Legionella sampling results indicate that concentrations of the bacteria are highest during the summertime months. Surveillance data also indicates more cases of Legionnaires’ disease during the summertime. 

As a result, a treatment that addresses these conditions must be performed in the summer. The city calls it Summertime hyperhalogenation, which is to add a one-time per year dosing of higher-than-normal levels of chlorine or bromine based biocide, to each cooling tower system between July and August 31.

Periodic hyperhalogenation is an effective method of limiting Legionella in recirculating water by preventing the risk of biofilm growth, which can be a host for Legionella.



4.9.1. Filing

Failure to submit declaration of a hyperhalogenation performed at least once each year between July 1 and August 31 can result in penalties. 

Upload the completed CT-SH-DF01 form to the NYC Registration Portal within 30 days of completing summertime hyperhalogenation.