San Bruno's Crestmoor Canyon preps for wildfires

“We’re currently working on a bunch of different stuff related to wildfire mitigation but Crestmoor Canyon is the centerpiece,” San Bruno Fire Chief Ari Delay said. He said the canyon hasn’t seen a fire in recent history, but years of letting nonnative eucalyptus invade the canyon, combined with lack of recent rain, have increased risks.

While this rainy season has seen isolated intense bursts of rain, nearly the entire state, including San Mateo County, remains in a “severe drought,” which entails a longer and more intense fire season, according to the National Integrated Drought Information System. Delay said short periods of precipitation in particular do little to soak burnable plant matter that can cause fires to spread and require prolonged rain to fully saturate.

“It’s going to be another tough year, and things are really drying out,” he said. “They’re starting to get fires in the valley already.” He added that while the Bay Area is often perceived to have reduced wildfire risk due to its climate, “when the conditions are right it has the potential to start a catastrophic fire.”

The city of San Bruno is responsible for several wooded areas at risk, the largest of which is Crestmoor Canyon, a roughly 76-acre property home mostly to eucalyptus trees. The trees were planted along portions of the canyon’s rim several decades ago in an effort to block wind, but have since spread, often pushing out native plants. They also have an increased ability to spread wildfire, particularly due to bark and leaves that collect near the base that burns hot and long and is easily picked up by wind.

Delay said the primary goal was to clear at least 100 feet of space between the canyon and the many homes and other buildings that line the rim. Access roads that run through the canyon are also being cleared.

“We’re going through and eliminating some of the smaller trees and brush so if a fire does come through, it doesn’t have those ladder fuels and starting fuels to get up and become a raging fire,” Jon Dorvitt, a Conservation Corps crew supervisor, said.

Clearing forest areas of vegetation likely to spread fires laterally as well as vertically into tree canopies is a key part of lessening severity of potential fires. The work is especially important in places where wildfires have been suppressed, leading to fuel buildup.

Dorvitt’s crew has camped on-site for several weeklong stints, the most recent of which ended Wednesday. The city is in contract with the Conservation Corps through at least 2025, and has paid for the work with restitution funds from the Pacific Gas and Electric explosion and fire of 2010, which occurred adjacent to the canyon. Delay said Conservation Corps labor is more cost effective than other contractors, with a worker costing $24 per hour.

Longer term plans to tackle wildfire risks in the canyon and the rest of the city are also in the works. The plans will require drafting documents identifying environmental impacts, a time-consuming first step in the process.

Delay said while small trees (those with trunk diameters less than 8 inches) or those within the 100-foot defensible zone do not require environmental study or mitigation efforts, removing fully grown trees can be a more complex and pricey endeavor. Future plans could include more tree removal, along with new paths constructed and a fire hydrant network installed within the canyon.

Additionally, the city has several city-owned wooded areas lined with homes that have similarly been invaded by eucalyptus trees. Delay expressed concern for the areas, and said the citywide effort will employ similar tactics in those spaces as in the canyon.

Native trees for the city are primarily Monterey pine and California live oak. Bay laurel, big leaf maple and California buckeye species are also present. Tasmanian blue gum eucalyptus, the species present in much of California, were brought to the state in the mid 19th century from Australia.

To find out more about the city’s efforts in the canyon, go to bit.ly/3vleSiA.

corey@smdailyjournal.com

(650) 344-5200, ext. 105