.691.391.090.790.389.98590.490.991.391.591.791.891.991.991.991.891.791.691.591.391.190.990.790.590.289.99089.790.090.390.590.690.890.890.990.990.990.990.890.890.790.690.590.490.290.189.99589.389.489.689.789.889.889.990.090.090.090.190.190.190.190.190.190.090.090.089.99889.689.689.689.789.789.789.889.889.889.889.989.989.989.989.989.989.989.989.989.9NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.00-inches of Retention for Zone 1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.75-inches of Retention for Zone 151015202530354045505560657075808590951003099.399.599.699.599.599.499.298.998.598.197.596.996.395.795.094.393.692.892.191.33598.899.299.399.299.299.199.098.798.397.997.396.896.295.694.994.293.592.892.091.34098.298.798.898.998.998.998.798.598.197.797.296.696.095.494.894.193.592.792.091.34597.498.198.598.698.698.698.498.297.897.496.996.495.895.394.794.093.492.792.091.35096.797.798.198.298.398.298.197.897.497.096.696.195.695.194.593.993.392.692.091.35596.297.297.697.897.997.897.697.397.096.696.295.895.394.894.393.893.292.691.991.36095.896.797.197.397.397.297.096.896.596.295.895.495.094.694.193.693.092.591.991.36595.396.196.596.696.696.596.396.295.995.695.395.094.694.293.893.492.992.491.891.37094.595.395.695.795.795.795.695.595.395.194.894.594.293.993.593.192.792.291.891.37593.694.294.594.794.894.894.894.794.694.494.294.093.893.593.292.892.592.191.791.38092.693.193.593.793.893.993.993.993.893.793.693.493.293.092.892.592.291.991.691.38591.792.192.492.692.892.993.093.093.092.992.992.892.692.592.392.292.091.891.591.39091.091.391.691.791.992.092.092.192.192.192.192.192.091.991.991.891.791.691.491.39590.790.891.091.091.191.291.291.391.391.491.491.491.491.491.491.491.491.491.391.39890.991.091.091.091.191.191.191.191.291.291.291.291.291.291.391.391.391.391.391.351015202530354045505560657075808590951003099.499.699.699.699.699.599.499.298.898.498.097.597.096.495.895.294.593.893.192.43599.099.399.499.499.499.399.299.098.798.397.997.496.896.395.795.194.593.893.192.44098.598.999.199.199.199.198.998.898.598.197.797.296.796.295.695.094.493.893.192.44597.898.498.798.898.898.898.798.598.297.997.497.096.596.095.594.994.393.793.192.45097.298.098.398.598.598.598.498.297.997.597.296.896.395.895.394.894.293.793.192.45596.797.597.998.198.298.198.097.897.597.296.896.596.095.695.194.794.193.693.092.46096.397.197.597.797.797.797.597.397.196.896.596.195.795.394.994.594.093.593.092.46595.996.697.097.297.297.196.996.896.696.396.095.795.495.194.794.393.993.492.992.47095.496.096.396.496.496.496.396.196.095.895.595.395.094.794.494.193.793.392.992.47594.695.195.495.595.695.695.595.495.395.295.094.894.694.494.193.893.593.292.892.48093.794.194.494.694.794.794.794.794.694.594.494.394.193.993.793.593.393.092.792.48592.993.293.593.693.893.893.993.993.993.893.893.793.693.593.493.293.092.892.692.49092.292.492.692.892.993.093.193.193.193.193.193.193.193.092.992.892.892.792.592.49591.992.092.192.292.392.392.492.492.592.592.592.592.592.592.592.592.592.592.592.49892.192.192.292.292.292.292.392.392.392.392.392.492.492.492.492.492.492.492.492.4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.25-inches of Retention for Zone 1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.50-inches of Retention for Zone 151015202530354045505560657075808590951003099.699.799.799.799.799.699.599.499.198.898.498.097.597.096.495.995.394.794.193.43599.299.499.599.599.599.499.399.299.098.698.397.897.496.996.495.895.294.694.093.44098.899.199.299.399.299.299.199.098.898.598.197.797.296.896.395.795.294.694.093.44598.298.798.999.099.099.098.998.898.698.397.997.597.196.696.195.695.194.694.093.45097.698.298.598.798.798.798.698.598.398.097.797.396.996.596.095.595.094.594.093.45597.197.998.298.498.498.498.398.297.997.797.497.096.696.395.895.494.994.593.993.46096.797.597.898.098.198.198.097.897.597.397.096.796.496.095.695.294.894.493.993.46596.497.197.497.697.697.697.497.397.196.996.696.496.195.795.495.194.794.393.993.47096.096.696.997.097.097.096.996.796.696.496.296.095.795.495.294.994.594.293.893.47595.595.996.196.296.396.396.296.196.095.995.795.595.395.194.994.694.494.193.793.48094.795.095.295.495.595.595.595.495.495.395.295.094.994.794.694.494.293.993.793.48593.894.194.494.594.694.794.794.794.794.794.694.594.494.394.294.193.993.893.693.49093.293.493.693.793.893.993.994.094.094.094.094.093.993.993.893.893.793.693.593.49592.993.093.193.293.293.393.393.493.493.493.593.593.593.593.593.593.593.593.493.49893.193.193.293.293.293.293.393.393.393.393.393.393.493.493.493.493.493.493.493.451015202530354045505560657075808590951003099.699.799.899.899.799.799.699.599.399.098.798.397.997.597.096.595.995.494.894.33599.399.599.699.699.699.599.599.399.298.998.698.297.897.496.996.495.995.494.894.34099.099.399.499.499.499.399.399.299.098.898.598.197.797.396.896.395.895.394.894.34598.598.999.199.199.199.199.199.098.898.698.397.997.697.296.796.395.895.394.894.35098.098.598.798.998.998.998.898.798.698.398.197.797.497.096.696.295.795.294.894.35597.598.198.498.698.698.698.698.598.398.197.897.597.196.896.496.095.695.294.794.36097.197.898.198.398.398.398.398.198.097.797.597.296.996.696.395.995.595.194.794.36596.897.497.897.998.098.097.997.797.597.397.196.996.696.396.095.795.495.094.794.37096.597.197.397.597.597.597.497.297.196.996.796.596.396.195.895.595.294.994.694.37596.196.596.796.896.896.896.896.796.696.496.396.196.095.895.595.395.194.894.594.38095.595.895.996.196.196.196.196.196.095.995.895.795.695.495.395.194.994.794.594.38594.795.095.195.395.395.495.495.495.495.495.395.295.195.094.994.894.794.694.494.39094.194.394.494.594.694.794.794.894.894.894.894.794.794.794.694.694.594.494.394.39593.893.994.094.094.194.194.294.294.294.394.394.394.394.394.394.394.394.394.394.39894.094.094.094.094.194.194.194.194.194.294.294.294.294.294.294.294.294.294.294.3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.75-inches of Retention for Zone 1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 4.00-inches of Retention for Zone 151015202530354045505560657075808590951003094.490.483.075.168.061.956.652.148.344.942.039.437.235.133.331.730.228.827.626.43591.888.882.074.567.661.556.451.948.144.841.939.437.135.133.331.730.228.827.626.44088.286.680.673.566.961.156.051.747.944.741.839.337.135.033.231.630.228.827.626.44583.983.878.772.366.160.455.651.447.744.541.739.237.035.033.231.630.128.827.626.45078.880.476.470.764.959.655.050.947.344.241.539.036.834.933.131.530.128.827.626.45573.276.473.668.763.558.654.250.346.943.941.238.836.734.833.031.530.128.727.526.46067.471.870.266.361.757.353.249.646.343.440.838.636.534.632.931.430.028.727.526.46561.466.766.363.459.555.651.948.645.542.940.438.236.234.432.831.329.928.727.526.47055.761.161.859.856.853.550.447.344.642.139.837.735.934.132.631.129.828.627.526.47550.155.256.555.653.550.948.345.743.341.139.037.135.433.832.330.929.728.527.426.48045.049.150.750.649.447.645.643.641.639.737.936.234.733.231.930.729.528.427.426.48540.343.244.544.844.343.442.140.739.237.836.335.033.732.531.330.229.228.227.326.49036.037.538.338.638.538.137.536.735.935.034.033.132.231.330.429.528.727.927.226.49531.732.132.332.432.332.232.031.731.431.030.630.229.729.328.828.327.927.426.926.49829.329.329.229.129.028.928.828.628.528.328.228.027.827.727.527.327.126.926.626.451015202530354045505560657075808590951003097.096.794.891.787.983.879.775.771.968.465.262.159.456.954.552.350.348.446.745.13595.295.593.890.987.383.479.375.471.768.365.062.159.356.854.452.350.348.446.745.14092.994.092.589.986.582.778.975.171.468.064.961.959.256.754.452.250.248.446.745.14590.291.990.988.685.581.978.274.671.167.764.661.759.156.654.352.250.248.446.745.15086.789.288.987.084.280.977.473.970.567.364.361.558.956.554.252.150.248.346.645.15582.786.186.484.982.679.676.473.169.966.863.961.258.656.354.152.050.148.346.645.16078.582.683.482.580.678.075.172.169.166.163.460.858.356.053.951.950.048.246.645.16574.278.679.879.578.176.073.570.768.065.362.760.257.955.753.651.749.948.246.645.17069.874.275.876.075.273.571.469.166.664.261.859.557.355.353.351.449.748.146.545.17565.469.671.471.971.570.468.866.964.962.760.658.656.654.752.851.149.547.946.545.18061.464.966.667.367.266.565.564.162.560.859.057.355.553.952.250.749.247.746.445.18557.660.161.662.262.362.061.360.459.358.156.855.454.052.751.350.048.747.446.245.19054.155.456.256.756.856.756.455.955.254.553.652.851.850.949.948.947.946.946.045.19550.150.550.750.850.850.850.650.450.249.949.549.148.748.247.747.246.746.145.645.19847.847.747.747.647.647.547.447.247.146.946.846.646.546.346.145.945.745.545.345.1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.25-inches of Retention in Zone 2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.50-inches of Retention in Zone 251015202530354045505560657075808590951003097.998.297.596.294.492.189.686.984.181.378.575.973.370.968.566.364.262.260.458.63596.797.396.895.693.891.789.286.683.881.178.475.773.270.868.566.364.262.260.458.64095.096.195.994.893.191.188.786.283.580.878.275.673.170.768.466.264.262.260.458.64593.094.794.693.792.290.388.185.683.180.577.975.472.970.668.366.264.162.260.458.65090.792.893.192.491.189.387.385.082.580.077.575.172.770.468.266.164.062.160.358.65588.090.691.190.789.788.186.384.181.879.477.074.772.470.168.065.964.062.160.358.66084.887.988.888.788.086.785.083.080.978.776.574.272.069.867.865.863.862.060.358.66581.584.986.286.385.884.883.481.779.877.875.773.671.569.567.565.563.761.960.258.67078.181.783.183.583.282.581.480.078.476.674.772.870.968.967.165.263.561.860.258.67574.978.179.680.280.279.879.077.976.575.073.471.770.068.366.564.863.261.660.158.68071.674.375.876.576.776.576.075.274.173.071.770.368.867.365.864.362.861.460.058.68568.670.671.872.572.872.772.471.971.270.369.368.367.165.964.763.562.261.059.858.69065.766.967.768.168.368.368.267.967.566.966.365.664.964.063.262.361.460.559.558.69562.763.063.263.363.463.463.363.263.062.862.562.261.861.461.060.560.159.659.158.69860.860.860.860.760.760.660.560.460.360.260.159.959.859.659.559.359.259.058.858.651015202530354045505560657075808590951003098.598.898.597.996.995.694.192.390.488.486.384.282.180.077.975.974.072.270.368.63597.598.298.097.496.595.393.792.090.288.286.284.182.079.977.975.974.072.170.368.64096.497.397.296.895.994.893.391.789.987.985.983.981.879.877.875.873.972.170.368.64594.896.196.396.095.294.192.791.289.487.685.683.681.679.677.775.873.972.170.368.65093.094.895.294.994.393.392.090.588.987.185.383.381.479.577.575.673.872.070.368.65591.093.293.793.693.192.391.189.888.286.684.882.981.179.277.375.573.772.070.268.66088.891.292.092.091.791.090.088.887.485.984.282.480.778.977.175.373.671.970.268.66586.288.989.990.290.089.588.787.686.485.083.481.880.278.576.875.173.471.870.268.67083.686.487.588.088.087.686.986.185.183.882.581.079.577.976.474.873.271.670.168.67581.083.684.985.585.685.384.984.283.482.481.280.078.677.275.874.372.971.570.068.68078.680.882.082.582.882.782.481.981.380.579.678.577.476.375.073.872.571.269.968.68576.177.778.779.379.679.779.579.278.878.277.576.775.974.974.072.971.970.869.768.69073.974.875.575.976.176.276.276.075.775.374.974.473.873.272.571.871.070.369.468.69571.571.872.072.172.272.272.272.172.071.971.771.471.270.970.670.269.969.569.068.69870.270.270.270.270.170.170.170.069.969.869.769.769.669.469.369.269.068.968.868.6Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention in Zone 2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.75-inches of Retention in Zone 2NDCIACNPercent