pedigree power, biomass facility - revised aq assessment ...€¦ · following further process...
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Contents
Executive Summary ........................................................................................................................... 1
1 Introduction .............................................................................................................................. 2
1.1 Background ....................................................................................................................................2
1.2 Site Location and Context ..............................................................................................................2
1.3 Existing Site Activities ....................................................................................................................2
1.4 Proposed Site Activities .................................................................................................................2
2 Legislation and Policy ................................................................................................................ 4
2.1 European Legislation .....................................................................................................................4
2.2 UK Legislation ................................................................................................................................4
2.3 Local Air Quality Management ......................................................................................................5
2.4 Industrial Pollution Control Legislation .........................................................................................6
2.5 Environmental Assessment Levels .................................................................................................6
2.6 Critical Loads and Levels ................................................................................................................7
3 Baseline .................................................................................................................................... 8
3.1 Local Air Quality Management ......................................................................................................8
3.2 Air Quality Monitoring ...................................................................................................................8
3.3 Background Pollutant Concentrations ........................................................................................ 10
3.4 Sensitive Receptors ..................................................................................................................... 11
4 Assessment Methodology........................................................................................................ 14
4.1 Dispersion Modelling .................................................................................................................. 14
4.2 Model Input Parameters............................................................................................................. 17
4.3 Baseline Concentrations ............................................................................................................. 20
4.4 15-minute Sulphur Dioxide Concentration Predictions ............................................................... 20
4.5 Deposition Rates ......................................................................................................................... 20
4.6 Assessment Criteria .................................................................................................................... 21
4.7 Modelling Uncertainty ................................................................................................................ 21
4.8 Environment Agency Dispersion Modelling Report Requirements ............................................. 22
5 Results .................................................................................................................................... 23
5.1 Sensitive Receptors ..................................................................................................................... 23
5.2 Ecological Receptors ................................................................................................................... 39
6 Conclusions ............................................................................................................................. 46
References ...................................................................................................................................... 47
Abbreviations .................................................................................................................................. 48
Appendix I Figures ...................................................................................................................... 50
Quality Assurance
Author: Checked by: Issued by:
Gabor Antony
MSc, MIEnvSc, MIAQM
Robert Edwards
BSc, MSc, MIEMA
Gabor Antony
MSc, MIEnvSc, MIAQM
Disclaimer
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control and notify ADAS UK Ltd.
This report has been commissioned for the exclusive use of the commissioning party unless otherwise
agreed in writing by ADAS UK Ltd; no other party may use, make use of or rely on the contents of the
report. No liability is accepted by ADAS UK Ltd for any of this report, other than for the purposes for which
it was originally prepared and provided.
Opinions and information provided in this report are on basis of ADAS UK Ltd using due skill, care and
diligence in the preparation of this report and no explicit warranty is provided as to its accuracy. It should
be noted that no independent verification of any of the documents supplied to ADAS UK Ltd has been
made.
Version History
Version Date Amendments
Draft 28th September 2015 Initial Report
Client Draft 5th October 2015 Reviewed and approved for client issue
First Issue 22nd October 2015 First issue following client approval
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 1
ADAS UK Ltd was commissioned by Pedigree Power to undertake an Air Quality Assessment for a proposed
Biomass Combustion and Wastewater Treatment Plant on land off Browns Road, Daventry.
The plant will comprise a biomass combustion plant, heat recovery boiler, two screw expanders (up to
1.0MWe of renewable electricity generation) and four evaporative waste water treatment units.
Atmospheric emissions from the proposed combustion processes have the potential to cause increases in
ground level pollutant concentrations. As such, an Air Quality Assessment was required to quantify
impacts in the vicinity of the site. This was submitted in support of the Planning Application.
Following further process design a number of exhaust gas parameters were revised from the values used
in the initial assessment. The dispersion modelling was therefore updated to take account of the amended
data and quantify impacts at both human and ecological receptors.
Impacts on existing pollutant concentrations were not predicted to be significant at any location within
the assessment extents.
Nitrogen and acid gas deposition rates were also predicted at the relevant ecological sites. Results
indicated that emissions from the installation would not significantly affect existing conditions at any
designation.
It should be noted that predicted impacts were predicted based on a worst-case assessment scenario of
the facility constantly emitting the maximum permitted concentration of each pollutant throughout an
entire year. As such, predicted concentrations and deposition rates are likely to overestimate actual
impacts.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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This Air Quality Assessment has been prepared by ADAS UK Ltd under instruction from Pedigree Power
for a proposed Biomass Combustion and Wastewater Treatment Plant (WwTP) on land off Browns Road,
Daventry.
Atmospheric emissions of combustion products from the proposed combustor unit have the potential to
cause increases in ground level pollutant concentrations. An Air Quality Assessment was therefore
required to consider impacts as a result of emissions from the installation in order to support the
Environmental Permit Application for the installation.
Following further process design a number of exhaust gas parameters were revised from the values used
in the initial assessment. The dispersion modelling was therefore updated to take account of the amended
data and the results are provided in the following report.
The site is located west of Daventry at approximate National Grid Reference (NGR): 455500, 262500 and
is bounded to the east by the Ford Distribution Centre, to the north by agricultural land, and to the west
and south by leisure and sport facilities. The total area of the site is approximately 0.6ha. Figure 1 in
Appendix I shows a location plan.
The plant will comprise a Combined Heat and Power (CHP) unit which will consist of a Biomass Combustion
Plant, heat recovery boiler and two screw expanders (up to 1.0MWe of renewable electricity generation)
and a WwTP containing four waste water treatment evaporator units with associated storage tanks.
Atmospheric emissions from the proposed combustion processes have the potential to cause increases in
ground level pollutant concentrations at sensitive receptor locations. As such, an Air Quality Assessment
was required to quantify impacts in the vicinity of the site. This is detailed in the following report.
The current activities on site include the processing of green waste (Earthworm Plc) with approximately
1% food waste, which is taken in to an existing Reception Hall where it is shredded and loaded into an in-
vessel composting (IVC) unit. After 5-days residence time in the 10 in-vessel cells the material is chopped
and conveyed out into the Maturation Hall.
Both buildings and the IVC vessels are under air extraction and the extracted air is treated in an existing
biofilter which is designed to reduce odour emissions from the processing activities.
As part of the proposed development green waste processing and composting will cease and the plant
will instead take in pre-shredded waste wood at a rate of up to 30,000 tonnes per annum. The biomass
will be delivered into a storage hall with 4-days capacity and then onto a self-feeder floor to supply the
proposed new biomass plant on demand.
The biomass will be fed into the combustion plant to create steam to supply 15 tonnes per hour of 190°C
steam at 22bar.The biomass plant will be free-standing in the yard between the two site buildings. Figure
1 shows a site layout plan.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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The steam generated will pass through two 500kWe screw expanders, which will generate electricity,
initially to meet on site demand with the balance exported to the grid. Once the steam has passed through
the screw expanders it will be ducted into the water process hall where it will operate four evaporators,
each with the capacity to process 1,800 litres of wastewater per hour. The evaporators will be skid-
mounted units, automated to run unattended 24-hours a day.
Waste water will be transported to the site via tanker and discharged into the two 98,000 litre storage
tanks located along the Waste Water Treatment Building. The holding tanks will supply the evaporators
on demand. Evaporated water vapour will either be condensed or vented to atmosphere. The condensed
water will be recirculated to one of the holding tanks and discharged to drain in some proportion,
depending on the remaining level of contamination.
Woody biomass fuel will be delivered into the storage hall at a rate of up to 30,000 tonnes per annum.
Different types of biomass will be loaded onto the self-feeding floor to average out variations in feedstock.
Waste water will be transported to the site via tanker and discharged into storage tanks. If there is a large
amount of re-distilling necessary, lower volumes of waste water will be imported. The exact volume of
water received will be scaled up or down according to the process capacity at that point in time, for
example if one of the evaporators were not working at full capacity then the intake of waste water will be
reduced in proportion. This will ensure that the storage capacity on site is never exceeded.
Steam from the CHP unit will be used to drive the screw expanders, generating electricity. The site power
needs will be drawn from the screw expanders electrical output and the balance generated will be sold
via a two-way meter to the National Grid.
Ash from the combustion plant totalling about 0.4 tonnes per day will be exported, along with the small
amount of dry solids from the evaporators, to composting operations at other sites.
All the steam generated will be delivered through the screw expanders to the evaporator units.
Wastewater stored in holding tanks can be run through any or all of the evaporator units. One of the units
will be equipped with a condenser which will be used for water streams that generate vapour that is
potentially too odorous to release directly to atmosphere or through a biofilter. The site will have a 40ft
containerised biofilter which will be used to abate odour emissions in extracted air from both the
feedstock store and the WwTP.
The condenser evaporator will be capable of re-distilling the vapour as much as is necessary to reduce the
odour and further clean and clarify the water for discharge to drain. Prior to the discharge of condensed
clean water to surface water it will be stored in a 72,000 litre galvanised steel water storage tank located
to the south of the Waste Water Treatment Building.
The combustion plant, screw expanders and evaporators will run 24-hours a day, 8,000-hours per year.
Biomass loading, wastewater reception and maintenance will be completed during the working day.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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European Union (EU) air quality legislation is provided within Directive 2008/50/EC, which came into force
on 11th June 2008. This Directive consolidated previous legislation which was designed to deal with specific
pollutants in a consistent manner and provided new air quality objectives for particulate matter with an
aerodynamic diameter of less than 2.5µm (PM2.5). The consolidated Directives include:
Directive 99/30/EC - the First Air Quality "Daughter" Directive - sets ambient Air Quality Limit Values (AQLVs) for nitrogen dioxide (NO2), oxides of nitrogen (NOx), sulphur dioxide, lead and particulate matter with an aerodynamic diameter of less than 10µm PM10;
Directive 2000/69/EC - the Second Air Quality "Daughter" Directive - sets ambient AQLVs for benzene and carbon monoxide; and,
Directive 2002/3/EC - the Third Air Quality "Daughter" Directive - seeks to establish long-term objectives, target values, an alert threshold and an information threshold for concentrations of ozone in ambient air.
The fourth daughter Directive was not included within the consolidation and is described as:
Directive 2004/107/EC - sets health-based limits on polycyclic aromatic hydrocarbons, cadmium, arsenic, nickel and mercury, for which there is a requirement to reduce exposure to as low as reasonably achievable.
The Air Quality Standards Regulations (2010) came into force on 11th June 2010 and transpose the EU
Directive 2008/50/EC into UK law. AQLVs were published in these regulations for 7 pollutants, as well as
Target Values for an additional 5 pollutants.
Part IV of the Environment Act (1995) requires UK government to produce a national Air Quality Strategy
(AQS) which contains standards, objectives and measures for improving ambient air quality. The most
recent AQS was produced by the Department for Environment, Food and Rural Affairs (DEFRA) (and its
devolved counter-parts in Scotland, Wales and Northern Ireland) and published in July 20071. The AQS
sets out Air Quality Objectives (AQOs) that are maximum ambient pollutant concentrations that are not
to be exceeded either without exception or with a permitted number of exceedences over a specified
timescale. These are generally in line with the AQLVs, although the requirements for compliance vary
slightly.
Table 1 presents the AQLVs and AQOs for the pollutants considered within this assessment.
Table 1 Air Quality Limit Values and Objectives
Pollutant Air Quality Limit Value
Concentration (µg/m3) Averaging Period
NO2 40 Annual mean
200 1-hour mean; not to be exceeded more than 18 times a year
PM10 40 Annual mean
50 24-hour mean; not to be exceeded more than 35 times a year
1 The Air Quality Strategy for England, Scotland, Wales and Northern Ireland, DEFRA, 2007.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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Pollutant Air Quality Limit Value
Concentration (µg/m3) Averaging Period
SO2
125 24-hour mean; not to be exceeded more than 3 times a year
350 1-hour mean; not to be exceeded more than 24 times a year
266 15-minute mean; not to be exceeded more than 35 times a year
C6H6 5 Annual mean
Pb 0.25 Annual mean
PM2.5 25 Annual mean
CO 10,000 8-hour running mean
Table 2 presents the Air Quality Target Values for pollutants considered within this assessment.
Table 2 Air Quality Target Values
Pollutant Air Quality Limit Value
Concentration (ng/m3) Averaging Period
As 6 Annual mean
Cd 5 Annual mean
Ni 20 Annual mean
Table 3 presents the critical levels for the protection of vegetation for pollutants considered within this
assessment.
Table 3 Critical Levels for the Protection of Vegetation
Pollutant Air Quality Limit Value
Concentration (µg/m3) Averaging Period
NOx 30 Annual mean
75 24-hour mean
SO2 20 Annual mean
Ammonia
(NH3)
3 Annual mean for all higher plants
1
Annual mean for sensitive lichen communities and bryophytes and
ecosystems where lichens & bryophytes are an important part of
the ecosystem’s integrity
Hydrogen
fluoride
(HF)
5 Daily mean
0.5 Weekly mean
It should be noted that the critical levels for NH3 and HF are provided in EA Guidance H1 Annex F - Air
Emissions2 and are not included within the Air Quality Standards Regulations (2010) or AQS.
