13. Air Quality 13.1 Introduction 13.2 Approach and Methods 13.3 Baseline Conditions 13.4 Potential Impacts 13.5 Potential Mitigation 13.6 Summary of Route Corridor Options Assessment 13.7 Scope of Stage 3 Assessment 13.8 References

13. Air Quality

13.1 Introduction

13.1.1 This chapter presents the assessment of the Stage 2 route corridor options for the Forth Replacement Crossing in terms of air quality.

13.1.2 Air quality studies are concerned with the presence or absence of airborne pollutants. This chapter outlines the relevant air quality management policy and legislation, describes the existing or ‘baseline’ air quality situation and identifies and compares the anticipated operational air quality impacts of each of the route corridor options. Potential air quality impacts during construction are considered separately in Chapter 17 (Disruption Due to Construction).

13.1.3 In the area surrounding the Forth Replacement Crossing, vehicle emissions are the dominant source of air pollution. For this reason and also because of the nature of the development, the assessment only considers those air pollutants emitted by vehicular traffic and which have been identified as being of most concern by the UK Government’s Air Quality Strategy and by UK and EU legislation.

13.1.4 The main pollutants that are produced by road traffic and which can lead to poor air quality include oxides of nitrogen (NO_x), comprising mainly nitric oxide (NO) and nitrogen dioxide (NO₂), carbon monoxide (CO), volatile organic compounds (VOCs), particularly benzene and 1,3-butadiene and fine particulate matter (PM_2.5, PM₁₀). However, for the purpose of the local air quality assessment presented in this chapter only NO₂, NO_x and PM₁₀ are assessed. Local authorities have identified NO₂ and PM₁₀, emitted by road traffic as the key pollutants of concern within this area of Scotland (refer to Section 13.3: Local Authority Review and Assessment of Air Quality). Other motor vehicle related pollutants are sufficiently controlled to have negligible impact in terms of local air quality. NOx concentrations are included due to the fact that local atmospheric chemistry determines related NO₂ concentrations.

13.1.5 Nitrogen deposition is also considered within the Stage 2 assessment as per DMRB guidance.

13.1.6 Scottish Transport Appraisal Guidance (STAG) (Transport Scotland, 2008) also identifies carbon dioxide (CO₂) as a pollutant of concern on a global level. Concentrations of CO₂ generated as a result of the Forth Replacement Crossing are therefore considered in the regional level assessment. In addition, concentrations of NO_x and PM₁₀ are considered in terms of total emissions as part of the regional level assessment.

13.2 Approach and Methods

Study Area

13.2.1 The study area considered for this Stage 2 assessment comprises an area covering the Forth Replacement Crossing corridor as well as areas to the north and south of the proposed replacement bridge. Figures 13.2a-c show the extent of the modelled road network and thus the extent of the study area for the air quality assessment.

Overall Approach

13.2.2 The assessment of air quality is made in terms of the difference between the air quality that would be likely with the proposed scheme (the Do-Something scenario) and without the proposed scheme (the ‘do-minimum scenario) for both the anticipated year of opening (2017) and the design year 15 years after opening (2032). The future ‘do minimum’ scenario assumes that the existing Forth Road Bridge is still in operation.

13.2.3 The Stage 2 air quality assessment of the route corridor options consists of the following components:

a review of the existing air quality situation;
collation of road traffic data and scoping out of local road links with changes in traffic flows or speeds too small to influence local air quality under each of the route corridor options;
an assessment of the changes in air quality at representative receptors arising from the operation of the Forth Replacement Crossing, as a result of the changing traffic flows on the proposed replacement bridge and adjoining road network for each of the route corridor options;
an assessment of the changes in nitrogen deposition at representative receptors arising from the operation of the Forth Replacement Crossing as a result of the changing traffic flows on the new replacement crossing and adjoining road network for each of the route corridor options; and
a comparison of changes in local population exposure to road traffic related air pollution for the current configuration and each of the route corridor options.

Assessment Methodology

13.2.4 The methodology used for the Stage 2 air quality assessment is based on DMRB Volume 11, Section 3, Part 1: HA207/07 (The Highways Agency et al., 2007). This document provides a three-stage appraisal methodology, using scoping, screening and detailed modelling techniques where appropriate to allow comparison of pollutant concentrations with the relevant European Union (EU) limit values and Scotland air quality objectives (see Table 13.3). The quantitative comparison of the route corridor options is based on the methodology included in STAG.

13.2.5 An assessment has been made of the concentrations of NO₂ and PM₁₀ at receptors near to the roads and junctions for the various route corridor options. Receptors were selected as those in closest proximity to the road, at junctions where congestion or a reduction in speed may be expected and at identified sensitive areas such as the designated Firth of Forth Special Protection Area (SPA) and Site of Special Scientific Interest (SSSI), St Margaret’s Marsh SSSI and Ferry Hills SSSI (see paragraph 13.3.31 for more information on these designated sites).

Modelling Methodology

Road Traffic Data and Scoping

13.2.6 Road traffic data were collated in terms of annual average daily (24 hour) traffic flows (AADT), daily average speed and percentage of heavy duty vehicles for the proposed replacement bridge and associated access road links and junctions for the base year (2005) and future assessment scenarios years 2017 and 2032. The data were firstly interrogated to scope out sections of road (links) where potential changes in traffic flows would not influence local air quality significantly using the DMRB thresholds:

road alignment will change by 5 m or more; or
daily traffic flows will change by 1,000 AADT or more or 10% change on road links; or
Heavy Duty Vehicle (HDV) flows will change by 200 AADT or more; or
daily average speed will change by 10 km/hr or more; or
peak hour speed will change by 20 km/hr or more.

Changes in Local Population Exposure

13.2.7 For each scoped in link for each northern and southern route corridor option, residential receptor counts were made for distance bandings 0-50m, 50-100m, 100-150m and 150-200m on either side of the road.

13.2.8 ArcGIS was used to generate buffer zones (0-50m; 0-100m; 0-150m; 0-200m) around the scoped in links and to count properties within each buffer zone. Figure 3.2 shows the four buffer zones for one scenario (North Corridor Option 1 in combination with South Corridor Option in 2032) and properties within the 200m buffer as an example.

13.2.9 The DMRB calculation procedure was then used to determine NO₂ and PM₁₀ concentrations within these distance bandings and, using weighting factors included in STAG, a population exposure score was derived for each scenario. These scores are relative and provide a means of comparing the effect of each route corridor option in terms of population exposure to road traffic related air pollution. It should be noted that STAG scores are based on average concentration net change per assessed property.

Changes in Air Quality and Nitrogen Deposition

13.2.10 Representative receptors were identified within the study area. The criteria for receptor selection included:

residential properties and other sensitive receptors, such as schools or locations within designated nature reserves which are closest to affected road links and where the greatest change in local air quality would be expected as a result of the Forth Replacement Crossing (i.e. where greatest change in traffic flows is predicted to occur); and
residential properties or locations within designated nature reserves where the highest concentrations of road traffic pollutants would be expected (e.g. around junctions).

13.2.11 DMRB HA207/07 includes a calculation procedure combining background air quality data with road traffic emissions to derive concentrations of NO_x, NO₂ and PM₁₀ and nitrogen deposition rates at each representative receptor. The background air quality concentrations were obtained from the National Air Quality Archive; this is further discussed in paragraphs 13.3.27 to 13.3.29. The years of assessment were for the baseline situation in 2005 (based on 2005 traffic survey data), 2017 and 2032 both with and without the proposed replacement bridge. It should be noted that DMRB emission factors only go as far as 2025 and therefore 2025 emission factors have been used for the 2032 scenarios. The results are compared directly to the air quality limit values and objectives as well as the critical load for calcareous grassland, saltmarsh fens, and neutral grassland which are the predominant habitats found in the SSSIs in the study area (see Table 13.8).

13.2.12 Assessment of designated sites within 200m either side of each route corridor option was carried out in accordance with the methodology outlined in Annex F of the DMRB HA207/07 which assesses the traffic related dry deposition of nitrogen (in kilograms per hectare per year). This requires that annual mean NO₂ concentrations are calculated for a transect up to 200m away from each of the affected roads (roads that have been scoped in) within or near a designated site. The calculations were carried out for 2017 and 2032 with and without the proposed replacement bridge at 20m intervals starting from the closest point from the road that lies within or in close proximity to the SSSI. When predicting future deposition rates, background nitrogen deposition rates (as presented in Table 13.10) were reduced by 2% per year in accordance with DMRB. This is because of predicted improvements in vehicle technologies and abatement equipment.

Total Pollutant Emissions

13.2.13 Total emissions of NO_x, PM₁₀ and CO₂ were calculated within the study area. All road links independent of whether or not they meet the DMRB criteria were included in the total emissions calculations. Total vehicle kilometres travelled along each road link were established using ArcGIS and available traffic data. Emission factors were derived using the dataset incorporated in the DMRB worksheets version 1.03c (July 2007). For each road link total pollutant emissions per year were calculated. Emissions established for each link were then added to generate the total mass of emissions for each assessed corridor option.

Baseline Conditions

13.2.14 Baseline conditions were assessed using the desk study based approach. Air Quality Review and Assessment documents from relevant local authorities have been reviewed and existing local air quality established using information from the reviewed reports and the national air quality archive.

13.2.15 Estimates of background air quality for pollutants NO_x, NO₂ and PM₁₀ have also been obtained from the national air quality archive. This is in the form of annual mean estimates aggregated for each one km grid square for 2004 and projections for future years from national mapping studies (www.airquality.co.uk).

13.2.16 In line with current guidance, background concentrations for future years (2017, 2032) were calculated using the netcen year adjustment calculator available on www.airquality.co.uk. The calculator includes factors for years up to 2020. As a consequence, the 2020 factor has been used to calculate background concentrations for 2032.

13.2.17 These mapping studies consider local sources, such as roads and industry, as well as sources from elsewhere in the UK and continental Europe.

Impact Assessment

13.2.18 The National Society for Clean Air (NSCA) guidance (NCSA, 2006) provides an example approach for assessing the significance of air quality impacts associated with a given development. These significance criteria have been used to quantify traffic effects for the individual sensitive receptors modelled. The significance of the impacts is then assessed through a series of questions with closed (yes and no) answers. Each question is addressed in descending order until the arrow points to one of the outcomes in the right hand column. This gives the relative priority which air quality considerations should be afforded with respect to the development proposal.

13.2.19 The NSCA guidance also provides further guidance on how to describe the significance of the impacts predicted from the air quality modelling for the pollutants NO₂ and PM₁₀. Two tables are presented that set out examples of descriptors for magnitude of change and significance (as shown below in Tables 13.1 and 13.2). The first step is to identify the descriptor of change in ambient concentrations for NO₂ and PM₁₀ (Table 13.1) according to the percentage change in annual mean concentrations (for both NO₂ and PM₁₀). The descriptor can then be used to assess the impact significance for the two pollutants in relation to changes in the absolute concentration forecast from the modelling with the Forth Replacement Crossing in place (Table 13.2).

