BRENTWOOD – In another step toward protecting Mount Diablo, 5 acres are now secured from future development following a donation by the Nunn family.

Known as the Nunn-Paulsen inholding, the land was donated to the nonprofit Save Mount Diablo by Bob Nunn in memory of his late father, Ron Nunn, who died in August at 92.

“Although my father had many stories to tell, one that always stuck with me and that I also share is when he could look and see Mount Diablo, he knew he was home,” Bob Nunn said in a statement.

According to Save Mount Diablo, the process to save the land took just over three months from “concept to close of escrow.”

The group said the donation brings it “one step closer to making the mountain whole and protected for current and future generations.”

“Protecting inholdings like this is critical to maintaining the integrity of Mount Diablo and Mount Diablo State Park,” said the nonprofit. “These privately held parcels have the potential to disrupt and threaten conservation efforts in the surrounding park if the inholdings were to be developed or poorly taken care of.”

Save Mount Diablo Executive Director Ted Clement thanked Nunn for the “generous donation” of the property.

“Privately owned inholdings within public parks are major land acquisition priorities for Save Mount Diablo, so we are deeply grateful that this year our wonderful supporters enabled us to complete two inholding acquisitions within Mount Diablo State Park,” said Clement.

Aside from the Nunn-Paulsen inholding, the nonprofit also finalized the 10-acre Balcerzak inholding parcel within Mount Diablo State Park in early September by paying off a $537,500 mortgage.

“Acquiring and protecting inholdings like the Nunn-Paulsen and Balcerzak inholdings are major accomplishments in our ongoing mission to save Mount Diablo and its sustaining wild lands,” said the group.

Clement said the nonprofit looks forward to working with California State Parks to eventually transfer the inholdings to the state, with assistance from Senate Bill 630, signed by Gov. Gavin Newsom in October.

SB 630 aims to expedite the acquisition of qualifying land for California State Parks by allowing the addition of lands with acquisition costs of $1 million or less to existing state parks without requiring multiple agency approvals, the group said.

For nearly two decades, California State Parks has not been able to add new land to Mount Diablo State Park because the park needs to obtain approval from other agencies before acquiring a property, said Clement.

“We look forward to working with our good partner California State Parks so that we can eventually transfer these inholdings to them with the assistance of a new law we helped champion to make such acquisitions by state parks easier,” he added.

Clement noted that a few privately owned inholdings remain on Mount Diablo, each under 100 acres.

“There are also other privately owned properties on the slopes of the mountain that are contiguous with state parks but not fully surrounded, and we are also trying to get those secured,” he said.

Though only 5 acres, the Nunn-Paulsen inholding is a “compact and biologically diverse gem,” with blue oak and live oak woodland, and oak savanna habitat, said Save Mount Diablo.

Among the species found are the California red-legged frog and Alameda whipsnake, which are special status species that “are likely to be present on the property,” said the group.

“They’re confirmed on the neighboring Three Springs property,” said Save Mount Diablo. “The serpentine rock on the Nunn-Paulsen land provides excellent growing conditions for rare plant species.”

The parcel also lies within a wildlife corridor between Mount Diablo State Park and Black Diamond Mines Regional Preserve.

Nunn has been a longtime supporter of the nonprofit. In the early 1990s, a deal between Nunn and the group enabled the acquisition of about 75 acres, which was named Three Springs.

The property was transferred to the California State Parks for inclusion in Mount Diablo State Park in 1992.

Nunn eventually served as a board member on Save Mount Diablo.

“Multi-generational East Bay families recognize Mount Diablo; it’s kind of our center. So the ongoing preservation of that area has always been important,” Nunn told this news organization.

Nunn said his father had always been an “ardent conservationist and preservationist.”

Ron was a fourth-generation Brentwood farmer and local developer. He was also an ardent conservationist, according to his son Bob. Ron died in August 2025 at the age of 92. (Photo courtesy of Bob Nunn).

“But at the same point in time, he didn’t necessarily savor being called that. It was more as a point of action and conscience, versus trying to make people believe that was the impression that he wanted to move forward (with),” Nunn said. “He did it because it was the right thing, not to gain attention.”

Nunn said the family has been active in land stewardship for decades.

“For example, we sold the development rights, a long-term agricultural property to help the Brentwood agricultural land trust,” he said. “My father previously dedicated a few acres to the East Contra Costa County Historical Society. … So it’s kind of a multi-generational mindset, conservation, and at times, donation and dedication, separate from any business relationships that we have.”

Nunn believes the family will continue to participate in land dedications and donations from time to time.

“Don’t be surprised if you see something a bit larger that takes place next year again. I’ll probably do it as an honor to my father,” said Nunn.