Air quality assessment – what every developer and design team should know and do
Submitting a planning proposal in an area where there are people and property within 350 metres of the site boundary? You need to undertake an air quality assessment and consider mitigation actions as early as possible.
There is an air quality crisis in the UK – and the property and construction sector has an important role to play in tackling air pollution. According to the Royal College of Physicians 40,000 deaths a year in the UK are attributable to outdoor air pollution, with the young, old and those with pre-existing lung or heart conditions, particularly at risk. The latest updated London Atmospheric Emissions Inventory showed that every person in London is breathing air that exceeds World Health Organisation (WHO) limits for a damaging type of particle known as PM2.5, and nearly 95% of Londoners live in areas that exceed the limit by 50% or more.
Air quality standards are concentrations recorded over a given time period, which are considered to be acceptable in terms of the effects of each pollutant on health and on the environment. These pollutants, measured in µg/m3, include particulate matter PM10 and PM2.5, nitrogen dioxide (NO2), ozone, sulphur dioxide, polycyclic aromatic hydrocarbons, benzene, carbon monoxide and lead.
The UK has National Air Quality Objectives (NAQOs) and an EU limit with which to comply – but these are being frequently exceeded. London is breaking legal and World Health Organisation limits for nitrogen dioxide (NO2) and particulate matter (PM), and is not expected to reach compliance with the legal limits on NO2 until at least 2025.
EU Directive 2008/50/EC1 on ambient air quality and cleaner air for Europe (the CAFÉ directive) sets out the ambient air quality standards for NO2 and PM10, to be achieved by 1st January 2010 and 2005 respectively. The Air Quality Standards Regulations 2010 implements the requirements of the Directive into UK legislation. The UK Government applied for a time extension for compliance with the NO2 limit values until 2015 for a number of areas throughout England and Defra on behalf of the UK Government produced new Draft Plans for consultation to improve air quality in the UK in order to meet the EU targets in the shortest possible time. The plan for the Greater London Area sets out a range of measures to reduce NO2 concentrations and indicates that with these measures air quality in London will be compliant by 2025.
A main factor causing this air pollution is diesel combustion – from cars and also diesel generators and diesel-powered machines, such as diggers used on construction sites, combined with dust thrown into the air by spoil lorries. Diesel vehicles emit about 40% of the capital’s total NOX emissions and a similar proportion for PM10. In 2015, it was estimated that up to 12% of NO2 and 15% of PM pollution in London comes from construction and demolition activity. It is only likely to get worse; given the number of major developments already underway and others to follow shortly.
In terms of air quality, the National Planning Policy Framework (NPPF) states that planning decisions on individual applications in England must prevent development from contributing to, or being put at unacceptable risk from, unacceptable levels of air pollution. Where a local authority’s review and assessment of its air quality identifies that air quality is likely to exceed the NAQOs, it designates these areas as Air Quality Management Areas (AQMAs) and draws up an Air Quality Action Plan (AQAP).
Planning policies promote compliance with or contribute towards achievement of EU limit values and NAQOs, taking into account the presence of Air Quality Management Areas (AQMAs) and the cumulative impacts on air quality from individual sites in local areas. Planning decisions will reflect whether the project complies with the Local Air Quality Action Plan.
For example, the London Plan (Ref. 13), ‘Improving air quality’ states that development proposals should:
- minimise increased exposure to existing poor air quality and make provision to address local problems of air quality (particularly within Air Quality Management Areas (AQMAs),
- be at least ‘air quality neutral’ andnot lead to further deterioriation of existing poor air quality (such as areas designated as AQMAs,
- ensure that where provision needs to be made to reduce emissions from a development, this is usually made on-site,
- where the development requires a detailed air quality assessment and biomass boilers are included, the assessment should forecast pollutant concentrations.
An Air Quality assessment typically establishes the baseline air quality, including sensitive receptors (locations that may be affected by dust emissions during demolition and construction or emissions from plant work during operation). Detailed calculations are undertaken to establish the likely emissions, with consideration of weather conditions and topography, to determine the resulting concentration of pollutants at the proposed development. Dust impacts during the construction phase and air quality impacts expected during the operation of the new development are assessed; and a mitigation strategy to limit residents’ and local community exposure to elevated concentrations of air pollutants is provided; along with a consideration of whether the proposals would meet the Air Quality Neutral benchmark emissions.
