domin<strong>at</strong>ed by n<strong>at</strong>ive conifer species with asparse assortment of exotic shrubs ando<strong>the</strong>r plants, though <strong>the</strong> speciescomposition and structure differed betweenneighborhoods. Some parcels were slightlysloped. Neighborhood 2 encompassed alarge area surrounding <strong>the</strong> “Y,” or <strong>the</strong>junction of Highways 50 and 89, including<strong>the</strong> tracts of Gardner Mountain, TahoeVista, Tahoe Island, St<strong>at</strong>e Name streets,and <strong>the</strong> area around <strong>the</strong> hospital.Neighborhood 3 was <strong>the</strong> tract consisting of<strong>the</strong> north-central part of <strong>the</strong> city.Neighborhood 4 was <strong>the</strong> Sierra Tract.Neighborhood 5 contained <strong>the</strong> Bijou and AlTahoe tracts. Neighborhood 6 was <strong>the</strong>affluent area of Heavenly Ski Resort andwas characterized by large, new homes,large lots, and dominance of n<strong>at</strong>ive coniferspecies. Slopes in this neighborhood weresignificant.A fire hazard analysis was conducted oneach parcel and <strong>the</strong>n compared qualit<strong>at</strong>ivelyto <strong>the</strong> fire hazard of neighboring parcels.The assessment was based on NFPA 299,which assigns a number score for riskfactors, compliance with PRC 4291,construction m<strong>at</strong>erials, and irrig<strong>at</strong>ion. Higherscores reflect higher fire hazard.Figure 1. -- Neighborhoods and characteristic lots as defined for this study. 1- Tahoe Keys; 2 – The Y; 3-North Central; 4- Sierra; 5- Bijou; 6- Heavenly.Lake Tahoe35 61424
The law (PRC 4291) requires homeownersto prune dead branches, clear needles ando<strong>the</strong>r litter from roofs and gutters, covervents with wire mesh, and clear treebranches for 3 m around chimney outlets.Characteristics known to contribute tostructural ignition potential, such as a woodroof and single-paned windows (Foote1991, White 2000, Quarles 2001, Quarles2002), were also r<strong>at</strong>ed.Compliance with PRC 4291 was analyzed interms of <strong>the</strong> cre<strong>at</strong>ion of defensible spacealone, maintenance alone, and <strong>the</strong>combin<strong>at</strong>ion of defensible space andmaintenance. Parcels demonstr<strong>at</strong>ing little orno defensible space were r<strong>at</strong>ed noncompliant.Parcels th<strong>at</strong> were non-compliantwith one or more of PRC 4291’smaintenance requirements were alsoconsidered non-compliant.Parcels were fur<strong>the</strong>r assessed for presenceof irrig<strong>at</strong>ion, construction m<strong>at</strong>erials, parcelsize, and <strong>the</strong> presence of hazardous decks.Defensible space r<strong>at</strong>ings were adjusted forsmall parcels to account for neighboringveget<strong>at</strong>ion th<strong>at</strong> would influence <strong>the</strong> parcel’sfire hazard. Decks were consideredhazardous if <strong>the</strong>y were made of wood andgre<strong>at</strong>er than 0.5 m high and were openunderne<strong>at</strong>h or had flammable m<strong>at</strong>erialstored underne<strong>at</strong>h <strong>the</strong>m.Parcels were classified as small and under<strong>the</strong> direct influence of <strong>the</strong> fire hazard ofimmedi<strong>at</strong>e neighbors if <strong>the</strong> distancebetween <strong>the</strong> house and <strong>the</strong> side boundariesof <strong>the</strong> parcel was less than 7 m on ei<strong>the</strong>rside, if <strong>the</strong> difference between <strong>the</strong> totalwidth of <strong>the</strong> parcel and <strong>the</strong> total width of <strong>the</strong>house was less than 14 m, or if <strong>the</strong>difference between <strong>the</strong> total length of <strong>the</strong>parcel and <strong>the</strong> total length of <strong>the</strong> house wasless than 14 m. Larger parcels wereconsidered independent of neighboringparcels.The fire hazard r<strong>at</strong>ings of <strong>the</strong> individualsmall parcels were adjusted to include <strong>the</strong>fire hazard of neighboring parcels. Smallparcels with good defensible space and“rel<strong>at</strong>ively better” maintenance were r<strong>at</strong>ed<strong>the</strong> same for defensible space as a mediumor large parcel with moder<strong>at</strong>e defensiblespace. Small parcels with good defensiblespace and “same” rel<strong>at</strong>ive maintenancewere r<strong>at</strong>ed <strong>the</strong> same for defensible spaceas a medium or large parcel with gooddefensible space.Neighborhoods were assigned a mean firehazard r<strong>at</strong>ing based on <strong>the</strong> fire hazards of<strong>the</strong> parcels th<strong>at</strong> were sampled within <strong>the</strong>neighborhoods. The point scoring system isfound in Table 1. The range of possiblescores is 9 – 80 or more, depending on <strong>the</strong>number of decks present.ResultsOverall fire hazard r<strong>at</strong>ingThe mean citywide fire hazard r<strong>at</strong>ing was 30(s.d. 6), due in large part to <strong>the</strong> city’sinfrastructure, including good access (wide,paved roads), <strong>the</strong> availability of w<strong>at</strong>er, and<strong>the</strong> presence of city and agency fire-fightingresources (Table 2). As expected, <strong>the</strong>Tahoe Keys exhibited <strong>the</strong> lowest firehazard, with a mean fire hazard r<strong>at</strong>ing of 24(s.d. 5), and <strong>the</strong> Heavenly Ski Area had <strong>the</strong>highest (38, s.d. 7). The r<strong>at</strong>ing for <strong>the</strong>remaining neighborhoods ranged from 28 to30.Lot sizeThe sampled lots in South Lake Tahoe weresmall. Mean lot size varied from 585 m 2 in<strong>the</strong> Sierra tract to 1211 m 2 in Heavenly. Thedifference in size is explained by <strong>the</strong>vari<strong>at</strong>ion in <strong>the</strong> depth of <strong>the</strong> lots r<strong>at</strong>her than<strong>the</strong>ir width. The mean lot width citywide was22 m (s.d. 8.5 m). The lot size in <strong>the</strong> Sierr<strong>at</strong>ract was significantly smaller than any o<strong>the</strong>rneighborhood in <strong>the</strong> city.5
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