Interagency Aviation Strategy - July 2008 - National Wildfire ...

For drops of water or foam (short term retardants), it was assumed the number of chains
of fireline built was 50% of the number of chains of fireline built using long term fire
retardant.
In the IAA, the effectiveness of retardant drops as it relates to rate of fire spread, the
amount of fireline produced is reduced linearly from its maximum value described by the
formula above. Maximum fireline production is assumed when the rate of fire spread is
equal to one chain/hour. The fireline production rate is decreased linearly so that the
fireline production rate is zero when the rate of fire spread is equal to eighty chains per
hour or greater in NFDRS fuel models A, L, S and T. These fuel models represent grass,
Alaska tundra and sagebrush. For the rest of the NFDRS fuel models, there was no
change from the forty chains per hour limit.
All dollar amounts displayed in this report are in 2004 dollars unless otherwise stated.
The current OMB Price Adjustment Index was used to calculate factors as follows to
move all dollars to 2004 dollars (Table 3).
The term Fire Suppression (FFF) Costs is used to describe the sum of the cost to suppress
a wildfire. These costs are accounted for in two ways, unit mission costs and average acre
(suppression) costs. Unit mission costs are “trip” costs for fire suppression resources.
For airtankers, these costs would be the flight costs (flight rate times hours flown) and
retardant cost. Retardant cost was assumed to be $0.72 per gallon. Average acre costs
include all other fire suppression costs expressed on a per acre basis.
The term Net Value Change (NVC) Costs is used to describe the algebraic sum of the
effects of a fire keeping in mind that some effect is negative and some positive. In
general, the algebraic sum is a negative number.
The term Fire Program Costs is used to describe the staffing of the airtanker, and is
generally the daily availability times the number of staffing days for an exclusive-use
contract. It also includes the module staffing costs.
Overview of the Wildfire Initial Response Assessment System (WIRAS)
The Wildfire Initial Response Assessment System (WIRAS) is a simulation model
designed to address the importance of wildfire occurrence and suppression response
dynamics in planning initial attack organizations. A key feature that distinguishes it from
other models is its ability to assess how the ebb and flow of fire occurrence intensity
across the landscape and over time affects the economic and physical performance of an
initial attack organization. This approach better addresses the value of resource mobility
and the consequence of peak demand requirements that are so important in determining
the size, location, and composition of an initial attack organization.
WIRAS models the dynamics of fire occurrence as it affects suppression activities by
using historically recorded fire times and locations from multiple fire seasons. This
approach preserves the spatial and temporal nature of fire occurrence with all its
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