A Bay Area couple paid $90,000 for a private street in San Francisco in 2015.

In 2017, Sen. Dianne Feinstein, a former resident of the street called Presidio Terrace, wrote a letter to city leaders urging them to reverse the sale.

City supervisors voted to overturn the sale.

Presidio Terrace is one of the most exclusive streets in San Francisco.

Thirty-five mega mansions sit behind a stone wall that surrounds most of the development. A black SUV with a private security company guards the entrance, which is closed to the public.

The street's enhanced security and isolated location at the top of the peninsula have attracted some of the wealthiest and most powerful politicians in California over the years, including Sen. Dianne Feinstein and House Minority Leader Nancy Pelosi.

In 2017, a Bay Area couple shook up the tony enclave when residents found out the couple had purchased the street, its sidewalks, and its shrubs for $90,000 in an online auction — without residents' knowledge. The city had put Presidio Terrace up for sale in 2015 after the homeowners' association failed to pay property taxes on the street for more than a decade.

Outraged residents sued the city and the couple. Last November, the San Francisco Board of Supervisors took the unprecedented step of overturning the sale.

Now the buyers, Michael Cheng and Tina Lam, are speaking out against the people who they say forced them to return the street, even though it was bought legally.

That includes Feinstein, a former Presidio Terrace resident.

Feinstein wrote a letter in defense of the rich residents

A month before the hearing, Feinstein wrote a letter to the San Francisco Board of Supervisors urging them to reverse the sale. She said it was the city's own bureaucratic blunder that cost residents the street in the first place.

"I would not have guessed bureaucracies still held surprises for me. But this one did," Feinstein, who lived at Presidio Terrace for more than 20 years, said.

Sen. Dianne Feinstein. J. Scott Applewhite/AP

For at least 17 years, the city's tax-collection office mailed tax bills for Presidio Terrace to a now-deceased bookkeeper who worked for the homeowners' association before retiring in the 1980s.

Over the years, the $14 annual property tax went unpaid by the people who live on Presidio Terrace. The bill racked up hundreds of dollars in penalties and interest.

In 2015, the city listed Presidio Terrace, along with 389 parcels, on the auction block. The Office of the Treasurer and Tax Collector notified residents at the same wrong address.

"The Treasurer/Tax Collector's office's insistence that taxpayers were wholly to blame for that office's own fiasco was breathtaking," Feinstein wrote.

"In the United States of America, no one should lose property at the hands of the government without knowing about it," she added.

In the letter, Feinstein acknowledged her own biases. She grew up at Presidio Terrace.

In 1985, Feinstein and her husband, financier Richard C. Blum, bought a 1909 Tudor mansion located across the street from her childhood home. The couple later passed the house down to their daughter, who sold the property for $9.5 million in 2013, according to public records.

The Presidio Terrace buyers said the rich will always get their way

Cheng said the letter from Feinstein has a lot to do with why he lost the street.

Cheng, a real estate investor, and his wife, Tina, a software engineer, believe supervisors voted in a way that would be pleasing to their wealthy and politically connected constituents.

"The most obvious interpretation I have is these are probably the richest residents of SF, with supervisors who like to have wealthy donors," Cheng said in a recent interview.

Sen. Dianne Feinstein and her husband bought a 1909 Tudor mansion on Presidio Terrace in 1985. Melia Robinson/Business Insider

"Even though Senator Feinstein had no jurisdiction over such local matters, one might imagine the words of the top Democrat in the country would carry enormous political clout on ambitious supervisors," he added.

Cheng, a self-described lifelong Democrat, said he supported Feinstein in her last election.

"To see her coming out, writing a letter specifically for this group of 35 homeowners instead of spending her time defending 40 million Californians —" he said. "I couldn't believe that."

Feinstein's office did not immediately respond to a request for comment.

Cheng is still grappling with the reverse of the sale.

The couple is suing the City of San Francisco to win their street back. They launched a GoFundMe page in January with the goal of raising $50,000 for their legal defense.