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5.0 Environmental Analysis 5.5 Air Quality <br />Avion Project SEIR <br />Page 5.5-13 <br />assessments, which determine the exposure of sensitive receptors to toxic emissions, should be <br />based on a 30-year exposure period; however, such assessments should be limited to the <br />period/duration of activities associated with the project (OEHHA 2015). Thus, if the duration of <br />proposed construction activities near any specific sensitive receptor were two years, the exposure <br />would be less than 6 percent of the total exposure period used for health risk calculation. <br />Therefore, because of the limited size of the project and the short duration of construction, DPM <br />generated by construction is not expected to create conditions where the probability is greater than <br />10 in 1 million of contracting cancer for the Maximally Exposed Individual or to generate ground- <br />level concentrations of non-carcinogenic toxic air contaminants that exceed a Hazard Index greater <br />than 1 for the Maximally Exposed Individual. Additionally, with ongoing implementation of U.S. EPA <br />and CARB requirements for cleaner fuels; off-road diesel engine retrofits; and new, low-emission <br />diesel engine types, the DPM emissions of individual equipment would be substantially reduced <br />over time. <br />Soils within the regional area are known to possess naturally occurring subsurface arsenic. <br />Consequently, dust generated from blasting operations required during project construction would <br />have the potential to release naturally occurring subsurface arsenic, which could result in short-term <br />exposure. <br />5.5.5.3 Significance of Impacts <br />Construction of the project would not expose sensitive receptors to substantial pollutant <br />concentrations, and impacts related to DPM would be less than significant. However, dust generated <br />from blasting operations required during project construction would have the potential to release <br />naturally occurring subsurface arsenic, which could result in short-term exposure that may result in <br />a significant impact. <br />5.5.5.4 Mitigation, Monitoring, Reporting <br />MM-AIR-1a: Arsenic Testing Protocol in Areas Requiring Blasting <br />Geocon shall obtain periodic random samples from select air-track borehole spoils or the ground <br />surface over the course of the blasting program. The number of samples shall vary and be based on <br />judgement depending on the size of the shot. The samples shall be assigned for analysis of arsenic <br />using U.S. Environmental Protection Agency Test Method 6010B with a reporting limit of <br />1.0 milligram per kilogram. The sampling shall be performed under the direct supervision of <br />Geocon’s Project Manager and Professional Geologist. <br />MM-AIR-1b: Blasting Dust Mitigation Plan <br />The following protocols shall be performed to minimize the generation of visible dust during the <br />hard rock blasting events: <br />• The areas shall be heavily watered prior to the planned blasting. The amount of water <br />applied shall depend on the size of the shot and composition of the materials exposed at the <br />top of the shot (i.e., topsoil vs. hard rock).