The main potential effects of the Proposed Development due to impacts on air quality include:

Transcription

1 9 AIR QUALITY 9.1 INTRODUCTION Terms of Reference for this Chapter This chapter presents an assessment of the likely significant effects due to emissions to air from construction, operation and decommissioning of the Keadby II project (henceforth the Proposed Development ). The baseline air quality environment around the Proposed Development site is described, potential effects identified, proposed mitigation measures listed and an assessment of the significance of residual effects is made. The main potential effects of the Proposed Development due to impacts on air quality include: effects on sensitive human and ecological receptors due to emissions from the combustion processes within the Proposed Development; effects on sensitive human receptors due to additional traffic generated during the construction and operational phase; and effects on sensitive human receptors due to dust emissions from construction activities. Keadby II was originally planned to be two industrial gas turbines operating on natural gas or fuel oil (the Consented Development). Recently, the plans for Keadby II have been revisited. The revised plans are for a plant design incorporating a single gas turbine, operating on natural gas only (the Proposed Development) with an associated waste heat boiler (WHB) and steam turbine. There are two possible options for the Proposed Development: a single-shaft design and a multi-shaft design. Both have been assessed in this chapter. This air quality assessment considers the emissions and environmental impacts of the Proposed Development and makes a comparison to the Consented Development. The 1992 Environmental Assessment made an assessment based on the results of atmospheric dispersion modelling. However, modelling approaches and assessment criteria have changed since that time; therefore in order to make the comparison with the Consented Development, the following process has been adopted. 1. The likely emissions from the Proposed Development have been assessed. 2. The likely emissions from the Consented Development have been assessed. 3. The likely significant effects on the environment from the Proposed Development have been assessed. 4. The likely significant effects on the environment from the Consented Development have been assessed. 5. Likely impacts from the Proposed and Consented Development have been compared. 9-1

2 6. Likely significant effects on the environment from the Proposed and Consented Developments have been compared. On the basis of the above assessment process, the main respects in which the applicant considers that the likely significant effects on the environment would differ from those described in the Environmental Assessment for the Consented Development have been described, In order to make a valid comparison, the air quality impacts of the Consented Development have been modelled using the same meteorological input data as for the Proposed Development. This approach has been taken for a number of reasons, including: the baseline has changed in terms of both air quality, meteorological data input to the model and the presence of features that can affect atmospheric dispersion; atmospheric dispersion modelling systems have advanced considerably; and there was no requirement in 1992 to assess effects on ecological receptors in the way that currently prevails. The Proposed Development will only be fuelled by natural gas; therefore no consideration is made of the impacts of emissions using liquid fuels. The emissions of interest for a gas fired plant are nitrogen dioxide (NO 2 ) in relation to human health, and oxides of nitrogen (NO x ) and deposition of nitrogen, in relation to sensitive ecological receptors Basis for the Assessment including the Realistic Worst Case Scenario It is assumed that the new plant (both Consented Development and Proposed Development) and the existing plant (Keadby I) will be operating at maximum capacity for 8,760 hours per annum, with the Proposed Development in supplementary firing mode which results in the highest NO x emissions, and lowest emission temperature. This approach is the most conservative approach, as in practice the plants will not operate at full capacity nor continuously; also the supplementary firing mode of operation will be occasional as required to meet demand. This approach also fully addresses potential cumulative impacts on air quality. In addition a maximum allowed NOx concentration of 50 mg / Nm 15% O 2 in the stack emissions has been assumed, whereas modern turbines are expected to perform well within this level. The detailed dispersion modelling is used to predict concentrations of pollutants at ground level locations outside the Proposed Development boundary, at sensitive human receptors and sensitive ecological receptors. Five years of hourly meteorological data are used, so that inter-annual variability is incorporated in the model. The results of the assessment are based upon the worst case result for any of the five meteorological years used. 9-2

3 For the purposes of this assessment the screening/ worst-case scenario conversion ratios for NO X and NO 2 recommended by the Environment Agency (1) have been used. Actual oxidation rates are dependent on the availability of O 3, distance from the source and wind speed. Hence, these conversion factors are considered conservative and are likely to result in higher estimations of the PC for NO 2 than would occur in reality. Some of the baseline data derived from local monitoring will include the contribution from the Keadby I plant whenever it was operating concurrently with sampling. However, Keadby I is understood to operate intermittently, and as a result understanding or isolating the contribution of Keadby I from the measured baseline is difficult. On this basis no correction to the baseline has been undertaken to account for existing contributions from Keadby I in assessing the impacts of Keady I and the Consented/Proposed Development together. This represents a worst case approach since Keadby I contributions may have been double-counted to some extent. The impacts at sensitive ecological receptors are defined on the basis of the highest impacts arising at any point on the designated habitat within the 10 km radius. Therefore, the predicted impacts may not actually be coincidental with the sensitive feature described. This approach is worst case. The significance of effects on ecological receptors is considered in the ecology assessment in Chapter 7 of this ES Consultation SSE is carrying out various formal and informal consultation activities as part of the s36 variation application. Consultation to date on the topic of air quality has been concerned with the Scoping Opinion (2). Scoping responses have been provided by several statutory consultees. The responses relevant to air quality are set out in the following table. (1) (2) Environmental Impact Assessment Scoping Report for the Keadby II Combined Cycle Gas Turbine Generating Station at Keadby, Lincolnshire; Regarding an application under the Electricity Generating Stations (Variation of Consents) (England and Wales) Regulations 2013 (March 2015) 9-3

