The centuries-old oak 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 seismic improvement project. The commission initially planned to kill the tree in May on short notice, which sparked a protest from Granny's neighbors.
SFPUC Project Manager Joseph Ortiz presented an estimate from a contractor, Mountain Cascade, which would charge $269,000 to dig a tunnel — steep, but significantly lower than the SFPUC's initial estimate of $437,000.
A tunnel might cause problems for more than the commission's piggy bank. Condensation on the surface of the pipeline may cause the oak's roots to wrap around the pipe and cause corrosion, said project arborist Matt Horowitz. Last week he excavated around the tree and found numerous roots that may be corroding a pipe already installed nearby.
Roots touching the new pipe may not cause the same damage as they did to the old pipe, which was built in the 1930s, said Mr. Ortiz.
The SFPUC told the Almanac that it doesn't track root-induced pipeline failures or corrosion in its databases. Manager Dave Briggs estimated three to four leaks plague the regional pipeline system each year, and that corrosion causes a portion of those.
"Leaks are indicative of reduced pipeline strength," he said. "It may also be helpful to know that our policy with tree roots is very standard and not something unique to the SFPUC. No pipeline owner wants roots on or near their pipelines."
Not everyone agrees that Granny's roots pose a threat. A report released two weeks ago by an arborist hired by the neighbors called the likelihood of damage "so small as to be irrelevant." Barrie Coate, who also works as an arborist for the City of Saratoga, wrote that the pipeline's depth should stop roots from reaching it.
Relocating Granny is also on the table, but no one knows where the tree's new home should be. Environmental Design Inc., a tree-transplanting company, estimated $275,000 for moving expenses if the oak goes to a nearby county-owned park. Mr. Ortiz added that relocating the tree to the park would require an official agreement with San Mateo County, which would take on the responsibility for the tree's care and maintenance.
On the other hand, scooting the tree closer to the home it currently overlooks would require demolishing landscapes on the adjacent properties.
Arborist Jane Herman also expressed concern that pruning the roots in preparation for a move could damage the oak's health.
Cost remains a priority, Mr. Ortiz said, since the commission is under pressure from people paying for water in the San Francisco area to keep rates low.
Granny's neighbors responded that the $40,000 estimated by Mountain Cascade for the tree's removal is misleadingly low. They noted that the costs of trenching, laying pipe, and the loss of goodwill between the utilities commission and the public should be factored into the price.
Mr. Ortiz agreed and said SFPUC is still considering all options. "Regardless of what we do, it will probably cost the same amount," he said.
With this in mind, the neighbors seemed to agree that tunneling under Granny is the most viable option. "The solution with the lowest impact for the tree is to leave it in place and tunnel underneath it, cutting as few roots as possible," said Charles Berkstresser, whose property is home to the oak tree, adding that their objective is to find an option that serves both the tree and the pipeline. The neighbors also said they don't want to delay what they acknowledged to be a very important project.
Both sides did agree on one item — Granny's roots, currently exposed by the excavated trench, will be wrapped in moist burlap for protection until a decision is made.
The commission and the neighbors will meet again in a couple weeks, after an SFPUC arborist alongside Mr. Coate further investigate the site.