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Chapter 24.51 Wildfire Hazard Zones


- Note

(Chapter added by Ordinance No. 177433, effective May 30, 2003.)

24.51.010 Purpose.

The purpose of this Chapter is to adopt the criteria that will be used to specify areas of the City to be classified as Wildfire Hazard Zones, so that roof materials may be limited.


24.51.020 Definitions

(Amended by Ordinance No. 180917, effective May 26, 2007.)  The definitions contained in this Section relate to Wildfire Hazard zones and considerations outlined in this Chapter.

A.   Chief means the Chief of Portland Fire & Rescue or the Chief’s duly authorized representative.

B.  Department of Forestry (DOF) means the State of Oregon Department of Forestry.

C.  Wildfire Hazard Zone means those areas of the City as determined by the Chief that rate a minimum score of 5 or higher using the following criteria developed by DOF:

1.  Topography hazard factor value

2.  Natural vegetative fuel hazard factor value

3.  Natural vegetative fuel distribution hazard factor value

D.  Wildfire Hazard Zone Map means the WHZM attached to Ordinance No. 177433 and as it may be amended from time to time based on the criteria herein.

E.  Hazard Factor. Hazard Factors are topography, certain natural vegetative fuels and natural, vegetative fuel distribution.  Any of these factors, or a combination thereof, may cause an area of the City to be included within a Wildfire Hazard Zone.

F.  Topography Hazard Factor Value means the hazard value as determined by DOF associated with site slope which effects the fire spread velocity.

G.  Natural Vegetative Hazard Factor Value means the numerical value assigned by DOF, extrapolated from the “Aids to Determining Fuel Models for Estimating Fire Behavior” published by the Forest Service, USDA Intermountain Forest and Range Experiment Station in 1982 as General Technical Report INT-122, for various common vegetation.

H.  Natural Vegetative Fuel Distribution Hazard Factor Value means the numerical value assigned by DOF for the percentage of site that is covered by vegetation described in 24.51.020 G.


24.51.030 Wildfire Hazard Zone Map Adoption.

A. Wildfire Hazard Zone Map Adoption.

1. A Wildfire Hazard Zone Map (WHZM) has been developed for the City of Portland through a review of topography, weather, type vegetation and fuel density. This map is dated October 11, 2002.

2. The WHZM dated October 11, 2002, is hereby adopted by reference and incorporated into this ordinance.

3. The Chief shall provide the Director with a copy of the official map adopted in Subsection one of this Section. Copies of the map shall be available for review in the Development Services Center, First Floor 1900 SW 4th Avenue, Portland Oregon.

B. Revisions to the Wildfire Hazard Zone Map.

1. The WHZM may be amended from time to time to either include or exclude properties as the facts may warrant.

2. The Chief shall have the authority to revise the Wildfire Hazard Zone Map.

3. All Wildfire Hazard Zone map revisions shall be determined using the criteria set forth below. Any site having a cumulative hazard value of five (5) or more shall be included in a wildfire hazard zone.

a. Topography Hazard Factor Value. The topography hazard value shall be calculated as follows:

(1) Determine site slope using the appropriate 7.5 minute quadrangle map published by the U.S. Geological Survey, USDI.

(2) Select appropriate hazard value using Table 1.

TABLE 1

APPROPRIATE TOPOGRAPHY
HAZARD FACTOR VALUE

Site Slope as determined by

the 7.5 minute quadrangle map

Hazard Value

Slopes 00 to < 03%

0

Slopes 03 to < 12%

1

Slopes 12 to < 20%

2

Slopes 20% or greater

3

b. Natural Vegetative Fuel Hazard Factor Value. The natural vegetative fuel hazard value shall be calculated as follows:

(1) Divide the jurisdiction into geographic areas which best describe the natural vegetation expected to occupy sites for the next 10 to 15 years.

(2) Select the appropriate hazard value from Table 2.

TABLE 2

NATURAL VEGETATIVE FUEL
HAZARD FACTOR VALUE
 

Natural Vegetative Fuel Description 1

Hazard Value 2

Limited

Little or no natural vegetative fuels are present.

0

Grass

Very little shrub or timber is present, generally less than one-third of the area. Main fuel is generally less than two feet in height. Fires are surface fires that move rapidly through cured grass and associated material. (Fuel model 1)

3

Grass

Open shrub lands and pine stands or scrub oak stands that cover one-third to two-thirds of the area. Main fuel is generally less that two feet in height. Fires are surface fires that spread primarily through the fine herbaceous fuels, either curing or dead. (Fuel model 2)

3

Grass

Beach grasses, prairie grasses, marshland grasses and wild or cultivated grains that have not been harvested. Main fuel is generally less than four feet in height, but considerable variation may occur. Fires are the most intense of the grass group and display high rates of spread under the influence of wind.(Fuel model 3)

3

Shrubs

Stands of mature shrubs have foliage known for its flammability, such as gorse, manzanita and snowberry. Main fuel is generally six feet or more tall. Fires burn with high intensity and spread very rapidly. (Fuel model 4)

3

Shrubs

Young shrubs with little dead material and having foliage not known for its flammability, such as laurel, vine maple and alders. Main fuel is generally three feet tall or less. Fires are generally carried in the surface fuels and are generally not very intense. (Fuel model 5)

1

Shrubs

Older shrubs with foliage having a flammability less than fuel model 4, but more than fuel model 5. Widely spaced juniper and sagebrush are represented by this group. Main fuel is generally less than six feet in height. Fires will drop to the ground at low wind speeds and in stand openings. (Fuel model 6)

2

Timber

Areas of timber with little undergrowth and small amounts of litter buildup. Healthy stands of lodgepole pine, spruce, fir and larch are represented by this group. Fires will burn only under severe weather conditions involving high temperatures, low humidity and high winds. (Fuel model 8)

