55A - SAN LORENZO SEWER LIFT STATION

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0 �� SAN i.oRENZO SEWER LIF1 ENViRONMENiA! IMPACT REPORT 3.1 AIR QUALITY i marginally detectable, ; -10 D/T is considered clearly detectable, but not yet highly offensive. When levels exceed 10 D,,7 and the odor is normally considered offensive, such as from sewage, a siMificant impact is presumed to exist, Odors may be released from the vents on a lift station and carried downwind. During the daytime, winds across the Project site are mainly from west to east and during nighttime, winds are east to west. Thus, any odor- sensitive development directly east or west of the lift station would be possibly affected by odors. The y distance extent of any odor "envelope" was estimated based upon normal and worst -case odor conditions. Tc estimate the odor level (in units of DPI') for a vent release of fresh versus stale sewage gas, an odor concentration of 30 DT was assumed for fresh sewage, and 2000 D/T for stagnant material. under normal operational conditions ( "fresh sewage "), the limit of marginal detectability (1 D /T) is 25 feet. The clearly offensive odor limit (10 D/T) is around 6 feet from the vent. No odor sensitive uses are located within 25 feet of the proposed San Lorenzo Lift Station; thus, impacts under normal operating conditions would be less than significant. During upset conditions with stagnant sewage in the system, the zone of clearly offensive odor would be around 75 feet from the source. Maintaining a distance buffer of at least 73 feet from the lift station to the nearest odor - sensitive property is anticipated to maimain potential worst -case odor conditions at less -than significant levels. The nearest sensitive receptor (i.e.. hotel unit to the west) is located at a distance of Mro7;imately 75.5 feet from the location of the nroposed exhaust fan for the lift station facility while the i nearest residential home is located approximately 1 0 feet northeast of the silepronosed exhaust fan. Additionally, effluent would be continuously moving through the wet well with a minimum retention tithe. As such, it is unlikely that any significant odors detectable above g ound will be generated. I However, due to the complexities in evaluating the sensitivity of nearby receptors to potential odor impacts associated with the proposed facility, and given the relative close proximity of the nearest sensitive receptor, i it is conservatively estimated that long -term operation of the proposed lift station may result in a significant odor impact for which mitigation would be required. i r Threshold 5.• Wouid the Project conflict with or obstruct implementation of applicable Air Quality Attainment Plan or Congestion Management Plan? Air Quolily Attainment Pion Consistency Analysis The Project site is located within the SCAB, which is characterized by relatively poor air duality. The SCAQMD has jurisdiction over an approximately 12,400 square -mile area consisting of the four -county Basin and the Los Angeles County and Riverside County portions of what use to be referred to as the Southeast Desert Air Basin. In these areas, the SCAQMD is principally responsible for air pollution control. and works directly with the Southern California Association of Governments (SCAG), county transportation commissions, local governments, as well as state and federal agencies to reduce emissions from stationary, mobile. and indirect sources to meet state and federal ambient air quality standards. Currently, state and federal air quality standards are exceeded in most parts of the Basin. In response, the SCAQMD has adopted a series of Air Quality Management Plans (_AQIVjPs) to meet the state and federal ambient air quality standards. AQMPs are updated regularly in order to more effectively reduce emissions, accotvmodate growth, and to minimize any negative fiscal impacts of air pollution control on the economy-. GAGS 55A -221