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Soil Investigations for Data Collection in the Delta Initial Study/Proposed Mitigated Negative Declaration 173 • Aircraft from the Sacramento International Airport and Bourges-Clarksburg Airport • Motorized boats along the Sacramento River Vibration sources include construction equipment, steel-wheeled trains, and traffic on rough roads. 3.13.2 Discussion a) Generation of a substantial temporary or permanent increase in ambient noise levels in the vicinity of the project excess of standards established in the local general plan or noise ordinance, or in other applicable local, state, or federal standards? Less than Significant Impact. Noise from the geotechnical drilling equipment is generally comparable to the noise produced by diesel trucks. The maximum noise from truck-mounted drill rigs and CPT rigs is 120 dba at the rig. The maximum noise from seismic geophysical surveys is 70 dba at 7 meters. While equipment is working, ambient noise levels will increase slightly. Short-term impacts resulting from the Proposed Project include increased localized noise level and small vibrations created primarily from the drill rig engine and short durations from the Standard Penetration Tests. While impacts to noise would be less than significant, implementation of Mitigation Measures MM AES-1b and NOI-1 would further avoid, minimize and/or reduce the potential for impacts. MM NOI-1: All equipment will be properly tuned and shall utilize appropriate mufflers. b) Generation of excessive ground borne vibration or ground borne noise levels? Less than Significant Impact. The vibrations from on-land truck mounted drill rigs and CPT rigs are minimal and vibrations are typically not detectable by people outside of the immediate area. Vibrations from the EnviroVibe Minibuggy vehicle are relatively small, but mild vibrations can typically be felt by people within approximately 50 feet of the EnviroVibe Minibuggy; at 100 feet, vibrations are typically not detectible by people. The levels of vibration are much smaller than vibrations required to induce damage in buildings and infrastructure. Vibrations from over-water soil boring explorations are minimal. The Shelby tube and piston samplers are collected by hydraulic pressure. No vibrations are produced from pushing tube samples. The Pitcher Barrel samples drills into the ground using rotary techniques (soil coring) producing no more vibrations than boring drilling. Therefore, potential impacts from the generation of ground borne vibration or noise levels would be less than significant.