Volume 2: Draft Gorst Planned Action Environmental Impact Statement

GORST PLANNED ACTION EIS | AFFECTED ENVIRONMENT, SIGNIFICANT IMPACTS, AND MITIGATION MEASURESLocalized Hot-Spot Air Quality ImpactsDevelopment under all studied alternatives would increase vehicle travel on existing public roads. However, it isunlikely that the increased traffic and congestion would cause localized air pollutant concentrations at localintersections to form a hot-spot (i.e., a localized area where air pollutant concentrations exceed NAAQS). PSCAAoperates ambient air pollution monitors at some of the most heavily congested intersections in the Puget Soundregion, and none of those monitors have indicated exceedances over the past several years. Furthermore, ongoingEPA motor vehicle regulations have provided steady decreases in tailpipe emissions from individual vehicles, and itis possible that those continuing decreases from individual vehicles could more than offset the increase in vehicletraffic. For these reasons, it is unlikely that air quality impacts at local intersections would be significant.Regional Air Quality ImpactsAlthough population and vehicle travel would increase in the Gorst study area, the increases in tailpipe emissionsfor all of the alternatives would be very small relative to the overall regional tailpipe emissions within the PugetSound air basin. Photochemical smog (the regional haze produced by ozone and fine particles) is caused byregional emissions throughout the Puget Sound region, rather than localized emissions from any individualneighborhood. Photochemical smog was a serious concern in the Puget Sound region before the late 1980s, butfederal tailpipe emission regulations have reduced vehicular emissions to the point that the region is currently adesignated attainment area for ozone.Prior to 2007, when the Puget Sound region was designated a nonattainment area or maintenance area for ozone,PSRC was required to periodically forecast regional tailpipe emissions of ozone precursors (nitrogen oxide [NOx]and VOC). To forecast the contribution of regional tailpipe emissions with regards to regional ozoneconcentrations, Ecology’s State Implementation Plan for ozone previously set allowable emissions budgets forPuget Sound regional transportation emissions, with the understanding that as long as regional emissions werebelow the allowable budgets then photochemical smog impacts would have been unlikely to resume. Regionaltransportation emission budgets were set for NOx and VOCs. Based on the most recent previous air qualityconformity analysis conducted by PSRC for ozone, forecasted regional emissions for its 2030 planning year were farbelow the allowable budgets (PSRC 2007):• NOx: 16 percent of budget• VOCs: 21 percent of budgetThus, PSRC’s 2007 analysis indicated the forecasted Puget Sound regional tailpipe emissions of NOx and VOC forthe 2030 planning year were well below the levels that would have caused an exceedance of the NAAQS. Becausethe increase in tailpipe emissions in the Gorst study area for the alternatives is very small compared to the overallregional tailpipe emissions (refer to Table 3.3-5 Gorst UGA Contribution to Forecast 2035 Puget Sound RegionalVMT) in the Puget Sound and because the region is currently designated an attainment area, it is concluded thatnone of the alternatives would result in a significant impact on regional air quality.Mobile Source Air ToxicsFuture development might require future improvements to existing roadways. When a street is widened and, as aresult, moves closer to receptors, the localized level of mobile source air toxics emissions could be higher, but thiscould be offset due to reductions in congestion (which are associated with lower mobile source air toxicsemissions). Furthermore, on a regional basis, EPA’s vehicle and fuel regulations (coupled with ongoing future fleetturnover) will over time cause substantial reductions that will cause region-wide mobile source air toxics levels tobe significantly lower than today in most cases.Local and Regional GHG EmissionsAs described later in this section, all of the alternatives would increase localized GHG emissions within the GorstUGA as a result of localized increases in population and employment. Total gross GHG emissions for WashingtonDraft | June 2013 3-36