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 Bureau of Watershed Management/Nonpoint 

Source Management of the Florida Department of Environmental Protection for their 

assistance in funding and administration of this project. A special thank you is also given 

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

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

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

various water management districts who reviewed 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 Efficiencies for Typical Stormwater 

 Management Systems 5-15 

 5.2 Performance Efficiency of Existing 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 for 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 Characterization 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 Characteristics from Light Industrial Stormwater 

 Studies 4-18 

4-10 Summary of Mean Stormwater Characteristics 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 Characteristics from Citrus Land Use Stormwater 

 Studies 4-21 

4-13 Summary of Mean Stormwater Characteristics 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 Characteristics from Undeveloped/Rangeland/ 

 Forest Stormwater Studies 4-23 

4-16 Summary of Mean Stormwater Characteristics 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 Hydrologic Soil Group Classifications 4-28 

4-19 Listing of NCDC Hourly Precipitation 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 Used 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 Retention Systems Based on Selected Research 

 Studies in Florida 5-5 

5-2 Treatment Efficiencies for Wet Detention 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 Efficiencies 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 Used 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 Typical 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 Values 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 Efficiencies 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 Efficiencies for 0.5 inch of Dry Retention for 

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

5-7 Calculated Annual Mass Removal Efficiencies 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 Required 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 State of Florida has been subject to regulation 

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

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

level by the Florida Department of Environmental 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 Outstanding 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 pollutant 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 Florida, 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 Stormwater 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 changes 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 evaluate existing design criteria for discharges to 

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

performed to quantify stormwater design criteria 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 constituents are commonly present in stormwater 

runoff, such as suspended solids, BOD, and heavy 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 stormwater 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 treatment 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 management 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 ERD. 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 Section 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 discussion of the performance efficiency of existing 

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

stormwater management design criteria are given 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 stormwater within the State of Florida has been 

subject to regulation to prevent pollution of Waters 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 districts, 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 use and reuse, water transfer, water quality, surface 

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

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

Program”. Paragraph 2a establishes the primary 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 after 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 designated 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 with appropriate soils and geology; to maintain 

the appropriate salinity regimes in estuaries needed 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 Department 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 stormwater management program by water management 

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

the State Stormwater Management Program to water 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 Management Regulation”, establishes guidelines 

for regulation of surface water management systems. 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 with 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 stormwater management systems designed within the 

State of Florida must “achieve at least 80% reduction of the annual average load of pollutants that 

would cause or contribute to violations 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 rebuttable 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 the minimum water quality levels which are necessary 

to protect the designated uses of a waterbody. 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 Harvesting; (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 -Navigation, Utility and Industrial Use. Water quality 

classifications are arranged in order of the degree 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 water 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 pollutants that would cause or contribute to violations of state water 

quality standards. 
FDEP \ STORMWATER TREATMENT REPORT 

2-3 

 Criteria for stormwater management systems 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 systems 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 outlined 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 retention 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. Specific design criteria are included for filter systems 

which includes guidelines on permeability, percent organic 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 developments such as single-family units, duplexes, 

triplexes, or quadruplexes which are 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 five 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 tributaries and rivers which ultimately discharge into the 

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

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

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

Southwest Florida Water Management District includes watersheds which discharge to tributaries 

and rivers which ultimately reach the west coast 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 Detention1 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 unit, 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-family residential projects, 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 functioning 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 Water Management – Stormwater Management Practices, 

Chapter 6. 
FDEP \ STORMWATER TREATMENT REPORT 

2-5 

 Figure 2-1. Approximate Boundaries for Water 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 management districts which have implemented a 

Comprehensive Surface Water Management Program 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 delegated responsibility for the Stormwater 

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

Florida Water Management Districts. Each of these 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 minimum 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 regulation of stormwater discharges to the Northwest 

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

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

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

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

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

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

Johns River, Suwannee River, Southwest Florida, 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 within 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 from full volume recovery in less than 72 hours in 

the St. Johns River, Suwannee River, and Southwest 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 District 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 are 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 referenced by the St. Johns River, Southwest 

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

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

the districts. However, volume recovery requirements 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 Southwest Florida or South Florida Water Management 

Districts. 
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 2-2 

 COMPARISON OF STORMWATER MANAGEMENT SYSTEM DESIGN 

 CRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDA

STORMWATER 

SYSTEM TYPE 

DESIGN 

PARAMETER 

CRITERIA 

St. Johns River Water 

Management District1

Suwannee River Water 

Management District2

Southwest Florida Water 

Management District3

South Florida Water 

Management District4

Retention Treatment 

Volume 

Off-line retention of the first 0.5" of runoff or 1.25" of runoff from the impervious area; whichever is greater 

Retention of the runoff from the first 1" of rainfall 

On-line retention of the runoff from 1" of rainfall 

Retention of the first 0.5" of runoff or 1.25" times the percentage of imperviousness; whichever is greater 

 On-line retention of the first 1" of 

runoff; or 1.25" of runoff from the impervious area plus 0.5” of runoff from entire basin; whichever is greater 

If project discharges to sink, then off-line or on-line retention of the runoff from the first 2" of rainfall 

If project < 100 ac, on-line retention of 0.5" of runoff 

 On-line retention that percolates 

the runoff from the 3-year/1-hour storm 

 Off-line retention of runoff from 

1" of rainfall 

 For projects with <40% 

impervious and only HSG A soils, 

on-line retention from 1" of rainfall or 1.25" of runoff from impervious areas 

 If project < 100 ac, off-line 

retention of 0.5" of runoff 

 Volume 

Recovery 

Provide design capacity in 72 hours using percolation, evaporation, or evapotranspiration 

Provide design capacity in 72 hours using percolation, evaporation, or evapotranspiration 

Treatment volume recovered in < 72 hours 

No more than half of treatment volume in 24 hours 

 Vegetation Stabilized with pervious material 

or permanent vegetative cover 

 Not Referenced Not Referenced Not Referenced 

References: 1. Chapter 40C-42 FAC - Environmental Resource Permits: Regulation of Stormwater Management Systems  2. Chapter 40B-4 - Regulations  3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District  4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

2-7
 TABLE 2-2 -- CONTINUED 

 COMPARISON OF STORMWATER FDEP \ STORMWATER TREATMENT REPORT 

 MANAGEMENT SYSTEM DESIGN 

 CRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDA

STORMWATER 

SYSTEM TYPE 

DESIGN 

PARAMETER 

CRITERIA 

St. Johns River Water 

Management District1

Suwannee River Water 

Management District2

Southwest Florida Water 

Management District3

South Florida Water 

Management District4

Underdrain 

System 

Treatment 

Volume 

Off-line storage of the first 0.5" of runoff or 1.25" of runoff from impervious area; whichever is greater 

 Not Referenced Not Referenced Not Referenced 

On-line retention of the first 1" of runoff; or 1.25" of runoff from the impervious area plus 0.5” of runoff from entire basin; whichever is greater 

Recovery 

Volume 

Provide design capacity in 72 hours using percolation, evaporation, or evapotranspiration 

 Not Referenced Not Referenced Not Referenced 

Provide at least 2 ft of indigenous soil between pond bottom and underdrain 

 Designed with a safety factor of 2  Vegetation Stabilized with permanent 

vegetative cover 

 Not Referenced Not Referenced Not Referenced 

References: 1. Chapter 40C-42 FAC - Environmental Resource Permits: Regulation of Stormwater Management Systems  2. Chapter 40B-4 - Regulations  3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District  4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

2-8
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 2-2 -- CONTINUED 

 COMPARISON OF STORMWATER MANAGEMENT SYSTEM DESIGN 

 CRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDA

STORMWATER 

SYSTEM TYPE 

DESIGN 

PARAMETER 

CRITERIA 

St. Johns River Water 

Management District1

Suwannee River Water 

Management District2

Southwest Florida Water 

Management District3

South Florida Water 

Management District4

Underground 

Exfiltration 

Treatment 

Volume 

Off-line storage of the first 0.5" of runoff or 1.25" of runoff from the impervious area; whichever is greater 

 Not Referenced Storage of the runoff from the first 

1” of rainfall 

Retention of the first 0.5" of runoff or 1.25" times the percentage of imperviousness; whichever is greater 

On-line retention of the first 1" of runoff; or 1.25" of runoff from the impervious area plus 0.5” of runoff from entire basin; whichever is greater 

If project < 100 acres, storage of 0.5” of runoff 

 Designed with a safety factor of 2 

Volume 

Recovery 

Recover design capacity within 72 hours by percolation only 

 Not Referenced Recover design capacity within 72 

hours by percolation only 

Recover design capacity in 1 hour 

Invert elevation of trench must be > 2 ft above SHWT 

References: 1. Chapter 40C-42 FAC - Environmental Resource Permits: Regulation of Stormwater Management Systems  2. Chapter 40B-4 - Regulations  3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District  4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

2-9
 TABLE 2-2 -- CONTINUED 

 COMPARISON OF STORMWATER FDEP \ STORMWATER TREATMENT REPORT 

 MANAGEMENT SYSTEM DESIGN 

 CRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDA

STORMWATER 

SYSTEM TYPE 

DESIGN 

PARAMETER 

CRITERIA 

St. Johns River Water 

Management District1

Suwannee River Water 

Management District2

Southwest Florida Water 

Management District3

South Florida Water 

Management District4

Wet Detention Treatment 

Volume 

First 1" of runoff or 2.5" of runoff from impervious area; whichever is greater 

Detention of the runoff from the first 1” of rainfall 

First 1" of runoff from watershed First 1" of runoff or 2.5" of runoff 

from impervious area; whichever is greater 

 If project discharges to sink, then 

off-line or on-line detention of the runoff from the first 2” of rainfall 

 Volume 

Recovery 

Bleed-down 50% of treatment volume in 24-30 hours 

Recover design capacity in < 72 hours 

50% in 60 hours; 100% in 120 hours 

50% of treatment volume in 24 hours 

 Residence 

Time 

Minimum 14-day wet season (June-October) 

 Not Referenced Not Referenced Not Referenced 

 Littoral Zone 30% of pond area at NWL Not Referenced Minimum of 35% of pond area, 

concentrated at outfall 

20% of pond area or 2.5% of the pond plus basin area 

 As an alternative to littoral zone: 

(a) 50% additional permanent pool volume; or (b) 0.5" retention pretreatment 

 Pond Depth Mean depth between 2-8 ft Not Referenced Not Referenced Recommended that 25-50% of 

pond area be > 12 ft 

 Maximum depth < 12 ft  Configuration Length:Width > 2:1 Not Referenced Not Referenced > 0.5 acre in size  100 ft minimum width 

References: 1. Chapter 40C-42 FAC - Environmental Resource Permits: Regulation of Stormwater Management Systems  2. Chapter 40B-4 - Regulations  3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District  4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

2-10
 TABLE 2-2 -- CONTINUED 

 COMPARISON OF STORMWATER FDEP \ STORMWATER TREATMENT REPORT 

 MANAGEMENT SYSTEM DESIGN 

 CRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDA

STORMWATER 

SYSTEM TYPE 

DESIGN 

PARAMETER 

CRITERIA 

St. Johns River Water 

Management District1

Suwannee River Water 

Management District2

Southwest Florida Water 

Management District3

South Florida Water 

Management District4

Swales Treatment 

Volume 

Percolate 80% of runoff from 3-hour/1-hour storm 

Percolate 80% of runoff from 3-hour/1-hour storm 

 Not Referenced Not Referenced 

 Volume 

Recovery 

Regain treatment volume in < 72 hours 

Regain treatment volume in < 72 hours 

 Not Referenced Not Referenced 

Dry Detention Use Restriction a. Where HGWT or soil 

 conditions limit use of other  BMPs b. Drainage basin areas < 5 acres 

None Not Referenced None 

Treatment 

Volume 

Off-line detention of the first 1" of runoff or 2.5" of runoff from impervious areas 

Detention of the runoff from the first 1" of rainfall 

 Not Referenced On-line or off-line detention of the 

first 0.75" of runoff or 1.88" times the percentage of imperviousness; whichever is greater 

 If project discharges to sink, then 

off-line or on-line detention of the runoff from the first 2" of rainfall 

 Volume 

Recovery 

Discharge of 50% of treatment volume in 24-30 hours 

Recover design capacity in < 72 hours 

 Not Referenced Recover 50% of treatment volume 

in 24 hours 

 Areas of standing water for no 

more than 3 days 

References: 1. Chapter 40C-42 FAC - Environmental Resource Permits: Regulation of Stormwater Management Systems  2. Chapter 40B-4 - Regulations  3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District  4. Basis of Review for Environmental Resource Permit Applications within the South Florida Water Management District 

 2-11
 TABLE 2-2 -- CONTINUED 

 COMPARISON OF STORMWATER FDEP \ STORMWATER TREATMENT REPORT 

 MANAGEMENT SYSTEM DESIGN 

 CRITERIA FOR WATER MANAGEMENT DISTRICTS IN FLORIDA

STORMWATER 

SYSTEM TYPE 

DESIGN 

PARAMETER 

CRITERIA 

St. Johns River Water 

Management District1

Suwannee River Water 

Management District2

Southwest Florida Water 

Management District3

South Florida Water 

Management District4

Detention 

with Filtration 

Treatment 

Volume 

Offline: first 1” of runoff or 2.5” of runoff from impervious area, whichever is greater

Detention of the runoff from the first 1" of rainfall 

On-line detention of the runoff from 1" of rainfall 

 Not Referenced 

 On-line: additional 0.5” of runoff 

from drainage basin above off-line volume 

If project discharges to sink, then off-line or on-line detention of the runoff from the first 2" of rainfall 

If project < 100 ac, on-line detention of 0.5" of runoff 

 Off-line detention of runoff from 

1" of rainfall

 If project < 100 ac, off-line 

detention of 0.5" of runoff

 Filter System Media washed with <1% silt, clay, 

and organic matter

Permeability $ surrounding soil Permeability $ surrounding soil Not Referenced 

 Media uniformity coefficient > 1.5 Media washed with <1% silt, clay, 

and organic matter

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

 Effective grain size from 0.20-

0.55 mm

Media uniformity coefficient > 1.5 Media uniformity coefficient > 1.5 

 Designed with safety factor of 2 Effective grain size from 0.20-

0.55 mm

Effective grain size from 0.20-0.55 mm

 Seasonal HGWT below invert of 

perforated pipe

Designed with safety factor of 2 Designed with safety factor of 2 

 Seasonal HGWT > 1 ft below 

centerline of perforated pipe

 Volume 

Recovery

Recover treatment volume in <72 hours 

Regain treatment volume in < 72 hours

Treatment volume available in < 36 hours

 Not Referenced 

Discharges to 

OFW, Class I or II 

Waters 

Treatment 

Volume 

In general, 50% additional treatment volume above standard criteria plus 50% additional PPV for wet detention

In general, 50% additional volume above standard criteria 

In general, 50% additional volume above standard criteria 

In general, 50% additional volume above standard criteria; plus additional measures such as pretreatment

References: 1. Chapter 40C-42 FAC - Environmental Resource Permits: Regulation of Stormwater Management Systems  2. Chapter 40B-4 - Regulations  3. Basis of Review for Environmental Resource Permit Applications within the Southwest Florida Water Management District  4. 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 specifically referenced by all the water management 

districts except the Suwannee River Water Management District. However, the Suwannee River 

Water Management District provides general detention 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 runoff 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 South Florida Water Management District. Residence 

time, perhaps the most significant factor in determining 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 District to 35% in the Southwest Florida Water 

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

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

River Water Management District specifies shallow 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 Management Districts. The Suwannee River Water 

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

Treatment volume requirements are somewhat variable, 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 Water Management District, and 0.5 inch of runoff (or 

1.88 inches x impervious area) in the South Florida 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 Districts, and complete recovery in 72 hours within the 

Suwannee River Water Management District. 

 Detention with filtration systems are referenced 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 districts 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 Water Management Districts for discharges to these 

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

District also requires an additional 50% permanent 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 quality 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 from developed 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 relate 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, including alternative design criteria, provided that the 

design criteria meet the overall objectives and water quality goals achieved by the design criteria 

provided by each of the water management districts. 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 Martin 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-development 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 loadings under post-development conditions are 

substantially greater with respect to treatment volume 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 Florida is fueled by the abundance of rainfall which 

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

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

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

generally abundant in Florida, annual precipitation 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 recorded 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 the State of Florida. According 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 location map for each of the 111 monitoring sites, is 

given in Appendix A.1. 

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

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

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

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

smoother transition for the contour lines in the vicinity 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 complete 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 

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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 previously, 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 precipitation 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 versions of the rainfall isopleths map are given in 

Appendix A.3. 
 Figure 3-2. Isopleths of Mean Annual Precipitation in Florida from 1971-2000. 

3-3

FDEP \ 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 Southeast 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 mean annual precipitation illustrated on Figure 3-2, a 

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

which occur throughout the state. For example, coastal 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 occurred in these areas are less than 0.2 inches. In contrast, areas 

within the Panhandle receive a large portion of their 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 State 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 meteorological 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 meteorological sites are indicated on Figure 3-3. In 

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

minimum amount of missing data. Years within the 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 identify 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 additional sites were begun between 1946 and 1949. The 

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

column of Table 3-1. Each entry includes the period 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 events occurring during the period of record for 

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

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

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

site was scanned to determine the total rainfall depth 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 defining individual rain events. Using this criterion, 

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

event, while rain events separated by six hours or more 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 climates present throughout much of the U.S., this 

definition fails to consider the small convective events 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. However, 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 utilized. 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 hours 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 indicate the start of a new independent runoff event. 

 The available data sets for each of the 11 meteorological 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 calculated. A probability distribution was performed on all 

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

the mean rainfall duration, the mean antecedent dry period, the annual rainfall depth 

contributed by each interval, the cumulative 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 percentage 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 state-wide average of 75.1%. Conversely, the Ft. 

Myers and Cross City monitoring sites appear to have 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 percentage of large rain events, with 5.3% of 

the Pensacola and Tallahassee and 3.9% of the Ft. Myers 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. Branford Cross City Ft. Myers

 Jacksonville

 Key West

 Melbourne

 Miami

 Orlando

 Pensacola

 Tallahassee

 Tampa

Percent of Annual Rainfall Events

Less 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 3-2 

PERCENTAGE OF ANNUAL RAIN EVENTS 

OCCURRING IN SELECTED EVENT INTERVALS 

RAINFALL 

STATION 

AVERAGE 

NUMBER 

OF 

RAIN 

EVENTS 

PERCENTAGE OF THE NUMBER OF RAIN 

EVENTS 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 

15.01-20.00 

 Branford 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 0.0 

 Cross 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 0.0 

 Ft. 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 0.0 

 Jacksonville 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 0.0 

 Key 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 0.0 

 Melbourne 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 0.0 

 Miami 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 0.0 

 Orlando 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 0.0 

 Pensacola 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 0.0 

 Tallahassee 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 0.0 

 Tampa 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 0.0 

Minimum 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 0.0 

Maximum 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 0.0 

Mean 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 

3-8 

FDEP \ 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 monitoring site, with a mean of 104 events measured 

per year. 

 Branford

 Cross City

 Ft. Myers

 Jacksonville

 Key West

 Melbourne

 Miami

 Orlando

 Pensacola

 Tallahassee

 Tampa

Number 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 period 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 season (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 for 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 

3-11 

Branford

Cross City

Fort Myers

Jacksonville

Key West

Melbourne

Miami

Orlando

Pensacola

Tallahassee

Tampa

Mean 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 effectiveness of stormwater treatment systems are 

closely linked to the quantity and quality of the generated 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 and 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 studies have been conducted within the State of 

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

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

into one of 12 general land use designations which 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 percentage imperviousness, vegetative cover, and 

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

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

categories represented by FLUCCS codes must often 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 similarities 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 characterization data for various pollutant categories 

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

suspended solids in each of the land use categories 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 sizes generally less than 1 acre and dwelling 

densities greater than one dwelling unit per acre; duplexes constructed on one-third to onehalf acre lots are also included in this category; internal roadways associated with the homes 

are also included 

Multi-Family 

Residential 

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

internal roadways associated with 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 areas 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 roadways associated with the development are 

also included 

Industrial Land uses include manufacturing, shipping and transportation services, sewage treatment 

facilities, water supply plants, and solid waste disposal; 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 land, undeveloped land which may be occupied by native 

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

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

single-family residential areas 

Mining/ 

Extractive 

Includes a wide variety of mining activities for resources such as phosphate, sand, gravel, 

clay, shell, etc. 

Wetlands Include a wide range of diverse wetland types, 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, rivers, reservoirs, and other open waterbodies 
FDEP \ STORMWATER TREATMENT REPORT 

4-3 

 

 TABLE 4-2 

 RUNOFF CHARACTERIZATION DATA AVAILABILITY

PARAMETER

GROUP SPECIES DATAAVAILABILITY LAND USES 

Suspended Solids TSS Good All 

Nutrients Total N

Total P

Good All 

NH3

NOx

TKN 

Ortho-P

Limited Limited

Metals Zinc

Lead 

Copper

Fair to Good Commercial, Residential,

and Highway 

 Cadmium

Nickel 

Diss. Metals

Poor to Fair Commercial, Residential,

and Highway 

Oxygen Demanding 

Substances 

BOD Fair to Good Commercial, Residential, 

and Highway

 COD Poor to Fair Commercial, Residential, 

and Highway

Oils, Greases, and 

Hydrocarbons 

Oil and Grease

TRPH

Poor Commercial, Residential, 

and Highway

 Specific Compounds Extremely Poor Commercial, Residential, 

and Highway

Pathogens Total Coliform

Fecal Coliform

Poor Commercial, Residential, 

and Highway

 E. Coli Extremely Poor Commercial, Residential, 

and Highway

 Runoff characterization data for zinc, lead, and copper are most commonly available for 

commercial, residential, and highway land uses. However, 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 biochemical oxygen demand (BOD) is fair to good in 

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

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

measured relatively infrequently, and the data availability 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 including these parameters are research projects, many 

of which are designed specifically to address these 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 commercial, 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 Harper during 1992-93 to identify significant 

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

many of the evaluated land uses was obtained 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, federal, 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 representing a wide range of rainfall and antecedent dry 

period conditions. Unfortunately, in a number of cases, 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 watershed 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 studies 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 insufficient number of sample events or address mixed 

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

potential pollutant loading information. 

 The Harper (1994) report includes all significant 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-intensity commercial, highway/transportation land use, 

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

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

to generate a database reflecting all significant characterization 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 listing of hydrologic and general characteristics for 

studies included in the combined database is given in Appendix B. 
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 4-3 

SUMMARY OF SELECTED STORMWATER CHARACTERIZATION 

STUDIES PERFORMED IN THE STATE OF FLORIDA 

REFERENCE 

LOCATION 

OF STUDY 

AREA 

LAND USE 

TYPE 

PARAMETERS 

MEASURED COMMENTS 

Federico 

(1977) 

Taylor Creek 

Drainage Basin, 

FL 

1. Pasture2. Dairy 3. Citrus

General Parameters, 

Nutrients 

An average of 43 daily composite samples collected in drainage ditches from July to September 1975. Data presented as concentration only with no hydrologic data for direct conversion to loading rates.

East Central 

Florida 

Regional 

Planning 

Council 

(ECFRPC) 

(1978) 

Central Florida 

Area 

1. Residential2. Commercial 3. Pasture 4. Well-drained 5. Flatwoods 6. Range 7. Lake 8. Swamp

Nutrients, BOD, 

Solids 

Presents summaries of studies conducted in Central Florida with results expressed in concentration and loading rate forms. 

Gaggiani, 

et al. 

(1978) 

Maitland, FL Primarily residential Nutrients, Major Ions, 

Heavy Metals 

Bulk precipitation and runoff samples were collected from 3 adjacent watersheds from April 1971 to June 1974. A total of 46 storm events were monitored. Data includes event mean concentration and mass loading for storm events. 

Miller

(1979) 

Southeast Florida 

Coastal Area 

1. 17.9 acres low-density

 residential 2. 58.3 acres highway basin 3. 20.4 acres commercial 4. 14.7 acres high-density  residential

None Report gives detailed hydrologic information on the four drainage 

basins. Results of runoff sampling programs are given in other publications by the author. 

Weinberg, 

et al. (1980) 

Broward County, 

FL 

26 acres of high-density 

residential

General Parameters, 

Nutrients

Grab samples and timed samples collected from 2 rain events during 1975. Insufficient data base.

Mattraw, et al. 

(1981) 

Broward County 3 separate areas:

1. 40.8-acre single-family  residential (43.9% imp.) 2. 58.3-acre 6-lane highway  (36.2% imp.) 3. 28.4-acre commercial (regional  shopping mall, 98% imp.)

General Parameters, 

Nutrients, Metals, 

Bacteria 

More than 30 flow-weighted samples collected from 1974-1977. Data presented as concentration and loadings. Detailed hydrology provided for each basin. 

4-5
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 4-3 -- CONTINUED 

SUMMARY OF SELECTED STORMWATER CHARACTERIZATION 

STUDIES PERFORMED IN THE STATE OF FLORIDA 

REFERENCE 

LOCATION 

OF STUDY 

AREA 

LAND USE 

TYPE 

PARAMETERS 

MEASURED COMMENTS 

Harper, et al. 

(1982) 

Orlando, FL 160 acres of high-density 

commercial and residential 

General Parameters, 

Solids, BOD, Metals, 

Nutrients 

Runoff collected from mixed residential and commercial watersheds during 1978 using manual and automatic techniques. Data presented in both concentration and loading rate forms but represents mixed land use. 

Waller

(1982) 

Dade County, FL 1. Commercial

2. State Park 3. Residential 4. Row Crops 5. Agricultural

General Parameters, 

Nutrients, Heavy 

Metals 

Runoff samples collected from June to October 1978 only for storms of intensity equal to or exceeding 1.0 inch/hour. Data cannot be used for loading rate estimation since typical less intense storm events were not monitored. 

Wanielista, 

et al. 

(1982) 

Orlando, FL 1. Residential

2. Commercial 

General Parameters, 

Nutrients, Metals 

Four runoff events were collected from separate residential and commercial watersheds from July to November 1978 using manual flow-weighted collection techniques. Data presented in both concentration and loading rate forms. However, the data base is small and covers only a portion of the year. Residential area receives heavy traffic volume from adjacent downtown area.

Yousef, et al. 

(1982) 

Orlando, FL Interstate Highway (I-4) General Parameters, 

Nutrients, Metals 

Runoff from highway bridges was collected from 11 storm events during August 1975. Data presented in concentration form only. Sampling program and hydrologic information sufficient to generate annual loadings, but data is specific to bridge or highway runoff only. 

German 

(1983) 

Maitland, FL 2 Sub-basins: 

Residential and Highway

General Parameters, 

Nutrients, Metals

39 runoff events sampled in residential areas and 17 samples in highway areas from 1975-1979.

McKenzie, 

et al. 

(1983) 

Miami, FL 1.43 acre Interstate Highway

(I-95) 

General Parameters, 

Nutrients, Metals 

Runoff collected during 5 storm events from November 1979 to May 1981 using automated instrumentation. Data presented as both concentration and loading rates, but is specific only to highway systems. 

Cullum (1984) 

Greg (1984) 

Boca Raton, FL 122 acres single-family 

residential

General Parameters, 

Nutrients

Detailed hydrologic concentration and mass loading data. However, only rain events in excess of 1 inch were sampled.

ECFRPC 

(1984) 

Central Florida 11 land use types Nutrients, BOD, 

Solids 

Presents concentration and loading rate information for expanded land use categories not presented in earlier 1978 publication. Data generated from Central Florida studies funded by ECFRPC. Hydrologic information is also provided.

4-6
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 4-3 -- CONTINUED 

SUMMARY OF SELECTED STORMWATER CHARACTERIZATION 

STUDIES PERFORMED IN THE STATE OF FLORIDA 

REFERENCE 

LOCATION 

OF STUDY 

AREA 

LAND USE 

TYPE 

PARAMETERS 

MEASURED COMMENTS 

Lopez, et al. 

(1984) 

Tampa Bay, FL A mixed-use urban watershed General Parameters, 

Nutrients, Heavy 

Metals 

Detailed study from 1975-1980 including streamflow, climate, physiographic and water quality data. Extremely detailed discussion of watershed characteristics. Data presented in both concentration and loading rate formats. Although land use is mixed, 3 of the 9 sites are approximately 70% residential which may be useful for single land use estimates.

Waller, et al. 

(1984) 

Coral Gables, FL 1. Commercial, Residential,

 Highway 2. Residential

Nutrients, Metals Sampled 3 runoff events during March and April 1982 using ponded 

water collected in a low area. Insufficient data for estimation of loading rates. Data given as concentrations only.

Miller

(1985) 

Broward/Dade 

Counties, FL 

1. Residential2. Highway 3. Commercial 4. Apartment

Nutrients, Suspended 

Solids, Lead 

Gives percent entrainment curves for various rain events. No actual concentration data or loading rate information supplied. 

Yousef, et al. 

(1985) 

Orlando, FL Interstate Highway (I-4) General Parameters, 

Nutrients, Metals 

Runoff collected from roadside swales during 17 storm events from 1982-1983 using automatic collection equipment. Data presented as both concentration and loading rates. Limited to highway land use only. Presents data on pollutant removal efficiencies of swales.

Harper, et al. 

(1985) 

Sanford, FL 54 acres low-density

residential area 

General Parameters, 

Nutrients, Metals 

Flow-weighted composite runoff samples collected for 22 storm events during 1984. Grass swales with raised inlets used for conveyance and treatment. Data presented as both concentration and loading rates. Detailed hydrologic and watershed information. Presence of swale drainage/treatment system limits usefulness for characterization data.

Harper (1985) Orlando, FL Highway runoff (ADT = 16,000)

4.0-acre watershed 

Heavy Metals Flow-weighted runoff samples collected at inlet to wet detention 

pond during 16 storm events from April 1983-May 1984 with a wide range of total rainfall and antecedent rainfall conditions. No pretreatment. Data presented as concentration only. Detailed hydrologic and rain event characteristics provided. Data used to evaluate fate of heavy metals.

Martin, et al. 

(1985) 

Orange County, 

FL 

Mixed use basin:

33% forest, 27% urban roadway, 

27% high-density residential, and 

13% low-density residential

General Parameters, 

Nutrients, Metals 

Study provides evaluation of performance efficiency of a detention pond-wetlands system. No actual characterization data provided. 

4-7
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 4-3 -- CONTINUED 

SUMMARY OF SELECTED STORMWATER CHARACTERIZATION 

STUDIES PERFORMED IN THE STATE OF FLORIDA 

REFERENCE 

LOCATION 

OF STUDY 

AREA 

LAND USE 

TYPE 

PARAMETERS 

MEASURED COMMENTS 

Howie, et al. 

(1986) 

Broward County, 

FL 

Highway Nutrients, Metals A total of 12 storm events were sampled from May to November 

1983. Samples were collected from swale flow and do not reflect direct runoff. Surficial aquifer also sampled.

Yousef, et al. 

(1986) 

Orlando, FL Interstate Highway (I-4) General Parameters, 

Nutrients, Metals 

Flow-weighted composite runoff samples collected over 13-month period in 1982-1983 using automatic equipment. Event mean concentrations given for measured parameters. Hydrologic data provided could be used to generate loading rates. Study limited to highway use only.

Fall 

(1987) 

Upper St. Johns 

River Basin 

222,486 acres of

primarily agriculture 

(70% pasture, 5% row crops) 

General Parameters, 

Nutrients, Metals 

Collection of 58 pumped discharge samples from 9 pumps from 1982-1987. Pumped discharges were not necessarily related to storm events. Data summarized by concentration only. No hydrologic data 

given for direct conversion to loading rates.

Fall, et al. 

(1987) 

Indian River 

County, FL 

27,720 acres agricultural basin 

(22,000 acres of citrus, remainder 

in pasture and drainage works)

General Parameters, 

Nutrients, Pesticides 

Samples of pumped agricultural discharge collected monthly from November 1984 to November 1985. Results given in terms of concentration only. No hydrologic data provided.

Hendrickson 

(1987) 

Brevard County, 

FL 

5681 acres agricultural area, row 

crops and rangeland 

General Parameters, 

Nutrients, Pesticides 

A total of 87 samples of pumped agricultural discharge were collected during August to December 1986. Data given as concentration only. Loading rates may be determined using hydrologic data given. This represents a ditched agricultural area.

Harper

(1988) 

Central Florida 

Area 

1. Interstate Highway

2. Residential 3. Commercial 

General Parameters, 

Nutrients, BOD, 

Solids, Metals 

Runoff collected from 5 watersheds during 8-12 storm events per watershed in 1987. Data presented in concentration form with hydrologic information on each watershed. Also gives removal efficiencies for stormwater management systems associated with each watershed along with groundwater effects.

Whalen, et al. 

(1988) 

Various 

Locations 

Around U.S. 

All General Types General Parameters, 

Nutrients, BOD, 

Heavy Metals, 

Organics

Excellent summary report of runoff studies conducted primarily in Florida. Also presents data on effectiveness of stormwater management systems for pollutant removal. 

Greg, et al. 

(1989) 

Boca Raton, FL Medium-density, residential (32.4 

acres with 37% impervious) 

Nutrients, Suspended 

Solids 

Six runoff events were collected from 1985 to January 1986 using automatic equipment. Study includes detailed hydrologic information. Data given as concentration only, but could be converted to loading rate with information provided.

4-8
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 4-3 -- CONTINUED 

SUMMARY OF SELECTED STORMWATER CHARACTERIZATION 

STUDIES PERFORMED IN THE STATE OF FLORIDA 

REFERENCE 

LOCATION 

OF STUDY 

AREA 

LAND USE 

TYPE 

PARAMETERS 

MEASURED COMMENTS 

Harper and Herr

(1993) 

DeBary, FL Low-intensity commercial,

50.7-acre watershed

General Parameters, 

Nutrients, Metals

Harper and Herr

(1994) 

Orange County, 

FL 

Single-family homes

on one-acre lots 

General Parameters, 

Nutrients, BOD, 

Suspended Solids, 

Metals

Four runoff events were collected from October 1993 to February 1994. Study includes hydrologic information. Data given as both concentration and areal loading rates. 

Bahk (1997) Ruskin, FL Agriculture – row crops

210-acre watershed 

General Parameters, 

Nutrients, Metals 

Total of 18 grab samples collected from drainage ditch from Feb. 1992-Sept. 1995. Data as concentration only. Even though collected as grab samples, large sample size gives data usefulness. No hydrologic data provided.

Rushton, et al. 

(1997) 

Tampa, FL Mixed land use; 30% rooftops and 

asphalt parking; 6% limestone 

storage; and 64% grassed storage

General Parameters, 

Nutrients, Metals 

Flow-weighted samples of pond inflow collected during 1993-1994.

ERD (2000) Bradfordville –

Tallahassee, FL 

Low-intensity commercial; 

asphalt parking areas; inlets and 

stormsewers; 8-acre drainage 

basin

General Parameters, 

Nutrients, Demand 

Parameters 

Flow-weighted composite samples collected during 12 storm events from Feb.-May 1999. Detailed hydrologic evaluation. 

ERD (2000) Bradfordville –

Tallahassee, FL 

Evaluated 3 separate areas:

1. 1.0-acre highway site on 6-lane  divided highway 2. 16.8-acre single-family  residential 3. 7.5-acre rural residential

General Parameters, 

Nutrients, Demand 

Parameters 

Flow-weighted composite samples collected during 11 events at highway site, 5 events at rural residential site, and 7 events at singlefamily residential site. Good hydrologic data provided. 

City of 

Tallahassee and 

ERD (2002) 

Tallahassee, FL 1. High-intensity commercial

2. Light industrial 3. Recreation/open space 4. Multi-family residential 5. Low-density residential 6. Single-family residential

Nutrients, Demand 

Parameters, Metals 

Flow-weighted composite samples collected at six land use characterization 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, FL 

210-acre row crop area General Parameters, 

Nutrients, Metals 

Total of 85 runoff samples collected from 1998-2001 using automatic refrigerated samplers. Also contains extensive rainfall quality data. 

4-9
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 4-3 -- CONTINUED 

SUMMARY OF SELECTED STORMWATER CHARACTERIZATION 

STUDIES PERFORMED IN THE STATE OF FLORIDA 

REFERENCE 

LOCATION 

OF STUDY 

AREA 

LAND USE 

TYPE 

PARAMETERS 

MEASURED COMMENTS 

ERD (2004) Orlando, FL Single-family residential; 2 

separate sub-basins: 52.9-acre 

and 19.4 acre 

General Parameters, 

Nutrients, Demand 

Parameters 

Flow-weighted composite samples collected during 25 storm events at one site and 8 events at the other site from June-Sept. 2003. 

Rushton (2004) Temple Terrace, 

FL 

132.4-acre mixed use basin 

including high-intensity 

commercial, multi-family 

residential, and golf course 

General Parameters, 

Nutrients, Metals, 

Bacteria 

Data collected as part of performance evaluation for a CDS unit. Excellent hydrologic data. Extensive water quality data for both inflow and outflow. 

Teague, et al. 

(2005) 

Florida 

Aquarium – 

Tampa, FL 

11.25-acre parking lot; 

combination of asphalt, cement, 

and pervious pavement 

Nutrients, Metals Flow-weighted samples collected during 56 storm events using 

refrigerated auto-sampler from 2000-2003. 

ERD (2005) 

Unpublished 

Data 

Orlando, FL 6.5-acre watershed centered along 

U.S. 441, 6-8 lane asphalt 

highway 

General Parameters, 

Nutrients, Metals 

Flow-weighted samples collected during 23 storm events using refrigerated auto-sampler from April-August 2004. 

ERD (2007) Winter Haven 43.9-acre basin with light 

industrial and warehouse land use 

General Parameters, 

Nutrients 

Flow-weighted samples collected during 10 storm events using autosampler from October 2005-March 2006. 

ERD (2007) Windermere 95.4-acre basin, single-family, dirt 

roads with grassed swales 

General Parameters, 

Nutrients 

Flow-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 studies 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 depths 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 program 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 the 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 exception 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 lead in stormwater runoff measured since 1990 are 

substantially lower than values measured prior 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 review is to provide estimates of event mean 

concentrations (emc) for each study included in the 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 loading discharging from the evaluated land use 

category for a given pollutant. 

4.1.2 Single-Family Residential

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

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

constructed on one-third to one-half acre lots are also 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 from 7.39-897 acres, with impervious percentages 

ranging from 6.1-65.0%. 

total annual runoff volume

total annual pollutant load for a given parameter emc = 
FDEP \ STORMWATER TREATMENT REPORT 

4-12 

 

 A summary of mean stormwater characteristics from single-family residential stormwater 

studies is given in Table 4-4. Each of the studies 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 total 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 -- 0.1671

 0.086 

Tampa - Charter Street U.S. EPA 

(1983) 2.31 0.400 13.0 33.0 -- -- -- -- -- 0.491

 0.053 

Maitland (3 basins) German (1983) 2.20 0.340 7.1 43.0 -- -- 0.014 0.350 0.008 0.2301 0.016 

St. Pete - Bear Creek Lopez, et al. 

(1984) 1.50 0.200 4.7 -- -- -- 0.009 -- -- 0.1281

 0.083 

Tampa - Kirby Street Lopez, et al. 

(1984) 

2.20 0.250 4.5 -- -- -- -- -- -- 0.0501 -- 

Tampa - St. Louis 

Street Ditch 

Lopez, et al. 

(1984) 

3.00 0.450 6.1 -- -- -- 0.016 -- -- 0.2131

 0.133 

Orlando Duplex Harper (1988) 4.62 1.691 9.5 63.2 0.005 0.015 0.033 0.464 0.020 0.0581 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 0.1321 0.045 

Springhill Subdivision, 

Palm Beach 

Greg, et al. 

(1989) 

1.18 0.307 -- 3.5 -- -- -- -- -- -- -- 

Tampa - 102nd 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 available 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 stormwater characterization sites utilize grassed 

swales exclusively for conveyance of stormwater 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 systems. 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 characteristics collected from residential areas 

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

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

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

lower for BOD, 46% lower for TSS, 47% lower for 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 runoff 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 concentrations were found to be significant at a 95% 

probability level. However, the observed differences 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% probability level for significant differences in TSS 

concentrations, and a 75% probability level for significant 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 -- 0.1671

 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 -- -- -- -- -- -- 0.0501 -- 

Tampa - St. Louis 

Street Ditch 

Lopez, et al. 

(1984) 

3.00 0.450 6.1 -- -- -- 0.016 -- -- 0.2131

 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 0.1321 0.045 

Tampa - 102nd 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 contains 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 characterization 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. Each 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 extremely limited for this land use category, with mean 

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

in estimation of mean values for lead concentrations. 

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

the multi-family studies are higher in concentration 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 -- -- -- -- -- 0.3411

 -- 

Miami - Kings Creek 

Apartments Miller (1979) 2.57 0.45 14.5 36.8 -- -- -- -- -- 0.0541

 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 -- -- -- -- -- 0.0761

 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 volumes 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 the 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 often left in a natural condition typical of open 

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

areas are estimated as the arithmetic mean of the mean 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, churches, 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 from 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 studies, 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 commercial areas are characterized by relatively low 

levels of total nitrogen, total phosphorus, and BOD, 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 received 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 

Study1 ECFRPC (1978) 0.89 0.16 3.6 146 -- -- -- -- -- 0.0682

 -- 

Ft. Lauderdale - Coral 

Ridge Mall Miller (1979) 1.10 0.10 5.4 45.0 -- -- 0.015 -- -- 0.3872

 0.128 

Tampa - Norma Park U.S. EPA 

(1983) 1.19 0.15 12.0 22.0 -- -- -- -- -- 0.0462

 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 0.1362

 0.168 

DeBary3 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 Center

COT and ERD 

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

Sarasota County 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 business 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 regional 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 the studies provide characterization data for BOD 

and TSS. Each of the studies also provides characterization 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 higher 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 -- 0.3871

 0.128 

Orlando - Downtown Area Wanielista 

(1982) 2.81 0.31 17.2 94.3 -- -- -- -- -- 0.5601

 0.165 

Dade County Waller (1984) 3.53 0.82 -- -- -- -- -- -- -- 0.1871 0.183 

Broward County Howie, et al. 

(1986) 2.15 0.15 -- -- -- -- -- -- -- 0.2411

 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 characterization data from light industrial areas is very 

limited in the existing literature. Only three studies 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 the 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 use 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 primarily of major highway systems, such as 

interstate highways, expressways, and major state and federal highway systems. In general, 

highway systems included under this category are considered to be heavily traveled, with constant 

traffic movement throughout the day. This land use category is typically characterized by a high 

degree of imperviousness. 

 A summary of hydrologic information from highway/transportation stormwater 

characterization studies is given in Table B.6. Eleven 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 major 4- or 6-lane highways. All of the systems 

provide drainage by curb and gutter systems. 

 A summary of emc values from highway/transportation 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 included measurements of heavy metals, including 

cadmium, chromium, copper, iron, nickel, lead, and 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 concentrations 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 -- 0.2821

 0.090 

I-95 Miami 

(Bridge) 

McKenzie, et al. 

(1983) 3.20 0.16 -- 42.0 0.001 0.010 0.040 -- -- 0.5901

 0.330 

Maitland German (1983) 1.30 0.240 -- 27.0 -- -- 0.012 0.350 0.009 0.0921 0.055 

I-4 Maitland 

Interchange Harper (1985) 1.40 0.17 -- -- 0.0025 0.004 0.038 0.341 0.003 0.1631

 0.071 

Maitland Blvd. Yousef, et al. 

(1986) 1.40 0.17 -- -- 0.0022 0.004 0.039 0.354 0.004 0.1811

 0.074 

I-4 EPCOT 

Interchange 

Yousef, et al. 

(1986) 3.16 0.42 -- -- 0.0016 0.003 0.024 0.205 0.003 0.0261

 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 0.2241 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 0.3431 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 summarized 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 stormwater 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 extremely varied, both in terms of agricultural 

activities and soil types. Agricultural activities such as cattle grazing and row crops are commonly 

conducted on poorly drained soils which are characterized 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 representative 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, citrus, and row crops. Sufficient characterization 

data currently exists within the literature to provide 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. Watershed 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 three 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 effects 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 quality data measured directly as runoff from 

the field area prior to entering adjacent canals and ditches and, as a result, does not include pollutant 

uptake and deposition of suspended solids and nutrients within conveyance systems located within 

the farm. As a result, the total nitrogen, total phosphorus, 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 studies involving citrus land use were identified during the 

literature review. Soil types represented in these studies are generally poorly drained soils, 

consisting of fine grain sands, peat, or muck. The water table elevations in most of these studies was 

controlled by furrows and lateral ditches to keep the 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, and 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 stormwater studies is given in Table 4-13. 

Each of the eight studies provide characterization data for total nitrogen and total phosphorus, 

with five of the studies providing information 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, although 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 concentrations 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 representation 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 Agriculture1 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/forest 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 range from Tallahassee to Miami. However, 

information on watershed area is not provided for any 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 undeveloped, 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 studies providing data for 

TSS. Heavy metal characteristics for copper, lead, and zinc are included in only one study. In 

general, undeveloped, rangeland, and forest land 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 includes a wide variety of mining activities for 

resources such as phosphate, sand, gravel, clay, and shell. Very little information 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 water quality violations and enforcement actions. The 

only reference which provides runoff characterization 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 summary of hydrologic data from the ECFRPC study is 

given in Table B.11. Although the watershed 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 Boggy Creek study only for total nitrogen and total 

phosphorus, with a mean total nitrogen concentration 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 wetlands include a wide range of diverse wetland 

types, such as hardwood wetlands, cypress stands, grassed wetlands, and mixed wetland 

associations. Wetland systems are routinely included in ongoing monitoring efforts, and wetland 

characterization data is available throughout the State 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 evaluated. 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 pollutant loading evaluations, the site-specific 

hydrologic characteristics of the wetlands under evaluation must be considered. As a result of the 

complexities of wetland systems, guidelines concerning 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, consists of open waterbodies such as lakes, 

reservoirs, streams, and rivers. Pollutant concentrations from these sources are a result of 

discharges from the waterbody during and following 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. Waterbodies often provide pollutant attenuation for 

watershed areas which are tributary to the waterbody. 

 Characterization data is currently available for a large number of waterbodies located 

within the State of Florida. These data are easily available through STORET, the LAKEWATCH 

Program at the University of Florida, water management 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 characterization data for general land use categories 

in Florida is given in Table 4-17 based upon the information provided in the previous sections. The 

values summarized in this table represent the mean emc values for each of the general land use 

categories discussed previously. 

 In general, the data summarized in Table 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 are associated with low-density residential. 

Increases in emc values occur when the land use intensity 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 commercial 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 nitrogen or phosphorus loadings, such as industrial and 

highway areas, are characterized by relatively low concentrations for these parameters. In contrast, 

agricultural areas, which would be expected to have 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 Residential1 1.61 0.191 4.7 23.0 0.0084 0.0024 0.0314

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 Agriculture2

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 / Forest 1.15 0.055 1.4 8.4 -- -- -- 

Mining / Extractive 1.18 0.15 7.63 60.03 0.0033 0.0023 0.0573

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 within the State of Florida. However, in areas 

where more site-specific runoff characterization information is available, the site-specific data 

should be used instead of the generalized data summarized in Table 4-17. 

 

 Several assumptions were made in assigning runoff concentrations to provide a more 

complete database for the general land use categories. 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 these 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 concentrations 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 volumes were calculated to evaluate variability 

in regional runoff generation and the performance efficiencies of dry retention systems. These 

calculations were performed using the SCS (Soil Conservation Service) Curve Number 

Methodology and the historical rainfall 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 separate calculations for the runoff volume 

generated from directly connected impervious areas (DCIA) and non-DCIA areas. An impervious 

area is considered to be directly connected if runoff from the area flows directly 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 concentrated shallow flow that is conveyed through a 

pervious area, such as a roadside swale, and then 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 considered to be directly connected. The SCS model 

assumes that runoff generated in these areas has the opportunity to infiltrate into the soil, depending 

upon the soil types and land cover characteristics, before significant runoff volumes begin to be 

generated within the area. The runoff generating 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 use and soil type. Theoretical values for curve 

numbers range from 0-100, with low values reflecting a low runoff potential and higher values 

reflecting a high runoff potential. Representative curve 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 provides an extensive listing of curve numbers for 

different hydrologic soil groups and land use covers. 

 The TR 55 document divides soil groups within 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 consideration 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 areas is absorbed by infiltration and does not become 

stormwater runoff. Soils classified in HSG D consist of clayey-type soils or soils with a high 

organic content which exhibit a low infiltration rate 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 volume 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 

Pi = event rainfall 

 QnDCIAi = rainfall excess for non-DCIA for rainfall event 

⎟

⎠

⎞ ⎜

⎝

⎛ - 10

nDCIA CN

1000 Soil Storage, S = 

(100 - DCIA)

CN * 100 - Imp) + 98 (Imp - DCIA) nDCIA CN = (

( P + 0.8S)

( P - 0.2S ) Q = i

2

i

nDCIAi
FDEP \ STORMWATER TREATMENT REPORT 

4-29 

 For the DCIA portion, rainfall excess is calculated using the following equation: 

When Pi 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 within the irregularities in 

the impervious surfaces and does not become stormwater runoff. After these surfaces become filled 

with the initial 0.1 inch of rainfall, additional rainfall begins to generate runoff on these surfaces. 

 One of the primary objectives of the hydrologic 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 impacts of variability in the sizes of individual rain 

events can best be evaluated using a continuous 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 rainfall 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 given in Table 4-19. Hourly precipitation data is 

available from 45 separate monitoring stations, with a period of hourly rainfall data ranging from 13-

64 years. 

 All available hourly precipitation data was obtained for each of the 45 monitoring stations 

listed in Table 4-19. For each site, a continuous 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 infiltration 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 insignificant loss in comparison with the overall volume of 

runoff generated during these design storm events. However, when performing continuous 

simulation modeling, the soil moisture condition at the time of the rain event can have a significant 

impact on the runoff volume generated from pervious areas. The Soil Conservation Service (SCS) 

has developed three antecedent soil moisture conditions to account for variability in runoff 

generation as a function of antecedent rainfall conditions. 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 

Q = ( P - 0.1) DCIA i 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 Airport (5612) 47 5073 47.52 9.89 0.44 

Moore Haven Lock 1 (5895) 43 4885 45.89 9.60 0.40 

Orlando International Airport (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 

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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 AMC I or III conditions is based upon the rate at 

which the soil storage is recovered following a rain event. Loss of soil moisture occurs as a result of 

several processes, one of which is evapotranspiration. 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 antecedent 5-day rainfall less than 0.5 inches would 

indicate a shift to antecedent moisture Condition I for the new rain event. During growing season 

conditions, this value increases to 1.4 inches. However, 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 conditions, this value increases to 2.1 inches. When 

performing continuous simulations, the SCS recommends 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 presented 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 cumulative 5-day rainfall using the relationships 

summarized in Table 4-21 (McCuen, 1982). Mathematical 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 for 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 runoff 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 given 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 event basis or for an annual period. The calculated C 

value for each combination of DCIA and curve number reflects the average runoff/rainfall ratio for a 

given meteorological monitoring site over the entire available period of record. The calculated 

runoff C value does not represent anticipated rainfall/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 individual rain events, discussed in the previous 

section, has the potential to impact rainfall/runoff relationships for individual rain events as well as 

on an annual basis. Areas which have a large number 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 characterized by a high frequency of large rain events which generate 

significant runoff. 

 The potential impacts of rainfall frequency distributions 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 coefficients. 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 residential areas are assumed to be 65% impervious, 

with 80% impervious assumed for commercial activities. Curve numbers for pervious areas are also 

included based on soil types and assumptions regarding 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 generated 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 Table 4-22. These estimates were calculated for 

each of the 45 NCDC hourly precipitation monitoring stations summarized in Table 4-19. This 

process resulted in a total of 1440 separate long-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 coefficients for each combination of monitoring site, land 

use, and curve number reflect the average annual runoff coefficient for the modeled monitoring sites 

over the entire available period of record. 

The runoff C values generated as a result of the process outlined above were evaluated using 

a K-means clustering algorithm to identify similarities and differences in annual runoff coefficients 

for each of the eight land use types and four soil groups across the State of Florida. The clustering 

algorithm attempts to minimize the squared error objective function, representing the distance 

measured between a data point and the center of a chosen 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 

% 

DCIA1

CURVE NUMBER (CN) 

FOR PERVIOUS AREAS 

HSG A HSG B HSG C HSG D 

Low-Density Residential 15 5 492 692 792 842

Single-Family Residential 

a. 25% impervious 

b. 40% impervious 

25 

40 

15 

25 

393 

393

613 

613

743 

743

803

803

High-Density Residential 65 50 393 613 743 803

Commercial 80 75 393 613 743 803

Highway4 

a. 50% impervious 

b. 75% impervious 

50 

75 

50 

75 

492

492

692

692

792

792

842

842

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 conducted 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 information in the model. This criterion is typically 

evaluated using the percentage of variance explained for each cluster model. A graph of the 

percentage of variance and annual runoff coefficients explained as a function of the number of 

clusters is given in Figure 4-2. As the curve begins to approach the 4- or 5-cluster models, the 

additional variance explained by adding an additional cluster to the model becomes incrementally 

small. Therefore, an appropriate number of clusters for the annual runoff coefficients model appears 

to be approximately 4 or 5. The 5-cluster analysis was selected as the final model because this 

model identified the Florida Keys as unique in terms 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, including 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 Florida. 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 Clusters

Percent 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 runoff generating characteristics are grouped together 

by color on this figure. Approximate areas represented 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 variability in rainfall events throughout the State. 

Portions of the Panhandle have been clustered together in an area which is impacted by a high 

number of large frontal events. Portions of the State along the Gulf Coast also appear to be similar 

runoff generating characteristics. Central and Central-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 evaluating runoff generation, pollutant loadings, and 

stormwater management system performance. 

 
FDEP \ STORMWATER TREATMENT REPORT 

4-37 

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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

W E

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 meteorological zones, counties without a monitoring 

site were grouped according to the meteorological 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 two 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 have 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 Table 4-24. The values summarized in this table reflect the mean 

runoff coefficients for each land use and hydrologic soil group and each meteorological monitoring 

site included in each of the five clusters. The values 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. 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. A non-DCIA curve number of 98 was also included in this 

analysis. The mean runoff C value for each combination of DCIA and curve number value was 

calculated using values from each of the meteorological monitoring sites within a given zone. The 

values summarized in Appendix C reflect the average long-term runoff coefficients for each of the 

five designated zones over a wide range of DCIA 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-development conditions by multiplying the mean annual 

rainfall depth for the given area, obtained from the Figures in Appendix A.3, times the appropriate 

runoff coefficient based upon the DCIA and curve 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 annual 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 variability 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 the calculated annual runoff coefficients. To 

illustrate the general relative relationships between DCIA, curve number, and annual runoff 

volumes, a set of average annual runoff coefficients was generated by calculating the mean 

runoff coefficient for each combination of DCIA and non-DCIA curve number for the five 

meteorological zones in Florida. A graphical summary 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 coefficient 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. 

12 in

1 ft Area (acres) x Mean Annual Rainfall (inches) x C Value x 
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

ul e

Percent DCIA (%)

Curve Number

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 relatively 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 90

Percent 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 meteorological zone is given in Figure 4-6. For this 

rainfall distribution, DCIA appears to have a relatively 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 relatively large increases in runoff coefficients. Changes in curve 

number appear to have a relatively small impact on runoff coefficient until the curve number 

begins to exceed a value of approximately 95. Above 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 mean 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 the 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 constructed in the Panhandle area, approximately 39-

40% of the annual rainfall would become stormwater runoff. On a state-wide average, 

approximately 37.5% of the rainfall which occurs 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 coefficients between the meteorological regions 

summarized in Figure 4-8 are due primarily to differences in the distribution of rain events 

which occur at each of these sites. For example, the Key West and Melbourne regional sites are 

characterized by a high percentage of annual events 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. Since larger rain events typically generate a 

larger proportion of stormwater runoff than smaller events, the annual runoff coefficients for 

these areas tend to be more elevated. 

The results summarized in Figure 4-8 have significant implications with respect to the 

performance efficiency of stormwater management systems, particularly systems that have 

design criteria based on providing treatment 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 event 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 stormwater 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 90

Percent 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 90

Percent 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 Distribution of C Values as a Function of DCIA 

 and Curve Number. 
FDEP \ STORMWATER TREATMENT REPORT 

4-46 

Zone 1Zone 2Zone 3Zone 4Zone 5

Annual 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 percentage of annual rainfall volume generated by rain 

events less than 0.1 inch at the designated meteorological 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. Based upon the assumption that impervious surfaces 

provide an initial abstraction of approximately 0.1 inch, no measurable runoff would be 

measured by rain events of this size. In contrast, 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 events can be expected to have a larger annual 

runoff coefficient. 
FDEP \ STORMWATER TREATMENT REPORT 

4-47 

Zone 1Zone 2Zone 3Zone 4Zone 5

Annual Abstraction Loss

as 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 1 Zone 2 Zone 3 Zone 4 Zone 5 Percent of Annual Rainfall Volume Less 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 rainfall depth lost to abstraction on impervious 

surfaces for each of the meteorological zones is given in Figure 4-11. In the Florida Keys (Zone 

3) area, approximately 21% of the total annual rainfall 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 processes between storm events. However, in the 

Panhandle (Zone 1) area, only 15% of the annual rainfall 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 1 Zone 2 Zone 3 Zone 4 Zone 5 Percent of Annual Rainfall Volume Greater 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 stormwater management techniques are much more 

efficient in removing and retaining pollutant loadings 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 management 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 typical stormwater management systems within 

Florida is presented along with a summary of the pollutant removal effectiveness achieved by the 

evaluated studies. Next, estimates of the pollutant removal effectiveness of common stormwater 

management systems are provided based upon current 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 often used interchangeably by engineers, even 

those who have been designing stormwater management 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 factors such as length of study, number of runoff events 

monitored, monitoring methodology, as well as completeness 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 performance efficiency. Some studies were identified 

which evaluated hybrid or experimental systems 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 estimates. 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 stormwater management facilities constructed within 

the State of Florida were included in this evaluation. 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 infiltration basins which are used to retain 

stormwater runoff on-site, thus reducing discharge to downstream waterbodies. Disposal of 

stormwater runoff occurs by infiltration into the 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 regain the available pond storage, construction of 

these systems is limited to areas with low groundwater 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 retention 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, depending on applicable design criteria. The pond is 

typically designed to hold a volume of stormwater, called the "treatment volume", which is 

equivalent to either the runoff generated by a specified 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 either on-line or off-line systems. Off-line 

systems typically provide storage for the treatment volume only. These systems typically utilize 

a weir structure to divert runoff into the retention pond until the treatment volume is reached. 

