4.2.7 Structure Ignition Zones Hanscombe Ltd. and ICLR (2019) suggest that removing combustible material and replacing it with rock, gravel, or pavers costs between $0.50 and $3.00 per square foot. These costs seem to only apply to retrofit. For new construction, presumably the cost to construct a non-combustible apron around the perimeter is the same as the cost for combustible landscaping. To retrofit zone 1A with a non-combustible apron would, therefore, cost about $2.50 to $15.00 per linear foot of house perimeter. The project team uses an approximate average of these two values: $8.00 per linear foot. To retrofit zones 1A and 1 to satisfy Section 3.4.1.2 can demand removing excess vegetation and ongoing vegetation control. Vaske et al. (2016) estimate the cost to remove excess vegetation in Colorado to be approximately $1,000 per acre, with a minimum cost of $1,000 for smaller properties. Maintaining priority zone 1 advises that “ground litter and downed trees should be removed at a frequency not less than annually,” referred to here as vegetation control. Spring or fall yard cleanup generally costs approximately $200 to remove old and dying branches and cut back shrubs (HomeAdvisor 2021, Canada YardPro 2021, Halifax Landscaping Pros 2020). Many homeowners clearly do yard cleanup anyway, regardless of whether their home is in the WUI. However, to be conservative and to include some cost for the activities recommended by the National WUI Guide, it seems reasonable to add some cost, for example $100 for a typical house per year, equivalent to a present value of $3,000 for a 75-year life and 3% real discount rate. That $100 annual figure is slightly lower than the $125 assumed in Multi-Hazard Mitigation Council (2019), but is in the same ballpark. The project team assumes this ongoing vegetation control cost applies up to an area of one acre, then scales linearly with acreage. The cost contributors to recommendations for zones 2 and 3 appear to resemble zone 1. Table 18 summarizes the initial clearing and maintenance costs for zones 1, 2, and 3. In the table, R refers to the approximate radius from the centre of the house, A is the total area of the priority zones, “clear” is the initial cost to clear the priority zones, “maintain” refers to maintenance costs, and “PV” to the present value using a 3% real discount rate and 75-year life. Figures are rounded to reduce the appearance of excess accuracy. Table 18. Initial clearing and maintenance costs for priority zones R (m) House
7.0
Zone 1A
8.5
A (acre)
Clear
Maintain/year
PV maintain
PV clear + maintain
0.06
Zone 1
17
0.2
$1,000
$100
$3,000
$4,000
Zones 1–2
37
1.0
$1,000
$100
$3,000
$4,000
Zones 1–3
107
9.0
$9,000
$900
$26,000
$35,000
FireSmart Canada (2020) describes Indigenous approaches to vegetation management, though not in monetary terms. It may be that the vegetation control costs estimated here could be reduced using these techniques. In any case, vegetation management, whether by methods described here or those described in FireSmart Canada (2020), can be described as using “naturally occurring resources or engineered use of natural resources, to provide adaptation or mitigation services to the gradual and/or sudden impacts of climate change or natural hazards,” the definition of natural infrastructure in Infrastructure Canada (ND, p. 18).
57
