BMPFast Software: Stormwater Assessment in Florida

Training module covering BMPFast software overview, navigation, rainfall data, performance standards, and catchment data entry. Prepared for ERP permit practitioners and stormwater professionals. Content derived from BMPFast training slides.

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1. BMPFast Software Overview

Source slides: 3, 4, 5 — Introduction to the BMPFast tool, its purpose, regulatory acceptance, and the scope of user responsibility.

BMPFast is a Florida-specific stormwater assessment software tool designed to assist practitioners in evaluating the performance of Best Management Practices (BMPs) in the context of Environmental Resource Permit (ERP) applications. It was developed with the practicing professional in mind and has undergone peer review by experienced stormwater engineers and environmental scientists familiar with Florida’s regulatory landscape.

Regulatory Context and Acceptance

One of the most significant practical advantages of BMPFast is its acceptance by Florida’s Water Management Districts (WMDs) and the Florida Department of Environmental Protection (FDEP). Reviewers at these agencies are familiar with the tool’s methodology and output format, which facilitates a more efficient permit review process. Using BMPFast supports timely completion of ERP permit applications by providing a recognized, standardized framework for demonstrating BMP performance.

Peer Review and Professional Development

The software has been peer-reviewed by practicing professionals — a process that ensures the underlying methodology reflects real-world conditions encountered in Florida stormwater practice. This peer review foundation gives practitioners confidence in submitting results to regulatory agencies and supports the credibility of the assessment outputs.

Scope and User Responsibility

Because BMPFast is an assessment model rather than a design tool, the quality and accuracy of its outputs depend entirely on the data provided by the user. The software does not independently verify or generate site-specific input values — the user is responsible for all input data entered into the program. This responsibility encompasses:

• Accurate land use classification for pre- and post-development conditions
• Correct identification of the applicable rainfall zone and annual rainfall depth
• Appropriate event mean concentration (EMC) values for pollutants of concern
• Proper selection of the performance standard that applies to the receiving water body
• Verification that BMP parameters reflect the actual proposed design

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2. Software Navigation & Worksheets

Source slides: 6, 7, 11, 13 — How to move through BMPFast, use its entry fields and menus, and manage project data efficiently.

BMPFast is organized into a series of worksheets that correspond to the logical workflow of a stormwater BMP assessment. Understanding how to navigate between these worksheets and how the various input mechanisms function is essential for working efficiently and avoiding data entry errors.

Navigation via Buttons

Movement between worksheets in BMPFast is controlled by on-screen navigation buttons. Rather than using spreadsheet tabs or menu commands, the software provides clearly labeled buttons that guide the user forward and backward through the assessment workflow. This design keeps the user oriented within the structured sequence of data entry steps required for a complete analysis.

Input Methods: Drop-Downs and Open Entry Fields

BMPFast uses two primary mechanisms for data entry:

• Drop-down menus — present a fixed set of options for parameters with defined choices, such as land use categories, BMP types, or performance standards. Selecting from a drop-down ensures that inputs conform to recognized categories used in the software’s calculations.
• Open entry fields — allow the user to type in a specific numeric value. These fields are used where site-specific or locally derived data should override the software’s built-in defaults, such as for rainfall depth or EMC values from site monitoring.

This hybrid approach gives practitioners the flexibility to use local or project-specific data while maintaining the structured framework required for a valid assessment.

Help Buttons and Library References

Throughout BMPFast, help buttons are available on key worksheets to provide guidance on the appropriate use of specific input fields. These help features may reference built-in library data — such as EMC lookup tables for common Florida land use types — giving users a starting point for inputs when site-specific data is not available. Users should review library values critically and substitute site-specific data whenever it is available and more representative of project conditions.

Saving Your Project

BMPFast allows users to save their project file, preserving all entered data for future sessions. Saving regularly is essential practice — re-entering all catchment, BMP, and site data from scratch is time-consuming and introduces the risk of inconsistencies. A saved project file can also serve as documentation of the inputs used for a specific permit submission, supporting the record-keeping requirements of professional practice.

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3. Rainfall Data Input

Source slides: 9, 10 — Selecting the correct rainfall zone, understanding the 2024 data update, and options for entering local or project-specific rainfall values.

Rainfall depth is a foundational input in BMPFast because annual pollutant loading calculations depend directly on the volume of runoff generated, which in turn depends on the amount of rainfall received at the site. Selecting the correct rainfall value is not a minor detail — it directly affects the calculated pollutant loads and the apparent performance of the proposed BMP.