4 Source Consultee Comment Response Natural England 2.2 Internationally and Nationally Designated Sites The ES should thoroughly assess the potential for the proposal to affect designated sites. European sites (for example, designated Special Areas of Conservation and Special Protection Areas) fall within the scope of the Conservation of Habitats and Species Regulations In addition paragraph 118 of the National Planning Policy Framework requires that potential Special Protection Areas, possible Special Areas of Conservation, listed or proposed Ramsar sites, and any site identified as being necessary to compensate for adverse impacts on classified, potential or possible SPAs, SACs and Ramsar sites be treated in the same way as classified sites. Under Regulation 61 of the Conservation of Habitats and Species Regulations 2010 an appropriate assessment needs to be undertaken in respect of any plan or project which is (a) likely to have a significant effect on a European site (either alone or in combination with other plans or projects) and (b) not directly connected with or necessary to the management of the site. Should a Likely Significant Effect on a European/Internationally designated site be identified or be uncertain, the competent authority (in this case the Local Planning Authority) may need to prepare an Appropriate Assessment, in addition to consideration of impacts through the EIA process. Sites of Special Scientific Interest (SSSIs) and sites of European or international importance (Special Areas of Conservation, Special Protection Areas and Ramsar sites) In this case the proposal is not directly connected with, or necessary to, the management of a European site. In our view it is likely that it will have a significant effect on internationally designated sites and therefore will require assessment under the Habitats Regulations. We welcome the intention to undertake a Habitats Regulations screening assessment as detailed in Section of the EIA Scoping Report. We recommend that this should form a separate section of the Environmental Statement entitled Information for Habitats Regulations Assessment. We note from Section of the report that effects on sensitive ecological receptors due to nitrogen and acid deposition will be considered. This should include consideration of effects on sensitive habitats which are interest features of the Humber Estuary and Thorne Moor SACs. We are pleased to note that the impacts on the Humber Estuary SAC of any variation to the existing water offtake will also be considered. 6. Air Quality Air quality in the UK has improved over recent decades but air pollution remains a significant issue; for example over 97% of sensitive habitat area in England is predicted to exceed the critical loads for ecosystem protection from atmospheric nitrogen deposition (England Biodiversity Strategy, Defra 2011). A priority action in the England Biodiversity Strategy is to reduce air pollution impacts on biodiversity. The planning system plays a key role in determining the location of developments which may give rise to pollution, either directly or from traffic generation, and hence planning decisions can have a significant impact on the quality of air, water and land. The assessment should take account of the risks of air pollution and how these can be managed or reduced. Further information on air pollution impacts and The impacts on sensitive ecological receptors have been assessed for both the Consented and the Proposed Development by air dispersion modelling using ADMS (see Section 9.4). The assessment followed the Environment Agency H1 guidance in terms of assessment of impacts on sensitive habitats, using the 1% of Critical Loads and Critical Levels threshold of significant contribution to potential impacts (see Section 9.2.2). The significance of effects on ecological receptors is reported in Chapter 7.

5 Source Consultee Comment Response the sensitivity of different habitats/designated sites can be found on the Air Pollution Information System ( Further information on air pollution modelling and assessment can be found on the Environment Agency website. Environment Agency North Lincolnshire Council Environmental Permitting The development will require a permit from the Environment Agency under the Environmental Permitting Regulations (England and Wales) We would advise you to contact Richard Croll, ( richard.croll@environment-agency.gov.uk) for further information and discussion about the permit application process. Under the Environmental Permitting (England and Wales) Regulations 2010 permitted sites should not cause harm to human health or pollution of the environment. The operator will be required to have appropriate measures in place at the site to prevent pollution to the environment, harm to environmental quality and human health, detriment to the surrounding amenity, offence to a human sense or damage to material property. Without such measure being in place, it is likely that we would reject any application received for an Environmental Permit under the Environmental Permitting (England and Wales) Regulations We expect new combustion developments to comply with the environmental performance standards in the EPR Technical Guidance Note: Combustion Activities (EPR1.01). We will justify any derogations we allow from these standards in our decisions. A permit application will need to include use of Best Available Techniques (BAT) or justification of alternative and/or choice of option where alternatives exist. Under the Environmental Permitting regime we will be including the following key areas of potential harm when making an assessment for the Permit: Management including energy efficiency and avoidance, recovery and disposal of wastes. Operations including liquid fuels, gaseous fuels and biomass. Emissions and monitoring including point source emissions to water, point source emissions to air, fugitive emissions and monitoring. Air Quality and control of Dust during Construction The scoping report notes that mitigation for the control of construction dust will be carried out in accordance with methods produced by the IAQM. This department can confirm that a dust mitigation plan will be required and subsequently approved before any construction can commence. The scoping report notes that the baseline air quality in the Keadby area is well below EU objectives. This department agrees with section concerning the potential effects that need to be included in the EIA. The use of the DMRB model to assess construction and operational traffic will also be required. ERM assessed impacts (Section 9.4.2) during operations for both the Consented and the Proposed Development by air dispersion modelling using ADMS, based upon maximum permitted emissions. Based upon the impacts to both human and ecological sensitive receptors, the Proposed Development is generally associated with lower impacts than the Consented Development. No further mitigation (see Section 9.5) is proposed at this stage, however it is expected the Proposed Development will have to comply with BAT in line with the recent changes introduced by the adoption of IED. ERM used the DMRB Screening Tool to assess impacts from construction and operational traffic (see Section 9.4.1), and ADMS (see Section 9.4.2) for operation of the gas turbines; for both the Consented and the Proposed Development.

6 Source Consultee Comment Response This department is pleased to note that an Atmospheric Dispersion model will be used for the assessment of for turbine designs and emission profiles, for both the previous consented development and for the proposed development.

7 9.1.4 Policy and Legislation Context Policy Policy relevant to the Proposed Development is set out in Chapter 3 of this ES. The table below identifies those policies that are relevant to air quality. Topic Overarching National Policy Statement for Energy(EN-1) National Policy Statement for Fossil Fuel Electricity Generating Infrastructure (EN-2) National Planning Policy Framework (NPPF) Planning Practice Guidance (PPG) North Lincolnshire Local Plan North Lincolnshire Core Strategy Air quality 5.2 Air quality and emissions 2.5 Air quality and emissions 11 Conserving and enhancing the historic environment Air quality - CS18 Sustainable resource use and Climate change Air Quality Standards and Guidelines for Human Health Within the UK the majority of the air quality standards relating to ambient air quality are based upon the European Union Air Quality Standards (1). The EU air quality standards relating to short and long term average concentrations nitrogen dioxide (NO 2 ) are pertinent to this assessment. The numerical values and averaging periods are discussed in Section Air Quality Standards and Guidelines for Ecology In addition to undertaking an assessment of the potential effects of emissions from the facility on human health, assessment of air quality impacts on protected ecological receptors has also been undertaken. Effects on sensitive ecological receptors primarily arise as a result of pollutant emissions by the following mechanisms: direct effects on flora due to increased concentrations of airborne pollutants; secondary effects on flora due to changes in soil chemistry brought about by deposition of pollutants to soil; and secondary effects on fauna due to changes in flora. (1) European Union (accessed April 2011) Air Quality Standards 9-7

