©2020 SOCOTEC UK Limited ENVIRONMENTAL PERMIT VARIATION SUPPORTING INFORMATION SAFRAN LANDING SYSTEMS (UK) LTD, GLOUCESTER
ANNEX I
MAJOR ACCIDENT PREVENTION POLICY (MAPP)
16
EMP 4.4.7.12 : Major Accident Prevention Policy (MAPP): Issue 1 : 14th March 2017
COMAH / Environmental Management
Procedure EMP 4.4.7.12 MAJOR ACCIDENT PREVENTION POLICY (MAPP)
Procedure Amendments Issue Effective Date Section Amendment Details No. Of Issue Ref. Initial Issue as a procedure. Previously available as a standalone 1 14/03/2017 N/A policy.
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Abbreviations used in this document:
COMAH – Control of Major Accident Hazards MAPP – Major Accident Prevention Policy ALARP – As Low As Reasonably Practicable CLP – Classification Labelling and Packaging regulations EMS – Environmental Management System EMP – Environmental Management Policy NDT – Non Destructive Testing AOD – Above Ordnance Datum
Contents 1-Purpose…………………………………………………………………..3 2-Scope………………………………………………………………….....3 3-Site Contact Details……………………………………………………..5 4-Site Information………………………………………………………….5 5-Major Accident Information……………………………………………16 6-Maintenance of Lower Tier Status……………………………………27 7-Change Management………………………………………………….29 8-Electroplating Chemicals Store……………….………………………29 9-Flammable Materials Store……………..…………………………….31 10-Surface Finishes Workshop……….………………………………...32 11-Effluent Treatment Plant……………………………………………..35 12-Material Processing (Heat Treatment, NDT, Shot Peen)………...36
Appendix A-Cyanide Dispersion Model………………………………..38 Appendix B-Major Site Risk Locations…………………………………58
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1 Purpose 1.1 This Major Accident Prevention Policy (MAPP) is submitted in order to comply with the Control of Major Accident Hazard regulations 2015. This facility is classified as a lower tier COMAH site due to the storage and use of hazardous chemicals on site. 2 Scope 2.1 Safran Landing Systems UK Limited, Cheltenham Road East, Gloucester is committed to complying fully with its duties under the Control of Major Accident Hazards Regulations 2015. This major accident prevention policy outlines the measures in place to effectively minimise the risk of a major accident and to mitigate the consequences should one occur.
The policy addresses the following risks:
On-site risks – to employees, visitors, contractors, service contractors, etc.; Offsite risks – to neighbouring persons and premises; and Environmental risks – principally from air and water pollution.
The policy addresses the following areas of the site where significant major hazards and incident potential has been identified:
Surface Finishes: risks of toxic chemical spillages and the possibility of toxic gas release; Materials Processing: fire/explosion risk and chemical spillages; Effluent Treatment Plant: spillage of toxic/corrosive chemicals; Electroplating Chemical Store: toxic chemicals; spillage and segregation Flammable Materials Store: fire/explosion risk.
For each of the above areas, the MAPP will address the following issues:
Organisation: management structure and lines of responsibility; Hazards: identification of significant hazards for each area; Precautions: procedures and systems of work in place to control the resultant risks; Emergency planning: measures to mitigate the consequences of any potential incident; Monitoring: arrangements for monitoring performance of the preventive measures; and Audit and review: procedures.
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The MAPP does not in itself contain all of the hazard control procedures but it refers to the relevant EMS/COMAH Operational Procedures, Operational Procedures, Fire and Evacuation, Procedures, Quality Procedures and Training Modules. The MAPP also documents the control procedures in place to ensure that chemical inventory and effluents are controlled to ensure that the site remains within the lower tier threshold limits at all times.
Responsibility for implementation of this policy lies with the line managers of the various departments affected, as detailed within the document itself. The company undertakes to ensure that adequate resources are provided for the implementation of the policy, together with resources for the necessary training, monitoring and audits needed to maintain it.
Signed:
Chris Wilson Position: Managing Director on behalf of Safran Landing Systems UK Limited
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3 Site Contact Details Operator: SAFRAN Landing Systems UK Limited Address: Cheltenham Road East, Gloucester GL2 9QH Contacts: Kim Toomer HS&E Manager Telephone: 0145 271 1587 E-mail: [email protected] 4 Site Information 4.1 The SAFRAN Landing Systems site is located in a mixed industrial and agricultural setting between Cheltenham and Gloucester at grid reference SO 881 222 (see Figure 1). The main manufacturing area is situated on the northern side of the Cheltenham Road East (B4063), with the Test and Development Department on the south side of the road on the boundary of Gloucestershire Airport. Situated to the west of the site is a golf course. Adjacent to the west boundary of the golf course is Churchdown, a suburb of Gloucester City. Down Hatherley Lane is positioned between the site and the golf course and provides a route for traffic to Down Hatherley village. This road connects the Cheltenham Road East with the main A38.
