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Control programme Part 2 – Disturbances to surroundings

Noise, structure-borne sound and vibrations are unwanted disturbances that arise around construction works. These types of sound mainly arise during above-ground construction next to open shafts.

Noise and vibrations are the factors that can cause most disturbance during the construction of the West Link. The sounds are mainly caused by our excavation works above ground when sheet piling or when removing aggregates. Below ground, it is drilling and blasting that create the most noise. The last two years are a quieter phase as this involves work with installations such as signalling and telecommunications systems in the tunnel.

Sound can reach us people in different ways, directly through the air or indirectly through solid materials. When we talk about noise, we are usually referring to sound transported through the air. Structure-borne sound is sound propagated through rock or buildings and then transported through the air. Vibrations spread in solid materials, rock or buildings, and can be felt but not heard directly.

Two thirds of the West Link tunnel run through rock, and we blast out underground rock step by step. Our blasting works give rise to structure-borne sound and vibrations that are limited in duration and limited to the immediate area of blasting operations. All buildings within 150 metres of the West Link construction have been assigned a maximum vibration value. These values have been set mainly to prevent our construction from damaging surrounding buildings and activities. When the construction of the West Link is in progress, we also measure vibrations in the nearby buildings.

One third of the tunnel runs through earth and clay, where we excavate open shafts. Before we can excavate the shafts, we need to get support structures in place by means of piling and sheet piling. We have inventoried sound-sensitive environments and calculated levels of noise and structure-borne sound in order to assess where we should put up shielding.

The control programmes
- Ground water, e.g. ground water level, water leaking into shafts
- Disturbances to surroundings, e.g. construction noise, vibrations
- Surface water, e.g. water level, water quality
- Flora and fauna, e.g. natural environment, fish
- Air quality, e.g. air quality above ground outside the work area
- Cultural environment, e.g. ancient monuments, vibration-sensitive settlements of historic cultural value