Sensitivity

13.2.20 As described above, the sensitivity of certain receptors has been considered by applying screening criteria to road links affected by the Forth Replacement Crossing. Receptor points within 200m of links that meet the DMRB criteria are considered as being potentially ‘susceptible’ to resulting changes in local air quality and are therefore included in the quantitative assessment.

Impact Magnitude

13.2.21 Table 13.1 below shows descriptors of magnitude of change.

Table 13.1: Examples of Descriptors for Changes in Ambient Concentrations of NO₂ and PM₁₀ (Source: NSCA, 2006)

Magnitude of Change	Annual Mean NO₂/PM₁₀
Very Large	Increase/decrease > 25%
Large	Increase/decrease 15-25%
Medium	Increase/decrease 10-15%
Small	Increase/decrease 5-10%
Very Small	Increase/decrease 1-5%
Extremely Small	Increase/decrease <1%

Impact Significance

13.2.22 The significance of impacts was determined according to a matrix of sensitivity and magnitude as illustrated in Table 13.2, in accordance with NSCA guidance.

Table 13.2: Examples of Descriptors for Impact Significance for NO₂ and PM₁₀ (Source NSCA, 2006)

Absolute Concentration in Relation to Standard	Extremely Small	Very Small	Small	Medium	Large	Very Large
Decrease with scheme
Above Standard with scheme	Slight beneficial	Slight beneficial	Substantial beneficial	Substantial beneficial	Very substantial beneficial	Very substantial beneficial
Above Standard without scheme Below with scheme	Slight beneficial	Moderate beneficial	Substantial beneficial	Substantial beneficial	Very substantial beneficial	Very substantial beneficial
Below Standard without scheme, but not Well Below	Negligible	Slight beneficial	Slight beneficial	Moderate beneficial	Moderate beneficial	Substantial beneficial
Well Below Standard without scheme	Negligible	Negligible	Slight beneficial	Slight beneficial	Slight beneficial	Moderate beneficial
Increase with scheme
Above Standard without scheme	Slight adverse	Slight adverse	Substantial adverse	Substantial adverse	Very substantial adverse	Very substantial adverse
Below Standard without scheme Above with scheme	Slight adverse	Moderate adverse	Substantial adverse	Substantial adverse	Very substantial adverse	Very substantial adverse
Below Standard with scheme, but not Well Below	Negligible	Slight adverse	Slight adverse	Moderate adverse	Moderate adverse	Substantial adverse
Well Below Standard with scheme	Negligible	Negligible	Slight adverse	Slight adverse	Slight adverse	Moderate adverse

Well Below standard = <75% of the standard level.
‘Standard’ in the context of this table relates to specific air quality objective or Limit Value in question

Limitations to Assessment

13.2.23 The base year in terms of traffic was taken to be 2005, using Transport Model for Scotland (TMfS05a) data. A later version is currently in preparation by MVA Consultancy on behalf of Transport Scotland, to include changes such as more recent alterations to the road network and anticipated major developments. However, TMfS05a represents the best data currently available and it is considered that these provide an acceptable proxy for the baseline traffic situation for the purposes of this assessment.

13.2.24 As described in paragraph 13.2.2, the years of assessment include future years of 2017 and 2032. There is an inherent limitation in the accuracy of background concentrations and vehicle emission factors projections so far into the future. However, the approach followed is consistent with current best practice and government guidance.

13.3 Baseline Conditions

Air Quality Policies, Legislation and Standards

Air Quality Limit Values and Objectives

13.3.1 Air quality limit values and objectives are quality standards for clean air. They can be used as assessment criteria for determining the significance of any potential changes in local air quality resulting from the development proposals.

13.3.2 EU air quality policy sets the scene for national policy. The ‘framework’ EU Directive on Ambient Air Quality Assessment and Management came into force in September 1996 (Directive 96/62/EC) and is intended as a strategic framework for tackling air quality consistently, through setting European-wide air quality limit values in a series of daughter directives, superseding and extending existing European legislation. The first four daughter directives have been placed into national legislation. These EU limit values have recently been consolidated in the Air Quality Standards (Scotland) Regulations 2007. A new EU Directive (Directive 2008/50/EC) has recently been announced that merges the four daughter directives and one Council decision into a single directive on air quality. The new Directive introduces a new limit value for fine particulate matter (PM_2.5) but does not change the existing air quality standards. This is yet to be transposed into UK policy.

13.3.3 In a parallel national process, the Environment Act was published in 1995. The Act required the preparation of a national air quality strategy setting air quality standards and objectives for specified pollutants and outlining measures to be taken by local authorities (through the system of Local Air Quality Management (‘LAQM’)) and by others ‘to work in pursuit of the achievement’ of these objectives. A National Air Quality Strategy (NAQS) was published in 1997 and subsequently reviewed and revised in 2000, and an addendum to the Strategy published in 2002. The current Strategy is that published in July 2007; (The Air Quality Strategy for England, Scotland, Wales and Northern Ireland, 2007). The objectives which are relevant to local air quality management have been set into Regulations (Air Quality (Scotland) Regulations 2000 and Air Quality (Scotland) Amendment Regulations 2002).

13.3.4 Table 13.3 sets out the EU air quality limit values and national air quality objectives for the pollutants of relevance to this study.

Table 13.3: EU Air Quality Limit Values and National Air Quality Objectives for Relevant Pollutants

Pollutant	Averaging Period	Objective/Limit Value	Compliance Date	Basis
Nitrogen dioxide (NO₂)	1 hour mean	200 µg/m³, not to be exceeded more than 18 times a year (99.8^th percentile)	31 Dec 2005	National
	1 hour mean		01 Jan 2010	EU
	Annual mean	40 µg/m³	31 Dec 2005	National
	Annual mean	40 µg/m³	01 Jan 2010	EU
Particulate matter (PM₁₀) Measurement technique: Gravimetric	Daily mean	50 µg/m³, not to be exceeded more than 35 times a year (90.4th percentile)	01 Dec 2004	National
	Daily mean		Not specified	EU
	Annual mean	40 µg/m³	31 Dec 2004	National
		40 µg/m³	Not specified	EU
		18 µg/m³	31 Dec 2010	National

Planning Policy

13.3.5 The key links between planning and air quality are with transport, industry and energy, since these are the main sources of air pollution. National planning policy is set out in Scottish Planning Policies (SPP), with SPP 17 ‘Planning for Transport’ being relevant to air quality assessments of new transport infrastructure. The Scottish Government has also published Planning Advice Notes (PANs) of which PAN75 ‘Planning for Transport’ is of relevance to this air quality assessment.

13.3.6 SPP17 (accompanied by PAN75) highlights the need to provide better integration between transport and land-use planning, as well as with other Government policies. SPP17 outlines a framework encouraging key travel generating uses to be in locations that support sustainable transport options, a move towards maximum car parking standards and broader transport assessments covering all modes of access, and the use of green travel plans and planning agreements to promote sustainable transport solutions. Sustainable transport options and green travel plans contribute to integrating transport and air quality such that air quality does not deteriorate as a result of new development.

Air Pollution Sources

Industrial Processes

13.3.7 Industrial air pollution sources are regulated through a system of operating permits or authorisations, requiring stringent emission limits to be met and ensuring that any releases are minimised or rendered harmless. Regulated (or prescribed) industrial processes are classified as Part A or Part B processes. Part A processes, regulated through the Integrated Pollution Prevention and Control (IPPC) system (EC Directive 96/91/EC on Integrated Pollution Prevention and Control) are regulated by SEPA. Part A processes have the potential for release of prescribed substances to air, land and water, and as such require an IPPC permit to operate. Part B processes are those regulated by the local authority through the Pollution Prevention and Control (PPC) system under the Pollution Prevention and Control (Scotland) Regulations 2000. Part B processes are smaller in scale than Part A processes and have the potential for release of prescribed substances to air only, requiring a PPC authorisation or permit to operate. Given the extent of the study area, it is likely that there are several Part B processes within the assessed area. However, due to the fact that they are controlled, it is considered unlikely that such processes would lead to a breach of air quality objectives.

13.3.8 There are a number of industrial processes regulated through the IPPC system within approximately 2km of the Forth Replacement Crossing, including, Dalmeny Tank Farm, South Queensferry (part of BP Exploration Co. Ltd), Shanks Chemical Services, several Sewage Treatment Works, Rosyth Royal Dockyards Ltd and the Grampian County Food Group Ltd. However, as these processes are controlled by SEPA and potential releases to air are tightly regulated it is considered that such processes would not lead to a breach of air quality objectives.

13.3.9 In addition to the processes in the immediate vicinity of the proposed replacement bridge, there are industrial sources which contribute to releases to air in Grangemouth, approximately 20km to the west of the proposed replacement bridge.

Local Authority Review and Assessment of Air Quality

13.3.10 Under the requirements of the Environment Act 1995 Part IV, local authorities are required to periodically review and assess air quality in their areas. If it is predicted that air quality concentrations will exceed national air quality objectives the local authority is required to declare an Air Quality Management Area (AQMA) around the area where the exceedance is predicted to occur.

City of Edinburgh Council

13.3.11 City of Edinburgh Council (CEC) undertook the first and second stages of the review and assessment which concluded that NO₂ required further investigation at Stage 3 review and assessment (CEC, 2000). This concluded that the annual mean NO₂ objective was predicted to be exceeded in 2005 in eight locations in Edinburgh. On this basis CEC subsequently designated an Air Quality Management Area (AQMA) for NO₂ covering the city centre, including the main roads into the city centre.

13.3.12 CEC produced an Air Quality Action Plan in July 2003 (CEC, 2003) which detailed measures to reduce NOx emissions in the AQMA in pursuit of the annual mean NO₂ objective.

13.3.13 A further Updating and Screening Assessment (USA) was carried out in 2006 which concluded that a second AQMA should be declared for the area around St Johns Road, west Edinburgh city centre. As a result, an AQMA for NO₂ was declared on 31 December 2006.

13.3.14 The study area does not include the centre of Edinburgh or any of the designated AQMAs due to the fact that road links do not meet the DMRB criteria as listed in paragraph 13.2.6. As a result, it is considered unlikely that any of the route corridor options would have a significant impact on the AQMAs in Edinburgh.

West Lothian Council

13.3.15 West Lothian Council (WLC) undertook the first and second stages of the review and assessment which concluded that all pollutants of concern would meet the relevant air quality objectives in the relevant years and hence no further assessment work was required.

13.3.16 The USA submitted in July 2006 concluded that all pollutants would continue to meet the relevant air quality objectives and therefore no further assessment would be required. For PM₁₀, however, it was indicated that there is a risk of exceeding the annual objective of 18µg/m³ in Linlithgow High Street. As a result it was recommended to continue the PM₁₀ monitoring at Linlithgow High Street.

