Fresno-Clovis Regional Wastewater Reclamation Facility Organic Upgrade Project

City of Fresno, 

Fresno-Clovis Regional Wastewater Reclamation Facility Organic Upgrade Project

2011 Outstanding Capital Project Award - California Association of Sanitation Agencies (CASA)
Service Type: 
Project Highlights: 
  • Maintained the function of the existing water system by matching the existing reservoir maximum water elevation.
  • Provided one reservoir structure with two internal basins for operational flexibility.
  • Demolished the existing steel tank after completion of the new reservoir.
  • Seismic considerations included that the reservoir be designed for hydrodynamic forces taking into effect the sloshing of the stored water inside the reservoir during an earthquake and the resultant forces exerted on the reservoir walls.
Fresno RWRF aerial
Carollo’s history with the City includes several projects at the Fresno-Clovis RWRF, including a digester gas/landfill gas feasibility study and a gas/turbine generator evaluation.

Carollo has provided design services for many of the City of Fresno’s wastewater treatment projects during the last 20 years, including design of the recent Fresno-Clovis Regional Wastewater Reclamation Facility Organics Upgrade Project. This project followed Carollo’s work on a master plan update, and was necessary to accommodate the plant’s larger industrial load and more stringent regulations.

The City of Fresno began experiencing a significant increase in organic loadings to the Regional Wastewater Reclamation Facility between 2000 and 2004. The increase was attributed to growth in industrial development within the community. The project’s intent was to increase the organic capacity of the existing secondary treatment facilities to handle these increased loads, return the treatment facilities to the original rated capacity, position the treatment plant to provide nutrient removal to meet possible future permit requirements, and to upgrade the existing solids handling facilities.

The project included two new activated sludge aeration basins, four new secondary sedimentation basins, a new return activated sludge/waste activated sludge pump station, retrofit of two existing dissolved air floatation thickeners (DAFTs), a new anaerobic digester, a new digester control building, and other miscellaneous improvements.

The two existing 60-foot-diameter DAFTs were evaluated and compared with other thickening alternatives. During the preliminary design phase, the existing units were operated at a number of surface loading and polymer feed rates to optimize and confirm operations. All mechanical equipment was replaced and the thickener control building was re-designed. All piping, mechanical, and electrical equipment was removed. A new electrical room was provided within the existing structure; and the pumps, piping, and mechanical equipment were removed; and an improved configuration of this mechanical and piping system was developed.


Early in the project, the City determined the organic loading to the RWRF was increasing significantly. In an initial planning phase, the City researched the sources of the increased loadings, modeled the existing treatment facilities, and developed a long-range Capital Improvement Plan to address its short-term needs and its long-term needs. The Capital Improvement Plan was one component of its Updated Master Plan and was the basis for the decision to design and construct the Organic Upgrade Project.


Based upon experience with previous design projects, RWRF management staff recognized the need for an increased level of operations and maintenance staff involvement in the facility layout and equipment selection. The design was a collaborative effort with management, operations, maintenance, and the design engineer meeting in frequent workshop settings. Workshops focused on key process areas or structures allowing staff to provide detailed comments. These were followed up with a very detailed decision log. Because of the high level of staff involvement, alternatives such as the reuse of a vacant Power Generation Building for the new blowers and rehabilitation of the existing primary sludge DAFTs to be used for WAS thickening were identified as potential cost savings measures. Using this approach, there were no comprehensive submittals of the entire project until the design completion; saving design time and effort.


Although the project was bid and built under a conventional design-bid-build format, the City not only requested the full-time on-site presence of the design engineer during construction, they also dedicated a senior operator to the project. The high level of onsite involvement of the design engineer and the operations staff especially during process shutdown and tie-ins were essential to a successful project. All shutdowns including the complete shutdown of a major effluent conveyance canal and the connection of two- 1,500 HP blowers into the existing aeration system were completed with no significant impacts on the project construction and the project was completed on-budget.