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Acoustical Analysis Report Griffith Energy Storage Project 4.0 PROJECT CONSTRUCTION 4.1 Noise Calculation Methodology Acoustic emission levels for activities associated with Project construction were based upon typical ranges of energy equivalent noise levels at construction sites,as documented by the United States Environmental Protection Agency(USEPA 1971) and the USEPA's"Construction Noise Control Technology Initiatives" (USEPA 1980).The USEPA methodology distinguishes between type of construction and construction stage. The basic model assumed spherical wave divergence from a point source located at the center of the Project site to each receptor structure. Furthermore,the model conservatively assumed that all pieces of construction equipment associated with an activity would operate simultaneously for the duration of that activity.An additional level of conservatism was built into the construction noise model by excluding potential shielding effects due to intervening structures and buildings along the propagation path from the site to receiver locations such as residential buildings. 4.2 Projected Noise Levels During Construction The construction processes are anticipated to occur during a period of approximately 15 months and begin in 2024. Project construction would generally consist of five major stages.The first stage would include mobilization,site preparation,fencing,and laydown.The second stage would involve excavation, trenching and trench backfill.The medium-voltage stations would sit on concrete foundations or driven piles, pending final design.The construction noise analysis conservatively assumes pile driving will be required for this activity as part of the second stage. Pile driving would be the worst-case option in terms of noise as opposed to using concrete foundations.The third stage includes installation of cables and utilities.The fourth stage includes construction and installation of the battery storage units,and also includes commissioning and testing.The final stage includes road paving.Table 5 summarizes the proposed equipment to be used for each stage and the associated noise level of the equipment.Table 6 summarizes the received construction noise levels at each NSA. Noise levels resulting from the construction activities would vary significantly depending on several factors such as the type and age of equipment,specific equipment manufacture and model,the operations being performed,and the overall condition of the equipment and exhaust system mufflers. Project construction would occur between 7:00 a.m.and 7:00 p.m.,in compliance with the County's Code.Although the County's ordinance may exempt daytime construction noise from the County's typical noise requirements,construction noise may still be considered an impact under CEQA.The Federal Transit Administration has published construction noise impact criteria levels of an 80 dBA 8- hour Leq for the day and a 70 dBA 8-hour Leq for the night for residential land uses.Table 6 shows that the highest construction noise levels at a non-participating receptor will be 63 dBA Leq and 69 dBA LmaX at NSA- 11.This level is below the FTA guidance level of 70 dBA Leq and is within the range of measured ambient LmaX values published in The San Joaquin County 2035 General Plan EIR, is within the range of measured ambient LmaX values published in The San Joaquin County 2035 General Plan EIR,which show an Lmax ranging from 51 to 66 dBA during the morning,58 to 78 dBA during the afternoon,and 47 to 68 dBA during the night. Due to these circumstances,the temporary increase in noise due to construction is considered to be a less than significant impact. OTETRA TECH 8 August 2023