His report called the commission's concern "simply not logical," as roots tend to stretch toward the soil's surface for oxygen and water, rather than down to the depth of the pipeline.
"I can certainly say that considering the many pipelines including those carrying high octane airplane fuel as well as water and sewage that exist in the ground in California and the many trees including species with far more aggressive roots than a valley oak that the likelihood of damage to this pipeline are so small as to be irrelevant," Mr. Coates concluded in his May 25 report.
The SFPUC sent a contractor last week to start excavating soil around the two pipelines already installed next to the tree to see whether the roots pose a threat. In an email obtained by a public records request, on May 17 Hetch Hetchy operations manager Kent Nelson told the commission's spokeswoman that condensation on the outside of pipes attracts roots, which then corrode the surface as they wrap around, leading to "premature (potentially catastrophic) pipeline failure." Therefore, the commission recommended removing the tree.
The 65-foot oak, dubbed "Granny," dodged the ax in May when a coalition of neighbors protested the SFPUC's short-notice announcement that it planned to get rid of the tree. Granny sits in the middle of a site at 827 15th Ave. in North Fair Oaks that's designated for a pipeline meant to carry water from the Hetch Hetchy as part of a $4.6 billion SFPUC seismic improvement project.
Mary Ann Mullen said 95 percent of households contacted in the area signed a petition to save the tree. The challenge, she said, may be maintaining public interest over time. According to Ms. Mullen, residents received a letter from the commission last week suggesting the pipeline installation might be delayed until fall.
"If this is an attempt to delay movement on this issue until things die down, the coalition will be here in six months as clearly focused as now," she said.
Relations between the SFPUC and Granny's neighbors remain strained. As two of the tree's advocates attempted to view the exploratory trench on June 6, commission arborist Matt Horowitz reportedly blocked access, first requiring them to wear hard hats, then saying they had to contact the company that owns the job site when the pair returned 45 minutes later, hard hats in hand.
Ms. Mullen said that makes it impossible for their own consulting arborist to reach an independent conclusion about the test results, particularly if the trench gets filled in.
SFPUC spokeswoman Maureen Barry said she was looking into the situation and thought it may be a matter of only allowing authorized personnel onto construction sites, but that it may be possible to schedule visits.
This story contains 519 words.
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