Air Quality Assessment

Energion Felindre Road

Pencoed

i

AQ051643 V3

Project Reference AQ051643

Revision V3 FINAL

Issue Date 18/10/2019

Author SCH

Approved JK

Client:

Energion

Prepared by:

Jo Kirk

Kairus Ltd

Ottery St Mary

Devon

EX11 1SL

T: 01404 811572

www.kairus.co.uk

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Contents

1 Introduction 1

2 Site Description 2

2.1 The Existing Site 2

2.2 The Proposed Development 3

3 Policy Context and Guidance 4

3.1 Air Quality 4

3.2 Planning Policy 7

3.3 Local Planning Policy 8

3.4 Additional Guidance 8

4 Methodology 9

4.1 Construction Phase 9

4.2 Operational Phase 12

5 Baseline Air Quality Assessment 20

5.1 Bridgend Council Review and Assessment of Air Quality 20

5.2 Carbon Monoxide 21

5.3 DEFRA Background Maps 21

5.4 Background Concentrations at Ecological Receptors 22

5.5 Air Quality at the Development Site 23

6 Construction Impacts 24

6.1 Site and Surroundings 24

6.2 Risk Assessment of Dust Impacts 24

6.3 Defining the Risk of Impacts 26

7 Operational Impacts (Human Health) 27

7.1 NO2 Concentrations 27

7.2 Carbon Monoxide 30

8 Operational Impacts (Ecological Receptors) 31

8.1 Comparison with Critical Levels 31

8.2 Comparison with Critical Loads 32

9 Mitigation 34

10 Conclusion 35

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1 Introduction

Kairus Ltd was commissioned by Energion to carry out an air quality assessment in associated with

the proposed development of a short-term operating reserve (STOR) peaking power plant on land

off Felindre Road, Pencoed (the ‘Site’). The Site lies within the administrative area of Bridgend

County Borough Council (BCBC).

An increasing proportion of the electricity generation capacity is coming from renewable sources. In

order to manage short term fluctuations in demand and supply, the national grid has access to a

number of reserve power generators, which can be used at short notice to cover any gaps in supply.

The proposed STOR plant at the Pencoed site comprises of 9 x 4.5 MW engines, fueled by natural

gas. It is expected that the engines would operate (if required) for up to 2500 hours per year. To

ensure a worst-case prediction of potential impacts the assessment has assumed 2500 hours of

operation per year.

This report addresses the impact of the proposed development on local air quality during the

operational phase. Potential sources of emissions are identified and assessed in the context of

existing air quality and emission sources and the nature and location of receptors.

The key pollutants considered within the assessment are oxides of nitrogen (NOx as NO2) and carbon

monoxide (CO), the primary pollutants arising from the combustion of natural gas.

The assessment has considered impacts associated with alternative engines and different emission

stacks to determine the most effective mitigation strategy to ensure impacts on identified receptors

are kept to a minimum.

Predicted ground level concentrations of both pollutants have been compared against the relevant

air quality standards and guidelines for the protection of human health and sensitive ecological

habitats.

A glossary of common air quality terminology is provided in Appendix A.

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2 Site Description

2.1 The Existing Site

The Site is located on land to the north of Felindre Road, to the east of the town of Pencoed. The

Site forms the northern part of two fields which lie directly adjacent to Felindre Road. The Site is

bounded by open fields and scrub land to the north, east, south and west. There is an existing sub-

station located to the south-west. To the north-east is a large field with stables associated with

Felindre Mill.

The nearest sensitive receptors (residential and educational premises) are Felindre Mill,

approximately 220 m north-east, the Old Mill, approximately 250 m south-east and the Pencoed

Travel lodge and Pencoed Growers Nursery, 280-300 m east. Bridgend College lies to the north over

400 m from the site boundary.

The location of the Site is shown below in Figure 2.1.

Figure 2.1: Site Location

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2.2 The Proposed Development

The proposed application is for the installation of nine 4.5 MW engines, fuelled by natural gas. The

engines would be housed in individual concrete containers within a single 4m high casing. The

emissions flues would terminate above the containers at 12 m above ground level. There would be a

total of 9 emission flues.

Also included on site would be a small welfare office and gas cabinet.

An indicative layout of the proposed development is shown in Figure 2.2.

Figure 2.2: Layout of Proposed Development

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3 Policy Context and Guidance

3.1 Air Quality

3.1.1 International Legislation and Policy

The EU Directive 2008/50/EC1 on ambient air quality and cleaner air for Europe (the CAFE directive)

sets out the ambient air quality standards for a number of pollutants and the dates by which these

objectives should be met. The Air Quality Standards Regulations 20102 implements the requirements

of the Directive into UK legislation. The Directive contains a series of limit values for the protection

of human health and critical levels for the protection of vegetation. These limit values are legally

binding and the UK may incur infringement action if it does not meet the required objective limits

within the agreed time limits. The UK is currently exceeding the objective limits for NO2 and PM10

within London and a number of other air quality zones within the UK.

2.3 Directive 2008/50/EC makes it clear that the ambient air quality standards shall not be

enforced where there is no regular public access and fixed habitation:

‘2. Compliance with the limit values directed at the protection of human health shall not be assessed

at the following locations:

(a) any locations situated within areas where members of the public do not have access and

there is no fixed habitation;

(b) in accordance with Article 2(1), on factory premises or at industrial installations to which

all relevant provisions concerning health and safety at work apply;

(c) on the carriageway of roads; and on the central reservations of roads except where there

is normally pedestrian access to the central reservation.’

3.1.2 National Legislation and The UK Air Quality Strategy

The Government's policy on air quality within the UK is set out in the Air Quality Strategy (AQS) for

England, Scotland, Wales and Northern Ireland (AQS) published in July 20073, pursuant to the

requirements of Part IV of the Environment Act 1995. The AQS sets out a framework for reducing

hazards to health from air pollution and ensuring that international commitments are met in the UK.

The AQS is designed to be an evolving process that is monitored and regularly reviewed.

The AQS sets standards and objectives for ten main air pollutants to protect health, vegetation and

ecosystems. These are benzene (C6H6), 1,3-butadiene (C4H6), carbon monoxide (CO), lead (Pb),

nitrogen dioxide (NO2), oxides of nitrogen (NOx), particulate matter (PM10, PM2.5), sulphur dioxide

(SO2), ozone (O3) and polycyclic aromatic hydrocarbons (PAHs).

The air quality standards are long-term benchmarks for ambient pollutant concentrations which

represent negligible or zero risk to health, based on medical and scientific evidence reviewed by the

Expert Panel on Air Quality Standards (EPAQS) and the World Health Organisation (WHO). These are

general concentration limits, above which sensitive members of the public (e.g. children, the elderly

and the unwell) might experience adverse health effects.

The air quality objectives are medium-term policy-based targets set by the Government which take

into account economic efficiency, practicability, technical feasibility and timescale. Some objectives

1 Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe

2 Air Quality Regulations 2010 – Statutory Instrument 2010 No. 1001

3 The Air Quality Strategy for England, Scotland, Wales and Northern Ireland – July 2007

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are equal to the EPAQS recommended standards or WHO guideline limits, whereas others involve a

margin of tolerance, i.e. a limited number of permitted exceedences of the standard over a given

period.

For some pollutants, there is both a long-term (annual mean) standard and a short-term standard.

In the case of NO2, the short-term standard is for a 1-hour averaging period, whereas for CO it is for

an 8-hour averaging period. These periods reflect the varying impacts on health of differing

exposures to pollutants (e.g. temporary exposure on the pavement adjacent to a busy road,

compared with the exposure of residential properties adjacent to a road).

Of the pollutants included in the AQS, NO2 and CO would be particularly relevant to this project as

these are the primary pollutants associated with emissions from combustion plant. The current

statutory standards and objectives for NO2 and CO in relation to human health are set out in

Appendix B.

The statutory standards and objectives apply to external air where there is relevant exposure to the

public over the associated averaging periods within each objective. Guidance is provided within

Local Air Quality Management Technical Guidance 2016 (LAQM.TG(16))4 issued by DEFRA for Local

Authorities on where the objectives apply, as detailed in Appendix B. The objectives do not apply in

workplace locations, to internal air or where people are unlikely to be regularly exposed (i.e. centre

of roadways).

3.1.3 Local Air Quality Management

Local authorities are seen to play a particularly important role. Section 82 of the Environment Act

1995 requires every local authority to conduct a review of the air quality from time to time within

the authority’s area. The recently released DEFRA technical guidance, LAQM.TG(16), describes a new

streamlined approach to the Local Air Quality Management (LAQM) regime, whereby every authority

has to undertake and submit a single Annual Status Report/Annual Progress Report within its area,

to identify whether the objectives have been or will be achieved at relevant locations by the

applicable date. If the objectives are not being met, the authority must declare an Air Quality

Management Area (section 83 of the Act) and prepare an action plan (section 84) which identifies

measures that will be introduced in pursuit of the objectives.

3.1.4 Medium Combustion Plant (MCP) Directive

Pollutant emissions from combustion plant with a rated input between 1 and 50 megawatts (MWth)

are regulated through the Medium Combustion Plant Directive (MCPD)5. The MCPD was transposed

into UK law in January 2018 through an amendment to the Environmental Permitting Regulations. All

MCP are required to meet the relevant emission limits set out within the Directive.

3.1.5 Industrial Emissions Directive

The Industrial Emissions Directive (2010/75/EU)6 came into force on the 6th January 2011, replacing

the seven existing Directives, including the Waste Incineration Directive (WID) and Large Combustion

Plant Directive (LDPD), implemented through the Environmental Permitting Regulations (EPR). The

4 DEFRA (2016) Local Air Quality Management. Technical Guidance LAQM.TG(16)

5 The European Parliament and the Council of the European Union (2015) Directive 2015/2193/EU of the European Parliament and of the

Council, available: http://eur-lex.europa.eu/legal-content/En/TXT/?uri=CELEX%3A32015L2193

6 Directive 2010/75/EU of the European Parliament & of the Council of 24th November 2010 on Industrial Emissions (Integrated Pollution

Prevention and Control) http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:334:0017:0119:en:PDF

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IED has been transposed into UK law via the Environmental Permitting (England and Wales)

(Amendment) Regulations 2013 (SI 2013 No, 390)7, which came into force on 27 February 2013.

