Agenda - Planning Commission - 06/02/2005

Home

and rate of spread, as describedin the Presco~ code: Zone 1 is the minimum 3a-foot firebreak immediately adjacent to the house or struc- ture limited to fire-resistant species, trees with high canopies, and tow-growing shrubs and ground covers. The guidelines call for the annual removal of dead leaves and the installation of an automatic irriga- tion system for domestic landscaping dur- ing hot, dry periods. Zone 2 is an addi- tiona( firebreak of 7o feet or more that may be required depending on the fire depart- ment's iudg'ment on the sufficiency of Zone I. Zone 3 is a fuel break transition zone. Here domestic piants should be iow-grow- ing, slow-burnin~, and Iow-volume species that blend with the landscape and require no water once established. Zone 4 is natu- ral open space where fuels have been mod- ified through shaded fuel breaks and mosaic islands to. reduce fuel loading, fuel continuity, and fire ladders. Where a road- way abuts open space in such a zone, the guidelines recommend reducing or marlin- in§ vegetation for a minimu~ distance of Ia feet from the roadway. PRESCOTT, ARIZONA Prescott has adopted the ICC model code but modified some of its language to fit the . specifics of/ts area and to add detail to cer- tain sec[ions. For example, the ICC code caJ[s for the local government to incorporate find- ings of fact that serve as a justification for the designation of wild[and areas. One of the aspects of the findings is to designate a spe- cific fuel madeira description of the mix of potentially flammable vegetative materials. The nature of the fuel model affects the flame The seasonal climatic conditions during the late spdng and early summer create numer- ous sedous difficulties regarding the control of and protection against fires in the City of Prescott. Average maximum [emperatures of 88.9 degrees in July Relative humidity: to [o ~5 percent in May and June Twenty-eight days of eztreme fire weather conditions from end of April through July Live fuel moisture in chaparral from 61.8 per- cent in April to 86.4 percent in August. (Anything under 80 percent will burn) Fuel moisture in t,ooo-hour ~eJs is 5 percent Winds: 35 to 40 miles per hour Numerous dry lightning strikes Prescott has predominantly fuel model 4 (chaparral), which is found in all of the "at dsk neighborhoods." This includes oak brush (scrub oak) and maozanita, UtJUzing fue~ model 4 scenarios,as an exam- pie, the rate of spread could be'7~t feet per minute. 'the Flame lengths could be 57 feet high. Burning brands can jump ahead o,~the fire for a distance of ;z,z miles and ignite additional fires. The fire could consume 5,641 acres in one hour and spread a dis- tance of 8.1 miles. The perimeter of the fire would be 9o,321 loot. This type of fire is uncontrollable by the on-duty fire forces due to lack et= staffing and iength¥ response times. This fire co'Id resuE in a major struc- rural conflagration. The fire could spread across the ~rescott Basin al: the interface. Further, the Prescott cede amplifies the requirements fpr the ye§elation management plan. The code requires that the modification of vegetative fuelmremoval of slash, snags, other §roundjfueis, ladder fuels, and dead trees and the thinning' of live trees-within 30 feet of the house or to the property line, whichever is less, be completed prior to any vertical.construction. Beyond 30 feet and up to isa feet of the house or property ~ine, the vegetative fuel modifica. lions must be completed before a certificate of occupancy can be issued. The code details requirements for the defensible space surrounding the structure. It prescribes the foltowin~ defensible space practices: · Decreasing the amouni of flammable vegetation · Increasing the amount of open space · Increasing the moisture content of vegetation · Planting less flammable plants · RearJ'anging existing plants Reducing trees to a maximum of zoo hydrated or 85 nonhydrated, healthy trees per acre with understory pruned and main- tained · Removing all combustible materials and vegetation from under decks m Continuing maintenance of the area · Maintaining the defensible space require- ments by the homeowners association and/or owner of the property. PINETOP-LAK£SIDE, ARIZONA The Pinetop-Lakeside code relatin§ to forest health and fire protection contains detailed guidance on the establishment of a three- ' zone plan to satisfy the defensib(e space requirements on ali parcels where there is a building' or structure ~nd fo.r v~cant parco s of (ess than two acres. The code describes a set of mandatory and recommended actions for property in each zone. Most notable is the reduction of tree density through on-site thin- ning to lower risk from fires. A. Zone t: Zero feet to to feet from build- ings, structures, decks, etc. t. Required Zone ~ Fuel Modification: a. Remove fuel ladders and reduce non-fire-resistant brush, leaving primarily fire- resistant specimens. b. Remove and destroy all insect- infested, diseased, and dead trees to prevent spread to healthy vegetation. '[ 10 ZONINGPRACTIC~. 3.o5 AM£RIEA~'t PlaNNING ASSOCIATION