Tires, Pajamas and Keys: A Treasure Hunt Inside San Francisco’s Sewers

What is the place where poo, pee and toilet paper come together? The toilet, which is connected to the sewer system. But what else can one find in the sewer?

In San Francisco, there are three wastewater treatment plants that treat the sanitary sewage (what is flushed down toilets or goes through kitchen or bathroom sinks and showers) and stormwater runoff (rainwater that hits rooftops and streets) that the sewer system collects.

Bar screen: a mechanical filter used to remove large objects, such as rags and plastics, from wastewater. It is part of the primary filtration flow and typically is the first, or preliminary, level of filtration, being installed at the influent to a wastewater treatment plant.

These three treatment plants are:

  • Oceanside Treatment Plant (treats 20% of the City’s wastewater) right by the San Francisco Zoo (and actually partially underneath it)
  • North Point Wet Weather Facility (only on during wet weather) around the Fisherman’s Wharf area
  • Southeast Treatment Plant (treats 80% of the City’s wastewater) in the Bayview-Hunters Point neighborhood.

With all the wastewater that goes into San Francisco’s three treatment plants, one may wonder what types of “interesting” items may be found in the sewers.

Besides the only things that are supposed to be flushed down the toilet (poo, pee and toilet paper), items such as dental floss, contact lenses, and a huge amount of the so-called “flushable” wipes, frequently end up in the underground sewer system and at the City’s three treatment plants. While toilets may seem like a welcoming place for all, including flushable wipes, toilets are not trashcans. Even though flushable wipes may be viewed similarly as toilet paper, they are not the same thing as they do not break down at all. Flushable wipes wrap around sewer pipes and lots of other treatment plant equipment, which in turn, result in costly damages for repair, and the need to manually remove them from the sewers throughout the City or treatment plants.

Southeast Wastewater Treatment Plant bar screens.
Wyman Fong, SFPUC Acting Chief of Operations at Oceanside Treatment Plant pulling the debris from the bar screens.

“At our three wastewater treatment plants, we see almost everything that you would find in a landfill. I have seen large pieces of wood, tires, electric cords… you name it, we’ve seen it!” said Jacob Hansen, SFPUC Bayside Operations Engineer, who is responsible for monitoring the SFPUC’s infrastructure in the Bayside collections system, which includes sewer pump stations.

Hansen and the SFPUC sewer operations team urges San Francisco residents and visitors to use the trash, compost and recycling bins to properly dispose of those items instead of flushing them down the toilet or throwing them in sinks.

Debris collected and discarded from bar screens. Most of the debris are flushable wipes.
Debris collected and discarded from bar screens. Most of the debris are flushable wipes.

At one point during the rainy season in early 2019, SFPUC sewer field crews had to pull out a pair of pajamas from a storm drain, which clogged the drain and caused ponding around the intersection. Often, crews receive calls to retrieve wedding rings, cell phones or keys, sometimes with a success, other times mostly perishing in the flow of wastewater on the way to the plants. When crews find large items like that one, they have to use all sorts of equipment, from ropes, to ladders and even cranes to safely remove the items.

Wyman Fong, SFPUC Acting Chief of Operations at Oceanside Treatment Plant said that “during an inspection of our East and West transport boxes in September 2019, tiny little albino colored plants were going in sand banks 35 feet below street level. They looked like skinny baby asparagus sprouts that have been grown without sunlight.” 

“Let’s do our part and flush only the 3 Ps (poo, pee and paper). Together we can prevent costly damages while helping to keep our sewer system working and protecting public health,” said Fong.

Debris collected and discarded from bar screens. Most of the debris are flushable wipes.
Debris collected and discarded from bar screens. Most of the debris are flushable wipes.
Containers will be taken to landfill.
Debris collected and discarded from bar screens. Most of the debris are flushable wipes.
Debris collected and discarded from bar screens. Most of the debris are flushable wipes.