Estimating O&M Costs

Effective maintenance of installed Best Management Practices (BMPs) is critical to maintaining performance of the BMPs throughout their life cycle. Section 12.3.5 of the new stormwater rule, effective June 28, 2024, recognizes this and requires all new permit applicants to “provide a cost estimate for the perpetual operation and maintenance of the stormwater management system.” The rule also specifies that the cost estimate should be in current dollars and include annual operating expenses and planned replacement of items at the end of their service life.  Along with the cost estimate, the applicant must also demonstrate that the operation and maintenance entity has the financial capability to perform the required operation and maintenance. This is demonstrated through the submission of Form 62-330.301(26), “Certification of Financial Capability for Perpetual Operations and Maintenance Entities,” with the permit application.

Doing a life cycle cost estimate can be tricky as not all infrastructure and equipment has the same service life. A typical service life could be 50 years or longer for pipes and structures, but BMPs with filters, wetland mats, valves, irrigation pumps, and other equipment will have much shorter service lives. So, the cost estimate for “perpetual operation” of multiple BMPs will include several replacement cycles for some parts with different individual service lives. You can determine the annual O&M cost in current dollars in a customized spreadsheet, analyzing each component of the stormwater system by its annual operating cost and estimated replacement interval. Thankfully, there are resources out there to help you.

If you have a more detailed project or simply want to use a ready-made form, the Florida Stormwater Association Educational Foundation, along with the Water Management Districts and the Florida Department of Environmental Protection has developed a BMP Life-Cycle Costing Tool. The tool is available on the FSA for members and non-members. While more complex than a spreadsheet method, the tool also provides guidance for completing the form, additional information on discount rates, and even suggested maintenance activities that should be included for various BMP types.  

Seascape Resorts Smart Pond Project: Maximizing Stormwater Efficiency through Innovation

Seascape Resorts recently increased developable land by reducing pond size. Employing available technology and relevant Florida permitting experience enabled Seascape to optimize land use and enhance flood resilience.

Key Benefits Realized

1. Significant Pond Size Reduction

The application of CMAC technology enables the dynamic water level control of an existing stormwater pond, maintaining its stormwater management function with half the traditional size. This downsizing preserved valuable land for other uses without compromising performance. The existing pond size was reduced by 54%, resulting in 2.51 acres of additional developable real estate.

2. Enhanced Flood Protection

Despite the reduced pond size, the CMAC system provides full attenuation and flood protection. It does so by reviewing real-time weather forecast data and intelligently releasing water ahead of large storm events, creating capacity when it is most needed. The system ensures compliance with local stormwater design standards and mitigates flood risk during high-intensity events.

3. Hurricane Resiliency

Engineered for extreme conditions, the CMAC system bolsters resiliency against large storm events such as hurricanes. Its predictive control algorithms adjust outflows in anticipation of weather changes, ensuring the infrastructure is primed for peak performance when disaster strikes.

4. 24/7 Monitoring and Automatic Control

The system features continuous remote monitoring and automatic control, allowing for hands-off operation and proactive stormwater management. The system also allows for human oversight and manual control when needed. Operators can oversee system performance in real-time, enhancing responsiveness and minimizing manual intervention.

5. Adaptive for the Future

The smart pond system is entirely configurable, designed to adapt to evolving environmental conditions or regulatory requirements. This future-proofing capability ensures long-term value and operational flexibility.

6. Reduced Peak Flows

Through real-time flow modulation, CMAC technology effectively reduces peak discharges, thus minimizing stress on downstream infrastructure and improving water quality outcomes.

Client Testimonial

“Implementing CMAC smart pond technology at Seascape has transformed our approach to stormwater management. We’ve reclaimed valuable land, strengthened our flood protection, and gained peace of mind knowing the system runs itself — all while preparing for the future. It’s been a game-changer for our resort.”

Paul Davis, Director of Development, Seascape Resorts

Comparing RSMS and WQEA Stormwater Credit Frameworks

Purpose: To distinguish the Regional Stormwater Management System (RSMS) framework (currently implementable and actively used by NST) from the Water Quality Enhancement Area (WQEA) framework (still under rule development), focusing on applicability, regulatory readiness, and credit generation mechanisms.