There are different types of receptors: A ‘human receptor’ refers to any location where a person or property may experience the adverse effects of airborne dust or dust soiling, or exposure to PM10 over a time period relevant to the air quality objectives, as defined in the Government’s technical guidance for Local Air Quality Management. An air quality assessment will normally be required where there is a ‘human receptor’ within 350m of the boundary of the site; or 50m of the route used by construction vehicles on the public highway, up to 500m from the site entrance(s). An air quality assessment will normally be required where there is an ‘ecological receptor’, such as a waterway, within 50m of the boundary of the site; or 50m of the route(s) used by construction vehicles on the public highway, up to 500m from the site entrance(s). The overall sensitivity of the development area to dust soiling, human health impacts and ecological receptors is determined by reviewing the sensitivity of the receptors and distance from the source. Also, a desk based review of potential industrial pollution sources should be undertaken to identify any significant industrial or waste management sources of air pollution that are likely to affect the proposed development with regard to air quality.
A set of robust mitigation measures covering every stage of the development is essential. Mitigation during construction phase might include good site management to control the dust emissions from demolition and construction and limit dispersion. These measures should be set out in the Dust Management Plan which would form part of the proposed development’s overall Construction Management Plan and be accompanied by a stakeholder communications plan.
Other measures include soft stripping inside buildings before demolition (retaining walls and windows in the rest of the building where possible, to provide a screen against dust), ensuring effective water suppression is used during demolition operations, and avoiding explosive blasting, and removing any biological debris or damp down such material before demolition. During the earthworks phase, re-vegetate earthworks and soil stockpiles to stabilise surfaces as soon as practicable, and only remove the cover in small areas during work and not all at once.
The Dust Management Plan should be approved by the local authority and is where all dust and air quality complaints should be recorded, along with the source and action taken. Regular site inspections should be carried out to monitor compliance with the plan and inspection results recorded. Solid screens or barriers should be erected around dusty activities or the site boundary that are at least as high as any stockpiles on site. All vehicles should switch off engines when stationary, and there should be an adequate water supply on the site for effective dust/particulate matter suppression. During construction, sand and other aggregates should be stored in bunded areas and not allowed to dry out, while fine powder materials should be delivered in enclosed tankers.
Water-assisted dust sweeper(s) should be used on the access and local roads, to remove, as necessary, any material tracked out of the site; hard surfaced haul routes should be installed and regularly cleaned. Another mitigation measure is to implement a wheel washing system (with rumble grids to dislodge accumulated dust and mud prior to leaving the site).
Including green infrastructure design – such as green roofs and walls, and tree and hedging landscaping – plays a significant mitigation role in reducing air pollution too. Green roofs and walls have multiple benefits beyond air pollution mitigation: supporting biodiversity, reducing energy consumption, managing runoff water, mitigating the urban heat island effect and noise pollution. Green infrastructure needs to be matched to the building’s context; for example, hedges are more effective in improving air quality than higher level trees in ‘street canyon’ settings, while road pollutants dispersion is improved by installing vegetation barriers in open road configurations.
The site’s parking spaces and proximity to road and rail links influences the transport impacts on air quality. Pollutant emissions from road traffic within the local road network will be impacted by whether any new roads are being laid as a result of the new development, or if there will be road humps used to limit traffic speeds and improve safety, which can in turn increase emissions through vehicles braking and then accelerating. Developing a detailed travel plan which encourages sustainable means of transport will also mitigate the impacts of increased traffic to the area
An efficient plant specification, as part of the development’s energy strategy, can have a positive impact on air quality. This could include for example, low NOx gas condensing boilers, air handling units with separate supply and extract fans or heat recovery units to reduce energy demand. If passive ventilation is not appropriate, mechanical ventilation that is equipped with filters could be specified to ensure the air quality remains high to protect future building users from poor air quality. NOx filters could be installed to the incoming air supply on adjacent buildings to provide building users with a clean air supply. Alternatively, locate plant equipment at an adequate distance from the road to ensure air intake is of better quality.
Undertaking an air quality assessment is often a requirement of the planning process, and essential for developers concerned with the health and wellbeing of the future building’s users and wider public’s health. Having this intelligence as early as possible means the most effective set of mitigation measures can be developed and implemented from design stage, and ultimately deliver a better building and stronger planning proposal.
Eight Associates offers basic and detailed air quality assessment services – please get in touch to discuss your requirements. T 020 7043 0418, firstname.lastname@example.org.