13.3.17 The Progress Report submitted in April 2007 states that Linlithgow High Street would potentially have to be declared an AQMA due to a number of exceedances of the PM₁₀ standard and the closeness to the annual mean objective. With regards to NO₂, the report concludes that there were no exceedances of relevant national objectives and therefore no further Detailed Assessment is required.

13.3.18 The study area does not include Linlithgow High Street due to the fact that road links outside the boundary of the study area do not meet the DMRB criteria as listed in paragraph 13.2.6. As a result, it is considered unlikely that any of the route corridor options would have a significant impact on the AQMA in Linlithgow.

Fife Council

13.3.19 Fife Council (FC) completed the second round of air quality review and assessment in 2003 with subsequent Progress Reports following in 2004 and 2005. The 2003 USA identified that high NO₂ concentrations were recorded at several kerbside locations within the Fife area. The 2004 Progress Report recommended to undertaking monitoring at the façade of buildings rather than kerbside locations to allow a better assessment of likely exposure. A revised monitoring programme was carried out in 2004 and automatic monitoring of NO₂ has been undertaken at two locations (Rosyth and Kincardine) in Fife.

13.3.20 In 2006 FC submitted an USA as part of the third round of air quality assessment. The USA concluded that it is unlikely that the air quality objective for NO₂ would be exceeded.

13.3.21 With regards to PM₁₀, the 2006 USA concluded that the 2004 air quality objective is unlikely to be exceeded but that the 2010 objective might be closely approached. It was recommended to continue automatic monitoring for a period covering at least one full year.

13.3.22 The 2007 Progress Report concluded that there is a risk of exceeding the NO₂ and PM₁₀ air quality objectives in Bonnygate, Cupar and a Detailed Assessment has been carried out during 2007. If the Detailed Assessment confirms the exceedance of relevant objectives, an Air Quality Management Area will have to be designated.

13.3.23 As Bonnygate is located more than 40km to the northeast of the proposed replacement bridge, it is very unlikely that any of the assessed corridor options will have an adverse impact on the existing air quality hotspot.

Local Air Quality Monitoring

13.3.24 There are a number of continuous monitoring stations within the areas of Edinburgh, Fife and West Lothian, however, only one of them is located within 5km of the proposed replacement bridge. The Council of Fife operates a mobile monitoring station in Rosyth at NGR 311752, 683515. In their 2007 Progress Report, Fife Council reports a NO₂ concentration of 26µg/m³ at this location for a six month period (October 2006 – March 2007).

13.3.25 City of Edinburgh, Fife and West Lothian Councils also operate extensive networks of diffusion tubes. However, only a limited number of tubes are located in the vicinity of the proposed replacement bridge. Table 13.4 lists diffusion tubes located in Rosyth, Fife, approximately 2km northwest of the proposed replacement bridge and associated measured NO₂ concentrations.

Table 13.4: Diffusion Tube Results for Rosyth, Fife

Diffusion Tube	Monitoring Type*	NGR	NO₂ Concentration
Diffusion Tube	Monitoring Type*	NGR	2004	2005	2006
Admiralty Rd	KS	312103, 683439	37	31	36
Admiralty Rd 1	RS (F)	312103, 683439	19	26	32
Admiralty Rd 2	RS (F)	312103, 683439	20	26	33
Admiralty Rd 3	RS (F)	312103, 683439	20	23	32

* KS – Kerbside; RS (F) – Roadside on building facade

13.3.26 The results in Table 13.4 show that for all monitored years the annual mean NO₂ air quality objective as shown in Table 13.3 was met.

Background Pollution Concentration

13.3.27 Estimated pollutant background concentrations from the national air quality archive for Edinburgh, Fife and West Lothian in 2005 (Baseline year for the assessment) are summarised in Tables 13.5, 13.6 and 13.7 below.

Table 13.5: Edinburgh Background Concentrations

Pollutant	2005 Annual Mean, µg/m³
Pollutant	CEC Area Mean	CEC Area Maximum	CEC Area Minimum
NO_x	18.5	41.6	6.4
NO₂	14.2	26.1	5.0
PM₁₀	14.4	20.3	11.6

Note: The data presented are nationally mapped annual means for each 1km grid square aggregated over the Edinburgh area.

Table 13.6: Fife Background Concentrations

Pollutant	2005 Annual Mean, µg/m³
Pollutant	Fife Area Mean	Fife Area Maximum	Fife Area Minimum
NO_x	7.3	21.7	3.9
NO₂	5.7	17.1	3.1
PM₁₀	11.8	16.8	10.3

Note: The data presented are nationally mapped annual means for each 1km grid square aggregated over the Fife area.

Table 13.7: West Lothian Background Concentrations

Pollutant	2005 Annual Mean, µg/m³
Pollutant	West Lothian Area Mean	West Lothian Area Maximum	West Lothian Area Minimum
NOx	10.6	26.5	4.8
NO₂	8.4	19.4	3.8
PM₁₀	13.7	21.9	11.3

The data presented are nationally mapped annual means for each 1km grid square aggregated over the West Lothian area.

13.3.28 The results indicate background concentrations of NO₂ and PM₁₀ are within applicable air quality standards (Table 13.3) although the maximum NO_x concentration in the CEC area exceeds the limit for the protection of ecosystems. The results do not take account of exposure or receptor location. It should also be noted that as these are background concentrations, levels would be expected to be higher at locations nearer to busy roads.

13.3.29 Industrial and vehicular emissions control has reduced ambient concentrations of NO_x and PM₁₀ over recent years and it is predicted that this trend will continue.

Nitrogen Deposition Rates

13.3.30 DMRB states that any nature conservation sites (‘designated sites’) and their characteristics should be identified as part of the air quality assessment. The designated sites that should be considered for an assessment are those for which the designated features are sensitive to air pollutants, either directly or indirectly, and which could be adversely affected by the effect of air pollution on vegetation within the nature conservation sites.

13.3.31 High levels of NO_x can have an adverse effect on vegetation, including leaf or needle damage and reduced growth. Deposition of pollutants derived from nitrogen oxide emissions contribute to acidification and/or eutrophication of sensitive habitats leading to loss of biodiversity.

13.3.32 Table 13.8 shows SSSIs within the study area, the reasons for their designation and critical loads for the features of special interest. The background nitrogen deposition rate (in kg/ha/yr) was taken from the APIS website (www.apis.co.uk) for grid references 312029, 678687 (Firth of Forth SPA & SSSI), 312070, 681475 (St Margaret’s Mash SSSI), 312545, 681673 (Ferry Hills SSSI). In accordance with the DMRB guidance, the total estimated background deposition rates are reduced by 2% per future year. Figure 13.1a-c shows the locations of assessed SSSIs within the study area.

Table 13.8: Nitrogen Critical Loads and Background Deposition Rates (2004)

SSSI Name	Features of Special Interest	Critical Load (kg N ha^-1 yr^-1)	Nitrogen Deposition (kg N ha^-1 yr^-1)
Firth of Forth	Neutral grassland	10-20	12.7
Firth of Forth	Fen, marsh and swamp	10-35	12.7
St Margaret’s Marsh	Saltmarsh fen; marsh and swamp	10-35	12.3
Ferry Hills	Calcareous grassland	15-25	12.3

DMRB Receptors

13.3.33 Thirty discrete receptor locations have been chosen to assess potential impacts of the route corridor options at various sensitive locations. Criteria as described in paragraph 13.2.4 were used to determine the most representative receptor locations. The same receptors have been used for all assessed route corridor options in order to allow comparison of impacts. Figure 13.2a-c and Table 13.9 show receptor locations in the northern (N) and southern (S) study areas.

Table 13.9: Individual Receptor Locations

Receptor	Grid Ref	Location Details
R1 (N)	NT 2987 8495	16 Sandybank, Halbeath
R2 (N)	NT2743 4645	The Bungalow; Dunfermline
R3 (N)	NT2334 4161	65 Park Lea, Rosyth
R4 (N)	NT3630 3508	Inverkeithing High School; Hillend Road
R5 (N)	NT3252 3467	Burleigh Cresent; Inverkeithing
R6 (N)	NT2259 3577	127 Parkside Street, Rosyth
R7 (N)	NT2190 3088	102 Castlandhill Road, Rosyth
R8 (N)	NT1940 3413	10 Castlandhill Road, Rosyth
R9 (N)	NT2436 2725	4 Mucklehill Park, Inverkeithing
R10 (N)	NT 2331 1036	St Margarets Hope; North Queensferry
R11 (N)	NT2630 0720	15 Ferry Barns Court, North Queensferry
R12 (S)	NT2400 8418	14 Farquhar Terrace, South Queensferry
R13 (S)	NT2866 8382	15 Hopetoun Road, South Queensferry
R14 (S)	NT2398 7919	41 Stoneyflats Cresent, South Queensferry
R15 (S)	NT2998 7509	2 Scotstoun Green, South Queensferry
R16 (S)	NT1542 7947	66 Echline Drive, South Queensferry
R17 (S)	NT1327 8475	7 Linnmill, South Queensferry
R18 (S)	NT2621 7176	12 Dundas Home Farm, South Queensferry
R19 (S)	NT9175 7629	9 Main Street, Newton
R20 (S)	NT1900 4112	95 King Edwards Way, Kirkliston
R21 (S)	NT9246 5067	2 Beatly Road, Winchburgh
R22 (S)	NT1927 3546	2 Millrig Cottages, Kirkliston
R23 (S)	NT2449 4934	2 Newmains Road, Kirkliston
R24 (S)	NT2559 4547	76 Main Street, Kirkliston
R25 (S)	NT1674 8150	14 Springfield Terrace, South Queensferry
R26 (S)	NT8799 7443	1 Winchburgh Road, Winchburgh
R27 (N)	NT1221 4467	239 Queensferry Road; Rosyth
R28 (N)	NT3999 8926	23 Westfield Grove, Crossgates
R29 (N)	NT4537 8685	Inverkeithing Road, Crossgates
R30 (N)	NT4478 3830	6 Letham Hill Avenue, Hillend

2005 – Base Year

13.3.34 In the year 2005, calculated NO₂ and PM₁₀ concentrations are well within the air quality objectives at all receptor locations. The highest concentration of NO₂ was calculated as 28.1µg/m³ at receptor R15, which is 70% of the air quality objective. The lowest concentration of NO₂ in 2005 was calculated as 10.4µg/m³ (26% of the air quality objective) at receptor R10. The highest concentration of PM₁₀ was established to be 21.3µg/m³ at receptor R15 and the lowest concentration was calculated as 13.44µg/m³ at receptor R17, which, in terms of percentage of the 2004 air quality objective represents, 54% and 34% respectively. A full list of results is presented in Appendix A13.1.