8 The European Habitats Directive (1) sets out the legal framework requiring EU member states to protect habitat sites supporting vulnerable and protected species, as listed within the Directive. This Directive was incorporated into UK domestic legislation by means of the Conservation of Habitats and Species Regulations 2010 (2). This Directive requires the protection of certain sites including Special Areas of Conservation (SACs), Special Protection Areas (SPAs) and Ramsar sites. In addition, impacts on ecological receptors through worsening air quality and through deposition of acid and nutrient nitrogen to soils are predicted at nationally important ecology sites in the form of Sites of Special Scientific Interest (SSSIs) and any relevant locally designated habitat sites. The relevant standards and guidelines that provide a framework for assessing impacts on sensitive ecological receptors are derived from a number of sources: air quality standards for NO x (annual mean) for the protection of habitats are derived from European Union Air Quality Directives and are included in the AQS; air quality guidelines for NO x (24 hour mean) have been derived by the Centre for Ecology and Hydrology (CEH) and are set out in H1; and guidelines for the assessment of acid and nutrient nitrogen deposition have been derived according to habitat type, and are set out on the UK Air Pollution Information Service (APIS) website (3). On the basis of the above legislative framework and guidance, relevant critical levels (that relate to airborne pollutants) and site specific critical loads (that relate to deposition of materials to soils) have been established. These values represent the environmental criteria used in this assessment. Industrial Emissions Directive (IED) The IED is the successor of seven existing Directives, including the IPPC Directive and in essence is concerned with minimising pollution from industrial sources throughout the European Union through the implementation of established Best Available Techniques (BAT) for pollution control. The IED entered into force on 6 January 2011 and was transposed into national legislation by Member States by 7 January In the UK, IED is implemented through the existing Environmental Permitting Regulations, but requires a somewhat different approach to previous regimes, insomuch as the achievement of BAT is the explicit priority. The permit conditions including emission limit values (ELVs) must be based on the Achievable Emission Levels published in BAT Reference (BREF) notes. BAT conclusions (documents containing information on the emission levels associated with the best available techniques, which act as a summary (1) Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora (2) Statutory Instrument 2010 No. 490 The Conservation of Habitats and Species Regulations 2010 (3) Centre for Ecology and Hydrology (2010) UK Air Pollution Information Service 9-8

9 of BREF notes) are the reference for setting permit conditions. To determine BAT, the European Commission organises an exchange of information between experts from the EU Member States, industry and environmental organisations. This work is coordinated by the European IPPC Bureau of the Institute for Prospective Technology Studies at the EU Joint Research Centre in Seville, Spain. This results in the adoption and publication by the Commission of the BAT conclusions and BAT Reference Documents. The IED contains certain elements of flexibility by allowing the licensing authorities to set less strict emission limit values in specific cases. Such measures are only applicable where an assessment shows that the achievement of emission levels associated with BAT as described in the BAT conclusions would lead to disproportionately higher costs compared to the environmental benefits due to: a) geographical location or the local environmental conditions; or b) the technical characteristics of the installation. The competent authority shall always document the reasons for the application of the flexibility measures in the permit including the result of the cost-benefit assessment. Chapter III of the IED on large combustion plants includes certain flexibility instruments (Transitional National Plan, limited lifetime derogation, etc.). At the Permitting stage, consideration will need to be given to whether the Proposed Development will need to comply with the BAT AELs. The presumption is that it will be expected to, as a derogation for new plant would be highly unlikely. Local Air Quality Management The Environment Act 1995 requires local authorities to periodically review and assess air quality. Initially, a screening process was undertaken by local authorities to identify which pollutants, of the eight in the AQS at the time of the screening process, may be in excess of the air quality standards. Where pollutant concentrations were identified to be in excess of the standards, local authorities undertook a further investigation to identify exactly where standards were exceeded. On the basis of the results of this investigation, Air Quality Management Areas (AQMAs) were declared for the relevant locations and local authorities have developed Air Quality Management Plans setting out measures that will be taken to improve air quality in these AQMAs. Following this initial staged process, there is an on-going review and assessment process, which periodically reviews local air quality, with regard to changes that may cause impacts on the local air quality. These might include: new roads; changes in road layouts; other new development; new industry, closure or changes in existing industry, etc. On the basis of this on-going process, local authorities may declare or revoke AQMAs and update action plans accordingly. Where appropriate, AQMAs in the vicinity of the Proposed Development have been considered and local air quality management reports have been used to inform the baseline air quality. 9-9

10 No Air Quality Management Areas (AQMAs) for NO 2 have been declared within the study area. There are AQMAs in Scunthorpe (about 6.5 km to the east of the Proposed Development location), but these are only for particulate matter and situated outside the study area for operational and construction traffic. These are not relevant to this study. Environmental Protection Act 1990 Section 79(1) of the Environmental Protection Act 1990 (EPA 1990) states: Subject to subsections (1A) to (6A) below, the following matters constitute statutory nuisances for the purposes of this Part, that is to say: (a) any premises in such a state as to be prejudicial to health or a nuisance; (b) smoke emitted from premises so as to be prejudicial to health or a nuisance; (c) fumes or gases emitted from premises so as to be prejudicial to health or a nuisance; (d) any dust, steam, smell or other effluvia arising on industrial, trade or business premises and being prejudicial to health or a nuisance; (e)any accumulation or deposit which is prejudicial to health or a nuisance; (f) any animal kept in such a place or manner as to be prejudicial to health or a nuisance; (fa) any insects emanating from relevant industrial, trade or business premises and being prejudicial to health or a nuisance; (fb) artificial light emitted from premises so as to be prejudicial to health or a nuisance; (g) noise emitted from premises so as to be prejudicial to health or a nuisance; (ga) noise that is prejudicial to health or a nuisance and is emitted from or caused by a vehicle, machinery or equipment in a street or in Scotland, road; and (h) any other matter declared by any enactment to be a statutory nuisance. Pertinent to this assessment, EPA 1990 requires the control of emissions of dust that may arise from the construction or operation of the Proposed Development, such that these emissions do not result in nuisance issues. This is relevant to the Proposed Development during construction and decommissioning phases. 9-10