Runoff discharges in excess of the volume bypass 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 additional volume may be provided above the treatment 

volume for peak attenuation of on-site discharges 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 constructed 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 constructed as linear pond areas along road rightof-way, within recreational sites such as playgrounds or athletic fields, within natural 

depressional areas, in open land, as part of the landscaping for a commercial site, or as a shallow 

swale. Dual use of facilities provides a method 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 through the soil, migrating toward the underlying 

groundwater, a variety of physical, chemical, and biological processes occur which retain a 

majority of the stormwater pollutants in the upper layers of the soil within the retention basin 

(Harper, 1985; Harper, 1988). Previous research 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. Concentrations of nutrients and heavy metals in 

groundwater beneath dry retention basins are typically lower in value than measured in 

stormwater runoff entering the retention system. 

Even though dry retention systems prevent direct 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 adjacent 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 been 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 Table 5-1. The first study, 

published in 1978 by the East Central Florida 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 approximately 61% for total phosphorus to more than 

90% for species of nitrogen. Information 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 rainfall/runoff events. Removal efficiencies are 

presented as a function of retention volume, with increasing removal efficiencies associated with 

increasing runoff volumes retained. This simulation assumes that the retention pond drains 

completely between rain events so that the design retention volume is available for the next 

storm event. Removal efficiencies 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 extensively 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 achieved in retention systems are regulated 

primarily by the amount of runoff volume retained. In general, the annual pollutant removal 

effectiveness of a retention system should increase as the retention volume increases. Since dry 

retention systems do not always recover the entire 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 Wanielista. The removal efficiencies proposed by 

Wanielista incorporate a first-flush effect which assumes that a large portion of the pollutant 

loading occurs in the initial portion 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 therefore, 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 does 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 efficiencies, 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 treatment 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 groundwater tables. A wet 

detention pond is simply a modified detention facility which is designed to include a permanent 

pool of water. These permanently wet ponds are designed to slowly release collected runoff 

through an outlet structure. A schematic diagram 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 detention systems occur through a variety of 

mechanisms, including physical processes such as sedimentation, chemical processes such as 

precipitation and adsorption, and biological uptake from 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 treatment volume above the orifice invert elevation is calculated for 

each facility based upon a specified depth of runoff over the contributing drainage basin area. 

Inputs of stormwater runoff equal to or less than the treatment volume leave the facility through 

an orifice in the outfall structure, percolation 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 rate 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, chemical, and biological processes 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 concentration 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 concentration 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 advantages 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 facilities provide only one or two of these basic 

removal methods for stormwater. A second advantage of wet detention systems is that the 

systems are not complex and can be relatively easily maintained. Wet detention systems do not 

have underdrain systems which can become clogged 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 standards regarding mean detention time, pond 

configuration, and depth. The majority of the 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 Table 5-2. Measured removal efficiencies for 

orthophosphorus, total phosphorus, TSS, and heavy metals 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. Removal 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 total phosphorus, BOD, and copper, while removal 

efficiencies for orthophosphorus, TSS, lead, 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. td=7 days 

b. td=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. td=2 days 

b. td=5 days 

c. td=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. td=1 day 

b. td=7 days 

c. td=14 days 

4 

33 

36 

56 

73 

88 

20 

56 

65 

-- 

-- 

-- 

-- 

-- 

-- 

32 

81 

92 

41 

88 

96 

-- 

-- 

-- 

MEAN VALUES1 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 system to remove total nitrogen was heavily 

dependent upon the proportion of total nitrogen present as organic nitrogen. Organic nitrogen is 

not readily available, either biologically or chemically, and there are relatively few mechanisms 

for removal of this species in a wet detention system. In contrast, both NOx and NH3 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 relatively poor. If inorganic species of NOx and NH3 represent 

the dominant nitrogen species found, then removal efficiencies for total nitrogen can be expected 

to increase. On an average basis, wet detention systems with a detention time of 14 days can be 

expected to provide a net removal of approximately 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 detention 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 observed 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 receives stormwater runoff from a light commercial 

area. Pollutant removal efficiencies are provided for pond detention times of 2, 5, and 14 days. 

In general, pollutant removal efficiencies obtained at a detention time of 2 days are lower than 

removal efficiencies obtained at a detention time of 14 days for all evaluated parameters. 

However, the lowest removal efficiencies in the study were obtained at the 5-day detention time. 

Rushton, et al. reports that the lower efficiencies observed during the 5-day detention time study 

period were highly influenced by one extreme storm 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). This study was performed on a wet detention pond 

in Melbourne where portions of the pond were isolated 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 detention time within the microcosms. The removal 

efficiencies achieved at the 14-day residence time 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 high 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 treatment 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 system (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 recovery 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) have been used commonly within the South 

Florida Water Management District (SFWMD) and the Southwest Florida Water Management 

District (SWFWMD). In the St. Johns River 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, and chemical processes such as precipitation 

and adsorption, are the primary mechanisms responsible 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 pollutants 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 processes 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 removal 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 filter 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 dry 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 flow of groundwater may actually create a system 

where substantially more mass leaves the stormwater facility on an annual basis than enters the 

system through stormwater runoff. 

However, it is possible for dry detention systems 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 more 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 retention pond system for some rain events. Onehundred percent removal is achieved for all runoff infiltrated through the pond bottom which is 

not intercepted by the underdrain system. Pollutant 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 removal effectiveness of dry detention systems are 

largely affected by the elevation of the underdrain 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, provided in Table 5-3, based on selected research studies performed in 

Florida. Each of these systems is constructed with a side bank filter system 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 infiltrated 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 

Study1

Leon County/ 

Commercial Side Bank 80 -- 92 98 93 -- -- -- 

Harper 

& Herr2

(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 below 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 underdrain for this pond was constructed several feet 

below the average groundwater table elevation surrounding the pond. For this reason, 

groundwater continually flowed from the surrounding 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, total phosphorus, and BOD for this treatment 

facility. 

Based on the research performed on dry detention 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 above the seasonal high groundwater table elevation 

will exhibit higher mass pollutant removal efficiencies 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 efficiencies for dry detention with filtration systems 

are highly variable. However, in order to provide comparative pollutant removal efficiencies for 

common stormwater management systems, theoretical pollutant removal efficiencies are 

assumed for dry detention with filtration systems based upon the assumption that 25% of the 

annual runoff volume which enters the pond infiltrates through the pond bottom. The estimated 

mass removal efficiencies for a dry detention with filtration system, based upon this assumption, 

is estimated to be approximately 30% for total nitrogen, 40% for total phosphorus, 90% for TSS, 

and 50% for BOD. These removal efficiencies may improve slightly if the treatment volume is 

increased beyond the standard design. Since the primary removal mechanism is the physical 

process of sedimentation of particles, the increased detention time provided by the additional 

treatment volume has the potential to increase system 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 control 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 discharge 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 single 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 ground with 100% removal efficiency. Removal 

processes such as settling, adsorption, and precipitation reactions occur in the detention facility 

during the drawdown period and also 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 off-line retention/detention systems based on 

studies conducted within the State of Florida is given 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 these studies was conducted by Harper (1988) in the 

Orlando area on residential and commercial watersheds, constructed within the City of Orlando, 

which provided a treatment volume of 0.5 inches over the contributing watershed area. 

Excellent removal efficiencies were achieved 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 watershed 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 provide 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 typical stormwater management systems used 

in the State of Florida is given 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, retention is considered any method of infiltrating 

water into the ground. This includes traditional retention 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 systems, retention provides the highest level of 

treatment possible. All stormwater runoff retained or infiltrated into the ground is assumed to 

have a 100% mass pollutant removal efficiency for the 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 divided 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% for 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 efficiencies are based upon anticipated settling of 

TSS within the pond and the range of listed pollutants 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 which 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 stormwater management facility and the regional 

meteorological characteristics in the vicinity of the study site. Since meteorological characteristics 

and design criteria for stormwater management systems vary widely throughout the State of Florida, 

performance efficiency data for a stormwater management 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 evaluation to provide estimates of the anticipated 

performance efficiencies of stormwater management systems within the State of Florida considering 

variations in design criteria and meteorological characteristics throughout the State. These analyses 

are then used to compare the anticipated performance efficiency of stormwater management systems 

constructed according to current design criteria with 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 equivalent to a certain depth of runoff, typically 0.5 

inch, over the project area, or the runoff generated from a specified rain event, typically 1 inch. 

Estimates of the annual mass removal efficiencies associated 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 zones over a wide range of DCIA percentages and 

non-DCIA curve numbers. These evaluations were conducted using a continuous simulation of 

runoff volumes generated on a hypothetical 1 acre site using the historical rainfall data sets for 

meteorological sites in each of the five zones. This analysis was performed for DCIA 

percentages ranging from 0-100 in 5-unit intervals 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 events 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 instantaneously routed into a theoretical dry retention 

pond with a treatment volume equivalent to a specified depth of runoff or the runoff from a 

specified rain event. A hypothetical drawdown 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, the 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 the 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 runoff 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 scientific 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 conservative 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 based 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 treatment volume retained within the system. As a 

result, removal efficiencies of 100% are achieved for all rainfall events which generate runoff 

volumes less than or equal to the available treatment volume within the pond. Rainfall events 

which generate runoff in excess of the available 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 retention 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 general, 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 increase. 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 stormwater 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% impervious 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 runoff 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 low percentage DCIA and low non-DCIA curve 

number values. On a state-wide average, a removal efficiency of 80% can only be achieved at 

DCIA percentages of 25-35% or less and non-DCIA curve numbers of approximately 45-55 or 

less. An example of a development which would 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 and non-DCIA curve numbers in excess of these 

values will fail to meet the 80% removal criterion with a retention treatment volume equivalent 

to 0.5 inch of runoff. 

 A graphical comparison of estimated annual 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 meteorological 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 REPORT 

TABLE 5-6 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFF 

Panhandle (Zone 1)

NONDCIA 

CN 

PERCENT DCIA 

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 91.8 91.5 88.3 84.0 79.5 75.0 70.7 66.6 62.9 59.6 56.5 53.6 51.1 48.7 46.6 44.6 42.8 41.1 39.6 38.1 35 88.2 89.1 86.6 82.8 78.6 74.3 70.1 66.2 62.6 59.3 56.3 53.5 51.0 48.7 46.5 44.6 42.8 41.1 39.6 38.1 40 84.0 86.3 84.4 81.2 77.4 73.4 69.4 65.7 62.2 59.0 56.0 53.3 50.8 48.5 46.4 44.5 42.7 41.1 39.6 38.1 45 79.6 82.9 81.9 79.3 75.9 72.2 68.5 65.0 61.7 58.6 55.7 53.0 50.6 48.4 46.3 44.4 42.7 41.0 39.5 38.1 50 74.8 79.1 79.0 77.0 74.1 70.8 67.4 64.1 61.0 58.0 55.3 52.7 50.4 48.2 46.2 44.3 42.6 41.0 39.5 38.1 55 70.1 74.9 75.6 74.2 71.9 69.1 66.1 63.0 60.1 57.3 54.7 52.3 50.0 47.9 46.0 44.2 42.5 40.9 39.5 38.1 60 65.5 70.4 71.7 71.1 69.4 67.0 64.4 61.7 59.1 56.5 54.1 51.8 49.6 47.6 45.8 44.0 42.4 40.9 39.5 38.1 65 61.0 65.8 67.5 67.6 66.4 64.7 62.5 60.2 57.8 55.5 53.3 51.1 49.1 47.2 45.5 43.8 42.3 40.8 39.4 38.1 70 56.7 61.1 63.1 63.6 63.1 61.9 60.2 58.3 56.3 54.3 52.3 50.3 48.5 46.8 45.1 43.5 42.1 40.7 39.4 38.1 75 52.7 56.6 58.6 59.3 59.3 58.6 57.5 56.0 54.4 52.7 51.0 49.3 47.7 46.1 44.6 43.2 41.8 40.5 39.3 38.1 80 49.1 52.2 54.1 55.0 55.2 54.9 54.2 53.2 52.1 50.8 49.4 48.0 46.6 45.3 44.0 42.7 41.5 40.3 39.2 38.1 85 46.1 48.3 49.7 50.5 50.8 50.8 50.5 49.9 49.2 48.3 47.3 46.3 45.2 44.2 43.1 42.1 41.0 40.0 39.1 38.1 90 43.5 44.8 45.6 46.1 46.4 46.5 46.4 46.1 45.7 45.2 44.6 44.0 43.3 42.6 41.9 41.1 40.4 39.6 38.9 38.1 95 41.1 41.5 41.8 41.9 42.0 42.1 42.0 41.9 41.8 41.6 41.3 41.1 40.8 40.4 40.1 39.7 39.3 38.9 38.5 38.1 98 39.8 39.8 39.8 39.8 39.8 39.7 39.7 39.6 39.5 39.4 39.3 39.2 39.1 39.0 38.9 38.7 38.6 38.4 38.3 38.1 

5-19
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 5-6 -- CONTINUED 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFF 

Central (Zone 2)

NONDCIA 

CN 

PERCENT DCIA 

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 97.0 96.7 94.8 91.7 87.9 83.8 79.7 75.7 71.9 68.4 65.2 62.1 59.4 56.9 54.5 52.3 50.3 48.4 46.7 45.1 35 95.2 95.5 93.8 90.9 87.3 83.4 79.3 75.4 71.7 68.3 65.0 62.1 59.3 56.8 54.4 52.3 50.3 48.4 46.7 45.1 40 92.9 94.0 92.5 89.9 86.5 82.7 78.9 75.1 71.4 68.0 64.9 61.9 59.2 56.7 54.4 52.2 50.2 48.4 46.7 45.1 45 90.2 91.9 90.9 88.6 85.5 81.9 78.2 74.6 71.1 67.7 64.6 61.7 59.1 56.6 54.3 52.2 50.2 48.4 46.7 45.1 50 86.7 89.2 88.9 87.0 84.2 80.9 77.4 73.9 70.5 67.3 64.3 61.5 58.9 56.5 54.2 52.1 50.2 48.3 46.6 45.1 55 82.7 86.1 86.4 84.9 82.6 79.6 76.4 73.1 69.9 66.8 63.9 61.2 58.6 56.3 54.1 52.0 50.1 48.3 46.6 45.1 60 78.5 82.6 83.4 82.5 80.6 78.0 75.1 72.1 69.1 66.1 63.4 60.8 58.3 56.0 53.9 51.9 50.0 48.2 46.6 45.1 65 74.2 78.6 79.8 79.5 78.1 76.0 73.5 70.7 68.0 65.3 62.7 60.2 57.9 55.7 53.6 51.7 49.9 48.2 46.6 45.1 70 69.8 74.2 75.8 76.0 75.2 73.5 71.4 69.1 66.6 64.2 61.8 59.5 57.3 55.3 53.3 51.4 49.7 48.1 46.5 45.1 75 65.4 69.6 71.4 71.9 71.5 70.4 68.8 66.9 64.9 62.7 60.6 58.6 56.6 54.7 52.8 51.1 49.5 47.9 46.5 45.1 80 61.4 64.9 66.6 67.3 67.2 66.5 65.5 64.1 62.5 60.8 59.0 57.3 55.5 53.9 52.2 50.7 49.2 47.7 46.4 45.1 85 57.6 60.1 61.6 62.2 62.3 62.0 61.3 60.4 59.3 58.1 56.8 55.4 54.0 52.7 51.3 50.0 48.7 47.4 46.2 45.1 90 54.1 55.4 56.2 56.7 56.8 56.7 56.4 55.9 55.2 54.5 53.6 52.8 51.8 50.9 49.9 48.9 47.9 46.9 46.0 45.1 95 50.1 50.5 50.7 50.8 50.8 50.8 50.6 50.4 50.2 49.9 49.5 49.1 48.7 48.2 47.7 47.2 46.7 46.1 45.6 45.1 98 47.8 47.7 47.7 47.6 47.6 47.5 47.4 47.2 47.1 46.9 46.8 46.6 46.5 46.3 46.1 45.9 45.7 45.5 45.3 45.1 

5-20
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 5-6 -- CONTINUED 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFF 

Florida Keys (Zone 3)

NONDCIA 

CN 

PERCENT DCIA 

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 87.6 89.1 87.6 84.8 81.5 77.8 74.3 70.9 67.8 64.9 62.1 59.6 57.2 55.0 52.9 51.0 49.2 47.6 46.0 44.5 35 83.5 86.5 85.6 83.4 80.4 77.0 73.6 70.4 67.4 64.5 61.9 59.4 57.0 54.9 52.8 51.0 49.2 47.5 46.0 44.5 40 79.3 83.5 83.4 81.7 79.1 76.0 72.9 69.8 66.9 64.2 61.6 59.1 56.9 54.7 52.7 50.9 49.1 47.5 46.0 44.5 45 74.9 80.3 80.9 79.7 77.6 74.9 72.0 69.1 66.4 63.7 61.2 58.9 56.6 54.6 52.6 50.8 49.1 47.5 45.9 44.5 50 70.5 76.7 78.1 77.6 75.9 73.5 70.9 68.3 65.7 63.2 60.8 58.5 56.4 54.4 52.5 50.7 49.0 47.4 45.9 44.5 55 66.3 72.9 75.0 75.1 73.9 71.9 69.6 67.3 64.9 62.6 60.3 58.1 56.1 54.1 52.3 50.6 48.9 47.4 45.9 44.5 60 62.1 68.9 71.7 72.4 71.6 70.1 68.2 66.1 64.0 61.8 59.7 57.7 55.7 53.8 52.1 50.4 48.8 47.3 45.9 44.5 65 58.0 64.9 68.1 69.3 69.1 68.0 66.5 64.7 62.8 60.9 59.0 57.1 55.2 53.5 51.8 50.2 48.7 47.2 45.8 44.5 70 54.4 60.9 64.2 65.8 66.2 65.6 64.5 63.0 61.5 59.8 58.1 56.3 54.6 53.0 51.4 49.9 48.5 47.1 45.8 44.5 75 51.1 57.0 60.4 62.2 62.9 62.7 62.1 61.0 59.8 58.4 56.9 55.4 53.9 52.4 51.0 49.6 48.3 47.0 45.7 44.5 80 48.5 53.5 56.5 58.3 59.1 59.3 59.1 58.5 57.6 56.6 55.4 54.2 52.9 51.6 50.4 49.2 47.9 46.8 45.6 44.5 85 46.7 50.3 52.7 54.2 55.1 55.5 55.6 55.3 54.9 54.2 53.4 52.6 51.6 50.6 49.6 48.5 47.5 46.5 45.5 44.5 90 45.4 47.6 49.1 50.2 51.0 51.4 51.7 51.7 51.5 51.2 50.8 50.3 49.7 49.0 48.3 47.6 46.8 46.1 45.3 44.5 95 44.8 45.6 46.2 46.7 47.1 47.3 47.5 47.6 47.6 47.5 47.4 47.2 47.0 46.7 46.4 46.1 45.7 45.3 44.9 44.5 98 45.2 45.3 45.4 45.4 45.5 45.5 45.5 45.6 45.5 45.5 45.5 45.4 45.3 45.3 45.2 45.0 44.9 44.8 44.7 44.5 

5-21
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 5-6 -- CONTINUED 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFF 

Coastal (Zone 4)

NONDCIA 

CN 

PERCENT DCIA 

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 94.0 94.2 92.1 88.8 84.8 80.5 76.3 72.4 68.6 65.2 62.0 59.1 56.4 53.9 51.7 49.5 47.6 45.8 44.1 42.6 35 91.1 92.3 90.7 87.7 84.0 79.9 75.9 72.0 68.4 65.0 61.9 59.0 56.3 53.9 51.6 49.5 47.6 45.8 44.1 42.6 40 87.8 90.0 88.9 86.4 82.9 79.1 75.3 71.5 68.0 64.7 61.6 58.8 56.2 53.8 51.5 49.4 47.5 45.7 44.1 42.6 45 84.0 87.2 86.8 84.7 81.6 78.1 74.5 70.9 67.5 64.3 61.3 58.6 56.0 53.6 51.4 49.4 47.5 45.7 44.1 42.6 50 79.9 84.0 84.3 82.7 80.1 76.9 73.5 70.2 66.9 63.9 61.0 58.3 55.8 53.5 51.3 49.3 47.4 45.7 44.1 42.6 55 75.6 80.4 81.4 80.4 78.2 75.4 72.3 69.2 66.2 63.3 60.5 57.9 55.5 53.2 51.1 49.2 47.3 45.6 44.0 42.6 60 71.3 76.5 78.1 77.6 75.9 73.6 70.9 68.0 65.2 62.5 59.9 57.4 55.1 53.0 50.9 49.0 47.2 45.6 44.0 42.6 65 67.1 72.4 74.4 74.5 73.3 71.4 69.1 66.6 64.1 61.6 59.2 56.9 54.7 52.6 50.6 48.8 47.1 45.5 44.0 42.6 70 63.0 68.1 70.3 70.8 70.2 68.9 67.0 64.9 62.7 60.5 58.3 56.1 54.1 52.1 50.3 48.6 46.9 45.4 43.9 42.6 75 59.2 63.7 65.9 66.7 66.6 65.7 64.4 62.7 60.9 59.0 57.1 55.2 53.3 51.5 49.8 48.2 46.7 45.2 43.8 42.6 80 55.8 59.4 61.4 62.3 62.4 61.9 61.1 59.9 58.6 57.1 55.5 53.9 52.3 50.7 49.2 47.8 46.4 45.0 43.8 42.6 85 52.7 55.2 56.7 57.5 57.7 57.6 57.1 56.4 55.5 54.5 53.3 52.1 50.8 49.6 48.3 47.1 45.9 44.7 43.6 42.6 90 49.7 51.1 52.0 52.5 52.8 52.8 52.6 52.2 51.7 51.1 50.3 49.6 48.7 47.9 47.0 46.1 45.2 44.3 43.4 42.6 95 46.7 47.1 47.4 47.5 47.6 47.6 47.5 47.3 47.1 46.8 46.5 46.2 45.8 45.4 44.9 44.5 44.0 43.5 43.0 42.6 98 44.9 44.9 44.8 44.8 44.7 44.7 44.6 44.5 44.3 44.2 44.1 44.0 43.8 43.6 43.5 43.3 43.1 42.9 42.7 42.6 

5-22
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 5-6 -- CONTINUED 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO 0.5-INCH OF RUNOFF 

Southeast Coastal (Zone 5)

NONDCIA 

CN 

PERCENT DCIA 

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 88.6 89.9 87.9 84.5 80.5 76.4 72.3 68.5 65.1 61.9 58.9 56.2 53.7 51.4 49.3 47.3 45.5 43.8 42.2 40.8 35 84.1 86.8 85.6 82.8 79.3 75.4 71.6 68.0 64.6 61.5 58.7 56.0 53.6 51.3 49.2 47.3 45.5 43.8 42.2 40.8 40 79.3 83.3 82.9 80.8 77.8 74.3 70.7 67.3 64.1 61.1 58.3 55.8 53.4 51.1 49.1 47.2 45.4 43.8 42.2 40.8 45 74.4 79.5 80.0 78.5 76.0 72.9 69.6 66.5 63.4 60.6 57.9 55.4 53.1 51.0 48.9 47.1 45.3 43.7 42.2 40.8 50 69.7 75.5 76.8 76.0 73.9 71.3 68.4 65.5 62.6 60.0 57.4 55.0 52.8 50.7 48.8 47.0 45.3 43.7 42.2 40.8 55 65.2 71.4 73.4 73.1 71.7 69.5 66.9 64.3 61.7 59.2 56.9 54.6 52.5 50.4 48.6 46.8 45.2 43.6 42.1 40.8 60 61.0 67.2 69.7 70.1 69.2 67.4 65.3 63.0 60.6 58.4 56.2 54.0 52.0 50.1 48.3 46.6 45.0 43.5 42.1 40.8 65 57.1 63.1 65.9 66.8 66.4 65.1 63.3 61.4 59.4 57.3 55.3 53.4 51.5 49.7 48.0 46.4 44.9 43.4 42.1 40.8 70 53.6 59.2 62.0 63.2 63.3 62.5 61.2 59.6 57.9 56.1 54.3 52.6 50.9 49.2 47.6 46.1 44.7 43.3 42.0 40.8 75 50.7 55.5 58.1 59.5 59.8 59.4 58.6 57.4 56.1 54.6 53.1 51.6 50.1 48.6 47.1 45.8 44.4 43.2 41.9 40.8 80 48.3 52.0 54.3 55.5 56.0 56.0 55.6 54.8 53.9 52.8 51.6 50.3 49.0 47.8 46.5 45.3 44.1 43.0 41.8 40.8 85 46.2 48.7 50.5 51.5 52.0 52.2 52.1 51.7 51.1 50.4 49.6 48.6 47.6 46.7 45.6 44.6 43.7 42.7 41.7 40.8 90 44.2 45.6 46.7 47.4 47.9 48.1 48.2 48.1 47.8 47.4 46.9 46.4 45.7 45.1 44.4 43.7 43.0 42.2 41.5 40.8 95 42.5 43.0 43.4 43.7 43.9 44.0 44.1 44.1 44.0 43.9 43.7 43.5 43.2 43.0 42.7 42.3 42.0 41.6 41.2 40.8 98 42.1 42.2 42.2 42.2 42.2 42.2 42.2 42.1 42.1 42.0 41.9 41.8 41.7 41.6 41.5 41.4 41.2 41.1 40.9 40.8 

5-23
FDEP \ STORMWATER TREATMENT REPORT 

5-24 

Zone 1Zone 2Zone 3Zone 4Zone 5

Treatment Efficiency (%)

50

55

60

65

70

75

Mean

Figure 5-5. Calculated Annual Mass Removal Efficiencies 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 efficiencies 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 stations with hourly precipitation data. At low 

values for DCIA and non-DCIA curve numbers, removal 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 end 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 90

Percent 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 Efficiencies 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 also 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 number, 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 treatment system with 1 inch of retention range 

from approximately 67.2-75.9% depending upon the particular meteorological region within the 

State. The highest estimated annual removal efficiencies 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 criteria 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 management systems outlined in the Water Resource 

Implementation Rule (Chapter 62-40 FAC). Annual mass removal efficiencies for retention 

systems vary substantially within the State of Florida between the designated meteorological 

zones. 

 The SJRWMD requires additional dry retention treatment volume when the retention 

pond is constructed as an on-line system. For on-line systems, the SJRWMD design criteria 

become either (1) 1-inch of runoff over the entire 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 summarized 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%, this 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 efficiency 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 the 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 anticipated 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 designed 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 according to a specified runoff volume. It is 

interesting to note that the anticipated removal efficiency of the dry retention system increases as the 

impervious percentage increases. This phenomenon occurs because the generated runoff volume 

from 1 inch of rainfall, which dictates the design 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 mass removal efficiencies for dry retention of 

the runoff from 1 inch of rainfall for a hypothetical 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 1 Zone 2 Zone 3

Zone 4Zone 5

Treatment Efficiency (%)

40

45

50

55

60

65

Mean

Figure 5-7. Calculated Annual Mass Removal Efficiencies 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 REPORT 

TABLE 5-7 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO THE RUNOFF FROM 1 INCH OF RAINFALL 

Panhandle (Zone 1)

NONDCIA 

CN 

PERCENT DCIA 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.9 16.6 29.4 38.8 45.8 50.9 53.8 52.8 52.6 52.8 53.3 53.9 54.3 54.0 53.9 53.9 54.1 54.3 54.4 54.3 54.2 35 1.4 16.8 29.4 38.8 45.8 50.9 53.5 52.7 52.5 52.7 53.2 53.9 54.2 53.9 53.8 53.9 54.1 54.3 54.4 54.3 54.2 40 2.0 17.1 29.5 38.9 45.8 50.9 53.1 52.4 52.3 52.6 53.1 53.8 54.1 53.9 53.8 53.9 54.0 54.3 54.4 54.3 54.2 45 2.9 17.5 29.6 38.9 45.8 50.9 52.6 52.1 52.1 52.4 53.0 53.7 54.0 53.8 53.7 53.8 54.0 54.3 54.4 54.3 54.2 50 4.0 18.0 29.8 39.0 45.8 51.0 52.0 51.7 51.8 52.2 52.9 53.6 53.8 53.6 53.6 53.8 54.0 54.2 54.3 54.3 54.2 55 5.2 18.6 30.1 39.1 45.8 51.0 51.3 51.2 51.4 52.0 52.7 53.5 53.6 53.5 53.5 53.7 53.9 54.2 54.3 54.2 54.2 60 6.8 19.5 30.5 39.3 45.9 50.8 50.4 50.6 51.0 51.7 52.5 53.3 53.4 53.3 53.4 53.6 53.8 54.2 54.3 54.2 54.2 65 8.7 20.5 31.0 39.5 46.0 49.4 49.5 49.9 50.5 51.3 52.2 53.1 53.0 53.1 53.2 53.5 53.8 54.1 54.2 54.2 54.2 70 11.0 21.9 31.7 39.9 46.3 47.7 48.3 49.1 50.0 50.9 51.9 52.7 52.7 52.8 53.0 53.3 53.7 54.0 54.2 54.2 54.2 75 13.9 23.8 32.8 40.5 44.7 46.0 47.1 48.2 49.3 50.5 51.6 52.1 52.2 52.5 52.8 53.1 53.5 54.0 54.1 54.1 54.2 80 18.0 26.7 34.5 40.0 42.5 44.3 45.8 47.2 48.6 49.9 51.0 51.3 51.7 52.0 52.5 52.9 53.4 53.9 54.0 54.1 54.2 85 23.8 30.9 35.1 38.3 40.9 43.0 44.8 46.4 48.0 49.3 49.9 50.5 51.0 51.5 52.1 52.6 53.2 53.7 53.8 54.0 54.2 90 30.0 33.5 36.4 38.9 41.0 42.9 44.7 46.4 47.3 48.2 49.0 49.7 50.4 51.1 51.7 52.4 53.0 53.4 53.7 53.9 54.2 95 39.2 40.9 42.2 43.3 44.3 45.3 46.2 47.0 47.8 48.6 49.3 50.0 50.7 51.3 52.0 52.5 52.8 53.2 53.6 53.9 54.2 98 47.2 47.7 48.2 48.7 49.1 49.6 50.0 50.4 50.8 51.2 51.6 51.9 52.2 52.4 52.7 53.0 53.2 53.5 53.7 54.0 54.2 

5-28
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 5-7 -- CONTINUED 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO THE RUNOFF FROM 1 INCH OF RAINFALL 

Central (Zone 2)

NONDCIA 

CN 

PERCENT DCIA 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.5 16.1 30.0 41.0 49.2 55.5 60.5 59.8 59.2 59.2 59.6 60.2 60.9 60.9 60.6 60.5 60.6 60.8 61.1 61.1 61.0 35 0.9 16.3 30.1 41.0 49.2 55.5 60.5 59.7 59.1 59.1 59.5 60.1 60.9 60.8 60.6 60.5 60.6 60.8 61.1 61.1 61.0 40 1.4 16.6 30.1 41.0 49.2 55.5 60.5 59.5 59.0 59.0 59.5 60.1 60.9 60.8 60.6 60.5 60.6 60.8 61.1 61.1 61.0 45 2.0 16.9 30.3 41.0 49.2 55.5 60.5 59.2 58.8 58.9 59.4 60.0 60.8 60.7 60.5 60.4 60.5 60.8 61.0 61.1 61.0 50 2.8 17.4 30.5 41.1 49.2 55.5 59.9 58.9 58.5 58.7 59.2 59.9 60.8 60.6 60.4 60.4 60.5 60.7 61.0 61.1 61.0 55 3.8 17.9 30.7 41.2 49.3 55.6 59.3 58.4 58.2 58.5 59.1 59.8 60.7 60.5 60.3 60.3 60.5 60.7 61.0 61.1 61.0 60 5.0 18.7 31.1 41.4 49.4 55.6 58.4 57.9 57.8 58.2 58.9 59.7 60.6 60.3 60.2 60.2 60.4 60.7 61.0 61.1 61.0 65 6.7 19.7 31.7 41.7 49.5 55.7 57.4 57.2 57.4 57.9 58.6 59.5 60.3 60.1 60.0 60.1 60.3 60.6 61.0 61.1 61.0 70 8.9 21.2 32.4 42.1 49.8 55.8 56.2 56.3 56.8 57.5 58.3 59.3 60.0 59.8 59.8 60.0 60.2 60.5 60.9 61.0 61.0 75 11.8 23.2 33.6 42.7 50.1 54.4 54.7 55.3 56.0 56.9 57.9 59.0 59.5 59.5 59.6 59.8 60.1 60.5 60.9 61.0 61.0 80 16.1 26.2 35.5 43.7 50.6 51.9 52.9 54.0 55.1 56.2 57.4 58.6 58.8 59.0 59.2 59.5 59.9 60.3 60.8 60.9 61.0 85 22.5 31.0 38.8 45.0 47.5 49.5 51.1 52.6 54.1 55.5 56.8 57.6 58.0 58.3 58.7 59.2 59.7 60.2 60.7 60.9 61.0 90 32.5 37.5 41.0 43.8 46.2 48.3 50.2 51.9 53.5 55.0 55.7 56.4 57.0 57.6 58.2 58.8 59.4 60.0 60.6 60.8 61.0 95 42.5 44.5 46.4 48.1 49.7 51.1 52.0 53.0 53.8 54.6 55.4 56.1 56.8 57.5 58.1 58.8 59.4 60.0 60.4 60.7 61.0 98 52.7 53.3 53.8 54.3 54.8 55.3 55.8 56.3 56.7 57.2 57.7 58.1 58.5 59.0 59.4 59.7 60.0 60.2 60.5 60.7 61.0 

5-29
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 5-7 -- CONTINUED 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO THE RUNOFF FROM 1 INCH OF RAINFALL 

Florida Keys (Zone 3)

NONDCIA 

CN 

PERCENT DCIA 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 1.3 15.6 28.1 38.0 45.8 52.1 57.2 56.9 56.4 56.3 56.7 57.2 57.9 58.1 57.9 57.8 57.8 58.0 58.2 58.5 58.3 35 1.7 15.8 28.1 38.0 45.8 52.1 57.2 56.6 56.2 56.2 56.5 57.1 57.9 58.0 57.8 57.7 57.8 58.0 58.2 58.5 58.3 40 2.1 16.1 28.2 38.0 45.8 52.1 57.2 56.2 55.9 56.0 56.4 57.0 57.8 57.9 57.7 57.7 57.8 57.9 58.2 58.4 58.3 45 2.6 16.3 28.3 38.1 45.8 52.1 56.6 55.8 55.6 55.8 56.2 56.9 57.7 57.8 57.6 57.6 57.7 57.9 58.2 58.4 58.3 50 3.3 16.6 28.4 38.1 45.8 52.1 55.9 55.3 55.2 55.5 56.1 56.8 57.6 57.7 57.5 57.5 57.7 57.9 58.2 58.4 58.3 55 4.1 17.0 28.6 38.2 45.8 52.1 55.1 54.7 54.8 55.2 55.8 56.6 57.5 57.5 57.4 57.4 57.6 57.8 58.1 58.4 58.3 60 5.1 17.5 28.8 38.3 45.9 52.1 54.1 54.0 54.3 54.9 55.6 56.4 57.3 57.3 57.2 57.3 57.5 57.8 58.1 58.4 58.3 65 6.4 18.2 29.2 38.5 46.0 52.2 53.0 53.3 53.7 54.4 55.2 56.2 57.1 57.0 57.0 57.2 57.4 57.7 58.1 58.4 58.3 70 8.0 19.3 29.7 38.8 46.2 51.3 51.8 52.3 53.1 53.9 54.9 55.9 56.7 56.7 56.8 57.0 57.3 57.6 58.0 58.3 58.3 75 10.3 20.9 30.6 39.2 46.4 49.3 50.3 51.3 52.3 53.3 54.4 55.6 56.2 56.3 56.5 56.8 57.1 57.5 58.0 58.3 58.3 80 13.8 23.3 32.1 40.0 45.2 47.2 48.7 50.0 51.3 52.6 53.9 55.1 55.5 55.8 56.1 56.5 56.9 57.4 57.9 58.2 58.3 85 18.9 27.2 34.8 39.8 42.8 45.1 47.0 48.7 50.3 51.8 53.2 54.2 54.6 55.1 55.6 56.1 56.7 57.2 57.8 58.1 58.3 90 27.6 32.3 36.1 39.2 41.8 44.1 46.1 47.9 49.6 51.3 52.2 53.0 53.7 54.4 55.0 55.7 56.4 57.0 57.6 58.0 58.3 95 37.5 39.7 41.7 43.5 45.3 46.9 48.1 49.1 50.1 51.0 51.9 52.7 53.4 54.2 54.9 55.6 56.3 57.0 57.6 57.9 58.3 98 48.6 49.2 49.8 50.4 51.0 51.6 52.1 52.7 53.2 53.7 54.3 54.8 55.2 55.7 56.2 56.7 57.1 57.4 57.7 58.0 58.3 

5-30
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 5-7 -- CONTINUED 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO THE RUNOFF FROM 1 INCH OF RAINFALL 

Coastal (Zone 4)

NONDCIA 

CN 

PERCENT DCIA 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.7 16.3 29.9 40.3 48.0 54.0 58.6 57.3 56.8 56.9 57.3 58.0 58.7 58.4 58.2 58.2 58.3 58.5 58.8 58.7 58.6 35 1.1 16.5 29.9 40.3 48.0 54.0 58.3 57.1 56.7 56.8 57.2 57.9 58.7 58.4 58.2 58.2 58.3 58.5 58.8 58.7 58.6 40 1.7 16.8 30.0 40.3 48.0 54.0 57.9 56.8 56.5 56.7 57.2 57.8 58.6 58.3 58.1 58.1 58.2 58.5 58.8 58.7 58.6 45 2.4 17.1 30.1 40.3 48.0 54.0 57.5 56.5 56.3 56.5 57.1 57.8 58.6 58.2 58.1 58.1 58.2 58.5 58.8 58.7 58.6 50 3.3 17.6 30.3 40.4 48.1 54.0 56.9 56.1 56.0 56.3 56.9 57.7 58.4 58.1 58.0 58.0 58.2 58.4 58.8 58.7 58.6 55 4.4 18.2 30.6 40.5 48.1 54.0 56.1 55.6 55.7 56.1 56.7 57.5 58.2 57.9 57.9 57.9 58.1 58.4 58.7 58.7 58.6 60 5.7 19.0 31.0 40.7 48.2 54.0 55.3 55.0 55.2 55.8 56.5 57.4 58.0 57.8 57.7 57.8 58.1 58.4 58.7 58.6 58.6 65 7.4 20.0 31.5 40.9 48.3 54.1 54.3 54.3 54.8 55.4 56.3 57.2 57.7 57.5 57.6 57.7 58.0 58.3 58.7 58.6 58.6 70 9.5 21.4 32.2 41.3 48.6 52.9 53.1 53.5 54.2 55.0 56.0 57.0 57.3 57.3 57.4 57.6 57.9 58.2 58.6 58.6 58.6 75 12.4 23.4 33.3 41.9 48.9 51.0 51.7 52.5 53.5 54.5 55.6 56.7 56.8 56.9 57.1 57.4 57.7 58.2 58.6 58.6 58.6 80 16.6 26.3 35.1 42.8 47.2 48.9 50.1 51.4 52.6 53.9 55.1 56.0 56.2 56.4 56.8 57.2 57.6 58.0 58.5 58.5 58.6 85 22.8 30.9 38.3 42.2 44.8 46.9 48.6 50.2 51.8 53.2 54.6 55.0 55.4 55.8 56.3 56.8 57.4 57.9 58.3 58.4 58.6 90 31.6 35.8 39.1 41.8 44.1 46.2 48.1 49.8 51.4 52.5 53.2 53.9 54.6 55.2 55.9 56.5 57.1 57.7 58.1 58.3 58.6 95 41.3 43.2 44.9 46.5 47.9 48.9 49.9 50.8 51.6 52.4 53.2 53.9 54.6 55.3 55.9 56.6 57.2 57.6 57.9 58.3 58.6 98 50.7 51.3 51.8 52.3 52.8 53.3 53.7 54.2 54.6 55.1 55.5 56.0 56.4 56.8 57.1 57.3 57.6 57.8 58.1 58.3 58.6 

5-31
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 5-7 – CONTINUED 

CALCULATED ANNUAL MASS REMOVAL EFFICENCY OF A DRY RETENTION POND 

WITH A TREATMENT VOLUME EQUIVALENT TO THE RUNOFF FROM 1 INCH OF RAINFALL 

Southeast Coastal (Zone 5)

NONDCIA 

CN 

PERCENT DCIA 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 1.1 15.9 28.4 37.9 45.0 50.5 54.9 54.0 53.6 53.6 54.0 54.5 55.2 55.2 54.9 54.9 55.0 55.1 55.4 55.5 55.3 35 1.6 16.1 28.4 37.9 45.0 50.5 54.7 53.7 53.4 53.4 53.9 54.4 55.2 55.1 54.9 54.8 54.9 55.1 55.4 55.5 55.3 40 2.3 16.4 28.5 37.9 45.0 50.5 54.2 53.3 53.1 53.3 53.7 54.4 55.1 55.0 54.8 54.8 54.9 55.1 55.4 55.5 55.3 45 3.1 16.8 28.6 37.9 45.0 50.5 53.6 52.9 52.8 53.1 53.6 54.2 55.0 54.9 54.7 54.7 54.9 55.1 55.4 55.4 55.3 50 4.0 17.2 28.8 38.0 45.0 50.5 52.8 52.4 52.4 52.8 53.4 54.1 54.9 54.7 54.6 54.6 54.8 55.0 55.3 55.4 55.3 55 5.2 17.8 29.1 38.1 45.0 50.5 52.0 51.8 52.0 52.5 53.2 53.9 54.7 54.5 54.5 54.5 54.7 55.0 55.3 55.4 55.3 60 6.4 18.6 29.4 38.2 45.1 50.5 51.0 51.1 51.5 52.1 52.9 53.7 54.4 54.3 54.3 54.4 54.7 54.9 55.3 55.4 55.3 65 8.0 19.6 29.9 38.5 45.2 49.7 50.0 50.4 51.0 51.7 52.6 53.5 54.1 54.0 54.1 54.3 54.6 54.9 55.2 55.4 55.3 70 10.2 20.9 30.7 38.9 45.5 48.1 48.8 49.5 50.4 51.3 52.3 53.3 53.7 53.7 53.9 54.1 54.4 54.8 55.2 55.3 55.3 75 13.0 22.9 31.8 39.5 45.0 46.4 47.5 48.6 49.7 50.8 51.9 53.0 53.2 53.3 53.6 53.9 54.3 54.7 55.1 55.3 55.3 80 16.9 25.7 33.5 40.0 42.7 44.6 46.1 47.5 48.9 50.2 51.5 52.3 52.6 52.9 53.3 53.7 54.1 54.6 55.1 55.2 55.3 85 22.5 29.7 34.9 38.3 41.0 43.1 45.0 46.6 48.1 49.6 50.8 51.3 51.8 52.3 52.8 53.4 53.9 54.5 55.0 55.2 55.3 90 29.1 32.9 36.0 38.6 40.9 42.9 44.7 46.4 47.9 48.9 49.7 50.4 51.1 51.8 52.4 53.1 53.7 54.3 54.8 55.1 55.3 95 38.4 40.1 41.8 43.4 44.5 45.5 46.5 47.4 48.2 49.0 49.8 50.5 51.2 51.9 52.5 53.2 53.8 54.3 54.7 55.0 55.3 98 47.4 47.9 48.4 48.9 49.4 49.9 50.4 50.8 51.3 51.7 52.1 52.6 53.0 53.4 53.8 54.1 54.3 54.6 54.8 55.1 55.3 

5-32
FDEP \ STORMWATER TREATMENT REPORT 

5-33 

 A 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, 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 5

Treatment 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 systems are referenced by the St. Johns River, 

Suwannee River, Southwest Florida, and South Florida 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 Districts. The design criteria established by the 

St. Johns River Water Management District provides 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 recommends 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 districts mentioned previously provides calculations for 

a treatment volume associated with the wet detention 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. However, research on wet detention ponds clearly 

indicates that the most significant factor impacting the performance efficiency of a wet detention 

pond is the residence time within the system - specifically, 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 depth 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 conceivably 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 District 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

365 days x ROPPV Detention Time, t (days) = 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 efficiencies 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 detention systems summarized in Table 5-2. The values 

summarized in Table 5-8 correspond closely to performance 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 Table 5-8, with the possible 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 detention systems designed within the South Florida 

Water Management District (SFWMD) are often excavated 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 areas 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 Florida, relatively few of these studies have evaluated 

the relationship between detention time and performance efficiency of the system. Only three of the 

studies summarized in Table 5-2 provide measurements of performance efficiency at designated 

detention times within the pond. The remaining studies lack either basic bathymetric information on 

the pond or estimates of annual runoff 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 significant 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 regional 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 seepage 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 with 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 waterbodies 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 Table 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 available 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 entered 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 residence time were observed to exhibit curvilinear 

relationships, with a relatively rapid initial removal for both nutrients, followed by a slow gradual 

increase in removal efficiency over an extended period 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

331

16 

631

62

57 

901

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 R2

 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 remaining 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 general, 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, td (days)

0 100 200 300 400 500

Removal Efficiency (%)

0

20

40

60

80

100

R2 = 0.897

2 Percent Removal 40.13 6.372 ln( ) 0.213 (ln( )) 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 suggests 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 efficiency of 80% can be achieved at a detention time 

of about 200 days. The upper limit for removal efficiencies 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, td (days)

0 100 200 300 400 500 600

Removal Efficiency (%)

0

20

40

60

80

100

R2 = 0.800

(4.38 )

43.75 Percent Removal

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 removal efficiency and detention time for total 

nitrogen was obtained using a hyperbolic equation. The final version of this equation is summarized 

on Figure 5-10. The R2

 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 total 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 NOx) and particulate 

nitrogen are removed relatively rapidly in wet detention 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 species. 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 Figure 5-10 indicates that a removal efficiency 

of approximately 40% can be achieved for total nitrogen 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 District 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. Although the estimated removal efficiencies for total 

phosphorus meet the goal of 80% removal for stormwater 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 systems, constructed with or without filtration/ 

underdrain systems, exhibit highly variable removal efficiencies which are influenced to a large 

extent by the relationships between the seasonal high groundwater table elevation and the pond 

bottom. Detention systems which provide infiltration 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, there 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 River and South Florida Water Management Districts 

which now discourage the use of dry detention systems (with or without filtration/underdrains) in 

new development. Since other stormwater management options are available, such as dry retention 

or wet detention, which provide reliable and predictable pollutant removal efficiencies, dry detention 

systems should be eliminated as a common stormwater 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 potential 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 FAC). This rule requires that stormwater 

management systems 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. If the stormwater 

management system discharges to a designated 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 meet 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 within 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 construction 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 constituent 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 phosphorus. 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 stormwater runoff is biochemical oxygen demand 

(BOD). Inputs of BOD into surface water can cause 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 been 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 

BODi = BODo x exp (-K x t) 

where: 

 BODt = BOD at time, t (mg/l) 

 BODo = 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 representation 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 total nitrogen or total phosphorus, as indicated in 

Figures 5-10 and 5-11. Therefore, if a stormwater 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 management options. Based on the discussion presented 

in Section 5, these systems provide predictable and 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 exfiltration, 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 construction of the system with respect to the 

groundwater table elevation. Dry detention systems which have performed well in field 

evaluations have performed similar to dry retention 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 annual 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 from the performance efficiency tables for dry 

retention provided in Appendix D which were utilized 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 number. If the treatment efficiency for a given combination of 

retention depth, DCIA percentage, and non-DCIA curve number exceeded 80%, the retention 

depth was interpolated using the next lower retention 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-wide 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% removal efficiency are lowest in the Central zone 

areas, with the highest retention depths required in the Panhandle areas. 

 A graphical illustration of state-wide average 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 REPORT 

TABLE 6-1 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 80% 

State-Wide Average

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.24 0.28 0.37 0.45 0.51 0.59 0.67 0.75 0.82 0.90 0.98 1.05 1.13 1.21 1.29 1.37 1.44 1.52 1.60 35 0.26 0.30 0.39 0.46 0.53 0.60 0.68 0.75 0.83 0.91 0.98 1.06 1.14 1.21 1.29 1.37 1.45 1.52 1.60 40 0.29 0.33 0.41 0.48 0.54 0.62 0.69 0.77 0.84 0.92 0.99 1.07 1.14 1.22 1.30 1.37 1.45 1.52 1.60 45 0.34 0.37 0.44 0.50 0.56 0.64 0.71 0.78 0.85 0.93 1.00 1.08 1.15 1.23 1.30 1.38 1.45 1.53 1.60 50 0.43 0.44 0.48 0.53 0.59 0.67 0.74 0.80 0.87 0.95 1.02 1.09 1.16 1.24 1.31 1.38 1.45 1.53 1.60 55 0.54 0.52 0.54 0.58 0.64 0.70 0.77 0.83 0.90 0.97 1.04 1.11 1.18 1.25 1.32 1.39 1.46 1.53 1.60 60 0.68 0.62 0.62 0.64 0.69 0.75 0.81 0.86 0.93 0.99 1.06 1.13 1.19 1.26 1.33 1.40 1.46 1.53 1.60 65 0.82 0.74 0.72 0.73 0.77 0.81 0.86 0.91 0.97 1.03 1.09 1.15 1.21 1.28 1.34 1.41 1.47 1.54 1.60 70 0.98 0.88 0.85 0.84 0.86 0.89 0.93 0.97 1.02 1.07 1.13 1.18 1.24 1.30 1.36 1.42 1.48 1.54 1.60 75 1.12 1.04 0.99 0.97 0.97 0.99 1.02 1.05 1.09 1.13 1.18 1.23 1.28 1.33 1.38 1.43 1.49 1.55 1.60 80 1.26 1.19 1.14 1.12 1.11 1.11 1.13 1.15 1.18 1.21 1.24 1.28 1.32 1.37 1.41 1.46 1.50 1.55 1.60 85 1.39 1.33 1.29 1.26 1.25 1.25 1.25 1.26 1.28 1.30 1.33 1.35 1.38 1.42 1.45 1.49 1.52 1.56 1.60 90 1.50 1.46 1.43 1.41 1.40 1.39 1.39 1.39 1.40 1.41 1.42 1.44 1.46 1.48 1.50 1.52 1.55 1.57 1.60 95 1.58 1.56 1.55 1.54 1.53 1.53 1.53 1.53 1.53 1.53 1.53 1.54 1.54 1.55 1.56 1.57 1.58 1.59 1.60 98 1.59 1.59 1.58 1.58 1.58 1.58 1.58 1.58 1.58 1.58 1.58 1.58 1.59 1.59 1.59 1.59 1.60 1.60 1.60 

6-4
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-1 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 80% 

Panhandle (Zone 1)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.25 0.36 0.45 0.52 0.63 0.71 0.80 0.90 0.99 1.08 1.17 1.27 1.36 1.45 1.55 1.64 1.73 1.83 1.92 35 0.29 0.39 0.46 0.54 0.64 0.72 0.82 0.91 1.00 1.09 1.18 1.27 1.37 1.46 1.55 1.64 1.74 1.83 1.92 40 0.35 0.43 0.49 0.58 0.67 0.75 0.84 0.93 1.02 1.11 1.20 1.29 1.38 1.47 1.56 1.65 1.74 1.83 1.92 45 0.44 0.47 0.54 0.62 0.70 0.78 0.87 0.95 1.04 1.13 1.21 1.30 1.39 1.48 1.57 1.66 1.74 1.83 1.92 50 0.56 0.55 0.60 0.67 0.74 0.82 0.90 0.98 1.06 1.15 1.23 1.32 1.41 1.49 1.58 1.66 1.75 1.83 1.92 55 0.71 0.67 0.69 0.74 0.80 0.87 0.95 1.02 1.10 1.18 1.26 1.34 1.43 1.51 1.59 1.67 1.75 1.84 1.92 60 0.89 0.81 0.81 0.83 0.88 0.94 1.01 1.07 1.15 1.22 1.30 1.37 1.45 1.53 1.60 1.68 1.76 1.84 1.92 65 1.07 0.98 0.95 0.96 0.99 1.03 1.08 1.14 1.21 1.27 1.34 1.41 1.48 1.55 1.62 1.70 1.77 1.85 1.92 70 1.24 1.15 1.11 1.10 1.11 1.14 1.18 1.23 1.28 1.34 1.40 1.46 1.52 1.58 1.65 1.72 1.78 1.85 1.92 75 1.42 1.33 1.29 1.27 1.27 1.28 1.30 1.33 1.37 1.42 1.47 1.52 1.57 1.62 1.68 1.74 1.80 1.86 1.92 80 1.58 1.50 1.46 1.43 1.42 1.43 1.44 1.46 1.49 1.52 1.55 1.59 1.63 1.68 1.72 1.77 1.82 1.87 1.92 85 1.73 1.67 1.63 1.60 1.59 1.58 1.59 1.59 1.61 1.63 1.65 1.68 1.71 1.74 1.77 1.80 1.84 1.88 1.92 90 1.85 1.82 1.79 1.77 1.75 1.74 1.74 1.74 1.74 1.75 1.76 1.77 1.79 1.81 1.83 1.85 1.87 1.90 1.92 95 1.94 1.92 1.91 1.90 1.89 1.88 1.88 1.87 1.87 1.87 1.87 1.88 1.88 1.88 1.89 1.90 1.90 1.91 1.92 98 1.94 1.93 1.93 1.93 1.92 1.92 1.92 1.92 1.92 1.92 1.92 1.91 1.92 1.92 1.92 1.92 1.92 1.92 1.92 

6-5
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-1 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 80% 

Central (Zone 2)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.22 0.24 0.32 0.40 0.46 0.51 0.60 0.67 0.73 0.80 0.87 0.94 1.01 1.08 1.15 1.22 1.29 1.36 1.43 35 0.23 0.24 0.33 0.41 0.46 0.52 0.60 0.67 0.73 0.80 0.88 0.94 1.01 1.08 1.15 1.22 1.29 1.36 1.43 40 0.23 0.26 0.35 0.42 0.47 0.53 0.61 0.68 0.74 0.81 0.88 0.95 1.01 1.09 1.16 1.22 1.29 1.36 1.43 45 0.24 0.28 0.37 0.43 0.48 0.55 0.62 0.69 0.74 0.82 0.89 0.95 1.02 1.09 1.16 1.22 1.29 1.36 1.43 50 0.27 0.32 0.39 0.45 0.49 0.57 0.64 0.70 0.76 0.83 0.90 0.96 1.03 1.10 1.16 1.23 1.30 1.37 1.43 55 0.35 0.38 0.42 0.47 0.52 0.59 0.66 0.71 0.77 0.84 0.91 0.97 1.04 1.11 1.17 1.23 1.30 1.37 1.43 60 0.45 0.44 0.46 0.50 0.56 0.62 0.68 0.73 0.80 0.86 0.93 0.98 1.05 1.11 1.18 1.24 1.30 1.37 1.43 65 0.57 0.52 0.53 0.56 0.61 0.66 0.71 0.76 0.83 0.89 0.95 1.00 1.06 1.13 1.19 1.25 1.31 1.37 1.43 70 0.70 0.65 0.63 0.65 0.68 0.72 0.76 0.81 0.87 0.92 0.97 1.03 1.09 1.14 1.20 1.25 1.31 1.37 1.43 75 0.84 0.78 0.76 0.75 0.77 0.80 0.83 0.88 0.92 0.96 1.01 1.06 1.11 1.17 1.22 1.27 1.32 1.38 1.43 80 0.98 0.92 0.90 0.89 0.89 0.91 0.93 0.96 0.99 1.02 1.07 1.11 1.15 1.20 1.24 1.29 1.34 1.38 1.43 85 1.12 1.07 1.04 1.03 1.02 1.03 1.04 1.06 1.08 1.11 1.14 1.17 1.20 1.24 1.27 1.31 1.35 1.39 1.43 90 1.24 1.21 1.19 1.18 1.17 1.17 1.18 1.19 1.20 1.21 1.23 1.25 1.27 1.30 1.32 1.35 1.38 1.40 1.43 95 1.35 1.34 1.33 1.33 1.32 1.32 1.32 1.33 1.33 1.34 1.34 1.35 1.36 1.37 1.38 1.39 1.41 1.42 1.43 98 1.39 1.39 1.39 1.39 1.39 1.39 1.39 1.40 1.40 1.40 1.40 1.41 1.41 1.41 1.42 1.42 1.42 1.43 1.43 

6-6
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-1 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 80% 

Florida Keys (Zone 3)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.31 0.35 0.43 0.49 0.57 0.65 0.72 0.81 0.89 0.96 1.05 1.13 1.21 1.29 1.37 1.45 1.53 1.62 1.70 35 0.37 0.39 0.45 0.52 0.60 0.67 0.74 0.82 0.91 0.98 1.06 1.14 1.22 1.30 1.38 1.46 1.54 1.62 1.70 40 0.49 0.46 0.50 0.56 0.63 0.70 0.77 0.85 0.92 0.99 1.07 1.15 1.22 1.31 1.39 1.46 1.54 1.62 1.70 45 0.68 0.56 0.56 0.60 0.66 0.73 0.80 0.87 0.94 1.01 1.09 1.17 1.24 1.32 1.39 1.47 1.54 1.62 1.70 50 0.87 0.69 0.64 0.66 0.72 0.78 0.83 0.90 0.97 1.04 1.11 1.18 1.25 1.33 1.40 1.47 1.55 1.63 1.70 55 1.06 0.84 0.76 0.76 0.79 0.83 0.88 0.94 1.01 1.07 1.14 1.20 1.27 1.35 1.42 1.48 1.55 1.63 1.70 60 1.26 1.02 0.91 0.87 0.86 0.89 0.94 1.00 1.05 1.11 1.17 1.23 1.29 1.36 1.43 1.49 1.56 1.63 1.70 65 1.45 1.20 1.07 1.00 0.98 1.00 1.02 1.06 1.10 1.15 1.21 1.26 1.32 1.39 1.44 1.50 1.57 1.64 1.70 70 1.62 1.37 1.25 1.16 1.12 1.10 1.11 1.14 1.17 1.21 1.26 1.30 1.36 1.41 1.46 1.52 1.58 1.64 1.70 75 1.77 1.55 1.42 1.33 1.27 1.24 1.24 1.25 1.26 1.29 1.32 1.36 1.40 1.45 1.49 1.54 1.60 1.65 1.70 80 1.90 1.71 1.59 1.49 1.42 1.38 1.36 1.36 1.36 1.38 1.40 1.43 1.46 1.49 1.53 1.57 1.61 1.65 1.70 85 1.98 1.84 1.72 1.64 1.58 1.54 1.51 1.49 1.49 1.49 1.50 1.51 1.52 1.55 1.57 1.60 1.63 1.66 1.70 90 2.00 1.91 1.83 1.76 1.71 1.67 1.64 1.62 1.61 1.60 1.60 1.60 1.61 1.62 1.63 1.64 1.66 1.68 1.70 95 1.92 1.88 1.84 1.81 1.79 1.77 1.75 1.73 1.71 1.70 1.70 1.69 1.69 1.68 1.68 1.69 1.69 1.69 1.70 98 1.79 1.78 1.77 1.76 1.75 1.74 1.74 1.73 1.72 1.72 1.71 1.71 1.71 1.70 1.70 1.70 1.70 1.70 1.70 

6-7
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-1 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 80% 

Coastal (Zone 4)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.23 0.27 0.37 0.44 0.50 0.59 0.67 0.73 0.81 0.89 0.96 1.04 1.12 1.20 1.27 1.35 1.43 1.51 1.59 35 0.24 0.29 0.39 0.45 0.51 0.60 0.67 0.74 0.82 0.90 0.97 1.05 1.13 1.20 1.28 1.36 1.43 1.51 1.59 40 0.26 0.33 0.41 0.46 0.52 0.61 0.69 0.75 0.83 0.91 0.98 1.05 1.13 1.21 1.28 1.36 1.43 1.51 1.59 45 0.31 0.37 0.43 0.48 0.55 0.63 0.70 0.76 0.85 0.92 0.99 1.06 1.14 1.21 1.29 1.36 1.44 1.51 1.59 50 0.40 0.42 0.46 0.51 0.59 0.66 0.72 0.79 0.87 0.93 1.00 1.08 1.15 1.22 1.29 1.37 1.44 1.51 1.59 55 0.51 0.48 0.51 0.56 0.63 0.69 0.75 0.82 0.89 0.95 1.02 1.09 1.16 1.23 1.30 1.37 1.44 1.51 1.59 60 0.65 0.58 0.59 0.63 0.68 0.73 0.78 0.85 0.92 0.98 1.04 1.11 1.18 1.24 1.31 1.38 1.45 1.51 1.59 65 0.80 0.72 0.70 0.71 0.74 0.78 0.84 0.90 0.95 1.01 1.07 1.14 1.20 1.26 1.33 1.39 1.45 1.52 1.59 70 0.96 0.86 0.82 0.81 0.83 0.87 0.91 0.95 1.00 1.05 1.11 1.17 1.22 1.28 1.34 1.40 1.46 1.52 1.59 75 1.10 1.01 0.97 0.95 0.95 0.97 0.99 1.02 1.07 1.11 1.16 1.21 1.26 1.31 1.37 1.42 1.47 1.53 1.59 80 1.24 1.16 1.11 1.09 1.08 1.08 1.10 1.12 1.15 1.19 1.22 1.26 1.30 1.35 1.39 1.44 1.49 1.53 1.59 85 1.36 1.30 1.26 1.23 1.22 1.22 1.23 1.24 1.25 1.28 1.30 1.33 1.36 1.40 1.43 1.47 1.50 1.54 1.59 90 1.47 1.43 1.40 1.38 1.37 1.36 1.36 1.37 1.38 1.39 1.40 1.42 1.44 1.46 1.48 1.50 1.53 1.56 1.59 95 1.54 1.53 1.52 1.51 1.51 1.50 1.50 1.50 1.50 1.51 1.51 1.52 1.52 1.53 1.54 1.55 1.56 1.57 1.59 98 1.56 1.56 1.56 1.56 1.56 1.56 1.56 1.56 1.56 1.56 1.56 1.56 1.57 1.57 1.57 1.58 1.58 1.58 1.59 

6-8
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-1 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 80% 

Southeast Coastal (Zone 5)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.26 0.36 0.44 0.50 0.59 0.68 0.76 0.85 0.93 1.02 1.10 1.19 1.28 1.36 1.45 1.54 1.62 1.71 1.80 35 0.33 0.40 0.46 0.53 0.62 0.70 0.78 0.87 0.95 1.03 1.12 1.20 1.29 1.37 1.46 1.54 1.62 1.71 1.80 40 0.41 0.45 0.50 0.57 0.65 0.73 0.81 0.89 0.97 1.05 1.13 1.22 1.30 1.38 1.46 1.55 1.63 1.71 1.80 45 0.55 0.52 0.56 0.63 0.69 0.76 0.84 0.92 0.99 1.07 1.15 1.23 1.31 1.39 1.47 1.55 1.63 1.72 1.80 50 0.71 0.63 0.65 0.69 0.75 0.81 0.88 0.95 1.03 1.10 1.18 1.25 1.33 1.41 1.48 1.56 1.64 1.72 1.80 55 0.89 0.78 0.76 0.78 0.82 0.87 0.93 1.00 1.06 1.13 1.21 1.28 1.35 1.42 1.50 1.57 1.64 1.72 1.80 60 1.07 0.94 0.89 0.88 0.91 0.95 1.00 1.05 1.11 1.17 1.24 1.31 1.37 1.44 1.51 1.58 1.65 1.73 1.80 65 1.25 1.11 1.04 1.02 1.02 1.04 1.07 1.12 1.17 1.23 1.28 1.34 1.40 1.47 1.53 1.60 1.66 1.73 1.80 70 1.41 1.28 1.20 1.16 1.15 1.15 1.17 1.20 1.24 1.29 1.33 1.39 1.44 1.50 1.56 1.61 1.67 1.74 1.80 75 1.57 1.44 1.36 1.31 1.29 1.28 1.29 1.30 1.33 1.36 1.40 1.44 1.49 1.54 1.58 1.63 1.69 1.74 1.80 80 1.70 1.59 1.52 1.47 1.43 1.41 1.41 1.42 1.43 1.45 1.48 1.51 1.54 1.58 1.62 1.66 1.71 1.75 1.80 85 1.80 1.72 1.66 1.61 1.57 1.55 1.54 1.54 1.54 1.55 1.57 1.59 1.61 1.63 1.66 1.69 1.73 1.76 1.80 90 1.87 1.81 1.77 1.73 1.71 1.69 1.67 1.66 1.66 1.66 1.67 1.67 1.69 1.70 1.72 1.73 1.75 1.77 1.80 95 1.88 1.85 1.84 1.82 1.81 1.79 1.79 1.78 1.77 1.77 1.77 1.77 1.77 1.77 1.77 1.78 1.78 1.79 1.80 98 1.83 1.82 1.82 1.81 1.81 1.81 1.80 1.80 1.80 1.80 1.80 1.79 1.79 1.79 1.79 1.79 1.80 1.80 1.80 

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 90

Percent DCIA (%)

20

40

60

80

100

Retention Depth (inches)

 Figure 6-2. State-wide Average Variations 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 previously, these variations are primarily due to the 

differences in the distribution of typical rain events. 

