Nutrient Loading Analysis, automated end to end.
From project boundary to submittal-ready Technical Report: SWMLabs performs the geospatial classification, ROC and nutrient loading calculations, and BMP treatment train analysis required under Sections 8.3–8.3.6 of the ERP Applicant's Handbook, Volume I - across all five Florida Water Management Districts.
5
Water Management Districts
6,894
WBIDs covered statewide
Technical Report output
Why this exists
Preparing a stormwater quality submittal means pulling site-specific criteria from disparate sources, then working through ROC lookups, nutrient loading arithmetic, and BMP sizing by hand - mechanical work that's easy to get wrong and hard to defend under agency review if the derivation isn't fully shown. SWMLabs automatically determines the location-based criteria - land use coverage, soil classification, rainfall depth, and applicable performance standard - and carries them through the full calculation and documentation, so the engineer can focus on the design decisions that require real judgment.
It replaces the spreadsheet and the separate BMP sizing tool with one workspace: the same Harper and Baker (2007) methodology the Handbook is built on, one Technical Report, every derivation shown.
Process
Seven steps, one submittal-ready report
Every step below reflects the platform's actual project flow - not a simplified version of it.
01 / 07
Define your project boundary
Draw or upload the project boundary directly on the map. This single input drives every downstream classification step - from HUC12 assignment to the Impaired Waters and OFW audit.
02 / 07
Automated geospatial classification
The platform resolves the project's HUC12 and WBID, assigns the meteorological zone and annual rainfall depth, and audits for Impaired Waters and Outstanding Florida Waters status - automatically, statewide.
03 / 07
Land use, DCIA, and Curve Number input
Enter land use, directly connected impervious area, and curve number for both the pre- and post-development condition, using the same worksheet pattern for each.
04 / 07
Post-development outfall placement
Place pins on the map marking each post-development outfall. Each pin resolves the receiving HUC12 and WBID, traces the downstream flowpath, and audits it for downstream Impaired Waters or OFWs - determining whether the Locational requirement binds at the outfall/group level, evaluated independently for TN and TP.
§8.3.3 – §8.3.405 / 07
Build the BMP treatment train
Add and connect BMP nodes on the routing canvas - retention, wet detention, fixed-efficiency, stormwater harvesting, and maintenance recovery - in the order water actually moves through the system.
06 / 07
Automated calculation
The platform runs the full ROC, nutrient loading, and BMP performance calculation, then determines the controlling - more stringent - reduction standard for the project.
07 / 07
Review results & generate your Technical Report
Review the Loading Summary and Routing Summary Table, confirm compliance, and generate a formatted Technical Report - ready to attach directly to your ERP submittal.
Rather click through it yourself? The live demo contains real projects you can explore - no account needed.
Explore the Live DemoBuilt on the Applicant's Handbook, not around it
Every calculation traces to a named section, table, or equation in Volume I of the ERP Applicant's Handbook. Nothing is fitted or estimated.
Regulatory Scope
Covers Sections 8.3 through 8.3.6 - standard, OFW, Impaired Waters, and redevelopment scenarios - applied uniformly across all five Water Management Districts and FDEP.
AH Vol. I, §8.3–8.3.6Dual-Path Binding Standard
The platform evaluates both the percentage-reduction requirement and the pre/post-development loading comparison for every project, and applies whichever is more stringent - independently for TN and TP.
AH Vol. I, §8.3.2Appendix N & O Lookups
Runoff coefficient and retention efficiency values are drawn directly from the zone-specific Appendix N and Appendix O tables, interpolated by meteorological zone, DCIA percentage, and curve number.
AH Vol. I, App. N, App. OPer-Node Treatment Train
The platform walks each catchment's flow path node by node, tracking volume, concentration, and load through every BMP in the order water actually reaches them - not as a single lumped calculation.
Harper & Baker (2007)Curve Numbers
Non-DCIA curve numbers are derived using standard TR-55 land cover and Hydrologic Soil Group classifications, with the lookup built directly into the land use worksheet - no separate reference table to consult.
TR-55, Table 2-2BMP Library
Retention, full retention, wet detention, fixed-efficiency, stormwater harvesting, and maintenance recovery BMPs are supported today, with new BMP types added on an ongoing basis. Every removal-efficiency methodology is fully sourced and documented in the platform's help center.
Appendix O, §9.5Where the geospatial data comes from
HUC12 / WBID & FLUCFCS
Sub-watershed boundaries and land cover classification sourced from FDEP.
Soils & HSG
Hydrologic Soil Group data sourced from the NRCS Soil Survey (SSURGO).
Rainfall & Met Zones
Mean annual rainfall depths and zone boundaries per Handbook Appendix M, geospatially located to the project.
Impaired Waters & OFW
FDEP Verified List impairments and Chapter 62-302 OFW designations, resolved automatically at each outfall.
Principle
No guessing when you place your seal
Transparency isn't a feature - it's the design constraint everything else is built around. The Engineer of Record, and the agency reviewer on the other end, should always be able to see exactly what the platform calculated and why.
Every value shows its work
ROC lookups, interpolation stages, BMP efficiency curves, and load derivations all appear in the Technical Report exactly as calculated - not as a final number with the method left implicit.
Every input and output is user-editable
Land use areas, DCIA%, curve numbers, EMC values, BMP geometry - the Engineer of Record can override any platform-derived value. Where a value has been changed, both the original and the substituted value are recorded, so the report always reflects the engineer's actual knowledge and design intent.
An audit trail, not a black box
Every override is logged with its section, parameter, platform-derived value, and the engineer's substituted value - giving both the Engineer of Record and the reviewing agency a complete, defensible record of every judgment call made on the project.
Output
What's in the Technical Report
The report exists to make the analysis legible - every input, every derivation, and every result laid out so the design intent is as clear to the reviewing agency as it is to the engineer who sealed it.
- 01Compliance Determination
- 02Site & Regulatory Context
- 03Land Use & Runoff Derivation
- 04Nutrient Loading Calculations
- 05BMP Treatment Train Documentation
- 06Project-Wide Loading Summary
- 07Override Log
See a real Technical Report
A complete report generated by the platform for a Hardee County project - every section and appendix, every derivation shown, ready for ERP submittal.
Sample report - Hardee County, FL.
Open full screenSample Technical Report
Hardee County, FL - the full PDF opens in your browser's viewer.
View the sample reportReady to run your first project?
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