The 120-foot redwood presiding over the Castilleja School campus didn't look sick. Its lush canopy sported dark green, shiny leaves and full branches. But it was a disaster waiting to happen, in danger of toppling in the next winter storm because of a rotting base, according to city arborists and a consultant hired by the school.
Neighbors, however, were suspicious. The tree might be a pawn in the school's current bid to expand its campus on Bryant Street, they said. Castilleja is proposing a 130-space underground parking structure under the plan, which also includes razing four buildings, adding a larger structure, and increasing its enrollment by 30 percent to 540 students.
The residents' group Protect Our Neighborhood's Quality of Life Now opposes the plan.
"Castilleja has proposed a huge new project that would ... increas(e) daily parking, noise and traffic," said Rob Levitsky, who lives next to the campus. "I have owned the house for 25 years and don't see any imminent threat (from the tree). But guess what? The tree is in the way of their project plans."
It's the kind of reaction that city arborists must respond to fairly frequently. Development pressures -- and some serious city gaffes -- have eroded the public's trust in the past few years. In response, the city has tried to educate people by being more transparent about tree removals. The Urban Forestry Division has held public meetings to demonstrate how some trees in question are hazardous, and it has performed advanced testing and even hired the occasional consultant to verify its findings.
Even so, in a town whose namesake is a redwood, city arborists acknowledge it's not easy to explain that a tree should be axed because of disease or age.
Palo Alto cuts down about 1 percent of its nearly 40,000 public trees from parks and streets annually, replacing them with newer, better-suited trees, Urban Forester Walter Passmore said. But all residents know is that mature, healthy-looking trees are disappearing.
Some neighborhoods have been more affected than others. According to the city's 2015 Urban Forest Master Plan, three south Palo Alto neighborhoods in particular have lost canopy: Charleston Meadows, Fairmeadow and Greenmeadow. Charleston Meadows saw a decrease largely because of developments such as Arbor Real and the Elks Club on El Camino Real. Fairmeadow and Greenmeadow have lost dying street trees, which when originally planted were fast-growing, short-lived species not well-adapted to the local climate, the master plan states.
South Palo Alto has 20 percent less tree canopy than the north end of the city, the plan notes. Also contributing to public sensitivity over trees was the 2009 clear-cutting of 50 mature trees along California Avenue as part of a streetscape-improvement project. It arguably became the flashpoint for distrust from which the city has yet to recover.
Residents have a long history of protecting their trees. As early as 1914, they formed a "Save Our Trees" campaign after the city planned to remove more than 70 trees from dirt roadways that year. Facing lawsuits, the city sought to protect speeding drivers who kept striking the trees in their new automobiles. Horses, it seemed, understood how to negotiate around the trees, which were sometimes located in the middle of roads. But the move to take out the hazards sparked such outrage that City Council members who voted in favor of the tree removals lost their council seats, according to local historians.
Nelson Ng, who lives across the street from the Castilleja redwood, summed up residents' feelings: "The trees are a part of our quality of life, but the trees are being cut down in front of us. We should really protect them just like we protect our children," he said.
Castilleja officials requested a permit to remove the tree after their arborist, Michael Bench, discovered its base had decayed while doing a survey of the campus' trees for the expansion proposal. City arborists who inspected the tree concurred it was hazardous and granted the permit. The school planned to remove the tree on Oct. 13, but residents protested after seeing a sign about the tree's impending demise.
During an Oct. 18 community meeting at Castilleja to discuss the redwood's removal, Passmore took a pragmatic approach while explaining concerns about the tree's safety.
"The role of the city is to be a neutral third party," he said, but the city has a responsibility to prevent injury to persons or property.
"The redwood is about one-third sound wood. It is on the edge of a significant risk of whole tree failure," he said.
"I don't believe there is an arborist who can truthfully tell you when this will fail. We always have some level of uncertainty. But I think the data is compelling. ... We cannot delay. We all know the risk."
City arborists take removal of any trees seriously, he said. Under city ordinance, redwoods with trunk diameters 18 inches or greater, and coast live oaks and valley oaks with 11.5-inch or greater diameter trunks, are protected from removal unless they pose hazards.