DCIA51015202530354045505560657075808590951003098.999.199.098.798.197.396.495.293.992.490.989.387.786.084.382.680.979.277.676.03598.198.698.698.397.797.096.194.993.792.390.889.287.685.984.282.580.979.277.676.04097.298.098.097.897.396.695.794.693.492.090.589.087.485.884.182.580.879.277.676.04596.197.197.397.196.796.195.294.293.091.790.388.887.285.684.082.480.779.177.676.05094.796.096.496.396.095.494.693.692.591.389.988.587.085.483.882.280.779.177.576.05593.094.895.395.395.194.693.993.091.990.889.588.186.785.283.682.180.679.077.576.06091.393.394.094.194.093.692.992.291.290.188.987.786.384.983.481.980.478.977.576.06589.491.692.492.792.692.391.891.190.389.388.387.185.884.583.181.780.378.877.476.07087.589.690.691.091.090.890.489.889.188.387.486.385.283.982.781.480.078.777.376.07585.487.488.589.089.189.088.788.387.787.086.285.384.383.382.180.979.778.577.376.08083.485.286.286.786.986.986.786.486.085.584.884.183.382.381.480.479.378.277.176.08581.682.983.784.284.484.584.484.284.083.683.182.581.981.280.479.678.877.976.976.09079.780.581.081.481.681.781.781.781.581.380.980.680.179.779.178.678.077.476.776.09577.978.278.478.578.678.778.778.678.678.478.378.278.077.877.577.377.076.776.376.09877.177.177.177.177.177.177.077.076.976.976.876.876.776.676.576.476.376.276.176.051015202530354045505560657075808590951003099.299.499.399.198.798.297.696.895.994.993.792.591.389.988.687.285.784.382.981.53598.699.099.098.898.598.097.496.695.794.793.692.491.289.888.587.185.784.382.981.54097.898.498.598.498.197.697.196.395.594.593.492.291.089.788.487.185.784.382.981.54596.997.898.097.997.697.296.796.095.194.293.192.090.889.688.387.085.684.282.981.55095.996.997.297.297.096.796.295.594.793.892.891.890.689.488.286.985.584.282.881.55594.695.996.396.496.396.095.695.094.293.492.491.490.389.288.086.785.484.182.881.56093.194.795.395.595.495.294.894.393.692.892.091.090.088.987.786.585.384.082.881.56591.793.494.194.494.494.293.993.492.892.191.390.589.588.587.486.385.183.982.781.57090.191.992.793.093.193.092.792.391.991.290.689.888.988.087.086.084.983.882.681.57588.590.291.091.591.691.691.491.190.790.289.688.988.287.486.585.684.683.682.681.58086.988.489.289.689.989.989.889.689.388.988.487.987.386.685.985.184.283.382.481.58585.486.587.287.687.988.087.987.887.687.387.086.686.185.685.084.483.783.082.381.59084.184.785.185.485.685.785.885.785.685.585.385.084.784.484.083.583.182.682.081.59582.782.983.183.283.383.383.483.483.483.383.283.183.082.882.682.482.282.081.881.59882.282.282.282.282.282.282.282.282.182.182.182.082.081.981.981.881.781.781.681.5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.50-inches of Retention in Zone 2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.25-inches of Retention in Zone 251015202530354045505560657075808590951003099.499.599.599.499.198.898.397.897.296.495.694.693.692.691.590.489.288.086.885.63598.999.299.299.198.998.698.197.697.096.395.494.593.592.591.490.389.288.086.885.64098.398.898.998.898.698.397.997.496.896.195.394.493.492.491.490.389.188.086.885.64597.598.398.498.498.297.997.597.196.595.895.094.293.292.391.290.289.187.986.885.65096.797.697.897.897.797.597.196.796.295.594.893.993.092.191.190.189.087.986.785.65595.796.897.197.297.196.996.696.295.795.194.493.692.891.990.989.988.987.886.785.66094.595.896.396.496.496.396.095.795.294.694.093.392.591.690.789.888.887.786.785.66593.394.795.395.595.695.595.395.094.594.093.492.892.191.390.489.588.687.686.685.67092.093.594.294.594.694.594.494.193.793.392.892.291.590.890.189.388.487.586.685.67590.892.192.993.293.493.493.393.192.892.492.091.590.990.389.688.988.287.386.585.68089.690.791.491.892.092.092.091.991.691.391.090.690.189.689.188.587.887.186.485.68588.489.289.890.290.490.590.590.490.390.189.889.589.288.888.487.987.486.886.285.69087.387.888.288.488.688.788.888.788.788.688.488.288.087.887.587.286.886.486.085.69586.286.486.686.786.886.886.986.986.986.886.886.786.786.686.486.386.186.085.885.69886.086.086.086.086.186.186.186.086.086.086.086.085.985.985.985.885.885.785.685.651015202530354045505560657075808590951003099.599.799.699.699.499.198.898.497.997.496.896.195.394.493.692.691.790.789.788.73599.299.499.499.499.299.098.698.297.897.396.695.995.294.493.592.691.690.789.788.74098.699.099.199.198.998.798.498.097.697.196.595.895.194.393.492.591.690.689.788.74598.098.698.898.798.698.498.197.897.496.996.395.694.994.193.392.591.590.689.688.75097.398.198.398.398.298.097.897.597.196.696.195.494.794.093.292.491.590.689.688.75596.697.497.797.897.797.697.497.196.796.395.895.294.593.893.092.291.490.589.688.76095.696.697.097.197.197.096.996.696.395.995.494.994.293.692.892.191.390.489.688.76594.595.796.296.496.596.496.396.095.795.494.994.493.993.392.691.991.190.389.588.77093.594.795.395.595.795.695.595.395.194.894.493.993.492.992.391.690.990.289.588.77592.593.694.294.594.794.794.794.594.394.093.793.392.992.491.991.390.790.189.488.78091.592.593.193.493.693.793.693.593.493.292.992.692.291.891.490.990.489.989.388.78590.691.391.892.192.392.492.492.492.392.191.991.791.491.190.890.490.089.689.288.79089.790.190.590.790.991.091.091.091.090.990.890.690.590.390.189.989.689.389.088.79588.989.189.289.389.489.589.589.589.589.589.589.489.489.389.289.289.088.988.888.79888.888.888.988.988.988.988.988.988.988.988.988.988.988.888.888.888.888.788.788.7NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.75-inches of Retention in Zone 2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.00-inches of Retention in Zone 251015202530354045505560657075808590951003099.799.799.799.799.699.499.198.898.598.197.697.096.495.895.094.393.592.791.891.03599.399.599.699.599.499.299.098.798.397.997.596.996.395.795.094.393.592.791.891.04099.099.299.399.399.299.098.898.598.297.897.396.896.295.694.994.293.492.691.891.04598.498.999.099.098.998.898.698.398.097.697.296.796.195.594.894.193.492.691.891.05097.898.598.698.798.698.598.398.097.797.497.096.595.995.494.794.093.392.591.891.05597.297.998.298.298.298.197.997.797.497.196.796.395.895.294.693.993.292.591.791.06096.597.397.697.797.797.697.597.397.096.896.496.095.595.094.493.893.192.491.791.06595.696.596.997.197.197.197.096.896.696.396.095.695.294.794.293.693.092.391.791.07094.695.696.196.396.496.496.496.396.195.895.595.294.894.493.993.492.892.291.691.07593.894.795.295.595.795.795.795.695.495.295.094.794.494.093.693.192.692.191.591.08093.093.894.394.694.894.994.994.894.794.594.394.193.893.593.192.892.491.991.491.08592.392.993.393.693.793.893.993.893.893.793.593.493.192.992.692.492.091.791.391.09091.692.092.392.592.692.792.792.792.792.792.692.592.492.292.191.991.791.591.291.09591.091.291.391.491.491.591.591.591.691.591.591.591.591.491.491.391.291.191.191.09891.091.091.091.091.191.191.191.191.191.191.191.191.191.191.091.091.091.091.091.051015202530354045505560657075808590951003099.799.899.899.899.799.699.499.198.898.598.197.797.296.796.195.594.994.293.592.73599.599.699.799.699.699.499.399.098.798.498.097.697.296.696.195.594.894.293.492.74099.299.499.599.599.499.399.198.998.698.397.997.597.196.696.095.494.894.193.492.74598.799.199.299.299.299.098.998.798.498.197.897.497.096.595.995.494.794.193.492.75098.298.898.998.998.998.898.698.498.297.997.697.296.896.495.895.394.794.193.492.75597.798.398.598.698.598.598.398.197.997.797.497.096.696.295.795.294.694.093.492.76097.197.898.098.198.198.197.997.897.697.497.196.896.496.095.695.194.593.993.392.76596.497.197.597.697.697.697.597.497.297.096.896.596.295.895.494.994.493.993.392.77095.696.496.897.097.197.197.096.996.896.696.496.195.895.595.194.794.293.893.392.77594.895.696.096.396.496.596.496.496.396.195.995.795.595.294.894.594.193.693.292.78094.194.895.395.595.795.895.895.795.795.595.495.295.094.894.594.293.893.593.192.78593.694.194.494.794.894.995.095.094.994.994.794.694.594.394.193.893.693.393.092.79093.193.493.693.893.994.094.194.194.194.094.093.993.893.793.693.493.393.192.992.79592.792.892.993.093.093.193.193.193.193.193.193.193.193.193.093.092.992.992.892.79892.792.792.792.792.792.892.892.892.892.892.892.892.892.892.892.892.792.792.792.7Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention in Zone 2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.25-inches of Retention in Zone 2NDCIACNPercent DCIA51015202530354045505560657075808590951003099.899.999.999.899.899.799.599.499.198.898.598.297.897.496.996.495.995.394.794.13599.699.799.799.799.799.699.499.399.098.898.598.197.897.496.996.495.995.394.794.14099.499.599.699.699.599.499.399.198.998.698.498.097.797.396.896.495.895.394.794.14599.099.399.499.499.399.299.198.998.798.598.297.997.697.296.896.395.895.294.794.15098.699.099.199.299.199.098.998.798.698.398.197.897.597.196.796.295.795.294.794.15598.198.698.898.898.898.798.698.598.398.197.997.697.397.096.696.195.795.294.694.16097.698.298.498.598.598.498.398.298.097.997.697.497.196.896.496.095.695.194.694.16597.097.697.998.098.198.098.097.997.797.697.497.296.996.696.295.995.595.094.694.17096.497.097.397.597.697.697.597.597.497.297.196.996.696.396.095.795.394.994.594.17595.796.496.796.997.097.197.097.096.996.896.796.596.396.195.895.595.294.894.594.18095.195.696.096.396.496.596.596.596.496.396.296.195.995.795.595.395.094.794.494.18594.695.095.395.695.795.895.895.895.895.895.795.695.595.395.295.094.894.694.394.19094.294.594.794.995.095.095.195.195.195.195.195.094.994.994.894.694.594.494.294.19593.994.094.194.294.394.394.394.494.494.494.494.494.494.394.394.394.294.294.194.19894.094.094.094.094.194.194.194.194.194.194.194.194.194.194.194.194.194.194.194.151015202530354045505560657075808590951003099.999.999.999.999.899.899.799.599.399.198.998.698.397.997.697.196.796.295.795.13599.799.899.899.899.799.799.699.499.299.098.898.598.297.997.597.196.796.295.795.14099.599.699.799.799.699.699.599.399.198.998.798.498.197.897.597.196.696.295.795.14599.299.499.599.599.599.499.399.299.098.898.698.398.197.797.497.096.696.195.695.15098.899.299.399.399.399.299.199.098.898.698.498.297.997.697.396.996.596.195.695.15598.498.999.099.199.099.098.998.898.698.598.398.097.897.597.296.996.596.195.695.16098.098.598.798.798.798.798.698.598.498.298.197.997.697.497.196.896.496.095.695.16597.598.098.398.498.498.498.398.298.198.097.897.697.497.296.996.696.395.995.695.17097.097.597.897.998.098.097.997.997.897.797.697.497.297.096.896.596.295.995.595.17596.497.097.297.497.597.597.597.597.497.397.297.196.996.896.596.396.195.895.595.18095.996.396.696.897.097.097.097.097.096.996.996.896.696.596.396.195.995.795.495.18595.495.896.196.296.496.596.596.596.596.596.496.396.396.196.095.995.795.595.395.19095.195.495.595.795.895.995.995.995.995.995.995.995.895.895.795.695.595.495.395.19595.095.095.195.295.295.395.395.395.395.495.495.495.395.395.395.395.395.295.295.19895.095.195.195.195.195.195.195.195.195.195.295.295.295.295.295.295.195.195.195.1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.00-inches of Retention in Zone 2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.75-inches of Retention in Zone 