Cooling Towers Testing and Treatment

Information and results for testing of Legionella bacteria in HVAC cooling towers

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Testing for the Legionella Bacteria

Out of an abundance of caution, HCPSS began proactively testing for the Legionella bacteria in September 2019. The school system tested samples from higher risk sites, namely all HVAC cooling towers across the school system.

This testing took place in the fall when the water in the cooling towers can be idle for extended periods of time due to low cooling load conditions. Testing was not conducted in response to any health concerns, or done to fulfill a requirement or request. This sampling is not required by federal, state or local regulations.

HCPSS has taken significant measures to improve the health and safety of our buildings to ensure that our students and staff have a safe and healthy learning environment. This includes going beyond required state, federal and local regulations to conduct comprehensive, proactive testing of our building’s systems and perform remediation when necessary. We have prioritized transparency and want to ensure that our community is aware of work being done. It is not uncommon to find various Legionella species in cooling towers. According to the Occupational Safety and Health Administration, there are at least 50 Legionella species, 20 of which cause human diseases; however, the presence of the organism does not necessarily equate to risk of infection. While the sampling and analytical procedures used are not specific enough to verify if the species detected are the ones that cause human disease, we feel the detection of any bacteria warrants chemical treatment and maintenance.

Legionella Test Results

Location Innitial Result (CFU/mL) Current Result (CFU/mL) Reports
Administration None Detected n/a
Atholton Elementary School None Detected n/a
Atholton High School 920.00 None Detected
Centennial High School None Detected n/a
Clarksville Elementary School None Detected n/a
Dunloggin Middle School None Detected n/a
Hammond High School 60.00 None Detected
Harpers Choice Middle School None Detected n/a
Howard High School Tower 1 Ground 20.00 None Detected
Howard High School Tower 2 Roof 40.00 None Detected
Howard High School Tower 3 n/a None Detected
Lake Elkhorn Middle School None Detected n/a
Laurel Woods Elementary School 40.00 None Detected
Long Reach High School 980.00 None Detected
Marriotts Ridge High School 40.00 None Detected
Mt. Hebron High School 40.00 None Detected
Oakland Mills High School None Detected n/a
Oakland Mills Middle School None Detected n/a
Reservoir High School None Detected n/a
River Hill High School 960.00 None Detected
St. John's Lane Elementary School None Detected n/a
Talbot Springs Elementary School None Detected n/a
West Friendship Elementary School 40.00 None Detected
Wilde Lake High School None Detected n/a

Frequently Asked Questions

Why isn’t testing being done at every school and facility?
Testing is done in HVAC cooling towers, which are only in place at 23 buildings. The list of locations can be found online.
If Legionella bacteria was found in my school’s cooling tower, is it safe to drink the water at school? Is it safe to wash my hands?
In testing, HCPSS collects samples from cooling towers, which are present only at the 23 buildings listed online and used to cool water as part of the building’s HVAC system. The school/office's drinking water or water used for other purposes does not come from the cooling towers.
If a test comes back positive, how is HCPSS getting rid of the Legionella bacteria?
If any Legionella bacteria is detected, remediation is performed, which includes chemical treatment and maintenance, such as super chlorination. After the remediation, another water sampling will be conducted to determine the effectiveness of the remediation. If the results continue to detect Legionella in the cooling tower, we will investigate and perform additional remediation until the testing comes back negative.
How were students, families and staff notified about this issue, and any applicable test results?
Information regarding Legionella testing was posted to the HCPSS website. An email was sent to staff and another to families. A separate email was sent to families at schools where cooling towers were found to have elevated levels.

HCPSS Contacts

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