 A summary of recommended design criteria for 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, equivalent 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 located 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 Table 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 90

Percent 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 for 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 90

Percent 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 predictable pollutant removal efficiencies and 

can play a significant part in stormwater management for virtually any type of development. 

However, as discussed in Section 5.2, wet detention 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 wet 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 occur, 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 anticipated depth of the anoxic zone within 

the pond based on the anticipated productivity of the pond. This concept is discussed further in 

Section 6.4. No restrictions are placed on the configuration 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 vegetation. 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 exceed 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 systems 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 treatment systems are used in series as part of a 

treatment train, the efficiency of the overall treatment train can be calculated using the following 

equation: 

Overall Treatment Train Efficiency (decimal) = Eff1 + (1 – Eff1) x Eff2 (Eq. 1) 

where: 

 Eff1 = efficiency of initial treatment system (decimal) 

 Eff2 = efficiency of second treatment system (decimal) 

After treatment in the initial system, a load reduction has occurred which is a function of the type 

of treatment provided. After migrating through the 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 associated 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 provide 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 Eff2, the efficiency of the initial treatment system (Eff1) would need to be 67% to achieve an 

overall treatment efficiency of 80%. 

Depending upon the characteristics of the development and the meteorological region, 

achieving an initial 67% annual mass load reduction using retention will require between 0.25-

0.75 inch of dry retention as pre-treatment. When pre-treatment is provided and the remaining 

stormwater is discharged into the wet detention pond, the overall treatment system will achieve a 

mass removal efficiency of 80% for total nitrogen. 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 outlined previously for evaluation of retention 

criteria based upon an 80% annual mass load reduction. 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 percentage and non-DCIA curve number. However, as 

DCIA percentages and non-DCIA curve numbers increase, retention treatment requirements also 

increase, approaching values ranging from 3.2-3.4 inches 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 detention systems are not capable of providing a 95% 

pollutant removal efficiency for either total nitrogen or total phosphorus, even at extended detention 

periods. Therefore, to achieve the 95% removal objective 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 reduction 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 Eff2, the efficiency of the initial 

treatment system (Eff1) would need to be 92% to achieve an overall treatment efficiency of 95%. 

When pre-treatment is provided and the remaining stormwater 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 REPORT 

TABLE 6-4 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 95% 

State-Wide Average

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.70 0.77 0.90 1.04 1.19 1.35 1.51 1.67 1.84 2.00 2.16 2.33 2.49 2.66 2.82 2.98 3.13 3.27 3.40 35 0.88 0.91 1.01 1.13 1.27 1.42 1.57 1.72 1.88 2.04 2.20 2.36 2.52 2.68 2.84 2.99 3.14 3.27 3.40 40 1.11 1.08 1.15 1.25 1.37 1.50 1.64 1.79 1.94 2.09 2.24 2.40 2.55 2.70 2.86 3.01 3.15 3.28 3.40 45 1.37 1.29 1.32 1.39 1.49 1.61 1.73 1.87 2.01 2.15 2.29 2.44 2.59 2.73 2.88 3.02 3.15 3.28 3.40 50 1.65 1.53 1.52 1.56 1.64 1.74 1.85 1.96 2.09 2.22 2.35 2.49 2.63 2.77 2.91 3.04 3.16 3.28 3.40 55 1.92 1.78 1.74 1.76 1.81 1.89 1.98 2.08 2.19 2.31 2.43 2.55 2.68 2.81 2.94 3.06 3.18 3.29 3.40 60 2.19 2.04 1.98 1.98 2.00 2.06 2.13 2.21 2.31 2.41 2.51 2.63 2.74 2.86 2.97 3.08 3.19 3.30 3.40 65 2.46 2.30 2.23 2.20 2.21 2.25 2.30 2.36 2.44 2.52 2.61 2.71 2.81 2.91 3.01 3.11 3.21 3.31 3.40 70 2.70 2.56 2.48 2.44 2.44 2.45 2.48 2.53 2.59 2.66 2.73 2.81 2.89 2.98 3.06 3.15 3.23 3.32 3.40 75 2.93 2.81 2.73 2.68 2.66 2.67 2.68 2.71 2.75 2.80 2.86 2.92 2.98 3.05 3.12 3.19 3.26 3.33 3.40 80 3.12 3.03 2.97 2.92 2.89 2.88 2.88 2.90 2.92 2.95 2.99 3.03 3.08 3.12 3.18 3.23 3.29 3.34 3.40 85 3.27 3.21 3.16 3.13 3.10 3.08 3.08 3.08 3.09 3.10 3.12 3.15 3.18 3.21 3.24 3.28 3.32 3.36 3.40 90 3.39 3.35 3.32 3.30 3.28 3.26 3.25 3.25 3.25 3.25 3.26 3.27 3.28 3.29 3.31 3.33 3.35 3.37 3.40 95 3.46 3.44 3.43 3.41 3.40 3.39 3.39 3.38 3.38 3.38 3.37 3.37 3.37 3.38 3.38 3.38 3.39 3.39 3.40 98 3.44 3.44 3.43 3.43 3.42 3.42 3.42 3.42 3.41 3.41 3.41 3.41 3.40 3.40 3.40 3.40 3.40 3.40 3.40 

6-17
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-4 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 95% 

Panhandle (Zone 1)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.82 0.92 1.09 1.28 1.46 1.66 1.86 2.06 2.26 2.46 2.66 2.86 3.06 3.26 3.47 3.65 3.79 3.90 3.95 35 1.11 1.08 1.21 1.37 1.56 1.74 1.93 2.12 2.31 2.51 2.70 2.90 3.09 3.29 3.49 3.66 3.79 3.90 3.95 40 1.43 1.32 1.38 1.51 1.67 1.84 2.02 2.20 2.38 2.57 2.75 2.94 3.13 3.32 3.51 3.68 3.80 3.90 3.95 45 1.75 1.60 1.61 1.70 1.82 1.97 2.13 2.30 2.47 2.64 2.82 3.00 3.18 3.36 3.54 3.69 3.81 3.90 3.95 50 2.06 1.89 1.87 1.93 2.02 2.14 2.28 2.42 2.58 2.74 2.90 3.06 3.23 3.41 3.57 3.71 3.82 3.91 3.95 55 2.36 2.19 2.14 2.18 2.24 2.34 2.45 2.58 2.71 2.85 3.00 3.15 3.30 3.46 3.61 3.73 3.83 3.91 3.95 60 2.64 2.48 2.43 2.44 2.49 2.56 2.65 2.75 2.87 2.99 3.12 3.25 3.39 3.53 3.65 3.76 3.84 3.91 3.95 65 2.91 2.78 2.72 2.72 2.75 2.80 2.86 2.95 3.04 3.15 3.26 3.37 3.49 3.60 3.70 3.78 3.86 3.92 3.95 70 3.18 3.07 3.02 3.01 3.02 3.05 3.10 3.16 3.24 3.32 3.40 3.50 3.59 3.67 3.75 3.81 3.88 3.92 3.95 75 3.46 3.37 3.32 3.30 3.30 3.31 3.34 3.38 3.44 3.50 3.56 3.62 3.68 3.74 3.79 3.84 3.90 3.93 3.95 80 3.72 3.65 3.60 3.58 3.57 3.57 3.58 3.60 3.63 3.67 3.70 3.73 3.77 3.80 3.84 3.88 3.91 3.93 3.95 85 3.83 3.81 3.79 3.78 3.77 3.77 3.77 3.77 3.78 3.79 3.81 3.82 3.84 3.86 3.89 3.91 3.92 3.94 3.95 90 3.92 3.90 3.89 3.89 3.88 3.88 3.88 3.88 3.88 3.89 3.89 3.90 3.90 3.91 3.92 3.93 3.93 3.94 3.95 95 3.96 3.95 3.95 3.95 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.95 3.95 3.95 3.95 98 3.96 3.96 3.96 3.96 3.96 3.96 3.95 3.95 3.95 3.95 3.95 3.95 3.95 3.95 3.95 3.95 3.95 3.95 3.95 

6-18
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-4 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 95% 

Central (Zone 2)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.44 0.55 0.69 0.82 0.96 1.11 1.25 1.40 1.54 1.69 1.83 1.98 2.12 2.26 2.41 2.55 2.70 2.84 2.99 35 0.54 0.61 0.74 0.87 1.00 1.14 1.28 1.42 1.56 1.71 1.85 1.99 2.13 2.28 2.42 2.56 2.71 2.85 2.99 40 0.69 0.71 0.81 0.93 1.06 1.19 1.32 1.46 1.60 1.74 1.87 2.01 2.15 2.29 2.43 2.57 2.71 2.85 2.99 45 0.88 0.86 0.91 1.01 1.13 1.25 1.38 1.51 1.64 1.77 1.90 2.04 2.17 2.31 2.45 2.58 2.72 2.85 2.99 50 1.11 1.04 1.06 1.13 1.22 1.33 1.45 1.57 1.69 1.82 1.95 2.07 2.20 2.33 2.46 2.59 2.73 2.86 2.99 55 1.36 1.25 1.23 1.27 1.35 1.43 1.54 1.64 1.76 1.87 2.00 2.12 2.24 2.36 2.49 2.61 2.74 2.86 2.99 60 1.61 1.48 1.44 1.45 1.50 1.57 1.65 1.75 1.84 1.95 2.06 2.17 2.28 2.40 2.52 2.63 2.75 2.87 2.99 65 1.86 1.72 1.66 1.66 1.68 1.73 1.79 1.87 1.95 2.05 2.14 2.24 2.34 2.45 2.55 2.66 2.77 2.88 2.99 70 2.10 1.96 1.89 1.87 1.88 1.91 1.96 2.01 2.08 2.15 2.24 2.32 2.41 2.50 2.60 2.69 2.79 2.89 2.99 75 2.33 2.20 2.13 2.10 2.09 2.11 2.14 2.18 2.23 2.29 2.35 2.42 2.49 2.57 2.65 2.73 2.82 2.90 2.99 80 2.54 2.44 2.37 2.33 2.32 2.32 2.33 2.36 2.39 2.43 2.48 2.53 2.59 2.65 2.71 2.78 2.85 2.92 2.99 85 2.73 2.65 2.60 2.57 2.55 2.54 2.54 2.55 2.57 2.59 2.62 2.66 2.70 2.74 2.79 2.83 2.88 2.94 2.99 90 2.88 2.84 2.81 2.78 2.77 2.76 2.75 2.75 2.76 2.77 2.78 2.80 2.82 2.84 2.87 2.90 2.93 2.96 2.99 95 3.00 2.98 2.97 2.96 2.95 2.94 2.94 2.94 2.94 2.94 2.94 2.94 2.94 2.95 2.95 2.96 2.97 2.98 2.99 98 3.02 3.01 3.01 3.01 3.01 3.00 3.00 3.00 2.99 2.99 2.99 2.99 2.99 2.99 2.99 2.99 2.99 2.99 2.99 

6-19
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-4 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 95% 

Florida Keys (Zone 3)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 2.25 1.96 1.71 1.72 1.82 1.96 2.13 2.30 2.48 2.67 2.86 3.05 3.24 3.43 3.59 3.69 3.79 3.88 3.98 35 2.32 2.40 2.10 2.05 2.07 2.15 2.28 2.44 2.60 2.76 2.94 3.12 3.30 3.48 3.60 3.70 3.79 3.88 3.98 40 2.42 2.47 2.55 2.38 2.36 2.38 2.46 2.58 2.73 2.87 3.03 3.19 3.36 3.52 3.61 3.70 3.79 3.89 3.98 45 2.55 2.58 2.62 2.70 2.65 2.64 2.67 2.75 2.87 3.00 3.13 3.28 3.43 3.54 3.62 3.71 3.80 3.89 3.98 50 2.69 2.70 2.73 2.79 2.85 2.90 2.89 2.94 3.03 3.14 3.25 3.38 3.47 3.56 3.64 3.72 3.81 3.89 3.98 55 2.83 2.84 2.86 2.89 2.95 3.00 3.07 3.14 3.21 3.28 3.35 3.43 3.50 3.58 3.66 3.74 3.82 3.90 3.98 60 2.98 2.98 2.99 3.01 3.06 3.10 3.15 3.21 3.28 3.34 3.41 3.47 3.54 3.61 3.68 3.75 3.83 3.90 3.98 65 3.13 3.13 3.12 3.14 3.17 3.21 3.25 3.30 3.35 3.41 3.47 3.52 3.59 3.65 3.71 3.78 3.84 3.91 3.98 70 3.29 3.28 3.26 3.28 3.30 3.33 3.36 3.40 3.44 3.49 3.54 3.59 3.64 3.69 3.74 3.80 3.86 3.92 3.98 75 3.44 3.42 3.41 3.42 3.44 3.45 3.47 3.50 3.54 3.58 3.61 3.65 3.69 3.74 3.78 3.83 3.88 3.93 3.98 80 3.59 3.57 3.57 3.57 3.58 3.59 3.60 3.62 3.65 3.67 3.70 3.73 3.76 3.79 3.82 3.86 3.90 3.94 3.98 85 3.75 3.74 3.73 3.73 3.72 3.72 3.73 3.74 3.76 3.77 3.79 3.81 3.83 3.85 3.87 3.89 3.92 3.95 3.98 90 3.91 3.89 3.88 3.87 3.87 3.87 3.87 3.87 3.87 3.88 3.88 3.89 3.90 3.91 3.92 3.93 3.95 3.96 3.98 95 3.99 3.99 3.99 3.99 4.00 3.99 3.98 3.98 3.98 3.97 3.97 3.97 3.97 3.97 3.97 3.97 3.97 3.97 3.98 98 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 3.99 3.99 3.99 3.99 3.99 3.98 3.98 3.98 3.98 3.98 

 6-20 
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-4 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 95% 

Coastal (Zone 4)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 0.62 0.73 0.85 1.00 1.15 1.31 1.47 1.63 1.79 1.95 2.11 2.28 2.44 2.60 2.76 2.93 3.09 3.25 3.41 35 0.83 0.85 0.96 1.09 1.23 1.37 1.52 1.68 1.83 1.99 2.15 2.30 2.46 2.62 2.78 2.94 3.10 3.26 3.41 40 1.09 1.04 1.10 1.21 1.32 1.46 1.60 1.74 1.89 2.04 2.19 2.34 2.49 2.65 2.80 2.95 3.11 3.26 3.41 45 1.38 1.27 1.28 1.35 1.45 1.56 1.69 1.82 1.95 2.10 2.24 2.38 2.53 2.68 2.82 2.97 3.12 3.27 3.41 50 1.68 1.53 1.50 1.53 1.60 1.70 1.80 1.91 2.04 2.17 2.30 2.43 2.57 2.71 2.85 2.99 3.13 3.27 3.41 55 1.98 1.81 1.75 1.74 1.79 1.86 1.94 2.04 2.14 2.25 2.37 2.50 2.62 2.75 2.88 3.01 3.15 3.28 3.41 60 2.27 2.08 2.00 1.98 1.99 2.04 2.10 2.18 2.26 2.36 2.46 2.57 2.69 2.80 2.92 3.04 3.17 3.29 3.41 65 2.55 2.36 2.26 2.22 2.21 2.23 2.28 2.34 2.40 2.48 2.57 2.66 2.76 2.86 2.97 3.08 3.19 3.30 3.41 70 2.82 2.63 2.52 2.47 2.45 2.45 2.47 2.51 2.56 2.62 2.69 2.76 2.85 2.93 3.02 3.12 3.22 3.31 3.41 75 3.06 2.89 2.79 2.72 2.68 2.67 2.68 2.70 2.73 2.77 2.82 2.88 2.94 3.01 3.09 3.16 3.25 3.33 3.41 80 3.25 3.13 3.04 2.97 2.92 2.90 2.89 2.89 2.91 2.93 2.96 3.00 3.05 3.10 3.16 3.22 3.28 3.35 3.41 85 3.42 3.32 3.25 3.20 3.15 3.12 3.10 3.09 3.09 3.10 3.11 3.14 3.16 3.20 3.24 3.28 3.32 3.37 3.41 90 3.53 3.47 3.42 3.38 3.35 3.32 3.29 3.28 3.27 3.26 3.27 3.27 3.29 3.30 3.32 3.34 3.36 3.39 3.41 95 3.56 3.53 3.51 3.49 3.47 3.45 3.44 3.43 3.42 3.41 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.41 3.41 98 3.49 3.48 3.48 3.47 3.46 3.46 3.45 3.45 3.44 3.44 3.43 3.43 3.43 3.42 3.42 3.42 3.42 3.42 3.41 

6-21
FDEP \ STORMWATER TREATMENT REPORT 

TABLE 6-4 -- CONTINUED 

REQUIRED RETENTION DEPTHS TO ACHIEVE AN 

ANNUAL REMOVAL EFFICIENCY OF 95% 

Southeast Coastal (Zone 5)

NDCIA 

CN 

Percent DCIA 

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

30 1.05 1.08 1.19 1.34 1.51 1.68 1.86 2.04 2.22 2.41 2.59 2.78 2.97 3.15 3.34 3.52 3.69 3.80 3.91 35 1.43 1.37 1.42 1.52 1.65 1.81 1.97 2.14 2.31 2.49 2.66 2.83 3.01 3.19 3.37 3.55 3.70 3.80 3.91 40 1.82 1.71 1.70 1.75 1.84 1.96 2.11 2.26 2.41 2.57 2.74 2.90 3.07 3.24 3.40 3.57 3.71 3.81 3.91 45 2.22 2.05 2.01 2.01 2.07 2.15 2.27 2.39 2.53 2.68 2.82 2.98 3.13 3.29 3.44 3.60 3.72 3.81 3.91 50 2.59 2.40 2.32 2.30 2.32 2.37 2.45 2.55 2.67 2.79 2.93 3.06 3.20 3.34 3.49 3.63 3.74 3.82 3.91 55 2.95 2.74 2.64 2.59 2.58 2.60 2.65 2.73 2.82 2.93 3.04 3.16 3.28 3.41 3.54 3.65 3.75 3.83 3.91 60 3.28 3.07 2.95 2.88 2.85 2.85 2.87 2.92 2.99 3.07 3.17 3.27 3.37 3.49 3.59 3.69 3.76 3.84 3.91 65 3.58 3.38 3.25 3.16 3.11 3.09 3.09 3.12 3.16 3.23 3.30 3.39 3.47 3.56 3.64 3.72 3.78 3.84 3.91 70 3.77 3.66 3.53 3.44 3.37 3.33 3.31 3.32 3.35 3.39 3.45 3.51 3.57 3.63 3.70 3.75 3.80 3.85 3.91 75 3.92 3.86 3.75 3.66 3.59 3.55 3.52 3.52 3.53 3.55 3.58 3.62 3.66 3.71 3.75 3.78 3.82 3.86 3.91 80 3.97 3.95 3.92 3.85 3.78 3.72 3.69 3.68 3.68 3.69 3.70 3.73 3.75 3.77 3.79 3.82 3.84 3.88 3.91 85 4.00 3.98 3.97 3.95 3.89 3.86 3.84 3.82 3.81 3.81 3.81 3.81 3.82 3.83 3.84 3.85 3.87 3.89 3.91 90 4.00 4.00 4.00 3.99 3.97 3.95 3.93 3.92 3.91 3.90 3.89 3.89 3.89 3.88 3.88 3.89 3.89 3.90 3.91 95 4.00 4.00 3.99 3.99 3.98 3.97 3.97 3.96 3.95 3.95 3.94 3.93 3.93 3.92 3.92 3.92 3.91 3.91 3.91 98 3.97 3.96 3.96 3.96 3.95 3.95 3.95 3.94 3.94 3.93 3.93 3.93 3.93 3.92 3.92 3.92 3.91 3.91 3.91 

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 90

Percent DCIA (%)

20

40

60

80

100

Retention Depth (inches)

Figure 6-5. Variations in Required Dry Retention 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 increase in pollutant loadings following development 

compared with loadings which discharge from the site under pre-development conditions. This 

analysis is conducted primarily for nitrogen and 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, with 50-75% ground cover and litter covering much of 

the soil. SCS curve numbers for use in hydrologic modeling are assumed for hydrologic soil groups 

(HSG) A, B, C, and D using the average curve numbers 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 Number1 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/natural areas are summarized in Table 6-6 for 

each of the regional meteorological zones. These 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 areas 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 

Mean1 0.011 0.049 0.103 0.147 

 1. Reflects state-wide average value 

Estimates of annual runoff depths for undeveloped/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. The 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/natural 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 annual runoff volume generated by each combination of 

meteorological zone and hydrologic soil group was calculated, assuming a theoretical area of 1 acre, 

using the annual runoff coefficients summarized 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 undeveloped/natural areas summarized in Table 4-17. For 

purposes of this analysis, total nitrogen concentrations 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 nitrogen 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 zone 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/natural 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 equal 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 pollutant removal efficiencies necessary to achieve no 

net increase in pollutant loadings following development, calculations of estimated annual mass 

loadings for nitrogen and phosphorus were performed for “typical” residential and commercial 

developments, including low-density residential, single-family residential, high-density residential, 

and commercial land use categories. 
FDEP \ STORMWATER TREATMENT REPORT 

6-27 

A summary of hydrologic assumptions used for the 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% impervious, with 80% impervious assumed for commercial 

activities. Highway land use categories are also included, based upon 50% and 75% impervious 

assumptions. Curve numbers for pervious areas are 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 

% 

DCIA1

CURVE NUMBER (CN) 

FOR PERVIOUS AREAS 

HSG A HSG B HSG C HSG D 

Low-Density Residential 15 5 492 692 792 842

Single-Family Residential 

a. 25% impervious 

b. 40% impervious 

25 

40 

15 

25 

393 

393

613 

613

743 

743

803

803

High-Density Residential 65 50 393 613 743 803

Commercial 80 75 393 613 743 803

Highway4 

a. 50% impervious 

b. 75% impervious 

50 

75 

50 

75 

492

492

692

692

792

792

842

842

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 identified 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 was calculated for each combination of development 

category, soil type, and zone. A summary of calculated 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 nitrogen and total phosphorus for typical land use 

categories were calculated by multiplying the estimated 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 loadings 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 development increases and soil permeability decreases. 

Calculated annual total phosphorus loadings for typical land use categories are summarized in Table 

6-13. The values summarized in this table are calculated 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 efficiencies 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 approximately 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. Required 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 efficiencies for nitrogen and phosphorus to 

achieve no net increase in loading under post-development conditions are due primarily to the 

differences in runoff characteristics for general land use categories between nitrogen and 

phosphorus. As seen in Table 4-17, nitrogen concentrations 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 efficiencies 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 highway 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 net 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 need supplemental stormwater treatment to achieve 

the goal of no net increase in nitrogen loadings. 

A stormwater management system designed for 80% removal will not achieve a condition of 

no net increase for total phosphorus for any of the evaluated 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 loadings 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 parameters 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 Management 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 5

Required 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 the previous paragraph is supported by specific 

research projects designed to address allowable depths for wet detention ponds. The depth 

limitation of 12 ft for wet detention ponds designed in the St. Johns River Water Management 

District appears to have been influenced by several 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 conclusion that wet detention ponds constructed to a 

depth of 12 ft would maintain aerobic conditions. 

 In order to understand factors which may impact the allowable depths for wet detention 

ponds, it is essential to understand that wet detention 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 assigned 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 reflected by dissolved oxygen concentrations in excess 

of 1 mg/l, this means that dissolved oxygen concentrations 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 correlated 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 anoxic conditions at a relatively shallow water depth, 

while lake systems exhibiting oligotrophic characteristics 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 with 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 evaluated with respect to the anticipated algal 

productivity within the pond rather than an arbitrary 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 significant 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 the likelihood of water quality violations at the 

outfall. 
FDEP \ STORMWATER TREATMENT REPORT 

6-44 

 Another advantage of deeper ponds is the increased 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 copper-based algicides, both of which decrease the 

performance efficiency of the pond and increase the likelihood of water quality violations at the 

pond outfall. 

 

6.4.2 Zonation and Stratification

Typical zonation in a pond or lake is illustrated 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 lower zone, commonly referred to as the hypolimnion, 

respiration exceeds photosynthesis, and the water 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 within the water column resulting in relatively large temperature 

differences between the upper warm epilimnion water and the lower cooler hypolimnion water. In 

Florida, temperature differences as high as 8-10EC can occur during the summer months between 

the epilimnion and the hypolimnion in a deep waterbody. 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 hypolimnion 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 conditions 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 

H2S and CO2, 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 result 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 result of absorption of solar energy by particles 

in the water column, either as a result of turbidity 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 matter are present in the water column. However, if 

significant suspended matter is not present in the water 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 stratification 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/m3

, then the potential for stratification 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 concentrations 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 (μg/l) 

 Once the anticipated algal production and chlorophyll-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 Rigler (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/m3

 according to the following equation: 
FDEP \ STORMWATER TREATMENT REPORT 

6-46 

where: 

 SD = Secchi disk depth (m) 

 Chyl-a = Chlorophyll-a concentration (mg/m3

) 

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 primarily from data generated on northern temperate 

lakes, these equations have been utilized extensively 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 source 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 within the State of Florida. This data search 

generated in excess of 65,000 measurements which 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. These 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 relationships 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 phosphorus. 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 examination of the Student T residuals and Cook’s 

D values. Approximately 327 data points were eliminated 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 R2

 = 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/m3) 

 TP = total phosphorus concentration (μg/l) 

The best-fit relationship obtained with Florida data is similar to that originally proposed by Dillon 

and Rigler (1974) with different coefficients and intercepts. The R2 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 lakes is given in Figure 6-14. The best-fit equation 

for this relationship is a hyperbolic equation which is summarized on Figure 6-14. The R2

value of 0.807 for this relationship indicates that 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/m3)

0 100 200 300 400

Secchi Depth (m)

0

1

2

3

4

5

6

(6.0632 )

(24.2386 0.3041 ) Secchi Depth (m) chylachyla

+

+ • =

R2=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 conditions in a non-colored waterbody, such as a 

wet detention pond, is directly related to the 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 important variable in determining the depth of 

anoxia. 

 A linear regression was developed to predict the depth of anoxia in a waterbody as a function 

of ambient concentrations of chlorophyll-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 developed 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 R2

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 that 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 (μg/l) + 0.02164 x chyl-a (mg/m3) 

 

R2

 = 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 μg/l < Total P < 498 μg/l 

 1 mg/m3

 < chyl-a < 332 mg/m3

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 R2 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 stormwater management system to 

meet the proposed modifications to existing stormwater 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 goals 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 State of Florida based on differences in total annual rainfall and 

the frequency distribution for individual rain events. In addition, design examples are also 

provided to illustrate treatment requirements necessary 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 requirements 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 rangeland/forest (fair condition) 

10 acres – isolated wetlands 

2. Ground Cover/Soil Types: Rangeland/Forest – Hydrologic 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 covered with lawns in good condition 

 B. Soil types will remain HSG D 

3. Impervious/DCIA Areas

 A. Residential areas will be 25% impervious, 75% of which will be DCIA 

 Impervious Area = 25% of residential 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 lawns in good condition in HSG D = 80 

 Areas of lawns = 90 acres total – 22.50 ac impervious area = 67.50 acres pervious area 

 Impervious area which is not DCIA = 22.50 ac – 16.88 ac = 5.62 ac 

 Assume a curve number of 98 for impervious areas 

 Non-DCIA curve number = 

Calculate Treatment Requirements for 80% Removal

Estimation of treatment requirements assumes that 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 

81.4

67.50 62

67.50 62 = ac + 5. ac ac (80) + 5. ac (98)
FDEP \ STORMWATER TREATMENT REPORT 

7-3 

The required dry retention depth is obtained by iterating 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 (Central 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 (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 = 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 (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 = 1.66 inches over the developed area.

2. Wet Detention

 Treatment Train Approach

Calculation of design criteria for a wet detention 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 phosphorus since other 

pollutants such as BOD and TSS are typically removed at a faster rate than nutrients. As 

discussed in Section 5.2.2, wet detention systems are capable of providing annual mass load 

reduction for phosphorus in excess of 80% at extended detention times (> 200 days). 

However, wet detention ponds are 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, pre-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 retention 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 %

5.46 + 200

44.72 x 200 = ( + t )(4 x t ) Eff

d

d 2.8

4.38

3.75 =
FDEP \ STORMWATER TREATMENT REPORT 

7-4 

Anticipated TP removal (Figure 5-9) = 

Eff = 40.13 + 6.372 ln (td) + 0.213 (ln td)

2

 = 40.13 + 6.372 ln (200) + 0.213 (ln 200)2 = 79.9% 

Although the wet detention pond approaches the 80% removal criteria for TP, the removal 

for TN is only 42.8%. Therefore, the remaining efficiency is achieved using dry detention. 

The required efficiency for the dry retention is calculated by Eq. 1 below: 

Treatment Train Efficiency = Eff1 + (1 – Eff1) x Eff 2 (Eq. 1) 

 where: Eff1 = required efficiency of dry retention 

 Eff2 = efficiency of wet detention 

0.8 = Eff1 + (1 – Eff1) x 0.428 

Eff1 = 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 efficiency 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 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 project conditions is 63.4%. 

For a dry retention depth of 1.00 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 project conditions 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% removal is 0.81 inch.
FDEP \ STORMWATER TREATMENT REPORT 

7-5 

Therefore, the required treatment train will consist of: 

a. 0.81 inch dry retention, followed by 

b. Wet detention pond with a 200-day mean residence time 

Based on the relationships given in Figures 5-9 and 5-10, the removal efficiencies 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 retention pre-treatment depth will 

not be significantly reduced. However, if the pond residence time is decreased below 200 days, 

then the dry retention pre-treatment depth will increase correspondingly. 

2. Wet Detention Pond Characteristics

The required physical characteristics 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 runoff inputs to pond

The annual runoff coefficient for the development can be estimated using the tables included 

in Appendix C (Zone 1). 

 For: DCIA = 18.75% and non-DCIA CN = 81.4 

 The estimated “C” value is obtained by iteration as discussed previously. 

 Annual C Value = 0.304 

 The annual rainfall for the Pensacola area = 65.5 inches (Appendix A.3) 

 Annual generated runoff volume = 

90 acres x 65.5 inches/year x 1 ft/12 inches x 0.304 = 149.34 ac-ft/yr 

The calculated efficiency of 65.0% for the dry retention pre-treatment means that 65.0% of 

the annual runoff volume will be infiltrated into the ground and will not discharge directly 

into the wet detention pond. The annual runoff 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 related to the anticipated algal productivity 

within the pond. Assuming that wet detention 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, the event mean concentration (emc) for TP 

in runoff can be obtained from Table 4-17: 

 TP = 0.327 mg/l (single-family residential) 

2. Calculate TP loading to wet detention pond

After the dry retention pre-treatment, the 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 previously 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. Assuming that inflow and outflow are approximately equal, 

the outflow will be 52.27 ac-ft. 

 Mean pond concentration = 

4.24 kg TP x 1 yr x 1 ac 

x 1 ft3

yr (52.27 + 28.64 ac-ft) 43,560 ft2 7.48 gal 

x 1 gal x 

106 mg = 0.042 mg TP/liter = 42 μg TP/liter 3.785 liter kg 

 = 21. kg TP/yr

10 mg

1 kg x

liter

0.3 mg x

gal

3.785 liter

x

ft

7.48 gal x

ac

43,560 ft 5 ac - ft/yr x 3 6

2

08 27 2.27
FDEP \ STORMWATER TREATMENT REPORT 

7-7 

4. Calculate mean chlorophyll-a concentration in pond

The relationship between TP and chlorophyll-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/m3

) 

 TP = total P concentration (μg/l) 

ln (chyl-a) = 1.058 ln (42) - 0.934 

chyl-a = e3.02 = 20.5 mg/m3

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/m3

) 

 6. Calculate depth of anoxic conditions in pond

 Using the relationship expressed 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 

(6.0632 + chyl - a)

24.2386 + 0.3041 chyl - a) SD = [( )( ]

 = m = 3. ft (6.0632 + 2 )

24.2386 + 0.3041 (2 ) SD = 1.15 76

0.5

[( ) 0.5 ]
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/m3

) 

 Total P = total phosphorus concentration (μg/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 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 depth. 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 these areas would provide a significant storage 

volume for collected solids. 

If the pond is modified, based on the results of the calculated anoxic zone depth, the 

calculations would need to be redone to estimate new values for total phosphorus, 

Secchi disk depth, chlorophyll-a, and depth of anoxia to demonstrate 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 efficiency 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 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 project conditions is 65.7%. 

For a dry retention depth of 0.25 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 project conditions 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% removal is 0.49 inch.

Therefore, the required treatment train will consist of: 

a. 0.49 inch dry retention, followed by 

b. Wet detention pond with a 200-day mean residence time 

2. Wet Detention Pond Characteristics

The required physical characteristics 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 runoff inputs to pond

The annual runoff coefficient for the development can be estimated using the tables included 

in Appendix C (Zone 2). 

 For: DCIA = 18.75% and non-DCIA CN = 81.4 

 The estimated “C” value is obtained by iteration as discussed previously. 

 Annual C Value = 0.253 

 The annual rainfall for the Orlando area = 50.0 inches (Appendix A.3) 

 Annual generated runoff volume = 

90 acres x 50.0 inches/year x 1 ft/12 inches x 0.253 = 94.92 ac-ft/yr 

The calculated efficiency of 65.0% for the dry retention pre-treatment means that 65.0% of 

the annual runoff volume will be infiltrated into the ground and will not discharge directly 

into the wet detention pond. The annual runoff 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 related to the anticipated algal productivity 

within the pond. Assuming that wet detention 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, the emc for TP in runoff can be obtained 

from Table 4-17: 

 TP = 0.327 mg/l (single-family residential) 

2. Calculate TP loading to wet detention pond

After the dry retention pre-treatment, the 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 previously 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 pond volume and the annual 

outflow: 

 = 18.21 ac-ft + 33.22 ac-ft = 51.43 ac-ft 

 = kg TP/yr

10 mg

1 kg x

liter

0.3 mg x

gal

3.785 liter

x

ft

7.48 gal x

ac

43,560 ft ac - ft/yr x 3 6

2

13.40 27 33.22
FDEP \ STORMWATER TREATMENT REPORT 

7-11 

 Mean pond concentration = 

2.69 kg TP x 1 yr x 1 ac 

x 1 ft3

yr 51.43 ac-ft 43,560 ft2 7.48 gal 

x 1 gal x 

106

 mg = 0.042 mg TP/liter = 42 μg TP/liter 3.785 liter kg 

4. Calculate mean chlorophyll-a concentration in pond

The relationship between TP and chlorophyll-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/m3

) 

 TP = total P concentration (μg/l) 

ln (chyl-a) = 1.058 ln (42) - 0.934 

chyl-a = e3.02 = 20.5 mg/m3

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/m3

) 

(6.0632 + chyl - a)

24.2386 + 0.3041 chyl - a) SD = [( )( ]

 = m = 3. ft (6.0632 + 2 )

24.2386 + 0.3041) (2 ) SD = 1.15 76

0.5

[( 0.5 ]
FDEP \ STORMWATER TREATMENT REPORT 

7-12 

 6. Calculate depth of anoxic conditions in pond

 Using the relationship expressed 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 (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/m3

) 

 Total P = total phosphorus concentration (μg/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 depth. 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 these areas would provide a significant storage 

volume for collected solids. 

If the pond is modified, based on the results of the calculated anoxic zone depth, the 

calculations would need to be redone to estimate new values for total phosphorus, 

Secchi disk depth, chlorophyll-a, and depth of anoxia to demonstrate 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 efficiency 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 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 project conditions is 65.0%. There is no need to conduct 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 treatment train will consist of: 

a. 0.75 inch dry retention, followed by 

b. Wet detention pond with a 200-day mean residence time 

2. Wet Detention Pond Characteristics

The required physical characteristics 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 runoff inputs to pond

The annual runoff coefficient for the development can be estimated 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/12 inches x 0.266 = 79.80 ac-ft/yr 
FDEP \ STORMWATER TREATMENT REPORT 

7-14 

The calculated efficiency of 65.0% for the dry retention pre-treatment means that 65.0% of 

the annual runoff volume will be infiltrated into the ground and will not discharge directly 

into the wet detention pond. The annual runoff 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 related to the anticipated algal productivity 

within the pond. Assuming that wet detention 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, the emc for TP in runoff can be obtained 

from Table 4-16: 

 TP = 0.327 mg/l (single-family residential) 

2. Calculate TP loading to wet detention pond

After the dry retention pre-treatment, the 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 previously 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 

 = kg TP/yr

10 mg

1 kg x

liter

0.3 mg x

gal

3.785 liter

x

ft

7.48 gal x

ac

43,560 ft ac - ft/yr x 3 6

2

11.26 27 27.93
FDEP \ STORMWATER TREATMENT REPORT 

7-15 

The remaining TP mass will be distributed between the pond volume and the annual 

outflow: 

 = 15.30 ac-ft + 27.93 ac-ft = 43.23 ac-ft

 Mean pond concentration = 

2.26 kg TP x 1 yr x 1 ac 

x 1 ft3

yr 43.23 ac-ft 43,560 ft2 7.48 gal 

x 1 gal x 

106

 mg = 0.042 mg TP/liter = 42 μg TP/liter 3.785 liter kg 

4. Calculate mean chlorophyll-a concentration in pond

The relationship between TP and chlorophyll-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/m3

) 

 TP = total P concentration (μg/l) 

ln (chyl-a) = 1.058 ln (42) - 0.934 

chyl-a = e3.02 = 20.5 mg/m3

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/m3

) 

(6.0632 + chyl - a)

24.2386 + 0.3041 chyl - a) SD = [( )( ]

 = m = 3. ft (6.0632 + 2 )

24.2386 + 0.3041) (2 ) SD = 1.15 76

0.5

[( 0.5 ]
FDEP \ STORMWATER TREATMENT REPORT 

7-16 

 6. Calculate depth of anoxic conditions in pond

 Using the relationship expressed 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 (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/m3

) 

 Total P = total phosphorus concentration (μg/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 depth. 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 these areas would provide a significant storage 

volume for collected solids. 

If the pond is modified, based on the results of the calculated anoxic zone depth, the 

calculations would need to be redone to estimate new values for total phosphorus, 

Secchi disk depth, chlorophyll-a, and depth of anoxia to demonstrate 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 requirements 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 rangeland/forest (fair condition) 

10 acres – isolated wetlands 

2. Ground Cover/Soil Types: Rangeland/Forest – Hydrologic 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 covered with lawns in good condition 

 B. Soil types will remain HSG D 

3. Impervious/DCIA Areas

 A. Residential areas will be 25% impervious, 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 good condition in HSG D = 80 

 Areas of lawns = 90 acres total – 22.50 ac impervious area = 67.50 acres pervious area 

 Impervious area which is not DCIA = 22.50 ac – 16.88 ac = 5.62 ac 

 Assume a curve number of 98 for impervious areas 

 

 Non-DCIA curve number = 

Calculate Treatment Requirements for 95% Removal (OFW Criteria)

Estimation of treatment requirements assumes that 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 (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 

The required dry retention depth is obtained by iterating between DCIA 

percentages of 10 and 20, and for non-DCIA CN values between 80 and 90. The 

required dry retention depth = 3.66 inches over the developed area.

B. Orlando Project (Zone 2)

If the project was located in Orlando, 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 6-4 (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.

81.4

67.50 62

67.50 62 = ac + 5. ac

 ac (80) + 5. ac (98)
FDEP \ STORMWATER TREATMENT REPORT 

7-19 

C. Key West Project (Zone 3)

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 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 detention 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 phosphorus since other 

pollutants such as BOD and TSS are typically removed 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, pre-treatment must be 

provided to enhance the total system performance efficiency to a minimum of 95% for both 

total nitrogen and total phosphorus. 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 retention 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 (td) + 0.213 (ln td)

2

 = 40.13 + 6.372 ln (100) + 0.213 (ln 100)2 = 70.5% 

Based on the estimated performance efficiency of the wet detention pond, 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 efficiency for the dry retention is calculated by 

Eq. 1 below: 

Treatment Train Efficiency = Eff1 + (1 – Eff1) x Eff 2 (Eq. 1) 

 where: Eff1 = required efficiency of dry retention 

 Eff2 = efficiency of wet detention 

 = 4 . %

4 + 00

4 x 00 = ( + t )

(4 x t ) Eff

d

d 1 9 .38 1

3.75 1

4.38

3.75 =
FDEP \ STORMWATER TREATMENT REPORT 

7-20 

For total nitrogen: 0.95 = Eff1 + (1 – Eff1) x 0.419 

Eff1 = 0.947 = 94.7% 

For total phosphorus: 0.95 = Eff1 + (1 – Eff1) x 0.705 

Eff1 = 0.831 = 83.1% 

The largest removal efficiency of 94.7% is required for total nitrogen. Therefore, this 

efficiency will dictate the required 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 efficiency 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, and for non-DCIA CN values between 80 and 90. The efficiency 

for the project conditions 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, and for non-DCIA CN values between 80 and 90. The efficiency 

for the project conditions 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% removal is 3.72 inches.

Therefore, the required treatment train will consist of: 

a. 3.72 inches dry retention, followed by 

b. Wet detention pond with a 100-day mean residence time 
FDEP \ STORMWATER TREATMENT REPORT 

7-21 

2. Wet Detention Pond Characteristics

The required physical characteristics 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 runoff inputs to pond

The annual runoff coefficient for the development can be estimated using the tables included 

in Appendix C (Zone 1). 

 For: DCIA = 18.75% and non-DCIA CN = 81.4 

 The estimated “C” value is obtained by iteration as discussed previously. 

 Annual C Value = 0.304 

 The annual rainfall for the Pensacola area = 65.5 inches (Appendix A.3) 

 Annual generated runoff volume = 

90 acres x 65.5 inches/year x 1 ft/12 inches x 0.304 = 149.34 ac-ft/yr 

The calculated efficiency of 94.7% for the dry retention pre-treatment means that 94.7% of 

the annual runoff volume will be infiltrated into the ground and will not discharge directly 

into the wet detention pond. The annual runoff 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 100 days = 2.17 ac-ft 

b. Estimate maximum allowable pond depth

The maximum allowable pond depth is directly related to the anticipated algal productivity 

within the pond. Assuming that wet detention 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, the event mean concentration (emc) for TP 

in runoff can be obtained from Table 4-17: 

 TP = 0.327 mg/l (single-family residential) 
FDEP \ STORMWATER TREATMENT REPORT 

7-22 

2. Calculate TP loading to wet detention pond

After the dry retention pre-treatment, the 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 previously 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 pond volume and the annual 

outflow: 

 = 2.17 ac-fat + 7.92 ac-ft = 10.09 ac-ft 

 Mean pond concentration = 

0.94 kg TP x 1 yr x 1 ac 

x 1 ft3

yr 10.09 ac-ft 43,560 ft2 7.48 gal 

x 1 gal x 

106

 mg = 0.076 mg TP/liter = 76 μg TP/liter 3.785 liter kg 

4. Calculate mean chlorophyll-a concentration in pond

The relationship between TP and chlorophyll-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/m3

) 

 TP = total P concentration (μg/l) 

ln (chyl-a) = 1.058 ln (76) - 0.934 

chyl-a = e3.648 = 38.4 mg/m3

 = kg TP/yr

10 mg

1 kg x

liter

0.3 mg x

gal

3.785 liter

x

ft

7.48 gal x

ac

43,560 ft ac - ft/yr x 3 6

2

3.19 27 7.92
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/m3

) 

 6. Calculate depth of anoxic conditions in pond

 Using the relationship expressed 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 

 where: 

 Depth of DO < 1 = anoxic depth (m) 

 Secchi = Secchi disk depth (m) 

 chyl-a = chlorophyll-a concentration (mg/m3

) 

 Total P = total phosphorus concentration (μg/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 for 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 depth. The specific design of the required 

system should be selected by a qualified aeration specialist. 

(6.0632 + chyl - a)

24.2386 + 0.3041 chyl - a) SD = [( )( ]

 = 0. m = ft (6.0632 + )

24.2386 + 0.3041) ( ) SD = 81 2.65

38.4

[( 38.4 ]
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 these areas would provide a significant storage 

volume for collected solids. 

If the pond is modified, based on the results of the calculated anoxic zone depth, the 

calculations would need to be redone to estimate new values for total phosphorus, 

Secchi disk depth, chlorophyll-a, and depth of anoxia to demonstrate 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 efficiency 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, and for non-DCIA CN values between 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, and for non-DCIA CN values between 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% removal is 2.24 inches.

Therefore, the required treatment train will consist of: 

a. 2.24 inches dry retention, followed by 

b. Wet detention pond with a 100-day mean residence time 
FDEP \ STORMWATER TREATMENT REPORT 

7-25 

2. Wet Detention Pond Characteristics

The required physical characteristics 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 runoff inputs to pond

The annual runoff coefficient for the development can be estimated using the tables included 

in Appendix C (Orlando). 

 For: DCIA = 18.75% and non-DCIA CN = 81.4 

 The estimated “C” value is obtained by iteration as discussed previously. 

 Annual C Value = 0.253 

 The annual rainfall for the Orlando area = 50.0 inches (Appendix A.3) 

 Annual generated runoff volume = 

90 acres x 50.0 inches/year x 1 ft/12 inches x 0.253 = 94.88 ac-ft/yr 

The calculated efficiency of 94.7% for the dry retention pre-treatment means that 94.7% of 

the annual runoff volume will be infiltrated into the ground and will not discharge directly 

into the wet detention pond. The annual runoff 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 100 days = 1.38 ac-ft 

B. Estimate maximum allowable pond depth

The maximum allowable pond depth is directly related to the anticipated algal productivity 

within the pond. Assuming that wet detention 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, the emc for TP in runoff can be obtained 

from Table 4-17: 

 TP = 0.327 mg/l (single-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 previously 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 pond volume and the annual 

outflow: 

 = 1.38 ac-ft + 5.03 ac-ft = 6.41 ac-ft 

Mean pond concentration = 

0.60 kg TP x 1 yr x 1 ac 

x 1 ft3

yr 6.41 ac-ft 43,560 ft2 7.48 gal 

x 1 gal x 

106

 mg = 0.076 mg TP/liter = 76 μg TP/liter 3.785 liter kg 

4. Calculate mean chlorophyll-a concentration in pond

The relationship between TP and chlorophyll-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/m3

) 

 TP = total P concentration (μg/l) 

ln (chyl-a) = 1.058 ln (76) - 0.934 

chyl-a = e3.65 = 38.4 mg/m3

 = kg TP/yr

10 mg

1 kg x

liter

0.3 mg x

gal

3.785 liter

x

ft

7.48 gal x

ac

43,560 ft ac - ft/yr x 3 6

2

2.03 27 5.03
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/m3

) 

 6. Calculate depth of anoxic conditions in pond

 Using the relationship expressed 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 

 where: 

 Depth of DO < 1 = anoxic depth (m) 

 Secchi = Secchi disk depth (m) 

 chyl-a = chlorophyll-a concentration (mg/m3

) 

 Total P = total phosphorus concentration (μg/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 for 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 depth. The specific design of the required 

system should be selected by a qualified aeration specialist. 

(6.0632 + chyl - a)

24.2386 + 0.3041 chyl - a) SD = [( )( ]

 = 0. m = ft (6.0632 + )

24.2386 + 0.3041) ( ) SD = 81 2.65

38.4

[( 38.4 ]
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 these areas would provide a significant storage 

volume for collected solids. 

If the pond is modified, based on the results of the calculated anoxic zone depth, the 

calculations would need to be redone to estimate new values for total phosphorus, 

Secchi disk depth, chlorophyll-a, and depth of anoxia to demonstrate 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 efficiency of 94.7% is achieved with a dry 

retention depth in excess 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, and for non-DCIA CN values between 80 and 90. The efficiency 

for the project conditions is 93.8%. 

The maximum retention depth of 4 inches listed in Appendix D fails 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 removal for both total nitrogen and total phosphorus 

for Zone 3 conditions without involving unreasonable dry retention requirements. 
FDEP \ STORMWATER TREATMENT REPORT 

7-29 

7.3 Design Example #3:

Stormwater Treatment to Meet the Post- Less Than or

Equal to Pre-Pollution Reduction Target Goal

Determine the water quality treatment requirements 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 rangeland/forest (fair condition) 

10 acres – isolated hardwood wetlands 

2. Ground Cover/Soil Types: Rangeland/Forest – Hydrologic 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 forest 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 coefficient 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 conditions (including wetland indicators and 

water level data) by the project biologist and engineer, it was determined 

that approximately 75% of the generated 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 acres 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 concentration for undeveloped land 

(rangeland-forest) = 1.15 mg/l (Table 4-17) 

 Pensacola: Annual TN Load = 

96.78 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 1.15 mg TN x 1 kg = 137.3 kg TN/yr yr ac ft3

 gal liter 106 mg 

Orlando: Annual TN Load = 

52.5 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 1.15 mg TN x 1 kg = 74.5 kg TN/yr yr ac ft3

 gal liter 106 mg 

Key West: Annual TN Load = 

47.7 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 1.15 mg TN x 1 kg = 67.7 kg TN/yr yr ac ft3

 gal liter 106 mg 

(2) Hardwood Wetland: Water quality monitoring was conducted in the 

hardwood wetland to establish ambient water quality characteristics. 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 ft2

x 7.48 gal x 

3.785 liter 

x 2.00 mg TN x 1 kg = 3.11 kg TN/yr ac ft3

 gal liter 106 mg 

Orlando: Annual TN Load = 

0.68 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 2.00 mg TN x 1 kg = 1.68 kg TN/yr ac ft3

 gal liter 106 mg 
FDEP \ STORMWATER TREATMENT REPORT 

7-32 

Key West: Annual TN Load = 

0.62 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 2.00 mg TN x 1 kg = 1.53 kg TN/yr ac ft3

 gal liter 106 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 meteorological 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 ft2

x 7.48 gal x 

3.785 liter 

x 0.055mg TP x 1 kg = 6.57 kg TP/yr yr ac ft3

 gal Liter 106 mg 

Orlando: Annual TP Load = 

52.5 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 0.055 mg TP x 1 kg = 3.56 kg TP/yr yr ac ft3

 gal Liter 106 mg 

Key West: Annual TP Load = 

47.7 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 0.055 mg TP x 1 kg = 3.24 kg TP/yr yr ac ft3

 gal liter 106 mg 
FDEP \ STORMWATER TREATMENT REPORT 

7-33 

(2) Hardwood Wetland: Water quality monitoring was conducted in the 

hardwood wetland to establish ambient water quality characteristics. This 

monitoring resulted in a mean TP concentration of 0.066 mg/l. 

 

 Pensacola: Annual TP Load = 

1.26 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 0.066 mg TP x 1 kg = 0.10 kg TP/yr ac ft3

 gal Liter 106 mg 

Orlando: Annual TP Load = 

0.68 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 0.066 mg TP x 1 kg = 0.055 kg TP/yr ac ft3

 gal Liter 106 mg 

Key West: Annual TP Load = 

0.62 ac-ft x 43,560 ft2

x 7.48 gal x 

3.785 liter 

x 0.066 mg TP x 1 kg = 0.05 kg TP/yr ac ft3

 gal liter 106 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 covered 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 will be 25% impervious, 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 good condition in HSG D = 80 

 Areas of lawns = 90 acres total – 22.50 ac impervious area = 67.50 acres pervious area 

 Impervious area which is not DCIA = 22.50 ac – 16.88 ac = 5.62 ac 

 Assume a curve number 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 volumes is not included for the 5-acre stormwater 

management area since runoff generated in these areas is incorporated into the performance 

efficiency estimates for the stormwater system. Also, runoff volumes are not calculated for 

the 5-acre wetland tract which 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 Pensacola area = 65.5 inches (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 

81.4

67.50 62

67.50 62 = ac + 5. ac

 ac (80) + 5. ac (98)
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 West area = 40.0 inches (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 included in estimates of post-development 

loadings since incidental mass inputs of pollutants to these systems are included in the 

estimation of removal effectiveness. 

