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LDraft Supplemental Environmental Impact Report Page IV.D-20 Forward Inc.Landfill 2014 Expansion Project �6 Together with hydrocarbons, the second group is probably responsible for the background smell associated with a landfill. The sensory perception of odorants has four L major dimensions: detectability,intensity, character, and hedonic tone. Odor detectability consists of a detection threshold and a recognition threshold. The detection threshold is the lowest concentration of an odorant that will elicit a sensory response in 50 percent of i the population. There is an awareness of the presence of an added substance,but not necessarily an odor sensation. The detection thresholds are determined using human subjects and sophisticated dilution equipment. LDetection thresholds are published for more than 900 chemicals. The recognition threshold is the minimum concentration that is recognized as having a characteristic odor quality by a segment of the population. Odor intensity refers to the perceived strength of the odor sensation, and odorant character is what the substance smells like (e.g., fishy, h., rancid,hay, sewer, turpentine, ammonia, etc.). Garbage has been demonstrated to possess an odor with an unpleasant tone. L Because offensive odors rarely cause any physical harm and no requirements for their control are included in state or federal air quality regulations,the SJVAPCD does not currently impose any rules or regulations that place quantifiable limitations on emissions of odorous substances, other than its Nuisance Rule 4102. Any actions related to odors are based on citizen complaints to local governments and the District. The SJVAPCD identifies a sanitary landfill as a type of facility that is a potential odor L source. Because there are one or more sensitive receptors within the screening trigger distance of one mile from the landfill property, potential odor impacts from the Project must be considered. The District has established the following significance threshold for j` odor problems: • More than one confirmed complaint per year averaged over a three-year period, or All • Three unconfirmed complaints per year averaged over a three-year period. On September 3,2014 the SJVAPCD were contacted to determine the history of odor and visible dust complaints. During the past three years, the SJVAPCD provide information on four odor complaints: two unconfirmed complaints (dated April 18, 2012 and September 12,2013) and two confirmed complaints (May 28, 2013 and October 9, 2013). After investigating the two confirmed complaints, the investigator concluded that as long as the Facility is operating within its permit limits, the District is very limited in its ability to control the odor.15 As part of the 2013 EIR, a survey was conducted during three days to make qualitative observations related to odor and visible dust emissions leaving the landfill. The landfill area was surveyed on November 8,2011 (starting at 1 p.m.);November 22, 2011 (starting at 12:30 p.m.);and December 5,2011 (starting at 10:30 a.m.). The same five locations were reviewed during each survey. A summary of the survey results is presented in Table IV.D-5. The survey locations are shown on Figure IV.D-1. Conditions were generally sunny with light to moderate breezes on each of the survey days. L Table IV.D-5 y is San Joaquin Valley Air Pollution Control District(SJVAPCD),Complaint Investigation,September 8,2014. L L