Steps followed in a monitoring cycle when an algae bloom is present
Staff increase the volume of the sampling sites and the frequency of the sampling. The number of sampling locations and the frequency of our sampling depend on the severity and location of the bloom at Detroit Reservoir.
Typical sample sites include:
- Blowout Creek
- Heater Creek
- Log Boom
- Log Boom at shallow spillway
- Packsaddle Park
- Intake to the Geren Island Water Treatment Facility—called Middle Intake
- Combined Filter Effluent (CFE)
The sampling process is similar to normal watershed operations in that staff sample for algae (type), algae enumerations (count), and toxins, and recording field observation data (wind, temperatures, etc.) as well as retrieving water quality data from an YSI datasonde.
Other strategies used to keep our drinking water safe during an algae bloom
In late May 2018, during the time of Salem’s drinking water advisory, we adjusted the chlorine and pH levels, flushed water lines, and added water from underground supplemental water systems to dilute the toxin, since it was first detected in the samples.
When an algae bloom is present, our first step is to modify the treatment of our drinking water through a combination of the following options:
- Shutting down the intake at Geren Island for short durations to allow water to pass by plant
- Utilizing a “roughing filter” to filter water before pumping water to finished water filter
- Blending raw river water to the subsurface groundwater
- Increasing the chlorine residual
- Decreasing the pH
- Flushing the distribution system