Ten feet below the surface of Tiffany Avenue just south of the Mission district, there is a 3-by-5-foot brick pipeline that carries waste, stormwater and sewage downhill to the Southeast Water Pollution Control Plant for treatment.
The tunnel, built in 1886, is part of a 1,000-mile citywide network of passageways that General Foreman Lorenzo Hale, of the San Francisco Public Utilities Commission, and his team steam-clean and inspect on a daily basis.
"We maintain it all year round," Hale said before entering the pipeline on a recent day. "Our purpose is to make sure this sewer keeps flowing and makes it to the plant."
The pipelines must be constantly repaired or replaced because they are 100 years old and older. Modern toiletries such as disposable wipes that don't decompose, grease emptied into sinks, and even low-flow toilets and tree roots can pose problems for the system.
The SFPUC has developed a plan to regularly replace or repair pipelines. The agency began with 4 miles of pipeline four years ago and is aiming to reach 12 miles this year, increasing the workload until crews are replacing or repairing 15 miles annually.
But the work doesn't end there.
"It's like the Golden Gate Bridge: When you're done painting the bridge you have to go back and start all over again," said SFPUC spokeswoman Lily Madjus.
The replacement and repair of the aging pipelines will complement a much larger project to replace The City's largest sewage plant, which already is under way, according to SFPUC General Manager Harlan Kelly Jr.
In the Sewer System Improvement Program, ratepayer money will go toward costs associated with the $2.7 billion project to replace "digesters," which break down solid materials.
"It gets 80 percent of our wastewater flow and it's failing," Kelly said of the Bayview-based plant. "We have lids that are collapsing and odors and gases are getting out. We are operating as best as possible and within our permit, but there will come a point where it's really going to be challenging."
That project is in the planning stages now and is expected to break ground in roughly five years.
Meanwhile, the pipeline repairs and replacements will continue so as to avoid situations such as the massive sinkhole at Second Avenue and Lake Street in May or the one that nearly swallowed an SFPUC truck on Waller Street last November.
"It's amazing how these systems are still operating, but they also have a higher rate of failure," Kelly said.
The repairs and replacements are where Hale and his team come in. They clean out pipelines using a high-pressure washer, then send down a robotic camera to take hundreds of photos in rapid succession. The photos give engineers a picture of what needs the most attention.
In some cases, Hale and his team will need to enter the pipelines for visual inspections. When they are below the surface of the streets, they need to be aware of broken or rusted portions of the pipe as much as they need to be aware of other pipes connecting to the main lines. All pipes are active, which means toilets, sinks, showers, dishwashers and washing machines discharge into the lines. Warnings to not stand in front of these feeder pipes are repeated often.
Under Tiffany Avenue, Greg Braswell, a systems optimizer for the SFPUC, made it a point to hoist himself out of the murky water that flowed at the bottom of the pipeline and onto what workers call the "rodent walkway" because he was "grossed out" by the discharge.
The location of discharge lines adds to the hazards of the job. Under Tiffany Avenue, one is located in the manhole, which makes timing for ascending and descending critical.
And despite the advanced age of the pipelines, the raw sewage stench is not as prevalent as one might imagine. Several manholes are opened during the process and there's a slight breeze. But the crew is aware that the air can change quickly, so everyone carries a gas meter to monitor carbon monoxide or hydrogen sulfide levels.
San Francisco's sewer system
3 Treatment plants
1,000 Miles of pipeline
80M Gallons of wastewater treated on a nonrainy day
575M Gallons of wastewater treated on a rainy day
40B Gallons of wastewater treated per year