Conclusiones del estudio

The Environmental Protection Agency has promulgated national ambient air quality stan- dards (NAAQS) and regulations for the protection of public health and welfare or of the environment in compliance with the Clean Air Act and its amendments. To assess the level of air quality impacts resulting from a given management alternative, the following methods and assumptions were used:

• The national ambient air quality standards were examined for six criteria air pollutants: carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), lead (Pb), particulate mat-

ter smaller than 10 microns in diameter (PM10), and sulfur dioxide (SO2) (US EPA 2001).

The directly emitted criteria pollutants are CO, NO2, SO2, and PM10. Ozone is a secondary

air pollutant resulting from photochemical reactions involving nitrogen oxides (NOx)

and reactive organic gases.

• Air quality designations for the surrounding area were determined. If the park, or a por- tion of a park, was within the boundaries of a non-attainment or the maintenance area for a given pollutant, ambient air quality concentrations were assumed to violate the na- tional ambient air quality standards for that pollutant. Capitol Reef National Park and the nearby areas are in attainment for all criteria pollutants.

• Air quality is achieved through reduction of pollutants and maintenance or improve- ment of visibility. Visibility can be degraded when fine particles in the air cover a large area, creating what is known as “regional haze.” Vehicle operations contribute to envi- ronmental problems such as smog, toxics, and global warming. Future air problems oc- cur due to pollution generated by fine particulates and fugitive dust contributes to pol- lution. Visibility impacts were determined by assessing particulate matter levels from lo- cal monitoring data or from qualitative evidence such as personal observations and pho- tographs.

The Environmental Protection Agency model AP-42 was used to estimate the amount of particulate emissions that could be locally generated by vehicles traveling the Burr Trail (EPA 2000). The model compiles standard air pollutant emission factors and then quantifies the amount of fugitive dust that would be generated by a 4,000 pound vehicle traveling ap- proximately one mile at 15 miles per hour on a dirt road surface (although the maximum de- sign speed on the Burr Trail is 25 miles per hour, 15 miles per hour was used to account for slowing and stopping by visitors who would likely be viewing sights and scenery). Table 10 shows that the amount of fugitive dust (PM10) generated per vehicle-mile traveled on a dirt

surface was 0.73 pounds more than would be generated by the same vehicle traveling on a gravel surface. The total number of all particulate size classes is expressed as the total ratio of dirt to gravel (or 1:1.54).

The air quality impacts of the various alternatives were assessed by comparing existing air quality levels and related values with expected pollutants generated by each alternative. Im- pact thresholds may be qualitative (e.g., photos of degraded visibility) or quantitative (e.g.,

based on impacts to air quality related values or federal air quality standards, or emissions based on emission factor models), depending on what type of information is appropriate or available. Cumulative impacts were analyzed qualitatively.

TABLE 10: FUGITIVE DUST GENERATED BY TRAVEL ON DIRT ROADS COMPARED TO GRAVEL ROADS

Impact thresholds for air quality depend on the type of pollutants produced, the back- ground air quality, and the resources in the environment that may be affected by airborne pollutants (air quality related values). Air quality related values include “visibility and those scenic, cultural, biological, and recreation resources of an area that are affected by air qual- ity” (43 Federal Register 15016) (U.S. Environmental Protection Agency 1999).

The cumulative impacts for air quality related values were based on the effects of air emis- sions from traffic and other motorized vehicles on the Burr Trail. A state implementation plan (SIP) for visibility issues affecting federal Class I areas such as Capitol Reef National Park is being prepared, but the Utah Division of Air Quality has not completed the SIP (U.S. Environmental Protection Agency 1999b). Therefore, a qualitative analysis was conducted. The assessment of airborne pollutants emitted from motorized sources and their contribu- tion to ground-level ozone or regional transport of ozone was limited to the location of the Burr Trail and the immediate surrounding area within the park. Emissions from regional point sources such as energy, mining, or construction were also considered.

Primary steps used for assessing impacts included 1) identifying state of Utah and local air quality standards for ozone and fugitive dust, 2) identifying air quality designation for the region, 3) identifying local ambient air quality data from monitoring sites in or within 100 miles of the park to determine the level of pollutants, and 4) determining visibility impair- ment from local monitoring data or qualitative evidence from park staff observation. To understand the effects of road modifications on air quality in the areas of concern, park staff, experts, monitoring data, and literature reviews were used to identify the information contained in this analysis.

Gravel Surface Dirt Surface Output Variance

Particle Size Pounds per Vehicle Mile Particle Size Pounds per Vehicle Mile

Pounds per Vehicle Mile

PM2.5 0.195 PM2.5 0.301 0.106

PM₁₀ 1.337 PM₁₀ 2.062 0.725

PM30 4.940 PM30 7.616 2.678

Air Quality Impacts were evaluated using these thresholds:

• Negligible: No changes in air quality and visibility would occur, or changes would be be- low or at the level of detection and if detected would have slight to imperceptible ef- fects.

• Minor: Changes in air quality and visibility would be measurable, though they would be small, temporary, or short-term and local. No air quality mitigation measure would be necessary.

• Moderate: Changes in air quality and visibility would be measurable, involving some consequences that would be relatively local. Air quality mitigation measures would be necessary, and the measures would likely be successful.

• Major: Changes in air quality and visibility would be measurable, would have substantial consequences, and would be noticed at the regional level, thereby influencing attain- ment of national standards. Air quality or visibility mitigation measures would be neces- sary, and the success of the measures could not be guaranteed.

• Duration: Short-term – Effects on air quality parameters and visibility last 7 days or less following initiation (e.g., vehicle passage or road maintenance work). Long-term – Ef- fects last more than 7 days following initiation. A 7-day evaluation period was selected because it best depicts the typical work week for construction and road maintenance projects.

Geographic Area Evaluated for Impacts. The analysis area included the immediate loca-

tion of the Burr Trail and the area surrounding the near-road environment where locally generated air pollutants may accumulate. Influence on the regional ambient air quality in- cluded the nearby power generation plats in Utah and Arizona. Cumulative effects that would occur both within and outside these areas were evaluated using the methods de- scribed in the “Cumulative Analysis” section.