The city does not have any say if a private-property owner chooses to remove other species of trees, however, unless the trees were planted as part of a city-approved development, such as an apartment complex or commercial site. The trees are also protected if they are of great age or historical significance and have been designated as "heritage" trees, of which there are seven: El Palo Alto; the Rinconada Oak at Rinconada Park; a coast redwood on private property on the 3700 block of La Donna Street; a dawn redwood on private property on the 1000 block of Forest Avenue; a silver maple on private property on the 1800 block of Edgewood Drive; an American elm on private property in the center of the San Alma Homeowners Association on Ponce Drive; and an Aleppo pine on private property on the 2200 block of Ramona Street.
Protected trees can be removed, pending a permit approval, under a number of circumstances, according to the city's Tree Technical Manual:
If it is dead, hazardous, a detriment to or crowding an adjacent protected tree; if the trunk is touching or is uplifting a foundation or damaging eaves or gutters on an existing building; and on projects other than a single-family residence if the tree reduces the permissible building area by more than 25 percent, among other exceptions as defined in the city's municipal code under section 8.10.050.
Also, if a protected tree presents an immediate danger, the city doesn't require a permit in advance. But the property owner must provide documentation showing why the tree poses that danger. If the city determines that an emergency does not exist, the price for illegally removing or damaging a tree can be high: $100 per inch of damage, according to the Tree Technical Manual.
City arborists follow protocols to determine a tree's care and its potential hazard following the International Society of Arboriculture standards and the city Tree Technical Manual. A perusal of either offers clues to an arborist's view of trees.
How arborists assess trees
When arborists do an initial assessment, they inspect the tree visually, 360 degrees. They look for decay; the position of limbs and stems; die-back of branch ends and leaves; the presence of cracks; cavities; the condition of the canopy; trunk narrowing at odd points; evidence of insects and other damage. They make a tree-evaluation checklist and fill out a questionnaire, which includes a hazard assessment.
And they make an important distinction: "Poor tree health may not reflect poor tree structure," according to the tree technical manual. And conversely, trees that are healthy looking might be structurally unsound. The first goal is to determine if the tree is hazardous but also if it could be treated to prevent it from becoming a hazard. The risk might be reduced by pruning or reducing the weight of branches, improving irrigation or watering regimens, treating for insect or disease infestation, supporting leaning trunks with cables or bracing, or removing objects that the tree would strike or interfere with, such as picnic tables in a park or a pedestrian pathway, the manual notes.
Certain tree species also pose greater risks. In a drought, certain eucaplyptus species drop limbs and whole trees can fall over without warning. The Bay Area has many of these trees. In February 2010, a limb missed -- by one foot -- falling on top of a resident out on a morning walk at Eleanor Pardee Park. City arborists determined six of the park's trees should be removed due to disease, their propensity for dropping limbs and their proximity to a children's playground.
That scenario -- one of relative risk -- is perhaps the most important factor that arborists must consider because of potential injury, Passmore said. Arborists constantly talk of "targets," whether a tree or its limbs are likely to endanger persons, homes or vehicles or to spark fires because they encroach on power lines. However, a tree that might be deemed hazardous in an urban environment might well be left alone near San Francisquito Creek or another sparsely populated area, he said.
On a recent drizzly afternoon, Passmore pointed out old oaks with sparse canopies and hollow trunks leaning toward the creek bank. Most are left to fall because they aren't a hazard to anyone and they provide habitat for wildlife, he said.
Assessing tree hazards also uses the laws of physics. A normal tree can usually handle wind gusts of 47 to 54 mph. But defects or conditions that affect a tree's stability can cause trees to fall at lower wind speeds, according to the International Society of Arboriculture "Best Practices Tree Risk Assessment" manual. But trees on the leeward side of buildings experience slower wind speeds than exposed street trees, so an arborist assessing a tree's hazard level in an urban environment might take location into account as well as local climate.
A dangerous tree
In the case of the Castilleja redwood, concern over risks to people and property, combined with predicted winds from approaching storms and decay and other weaknesses, ultimately led the arborists' concern that the tree could fall as soon as the next storm, Passmore said.
Bench, consulting arborist for Castilleja, first noticed decay around the redwood's base while assessing the other 168 trees on the property, 57 of which could be removed if the development proposal goes through.
A "lignotuber," a starchy enlargement of some tree roots, protects the tree from fire damage by storing water and nutrients for use after a blaze. On the Castilleja redwood, it was riddled with decay. But the city's Urban Forestry Division, considering the tree's protected status (it has a 71-inch-diameter trunk), required additional assessment using a drill test to determine the extent of decay. Boring 22 holes, each 18 inches deep, into the tree's base, Bench developed a map that showed the base was two-thirds decayed.
