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Source Protection, Observation and Treatment Keeps Water Pure

May 08, 2020

Clear Lake, where the McKenzie River begins

Clean water starts at the source

For decades, we have worked to protect the McKenzie River, our primary water source. The river emerges from Clear Lake, high in the Cascade Mountains, before flowing 85 miles to Hayden Bridge Water Filtration Plant, where we draw water from the river.

We employ a multi-faceted approach to protecting the river, which includes multiple monitoring sites throughout the McKenzie River watershed and at Cougar and Blue River reservoirs.

But monitoring alone isn't enough to guarantee clean, healthy water at the tap, especially with cyanobacteria harmful algal blooms (cyanoHABs) become more common in the reservoirs. We have recently made some changes to our filtration and treatment protocols to prevent cyanotoxins that are harmful to humans and pets from getting into the drinking water delivered to homes and businesses.

Source protection continues

Our staff work aggressively to protect this outstanding source for current and future generations, and we have been proactive in addressing threats, including cyanoHABs. Some species of cyanobacteria produce cyanotoxins.

In July 2018, in response to problems found in some Oregon watersheds, the Oregon Health Authority began regulating drinking water for the cyanotoxins microcystin and cylindrospermopsin. EWEB has performed all required monitoring and has not detected cyanotoxins at the filtration plant's water intake. Read more about cyanotoxins.

Observation and vigilance in place

Recent climate change research in the Pacific Northwest shows that with higher temperatures, earlier snow melt, and longer, drier summers, the McKenzie Watershed and surrounding areas will experience more abundant cyanoHABs that will start earlier in the spring and last longer into the fall.

Climate change impacts are already causing increased wildfires, which can increase nutrients in reservoirs, fueling cyanoHAB production. We are studying the impacts of the recent Rebel (2018) and Terwilliger (2019) wildfires on Cougar Reservoir with Oregon State University. We also partnered with the U.S. Geological Survey to install real-time water quality sensors below Cougar Reservoir, Blue River Reservoir, in the McKenzie River, and at the filtration plant water intake to measure blue green algae activity (and other water quality parameters) as an early warning system.

EWEB maintains a close partnership with the U.S. Army Corps of Engineers, which operates Cougar and Blue River reservoirs, where cyanoHABs occur. EWEB, the USGS, and the Corps partnered to add a real-time water quality sensor in Cougar Reservoir in 2020. It measures blue green algae activity at multiple depths to direct sample collection efforts and can guide Army Corps reservoir operations to reduce downstream impacts to drinking water.

To ensure proactive monitoring and decision-making, our expert staff continues to build on the source water protection, monitoring and treatment programs.

Treatment and filtration tactics

The most important line of defense to prevent cyanotoxins from entering Eugene's drinking water supply is the filtration plant, where staff monitor the early warning systems and react with appropriate treatment changes to mitigate for cyanotoxins.

Our Water Quality Lab recently added analytical equipment capable of quickly and accurately assessing the presence of cyanotoxins at low levels, and at much reduced cost compared with shipping to out-of-state laboratories. This allows us to make rapid decisions about monitoring and water treatment strategies to mitigate any impacts to drinking water.

In addition, the filtration plant was converted to biological filtration in 2018 and this has demonstrated effectiveness in removing cyanotoxins. If cyanotoxins reach the filtration plant water intake, the biologically active filters can "eat" the toxins as a food source, effectively removing them as the water flows through the filters. We can also utilize activated carbon and chlorination as effective means to treat cyanotoxins.