Walking through Marvin Gaye Park, it’s hard to imagine the numbers that used to define this stretch of public land in the District of Columbia’s Ward 7.

Fifteen thousand hypodermic needles once littered its now grassy knoll. More than 7 million pounds of trash clogged the nearby stretch of Watts Branch, a tributary of the Anacostia River. And almost 100 vehicles had been abandoned in the stream and surrounding landscape, some of them doused in gasoline and set on fire.

But a nonprofit that was key to reviving this stream and park decided years ago that this spot — where the needles and numbers were just symptoms of poverty, crime and neglect — was the place to begin the restoration.

Steve Coleman, executive director of Washington Parks and People, which began work on the project in 1997, said the group put up signs declaring this former epicenter of crime to be an amphitheater and park named after the legendary singer who had grown up in this neighborhood, Marvin Gaye.

Coleman’s group had been leading trash cleanups in the park and stream, but realized that any successful effort to revive both of these assets needed to involve the community.

“That was key, because there had been this notion that the human needs and environmental needs were mutually exclusive, that you couldn’t have both. But what we found was they were interdependent,” Coleman said.

He said the cleanup needed a plan, and the nonprofit looked locally: to “the seniors who have memories and the kids who have dreams,” to help form it.

The “Down by the Riverside” campaign was launched in 2001 with a goal of restoring the waterway and surrounding area from an eyesore to a community gathering spot. The plan included action points for addressing issues like sewer leaks, crime and trash as part of a coordinated effort with the community, city and local nonprofits.

A dozen years later, the project is an example of how restoring a stream can help revive both a park and a community. It’s a testament to the transformation that can occur when hundreds of residents, dozens of agencies and millions of dollars converge on an utterly neglected stretch of an urban stream.

“We really have to show urban dwellers that they’re in an environment worth protecting in the cities and that their actions are important in protecting the larger environment, and that’s the Chesapeake Bay,” said Peter Hill, chief of the planning and restoration branch of the District Department of the Environment’s Watershed Protection Division. “It’s expensive, but the payoff is so much bigger.”

Hill was the project manager for the Watts Branch restoration until 2011, just before DDOE began construction on the stream.

He can’t talk about the work that’s led to a healthier stream without mentioning an alphabet soup of organizations — both local and federal, public and private — that contributed to the project.

Parks and People estimates that $30 million of public and private funding has been invested in the stream, park and surrounding area since the project began.

While Parks and People worked with volunteers to pick up trash and engage the community, the District’s Department of Transportation paved a bike trail that runs alongside the stream. Soon, new playgrounds were being erected and hundreds of trees planted, some with National Fish and Wildlife Foundation funds.

In the watershed, major roadways were outfitted with better stormwater controls and a new high school was built with advanced stormwater management, earning it a LEED gold certification.

“It’s really, in my mind, an unprecedented collaboration and targeting

of resources in an urban watershed,” Hill said.

On a sunny mid-September day, the work crews were long gone.

On one end of the 1.7-mile stretch of stream that’s been the project’s focus, park benches and sidewalks were full of people. Some waved hello to Hill, familiar by now with his green DDOE shirt. He pointed out projects along the way where the workers removed invasive plant species and concrete walls and slowed the pace of the stream to reduce erosion.

Near the mouth of the branch, a Bandalone trash trap kept three basketballs and dozens of plastic bottles from continuing downstream. Native vegetation along the water has grown thick since it was planted in early 2011 when construction on the stream began.

Josh Burch, the DDOE’s Watts Branch project manager since 2009, said that residents have had to get used to the fact that they can’t see the stream as easily through the thick plant buffers that now help filter out stormwater pollution.

But, because of work to slow the stream’s flow and reduce erosion, they can hear the stream again.

At several points along the creek, rock formations slow the water to a cascading trickle as it gathers into newly formed ponds. Those cascades are the source of the streamlike sound that had been lost when, in the past, city crews worked to straighten the stream to move the water more quickly, Burch said.

“Before, what people wanted to do was get water out of your neighborhood as fast as possible,” Burch said, citing concerns about flooding that guided most stream decisions in the past. “We didn’t look at streams as resources; we looked at them as nuisances.”

Burch and others who’ve worked along the stream have also had the chance to interact with the residents who have watched this stream evolve over the decades.

He said an older woman he knows only as “Miss Johnson,” who lives in a cinder block house nearby, once called him to complain about some larger trees his department was cutting down along the stream.

She said she cried to see trees cut down along a stream in which, decades ago, her church used to baptize its members.

Burch told her that the trees were removed in an effort to return the stream, which had been straightened at some point, to its natural path. This and other efforts, he explained, would help recreate a slower stream with the pools of water she remembers.

“Now, I advised her that no one should be getting in the water because, although it looks OK, it’s still too dirty,” Burch said. “But, as the project’s gone on, when I’ve seen her, she’s always giving me positive reviews of what we’ve done.”

Other residents, while quick to thank the department for its work, say that the dual projects of reviving both the stream and the community are ongoing.

Like many in this neighborhood, Gerald Henneghan moved away in 1994 after growing up here. But he returned in 2010 to find the community in the midst of revitalization.

Henneghan said a family of deer now frequents the area and “other critters” that come with the additional wildlife have helped to reduce the rodents that used to be a problem.

“We’re very appreciative of the re-trailing that they did, the trees planted and everything. The air feels cleaner and it smells better and everything,” said Henneghan, who has worked with Burch on science projects for the children he home-schools nearby.

“It’s been great. And of course, he’s been great (Burch), because he’s helped me a lot with my homeschool kids. We’ve done a lot of science projects, we have also done a pictorial essay on the project as it was being constructed.”

But, despite improved appearances, he said some of the community’s biggest problems still persist. “It appears to be safe and tranquil right now, but that park is used a lot for heroin addicts and people using PCP. They go down to the creek and shoot up their drugs,” he said.

Coleman said residents like Henneghan have helped make the project a success — although one that’s ongoing.

“You can have all the money in the world, but if you don’t have the community with you and leading the way, that money will be poorly spent,” he said.

He says the amount of money that’s required to do such urban restorations well is “not worth spending” if the community isn’t onboard and committed to maintaining the improvements.

Others have wondered if such high-dollar projects are worth their price tag in the broader scheme of restoring the Chesapeake Bay, when far less money is required to restore streams in more rural areas.

But a recent study by the U.S. Geological Survey of the Watts Branch project found that such urban stream restorations have economic as well as environmental and social benefits.

The study found that restoration work on Watts Branch contributed $2.6 million and 45 jobs, directly or indirectly, to the local economy in 2011 alone, while adding $3.4 million to the broader DC economy. The USGS said the study showed such focused urban projects are a worthwhile investment and worthy of replication across the country.

Hill says that no one yardstick can be used to measure the overall success of projects like this. But there are several that are worth using.

His department continues to conduct water quality monitoring to determine whether work on and around the stream has reduced sediment and bacteria levels. The department is waiting for the latest test results, which have been taking place since stream construction was completed in 2012. They might confirm the staff’s hunches — they are shooting for a 50 percent reduction in sediment loads.

“It has gotten better, for sure. But you definitely need to be in it for the long run,” Hill said. “It’s not one of those things where you can do it and walk away and say, ‘mission accomplished.’ ”