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  4. Filterra Bioretention
A landscaped median with trees and shrubs runs alongside a road, bordered by a sidewalk and storm drain.

Filterra® Bioretention

Filterra is similar to bioretention, but has been optimized for high volume/flow treatment and high pollutant removal. Its small footprint allows it to be used on highly developed sites such as landscaped areas, parking lots and streetscapes.
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How Filterra Works

Stormwater runoff enters the Filterra system through a curb-inlet opening or pipe and flows through a specially designed filter media mixture contained in a landscaped concrete container. The filter media captures and immobilizes pollutants; those pollutants are then decomposed, volatilized and incorporated into the biomass of the Filterra system’s micro/macro fauna and flora. Stormwater runoff flows through the media and into an underdrain system at the bottom of the container, where the treated water is discharged.

Filterra Features and Benefits

Features Benefits
High media flow rate (up to 324" per hour) Reduced footprint compared with traditional bioretention

Third party field testing confirmed that Filterra meets state regulatory requirements for pollutant removal under TAPE and TARP testing

Regulatory Compliance

Filterra offers the most cost effective stormwater treatment system featuring low cost, easy installation and simple maintenance

Value

Landscaping enhances the appearance of your site making it more attractive while removing pollutants

Adds aesthetic appeal to your site

Available in multiple configurations and sizes

Flexibility to meet site-specific needs

No confined space access, and activation is included with the purchase of every system

Simple and easy maintenance

 

Filterra Media – Proven Pollutant Removal

At the heart of all Filterra systems is Filterra engineered media; a specified gradation of washed aggregate and organic material homogeneously blended under strict quality controlled conditions. The filter media has been optimized to operate under high flow rates (up to 324 inches/hour) while maintaining pollutant removal performance. Filterra media is tested for hydraulic functionality, fertility, and particle size distribution to ensure uniform performance.

MEASURED POLLUTANT REMOVAL PERFORMANCE
Pollutant Median Removal Efficiency Median Effluent Concentration (mg/L)
Total Suspended Solids 87%1 8.02
Total Phosphorus (TAPE) 80% 0.05
Total Nitrogen 34% 0.33
Total Copper 79% 0.011
Dissolved Copper 56% 0.007
Total Zinc 70% 0.04
Dissolved Zinc 66% 0.02
Hydrocarbons3 87% 0.71

Source: Contech (TAPE) 2024
1. 2024 TAPE Results for influent concentrations 100-200 mg/L
2. 2024 TAPE Results for influent concentrations <100 mg/L
3. Source: Herrera (TAPE) 2009

Some jurisdictions recognize different removal rates - see your Contech Stormwater Consultant for performance expectations.

Select Filterra Approvals

Filterra is approved through numerous local, state and federal verification programs, including:

  • New Jersey Department of Environmental Protection (NJ DEP) 
  • Washington Department of Ecology (GULD) – Basic, Enhanced, Phosphorus, and Oil
  • Maryland Department of the Environment - Environmental Site Design (ESD)
  • Texas Commission on Environmental Quality (TCEQ)
  • Virginia Department of Environmental Quality (VA DEQ)
  • Maine Department of Environmental Protection (ME DEP)
  • Atlanta, GA Regional Commission
  • Los Angeles County, CA - Alternate to Attachment H
  • City of Portland, Oregon Bureau of Environmental Services
  • North Carolina Department of Environmental Quality (NC DEQ)

Filterra Configurations

  • Filterra Offline
  • Filterra Peak Diversion
  • Filterra Internal Bypass Curb
  • Filterra Sediment Chamber (Maryland only)
  • Filterra Bioscape Vault
  • Filterra Bioscape Valut Basin 
  • Filterra Bioscape

Filterra Installation and Maintenance

We make it easy for you...

  • Vegetation selection guidance based on your climate zone.
  • Activation is included with every system
  • Ongoing maintenance is simple.
  • Clean biofiltration bay with simple landscape tools (rake and shovel).
  • No confined space entry required when vegetation specified.
  • Everything can be accessed from the surface
Filterra stormwater bioretention system offline configuration.
Filterra Offline

The Filterra Offline configuration is the most economical and simplest Filterra configuration. It utilizes a downstream catch basin or curb inlet for bypass flows allowing for the shallowest profile and most flexible design of any of the Filterra configurations. It is ideal for both new and retrofit projects.

Cross-section of a composting toilet showing waste input, composting chamber, and output pathway.
Filterra Offline Manhole

The Filterra Offline Manhole utilizes a simple pipe connection and can be buried deep, making it ideal for urban or tight areas with limited horizontal space.

Filterra stormwater bioretention system, peak diversion configuration.
Filterra Peak Diversion

The Filterra Peak Diversion provides treatment and high-flow bypass in one structure, eliminating the need for an external bypass structure. This configuration also allows for multiple inlet options, including curb inlets, pipe inlets, and grate inlets.

Cutaway diagram of a concrete filtration tank with labeled bypass, showing internal layers of gravel and sand.
Filterra Peak Diversion Manhole

The Filterra Peak Diversion Manhole provides treatment and high-flow bypass in one structure, eliminating the need for an external bypass structure. This configuration also allows for pipe inlets and grate inlets.

Filterra stormwater bioretention system, internal bypass curb configuration.
Filterra Internal Bypass Curb

The Filterra Internal Bypass Curb incorporates a curb inlet treatment chamber and internal high flow bypass in a single structure. This eliminates the need for a separate bypass structure and enables placement in a “sag” or “sump” condition.