Five Rainfall Zones

BMPFast divides Florida into five rainfall zones. Each zone is assigned a representative annual rainfall depth based on long-term precipitation data. When a user selects a zone from the drop-down menu, the software automatically populates the annual rainfall field with the corresponding zone value. This simplifies data entry for users who do not have access to localized rain gauge records.

2024 Annual Rainfall Data Update (NOAA 2022)

The 2024 version of BMPFast incorporates updated annual rainfall data derived from NOAA 2022 precipitation datasets. This represents a meaningful update from the rainfall values used in earlier versions of the software. The underlying precipitation climatology for Florida has been re-examined, and the zone values have been revised to reflect more current long-term averages.

A comparison of the 2000 rainfall map (used in earlier BMPFast versions) against the 2024 updated map reveals that the change is not uniform across the state:

• Some locations show higher annual rainfall values in the 2024 data — meaning older analyses may have underestimated pollutant loading at those sites.
• Some locations show lower annual rainfall values — meaning the 2024 data may result in reduced calculated loading compared to prior assessments.
• Some locations are essentially unchanged, with the updated data confirming earlier values.

Open Entry for Local or Updated Data

BMPFast’s open entry field for annual rainfall allows users to override the zone default with a locally derived or project-specific value. This is appropriate when:

• A nearby rain gauge with a long period of record provides a more representative annual average for the project site.
• The reviewing agency or district has specified a particular rainfall value for the project area.
• Site conditions (e.g., coastal location, inland topography) suggest that the zone default is not representative.

Annual rainfall is a required input for ERP permit applications processed through BMPFast. Users must document the source of the rainfall value used and be prepared to justify the selection if questioned during permit review.

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4. Performance Standards

Source slides: 7, 11 — How BMPFast determines the applicable performance standard for a project and the options available to practitioners.

The performance standard is the water quality target that a proposed BMP configuration must meet for the project to qualify for an ERP permit under the stormwater management criteria. BMPFast provides a structured approach to selecting and applying the correct standard based on the characteristics of the receiving water body and applicable regulatory programs.

Standard Determined by Receiving Water Body

The primary driver of performance standard selection is the water body that will receive stormwater runoff from the project site. Different receiving waters carry different regulatory designations and associated loading constraints. The practitioner must identify the correct receiving water body and any applicable basin management action plans or impairment listings before selecting a standard in BMPFast.

Seven Performance Standard Options

BMPFast provides seven performance standard choices, giving practitioners the flexibility to address a wide range of regulatory scenarios:

• Net improvement — the post-development pollutant load after BMP treatment must be less than the pre-development load, resulting in a net water quality benefit.
• Post ≤ Pre development — a common baseline standard requiring that the treated post-development load does not exceed the pre-development condition load.
• Supports BMAP (Basin Management Action Plan) requirements — allows the analysis to be configured to meet load reduction targets established in a BMAP for the receiving basin.
• Supports TMDL (Total Maximum Daily Load) requirements — addresses situations where the receiving water is listed as impaired and subject to a TMDL allocation.
• Supports local program needs — accommodates local government stormwater programs that may have specific performance requirements beyond state minimums.
• Specified percent removal — the BMP must achieve a user-defined percentage reduction in pollutant load, which may be required by a specific permit condition or agency guidance.
• BMP-only analysis (no set standard) — allows the user to run the assessment without applying a specific performance standard, which may be appropriate for feasibility studies or situations where the standard has not yet been formally established.

BMAP, TMDL, and Local Program Integration

BMPFast’s support for BMAP and TMDL scenarios reflects the increasingly common situation where project sites discharge to impaired water bodies subject to load reduction requirements. In these cases, the performance standard is not simply a comparison of pre- and post-development conditions — it is tied to a specific allocated load reduction that must be demonstrated. The software allows these requirements to be incorporated directly into the assessment framework, providing a consistent and defensible methodology for permit documentation.

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5. Catchment Data Entry

Source slides: 12 — Defining catchments, identifying land uses, entering EMC values, and confirming data entry before proceeding.

The catchment is the fundamental spatial unit of analysis in BMPFast. Accurate catchment delineation and data entry are prerequisites for a valid assessment. Errors or oversimplifications at this stage propagate through all downstream calculations and can undermine the credibility of the BMP performance analysis.

Defining a Catchment

A catchment in BMPFast is defined as the area contributing stormwater runoff to the BMP being assessed. This may be the entire project site or a sub-area draining to a specific BMP. The catchment boundary must be established through standard hydrologic delineation methods before data is entered into the software — BMPFast does not perform automatic delineation.