Combustion activities listed in Section 1.1, Part (A) 1 of Schedule 1 of the Environmental Permitting

Regulations will normally require an environmental permit issued by Natural Resources Wales.

This section includes:

• Combustion appliances with an aggregated rated thermal input of greater than 50MW, or

• Appliances with a rated thermal input of greater than 3MW which burn fuel manufactured

from, or comprising, waste (unless they are carried on as part of a Part B activity, in which they

will normally fall to the Local Authority for regulation)

The proposed combustion activities will include a total of nine 4.5 MW gas fired engines (a total of

40.5 MW). As such, the plant will not be regulated under IED.

3.1.6 Control of Dust and Particulates Associated with Construction

Section 79 of the Environmental Protection Act (1990)8 states that where a statutory nuisance is

shown to exist, the local authority must serve an abatement notice. Statutory nuisance is defined

as:

• 'any dust or other effluvia arising on industrial, trade or business premises and being prejudicial

to health or a nuisance', and

• 'any accumulation or deposit which is prejudicial to health or a nuisance'.

Failure to comply with an abatement notice is an offence and if necessary, the local authority may

abate the nuisance and recover expenses. In the context of the proposed development, the main

potential for nuisance of this nature would arise during the construction phase - potential sources

being the clearance, earthworks, construction and landscaping processes.

There are no statutory limit values for dust deposition above which 'nuisance' is deemed to exist -

'nuisance' is a subjective concept and its perception is highly dependent upon the existing conditions

and the change which has occurred. However, research has been undertaken by a number of parties

to determine community responses to such impacts and correlate these to dust deposition rates.

However, impacts remain subjective and statutory limits have yet to be derived.

3.1.7 Critical Levels and Loads for Designated Ecological Sites

Critical loads and levels are used for assessing the risk of air pollution impacts on ecosystems. Critical

loads (CLOs) are defined as 'a quantitative estimate of exposure to one or more pollutants below

which significant harmful effects on specified sensitive elements of the environment do not occur

according to present knowledge'9.

Empirical CLOs for nutrient nitrogen are set under the Convention on Long-Range Transboundary Air

Pollution. They are based on empirical evidence such as observations from experiments and gradient

studies. CLOs are assigned to habitat classes defined within the European Nature Information

System (EUNIS)10 which enables consistency of habitat terminology and understanding. CLOs are

given as ranges and reflect the variation in ecosystem response across Europe.

7 Environmental Permitting (England and Wales) (Amendment) Regulations 2013 – Statutory Instrument 2013 No.390

8 Secretary of State, The Environment Act 1990 HMSO

9 http://www.unece.org/env/lrtap/WorkingGroups/wge/definitions.htm

10 http://eunis.eea.europa.eu/index.jsp

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CLOs for use in impacts assessments, which were revised in June 2010, are provided on the Air

Pollution Information System (APIS)11. The impact of the development on nutrient nitrogen and acid

(from nitrogen) deposition has been assessed and relevant identified sensitive ecological receptors

against the CLO’s set out on the APIS website. The CLO of relevance are set out in Appendix B.

3.2 Planning Policy

3.2.1 National Planning Policy

Published in November 2016, Planning Policy Wales (PPW)12 sets out the land use planning policies

of the Welsh Government. This is supplemented by a series of Technical Advice Notes.

At the heart of the PPW is a presumption in favour of sustainable development to ensure that social,

economic and environmental issues are balanced and integrated by the decision-maker when

determining planning applications (paragraph 4.2.2). It requires Local Plans to be consistent with the

principles and policies set out in the PPW with the objective of contributing to the achievement of

sustainable development.

Paragraph 4.26 states that ‘those proposing development also have a responsibility to provide

sufficient information to enable the decision maker to make an informed judgement on whether the

proposed development is sustainable’.

Paragraph 4.3 sets out the ‘Sustainable Development Principle’, established in the Wellbeing of

Future Generations (Wales) Act13. This ensures the needs of the present are met without

compromising the ability of future generations to meet their needs.

In dealing specifically with air quality, chapter 13, paragraph 13.10.1 states ‘the planning system

should determine whether a development is an acceptable use of land and should control other

development in proximity to potential sources of pollution rather than seeking to control the

processes or substances used in any particular development.’

Paragraph 13.10.3 continues ’where pollution considerations, which may be relevant to a pollution

control authorisation or license or result from the need to comply with any statutory environmental

quality standards or objectives, affect the use and development of land they can be material planning

considerations. This provision extends to air quality objectives set out under Part IV of the

Environment Act 1995 and the local authority’s action plans for Air Quality Management Areas.’

Section 13.12 refers to the potential for pollution affecting the use of land as being a material

consideration in deciding whether to grant planning permission. Possible material considerations in

determining applications for potentially polluting developments include:

• Location, taking into account such considerations as the reasons for selecting the chosen site

itself;

• Impact on health and amenity;

• The risk and impact of potential pollution from the development, insofar as this might have an

effect on the use of other land and the surrounding environment (the environmental regulatory

regime may well have an interest in these issues, particularly if the development would impact

on an Air Quality Management Area or a SAC);

• Prevention of nuisance;

11 www.apis.ac.uk

12 Welsh Government (2016) Planning Policy Wales Edition 9, November 2016

13 Welsh Government (2015) Well-being of Future Generations (Wales) Act 2015

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• Impact on the road and other transport networks, and in particular on traffic generation; and

• The need, where relevant, and feasibility of restoring the land to standards sufficient for an

appropriate after use.

3.3 Local Planning Policy

3.3.1 Bridgend Local Development Plan (2006 to 2021)

The Bridgend Local Development Plan14 was adopted in September 2013 and sets out the

development strategy for the county up to 2021, incorporating current objectives and policies to

govern planning decisions across the district.

Local Development Plan Objective 2: To protect and enhance the Environment Obj 2b is to

‘safeguard the quality of water, air, soil and tackle all sources of pollution’.

Strategic Policy SP2: Design and Sustainable Place Making requites that ‘all development should

contribute to creating high quality, attractive, sustainable places which enhance the community in

which they are located by……8) avoiding or minimising noise, air soil and water pollution’.

Policy ENV7: natural Resource Protection and Public Health states that ‘development proposals will

only be permitted where it can be demonstrated that they would not cause a new, or exacerbate an

existing, unacceptable risk to harm to health, biodiversity and or local amenity due to …..10 air

pollution’.

3.4 Additional Guidance

3.4.1 IAQM Position Statement on Assessment of STOR

In September 2017, the IAQM issued a position statement for consultation on the ‘Assessment of Air

Quality Impacts from STOR facilities and other limited-hours-of-operation plant’15. The guidance set

out within the position statement has been taken into consideration when undertaking the

assessment.

14 Bridgend County Brough Council, Local Development Plan 2006 to 2021, Adopted September 2013

15 IAQM (2017) Assessment of Air Quality Impacts from STOR facilities and other limited-hours-of-operation plant, Position Statement for

Consultation

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4 Methodology

4.1 Construction Phase

4.1.1 Construction Traffic

During construction of the proposed development, lorries will require access to the Site to deliver

and remove materials; earthmoving plant and other mobile machinery may also work on site

including generators and cranes. These machines produce exhaust emissions; of particular concern

are emissions of NO2 and PM10.

Based on the development proposals it is anticipated that there would be no more than 5-10

additional Heavy Duty Vehicles (HDV) generated on the adjacent road network on any given day.

The recently updated Environmental Protection UK (EPUK) and Institute of Air Quality Management

(IAQM) air quality guidance16 sets out criteria to assist in establishing when an air quality assessment

will be required. These criteria indicate that significant impacts on air quality are unlikely to occur

where a development results in less than 25 HDV movements per day in locations within or adjacent

to an AQMA and less than 100 HDV outside of an AQMA. The Site does not fall within an AQMA and

therefore it is anticipated that construction traffic generated by the proposed development would

result in a negligible impact on local pollution concentrations and has not been considered any

further in this assessment.

4.1.2 Construction Dust

The main air quality impacts that may arise during construction activities are dust deposition

resulting in the soiling of surfaces e.g. cars, window sills; visible dust plumes and elevated PM10

concentrations as a result of dust generating activities on the site. These dust emissions can give rise

to annoyance at nearby receptors due to the soiling of surfaces by the dust.

Separation distance is also an important factor. Research indicates that particles greater than 30μm,

will largely deposit within 100 metres of sources, while intermediate particles (10-30μm) are likely to

travel 100 –250m17 under normal meteorological conditions before returning to the surface.

Particles of greater than 30µm are responsible for the majority of dust annoyance. Consequently,

significant dust annoyance is usually limited to within a few hundred metres of its source. Smaller

particles (<10μm) are deposited slowly and can travel up to 1 km; however, the most significant

impacts on short term concentrations of PM10 occur within a shorter distance from source. This is

due to the rapid decrease in concentrations with increasing distance from the source due to

dispersion.

The assessment of construction impacts has followed the methodology set out within guidance

produced by the IAQM on assessing impacts from construction activities18.

In order to assess the potential impacts, the activities on construction sites are divided into four

categories. These are:

• demolition (removal of existing structures);

• earthworks (soil-stripping, ground-leveling, excavation and landscaping);

• construction (activities involved in the provision of a new structure); and

16 EPUK & IAQM (May 2017) Land-Use Planning & Development Control: Planning for Air Quality

17 Arup, The Environmental Effects of Dust at Surface Mineral Workings. (Report to the DETR)

18 IAQM (January 2014) Guidance on the Assessment of Dust from Demolition and Construction. Version 1.1

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• trackout (the transport of dust and dirt from the construction site onto the public road

network where it may be deposited and then re-suspended by vehicles using the network).

For each activity, the risk of dust annoyance, health and ecological impact is determined using three

risk categories: low, medium and high risk. The risk category may be different for each of the four

activities. The risk magnitude identified for each of the construction activities is then compared to

the number of sensitive receptors in the near vicinity of the site in order to determine the risks

posed by the construction activities to these receptors.

Step 1: Screen the Need for an Assessment

The first step is to screen the requirement for a more detailed assessment. An assessment is

required where there is:

• a ‘human receptor’ within 350m of the boundary of the site or 50m of the route(s) used by

construction vehicles on the public highway, up to 500m from the site entrance(s); and/or

• an ‘ecological receptor’ within 50m of the boundary of the site; or 50m of the route(s) used by

the construction vehicles on the public highway, up to 500m from the site entrance(s).

