Crossrail Contract 405 involved the construction of the new 240m long and 30m deep 3-level box for the new Crossrail Paddington Station in Westminster. Constructed over a 6 year using major diaphragm walling techniques in close proximity to noise and vibration sensitive assets period including occupied multi-storey office blocks; a Grade I listed building known as MacMillan House (NR Estates); and the London Hilton Hotel.
Southdowns managed the continuous monitoring of construction dust, vibration and noise over a period of more than 6 years at local sensitive receptors, including a number of Special Case receptors and residential properties. This required careful liaison with private and public stakeholders to arrange access for scheduled and unscheduled site visits for equipment maintenance and re-location purposes. Monitoring data was managed and reported to the client via monthly and bi-weekly reports with specific interests in demonstrating compliance with special case trigger action plan requirements. Over 100 attended day and night-time noise and vibration surveys were undertaken throughout the duration of the project, focussing on the commencement of major phases of construction. Attended noise surveys include audits of Best Practicable Means (BPM) and observations of mitigation to ensure that all possible measures are employed on site. Specific surveys were designed to measure the vibration transfer functions between external locations and various internal locations within the sensitive buildings as part of the detailed vibration risk assessments carried out. During particularly sensitive demolition and re-construction works within, and in close proximity to, the original featured 19th century station fabric, up to 8 no. web based vibration monitors were installed which were individually linked to flashing beacons to provide instant notifications to site operatives when vibration thresholds were exceeded.
Diaphragm walling was required within 5m of the heritage assets. Working collaboratively with the Environment and Heritage teams, trials using various sized breaking machines were conducted to enable assessments of vibration damage risk to the heritage assets and to inform the risk of human disturbance to Union led train driver personnel. The Parliamentary U&As given to building owners along Eastbourne Terrace required separate consideration of airborne noise, groundborne vibration and structureborne noise inside the affected buildings. A major mitigation protocol was developed for the works considering all the constraints. Secondary glazing was installed along large swathes of the office and hotel facades overlooking the worksite to reduce airborne noise ingress into occupied rooms including train driver accommodation. External Trigger Action Levels were developed for both noise and vibration at each receptor, and certain sized machines and techniques were restricted from use within zoned areas. The results of the trials enabled our client to gain permission to relax the contractual vibration screening limits applied to the heritage assets, allowing the work to be completed more effectively and maintain programme. The on-site mitigation package required the use of innovative techniques for d-wall break down (by avoiding use of hydraulic breakers) including: diamond drilling; hydraulic muncher and toothed excavator attachments; and coring, bursting and wire sawing. The findings of the technical work were
documented in a comprehensive Trigger Action Plan for the Grade I Listed MacMillan House and the London Hilton Hotel implemented throughout the works.
We were part of the community liaison activities during these works ensuring that affected parties were kept informed of the technical work and mitigation measures being employed. Crossrail published our work on their Legacy Learning web-site recognising the innovative work as ‘world class’. Learning Legacy – Vibration Management and Heritage Assets
Provided a multi-disciplinary assessment of proposed changes to the temporary office arrangements near to Eastbourne Terrace, providing a detailed report in accordance with Crossrail’s environmental design management procedures to ensure compliance with the project’s environmental minimum requirements.
Noise from plant associated with the ventilation and cooling systems for the new station has been calculated to determine compliance with Crossrail’s Information Paper D25 controlling the noise from fixed installations.