Filterra stormwater bioretention system, sediment chamber configuration.
Filterra Sediment Chamber (Maryland only)

The Filterra Sediment Chamber includes a pretreatment sediment chamber that provides a settling area for large debris and sediment prior to water entering the media bay.

Filterra Bioscape vault stormwater bioretention system.
Filterra Bioscape Vault

The Filterra Bioscape Vault utilizes an open top configuration and downstream catch basin or curb inlet for bypass flows allowing for a shallow profile. Internal Bypass configurations are also available in some locations.

Filterra Bioscape vault basin stormwater bioretention system.
Filterra Bioscape Vault Basin

The Filterra Bioscape Vault Basin allows for a vault based system to be fully integrated into the landscape. Multiple inlet options are available via the side slopes, including sheet flow. Bypass is typically achieved via an upstream structure.

Filterra Bioscape stormwater bioretention system.
Filterra Bioscape

The Filterra Bioscape utilizes all of the Filterra components, but without the concrete structure, allowing for multiple inlets and installation directly into a basin. Bypass is achieved via an upstream structure.

Filterra Bioretention Solutions Guide

Stormwater Management Solutions Brochure

Filterra FAQs

The best solution depends on several project-specific factors, including regulatory requirements, drainage area, treatment flow or volume, available footprint, hydraulic grade, depth constraints, and maintenance access. Filterra is often a good fit where a compact, landscape-integrated biofiltration solution is desired, while Modular Wetlands Linear may be better suited for projects that require a subsurface or vault-based system with higher treatment capacity or different site layout constraints. Your local Contech Stormwater Consultant can help evaluate the project requirements and recommend the most appropriate system for your site.

Filterra systems can be used successfully in cold-weather environments when they are properly designed, installed, and maintained. A common concern is whether the biofiltration media will freeze. In practice, if conditions are cold enough for the media to become fully frozen, there is typically limited stormwater runoff occurring at that time. As snow and ice begin to melt, systems designed with adequate drainage and appropriate pretreatment generally recover and resume normal function. For additional information on this topic, please refer to this blog post - Biofiltration in Cold Climates: Risks, Realities, and Proven Design Strategies

With proper inspection and routine maintenance, Filterra media has been documented to perform for more than 20 years. Actual service life may vary based on site conditions, pollutant loading, sediment accumulation, and maintenance frequency.

The required elevation difference, or hydraulic drop, for a Filterra system varies depending on the applicable regulatory approval, system configuration, and site conditions. A typical Filterra system requires approximately 30 inches of elevation difference from inlet to outlet. Shallow configurations may be available for certain applications. Contact your local Contech Stormwater Consultant to evaluate your site and determine the appropriate configuration.

The project engineer or landscape architect typically specifies the plant for the site. Contech can provide guidance and a list of pre-approved plants suitable for different hardiness zones. If a preferred plant is not included on the pre-approved plant list, Contech can review it for acceptance on a project-specific basis. 

Filterra systems use double-shredded wood or bark mulch that meets Contech’s specification requirements. The mulch can typically be sourced from local landscape material suppliers. For full mulch specifications, contact your local Contech representative.

The Filterra system can be designed outside of a precast structure as a Bioscape configuration.

Yes. Filterra can be used in a raised planter configuration when stormwater can enter at the top of the media and mulch layer and discharge from the bottom of the system. In these applications, the top of the vault may be placed above grade, typically using a cast-in-place configuration. Standard precast Filterra systems are typically installed with the top of the unit flush with finished grade.

A Filterra open-top vault configuration can be manufactured and delivered as a more complete system, with internal components and, depending on vault size, stone and media preinstalled. This can simplify installation, improve quality control, and reduce the amount of field assembly required. Vault-less Filterra Bioscape systems integrate well into landscaped areas and can provide greater layout flexibility, but typically require more on-site installation of internal components, stone, and media.

Trees and plants in a Filterra bioretention system do not need to be replaced on a fixed schedule. With proper species selection and routine maintenance, trees can often last 10–20 years or more.

Plants should only be replaced when they show signs of disease, pest infestation, or decline that cannot be corrected through maintenance.

For a complete list of recommended plants, please visit: https://www.conteches.com/technical-guides/search/?filter=OOIA4XCWXG

Yes, it is possible, but it depends on the elevation and the location of the pipe inlet relative to the curb.  Typically, if both are needed, we recommend a Filterra Peak Diversion configuration.

The Filterra with Sediment Chamber is a special configuration for the state of Maryland. For information about Filterra with Sediment Chamber, we recommend you contact Contech’s local Stormwater Consultant in Maryland, noted below. 

Matthew Griffin, P.E. (Maryland)
Stormwater Area Manager
901 Elkridge Landing Road, Suite 350|Linthicum Heights, MD 21090
Primary (Mobile) Telephone 410.736.2134 Secondary Telephone 443.457.1503 
[email protected]

The maximum treatment flow rate of the Filterra system is up to 324”/hr per TAPE approval. The maximum bypass flow rate varies based on system configuration.

Many Georgia municipalities offer stormwater utility fee credits for implementing Best Management Practices (BMPs) that reduce runoff volume and improve water quality. 

Since Filterra is a high-performance bioretention system designed to treat stormwater runoff and improve water quality, it may qualify for such credits. However, eligibility and the amount of credit can vary by jurisdiction. It is recommended that you consult your local Contech Stormwater Consultant for specifics. 

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