11 9.1.5 Supporting Information for this Chapter Information on the results of baseline surveys and other studies is provided in a series of Appendices as set out below: Annex G1 Background Conditions and Critical Loads at Sensitive Ecological Sites (APIS 29 September 2015);and Annex G2 Model Results. 9.2 ASSESSMENT METHODOLOGY Introduction The potential for impacts on air quality due to emissions arising from the Proposed Development are assessed by comparing the predicted impacts against standards and guidelines for the protection of human health and, when considering operational emissions, critical loads and levels for the protection of sensitive ecology as described in Section The effects from the Proposed Development are assessed in terms of: Process Contribution (PC), which is the impact associated with emissions from the Proposed Development only; and Predicted Environmental Concentration (PEC), which is the impact associated with emissions from the Proposed Development added to the existing background conditions Assessment Criteria Overview The potential effects of the emissions from the Proposed Development on human health are assessed by comparison to air quality standards and guidelines. The assessment criteria used to establish the potential for likely significant effects on human health are set out in this section. The potential for likely significant effects on sensitive habitats are identified through comparison with relevant critical loads and critical levels. Assessment Criteria for Sensitive Human Receptors The statutory criteria used in this EIA for assessment of impacts at sensitive human receptors are derived from the UK Air Quality Standards (AQS), which are derived from and consistent with EU Air Quality Directives and are set out in Table

12 Table 9.1 Air Quality Criteria for the Protection of Human Health Pollutant Averaging Period and Statistic Assessment Criterion (µg/m 3 ) Source NO 2 Annual 40 UK/EU AQS NO 2 1 hour mean, not to be exceeded 200 UK/EU AQS more than 18 times per year PM 10 Annual 40 UK/EU AQS PM 2.5 Annual 20 UK/EU AQS Assessment Criteria for the Protection of Sensitive Ecological Receptors Effects relating directly to air quality (i.e. NO x ) are not assessed on a habitat or species-specific basis; rather they are assessed by performance against a standard which is applied for all locations. These are set out in Table 9.2. Table 9.2 Air Quality Critical Levels (AQCL) used for the Assessment of Impacts on Sensitive Ecological Receptors Pollutant Averaging Period and Statistic Assessment Source Criterion (µg/m 3 ) NO x Annual mean 30 H1 (1) and AQS (2) NO x 24 hour maximum 75 H1 and APIS (3) (1) H1: Derived from the Environment Agency H1 guidance documents version 2.2. (2) UK/EU AQS: Air Quality Standard these are currently legally binding in the UK and are derived from the Clean Air For Europe (1) (CAFE) programme. (3) APIS: Derived from guidelines presented on the APIS website. Effects relating to acid and nutrient nitrogen deposition are considered more habitat and species specific; the site-specific critical loads (CL) are set out in Annex G1 for the sensitive ecological receptors of interest. The impacts at sensitive ecological receptors are defined on the basis of the highest impacts arising at any point on the designated habitat within the 10km radius. Therefore, the predicted impacts may not actually be coincidental with the sensitive feature described. This approach is worst case. Significance Criteria for Effects on Human Health In relation to effects on sensitive human receptors, the significance of effects used in the EIA process is determined based on guidance developed jointly by Environmental Protection UK (EPUK) and the UK Institute of Air Quality Management (IAQM) (2). The criteria presented in Table 9.3 have been used to assess impacts at individual human receptors. The process considers two factors: (1) (2) Institute for Air Quality Management (2015) Guidance on land-use planning and development control: Planning for air quality

13 the PC as a percentage of the air quality standard or guideline (the Air Quality Assessment Level or AQAL); and the PEC in the context of the AQAL. Table 9.3 Criteria for Assessing Impact Magnitude at Individual Human Receptors (taken from IAQM guidance) Long term average PEC at receptor as percentage of AQAL PC as a percentage of AQAL PC 1% PC 2-5% PC 6-10% PC >10% PEC 75% or less of AQAL Negligible Negligible Slight Moderate PEC 76% to 94% of AQAL Negligible Slight Moderate Moderate PEC 95% to 102% of AQAL Slight Moderate Moderate Substantial PEC 103% to 109% of Moderate Moderate Substantial Substantial AQAL PEC 110% or more of AQAL Moderate Substantial Substantial Substantial Short term PC < 10% 10 20% 20-50% > 50% (not dependent on baseline conditions) Negligible Slight Moderate Substantial As set out in the IAQM guidance, the assessment framework shown in Table 9.3 for describing impacts can be used as a starting point to assessing the significance of effects. The actual significance of the effect takes into account the sensitivity of the individual receptors. The following matrix sets out a framework for deriving the likely significance of effects on people as a result of impacts on air quality. It is not intended to be prescriptive but rather an illustration of how professional judgement has been applied in accordance with the guidance provided by IAQM on assessing significance. Table 9.4 Determination of Significance of an Impact on Human receptors Sensitivity of Receptor Low: areas of transient occupation, no permanent dwellings Medium: general population, permanent dwellings, villages, towns High: hospitals with intensive care or high dependency units, schools Magnitude according to IAQM Guidance Slight Moderate Substantial Not Significant Minor Moderate Minor Moderate Major Moderate Major Major In principle the significance matrix as presented in Table 9.4 applies universally to all receptors, and all impacts on these receptors, as the receptor or impact-specific considerations are factored into the assignment of magnitude and sensitivity designations that enter into the matrix. However, when considering impacts on human health due to inhalation of airborne pollutants, all sensitive human receptors are defined as medium sensitivity; high sensitivity refers to only a small number of cases where particularly vulnerable individuals are present, for example, hospitals with intensive care or high dependency units. This reflects the assumption that within the general population all humans are considered to be equally sensitive to air pollution. 9-13

