14 ATTACHMENT 04 - Laserfiche WebLink

If an exception is not feasible, noise mitigation measures would be required to reduce the noise 22 feet away by approximately 5 to 6 dBA. The only practical option would be a sound wall or a specially-designed wooden fence structure capable of reducing noise levels by 5 to 6 dBA. Based on the proposed plans for the 7-Eleven carwash, the clearance at the exit would have a height of eight feet; therefore, the minimum height for the proposed noise barrier would also need to be eight feet. The proposed noise barrier would start at the wall of the exit and extend slightly east, just outside the exit driveway of the carwash. Positioning the wall a few feet away from the edge of the exit driveway is recommended for the benefit of the carwash customers. The total length of the proposed noise barrier, which is shown in Figure 5, would be approximately 55 to 60 feet. The southernmost section of the proposed barrier extends beyond point of required mitigation due to the corner effects of noise barriers. This extension is recommended to ensure effectiveness of the sound mitigation measure. The proposed noise barrier design consists of a fence with two solid wood layers rigidly connected. There should be no holes or gaps anywhere along either layer of wood. Furthermore, there should not be any gap where the fence touches the ground. All joints between the wooden boards or sheets of wood should be supported by structural elements or caulked. Additionally, a layer of sound-absorptive material could be applied between the two parallel wooden fence layers. An alternative design could include a sound wall of the same dimensions made out of stucco or blocks. Similar to the wooden fence design, sound walls made of these materials would also need to be solid, with no holes or gaps on the wall or at the base of the wall where it meets the ground. The total noise reduction that could be expected from both the proposed fence and the sound wall designs would be at least 5 to 6 dBA. Figure 5 shows the predicted noise levels just inside the proposed noise barrier and the distance at which these levels were calculated. Figure 6 shows the predicted noise levels at the south and southeast locations of the property line, assuming the 8- to 10-foot noise barrier was constructed as shown. A noise expert should be consulted during the final design phase of the project to confirm final design and dimensions. Page 17