To the north is mainly agricultural land with some residential housing within a few hundred metres. Down Hatherley village is approximately one Kilometre from the north perimeter fence. North-east of the site there are sports facilities including a club building and sports fields.
Adjacent to the east perimeter fence is a small industrial development with a variety of commercial and light industrial units. To the east of the site is agricultural land.
Aircraft landing gear is manufactured and assembled on the site and has been under various company names since 1938. The buildings date from the late 1930's to 1980's and the site currently covers some 42,000m2. 980 people are currently employed at this location. The site in total comprises 16 buildings. One building on adjacent land (extending to the north bank of Hatherley Brook and Dowty Sports and Social Club grounds) is currently owned by Dowty Propellers for blade testing. 15 of these buildings are on the north side of the road with one to the south.
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Figure 1: Site map and surrounding areas 4.2 Surrounding Occupation To the west of the site is a golf course. Adjacent to the west boundary of the golf course is Churchdown, a suburb of Gloucester. Down Hatherley Lane is situated between the site boundary and the golf course. Land to the north of the site is predominantly used for agriculture, with some residential housing a few hundred metres from the site. The Village of Down Hatherley is located approximately 1 kilometre from the north perimeter fence. North east of the site there are sports fields and Dowty Sports and Social Club building. Adjacent to the eastern perimeter is a small industrial development. To the south of the site there are more industrial units, as well as Gloucestershire Airport. 4.3 Site Processes The site produces landing gear and landing gear components for a range of military and civil aircraft, including components, for various companies including Airbus and Boeing.
Machining Including turning, grinding, milling and internal boring of landing gear components. Materials Processing
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Heat treatment of components including quenching, normalising and stress relief. Surface Treatments Shot peening and grit blasting. Non-destructive Testing X-ray, ultrasonic, magnaflux and dye penetrant inspection. Electroplating Cadmium, chromium, nickel. Chemicals used include cadmium cyanide, chromic acid, hydrofluoric acid, sulphuric acid. Dichromate and nitric acid are used in passivation processes. This is the principal area where hazardous chemicals are used subject to the COMAH Regulations and the remainder of the report will focus on this area. Painting Spray painting and touch up with both water and solvent based paints
4.4 Quantities of Hazardous Materials on Site Methodology of COMAH Calculation and Verification Certain substances found on site are classified under the Regulations as:
• Categories H1 & H2 Acute Toxic • Category H3 STOT Specific Target Organ Toxicity; • Categories E1 and E2 Hazardous to the Aquatic Environment • Category P5b Flammable Liquids
The COMAH classification (‘Upper or Lower Tier’) and the level of the COMAH classified chemicals that can be held on site is determined by calculation of the COMAH score. This calculates the impact of the amount of chemical by each hazardous category compared with threshold values found within the regulations.
The COMAH score is established based upon maximum values for COMAH chemicals relating to: • Tank/Vat Quantity This comprises the quantity of substances held in department vats/tanks, which are categorised under COMAH (at the concentrations that they are used). The calculation value is stable unless there is a change in process, at which stage the calculation is re-evaluated prior to the change to assess the effect. • Stores Quantity This comprises the quantity of chemicals held within the stores, which are categorised under COMAH. There is a report generated each week to check against the maximum quantity. Any product which is reclassified or new product purchased which is categorised under COMAH is included in the list and the calculations.
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• Shop Stock Figures These are the quantities of chemical which are stored on site but do not appear on the Stores stock levels. These quantities are relatively stable and have been set at maximum levels. Any change in the storage arrangements or quantities needs to be agreed with the HS&E Department. • Waste Quantity There are, on occasions, small quantities of waste chemicals classified under COMAH, which require disposal. These are stored on site until there is a sufficient quantity for a waste contractor to be contacted to arrange for disposal. A procedure is in place within the Surface Finishes Shop to ensure none of the concentrate waste stored is of sufficient concentration to be classified under COMAH. The maximum foreseeable quantity levels have been included within the COMAH Calculation
COMAH Score Calculation Using the process outlined in section 4.4 and maximum values of COMAH chemicals held on site, the COMAH score has been established and is found on the ‘P Drive’ - COMAH Scoring Calculation. Based upon the calculation, the site is classified as ‘Lower Tier’. The calculation is reviewed either annually or if there are significant process changes or chemical purchases that may impact upon the potential score.
