Maps of San Francisco show eight blocks of Tompkins Avenue in Bernal Heights before it disappears and an additional three blocks once it exists again. But the block between Nevada and Putnam streets is blank.

Is this some weird city street purgatory? Or a Harry Potter-type situation where the street is magically concealed?

No, that vanished block of Tompkins exists, but the city has decided not to “accept” it. Not my problem, City Hall has decided about that one block of Tompkins. Plus many, many more blocks all over San Francisco.

The city has 1,017 miles of streets, but City Hall has accepted only 869 of them. That leaves 148 miles — including the unmapped stretch of Tompkins — that the city considers “unaccepted,” often because they’re on steep hillsides and were never paved or because they’re narrower than regular streets.

The city, therefore, has no responsibility for maintaining those stretches. According to the city itself, of course.

If only we could unaccept city taxes.

So who is responsible for maintaining unaccepted streets? The property owners who live alongside them — whether they want the job or not.

“That’s just how it works,” said Rachel Gordon, spokeswoman for the Public Works Department. “The city doesn’t want to take care of streets and staircases that don’t meet regular city standards. ... Hopefully when people buy property and move in, they do due diligence to find out what their responsibilities are.”

Neighbors alongside Tompkins found out about this quirky bit of city bureaucracy once the unaccepted block turned into a steep stretch of despair, growing intolerable in the early 2000s. Trees were uncared for and overgrown, making it dark and sketchy, even during the daytime. Homeless people set up camp. Drug dealers peddled their wares. Thieves dumped empty Amazon boxes, briefcases and backpacks after swiping their contents. The concrete staircase became broken and unsafe.

“It was disgusting,” explained Vicky Rideout, who lives near the stretch. “Full of weeds. Full of trash. Twenty years’ worth of trash had accumulated here because it was no one’s job to pick it up.”

You know how much trash exists on streets the city has accepted, so you can only imagine what it’s like on the unaccepted ones.

“It stank,” Rideout continued. “That’s what I remember the most — how much it smelled. There was a lot of human feces, animal feces.”

You also know how much poop exists on streets the city has accepted, so, again, you can only imagine what it’s like on the unaccepted ones.

“It was a no man’s land that nobody took responsibility for, so people felt like they could trash it,” said another neighbor, Andre Rothblatt.

But don’t worry — this story has a happy ending. Eventually.

In 2007, Rideout and Rothblatt teamed up to do something about the awful block.

“We call ourselves the OGs — the original gardeners,” Rothblatt said.

They won a $15,000 community challenge grant from the city to landscape the hill, but with no water, the unaccepted bit of Tompkins fell back into disrepair during the drought.

They tried again with additional neighbors in 2016, this time applying for and receiving a water meter for irrigation from the Public Utilities Commission. They partnered with the San Francisco Parks Alliance to win a variety of grants, including another community challenge grant from the city, this time for $100,000.

Rothblatt, an architect, designed a gorgeous new staircase with zigzags of colored tile, getting approval from Public Works to redo the staircase and from the Arts Commission for the tile work. The neighbors also secured permission from the San Francisco Municipal Transportation Agency to close the stairs for repairs.

Yes, even though the city doesn’t want to care for the beleaguered street, it still put the neighbors who stepped up through the bureaucratic wringer.

“The structure of government right now is there are way more people whose job it is to slow you down and stop you than to help you,” Rideout said. “We did encounter challenges and slowdowns and obstacles and ‘No, you can’t cut these trees down’ and ‘You have to turn in these tile plans three times.’

“None of us was standing around saying, ‘I really want a project. I have too much time on my hands,’” she continued.

Rothblatt agreed, adding, “There were a lot of calls that went unanswered. I would wait two weeks and call again and get a response three months later if at all.”

Altogether, Rothblatt and Rideout estimate their little group has devoted at least 600 hours in the past year alone to improving a street they never wanted responsibility for in the first place.

Gordon of Public Works said the department was active in improving the block starting in 2016 by pruning trees and clearing brush. She said it helped the neighbors get the water meter, repair the stairs and secure grant money for the project. The department will continue to provide tools for cleanups and remove bags of debris, she added.

“It’s been a good partnership involving residents, the nonprofit (San Francisco Parks Alliance) and city government,” Gordon said. “We’re thankful that neighbors give their time to improve their community.”

The results are stunning. Lovely plants, flowers and trees dot the hillside. The staircase with its colorful tile is a cheerful splash of public art that will probably become a photo hot spot. Best of all, there’s no more trash and no more poop, and pedestrians can safely pass through any time of day.

“We’re very happy and proud,” Rothblatt said. “People respect it more and treat it better. It’s a huge improvement. We did it.”

And they have to continue to do it. The block remains unaccepted, and its upkeep remains firmly on the shoulders of its neighbors. They’ve scheduled garden workdays and are hoping for the best.

“We don’t have a single person who knows the first thing about gardening,” Rideout said.

Let’s hope they figure it out.

San Francisco Chronicle columnist Heather Knight appears Sundays and Tuesdays. Email: hknight@sfchronicle.com Twitter: @hknightsf