13.3.35 Forecast concentrations for both NO₂ and PM₁₀ in 2017 and 2032 are lower than those experienced in the base year (2005). This is to be expected due to predicted improvements in vehicle technology.

13.3.36 With regards to nitrogen deposition, Table 13.10 shows the existing nitrogen deposition rates in 2005 for the five assessed SSSIs.

Table 13.10: Nitrogen Deposition Rates in 2005

Receptor Name	Dry Deposition in 2005 (Kg/N/ha/yr)	Total Deposition Rate in 2005 (Kg/N/ha/yr)	Critical Load (Kg/N/ha/yr)
Firth of Forth SPA & SSSI 1	1.07	12.49	10-35
Firth of Forth SPA & SSSI 2	2.03	13.30	10-35
St Margaret’s Marsh SSSI	1.54	12.69	10-35
Ferry Hills SSSI 1	2.29	12.68	15-25
Ferry Hills SSSI 2	1.96	12.89	15-25

13.3.37 Table 13.10 shows that in 2005 the lower levels of critical load bands are exceeded for all assessed SSSIs, with the exception of Ferry Hills SSSI.

13.4 Potential Impacts

13.4.1 The results of the assessment of local air quality impacts associated with the Forth Replacement Crossing are presented below in terms of predicted air quality at local receptors, changes in local population exposure to air pollution and changes in nitrogen deposition at sensitive receptor sites. The results are presented by providing a baseline concentration (2005) and comparing the do minimum and do something scenarios for the years 2017 and 2032.

13.4.2 For consistency with the other environmental assessments, this chapter reports air quality separately for each of the northern and southern route corridor options. However, it is acknowledged that there may be slight variations in traffic flows depending on the combinations of options (e.g. North Corridor Option 1 when combined with either South Corridor Option 1 or South Corridor Option 2) and this could have consequent implications in terms of air quality. These combinations were therefore modelled, but with the exception of a small number of receptors the magnitude of change and significance categories for each option was unaffected by the different combinations. Where the magnitude or significance varies this is identified within this chapter, and the source pollution calculations for the combinations assessment are provided in Appendix A13.1. Population exposure differed between combinations and is therefore not reported for each route corridor option separately.

13.4.3 Tables showing percentages of change of pollutant concentrations between the do minimum and do something scenarios are presented in Appendix A13.1 for 2017 and 2032 and described below in terms of magnitude of change and significance.

Northern Route Corridor Options

North Corridor Option 1

Assessment of Residential Receptors - NO₂

13.4.4 For North Corridor Option 1, at all locations and for both do minimum and do something scenarios in 2017 and 2032 the predicted NO₂ concentrations are less than 45% of the air quality objective. These concentrations are considered to be well within the air quality objective.

13.4.5 Percentage changes for NO₂ vary between 0 and 37.6% in 2017 and between 0 and 42.1% in 2032. Receptors in the vicinity of roads which are predicted to undergo reductions in traffic as a result of the proposed scheme are likely to experience an improvement of air quality and receptors in the vicinity of new proposed road links are likely to experience deterioration as summarised in Table 13.11.

13.4.6 With reference to Table 13.2, the majority of concentration increases and decreases can be described as of Negligible significance for NO₂ in 2017 and 2032.

13.4.7 There is one receptor (R10) that is predicted to experience Moderate Adverse significance impacts with regards to NO₂ concentrations as a result of the proposed Forth Replacement Crossing for both assessed years. In 2017, one out of the 15 assessed receptor locations (R11) is predicted to experience Moderate Beneficial significance impacts. One receptor location (R9) is likely to experience Slight Adverse significance impacts as a result of the Forth Replacement Crossing. In 2032 one receptor location (R7) is predicted to experience Slight Adverse significance impacts and the impact significance of the Forth Replacement Crossing at one receptor (R29) can be described as Sight Beneficial.

13.4.8 Receptor R10 would be located along a new section of carriageway, which explains the larger deterioration at this receptor. Receptor R11 is located in the immediate vicinity of the existing Forth Road Bridge. It is predicted that traffic flows would be diverted to the proposed Forth Replacement Crossing, hence traffic flows are significantly reduced and air quality improved along the existing links.

Table 13.11: Annual Mean NO₂ Magnitude of Change and Significance (in accordance with NSCA guidance) – North Corridor Option 1

Magnitude	Significance
Magnitude	Improvement	Deterioration	No Change
Year of Opening (2017)
Very Large	R11 (Moderate Beneficial)	R10 (Moderate Adverse)
Large
Medium
Small		R9 (Slight Adverse)
Very Small	R3 (Negligible)	R5 (Negligible) R7 (Negligible)
Extremely Small	R8 (Negligible) R29 (Negligible)	R4 (Negligible) R6 (Negligible) R27 (Negligible)	R1, R2, R28, R30
Design Year (2032)
Very Large	R11 (Moderate Beneficial)	R10 (Moderate Adverse)
Large
Medium
Small	R29 (Slight Beneficial)	R7 (Slight Adverse)
Very Small	R1 (Negligible) R4 (Negligible) R8 (Negligible) R30 (Negligible)	R2 (Negligible) R3 (Negligible) R9 (Negligible)
Extremely Small	R27 (Negligible)	R6 (Negligible) R28 (Negligible)	R5

13.4.9 There are slight variations in annual mean NO₂ magnitude of change at receptors R3 (in 2032), R8 (in 2017) and R29 (in 2017) depending on what combination of route corridor options is selected. However, the overall significance is not affected by these variations.

Assessment of Residential Receptors - PM₁₀

13.4.10 Predicted concentrations for PM₁₀ for both the do minimum and do something scenario in 2017 and 2032 are less 90% of the 2010 air quality objective. These concentrations are within but not well within the air quality objective.

13.4.11 Percentages changes for PM₁₀ vary between 0 and 11.7% in 2017 and between 0 and 14.2% in 2032. Table 13.12 shows which receptors are predicted to experience improvement and deterioration with respect to local PM₁₀ concentrations.

13.4.12 With regards to PM₁₀, the impact on the majority of receptors can be described as Negligible for both assessed years. In 2017, there are three locations where the impact is Slight Adverse (R7, R9, R10) and one location which is likely to experience a Slight Beneficial impact (R11). In 2032, two receptor locations (R7, R10) are likely to experience Slight Adverse impacts and the PM₁₀ concentration change at two receptors (R8, R11) is predicted to be Slight Beneficial.

13.4.13 As with N0₂, deterioration at R10 and improvement at R11 can be explained due to proximity to a new section of carriageway and to the existing Forth Crossing respectively.

Table 13.12: Annual Mean PM₁₀ Magnitude of Change and Significance (in accordance with NSCA guidance) – North Corridor Option 1

Magnitude	Significance
Magnitude	Improvement	Deterioration	No Change
Year of Opening (2017)
Very Large
Large
Medium
Small	R11 (Slight Beneficial)	R10 (Slight Adverse)
Very Small		R7 (Slight Adverse) R9 (Slight Adverse)
Extremely Small	R1 (Negligible) R8 (Negligible) R29 (Negligible)	R5 (Negligible) R6 (Negligible)	R2, R3, R4, R27 - R30
Design Year (2032)
Very Large
Large
Medium	R11 (Slight Beneficial)
Small		R10 (Slight Adverse)
Very Small	R8 (Slight Beneficial) R29 (Negligible) R30 (Negligible)	R7 (Slight Adverse)
Extremely Small	R4 (Negligible) R5 (Negligible) R27 (Negligible) R28 (Negligible)	R2 (Negligible) R3 (Negligible) R6 (Negligible) R9 (Negligible)	R1

Changes in Local Population Exposure (NO₂ and PM₁₀)

13.4.14 The results of comparing predicted concentrations of NO₂ and PM₁₀ using the STAG methodology are presented in Appendix A13.2 for years 2017 and 2032. STAG assessment scores provide a useful indication of change in local population exposure to air pollution.

13.4.15 For North Corridor Option 1, results using the STAG assessment show that there would be virtually no change in local population exposure to air pollution for either NO₂ or PM₁₀ in 2017 or 2032 compared to the do minimum. Population exposure is illustrated below in Table 13.13.

Table 13.13: Local Population Exposure of NO₂ and PM₁₀– North Corridor Option 1

Route Corridor Combination	NO₂			PM₁₀
Route Corridor Combination	Deterioration	Improvement	STAG Score	Deterioration	Improvement	STAG Score
2017
North Corridor Option 1 (with South Corridor Option 1)	3692	3316	-0.004	3923	3085	-0.0013
North Corridor Option 1 (with South Corridor Option 2)	2847	3969	-0.082	3174	3642	-0.014
2032
North Corridor Option 1 (with South Corridor Option 1)	3708	5472	-0.022	3494	5686	-0.011
North Corridor Option 1 (with South Corridor Option 2)	3026	6275	-0.082	2825	6476	-0.021

13.4.16 A total of 7008 properties are located within 200m of road links affected by the N1S1 option in 2017, with 9180 affected by 2032.

13.4.17 A total of 6816 properties are located within 200m of road links affected by North Corridor Option 1 / South Corridor Option 2 in 2017, with 9301 properties affected by North Corridor Option 1 / South Corridor Option 2 in 2032.

Changes in Nitrogen Deposition

13.4.18 The results of estimating nitrogen deposition at identified SSSIs (St Margarets Marsh; Ferry Hills 1 and 2) for North Corridor Option 1 are presented in Tables 13.14 to 13.16. Figure 13.1 shows the location of these SSSIs.

Table 13.14: St Margaret’s Marsh SSSI (NGR312467 681432) – North Corridor Option 1

Transect Distance	Dry deposition on Transect in 2017 (Kg/N/ha/yr)		Total deposition rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
5m (closest to road link)	-	1.73	-	10.49	10-35
25m	-	1.40	-	10.16
45m	1.10	1.18	9.85	9.93

13.4.19 The predicted contribution from local traffic to nitrogen deposition rates at St Margaret’s SSSI varies between 1.10 Kg/N/ha/yr for the do minimum scenario (at 45 m distance) and 1.73 Kg/N/ha/yr for the do something scenario (at 5m distance). The closest road to the SSSI is located at 5m distance but only exists in the do something scenario. The lower value of the critical load band is exceeded at up to 45m from the closest road in the do something scenario. In the do minimum scenario, the critical load level would be met at all distances from the road. The impact of the Forth Replacement Crossing would increase the nitrogen deposition by 0.08 Kg/N/ha/yr at 45m distance.

Table 13.15: Ferry Hills 1 SSSI (NGR 312493 683361) – North Corridor Option 1

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
15m (closest to road link)	1.58	1.59	9.92	9.93	15-25

13.4.20 The predicted contribution from local traffic to nitrogen deposition rates at the Ferry Hills 1 SSSI differs between 1.58 Kg/N/ha/yr for the do minimum scenario and 1.59 Kg/N/ha/yr for the do something scenario. The nitrogen deposition increase resulting from North Corridor Option 1 / South Corridor Option 1 is 0.01 Kg/N/ha/yr. At the closest point to the road the critical load for calcareous grassland is met for scenarios with and without the development.