4.5 Dangerous Substances – Information Metal Cyanides Solid cyanide salts are used for making up plating bath solutions. The plating bath solutions consist of a mixture of metal cyanide salts and complexes with other low hazard constituents. This section considers the properties of these salts as if they were sodium cyanide. The toxicity of all cyanide salts and their behaviour on contact with acids are similar so this is considered to be a valid assumption in the context of the COMAH requirements.
Storage All cyanide salts are purchased and stored as solids of about 99% purity. The solids contain low concentrations of impurities such as hydroxide, carbonate and formate, which do not give rise to a significant hazard. The maximum quantity of solid cyanide salts stored on site does not exceed 125kg, and these are kept in a secure electroplating chemicals store. Plating Solutions Over time the quantity of cyanide solution present on site has reduced as a result of process amendments.
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Physical and Chemical Behaviour Solids Melting point: 5600C Density: 1.6 – 1.62 Solubility in water: 34% at 150C
Moisture and carbon dioxide in the air will evolve hydrogen cyanide very slowly. Contact with acid liberates hydrogen cyanide gas. Cyanides may react violently with oxidising agents.
Plating Solutions Complex metal cyanide solutions in water.
Boiling point: about 1050C Freezing point: about 10C Specific gravity: 1.25
Contact with acids will liberate hydrogen cyanide gas, but the solutions contain at least - 2- 20g/l OH and at least 80 g/l CO3 so there needs to be a significant ratio of acid to plating solution before HCN is evolved.
Hazards to Health
Total CN in Effect body (mg) 10-30 Rapid pulse, breathing difficulties, dizziness and weakness in the legs 20-60 Collapse leading to unconsciousness 50-90 Collapse, slow gasping breaths, death if untreated
It is stated that an average person can detoxify 30mg CN/hour. (Information from Univar)
The routes of entry are ingestion, absorption through the skin and inhalation of HCN. In the strongly alkaline solutions used by the company, the vapour pressure will be low, so inhalation risk will be negligible unless the solutions were acidified.
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Environmental Hazards Toxicity is similar to that of HCN (see below).It is substantially biodegradable in water. In 14 days 99.8% of CN ions at a level of 35mg/l will be degraded and 60% at 180 mg/l. The no effect level for biological treatment processes is 10mg/l.
Hydrogen Cyanide HCN is normally only present in very low quantities in the liquid or gas phase. It may be evolved accidentally by the mixing of cyanide solutions with acids.
Storage No HCN is stored on site.
Physical and Chemical Behaviour
Pure HCN is a liquid with the following properties:
Boiling point: 260C Freezing point: -140C Specific gravity: 0.688
Detection
By fixed cyanide detection system in the Surface Finishes department and the basement area.
Hazards to Health
Total CN in Effect body (mg) 10-30 Rapid pulse, breathing difficulties, dizziness and weakness in the legs 20-60 Collapse leading to unconsciousness 50-90 Collapse, slow gasping breaths, death if untreated
It is stated that an average person can detoxify 30mg CN/hour.
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The main route of entry is inhalation of HCN.
WEL: 10ppm
Figure 2 shows the time taken to achieve a given effect at various concentrations. (Information from Univar) Page 10 Environmental Hazards
Whilst its acute toxicity effects are well known, HCN is not believed to have any chronic effects on humans or other animal species. The enzyme Rhodenase enables detoxification to harmful substances. HCN is also not known to have any detrimental effect on vegetation.
Environmental considerations are therefore only based on the consideration of exposure of animal life to concentrations likely to cause acute toxicity effects.
Atmospheric
HCN vapour is lighter than air and its diffusion characteristics are such that it is dispersed easily. This means that it would be unlikely that ground contamination would occur in concentrations large enough to cause acute toxicity.
Residual HCN is washed out of atmosphere and rendered non-toxic by microbial activity or water hydrolysis.
Aquatic
HCN is completely miscible in water and its release into a water course could cause the death of aquatic species including fish before significant dilution takes place. The LC50 for Daphnia magna (48 hours) is 1.8mg/l, implying that HCN is toxic to invertebrates. The LC50 for rainbow trout (96 hours) is 570g/l, implying that HCN is very toxic to fish.
HCN is not persistent and does not accumulate in the aquatic environment and degradation rates are similar to those for NaCN given above.
Note: Ammonia gas is no longer stored or used on site.
