Environmental Assessment

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES CHAPTER 3
come from the south and southwest. From October through March, winds come from predominately the
south and southwest.
Temperature changes throughout the day affect how particulate matter and other pollutants are dispersed.
Daytime heating causes pollutants to rise along with heated air. Surface cooling at night can create
downslope winds that carry pollutants from higher elevations to lower lying areas. Pollutants may pool in
the lower areas or exit to the northeast following several dry drainages.
Visual
Smoke emissions vary with combustion efficiency and quantity of fuel consumed. Machine and hand
piles tend to produce more smoke (per ton of fuel consumed) than other burns because much of the
consumption occurs during inefficient smoldering phase of combustion. The overall factor in the amount
of emissions produced lies solely in the amount of fuel consumed.
Environmental Effects
Alternative 1: With no fuel reduction activities proposed under Alternative 1, a high intensity wildfire
would be expected to produce an average of approximately 195 tons of smoke particular matter (PM) of
10 microns or less in size (PM10) per acre. In large accumulations of downed fuels and/or dense stands,
PM quantities can exceed this estimate. Conditions, especially in forest stands under summer conditions,
are usually windy, hotter, and drier. As a result, fires consume greater amounts of down woody material
(coarse woody material) in addition to litter, duff, and foliage materials. Residents of the City of Bend,
although approximately 20 or more miles to the northwest of the planning area, would be expected to be
impacted by smoke generated by intense wildfire events.
These levels of smoke production are also expected to impact activities and people using the facilities at
the Pine Mountain Observatory. Astronomy requires clear, unobstructed skies. Wildfires emit 50 to 70
percent more emissions than do prescribe fires. Smoke diffuses and scatters light and creates hazy
atmospheric conditions. PM10 and smaller particles can remain suspended in the atmosphere for
extended periods of time. This greatly reduces the ability to conduct astronomical research that utilizes
optical telescopes such as those at the Pine Mountain Observatory. This is further compounded by the
fact that wildfires can emit smoke over a period of weeks or months which can adversely affect research
activities over a much longer period of time.
Alternatives 2 and 3: Table 3-26 displays the total estimated PM10 emission associated with fuel
treatment activities under both Alternatives 2 and 3 under planned burn prescriptions. It is important to
note that these estimates may vary and either increase or decrease depending upon the actual conditions
under which the prescribe burns are implemented. These estimates are for the total project. As
implementation is likely to be spread over a period of a decade or more, yearly PM10 emission levels
would be much less.
Table 3-26 Total Estimated PM10 Emissions for Alternatives 2 and 3
Treatment Prescription
Total Estimated Tonnage of PM10
Alt 2 Alt 3
Landing Piles 15 tons 15 tons
Underburning (Includes Drip
and Broadcast)
1,628 tons 1,524 tons
Machine and Hand Piles 1 ton 1 ton
Total 1,644 tons 1,324
3-57