Step 2A: Define the Potential Dust Emission Magnitude

This is based on the scale of the anticipated works and the proximity of nearby receptors. The risk is

classified as small, medium or large for each of the four categories.

Demolition: The potential dust emission classes for demolition are:

• Large: Total building volume >50,000m3, potentially dusty construction material (e.g.

Concrete), on site crushing and screening, demolition activities >20m above ground level;

• Medium: total building volume 20,000m3 – 50,000m3, potentially dusty construction material,

demolition activities 10-20 m above ground level; and

• Small: total building volume <20,000m3, construction material with low potential for dust

release (e.g. metal cladding or timber), demolition activities <10m above ground, demolition

during wetter months.

Earthworks: This involves excavating material, haulage, tipping and stockpiling. The potential dust

emission classes for earthworks are:

• Large: Total site area >10,000m2, potentially dusty soil type (e.g. clay, which will be prone to

suspension when dry due to small particle size), >10 heavy earth moving vehicles active at any

one time, formation of bunds >8 m in height, total material moved >100,000 tonnes;

• Medium: Total site area 2,500 m2 – 10,000m2, moderately dusty soil (e.g. silt), 5 – 10 heavy

earth moving vehicles active at any one time, formation of bunds 4m – 8m in height, total

material moved 20,000 tonnes- 100,000 tonnes; and

• Small: Total site area <2,500m2, soil type with large grain size (e.g. sand), <5 heavy earth

moving vehicles active at any one time, formation of bunds <4 m in height, total material

moved <20,000 tonnes, earthworks during wetter months.

Construction: The important issues here when determining the potential dust emission magnitude

include the size of the building(s)/infrastructure, method of construction, construction materials,

and duration of build. The categories are:

• Large: Total building volume >100,000m3, on site concrete batching, sandblasting;

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• Medium: Total building volume 25,000m3 – 100,000m3, potentially dusty construction material

(e.g. concrete), on site concrete batching; and

• Small: Total building volume <25,000m3, construction material with low potential for dust

release (e.g. metal cladding or timber).

Trackout: The risk of impacts occurring during trackout is predominantly dependent on the number

of vehicles accessing the Site on a daily basis. However, vehicle size and speed, the duration of

activities and local geology are also factors which are used to determine the emission class of the

Site as a result of trackout. The categories are:

• Large: >50 HDV (>3.5t) outward movements in any one day, potentially dusty surface material

(e.g. high clay content), unpaved road length > 100m;

• Medium: 10-50 HDV (>3.5t) outward movements in any one day, moderately dusty surface

material (e.g. high clay content, unpaved road length 50-100m; and

• Small: <10 HDV (>3.5t) outward movements in any one day, surface material with low

potential for dust release, unpaved road length >50m.

Step 2B: Defining the Sensitivity of the Area

The sensitivity of the area is defined for dust soiling, human health (PM10) and ecological receptors.

The sensitivity of the area takes into account the following factors:

• the specific sensitivities of receptors in the area;

• the proximity and number of receptors;

• in the case of PM10, the local background concentration; and

• site specific factors, such as whether there are natural shelters, such as trees, to reduce the

risk of wind-blown dust.

Appendix C, Table C1 is used to define the sensitivity of different types of receptors to dust soiling,

health effects and ecological effects.

Based on the sensitivities assigned to the different receptors surrounding the site and numbers of receptors within certain distances of the site, a sensitivity classification can be defined for each. Tables C2 to C4, Appendix C indicate the criteria used to determine the sensitivity of the area to dust soiling, human health and ecological impacts.

Define the Risk of Impacts

The final step is to combine the dust emission magnitude determined in step 2A with the sensitivity

of the area determined in step 2B to determine the risk of impacts with no mitigation applied. Tables

C5 to C7, Appendix C, indicate the method used to assign the level of risk for each construction

activity. The identified level of risk is then used to determine measures for inclusion within a site-

specific Construction Management Plan (CMP) aimed at reducing dust emissions and hence reducing

the impact of the construction phase on nearby receptors. The mitigation measures are drawn from

detailed mitigation set out within the IAQM guidance document.

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4.2 Operational Phase

4.2.1 Stack Emissions

Scope

The scope of the impact assessment for stack emissions from the proposed site has been

determined in the following way:

• Review of air quality data for the area surrounding the Site, including data from the DEFRA Air

Quality Information Resource (UK-AIR) and the Air Pollution Information System (APIS);

• Desk study to confirm the location of nearby areas that may be sensitive to changes in local air

quality: and

• Review of available engines for installation at the Site;

• Review of emission parameters for the proposed development and dispersion modelling using

the ADMS Roads Extra dispersion model (Version 4.1.1, January 2018) to predict ground level

concentrations of pollutants at sensitive human and habitat receptor locations.

Emissions from the generators would be emitted through nine emission flues (one flue per engine)

12 m above ground level. Following a review of possible engines it was identified that the Siemens

GE J624 4.5 MW engines to be the cleanest in terms of emissions. These have therefore been

selected for use at the Site. Emission parameters used in the modelling assessment are provided in

Appendix D.

It is anticipated that the generators would operate for between 2,000-2,500 hours per year. The

assessment has assumed a total of 2,500 hours to ensure a worst-case assessment.

For assessing short-term concentrations (hourly, 8-hourly and 24-hourly), worst-case emission limits

have been assumed for the purposes of the modelling assessment and the plant is assumed to be

operating at full load, 100% of the time. This is clearly an extreme worst-case but allows for the fact

that the plant may be operating during worst-case meteorological conditions. For long-term

concentrations (annual mean and 24-hourly mean concentrations), the generators are assumed to

be operating continuously but with the emission rate adjusted for the number of operational hours

per year (2,500 hours per year).

Environment Agency guidance (now withdrawn)19 has been used in relation to the input data for the

prediction of annual average impacts from an intermittent process. On this basis, the model has

been set up to assume the operation of the plant for the entire year, however the emissions have

been reduced by a factor of 6 (8760/2500) in order that the same total mass emission is released

that would be the case for only 2,500 hours per year. The guidance states:

“You should describe how the concentrations of releases vary over time to ensure that representative

operational situations have been assessed. Also describe the plant load at which the emissions are

applicable, e.g. batch or continuous, average load or peak load. It may be necessary to evaluate

more than one operating scenario to ensure that the risks resulting from the worst-case situation

have been assessed.

The emissions released from these different operational situations should be related to those that

result in long term effects (e.g. continuous releases over a long-time period, or regular batch

releases, that do not result in great variation in concentration) and those that result in short-term

19 Environment Agency, H1 Environmental Risk Assessment Annex (f) Air Emissions, 2009

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effects caused by intermittent or periodic peak emissions at relatively high concentrations released

over a short period of time. “former H1 Annex f, p8.

“Different process options may lead to variations on the pattern of releases. For example, a process

operated intermittently may give lower annual concentrations but an increased frequency of short-

term peaks compared to one run continuously. Furthermore, although the long-term average

concentration may have been rendered acceptable by generally good dispersion there may, on

occasions, be unacceptable short-term peaks.” former H1 Annex f, p15.

Local Meteorological Data

The dispersion modelling has been carried out using five years (2013 - 2017) of hourly sequential

meteorological data in order to take account of inter-annual variability and reduce the effect of any

atypical conditions. Data from the meteorological station at Cardiff has been used for the

assessment, which is considered to be the closest and most representative meteorological site to

Pencoed.

A windrose for all years of meteorological data are presented in Appendix E.

Building Downwash/Entrainment

The presence of buildings close to emission sources can significantly affect the dispersion of

pollutants by leading to downwash. This occurs when a building distorts the wind flow, creating

zones of increased turbulence. Increased turbulence causes the plume to come to ground earlier

than otherwise would be the case and result in higher ground level concentrations closer to the

stack.

Downwash effects are only significant where building heights are greater than 40% of the emission

release height. The downwash structures also need to be sufficiently close for their influence to be

significant.

The container in which the generating units would be located is approximately 4m in height. This

building has been included in the dispersion model to account for potential downwash effects. There

are no other significant buildings in the vicinity of the Site. Details of the buildings included in the

modelling are set out in Figure D1 in Appendix D.

Nitric Oxide to NO2 Conversion

Oxides of nitrogen (NOx) emitted to atmosphere as a result of combustion will consist largely of nitric

oxide (NO), a relatively innocuous substance. Once released into the atmosphere, NO is oxidised to

NO2. The proportion of NO converted to NO2 depends on a number of factors including wind speed,

distance from the source, solar irradiation and the availability of oxidants, such as ozone (O3).

A conversion ratio of 70% NOx:NO2 has been assumed for comparison of predicted concentrations

with the long-term objectives for NO2. A conversion ratio of 35% has been utilised for the

assessment of short-term impacts, as recommended by Environment Agency guidance20.

Baseline NOx Emissions

The A473 is located to the west of the Site and is a potentially significant source of traffic related

emissions in the area which may impact air quality at a number of the selected sensitive receptors,

particularly those located within 200 m of the road. Local traffic related NOx emissions have

therefore been taken into account when calculating baseline NO2 concentrations.

20 AQMAU, Conversion Rates for NOx and NO2.

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Local traffic emissions have been modelled using the ADMS Roads Extra (Version 4.1.1) model and

the resulting NO2 concentrations predicted at each receptor location added to DEFRA background

NO2 concentrations (Table 5.2) to provide total baseline concentrations. Details on the approach

used to model road emissions is set out in Appendix F.

Sensitive Human Health Receptors

The term 'sensitive receptors' includes any persons, locations or systems that may be susceptible to

changes as a consequence of the proposed development. As detailed in Appendix B annual mean

objectives are relevant at the facades of residential buildings, schools, hospitals and care homes.

The sensitive receptors which have been used for modelling purposes are provided in Table 4.1 and

their locations shown in Figure 4.1 These include the nearest residential and educational receptors

to the Site which represent long-term and short-term exposure and local footpaths which represent

short-term exposure.

Impacts have also been modelled on a receptor grid and contour plots of predicted annual mean and

short-term concentration are provided.

