75D - PH ZONING ORD AND CUP CALIFORNIA PALMS

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i At build out, traffic along Harbor Boulevard is projected to increase from about 42,000 ADT to 47,000 ADT. This increase would raise future noise levels by 0.5 dBA CNEL. Future noise levels in the habitable areas would be raised accordingly, but would remain under 60 dBA CNEL and the impact remains less than significant. HabitablelnteriorAreas As noted, the project would be subject to estate-mandated 45 dBA CAiEL interior noise standard. Table 6 fi demonstrates that the Harbor Boulevard 70 dBA CNEL contour would lie at a distance of about 73 feet from the roadway centerline or about 22 feet from the curb line. The most proximate structures are located approximately 65 feet from the cemerline of the road and exterior traffic noise is calculated at about 70.6 dBA CNEL. At build out, this level would fiuther be increased by about 0.5 dBA and exterior noise at the most proximate rooms along Harbor Boulevazd would be increased accordingly. Monitoring in Room 462 located along Harbor Boulevazd, indicates an existing, in-room CNEL of approximately 50.7 dBA. This level would also raise by about 0.5 dBA to approximately 51.2 dBA CNEL at build out. Based on ~ a 45 dBA CNEL interior standard, the impact of noise on the proposed land use is potentially significam. Mitigation As noted, interior noise levels have been shown to exceed the 45 dBA CNEL interior noise standard and the impact is potentially significam. The following measures would ensure that imerior noise levels aze reduced to less than State's 45 dBA CNEL interior standard. The following measure is required for all rooms: • All rooms are to include forced air ventilation allowing the residems to leave windows closed reducing interior noise levels. Additionally, the following shall be applied to those units that face onto Harbor Boulevazd. • The developer shall specify a minimum STC rating of 29 for all window and/or door assemblies that from along Harbor Boulevard (west facing). These windows and/or doors aze to be well fitting with vinyl (or equivalent) gaskets that form an air-tight fitting. • Ali exterior fittings that enter the structures (e.g., electrical conduits, HVAC ducts) along Hazbor Boulevard are to be sealed with caulk such that the fittings are rendered as air-tight. Any metal duct-work that is exposed to the exterior environmem shall be enclosed and insulated to avoid noise iraosference through the ducting. • Any in-room air conditioning units placed along Harbor Boulevard shall be placed in baffled enclosures reducing transmitted noise, but allowing for airflow. • The Applicant shall abide by any other conditions set forth by the City of Sawa Ana Planning Departmem. Residuollmpad ~ The Naise Guidebook (HUD, 1985) presems Sound Transmission Class (STC) ratings for various types of construction materials and techniques. The STC rating is the official rating endorsed by the American Society of Testing and Measuremem and can be used as a guide in determining what type of construction is needed to reduce noise. Conversely, these same principles can be used to determine interior noise for a given type of constriction. An STC is a ineasure of a material's ability to reduce sound and is equal to the number of decibels a sound is reduced as it passes through tbe material. Thus, a high STC rating indicates a good insulating material. For example, if the external noise is 72 dBA and the desired imerior level is 45 dBA, a partition of 27 STC is required. Because of minor differences in ratings, as well as construction flaws, gaps, seams, openings, ducting, etc., field studies indicate that laboratory-derived STC ratings may be overstated by as much as 5 dBA (HUD puts this 13 75D-133