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Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.

GENERAL INFORMATION: 503-823-7404

1120 SW Fifth Ave, Suite 600, Portland, OR 97204

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Microbiological

The rules relating to surface water treatment also deal with microbiological issues, namely treatment to inactivate Giardia and Cryptosporidium.


The Total Coliform Rule is in the process of being revised. 

Total Coliform Rule (1990)

Effective December 31, 1990, this rule provides an updated framework for monitoring coliform bacteria, which serve as an early warning system for detecting conditions favorable to waterborne pathogens.
Requirements for the Portland water system include:

  • A current monitoring plan approved by the State of Oregon.

  • Collecting and analyzing a minimum of 210 water samples from its distribution system each month.

  • Total coliform bacteria must be absent in 95 percent of the samples; for each positive coliform sample, three resamples must be collected and analyzed within 24 hours.

  • Any E. coli positive sample followed by a positive total coliform sample, or a positive total coliform sample followed by a positive E. coli sample is a violation of the rule.

The State of Oregon approved the Portland Water Bureau's coliform monitoring plan in 1990. This plan was revised in 2005.The Portland Water Bureau collects and analyzes between 250-350 samples per month; most sampling sites are dedicated sampling stations. There have been no maximum contaminant level, monitoring, or reporting violations. The Portland Water Bureau continues to evaluate its monitoring plan and results to ensure ongoing compliance.

Long Term 2 Enhanced Surface Water Treatment Rule (2006)

Published in December 2005, the Long Term 2 Surface Water Treatment Rule (LT2) applies to surface water or groundwater under direct influence of surface water (GWUDI) systems, increasing the regulation of Cryptosporidium. LT2 also addresses the regulation of Cryptosporidium, Giardia and Viruses in open reservoirs.