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Figure 2: HCN Toxicity
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4.6 Geology and Hydrology
Geology Based on the British Geological Survey 1:50,000 solid and drift maps (sheet 216) and the Policy and Practice for Protection of Groundwater the site appears to comprise:
Made Ground with associated underground services and foundations. Alluvial deposits associated with Hatherley Brook and Normans Brook. Bedrock comprising limestone of the Blue Lias (Lower Lias), Jurassic period. The thickness of the Lower Lias is about 50m and the bedrock dips toward the east. The Lower Lias is underlain by the Mercia Mudstone Group (MMG) of the Triassic period. Rocks from the MMG are exposed to the north-west of the site.
Hydrogeology The alluvial deposits are classified as a minor aquifer, generally only able to support locally important abstractions, and are likely to be in hydraulic continuity with local surface water courses. The Lower Lias is classified as minor aquifer, being of varied permeability and is considered to be a limited groundwater resource. Flow mechanism is by fracture flow in permeable horizons. The underlying Murcia Mudstone Group is a non-aquifer. Shallow groundwater below the site may be expected to occur as perched water, possibly discontinuous within the granular made ground and alluvial deposits. Deeper groundwater is anticipated in the Lower Lias, which is largely unconfined. The flow of perched groundwater is believed to be in a north/north-westerly direction towards Hatherley Brook. The flow direction of deeper groundwater is likely to be towards the south-east and the direction of the dip of the bedrock.
Potential Contaminant Pathways and Receptors The main potential receptor of contamination arising from a loss of containment on site is Hatherley Brook. The key potential pathways are:
Volatisation of potential contaminants in the made ground and alluvial deposits. Rapid surface water run-off of free phase or dissolved phase contaminants into Hatherley brook which runs through the northern section of the site. Migration of contaminants through the made ground to perched groundwater.
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Migration of dissolved phase contaminants within the perched water table down a hydraulic gradient providing base flow into Hatherley Brook. Migration of dissolved phase contaminants through preferential flow pathways in the made ground and alluvial deposits to permeable horizons in the Blue Lias. The environmental sensitivity of the site's environmental setting is considered to be ‘high’ in regards to surface waters, but ‘low to moderate’ in regards to groundwater.
Hydrology The site is relatively level and is at an elevation of about 20m AOD. Streams in the vicinity include Hatherley Brook (which flows through the site) and Normans Brook which flows through the adjacent golf course. Normans Brook flows in a north-westerly direction through the golf course approximately 550m from the site boundary before joining Hatherley Brook. Within the golf course is a large pond visited by and nested upon by several swans. Hatherley Brook flows into the River Severn approximately 6km to the west of the site. There is one licensed water abstraction from Hatherley Brook within 2km of the site. This is located at Brickhampton Court Farm about 750m to the west of the site. There are no licensed groundwater abstractions within 2km of the site.
4.7 Meteorology Prevailing Wind Wind direction is predominantly south-westerly, in the direction of Staverton village, 2 km from the site boundary.
4.8 Flooding Flooding from Hatherley Brook The year 2007 saw flooding in the Gloucestershire area at its worst in living memory. During this period the brook did not remain within its banks and some areas of the site were flooded. This included the building housing the Electroplating Chemical Store, Highly Flammable store and the oil store. No chemicals or substances were washed out of the storage containers, sacks or vessels due to the inherent containment systems and racking heights. In 2015 flood risk assessment was undertaken and all suggested improvements were implemented.
4.9 Seismic Events Earthquake Earthquakes are not seen as a significant risk. Since the original site development there is no record of any significant impact from earthquakes.
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In addition the British Geological Survey hazard map places the Gloucestershire area in an area defined as 5.0-6.0 on the European Macroseismic Scale (EMS 98). The intensity definitions from that scale are as follows: EMS 5 - Felt by most indoors, small objects fall over. EMS 6 - People run out in alarm, slight damage to buildings (plaster cracks). The plant buildings are steel framed structures with inherent flexibility. They are not expected to suffer any damage from a level 5.0 – 6.0 intensity event. Likewise it is not anticipated that an event of this magnitude would cause any plant structural failure.
4.10 External Activities
Major Hazard Installations No major hazard installations are known within the vicinity of the site.
Pipelines There are no known pipelines carrying hazardous materials across the site.
Theft, Arson and Terrorism The site is subject to 24-hour security patrols and has a secure perimeter fence.
Overhead Power Lines No overhead power lines cross the site.
Aircraft Crash The site is adjacent to Gloucestershire Airport (Staverton). The airport is used by light aircraft predominantly which do overfly the site. A possible aircraft crash would be dealt with by following the usual site emergency evacuation and response (Company Procedure Instruction No. PCD-GLO-122).
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5 Major Accident Information 5.1 Introduction Hazard Identification Potential major accident hazards were identified by way of a team based approach involving all interested departments and staff.
