DETAILED AIR QUALITY ASSESSMENT FOR THE PROPOSED ENERGY FROM WASTE FACILITY IN CARDIFF MÔR HAFREN BIO POWER LIMITED BLYTHE HOUSE, BLYTHE PARK ...
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DOC 35 Version 2 - Clean
DETAILED AIR QUALITY ASSESSMENT FOR
THE PROPOSED ENERGY FROM WASTE
FACILITY IN CARDIFF
MÔR HAFREN BIO POWER LIMITED
BLYTHE HOUSE, BLYTHE PARK, CRESSWELL
STOKE ON TRENT ST11 9RD
Report Issue No: 7
Report Date: January 2021
Report Author: Amanda Owen
Environmental Visage Limited Executive Summary Detailed atmospheric dispersion modelling has been undertaken of emissions to atmosphere from the proposed Energy Recovery Facility (ERF) to be developed by Môr Hafren Bio Power Ltd on a brownfield site off Newlands Road, in Cardiff. Modelling of emissions from the ERF was undertaken for a scenario that represents normal operating conditions while operating at maximum output and discharging emissions to atmosphere via a 70 metre high chimney. The modelling was undertaken using ADMS Version 5.2 and incorporated data on local infrastructure including buildings and the neighbouring wind turbine, terrain, surface roughness and five-years’ worth of meteorological conditions to produce a detailed and comprehensive assessment of plume dispersion. Adjacent structures were shown initially to have a significant impact on the dispersion of emissions from the 70-metre high chimney. A sensitivity analysis was also run to assess any impact of the nearby estuary on dispersion conditions. Hourly average meteorological data for the Cardiff Airport measurement station for the years 2015 to 2019 was used to determine maximum Process Contributions across a 4km x 4km receptor grid (20 metre grid spacing), as well as at nearby sensitive receptor locations. The model predicted that Process Contributions for all pollutants prescribed for control by the Industrial Emissions Directive (IED), and based on the Achievable Emission Levels specified in the BREF Note for Waste Incineration under normal operational conditions, would be well below objective limits defined within the Air Quality Regulations, or relevant Environmental Assessment Levels recommended by NRW. The inclusion of the wind turbine data into each of the models, resulted in higher overall concentrations than previously reported, in line with the earlier sensitivity analysis, and thereby provides a worst-case assessment at every stage. Modelling predicted that under normal daily average operating conditions the maximum annual average Process Contribution for NO 2 would be about 2.0 µg m-3, approximately 5% of the 40 µg m-3 annual objective value. The location of the maximum Process Contribution is predicted to be about 390 metres to the east of the ERF chimney, with values considerably lower farther afield. The Process Contributions for each of the other IED pollutants indicated that there would be no exceedance of their respective AQS objective values or relevant environmental assessment levels. The results from a cumulative impact assessment with other developments proposed locally concluded that there is no significant difference between the model predictions for Môr Hafren site in isolation and the combined emissions scenario at the location of the maximum Process Contribution across the 4km x 4km modelled grid, or at nearby residential properties, and the overall impacts continue to be screened as insignificant at either the initial or secondary assessment stage. Cumulative contributions to levels of nutrient Nitrogen deposition are screened as insignificant when assessed against the specified Critical Loads for most sensitive ecological receptors, although eight sites, including locations within the Gwent Levels and one modelled area of the Severn Estuary and various SINCs cannot be screened. Exceedance of a Critical Load is not a quantitative estimate of damage to a particular habitat, but instead represents the point at which significant harmful effects do not occur according to present knowledge. As such, and as the cumulative Process Contributions do not result in an exceedance of the nutrient Nitrogen Critical Load at any site where one currently does not exist, it is considered that the potential for the development of the Môr Hafren facility to have a significant negative impact on nutrient Nitrogen levels at local ecological sites, is limited. Consideration of the operational odour management procedures to be implemented by Môr Hafren Bio Power Ltd when the ERF is operational, indicate that odour control will be effective, and any fugitive emissions from the process buildings should not be a cause for reasonable complaint from nearby residential and commercial properties. Detailed modelling of odour release from a 50 metre high odour vent showed that the maximum hourly average Process Contribution would be about two thirds of the 3.0 OUE m-3 EAL for moderately offensive odour. The corresponding values at nearby residential properties were shown to be about 0.6 OUE m-3 or less, and are unlikely to be perceptible to members of the general public with a “typical” sense of smell. The overall conclusion from detailed modelling of emissions from the proposed Môr Hafren Bio Power ERF is that the potential impact on local air quality is likely to be small and is unlikely to result in a significant threat to the health of people living and working nearby. Môr Hafren Bio Power Ltd – Air Quality Assessment i
Environmental Visage Limited
Glossary of Terms
Acronym / Abbreviation Meaning
ADMS Atmospheric Dispersion Modelling System
AQMA Air Quality Management Area
Cd Cadmium
CERC Cambridge Environmental Research Consultants
CO Carbon Monoxide
EAL Environmental Assessment Level
EPUK Environmental Protection UK
ERF Energy Recovery Facility
HCl Hydrogen Chloride
HF Hydrogen Fluoride
Hg Mercury
IAQM Institute of Air Quality Management
m Metre
MWe Mega Watt (electrical)
MWth Mega Watt (thermal)
NO2 Nitrogen Dioxide
NOx Oxides of Nitrogen
NRW Natural Resources Wales
Pb Lead
OUE m-3 Odour Unit per cubic metre
OUE s-1 Odour Unit per Second
PC Process Contribution
PEC Predicted Environmental Concentration
pg Picogram (10-12 g)
PM2.5 Particulate Matter (less than 2.5 µm diameter)
PM10 Particulate Matter (less than 10 µm diameter)
RDF Refuse Derived Fuel
SO2 Sulphur Dioxide
TDI Tolerable Daily Intake
Tl Thallium
TWI Tolerable Weekly Intake
VOCs Volatile Organic Compounds
% Percent
µg m-3 Micro grams per cubic metre
Môr Hafren Bio Power Ltd – Air Quality Assessment ii
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Contents
Executive Summary ...................................................................................................................................i
Glossary of Terms .................................................................................................................................... ii
Contents .................................................................................................................................................. iii
Figures ..................................................................................................................................................... iv
Tables .......................................................................................................................................................v
Issue and Revision Record...................................................................................................................... vi
List of Revisions ...................................................................................................................................... vi
1. Introduction ............................................................................................................................ 1
1.1 ADMS Model ......................................................................................................................... 1
1.2 Modelling Uncertainty ............................................................................................................ 1
2. Modelling Input Data ............................................................................................................. 3