Table 4.1: Location of Receptors used in ADMS Modelling Assessment

Receptor Number

Receptor Location OS Grid Reference Receptor Height (m)

1 Felindre Mill (residential, long-term exposure)

297095, 181523 1.5

2 The Old Mill (residential, long-term exposure)

297140, 181354 1.5

3 Pencoed Travel Lodge (short-term exposure)

297171, 181430 1.5

4 Pencoed Growers Nursery (short-term exposure)

297163, 181514 1.5

5 Bridgend College (educational, long-term exposure)

296836, 181784 1.5

6 Football Pitch (short-term exposure) 296638, 181706 1.5

7 Penybont Road (residential, long-term exposure)

296362, 181936 1.5

8 12-2 The Green (residential, long-term exposure)

296352, 181686 1.5

9 71 Felindre Avenue (residential, long-term exposure)

296407, 181515 1.5

10 16 Felindre Avenue (residential, long-term exposure)

296314, 181353 1.5

11 Pencoed School (educational, long-term exposure)

296016, 181107 1.5

12 School Football Pitch (short-term exposure) 296125, 181120 1.5

13 River Footpath (short-term exposure) 296380, 181385 1.5

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Table 4.1: Location of Receptors used in ADMS Modelling Assessment

Receptor Number

Receptor Location OS Grid Reference Receptor Height (m)

14 Footpath 296384, 181185 1.5

15 Velindre Farm (residential, long-term exposure)

297203, 181235 1.5

16 Residential property (residential, long-term exposure)

297507, 181353 1.5

Figure 4.1: Sensitive Human Receptor used in Modelling

Operational Traffic

The proposed development is run automatically, with intermittent maintenance visits therefore

there would be very few trips generated on the adjacent road network during operation. Based on

the screening criteria set out in the EPUK/IAQM air quality guidance (i.e. a change of 500 light duty

vehicles (LDV) and 100 HDV at locations outside an AQMA) no further assessment of traffic impacts

is required.

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Sensitive Habitats and Ecosystems

The assessment of impacts on sensitive habitats and ecosystems have been undertaken in

accordance with the DEFRA and Environment Agency’s Risk Assessment Guidance 21. This follows the

recommended approach as set out in the Natural Resources Wales website22.

The following habitat sites have been considered:

• Special Areas of Conservation (SACs) and candidate SACs (cSACs) designated under the EC

Habitats Directive23;

• Special Protection Areas (SPAs) and potential SPAs designated under the EC Birds Directive24;

• Ramsar Sites designated under the Convection on Wetlands of International Importance25;

• Sites of Special Scientific Interest (SSSI);

• National Nature Reserves (NNR);

• Local Nature Reserved (LNR); and

• ancient woodland.

Based on information provided on the DEFRA MAGIC website (http://magic.defra.gov.uk/) there

are two SACs located within 10 km of the Site and two SSSI’s within 2 km of the Site. Habitat

receptor designations relevant to the assessment are presented in Table 4.2. The location of the

receptors within the Usk River and Severn Estuary closest to the Site are set out in Figures 4.2 and

4.3.

Table 4.2: Sites of Ecological Interest

Receptor Number

Habitat Site OS Grid Reference Description

E1 Coed Y Mwstwr Woodlands SSSI

295260, 181149 1.6 km SW Deciduous woodland supporting rare bat population and rich ground flora

E2 Bryanna a Wren Tarw SSSI 297281, 182404 0.9 km N neutral and acidic grassland

E3 Blackmill Woodlands SAC 293085, 185515 5.6 km NW Old Sessile Oak Woodland

E4 Glaswell Tiroedd SAC 287508, 183091 9.4 km NW Molinia meadows supporting heath, grasses, rushes and small sedges

Where sensitive ecological receptors are present, predicted ground level concentrations of NOx are

compared with relevant critical levels, thresholds of airborne pollutant concentrations above which

damage may be sustained to sensitive plants and animals.

The critical levels are based on monitoring criteria and only apply in the following areas:

• More than 20 km from agglomerations; and

• More than 5 km away from other built up areas, industrial installations motorways ad major

roads with a traffic count of more than 50,000 vehicles per day.

21 https://www.gov.uk/guidance/air-emissions-risk-assessment-for-your-environmental-permit

22 https://naturalresources.wales/permits-and-permissions/environmental-permits/horizontal-guidance/?lang=en

23 Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora.

24 Council Directive 79/409/EEC on the conservation of wild birds

25 Ramsar (1971), The Convention of Wetlands of International Importance especially as Waterfowl Habitat

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Nationally around 37% of designated sites currently fall outside the above criteria and are therefore

excluded from the objectives, however, the Environment Agency’s H1 (now revoked) guidance states

that “the critical levels should be applied at all locations as a matter of policy, as they represent a

standard against which to judge ecological harm.”

For European sites within 10 km and SSSIs within 2 km, an assessment of deposition impacts

(nutrient nitrogen and acidity) is also provided. Critical loads refer to the threshold beyond which

deposition of pollutants to water or land results in measurable damage to vegetation and habitats.

The predicted NOx concentrations are used to determine acid and nutrient nitrogen deposition rates,

using typical deposition velocities.

Guidance produced by the Environment Agency on assessing emissions to air in relation to the

Habitats Directive (AQTAG06)26 sets out empirical methods for calculating nitrogen deposition (N-

deposition) rates based on calculated NOx concentrations and deposition velocity using the following

formula:

Dry deposition flux (µg/m2/yr) = ground level concentration (µg/m3) x deposition velocity (m/s)

The AQTAG06 guidance only provides deposition velocities for grassland (0.0015 m/s) and forest

habitats (0.003 m/s). The deposition rate for grassland has been used for receptors E2 and E4, and

the rate for forests used for E1 and E3.

The resulting dry deposition rate (µg/m2/s) can be converted to N-deposition in kg/ha/yr by

multiplying by a factor of 96.

To calculate Acid (N) deposition a factor of 6.84 is applied to the calculated dry deposition flux using

a factor of 6.84, as set out in the AQTAG06 guidance27.

The maximum predicted deposition rates are compared with site specific critical loads obtained from

APIS, as set out in Appendix B.

4.2.2 Significance of Impacts

Construction Phase

The IAQM assessment methodology recommends that significance criteria are only assigned to the

identified risk of dust impacts occurring from a construction activity following the application of

appropriate mitigation measures. For almost all construction activities, the application of effective

mitigation should prevent any significant effects occurring to sensitive receptors and therefore the

residual effects will normally be negligible

Human Health

The guidance issued by EPUK & IAQM relates to Air Quality considerations within the planning

process and sets criterion which identify the need for an Air Quality Assessment, the type of Air

Quality assessment required, and the significance of any predicted impact.

26 Environment Agency, Habitats Directive: Technical Guidance on Detailed Modelling Approach for an Appropriate Assessment for

Emissions to Air, Updated Version, Approved March 2014

27 For example 1kg N/ha/yr = 0.071 keq/ha/yr

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The guidance suggests expressing the magnitude of incremental change in concentrations as a

proportion of an Air Quality Assessment Level (AQAL) such as the air quality objectives set out in

Appendix B.

The significance of impact is then identified based on the incremental change in the context of the

new total concentrations and its relationship with the assessment criteria, noting whether the

impact is adverse or beneficial based on a positive or negative change in concentrations. The criteria

suggested for assigning significance are set out in Table 4.3.

These criteria have been derived for assessing impacts in terms of long-term concentrations. For

assessing short-term impacts, the guidance suggests that any change of less than 10% of the AQAL

are described as ‘negligible’, regardless of existing air quality. Where the short-term process

concentrations are 10-20% of the AQAL the severity of the impact is described as ‘small’. Impacts of

20-50% and over 50% are described as ‘medium’ and ‘large’, respectively.

Table 4.3: Impact Descriptors for Individual Receptors

Long-term Average Concentration at Receptor in Assessment Year

% Change in Concentrations Relative to Air Quality Assessment Level (AQAL)

1 2-5 6-10 >10

75% or less of AQAL Negligible Negligible Minor Moderate

76-94% of AQAL Negligible Minor Moderate Moderate

95-102% of AQAL Minor Moderate Moderate Major

103-109% of AQAL Moderate Moderate Major Major

110% of AQAL Moderate Major Major Major

AQAL – Air Quality Assessment Level which in this assessment refers to the Air Quality Objectives set out in Appendix B

Table B1.

The percentage change in concentration should be rounded to a whole number

The table should only be used with annual mean concentrations

The descriptors are for individual receptors only: overall significance should be based on professional judgment

When defining the concentrations as a percentage of the AQAL use the ’without scheme’ concentration where there is a

decrease in pollutant concentrations and the ‘with scheme’ concentrations for an increase

The total concentration categories reflect the degree of potential harm by reference to the AQAL value. At exposure, less

than 75% of this value i.e. well below, the degree of harm is likely to be small. As exposure approaches and exceeds the

AQAL, the degree of harm increases. This change naturally becomes more important when the result is an exposure that

is approximately equal to, or greater than the AQAL

It is unwise to ascribe too much accuracy to incremental changes or background concentrations, and this is especially

important when total concentrations are close to the AQAL. For a given year, it is impossible to define the new total

concentrations without recognising the inherent uncertainty, which is why there is a category that has a range around

the AQAL, rather than being exactly equal to it.

Habitat Sites

The Environment Agency’s environmental risk assessment guidance specifies criteria to enable the

potential significance of an impact to be determined. For this process contribution (PC), the impact is

deemed not significant if the annual mean PC is less than 1% of the critical level or load and the

short-term PC is less than 10% of the critical level or load. If either of these criteria are exceeded,

they are not necessarily significant however, it is then necessary to consider the total predicted

environmental concentrations (PEC) of deposition (PC plus the background contribution).

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For SPAs, SACS, Ramsar sites and SSSI if the following criteria apply then the emissions are classed as

insignificant:

• The long-term PC is greater than 1% and the PEC is less than 70% of the long-term standard.

For local nature sites the following criteria can be used to determine if emissions are insignificant:

• The short-term PC is less than 100% of the short-term environmental standard

• The long-term PC is less than 100% of the long-term environmental standard.

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5 Baseline Air Quality Assessment

5.1 Bridgend Council Review and Assessment of Air Quality

BCBC has completed a number of detailed assessments of air quality for the borough which has

concluded that air quality across the majority of the district remains below the relevant air quality

objectives. However, as a result of recent monitoring which recorded exceedences of the annual

mean NO2 objective the Council are in the process of declaring an AQMA covering Park Street in

Bridgend. The AQMA is located approximately 5 km south-west of the Site and therefore is not

considered relevant to this assessment.