From Table 4-17, mean emc values for total nitrogen 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:

 

 = kg TN/yr

10 mg

1 kg x liter

2.0 mg x gal

3.785 liter x ft7.48 gal x ac

43,560 ft x yr

ac - ft

3 6

2

381 149.3 7
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

 = kg TP/yr

10 mg

1 kg x liter

mg x gal

3.785 liter x ft7.48 gal x ac

43,560 ft x

yr

ac - ft

3 6

2

60.2 149.3 0.327

 = kg TN/yr

10 mg

1 kg x liter

2.0 mg x gal

3.785 liter x ft7.48 gal x ac

43,560 ft x yr

ac - ft

3 6

2

242.0 94.8 7

 = kg TP/yr

10 mg

1 kg x liter

mg x gal

3.785 liter x ft7.48 gal x ac

43,560 ft x

yr

ac - ft

3 6

2

38.2 94.8 0.327

 = kg TN/yr

10 mg

1 kg x liter

2.0 mg x gal

3.785 liter x ft7.48 gal x ac

43,560 ft x yr

ac - ft

3 6

2

179.2 70.2 7

 = kg TP/yr

10 mg

1 kg x liter

mg x gal

3.785 liter x ft7.48 gal x ac

43,560 ft x

yr

ac - ft

3 6

2

28.3 70.2 0.327
FDEP \ STORMWATER TREATMENT REPORT 

7-37 

7. Calculate required removal efficiencies to achieve post- less than 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 that only dry retention and wet detention are 

capable of approaching the desired pollutant reduction goal. 

1. Dry Retention: For dry retention, the removal efficiencies for TN and TP are identical 

since the removal efficiency is based on the portion of the annual runoff volume which is 

infiltrated. The required removal is the larger 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 phosphorus. 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), the 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 project 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 project conditions is 91.0%. 

By iterating between 2.50 inches (88.9%) and 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 located in Orlando, 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 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), the 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 project 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 project conditions is 88.9%. 

By iterating between 1.50 inch (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, the annual load reduction is 61.4% 

for total nitrogen and 88.4% for total phosphorus. 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 between DCIA percentages of 10 and 20, 

and for non-DCIA CN values between 80 and 90. 

From Appendix D (Zone 3), the 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 project 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 project 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 detention pond is based on determining the detention 

time required to achieve the post- < pre-pollutant removal efficiencies for TN and TP listed 

previously. For practical purposes, this efficiency is assumed to apply to nitrogen and 

phosphorus since other pollutants such as BOD and TSS are typically removed at a faster 

rate than nutrients. As discussed in Section 5.2.2, wet detention 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 total nitrogen in wet detention 

ponds appears to peak at approximately 45%. As a result, wet detention alone is not capable 

of achieving the required 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, pre-treatment must be 

provided to enhance the total system performance efficiency 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 retention appears to be the pre-treatment system 

of choice for this application. There are many combinations of dry retention and wet 

detention which can provide the desired removals. 

Assume that the primary component 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 (td) + 0.213 (ln td)

2

 = 40.13 + 6.372 ln (150) + 0.213 (ln 150)2 = 77.4% 

2A. PENSACOLA (ZONE 1) PROJECT

Since a wet detention pond cannot meet both the 89.0% removal criteria for TP and the 63.2% 

removal for TN, the remaining efficiency is achieved using dry retention. 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 = Eff1 + (1 – Eff1) x Eff 2 (Eq. 1) 

 = %

5.46 + 0

44.72 x 0 = ( + t )

(4 x t ) Eff

d

d 42.5

15

15

4.38

3.75 =
FDEP \ STORMWATER TREATMENT REPORT 

7-40 

 where: Eff1 = required efficiency of dry retention 

 Eff2 = efficiency of wet detention (42.5% for TN) 

Overall Eff. = 0.632 = Eff1 + (1 – Eff1) x 0.425 

Eff1 = 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 efficiency 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 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 project conditions 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% removal is 0.24 inch.

Therefore, the required treatment train will consist of: 

a. 0.24 inch dry retention, followed by 

b. Wet detention pond with a 150-day mean residence time 

Based on the relationships given in Figures 5-9 and 5-10, the removal efficiencies for TN and TP 

increase little at detention times in excess of 100-150 days. Although the pond size may be 

increased (if desired) for fill or other purposes, the required dry retention pre-treatment depth will 

not be significantly reduced. However, if the pond residence time is decreased below 150 days, 

then the dry retention pre-treatment depth will increase correspondingly. 

2. Wet Detention Pond Characteristics

The required physical characteristics 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 runoff inputs to pond

The annual runoff coefficient for the development can be estimated using the tables included 

in Appendix C (Zone 1). 
FDEP \ STORMWATER TREATMENT REPORT 

7-41 

 For: DCIA = 18.75% and non-DCIA CN = 81.4 

 The estimated “C” value is obtained by iteration as discussed previously. 

 Annual C Value = 0.304 

 The annual rainfall for the Pensacola area = 65.5 inches (Appendix A.3) 

 Annual generated runoff volume = 

90 acres x 65.5 inches/year x 1 ft/12 inches x 0.304 = 149.3 ac-ft/yr 

The calculated efficiency of 36.0% for the dry retention pre-treatment means that 36.0% of 

the annual runoff volume will be infiltrated into the ground and will not discharge directly 

into the wet detention pond. The annual runoff 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 related to the anticipated algal productivity 

within the pond. Assuming that wet detention 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, the event mean concentration (emc) for TP 

in runoff can be obtained from Table 4-16: 

 TP = 0.327 mg/l (single-family residential) 

2. Calculate TP loading to wet detention pond

After the dry retention pre-treatment, the annual runoff input to the pond = 95.55 

ac-ft/yr 

 TP load to pond = 

 = kg TP/yr

10 mg

1 kg x

liter

0.3 mg x

gal

3.785 liter

x

ft

7.48 gal x

ac

43,560 ft ac - ft/yr x 3 6

2

38.53 27 95.55
FDEP \ STORMWATER TREATMENT REPORT 

7-42 

3. Calculate TP concentration in pond

At the proposed 150-day residence time, the TP removal was previously 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 distributed within the pond permanent pool volume (39.27 ac-ft) 

and the pond outflow. Assuming that inflow and outflow are approximately equal, 

the outflow volume is 95.55 ac-ft. 

Mean pond concentration = 

8.71 kg TP x 1 yr x 1 ac 

x 1 ft3

yr 95.55 + 39.27 ac-ft 43,560 ft2 7.48 gal 

x 1 gal x 

106

 mg = 0.052 mg TP/liter = 52 μg TP/liter 3.785 liter kg 

 

4. Calculate mean chlorophyll-a concentration in pond

The relationship between TP and chlorophyll-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/m3

) 

 TP = total P concentration (μg/l) 

ln (chyl-a) = 1.058 ln (52) - 0.934 

chyl-a = e3.25 = 25.7 mg/m3

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: 

(6.0632 + chyl - a)

24.2386 + 0.3041 chyl - a) SD = [( )( ]
FDEP \ STORMWATER TREATMENT REPORT 

7-43 

where: SD = Secchi disk depth (m) 

chyl-a = chlorophyll-a (mg/m3

) 

 6. Calculate depth of anoxic conditions in pond

 Using the relationship expressed 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 

 where: 

 Depth of DO < 1 = anoxic depth (m) 

 Secchi = Secchi disk depth (m) 

 chyl-a = chlorophyll-a concentration (mg/m3

) 

 Total P = total phosphorus concentration (μg/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 estimated 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 depth. 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 these areas would provide a significant storage 

volume for collected solids. 

If the pond is modified, based on the results of the calculated anoxic zone depth, the 

calculations would need to be redone to estimate new values for total phosphorus, 

Secchi disk depth, chlorophyll-a, and depth of anoxia to demonstrate that the new 

design meets the required permanent pool volume above the zone of anoxia. 

 = m = . ft (6.0632 + 2 )

24.2386 + 0.3041 (2 ) SD = 1.01 3 31

5.7

[( ) 5.7 ]
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 pond cannot meet both the 90.5% removal criteria for TP and the 68.5% 

removal for TN, the remaining efficiency is achieved using dry retention. 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 = Eff1 + (1 – Eff1) x Eff 2 (Eq. 1) 

 where: Eff1 = required efficiency of dry retention 

 Eff2 = efficiency of wet detention (42.5% for TN) 

Overall Eff. = 0.685 = Eff1 + (1 – Eff1) x 0.425 

Eff1 = 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 required 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 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 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% removal is 0.23 inch.

Therefore, the required treatment train will consist of: 

a. 0.23 inch dry retention, followed by 

b. Wet detention pond with a 150-day mean residence time 
FDEP \ STORMWATER TREATMENT REPORT 

7-45 

2. Wet Detention Pond Characteristics

The required physical characteristics 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 runoff inputs to pond

The annual runoff coefficient for the development can be estimated using the tables included 

in Appendix C (Zone 2). 

 For: DCIA = 18.75% and non-DCIA CN = 81.4 

 The estimated “C” value is obtained by iteration as discussed previously. 

 Annual C Value = 0.253 

 The annual rainfall for the Orlando area = 50.0 inches (Appendix A.3) 

 Annual generated runoff volume = 

90 acres x 50.0 inches/year x 1 ft/12 inches x 0.253 = 94.88 ac-ft/yr 

The calculated efficiency of 45.2% for the dry retention pre-treatment means that 45.2% of 

the annual runoff volume will be infiltrated into the ground and will not discharge directly 

into the wet detention pond. The annual runoff 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 related to the anticipated algal productivity 

within the pond. Assuming that wet detention 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, the emc for TP in runoff can be obtained 

from Table 4-17: 

 TP = 0.327 mg/l (single-family residential) 
FDEP \ STORMWATER TREATMENT REPORT 

7-46 

2. Calculate TP loading to wet detention pond

After the dry retention pre-treatment, the 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 previously 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 will 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 will be 51.99 ac-ft. 

 

Mean pond concentration = 

4.74 kg TP x 1 yr x 1 ac 

x 1 ft3

yr 21.37 + 51.99 ac-ft 43,560 ft2 7.48 gal 

x 1 gal x 

106

 mg = 0.052 mg TP/liter = 52 μg TP/liter 3.785 liter kg 

4. Calculate mean chlorophyll-a concentration in pond

The relationship between TP and chlorophyll-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/m3

) 

 TP = total P concentration (μg/l) 

ln (chyl-a) = 1.058 ln (52) - 0.934 

chyl-a = e3.25 = 25.7 mg/m3

 = kg TP/yr

10 mg

1 kg x

liter

0.3 mg x

gal

3.785 liter

x

ft

7.48 gal x

ac

43,560 ft ac - ft/yr x 3 6

2

20.97 27 51.99
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/m3

) 

 6. Calculate depth of anoxic conditions in pond

 Using the relationship expressed 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 

 where: 

 Depth of DO < 1 = anoxic depth (m) 

 Secchi = Secchi disk depth (m) 

 chyl-a = chlorophyll-a concentration (mg/m3

) 

 Total P = total phosphorus concentration (μg/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 depth. The specific design of the required 

system should be selected by a qualified aeration specialist. 

(6.0632 + chyl - a)

24.2386 + 0.3041 chyl - a) SD = [( )( ]

 = m = ft (6.0632 + 2

24.2386 + 0.3041) (2 ) SD = 1.01 3.31

5.7)

[( 5.7 ]
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 these areas would provide a significant storage 

volume for collected solids. 

If the pond is modified, based on the results of the calculated anoxic zone depth, the 

calculations would need to be redone to estimate new values for total phosphorus, 

Secchi disk depth, chlorophyll-a, and depth of anoxia to demonstrate 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 pond fails to meet the 88.4% removal criteria for TP and the 61.4% removal 

for TN, the remaining efficiency is achieved using dry retention. 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 = Eff1 + (1 – Eff1) x Eff 2 (Eq. 1) 

 where: Eff1 = required efficiency of dry retention 

 Eff2 = efficiency of wet detention (42.5% for TN) 

0.614 = Eff1 + (1 – Eff1) x 0.425 

Eff1 = 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 efficiency 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 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 project conditions is 42.9%. 

By iterating between 0.00 inch (0.0%) and 0.25 inch (42.9%), the dry retention depth required to 

achieve 32.9% removal is 0.19 inch.

Therefore, the required treatment 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 characteristics 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 runoff inputs to pond

The annual runoff coefficient for the development can be estimated 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/12 inches x 0.266 = 79.8 ac-ft/yr 

The calculated efficiency of 32.9% for the dry retention pre-treatment means that 32.9% of 

the annual runoff volume will be infiltrated into the ground and will not discharge directly 

into the wet detention pond. The annual runoff 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 related to the anticipated algal productivity 

within the pond. Assuming that wet detention 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, the emc for TP in runoff can be obtained 

from Table 4-17: 

 TP = 0.327 mg/l (single-family residential) 

2. Calculate TP loading to wet detention pond

After the dry retention pre-treatment, the 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 previously 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 distributed within the pond permanent pool volume (22.01 ac-ft) 

and the pond outflow. Assuming that inflow and outflow are approximately equal, 

the outflow volume is 53.55 ac-ft. 

 

Mean pond concentration = 

4.88 kg TP x 1 yr x 1 ac 

x 1 ft3

yr 22.01 + 53.55 ac-ft 43,560 ft2 7.48 gal 

x 1 gal x 

106

 mg = 0.052 mg TP/liter = 52 μg TP/liter 3.785 liter kg 

 = kg TP/yr

10 mg

1 kg x

liter

0.3 mg x

gal

3.785 liter

x

ft

7.48 gal x

ac

43,560 ft ac - ft/yr x 3 6

2

21.60 27 53.55
FDEP \ STORMWATER TREATMENT REPORT 

7-51 

4. Calculate mean chlorophyll-a concentration in pond

The relationship between TP and chlorophyll-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/m3

) 

 TP = total P concentration (μg/l) 

ln (chyl-a) = 1.058 ln (52) - 0.934 

chyl-a = e3.25 = 25.7 mg/m3

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/m3

) 

 

 6. Calculate depth of anoxic conditions in pond

 Using the relationship expressed 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 

(6.0632 + chyl - a)

24.2386 + 0.3041 chyl - a) SD = [( )( ]

 = m = ft (6.0632 + 2 )

24.2386 + 0.3041) (2 ) SD = 1.01 3.31

5.7

[( 5.7 ]
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/m3

) 

 Total P = total phosphorus concentration (μg/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 depth. 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 these areas would provide a significant storage 

volume for collected solids. 

If the pond is modified, based on the results of the calculated anoxic zone depth, the 

calculations would need to be redone to estimate new values for total phosphorus, 

Secchi disk depth, chlorophyll-a, and depth of anoxia to demonstrate 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 which 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 conditions. The design examples provide 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 consists of a 100-acre rangeland/forest parcel which 

is converted into a single-family residential community with a DCIA percentage of 18.7% and a 

non-DCIA curve number of 81.4. 

 A comparison of existing and proposed dry retention stormwater treatment requirements, 

based upon the hypothetical 100-acre parcel, is given in Table 7-1 for developments in Pensacola, 

Orlando, and Key West. Existing requirements for 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 based upon SJRWMD design criteria, 

while dry retention treatment requirements for the Key West site 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 site, the dry retention requirement 

would be 0.5 inch for an off-line system and 1.00 inch for an on-line system. 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, the dry retention system 

would have to provide a treatment volume of 1.52 inches of runoff. In the Orlando area, the 

required dry retention treatment volume would be 0.94 inch, with a dry retention requirement of 

1.66 inches in the Key West area. 
FDEP \ STORMWATER TREATMENT REPORT 

7-54 

 As seen in Table 7-1, the existing design criteria for dry retention in the Pensacola and Key 

West areas fall well short of the actual dry retention treatment volume required to achieve an 80% 

annual pollutant removal efficiency. For a project designed in the Orlando area, based upon 

SJRWMD design criteria, the dry retention requirement for an off-line system would fail to meet the 

80% pollutant removal goal, while the pollutant removal goal would be exceeded by an on-line 

retention system with 1.00 inch of dry retention. 

 Existing and proposed dry retention requirements are also provided for developments which 

discharge to OFWs which are assumed to be designed according to the 95% pollutant reduction 

target goal outlined in Chapter 62-40 FAC. The applicable design criteria for each of the three 

project areas is 50% additional dry retention treatment volume above the amount necessary to 

achieve 80% pollutant removal. For projects designed in the Pensacola and Key West areas, this 

treatment volume requirement becomes 0.75 inch. If a development is constructed in the Orlando 

area, the current dry retention requirement becomes 0.75 inch for off-line systems and 1.50 inch for 

on-line systems. However, the actual dry retention 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 inches 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 nitrogen range from 61.4-68.5%. These values indicate that a pollutant removal 

efficiency of 80% is not required for 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 stormwater management systems designed for an 80% 

pollutant removal will fail to achieve post < pre-development loadings for total phosphorus. Based 

upon these values, it is apparent that a stormwater management system designed to achieve 80% 

pollutant removal will remove more than the required amount of total nitrogen, while removing less 

than the required amount of total phosphorus. A stormwater management system designed to 

achieve a true 95% reduction in pollutant loadings will remove substantially more total nitrogen and 

total phosphorus than required to achieve post < pre-development loadings. 

 Based upon the comparative information 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 phosphorus is an ineffective method for achieving compliance with water quality 

or anti-degradation criteria. A much more effective method of addressing 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 hypothetical 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 requirements necessary to achieve a 95% pollutant removal 

goal. If post < pre-development criteria are utilized, there would be no need for supplemental 

design criteria for discharges into OFWs since all projects would result in no net increase in 

pollutant loadings into the receiving waterbody. However, it should be noted that the post < predevelopment dry retention design criteria listed at the bottom of Table 7-1 are based upon the 

removal efficiencies required for total phosphorus. Since all constituents are removed at the same 

rate using dry retention, 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 and proposed wet detention stormwater treatment requirements to 

achieve the evaluated design objectives is given in Table 7-2. Under existing conditions, wet 

detention systems designed in the 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 criteria. These criteria specify a treatment volume of 1 inch of 

runoff, with a minimum 14-day wet season detention time and a maximum pond depth of 12 feet. 

The project constructed in the Key West area would be designed according 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 greater than 12 feet. 

 A summary of proposed wet detention design criteria necessary to achieve the 80% 

pollutant removal goal is provided in Table 7-2. For this analysis, the treatment volume is assumed 

to be the same as under existing design criteria. Although this treatment volume is often termed the 

“water quality” component of the system, it has very little impact on the overall performance 

efficiency of the system and primarily regulates the drawdown characteristics of the pond following 

a storm event. The design example assumes a wet detention pond with a detention pond of 150 

days since this design tends to maximize removal efficiencies for nitrogen 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 removal 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-treatment 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, and 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 are constructed deeper than the anticipated depth of anoxia may require 

supplemental aeration or circulation to maintain aerobic conditions. It should be noted that, while 

this design will meet the 80% pollutant removal goal for total nitrogen, the overall pollutant removal 

for total phosphorus will substantially 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 would remain 

unchanged. Under the proposed alternative wet detention design, the treatment volumes are 

assumed to be the same as those provided under existing conditions since the treatment volumes 

have little impact on overall system performance. The example summarized in a previous section 

utilizes a 100-day detention pond, although other detention times could be utilized as well. The 

remaining dry retention pre-treatment necessary to boost the overall performance 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 retention requirements are necessary primarily to boost the removal 

efficiency for total nitrogen to 95%, while the removal efficiency for total phosphorus will 

substantially exceed 95%. 
TABLE 7-2 

COMPARISON OF EXISTING AND REQUIRED WET 

DETENTION STORMWATER TREATMENT REQUIREMENTS 

DESIGN 

OBJECTIVE 

TREATMENT REQUIREMENT BY REGION 

PENSACOLA - ZONE 1 

(FDEP) 

ORLANDO - ZONE 2 

(SJRWMD) 

KEY WEST - ZONE 3 

(SFWMD) 

80% Pollutant Removala. Existing 1. 1" of runoff treatment volume 

2. no specified detention time 3. depth < 12 feet 

1. 1" of runoff treatment volume 2. minimum 14-day detention time 3. depth < 12 feet 

1. 1" of runoff treatment volume 2. no specified detention time 3. 25-50% > 12 feet 

b. Proposed 1. 1" of runoff treatment volume 

2. 200-day detention time 3. 0.69" retention pre-treatment 4. maximum depth based on water quality 

1. 1" of runoff treatment volume 2. 200-day detention time 3. 0.45" retention pre-treatment 4. maximum depth based on water quality 

1. 1" of runoff treatment volume 2. 200-day detention time 3. 0.66" retention pre-treatment 4. maximum depth based on water quality 

95% Pollutant Removal (OFW)a. Existing 1. 1.5" of runoff treatment volume 

2. no specified detention time 3. depth < 12 feet 

1. 1.5" of runoff treatment volume 2. minimum 14-day detention time 3. depth < 12 feet 

1. 1.5"of runoff treatment volume 2. no specified detention time 3. 25-50% > 12 feet 

b. Proposed 1. 1.5" of runoff treatment volume 

2. 100-day detention time 3. 2.45" dry retention pre-treatment 

1. 1.5" of runoff treatment volume 2. 100-day detention time 3. 1.63" dry retention pre-treatment 

1. 1.5" of runoff treatment volume 2. 100-day detention time 3. >4" dry retention pre-treatment 

Post ≤ 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 volume 

2. 150-day wet detention 3. 0.24" dry retention pre-treatment 

1. 1.5” of runoff treatment volume 2. 150-day wet detention 3. 0.23" dry retention pre-treatment 

1. 1.5” of runoff treatment volume 2. 150-day wet detention 3. 0.19" dry retention pre-treatment 

7-56

FDEP \ STORMWATER TREATMENT REPORT 
FDEP \ STORMWATER TREATMENT REPORT 

7-57 

 Proposed wet detention treatment requirements necessary to achieve post < pre-development 

loadings are summarized at the 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-development loadings is 

provided in the bottom row of Table 7-2. This can be accomplished 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 are 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 wet 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 provided in the previous sections, it is apparent that the most 

appropriate method of developing stormwater treatment requirements is to utilize a post < predevelopment loading conditions. Developing stormwater design criteria to achieve an arbitrary 

80% pollutant removal goal will provide 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 nitrogen and total phosphorus necessary to achieve a 

post < pre-development loading, while resulting in substantially elevated stormwater treatment 

requirements and costs compared with existing conditions. 
FDEP \ STORMWATER TREATMENT REPORT 

SECTION 8 

REFERENCES 

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 Bahk, B. and M. Kehoe. (1997). "A Survey of Outflow Water Quality from Detention 

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 Carr, D.W. and M.J. Kehoe. (1997). “Outfall Water Quality from Wet Detention Systems.” 

Southwest Florida Water Management District, Environmental Section/Resource Projects 

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 Chow, V.T.; Maidment, D.R.; and Mays, L.W. (1988). “Applied Hydrology.” New York: 

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 Cullum, M.G. (1984). "Evaluation of the Water Management System at a Single-Family 

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 DB Environmental, Inc. (2005). “Quantifying the Effect of a Vegetated Littoral Zone on 

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 Dillon, P.J., and F.H. Rigler. (1974). “The Phosphorus-Chlorophyll Relationship in Lakes.” 

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8-1 
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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. 

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 Fall, C. (1987). "Characterization of Agricultural Pump Discharge Quality in the Upper St. 

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 Fall, C. (1990). "Characterization of Agricultural Pump Discharge Quality in the Upper St. 

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 Federico, A.C. (1977). "Investigations of the Relationship Between Land Use, Rainfall, 

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Nonpoint Source Management Department. Tallahassee, FL. 

 Gaggiani, N.G. and A.G. Lamonds. (1978). "Chemical and Biological Quality of Lakes 

Faith, Hope and Charity at Maitland, Florida, with Emphasis on the Effects on Storm Runoff and 

Bulk Precipitation, 1971-74." U.S. Geological survey Open-File Report 77-491, Tallahassee, FL. 
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8-3 

 German, E.R. (1983). "Water Quality of Lakes Faith, Hope, Charity and Lucien, 1979-79, 

in an Area of Residential Development and Highway Construction 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 Subdivision 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 Surface Water Management System 

at a Single-Family Residential Development: Springhill Subdivision." South Florida Water District 

Tech. Pub. 89, West Palm Beach, FL. 

 Gupta, M.K. (1981). "Constituents of Highway Runoff." Executive Summary, Volume VI 

- Final Report. Federal Highway Administration Report #FHWA/RD-81/047, Washington, D.C. 

 Gupta, M.K., R.W. Agnew, D. Gruber, and W. Kreutzberger. (1981). "Constituents of 

Highway Runoff." Characteristics of Highway Runoff from Operating 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 Metals from Highway Runoff in Stormwater 

Management Systems." Ph.D. Dissertation for the University of Central Florida, Orlando, FL. 

 Harper, H.H. (1988). "Effects of Stormwater Management Systems on Groundwater 

Quality." FDEP Project #WM190. Florida Department of Environmental Regulation, Tallahassee, 

FL. 

 Harper, H.H. (1994). "Stormwater Loading 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 4th Biennial Stormwater Research Conference, Southwest 

Florida Water Management District, Clearwater, FL, October 18-20, 1995. 

 

 Harper, H.H. and J.L. Herr. (1993). "Treatment Efficiencies of Detention 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). Bradfordville Stormwater Study.” Final 

Report prepared for the Board of County Commissioners, Leon County, FL. 

 Harper, H.H., M.P. Wanielista, 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 Stormwater Runoff in a hardwood Wetland." Lake and 

Reservoir Management - Proceedings of the Fifth Annual Conference and International Symposium 

on Applied Lake and Watershed Management, Lake Geneva, WI, November 13-16, 1985. 
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8-4 

 Harper, H.H., M.P. Wanielista, Y.A. Yousef, and D. Didomenico. (1982). "Lake Eola 

Restoration: Water Quality Background and Stormwater Management Practices." University of 

Central Florida, Orlando, FL. 

 Hendrickson, J. (1987). "Effect of the Willowbrook Farms Detention Basin on the Quality 

of Agricultural Runoff." St. Johns River Water Management District, Contract #WM108, Palatka, 

FL. 

 Hendrickson, J. (No date given). Unpublished data on 3 citrus sites in Florida. 

 Holler, J.D. (1989). “Water Quality Efficiency of an Urban Commercial 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 Function." Draft Report for the 

Southwest Florida Water Management District - SWIM Section. 

 Howie, B. and B.G. Waller. (1986). "Chemical Effects of Highway Runoff on the Surficial 

Aquifer, Broward County, 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 Report.” Southwest Florida Water Management 

District, Environmental Section, Brooksville, FL. 

 Lopez, M.A. and R.F. Giovannelli. (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, and R.M. Finn. (1980). "Urban Stormwater 

Management and Technology: Case Histories." EPA 68-03-2617. Cincinnati, OH. 

 Martin, E.H., and Miller, R.A. (1987). “Efficiency of an Urban Stormwater Detention 

System.” Proceedings of the Fourth International Conference on Urban Storm Drainage. 

 Mattraw, Jr., H.C., and R.A. Miller. (1981). "Stormwater Quality Processes for Three 

Land-Use Areas in Broward County, Florida." U.S. Geological Survey Report #USGS/WRI 81-23, 

Tallahassee, FL. 

 Mattraw, Jr., H.C., J. Hardee, and R.A. Miller. (1978). "Urban Stormwater Runoff Data for 

a Residential Area, Pompano Beach, Florida." U.S. Geological Survey Open-File Report 78-324, 

Tallahassee, FL. 

 McCuen, R.H. (1982). “A Guide to Hydrologic Analysis Using SCS Methods.” 

Englewood Cliffs, NJ: Prentice-Hall, Inc. 
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8-5 

McKenzie, D.J. and G.A. Irwin. (1983). "Water Quality Assessment of Stormwater Runoff 

from a Heavily Used Urban Highway Bridge in Miami, Florida." U.S. Geological Survey Water 

Resources Investigations Report 83-4153, Tallahassee, FL. 

 Miller, R.A. (1979). "Characteristics of Four Urbanized Basins in South Florida." U.S. 

Department of the Interior Geological Survey Open- File Report 79-694. Tallahassee, FL. 

 Miller, R.A. (1985). "Percentage Entrainment of Constituent Loads in Urban Runoff, South 

Florida." U.S. Geological Survey Water Resources Investigations Report 84-4329. Tallahassee, 

FL. 

 Miller, W.L. (1988). "Description and Evaluation of the Effects of Urban and Agricultural 

Development on the Surficial Aquifer System, Palm Beach County, Florida." U.S. Geological 

Survey Water Resources Investigations Report 88-4056, Tallahassee, FL. 

 Post, Buckley, Schuh & Jernigan, Inc. (1982). “Evaluation of Two Best Management 

Practices: A Grassy Swale and a Retention/Detention Pond.” Brevard 208 Continuing Planning 

Process. EPA Grant No. 067-301.00. 

 Rushton, B.T., and C.W. Dye. (1993). “An In-depth Analysis of a Wet Detention 

Stormwater System.” Southwest Florida Water Management District, Brooksville, FL. 

 

 Rushton, B., C. Miller, and C. Hull. (1995). “Residence Time as a Pollutant Removal 

Mechanism in Stormwater Detention Ponds.” Proceedings of the Fourth Biennial Stormwater 

Research Conference, Clearwater Beach, FL, October 18-20, 1995. 

 Sawka, G.J., D.W. Black, 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 Detention Ponds.” Wat. Sci. Tech. Vol. 22, No. 10/11, pp. 197-

204. 

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Stormwater Runoff Routed Through a Detention Pond-Wetlands System in Central Florida.” Water 

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8-6 

 United States Geological Survey (USGS). (1985). "Percentage Entrainment of Constituent 

Loads in Urban Runoff, South Florida." Water Resources Investigations Report No. 84-4329. 

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Improve Lake Water Quality." EPA Grant 600/82-048. 

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Man-Made Lake on Groundwater Quality." South Florida Water Management District Tech. Pub. 

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Runoff Quality Relationships and Treatment Efficiencies of Selected Stormwater Management 

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of Drainage Systems from Highway Bridges of Pollution Control." Transportation Research 

Record 896, Hydrology and Hydraulics: 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 Contaminants by Roadside Swales." Florida 

Department of Transportation, Publication FL-ER-30-85, Tallahassee, FL. 

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FL. 
FDEP \ STORMWATER TREATMENT REPORT 

APPENDICES 
FDEP \ STORMWATER TREATMENT REPORT 

APPENDIX A 

PRECIPITATION DATA 

A.1 Summary of Monthly and Annual Precipitation at Florida Monitoring 

Sites from 1971-2000 

A.2 Geographical Coordinates and Mean Annual Rainfall for Florida 

Meteorological Monitoring Sites for Available Period of Record 

A.3 Expanded Views of Rainfall Isopleths by Region 

A.4 Frequency Distribution of Rain Events 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 UNITED STATES NO. 81

Monthly Station Normals

of Temperature, Precipitation,

and Heating and Cooling

Degree Days

1971 - 2000

08

FLORIDA

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

NATIONAL ENVIRONMENTAL SATELLITE, DATA, AND INFORMATION SERVICE

NATIONAL CLIMATIC DATA CENTER

ASHEVILLE, 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 heating and cooling degree days (base 65 degrees F). Normals stations include both National Weather Service 

Cooperative Network and Principal Observation (First-Order) locations in the 50 states, Puerto Rico, the Virgin Islands, and Pacific Islands. 

Abbreviations: 

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) prescribed standards of data completeness for the 1961-1990 WMO Standard Normals. 

For full qualification, no more than three consecutive year-month values can be missing for a given month or no more than five overall values can be 

missing for a given month (out of 30 values). Stations meeting these standards are indicated with a '+' sign in Flag 2. Otherwise, stations are included in 

the normals if they have at least 10 year-month values for each month and have been active since January 1999 or were a previous normals station. 

Map Legend: Numbers correspond to ‘No.’ in Station Inventory; Shaded Circles indicate Temperature and Precipitation Stations, Triangles (Point Up) 

indicate Precipitation-Only Stations, Triangles (Point Down) indicate Temperature-Only 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 inconsistencies 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, inconsistencies can lead to a nonclimatic bias in one period of a station’s record relative to another, yielding an “inhomogeneous” data record. Adjustments and estimations can make a 

climate record “homogeneous” and serially complete, and allow a climate 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 normals, as it addresses inhomogeneity and missing 

data value problems using several steps. The technique developed by Karl et al. (1986) is used to adjust monthly maximum and minimum temperature 

observations of conterminous U.S. stations to a consistent midnight-to-midnight schedule. All monthly temperature averages and precipitation totals are 

cross-checked against archived daily observations to ensure internal consistency. Each 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 neighboring values exist. Missing or discarded temperature and precipitation observations are replaced using a 

weighting function derived from the observed relationship between a candidate’s monthly observations and those of up to 20 neighboring stations whose 

observations are most strongly correlated with the candidate site. For temperature estimates, neighboring stations were selected from the U.S. 

Historical Climatology Network (USHCN; Karl et al. 1990). For precipitation estimates, all available stations were potential neighbors, maximizing 

station density for estimating the more spatially 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 series is reconstructed 

using a weighted average of first difference observations (the difference from one year to the next) for neighboring stations with the highest correlation 

with the candidate. The underlying assumption behind this methodology is that temperatures over a region have similar tendencies in variation. If this 

assumption is violated, the potential discontinuity is evaluated for statistical significance. Where significant discontinuities 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 between discontinuities. Consequently, if multiple changes occur within 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 precipitation are computed simply by averaging the appropriate 30 values from 

the 1971-2000 record. The monthly average temperature normals are computed by averaging the corresponding monthly maximum and minimum 

normals. The annual temperature normals are calculated by taking the average of the 12 monthly normals. The annual precipitation and degree day 

normals are the sum of the 12 monthly normals. Trace precipitation totals are shown as zero. Precipitation totals include rain and the liquid equivalent 

of frozen and freezing precipitation (e.g., snow, sleet, freezing rain, and hail). For many NWS locations, 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 stations, estimated degree day 

totals are based on a modification of the rational conversion formula developed by Thom (1966), using daily spline-fit means and standard deviations of 

average temperature as inputs. 

References:

Easterling, D.R, and T.C. Peterson, 1995: A new method for detecting and adjusting for undocumented discontinuities in climatological 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 Climatology Network (GHCN) quality control of monthly 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, Geneva: World Meteorological Organization. 

Release Date: Revised 02/2002* National Climatic Data Center/NESDIS/NOAA, Asheville, North Carolina
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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 Longitude 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 Longitude 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 AUG 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 AUG SEP OCT NOV DEC ANNUAL
FDEP \ STORMWATER TREATMENT REPORT 

A.2 Geographical Coordinates and Mean Annual Rainfall for Florida 

Meteorological Monitoring Sites for 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 Rainfall Isopleths by Region 










	





	

	

	


 



	







	

 	














	 




	


   

        	 
 	 





 


	  



 

	  	  










 	 	 
 	

















































	


	






		





	

	

	

	



	

		

	

		

	







	

 





	

	
	


	


	



	


	
	

	


	








	

	


		













	


		
	

	

	





	








 





 









 











 























 



 	












 














   	
 


































	
















	

		




		







	



 	




	




		





















	


	




	










 














	





	



	


		





	







 



 

 





 





     







	 
  













 






 	












		 	 
		

	 

 

























	

















	



	



		





	












	


	










 





 

   













   	








 











	









 	







    











 
 	
	 


 





FDEP \ STORMWATER TREATMENT REPORT 

A.4 Frequency Distribution of Rain Events in Selected Meteorological Regions
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 62.17 100.00

126.24 62.17

Missing 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 Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 64.55 100.00

123.80 64.55

Missing Years:

TALLAHASSEE MUNI AP (8758)

from 1959 to 2005 (n=45)

(minimum number of months per year at site =9)

1961, 1987
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 52.27 100.00

106.49 52.27

Missing Years:

BRANFORD (3543)

from 1945 to 2004 (n=53)

(minimum number of months per year at site =9)

1947, 1950, 1951, 1973, 1998, 2001, 2002
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 50.03 100.00

126.69 50.03

Missing Years:

ORLANDO INTL ARPT (6628)

from 1942 to 2005 (n=62)

(minimum number of months per year at site =9)

1945, 1974
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 47.52 100.00

107.94 47.52

Missing 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 Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 39.07 100.00

127.56 39.07

Missing Years:

KEY WEST WB CITY (4575)

from 1942 to 2005 (n=63)

(minimum number of months per year at site =9)

1952
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 53.13 100.00

108.96 53.13

Missing 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, 2001
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 55.14 100.00

105.64 55.14

Missing 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, 1998
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 46.07 100.00

111.77 46.07

Missing 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, 2002
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 52.96 100.00

127.31 52.96

Missing Years:

JACKSONVILLE (4371)

from 1942 to 2005 (n=64)

(minimum number of months per year at site =9)
Rainfall Event 

Range 

(in)

Number of 

Annual Events 

in Range

Mean 

Rainfall 

Depth 

(in)

Mean 

Rainfall 

Duration 

(hr)

Antecedent 

Dry Period 

(days)

Annual 

Event 

Volume

Cumulative 

Annual Event 

Volume 

(inches)

Cumulative 

Percent of 

Total Rainfall

0.00-0.10 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 56.92 100.00

158.14 56.92

Missing 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 

WATERSHED REFERENCE 

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 homes 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 - 102nd Avenue 70.0 N/A Single-family residential 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-family 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 residential 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 

WATERSHED REFERENCE 

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 

WATERSHED REFERENCE 

AREA 

(acres) 

PERCENT 

IMPERVIOUS 

(%) 

LAND USE DRAINAGE 

SYSTEM 

Orlando Areawide 

Study1

-- 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 Commercial 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 commercial strip development 
FDEP \ STORMWATER TREATMENT REPORT 

 TABLE B.4 

 SUMMARY OF HYDROLOGIC CHARACTERISTICS 

 FROM HIGH-INTENSITY COMMERCIAL STORMWATER 

 STUDIES IN FLORIDA

LOCATION 

PARAMETER 

WATERSHED REFERENCE 

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 

WATERSHED REFERENCE 

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 

WATERSHED REFERENCE 

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 

WATERSHED REFERENCE 

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, fine 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 

WATERSHED REFERENCE 

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 Placid, 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 -- Poorly drained sand Citrus Fall (1995) 

Charlotte/DeSoto Counties (4 sites) 184-602 Poorly 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 

WATERSHED REFERENCE 

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 sites) 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 

WATERSHED REFERENCE 

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 DCIA 
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 0.006 0.048 0.090 0.132 0.175 0.217 0.259 0.301 0.343 0.386 0.428 0.470 0.512 0.554 0.596 0.639 0.681 0.723 0.765 0.807 0.849

35 0.009 0.051 0.093 0.135 0.177 0.219 0.261 0.303 0.345 0.387 0.429 0.471 0.513 0.555 0.597 0.639 0.681 0.723 0.765 0.807 0.849

40 0.014 0.056 0.098 0.139 0.181 0.223 0.265 0.307 0.348 0.390 0.432 0.474 0.515 0.557 0.599 0.641 0.682 0.724 0.766 0.808 0.849

45 0.020 0.062 0.103 0.145 0.186 0.228 0.269 0.311 0.352 0.394 0.435 0.476 0.518 0.559 0.601 0.642 0.684 0.725 0.767 0.808 0.849

50 0.029 0.070 0.111 0.152 0.193 0.234 0.275 0.316 0.357 0.398 0.439 0.480 0.521 0.562 0.603 0.644 0.685 0.726 0.767 0.808 0.849

55 0.039 0.079 0.120 0.161 0.201 0.242 0.282 0.323 0.363 0.404 0.444 0.485 0.525 0.566 0.606 0.647 0.687 0.728 0.768 0.809 0.849

60 0.052 0.092 0.132 0.172 0.212 0.252 0.291 0.331 0.371 0.411 0.451 0.491 0.531 0.570 0.610 0.650 0.690 0.730 0.770 0.810 0.849

65 0.069 0.108 0.147 0.186 0.225 0.264 0.303 0.342 0.381 0.420 0.459 0.498 0.537 0.576 0.615 0.654 0.693 0.732 0.771 0.810 0.849

70 0.092 0.130 0.167 0.205 0.243 0.281 0.319 0.357 0.395 0.433 0.471 0.508 0.546 0.584 0.622 0.660 0.698 0.736 0.774 0.812 0.849

75 0.121 0.158 0.194 0.230 0.267 0.303 0.340 0.376 0.412 0.449 0.485 0.522 0.558 0.595 0.631 0.667 0.704 0.740 0.777 0.813 0.849

80 0.162 0.196 0.230 0.265 0.299 0.334 0.368 0.402 0.437 0.471 0.506 0.540 0.574 0.609 0.643 0.678 0.712 0.746 0.781 0.815 0.849

85 0.220 0.252 0.283 0.315 0.346 0.378 0.409 0.441 0.472 0.503 0.535 0.566 0.598 0.629 0.661 0.692 0.724 0.755 0.787 0.818 0.849

90 0.312 0.339 0.366 0.393 0.419 0.446 0.473 0.500 0.527 0.554 0.581 0.608 0.634 0.661 0.688 0.715 0.742 0.769 0.796 0.823 0.849

95 0.478 0.496 0.515 0.533 0.552 0.571 0.589 0.608 0.626 0.645 0.664 0.682 0.701 0.719 0.738 0.757 0.775 0.794 0.812 0.831 0.849

98 0.656 0.666 0.676 0.685 0.695 0.705 0.714 0.724 0.734 0.743 0.753 0.763 0.772 0.782 0.792 0.801 0.811 0.821 0.830 0.840 0.849

Zone 1

Mean Annual Runoff Coefficients (C Values) as a Function 

of DCIA Percentage and Non-DCIA Curve Number (CN)

NDCIA 

CN

Percent DCIA
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 0.002 0.043 0.083 0.123 0.164 0.204 0.244 0.285 0.325 0.366 0.406 0.446 0.487 0.527 0.567 0.608 0.648 0.688 0.729 0.769 0.809

35 0.004 0.044 0.085 0.125 0.165 0.205 0.246 0.286 0.326 0.366 0.407 0.447 0.487 0.528 0.568 0.608 0.648 0.689 0.729 0.769 0.809

40 0.007 0.047 0.087 0.127 0.167 0.207 0.248 0.288 0.328 0.368 0.408 0.448 0.488 0.528 0.569 0.609 0.649 0.689 0.729 0.769 0.809

45 0.010 0.050 0.090 0.130 0.170 0.210 0.250 0.290 0.330 0.370 0.410 0.450 0.490 0.530 0.570 0.610 0.650 0.690 0.729 0.769 0.809

50 0.015 0.055 0.095 0.134 0.174 0.214 0.254 0.293 0.333 0.373 0.412 0.452 0.492 0.531 0.571 0.611 0.651 0.690 0.730 0.770 0.809

55 0.022 0.061 0.101 0.140 0.179 0.219 0.258 0.298 0.337 0.376 0.416 0.455 0.494 0.534 0.573 0.613 0.652 0.691 0.731 0.770 0.809

60 0.030 0.069 0.108 0.147 0.186 0.225 0.264 0.303 0.342 0.381 0.420 0.459 0.498 0.537 0.576 0.615 0.654 0.693 0.731 0.770 0.809

65 0.042 0.080 0.119 0.157 0.195 0.234 0.272 0.311 0.349 0.387 0.426 0.464 0.502 0.541 0.579 0.618 0.656 0.694 0.733 0.771 0.809

70 0.057 0.095 0.133 0.170 0.208 0.245 0.283 0.321 0.358 0.396 0.433 0.471 0.509 0.546 0.584 0.621 0.659 0.697 0.734 0.772 0.809

75 0.079 0.116 0.152 0.189 0.225 0.262 0.298 0.335 0.371 0.408 0.444 0.481 0.517 0.554 0.590 0.627 0.663 0.700 0.736 0.773 0.809

80 0.111 0.146 0.181 0.216 0.251 0.285 0.320 0.355 0.390 0.425 0.460 0.495 0.530 0.565 0.600 0.635 0.670 0.705 0.740 0.774 0.809

85 0.160 0.192 0.225 0.257 0.290 0.322 0.355 0.387 0.420 0.452 0.485 0.517 0.550 0.582 0.614 0.647 0.679 0.712 0.744 0.777 0.809

90 0.242 0.270 0.299 0.327 0.355 0.384 0.412 0.440 0.469 0.497 0.526 0.554 0.582 0.611 0.639 0.667 0.696 0.724 0.753 0.781 0.809

95 0.404 0.424 0.444 0.464 0.485 0.505 0.525 0.546 0.566 0.586 0.606 0.627 0.647 0.667 0.688 0.708 0.728 0.749 0.769 0.789 0.809

98 0.595 0.605 0.616 0.627 0.638 0.648 0.659 0.670 0.680 0.691 0.702 0.713 0.723 0.734 0.745 0.756 0.766 0.777 0.788 0.799 0.809

Zone 2

Mean Annual Runoff Coefficients (C Values) as a Function 

of DCIA Percentage and Non-DCIA Curve Number (CN)

NDCIA 

CN

Percent DCIA
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 0.008 0.047 0.087 0.126 0.165 0.205 0.244 0.283 0.323 0.362 0.401 0.441 0.480 0.519 0.559 0.598 0.637 0.677 0.716 0.756 0.795

35 0.012 0.051 0.090 0.129 0.168 0.207 0.247 0.286 0.325 0.364 0.403 0.442 0.482 0.521 0.560 0.599 0.638 0.677 0.717 0.756 0.795

40 0.016 0.055 0.094 0.133 0.172 0.211 0.250 0.289 0.328 0.367 0.406 0.445 0.483 0.522 0.561 0.600 0.639 0.678 0.717 0.756 0.795

45 0.022 0.061 0.099 0.138 0.177 0.215 0.254 0.292 0.331 0.370 0.408 0.447 0.486 0.524 0.563 0.602 0.640 0.679 0.718 0.756 0.795

50 0.029 0.067 0.105 0.144 0.182 0.220 0.259 0.297 0.335 0.374 0.412 0.450 0.488 0.527 0.565 0.603 0.642 0.680 0.718 0.757 0.795

55 0.037 0.075 0.113 0.151 0.189 0.227 0.265 0.302 0.340 0.378 0.416 0.454 0.492 0.530 0.568 0.605 0.643 0.681 0.719 0.757 0.795

60 0.048 0.085 0.123 0.160 0.197 0.235 0.272 0.309 0.347 0.384 0.421 0.459 0.496 0.533 0.571 0.608 0.645 0.683 0.720 0.758 0.795

65 0.061 0.098 0.134 0.171 0.208 0.244 0.281 0.318 0.355 0.391 0.428 0.465 0.501 0.538 0.575 0.611 0.648 0.685 0.721 0.758 0.795

70 0.078 0.114 0.149 0.185 0.221 0.257 0.293 0.329 0.365 0.400 0.436 0.472 0.508 0.544 0.580 0.616 0.651 0.687 0.723 0.759 0.795

75 0.100 0.135 0.170 0.204 0.239 0.274 0.308 0.343 0.378 0.413 0.447 0.482 0.517 0.552 0.586 0.621 0.656 0.691 0.725 0.760 0.795

80 0.131 0.164 0.197 0.231 0.264 0.297 0.330 0.363 0.397 0.430 0.463 0.496 0.529 0.562 0.596 0.629 0.662 0.695 0.728 0.762 0.795

85 0.177 0.208 0.239 0.269 0.300 0.331 0.362 0.393 0.424 0.455 0.486 0.517 0.548 0.579 0.609 0.640 0.671 0.702 0.733 0.764 0.795

90 0.252 0.279 0.306 0.333 0.360 0.388 0.415 0.442 0.469 0.496 0.523 0.550 0.578 0.605 0.632 0.659 0.686 0.713 0.741 0.768 0.795

95 0.399 0.419 0.439 0.458 0.478 0.498 0.518 0.538 0.557 0.577 0.597 0.617 0.637 0.656 0.676 0.696 0.716 0.735 0.755 0.775 0.795

98 0.578 0.589 0.600 0.611 0.622 0.633 0.643 0.654 0.665 0.676 0.687 0.697 0.708 0.719 0.730 0.741 0.752 0.762 0.773 0.784 0.795

Zone 3

Mean Annual Runoff Coefficients (C Values) as a Function 

of DCIA Percentage and Non-DCIA Curve Number (CN)

NDCIA 

CN

Percent DCIA
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 0.004 0.045 0.086 0.127 0.168 0.209 0.250 0.291 0.332 0.373 0.414 0.455 0.496 0.536 0.577 0.618 0.659 0.700 0.741 0.782 0.823

35 0.007 0.048 0.089 0.129 0.170 0.211 0.252 0.293 0.333 0.374 0.415 0.456 0.497 0.537 0.578 0.619 0.660 0.701 0.741 0.782 0.823

40 0.011 0.051 0.092 0.133 0.173 0.214 0.254 0.295 0.336 0.376 0.417 0.458 0.498 0.539 0.579 0.620 0.661 0.701 0.742 0.782 0.823

45 0.016 0.056 0.096 0.137 0.177 0.217 0.258 0.298 0.339 0.379 0.419 0.460 0.500 0.540 0.581 0.621 0.662 0.702 0.742 0.783 0.823

50 0.022 0.062 0.102 0.142 0.182 0.222 0.262 0.302 0.342 0.382 0.423 0.463 0.503 0.543 0.583 0.623 0.663 0.703 0.743 0.783 0.823

55 0.030 0.070 0.109 0.149 0.189 0.228 0.268 0.308 0.347 0.387 0.427 0.466 0.506 0.546 0.585 0.625 0.664 0.704 0.744 0.783 0.823

60 0.040 0.080 0.119 0.158 0.197 0.236 0.275 0.314 0.353 0.393 0.432 0.471 0.510 0.549 0.588 0.627 0.667 0.706 0.745 0.784 0.823

65 0.054 0.092 0.131 0.169 0.208 0.246 0.285 0.323 0.362 0.400 0.438 0.477 0.515 0.554 0.592 0.631 0.669 0.708 0.746 0.785 0.823

70 0.071 0.109 0.147 0.184 0.222 0.259 0.297 0.335 0.372 0.410 0.447 0.485 0.522 0.560 0.598 0.635 0.673 0.710 0.748 0.785 0.823

75 0.096 0.132 0.168 0.205 0.241 0.277 0.314 0.350 0.387 0.423 0.459 0.496 0.532 0.568 0.605 0.641 0.678 0.714 0.750 0.787 0.823

80 0.130 0.165 0.199 0.234 0.268 0.303 0.338 0.372 0.407 0.442 0.476 0.511 0.546 0.580 0.615 0.650 0.684 0.719 0.754 0.788 0.823

85 0.182 0.214 0.246 0.278 0.310 0.342 0.374 0.406 0.438 0.470 0.502 0.534 0.566 0.599 0.631 0.663 0.695 0.727 0.759 0.791 0.823

90 0.266 0.294 0.322 0.350 0.378 0.406 0.433 0.461 0.489 0.517 0.545 0.573 0.600 0.628 0.656 0.684 0.712 0.740 0.767 0.795 0.823

95 0.429 0.449 0.469 0.488 0.508 0.528 0.547 0.567 0.587 0.606 0.626 0.646 0.665 0.685 0.705 0.725 0.744 0.764 0.784 0.803 0.823

98 0.616 0.626 0.636 0.647 0.657 0.667 0.678 0.688 0.699 0.709 0.719 0.730 0.740 0.750 0.761 0.771 0.782 0.792 0.802 0.813 0.823

Zone 4

Mean Annual Runoff Coefficients (C Values) as a Function 

of DCIA Percentage and Non-DCIA Curve Number (CN)

NDCIA 

CN

Percent DCIA
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 0.008 0.048 0.088 0.128 0.168 0.208 0.248 0.288 0.328 0.368 0.408 0.448 0.488 0.528 0.568 0.608 0.648 0.688 0.728 0.768 0.808

35 0.012 0.052 0.092 0.132 0.171 0.211 0.251 0.291 0.331 0.370 0.410 0.450 0.490 0.529 0.569 0.609 0.649 0.689 0.728 0.768 0.808

40 0.018 0.057 0.097 0.136 0.176 0.215 0.255 0.294 0.334 0.373 0.413 0.452 0.492 0.531 0.571 0.611 0.650 0.690 0.729 0.769 0.808

45 0.025 0.064 0.103 0.142 0.182 0.221 0.260 0.299 0.338 0.377 0.417 0.456 0.495 0.534 0.573 0.612 0.651 0.691 0.730 0.769 0.808

50 0.034 0.072 0.111 0.150 0.189 0.227 0.266 0.305 0.343 0.382 0.421 0.460 0.498 0.537 0.576 0.614 0.653 0.692 0.731 0.769 0.808

55 0.044 0.082 0.121 0.159 0.197 0.235 0.273 0.312 0.350 0.388 0.426 0.464 0.502 0.541 0.579 0.617 0.655 0.693 0.732 0.770 0.808

60 0.057 0.095 0.132 0.170 0.207 0.245 0.282 0.320 0.357 0.395 0.433 0.470 0.508 0.545 0.583 0.620 0.658 0.695 0.733 0.770 0.808

65 0.073 0.110 0.147 0.183 0.220 0.257 0.294 0.330 0.367 0.404 0.441 0.477 0.514 0.551 0.588 0.624 0.661 0.698 0.735 0.771 0.808

70 0.093 0.129 0.165 0.201 0.236 0.272 0.308 0.344 0.379 0.415 0.451 0.486 0.522 0.558 0.594 0.629 0.665 0.701 0.737 0.772 0.808

75 0.120 0.155 0.189 0.223 0.258 0.292 0.327 0.361 0.395 0.430 0.464 0.498 0.533 0.567 0.602 0.636 0.670 0.705 0.739 0.774 0.808

80 0.157 0.189 0.222 0.254 0.287 0.319 0.352 0.385 0.417 0.450 0.482 0.515 0.547 0.580 0.613 0.645 0.678 0.710 0.743 0.775 0.808

85 0.209 0.239 0.269 0.299 0.329 0.359 0.389 0.419 0.449 0.479 0.509 0.538 0.568 0.598 0.628 0.658 0.688 0.718 0.748 0.778 0.808

90 0.292 0.318 0.343 0.369 0.395 0.421 0.447 0.472 0.498 0.524 0.550 0.576 0.602 0.627 0.653 0.679 0.705 0.731 0.756 0.782 0.808

95 0.445 0.464 0.482 0.500 0.518 0.536 0.554 0.572 0.590 0.609 0.627 0.645 0.663 0.681 0.699 0.717 0.736 0.754 0.772 0.790 0.808

98 0.614 0.624 0.633 0.643 0.653 0.662 0.672 0.682 0.692 0.701 0.711 0.721 0.730 0.740 0.750 0.760 0.769 0.779 0.789 0.798 0.808

Zone 5

Mean Annual Runoff Coefficients (C Values) as a Function 

of DCIA Percentage and Non-DCIA Curve Number (CN)

NDCIA 

CN

Percent DCIA
FDEP \ STORMWATER TREATMENT REPORT 

APPENDIX D 

CALCULATED PERFORMANCE EFFICIENCY 

OF DRY RETENTION AS A FUNCTION OF 

DCIA AND NON-DCIA CURVE NUMBER 

 
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 86.2 81.3 73.3 65.5 58.7 53.0 48.3 44.2 40.8 37.9 35.3 33.1 31.1 29.4 27.8 26.4 25.1 24.0 22.9 21.9

35 81.6 78.7 71.7 64.5 58.0 52.5 47.9 44.0 40.6 37.7 35.2 33.0 31.0 29.3 27.8 26.4 25.1 23.9 22.9 21.9

40 76.4 75.5 69.6 63.1 57.1 51.9 47.4 43.6 40.3 37.5 35.0 32.9 30.9 29.2 27.7 26.3 25.1 23.9 22.9 21.9

45 70.7 71.7 67.2 61.4 55.9 51.0 46.8 43.1 40.0 37.2 34.8 32.7 30.8 29.1 27.6 26.3 25.0 23.9 22.9 21.9

50 64.7 67.5 64.2 59.4 54.5 50.0 46.0 42.6 39.5 36.9 34.6 32.5 30.7 29.0 27.5 26.2 25.0 23.9 22.9 21.9

55 58.6 62.8 60.9 57.0 52.7 48.7 45.1 41.8 39.0 36.5 34.2 32.3 30.5 28.9 27.4 26.1 24.9 23.9 22.9 21.9

60 52.8 57.8 57.1 54.2 50.7 47.1 43.9 40.9 38.3 35.9 33.8 31.9 30.2 28.7 27.3 26.0 24.9 23.8 22.8 21.9

65 47.3 52.6 53.0 51.1 48.3 45.3 42.5 39.8 37.4 35.3 33.3 31.5 29.9 28.4 27.1 25.9 24.8 23.8 22.8 21.9

70 42.2 47.3 48.6 47.6 45.6 43.2 40.8 38.5 36.4 34.4 32.6 31.0 29.5 28.1 26.9 25.7 24.7 23.7 22.8 21.9

75 37.8 42.2 43.9 43.7 42.4 40.7 38.8 36.9 35.1 33.4 31.8 30.4 29.0 27.8 26.6 25.5 24.5 23.6 22.7 21.9

80 34.0 37.5 39.1 39.4 38.8 37.7 36.4 34.9 33.5 32.1 30.8 29.5 28.3 27.2 26.2 25.2 24.3 23.5 22.7 21.9

85 30.8 33.1 34.3 34.8 34.7 34.2 33.4 32.5 31.4 30.4 29.4 28.4 27.4 26.5 25.7 24.8 24.1 23.3 22.6 21.9

90 27.9 29.2 29.9 30.3 30.3 30.2 29.8 29.3 28.8 28.2 27.5 26.8 26.2 25.5 24.9 24.2 23.6 23.0 22.5 21.9

95 25.3 25.6 25.8 25.9 26.0 25.9 25.8 25.6 25.4 25.2 24.9 24.6 24.3 24.0 23.6 23.3 23.0 22.6 22.3 21.9

98 23.8 23.8 23.8 23.7 23.7 23.6 23.5 23.4 23.3 23.2 23.1 23.0 22.9 22.8 22.6 22.5 22.4 22.2 22.1 21.9

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 91.8 91.5 88.3 84.0 79.5 75.0 70.7 66.6 62.9 59.6 56.5 53.6 51.1 48.7 46.6 44.6 42.8 41.1 39.6 38.1

35 88.2 89.1 86.6 82.8 78.6 74.3 70.1 66.2 62.6 59.3 56.3 53.5 51.0 48.7 46.5 44.6 42.8 41.1 39.6 38.1

40 84.0 86.3 84.4 81.2 77.4 73.4 69.4 65.7 62.2 59.0 56.0 53.3 50.8 48.5 46.4 44.5 42.7 41.1 39.6 38.1

45 79.6 82.9 81.9 79.3 75.9 72.2 68.5 65.0 61.7 58.6 55.7 53.0 50.6 48.4 46.3 44.4 42.7 41.0 39.5 38.1

