Environmental Assessment

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES CHAPTER 3
These treatment areas reduce fuel loadings, reduce the risk of spotting, increase the potential for control,
and provide additional safety for both the public and firefighters to safely enter and leave the area in case
of a wildfire event. All or portions of some safety corridor units do not have adjacent fuel or vegetation
treatment units. In Alternative 2, this includes units F08, F19, F29, and F31 along Road 23 and units F28,
F33, and F41 along Road 18. In Alternative 3, this includes units F08, F19, F27, F29, and F33 along
Road 23 and units F33, and F41 along Road 18. In these areas, both the public and firefighters would
face a higher risk of being trapped by a wildfire event or having a less safe route than areas with
additional treatments adjacent to the safety corridor unit. Both alternatives provide a greater level of
safety for ingress and egress than the no action alternative, which provides no treatment along roads and
provides no safe ingress or egress. Both alternatives also reduce the risk of a wildfire approaching from
the west or southwest from reaching the observatory.
Alternative 3, approximately 537 acres of defensible space would be created along approximately 13
miles of road in the same units as Alternative 2 with the following exceptions: units F25 and F26 are
dropped from Alternative 3. With the exception of units F08, F19, and F27, the average width of each
unit would be 300 feet or approximately 150 feet on each side of the road. The average width of unit F08,
F19, and F27 would be approximately 400 feet or approximately 200 feet on either side of the road
because units F25 and F26 would not be treated under this alternative. Like Alternative 2, adjacent
vegetation units would also contribute to the establishment of defensible space along these roads.
Both action alternatives propose thinning, mowing, and the use of prescribe fire either singly or in
combination to reduce fuel loadings. Thinning is potentially effective at reducing the probability of
crown-fire spread and is precise in that specific trees are targeted and removed from the fuel bed.
This creates discontinuities in both the vertical and horizontal fuel beds and has been shown to be
effective at reducing the impacts of a wildfire event. As an example, the 1999 Spring River Butte
Fire started in a 75 acre stand of unthinned trees and was moving towards the Sunriver Resort when it
entered a 30 acre stand that had been previously thinned. The fire dropped from the crowns of the
trees to the ground allowing the fire to be controlled and limiting the burned area to approximately
112 acres. In untreated areas or portions of treated units, the risk of a crown fire would remain and
continue to increase with increasing fuel loadings and stand densities.
Prescribe burning and mowing affects potential fire behavior by reducing fuel continuity on the
ground. This slows the rate of spread, which reduces intensity and flame lengths and the likelihood of
fire spreading into ladder fuels and the crowns of trees. The risk and probability of a crown fire
would be reduced under both action alternatives. Alternative 2, because it physically treats more
acres with fuel reduction, vegetation, and a combination of treatments, has a greater reduction in the
risk and probability of such an event than does Alternative 3. Given the distribution of treatments on
the landscape, there is little or no difference on the risk to protection of important resources, such as
other improvements, facilities, and wildlife habitat under either of the two action alternatives.
All Alternatives (long-term): In 10 years or longer, Alternative 2 provides greater protection than
does Alternative 3 because it places more acres into the low fire behavior potential category and has
fewer acres in the moderate potential category (Table 3-48). Treatments to maintain or reduce fire
behavior potential levels would be needed much sooner under Alternative 3 as more acres move into
higher risk fuel loadings.
Acres with current high fuel loads would require multiple treatments of existing accumulations to
achieve the desired results. In the areas where restoration/maintenance of historic fire regimes is
proposed, prescribe fire activities would need to be implemented approximately every 8 to 15 years to
maintain the desired conditions (Fire/Fuels and Air Quality Report).
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