Under San Francisco’s 49 square-miles, there is a city built under the City – San Francisco’s sewer system.

Under the buildings, streets and parks where San Franciscans work, live and play, the sewer system infrastructure works 24/7 to protect public health and the environment. Protecting the health of San Francisco’s beaches and water quality is especially important during the wet weather season that begins in October and ends in May.

It takes a special kind of person to spend many hours each week underground in the City’s sewer system’s pipes, boxes and discharge structures. Fortunately, the SFPUC has an entire team dedicated to just this kind of work. In fact, this summer, SFPUC staff worked closely with survey crews to inspect and document the condition and measurements of many of its critical collection system facilities. San Francisco is the only coastal city in California that has a combined sewer system that captures and treats both the sewage from homes and businesses and rain runoff or “stormwater.”  

The sewer system is designed to have extra capacity to handle the increase in flows generated from storms. Drains, pipes, pump stations and transport-storage boxes that comprise San Francisco’s “collection system” portion of its sprawling combined sewer system are designed to collect, store and transport wastewater (sewage and stormwater) to the treatment plants. Upgrading and maintaining the infrastructure of the collection system is a critical part of the work performed by the Collection System Division (CSD) of the SFPUC’s Wastewater Enterprise.

According to CSD Assistant Engineer Megan Abadie, huge storage boxes have been installed across the City’s sewer system to hold all the extra stormwater that accumulates from huge storms. If the storm is really big, our system has outfall structures that provide primary-level treatment before any overflow or discharge occurs.

Because San Francisco’s combined sewer system must be ready for rains, SFPUC crews make the most out of the dry weather months. It’s this time of year, May through October, that it is safe for crews to enter these facilities, conduct surveys, condition assessments and perform any necessary repairs to ensure the collection system is in a state of good repair when the rainy season arrives.

All summer, CSD crew members entered any one of the City’s 35 Combined Sewer Overflow (CSO) structures to take exact measurements of important dimensions such as elevation with high-tech equipment and survey tools. Developing these precise 3-D models of the SFPUC’s facilities allows for the ability to continually monitor and improve the system.

“People are surprised when I tell them what I do,” said Abadie. “But I take a lot of pride in my work because I know that what I do every day helps protect the City and makes sure that we’re doing our job and that our system works.”

Learn more about Megan and the work she and her team do every day in the video below or in this KQED podcast that features a combined sewer discharge inspection and survey with the crew pictured above.