Noise Technical Reports
Based on the California Environmental Quality Act (CEQA) guidelines, there are several noise significance criteria, including whether a project would result in:
- Exposure of persons to or generation of noise levels in excess of standards established in the local general plan or noise ordinance or applicable standards of other agencies;
- A substantial temporary, periodic, or permanent increase in ambient noise levels in the project vicinity above levels existing without the project; or
- Exposure of persons to or generation of excessive ground-borne vibration or ground-borne noise levels.
For most projects, short-term community noise impacts from diesel-powered construction equipment and trucks is the primary concern. In some circumstances, long-term operational impacts from increased traffic and mechanical equipment such as heating, ventilation, and air conditioning (HVAC) systems can be an issue if receptors are near or adjacent to a project site. For a large industrial project such as a power plant, the use of large fans in air-cooled condensers can be a significant source of noise.
Our standard approach to noise analysis is both quantitative and qualitative. This approach includes calculation of logarithmically attenuated construction noise levels at receptor locations for comparison with community noise standards and discussion of the existing noise sources at or near a project site, usually traffic. In some cases, collection of background noise measurements may be needed. If there is an airport within 2 miles of the project site, evaluation of aircraft noise upon the project is usually required.
For quantitative analysis of construction noise impacts on nearby receptors, we use the U.S. Department of Transportation (DOT) Federal Highway Administration (FHWA) methodology, which utilizes typical noise levels based on actual noise measurements collected during the Boston “Big Dig” project (1991-2006). The FHWA method contains reference noise levels for over 50 types of construction equipment in common use, such as bulldozers, excavators, graders, and heavy trucks. Noise impacts are evaluated against community noise standards contained in the noise element of the City or County general plan for the vicinity of a project site.
Where needed, operational noise impacts from traffic or mechanical equipment can also be calculated or modeled using characteristic reference noise levels from technical publications and manufacturer data. The estimated noise impacts are then compared to applicable significance criteria as noted above. Once the significance of the noise impacts is determined, the analysis methodology and results are documented in a Noise Technical Report, which supports the CEQA document.