Major accident hazards were identified as being in the following areas: Raw materials unloading, transport and storage Process areas and basement in surface finishes shop Effluent treatment plant Materials Processing furnace operation NDT Materials Processing Titanium Acid etch line
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EMP 4.4.7.12 : (MAPP): Issue 1 : 14th March 2017
5.2 Hazard Identification and Analysis Raw Materials Unloading, Transport and Storage
No. Event description Cause Prevention and control measures Mitigation measures Consequences Likelihood and risk acceptability 1 Spillage of solid Pallet dropped on Training of FLT drivers. Spillage seen immediately and In wet weather a Drum dropped once in 10 years. sodium cyanide. unloading. shovelled into empty drum. small amount (<5kg) 1% of the time there will be Packaging designed to CLP could go to drain. spillage from drum. standards. In wet conditions spillage Following spillage there will be a containment kits (available at key This could produce a significant concentration in the points around site) would be used. significant fish kill in drain 10% of times. Procedure the brook if to plug discharge fails 1% of the The procedures in Company uncontrolled. time. Procedure Instruction No 245 for Major fish kill every 1x106 years. plugging the discharge points from MAJOR the interceptors to the brook are ENVIRONMENTAL EXTREMELY UNLIKELY actioned. ACCIDENT RISK As Low As Reasonably Practicable (ALARP) 2 Spillage of solid Spillage in Electroplating Only closed containers handled. Spillage seen immediately and Spillage contained N/A sodium cyanide. Chemical Store. shovelled into empty drum. within store. No Electrochemical plating store access change of NaCN restricted. entering surface water drainage. Liquid storage on portable bunds to contain any possible leakage and NOT A MAJOR thus keep water off the floor, area ACCIDENT covered.
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3 Spillage of solid Spillage during transit to Training of FLT drivers. Spillage seen immediately and In wet weather a Drum dropped once in 10 years. sodium cyanide. surface finishes shop shovelled into empty drum. small amount (<5kg) 1% of the time there will be Packaging designed to CLP could go to drain. spillage from drum. standards. In wet conditions spillage Following spillage there will be a containment kits (available at key This could produce a significant concentration in the points around site) would be used. significant fish kill in drain 10% of times. Procedure the brook if to plug discharge fails 1% of the uncontrolled. time. The procedures in EMP for plugging the discharge points from MAJOR Major fish kill every 1x106 years. the interceptors to the brook are ENVIRONMENTAL actioned. ACCIDENT EXTREMELY UNLIKELY RISK ALARP
No. Event description Cause Prevention and control measures Mitigation measures Consequences Likelihood and risk acceptability 4 Spillage of liquid Leak while emptying waste All liquid waste diluted to <1% very Spillage seen immediately and Small spillage only of N/A waste to drain. tanks to tanker. toxic and <7% toxic prior to storage. tanker loading stopped. dilute waste.
All tanker filling operations are Spillage containment kits NOT A MAJOR supervised by effluent treatment (available at key points around ACCIDENT plant staff. site) would be used.
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The procedures in Company Procedure Instruction No 245 for plugging the discharge points from the interceptors to the brook are actioned N/A 5 Fire Fire in flammable store No smoking area Automatic fire detection system Fire unlikely to spread to electrochemical Electrical equipment suitable for Extinguishers plating store flammable atmosphere Solid wall separation from Cyanides not electrochemical plating store flammable
HCN would only be formed if water present
HCN would be burnt in fire
Small particles of cyanide may be entrained and dispersed but this would be small amounts and would have no significant effect off site
NOT A MAJOR ACCIDENT
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Floodwater has 6 Flooding of Flooding of Hatherley Chemicals / substances are held in 24 hour security and CCTV will entered this storage With the chemicals /substances Electroplating Brook waterproof lidded containers or monitor brook height therefore area once and has being relocated in racking well Chemical Store / plastic lined sacks. appropriate action will be taken to been close to flooding above the potential extreme Oil store and Chemicals /substances held on racks prevent chemicals /substances in on another occasion flooding level, the risk factor is Flammable Store. above potential flood water level. the store being in contact with due to extreme now rated as extremely low. These are all held in an enclosed flood water. weather conditions. storage location. No chemicals were RISK ALARP Oils and Highly flammable lost from storage substances are held in sealed containers sacks containers and are contained within during the flooding. enclosed storage. However external packaging was damaged at the time.
