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Environmental Checklist Noise and Vibration Environmental Consistency Checklist Pursuant to CEQA Guidelines Section 15183 83 and sound power level is the equivalent noise level (Leq). Leq is defined as the single steady A- weighted level that is equivalent to the same amount of energy as that contained in the actual fluctuating levels over a period of time (essentially, the hourly noise level). The relationship between peak hourly Leq values and associated DNL values depends on the distribution of traffic over the entire day (Federal Transit Administration [FTA] 2018). There is no precise way to convert a peak hourly Leq value to a DNL value. However, in urban areas near heavy traffic, the peak hourly Leq value is typically 2 to 4 dBA lower than the daily DNL value. In less heavily developed areas, such as suburban areas, the peak hourly Leq is often equal to the daily DNL value. The project site is located within an urban area where peak hourly Leq value would be typically 2 to 4 dBA lower than the daily DNL value. A 24-hour ambient noise measurement was conducted on the project site from 10:30 a.m. on Monday, May 24, 2021 to 10:30 a.m. on Tuesday, May 25, 2021. The primary source of ambient noise was traffic along Halcyon Drive which lies adjacent to the southern boundary of the project site. The noise monitoring results show that the daytime ambient noise levels averaged 58.5 dBA Leq, nighttime noise levels averaged 53.4 dBA Leq and the 24-hour weighted average CNEL was 61.5 dBA CNEL (included as Appendix NOI). Vibration Vibration is sound radiated through the ground. The rumbling sound caused by the vibration of room surfaces is called groundborne noise. Groundborne vibration is almost exclusively a concern inside buildings and is rarely perceived as a problem outdoors. Groundborne vibration related to human annoyance is generally related to root mean square (RMS) velocity levels expressed in vibration decibels (VdB). However, construction-related groundborne vibration in relation to its potential for building damage can also be measured in inches per second (in/sec) peak particle velocity (PPV) (FTA 2018). Based on the FTA’s Transit Noise and Vibration Impact Assessment and the Caltrans Transportation and Construction Guidance Manual, vibration levels decrease by 6 VdB with every doubling of distance. The background vibration velocity level in residential and educational areas is usually around 50 VdB (FTA 2018). The threshold of perception for humans is approximately 65 VdB. A vibration velocity level of 75 VdB is the approximate dividing line between barely perceptible and distinctly perceptible levels for many people. Most perceptible indoor vibration is caused by sources inside buildings, such as operation of mechanical equipment, movement of people, or the slamming of doors. Typical outdoor sources of perceptible groundborne vibration are construction equipment, steel-wheeled trains, and traffic on rough roads. If a roadway is smooth, the groundborne vibration from traffic is rarely perceptible. The range of interest is from approximately 50 VdB, which is the typical background vibration velocity level, to 100 VdB, which is the general threshold where minor damage can occur in fragile buildings. Groundborne vibration levels in excess of 95 VdB would damage extremely fragile historic buildings. The following describes the analysis included in the General Plan EIR and also provides a streamlined review to determine whether there would be project-specific impacts that are either 1) peculiar to the project or the parcel on which the project is located, 2) were not previously analyzed in the General Plan EIR as significant effects, 3) are potentially significant off-site impacts and cumulative impacts that were not previously discussed in the General Plan EIR, and 4) are now determined to have a more severe impact than discussed in the General Plan EIR due to substantial new information.