Florida Stormwater Permitting: Nutrient Management and the 2024 ERP Applicant’s Handbook

Florida Department of Environmental Protection · Environmental Resource Permitting Program · 2024

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1. Course Introduction & Objectives

Section 1 of 8 · Source slides 1–2

This course provides a comprehensive overview of stormwater permitting in Florida, with emphasis on nutrient management and its relationship to surface water quality. Participants will gain a working understanding of the regulatory framework, the scientific basis for design standards, and the implementation of the most current state guidance — the 2024 ERP Applicant’s Handbook Volume 1.

Course Overview

Florida’s stormwater permitting system has evolved over more than five decades, driven by growing evidence linking urban runoff to surface water degradation. Understanding this evolution — from early local codes through the current statewide Environmental Resource Permitting (ERP) framework — is essential for practitioners designing, reviewing, or managing stormwater systems in the state.

Key Topics

• Florida stormwater permitting overview — the structure of the Environmental Resource Permitting program and the role of the Florida Department of Environmental Protection (FDEP) and Water Management Districts.
• Nutrient management and surface water impacts — the science connecting nitrogen and phosphorus loading from stormwater to biological impairment in Florida’s lakes, rivers, and coastal waters.
• Local and state program evolution — a chronological review of how stormwater regulations developed from county-level codes in the early 1970s to today’s statewide standards.
• 2024 Applicant’s Handbook Vol. 1 implementation — practical guidance on applying the most current FDEP design criteria for stormwater management systems.

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2. Surface Water Quality & Nutrient Enrichment

Section 2 of 8 · Source slides 3–5

Nutrient enrichment is the primary driver of biological impairment in Florida’s surface waters. Stormwater runoff from developed land delivers nitrogen and phosphorus at rates that far exceed natural background levels, triggering a cascade of ecological responses that degrade water quality, reduce dissolved oxygen, and diminish the recreational and ecological value of water bodies.

Trophic State Index (TSI)

The Trophic State Index (TSI) is a numerical scoring system used to classify the biological productivity — or trophic state — of a water body. Originally developed by Carlson (1977) and adapted for Florida conditions by FDEP, TSI integrates measurements of chlorophyll-a, Secchi disk depth, and total phosphorus to produce a single index value. The TSI is the primary metric Florida uses to assess lake health and to identify water bodies in need of restoration.

TSI Classification Ranges

Florida’s TSI framework divides water bodies into three broad trophic categories, each reflecting a different level of nutrient enrichment and biological productivity:

A high TSI value is a reliable indicator of poor water quality associated with nutrient excess. Eutrophic conditions create conditions favorable to harmful algal blooms, fish kills, and the loss of submerged aquatic vegetation — all of which impair the designated uses of Florida’s water bodies.

Florida Impaired Waters: 2022 FDEP Report

FDEP’s 2022 Integrated Water Quality Assessment Report provides the most current statewide picture of surface water condition. The scale of impairment documented in that report underscores the urgency of effective stormwater nutrient management.

• Nutrients (nitrogen and phosphorus) — the leading cause of impairment; excess loading drives algae blooms, oxygen depletion, and habitat loss.
• Bacteria (fecal coliform and E. coli) — often co-transported with nutrient-laden runoff from urban and agricultural landscapes; results in beach and shellfish harvest closures.
• Dissolved oxygen (DO) — frequently a secondary consequence of nutrient enrichment; decomposing algae blooms consume oxygen, creating hypoxic conditions lethal to fish and invertebrates.

Annual Measurement Basis

Florida’s stormwater rules evaluate both runoff volume and nutrient loading on an annual basis. This approach accounts for the full distribution of storm events across a year — including frequent small storms that individually seem minor but collectively deliver the majority of annual pollutant loads. Designing stormwater systems to capture and treat the range of annual rainfall events, rather than only large design storms, is fundamental to achieving meaningful water quality improvements.

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3. Local Stormwater Programs

Section 3 of 8 · Source slides 6–7

Before Florida enacted statewide stormwater rules, individual counties and municipalities took the initiative to develop local stormwater management codes. Orange County’s program — one of the earliest in the nation — established a technical and regulatory model that influenced subsequent local and eventually state-level programs across Florida.

Orange County’s Pioneering Program

In the early 1970s, Orange County developed one of the first local stormwater management codes in the United States. The program was a direct response to the rapid urbanization of Central Florida and the visible degradation of local lakes and waterways that accompanied development. Rather than simply managing peak flows for flood control — the dominant engineering approach of the era — Orange County’s code explicitly targeted water quality through runoff volume reduction.