2.1 Introduction ............................................................................................................................ 3
2.2 Site Location and Local Setting ............................................................................................. 3
2.3 Plant Details .......................................................................................................................... 4
2.4 Emissions Data...................................................................................................................... 4
2.5 Atmospheric Chemistry ......................................................................................................... 5
2.6 Meteorological Data .............................................................................................................. 6
2.7 Local Environmental Conditions ............................................................................................ 7
2.7.1 Surface Roughness ............................................................................................................... 7
2.7.2 Nearby Buildings and Structures ........................................................................................... 7
2.7.3 Local Terrain.......................................................................................................................... 8
2.7.4 Output Grid ............................................................................................................................ 9
2.7.5 Background Air Quality ........................................................................................................ 11
2.7.6 Coastal Influences………………………………………………………………………………...12
2.8 Chimney Height Assessment .............................................................................................. 12
2.8.1 D1 Chimney Height Calculation .......................................................................................... 12
2.8.2 Iterative Modelling of Chimney Height ................................................................................ 13
3. Detailed Modelling – Air Quality Assessment ..................................................................... 15
3.1 Modelled Parameters .......................................................................................................... 15
3.2 Determining Significance ..................................................................................................... 15
3.3 Other Assessment Criteria .................................................................................................. 16
3.4 Nitrogen Dioxide (NO2) ........................................................................................................ 16
3.5 Sulphur Dioxide (SO2) ......................................................................................................... 19
3.6 Carbon Monoxide (CO) ....................................................................................................... 20
3.7 Particulates (PM10) .............................................................................................................. 20
3.8 Particulates (PM2.5) .............................................................................................................. 21
3.9 Volatile Organic Compounds (VOCs) ................................................................................. 21
3.10 Hydrogen Chloride (HCl) ..................................................................................................... 22
3.11 Hydrogen Fluoride (HF) ....................................................................................................... 22
3.12 Ammonia (NH3) ................................................................................................................... 23
3.13 Cadmium and Thallium (Cd & Tl) ........................................................................................ 23
3.14 Mercury and its Compounds (Hg) ....................................................................................... 24
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3.15 Group 3 Metals .................................................................................................................... 24
3.16 Dioxins & Furans ................................................................................................................. 26
4. Air Quality Impact at Specific Receptors ............................................................................. 28
5. Air Quality Impact at Air Quality Monitoring Receptors ....................................................... 29
6. Impact of Emissions on Nearby Ecological Receptors........................................................ 30
6.1 Assessment Relative to Critical Level Values ..................................................................... 30
6.2 Assessment Relative to Critical Load Values for Nitrogen and Acid Deposition ................ 33
7. Cumulative Impact with Other Proposed Developments .................................................... 38
8. Odour ................................................................................................................................... 49
8.1 Introduction .......................................................................................................................... 49
8.2 Odour Management Procedures in the OMP ...................................................................... 49
Waste Reception ................................................................................................................................ 50
Waste Handling and Processing Facility ........................................................................................... 50
Building Arrangement and Ventilation ............................................................................................... 50
Ventilation Flows and Odour Treatment - Normal Operation ............................................................ 51
Ventilation Flows and Odour Treatment - Abnormal Operation and Shutdowns ............................... 51
Conclusion ......................................................................................................................................... 51
8.3 Detailed Atmospheric Dispersion Modelling ........................................................................ 52
Emissions Data .................................................................................................................................. 52
Determining Significance ................................................................................................................... 52
Results from Detailed Modelling of Odour Release ........................................................................... 54
Increase in Odour at Specific Receptors ........................................................................................... 55
Odour Concentration at the Site Boundary ........................................................................................ 57
Conclusions........................................................................................................................................ 58
9. Conclusions ......................................................................................................................... 59
10. References .......................................................................................................................... 61
Figures
Figure 1 The Local Setting Showing the Location of the ERF Development Site ............................... 3
Figure 2 Variation in Hourly Average NOX, NO2 and Ozone Concentrations at the Cardiff Centre
AURN Site – January to April 2018 .................................................................................................. 5
Figure 3 2019 Windrose for the Cardiff Airport Measurement Station ................................................ 6
Figure 4 Site Layout as Modelled ........................................................................................................ 8
