Corrib Onshore Pipeline Appropriate Hazard Distance G.J. Costello GJC Page 1 of 3 1. My name is Gerry Costello. I am the Deputy Project Director for the Corrib Project for Shell E&P Ireland Limited. Details of my qualifications and experience are contained in the Introductory statement I gave earlier. 2. Now that this Oral Hearing has heard the statements from my colleagues that cover a range of technical and safety aspects I would like to turn to the subject of “appropriate hazard distance”. 3. In their letter of 2nd November 2009 An Bord Pleanála stated that “having regard to the fact that Ireland has not adopted a risk-based framework for decision-making on major hazard pipelines (transporting wet gas) .....the Board should, therefore, adopt a standard for the Corrib upstream untreated gas pipeline that the routing proximity to a dwelling shall not be less than the appropriate hazard distance for the pipeline in the event of a pipeline failure. The appropriate hazard distance shall be calculated for the specific pipeline proposed such that a person at that distance from the pipeline would be safe in the event of a failure of the pipeline.” 4. An Bord Pleanála further stated on 29th January 2010 ”the intent of the Board is to ensure that persons standing beside the dwellings will not receive a dangerous dose of thermal radiation in the worst case scenario of a full-bore rupture of the pipeline at maximum pressure”. 5. It is noted that subsequent to An Bord Pleanála’s letters in November 2009 and January 2010, the Petroleum (Exploration and Extraction) Safety Act was passed into law in April 2010 (only certain sections of which have to date been commenced). In section 13I of the Electricity Regulation Act 1999 as amended by the Petroleum (Exploration and Extraction) Safety Act 2010 which will apply to the Corrib onshore pipeline when it comes into force, it is specified that a risk-based petroleum safety framework be established and implemented 6. Risk is a function of two variables, likelihood and consequence [SLIDE 1]. 7. It is necessary to take both into account when assessing risk as assessing one without the other tends to distort the perception of risk. Considering a harmful consequence without regard to extremely low likelihood results in an overstatement or exaggeration of risk [SLIDE 2]. 8. Notwithstanding that the application of a pure consequence based acceptance criteria when assessing pipeline safety is unprecedented, SEPIL has endeavoured to fulfil An Bord Pleanála’s requirement. In order to do this the pipeline has been re-routed such that it is as far from existing occupied dwellings as is technically practical, operating pressures have been reduced, and Maximum Allowable Operating Pressures (MAOP) established accordingly. 9. Whilst endeavouring to meet An Bord Pleanála’s requirement, SEPIL considers that an instantly ignited full-bore rupture is only a theoretical possibility because: A) The Design Factor of 0.3 as adopted for the Corrib onshore pipeline is specified in the Codes in order that there can be complete assurance that the pipeline will not rupture. B) Records of pipeline failures in Europe show that no pipeline with wall thickness greater than 15mm has ruptured. Corrib pipeline wall thickness at 27.1mm is almost twice as thick and thus even less likely to fail in rupture mode. 10. An instantly ignited full-bore rupture event scenario assumes an unrealistic accumulation of control failures. The figure below provides an overview of the key preventative barriers that have been described in preceding Statements. Either individually or in combination These barriers, including the adoption of a Design Factor of 0.3, serve to ensure a pipeline failure does not occur. [SLIDE 3]. 11. As we saw in the Statement from Mr. Crossthwaite the individual risk predictions for the occupant of the nearest occupied dwelling to the onshore pipeline is one in 50 thousand million per year of receiving a dangerous dose as a result of pipeline failure. Mr. Crossthwaite stated ‘the predicted risk from the pipeline to a person in the housing closest to the pipeline is similar to the range of values calculated for the risk of a person being killed by a meteorite and
1. My name is Gerry Costello. I am the Deputy Project Director for the Corrib Project for Shell E&P Ireland Limited. Details of my qualifications and experience are contained in the Introductory statement I gave earlier.
2. Now that this Oral Hearing has heard the statements from my colleagues that cover a range of technical and safety aspects I would like to turn to the subject of “appropriate hazard distance”.
3. In their letter of 2nd November 2009 An Bord Pleanála stated that “having regard to the fact that Ireland has not adopted a risk-based framework for decision-making on major hazard pipelines (transporting wet gas) .....the Board should, therefore, adopt a standard for the Corrib upstream untreated gas pipeline that the routing proximity to a dwelling shall not be less than the appropriate hazard distance for the pipeline in the event of a pipeline failure. The appropriate hazard distance shall be calculated for the specific pipeline proposed such that a person at that distance from the pipeline would be safe in the event of a failure of the pipeline.”
4. An Bord Pleanála further stated on 29th January 2010 ”the intent of the Board is to ensure that persons standing beside the dwellings will not receive a dangerous dose of thermal radiation in the worst case scenario of a full-bore rupture of the pipeline at maximum pressure”.
5. It is noted that subsequent to An Bord Pleanála’s letters in November 2009 and January 2010, the Petroleum (Exploration and Extraction) Safety Act was passed into law in April 2010 (only certain sections of which have to date been commenced). In section 13I of the Electricity Regulation Act 1999 as amended by the Petroleum (Exploration and Extraction) Safety Act 2010 which will apply to the Corrib onshore pipeline when it comes into force, it is specified that a risk-based petroleum safety framework be established and implemented
6. Risk is a function of two variables, likelihood and consequence [SLIDE 1].
7. It is necessary to take both into account when assessing risk as assessing one without the other tends to distort the perception of risk. Considering a harmful consequence without regard to extremely low likelihood results in an overstatement or exaggeration of risk [SLIDE 2].
