environmental permit variation west newton a wellsite€¦ · rathlin energy (uk) limited west...

Title Name Signature

Prepared By HSE & Permit Advisor Sean Smart

Reviewed By HSE and Planning Manager Jonathan Foster

Approved By Country Manager Tom Selkirk

COPYRIGHT

© 2018 Rathlin Energy (UK) Limited. All Rights Reserved.

The contents of this document may not be reproduced or copied without the express written

permission of Rathlin Energy (UK) Limited.

Gas Management Plan

Environmental Permit

Variation

West Newton A

Wellsite

East Riding of Yorkshire

PEDL 183

December 2018

www.rathlin-energy.co.uk

Rathlin Energy (UK) Limited West Newton A Permit Variation

RE-EPRA-WNA-GMP-010 of 40

APPROVAL LIST

Title Name Signature

Prepared By HSE & Permit Advisor Sean Smart

Reviewed By HSE and Planning Manager Jonathan Foster

Approved By Country Manager Tom Selkirk

COPYRIGHT

© 2018 Rathlin Energy (UK) Limited. All Rights Reserved.

The contents of this document may not be reproduced or copied without the express written

permission of Rathlin Energy (UK) Limited.



Table of Contents

1. Introduction ..................................................................................................................... 5

2. Scope ............................................................................................................................... 6

3. Definitions ....................................................................................................................... 7

4. Roles and Responsibilities ................................................................................................ 9

5. Applicable Legislation and Industry Guidance ................................................................. 11

5.1 Environmental Permitting (England and Wales) Regulations 2016 ......................................... 11

5.1.1 Mining Waste Activity .............................................................................................................. 11

5.1.2 Industrial Emissions Activity ..................................................................................................... 11

5.2 Onshore Oil & Gas Sector Guidance August 2016 ................................................................... 12

5.3 Industry Recommended Practices ........................................................................................... 13

5.3.1 API RP 521 Pressure-Relieving and Depressuring Systems ...................................................... 13

5.3.2 API 537 Flare Details for General Refinery and Petrochemical Service ................................... 13

5.3.3 BS 5908-1:2012 ........................................................................................................................ 13

5.3.4 BS 5908-2:2012 ........................................................................................................................ 13

6. Gas Management Plan ................................................................................................... 14

6.1 Objectives of the Gas Management Plan ................................................................................. 14

6.2 Distribution of the Gas Management Plan .............................................................................. 14

6.3 Alterations to the Gas Management Plan ................................................................................ 14

6.4 Changes to Operations, Processes or Equipment .................................................................... 14

7. Overview of the Development ........................................................................................ 15

7.1 West Newton A Wellsite .......................................................................................................... 15

7.2 Site Location ............................................................................................................................. 15

8. Identification of Waste Gas Streams ............................................................................... 16

9. Best Available Technique................................................................................................ 17

9.1 Definition of BAT ...................................................................................................................... 17

9.2 BAT Assessment for Waste Gas from Hydrocarbon Exploration ............................................. 17

10. Best Available Technique Assessment for Well Testing Operations .................................. 19

10.1 BAT Assessment ....................................................................................................................... 19

10.1.1 Enclosed Ground Flare ............................................................................................................. 19

10.1.2 Shrouded Ground Flare ............................................................................................................ 20

10.1.3 Elevated Pipe Flare ................................................................................................................... 20

10.2 BAT Conclusion for Well Testing Operations ........................................................................... 21

11. Management of Gas - Well Testing Operations ............................................................... 22

11.1 Gas Composition ...................................................................................................................... 23



11.2 Well Clean Up Operations ........................................................................................................ 24

11.2.1 PW Well Test Shrouded Ground Flare ..................................................................................... 24

11.3 Extended Well Testing ............................................................................................................. 25

11.3.1 AEREON CEB4500 ..................................................................................................................... 26

12. Management of Vapour Recovery .................................................................................. 28

12.1 Recovery of VOCs from Oil Storage Tanks ............................................................................... 28

12.2 Recovery of VOCs from Road Tankers ..................................................................................... 28

12.3 Containment of Emissions ....................................................................................................... 28

12.4 Maintenance and Servicing Procedures ................................................................................... 29

12.5 Implementation of Pollution Control Measures ...................................................................... 29

12.6 Arrangements for Monitoring and Recording .......................................................................... 29

13. Environmental Management and Monitoring ................................................................. 30

13.1 Odour ....................................................................................................................................... 30

13.2 Air Monitoring .......................................................................................................................... 30

13.3 Emissions Calculation ............................................................................................................... 30

14. Emergency Response Procedures .................................................................................... 31

14.1 Spillages .................................................................................................................................... 31

14.2 Well Shut In .............................................................................................................................. 31

Appendix 1 – Indicative Site Layout Plan ..................................................................................... 33

Appendix 2 – Air Quality Impact Assessment .............................................................................. 35

Appendix 3 – PW Flare Design .................................................................................................... 37

Appendix 4 – CEB4500 Design ..................................................................................................... 39



1. INTRODUCTION

Rathlin Energy (UK) Limited (Rathlin) is a private company with its head office in Beverley, East Riding

of Yorkshire. Rathlin is a petroleum exploration, development and production company with

operations in the United Kingdom. Rathlin is the operator of PEDL183.

The purpose of this document is to outline the gas management arrangements to be implemented at

the West Newton A wellsite and demonstrate how Rathlin will manage waste gases associated within

its operations.



2. SCOPE

This Gas Management Plan is applicable to the West Newton A wellsite in accordance with

environmental permits and planning consent.

It is applicable to Rathlin, its contractors and subcontractors and can be used in support of applications

to the Environment Agency under the Environmental Permitting (England and Wales) Regulations

2016 (EPR2016).



3. DEFINITIONS

⁰: Degrees

ALARP: As Low as Reasonably Practicable

API: American Petroleum Institute

BAT: Best Available Technique

BS: British Standard

Casing: Steel tubes lining the wall of the borehole

Cold Venting: The release of unburned gas to atmosphere

Combustion: A burning process (see also incineration)

DST: Drill Stem Test

Emissions: Released into the environment

ESD: Emergency Shut Down

Extractive Waste: Waste resulting from the prospecting, extraction, treatment and storage of

mineral resources and the working of quarries

EWT: Extended Well Test

Flash-Back: Combustion within the gas supply pipe (pipe outlets)

Flowrate: The rate at which fluid passes through per unit of time

GOR: Gas to Oil Ratio

GWP: Global Warming Potential

Hazardous Waste: As defined by Article 3(2), 7 and Annex III of the Waste Framework Directive

Hierarchy: In order of priority

Hydrocarbons: Any class of compounds containing only hydrogen and carbon

Inch: Equivalent to 2.54cm

Incineration: The destruction of waste by controlled burning at high temperatures

Installation: A stationary technical unit where one or more activities are carried on; and

any other location on the same site where any other directly associated

activities are carried on

mmscf: Million standard cubic feet

mmscfd: Million standard cubic feet per day

PEDL: Petroleum Exploration and Development Licence.

Petroleum: A complex mixture of naturally occurring hydrocarbon compounds found in

rock and takes the form of a solid, liquid or gas

Pipework: A system of pipes used for transporting natural gas, oil and any other

produced fluids to their respective storage vessels onsite



Produced Fluids: Any fluid produced from a wellbore, a typical example being oil, condensate

or formation water

PVT: Pressure, Volume, Temperature

Reservoir: The rock within which hydrocarbons are encountered and confined to

Sour Gas: Natural gas with a hydrogen sulphide content of 4ppm or above

Thermocouple: A sensor used to measure temperature

Turbulence: Violent or unsteady movement of air

Turndown Rate: The ration of the maximum capacity to minimum capacity

UK: United Kingdom

Waste: Any substance or material that has or no longer has a purpose and, therefore,

must be discarded

Well Control: Equipment and procedures used to prevent or direct the flow of formation

fluids

Wellhead: The system of spools, valves and assorted adapters, which is the interface

between the wellbore and surface equipment

WNA-1: West Newton A, Well 1

WNA-2: West Newton A, Well 2



4. ROLES AND RESPONSIBILITIES

Role Key Responsibilities

Chairman of the Board

The Chairman of the Board is overall responsible for all Rathlin business activities and has to ensure that suitable and sufficient systems, processes and resources are provided to adhere to the HSE Management System, legislative and regulative requirements in relation to this plan.

The Chairman of the Board shall:

Apply HSE Management System standards and procedures throughout the project;

Provide suitable and sufficient input and resources required to maintain an effective HSE Management System;

Stipulates project requirements and conditions, e.g. budget, time constraints, milestones and feedback; and

Ensure that a proactive and robust system is in place for gas management during well testing operations, production operations, associated workover operations and well abandonment operations.

Country Manager

The Country Manager is responsible for:

The communication and implementation of the Gas Management Plan;

The communication of the Environmental Management System structure and responsibilities to the Wellsite Supervisor;

Providing assistance and guidance in the update and approval of the Gas Management Plan;

Ensuring that legislative compliance is maintained through the provision of adequate competent resources;

Ensuring that competent personnel are available to implement, monitor and assess the requirements of the Gas Management Plan;

Ensuring that roles and responsibilities are identified and the assessment of individuals is recorded;

Selecting contractors who can meet Rathlin’s HSE standards through a robust tendering and/or selection process and the monitoring of contractors to ensure that these standards are being met;

Identify training requirements and where required, provide training for those involved in the identification of leaks and the repair of those leaks;

The development and training of staff or assessing the competence of contractors so that they are competent and capable of carrying out their work to the required standards;

Ensuring that emergency response procedures are developed, maintained, communicated and tested for effectiveness; and

Conducting periodic audits of compliance and communicating environmental performance, significant findings and non-conformances.



Role Key Responsibilities

Wellsite Supervisor

The Wellsite Supervisor is responsible for:

Ensuring that leadership is clearly established and promoting a high degree of HSE awareness through communication of HSE Policies and responsibilities;

Ensuring that defined practices and processes are communicated;

Ensuring that, where required, monitoring and reporting relating to regulatory compliance is carried out;

Ensuring that leaks and fugitive emissions are reported and investigated in accordance with Rathlin’s HSE policies;

Ensuring that where required, emissions are sampled to determine source and composition of the emission;

Ensuring that all incidents, involving, or having the potential to cause, injury or harm to personnel, damage to infrastructure or the environment are thoroughly investigated;

Ensuring that emergency response plans are tested on a regular basis, recording the results, identifying, implementing and communicating corrective actions; and

Ensuring that complaints are reported to Rathlin and thoroughly investigated.

All personnel

All personnel are to follow the requirements of this Gas Management Plan and cooperate fully with senior management.

All personnel must take reasonable care to ensure that their actions do not have an adverse impact on the environment. Personnel must not intentionally or recklessly interfere with, or misuse anything that is provided in the interest of health, safety and the environment.



5. APPLICABLE LEGISLATION AND INDUSTRY GUIDANCE

Activities associated with the flaring of hydrocarbons onshore UK fall to be considered within the

scope of a number of environmental legislation. A review of the use of flares against environmental

legislation has identified the following legislation as being applicable.

5.1 Environmental Permitting (England and Wales) Regulations 2016

Activities involving the flaring of natural gas during onshore oil and gas operations will require an

environmental permit under EPR2016. There are two (2) environmental permits currently applicable

to flaring of natural gas activities, these are:

A Mining Waste Activity permit, covering the management of extractive waste; and

An Industrial Emissions Activity permit, covering the incineration of hazardous waste in a plant

with a capacity greater than 10 tonnes per day.

5.1.1 Mining Waste Activity

Schedule 20 of EPR2016 transposes the requirements of The Mining Waste Directive 2006/21/EC,

which requires that extractive wastes are managed in such a way that it minimises harm to human

health and the impact on the environment. It applies to the management of waste resulting from the

prospecting, extracting, treatment and storage of mineral resources and working quarries, which the

Mining Waste Directive refers to as extractive waste. The waste can take the form of a solid, liquid or

gas.

Schedule 20 of EPR2016 defines a mining waste operation as being the management of extractive

waste, whether or not it involves a waste facility. Under EPR2016, an environmental permit is required

to authorise a mining waste operation. For clarity, the extractive waste associated with flaring

activities includes the flaring of natural gas not exceeding 10 tonnes per day as a mining waste activity.

5.1.2 Industrial Emissions Activity

The Industrial Emissions Directive 2010/75/EU lays down rules on integrated prevention of pollution

arising from industrial activities, whilst also laying down rules designed to prevent or, where that is

not practicable, to reduce emissions into the air, water and land and to prevent the generation of

waste, in order to achieve a high level of protection of the environment taken as a whole.

EPR2016 transposes the requirements of the Industrial Emissions Directive namely Schedule 1, Part 2

which details a number of activities that are classified as an Industrial Emissions activity, this includes

Chapter 5 – Waste Management, Section 5.1 Incineration and Co-Incineration of Waste. EPR2016

requires an environmental permit to authorise an installation operation for the incineration and co-

incineration of waste specifically:

Part A(1)

(a) The incineration of hazardous waste in a waste incineration plant or waste co-incineration

plant with a capacity exceeding 10 tonnes per day;

(b) The incineration of non-hazardous waste in a waste incineration plant or waste co-

incineration plant with a capacity exceeding 3 tonnes per hour; and

(c) The incineration, other than incidentally in the course of burning landfill gas or solid or

liquid waste, of any gaseous compound containing halogens.



5.2 Onshore Oil & Gas Sector Guidance August 2016

In August 2016, the Environment Agency published its sector guidance. The document provides

guidance on permitting requirements specific to onshore oil and gas activities, including the

management of extractive wastes and the operating of an installation.

Relevant to this Gas Management Plan, the sector guidance makes specific reference to Flaring

Systems and states under Types of flaring system that ‘At present there is no published and commonly

accepted Best Available Technique for flaring systems at onshore oil and gas operations, such as a BAT

Reference document. In the absence of this, and taking a precautionary approach, we consider

enclosed flares to generally provide the best environmental performance for incinerating waste gases.

An enclosed flare is usually characterised by the following features:

the burners are housed in a thermally insulated enclosure

the burners are designed to operate within an enclosure

there is a mechanism to control combustion air feed rate to optimize combustion

However, we will consider other types of flaring systems, including shrouded flares (NB. it is not

sufficient to retrofit a shroud around the flame of an open flare) or elevated pipe flares (for sour gas

and safety flares only). Where an alternative system is proposed, the operator will need to demonstrate

that an enclosed flare is not suitable for their operation and there will not be a worse environmental

impact as a consequence of applying the alternative techniques.

The Environment Agency will assess alternative flare types and designs on a case by case basis.’

With respect to Design of a flaring system the sector guidance states ‘For all flaring applications you

must consider the following in the design of flare systems and describe it in your permit application or

pre-application submission:

waste gas flow rate: the flare must be designed to operate efficiently across the range of

expected waste gas flow rates. Flares have a poor turndown efficiency, which means a large

flare is insufficient when operated a low flow. For a wide flow range you may need to install 2

flares, for high and low flow; or install a multiple burner flare, where the burners can be

operated independently

stack height: to ensure adequate dispersion of the exhaust gases

noise and vibration: especially for flares with a high flow rate

light

smoke: there must be no visible smoke from the flare, if smoking is likely a smoke suppression

system should be included

duration

management of sour gas and odour control

If your proposed flare is not an enclosed flare, you must provide a through justification, which includes

the applicability limitations that make an enclosed flare unsuitable and supporting evidence to

demonstrate that the environmental performance of your proposed technique will be equivalent to

that of an enclosed flare.

To demonstrate equivalence, you must ensure that:

there is adequate phase separation



the shrouded flare is big enough for the gas flow expected and that if it turns out not to be

then the gas flow can and will be choked back

equally that a support gas will be provided to avoid the flare going out due to low flow

the shroud is sufficiently high to give adequate dispersion and an assessment of the flame

length has been made to prevent the flame impinging or escaping from the enclosure

a noise impact assessment has been done on the design proposed across the gas flow range

expected

If this is not possible you should propose additional mitigation measures to minimise the environmental

impact of the operation. The Environment Agency may incorporate additional requirements or

restrictions into your permit, if it considers that the technique selected does not provide equivalent

environmental performance. An example of this could be limiting the duration of flaring or limiting the

cumulative volumes of gas which can be flared.’

5.3 Industry Recommended Practices

Relevant to the determination of BAT is having regard to other industry guidance and practices, such

as health and safety. A determining factor of BAT is whether the technique is available and, in the

context of other industry guidance and practices, available can also refer to whether or not it is

‘allowable for use’.

The following section sets out the industry guidance and/or recommended practices that are relevant

to the incineration of waste gases by flare and what constraints they pose in the context of BAT

assessment.

5.3.1 API RP 521 Pressure-Relieving and Depressuring Systems

This standard is applicable to pressure-relieving and vapour depressuring systems. Although intended

for use primarily in oil refineries, it is also applicable to petrochemical facilities, gas plants, liquefied

natural gas (LNG) facilities, and oil and gas production facilities. The information provided is designed

to aid in the selection of the system that is most appropriate for the risks and circumstances involved

in various installations.

5.3.2 API 537 Flare Details for General Refinery and Petrochemical Service

This standard specifies the requirements and provides guidance for the selection, design,

specification, operation and maintenance of flares and related combustion and mechanical

components used in pressure-relieving and vapour-depressurising systems for petroleum,

petrochemical and natural gas industries.

Although this international standard is intended for new flares and related equipment, it is also

possible to use it and evaluate existing flare facilities.

5.3.3 BS 5908-1:2012

This British Standard provides recommendations and guidance for the control of fire and explosion

risks on sites at which chemicals are stored or processed in significant quantities.

5.3.4 BS 5908-2:2012

BS 5908-2:2012 offers guidance on the legislation and standards applicable to onshore industrial

premises that handle significant quantities of flammable gases, liquids or dusts.



6. GAS MANAGEMENT PLAN

6.1 Objectives of the Gas Management Plan

The objective of this Gas Management Plan is to ensure that any waste gas that arises as part of the

West Newton A operations is managed in such a way so as to reduce the quantities of gas emitted to

air and minimise environmental impacts so far as available techniques allow.

This objective will be achieved by:

Identifying Waste Gas Streams;

Establishing Best Available Techniques (BAT) to manage identified Waste Gas Streams;

Implement a programme of Management based on BAT;

Implementing Monitoring and Recording Schemes; and

Reviewing the Gas Management Plan and revise where necessary.

6.2 Distribution of the Gas Management Plan

Rathlin will communicate the Gas Management Plan to the Wellsite Supervisor, stored within his office

and be made available for review by regulatory bodies. It will be issued as an electronic version or

paper copy with a copy of the receipt or transmittal recorded by Rathlin.

The Gas Management Plan will be communicated to site personnel during site induction and a record

of induction will be recorded. A copy of the Gas Management Plan will be displayed and made

available on site to all personnel during operations.

6.3 Alterations to the Gas Management Plan

Any required changes or deviations from this Gas Management Plan are to be referred to Rathlin or

to the Wellsite Supervisor in the first instance. No changes to, or deviations from, this Gas

Management Plan are to be implemented until the required changes or deviations have been

reviewed and approved by Rathlin. Alterations to the plan will be submitted to the Environment

Agency for approval; however, alterations may be implemented as an immediate control measure to

resolve an identified problem prior to notification to the Environment Agency.

6.4 Changes to Operations, Processes or Equipment

In the event that there are significant or material changes to operations, processes or equipment

during the West Newton A exploratory operations, Rathlin will review the Gas Management Plan.

Rathlin will communicate a copy of any revised Gas Management Plan to the Wellsite Supervisor and

forward a copy to the Environment Agency.



7. OVERVIEW OF THE DEVELOPMENT

7.1 West Newton A Wellsite

The West Newton wellsite was constructed in second quarter 2013 in preparation for the undertaking

of exploratory operations.

The site was constructed by means of removing the topsoil and storing it on the eastern and southern

boundary of the site. The subsoil was then cut to fill creating a level plateau. A perimeter ditch was

then excavated around the perimeter of the site to aid environmental containment. A 1mm fully

welded HDPE membrane was then laid across the site and perimeter containment ditches, protected

above and below by a layer of non-needle punch geotextile. Above the impermeable membrane and

geotextile was laid geogrid overlaid by a 300mm layer of MOT Type 1 stone.

A single exploratory borehole, West Newton A-1 well (WNA-1) was drilled from the wellsite in 2013.

The West Newton A wellsite was then the subject of an environmental permit application to enable

Rathlin to continue to undertake exploratory operations at the wellsite. The environmental permit

(EPR/BB3001FT) was subsequently issued in April 2014 which permitted the undertaking of well

testing operations at the wellsite and the drilling of a second borehole, subsequently named West

Newton A-2 well (WNA-2).