14 Screening Criteria for Potential Ecological Effects In relation to potential impacts on sensitive ecological receptors, there are specific criteria that are used in this assessment derived from H1. These relate to the contribution from an emission source and the Critical Loads and Critical Levels (CLs) set for the protection of sites designated under the Habitats Regulations. The criteria presented in Table 9.5 have been used to determine whether more detailed assessment of the effects on sensitive ecological receptors is required (and where it is required this is presented in Chapter 7). Table 9.5 Criteria used in Assessing Impacts at Sensitive Ecological Receptors Criterion Long Term PC < 1% of AQCL/CL PC > 1% of AQCL/CL and PEC < 70% of AQCL/CL PC > 1% of AQCL/CL and PEC > 70% of AQCL/CL Short Term PC < 10% of AQCL/CL Assessment Actions Insignificant contribution and no further assessment required Unlikely to make a significant (1) contribution Significant contribution and therefore detailed assessment required Insignificant contribution and no further assessment required Unlikely to make a significant contribution PC > 10% of AQCL/CL and PEC < 70% of AQCL/CL PC > 10% of AQCL/CL and PEC > 70% of Significant contribution and therefore detailed AQCL/CL assessment required (1) The term significant is used here in the context of its meaning within the H1 guidance and not within the context of the EIA Regulations H1 guidance states that process contributions can be considered insignificant if: the long term process contribution is <1% of the long term environmental standard; and the short term process contribution is <10% of the short term environmental standard. Process contributions below these criteria are not taken forward for assessment and are considered in the ecological assessment to have no significant effects. Where a process contribution exceeds the insignificant contribution criterion but is below 70% of the CL this is deemed unlikely to make a significant contribution but may be subject to further ecological assessment where factors such as cumulative/in combination effects may require consideration and the PEC is close to the assessment criterion of 70%. In line with H1 guidance, where a significant contribution is identified further more detailed consideration is necessary as part of the ecological assessment The Dispersion Modelling Approach Introduction The assessment of emissions from the Proposed Development when operational uses dispersion modelling to predict the ground level increases in 9-14

15 pollution concentrations attributable to the Proposed Development emissions, and combines this with the baseline pollution concentration to establish whether there is the potential for significant effects on human health to occur (see Section 9.2.2) or for thresholds to be exceeded beyond which there is the potential for significant effects on ecology to occur. Where such thresholds are exceeded for ecological receptors more detailed assessment is provided in Chapter 7. The detailed dispersion modelling is used to predict concentrations of pollutants at ground level locations outside the Proposed Development boundary, at sensitive human receptors and sensitive ecological receptors. Five years of hourly meteorological data are used, so that inter-annual variability is incorporated in the model. The results of the assessment are based upon the worst case result for any of the five meteorological years used. General Considerations The operational impacts from the combustion process were assessed using the ADMS (Atmospheric Dispersion Modelling System) version 5.1. ADMS is one of a new generation of dispersion models which describe the atmospheric boundary layer properties. ADMS allows for the modelling of dispersion under convective meteorological conditions using a skewed Gaussian concentration distribution. It is able to simulate the effects of terrain and building downwash simultaneously. It can also calculate concentrations for direct comparison with air quality standards or guidelines. Plant Assumptions It is assumed that Keadby II (both Consented Development design and Proposed Development design) and the existing Keadby I will be operating at maximum capacity for 8,760 hours per annum, with the Proposed design in supplementary firing mode (higher NOx emissions, lower temperature). No consideration of different emissions during start-up and shutdown has been made. At the time of this assessment, two options with regards to the Proposed Development are being considered: single-shaft or multi-shaft. Single-shaft and multi-shaft configurations have different site layouts and building dimensions. Table 9.6 shows the emission parameters as used in the model. The stack height used in this assessment is 75 m. Modelling a stack height of 75 m provides a worse-case scenario for this assessment in regard to predicted air quality impacts. 9-15

16 Table 9.6 Emission Parameters (per stack) Parameter Keadby I as built Consented Development (1992) Proposed Development single-shaft Proposed Development multi-shaft Number of stacks Stack location, OS , , Grid , , , , Stack height, m Stack tip diameter, m Exit temperature, K Exit velocity, m/s Emission concentration NO x, mg /Nm 3 Emission rate NO x, g/s 15% 15% O 2 O per stack total per stack total 15% O 2 15% O total 66.2 total Meteorological Data Selection The meteorological data used in the model must be reflective of the local conditions. There are only a limited number of meteorological stations in the UK which measure all of the parameters required by the model. A review of available meteorological sites was undertaken, which focussed on the surrounding land use, the surrounding terrain and relative proximity to the coast. On the basis of these criteria, the nearest meteorological station considered representative of conditions is at Robin Hood Doncaster Airport. This is located approximately 20 km southwest of the Proposed Development. Both the recording station and the Proposed Development are located inland and have similar surrounding land use, and similar flat terrain. Five years of meteorological data ( , inclusive) were used for this assessment. The wind roses for are presented in Figure 9.1 and show that the prevailing wind direction at Robin Hood Doncaster Airport is mainly from the southwest; in 2010 a significant northern component was observed. Consideration of Terrain Effects Changes in terrain elevations (i.e. hills or mountains) can have a significant impact on dispersion of emissions, in terms of funnelling of plumes and changing local wind flows. Terrain effects are typically considered important where there are sustained gradients of 1:10 or greater. The Development area is situated in the River Trent flood plain, in a relatively flat area. The terrain elevation is not significant, with no peaks in excess of 100 m above mean sea level (AMSL) within 10 km of the site. There are no sustained gradients of 1:10 or greater in the vicinity of the Proposed Development and therefore terrain was not included in the model. 9-16