1

Timber

Areas of timber with more surface litter than fuel model 8. Closed stands of healthy ponderosa pine and white oak are in this fuel model. Spread of fires will be aided by rolling or blowing leaves. (Fuel model 9)

2

Timber

Areas of timber with heavy buildups of ground litter caused by over-maturity or natural events of wind throw or insect infestations. Fires are difficult to control due to large extent of ground fuel. (Fuel model 10)

3

1. Some areas may contain vegetative fuels other than those listed in Table 2.  Additional natural fuel hazard factors may be found  in “Aids to Determining Fuel Models for Estimating Fire Behavior” published by the Forest Service, USDA Intermountain Forest and Ranger Experiment Station in 1982 as General Technical Report INT-122.  Vegetative fuel hazard factors determined using General Technical Report INT-122 shall be used  as alternative factors, for review under this chapter, as the facts warrant.

2. Due to various factors, such as variations in local vegetation species or vegetation conditions, the fuel models used in Table 2 may not accurately portray wildfire behavior.  The Chief may make modifications to the hazard values as necessary to accurately reflect the following characteristics:

(a) A hazard value of 1 shall describe vegetation that typically produces a flame length of up to 5 feet, a wildfire which exhibits very little spotting, torching, or crowning, and which results in a burned area that can normally be entered within 15 minutes.

(b) A hazard value of 2 shall describe vegetation that typically produces a flame length of 5 to 8 feet, a wildfire which exhibits sporadic spotting, torching, or crowning, and which results in a burned area that can normally be entered within one hour.

(c) A hazard value of 3 shall describe vegetation that typically produces a flame length of over 8 feet, a wildfire that exhibits frequent spotting, torching, or crowning, and which results in a burned area that normally cannot be entered for over one hour.

c. Natural Vegetative Fuel Distribution Hazard Factor Value . To determine the natural vegetative fuel distribution hazard factor value:

(1) Determine the percentage of each individual area that is covered by vegetation.

(2) Using the calculated percentage, assign a value using Table 3.

TABLE 3

NATURAL VEGETATIVE FUEL
DISTRIBUTION HAZARD FACTOR
 

Natural Vegetative Fuel Distribution

Hazard Value

0 to 10% of the area

0

10 to 25% of the area

1

25 to 40% of the area

2


24.51.040 Map Revision Process

A. Wildfire Hazard Zones may be applied to or removed from areas of the City as follows:

1. During periodic review by the Chief, based upon the criteria listed in section 24.51.030. Periodic review shall occur every 5 years.

2. Upon request to the Chief by any property owner, prior to periodic review, on the grounds that conditions have changed.

B. Prior to applying the Wildfire Hazard Zone to any property the Chief shall provide notice of such proposed zoning and provide a date for a public hearing.

The notice shall be sent to all properties to which the zone would be applied. The notice shall be sent fourteen days prior to the date of the hearing. Extensions of time for the hearing may be requested and may be provided by the Chief. The notice shall provide information regarding the City’s intention to apply the Wildfire Zone, the reasons therefore and the time and place for the hearing.

Within 7 days of the hearing the Chief shall issue a written decision, based upon the criteria listed above, and which shall include findings supporting that decision and shall contain information regarding the right to appeal the Chief’s decision to the Bureau of Development Service’s Appeals Board (Board). A copy of the decision shall be sent to all properties that received notice of the City’s intention to include these properties within a Wildfire Hazard Zone.

C. When a property owner provides the Chief with a written request that the Wildfire Hazard Zone be removed from specific property the Chief shall consider the request and, based upon the criteria listed above, shall either approve or deny the request.

Such action by the Chief shall occur within 14 days of the date of the request and shall be in writing, shall include findings based upon the facts and criteria and shall contain information regarding the right to appeal the Chief’s decision to the Board. This decision shall be mailed to the property owner requesting the change in status.


24.51.050 Appeals of Decisions Made by the Chief

Notwithstanding any contradictory portion of Code Section 24.10.080:

A. Any decision made by the Chief, regarding the application of a Wildfire Hazard Zone to any area in the City, may be appealed to the Bureau of Development Services Board of Appeals (Board) solely in accordance with this subsection. In considering such appeals the Board shall act solely in accord with this section.

B. Such appeal shall be in writing and shall be filed with the Board within fourteen days of the date of the Chief’s decision. The appeal shall include a statement regarding the elements of the Chief’s decision with which the appellant takes issue. Reference to facts and the criteria listed above, is required.

C. A copy of the appeal shall be provided to the Chief at the same time that it is filed with the Board. The Chief shall have fourteen days from the date of the appeal to respond, in writing, to the Board and all appellants.

D. The Board shall issue a notice of a hearing date and the place and time of the hearing. Notice shall be provided to the appellants and the Chief.

E. The Board shall then hold a hearing upon any such appeal. After considering the issues raised on appeal, and the reasonableness of the Chief’s interpretation of applicable criteria, the Board shall, by majority vote, affirm or modify the Chief’s decision. The Board’s decision shall be based solely upon the criteria set out in this Chapter and shall include findings addressing the facts and the criteria. The decision of the Board shall have full force and effect. A certified copy of the decision shall be delivered to the appellant.

Any appeal of the Board’s decision shall by writ of review.


24.51.060 General

(Amended by Ordinance Nos. 178745 and 179125, effective April 1, 2005.)

A. In addition to the other City codes, all structures located in wildfire hazard zones as identified in the Wildfire Hazard Zone map shall meet the applicable requirements in the State of Oregon Structural Specialty Code or the Residential Specialty Code as applicable.

B. The requirements in Chapter 24.75, Uniform Building Address System, supercede the requirements found in OSSC Appendix L, Section L101.7, for premises identification.