The TAPE Process: Assessing Emerging Technologies in Stormwater

Filterra Bioretention Diagram, Contech Engineered Solutions

The Technology Assessment Protocol – Ecology (TAPE) Program is the Washington State Department of Ecology’s process for evaluating and approving emerging stormwater treatment Stormwater Control Measures (SCMs). New stormwater treatment SCMs that are not in the current Stormwater Manual or have not been approved by TAPE must first be approved by Ecology's TAPE Program, an effective way to keep up with emerging technologies.

The TAPE program

It can be hard to keep up with new methods for managing stormwater when the technology changes so rapidly. While no regulators are immune to this problem, the Washington Department of Ecology has developed a program that lets them keep apace. The Technology Assessment Protocol Ecology (TAPE) process is designed to certify emerging treatments, and is so successful that it has been adopted by other states and municipalities across the country.

TAPE is run by the Washington Department of Ecology and assisted by the Washington Stormwater Center. The process is peer-reviewed by a paid Board of External Reviewers with industry expertise who assess performance data to determine whether the stormwater technology should be certified. The performance data is collected by putting the candidate treatment under rainfall conditions “typical of the Pacific Northwest,” and comparing against the design and performance goals from the stormwater management manuals for Washington. The performance goals break into five categories: pretreatment, basic treatment, dissolved metals treatment, phosphorus treatment, and oil treatment. Technologies are submitted to the Washington Department of Ecology, and simply need to follow the TAPE process, prepare the technology, and send in the application to be considered. The technologies that pass through TAPE meet or exceed the performance of existing technologies and are put forward with notes for which previous treatments they can replace.

Through the Red TAPE: Approved Technologies

Emerging technologies that pass through the Board of External Reviewers are published, along with their performance data. The devices that receive TAPE designation are categorized based on treatment type. These categories are similar to those for performance, but aren’t identical. Approved stormwater treatments are typed as either pretreatment, basic, enhanced, oil, phosphorous, or construction. This approval isn’t the final step though, and it’s important to note that local jurisdictions still need to approve installation. To get an idea of the caliber of stormwater innovation required to pass TAPE, here are a few technologies that have gotten approval for enhanced treatment:

Filterra Bioretention

Approved in eight states, the Filterra is designed to function similarly to bioretention, but has even higher pollutant removal. It’s often used at smaller sites similar where surface area is at a premium due to its small footprint. The system is able to handle high flow volumes and can be used in lieu of bioretention as a stand-alone treatment, or in series with other SCMs. The Filterra system starts at a curb-inlet opening or pipe, where stormwater runoff enters and flows through a proprietary media within a landscaped concrete container. The media traps pollutants so that they decompose and are incorporated into the biomass. While pollutants are trapped, the stormwater itself continues on and flows through an underdrain at the bottom of the container to be discharged.   

The Filterra is an important technology to receive TAPE accreditation because it can help meet the need for end-of-pipe enhanced treatment. The Washington State Department of Transportation recognizes that this emerging technology aligns with the treatment provided by constructed wetlands, which require both a larger area and frequent maintenance that can be difficult to allocate in urban areas. Biofiltration swales, which also provide a similar style of stormwater treatment and take up less space, are only approved for basic treatment. This leaves the Filterra’s enhanced treatment rating as the more versatile alternative.


Aqua-Swirl™ Stormwater Treatment System is a custom flow-through water quality device intended to remove “sediment, debris and free floating oil by utilizing hydrodynamic separation technology.” With no moving parts, it operates as a gravity-driven separator with a single swirl chamber able to be combined modularly.  In passing through the TAPE process, the Aqua-Swirl achieved over 85% sediment removal. Small and light, the Aqua-Swirl doesn’t even need heavy lifting equipment for installation! For maintenance, the units are designed to be accessed from the surface so that there is no need for confined space entry.

These are just two examples of emerging stormwater technologies certified by TAPE, which has approved tens of devices in each of its qualifying categories. If you’d like to learn more, or have questions about implementing this technology, don’t hesitate to reach out to us!