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Surface EMP 4.4.7.12 : (MAPP): Issue 1 : 14th March 2017 Finishes Shop
No. Event description Cause Prevention and control measures Mitigation measures Consequences Likelihood and risk acceptability 7 Leakage of plating Corrosion/damage Tanks bunded in basement area Bunds inspected regularly Spillage contained in N/A solutions from tank basement bund Bunds separated to prevent mixing of Basement spillage procedure reactive chemicals (COMAH/EMS 4.4.7.4) in place to NOT A MAJOR deal with spillage to basement ACCIDENT bunds 8 Overflow of plating Operator error Tanks bunded in basement area Bunds inspected regularly Spillage contained in N/A solution tank basement bund Bunds separated to prevent mixing of Basement spillage procedure reactive chemicals (COMAH/EMS 4.4.7.4) in place to NOT A MAJOR deal with spillage to basement ACCIDENT All tanks are covered by a written bunds process specification
Fill levels are controlled by timers on the water pumps and all chemical additions are controlled and authorised by the materials laboratory
Tank contents are analysed every two weeks and tank level is checked at the same time. 9 HCN generation Mixing of acid and cyanide Tanks are separately bunded so for The solutions containing cyanide The dispersion model The likelihood of the event is plating solutions in bund mixing to occur it would require the are highly alkaline with (OH- and in Appendix 1 predicts very low – it would require the
2- due to simultaneous tank rupture of two tanks and the bunding CO3 ) which would result in the a maximum airborne rupture of two tanks and failure rupture and separated slow evolution of HCN gas and concentration of of the separated bunding
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EMP 4.4.7.12 : (MAPP): Issue 1 : 14th March 2017
bund failure thus a slowly rising concentration 30mg/m3 at 1.7m in air allowing plenty of time to above ground level at Slow evolution of HCN and Bunds regularly inspected evacuate on activation of the a distance of 100m detection and alarm system cyanide alarms from the LEV would allow escape of shop
All staff involved in chemical discharge stacks personnel Access to the basement bund area additions and transport are trained regarding compatibility of chemicals below the cyanide solution tanks is This level is below Off-site risk low (see dispersion and correct additions for each tank not allowed while production is in that required to create calculations in Appendix 1) progress - permit system is in any symptoms
All tanks are clearly marked with place to control entry RISK ALARP
details of their hazardous
components
No. Event description Cause Prevention and control measures Mitigation measures Consequences Likelihood and risk acceptability 9 HCN generation Gas detection systems are MAJOR ON-SITE (continued) provided in the Surface Finishes ACCIDENT Shop and bund areas linked to a cyanide gas alarm system MINMAL OFF-SITE EFFECTS A cyanide alarm evacuation procedure is in place and all plating shop staff has been trained in its operation
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Effluent Treatment Plant
No. Event description Cause Prevention and control measures Mitigation measures Consequences Likelihood and risk acceptability 10 Loss of Rupture of treatment or Treatment tanks fitted with high level Regular bund inspections Spill of chemical to The likelihood of the event is containment chemical storage tanks alarms the environment very low – it would require the Access restricted to trained rupture of a tank and failure of Treatment plant floor bunded ad operators MAJOR the floor membrane fitted with impermeable membrane ENVIRONMENTAL Spillage containment kits ACCIDENT RISK ALARP Membrane proving pipes fitted to (available at key points around show if membrane leaks site) would be used.
The procedures in Company Procedure Instruction No 245 for plugging the discharge points from the interceptors to the brook are actioned 11 Spillage of Leak while emptying waste All liquid waste diluted to <1% very Spillage seen immediately and Small spillage only of N/A chemicals to drain tanks to tanker or while toxic and <7% toxic prior to storage. tanker loading stopped. dilute waste. unloading treatment chemicals All tanker filling operations are Spillage containment kits NOT A MAJOR supervised by effluent treatment (available at key points around ACCIDENT plant staff site) would be used.