Table 13.16: Ferry Hills 2 SSSI (NGR 312615 681202) – North Corridor Option 1

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
0m	1.23	-	9.98	-	15-25
20m	1.22	-	9.97	-
40m	1.01	-	9.76	-
60m	0.84	-	9.60	-
80m	0.76	-	9.51	-
100m	0.71	-	9.46	-
120m	0.68	-	9.43	-
140m (closest to road link)	0.66	0.68	9.41	9.43

13.4.21 The predicted contribution from local traffic to nitrogen deposition rates at the Ferry Hills 2 SSSI at 140m distance ranges between 0.66 Kg/N/ha/yr for the do minimum and 0.68 Kg/N/ha/yr for the do something scenario. The closest road in the do something scenario is located at 140m distance from the SSSI. The nitrogen deposition increase resulting from route corridor option N1S1 is 0.02 Kg/N/ha/yr. The critical load for calcareous grassland is met for scenarios with and without the development.

North Corridor Option 2

Assessment of Residential Receptors - NO₂

13.4.22 For North Corridor Option 2, at all locations and for both do minimum and do something scenarios in 2017 and 2032 the predicted NO₂ concentrations were less than 43% of the air quality objective. These concentrations are considered to be well within the air quality objective.

13.4.23 Percentages of change for NO₂ vary between 0 and 37.6% in 2017 and between 0 and 42.1% in 2032 respectively. Receptors in the vicinity of roads which are predicted to undergo reductions in traffic as a result of the proposed scheme are likely to experience an improvement of air quality and receptors in the vicinity of new proposed road links are likely to experience as shown in Table 13.17 below.

13.4.24 With reference to Table 13.2, the majority of concentration increases and decreases can be described as Negligible in significance for both NO₂ and PM₁₀ in 2017 and 2032.

13.4.25 There is one receptor (R10) that is predicted to experience Moderate Adverse significance impacts with regards to NO₂ concentrations as a result of the Forth Replacement Crossing in both assessed years 2017 and 2032. In 2017 one out of the 15 assessed receptor locations (R11) is predicted to experience Moderate Beneficial significance impacts. The impact of the Forth Replacement Crossing at two receptor locations (R2, R9) can be described as Slight Beneficial. In 2032, one receptor (R7) is likely to experience Slight Adverse significance impacts as a result of the Forth Replacement Crossing and three receptors (R2, R9, R29) are predicted to experience Slight Beneficial significance impacts.

Table 13.17: Annual Mean NO₂ Magnitude of Change and Significance (in accordance to NSCA guidance) – North Corridor Option 2

Magnitude	Significance
Magnitude	Improvement	Deterioration	No Change
Year of Opening (2017)
Very Large	R11 (Moderate Beneficial)	R10 (Moderate Adverse)
Large
Medium
Small	R2 (Slight Beneficial) R9 (Slight Beneficial)
Very Small	R3 (Negligible) R6 (Negligible) R7 (Negligible)	R4 (Negligible) R5 (Negligible)
Extremely Small	R8 (Negligible) R30 (Negligible)		R1, R27, R28, R29
Design Year (2032)
Very Large	R11 (Moderate Beneficial)	R10 (Moderate Adverse)
Large
Medium
Small	R2 (Slight Beneficial) R9 (Slight Beneficial) R29 (Slight Beneficial)	R7 (Slight Adverse)
Very Small	R1 (Negligible) R3 (Negligible) R6 (Negligible) R8 (Negligible) R27 (Negligible) R30 (Negligible)	R5 (Negligible)
Extremely Small	R4 (Negligible)		R28

13.4.26 As explained in paragraph 13.4.2, Table 13.17 presents North Corridor Option 2 in combination with South Corridor Option 1. There are slight variations in magnitude of change at receptors R3 (in 2032), R4 (in 2017 and 2032), R5 (in 2017), R27 (in 2032) and R30 (in 2017) if North Corridor Option 2 is instead combined with South Corridor Option 2, however, the overall significance is not affected by these variations.

Assessment of Residential Receptors – PM₁₀

Predicted concentrations for PM₁₀ for both the do minimum and do something scenario in 2017 and 2032 were less than 90% of the 2010 air quality objective. These concentrations are within but not well within the air quality objective.

13.4.27 Percentages of change for PM₁₀ vary between 0 and 11.7% in 2017 and between 0 and 14.2% in 2032. Table 13.18 shows which receptors are predicted to experience improvement and deterioration with respect to local PM₁₀ concentrations.

13.4.28 With regards to PM₁₀, the impact on the vast majority of receptors can be described as Negligible. In 2017 there are two locations where the impact is Slight Adverse (R5, R10) and three locations (R2, R3, R11) which are likely to experience a Slight Beneficial effect. In 2032, two receptor locations (R7, R10) are predicted to experience Slight Adverse impacts as a result of the Forth Replacement Crossing and the number of receptors predicted to be Slight Beneficial increases to five.

13.4.29 As with N0₂, deterioration at Receptor R10 and improvement at Receptor R11 can be explained due to proximity to a new section of carriageway and to the existing Forth Crossing respectively.

Table 13.18: Annual Mean PM₁₀ Magnitude of Change and Significance (in accordance with NSCA guidance) – North Corridor Option 2

Magnitude	Significance
Magnitude	Improvement	Deterioration	No Change
Year of Opening (2017)
Very Large
Large
Medium
Small	R11 (Slight Beneficial)	R10 (Slight Adverse)
Very Small	R2 (Slight Beneficial) R3 (Slight Beneficial)	R5 (Slight Adverse)
Extremely Small	R1 (Negligible) R6 (Negligible)	R7 (Negligible)	R4, R8, R9, R27-R30
Design Year (2032)
Very Large
Large
Medium	R11 (Slight Beneficial)
Small		R10 (Slight Adverse)
Very Small	R2 (Slight Beneficial) R6 (Slight Beneficial) R8 (Slight Beneficial) R9 (Slight Beneficial) R29 (Negligible) R30 (Negligible)	R7 (Slight Adverse)
Extremely Small	R1 (Negligible) R3 (Negligible) R4 (Negligible) R27 (Negligible) R28 (Negligible)		R5

13.4.30 There are slight variations in annual mean PM₁₀ magnitude of change at receptor R5 in 2017 and 2032 depending on which combination of route corridor options is selected. As explained in paragraph 13.4.2, Table 13.18 presents North Corridor Option 1 in combination with South Corridor Option 1. However, if this was combined with South Corridor Option 2, the significance of impact would be lower (Negligible in 2017 and Slight Beneficial in 2032).

Changes in Local Population Exposure (NO₂ and PM₁₀)

13.4.31 The results of comparing predicted concentrations of NO₂ and PM₁₀ using the STAG methodology are presented in Appendix A13.2 for years 2017 and 2032. The STAG assessment scores provide a useful indication of change in local population exposure to air pollution.

13.4.32 For North Corridor Option 1, results using the STAG assessment show that there would be virtually no change in local population exposure to air pollution for either NO₂ or PM₁₀ in 2017 or 2032 compared to the do minimum. Population exposure is illustrated below in Table 13.19.

Table 13.19: Local Population Exposure of NO₂ and PM₁₀– North Corridor Option 2

Route Corridor Combination	NO2			PM10
Route Corridor Combination	Deterioration	Improvement	STAG Score	Deterioration	Improvement	STAG Score
2017
North Corridor Option 2 (with South Corridor Option 1)	2742	4035	-0.093	2747	4030	-0.021
North Corridor Option 2 (with South Corridor Option 2)	1891	4493	-0.149	2137	4247	-0.030
2032
North Corridor Option 2 (with South Corridor Option 1)	2412	7202	-0.090	2312	7302	-0.027
North Corridor Option 2 (with South Corridor Option 2)	2159	6770	-0.120	2077	6852	-0.031

13.4.33 A total of 6777 properties are located within 200m of road links affected by N2S1 route corridor option in 2017, with 9614 affected by 2032.

13.4.34 A total of 6384 properties are located within 200m of road links affected by N2S2 route corridor option in 2017, with 8929 affected by 2032.

Changes in Nitrogen Deposition

13.4.35 The results of estimating nitrogen deposition at identified SSSI for North Corridor Option 2 are presented in Tables 13.20 to 13.22. This presents North Corridor Option 2 as combined with South Corridor Option 1, however there are no significant changes in nitrogen deposition between this and the alternative combination with South Corridor Option 2.

Table 13.20: St Margaret’s Marsh SSSI (NGR 312467 681432) – North Corridor Option 2

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
5m (closest distance to road link)	-	1.71	-	10.45	10-35
25m	-	1.84	-	10.60
45m	1.10	1.78	9.85	10.55
85m	0.90	1.32	9.65	10.07
105m	0.85	1.12	9.60	9.87

13.4.36 The maximum contributions from local traffic to nitrogen deposition rates at the St Margaret’s Marsh SSSI unit was calculated to be 1.10 Kg/N/ha/yr for the do minimum scenario (at 45m distance) and 1.84 Kg/N/ha/yr (at 25m) for the do something scenario. The resulting increase of nitrogen deposition rates equates to 0.68 Kg/N/ha/yr at 45m distance. Critical loads for neutral grassland, fen marsh and swamp would be met at a distance of 105m from North Corridor Option 2 in the do something scenario.

Table 13.21: Ferry Hills 1 SSSI (NGR 312615 681202) – North Corridor Option 2

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
15m (closest distance to road link)	1.58	1.52	9.92	9.86	15-25
35m	1.44	1.49	9.77	9.82
55m	1.34	1.53	9.68	9.87
75m	1.28	1.64	9.61	9.97
95m	1.24	1.84	9.58	10.18
115m	1.22	2.12	9.56	10.46
135m	1.21	1.98	9.55	10.32
155m	1.19	1.69	9.52	10.02
175m	1.18	1.50	9.51	9.84
195m	1.17	1.39	9.51	9.72

13.4.37 The maximum predicted contribution from local traffic to nitrogen deposition rates at the Ferry Hills 1 SSSI in the do minimum scenario equates to 1.58 Kg/N/ha/yr (at 15m distance) and is decreasing with distance from the road. The contribution from local road traffic for the do something scenario is 1.52 Kg/N/ha/yr (at 15m distance). The increase in nitrogen deposition with increasing distance to the road link in the do something scenario is caused by another road link in the vicinity of the SSSI unit. The SSSI is located between the existing A90 and a new proposed road which forms part of corridor option North 2 / South 1. At the closest point (15m distance) to either of the road links the critical load for calcareous grassland is met for scenarios with and without the development.

