Reso PC15-01 PC Reso (3051 ) to Adopt Initial Study-Mitigated Negative Declaration - La Palma

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3.0 Environmental Impact Checklist construction noise threshold of 110 dBA at 25 feet in a residential district.Trucks,the highest noise generator amongst the project construction equipment, which typically generate noise levels of 88 dBA at 50 feet, would generate a noise level of 94 dBA at 25 feet)At the nearest sensitive receptor located 13 feet southeast of a proposed project structure, construction noise levels would be approximately 100 dBA and would not exceed the City's construction noise threshold. The project would comply with the City's construction scheduling requirements to ensure that noise is limited in duration and would be prohibited between the hours of 8 PM and 7 AM weekdays or at any time on weekends and holidays. During the long-term occupancy of the homes, the project would not expose persons to noise levels in excess of the 65 dBA standard established under the General Plan for medium/medium-high density residential uses.The project area is in a noise contour that experiences exterior traffic noise levels ranging from 55 to 60 dBA (City of Redwood City 2010b).Per the City's requirements, this existing noise level is conditionally acceptable and new developments within conditionally acceptable noise environments should be undertaken only after noise reduction requirements are analyzed. Mitigation Measure NOI-1 would require the project applicant to incorporate noise reduction building materials to ensure that noise levels are acceptable and less than significant for the new residents. Mitigation Measure NOI-1: The applicant shall be required to submit to Planning Services for review and approval prior to issuance of Building Permits,a detailed analysis of noise reduction measures to be incorporated into the project. The analysis shall identify noise- reducing building materials, such as windows and doors with high Sound Transmission Class (STC) ratings or forced-air mechanical ventilation systems. Adjacent residential and nearby commercial development land uses surrounding the project site are not substantial noise generators. Noise levels generated by the project would be similar to the noise levels generated by the existing residential uses on-site. With implementation of Mitigation Measure NOI-1,project impacts related to exposing persons to or generating noise Ievels in excess of applicable standards would be less than significant. b) Expose persons to or generate excessive groundborne vibration or groundborne noise levels? Less-than-Significant Impact. Construction of the project would require excavation and grading activities that may generate minor groundborne vibrations. Vibration levels are dependent on the soil types at the construction-site and the type of equipment used. The closest sensitive receptor is a two-story apartment building located adjacent to the project site approximately 13 feet southeast from a proposed project structure. As groundborne vibration amplitudes dissipate and decrease with distance,vibration generated on the project site is not expected to significantly impact nearby residences. The construction methods would not generate excessive vibrations through the ground and would be restricted to the 16 month construction period and permitted daytime construction hours. Post-construction, the proposed Noise levels decrease at a rate of 6 dBA per doubling of distance between the noise source and receptor. La Palma Subdivision Project Final Initial Study/Mitigated Negative Declaration 50