Three cops, two with LAPD and one with Amtrak, went to a Union Pacific railroad bridge that spans Reseda Boulevard in Northridge to inspect a homeless community perched atop a bluff with a commanding view.

It sat just a few feet from the rails, a line of tents and piles of trash on a spot that for years has lured those who wanted a place to settle down.

A scenario that upsets those who want them to leave.

As many as 20 people have lived here at one time, with the use of drugs, including heroin and meth, common, homeless advocates say. Residents in nearby neighborhoods have complained of thefts and burglaries they blame on the homeless.

The officers found “bunkers” here, too — holes in the ground covered with pieces of wood wedged up against a concrete wall: Tiny dwellings.

“It was a real little city,” said Don Larson, who runs the nonprofit Clean Streets Clean Starts and has been helping to scoop up trash and debris from San Fernando Valley streets for years.

A week or so after the LAPD and Amtrak’s June 11 visit, Larson and volunteers with the nonprofit, some of them homeless, began clearing out the mounds of garbage pushing up against the tracks. They also removed a collection of shopping carts.

They left alone the tents and personal property.

Fifteen days later, this past Wednesday, what was once 10 camps strung out along the tracks in this stretch, just north of the Reseda-Parthenia Street intersection, was five.

Most of the trash was gone, but new piles had begun to rise up.

That’s the cycle that has existed for years along the train route here, which runs northwest through the San Fernando Valley, from Burbank to Chatsworth and into Ventura County.

This ebb and flow likely plays out all across Southern California, as law enforcement, homeless advocates, the general public and the homeless themselves struggle with how to deal with the growing problem of people living on the streets.

Metrolink commuters and regular Amtrak riders know the drill.

“If you keep your eyes open out of (the) windows, you’re going to see tents,” Larson said.

Rita Dunn is here after getting pushed off of another property after the owner called police, she said. She has been in the general area for 10 months.

“We’re all waiting to be kicked out of here,” said Dunn, 39. “It pretty much takes all your time to be moving around.”

Dunn, one the 60,000 estimated homeless people living in Los Angeles County, paused as a train roared by.

“It’s so loud,” said Kimberly, her 57-year-old friend who requestd that her last name not be used in this story.

“I never, ever thought I would end up out here,” Dunn said.

“When you get to the bottom of the barrel, and then the bottom falls out of the barrel, how deep does it really go?” she said. “I guess we’ll find out.”

Homeless advocates said police came out in December, after a burglary was reported at a business near De Soto Ave and Prairie Street in Chatsworth. In May, police came out again after a dog bit a homeless advocate near the tracks at Corbin Avenue; the dog apparently belonged to one of the homeless people.

Los Angeles officials have pushed the homeless out of some areas of the city.

The strategy of LAPD and Amtrak in this area is unclear, because their officials didn’t respond to questions about incidents along the Union Pacific tracks over the last few months.

Living near the tracks, some say, is preferable to setting up camp on sidewalks or streets. Kimberly feels safer here.

In March, a federal judge ordered Los Angeles to stop seizing and destroying some homeless people’s property until the city builds enough shelter space to accommodate them. The LAPD says if the land is private, the homeless people can be moved at times, the agency explained in a Facebook post.

Like other parts of the city, City Council District 12 – which covers Chatsworth, Northridge, Porter Ranch and other nearby neighborhoods in the Valley’s northwest – saw an increase of homeless people in the city’s annual count.

Stil, the numbers here are relatively small. Volunteers with the Los Angeles Homeless Services Authority counted 583 homeless people in the district one night this past January, a 2 percent increase over the year before. The count’s total was the smallest of any district in the city this year.

With so many living so close to freight and passenger trains barreling along the tracks, Larson and others said they’ve documented at least six deaths from homeless people getting hit over the last decade in this stretch. It’s unclear how many were suicides.

Kimberly, the homeless woman, said she once had her own business and a house but suffered setbacks and ended up next to the tracks.

“Nobody wants to live like this,” she said.