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5.7 NOISE representing each piece of equipment that produces a significant amount of noise. The sound power levels representing the standard performance of each of these components are assigned based either on field measurements of similar equipment made at other existing plants, data supplied by manufacturers, or information found in the technical literature. Using these standard power levels as a basis,the model calculates the sound pressure level that would occur at each receptor from each source after losses from distance,air absorption, blockages, etc. are considered. The sum of all these individual levels is the total plant level at the modeling point. The A-weighted sound power levels for the major noise sources used in the model are summarized in Table 5.7-11. TABLE 5.7-11 Summary of Sound Power Levels Used to Model LEC Plant Operations Plant Component Sound Power Level, dBA Combustion Turbine Generator 115 Steam Turbine Generator 111 HRSG 106 Stack 104 Cooling Tower 116 GSU Transformers 105 Operational noise from LEC,with noise control incorporated in the design,is not anticipated to exceed 45 dBA at M1 or M2,44 dBA at M3 or 42 dBA at M4. These levels are consistent with the City of Lodi s 5 dBA increase over nighttime ambient(Leq) levels. They also comply with San Joaquin County's 45 dBA nighttime limits for stationary sources and result in increases of 5 dBA or less above existing L90's consistent with the CEC's CEQA criteria. The specifications for the requisite noise controls will be refined during the detailed project design phase and may include silencers,barriers or enclosures. 5.7.3.3.4 Tonal Noise At the nearby residential locations,no significant tones are anticipated. That is not to say that audible tones are impossible—certain sources within the plant, such as the combustion turbine inlets,transformers,pump motors, and cooling tower fan gearboxes have been known to sometimes produce significant tones. LEC will anticipate the potential for audible tones in the final design and specification of the plant's equipment and take necessary steps to prevent sources from emitting tones that might be disturbing at the nearest receptors. 5.7.3.3.5 Ground and Airborne Vibration Similar combined-cycle facilities have not resulted in ground or airborne vibration impacts. The proposed project is primarily driven by gas turbines exhausting into a HRSG duct and a stack silencer. These very large ducts reduce low-frequency noise,which is the main source of airborne-induced vibration of structures. It is LEC's intention to anticipate the potential for low-frequency noise in the design and specification of the plant's equipment and take necessary steps to prevent ground or airborne vibration impacts. SAC/371322/08234009(LEC_5.7_NOISE.DOC) 5.7-15