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The City of Portland, Oregon

Development Services

From Concept to Construction

Phone: 503-823-7300


1900 SW 4th Ave, Portland, OR 97201

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New Sizing Standard Required for Contech StormFilter with ZPG

Rain Garden

As the City of Portland develops, impervious surfaces such as parking lots, roadways, and rooftops increase the pollution levels and temperature of stormwater transported to streams, rivers, and groundwater resources. Managing stormwater runoff helps protect Portland’s waterways, benefitting human health, fish and wildlife habitat, and recreational resources. 

Stormwater management is also critical in terms of protecting Portland’s sanitary and stormwater infrastructure. Increased stormwater runoff contributes to combined sewer overflows (CSOs), basement sewer backups, and localized flooding. 

BES requires vegetated stormwater management systems such as ecoroofs, planters, and rain gardens to the maximum extent feasible because of the multiple benefits these systems provide. Where green systems aren’t feasible BES may approve Manufactured Stormwater Treatment Technologies (MSTTs) that meet Portland’s stormwater management requirements.  

BES reviews and approves MSTTs for use in Portland based on test results confirming performance over an extended period, as well as maintenance requirements. There are currently four MSTTs on BES’ list of approved devices (see  

BES approved a MSTT, the Contech StormFilter with ZPG, in 2002 under the review criteria in place at the time. In 2017 BES re-assessed the performance of the device under updated review criteria and has re-approved the StormFilter with a new sizing standard (see ) which requires a larger system for a given drainage area than previously approved. BES will phase the required adoption of the new sizing standard for the Contech StormFilter with ZPG as follows: 

  • BES will require all projects/permits to incorporate the new sizing standard starting January 1st, 2018.
  • Projects approved for use with the old sizing standard will be vested in that standard if the “in date” on the permit is prior to January 1st, 2018.
  • A prior Early Assistance/Pre-Application Conference alone does not vest a project in the old sizing standard. 

If you have questions about the new Contech StormFilter sizing standard, please send an email to If you have questions about how this might impact your permit, please call the BES Development Review Hotline (503-823-7761).