Comparison Table: RSMS vs. WQEA

FeatureRSMS (Regional Stormwater Management System)WQEA (Water Quality Enhancement Area)
Governing RulesChapter 62-330, F.A.C. + ERP Applicant’s Handbook Vol. I (Sec. 9.7.3)Chapter 62-330, F.A.C. + ERP Applicant’s Handbook Vol. I + Chapter 62-332, F.A.C. (draft rule)
Regulatory StatusFully authorized and in effect nowRulemaking not yet finalized (est. late 2025)
Permitting PathwayEnvironmental Resource Permit (ERP)Environmental Resource Permit (ERP) with additional WQEA rules
Credit AvailabilityAvailable now via existing permitted RSMSsFuture—credits can be issued only after rule adoption + permit + construction + credit release
Treatment TypeEngineered stormwater ponds, e.g., technological enhancementsNatural systems, e.g., constructed wetlands, ecological enhancements
Use Cases-Off-site compensating treatment  
-ERP net improvement and nutrient reduction standard
-Off-site compensating treatment
-ERP net improvement and nutrient reduction standard  
-BMAP allocations (via Ch. 62-306)
OwnershipPublic or privatePublic or private
Land TypeStormwater ponds from developed/urbanized parcels or transportation facilitiesNatural or restored lands (may be co-located with wetland banks)  
Service Area DeterminationHUC 12 subwatershed; Smaller service areasRequires detailed fate & transport modeling; Larger service areas
Locational Valuation Factor (LVF)Not required within same HUC 12Mandatory; applies to each credit trade
Credit MaturityImmediate release upon permit approvalPhased release with performance monitoring and site success

Common Features of Both Frameworks

Standalone ERP Permit: Each facility type is permitted as a discrete ERP project.
Excess Treatment = Credits: Credits are based on treatment beyond what’s required for the developed drainage area or based on water quality “lift” (determined like a mitigation bank – with success criteria and monitoring).
Defined Service Area: Credit use is restricted to a defined service area.
Long-Term Assurance: Owners of an RSMS and WQEA must demonstrate perpetual maintenance, financial assurance, and responsible party designation.
Professional Operator: Must be a capable entity with performance verification protocols in place.
Tracking & Ledger: Both frameworks require a credit ledger that documents generation, allocation, and availability.
Use Restrictions:
o May not offset localized water quality impacts
o Not applicable to water quantity or floodplain requirements
o Credits cannot double-count for ERP and BMAP reductions

Use Case Guidance and Observation

• Developers needing immediate nutrient credit solutions should turn to NST’s RSMS approach, which is fully actionable today. With the new stormwater rule deadline looming and more stringent performance requirements, the availability of off-site nutrient credits will be essential to avoiding costly development impacts or time-consuming project redesigns.

Developer Update: Seascape Resorts Smart Pond Installation

We’re thrilled to announce our latest Smart Pond installation at Seascape Resort! This CMAC (Continuous Monitoring & Adaptive Control) system delivers real-time flood control and improved water quality, protecting both local communities and Florida’s natural ecosystems.

We’re proudly serving businesses, municipalities, and residential communities across Florida with sustainable stormwater solutions. Want your own Smart Pond? 📩 Contact us at info@nationalstormwater.com

Applying the Wetland Treatment Rule to Establish Wetland Assimilative Capacity for Stormwater Discharges

With the implementation of Florida’s updated stormwater rule, design flexibility has increased—particularly through the use of off-site compensatory treatment and Regional Stormwater Management Systems (RSMS). However, these strategies may lead to the discharge of partially treated stormwater runoff to wetlands.

While this approach offers permitting efficiency, it also raises a key technical question:
How do we demonstrate that a wetland has the assimilative capacity to receive this runoff without causing an adverse impact?

📜 Regulatory Background: Rule 62-611, F.A.C.

The good news is wetlands are consumers of nutrients. In fact, wetlands need nutrients to thrive. The issue is determining the total amount of nutrients that can be assimilated by a wetland system while remaining within healthy limits. The answer lies in Chapter 62-611, F.A.C., Florida’s Wetlands Application Rule, which outlines procedures to evaluate wetland assimilative capacity. Originally developed for wastewater treatment wetlands, this rule can also be applied to stormwater discharges—especially in the context of project designs that discharge partially treated runoff to natural wetlands while using off-site compensatory treatment within the same watershed.

