Stormwater Terminology Every Property Manager Should Know

Managing a commercial property means more than maintaining buildings and landscaping – it also means understanding how stormwater systems work and what regulators expect. While engineers handle design, property managers are often responsible for inspections, maintenance, and compliance. Knowing the right terminology helps you communicate effectively with inspectors, contractors, and local agencies, and avoid costly compliance issues.

Below is a practical, property-manager-focused guide to essential stormwater terms you’re likely to encounter. This glossary emphasizes operations, maintenance, and compliance – without overlapping design-heavy engineering definitions.

Core Stormwater Concepts

Stormwater Runoff

Rainfall or snowmelt that flows over impervious surfaces such as roofs, parking lots, and roadways instead of soaking into the ground. On developed sites, runoff can pick up sediment, nutrients, oils, and trash before entering stormwater systems.

Impervious Surface

Any surface that prevents water from infiltrating into the soil, including asphalt, concrete, rooftops, and compacted gravel. Higher impervious cover typically increases runoff volume and pollution potential.

Waters of the State / Waters of the U.S.

Regulatory terms used to define protected water bodies such as streams, rivers, lakes, wetlands, and tidal waters. Discharges from your property may ultimately drain to these waters, triggering compliance requirements.

Stormwater Infrastructure Terms

Storm Drain / Inlet

An opening – often a grate or curb inlet – that collects surface runoff and conveys it into an underground stormwater system. Keeping inlets free of debris is a basic but critical maintenance responsibility.

Stormwater Conveyance System

The network of pipes, swales, channels, and structures that move stormwater through a site. Blockages or failures in conveyance systems can cause localized flooding and erosion.

Outfall

The point where stormwater discharges from a pipe, channel, or structure into a downstream system or water body. Outfalls are commonly inspected for erosion, sediment buildup, and signs of illicit discharge.

Riser Structure

A vertical structure, often found in ponds, that controls the rate at which water is released. Debris accumulation around risers is a frequent maintenance issue noted during inspections.

Best Management Practices (BMPs)

Stormwater BMP

A Best Management Practice is any structural or non-structural measure used to manage stormwater quantity and quality. Property managers are typically responsible for maintaining installed BMPs according to approved plans.

Structural BMPs

Physical systems designed to treat or control stormwater, such as:

• Detention and retention ponds
• Bioretention facilities
• Hydrodynamic separators
• Stormwater vaults

These systems require routine inspection and maintenance to remain compliant.

Non-Structural BMPs

Operational practices that reduce stormwater pollution, including good housekeeping, spill prevention, employee training, and proper material storage.

Common Stormwater Facilities on Commercial Properties

Detention Pond (Dry Pond)

A basin designed to temporarily store stormwater and release it slowly. Detention ponds are typically dry between storm events and focus on flood control rather than water quality treatment.

Retention Pond (Wet Pond)

A pond that maintains a permanent pool of water and provides both water quality treatment and flow control. Excessive vegetation, sediment accumulation, or algae growth can indicate maintenance issues.

Bioretention Facility (Rain Garden)

A landscaped area that filters runoff through engineered soil and vegetation. Proper mulch depth, vegetation health, and sediment removal are essential for performance.

Swale

A shallow, vegetated channel that conveys and treats stormwater. Swales rely on proper grading and vegetation; erosion or bare spots reduce effectiveness.

Stormwater Vault

An underground structure used for storage or treatment, often housing proprietary devices. Vaults require confined-space-aware maintenance and documented cleanouts.

Inspection, Maintenance & Compliance Terms

Stormwater Inspection

A visual and/or measured evaluation of stormwater facilities to confirm they are functioning as designed. Many jurisdictions require inspections annually or after major storm events.

Maintenance Plan / O&M Manual

A document outlining inspection frequency, maintenance tasks, and responsible parties. Property managers are often expected to follow this plan and keep records.

Sediment Accumulation

The buildup of soil and debris within stormwater systems. Excess sediment reduces storage capacity and treatment efficiency and is a common cause of non-compliance.

Erosion

The wearing away of soil caused by flowing water. Erosion near inlets, outfalls, and embankments can lead to structural failure if left unaddressed.

Illicit Discharge

Any discharge to the stormwater system that is not composed entirely of stormwater, such as wash water, oils, or chemicals. These are prohibited and can result in enforcement actions.

Regulatory & Permit Language Property Managers See

MS4 (Municipal Separate Storm Sewer System)

A publicly owned stormwater system regulated under federal and state programs. Many local inspection and maintenance requirements stem from MS4 permits.

NPDES Permit

A permit issued under the National Pollutant Discharge Elimination System that regulates stormwater discharges. While property managers may not hold the permit directly, site compliance still matters.

Notice of Violation (NOV)

A formal notice issued by a regulatory authority indicating non-compliance. Prompt corrective action and documentation are critical once an NOV is received.

Why Stormwater Terminology Matters

Understanding stormwater terminology empowers property managers to:

• Communicate clearly with inspectors, engineers, and maintenance providers
• Identify issues before they become violations
• Budget appropriately for inspections and maintenance
• Protect property value and downstream waterways

You don’t need to be a stormwater engineer – but knowing the language helps you manage risk and stay compliant.

Looking for help with stormwater inspections or maintenance? Working with a qualified stormwater professional ensures your systems are inspected, maintained, and documented according to local requirements – so nothing gets lost in translation.

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