wildfire hazard and risk assessment
It is important to distinguish between wildfire hazards and wildfire risks, to understand the difference between hazard and risk, and to review the fundamental safety precepts that a sound and prudent assessment of wildfire hazards and wildfire risks entail.
The assessment of wildfire hazard entails thorough consideration of the specific, on-site conditions of a proposed or existing building project that may or may not be conducive to the rapid spread or increasing intensity of fire. It requires consideration of the development plan, the variety of activities (uses and misuses) that can occur at the site, the site’s local topography, the nature and extent of immediately available fuels on the site, the orientation of the site within its topography, and the range of weather or seasonal conditions to which the site can be exposed, including prolonged sunlight, extreme winds or elevated temperatures.
The assessment of wildfire risk does not focus on the site itself, but rather on adjacent and more distant off-site properties, lives, facilities and assets that could be placed at risk if fire spreads from the site. It requires a thorough examination of the terrain, vegetation and structures surrounding the site, as well as the people, activities, facilities and evacuation routes within that terrain that could be exposed to fire emanating and spreading from the site. And it examines the resources available to contain and suppress fire emanating and spreading from the site.
In the assessment of wildfire hazards and risks, two fundamental questions must be addressed:
Are the hazards posed by the site localized and contained to the site or are they expansive and contagious?
If a hazard posed by the site is expansive and contagious, are the risks posed to off-site properties limited or ruinous?
Both questions are heuristic not statistical or probabilistic. Put aside what perceptions of past experience indicate may be the probability of an occurrence at the site, and instead ask: Is the occurrence possible?
In the context of the extreme hazards and catastrophic risks of wildfire, prudence dictates a greater degree of certainty than probability analysis can provide. Because probability analysis is merely an estimate based on past experience, it is subject to a variety of misperceptions, errors and biases that can prove disastrously wrong. It can, for example, misperceive the totality of past experience on which an estimate is based, or it can fail to appreciate how subtle changes in the current and future era render the circumstances of past experiences less relevant to the prediction of current or future outcomes. Or it can inject a variety of biases or errors into its estimate.
Our recent experience with the coronavirus illustrates how such misperceptions of past experience or subtle changes in current or future circumstances can create a false sense of confidence with disastrous effects. Recently, the public health assumption — based on past observations of other viruses — that asymptomatic individuals would not be contagious has resulted in widespread exposure to and unanticipated spread of infection far beyond all statistical predictions. In the similarly contagious and catastrophic context of wildfire, that is why an appropriate hazard-risk assessment simply asks: What is possible? If fire emanated at the site, where and how could it spread under different wind, temperature and weather conditions?
If the examination of potential activities, local topography and fuel sources demonstrates that the possibility of spread is entirely local and there is no possibility of spread to adjacent properties, there is no need to consider the second question. If, however, the examination of potential activities, local topography, weather and fuel sources indicates that the spread of fire to adjacent properties is possible under extreme conditions, we must then consider whether — under such conditions — the spread of fire would be contained with high certainty, or whether its spread could become contagious and ruinous?
This latter determination requires a more comprehensive examination of the surrounding terrain, surrounding fuel sources and potential pathways to assess the extent and directions of possible fire spread. If that examination indicates that the possibility of fire spread emanating from the site could be contagious and ruinous, the proposed project should be rejected unless and until it demonstrates that the possible spread of fire from the site is eliminated or contained under extreme conditions with high certainty.
Rather than an informed analysis and assessment of specific hazards and risks, the Safety element of Portola Valley’s General Plan relies on a concept of “acceptable risk.” It defines “acceptable risk” as “the level of risk that the majority of citizens accept without expecting governmental action to provide protection.” For example,
“if the chances are one in a thousand that the site will be flooded in any given year, local citizens will probably accept that risk without asking for special protection. If the chances of flooding are one in ten, however, either governmental regulations would be enacted to keep people from building on the site (in order to protect life and property) or property owners would ask the government to build protection devices to control the flood waters.”
In light of the hazards confronting Portola Valley — earthquake, wildfire, landslide, flooding — the deficiencies in this form of risk assessment are both glaring and dangerous. First, the assessment of risk outlined in the Safety element embraces the erroneous notion that the probability of a future catastrophe can be predicted or calculated with assurance. It cannot. Second, it fails to structure the systematic examination of risks to third parties and properties that a hazardous project poses. Third, it effectively presumes that hazardous projects may proceed unless and until political action is organized to stop or mitigate them. And fourth, it fails to assign or delegate responsibility to a specific body or official to protect Town residents from hazardous projects that can create contagious and ruinous consequences.
These deficiencies become particularly glaring and dangerous in the context of wildfire. Much like a viral pandemic, wildfire is typically spawned from unappreciated hazards that unexpectedly converge in a contagious, fast-spreading conflagration. Sound land use planning and enforcement are the first and perhaps most important line of defense in preventing the occurrence and rapid spread of wildfire. For example, the General Plan’s Introduction, its Land Use element and Open Space element all call for open space preservation of steep, fire prone ravines free from further development, precisely because of their hazardous conditions. The Safety element and the municipal code need to implement these policies with suitably wise hazard and risk policies.
That is not to say that the wildfire hazards open space lands present should go unaddressed or unmitigated. The Town can and should adopt appropriate ordinances to require open space property owners to abate and mitigate the risks that extreme on-site hazards pose to off-site neighbors.
In particular, the Safety element and implementing ordinances of the Town should be supplemented to require and assign specific responsibility for the comprehensive, systematic assessment of the wildfire hazards and risks within Town. This is especially true in the context of any new development within Town. Where the assessment reveals that on-site hazards are extreme and contagious and the risks to surrounding neighbors are potentially ruinous, a development project should be stopped until and unless the hazards are appropriately addressed and its risk to surrounding neighbors is eliminated. The economic interests of one developer do not justify the creation and transference of ruinous risk to its many neighbors.
The Woodside Fire Protection District has said that it has no authority to stop a hazardous project based on the fire risks it poses to neighboring residents and properties. It says it can identify the wildfire hazards and risks, as it has done with Stanford’s proposed housing project in the Alpine Canyon, but only the Town or Stanford can stop the project from proceeding. Who then is responsible in Town government to assess the hazards of Stanford’s proposed project and the risks those hazards create for the residents and properties surrounding Stanford’s proposed project?
When, on January 30, 2020, citizens of Portola Valley asked the Chairman of the Planning Commission whether the Commission was aware of the Fire District’s written concerns and would act to resolve them before proceeding further with Stanford’s project, the answer was No and No.
The safety of Portola Valley and its residents demands more — much more — transparency, accountability, and responsibility. Read and sign PVNU’s February 12, 2020 letter to the Town Council.