Figure 5 Variation in Maximum Annual Average Process Contribution of NO 2 (µg m-3) with Different
Stack Heights ................................................................................................................................. 13
Figure 6 Variation in Maximum Hourly Average Process Contribution of NO 2 (µg m-3) with Different
Stack Heights ................................................................................................................................. 14
Figure 7 Maximum Annual Average Process Contribution for NO2................................................... 18
Figure 8 Maximum Hourly Average Process Contribution for NO2 ................................................... 19
Figure 9 Levels of Nutrient Nitrogen Deposition from the Môr Hafren Bio Power Limited Facility –
Meteorological data from 2015 ....................................................................................................... 34
Figure 10 Levels of Nutrient Nitrogen Deposition from the Môr Hafren Bio Power Limited Facility –
Meteorological data from 2018 ....................................................................................................... 34
Figure 11 Maximum Annual Average Process Contribution for NO2 – Cumulative Impact……………42
Figure 12 Cumulative Levels of Nutrient Nitrogen Deposition – Meteorological data from 2015……..45
Figure 13 Cumulative Levels of Nutrient Nitrogen Deposition – Meteorological data from 2018….....46
Figure 14 Predicted Odour Concentrations in the Vicinity of the Proposed ERF – 50 Metre High
Odour Vent - 98th Percentile of Hourly Averages (OUE m-3) .......................................................... 55
Figure 15 Location of Boundary Receptors Included in the Odour Assessment................................. 57
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Tables
Table 1 Emission Source Parameters – Preliminary Sensitivity Analysis……………………..……….4
Table 2 Modelled Emissions Data………………………………………………………………………….4
Table 3 Modelled Meteorological Parameters…………………………………………………………….6
Table 4 Modelled Building Data……………………………………………………………………………..7
Table 5 Specific Receptors Included in Detailed Modelling……………………………………………...9
Table 6 Background Air Quality Data in the Vicinity of the Development Site (2021)……………….11
Table 7 Results from Iterative Chimney Height Assessment – Annual and Hourly Average NO2
Process Contributions…………………………………………………………………………….13
Table 8 Definition of Impact Magnitude for Changes in Annual Mean Nitrogen Dioxide and PM10
Concentration………………………………………………………………………………………15
Table 9 Results from Detailed Assessment for Nitrogen Dioxide and Oxides of Nitrogen………….17
Table 10 Maximum Process Contribution for Sulphur Dioxide…………………………………………..19
Table 11 Modelling Predictions for Carbon Monoxide……………………………………………………20
Table 12 Maximum Process Contribution for Particulates (PM10) ...................................................... 20
Table 13 Modelling Predictions for Particulates (PM2.5) ..................................................................... 21
Table 14 Maximum Process Contribution for VOCs .......................................................................... 21
Table 15 Maximum Process Contribution for Hydrogen Chloride ...................................................... 22
Table 16 Maximum Process Contribution for Hydrogen Fluoride ...................................................... 22
Table 17 Maximum Process Contribution for Ammonia ..................................................................... 23
Table 18 Maximum Process Contribution for Cadmium and Thallium ............................................... 23
Table 19 Maximum Process Contribution for Mercury and its Compounds ....................................... 24
Table 20 Maximum Annual Average Process Contribution for Group 3 Metals – Step 1 Screening . 25
Table 21 Maximum Predicted Environmental Concentration for Group 3 Metals where PC
(0.005 ng m-3) Does Not Immediately Screen as Insignificant .............................................................. 25
Table 22 Guidance for the Step 2 Assessment of Group 3 Metals .................................................... 26
Table 23 Maximum Annual Average Process Contributions for Arsenic and Chromium (VI),– Step 2
Screening ....................................................................................................................................... 26
Table 24 Maximum Process Contribution for Dioxins & Furans......................................................... 26
Table 25 Results from Detailed Assessment for Nitrogen Dioxide and Particulates (PM10) at Specific
Receptors – Impact Due to the Operation of the ERF ................................................................... 28
Table 26 Results from Detailed Assessment for Nitrogen Dioxide at Nearby Air Quality Monitoring
Locations – Impact Due to the Operation of the ERF .................................................................... 29
Table 27 Critical Levels for Oxides of Nitrogen, Sulphur Dioxide, Ammonia and Hydrogen Fluoride 30
Table 28 Critical Levels Assessment for Oxides of Nitrogen (NO X) and Sulphur Dioxide (SO2) ....... 31
Table 29 Critical Levels Assessment for Ammonia (NH3) and Hydrogen Fluoride (HF) .................... 32
Table 30 Results from Detailed Modelling of Nitrogen Deposition in Relation to Site-Specific Critical
Loads……………………………………………………………………………………………………….33
Table 31 Results from Detailed Modelling of Acid Deposition (As Nitrogen) in Relation to Site-
Specific Critical Loads .................................................................................................................... 36
Table 32 Results from Detailed Modelling of Acid Deposition from all Appropriate Pollutant Sources
(keq) in Relation to Site-Specific Critical Loads ............................................................................. 36
Table 33 Emission Source Parameters ............................................................................................... 38
Table 34 Modelled Emissions Data .................................................................................................... 38
Table 35 Additional Receptors for Cumulative Assessment .............................................................. 39
Table 36 Results of Pollutant Concentrations from Cumulative Assessment .................................... 40
Table 37 Results from Detailed Assessment of Cumulative Nitrogen Dioxide at Human Health
Receptors ....................................................................................................................................... 41
Table 38 Cumulative Contributions to Nutrient Nitrogen Deposition at Sensitive Ecological
Receptors…………………………………………………………………………………………………..44
Table 39 Cumulative Contributions to Acid Deposition (As Nitrogen) in Relation to Site-Specific
Critical Loads ................................................................................................................................ ..47
Table 40 Cumulative Contributions to Acid Deposition from all Appropriate Pollutant Sources (keq) in Relation
to Site-Specific Critical Loads………………………………………………..……………………………………….48
Table 41 Emission Source Parameters Used in the Detailed Modelling Study………………………..52
Table 42 Results of Detailed Modelling – Maximum Process Contribution to Ground Level Odour
Concentration……………………………………………………………………………………….….….54
Table 43 Results of Detailed Modelling of Odour at Specific Receptors……………………………….56
Table 44 Results of Detailed Modelling of Odour at the Site Boundary ............................................. 57
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Issue and Revision Record
Issue Date Author Review / Authorise Description
1 18/03/2020 Geoff Fynes Amanda Owen Initial Draft
2 30/03/2020 Geoff Fynes Amanda Owen Second Draft
3 27/04/2020 Geoff Fynes Amanda Owen Third Draft
4 21/05/2020 Geoff Fynes Amanda Owen Final Version
5 17/06/2020 Geoff Fynes Amanda Owen Final Version
6 26/08/2020 Amanda Owen ENVISAGE Update from planning pre-app.