251015202530354045505560657075808590951003099.999.999.999.999.999.899.899.699.599.399.198.998.698.398.097.797.396.996.496.03599.899.899.999.899.899.899.799.699.499.299.098.898.598.398.097.697.396.996.496.04099.699.799.799.799.799.799.699.599.399.199.098.798.598.297.997.697.296.896.496.04599.499.599.699.699.699.599.499.399.299.098.898.698.498.297.997.597.296.896.496.05099.199.399.499.499.499.499.399.299.198.998.798.598.398.197.897.597.296.896.496.05598.799.199.299.299.299.299.199.098.998.798.698.498.298.097.797.497.196.896.496.06098.498.898.999.099.098.998.998.898.798.598.498.298.097.897.697.397.096.796.496.06598.098.498.698.698.798.698.698.598.498.398.298.097.997.797.597.296.996.796.396.07097.597.998.298.398.398.398.398.298.298.198.097.897.797.597.397.196.896.696.396.07597.097.497.797.897.997.997.997.997.897.897.797.697.497.397.196.996.796.596.396.08096.596.997.297.397.497.597.597.597.597.497.497.397.297.196.996.896.696.496.296.08596.196.496.796.896.997.097.097.197.197.097.096.996.996.896.796.696.496.396.196.09095.996.196.296.396.496.596.596.696.696.696.696.696.596.596.496.396.396.296.196.09595.895.895.996.096.096.096.196.196.196.196.196.196.196.196.196.196.196.096.096.09895.995.995.995.995.995.995.996.096.096.096.096.096.096.096.096.096.096.096.096.051015202530354045505560657075808590951003099.999.999.999.999.999.999.899.799.699.599.399.198.998.698.498.197.897.497.096.73599.899.999.999.999.899.899.899.799.599.499.299.098.898.698.398.097.797.497.096.74099.799.899.899.899.899.799.799.699.599.399.299.098.898.598.398.097.797.497.096.74599.599.799.799.799.799.699.699.599.499.299.198.998.798.598.298.097.797.497.096.75099.399.599.599.599.599.599.499.399.299.198.998.898.698.498.297.997.697.397.096.75598.999.299.399.499.499.399.399.299.199.098.898.798.598.398.197.997.697.397.096.76098.699.099.199.299.299.199.199.098.998.898.798.598.498.298.097.897.597.397.096.76598.398.798.898.998.998.998.898.898.798.698.598.498.298.197.997.797.597.296.996.77097.998.398.598.598.698.698.698.598.498.498.398.298.097.997.797.697.497.296.996.77597.597.898.198.298.298.398.298.298.298.198.097.997.897.797.697.497.397.196.996.78097.197.497.697.797.897.997.997.997.997.897.897.797.697.597.497.397.297.096.896.78596.797.097.197.397.497.497.597.597.597.597.597.497.497.397.297.197.096.996.896.79096.596.696.896.997.097.097.197.197.197.197.197.197.197.097.096.996.996.896.796.79596.496.596.596.696.696.796.796.796.796.796.896.896.896.896.796.796.796.796.796.79896.596.596.596.696.696.696.696.696.696.696.696.696.696.696.696.696.796.796.796.7NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.25-inches of Retention in Zone 2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.50-inches of Retention in Zone 251015202530354045505560657075808590951003099.999.9100.0100.099.999.999.999.899.799.699.499.399.198.998.698.498.197.897.597.23599.999.999.999.999.999.999.899.799.699.599.499.299.098.898.698.498.197.897.597.24099.899.899.999.899.899.899.799.799.699.599.399.299.098.898.698.398.197.897.597.24599.699.799.899.799.799.799.799.699.599.499.299.198.998.798.598.398.197.897.597.25099.499.699.699.699.699.699.599.599.499.399.199.098.898.798.598.398.097.897.597.25599.199.499.599.599.599.599.499.399.299.199.098.998.798.698.498.298.097.797.597.26098.999.299.399.399.399.399.299.299.199.098.998.898.698.598.398.197.997.797.597.26598.698.999.099.199.199.199.099.098.998.898.798.698.598.498.298.097.997.797.497.27098.398.698.798.898.898.898.898.898.798.698.598.598.398.298.198.097.897.697.497.27597.998.298.498.598.598.598.598.598.498.498.398.398.298.198.097.897.797.697.497.28097.597.898.098.198.298.298.298.298.298.198.198.098.097.997.897.797.697.597.397.28597.297.497.697.797.897.897.997.997.997.997.897.897.897.797.697.697.597.497.397.29097.097.197.297.397.497.497.597.597.597.597.597.597.597.597.597.497.497.397.397.29596.997.097.097.197.197.297.297.297.297.297.297.397.397.397.397.397.297.297.297.29897.097.197.197.197.197.197.197.197.197.297.297.297.297.297.297.297.297.297.297.251015202530354045505560657075808590951003099.9100.0100.0100.0100.099.999.999.899.899.799.699.499.399.198.998.798.498.297.997.63599.999.999.999.999.999.999.999.899.799.699.599.499.299.098.898.698.498.297.997.64099.899.999.999.999.999.899.899.799.799.699.599.399.299.098.898.698.498.297.997.64599.799.899.899.899.899.899.799.799.699.599.499.399.198.998.898.698.498.197.997.65099.699.799.799.799.799.799.699.699.599.499.399.299.098.998.798.598.398.197.997.65599.399.599.699.699.699.699.599.499.499.399.299.198.998.898.698.598.398.197.997.66099.199.399.499.499.499.499.499.399.299.299.199.098.898.798.698.498.298.197.897.66598.899.199.299.399.399.299.299.199.199.098.998.898.798.698.598.398.298.097.897.67098.698.898.999.099.099.099.099.098.998.898.898.798.698.598.498.398.198.097.897.67598.298.598.698.798.798.898.898.798.798.698.698.598.498.498.398.298.097.997.897.68097.998.198.398.498.498.598.598.598.498.498.498.398.398.298.198.198.097.997.797.68597.697.897.998.098.198.198.298.298.298.298.198.198.198.098.097.997.997.897.797.69097.497.597.697.797.897.897.897.997.997.997.997.997.997.997.897.897.897.797.797.69597.497.497.597.597.597.697.697.697.697.697.797.797.797.797.797.797.797.697.697.69897.597.597.597.597.597.597.697.697.697.697.697.697.697.697.697.697.697.697.697.6NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.75-inches of Retention in Zone 2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 4.00-inches of Retention in Zone 251015202530354045505560657075808590951003082.781.275.569.363.658.654.250.447.044.141.439.137.135.233.532.030.629.328.127.03577.878.273.668.062.758.053.750.046.843.941.339.037.035.133.431.930.529.228.127.04072.774.971.566.661.757.253.249.646.443.641.138.936.835.033.431.930.529.228.127.04567.371.369.064.960.556.352.549.146.043.340.938.736.734.933.331.830.529.228.127.05061.867.466.362.959.155.351.748.545.642.940.638.536.534.833.231.730.429.228.027.05556.563.263.260.757.454.050.847.845.042.540.238.236.334.633.131.730.429.128.027.06051.558.859.958.255.552.649.746.944.342.039.837.936.134.432.931.630.329.128.027.06546.754.356.255.453.450.948.345.943.541.339.337.535.834.232.831.430.229.028.027.07042.449.752.352.250.848.946.844.642.540.538.737.035.433.932.531.330.129.028.027.07538.845.148.048.647.946.544.843.141.339.537.936.334.933.532.231.129.928.927.927.08035.540.743.444.544.443.742.541.139.738.336.935.534.233.031.930.829.728.827.927.08532.736.538.739.940.340.139.538.637.636.535.434.433.332.331.330.429.528.627.827.09030.632.834.335.235.735.835.635.234.734.133.432.731.931.230.429.729.028.327.627.09529.129.830.330.730.931.031.031.030.830.630.330.029.729.429.028.628.227.827.427.09828.528.528.628.628.628.628.628.528.528.428.328.228.027.927.827.627.527.327.227.051015202530354045505560657075808590951003087.689.187.684.881.577.874.370.967.864.962.159.657.255.052.951.049.247.646.044.53583.586.585.683.480.477.073.670.467.464.561.959.457.054.952.851.049.247.546.044.54079.383.583.481.779.176.072.969.866.964.261.659.156.954.752.750.949.147.546.044.54574.980.380.979.777.674.972.069.166.463.761.258.956.654.652.650.849.147.545.944.55070.576.778.177.675.973.570.968.365.763.260.858.556.454.452.550.749.047.445.944.55566.372.975.075.173.971.969.667.364.962.660.358.156.154.152.350.648.947.445.944.56062.168.971.772.471.670.168.266.164.061.859.757.755.753.852.150.448.847.345.944.56558.064.968.169.369.168.066.564.762.860.959.057.155.253.551.850.248.747.245.844.57054.460.964.265.866.265.664.563.061.559.858.156.354.653.051.449.948.547.145.844.57551.157.060.462.262.962.762.161.059.858.456.955.453.952.451.049.648.347.045.744.58048.553.556.558.359.159.359.158.557.656.655.454.252.951.650.449.247.946.845.644.58546.750.352.754.255.155.555.655.354.954.253.452.651.650.649.648.547.546.545.544.59045.447.649.150.251.051.451.751.751.551.250.850.349.749.048.347.646.846.145.344.59544.845.646.246.747.147.347.547.647.647.547.447.247.046.746.446.145.745.344.944.59845.245.345.445.445.545.545.545.645.545.545.545.445.345.345.245.044.944.844.744.5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.25-inches of Retention for Zone 3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 351015202530354045505560657075808590951003089.792.391.690.388.486.283.881.378.776.273.871.569.367.365.363.461.659.958.356.73586.689.889.888.987.285.383.180.778.275.873.571.369.267.165.263.361.659.958.356.74082.987.187.987.385.984.282.280.077.775.473.271.069.067.065.163.261.559.858.256.74579.384.485.785.584.583.081.279.277.174.972.870.768.766.864.963.161.459.858.256.75075.881.483.283.582.881.680.178.376.374.372.370.368.466.564.763.061.359.758.256.75572.278.380.581.280.980.178.877.275.473.571.769.868.066.264.562.861.259.758.256.76069.075.077.678.678.778.377.375.974.372.771.069.267.565.964.262.661.159.658.156.76565.771.674.475.876.376.275.574.473.171.770.168.667.065.463.962.460.959.558.156.77062.568.271.272.873.673.873.472.771.670.469.167.766.364.963.562.160.759.358.056.77559.864.967.969.770.671.171.070.669.868.967.866.765.564.262.961.760.459.257.956.78057.561.864.666.467.568.168.268.067.667.066.265.364.363.362.261.260.058.957.856.78556.059.361.663.164.264.865.165.164.964.664.163.562.862.161.360.459.558.657.756.79055.457.458.960.060.861.361.761.961.961.861.661.360.960.559.959.458.858.157.456.79555.556.256.857.357.758.158.358.558.658.758.758.658.558.458.257.957.757.457.156.79856.556.656.856.957.057.157.157.257.257.257.257.257.257.257.157.157.056.956.856.751015202530354045505560657075808590951003091.193.794.092.991.790.388.686.885.083.181.179.177.275.373.571.870.168.567.065.53588.691.892.291.690.789.587.986.384.582.780.878.977.075.273.471.770.168.567.065.54085.989.490.490.389.688.587.185.683.982.280.478.676.875.073.371.670.068.566.965.54582.586.988.588.788.287.386.184.883.381.780.078.276.574.873.171.569.968.466.965.55079.484.486.486.986.786.085.083.982.581.079.477.876.174.572.971.369.868.366.965.55576.681.984.084.985.084.583.782.881.680.378.877.375.774.272.771.269.768.366.965.56073.879.181.682.783.082.882.381.680.679.478.176.775.273.872.470.969.568.266.865.56571.176.478.980.380.880.980.680.179.478.477.275.974.673.372.070.769.468.066.865.57068.673.576.277.678.478.878.778.577.977.176.275.173.972.871.570.369.167.966.765.57566.370.673.374.975.976.476.676.576.175.674.974.073.072.071.069.968.867.766.665.58064.368.070.572.173.273.974.274.374.173.873.372.671.971.170.269.368.467.566.565.58563.165.967.969.470.471.271.671.871.871.671.370.970.569.969.368.667.967.166.365.59062.764.565.967.067.868.468.869.169.269.269.168.968.768.468.067.667.166.666.165.59563.364.064.665.165.565.866.166.366.466.566.666.666.666.566.466.366.166.065.765.59864.764.865.065.165.265.365.465.565.565.665.665.665.665.765.765.665.665.665.565.5Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention for Zone 3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 3NDCIACNPercent DCIA51015202530354045505560657075808590951003092.194.595.294.893.792.791.590.288.787.385.784.282.681.079.477.876.374.873.472.03590.092.993.993.592.791.990.889.688.286.985.483.982.480.879.377.776.274.873.472.04087.891.292.292.291.791.090.189.087.786.485.083.682.180.679.177.676.274.773.372.04585.489.090.390.790.590.089.288.287.085.984.683.281.880.478.977.576.174.773.372.05082.386.788.489.289.288.988.287.386.385.284.182.881.580.178.777.375.974.673.372.05579.784.486.687.487.687.587.086.385.484.583.582.381.179.878.477.175.874.573.272.06077.482.384.485.585.986.085.785.184.483.782.881.780.679.478.176.975.674.473.272.06575.379.882.283.484.184.284.183.883.382.781.981.080.078.977.876.675.474.373.172.07073.177.579.981.382.082.382.482.382.081.580.980.179.378.377.376.375.274.173.172.07571.275.177.478.979.780.380.580.680.480.179.779.178.477.676.775.874.973.973.072.08069.672.875.076.477.478.178.578.778.778.578.277.877.376.776.075.274.573.772.872.08568.571.072.974.275.175.876.376.676.776.776.676.376.075.575.174.573.973.372.772.09068.469.971.272.273.073.674.074.374.574.674.674.674.474.273.973.673.372.972.472.09569.370.070.571.071.471.772.072.272.472.572.672.672.672.672.672.572.472.372.272.09870.971.071.271.371.471.571.671.771.871.871.971.972.072.072.072.072.072.072.072.051015202530354045505560657075808590951003092.895.295.995.995.394.393.392.391.290.188.887.686.384.983.682.380.979.678.277.03591.093.894.794.994.393.592.791.890.889.788.587.386.084.883.582.280.879.578.277.04089.192.393.593.693.392.792.091.290.389.288.187.085.884.683.382.080.879.578.277.04587.290.791.992.292.191.891.290.589.788.787.786.685.584.383.181.980.779.478.277.05085.188.690.190.790.990.790.489.789.088.187.186.285.184.082.981.780.579.378.177.05582.486.588.389.289.689.689.388.888.287.486.685.784.783.782.781.580.479.278.177.06080.284.586.687.788.188.288.187.787.286.685.985.184.383.382.481.380.279.178.077.06578.482.684.785.986.586.786.786.586.185.685.184.483.782.982.081.080.079.078.077.07076.780.682.784.084.785.185.285.184.984.684.183.683.082.381.580.779.878.877.977.07575.178.580.782.082.883.383.583.683.583.383.182.782.281.681.080.379.578.677.877.08073.876.778.679.980.781.381.781.982.082.081.881.681.280.880.379.779.178.477.777.08572.975.176.777.978.879.479.980.280.380.480.480.380.179.879.579.078.678.177.577.09072.974.375.476.377.077.678.078.478.678.778.878.878.878.678.578.278.077.777.377.09574.074.675.175.575.976.276.576.877.077.177.277.377.377.377.377.377.277.277.177.09875.875.976.076.276.376.476.476.576.676.776.776.876.876.976.976.976.976.977.077.0NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.50-inches