SAN FRANCISCO (Map, News) - The Stern Grove redwood whose crashing branch killed a 50-year-old San Francisco woman earlier this month had significant structural defects and was at risk of falling, according to an arborist’s report.

Pleasanton-based HortScience identified 603 of Stern Grove’s 2,600 trees — including 95 redwoods — as potential hazards, according to a report crafted for San Francisco’s Recreation and Park Department in January 2004.

The tree whose branch fell and killed Kathleen Bolton on April 14 in the concert-meadow parking lot was described as “in decline, with extensive dieback of large branches and significant structural defects which cannot be abated,” according to the report.

“If The City knew this was a hazard, they should have done something to prevent what has happened,” said Kathy Skillicorn, one of Bolton’s close friends. “Her death was needless.”

While some Stern Grove trees with a “high” hazard rating were recommended for removal, the deadly one — and two next to it with the same rating — were recommended for an inspection of their upper limbs, according to the report.

HortScience recommended removing the majority of trees given a “very high” hazard rating within one year, and addressing “high” rated trees within three.

Jim Clark, a consultant for HortScience, said he did not know why the report recommended some trees for removal and not others.

City crews have been following the HortScience recommendations since they were made, according to Recreation and Parks Department Spokeswoman Rose Dennis.

“On an ongoing basis, all those trees are looked at,” Dennis said. “Our first line was dealing with the worst trees, which this tree was not. And the reality is [that] tree failure can happen at any time.”

Neighbors who walk regularly in Stern Grove say that falling branches — or even whole trees — are not uncommon. Felicia Zeiger said she was trapped in the concert-meadow parking lot for two hours March 17 after a eucalyptus branch crashed down, blocking the exit.

“For them to say it was a freak accident is baloney,” Zeiger said.

Bolton’s family is “devastated,” said Skillicorn, who would not discuss whether they are considering legal action against the city.

No claims have been filed with the City Attorney’s Office, according to spokesman Matt Dorsey.

Despite the warnings of some neighbors, Steven Haines, executive director of the annual Stern Grove Festival, said he’s optimistic that the accident won’t deter an estimated 100,000 from turning out to the concert meadow this summer.

bwinegarner@examiner.com