Under Section 82 of the Environment Act (1995) (Part IV) Local Authorities (LAs) are required to
periodically review and assess air quality within their area of jurisdiction under the system of Local Air
Quality Management (LAQM). This review and assessment of air quality involves considering present and
2 Horizontal Guidance Note H1 - Annex (f), Environment Agency, 2010.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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likely future air quality against the AQOs. If it is predicted that levels at locations of relevant exposure
(normally residential properties) are likely to be exceeded, the LA is required to declare an Air Quality
Management Area (AQMA). For each AQMA the LA is required to produce an Air Quality Action Plan, the
objective of which is to reduce pollutant concentrations in pursuit of the AQOs.
Atmospheric emissions from industry are controlled in England through the Environmental Permitting
(England and Wales) Regulations (2010) and subsequent amendments. The development will be classified
as a Part A1 process under the Regulations, and as such will operate under the requirements of an
environmental permit as defined by the EA. Amongst conditions of operation will be stated Emission Limit
Values (ELVs) for various pollutants produced by the process, as well as best practice guidelines for fugitive
dust and odour control. Compliance with these conditions must be demonstrated through periodic
monitoring requirements, which have been set in order to limit potential impacts in the surrounding area.
An Environmental Assessment Level (EAL) is the concentration of a substance, which, in a particular
environmental medium, the regulators regard as an appropriate value to enable a comparison between
the environmental effects of different substances in that medium and between environmental effects in
different media, enabling the summation of those effects.
Ideally EALs to fulfil this objective would be defined for each pollutant:
Based on the sensitivity of particular habitats or receptors (in particular three main types of receptor should be considered, protection of human health, protection of natural ecosystems and protection of specific sensitive receptors, e.g. materials, commercial activities requiring a particular environmental quality);
Be produced according to a standardised protocol to ensure that they are consistent, reproducible and readily understood;
Provide similar measure of protection for different receptors both within and between media; and,
Take account of habitat specific environmental factors such as pH, nutrient status, bioaccumulation, transfer and transformation processes where necessary.
EALs used in this assessment were obtained from H1 Annex F - Air Emissions2 and are summarised in
Table 4.
Table 4 Environmental Assessment Levels
Pollutant Environmental Assessment Level (µg/m3)
Long Term (Annual) Short Term (1-hour)
Hydrogen chloride (HCl) - 750
HF 16 160
Benzo-a-pyrene (BaP) 0.00025 -
Hg 0.25 7.5
Polychlorinated biphenyls (PCBs) 0.2 6
Antimony (Sb) 5 150
As 0.003 -
Chromium (Cr), Cr (II) and Cr (III) 5 150
Cr (VI) 0.0002 -
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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Pollutant Environmental Assessment Level (µg/m3)
Long Term (Annual) Short Term (1-hour)
Copper (Cu) 10 200
Manganese (Mn) 0.15 1,500
Vanadium (V) 5 1
It should be noted that the EAL for As of 0.003μg/m3 is lower than the Air Quality Target Value of
0.006μg/m3 and has therefore been used throughout this assessment.
A critical load is defined by the UK Air Pollution Information System (APIS)3 as:
"A quantitative estimate of exposure to deposition of one or more pollutants, below which significant
harmful effects on sensitive elements of the environment do not occur, according to present
knowledge. The exceedance of a critical load is defined as the atmospheric deposition of the pollutant
above the critical load."
A critical level is defined as:
"Threshold for direct effects of pollutant concentrations according to current knowledge. Exceedance
of a critical level is defined as the atmospheric concentration of the pollutant above the critical level."
A critical load refers to deposition of a pollutant, while a critical level refers to pollutant concentrations in
the atmosphere (which usually have direct effects on vegetation or human health).
When pollutant loads (or concentrations) exceed the critical load or level it is considered that there is a
risk of harmful effects. The excess over the critical load or level is termed the exceedence. A larger
exceedence is often considered to represent a greater risk of damage.
Maps of critical loads and levels and their exceedences have been used to show the potential extent of
pollution damage and aid in developing strategies for reducing pollution. Decreasing deposition below
the critical load is seen as means for preventing the risk of damage. However, even a decrease in the
exceedence may infer that less damage will occur.
Critical loads have been designated within the UK based on the sensitivity of the receiving habitat and
have been reviewed for the purpose of this assessment.
3 UK Air Pollution Information System, www.apis.ac.uk.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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Existing air quality conditions in the vicinity of the site were identified in order to provide a baseline for
assessment. These are detailed in the following Sections.
As required by the Environmental Act (1995), Daventry District Council (DDC) has undertaken a Review
and Assessment of air quality within its area of jurisdiction. This process has indicated that air quality is
generally good in DDC's area of jurisdiction and as such, no AQMAs have been declared.
Monitoring of pollutant concentrations is undertaken by DDC using periodic methods throughout their
area of jurisdiction. A review of the most recent Air Quality Progress Report4 indicated the closest diffusion
tube monitor to the proposed development is N26 on Braunston Road at NGR: 456477, 262953. This is
approximately 1km east of the site at a kerbside location. Recent monitoring results are shown in Table 5.
Table 5 DDC Diffusion Tube Monitoring Results
Site ID Location Type Distance to
Application Site
Located
Within
AQMA?
Annual Mean NO2
Concentrations (µg/m3)
2013
N25 Ashby Road Kerbside 1.6km east No 22.90
N26 Braunston Road Kerbside 1.0km east No 20.65
As indicated in Table 5, there have not been exceedences of the annual mean AQO for NO2 at the closest
diffusion tubes during 2013. Reference should be made to Figure 1 for DDC’s non-automatic monitoring
locations in the vicinity of the site.
Monitoring of heavy metals is carried out by DEFRA at 24 sites throughout the UK. The closest monitoring
location to the facility with validated data capture is Walsall Bilston Lane (NGR: 397197, 298370) at an
'urban industrial' location situated approximately 68km north-west of the facility. It is noted that the
closest monitoring site is at Fenny Compton, 17km south-west of the proposed development site. Given
that monitoring data was only available for a period of one month during December 2014 at this site, it is
not considered to be a representative source of monitoring data, and as such was not considered further
within this assessment. The most recent data available from the Walsall Bilston Lane site is from 2014, as
summarised in Table 6.
Table 6 Metals Monitoring Results
Species 2014 Annual Mean Concentration (ng/m3)
As 1.24
Cd 2.72
Cr 3.72
Cu 85.37
4 2013 Air Quality Progress Report for Daventry District Council, DDC, 2014.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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Species 2014 Annual Mean Concentration (ng/m3)
Hg (total gaseous mercury for 2013) 2.30
Mn 12.44
Ni 2.34
Pb 73.68
V 1.13
Monitoring of dioxins and PCBs is undertaken throughout the UK through the Toxic Organic Micro
Pollutants (TOMPs) network. Throughout this report, the term 'dioxins' is taken to mean the family of 210
compounds or congeners comprising polychlorinated dibenzodioxins (PCDDs) and polychlorinated
dibenzofurans (PCDFs). If both PCDDs and PCDFs are present, these have been referred to as PCDD/Fs.
The summation of the concentrations of 17 toxic PCDD and PCDF congeners, weighted relative to the
toxicity of 2,3,7,8-TCDD, is given in the form of Toxic Equivalents (TEQ).
There are very few TOMPs monitoring sites in England, with the closest to the application site being at
London Nobel House at an 'urban background' location. The most recent data available from this site is
from 2010 and is summarised in Table 7.
Table 7 Dioxins and Furans and Polychlorinated Biphenyls Monitoring Results
Species Unit 2010 Annual Mean Concentration
PCDD/Fs TEQ fg/m3 38.60
PCBs pg/m3 15.7*
Note: * Based on Σ7PCB = Sum of PCB 28+31, PCB 52, PCB 90/101, PCB 118, PCB 138, PCB 153+132, PCB180
Monitoring of BaP is undertaken throughout the UK by the PAH network. The closest monitoring site is
Birmingham Tyburn at an 'urban background' location. The most recent data available from this site is
from 2014 and is summarised in Table 8.
Table 8 Benzo-a-pyrene Monitoring Results
Species 2014 Annual Mean Concentration (ng/m3)
BaP 0.21
Concentrations of HCl and SO2 are monitored in the UK through the UK Eutrophying and Acidifying
Pollutants (UKEAP) network. The closest site to the development is Sutton Bonnington. The most recent
data available from this site is from 2014, as summarised in Table 9.
Table 9 Acid Gas Monitoring Results
Species 2014 Annual Mean Concentration (µg/m3)
HCl 0.25
SO2 0.80
Baseline concentrations of HF are not measured locally or nationally, since these are not generally of
concern in terms of local air quality. However, the EPAQS report "Guidelines for halogens and hydrogen
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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halides in ambient air for protecting human health against acute irritancy effects" contains some
estimates of baseline levels. This indicates that measured concentrations have been in the range of
0.036μg/m3 to 2.35μg/m3.
In lieu of local monitoring, the maximum measured baseline HF concentration has been used for the
purpose of this assessment.
Concentrations of NH3 are also monitored through the UKEAP network. The closest site to the
development is Drayton 3. The most recent data available from this site is from 2014, as summarised in
Table 10.
Table 10 Ammonia Monitoring Results
Species 2014 Annual Mean Concentration (µg/m3)
NH3 1.04
Predictions of background pollutant concentrations on a 1km by 1km grid basis have been produced by
DEFRA for the entire of the UK to assist LAs in their Review and Assessment of air quality. The site is
located in grid square NGR: 455500, 262500. The most recent data for this location, released in June 2014,
was downloaded from the DEFRA website5 for the purpose of this assessment and is summarised in
Table 11.
Table 11 Predicted Background Pollutant Concentrations
Species 2015 Annual Mean Concentration (µg/m3)
NOx 16.80
NO2 12.31
PM10 17.11
PM2.5 11.27
SO2 2.63
C6h6 0.218
CO 261
It should be noted that background concentrations of NO2, NOx, PM10 and PM2.5 were predicted for 2015
in order to consider the closest possible opening year of the plant. The background concentration of
benzene was predicted for 2010, whilst SO2 and CO were predicted for 2001. These are the most recent
predictions available from DEFRA and are therefore considered to provide a reasonable representation of
background concentrations in the vicinity of the site.
5 http://uk-air.defra.gov.uk/data/laqm-background-maps?year=2011.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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A sensitive receptor is defined as any location which may be affected by changes in air quality. These have
been defined for human and ecological receptors in the following sections.
A desk-top study was undertaken in order to identify any sensitive receptor locations in the vicinity of the
site that required specific consideration during the assessment. These are summarised in Table 12.
Table 12 Sensitive Receptor Locations
Receptor NGR (m)
ID Location X Y
R1 Elderstubbs Farm 455317.0 262489.2
R2 Ashtree Farm 454935.2 261809.6
R3 The Tollgate 455279.1 261822.4
R4 Drayton Lodge 455689.1 261933.6
R5 15 The Cherwell 455818.2 262123.7
R6 12 The Leam 455862.8 262220.9
R7 46 The Witham 455951.7 262338.2
R8 1 Eden Close 456091.7 262494.3
R9 Ford Centre Service Yard 455538.0 262591.0
The sensitive receptors identified in Table 12 represent worst-case locations. However, this is not an
exhaustive list and there may be other locations within the vicinity of the site that may experience air
quality impacts as a result of the development that have not been individually identified above. Reference
should be made to Figure 1 for a graphical representation of sensitive receptor locations.
Atmospheric emissions from the facility have the potential to impact on receptors of ecological sensitivity
within the vicinity of the site. A study was undertaken to identify any habitat sites within 10km of the
source as required by the EA's H1 guidance2 for:
Special Areas of Conservation (SACs) and candidate SACs (cSACs) designated under the EC Habitats Directive;
Special Protection Areas (SPAs) and potential SPAs designated under the EC Birds Directive; and
Ramsar Sites designated under the Convention on Wetlands of International Importance.
And also within 2km of the source for:
Sites of Special Scientific Interest (SSSI) established by the 1981 Wildlife and Countryside Act;
National Nature Reserves (NNR);
Local Nature Reserves (LNR);
Local Wildlife Sites (LWS, Sites of Interest for Nature Conservation, SINC and Sites of Local Interest for Nature Conservation, SLINC); and
Ancient woodlands.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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The study was completed using the Multi-Agency Geographic Information for the Countryside (MAGIC)
web-based interactive mapping service6, which draws together information on key environmental
schemes and designations for any statutory designations. A further data search was prepared by the
Northamptonshire Biodiversity Records Centre (NBRC) to identify any non-statutory sites within 2km of
the proposed installation.
A summary of the identified ecological receptors is provided in Table 13. It should be noted that a number
of receptors have been identified on each designation to provide consideration of impacts throughout the
relevant site.
Table 13 Ecological Receptor Locations
Receptor NGR (m)
ID Location X Y
ER1 Elderstubbs Farm Pasture LWS 454945 262526
ER2 Elderstubbs Farm Pasture LWS 455048 262449
ER3 Elderstubbs Farm Pasture LWS 455121 262345
ER4 Oak Spinney (Daventry) LWS 455799 261354
ER5 Pond Spinney LWS 455917 261185
ER6 Staverton Clump LWS 454907 261279
ER7 Staverton Wood LWS 455116 261523
ER8 Staverton Wood LWS 455329 261399
ER9 Stepnell Spinney LWS 455606 261537
ER10 Stepnell Spinney LWS 455718 261586
Reference should be made to Figure 1 for maps of the sensitive ecological receptor locations.
