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Santa Clara County Wildland Urban Interface

Published on: 7/5/2013 10:31 AM
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Years of experience by the California fire service have led to a new strategy for reducing the chance of building loss or damage due to wildfire, with new regulations that are now mandatory within the Wildland Urban Interface (WUI). It is a two-pronged approach – providing defensible space and constructing a more ignition-resistant structure.

 
 IS MY PROPERTY IN THE WILDLAND URBAN INTERFACE? more...
 
EXTERIOR WILDFIRE EXPOSURE PROTECTION:
 
Buildings are now required to be constructed so that they have less chance of catching fire from burning embers from wildfires. Most of the highest wildfi​re losses take place during hot, windy days or nights when flames spread so fast that many buildings catch fire and overwhelm available firefighting forces. Many buildings ignite when burning embers land on wood roofs, blow in through vents, pile up in cracks, or become lodged under boards. By constructing buildings in a way that reduces the ability of embers to intrude, a major cause of structure ignition is reduced.
 
Recently adopted building codes reduce the risk of burning embers igniting buildings. Standards are already in effect for roofs, attic vents, siding, exterior doors, decking, windows, eaves, wall vents and enclosed overhanging decks.

Fire-resistive roofs

Fire-resistive roofs, doors, windows, siding and decks provide protection against ignition from burning embers from a wildfire.

 

Chapter 7A of the County Building Code lists all the requirements. For further information, contact the County Building Inspection Office at (408) 299-5700, and see the “WUI Construction Fact Sheet” below.
 
 
 

WUI Defensible Space Fire 

This wildfire burned everything in its path right up to the edge of the defensible space provided by the owner.


DEFENSIBLE SPACE:

Providing a 30-100 ft. zone around all structures where flammable vegetation is reduced keeps direct flames and heat away from the side of the building. This means modifying the fuel to reduce the wildfire threat and provide an opportunity for firefighters to effectively defend a structure from an oncoming wildfire.

Providing defensible space does not mean scraping away all vegetation from the landscape. Landscaping can be designed to create an attractive well-vegetated property that also provides effective defensible space.

 

 

Removal of dead vegetation, reduction of "ladder fuels" by thinning brush and limbing-up trees, and replacement of highly flammable plants, such as Eucalyptus or Scotch Broom with fire-resistive plants are all part of a good vegetation planning and management program. This applies even to existing structures. Requirements are listed in Chapter 49 of the County Fire Code

Taking steps to provide and maintain adequate defensible space can make the difference between a home that is destroyed by fire and one that survives!


FIRE HAZARD ZONES:
While all of California is subject to some degree of fire hazard, there are specific features that make some areas more hazardous. The California Department of Forestry and Fire Protection (CAL FIRE) is required by law to map areas of significant fire hazards based on fuels, terrain, weather, and other relevant factors.

The Fire Hazard Severity Zone maps were developed using a science-based and field tested computer model that assigns a hazard score based on the factors that influence fire likelihood and fire behavior. Many factors are considered such as fire history, existing and potential fuel (natural vegetation), flame length, blowing embers, terrain, and typical weather for the area. The State identified three hazard zones in State and Local Responsibility Areas: "Moderate", "High" and "Very High".

TO FIND OUR WHETHER THESE REQUIREMENTS APPLY TO YOUR PROPERTY:
C
ontact us via e-mail to our Land Development Deputy Mac.Bala@pln.sccgov.org or call (408)  299-5763 for assistance. We are also available at our public counter on Wednesdays and Fridays (8 am - 12 pm and 1 pm - 5 pm). Please have the property address or Assessor’s parcel number available

VIEW THE ADOPTED WILDAND URBAN INTERFACE FIRE AREA MAP:
The map is available for download in two formats; a PDF file, which gives you a general overview of the County, and a Google Earth file, which you can expand to see views down to street level. To view the Google Earth file you will need to have the Google Earth program installed on your computer. Google Earth can be downloaded free from: http://earth.google.com/download-earth.html. Also, you need to turn off the NASA option (uncheck the box by NASA in the Google Earth side menu) to view the WUI map. 

IMPORTANT:  Areas within city limits may be included in hazard areas, but are not color-coded on this map. This map only shows the Wildland Urban Interface in the unincorporated areas of Santa Clara County. If you are within city limits you will need to contact that city's authority to find out whether your property is in the Wildland Urban Interface. You may find contact information for the cities within our County on our FIND YOUR JURISDICTION page.

 
 

BACKGROUND:
The County Board of Supervisors approved the original Santa Clara County Wildland Urban Interface Fire Area Map in January of 2008. This map includes both the State Response Area as designated by Cal Fire in 2007, and the former Santa Clara County Hazardous Fire Area as approved by the Board in 1976. Due to the availability of new mapping technology, the Local Response Area portion of the map has been updated by the County and combined with the existing State Response Area data to form a single Wildland Urban Interface Fire Area map. The Board of Supervisors adopted the map on February 24, 2009. 

 
 

The State broke the map into three zones: Moderate, High and Very High Hazard Severity Zones. For the sake of simplicity, the Fire Marshal has broken the new map down into only two zones: the main body of the Wildland Urban Interface and the "Very High Fire Hazard Severity Zone" within the "Wildland Urban Interface". The difference between requirements in the two zones is simply that in addition to the 30 ft. clearance required for all structures located in the Wildland Urban Interface, those properties located in the "Very High" zone must provide an additional 70 ft. of fuel modification due to the extreme fire hazard associated with conditions in those areas. The construction standards are the same throughout the Wildland Urban Interface Fire Area, regardless of zone.

DOWNLOAD MORE INFORMATION:

WUI Project Background (PDF)

 
 

WUI Project Background-Spanish (PDF)

 
 
 

Fire Hazard Zone Fact Sheet (PDF)

 
 

WUI Construction Fact Sheet (PDF)

 
 

Fire Hazard Zone Non-technical Primer (PDF)

 
 

Cal Fire’s WUI FAQs (PDF)

 
 

SCC Construction Projects Handbook APR 08

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