9-404.080 - ACOUSTICAL STUDIES - WHEN REQUIRED

(a)

Scope of Study. The Zoning Administrator shall require an acoustical study, at the applicant's cost, that includes field measurement of noise levels for any proposed project that would locate a noise source with the potential to increase noise levels to levels exceeding limits in Table 9-404.050. Acoustical studies must identify noise sources and magnitudes, describe existing and future noise exposure, and propose mitigation measures for any on-site generated noise in order to ensure that the noise exposure limits in Table 9-404.050 are not exceeded. The acoustical study shall include the following information:

(1)

A general description of the project and its general location, with appropriate maps, and the noise sources of concern;

(2)

A description of the methodology that will be used to assess noise impacts, including a listing of all assumptions and data used in any computer models.

(A)

Computer models that will be used for noise predictions shall be standard versions approved by the FHWA, FAA, Caltrans, or other government agencies.

(B)

For traffic noise studies, the computer models, SOUND32 or other proprietary models based on the 1978 "FHWA Highway Traffic Noise Prediction Model (FHWA-RD-77-108)" shall be used. The FHWA's new "Traffic Noise Model" (TNM) shall be used after its phase in date. For aircraft noise studies, the latest version of the FAA's "Integrated Noise Model" (INM) shall be used.

(C)

If standard government approved models do not exist (e.g., for railroad and industrial noise sources), a description of the consultant's analysis model shall be provided.

(3)

A description of existing and future noise levels on the project site together with a comparison of these noise levels to the noise level standards specified in Table 9-404,040 and the noise exposure-land use requirements in Table 9-404.050.

(4)

Recommended mitigation measures to achieve compliance with the standards specified by Tables 9- 404.040 and 9-404.050 (i.e., noise barriers, site design, setbacks, equipment modification, structure sound proofing), or a detailed explanation stating why mitigation is infeasible.

(b)

Establishing Ambient Noise. When the Zoning Administrator has determined that there could be an existing condition that would necessitate adjusting the standards, an acoustical study shall be performed to establish ambient noise levels. In order to determine if adjustments to the standards should be made upwards, a minimum 24-hour duration noise measurement shall be conducted. The noise measurements shall collect data utilizing noise metrics that are consistent with the noise standards presented in Table 9- 404.050. An arithmetic average of ambient noise levels during the three loudest hours should be made to demonstrate that ambient noise levels regularly exceed the noise standards.