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Mountain House Specific Plan III — ............................................................................................................................................................................... On school sites and other noise-sensitive land uses,any outdoor instructional areas or areas which require — speech audibility will be located outside the 60 dB Ldn noise contour or shielded from mobile noise in excess of 60 dB Ldn. — Noise studies prepared by EDAW have identified noise-reducing barriers sufficient to meet the needed mitigation for noise generated from major and minor Arterials. Noise levels in primary outdoor use areas of new residential development will not exceed an Ldn of 60 dB unless the project design includes reasonable mitigation measures to reduce noise in outdoor activity areas to as close to an Ldn of 60 dB as _ possible. Where it is not possible to reduce noise in outdoor activity areas to an Ldn of 60 dB or less using practical application of the best available noise reduction measures,an exterior noise level of up to an Ldn of 65 dB may be allowed. Under no circumstances will interior noise levels exceed an Ldn of 45 dB. 11.2.2 Specific Plan III Description As part of this Specific Plan. a noise analysis was prepared to identify expected noise levels and appropriate mitigations and sound wall locations and heights. Existing noise-sensitive land uses within the planning area include 49 residences in the northwest portion of the project site(Grant Line Village), four residences in the central portion of the site, and one residence in the northern portion of the project site along the south side of Grant Line Road. The sound barriers identified in Table 11-1 and Figure I1-1 will reduce exterior noise levels at the residences along Grant Line Road to below 65 dBA Ldn/CNEL. This mitigation shall be funded through fair-share payments by the applicants for development within Specific Plan III. The existing noise environment on and within the vicinity of the Specific Plan III project site is influenced primarily by surface transportation noise emanating from vehicular traffic on area roadways, such as — Interstate 205 (I-205),Mountain House Parkway, and Grant Line Road. Agricultural activities within and adjacent to Specific Plan III also contribute to the existing background noise levels. — Specific Plan III is also influenced by aircraft flyover noise from the Byron Airport located approximately — five miles to the northwest in Contra Costa County. Portions of Neighborhoods A/B, and D fall within the area of potential noise impact from Byron Airport. See Figure 11-2. Light plane operations to and from _ the airport would produce minimal noise impacts on the Specific Plan III area as most of these aircraft would pass over the Specific Plan III area at heights that make their presence largely unnoticeable. _ Nonetheless, Specific Plan III implements the Master Plan requirement that home buyers in the airport 11 -2 Draft 03/14/05 ...............................................................................................................................................................................