RES 211231 Exhibit A - Laserfiche WebLink

Environmental Checklist and City of Pleasanton–10x Genomics Project Environmental Evaluation Initial Study/Mitigated Negative Declaration 108 FirstCarbon Solutions Https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480024/ISMND/wp/21480024 10x Genomics Project Full Screencheck ISMND.docx existing vehicle-generated noise on these local roadways. Typically, a doubling of the Average Daily Traffic (ADT) hourly volumes on a roadway segment is required in order to result in an increase of 3 dBA in traffic noise levels; which, as discussed in the characteristics of noise discussion above, is the lowest change that can be perceptible to the human ear in outdoor environments. Project-related construction trips would not be expected to double the hourly traffic volumes along any roadway segment in the project vicinity. For this reason, short-term intermittent noise from construction trips would be minor when averaged over a longer time-period and would not be expected to result in a perceptible increase in hourly- or daily-average traffic noise levels in the project vicinity. Therefore, short-term construction-related noise impacts associated with the transportation of workers and equipment to the project site would be less than significant. Construction Equipment Operational Noise The second type of short-term noise impact is related to noise generated during construction on the project site. Construction is completed in discrete steps, each of which has its own mix of equipment and, consequently, its own noise characteristics. These various sequential phases would change the character of the noise generated on the site and, therefore, the noise levels surrounding the site as construction progresses. Despite the variety in the type and size of construction equipment, similarities in the dominant noise sources and patterns of operation allow construction related noise ranges to be categorized by work phase. Typical operating cycles for these types of construction equipment may involve 1 or 2 minutes of full-power operation followed by 3 or 4 minutes at lower power settings. Impact equipment such as pile drivers is not expected to be used during construction of this project. The site preparation phase, which includes excavation and grading of the site, tends to generate the highest noise levels because the noisiest construction equipment is earthmoving equipment. Earthmoving equipment includes excavating machinery and compacting equipment, such as bulldozers, draglines, backhoes, front loaders, roller compactors, scrapers, and graders. Typical operating cycles for these types of construction equipment may involve one or two minutes of full power operation followed by three or four minutes at lower power settings. Construction of the project is expected to require the use of scrapers, bulldozers, water trucks, haul trucks, and pickup trucks. According to the City’s noise ordinance, the project must comply with limitations on construction equipment noise levels of 83 dBA Lmax at a distance of 25 feet. A characteristic of sound is that each doubling of sound sources with equal strength increases a sound level by 3 dBA. Assuming compliance with the City’s equipment noise limitations and that each piece of construction equipment operates at a minimum distance from each other, a reasonable worst-case combined noise level during this phase of construction would be 85 dBA Lmax at a distance of 25 feet from the acoustic center of a multiple pieces of construction equipment operating simultaneously at full power. The acoustical center reference is used because construction equipment must operate at some distance from one another on a project site, and the combined noise level as measured at a single point on the project boundary would be the worst-case maximum noise level. This would result in a reasonable worst-case hourly average of 81 dBA Leq. All construction noise level calculations are provided in Appendix H.