The procedures in Company Procedure EMP 4.4.6.3 for closing
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the discharge points on the surface water interceptors to the brook are actioned
Materials Processing
No. Event description Cause Prevention and control measures Mitigation measures Consequences Likelihood and risk acceptability 12 Endothermic gas Temperature of furnace Furnace temperature control with Equipment damage Industry standard protective explosion falling below 6500C emergency shut down and purge systems Missiles from explosion causing RISK ALARP injury and damage
MAJOR ON-SITE ACCIDENT 13 Fire in oil quench Ignition of quench oils Low flammability oils used Quench tanks have CO2 flood Equipment and Industry standard fire detection tanks systems building damage and suppression systems
MAJOR ON-SITE RISK ALARP ACCIDENT 14 Explosion in salt Ingress of water Salt bath under a protective hood Fire brigade instructed that water Equipment damage RISK ALARP bath is not used near salt bath in an Regular inspections of the roof for emergency Missiles from leaks explosion causing injury and damage MAJOR ON-SITE ACCIDENT
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Materials Processing NDT Titanium Acid Etch Line
No. Event description Cause Prevention and control measures Mitigation measures Consequences Likelihood and risk acceptability
1 Leakage of solution Tank failure / pump Tanks are fully bunded and are acid Bunds Inspected regularly as Spillage contained in from tank leakage/ pipe leaking/ resistant constructed with acid required under EMP. 4.4.6.7 tank bunding N/A failing resistant materials. NOT A MAJOR ACCIDENT
Overfilling of tank Operator error Tanks are fully bunded and are acid 2 resistant constructed with acid resistant materials. Spillage contained in N/A All solutions are covered by a written tank bunding process specification to control concentration and volume. Bunds Inspected regularly as NOT A MAJOR required under EMP. 4.4.6.7 ACCIDENT Fill levels are controlled by markings at correct working level. All chemical additions are controlled and authorised by the Process Laboratory
Tank contents are analysed every 4 weeks. A working practice of checking tank levels on a daily basis is used.
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3 Discharge to Effervescent during Solution level in tanks kept as Solution height checked at regular Nil discharge under RISK ALARP atmosphere. emersion minimal. intervals. specified operating in tank. Ambient temperature of solutions in conditions. tanks. Discharges measured from discharge stack, no significant NOT A MAJOR discharge found. ACCIDENT
4 Raw Material Bund inspected regularly as Storage: Container failure / bund Held in separate plastic chemical required under EMP. 4.4.6.7. Spillage contained in RISK ALARP Acids; Hydrofluoric leakage resistant bund to prevent acid mix in 2∙5 L containers to minimise storage bund. and Nitric Acid the event of leakage. 45 L carboys handling risk when topping up spillage /leakage for initial filling and 2∙5 L containers tanks. from containers. stored for top up purposes. Spillage retention kit is available. (plus Sodium Carbonate for neutralisation)
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6 Maintenance of Lower Tier Status Introduction Strict procedures are required to ensure that the site remains within the lower tier threshold limits for chemical at all times. There are two distinct aspects involved:
Strict control of site stock levels and purchasing of chemicals that fall within the categories included in the COMAH calculation; and Control of waste solutions to ensure that they do not take the site above the threshold.
6.1 Order Quality Control Organisation
HS&E Department
Procurement Teams Department Process Operators
Procedures All chemical stocks within the scope of COMAH are subject to the Order Quantity Control Procedure (COMAH/EMS Operational Procedure EMP 4.4.6.9). The procurement personnel are responsible for authorising all chemical orders against the maximum stockholdings set out in form EMP 4.4.6.9A
All "safe" orders are based on the worst case scenario – i.e. the COMAH calculation accounts for our safety stock level PLUS stock in use PLUS the order quantity. Orders will not be authorised when site stock is above the safety stock level. Records Records are held with the procurement department. The Environmental Department is responsible for maintaining and updating the stock and order quantities on form EMP 4.4.6.9A
Monitoring Shop stock levels (including chemicals in use in solutions) shall be monitored every week by the process technicians according to the Shop Substance Control For reference only when printed unless otherwise specified. Check revision level prior to use for possible updates Page 27/59 This document is the property of Safran Landing Systems UK Ltd. It must not be reproduced or communicated without its permission
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Procedure (COMAH/EMS Operational Procedure EMP 4.4.6.10). Stores stock shall be monitored weekly by the store person. The HS&E team will check these figures weekly against the maximum stockholdings set out in EMP 4.4.6.9A
Audit Audits will be carried out or arranged by the health, safety and environment department and the system shall be audited at least annually by an external auditor.
6.2 Change Management Organisation Responsibility for maintenance of lower tier status and approval of all process changes affecting this lies with the HS&E department.
Procedure Refer to COMAH Lower Tier Control Procedure (COMAH/EMS Operations Procedure 4.4.6.8).
Audit Procedures should be audited by an external auditor annually (as a minimum).
6.3 Effluent Dilution Procedure Organisation Procedures are carried out routinely by Surface Finishes technicians. Management responsibility lies with the Surface Finishes Department Manager.
Procedure Spent plating solutions are transferred to the waste holding tanks according to the procedure MANP 3.3.575 after analysing a sample to decide on the appropriate tank and dilution necessary to remove the solution from COMAH classification.
A quantity of mains water determined by the analysis is added to the tank to dilute the chemical according to the Plating Waste Holding Tanks Dilution Procedure (COMAH/EMS Operational Procedure 4.4.6.4).
Records Records are kept in the Holding Tank Logbook located in the Surface Finishes Department. (Excel spreadsheet.)
