The power went out days after Barklee Sanders moved to San Francisco’s Treasure Island last year. Then it happened again. And again and again and again.

Food in Sanders’ fridge has repeatedly spoiled because of the outages. His toilet often backs up. And the situation worsened this year: Treasure Island homes and businesses have lost electricity at least 12 times so far, more than double the number of outages in 2018 and higher than each year since 2012, according to local officials.

“We all think, as residents, that it’s pretty ridiculous that we can’t have steady power in the middle of the Bay Area,” Sanders said.

Leaders at the city’s Treasure Island Development Authority blame the outages largely on aging infrastructure they inherited from the Navy decades ago. The authority — not Pacific Gas and Electric Co. — is in charge of the electrical grid on the island. New equipment will be installed because of a long-planned building boom, officials say, but the whole project will take years to complete.

Sanders, a 25-year-old technology worker, has tried to take matters into his own hands. He made a video and manages a website dedicated to the problem, and he urged local officials to provide backup batteries to homes on the island.

So far, he hasn’t had much success on the battery front. But he isn’t giving up.

“I could pay to live somewhere else,” Sanders said. “But (then) I’m kind of abandoning that community that doesn’t have that privilege and can speak up and has this knowledge and resources and awareness.”

Frustrated with a lack of action on rolling batteries out across the island, Sanders has resolved to at least install his own home battery because he said “the only way to really get people to understand the situation is to give examples of it working.”

Though the authority is not rushing to place batteries in every Treasure Island residence, it is preparing some other improvements to the electrical system.

Robert Beck, the authority’s director, told The Chronicle he recently authorized installing a half-dozen recloser devices that will help prevent lengthy outages from momentary disturbances such as a goose colliding with a power line — which is not an uncommon occurrence. The island’s aging above-ground power lines are highly vulnerable to such disruptions.

“We have a lot of geese,” Beck said.

He said he has also authorized the installation of indicator lights that will help crews locate problems with underground infrastructure that serves the island.

Even more relief for Treasure Island should arrive late next year, when old switchgear that transfers power from underwater cables into multiple distribution channels on the island is replaced. Once the new, more resilient equipment is up and running in December 2020, Beck said he “would be shocked if we had five outages the following year.”

“That’s going to dramatically improve the reliability and the performance of the system here,” he said.

Ultimately, the overhead power lines on the island will be replaced with modern underground lines as the system is upgraded in connection with a development project scheduled to produce some 8,000 new homes to the area, officials say. But the project will take more than a decade to complete.

“The city is in this challenging period where you don’t want to sink a ton of money into improving a system you know you’re going to tear up,” said Barbara Hale, assistant general manager for power at the San Francisco Public Utilities Commission.

Treasure Island’s utility infrastructure is mostly controlled by the development authority, which also sets rates for electric service. The city utilities commission acts like a contractor, Hale said, performing maintenance and other operational work, but it does not decide which equipment is replaced, when or how.

The situation would be different in the rest of San Francisco if the city succeeds in its attempt to take over PG&E’s local power lines. Treasure Island’s woes would not be replicated elsewhere, Hale said, because the city would be in full control.

“We would be the owners and operator of the system,” Hale said. “We would be setting the rates, establishing the approach for service and for improvement of the system over time.”

Still, the persistent power outages at Treasure Island have rankled residents and the people who advocate for them, particularly because of its demographics.

The island’s population is around 3,000, according to census data. In the data, the median household income was $52,143, a little more than half the figure for San Francisco at large. Thirty-four percent of residents were Hispanic and 17% were black — both figures higher than in the rest of the city.

“No one else in San Francisco has to live in these kind of conditions,” Supervisor Matt Haney, who represents Treasure Island, said of the frequent outages. “Treasure Island is a mostly low- and middle-income community, and folks there feel like they are treated as second-class citizens, and that this constant power outage issue is evidence of that. It’s completely inequitable.”

Haney has pushed local officials for more urgent solutions to the outage problem and said he ultimately wants to “see them happen a lot less and, ideally, never.”

Some of the electric equipment on the island dates to the 1930s, Beck said. Today, the island gets power from underwater cables that run to Oakland, where they continue partially underground and partially above ground to a substation by the port.

Most of the outages residents experience result from problems with on-island infrastructure, Heck said. However, that is not always the case: In November, a crew on the East Bay side struck an underground electric line serving Treasure and Yerba Buena islands while digging, he said, and the problem took days to fix. Emergency generators brought power back but then the one on Treasure Island failed, causing residents to lose power again.

Power outages aren’t the only hardships that residents have faced.

For decades, many have worried about radioactive and chemical contamination left behind by military operations. According to Navy records, 1,296 potentially dangerous radioactive objects, most small pieces of metal or debris tainted with radium-226, have been found and removed throughout the north and northwest ends of the island from 2006 through October 30.

The Chronicle reported earlier this year that in the 1990s, the U.S. Environmental Protection Agency considered the island hazardous enough to be designated a federal Superfund waste site, although it was never added to the Superfund list. The Navy, city and state agencies have said the island poses no safety issues for residents, and according to the site’s developer, the cleanup has made “significant progress” under state oversight “to ensure the island is safe for development.”

The November power outage took a toll at the Treasure Island restaurant Mersea, which lost a lot of business when it had to stay closed on a Saturday, according to co-founder MeeSun Boice. On that Sunday, the restaurant had to cancel the reservation of a group of 30 people before it learned it actually would have power. But it was too late to get the group back, Boice said.

Still, she said the development authority had done its best to help her out.

“I’m hoping,” Boice said. “I might have to buy myself a generator, so I’d have to incur that cost, but I’m going to survive one way or the other.”

Chronicle staff writers Jason Fagone and Cynthia Dizikes contributed to this report.

J.D. Morris is a San Francisco Chronicle staff writer. Email: jd.morris@sfchronicle.com Twitter: @thejdmorris