Table 13.22: Ferry Hills 2 SSSI (NGR 312493 683361) – North Corridor Option 2

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
0m	1.23	-	9.98	-	15-25
20m	1.22	-	9.97	-
40m	1.01	-	9.76	-
60m	0.84	-	9.60	-
80m	0.76	-	9.51	-
100m	0.71	-	9.46	-
120m	0.68	-	9.43	-
140m	0.66	-	9.41	-
160m	0.64	0.65	9.39	9.40

13.4.38 The contribution from local traffic to nitrogen deposition rates at the Ferry Hills 2 SSSI is predicted to be 0.64 Kg/N/ha/yr for the do minimum scenario and 0.65 Kg/N/ha/yr for the do something scenario at 160m distance (closest road distance to the SSSI in the do something scenario). The nitrogen deposition increase resulting North Corridor Option 2 / South Corridor Option 1 is 0.01 Kg/N/ha/yr. The critical load for calcareous grassland is met for scenarios with and without the development.

Southern Route Corridor Options

South Corridor Option 1

Assessment of Residential Receptors - NO₂

13.4.39 For South Corridor Option 1, at all locations and for both do minimum and do something scenarios in 2017 and 2032 the predicted NO₂ concentrations are less than 43% of the air quality objective. These concentrations are considered to be well within the air quality objective.

13.4.40 Percentages changes for NO₂ vary between 0 and 37.6% in 2017 and between 0 and 42.1% in 2032. Receptors in the vicinity of roads which are predicted to undergo reductions in traffic as a result of the proposed scheme are likely to experience a change in air quality are summarised in Table 13.23.

13.4.41 In 2017, two out of the 15 assessed receptor locations (R12, R14) are predicted to experience Moderate Beneficial impacts. Three receptor locations are likely to experience Slight Adverse significance impacts as a result of the Forth Replacement Crossing. In 2032 five receptor locations are predicted to experience Slight Adverse significance impacts and the impact of the Forth Replacement Crossing at four receptors can be described as Moderate to Sight Beneficial significance.

Table 13.23: Annual Mean NO₂ Magnitude of Change and Significance (in accordance with NSCA guidance) – South Corridor Option 1

Magnitude	Significance
Magnitude	Improvement	Deterioration	No Change
Year of Opening (2017)
Very Large	R12 (Moderate Beneficial) R14 (Moderate Beneficial)
Large		R17 (Slight Adverse) R18 (Slight Adverse)
Medium
Small		R21 (Slight Adverse)
Very Small	R13 (Negligible) R19 (Negligible)	R15 (Negligible) R16 (Negligible) R20 (Negligible) R22 (Negligible) R23 (Negligible) R24 (Negligible) R25 (Negligible)
Extremely Small		R26 (Negligible)
Design Year (2032)
Very Large	R12 (Moderate Beneficial) R14 (Moderate Beneficial)
Large		R17 (Slight Adverse) R18 (Slight Adverse)
Medium
Small	R13 (Slight Beneficial) R15 (Slight Beneficial)	R16 (Slight Adverse) R20 (Slight Adverse) R22 (Slight Adverse)
Very Small	R23 (Negligible) R24 (Negligible)	R25 (Negligible) R26 (Negligible)
Extremely Small		R21 (Negligible)	R19

13.4.42 There are slight variations in magnitude of change if South Corridor Option 1 is combined with North Corridor Option 2 instead of North Corridor Option 1. However, the significance of impacts as listed in Table 13.23 would be unchanged except for the following minor shifts:

2017: R15 (to Negligible), R20 and R22 (to Slight Adverse) and R23 (to No Change).
2032: R13 (to Slight Beneficial), R19 (to No Change), R22 (to Slight Adverse), and R24 to Negligible).

Assessment of Residential Receptors – PM₁₀

13.4.43 Percentages changes for PM₁₀ vary between 0 and 11.7% in 2017 and between 0 and 14.2% in 2032. Table 13.24 shows which receptors are predicted to experience improvement and deterioration with respect to local PM₁₀ concentrations.

13.4.44 Predicted concentrations for PM₁₀ for both the do minimum and do something scenario in 2017 and 2032 are less than 89% of the 2010 air quality objective. These concentrations are within but not well within the air quality objective.

13.4.45 The impact on the vast majority of receptors can be described as Negligible significance for both assessed years. In 2017, there are two locations where the impact is Slight Beneficial (R12, R14). In 2032, two receptor locations (R20, R18) are likely to experience Slight Adverse significance impacts and the PM₁₀ impact significance at three receptors is predicted to be Slight Beneficial (R12, R14, R15).

Table 13.24: Annual Mean PM₁₀ Magnitude of Change and Significance (in accordance with NSCA guidance) – South Corridor Option 1

Magnitude	Significance
Magnitude	Improvement	Deterioration	No Change
Year of Opening (2017)
Very Large
Large
Medium	R14 (Slight Beneficial)
Small	R12 (Slight Beneficial)
Very Small	R13 (Negligible)	R17 (Negligible) R18 (Negligible) R21 (Negligible)
Extremely Small	R19 (Negligible)	R15 (Negligible) R16 (Negligible) R22 (Negligible)	R20, R23-R26
Design Year (2032)
Very Large
Large
Medium	R12 (Slight Beneficial) R14 (Slight Beneficial)
Small		R18 (Slight Adverse)
Very Small	R13 (Negligible) R15 (Slight Beneficial) R23 (Negligible) R24 (Negligible)	R16 (Negligible) R17 (Negligible) R20 (Slight Adverse)
Extremely Small		R19 (Negligible) R22 (Negligible)	R21, R25, R26

13.4.46 There are slight variations in magnitude of change if South Corridor Option 1 is combined with North Corridor Option 2 instead of North Corridor Option 1. However, the significance of impacts as listed in Table 13.24 would be unchanged except for the following minor shifts:

2017: R20; R24 and R26 (to Negligible), R22 (to Slight Adverse) and R15 and R21 (to No Change).
2032: R19 and R22 (to Negligible), R18 (to Slight Adverse) and R21 and R26 (to No Change).

Changes in Local Population Exposure (NO₂ and PM₁₀)

13.4.47 The results of comparing predicted concentrations of NO₂ and PM₁₀ using the STAG methodology are presented in Appendix A13.2 for years 2017 and 2032. The STAG assessment scores provide a useful indication of change in local population exposure to air pollution.

13.4.48 For South Corridor Option 1, results using the STAG assessment show that there would be virtually no change in local population exposure to air pollution for either NO₂ or PM₁₀ in 2017 or 2032 compared to the do minimum. Population exposure is illustrated below in Table 13.25.

Table 13.25: Local Population Exposure of NO₂ and PM₁₀ – South Corridor Option 1

Route Corridor Combination	NO2			PM10
Route Corridor Combination	Deterioration	Improvement	STAG Score	Deterioration	Improvement	STAG Score
2017
South Corridor Option 1 (with North Corridor Option 1)	3692	3316	-0.004	3923	3085	-0.0013
South Corridor Option 1 (with North Corridor Option 2)	2742	4035	-0.093	2747	4030	-0.021
2032
South Corridor Option 1 (with North Corridor Option 1)	3708	5472	-0.022	3494	5686	-0.011
South Corridor Option 1 (with North Corridor Option 2)	2412	7202	-0.090	2312	7302	-0.027

13.4.49 A total of 7008 properties are located within 200m of road links affected by the N1S1 route corridor option in 2017, with 9180 affected by 2032.

13.4.50 A total of 6777 properties are located within 200m of road links affected by N2S1 route corridor option in 2017, with 9614 affected by 2032.

Changes in Nitrogen Deposition

13.4.51 The results of estimating nitrogen deposition at identified SPAs and SSSIs (Firth of Forth 1 and 2) for South Corridor Option 1 are presented in Tables 13.26 and 13.27. Figure 13.1 shows the location of assessed sensitive SSSIs.

Table 13.26: Firth of Forth SPA & SSSI 1 (NGR 311783 678806) – South Corridor Option 1

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
10m (closest distance to road link)	1.78	0.88	10.75	9.85	10-20
20m	1.58	-	10.55	-
40m	1.30	-	10.27	-
60m	1.12	-	10.08	-
80m	0.99	-	9.96	-

13.4.52 At a distance of 10m from the road, the predicted contribution from local traffic to nitrogen deposition rates at the Firth of Forth 1 SPA & SSSI ranges between 1.78 Kg/N/ha/yr for the do minimum scenario and 0.88 Kg/N/ha/yr for the do something scenario. At 10m distance from the SSSI the Forth Replacement Crossing would decrease nitrogen deposition rates by 0.9 Kg/N/ha/yr. Critical loads for neutral grassland, fen marsh and swamp would be met at any distance from the road with the Forth Replacement Crossing in place.

Table 13.27: Firth of Forth SPA & SSSI 2 (NGR 312546 678691) – South Corridor Option 1

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
180m (closest distance to road link)	0.77	0.80	9.85	9.88	10-20

13.4.53 The predicted contribution from local traffic to nitrogen deposition rates at the closest point between the Firth of Forth SPA and SSSI and the road varies between 0.77 Kg/N/ha/yr and 0.8 Kg/N/ha/yr in the do minimum and do something scenarios. The impact of the Forth Replacement Crossing would increase nitrogen deposition by 0.03 Kg/N/ha/yr. The total deposition rate shows that with or without the Forth Replacement Crossing, the lower end of the critical load for neutral grassland, fen marsh and swamps would be met.

South Corridor Option 2

Assessment of Residential Receptors - NO₂

13.4.54 At all locations and for both do minimum and do something scenarios in 2017 and 2032 the predicted NO₂ concentrations are less than 45% of the air quality objective. These concentrations are considered to be well within the air quality objective (in accordance with the definition provided in Table 13.2).

13.4.55 Percentages of change for NO₂ vary between 0 and 37.6% in 2017 and between 0 and 42.1% in 2032 respectively. Receptors in the vicinity of roads which are predicted to undergo reductions in traffic as a result of the proposed scheme are likely to experience an improvement of air quality and receptors in the vicinity of new proposed road links are likely to experience deterioration as shown in Table 13.28.

13.4.56 In 2017, two out of the 15 assessed receptor locations (R12, R14) are predicted to experience Moderate Beneficial significance impacts. Three receptor locations are predicted to experience Slight Adverse significance impacts and the impact of the Forth Replacement Crossing at five receptors can be described as Slight Beneficial. In 2032, eight receptor locations can be described as either Moderate Beneficial or Slight Beneficial in terms of impacts from the Forth Replacement Crossing, one receptor (R17) is predicted to experience Slight Adverse significance impacts.

