Major San Francisco Sewage Flooding Likely to Recur
Outfall Closure Makes City More Vulnerable in Atmospheric River Events
Oakland, CA — Torrents of raw sewage erupting out of San Francisco manholes flooding some forty homes last December is likely to happen again, according to documents posted by Public Employees for Environmental Responsibility (PEER) and the local group Solutions Not Sandbags. Closure of a major outfall in 2021 dramatically reduced the capacity of the City’s “combined sewers” to contain sewage during heavy rains. Forecasters predict that the type of atmospheric river that occasioned this flooding may become a staple of Bay Area weather.
During New Year’s week this year, major rains precipitated flooding that inundated more than 40 homes in San Francisco’s Marina area with more than a foot of raw sewage. Affected homeowners, including San Francisco 49-er legend Joe Montana, have filed suit against the City and its Public Utilities Commission (PUC), which operates its sewage system.
Documents obtained by Solutions Not Sandbags indicate that the flooding was caused by the PUC’s closure of the Pierce Street outfall, which was the largest combined sewer outfall in the City’s northeastern area, and that —
- When the PUC decided in 2018 to close the outfall instead of repairing it, the agency only considered minor storms when calculating the risk of damage by the outfall closure;
- Even in the minor storms, the PUC knew that flooding would get worse but decided to close the outfall anyway without adding any compensating capacity; and
- After storms in October 2021, just weeks after the closure, neighbors reported seeing toilet paper, dead rats, feces, and grease floating along Marina Blvd.
“The Marina sewer flooding wasn’t an ‘accident’ – it was the direct result of a series of choices made by leaders at the PUC. Addressing the issue will take a complete change of direction,” said David Hooper of Solutions Not Sandbags, which is demanding that the PUC re-activate the Pierce St. outfall or provide equivalent protection. “It is outrageous that the PUC has not acted to offset the excess flows that we all know will happen again even during minor storms.”
When the Pierce St. outfall closed, the San Francisco Bay Regional Water Quality Control Board proposed that the City spend $600 million to expand the capacity of sewer systems in low-lying neighborhoods. That September 2021 announcement cited, “Sewer overflows in these areas occur frequently after heavy rainstorms, posing risks to human health and groundwater quality.”
On July 23, 2023, this same state Regional Water Quality Control Board issued an order to the PUC demanding a description of actions it had taken to prevent future flooding events. That demand may lead to an enforcement action against the PUC if conditions have not improved.
“If the Bay Area enters a pattern of atmospheric river-type heavy rain events, we will see more of these sewage tsunamis,” stated Pacific PEER Director Jeff Ruch, noting that sea level rise also increases concerns over closure of this outfall because as the Bay rises, it is harder for water to get out of the outfalls. “The effects of closing just one outfall makes the impacts of sea level rise even more severe on local homes and businesses.”