1. Construction noise levels at and near locations on the project site would fluctuate depending on the particular type, number, and duration of use of various pieces of construction equipment. The effect of construction noise would depend upon how much noise would be generated by construction, the distance between construction activities and the nearest noise-sensitive uses, and the existing noise levels at those uses. Construction noise would be intermittent, extended over a period of four months.

    The noisiest phases of construction would generate approximately 89 Leq (energy-equivalent noise level ) at 50 feet (U.S. EPA, 1971). The receptors nearest proposed construction activity would be the existing Boccardo Corporation offices to the south of the site and residences approximately 40 feet from the eastern property line of project site. Consequently, construction noise during construction would generate noise levels up to approximately 90 Leq at the nearest residences during regrading and resurfacing activities.

    Given ambient noise levels at these residences, construction noise would be noticeable but many residences are less occupied during the daytime. Construction noise would be annoying to workers in offices on the north side of the Boccardo Corporation Building. During nighttime, temporary construction-related noise could be more noticeable (since background noise is lower) and could annoy the closest residents given the more sensitive nature of the nighttime period. Therefore, without appropriate limitations on allowable hours of construction, this temporary impact would be significant.

    Operational noise would be generated by transformers on the substation site. The potential for noise impacts from the transformers is addressed in a Noise Impact Assessment study prepared for the proposed project (Wilson, Ihrig, & Associates, 1996; PG&E, 1997b). This study found that the two transformers proposed for the site would each generate a noise level of 67 dBA, and a composite noise level of 70 dBA at a distance of one foot. The report predicts a resultant noise level of 41 to 47 dBA at the property line. The projected noise level at the eastern property line due to the transformers would be one dBA above the nighttime Noise Ordinance standard of 46 dBA. However, the project design includes construction of an eight-foot high sound barrier. If the sound barrier is sufficient to block the line-of-sight between the transformers and the residences to the east, additional noise reduction of approximately 10 dBA would result and the operating noise from the transformer would be 37 dBA at the property line (Wilson Ihrig & Associates, 1997). The barrier would bring the noise level below the nighttime Noise Ordinance standard. Additional mitigation is not required.

Mitigation Measures

The following mitigation measures would reduce the potential impact to a less than significant level:

Mitigation Measure X.a-1: To reduce the construction noise effects, PG&E shall require construction contractors to limit noisy construction activities to the least noise-sensitive times of day and week (e.g., 7:00 a.m. to 6:00 p.m., Monday through Friday).

Mitigation Measure X.a-2: To reduce the construction noise effects, PG&E shall require all contractors to adequately muffle and maintain construction equipment used on the site.

Mitigation Measure X.a-3: To reduce the construction noise effects, PG&E shall require all contractors to locate all stationary construction equipment (i.e., compressors and generators) as far as practicable from the eastern property line.

  1. As discussed in the response to Item X.a., the noise levels resulting from project operation would be less than ambient noise levels and would not be considered severe.
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