Critical loads have been designated within the UK based on the sensitivity and relevant features of the
receiving habitat. A review of the APIS website3 was undertaken in order to identify the most suitable
habitat description and associated critical load for the area of each designation considered within the
model. This was undertaken using the 'search by location' and 'habitat/pollutant impacts' functions within
APIS. The habitat types within each designation are listed in accordance with the UK Biodiversity Action
Plan (BAP) criteria, which are then split further by the European Nature Information System (EUNIS)
habitat type. These were reviewed, along with the habitat maps available through MAGIC and the NBRC,
to define the relevant classification at each of the receptor locations. It should be noted that separate
habitat types are often listed for European and National designations, although the geographical areas
covered are the same. When this was the case the most suitable classification for the area of interest was
selected. The relevant critical loads are presented in Table 14.
Table 14 Critical Loads
Re
cep
tor
APIS Habitat Critical Load Class
Critical Load
Nitrogen Critical Load (kgN/ha/yr)
Acid (keq/ha/yr)
Low High CLmaxS CLminN CLmaxN
ER1
Neutral Grassland 20 30 3.89 0.85 4.75 ER2
ER3
6 Multi-Agency Geographic Information for the Countryside, www.magic.gov.uk.
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Re
cep
tor
APIS Habitat Critical Load Class
Critical Load
Nitrogen Critical Load (kgN/ha/yr)
Acid (keq/ha/yr)
Low High CLmaxS CLminN CLmaxN
ER4 Broadleaved, Mixed and Yew Woodland 10 20 2.57 0.36 2.92
ER5 Broadleaved, Mixed and Yew Woodland 10 20 2.57 0.36 2.92
ER6 Broadleaved, Mixed and Yew Woodland 10 20 1.01 0.14 1.16
ER7 Broadleaved, Mixed and Yew Woodland 10 20 2.57 0.36 2.92
ER8
ER9 Broadleaved, Mixed and Yew Woodland 10 20 2.57 0.36 2.92
ER10
It should be noted that the information shown in Table 14 represents the most sensitive habitat within
each designation for pollutant deposition.
Background deposition rates at each ecological receptor location were obtained from the APIS website
using the 'search by location' function and are summarised in Table 15.
Table 15 Background Deposition Rates
Receptor APIS Habitat Critical Load Class
Deposition Rate
Nitrogen (kgN/ha/yr)
Acid (keq/ha/yr)
S N
ER1
Neutral Grassland 19.18 0.26 1.49 ER2
ER3
ER4 Broadleaved, Mixed and Yew Woodland 33.18 0.32 2.37
ER5 Broadleaved, Mixed and Yew Woodland 33.18 0.32 2.37
ER6 Broadleaved, Mixed and Yew Woodland 33.46 0.29 2.39
ER7 Broadleaved, Mixed and Yew Woodland 33.18 0.32 2.37
ER8
ER9 Broadleaved, Mixed and Yew Woodland 33.18 0.32 2.37
ER10
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Emissions associated with the proposed combustion unit have the potential to cause increases in pollutant
concentrations in the vicinity of the site. These have been quantified through dispersion modelling in
accordance with the methodology outlined in the following Sections.
An industry standard atmospheric dispersion model, ADMS 5, was used to model releases of the identified
substances. The dispersion modelling procedure was as follows:
Information on stack dimensions and position were obtained via plans from Earthworm;
Process conditions were obtained from Earthworm;
Emission rates were calculated based on combustor specifications obtained from Earthworm;
Appropriate data to describe meteorological conditions in the vicinity of the site was obtained from the UK Met Office;
A receptor grid of potentially sensitive locations was identified in the vicinity of the installation using digital mapping;
The above information was entered into the dispersion model;
The dispersion model was run to determine pollutant levels in the vicinity of the site. The results interpretation was based on the 5-year average modelled concentration at any location of relevant exposure; and,
The study results were compared with the relevant assessment criteria.
Dispersion modelling was undertaken using ADMS 5.1 (v5.1.2.0), which has been developed by Cambridge
Environmental Research Consultants (CERC) Ltd. ADMS 5 is a steady-state atmospheric dispersion model
that is based on modern atmospheric physics. It is a new generation model utilising boundary layer height
and Monin-Obukhov length to describe the atmospheric boundary layer and a skewed Gaussian
concentration distribution to calculate dispersion under convective conditions.
The model utilises hourly meteorological data to define conditions for plume rise, transport and diffusion.
It estimates the concentration for each source and receptor combination for each hour of input
meteorology, and calculates user-selected long-term and short-term averages.
ADMS 5 has been chosen because it is "fitted for the purpose of the modelling procedure" as defined by
the guidelines published by the Royal Meteorological Society (Britter et al, 1995 and Ireland et al, 2006).
The group that leads the development of ADMS 5 is CERC, but the UK Met Office and others have made
significant contributions. The model has been extensively validated against site measurements. Details of
these validation studies and information on the development of ADMS are available on the CERC website.
The dispersion modelling considered the combustor unit to be operational under normal conditions
continuously 24-hours per day throughout the year, as such providing a robust assessment of likely
operating conditions. Abnormal operating conditions would only occur during the start-up of the plant.
The unit will be installed with a gas oil start-up burner, for bed preheating, which would produce up to
2MWth independently of the bed. This will allow rapid start-up and full load is readily attained from cold
in approximately 1-hour.
The plant will be expected to operate seven days per week 24-hours per day outside of the planned
inspection and maintenance period which would only occur once per year. Therefore, the abnormal
operating conditions associated with the start-up of the combustor unit are not considered to have any
significant impact on the surrounding environment. As such, abnormal operations have not been
considered further within this assessment.
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The scenarios considered in the modelling assessment are summarised in Table 16.
Table 16 Dispersion Modelling Scenarios
Parameter Modelled As
Short Term Long Term
NO2 99.79%-ile 1-hour mean Annual mean
NOx 24-hour mean Annual mean
PM10 90.41%-ile 24-hour mean Annual mean
SO2
99.9%-ile 15-minute mean Annual mean
Annual mean 99.73%-ile 1-hour mean
99.18%-ile 24-hour mean
Total volatile organic compounds (VOCs) as C6H6 - Annual mean
HCl 1-hour mean -
HF
1-hour mean
Annual mean 24-hour mean
7-day mean
CO 8-hour mean -
Cd and Tl (as Cd) - Annual mean
Hg 1-hour mean Annual mean
Metals (total Sb, As, Pb, Cr, Co, Cu, Mn, Ni, V and
their compounds) 1-hour mean Annual mean
PCBs 1-hour mean Annual mean
BaP - Annual mean
Dioxins and furans (PCDD/Fs) - Annual mean
Nitrogen deposition - Annual deposition
Acid deposition - Annual deposition
Some short-term air quality criteria are framed in terms of the number of occasions in a calendar year on
which the concentration should not be exceeded. As such, the percentiles (%-ile) shown in Table 16 were
selected to represent the relationship between the permitted number of exceedences of short-period
concentrations and the number of periods within a calendar year.
Predicted pollutant concentrations were summarised in the following formats:
Process contribution (PC) - Predicted pollutant concentration as a result of emissions from the facility only; and
Predicted environmental concentration (PEC) - Total predicted pollutant concentration as a result of emissions from the facility and existing baseline levels.
Predicted ground level pollutant concentrations and deposition rates were compared with the relevant
AQLVs, EALs, Critical Levels and Critical Loads identified. These criteria are collectively referred to as
Environmental Quality Standards (EQSs).
Combustion products from the proposed combustor unit will be emitted from a dedicated stack. Plant
operating conditions were provided by Earthworm Plc. Relevant details are presented in Table 17.
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Table 17 Process Conditions
Parameter Value Unit
Stack location 455472.3, 262573.0 NGR (X, Y; m)
Internal Stack diameter 1.05 m
Stack height 17.2 M
Flue gas efflux velocity (actual) 13.509 m/s
Flue gas temperature 150 °C
Flue gas volumetric flow rate (actual) 42,110 m3/h
Reference should be made to Figure 1 for a graphical representation of the proposed stack location.
The pollutants considered within this assessment and their associated ELVs at a temperature of 273,15K,
at 11% reference oxygen, as stated within the Industrial Emissions Directive (IED), are shown in Table 18.
Table 18 Pollutants and Emission Limit Values
Pollutant Emission Limit Value (mg/Nm3)
NOx 200
Particulate matter (PM) 10
SO2 50
Total VOCs 10
HCl 10
HF 1
CO (as half-hourly average value) 100
Cd and Tl 0.05
Hg 0.05
Metals (total Sb, As, Pb, Cr, Co, Cu, Mn, Ni, V and their
compounds)
0.5
PCDD/Fs 1 x 10-7 TEQ
NH3 0.5406
BaP 1.5 x 10-4
PCBs 0.005
It should be noted that ELVs have not been designated for NH3, BaP and PCBs in the IED. As such, suitable
concentrations were determined based on the following:
NH3 - experience of similar facilities and the likely performance of the potential plant;
BaP - The highest recorded emission concentration from the EA's public register was 0.105µg/m3 at 11% O2; and
PCBs - The waste incineration BREF provides a range of values for PCB emissions to air from European municipal waste incineration plants. This states that the annual average total PCB concentration is less than 0.005mg/Nm3 (dry, 11% oxygen, 273.15K). In lieu of other available data, this has been assumed to be the emission concentration for the facility.
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Mass emission rates for use in the assessment were derived from the ELVs shown in Table 18 and are
summarised in Table 19. This represents a conservative assessment approach with emissions assumed to
be the maximum permitted with the plant operating in accordance with the relevant authorisation limits.
Table 19 Mass Emission Rates
Pollutant NOx Emissions
Concentration (mg/m3) Actual Mass Emission Rate (g/s)
NOx 129.0780 1.509854
PM 6.4539 0.075493
SO2 32.2695 0.377464
Total VOCs 6.4539 0.075493
HCl 6.4539 0.075493
HF 0.6454 0.007549
CO 64.5390 0.754927
Cd and Tl 0.0323 0.000377
Hg 0.0323 0.000377
Metals 0.3227 0.003775
PCDD/Fs 6.45 x 10-8 7.55 x 10-10
NH3 0.3489 0.004081
BaP 0.0001 0.000001
PCBs 0.0032 0.000038
Emissions of total NOx from combustion processes are predominantly in the form of nitric oxide (NO).
Excess oxygen in the combustion gases and further atmospheric reactions cause the oxidation of NO to
NO2. Comparisons of ambient NO and NO2 concentrations in the vicinity of point sources in recent years
has indicated that it is unlikely that more than 30% of the NOx is present at ground level as NO2.
Ambient NOx concentrations have been predicted through dispersion modelling. NO2 concentrations
reported in the results section assume 70% conversion from NOx to NO2 for annual means and a 35%
conversion for short term (hourly) concentrations, based upon Environment Agency (EA) methodology7.
The ELV for PM is stated as total dust. However, for the purposes of dispersion modelling it was considered
that the entire PM emission consisted of only PM10 or PM2.5. This allowed the maximum ground level
impacts, with respect to the relevant criteria, to be assessed. Actual plant emissions of PM are unlikely to
only consist of only one PM fraction, resulting in a worst-case assessment.
The ELV for VOC is stated as total organic carbon (TOC). However, for the purposes of dispersion modelling
it was considered that the entire TOC emission consisted of only benzene. This allowed the maximum
ground level impacts to be assessed with respect to the AQLV. Actual plant emissions of TOC are unlikely
to only consist of one species, resulting in a worst-case assessment. It should be noted that emissions
were modelled as TOC and results factored to benzene using the relative atomic mass to carbon ratio.
7 Conversion Ratios for NOx and NO2, Environment Agency, undated.
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The ELV for Cd and Tl is stated as a total of both metals. However, for the purposes of dispersion modelling
it was considered that the entire emission consisted of only Cd. This allowed the maximum ground level
impacts, with respect to the EQS to be assessed. Actual plant emissions of Cd and Tl are unlikely to consist
of only one species, resulting in a worst-case assessment.
The ELV for Sb, As, Pb, Cr, Co, Cu, Mn, Ni and V is stated as total Group 3 metals. Due to the low EQSs that
have been designated for Cr (VI), As and Ni, the EA has issued guidance8 on the modelling of Group 3
metals in support of energy recovery plants. This was reviewed for the purpose of this assessment and
the following staged approach adopted:
Potential impacts on annual mean Cr(VI), As and Ni and 1-hour mean V concentrations were assessed as these represent the lowest EQSs;
Stage 1 - The full metal emission was considered to consist of only one species. Any species with predicted exceedences of the EQSs or that could not be screened out in accordance with the EA criteria were progressed to Stage 2;
Stage 2 - The emission was apportioned equally between the relevant species. This resulted in 11% of the ELV being apportioned to each metal. Any species with predicted exceedences of the EQSs or that could not be screened out in accordance with the EA criteria were progressed to Stage 3; and
Stage 3 - Review EA data for specific species.
Emissions were assumed to be constant, with the plant in operation 24-hours per day, 365- days per year.
