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Hacienda Mixed Use Rezoning Initial Study of attenuation (lessening) is about six decibels (dBA) for every doubling of distance from a point source.' Average construction related noise levels would generally be maintained below 80 dBA throughout project construction at distances of approximately 50 feet from the noise source. Distances of approximately 200 feet would generally maintain average noise levels below 70 dBA. Construction due to implementation of the proposed zone change on the BRE project site and potentially on the Roche Molecular Systems site would cause temporary noise impacts on the nearby Siena housing development. The proposed zone change itself would not result in any construction or construction noise. Title 24 of the California Code of Regulations establishes uniform noise insulation standards for residential structures. Title 24 requires that residential structures (other than detached single- family dwellings) be designed to prevent the intrusion of exterior noise so that the noise level with windows closed, attributable to exterior sources, shall not exceed 45 dBA in any habitable room. In addition, the General Plan Noise Element includes standards for indoor and outdoor noise, when noise studies are required, and a requirement that noise mitigation is included as a condition of project approval. Residential development in areas with outside noise levels up to 75 dBA is conditionally allowed and would require an acoustical study and mitigation. Thus any residential development that might occur to implement the proposed zone change would be required to meet the noise standards of the General Plan. Development due to the proposed zone change would not include any activities that would result in excessive groundbome vibration or noise. The future residential and commercial land uses would not increase ambient noise levels in the project vicinity above existing ambient noise levels in the area. Construction and operational noise will be addressed in more detail, including any impacts on sensitive noise receptors, in the environmental review documents subject to the California EnvimnmentalQuak'tyAct at the time development plans are proposed for the project sites. In addition, vibration impacts from the nearby BART Station on proposed residential land uses will also be analyzed at that time. Mitigation measures, if warranted, would be included as part of that process. No Impact. The site is not in the vicinity of a private airstrip or within 2 miles of a public airport. Less Than Potentially Significant with Less Than No Significant Mitigation Significant Impact Impact Incorporation Impact 12. Population and Housing Would the project: a) Induce substantial population growth in an area, either X directly (for example, by proposing new homes and businesses) or indirectly (for example, through extension of roads or other infrastructure)? b) Displace substantial numbers of existing housing, g necessitating the construction of replacement housing elsewhere? c) Displace substantial numbers of people, necessitating the g construction of replacement housing elsewhere? 7 Thus 86 dBA at 25 feet would attenuate to 80 dBA at 50 feet, 74 dBA at 100 feet, 68 dBA at 200 feet and 62 dBA at 400 feet while 83 dBA at 25feenoijld attenuate to-71 dBAat3Rfeet, 7t_dBA -at -1.00 feet, and -6-5- dBA -at 200 feet 8 dbA A weighted decibels. Draft, Subject to Revision 21 8/31/2009