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i MOUNTAIN HOUSF PROPOSED ALTAMONT HEIGHTS TENTATIVE MAP 4. ENVIRONMENTAL CHECKLIST 4.11 NoisF .. I Less Than I Potential SPIIIEIR:, Significant significant Requires Impact Due New New Impact Additional to Mitigation Additional Addiiional Less Than Adequately Review-No Measures in Impact Not Mitigation Signiricaat Addressed in Significant Project Addressed in Measures Issue or No Impact SPIIIEIR Impact Description SPIiIEIR Required 11. NOISE. Would the project result in: a) Exposure of persons to or generation LJI Of noise levels in excess of standards ❑ • ❑ , ❑L established in the local general plan or noise ordinance,or applicable standards of other agencies? b) Exposure of persons to or generation ■ of excessive ground borne vibration F ❑ ❑ El ❑ ❑ or ground borne noise levels? c) A substantial permanent increase in ❑ ■ ❑ ❑ El ❑ ambient noise levels in the project vicinity above levels existing without the project? d) A substantial temporary or periodic ❑ ■ F1 El O. L1increase in ambient noise levels in , the project vicinity above levels existing without the project? ` e) For a project located within an ■ ❑% Q El ❑ airport land use plan or,where such a plan has not been adopted,within two miles of a public airport or public use airport,would the project expose people residing or working in the project area to excessive noise levels? f) For a project within the vicinity of a ■ F1 ❑ ❑ ❑ ❑ private airstrip,would the project expose people residing or working in the project area to excessive noise levels? SETTING The primary current source of noise at the project site is traffic from Grant Line Road and Interstate 205 (1-205). The center of the site is approximately 1,200 feet south of Grant Line Road and 2,500 feet north of I-205. Construction of Mountain House Community neighborhoods to the north also contributes to the existing background noise levels. The project site is located approximately 7.5 miles southeast of the Byron Airport in Contra Costa County and is also influenced by aircraft fly-over noise. According to the MSIR,portions of Neighborhood A, in which the project site is located, fall within the noise impact area of the airport. As a part of the SPIIIEIR analysis, a noise survey was conducted in May 2004 to document the ambient noise environment at various locations in the.planning area, in which the proposed project is located. Based on the measurements taken, average daytime noise levels (in dBA Leq) in the planning area range from the high 50s to the upper 60s depending F 4-54 i