Noise
Noise created through the process of aggregate recycling can have a significant impact on the environment. It is therefore important to recognise this and manage it carefully.
The Integrated Pollution Prevention Control (IPPC) Directive, as implemented in Scotland and Northern Ireland through the Pollution Prevention and Control (PPC) Regulations, and through the Environmental Permitting Regulations in England and Wales includes noise as one of the environmental effects to be considered. Also stand–alone recycling facilities and those associated with mineral and waste operations will be subject to local authority control under the statutory nuisance provisions of the Environmental Protection Act 1990 as amended. An abatement notice can be served by the Local Authority where a statutory noise nuisance occurs in an area. This may specify necessary works and a timescale for the notice to be complied with. Failure to comply with the notice is an offence.
Section 60 of the Control of Pollution Act 1974 allows local authorities to serve a notice on any construction and demolition operations that are being, or are going to be, carried out, and specify the plant or machinery that can or cannot be used, working hours, and levels of noise that may be emitted.
Guidance on the interaction between control of noise imposed by planning conditions and by statutory nuisance legislation is given in:
Noise from the production of recycled aggregates is normally not sufficiently high to cause physical damage to property or hearing, but it may well be high enough to cause disturbance. Noise is therefore a 'nuisance' issue for recycled aggregates operations.
Crushing and Screening
Crushing and screening plants are normally hydraulically activated with the hydraulic pressure generated by a diesel engine, which is one source of noise. In both, noise is also created by material impacting the metal hoppers and chutes of the machine. The crusher produces noise from the impact of the jaws or hammers on the material. In screens, the movement of the material across the screen surface can cause noise.
Vehicle Movements
Also, there is the noise associated with vehicle movements, including tipping and loading of material and the actual vehicles themselves; for example: the noise from large diesel engines, hissing air brakes, the body of an empty lorry going over a bump in the road (known as a ‘body slap’), bleepers that come on when the reverse gear is selected and are used to protect people by warning them that a vehicle is reversing (a common cause of complaint).
Where possible the plant should be located away from noise sensitive neighbours and vehicle routes arranged so that reversing is not required. Reversing generally requires revving of engines and the possible use of audible reversing warnings, where alternatives to reversing alarms cannot be found.
Manage and Control the Way Plant is used
Site management should try and programme working as far as possible to match the surrounding noise climate and sensitivities. Councils normally expect contractors to adhere to the following hours of work, where the work causes noise audible at the site boundary in residential areas: Monday to Friday 8:00 am to 6:30 pm, Saturday 8:00 am to 1:00 pm, and Sundays and Bank Holidays: No working. However, in the commercial centre of cities, the office workers would be working during the day and so the area would be more sensitive to noise than in the evenings.
Where noise operations are unavoidable it is recommended to maintain good community relations and warn nearby residents in advance. It may be possible to substitute newer quieter plant for existing plant, so that the actual noise output forms part of the purchasing decision.
The Noise Emission in the Environment by Equipment for use Outdoors Regulations 2001 (SI 2001/1701) set maximum noise output levels for construction plant made or imported into the EC.
Silence Existing Plant
It may be possible to carry out simple modifications of existing plant, for example by lining chutes with resilient material, so as to reduce noise.
Use fences and bunds - This is a common way of reducing noise beyond the site boundary. To be effective, they should obscure the line of sight between the noise source and the receptor, but without having an adverse visual impact in their own right. Sometimes temporary stockpiles can be located to act as noise barriers.
Enclose noise sources - A more expensive way of reducing noise is to enclose permanent crushers and screens within a building, with the added benefit of reducing dust emissions. Also, dust mitigation measures such as covers for chutes can help reduce noise.
Strategic approaches to noise reduction - A strategic decision at the planning stage, which can affect noise levels and who is affected, is whether crushing occurs on or off site. Both options need weighing up, as there is the perceived noise associated with the mobile crusher while the latter results in more traffic movement and noise. One local authority states the following items should be considered by Contractors as the best practicable means to minimise noise on the site.
The list is not exhaustive, and could equally be applied to the use of recycling equipment for aggregate, concrete and asphalt:
- The quietest plant and machinery available should be used. For example, hoists and cement mixers should be electrically powered wherever possible.
All equipment should be properly maintained, so that no unnecessary noise is caused. - Acoustic covers to such items as compressors and generators should always be kept in place.
- When machinery is not actually in use, it should be switched off and not left running.
- Stationary noise sources should be sited, whenever possible, away from noise sensitive areas, such as nearby dwellings. Acoustic barriers should be used to shield such noise sources. These can be purpose-built, or sometimes materials on site, such as bricks, sheds or even mounds of earth can be used.
- Employees should be informed of the noise control measures required by, or agreed with the Council and should receive training where necessary.