Table 13.28: Annual Mean NO₂ Magnitude of Change and Significance (in accordance with NSCA guidance) – South Corridor Option 2

Magnitude	Significance
Magnitude	Improvement	Deterioration	No Change
Year of Opening (2017)
Very Large	R12 (Moderate Beneficial) R14 (Moderate Beneficial)
Large	R15 (Slight Beneficial)	R17 (Slight Adverse)
Medium	R21 (Slight Beneficial) R23 (Slight Beneficial) R24 (Slight Beneficial)	R20 (Slight Adverse)
Small	R19 (Slight Beneficial)	R22 (Slight Adverse)
Very Small		R13 (Negligible) R16 (Negligible) R25 (Negligible)
Extremely Small			R18, R26
Design Year (2032)
Very Large	R12 (Moderate Beneficial) R14 (Moderate Beneficial) R15 (Moderate Beneficial)
Large	R23 (Slight Beneficial)	R17 (Slight Adverse)
Medium	R21 (Slight Beneficial) R22 (Slight Beneficial) R24 (Slight Beneficial)
Small	R19 (Slight Beneficial)	R20 (Slight Adverse)
Very Small		R13 (Negligible) R16 (Negligible) R25 (Negligible) R26 (Negligible)
Extremely Small		R18 (Negligible)

13.4.57 There are slight variations in magnitude of change at receptors R20 (in 2017) and R26 (in 2032) if South Corridor Option 2 is combined with North Corridor Option 2. However, the significance of impact would be lower (R20 - Negligible in 2017) or the same (R26 - Negligible in 2032).

Assessment of Residential Receptors – PM₁₀

13.4.58 Predicted concentrations for PM₁₀ for both the do minimum and do something scenario in 2017 and 2032 are less than 90% of the 2010 air quality objective. These concentrations are within but not well within the air quality objective.

13.4.59 Percentages of change for PM₁₀ vary between 0 and 11.7% in 2017 and between 0 and 14.2% in 2032. Table 13.29 shows which receptors are predicted to experience improvement and deterioration with respect to local PM₁₀ concentrations.

13.4.60 With regards to PM₁₀, the impact on the vast majority of receptors can be described as Negligible significance in both 2017 and 2032. In 2017 there are three locations (R17, R20, R22) where the impact is Slight Adverse significance and four locations which are likely to experience a Slight Beneficial effect (R12, R14, R15, R24). The significance at two receptor locations (R17, R20) ranges between Slight Adverse and Negligible depending on which northern route corridor option combination is assessed. In 2032, the number of receptors with a Slight Adverse effect is two (R17, R20) and five receptor locations are predicted to experience Slight Beneficial impacts. A summary of significance for all receptors is provided in Appendix A13.1.

Table 13.29: Annual Mean PM₁₀ Magnitude of Change and Significance (in accordance with NSCA guidance) – South Corridor Option 2

Magnitude	Significance
Magnitude	Improvement	Deterioration	No Change
Year of Opening (2017)
Very Large
Large
Medium	R14 (Slight Beneficial)
Small	R12 (Slight Beneficial) R15 (Slight Beneficial) R24 (Slight Beneficial)
Very Small	R19 (Negligible) R21 (Negligible) R23 (Negligible)	R17 (Slight Adverse) R20 (Slight Adverse) R22 (Slight Adverse)
Extremely Small		R16 (Negligible) R25 (Negligible)	R13, R18, R26
Design Year (2032)
Very Large
Large
Medium	R12 (Slight Beneficial) R14 (Slight Beneficial)
Small	R15 (Slight Beneficial) R24 (Slight Beneficial)	R17 (Slight Adverse)
Very Small	R19 (Negligible) R21 (Negligible) R22 (Slight Beneficial)	R20 (Slight Adverse)
Extremely Small		R16 (Negligible) R25 (Negligible)	R13, R18, R26

Changes in Local Population Exposure (NO₂ and PM₁₀)

13.4.61 The results of comparing predicted concentrations of NO₂ and PM₁₀ using the STAG methodology are presented in Appendix A13.2 for years 2017 and 2032. The STAG assessment scores provide a useful indication of change in local population exposure to air pollution.

13.4.62 For South Corridor Option 2, results using the STAG assessment show that there would be virtually no change in local population exposure to air pollution for either NO₂ or PM₁₀ in 2017 or 2032 compared to the do minimum. Population exposure is illustrated below in Table 13.30.

Table 13.30: Local Population Exposure of NO₂ and PM₁₀ – South Corridor Option 2

Route Corridor Combination	NO2			PM10
Route Corridor Combination	Deterioration	Improvement	STAG Score	Deterioration	Improvement	STAG Score
Year of Opening (2017)
South Corridor Option 2 (with North Corridor Option 1)	2847	3969	-0.082	3174	3642	-0.014
South Corridor Option 2 (with North Corridor Option 2)	1891	4493	-0.149	2137	4247	-0.030
Design Year (2032)
South Corridor Option 2 (with North Corridor Option 1)	3026	6275	-0.082	2825	6476	-0.021
South Corridor Option 2 (with North Corridor Option 2)	2159	6770	-0.120	2077	6852	-0.031

13.4.63 A total of 6816 properties are located within 200m of road links affected by South Corridor Option 2 / North Corridor Option 1 in 2017, with 9301 properties affected by South Corridor Option 2 / North Corridor Option 1 in 2032.

13.4.64 A total of 6384 properties are located within 200m of road links affected by N2S2 route corridor option in 2017, with 8929 affected by 2032.

Changes in Nitrogen Deposition

13.4.65 The results of estimating nitrogen deposition at identified SPAs and SSSIs (Firth of Forth 1 and 2) for South Corridor Option 2 are presented in Tables 13.31 and 13.32. Figure 13.1 shows the location of assessed sensitive SSSIs.

Table 13.31: Firth of Forth SPA & SSSI 1 (NGR 311783 678806) – South Corridor Option 2

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
10m (closest distance to road link)	1.78	0.88	10.75	9.85	10-20
20m	1.58	-	10.55	-
40m	1.30	-	10.27	-
60m	1.12	-	10.08	-
80m	0.99	-	9.96	-

13.4.66 At a distance of 10m from the road, the predicted contribution from local traffic to nitrogen deposition rates at the Firth of Forth SPA and SSSI 1 ranges between 1.78 Kg/N/ha/yr for the do minimum scenario and 0.88 Kg/N/ha/yr for the do something scenario. At 10m distance from the SSSI the Forth Replacement Crossing would decrease nitrogen deposition rates by 0.9 Kg/N/ha/yr. Critical loads for neutral grassland, fen marsh and swamp would be met at any distance from the road with the Forth Replacement Crossing in place.

Table 13.32: Firth of Forth SPA & SSSI 2 (NGR 312546 678691) – South Corridor Option 2

Transect Distance	Dry Deposition on Transect in 2017 (Kg/N/ha/yr)		Total Deposition Rate in 2017 (Kg/N/ha/yr)		Critical Load (Kg/N/ha/yr)
Transect Distance	Do Minimum	Do Something	Do Minimum	Do Something	Critical Load (Kg/N/ha/yr)
180m (closest distance to road link)	0.77	0.80	9.85	9.88	10-20

13.4.67 The predicted contribution from local traffic to nitrogen deposition rates at the closest point between the Firth of Forth SPA and SSSI and the road varies between 0.77 Kg/N/ha/yr and 0.8 Kg/N/ha/yr in the do minimum and do something scenarios. The impact of the Forth Replacement Crossing would increase nitrogen deposition by 0.03 Kg/N/ha/yr. The total deposition rate shows that with or without the Forth Replacement Crossing, the lower end of the critical load for neutral grassland, fen marsh and swamps would be met.

Regional Assessment

13.4.68 In order to assess the wider impact of the northern and southern route corridor options, total emissions of NOx, PM10 and CO₂ have been calculated within the study area for route corridor combinations and results are shown in Table 13.33. Total vehicle kilometres travelled (vkt) under each of the route corridor options are also shown in Table 13.33.

Table 13.33: Total Emissions (tonnes/annum)

Pollutant	Do Minimum	North Corridor Option 1 / South Corridor Option 1	North Corridor Option 1 / South Corridor Option 2	North Corridor Option 2 / South Corridor Option1	North Corridor Option 2 / South Corridor Option 2
Year of Opening (2017)
Total vkt	3,724,156	3,950,763	3,830,672	3,514,829	3,351,925
NO_x	559.5	611.3	610.7	533.9	526.6
PM₁₀	18.8	20.1	19.9	17.0	16.7
CO₂	274975.9	290549.3	286910.5	254033.8	247466.3
Design Year (2032)
Total vkt	5,142,239	4,883,780	4,673,525	4,347,951	4,082,016
NO_x	664.8	735.0	723.3	638.7	621.2
PM₁₀	24.6	24.9	24.2	21.6	20.5
CO₂	365547.8	352682.8	344049.1	307424.9	296013.9

13.4.69 Graphs 13.1 to 13.6 visualise the data presented in Table 13.33. The lowest overall NO_x, PM₁₀ and CO₂ emissions for both 2017 and 2032 are predicted to occur in North Corridor Option 2 / South Corridor Option 2.

13.4.70 Graph 13.6 shows a decrease in 2032 CO₂ emissions for all route corridor options relative to the do minimum. This is likely to be a result of decreased congestion and decreasing total vehicle kilometres travelled. In 2017 (Graph 13.5) there is a slight increase in emissions between the do minimum and route corridor options North Corridor Option 1 / South Corridor Option 1 and North Corridor Option 1 / South Corridor Option 2. This trend is also reflected in the total vehicle kilometres travelled.

Graph 13.1: Total NOx emissions – 2017

Graph 13.2: Total NOx emissions – 2032

Graph 13.3: Total PM₁₀ emissions – 2017

Graph 13.4: Total PM₁₀ emissions – 2032

Graph 13.5: Total CO₂ emissions – 2017

Graph 13.6: Total CO₂ emissions - 2032

13.4.71 The assessment described above provides an indication of total emissions within the study area and allows a comparison of the different corridor options in terms of total emissions. However, the study area is relatively small in terms of regional or global emissions.

13.4.72 The Transport Model for Scotland (TMfS05a) includes an environmental appraisal module (ENEVAL) which provides information on pollutants associated with transport. ENEVAL data on CO₂ emissions was produced for an extended area covering the South East of Scotland Transport Partnership (SESTran) area which includes the Scottish Borders, East Lothian, Midlothian, City of Edinburgh, West Lothian, Falkirk, Clackmannanshire and Fife.

13.4.73 The 2017 ENEVAL emissions calculated for this wider study area do not quite follow the trend shown in Graph 13.5, as ENEVAL shows small increases in CO₂ emissions (<0.4%) for all assessed corridor options when compared to the do minimum. However, these increases fall within the expected variability of the modelling process. 2032 ENEVAL data were not available at the time of assessment.

13.4.74 The wider study area CO₂ data are therefore considered to be broadly similar for all corridor options, including the do-minimum. As they do not assist in differentiating between corridor options, ENEVAL data are not reproduced in this report.

