What Is Bioretention? A Green Infrastructure Solution for Industrial Stormwater

Bioretention system with trees, shrubs, and engineered landscaping at a commercial facility, designed to capture and treat stormwater runoff for compliance and pollution removal. — *Photo by Guzzardo Partnership, licensed under CC BY-SA 4.0.*

A Natural Solution to Industrial Stormwater Pollution

Bioretention is a type of green stormwater infrastructure that uses soil, plants, and filtration to remove pollutants from runoff before it enters waterways. Bioretention is a best management practice (BMP) recommended by the U.S. Environmental Protection Agency (EPA) and is often designed to look like simple landscaping features to provide effective and attractive stormwater management¹.

How Bioretention Works

Bioretention systems treat stormwater through a combination of:

Filtration through engineered soil layers
Adsorption of pollutants onto soil particles
Uptake of nutrients and metals by plants

Originally developed in the early 1990s by the Maryland Department of Environmental Resources, these systems have proven highly effective at reducing concentrations of:

Heavy metals
Nitrogen
Phosphorus

Studies show that properly designed bioretention systems can remove up to 90% of total suspended solids (TSS), 70 to 85% of phosphorus, and 60 to 75% of total nitrogen from stormwater runoff^2,3. These reductions help improve downstream water quality and support regulatory compliance.

Bioretention bioswale in the landscaped median of Grange Avenue, Greendale, Wisconsin, showing stormwater vegetation and infiltration in an urban setting. — *Photo by Aaron Volkening, licensed under CC BY 2.0.*

Regulatory Benefits for Industrial Facilities

Under the National Pollutant Discharge Elimination System (NPDES) permit program, industrial facilities are required to implement BMPs that reduce pollutants in stormwater discharges. Bioretention is considered a structural BMP that can help facilities:

Achieve effluent limits for nutrients and metals
Meet the terms of their Stormwater Pollution Prevention Plan (SWPPP)
Reduce monitoring burdens over time

For industries subject to the Multi-Sector General Permit (MSGP), bioretention provides a practical and often cost-effective option for meeting permit conditions and reducing discharge volumes.

What Does a Bioretention System Look Like?

A typical bioretention system may resemble a rain garden or planted depression next to a parking lot, loading dock, or access road. Components include:

Grass buffer, which slows incoming runoff
Sand bed filter that distributes water and slows flow
Ponding area to capture and treat runoff via infiltration

In areas with low-infiltration soils (e.g., clay), an underdrain can direct treated runoff into the storm sewer system. Overflow structures help manage extreme storm events without damaging the system¹.

Cross-sectional diagram of a bioretention area showing stormwater runoff, infiltration through soil layers, and evapotranspiration in a landscaped basin used for sustainable drainage and environmental compliance. — *Source: USEPA Storm Water Technology Fact Sheet: Bioretention (1999)*

Key Design Considerations for Industrial Facilities

When designing bioretention for industrial applications, several factors are critical:

Sizing: Account for drainage area, impervious surface coverage, and target storm events.
Pretreatment: Use grass buffers or sediment forebays to remove larger debris and extend filter life.
Media selection: Engineered soil mixes for bioretention vary based on design goals, infiltration requirements, and pollutant targets. Typical mixes include 50 to 65% coarse sand, 25 to 35% topsoil, and 10 to 15% compost or organic matter by volume⁴.
Vegetation: Native, deep-rooted plants are preferred for their tolerance to saturated conditions and pollutant uptake capabilities.
Underdrains and overflow: Necessary for clay soils or areas with high groundwater tables to prevent standing water.

Why Use Bioretention for Industrial Sites?

Bioretention systems provide a range of benefits for industrial stormwater management:

Removes key pollutants (nutrients, metals, oils, solids)
Reduces runoff volumes and peak flow
Can be retrofitted into existing spaces (e.g., parking lots, medians)
Blends into the landscape and improves curb appeal
Requires minimal maintenance (e.g., weeding, mulching, sediment removal)

Industrial clients often install bioretention cells at the base of loading docks, parking areas, or equipment yards to filter runoff and reduce NPDES permit noncompliance risk.

When Is Bioretention Not Ideal?

While bioretention is a versatile tool, it may not be suitable in every situation:

High pollutant loading areas (e.g., uncovered material storage yards)
Space-constrained industrial facilities
Poor infiltration sites without drainage solutions

In these cases, alternative stormwater treatment structures like sand filters, infiltration trenches, or underground detention systems may offer better performance.

Need Help with Stormwater Management or Designing a Bioretention System?

While there’s no one-size-fits-all solution to stormwater pollution, bioretention systems are a practical and cost-effective option, especially for industrial properties.

PSARA provides stormwater BMP design, permitting, and compliance support. If your facility needs help meeting effluent limits or implementing effective BMPs, contact us.

References

Footnotes

U.S. EPA. Storm Water Technology Fact Sheet: Bioretention, EPA 832-F-99-012 (1999).
Prince George’s County, Maryland. Low Impact Development Design Manual (2000).
Center for Watershed Protection. Design of Stormwater Filtering Systems (1996).
Minnesota Pollution Control Agency. Engineered (Bioretention) Media Mixes for Stormwater Applications (2023).