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("„ hI Mo Town C:^ nt � 13A of vti, Saantis. Ana Its v« w of I nv�mnm ntal NoNe A naly[�N Page 2 of b .kdfie 29, 2023 They are insufficient to determine 24-hour weighted average noise metrics, such as Community Noise Equivalent Level (CNEL), which is the basis of the noise standards in the City of Santa Ana General Plan. The selected monitoring locations do not represent noise conditions on the Lake Dianne Apartments complex, which is located immediately northeast of the project site. The apartments here represent the closest sensitive receivers to the sources of noise associated with the project. The monitoring locations selected for the baseline noise evaluation are almost all on busy streets or close to freeways, which do not represent quieter locations that are set back and/or shielded from major traffic routes — such as the apartments on the Lake Dianne property. • In Table 4.9-4, the MEMU EIR provides "reference" CNEL values for an extensive list of road segments around the Overlay Zone area, which have been calculated using the Federal Highway Administration Noise Prediction Model. However, these projected noise levels are for hypothetical off -site receivers located very close to busy streets (50-ft from the centerline) and do not help characterize ambient noise conditions for receivers further away from major traffic routes and/or shielded by intervening structures THRESHOLDS OF SIGNIFICANCE The noise impact assessment for the MEMU was based on thresholds of significance defined on page 4.9-14 of the EIR. • As we would expect, reference is made to Appendix G of the CEQA Guidelines; however, the significance thresholds themselves are problematic for the following reasons: - Temporary/Periodic Impacts are Excluded CEQA Guidelines require that both temporary/periodic and permanent noise impacts be identified and addressed. However, the thresholds of significance proposed in the MEMU EIR would apply to operational (permanent) noise impacts only. - Increase of less than 3 dBA The preparers propose that any increase in noise, whether temporary or long-term, should be considered insignificant if it is less than 3 dBA. While it is true that a noise increase of 3 dBA would not be discernable to most people, it is also possible that a 3 dBA increase could make the difference between complying with local noise regulations (City of Santa Ana Municipal Code and General Plan) and not. In other words, there may be situations where a 3 dBA increase in noise level would — according to the CEQA Guidelines, as quoted on page 4.9-14 of the EIR — constitute a "significant adverse impact". - Increase of less than 3 dBA. more than 5 dBA The MEMU EIR suggests that a noise level increase of more than 3 dBA but less than 5 dBA should be considered less than significant so long as the CNEL at sensitive land uses, including residential uses, is below 65. However, it would be quite possible for noise from the project to exceed the allowed limits according to the Santa Ana Municipal Code while remaining well below the proposed CNEL 65 significance threshold. For example, the nighttime noise limit in the Municipal Code for continuous noise — such as air- conditioning — is 50 dBA (SAMC Section 18-312), for receivers where the ambient (nighttime) noise level is less than 50 dBA, which is likely the case for much of the Lake Dianne property. In