Under normal conditions, flush your toilet and the bowl contents travel through a series of underground pipes to a water treatment facility for sanitizing. Same with dirty dishwater.
But enter recent robust rainfalls and some unusual things are happening with sewage, including in Berkeley.
A maintenance hole at Page and Second streets in West Berkeley was one of three in the vicinity to overflow on New Year’s Eve during the heaviest rain of the season, according to the East Bay Municipal Utility District (EBMUD), which owns the outlet.
For at least a little while, raw sewage seeped into the street, flowing into the gutter. Alerted to a rapid rise by systemwide real-time data that measures sewage levels, EBMUD tested the Berkeley overflow site the next day, said Andrea Pook, a spokesperson for the utility, which owns the outlet.
“We didn’t see anything to clean up,” she said, meaning the utility found no public health hazard.
The other two seeping maintenance holes, both also operated by EBMUD, were in Albany along the Eastshore Highway and in Alameda at Broadway and Clement avenues.
EMBUD owns maintenance holes along its wastewater lines. The city of Berkeley also owns holes, servicing it sewage system.
Berkeley has not experienced any overflows from recent storms in city-operated sewers. “We have steadily upgraded over 90 percent of City sewer lines over the past 35 years to prevent or minimize infiltration of storm water,” said city spokesperson Matthai Chakko.
More details on the EBMUD overflows are expected soon as part of a report the utility is required to submit to the state for any sewage leak, Pook said.
System overflows or releases are rare, Pook said. For the past three years, she said, the only other incidents were in 2021, when a maintenance holes at Point Isabel in Richmond had a “small” overflow, and in 2020, when almost 50 gallons of sewage and water was discharged from Oakland’s Alice Street overflow facility, related to a power outage.
Persistent storms test sewer systems. During periods of heavy rain, water in saturated soils seeps into sewage pipes through cracks, gaps or holes. Clogged or blocked pipes add to heavy flow issues.
This vulnerability begins with the private sewage lines leading from a house or building to underground city or municipality pipes, usually running beneath streets.
In Berkeley, it keeps going in city pipes as they drain west to a large 5-foot diameter EBMUD pipe called an interceptor, running near the East Bay shoreline.
The interceptor collects sewage from multiple communities and transports it to the utility’s water treatment plant in Oakland, near the Bay Bridge.
On a regular sunny day, the interceptor averages about 50 million gallons of wastewater daily, Pook said.
“On a bad storm day, we see 10 times what we normally get in terms of wastewater flow,” she said. “On Dec. 31, we saw 13 times our average wastewater flows, or 650 million gallons a day of sewage, mixed with stormwater.”
The system was stressed, Pook said. Maintenance hole overflow was one indication of this.
“The large interceptor can fill; the tube that leads from the interceptor pipe up to the street level manhole can fill and overflow around the edges of the manhole cover at the surface. Occasionally there may be a small spill of this wastewater made of mostly rainwater. [It] flowed from the street to the storm drains/gutters,” Pook explained.
With indications the interceptor pipe was reaching capacity, EBMUD pumped wastewater to overflow storage located at Point Isabel, she said.
To take off more pressure, EBMUD released untreated wastewater from overflow facilities in Oakland and Alameda into the Oakland Estuary. The sites are at San Leandro Creek, at the foot of Alice Street in Oakland and near Barnhill Marina in Alameda.
Pook said an estimated 4.7 million gallons of sewage were released into bay waters.
The overflow facilities, essentially boxed valves, are “designed to relieve high levels in the interceptor and prevent sewage from backing up and overflowing into the street,” Pook said.
In those heavy New Year’s Eve rains, EBMUD treated 98-99% of its wastewater, discharging 1-2% of the flows, she said.
“It’s good we were able to handle most of it,” she said. “In the ideal world, no one wants to have discharge in the bay.”
Pook said she believes this was the first time Berkeley’s Page Street maintenance hole had overflowed.
There have been no EBMUD sewage overflows or releases since Dec. 31, she said.
Old sewage lines
The best way to protect the system from overflows is by repairing and replacing old sewage lines, Pook stressed, including city and private lines.
The utility is in the middle of a major infrastructure upgrade, funded in part by controversial rate hikes. The drought, ironically, reduced the utility’s income from water, which it cited as a main reason for increasing rates.
In response to the Dec;. 31 sewage releases, Sejal Choksi-Chugh, executive director of San Francisco BayKeeper, a nonprofit focused on the health of the San Francisco Bay, issued a statement:
“We can see that climate change is fueling more and more violent storms, yet the Bay Area’s sewage treatment plants are sorely outdated. Much of our sewage treatment system is unable to handle the increasing frequency and intensity of our regular winter storms.
“There’s a two-part solution that requires significant infrastructure investments. First, sewage pipes need to be repaired, updated, and maintained to prevent large volumes of storm water from entering the sewer system. And more importantly, sewage treatment plants need to be updated so that they’re not discharging raw sewage into the Bay.”
BayKeeper has warned people to stay out of bay waters during stormy weather.
EBMUD posted warning signs outside the overflow facilities, Pook said, a routine measure with sewage spills or releases.