Construction is proceeding rapidly on an approximately $165-million contract to build a new wastewater treatment plant on San Francisco's Treasure Island, an artificial island originally built by the U.S. Army Corps of Engineers in the 1930s. The 3.5-million-gallon-per-day Treasure Island Water Resource Recovery Facility is part of the San Francisco Public Utility Commission’s (SFPUC) $11.8-billion, 10-year capital program to enhance resilience and housing options for Bay Area residents.

Some 20,000 new residents are expected to occupy Treasure Island by 2036, eight times the current population. The new plant, located on a 50,000-sq-ft site at the northeast tip of the island, is a critical component of a long-term sustainability plan—ensuring that reclaimed water can be reused efficiently and providing for anticipated green spaces, hotels, restaurants, shops and entertainment venues. It will provide some 1.3 million gallons per day for Treasure Island and adjacent Yerba Buena Island and an annual average recycled water treatment capacity of 400,000 gallons per day for Treasure Island.

The design-build team led by PCL Construction and Stantec began work in January 2023, with a tight three-year schedule. “I’ve never seen a three-year project this complex,” says Jignesh Desai, commission project manager. “It’s a once-in-a-lifetime opportunity as a public servant—to build a plant that’s sustainable.” The facility has earned an Envision Platinum sustainable infrastructure rating.

The treatment facility includes a liquid and solid stream comprised of coarse screens, grit removal, fine screens, biological nutrient feed, a membrane bioreactor and ultraviolet disinfection. Additional features include recycled water pumping, wetlands, stormwater pipe discharge, aerated solids holding tank, solids thickening, a recycled water on-site dispenser and an administration and maintenance building.

These embody the wastewater industry’s shift to “resource recovery” methods, notes Desai. Treasure Island, once owned by the U.S. Navy, is now owned by the city of San Francisco, with a development agency serving as master builder for the planned new residential developments. SFPUC issued RFQs and RFPs in 2019, but the pandemic delayed bid award until 2023.

The design-build team of Stantec and PCL began value-engineering the project even before signing the contract, says Baird Kerr, PCL senior project manager. The commission "provided a conceptual plan and we bid on that, then incorporated our ideas.”

These included compressing the site to reduce quantities of pipe and pavement required, deferring equipment orders that weren’t immediately needed and putting deep foundation packages out early on, he notes. Crews will install more than 6,000 cu yd of concrete and some 17,500 linear ft of pipes.

“During the bidding stage, one thing we agreed upon was that we don’t need piles for the foundations—it’s all mat slab,” says Khaled Ammari, PCL project manager. “We eliminated the need for dewatering on the project.” The team also suggested using crushed rock to achieve compaction for the membrane bioreactor structure and shotcrete versus cast-in-place concrete for five buildings.

“It’s a massive structure coupled with an influence pumping station,” adds Billy Wong, Stantec principal engineer. The team relocated a detention basin so that the structure could be built above ground, requiring only 6 ft of excavation versus 27 ft and “creating a more operator-friendly situation” during operations and maintenance. Moreover,  the original concept had two screening processes to remove materials, but “we came up with equipment that can do both stages in one package,” he says. Value engineering saved some $5 million, according to project officials.

Construction is 70% construction complete, says Desai, with buildings topped out and solar panels being installed. “The plan is to introduce clean water for testing and instrumentation in spring,” he says. “Currently all major equipment is on site, including a long-lead item, a transformer that took 18 months to get there.” A key challenge will be learning how to operate and maintain a nutrient removal facility that is among the first of its kind for the Bay Area.

The facility replaces the old 1970s-era plant that didn’t comply with the region’s evolving requirements. “Typically a plant has primary and secondary treatment,” says Ammari. “The secondary treatment usually involves clarifiers. For this project we’re using bionutrient removal and membrane bioreactors. It mixes the sludge introduced in the secondary phase and breaks up organic pollutants, aerobic bacteria and nutrients. They settle, so you can separate them and proceed to tertiary treatment.”

Planning for the Future

SFPUC’s $11.8-billion, 10-year plan comprises sewer improvements, rolling capital projects and a facility infrastructure program that includes the Treasure Island facility, says Bessie Tam, capital program director. Major projects in play currently include $3 billion in upgrades to the Southeast Treatment Plant, where a biosolids digesters facilities project and biogas utilization system are underway. PCL and Stantec were awarded the $121-million design-build contract for the biogas system in January. 

MWH/Webcor is building the $2.3 billion, 400,000-sq-ft biosolids digesters facilities, with a majority of the concrete and steel work on the dewatering buildings completed and a planned 2026 completion.

SFPUC has also committed over $1 billion for a planned mainstream nutrient reduction project at the Southeast plant, adds Tam.

The Treasure Island facility is on track to achieve goals of more than 4,000 volunteer hours, as well as a 17.9% goal for Local Business Enterprise design contracts and 15.8% goal for construction contracts. The commission and the team also coordinated with numerous city and state stakeholders ranging from the public health department to the arts commission to other water agencies.

The city's development authority is coming in later to develop infrastructure outside of the facility perimeter, notes Wong. "There was a lot of external stakeholder coordination to make sure the facility functions before the developer is ready to build its own pipelines and force mains."