Water districts fortify fire defense
Facilities secured so supply will still flow if power lines are down
Marin County's two main water suppliers are working to fortify their treatment plants, pumps, water tanks and other facilities in anticipation of a potentially dangerous fire season following two years of severe drought.
In addition to clearing fuel breaks, trimming tree canopies and removing brush and vegetation, the Marin Municipal Water District and North Marin Water District have secured new generators and other tools to ensure that water keeps flowing in disasters.
Despite the significant rainfall in late 2021 and showers this spring, fire officials say the rain was not enough to reverse the impact of drought in the past decade. Grass fires have already begun springing up, but it is the increasing number of dead or dying trees that worries fire officials.
“We are in a significant chronic drought,” said Chief Jason Weber of the Marin County Fire Department. “Our heavier fuels are feeling that stress. We've seen redwood trees dying that historically have done OK here. Pines and firs are nearing the end of their life.”
The Marin Municipal Water District, which serves 191,000 residents, is particularly vulnerable to wildfire given that its reservoirs and supply systems stretch across 22,000 acres of the fire-prone Mount Tamalpais watershed. Nearly 80 years have passed since the mountain had its last major blaze, allowing vegetation and trees on the mountain to build up and encroach new areas
through the decades. The wildfire risk has been exacerbated through diseases such as sudden oak death, the proliferation of highly flammable invasive brush and more extreme weather patterns, all of which have been worsened by climate change.
A major fire could threaten the district's ability to pump water, whether by knocking out power lines or damaging its storage tanks, treatment plants and pump stations. The district has more than 190 facilities scattered throughout the watershed that require fire prevention work such as trimming trees and clearing defensible space.
In 2019, the district adopted an updated plan to invest $13.5 million over five years toward fire prevention projects. The projects include clearing thousands of acres of fuel breaks and vegetation; regularly using prescribed burns for the first time in more than 15 years; addressing diseased woodlands, controlling the encroachment of Douglas fir trees into grasslands and oak woodlands; and reestablishing native plants while clearing out invasive species.
A new tool acquired through an $800,000 state grant will allow the district to create digital maps to predict how its vegetation clearing and limb cutting work would affect wildfire behavior. A recent assessment of the Potrero Meadow forest land located northwest of Mt. Tamalpais found that fire prevention measures such as cutting tree limbs would reduce maximum flame heights from 20 feet to about 4 four feet and reduce the rate of spread from up to 22 feet per minute to 4 feet per minute.
“We're not trying to stop wildfire, we're trying to influence the behavior of fire area,” Shaun Horne, the utility's water resources manager, told the district board on Tuesday.
Horne said the district plans to use the tool to model other areas of the watershed to guide projects.
The district is also set to complete the installation of three permanent generators at its largest treatment site, the San Geronimo Treatment Plant in Woodacre. The project, which has an estimated cost of $5.3 million, will allow the plant to continue operating at full capacity, treating up to 35 million gallons per day, during Pacific Gas and Electric Co. power shutoffs and other outages.
Previously, the district used portable generators that did not provide as much power. The permanent generators are set to be operable by June 30 with full project completion expected in September, according to Darren Machado, a district official.
The district has purchased another 22 portable generators that can be deployed at pump stations and other sites to keep the transmission system running.
The North Marin Water District, which serves about 64,000 residents in Novato and several West Marin communities, has also been clearing out trees and other plants around the 60 water tanks, treatment plants and pump stations in recent months.
The district also has secured an additional five portable generators, for a total of nine, that it can deploy at its pump stations in case of a power outage, said Robert Clark, a district supervisor.
One of the main concerns is the potential for fires heating the ground to the point that it could melt some of the plastic pipes in the Novato area, Clark said.
The district is no stranger to the destruction wildfires can wreak. The 1995 Mount Vision fire took out two major storage tanks along with more than 40 homes. Both tanks have been rebuilt with larger concrete replacements.
The Woodward wildfire in the Point Reyes National Seashore in 2020 came close to burning down other facilities serving West Marin, Clark said.
“That's a really big concern about infrastructure being lost,” Clark said. “It takes a long time to replace.”