SU0014502 - Laserfiche WebLink

Home Browse Search

Administrative Draft Environmental Impact Report Gill Medical Center Project relatively slow-turning main rotor.This noise is more pronounced when the helicopter is on the ground and decreases as the aircraft ascends. As such, helicopter operations when the helicopter is on the ground (landing and takeoff events), has been calculated using the Sound PLAN 3D noise model.The results of this model can be found in Draft EIR Appendix H. Previous noise measurements taken by ECORP Consulting, Inc., using a Larson Davis SounclExpert LxT precision sound level meter, of a single helicopter taking off generates a noise level of 87.0 dBA Lmax at 330 feet distant, and 87.9 dBA Lmax at the same distance while landing, with each event lasting less than five minutes in duration. (Lmax is the maximum A-weighted noise level during the measurement period.) Thus, based on an attenuation rate of 6 dBA per doubling of distance, a noise level of 124.3 dBA Lmax at a distance of 5 feet can be expected and was used in the modeling. Table 4.15-13 shows the predicted helicopter activity Project noise levels at nearby sensitive receptors and Figure 4.15-3. Project Onsite Exempt Source Noise Generation depicts the predicted noise levels and site locations listed in Table 4.15-13. As shown in Table 4.15-13, noise levels could reach up to 91.8 dBA at the nearby noise- sensitive receptors during helicopter landing and takeoff events. These events, similar to an emergency siren, would be intermittent and temporary, enduring less than one minute, and therefore would not constitute a substantial change in the existing noise environment. Additionally, per Section 9-1025.9, Noise, of the County's Municipal Code any mechanical device, apparatus or equipment used, related to, or connected with, emergency activities or emergency work shall be exempt from noise standards. Furthermore, as previously mentioned, the noise generated from a helicopter is more pronounced when the helicopter is on the ground and decreases as the aircraft ascends. An observation by ECORP Consulting, Inc. during the event of a helicopter takeoff, approximately 300 feet from where the helipad is located, found a noise level of approximately 70.2 dBA when the helicopter was approximately 85 feet above the ground.Thus, once in flight the helicopter would have a rapidly reducing noise effect on the surrounding noise environment. Noise 4.15-30 October 2021