The technical basis for this approach — including design guidance, sizing methods, and supporting data — was formally published in 1978. This document provided the engineering community with the tools needed to implement the county’s retention-based stormwater standard and served as a foundational reference for programs that followed.

Spread of Local Programs Across Florida

Orange County’s experience demonstrated that locally enforceable stormwater standards were both technically feasible and effective. Over the following decades, many Florida municipalities and counties developed their own stormwater codes and stormwater management plans, each tailored to local hydrology, soils, and water quality priorities. While these programs varied in their specific requirements, they shared the common goal of reducing the volume and pollutant load of runoff reaching Florida’s lakes, rivers, springs, and estuaries.

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4. Florida State Stormwater Rules History

Section 4 of 8 · Source slides 8–11

Florida’s statewide stormwater regulatory framework developed over nearly four decades, from the nation’s first stormwater quality rule in 1981 through a series of revisions driven by evolving science, administrative restructuring, and ultimately the recognition that existing standards were not achieving their intended water quality outcomes.

Chapter 62-25: The Nation’s First Stormwater Quality Rule (1981)

Florida adopted Chapter 62-25, F.A.C. in 1981 — making it the first statewide stormwater quality rule in the United States. The rule established a performance-based standard centered on the removal of total suspended solids (TSS) as a surrogate for overall pollutant load reduction.

Chapter 62-40 and Water Management District Administration (2005)

In 2005, the stormwater program was reorganized under Chapter 62-40, F.A.C., which assigned primary administrative responsibility to FDEP and the five Water Management Districts. This shift acknowledged the regional diversity of Florida’s hydrology and allowed each District to develop design criteria appropriate to its geographic area.

• FDEP retained overall rulemaking authority and set statewide performance standards.
• Water Management Districts developed regional design criteria and BMP specifications through their individual ERP programs, resulting in varying technical requirements across different parts of the state.

Performance Gap: Research Findings

As research on stormwater BMP performance accumulated through the 1990s and early 2000s, a critical problem emerged: stormwater systems designed and constructed under the existing criteria were not consistently achieving the required pollutant reductions — particularly for nutrients. The TSS-based standard, while straightforward to apply, did not reliably predict nitrogen or phosphorus removal. Systems that met the TSS rule on paper often failed to deliver meaningful nutrient load reductions to receiving waters.

Repeal of Chapter 62-25 (2017)

Chapter 62-25 was formally repealed in 2017, replaced by the new statewide stormwater rule incorporated into the ERP framework. The repeal marked the end of the TSS-based performance standard era and the beginning of a nutrient-focused, scientifically defensible design approach.

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5. ERD Stormwater Effectiveness Study

Section 5 of 8 · Source slides 12–14

The ERD Stormwater Effectiveness Study was the scientific cornerstone of Florida’s transition to a nutrient-based stormwater design standard. Commissioned by FDEP and completed in 2007, the study provided the technical evidence and design tools that ultimately underpinned both the statewide rule revision and the 2024 ERP Applicant’s Handbook.

Background and Commission

In 2006, FDEP contracted Environmental Research & Design, Inc. (ERD) to conduct a rigorous, independent evaluation of the stormwater design criteria then in use across Florida’s Water Management Districts. The central question was whether those criteria — as actually implemented in the field — were achieving the pollutant reduction performance required by Chapter 62-40.

Methodology and Scope

ERD’s analysis evaluated stormwater BMP performance using a combination of field monitoring data, literature review, and modeling. The study examined how different types of BMPs — retention ponds, detention ponds, swales, and others — performed in removing total nitrogen (TN) and total phosphorus (TP) under Florida-specific conditions, including the state’s subtropical rainfall patterns, highly variable soils, and flat topography.

• Nitrogen and phosphorus loading analysis — quantified the pollutant loads generated by different land uses under annual rainfall conditions.
• Removal efficiency evaluation — assessed the actual TN and TP removal achieved by existing BMP designs relative to the loads applied.
• Design methodology development — produced scientifically defensible methods for sizing BMPs to achieve specific nutrient reduction targets.
• Annual rainfall basis — the entire analysis was framed around annual loading and removal, consistent with the regulatory standard.

The 2007 ERD Report

The study’s findings were published in 2007 as a comprehensive technical report. The report included design tables, performance figures, and worked design examples that practitioners could use directly to size and evaluate stormwater BMPs for nutrient removal. Its practical format made it immediately usable by engineers and environmental consultants.