17 Figure 9.1 Wind Roses for Robin Hood Doncaster Airport ( ) (UK Met Office) 9-17

18 Consideration of Surface Roughness Effects The surface roughness length is a representation of the disruption of airflow close to the ground due to obstructions and protuberances, such as buildings, trees and hedges. In this case a surface roughness of 0.25 m has been used. This surface roughness value reflects the agricultural land use surrounding the site. Consideration of Building Downwash When air flow passes over buildings, a phenomenon known as building downwash occurs where the air is entrained in the lee of the building and drawn down to ground level. This phenomenon can bring the plume from the stack down to ground level more quickly than would otherwise be the case, and therefore increase the ground level concentration relative to a case where there are no buildings. All buildings that are greater than one third of the stack height, within five stack heights of the stack, are included. Within the model, buildings are conceptually considered as a block shape, as the model cannot take into account downwash effects around a complex building shape. On this basis, the buildings have been modelled as cuboids. The buildings used in the model and their dimensions are presented in Table 9.7. Other buildings shown in layout plans are not relevant from an atmospheric dispersion perspective. Table 9.7 Buildings Included in the Model Building Name 1 Centre coordinates Length Width Height Angle from North OS Grid m m m N Keadby I Model Keadby I Consented Development (1992 model) 10UHA UMC Keadby I Proposed Development (single-shaft model) HRSG GT Keadby I Proposed Development (multi-shaft model) HRSG GT Building Keadby I as per site layout drawings provided by SSE 9-18

19 Conversion of NO x to NO 2 Oxides of nitrogen (NO X ) emitted to atmosphere as a result of gas combustion will consist largely of nitrous oxide (NO), a relatively innocuous substance. Once released into the atmosphere, NO is oxidised to NO 2, which is of concern with respect to human health. The proportion of NO oxidised to NO 2 depends on a number of factors and is limited by the availability of oxidants, such as ozone (O 3 ). For the purposes of this assessment the screening/ worst-case scenario conversion ratios for NO X and NO 2 recommended by the Environment Agency (1) have been used. For long term average concentrations, the conversion of NO to NO 2 is 70%. For short term average concentrations, the conversion of NO to NO 2 is 35%. Actual oxidation rates are dependent on the availability of O 3, distance from the source and wind speed. Hence, these conversion factors are considered conservative and are likely to result in higher estimations of the PC for NO 2 than would occur in reality. Derivation of Acid and Nutrient Nitrogen Deposition The deposition of acid and nutrient nitrogen is not directly modelled but is derived from the PC predicted at each sensitive ecological receptor for each pollutant of interest. The derivation is based upon Environment Agency guidance (2) and uses the conversion factors set out in Table 9.8 and Table 9.9. The factors take into account the difference in deposition velocity and mechanisms experienced in forests, and grasslands and other nonarboreal areas. Table 9.8 Factors for Conversion of PC to Acid Deposition Pollutant Deposition Velocity - Grasslands (m s -1 ) Deposition Velocity - Forests (m s -1 ) Conversion Factor (µg m -2 s -1 to kg ha -1 year -1 ) NO Conversion Factor (kg ha -1 year -1 to keq ha -1 year -1 ) Table 9.9 Factors for Conversion of PC to Nutrient Nitrogen Deposition Pollutant Deposition Velocity - Grasslands (m s -1 ) Deposition Velocity - Forests (m s -1 ) NO x as NO Conversion Factor (µg m -2 s -1 to kg ha -1 year -1 ) (1) (2) AQTAG06 Technical Guidance on Detailed Modelling Approach for an Appropriate Assessment for Emissions to Air, Environment Agency, produced 06/02/04, Version

20 9.2.4 Traffic Impacts Guidance from the Institute of Air Quality Management (1) states that impacts on air quality are potentially significant when there are greater than 100 additional Heavy Goods Vehicles (HGVs) AADT (annual average daily traffic) or 500 Light Duty Vehicles (LDV) AADT generated by a scheme. From the traffic and transport chapter (Table 11.18; Section 12.4) it is clear that the threshold for additional HGV traffic will be exceeded during the construction phase. This would also have been the case for construction of the Consented Development. The potential increases in NO 2 and PM 10 at roadside receptors are predicted using the DMRB screening tool (2). It should be noted that for NO 2, the predicted NO x concentrations will be converted using the NO x to NO 2 conversion tool provided by Defra, understanding that the conversion factor built in to DMRB is no longer valid. Using the DMRB screening approach, two scenarios were considered: Do-Nothing 2017 (base case); and Do-Something 2017 (construction). The traffic data used in the assessment is set out in Table of Section 12.4, which sets out the change in traffic flows on the A18 and A161 during the key time periods. Baseline flows shown in this table include observed traffic and committed traffic from the Lincolnshire Lakes scheme and the Scunthorpe United football club Issues Scoped out of Further Detailed Assessment General Considerations There are several issues that have been considered and subsequently scoped out of the detailed air quality impact assessment on the basis that the expected impacts on air quality would be negligible and could therefore not lead to significant effects on receptors. These are discussed below. Emissions from On-site Mobile and Non-mobile Construction Plant Emissions from mobile and non-mobile on-site construction plant during the construction phase of the Proposed Development are considered to be negligible. During construction there will be a requirement for mobile and nonmobile plant, which are sources of emissions; for example, excavators, dump trucks and generators. Whilst it is acknowledged that these will have some impact on air quality, considering the size of the site and the schedule of operations, the emissions arising from these are anticipated to be negligible and have not been considered further. (1) IAQM (2015) Land-Use Planning & Development Control: Planning For Air Quality (2) UK Highways Agency (2007) Design Manual for Roads and Bridges Volume 11, Section 3, Part 1 Air Quality 9-20

21 Construction Dust Assessment The construction of the Proposed Development has the potential to generate airborne dust, and potentially have a significant impact on amenity at sensitive nearby receptors. Implementation of best practice measures for dust management (as described in the construction environmental management plan) during construction is expected to render residual impacts negligible. Furthermore, these emissions will be of the same magnitude for whichever design (Consented or Proposed) is being constructed. On this basis, dust impacts are not considered in detail here. Emissions from Operational Traffic As discussed in Section the total operational traffic (HGV + LDV) is expected to be lower than 100 additional AADT. On this basis the emissions arising from operational traffic are anticipated to be negligible and have not been considered further. 9.3 BASELINE CONDITIONS AND RECEPTORS Overview This section sets out the existing baseline conditions in the vicinity of the Proposed Development. The description includes details of sensitive human and ecological receptors and their locations with respect to the Proposed Development. Baseline conditions (for example, wind speed and direction) that are relevant to the dispersion of atmospheric pollutants are described in Section Baseline Air Quality Overview The baseline conditions in the area of influence depend upon local and regional sources of emissions to air, both natural and anthropogenic. This section describes the baseline conditions in the area of influence with regard to existing: concentrations of airborne pollutants in the vicinity of the Proposed Development, at sensitive human and ecological receptors; and rates of deposition of acid and nutrient nitrogen at sensitive habitats. The Proposed Development site is located in a primarily rural area. However, there are local sources of emissions of which the most significant is the adjacent existing Keadby I station. Emissions from Keadby I will contribute to the baseline NO 2 and NO x concentrations and acid and nutrient deposition rates. 9-21