This is considered to be a worst-case assessment scenario as plant shut-down or periods of reduced work
load are not reflected in the modelled emissions.
Ambient concentrations for human receptors were predicted over the area NGR: 454700, 261800 to
456200, 263300. A second Cartesian Grid was utilised to predict impacts at sensitive ecological receptors
over the area NGR: 454200, 261150 to 456700, 263650. The two Cartesian grids with the resolution of
20 and 25m respectively were included in the model. It should be noted that these are less than 1.5 times
the stack height, in accordance with the relevant Environment Agency guidance. Results were
subsequently used to produce contour plots within the Surfer software package.
Ordnance Survey Landform Panorama terrain data was included for the site and surrounding area in order
to take account of the specific flow field produced by variations in ground height throughout the
assessment extents. This was pre-processed using the dedicated terrain function within ADMS 5.
The dispersion of substances released from elevated sources can be influenced by the presence of
buildings close to the emission point. Structures can interrupt the wind flows and cause significantly
higher ground-level concentrations close to the source than would arise in the absence of the buildings.
Analysis of the site layout indicated that a number of structures in the vicinity of the combustor unit
should be included within the model in order to take account of effects on pollutant dispersion. Building
input geometries are shown in Table 20.
8 Releases from municipal waste incinerators - Guidance to applicants on impact assessment for group 3 metals stack, EA, 2012.
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Table 20 Building Geometries
Building NGR (m) Height (m)
Length/ Diameter (m)
Width (m)
Angle (˚)
ID Description X Y
1 Fuel Hall 455443.4 262620.8 9.30 45.00 30.00 69.0
2 Walking Floor 455452.3 262596.9 5.00 6.00 14.50 69.0
3 WwTP 455475.4 262548.1 8.80 35.30 23.00 69.0
4 Offices 455485.9 262511.7 6.50 13.20 14.40 66.0
5 Wastewater Tank 1 455476.9 262523.4 3.04 5.50 - -
6 Wastewater Tank 2 455490.3 262528.6 3.04 7.30 - -
7 Wastewater Tanks 3 455483.6 262526.0 3.04 7.30 - -
8 Filters and Condensate Tank 455465.5 262570.2 3.00 5.00 8.20 69.0
9 Biomass Combustion Plant 455472.3 262573.0 17.20 8.15 - -
10 Proposed Biofilter 455497.8 262517.0 2.60 12.20 2.40 66.0
11 Ford Centre 455646.8 262761.7 9.00 238.10 604.50 72.8
12 Existing Biofilter 455483.8 262526.2 3.00 23.00 11.46 69.0
Reference should be made to Figure 1 for a graphical representation of the modelled building layout and
for the ADMS 5 model input.
A roughness length (z0) of 0.5m was used in the dispersion modelling study. This value of z0 is considered
appropriate for the morphology of the assessment area and is suggested within ADMS 5 as being suitable
for 'parkland, open suburbia'. A roughness length (z0) of 0.2m was considered appropriate for the
morphology of the meteorological station and is suggested within ADMS 5 as being suitable for
'agricultural areas (min)'.
The Monin-Obukhov length provides a measure of the stability of the atmosphere. A minimum Monin-
Obukhov length of 30m was used in the dispersion modelling study. This value is considered appropriate
for the nature of the assessment area and is suggested within ADMS 5 as being suitable for 'mixed
urban/industrial'. A minimum Monin-Obukhov length of 10m was considered appropriate for the
morphology of the meteorological station and is suggested within ADMS 5 as being suitable for 'small
towns < 50,000'.
Meteorological data used in this assessment was taken from Church Lawford meteorological station, over
the period 1st January 2010 to 31st December 2014 (inclusive). Church Lawford meteorological station is
located at NGR: 445632, 273629 which is approximately 18km north-west of the proposed development.
LAQM.TG(09)9 recommends meteorological stations within 30km of an assessment area as being suitable
for detailed modelling.
9 Local Air Quality Management Technical Guidance LAQM.TG(09), DEFRA, 2009.
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All meteorological data used in the assessment was provided by the UK Met Office. Reference should be
made to Figure 2 for wind roses of the utilised meteorological data.
A review of existing data in the vicinity of the site was undertaken in Section 3 of this report in order to
define baseline pollutant levels. These were subsequently utilised in the assessment to represent existing
concentrations in the vicinity of the site.
It is not possible to add short-term peak baseline and process concentrations. This is because the
conditions which give rise to peak ground-level concentrations of substances emitted from an elevated
source at a particular location and time are likely to be different to the conditions which give rise to peak
concentrations due to emissions from other sources. This point is addressed in EA guidance H12, which
advises that an estimate of the maximum combined pollutant concentration can be obtained by adding
the maximum predicted short-term concentration due to emissions from the source to twice the annual
mean baseline concentration. This approach was adopted throughout the assessment.
Throughout the assessment, 15-minute mean SO2 concentrations have been calculated using the following
correction factor based upon empirical relationships with the 99.9th%-ile of 1-hour means, as described in
EA guidance H1:
99.9th%-ile of 15-minute means = 1.34 x 99.9th%-ile of 1-hour means.
Deposition rates were calculated using the conversion factors provided within EA document 'Technical
Guidance on Detailed Modelling approach for an Appropriate Assessment for Emissions to Air AQTAG
06'10. Predicted pollutant concentrations were multiplied by the relevant deposition velocity and
conversion factor to calculate the speciated dry deposition flux.
The conversion factors used are presented within Table 21.
Table 21 Deposition Rates
Pollutant Deposition Velocity (m/s) Conversion Factor (μg/m2/s to
kg/ha/yr of pollutant species) Grassland Forest
NO2 0.0015 0.003 96.0
SO2 0.0120 0.024 157.7
NH3 0.02 0.03 259.7
HCl 0.025 0.06 306.7
Due to the nature of the modelling area the deposition velocity for 'grassland' was used for the calculation
of deposition throughout the assessment.
Acid deposition occurs as a result of NO2, NH3, SO2 and HCl. Predicted ground level pollutant
concentrations of all these species were converted to kilo-equivalent ion depositions (keq/ha/yr) for
comparison with the critical load for acid deposition at each of the identified ecological receptors.
10 Technical Guidance on Detailed Modelling approach for an Appropriate Assessment for Emissions to Air AQTAG 06, EA, 2006.
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The conversion to units of equivalents, a measure of the potential acidifying effect of a species, was
undertaken by multiplying the dry deposition flux by the standard conversion factors shown in Table 22.
Table 22 Conversion Factors to Units of Equivalents
Species Conversion Factor from kg/ha/yr to keq/ha/yr
N Divide by 14
S Divide by 16
HCl Divide by 35.5
The total N proportion was calculated from NO2 and NH3 concentrations, whilst the HCl equivalent was
added to the S proportion, in accordance with the methodology outlined in AQTAG 0610. The proportion
of the EQS consisting of the PC and PEC were then calculated using the tool available on the APIS website.
The effects of wet HCl deposition was undertaken using the 'falling drop method' included within ADMS 5,
with an initial pH value of droplets above the plume of 5.6, as detailed within the ADMS 5 user guide11.
Plume depletion was turned off in order to provide a worst-case assessment. The modelled outputs in
μg/m2/s were multiplied by 8.63, as provided in AQTAG 0610, to provide deposition in keq/ha/yr.
HCl deposition was then defined as the maximum calculated wet or dry value.
EA Horizontal Guidance Note H1 states that:
"process contributions can be considered insignificant if:
the long term process contribution is <1% of the long term environmental standard; and,
the short term process contribution is <10% of the short term environmental standard."
In addition, the following screening criteria are outlined in EA guidance document "Guidance to Applicants
on Impact Assessment for Group 3 Metals Stack Releases - V.3 September 2012" for metal concentrations:
Long-term PC <1% and short-term PC <10%; or,
Long-term and short-term PEC <100% (taking likely modelling uncertainties into account).
For screening purposes only, the EA methodology assumes that Cr (VI) comprises 20% of the total
background Cr.
Predicted PCs have been compared to the relevant EQSs and the criteria stated above. Where the impact
is within these parameters, the EA concludes that impacts associated with an installation are acceptable.
Uncertainty in dispersion modelling predictions can be associated with a variety of factors, including:
Model uncertainty - due to model limitations;
Data uncertainty - due to errors in input data, including emission estimates, land use characteristics and meteorology; and,
Variability - randomness of measurements used.
Potential uncertainties in model results have been minimised as far as practicable and worst-case inputs
used in order to provide a robust assessment. This included the following:
11 ADMS 5 Atmospheric Dispersion Modelling System User Guide Version 5.1, CERC, 2015.
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Choice of model - ADMS 5 is a commonly used atmospheric dispersion model and results have been verified through a number of studies to ensure predictions are as accurate as possible;
Meteorological data - Modelling was undertaken using 5-years of annual meteorological data sets from a representative observation site to take account of local conditions;
Plant operating conditions - Plant operating conditions were provided by Earthworm Plc based on the anticipated fuel and plant size. As such, these are considered to be representative of operating conditions;
Emission rates - Emission rates were derived from the relevant ELVs and therefore represent the maximum potential emissions with the plant operating within the conditions of the IED. Emissions were also assumed to be constant throughout the modelling period, which does not allow for plant shut down or reduced load. These assumptions are likely to overestimate actual emissions and therefore result in a worst case assessment;
Background concentrations - Obtained from the DEFRA mapping study and national monitoring networks. Although these may underestimate actual concentrations in the vicinity of pollutant sources, such as roads, they are considered suitable for an assessment of this nature;
Receptor locations - A Cartesian Grid was included in the model in order to calculate maximum predicted concentrations throughout the assessment extents. Receptor points were also included at sensitive locations to provide additional consideration of these areas; 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 pollutant concentrations.
Results were considered in the context of the relevant AQLVs, AQOs and EALs. It is considered that the
use of the stated measures to reduce uncertainty and the use of worst-case assumptions when necessary
has resulted in model accuracy of an acceptable level.
The EA dispersion modelling report requirements and their reference locations within the report is
summarised in Table 23.
Table 23 Dispersion Modelling Report Requirements
Item Reference within Report
Location map Figure 1
Site plan Figure 1
List of pollutants modelled and relevant air quality
guidelines
Table 16, Table 1, Table 2, Table 3 and Table 4
Details of modelled scenarios Table 16
Details of relevant ambient concentrations used Table 5, Table 6, Table 7, Table 8, Table 9 and Table 10
Model description and justification Section 4.1
Special model treatments used Section 4
Table of emission parameters used Table 18 and Table 19
Details of modelled domain and receptors Sections 4.2.2, 3.4.1 and 3.4.2
Details of meteorological data used (including origin)
and justification
Section 4.2.7
Details of terrain treatment Section 4.2.3
Details of building treatment Section 4.2.4
Sensitivity analysis Section 4.7
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Dispersion modelling was undertaken with the inputs described in Section 4. Reference should be made
to Figures 3 to 34 in Appendix I for graphical representations of predicted pollutant concentrations,
inclusive of background, throughout the assessment extents.
It should be noted that the data shown in the Figures are predictions from the meteorological data set
which resulted in the maximum pollutant concentration. For example, the maximum annual mean NO2
concentration was predicted using the 2011 meteorological data set. As such, the contours shown in
Figure 3 were produced from the 2011 model outputs.
Predicted concentrations of each pollutant at the sensitive receptor locations identified in Table 11 are
summarised in the following Sections.
Annual Mean
Predicted annual mean NO2 concentrations are summarised in Table 24. Figure 3 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 24 Predicted Annual Mean NO2 Concentrations
Receptor Predicted Annual Mean NO2
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 1.57 13.88 3.92 34.70
R2 Ashtree Farm 0.30 12.61 0.75 31.53
R3 The Tollgate 0.34 12.65 0.84 31.62
R4 Drayton Lodge 0.20 12.51 0.50 31.27
R5 15 The Cherwell 0.43 12.74 1.07 31.85
R6 12 The Leam 0.57 12.88 1.41 32.19
R7 46 The Witham 0.61 12.92 1.52 32.29
R8 1 Eden Close 0.36 12.67 0.91 31.69
R9 Ford Centre Service Yard 9.45 21.76 23.62 54.39
As indicated in Table 24, predicted concentrations of NO2 were below the annual mean EQS at all sensitive
receptor locations.
As indicated in Table 24, the PC proportion of the EQS is more than 1% at five receptor locations. However,
the PEC is less than the EQS at all locations. As such, impacts are not considered to be significant. It should
be noted that the assessment considered the facility emitting the maximum permitted pollutant
concentration at all times. As such, predicted concentrations are likely to be an overestimation of actual
impacts.
1-hour Mean
Predicted 99.79%-ile NO2 concentrations are summarised in Table 25. Figure 4 provides graphical
representations of predicted concentrations throughout the assessment area.
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Table 25 Predicted 99.79%-ile 1-hour Annual Mean NO2 Concentrations
Receptor Predicted 99.79%-ile 1-hour
Mean NO2 Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 15.13 39.75 7.56 19.87
R2 Ashtree Farm 2.39 27.01 1.19 13.50
R3 The Tollgate 2.79 27.41 1.39 13.70
R4 Drayton Lodge 2.98 27.60 1.49 13.80
R5 15 The Cherwell 4.15 28.77 2.08 14.39
R6 12 The Leam 4.67 29.29 2.34 14.65
R7 46 The Witham 4.51 29.13 2.25 14.56
R8 1 Eden Close 3.86 28.48 1.93 14.24
R9 Ford Centre Service Yard 63.91 88.53 31.96 44.27
As indicated in Table 25, predicted concentrations of NO2 were below the annual mean AQO at all
sensitive receptor locations.
