Ten mature eucalyptus trees in Eleanor Pardee Park are in poor condition and should be removed, according to an independent arborist's report.
The City of Palo Alto hired the consultant to determine the safety and condition four manna gums (Eucalyptus viminalis) and five blue gums (Eucalyptus globulus) that surround the children's play area.
Sixteen trees attracted attention after several large limbs suddenly crashed to the pavement in January, nearly striking a man who was strolling near the park.
The city removed five trees earlier this year after they were determined to be hazards. A sixth tree is scheduled for removal in a few weeks, now that nesting birds have vacated the tree, according to Paul Dornell, assistant director of public works operations.
Residents' groups have come out strongly on both sides of the issue, with some demanding removal of all 16 trees and others for their preservation.
Torrey Young, registered consulting arborist for Dryad LLC of Castro Valley, gave a presentation to about 25 residents on Sept. 23 at Lucie Stern Community Center regarding his findings. The conclusion: All 10 trees pose a hazard to residents and property and should be removed.
"It is my opinion that the high-traffic nature of the site combined with the method and long-term impacts of previous pruning renders inevitable the need to eventually remove these trees," Young wrote in his report. www.cityofpaloalto.org/civica/filebank/blobdload.asp?BlobID=24668
Most conditions cannot be remedied and stopgap measures are minimal, he said. The trees currently have a significant potential for failure of smaller limbs and branches and potential for larger limbs and stems to fail, he said.
Young said he did not evaluate one additional tree already scheduled for removal.
Risk assessments for each tree were based on ratings following the Pacific Northwest Chapter International Society of Arborists' Certified Tree Risk Assessor Program protocol. Each tree has a metal marker: 1, 5, 6, 9 and 11-16 that residents can see at the site.
Two trees, numbers 5 and 6, were given risk ratings of 10, with 12 being the most hazardous.
Young characterized tree 5 as "extreme. Failure is occurring. Immediate action is required." Five other trees were rated 9 and three merited an 8. In some cases, the trees could be retained for one or two years with monitoring before there should be concern for failure, Young noted.
The large trees, some of which are up to 58 inches in diameter, have suffered from years of pruning techniques that weakened the branches and made the trees vulnerable to sulfur fungus, a condition that cannot be remedied and leads to extensive trunk decay that "suggests there is also a potential for whole-tree failures," he added.
An earlier report by Eric Krebs, managing arborist for the the city's Public Works Department, also concluded that pruning techniques (in earlier decades) contributed to the overall failure the trees are now experiencing.
"These trees are very large and majestic, providing critical shade to community park and playground as well as adjacent homes and streets, Unfortunately this very size and location also renders them a significant risk.
"All large landscape trees, regardless of species or condition, present some degree of risk in proximity to people, vehicles, structures and utilities.
"Some risk is often accepted in consideration of the dramatic aesthetic and functional benefits of living with large trees. However, this site presents multiple targets to tree failures, including pedestrians and park users, adjacent utility lines and residential streets and parking as well as homes.
"Whole-tree failure would inevitably result in catastrophic damage with a high risk for injury as well," he noted.
Young said long-term, phased removal of the trees would require substantial and continuous maintenance that would add to costs.
Removing all 10 trees at once and promptly replanting with native species would entail substantial cost initially but would eliminate maintenance and debris cleanup over the long term, he said.
The benefits of a large tree canopy would also be lost for a number of years. But the city would not be exposed to lawsuits and other financial burdens if the trees caused injury, according to Young. He recommended replanting with California native species, such as California live oak, valley oak, black oak and coast redwood.
The city has not yet made a decision regarding immediate or phased removal. "Staff will now meet to quickly develop a work plan and present that plan to senior management," Dornell said.