WNA-2 is to be drilled in accordance with the existing environmental permit and as such this Gas

Management Plan is relevant to the well testing of the WNA-2 well and will be the principle document

for the management of waste gases at the West Newton wellsite following approval from the

Environment Agency in the form of a varied environmental permit.

7.2 Site Location

The proposed West Newton exploratory operations are being undertaken at the following location:

West Newton A Wellsite

Rathlin Energy (UK) Limited

Fosham Road

Marton

Hull

HU11 5DA

National Grid Ref: TA 19268 39131

Site Area: 0.975 hectares

A Site Location Plan has been provided within Site Plans Document (RE-EPRA-WNA-SP-004).

A Site Layout Plan has been provided within Appendix 1.



8. IDENTIFICATION OF WASTE GAS STREAMS

An assessment of the activities to be undertaken during the proposed well testing operations has been

undertaken to identify potential activities that may give rise to waste gas streams and is summarised

in Table 8.1 below.

Activity Process Equipment Emission Point EWC Total Quantity1

Well Clean Up Flaring Shrouded Flare Flare Tip 16 05 04* 20mmscf 351 Tonnes

Extended Well Test2

Flaring Enclosed Flare Flare Tip 16 05 04* 180mmscf 3160 Tonnes

Oil Storage & Transfer

Oil Storage / Transfer

Storage Tanks Single Vent Point

- Residual Volumes

Table 8.1: Identification of Waste Gas Streams

1 Tonnes derived conversion conditions of 0.62 specific gravity, 273.15K & 101.325 kPa at 0oC 2 Should an EWT be undertaken of oil and associated natural gas a shrouded flare may be used, however the total amount flared would be far less than 180mmscf as stated.



9. BEST AVAILABLE TECHNIQUE

The primary purpose of this Gas Management Plan is to consider what is the Best Available Technique

(BAT) for management of waste gas at the West Newton A wellsite.

9.1 Definition of BAT

BAT is defined within the Industrial Emissions Directive (2010/75/EU) as ‘the most effective and

advanced stage in the development of activities and their methods of operation which indicates the

practical suitability of particular techniques for providing the basis for emission limit values and other

permit conditions designed to prevent and, where that is not practicable, to reduce emissions and the

impact on the environment as a whole:

(a) ‘techniques’ includes both the technology used and the way in which the installation is designed,

built, maintained, operated and decommissioned;

(b) ‘available techniques’ means those developed on a scale which allows implementation in the

relevant industrial sector, under economically and technically viable conditions, taking into

consideration the costs and advantages, whether or not the techniques are used or produced inside

the Member State in question, as long as they are reasonably accessible to the operator;

(c) ‘best’ means most effective in achieving a high general level of protection of the environment as a

whole;’

9.2 BAT Assessment for Waste Gas from Hydrocarbon Exploration

This BAT Assessment has been undertaken for each of the identified sources of waste gas as identified

within Section 8. In order to determine BAT for the disposal of natural gas during hydrocarbon

exploration, a number of alternate techniques must be considered, having due regard to the hierarchy

of waste management, namely:

• Harness natural gas for alternative use;

• Cold venting of natural gas directly to atmosphere; and

• Incineration of natural gas by flare.

Whilst the harnessing of natural gas for alternative use, such as electricity generation, during the well

testing operations is technically feasible, it requires the installation of processing and electricity

generating equipment on site and a connection to the national grid. For the processing and electricity

generating equipment to be operated safely and efficiently, the equipment needs to be specified

based on established gas composition and flow rates. The purpose of the well test is to prepare the

well for production by allowing gas flow to surface to allow the well to reach a state of steady state

production. During the initial phase flowrates may fluctuate and, therefore, the production of

electricity cannot be considered BAT during the testing phase.

Hydrocarbon gases, such as methane (CH4), have a Global Warming Potential (GWP) twenty-eight (28)

times greater than carbon dioxide (CO2e), based on a 100-year time horizon3, therefore, venting of

unburnt hydrocarbons represents an increased environmental impact over flaring of natural gas. In

addition, the venting of large volumes of hydrocarbons presents an increased risk of fire and/or

explosion. Ordinarily, venting of natural gas is only considered in the event that low volumes of natural

gas is anticipated and, evidence is available to support the cost of installing a flare unit for this activity

would be disproportionate to the environmental benefit and subject also to the health and safety risk

of cold venting having been deemed as being as Low as Reasonably Practicable (ALARP). When

3Derived from Climate Change 2014 Synthesis Report



determining BAT for onshore oil and gas exploratory operations, the following points are considered

with respect to cold venting:

• An increase in environmental impact;

• An increase of the risks associated with safety; and

• Minimal cost increase using a flare, which in turn reduces both environmental impact and

safety risks.

As outlined above, the harnessing of natural gas during well testing for alternative use cannot be

considered BAT due to operations being of a temporary nature.

Cold venting of waste gases can be considered in the event that the volume of waste gas is significantly

low and the cost to install a flare unit is disproportionate to environmental benefit. This would be

applicable to activities involving storage and transfer of crude oil where Volatile Organic Compounds

(VOCs) may be emitted. Whilst it is feasible to have a feed line from the tank vents to a flare unit there

is a high risk of “flare-blowback” and this could ignite the gas inside the atmospheric stock tanks which

in turn could explode causing serious injury and possible fatality, All atmospheric stock tanks should

be vented to air via a common vent header line.

The incineration of natural gas is considered to be the preferred management technique for waste gas

where technically possible. This would be applicable to the well testing operations where high volumes

of natural gas will be produced. A further BAT Assessment for the ‘Type of Flare’ systems has been

provided in Section 10.



10. BEST AVAILABLE TECHNIQUE ASSESSMENT FOR WELL TESTING OPERATIONS

Having established, for the purpose of this assessment, that BAT for the management of waste gases

from well testing is incineration by flare, the following section sets out an assessment of BAT with

respect to ‘Types of flare systems’.

10.1 BAT Assessment

The following Types of flare systems have been assessed for the purpose of determining BAT for

hydrocarbon exploration onshore UK:

Enclosed ground flare;

Shrouded ground flare; and

Elevated pipe flare.

Each flare has been assessed against the following criteria:

Its ability to safely incinerate natural gas with high methane content across a significantly

variable range of flowrates and inlet pressures, such as those likely to be experienced during

the initial phase of hydrocarbon exploration; and

Environmental performance.

For the purpose of this BAT assessment, cost has not been included. Whilst economic viability is a

consideration of BAT, technical viability and environmental performance are the most critical

consideration.

The findings of the assessment, together with a conclusion of BAT are detailed in the following

subsections.

10.1.1 Enclosed Ground Flare

Enclosed flares, such as those used in landfill, are designed with either a single or multiple burner, to

incinerate natural gas with low methane content, typically around 56% methane and 31% carbon

dioxide4. These flares are limited insofar as inlet pressure and flowrate capabilities, therefore, can only

be used for oilfield purposes when there is significant confidence that any associated natural gas

pressures and/or flow rate is low. Examples where enclosed landfill type ground flares can be used for

oilfield purposes are EWT and production of oil with low gas to oil ratio (GOR) or coal bed methane,

where it is known that the methane content is high but the pressures and flows are low.

Enclosed flares have been designed and do exist specifically for oilfield purposes, however, from

experience, their environmental performance is based on consistent pressures and flow rates.

Enclosed ground flares are more sophisticated than open pipe flares or shrouded ground flares and

are not easily modified to accommodate increase in support gas to sustain combustion efficiency.

Recent experience of a sophisticated enclosed ground flare being used onshore UK for hydrocarbon

exploration resulted in poor environmental performance due to an inability to combust natural gas

during periods of low inlet pressure, circa 1.2 bar(g). Below 1.2 bar(g) natural gas was effectively being

cold vented with no feasible way of increasing support gas to sustain combustion efficiency. Likewise,

the enclosed ground flare had a modest maximum flow rate, which in turn, restricted the ability to

‘rock the well’ in an attempt to sustain a consistent flow rate.

Sophisticated enclosed ground flares that achieve high environmental performance are designed and

constructed to operate in a narrow operating envelope, based on known gas compositions, flow rates

4 Environment Agency Guidance on Landfill Gas Flaring Version 2.1



and pressures. Evidence to support this being the case is contained within the Mott MacDonald report.

In response to a questionnaire, flare manufacturer Zeeco states ‘We would not decide on the flare

design based on what the customer is doing on their site. We would take their process data and select

the best flare to achieve their specified goals. Often we don’t know what the application is. We simply

look at the gas composition and condition of supply to our battery limit along with the customers

desired result and availability of utilities.’

The limitations of low pressure and maximum flow rate, when used during the initial phase of

hydrocarbon exploration, DST or well clean-up, where the gas composition, pressure and flow rates

are unknown will inevitably result in a poor environmental performance and a protracted well

operation. Once the initial phase of well testing such as well clean-up, has established gas

composition, consistent pressures and flow rate the industry generally accepts that an enclosed

ground flare can then be specified and subsequently used for Extended Well Tests and production.

10.1.2 Shrouded Ground Flare

A shrouded flare, is essentially an open pipe flare, which is designed to incinerate natural gas with high

methane content across a significantly variable range of flowrates and inlet pressures, such as those

likely to be experienced during the initial phase of hydrocarbon exploration, such as DST, well clean-

up or initial flow testing, where the gas composition, pressure and flow rates are unknown. Whilst

having lower combustion efficiency due to not having multiple burners, a shrouded flare provides

confidence of natural gas combustion across the significantly variable range of flowrates and inlet

pressures. Historically, pre August 2013, open pipe flares have been used extensively onshore UK

without significant impact or concern.

Due to their simplicity of design, shrouded ground flares can be easily modified to aid combustion

efficiency at low inlet pressures. This can be achieved by increasing the flow of support gas (propane).

The shroud placed around the flare tip aids in the reduction of the environmental impact, with respect

to noise and visual impact. The size of the shroud is largely dictated by transportation restrictions

onshore UK. As stated in National Planning Policy Framework (NPPF), minerals, which includes oil and

gas, ‘can only be worked where they are found’, often resulting in wellsites being located in areas with

minimal and restrictive highway infrastructure.

10.1.3 Elevated Pipe Flare

Elevated pipe flares generally have a single burner flare tip, elevated some metres above ground to

provide greater dispersion performance. The flare tip is not enclosed nor is it shrouded, resulting in a

visible flame and no noise attenuation.

Elevated flares are capable of incinerating natural gas with high methane content across a significantly

variable range of flowrates and inlet pressures, such as those likely to be experienced during the initial

phase of hydrocarbon exploration, such as DST or well clean-up, where the gas composition, pressure

and flow rates are unknown.

Unlike an enclosed ground flare, which uses a multi-burner design to increase residence time to

improve combustion efficiency, elevated pipe flares have the ability to introduce air or steam, which

is injected into the gas to generate turbulence. This is referred to as air or steam assist. Generating

turbulence improves combustion efficiency by allowing the methane to mix with the air, resulting in

greater methane destruction.

Elevated pipe flares are suitable for use as a safety flare during drilling or H2S service, where the concentration of H2S is expected to be high. The risk of unburnt H2S being present or high



concentrations of SO2, as a result of incineration, is a significant health and safety consideration, mitigated by elevating the release point to increase dispersion.

10.2 BAT Conclusion for Well Testing Operations

A number of Types of flares have been assessed with respect to BAT for well testing.

Sophisticated enclosed ground flares that achieve high environmental performance are designed and

constructed to operate in a narrow operating envelope, based on known gas compositions, flow rates

and pressures. The limitations of low pressure and maximum flow rate, when used during the initial

phase of well testing, DST, well clean-up or where the gas composition, pressure and flow rates are

unknown and generally varied, has the potential to result in a poor environmental performance and a

protracted well operation, when operating outside of a narrow operating envelope.

Whilst it is accepted that the elevated pipe flares are an appropriate type of flaring system for

incineration of natural gas with a high concentration of H2S, they are generally not suitable for

operating in a non-industrial environment, due to increased visibility and noise (environmental

considerations). Where health and safety becomes the overarching factor, as is the case with high

concentrations of H2S, then a compromise is struck with respect to environmental considerations.

Shrouded ground flares, having been designed around an open pipe flare, provide for the incineration

of natural gas with high methane content across a significantly variable range of flowrates and inlet

pressures, such as those likely to be experienced during the initial phase of hydrocarbon exploration,

DST or well clean-up, where the gas composition, pressure and flow rates are unknown. They provide

the Operator with confidence that natural gas can be destroyed, albeit at a slightly reduced

combustion efficiency. Nevertheless, the ability to function across variable flowrates and pressures is

a significant safety consideration and one, which outweighs a slight reduction in environmental

performance.

In some circumstances, should an EWT be undertaken for oil, the associated natural gas may not

produce at either a consistent rate or composition as this would depend on the flowing bottom hole

pressure, surface pressure, and separator pressure as well as the PVT properties of the hydrocarbon.

Most of these factors would still remain unknown prior to an EWT. Due to this uncertainty a shrouded

ground flare is considered BAT for the extended well testing of oil where there are still uncertainties

over associated natural gas.

For the reasons set out in Section 10.2, BAT for the incineration of waste gases during well clean- up

operations is a shrouded ground flare.

In the event an Extended Well Test is to be undertaken an enclosed ground flare, in most

circumstances, can be considered BAT as the necessary flowrates and other performance data will

have been established following the well clean up operations.

Where an enclosed ground flare cannot be considered BAT during EWT, due to testing an oil reservoir

with associated natural gas, a shrouded ground flare is considered BAT due to the units capability to

operate efficiency with inconsistent flowrates and prevent the likelihood of a cold venting scenario as

described within Section 10.1.1.



11. MANAGEMENT OF GAS - WELL TESTING OPERATIONS

Well testing operations will be managed and controlled by the Wellsite Supervisor. The Wellsite

Supervisor is ultimately in charge and responsible for the operations which take place onsite, ensuring

that the work is completed in accordance with all regulatory requirements and company policies. The

operators of the temporary well testing equipment package report directly to the Wellsite Supervisor.

Any instructions for operating the equipment are received from the Wellsite Supervisor who is also

responsible for verifying the information and data being collected.

Prior to operating the flare and temporary well test package, site operatives will be required to

commission the equipment in accordance with their standard procedures. The installation and

commissioning of the equipment will be recorded. Any issues will also be recorded and will be resolved

before operations are allowed to commence. Furthermore, a pre-operational check list will be

completed in accordance with the equipment operators and manufacturers requirements. The flare

units will be operated within its technical specification at all times.

The exact equipment required during the well test will be dependent on the gas pressure of the well.

The flow from the well will be directed via a choke manifold. which is used to control the flow and well

pressures and can be adjusted to suit the varying parameters.

Once the flow has passed through the choke manifold and subject to well conditions, the well will flow

into a separator. The purpose of the separator is to remove any fluids that may be contained in the

gas.

Gas will be flowed from the separator, through a knock out pot, which removes any residual fluids

suspended in the gas, which is important in ensuring a good flame within the flare units. Finally, the

gas will flow into the flare unit where it will be incinerated. The flaring operation, with its associated

fluids knocked-out, will minimise the amount and harmfulness of any residues. Good combustion

conditions with the correct temperature, residence time and sufficient turbulence are key to securing

this.

Any fluids flowed from the well are captured in an atmospheric gauge tank, with a vent stack system.

Atmospheric gauge tanks are used for processing and the temporary storage of well fluids. The

atmospheric tank is protected from overpressure and under pressure by an adequately sized vent

system.

Throughout the well testing operations, there are a number of elements which can be varied to enable

the equipment to operate optimally. The primary locations for varying the parameters are at the choke

manifold and the flare.

The choke manifold is a series of valves, which can be restricted to control the flow from the well. The

flare is controlled by changing the flow rate, louvres and temperature.

A safe working zone will be designated around the flare whilst in operation.

A number of safety devices will be installed as part of the temporary well testing equipment package.

Such equipment may include:

• Actuated Valves

• Pressure Relief Valves; and

• Monitoring equipment including pressure gauges, flow rate and gas composition.



Subject to the relevant well control procedures the well can be shut back in if required and this will

occur at specified periods within the testing programme. This enables the build-up of pressure within

the wellbore to be monitored during this period.

Natural gas is considered a hazardous material and a review of the Waste Directive Annex III has

identified a suitable waste reference code for natural gas. The appropriate waste reference is H3-A,

which is classified as highly flammable. There is no corresponding entry within the European Waste

Catalogue (EWC) codes, which is considered appropriate for the waste stream. However, the Sector

Guidance published by the Environment Agency states that EWC code 16 05 04* should be applied.

An Air Quality Impact Assessment has been undertaken by SOCOTEC UK Limited encompassing the

potential impact both well clean up operations and the EWT will have on local air quality. This has

been provided within Appendix 2 and concludes that the impact from well testing operations,

specifically the incineration of natural gas, is negligible.

A description of the proposed well clean up and extended well testing operations has been provided

in Section 11.2 and 11.3 respectively.

11.1 Gas Composition

A summary of the expected gas composition is provided below in Table 11.1. This information has

been obtained from the analysis of gas samples collected from the WNA-1 well test.

WNA-1 Gas Composition

Samples

1 2 3

Component

N2 3.572 2.746 2.691

CO2 0.704 0.734 0.636

nC1 89.563 90.182 90.424

nC2 4.350 4.411 4.405

nC3 1.062 1.090 1.072

iC4 0.150 0.161 0.155

nC4 0.276 0.295 0.283

Neo-C5 0.004 0.004 0.004

iC5 0.101 0.110 0.103

nC5 0.091 0.099 0.091

C6 0.072 0.085 0.073

Benzene 0.015 0.021 0.016

C7 0.030 0.042 0.032

Toluene 0.001 0.002 0.002

C8 0.008 0.014 0.010

Ethylbenzene <0.001 <0.001 <0.001

M- and P- Xylenes <0.001 <0.001 <0.001

O- Xylene <0.001 <0.001 <0.001

C9 0.001 0.003 0.002

C10 <0.001 0.001 0.001

C11 <0.001 <0.001 <0.001

C12 <0.001 <0.001 <0.001

C13 <0.001 <0.001 <0.001

C14 <0.001 <0.001 <0.001

C15 <0.001 <0.001 <0.001

Total: 100.000 100.000 100.000 Table 11.1: WNA-1 Gas Composition



11.2 Well Clean Up Operations

Rathlin will undertake a number of well clean up activities on the WNA-2 well. Following the perforation of the casing and following any well treatments that may be undertaken, the formation will be evaluated by means of flow testing. The purpose of an initial flow test or well clean up is to prepare the well for an Extended Well Test (EWT).

Natural gas is flowed to surface (ordinarily unaided), together with any produced fluids (oil, condensate and/or formation water). Once at surface, natural gas and produced fluids will be flowed to a three phase separator, which will separate out oil/condensate, formation water and natural gas. Natural gas will be flowed through a knock out pot and incinerated by a flare unit.

The PW Well Test Shrouded Flare (PW Flare) has been identified as a suitable unit (in accordance with the identified BAT in Section 10 of this Gas Management Plan) for incinerating natural gas during the well clean up operations. The PW Flare, due to its design, provides Rathlin with the confidence that natural gas produced can be can be destroyed with a high level of combustion efficiency. The PW Flare has the ability to destroy natural gas with high methane content and is able to function across the variable flowrates and pressures, which will be associated with the well clean up operations. The cumulative incineration of natural gas during this phase is anticipated to be 20mmscf.

11.2.1 PW Well Test Shrouded Ground Flare

The PW Flare is currently the only known flare available onshore UK, which can meet the operational requirements of common well testing operations such as well clean up and initial flow tests. The following section sets out the current design and construction of the PW Flare, together with safety considerations and its environmental performance.

Appendix 3 contains a schematic of the PW Flare an indicative Planning and Instrumentation Diagram for the well test spread. The exact configuration will be as describe below. However, an indicative schematic has been provided.

11.2.1.1 Flare Design

The flare was manufactured to an open pipe flare design of a single 78mm (3.068”) diameter open pipe flare, elevated 3.1m above ground, with an 8.5m long by 2m diameter steel shroud. The 78mm (3.068”) open pipe flare is concentric within a 356mm (14”) diameter steel pipe, with a pilot line and air assist line running up the outside.

Both the pilot line and the air assist line extend to the flare tip. The pilot line delivers propane, from tanks located a safe and sufficient distance from the flare, to a continuously lit flame, providing a reliable and secure means of ignition at the flare tip. The air assist line delivers air to the flare tip from an air compressor, generating turbulence and increasing combustion efficiency. The air compressor is a typical mobile design, which is noise attenuated.

