An infirm homeless man relocates minutes before a water truck comes by to hose down his place on the sidewalk. Mark Richards for Al Jazeera America

In San Francisco, a crew from the Department of Public Works has been cleaning down the sidewalk in the Mid-Market area most nights in an effort to deal with the effects of local homelessness. Mark Richards for Al Jazeera America

SAN FRANCISCO — The crack-cocaine users who sleep across the street from Victoria — or "bubble boys," as she has nicknamed them, after a slang term for drug use — screamed when Department of Public Works employees sprayed them with high-powered hoses a few weeks ago, she says.

It was about 4:30 a.m. in the Mid-Market area of downtown San Francisco, a few hours before the daily arrival of tech industry employees, whose firms recently moved into the neighborhood. DPW workers gave the sleeping young men four warnings and then started spraying, said Victoria, 52, who only offered her first name out of a mistrust of police common among San Francisco’s homeless people.

Victoria described herself as a "polite," obliging homeless woman who picks up and leaves when asked by the authorities. She said the young men were given fair warning by the cleanup crew. But the sight of them being hosed was disturbing. "They were screaming," she said.

Three years ago, San Francisco’s city government backed a program to bring Silicon Valley tech into the heart of the city around the Tenderloin, traditionally home to the city’s have-lesses. That triggered what San Franciscans call the "second tech boom," which attracted a stream of moneyed young professionals, whom many critics have blamed for driving up the cost of living in the city and for pushing many lower-income people out of their apartments.

But now advocates for San Francisco’s homeless — and the homeless themselves — are also worried that some DPW workers may now literally be washing away the homeless from the central streets as the city makes way for tech workers. "There was a very orchestrated campaign to gentrify the Mid-Market area and draw in tech companies and offer them a tax break to move into that area," said Jennifer Friedenbach, director of the Coalition on Homelessness, a San Francisco advocacy group. "What goes hand in hand with that is displacement of poor people."