Significance for Current Practice

The ERD study’s lasting contribution was establishing that stormwater BMP design for nutrient removal must be grounded in actual pollutant loading calculations — not simply geometric or hydraulic rules of thumb. By quantifying the relationship between BMP design parameters, rainfall, land use, and nutrient removal, the study created the analytical foundation for Florida’s current stormwater permitting standards.

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Topic 6: Statewide Stormwater Rule Development

Section 6 of 8 — Regulatory History & Rulemaking Process

Background: The Long Road to a Statewide Rule

Florida’s stormwater management framework evolved largely through regional Water Management District (WMD) rules for decades. Efforts to unify these standards at the state level through FDEP’s Environmental Resource Permitting (ERP) program began in earnest in the late 2000s but encountered a prolonged pause before ultimately reaching completion in 2024. Understanding this timeline illuminates why the final rule carries the technical depth it does — and why local practitioners now face a significant transition.

The 2010 Technical Advisory Committee

The first formal statewide rulemaking cycle began with FDEP convening a Technical Advisory Committee (TAC) in 2010. Over the course of that cycle, the TAC held eight meetings, working through technical questions on BMP performance, pollutant loading, water quality targets, and the structure of what would become the Applicant’s Handbook. Draft language was produced and circulated, but the rule effort stalled before reaching final adoption.

The Clean Waterways Act (2020): A Legislative Restart

Florida’s Clean Waterways Act, enacted in 2020, provided the legislative directive that restarted the statewide stormwater rulemaking. The Act tasked FDEP with developing uniform stormwater management standards applicable statewide under the ERP program, with an emphasis on protecting impaired waters and Outstanding Florida Waters (OFWs). This legislative mandate gave the rulemaking process renewed urgency and a clear statutory foundation.

The 2020–2021 Technical Advisory Committee

Following the Clean Waterways Act, FDEP convened a new TAC that met 13 times between 2020 and 2021. This second committee built on the prior decade of BMP research, updated pollutant removal efficiencies, and addressed emerging issues including:

• Revised BMP efficiency data from Florida-specific field studies
• Treatment train approaches combining multiple BMP types
• Compensating treatment mechanisms for sites with geometric or hydrologic constraints
• Integration of impaired water body designations and OFW classifications into performance standards
• Long-term operation and maintenance requirements and cost estimation frameworks

Final TAC Report and Handbook Publication

The 2020–2021 TAC issued its final report in March 2022, providing FDEP with the technical consensus needed to finalize rule language. After the requisite rulemaking procedures, the Applicant’s Handbook Volume I — establishing statewide performance standards and BMP requirements — was officially published on June 28, 2024. Full implementation by all regulated entities is required by December 28, 2025.

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Topic 7: 2024 ERP Applicant’s Handbook & Standards

Section 7 of 8 — Performance Standards, Treatment Requirements & Regional Implementation

Overview of the 2024 Framework

The 2024 ERP Applicant’s Handbook Volume I establishes a tiered performance standard system that moves Florida’s stormwater regulation from a uniform volumetric retention approach toward one calibrated to the ecological sensitivity of receiving waters. Rather than applying a single statewide design storm threshold, the new framework differentiates requirements based on where a project is located (HUC-12 watershed) and what waters receive its runoff.

Performance Standards Tied to Water Classification

The Handbook establishes seven distinct performance standards, each linked to the classification of the downstream receiving water body. The primary differentiators are:

• HUC-12 watershed location of the project site
• Impaired water body designation — whether the receiving water is listed as impaired under Section 303(d) of the Clean Water Act
• Outstanding Florida Waters (OFW) classification — the highest protection tier, applicable to waters designated for exceptional ecological or recreational value

The Seven Performance Standards

The seven performance standards progress from baseline water quality protection to enhanced treatment for the most sensitive receiving waters. They address total nitrogen (TN), total phosphorus (TP), total suspended solids (TSS), and in some cases biochemical oxygen demand (BOD), with numeric pollutant load reduction targets that must be demonstrated through BMP design calculations. Higher-tier standards apply when a project drains to:

• Waters impaired for nutrients (nitrogen or phosphorus)
• Waters impaired for turbidity or sediment
• Outstanding Florida Waters requiring no net degradation
• Waters within specific TMDL (Total Maximum Daily Load) basins with established waste load allocations

Note: The table above provides a generalized summary of standard tiers. Practitioners must consult the Applicant’s Handbook Volume I and applicable WMD Volume II directly to determine the precise standard applicable to a specific project location and receiving water classification.