50 74.8 79.1 79.0 77.0 74.1 70.8 67.4 64.1 61.0 58.0 55.3 52.7 50.4 48.2 46.2 44.3 42.6 41.0 39.5 38.1

55 70.1 74.9 75.6 74.2 71.9 69.1 66.1 63.0 60.1 57.3 54.7 52.3 50.0 47.9 46.0 44.2 42.5 40.9 39.5 38.1

60 65.5 70.4 71.7 71.1 69.4 67.0 64.4 61.7 59.1 56.5 54.1 51.8 49.6 47.6 45.8 44.0 42.4 40.9 39.5 38.1

65 61.0 65.8 67.5 67.6 66.4 64.7 62.5 60.2 57.8 55.5 53.3 51.1 49.1 47.2 45.5 43.8 42.3 40.8 39.4 38.1

70 56.7 61.1 63.1 63.6 63.1 61.9 60.2 58.3 56.3 54.3 52.3 50.3 48.5 46.8 45.1 43.5 42.1 40.7 39.4 38.1

75 52.7 56.6 58.6 59.3 59.3 58.6 57.5 56.0 54.4 52.7 51.0 49.3 47.7 46.1 44.6 43.2 41.8 40.5 39.3 38.1

80 49.1 52.2 54.1 55.0 55.2 54.9 54.2 53.2 52.1 50.8 49.4 48.0 46.6 45.3 44.0 42.7 41.5 40.3 39.2 38.1

85 46.1 48.3 49.7 50.5 50.8 50.8 50.5 49.9 49.2 48.3 47.3 46.3 45.2 44.2 43.1 42.1 41.0 40.0 39.1 38.1

90 43.5 44.8 45.6 46.1 46.4 46.5 46.4 46.1 45.7 45.2 44.6 44.0 43.3 42.6 41.9 41.1 40.4 39.6 38.9 38.1

95 41.1 41.5 41.8 41.9 42.0 42.1 42.0 41.9 41.8 41.6 41.3 41.1 40.8 40.4 40.1 39.7 39.3 38.9 38.5 38.1

98 39.8 39.8 39.8 39.8 39.8 39.7 39.7 39.6 39.5 39.4 39.3 39.2 39.1 39.0 38.9 38.7 38.6 38.4 38.3 38.1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.25-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 1
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 94.0 94.9 93.4 91.0 88.1 85.0 81.8 78.7 75.5 72.6 69.7 67.0 64.5 62.1 59.8 57.7 55.7 53.8 52.1 50.5

35 91.2 93.0 91.9 89.8 87.2 84.2 81.2 78.2 75.2 72.3 69.5 66.8 64.3 62.0 59.7 57.6 55.7 53.8 52.1 50.5

40 88.1 90.5 90.1 88.3 86.0 83.3 80.5 77.6 74.7 71.9 69.2 66.6 64.1 61.8 59.6 57.6 55.6 53.8 52.1 50.5

45 84.5 87.7 87.9 86.5 84.5 82.1 79.5 76.8 74.0 71.4 68.8 66.3 63.9 61.6 59.5 57.5 55.5 53.7 52.0 50.5

50 80.8 84.6 85.2 84.4 82.8 80.7 78.3 75.8 73.3 70.7 68.3 65.9 63.6 61.4 59.3 57.3 55.5 53.7 52.0 50.5

55 77.1 81.1 82.2 81.9 80.7 79.0 76.9 74.6 72.3 70.0 67.6 65.4 63.2 61.1 59.1 57.2 55.3 53.6 52.0 50.5

60 73.2 77.5 79.0 79.1 78.3 76.9 75.2 73.2 71.1 69.0 66.9 64.7 62.7 60.7 58.8 56.9 55.2 53.5 51.9 50.5

65 69.6 73.8 75.4 75.8 75.5 74.5 73.2 71.5 69.7 67.8 65.9 63.9 62.0 60.2 58.4 56.7 55.0 53.4 51.9 50.5

70 66.1 69.9 71.7 72.3 72.3 71.7 70.8 69.5 68.0 66.4 64.7 63.0 61.3 59.6 57.9 56.3 54.8 53.3 51.8 50.5

75 62.7 66.0 67.8 68.6 68.8 68.5 67.9 67.1 65.9 64.7 63.3 61.8 60.3 58.8 57.3 55.9 54.5 53.1 51.7 50.5

80 59.6 62.2 63.8 64.7 65.1 65.1 64.8 64.2 63.4 62.5 61.4 60.3 59.1 57.8 56.6 55.3 54.0 52.8 51.6 50.5

85 56.8 58.7 60.0 60.8 61.2 61.4 61.3 61.0 60.5 59.9 59.1 58.3 57.4 56.5 55.5 54.5 53.5 52.5 51.4 50.5

90 54.5 55.6 56.4 57.0 57.3 57.5 57.5 57.4 57.2 56.8 56.4 55.9 55.4 54.7 54.1 53.4 52.7 51.9 51.2 50.5

95 52.5 52.9 53.2 53.3 53.5 53.6 53.6 53.6 53.5 53.4 53.2 53.0 52.8 52.5 52.2 51.9 51.6 51.2 50.8 50.5

98 51.7 51.7 51.7 51.7 51.7 51.7 51.7 51.6 51.6 51.5 51.4 51.3 51.3 51.2 51.1 51.0 50.8 50.7 50.6 50.5

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 95.3 96.5 95.9 94.4 92.5 90.3 87.9 85.5 83.1 80.6 78.2 75.8 73.6 71.4 69.2 67.2 65.3 63.4 61.6 60.0

35 93.1 94.9 94.6 93.3 91.6 89.5 87.3 85.0 82.7 80.3 77.9 75.6 73.4 71.2 69.1 67.1 65.2 63.4 61.6 60.0

40 90.7 93.0 93.0 92.0 90.5 88.6 86.6 84.4 82.1 79.9 77.6 75.4 73.2 71.1 69.0 67.0 65.2 63.3 61.6 60.0

45 88.0 90.7 91.0 90.5 89.2 87.5 85.6 83.6 81.5 79.3 77.2 75.0 72.9 70.9 68.8 66.9 65.1 63.3 61.6 60.0

50 85.0 88.0 88.8 88.6 87.6 86.2 84.5 82.7 80.7 78.7 76.6 74.6 72.6 70.6 68.6 66.8 65.0 63.2 61.6 60.0

55 81.8 85.3 86.4 86.3 85.7 84.6 83.2 81.5 79.8 77.9 75.9 74.0 72.1 70.2 68.4 66.6 64.8 63.1 61.5 60.0

60 78.7 82.3 83.6 83.9 83.5 82.7 81.5 80.1 78.6 76.9 75.1 73.4 71.6 69.8 68.0 66.3 64.7 63.0 61.5 60.0

65 75.6 79.1 80.6 81.2 81.0 80.5 79.6 78.5 77.2 75.7 74.1 72.5 70.9 69.3 67.6 66.0 64.4 62.9 61.4 60.0

70 72.7 75.9 77.5 78.2 78.3 78.0 77.4 76.5 75.5 74.2 72.9 71.5 70.1 68.6 67.1 65.6 64.2 62.7 61.3 60.0

75 69.9 72.7 74.2 75.0 75.3 75.2 74.8 74.2 73.4 72.5 71.4 70.3 69.1 67.8 66.5 65.1 63.8 62.5 61.2 60.0

80 67.2 69.5 70.8 71.7 72.1 72.1 72.0 71.6 71.1 70.4 69.6 68.7 67.8 66.7 65.6 64.5 63.4 62.2 61.1 60.0

85 64.8 66.5 67.6 68.3 68.7 68.9 68.9 68.7 68.4 68.0 67.5 66.8 66.1 65.4 64.5 63.7 62.8 61.8 60.9 60.0

90 62.7 63.7 64.4 65.0 65.3 65.5 65.6 65.6 65.5 65.2 65.0 64.6 64.2 63.7 63.1 62.6 61.9 61.3 60.6 60.0

95 61.1 61.5 61.8 62.0 62.1 62.2 62.3 62.3 62.3 62.2 62.1 62.0 61.8 61.6 61.4 61.2 60.9 60.6 60.3 60.0

98 60.7 60.7 60.7 60.8 60.8 60.8 60.8 60.8 60.7 60.7 60.7 60.6 60.6 60.5 60.4 60.3 60.3 60.2 60.1 60.0

Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 96.1 97.3 97.2 96.3 94.9 93.4 91.6 89.7 87.8 85.8 83.8 81.8 79.9 77.9 76.0 74.2 72.4 70.6 68.9 67.3

35 94.5 96.1 96.2 95.4 94.1 92.7 91.0 89.2 87.4 85.5 83.5 81.6 79.7 77.8 75.9 74.1 72.3 70.6 68.9 67.3

40 92.5 94.5 94.8 94.2 93.2 91.9 90.3 88.6 86.9 85.0 83.2 81.3 79.5 77.6 75.8 74.0 72.3 70.6 68.9 67.3

45 90.4 92.7 93.2 92.8 92.0 90.9 89.4 87.9 86.3 84.5 82.8 81.0 79.2 77.4 75.6 73.9 72.2 70.5 68.9 67.3

50 88.0 90.6 91.3 91.2 90.6 89.7 88.4 87.0 85.5 83.9 82.2 80.5 78.8 77.1 75.4 73.7 72.1 70.4 68.9 67.3

55 85.4 88.2 89.2 89.3 88.9 88.2 87.2 86.0 84.6 83.1 81.6 80.0 78.4 76.7 75.1 73.5 71.9 70.3 68.8 67.3

60 82.7 85.7 86.9 87.2 87.0 86.5 85.7 84.7 83.5 82.2 80.8 79.3 77.8 76.3 74.8 73.2 71.7 70.2 68.8 67.3

65 80.1 83.1 84.4 84.9 84.9 84.5 83.9 83.1 82.1 81.0 79.8 78.5 77.1 75.7 74.3 72.9 71.5 70.1 68.7 67.3

70 77.6 80.3 81.7 82.4 82.5 82.4 81.9 81.3 80.6 79.7 78.6 77.5 76.3 75.1 73.8 72.5 71.2 69.9 68.6 67.3

75 75.2 77.6 79.0 79.7 80.0 79.9 79.7 79.3 78.7 78.0 77.2 76.3 75.3 74.2 73.1 72.0 70.9 69.7 68.5 67.3

80 73.0 74.9 76.1 76.8 77.2 77.3 77.3 77.0 76.6 76.1 75.5 74.8 74.0 73.2 72.3 71.4 70.4 69.4 68.4 67.3

85 70.9 72.3 73.3 73.9 74.3 74.5 74.6 74.5 74.3 73.9 73.5 73.1 72.5 71.9 71.2 70.5 69.8 69.0 68.2 67.3

90 69.2 70.0 70.6 71.1 71.4 71.6 71.7 71.7 71.7 71.5 71.3 71.1 70.7 70.4 70.0 69.5 69.0 68.5 67.9 67.3

95 67.8 68.1 68.4 68.6 68.7 68.9 68.9 69.0 69.0 69.0 68.9 68.9 68.7 68.6 68.5 68.3 68.1 67.8 67.6 67.3

98 67.7 67.7 67.7 67.8 67.8 67.8 67.8 67.8 67.8 67.8 67.8 67.8 67.7 67.7 67.6 67.6 67.5 67.5 67.4 67.3

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 96.8 97.8 98.0 97.5 96.5 95.3 94.0 92.5 90.9 89.3 87.7 86.0 84.3 82.7 81.0 79.3 77.7 76.1 74.6 73.1

35 95.5 96.9 97.1 96.7 95.8 94.7 93.5 92.1 90.6 89.0 87.4 85.8 84.1 82.5 80.9 79.3 77.7 76.1 74.6 73.1

40 93.9 95.6 96.0 95.7 95.0 94.0 92.8 91.5 90.1 88.6 87.1 85.5 83.9 82.3 80.7 79.2 77.6 76.1 74.6 73.1

45 92.1 94.2 94.7 94.5 93.9 93.1 92.0 90.8 89.5 88.1 86.6 85.1 83.6 82.1 80.6 79.0 77.5 76.0 74.5 73.1

50 90.3 92.5 93.1 93.1 92.7 92.0 91.1 90.0 88.8 87.5 86.1 84.7 83.3 81.8 80.3 78.9 77.4 75.9 74.5 73.1

55 88.2 90.5 91.3 91.4 91.2 90.7 89.9 89.0 87.9 86.8 85.5 84.2 82.8 81.5 80.1 78.6 77.2 75.8 74.4 73.1

60 85.9 88.3 89.3 89.6 89.6 89.2 88.6 87.8 86.9 85.9 84.7 83.5 82.3 81.0 79.7 78.4 77.0 75.7 74.4 73.1

65 83.5 86.0 87.2 87.7 87.7 87.5 87.0 86.4 85.7 84.8 83.8 82.8 81.7 80.5 79.3 78.1 76.8 75.6 74.3 73.1

70 81.4 83.7 85.0 85.5 85.7 85.6 85.3 84.8 84.2 83.5 82.7 81.8 80.9 79.9 78.8 77.7 76.5 75.4 74.2 73.1

75 79.4 81.4 82.5 83.2 83.5 83.5 83.3 83.0 82.6 82.1 81.4 80.7 79.9 79.1 78.1 77.2 76.2 75.2 74.1 73.1

80 77.4 79.1 80.1 80.8 81.1 81.2 81.2 81.0 80.8 80.4 79.9 79.4 78.8 78.1 77.3 76.5 75.7 74.9 74.0 73.1

85 75.7 76.9 77.7 78.3 78.6 78.8 78.9 78.9 78.7 78.5 78.2 77.8 77.4 76.9 76.3 75.8 75.1 74.5 73.8 73.1

90 74.2 74.9 75.4 75.9 76.2 76.4 76.5 76.5 76.5 76.4 76.3 76.1 75.8 75.5 75.2 74.8 74.4 74.0 73.6 73.1

95 73.1 73.3 73.6 73.8 73.9 74.0 74.1 74.2 74.2 74.2 74.2 74.2 74.1 74.0 73.9 73.8 73.6 73.5 73.3 73.1

98 73.1 73.1 73.2 73.2 73.3 73.3 73.3 73.3 73.3 73.3 73.3 73.3 73.3 73.3 73.3 73.2 73.2 73.2 73.1 73.1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.50-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.25-inches of Retention for Zone 1
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 97.3 98.1 98.4 98.2 97.6 96.6 95.6 94.4 93.2 91.8 90.4 89.0 87.6 86.1 84.7 83.3 81.8 80.4 79.0 77.6

35 96.1 97.4 97.7 97.6 97.0 96.1 95.1 94.0 92.8 91.5 90.2 88.8 87.4 86.0 84.6 83.2 81.8 80.4 79.0 77.6

40 94.9 96.4 96.8 96.7 96.2 95.5 94.5 93.5 92.4 91.1 89.9 88.5 87.2 85.8 84.4 83.1 81.7 80.3 78.9 77.6

45 93.5 95.3 95.8 95.7 95.3 94.6 93.8 92.9 91.8 90.6 89.5 88.2 86.9 85.6 84.2 82.9 81.6 80.2 78.9 77.6

50 92.0 93.9 94.5 94.5 94.2 93.7 93.0 92.1 91.2 90.1 89.0 87.8 86.6 85.3 84.0 82.8 81.5 80.2 78.9 77.6

55 90.3 92.3 93.0 93.1 92.9 92.5 92.0 91.2 90.4 89.4 88.4 87.3 86.1 85.0 83.8 82.6 81.3 80.1 78.8 77.6

60 88.4 90.5 91.3 91.5 91.5 91.2 90.8 90.1 89.4 88.6 87.7 86.7 85.6 84.5 83.4 82.3 81.1 80.0 78.8 77.6

65 86.4 88.4 89.4 89.8 89.9 89.7 89.4 88.9 88.3 87.6 86.8 86.0 85.0 84.0 83.0 82.0 80.9 79.8 78.7 77.6

70 84.4 86.4 87.4 88.0 88.1 88.1 87.9 87.5 87.0 86.4 85.8 85.1 84.3 83.4 82.5 81.6 80.6 79.6 78.6 77.6

75 82.6 84.4 85.4 86.0 86.2 86.3 86.2 85.9 85.6 85.1 84.6 84.0 83.4 82.7 81.9 81.1 80.3 79.4 78.5 77.6

80 81.0 82.4 83.3 83.9 84.2 84.3 84.3 84.2 84.0 83.7 83.3 82.8 82.4 81.8 81.2 80.6 79.9 79.1 78.4 77.6

85 79.4 80.5 81.2 81.7 82.0 82.2 82.3 82.3 82.2 82.0 81.8 81.5 81.2 80.8 80.4 79.9 79.3 78.8 78.2 77.6

90 78.1 78.8 79.3 79.6 79.9 80.1 80.2 80.3 80.3 80.2 80.1 80.0 79.8 79.6 79.3 79.0 78.7 78.4 78.0 77.6

95 77.3 77.5 77.8 77.9 78.1 78.2 78.3 78.3 78.4 78.4 78.4 78.4 78.4 78.3 78.2 78.1 78.0 77.9 77.7 77.6

98 77.4 77.5 77.5 77.6 77.6 77.7 77.7 77.7 77.7 77.7 77.7 77.7 77.7 77.7 77.7 77.7 77.7 77.6 77.6 77.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 97.9 98.5 98.6 98.6 98.3 97.6 96.7 95.8 94.8 93.7 92.5 91.3 90.0 88.8 87.5 86.2 85.0 83.7 82.4 81.2

35 96.7 97.8 98.1 98.1 97.8 97.1 96.3 95.4 94.4 93.4 92.2 91.1 89.9 88.7 87.4 86.2 84.9 83.7 82.4 81.2

40 95.6 97.0 97.5 97.4 97.1 96.6 95.8 94.9 94.0 93.0 91.9 90.8 89.7 88.5 87.3 86.0 84.8 83.6 82.4 81.2

45 94.5 96.1 96.6 96.6 96.3 95.8 95.2 94.4 93.5 92.6 91.6 90.5 89.4 88.3 87.1 85.9 84.7 83.6 82.4 81.2

50 93.3 95.0 95.5 95.6 95.4 94.9 94.4 93.7 93.0 92.1 91.1 90.1 89.1 88.0 86.9 85.8 84.6 83.5 82.3 81.2

55 91.9 93.7 94.3 94.4 94.2 93.9 93.5 92.9 92.2 91.4 90.6 89.6 88.7 87.7 86.6 85.6 84.5 83.4 82.3 81.2

60 90.4 92.1 92.8 93.0 93.0 92.8 92.4 91.9 91.3 90.6 89.9 89.1 88.2 87.3 86.3 85.3 84.3 83.3 82.2 81.2

65 88.7 90.4 91.2 91.5 91.6 91.5 91.2 90.8 90.3 89.8 89.1 88.4 87.6 86.8 85.9 85.0 84.1 83.1 82.2 81.2

70 87.0 88.6 89.4 89.9 90.1 90.1 89.9 89.6 89.2 88.7 88.2 87.6 86.9 86.2 85.4 84.6 83.8 83.0 82.1 81.2

75 85.3 86.8 87.7 88.2 88.4 88.5 88.4 88.2 87.9 87.6 87.1 86.7 86.1 85.5 84.9 84.2 83.5 82.8 82.0 81.2

80 83.8 85.1 85.8 86.3 86.7 86.8 86.8 86.7 86.5 86.3 86.0 85.6 85.2 84.7 84.2 83.7 83.1 82.5 81.9 81.2

85 82.5 83.4 84.0 84.5 84.8 85.0 85.0 85.0 84.9 84.8 84.6 84.4 84.1 83.8 83.4 83.1 82.6 82.2 81.7 81.2

90 81.4 81.9 82.4 82.7 82.9 83.1 83.2 83.3 83.3 83.3 83.2 83.1 82.9 82.8 82.6 82.3 82.1 81.8 81.5 81.2

95 80.7 80.9 81.1 81.2 81.4 81.5 81.6 81.6 81.7 81.7 81.7 81.7 81.7 81.7 81.6 81.6 81.5 81.4 81.3 81.2

98 80.9 80.9 81.0 81.0 81.1 81.1 81.1 81.2 81.2 81.2 81.2 81.2 81.2 81.2 81.2 81.2 81.2 81.2 81.2 81.2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.75-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.00-inches of Retention for Zone 1
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.4 98.8 98.9 98.9 98.7 98.2 97.6 96.8 95.9 95.0 94.0 93.0 91.9 90.8 89.7 88.6 87.5 86.3 85.2 84.1

35 97.2 98.1 98.4 98.5 98.3 97.9 97.2 96.5 95.6 94.7 93.8 92.8 91.8 90.7 89.6 88.5 87.4 86.3 85.2 84.1

40 96.2 97.4 97.8 97.9 97.8 97.3 96.8 96.1 95.3 94.4 93.5 92.6 91.6 90.5 89.5 88.4 87.3 86.2 85.1 84.1

45 95.3 96.7 97.2 97.3 97.1 96.7 96.2 95.5 94.8 94.0 93.2 92.3 91.3 90.3 89.3 88.3 87.2 86.2 85.1 84.1

50 94.3 95.8 96.3 96.5 96.3 95.9 95.5 94.9 94.3 93.6 92.8 91.9 91.0 90.1 89.1 88.1 87.1 86.1 85.1 84.1

55 93.2 94.8 95.3 95.4 95.3 95.0 94.6 94.2 93.6 93.0 92.3 91.5 90.6 89.8 88.9 87.9 87.0 86.0 85.0 84.1

60 92.0 93.5 94.1 94.3 94.2 94.0 93.7 93.3 92.8 92.3 91.6 90.9 90.2 89.4 88.6 87.7 86.8 85.9 85.0 84.1

65 90.6 92.0 92.7 92.9 93.0 92.9 92.7 92.4 92.0 91.5 90.9 90.3 89.7 89.0 88.2 87.4 86.6 85.8 84.9 84.1

70 89.1 90.4 91.1 91.5 91.6 91.6 91.5 91.3 91.0 90.5 90.1 89.6 89.0 88.4 87.8 87.1 86.4 85.6 84.8 84.1

75 87.6 88.8 89.5 90.0 90.2 90.3 90.2 90.1 89.8 89.5 89.2 88.8 88.3 87.8 87.3 86.7 86.1 85.4 84.7 84.1

80 86.2 87.2 87.9 88.4 88.6 88.8 88.8 88.7 88.6 88.4 88.1 87.8 87.5 87.1 86.7 86.2 85.7 85.2 84.6 84.1

85 85.0 85.8 86.4 86.8 87.0 87.2 87.3 87.3 87.2 87.1 86.9 86.8 86.5 86.3 86.0 85.6 85.3 84.9 84.5 84.1

90 84.0 84.5 84.9 85.2 85.4 85.6 85.7 85.7 85.7 85.7 85.7 85.6 85.5 85.4 85.2 85.0 84.8 84.6 84.3 84.1

95 83.4 83.6 83.8 84.0 84.1 84.2 84.3 84.3 84.4 84.4 84.4 84.4 84.4 84.4 84.4 84.3 84.3 84.2 84.1 84.1

98 83.7 83.7 83.8 83.8 83.9 83.9 83.9 84.0 84.0 84.0 84.0 84.0 84.0 84.1 84.1 84.1 84.1 84.1 84.1 84.1

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.7 99.1 99.1 99.1 99.0 98.7 98.2 97.6 96.8 96.1 95.2 94.3 93.4 92.5 91.5 90.5 89.5 88.5 87.4 86.4

35 97.7 98.4 98.6 98.7 98.6 98.4 97.9 97.3 96.6 95.8 95.0 94.2 93.3 92.3 91.4 90.4 89.4 88.4 87.4 86.4

40 96.7 97.8 98.2 98.3 98.2 98.0 97.5 96.9 96.3 95.5 94.8 93.9 93.1 92.2 91.3 90.3 89.3 88.4 87.4 86.4

45 95.9 97.2 97.6 97.8 97.7 97.4 97.0 96.4 95.8 95.2 94.4 93.7 92.8 92.0 91.1 90.2 89.3 88.3 87.4 86.4

50 95.1 96.5 97.0 97.1 97.0 96.7 96.3 95.9 95.3 94.7 94.1 93.3 92.6 91.7 90.9 90.0 89.2 88.2 87.3 86.4

55 94.3 95.6 96.1 96.3 96.2 95.9 95.6 95.2 94.7 94.2 93.6 92.9 92.2 91.5 90.7 89.9 89.0 88.2 87.3 86.4

60 93.3 94.6 95.1 95.3 95.2 95.0 94.8 94.4 94.0 93.6 93.0 92.4 91.8 91.1 90.4 89.6 88.9 88.1 87.2 86.4

65 92.2 93.4 93.9 94.1 94.1 94.0 93.8 93.6 93.2 92.9 92.4 91.9 91.3 90.7 90.0 89.4 88.7 87.9 87.2 86.4

70 90.8 91.9 92.5 92.8 92.9 92.9 92.8 92.6 92.4 92.0 91.6 91.2 90.7 90.2 89.6 89.1 88.4 87.8 87.1 86.4

75 89.5 90.5 91.1 91.5 91.6 91.7 91.7 91.6 91.4 91.1 90.8 90.4 90.1 89.6 89.2 88.7 88.1 87.6 87.0 86.4

80 88.2 89.1 89.7 90.1 90.3 90.4 90.4 90.4 90.3 90.1 89.9 89.6 89.3 89.0 88.6 88.2 87.8 87.4 86.9 86.4

85 87.1 87.8 88.3 88.6 88.9 89.0 89.1 89.1 89.0 89.0 88.8 88.7 88.5 88.3 88.0 87.7 87.4 87.1 86.8 86.4

90 86.3 86.7 87.0 87.3 87.5 87.6 87.7 87.8 87.8 87.8 87.7 87.7 87.6 87.5 87.3 87.2 87.0 86.8 86.6 86.4

95 85.8 85.9 86.1 86.2 86.3 86.4 86.5 86.6 86.6 86.6 86.7 86.7 86.7 86.7 86.6 86.6 86.6 86.5 86.5 86.4

98 86.0 86.1 86.1 86.2 86.2 86.2 86.3 86.3 86.3 86.3 86.3 86.3 86.4 86.4 86.4 86.4 86.4 86.4 86.4 86.4

Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.25-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.9 99.3 99.3 99.3 99.2 99.0 98.6 98.2 97.5 96.9 96.2 95.4 94.6 93.8 92.9 92.0 91.1 90.2 89.3 88.3

35 98.2 98.7 98.8 98.9 98.9 98.7 98.4 97.9 97.3 96.7 96.0 95.2 94.5 93.6 92.8 91.9 91.1 90.2 89.2 88.3

40 97.2 98.1 98.4 98.5 98.5 98.4 98.0 97.6 97.0 96.4 95.7 95.0 94.3 93.5 92.7 91.8 91.0 90.1 89.2 88.3

45 96.4 97.5 97.9 98.1 98.1 97.9 97.6 97.1 96.6 96.1 95.4 94.8 94.1 93.3 92.5 91.7 90.9 90.1 89.2 88.3

50 95.8 97.0 97.4 97.6 97.6 97.4 97.0 96.6 96.2 95.6 95.1 94.5 93.8 93.1 92.4 91.6 90.8 90.0 89.2 88.3

55 95.1 96.3 96.8 96.9 96.9 96.7 96.4 96.0 95.6 95.1 94.6 94.1 93.5 92.8 92.1 91.4 90.7 89.9 89.1 88.3

60 94.4 95.5 95.9 96.1 96.0 95.9 95.7 95.3 95.0 94.6 94.1 93.6 93.1 92.5 91.9 91.2 90.5 89.8 89.1 88.3

65 93.4 94.5 94.9 95.1 95.1 95.0 94.8 94.6 94.3 93.9 93.6 93.1 92.6 92.1 91.5 90.9 90.3 89.7 89.0 88.3

70 92.3 93.2 93.7 93.9 94.0 94.0 93.9 93.7 93.5 93.2 92.9 92.5 92.1 91.7 91.2 90.7 90.1 89.5 88.9 88.3

75 91.0 91.9 92.4 92.7 92.9 92.9 92.9 92.8 92.6 92.4 92.2 91.9 91.5 91.1 90.7 90.3 89.9 89.4 88.9 88.3

80 89.9 90.6 91.1 91.5 91.7 91.8 91.8 91.8 91.7 91.5 91.3 91.1 90.9 90.6 90.3 89.9 89.6 89.2 88.8 88.3

85 88.9 89.5 89.9 90.2 90.4 90.5 90.6 90.6 90.6 90.5 90.4 90.3 90.1 89.9 89.7 89.5 89.2 89.0 88.7 88.3

90 88.1 88.5 88.8 89.0 89.2 89.3 89.4 89.4 89.5 89.5 89.4 89.4 89.3 89.2 89.1 89.0 88.9 88.7 88.5 88.3

95 87.7 87.8 88.0 88.1 88.2 88.3 88.4 88.4 88.5 88.5 88.5 88.5 88.5 88.5 88.5 88.5 88.5 88.4 88.4 88.3

98 87.9 88.0 88.0 88.1 88.1 88.1 88.2 88.2 88.2 88.2 88.3 88.3 88.3 88.3 88.3 88.3 88.3 88.3 88.3 88.3

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.1 99.4 99.5 99.4 99.3 99.2 99.0 98.6 98.1 97.5 96.9 96.2 95.5 94.8 94.1 93.3 92.4 91.6 90.8 89.9

35 98.6 99.0 99.1 99.1 99.1 99.0 98.7 98.4 97.9 97.3 96.7 96.1 95.4 94.7 94.0 93.2 92.4 91.6 90.8 89.9

40 97.7 98.4 98.6 98.7 98.7 98.7 98.5 98.1 97.6 97.1 96.5 95.9 95.2 94.6 93.8 93.1 92.3 91.5 90.8 89.9

45 96.9 97.8 98.2 98.4 98.4 98.3 98.1 97.7 97.3 96.8 96.2 95.7 95.0 94.4 93.7 93.0 92.2 91.5 90.7 89.9

50 96.3 97.3 97.8 98.0 98.0 97.9 97.6 97.2 96.9 96.4 95.9 95.4 94.8 94.2 93.5 92.9 92.2 91.4 90.7 89.9

55 95.7 96.8 97.3 97.4 97.4 97.3 97.0 96.7 96.4 96.0 95.5 95.0 94.5 93.9 93.3 92.7 92.0 91.4 90.7 89.9

60 95.2 96.2 96.6 96.8 96.7 96.6 96.4 96.1 95.8 95.4 95.0 94.6 94.1 93.6 93.1 92.5 91.9 91.3 90.6 89.9

65 94.5 95.3 95.8 95.9 95.9 95.8 95.7 95.4 95.2 94.9 94.5 94.1 93.7 93.3 92.8 92.3 91.7 91.1 90.6 89.9

70 93.5 94.3 94.7 94.9 95.0 94.9 94.8 94.7 94.5 94.2 93.9 93.6 93.3 92.9 92.4 92.0 91.5 91.0 90.5 89.9

75 92.4 93.2 93.6 93.8 93.9 93.9 93.9 93.8 93.7 93.5 93.3 93.0 92.7 92.4 92.1 91.7 91.3 90.9 90.4 89.9

80 91.3 92.0 92.4 92.6 92.8 92.9 92.9 92.9 92.8 92.7 92.6 92.4 92.1 91.9 91.6 91.3 91.0 90.7 90.3 89.9

85 90.4 90.9 91.3 91.5 91.7 91.8 91.9 91.9 91.9 91.8 91.7 91.6 91.5 91.3 91.1 90.9 90.7 90.5 90.2 89.9

90 89.7 90.0 90.3 90.5 90.6 90.8 90.8 90.9 90.9 90.9 90.9 90.8 90.8 90.7 90.6 90.5 90.4 90.2 90.1 89.9

95 89.3 89.4 89.6 89.7 89.8 89.8 89.9 90.0 90.0 90.0 90.1 90.1 90.1 90.1 90.1 90.1 90.0 90.0 90.0 89.9

98 89.6 89.6 89.6 89.7 89.7 89.7 89.8 89.8 89.8 89.8 89.9 89.9 89.9 89.9 89.9 89.9 89.9 89.9 89.9 89.9

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.00-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.75-inches of Retention for Zone 1
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.3 99.5 99.6 99.5 99.5 99.4 99.2 98.9 98.5 98.1 97.5 96.9 96.3 95.7 95.0 94.3 93.6 92.8 92.1 91.3

35 98.8 99.2 99.3 99.2 99.2 99.1 99.0 98.7 98.3 97.9 97.3 96.8 96.2 95.6 94.9 94.2 93.5 92.8 92.0 91.3

40 98.2 98.7 98.8 98.9 98.9 98.9 98.7 98.5 98.1 97.7 97.2 96.6 96.0 95.4 94.8 94.1 93.5 92.7 92.0 91.3

45 97.4 98.1 98.5 98.6 98.6 98.6 98.4 98.2 97.8 97.4 96.9 96.4 95.8 95.3 94.7 94.0 93.4 92.7 92.0 91.3

50 96.7 97.7 98.1 98.2 98.3 98.2 98.1 97.8 97.4 97.0 96.6 96.1 95.6 95.1 94.5 93.9 93.3 92.6 92.0 91.3

55 96.2 97.2 97.6 97.8 97.9 97.8 97.6 97.3 97.0 96.6 96.2 95.8 95.3 94.8 94.3 93.8 93.2 92.6 91.9 91.3

60 95.8 96.7 97.1 97.3 97.3 97.2 97.0 96.8 96.5 96.2 95.8 95.4 95.0 94.6 94.1 93.6 93.0 92.5 91.9 91.3

65 95.3 96.1 96.5 96.6 96.6 96.5 96.3 96.2 95.9 95.6 95.3 95.0 94.6 94.2 93.8 93.4 92.9 92.4 91.8 91.3

70 94.5 95.3 95.6 95.7 95.7 95.7 95.6 95.5 95.3 95.1 94.8 94.5 94.2 93.9 93.5 93.1 92.7 92.2 91.8 91.3

75 93.6 94.2 94.5 94.7 94.8 94.8 94.8 94.7 94.6 94.4 94.2 94.0 93.8 93.5 93.2 92.8 92.5 92.1 91.7 91.3

80 92.6 93.1 93.5 93.7 93.8 93.9 93.9 93.9 93.8 93.7 93.6 93.4 93.2 93.0 92.8 92.5 92.2 91.9 91.6 91.3

85 91.7 92.1 92.4 92.6 92.8 92.9 93.0 93.0 93.0 92.9 92.9 92.8 92.6 92.5 92.3 92.2 92.0 91.8 91.5 91.3

90 91.0 91.3 91.6 91.7 91.9 92.0 92.0 92.1 92.1 92.1 92.1 92.1 92.0 91.9 91.9 91.8 91.7 91.6 91.4 91.3

95 90.7 90.8 91.0 91.0 91.1 91.2 91.2 91.3 91.3 91.4 91.4 91.4 91.4 91.4 91.4 91.4 91.4 91.4 91.3 91.3

98 90.9 91.0 91.0 91.0 91.1 91.1 91.1 91.1 91.2 91.2 91.2 91.2 91.2 91.2 91.3 91.3 91.3 91.3 91.3 91.3

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.4 99.6 99.6 99.6 99.6 99.5 99.4 99.2 98.8 98.4 98.0 97.5 97.0 96.4 95.8 95.2 94.5 93.8 93.1 92.4

35 99.0 99.3 99.4 99.4 99.4 99.3 99.2 99.0 98.7 98.3 97.9 97.4 96.8 96.3 95.7 95.1 94.5 93.8 93.1 92.4

40 98.5 98.9 99.1 99.1 99.1 99.1 98.9 98.8 98.5 98.1 97.7 97.2 96.7 96.2 95.6 95.0 94.4 93.8 93.1 92.4

45 97.8 98.4 98.7 98.8 98.8 98.8 98.7 98.5 98.2 97.9 97.4 97.0 96.5 96.0 95.5 94.9 94.3 93.7 93.1 92.4

50 97.2 98.0 98.3 98.5 98.5 98.5 98.4 98.2 97.9 97.5 97.2 96.8 96.3 95.8 95.3 94.8 94.2 93.7 93.1 92.4

55 96.7 97.5 97.9 98.1 98.2 98.1 98.0 97.8 97.5 97.2 96.8 96.5 96.0 95.6 95.1 94.7 94.1 93.6 93.0 92.4

60 96.3 97.1 97.5 97.7 97.7 97.7 97.5 97.3 97.1 96.8 96.5 96.1 95.7 95.3 94.9 94.5 94.0 93.5 93.0 92.4

65 95.9 96.6 97.0 97.2 97.2 97.1 96.9 96.8 96.6 96.3 96.0 95.7 95.4 95.1 94.7 94.3 93.9 93.4 92.9 92.4

70 95.4 96.0 96.3 96.4 96.4 96.4 96.3 96.1 96.0 95.8 95.5 95.3 95.0 94.7 94.4 94.1 93.7 93.3 92.9 92.4

75 94.6 95.1 95.4 95.5 95.6 95.6 95.5 95.4 95.3 95.2 95.0 94.8 94.6 94.4 94.1 93.8 93.5 93.2 92.8 92.4

80 93.7 94.1 94.4 94.6 94.7 94.7 94.7 94.7 94.6 94.5 94.4 94.3 94.1 93.9 93.7 93.5 93.3 93.0 92.7 92.4

85 92.9 93.2 93.5 93.6 93.8 93.8 93.9 93.9 93.9 93.8 93.8 93.7 93.6 93.5 93.4 93.2 93.0 92.8 92.6 92.4

90 92.2 92.4 92.6 92.8 92.9 93.0 93.1 93.1 93.1 93.1 93.1 93.1 93.1 93.0 92.9 92.8 92.8 92.7 92.5 92.4

95 91.9 92.0 92.1 92.2 92.3 92.3 92.4 92.4 92.5 92.5 92.5 92.5 92.5 92.5 92.5 92.5 92.5 92.5 92.5 92.4

98 92.1 92.1 92.2 92.2 92.2 92.2 92.3 92.3 92.3 92.3 92.3 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.25-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.50-inches of Retention for Zone 1
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.6 99.7 99.7 99.7 99.7 99.6 99.5 99.4 99.1 98.8 98.4 98.0 97.5 97.0 96.4 95.9 95.3 94.7 94.1 93.4

35 99.2 99.4 99.5 99.5 99.5 99.4 99.3 99.2 99.0 98.6 98.3 97.8 97.4 96.9 96.4 95.8 95.2 94.6 94.0 93.4

40 98.8 99.1 99.2 99.3 99.2 99.2 99.1 99.0 98.8 98.5 98.1 97.7 97.2 96.8 96.3 95.7 95.2 94.6 94.0 93.4

45 98.2 98.7 98.9 99.0 99.0 99.0 98.9 98.8 98.6 98.3 97.9 97.5 97.1 96.6 96.1 95.6 95.1 94.6 94.0 93.4

50 97.6 98.2 98.5 98.7 98.7 98.7 98.6 98.5 98.3 98.0 97.7 97.3 96.9 96.5 96.0 95.5 95.0 94.5 94.0 93.4

55 97.1 97.9 98.2 98.4 98.4 98.4 98.3 98.2 97.9 97.7 97.4 97.0 96.6 96.3 95.8 95.4 94.9 94.5 93.9 93.4

60 96.7 97.5 97.8 98.0 98.1 98.1 98.0 97.8 97.5 97.3 97.0 96.7 96.4 96.0 95.6 95.2 94.8 94.4 93.9 93.4

65 96.4 97.1 97.4 97.6 97.6 97.6 97.4 97.3 97.1 96.9 96.6 96.4 96.1 95.7 95.4 95.1 94.7 94.3 93.9 93.4

70 96.0 96.6 96.9 97.0 97.0 97.0 96.9 96.7 96.6 96.4 96.2 96.0 95.7 95.4 95.2 94.9 94.5 94.2 93.8 93.4

75 95.5 95.9 96.1 96.2 96.3 96.3 96.2 96.1 96.0 95.9 95.7 95.5 95.3 95.1 94.9 94.6 94.4 94.1 93.7 93.4

80 94.7 95.0 95.2 95.4 95.5 95.5 95.5 95.4 95.4 95.3 95.2 95.0 94.9 94.7 94.6 94.4 94.2 93.9 93.7 93.4

85 93.8 94.1 94.4 94.5 94.6 94.7 94.7 94.7 94.7 94.7 94.6 94.5 94.4 94.3 94.2 94.1 93.9 93.8 93.6 93.4

90 93.2 93.4 93.6 93.7 93.8 93.9 93.9 94.0 94.0 94.0 94.0 94.0 93.9 93.9 93.8 93.8 93.7 93.6 93.5 93.4

95 92.9 93.0 93.1 93.2 93.2 93.3 93.3 93.4 93.4 93.4 93.5 93.5 93.5 93.5 93.5 93.5 93.5 93.5 93.4 93.4

98 93.1 93.1 93.2 93.2 93.2 93.2 93.3 93.3 93.3 93.3 93.3 93.3 93.4 93.4 93.4 93.4 93.4 93.4 93.4 93.4

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.6 99.7 99.8 99.8 99.7 99.7 99.6 99.5 99.3 99.0 98.7 98.3 97.9 97.5 97.0 96.5 95.9 95.4 94.8 94.3

35 99.3 99.5 99.6 99.6 99.6 99.5 99.5 99.3 99.2 98.9 98.6 98.2 97.8 97.4 96.9 96.4 95.9 95.4 94.8 94.3

40 99.0 99.3 99.4 99.4 99.4 99.3 99.3 99.2 99.0 98.8 98.5 98.1 97.7 97.3 96.8 96.3 95.8 95.3 94.8 94.3

45 98.5 98.9 99.1 99.1 99.1 99.1 99.1 99.0 98.8 98.6 98.3 97.9 97.6 97.2 96.7 96.3 95.8 95.3 94.8 94.3

50 98.0 98.5 98.7 98.9 98.9 98.9 98.8 98.7 98.6 98.3 98.1 97.7 97.4 97.0 96.6 96.2 95.7 95.2 94.8 94.3

55 97.5 98.1 98.4 98.6 98.6 98.6 98.6 98.5 98.3 98.1 97.8 97.5 97.1 96.8 96.4 96.0 95.6 95.2 94.7 94.3

60 97.1 97.8 98.1 98.3 98.3 98.3 98.3 98.1 98.0 97.7 97.5 97.2 96.9 96.6 96.3 95.9 95.5 95.1 94.7 94.3

65 96.8 97.4 97.8 97.9 98.0 98.0 97.9 97.7 97.5 97.3 97.1 96.9 96.6 96.3 96.0 95.7 95.4 95.0 94.7 94.3

70 96.5 97.1 97.3 97.5 97.5 97.5 97.4 97.2 97.1 96.9 96.7 96.5 96.3 96.1 95.8 95.5 95.2 94.9 94.6 94.3

75 96.1 96.5 96.7 96.8 96.8 96.8 96.8 96.7 96.6 96.4 96.3 96.1 96.0 95.8 95.5 95.3 95.1 94.8 94.5 94.3

80 95.5 95.8 95.9 96.1 96.1 96.1 96.1 96.1 96.0 95.9 95.8 95.7 95.6 95.4 95.3 95.1 94.9 94.7 94.5 94.3

85 94.7 95.0 95.1 95.3 95.3 95.4 95.4 95.4 95.4 95.4 95.3 95.2 95.1 95.0 94.9 94.8 94.7 94.6 94.4 94.3

90 94.1 94.3 94.4 94.5 94.6 94.7 94.7 94.8 94.8 94.8 94.8 94.7 94.7 94.7 94.6 94.6 94.5 94.4 94.3 94.3

95 93.8 93.9 94.0 94.0 94.1 94.1 94.2 94.2 94.2 94.3 94.3 94.3 94.3 94.3 94.3 94.3 94.3 94.3 94.3 94.3

98 94.0 94.0 94.0 94.0 94.1 94.1 94.1 94.1 94.1 94.2 94.2 94.2 94.2 94.2 94.2 94.2 94.2 94.2 94.2 94.3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.75-inches of Retention for Zone 1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 4.00-inches of Retention for Zone 1
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 94.4 90.4 83.0 75.1 68.0 61.9 56.6 52.1 48.3 44.9 42.0 39.4 37.2 35.1 33.3 31.7 30.2 28.8 27.6 26.4

35 91.8 88.8 82.0 74.5 67.6 61.5 56.4 51.9 48.1 44.8 41.9 39.4 37.1 35.1 33.3 31.7 30.2 28.8 27.6 26.4

40 88.2 86.6 80.6 73.5 66.9 61.1 56.0 51.7 47.9 44.7 41.8 39.3 37.1 35.0 33.2 31.6 30.2 28.8 27.6 26.4

45 83.9 83.8 78.7 72.3 66.1 60.4 55.6 51.4 47.7 44.5 41.7 39.2 37.0 35.0 33.2 31.6 30.1 28.8 27.6 26.4

50 78.8 80.4 76.4 70.7 64.9 59.6 55.0 50.9 47.3 44.2 41.5 39.0 36.8 34.9 33.1 31.5 30.1 28.8 27.6 26.4

55 73.2 76.4 73.6 68.7 63.5 58.6 54.2 50.3 46.9 43.9 41.2 38.8 36.7 34.8 33.0 31.5 30.1 28.7 27.5 26.4

60 67.4 71.8 70.2 66.3 61.7 57.3 53.2 49.6 46.3 43.4 40.8 38.6 36.5 34.6 32.9 31.4 30.0 28.7 27.5 26.4

65 61.4 66.7 66.3 63.4 59.5 55.6 51.9 48.6 45.5 42.9 40.4 38.2 36.2 34.4 32.8 31.3 29.9 28.7 27.5 26.4

70 55.7 61.1 61.8 59.8 56.8 53.5 50.4 47.3 44.6 42.1 39.8 37.7 35.9 34.1 32.6 31.1 29.8 28.6 27.5 26.4

75 50.1 55.2 56.5 55.6 53.5 50.9 48.3 45.7 43.3 41.1 39.0 37.1 35.4 33.8 32.3 30.9 29.7 28.5 27.4 26.4

80 45.0 49.1 50.7 50.6 49.4 47.6 45.6 43.6 41.6 39.7 37.9 36.2 34.7 33.2 31.9 30.7 29.5 28.4 27.4 26.4

85 40.3 43.2 44.5 44.8 44.3 43.4 42.1 40.7 39.2 37.8 36.3 35.0 33.7 32.5 31.3 30.2 29.2 28.2 27.3 26.4

90 36.0 37.5 38.3 38.6 38.5 38.1 37.5 36.7 35.9 35.0 34.0 33.1 32.2 31.3 30.4 29.5 28.7 27.9 27.2 26.4

95 31.7 32.1 32.3 32.4 32.3 32.2 32.0 31.7 31.4 31.0 30.6 30.2 29.7 29.3 28.8 28.3 27.9 27.4 26.9 26.4

98 29.3 29.3 29.2 29.1 29.0 28.9 28.8 28.6 28.5 28.3 28.2 28.0 27.8 27.7 27.5 27.3 27.1 26.9 26.6 26.4

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 97.0 96.7 94.8 91.7 87.9 83.8 79.7 75.7 71.9 68.4 65.2 62.1 59.4 56.9 54.5 52.3 50.3 48.4 46.7 45.1

35 95.2 95.5 93.8 90.9 87.3 83.4 79.3 75.4 71.7 68.3 65.0 62.1 59.3 56.8 54.4 52.3 50.3 48.4 46.7 45.1

40 92.9 94.0 92.5 89.9 86.5 82.7 78.9 75.1 71.4 68.0 64.9 61.9 59.2 56.7 54.4 52.2 50.2 48.4 46.7 45.1

45 90.2 91.9 90.9 88.6 85.5 81.9 78.2 74.6 71.1 67.7 64.6 61.7 59.1 56.6 54.3 52.2 50.2 48.4 46.7 45.1

50 86.7 89.2 88.9 87.0 84.2 80.9 77.4 73.9 70.5 67.3 64.3 61.5 58.9 56.5 54.2 52.1 50.2 48.3 46.6 45.1

55 82.7 86.1 86.4 84.9 82.6 79.6 76.4 73.1 69.9 66.8 63.9 61.2 58.6 56.3 54.1 52.0 50.1 48.3 46.6 45.1

60 78.5 82.6 83.4 82.5 80.6 78.0 75.1 72.1 69.1 66.1 63.4 60.8 58.3 56.0 53.9 51.9 50.0 48.2 46.6 45.1

65 74.2 78.6 79.8 79.5 78.1 76.0 73.5 70.7 68.0 65.3 62.7 60.2 57.9 55.7 53.6 51.7 49.9 48.2 46.6 45.1

70 69.8 74.2 75.8 76.0 75.2 73.5 71.4 69.1 66.6 64.2 61.8 59.5 57.3 55.3 53.3 51.4 49.7 48.1 46.5 45.1

75 65.4 69.6 71.4 71.9 71.5 70.4 68.8 66.9 64.9 62.7 60.6 58.6 56.6 54.7 52.8 51.1 49.5 47.9 46.5 45.1

80 61.4 64.9 66.6 67.3 67.2 66.5 65.5 64.1 62.5 60.8 59.0 57.3 55.5 53.9 52.2 50.7 49.2 47.7 46.4 45.1

85 57.6 60.1 61.6 62.2 62.3 62.0 61.3 60.4 59.3 58.1 56.8 55.4 54.0 52.7 51.3 50.0 48.7 47.4 46.2 45.1

90 54.1 55.4 56.2 56.7 56.8 56.7 56.4 55.9 55.2 54.5 53.6 52.8 51.8 50.9 49.9 48.9 47.9 46.9 46.0 45.1

95 50.1 50.5 50.7 50.8 50.8 50.8 50.6 50.4 50.2 49.9 49.5 49.1 48.7 48.2 47.7 47.2 46.7 46.1 45.6 45.1

98 47.8 47.7 47.7 47.6 47.6 47.5 47.4 47.2 47.1 46.9 46.8 46.6 46.5 46.3 46.1 45.9 45.7 45.5 45.3 45.1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.25-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.50-inches of Retention in Zone 2
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 97.9 98.2 97.5 96.2 94.4 92.1 89.6 86.9 84.1 81.3 78.5 75.9 73.3 70.9 68.5 66.3 64.2 62.2 60.4 58.6

35 96.7 97.3 96.8 95.6 93.8 91.7 89.2 86.6 83.8 81.1 78.4 75.7 73.2 70.8 68.5 66.3 64.2 62.2 60.4 58.6

40 95.0 96.1 95.9 94.8 93.1 91.1 88.7 86.2 83.5 80.8 78.2 75.6 73.1 70.7 68.4 66.2 64.2 62.2 60.4 58.6

45 93.0 94.7 94.6 93.7 92.2 90.3 88.1 85.6 83.1 80.5 77.9 75.4 72.9 70.6 68.3 66.2 64.1 62.2 60.4 58.6

50 90.7 92.8 93.1 92.4 91.1 89.3 87.3 85.0 82.5 80.0 77.5 75.1 72.7 70.4 68.2 66.1 64.0 62.1 60.3 58.6

55 88.0 90.6 91.1 90.7 89.7 88.1 86.3 84.1 81.8 79.4 77.0 74.7 72.4 70.1 68.0 65.9 64.0 62.1 60.3 58.6

60 84.8 87.9 88.8 88.7 88.0 86.7 85.0 83.0 80.9 78.7 76.5 74.2 72.0 69.8 67.8 65.8 63.8 62.0 60.3 58.6

65 81.5 84.9 86.2 86.3 85.8 84.8 83.4 81.7 79.8 77.8 75.7 73.6 71.5 69.5 67.5 65.5 63.7 61.9 60.2 58.6

70 78.1 81.7 83.1 83.5 83.2 82.5 81.4 80.0 78.4 76.6 74.7 72.8 70.9 68.9 67.1 65.2 63.5 61.8 60.2 58.6

75 74.9 78.1 79.6 80.2 80.2 79.8 79.0 77.9 76.5 75.0 73.4 71.7 70.0 68.3 66.5 64.8 63.2 61.6 60.1 58.6

80 71.6 74.3 75.8 76.5 76.7 76.5 76.0 75.2 74.1 73.0 71.7 70.3 68.8 67.3 65.8 64.3 62.8 61.4 60.0 58.6

85 68.6 70.6 71.8 72.5 72.8 72.7 72.4 71.9 71.2 70.3 69.3 68.3 67.1 65.9 64.7 63.5 62.2 61.0 59.8 58.6

90 65.7 66.9 67.7 68.1 68.3 68.3 68.2 67.9 67.5 66.9 66.3 65.6 64.9 64.0 63.2 62.3 61.4 60.5 59.5 58.6

95 62.7 63.0 63.2 63.3 63.4 63.4 63.3 63.2 63.0 62.8 62.5 62.2 61.8 61.4 61.0 60.5 60.1 59.6 59.1 58.6

98 60.8 60.8 60.8 60.7 60.7 60.6 60.5 60.4 60.3 60.2 60.1 59.9 59.8 59.6 59.5 59.3 59.2 59.0 58.8 58.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.5 98.8 98.5 97.9 96.9 95.6 94.1 92.3 90.4 88.4 86.3 84.2 82.1 80.0 77.9 75.9 74.0 72.2 70.3 68.6

35 97.5 98.2 98.0 97.4 96.5 95.3 93.7 92.0 90.2 88.2 86.2 84.1 82.0 79.9 77.9 75.9 74.0 72.1 70.3 68.6

40 96.4 97.3 97.2 96.8 95.9 94.8 93.3 91.7 89.9 87.9 85.9 83.9 81.8 79.8 77.8 75.8 73.9 72.1 70.3 68.6

45 94.8 96.1 96.3 96.0 95.2 94.1 92.7 91.2 89.4 87.6 85.6 83.6 81.6 79.6 77.7 75.8 73.9 72.1 70.3 68.6

50 93.0 94.8 95.2 94.9 94.3 93.3 92.0 90.5 88.9 87.1 85.3 83.3 81.4 79.5 77.5 75.6 73.8 72.0 70.3 68.6

55 91.0 93.2 93.7 93.6 93.1 92.3 91.1 89.8 88.2 86.6 84.8 82.9 81.1 79.2 77.3 75.5 73.7 72.0 70.2 68.6

60 88.8 91.2 92.0 92.0 91.7 91.0 90.0 88.8 87.4 85.9 84.2 82.4 80.7 78.9 77.1 75.3 73.6 71.9 70.2 68.6

65 86.2 88.9 89.9 90.2 90.0 89.5 88.7 87.6 86.4 85.0 83.4 81.8 80.2 78.5 76.8 75.1 73.4 71.8 70.2 68.6

70 83.6 86.4 87.5 88.0 88.0 87.6 86.9 86.1 85.1 83.8 82.5 81.0 79.5 77.9 76.4 74.8 73.2 71.6 70.1 68.6

75 81.0 83.6 84.9 85.5 85.6 85.3 84.9 84.2 83.4 82.4 81.2 80.0 78.6 77.2 75.8 74.3 72.9 71.5 70.0 68.6

80 78.6 80.8 82.0 82.5 82.8 82.7 82.4 81.9 81.3 80.5 79.6 78.5 77.4 76.3 75.0 73.8 72.5 71.2 69.9 68.6

85 76.1 77.7 78.7 79.3 79.6 79.7 79.5 79.2 78.8 78.2 77.5 76.7 75.9 74.9 74.0 72.9 71.9 70.8 69.7 68.6

90 73.9 74.8 75.5 75.9 76.1 76.2 76.2 76.0 75.7 75.3 74.9 74.4 73.8 73.2 72.5 71.8 71.0 70.3 69.4 68.6

95 71.5 71.8 72.0 72.1 72.2 72.2 72.2 72.1 72.0 71.9 71.7 71.4 71.2 70.9 70.6 70.2 69.9 69.5 69.0 68.6

98 70.2 70.2 70.2 70.2 70.1 70.1 70.1 70.0 69.9 69.8 69.7 69.7 69.6 69.4 69.3 69.2 69.0 68.9 68.8 68.6

Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.75-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.9 99.1 99.0 98.7 98.1 97.3 96.4 95.2 93.9 92.4 90.9 89.3 87.7 86.0 84.3 82.6 80.9 79.2 77.6 76.0

35 98.1 98.6 98.6 98.3 97.7 97.0 96.1 94.9 93.7 92.3 90.8 89.2 87.6 85.9 84.2 82.5 80.9 79.2 77.6 76.0

40 97.2 98.0 98.0 97.8 97.3 96.6 95.7 94.6 93.4 92.0 90.5 89.0 87.4 85.8 84.1 82.5 80.8 79.2 77.6 76.0

45 96.1 97.1 97.3 97.1 96.7 96.1 95.2 94.2 93.0 91.7 90.3 88.8 87.2 85.6 84.0 82.4 80.7 79.1 77.6 76.0

50 94.7 96.0 96.4 96.3 96.0 95.4 94.6 93.6 92.5 91.3 89.9 88.5 87.0 85.4 83.8 82.2 80.7 79.1 77.5 76.0

55 93.0 94.8 95.3 95.3 95.1 94.6 93.9 93.0 91.9 90.8 89.5 88.1 86.7 85.2 83.6 82.1 80.6 79.0 77.5 76.0

60 91.3 93.3 94.0 94.1 94.0 93.6 92.9 92.2 91.2 90.1 88.9 87.7 86.3 84.9 83.4 81.9 80.4 78.9 77.5 76.0

65 89.4 91.6 92.4 92.7 92.6 92.3 91.8 91.1 90.3 89.3 88.3 87.1 85.8 84.5 83.1 81.7 80.3 78.8 77.4 76.0

70 87.5 89.6 90.6 91.0 91.0 90.8 90.4 89.8 89.1 88.3 87.4 86.3 85.2 83.9 82.7 81.4 80.0 78.7 77.3 76.0

75 85.4 87.4 88.5 89.0 89.1 89.0 88.7 88.3 87.7 87.0 86.2 85.3 84.3 83.3 82.1 80.9 79.7 78.5 77.3 76.0

80 83.4 85.2 86.2 86.7 86.9 86.9 86.7 86.4 86.0 85.5 84.8 84.1 83.3 82.3 81.4 80.4 79.3 78.2 77.1 76.0

85 81.6 82.9 83.7 84.2 84.4 84.5 84.4 84.2 84.0 83.6 83.1 82.5 81.9 81.2 80.4 79.6 78.8 77.9 76.9 76.0

90 79.7 80.5 81.0 81.4 81.6 81.7 81.7 81.7 81.5 81.3 80.9 80.6 80.1 79.7 79.1 78.6 78.0 77.4 76.7 76.0

95 77.9 78.2 78.4 78.5 78.6 78.7 78.7 78.6 78.6 78.4 78.3 78.2 78.0 77.8 77.5 77.3 77.0 76.7 76.3 76.0

