Health advisory issued for Dorena Reservoir

The Oregon Health Authority (OHA) reported on Wednesday that a recreational health advisory had been instituted at Dorena Lake, six miles east of Cottage Grove, after the presence of harmful algae had been detected. Drinking water in Cottage Grove, which originates in Dorena Reservoir, is currently unaffected.

According to a press release issued by OHA, “Harmful algae at this level are likely to be associated with cyanotoxin concentrations that can be harmful to humans and animals.”

Currently, OHA has advised that residents who draw in-home water directly from the affected area use an alternative water source due to the inability of private treatment systems to remove algae toxins. Public treatment water systems, according to OHA, can reduce the toxin through proper filtration and disinfection.

The Cottage Grove City manager’s office referred questions to the Row River water treatment facility’s superintendent Ray Pardee.

"Drinking water is safe," Pardee said. "We are testing the water that we bring to the water treatment plant from the Row River that comes from Dorena Reservoir and the tests we have done so far have not detected any of the toxins the bloom could produce." 

Recreational visitors were advised to be alert and to avoid areas with visible scum that appears foamy, thick or that is pea-green, blue-green or brownish-red in color.

“People should avoid swimming and high-speed water activities such as water skiing or power boating, in areas where blooms are identified. Although toxins are not absorbed through the skin, people who have skin sensitivities may experience a puffy red rash at the affected area,” the press release read.

Officials also advised that individuals not drink water directly from Dorena Reservoir or eat fresh fish caught in its waters.

During Monday night’s city council meeting, Cottage Grove City Manager Richard Meyers told the board that the city would be testing water coming from Dorena at the intake of the Row River treatment facility every week, citing the no-drinking orders issued in Salem over the last month after officials discovered cyanotoxin in the public drinking water. Meyers informed the board that the toxin had been found in Dorena Reservoir in the past and that the city was exploring options should the algae be detected in the city’s drinking water due to the possibility that the current treatment process used at the city’s facility could cause additional toxins to be released from the algae if it is present.

"I think what he’s (Meyer) referring to is the harmful bloom cells," Pardee said. "That if they contain toxins and it enters the intake and comes to the treatment plant, we do use a process called oxidation and it could reputrue the intact algae cells and if those cells contained toxins, it would release the toxins in the water and it would concentrate the toxin in the water. A lot of ifs." 

Pardee said if the toxins were detected, the treatment facility would halt the oxidation process and make adjustments to the treatment process. 

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