Compensating Treatment: Overtreatment and Off-Site Options

Recognizing that not all sites can physically accommodate the BMP footprint needed to meet higher performance standards, the Handbook explicitly allows compensating treatment through two mechanisms:

Maintenance Cost Estimates and Inspection Requirements

A notable departure from prior practice is the Handbook’s explicit requirement for long-term operation and maintenance (O&M) planning. Applicants must now:

• Prepare maintenance cost estimates for all permitted stormwater BMPs at the time of application
• Document inspection schedules specifying frequency and inspection parameters for each BMP type
• Identify the responsible entity for ongoing maintenance and provide evidence of financial assurance where required
• Submit O&M records to the permitting authority as a condition of permit compliance

Volume II: Regional Conditions by WMD

While Volume I establishes the statewide framework, each of Florida’s five Water Management Districts has developed a Volume II that addresses regional hydrologic, geologic, and ecological conditions not captured at the statewide level. Volume II documents may specify:

• Regional BMP design modifications for karst terrain, coastal floodplains, or highly permeable sandy soils
• District-specific impaired water listings and applicable TMDLs not addressed in Volume I
• Locally applicable vegetative species lists for bioretention and filter strips
• Additional performance standard overlays for specific priority water bodies within each district’s jurisdiction

Practitioners operating across multiple WMD jurisdictions must be familiar with both the statewide Volume I standards and the applicable regional Volume II supplement(s) for each project location.

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Topic 8: BMPFast Software & Summary

Section 8 of 8 — Computational Tools, Adaptability & Course Conclusions

Introduction to BMPFast

BMPFast is a stormwater BMP design and compliance calculation software tool developed to support engineering analysis under Florida’s evolving stormwater management criteria. As the 2024 ERP Handbook introduced performance-based standards requiring quantitative pollutant load removal calculations — rather than simple volumetric or area-based sizing — the need for a flexible, research-calibrated computation platform became essential for practicing engineers and permit applicants.

Compliance Calculations Under 2024 Criteria

BMPFast is specifically designed to support compliance with the 2024 ERP Applicant’s Handbook performance standards. Its core calculation capabilities include:

• Pollutant event mean concentration (EMC) inputs by land use category and runoff volume
• BMP-specific removal efficiency coefficients drawn from Florida field research databases
• Treatment train analysis — calculating cumulative removal across sequential BMP combinations
• Comparison of achieved pollutant load reductions against the applicable performance standard tier
• Compensating treatment calculations — modeling overtreatment credits and off-site equivalency

A Flexible, Adaptable Platform

A defining characteristic of BMPFast is its design for adaptability. Florida’s stormwater science continues to evolve — new BMP types are field-tested, removal efficiency data are updated, and regulatory standards will continue to be refined through future rulemaking cycles. BMPFast is structured so that:

• BMP efficiency coefficients can be updated as new research data become available without requiring a full software rebuild
• New BMP categories can be added to the tool’s library as novel practices gain regulatory acceptance
• Performance standard tiers and trigger thresholds can be recalibrated when the Handbook is revised
• Regional (Volume II) parameter sets can be incorporated for WMD-specific conditions

This flexibility means that investment in learning and using BMPFast is not tied to a single regulatory snapshot — the tool is intended to remain relevant through the next cycle of rule refinements, just as the BMP research program itself is a continuous enterprise rather than a one-time effort.

Supporting Timely Water Quality Management Plans

Beyond individual project permitting, BMPFast supports watershed-scale water quality management planning. Because the tool can rapidly evaluate multiple BMP configurations and treatment train combinations, it enables practitioners and local governments to:

• Screen retrofit BMP opportunities across existing developed areas for stormwater master planning
• Evaluate alternative development configurations for water quality outcomes early in site planning
• Quantify load reductions achievable through proposed capital improvement programs for TMDL compliance reporting
• Support basin-scale off-site treatment credit programs by establishing consistent calculation methodologies

Course Summary: From Local Codes to 2024 State Rules

The arc traced across this module — from the early nutrient dynamics research of the 1970s and 1980s, through local BMP ordinances in the 1990s, through successive WMD program development, to the 2024 statewide ERP Handbook — reflects the maturation of stormwater science and regulation in Florida over roughly five decades. Several overarching themes emerge from this history:

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Appendix: Quick-Reference Cards

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