Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
emissions of NOx, which become particulate ammonium nitrate in the atmosphere; and the
suspension of road dust by tires. Vehicles also produce PM10 from brake pad and tire wear.
High levels of particulates have also been known to exacerbate chronic respiratory ailments, such
as bronchitis and asthma, and have been associated with increased emergency room visits and
hospital admissions. PM2.5 is, furthermore, the primary cause of reduced visibility (haze) in parts
of the U.S., including many national parks and wilderness areas. Particles can be carried over
long distances by wind and then settle on ground or water. The effects of this settling include:
making lakes and streams acidic; changing the nutrient balance in coastal waters and large river
basins; depleting the nutrients in soil; damaging sensitive forests and farm crops; and affecting
the diversity of ecosystems. Particle pollution can stain and damage stone and other materials,
including culturally important objects such as statues and monuments.
Sulfur Dioxide
Sulfur dioxide (SO2) is a colorless acid gas with a strong odor that is produced by the combustion
of sulfur-containing fuels such as oil, coal, and diesel. It has the potential to damage materials and
can have health effects, contributing to respiratory illness particularly in children and the elderly,
and aggravating existing heart and lung diseases. SO2 can irritate lung tissue and increase the risk
of acute and chronic respiratory disease. SO2 aerosols are also implicated in visibility impairment
because they scatter and absorb light. SO2 in the presence of a catalyst such as NO2 can form
sulfuric acid (H2SO4) in the atmosphere, resulting in acid rain which damages trees, crops,
historic buildings and monuments, and acidifies soils, lakes, and streams, often reducing or
eliminating aquatic life. SO2 and the pollutants formed from SO2, such as sulfate particles, can be
transported over long distances and deposited far from the point of origin. This means that
problems with SO2 are not confined to areas where it is emitted. The only sources of SO2 for the
proposed project would be diesel generators and mobile sources.
Attainment Status
Federal regulations designate Air Quality Control Regions (AQCRs) in violation of the NAAQS
as nonattainment areas. Federal regulations designate AQCRs with levels below the NAAQS as
attainment areas. McKinley County and, therefore, the proposed action is in the Southwestern
Mountains-Augustine Plains Intrastate Air Quality Control Region (AQCR 156) (40 CFR
81.241). EPA has designated McKinley County as an attainment area for all criteria pollutants
(USEPA, 2011b). Because the project is in an attainment area, the air conformity regulations do
not apply. However, the project’s emissions and the de minimis thresholds (that is, the minimum
threshold for which a conformity determination must be performed) under the general
conformity rules were carried forward to determine the level of impact under NEPA.
Class I Areas
The CAA outlines different levels or classes of air quality protection. Generally, Class I areas are
the most pristine and any substantial emission sources located in or near them have strict limits
set by regulatory agencies. EPA provides rigorous safeguards to prevent deterioration of the air
quality in Class I areas as specified in 40 CFR §81.421(e). The Prevention of Significant
Deterioration (PSD) program designates EPA Mandatory Class I areas as all international parks,
all national wilderness areas, and national memorial parks that exceed 5,000 acres, and all
DEIS for Roca Honda Mine, Cibola National Forest 183