7 (DRAFT) 13/01/2021 Amanda Owen ENVISAGE Amended AQA – Draft for team review
7 (FINAL DRAFT) 15/01/2021 Amanda Owen ENVISAGE Amended AQA – Final Draft for team review
7 29/01/2021 Amanda Owen ENVISAGE Final Issue 7 – Team Comments Included
List of Revisions
Section and Changes in Version 7
Summary of Change
Page Number January 2021
Executive
Updated to reflect the changes detailed below.
Summary pg. i
Removing the receptor which denoted Eastern High
S 2.2 pg. 3 Updated Figure 1 School and renumbering the remaining human
health receptors.
Cumulative assessment now includes information
Changes to the
from recent planning applications, and excludes
S. 2.3 pg. 4; cumulative
existing sites which would already be accounted for
assessment
in the background data, including Trident Park.
Addition of Ammonia
S. 2.4 pg. 4; Ammonia has now been included in the modelling
into the modelling
exercise and is reported in full in Section 3.12.
exercise
Version 7 of the Air Quality Assessment applies
Updated
S 2.6 pg. 6 meteorological conditions from 2015 – 2019 and
meteorological data
Section 2.6 has therefore been updated.
A spatially variable surface roughness file has been
Changes to the
included in the final model runs in order to more
S. 2.7.1 pg. 7 surface roughness
accurately detail the land-use in the area, and the
data
presence of the estuary in close proximity to the site.
Data on the nearby wind turbine has been reviewed
and updated in line with the turbine actually installed,
which varied from the planning data previously
assessed. The effects of the turbine have been
Inclusion of wind
S 2.7.2 pg. 8 included in all modelling, rather than as a single
turbine data
sensitivity check. Hence the results throughout the
report represent process contributions resulting from
emissions from the Môr Hafren facility with the wind
turbine assumed to be operational.
A spatially variable terrain file has been included in
Changes to the terrain
S. 2.7.3 pg. 9 the final model runs in order to more accurately
data
detail the local terrain in close proximity to the site.
Cardiff Council changed its NO2 monitoring locations
in 2018 and hence the receptor locations have been
S. 2.7.4 pg. 9 - 10 Updated AQ receptors updated to reflect this most currently available data.
Eastern High School has also been removed from
the human health receptors
Data from the DEFRA air quality background maps
S. 2.7.5 Table 7 Updated background
has been updated and includes information on
pg. 11 data
calibration factors for NO2 and NOx.
A sensitivity analysis on the inclusion of coastal
S. 2.7.6 pg. 12 Coastal influences influences has been undertaken and is presented in
this new section.
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Section and Changes in January
Summary of Change
Page Number 2021 Version
Modelled parameters Section updated to include changes to the modelled
S. 3.1 pg. 15
updated parameters (as above).
New Section (S. 3.12) Included for Ammonia. All
sections reviewed and updated as necessary to
S. 3.4 – 3.16 Updated results account for the changes in the baseline modelling,
pgs. 16 - 27 sections modelling spatially variable terrain and surface
roughness data and including the effects of the wind
turbine as standard.
As per the gridded (maximum location) results, the
Updated receptor receptor models have included spatially variable
S. 4 pg. 28
results terrain and surface roughness data and include the
effects of the wind turbine as standard.
The location of a number of monitoring sites
changed in 2018 and updated locations and
Updated AQ background data have now been included.
S. 5 pg. 29 monitoring location Also, and as per the gridded (maximum location)
receptor data results, the receptor models have included spatially
variable terrain and surface roughness data and
include the effects of the wind turbine as standard.
As per the gridded (maximum location) results, the
Updated results for
receptor models have included spatially variable
S. 6 pgs. 30 - 37 ecological receptor
terrain and surface roughness data and include the
locations
effects of the wind turbine as standard.
Cumulative impact assessment considering:
• Planning Reference 20/01279/MJR – Land at
Rover Way – S73 to vary time limit of outline
planning permission 17/02130/MJR for,
amongst other things, 9.5 MW biomass facility;
• Planning Reference 20/01626/MNR –
Replacement Chimneys to Boiler Room;
Revised cumulative
S. 7 pgs. 38 - 48 • Planning Reference 20/0748 – Uskmouth
impact assessment
Power Station (within Newport Council’s
boundary).