Air quality in the town of Pencoed has not been found to be exceeding the relevant objective limits

during the review and assessment process.

5.1.1 Automatic Monitoring

BCBC operate two automatic monitoring sites within the borough. One monitors sulphur dioxide

concentrations at Rhiwceiliog and therefore is not of relevance to this assessment. The other is

located at Ewenny Cross, over 6km to the south-west and therefore not considered representative

for use in this baseline assessment.

5.1.2 Non-Automatic Monitoring Sites

BCBC measure NO2 using diffusion tubes at numerous locations across the borough. The Council

have recently added a number of additional monitoring sits to the network which includes locations

in Pencoed, however data for these sites won’t be reported until later in 2019.

Of the current monitoring locations reported in the 2018 Annual Status Report (ASR)28 , all are

located within Bridgend, over 3 km from the Site. With the exception of monitoring carried out on

Park Street, which found concentrations exceeding the annual mean NO2 objective at one location

during 2017, all other monitoring found concentrations to be meeting the annual mean NO2

objective throughout Bridgend during the 2017 monitoring year.

It is not possible to monitor short-term NO2 concentrations using diffusion tubes, however,

research29 has concluded that exceedances of the 1-hour mean objective are generally unlikely to

occur where annual mean concentrations are below 60 µg/m3. Based on the monitoring data set out

within the BCBC 2018 ASR it is unlikely that the short-term objective is being exceeded at any

location within the borough.

5.1.3 Baseline Modelling Results

The results of the baseline modelling assessment are set out in Table 5.1 below. The data shows

annual mean NO2 concentrations at less than 75% of the objective at all receptor locations. This also

indicates that short-term NO2 concentrations at the selected receptors are also considerably below

the 1-hour objective limit.

28 Bridgend County Borough Council, 2018 Annual Air Quality Progress Report for Bridgend County Borough Council, August 2018

29 D Laxen and B Marner: Analysis of the relationship between 1-hour and annual mean nitrogen dioxide at UK roadside and kerbside

monitoring sites (July 2003).

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Table 5.1: Baseline NO2 Concentrations Predicted at Selected Receptors

Receptor Number

Receptor Location Annual Mean NO2 (µg/m3)

1 Felindre Mill (residential, long-term exposure)

9.9

2 The Old Mill (residential, long-term exposure)

9.9

3 Pencoed Travel Lodge (short-term exposure)

9.9

4 Pencoed Growers Nursery (short-term exposure)

9.9

5 Bridgend College (educational, long-term exposure)

12.4

6 Football Pitch (short-term exposure) 12.9

7 Penybont Road (residential, long-term exposure)

12.1

8 12-2 The Green (residential, long-term exposure)

12.3

9 71 Felindre Avenue (residential, long-term exposure)

12.9

10 16 Felindre Avenue (residential, long-term exposure)

12.3

11 Pencoed School (educational, long-term exposure)

11.3

12 School Football Pitch (short-term exposure) 12.0

13 River Footpath (short-term exposure) 12.7

14 Footpath 14.4

15 Velindre Farm (residential, long-term exposure)

9.9

16 Residential property (residential, long-term exposure)

9.8

5.2 Carbon Monoxide

Monitoring of background CO concentrations is not currently undertaken by BCBC; therefore,

concentrations have been obtained from the Defra background maps. The CO mapping is based on

2001 monitoring data and factors are available to project the concentrations to future years. The

annual mean CO concentration in the vicinity of the Site is set out in Table 5.2.

5.3 DEFRA Background Maps

Additional information on estimated background pollutant concentrations has been obtained from

the DEFRA background maps provided on UK-AIR, the Air Quality Information Resource (http://uk-

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air.defra.gov.uk). Estimated air pollution concentrations for NOx, NO2 and PM10 have been extracted

from the 2015 background pollution maps for the UK and are set out in Table 5.2. These maps are

available in 1 km x 1 km grid squares and provide an estimate of concentrations between 2015 and

2030. Concentrations for 2017 have been taken from the grid squares 297500, 181500 and 296500,

181500 and used for the relevant receptors which fall within these areas.

The PM10 and NOx background maps are provided not only as total concentrations but are also

broken down into sector contributions (i.e. primary A roads and brake tyre). However, as this

assessment is considering the impact of the proposed development on existing air quality,

background concentrations from all sources should be considered. Therefore, data presented in

Table 5.1 provides total background concentrations for all pollutants.

CO concentrations have been taken from the 2001 background maps and factored to 2017 using a

factor of 0.433.

The data indicates that background concentrations of all pollutants in the vicinity of the Site are less

than 30 % of the relevant objectives.

Table 5.2: Annual Mean Background Air Pollution Concentrations

Pollutant OS 296500, 181500 OS 297500, 181500 Objective

CO 0.101 mg/m3 0.105 mg/m3 10 mg/m3

NOx 15.9 µg/m3 13.0 µg/m3 -

NO2 11.8 µg/m3 9.8 µg/m3 40 µg/m3

PM10 12.5 µg/m3 11.7 µg/m3 40 µg/m3

5.4 Background Concentrations at Ecological Receptors

Background concentrations of NOx and background nitrogen and acid deposition rates have been

obtained from the APIS website and are set out in Table 5.3.

Table 5.3: Background Data at Ecological Receptors

Ecological Receptor Annual NOx Concentration (µg/m3)

24-hour NOx Concentration (µg/m3)1

N-Deposition (kgN/ha/yr)

N Acid Deposition (keq/ha/yr)

E1 Coed Y Mwstwr Woodlands SSSI

21.8 25.7 25.9 1.85

E2 Bryanna a wren tarw SSSI 17.1 20.1 16.9 1.21

E3 Blackmill Woodlands SAC 11.2 13.2 26.0 1.86

E4 Glaswell Turiedd SAC 14.5 17.1 14.1 1.01

1 calculated from 1-hour NOx (2* annual mean) multiplied y a factor of 0.59 as set out in DEFRA/EA risk assessment guidance

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The data shows that NOx concentrations at the four habitat sites are below the annual mean and 24-

hour objective. However, the N-deposition rates are exceeding the critical loads at receptors E1 and

E3.

5.5 Air Quality at the Development Site

The Site is located to the east of the town of Pencoed in a background location away from the main

road network. Based on the baseline concentrations set out in Table 5.1 and the DEFRA data set out

in Table 5.2 annual mean and 1-hour NO2 concentrations and PM10 and CO concentrations are

expected to be meeting the relevant objective limits at the Site.

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6 Construction Impacts

6.1 Site and Surroundings

A summary of the proposed development is provided in Section 2 of this report.

There are a number of residential properties within 350 m of the Site therefore an assessment of

construction impacts in relation to human health and nuisance has been undertaken.

Dust emissions from construction activities are unlikely to result in significant impacts on ecologically

sensitive receptors beyond 50 m from the site boundary. A review of data held on the DEFRA MAGIC

website shows no sites designated as important for wildlife within 50m of the Site therefore impacts

on ecological receptors has not been considered any further within this assessment.

As discussed in Section 5, the PM10 concentrations, taken from the DEFRA background maps, in the

vicinity of the Site are expected to be below the relevant objective limits (Table 5.2). The data

indicates background concentrations in the region of 12 µg/m3. Based on professional judgment, it is

anticipated that PM10 concentrations at the Site and at adjacent properties are unlikely to be much

higher than background, therefore PM10 concentrations are expected to be below 24µg/m3.

The precise behaviour of the dust, its residence time in the atmosphere, and the distance it may

travel before being deposited would depend upon a number of factors. These include wind

direction and strength, local topography and the presence of intervening structures (buildings, etc.)

that may intercept dust before it reaches sensitive locations. Furthermore, dust would be naturally

suppressed by rainfall.

The windrose’ for the area are provided in Appendix E, which show that prevailing winds are from the west. Areas most consistently affected by dust are those influenced by prevailing winds and as such are generally located downwind of an emission source. Therefore, the highest risk of impacts would occur at receptors to the east of the Site, which would include Felindre Mill, The Old Mill and Pencoed Growers Nursery, which would be considered as high sensitivity receptors.

6.2 Risk Assessment of Dust Impacts

6.2.1 Defining the Dust Emission Magnitude

With reference to the criteria detailed in section 4, the dust emission magnitude for each of the

categories demolition, earthworks, construction and trackout have been determined. These have

been summarised in Table 6.1.

Table 6.1: Dust Emission Magnitudes

Activity Criteria Dust Emission Magnitude

Demolition No demolition required N/A

Earthworks Building site area <2500 m2, 1-2HDV on site. Small

Construction Building volume <10,000m3, main construction material brick and concrete

Small

Trackout Between 5-10 HDV (>3.5t) movements per day Small

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6.2.2 Sensitivity of Surrounding Area

Using the criteria set out in Tables C.2 and C.3, Appendix C, the sensitivity of the surrounding area to

impacts from dust emissions has been determined and are set out in Table 6.2.

Dust Soiling

There are no residential units within 20m of the Site boundary, the nearest being properties to the

north-east at Felindre Mill, 220 m from the Site. The sensitivity of the surrounding area in relation to

dust soiling effects is therefore considered to be low.

There will be between 5-10 HDV (>3.5t) movements per day during the construction phase which are

expected to travel to and from the Site along Felindre Road. As a general guide, significant impacts

from trackout may occur up to 500 m from large sites, 250 m from medium sites and 50 m from

small sites, as measured from the site exit. There are no residential properties located on Felindre

Road within 250m of the site access point. The sensitivity of the area to dust soiling effects from

trackout is therefore considered to be low.

PM10 Effects

As previously discussed, annual mean PM10 concentrations in the vicinity of the Site are expected to

be below 24 µg/m3. Based on the proximity of sensitive receptors to the site boundary and the local

concentrations of PM10 the sensitivity of the surrounding area is considered to be low with regards

human health impacts.

