SAN JOSE — When San Jose residents debated how best to deal with the dirty, urine-smelling pedestrian tunnel that runs under the Alameda, many pushed for closing up the walkway for good.

But Robert “Dave” Thomas and his daughter Taylor Thomas rallied against that idea and are now on a mission not only to make the passage usable again but to turn it into a local attraction as one of the few remaining pedestrian tunnels in the city. Their efforts have caught the attention of their neighbors, who say the tunnel project embodies the difference a few do-gooders can make in the community.

“Everybody who has a couple hours on their hands can do something like that: maybe not as big as the tunnel but just a small thing,” said Valerie Zeller, who lives in the area. “Dave is the kind of person who encourages people to do more.”

The tunnel dilemma’s also become a hot topic on Nextdoor — a popular online chat forum for neighbors — over the past few months. Rose Garden area residents say the tunnel, which runs between Towne 3 Cinemas and Downtown College Preparatory, has posed a problem for years. Built in 1928 in memory of two students killed when hit by cars on the Alameda, the passage was supposed to make crossing a busy street safer; instead it has fallen out of use, and some argue that it has become a safety hazard in its own right as a loitering spot for the homeless.

“At one point it was more of a quality-of-life thing where you had some trash and it smelled bad,” said Christopher Russell, who started taking his daughter and dog through the walkway again after Thomas began his improvements. “But when there are folks camping out down there and they’re blocking the tunnel off, it’s unusable.”

The issue stumped the community on Nextdoor. But then late last month Thomas, who lives just two blocks from the walkway, suggested forming a “friends of the tunnel” group to begin cleaning the passage up.

“My dad is the guy in the neighborhood that everybody knows,” Thomas’ 22-year-old daughter said. “He’s the old guy that never quits. He always has to find something to do, and when he does something he does it to the absolute best of his ability and beyond. There’s absolutely no procrastinating.”

Thomas and his daughter are going full bore in cleaning up the tunnel. Now about a month into their work, they have helped relocate Ivan Ettel, the homeless man who was living in the tunnel, personally bringing him to Valley Medical Center for care and assisting his move back to Santa Cruz (they have not heard from Ettel since). They have shoveled out trash and human feces and powerwashed the walkway’s interior.

But their ambitions have grown. A self-confessed “civic vandal,” Thomas, 68, also has put convex mirrors at boths ends of the tunnel and installed custom-made chain-link gates where the old ones were torn out. Each entrance is now marked by signs that the tunnel masterminds say are just for fun to make people think: the signs read “One World,” “One Tunnel,” “Yay Tunnel” and “Yay You.”

There’s more to come. The father-daughter duo have begun to paint the tunnel walls with a mural promoting “random acts of kindness,” using materials donated by another resident who works at Dunn-Edwards Paints. They envision each person who enters the tunnel picking a number that will correspond to a heart-shaped section of the mural: each heart will instruct a different small action aimed at lightening someone’s day.

Thomas’ farther-reaching tunnel dreams include an LED installation that would light the ceiling with moving pictures.

“I see things 10 or 15 years in the future,” he said.

Thomas hopes to work with the city to make his vision happen, perhaps through a public-private partnership in which the tunnel is primarily maintained by a volunteer group organized by Thomas. When he discussed the idea formally with Jack Swallow, one of the city’s District 6 council assistants, Swallow said that the Department of Transportation (DOT) and Public Works Department were leaning toward closing the tunnel but open to input. City staff told Thomas on June 8 that an employee in the DOT will reach out within a few weeks.

Russell recognizes that city officials are busy but hopes they can support Thomas, particularly since right now the improvements are coming out of Thomas’ own pocket: his original budget was $2,500, and he expects to spend up to $7,500 by the time he is finished.

Thomas is known by neighbors for his donations of both time and money. A master float builder who also works in real estate investment and the marine tour industry, he is the artist behind floats at San Francisco’s Pride and Chinese New Year parades and once staged a surprise float party for local kids during a San Jose Holiday Parade. He built stage props for Trace Elementary School and still donates supplies to the school long after his children stopped attending. His generosity spreads abroad, too. He has sponsored an orphaned Chinese girl’s move to the United States to live with her grandmother, paying for the girl’s private schooling and braces.

So for Thomas, the pedestrian tunnel is just one more personal project.

“We’re not going to become the tunnel trolls,” Thomas said, laughing. “It’s just a couple shovelfuls and then the neighborhood can have it back.”

Contact Hannah Knowles at 408-920-5767. Follow her at Twitter.com/KnowlesHannah.