FAQ: Water Quality

What about the mid-Willamette source’s water quality? 

The watershed that feeds the Willamette River is very large and produces consistent,  high volume  flows. This section of the Willamette River has been tested extensively over the last decade, and results have found it to be a quality drinking water source. The impacts from upstream urban and rural activities on the river’s water quality in the mid-Willamette area is minimal.  The intake for the mid-Willamette option is in Wilsonville, miles upstream from Portland and the Portland Harbor superfund site.

How will mid-Willamette water be treated?

Steps for the new state of the art Willamette Water Suppy System treatment plant will include enhanced coagulation sedimentation, ozone and ultraviolet treatment, granulated activated carbon filtration, sand filtration, and chlorine disinfection (learn more here), which provide treatment specifically for the types of contaminants that might be present from upstream influences.

How would an algal bloom in the Willamette River affect water quality?

The filtration plant will use a multiple step filtration and treatment process that is very effective at removing organic material including algae. Most algal species are not toxic, but if a toxic algae event were to occur treatment processes are effective at removing algae and associated toxins. If there were any issues that would cause the filtration plant to be less effective at removing algae and associated toxins, TVWD, Hillsboro and Beaverton would use one of their other sources to serve customers and avoid any risk to public health.

How would a fire in the Willamette Valley or upper reaches of the Willamette River affect water quality?

The Willamette is the largest watershed in Oregon with 13 major tributaries along its 300 mile stretch. The vast size of the watershed alone would reduce the impact of a forest fire in one of the sub-watersheds on overall water quality in the Willamette River. It is unlikely that a forest fire would impact the entire watershed.

In the rare event a forest fire were large enough to significantly impact water quality in the main stem of the Willamette River, the water treatment and filtration process—like those used at the Willamette River Water Treatment Plant in Wilsonville, would serve as a barrier and remove any impurities caused by the fire.

If, for some unforeseen reason, the event is extreme enough that the filtration plant was unable to treat drinking water to standards set by the State of Oregon and the Environmental Protection Agency, TVWD, Hillsboro and Beaverton would turn to one of their other sources of water to serve their customers. This is another example of why having more than one supply of water is critical to a reliable water system.

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Our Reliable Water

Program Timeline

Developing the new Willamette water source will take over a decade.

Willamette Water Supply Program

Willamette Water Supply Program