Example of spectrogram used to diagnose source of higher than normal vibration levels
Vibration and Noise Analysis for BART Walnut Creek
Bay Area Rapid Transit District
The San Francisco Bay Area Rapid Transit District is planning to install a new double crossover between the C1 and C2 tracks in the Pleasant Hill area. The crossover is located close to a number of residences and the additional noise and vibration from the crossover has the potential of causing impacts. ATS analyzed potential impacts for the environmental assessment phase and finalized the recommendations for the final design.
The ATS studies for the environmental assessment showed that sound walls would be necessary to reduce noise levels and that vibration levels would be close to the Federal Transit Administration impact thresholds. Through more detailed measurements during the final design, ATS was able to demonstrate that the current vibration levels are higher than normal because of the mix of concrete and wood ties that is currently installed. As part of the crossover construction, all the wood ties will be replaced with concrete ties, which will reduce vibration levels. As a result, no additional vibration mitigation will be required.