The Project site consists of approximately 26.5 acres, with 1.4 miles of discharge pipeline, and the construction staging areas (on site at the WWTP and the 20 foot staging area along the pipeline alignment). The existing wastewater treatment system at the WWTP consists of an influent pump station, mechanical bar screen, an aerated grit tank, three primary sedimentation basins, two aeration ponds (typically used in water), three facultative oxidation ponds, a lemna pond, an overland flow system, a chlorine disinfection system, and restoration wetlands. Solids collected from the primary sedimentation basins are treated in an anaerobic digester and then are dewatered in three on-site sludge lagoons. Treated solids are land applied on the City's overland flow slopes and the upland areas of the restoration wetlands. Treated effluent is discharged to the Willow Slough Bypass and/or through the Davis restoration wetlands to the Conaway Ranch Toe Drain, both of which are considered Waters of the United States under the Clean Water Act and tributary to the Yolo Bypass.
The Project consists of new secondary treatment, tertiary treatment, and solids handling facilities. Specifically, the improvements include an activated sludge process including biological reactor vessels and secondary clarifiers for solids separation; new filtration facilities; additional disinfection facilities; and mechanical solids thickening, dewatering, and storage facilities. Use of the existing ponds will change from treatment to storage, and the overland flow system will be decommissioned as part of the WWTP treatment process. In addition, the Project also includes the construction of flood protection around certain WWTP facilities to reduce impacts associated with potential flooding. The restoration wetlands will remain in place.