The flare is designed to operate across a wide flow range of between 0.0mmscfd and 6.5mmscfd. The exact design of the PW Flare is operation specific as the diameter of the open pipe is interchangeable

To mitigate against the flame entering the outlets, commonly referred to as ‘flash-back’, the flare will be fitted with a ‘quick closing valve’ and fail-safe spring return pneumatic actuator. A thermocouple will be fitted downstream of the outlet and a gas pressure transmitter will be installed within the gas delivery pipe, upstream of the outlet. The thermocouple will detect the presence of an initial ‘flash-back’, sending a signal to the ‘quick closing valve’ to activate closure of the valve.

The pilot line and air assist line are to remain in place, so too are the thermocouples and data logging facility. Propane tanks, which provide a continuous fuel source to the pilot light, will be located at safe and sufficient distance from the flare so as not to be affected by radiant heat emitted from the flare.

11.2.1.2 Combustion Efficiency



Combustion efficiency of a flare is generally based upon the flares ability to destroy methane, which in turn produces carbon dioxide (CO2) and water (H2O). The combustion efficiency of higher hydrocarbons, such as benzene and PAHs, is generally expected to be lower.

Higher combustion efficiency is achieved by increasing the residence time at the flare tip, allowing time for the methane to mix with air, resulting in greater methane destruction.

Rathlin understands that the PW Flare has been the subject of assessment by an independent service provider specialising in stack emissions testing. PW Well Test has confirmed that the combustion efficiency observed during past operations was in excess of 98%.

11.2.1.3 Flame Length

The PW Flare has been used by a number of onshore oil & gas operators for well testing operations. During each use it was recorded by PWWT that the flame height did not exceed the shroud height. No visible plume has been observed during well testing operations.

During use of the flare, the flame length will be continually monitored visually by the dedicated flare operator, who will be positioned immediately adjacent to the flare. Provision will be available on site to mitigate flame visibility should actual performance differ from the predictions not least due to the flare operator being in continuous communication with the choke manifold operator. In this regard, it is important that the flare is not viewed in isolation of the well test package.

Although unlikely, during initial start-up of the well clean up, there may be a short period of time when the flame may be slightly visible above the shroud. This is to be expected, as the choke operator adjusts flowrates and pressures in order to establish a consistent flow, control flame height so it is not visible and optimise the combustion temperature.

During well testing operations, the adjustable choke box will be used to control well pressure on a small choke setting. During the well clean up, should the flame length start to exceed the shroud height, the flow rate will be reduced at the choke manifold. In turn, this will reduce the inlet flow rate of natural gas to the flare, resulting in a reduction in flame length.

When the well is flowing, the well test package is continuously manned and periodic checks of the flare are undertaken, including temperature and flame condition. A dedicated well test operative will be assigned to continuously monitor the flare during testing operations and shall be in full communication with the dedicated choke manifold operator, advising the choke manifold operator of the flame characteristics. Choke adjustments are normally carried out in 4/64” increments, with upstream and downstream pressures monitored throughout.

If necessary, due to any safety concerns, the well can be shut in at the choke manifold. The well test package will have an active Emergency Shutdown (ESD) system in operation throughout the well testing operation. All well testing personnel must be trained in its use, including how to shut in the well in the event of an emergency.

11.3 Extended Well Testing

Once the well clean up phase is completed the WNA-2 well will be shut in whilst the shrouded flare is substituted for an enclosed flare/incinerator.

A number of EWT will be undertaken as part of the well testing activities following on from the well clean up phase.

Similarly, as with the clean up phase, natural gas will be flowed to surface together with any produced fluids (oil/condensate and formation water). The natural gas and produced fluids will be separated by the three phase separator where natural gas will be incinerated, with oil/condensate and formation water being separated and stored in separate storage tanks for subsequent offsite removal.



Rathlin has identified a Certified ultra-low Emission Burner (CEB) as a suitable unit (in accordance with the identified BAT in Section 10 of this Gas Management Plan) for incinerating natural gas during the EWT operations. The exact model, Certified ultra-low Emission Burner 4500 (CEB4500), due to its design, provides Rathlin with the confidence that any natural gas produced can be destroyed with a high level of combustion efficiency, provided that flowrates and pressures are at a steady state. The cumulative incineration of natural gas during this phase is anticipated to be circa 180mmscf.

However, it should be noted that in the event an EWT is undertaken for oil then the PW Flare may be used for the incineration of associated gas, due to its ability to effectively incinerate gas with inconsistent flowrates and pressures. In this event it is the total volume flared for this phase will be far less than 180mmscf.

11.3.1 AEREON CEB4500

The CEB4500 has a better environmental performance than the typical enclosed ground flares used by operators onshore UK. It meets the necessary requirements to undertake EWT operations. The following section sets out the current design and construction of the CEB4500 together with its environmental performance.

Appendix 4 contains a schematic of the CEB4500 with the proposed configuration for a 3.5mmscfd flow rate together with further manufacturing details.

11.3.1.1 CEB Design

The CEB4500 unit is of cuboid shape with approximate dimensions, 2.8m (L) x 2.4m (W) x 6m (H) and has been designed to produce low emissions and very high VOC destruction efficiencies (up to 99.99%). The CEB4500 has been designed to prevent smoke, soot, odour and visible flame.

The maximum capacity of the CEB4500 unit is 3.5mmscfd and operates a turndown ratio of 10:1 ensuring that in the event of lower than expected flow rates, it has the scope to ensure that the combustion efficiency remains high (99%). The temperature range of the CEB4500 is 900oC – 1,200oC.

A pilot line is present delivering propane from the tanks located a safe and sufficient distance from the unit. The pilot line delivers propane from external tanks ensuring a continuously lit flame, providing a reliable and secure means of ignition.

In order to enhance the efficiency of the thermal oxidation reaction, the CEB4500 operates an air-to-fuel ratio of roughly 15:1. The high excess air ensures that an efficient reaction takes place with a high destruction efficiency.

11.3.1.2 Combustion Efficiency

Combustion efficiency of a flare is generally based upon the flares ability to destroy methane, which in turn produces carbon dioxide (CO2) and water (H2O). The combustion efficiency of higher hydrocarbons, such as benzene and PAHs, is generally expected to be lower.

Higher combustion efficiency is achieved by increasing the residence time at the flare tip, allowing time for the methane to mix with air, resulting in greater methane destruction. The mixture of gas and air within the CEB4500 passes through a knitted metal fibre media separating the flow into numerous small streams and ignited to form millions of small, surface resident mini-flames, ensuring a more efficient combustion.

The Combustion Efficiency of the CEB4500 unit is stated at 99.99%, well above the Environment Agency minimum requirement of 98%.



11.3.1.3 Flame Length

Due to the design of the CEB4500, as detailed above, resulting in an extremely high combustion efficiency, flame height is relatively short. The thermal reaction results in very short, non-luminous blue flames, which is why the CEB4500 has a relatively short stack.

When the well is flowing, the well test package is continuously manned and periodic checks of the flare are undertaken, including temperature and flame condition. A dedicated well test operative will be assigned to continuously monitor the flare during testing operations and shall be in full communication with the dedicated choke manifold operator, advising the choke manifold operator of the flame characteristics. Choke adjustments are normally carried out in 4/64” increments, with upstream and downstream pressures monitored throughout.

If necessary, due to any safety concerns, the well can be shut in at the choke manifold. The well test package will have an active Emergency Shutdown (ESD) system in operation throughout the well testing operation. All well testing personnel must be trained in its use, including how to shut in the well in the event of an emergency.



12. MANAGEMENT OF VAPOUR RECOVERY

Vapours containing potential VOCs are generated from the agitation of crude oil as it is transferred in

to crude oil storage tanks and road tankers. A Vapour Recovery Plan has been produced and will be

adhered to by Rathlin.

During the transfer, loading and unloading of crude oil, there is the potential for VOCs to be emitted

to atmosphere from storage tank vents and road tanker inspection hatches. The BAT for the

management of vapour recovery has been established within Section 9.2.

Details of the proposed vapour recovery measures to be implemented within the West Newton A

wellsite are summarised below.

12.1 Recovery of VOCs from Oil Storage Tanks

Vapours within crude oil storage tanks will be vented to atmosphere from a single co-joined vent stack

connecting all crude oil storage tanks located within the West Newton A wellsite.

Rathlin propose to install a VOC scrubber on the single co-joined vent stack to recover VOCs from

vapours emitted from the crude oil storage tanks.

The scrubber will be designed to allow the capture and recovery of VOCs from vapours being vented

during the following operations:

1. Loading (filling) of crude oil storage tanks;

2. Transfer of crude oil between crude oil storage tanks; and

3. Back venting of vapours from loading (filling) road tankers used in the transportation of crude

oil offsite to the local refinery.

For safety and environmental reasons, the scrubber to be installed must be capable of allowing air

flow both in to, and out of, the crude oil storage tanks to prevent over-pressurisation and under-

pressurisation of the crude oil storage tank.

The Crude Oil Vapour Risk Assessment has assessed the risk from VOCs emitted to atmosphere with

no VOC scrubber installed as ‘not significant’ and the risk of VOCs emitted to atmosphere with a VOC

scrubber installed as ‘Insignificant’.

12.2 Recovery of VOCs from Road Tankers

During the loading of road tankers used for the transportation of crude oil offsite, vapours within the

road tanker are back vented to the crude oil storage tank. The vapours flow from the road tanker via

a flexible hose, to the crude oil storage tank where they will be managed in accordance with the

Vapour Recovery Plan

The Crude Oil Vapour Risk Assessment has assessed the risk from VOCs emitted to atmosphere from

the road tanker as ‘not significant’.

The Crude Oil Vapour Risk Assessment has assessed the risk from VOCs emitted to atmosphere from

the back venting of vapours to the crude oil storage tank with no VOC scrubber installed as ‘not

significant’ and the risk of VOCs emitted to atmosphere with a VOC scrubber installed as ‘insignificant’.

12.3 Containment of Emissions

There is the potential for vapours containing VOCs to be contained within pipes, hoses etc. used within

crude oil transfer and loading operations.



Where practicable, pipes, hoses etc. will remain sealed until cessation of operations thus reducing the

likelihood of potential emissions. Where possible, purging of the system is to be undertaken prior to

breaking containment.

Tanks and pipework containing potential emissions are to be checked on a regular basis by the service

provider and the Wellsite Supervisor for leaks and / or damage to the containment system. All checks

are to be recorded and a record held within the Wellsite Supervisor’s office and be available for review

by regulatory bodies.

12.4 Maintenance and Servicing Procedures

Maintenance and servicing of storage tanks, equipment, pipework, hoses, scrubbers etc. will be

undertaken in accordance with the manufacturer’s recommendations. Rathlin will ensure that the risk

of potential emissions from the breaking of containment during maintenance and servicing of

equipment is reduced to a minimum and the potential for equipment failure is reduced. Control

measures to eliminate or reduce potential emissions include, but are not limited to:

Purging equipment prior to breaking containment;

Conducting maintenance or servicing inside buildings or covered areas where practicable;

Containment of emissions; and

Compliance with waste storage / disposal procedures.

12.5 Implementation of Pollution Control Measures

Control measures shall be implemented to prevent the emission of vapours containing VOCs, whose

emission to air could cause pollution. Control measures to be implemented include, but are not limited

to:

Installation of VOC scrubbers on the single co-joined vent stack;

Tank levels monitored to prevent overfilling;

Transfer of products to be monitored by wellsite personnel;

Checks of containment and transfer systems to ensure integrity is maintained;

Where possible, breaking containment to be undertaken at cessation of operations;

Purge equipment prior to breaking containment;

Plug / cap tanks, pipes, hoses etc. after breaking containment;

Wellsite / vehicle spillage kits to be readily available;

Spillages to be remediated immediately;

All spillages to be reported;

Emergency response plan established / tested; and

Training on environmental awareness for wellsite personnel.

12.6 Arrangements for Monitoring and Recording

The Wellsite Supervisor is to undertake daily environmental monitoring and a record is to be held

onsite. Environmental monitoring is to include checks on wellsite equipment, secondary containment

systems and hazardous materials for visible signs of leaks, damage or contamination. The

Environmental Checklist is to include components and equipment that have the potential to emit

vapours containing VOCs including, but not limited to:

Crude oil storage tanks, associated pipework and vent stacks;

VOC scrubbers; and

Pipes and hoses etc. used in the transfer of crude oil.



13. ENVIRONMENTAL MANAGEMENT AND MONITORING

The West Newton A wellsite will be managed in such a way as to ensure that all operations will be

undertaken in such a way as to minimise environmental impact. Management and Monitoring regimes

will be implemented at the wellsite by Rathlin to which contractors and subcontractors much adhere

to.

13.1 Odour

An Odour Management Plan (OMP) is currently in place for the West Newton A wellsite. Forthcoming

operations relating to well testing will be the subject of the OMP (RE-EPRA-WNA-OMP-009) which will

be in place for operations conducted at the West Newton A wellsite. The OMP will be the subject of

review by the Environment Agency as part of a permit variation process.

The OMP has identified a number of potential sources of odour together with the mitigation measures

that will be used to ensure that Odour is eliminated so far as reasonably practicable. The Odour

Management Plan also details monitoring techniques such as sniff testing, emissions monitoring and

grab sampling.

13.2 Air Monitoring

Prior to the commencement of operations, baseline air quality samples will be collected at the West

Newton A wellsite. The main source of air emissions from the operations will be the incineration of

natural gas during the well clean up and EWT operations.

The scheme of monitoring will be consistent with the parameters and methodologies previously

approved by the Environment Agency. The monitoring regime will involve the collection of a

representative baseline sample during periods where either no or limited operations are taking place

at the wellsite.

The same parameters will then be sampled for, analysed and the findings issued to the Environment

Agency in accordance with the requirements of the West Newton A environmental permit.

13.3 Emissions Calculation

Previous operations at the West Newton A wellsite required a method to calculate the point source

emissions to air from the flare unit. The calculation method will be necessary to establish the

emissions to air as a result of natural gas being combusted during the well testing operations and

remains relevant.



14. EMERGENCY RESPONSE PROCEDURES

In the event of an incident occurring, the Wellsite Supervisor is to comply with the Wellsite Emergency

Response Plan ensuring, if safe to do so, immediate action is undertaken to isolate, contain and

prevent an incident.

In addition, Rathlin will inform Emergency Services of the location of the wellsite and will be notified

of circumstances in which they may be called out to attend. This will aid the emergency services

developing an emergency response plan of their own specifically for the operations and wellsite.

14.1 Spillages

Spillages of crude oil during the transfer or over filling of vessels will result in associated vapour being

dispersed to the local environment.

Spillages occurring during the transfer of crude oil are not to be hosed down or detergents used to

remediate the spillage. Remediation of the spillage is to be undertaken and the contaminated stone

is to be removed, segregated and disposed of to an Environment Agency licensed facility as hazardous

waste.

Spillage response equipment is located onsite. During site inductions, personnel will be shown the

location of spillage equipment, how to use the equipment correctly and how to store and use materials

safely.

Spillage equipment is to be labelled and checked on a regular basis by the Wellsite Supervisor and

unserviceable items quarantined and replaced.

14.2 Well Shut In

The Borehole Sites and Operations Regulations 1995 requires that a site specific health and safety

document is produced for wellsite operations and requires a plan for the prevention of fire and

explosions including particular provisions for preventing uncontrolled escape of flammable gasses.

In the unlikely event of an emergency situation arising during the well testing operation, for example

a failed component or exceedance in pressure leading to one of a number of pressure relief valves

within the well test package being activated, the well will be shut in with any residual gas remaining

within pipework incinerated.

Primary well control during a well testing is the choke manifold, which must be fully certified and

pressure tested to ensure it is sufficient to withstand the anticipated well pressures.

Secondary well control, as an example, can be an active ESD, which consists of a hydraulically operated

Surface Safety Valve (SSV) located between the wellhead and the choke. Depending on the nature of

the emergency situation, the well will be shut in at the choke if there is any visual indicator of a

potential emergency situation starting to occur. If the emergency situation is not so obvious, such as

pressure build-up within the well test package, high pressure sensors located at the choke and

possibly, at the three (3) phase separator, will send an electronic signal to the SSV, which will close,

isolating the well from the well testing package.



*** Page Left Blank Intentionally ***



APPENDIX 1 – INDICATIVE SITE LAYOUT PLAN

THIS DOCUMENT IS THE PROPERTY OF RATHLIN ENERGY (UK)LIMITED. IT CONTAINS PROPRIETARY AND CONFIDENTIAL

INFORMATION WHICH MUST NOT BE DUPLICATED, USED ORDISCLOSED OTHER THAN AS EXPRESSLY AUTHORISED BY

RATHLIN ENERGY (UK) LIMITED OR ITS REPRESENTATIVE © 2018

DATEREV

SITE

DWG NO.

TITLE

PROJECT

Rathlin Energy (UK) LIMITED

BY DETAILS

SCALESIZE A3

1:500

RE-EPR-WNA-SP-004-2

DEC180 ORIGINAL ISSUEJFAPR

WEST NEWTON AWELLSITE

THE ORDNANCE SURVEY DATA ON THIS PLAN HAS BEENREPRODUCED FROM ORDNANCE SURVEY ® BY PERMISSION OFORDNANCE SURVEY ® ON BEHALF OF THE CONTROLLER OF HERMAJESTY'S STATIONERY OFFICE. © CROWN COPYRIGHT 2018.ALL RIGHTS RESERVED. LICENCE No. 100022432

KEY:

SITE BOUNDARY

WEST NEWTON A-2APPRAISAL WELL

SHEET 1 OF 1

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INDICATIVE WELLCLEAN-UP PLAN

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APPENDIX 2 – AIR QUALITY IMPACT ASSESSMENT

RATHLIN ENERGY (UK) LIMITED Air quality assessment of the flaring of natural gas from the testing of a well West Newton A Carried out for:

Carried out by:

Date 26 November 2018 Report No. LSO181038 Issue 2

Rathlin Energy (UK) Limited SOCOTEC UK Limited Unit D Bankside Trade Park Cirencester Gloucestershire GL7 1YT

©2018 SOCOTEC UK Limited Air quality assessment of the flaring of natural gas Rathlin Energy (UK) Limited, West Newton A

26 November 2018 Report No LSO181038 Issue 2 Page 2 of 68

ISSUE HISTORY

Issue Date Approved

181038,1 16 November 2018 N Ford

First issue

181038,2 26 November 2018 N Ford

Minor amendments to text and formatting following client review This Report has been prepared by SOCOTEC UK Limited with all reasonable skill and care, within the terms and conditions of the contract between SOCOTEC UK Limited and the Client (“Contract”) and within the limitations of the resources devoted to it by agreement with the Client. Any reliance upon the Report is subject to the Contract terms and conditions. This Report is confidential between the Client and SOCOTEC UK Limited. SOCOTEC UK Limited accepts no responsibility whatsoever to third parties to whom this document, or any part thereof, is made known. Any such party relies upon the Report at their own risk. The Contracts (Rights of Third Parties) Act 1999 does not apply to this Report nor the Contract and the provisions of the said Act are hereby excluded. This Report shall not be used for engineering or contractual purposes unless signed above by the author, checker and the approver for and on behalf of SOCOTEC UK Limited and unless the Report status is ‘Final’. Unless specifically assigned or transferred within the terms and conditions of the Contract, SOCOTEC UK Limited asserts and retains all Copyright and other Intellectual Property Rights in and over the Report and its contents. The Report may not be copied or reproduced, in whole or in part, without the written authorisation from SOCOTEC UK Limited. SOCOTEC UK Limited shall not be liable for any use of the Report for any purpose other than that for which it was originally prepared. Whilst every effort has been made to ensure the accuracy of the data supplied and any analysis interpretation derived from it, the possibility exists of variations in the ground and groundwater conditions around and between the exploratory positions. No liability can be accepted for any such variations in these conditions. Furthermore, any recommendations are specific to the development as detailed in this Report and no liability will be accepted should they be used for the design of alternative schemes without prior consultant with SOCOTEC UK Limited.