As indicated in Table 25, the PC proportion of the EQS is less than 10% at all receptor locations with the
exception of R9. However, the PEC is significantly below the EQS at all locations. As such, impacts are not
considered to be significant. It should be noted that the assessment assumes that the facility is emitting
the maximum permitted pollutant concentration at all times. As such, predicted concentrations are likely
to be an overestimation of actual impacts.
Annual Mean PM10
Predicted annual mean PM10 concentrations are summarised in Table 26. Figure 5 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 26 Predicted Annual Mean PM10 Concentrations
Receptor Predicted Annual Mean PM10
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.11 17.22 0.28 43.06
R2 Ashtree Farm 0.02 17.13 0.05 42.83
R3 The Tollgate 0.02 17.13 0.06 42.84
R4 Drayton Lodge 0.01 17.12 0.04 42.81
R5 15 The Cherwell 0.03 17.14 0.08 42.85
R6 12 The Leam 0.04 17.15 0.10 42.88
R7 46 The Witham 0.04 17.15 0.11 42.88
R8 1 Eden Close 0.03 17.14 0.07 42.84
R9 Ford Centre Service Yard 0.67 17.78 1.69 44.46
As indicated in Table 26, predicted concentrations of PM10 were below the annual mean AQO at all
sensitive receptors.
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As indicated in Table 26, the PC proportion of the EQS is less than 1% at all but one receptor locations.
However, at this location the PEC is considerably lower than the EQS. As such, impacts on annual mean
PM10 concentrations are considered to be insignificant. Furthermore this is a non-sensitive area which
would not be considered relevant to the AQO, as outlined in Table 1. As such, they are not considered
relevant to the assessment.
24-hour Mean PM10
Predicted 90.41%-ile 24-hour mean PM10 concentrations are summarised in Table 27. Figure 6 provides
graphical representations of predicted concentrations throughout the assessment area.
Table 27 Predicted 90.41%-ile 24-hour Mean PM10 Concentrations
Receptor
Predicted 90.41%-ile 24-hour
Mean PM10 Concentration
(µg/m3)
Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.45 34.67 0.89 69.33
R2 Ashtree Farm 0.09 34.31 0.18 68.62
R3 The Tollgate 0.09 34.31 0.18 68.62
R4 Drayton Lodge 0.06 34.28 0.12 68.56
R5 15 The Cherwell 0.12 34.34 0.25 68.69
R6 12 The Leam 0.16 34.38 0.32 68.76
R7 46 The Witham 0.16 34.38 0.32 68.76
R8 1 Eden Close 0.10 34.32 0.19 68.63
R9 Ford Centre Service Yard 2.44 36.66 4.88 73.32
As indicated in Table 27, predicted concentrations of PM10 were below the 24-hour mean AQO at all
sensitive receptors.
As indicated in Table 27, the PC proportion of the EQS is less than 10% at all receptor locations. As such,
impacts on 24-hour mean PM10 concentrations are considered to be insignificant in accordance with the
EA screening criteria.
Annual Mean PM2.5
Predicted annual mean PM2.5 concentrations are summarised in Table 28. Figure 7 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 28 Predicted Annual Mean PM2.5 Concentrations
Receptor Predicted Annual Mean PM2.5
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.11 11.38 0.45 45.53
R2 Ashtree Farm 0.02 11.29 0.09 45.17
R3 The Tollgate 0.02 11.29 0.10 45.18
R4 Drayton Lodge 0.01 11.28 0.06 45.14
R5 15 The Cherwell 0.03 11.30 0.12 45.20
R6 12 The Leam 0.04 11.31 0.16 45.24
R7 46 The Witham 0.04 11.31 0.17 45.25
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Receptor Predicted Annual Mean PM2.5
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R8 1 Eden Close 0.03 11.30 0.10 45.18
R9 Ford Centre Service Yard 0.67 11.94 2.70 47.78
As indicated in Table 28, predicted concentrations of PM2.5 were below the annual mean AQO at all
sensitive receptors.
As indicated in Table 28, the PC proportion of the EQS is less than 1% at all but one receptor locations.
However, at this location the PEC is considerably lower than the EQS. As such, impacts on annual mean
PM2.5 concentrations are considered to be insignificant. Furthermore this is a non-sensitive area which
would not be considered relevant to the AQO, as outlined in Table 1. As such, they are not considered
relevant to the assessment.
24-hour Mean
Predicted 99.18%-ile 24-hour mean SO2 concentrations are summarised in Table 29. Figure 8 provides
graphical representations of predicted concentrations throughout the assessment area.
Table 29 Predicted 99.18%-ile 24-hour Mean SO2 Concentrations
Receptor Predicted 99.18%-ile 24-hour
Mean SO2 Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 2.22 7.48 1.77 5.98
R2 Ashtree Farm 0.44 5.70 0.35 4.56
R3 The Tollgate 0.45 5.71 0.36 4.57
R4 Drayton Lodge 0.30 5.56 0.24 4.45
R5 15 The Cherwell 0.61 5.87 0.48 4.69
R6 12 The Leam 0.80 6.06 0.64 4.85
R7 46 The Witham 0.79 6.05 0.63 4.84
R8 1 Eden Close 0.47 5.73 0.38 4.59
R9 Ford Centre Service Yard 12.20 17.46 9.76 13.97
As indicated in Table 29, predicted 99.18%-ile 24-hour mean SO2 concentrations were below the relevant
EQS at all sensitive receptor locations
As indicated in Table 29, the PC proportion of the EQS is less than 10% at all receptor locations. As such,
impacts on 24-hour mean SO2 concentrations are considered to be insignificant in accordance with the EA
screening criteria.
1-hour Mean
Predicted 99.73%-ile 1-hour mean SO2 concentrations are summarised in Table 30. Figure 9 provides
graphical representations of predicted concentrations throughout the assessment area.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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Table 30 Predicted 99.73%-ile 1-hour Mean SO2 Concentrations
Receptor Predicted 99.73%-ile 1-hour
Mean SO2 Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 10.28 15.54 2.94 4.44
R2 Ashtree Farm 1.68 6.94 0.48 1.98
R3 The Tollgate 1.97 7.23 0.56 2.07
R4 Drayton Lodge 2.10 7.36 0.60 2.10
R5 15 The Cherwell 2.94 8.20 0.84 2.34
R6 12 The Leam 3.30 8.56 0.94 2.44
R7 46 The Witham 3.18 8.44 0.91 2.41
R8 1 Eden Close 2.70 7.96 0.77 2.27
R9 Ford Centre Service Yard 45.13 50.39 12.89 14.40
As indicated in Table 30, predicted 99.73%-ile 1-hour mean SO2 concentrations were below the relevant
EQS at all sensitive receptor locations.
As indicated in Table 30, the PC proportion of the EQS is less than 10% at all but one receptor locations.
However, the PEC is significantly below the EQS at all locations. As such, impacts are not considered to be
significant. It should be noted that the assessment assumed that the facility would be emitting the
maximum permitted pollutant concentration at all times. As such, predicted concentrations are likely to
be an overestimation of actual impacts.
15-minute Mean
Predicted 99.9%-ile 15-minute mean SO2 concentrations are summarised in Table 31. Figure 10 provides
graphical representations of predicted concentrations throughout the assessment area.
Table 31 Predicted 99.9%-ile 15-minute Mean SO2 Concentrations
Receptor Predicted 99.9%-ile 15-minute
Mean SO2 Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 16.01 21.27 6.02 7.99
R2 Ashtree Farm 2.42 7.68 0.91 2.89
R3 The Tollgate 2.96 8.22 1.11 3.09
R4 Drayton Lodge 3.10 8.36 1.16 3.14
R5 15 The Cherwell 4.11 9.37 1.55 3.52
R6 12 The Leam 4.64 9.90 1.75 3.72
R7 46 The Witham 4.49 9.75 1.69 3.66
R8 1 Eden Close 4.00 9.26 1.50 3.48
R9 Ford Centre Service Yard 61.80 67.06 23.23 25.21
As indicated in Table 31, predicted 99.9%-ile 15-minute mean SO2 concentrations were below the relevant
EQS at all sensitive receptor locations.
As indicated in Table 31, the PC proportion of the EQS is less than 10% at all but one receptor locations.
However, the PEC is significantly below the EQS at all locations. As such, impacts are not considered to be
significant. It should be noted that the assessment assumed that the facility would be emitting the
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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maximum permitted pollutant concentration at all times. As such, predicted concentrations are likely to
be an overestimation of actual impacts.
Predicted annual mean VOC concentrations (as C6H6) concentrations are summarised in Table 32.
Figure 11 provides graphical representations of predicted concentrations throughout the assessment
area.
Table 32 Predicted Annual Mean VOC (as C6H6) Concentrations
Receptor Predicted Annual Mean VOC (as
C6H6) Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.11 0.55 2.24 10.96
R2 Ashtree Farm 0.02 0.46 0.43 9.15
R3 The Tollgate 0.02 0.46 0.48 9.20
R4 Drayton Lodge 0.01 0.45 0.28 9.00
R5 15 The Cherwell 0.03 0.47 0.61 9.33
R6 12 The Leam 0.04 0.48 0.81 9.53
R7 46 The Witham 0.04 0.48 0.87 9.59
R8 1 Eden Close 0.03 0.46 0.52 9.24
R9 Ford Centre Service Yard 0.67 1.11 13.50 22.22
As indicated in Table 32, predicted annual mean VOC (as C6H6) concentrations were below the relevant
EQS at all sensitive receptor locations.
As indicated in Table 32, the PC proportion of the EQS is above 1% at two receptor locations. However, at
these locations the PEC is considerably lower than the EQS. As such, impacts on annual mean VOC
(as C6H6) concentrations are considered to be insignificant.
Predicted 1-hour mean HCl concentrations are summarised in Table 33. Figure 12 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 33 Predicted 1-hour Mean HCl Concentrations
Receptor Predicted 1-hour Mean HCl
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 3.06 3.56 0.41 0.47
R2 Ashtree Farm 0.46 0.96 0.06 0.13
R3 The Tollgate 0.58 1.08 0.08 0.14
R4 Drayton Lodge 0.64 1.14 0.09 0.15
R5 15 The Cherwell 0.74 1.24 0.10 0.16
R6 12 The Leam 0.74 1.24 0.10 0.16
R7 46 The Witham 0.72 1.22 0.10 0.16
R8 1 Eden Close 0.71 1.21 0.09 0.16
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Receptor Predicted 1-hour Mean HCl
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R9 Ford Centre Service Yard 10.17 10.67 1.36 1.42
As indicated in Table 33, predicted 1-hour mean HCl concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 33, the PC proportion of the EQS is less than 10% at all receptor locations. As such,
impacts on annual mean HCl concentrations are considered to be insignificant in accordance with the EA
screening criteria.
Annual Mean
Predicted annual mean HF concentrations are summarised in Table 34. Figure 13 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 34 Predicted Annual Mean HF Concentrations
Receptor Predicted Annual Mean HF
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.01 2.36 0.07 14.76
R2 Ashtree Farm 0.00 2.35 0.01 14.70
R3 The Tollgate 0.00 2.35 0.02 14.70
R4 Drayton Lodge 0.00 2.35 0.01 14.70
R5 15 The Cherwell 0.00 2.35 0.02 14.71
R6 12 The Leam 0.00 2.35 0.03 14.71
R7 46 The Witham 0.00 2.35 0.03 14.71
R8 1 Eden Close 0.00 2.35 0.02 14.70
R9 Ford Centre Service Yard 0.07 2.42 0.42 15.11
As indicated in Table 34, predicted annual mean HF concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 34, the PC proportion of the EQS is less than 1% at all receptor locations. As such,
impacts on annual mean HF concentrations are considered to be insignificant in accordance with the EA
screening criteria.
1-hour Mean
Predicted 1-hour mean HF concentrations are summarised in Table 35. Figure 14 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 35 Predicted 1-hour Mean HF Concentrations
Receptor Predicted 1-hour Mean HF
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.31 5.01 0.19 3.13
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Receptor Predicted 1-hour Mean HF
Concentration (µg/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R2 Ashtree Farm 0.05 4.75 0.03 2.97
R3 The Tollgate 0.06 4.76 0.04 2.97
R4 Drayton Lodge 0.06 4.76 0.04 2.98
R5 15 The Cherwell 0.07 4.77 0.05 2.98
R6 12 The Leam 0.07 4.77 0.05 2.98
R7 46 The Witham 0.07 4.77 0.05 2.98
R8 1 Eden Close 0.07 4.77 0.04 2.98
R9 Ford Centre Service Yard 1.02 5.72 0.64 3.57
As indicated in Table 35, predicted 1-hour mean HF concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 35, the PC proportion of the EQS is less than 10% at all receptor locations. As such,
impacts on 1-hour mean HF concentrations are considered to be insignificant in accordance with the EA
screening criteria.
