3.12 AIR QUALITY

An air quality analysis was conducted for the beltway project. Results of the evaluation are summarized here; more detailed information is provided in the Air Quality Analysis (Appendix B).

3.12.1 Existing Conditions

Based on the most currently published data, the Nebraska Department of Environmental Quality (1998) reports that all of Nebraska is in attainment with the National Ambient Air Quality Standards (NAAQS) for particulate matter (PM ₁₀ ) and carbon monoxide.

3.12.2 Impacts of the Four Finalist Alternatives

Construction Impacts. Construction impacts generated from internal combustion engines and fugitive dust generated during excavation, grading and site preparation will cause a short term impact on ambient air quality. Of these emissions, fugitive dust will be the most predominant. Dust generated from these activities is generally large particles which are redeposited in close proximity to the construction site. However, a fraction of the dust is composed of small particles referred to as PM ₁₀ which can remain airborne for an indefinite period of time.

Impacts from Vehicle Emissions. A long term increase in the carbon monoxide levels proximal to the beltway alignment will be caused by the additional vehicular traffic. As such, an air quality analysis was conducted for the beltway project (Appendix B). Since Nebraska is in compliance with NAAQS, a regional analysis was not required; therefore, the evaluation focused on a project-level analysis. Although there are several criteria pollutants associated with mobile sources, FHWA considers carbon monoxide to be the most significant criteria pollutant of concern for a project-level analysis (FHWA, 1986); therefore, only evaluation of carbon monoxide is required for compliance purposes.

The air quality analysis for carbon monoxide was conducted based on the most conservative assumptions which assumed worst-case conditions for all variables. The highest predicted carbon monoxide levels proximal to the beltway segments with the highest traffic volumes are listed in Table 3.12 along with the NAAQS criteria levels. NAAQS levels may be equaled, but not exceeded.

Table 3.12

HIGHEST 1-HOUR AND 8-HOUR CARBON MONOXIDE CONCENTRATIONS

FOR WORST-CASE LOCATIONS

Based on the air quality analysis, the carbon monoxide contribution at these beltway locations together with the background carbon monoxide concentration is within the 1-hour and 8-hour concentration limits established in the NAAQS at all receptors. Since the worst-case roadway segments and interchanges are in compliance, it is reasonable to assume that all the beltway roadway segments and interchanges will be in compliance with the NAAQS. The increase in carbon monoxide is considered insignificant.

3.12.3 Proposed Mitigation

If objectionable dust levels occur during construction, dust will be controlled by timely applications of water and temporary seeding to the areas of construction.

No mitigation is proposed for vehicle emissions.

3.12.4 No-Build Alternative

Use of unpaved County roads will continue to generate dust over the long-term. Construction impacts associated with improvements to these section line roads and other planned roadway network improvements will generate temporary increases in dust. Increased vehicular traffic on existing roadways will increase local levels of carbon monoxide.