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Baseline 2020: Air
Quality
Source and Assumptions
The Utah Division of Air Quality monitors pollutants and implements regulatory policies
to protect public health. When concentrations of certain pollutants are expected to exceed
the maximum thresholds allowed by federal law, the Division takes actions to achieve and
maintain the minimum air quality standards. As part of this process the state has the
State Implementation Plan (SIP) in place. For certain pollutants the Division's planning
branch conducts simulation modeling to understand the effects of weather on the
development and buildup of air pollution. Air emissions are also projected for five major
pollutants:
- Carbon Monoxide (CO)
- Nitrogen Oxides (NOx)
- Particulate Matter (PM10)
- Sulfur Oxides (SOx)
- Volatile Organic Compounds (VOC)
To project emissions for these pollutants the Division does the following:
- Conducts an emissions inventory of point sources (stationary, commercial, or industrial
sources that emit more than 100 ton/yr of a monitored pollutant. Utah has approximately
300 monitored point sources); mobile sources (highway vehicles); and area sources
(non-road mobile and stationary sources that are too small or numerous to be monitored
individually). The annual emissions inventory quantifies the amount of pollution emitted
in each county. This type of inventory provides only a very coarse representation of the
spatial and temporal distribution of the pollutants.
- Incorporates known technological advances that will be accepted in the marketplace and
assist in reducing emissions. These include cleaner engines, fleet turnover, and other
technologies. The Environmental Protection Agency promulgates rules for crediting
reductions to a State's emissions inventory based upon demonstrated technology. Based upon
these rules, and at times upon the expectation that such rules will be in place, the state
is allowed to adjust future emissions projections accordingly. This is true for all
emission sources, including large industrial sources and automobiles.
Characteristics and Trends
The emissions of all five major air pollutants are projected to increase from 1995 to
2020, despite general decreases in the previous 25 years. The Greater Wasatch Area has met
the ozone standard since 1990 and has been redesignated as an attainment area for ozone.
An "ozone maintenance plan", outlined in the SIP, is in place and will be
carried out. The standards for CO and PM10 have been met since 1994. The largest percent
increases are expected to be in volatile organic compounds (VOC), fine particulates
(PM10), and nitrous oxides (NOx).
Major Issues and Findings
The anticipated growth in emissions in the Greater Wasatch Area introduces several
major issues and findings that are relevant to the understanding of the baseline and the
development of alternative scenarios. These include the following:
- Based on the ambient air monitoring of the past seven years, the increase in PM10 may
pose the most pressing problem in terms of meeting the National Ambient Air Quality
Standards (NAAQS). Past monitoring data indicates that the new particulate standards
(PM) will be difficult to attain at current emissions levels. Because NOx is an important
contributor to PM formation, the increase in levels of both PM10 and NOx pose a
significant challenge for the future.
- NOx in combination with VOC become ozone. Salt Lake and Davis counties have been
redesignated to attainment for ozone. Past monitoring data for ozone indicates that the
new ozone standard may be difficult to attain depending on meteorological conditions in a
given year. Automobiles are the single largest source of NOx and VOC and emissions in both
are projected to grow.
- CO is also projected to grow substantially. This problem is highly localized, with
the greatest concentrations occurring in the vicinity of road intersections. However, more
important than overall growth of the CO inventory is the spatial distribution of these
emissions.
- The new NAAQs are stricter and will make attainment much more difficult. Air quality
is a major challenge and a possible constraint to future growth in the Greater Wasatch
Area.
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