The City of San Luis Obispo’s 804 cubic meter/hour (5.1 million gallon per day) average dry weather flow (ADWF) Wastewater Reclamation Facility (WRF) serves over 41,000 residents, as well as the county airport, and California Polytechnic University. Plant effluent is discharged to San Luis Obispo Creek, the county’s most significant wetland’s area between the treatment plant and the Pacific Ocean. Prior to the plant improvement project, the City’s plant effluent did not meet effluent limitations specified in its National Pollutant Discharge Elimination (NPDES) permit. The effluent was too high in ammonia, and at times, it also exceeded limits set for color, surfactants (Methyl Blue Activated Substances, or MBAS), turbidity, and oil and grease. This, coupled with the effluent’s warm temperature, was disrupting the ecological balance of San Luis Obispo Creek. The creek’s once thriving population of both warm and cold water fish, particularly steelhead trout, was declining. In 1987, the California Regional Water Quality Control Board (CRWQCB) issued a cease and desist order requiring the City to comply with the conditions of its NPDES permit. Through innovative application of existing technology, Brown and Caldwell implemented a new flow scheme that included activated sludge process, cooling tower, filtration and chlorination to improve overall quality of effluent. To assess the effectiveness of the recommended processes, Brown and Caldwell conducted a pilot testing program for one year. The pilot study showed that MBAS can be reduced by the activated sludge process, and all the receiving water requirements for color, turbidity, temperature, and MBAS can be met with dual-media filters (with cooling towers and chlorination) instead of an expensive granular activated carbon system, saving the City about $3 million in construction cost. This paper highlights an innovative solution that has successfully enabled the City to comply with its cease and desist order requirements.