Existing plant, including Trident Park, Celsa Steel
Sections Mill, Tremorfa Melt Shop, and the Welsh
Water Anaerobic Digestion Facility are incorporated
through the inclusion of the existing background
concentrations.
S 8. Potential
Impact of the
Nearby Wind Section removed as the wind turbine effects have
Section removed
Turbine at G24 been included in each model run.
Innovations
Limited
S. 9 pg. 59
Updated to reflect the revised results.
Conclusions
S. 10 pg. 60
Updated as required.
References
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1. Introduction
Môr Hafren Bio Power Ltd proposes to develop an Energy Recovery Facility (ERF) with an associated
power generation facility, on land off Newlands Road, Cardiff. The ERF will be fully compliant with the
operational requirements specified by the Industrial Emissions Directive (IED) for waste incineration
plants. The ERF will be fuelled by residual waste (i.e. that commercial and industrial waste remaining
post treatment and otherwise destined for landfill), to provide electricity to the local area via the National
Grid and has the potential to provide heat to adjacent developments.
The proposed ERF will use moving grate technology with a steam raising heat recovery boiler. Steam
will drive a condensing steam turbine generator set, with turbine pass out steam being used to provide
heat to the site and a wider heat network if viable. The plant will contribute to Wales’ carbon reduction
targets, and will also contribute to sustainable waste management through using residual waste as
feedstock, ensuring that waste is diverted from landfill and managed further up the waste hierarchy.
The proposed ERF will have an approximate output rating of approximately 15MWe and will operate
continuously, 24 hours per day, with an approximate average of 8,000 operational hours per year, being
offline for approximately 10% of the year for maintenance purposes.
Detailed atmospheric dispersion modelling of process emissions has been undertaken in support of
planning and environmental permit applications for the ERF. The objective of the modelling exercise
was to assess the potential impact on local air quality of process emissions from the ERF, in terms of
ground level concentrations of pollutants designated by the Welsh Air Quality Regulations and other
relevant environmental assessment levels (EALs) recommended by Natural Resources Wales (NRW).
Modelling was based upon emissions and process data, and site drawings supplied by CoGen Ltd and
its technology providers.
This report describes the data used, the methodology adopted, assumptions made and the results
generated by the model.
1.1 ADMS Model
The modelling software used was ADMS Version 5.2, one of a range of models available for assessing
the impact on local air quality of pollutant emissions to atmosphere. Those used routinely in the UK for
this sort of application include United States Environmental Protection Agency (US-EPA) models such
as AERMOD, and the ADMS models developed in the UK by Cambridge Environmental Research
Consultants (CERC)1.
The ADMS model can be used to assess ambient pollutant concentrations arising from a wide variety
of emissions sources associated with an industrial process. It can be used for initial screening or more
refined determination of ground level pollutant concentrations on either a short-term basis (up to 24 hour
averages) or longer term (monthly, quarterly or annual averages).
1.2 Modelling Uncertainty
Atmospheric dispersion modelling is not a precise science and results can be impacted by a variety of
factors such as:
• Model uncertainty - due to limitations in the dispersion algorithms incorporated into the model
and their ability to replicate “real life” situations;
• Data uncertainty - due to potential errors associated with emission estimates, discharge
characteristics, land use characteristics and the relevance of the meteorological data to a
particular location; and,
• Variability - randomness of measurements used.
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CERC models are continually validated against available measured data obtained from real world
situations, field campaigns and wind tunnel experiments. Validation of the ADMS dispersion models
has been performed using many experimental datasets that test different aspects of the models, for
instance: ground / high level sources, passive and buoyant releases, buildings, complex terrain,
chemistry, deposition and plume visibility. These studies are both short-term as well as annual, and
involve tracer gases or specific pollutants of interest.
Potential uncertainties in model results derived from the current study have been minimised as far as
practicable, and a series of worst-case assumptions have been applied to the input data in order to
provide a robust assessment. This included the following:
• Selection of the dispersion model - ADMS 5.2 is a commonly used atmospheric dispersion
model and results have been verified through a number of inter-comparison studies to ensure
that model predictions are as accurate as possible;
• Meteorological data - Modelling was undertaken using hourly average meteorological data from
the nearby Cardiff Airport measurement station which is considered to be the most
representative of local conditions;
• ERF operating conditions – The detailed design of the ERF has yet to be finalised, however,
the operating conditions were based upon process information supplied by Standardkessel
Baumgarte GmbH (technology providers), which is considered to be representative of the
operation of the proposed ERF in Cardiff;
• Receptor locations - A 4km x 4km Cartesian Grid (20 metre grid spacing) was utilised in the
model in order to calculate maximum predicted concentrations in the vicinity of the ERF. Specific
receptor locations were also included in the model to provide detailed assessment at these
sensitive locations; and,
• Variability - All model inputs are as accurate as possible and worst-case conditions were
considered as necessary in order to ensure a robust assessment of potential odour
concentrations.
Results were considered in the context of Welsh AQS objective values and relevant environmental
assessment levels recommended by NRW. The application of the above measures to reduce uncertainty
and the use of a series of worst-case assumptions relating to the operational performance of the process
should result in model accuracy of an acceptable level.
Môr Hafren Bio Power – Air Quality Assessment 2Environmental Visage Limited
2. Modelling Input Data
2.1 Introduction
This section provides a summary of the input data used in the model.
2.2 Site Location and Local Setting
The ERF will be located on land off Newlands Road, Cardiff – Ordnance Survey Coordinates ST 23628
79471. Figure 1 shows the local setting with the location of the chimney associated with the ERF marked
with a red star.