of Retention for Zone 3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.25-inches of Retention for Zone 351015202530354045505560657075808590951003093.395.696.496.696.395.694.793.892.992.091.089.988.887.886.685.584.383.282.080.83591.894.495.495.795.594.894.193.392.591.690.789.788.687.686.585.484.383.182.080.84090.293.194.394.794.594.093.492.792.091.290.489.488.487.486.385.384.283.182.080.84588.691.893.193.593.493.192.692.191.590.889.989.088.187.186.285.184.183.081.980.85086.990.391.692.192.292.191.891.490.990.289.588.687.786.985.985.084.082.981.980.85584.988.389.990.691.091.190.990.690.289.688.988.187.486.685.784.883.882.981.980.86082.786.488.289.289.789.989.989.789.388.888.287.686.986.285.484.683.782.881.880.86580.984.686.787.788.488.688.788.688.387.987.586.986.485.785.084.383.582.681.880.87079.683.085.086.286.887.287.487.487.287.086.686.285.785.284.684.083.282.581.780.87578.381.483.284.485.285.785.986.086.085.885.685.385.084.684.183.582.982.381.680.88077.279.881.582.783.584.084.384.584.684.684.584.484.183.883.583.182.682.081.580.88576.678.579.980.981.782.282.783.083.283.383.383.383.283.082.882.582.181.781.380.89076.477.778.779.580.280.781.181.481.781.982.082.182.182.081.981.881.681.481.180.89577.678.178.679.079.479.780.080.380.580.680.880.980.981.081.081.081.081.080.980.89879.579.779.879.980.080.180.280.380.480.580.580.680.680.780.780.880.880.880.880.851015202530354045505560657075808590951003093.895.996.797.097.096.695.895.094.293.492.691.790.889.888.987.986.985.984.983.93592.494.995.896.296.395.995.294.593.893.192.391.590.689.788.787.886.885.984.983.94091.093.894.995.495.495.194.593.993.392.792.091.290.489.588.687.786.885.884.883.94589.792.793.994.594.494.293.893.392.892.391.690.990.189.288.487.686.785.884.883.95088.291.492.893.393.393.393.092.792.391.891.290.589.889.088.287.486.685.784.883.95586.990.091.391.992.292.292.291.991.691.290.790.189.488.787.987.286.485.684.783.96085.088.289.790.691.091.291.291.190.990.590.189.688.988.387.787.086.385.584.783.96583.286.488.289.289.890.190.290.290.089.789.488.988.487.987.386.786.185.484.683.97081.785.086.787.888.588.989.189.189.188.888.688.287.887.486.986.485.885.284.683.97580.883.585.386.487.187.687.988.087.987.987.787.487.186.886.486.085.685.084.583.98080.082.383.884.985.686.286.586.686.786.886.786.686.486.285.985.685.284.884.483.98579.581.282.583.484.184.685.085.385.585.685.685.685.585.485.385.184.984.684.283.99079.580.681.582.282.883.383.683.984.284.384.584.684.684.684.684.584.484.384.183.99580.681.181.581.982.282.582.883.083.283.483.583.683.783.883.983.983.983.983.983.99882.482.682.782.882.983.183.283.283.383.483.583.583.683.783.783.783.883.883.983.9NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.75-inches of Retention for Zone 3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.00-inches of Retention for Zone 351015202530354045505560657075808590951003094.196.297.097.397.497.296.796.095.294.593.893.092.391.590.689.888.988.087.186.23592.995.396.296.696.896.696.195.594.894.293.592.892.191.390.589.788.888.087.186.24091.794.395.495.996.195.995.595.094.493.893.292.591.991.190.489.588.787.987.186.24590.693.394.695.195.395.194.894.493.993.492.892.291.690.990.289.488.687.987.186.25089.492.393.694.294.394.294.093.793.392.992.591.991.390.790.089.388.587.887.086.25588.291.292.593.193.393.393.293.092.792.492.091.591.090.489.789.188.487.787.086.26087.089.791.191.892.192.392.392.292.091.891.591.090.690.189.588.988.287.686.986.26585.388.189.690.591.091.391.491.491.391.190.990.590.189.789.188.688.187.586.986.27083.886.688.289.289.890.290.490.590.590.490.289.989.689.288.888.387.987.486.886.27582.985.386.987.988.689.189.389.589.689.589.489.289.088.788.388.087.687.286.786.28082.284.385.786.787.487.988.288.488.588.588.588.488.388.187.887.687.387.086.686.28581.983.484.685.586.186.686.987.287.487.587.587.587.587.487.387.187.086.886.586.29082.183.083.884.585.085.485.786.086.286.486.586.686.786.786.786.786.686.586.486.29583.083.583.984.284.584.885.085.285.485.685.785.885.986.086.186.286.286.286.386.29884.884.985.085.185.385.485.585.685.685.785.885.985.986.086.086.186.186.286.286.251015202530354045505560657075808590951003094.396.497.297.597.697.697.396.896.195.494.794.193.492.792.091.390.589.788.988.13593.395.696.596.997.197.196.896.395.795.194.593.993.292.691.991.290.489.788.988.14092.394.795.896.396.596.596.395.895.394.794.293.693.092.491.791.190.389.688.988.14591.293.995.095.695.995.995.695.294.894.393.893.392.892.291.690.990.289.588.888.15090.393.094.294.995.195.194.994.694.393.893.493.092.592.091.490.890.189.588.888.15589.392.193.494.094.294.294.193.993.793.393.092.692.291.791.290.690.089.488.888.16088.491.092.292.993.193.393.393.293.092.892.592.291.891.490.990.489.989.388.788.16587.289.690.991.692.192.392.492.492.392.292.091.791.491.090.790.289.789.288.788.17085.888.289.590.591.091.391.591.691.691.591.491.290.990.690.389.989.589.088.688.17584.787.088.389.289.990.390.690.790.890.890.790.690.490.289.989.689.288.988.588.18084.085.987.288.188.889.289.689.889.990.090.089.989.889.789.589.289.088.788.488.18583.885.386.387.187.788.288.588.889.089.189.189.189.189.189.088.888.788.588.388.19084.185.085.886.486.887.287.587.888.088.188.388.388.488.488.488.488.388.388.288.19585.185.585.986.286.586.786.987.187.387.487.587.787.887.887.988.088.088.188.188.19886.786.886.987.087.187.287.387.487.587.687.687.787.887.887.987.988.088.088.188.1Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention for Zone 3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.25-inches of Retention for Zone 3NDCIACNPercent DCIA51015202530354045505560657075808590951003094.696.597.397.797.897.997.797.496.896.295.694.994.493.793.192.491.891.190.489.63593.695.996.797.197.397.497.397.096.595.995.394.794.293.693.092.491.791.090.389.64092.895.196.196.696.897.096.896.596.095.595.094.594.093.492.892.291.691.090.389.64591.894.395.496.096.396.496.396.095.695.194.794.293.793.292.792.191.690.990.389.65091.093.694.895.495.795.895.695.495.094.794.393.993.593.092.592.091.590.990.389.65590.292.894.094.795.095.094.994.794.594.293.993.593.292.892.391.891.390.890.289.66089.492.093.293.894.094.194.294.093.993.793.493.192.992.592.191.791.290.790.289.66588.790.992.092.793.193.393.393.393.293.192.992.792.592.291.891.491.190.690.189.67087.589.690.891.692.192.392.592.592.592.592.492.292.091.891.591.290.990.590.189.67586.488.489.790.491.091.391.691.791.891.891.891.791.691.491.290.990.790.390.089.68085.887.488.689.490.090.490.790.991.091.191.191.191.090.990.890.690.490.289.989.68585.586.887.788.589.089.489.890.090.290.390.490.490.490.490.490.390.190.089.889.69085.886.687.387.988.388.789.089.289.489.689.789.889.889.989.989.989.889.889.789.69586.987.287.687.888.188.388.588.788.989.089.189.289.389.489.589.589.589.689.689.69888.488.588.688.788.888.988.989.089.189.189.289.389.389.489.489.589.589.689.689.651015202530354045505560657075808590951003094.996.797.497.898.098.098.097.897.496.996.395.795.194.694.093.492.892.291.690.93593.996.096.997.397.597.697.797.497.196.696.095.594.994.493.993.392.792.291.690.94093.195.496.396.897.197.297.297.196.796.295.795.294.794.393.793.292.792.191.590.94592.494.795.796.396.696.896.896.696.295.895.495.094.594.193.693.192.692.191.590.95091.694.095.295.896.196.396.296.095.895.495.194.794.393.993.493.092.592.091.590.95591.093.494.695.295.695.795.695.495.294.994.694.394.093.693.392.892.491.991.490.96090.492.793.994.694.894.994.994.894.694.494.293.993.793.493.092.792.391.991.490.96589.892.093.093.693.994.194.294.194.093.993.793.593.393.192.892.592.191.891.490.97089.090.991.992.693.093.293.393.493.493.393.293.192.992.892.592.292.091.691.390.97588.089.790.891.692.092.392.592.692.792.792.792.692.592.492.292.091.891.591.290.98087.388.889.890.591.091.491.791.892.092.092.192.192.192.091.891.791.691.491.290.98587.088.189.089.790.190.590.891.191.391.491.591.591.591.591.591.491.391.291.190.99087.288.088.689.189.589.990.290.490.690.790.890.991.091.091.191.191.191.091.090.99588.388.788.989.289.489.689.890.090.190.290.490.590.690.790.790.890.890.990.990.99889.789.889.990.090.190.290.390.390.490.590.590.690.690.790.790.890.890.990.990.9NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.00-inches of Retention for Zone 3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.75-inches of Retention for Zone 351015202530354045505560657075808590951003095.296.997.597.998.198.298.298.197.897.596.996.495.895.394.794.293.793.192.692.03594.196.297.097.597.797.897.997.897.597.296.796.295.695.194.694.193.693.192.592.04093.495.696.697.097.397.597.597.497.296.896.495.995.495.094.594.093.593.092.592.04592.895.096.096.696.997.197.197.196.896.596.195.795.294.894.493.993.593.092.592.05092.194.495.596.196.596.796.796.696.396.195.795.495.094.694.293.893.492.992.592.05591.593.895.095.696.096.296.296.095.995.695.395.094.794.494.093.793.392.992.492.06091.193.394.495.195.595.695.595.595.395.194.994.794.494.193.893.593.292.892.492.06590.792.793.894.494.794.894.994.994.894.694.594.394.093.893.693.393.092.792.492.07090.392.092.993.493.894.094.294.294.194.194.093.893.793.593.493.192.992.692.392.07589.490.991.892.593.093.293.493.593.593.593.493.493.393.293.192.992.792.592.292.08088.790.191.091.692.092.392.692.792.892.992.992.992.992.992.892.692.592.392.292.08588.489.490.290.791.291.591.892.092.192.392.492.492.592.592.492.492.392.292.192.09088.589.289.790.290.690.991.291.491.691.791.991.992.092.092.092.192.192.192.092.09589.689.990.190.490.690.890.991.191.291.391.491.591.691.791.891.891.991.992.092.09890.890.991.091.191.291.291.391.491.491.591.691.691.791.791.891.891.991.992.092.051015202530354045505560657075808590951003095.597.097.698.098.298.398.398.398.197.997.596.996.495.995.494.994.493.993.492.93594.496.397.297.697.998.098.098.097.997.697.296.796.395.895.394.894.493.993.492.94093.695.896.897.297.597.697.797.797.697.396.996.596.195.695.294.794.393.893.492.94593.295.396.396.897.197.397.497.497.397.096.696.395.995.495.094.694.293.893.392.95092.694.795.896.496.797.097.197.096.996.696.396.095.695.294.994.594.193.793.392.95592.194.295.396.096.496.696.796.696.496.295.995.695.395.094.794.494.093.793.392.96091.793.894.995.595.996.196.196.095.995.895.595.395.094.894.594.293.993.693.292.96591.493.394.495.095.495.595.595.595.495.395.194.994.794.594.394.093.893.593.292.97091.292.993.894.394.594.794.894.994.894.894.794.594.494.294.093.993.793.493.192.97590.792.092.893.393.794.094.194.294.294.294.294.194.093.993.893.793.593.393.192.98089.991.191.992.592.993.293.493.593.693.693.793.693.693.693.593.493.393.293.092.98589.790.591.291.792.192.492.792.893.093.093.193.293.293.293.293.293.193.193.092.99089.790.390.891.291.591.892.092.292.492.592.792.892.892.992.992.992.992.992.992.99590.690.991.191.391.591.791.992.092.292.392.492.492.592.692.792.792.892.892.892.99891.891.992.092.092.192.292.292.392.492.492.592.592.692.692.792.792.892.892.892.9NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.25-inches