Background
Barhale were appointed to deliver this project which saw the diversion of a large diameter sewer in Ruislip in order to allow HS2 construction to progress. We were commissioned to undertake noise, vibration and dust monitoring for the duration of the works and to advise on variations to the section 61 application for periods of weekend and night time tunnelling.
What we did
Baseline Noise Survey
Baseline noise levels were measured prior to commencement of HS2 construction works in the vicinity of the Greenway Sewer Diversion works.
A review of measured sound levels revealed exceedances of the noise limits set by the Section 61 consent from the London Borough of Hillingdon. These exceedances occurred predominantly during the night and early morning hours (07:00-08:00) and were attributed to ambient sound levels rather than the construction activities.
We were tasked with re-baselining ambient sound levels accounting for variability in noise levels and providing meaningful action levels for the works. The revised baseline sound levels were added to the predicted construction noise levels to establish more effective trigger levels and limits.
Challenges Identified:
- Noise Exceedances: The upper noise limit in the Section 61 consent was based on predicted construction noise levels, which were often below the ambient sound levels. This led to exceedances during night-time and early morning hours.
- Ambient Noise Factors: Regular operation of trains on the Chiltern Railway and birdsong, particularly during the dawn chorus, contributed to the variation in baseline sound levels.
- Concurrent Works: Works by SCS JV as part of the HS2 West Ruislip portal project also influenced the noise levels, necessitating a cumulative assessment of construction noise.
Noise Monitoring
We undertook continuous noise and vibration monitoring, that provided the clinet with live access and email alerts for exceedances. The monitoring systems we used conformed to the HS2 Technical Standard for Sound, Noise, and Vibration Instrumentation and Monitoring.
Conclusion
The re-baseline exercise considered hourly resolution to account for varying ambient sound levels throughout the night, ensuring effective noise management and compliance with the Section 61 consent.
Continuous monitoring and adherence to best practicable means demonstrated the project team’s commitment to minimizing noise impacts on the surrounding community.
