Comparing Structural vs. Non-Structural Stormwater BMPs

Stormwater regulations across the Mid-Atlantic continue to tighten – and for good reason. As development increases and rainfall patterns shift, effective stormwater management is essential for protecting local waterways, reducing flood risks, and maintaining compliance.

At the center of these efforts are Best Management Practices (BMPs): the tools, strategies, and systems used to control runoff, improve water quality, and meet state and local requirements. But not all BMPs work the same way.

Understanding the difference between structural and non-structural BMPs is foundational for anyone responsible for commercial, industrial, or multi-family properties. Here’s a practical, “back-to-basics” comparison – and what each type means for ongoing maintenance, budgeting, and compliance across Maryland, DC, Northern Virginia, and Delaware.

What Are Structural Stormwater BMPs?

Structural BMPs are physical, built systems designed to control, capture, filter, or treat stormwater. They are engineered solutions that require design, construction, and ongoing maintenance to function properly.

Common Structural BMPs

These include:

• Retention (Wet) Ponds
  Designed to hold a permanent pool of water while treating runoff through settling and biological processes.
• Detention (Dry) Ponds
  Temporarily store runoff during storms and release it slowly to reduce peak flows.
• Bioswales & Bioretention Facilities (Rain Gardens)
  Use engineered soil and vegetation to filter runoff and remove pollutants.
• Underground Stormwater Vaults
  Store or treat runoff in areas with limited space – common in urban and commercial sites.
• Contech StormFilter® Systems & Other Proprietary Devices
  Cartridge-based systems that remove sediment, oils, nutrients, and other pollutants.
• Sand Filters & Media Filters
  Treat runoff through layered filtration beds.

Structural BMP Benefits

• Highly effective at pollutant removal
• Address volume control, water quality, and peak flow reduction
• Required for many development and redevelopment projects
• Can handle large drainage areas

Structural BMP Challenges

• Require routine inspection and maintenance
• Can accumulate sediment, debris, and invasive vegetation
• May need periodic rehabilitation (e.g., regrading, replanting, cartridge replacement, dredging)
• Higher upfront cost compared to non-structural strategies

For property managers, structural BMPs are an investment – but one that only performs if properly maintained.

What Are Non-Structural Stormwater BMPs?

Non-structural BMPs are operational, procedural, or design-based strategies that reduce stormwater impacts without requiring built infrastructure.

These BMPs focus on prevention, minimizing pollution and reducing runoff at the source.

Common Non-Structural BMPs

Examples include:

• Good housekeeping practices (spill prevention, routine sweeping, proper waste handling)
• Pollution prevention plans (P2 Plans)
  
• Landscaping choices that reduce runoff (native plants, reduced impervious areas)
• Public education and signage
  
• Illicit discharge detection and elimination (IDDE) programs
  
• Nutrient-smart landscaping and fertilizer reduction
  
• Rainwater harvesting policies
  
• Maintenance programs that reduce pollutant buildup
  (like regular storm drain cleaning or parking lot sweeping)

Non-Structural BMP Benefits

• Cost-effective
• Support long-term compliance
• Improve overall site cleanliness and safety
• Reduce the load placed on structural BMPs

Non-Structural BMP Challenges

• Require staff training and consistent implementation
• Results may be less visible to property managers
• Must be routinely documented for regulatory compliance
• Typically work best when paired with structural systems
  

Why You Need Both: The Best Approach for Compliance

Most commercial and multifamily properties in the Chesapeake Bay watershed – including Maryland, DC, Northern Virginia, and Delaware – rely on a combination of both BMP types.

Structural BMPs

Manage the physical runoff, control peak flows, and remove pollutants.

Non-Structural BMPs

Reduce pollution before it enters the stormwater system and support regulatory documentation.

Together, they create a complete stormwater compliance strategy that:

• Protects local waterways
• Reduces maintenance emergencies
• Improves long-term site performance
• Helps avoid violations and fines
• Supports MS4 and Chesapeake Bay TMDL requirements

What This Means for Property Managers and Owners

If you’re responsible for stormwater compliance, here’s what matters most:

1. Know what BMPs your property has

Many facilities have multiple BMP types – and some property managers inherit systems without complete documentation.

2. Maintain structural BMPs consistently

Retention ponds, bioretention areas, storm filters, and vaults must be inspected and serviced regularly to remain compliant.

3. Document non-structural BMP programs

Regulators require records demonstrating pollution-prevention practices.

4. Conduct routine inspections

Professional oversight helps catch issues early – before they become expensive or lead to violations.

5. Plan for long-term budgets

Structural BMPs may need periodic restoration (replanting, sediment removal, repairs).

iSTORMWATER: Your Partner for Complete Stormwater BMP Support

Our team works with commercial property managers, government contractors, and developers across MD, DC, Northern Virginia, and DE to keep facilities compliant and performing.

We offer:

• Structural BMP inspections, maintenance, installation & repairs
• Vault and StormFilter® cartridge cleaning
• Pond maintenance and dredging
• Bioretention restoration and vegetation management
• Non-structural BMP program support
• Stormwater compliance documentation
• Emergency service and corrective action plans

If you’re unsure what BMPs your site has – or whether they’re functioning properly – we can help.

📞 Call us at (410) 231-3455 or 💬 Contact us online.