98 77.1 77.1 77.1 77.1 77.1 77.1 77.0 77.0 76.9 76.9 76.8 76.8 76.7 76.6 76.5 76.4 76.3 76.2 76.1 76.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.2 99.4 99.3 99.1 98.7 98.2 97.6 96.8 95.9 94.9 93.7 92.5 91.3 89.9 88.6 87.2 85.7 84.3 82.9 81.5

35 98.6 99.0 99.0 98.8 98.5 98.0 97.4 96.6 95.7 94.7 93.6 92.4 91.2 89.8 88.5 87.1 85.7 84.3 82.9 81.5

40 97.8 98.4 98.5 98.4 98.1 97.6 97.1 96.3 95.5 94.5 93.4 92.2 91.0 89.7 88.4 87.1 85.7 84.3 82.9 81.5

45 96.9 97.8 98.0 97.9 97.6 97.2 96.7 96.0 95.1 94.2 93.1 92.0 90.8 89.6 88.3 87.0 85.6 84.2 82.9 81.5

50 95.9 96.9 97.2 97.2 97.0 96.7 96.2 95.5 94.7 93.8 92.8 91.8 90.6 89.4 88.2 86.9 85.5 84.2 82.8 81.5

55 94.6 95.9 96.3 96.4 96.3 96.0 95.6 95.0 94.2 93.4 92.4 91.4 90.3 89.2 88.0 86.7 85.4 84.1 82.8 81.5

60 93.1 94.7 95.3 95.5 95.4 95.2 94.8 94.3 93.6 92.8 92.0 91.0 90.0 88.9 87.7 86.5 85.3 84.0 82.8 81.5

65 91.7 93.4 94.1 94.4 94.4 94.2 93.9 93.4 92.8 92.1 91.3 90.5 89.5 88.5 87.4 86.3 85.1 83.9 82.7 81.5

70 90.1 91.9 92.7 93.0 93.1 93.0 92.7 92.3 91.9 91.2 90.6 89.8 88.9 88.0 87.0 86.0 84.9 83.8 82.6 81.5

75 88.5 90.2 91.0 91.5 91.6 91.6 91.4 91.1 90.7 90.2 89.6 88.9 88.2 87.4 86.5 85.6 84.6 83.6 82.6 81.5

80 86.9 88.4 89.2 89.6 89.9 89.9 89.8 89.6 89.3 88.9 88.4 87.9 87.3 86.6 85.9 85.1 84.2 83.3 82.4 81.5

85 85.4 86.5 87.2 87.6 87.9 88.0 87.9 87.8 87.6 87.3 87.0 86.6 86.1 85.6 85.0 84.4 83.7 83.0 82.3 81.5

90 84.1 84.7 85.1 85.4 85.6 85.7 85.8 85.7 85.6 85.5 85.3 85.0 84.7 84.4 84.0 83.5 83.1 82.6 82.0 81.5

95 82.7 82.9 83.1 83.2 83.3 83.3 83.4 83.4 83.4 83.3 83.2 83.1 83.0 82.8 82.6 82.4 82.2 82.0 81.8 81.5

98 82.2 82.2 82.2 82.2 82.2 82.2 82.2 82.2 82.1 82.1 82.1 82.0 82.0 81.9 81.9 81.8 81.7 81.7 81.6 81.5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.50-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.25-inches of Retention in Zone 2
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.4 99.5 99.5 99.4 99.1 98.8 98.3 97.8 97.2 96.4 95.6 94.6 93.6 92.6 91.5 90.4 89.2 88.0 86.8 85.6

35 98.9 99.2 99.2 99.1 98.9 98.6 98.1 97.6 97.0 96.3 95.4 94.5 93.5 92.5 91.4 90.3 89.2 88.0 86.8 85.6

40 98.3 98.8 98.9 98.8 98.6 98.3 97.9 97.4 96.8 96.1 95.3 94.4 93.4 92.4 91.4 90.3 89.1 88.0 86.8 85.6

45 97.5 98.3 98.4 98.4 98.2 97.9 97.5 97.1 96.5 95.8 95.0 94.2 93.2 92.3 91.2 90.2 89.1 87.9 86.8 85.6

50 96.7 97.6 97.8 97.8 97.7 97.5 97.1 96.7 96.2 95.5 94.8 93.9 93.0 92.1 91.1 90.1 89.0 87.9 86.7 85.6

55 95.7 96.8 97.1 97.2 97.1 96.9 96.6 96.2 95.7 95.1 94.4 93.6 92.8 91.9 90.9 89.9 88.9 87.8 86.7 85.6

60 94.5 95.8 96.3 96.4 96.4 96.3 96.0 95.7 95.2 94.6 94.0 93.3 92.5 91.6 90.7 89.8 88.8 87.7 86.7 85.6

65 93.3 94.7 95.3 95.5 95.6 95.5 95.3 95.0 94.5 94.0 93.4 92.8 92.1 91.3 90.4 89.5 88.6 87.6 86.6 85.6

70 92.0 93.5 94.2 94.5 94.6 94.5 94.4 94.1 93.7 93.3 92.8 92.2 91.5 90.8 90.1 89.3 88.4 87.5 86.6 85.6

75 90.8 92.1 92.9 93.2 93.4 93.4 93.3 93.1 92.8 92.4 92.0 91.5 90.9 90.3 89.6 88.9 88.2 87.3 86.5 85.6

80 89.6 90.7 91.4 91.8 92.0 92.0 92.0 91.9 91.6 91.3 91.0 90.6 90.1 89.6 89.1 88.5 87.8 87.1 86.4 85.6

85 88.4 89.2 89.8 90.2 90.4 90.5 90.5 90.4 90.3 90.1 89.8 89.5 89.2 88.8 88.4 87.9 87.4 86.8 86.2 85.6

90 87.3 87.8 88.2 88.4 88.6 88.7 88.8 88.7 88.7 88.6 88.4 88.2 88.0 87.8 87.5 87.2 86.8 86.4 86.0 85.6

95 86.2 86.4 86.6 86.7 86.8 86.8 86.9 86.9 86.9 86.8 86.8 86.7 86.7 86.6 86.4 86.3 86.1 86.0 85.8 85.6

98 86.0 86.0 86.0 86.0 86.1 86.1 86.1 86.0 86.0 86.0 86.0 86.0 85.9 85.9 85.9 85.8 85.8 85.7 85.6 85.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.5 99.7 99.6 99.6 99.4 99.1 98.8 98.4 97.9 97.4 96.8 96.1 95.3 94.4 93.6 92.6 91.7 90.7 89.7 88.7

35 99.2 99.4 99.4 99.4 99.2 99.0 98.6 98.2 97.8 97.3 96.6 95.9 95.2 94.4 93.5 92.6 91.6 90.7 89.7 88.7

40 98.6 99.0 99.1 99.1 98.9 98.7 98.4 98.0 97.6 97.1 96.5 95.8 95.1 94.3 93.4 92.5 91.6 90.6 89.7 88.7

45 98.0 98.6 98.8 98.7 98.6 98.4 98.1 97.8 97.4 96.9 96.3 95.6 94.9 94.1 93.3 92.5 91.5 90.6 89.6 88.7

50 97.3 98.1 98.3 98.3 98.2 98.0 97.8 97.5 97.1 96.6 96.1 95.4 94.7 94.0 93.2 92.4 91.5 90.6 89.6 88.7

55 96.6 97.4 97.7 97.8 97.7 97.6 97.4 97.1 96.7 96.3 95.8 95.2 94.5 93.8 93.0 92.2 91.4 90.5 89.6 88.7

60 95.6 96.6 97.0 97.1 97.1 97.0 96.9 96.6 96.3 95.9 95.4 94.9 94.2 93.6 92.8 92.1 91.3 90.4 89.6 88.7

65 94.5 95.7 96.2 96.4 96.5 96.4 96.3 96.0 95.7 95.4 94.9 94.4 93.9 93.3 92.6 91.9 91.1 90.3 89.5 88.7

70 93.5 94.7 95.3 95.5 95.7 95.6 95.5 95.3 95.1 94.8 94.4 93.9 93.4 92.9 92.3 91.6 90.9 90.2 89.5 88.7

75 92.5 93.6 94.2 94.5 94.7 94.7 94.7 94.5 94.3 94.0 93.7 93.3 92.9 92.4 91.9 91.3 90.7 90.1 89.4 88.7

80 91.5 92.5 93.1 93.4 93.6 93.7 93.6 93.5 93.4 93.2 92.9 92.6 92.2 91.8 91.4 90.9 90.4 89.9 89.3 88.7

85 90.6 91.3 91.8 92.1 92.3 92.4 92.4 92.4 92.3 92.1 91.9 91.7 91.4 91.1 90.8 90.4 90.0 89.6 89.2 88.7

90 89.7 90.1 90.5 90.7 90.9 91.0 91.0 91.0 91.0 90.9 90.8 90.6 90.5 90.3 90.1 89.9 89.6 89.3 89.0 88.7

95 88.9 89.1 89.2 89.3 89.4 89.5 89.5 89.5 89.5 89.5 89.5 89.4 89.4 89.3 89.2 89.2 89.0 88.9 88.8 88.7

98 88.8 88.8 88.9 88.9 88.9 88.9 88.9 88.9 88.9 88.9 88.9 88.9 88.9 88.8 88.8 88.8 88.8 88.7 88.7 88.7

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.75-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.00-inches of Retention in Zone 2
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.7 99.7 99.7 99.7 99.6 99.4 99.1 98.8 98.5 98.1 97.6 97.0 96.4 95.8 95.0 94.3 93.5 92.7 91.8 91.0

35 99.3 99.5 99.6 99.5 99.4 99.2 99.0 98.7 98.3 97.9 97.5 96.9 96.3 95.7 95.0 94.3 93.5 92.7 91.8 91.0

40 99.0 99.2 99.3 99.3 99.2 99.0 98.8 98.5 98.2 97.8 97.3 96.8 96.2 95.6 94.9 94.2 93.4 92.6 91.8 91.0

45 98.4 98.9 99.0 99.0 98.9 98.8 98.6 98.3 98.0 97.6 97.2 96.7 96.1 95.5 94.8 94.1 93.4 92.6 91.8 91.0

50 97.8 98.5 98.6 98.7 98.6 98.5 98.3 98.0 97.7 97.4 97.0 96.5 95.9 95.4 94.7 94.0 93.3 92.5 91.8 91.0

55 97.2 97.9 98.2 98.2 98.2 98.1 97.9 97.7 97.4 97.1 96.7 96.3 95.8 95.2 94.6 93.9 93.2 92.5 91.7 91.0

60 96.5 97.3 97.6 97.7 97.7 97.6 97.5 97.3 97.0 96.8 96.4 96.0 95.5 95.0 94.4 93.8 93.1 92.4 91.7 91.0

65 95.6 96.5 96.9 97.1 97.1 97.1 97.0 96.8 96.6 96.3 96.0 95.6 95.2 94.7 94.2 93.6 93.0 92.3 91.7 91.0

70 94.6 95.6 96.1 96.3 96.4 96.4 96.4 96.3 96.1 95.8 95.5 95.2 94.8 94.4 93.9 93.4 92.8 92.2 91.6 91.0

75 93.8 94.7 95.2 95.5 95.7 95.7 95.7 95.6 95.4 95.2 95.0 94.7 94.4 94.0 93.6 93.1 92.6 92.1 91.5 91.0

80 93.0 93.8 94.3 94.6 94.8 94.9 94.9 94.8 94.7 94.5 94.3 94.1 93.8 93.5 93.1 92.8 92.4 91.9 91.4 91.0

85 92.3 92.9 93.3 93.6 93.7 93.8 93.9 93.8 93.8 93.7 93.5 93.4 93.1 92.9 92.6 92.4 92.0 91.7 91.3 91.0

90 91.6 92.0 92.3 92.5 92.6 92.7 92.7 92.7 92.7 92.7 92.6 92.5 92.4 92.2 92.1 91.9 91.7 91.5 91.2 91.0

95 91.0 91.2 91.3 91.4 91.4 91.5 91.5 91.5 91.6 91.5 91.5 91.5 91.5 91.4 91.4 91.3 91.2 91.1 91.1 91.0

98 91.0 91.0 91.0 91.0 91.1 91.1 91.1 91.1 91.1 91.1 91.1 91.1 91.1 91.1 91.0 91.0 91.0 91.0 91.0 91.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.7 99.8 99.8 99.8 99.7 99.6 99.4 99.1 98.8 98.5 98.1 97.7 97.2 96.7 96.1 95.5 94.9 94.2 93.5 92.7

35 99.5 99.6 99.7 99.6 99.6 99.4 99.3 99.0 98.7 98.4 98.0 97.6 97.2 96.6 96.1 95.5 94.8 94.2 93.4 92.7

40 99.2 99.4 99.5 99.5 99.4 99.3 99.1 98.9 98.6 98.3 97.9 97.5 97.1 96.6 96.0 95.4 94.8 94.1 93.4 92.7

45 98.7 99.1 99.2 99.2 99.2 99.0 98.9 98.7 98.4 98.1 97.8 97.4 97.0 96.5 95.9 95.4 94.7 94.1 93.4 92.7

50 98.2 98.8 98.9 98.9 98.9 98.8 98.6 98.4 98.2 97.9 97.6 97.2 96.8 96.4 95.8 95.3 94.7 94.1 93.4 92.7

55 97.7 98.3 98.5 98.6 98.5 98.5 98.3 98.1 97.9 97.7 97.4 97.0 96.6 96.2 95.7 95.2 94.6 94.0 93.4 92.7

60 97.1 97.8 98.0 98.1 98.1 98.1 97.9 97.8 97.6 97.4 97.1 96.8 96.4 96.0 95.6 95.1 94.5 93.9 93.3 92.7

65 96.4 97.1 97.5 97.6 97.6 97.6 97.5 97.4 97.2 97.0 96.8 96.5 96.2 95.8 95.4 94.9 94.4 93.9 93.3 92.7

70 95.6 96.4 96.8 97.0 97.1 97.1 97.0 96.9 96.8 96.6 96.4 96.1 95.8 95.5 95.1 94.7 94.2 93.8 93.3 92.7

75 94.8 95.6 96.0 96.3 96.4 96.5 96.4 96.4 96.3 96.1 95.9 95.7 95.5 95.2 94.8 94.5 94.1 93.6 93.2 92.7

80 94.1 94.8 95.3 95.5 95.7 95.8 95.8 95.7 95.7 95.5 95.4 95.2 95.0 94.8 94.5 94.2 93.8 93.5 93.1 92.7

85 93.6 94.1 94.4 94.7 94.8 94.9 95.0 95.0 94.9 94.9 94.7 94.6 94.5 94.3 94.1 93.8 93.6 93.3 93.0 92.7

90 93.1 93.4 93.6 93.8 93.9 94.0 94.1 94.1 94.1 94.0 94.0 93.9 93.8 93.7 93.6 93.4 93.3 93.1 92.9 92.7

95 92.7 92.8 92.9 93.0 93.0 93.1 93.1 93.1 93.1 93.1 93.1 93.1 93.1 93.1 93.0 93.0 92.9 92.9 92.8 92.7

98 92.7 92.7 92.7 92.7 92.7 92.8 92.8 92.8 92.8 92.8 92.8 92.8 92.8 92.8 92.8 92.8 92.7 92.7 92.7 92.7

Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.25-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.8 99.9 99.9 99.8 99.8 99.7 99.5 99.4 99.1 98.8 98.5 98.2 97.8 97.4 96.9 96.4 95.9 95.3 94.7 94.1

35 99.6 99.7 99.7 99.7 99.7 99.6 99.4 99.3 99.0 98.8 98.5 98.1 97.8 97.4 96.9 96.4 95.9 95.3 94.7 94.1

40 99.4 99.5 99.6 99.6 99.5 99.4 99.3 99.1 98.9 98.6 98.4 98.0 97.7 97.3 96.8 96.4 95.8 95.3 94.7 94.1

45 99.0 99.3 99.4 99.4 99.3 99.2 99.1 98.9 98.7 98.5 98.2 97.9 97.6 97.2 96.8 96.3 95.8 95.2 94.7 94.1

50 98.6 99.0 99.1 99.2 99.1 99.0 98.9 98.7 98.6 98.3 98.1 97.8 97.5 97.1 96.7 96.2 95.7 95.2 94.7 94.1

55 98.1 98.6 98.8 98.8 98.8 98.7 98.6 98.5 98.3 98.1 97.9 97.6 97.3 97.0 96.6 96.1 95.7 95.2 94.6 94.1

60 97.6 98.2 98.4 98.5 98.5 98.4 98.3 98.2 98.0 97.9 97.6 97.4 97.1 96.8 96.4 96.0 95.6 95.1 94.6 94.1

65 97.0 97.6 97.9 98.0 98.1 98.0 98.0 97.9 97.7 97.6 97.4 97.2 96.9 96.6 96.2 95.9 95.5 95.0 94.6 94.1

70 96.4 97.0 97.3 97.5 97.6 97.6 97.5 97.5 97.4 97.2 97.1 96.9 96.6 96.3 96.0 95.7 95.3 94.9 94.5 94.1

75 95.7 96.4 96.7 96.9 97.0 97.1 97.0 97.0 96.9 96.8 96.7 96.5 96.3 96.1 95.8 95.5 95.2 94.8 94.5 94.1

80 95.1 95.6 96.0 96.3 96.4 96.5 96.5 96.5 96.4 96.3 96.2 96.1 95.9 95.7 95.5 95.3 95.0 94.7 94.4 94.1

85 94.6 95.0 95.3 95.6 95.7 95.8 95.8 95.8 95.8 95.8 95.7 95.6 95.5 95.3 95.2 95.0 94.8 94.6 94.3 94.1

90 94.2 94.5 94.7 94.9 95.0 95.0 95.1 95.1 95.1 95.1 95.1 95.0 94.9 94.9 94.8 94.6 94.5 94.4 94.2 94.1

95 93.9 94.0 94.1 94.2 94.3 94.3 94.3 94.4 94.4 94.4 94.4 94.4 94.4 94.3 94.3 94.3 94.2 94.2 94.1 94.1

98 94.0 94.0 94.0 94.0 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1 94.1

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.9 99.9 99.9 99.9 99.8 99.8 99.7 99.5 99.3 99.1 98.9 98.6 98.3 97.9 97.6 97.1 96.7 96.2 95.7 95.1

35 99.7 99.8 99.8 99.8 99.7 99.7 99.6 99.4 99.2 99.0 98.8 98.5 98.2 97.9 97.5 97.1 96.7 96.2 95.7 95.1

40 99.5 99.6 99.7 99.7 99.6 99.6 99.5 99.3 99.1 98.9 98.7 98.4 98.1 97.8 97.5 97.1 96.6 96.2 95.7 95.1

45 99.2 99.4 99.5 99.5 99.5 99.4 99.3 99.2 99.0 98.8 98.6 98.3 98.1 97.7 97.4 97.0 96.6 96.1 95.6 95.1

50 98.8 99.2 99.3 99.3 99.3 99.2 99.1 99.0 98.8 98.6 98.4 98.2 97.9 97.6 97.3 96.9 96.5 96.1 95.6 95.1

55 98.4 98.9 99.0 99.1 99.0 99.0 98.9 98.8 98.6 98.5 98.3 98.0 97.8 97.5 97.2 96.9 96.5 96.1 95.6 95.1

60 98.0 98.5 98.7 98.7 98.7 98.7 98.6 98.5 98.4 98.2 98.1 97.9 97.6 97.4 97.1 96.8 96.4 96.0 95.6 95.1

65 97.5 98.0 98.3 98.4 98.4 98.4 98.3 98.2 98.1 98.0 97.8 97.6 97.4 97.2 96.9 96.6 96.3 95.9 95.6 95.1

70 97.0 97.5 97.8 97.9 98.0 98.0 97.9 97.9 97.8 97.7 97.6 97.4 97.2 97.0 96.8 96.5 96.2 95.9 95.5 95.1

75 96.4 97.0 97.2 97.4 97.5 97.5 97.5 97.5 97.4 97.3 97.2 97.1 96.9 96.8 96.5 96.3 96.1 95.8 95.5 95.1

80 95.9 96.3 96.6 96.8 97.0 97.0 97.0 97.0 97.0 96.9 96.9 96.8 96.6 96.5 96.3 96.1 95.9 95.7 95.4 95.1

85 95.4 95.8 96.1 96.2 96.4 96.5 96.5 96.5 96.5 96.5 96.4 96.3 96.3 96.1 96.0 95.9 95.7 95.5 95.3 95.1

90 95.1 95.4 95.5 95.7 95.8 95.9 95.9 95.9 95.9 95.9 95.9 95.9 95.8 95.8 95.7 95.6 95.5 95.4 95.3 95.1

95 95.0 95.0 95.1 95.2 95.2 95.3 95.3 95.3 95.3 95.4 95.4 95.4 95.3 95.3 95.3 95.3 95.3 95.2 95.2 95.1

98 95.0 95.1 95.1 95.1 95.1 95.1 95.1 95.1 95.1 95.1 95.2 95.2 95.2 95.2 95.2 95.2 95.1 95.1 95.1 95.1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.00-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.75-inches of Retention in Zone 2
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.9 99.9 99.9 99.9 99.9 99.8 99.8 99.6 99.5 99.3 99.1 98.9 98.6 98.3 98.0 97.7 97.3 96.9 96.4 96.0

35 99.8 99.8 99.9 99.8 99.8 99.8 99.7 99.6 99.4 99.2 99.0 98.8 98.5 98.3 98.0 97.6 97.3 96.9 96.4 96.0

40 99.6 99.7 99.7 99.7 99.7 99.7 99.6 99.5 99.3 99.1 99.0 98.7 98.5 98.2 97.9 97.6 97.2 96.8 96.4 96.0

45 99.4 99.5 99.6 99.6 99.6 99.5 99.4 99.3 99.2 99.0 98.8 98.6 98.4 98.2 97.9 97.5 97.2 96.8 96.4 96.0

50 99.1 99.3 99.4 99.4 99.4 99.4 99.3 99.2 99.1 98.9 98.7 98.5 98.3 98.1 97.8 97.5 97.2 96.8 96.4 96.0

55 98.7 99.1 99.2 99.2 99.2 99.2 99.1 99.0 98.9 98.7 98.6 98.4 98.2 98.0 97.7 97.4 97.1 96.8 96.4 96.0

60 98.4 98.8 98.9 99.0 99.0 98.9 98.9 98.8 98.7 98.5 98.4 98.2 98.0 97.8 97.6 97.3 97.0 96.7 96.4 96.0

65 98.0 98.4 98.6 98.6 98.7 98.6 98.6 98.5 98.4 98.3 98.2 98.0 97.9 97.7 97.5 97.2 96.9 96.7 96.3 96.0

70 97.5 97.9 98.2 98.3 98.3 98.3 98.3 98.2 98.2 98.1 98.0 97.8 97.7 97.5 97.3 97.1 96.8 96.6 96.3 96.0

75 97.0 97.4 97.7 97.8 97.9 97.9 97.9 97.9 97.8 97.8 97.7 97.6 97.4 97.3 97.1 96.9 96.7 96.5 96.3 96.0

80 96.5 96.9 97.2 97.3 97.4 97.5 97.5 97.5 97.5 97.4 97.4 97.3 97.2 97.1 96.9 96.8 96.6 96.4 96.2 96.0

85 96.1 96.4 96.7 96.8 96.9 97.0 97.0 97.1 97.1 97.0 97.0 96.9 96.9 96.8 96.7 96.6 96.4 96.3 96.1 96.0

90 95.9 96.1 96.2 96.3 96.4 96.5 96.5 96.6 96.6 96.6 96.6 96.6 96.5 96.5 96.4 96.3 96.3 96.2 96.1 96.0

95 95.8 95.8 95.9 96.0 96.0 96.0 96.1 96.1 96.1 96.1 96.1 96.1 96.1 96.1 96.1 96.1 96.1 96.0 96.0 96.0

98 95.9 95.9 95.9 95.9 95.9 95.9 95.9 96.0 96.0 96.0 96.0 96.0 96.0 96.0 96.0 96.0 96.0 96.0 96.0 96.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.9 99.9 99.9 99.9 99.9 99.9 99.8 99.7 99.6 99.5 99.3 99.1 98.9 98.6 98.4 98.1 97.8 97.4 97.0 96.7

35 99.8 99.9 99.9 99.9 99.8 99.8 99.8 99.7 99.5 99.4 99.2 99.0 98.8 98.6 98.3 98.0 97.7 97.4 97.0 96.7

40 99.7 99.8 99.8 99.8 99.8 99.7 99.7 99.6 99.5 99.3 99.2 99.0 98.8 98.5 98.3 98.0 97.7 97.4 97.0 96.7

45 99.5 99.7 99.7 99.7 99.7 99.6 99.6 99.5 99.4 99.2 99.1 98.9 98.7 98.5 98.2 98.0 97.7 97.4 97.0 96.7

50 99.3 99.5 99.5 99.5 99.5 99.5 99.4 99.3 99.2 99.1 98.9 98.8 98.6 98.4 98.2 97.9 97.6 97.3 97.0 96.7

55 98.9 99.2 99.3 99.4 99.4 99.3 99.3 99.2 99.1 99.0 98.8 98.7 98.5 98.3 98.1 97.9 97.6 97.3 97.0 96.7

60 98.6 99.0 99.1 99.2 99.2 99.1 99.1 99.0 98.9 98.8 98.7 98.5 98.4 98.2 98.0 97.8 97.5 97.3 97.0 96.7

65 98.3 98.7 98.8 98.9 98.9 98.9 98.8 98.8 98.7 98.6 98.5 98.4 98.2 98.1 97.9 97.7 97.5 97.2 96.9 96.7

70 97.9 98.3 98.5 98.5 98.6 98.6 98.6 98.5 98.4 98.4 98.3 98.2 98.0 97.9 97.7 97.6 97.4 97.2 96.9 96.7

75 97.5 97.8 98.1 98.2 98.2 98.3 98.2 98.2 98.2 98.1 98.0 97.9 97.8 97.7 97.6 97.4 97.3 97.1 96.9 96.7

80 97.1 97.4 97.6 97.7 97.8 97.9 97.9 97.9 97.9 97.8 97.8 97.7 97.6 97.5 97.4 97.3 97.2 97.0 96.8 96.7

85 96.7 97.0 97.1 97.3 97.4 97.4 97.5 97.5 97.5 97.5 97.5 97.4 97.4 97.3 97.2 97.1 97.0 96.9 96.8 96.7

90 96.5 96.6 96.8 96.9 97.0 97.0 97.1 97.1 97.1 97.1 97.1 97.1 97.1 97.0 97.0 96.9 96.9 96.8 96.7 96.7

95 96.4 96.5 96.5 96.6 96.6 96.7 96.7 96.7 96.7 96.7 96.8 96.8 96.8 96.8 96.7 96.7 96.7 96.7 96.7 96.7

98 96.5 96.5 96.5 96.6 96.6 96.6 96.6 96.6 96.6 96.6 96.6 96.6 96.6 96.6 96.6 96.6 96.7 96.7 96.7 96.7

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.25-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.50-inches of Retention in Zone 2
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.9 99.9 100.0 100.0 99.9 99.9 99.9 99.8 99.7 99.6 99.4 99.3 99.1 98.9 98.6 98.4 98.1 97.8 97.5 97.2

35 99.9 99.9 99.9 99.9 99.9 99.9 99.8 99.7 99.6 99.5 99.4 99.2 99.0 98.8 98.6 98.4 98.1 97.8 97.5 97.2

40 99.8 99.8 99.9 99.8 99.8 99.8 99.7 99.7 99.6 99.5 99.3 99.2 99.0 98.8 98.6 98.3 98.1 97.8 97.5 97.2

45 99.6 99.7 99.8 99.7 99.7 99.7 99.7 99.6 99.5 99.4 99.2 99.1 98.9 98.7 98.5 98.3 98.1 97.8 97.5 97.2

50 99.4 99.6 99.6 99.6 99.6 99.6 99.5 99.5 99.4 99.3 99.1 99.0 98.8 98.7 98.5 98.3 98.0 97.8 97.5 97.2

55 99.1 99.4 99.5 99.5 99.5 99.5 99.4 99.3 99.2 99.1 99.0 98.9 98.7 98.6 98.4 98.2 98.0 97.7 97.5 97.2

60 98.9 99.2 99.3 99.3 99.3 99.3 99.2 99.2 99.1 99.0 98.9 98.8 98.6 98.5 98.3 98.1 97.9 97.7 97.5 97.2

65 98.6 98.9 99.0 99.1 99.1 99.1 99.0 99.0 98.9 98.8 98.7 98.6 98.5 98.4 98.2 98.0 97.9 97.7 97.4 97.2

70 98.3 98.6 98.7 98.8 98.8 98.8 98.8 98.8 98.7 98.6 98.5 98.5 98.3 98.2 98.1 98.0 97.8 97.6 97.4 97.2

75 97.9 98.2 98.4 98.5 98.5 98.5 98.5 98.5 98.4 98.4 98.3 98.3 98.2 98.1 98.0 97.8 97.7 97.6 97.4 97.2

80 97.5 97.8 98.0 98.1 98.2 98.2 98.2 98.2 98.2 98.1 98.1 98.0 98.0 97.9 97.8 97.7 97.6 97.5 97.3 97.2

85 97.2 97.4 97.6 97.7 97.8 97.8 97.9 97.9 97.9 97.9 97.8 97.8 97.8 97.7 97.6 97.6 97.5 97.4 97.3 97.2

90 97.0 97.1 97.2 97.3 97.4 97.4 97.5 97.5 97.5 97.5 97.5 97.5 97.5 97.5 97.5 97.4 97.4 97.3 97.3 97.2

95 96.9 97.0 97.0 97.1 97.1 97.2 97.2 97.2 97.2 97.2 97.2 97.3 97.3 97.3 97.3 97.3 97.2 97.2 97.2 97.2

98 97.0 97.1 97.1 97.1 97.1 97.1 97.1 97.1 97.1 97.2 97.2 97.2 97.2 97.2 97.2 97.2 97.2 97.2 97.2 97.2

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.9 100.0 100.0 100.0 100.0 99.9 99.9 99.8 99.8 99.7 99.6 99.4 99.3 99.1 98.9 98.7 98.4 98.2 97.9 97.6

35 99.9 99.9 99.9 99.9 99.9 99.9 99.9 99.8 99.7 99.6 99.5 99.4 99.2 99.0 98.8 98.6 98.4 98.2 97.9 97.6

40 99.8 99.9 99.9 99.9 99.9 99.8 99.8 99.7 99.7 99.6 99.5 99.3 99.2 99.0 98.8 98.6 98.4 98.2 97.9 97.6

45 99.7 99.8 99.8 99.8 99.8 99.8 99.7 99.7 99.6 99.5 99.4 99.3 99.1 98.9 98.8 98.6 98.4 98.1 97.9 97.6

50 99.6 99.7 99.7 99.7 99.7 99.7 99.6 99.6 99.5 99.4 99.3 99.2 99.0 98.9 98.7 98.5 98.3 98.1 97.9 97.6

55 99.3 99.5 99.6 99.6 99.6 99.6 99.5 99.4 99.4 99.3 99.2 99.1 98.9 98.8 98.6 98.5 98.3 98.1 97.9 97.6

60 99.1 99.3 99.4 99.4 99.4 99.4 99.4 99.3 99.2 99.2 99.1 99.0 98.8 98.7 98.6 98.4 98.2 98.1 97.8 97.6

65 98.8 99.1 99.2 99.3 99.3 99.2 99.2 99.1 99.1 99.0 98.9 98.8 98.7 98.6 98.5 98.3 98.2 98.0 97.8 97.6

70 98.6 98.8 98.9 99.0 99.0 99.0 99.0 99.0 98.9 98.8 98.8 98.7 98.6 98.5 98.4 98.3 98.1 98.0 97.8 97.6

75 98.2 98.5 98.6 98.7 98.7 98.8 98.8 98.7 98.7 98.6 98.6 98.5 98.4 98.4 98.3 98.2 98.0 97.9 97.8 97.6

80 97.9 98.1 98.3 98.4 98.4 98.5 98.5 98.5 98.4 98.4 98.4 98.3 98.3 98.2 98.1 98.1 98.0 97.9 97.7 97.6

85 97.6 97.8 97.9 98.0 98.1 98.1 98.2 98.2 98.2 98.2 98.1 98.1 98.1 98.0 98.0 97.9 97.9 97.8 97.7 97.6

90 97.4 97.5 97.6 97.7 97.8 97.8 97.8 97.9 97.9 97.9 97.9 97.9 97.9 97.9 97.8 97.8 97.8 97.7 97.7 97.6

95 97.4 97.4 97.5 97.5 97.5 97.6 97.6 97.6 97.6 97.6 97.7 97.7 97.7 97.7 97.7 97.7 97.7 97.6 97.6 97.6

98 97.5 97.5 97.5 97.5 97.5 97.5 97.6 97.6 97.6 97.6 97.6 97.6 97.6 97.6 97.6 97.6 97.6 97.6 97.6 97.6

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.75-inches of Retention in Zone 2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 4.00-inches of Retention in Zone 2
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 82.7 81.2 75.5 69.3 63.6 58.6 54.2 50.4 47.0 44.1 41.4 39.1 37.1 35.2 33.5 32.0 30.6 29.3 28.1 27.0

35 77.8 78.2 73.6 68.0 62.7 58.0 53.7 50.0 46.8 43.9 41.3 39.0 37.0 35.1 33.4 31.9 30.5 29.2 28.1 27.0

40 72.7 74.9 71.5 66.6 61.7 57.2 53.2 49.6 46.4 43.6 41.1 38.9 36.8 35.0 33.4 31.9 30.5 29.2 28.1 27.0

45 67.3 71.3 69.0 64.9 60.5 56.3 52.5 49.1 46.0 43.3 40.9 38.7 36.7 34.9 33.3 31.8 30.5 29.2 28.1 27.0

50 61.8 67.4 66.3 62.9 59.1 55.3 51.7 48.5 45.6 42.9 40.6 38.5 36.5 34.8 33.2 31.7 30.4 29.2 28.0 27.0

55 56.5 63.2 63.2 60.7 57.4 54.0 50.8 47.8 45.0 42.5 40.2 38.2 36.3 34.6 33.1 31.7 30.4 29.1 28.0 27.0

60 51.5 58.8 59.9 58.2 55.5 52.6 49.7 46.9 44.3 42.0 39.8 37.9 36.1 34.4 32.9 31.6 30.3 29.1 28.0 27.0

65 46.7 54.3 56.2 55.4 53.4 50.9 48.3 45.9 43.5 41.3 39.3 37.5 35.8 34.2 32.8 31.4 30.2 29.0 28.0 27.0

70 42.4 49.7 52.3 52.2 50.8 48.9 46.8 44.6 42.5 40.5 38.7 37.0 35.4 33.9 32.5 31.3 30.1 29.0 28.0 27.0

75 38.8 45.1 48.0 48.6 47.9 46.5 44.8 43.1 41.3 39.5 37.9 36.3 34.9 33.5 32.2 31.1 29.9 28.9 27.9 27.0

80 35.5 40.7 43.4 44.5 44.4 43.7 42.5 41.1 39.7 38.3 36.9 35.5 34.2 33.0 31.9 30.8 29.7 28.8 27.9 27.0

85 32.7 36.5 38.7 39.9 40.3 40.1 39.5 38.6 37.6 36.5 35.4 34.4 33.3 32.3 31.3 30.4 29.5 28.6 27.8 27.0

90 30.6 32.8 34.3 35.2 35.7 35.8 35.6 35.2 34.7 34.1 33.4 32.7 31.9 31.2 30.4 29.7 29.0 28.3 27.6 27.0

95 29.1 29.8 30.3 30.7 30.9 31.0 31.0 31.0 30.8 30.6 30.3 30.0 29.7 29.4 29.0 28.6 28.2 27.8 27.4 27.0

98 28.5 28.5 28.6 28.6 28.6 28.6 28.6 28.5 28.5 28.4 28.3 28.2 28.0 27.9 27.8 27.6 27.5 27.3 27.2 27.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 87.6 89.1 87.6 84.8 81.5 77.8 74.3 70.9 67.8 64.9 62.1 59.6 57.2 55.0 52.9 51.0 49.2 47.6 46.0 44.5

35 83.5 86.5 85.6 83.4 80.4 77.0 73.6 70.4 67.4 64.5 61.9 59.4 57.0 54.9 52.8 51.0 49.2 47.5 46.0 44.5

40 79.3 83.5 83.4 81.7 79.1 76.0 72.9 69.8 66.9 64.2 61.6 59.1 56.9 54.7 52.7 50.9 49.1 47.5 46.0 44.5

45 74.9 80.3 80.9 79.7 77.6 74.9 72.0 69.1 66.4 63.7 61.2 58.9 56.6 54.6 52.6 50.8 49.1 47.5 45.9 44.5

50 70.5 76.7 78.1 77.6 75.9 73.5 70.9 68.3 65.7 63.2 60.8 58.5 56.4 54.4 52.5 50.7 49.0 47.4 45.9 44.5

55 66.3 72.9 75.0 75.1 73.9 71.9 69.6 67.3 64.9 62.6 60.3 58.1 56.1 54.1 52.3 50.6 48.9 47.4 45.9 44.5

60 62.1 68.9 71.7 72.4 71.6 70.1 68.2 66.1 64.0 61.8 59.7 57.7 55.7 53.8 52.1 50.4 48.8 47.3 45.9 44.5

65 58.0 64.9 68.1 69.3 69.1 68.0 66.5 64.7 62.8 60.9 59.0 57.1 55.2 53.5 51.8 50.2 48.7 47.2 45.8 44.5

70 54.4 60.9 64.2 65.8 66.2 65.6 64.5 63.0 61.5 59.8 58.1 56.3 54.6 53.0 51.4 49.9 48.5 47.1 45.8 44.5

75 51.1 57.0 60.4 62.2 62.9 62.7 62.1 61.0 59.8 58.4 56.9 55.4 53.9 52.4 51.0 49.6 48.3 47.0 45.7 44.5

80 48.5 53.5 56.5 58.3 59.1 59.3 59.1 58.5 57.6 56.6 55.4 54.2 52.9 51.6 50.4 49.2 47.9 46.8 45.6 44.5

85 46.7 50.3 52.7 54.2 55.1 55.5 55.6 55.3 54.9 54.2 53.4 52.6 51.6 50.6 49.6 48.5 47.5 46.5 45.5 44.5

90 45.4 47.6 49.1 50.2 51.0 51.4 51.7 51.7 51.5 51.2 50.8 50.3 49.7 49.0 48.3 47.6 46.8 46.1 45.3 44.5

95 44.8 45.6 46.2 46.7 47.1 47.3 47.5 47.6 47.6 47.5 47.4 47.2 47.0 46.7 46.4 46.1 45.7 45.3 44.9 44.5

98 45.2 45.3 45.4 45.4 45.5 45.5 45.5 45.6 45.5 45.5 45.5 45.4 45.3 45.3 45.2 45.0 44.9 44.8 44.7 44.5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.25-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 3
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 89.7 92.3 91.6 90.3 88.4 86.2 83.8 81.3 78.7 76.2 73.8 71.5 69.3 67.3 65.3 63.4 61.6 59.9 58.3 56.7

35 86.6 89.8 89.8 88.9 87.2 85.3 83.1 80.7 78.2 75.8 73.5 71.3 69.2 67.1 65.2 63.3 61.6 59.9 58.3 56.7

40 82.9 87.1 87.9 87.3 85.9 84.2 82.2 80.0 77.7 75.4 73.2 71.0 69.0 67.0 65.1 63.2 61.5 59.8 58.2 56.7

45 79.3 84.4 85.7 85.5 84.5 83.0 81.2 79.2 77.1 74.9 72.8 70.7 68.7 66.8 64.9 63.1 61.4 59.8 58.2 56.7

50 75.8 81.4 83.2 83.5 82.8 81.6 80.1 78.3 76.3 74.3 72.3 70.3 68.4 66.5 64.7 63.0 61.3 59.7 58.2 56.7

55 72.2 78.3 80.5 81.2 80.9 80.1 78.8 77.2 75.4 73.5 71.7 69.8 68.0 66.2 64.5 62.8 61.2 59.7 58.2 56.7

60 69.0 75.0 77.6 78.6 78.7 78.3 77.3 75.9 74.3 72.7 71.0 69.2 67.5 65.9 64.2 62.6 61.1 59.6 58.1 56.7

65 65.7 71.6 74.4 75.8 76.3 76.2 75.5 74.4 73.1 71.7 70.1 68.6 67.0 65.4 63.9 62.4 60.9 59.5 58.1 56.7

70 62.5 68.2 71.2 72.8 73.6 73.8 73.4 72.7 71.6 70.4 69.1 67.7 66.3 64.9 63.5 62.1 60.7 59.3 58.0 56.7

75 59.8 64.9 67.9 69.7 70.6 71.1 71.0 70.6 69.8 68.9 67.8 66.7 65.5 64.2 62.9 61.7 60.4 59.2 57.9 56.7

80 57.5 61.8 64.6 66.4 67.5 68.1 68.2 68.0 67.6 67.0 66.2 65.3 64.3 63.3 62.2 61.2 60.0 58.9 57.8 56.7

85 56.0 59.3 61.6 63.1 64.2 64.8 65.1 65.1 64.9 64.6 64.1 63.5 62.8 62.1 61.3 60.4 59.5 58.6 57.7 56.7

90 55.4 57.4 58.9 60.0 60.8 61.3 61.7 61.9 61.9 61.8 61.6 61.3 60.9 60.5 59.9 59.4 58.8 58.1 57.4 56.7

95 55.5 56.2 56.8 57.3 57.7 58.1 58.3 58.5 58.6 58.7 58.7 58.6 58.5 58.4 58.2 57.9 57.7 57.4 57.1 56.7

98 56.5 56.6 56.8 56.9 57.0 57.1 57.1 57.2 57.2 57.2 57.2 57.2 57.2 57.2 57.1 57.1 57.0 56.9 56.8 56.7

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 91.1 93.7 94.0 92.9 91.7 90.3 88.6 86.8 85.0 83.1 81.1 79.1 77.2 75.3 73.5 71.8 70.1 68.5 67.0 65.5

35 88.6 91.8 92.2 91.6 90.7 89.5 87.9 86.3 84.5 82.7 80.8 78.9 77.0 75.2 73.4 71.7 70.1 68.5 67.0 65.5

40 85.9 89.4 90.4 90.3 89.6 88.5 87.1 85.6 83.9 82.2 80.4 78.6 76.8 75.0 73.3 71.6 70.0 68.5 66.9 65.5

45 82.5 86.9 88.5 88.7 88.2 87.3 86.1 84.8 83.3 81.7 80.0 78.2 76.5 74.8 73.1 71.5 69.9 68.4 66.9 65.5

50 79.4 84.4 86.4 86.9 86.7 86.0 85.0 83.9 82.5 81.0 79.4 77.8 76.1 74.5 72.9 71.3 69.8 68.3 66.9 65.5

55 76.6 81.9 84.0 84.9 85.0 84.5 83.7 82.8 81.6 80.3 78.8 77.3 75.7 74.2 72.7 71.2 69.7 68.3 66.9 65.5

60 73.8 79.1 81.6 82.7 83.0 82.8 82.3 81.6 80.6 79.4 78.1 76.7 75.2 73.8 72.4 70.9 69.5 68.2 66.8 65.5

65 71.1 76.4 78.9 80.3 80.8 80.9 80.6 80.1 79.4 78.4 77.2 75.9 74.6 73.3 72.0 70.7 69.4 68.0 66.8 65.5

70 68.6 73.5 76.2 77.6 78.4 78.8 78.7 78.5 77.9 77.1 76.2 75.1 73.9 72.8 71.5 70.3 69.1 67.9 66.7 65.5

75 66.3 70.6 73.3 74.9 75.9 76.4 76.6 76.5 76.1 75.6 74.9 74.0 73.0 72.0 71.0 69.9 68.8 67.7 66.6 65.5

80 64.3 68.0 70.5 72.1 73.2 73.9 74.2 74.3 74.1 73.8 73.3 72.6 71.9 71.1 70.2 69.3 68.4 67.5 66.5 65.5

85 63.1 65.9 67.9 69.4 70.4 71.2 71.6 71.8 71.8 71.6 71.3 70.9 70.5 69.9 69.3 68.6 67.9 67.1 66.3 65.5

90 62.7 64.5 65.9 67.0 67.8 68.4 68.8 69.1 69.2 69.2 69.1 68.9 68.7 68.4 68.0 67.6 67.1 66.6 66.1 65.5

95 63.3 64.0 64.6 65.1 65.5 65.8 66.1 66.3 66.4 66.5 66.6 66.6 66.6 66.5 66.4 66.3 66.1 66.0 65.7 65.5

98 64.7 64.8 65.0 65.1 65.2 65.3 65.4 65.5 65.5 65.6 65.6 65.6 65.6 65.7 65.7 65.6 65.6 65.6 65.5 65.5

Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 92.1 94.5 95.2 94.8 93.7 92.7 91.5 90.2 88.7 87.3 85.7 84.2 82.6 81.0 79.4 77.8 76.3 74.8 73.4 72.0

35 90.0 92.9 93.9 93.5 92.7 91.9 90.8 89.6 88.2 86.9 85.4 83.9 82.4 80.8 79.3 77.7 76.2 74.8 73.4 72.0

40 87.8 91.2 92.2 92.2 91.7 91.0 90.1 89.0 87.7 86.4 85.0 83.6 82.1 80.6 79.1 77.6 76.2 74.7 73.3 72.0

45 85.4 89.0 90.3 90.7 90.5 90.0 89.2 88.2 87.0 85.9 84.6 83.2 81.8 80.4 78.9 77.5 76.1 74.7 73.3 72.0

50 82.3 86.7 88.4 89.2 89.2 88.9 88.2 87.3 86.3 85.2 84.1 82.8 81.5 80.1 78.7 77.3 75.9 74.6 73.3 72.0

55 79.7 84.4 86.6 87.4 87.6 87.5 87.0 86.3 85.4 84.5 83.5 82.3 81.1 79.8 78.4 77.1 75.8 74.5 73.2 72.0

60 77.4 82.3 84.4 85.5 85.9 86.0 85.7 85.1 84.4 83.7 82.8 81.7 80.6 79.4 78.1 76.9 75.6 74.4 73.2 72.0

65 75.3 79.8 82.2 83.4 84.1 84.2 84.1 83.8 83.3 82.7 81.9 81.0 80.0 78.9 77.8 76.6 75.4 74.3 73.1 72.0

70 73.1 77.5 79.9 81.3 82.0 82.3 82.4 82.3 82.0 81.5 80.9 80.1 79.3 78.3 77.3 76.3 75.2 74.1 73.1 72.0

75 71.2 75.1 77.4 78.9 79.7 80.3 80.5 80.6 80.4 80.1 79.7 79.1 78.4 77.6 76.7 75.8 74.9 73.9 73.0 72.0

80 69.6 72.8 75.0 76.4 77.4 78.1 78.5 78.7 78.7 78.5 78.2 77.8 77.3 76.7 76.0 75.2 74.5 73.7 72.8 72.0

85 68.5 71.0 72.9 74.2 75.1 75.8 76.3 76.6 76.7 76.7 76.6 76.3 76.0 75.5 75.1 74.5 73.9 73.3 72.7 72.0

90 68.4 69.9 71.2 72.2 73.0 73.6 74.0 74.3 74.5 74.6 74.6 74.6 74.4 74.2 73.9 73.6 73.3 72.9 72.4 72.0

95 69.3 70.0 70.5 71.0 71.4 71.7 72.0 72.2 72.4 72.5 72.6 72.6 72.6 72.6 72.6 72.5 72.4 72.3 72.2 72.0

98 70.9 71.0 71.2 71.3 71.4 71.5 71.6 71.7 71.8 71.8 71.9 71.9 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 92.8 95.2 95.9 95.9 95.3 94.3 93.3 92.3 91.2 90.1 88.8 87.6 86.3 84.9 83.6 82.3 80.9 79.6 78.2 77.0

35 91.0 93.8 94.7 94.9 94.3 93.5 92.7 91.8 90.8 89.7 88.5 87.3 86.0 84.8 83.5 82.2 80.8 79.5 78.2 77.0

40 89.1 92.3 93.5 93.6 93.3 92.7 92.0 91.2 90.3 89.2 88.1 87.0 85.8 84.6 83.3 82.0 80.8 79.5 78.2 77.0

45 87.2 90.7 91.9 92.2 92.1 91.8 91.2 90.5 89.7 88.7 87.7 86.6 85.5 84.3 83.1 81.9 80.7 79.4 78.2 77.0

50 85.1 88.6 90.1 90.7 90.9 90.7 90.4 89.7 89.0 88.1 87.1 86.2 85.1 84.0 82.9 81.7 80.5 79.3 78.1 77.0

55 82.4 86.5 88.3 89.2 89.6 89.6 89.3 88.8 88.2 87.4 86.6 85.7 84.7 83.7 82.7 81.5 80.4 79.2 78.1 77.0

60 80.2 84.5 86.6 87.7 88.1 88.2 88.1 87.7 87.2 86.6 85.9 85.1 84.3 83.3 82.4 81.3 80.2 79.1 78.0 77.0

65 78.4 82.6 84.7 85.9 86.5 86.7 86.7 86.5 86.1 85.6 85.1 84.4 83.7 82.9 82.0 81.0 80.0 79.0 78.0 77.0

70 76.7 80.6 82.7 84.0 84.7 85.1 85.2 85.1 84.9 84.6 84.1 83.6 83.0 82.3 81.5 80.7 79.8 78.8 77.9 77.0

75 75.1 78.5 80.7 82.0 82.8 83.3 83.5 83.6 83.5 83.3 83.1 82.7 82.2 81.6 81.0 80.3 79.5 78.6 77.8 77.0

80 73.8 76.7 78.6 79.9 80.7 81.3 81.7 81.9 82.0 82.0 81.8 81.6 81.2 80.8 80.3 79.7 79.1 78.4 77.7 77.0

85 72.9 75.1 76.7 77.9 78.8 79.4 79.9 80.2 80.3 80.4 80.4 80.3 80.1 79.8 79.5 79.0 78.6 78.1 77.5 77.0

90 72.9 74.3 75.4 76.3 77.0 77.6 78.0 78.4 78.6 78.7 78.8 78.8 78.8 78.6 78.5 78.2 78.0 77.7 77.3 77.0

95 74.0 74.6 75.1 75.5 75.9 76.2 76.5 76.8 77.0 77.1 77.2 77.3 77.3 77.3 77.3 77.3 77.2 77.2 77.1 77.0

98 75.8 75.9 76.0 76.2 76.3 76.4 76.4 76.5 76.6 76.7 76.7 76.8 76.8 76.9 76.9 76.9 76.9 76.9 77.0 77.0

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.50-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.25-inches of Retention for Zone 3
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 93.3 95.6 96.4 96.6 96.3 95.6 94.7 93.8 92.9 92.0 91.0 89.9 88.8 87.8 86.6 85.5 84.3 83.2 82.0 80.8

35 91.8 94.4 95.4 95.7 95.5 94.8 94.1 93.3 92.5 91.6 90.7 89.7 88.6 87.6 86.5 85.4 84.3 83.1 82.0 80.8

40 90.2 93.1 94.3 94.7 94.5 94.0 93.4 92.7 92.0 91.2 90.4 89.4 88.4 87.4 86.3 85.3 84.2 83.1 82.0 80.8

45 88.6 91.8 93.1 93.5 93.4 93.1 92.6 92.1 91.5 90.8 89.9 89.0 88.1 87.1 86.2 85.1 84.1 83.0 81.9 80.8

50 86.9 90.3 91.6 92.1 92.2 92.1 91.8 91.4 90.9 90.2 89.5 88.6 87.7 86.9 85.9 85.0 84.0 82.9 81.9 80.8

55 84.9 88.3 89.9 90.6 91.0 91.1 90.9 90.6 90.2 89.6 88.9 88.1 87.4 86.6 85.7 84.8 83.8 82.9 81.9 80.8

60 82.7 86.4 88.2 89.2 89.7 89.9 89.9 89.7 89.3 88.8 88.2 87.6 86.9 86.2 85.4 84.6 83.7 82.8 81.8 80.8

65 80.9 84.6 86.7 87.7 88.4 88.6 88.7 88.6 88.3 87.9 87.5 86.9 86.4 85.7 85.0 84.3 83.5 82.6 81.8 80.8

70 79.6 83.0 85.0 86.2 86.8 87.2 87.4 87.4 87.2 87.0 86.6 86.2 85.7 85.2 84.6 84.0 83.2 82.5 81.7 80.8

75 78.3 81.4 83.2 84.4 85.2 85.7 85.9 86.0 86.0 85.8 85.6 85.3 85.0 84.6 84.1 83.5 82.9 82.3 81.6 80.8

80 77.2 79.8 81.5 82.7 83.5 84.0 84.3 84.5 84.6 84.6 84.5 84.4 84.1 83.8 83.5 83.1 82.6 82.0 81.5 80.8

85 76.6 78.5 79.9 80.9 81.7 82.2 82.7 83.0 83.2 83.3 83.3 83.3 83.2 83.0 82.8 82.5 82.1 81.7 81.3 80.8

90 76.4 77.7 78.7 79.5 80.2 80.7 81.1 81.4 81.7 81.9 82.0 82.1 82.1 82.0 81.9 81.8 81.6 81.4 81.1 80.8

95 77.6 78.1 78.6 79.0 79.4 79.7 80.0 80.3 80.5 80.6 80.8 80.9 80.9 81.0 81.0 81.0 81.0 81.0 80.9 80.8

98 79.5 79.7 79.8 79.9 80.0 80.1 80.2 80.3 80.4 80.5 80.5 80.6 80.6 80.7 80.7 80.8 80.8 80.8 80.8 80.8

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 93.8 95.9 96.7 97.0 97.0 96.6 95.8 95.0 94.2 93.4 92.6 91.7 90.8 89.8 88.9 87.9 86.9 85.9 84.9 83.9

35 92.4 94.9 95.8 96.2 96.3 95.9 95.2 94.5 93.8 93.1 92.3 91.5 90.6 89.7 88.7 87.8 86.8 85.9 84.9 83.9

40 91.0 93.8 94.9 95.4 95.4 95.1 94.5 93.9 93.3 92.7 92.0 91.2 90.4 89.5 88.6 87.7 86.8 85.8 84.8 83.9

45 89.7 92.7 93.9 94.5 94.4 94.2 93.8 93.3 92.8 92.3 91.6 90.9 90.1 89.2 88.4 87.6 86.7 85.8 84.8 83.9

50 88.2 91.4 92.8 93.3 93.3 93.3 93.0 92.7 92.3 91.8 91.2 90.5 89.8 89.0 88.2 87.4 86.6 85.7 84.8 83.9

55 86.9 90.0 91.3 91.9 92.2 92.2 92.2 91.9 91.6 91.2 90.7 90.1 89.4 88.7 87.9 87.2 86.4 85.6 84.7 83.9

60 85.0 88.2 89.7 90.6 91.0 91.2 91.2 91.1 90.9 90.5 90.1 89.6 88.9 88.3 87.7 87.0 86.3 85.5 84.7 83.9

65 83.2 86.4 88.2 89.2 89.8 90.1 90.2 90.2 90.0 89.7 89.4 88.9 88.4 87.9 87.3 86.7 86.1 85.4 84.6 83.9

70 81.7 85.0 86.7 87.8 88.5 88.9 89.1 89.1 89.1 88.8 88.6 88.2 87.8 87.4 86.9 86.4 85.8 85.2 84.6 83.9

75 80.8 83.5 85.3 86.4 87.1 87.6 87.9 88.0 87.9 87.9 87.7 87.4 87.1 86.8 86.4 86.0 85.6 85.0 84.5 83.9

80 80.0 82.3 83.8 84.9 85.6 86.2 86.5 86.6 86.7 86.8 86.7 86.6 86.4 86.2 85.9 85.6 85.2 84.8 84.4 83.9

85 79.5 81.2 82.5 83.4 84.1 84.6 85.0 85.3 85.5 85.6 85.6 85.6 85.5 85.4 85.3 85.1 84.9 84.6 84.2 83.9

90 79.5 80.6 81.5 82.2 82.8 83.3 83.6 83.9 84.2 84.3 84.5 84.6 84.6 84.6 84.6 84.5 84.4 84.3 84.1 83.9

95 80.6 81.1 81.5 81.9 82.2 82.5 82.8 83.0 83.2 83.4 83.5 83.6 83.7 83.8 83.9 83.9 83.9 83.9 83.9 83.9

98 82.4 82.6 82.7 82.8 82.9 83.1 83.2 83.2 83.3 83.4 83.5 83.5 83.6 83.7 83.7 83.7 83.8 83.8 83.9 83.9

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.75-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.00-inches of Retention for Zone 3
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 94.1 96.2 97.0 97.3 97.4 97.2 96.7 96.0 95.2 94.5 93.8 93.0 92.3 91.5 90.6 89.8 88.9 88.0 87.1 86.2

35 92.9 95.3 96.2 96.6 96.8 96.6 96.1 95.5 94.8 94.2 93.5 92.8 92.1 91.3 90.5 89.7 88.8 88.0 87.1 86.2

40 91.7 94.3 95.4 95.9 96.1 95.9 95.5 95.0 94.4 93.8 93.2 92.5 91.9 91.1 90.4 89.5 88.7 87.9 87.1 86.2

45 90.6 93.3 94.6 95.1 95.3 95.1 94.8 94.4 93.9 93.4 92.8 92.2 91.6 90.9 90.2 89.4 88.6 87.9 87.1 86.2

50 89.4 92.3 93.6 94.2 94.3 94.2 94.0 93.7 93.3 92.9 92.5 91.9 91.3 90.7 90.0 89.3 88.5 87.8 87.0 86.2

55 88.2 91.2 92.5 93.1 93.3 93.3 93.2 93.0 92.7 92.4 92.0 91.5 91.0 90.4 89.7 89.1 88.4 87.7 87.0 86.2

60 87.0 89.7 91.1 91.8 92.1 92.3 92.3 92.2 92.0 91.8 91.5 91.0 90.6 90.1 89.5 88.9 88.2 87.6 86.9 86.2

65 85.3 88.1 89.6 90.5 91.0 91.3 91.4 91.4 91.3 91.1 90.9 90.5 90.1 89.7 89.1 88.6 88.1 87.5 86.9 86.2

70 83.8 86.6 88.2 89.2 89.8 90.2 90.4 90.5 90.5 90.4 90.2 89.9 89.6 89.2 88.8 88.3 87.9 87.4 86.8 86.2

75 82.9 85.3 86.9 87.9 88.6 89.1 89.3 89.5 89.6 89.5 89.4 89.2 89.0 88.7 88.3 88.0 87.6 87.2 86.7 86.2

