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3.Response to Comments ` • the Draft EIR appears to evaluate odor impacts using only the increase in H2S concentrations. Commenter states that total H2S concentrations should be evaluated to determine ifH2S odors would cause significant nuisance and annoyance impacts. r The DEIR focused on hydrogen sulfide H2S as the most likely source of unpleasant odors to the surrounding residences. No comments regarding potential odor were received during the scoping process. For hydrogen sulfide,the DEIR relied on the ambient air standard of 0.03 ppm (42 ug/m3)as established by California Air Resources Board(CARB) as a standard to prevent odors. This standard, which was established by GARB in 1970,was reviewed again in 1985 (GARB, 1985), and it confirmed that the 0.03 standard be maintained. The 1985 report relied on twenty six ` publications in which their results were based on a variety of room-test and instrumental air- dilution methods. The report states that there is considerable uncertainty in determining the levels invoking odor responses,mainly because people vary a great deal among themselves as y regards to their sensitivity to this and other odors. The standard deviation,a statistical measure of this variation,was found to vary by a factor of 4-fold. The 1985 CARB report states that,based on their research and research by other authors, it may be concluded that, as a provisional rule,an unpleasant odor is at or above the threshold of annoyance for half the people when its concentration reaches 5 times the average threshold of 1111110 detection. The report states that,when this multiplier is applied to the odor detection threshold of hydrogen sulfide, it indicates that the threshold of odor annoyance for this compound is about 0.04 ppm. The report also concludes that: 6 "Assuming the same standard deviation as for odor detection, it may be estimated that, at the present ambient standard of 0.03 ppm hydrogen sulfide,about 40%of people exposed 6 would experience annoyance from the odor." The report then concludes that the present odor standard of 0.03 ppm should remain.Note that Lthis is the same CARB report that was cited by the commenter. The project site consists of agricultural land that is currently fallow.Therefore,the DEIR does not contain an analysis of existing hydrogen sulfide ambient concentrations,as no sources have been 1. identified (other than the proposed project,which is the subject of the odor analysis). [Reference: California Air Resources Board(CARB), The Perception of Hydrogen Sulfide Odor L in Relation to Setting an Ambient Standard,ARB Report No. A4-046-33,April 1985.] 1 Response to Comment B-57 6. Commenter states that the Draft EIR failed to evaluate the public health impacts of crystalline silica emissions from quarrying operations. Commenter states that the Project will generate V large amounts offugitive dust that contain crystalline silica, but the DEIR did not estimate crystalline silica emissions from the Project and generally does not include the type of L information required to estimate these emissions. Commenter states that the Applicant should be required to measure crystalline silica in core samples collected from its deposits and the Draft EIR should be revised to analyze the public health risks from these emissions. LCemex Vernalis Quarry Mining and Reclamation Pmje 3-21 ESA 1203015 Final Emirmmental Impact Report June 2009 L