Contech Kraken Membrane Filter

The Bureau of Environmental Services approves the Contech Kraken Membrane Filter for use in the City of Portland on private property with the conditions detailed below. The Kraken is not approved for use in the right-of-way, based on the Bureau of Environmental Services considerations about the logistical efficiency of the bureau's right-of-way maintenance operations for manufactured stormwater treatment technology, including the program changes (e.g. equipment and supplies) that would be required to service the Kraken.   

Conditions of use

1. All configurations covered in the Washington State Department of Ecology Technology Assessment Protocol approval for the Kraken Membrane Filter are approved for Total Suspended Solids (TSS) removal. Selection of a specific configuration is the responsibility of the project designer.  
2. Use of the Kraken does not exempt a project or site from required flow control requirements, operations and maintenance requirements, or other applicable requirements of the Stormwater Management Manual.
3. Bio Clean-certified providers should be utilized for activation, inspection and maintenance of the system.

Operations and maintenance requirements (field installations)

The Washington State Department of Ecology General Use Level Designation for the Kraken, published in December 2019, provides a summary of the available data concerning the frequency of maintenance required during field trials of the Kraken. The document includes the following statement concerning issues to be addressed by the company: "Conduct hydraulic testing to obtain information about maintenance requirements on a site with runoff that is more typical of the Pacific Northwest."

Project designer responsibilities

1. Ensure that the Conditions of Use are met.
2. Ensure the project meets all applicable requirements of the City of Portland Stormwater Management Manual, including the Stormwater Infiltration and Discharge Hierarchy.
3. Ensure the design and installation of the units are appropriate for the project goals, site conditions, long-term maintenance requirements, and any other site-specific design requirements.
4. Size units to meet the current Portland Stormwater Management Manual Performance Design Approach and pollution reduction requirements. The pollution reduction capacity is flow-based and assumes a treatment flow intensity of 0.19 inches per hour, with a 5-minute time of concentration, and a 0.90 runoff coefficient using the Rational Method with treatment rates based upon Washington State Department of Ecology General Use Level Designation approved flow rates. The treatment capacities for the Kraken Membrane Filter, based on those assumptions, are provided in Table 1. For sites with different times of concentration, different rainfall intensities may be appropriate.

Sizing units to meet the current Stormwater Management Manual presumptive design approach and pollution reduction requirements. Each 30.75-inch-tall cartridge has 170 square feet of surface area and a design flow rate of 0.019 cfs.

5. Each site plan must be reviewed by Bio Clean before the City of Portland can approve the unit(s) for site installation. A letter certifying the project has been designed to the manufacturer's specification must be submitted to the Bureau of Environmental Services prior to approval of the building permit plan. The project designer is highly encouraged to work with Bio Clean prior to the appropriate review milestone to optimize placement and performance of the unit(s).  
6. If the project designer wishes to vary from these conditions of approval, the project designer must use the Performance Design Approach required by the Stormwater Management Manual. 

General conditions

1. The Bureau of Environmental Services may at any time suspend or revoke approval if the performance of the technology does not meet performance criteria, if there are changes to the Technology Assessment Protocol certification, or the performance criteria change due to local, state, or federal pollution reduction standards.
2. If any changes, updates, or revisions occurred to the Kraken Membrane Filter, the applicant must obtain Washington State Department of Ecology Technology Assessment Protocol General Use Level Designation certification and re-apply following submission guidelines in effect at the time of application.  

More information on the product can be found on the manufacturer's product website. 

Approved: January 2021 under the requirements of the 2016 Stormwater Management Manual.