Predicted maximum daily running 8-hour mean CO concentrations are summarised in Table 36. Figure 15
provides graphical representations of predicted concentrations throughout the assessment area.
Table 36 Predicted Maximum Daily Running 8-hour Mean CO Concentrations
Receptor
Predicted Maximum Daily
Running 8-hour mean CO
Concentration (mg/m3)
Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.0011 0.52 0.01 5.23
R2 Ashtree Farm 0.0002 0.52 0.00 5.22
R3 The Tollgate 0.0002 0.52 0.00 5.22
R4 Drayton Lodge 0.0001 0.52 0.00 5.22
R5 15 The Cherwell 0.0003 0.52 0.00 5.22
R6 12 The Leam 0.0004 0.52 0.00 5.22
R7 46 The Witham 0.0004 0.52 0.00 5.22
R8 1 Eden Close 0.0003 0.52 0.00 5.22
R9 Ford Centre Service Yard 0.0066 0.53 0.07 5.29
As indicated in Table 36, predicted maximum daily running 8-hour mean CO concentrations were below
the relevant EQS at all sensitive receptor locations.
As indicated in Table 36, the PC proportion of the EQS is less than 10% at all receptor locations. As such,
impacts on maximum daily running 8-hour mean CO concentrations are considered to be insignificant in
accordance with the EA screening criteria.
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Predicted annual mean Cd concentrations are summarised in Table 37. Figure 16 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 37 Predicted Annual Mean Cd Concentrations
Receptor Predicted Annual Mean Cd
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.56 3.28 11.19 65.59
R2 Ashtree Farm 0.11 2.83 2.15 56.55
R3 The Tollgate 0.12 2.84 2.40 56.80
R4 Drayton Lodge 0.07 2.79 1.42 55.82
R5 15 The Cherwell 0.15 2.87 3.06 57.46
R6 12 The Leam 0.20 2.92 4.03 58.43
R7 46 The Witham 0.22 2.94 4.33 58.73
R8 1 Eden Close 0.13 2.85 2.60 57.00
R9 Ford Centre Service Yard 3.37 6.09 67.39 121.79
As indicated in Table 37, predicted annual mean Cd concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 37, the EA criteria for 'insignificant' impacts was not achieved for annual mean Cd
concentrations. However, this represents an extreme worst-case where the entire ELV for Cd and Tl was
considered to consist of only one species. As such, actual concentrations are likely to be lower than those
predicted. Additionally, the maximum PEC proportion of the EQS at receptor locations which are
considered relevant to the EQS was 65.59%. This provides significant headroom and it is therefore
considered unlikely that exceedences of the EQS for annual mean Cd would occur at relevant locations as
a result of emissions from the installation.
The modelling results indicated exceedences of the annual mean EQS for Cd at one location. However,
this receptor is representative of non-sensitive areas which would not be considered relevant to the
annual mean EQS. As such, it is not considered relevant to the assessment.
Annual Mean
Predicted annual mean Hg concentrations are summarised in Table 38. Figure 17 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 38 Predicted Annual Mean Hg Concentrations
Receptor Predicted Annual Mean Hg
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.56 2.86 0.22 1.14
R2 Ashtree Farm 0.11 2.41 0.04 0.96
R3 The Tollgate 0.12 2.42 0.05 0.97
R4 Drayton Lodge 0.07 2.37 0.03 0.95
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Receptor Predicted Annual Mean Hg
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R5 15 The Cherwell 0.15 2.45 0.06 0.98
R6 12 The Leam 0.20 2.50 0.08 1.00
R7 46 The Witham 0.22 2.52 0.09 1.01
R8 1 Eden Close 0.13 2.43 0.05 0.97
R9 Ford Centre Service Yard 3.37 5.67 1.35 2.27
As indicated in Table 38, predicted annual mean Hg concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 38, the PC proportion of the EQS is less than 1% at all but one receptor locations.
However, this receptor is representative of non-sensitive areas which would not be considered relevant
to the annual mean EQS. As such, it is not considered relevant to the assessment.
1-hour Mean
Predicted Maximum 1-hour mean Hg concentrations are summarised in Table 39. Figure 18 provides
graphical representations of predicted concentrations throughout the assessment area.
Table 39 Predicted Maximum 1-hour Mean Hg Concentrations
Receptor Predicted Maximum 1-hour
Mean Hg Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 15.28 19.88 0.20 0.27
R2 Ashtree Farm 2.28 6.88 0.03 0.09
R3 The Tollgate 2.88 7.48 0.04 0.10
R4 Drayton Lodge 3.19 7.79 0.04 0.10
R5 15 The Cherwell 3.67 8.27 0.05 0.11
R6 12 The Leam 3.68 8.28 0.05 0.11
R7 46 The Witham 3.61 8.21 0.05 0.11
R8 1 Eden Close 3.53 8.13 0.05 0.11
R9 Ford Centre Service Yard 50.77 55.37 0.68 0.74
As indicated in Table 39, predicted Maximum 1-hour mean Hg concentrations were below the relevant
EQS at all sensitive receptor locations.
As indicated in Table 39, the PC proportion of the EQS is less than 10% at all receptor locations. As such,
impacts on 1-hour mean Hg concentrations are considered to be insignificant in accordance with the EA
screening criteria.
A staged assessment methodology was utilised for the prediction of grouped metal concentrations as
outlined previously. Potential impacts on annual mean Cr (VI), As and Ni and 1-hour mean V
concentrations were assessed as these represent the lowest EQSs. The results are outlined below.
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Stage 1
Predicted concentrations with the full metal emission considered to consist of only one species, based on
results at the most significantly affected relevant receptor location, are summarised in Table 40.
Table 40 Predicted Metal Concentrations - Stage 1
Pollutant Averaging
Period EQS (ng/m3)
PC (ng/m3) PEC (ng/m3)
Predicted PC Proportion
of EQS (%)
Predicted
PEC
Proportion
of EQS (%)
As Annual 3 5.60 186.70 6.84 228.03
Cr (VI) Annual 0.2 5.60 2,800.47 6.34 3,172.47
Ni Annual 20 5.60 28.00 7.94 39.70
V 1-hour 1,000 508.38 50.84 510.64 51.06
As indicated in Table 40, the EA criteria were exceeded for predicted PCs for all considered metals. The
predicted annual mean Ni and the 1-hour mean V concentrations were below the relevant EQS at all
relevant sensitive receptor locations. It is considered unlikely that exceedences of the relevant EQS would
occur for Ni and V. As such, the second EA criteria is achieved and there was no requirement to proceed
to a Stage 2 Assessment for these species.
As and Cr (VI) were progressed to the Stage 2 Assessment.
Stage 2
Predicted concentrations with the metal emission distributed equally between all species are summarised
in Table 41.
Table 41 Predicted Metal Concentrations - Stage 2
Pollutant Averaging
Period EQS (ng/m3)
PC (ng/m3) PEC (ng/m3)
Predicted PC Proportion
of EQS (%)
Predicted
PEC
Proportion
of EQS (%)
As Annual 3 0.62 20.54 1.86 61.87
Cr (VI) Annual 0.2 0.62 308.05 1.36 680.05
As indicated in Table 41, the EA criteria were exceeded for predicted PCs of As and Cr (VI).
Due to the low PEC of As it is considered unlikely that exceedences of the relevant EQS would occur. As
such, the second EA criteria is achieved and there was no requirement to proceed to a Stage 3 Assessment
for this species.
Cr (VI) was progressed to a Stage 3 Assessment.
Stage 3
The third stage of the assessment was to consider site specific assumptions. The facility will incorporate a
flue gas treatment system to remove heavy metals from the exhaust gas stream before emission to
atmosphere. The flue gas treatment system will have to be Best Available Technique (BAT) for the sector
and as such will be similar to those in use at other UK incineration and gasification facilities. It is therefore
anticipated that the performance of the proposed flue gas treatment system will be as effective in
removing heavy metals as the same system employed at a typical facility.
An analysis of the metal content in air pollution control residues recorded over three years between 2008
and 2010 at the Wilton 10 Biomass Facility was undertaken in order to determine the likely proportion of
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 34
each species. This facility utilises similar materials to those proposed for the Daventry proposal and
therefore the data is considered suitable for an assessment of this nature. The results are summarised in
Table 42.
Table 42 Metal Data from the Wilton 10 Biomass Facility
Pollutant Measured Concentration as Proportion of ELV (%)
Minimum Mean Maximum
As 0.12 0.82 1.60
Cr 0.64 1.87 3.57
Co 0.08 0.25 0.53
Cu 0.43 2.88 5.02
Mn 6.08 15.93 28.34
Ni 0.83 3.63 7.10
Pb 1.40 10.65 19.15
Sb - - -
Sn - - -
V 0.05 0.10 0.18
Total metals 9.63 36.14 65.47
Note: Sb and Sn are not monitored in the air pollution control residues.
As shown in Table 42, Cr emissions, including a proportion of Cr (VI), contribute a maximum of 3.57% of
the ELV.
The EA guidance also provides data on the proportion of Cr (VI) in total Cr. This indicates the total Cr
emission consists of 0.32% of Cr (VI). Applying these data to the measured Cr proportion shown in Table 42
and the total metals ELV provides an emission rate for Cr (VI) of 5.73 x 10-5mg/m3 The predicted maximum
PC and PEC utilising this data is summarised in Table 43.
Table 43 Predicted Metal Concentrations - Stage 3
Pollutant Averaging
Period EQS (ng/m3)
PC (ng/m3) PEC (ng/m3)
Predicted PC Proportion
of EQS (%)
Predicted
PEC
Proportion
of EQS (%)
Cr (VI) Annual 0.2 0.0006 0.32 0.74 372.32
As indicated in Table 43, the predicted PC proportion of the EQS is significantly less than 1%. This therefore
complies with the EA criteria, although it is noted that the EQS is predicted to be exceeded, mainly due to
the high background value utilised within the assessment.
Chromium
Predicted annual mean Cr (VI) concentrations using the Stage 3 Assessment results are summarised in
Table 44. Figure 19 provides graphical representations of predicted concentrations throughout the
assessment area.
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Table 44 Predicted Annual Mean Cr (VI) Concentrations
Receptor Predicted Annual Mean Cr (VI)
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.0006 0.74 0.32 372.32
R2 Ashtree Farm 0.0001 0.74 0.06 372.06
R3 The Tollgate 0.0001 0.74 0.07 372.07
R4 Drayton Lodge 0.0001 0.74 0.04 372.04
R5 15 The Cherwell 0.0002 0.74 0.09 372.09
R6 12 The Leam 0.0002 0.74 0.12 372.12
R7 46 The Witham 0.0002 0.74 0.12 372.12
R8 1 Eden Close 0.0001 0.74 0.07 372.07
R9 Ford Centre Service Yard 0.0039 0.75 1.93 373.93
As indicated in Table 44, predicted annual mean Cr (VI) concentrations were above the relevant EQS at all
sensitive receptor locations. This is due to the background concentration of 0.74ng/m3, which exceeds the
EQS as a base condition.
As indicated in Table 44, the PC proportion of the EQS is less than 1% at all but one receptor location.
However, this receptor is representative of non-sensitive areas which would not be considered relevant
to the annual mean EQS. As such, it is not considered relevant to the assessment. Therefore, impacts on
annual mean Cr(VI) concentrations are considered to be insignificant in accordance with the EA screening
criteria
Arsenic
Predicted annual mean As concentrations using the Stage 2 Assessment results are summarised in
Table 45. Figure 20 provide graphical representations of predicted concentrations throughout the
assessment area.
Table 45 Predicted Annual Mean As Concentrations
Receptor Predicted Annual Mean As
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.62 1.86 20.54 61.87
R2 Ashtree Farm 0.12 1.36 3.94 45.27
R3 The Tollgate 0.13 1.37 4.41 45.74
R4 Drayton Lodge 0.08 1.32 2.61 43.94
R5 15 The Cherwell 0.17 1.41 5.62 46.95
R6 12 The Leam 0.22 1.46 7.40 48.74
R7 46 The Witham 0.24 1.48 7.94 49.27
R8 1 Eden Close 0.14 1.38 4.78 46.11
R9 Ford Centre Service Yard 3.71 4.95 123.72 165.05
As indicated in Table 45, the EA criteria for 'insignificant' impacts was not achieved for annual mean As
concentrations. However, the maximum PEC proportion of the EQS at receptor locations which are
considered relevant to the EQS was 61.87%. This provides significant headroom and it is therefore
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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considered unlikely that exceedences of the EQS for annual mean As would occur at relevant locations as
a result of emissions from the installation.
The modelling results indicated exceedences of the annual mean EQS for As at one location. However,
this receptor is representative of non-sensitive areas which would not be considered relevant to the
annual mean EQS. As such, it is not considered relevant to the assessment.
Nickel
Predicted annual mean Ni concentrations using the Stage 2 Assessment results are summarised in
Table 46. Figure 21 provides graphical representations of predicted concentrations throughout the
assessment area.
