Watershed (algae) monitoring
The City also monitors conditions in the North Santiam River and Detroit Reservoir. Algae and cyanotoxins, in addition to other water quality parameters, are monitored in the watershed. Data collected from the watershed can be used to adjust drinking water treatment processes at Geren Island, if needed. This allows us to provide high quality water to our residents and customers.
Monitoring in the watershed typically begins in April or May and ends in September or October (algae season), depending on the weather conditions and Detroit Reservoir water levels.
Preparation for algae season
Algal blooms, a common occurrence in surface water, have been visible in Detroit Reservoir, from spring through fall for the last few years. Some algal blooms are known to produce harmful
cyanotoxins, but others do not. In May 2018, water quality samples revealed that cyanotoxins were detected in Salem's drinking water distribution system above a Health Advisory Level (HAL) for the first time. In response, a drinking water advisory was issued, based upon the level of cyanotoxins detected, to vulnerable populations in Salem.
To ensure safe drinking water for Salem residents and address
new drinking water regulations from the
Oregon Health Authority, the City of Salem follows a robust water quality sampling and testing process.
During algae season, we are required to sample drinking water for cyanotoxins in two locations: (1) before treatment, from the intake to the water filtration plant prior to any treatment (source water); and (2) after treatment, the point at which the treated water enters the distribution system (treated water) if there is a detection above 0.3 parts per billion (ppb) in the untreated source water.
We are following the required sampling protocol and taking additional samples in the watershed, at different steps in the treatment process and in the water distribution system. This way, we can be sure whether the treatment is working. And, these additional tests allow our staff to better assess changing conditions in the treated water and add more treatment steps if needed to provide safe water.
When algae is present in Detroit Reservoir
As soon as algal blooms are seen at the Log Boom in Detroit Lake, the sampling frequency increases to five days per week at the Intake. This water quality data
will be posted to our website.
When cyanotoxins are present in Detroit Reservoir
If cyanotoxins from the algal blooms are also detected in Detroit Reservoir, additional drinking water treatment processes will be triggered at the Geren Island Water Treatment Facility.
If cyanotoxins are detected at the Intake, the sampling frequency immediately increases to seven days per week and drinking water treatment processes are modified to include increased chlorine dosage and/or powdered activated carbon. Additional sampling locations, (including Aldersgate - entrance to Salem's drinking water distribution system), are also activated to provide additional water quality data.