Sound, vibration and mitigation
The Environmental Statement distinguishes sound issues arising from construction and those arising from operation. During the construction phase, reliance will be placed heavily on the application of the Code of Construction Practice (COCP).
The full details of the approach to the construction process can be found in Volume 2 section 6.3 and Volume 5: Appendix CT-003-000/1. The approach puts the onus firmly onto the contractors undertaking the construction work. They will be monitored and the monitoring data will be made available to the local authorities – though it is not clear from the Environmental Statement report, CFA 11, para 11.3.3, page 206, what the intervals will be for supplying monitoring data to the local authorities.
It is anticipated by HS2 Ltd that in accordance with the COCP, there will be appropriate visual and sound mitigation screening around sites and areas of work. This should operate in tandem with noise and vibration control at source through the use of quiet and low vibration equipment in all its forms. There will also be control and monitoring on working hours. There should also be specific mitigation measures to protect properties with individual issues due to their location particularly close to construction works.
HS2 Ltd.’s assessment of the results of such measures is that:
- “the avoidance and mitigation measures reduce noise inside all dwellings from the construction activities such that it is does (sic) not reach a level where it would significantly affect residents.” (CFA 11 report, para 11.4.11, page 208)
- “the measures also reduce the adverse effects of outdoor construction noise on the acoustic character around the local residential communities such that the effects are not considered to be significant.” (CFA 11 report, para 11.4.12, page 208)
A range of avoidance and mitigation measures are also proposed for the operations phase. These include:
- Track specified to reduce noise
- Design to reduce aerodynamic noise from pantographs
- A maintenance regime specified to reduce noise
- Incorporation of noise barriers in the form of landscape earthworks, noise fence barriers, and/or “low-level” barriers on viaducts.
Locations of noise barriers are shown in the series of maps which can be seen in the map series SV-05 (Volume 2, CFA 11 Map Book). There it can be seen that across Stoke Mandeville and the west of Aylesbury, noise barriers will vary in height from 3 metres to 5 metres with the resultant variation in the spread of airborne noise effects. There will also be visual screening of barriers where considered appropriate.
Again, where specific properties are affected severely, additional mitigation will be offered in the form of insulation.
The Environmental Statement then concludes that (by para number in the CFA 11 report):
- “11.5.29 – The mitigation measures reduce noise inside all dwellings such that it does not reach a level where it would significantly affect residents.
- 11.5.30 – The avoidance and mitigation measures in this area will avoid noise and vibration adverse effects on the majority of receptors and communities including shared open areas.
- 11.5.31 Taking account of the avoidance and mitigation measures and the local context, the residual permanent noise adverse effects on the acoustic character of the communities closest to the Proposed Scheme at the southern edge of Stoke Mandeville; the western edge of Stoke Mandeville; the south-western edge of Aylesbury; and Sedrup are considered significant.
- 11.5.32 – Beneficial noise effects have been identified on the acoustic character around dwellings facing the Risborough Road in Stoke Mandeville due to a reduction in road traffic caused by the Proposed Scheme. The church of St Mary the Virgin at Stoke Mandeville would also benefit from this reduction.
- 11.5.33 – On a worst case basis, a significant noise effect has been identified on BookerParkSchool. There is a minor risk that noise from the Proposed Scheme disturbs outdoor teaching activities, or teaching activities inside when the windows are open.
- 11.5.34 – HS2 Ltd will continue to seek reasonably practicable measures to further reduce or avoid these significant effects. In doing so HS2 Ltd will continue to engage with stakeholders to fully understand the receptor, its use and the benefit of the measures. The outcome of these activities will be reflected in the Environmental Minimum Requirements.”