Land use in the vicinity of the development site area is a mixture of industrial / commercial, residential
and open scrubland, with the nearest residential property approximately 250 metres to the south-east
of the development site. Specific receptors included in the model are shown by the blue circles on the
plan and represent locations where members of the general public may be present for significant periods
of time, either through residence or occupation.
Figure 1 The Local Setting Showing the Location of the ERF Development Site
Location of the
ERF Development
Site
Ordnance Survey on behalf of the Controller of Her Majesty’s Stationary Office, © Crown Copyright
100055158 Environmental Visage Limited (2021)
Môr Hafren Bio Power – Air Quality Assessment 3Environmental Visage Limited 2.3 Plant Details The ADMS model requires emission sources to be defined in terms of dimensions, location and physical characteristics of temperature and velocity. This modelling study has been carried out to assess the potential impact on local air quality due to releases of atmospheric pollutants from the chimney associated with the ERF. The ERF will consist of purpose-built process buildings that will incorporate the waste reception, storage and handling area, and the waste incineration line and associated power generation equipment. There is also an air-cooled condenser to recover water from the steam turbine exhaust. There will be vehicle movements associated with the operation of the ERF, including delivery of waste to the site, transfer of materials within the site, and removal of solid residues from the site. Air quality impacts associated with vehicular movements into and out of the development site are dealt with in a separate report (Assessment of the Impact of Traffic Emissions From the Proposed Môr Hafren Energy Recovery Facility), and therefore have not been included in this air quality assessment. The results from modelling presented in this document focus primarily on emissions from the chimney of the ERF, as well as those from other developments proposed in the locality which could have a cumulative impact, in combination with the Môr Hafren ERF. The ERF will be operational for approximately 8,000 hours (about 91%) a year. The remainder of the time the facility will be offline for routine maintenance. However, the model was run to calculate annual average Process Contributions for all 8,760 or 8,784 hours of the year, therefore representing a worst- case condition. 2.4 Emissions Data The operation of the ERF will be regulated by Natural Resources Wales in line with the conditions of an Environmental Permit that will be required to operate the facility. The process will be regulated under the Environmental Permitting Regulations (England and Wales) 2016, as amended. The plant will be operated in accordance with conditions for waste incineration plant as defined by the Industrial Emissions Directive (European Community – Directive 2010/75/EU) (IED), and the BAT Achievable Emission Levels included in the revised EIPPC BREF Note for waste incineration processes 2. Accordingly, the air quality assessment was undertaken on the basis of these emission values. The modelled source and emissions data used in the assessment are summarised in Table 1 and Table 2 respectively. The discharge data were provided by CoGen Ltd3. Table 1 Emission Source Parameters – Preliminary Sensitivity Analysis Parameter Value Stack Height (m) 47 to 90 Stack Diameter (m) 1.75 Efflux Temperature (° C) 145 Fluegas Volumetric Flowrate (Am3 hr-1) 153,394 Fluegas Volumetric Flowrate (Nm3 hr-1) 100,183 Efflux Velocity (m s-1) 17.7 Location (x,y) 323617,179494 Table 2 Modelled Emissions Data Substance Emission Limit (mg Nm-3) Mass Emission Rate (g/s) Nitrogen Oxides (as NO2) 120 3.762 Sulphur Dioxide 30 0.94 Carbon Monoxide 50 1.567 Particulates (PM10) 5 0.157 VOCs 10 0.313 HCl 6 0.188 HF 1 0.031 Ammonia 10 0.313 Cadmium and Thallium / Mercury 0.02 6.27E-04 Other Metals – Sb, As, Pb, Cr, Co, Cu, Mn, Ni, V 0.3 9.40E-03 Dioxins & Furans (ng Nm-3) 0.04 1.25E-09 Môr Hafren Bio Power – Air Quality Assessment 4
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The pollutant emission rates calculated for this condition represent normal operating conditions with
emissions throughout the year at the maximum levels that are expected to be included as conditions in
the environmental permit for the ERF. When operational, emissions from the proposed ERF will be lower
than the above Emission Limit Values, and this approach therefore represents a worst-case basis for
assessment. The emission limit values are based on the Achievable Emission Levels specified in the
revised EIPPC BREF Note for waste incineration plant.
2.5 Atmospheric Chemistry
All combustion processes emit Oxides of Nitrogen (NOX), made up predominantly of a mixture of Nitric
Monoxide (NO) and Nitrogen Dioxide (NO2). The relative proportions of NO to NO2 in the Oxides of
Nitrogen depend on a number of operational parameters, most notably the Nitrogen content of the fuel,
the combustion temperature and the excess Oxygen concentration.
The atmospheric chemistry module of ADMS was not used for calculating predicted ground-level
concentrations of Nitrogen Dioxide (NO2). Instead, a procedure recommended by the UK Government4,
as applied by NRW 5, was used to calculate annual average and hourly average NO2 ground-level
concentrations from the annual average NOX concentrations reported by the model.
The procedure is based upon the following formulae, on the basis that the atmospheric chemistry
module of ADMS was not utilised:
Equation 1 Calculation of Annual Average NO2 Predicted Environmental Concentration (PEC)
(Annual NOX Modelled + Annual NO2 Monitored)
Equation 2 Calculation of Hourly Average NO2 Predicted Environmental Concentration (PEC)
(Hourly NOX Modelled x 0.5) + (Annual NO2 Monitored x 2)
This method may overestimate the PEC for NO2 in close proximity to the site because conversion of
NOX to NO2 is unlikely to be instantaneous, as it requires mixing of the plume with the ambient air and
its associated oxidant species such as Ozone (O3) etc.