🔬 Key Wetland Capacity Criteria

Rule 62-611 sets specific hydraulic and nutrient loading limits for discharges to artificial treatment wetlands and natural (receiving) wetlands. We will use the more stringent limits for natural wetlands in this procedure:

Hydraulic Loading:
≤ 2 inches/week (annual average)
Detention Time: > 14 days (annual average)

Nutrient Loading (Assimilative Capacity)
Total Nitrogen (TN): < 25 g/m²/year
Total Phosphorus (TP): < 3.0 g/m²/year

Discharge Limits:
To Receiving Wetlands: TN = 3 mg/L, TP = 1 mg/L

 

🚧 How This Applies to Projects

Typical event mean concentrations (EMCs) for project runoff are already below the discharge limits. For example, the EMCs for roadway projects are:

TN: 1.52 mg/L

– TP: 0.20 mg/L

This means that for many projects, discharges to wetlands may comply with Rule 62-611 without additional nutrient treatment, as long as the wetland has sufficient assimilative and hydraulic capacity.

📌 Why This Matters

By applying the wetland assimilative loading criteria under Rule 62-611, engineers can demonstrate regulatory compliance for wetland discharges from partially treated stormwater systems. This can support more cost-effective stormwater designs, reduce the need for additional BMPs or treatment infrastructure, and allow the use of off-site compensating treatment to achieve full compliance with the new, more stringent performance criteria later this year.

📂 Downloadable Design Example

To help illustrate this approach, we’ve provided a downloadable spreadsheet example that walks through the process of evaluating a wetland’s assimilative and hydraulic capacity for a representative stormwater discharge scenario. Note that other developments that discharge to the same wetland system may add to the cumulative loading, so provisions for calculating this loading are included in the spreadsheet.

📥Download the Design Example Spreadsheet

🧰 Tips for Stormwater Engineering Consultants:

– Use Rule 62-611 procedures to evaluate wetland assimilative loading capacity.

– Ensure discharge concentrations and loading rates from your project are within allowable thresholds for the receiving wetlands.

– Consider the cumulative loading from other developments within the same basin that may discharge to the same wetlands.

– Larger wetland systems are more likely to assimilate additional nutrient loading without adverse impact.

– Coordinate with the WMD early in design to confirm consistency with the ERP Rules and Applicant’s Handbook.

Immediately Available: Tampa Bay Stormwater Nutrient Credits (SNCs)

Stormwater Nutrient Credits (SNCs) are available for purchase in the Tampa Bay HUC-8 Service Area within the Southwest Florida Water Management District (SWFWMD). This program functions like wetland mitigation banking, allowing public and private developers to meet stormwater treatment requirements by purchasing off-site credits.

By utilizing SNCs, developers can streamline compliance, reduce on-site infrastructure costs, and contribute to regional water quality improvements. This approach provides a flexible, cost-effective solution for meeting regulatory requirements while supporting sustainable development.

If you are interested in purchasing credits or learning more, please fill out the contact form, or email us at info@nationalstormwater.com.

Halifax River Stormwater Nutrient Credits (SNCs) Available Now

Stormwater Nutrient Credits (SNCs) are available for purchase in the Halifax River HUC-12 Service Area within the St. Johns River Water Management District (SJRWMD). This program functions like wetland mitigation banking, allowing public and private developers to meet stormwater treatment requirements by purchasing off-site credits.

By utilizing SNCs, developers can streamline compliance, reduce on-site infrastructure costs, and contribute to regional water quality improvements. This approach provides a flexible, cost-effective solution for meeting regulatory requirements while supporting sustainable development.

If you are interested in purchasing credits or learning more, please fill out the contact form, or email us at info@nationalstormwater.com.

Understanding Grandfathering for Conceptual ERPs Under Florida’s Updated Stormwater Rules

The June 28, 2024, updates to Chapter 62-330, F.A.C. and the Environmental Resource Permit Applicant’s Handbook Volume I (AH I) brought significant changes to stormwater design and treatment standards. For projects with Conceptual Environmental Resource Permits (ERPs) issued prior to this date, the key question is: Do the new treatment performance standards apply to future construction phases under an existing conceptual ERP?

📝 Rule Background: AH I, Section 3.1.2(e)3

Section 3.1.2(e)3 of the updated AH I provides that if a construction phase is consistent with an unexpired conceptual ERP, it may continue using the stormwater criteria that were in effect at the time the conceptual approval was issued—commonly referred to as grandfathering. However, if modifications to the construction phase cause substantially different water resource impacts, the project will be subject to the new standards.

📌 Why Verifying Grandfathering Status Is Important

While the grandfathering provision is clearly stated, the determination of what constitutes “substantially different water resource impacts” can be subjective. This is why it is highly advisable for consulting engineers to seek confirmation from the Water Management District (WMD) that a project phase remains eligible for grandfathering.

