Mill Meadow Reservoir Algal Bloom Monitoring 2019

Warning Advisory

  • Do not swim or water ski in this area.
  • Avoid areas of algae scum when boating.
  • Keep animals away.
  • Do not ingest the water.
  • Clean fish well and discard guts.

Report a Bloom

24-Hour DEQ Environment Incidents Line: (801) 536-4123

Call Utah Poison Control Center

If you believe you or your pet have been exposed to a harmful algal bloom, call (800) 222-1222.

Get BloomWatch App

Help us track cyanobacteria blooms with your smartphone. Go to for more info.

Update September 16, 2019

Mill Meadow Reservoir, September 11, 2019

The Central Utah Public Health Department (CUPHD) issued a Warning Advisory for Mill Meadow Reservoir on September 16, 2019.

Cyanobacteria cell count concentrations for samples collected by the Division of Water Quality (DWQ) at the north end of Mill Meadow Reservoir on September 11, 2019, exceeded the recreation health-based threshold for a Warning Advisory. Aphanizomenon was the primary taxon in the samples. Toxin test results received from the Utah Public Health Lab (UPHL) showed microcystin levels also exceeded the recreation health-based threshold for a Warning Advisory. Anatoxin-a levels were below the advisory threshold.

The DWQ monitoring crew observed visible cyanobacteria that resembled grass clippings, isolated clumps of bloom material, and cyanobacteria that resembled spherical nodules. These cyanobacteria were consistent throughout the water column. The crew observed a lot of past bloom material along the shore.

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/ml), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.

Data Summary

  • Sample type: Elbow-depth integrated composite sample
  • Sample date: September 11, 2019
  • Microcystin: 4.2 micrograms per liter (µg/L)
  • Anatoxin-a: <0.10 µg/L
  • Cyanobacteria cell counts: 90,021 cells per milliliter (cells/mL)

Update August 30, 2019

Mill Meadow Reservoir, August 27, 2019

The Division of Water Quality (DWQ) received a report of a cyanobacteria bloom at Mill Meadow Reservoir on August 27, 2019. It’s recommended that the public not swim or water ski in areas of scum, avoid boating in areas of scum, not ingest untreated water, and keep animals away from the water. Visitors are cautioned to be mindful of water conditions, as blooms may move or disperse depending on temperature, wind, and weather.

The Central Utah Health Department will collect samples at Mill Meadow Reservoir next week.