80 82.2 84.3 85.7 86.7 87.4 87.9 88.2 88.4 88.5 88.5 88.5 88.4 88.3 88.1 87.8 87.6 87.3 87.0 86.6 86.2

85 81.9 83.4 84.6 85.5 86.1 86.6 86.9 87.2 87.4 87.5 87.5 87.5 87.5 87.4 87.3 87.1 87.0 86.8 86.5 86.2

90 82.1 83.0 83.8 84.5 85.0 85.4 85.7 86.0 86.2 86.4 86.5 86.6 86.7 86.7 86.7 86.7 86.6 86.5 86.4 86.2

95 83.0 83.5 83.9 84.2 84.5 84.8 85.0 85.2 85.4 85.6 85.7 85.8 85.9 86.0 86.1 86.2 86.2 86.2 86.3 86.2

98 84.8 84.9 85.0 85.1 85.3 85.4 85.5 85.6 85.6 85.7 85.8 85.9 85.9 86.0 86.0 86.1 86.1 86.2 86.2 86.2

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 94.3 96.4 97.2 97.5 97.6 97.6 97.3 96.8 96.1 95.4 94.7 94.1 93.4 92.7 92.0 91.3 90.5 89.7 88.9 88.1

35 93.3 95.6 96.5 96.9 97.1 97.1 96.8 96.3 95.7 95.1 94.5 93.9 93.2 92.6 91.9 91.2 90.4 89.7 88.9 88.1

40 92.3 94.7 95.8 96.3 96.5 96.5 96.3 95.8 95.3 94.7 94.2 93.6 93.0 92.4 91.7 91.1 90.3 89.6 88.9 88.1

45 91.2 93.9 95.0 95.6 95.9 95.9 95.6 95.2 94.8 94.3 93.8 93.3 92.8 92.2 91.6 90.9 90.2 89.5 88.8 88.1

50 90.3 93.0 94.2 94.9 95.1 95.1 94.9 94.6 94.3 93.8 93.4 93.0 92.5 92.0 91.4 90.8 90.1 89.5 88.8 88.1

55 89.3 92.1 93.4 94.0 94.2 94.2 94.1 93.9 93.7 93.3 93.0 92.6 92.2 91.7 91.2 90.6 90.0 89.4 88.8 88.1

60 88.4 91.0 92.2 92.9 93.1 93.3 93.3 93.2 93.0 92.8 92.5 92.2 91.8 91.4 90.9 90.4 89.9 89.3 88.7 88.1

65 87.2 89.6 90.9 91.6 92.1 92.3 92.4 92.4 92.3 92.2 92.0 91.7 91.4 91.0 90.7 90.2 89.7 89.2 88.7 88.1

70 85.8 88.2 89.5 90.5 91.0 91.3 91.5 91.6 91.6 91.5 91.4 91.2 90.9 90.6 90.3 89.9 89.5 89.0 88.6 88.1

75 84.7 87.0 88.3 89.2 89.9 90.3 90.6 90.7 90.8 90.8 90.7 90.6 90.4 90.2 89.9 89.6 89.2 88.9 88.5 88.1

80 84.0 85.9 87.2 88.1 88.8 89.2 89.6 89.8 89.9 90.0 90.0 89.9 89.8 89.7 89.5 89.2 89.0 88.7 88.4 88.1

85 83.8 85.3 86.3 87.1 87.7 88.2 88.5 88.8 89.0 89.1 89.1 89.1 89.1 89.1 89.0 88.8 88.7 88.5 88.3 88.1

90 84.1 85.0 85.8 86.4 86.8 87.2 87.5 87.8 88.0 88.1 88.3 88.3 88.4 88.4 88.4 88.4 88.3 88.3 88.2 88.1

95 85.1 85.5 85.9 86.2 86.5 86.7 86.9 87.1 87.3 87.4 87.5 87.7 87.8 87.8 87.9 88.0 88.0 88.1 88.1 88.1

98 86.7 86.8 86.9 87.0 87.1 87.2 87.3 87.4 87.5 87.6 87.6 87.7 87.8 87.8 87.9 87.9 88.0 88.0 88.1 88.1

Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.25-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 94.6 96.5 97.3 97.7 97.8 97.9 97.7 97.4 96.8 96.2 95.6 94.9 94.4 93.7 93.1 92.4 91.8 91.1 90.4 89.6

35 93.6 95.9 96.7 97.1 97.3 97.4 97.3 97.0 96.5 95.9 95.3 94.7 94.2 93.6 93.0 92.4 91.7 91.0 90.3 89.6

40 92.8 95.1 96.1 96.6 96.8 97.0 96.8 96.5 96.0 95.5 95.0 94.5 94.0 93.4 92.8 92.2 91.6 91.0 90.3 89.6

45 91.8 94.3 95.4 96.0 96.3 96.4 96.3 96.0 95.6 95.1 94.7 94.2 93.7 93.2 92.7 92.1 91.6 90.9 90.3 89.6

50 91.0 93.6 94.8 95.4 95.7 95.8 95.6 95.4 95.0 94.7 94.3 93.9 93.5 93.0 92.5 92.0 91.5 90.9 90.3 89.6

55 90.2 92.8 94.0 94.7 95.0 95.0 94.9 94.7 94.5 94.2 93.9 93.5 93.2 92.8 92.3 91.8 91.3 90.8 90.2 89.6

60 89.4 92.0 93.2 93.8 94.0 94.1 94.2 94.0 93.9 93.7 93.4 93.1 92.9 92.5 92.1 91.7 91.2 90.7 90.2 89.6

65 88.7 90.9 92.0 92.7 93.1 93.3 93.3 93.3 93.2 93.1 92.9 92.7 92.5 92.2 91.8 91.4 91.1 90.6 90.1 89.6

70 87.5 89.6 90.8 91.6 92.1 92.3 92.5 92.5 92.5 92.5 92.4 92.2 92.0 91.8 91.5 91.2 90.9 90.5 90.1 89.6

75 86.4 88.4 89.7 90.4 91.0 91.3 91.6 91.7 91.8 91.8 91.8 91.7 91.6 91.4 91.2 90.9 90.7 90.3 90.0 89.6

80 85.8 87.4 88.6 89.4 90.0 90.4 90.7 90.9 91.0 91.1 91.1 91.1 91.0 90.9 90.8 90.6 90.4 90.2 89.9 89.6

85 85.5 86.8 87.7 88.5 89.0 89.4 89.8 90.0 90.2 90.3 90.4 90.4 90.4 90.4 90.4 90.3 90.1 90.0 89.8 89.6

90 85.8 86.6 87.3 87.9 88.3 88.7 89.0 89.2 89.4 89.6 89.7 89.8 89.8 89.9 89.9 89.9 89.8 89.8 89.7 89.6

95 86.9 87.2 87.6 87.8 88.1 88.3 88.5 88.7 88.9 89.0 89.1 89.2 89.3 89.4 89.5 89.5 89.5 89.6 89.6 89.6

98 88.4 88.5 88.6 88.7 88.8 88.9 88.9 89.0 89.1 89.1 89.2 89.3 89.3 89.4 89.4 89.5 89.5 89.6 89.6 89.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 94.9 96.7 97.4 97.8 98.0 98.0 98.0 97.8 97.4 96.9 96.3 95.7 95.1 94.6 94.0 93.4 92.8 92.2 91.6 90.9

35 93.9 96.0 96.9 97.3 97.5 97.6 97.7 97.4 97.1 96.6 96.0 95.5 94.9 94.4 93.9 93.3 92.7 92.2 91.6 90.9

40 93.1 95.4 96.3 96.8 97.1 97.2 97.2 97.1 96.7 96.2 95.7 95.2 94.7 94.3 93.7 93.2 92.7 92.1 91.5 90.9

45 92.4 94.7 95.7 96.3 96.6 96.8 96.8 96.6 96.2 95.8 95.4 95.0 94.5 94.1 93.6 93.1 92.6 92.1 91.5 90.9

50 91.6 94.0 95.2 95.8 96.1 96.3 96.2 96.0 95.8 95.4 95.1 94.7 94.3 93.9 93.4 93.0 92.5 92.0 91.5 90.9

55 91.0 93.4 94.6 95.2 95.6 95.7 95.6 95.4 95.2 94.9 94.6 94.3 94.0 93.6 93.3 92.8 92.4 91.9 91.4 90.9

60 90.4 92.7 93.9 94.6 94.8 94.9 94.9 94.8 94.6 94.4 94.2 93.9 93.7 93.4 93.0 92.7 92.3 91.9 91.4 90.9

65 89.8 92.0 93.0 93.6 93.9 94.1 94.2 94.1 94.0 93.9 93.7 93.5 93.3 93.1 92.8 92.5 92.1 91.8 91.4 90.9

70 89.0 90.9 91.9 92.6 93.0 93.2 93.3 93.4 93.4 93.3 93.2 93.1 92.9 92.8 92.5 92.2 92.0 91.6 91.3 90.9

75 88.0 89.7 90.8 91.6 92.0 92.3 92.5 92.6 92.7 92.7 92.7 92.6 92.5 92.4 92.2 92.0 91.8 91.5 91.2 90.9

80 87.3 88.8 89.8 90.5 91.0 91.4 91.7 91.8 92.0 92.0 92.1 92.1 92.1 92.0 91.8 91.7 91.6 91.4 91.2 90.9

85 87.0 88.1 89.0 89.7 90.1 90.5 90.8 91.1 91.3 91.4 91.5 91.5 91.5 91.5 91.5 91.4 91.3 91.2 91.1 90.9

90 87.2 88.0 88.6 89.1 89.5 89.9 90.2 90.4 90.6 90.7 90.8 90.9 91.0 91.0 91.1 91.1 91.1 91.0 91.0 90.9

95 88.3 88.7 88.9 89.2 89.4 89.6 89.8 90.0 90.1 90.2 90.4 90.5 90.6 90.7 90.7 90.8 90.8 90.9 90.9 90.9

98 89.7 89.8 89.9 90.0 90.1 90.2 90.3 90.3 90.4 90.5 90.5 90.6 90.6 90.7 90.7 90.8 90.8 90.9 90.9 90.9

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.00-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.75-inches of Retention for Zone 3
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 95.2 96.9 97.5 97.9 98.1 98.2 98.2 98.1 97.8 97.5 96.9 96.4 95.8 95.3 94.7 94.2 93.7 93.1 92.6 92.0

35 94.1 96.2 97.0 97.5 97.7 97.8 97.9 97.8 97.5 97.2 96.7 96.2 95.6 95.1 94.6 94.1 93.6 93.1 92.5 92.0

40 93.4 95.6 96.6 97.0 97.3 97.5 97.5 97.4 97.2 96.8 96.4 95.9 95.4 95.0 94.5 94.0 93.5 93.0 92.5 92.0

45 92.8 95.0 96.0 96.6 96.9 97.1 97.1 97.1 96.8 96.5 96.1 95.7 95.2 94.8 94.4 93.9 93.5 93.0 92.5 92.0

50 92.1 94.4 95.5 96.1 96.5 96.7 96.7 96.6 96.3 96.1 95.7 95.4 95.0 94.6 94.2 93.8 93.4 92.9 92.5 92.0

55 91.5 93.8 95.0 95.6 96.0 96.2 96.2 96.0 95.9 95.6 95.3 95.0 94.7 94.4 94.0 93.7 93.3 92.9 92.4 92.0

60 91.1 93.3 94.4 95.1 95.5 95.6 95.5 95.5 95.3 95.1 94.9 94.7 94.4 94.1 93.8 93.5 93.2 92.8 92.4 92.0

65 90.7 92.7 93.8 94.4 94.7 94.8 94.9 94.9 94.8 94.6 94.5 94.3 94.0 93.8 93.6 93.3 93.0 92.7 92.4 92.0

70 90.3 92.0 92.9 93.4 93.8 94.0 94.2 94.2 94.1 94.1 94.0 93.8 93.7 93.5 93.4 93.1 92.9 92.6 92.3 92.0

75 89.4 90.9 91.8 92.5 93.0 93.2 93.4 93.5 93.5 93.5 93.4 93.4 93.3 93.2 93.1 92.9 92.7 92.5 92.2 92.0

80 88.7 90.1 91.0 91.6 92.0 92.3 92.6 92.7 92.8 92.9 92.9 92.9 92.9 92.9 92.8 92.6 92.5 92.3 92.2 92.0

85 88.4 89.4 90.2 90.7 91.2 91.5 91.8 92.0 92.1 92.3 92.4 92.4 92.5 92.5 92.4 92.4 92.3 92.2 92.1 92.0

90 88.5 89.2 89.7 90.2 90.6 90.9 91.2 91.4 91.6 91.7 91.9 91.9 92.0 92.0 92.0 92.1 92.1 92.1 92.0 92.0

95 89.6 89.9 90.1 90.4 90.6 90.8 90.9 91.1 91.2 91.3 91.4 91.5 91.6 91.7 91.8 91.8 91.9 91.9 92.0 92.0

98 90.8 90.9 91.0 91.1 91.2 91.2 91.3 91.4 91.4 91.5 91.6 91.6 91.7 91.7 91.8 91.8 91.9 91.9 92.0 92.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 95.5 97.0 97.6 98.0 98.2 98.3 98.3 98.3 98.1 97.9 97.5 96.9 96.4 95.9 95.4 94.9 94.4 93.9 93.4 92.9

35 94.4 96.3 97.2 97.6 97.9 98.0 98.0 98.0 97.9 97.6 97.2 96.7 96.3 95.8 95.3 94.8 94.4 93.9 93.4 92.9

40 93.6 95.8 96.8 97.2 97.5 97.6 97.7 97.7 97.6 97.3 96.9 96.5 96.1 95.6 95.2 94.7 94.3 93.8 93.4 92.9

45 93.2 95.3 96.3 96.8 97.1 97.3 97.4 97.4 97.3 97.0 96.6 96.3 95.9 95.4 95.0 94.6 94.2 93.8 93.3 92.9

50 92.6 94.7 95.8 96.4 96.7 97.0 97.1 97.0 96.9 96.6 96.3 96.0 95.6 95.2 94.9 94.5 94.1 93.7 93.3 92.9

55 92.1 94.2 95.3 96.0 96.4 96.6 96.7 96.6 96.4 96.2 95.9 95.6 95.3 95.0 94.7 94.4 94.0 93.7 93.3 92.9

60 91.7 93.8 94.9 95.5 95.9 96.1 96.1 96.0 95.9 95.8 95.5 95.3 95.0 94.8 94.5 94.2 93.9 93.6 93.2 92.9

65 91.4 93.3 94.4 95.0 95.4 95.5 95.5 95.5 95.4 95.3 95.1 94.9 94.7 94.5 94.3 94.0 93.8 93.5 93.2 92.9

70 91.2 92.9 93.8 94.3 94.5 94.7 94.8 94.9 94.8 94.8 94.7 94.5 94.4 94.2 94.0 93.9 93.7 93.4 93.1 92.9

75 90.7 92.0 92.8 93.3 93.7 94.0 94.1 94.2 94.2 94.2 94.2 94.1 94.0 93.9 93.8 93.7 93.5 93.3 93.1 92.9

80 89.9 91.1 91.9 92.5 92.9 93.2 93.4 93.5 93.6 93.6 93.7 93.6 93.6 93.6 93.5 93.4 93.3 93.2 93.0 92.9

85 89.7 90.5 91.2 91.7 92.1 92.4 92.7 92.8 93.0 93.0 93.1 93.2 93.2 93.2 93.2 93.2 93.1 93.1 93.0 92.9

90 89.7 90.3 90.8 91.2 91.5 91.8 92.0 92.2 92.4 92.5 92.7 92.8 92.8 92.9 92.9 92.9 92.9 92.9 92.9 92.9

95 90.6 90.9 91.1 91.3 91.5 91.7 91.9 92.0 92.2 92.3 92.4 92.4 92.5 92.6 92.7 92.7 92.8 92.8 92.8 92.9

98 91.8 91.9 92.0 92.0 92.1 92.2 92.2 92.3 92.4 92.4 92.5 92.5 92.6 92.6 92.7 92.7 92.8 92.8 92.8 92.9

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.25-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.50-inches of Retention for Zone 3
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 95.8 97.2 97.8 98.1 98.2 98.4 98.4 98.4 98.3 98.2 97.9 97.5 97.0 96.5 96.0 95.5 95.0 94.6 94.1 93.6

35 94.7 96.5 97.3 97.7 98.0 98.1 98.2 98.2 98.1 97.9 97.7 97.3 96.8 96.3 95.9 95.4 95.0 94.5 94.1 93.6

40 93.9 95.9 96.9 97.4 97.7 97.8 97.9 97.9 97.9 97.7 97.4 97.0 96.6 96.2 95.8 95.3 94.9 94.5 94.1 93.6

45 93.4 95.5 96.5 97.0 97.3 97.5 97.6 97.7 97.6 97.4 97.1 96.8 96.4 96.0 95.6 95.2 94.8 94.5 94.1 93.6

50 93.1 95.1 96.0 96.6 97.0 97.2 97.3 97.4 97.3 97.1 96.8 96.5 96.2 95.8 95.5 95.1 94.8 94.4 94.0 93.6

55 92.5 94.6 95.6 96.2 96.6 96.9 97.0 97.0 96.9 96.7 96.5 96.2 95.9 95.6 95.3 95.0 94.7 94.3 94.0 93.6

60 92.2 94.1 95.2 95.9 96.3 96.5 96.6 96.6 96.4 96.3 96.1 95.9 95.6 95.4 95.1 94.8 94.6 94.3 94.0 93.6

65 92.0 93.8 94.8 95.5 95.9 96.1 96.1 96.0 96.0 95.9 95.7 95.5 95.3 95.1 94.9 94.7 94.4 94.2 93.9 93.6

70 91.9 93.5 94.4 95.0 95.3 95.4 95.4 95.5 95.5 95.4 95.3 95.2 95.0 94.8 94.7 94.5 94.3 94.1 93.9 93.6

75 91.8 93.0 93.7 94.1 94.4 94.7 94.8 94.9 94.9 94.9 94.8 94.7 94.7 94.5 94.4 94.3 94.2 94.0 93.8 93.6

80 91.1 92.1 92.8 93.3 93.7 94.0 94.1 94.2 94.3 94.3 94.3 94.3 94.3 94.2 94.2 94.1 94.0 93.9 93.8 93.6

85 90.7 91.6 92.2 92.6 93.0 93.2 93.4 93.6 93.7 93.8 93.8 93.9 93.9 93.9 93.9 93.9 93.8 93.8 93.7 93.6

90 90.8 91.3 91.8 92.1 92.4 92.7 92.9 93.0 93.2 93.3 93.4 93.5 93.5 93.6 93.6 93.7 93.7 93.7 93.7 93.6

95 91.5 91.7 92.0 92.2 92.3 92.5 92.7 92.8 92.9 93.0 93.1 93.2 93.3 93.4 93.4 93.5 93.5 93.6 93.6 93.6

98 92.6 92.7 92.8 92.9 92.9 93.0 93.1 93.1 93.2 93.2 93.3 93.3 93.4 93.4 93.4 93.5 93.5 93.6 93.6 93.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 96.1 97.4 97.9 98.1 98.3 98.4 98.5 98.5 98.5 98.4 98.2 97.9 97.4 97.0 96.5 96.1 95.6 95.2 94.7 94.3

35 95.0 96.7 97.4 97.8 98.0 98.2 98.3 98.3 98.3 98.2 98.0 97.7 97.3 96.9 96.4 96.0 95.5 95.1 94.7 94.3

40 94.1 96.1 97.0 97.5 97.8 97.9 98.0 98.1 98.1 98.0 97.8 97.5 97.1 96.7 96.3 95.9 95.5 95.1 94.7 94.3

45 93.6 95.7 96.7 97.2 97.5 97.7 97.8 97.8 97.8 97.7 97.5 97.3 96.9 96.5 96.2 95.8 95.4 95.0 94.7 94.3

50 93.3 95.4 96.3 96.8 97.1 97.4 97.5 97.6 97.6 97.5 97.3 97.0 96.7 96.4 96.0 95.7 95.3 95.0 94.6 94.3

55 93.0 94.9 95.9 96.4 96.8 97.1 97.3 97.3 97.3 97.1 96.9 96.7 96.4 96.1 95.9 95.5 95.2 94.9 94.6 94.3

60 92.7 94.5 95.5 96.1 96.5 96.8 97.0 97.0 96.9 96.8 96.6 96.4 96.2 95.9 95.7 95.4 95.1 94.9 94.6 94.3

65 92.4 94.2 95.2 95.8 96.2 96.5 96.6 96.6 96.5 96.4 96.2 96.1 95.9 95.7 95.5 95.2 95.0 94.8 94.6 94.3

70 92.5 94.0 94.9 95.5 95.8 96.0 96.0 96.0 96.0 95.9 95.8 95.7 95.6 95.4 95.2 95.1 94.9 94.7 94.5 94.3

75 92.5 93.7 94.5 94.9 95.1 95.3 95.4 95.5 95.5 95.5 95.4 95.3 95.3 95.1 95.0 94.9 94.8 94.6 94.5 94.3

80 92.2 93.1 93.7 94.1 94.4 94.6 94.8 94.9 94.9 95.0 95.0 94.9 94.9 94.8 94.8 94.7 94.6 94.5 94.4 94.3

85 91.7 92.5 93.0 93.4 93.7 94.0 94.1 94.3 94.4 94.5 94.5 94.5 94.5 94.5 94.5 94.5 94.5 94.4 94.4 94.3

90 91.7 92.2 92.6 92.9 93.2 93.4 93.6 93.7 93.9 94.0 94.0 94.1 94.2 94.2 94.3 94.3 94.3 94.3 94.3 94.3

95 92.4 92.6 92.8 92.9 93.1 93.2 93.4 93.5 93.6 93.7 93.8 93.9 93.9 94.0 94.1 94.1 94.2 94.2 94.3 94.3

98 93.3 93.4 93.5 93.6 93.6 93.7 93.7 93.8 93.8 93.9 93.9 94.0 94.0 94.1 94.1 94.2 94.2 94.2 94.3 94.3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.75-inches of Retention for Zone 3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 4.00-inches of Retention for Zone 3
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 90.1 86.6 79.2 71.4 64.5 58.6 53.5 49.2 45.5 42.3 39.5 37.1 34.9 33.0 31.3 29.7 28.3 27.1 25.9 24.8

35 86.2 84.3 77.8 70.5 63.9 58.2 53.2 49.0 45.3 42.2 39.4 37.0 34.9 33.0 31.2 29.7 28.3 27.0 25.9 24.8

40 81.6 81.5 75.9 69.3 63.1 57.6 52.8 48.7 45.1 42.0 39.3 36.9 34.8 32.9 31.2 29.7 28.3 27.0 25.9 24.8

45 76.5 78.1 73.7 67.8 62.0 56.8 52.2 48.2 44.8 41.8 39.1 36.8 34.7 32.8 31.1 29.6 28.3 27.0 25.9 24.8

50 71.0 74.2 71.0 65.9 60.7 55.8 51.5 47.7 44.4 41.4 38.9 36.6 34.5 32.7 31.1 29.6 28.2 27.0 25.9 24.8

55 65.3 69.9 67.9 63.7 59.1 54.7 50.6 47.0 43.8 41.1 38.5 36.3 34.4 32.6 31.0 29.5 28.2 27.0 25.8 24.8

60 59.7 65.2 64.4 61.2 57.2 53.2 49.6 46.2 43.2 40.6 38.2 36.1 34.1 32.4 30.8 29.4 28.1 26.9 25.8 24.8

65 54.2 60.2 60.5 58.2 55.0 51.5 48.2 45.2 42.4 39.9 37.7 35.7 33.8 32.2 30.7 29.3 28.0 26.9 25.8 24.8

70 49.1 54.9 56.1 54.7 52.3 49.4 46.6 43.9 41.4 39.2 37.1 35.2 33.5 31.9 30.5 29.1 27.9 26.8 25.8 24.8

75 44.3 49.4 51.1 50.7 49.1 46.9 44.6 42.3 40.1 38.1 36.3 34.6 33.0 31.5 30.2 28.9 27.8 26.7 25.7 24.8

80 40.0 44.1 45.8 46.0 45.2 43.7 42.0 40.2 38.5 36.8 35.2 33.7 32.3 31.0 29.8 28.7 27.6 26.6 25.7 24.8

85 36.2 38.9 40.4 40.8 40.6 39.8 38.8 37.5 36.3 35.0 33.7 32.5 31.4 30.2 29.2 28.2 27.3 26.4 25.6 24.8

90 32.8 34.2 35.0 35.4 35.4 35.1 34.6 33.9 33.2 32.4 31.6 30.8 29.9 29.1 28.3 27.6 26.9 26.1 25.5 24.8

95 29.3 29.7 29.9 30.0 29.9 29.8 29.7 29.4 29.1 28.8 28.5 28.1 27.7 27.3 26.9 26.5 26.1 25.6 25.2 24.8

98 27.2 27.2 27.2 27.1 27.0 27.0 26.8 26.7 26.6 26.5 26.3 26.2 26.0 25.9 25.7 25.5 25.4 25.2 25.0 24.8

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 94.0 94.2 92.1 88.8 84.8 80.5 76.3 72.4 68.6 65.2 62.0 59.1 56.4 53.9 51.7 49.5 47.6 45.8 44.1 42.6

35 91.1 92.3 90.7 87.7 84.0 79.9 75.9 72.0 68.4 65.0 61.9 59.0 56.3 53.9 51.6 49.5 47.6 45.8 44.1 42.6

40 87.8 90.0 88.9 86.4 82.9 79.1 75.3 71.5 68.0 64.7 61.6 58.8 56.2 53.8 51.5 49.4 47.5 45.7 44.1 42.6

45 84.0 87.2 86.8 84.7 81.6 78.1 74.5 70.9 67.5 64.3 61.3 58.6 56.0 53.6 51.4 49.4 47.5 45.7 44.1 42.6

50 79.9 84.0 84.3 82.7 80.1 76.9 73.5 70.2 66.9 63.9 61.0 58.3 55.8 53.5 51.3 49.3 47.4 45.7 44.1 42.6

55 75.6 80.4 81.4 80.4 78.2 75.4 72.3 69.2 66.2 63.3 60.5 57.9 55.5 53.2 51.1 49.2 47.3 45.6 44.0 42.6

60 71.3 76.5 78.1 77.6 75.9 73.6 70.9 68.0 65.2 62.5 59.9 57.4 55.1 53.0 50.9 49.0 47.2 45.6 44.0 42.6

65 67.1 72.4 74.4 74.5 73.3 71.4 69.1 66.6 64.1 61.6 59.2 56.9 54.7 52.6 50.6 48.8 47.1 45.5 44.0 42.6

70 63.0 68.1 70.3 70.8 70.2 68.9 67.0 64.9 62.7 60.5 58.3 56.1 54.1 52.1 50.3 48.6 46.9 45.4 43.9 42.6

75 59.2 63.7 65.9 66.7 66.6 65.7 64.4 62.7 60.9 59.0 57.1 55.2 53.3 51.5 49.8 48.2 46.7 45.2 43.8 42.6

80 55.8 59.4 61.4 62.3 62.4 61.9 61.1 59.9 58.6 57.1 55.5 53.9 52.3 50.7 49.2 47.8 46.4 45.0 43.8 42.6

85 52.7 55.2 56.7 57.5 57.7 57.6 57.1 56.4 55.5 54.5 53.3 52.1 50.8 49.6 48.3 47.1 45.9 44.7 43.6 42.6

90 49.7 51.1 52.0 52.5 52.8 52.8 52.6 52.2 51.7 51.1 50.3 49.6 48.7 47.9 47.0 46.1 45.2 44.3 43.4 42.6

95 46.7 47.1 47.4 47.5 47.6 47.6 47.5 47.3 47.1 46.8 46.5 46.2 45.8 45.4 44.9 44.5 44.0 43.5 43.0 42.6

98 44.9 44.9 44.8 44.8 44.7 44.7 44.6 44.5 44.3 44.2 44.1 44.0 43.8 43.6 43.5 43.3 43.1 42.9 42.7 42.6

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.25-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 4
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 95.6 96.4 95.6 94.1 92.1 89.6 86.8 83.9 81.0 78.1 75.3 72.7 70.1 67.7 65.4 63.3 61.2 59.3 57.4 55.7

35 93.5 94.9 94.5 93.2 91.3 89.0 86.3 83.5 80.7 77.9 75.1 72.5 70.0 67.6 65.4 63.2 61.2 59.3 57.4 55.7

40 91.0 93.1 93.0 92.0 90.3 88.1 85.7 83.0 80.2 77.5 74.9 72.3 69.8 67.5 65.3 63.1 61.1 59.2 57.4 55.7

45 88.1 90.9 91.3 90.5 89.1 87.1 84.8 82.3 79.7 77.1 74.5 72.0 69.6 67.3 65.1 63.0 61.1 59.2 57.4 55.7

50 85.0 88.4 89.2 88.8 87.6 85.9 83.8 81.5 79.0 76.5 74.1 71.7 69.3 67.1 65.0 62.9 61.0 59.1 57.4 55.7

55 81.7 85.7 86.8 86.8 85.9 84.5 82.6 80.5 78.2 75.9 73.5 71.2 69.0 66.8 64.8 62.8 60.9 59.1 57.4 55.7

60 78.4 82.6 84.1 84.4 83.9 82.7 81.1 79.2 77.2 75.0 72.8 70.7 68.6 66.5 64.5 62.6 60.8 59.0 57.3 55.7

65 75.0 79.3 81.1 81.7 81.5 80.7 79.4 77.8 76.0 74.0 72.0 70.0 68.0 66.1 64.2 62.3 60.6 58.9 57.3 55.7

70 71.7 75.9 77.9 78.7 78.7 78.2 77.3 76.0 74.4 72.7 71.0 69.1 67.3 65.5 63.8 62.0 60.4 58.8 57.2 55.7

75 68.7 72.5 74.4 75.4 75.6 75.3 74.7 73.7 72.5 71.1 69.6 68.0 66.4 64.8 63.2 61.6 60.1 58.6 57.1 55.7

80 65.9 69.0 70.8 71.7 72.1 72.1 71.7 71.0 70.1 69.0 67.8 66.6 65.2 63.9 62.5 61.1 59.7 58.3 57.0 55.7

85 63.5 65.7 67.1 67.9 68.3 68.3 68.1 67.7 67.1 66.4 65.5 64.6 63.6 62.5 61.4 60.3 59.1 58.0 56.8 55.7

90 61.2 62.4 63.2 63.8 64.1 64.2 64.1 63.9 63.6 63.2 62.7 62.1 61.4 60.7 59.9 59.1 58.3 57.4 56.6 55.7

95 58.7 59.1 59.4 59.6 59.7 59.7 59.7 59.7 59.5 59.4 59.1 58.9 58.6 58.2 57.9 57.5 57.1 56.6 56.2 55.7

98 57.5 57.5 57.5 57.5 57.5 57.4 57.4 57.3 57.2 57.1 57.0 56.9 56.8 56.6 56.5 56.4 56.2 56.0 55.9 55.7

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 96.6 97.5 97.2 96.4 95.2 93.7 91.9 90.0 87.9 85.7 83.5 81.2 79.0 76.9 74.8 72.8 70.9 69.1 67.3 65.6

35 95.0 96.3 96.2 95.6 94.5 93.1 91.4 89.6 87.5 85.4 83.2 81.1 78.9 76.8 74.8 72.8 70.9 69.0 67.2 65.6

40 93.0 94.9 95.1 94.6 93.6 92.4 90.8 89.0 87.1 85.1 82.9 80.8 78.7 76.7 74.7 72.7 70.8 69.0 67.2 65.6

45 90.8 93.1 93.6 93.4 92.6 91.5 90.0 88.4 86.5 84.6 82.6 80.5 78.5 76.5 74.5 72.6 70.7 68.9 67.2 65.6

50 88.3 91.1 92.0 91.9 91.4 90.4 89.1 87.6 85.9 84.0 82.1 80.1 78.2 76.2 74.3 72.5 70.6 68.9 67.2 65.6

55 85.7 89.0 90.1 90.2 89.9 89.1 88.0 86.6 85.1 83.4 81.5 79.7 77.8 75.9 74.1 72.3 70.5 68.8 67.1 65.6

60 83.1 86.6 87.9 88.3 88.1 87.6 86.7 85.5 84.1 82.5 80.8 79.1 77.3 75.6 73.8 72.1 70.4 68.7 67.1 65.6

65 80.4 83.9 85.5 86.1 86.1 85.8 85.1 84.1 82.9 81.5 80.0 78.4 76.8 75.1 73.5 71.8 70.2 68.6 67.1 65.6

70 77.7 81.2 82.8 83.6 83.9 83.7 83.2 82.4 81.4 80.3 78.9 77.5 76.0 74.5 73.0 71.5 70.0 68.5 67.0 65.6

75 75.2 78.4 80.1 81.0 81.3 81.3 81.0 80.4 79.6 78.7 77.6 76.4 75.1 73.8 72.4 71.0 69.6 68.3 66.9 65.6

80 73.0 75.6 77.2 78.1 78.5 78.6 78.4 78.1 77.5 76.8 75.9 74.9 73.9 72.8 71.6 70.4 69.2 68.0 66.8 65.6

85 71.1 73.0 74.2 75.0 75.4 75.6 75.5 75.3 74.9 74.4 73.8 73.1 72.3 71.4 70.5 69.6 68.6 67.6 66.6 65.6

90 69.4 70.5 71.2 71.7 72.0 72.2 72.2 72.1 71.9 71.6 71.2 70.8 70.3 69.7 69.1 68.5 67.8 67.1 66.3 65.6

95 67.6 67.9 68.1 68.3 68.4 68.5 68.5 68.5 68.4 68.3 68.2 68.0 67.8 67.6 67.3 67.0 66.7 66.3 65.9 65.6

98 66.7 66.8 66.8 66.8 66.8 66.7 66.7 66.7 66.6 66.6 66.5 66.4 66.3 66.3 66.1 66.0 65.9 65.8 65.7 65.6

Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 97.3 98.0 98.0 97.5 96.8 95.8 94.6 93.3 91.8 90.2 88.5 86.8 85.0 83.2 81.4 79.6 77.9 76.2 74.5 72.9

35 95.9 97.2 97.3 96.9 96.2 95.3 94.2 92.9 91.5 89.9 88.3 86.6 84.8 83.0 81.3 79.5 77.8 76.2 74.5 72.9

40 94.5 96.0 96.3 96.1 95.5 94.6 93.6 92.4 91.1 89.6 88.0 86.3 84.6 82.9 81.2 79.5 77.8 76.1 74.5 72.9

45 92.7 94.6 95.1 95.0 94.6 93.9 93.0 91.8 90.6 89.1 87.6 86.0 84.4 82.7 81.0 79.3 77.7 76.1 74.5 72.9

50 90.7 93.1 93.8 93.8 93.6 93.0 92.1 91.1 89.9 88.6 87.2 85.7 84.1 82.4 80.8 79.2 77.6 76.0 74.5 72.9

55 88.6 91.3 92.2 92.5 92.3 91.9 91.2 90.3 89.2 88.0 86.6 85.2 83.7 82.1 80.6 79.0 77.5 75.9 74.4 72.9

60 86.4 89.3 90.5 90.9 90.9 90.6 90.0 89.2 88.3 87.2 86.0 84.6 83.2 81.8 80.3 78.8 77.3 75.8 74.4 72.9

65 84.3 87.2 88.5 89.1 89.2 89.0 88.6 88.0 87.2 86.3 85.2 84.0 82.7 81.3 79.9 78.5 77.1 75.7 74.3 72.9

70 82.1 85.0 86.4 87.1 87.4 87.3 87.0 86.6 85.9 85.1 84.2 83.1 82.0 80.7 79.5 78.2 76.9 75.6 74.3 72.9

75 80.1 82.7 84.1 84.9 85.3 85.4 85.2 84.9 84.4 83.7 82.9 82.0 81.1 80.0 78.9 77.7 76.6 75.4 74.2 72.9

80 78.2 80.4 81.7 82.5 83.0 83.2 83.1 82.9 82.5 82.0 81.4 80.7 79.9 79.1 78.1 77.1 76.1 75.1 74.0 72.9

85 76.7 78.3 79.3 80.1 80.5 80.7 80.7 80.6 80.4 80.1 79.6 79.1 78.5 77.8 77.1 76.4 75.5 74.7 73.8 72.9

90 75.4 76.3 77.0 77.5 77.8 78.0 78.1 78.0 77.9 77.7 77.5 77.1 76.8 76.3 75.9 75.3 74.8 74.2 73.6 72.9

95 74.2 74.5 74.7 74.9 75.0 75.1 75.1 75.1 75.1 75.0 74.9 74.8 74.6 74.5 74.3 74.0 73.8 73.5 73.3 72.9

98 73.7 73.7 73.7 73.7 73.7 73.7 73.7 73.7 73.7 73.6 73.6 73.6 73.5 73.4 73.4 73.3 73.2 73.1 73.0 72.9

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 97.8 98.4 98.5 98.2 97.7 97.1 96.2 95.3 94.2 93.0 91.7 90.4 89.0 87.5 86.0 84.5 83.0 81.5 80.0 78.5

35 96.7 97.7 97.9 97.7 97.3 96.6 95.8 94.9 93.9 92.8 91.5 90.2 88.8 87.4 85.9 84.4 82.9 81.4 80.0 78.5

40 95.5 96.8 97.1 97.0 96.6 96.1 95.4 94.5 93.5 92.4 91.2 89.9 88.6 87.2 85.8 84.3 82.9 81.4 80.0 78.5

45 94.1 95.7 96.2 96.2 95.9 95.4 94.8 94.0 93.1 92.0 90.9 89.7 88.4 87.0 85.6 84.2 82.8 81.3 79.9 78.5

50 92.5 94.4 95.1 95.2 95.0 94.6 94.1 93.3 92.5 91.5 90.5 89.3 88.1 86.8 85.4 84.1 82.7 81.3 79.9 78.5

55 90.8 93.0 93.8 94.0 94.0 93.7 93.2 92.6 91.8 91.0 90.0 88.9 87.7 86.5 85.2 83.9 82.5 81.2 79.9 78.5

60 88.9 91.3 92.3 92.7 92.8 92.6 92.2 91.7 91.0 90.3 89.4 88.4 87.3 86.1 84.9 83.7 82.4 81.1 79.8 78.5

65 87.1 89.6 90.7 91.3 91.4 91.3 91.1 90.6 90.1 89.4 88.6 87.7 86.8 85.7 84.6 83.4 82.2 81.0 79.8 78.5

70 85.4 87.8 89.0 89.6 89.9 89.9 89.7 89.4 89.0 88.4 87.7 87.0 86.1 85.1 84.1 83.1 82.0 80.8 79.7 78.5

75 83.8 85.9 87.1 87.8 88.2 88.3 88.2 88.0 87.7 87.2 86.7 86.0 85.3 84.4 83.6 82.6 81.6 80.6 79.6 78.5

80 82.2 84.0 85.2 85.9 86.3 86.4 86.5 86.4 86.2 85.8 85.4 84.9 84.3 83.6 82.9 82.1 81.2 80.4 79.5 78.5

85 81.0 82.3 83.2 83.8 84.2 84.4 84.5 84.5 84.4 84.2 83.9 83.5 83.0 82.5 82.0 81.4 80.7 80.0 79.3 78.5

90 80.0 80.7 81.3 81.8 82.1 82.3 82.4 82.4 82.4 82.2 82.1 81.8 81.6 81.2 80.9 80.5 80.0 79.6 79.1 78.5

95 79.1 79.4 79.6 79.8 79.9 80.0 80.1 80.1 80.1 80.1 80.0 79.9 79.8 79.7 79.6 79.4 79.2 79.0 78.8 78.5

98 79.0 79.0 79.0 79.1 79.1 79.1 79.1 79.1 79.0 79.0 79.0 79.0 78.9 78.9 78.8 78.8 78.7 78.7 78.6 78.5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.50-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.25-inches of Retention for Zone 4
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.2 98.7 98.8 98.7 98.4 97.9 97.3 96.5 95.7 94.8 93.8 92.8 91.7 90.5 89.3 88.0 86.7 85.4 84.1 82.8

35 97.3 98.1 98.3 98.2 97.9 97.5 96.9 96.2 95.5 94.6 93.6 92.6 91.5 90.4 89.2 87.9 86.7 85.4 84.1 82.8

40 96.2 97.4 97.7 97.7 97.4 97.0 96.5 95.9 95.1 94.3 93.4 92.4 91.3 90.2 89.0 87.8 86.6 85.4 84.1 82.8

45 95.1 96.5 96.9 97.0 96.8 96.5 96.0 95.4 94.7 93.9 93.1 92.1 91.1 90.0 88.9 87.7 86.5 85.3 84.1 82.8

50 93.9 95.5 96.0 96.1 96.0 95.8 95.4 94.8 94.2 93.5 92.7 91.8 90.8 89.8 88.7 87.6 86.4 85.2 84.0 82.8

55 92.4 94.3 95.0 95.2 95.2 95.0 94.6 94.2 93.6 93.0 92.2 91.4 90.5 89.5 88.5 87.4 86.3 85.2 84.0 82.8

60 90.9 92.9 93.7 94.1 94.2 94.0 93.8 93.4 92.9 92.4 91.7 90.9 90.1 89.2 88.2 87.2 86.2 85.1 83.9 82.8

65 89.4 91.4 92.4 92.9 93.0 93.0 92.8 92.5 92.1 91.6 91.0 90.4 89.6 88.8 87.9 87.0 86.0 84.9 83.9 82.8

70 87.9 89.9 90.9 91.5 91.7 91.8 91.7 91.5 91.2 90.7 90.3 89.7 89.0 88.3 87.5 86.6 85.7 84.8 83.8 82.8

75 86.5 88.4 89.4 90.0 90.3 90.5 90.4 90.3 90.1 89.7 89.3 88.9 88.3 87.7 87.0 86.2 85.4 84.6 83.7 82.8

80 85.3 86.8 87.8 88.4 88.8 88.9 89.0 88.9 88.8 88.6 88.3 87.9 87.4 86.9 86.4 85.7 85.1 84.4 83.6 82.8

85 84.3 85.4 86.2 86.7 87.1 87.3 87.4 87.4 87.3 87.2 87.0 86.7 86.4 86.0 85.6 85.1 84.6 84.0 83.4 82.8

90 83.5 84.1 84.7 85.0 85.3 85.5 85.7 85.7 85.7 85.6 85.5 85.4 85.2 84.9 84.7 84.4 84.0 83.7 83.3 82.8

95 82.9 83.2 83.4 83.6 83.7 83.8 83.9 83.9 83.9 83.9 83.9 83.8 83.8 83.7 83.6 83.5 83.3 83.2 83.0 82.8

98 83.0 83.1 83.1 83.1 83.1 83.1 83.2 83.2 83.2 83.1 83.1 83.1 83.1 83.1 83.0 83.0 83.0 82.9 82.9 82.8

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.5 99.0 99.1 99.0 98.7 98.4 98.0 97.4 96.8 96.1 95.3 94.5 93.6 92.6 91.6 90.6 89.5 88.4 87.3 86.1

35 97.8 98.5 98.6 98.6 98.4 98.1 97.7 97.1 96.5 95.9 95.1 94.3 93.4 92.5 91.5 90.5 89.4 88.4 87.3 86.1

40 96.9 97.8 98.1 98.1 98.0 97.7 97.3 96.8 96.2 95.6 94.9 94.1 93.3 92.4 91.4 90.4 89.4 88.3 87.2 86.1

45 95.9 97.1 97.5 97.6 97.5 97.2 96.8 96.4 95.9 95.3 94.6 93.8 93.0 92.2 91.3 90.3 89.3 88.3 87.2 86.1

50 94.9 96.3 96.7 96.9 96.8 96.6 96.3 95.9 95.4 94.9 94.2 93.6 92.8 92.0 91.1 90.2 89.2 88.2 87.2 86.1

55 93.7 95.3 95.9 96.1 96.1 95.9 95.7 95.3 94.9 94.4 93.8 93.2 92.5 91.7 90.9 90.0 89.1 88.1 87.1 86.1

60 92.5 94.1 94.9 95.1 95.2 95.1 95.0 94.7 94.3 93.9 93.4 92.8 92.1 91.4 90.6 89.8 88.9 88.0 87.1 86.1

65 91.2 92.9 93.7 94.1 94.3 94.3 94.1 93.9 93.6 93.2 92.8 92.3 91.7 91.0 90.3 89.6 88.8 87.9 87.1 86.1

70 89.9 91.6 92.5 92.9 93.2 93.2 93.2 93.0 92.8 92.5 92.1 91.7 91.2 90.6 90.0 89.3 88.6 87.8 87.0 86.1

75 88.7 90.2 91.2 91.7 92.0 92.1 92.1 92.0 91.9 91.6 91.3 91.0 90.5 90.1 89.5 88.9 88.3 87.6 86.9 86.1

80 87.7 89.0 89.8 90.3 90.7 90.9 90.9 90.9 90.8 90.6 90.4 90.1 89.8 89.4 89.0 88.5 88.0 87.4 86.8 86.1

85 86.9 87.8 88.5 89.0 89.3 89.5 89.6 89.6 89.6 89.5 89.4 89.2 88.9 88.7 88.3 88.0 87.6 87.1 86.6 86.1

90 86.3 86.8 87.3 87.6 87.9 88.0 88.2 88.2 88.3 88.2 88.2 88.1 87.9 87.8 87.6 87.3 87.1 86.8 86.5 86.1

95 85.9 86.1 86.3 86.5 86.6 86.7 86.8 86.8 86.8 86.9 86.9 86.8 86.8 86.8 86.7 86.6 86.5 86.4 86.3 86.1

98 86.1 86.2 86.2 86.2 86.3 86.3 86.3 86.3 86.3 86.3 86.3 86.3 86.3 86.3 86.3 86.2 86.2 86.2 86.2 86.1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.75-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.00-inches of Retention for Zone 4
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.8 99.2 99.2 99.2 99.0 98.8 98.4 98.0 97.5 97.0 96.3 95.7 94.9 94.2 93.3 92.5 91.6 90.6 89.7 88.7

35 98.1 98.7 98.9 98.8 98.7 98.5 98.2 97.8 97.3 96.8 96.2 95.5 94.8 94.0 93.2 92.4 91.5 90.6 89.7 88.7

40 97.4 98.2 98.4 98.5 98.4 98.2 97.9 97.5 97.0 96.5 96.0 95.3 94.6 93.9 93.1 92.3 91.5 90.6 89.6 88.7

45 96.5 97.6 97.9 98.0 97.9 97.8 97.5 97.1 96.7 96.2 95.7 95.1 94.4 93.7 93.0 92.2 91.4 90.5 89.6 88.7

50 95.7 96.9 97.3 97.4 97.4 97.3 97.0 96.7 96.3 95.9 95.4 94.8 94.2 93.6 92.8 92.1 91.3 90.5 89.6 88.7

55 94.8 96.1 96.6 96.8 96.8 96.7 96.5 96.2 95.9 95.5 95.0 94.5 94.0 93.3 92.7 91.9 91.2 90.4 89.6 88.7

60 93.7 95.1 95.7 96.0 96.0 96.0 95.9 95.6 95.4 95.0 94.6 94.1 93.6 93.1 92.4 91.8 91.1 90.3 89.5 88.7

65 92.6 94.1 94.8 95.1 95.2 95.2 95.2 95.0 94.7 94.4 94.1 93.7 93.2 92.7 92.2 91.6 90.9 90.2 89.5 88.7

70 91.5 92.9 93.7 94.1 94.3 94.4 94.3 94.2 94.0 93.8 93.5 93.2 92.8 92.3 91.8 91.3 90.7 90.1 89.4 88.7

75 90.5 91.8 92.6 93.0 93.3 93.4 93.4 93.4 93.3 93.1 92.8 92.6 92.2 91.9 91.4 91.0 90.5 89.9 89.3 88.7

80 89.6 90.7 91.4 91.9 92.2 92.3 92.4 92.4 92.4 92.3 92.1 91.9 91.6 91.3 91.0 90.6 90.2 89.7 89.2 88.7

85 88.9 89.7 90.3 90.7 91.0 91.2 91.3 91.4 91.4 91.3 91.2 91.1 90.9 90.7 90.4 90.1 89.8 89.5 89.1 88.7

90 88.4 89.0 89.3 89.6 89.9 90.0 90.1 90.2 90.2 90.2 90.2 90.1 90.1 89.9 89.8 89.6 89.4 89.2 89.0 88.7

95 88.2 88.4 88.6 88.7 88.9 89.0 89.0 89.1 89.1 89.2 89.2 89.2 89.1 89.1 89.1 89.0 89.0 88.9 88.8 88.7

98 88.6 88.6 88.6 88.7 88.7 88.7 88.7 88.8 88.8 88.8 88.8 88.8 88.8 88.8 88.8 88.8 88.8 88.7 88.7 88.7

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.0 99.3 99.4 99.3 99.2 99.0 98.8 98.5 98.1 97.6 97.1 96.6 95.9 95.3 94.6 93.9 93.1 92.4 91.5 90.7

35 98.4 98.9 99.1 99.1 99.0 98.8 98.6 98.3 97.9 97.4 96.9 96.4 95.8 95.2 94.5 93.8 93.1 92.3 91.5 90.7

40 97.8 98.5 98.7 98.7 98.7 98.5 98.3 98.0 97.6 97.2 96.8 96.2 95.7 95.1 94.4 93.8 93.0 92.3 91.5 90.7

45 97.1 98.0 98.2 98.3 98.3 98.2 98.0 97.7 97.4 97.0 96.5 96.0 95.5 94.9 94.3 93.7 93.0 92.2 91.5 90.7

50 96.3 97.4 97.8 97.9 97.9 97.8 97.6 97.3 97.0 96.7 96.3 95.8 95.3 94.7 94.2 93.5 92.9 92.2 91.4 90.7

55 95.6 96.7 97.2 97.3 97.3 97.3 97.1 96.9 96.6 96.3 95.9 95.5 95.0 94.5 94.0 93.4 92.8 92.1 91.4 90.7

60 94.7 95.9 96.4 96.7 96.7 96.7 96.6 96.4 96.2 95.9 95.5 95.2 94.8 94.3 93.8 93.2 92.7 92.0 91.4 90.7

65 93.8 95.0 95.6 95.9 96.0 96.0 95.9 95.8 95.6 95.4 95.1 94.8 94.4 94.0 93.5 93.0 92.5 91.9 91.3 90.7

70 92.8 94.0 94.7 95.0 95.2 95.3 95.3 95.2 95.0 94.8 94.6 94.3 94.0 93.7 93.3 92.8 92.3 91.8 91.3 90.7

75 91.9 93.1 93.7 94.1 94.3 94.5 94.5 94.4 94.3 94.2 94.0 93.8 93.5 93.2 92.9 92.5 92.1 91.7 91.2 90.7

80 91.2 92.1 92.7 93.1 93.4 93.5 93.6 93.6 93.6 93.5 93.4 93.2 93.0 92.8 92.5 92.2 91.9 91.5 91.1 90.7

85 90.6 91.3 91.8 92.2 92.4 92.6 92.7 92.7 92.7 92.7 92.6 92.5 92.4 92.2 92.0 91.8 91.6 91.3 91.0 90.7

90 90.2 90.6 91.0 91.2 91.4 91.6 91.7 91.8 91.8 91.8 91.8 91.8 91.7 91.6 91.5 91.4 91.2 91.1 90.9 90.7

95 90.1 90.3 90.4 90.6 90.7 90.7 90.8 90.9 90.9 91.0 91.0 91.0 91.0 91.0 90.9 90.9 90.9 90.8 90.8 90.7

98 90.5 90.5 90.5 90.6 90.6 90.6 90.6 90.7 90.7 90.7 90.7 90.7 90.7 90.7 90.7 90.7 90.7 90.7 90.7 90.7

Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.25-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.1 99.4 99.5 99.5 99.4 99.2 99.0 98.8 98.5 98.1 97.7 97.2 96.7 96.2 95.6 95.0 94.3 93.7 93.0 92.3

35 98.7 99.1 99.2 99.2 99.2 99.0 98.9 98.6 98.3 98.0 97.5 97.1 96.6 96.1 95.5 94.9 94.3 93.6 93.0 92.3

40 98.1 98.7 98.9 98.9 98.9 98.8 98.6 98.4 98.1 97.8 97.4 96.9 96.5 96.0 95.4 94.9 94.2 93.6 92.9 92.3

45 97.6 98.3 98.5 98.6 98.6 98.5 98.3 98.1 97.9 97.5 97.2 96.8 96.3 95.8 95.3 94.8 94.2 93.6 92.9 92.3

50 96.9 97.8 98.1 98.2 98.2 98.1 98.0 97.8 97.6 97.3 96.9 96.6 96.1 95.7 95.2 94.7 94.1 93.5 92.9 92.3

55 96.2 97.2 97.6 97.7 97.8 97.7 97.6 97.4 97.2 96.9 96.6 96.3 95.9 95.5 95.0 94.5 94.0 93.5 92.9 92.3

60 95.5 96.6 97.0 97.2 97.3 97.2 97.1 97.0 96.8 96.6 96.3 96.0 95.6 95.3 94.8 94.4 93.9 93.4 92.8 92.3

65 94.7 95.8 96.3 96.5 96.6 96.7 96.6 96.5 96.3 96.1 95.9 95.6 95.3 95.0 94.6 94.2 93.8 93.3 92.8 92.3

70 93.9 95.0 95.5 95.8 96.0 96.0 96.0 95.9 95.8 95.7 95.5 95.2 95.0 94.7 94.4 94.0 93.6 93.2 92.7 92.3

75 93.1 94.1 94.7 95.0 95.2 95.3 95.3 95.3 95.2 95.1 95.0 94.8 94.6 94.3 94.1 93.8 93.4 93.1 92.7 92.3

80 92.5 93.3 93.8 94.1 94.4 94.5 94.6 94.6 94.6 94.5 94.4 94.3 94.1 93.9 93.7 93.5 93.2 92.9 92.6 92.3

85 91.9 92.6 93.0 93.3 93.5 93.7 93.8 93.8 93.8 93.8 93.8 93.7 93.6 93.5 93.3 93.2 93.0 92.7 92.5 92.3

90 91.6 92.0 92.3 92.5 92.7 92.9 93.0 93.0 93.1 93.1 93.1 93.1 93.0 93.0 92.9 92.8 92.7 92.6 92.4 92.3

95 91.6 91.8 91.9 92.0 92.1 92.2 92.3 92.3 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.3 92.3 92.3

98 92.0 92.0 92.1 92.1 92.1 92.1 92.2 92.2 92.2 92.2 92.2 92.2 92.2 92.3 92.3 92.3 92.3 92.3 92.3 92.3

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.3 99.5 99.6 99.6 99.5 99.4 99.2 99.0 98.8 98.5 98.1 97.7 97.3 96.9 96.4 95.9 95.3 94.7 94.1 93.5

35 98.9 99.2 99.4 99.4 99.3 99.2 99.1 98.9 98.6 98.3 98.0 97.6 97.2 96.8 96.3 95.8 95.3 94.7 94.1 93.5

40 98.4 98.9 99.1 99.1 99.1 99.0 98.9 98.7 98.5 98.2 97.9 97.5 97.1 96.7 96.2 95.7 95.2 94.7 94.1 93.5

45 97.9 98.5 98.8 98.8 98.8 98.7 98.6 98.5 98.3 98.0 97.7 97.3 97.0 96.6 96.1 95.6 95.1 94.6 94.1 93.5

50 97.4 98.1 98.4 98.5 98.5 98.4 98.3 98.2 98.0 97.7 97.5 97.1 96.8 96.4 96.0 95.5 95.1 94.6 94.0 93.5

55 96.7 97.6 97.9 98.1 98.1 98.1 98.0 97.9 97.7 97.4 97.2 96.9 96.6 96.2 95.9 95.4 95.0 94.5 94.0 93.5

60 96.2 97.1 97.5 97.6 97.7 97.7 97.6 97.5 97.3 97.1 96.9 96.6 96.4 96.0 95.7 95.3 94.9 94.5 94.0 93.5

65 95.5 96.4 96.9 97.1 97.2 97.2 97.1 97.0 96.9 96.7 96.6 96.3 96.1 95.8 95.5 95.1 94.8 94.4 93.9 93.5

70 94.9 95.7 96.2 96.4 96.6 96.6 96.6 96.5 96.5 96.3 96.2 96.0 95.8 95.5 95.2 94.9 94.6 94.3 93.9 93.5

75 94.2 95.0 95.4 95.7 95.9 96.0 96.0 96.0 95.9 95.9 95.7 95.6 95.4 95.2 95.0 94.7 94.5 94.2 93.8 93.5

80 93.5 94.2 94.7 95.0 95.2 95.3 95.4 95.4 95.4 95.3 95.3 95.1 95.0 94.9 94.7 94.5 94.3 94.0 93.8 93.5

85 93.1 93.6 94.0 94.3 94.5 94.6 94.7 94.7 94.8 94.7 94.7 94.6 94.6 94.5 94.4 94.2 94.1 93.9 93.7 93.5

90 92.8 93.1 93.4 93.6 93.8 93.9 94.0 94.1 94.1 94.1 94.1 94.1 94.1 94.0 94.0 93.9 93.8 93.7 93.6 93.5

95 92.8 93.0 93.1 93.2 93.3 93.3 93.4 93.5 93.5 93.5 93.6 93.6 93.6 93.6 93.6 93.6 93.6 93.6 93.5 93.5

98 93.2 93.2 93.3 93.3 93.3 93.3 93.4 93.4 93.4 93.4 93.4 93.4 93.5 93.5 93.5 93.5 93.5 93.5 93.5 93.5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.00-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.75-inches of Retention for Zone 4
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.4 99.6 99.6 99.6 99.6 99.5 99.4 99.2 99.0 98.8 98.5 98.2 97.8 97.4 97.0 96.5 96.1 95.6 95.0 94.5

35 99.1 99.4 99.5 99.5 99.4 99.4 99.2 99.1 98.9 98.7 98.4 98.1 97.7 97.3 96.9 96.5 96.0 95.5 95.0 94.5

40 98.7 99.1 99.2 99.3 99.2 99.2 99.1 98.9 98.7 98.5 98.2 97.9 97.6 97.2 96.8 96.4 96.0 95.5 95.0 94.5

45 98.2 98.8 98.9 99.0 99.0 98.9 98.8 98.7 98.5 98.3 98.1 97.8 97.5 97.1 96.8 96.3 95.9 95.5 95.0 94.5

50 97.7 98.4 98.6 98.7 98.7 98.7 98.6 98.5 98.3 98.1 97.9 97.6 97.3 97.0 96.6 96.3 95.9 95.4 95.0 94.5

55 97.2 98.0 98.2 98.4 98.4 98.4 98.3 98.2 98.1 97.9 97.6 97.4 97.1 96.8 96.5 96.2 95.8 95.4 94.9 94.5

