The existing wastewater treatment plant, located at 160 Atascadero Road in Morro Bay, was originally constructed in 1953 and upgraded in 1964, 1982, and 1984. It was designed to treat an average dry weather flow of 2.06 million gallons per day through a primary process (solids removal), and the secondary (biological) treatment system can treat up to a nominal capacity of 1.0 million gallons per day.
The existing wastewater treatment plant is jointly owned and operated between the City of Morro Bay and Cayucos Sanitary District and currently serves a combined population of approximately 14,000 people. The plant has been operated under a National Pollution Discharge Permit, and the Waste Discharge Requirements were updated and adopted by the Regional Water Quality Control Board in 2017. The plant has operated under a modified discharge permit from full secondary treatment requirements since its last upgrade in 1984, to allow for partially treated wastewater to be discharged during wet weather periods when the plant cannot fully treat incoming wastewater flows. However, the updated Waste Discharge Requirements, which became effective in March 2018, no longer include this waiver.
In June 2018, the City received a Time Schedule Order from the Regional Water Quality Control Board which requires full permit compliance by Feb. 28, 2023. If this deadline or other intermediate deadlines stipulated in the Compliance Schedule are not met, the City will face both mandatory and discretionary fines from the Regional Water Quality Control Board.
In addition to the Time Schedule Order, the California Coastal Commission (CCC) denied a Coastal Development Permit (CDP) to upgrade the existing wastewater treatment plant in 2013. The CCC requires the City to construct a new wastewater treatment facility in an inland location away from the coastal zone to avoid coastal hazards including sea-level rise, tsunami and flood inundation.