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X. NOISE <br /> X-1 . Potentially Significant Impact • Noise-Sensitive Lan_ .Ises <br /> [ Impact 4 . 16-11 <br /> Residential development , schools , and other <br /> noise-sensitive land uses on the Project Site would be <br /> exposed to excessive noise levels , especially in the area <br /> between Grant Line Road and I-205 . <br /> Finding : Changes or alterations have been required in, <br /> or incorporated into , the Project which avoid or <br /> substantially lessen the significant environmental effect <br /> as identified in the FEIR to a non-significant level . <br /> These mitigation measures are listed below. <br /> Statement of Fact : The impact will be reduced by the <br /> following : <br /> • See Attachment C-1 , Section J. 1 . <br /> • Locating noise-sensitive land uses as far as possible <br /> from major roadways is the preferable solution. When <br /> this is not feasible, or desirable, earth berms , or <br /> sound walls shall be built between the noise source <br /> and the noise-impacted area . Typically, an earth <br /> berm provides 3 dB of additional noise attenuation <br /> over a sound wall of the same height . A sound wall <br /> at the top of an earth berm is more aesthetically <br /> pleasing than a sound wall of the same total height <br /> but , its performance to act as a noise barrier is <br /> inferior to an earth berm. Further noise level <br /> reductions to an Ldn of 60 dB could be achieved <br /> through proper site planning and building <br /> orientation, construction of earth berms or sound <br /> walls , or a combination of more than one of these <br /> methods . Site-specific mitigation measures shall be <br /> determined on a case-by-case basis . <br /> • Schools shall not be sited in areas exposed to noise <br /> levels above an Ldn of 60 dB. The land use plan <br /> should be revised to relocate two proposed high <br /> schools and three elementary schools . [ In the <br /> alternative berms and soundwalls can be utilized. ] <br /> • At the time of the Specific Plan, acoustical studies <br /> are required for noise-sensitive land uses proposed <br /> to be located in areas exposed to noise levels above <br /> an Ldn of 60 dB . Appropriate mitigation measures <br /> must be recommended in these studies and implemented <br /> by the appropriate party to ensure that the Ldn of <br /> 60 dB is not exceeded . <br /> C2-74 <br /> 0189r/0202r <br />