As described in Response OSEC-401, lifecycle emissions analyses are not required under CEQA. The exact types of solar technology to be installed as part of Project site development and the sources of the solar technology materials have not yet been defined and could not be known during preparation of the Draft EIR. In addition, materials may be manufactured in response to market demand may change over time, and different manufacturers may use different processes and materials or change processes and materials over time. Quantification of lifecycle emissions of the solar technology would thus be speculative, and was not undertaken for the Draft EIR.
[See page 5-360 for the original comment] See Response OSEC-384.
[See page 5-360 for the original comment] Groundborne vibrations generated during construction are addressed in Section 4.J, Noise and Vibration. The 2004 American Association of State Highway and Transportation Officials (AASHTO) guidelines include references for underground utility criteria, citing studies indicating that vibration under the ground surface is lower than that measured at the ground surface.
The Caltrans measure of the threshold of architectural damage for conventional sensitive structures is 0.5 in/sec PPV for new residential structures and modern commercial buildings and 0.25 in/sec PPV for historic and older buildings was used in analyzing vibration impacts. Underground or restrained concrete structures can withstand vibration of 10.0 in/sec (254 mm/s) before the appearance of threshold cracks. Thus, underground utilities are less sensitive than surface structures.
As discussed on Draft EIR page 4.J-22, pile driving can result in peak particle velocity (PPV) of up to 1.5 in/sec at a distance of 25 feet (FTA, 2006), but typically average about 0.644 PPV at that distance. All other construction activities would have substantially lower vibration inducing potential. Vibration from pile driving could potentially reach levels in excess of the 4.0 in/sec AASHTO criteria at distances between 10 to 15 feet. Thus, pile driving within 10-15 feet of an underground pipeline could cause damage to the pipeline, resulting in a significant impact. Consequently, Mitigation Measure 4.J-2c is hereby added to the Draft EIR:
Mitigation Measure 4.J-2c: All development sites requiring pile driving shall have underground utility7 surveys completed before a building permit is issued to demonstrate that pile driving will be located a minimum 15 feet from buried utilities. Underground utilities surveys