Table 6.2: Sensitivity of Receptors

Potential Impact Sensitivity at Site

Dust Soiling (earthworks and construction)

Receptor Sensitivity High

Number of Receptors 4-5 between 200-300 m

Sensitivity of the area Low

Dust Soiling (trackout) Receptor Sensitivity High

Number of Receptors None

Sensitivity of the area Low

Human Health (earthworks and construction)

Receptor Sensitivity High

Annual Mean PM10 Concentration < 24 μg/m3

Number of Receptors 4-5 between 200-300 m

Sensitivity of the area Low

Human Health (trackout)

Receptor Sensitivity High

Annual Mean PM10 Concentration < 24 μg/m3

Number of Receptors None

Sensitivity of the area Low

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6.3 Defining the Risk of Impacts

The dust emission magnitude as set out in Table 6.1 is combined with the sensitivity of the area

(Table 6.2) to determine the risk of both dust soiling and human health impacts, assuming no

mitigation measures applied at site. The risk of impacts associated with each activity is provided in

Table 6.3 below and has been used to identify the requirement for any site-specific mitigation

measures.

Table 6.3: Summary of Effects Without Mitigation

Source Dust Soiling PM10 Effect

Demolition N/A N/A

Earthworks Negligible Negligible

Construction Negligible Negligible

Trackout Negligible Negligible

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7 Operational Impacts (Human Health)

7.1 NO2 Concentrations

7.1.1 Annual Mean NO2

The predicted annual mean NO2 process contribution (PC) and the predicted environmental

concentration (PEC (PC plus baseline)) at each of the sensitive receptor locations representing long-

term exposure are presented in Table 7.1. The annual mean NO2 PC contribution from the proposed

engines are presented as a contour plot in Figure 7.1.

Baseline concentrations have been taken from the modelled results for each receptor as set out in

Table 5.1. The calculated PEC takes account of both DEFRA background concentrations and local

traffic emissions as set out in Appendix F.

Table 7.1: Predicted Annual Mean Ground Level Concentrations of NO2 based on GE J624

Engines (µg/m3)

Receptor PC

Annual NO2

PC

%age of AQS

PEC

Annual NO2

PEC

%age of AQS

Impact Significance

1 0.5 1.3 10.5 26.3 Negligible

2 0.7 1.8 10.7 26.7 Negligible

5 0.2 0.5 12.6 31.5 Negligible

7 0.1 0.1 12.1 30.3 Negligible

8 0.1 0.2 12.4 31.0 Negligible

9 0.2 0.4 13.0 32.6 Negligible

10 0.2 0.4 12.5 31.2 Negligible

11 0.1 0.2 12.0 29.9 Negligible

15 0.5 1.1 10.4 25.9 Negligible

16 0.2 0.5 10.0 25.1 Negligible

The PC is greater than 1% of the annual mean objective at receptors 1, 2 and 15 presented in Table

7.1. The impact of the proposed engines cannot, therefore, be classed as ‘not significant’ at these

locations without further consideration.

The contour plot presented in Figures 7.1 shows that the highest impacts occur to the east of the

application site within the adjacent field. There are no relevant receptors in this location. The

contour plot shows that at all locations of relevant exposure the change in annual mean NO2 as a

result of the operational site would be less than 1 µg/m3, less than 2% of the objective limit of 40

µg/m3.

The predicted impacts have further been considered in terms of the total annual mean NO2

concentrations (PEC) at the 10 receptors (PC plus baseline concentrations), also presented in Table

7.1. The PEC remains at less than 35% of the annual mean objective at all 10 receptors.

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Using the significance criteria set out in Table 4.3, the PC, which equates to less than 2% of the

objective limit.

The guidance set out by DEFRA and the EA for screening of emissions from point sources indicates

that where the PEC is less than 70% of the long-term objective no further assessment is required.

This would indicate that the impact of emissions from the proposed site in conjunction with

background concentrations are not significant.

The IAQM guidance provides further discussion on determining the significance of effects and sets

out the follow (Table 4.3, footnote 6) ‘the total concentration categories reflect the degree of

potential harm by reference to the objective limit (AQAL). At exposure less than 75% of this value i.e.

well below, the degree of harm is likely to be small’.

Based on professional judgement, taking into account the DEFRA, EA and IAQM guidance the impact

of the proposals are not considered to be significant given that total concentrations remain at less

than 35% of the objective limit at all locations and the PC would be less than 2% of the limit value.

Figure 7.1: Annual Mean NO2 as the Process Contribution (µg/m3)

7.1.2 99.8th Percentile NO2

The predicted short-term (hourly) NO2 PC and the PEC at each of the sensitive receptor locations is

presented in Table 7.2. A contour plot of the short-term PC contribution is presented in Figure 7.2.

At all the selected receptor locations the PC from the engines is less than 10% of the short-term

objective limit of 200 µg/m3, therefore based on the DEFRA and EA guidance impacts are considered

to be’ not significant’.

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The contour plot set out in Figure 7.2 shows the distribution of emissions from the Site. Short-term

concentrations are less than 1µg/m3 at all sensitive receptors, which is less than 1% of the objective

limit of 200 µg/m3. Based on the IAQM guidance the impact is also deemed to be negligible.

Further consideration of the short-term NO2 emissions, taking into account baseline NO2

concentrations (2 * annual mean baseline concentrations), shows the total NO2 concentrations (PEC)

at all receptors would be less than 15% of the objective limit.

It should also be considered that the predictions are based on the assumption that the engines

would be operating continually through the year, however in reality the engines would operate for

no more than 2500 hours per year. The predicted impacts are therefore an over-estimate of

potential impacts.

Based on professional judgement, taking into account the above discussion, impacts from the

operational site are not considered to be significant given the low level of overall exposure and total

concentrations remaining well below the objective.

Table 7.2: Predicted 99.8th Percentile of 1-Mean Ground Level Concentrations of NO2 (µg/m3)

Receptor PC

99.8th %ile NO2

PC

%age of AQS

PEC

99.8thile NO2

PEC

%age of AQS

Impact Magnitude

1 0.9 0.5 20.9 10.5 Negligible

2 1.3 0.6 21.2 10.6 Negligible

3 1.0 0.5 20.8 10.4 Negligible

4 0.8 0.4 20.7 10.3 Negligible

5 0.3 0.2 25.2 12.6 Negligible

6 0.3 0.2 26.2 13.1 Negligible

7 0.1 0.0 24.2 12.1 Negligible

8 0.2 0.1 24.8 12.4 Negligible

9 0.3 0.1 26.0 13.0 Negligible

10 0.3 0.1 24.9 12.5 Negligible

11 0.2 0.1 23.9 12.0 Negligible

12 0.2 0.1 24.2 12.1 Negligible

13 0.3 0.2 25.8 12.9 Negligible

14 0.4 0.2 29.1 14.6 Negligible

15 0.8 0.4 20.6 10.3 Negligible

16 0.4 0.2 20.0 10.0 Negligible

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Figure 7.3: 99.8th Percentile of 1-Hour Mean NO2 as the Process Contribution (µg/m3)

7.2 Carbon Monoxide

The predicted maximum 8-hour mean CO process contribution and the PEC at each of the sensitive

receptor locations is presented in Table 7.3.

The predicted PC at all sensitive receptors is less than 10% of the objective limit of 10 mg/m3,

therefore based on the DEFRA assessment criteria the impact of emissions from the operational site

can be classed as not significant in terms of CO.

Table 7.3: Predicted maximum 8-Hour Mean Ground Level CO Concentration based on MTU

Engines (mg/m3)

Receptor PC

8-Hour CO

PC

%age of AQS

PEC

8-Hour CO

PEC

%age of AQS

1 0.10 1.0 0.21 2.1

2 0.10 1.0 0.20 2.0

3 0.07 0.7 0.18 1.8

4 0.08 0.8 0.19 1.8

5 0.09 0.9 0.19 1.9

6 0.07 0.7 0.17 1.7

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Table 7.3: Predicted maximum 8-Hour Mean Ground Level CO Concentration based on MTU

Engines (mg/m3)

Receptor PC

8-Hour CO

PC

%age of AQS

PEC

8-Hour CO

PEC

%age of AQS

7 0.04 0.4 0.14 1.4

8 0.07 0.7 0.17 1.7

9 0.09 0.9 0.19 1.9

10 0.06 0.6 0.16 1.6

11 0.03 0.3 0.13 1.3

12 0.04 0.4 0.14 1.4

13 0.07 0.7 0.17 1.7

14 0.06 0.6 0.16 1.6

15 0.10 1.0 0.20 2.0

16 0.04 0.4 0.14 1.5

8 Operational Impacts (Ecological Receptors)

8.1 Comparison with Critical Levels

8.1.1 Airborne NOx

A summary of the maximum predicted ground level NOx PC and PEC at the selected ecological

receptors is presented in Table 8.1 for annual mean and Table 8.2 for 24-hour concentrations.

Table 8.1: Maximum Predicted Annual Mean NOx Concentrations at Sensitive Habitat

Receptors based on GE J624 Engines (µg/m3)

Habitat Site Critical Level, CL

PC PC (as a %age of the CL)

PEC PEC (as a %age of the CL)

E1 30 0.04 0.1 21.8 72.8

E2 30 0.05 0.2 17.1 57.1

E3 30 0.003 <0.1 11.2 37.4

E4 30 0.002 <0.1 14.5 48.3

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Table 8.2: Maximum Predicted 24-hour NOx Concentrations at Sensitive Habitat Receptors

based on GE J624 Engines (µg/m3)

Habitat Site Critical Level, CL

PC PC as a %age of the CL

PEC PEC as % of CL

E1 75 1.1 1.5 26.8 35.8

E2 75 1.8 2.4 21.9 29.3

E3 75 0.2 0.3 13.5 17.9

E4 75 0.1 0.2 17.2 22.9

The predicted NOx PC is less than 1% of the annual mean critical level and less than 10% of the 24-

hour critical level at all four receptors as a result of emissions from the GE J624 engines. Impacts at

these locations can be classed as not significant and no further consideration of potential impacts is

considered necessary.

8.2 Comparison with Critical Loads

8.2.1 Predicted Nutrient Nitrogen Deposition

Impacts on nutrient nitrogen deposition have been predicted at the designated habitat sites set out

in Table 4.2. A summary of nutrient nitrogen deposition as a result of the operational site compared

to critical loads (CLO) are provided in Table 8.3.

