52.


The Environmental Protection UK guidance document ‘Development Control: Planning for Air Quality 2010 Update’ (EPUK 2010) provides an example of criteria for magnitude of change and related significance of quantified impacts as a result of a development. Table 20.15 presents the magnitude of change in air pollutant concentration descriptors.


Table 20.15 Definitions of the Different Magnitude Levels for Receptors Magnitude of Change Large


Medium Small


Imperceptible


20.4.3.2.3 Significance 53.


Increase 5 – 10% Increase 1 – 5% Increase < 1%


The impact significance descriptors that take account of the magnitude of change and the concentration in relation to the air quality Objectives are shown in Table 20.16.


Table 20.16 Air Quality Impact Descriptors for Changes to Annual Mean Pollutant Concentrations at a Receptor


Absolute Concentration in Relation to Objective / Limit Value at Receptors


Above Objective / Limit Value With Scheme (>40 µg.m-3)


Just Below Objective / Limit Value With Scheme (36 – 40 µg.m-3)


Below Objective / Limit Value With Scheme (30 – 36 µg.m-3)


Well Below Objective / Limit Value With Scheme (<30 µg.m-3)


Magnitude of Change Large


Major Adverse


Moderate Adverse


Minor Adverse Minor Adverse


Medium


Moderate Adverse


Moderate Adverse


Minor Adverse Negligible


Small


Minor Adverse Minor Adverse


Negligible Negligible


Note: Well below Objective = < 75% of the Objective level. An ‘imperceptible’ change would be described as ‘negligible’, in accordance with EPUK guidance (EPUK 2010).


Annual Mean NO2/PM10 Increase > 10%


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm


Chapter 20 Air Quality Page 21


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