of Retention for Zone 3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.50-inches of Retention for Zone 351015202530354045505560657075808590951003095.897.297.898.198.298.498.498.498.398.297.997.597.096.596.095.595.094.694.193.63594.796.597.397.798.098.198.298.298.197.997.797.396.896.395.995.495.094.594.193.64093.995.996.997.497.797.897.997.997.997.797.497.096.696.295.895.394.994.594.193.64593.495.596.597.097.397.597.697.797.697.497.196.896.496.095.695.294.894.594.193.65093.195.196.096.697.097.297.397.497.397.196.896.596.295.895.595.194.894.494.093.65592.594.695.696.296.696.997.097.096.996.796.596.295.995.695.395.094.794.394.093.66092.294.195.295.996.396.596.696.696.496.396.195.995.695.495.194.894.694.394.093.66592.093.894.895.595.996.196.196.096.095.995.795.595.395.194.994.794.494.293.993.67091.993.594.495.095.395.495.495.595.595.495.395.295.094.894.794.594.394.193.993.67591.893.093.794.194.494.794.894.994.994.994.894.794.794.594.494.394.294.093.893.68091.192.192.893.393.794.094.194.294.394.394.394.394.394.294.294.194.093.993.893.68590.791.692.292.693.093.293.493.693.793.893.893.993.993.993.993.993.893.893.793.69090.891.391.892.192.492.792.993.093.293.393.493.593.593.693.693.793.793.793.793.69591.591.792.092.292.392.592.792.892.993.093.193.293.393.493.493.593.593.693.693.69892.692.792.892.992.993.093.193.193.293.293.393.393.493.493.493.593.593.693.693.651015202530354045505560657075808590951003096.197.497.998.198.398.498.598.598.598.498.297.997.497.096.596.195.695.294.794.33595.096.797.497.898.098.298.398.398.398.298.097.797.396.996.496.095.595.194.794.34094.196.197.097.597.897.998.098.198.198.097.897.597.196.796.395.995.595.194.794.34593.695.796.797.297.597.797.897.897.897.797.597.396.996.596.295.895.495.094.794.35093.395.496.396.897.197.497.597.697.697.597.397.096.796.496.095.795.395.094.694.35593.094.995.996.496.897.197.397.397.397.196.996.796.496.195.995.595.294.994.694.36092.794.595.596.196.596.897.097.096.996.896.696.496.295.995.795.495.194.994.694.36592.494.295.295.896.296.596.696.696.596.496.296.195.995.795.595.295.094.894.694.37092.594.094.995.595.896.096.096.096.095.995.895.795.695.495.295.194.994.794.594.37592.593.794.594.995.195.395.495.595.595.595.495.395.395.195.094.994.894.694.594.38092.293.193.794.194.494.694.894.994.995.095.094.994.994.894.894.794.694.594.494.38591.792.593.093.493.794.094.194.394.494.594.594.594.594.594.594.594.594.494.494.39091.792.292.692.993.293.493.693.793.994.094.094.194.294.294.394.394.394.394.394.39592.492.692.892.993.193.293.493.593.693.793.893.993.994.094.194.194.294.294.394.39893.393.493.593.693.693.793.793.893.893.993.994.094.094.194.194.294.294.294.394.3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.75-inches of Retention for Zone 3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 4.00-inches of Retention for Zone 351015202530354045505560657075808590951003090.186.679.271.464.558.653.549.245.542.339.537.134.933.031.329.728.327.125.924.83586.284.377.870.563.958.253.249.045.342.239.437.034.933.031.229.728.327.025.924.84081.681.575.969.363.157.652.848.745.142.039.336.934.832.931.229.728.327.025.924.84576.578.173.767.862.056.852.248.244.841.839.136.834.732.831.129.628.327.025.924.85071.074.271.065.960.755.851.547.744.441.438.936.634.532.731.129.628.227.025.924.85565.369.967.963.759.154.750.647.043.841.138.536.334.432.631.029.528.227.025.824.86059.765.264.461.257.253.249.646.243.240.638.236.134.132.430.829.428.126.925.824.86554.260.260.558.255.051.548.245.242.439.937.735.733.832.230.729.328.026.925.824.87049.154.956.154.752.349.446.643.941.439.237.135.233.531.930.529.127.926.825.824.87544.349.451.150.749.146.944.642.340.138.136.334.633.031.530.228.927.826.725.724.88040.044.145.846.045.243.742.040.238.536.835.233.732.331.029.828.727.626.625.724.88536.238.940.440.840.639.838.837.536.335.033.732.531.430.229.228.227.326.425.624.89032.834.235.035.435.435.134.633.933.232.431.630.829.929.128.327.626.926.125.524.89529.329.729.930.029.929.829.729.429.128.828.528.127.727.326.926.526.125.625.224.89827.227.227.227.127.027.026.826.726.626.526.326.226.025.925.725.525.425.225.024.851015202530354045505560657075808590951003094.094.292.188.884.880.576.372.468.665.262.059.156.453.951.749.547.645.844.142.63591.192.390.787.784.079.975.972.068.465.061.959.056.353.951.649.547.645.844.142.64087.890.088.986.482.979.175.371.568.064.761.658.856.253.851.549.447.545.744.142.64584.087.286.884.781.678.174.570.967.564.361.358.656.053.651.449.447.545.744.142.65079.984.084.382.780.176.973.570.266.963.961.058.355.853.551.349.347.445.744.142.65575.680.481.480.478.275.472.369.266.263.360.557.955.553.251.149.247.345.644.042.66071.376.578.177.675.973.670.968.065.262.559.957.455.153.050.949.047.245.644.042.66567.172.474.474.573.371.469.166.664.161.659.256.954.752.650.648.847.145.544.042.67063.068.170.370.870.268.967.064.962.760.558.356.154.152.150.348.646.945.443.942.67559.263.765.966.766.665.764.462.760.959.057.155.253.351.549.848.246.745.243.842.68055.859.461.462.362.461.961.159.958.657.155.553.952.350.749.247.846.445.043.842.68552.755.256.757.557.757.657.156.455.554.553.352.150.849.648.347.145.944.743.642.69049.751.152.052.552.852.852.652.251.751.150.349.648.747.947.046.145.244.343.442.69546.747.147.447.547.647.647.547.347.146.846.546.245.845.444.944.544.043.543.042.69844.944.944.844.844.744.744.644.544.344.244.144.043.843.643.543.343.142.942.742.6NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.25-inches of Retention for Zone 4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 451015202530354045505560657075808590951003095.696.495.694.192.189.686.883.981.078.175.372.770.167.765.463.361.259.357.455.73593.594.994.593.291.389.086.383.580.777.975.172.570.067.665.463.261.259.357.455.74091.093.193.092.090.388.185.783.080.277.574.972.369.867.565.363.161.159.257.455.74588.190.991.390.589.187.184.882.379.777.174.572.069.667.365.163.061.159.257.455.75085.088.489.288.887.685.983.881.579.076.574.171.769.367.165.062.961.059.157.455.75581.785.786.886.885.984.582.680.578.275.973.571.269.066.864.862.860.959.157.455.76078.482.684.184.483.982.781.179.277.275.072.870.768.666.564.562.660.859.057.355.76575.079.381.181.781.580.779.477.876.074.072.070.068.066.164.262.360.658.957.355.77071.775.977.978.778.778.277.376.074.472.771.069.167.365.563.862.060.458.857.255.77568.772.574.475.475.675.374.773.772.571.169.668.066.464.863.261.660.158.657.155.78065.969.070.871.772.172.171.771.070.169.067.866.665.263.962.561.159.758.357.055.78563.565.767.167.968.368.368.167.767.166.465.564.663.662.561.460.359.158.056.855.79061.262.463.263.864.164.264.163.963.663.262.762.161.460.759.959.158.357.456.655.79558.759.159.459.659.759.759.759.759.559.459.158.958.658.257.957.557.156.656.255.79857.557.557.557.557.557.457.457.357.257.157.056.956.856.656.556.456.256.055.955.751015202530354045505560657075808590951003096.697.597.296.495.293.791.990.087.985.783.581.279.076.974.872.870.969.167.365.63595.096.396.295.694.593.191.489.687.585.483.281.178.976.874.872.870.969.067.265.64093.094.995.194.693.692.490.889.087.185.182.980.878.776.774.772.770.869.067.265.64590.893.193.693.492.691.590.088.486.584.682.680.578.576.574.572.670.768.967.265.65088.391.192.091.991.490.489.187.685.984.082.180.178.276.274.372.570.668.967.265.65585.789.090.190.289.989.188.086.685.183.481.579.777.875.974.172.370.568.867.165.66083.186.687.988.388.187.686.785.584.182.580.879.177.375.673.872.170.468.767.165.66580.483.985.586.186.185.885.184.182.981.580.078.476.875.173.571.870.268.667.165.67077.781.282.883.683.983.783.282.481.480.378.977.576.074.573.071.570.068.567.065.67575.278.480.181.081.381.381.080.479.678.777.676.475.173.872.471.069.668.366.965.68073.075.677.278.178.578.678.478.177.576.875.974.973.972.871.670.469.268.066.865.68571.173.074.275.075.475.675.575.374.974.473.873.172.371.470.569.668.667.666.665.69069.470.571.271.772.072.272.272.171.971.671.270.870.369.769.168.567.867.166.365.69567.667.968.168.368.468.568.568.568.468.368.268.067.867.667.367.066.766.365.965.69866.766.866.866.866.866.766.766.766.666.666.566.466.366.366.166.065.965.865.765.6Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention for Zone 4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 4NDCIACNPercent DCIA51015202530354045505560657075808590951003097.398.098.097.596.895.894.693.391.890.288.586.885.083.281.479.677.976.274.572.93595.997.297.396.996.295.394.292.991.589.988.386.684.883.081.379.577.876.274.572.94094.596.096.396.195.594.693.692.491.189.688.086.384.682.981.279.577.876.174.572.94592.794.695.195.094.693.993.091.890.689.187.686.084.482.781.079.377.776.174.572.95090.793.193.893.893.693.092.191.189.988.687.285.784.182.480.879.277.676.074.572.95588.691.392.292.592.391.991.290.389.288.086.685.283.782.180.679.077.575.974.472.96086.489.390.590.990.990.690.089.288.387.286.084.683.281.880.378.877.375.874.472.96584.387.288.589.189.289.088.688.087.286.385.284.082.781.379.978.577.175.774.372.97082.185.086.487.187.487.387.086.685.985.184.283.182.080.779.578.276.975.674.372.97580.182.784.184.985.385.485.284.984.483.782.982.081.180.078.977.776.675.474.272.98078.280.481.782.583.083.283.182.982.582.081.480.779.979.178.177.176.175.174.072.98576.778.379.380.180.580.780.780.680.480.179.679.178.577.877.176.475.574.773.872.99075.476.377.077.577.878.078.178.077.977.777.577.176.876.375.975.374.874.273.672.99574.274.574.774.975.075.175.175.175.175.074.974.874.674.574.374.073.873.573.372.99873.773.773.773.773.773.773.773.773.773.673.673.673.573.473.473.373.273.173.072.951015202530354045505560657075808590951003097.898.498.598.297.797.196.295.394.293.091.790.489.087.586.084.583.081.580.078.53596.797.797.997.797.396.695.894.993.992.891.590.288.887.485.984.482.981.480.078.54095.596.897.197.096.696.195.494.593.592.491.289.988.687.285.884.382.981.480.078.54594.195.796.296.295.995.494.894.093.192.090.989.788.487.085.684.282.881.379.978.55092.594.495.195.295.094.694.193.392.591.590.589.388.186.885.484.182.781.379.978.55590.893.093.894.094.093.793.292.691.891.090.088.987.786.585.283.982.581.279.978.56088.991.392.392.792.892.692.291.791.090.389.488.487.386.184.983.782.481.179.878.56587.189.690.791.391.491.391.190.690.189.488.687.786.885.784.683.482.281.079.878.57085.487.889.089.689.989.989.789.489.088.487.787.086.185.184.183.182.080.879.778.57583.885.987.187.888.288.388.288.087.787.286.786.085.384.483.682.681.680.679.678.58082.284.085.285.986.386.486.586.486.285.885.484.984.383.682.982.181.280.479.578.58581.082.383.283.884.284.484.584.584.484.283.983.583.082.582.081.480.780.079.378.59080.080.781.381.882.182.382.482.482.482.282.181.881.681.280.980.580.079.679.178.59579.179.479.679.879.980.080.180.180.180.180.079.979.879.779.679.479.279.078.878.59879.079.079.079.179.179.179.179.179.079.079.079.078.978.978.878.878.778.778.678.5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.50-inches of Retention for Zone 4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.25-inches of Retention for Zone 