Table 8.3: Predicted Nutrient Nitrogen Deposition at Sensitive Habitat Receptors based on J624

Engines

Habitat Site Critical Load (kg N/ha/yr)

PC (kg N/ha/yr)

PC as a %age of the

CLO

PEC PEC (as %age of the

CLO)

E1 10 0.012 0.1 25.9 259

E2 20 0.007 <0.1 16.9 84

E3 10 0.001 <0.1 26.0 260

E4 15 <0.001 <0.1 14.1 94

Predicted nutrient nitrogen deposition from the site are predicted to be less than 1% of the relevant

CLOs at all four receptors, therefore impacts in these locations is considered to be not significant and

does not need any further consideration.

8.2.2 Predicted Nitrogen Acid Deposition

Nitrogen acid deposition predicted at each of the habitat sites are set out in Tables 8.4.

The PC predicted at all four habitat sites is less than 1% of the CLO therefore impacts in terms of acid

nitrogen deposition are deemed to be not significant.

33

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Table 8.4: Predicted Nitrogen Acid Deposition at Sensitive Habitat Receptors based on MTU

Engines

Habitat Site Critical Load (keq/ha/yr)

PC (keq/ha/yr)

PC as a %age of the

CLO

PEC (keq/ha/yr)

PEC (as %age of the

CLO)

E1 1.86 <0.001 <0.1 1.85 99

E2 1.41 <0.001 <0.1 1.21 85

E3 1.23 <0.001 <0.1 1.86 151

E4 1.11 <0.001 <0.1 1.01 91

34

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9 Mitigation

9.1.1 Construction Phase

The control of dust emissions from construction site activities relies upon management provisions

and mitigation techniques to reduce emissions of dust and limit dispersion. Where dust emission

controls have been used effectively, large-scale operations have been successfully undertaken

without impacts to nearby properties.

The proposed development has been identified as having a negligible risk for causing dust soiling

effects during the construction phase and impacts on nearby sensitive receptors are unlikely to be

significant. No site-specific mitigation is therefore recommended beyond that carried out as

standard practice.

9.1.2 Operational Phase

The proposed engines have been selected for use at the Site as they have been found to be the

cleanest in terms of emissions compared to others available on the market. Emissions from the

operational site have been found to be not significant in terms of human exposure and impacts on

the identified habitat sites. No further mitigation of operational impacts is considered necessary.

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10 Conclusion

Kairus Ltd was commissioned by Energion Ltd to carry out an air quality assessment in connection

with a proposed development of a short-term operating reserve (STOR) peaking power plant on land

of Felindre Road, Pencoed (the Site).

Following a review of a number of engine types the Siemens GE J624 4.5 MW engine has been found

to be the cleanest in terms of emissions. The proposed scheme therefore includes for nine 4.5 MW

GE J624 engines.

Due to the small nature of the development and the separation distances between the Site and the

nearest sensitive receptors there would be a negligible risk of effects from dust and vehicle

emissions during the construction phase. No mitigation beyond those undertaken as standard

practice are therefore required during this phase of the development.

Detailed air quality modelling using the ADMS dispersion model has been undertaken to predict the

impacts associated with stack emissions from the nine 4.5MW generating units at the Site. As a

worst-case, emissions from the stacks have been assumed to occur for the entire year when

compared against the short-term air quality limits and for 2500 hours for long-term air quality limits.

The predicted impacts are based on worst-case emissions given that the site is anticipated to

operate for between 2000-2500 hours per year.

Emissions from the operational site have been found to be not significant in terms of human

exposure and impacts on the identified habitat sites.

Based on the findings of this assessment air quality does not pose a constraint to development of

the Site as proposed.

36

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Appendix A – Air Quality Terminology

Term Definition

Accuracy A measure of how well a set of data fits the true value.

Air quality objective Policy target generally expressed as a maximum ambient concentration to be achieved, either without exception or with a permitted number of exceedences within a specific timescale (see also air quality standard).

Air quality standard The concentrations of pollutants in the atmosphere which can broadly be taken to achieve a certain level of environmental quality. The standards are based on the assessment of the effects of each pollutant on human health including the effects on sensitive sub groups (see also air quality objective).

Ambient air Outdoor air in the troposphere, excluding workplace air.

Annual mean The average (mean) of the concentrations measured for each pollutant for one year. Usually this is for a calendar year, but some species are reported for the period April to March, known as a pollution year. This period avoids splitting winter season between 2 years, which is useful for pollutants that have higher concentrations during the winter months.

AQMA Air Quality Management Area.

DEFRA Department for Environment, Food and Rural Affairs.

EIA regulations Environmental Impact Assessment regulations

Exceedence A period of time where the concentrations of a pollutant is greater than, or equal to, the appropriate air quality standard.

Fugitive emissions Emissions arising from the passage of vehicles that do not arise from the exhaust system.

IPPC Integrated Pollution Prevention and Control

LAQM Local Air Quality Management.

LAPPC Local Air Pollution Prevention and Control

NO Nitrogen monoxide, a.k.a. nitric oxide.

NO2 Nitrogen dioxide.

NOx Nitrogen oxides.

O3 Ozone.

Percentile The percentage of results below a given value.

PM10 Particulate matter with an aerodynamic diameter of less than 10 micrometres.

Ratification (Monitoring)

Involves a critical review of all information relating to a data set, in order to amend or reject the data. When the data have been ratified they represent the final data to be used (see also validation).

µgm-3 micrograms per cubic metre

A measure of concentration in terms of mass per unit volume. A concentration of 1ug/m3 means that one cubic metre of air contains one microgram (millionth of a gram) of pollutant.

UKAS United Kingdom Accreditation Service.

Uncertainty A measure, associated with the result of a measurement, which characterizes the range of values within which the true value is expected to lie. Uncertainty is usually expressed as the range within which the true value is expected to lie with a 95% probability, where standard statistical and other procedures have been used to evaluate this figure. Uncertainty is more clearly defined than the closely related parameter 'accuracy', and has replaced it on recent European legislation.

USA Updating and Screening Assessment.

Validation (modelling)

Refers to the general comparison of modelled results against monitoring data carried out by model developers.

Validation (monitoring)

Screening monitoring data by visual examination to check for spurious and unusual measurements (see also ratification).

Verification (modelling)

Comparison of modelled results versus any local monitoring data at relevant locations.

37

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Appendix B – Assessment Criteria

Table B1: Relevant Objectives for the Protection of Human Health

Pollutant Concentrations Measured As Date to be Achieved by

Nitrogen Dioxide (NO2) 200 µgm-3 not to be exceeded more than 18 times per year

1-hour mean 31 December 2005

40 µgm-3 Annual mean 31 December 2005

Carbon Monoxide (CO) 10 mgm-3 8-hour 31 December 2003

Table B2: Locations Where Air Quality Objectives Apply

Averaging Period

Objectives should apply at: Objectives should generally not apply at:

Annual Mean All locations where members of the public might be regularly exposed. Building facades of residential properties, schools, hospitals, care home etc.

Building facades of offices or other places of work where members of the public do not have regular access. Hotels, unless people live there as their permanent residence.

Gardens of residential properties.

Kerbside sites (as opposed to locations at the building facade), or any other location where public exposure is expected to be short term.

24 Hour Mean

All locations where the annual mean objective would apply together with hotels. Gardens of residential properties.

Kerbside sites (as opposed to locations at the building façade), or any other location where public exposure is expected to be short term.

1 Hour Mean All locations where the annual mean and 24-hour mean objectives apply.

Kerbside Sites (e.g. pavements of busy shopping streets).

Those parts of car parks, bus stations and railway stations etc. which are not fully enclosed, where the public might reasonably be expected to spend 1-hour or more. Any outdoor locations where the public might reasonably be expected to spend 1-hour or longer.

Kerbside sites where the public would not be expected to have regular access.

38

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Table B2: Critical Levels for Ecological Receptors

Pollutant Averaging Period Concentration (μg/m3)

Oxides of Nitrogen (NOx) Annual Mean 30

Daily Mean 75

Table B3: Critical Loads for Nutrient Nitrogen Deposition

Habitat Critical Load

(kg N/ha/yr)

Background Deposition (kg N/ha/yr)

Coed Y Mwstwr Woodlands SSSI 10-20 25.9

Bryanna a Wren Tarw SSSI 20-30 16.94

Blackmill Woodlands SAC 10-15 26.04

Glaswell Tiroedd SAC 15-25 14.07

Table B4: Critical Loads for Acid (Nitrogen) Deposition

Habitat Critical Load

(keq/ha/yr)

Background Deposition (keq/ha/yr)

Coed Y Mwstwr Woodlands SSSI MinCLMaxN: 0.357

MaxCLMaxN: 11.253

1.85

Bryanna a Wren Tarw SSSI MinCLMaxN: 1.410

MaxCLMaxN: 1.2.48

1.21

Blackmill Woodlands SAC MinCLMaxN: 1.231

MaxCLMaxN: 1.237

1.86

Glaswell Tiroedd SAC MinCLMaxN: 1.110

MaxCLMaxN: 2.180

1.01

39

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Appendix C – Assessment Criteria for Construction Impact Assessment

Table C1: Examples of Factors Defining Sensitivity of an Area

Sensitivity of Area

Dust Soiling Human Receptors Ecological Receptors

High Users can reasonably expect

enjoyment of a high level of amenity

The appearance, aesthetics or value

of their property would be

diminished by soiling’

The people or property would

reasonably be expected to be

present continuously, or at least

regularly for extended periods, as

part of the normal pattern of use of

the land.

E.g. dwellings, museums and other

important collections, medium and

long term car parks and car

showrooms.

10 – 100 dwellings within 20 m

of site.

Local PM10 concentrations close

to the objective (e.g. annual

mean 36 -40 μg/m3).

E.g. residential properties,

hospitals, schools and

residential care homes.

Locations with an international

or national designation and the

designated features may be

affected by dust soiling.

Locations where there is a

community of a particularly

dust sensitive species such as

vascular species included in the

Red List for Great Britain.

E.g. A Special Area of

Conservation (SAC).

Medium Users would expect to enjoy a

reasonable level of amenity, but

would not reasonably expect to enjoy

the same level of amenity as in their

home.

The appearance, aesthetics or value

of their property could be diminished

by soiling

The people or property wouldn’t

reasonably be expected to be

present here continuously or

regularly for extended periods as part

of the normal pattern of use of the

land.

E.g. parks and places of work.

Less than 10 receptors within

20 m.

Local PM10 concentrations

below the objective (e.g.

annual mean 30-36 μg/m3).