CONTENTS

Page No. COVER ISSUE HISTORY 1 CONTENTS 2 0 SUMMARY 5 1 INTRODUCTION 6 1.1 Scope of study 6 1.2 General approach 6 1.3 Structure of report 7 2 POLICY CONTEXT AND ASSESSMENT CRITERIA 8 2.1 Context of assessment 8 2.2 Pollutants from natural gas combustion 8 2.3 Environmental Standards 9 2.3.1 Application of environmental standards 11 2.4 Background air quality around West Newton 11 2.5 Assessment criteria 13 2.5.1 Criteria relevant to human health 14 2.5.2 Criteria for deposition to ground 14 2.5.3 Criteria relevant to protected conservation areas 15 2.5.4 Significance of impact 16 3 MODELLING METHODOLOGY 18 3.1 Assessment area 18 3.2 Buildings 22 3.3 Meteorology 22 3.4 Surface characteristics 23 3.4.1 Surface roughness 24 3.4.2 Surface albedo 25 3.4.3 Monin Obukhov length 25 3.4.4 Priestley Taylor parameter 26 3.4.5 Terrain 27



3.5 Pollutant releases and conditions 28 3.6 Modelling scenarios 30 4 MODELLING RESULTS 31 4.1 Impact of process releases 31 4.2 Impact of process releases at the neighbouring public footpaths 33 4.3 Impact of process releases at residential locations 34 4.4 Impact of releases at sensitive nature conservation sites 35 4.5 Sensitivity analyses 38 4.5.1 Meteorological conditions 38 4.5.2 Model selection 39 4.6 Modelling uncertainty 40 5 CONCLUSIONS 42 6 REFERENCES 43 Annex A Dispersion model contour plots 45 Annex B Modelling files 50 Annex C Conversion of nitrogen monoxide to nitrogen dioxide 51 Annex D Meteorological data (Leconfield) 55 Annex E Discrete receptors 60



0 SUMMARY Rathlin Energy UK Limited propose to develop an existing well site, known as the West Newton A, by drilling a new borehole and flow testing two zones. The drilling of the well is covered by an existing environmental permit, although a variation will be required to enable the disposal of any produced natural gas by flaring. As part of the permit variation process the dispersion of releases to atmosphere associated with the proposed temporary flaring at the West Newton A well site will need to be assessed to determine their impact on ambient concentrations of important pollutants around the local area. The main source of pollutant releases during flaring will be from the combustion of any produced natural gas. This assessment considered releases of nitrogen oxides, carbon monoxide, volatile organic compounds and sulphur dioxide. The assessment was undertaken using the UK ADMS 5.2 modelling system Maximum pollutant process contributions from the proposed flaring operations occur within the well site boundary. Maximum process contributions of nitrogen dioxide and benzene exceeded the Environment Agency’s screening criteria, although all other pollutants considered were determined to be insignificant with respect to air quality impact. It is not considered that statutory air quality standards would be applicable within the well site boundary. Beyond the location of the maximum process contributions reduce significantly with distance Along the public footpaths, some of which run close to the well site boundary, it might be expected that short term environmental standards would apply in view of the potential frequent, but short term, human exposure. All short term process contributions at the nearest footpaths are considered insignificant based on Environment Agency assessment criteria and are considered unlikely to pose any threat to continued attainment of the applicable ambient air quality standards. At the neighbouring residential locations, where frequent and long term human exposure might be expected, all pollutant process contributions were considered insignificant based on Environment Agency assessment criteria and unlikely to threaten, or have any meaningful influence on, ambient air quality standard attainment. The air quality impact significance of flaring operations, based on Institute of Air Quality Management descriptors, is classed as ‘negligible’ at all neighbouring residential locations for all pollutants. At local conservation sites sensitive to nitrogen and acid deposition (Lambwath Meadows site of special scientific interest and Hornsea Mere special protection area) maximum process contributions are considered to be insignificant based on Environment Agency assessment criteria and considered unlikely to pose any threat to, or have any substantial influence on, the attainment of critical levels and critical loads. It is concluded that pollutant releases from the proposed natural gas flaring are unlikely to pose any substantial risk to, or have any significant influence on, the attainment of environmental standards in the vicinity of the West Newton A well site. Necessary assumptions made to undertake the modelling are considered to have the effect of substantially overestimating the process contribution to ambient concentrations. It is considered that the predicted process impact reported herein is a conservative assessment and the conclusions reached therefore incorporate a reasonable margin of comfort in spite of the inevitable uncertainty of such modelling studies.



1 INTRODUCTION Rathlin Energy (UK) Limited (Rathlin) placed a contract with SOCOTEC UK Limited (SOCOTEC) to undertake an assessment of the impact on local air quality of a temporary flaring operation at their West Newton A well site near Hornsea in the East Riding of Yorkshire.

1.1 Scope of study Rathlin propose to develop an existing well site, known as West Newton A, by drilling a new borehole and flow testing two zones. The drilling of the well is covered by an existing environmental permit (BB3001FT), although a variation will be required to enable the disposal of any produced natural gas by flaring. As part of the permit variation process Rathlin have asked that the dispersion of releases to atmosphere associated with the proposed temporary flaring at the West Newton A well site be assessed to determine their impact on ambient concentrations of important pollutants around the local area. The main source of pollutant releases during flaring will be from the combustion of any produced natural gas. The main pollutants of concern from the combustion of natural gas are nitrogen oxides, carbon monoxide, volatile organic compounds and sulphur dioxide. The purpose of this study is to determine whether, under the proposed operating regime, releases of these pollutants to atmosphere are likely to be dispersed adequately in the context of applicable environmental standard attainment. 1.2 General approach The approach taken comprised the following main stages: Determine a suitable modelling tool for the assessment. Collect appropriate representative operational data for the flares intended for use for input to the model. Establish the proposed operational arrangements and likely maximum natural gas disposal rates. Establish the location of the flare discharge relative to proposed permanent and temporary buildings and

structures on the well site. Establish the locations of any sensitive areas that might be impacted by releases from the site including

neighbouring residential properties, public footpaths and nature conservation areas. Obtain information on local background concentrations of important pollutants. Obtain 5 years’ recent meteorological data from a measurement station representative of the well site location. Model the dispersion of releases from the proposed flaring operations to determine the process contribution to

ambient concentrations of selected pollutants over the local area with particular attention to locations of human exposure and sensitive nature conservation sites.

Assess the predicted process contributions and established background concentrations with reference to applicable environmental standards to determine compliance.

Undertake sensitivity analyses on the results for other important variable parameters and assess compliance with applicable environmental standards.

Further details of the approach taken and model input information are provided in the following sections.



1.3 Structure of the report This report provides an assessment of the impact of releases from proposed natural gas flaring on local air quality in the vicinity of the West Newton A well site. The approach to the assessment has been described above. The following sections provide a detailed commentary on the assessment and conclusions: Section 2 Air quality standards and assessment criteria Section 3 The model methodology employed and important input data Section 4 The results of the assessment including sensitivity analyses Section 5 Conclusions of the assessment



2 POLICY CONTEXT AND ASSESSMENT CRITERIA Rathlin Energy (UK) Limited propose to develop the existing well site, known as the West Newton A well site, near Hornsea in the East Riding of Yorkshire. The site is currently operational and has an environmental permit. The proposed development involves the drilling of a new borehole (WNA-2) in order test its commercial viability. Two zones will be flow tested. It is necessary to have facilities in place to dispose of any produced natural gas during the well clean up and subsequent flow testing of each zone. Rathlin propose to dispose of any produced natural gas by flaring. While the drilling of the new borehole falls within the current environmental permit, a variation will be necessary to cover the proposed temporary flaring of any natural gas produced. The West Newton A well site is near the village of West Newton and around 8 km to the south of Hornsea and 12 km north east of Hull and is in a rural area. The surrounding land is largely agricultural. There are individual residential dwellings in the area, with the nearest being around 530 m to the south west of the well site. Lambwath Meadows site of special scientific interest is the closest statutory site designated for ecology at around 1 km to the north east of the well site.

2.1 Context of assessment As part of the permitting application it is necessary to demonstrate the likely impact of proposed operations on local ambient concentrations of important pollutants. It is in this context that the proposed operations are being examined to determine their additional contribution to the existing concentrations of important pollutants and therefore determine compliance with applicable air quality standards and environmental benchmarks. Local Authorities are required to assess compliance with applicable air quality objectives. Where the objectives are unlikely to be met the Local Authority is required to declare an Air Quality Management Area (AQMA) and prepare proposals for remedial action to achieve the required objective. There are no declared AQMAs in the immediate vicinity of West Newton A well site or within the East Riding of Yorkshire Council area. A survey of planning and permitting applications provides no indication of any significant developments in the area which might have an influence on background concentrations of the pollutants of interest in this case. The Environment Agency play an important role in relation to local air quality management by ensuring that processes under their regulatory control do not contribute any significant threat to the attainment of air quality standards. It is in this context that, as part of the environmental permitting process, it is necessary to demonstrate the impact of site operations on local air quality in the context of the published guidance provided by the Environment Agency1. 2.2 Pollutants from natural gas combustion The source of pollutant releases to atmosphere considered in this assessment will be from the combustion of natural gas which gives rise to releases of oxides of nitrogen (NOx) and carbon monoxide (CO). Oxides of nitrogen are generally considered to comprise primarily of nitrogen monoxide (NO) and nitrogen dioxide (NO2). While NOx from road transport is a major contributor to ground level concentrations, emissions from



combustion processes are also significant. Oxides of nitrogen are associated with lung damage and enhanced sensitivity to allergens. Emissions from combustion primarily consist of nitrogen monoxide, although reaction in the atmosphere results in conversion to nitrogen dioxide, which is the primary nitrogen oxide of interest with respect to ambient pollution. The emission of nitrogen oxides and their transformation products can cause a wide range of environmental effects including acidification and eutrophication Carbon monoxide (CO) is a product of incomplete combustion of the fuel and is therefore related to combustion efficiency. It reacts with other pollutants to form ground level ozone and has implications for neurological health. With incomplete combustion there is also the risk of elevated levels of volatile organic compounds (VOCs) which can give rise to odours and influence ground level ozone formation. There will also be a release of sulphur dioxide (SO2) which will be dependent on the sulphur content of the natural gas. Fugitive releases of natural gas, principally methane, are considered unlikely to be significant. Leakages from associated transport pipework on the site are likely to be minimal as the necessary surface pipework will be designed to minimise the number of connections, pressure tested prior to use and maintained in accordance with industry best practice. It is therefore considered that leakages from this temporary arrangement will not be significant and as such fugitive releases are not considered within this assessment. It is not expected that there will be any significant odour impact as a result of release of volatile organic compounds from site operations. The nearest residential locations are around 550 m from the well site and as such would not be expected to experience any substantial odour impact from low level releases during site operations. This assessment considers the air quality impact of the following pollutants resulting from natural gas flaring: Nitrogen oxides (NOx, consisting of nitrogen monoxide (NO) and nitrogen dioxide (NO2)) Sulphur dioxide (SO2) Carbon monoxide (CO) Volatile organic compounds (higher organic proportion of VOC releases (C6+) – assessed as benzene) Methane (the lower organic proportion of the VOC releases (C5 and below) – assessed as methane) 2.3 Environmental Standards The UK’s air quality strategy is based on meeting obligations within the European Union (EU) Ambient Air Quality Directive (2008/50/EC, 21 May 2008)2 and the Fourth Daughter Directive (2004/107/EC, relating to metals and hydrocarbons)3. These directives specify legally binding limit values and target values. Limit values are set for individual pollutants and are made up of a concentration value, an averaging time over which it is to be measured, the number of exceedances allowed per year, if any, and a date by which it must be achieved. Some pollutants have more than one limit value covering different endpoints or averaging times. Target values are set out in the same way as limit values and are to be attained where possible by taking all necessary measures not entailing disproportionate costs. The Air Quality (Standards) Regulations 20104 transpose into English law the requirements of Directives 2008/50/EC and 2004/107/EC on ambient air quality. Equivalent regulations have been made by the devolved administrations in Scotland, Wales and Northern Ireland. Schedules 2 and 3 of the Regulations specify limit and target values respectively. Table 2.1 summarises the applicable limit values for the pollutants considered in this assessment as at 2018.

http://www.legislation.gov.uk/uksi/2010/1001/contents/made



The limit values below are expressed as concentrations recorded over a specified time period which are considered to be acceptable in terms of current knowledge of the impact on health and the environment. Limit values are legally binding time averaged limits which must not be exceeded and which the UK is obliged to meet. In the case of target values these are values which are expected to be met by a specified date. Table 2.1 Ambient Air Directive Limit Values and Target Values Pollutant Basis Concentration Carbon monoxide (CO) running 8 hour mean across a 24 hour period 10 mg/m3

Nitrogen dioxide (NO2) 1 hour mean (99.79 percentile – 18 exceedances per year) 200 µg/m3 annual mean 40 µg/m3

Sulphur dioxide (SO2) 15 minute mean (99.90 percentile – 35 exceedances per yeara 266 µg/m3 1 hour mean (99.72 percentile – 24 exceedances per year) 350 µg/m3 24 hour mean (99.18 percentile – 3 exceedances per year) 125 µg/m3

PM2.5 annual mean 25 µg/m3 Benzene annual mean 5 µg/m3 a. Target value included in Environment Agency guidance1. b. Annual means refer to a calendar year. c. Running 8 hour mean for each daily period commences at 1700 on the previous day and is updated every hour for the following 24 hours. Critical levels are specified for sulphur dioxide and nitrogen oxides in relation to the protection of ecological conservation areas as shown in Table 2.2. Table 2.2 Critical levels for the protection of ecological conservation areas Pollutant Basis Concentration

Nitrogen oxides (as NO2) annual mean 30 µg/m3 daily mean 75 µg/m3

Sulphur dioxide (SO2) annual meana 10 µg/m3 a. refers to the lower limit for sensitive lichen communities & bryophytes and ecosystems where lichens & bryophytes are an important part of the ecosystem’s integrity. The upper limit where lichens are not present is 20 µg/m3. In addition, for the purposes of assessing the significance of pollutants in the ambient atmosphere the Environment Agency also publish Environmental Assessment Levels (EALs) for the protection of human health1. The EALs relevant to this study are summarised in Table 2.3. Table 2.3 Environmental Assessment Levels Pollutant Basis Concentration Carbon monoxide hourly mean 30000 µg/m3 Benzene hourly mean 195 µg/m3

Nitrogen monoxide (NO) hourly mean 4400 µg/m3 annual mean 310 µg/m3

Methane (CH4)a hourly mean 21420 µg/m3 annual mean 7140 µg/m3



a. The annual mean EAL for methane is based on an 8 hour time weighted average workplace exposure limit of 1000 ppm (NIOSH5) and is converted to long term and short term EALs based on the methodology specified in H1, Annex F6 and the Health and Safety Executive’s EH40/20057. The EAL for methane is considered to be applicable in the assessment of the group of lower aliphatic hydrocarbon gases (C1 to C5). This is considered a precautionary approach as equivalent EALs for the remainder of the group (ethane, propane, butane and pentane) are considerably higher than methane. 2.3.1 Application of environmental standards The Air Quality Standards Regulations 20104 specify legally binding concentrations of pollutants in the atmosphere which can broadly be taken to achieve a certain level of environmental quality. The Regulations define ambient air as; “…outdoor air in the troposphere, excluding workplaces where members of the public do not have regular access.” Compliance with limit values for the protection of human health does not need to be assessed (Schedule 1, Part 1) at the following locations: a) any location situated within areas where members of the public do not have access and there is no fixed habitation; b) on factory premises or at industrial locations to which all relevant provisions concerning health and safety at work apply; c) on the carriageway of roads and on the central reservation of roads except where there is normally pedestrian access to the central reservation. It is therefore considered that compliance with environmental benchmarks should concentrate on areas where members of the general public are present over the entire duration of the concentration averaging period specific to the relevant standard. For the longer averaging periods the standards are considered to apply around the frontage of premises such as residential properties, schools and hospitals. The shorter term limit value (1 hour or 1 day means) applies at these locations and other areas where exposure is likely to be of one hour or more on a regular basis. In this context this assessment of compliance with environmental benchmarks in respect of protection of human health is considered at the nearest residential locations in the vicinity of the West Newton A wellsite. There will also be the likelihood of short term human exposure on the public footpaths in the area which run near the well site boundary. The assessment of compliance with critical loads and critical levels with respect to ecological impact is assessed at the conservation sites required for assessment within Environment Agency guidance1 (see section 2.5.3). 2.4 Background air quality around West Newton In considering the overall impact of a project, such as this herein, on local air quality and compliance with environmental benchmarks, it is necessary not only to consider the contribution from the proposed source but also the existing levels of pollutants of interest. Background air quality data for the area around the West Newton A well site are available from DEFRA’s air quality archive (http://uk-air.defra.gov.uk/data/pcm-data). The archive provides estimated background concentrations of important pollutants for 1km2 areas for the UK. The latest available background levels for the area within an approximate 1 km radius of the West Newton A well site (centre 519250

http://uk-air.defra.gov.uk/data/pcm-data



439090) were used for this assessment. Within this area there were 12 points at which background concentrations were available. Table 2.4 summarises the background pollutant concentrations obtained from the air quality archive for the assessment area. The values reported are the mean and maximum of the 12 points for which data were available. Table 2.4 Background pollutant concentrations from the DEFRA archive Pollutant Averaging basis Concentration (µg/m3)

Maximum Mean Nitrogen dioxide (2016) annual mean 9.98 9.54 Total nitrogen oxides (2016) annual mean (as NO2) 13.90 13.22 Nitrogen monoxide (2016)a annual mean 2.47 2.36 Carbon monoxide (2010) maximum 8 hour rolling mean 1475 1456 Sulphur dioxide (2016) annual mean 2.20 2.14 Benzene (2016) annual mean 0.29 0.28 a. calculated based on the difference between total nitrogen oxides and nitrogen dioxide assuming total nitrogen oxides is the sum of nitrogen monoxide and nitrogen dioxide. East Riding of Yorkshire Council8 undertakes non-automatic air quality monitoring, although the nearest stations are around 8 km from the West Newton A well suite around Hornsea. No automatic monitoring is undertaken by the Council. It is considered that there are no monitoring stations within the area considered to be influenced by releases from proposed flaring operations at the West Newton A well site. Periodic measurements of background concentrations are undertaken by Rathlin around the West Newton B well site boundary which is around 2 km south east of the West Newton A well site. While not considered representative of the general area neighbouring the West Newton B well site the measurements do indicate generally good agreement with the DEFRA background concentrations in Table 2.4. As might be expected, due to the closeness of the monitoring point to well site operations, concentrations of benzene are somewhat higher than the DEFRA values for the general neighbouring area, although measured levels of methane are lower than the background assumed in this assessment. In the absence of locally measured background concentrations for the pollutants of interest, the maximum values from the DEFRA archive across the assessment area have been employed within this assessment. The use of the DEFRA maximum value for each pollutant is considered a precautionary approach which will most likely overestimate the existing background concentrations in the important areas of human exposure around the West Newton area. The annual mean background concentration of methane employed in this assessment (1356 µg/m3) is based on the Northern Hemisphere average9 and is slightly higher than the background measurements reported by the Environment Agency for 2001-2003 (1278 µg/m3)10. When considering the combination of estimated process contributions and background concentrations it should be noted that background concentrations are generally available as annual mean values and as such simple addition when considering short term air quality standards may not be appropriate. Guidance from the Environment Agency1 suggests a simplified method for combining estimated process contributions and background concentrations. For comparison with long term standards the overall concentration is the sum of the process contribution (annual mean) and background concentration (annual mean). For comparison with short term standards the Environment Agency suggest the sum of the process contribution (hourly or daily mean) and twice the background concentration (annual mean). This methodology has been employed in this assessment.



