Draft Environmental Impact Report - East Bay Municipal Utility District

Estates Reservoir Replacement Draft Environmental Impact ReportAir Quality“Heavy Construction Operations;” and AP-42 Chapter 13.2.2 “Unpaved Roads,”Figure 13.2.2-2 (USEPA 2006). For the BAAQMD control measures listed in Section3.7.4 below, an equivalent soil to moisture ratio of 5:1 was assumed for all feasiblemeasures, which reduces fugitive dust emissions by 95 percent from uncontrolledlevels.For demolition of the roof structure, fugitive dust (as PM 10 ) was estimated as0.00042 pound per cubic foot of building volume unmitigated as specified in theBAAQMD CEQA Guidelines (BAAQMD 1999) Section 3.3 and AP-42Chapter 13.2.3 “Heavy Construction Operations”, where control for structuredemolition is wet suppression, which is estimated to reduce dust emissions byabout 75 percent for a nominal (average) moisture ratio.EBMUD estimates that the reservoir roof area is about 109,000 square feet (2.5 acres)while the floor area of the existing basin is about 120,000 square feet (2.75 acres).The existing paved perimeter access road is about 1,300 feet in length, covering anarea of about 0.5 acres. These areas were used to determine fugitive dust emissionsusing the BAAQMD protocol.Off-site Vehicle EmissionsA relatively small source of emissions compared to on-site equipment, off-site vehicleemissions comprise heavy-duty truck emissions and emissions from worker commutetrips in light-duty vehicles. Commuter trip estimates developed by EBMUD wereused as the basis using the emissions estimation methodology given in the BAAQMDCEQA Guidelines Section 3.4, Tables 9, 10 and 11. Similarly, heavy-duty truck tripestimates developed by EBMUD were translated into emissions utilizing CaliforniaAir Resource Board's (CARB) EMFAC 2007 computer program (i.e., determination ofemission factors).Dispersion ModelingFor on-site emissions, USEPA’s SCREEN Version 96043 was used to model theGaussian dispersion of emissions to obtain ambient impacts. For combustionemissions from construction equipment, a single equivalent point source (stack) wasmodeled to yield maximum potential downwind impact from the construction site,which is highly conservative and thus tends to overestimate impacts. Fugitive dustemissions were modeled as an equilateral area source with zero release height, whichis also conservative and thus tends to overestimate impacts. For screening dispersionmodeling, the annual average wind speed of 3.9 meters per second (NOAA 2008) wasassumed for neutral Stability Class D. Detailed calculation and modeling templatesare included in the Air Quality Technical Report (ENTRIX 2009).sb09_001.doc 3-7.2 7/22/2009