Table 46 Predicted Annual Mean Ni Concentrations
Receptor Predicted Annual Mean Ni
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.62 2.96 3.08 14.78
R2 Ashtree Farm 0.12 2.46 0.59 12.29
R3 The Tollgate 0.13 2.47 0.66 12.36
R4 Drayton Lodge 0.08 2.42 0.39 12.09
R5 15 The Cherwell 0.17 2.51 0.84 12.54
R6 12 The Leam 0.22 2.56 1.11 12.81
R7 46 The Witham 0.24 2.58 1.19 12.89
R8 1 Eden Close 0.14 2.48 0.72 12.42
R9 Ford Centre Service Yard 3.71 6.05 18.56 30.26
As indicated in Table 46, predicted annual mean Ni concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 46, the PC proportion of the EQS is above 1% at a number of receptors. However,
the PEC is significantly below the EQS at all locations. As such, the resultant impacts are not considered
to be significant.
Vanadium
Predicted maximum 1-hour mean V concentrations using the Stage 1 Assessment results are summarised
in Table 47. Figure 22 provides graphical representations of predicted concentrations throughout the
assessment area.
Table 47 Predicted Maximum 1-hour Mean V Concentrations
Receptor Predicted Maximum 1-hour
Mean V Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 153.04 155.30 15.30 15.53
R2 Ashtree Farm 22.86 25.12 2.29 2.51
R3 The Tollgate 28.84 31.10 2.88 3.11
R4 Drayton Lodge 31.94 34.20 3.19 3.42
R5 15 The Cherwell 36.80 39.06 3.68 3.91
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Receptor Predicted Maximum 1-hour
Mean V Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R6 12 The Leam 36.81 39.07 3.68 3.91
R7 46 The Witham 36.12 38.38 3.61 3.84
R8 1 Eden Close 35.39 37.65 3.54 3.77
R9 Ford Centre Service Yard 508.38 510.64 50.84 51.06
As indicated in Table 47, predicted maximum 1-hour mean V concentrations were below the relevant EQS
at all sensitive receptor locations.
As indicated in Table 47, the PC proportion of the EQS is above 10% at two receptors using the Stage 1
Assessment results. However, the PEC is significantly below the EQS at all locations. As such, the resultant
impacts are not considered to be significant.
Annual Mean
Predicted annual mean PCB concentrations are summarised in Table 48. Figure 23 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 48 Predicted Annual Mean PCB Concentrations
Receptor Predicted Annual Mean PCB
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.06 0.07 0.03 0.04
R2 Ashtree Farm 0.01 0.03 0.01 0.01
R3 The Tollgate 0.01 0.03 0.01 0.01
R4 Drayton Lodge 0.01 0.02 0.00 0.01
R5 15 The Cherwell 0.02 0.03 0.01 0.02
R6 12 The Leam 0.02 0.04 0.01 0.02
R7 46 The Witham 0.02 0.04 0.01 0.02
R8 1 Eden Close 0.01 0.03 0.01 0.01
R9 Ford Centre Service Yard 0.34 0.36 0.17 0.18
As indicated in Table 48, predicted annual mean PCB concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 48, the PC proportion of the EQS is significantly below the 1% at all receptor
locations. As such, impacts on annual mean PCB concentrations are considered to be insignificant in
accordance with the EA screening criteria.
1-hour Mean
Predicted Maximum 1-hour mean PCB concentrations are summarised in Table 49. Figure 24 provides
graphical representations of predicted concentrations throughout the assessment area.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 38
Table 49 Predicted Maximum 1-hour Mean PCB Concentrations
Receptor Predicted 1-hour Mean PCB
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 1.54 1.57 0.03 0.03
R2 Ashtree Farm 0.23 0.26 0.00 0.00
R3 The Tollgate 0.29 0.32 0.00 0.01
R4 Drayton Lodge 0.32 0.35 0.01 0.01
R5 15 The Cherwell 0.37 0.40 0.01 0.01
R6 12 The Leam 0.37 0.40 0.01 0.01
R7 46 The Witham 0.36 0.39 0.01 0.01
R8 1 Eden Close 0.36 0.39 0.01 0.01
R9 Ford Centre Service Yard 5.12 5.15 0.09 0.09
As indicated in Table 49, predicted Maximum 1-hour mean PCB concentrations were below the relevant
EQS at all sensitive receptor locations.
As indicated in Table 49, the PC proportion of the EQS is considerably below the 10% at all receptor
locations. As such, impacts on 1-hour mean PCB concentrations are considered to be insignificant in
accordance with the EA screening criteria.
Predicted annual mean BaP concentrations are summarised in Table 50. Figure 25 provides graphical
representations of predicted concentrations throughout the assessment area.
Table 50 Predicted Annual Mean BaP Concentrations
Receptor Predicted Annual Mean BaP
Concentration (ng/m3) Proportion of the EQS (%)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 0.0015 0.21 0.59 84.59
R2 Ashtree Farm 0.0003 0.21 0.11 84.11
R3 The Tollgate 0.0003 0.21 0.13 84.13
R4 Drayton Lodge 0.0002 0.21 0.08 84.08
R5 15 The Cherwell 0.0004 0.21 0.16 84.16
R6 12 The Leam 0.0005 0.21 0.21 84.21
R7 46 The Witham 0.0006 0.21 0.23 84.23
R8 1 Eden Close 0.0003 0.21 0.14 84.14
R9 Ford Centre Service Yard 0.0089 0.22 3.58 87.58
As indicated in Table 50, predicted annual mean BaP concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 50, the PC proportion of the EQS is less than 1% at all but one receptor locations.
However, at this location the PEC is considerably lower than the EQS. As such, impacts on annual mean
BaP concentrations are considered to be insignificant. Furthermore this is a non-sensitive area which
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 39
would not be considered relevant to the AQO, as outlined in Table 1. As such, they are not considered
relevant to the assessment..
Predicted PCDD/F concentrations are summarised in Table 51. Reference should be made to Figure 26
and Figure 27 for graphical representations of predicted concentrations throughout the assessment
extents. It should be noted that EQSs have not been designated for this pollutant species and
concentrations are reported for completeness only.
Table 51 Predicted PCDD/F Concentrations
Receptor Predicted Annual Mean PCDD/F
Concentration (fg/m3)
Predicted Maximum 1-hour Mean
PCDD/F Concentration (fg/m3)
ID Location PC PEC PC PEC
R1 Elderstubbs Farm 1.11 39.71 30.41 107.61
R2 Ashtree Farm 0.21 38.81 4.54 81.74
R3 The Tollgate 0.24 38.84 5.73 82.93
R4 Drayton Lodge 0.14 38.74 6.35 83.55
R5 15 The Cherwell 0.30 38.90 7.31 84.51
R6 12 The Leam 0.40 39.00 7.31 84.51
R7 46 The Witham 0.43 39.03 7.18 84.38
R8 1 Eden Close 0.26 38.86 7.03 84.23
R9 Ford Centre Service Yard 6.70 45.30 101.00 178.20
As indicated in Table 51, the maximum modelled annual mean process contribution for dioxins and furans
associated with the operation of the facility was 1.11fg/m3 and is not expected to significantly increase
the airborne concentration or deposition rate of dioxins and furans above that already experienced in the
area. The corresponding predicted maximum 1-hour mean dioxins and furans concentration is
30.41fg/m3.This means that assuming the maximum hourly PC throughout the whole day, an average
body mass of 70kg, a worst-case adult breathing rate12 of 20m3/day and assuming that all dioxins and
furans inhaled are absorbed by the individual (i.e. none are exhaled), the uptake of dioxins and furans via
inhalation is estimated to be 0.014% of the tolerable daily intake recommended by the Committee On
Toxicity Of Chemicals in Food, Consumer Products and the Environment (COT)13. The potential effects of
dioxins released by the proposed facility can therefore be considered insignificant.
12 Technical Support Document for Exposure Assessment and Stochastic Analysis, Office of Environmental Health Hazard
Assessment California Environmental Protection Agency, 2000. 13 Statement on the Tolerable Daily Intake for Dioxins and Dioxin-like Polychlorinated Biphenyls, COT, undated.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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Annual Mean
Predicted annual mean NOx concentrations at the ecological receptors are summarised in Table 52.
Reference should be made to Figure 28 for a graphical representation of predicted concentrations
throughout the assessment extents.
Table 52 Predicted Annual Mean NOx Concentrations
Receptor Predicted Annual Mean NOx
Concentration (µg/m3) Proportion of the EQS (%)
ID Designation PC PEC PC PEC
ER1 Elderstubbs Farm Pasture LWS 0.56 17.36 1.85 57.85
ER2 Elderstubbs Farm Pasture LWS 0.95 17.75 3.17 59.17
ER3 Elderstubbs Farm Pasture LWS 1.10 17.90 3.67 59.67
ER4 Oak Spinney (Daventry) LWS 0.16 16.96 0.52 56.52
ER5 Pond Spinney LWS 0.14 16.94 0.45 56.45
ER6 Staverton Clump LWS 0.28 17.08 0.95 56.95
ER7 Staverton Wood LWS 0.35 17.15 1.16 57.16
ER8 Staverton Wood LWS 0.26 17.06 0.88 56.88
ER9 Stepnell Spinney LWS 0.22 17.02 0.73 56.73
ER10 Stepnell Spinney LWS 0.20 17.00 0.66 56.66
As indicated in Table 52, predicted annual mean NOx concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 52, the PC proportion of the EQS is slightly above 1% at a number of receptors.
However, the PEC is less than the EQS at all locations. As such, impacts are not considered to be significant.
It should be noted that the assessment assumed that the facility would be emitting the maximum
permitted pollutant concentration at all times. As such, predicted concentrations are likely to be a
significant overestimation of actual impacts.
24-hour Mean
Predicted 24-hour mean NOx concentrations at the ecological receptors are summarised in Table 53.
Reference should be made to Figure 29 for a graphical representation of predicted concentrations
throughout the assessment extents.
Table 53 Predicted 24-hour Mean NOx Concentrations
Receptor Predicted 24-hour Mean NOx
Concentration (µg/m3) Proportion of the EQS (%)
ID Designation PC PEC PC PEC
ER1 Elderstubbs Farm Pasture LWS 11.79 45.39 15.72 60.52
ER2 Elderstubbs Farm Pasture LWS 11.36 44.96 15.14 59.94
ER3 Elderstubbs Farm Pasture LWS 15.73 49.33 20.98 65.78
ER4 Oak Spinney (Daventry) LWS 1.92 35.52 2.56 47.36
ER5 Pond Spinney LWS 2.21 35.81 2.94 47.74
ER6 Staverton Clump LWS 2.66 36.26 3.54 48.34
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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Receptor Predicted 24-hour Mean NOx
Concentration (µg/m3) Proportion of the EQS (%)
ID Designation PC PEC PC PEC
ER7 Staverton Wood LWS 3.40 37.00 4.53 49.33
ER8 Staverton Wood LWS 3.16 36.76 4.21 49.01
ER9 Stepnell Spinney LWS 2.67 36.27 3.56 48.36
ER10 Stepnell Spinney LWS 2.71 36.31 3.61 48.41
As indicated in Table 53, predicted 24-hour mean NOx concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 53, the PC proportion of the EQS is slightly above 10% at a number of receptors.
However, the PEC is less than the EQS at all locations. As such, impacts are not considered to be significant.
It should be noted that the assessment considered the facility emitting the maximum permitted pollutant
concentration at all times. As such, predicted concentrations are likely to be a significant overestimation
of actual impacts.
Predicted annual mean SO2 concentrations at the ecological receptors are summarised in Table 54.
Reference should be made to Figure 30 for a graphical representation of predicted concentrations
throughout the assessment extents.
Table 54 Predicted Annual Mean SO2 Concentrations
Receptor Predicted Annual Mean SO2
Concentration (µg/m3) Proportion of the EQS (%)
ID Designation PC PEC PC PEC
ER1 Elderstubbs Farm Pasture LWS 0.14 2.77 0.70 13.85
ER2 Elderstubbs Farm Pasture LWS 0.24 2.87 1.19 14.34
ER3 Elderstubbs Farm Pasture LWS 0.28 2.91 1.38 14.53
ER4 Oak Spinney (Daventry) LWS 0.04 2.67 0.20 13.35
ER5 Pond Spinney LWS 0.03 2.66 0.17 13.32
ER6 Staverton Clump LWS 0.07 2.70 0.35 13.50
ER7 Staverton Wood LWS 0.09 2.72 0.44 13.59
ER8 Staverton Wood LWS 0.07 2.70 0.33 13.48
ER9 Stepnell Spinney LWS 0.05 2.68 0.27 13.42
ER10 Stepnell Spinney LWS 0.05 2.68 0.25 13.40
As indicated in Table 54, predicted annual mean SO2 concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 54, the PC proportion of the EQS is slightly above 1% at two receptors. However, the
PEC is less than the EQS at all locations. As such, impacts are not considered to be significant. It should be
noted that the assessment assumed that the facility would be emitting the maximum permitted pollutant
concentration at all times. As such, predicted concentrations are likely to be a significant overestimation
of actual impacts.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 42
Predicted annual mean NH3 concentrations at the ecological receptors are summarised in Table 55.
Reference should be made to Figure 31 for a graphical representation of predicted concentrations
throughout the assessment extents.