Table 2.5 summarises the pollutant background concentrations adopted for this assessment. Background levels specific to the nature conservation sites considered are obtained from the Air Pollution Information System (APIS - www.apis.ac.uk) and are discussed later. Table 2.5 Background concentrations adopted in the assessment Pollutant Averaging basis Background concentration

µg/m3 % of standard Ambient Air Directive Limit Values and Target Values Carbon monoxide (CO) 8 hour mean 1475 15

Nitrogen dioxide (NO2) 1 hour mean a 20.0 10 annual mean 10.0 25

Sulphur dioxide (SO2) 15 minute meanb 5.9 2 1 hour meana 4.4 1 24 hour meanc 2.6 2

Benzened annual mean 0.29 6 Environmental assessment levels Carbon monoxide hourly meane 2109 7 Benzened hourly meana 0.6 0.3

Nitrogen monoxide (NO) hourly meana 5.0 0.1 annual mean 2.5 0.8

Methane (CH4)f hourly meana 2712 13 annual mean 1356 19

a.One hour mean is determined from annual mean value using a conversion factor of 2.01. b.15 minute mean is determined from the hourly mean using a conversion factor of 1.341. c.24 hour mean is determined from the hourly mean using a conversion factor of 0.591. d.Volatile organic compounds (C6 and above) are assessed against the limit value for benzene in accordance with Environment Agency guidance1. e.One hour mean is determined from 8 hour mean using a conversion factor of 1.431. f. Lower volatile organic compounds (methane, ethane, propane, butane, pentane) are assessed against the limit for methane. 2.5 Assessment criteria The Environment Agency1 provides a methodology for assessing the impact and determining the acceptability of emissions to atmosphere on ambient air quality for human health and nature conservation areas and for deposition to ground. Two stages of assessment are recommended. Screening assessment – based on standard dispersion factors the ambient impact of releases to atmosphere may be estimated. The estimates tend to be very conservative since no account is taken of plume rise, meteorological conditions or the locations of the sensitive receptors where impact is to be assessed. The estimates are compared with the assessment criteria discussed in sections 2.5.1 to 2.5.3. Where a release can be demonstrated to be ‘insignificant’ it may be screened out. Where this is not possible a further detailed assessment is required. Detailed assessment – based on atmospheric dispersion modelling taking into account the factors which influence dispersion and ambient impact (e.g. meteorology, release conditions, locations of sensitive receptors,

http://www.apis.ac.uk/



etc.). Process contributions and predicted environmental concentrations are compared with the same assessment criteria. Where conditions for excluding the release from further consideration cannot be made a detailed cost benefit assessment will be necessary. In this assessment all releases have been assessed using detailed modelling approach only. The criteria considered in this assessment are described below. 2.5.1 Criteria relevant to human health The contribution of the process (PC) to the ambient concentration of a given pollutant is considered insignificant, and requiring no further assessment, if both of the following conditions are met:

the long term PC is less than 1% of the long term environmental standard the short term PC is less than 10% of the short term environmental standard

If these conditions are not met then the corresponding predicted environmental concentration (PEC, PC + background concentration) should be assessed. The process contribution is considered insignificant and requiring no further assessment, if both of the following conditions are met:

the short-term PC is less than 20% of the short term standard minus twice the long term background concentration

the long-term PEC is less than 70% of the long-term environmental standard If these conditions are not met then the compliance of the process with Best Available Technique (BAT) will need to be assessed. No further action is necessary if it can be demonstrated that both of the following apply:

proposed emissions comply with BAT associated emission levels (AELs) or the equivalent requirements where there is no BAT AEL

the resulting PECs won’t exceed environmental standards Failure to meet these criteria requires that a cost-benefit analysis be undertaken for consideration by the Environment Agency. 2.5.2 Criteria for deposition to ground Where any of the substances in Table 2.6 are released it is required that the impact they have when absorbed by soil and leaves (termed ‘deposition’) is assessed. If the PC to ground for any of these substances is below 1% of the limit it is insignificant and requires no further assessment. Where the PC to ground is 1% of the limit or greater a further assessment will be necessary. In this case none of the substances in Table 2.6 are considered to be released in a quantity sufficient to merit an assessment for deposition to ground.

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

https://www.gov.uk/guidance/best-available-techniques-environmental-permits

https://www.gov.uk/guidance/air-emissions-risk-assessment-for-your-environmental-permit#screen-out-insignificant-pecs



Table 2.6 Limits for deposition to ground

Substance Deposition limit (PC to ground)

µg/m2/day Arsenic 0.02 Cadmium 0.009 Chromium 1.5 Copper 0.25 Fluoride 2.1 Lead 1.1 Mercury 0.004 Molybdenum 0.016 Nickel 0.11 Selenium 0.012 Zinc 0.48

2.5.3 Criteria relevant to protected conservation areas Where there are protected conservation areas in the vicinity of the release it is necessary to consider the impact of following pollutants:

nitrogen oxides (long and short term bases) sulphur dioxide (long term basis) ammonia (long term basis) hydrogen fluoride (long and short term bases) nutrient nitrogen and acid deposition

In this case releases of nitrogen oxides and sulphur dioxide are considered, together with their impact in relation to the deposition of nutrient nitrogen and acid.

An assessment is required where the release is within 10 km (15 km if the site is a large electric power station or refinery) of any of the following designated sites:

special protection area (SPA) special area of conservation (SAC) Ramsar site (protected wetland of international importance)

or within 2 km of a:

site of special scientific interest (SSSI) local nature site (ancient wood, local wildlife site (LWS) and national or local nature reserve (NNR, LNR))

If the PC at a SPA, SAC, Ramsar or SSSI meets both of the following criteria, it is insignificant and no further assessment is required:

the short-term PC is less than 10% of the short-term environmental standard for protected conservation areas

the long-term PC is less than 1% of the long-term environmental standard for protected conservation areas



If these criteria are not met then the corresponding PEC should be assessed. The emission is considered insignificant if:

the long term PC is greater than 1% and the corresponding PEC is less than 70% of the long term environmental standard,

If either of the following criteria are met a further more detailed consideration of ecological impact is required:

the long term PC is greater than 1% and the long term PEC is greater than 70% of the long term environmental standard

the short term PC is greater than 10% of the short term environmental standard For local nature sites releases are considered to be insignificant where both of the following criteria are met:

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

A failure to meet the above criteria requires a further more detailed consideration of ecological impact. Environmental standards for conservation areas such as critical levels for ambient air and critical loads for nitrogen and acid deposition are considered to be specific to the habitat types associated with each conservation site. APIS provides acidity and nitrogen deposition critical loads for designated features within every SAC, SPA or A/SSSI in the UK. 2.5.4 Significance of impact Environmental Protection UK (EP UK) and the Institute of Air Quality Management (IAQM) have published guidance on the impact of pollutant releases in the context of existing air quality assessment levels11 (i.e. AAD limit and target values etc.). Their categorisation is shown in Table 2.7.

Table 2.7 Impact descriptor for individual receptors

Long term average concentration at receptor in assessment year

% change in concentration relative to Air Quality Assessment Level (AQAL) 1 2-5 6-10 >10

75% or less of AQAL Negligible Negligible Slight Moderate 76-94% of AQAL Negligible Slight Moderate Moderate 95-102% of AQAL Slight Moderate Moderate Substantial 103-109% of AQAL Moderate Moderate Substantial Substantial 110% or more of AQAL Moderate Substantial Substantial Substantial

In this case impact is considered as the change in the concentration of an air pollutant, as experienced by a receptor. This may have an effect on the health of a human receptor, depending on the severity of the impact and a range of other contributing factors. The descriptor in itself is not considered a measure of effect. IAQM guidance indicates that for any point source some consideration must also be given to the impacts resulting from short term, peak concentrations of those pollutants that can affect health through inhalation. Background concentrations are considered less important in determining the severity of impact for short term concentrations.



Short term concentrations in this context are those averaged over periods of an hour or less. These are exposures that would be regarded as acute and will occur when a plume from an elevated source affects airborne concentrations experienced by a receptor over an hour or less. Where such peak short term concentrations from an elevated source are in the range 10-20% of the relevant AQAL, then their magnitude can be described as small, those in the range 20-50% medium and those above 50% as large. These are the maximum concentrations experienced in any year and the severity of this impact can be described as slight, moderate and substantial respectively, without the need to reference background or baseline concentrations. Table 2.8 summarises these descriptors. Table 2.8 Impact descriptors for short term process contributions

Short term process contribution (% AQAL) Magnitude Severity 11-20 Small Slight 21-50 Medium Moderate >51 Large Substantial

Background concentrations are not unimportant, but they will, on an annual average basis, be a much smaller quantity than the peak concentration caused by a substantial plume and it is the contribution that is used as a measure of the impact, not the overall concentration at a receptor. In most cases, the assessment of impact severity for a proposed development will be governed by the long term exposure experienced by receptors and it will not be a necessity to define the significance of effects by reference to short term impacts. The severity of the impact will be substantial when there is a risk that the relevant AQAL for short term concentrations is approached through the presence of the new source, taking into account the contribution of other prominent local sources.



3 MODELLING METHODOLOGY The contributions to ambient concentrations of the selected pollutant releases from the proposed flaring operations have been modelled using the Atmospheric Dispersion Modelling System (ADMS) version 5.2. The use of this modelling tool is accepted by the Environment Agency and UK Local Authorities for regulatory purposes. ADMS and the United States Environmental Protection Agency’s (US EPA) AERMOD modelling systems are the two most widely used air dispersion models for regulatory purposes worldwide. Both are based on broadly similar principles. In this case ADMS 5.2 has been employed for the assessment, although the results have been compared with those obtained from the same modelling using the AERMOD system in order to provide confidence in the assessment findings. ADMS 5.2 requires a range of information in order to perform the modelling. The primary information required is discussed below. 3.1 Assessment area The area over which the assessment was undertaken is a 2 km x 2 km area with the well site (519250 439090) located approximately at the centre. Figure 3.1 illustrates the location of the site, the surrounding area and nearest residential locations and footpaths. Figure 3.2 illustrates the assessment area, the site layout and the immediate surrounding area A general grid with receptors spaced at 20 m intervals (i.e. 10201 points for a 101 x 101 grid) was used to assess the process contribution to ground level concentrations over the assessment area in Figure 3.2. The grid was considered at an elevation of 1.5 m. This is intended to represent the typical height of human exposure. In addition to the receptor grid, 25 receptors (1 to 8 in Figure 3.2 and 9 to 25 in Figure 3.1) were positioned at residential locations in the vicinity of the well site. These receptors were placed at an elevation of 1.5 m and are described in Table 3.1. These are intended to correspond to the nearest location of most frequent human exposure in the vicinity of the well site. It is also expected that there will be human exposure, although less frequent and of a much shorter duration, along the public footpaths running close the site. In order to monitor the likely impact of well site releases on air quality, 54 receptors were placed, at a height of 1.5m, along the length of the routes as illustrated in Figure 3.1 (green dots). These receptors are described in Annex E. There are a number of tracks in the area which are generally used for farm access and which are not considered to be locations of frequent human exposure where air quality standards for human health would be expected to apply, (as defined in section 2.3.1). These locations are not considered in this assessment. Receptors are also located at the site boundary to determine the maximum off-site process contributions to pollutant concentrations. These receptors are described in Annex E.



Figure 3.1 Location of the West Newton A well site

For the purposes of the assessment the receptors were considered in groups as described below: 1 to 25 Residential locations (see Table 3.1) 26 to 46 Footpath FP1 (see Figure 3.1) 47 to 62 Footpath FP9 (see Figure 3.1) 63 to 79 Footpath FP18 (see Figure 3.1) 80 to 100 Site boundary (see Figure 3.1) Annex E describes the location of these discrete receptors.



Figure 3.2 West Newton A well site layout and assessment area



Table 3.1 Location of residential receptors Receptor (see Figure 3.1)

Positiona Easting

(m) Northing

(m) 1 Caley Cottage 701 m E 519947 439168 2 High Fosham Cottage 743 m E 519991 439142 3 Black Bush 675 m E 519892 439301 4 Marton Farm 779 m W 518481 439216 5 Wood End House 635 m W 518625 438977 6 Church House 535 m SW 518916 438673 7 Old School House 582 m SW 518948 438593 8 White House farm 842 m SW 518618 438534 9 Straits Farm 1082 m N 519571 440124

10 Piper Garth 1046 m W 518214 439235 11 Heywood Farm 1167 m W 518095 439261 12 Treasure Cottage 1307 m W 517952 439248 13 Wood House 1155 m S 519077 437949 14 The Cottage 1174 m S 519367 437922 15 The Crescent 1151 m S 519501 437967 16 Model Farm 1448 m SE 519912 437803 17 Mount Pleasant 1544 m SE 520163 437846 18 Old Farm Cottage 1675 m SE 520352 437829 19 Low Fosham 1657 m E 520878 438786 20 Manor House 1126 m NE 519804 440071 21 East Lambwath Road 1177 m N 519433 440253 22 West Lambwath Road 1418 m N 519292 440508 23 Longdykes Farm 1912 m NW 518325 440764 24 Whitedale Farm 2306 m NW 517744 440838 25 Westlands 2181 m NW 518070 440926 a. Location of the receptor relative to the centre of the West Newton A well site. It is also necessary to consider the impact of releases on any local statutory designated sites. Following a review of all sites in the local area, two conservation sites, met the criteria for assessment (see 2.5.3) as described in Table 3.2. Table 3.2 Location of receptors at nature conservation sites

Receptor Positiona Easting

(m) Northing

(m) 101

Lambwath Meadows SSSI

1.0 km NE 520092 439700 102 1.1 km NE 520242 439657 102 1.6 km E 520789 439643 104 1.7 km E 520946 439500 105 2.0 km E 521200 439353 106 Hornsea Mere SPA 7.0 km N 517983 446004 a. Location of the edge of the habitat closest to the West Newton A well site.



For each nature conservation site discrete receptors were located at the edge of the site closest to the well site as described in Table 3.2. In the case of the Lambwath Meadows SSSI, which is relatively close to the well site, five receptors were used to describe the boundary of the site (see Figure 3.1). 3.2 Buildings The presence of buildings close to a discharge flue can have a significant influence on the dispersion of releases. The most significant impact can be the downwash of a plume around a building causing increased concentrations in the immediate area around the building. Buildings can also disturb the wind flow causing a turbulent wake downwind which can also affect dispersion. It is normally considered that buildings within 5 times the height of release or within 5 times the height of the building should be considered in any modelling. Following a review of site plans provided by Rathlin12, it was concluded that there are no structures within the well site which have a significant influence on dispersion of releases from the proposed flaring. As such the effect of buildings within this assessment is not considered. It is intended that two flares be employed, although these will not operate simultaneously. During the well clean up phase for each zone produced natural gas will be flared using a PW Well Test shrouded ground flare. For the extended well test phases an AEREON CEB 4500 flare, with a somewhat greater design throughput, will be employed for disposal of produced natural gas. Figure 3.2 illustrates the approximate position of the flares (red dot). Table 3.3 describes the release point locations for the two flares considered. Table 3.3 Location of release points

Equipment Height of

releasec (m) Area of release

(m2) Easting

(m) Northing

(m) PW Well Test flare for well clean up activities 12.2 3.1

519250 439091 AEREON CEB 4500 for extended well testing 6.2 7.8

3.3 Meteorology For this modelling assessment hourly sequential meteorological data from the nearest suitable meteorological station to the area was obtained. The data, provided by the UK Met Office, was from the Leconfield station and covered the 5 year period 2013 to 2017. The Leconfield station is around 18 km north west of the West Newton A well site at an elevation of 7 m, compared with the site elevation of around 11 m. The UK Meteorological Office also suggested the Hull Park East station as a possible source of meteorological data: Station Position Elevation Data coverage Hull Park East 11 km SW 2 m Missing cloud and wind data Considering the proximity of the station, elevation and data coverage, it was considered that data from the Leconfield station provided measurements most representative of the conditions around West Newton.



The data included, among other parameters, hourly measurements of wind speed and direction. Figure 3.3 illustrates a composite wind rose for the Leconfield station. It may be seen that the wind has significant westerly and south westerly components. Annex D provides a more detailed analysis of the meteorological data used. Figure 3.3 Composite windrose for the Leconfield station (2013 to 2017)

3.4 Surface characteristics The characteristics of the surrounding surfaces and the land use within the assessment area have an important influence in determining turbulent fluxes and hence the stability of the boundary layer and atmospheric dispersion. In ADMS it is necessary to consider the following parameters which describe land use and surface properties: Surface roughness Surface albedo Minimum Monin Obukhov length Priestley Taylor parameter



3.4.1 Surface roughness

The roughness length represents the aerodynamic effects of surface friction and is physically defined as the height at which the extrapolated surface layer wind profile tends to zero. This value is an important parameter used by meteorological pre-processors to interpret the vertical profile of wind speed and estimate friction velocities which are, in turn, used to define heat and momentum fluxes and, consequently, the degree of turbulent mixing. The surface roughness length is related to the height of surface elements. Typically, the surface roughness length is approximately 10% of the height of the main surface features. Surface roughness is higher in built up areas than in rural locations. A range of typical roughness values for common land use types are provided within ADMS:

Land use

Surface roughness (m)

Ice 0.00001 Snow 0.00005 Sea 0.0001 Short grass 0.005 Open grassland 0.02 Root crops 0.1 Agricultural areas 0.2-0.3 Parkland, open suburbia 0.5 Cities, woodland 1.0 Large urban areas 1.5

The West Newton A well site is located in a rural location largely surrounded by flat agricultural land with the nearest residential location around 530 m to the south west. A surface roughness of 0.3 m has been selected. A sensitivity analysis has been undertaken considering variations in surface roughness of between 0.05 and 0.5 m. This resulted in the following variations in predicted mean and maximum hourly and annual process contributions of nitrogen dioxide over the residential receptors (1 to 25, see Figures 3.1 and 3.2):

Surface roughness (m)

Change (%) in predicted PC of nitrogen dioxide over the residential receptors (1 to 25) compared with base case of a surface roughness of 0.3 m

Mean Maximum Long term Short term Long term Short term

0.05 -34.3 8.8 -34.5 0.9 0.1 -21.6 8.6 -22.0 3.0 0.2 -8.6 4.0 -8.8 2.2 0.4 6.5 -3.6 6.7 -2.6 0.5 11.7 -6.5 12.2 -5.5

It is considered that the selected surface roughness is reasonably representative of the area of influence and tends towards a more conservative estimate of the range likely to be most descriptive of the general assessment area. This selection does not introduce uncertainties which are significant in the context of the conclusions reached in section 4.



3.4.2 Surface albedo The surface albedo is the ratio of reflected to incident shortwave solar radiation at the surface of the earth and lies in the range 0 to 1. This parameter is dependent upon surface characteristics and varies throughout the year. Surface albedo is higher (higher proportion of reflected radiation) when the ground is snow covered. Based on the recommendations of Oke (1987), ADMS provides default values of 0.6 for snow-covered ground and 0.23 for non-snow covered ground, respectively. In this case a value for surface albedo of 0.23 has been employed. 3.4.3 Monin Obukhov length The Monin Obukhov length provides a measure of the stability of the atmosphere and allows for the effect of heat production in cities which may not be represented by the meteorological data. In urban areas heat generated from buildings and traffic warms the air above which has the effect of preventing the atmosphere from becoming very stable. Generally the larger the area the greater the effect. In stable conditions the Monin Obukhov length will not fall below a minimum value with the value becoming larger depending on the size of the city. The minimum value of the Monin Obukhov length generally lies between 1 and 200 m with 1 corresponding to a rural area. ADMS provides the following guidance on minimum Obukhov length:

Population size Minimum Obukhov length (m) Large conurbations (>1 million) 100 Cities and large towns 30 Mixed urban/industrial 30 Small towns 10 Rural area 1

In this case the area is considered to be typical of a rural area. A minimum Monin Obukhov length of 1 m has been employed. A sensitivity analysis has been undertaken considering minimum Monin Obukhov lengths in the range 2 to 20 m. This resulted in the following variations in predicted maximum and mean hourly and annual process contributions of nitrogen dioxide over the residential receptors (1 to 25, see Figures 3.1 and 3.2):

Minimum Monin Obukhov length (m)

Change (%) in predicted PC of nitrogen dioxide over the residential receptors (1 to 25) compared with base case of a minimum Monin Obukhov length of 1 m


2 0 0 0 0 5 0 0 0 0 10 -0.1 0 0 0 15 0 0 0 0 20 0.5 0.1 0 0

The variations are insignificant over the length range considered to be descriptive of the assessment area and not likely to influence the conclusions reached in section 4. AERMOD does require that the minimum Monin Obukhov length be specified.



3.4.4 Priestley Taylor parameter The Priestley Taylor parameter represents the surface moisture available for evaporation. Areas where moisture availability is greater will experience a greater proportion of incoming solar radiation released back to atmosphere in the form of latent heat, leaving less available in the form of sensible heat and, thus, decreasing convective turbulence. The Priestley Taylor parameter lies between 0 and 3. Based on suggestions by Holstag and van Ulden, ADMS provides default values of:

Land type Priestley Taylor parameter Dry bare earth 0 Dry grassland 0.45 Moist grassland 1

In this case the area is considered to be representative of moist grassland and a value of 1.0 for the Priestley Taylor parameter has been employed. A sensitivity analysis has been undertaken considering Priestley Taylor parameters in the range 0 to 1.5. This resulted in the following variations in predicted maximum and mean hourly and annual process contributions of nitrogen dioxide averaged over the residential receptors (1 to 25, see Figures 3.1 and 3.2).

Priestley Taylor parameter

Change (%) in predicted PC of nitrogen dioxide over the residential receptors (1 to 25) compared with base case of a Priestley Taylor parameter of 1


1.5 -16.5 -0.2 -15.3 0.4 0.5 -5.5 -3.6 -4.6 -1.7 0 16.1 -1.3 15.6 1.0

The variations are largely insignificant and not likely to influence the conclusions reached in section 4. It is considered that the use of the model default value (for moist grass land) is likely to be most representative of the area. It may be noted that AERMOD uses the Bowen ratio to describe available surface moisture rather than the Priestley Taylor parameter. The following default values are provided from Paine (1987). Land use Bowen ratio

(-variation with season) Water 0.1 Deciduous forest 0.6-2.0 Coniferous forest 0.6-2.0 Swamp 0.2-2.0 Cultivated land 1.0-2.0 Grassland 1.0-2.0 Urban 2.0-4.0 Desert shrubland 5.0-10.0 For the modelling herein a value of 1.0 was employed for the Bowen ratio.



