PMI San Francisco Bay Area Sustainability Program

Dec. 9, 2020 Event Recap—You Flush and My Job Begins

The Sustainability Program held its December event, and I won’t waste any details. Everything flowed well at the “You Flush and My Job Begins” webinar. Special guest speakers Bessie Tam and Steve Robinson of the San Francisco Public Utilities (SFPU) joined us and shared their passion for sustainability. Bessie is a senior project manager with SFPU and director-at-large of PMI-SFBAC. Steve is the director of the Wastewater Capital Program with SFPU. Both Bessie and Steve are civil engineers, and they have dedicated a large portion of their careers to wastewater.

Steve introduced us to the San Francisco sewer system. The SFPU has a system unique to most sewer systems on the west coast. The SFPU system treats ALL wastewater. They have a “combined” system that utilizes one system to treat both sanitary waste as well as storm water. Most cities have two separate systems that require two different pipe systems. In SF, there is only one pipe system for both.

SSIP sustainable goals

“Water is life. Sanitation has done as much for public health (since Roman times) as clean water, if not more.” Stephen tells us that wastewater isn’t actually waste, but a valuable resource to sustainability. The SF sewer system has been operating since 1849 and, since then, has been gravity fed. SF has been cultivated into eight watersheds with three treatment facilities, 27 pump stations and over 1,000 miles of pipes. 400 billion gallons are treated per year in this 100-year-old system.

There are always difficulties when improving on systems; however, the sewer poses a particular difficulty in trying to improve upon it. According to Steve, “improving the sustainability of the sewer system is equivalent to repairing the outside of an airplane mid-flight.” Approximately 30% of the SF sewer system is over 100 years old. Currently one third of the Southeast Treatment Plant is under construction as the flow keeps flowing.

On the project level, Bessie guided us through all the undertakings of projects like these in a major metropolitan area. “It would be much harder (if not impossible) to code, develop AI or work on cool technologies if everyone had to worry about where our poop goes.” Inherently, the SF sewer system is already quite sustainable. By design, there are fewer miles of pipes to maintain than other systems. “We take advantage of gravity, and everything flows downhill.” Most of the equipment also has a long-design life, spanning 30-100 years.

Trenchless Rehab Method: Cured in Place Line

There are many things to consider before a construction project begins: rural and residential impacts, commercial influences, bus lines and traffic routes, utilities effects, etc. However, what I didn’t consider is they also tailor their construction methods to meet the needs of the city as well. A typical construction footprint wouldn’t be feasible in the condensed and compact streets of San Francisco's historic neighborhoods. The SFPU employs a trenchless “cure-in-place liner” method that allows them to work construction projects while generating a footprint the width of a semi-truck.

Up at the program level, Steve took us through the Sewer System Improvement Program and capital planning strategy. They operate within a typical two-year budget and 10-year capital plan. New this year is the continuation of that plan, looking another 10 years forward within a 20-year planning horizon.

Green bonds are unique to SFPU’s plan. SFPU sells green bonds to help finance projects. They have the first U.S. Muni green bond listed on the European Stock Exchange. The bonds are linked with the United Nations sustainable development goals. SFSU is “part of the global economy supporting the sustainability movement.”

Sewer System Improvement Program Fatberg

Finally, the night wouldn’t be complete without a surprise. They introduced us to the very real creation called a FATBERG: a very large mass of solid waste in a sewage system, consisting specifically of congealed fat and personal hygiene products that have been flushed down toilets and must be jack hammered out of the system. For a real treat, search some images; that’s some dangerous waste!

The city of pipes and flowing material beneath our feet has always seemed like a mystery to me. The process of moving billions of gallons to millions of people is no small feat, and the way that the SFPU functions was eye opening. A (combined) system as old as the gold rush, gravity fed and designed with sustainability in mind is a triumph of project management and civil engineering.

Michael Cavanaugh

Michael Cavanaugh

Michael Cavanaugh is the PMI-SF BAC Sustainability Program web page project manager.

Note from the director of sustainability: Don’t miss the upcoming Sustainability Program event on January 20, 2021: Data Center Sustainability—Water and Wastewater Impacts with guest speaker Dave McCabe.