60 96.7 97.5 97.8 98.0 98.0 98.0 98.0 97.9 97.7 97.6 97.4 97.2 96.9 96.7 96.4 96.0 95.7 95.3 94.9 94.5

65 96.2 96.9 97.3 97.5 97.6 97.6 97.6 97.5 97.4 97.2 97.1 96.9 96.7 96.4 96.2 95.9 95.6 95.2 94.9 94.5

70 95.6 96.4 96.8 97.0 97.1 97.1 97.1 97.1 97.0 96.9 96.7 96.6 96.4 96.2 96.0 95.7 95.4 95.1 94.8 94.5

75 95.0 95.7 96.1 96.4 96.5 96.6 96.6 96.6 96.5 96.5 96.4 96.2 96.1 95.9 95.7 95.5 95.3 95.0 94.8 94.5

80 94.5 95.1 95.5 95.7 95.9 96.0 96.0 96.1 96.0 96.0 95.9 95.9 95.8 95.6 95.5 95.3 95.1 94.9 94.7 94.5

85 94.0 94.5 94.8 95.1 95.2 95.4 95.4 95.5 95.5 95.5 95.5 95.4 95.4 95.3 95.2 95.1 94.9 94.8 94.7 94.5

90 93.8 94.1 94.3 94.5 94.6 94.8 94.8 94.9 94.9 95.0 95.0 95.0 94.9 94.9 94.9 94.8 94.7 94.7 94.6 94.5

95 93.8 94.0 94.1 94.2 94.2 94.3 94.4 94.4 94.4 94.5 94.5 94.5 94.5 94.5 94.5 94.5 94.5 94.5 94.5 94.5

98 94.2 94.2 94.2 94.3 94.3 94.3 94.3 94.4 94.4 94.4 94.4 94.4 94.4 94.5 94.5 94.5 94.5 94.5 94.5 94.5

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.5 99.7 99.7 99.7 99.7 99.6 99.5 99.4 99.2 99.0 98.8 98.5 98.2 97.8 97.5 97.1 96.7 96.2 95.8 95.3

35 99.2 99.5 99.5 99.6 99.5 99.5 99.4 99.2 99.1 98.9 98.7 98.4 98.1 97.8 97.4 97.0 96.6 96.2 95.8 95.3

40 98.9 99.2 99.4 99.4 99.4 99.3 99.2 99.1 98.9 98.8 98.5 98.3 98.0 97.7 97.3 97.0 96.6 96.2 95.7 95.3

45 98.5 98.9 99.1 99.2 99.2 99.1 99.0 98.9 98.8 98.6 98.4 98.2 97.9 97.6 97.3 96.9 96.5 96.2 95.7 95.3

50 98.0 98.6 98.8 98.9 98.9 98.9 98.8 98.7 98.6 98.4 98.2 98.0 97.7 97.5 97.2 96.8 96.5 96.1 95.7 95.3

55 97.6 98.3 98.5 98.6 98.6 98.6 98.6 98.5 98.4 98.2 98.0 97.8 97.6 97.3 97.0 96.7 96.4 96.1 95.7 95.3

60 97.2 97.8 98.1 98.3 98.3 98.3 98.3 98.2 98.1 98.0 97.8 97.6 97.4 97.2 96.9 96.6 96.3 96.0 95.7 95.3

65 96.7 97.4 97.7 97.9 97.9 98.0 97.9 97.9 97.8 97.7 97.5 97.4 97.2 97.0 96.7 96.5 96.2 95.9 95.6 95.3

70 96.2 96.9 97.2 97.4 97.5 97.6 97.5 97.5 97.4 97.3 97.2 97.1 96.9 96.8 96.6 96.3 96.1 95.9 95.6 95.3

75 95.7 96.3 96.7 96.9 97.0 97.1 97.1 97.1 97.0 97.0 96.9 96.8 96.7 96.5 96.4 96.2 96.0 95.8 95.5 95.3

80 95.3 95.8 96.1 96.3 96.5 96.5 96.6 96.6 96.6 96.6 96.5 96.4 96.4 96.3 96.1 96.0 95.8 95.7 95.5 95.3

85 94.8 95.2 95.5 95.7 95.9 96.0 96.1 96.1 96.1 96.1 96.1 96.1 96.0 96.0 95.9 95.8 95.7 95.6 95.4 95.3

90 94.6 94.9 95.1 95.2 95.4 95.5 95.5 95.6 95.6 95.7 95.7 95.7 95.7 95.6 95.6 95.6 95.5 95.4 95.4 95.3

95 94.7 94.8 94.9 95.0 95.0 95.1 95.2 95.2 95.2 95.3 95.3 95.3 95.3 95.3 95.3 95.3 95.3 95.3 95.3 95.3

98 95.0 95.0 95.1 95.1 95.1 95.1 95.2 95.2 95.2 95.2 95.2 95.2 95.2 95.3 95.3 95.3 95.3 95.3 95.3 95.3

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.25-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.50-inches of Retention for Zone 4
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.7 99.7 99.7 99.7 99.7 99.7 99.6 99.5 99.3 99.2 99.0 98.7 98.5 98.2 97.9 97.5 97.2 96.8 96.4 96.0

35 99.3 99.5 99.6 99.6 99.6 99.6 99.5 99.4 99.2 99.1 98.9 98.7 98.4 98.1 97.8 97.5 97.1 96.8 96.4 96.0

40 99.0 99.3 99.4 99.5 99.5 99.4 99.3 99.2 99.1 99.0 98.8 98.6 98.3 98.1 97.8 97.4 97.1 96.7 96.4 96.0

45 98.7 99.1 99.2 99.3 99.3 99.3 99.2 99.1 99.0 98.8 98.7 98.4 98.2 98.0 97.7 97.4 97.1 96.7 96.4 96.0

50 98.3 98.8 99.0 99.1 99.1 99.0 99.0 98.9 98.8 98.7 98.5 98.3 98.1 97.8 97.6 97.3 97.0 96.7 96.3 96.0

55 98.0 98.5 98.7 98.8 98.8 98.8 98.8 98.7 98.6 98.5 98.3 98.1 97.9 97.7 97.5 97.2 96.9 96.6 96.3 96.0

60 97.6 98.1 98.4 98.5 98.5 98.5 98.5 98.5 98.4 98.3 98.1 98.0 97.8 97.6 97.4 97.1 96.9 96.6 96.3 96.0

65 97.1 97.7 98.0 98.2 98.2 98.2 98.2 98.2 98.1 98.0 97.9 97.7 97.6 97.4 97.2 97.0 96.8 96.5 96.3 96.0

70 96.7 97.3 97.6 97.8 97.9 97.9 97.9 97.9 97.8 97.7 97.6 97.5 97.4 97.2 97.1 96.9 96.7 96.5 96.2 96.0

75 96.3 96.8 97.1 97.3 97.4 97.5 97.5 97.5 97.5 97.4 97.3 97.2 97.1 97.0 96.9 96.7 96.6 96.4 96.2 96.0

80 95.9 96.4 96.6 96.8 97.0 97.0 97.1 97.1 97.1 97.0 97.0 96.9 96.9 96.8 96.7 96.6 96.4 96.3 96.1 96.0

85 95.6 95.9 96.1 96.3 96.4 96.5 96.6 96.6 96.7 96.7 96.6 96.6 96.6 96.5 96.5 96.4 96.3 96.2 96.1 96.0

90 95.3 95.6 95.7 95.9 96.0 96.1 96.1 96.2 96.2 96.3 96.3 96.3 96.3 96.2 96.2 96.2 96.1 96.1 96.0 96.0

95 95.4 95.5 95.6 95.6 95.7 95.8 95.8 95.8 95.9 95.9 95.9 96.0 96.0 96.0 96.0 96.0 96.0 96.0 96.0 96.0

98 95.7 95.7 95.7 95.8 95.8 95.8 95.8 95.8 95.9 95.9 95.9 95.9 95.9 95.9 95.9 95.9 95.9 96.0 96.0 96.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.7 99.8 99.8 99.8 99.8 99.8 99.7 99.6 99.5 99.3 99.1 99.0 98.7 98.5 98.2 97.9 97.6 97.3 96.9 96.5

35 99.5 99.6 99.7 99.7 99.7 99.7 99.6 99.5 99.4 99.2 99.1 98.9 98.7 98.4 98.2 97.9 97.6 97.2 96.9 96.5

40 99.2 99.4 99.5 99.6 99.6 99.5 99.5 99.4 99.3 99.1 99.0 98.8 98.6 98.4 98.1 97.8 97.5 97.2 96.9 96.5

45 98.9 99.2 99.4 99.4 99.4 99.4 99.3 99.2 99.1 99.0 98.9 98.7 98.5 98.3 98.0 97.8 97.5 97.2 96.9 96.5

50 98.6 99.0 99.1 99.2 99.2 99.2 99.1 99.1 99.0 98.9 98.7 98.6 98.4 98.2 97.9 97.7 97.4 97.1 96.8 96.5

55 98.2 98.7 98.9 99.0 99.0 99.0 98.9 98.9 98.8 98.7 98.6 98.4 98.2 98.1 97.8 97.6 97.4 97.1 96.8 96.5

60 97.9 98.4 98.6 98.7 98.8 98.8 98.7 98.7 98.6 98.5 98.4 98.3 98.1 97.9 97.7 97.5 97.3 97.1 96.8 96.5

65 97.6 98.0 98.3 98.4 98.5 98.5 98.5 98.4 98.4 98.3 98.2 98.1 97.9 97.8 97.6 97.4 97.2 97.0 96.8 96.5

70 97.1 97.6 97.9 98.1 98.1 98.2 98.2 98.2 98.1 98.1 98.0 97.9 97.7 97.6 97.5 97.3 97.1 96.9 96.7 96.5

75 96.8 97.2 97.5 97.7 97.8 97.8 97.9 97.8 97.8 97.8 97.7 97.6 97.5 97.4 97.3 97.2 97.0 96.9 96.7 96.5

80 96.4 96.8 97.1 97.3 97.4 97.4 97.5 97.5 97.5 97.4 97.4 97.3 97.3 97.2 97.1 97.0 96.9 96.8 96.7 96.5

85 96.2 96.5 96.7 96.8 96.9 97.0 97.0 97.1 97.1 97.1 97.1 97.1 97.0 97.0 96.9 96.9 96.8 96.7 96.6 96.5

90 95.9 96.1 96.3 96.4 96.5 96.6 96.6 96.7 96.7 96.7 96.8 96.8 96.8 96.7 96.7 96.7 96.7 96.6 96.6 96.5

95 96.0 96.1 96.1 96.2 96.3 96.3 96.4 96.4 96.4 96.5 96.5 96.5 96.5 96.5 96.5 96.5 96.5 96.5 96.5 96.5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.75-inches of Retention for Zone 4

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 4.00-inches of Retention for Zone 4
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 83.0 80.8 74.1 67.0 60.7 55.3 50.7 46.8 43.4 40.4 37.8 35.5 33.5 31.7 30.1 28.6 27.3 26.1 25.0 24.0

35 77.3 77.4 72.0 65.6 59.8 54.7 50.2 46.4 43.1 40.2 37.6 35.4 33.4 31.6 30.0 28.6 27.3 26.1 25.0 24.0

40 71.3 73.5 69.4 63.9 58.6 53.8 49.6 45.9 42.7 39.9 37.4 35.2 33.3 31.5 30.0 28.5 27.3 26.1 25.0 24.0

45 65.3 69.3 66.5 61.9 57.2 52.8 48.8 45.3 42.3 39.6 37.1 35.0 33.1 31.4 29.9 28.5 27.2 26.0 25.0 24.0

50 59.6 64.8 63.4 59.6 55.5 51.6 47.9 44.7 41.7 39.2 36.8 34.8 32.9 31.3 29.8 28.4 27.2 26.0 25.0 24.0

55 54.0 60.2 59.9 57.1 53.7 50.2 46.9 43.9 41.1 38.7 36.5 34.5 32.7 31.1 29.6 28.3 27.1 26.0 24.9 24.0

60 49.0 55.7 56.3 54.4 51.6 48.6 45.6 42.9 40.4 38.1 36.0 34.1 32.4 30.9 29.5 28.2 27.0 25.9 24.9 24.0

65 44.5 51.0 52.5 51.4 49.3 46.8 44.2 41.8 39.5 37.4 35.5 33.7 32.1 30.6 29.3 28.1 26.9 25.9 24.9 24.0

70 40.5 46.5 48.5 48.1 46.6 44.7 42.6 40.5 38.4 36.6 34.8 33.2 31.7 30.3 29.1 27.9 26.8 25.8 24.9 24.0

75 37.0 42.0 44.2 44.5 43.7 42.2 40.6 38.9 37.2 35.5 34.0 32.5 31.2 29.9 28.8 27.7 26.7 25.7 24.8 24.0

80 33.9 37.8 39.8 40.5 40.2 39.4 38.2 36.9 35.6 34.2 32.9 31.7 30.5 29.4 28.4 27.4 26.5 25.6 24.8 24.0

85 31.1 33.8 35.4 36.1 36.3 35.9 35.3 34.5 33.5 32.5 31.5 30.5 29.6 28.7 27.8 27.0 26.2 25.4 24.7 24.0

90 28.7 30.2 31.2 31.8 32.0 32.0 31.7 31.3 30.8 30.2 29.6 29.0 28.3 27.6 27.0 26.4 25.7 25.1 24.6 24.0

95 26.6 27.0 27.4 27.6 27.7 27.7 27.7 27.6 27.4 27.2 26.9 26.6 26.3 26.0 25.7 25.4 25.0 24.7 24.3 24.0

98 25.7 25.7 25.7 25.7 25.7 25.6 25.6 25.5 25.4 25.3 25.2 25.1 25.0 24.8 24.7 24.6 24.4 24.3 24.1 24.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 88.6 89.9 87.9 84.5 80.5 76.4 72.3 68.5 65.1 61.9 58.9 56.2 53.7 51.4 49.3 47.3 45.5 43.8 42.2 40.8

35 84.1 86.8 85.6 82.8 79.3 75.4 71.6 68.0 64.6 61.5 58.7 56.0 53.6 51.3 49.2 47.3 45.5 43.8 42.2 40.8

40 79.3 83.3 82.9 80.8 77.8 74.3 70.7 67.3 64.1 61.1 58.3 55.8 53.4 51.1 49.1 47.2 45.4 43.8 42.2 40.8

45 74.4 79.5 80.0 78.5 76.0 72.9 69.6 66.5 63.4 60.6 57.9 55.4 53.1 51.0 48.9 47.1 45.3 43.7 42.2 40.8

50 69.7 75.5 76.8 76.0 73.9 71.3 68.4 65.5 62.6 60.0 57.4 55.0 52.8 50.7 48.8 47.0 45.3 43.7 42.2 40.8

55 65.2 71.4 73.4 73.1 71.7 69.5 66.9 64.3 61.7 59.2 56.9 54.6 52.5 50.4 48.6 46.8 45.2 43.6 42.1 40.8

60 61.0 67.2 69.7 70.1 69.2 67.4 65.3 63.0 60.6 58.4 56.2 54.0 52.0 50.1 48.3 46.6 45.0 43.5 42.1 40.8

65 57.1 63.1 65.9 66.8 66.4 65.1 63.3 61.4 59.4 57.3 55.3 53.4 51.5 49.7 48.0 46.4 44.9 43.4 42.1 40.8

70 53.6 59.2 62.0 63.2 63.3 62.5 61.2 59.6 57.9 56.1 54.3 52.6 50.9 49.2 47.6 46.1 44.7 43.3 42.0 40.8

75 50.7 55.5 58.1 59.5 59.8 59.4 58.6 57.4 56.1 54.6 53.1 51.6 50.1 48.6 47.1 45.8 44.4 43.2 41.9 40.8

80 48.3 52.0 54.3 55.5 56.0 56.0 55.6 54.8 53.9 52.8 51.6 50.3 49.0 47.8 46.5 45.3 44.1 43.0 41.8 40.8

85 46.2 48.7 50.5 51.5 52.0 52.2 52.1 51.7 51.1 50.4 49.6 48.6 47.6 46.7 45.6 44.6 43.7 42.7 41.7 40.8

90 44.2 45.6 46.7 47.4 47.9 48.1 48.2 48.1 47.8 47.4 46.9 46.4 45.7 45.1 44.4 43.7 43.0 42.2 41.5 40.8

95 42.5 43.0 43.4 43.7 43.9 44.0 44.1 44.1 44.0 43.9 43.7 43.5 43.2 43.0 42.7 42.3 42.0 41.6 41.2 40.8

98 42.1 42.2 42.2 42.2 42.2 42.2 42.2 42.1 42.1 42.0 41.9 41.8 41.7 41.6 41.5 41.4 41.2 41.1 40.9 40.8

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.25-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 5
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 91.4 93.0 92.4 90.8 88.5 85.9 83.0 80.1 77.2 74.4 71.6 69.1 66.7 64.4 62.3 60.2 58.3 56.5 54.8 53.2

35 87.7 90.5 90.4 89.2 87.2 84.8 82.2 79.5 76.7 73.9 71.3 68.8 66.5 64.2 62.1 60.2 58.3 56.5 54.8 53.2

40 83.8 87.6 88.1 87.2 85.7 83.6 81.2 78.7 76.0 73.4 70.9 68.5 66.2 64.1 62.0 60.0 58.2 56.4 54.8 53.2

45 80.0 84.4 85.6 85.1 83.9 82.2 80.0 77.7 75.3 72.8 70.4 68.1 65.9 63.8 61.8 59.9 58.1 56.4 54.7 53.2

50 76.0 81.1 82.7 82.8 82.0 80.5 78.7 76.6 74.4 72.1 69.8 67.7 65.6 63.5 61.6 59.8 58.0 56.3 54.7 53.2

55 72.3 77.7 79.7 80.2 79.8 78.7 77.2 75.3 73.3 71.2 69.2 67.1 65.1 63.2 61.3 59.6 57.9 56.2 54.7 53.2

60 68.9 74.2 76.5 77.4 77.4 76.6 75.4 73.9 72.1 70.2 68.3 66.4 64.6 62.8 61.0 59.3 57.7 56.1 54.6 53.2

65 65.5 70.7 73.3 74.5 74.7 74.4 73.5 72.2 70.7 69.1 67.4 65.7 64.0 62.3 60.7 59.1 57.5 56.0 54.6 53.2

70 62.6 67.4 70.0 71.3 71.9 71.8 71.2 70.3 69.1 67.7 66.3 64.7 63.2 61.7 60.2 58.7 57.3 55.9 54.5 53.2

75 60.1 64.2 66.7 68.1 68.8 68.9 68.7 68.0 67.1 66.1 64.9 63.6 62.3 60.9 59.6 58.3 57.0 55.7 54.4 53.2

80 58.0 61.3 63.5 64.8 65.5 65.9 65.8 65.4 64.8 64.0 63.1 62.1 61.1 60.0 58.9 57.7 56.6 55.4 54.3 53.2

85 56.4 58.8 60.4 61.5 62.2 62.5 62.6 62.4 62.0 61.6 61.0 60.3 59.5 58.7 57.9 57.0 56.0 55.1 54.1 53.2

90 55.1 56.4 57.4 58.1 58.6 58.9 59.0 59.0 58.9 58.7 58.4 58.0 57.6 57.1 56.5 55.9 55.3 54.6 53.9 53.2

95 53.7 54.2 54.6 54.9 55.2 55.4 55.5 55.6 55.6 55.5 55.5 55.3 55.2 55.0 54.7 54.5 54.2 53.9 53.5 53.2

98 53.9 54.0 54.0 54.1 54.1 54.1 54.1 54.1 54.1 54.0 54.0 53.9 53.9 53.8 53.7 53.6 53.5 53.4 53.3 53.2

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 93.5 94.8 94.6 93.7 92.3 90.6 88.7 86.5 84.3 82.1 79.8 77.6 75.4 73.3 71.3 69.4 67.5 65.8 64.1 62.5

35 90.2 92.6 92.9 92.3 91.1 89.6 87.8 85.9 83.8 81.6 79.5 77.3 75.2 73.1 71.2 69.3 67.5 65.7 64.0 62.5

40 87.0 90.2 91.0 90.7 89.7 88.4 86.8 85.0 83.1 81.1 79.0 77.0 74.9 72.9 71.0 69.1 67.4 65.7 64.0 62.5

45 83.7 87.6 88.8 88.8 88.1 87.1 85.7 84.1 82.3 80.4 78.5 76.5 74.6 72.7 70.8 69.0 67.3 65.6 64.0 62.5

50 80.5 84.8 86.4 86.8 86.4 85.5 84.4 83.0 81.4 79.7 77.9 76.0 74.2 72.3 70.5 68.8 67.1 65.5 64.0 62.5

55 77.3 82.0 83.9 84.5 84.4 83.9 83.0 81.8 80.3 78.8 77.1 75.4 73.7 72.0 70.3 68.6 67.0 65.4 63.9 62.5

60 74.4 79.1 81.1 82.0 82.2 82.0 81.3 80.3 79.2 77.8 76.3 74.7 73.1 71.5 69.9 68.3 66.8 65.3 63.9 62.5

65 71.8 76.1 78.3 79.5 79.9 79.9 79.5 78.7 77.8 76.6 75.3 73.9 72.4 71.0 69.5 68.0 66.6 65.2 63.8 62.5

70 69.2 73.2 75.5 76.8 77.4 77.6 77.4 76.9 76.2 75.3 74.2 72.9 71.6 70.3 69.0 67.7 66.3 65.0 63.7 62.5

75 67.0 70.6 72.8 74.1 74.8 75.1 75.1 74.8 74.3 73.6 72.7 71.7 70.7 69.5 68.4 67.2 66.0 64.8 63.6 62.5

80 65.3 68.1 70.0 71.3 72.1 72.5 72.6 72.5 72.2 71.7 71.0 70.3 69.4 68.5 67.6 66.6 65.6 64.5 63.5 62.5

85 63.9 66.0 67.5 68.6 69.3 69.7 69.9 69.9 69.8 69.5 69.0 68.5 67.9 67.2 66.5 65.8 65.0 64.2 63.3 62.5

90 63.0 64.3 65.2 65.9 66.4 66.8 67.0 67.1 67.0 66.9 66.7 66.4 66.1 65.7 65.2 64.7 64.2 63.6 63.1 62.5

95 62.3 62.8 63.1 63.4 63.6 63.8 63.9 64.0 64.1 64.1 64.1 64.0 63.9 63.8 63.6 63.4 63.2 63.0 62.7 62.5

98 62.6 62.7 62.8 62.8 62.9 62.9 62.9 62.9 62.9 62.9 62.9 62.9 62.9 62.8 62.8 62.7 62.7 62.6 62.5 62.5

Mean Annual Mass Removal Efficiencies for 1.00-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 95.1 96.1 96.0 95.4 94.5 93.3 91.9 90.4 88.7 86.9 85.1 83.3 81.5 79.7 77.8 76.1 74.4 72.7 71.1 69.5

35 92.3 94.2 94.5 94.2 93.4 92.4 91.1 89.7 88.2 86.5 84.8 83.0 81.2 79.5 77.7 76.0 74.3 72.6 71.1 69.5

40 89.3 92.0 92.8 92.8 92.2 91.3 90.2 88.9 87.5 85.9 84.3 82.6 80.9 79.2 77.5 75.8 74.2 72.6 71.0 69.5

45 86.5 89.8 90.9 91.2 90.9 90.1 89.2 88.0 86.7 85.3 83.8 82.2 80.6 78.9 77.3 75.7 74.1 72.5 71.0 69.5

50 83.8 87.5 88.9 89.5 89.3 88.8 88.0 87.0 85.8 84.5 83.1 81.7 80.2 78.6 77.0 75.5 73.9 72.4 71.0 69.5

55 81.2 85.1 86.8 87.5 87.5 87.2 86.6 85.8 84.8 83.7 82.4 81.1 79.7 78.2 76.7 75.3 73.8 72.3 70.9 69.5

60 78.6 82.7 84.6 85.4 85.6 85.5 85.1 84.5 83.7 82.7 81.6 80.4 79.1 77.8 76.4 75.0 73.6 72.2 70.9 69.5

65 76.4 80.3 82.2 83.1 83.6 83.7 83.5 83.1 82.4 81.6 80.7 79.6 78.5 77.2 76.0 74.7 73.4 72.1 70.8 69.5

70 74.3 77.7 79.7 80.8 81.5 81.7 81.7 81.4 80.9 80.3 79.5 78.7 77.7 76.6 75.4 74.3 73.1 71.9 70.7 69.5

75 72.4 75.4 77.3 78.5 79.2 79.6 79.7 79.6 79.3 78.8 78.2 77.5 76.7 75.8 74.8 73.8 72.7 71.7 70.6 69.5

80 70.8 73.3 75.1 76.2 76.9 77.4 77.6 77.6 77.4 77.1 76.7 76.2 75.5 74.8 74.0 73.2 72.3 71.4 70.5 69.5

85 69.8 71.6 72.9 73.9 74.6 75.0 75.3 75.4 75.4 75.2 75.0 74.6 74.1 73.6 73.0 72.4 71.7 71.0 70.3 69.5

90 69.2 70.3 71.1 71.8 72.3 72.6 72.9 73.0 73.1 73.1 72.9 72.7 72.5 72.2 71.8 71.4 71.0 70.5 70.0 69.5

95 68.9 69.3 69.7 70.0 70.2 70.4 70.5 70.6 70.7 70.7 70.7 70.7 70.6 70.5 70.4 70.3 70.1 69.9 69.7 69.5

98 69.4 69.5 69.6 69.6 69.7 69.7 69.8 69.8 69.8 69.8 69.8 69.8 69.8 69.8 69.7 69.7 69.7 69.6 69.6 69.5

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 96.3 97.1 97.0 96.5 95.9 95.0 93.9 92.8 91.5 90.2 88.7 87.2 85.7 84.1 82.6 81.1 79.5 78.0 76.5 75.1

35 93.9 95.4 95.6 95.4 95.0 94.2 93.2 92.2 91.0 89.7 88.3 86.9 85.4 83.9 82.4 81.0 79.5 78.0 76.5 75.1

40 91.3 93.5 94.1 94.2 93.9 93.3 92.4 91.5 90.4 89.2 87.9 86.5 85.1 83.7 82.3 80.8 79.4 77.9 76.5 75.1

45 88.8 91.5 92.5 92.8 92.7 92.2 91.5 90.6 89.6 88.6 87.4 86.1 84.8 83.4 82.0 80.6 79.2 77.8 76.4 75.1

50 86.4 89.6 90.8 91.3 91.4 91.0 90.4 89.7 88.8 87.9 86.8 85.6 84.4 83.1 81.8 80.4 79.1 77.7 76.4 75.1

55 84.2 87.5 89.0 89.7 89.8 89.6 89.2 88.6 87.9 87.1 86.1 85.0 83.9 82.7 81.5 80.2 78.9 77.6 76.3 75.1

60 81.9 85.4 87.1 87.9 88.2 88.1 87.9 87.4 86.9 86.2 85.3 84.4 83.3 82.2 81.1 79.9 78.7 77.5 76.3 75.1

65 80.0 83.4 85.1 86.0 86.4 86.5 86.4 86.1 85.7 85.1 84.4 83.6 82.7 81.7 80.7 79.6 78.5 77.4 76.2 75.1

70 78.3 81.3 83.0 84.0 84.5 84.8 84.8 84.7 84.4 83.9 83.4 82.7 81.9 81.1 80.2 79.3 78.2 77.2 76.1 75.1

75 76.6 79.3 80.9 81.9 82.6 83.0 83.1 83.1 82.9 82.6 82.2 81.6 81.0 80.4 79.6 78.8 77.9 77.0 76.0 75.1

80 75.3 77.4 78.9 79.9 80.6 81.1 81.3 81.4 81.3 81.1 80.8 80.4 80.0 79.5 78.9 78.2 77.5 76.7 75.9 75.1

85 74.4 76.0 77.2 78.0 78.7 79.1 79.4 79.5 79.5 79.5 79.3 79.1 78.8 78.4 78.0 77.5 76.9 76.3 75.7 75.1

90 73.9 74.9 75.7 76.3 76.8 77.1 77.4 77.6 77.7 77.7 77.7 77.6 77.4 77.2 76.9 76.6 76.3 75.9 75.5 75.1

95 74.0 74.4 74.7 75.0 75.2 75.4 75.6 75.7 75.8 75.9 75.9 75.9 75.9 75.8 75.7 75.6 75.5 75.4 75.2 75.1

98 74.8 74.9 75.0 75.0 75.1 75.1 75.1 75.2 75.2 75.2 75.2 75.2 75.2 75.2 75.2 75.2 75.2 75.1 75.1 75.1

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.50-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.25-inches of Retention for Zone 5
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 97.2 97.7 97.7 97.4 96.8 96.2 95.4 94.4 93.5 92.4 91.2 90.0 88.7 87.4 86.1 84.8 83.4 82.1 80.8 79.4

35 95.1 96.3 96.6 96.4 96.0 95.5 94.7 93.9 93.0 91.9 90.8 89.7 88.5 87.2 85.9 84.6 83.3 82.0 80.7 79.4

40 92.9 94.7 95.2 95.2 95.0 94.6 94.0 93.2 92.4 91.4 90.4 89.3 88.2 87.0 85.7 84.5 83.2 82.0 80.7 79.4

45 90.7 93.0 93.7 94.0 94.0 93.7 93.2 92.5 91.7 90.9 89.9 88.9 87.8 86.7 85.5 84.3 83.1 81.9 80.7 79.4

50 88.5 91.2 92.2 92.7 92.8 92.6 92.2 91.7 91.0 90.2 89.4 88.4 87.4 86.4 85.3 84.1 83.0 81.8 80.6 79.4

55 86.5 89.4 90.7 91.3 91.5 91.5 91.2 90.7 90.2 89.5 88.7 87.9 87.0 86.0 85.0 83.9 82.8 81.7 80.6 79.4

60 84.6 87.5 89.0 89.8 90.2 90.2 90.0 89.6 89.2 88.6 88.0 87.3 86.4 85.6 84.6 83.6 82.6 81.6 80.5 79.4

65 82.9 85.8 87.4 88.3 88.6 88.7 88.7 88.5 88.1 87.7 87.2 86.6 85.8 85.1 84.2 83.3 82.4 81.4 80.5 79.4

70 81.4 84.1 85.6 86.5 87.0 87.2 87.2 87.2 87.0 86.6 86.2 85.7 85.1 84.5 83.7 83.0 82.1 81.3 80.4 79.4

75 80.2 82.4 83.8 84.7 85.2 85.6 85.8 85.8 85.7 85.5 85.2 84.8 84.3 83.8 83.2 82.5 81.8 81.1 80.3 79.4

80 78.9 80.8 82.0 82.9 83.5 84.0 84.2 84.3 84.3 84.2 84.0 83.7 83.4 83.0 82.5 82.0 81.4 80.8 80.1 79.4

85 78.1 79.5 80.5 81.3 81.9 82.3 82.6 82.8 82.8 82.8 82.7 82.5 82.3 82.1 81.7 81.4 81.0 80.5 80.0 79.4

90 77.8 78.6 79.3 79.9 80.4 80.7 80.9 81.1 81.2 81.3 81.3 81.2 81.1 81.0 80.9 80.6 80.4 80.1 79.8 79.4

95 78.0 78.4 78.7 78.9 79.1 79.3 79.5 79.6 79.7 79.8 79.9 79.9 79.9 79.9 79.9 79.8 79.8 79.7 79.6 79.4

98 79.0 79.0 79.1 79.2 79.2 79.3 79.3 79.4 79.4 79.4 79.5 79.5 79.5 79.5 79.5 79.5 79.5 79.5 79.5 79.4

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 97.8 98.3 98.3 98.0 97.5 97.0 96.4 95.6 94.8 93.9 93.0 92.0 91.0 89.9 88.7 87.6 86.4 85.2 84.0 82.9

35 96.2 97.1 97.3 97.1 96.8 96.3 95.8 95.1 94.4 93.6 92.7 91.7 90.7 89.7 88.6 87.4 86.3 85.2 84.0 82.9

40 94.3 95.7 96.1 96.1 95.9 95.6 95.2 94.5 93.8 93.1 92.3 91.4 90.4 89.4 88.4 87.3 86.2 85.1 84.0 82.9

45 92.3 94.2 94.8 95.0 94.9 94.8 94.4 93.9 93.3 92.6 91.8 91.0 90.1 89.2 88.2 87.1 86.1 85.0 83.9 82.9

50 90.3 92.5 93.4 93.8 93.9 93.8 93.6 93.1 92.6 92.0 91.3 90.5 89.7 88.8 87.9 87.0 86.0 84.9 83.9 82.9

55 88.4 90.9 92.0 92.6 92.8 92.8 92.6 92.3 91.8 91.3 90.7 90.0 89.3 88.5 87.6 86.7 85.8 84.8 83.9 82.9

60 86.8 89.3 90.6 91.3 91.6 91.7 91.6 91.3 91.0 90.6 90.0 89.4 88.8 88.1 87.3 86.5 85.6 84.7 83.8 82.9

65 85.3 87.7 89.1 90.0 90.4 90.5 90.5 90.3 90.0 89.7 89.3 88.8 88.2 87.6 86.9 86.2 85.4 84.6 83.7 82.9

70 83.9 86.3 87.7 88.5 88.9 89.2 89.2 89.1 89.0 88.8 88.4 88.0 87.6 87.1 86.5 85.8 85.1 84.4 83.7 82.9

75 82.9 84.9 86.2 87.0 87.4 87.7 87.9 87.9 87.9 87.7 87.5 87.2 86.9 86.4 86.0 85.4 84.8 84.2 83.6 82.9

80 81.9 83.5 84.6 85.4 85.9 86.3 86.5 86.7 86.7 86.6 86.5 86.3 86.1 85.7 85.4 84.9 84.5 84.0 83.4 82.9

85 81.1 82.3 83.3 84.0 84.5 84.9 85.1 85.3 85.4 85.4 85.4 85.3 85.1 84.9 84.7 84.4 84.1 83.7 83.3 82.9

90 80.9 81.7 82.3 82.8 83.2 83.5 83.8 84.0 84.1 84.2 84.2 84.2 84.1 84.0 83.9 83.8 83.6 83.4 83.1 82.9

95 81.3 81.6 81.9 82.1 82.3 82.5 82.6 82.8 82.9 83.0 83.0 83.1 83.1 83.1 83.1 83.1 83.1 83.0 82.9 82.9

98 82.3 82.3 82.4 82.5 82.5 82.6 82.6 82.7 82.7 82.7 82.8 82.8 82.8 82.8 82.9 82.9 82.9 82.9 82.9 82.9

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 1.75-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.00-inches of Retention for Zone 5
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.2 98.7 98.6 98.5 98.1 97.6 97.1 96.5 95.9 95.1 94.3 93.5 92.6 91.7 90.7 89.7 88.7 87.7 86.6 85.6

35 97.0 97.7 97.8 97.7 97.5 97.0 96.6 96.1 95.4 94.7 94.0 93.2 92.4 91.5 90.6 89.6 88.6 87.6 86.6 85.6

40 95.3 96.5 96.9 96.8 96.6 96.3 96.0 95.5 95.0 94.3 93.6 92.9 92.1 91.3 90.4 89.5 88.5 87.6 86.6 85.6

45 93.6 95.2 95.7 95.8 95.7 95.6 95.3 94.9 94.4 93.9 93.2 92.6 91.8 91.0 90.2 89.3 88.4 87.5 86.5 85.6

50 91.9 93.7 94.5 94.7 94.8 94.8 94.6 94.3 93.8 93.3 92.8 92.1 91.5 90.7 90.0 89.1 88.3 87.4 86.5 85.6

55 90.1 92.2 93.2 93.6 93.8 93.9 93.8 93.5 93.2 92.7 92.2 91.7 91.1 90.4 89.7 88.9 88.1 87.3 86.5 85.6

60 88.6 90.8 91.9 92.5 92.8 92.9 92.9 92.7 92.4 92.0 91.6 91.1 90.6 90.0 89.4 88.7 88.0 87.2 86.4 85.6

65 87.2 89.4 90.6 91.3 91.7 91.9 91.9 91.8 91.6 91.3 90.9 90.6 90.1 89.6 89.0 88.4 87.8 87.1 86.3 85.6

70 86.0 88.1 89.3 90.1 90.6 90.8 90.8 90.8 90.6 90.4 90.2 89.9 89.5 89.1 88.6 88.1 87.5 86.9 86.3 85.6

75 85.1 87.0 88.1 88.8 89.3 89.5 89.6 89.7 89.6 89.6 89.4 89.1 88.9 88.5 88.2 87.7 87.2 86.7 86.2 85.6

80 84.5 85.8 86.8 87.5 87.9 88.2 88.4 88.6 88.6 88.6 88.5 88.3 88.1 87.9 87.6 87.3 86.9 86.5 86.1 85.6

85 83.8 84.8 85.6 86.1 86.6 87.0 87.2 87.4 87.5 87.5 87.5 87.5 87.4 87.2 87.0 86.8 86.5 86.3 85.9 85.6

90 83.5 84.2 84.7 85.2 85.6 85.8 86.1 86.2 86.4 86.5 86.5 86.5 86.5 86.5 86.4 86.3 86.1 86.0 85.8 85.6

95 83.9 84.2 84.5 84.7 84.9 85.1 85.2 85.3 85.4 85.5 85.6 85.6 85.7 85.7 85.7 85.7 85.7 85.7 85.6 85.6

98 84.9 85.0 85.1 85.1 85.2 85.2 85.3 85.3 85.4 85.4 85.4 85.5 85.5 85.5 85.5 85.5 85.6 85.6 85.6 85.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.6 98.9 98.9 98.8 98.6 98.2 97.7 97.2 96.7 96.0 95.3 94.6 93.9 93.1 92.3 91.4 90.6 89.6 88.7 87.8

35 97.6 98.1 98.3 98.2 98.0 97.6 97.2 96.8 96.3 95.7 95.0 94.4 93.7 92.9 92.1 91.3 90.5 89.6 88.7 87.8

40 96.2 97.1 97.4 97.4 97.3 97.0 96.7 96.3 95.9 95.3 94.7 94.1 93.4 92.7 92.0 91.2 90.4 89.5 88.7 87.8

45 94.7 96.0 96.5 96.5 96.5 96.3 96.0 95.8 95.4 94.9 94.3 93.8 93.2 92.5 91.8 91.0 90.3 89.5 88.6 87.8

50 93.2 94.8 95.3 95.6 95.6 95.5 95.4 95.2 94.8 94.4 93.9 93.4 92.8 92.2 91.6 90.9 90.1 89.4 88.6 87.8

55 91.6 93.4 94.2 94.5 94.7 94.7 94.7 94.5 94.2 93.9 93.4 93.0 92.5 91.9 91.3 90.7 90.0 89.3 88.5 87.8

60 90.1 92.0 93.0 93.5 93.8 93.9 93.9 93.8 93.5 93.2 92.9 92.5 92.0 91.6 91.0 90.4 89.8 89.2 88.5 87.8

65 88.9 90.8 91.8 92.4 92.8 93.0 93.1 93.0 92.8 92.6 92.3 92.0 91.6 91.2 90.7 90.2 89.6 89.1 88.4 87.8

70 87.8 89.6 90.7 91.4 91.8 92.1 92.1 92.1 92.0 91.8 91.6 91.4 91.1 90.7 90.3 89.9 89.4 88.9 88.4 87.8

75 86.9 88.6 89.6 90.3 90.8 91.0 91.1 91.1 91.1 91.0 90.9 90.7 90.5 90.2 89.9 89.5 89.2 88.7 88.3 87.8

80 86.4 87.7 88.6 89.2 89.6 89.9 90.0 90.1 90.2 90.2 90.1 90.0 89.8 89.7 89.4 89.2 88.9 88.5 88.2 87.8

85 85.9 86.9 87.5 88.0 88.4 88.7 88.9 89.1 89.2 89.3 89.3 89.2 89.2 89.1 88.9 88.8 88.6 88.3 88.1 87.8

90 85.6 86.2 86.7 87.1 87.5 87.8 88.0 88.1 88.3 88.4 88.4 88.4 88.4 88.4 88.4 88.3 88.2 88.1 87.9 87.8

95 86.1 86.4 86.6 86.8 87.0 87.1 87.3 87.4 87.5 87.6 87.7 87.7 87.8 87.8 87.8 87.8 87.8 87.8 87.8 87.8

98 87.1 87.2 87.2 87.3 87.3 87.4 87.4 87.5 87.5 87.6 87.6 87.6 87.7 87.7 87.7 87.7 87.7 87.8 87.8 87.8

Mean Annual Mass Removal Efficiencies for 2.50-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.25-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 98.9 99.1 99.1 99.1 98.9 98.6 98.2 97.8 97.3 96.7 96.2 95.5 94.9 94.2 93.5 92.8 92.0 91.2 90.4 89.6

35 98.1 98.5 98.6 98.6 98.4 98.1 97.7 97.4 96.9 96.4 95.9 95.3 94.7 94.1 93.4 92.7 91.9 91.2 90.4 89.6

40 97.0 97.7 97.9 97.9 97.8 97.5 97.2 96.9 96.5 96.1 95.6 95.0 94.5 93.9 93.2 92.5 91.8 91.1 90.3 89.6

45 95.6 96.7 97.1 97.1 97.1 96.9 96.6 96.4 96.1 95.7 95.2 94.7 94.2 93.6 93.0 92.4 91.7 91.0 90.3 89.6

50 94.3 95.6 96.1 96.3 96.3 96.2 96.0 95.8 95.6 95.3 94.9 94.4 93.9 93.4 92.8 92.2 91.6 91.0 90.3 89.6

55 92.9 94.4 95.0 95.3 95.4 95.4 95.4 95.3 95.1 94.8 94.4 94.0 93.6 93.1 92.6 92.1 91.5 90.9 90.2 89.6

60 91.6 93.2 93.9 94.3 94.6 94.7 94.7 94.6 94.5 94.2 93.9 93.6 93.2 92.8 92.3 91.8 91.3 90.8 90.2 89.6

65 90.3 92.0 92.8 93.4 93.7 93.9 94.0 93.9 93.8 93.6 93.4 93.1 92.8 92.4 92.0 91.6 91.1 90.6 90.1 89.6

70 89.3 90.9 91.8 92.4 92.8 93.1 93.2 93.2 93.1 93.0 92.8 92.6 92.3 92.0 91.7 91.3 90.9 90.5 90.1 89.6

75 88.5 89.9 90.9 91.5 91.9 92.2 92.3 92.4 92.3 92.2 92.1 92.0 91.8 91.6 91.3 91.0 90.7 90.4 90.0 89.6

80 88.1 89.2 90.0 90.6 91.0 91.2 91.4 91.5 91.5 91.5 91.4 91.4 91.3 91.1 90.9 90.7 90.5 90.2 89.9 89.6

85 87.8 88.6 89.2 89.6 90.0 90.2 90.4 90.5 90.6 90.7 90.7 90.7 90.7 90.6 90.5 90.3 90.2 90.0 89.8 89.6

90 87.5 88.0 88.4 88.8 89.1 89.3 89.5 89.7 89.8 89.9 90.0 90.0 90.0 90.0 90.0 89.9 89.9 89.8 89.7 89.6

95 87.9 88.2 88.4 88.6 88.7 88.9 89.0 89.1 89.2 89.3 89.4 89.4 89.5 89.5 89.5 89.6 89.6 89.6 89.6 89.6

98 88.9 88.9 89.0 89.0 89.1 89.1 89.2 89.2 89.3 89.3 89.4 89.4 89.4 89.5 89.5 89.5 89.5 89.5 89.6 89.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.1 99.3 99.3 99.2 99.1 98.9 98.6 98.2 97.8 97.3 96.8 96.3 95.7 95.1 94.5 93.8 93.2 92.5 91.8 91.0

35 98.4 98.8 98.9 98.8 98.7 98.5 98.2 97.8 97.5 97.0 96.6 96.1 95.5 94.9 94.4 93.7 93.1 92.4 91.7 91.0

40 97.5 98.1 98.3 98.3 98.2 98.0 97.7 97.4 97.1 96.7 96.3 95.8 95.3 94.8 94.2 93.6 93.0 92.4 91.7 91.0

45 96.4 97.3 97.6 97.6 97.6 97.4 97.2 96.9 96.7 96.4 96.0 95.5 95.1 94.6 94.0 93.5 92.9 92.3 91.7 91.0

50 95.2 96.3 96.7 96.9 96.9 96.8 96.6 96.4 96.2 96.0 95.6 95.2 94.8 94.3 93.9 93.4 92.8 92.2 91.6 91.0

55 94.0 95.3 95.8 96.0 96.1 96.1 96.0 95.9 95.7 95.5 95.2 94.9 94.5 94.1 93.6 93.2 92.7 92.2 91.6 91.0

60 92.8 94.1 94.8 95.1 95.3 95.4 95.4 95.3 95.2 95.0 94.8 94.5 94.1 93.8 93.4 93.0 92.5 92.1 91.6 91.0

65 91.7 93.0 93.8 94.2 94.5 94.6 94.7 94.7 94.6 94.5 94.3 94.0 93.8 93.5 93.1 92.8 92.4 91.9 91.5 91.0

70 90.7 92.0 92.8 93.3 93.7 93.9 94.0 94.1 94.0 93.9 93.8 93.6 93.3 93.1 92.8 92.5 92.2 91.8 91.4 91.0

75 89.9 91.1 91.9 92.5 92.9 93.2 93.3 93.3 93.3 93.3 93.2 93.0 92.9 92.7 92.5 92.3 92.0 91.7 91.4 91.0

80 89.4 90.5 91.2 91.7 92.1 92.3 92.5 92.6 92.6 92.6 92.5 92.5 92.4 92.3 92.1 92.0 91.8 91.5 91.3 91.0

85 89.3 90.0 90.5 90.9 91.3 91.5 91.6 91.8 91.8 91.9 91.9 91.9 91.9 91.8 91.7 91.6 91.5 91.4 91.2 91.0

90 89.1 89.6 89.9 90.2 90.5 90.7 90.9 91.0 91.1 91.2 91.3 91.3 91.3 91.4 91.3 91.3 91.3 91.2 91.1 91.0

95 89.5 89.7 89.9 90.0 90.2 90.3 90.4 90.5 90.6 90.7 90.8 90.8 90.9 90.9 91.0 91.0 91.0 91.0 91.0 91.0

98 90.3 90.4 90.5 90.5 90.6 90.6 90.6 90.7 90.7 90.8 90.8 90.8 90.9 90.9 90.9 90.9 91.0 91.0 91.0 91.0

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.00-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 2.75-inches of Retention for Zone 5
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.3 99.4 99.5 99.4 99.3 99.1 98.9 98.6 98.2 97.8 97.4 96.9 96.4 95.8 95.3 94.7 94.1 93.5 92.9 92.2

35 98.7 99.0 99.1 99.0 99.0 98.8 98.5 98.2 97.9 97.5 97.1 96.7 96.2 95.7 95.2 94.6 94.1 93.5 92.9 92.2

40 98.0 98.4 98.6 98.6 98.5 98.4 98.1 97.8 97.5 97.2 96.9 96.5 96.0 95.5 95.0 94.5 94.0 93.4 92.8 92.2

45 97.0 97.7 98.0 98.0 98.0 97.8 97.7 97.4 97.1 96.9 96.6 96.2 95.8 95.3 94.9 94.4 93.9 93.4 92.8 92.2

50 96.0 96.9 97.3 97.4 97.4 97.3 97.1 96.9 96.7 96.5 96.3 95.9 95.5 95.1 94.7 94.3 93.8 93.3 92.8 92.2

55 94.9 96.0 96.4 96.6 96.7 96.7 96.6 96.4 96.3 96.1 95.9 95.6 95.3 94.9 94.5 94.1 93.7 93.2 92.7 92.2

60 93.9 95.0 95.5 95.8 96.0 96.0 96.0 95.9 95.8 95.7 95.5 95.2 94.9 94.6 94.3 93.9 93.5 93.1 92.7 92.2

65 92.8 94.0 94.6 95.0 95.2 95.3 95.4 95.4 95.3 95.2 95.0 94.8 94.6 94.3 94.0 93.7 93.4 93.0 92.6 92.2

70 91.9 93.0 93.7 94.1 94.4 94.6 94.8 94.8 94.8 94.7 94.6 94.4 94.2 94.0 93.8 93.5 93.2 92.9 92.6 92.2

75 91.1 92.2 92.9 93.4 93.7 94.0 94.1 94.2 94.2 94.1 94.1 94.0 93.8 93.6 93.5 93.3 93.0 92.8 92.5 92.2

80 90.6 91.5 92.2 92.7 93.0 93.3 93.4 93.5 93.5 93.6 93.5 93.4 93.4 93.3 93.2 93.0 92.8 92.6 92.4 92.2

85 90.5 91.2 91.7 92.0 92.3 92.5 92.7 92.8 92.9 92.9 92.9 92.9 92.9 92.9 92.8 92.7 92.6 92.5 92.4 92.2

90 90.5 90.9 91.2 91.5 91.7 91.9 92.0 92.1 92.2 92.3 92.4 92.4 92.4 92.5 92.4 92.4 92.4 92.3 92.3 92.2

95 90.7 90.9 91.1 91.2 91.4 91.5 91.6 91.7 91.8 91.9 92.0 92.0 92.1 92.1 92.1 92.2 92.2 92.2 92.2 92.2

98 91.6 91.6 91.7 91.7 91.8 91.8 91.8 91.9 91.9 92.0 92.0 92.0 92.1 92.1 92.1 92.1 92.2 92.2 92.2 92.2

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.5 99.6 99.6 99.5 99.4 99.3 99.1 98.9 98.5 98.2 97.8 97.4 96.9 96.5 96.0 95.4 94.9 94.4 93.8 93.2

35 98.9 99.2 99.2 99.2 99.1 99.0 98.8 98.6 98.3 97.9 97.6 97.2 96.8 96.3 95.8 95.4 94.9 94.3 93.8 93.2

40 98.3 98.7 98.8 98.8 98.8 98.7 98.5 98.2 97.9 97.6 97.3 97.0 96.6 96.2 95.7 95.3 94.8 94.3 93.8 93.2

45 97.5 98.1 98.3 98.4 98.3 98.2 98.0 97.8 97.6 97.3 97.1 96.8 96.4 96.0 95.6 95.1 94.7 94.2 93.7 93.2

50 96.6 97.4 97.7 97.8 97.8 97.7 97.6 97.4 97.2 97.0 96.7 96.5 96.1 95.8 95.4 95.0 94.6 94.2 93.7 93.2

55 95.7 96.6 97.0 97.2 97.2 97.2 97.1 96.9 96.8 96.6 96.4 96.2 95.9 95.6 95.2 94.9 94.5 94.1 93.7 93.2

60 94.8 95.8 96.2 96.4 96.5 96.5 96.5 96.4 96.3 96.2 96.1 95.9 95.6 95.3 95.0 94.7 94.4 94.0 93.6 93.2

65 93.8 94.8 95.4 95.7 95.8 95.9 95.9 95.9 95.9 95.8 95.7 95.5 95.3 95.1 94.8 94.5 94.2 93.9 93.6 93.2

70 93.0 94.0 94.5 94.9 95.1 95.3 95.4 95.4 95.4 95.4 95.3 95.1 95.0 94.8 94.5 94.3 94.1 93.8 93.5 93.2

75 92.2 93.1 93.7 94.1 94.4 94.7 94.8 94.9 94.9 94.9 94.8 94.7 94.6 94.4 94.3 94.1 93.9 93.7 93.5 93.2

80 91.7 92.5 93.1 93.5 93.8 94.1 94.2 94.3 94.3 94.3 94.3 94.3 94.2 94.1 94.0 93.9 93.7 93.6 93.4 93.2

85 91.5 92.1 92.6 93.0 93.2 93.4 93.6 93.7 93.7 93.8 93.8 93.8 93.8 93.7 93.7 93.6 93.6 93.5 93.3 93.2

90 91.6 91.9 92.2 92.5 92.7 92.9 93.0 93.1 93.2 93.2 93.3 93.3 93.4 93.4 93.4 93.4 93.4 93.3 93.3 93.2

95 91.9 92.0 92.2 92.3 92.4 92.5 92.6 92.7 92.8 92.9 92.9 93.0 93.1 93.1 93.1 93.2 93.2 93.2 93.2 93.2

98 92.6 92.6 92.7 92.7 92.8 92.8 92.9 92.9 92.9 93.0 93.0 93.0 93.1 93.1 93.1 93.1 93.2 93.2 93.2 93.2

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.25-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.50-inches of Retention for Zone 5
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.7 99.7 99.7 99.6 99.5 99.4 99.3 99.1 98.8 98.5 98.2 97.8 97.4 97.0 96.5 96.1 95.6 95.1 94.6 94.1

35 99.1 99.3 99.4 99.3 99.3 99.2 99.0 98.8 98.6 98.3 98.0 97.6 97.3 96.9 96.4 96.0 95.5 95.1 94.6 94.1

40 98.6 98.9 99.0 99.0 99.0 98.9 98.7 98.5 98.3 98.0 97.7 97.4 97.1 96.7 96.3 95.9 95.4 95.0 94.5 94.1

45 97.9 98.4 98.6 98.6 98.6 98.5 98.4 98.2 98.0 97.7 97.5 97.2 96.9 96.5 96.2 95.8 95.4 95.0 94.5 94.1

50 97.1 97.8 98.1 98.2 98.2 98.1 98.0 97.8 97.6 97.4 97.2 96.9 96.7 96.4 96.0 95.7 95.3 94.9 94.5 94.1

55 96.4 97.1 97.5 97.6 97.6 97.6 97.5 97.4 97.2 97.0 96.9 96.7 96.4 96.2 95.9 95.5 95.2 94.8 94.5 94.1

60 95.5 96.4 96.8 96.9 97.0 97.0 97.0 96.9 96.8 96.7 96.6 96.4 96.2 95.9 95.7 95.4 95.1 94.7 94.4 94.1

65 94.7 95.5 96.0 96.3 96.4 96.5 96.4 96.4 96.4 96.3 96.2 96.1 95.9 95.7 95.5 95.2 94.9 94.7 94.4 94.1

70 93.9 94.7 95.3 95.5 95.7 95.8 95.9 95.9 95.9 95.9 95.9 95.7 95.6 95.4 95.2 95.0 94.8 94.6 94.3 94.1

75 93.2 94.0 94.5 94.8 95.1 95.2 95.4 95.5 95.5 95.5 95.4 95.4 95.3 95.1 95.0 94.8 94.7 94.5 94.3 94.1

80 92.6 93.3 93.8 94.2 94.5 94.7 94.9 95.0 95.0 95.0 95.0 95.0 94.9 94.8 94.7 94.6 94.5 94.4 94.2 94.1

85 92.5 93.0 93.4 93.8 94.0 94.2 94.3 94.4 94.5 94.5 94.5 94.6 94.5 94.5 94.4 94.4 94.3 94.3 94.2 94.1

90 92.6 92.9 93.1 93.3 93.5 93.7 93.8 93.9 94.0 94.1 94.1 94.1 94.2 94.2 94.2 94.2 94.2 94.1 94.1 94.1

95 92.9 93.0 93.1 93.2 93.3 93.4 93.5 93.6 93.7 93.7 93.8 93.8 93.9 93.9 94.0 94.0 94.0 94.0 94.0 94.1

98 93.5 93.5 93.6 93.6 93.6 93.7 93.7 93.8 93.8 93.8 93.9 93.9 93.9 93.9 94.0 94.0 94.0 94.0 94.0 94.1

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

30 99.8 99.8 99.7 99.7 99.6 99.5 99.4 99.2 99.0 98.8 98.5 98.1 97.8 97.4 97.0 96.6 96.2 95.7 95.2 94.8

35 99.3 99.5 99.5 99.5 99.4 99.3 99.2 99.0 98.8 98.6 98.3 98.0 97.7 97.3 96.9 96.5 96.1 95.7 95.2 94.8

40 98.8 99.1 99.2 99.2 99.1 99.1 99.0 98.8 98.6 98.3 98.1 97.8 97.5 97.2 96.8 96.4 96.0 95.6 95.2 94.8

45 98.3 98.6 98.8 98.8 98.8 98.8 98.6 98.5 98.3 98.1 97.8 97.6 97.3 97.0 96.7 96.3 96.0 95.6 95.2 94.8

50 97.6 98.1 98.4 98.4 98.5 98.4 98.3 98.1 98.0 97.8 97.5 97.3 97.1 96.8 96.5 96.2 95.9 95.5 95.1 94.8

55 96.9 97.6 97.8 98.0 98.0 97.9 97.9 97.7 97.6 97.4 97.3 97.1 96.9 96.7 96.4 96.1 95.8 95.4 95.1 94.8

60 96.2 96.9 97.2 97.4 97.5 97.5 97.4 97.3 97.2 97.1 97.0 96.8 96.7 96.4 96.2 96.0 95.7 95.4 95.1 94.8

65 95.5 96.2 96.6 96.8 96.9 96.9 96.9 96.9 96.8 96.8 96.7 96.6 96.4 96.2 96.0 95.8 95.6 95.3 95.0 94.8

70 94.7 95.4 95.9 96.2 96.3 96.4 96.4 96.4 96.4 96.4 96.3 96.3 96.1 96.0 95.8 95.6 95.4 95.2 95.0 94.8

75 94.1 94.8 95.2 95.5 95.7 95.8 95.9 96.0 96.0 96.0 96.0 95.9 95.8 95.7 95.6 95.5 95.3 95.1 95.0 94.8

80 93.5 94.1 94.5 94.9 95.1 95.3 95.4 95.5 95.6 95.6 95.6 95.6 95.5 95.4 95.4 95.3 95.1 95.0 94.9 94.8

85 93.3 93.8 94.1 94.4 94.7 94.8 95.0 95.1 95.1 95.2 95.2 95.2 95.2 95.2 95.1 95.1 95.0 94.9 94.9 94.8

90 93.4 93.7 93.9 94.1 94.3 94.4 94.5 94.6 94.7 94.8 94.8 94.8 94.8 94.9 94.9 94.9 94.8 94.8 94.8 94.8

95 93.7 93.8 93.9 94.0 94.1 94.2 94.3 94.3 94.4 94.5 94.5 94.6 94.6 94.6 94.7 94.7 94.7 94.7 94.8 94.8

98 94.2 94.3 94.3 94.3 94.4 94.4 94.4 94.5 94.5 94.5 94.6 94.6 94.6 94.6 94.7 94.7 94.7 94.7 94.8 94.8

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 3.75-inches of Retention for Zone 5

NDCIA 

CN

Percent DCIA

Mean Annual Mass Removal Efficiencies for 4.00-inches of Retention for Zone 5