3.4.5 Terrain Terrain data was obtained for the assessment area from the Ordnance Survey Land-form Panorama DTM data base. There is a very small change in general elevation across the main assessment area. The ground rises towards the south east over the assessment area at an average gradient of less than 1% as shown in Figure 3.4. Figure 3.4 Ground elevation within assessment area

A sensitivity analysis was undertaken to determine the impact of consideration of terrain in the assessment in contrast to the assumption of a flat assessment area. The sensitivity of the predicted annual and hourly process contributions of nitrogen dioxide across the residential receptors (1 to 25, see Figures 3.1 and 3.2) to consideration of terrain was examined as below.

Terrain

Change (%) in predicted PC of nitrogen dioxide over the residential receptors (1 to 25) compared with base case of a flat assessment area

Mean Maximum Long term Short term Long term Mean

Elevated 0.5 0.1 -0.1 0.3 General guidance suggests that consideration of terrain is not necessary at gradients of less than 5%. In this case it is not considered that the difference between a flat and elevated assessment area is likely to have any significant



impact on the assessment outcomes, although for avoidance of doubt an elevated assessment area has been considered in the overall air quality assessment as it appears to provide marginally higher predicted process contributions. This is considered a precautionary approach. 3.5 Pollutant releases and conditions Two flares are proposed for use during the well clean up and flow test phases of the operation. During well clean up a PW Well Services shrouded ground flare is proposed for disposal of up to 2.5 MMscfd of natural gas. For the extended flow test activities a AEREON CEB 4500 flare is proposed with a maximum disposal rate of 3.5 MMscfd of natural gas. The release conditions for each flare have been assessed in Table 3.5, based on the assumed natural gas composition provided by Rathlin12 in Table 3.4. Table 3.34Natural gas composition Parameter Value Methane % v/v 90.06 C2 % v/v 4.39 C3 % v/v 1.07 C4 % v/v 0.44 C5 % v/v 0.20 C6+ % v/v 0.14 Nitrogen % v/v 3.00 Carbon dioxide % v/v 0.69 Total sulphura mg/Nm3 50

Lower heating value MJ/kg 46.4

MJ/Nm3 37.0

Higher heating value MJ/kg 51.5

MJ/Nm3 41.1 a. The National Grid indicate that the total sulphur content of supplied natural gas is less than 50 mg/m3 (www.nationalgrid.com/industry-information/gas-transmission-system-operation/gas-quality). For this assessment a sulphur content in natural gas of 50 mg/m3 has been assumed. Table 3.5 Flare exhaust gas conditions Flare AEREON PW

Disposal rate MMscfd 3.5 2.5 Nm3/s 1.08 0.77

Heat releasea MW 44.6 31.8 Btu/s 42251 30179

Exhaust gas temperatureb oC 1000 1000 Exhaust gas flow rate (actual)c m3/s 96.5 68.9 Flue area m2 7.8 3.1 Velocity m/s 12.4 21.9 Carbon dioxide released g/s 2266 1618 Water vapour released g/s 1760 1278

http://www.nationalgrid.com/industry-information/gas-transmission-system-operation/gas-quality



a. Based on a combustion efficiency of 100%. b. Assumes a radiation loss of 10%. c. Assumes an excess air level of 85%, equivalent to an oxygen content in the exhaust gas of 10.0% by volume, dry basis. d. Determined from gas composition and gas disposal rate. Pollutant releases are estimated in Table 3.6 based on the emission factors for industrial flares published by the US EPA in their AP42 document13. Table 3.6 Pollutant releases from flare operations Flare AEREON PW Disposal rate MMscfd 3.5 2.5 Emission factors (g/MJ heat input)a Organic compounds 0.060 Nitrogen oxides 0.029 Carbon monoxide 0.133 Release rates (g/s) Organic compounds (C6 and above as benzene) 2.68 (0.27) – 0.10 1.92 (0.19) Nitrogen oxides 1.29 (1.29) – 0.34 0.93 (0.92) Carbon monoxide 5.93 (7.11) – 0.19 4.24 (5.08) Sulphur dioxideb 0.108 0.077 Methane (C5 and below as methane) 2.41 1.73 a. Based on higher heating value. b. Based on a total natural gas sulphur content of 50 mg/Nm3. Release rates determined based on the corresponding EMEP-EEA emission factors14 are provided in brackets in the above table. It should be noted that the value for total hydrocarbons refers to the non-methane fraction. In this case a precautionary approach is adopted with the higher of the release rates in each case employed in the assessment. The values in bold for the AEREON flare represent to manufacturers claimed perfromace15. It is noted that these values are substantially lower than releases determined from either AP-42 or EMEP-EEA emission factors. The use of values selected for nitrogen oxides and carbon monoxide for the assessment represent a precautionary approach for the AEREON flare. The release of total hydrocarbons based on AP-42 factors includes the methane and lower hydrocarbon proportions. The EMEP-EEA factor for volatile organic compounds relates to the non-methane fraction. Experience suggests that a significant proportion of the volatile organic compounds emission will be methane and lower hydrocarbons and that that the concentration of higher hydrocarbons (C6 and above) present in the flue gas will generally be representative of the proportion of higher hydrocarbons in the natural gas fuel16. It is considered that the use of the EMEP-EEA emission factor for non-methane organic compounds is reasonably representative of the C6 and above fraction of the releases. The release of C5 and below organic compounds, expressed as methane, is based on the difference between the AP-42 and EMEP-EEA factors.



3.6 Modelling scenarios ADMS 5.2 has been employed to estimate process contributions to ambient pollutant concentrations based on the general conditions specified above. For the initial assessment the model has been run using meteorological data for each of five years (2013 to 2017). Rathlin are unable to fully specify the operating period for the flares, although it is expected that this will be a temporary operation. For the purposes of this assessment a worst case condition is considered where one of the flares will operate at full load continuously year round. It is known that the flares will not operate simultaneously. Year round operation has therefore been considered for the PW flare alone and the AEREON flare alone. The greater of the impact from the two flares will therefore represent the worst case. In addition, sensitivity analyses have been undertaken to look at the impact on air quality of model selection. The US EPA’s AERMOD modelling system is a widely used model for determining the dispersion of releases to air and their subsequent ambient impact and is accepted by the Environment Agency and UK Local Authorities for regulatory purposes. To determine the influence of the model selection, part of the assessment was repeated using the AERMOD model.



4 MODELLING RESULTS ADMS 5.2 has been run for the operating scenarios described in Section 3.6. The results of the modelling are discussed below. In this section results are presented in tabular form, while in Annex A contour plots are provided which illustrate the estimated process contribution to ambient pollutant concentrations over the entire assessment area. The initial part of this assessment is used to determine the maximum air quality impact for each flaring arrangement in order to identify those pollutants which are clearly insignificant in terms of air quality impact and those which may require further assessment. The second part of the assessment then considers in detail the impact of process contributions of selected pollutants at worst case conditions at sensitive locations, where air quality standards are most likely to be applicable, to determine their significance in the context of standard compliance. 4.1 Impact of process releases Tables 4.1 and 4.2 detail the estimated maximum process contributions and corresponding predicted environmental concentrations for operation of the AEREON and PW flares respectively. Table 4.1 Maximum process contributions for operation of the AEREON flare

Pollutant Averaging basis

Process contribution Background Predicted environmental concentration

µg/m3 % of

standard µg/m3 µg/m3

% of standard

Carbon monoxide 8 hour 1126 11.3 1475 2601 26.0

Nitrogen dioxide 1 hour 57.2 28.6 20.0 77.2 38.6 annual 2.2 5.5 10.0 12.2 30.5

Sulphur dioxide 15 min 16.9 6.4 5.9 22.8 8.6 1 hour 12.6 3.6 4.4 17.0 4.9

24 hour 5.3 4.2 2.6 7.9 6.3 Benzene annual 0.7 13.1 0.3 0.9 18.9 Carbon monoxide 1 hour 3378 11.3 2109 5487 18.3 Benzene 1 hour 128 65.8 0.6 129 66.1

Nitrogen monoxide 1 hour 401 9.1 5.0 406 9.2 annual 2.0 0.7 2.5 4.5 1.5

Methane 1 hour 1145 5.3 2712 3857 18.0 annual 5.8 0.1 1356 1362 19.1



Table 4.2 Maximum process contributions for operation of the PW flare

Pollutant Averaging

basis

Process contribution Background Predicted environmental

concentration

µg/m3 % of

standard µg/m3 µg/m3

% of standard

Carbon monoxide 8 hour 82.2 0.8 1475 1557 15.6

Nitrogen dioxide 1 hour 5.1 2.5 20.0 25.1 12.5 annual 0.5 1.4 10.0 10.5 26.4

Sulphur dioxide 15 min 1.3 0.5 5.9 7.2 2.7 1 hour 1.2 0.3 4.4 5.6 1.6

24 hour 0.6 0.5 2.6 3.2 2.6 Benzene annual 0.2 3.2 0.3 0.4 9.0 Carbon monoxide 1 hour 114 0.4 2109 2223 7.4 Benzene 1 hour 4.3 2.2 0.6 4.9 2.5

Nitrogen monoxide 1 hour 13.6 0.3 5.0 18.6 0.4 annual 0.5 0.2 2.5 3.0 1.0

Methane 1 hour 38.8 0.2 2712 2751 12.8 annual 1.5 <0.1 1356 1357 19.0

The reported maximum process contributions in Tables 4.1 and 4.2 represent the process contribution at the location of maximum impact. At all other locations within the assessment area the process contributions are less and in most cases significantly less than those at the location of maximum impact. As illustrated in Figures A.1 to A.4 maximum process contributions occur within the well site boundary and diminish rapidly with distance from the well site. For all pollutants and averaging bases the AEREON flare provides higher maximum process contributions. For sulphur dioxide, nitrogen monoxide and methane all process contributions are considered insignificant based on Environment Agency assessment criteria (i.e. the short term process contribution is less than 10% of the short term environmental standard and where applicable the long term process contribution is less than 1% of the long term environmental standard). In addition, for carbon monoxide the process contributions are less than 20% of the environmental standard less the background concentration and as such may be considered insignificant. The process contributions of sulphur dioxide, nitrogen monoxide, methane and carbon monoxide may be screened out of any further assessment on the basis that they have an insignificant air quality impact. Nitrogen dioxide and benzene cannot be screened out on the basis of their maximum process contributions and require further assessment. It may be noted that the maximum process contributions of nitrogen monoxide and benzene associated with operation of the PW flare (Table 4.2) meet screening requirements. In mitigation, it is expected that neither flare will operate for a significant period in comparison to the long term averaging basis (i.e. a calendar year) and as such long term process contributions are likely to be significant over



estimates. It is recognised however, that the failure to screen out both nitrogen dioxide and benzene is due to their short term process contributions. It is not expected that air quality standards would be applicable within the well site. The closest locations to the well site where frequent human exposure might be expected are the public footpaths and the neighbouring residential areas. Short term air quality standards would be expected to apply on the footpaths, while both long and short term standards are applicable at residential locations. The following sections consider process contributions from flaring at these locations. 4.2 Impact of process releases at the neighbouring public footpaths The nearest location where there is routine access to the general public is the footpaths running to the east of the well site (Footpaths FP 9 and 18 – see Figure 3.1). Discrete receptors were located on these footpaths and others in the area as discussed in section 3.1, in order to determine the air quality impact of pollutant releases from the well site. Table 4.3 summarises the maximum process contributions and predicted environmental concentrations at the footpaths for operation of the PW and AEREON flares. Table 4.3 Maximum process contributions and predicted environmental concentrations at the public footpaths

Pollutant Averaging

basis

Process contribution Predicted environmental

concentration % of standard

PW AEREON PW AEREON Carbon monoxide 8 hour 0.4 0.7 15.2 15.4

Nitrogen dioxide 1 hour 1.4 2.1 11.4 12.1 annual 0.9 1.5 25.9 26.5

Sulphur dioxide 15 min 0.3 0.4 2.5 2.6 1 hour 0.2 0.3 1.4 1.5

24 hour 0.3 0.5 2.4 2.6 Benzene annual 2.2 3.5 8.0 9.3 Carbon monoxide 1 hour 0.1 0.2 7.2 7.3 Benzene 1 hour 0.9 1.4 1.2 1.7

Nitrogen monoxide 1 hour 0.1 0.2 0.2 0.3 annual 0.1 0.2 0.9 1.0

Methane 1 hour 0.1 0.1 12.7 12.8 annual <0.1 <0.1 19.0 19.0

For carbon monoxide, sulphur dioxide, nitrogen monoxide and benzene short term process contributions were less than 10% of the short term environmental standard and where applicable long term process contributions were less than 1% of the long term environmental standard. For both nitrogen dioxide and benzene short term process contributions were less than 20% of the short term environmental standard less the background concentration and long term predicted environmental concentrations were less than 70% of the long term environmental standard.



The maximum process contributions of nitrogen dioxide and benzene at each individual receptor describing the footpaths are presented in Tables E.2 and E.3. For both flares process contributions of all pollutants at the nearby public footpaths are considered insignificant based on Environment Agency assessment criteria and require no further assessment. It is considered unlikely that process contributions from flare operations will have any meaningful influence on air quality standard attainment at the nearest public footpaths. 4.3 Impact of process releases at residential locations In order to determine the impact of well site flaring releases at locations of frequent human exposure discrete receptors were positioned at the residential locations in the vicinity of the West Newton A well site (Table 3.1 and Figures 3.1 and 3.2). These are considered to be the only locations in the vicinity of the well site to which the public normally have access and where human exposure for both the long and short term air quality standard averaging periods is likely. Table 4.4 compares the maximum process contributions over the residential receptor group for operation of the PW and AEREON flares. Table 4.4 Maximum process contributions and predicted environmental concentrations

at the neighbouring residential locations

Pollutant Averaging

basis

Process contribution Predicted environmental

concentration % of standard

PW AEREON PW AEREON Carbon monoxide 8 hour 0.2 0.3 14.9 15.0



24 hour 0.1 0.2 2.2 2.3 Benzene annual 1.1 1.5 6.9 7.3 Carbon monoxide 1 hour 0.1 0.1 7.1 7.1 Benzene 1 hour 0.4 0.6 0.7 0.9


Methane 1 hour <0.1 <0.1 12.7 12.7 annual <0.1 <0.1 19.0 19.0

For carbon monoxide, nitrogen dioxide, sulphur dioxide, nitrogen monoxide and benzene short term process contributions were less than 10% of the short term environmental standard and where applicable long term process contributions were less than 1% of the long term environmental standard. For benzene short term process contributions were less than 20% of the short term environmental standard less the background concentration and long term predicted environmental concentrations were less than 70% of the long term environmental standard.



The maximum process contributions of nitrogen dioxide and benzene at each individual residential receptor are presented in Tables E.2 and E.3. For both flares process contributions of all pollutants at the neighbouring residential locations are considered insignificant based on Environment Agency assessment criteria and require no further assessment. It is considered unlikely that process contributions from flare operations pose a significant risk to, or have any meaningful influence on, air quality standard attainment at the nearest residential locations. Table 4.5 summarises the assessment of the environmental significance of the impact of maximum long term pollutant contributions from flaring operations in the context of IAQM descriptors (see section 2.5.4) at the neighbouring residential locations. Table 4.5 Significance of the air quality impact of process contributions at residential locations

Substance Process contribution

Predicted environmental concentration IAQM descriptor

% of long term environmental standard

NO2 0.6 26 Negligible Benzene 1.5 7 Negligible NO 0.1 1 Negligible

Methane <0.1 19 Negligible The significance of the impact of the maximum process contributions of the substances considered is classed as ‘negligible’ at the nearest residential locations. 4.4 Impact of process releases at sensitive nature conservation sites Two statutory designated sites requiring assessment, based on Environment Agency criteria (see section 2.5.3), were identified in the vicinity of the West Newton A well site as discussed in section 3.1. The main pollutants of interest at these sites are nitrogen oxides, nitrogen dioxide and sulphur dioxide. For the purposes of the assessment of process contributions at these sites discrete receptors were placed on each site boundary closest to the well site as described in Table 3.2. The critical loads and levels adopted for these sites for use in this assessment have been obtained from the UK Air Pollution Information System (APIS) and are summarised in Table 4.6. In the selection of critical loads the minimum for the most sensitive habitat within each site has been selected. Where the nitrogen critical load is provided as a range the minimum in that range has been adopted for the assessment. This represents a worse case precautionary approach to the assessment and will most likely result in an overestimate of impact. The background concentrations at each site, as obtained from APIS, are summarised in Table 4.7. These represent the maximum background concentration across the entire site and as such there will be parts of these sites which experience somewhat lower background concentrations. This represents precautionary approach.



Table 4.6 Site relevant critical loads and levels Site Lambwath Meadows SSSI Hornsea Mere SPA Critical levels for nitrogen oxides and sulphur dioxide (see Table 2.2) Annual mean NOx µgNO2/m3 30 Daily mean NOx µgNO2/m3 75 Annual mean SO2 µgSO2/m3 10 Critical load for nitrogen deposition Most sensitive habitat Neutral grassland Standing open water and canalsb

N deposition CL kgN/ha/y 20-30 5-10 Critical loads for acid deposition Most sensitive habitat Neutral grassland Standing open water and canalsb

Minimum CLminN keq 0.438 0.321 Minimum CLmaxS keq 1.570 0.157 Minimum CLmaxN keq 2.800 0.478 a. Critical levels and critical loads are the minimum specified for most sensitive habitat within the site. b. Although sensitive to nitrogen and acid deposition critical loads were not specified for Hornsea Mere SPA. For the purposes of the assessment the critical loads typical of a standing and open water and canals habitat have been selected. Table 4.7 Site relevant background concentrations Site Lambwath Meadows SSSI Hornsea Mere SPA Nitrogen oxides annual mean µgNO2/m3 13.47 12.70 Sulphur dioxide annual mean µgSO2/m3 0.68 0.71 Nitrogen deposition kgN/ha/y 23.8 12.32 Nitrogen acid deposition keq/ha y 1.7 0.88 Sulphur acid deposition keq/ha y 0.3 0.28 a. Background concentrations are the maximum across the entire site. Process contributions at the these sites were greatest with operation of the AEREON flare and as such the following assessment is undertaken assuming a full calendar year’s operation of the AEREON flare operating continuously at its maximum disposal rate. In practice this is considered a significant over estimate of both natural gas disposal and operational duration. The maximum process contributions to concentrations of nitrogen oxides and sulphur dioxide at the conservation sites are summarised in Table 4.8.



Table 4.8 Maximum process contributions of nitrogen oxides and sulphur dioxide at the conservation sites Site Lambwath Meadows SSSI Hornsea Mere SPA Nitrogen oxidesa

Maximum annual mean PC µgNO2/m3 0.1666 0.0085

% CL 0.6 <0.1 Background concentration µgNO2/m3 13.47 12.70

Maximum annual mean PEC µgNO2/m3 13.63 12.71

% CL 45 42

Maximum daily mean PC µgNO2/m3 1.54 0.16

% CL 2.0 0.2 Back ground concentration µgNO2/m3 26.9 25.4

Maximum daily mean PEC µgNO2/m3 28.4 25.6

% CL 39 34 Sulphur dioxide

Maximum annual mean PC µgSO2/m3 0.0139 0.0007

% CL 0.1 <0.01 Background concentration µgSO2/m3 0.68 0.71

Maximum annual mean PEC µgSO2/m3 0.69 0.71

% CL 7 7 a. Total nitrogen oxides are expressed as NO2.

At both sites process contributions of nitrogen oxides and sulphur dioxide are less than 1% of the applicable critical levels and as such are considered insignificant. The determination of nitrogen deposition at the selected nature conservation sites is summarised in Table 4.9. The determination was undertaken in accordance with the guidance in AQTAG 0618 and considered dry deposition only. Guidance indicates that wet deposition over relatively short distances is unlikely to be significant.

Table 4.9 Nitrogen deposition at the conservation sites Site Lambwath Meadows SSSI Hornsea Mere SPA

Maximum process N deposition µgNO2/m2/sa 0.00035 0.00002

kgN/ha/y 0.034 0.002 % CLb 0.17 0.03

Back ground concentration kN/ha y 23.80 12.32

Maximum annual mean PEC kN/ha y

% CLb 23.97 12.35 119 246

a. Determination of deposition is based on the deposition velocity for forest terrain18. b. The critical load selected is the minimum of the range specified for the most sensitive habitat over the entire site. The process contribution to nutrient nitrogen deposition at the both sites is less than 1% the applicable critical load and is therefore considered insignificant. While there is exceedance of the critical loads at these sites, this is due to an existing large background deposition and it is not considered that process contributions from well site flaring operations have any significant influence on critical load compliance.



