PDFWAC 51-55-0300
Wildland-urban interface areas.
301 General.
301.1 Scope. Wildland urban interface areas shall be determined using the Washington wildland urban interface map (WA-WUI). WA-WUI designations are permitted to be modified, upon approval of a finding of fact in accordance with Section 302.
User note: The WA-WUI map is available at https://geo.wa.gov/maps/786aaa1dbbd748e6ae04bc43c8f127fe/explore.
301.2 Construction in wildland-urban interface or intermix areas. Where a structure is proposed to be constructed in an area designated by the WA-WUI map as wildland-urban interface or intermix, the construction shall comply with the provisions of this code.
301.3 Construction in wildlands areas. Where a structure is proposed to be constructed in an area designated by the WA-WUI map as wildlands, the applicable wildland urban interface area designation shall be based on a finding of fact in accordance with Section 302.
302 Wildland-urban interface area designations.
302.1 General. Wildland urban interface area designations are permitted to be established in accordance with this section.
302.2 Finding of fact. The applicable wildland urban interface designation shall be based on a finding of fact. The finding of fact shall comply with the provisions of Appendix E or is permitted to be based on the worksheet and procedures in Section 302.3.
302.3 Simplified wildland urban interface designation worksheet. The wildland urban interface designation is permitted to be established using the procedure outlined in Table 302(1), using the worksheet in Table 302(2).
302.3.1 Area to be evaluated. For the purposes of establishing structure and vegetation densities, the area covered by a square of 1320 feet on a side (40 acres) shall be evaluated. The square area shall be located such that the site under consideration is in its center, except where the square would overlap a water body shown on the WA-WUI map with a surface area greater than 200,000 square feet, the location shall be adjusted such that no part of the square overlaps the water body.
Table 302.3(1)
Outline of Simplified Procedure for Determining Wildland Interface Designation
For the area to be evaluated in Section 302.3.1: |
1. Determine structure density category (uninhabited, very low, low, medium, or high). |
2. Determine vegetation density category (nonvegetated or vegetated). |
3. Determine proximity category (near or distant). |
4. Based on structure density, vegetation density, and proximity categories, determine if compliance with this code is required (WUIC applies, WUIC does not apply). |
5. Where compliance with this code is required, determine wildland urban interface area designation (intermix or interface). |
302.3.2 Structure density category. The structure density category shall be determined by counting the number of structures within the area to be evaluated per Section 302.3.1. The structure density category shall be determined as follows:
UNINHABITED: | 0 structures |
VERY LOW: | 1 structure |
LOW: | 2 to 8 structures |
MEDIUM: | 9 to 120 structures |
HIGH: | more than 120 structures |
302.3.3 Vegetation density category. Vegetation coverage within the area to be evaluated per Section 302.3.1 shall be determined in accordance with Chapter 9. Vegetation density shall be determined by dividing the vegetation coverage by 1,742,400 square feet (40 acres). Where the vegetation density is less than 50 percent, the vegetation density category for the site shall be nonvegetated. Where the vegetation density is 50 percent or more, the vegetation density category for the site shall be vegetated.
302.3.4 Proximity category. The distance from the site being evaluated to a high-density vegetated area shall be measured from the closest edge of the site boundary to the closest edge of the nearest high-density vegetated area. Where the distance is less than 1.5 miles, the proximity category shall be near. Where the distance is 1.5 miles or more, the proximity category shall be distant.
302.3.5 WUIC applicability. The WUIC shall apply, and the site shall be designated as intermix or interface in accordance with Section 302.3.6 under either of the following conditions:
1. The structure density category is very low to high, and the vegetation density category is vegetated.
2. The structure density category is very low to high, and the proximity category is near.
The WUIC shall not apply under either of the following conditions:
1. The structure density category is uninhabited, and the site is not located within an area designated as intermix or interface on the WA-WUI map.
2. The structure density category is uninhabited to high, the vegetation density category is nonvegetated, and the proximity category is distant.
302.3.6 Wildland urban interface area designation. Where required by Section 302.3.5, the site shall be designated as intermix or interface in accordance with Section 302.3.6.1 or 302.3.6.2.
302.3.6.1 Intermix designation. The site shall be designated as intermix where the structure density category is very low to high, and the vegetation density category is vegetated.
302.3.6.2 Interface designation. The site shall be designated as interface where the structure density category is very low to high, and the proximity category is near.
Table 302(1). Outline of simplified procedure for determining wildland interface designation
1. Determine structure density category in accordance with Section 302.3.2. Numbers in table are the number of structures within the area determined by Section 302.3.1. | ||||||||
UNINHABITED | VERY LOW | LOW | MEDIUM | HIGH | ||||
0 | 1 | 2 TO 8 | 9 TO 120 | MORE THAN 120 | ||||
2. Determine vegetation density category within the area determined by Section 302.3.1. | ||||
NONVEGETATED | VEGETATED | |||
Less than 50% vegetated | 50% or more vegetated | |||
3. Determine proximity category to the nearest high-density vegetated area. | ||||
NEAR | DISTANT | |||
Less than 1.5 mi (2.414 km) | 1.5 mi (2.414 km) or more | |||
4. Use structure density, vegetation density, and proximity categories from above to determine if WUIC applies. | ||||
WUIC Applies | WUIC Does Not Apply | |||
• Structure density category is very low to high; and | • Structure density category is uninhabited; and | |||
• Vegetation density category is vegetated. | • The site is not located within an area designated as intermix or interface on the WA-WUI map. | |||
• Structure density category is very low to high; and | • Structure density category is uninhabited to high; and | |||
• Proximity category is near. | • Vegetation density category is nonvegetated; and | |||
• Proximity category is distant. | ||||
5. Where WUIC applies, the site shall be designated as intermix or interface as follows: | ||||
INTERMIX | INTERFACE | |||
• Structure density category is very low to high; and | • Structure density category is very low to high; and | |||
• Vegetation density category is vegetated. | • Proximity category is near. | |||
Table 302(2). Worksheet for simplified procedure for determining wildland interface designation
302.4 Review of wildland-urban interface areas. The code official shall review for approval evaluated areas for new or modified findings of fact. Where a new or modified findings of fact are approved, the code official shall recommend to WADNR a modification to the wildland-urban interface areas mapping.