🛡️ Benefits of a Grandfathering Verification Request:

  • Regulatory Certainty: Avoid disputes during the review process by documenting the project’s eligibility to use prior design standards.
  • Cost Savings: Prevent unnecessary redesigns or upgrades to meet new standards.
  • Permitting Efficiency: Minimize review delays by demonstrating consistency with the conceptual ERP upfront.

📄 How to Submit a Request

The verification request should include:

  • A reference to AH I, Section 3.1.2(e)3 and the project’s conceptual ERP number.
  • A statement that the construction phase remains consistent with the conceptual approval.
  • A narrative explaining any modifications and why they do not result in substantially different water resource impacts.
  • Supporting documents such as site plans, comparison tables, and design reports.

📂 Get a Head Start:

To assist you, we have provided a draft Grandfathering Verification Request letter that you can tailor to your projects.

📥 Download the Draft Grandfathering Verification Request Letter

By taking this proactive step, consulting engineers can streamline the permitting process, protect their project timelines, and reduce uncertainty under Florida’s evolving stormwater regulations.

FAQs About Regional Stormwater Management Systems (RSMS) 

1. What is a Regional Stormwater Management System (RSMS)?

    An RSMS is a facility designed, constructed, and maintained to manage stormwater for one to multiple parcels and may serve one or more projects within a defined drainage area (you can think of this like the service area of a mitigation bank). Its purpose is to prevent flooding, reduce pollution, and manage stormwater discharges for a larger area compared to a conventional system. 

    2. How does an RSMS differ from traditional stormwater management systems? 

    Unlike stormwater management systems that are integrated within a development project, an RSMS is permitted as a standalone stormwater management system to serve multiple projects in a defined area. It also provides a mechanism for accountable nutrient reduction across a HUC 12 or potentially larger watershed, enabling more efficient land use and potentially lower development costs through offsite compensatory treatment credits (aka Stormwater Nutrient Credits)​​. 

    3. What are the main advantages of using an RSMS? 

    – Cost Efficiency: Offsite treatment infrastructure can reduce site development costs. 

      – Improved Water Quality: Centralized treatment in larger, professionally managed stormwater facilities achieve higher pollutant removal rates. 

      – Flexibility in Development: Developers may reduce on-site treatment requirements by utilizing offsite credits. 

      – Comprehensive Watershed Management: Better tracking and accountability of stormwater nutrient reduction at a watershed scale​​. 

      4. How are pollutant load reductions allocated in an RSMS? 

      RSMS facilities track pollutant removal in pounds or kilograms, ensuring allocations do not exceed their permitted treatment capacity. Records of these allocations must be maintained permanently by the RSMS permit holder and reported as specified in Sections 9.7.3 and 12.6(d) of the Applicant’s Handbook​.

      5. What permitting requirements apply to RSMS?

      RSMS must be permitted under the Environmental Resource Permit (ERP) program. This includes demonstrating reasonable assurance of compliance with water quality standards, long-term operations and maintenance, and accurate tracking of nutrient load reductions​​.

      6. How does an RSMS provide stormwater nutrient credits (SNCs)? 

      An RSMS can generate SNCs by documenting excess treatment capacity in an accounting ledger, much like a wetland mitigation bank. These credits can then transferred to other entities within the same service area (e.g. hydrologically connected or within the same watershed) to offset their pollutant loading requirements​​. Keep in mind that the user of an SNC must still meet the water quantity requirements of ERP (e.g. pre-post rate control) and must demonstrate that the discharge of less than fully treated stormwater does not adversely impact any downstream waters. 

      7. Who is responsible for maintaining an RSMS?

      The permit holder of the RSMS is responsible for its operation, maintenance, and compliance with all applicable regulations. This includes maintaining accurate records of stormwater treatment allocations and ensuring that the system operates within its design capacity​.

      8. Does the user of SNCs have any ongoing responsibilities after the credits are transferred to their project from an RSMS?  

      No. Like a wetland mitigation credit, the purchaser bears no long-term responsibility for the continued operations and maintenance of the nutrient credit generating project. That obligation falls solely on the RSMS permit holder.  

      Harvard: NST’s Role in Babcock Ranch’s Resilience During Hurricane Ian

      Our collaboration with Babcock Ranch ensured effective stormwater management during Hurricane Ian. The innovative smart pond systems diverted water and recharged wetlands, preventing flooding and protecting the community. By integrating advanced technology and sustainable design, Babcock Ranch remained resilient while surrounding areas were severely impacted. This partnership demonstrates how smart stormwater solutions enhance community resilience against extreme weather events.