The determination of the process contribution to acid deposition at these sites is summarised in Table 4.10 Table 4.10 Acid deposition at conservation sites Site Lambwath Meadows SSSI Hornsea Mere SPA

Nitrogen acid deposition µgNO2/m2/sa 0.00035 0.00002

kgN/ha/y 0.034 0.002 keq/ha y 0.0024 0.0001

Sulphur acid deposition µgSO2/m2/sa 0.00034 0.00002

kgS/ha/y 0.0528 0.0027 keq/ha y 0.0033 0.0002

Total process acid deposition keq/ha/y 0.0057 0.0003

% CLb,c 0.20 0.06 Total background acid deposition keq/ha/y 2.00 1.16

Maximum annual mean PEC keq/ha y 2.01 1.16

% CLb,c 72 243 a. Determination of deposition is based on the deposition velocity for forest terrain18. b. Calculations of process contribution and predicted environmental concentrations were undertaken using the APIS critical load tool. c. The critical loads selected are the minimum specified for all habitats over the entire site. The process contributions to acid deposition at both sites are less than 1% of the applicable critical loads and as such are considered insignificant. While there is exceedance of the critical load at the Hornsea Mere SPA, this is due to an existing large background deposition and it is not considered that the process contribution from well site flaring has any significant influence on critical load compliance. At the sites sensitive to nitrogen and acid deposition maximum process contributions are considered to be insignificant in relation to the applicable critical levels and critical loads. 4.5 Sensitivity analyses In the assessment of the impact of process contributions the worst case results have been reported. For the assessment process contributions were modelled for each of 5 years’ meteorological data using the ADMS modelling system. A sensitivity analysis was undertaken to determine the influence of meteorological conditions and model selection on the findings of the assessment and hence provide some measure of their robustness. 4.5.1 Meteorological conditions Table 4.11 summarises the influence of meteorological conditions on maximum process contributions for the discrete receptor groups describing the neighbouring residential locations, the local footpaths, the well site boundary and ecological conservation sites (see Annex E).



Table 4.11 Influence of meteorological conditions on maximum process contribution

Pollutant Averaging

basis

Maximum process contribution (ratio of maximum to minimum year)

Residential Footpaths Well site boundary

Conservation sites

Carbon monoxide 8 hour 1.3 1.1 2.9 1.1



24 hour 1.9 1.4 3.0 1.4

PM10 24 hour 2.2 1.4 2.7 1.5 annual 1.1 1.0 4.0 1.0

PM2.5 annual 1.1 1.0 4.0 1.0 Benzene annual 1.1 1.0 4.0 1.0 Carbon monoxide

1 hour 2.2 1.4 2.7 1.5

Benzene 1 hour 1.1 1.0 4.0 1.0


Annual variations in meteorological conditions show up to a fourfold difference between maximum and minimum process contributions for locations around the site boundary. This reduces for locations which are further from the site (i.e. residential locations). This assessment is based on the maximum process contribution for all the years considered at each location and as such will be an over estimation for most years. 4.5.2 Model selection The main assessment has been undertaken using the ADMS modelling system. The US EPA’s AERMOD model is also widely used for regulatory purposes worldwide. To determine how the model used may have influenced the findings of the assessment, the AERMOD model was employed to predict process contributions for operation of the AEREON flare over the important averaging bases at 2013 meteorological conditions. Table 4.12 illustrates the comparison between the ADMS and AERMOD model predictions for important averaging bases over the receptor groups. Table 4.12 Maximum process contributions (variation with model)

Pollutant Averaging

basis

Maximum process contribution (ratio of ADMS to AERMOD - 2013)

Residential Footpaths Lambwath

Meadows SSSI Hornsea Mere

SPA Carbon monoxide 8 hour 1.2 1.9 1.2 0.9


Sulphur dioxide 24 hour 2.5 4.1 1.3 1.0

In general the AERMOD model provides a somewhat lower predicted ambient process contribution compared with ADMS for receptor groups which are reasonably close to the well site. At more distant receptors (i.e. Hornsea Mere



SPA) there is good agreement between the two models Bearing in mind the margin available in the assessment of air quality standard compliance and the maximum impact relative to critical loads and levels at the ecological receptors, it is not considered that the differences exhibited due to model selection will have any substantial impact on the conclusions of this assessment. In most cases model predictions from the ADMS model employed in this assessment are greater than the corresponding predicted process contributions from AERMOD. 4.6 Modelling uncertainty The use of models to predict the dispersion of releases has associated uncertainties. The main uncertainties in this assessment result from: It is assumed that each flare will operate at its maximum design disposal rate. In practice the disposal rate is

likely to be significantly lower on occasions than that modelled in this assessment. The assessment is also based on continuous flare operation over a calendar year. In practice the duration of flaring will be substantially less. This provides what is considered to be a significant over estimate of process releases in practice. As such the process contributions and subsequent ambient impact for all pollutants are likely to be an overestimate of those in practice, in particular for those assessed over the long term averaging bases.

The release rates upon which the assessment is based are consistent with the operation of flares at accepted

generic emission rates. It is claimed that the AEREON flare will operate significantly more efficiently than suggested by standard emission factors (see Table 3.6). In practice it is therefore likely that pollutant release rates will be somewhat lower, and in some cases substantially lower, than the levels assumed in this assessment. This will result in an overestimate of ambient impact.

Conversion rates for nitrogen monoxide to nitrogen dioxide of 35% and 70% have been employed as recommended by the Environment Agency1 for short and long term air quality impacts respectively. These are generally considered to be quite conservative estimates. Conversion rates over the relatively short distances considered in this assessment are likely to be substantially lower than those assumed with estimates based on the Janssen equation17. This indicates a likely overestimate of the significance of process releases (see Annex C and Table E.1) of nitrogen dioxide and associated nitrogen and acid deposition.

The meteorological conditions upon which the assessment was based vary from year to year and influence

ambient impact. A sensitivity analysis has shown the differences expected due to changes in meteorological conditions for a five year period. This assessment is based on the year providing the maximum impact for each location and pollutant and as such is likely to be an overestimate for most meteorological years.

The model used can influence predictions of ambient impact. In this case a sensitivity analysis of the two most

widely used models for regulatory purposes indicated that the conclusions of the assessment were not dependent on the selection of model. The ADMS model employed for this assessment provides a somewhat higher predicted ambient impact compared with AERMOD for most of the important locations neighbouring the well site. It is considered that model selection has no significant influence on the overall outcome of the assessment.

The necessary assumptions made regarding surface characteristics (section 3.4) can have either a negative or positive impact on modelling outcomes. A sensitivity analysis indicates that variations due to the assumed surface characteristics are unlikely to be significant in terms of the conclusions of the assessment. The potential for any impact is mitigated by the selection of descriptive parameters considered representative of the assessment area.



There are inherent uncertainties associated with the use of air dispersion models to predict the ambient impact of releases. With this in mind the assessment herein has been undertaken using conservative assumptions which tend towards an over estimation of the ambient impact. It is considered that the assessment has taken a precautionary approach and the conclusions reached therefore incorporate a reasonable margin of comfort in spite of the inevitable uncertainty of such modelling studies.



5 CONCLUSIONS Rathlin Energy UK Limited propose to develop an existing well site, known as the West Newton A, by drilling a new borehole and flow testing two zones. The drilling of the well is covered by an existing environmental permit, although a variation will be required to enable the disposal of any produced natural gas by flaring. As part of the permit variation process the dispersion of releases to atmosphere associated with the proposed temporary flaring at the West Newton A well site will need to be assessed to determine their impact on ambient concentrations of important pollutants around the local area. The main source of pollutant releases during flaring will be from the combustion of any produced natural gas. This assessment considered releases of nitrogen oxides, carbon monoxide, volatile organic compounds and sulphur dioxide. The assessment was undertaken using the UK ADMS 5.2 modelling system Maximum pollutant process contributions from the proposed flaring operations occur within the well site boundary. Maximum process contributions of nitrogen dioxide and benzene exceeded the Environment Agency’s screening criteria, although all other pollutants considered were determined to be insignificant with respect to air quality impact. It is not considered that statutory air quality standards would be applicable within the well site boundary. Beyond the location of the maximum process contributions reduce significantly with distance Along the public footpaths, some of which run close to the well site boundary, it might be expected that short term environmental standards would apply in view of the potential frequent, but short term, human exposure. All short term process contributions at the nearest footpaths are considered insignificant based on Environment Agency assessment criteria and are considered unlikely to pose any threat to continued attainment of the applicable ambient air quality standards. At the neighbouring residential locations, where frequent and long term human exposure might be expected, all pollutant process contributions were considered insignificant based on Environment Agency assessment criteria and unlikely to threaten, or have any meaningful influence on, ambient air quality standard attainment. The air quality impact significance of flaring operations, based on Institute of Air Quality Management descriptors, is classed as ‘negligible’ at all neighbouring residential locations for all pollutants. At local conservation sites sensitive to nitrogen and acid deposition (Lambwath Meadows site of special scientific interest and Hornsea Mere special protection area) maximum process contributions are considered to be insignificant based on Environment Agency assessment criteria and considered unlikely to pose any threat to, or have any substantial influence on, the attainment of critical levels and critical loads. It is concluded that pollutant releases from the proposed natural gas flaring are unlikely to pose any substantial risk to, or have any significant influence on, the attainment of environmental standards in the vicinity of the West Newton A well site. Necessary assumptions made to undertake the modelling are considered to have the effect of substantially overestimating the process contribution to ambient concentrations. It is considered that the predicted process impact reported herein is a conservative assessment and the conclusions reached therefore incorporate a reasonable margin of comfort in spite of the inevitable uncertainty of such modelling studies.



6 REFERENCES

1. Environment Agency and Department for Environment Food and Rural Affairs, Risk assessment for specific activities, environmental permits, Environmental Management guidance: Air emissions risk assessment for your environmental permit, 2 August 2016 (www.gov.uk/guidance/air-emissions-risk-assessment-for-your-environmental-permit#environmental-standards-for-air).

2. Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air

quality and cleaner air for Europe. 3. Directive 2004/107/EC of the European Parliament and of the Council of 15 December 2004 relating to

arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air.

4. SI 2010:1001, Environmental Protection, The Air Quality Standards Regulations 2010. 5. Institute for Occupational Safety and Health, International Chemical Safety Card 0291, 22 July 2015. 6. Environment Agency, “Horizontal guidance note H1 – Annex (f) Air Emissions”, version 2.2, December 2011

(withdrawn 1 February 2016). 7. Health and Safety Executive, EH40/2005 Workplace exposure limits, March 2013. 8. East Riding of Yorkshire Council, 2018 air quality annual status report, June 2018. 9. British Geological Survey, Air quality and greenhouse gas monitoring in the Vale of Pickering, 2018

(http://www.bgs.ac.uk). 10. Environment Agency, UK Air Pollutants – Key Factors and monitoring data, Report SC 030174, April 2006.

11. EP UK & IAQM, Land use planning development and control: planning for air quality, January 2017. 12. Private communication, email S Smart (Zetland Group) to N Ford (SOCOTEC), dated 5 November 2018. 13. ‘Compilation of Air Pollutant Emission Factors’, Volume 1, 5th Edition, January 1995, United States

Environmental Protection Agency. 14. EMEP/EEA, Emissions inventory guidebook 2016, 30 September 2016. 15. AEREON, Product specification, enclosed combustion systems CEB 4500. 16. National Environmental Research Institute, Emissions from Decentralised CHP plants 2007, Project 5 report

– Emission factors and emission inventory for decentralised CHP production, NERI Technical report 786, 2010.

17. Janssen LHJM, Van Wakeren JHA, Van Duuren H and Elshout A J, 1988, A classification of NO oxidation

rates in power plant plumes based on atmospheric conditions, Atmospheric Environment, 22, 43-53.

http://www.gov.uk/guidance/air-emissions-risk-assessment-for-your-environmental-permit#environmental-standards-for-air

http://www.gov.uk/guidance/air-emissions-risk-assessment-for-your-environmental-permit#environmental-standards-for-air

http://www.bgs.ac.uk/



18. AQTAG 06, Technical Guidance on Detailed Modelling Approach for an Appropriate Assessment for

Emissions to Air, Environment Agency Air Quality Monitoring and Assessment Unit, 20th April 2010.



Annex A Dispersion modelling contour plots The results of the modelling of the impact of pollutant releases from the proposed flaring operations on local ambient ground level concentrations are presented in tabular form in Section 4. In Annex A examples of the long term and short term dispersion pattern for nitrogen dioxide and benzene, the most significant pollutants with regard to air quality impact, are presented for operation of the AEREON flare. The AEREON flare has the larger disposal rate and provides the greatest air quality impact across the assessment area. The results relate to modelling of site operation under the conditions (operational arrangement and meteorological year) which provide the maximum process contributions. All results are presented as the maximum contribution of the process (excluding existing background concentrations), expressed as a percentage of the applicable ambient air directive limit or environmental assessment level as appropriate. The plots are considered over an area of 2 km x 2km which includes the immediate area around the West Newton A well site and the nearest residential neighbours. For presentational purposes some plots feature contours below 1% and 10% of long term and short term air quality standards respectively. Values below these levels are generally considered to be insignificant in terms of air quality impact. The following figures are presented: Figure 1 Predicted maximum process contributions of nitrogen dioxide (AAD limit 99.8 percentile of 1 hour means – 2015) Figure 2 Predicted maximum process contributions of nitrogen dioxide (AAD limit annual mean - 2015) Figure 3 Predicted maximum process contributions of benzene (EAL limit hourly mean – 2017) Figure 4 Predicted maximum process contributions of benzene (AAD limit annual mean - 2015)



Figure 1 Predicted maximum process contributions of nitrogen dioxide (AAD limit 99.8 percentile of 1 hour means – 2015)



Figure 2 Predicted maximum process contributions of nitrogen dioxide (AAD limit annual mean - 2015)



Figure 3 Predicted maximum process contributions of benzene (EAL limit hourly mean – 2017)



Figure 4 Predicted maximum process contributions of benzene (AAD limit annual mean - 2015)



ANNEX B Model input data The input data used in the current assessment have been provided under separate cover. Electronic files containing the input data used in the modelling of the maximum process contributions of all pollutants considered have been provided as detailed below: Carbon monoxide (CO) 8 hour mean WNA AER 2014.APL

Nitrogen dioxide (NO2) 1 hour mean WNA AER 2015.APL annual mean WNA AER 2015.APL

Sulphur dioxide (SO2) 15 minute mean WNA AER 2015.APL 1 hour mean WNA AER 2015.APL 24 hour mean WNA AER 2015.APL

Benzene annual mean WNA AER 2015.APL Carbon monoxide hourly mean WNA AER 2017.APL Benzene hourly mean WNA AER 2015.APL

Nitrogen monoxide (NO) hourly mean WNA AER 2017.APL annual mean WNA AER 2015.APL

Methane hourly mean WNA AER 2017.APL Methane annual mean WNA AER 2015.APL



ANNEX C Conversion of nitrogen monoxide to nitrogen dioxide The majority of oxides of nitrogen released will be in the form of nitrogen monoxide. While conversion to nitrogen dioxide will occur in the atmosphere it is unlikely that all of the nitrogen oxides in the flue emission will be in the form of nitrogen dioxide at ground level. It may be noted that for this type of assessment the Environment Agency1 recommend that conversion rates of 35% and 70% be considered for short and long term air quality impacts respectively. These are considered quite conservative estimates. These conversion rates have been used in this assessment and represent a precautionary approach which will, it is considered, significantly over estimate the process contribution to ground level concentrations of nitrogen dioxide at most locations and as such provide a reasonable margin of headroom which should go some way to offsetting the inevitable uncertainties associated with this type of assessment and the necessary modelling assumptions. There are methodologies available which enable a more representative estimation of conversion rates at specific locations, largely based on distance from the point of release. Based on a study of Dutch power station plumes, Janssen et al18 determined an approximate relationship between the conversion of NO to NO2 and the distance from the point of release as below:

2 1 x

x

NOA e

NO

where A is the ozone parameter describing the oxidation of NO to NO2 in the presence of ozone and the photolysis

of NO2 by sunlight to reform NO. α is the wind parameter which expresses conversion rates in respect of downwind distance based on wind speed at plume height and ozone concentration. x is the downwind distance (km)

The values of A and α depend on ozone concentration, incoming solar radiation and wind speed. Janssen developed empirical values for these based on seasonal measurements of conditions in the Netherlands. It is assumed that a similar relationship is applicable in the UK. Janssen proposed the following seasonal values for A and α: Winter (December to February)

Background ozone concentration (ppb)

Wind speed at plume height (m/s) 0-5 5-15 >15

A α A α A α 0-10 0.49 0.05 0.49 0.05 0.49 0.05 10-20 0.74 0.07 0.74 0.07 0.74 0.07 20-30 0.83 0.07 0.83 0.07 0.83 0.10 30-40 0.87 0.07 0.87 0.07 0.87 0.15



Spring/Autumn (March to May and September to November)



A α A α A α 10-20 0.635 0.10 0.635 0.10 0.635 0.10 20-30 0.74 0.10 0.74 0.10 0.74 0.15 30-40 0.80 0.10 0.80 0.10 0.80 0.25 40-60 0.85 0.10 0.85 0.15 0.85 0.30 Summer (June to August)



A α A α A α 20-30 0.67 0.10 0.67 0.10 0.67 0.10 30-40 0.74 0.10 0.74 0.15 0.74 0.25 40-60 0.81 0.15 0.81 0.25 0.81 0.35 60-120 0.88 0.20 0.88 0.35 0.88 0.45 120-200 0.93 0.40 0.93 0.65 0.93 0.80 Janssen indicates that ‘the method presented therefore proved to be highly suitable to predict NO2/NOx ratios in power plant plumes under widely varying atmospheric conditions’. An assessment of the meteorological data for the Leconfield station over the period employed in this assessment (2013 to 2017) indicated the following seasonal distribution of wind speed.

Season Frequency in wind speed category (%) Mean wind

speed (m/s) 0-5 m/s 5-15 m/s >15 m/s Winter 61.3 38.6 0.1 4.6 Spring/Autumn 71.8 28.2 0.0 3.8 Summer 78.7 21.3 0.0 3.5 Seasonal wind speed

0-5

5-15

>15

0

10

20

30

40

50

60

70

80

WinterSpring/Autumn

Summer

Freq

uenc

y (%

)

The wind speed is largely below the 15 m/s category for all seasons, with an overall average of 3.9 m/s.



The nearest automatic station monitoring station which includes measurement of ozone is the Hull Freetown station (UKA00450) which is located around 14 km south west of West Newton (509482 429322). An analysis of hourly average data for 2017 indicated the following seasonal concentrations:

Season Frequency in ozone concentration category (%)

Mean 0-10 10-20 20-30 30-40 40-60 60-120 120-200

ppb Winter 31.3 27.2 26.0 13.8 1.7 0.0 0.0 17.3 Spring/Autumn 12.8 23.8 31.2 24.4 7.8 0.0 0.0 24.0 Summer 6.9 30.3 39.7 19.8 3.3 0.0 0.0 23.2 Seasonal ozone concentration

0

5

10

15

20

25

30

35

40

45

10 20 30 40 60 120 200

Freq

uenc

y (%

)

Ozone concentration (ppb)

Winter Spring/Autumn Summer

Based the values of wind speed and ozone concentration and Janssen’s empirical relationship, it is considered that the following seasonal values for the parameters A and α are appropriate:

Season Wind speed

(m/s) Ozone

concentration (ppb) A α

Winter 5-15 10-20 0.74 0.07 Spring/Autumn 5-15 20-30 0.74 0.10 Summer 5-15 20-30 0.67 0.10 It is likely that a small amount of the nitrogen oxides emitted will be in the form of nitrogen dioxide. For the purposes of this assessment it is assumed that 10% of nitrogen oxides comprise nitrogen dioxide and as such Janssen’s relationship for this situation is described by:



2 (1 ) 1 x

x

NOy y A e

NO

where y is the fraction of nitrogen oxides present as nitrogen dioxide at the point of release. Based on Janssen’s relationship the following seasonal conversion rates are estimated with distance from the source.

Estimated seasonal NO to NO2 conversion rates

0

5

10

15

20

25

0 200 400 600 800 1000 1200 1400 1600 1800 2000

% c

onve

rsio

n of

NO

to N

O2

Distance from release point (m)

Winter Spring/Autumn Summer

The conversion rates expected for locations within 1 km of the source are significantly less than those assumed within the assessment.



