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?
The Willamette Water Supply Program will design and build a water filtration plant similar to the one currently operating in Wilsonville. Wilsonville has used the Willamette River as a drinking water source for more than a decade and has never had a water quality violation. The Willamette River Water Treatment Plant has multiple methods to treat the water for contaminants and produces top quality drinking water. The treatment process includes conventional filtration, ozone, and activated carbon, 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 plan 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 and Hillsboro 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 and the City of Hillsboro 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.