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Trail in Portola Valley

Maintaining the safety of the community

The combination of fire protection measures for the housing development and management of the large oak woodland will make Portola Valley safer by lowering fire risk for the surrounding residents and the community.

Fire Safety

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Fire safety is a top priority for the entire Portola Terrace project. Fire protection measures are incorporated into both the housing development and Stanford’s management of the large oak woodland. The housing is clustered on only 6 acres (about 8 percent) of the 75-acre property. It is designed with native, drought-tolerant landscaping, constructed with fire-resistant building materials, and built with the appropriate defensible space surrounding the structures to meet all codes. In addition, high-voltage power lines along Alpine Road are undergrounded and water capacity to the entire property is enhanced through water service to the housing units.

The remaining 69 acres of the property will be maintained as an oak woodland to reduce fire hazards under prescriptions described in a Vegetation Management Plan (VMP). The VMP provides long-term strategies for reducing fuel loads and managing vegetation to minimize fire hazard and protect ecological values and resources on the property. It was prepared by a team of leading fire experts (Panorama Environmental, Inc., Spatial Informatics Group, and Prometheus Fire Consulting) in close consultation with the Woodside Fire Protection District (WFPD).

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Figure 1: Modeled Integrated Hazard - Current condition

Vegetation Management Plan Summary

Two fire behavior modeling programs were used to assess the probability and intensity of fire on the property (referred to as “integrated hazard”) and to identify effective ways to lower the likelihood of a fire outbreak and spread. The VMP is based on the results of the modeling programs. Under current conditions, nearly all areas of the property were shown to need some form of vegetation treatment to reduce fire hazard. The modeling further indicates that fire safety on the entire property is significantly improved with the treatments specified in the VMP, which is part of the development application for Portola Terrace. Average flame lengths are greatly diminished from 4.8 feet to 0.7 feet and “integrated hazard” dramatically decreases by as much as 99 percent. This greatly reduces fire risk to surrounding homes and infrastructure.

The two images show the integrated hazard level on the property under current conditions and after implementation of the comprehensive treatments described in the VMP. After treatment, the entire property is re-characterized as only having areas of Lowest and Low Hazard.

Vegetation Treatment

The VMP examines the various vegetation types on the property—predominantly areas of oak woodland and defensible space around structures – and recommends specific treatment methods by type to reduce the potential for wildfire. There are initial and ongoing treatment methods and they range from manual planting, cutting and removal of vegetation to grazing and mastication with manual support. These treatment methods accomplish multiple objectives for the various types of vegetation on the property, including:

  • meeting and maintaining CAL FIRE and WFPD requirements for defensible space;
  • reducing fuel volumes to be on par with very low severity fire;
  • reducing fuel flammability and cultivating generally native and fire-resistant plants;
  • establishing and maintaining fuel discontinuity;
  • reducing the possibility of fire traveling through tree crown and maintaining separation;
  • maintaining healthy, dominant, natural, and fire-resistant vegetation;
  • maintaining “active dusky-footed woodrat nest sites.”

A new permanent road will be constructed from Alpine Road up to the middle of the property to allow for Class III or greater fire engine access and staging for fire management and maintenance activities only. It will be gated and closed to the public. Environmental protections are also incorporated into the VMP, including protection of significant trees, nesting birds, San Francisco dusky-footed woodrats, California red-legged frogs, and archaeological resources. 

Portola Valley Trees

Vegetation Management Plan

The university has completed annual vegetation management efforts in years past as part of its ongoing stewardship of its lands and performed vegetation management on the property earlier this year, independent of our proposed project and the VMP. The same team of consultants that prepared the VMP was hired to prepare the scope of work for this vegetation management effort in consultation with WFPD.

Vegetation Management Plan Executive Summary
Vegetation Management Plan