OAKLAND — Morning skies may have been overcast Sunday, but the atmosphere in Dimond Park was sunny and bright. City officials, staff and volunteers gathered to celebrate an environmental project and the community organization that helped make it happen.

The occasion was the grand opening of the Sausal Creek Restoration Project, the renewal of an 800-foot section of the creek that runs through a portion of the park. But the event really celebrated a successful partnership between the city of Oakland and the dedicated volunteers of the Friends of Sausal Creek.

What was once a culvert and concrete spillway has been transformed into a widened natural creek ringed by native plants and designed to accommodate native rainbow trout and other animal species.

The $3.9 million project will stabilize the creek channel to prevent damage to the foundations of adjoining homes, decrease erosion and improve the ability of the creek to handle floods.

Along with the new plants, the project included the planting of 80 new trees, construction of a new walkway and new public restrooms. The $3.9 million price tag was funded through grants from the California Natural Resources Agency, other state agencies and Measure DD, a bond measure approved by Oaklanders to improve Lake Merritt and other natural resources within the city.

Sunday’s gathering also included the 12th annual Dimond Park Open House and Community Picnic and celebrated the 20th anniversary of the Friends.

Along with tours of the restoration area and nearby Dimond Canyon, the event included representatives of other community organizations, games and a performance by Circus Bella.

While the city provided the construction crews and managed the project, the Friends of Sausal Creek played an integral role in bringing the creek back to life.

Members cultivated the plants at the group’s native plant nursery at Joaquin Miller Park and helped with outreach during a series of public hearings on the project.

It’s all part of the group’s mission that included restoring portions of Dimond Canyon in 2001. Sausal Creek flows roughly from Skyline Boulevard to the Oakland Estuary. Many sections of the creek have been buried over the years but “daylighting” the water returns the natural beauty of this environmental system, said Richard Kaufmann, a member of the Friends board of directors.

“We have this incredible urban forest that a lot of time we take for granted,” he said. “We tend to look at it as more of a liability than an asset.”

“There are problems with many creeks, so you bury them,” he added. “In recent years, we have come to realize that there are a lot of advantages in not doing that.”

The group’s volunteers put in 9,000 to 10,000 hours maintaining the watershed. Despite the hard work, volunteers are drawn to the work by a desire to serve, according to Kaufmann.

“I think people have a natural desire to want to give back and invest something in themselves and their community,” he said. “When you see something like this that’s worth investing in, it gives you a sense of ownership in your own place.”

Veterinarian Eleanor Dunn, a founding member of the group, has worked more than a few weekends on outdoor projects and took part in the 2001 Dimond Canyon project.

“Over the course of the years, it’s has been up and down and it’s been various things,” she said of her involvement, “Whatever the organization needs to keep going.”

Executive Director Kimra McAfee thanked the project’s supporters.

“We have a new creek, we have new habitat, and we have new trees,” she said. “It’s really hard to believe that these stakes are going to become trees, but you can go up to the canyon and see all the growth that has happened in just 15 years.”

The Friends are creating a financial endowment, said board member Carl Kohnert.

The group’s two-decade-long environmental involvement is almost a generational contribution, he said. “We existed for a generation, and our goal is to exist for future generations too,” Kohnert said.