451015202530354045505560657075808590951003098.298.798.898.798.497.997.396.595.794.893.892.891.790.589.388.086.785.484.182.83597.398.198.398.297.997.596.996.295.594.693.692.691.590.489.287.986.785.484.182.84096.297.497.797.797.497.096.595.995.194.393.492.491.390.289.087.886.685.484.182.84595.196.596.997.096.896.596.095.494.793.993.192.191.190.088.987.786.585.384.182.85093.995.596.096.196.095.895.494.894.293.592.791.890.889.888.787.686.485.284.082.85592.494.395.095.295.295.094.694.293.693.092.291.490.589.588.587.486.385.284.082.86090.992.993.794.194.294.093.893.492.992.491.790.990.189.288.287.286.285.183.982.86589.491.492.492.993.093.092.892.592.191.691.090.489.688.887.987.086.084.983.982.87087.989.990.991.591.791.891.791.591.290.790.389.789.088.387.586.685.784.883.882.87586.588.489.490.090.390.590.490.390.189.789.388.988.387.787.086.285.484.683.782.88085.386.887.888.488.888.989.088.988.888.688.387.987.486.986.485.785.184.483.682.88584.385.486.286.787.187.387.487.487.387.287.086.786.486.085.685.184.684.083.482.89083.584.184.785.085.385.585.785.785.785.685.585.485.284.984.784.484.083.783.382.89582.983.283.483.683.783.883.983.983.983.983.983.883.883.783.683.583.383.283.082.89883.083.183.183.183.183.183.283.283.283.183.183.183.183.183.083.083.082.982.982.851015202530354045505560657075808590951003098.599.099.199.098.798.498.097.496.896.195.394.593.692.691.690.689.588.487.386.13597.898.598.698.698.498.197.797.196.595.995.194.393.492.591.590.589.488.487.386.14096.997.898.198.198.097.797.396.896.295.694.994.193.392.491.490.489.488.387.286.14595.997.197.597.697.597.296.896.495.995.394.693.893.092.291.390.389.388.387.286.15094.996.396.796.996.896.696.395.995.494.994.293.692.892.091.190.289.288.287.286.15593.795.395.996.196.195.995.795.394.994.493.893.292.591.790.990.089.188.187.186.16092.594.194.995.195.295.195.094.794.393.993.492.892.191.490.689.888.988.087.186.16591.292.993.794.194.394.394.193.993.693.292.892.391.791.090.389.688.887.987.186.17089.991.692.592.993.293.293.293.092.892.592.191.791.290.690.089.388.687.887.086.17588.790.291.291.792.092.192.192.091.991.691.391.090.590.189.588.988.387.686.986.18087.789.089.890.390.790.990.990.990.890.690.490.189.889.489.088.588.087.486.886.18586.987.888.589.089.389.589.689.689.689.589.489.288.988.788.388.087.687.186.686.19086.386.887.387.687.988.088.288.288.388.288.288.187.987.887.687.387.186.886.586.19585.986.186.386.586.686.786.886.886.886.986.986.886.886.886.786.686.586.486.386.19886.186.286.286.286.386.386.386.386.386.386.386.386.386.386.386.286.286.286.286.1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.75-inches of Retention for Zone 4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.00-inches of Retention for Zone 451015202530354045505560657075808590951003098.899.299.299.299.098.898.498.097.597.096.395.794.994.293.392.591.690.689.788.73598.198.798.998.898.798.598.297.897.396.896.295.594.894.093.292.491.590.689.788.74097.498.298.498.598.498.297.997.597.096.596.095.394.693.993.192.391.590.689.688.74596.597.697.998.097.997.897.597.196.796.295.795.194.493.793.092.291.490.589.688.75095.796.997.397.497.497.397.096.796.395.995.494.894.293.692.892.191.390.589.688.75594.896.196.696.896.896.796.596.295.995.595.094.594.093.392.791.991.290.489.688.76093.795.195.796.096.096.095.995.695.495.094.694.193.693.192.491.891.190.389.588.76592.694.194.895.195.295.295.295.094.794.494.193.793.292.792.291.690.990.289.588.77091.592.993.794.194.394.494.394.294.093.893.593.292.892.391.891.390.790.189.488.77590.591.892.693.093.393.493.493.493.393.192.892.692.291.991.491.090.589.989.388.78089.690.791.491.992.292.392.492.492.492.392.191.991.691.391.090.690.289.789.288.78588.989.790.390.791.091.291.391.491.491.391.291.190.990.790.490.189.889.589.188.79088.489.089.389.689.990.090.190.290.290.290.290.190.189.989.889.689.489.289.088.79588.288.488.688.788.989.089.089.189.189.289.289.289.189.189.189.089.088.988.888.79888.688.688.688.788.788.788.788.888.888.888.888.888.888.888.888.888.888.788.788.751015202530354045505560657075808590951003099.099.399.499.399.299.098.898.598.197.697.196.695.995.394.693.993.192.491.590.73598.498.999.199.199.098.898.698.397.997.496.996.495.895.294.593.893.192.391.590.74097.898.598.798.798.798.598.398.097.697.296.896.295.795.194.493.893.092.391.590.74597.198.098.298.398.398.298.097.797.497.096.596.095.594.994.393.793.092.291.590.75096.397.497.897.997.997.897.697.397.096.796.395.895.394.794.293.592.992.291.490.75595.696.797.297.397.397.397.196.996.696.395.995.595.094.594.093.492.892.191.490.76094.795.996.496.796.796.796.696.496.295.995.595.294.894.393.893.292.792.091.490.76593.895.095.695.996.096.095.995.895.695.495.194.894.494.093.593.092.591.991.390.77092.894.094.795.095.295.395.395.295.094.894.694.394.093.793.392.892.391.891.390.77591.993.193.794.194.394.594.594.494.394.294.093.893.593.292.992.592.191.791.290.78091.292.192.793.193.493.593.693.693.693.593.493.293.092.892.592.291.991.591.190.78590.691.391.892.292.492.692.792.792.792.792.692.592.492.292.091.891.691.391.090.79090.290.691.091.291.491.691.791.891.891.891.891.891.791.691.591.491.291.190.990.79590.190.390.490.690.790.790.890.990.991.091.091.091.091.090.990.990.990.890.890.79890.590.590.590.690.690.690.690.790.790.790.790.790.790.790.790.790.790.790.790.7Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention for Zone 4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.25-inches of Retention for Zone 4NDCIACNPercent DCIA51015202530354045505560657075808590951003099.199.499.599.599.499.299.098.898.598.197.797.296.796.295.695.094.393.793.092.33598.799.199.299.299.299.098.998.698.398.097.597.196.696.195.594.994.393.693.092.34098.198.798.998.998.998.898.698.498.197.897.496.996.596.095.494.994.293.692.992.34597.698.398.598.698.698.598.398.197.997.597.296.896.395.895.394.894.293.692.992.35096.997.898.198.298.298.198.097.897.697.396.996.696.195.795.294.794.193.592.992.35596.297.297.697.797.897.797.697.497.296.996.696.395.995.595.094.594.093.592.992.36095.596.697.097.297.397.297.197.096.896.696.396.095.695.394.894.493.993.492.892.36594.795.896.396.596.696.796.696.596.396.195.995.695.395.094.694.293.893.392.892.37093.995.095.595.896.096.096.095.995.895.795.595.295.094.794.494.093.693.292.792.37593.194.194.795.095.295.395.395.395.295.195.094.894.694.394.193.893.493.192.792.38092.593.393.894.194.494.594.694.694.694.594.494.394.193.993.793.593.292.992.692.38591.992.693.093.393.593.793.893.893.893.893.893.793.693.593.393.293.092.792.592.39091.692.092.392.592.792.993.093.093.193.193.193.193.093.092.992.892.792.692.492.39591.691.891.992.092.192.292.392.392.492.492.492.492.492.492.492.492.492.392.392.39892.092.092.192.192.192.192.292.292.292.292.292.292.292.392.392.392.392.392.392.351015202530354045505560657075808590951003099.399.599.699.699.599.499.299.098.898.598.197.797.396.996.495.995.394.794.193.53598.999.299.499.499.399.299.198.998.698.398.097.697.296.896.395.895.394.794.193.54098.498.999.199.199.199.098.998.798.598.297.997.597.196.796.295.795.294.794.193.54597.998.598.898.898.898.798.698.598.398.097.797.397.096.696.195.695.194.694.193.55097.498.198.498.598.598.498.398.298.097.797.597.196.896.496.095.595.194.694.093.55596.797.697.998.198.198.198.097.997.797.497.296.996.696.295.995.495.094.594.093.56096.297.197.597.697.797.797.697.597.397.196.996.696.496.095.795.394.994.594.093.56595.596.496.997.197.297.297.197.096.996.796.696.396.195.895.595.194.894.493.993.57094.995.796.296.496.696.696.696.596.596.396.296.095.895.595.294.994.694.393.993.57594.295.095.495.795.996.096.096.095.995.995.795.695.495.295.094.794.594.293.893.58093.594.294.795.095.295.395.495.495.495.395.395.195.094.994.794.594.394.093.893.58593.193.694.094.394.594.694.794.794.894.794.794.694.694.594.494.294.193.993.793.59092.893.193.493.693.893.994.094.194.194.194.194.194.194.094.093.993.893.793.693.59592.893.093.193.293.393.393.493.593.593.593.693.693.693.693.693.693.693.693.593.59893.293.293.393.393.393.393.493.493.493.493.493.493.593.593.593.593.593.593.593.5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.00-inches of Retention for Zone 4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.75-inches of Retention for Zone 451015202530354045505560657075808590951003099.499.699.699.699.699.599.499.299.098.898.598.297.897.497.096.596.195.695.094.53599.199.499.599.599.499.499.299.198.998.798.498.197.797.396.996.596.095.595.094.54098.799.199.299.399.299.299.198.998.798.598.297.997.697.296.896.496.095.595.094.54598.298.898.999.099.098.998.898.798.598.398.197.897.597.196.896.395.995.595.094.55097.798.498.698.798.798.798.698.598.398.197.997.697.397.096.696.395.995.495.094.55597.298.098.298.498.498.498.398.298.197.997.697.497.196.896.596.295.895.494.994.56096.797.597.898.098.098.098.097.997.797.697.497.296.996.796.496.095.795.394.994.56596.296.997.397.597.697.697.697.597.497.297.196.996.796.496.295.995.695.294.994.57095.696.496.897.097.197.197.197.197.096.996.796.696.496.296.095.795.495.194.894.57595.095.796.196.496.596.696.696.696.596.596.496.296.195.995.795.595.395.094.894.58094.595.195.595.795.996.096.096.196.096.095.995.995.895.695.595.395.194.994.794.58594.094.594.895.195.295.495.495.595.595.595.595.495.495.395.295.194.994.894.794.59093.894.194.394.594.694.894.894.994.995.095.095.094.994.994.994.894.794.794.694.59593.894.094.194.294.294.394.494.494.494.594.594.594.594.594.594.594.594.594.594.59894.294.294.294.394.394.394.394.494.494.494.494.494.494.594.594.594.594.594.594.551015202530354045505560657075808590951003099.599.799.799.799.799.699.599.499.299.098.898.598.297.897.597.196.796.295.895.33599.299.599.599.699.599.599.499.299.198.998.798.498.197.897.497.096.696.295.895.34098.999.299.499.499.499.399.299.198.998.898.598.398.097.797.397.096.696.295.795.34598.598.999.199.299.299.199.098.998.898.698.498.297.997.697.396.996.596.295.795.35098.098.698.898.998.998.998.898.798.698.498.298.097.797.597.296.896.596.195.795.35597.698.398.598.698.698.698.698.598.498.298.097.897.697.397.096.796.496.195.795.36097.297.898.198.398.398.398.398.298.198.097.897.697.497.296.996.696.396.095.795.36596.797.497.797.997.998.097.997.997.897.797.597.497.297.096.796.596.295.995.695.37096.296.997.297.497.597.697.597.597.497.397.297.196.996.896.696.396.195.995.695.37595.796.396.796.997.097.197.197.197.097.096.996.896.796.596.496.296.095.895.595.38095.395.896.196.396.596.596.696.696.696.696.596.496.496.396.196.095.895.795.595.38594.895.295.595.795.996.096.196.196.196.196.196.196.096.095.995.895.795.695.495.39094.694.995.195.295.495.595.595.695.695.795.795.795.795.695.695.695.595.495.495.39594.794.894.995.095.095.195.295.295.295.395.395.395.395.395.395.395.395.395.395.39895.095.095.195.195.195.195.295.295.295.295.295.295.295.395.395.395.395.395.395.3NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.25-inches of Retention for Zone 4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.50-inches of Retention for Zone 