22 Reasonable Worst Case Scenario for Assessment The baseline data are based upon recent monitoring and other currently available information. For the large majority of pollutants the future baseline concentrations are likely to be similar to present, however it is understood that, in the case of some pollutants, it is foreseeable that concentrations may change. In particular for NO 2 and NO x, there are national policies in place, the aim of which is to decrease concentrations of these pollutants, particularly in locations where they are elevated (i.e. adjacent to busy roads), theoretically improving baseline conditions. However, there is research (1) which indicates that, in urban environments at least, these policies do not appear to be reducing concentrations of these pollutants as expected. On the basis of the point outlined above, using current baseline pollution concentrations to represent future baseline concentrations represents a pragmatic and reasonable approach. In addition, some of the baseline data derived from local monitoring will include the contribution from the Keadby I plant whenever it was operating concurrently with sampling. However, Keadby I is understood to operate intermittently, and as a result understanding or isolating the contribution of Keadby I from the measured baseline is difficult. On this basis no correction to the baseline has been undertaken to account for existing contributions from Keadby I in assessing the impacts of Keady I and the Consented/Proposed Development together. This represents a worst case approach since Keadby I contributions may have been double-counted to some extent. Summary of Data Sources - Human Receptors There are relatively limited baseline data available reflecting the overall good air quality in the study area. There are no Automatic Urban and Rural Network (AURN) monitoring sites within the immediate vicinity of the Proposed Development. North Lincolnshire District Council (NLINCS) have several sites within the area which monitor NO 2 concentrations using diffusion tubes. However, there are only two sites operated by NLINCS within the study area at a location which are considered representative for the surroundings (rural area) of the Proposed Development. A1077 (Orbital Road) site is at a rural roadside, approximately 3.5 km to the east of the Proposed Development. Keadby Bridge site is at a suburban roadside, approximately 1 km to the southeast of the Proposed Development. Although in a suburban setting, this site is included for baseline assessment, due to its close proximity to the Proposed Development. In the UK, a national modelling exercise has been undertaken to identify baseline concentrations of several pollutants (2). These interpolated mapping data are representative of general baseline concentrations, away from specific (1) Defra (2012) Local Air Quality Management: Note on Projecting NO 2 Concentrations (2) Defra (2011) Interpolated mapping data: Local Air Quality Management Support

23 local sources of emissions (i.e. roads and industrial sources). To further support the data from the diffusion tube monitoring, these data have been used to derive the baseline concentrations for NO 2. These baseline concentrations are substantially below the concentrations specified in the relevant air quality standards. The most up to date mapping is 2011, which has been validated against monitoring results. Diffusion Tube Monitoring The results of the diffusion tube monitoring during 2008 to 2011 (Keadby I was operating for some of this period) are presented in Table 9.10, noting that monitoring was ceased after The monitoring data are presented as bias-adjusted where the raw data are multiplied by a factor to account for errors in the diffusion tube methodology. The annual mean background concentrations for both sites are below the NO 2 AQS objective of 40 µg m -3. On average, the suburban monitoring site shows higher concentrations than the rural site, as is expected taking into account the nature of the monitoring locations. Data from this site are used as traffic baseline NO 2 concentrations. Comparisons of the baseline air quality for protection of human health have been made to air quality standards as specified in Table 9.1. Table 9.10 Annual Mean NO 2 Concentrations from Diffusion Tube Monitoring (µg m -3 ) Diffusion Tube Location Average A1077 Orbital Road (rural) Keadby Bridge (suburban) Air Quality Objectives Source: Extracted from Air Quality Reports produced by the NPTCB Council. Defra Mapping The baseline concentration for the Proposed Development location derived from the Defra mapping data (1) for 2011 is 13.7µg m -3 for NO 2. This is well within the 40 µg m -3 annual mean air quality standard but somewhat lower than the diffusion tube results (Table 9.10), this is due to the diffusion tube locations being close to roadsides and thereby presenting higher concentrations (closer to the maxima in the area), whilst the Defra maps present an average concentration over a 1 km x 1 km grid square. PM 10 baseline concentration for the traffic assessment was also derived from Defra mapping data extrapolated to 2017 for the Proposed Development location, and is 18 µg m -3. (1)

24 Summary of Baseline Data Used in the Assessment Human Receptors Table 9.11 sets out the baseline data used as the basis for the impact assessment along with the sources of these data. The annual mean Air Quality Standards are also presented for comparison, where these are applicable. Table 9.11 Baseline Pollution Data used in the Assessment of Impacts at Sensitive Human Receptors Pollutant Annual mean AQS Baseline Source (µg m -3 ) concentration (µg m -3 ) NO 2 40 (human) 21.1 Average of A1077 Orbital Road and Keadby Bridge (see Table 9.10) Receptors In order to assess short term impacts, the short term baseline concentrations have been derived by multiplying the long term derived baseline by a factor of 2 (1). Summary of Baseline Data Used in the Assessment Ecological Receptors Baseline rates for nutrient nitrogen and acid deposition for sensitive ecological receptors (habitats) were derived from the APIS website. Baseline deposition is set out on a site-by-site basis for the habitat sites of interest. The baseline concentrations and deposition rates at sensitive ecological receptors for acid, nutrient nitrogen and NO x are set out in Annex G1 along with further details of the receptors. Sensitive Human Receptors The air quality standards and guidelines for the protection of sensitive human receptors apply at all off-site locations. On this basis, the assessment considers the maximum impacts predicted anywhere outside the Proposed Development site boundary. Based upon H1, the assessment area of influence comprises an area within a radius of 10 km of the Proposed Development. In order to capture the maximum off-site impacts the dispersion model utilises a grid of receptors. Environment Agency guidance (2) suggests that the grid resolution is no greater than 1.5 times the stack height (in this case 1.5 x 60 m means a grid resolution of no greater than 90 m. Sensitive Ecological Receptors In accordance with the requirements of Annex F of H1, consideration is given to sensitive ecological sites: (1) Defra (2009) Local Air Quality Management Technical Guidance Note TG(09) (2) Environment Agency (2012) Dispersion Modelling Frequently Asked Questions 9-24