Table 55 Predicted Annual Mean NH3 Concentrations
Receptor Predicted Annual Mean NH3
Concentration (µg/m3) Proportion of the EQS (%)
ID Designation PC PEC PC PEC
ER1 Elderstubbs Farm Pasture LWS 0.0015 1.04 0.05 34.72
ER2 Elderstubbs Farm Pasture LWS 0.0026 1.04 0.09 34.75
ER3 Elderstubbs Farm Pasture LWS 0.0030 1.04 0.10 34.77
ER4 Oak Spinney (Daventry) LWS 0.0004 1.04 0.01 34.68
ER5 Pond Spinney LWS 0.0004 1.04 0.01 34.68
ER6 Staverton Clump LWS 0.0008 1.04 0.03 34.69
ER7 Staverton Wood LWS 0.0009 1.04 0.03 34.70
ER8 Staverton Wood LWS 0.0007 1.04 0.02 34.69
ER9 Stepnell Spinney LWS 0.0006 1.04 0.02 34.69
ER10 Stepnell Spinney LWS 0.0005 1.04 0.02 34.68
As indicated in Table 55, predicted annual mean NH3 concentrations were below the relevant EQS at all
sensitive receptor locations.
As indicated in Table 55, the PC proportion of the EQS is less than 1% at all receptor locations. As such,
impacts on annual mean NH3 concentrations are considered to be insignificant in accordance with the EA
screening criteria.
Predicted annual mean nitrogen deposition rates are summarised in Table 56. Reference should be made
to Figure 32 for a graphical representation of predicted concentrations throughout the assessment
extents.
Table 56 Predicted Annual Mean Nitrogen Deposition Rates
Receptor Predicted Annual Mean Nitrogen
Deposition Concentration (kg N/ha/yr)
Proportion of the EQS (%)
Low EQS High EQS
ID PC PEC PC PEC PC PEC
ER1 0.09 19.27 0.44 96.34 0.29 64.23
ER2 0.15 19.33 0.75 96.65 0.50 64.43
ER3 0.17 19.35 0.87 96.77 0.58 64.51
ER4 0.02 33.20 0.25 332.05 0.12 166.02
ER5 0.02 33.20 0.22 332.02 0.11 166.01
ER6 0.04 33.50 0.45 335.05 0.22 167.52
ER7 0.06 33.24 0.55 332.35 0.28 166.18
ER8 0.04 33.22 0.42 332.22 0.21 166.11
ER9 0.03 33.21 0.34 332.14 0.17 166.07
ER10 0.03 33.21 0.31 332.11 0.16 166.06
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 43
As indicated in Table 56, predicted annual mean nitrogen deposition rates were above the relevant EQS
at a number of sensitive receptor locations. This is due to the high background deposition rates, which
exceed the EQSs as a base condition.
As indicated in Table 56, the PC proportion of the EQS is less than 1% at all receptor locations. As such,
impacts on annual mean nitrogen deposition rates are considered to be insignificant in accordance with
the EA screening criteria.
Hydrogen Chloride Deposition
Wet and dry HCl deposition rates were predicted. The results are shown in Table 57. These are the
maximum values predicted for any of the five meteorological data sets modelled.
Table 57 Predicted HCl Deposition Rates
Receptor Predicted HCl Deposition Rates (keq/ha/yr)
ID Designation Wet Dry
ER1 Elderstubbs Farm Pasture LWS 0.0000 0.0012
ER2 Elderstubbs Farm Pasture LWS 0.0000 0.0012
ER3 Elderstubbs Farm Pasture LWS 0.0000 0.0012
ER4 Oak Spinney (Daventry) LWS 0.0000 0.0003
ER5 Pond Spinney LWS 0.0000 0.0003
ER6 Staverton Clump LWS 0.0000 0.0003
ER7 Staverton Wood LWS 0.0000 0.0004
ER8 Staverton Wood LWS 0.0000 0.0003
ER9 Stepnell Spinney LWS 0.0000 0.0003
ER10 Stepnell Spinney LWS 0.0000 0.0004
Total Acid Deposition
Total acid deposition rates were predicted. The results are shown in Table 58. These include contributions
from NO2, NH3, SO2 and the maximum of wet or dry HCl.
Table 58 Predicted Annual Mean Acid Deposition Rates
Receptor Predicted Annual Mean Acid Deposition Rate (keq/ha/yr) Proportion of the EQS (%)*
ID S N HCl PC PEC
ER1 0.0164 0.0046 0.0012 0.4 37.3
ER2 0.0281 0.0078 0.0012 0.8 37.7
ER3 0.0325 0.0090 0.0012 0.8 37.7
ER4 0.0046 0.0013 0.0003 0.3 92.5
ER5 0.0040 0.0011 0.0003 0.3 92.5
ER6 0.0084 0.0023 0.0003 0.9 231.9
ER7 0.0103 0.0029 0.0004 0.3 92.5
ER8 0.0078 0.0022 0.0003 0.3 92.5
ER9 0.0065 0.0018 0.0003 0.3 92.5
ER10 0.0058 0.0016 0.0004 0.3 92.5
Note: * Based on the Critical Load Function Tool of the APIS Website3
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 44
As indicated in Table 58, predicted annual mean acid deposition rates were below the relevant EQS at all
but one sensitive receptor locations. This is due to the high background deposition rates, which exceed
the EQSs as a base condition.
As indicated in Table 58, the PC proportion of the EQS is less than 1% at all receptor locations. As such,
impacts on annual mean acid deposition rates are considered to be insignificant in accordance with the
EA screening criteria.
Weekly Mean
Predicted maximum weekly mean HF concentrations are summarised in Table 59. Reference should be
made to Figure 33 for a graphical representation of predicted concentrations throughout the assessment
extents.
Table 59 Predicted Maximum Weekly Mean HF Concentrations
Receptor Predicted Maximum Weekly Mean
HF Concentration (µg/m3) Proportion of the EQS (%)
ID Designation PC PEC PC PEC
ER1 Elderstubbs Farm Pasture LWS 0.02 4.72 3.64 943.64
ER2 Elderstubbs Farm Pasture LWS 0.03 4.73 5.74 945.74
ER3 Elderstubbs Farm Pasture LWS 0.04 4.74 7.40 947.40
ER4 Oak Spinney (Daventry) LWS 0.00 4.70 0.87 940.87
ER5 Pond Spinney LWS 0.00 4.70 0.93 940.93
ER6 Staverton Clump LWS 0.01 4.71 1.22 941.22
ER7 Staverton Wood LWS 0.01 4.71 1.49 941.49
ER8 Staverton Wood LWS 0.01 4.71 1.24 941.24
ER9 Stepnell Spinney LWS 0.00 4.70 0.95 940.95
ER10 Stepnell Spinney LWS 0.01 4.71 1.12 941.12
As indicated in Table 59, predicted maximum weekly mean HF concentrations were above the relevant
EQS at all sensitive receptor locations. This is due to the background concentration of 4.70µg/m3, which
exceeds the EQS as a base condition.
As indicated in Table 59, the PC proportion of the EQS is less than 10% at all receptor locations. As such,
impacts on weekly mean HF concentrations are considered to be insignificant in accordance with the EA
screening criteria.
24-hour Mean
Predicted maximum 24-hour mean HF concentrations are summarised in Table 60. Reference should be
made to Figure 34 for a graphical representation of predicted concentrations throughout the assessment
extents.
Table 60 Predicted Maximum 24-hour Mean HF Concentrations
Receptor Predicted Maximum 24-hour Mean
HF Concentration (µg/m3) Proportion of the EQS (%)
ID Designation PC PEC PC PEC
ER1 Elderstubbs Farm Pasture LWS 0.06 4.76 1.18 95.18
ER2 Elderstubbs Farm Pasture LWS 0.06 4.76 1.14 95.14
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 45
Receptor Predicted Maximum 24-hour Mean
HF Concentration (µg/m3) Proportion of the EQS (%)
ID Designation PC PEC PC PEC
ER3 Elderstubbs Farm Pasture LWS 0.08 4.78 1.57 95.57
ER4 Oak Spinney (Daventry) LWS 0.01 4.71 0.19 94.19
ER5 Pond Spinney LWS 0.01 4.71 0.22 94.22
ER6 Staverton Clump LWS 0.01 4.71 0.27 94.27
ER7 Staverton Wood LWS 0.02 4.72 0.34 94.34
ER8 Staverton Wood LWS 0.02 4.72 0.32 94.32
ER9 Stepnell Spinney LWS 0.01 4.71 0.27 94.27
ER10 Stepnell Spinney LWS 0.01 4.71 0.27 94.27
As indicated in Table 60, predicted maximum 24-hour mean HF concentrations were below the relevant
EQS at all sensitive receptor locations.
As indicated in Table 60, the PC proportion of the EQS is less than 10% at all receptor locations. As such,
impacts on 24-hour mean HF concentrations are considered to be insignificant in accordance with the EA
screening criteria.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 46
ADAS UK Ltd was commissioned by Pedigree Power to undertake an Air Quality Assessment for a proposed
Biomass and Wastewater Treatment Plant on land off Browns Road, Daventry.
The plant will comprise a combustion plant, two screw expanders (up to 1.0MWe of renewable electricity
generation) and four evaporator waste water treatment units.
Following further process design a number of exhaust gas parameters were revised from the values used
in the initial assessment. The ADMS 5 dispersion modelling was therefore updated to take account of the
amended data. Impacts at both human and ecological receptors were quantified and the results compared
with the relevant EQS.
Impacts on existing pollutant concentrations were not predicted to be significant at any location within
the assessment extents in accordance with the EA criteria.
Nitrogen and acid gas deposition rates were also predicted at the relevant ecological sites. Results
indicated that emissions from the installation would not significantly affect existing conditions at any
designation.
Impacts were predicted based on a worst-case assessment scenario of the facility constantly emitting the
maximum permitted concentration of each pollutant throughout an entire year. As such, predicted
concentrations and deposition rates are likely to overestimate actual impacts.
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 47
1 The Air Quality Strategy for England, Scotland, Wales and Northern Ireland, DEFRA, 2007
2 Horizontal Guidance Note H1 - Annex (f), Environment Agency, 2010
3 UK Air Pollution Information System, www.apis.ac.uk
4 2013 Air Quality Progress Report for Daventry District Council, DDC, 2014
5 http://uk-air.defra.gov.uk/data/laqm-background-maps?year=2011
6 Multi-Agency Geographic Information for the Countryside, www.magic.gov.uk
7 Conversion Ratios for NOx and NO2, Environment Agency, undated
8 Releases from municipal waste incinerators - Guidance to applicants on impact assessment for
group 3 metals stack, EA, 2012
9 Local Air Quality Management Technical Guidance LAQM.TG(09), DEFRA, 2009
10 Technical Guidance on Detailed Modelling approach for an Appropriate Assessment for
Emissions to Air AQTAG 06, EA, 2006
11 ADMS 5 Atmospheric Dispersion Modelling System User Guide Version 5.1, CERC, 2015
12 Technical Support Document for Exposure Assessment and Stochastic Analysis, Office of
Environmental Health Hazard Assessment California Environmental Protection Agency, 2000.
13 Statement on the Tolerable Daily Intake for Dioxins and Dioxin-like Polychlorinated Biphenyls,
Committee On Toxicity Of Chemicals in Food, Consumer Products and the Environment, undated
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 48
ADM Atmospheric Dispersion Modelling APIS Air Pollution Information System AQLV Air Quality Limit Value AQMA Air Quality Management Area AQO Air Quality Objective AQS Air Quality Strategy As Arsenic BaP Benzo-a-pyrene BAT Best Available Technique C6H6 Benzene Cd Cadmium CERC Cambridge Environmental Research Consultants CO Carbon monoxide Cr Chromium Cu Copper DEFRA Department for Environment, Food and Rural Affairs DDC Daventry District Council EA Environment Agency EAL Environmental Assessment Level ELV Emission Limit Value EQS Environmental Quality Standard EU European Union HCl Hydrogen chloride HF Hydrogen fluoride Hg Mercury IED Industrial Emissions Directive LA Local Authority LAQM Local Air Quality Management LNR Local Nature Reserves LWS Local Wildlife Site MAGIC Multi-Agency Geographic Information for the Countryside Mn Manganese NGR National Grid Reference NH3 Ammonia Ni Nickel NNR National Nature Reserves NO Nitrogen oxide NO2 Nitrogen dioxide NOx Oxides of nitrogen PAH Polycyclic aromatic hydrocarbon Pb Lead PC Process contribution PCB Polychlorinated biphenyl PCDD Polychlorinated dibenzodioxins PCDF Polychlorinated dibenzofurans PEC Predicted environmental concentration PM Particulate matter PM10 Particulate matter with an aerodynamic diameter of less than 10μm PM2.5 Particulate matter with an aerodynamic diameter of less than 2.5μm SAC Special Area of Conservation Sb Antimony
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
© ADAS 49
SINC Sites of Interest for Nature Conservation SLINC Sites of Local Interest for Nature Conservation SO2 Sulphur dioxide SPA Special Protection Area SSSI Site of Special Scientific Interest TEQ Toxic Equivalents TOC Total organic carbon TOMPS Toxic Organic Micro Pollutants UKEAP UK Eutrophying and Acidifying Pollutants V Vanadium VOC Volatile Organic Compound WID Waste Incineration Directive z0 Roughness length
Proposed Biomass and Waste Water Treatment Plant - Browns Road, Daventry Air Quality Assessment
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