8. Notwithstanding that the application of a pure consequence based acceptance criteria when assessing pipeline safety is unprecedented, SEPIL has endeavoured to fulfil An Bord Pleanála’s requirement. In order to do this the pipeline has been re-routed such that it is as far from existing occupied dwellings as is technically practical, operating pressures have been reduced, and Maximum Allowable Operating Pressures (MAOP) established accordingly.
9. Whilst endeavouring to meet An Bord Pleanála’s requirement, SEPIL considers that an instantly ignited full-bore rupture is only a theoretical possibility because:
A) The Design Factor of 0.3 as adopted for the Corrib onshore pipeline is specified in the Codes in order that there can be complete assurance that the pipeline will not rupture.
B) Records of pipeline failures in Europe show that no pipeline with wall thickness greater than 15mm has ruptured. Corrib pipeline wall thickness at 27.1mm is almost twice as thick and thus even less likely to fail in rupture mode.
10. An instantly ignited full-bore rupture event scenario assumes an unrealistic accumulation of control failures. The figure below provides an overview of the key preventative barriers that have been described in preceding Statements. Either individually or in combination These barriers, including the adoption of a Design Factor of 0.3, serve to ensure a pipeline failure does not occur. [SLIDE 3].
11. As we saw in the Statement from Mr. Crossthwaite the individual risk predictions for the occupant of the nearest occupied dwelling to the onshore pipeline is one in 50 thousand million per year of receiving a dangerous dose as a result of pipeline failure. Mr. Crossthwaite stated ‘the predicted risk from the pipeline to a person in the housing closest to the pipeline is similar to the range of values calculated for the risk of a person being killed by a meteorite and
approximately one thousand times less than the likelihood of an aircraft crash onto an acre of land in this location’. [SLIDE 4]
12. The additional detailed studies carried out by SEPIL therefore show there is a very low level of risk at the nearest occupied dwelling and I would urge that this be considered by An Bord Pleanála when reviewing the methodology and calculations applied by SEPIL in response to their requirement.
13. I will now outline the methodology and calculations applied, and conclusions reached.
14. The full details of how An Bord Pleanála’s “appropriate hazard distance” requirement has been applied to the Corrib pipeline are contained in Appendix Q6.5(i).
15. SEPIL has taken the parameters provided by An Bord Pleanála (full bore rupture at maximum pressure of 100 barg downstream of the LVI and 150barg upstream and at the LVI) and has applied models that assume a person stands in the open beside a dwelling, exposed to the event. SEPIL has then demonstrated that all dwellings provide safe shelter by showing conclusively that an individual who seeks shelter in or behind the dwelling would not receive a dangerous dose in the event of a full bore rupture.
16. As An Bord Pleanála’s request does not use an approach from international standards or codes to perform this theoretical calculation SEPIL has had to make several assumptions but where possible SEPIL has taken values from international codes and standards used in the application of consequence analysis as part of a QRA.
17. SEPIL has erred on the side of conservatism by adopting the following assumptions:
A. Pressures are at MAOP (150barg and 100barg) – in fact the onshore pipeline will normally operate at pressures in the region of 85 barg
B. The dwellings providing safe shelter are made of wood – in fact they are typically of stone construction
C. Releases downstream of the LVI will be from both sides of the rupture – no credit is taken for the LVI closing during the course of the release
D. All releases are for a pipeline in a trench – in fact over 50% of the pipeline will be in a tunnel
E. The gas instantly ignites – in fact there is unlikely to be an ignition source present, particularly within the bay, and whilst later ignition is more probable the heat generated would be less
F. Persons are permanently located outdoors, beside dwellings – in fact a majority of the time is spent indoors or away from the vicinity
G. Persons wait for 5 seconds before moving to shelter
18. In order to determine if a person is safe the following criteria are applied:
A. It must be established that at no time is the person exposed to a thermal flux in excess of 31.5 kW/m
2 (this is an absolute amount of heat that the person would receive at the start
of the event, i.e. during the 5 seconds before they move, when thermal loading is most intense)
B. It must be established that persons moving to the shelter of the dwelling do so without receiving a cumulative dangerous dose in excess of 1000 thermal dose units (representing a 1% chance of fatality)
C. It must be established that the dwelling provides safe shelter for the full duration of the event
19. Based on these assumptions and criteria the result of the consequence based calculations show that the distance at which a person standing beside a dwelling would not receive a dangerous dose in the event of an instantly ignited full bore rupture of the pipeline at maximum pressure, without regard to likelihood, is 216m.
20. The results of the consequence-based analysis is expressed as a contour line plotted on aerial photographs in Appendix Q6.5(i), an example of which is shown here [SLIDE 5].
21. For comparison purposes, the code based Building Proximity Distance for the Corrib pipeline of 3m is also plotted; this is the minimum safe distance between the pipeline and a normally occupied building. Also shown in the top right hand corner of the aerial photograph is a risk transect for the pipeline based on an MAOP of 100 barg showing that the risk of receiving a dangerous dose or more for a person at the nearest occupied dwelling (234m) is one chance in 50 thousand million per year.
22. Even when based on the conservative assumptions listed above and adopted in the calculation of the “appropriate hazard distance” the contour plot shows that there are no occupied dwellings within the 216m contour.
23. It is therefore concluded that An Bord Pleanála’s requirement is met, and that the pipeline is at an appropriate hazard distance from all dwellings along its route.
