Background In the spring of 2023 CU experienced a taste and odor issue large enough to impact customer reactions. An upstream utility, Etowah Utilities, first notified CU of a taste and odor issue where customers were complaining of an earthy smell and taste. Near this same time, complaints asserting a dirt smell and taste of the water began to flood in from CU customers. At this point, CU began collaboration with surrounding utilities and regulatory agencies to assess the impact and begin to formulate corrective action. As this was a not-seen-before event, at least on this scale, a wide-ranging investigation ensued. Cleveland Utilities (CU) provides clean and safe drinking water to serve customers within the City of Cleveland and the surrounding service area. CU’s two major facilities are the Cleveland Filter Plant (CFP), which is fully owned and operated by CU, and the Hiwassee Utility Commission’s Water Treatment Plant (HUC), which is operated and maintained by CU under contract to the Hiwassee Utilities Commission. IN addition to Cleveland Utilities customer’s, HUC is the sole water provider to two other utility districts in addition a portion of the Athens Utilities Board service area. Currently, the CFP provides approximately 50 percent of the water demand (8 mgd), HUC approximately 45 percent (~6 mgd), and Waterville Springs WTP and Eastside Utility District providing the remainder. CU’s CFP has traditionally deployed a bag fed powder activated carbon (PAC) feed system to address short-term or acute taste and odor anomalies but were not equipped to address such a ubiquitous issue. They began to feed PAC at the highest rate possible, but this had little to no effect improving the taste and odor of the drinking water due to the equipment limitations. Raw water quality samples taken at the plant intake and finished water samples found methyl-isoborneol (MIB) concentrations were significantly above the odor threshold (around 10 ng/L). The odor threshold is defined as the MIB concentration at which most people can detect these compounds through smell. Other samples taken from the Hiwassee River have been as high as 280 ng/L, exponentially above the threshold. Highlights This presentation will highlight the incident from its inception up through the current date of the presentation. Highlights will include the following: • CU’s public relations actions taken to educate their customers and provide up to date information as the action plans developed. • CU’s sampling, testing and collaboration with other agencies to assess the issue and formulate actionable steps to treat the elevated MIB and be ready for future incidents. • CU’s long-term plan to address the treatment processes at CFP and operation at HUC WTP, including considerations for the following treatment modalities: o Powdered activated carbon (PAC) o Granular activated carbon (GAC) o Ozone, o Ozone advanced oxidation process (AOP), o Ultraviolet (UV) AOP • A summary of potential causes and an overview of other regional agency actions.