3.0 Affected Environment - Knik Arm Bridge and Toll Authority

Knik Arm Crossing DraftFinal EIS
Affected Environment
3.5.1.3 Critical pollutants
3.5.1.3.1 Carbon monoxide
Motor vehicles are the primary source of CO in the Anchorage area. The highest levels
of CO are emitted by vehicles in the first 5 to 10 minutes after start-up while the vehicle
engine is cold. Anchorage’s cold winter temperatures increase the number and duration of
“cold-start” emissions. Other sources of CO in the Anchorage area include combustion of all
kinds, including heating of buildings, aircraft use, and wood burning. National Ambient Air
Quality Standards are listed in Table 3-13.
Table 3-13. National Ambient Air Quality Standards
Pollutant Primary Secondary
SO 2
3-hour average a 1,300 μg/m 3
24-hour average a 365 μg/m 3
Annual average 80 μg/m 3
PM 10
24-hour average a 150 μg/m 3 150 μg/m 3
Annual average 50 μg/m 3 50 μg/m 3
PM 2.5
24-hour average c 65 μg/m 3 65 μg/m 3
Annual average d 15 μg/m 3 15 μg/m 3
CO
1-hour average a
8-hour average a
O 3
35 ppm b
9 ppm b
8-hour average a 0.080 ppm 0.080 ppm
NO 2
Annual average 0.053 ppm 0.053 ppm
Pb
Calendar quarter average 1.5 μg/m 3 1.5 μg/m 3
a Not to be exceeded more than once per year
b
Equivalent to 40 and 10 milligrams/m 3 for the 1- and 8-hour averages, respectively
c Attained when 99th percentile value in 3-year period is below standard level
d Standard is based on a spatial average of concentration on a neighborhood scale
A 3-year summary of air quality data for monitors nearest the project area is provided in
Table 3-14. CO is one of the pollutants of primary concern in the Anchorage and Mat-Su
areas). CO is monitored only in the wintertime, when CO emissions and meteorology
combine to produce the highest CO concentrations.
Page 3-98 12/18/07