Michelson Wastewater Reclamation Plant (MWRP) treatment process includes a tertiary filtration step. MWRP utilizes seven dual media gravity filters with combined flow rates averaging 13 MGD. Historically, the filters often developed underdrain problems leading to media loss and elevated coliform counts in the tertiary effluent. Undetected filter media loss leads to increased costs in filter media replacement and increased chemical consumption at the disinfection and pH control facilities. In the past, MWRP tried to use individual filter turbidimeters to alleviate this problem. However, the turbidimeters were found ineffective due to their low sensitivity threshold. In April-May of 2000, MWRP performed a demonstration study of the Chemtrac(R) PC2400D online particle counter to monitor individual filter cells effluent particle distribution. Based on the results of this study, MWRP equipped all seven tertiary filters with this online particle counter model (2001). The particle counters proved to be an effective tool in monitoring individual filter cell integrity. MWRP linked the proprietary Chemtrac(R) particle counters Dynamic Data Exchange (DDE) software with the existing Wonderware based SCADA system to enhance the monitoring process, and developed the guidelines for warning of the onset of extensive media loss. Includes tables, figures, appendices.