Atmospheric chemistry in the vicinity of the ERF development site is not constant, as shown by data
recorded at the Cardiff Centre AURN urban background monitoring station, which is located
approximately 6.0 km to the west of the development site. This is an urban background monitoring site,
and provides a good indication of the variability of the atmospheric chemistry in the vicinity of the
development site. Data for January to April 2018 show the variability of hourly average NOX, NO2 and
Ozone concentrations, and indicate that the availability of atmospheric oxidants such as Ozone is much
lower at certain times, and varies significantly on a daily basis.
Figure 2 Variation in Hourly Average NOX, NO2 and Ozone Concentrations at the Cardiff Centre
AURN Site – January to April 2018
Môr Hafren Bio Power – Air Quality Assessment 5Environmental Visage Limited
As can be seen, the NOX and Ozone trends tend to mirror one another, with NO2 comprising the majority
of the NOX for much of the time when Ozone concentrations are higher. Similar patterns are exhibited
for other months throughout the year.
The NOX / NO2 concentrations are markedly higher when Ozone concentrations are lower, with NOX
being the dominant species (due to the higher levels of NO). Under these variable conditions, the
atmospheric transformation of the NO in the NOX to NO2, associated with emissions from the proposed
ERF, will be affected to a varying degree. Accordingly, there is likely to be a proportion of the year when
the atmospheric chemistry in the vicinity of the development site may be restricted in its capacity to
convert all of the NO in the NOX to NO2 and the model predictions may overestimate the significance of
annual average NO2 predictions at receptors in the vicinity of the ERF development site.
2.6 Meteorological Data
Hourly averaged meteorological data from the Cardiff Airport measurement station, located
approximately 20 km to the west of the ERF development site was applied to the models. Data for 2015
to 2019 were utilised in the detailed modelling assessment. The 2019 windrose for the Cardiff Airport
measurement station is shown in Figure 3.
Figure 3 2019 Windrose for the Cardiff Airport Measurement Station
350° 0° 10°
340° 20°
800
330° 30°
320° 40°
600
310° 50°
300° 60°
400
290° 70°
200
280° 80°
270° 90°
260° 100°
250° 110°
240° 120°
230° 130°
220° 140°
210° 150°
200° 160°
190° 180° 170°
0 3 6 10 16 (knots)
Wind speed
0 1.5 3.1 5.1 8.2 (m/s)
The data indicate a predominance of winds from a westerly and easterly to north-easterly direction. The
meteorological data included nine parameters defined in Table .
Table 3 Modelled Meteorological Parameters
Parameter Description
YEAR Year of observation
TDAY Julian Day (1 to 366) of observation
THOUR Hour of Observation
T0C Temperature (º C)
U Wind speed (m s-1)
PHI Wind Direction (nearest 10 degrees)
P Precipitation (mm)
CL Cloud cover (Oktas)
RHUM Relative Humidity (%)
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2.7 Local Environmental Conditions
Local environmental conditions describe the factors that might influence the dispersion process (such
as nearby structures, sharply rising terrain, etc.) and also describe the locations at which pollutant
concentrations are to be predicted. These include:
2.7.1 Surface Roughness
Surface roughness defines the amount of near-ground turbulence that occurs as a consequence of
surface features, such as land use (i.e. agriculture, water bodies, urbanisation, open parkland,
woodland, etc.). Agricultural areas may have a surface roughness of approximately 0.2m to 0.3m
whereas large cities and woodlands may have a roughness of 1 to 1.5m.
Land use in the immediate vicinity of the development site is predominantly industrial and commercial,
with open scrubland farther afield, and given the absence of tall structures in the immediate vicinity of
the site, as well as the proximity of the open scrubland, a surface roughness factor of 0.2 metres would
be considered appropriate. However, ADMS 5.2 has the ability to include a spatially variable surface
roughness file which enables differing land-uses to be taken into account across the modelled area and,
as the site is located close to the Severn Estuary which would have a very low surface roughness, a
spatially variable file was included in the final modelling assessment, being applied to each of the models
which considered the Môr Hafren Energy Recovery Facility in isolation.
When undertaking the cumulative assessment, and due to the limited number of data points that can be
included in the spatially variable files, the assessments assumed a single surface roughness value of
0.2 metres to describe the local conditions. This roughness value was the most prevalent roughness
reported across the smaller 4km x 4km modelled grid applied in the locality of the proposed Môr Hafren
ERF and hence was considered to be appropriate for use as a generic value for modelling the wider
area.
Due to its location some distance from the Môr Hafren site, a separate surface roughness is required to
describe the land-use around the meteorological monitoring station at Cardiff Airport, as this would not
be included in the spatially variable file. The surface roughness applied to the meteorological monitoring
station was 0.1 metres, which is representative of land which might contain root crops, indicative of the
very flat areas around the airport and the runways.
2.7.2 Nearby Buildings and Structures
The proximity of solid structures, such as buildings, to an emission source can affect the dispersion of
a plume emitted from an adjacent chimney, particularly in the vicinity of that structure. The potential
impact of this occurring was assessed based on the buildings data presented in Table 4, and graphically
in Figure 4.