E.g. office and shop workers

but will generally not include

workers occupationally

exposed to PM10 as protection

is covered by the Health and

Safety at Work legislation.

Locations where there is a

particularly important plant

species, where its dust

sensitivity is uncertain or

unknown.

Locations with a national

designation where the features

may be affected by dust

deposition

E.g. A Site of Special Scientific

Interest (SSSI) with dust

sensitive features.

Low The enjoyment of amenity would not

reasonably be expected.

Property would not reasonably be

expected to be diminished in

appearance, aesthetics or value by

soiling.

There is transient exposure, where

the people or property would

reasonably be expected to be

present only for limited periods of

time as part of the normal pattern of

use of the land.

E.g. playing fields, farmland unless

commercially sensitive horticultural,

footpaths, short lived car [parks and

roads.

Locations where human

exposure is transient.

No receptors within 20 m.

Local PM10 concentrations well

below the objectives (less than

75%).

E.g. public footpaths, playing

fields, parks and shopping

streets.

Locations with a local

designation where the features

may be affected by dust

deposition.

E.g. Local Nature Reserve with

dust sensitive features.

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Table C2: Sensitivity of the Area to Dust Soiling on People and Property

Receptor Sensitivity

Number of Receptors

Distance from the Source (m)

<20 <50 <100 <350

High

>100 High High Medium Low

10-100 High Medium Low Low

1-10 Medium Low Low Low

Medium >1 Medium Low Low Low

Low >1 Low Low Low Low

Table C3: Sensitivity of the Area to Human Health Impacts

Receptor Sensitivity

Annual Mean PM10

Concentration

Number of Receptors

Distance from Source (m)

<20 <50 <100 <200 <350

High >32 μg/m3 >100 High High High Medium Low

10-100 High High Medium Low Low

1-10 High Medium Low Low Low

28-32 μg/m3 >100 High High Medium Low Low

10-100 High Medium Low Low Low

1-10 High Medium Low Low Low

24-28 μg/m3 >100 High Medium Low Low Low

10-100 High Medium Low Low Low

1-10 Medium Low Low Low Low

<24 μg/m3 >100 Medium Low Low Low Low

10-100 Low Low Low Low Low

1-10 Low Low Low Low Low

Medium >32 μg/m3 >10 High Medium Low Low Low

1-10 Medium Low Low Low Low

28-32 μg/m3 >10 Medium Low Low Low Low

1-10 Low Low Low Low Low

24-28 μg/m3 >10 Low Low Low Low Low

1-10 Low Low Low Low Low

<24 μg/m3 >10 Low Low Low Low Low

1-10 Low Low Low Low Low

Low - >1 Low Low Low Low Low

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Table C4: Sensitivity of the Area to Ecological Impacts

Receptor Sensitivity Distance from the Source (m)

<20 <50

High High Medium

Medium Medium Low

Low Low Low

Table C5: Risk of Dust Impacts from Demolition

Sensitivity of Area Large Medium Small

High High Risk Medium Risk Medium Risk

Medium High Risk Medium Risk Low Risk

Low Medium Risk Low Risk Negligible

Table C6: Risk of Dust Impacts from Earthworks/Construction

Table 4.6: Risk of Dust Impacts from Earthworks/ Construction

Sensitivity of Area Large Medium Small

High High Risk Medium Risk Low Risk

Medium Medium Risk Medium Risk Low Risk

Low Low Risk Low Risk Negligible

Table C7: Risk of Dust Impacts from Trackout

Table 4.7: Risk of Dust Impacts from Trackout

Sensitivity of Area Large Medium Small

High High Risk Medium Risk Low Risk

Medium Medium Risk Low Risk Negligible

Low Low Risk Low Risk Negligible

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Appendix D – Emission Parameters

Table D1: Release Parameters

Parameter GE J624 Unit

Number of Units 9

Number of Stacks 9

Stack Height (m) 12

Effective Stack Diameter (m) 0.6

Temperature of Release (K) 621

Actual Flow rate (Am3/s) 0.7

Emission Velocity at Stack Exit (m/s) 2.3

Table D2: Emissions

Pollutant MTU Unit (2 x engines per flue)

NOx Short-term (g/s)

Long-term (g/s)

0.073

0.021

CO Short-term (g/s) 0.305

Figure D1: Location of Buildings Used in Model

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Appendix E – Cardiff Windrose’

Figure E1: 2017 Windrose

Figure E2: 2016 Windrose

0

0

3

1.5

6

3.1

10

5.1

16

8.2

(knots)

(m/s)

Wind speed

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8.2

(knots)

(m/s)

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Figure E3: 2015 Windrose

Figure E4: 2014 Windrose

0

0

3

1.5

6

3.1

10

5.1

16

8.2

(knots)

(m/s)

Wind speed

0° 10°20°

30°

40°

50°

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(m/s)

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45

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Figure E4: 2013 Windrose

0

0

3

1.5

6

3.1

10

5.1

16

8.2

(knots)

(m/s)

Wind speed

0° 10°20°

30°

40°

50°

60°

70°

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160°170°180°190°

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100

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Appendix F –Methodology Employed for Modelling Roads Emissions

Introduction

NOx emissions due to local traffic emissions have been predicted using the ADMS-Roads Extra

dispersion model (version 4.1.1). This is a commercially available dispersion model and has been

widely validated for this type of assessment and used extensively in the Air Quality Review and

Assessment process.

The model uses detailed information regarding traffic flows on the local road network and local

meteorological conditions to predict pollution concentrations at specific locations selected by the

user. Meteorological data from Cardiff for 2017 has been used for the assessment.

Emissions Data

The model uses traffic flow data and vehicle related emission factors to predict road specific

concentrations of NOx at sensitive receptors selected by the user. The assessment has predicted air

quality during 2017 to allow verification against local monitoring data and provide traffic related

emissions to inform the baseline at each receptor location. The emission factors release by DEFRA in

November 2017, provide in the emissions factor toolkit EFT2017_v8.0 have been used to predict

traffic related emissions of NOx. These are the latest emission factors available.

The predicted concentrations of NOx have been converted to NO2 using the LAQM calculator

(Version 6.1, released October 2017) available on the DEFRA air quality website (http://uk-

air.defra.gov.uk).

Traffic Data

Base traffic flows for 2017 for the adjacent road network have been taken from the Department of

Transport (DfT) online traffic data set (http://www.dft.gov.uk/traffic-counts/download.php). The

traffic data used within the assessment are provided in Table F1.

Additional traffic has been obtained for Cowbridge Road (A473) in Bridgend, to allow verification of

the model results against local monitoring.

The location of roads used in the modelling assessment are shown in Figure 4.1.

Table F1: Traffic Data used in ADMS Model

Road Link Speed (kph) %HGV 2017 Base

A473 64 (25 at roundabouts and junctions)

4.9 13656

Cowbridge Road (A473) 56 1.4 20856

Verification of Model Results

It is recommended that the model results are compared with measured data to determine whether

the model results need adjusting to more accurately reflect local air quality. This process is known

as verification.

LAQM.TG(16) recommends that model predictions should be within 25% (preferably 10%) of

monitored concentrations for the model to be predicting with any degree of accuracy. Also, the

guidance recommends that any adjustment factors applied to model results should be calculated

47

AQ051643 V2

based on verification using monitoring sites in a similar location i.e. roadside, intermediate or

background sites.

To verify the model results, the ADMS model has been used to predict NOx concentrations at the

Bridgend monitoring sites 105 and 106, located on Cowbridge Road. The initial modelling found that

the ADMS model was under predicting NOx concentrations by an average of 32%. An adjustment

factor has therefore been calculated using the methodology set out in LAQM.TG(16) as detailed

below.

Most nitrogen dioxide (NO2) is produced in the atmosphere by reaction of nitric oxide (NO) with

ozone. It is therefore most appropriate to verify the model in terms of primary pollutant emissions.

Verification of concentrations predicted by the ADMS model has followed the methodology

presented in LAQM.TG(16).

The model output of road-NOx (i.e. the component of total NOx coming from road traffic) has been

compared with the ‘measured’ road-NOx (Figure F1). The ‘measured’ road NOx has been calculated

from the measured NO2 concentrations by using the DEFRA NOx from NO2 calculator available on the

UK-AIR website.

Figure F1: Comparison of Modelled Road NOx with Measured Road NOx

Figure F1 shows that the ADMS model is under-predicted the road-NOx concentrations at the

monitoring sites. An adjustment factor has therefore been determined as the ratio between the

measured road-NOx contribution and the modelled road-NOx contribution, forced through zero

(1/0.3171 = 3.15). This factor has been applied to the modelled road-NOx concentration for each

location to provide an adjusted modelled road-NOx concentration.

The annual mean road-NO2 concentration was determined using the DEFRA NOx:NO2 spread sheet

calculation tool and added to the background NO2 concentration to produce a total adjusted NO2

concentration.

Figure F2 shows the adjusted modelled total NO2 vs monitored NO2. There is good agreement

between the best fit line forced through zero and the 1:1 line therefore no secondary adjustment

factor is required.

y = 0.3171x

0

20

40

60

80

100

120

140

160

180

200

0 50 100 150 200

Mo

de

lled

Ro

ad

NO

x

Measured Road NOx

48

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Figure F2: Comparison of Modelled NO2 with Measured NOx

There is good agreement, but the best fit line forced through zero still has a slight departure from a

1:1 line, thus a secondary adjustment factor, to be applied to the adjusted modelled total NO2, was

calculated (1/1.0141=0.986).

After carrying out an initial adjustment there was a need for only a very small secondary adjustment

of NO2. The final adjustment modelled values are shown in Figure F3.

Figure F3: Comparison of Adjusted Modelled NO2 with Measured NO2

The adjustment factor of 3.15 has been applied to the modelled NOx-road concentrations predicted

at the selected receptor locations. The predicted NO2-road concentrations, calculated using the NOx-

y = 1.0141x

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100

Ad

jus

ted

Mo

de

lled

NO

2

Measured Road NO2

y = 1x

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100

Fin

al A

dju

ste

d M

od

ell

ed

NO

2

Measured Road NO2

49

AQ051643 V2

NO2 converter tool, have subsequently been added to background NO2 concentrations and adjusted

by 0.986 to provide the final baseline annual mean NO2 concentrations at each receptor.