451015202530354045505560657075808590951003099.799.799.799.799.799.799.699.599.399.299.098.798.598.297.997.597.296.896.496.03599.399.599.699.699.699.699.599.499.299.198.998.798.498.197.897.597.196.896.496.04099.099.399.499.599.599.499.399.299.199.098.898.698.398.197.897.497.196.796.496.04598.799.199.299.399.399.399.299.199.098.898.798.498.298.097.797.497.196.796.496.05098.398.899.099.199.199.099.098.998.898.798.598.398.197.897.697.397.096.796.396.05598.098.598.798.898.898.898.898.798.698.598.398.197.997.797.597.296.996.696.396.06097.698.198.498.598.598.598.598.598.498.398.198.097.897.697.497.196.996.696.396.06597.197.798.098.298.298.298.298.298.198.097.997.797.697.497.297.096.896.596.396.07096.797.397.697.897.997.997.997.997.897.797.697.597.497.297.196.996.796.596.296.07596.396.897.197.397.497.597.597.597.597.497.397.297.197.096.996.796.696.496.296.08095.996.496.696.897.097.097.197.197.197.097.096.996.996.896.796.696.496.396.196.08595.695.996.196.396.496.596.696.696.796.796.696.696.696.596.596.496.396.296.196.09095.395.695.795.996.096.196.196.296.296.396.396.396.396.296.296.296.196.196.096.09595.495.595.695.695.795.895.895.895.995.995.996.096.096.096.096.096.096.096.096.09895.795.795.795.895.895.895.895.895.995.995.995.995.995.995.995.995.996.096.096.051015202530354045505560657075808590951003099.799.899.899.899.899.899.799.699.599.399.199.098.798.598.297.997.697.396.996.53599.599.699.799.799.799.799.699.599.499.299.198.998.798.498.297.997.697.296.996.54099.299.499.599.699.699.599.599.499.399.199.098.898.698.498.197.897.597.296.996.54598.999.299.499.499.499.499.399.299.199.098.998.798.598.398.097.897.597.296.996.55098.699.099.199.299.299.299.199.199.098.998.798.698.498.297.997.797.497.196.896.55598.298.798.999.099.099.098.998.998.898.798.698.498.298.197.897.697.497.196.896.56097.998.498.698.798.898.898.798.798.698.598.498.398.197.997.797.597.397.196.896.56597.698.098.398.498.598.598.598.498.498.398.298.197.997.897.697.497.297.096.896.57097.197.697.998.198.198.298.298.298.198.198.097.997.797.697.597.397.196.996.796.57596.897.297.597.797.897.897.997.897.897.897.797.697.597.497.397.297.096.996.796.58096.496.897.197.397.497.497.597.597.597.497.497.397.397.297.197.096.996.896.796.58596.296.596.796.896.997.097.097.197.197.197.197.197.097.096.996.996.896.796.696.59095.996.196.396.496.596.696.696.796.796.796.896.896.896.796.796.796.796.696.696.59596.096.196.196.296.396.396.496.496.496.596.596.596.596.596.596.596.596.596.596.5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.75-inches of Retention for Zone 4NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 4.00-inches of Retention for Zone 451015202530354045505560657075808590951003083.080.874.167.060.755.350.746.843.440.437.835.533.531.730.128.627.326.125.024.03577.377.472.065.659.854.750.246.443.140.237.635.433.431.630.028.627.326.125.024.04071.373.569.463.958.653.849.645.942.739.937.435.233.331.530.028.527.326.125.024.04565.369.366.561.957.252.848.845.342.339.637.135.033.131.429.928.527.226.025.024.05059.664.863.459.655.551.647.944.741.739.236.834.832.931.329.828.427.226.025.024.05554.060.259.957.153.750.246.943.941.138.736.534.532.731.129.628.327.126.024.924.06049.055.756.354.451.648.645.642.940.438.136.034.132.430.929.528.227.025.924.924.06544.551.052.551.449.346.844.241.839.537.435.533.732.130.629.328.126.925.924.924.07040.546.548.548.146.644.742.640.538.436.634.833.231.730.329.127.926.825.824.924.07537.042.044.244.543.742.240.638.937.235.534.032.531.229.928.827.726.725.724.824.08033.937.839.840.540.239.438.236.935.634.232.931.730.529.428.427.426.525.624.824.08531.133.835.436.136.335.935.334.533.532.531.530.529.628.727.827.026.225.424.724.09028.730.231.231.832.032.031.731.330.830.229.629.028.327.627.026.425.725.124.624.09526.627.027.427.627.727.727.727.627.427.226.926.626.326.025.725.425.024.724.324.09825.725.725.725.725.725.625.625.525.425.325.225.125.024.824.724.624.424.324.124.051015202530354045505560657075808590951003088.689.987.984.580.576.472.368.565.161.958.956.253.751.449.347.345.543.842.240.83584.186.885.682.879.375.471.668.064.661.558.756.053.651.349.247.345.543.842.240.84079.383.382.980.877.874.370.767.364.161.158.355.853.451.149.147.245.443.842.240.84574.479.580.078.576.072.969.666.563.460.657.955.453.151.048.947.145.343.742.240.85069.775.576.876.073.971.368.465.562.660.057.455.052.850.748.847.045.343.742.240.85565.271.473.473.171.769.566.964.361.759.256.954.652.550.448.646.845.243.642.140.86061.067.269.770.169.267.465.363.060.658.456.254.052.050.148.346.645.043.542.140.86557.163.165.966.866.465.163.361.459.457.355.353.451.549.748.046.444.943.442.140.87053.659.262.063.263.362.561.259.657.956.154.352.650.949.247.646.144.743.342.040.87550.755.558.159.559.859.458.657.456.154.653.151.650.148.647.145.844.443.241.940.88048.352.054.355.556.056.055.654.853.952.851.650.349.047.846.545.344.143.041.840.88546.248.750.551.552.052.252.151.751.150.449.648.647.646.745.644.643.742.741.740.89044.245.646.747.447.948.148.248.147.847.446.946.445.745.144.443.743.042.241.540.89542.543.043.443.743.944.044.144.144.043.943.743.543.243.042.742.342.041.641.240.89842.142.242.242.242.242.242.242.142.142.041.941.841.741.641.541.441.241.140.940.8NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.25-inches of Retention for Zone 5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 551015202530354045505560657075808590951003091.493.092.490.888.585.983.080.177.274.471.669.166.764.462.360.258.356.554.853.23587.790.590.489.287.284.882.279.576.773.971.368.866.564.262.160.258.356.554.853.24083.887.688.187.285.783.681.278.776.073.470.968.566.264.162.060.058.256.454.853.24580.084.485.685.183.982.280.077.775.372.870.468.165.963.861.859.958.156.454.753.25076.081.182.782.882.080.578.776.674.472.169.867.765.663.561.659.858.056.354.753.25572.377.779.780.279.878.777.275.373.371.269.267.165.163.261.359.657.956.254.753.26068.974.276.577.477.476.675.473.972.170.268.366.464.662.861.059.357.756.154.653.26565.570.773.374.574.774.473.572.270.769.167.465.764.062.360.759.157.556.054.653.27062.667.470.071.371.971.871.270.369.167.766.364.763.261.760.258.757.355.954.553.27560.164.266.768.168.868.968.768.067.166.164.963.662.360.959.658.357.055.754.453.28058.061.363.564.865.565.965.865.464.864.063.162.161.160.058.957.756.655.454.353.28556.458.860.461.562.262.562.662.462.061.661.060.359.558.757.957.056.055.154.153.29055.156.457.458.158.658.959.059.058.958.758.458.057.657.156.555.955.354.653.953.29553.754.254.654.955.255.455.555.655.655.555.555.355.255.054.754.554.253.953.553.29853.954.054.054.154.154.154.154.154.154.054.053.953.953.853.753.653.553.453.353.251015202530354045505560657075808590951003093.594.894.693.792.390.688.786.584.382.179.877.675.473.371.369.467.565.864.162.53590.292.692.992.391.189.687.885.983.881.679.577.375.273.171.269.367.565.764.062.54087.090.291.090.789.788.486.885.083.181.179.077.074.972.971.069.167.465.764.062.54583.787.688.888.888.187.185.784.182.380.478.576.574.672.770.869.067.365.664.062.55080.584.886.486.886.485.584.483.081.479.777.976.074.272.370.568.867.165.564.062.55577.382.083.984.584.483.983.081.880.378.877.175.473.772.070.368.667.065.463.962.56074.479.181.182.082.282.081.380.379.277.876.374.773.171.569.968.366.865.363.962.56571.876.178.379.579.979.979.578.777.876.675.373.972.471.069.568.066.665.263.862.57069.273.275.576.877.477.677.476.976.275.374.272.971.670.369.067.766.365.063.762.57567.070.672.874.174.875.175.174.874.373.672.771.770.769.568.467.266.064.863.662.58065.368.170.071.372.172.572.672.572.271.771.070.369.468.567.666.665.664.563.562.58563.966.067.568.669.369.769.969.969.869.569.068.567.967.266.565.865.064.263.362.59063.064.365.265.966.466.867.067.167.066.966.766.466.165.765.264.764.263.663.162.59562.362.863.163.463.663.863.964.064.164.164.164.063.963.863.663.463.263.062.762.59862.662.762.862.862.962.962.962.962.962.962.962.962.962.862.862.762.762.662.562.5Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention for Zone 5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 5NDCIACNPercent DCIA51015202530354045505560657075808590951003095.196.196.095.494.593.391.990.488.786.985.183.381.579.777.876.174.472.771.169.53592.394.294.594.293.492.491.189.788.286.584.883.081.279.577.776.074.372.671.169.54089.392.092.892.892.291.390.288.987.585.984.382.680.979.277.575.874.272.671.069.54586.589.890.991.290.990.189.288.086.785.383.882.280.678.977.375.774.172.571.069.55083.887.588.989.589.388.888.087.085.884.583.181.780.278.677.075.573.972.471.069.55581.285.186.887.587.587.286.685.884.883.782.481.179.778.276.775.373.872.370.969.56078.682.784.685.485.685.585.184.583.782.781.680.479.177.876.475.073.672.270.969.56576.480.382.283.183.683.783.583.182.481.680.779.678.577.276.074.773.472.170.869.57074.377.779.780.881.581.781.781.480.980.379.578.777.776.675.474.373.171.970.769.57572.475.477.378.579.279.679.779.679.378.878.277.576.775.874.873.872.771.770.669.58070.873.375.176.276.977.477.677.677.477.176.776.275.574.874.073.272.371.470.569.58569.871.672.973.974.675.075.375.475.475.275.074.674.173.673.072.471.771.070.369.59069.270.371.171.872.372.672.973.073.173.172.972.772.572.271.871.471.070.570.069.59568.969.369.770.070.270.470.570.670.770.770.770.770.670.570.470.370.169.969.769.59869.469.569.669.669.769.769.869.869.869.869.869.869.869.869.769.769.769.669.669.551015202530354045505560657075808590951003096.397.197.096.595.995.093.992.891.590.288.787.285.784.182.681.179.578.076.575.13593.995.495.695.495.094.293.292.291.089.788.386.985.483.982.481.079.578.076.575.14091.393.594.194.293.993.392.491.590.489.287.986.585.183.782.380.879.477.976.575.14588.891.592.592.892.792.291.590.689.688.687.486.184.883.482.080.679.277.876.475.15086.489.690.891.391.491.090.489.788.887.986.885.684.483.181.880.479.177.776.475.15584.287.589.089.789.889.689.288.687.987.186.185.083.982.781.580.278.977.676.375.16081.985.487.187.988.288.187.987.486.986.285.384.483.382.281.179.978.777.576.375.16580.083.485.186.086.486.586.486.185.785.184.483.682.781.780.779.678.577.476.275.17078.381.383.084.084.584.884.884.784.483.983.482.781.981.180.279.378.277.276.175.17576.679.380.981.982.683.083.183.182.982.682.281.681.080.479.678.877.977.076.075.18075.377.478.979.980.681.181.381.481.381.180.880.480.079.578.978.277.576.775.975.18574.476.077.278.078.779.179.479.579.579.579.379.178.878.478.077.576.976.375.775.19073.974.975.776.376.877.177.477.677.777.777.777.677.477.276.976.676.375.975.575.19574.074.474.775.075.275.475.675.775.875.975.975.975.975.875.775.675.575.475.275.19874.874.975.075.075.175.175.175.275.275.275.275.275.275.275.275.275.275.175.175.1NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.50-inches of Retention for Zone 5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.25-inches of Retention for Zone 551015202530354045505560657075808590951003097.297.797.797.496.896.295.494.493.592.491.290.088.787.486.184.883.482.180.879.43595.196.396.696.496.095.594.793.993.091.990.889.788.587.285.984.683.382.080.779.44092.994.795.295.295.094.694.093.292.491.490.489.388.287.085.784.583.282.080.779.44590.793.093.794.094.093.793.292.591.790.989.988.987.886.785.584.383.181.980.779.45088.591.292.292.792.892.692.291.791.090.289.488.487.486.485.384.183.081.880.679.45586.589.490.791.391.591.591.290.790.289.588.787.987.086.085.083.982.881.780.679.46084.687.589.089.890.290.290.089.689.288.688.087.386.485.684.683.682.681.680.579.46582.985.887.488.388.688.788.788.588.187.787.286.685.885.184.283.382.481.480.579.47081.484.185.686.587.087.287.287.287.086.686.285.785.184.583.783.082.181.380.479.47580.282.483.884.785.285.685.885.885.785.585.284.884.383.883.282.581.881.180.379.48078.980.882.082.983.584.084.284.384.384.284.083.783.483.082.582.081.480.880.179.48578.179.580.581.381.982.382.682.882.882.882.782.582.382.181.781.481.080.580.079.49077.878.679.379.980.480.780.981.181.281.381.381.281.181.080.980.680.480.179.879.49578.078.478.778.979.179.379.579.679.779.879.979.979.979.979.979.879.879.779.679.49879.079.079.179.279.279.379.379.479.479.479.579.579.579.579.579.579.579.579.579.451015202530354045505560657075808590951003097.898.398.398.097.597.096.495.694.893.993.092.091.089.988.787.686.485.284.082.93596.297.197.397.196.896.395.895.194.493.692.791.790.789.788.687.486.385.284.082.94094.395.796.196.195.995.695.294.593.893.192.391.490.489.488.487.386.285.184.082.94592.394.294.895.094.994.894.493.993.392.691.891.090.189.288.287.186.185.083.982.95090.392.593.493.893.993.893.693.192.692.091.390.589.788.887.987.086.084.983.982.95588.490.992.092.692.892.892.692.391.891.390.790.089.388.587.686.785.884.883.982.96086.889.390.691.391.691.791.691.391.090.690.089.488.888.187.386.585.684.783.882.96585.387.789.190.090.490.590.590.390.089.789.388.888.287.686.986.285.484.683.782.97083.986.387.788.588.989.289.289.189.088.888.488.087.687.186.585.885.184.483.782.97582.984.986.287.087.487.787.987.987.987.787.587.286.986.486.085.484.884.283.682.98081.983.584.685.485.986.386.586.786.786.686.586.386.185.785.484.984.584.083.482.98581.182.383.384.084.584.985.185.385.485.485.485.385.184.984.784.484.183.783.382.99080.981.782.382.883.283.583.884.084.184.284.284.284.184.083.983.883.683.483.182.99581.381.681.982.182.382.582.682.882.983.083.083.183.183.183.183.183.183.082.982.99882.382.382.482.582.582.682.682.782.782.782.882.882.882.882.982.982.982.982.982.9NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 