Hillsborough Fire Hazard Reduction Projects
Defensible Space Fuel Reduction 2013
In Hillsborough during the summer and fall of 2013, the Town’s ambitious Open Space Vegetation Management Project will utilize CAL FIRE Hand Crews to create 20 acres of Defensible Space Zones between 8 of the Town’s open-space areas and neighboring residential properties. This fuel reduction project will have an immediate impact on the neighboring community, with targeted fuel reduction in the critical defensible space zones. Hillsborough is actively seeking proposals to perform additional fuel reduction and vegetation management on approximately 88 acres of High Priority Fire Management Areas (HPFMAs) within the 240 acres of open space lands owned by the Town.
Hillsborough Open Space Vegetation Management Project
The Town of Hillsborough is a hillside community located within the San Francisco Bay Peninsula. The Town owns nine open space areas within the incorporated limits which range in size from approximately 1.6 acres to approximately 53.8 acres, totaling approximately 240 acres. The open space areas are undeveloped with rugged, steep, and heavily vegetated terrain. A wildland/urban interface exists where these open space areas border residential properties.
In 2006, the Town completed a vegetation/biological survey of its open space areas as an initial step in its open space area planning and management processes. This survey provided baseline vegetation community data, data of habitat for sensitive species, and information about fuel load characteristics to guide future vegetation management and fire management planning. In 2008, the Town completed the Vegetation Management Strategies and Guidelines report for its open space areas.
In 2009, the Town Council approved the Task Force’s list of project priorities, of which Wildfire Management was a top priority. In response to the Task Force’s approved list of priority projects, the Town issued RFPs to implement this priority project.
The project will comply with NEPA and CEQA requirements and state and federal Endangered Species Act requirements, as described in the final Initial Study/Mitigated Negative Declaration document and the Biological Opinion.
The project area is located approximately four miles south of the San Francisco International Airport and approximately two miles north of SR 92, between Interstate 280 (I-280) and Highway 101 in San Mateo County, California. The project area consists of eight of the nine Town-owned open-space areas, all of which are adjacent to residential development. The open spaces contain canyons and hillsides in elevations from approximately 100 feet to 615 feet above sea level. Detailed maps are provided in the RFP.
Fuel reduction and vegetation management activities are planned within approximately 88 acres of the total 240 acres of open space lands owned by the Town. Treatment acre estimates were derived using GIS mapping software and should be considered a reasonably accurate plan view estimate of treatment areas.
Two general types of fuel reduction will be implemented on approximately 88 acres: about half (approximately 42 acres) will be work within Defensible Space Zones (“DSZ”), with the remaining acres (approximately 46 acres) to be work in High Priority Fire Management Areas. Although work in these two types of treatment areas is similar, more intensive fuel reduction is required in the designated DSZ as compared to the amount of vegetation treated within the designated High Priority Fire Management Areas. Final work areas will be ‘field fit’ to avoid sensitive biological constraints such as restrictions around creeks and sensitive species habitats, but the overall total work area will remain at approximately 88 (plan view) acres. Some vegetation to be treated is located in hazardous condition areas such as very steep hillsides, inaccessible hike-in sites, areas without access to water, sites with poison oak and other hazards that will require special methods or safety practices.
Description of Work to Be Performed
Two types of treatment areas are defined for this project: Defensible Space Zones (“DSZ”) and High Priority Fire Management Areas (HPFMA). The Town estimates that work will take place in approximately 42 acres of DSZ and approximately 46 acres of HPFMA, for a total of 88 acres.
Hillsborough anticipates that the initial clearing will be accomplished in Year 1, and maintenance/follow-up work will be conducted in Years 2 and 3 of any contract awarded.
Work within Designated Defensible Space Zones
Work to be performed in the DSZ is estimated at approximately 42 acres. DSZ’s are located in eight (8) of the Town’s open space areas. Treatment activities will take place over the course of 3 years, with the majority of fuel removal conducted in Year 1, and work in Years 2 and 3 focused on maintaining the area and controlling invasive plants that re-establish in the treatment areas.
The goal of fuel reduction within the DSZ is to (a) reduce overall fuel load by removing approximately 1/3 to 1/2 of the understory vegetation, (b) reduce or eliminate fuel ladders, and (c) remove greenwaste from the DSZ. Fuel ladders are defined as the vegetation connecting the ground and the tree canopy that can spread a fire from the forest floor into the forest canopy. Native shrubs and vegetation shall be avoided when possible during fuel reduction efforts. Live tree removal is not anticipated. However, some saplings (4 inches or less in diameter at breast height (“DBH”)) may be thinned to create spaces between trees in dense forested areas. Some diseased and dead trees may be felled. Downed trees < 12 DBH may also need to be removed.
Approximately 1/3 to 1/2 of understory vegetation within designated DSZ will be removed.
Work within Designated High Priority Fire Management Areas
High Priority Fire Management Areas (“HPFMAs”) are contained in four (4) open space areas as indicated in Attachment B.1. The final configuration of work areas for HPFMAs within these sites will be ‘field fit’ to avoid sensitive resources such as creeks and sensitive species, reducing areas shown on Attachment B to the final High Priority Fire Management treatment areas, which will be approximately 46 acres. Treatment activities will take place over the course of 3 years, with the majority of fuel removal conducted in Year 1, and work in Years 2 and 3 focused on maintaining the area and controlling invasive plants that re-establish in the treatment areas.
The goal of fuel reduction work within designated High Priority Fire Management Areas is to (a) remove approximately 1/4 to 1/3 of the understory vegetation, (b) to reduce fuel ladders, and (c) control invasive plants, as possible, within the context of fuel management activities.
Unlike within DSZ Treatment Areas, removal of greenwaste is not required within these areas. However greenwaste left in place must be treated in a manner that will expedite breakdown of materials, and stored in a manner that will discourage ignition and minimize visual impacts. See a more detailed description of greenwaste treatments below and in the Town’s adopted Greenwaste Management Plan.
As described above for DSZ, native shrubs and trees within High Priority Fire Management Areas will be avoided when possible. The removal of large, live trees is not anticipated. However, some small trees and saplings may be thinned to create spaces between trees in dense forested areas.
Approximately 1/4 to 1/3 of understory vegetation within High Priority Fire Management Areas will be removed.
Maintenance of DSZ and High Priority Fire Management Areas
The town anticipates completing the initial vegetation treatment during the first year. Following Initial Vegetation Removal, 2 years of site maintenance in both DSZ and High Priority Fire Management Areas will be conducted. Maintenance activities will be similar in both treatment areas, intended to preserve low fuel loads and control invasive plants such as French Broom, Pampas Grass, or blackwood acacia that may re-colonize the sites following initial site treatments.