City of Petaluma,
Ellis Creek Water Recycling Facility
- Consolidation of two aged plants into one 8.0-mgd plant at Lakeville Highway
- Treatment alternatives evaluation including process modeling
- Metals, organics, and nutrient removal via wetlands treatment
- Solids treatment and handling
- California Title 22 tertiary unrestricted use and secondary disinfected use
- Odor control
- Secured over $4 million in grants to pay for a "Wetlands Park"
- Planning/design decisions considered sustainability and ecological footprint
Carollo Engineers provided facility planning, predesign, permitting, and final design for the new 8.0-mgd (average annual flow) water recycling facility for the City of Petaluma.
The planning phase evaluated multiple treatment alternatives including advanced facultative ponds, trickling filters, aerated lagoons, primary clarifiers followed by oxidation ponds, activated sludge, extended aeration and wetlands treatment. Carollo performed process modeling for each alternative to determine sizing, developed the cost for each alternative, and performed a detailed evaluation to compare neighborhood impacts, public amenities, and sustainability. Additional wastewater treatment considerations included reliability and biosolids production.
The selected processes included a headworks, odor control using soil bed biofilters, extended aeration secondary treatment, secondary clarifiers, RAS/WAS pump stations, modifications to the existing oxidation ponds for storage and wet weather treatment, tertiary treatment, and biosolids treatment and storage. The City Council also elected to include advanced wetlands treatment for metals, organics, and nutrient removal. Thirty acres of vegetative wetlands remove algae from the oxidation ponds, and an additional thirty acres of polishing wetlands provide advanced treatment of the effluent prior to river discharge. As part of the wetlands and overall site development, over 3.5 miles of trails were created and native landscaping provided for public amenities. Carollo helped secure over $4 million in grant funding to help pay for the wetlands and public amenities.
Tertiary treatment includes continuous backwash filters and ultraviolet light (UV) disinfection to meet California Title 22 unrestricted reuse standards. The tertiary process is sized at 4 mgd to meet the initial demand for urban reuse. The plant will also continue to produce up to 4 mgd of secondary disinfected effluent for existing agricultural users.
Solids treatment and handling includes a gravity belt thickener, phased digestion, and centrifuge dewatering. The design of the solids treatment process meets Class A solids requirements.
Effluent is discharged to the Petaluma River during the winter months and used for irrigation of agricultural crops, golf courses, parks, and landscaping during the summer months.
One of the primary goals of the project was to design and build an ecologically and economically sustainable facility. The project team incorporated sustainability criteria, The Natural Step framework, the Ecological Footprint process, and the Leadership in Energy and Environmental Design (LEED) process, into the evaluation of alternatives, planning, and design of the facility.
The sustainability criteria used to evaluate process and treatment alternatives included water reuse, energy use for facility construction and operation, the embodied energy to construct the facilities as represented by quantity of concrete and quantity of earthwork, chemical use in operating the facilities, air emissions, land use, and habitat. Based on its comparable cost and lowest ecological footprint, the team selected extended aeration followed by wetlands as the preferred alternative.
During design, the Carollo team adopted a sustainable design approach that considered and evaluated a wide range of green building practices and sustainable design concepts including the use of recycled building materials, passive-solar techniques for building heating/cooling, and alternative energy sources, including roof-installed photovoltaic cells.
The sustainability features incorporated into the final design and construction include:
- Green building techniques for the administration building, (to LEED silver standards) including a vegetated roof and a passive solar and a geothermal pump for HVAC.
- Use of fly ash in the concrete mix.
- Creation of a fresh water treatment wetlands.
- Preservation of tidal wetlands.
- Development of a community amenity with trails and native plantings.
Carollo also was responsible for site and environmental permitting, including a 404 permit from the Army Corps of Engineers for protection of wetlands. The project site is sensitive with existing seasonal wetlands, a tidal marsh, riparian habitat and a creek onsite, and endangered and sensitive species. Special consideration for construction mitigation was required for all these elements and also for a heron and egret rookery located onsite.
Public involvement was a key aspect of the project. Citizens served on the technical advisory group for the planning effort. And Carollo conducted many public meetings and city council meetings to involve the public in the process. This project garnered support from many environmental communities including the Petaluma River Keeper. An organization was even developed around support of this project – the Petaluma Wetlands Alliance.