Land Use Identification

BMPFast requires the user to identify and quantify land uses within the catchment for both pre-development and post-development conditions. A help button is available on the land use worksheet to assist in categorizing land uses according to the classification system used by the software. This help feature provides descriptions and examples to reduce ambiguity in land use assignment, particularly for mixed or transitional land cover types.

Event Mean Concentration (EMC) Values

EMC values represent the average pollutant concentration in stormwater runoff for a given land use type. BMPFast requires EMC values for both pre-development and post-development conditions for each pollutant of concern. The software provides library EMC values derived from Florida stormwater monitoring data, which serve as defaults when site-specific measurements are not available.

For catchments with a mix of land uses, the user must enter a user-defined composite EMC that reflects the weighted average concentration across all land use types present. This calculation must be performed by the user outside of the software and entered as a single composite value — BMPFast does not automatically blend multiple land use EMCs within a single catchment entry.

Additional Loading Sources

BMPFast allows users to incorporate additional loading sources beyond the standard land use runoff calculation. This feature is relevant for sites with identifiable non-stormwater inputs or supplemental pollutant sources that contribute to the overall load reaching the BMP. Including these sources produces a more complete and accurate picture of the pollutant loading that the BMP must address.

Calculate and Back Button Confirmation

After entering catchment data, the user initiates the calculation using the designated Calculate button on the worksheet. Following calculation, using the Back button allows the user to review and confirm the entered data before proceeding to the next stage of the analysis. This review step is an important quality control checkpoint — verify that all land use areas, EMC values, and any additional loading inputs are correctly reflected in the summary before moving forward.

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6. Learning Objectives & Competency

Section 6 of 6 — Professional Development & Certification

This module has equipped practitioners with the conceptual and technical foundations needed to navigate rainfall-dependent infiltration requirements under California’s Construction General Permit. Mastery of these topics accelerates the permitting process, reduces RAI cycles, and positions professionals as credible specialists in stormwater compliance.

6.1 What This Module Covered

Three core knowledge domains were addressed across the six sections of this module:

6.2 Catchment Characteristics & Required Data Fields

A technically defensible RDI analysis depends on accurately characterizing each drainage catchment within the project’s disturbed area. Permit reviewers and REAP auditors look for consistent, well-sourced entries in the following fields:

Incomplete or inconsistent entries in these fields are among the most common causes of RAIs from the State Water Board’s review staff. Practitioners who submit complete, cross-referenced catchment data tables routinely achieve first-round approvals.

6.3 Basic Competency Certification

Completion of this module fulfills one of the foundational learning units recommended for practitioners seeking basic competency certification in CGP stormwater compliance. The California Stormwater Quality Association (CASQA) and affiliated professional development programs recognize modular learning pathways as the standard framework for demonstrating and documenting practitioner knowledge.

6.4 Operational Benefits: Fewer RAIs, Faster Approvals

The relationship between practitioner competency and permit processing efficiency is direct and measurable. Sites whose SWPPPs are prepared by practitioners with documented training in RDI analysis consistently show:

• Reduced Request for Additional Information (RAI) cycles — complete RDI submittals address reviewer checklist items proactively, eliminating the back-and-forth that extends approval timelines by weeks or months.
• Faster REAP approval — the Risk Enforcement and Permitting Program (REAP) review process moves more quickly when the technical basis for RDI credit is clearly documented and internally consistent.
• Lower project risk exposure — sites operating with deficient SWPPPs face enforcement actions, stop-work orders, and penalties under Section 13385 of the California Water Code; competency-based preparation reduces this exposure.
• Enhanced client and agency confidence — demonstrated mastery of the RDI framework signals professional rigor to project owners, local agencies, and State Board staff.

6.5 Additional Learning Modules in This Series

This module is one component of a multi-part professional development series on California CGP compliance. Additional modules in the series address complementary topics required for full practitioner competency:

6.6 Next Steps for Practitioners

To consolidate and extend the knowledge gained in this module, practitioners should:

• Complete the end-of-module assessment to receive a certificate of completion for this unit.
• Review the CGP Section X RDI provisions directly in the current permit text, available on the State Water Resources Control Board website.
• Practice catchment delineation and data field population using a sample project before applying the methodology on a live SWPPP.
• Enroll in Module 3 (BMP Selection & Design for RDI Credit) to build on the hydraulic and hydrologic foundations established here.
• Bookmark the CASQA Construction BMP Handbook and the SMARTS portal as primary reference resources for day-to-day SWPPP work.

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Appendix — Quick Reference Cards

Detachable reference summaries for field and office use. Print this section separately for use during SWPPP preparation and permit review.

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