PHOTO 1
One pipeline segment passed through a national wildlife refuge and wetland and a major highway to a highly developed industrial area.

PHOTO 2
The recycled water pump station was designed with enough capacity to handle the City’s current and future needs.

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1. Integrated Approach

Air - The Water Recycling Facility uses energy-efficient pumps to reduce impacts on air quality. During construction, recycled water used for dust control protected air quality.

Water - The project allows the City to stay within its allotted potable water supply and provides water for community needs, economic growth, and a drought-proof water supply. Recycling protects San Francisco Bay by reducing discharges that can dilute salt content in the bay and surrounding salt marshes.

Land - Building on available land at the existing SBSA site was efficient land use. Constructing the facility 20-ft. below grade avoided blocking the view. Placing recycled water pipelines in existing roadways, utility easements, and under a bike-path reduced additional land impacts.

2. Quality

The project was on schedule and within budget despite rapidly-rising construction costs. Facility construction and customer retrofits met the targeted opening day. Cost estimates and facility costs were within final planning estimates used for rate setting and bond financing.

The City overcame vocal opposition by addressing concerns and making changes desired by the community while affirming the need for recycled water. Local businesses using recycled water increased from 25 to 57 in the first year. Even more customers are expected to use recycled water as the distribution system is extended.

The project will help Redwood City stay within its potable water allotment from San Francisco's regional system. As the recycled water system expands, additional surface water supply will become available for revitalization and growth and provide increased drought proofing and reliability. The client is extremely pleased with the project.

3. Originality and Innovation

Innovative filter upgrade. Large diameter media improved filtration at the SBSA Wastewater Treatment Plant (WWTP). Replacing conventional anthracite/sand media with coarser, monomedia anthracite reduced backwashing, media loss, and air entrainment. Operations are further improved by air scouring retained solids from media, followed by low-rate water backwash to flush solids from filters. Filter retrofits significantly increased filtering effectiveness at the WWTP. Filter runtimes are about 500% longer and effluent quality exceeds discharge requirements, including California's tertiary recycled water standard. The combined air-water backwash technique also restores media efficiency. It improves treatment efficiency, lowers water use, extends media life, and reduces O&M costs.

Pipeline beneath bike-path. Installing a pipeline to the Seaport area meant passing through a wildlife refuge, wetlands, and a major highway. When the City learned that the California Transportation Agency (Caltrans) planned to widen Highway 101 and construct a bike path as a mitigation measure, they asked permission to install a recycled water pipeline within the bike-path. Caltrans allowed the City to incorporate the pipeline design into their overall

4. Complexity

Filter Efficiency. Filter efficiency was substantially improved by replacing anthracite/sand media with coarser, mono-media anthracite and combining air scouring with backwashing to restore media efficiency, improve treatment, reduce costs and water use, and extend media life.

Pipeline separation issues. The pipeline went through highly-developed areas where pipes were close together. When installing a 30-inch recycled water pipeline alongside a 20-inch potable water backup pipeline, there was only a 4-ft separation, not the preferred 10-ft. separation. To provide a safety margin, water pressure for the potable water system was set 10 psi higher than the recycled water system pressure, preventing leaks from the recycled water system from entering the potable water system due to insufficient water pressure.

Pipeline through wetlands. A major distribution pipeline crossed a wildlife refuge, wetlands, and major highway. Coincidentally, Caltrans planned highway widening nearby that included installation of a bike-path as a mitigation measure. Because Redwood City would maintain the bike-path, Caltrans agreed to a teaming proposal. Kennedy/Jenks fast-tracked design of this pipeline to allow installation in the bikepath as part of the Caltrans work. Using Caltrans' wetlands permits to place pipeline under the bikepath reduced construction time and costs.

Difficult soil conditions. To avoid blocking neighbors' view, the tank was constructed 20-feet below grade in bay mud. Kennedy/Jenks adjusted for unstable soil by designing a single structure, with common wall construction between components, allowing the facility to rest securely on bay mud. Pipeline soil problems were addressed by using restrained joints, instead of thrust blocks, and petrolatum tape wraps and sacrificial anodes.

Community involvement. The City defused opposition to recycled water by forming a community task force to gather recommendations for achieving the City's water supply goals. The task force met for one year with informational support from the City and Kennedy/Jenks. The project succeeded because the City worked to build community understanding and cooperation.

Harmony between agencies. Kennedy/Jenks prepared the two-phase engineering feasibility study defining the roles and responsibilities of Redwood City and SBSA. A formal contractual agreement governed the construction and operation of the recycled water facilities at the SBSA site.

Pipeline issues. Pipeline construction involved sharing space with several utilities. Although the State prefers 10-ft separation between water, wastewater, and reclaimed water pipelines, several areas had only 4-ft. wall-to-wall separation. Kennedy/Jenks provided a pressure differential between recycled water and potable systems to prevent recycled water from entering the potable water system in case of accidental cross connection. Installers avoided fiber optic lines during construction.

Recycled water market. Due to opposition to recycled water use at schools and parks, the City marketed to businesses and industrial clients with the following benefits:

• Lower on-going cost of landscape irrigation water
  
• City responsibility for retrofitting sites for landscape irrigation
  
• City guidance for retrofitting industrial facilities
  
• Drought-proof water supply for landscape
  
• Simple application process
  

5. Social and Economic Advancement

Redwood City has 76,000 residents and one drinking water supply. Increasing conservation and using recycled water for commercial/industrial uses will free more surface water for potable uses. The City anticipates replacing 20% of potable water demand by 2009 when Phase I is completed. As the system expands, recycled water use is expected to increase, providing for current uses, continued economic development and growth, and a drought-proof supply for future shortages.

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