25 Special Protection Areas (SPAs), Special Areas of Conservation (SACs) or Ramsar sites within 10 km of the installation; and Sites of Special Scientific Interest (SSSIs), National Nature Reserves (NNRs), Local Nature Reserves (LNRs), local wildlife sites (LWS), Sites of Nature Conservation Importance (SNCIs) and ancient woodland within 2 km of the location of the installation (1). The issue for ecosystems is the possibility that the deposition rate of acid (keq/ha/yr) or nutrient nitrogen (kg N/ha/yr) may be in excess of the amount that the ecosystem can tolerate. The point at which this occurs is termed the critical load. For acidic deposition, the critical load of a habitat site is determined mostly by the underlying geology and the soils. Alkaline soils have an innate capacity for neutralising acidic deposition, whereas acidic soils do not. The other factor is the type of vegetation present at the habitat. Defining critical loads for habitats is difficult, therefore, since it requires knowledge of both factors and represents a considerable mapping exercise for all habitats in the UK. Nutrient nitrogen is also assessed relative to a critical load, but in this case, the critical load can be determined largely on the basis of the species or habitat type affected. Critical loads have been determined for a number of habitat types at the European level and have been the subject of a series of workshops held under the auspices of the United Nations Economic Council for Europe (UNECE). Essentially, the critical loads reflect the way different plants have adapted to differing availabilities of nutrient. Those in nutrient deficient environments, for example coastal sand dunes, will be intolerant of excess nitrogen from aerial deposition. The critical loads used in this assessment are obtained from the Air Pollution Information System (APIS) (2) website, based on the simple site-based assessment tool. The Simple Site-based Assessment is a tool based on a search by location which can be used to provide background NO x concentrations, background nitrogen/ acid deposition, critical loads and critical levels at a particular location throughout the UK. These are based on national maps of air pollutant exposure and critical loads/ critical levels. The maps are those documented in the 2001 National Expert Group on Transboundary Pollution (NEGTAP) report (3). The critical loads/ critical levels are linked to a specific habitat type, which are only available for a limited number of habitat types. In this case, the value for the most similar habitat is assigned to the habitat being considered. In addition, the retrieved data from a location search is drawn from a base map with much larger grid resolutions of 1 to 5 km. Uncertainties related to subgrid variability are not captured within the 1 km or 5 km average and so, the (1) The Environment Agency specify within H1 Guidance Annex F that in certain cases the study area may need to be 15 km and SSSIs and local sites within 10 km considered in the assessment. However, this applies only to the largest emission sources and in this case, the emissions from the plant and the nature of the receiving environment are considered such that a study area of 10 km is sufficient, considering SSSIs and local sites within 2 km. (2) (3)

26 simple site-based method is used only as a broad indication of the likely pollutant impact at a specific location, as local factors may modify feature sensitivity/ response to a particular pollutant. There are, therefore, uncertainties in both the best estimates of the critical loads/ critical levels and in the assignment of habitats. In order to best determine the most appropriate habitat type, the process has been cross referenced with the ecological assessment. A review of the sensitive habitats has been undertaken using the MAGIC website (1) and in conjunction with the ecology assessment (see Annex E4). The relevant receptors are listed in Table 9.12; the locations are presented in Figure 9.2. SPAs within the study area did not contain any sensitive habitats other than those which are also contained within an SAC, and are therefore not specifically assessed (see Annex E4). No LNRs or NNRs have been identified within the appropriate radius of the Proposed Development site. In terms of the dispersion modelling, impacts on the receptors are captured using a grid of receptors defined throughout each habitat. Table 9.12 Sensitive Ecological Sites Sites Distance from SPA/S Ramsar SSSI LWS SNCI stack (km) AC Site Humber Estuary 1.0 X X X Thorne Moor 7.1 X X Hatfield Moor 7.1 X X Keadby Boundary Drain 1.0 X Keadby Warping Drain 0.67 X Keadby Wet Grassland 0.21 X Keadby Wetland 0.18 X South Soak Drain, Keadby 0.16 X Stainforth and Keadby Canal 0.12 X Corridor Three Rivers 0.6 X Keadby Power Station 0.15 X Three Rivers Marsh 0.48 X Source: Background conditions (ambient concentration, acid deposition and nitrogen deposition) for the identified ecological receptors have been obtained from the APIS website and presented in Annex G1 together with the critical loads. In many areas of the UK, the baseline conditions are already in excess of critical loads and critical levels at many sensitive ecological receptors. It can be seen from Annex G1 that this is also the case for certain ecological sites identified in Table 9.12; the background acid and nitrogen deposition rates have already exceeded the critical loads for acid and nitrogen. Sulphur and nitrogen oxides from existing industrial sources and transport are major contributors to acidification (2). (1) Multi Agency Geographic Information for the Countryside (MAGIC) (2009) (2) Fourth Report of the Review Group on Acid Rain (1997)

27 PROJECTION: British National Grid Proposed Development Boundary 0 1 Statutory Designated Site SOURCE: Kilometres Ecological Receptors Non - Statutory Designated Site 2 SCALE: See Scale Bar VERSION: A SIZE: A4 DRAWN: GB PROJECT: CHECKED: YV DATE: 22/12/2015 APPROVED: KM Sources: Esri, DeLorme, NAVTEQ, USGS, Intermap, ipc, NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), TomTom, 2013 ± Figure 9.2 Sensitive Ecological Sites Path: P:\Projects\ _KeadbyGIS_GB_KM\MAPS\EIA\09_Air\ _SensitiveEcologicalSites_A01.mxd