HCPSS Legionella Testing on Cooling Towers – Updated October 21st

Information can be found on the HCPSS website:

Legionella Testing on Cooling Towers

October 18th, 2019

UPDATE: October 21, 2019. A previous version of this News item had incomplete information and has been updated.

Out of an abundance of caution and based on industry best practices, HCPSS began proactively testing for the bacteria Legionella in September 2019. The school system tested samples from higher risk sites, namely all cooling towers across the school system. Proactive sampling is not required by federal, local or state regulations.

It is not uncommon to find various Legionella species in building water systems used to cool water as part of the building’s HVAC system. This is not drinking water or water that is used for any other purpose. According to the Occupational Safety and Health Administration (OSHA), there are at least 50 legionella species, only 20 of which cause human diseases. The presence of the organism cannot be directly equated to risk of infection. However, the detection of the genus Legionella at elevated levels suggests additional treatment and maintenance is warranted.

If elevated levels are found, remediation includes additional chemical treatment and maintenance, such as super chlorination. Monitoring is done with confirmatory sampling.

The September 2019 Legionella test results are available online. All cooling towers where the bacteria was discovered have been treated. Additional testing will confirm the absence of Legionella or the need for further remediation.

HCPSS will continue to test all cooling towers annually, in the fall when the water in the cooling towers can be idle for extended periods of time due to low cooling load conditions. Moving forward, as testing is completed and remediation work occurs, schools will provide regular updates to their communities.

Cooling towers are only located at the following locations:

  • Atholton Elementary School
  • Atholton High School
  • Department of Education building
  • Centennial High School
  • Clarksville Elementary School
  • Cradlerock Elementary School/Lake Elkhorn Middle School
  • Dunloggin Middle School
  • Forest Ridge Elementary School
  • Hammond High School
  • Harper’s Choice Middle School
  • Howard High School (ground cooling tower)
  • Howard High School (roof cooling tower)
  • Laurel Woods Elementary School
  • Long Reach High School
  • Marriotts Ridge High School
  • Mt. Hebron High School
  • Oakland Mills High School
  • Oakland Mills Middle School
  • River Hill High School
  • Reservoir High School
  • St. John’s Lane Elementary School
  • Talbott Springs Elementary School
  • West Friendship Elementary School
  • Wilde Lake High School

HCPSS Contacts:

  • Christopher Madden, Certified Industrial Hygienist/IEQ Manager, Office of the Environment
  • Larsen Angel, Mechanical Engineering Manager, Department of School Facilities


In the PDF noted above…ten locations are noted with “Legionella spp”…they include:

  • Long Reach HS
  • Atholton HS
  • River Hill HS
  • Marriotts Ridge HS
  • Mt. Hebron HS
  • West Friendship ES
  • Howard HS Tower 1 (Ground)
  • Howard HS Tower 2 (Roof)
  • Hammond HS
  • Laurel Woods ES

Scott E

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