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Grand Avenue Widening Project Environmental Impact Report Section 3.0 The peak hour volumes and LOSS at the three Grand Avenue intersections identified earlier were used in the CALINE4 modeling. The LOSS determine the congestion levels and, therefore, the travel speeds and CO emissions at these intersections. Eight hour CO levels were projected using the methodology described in the Caltrans Air Qualit Technical Analysis Notes. This method essentially uses a persistence factor which is multiplied times the one hour emission projections. The projected eight hour ambient concentration is then added to the product. The persistence factor can be estimated using the highest ratio of eight hour to one hour second annual maximum CO concentrations from the most recent three years for which data is available. For the proposed Grand Avenue widening, a persistence factor of 0.7 was used. The data and results of the CALINE4 modeling for the proposed Grand Avenue widening are provided in the appendix of the AirQuality Assessment technical report. Generally, the one hour CO level is considered the peak maximum CO level since it is the highest CO measured for an hour. According to the Caltrans Air Quality Technical Analysis Notes, changes in meteorology and traffic over time disperse CO concentration levels and cause them to be less severe. Therefore, it is highly unlikely that the one hour CO levels would persist for a full eight hours. As a result, a one hour CO level is considered generally the peak level and is usually higher than an eight hour CO level. SCAG identified two air quality policies in the growth management chapter of the Regional Comprehensive Plan and Guide. The proposed Grand Avenue widening alternatives were evaluated for consistency with these air quality policies. 3.4.4 IMPACTS RELATED TO AIR QUALITY Short and long term air quality impacts were assessed. Short term impacts would occur during grading and construction activities for the widening alternatives. Long term impacts would occur during operation of the widened segment of Grand Avenue. hnpacts of Alternative 1 Related to Air Quality Short Term Air Quality Impacts Under Alternative 1 Construction under Alternative 1 will include two major components. The first will be the removal of the existing road pavement, sidewalks and landscaping, and the demolition and removal of existing structures such as commercial and residential structures. The second component consists of grading the right-of-way and construction of the road surface, sidewalks, sound walls and landscaping. In general, the equipment for these demolition and construction activities will consist of several pieces of heavy equipment, such as scrapers, tractors and graders. Another type of equipment that would be used would be large dump trucks, for hauling wastes from the site and materials to the site. There would generally only be one or two dump trucks working at the site at any one time. For this analysis, it was assumed that up to three pieces of heavy equipment would be operated simultaneously, as described below. F.IPRO.I-ENVIGrand eirWew Text - GrandlSection 3 SplitlSection 3.4.doc Page 3.4-9