13.5 Potential Mitigation

13.5.1 The results of the Stage 2 assessment indicate that it is unlikely that exceedances of relevant air quality objectives and limit values would occur as a result of the proposed Forth Replacement Crossing. However, it is not feasible at DMRB Stage 2 to identify requirements for mitigation for either local air quality or the impacts of air quality on vegetation at designated sites (other than avoiding these areas where possible; refer to Chapter 9: Ecology and Nature Conservation). The requirement for mitigation will be reviewed during DMRB Stage 3.

13.5.2 Generic measures in relation to air quality during construction are outlined in Chapter 17 (Disruption Due to Construction).

13.6 Summary of Route Corridor Options Assessment

Northern Route Corridor Options

Changes in Population Exposure

13.6.1 Assessment scores represent differences in overall pollutant concentrations averaged over the number of properties affected and are calculated by subtracting the overall do minimum scenario score from the overall do something scenario score. A negative score therefore represents an improvement from the do minimum to the do something and a positive score represents a worsening of local air quality.

13.6.2 In terms of overall air quality, Table 13.34 (summarising from the STAG calculations) shows that under all of the route corridor options, there is predicted to be virtually no change in local population exposure to air pollution as a result of the Forth Replacement Crossing. Of the four route corridor options, North Corridor Option 2 / South Corridor Option 2 is predicted to result in the greatest change in air quality showing a very slight improvement (compared to the do minimum scenario) but these changes remain very small.

Table 13.34: Assessment Scores for 2017 and 2032 for Route Corridor Options

Route Corridor Option	2017		2032
Route Corridor Option	NO₂	PM₁₀	NO₂	PM₁₀
North Corridor Option 1 / South Corridor Option 1	-0.004	-0.0013	-0.022	-0.011
North Corridor Option 2 / South Corridor Option 1	-0.093	-0.021	-0.090	-0.027
North Corridor Option 1 / South Corridor Option 2	-0.082	-0.0143	-0.082	-0.021
North Corridor Option 2 / South Corridor Option 2	-0.149	-0.0296	-0.120	-0.031

Note: The assessment scores are based on average concentration change per assessed property and comparative to the do minimum scenario.

13.6.3 When comparing North Corridor Option 1 with North Corridor Option 2, it can be concluded that North Corridor Option 2 is predicted to result in a slightly higher improvement of local air quality when combined with both, South Corridor Option 1 and South Corridor Option 2, but again the changes are very small.

Changes in Air Quality and Nitrogen Deposition

Assessment of Designated Sites

13.6.4 The traffic related nitrogen deposition rates show that for the Firth of Forth SPA and SSSI 2 and both assessed Ferry Hill SSSI units critical loads of nitrogen will not be exceeded with or without the development.

13.6.5 The assessed Firth of Forth SPA and SSSI 1 in vicinity to the existing Forth Road Bridge will experience an improvement of equal scale for all assessed route corridor options.

13.6.6 It is predicted that critical loads for St Margaret’s Marsh SSSI will be exceeded for all do something route corridor options. It has been calculated that North Corridor Option 1 / South Corridor Option 2 route corridor option will have the least detrimental impact on the St Margaret’s Marsh SSSI.

Assessment of Residential Receptors

13.6.7 The assessment of individual residential receptors has shown that NO₂ concentrations modelled at all receptors are forecast to remain well within the air quality objectives and EU limit values. There is one receptor (R10) that is likely to experience Moderate Adverse impacts in all the assessed route corridor options.

13.6.8 The assessment has shown that PM₁₀ concentrations are predicted to remain below but not well below the air quality objective and EU limit value. The majority of receptors will experience Negligible impacts as a result of the Forth Replacement Crossing independent of which route corridor option is taken forward.

Regional Assessment

13.6.9 Total vehicle kilometres travelled are smaller for North Corridor Option 2 compared to North Corridor Option 1 in both assessment years 2017 and 2032.

13.6.10 In 2017, North Corridor Option 2 is predicted to result in a decrease of NO_x, PM₁₀ and CO₂ emissions compared to the do minimum whilst North Corridor Option 1 is predicted to result in an increase.

13.6.11 In 2032, CO₂ emissions are predicted to decrease compared to the do minimum for both northern route orridor options. The higher decrease is predicted to occur as a result of North Corridor Option 2. NO_x concentrations in 2032 are predicted to increase for North Corridor Option 1 when compared to the do minimum but decrease for North Corridor Option 2. In 2032, PM₁₀ concentrations are predicted to be higher for North Corridor Option 1 compared to North Corridor Option 2 and decrease for North Corridor Option 2 compared to the do minimum scenario. PM₁₀ concentrations for North Corridor Option 1 decrease or increase compared to the do minimum depending on which South Corridor Option it is combined with.

13.6.12 It should be noted that 2017 CO₂ data produced by ENEVAL for the wider area show no significant difference between emission levels for all assessed route corridor options and the do minimum.

Southern Route Corridor Options

Changes in Population Exposure

13.6.13 When comparing South Corridor Option 1 with South Corridor Option 2 with regards to population exposure, South Corridor Option 2 is predicted to result in the greater change in air quality showing a slightly higher improvement (compared to the do minimum), as shown in Table 13.35 below.

Table 13.35: Assessment Scores for 2017 and 2032 for Route Corridor Options

Route Corridor Option	2017		2032
Route Corridor Option	NO₂	PM₁₀		NO₂
South Corridor Option 1/ North Corridor Option 1	-0.004	-0.0013	-0.022	-0.011
South Corridor Option 2/ North Corridor Option 1	-0.082	-0.0143	-0.082	-0.021
South Corridor Option 1/ North Corridor Option 2	-0.093	-0.021	-0.090	-0.027
South Corridor Option 2/ North Corridor Option 2	-0.149	-0.0296	-0.120	-0.031

Note: The assessment scores are based on average concentration change per assessed property and comparative to the do minimum scenario.

Changes in Air Quality and Nitrogen Deposition

Assessment of Designated Sites

13.6.14 The traffic related nitrogen deposition rates show that for the Firth of Forth SPA and SSSI 2 and both assessed Ferry Hill SSSI units critical loads of nitrogen will not be exceeded with or without the development.

13.6.15 The assessed Firth of Forth SPA and SSSI 1 in the vicinity of the Forth Road Bridge will experience an improvement of equal scale for all assessed route corridor options.

13.6.16 It is predicted that critical loads for St Margaret’s Marsh SSSI will be exceeded for all do something route corridor options. It has been calculated that South Corridor Option 2 / North Corridor Option 1 will have the least detrimental impact on the St Margaret’s Marsh SSSI.

Assessment of Residential Receptors

13.6.17 The assessment of individual residential receptors has shown that NO₂ concentrations modelled at all receptors are forecast to remain well within the air quality objectives and EU limit values.

13.6.18 The assessment has shown that PM₁₀ concentrations are predicted to remain below but not well below the air quality objective and EU limit value. The majority of receptors will experience Negligible impacts as a result of the Forth Replacement Crossing independent of which route corridor option is taken forward.

Regional Assessment

13.6.19 Table 13.36 shows that total vehicle kilometres travelled are smaller for South Corridor Option 2 compared to South Corridor Option 1 in both assessment years 2017 and 2032.

13.6.20 Emissions for all assessed pollutants are lower for South Corridor Option 2 compared to South Corridor Option 1. However, depending on which northern corridor option is combined with South Corridor Option 2, concentrations of NO_x, PM₁₀ and CO₂ decrease (South Corridor Option 2 / North Corridor Option 2) or increase (South Corridor Option 2 / North Corridor Option 1) compared to the concentrations calculated for the do minimum scenario, with the exception of PM₁₀ and CO₂ in the 2032 scenario. Similarly, depending on which northern corridor option is combined with South Corridor Option 1, pollutant concentrations decrease (South Corridor Option1 / North Corridor Option 2) or increase (South Corridor Option 1 / North Corridor Option 1) compared to the do minimum scenario.

13.6.21 In 2032, CO₂ emissions for all scenarios are lower than the calculated emissions in the do minimum scenario.

13.6.22 It should be noted that 2017 CO₂ data produced by ENEVAL for the wider area show no significant difference between emission levels for all assessed route corridor options and the do minimum.

13.7 Scope of Stage 3 Assessment

13.7.1 The Stage 3 assessment will be undertaken in accordance with DMRB Volume 11, Section 3, Part 1: HA207/07 which requires at assessment of local air quality effects using a suitable model.

13.7.2 Dispersion modelling using ADMS-Roads (or similar model) will be carried out for the operational phase, covering an area similar to the study area used in the Stage 2 assessment. The dispersion model will be used to calculate concentrations of NO₂ and PM₁₀ at sensitive receptors and contour plots of pollutant concentrations will also be prepared.

13.7.3 The results for the different years will be evaluated against the relevant air quality criteria in that year for the situations with and without the scheme. The significance of these effects will then be assessed using NSCA guidance. Additionally, regional air quality impacts due to the total emissions anticipated as a result of the scheme will be assessed.

13.7.4 A qualitative assessment of an alternative do minimum assessment will be carried out. The approach and degree of assessment will depend on traffic data availability.

13.7.5 Construction effects will be assessed through a qualitative assessment of potential sources of air pollutant emissions from construction activities and through the formulation of appropriate mitigation and control measures to be placed within a formal Code of Construction Practice (CoCP).

13.8 References

Air Quality (Scotland) Regulations 2000 and Air Quality (Scotland) Amendment Regulations 2002.

City of Edinburgh Council (2000). Review and Assessment of Air Quality Stage 3.

City of Edinburgh Council (2002). Review and Assessment of Air Quality Stage 4.

City of Edinburgh Council (2003). Air Quality Action Plan: NO₂ Air Pollution.

City of Edinburgh Council (2003). Updating and Screening Assessment, Local Air Quality Management Phase 2.

Directive 2008/50/EC - Ambient Air Quality and Cleaner Air for Europe.

Directive 96/62/EC - Ambient Air Quality Assessment and Management

NSCA (2006). Development Control: Planning for Air Quality. Environmental Protection UK. National Society for Clean Air.

The Air Quality Standards (Scotland) Regulations 2007, HMSO.

The Air Quality Strategy for England, Scotland, Wales and Northern Ireland, Department of Environment, Food and Rural Affairs, The Stationery Office, July 2007.

The Highways Agency et al. (2007). Design Manual for Roads and Bridges (DMRB), Volume 11, Section 3, Part 1 Air Quality, HA207/07. The Highways Agency, Scottish Executive, The National Assembly for Wales and The Department of Regional Development Northern Ireland.

The Scottish Executive (2002). Scottish Planning Policy 2 (SPP2) – Economic Development.

The Scottish Executive (2005). Planning Advice Note 75 (PAN 75) – Planning for Transport.

The Scottish Executive (2005). Scottish Planning Policy 17 (SPP17) – Transport & Planning.

Transport Scotland (2008). Scottish Transport Appraisal Guidance. The Scottish Government.