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Council pauses reservoir mixer design after sampling shows no stratification
Summary
Reservoir temperature profiling found uniform temperature and a transient low chlorine residual likely from a dosing leak; staff offered options and the council directed a pause with resampling next summer and an engineering review of tank-coating video.
City staff reported results from reservoir sampling and recommended the council choose whether to proceed with mixer design, pause for more data, or cancel the project.
"It was 71 degrees from top to bottom. There was no stratification," staff member Jayman said, describing temperature profiling using a submersible drone. He added that chlorine residuals were lower in the top half of the tank, likely because a dosing pump failure over the weekend had reduced dosing until it was fixed.
Given the sampling results, staff offered three options: complete the mixer design (estimated $100,000–$150,000 to install), pause design and resample next summer, or shelve the project. Council members largely favored pausing design and retesting in hot weather to see whether stratification appears at a different time of year. Staff also offered to have coatings experts review internal tank video at modest cost to identify any maintenance needs while the design is on hold.
The council asked staff to schedule summer sampling and to return with updated recommendations and cost estimates before advancing to construction.