City Managing Arborist Dave Dockter, who also examined the tree, said he believes the redwood's roots are rotted. But examining the roots further by excavation could have further destabilized the tree.
During the Oct. 18 meeting with residents, he also noted that a second, 90-foot trunk that did not show signs of decay would also likely topple if left standing. A tree's energy comes from the leaves. Removing the larger decayed trunk would eliminate much of the leaf canopy used by both trunks, he said. The remaining trunk was likely to topple because it would not have enough energy to repair the damage. Most healthy trees can handle only an eight-inch-diameter wound; the tree could not handle the enormous 44-inch-diameter wound caused by felling the diseased trunk, he said. After decades of support from the main stem, the second trunk also did not have enough strength to resist winds and its own heavy branches.
But residents remained skeptical. They hired their own arborist to examine the tree. Nanci Kauffman, Castilleja's head of school, agreed to the examination.
"I want to address the elephant in the room. I understand there is such a lack of trust," she said of relations between the school and some members of the community.
Passmore said he was not opposed to the outside opinion, but he offered a caveat:
"There are no 100 percents in the tree business. If you get 10 arborists, you will get 12 different opinions."
Differences of opinion
That turned out to be a somewhat accurate prediction.
Deborah Ellis, a consulting arborist hired by Protect Our Neighborhood Quality of Life Now, concurred that the lignotuber at the trunk base was dead. But a mallet test or "trunk sounding" she did to tap the trunk for loose bark and decay did not find abnormalities on the main trunk seven feet up, she wrote in an Oct. 24 report.
A more sophisticated sonic tomography test would map a picture of the trunk. But Ellis was concerned that removing the dead mass in order to do a tomography study wouldn't destabilize the tree. The test also would not map the tree's underground roots to determine the amount of root rot, she said.
She did concur that removing the larger trunk could put the second trunk at risk.
"The long-term stability of the entire redwood tree is questionable. ... If complete safety relative to the redwood must be guaranteed, then the tree should be removed," she wrote.
The residents decided they would not pursue a further analysis, and Castilleja, which already had a permit to remove the tree, hired an arborist to begin taking it down on Oct. 26. The tree is one of 81 in the city removed or permitted for removal since April 20, 2015, city records show.
Ron Walker, a certified tree-risk assessor and arborist who cut down the redwood, put his own observations of the redwood's safety in starker terms.
"I wouldn't live in this house," Walker said, pointing to the adjacent home. "The tree looks 'healthy' but it wasn't secure. Its structural stability was shot."
Cutting off the branches exposed other defects that could lead to the tree falling at any time, he said. Both trunks had probably been topped at one time, causing the tree to send out new growth, which became new tops. But these multiple branch tops are points of weakness that can fall to the earth like spears.
"I've seen redwoods break off these branches and slice a home in half and kill a family," he said.
But even though the final segment of trunk was hauled away on Nov. 3, the full extent of decay still isn't known, nor is it apparent to the eye. The true damage likely won't be known until the stump is removed or until nature's processes expose the decay.
Walker cut the tree a few feet above the dead footing, exposing what appeared to be an undecayed tree.
Removing the entire trunk below that point would have cost Castilleja thousands of additional dollars. It isn't necessary until, or if, the school is able to build on the site, he said.
As for the larger question of city arborists' motives in removing trees, Catherine Martineau, executive director of the Palo Alto tree-advocacy nonprofit Canopy, rejected notions that the arborists are influenced by developers.
"In general (arborists) don't want to remove the trees. People in tree departments are tree lovers too -- but they are pragmatic tree lovers. They have to contend with regulations. What the public sees are the cases that are not ideal. They perceive the trees are hacked when they are cut for power-line clearances (for instance), and that reinforces the idea that city staff doesn't know what they are doing," she said.
But Martineau said residents can have confidence in the city. Since Passmore was hired after the 2009 debacle, the Public Works Department has a completely new team of tree professionals, she said.
"Walter is eminently qualified. He's also interested in working with the community and bringing a more equitable canopy cover throughout the city. Since Walter arrived, he has put a team in place that is very concerned with the welfare of the city's trees, and he is very patient. He will go to whatever lengths are needed to protect the trees, and he has also not provided permits for every project.
"He doesn't rubber stamp the removal of trees," Martineau said.