CORRESPONDENCE - 75A (COMMENT) - Laserfiche WebLink

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Chapter 4 Environmental Setting, Impacts, and Mitigation Measures A&14.8-6 Prior to issuance of building permits, building plans shall sped the STC rating of windows and doors far all residential land uses. Vindow and door ratings shall be sufficient to reduce the interior noise level to a CNEL of 45 dBA or less, and shall be determined by a quaked acoustical consultant as part of the f nal engineering design oj'the project. As previously discussed, implementation of the proposed project would lead to the development of high - density residential uses in areas that exceed the 65 dBA CNEL "Desirable Maximum," and this would be considered a significant impact. However, implementation of mitigation measure MM4.8-5 would ensure that exterior living spaces, such as porches and patios, are constructed in a manner that noise levels do not exceed the 65 dBA CNEL. Further implementation of mitigation measure MM4.8-6 would ensure that interior living spaces of the residential units do not exceed 45 dBA CNEL. Therefore, this impact would be reduced to a level of less than significant. In addition, the HVAC systems that would be installed for the new residential development associated with the proposed project can result in noise levels that average between 50 and 65 dBA Lq at 50 feet from the equipment. As 24-hour CNEL noise levels are about 6.7 dBA greater than 24-hour Leg measurements, this means that the HVAC equipment associated with the retail -commercial buildings could generate community noise levels that average between 57 to 72 dBA CNEL at 50 feet when the equipment is operating constantly over 24 hours. These HVAC units would be mounted on the rooftops of the proposed buildings and would be screened from view by building features. However, the installation of shielding around these HVAC systems would be required as part of the proposed project, as stated in mitigation measure MM4.8-7 below. MM4.8-7 Each project applicant shall provide proper shielding for all new HVAC systems used by the proposed residential and mixed use buildings to achieve an attenuation of 13 dBA at 50 feet from the equipment. The shielding installed around these systems would typically reduce noise levels by approximately 15 dBA, which could reduce HVAC system noise to approximately 50 dBA Lrq at 50 feet from the equipment, which would be approximately 56.7 dBA CNEL. Implementation of mitigation measure MM4.8-7 would ensure that impacts related to the HVAC systems would remain below the 65 dBA CNEL "Desirable Maximum" exterior noise level guideline established in the City's General Plan for high density residential uses. As such impacts to residents of the proposed project relating to HVAC systems would be less than significant. Threshold Would the project result in the exposure of persons to or generation of excessive groundborne vibration or groundborne noise levels? Impact 4.8-3 Operation of the proposed project would not generate and expose sensitive receptors on site or off site to excessive groundborne vibration or groundborne noise levels. This is considered a less -than -significant impact. During operation of the proposed project, background operational vibration levels would be expected to average around 50 VdB, as discussed previously in this section. This is substantially less than the 85 VdB 4.8-24 City of Santa Ana Transit Zoning Code (SD 84A and SD 848) EIR