Bay Area environmental advocates are calling for more investment in sewer infrastructure after the ongoing series of winter storms caused the release of raw sewage directly into the San Francisco Bay.

Sewage treatment plants overseen by the East Bay Municipal Utility District overflowed multiple times in Oakland and Alameda on Dec. 31, according to the district.

Overflows of raw and partially processed sewage also occurred at manholes in Albany, Berkeley and Alameda, EBMUD said last week.

“Sanitary sewer overflows are caused when rain enters the sanitary sewer system and overwhelms the storage and treatment capacity of EBMUD’s treatment plants,” EBMUD said in a statement. “Ideally, sanitary sewer systems treat human waste from toilets, showers, and sinks, with little impact from rainfall.”

Officials with the nonprofit San Francisco Baykeeper argued that modernizing the region’s sewage treatment infrastructure would prevent future sewage pollution that can sicken people and kill plants and animals.

People are encouraged to stay out of the Bay and local bodies of water that feed into the Bay for at least 72 hours after a major storm ends.

“We can see that climate change is fueling more and more violent storms, yet the Bay Area’s sewage treatment plants are sorely outdated,” San Francisco Baykeeper executive director Sejal Choksi-Chugh said in a statement. “Much of our sewage treatment system is unable to handle the increasing frequency and intensity of our regular winter storms.”

EBMUD lifted its advisory about the sewage discharge on Thursday. Bay Area residents can contact EBMUD with questions about sewer overflows by calling 510-287-1651 between 8 a.m. and 4:30 p.m. Monday through Friday or 866-403-2683 after business hours.