Recreational Waters Bacterial Monitoring


The Recreational Waters Bacterial Monitoring Program, conducted by the City of Bozeman, regularly monitors bacterial loads in the waters associated with public beaches within Gallatin County during times of peak use, and takes necessary corrective actions to protect public health.

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Note: Samples are collected during one week per month. There are limits to the conclusions that can be made regarding safety during untested periods.

Program Actions include:

  • Collection of surface water samples at beaches on a scheduled basis by the City of Bozeman Recreation Department.
  • Testing of all scheduled surface water samples for the presence of E. coli bacteria at the City of Bozeman Water Reclamation Facility laboratory.
  • Timely notification of the public of results via the City-County Health Department web site and via public advisories, when needed.

Monitoring and Water Quality Standards:

Samples are collected for five consecutive days, a minimum of 24 hours apart, once per month June-September.  The actual sampling season may vary slightly.  Samples will be tested for the number of colony forming units of E. coli bacteria per 100 mL of sample.

The Montana Department of Environmental Quality’s E. coli standard for full body contact (swimming) is 235 organisms per 100 ml for a single sample or a geometric mean of 126 colonies per 100 ml for all samples collected within a sampling period (Equation 1).  Should either of these values be exceeded, the responsible health officer will use their discretion to take additional steps to inform the public of the associated health risks.

Equation 1: Geometric Mean = nth root of: (S1 x S2 x …Sn), where S1 through Sn represent the results for the n samples.

For more details about this program, see the Recreational Waters Bacterial Monitoring Sampling and Analysis Plan.


If you have any questions or concerns, please contact Gallatin City-County Health Department at (406) 582-3120 or GLWQD at (406) 582-3168.