Table 4 Modelled Building Data
Length Width Projected Angle
Building Height (m)
(m) (m) Width (m) (Degrees)
Boiler House 46.45 45.7 24.8 52.0 38
Waste Bunker 37.5 40.0 30.8 50.5 38
Waste Reception 15.0 40.0 27.3 48.4 38
Admin Block 23.5 16.8 27.3 32.1 38
Turbine Hall 20.0 22.9 14.9 27.3 38
Fluegas Treatment (FGT) 22.1 19.7 17.1 26.1 38
Air Cooled Condenser
20.7 46.9 16.8 49.8 38
(ACC)
Môr Hafren Bio Power – Air Quality Assessment 7Environmental Visage Limited Figure 4 Site Layout as Modelled Additionally, and in a change to the initial modelling assessment, information on the local wind turbine at G24 Innovations Limited has been included in each modelling run. The ADMS 5.2 model can calculate the changes in the flow field due to the rotation of a local wind turbine, and subsequently calculates how this modified flow field affects dispersion of emissions from a nearby source. Although wind turbine data was included in the initial models, it has come to light that a different turbine type to that initially modelled was installed at the G24 Innovations site. As such, the models were run to include information on the installed Enercon EP2-E-82 unit, and this data was included within all models in order to report a worst-case assessment of the impact of the aerial emissions from the Môr Hafren Energy Recovery Facility, whilst the wind turbine is operational. As such, the results reported in Tables 9 - 39 include the effects of the wind turbine and show increased contributions to those previously reported. The installed Enercon EP2-E-82 wind turbine unit has the following specification: Power: 2,300 kW Rotor Diameter: 82.0 m Hub Height: 79.0 m Tip Height: 120.0 m Wind Speed: 2.5 – 34.0 m/s An “Additional Input” “AAI” wind turbine data file was created for inclusion within the model, specifying the location and the wind velocity / thrust coefficient data for the turbine. 2.7.3 Local Terrain Local terrain can affect wind flow patterns and, consequently, can affect the dispersion of atmospheric pollutants. The effects of terrain are not normally noticeable where the gradient is less than 10%. Ordnance Survey mapping for the area shows the absence of significant terrain in the vicinity of the ERF development site. Môr Hafren Bio Power – Air Quality Assessment 8
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However, in order to ensure that account was taken of any relevant change in gradient across the
modelled grid, a spatially variable terrain file was included when modelling the Môr Hafren ERF in
isolation. When undertaking the cumulative assessment, and due to the limited number of data points
that can be included in the spatially variable files, terrain data was not included.
2.7.4 Output Grid
When setting up a receptor grid it is important to ensure that there are sufficient receptor points to be
able to accurately predict the magnitude and location of the maximum Process Contribution. If the grid
of receptor points is too widely spaced, the maximum concentration may be missed. Modelling was
undertaken using a 4km x 4km grid with 20 metre grid spacing.
Twenty-two receptors, representing nearby residential properties or locations where people may
congregate for significant periods of time, were entered into the model, as shown in the following table.
Specific receptors were also included to represent locations where Cardiff Council undertakes NO 2
monitoring, as well as the location of designated ecological habitat sites within 10 km of the site.
Table 5 Specific Receptors Included in Detailed Modelling
Distance from
Receptor No. X Y Receptor Name
Site (m)
1 323778 179291 259 Newlands Road, Trowbridge, Cardiff
2 323189 179114 572 Newton Road, Trowbridge, Cardiff
3 323037 179729 626 Valley View, Trowbridge, Cardiff
St John Lloyd R.C. Primary School,
4 323223 180086 711
Brynbala Way, Trowbridge, Cardiff
Meadowlane Primary School, Plas y
5 323893 180450 995
Biswail, Trowbridge, Cardiff
6 323498 180050 569 Trowbridge, Cardiff
7 323749 180058 579 Trowbridge, Cardiff
8 323962 180067 669 Matthysens Way, Trowbridge, Cardiff
Shire Newton, Wentloog Road,
9 323927 179045 546
Trowbridge, Cardiff
Redland Property Services, Wentloog
10 324599 179021 1,090
Road, Trowbridge, Cardiff
11 324250 180116 887 Trowbridge, Cardiff
12 322510 179603 1,112 Harris Avenue, Rumney, Cardiff
13 323467 178873 639 Wentloog Avenue, Trowbridge, Cardiff
14 323938 178465 1,078 Newton Road, Trowbridge, Cardiff
15 323481 178553 951 Newton Road, Trowbridge, Cardiff
16 322317 179112 1,355 Greenway Road, Rumney, Cardiff
Wentloog Road, Wentlooge, Peterstone
17 325230 178966 1,697
Wentlooge, Newport
18 323004 178047 1,571 Rumney, Cardiff
Greenway Primary School, Llanstephan
19 322196 179540 1,422
Road, Rumney, Cardiff
Saint Illtyds Roman Catholic High School,
20 322770 180455 1,281
Newport Road, Llanrumney, Cardiff
87 Harris Avenue, 87, Harris Avenue,
21 322714 179882 983
Rumney, Cardiff
Wentloog Road, Wentlooge, Peterstone
22 325158 179254 1,560
Wentlooge, Newport
NO2 Monitoring Distance from
X Y Receptor Name
Receptors Site (m)
81 319387 176980 4,921 Stephenson Court
86 318452 178805 5,211 19 Fairoak Road
101 318416 176525 5,989 Cardiff Centre AURN
102 318416 176525 5,989 Cardiff Centre AURN
103 318416 176525 5,989 Cardiff Centre AURN
131 319292 176932 5,027 Dragon Court
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