Acoustics case study
HS2 Euston Station Development
Background
In addition to obvious improvements in connectivity with other cities, the planned arrival of HS2 at Euston is expected to be hugely beneficial in the long term to the local area. However, the findings of the Environmental Statement identified potential for significant adverse impact due to construction works upon local receptors.
This was understandably concerning for a number of charitable organisations located very close to the station, including the Royal College of GP’s, Wellcome Trust and the Magic Circle.
We represented these organisations and gave evidence to the Commons select committee considering the HS2 Bill explaining the importance of giving appropriate consideration to their concerns.
Our representations were successful and resulted in HS2 making various commitments and putting agreements in place to minimise the impact on my clients’ activities.
Challenge
The predicted levels of noise and vibration varied significantly at the 12 different buildings and at different stages of the Station works. The building uses were also highly variable and so the potential acoustic impacts were many and varied. One of the most serious issues was that every future GP in England sits their final exams in the Royal College of GP’s building and the rooms being used were located right in the thick of construction works. The “doomsday scenario”, which had to be avoided at all costs, was insufficient GP’s coming into the NHS. Furthermore, the College directly abuts a building which was due to be demolished.
Solution
Initially, we felt that the best way to convince the Commons Select Committee of our case was to established how “acoustically resilient” each building was in its current state. We estimated the facade sound insulation (by visual inspection) for every noise sensitive space and determined what level of construction noise could be tolerated inside each room, based on both the existing ambient noise level and use of each space. Adding the facade sound insulation to the internal noise limit gave a good indication of how loud construction noise could be outside before the space became unusable.
Comparing these limits to the predicted noise levels in the ES highlighted which rooms would be problematical and from this we were able to ascertain the likely mitigation required. A similar approach was adopted to evaluating construction vibration.
This was successful, as the Select Committee’s report required HS2 to provide the necessary protection from the effects of noise and vibration by way of legally-binding agreements between HS2 and each organisation.
Before works could start, HS2’s acoustic consultant conducted a more detailed study of each building with our assistance so we could agree a reasonable criterion, façade reduction and therefore external noise limit for each sensitive space, whilst on site. This collaborative approach, coupled with our knowledge of the buildings, helped speed the process up significantly and HS2’s acoustician agreed that our pragmatic approach was sensible. The experience of working for “the other side” (i.e. on Crossrail for a contractor) enabled us to take a balanced view to protect my clients whilst avoiding the expense to the taxpayer of unnecessary mitigation.
Although this approach was deemed acceptable for the majority of the hundreds of rooms involved, HS2 agreed to measure the actual façade sound insulation for the most sensitive rooms. We used their results to create auralisations in the actual spaces (ie. by playing recordings of construction noise using a loudspeaker) to allow the building users to experience what the construction would sound like. Very few people can imagine this based on just a decibel level.
These practical demonstrations convinced the RCGP’s Board of Trustees that they did not need to relocate their exam suite which avoided considerable disruption and also saved the HS2 project a vast amount of money.
Trigger Action Plans were drawn up by HS2 as a result and agreed with each group member. These identified any mitigation works needed (mainly secondary glazing). The mitigation was completed prior to construction starting and, to date, all HS2 works have been successfully completed with no adverse impact.