ANNEX D Meteorological data For this modelling assessment hourly sequential meteorological data provided by the UK Met Office from the Leconfield station was employed and covered the 5 year period 2013 to 2017. Further details of the data employed are provided in this section. D.1 Windroses In section 3.3 a cumulative wind rose for the period 2013 to 2017 is presented. The windroses for each individual year of data used are illustrated below. Figure D.1 Leconfield 2013



Figure D.2 Leconfield 2014




D.2 Data analysis and characteristics

Analyses of the wind direction, wind speed and precipitation are summarised in Tables D.1 and D.2 for the period 2013 to 2017. Table D.1 Wind speed and direction (2013 to 2017) for Leconfield

Wind direction blowing from

Wind speed (m/s) 0.3-2.1 2.1-3.6 3.6-5.7 5.7- 8.8 8.8-11.1 > 11.1 Total

Frequency (% of time) N 2.5 2.8 2.1 1.0 0.1 0.0 8.4 NE 1.5 2.2 2.6 1.2 0.1 0.0 7.6 E 1.9 2.6 3.0 1.1 0.1 0.0 8.8 SE 1.8 1.9 1.8 0.5 0.0 0.0 5.9 SE 2.5 4.3 5.0 2.9 0.3 0.1 15.1 SW 2.0 4.3 6.9 6.2 1.1 0.4 20.9 W 3.6 6.8 8.3 6.1 0.8 0.2 25.7 NW 2.4 2.1 2.1 0.8 0.0 0.0 7.4 Calm 0.2 a. Missing data is ignored from the determination of percentage frequency Table D.2 Rainfall and wind direction (2013 to 2017) for Leconfield

Wind direction Blowing from

Rain fall (mm/h) Dry 0.1-0.3 0.3-0.6 0.6-0.9 0.9-1.2 1.2-1.5 >1.5

Frequency (% of time) N 7.3 0.4 0.3 0.1 0.1 0.0 0.2 NE 6.8 0.3 0.2 0.1 0.1 0.0 0.1 E 8.1 0.3 0.2 0.1 0.1 0.0 0.1 SE 5.1 0.3 0.2 0.1 0.1 0.0 0.2 SE 13.2 0.7 0.6 0.1 0.2 0.1 0.2 SW 19.4 0.7 0.4 0.1 0.1 0.0 0.2 W 24.5 0.5 0.3 0.1 0.1 0.0 0.2 NW 6.7 0.3 0.2 0.1 0.1 0.0 0.1 Calm 0.3 0.0 0.0 0.0 0.0 0.0 0.0 Total 91.2 3.4 2.4 0.7 0.8 0.3 1.2 a. Missing data is ignored from the determination of percentage frequency. The main data characteristics are summarised in Table D.3.



Table D.3 Dataset characteristics (2013 to 2017) for Leconfield No. days data 1826 No. hours data 43824 No. calm hours (<0.3 m/s) 84 0.19 % No. dry hours (<0.1 mm/h) 39960 91.26 % Mean wind speed (m/s) 3.9 No. missing records 38 0.09 % Available records 43786 99.91 %



ANNEX E Discrete receptors

Discrete receptors were used to monitor the process contribution to ambient pollutant concentrations at a range of locations including the footpaths near to the site and the site boundary as illustrated in Figure 3.1. Details of their location are provided in Table E.1, together with the predicted nitrogen monoxide to nitrogen dioxide conversion rate (see Annex C). All receptors were at an elevation of 1.5 m, except for those at the conservation sites (101 to 106) which are at ground level (0m). The locations of the residential receptors are included for completeness. The receptors fall into the following groups: 1 to 25 Residential locations (see Table 3.1) 26 to 46 Footpath FP1 (see Figure 3.1) 47 to 62 Footpath FP9 (see Figure 3.1) 63 to 79 Footpath FP18 (see Figure 3.1) 80 to 100 Site boundary (see Figure 3.1) 101 to 105 Lambwath Meadows SSSI (see Table 3.2) 106 Hornsea Mere SPA (see Table 3.2) Table E.1 Receptor locations


(m) Northing

(m) NO to NO2 conversion

rate (%) 1 701 m E 519947 439168 14.5 2 743 m E 519991 439142 14.8 3 675 m E 519892 439301 14.3 4 779 m W 518481 439216 15.0 5 635 m W 518625 438977 14.1 6 535 m SW 518916 438673 13.5 7 582 m SW 518948 438593 13.8 8 842 m SW 518618 438534 15.4 9 1082 m N 519571 440124 16.8

10 1046 m W 518214 439235 16.6 11 1167 m W 518095 439261 17.3 12 1307 m W 517952 439248 18.2 13 1155 m S 519077 437949 17.3 14 1174 m S 519367 437922 17.4 15 1151 m S 519501 437967 17.2 16 1448 m SE 519912 437803 19.0 17 1544 m SE 520163 437846 19.5 18 1675 m SE 520352 437829 20.3 19 1657 m E 520878 438786 20.2 20 1126 m NE 519804 440071 17.1 21 1177 m N 519433 440253 17.4 22 1418 m N 519292 440508 18.8



Table E.1 continued


(m) Northing


rate (%) 23 1912 m NW 518325 440764 21.6 24 2306 m NW 517744 440838 23.7 25 2181 m NW 518070 440926 23.1 26 553 m W 518713.6 439225 13.6 27 553 m W 518731.2 439283.6 13.6 28 567 m NW 518742.9 439345.1 13.7 29 584 m NW 518760.4 439409.5 13.8 30 612 m NW 518775.1 439476.9 14.0 31 634 m NW 518804.4 439541.4 14.1 32 643 m NW 518845.4 439591.1 14.1 33 650 m NW 518895.2 439635.1 14.2 34 674 m NW 518936.2 439687.8 14.3 35 703 m N 518988.9 439743.5 14.5 36 736 m N 519021.1 439790.3 14.7 37 747 m N 519021.1 439802.1 14.8 38 797 m N 518994.8 439846 15.1 39 823 m N 519050.4 439889.9 15.3 40 847 m N 519100.2 439925.1 15.4 41 876 m N 519167.6 439963.2 15.6 42 910 m N 519237.9 440001.2 15.8 43 958 m N 519299.4 440048.1 16.1 44 1001 m N 519355.1 440086.2 16.3 45 1053 m N 519422.4 440130.1 16.7 46 1091 m N 519469.3 440159.4 16.9 47 1034 m N 519484 440097.9 16.5 48 971 m N 519504.5 440027.6 16.2 49 923 m N 519516.2 439974.9 15.9 50 879 m N 519536.7 439922.1 15.6 51 812 m N 519542.5 439848.9 15.2 52 752 m NE 519554.3 439778.6 14.8 53 697 m NE 519557.2 439717.1 14.5 54 648 m NE 519577.7 439649.7 14.2 55 597 m NE 519589.4 439582.4 13.9 56 562 m NE 519601.1 439529.6 13.6 57 520 m NE 519574.8 439497.4 13.4 58 474 m NE 519516.2 439482.8 13.1 59 420 m NE 519513.2 439418.3 12.7 60 364 m NE 519501.5 439353.9 12.4 61 318 m NE 519498.6 439289.4 12.1 62 280 m NE 519486.9 439239.6 11.8 63 386 m E 519633.3 439140.1 12.5



Table E.1 continued


(m) Northing


rate (%) 64 375 m E 519624.6 439084.4 12.4 65 371 m E 519609.9 439002.4 12.4 66 392 m SE 519604.1 438923.3 12.6 67 423 m SE 519595.3 438847.1 12.8 68 464 m SE 519586.5 438771 13.0 69 507 m SE 519580.6 438706.5 13.3 70 560 m SE 519580.6 438639.2 13.6 71 620 m SE 519566 438557.1 14.0 72 645 m SE 519542.5 438516.1 14.2 73 796 m S 519516.2 438340.4 15.1 74 927 m S 519525 438205.6 15.9 75 861 m S 519519.1 438273 15.5 76 711 m S 519522 438434.1 14.6 77 994 m S 519525 438135.3 16.3 78 1071 m S 519516.2 438053.3 16.8 79 1172 m S 519519.1 437950.8 17.4 80 110 m N 519228.8 439198.9 10.7 81 110 m N 519252.1 439201.2 10.7 82 114 m N 519275.5 439202.4 10.8 83 120 m N 519294.1 439202.4 10.8 84 127 m NE 519311.6 439202.4 10.8 85 117 m NE 519311.6 439190.7 10.8 86 102 m NE 519309.3 439174.4 10.7 87 84 m NE 519306.9 439153.4 10.6 88 70 m NE 519304.6 439134.7 10.5 89 60 m NE 519303.4 439118.4 10.4 90 54 m E 519303.4 439098.6 10.4 91 51 m E 519301.1 439085.8 10.3 92 48 m E 519294.1 439073 10.3 93 28 m SE 519270.8 439073 10.2 94 16 m S 519255.6 439076.5 10.1 95 8 m SW 519244 439085.8 10.1 96 18 m NW 519239.3 439105.6 10.1 97 38 m N 519235.8 439126.6 10.3 98 55 m N 519234.7 439144.1 10.4 99 77 m N 519233.5 439166.2 10.5

100 94 m N 519233.5 439183.7 10.6 101 1039 m NE 520092 439700 16.6 102 1142 m NE 520242 439657 17.2 103 1635 m E 520789 439643 20.0 104 1745 m E 520946 439500 20.7



Table E.1 continued


(m) Northing


rate (%) 105 1968 m E 521200 439353 21.9 106 7028 m N 517983 446004 43.6 a. Position of receptor relative to the centre of the West Newton A well site. Tables E.2 and E.3 detail the results of the assessment for the PW and AEREON flares respectively for the discrete receptors. The maximum long term and short term process contributions of nitrogen dioxide and benzene are expressed as a proportion of the applicable air quality standard. Table E.2 Maximum process contributions at the discrete receptors – PW flare

Receptor Nitrogen dioxide Benzene

1 hour mean annual mean annual mean 1 hour mean % air quality standard

1 0.47 0.48 1.12 0.30 2 0.44 0.45 1.04 0.27 3 0.49 0.41 0.97 0.31 4 0.38 0.10 0.24 0.25 5 0.52 0.23 0.53 0.32 6 0.61 0.21 0.48 0.41 7 0.57 0.17 0.39 0.36 8 0.36 0.14 0.33 0.23 9 0.27 0.17 0.40 0.17

10 0.26 0.08 0.18 0.17 11 0.23 0.06 0.15 0.15 12 0.19 0.06 0.14 0.13 13 0.23 0.06 0.14 0.15 14 0.22 0.05 0.12 0.15 15 0.23 0.05 0.11 0.16 16 0.17 0.03 0.08 0.12 17 0.16 0.03 0.07 0.12 18 0.15 0.03 0.07 0.11 19 0.17 0.10 0.24 0.11 20 0.26 0.22 0.52 0.19 21 0.24 0.12 0.27 0.15 22 0.19 0.07 0.16 0.12 23 0.12 0.03 0.07 0.11 24 0.11 0.02 0.05 0.12 25 0.11 0.02 0.06 0.14 26 0.57 0.13 0.30 0.38 27 0.52 0.10 0.24 0.39 28 0.51 0.09 0.21 0.37



Table E.2 continued



29 0.50 0.08 0.19 0.36 30 0.49 0.08 0.19 0.33 31 0.46 0.08 0.19 0.32 32 0.46 0.09 0.20 0.31 33 0.47 0.09 0.22 0.32 34 0.45 0.10 0.24 0.31 35 0.45 0.11 0.25 0.28 36 0.43 0.10 0.25 0.27 37 0.42 0.10 0.24 0.26 38 0.39 0.10 0.22 0.24 39 0.36 0.09 0.22 0.24 40 0.34 0.09 0.22 0.23 41 0.34 0.10 0.23 0.22 42 0.32 0.11 0.25 0.21 43 0.30 0.12 0.28 0.20 44 0.29 0.13 0.30 0.19 45 0.28 0.14 0.32 0.18 46 0.26 0.14 0.33 0.17 47 0.28 0.16 0.37 0.18 48 0.31 0.19 0.43 0.19 49 0.33 0.21 0.49 0.21 50 0.35 0.24 0.55 0.22 51 0.39 0.27 0.64 0.24 52 0.43 0.33 0.77 0.30 53 0.47 0.39 0.91 0.37 54 0.52 0.47 1.09 0.35 55 0.57 0.55 1.28 0.36 56 0.61 0.60 1.40 0.38 57 0.68 0.65 1.53 0.42 58 0.76 0.71 1.65 0.47 59 0.88 0.82 1.91 0.54 60 1.05 0.92 2.14 0.65 61 1.22 0.93 2.18 0.75 62 1.35 0.94 2.20 0.86 63 0.96 0.85 1.98 0.61 64 1.01 0.81 1.89 0.62 65 0.99 0.49 1.15 0.63 66 0.83 0.26 0.60 0.58 67 0.76 0.18 0.41 0.52 68 0.69 0.14 0.33 0.47



Table E.2 continued



69 0.63 0.12 0.28 0.42 70 0.57 0.10 0.23 0.38 71 0.48 0.09 0.20 0.35 72 0.46 0.08 0.19 0.32 73 0.36 0.07 0.16 0.24 74 0.30 0.06 0.14 0.21 75 0.33 0.06 0.15 0.23 76 0.41 0.08 0.18 0.28 77 0.27 0.05 0.13 0.19 78 0.25 0.05 0.12 0.17 79 0.22 0.05 0.11 0.15 80 1.10 0.20 0.47 1.38 81 1.42 0.32 0.74 1.44 82 1.97 0.58 1.35 1.57 83 2.36 0.85 1.99 1.63 84 2.42 1.13 2.65 1.87 85 2.45 1.15 2.69 1.95 86 2.41 1.09 2.55 1.86 87 2.24 0.88 2.07 1.79 88 1.73 0.56 1.32 2.08 89 1.02 0.32 0.74 1.33 90 0.77 0.23 0.53 1.26 91 0.65 0.14 0.34 0.85 92 0.25 0.04 0.09 0.48 93 0.01 <0.01 <0.01 0.02 94 <0.01 <0.01 <0.01 <0.01 95 <0.01 <0.01 <0.01 <0.01 96 <0.01 <0.01 <0.01 <0.01 97 0.06 0.01 0.02 0.11 98 0.30 0.04 0.10 0.53 99 0.72 0.11 0.26 1.07

100 0.95 0.17 0.39 1.25 101 0.29 0.23 0.54 0.19 102 0.25 0.19 0.45 0.17 103 0.17 0.13 0.30 0.11 104 0.16 0.14 0.33 0.11 105 0.15 0.14 0.33 0.11 106 0.05 0.01 0.03 0.05



Table E.3 Maximum process contributions at the discrete receptors – AEREON flare



1 0.63 0.61 1.45 0.40 2 0.58 0.56 1.35 0.37 3 0.65 0.54 1.28 0.42 4 0.50 0.13 0.32 0.34 5 0.69 0.29 0.70 0.45 6 0.82 0.27 0.64 0.57 7 0.76 0.21 0.51 0.49 8 0.48 0.18 0.42 0.30 9 0.35 0.21 0.51 0.23

10 0.34 0.09 0.22 0.23 11 0.29 0.08 0.19 0.19 12 0.24 0.07 0.17 0.17 13 0.30 0.07 0.17 0.20 14 0.28 0.06 0.15 0.20 15 0.30 0.06 0.14 0.20 16 0.21 0.04 0.09 0.16 17 0.20 0.04 0.09 0.15 18 0.19 0.04 0.09 0.14 19 0.20 0.13 0.30 0.14 20 0.33 0.28 0.67 0.25 21 0.31 0.14 0.34 0.20 22 0.23 0.08 0.20 0.16 23 0.15 0.04 0.09 0.12 24 0.13 0.03 0.06 0.11 25 0.13 0.03 0.07 0.13 26 0.76 0.17 0.39 0.53 27 0.68 0.13 0.32 0.53 28 0.68 0.11 0.27 0.51 29 0.66 0.10 0.25 0.50 30 0.64 0.10 0.24 0.46 31 0.61 0.10 0.25 0.44 32 0.61 0.11 0.26 0.43 33 0.62 0.12 0.28 0.44 34 0.59 0.13 0.30 0.40 35 0.60 0.13 0.32 0.38 36 0.56 0.13 0.31 0.36 37 0.55 0.13 0.31 0.36 38 0.50 0.12 0.28 0.32 39 0.48 0.12 0.28 0.32 40 0.45 0.12 0.28 0.31



Table E.3 continued



41 0.44 0.12 0.29 0.28 42 0.42 0.13 0.32 0.28 43 0.38 0.15 0.35 0.26 44 0.38 0.16 0.38 0.25 45 0.36 0.17 0.41 0.23 46 0.34 0.18 0.42 0.22 47 0.37 0.20 0.48 0.24 48 0.40 0.23 0.56 0.25 49 0.43 0.26 0.63 0.28 50 0.46 0.30 0.72 0.29 51 0.51 0.35 0.84 0.32 52 0.57 0.42 1.02 0.41 53 0.63 0.50 1.20 0.50 54 0.70 0.61 1.46 0.47 55 0.77 0.72 1.72 0.49 56 0.83 0.79 1.90 0.53 57 0.93 0.88 2.10 0.59 58 1.06 0.96 2.29 0.67 59 1.24 1.13 2.71 0.78 60 1.53 1.31 3.14 0.97 61 1.83 1.39 3.34 1.16 62 2.10 1.48 3.54 1.39 63 1.38 1.17 2.80 0.89 64 1.45 1.13 2.69 0.93 65 1.43 0.69 1.65 0.93 66 1.16 0.36 0.85 0.85 67 1.03 0.24 0.57 0.75 68 0.94 0.19 0.44 0.65 69 0.85 0.15 0.37 0.58 70 0.76 0.13 0.30 0.53 71 0.64 0.11 0.26 0.47 72 0.62 0.10 0.25 0.44 73 0.47 0.08 0.20 0.33 74 0.39 0.07 0.17 0.28 75 0.42 0.08 0.19 0.30 76 0.53 0.09 0.23 0.38 77 0.36 0.07 0.16 0.26 78 0.33 0.06 0.15 0.22 79 0.29 0.06 0.14 0.20 80 3.40 0.68 1.62 4.18



Table E.3 continued



81 4.20 1.05 2.52 4.39 82 5.45 1.80 4.31 4.58 83 6.30 2.49 5.95 4.50 84 6.14 3.03 7.24 4.24 85 6.89 3.38 8.08 4.78 86 8.07 3.85 9.21 5.77 87 10.34 4.34 10.39 7.66 88 12.49 4.34 10.37 10.15 89 12.19 3.94 9.42 11.24 90 12.55 3.68 8.80 14.19 91 12.04 2.80 6.71 14.27 92 8.59 1.20 2.88 12.74 93 2.69 0.43 1.04 13.72 94 2.40 0.24 0.59 6.48 95 2.96 1.02 2.43 58.02 96 2.31 0.37 0.89 5.84 97 3.88 0.59 1.42 7.37 98 4.18 0.69 1.64 7.26 99 4.06 0.73 1.73 5.85

100 3.71 0.73 1.75 4.76 101 0.37 0.29 0.70 0.25 102 0.33 0.24 0.58 0.22 103 0.22 0.16 0.38 0.14 104 0.20 0.17 0.41 0.14 105 0.18 0.17 0.41 0.12 106 0.07 0.01 0.04 0.07

END OF REPORT

Contact:

Dr Nick Ford Socotec UK Ltd Unit D Bankside Trade Park Cirencester Gloucestershire GL7 1YT T: 07768 257628 E: [email protected]



APPENDIX 3 – PW FLARE DESIGN

Flare outlet configuration : 1 off 3.068” ID pipe exitFlow rate(MMscf/d)

TipInlet(Psia)

TipExit(Psia)

Differentialpressure(Psia)

FlareTemperature(°F)

ExitVelocity(ft/sec)

Flame Length (1)

(ft)Noise at20ft fromstack (2)

(dB)1.0 14.87 14.7 0.17 681.3 226.0 16.68 (5.08m) 93.721.5 15.09 14.7 0.39 783.5 339.0 20.24 (6.17m) 95.482.0 15.39 14.7 0.6971 854.1 452.0 23.22 (7.08) 96.732.5 15.8 14.7 1.1 905.7 564.9 25.84 (7.87m) 97.70

(1) Flare length calculation

The flare length calculation:ft³/hr x LHV = Q (BTU/Hr)

L = 0.003936*Q^0.4776

LHV = Lower heat value = HHV * 0.9

HHV = 39.05 MJ/m³ = 1048.1 BTU/ft³

Gas S.G. = 0.618

(2) API/Brzustowski heat radiation and noise methodOnce the flame shape is known, these models may be simply represented by the equation:

KF Q

D

.

4 2

K, Thermal radiation at the specified distance from the mid point of the flame.

F, Flame emissivity.

Q, total heat release from the flame.

D, Distance from the receptor to the mid point of the flame.

Mark Ball

Well Test Support Engineer



APPENDIX 4 – CEB4500 DESIGN

Document Title: CEB® Technical File

Rev. No.: 0 dated 21st- JAN 2017

CEB.4500.xxx page 2/2

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