1.75-inches of Retention for Zone 5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.00-inches of Retention for Zone 551015202530354045505560657075808590951003098.298.798.698.598.197.697.196.595.995.194.393.592.691.790.789.788.787.786.685.63597.097.797.897.797.597.096.696.195.494.794.093.292.491.590.689.688.687.686.685.64095.396.596.996.896.696.396.095.595.094.393.692.992.191.390.489.588.587.686.685.64593.695.295.795.895.795.695.394.994.493.993.292.691.891.090.289.388.487.586.585.65091.993.794.594.794.894.894.694.393.893.392.892.191.590.790.089.188.387.486.585.65590.192.293.293.693.893.993.893.593.292.792.291.791.190.489.788.988.187.386.585.66088.690.891.992.592.892.992.992.792.492.091.691.190.690.089.488.788.087.286.485.66587.289.490.691.391.791.991.991.891.691.390.990.690.189.689.088.487.887.186.385.67086.088.189.390.190.690.890.890.890.690.490.289.989.589.188.688.187.586.986.385.67585.187.088.188.889.389.589.689.789.689.689.489.188.988.588.287.787.286.786.285.68084.585.886.887.587.988.288.488.688.688.688.588.388.187.987.687.386.986.586.185.68583.884.885.686.186.687.087.287.487.587.587.587.587.487.287.086.886.586.385.985.69083.584.284.785.285.685.886.186.286.486.586.586.586.586.586.486.386.186.085.885.69583.984.284.584.784.985.185.285.385.485.585.685.685.785.785.785.785.785.785.685.69884.985.085.185.185.285.285.385.385.485.485.485.585.585.585.585.585.685.685.685.651015202530354045505560657075808590951003098.698.998.998.898.698.297.797.296.796.095.394.693.993.192.391.490.689.688.787.83597.698.198.398.298.097.697.296.896.395.795.094.493.792.992.191.390.589.688.787.84096.297.197.497.497.397.096.796.395.995.394.794.193.492.792.091.290.489.588.787.84594.796.096.596.596.596.396.095.895.494.994.393.893.292.591.891.090.389.588.687.85093.294.895.395.695.695.595.495.294.894.493.993.492.892.291.690.990.189.488.687.85591.693.494.294.594.794.794.794.594.293.993.493.092.591.991.390.790.089.388.587.86090.192.093.093.593.893.993.993.893.593.292.992.592.091.691.090.489.889.288.587.86588.990.891.892.492.893.093.193.092.892.692.392.091.691.290.790.289.689.188.487.87087.889.690.791.491.892.192.192.192.091.891.691.491.190.790.389.989.488.988.487.87586.988.689.690.390.891.091.191.191.191.090.990.790.590.289.989.589.288.788.387.88086.487.788.689.289.689.990.090.190.290.290.190.089.889.789.489.288.988.588.287.88585.986.987.588.088.488.788.989.189.289.389.389.289.289.188.988.888.688.388.187.89085.686.286.787.187.587.888.088.188.388.488.488.488.488.488.488.388.288.187.987.89586.186.486.686.887.087.187.387.487.587.687.787.787.887.887.887.887.887.887.887.89887.187.287.287.387.387.487.487.587.587.687.687.687.787.787.787.787.787.887.887.8Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention for Zone 5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.25-inches of Retention for Zone 5NDCIACNPercent DCIA51015202530354045505560657075808590951003098.999.199.199.198.998.698.297.897.396.796.295.594.994.293.592.892.091.290.489.63598.198.598.698.698.498.197.797.496.996.495.995.394.794.193.492.791.991.290.489.64097.097.797.997.997.897.597.296.996.596.195.695.094.593.993.292.591.891.190.389.64595.696.797.197.197.196.996.696.496.195.795.294.794.293.693.092.491.791.090.389.65094.395.696.196.396.396.296.095.895.695.394.994.493.993.492.892.291.691.090.389.65592.994.495.095.395.495.495.495.395.194.894.494.093.693.192.692.191.590.990.289.66091.693.293.994.394.694.794.794.694.594.293.993.693.292.892.391.891.390.890.289.66590.392.092.893.493.793.994.093.993.893.693.493.192.892.492.091.691.190.690.189.67089.390.991.892.492.893.193.293.293.193.092.892.692.392.091.791.390.990.590.189.67588.589.990.991.591.992.292.392.492.392.292.192.091.891.691.391.090.790.490.089.68088.189.290.090.691.091.291.491.591.591.591.491.491.391.190.990.790.590.289.989.68587.888.689.289.690.090.290.490.590.690.790.790.790.790.690.590.390.290.089.889.69087.588.088.488.889.189.389.589.789.889.990.090.090.090.090.089.989.989.889.789.69587.988.288.488.688.788.989.089.189.289.389.489.489.589.589.589.689.689.689.689.69888.988.989.089.089.189.189.289.289.389.389.489.489.489.589.589.589.589.589.689.651015202530354045505560657075808590951003099.199.399.399.299.198.998.698.297.897.396.896.395.795.194.593.893.292.591.891.03598.498.898.998.898.798.598.297.897.597.096.696.195.594.994.493.793.192.491.791.04097.598.198.398.398.298.097.797.497.196.796.395.895.394.894.293.693.092.491.791.04596.497.397.697.697.697.497.296.996.796.496.095.595.194.694.093.592.992.391.791.05095.296.396.796.996.996.896.696.496.296.095.695.294.894.393.993.492.892.291.691.05594.095.395.896.096.196.196.095.995.795.595.294.994.594.193.693.292.792.291.691.06092.894.194.895.195.395.495.495.395.295.094.894.594.193.893.493.092.592.191.691.06591.793.093.894.294.594.694.794.794.694.594.394.093.893.593.192.892.491.991.591.07090.792.092.893.393.793.994.094.194.093.993.893.693.393.192.892.592.291.891.491.07589.991.191.992.592.993.293.393.393.393.393.293.092.992.792.592.392.091.791.491.08089.490.591.291.792.192.392.592.692.692.692.592.592.492.392.192.091.891.591.391.08589.390.090.590.991.391.591.691.891.891.991.991.991.991.891.791.691.591.491.291.09089.189.689.990.290.590.790.991.091.191.291.391.391.391.491.391.391.391.291.191.09589.589.789.990.090.290.390.490.590.690.790.890.890.990.991.091.091.091.091.091.09890.390.490.590.590.690.690.690.790.790.890.890.890.990.990.990.991.091.091.091.0NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.00-inches of Retention for Zone 5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 2.75-inches of Retention for Zone 551015202530354045505560657075808590951003099.399.499.599.499.399.198.998.698.297.897.496.996.495.895.394.794.193.592.992.23598.799.099.199.099.098.898.598.297.997.597.196.796.295.795.294.694.193.592.992.24098.098.498.698.698.598.498.197.897.597.296.996.596.095.595.094.594.093.492.892.24597.097.798.098.098.097.897.797.497.196.996.696.295.895.394.994.493.993.492.892.25096.096.997.397.497.497.397.196.996.796.596.395.995.595.194.794.393.893.392.892.25594.996.096.496.696.796.796.696.496.396.195.995.695.394.994.594.193.793.292.792.26093.995.095.595.896.096.096.095.995.895.795.595.294.994.694.393.993.593.192.792.26592.894.094.695.095.295.395.495.495.395.295.094.894.694.394.093.793.493.092.692.27091.993.093.794.194.494.694.894.894.894.794.694.494.294.093.893.593.292.992.692.27591.192.292.993.493.794.094.194.294.294.194.194.093.893.693.593.393.092.892.592.28090.691.592.292.793.093.393.493.593.593.693.593.493.493.393.293.092.892.692.492.28590.591.291.792.092.392.592.792.892.992.992.992.992.992.992.892.792.692.592.492.29090.590.991.291.591.791.992.092.192.292.392.492.492.492.592.492.492.492.392.392.29590.790.991.191.291.491.591.691.791.891.992.092.092.192.192.192.292.292.292.292.29891.691.691.791.791.891.891.891.991.992.092.092.092.192.192.192.192.292.292.292.251015202530354045505560657075808590951003099.599.699.699.599.499.399.198.998.598.297.897.496.996.596.095.494.994.493.893.23598.999.299.299.299.199.098.898.698.397.997.697.296.896.395.895.494.994.393.893.24098.398.798.898.898.898.798.598.297.997.697.397.096.696.295.795.394.894.393.893.24597.598.198.398.498.398.298.097.897.697.397.196.896.496.095.695.194.794.293.793.25096.697.497.797.897.897.797.697.497.297.096.796.596.195.895.495.094.694.293.793.25595.796.697.097.297.297.297.196.996.896.696.496.295.995.695.294.994.594.193.793.26094.895.896.296.496.596.596.596.496.396.296.195.995.695.395.094.794.494.093.693.26593.894.895.495.795.895.995.995.995.995.895.795.595.395.194.894.594.293.993.693.27093.094.094.594.995.195.395.495.495.495.495.395.195.094.894.594.394.193.893.593.27592.293.193.794.194.494.794.894.994.994.994.894.794.694.494.394.193.993.793.593.28091.792.593.193.593.894.194.294.394.394.394.394.394.294.194.093.993.793.693.493.28591.592.192.693.093.293.493.693.793.793.893.893.893.893.793.793.693.693.593.393.29091.691.992.292.592.792.993.093.193.293.293.393.393.493.493.493.493.493.393.393.29591.992.092.292.392.492.592.692.792.892.992.993.093.193.193.193.293.293.293.293.29892.692.692.792.792.892.892.992.992.993.093.093.093.193.193.193.193.293.293.293.2NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.25-inches of Retention for Zone 5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.50-inches of Retention for Zone 551015202530354045505560657075808590951003099.799.799.799.699.599.499.399.198.898.598.297.897.497.096.596.195.695.194.694.13599.199.399.499.399.399.299.098.898.698.398.097.697.396.996.496.095.595.194.694.14098.698.999.099.099.098.998.798.598.398.097.797.497.196.796.395.995.495.094.594.14597.998.498.698.698.698.598.498.298.097.797.597.296.996.596.295.895.495.094.594.15097.197.898.198.298.298.198.097.897.697.497.296.996.796.496.095.795.394.994.594.15596.497.197.597.697.697.697.597.497.297.096.996.796.496.295.995.595.294.894.594.16095.596.496.896.997.097.097.096.996.896.796.696.496.295.995.795.495.194.794.494.16594.795.596.096.396.496.596.496.496.496.396.296.195.995.795.595.294.994.794.494.17093.994.795.395.595.795.895.995.995.995.995.995.795.695.495.295.094.894.694.394.17593.294.094.594.895.195.295.495.595.595.595.495.495.395.195.094.894.794.594.394.18092.693.393.894.294.594.794.995.095.095.095.095.094.994.894.794.694.594.494.294.18592.593.093.493.894.094.294.394.494.594.594.594.694.594.594.494.494.394.394.294.19092.692.993.193.393.593.793.893.994.094.194.194.194.294.294.294.294.294.194.194.19592.993.093.193.293.393.493.593.693.793.793.893.893.993.994.094.094.094.094.094.19893.593.593.693.693.693.793.793.893.893.893.993.993.993.994.094.094.094.094.094.151015202530354045505560657075808590951003099.899.899.799.799.699.599.499.299.098.898.598.197.897.497.096.696.295.795.294.83599.399.599.599.599.499.399.299.098.898.698.398.097.797.396.996.596.195.795.294.84098.899.199.299.299.199.199.098.898.698.398.197.897.597.296.896.496.095.695.294.84598.398.698.898.898.898.898.698.598.398.197.897.697.397.096.796.396.095.695.294.85097.698.198.498.498.598.498.398.198.097.897.597.397.196.896.596.295.995.595.194.85596.997.697.898.098.097.997.997.797.697.497.397.196.996.796.496.195.895.495.194.86096.296.997.297.497.597.597.497.397.297.197.096.896.796.496.296.095.795.495.194.86595.596.296.696.896.996.996.996.996.896.896.796.696.496.296.095.895.695.395.094.87094.795.495.996.296.396.496.496.496.496.496.396.396.196.095.895.695.495.295.094.87594.194.895.295.595.795.895.996.096.096.096.095.995.895.795.695.595.395.195.094.88093.594.194.594.995.195.395.495.595.695.695.695.695.595.495.495.395.195.094.994.88593.393.894.194.494.794.895.095.195.195.295.295.295.295.295.195.195.094.994.994.89093.493.793.994.194.394.494.594.694.794.894.894.894.894.994.994.994.894.894.894.89593.793.893.994.094.194.294.394.394.494.594.594.694.694.694.794.794.794.794.894.89894.294.394.394.394.494.494.494.594.594.594.694.694.694.694.794.794.794.794.894.8NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 3.75-inches of Retention for Zone 5NDCIACNPercent DCIAMean Annual Mass Removal Efficiencies for 4.00-inches of Retention for Zone 5