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*:/:I1-3111ia <br />CO HOTSPOTS <br />Areas of vehicle congestion have the potential to create pockets of CO called hot spots. These pockets have <br />the potential to exceed the state one hour standard of 20 ppm of the eight hour standard of 9 ppm. Because <br />CO is produced in greatest quantities from vehicle combustion and does not readily disperse into the <br />atmosphere, adherence to ambient air quality standards is typically demonstrated through an analysis of <br />localized CO concentrations. Hot spots are typically produced at intersections, where traffic congestion is <br />highest because vehicles queue for longer periods and are subject to reduced speeds. With the turnover of <br />older vehicles, introduction of cleaner fuels, and implementation of control technology on industrial facilities, <br />CO concentrations in the SoCAB and in the state have steadily declined. <br />In 2007, the SoCAB was designated in attainment for CO under both the California AAQS and National <br />AAQS. The CO hot spot analysis conducted for the attainment by SCAQMD for busiest intersections in Los <br />Angeles during the peak morning and afternoon periods plan did not predict a violation of CO standards. 8 <br />As identified in SCAQMD's 2003 AQMP and the 1992 Federal Attainment Plan for Carbon Monoxide (1992 <br />CO Plan), peak carbon monoxide concentrations in the SoCAB in previous years, prior to fedesignation, were <br />a result of unusual meteorological and topographical conditions and not a result of congestion at a particular <br />intersection. Under existing and future vehicle emission rates, a project would have to increase traffic volumes <br />at a single intersection by more than 44,000 vehicles per hour�or 24,000 vehicles per hour where vertical <br />and/or horizontal air does not mix in order to generate a significant CO impact (BAAQMD 2017). <br />LOCALIZED SIGNIFICANCE THRESHOLDS <br />SCAQMD developed LSTs for emissions of NO2, CO, PMto, and PM25 generated at the project site (offsite <br />mobile -source emissions are not included in the LST analysis). LSTs represent the maximum emissions at a <br />project site that are not expected to cause of contribute to an exceedance of the most stringent federal of <br />state AAQS and are shown in Table 5, SCAQMD L ocak.Zed Significance Thresholds. <br />Table 5 SCAQMD Localized Significance Thresholds <br />Air Pollutant (Relevant AAQS) <br />Concentration <br />1-Hour CO Standard (CAAQS) <br />20 ppm <br />8-Hour CO Standard (CAAQS) <br />9.0 ppm <br />1-Hour NO2 Standard (CAAQS) <br />0.18 ppm <br />Annual NO2 Standard (CAAQS) <br />0.03 ppm <br />244iour PMio Standard - Construction (SCAQMD)i <br />10.4 Ng/m3 <br />244iour PM25 Standard - Construction (SCAQMD)i <br />10.4 Ng/m3 <br />244Hour PMio Standard - Operation (SCAQMD)i <br />2.5 Ng/m3 <br />2441our PM25 Standard - Operation (SCAQMD)i <br />2.5 Ng/m3 <br />Souroe: SCAQMD 2015b. <br />ppm — parts per million; pg/m'— micrograms per cubic meter <br />Threshold is based on SCAQMD Rule 403. Since the SoCAB is in nonattainment for PMin and PMzs, the threshold is established man allowable change in <br />concentration. Therefore, background concentration is inesvent <br />8 The tout intersections weir: Lung Beach Boulevard and Imperial f-lighway; Wilshire Boulevard and Veteran Avenue; Sunset Boulevard and f-lighland <br />Avenue; and La Cienega Boulevard and Century Boulevard. The busiest intersection evaluated (Wilshire and Veteran) had a daily traffic volume of <br />appmsimately 100,000 vehicles per daywith LOS E in the morning peak hour and LOS F in the evening peak hour. <br />75C-153 <br />