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Filtering the Water

The Green River Filtration Facility by Air in April 2015

After nine years in the making, filtered water has finally hit the streets – or the pipes in the streets.

With the completion of the Green River Filtration Facility, filtering and disinfecting the water supply is our primary water treatment process.

Filtration improves the water by:

• Protecting against contaminants such as cryptosporidium

• Improving the taste and clarity of water

• Reducing the amount of silt and sand entering water pipes

• Minimizing natural organic material in water, which helps reduce byproducts from disinfection processing


Why Do We Filter?

Tacoma Water provides direct service to more than 300,000 people in the City of Tacoma, Pierce and King counties, and several other municipal water suppliers. Our primary water supply is the unfiltered Green River, which began supplying Tacoma its water in 1913. Until 2015, the Green River was one of the few remaining major unfiltered surface water supplies in the U.S.

In January 2006, the Environmental Protection Agency required that, in order to meet new national standards for public health protection, water utilities provide treatment for the removal of cryptosporidium, a pathogen that can cause disease in humans.

After much study and public input, the result was the decision to filter our water supply, and build the Green River Filtration Facility at the Tacoma Water Headworks, near the town of Cumberland in south King County.

Levels of cryptosporidium remain low in the Green River water supply. We do not currently have any issues with this organism.


Learn More About Our New Facility