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Monitoring The contents of the holding tanks are monitored when chemicals are added to ensure that toxic chemicals are within the required dilution levels. (Note the holding tanks are only used now in emergencies.)
Audit Checks on the procedure and records will be carried out by the Surface Finishes Department Manager and the system will be audited at least annually by an external auditor.
7 Change Management Organisation Responsibility for maintenance of lower tier status and approval of all process changes affecting this lies with the HS&E department.
Procedure Refer to COMAH Lower Tier Control Procedure (COMAH/EMS Operations Procedure 4.4.6.8).
Audit Procedures should be audited at least annually by external auditor.
8 Electroplating Chemical Store Organisation
Logistics Manager
Stores Team Leader
Storeperson
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Significant Hazards and Precautions
Hazardous situation: Spillage due to chemical container rupture.
Precautions: Toxic chemicals are stored in solid form. The small amounts of liquids stored are positioned on portable bunds. Access by authorised persons only (store locked). No chemicals to be transported on out shifts.
Overall Risk: Low
Emergency Planning Spillage containment kits available around the site. Small spillage kit held in store. Emergency response co-ordinated through security lodge (24 hour cover). Staff trained in emergency spillage procedures for the store. Risk cards for significant areas of the factory are held at security for emergency services attending an incident at site.
Monitoring Spillage kits checked monthly and following use.
Audit Operating procedures are audited every two years. Visits to the store are carried out by Environmental Agency Officers as part of ‘Part A’ authorisation visits. Independent audit by an external auditor annually.
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9 Flammable Store Organisation
Logistics Manager
Stores Team Leader
Storeperson
Significant Hazards and Precautions Hazardous situation: Fire/explosion due to ignition of flammable and highly flammable liquids.
Precautions: All electrical fittings are suitable for flammable atmospheres. Store is bunded. Access by authorised persons only (store locked). No electrical equipment (including mobile telephones) allowed in the store.
Overall Risk: Low
Emergency Planning Spillage containment kits available around the site. Emergency procedures in place to plug interceptors and prevent escape of chemical spillages to the environment. Emergency response co-ordinated through the security department (24 hour cover). Store staff trained in emergency spillage procedures for this area Risk cards for all areas of the factory are held at security for emergency services attending an incident at site.
Monitoring Fire and Rescue visit as part of inspection and familiarisation visits.
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Audit Independent audit by an external auditor annually.
10 Surface Finishes Organisation
Processes Manager
Team Leaders
Process Operators Process Engineers
Health and Safety Co-ordinator
Significant Hazards and Precautions Hazardous situation: Inadvertent mixing of incompatible plating solutions on rupture of plating tanks. Incorrect chemical additions at plating tanks.
Hazards: Exposure of personnel to toxic HCN gas in the Surface Finishes Shop. Exposure of personnel in basement bund area to HCN gas. Exposure of persons outside the building to HCN gas.
Risk Discussion: A calculation is attached at Appendix 1 showing the results of the inadvertent mixing of a cyanide tank with an acid tank. The likelihood of this event is very low – tanks are separately bunded so for mixing to occur it would require the rupture of two tanks as well as the bunding. - 2- The solutions containing cyanide are highly alkaline with (OH and CO3 ) which would result in the slow evolution of HCN gas and thus a slowly rising concentration in air allowing plenty of time to evacuate on activation of the cyanide alarms. The dispersion model in Appendix 1 predicts a maximum airborne concentration of 30mg/m3 at 1.7m above ground level at a distance of 100m from the LEV discharge stacks. Proprietary information from Univar suggests that this level is below that required to create any symptoms (see figure 2).
Overall Risk: Low
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Precautions: All plating tanks containing cyanide-based solutions are separately bunded, so that in the highly unlikely event of two tanks failing there would be no mixing of incompatible plating solutions below the tanks. All staff involved in chemical additions and transport are trained regarding compatibility of chemicals and correct additions for each tank. Training records are held in Surface Finishes Shop. All tanks are clearly marked with details of their hazardous components. Access to the basement bund area below the cyanide solution tanks is not allowed while production is in progress. A permit system is in place to control entry. Exposure of persons outside in the event of an emergency is considered an insignificant risk due to the small quantities of gas likely to be involved and the dilution effect when exhausted through the LEV system.
Hazardous situation: Release of plating solutions on rupture of plating tanks. Spillage of chemicals during transport or additions to plating tanks. Rupture of concentrated waste tanks or spillage during tanker loading from concentrated waste tanks.
Risks: Environmental risk – harmful chemical spillages entering the environment.
Risk Discussion: All process tanks and waste tanks are bunded so the risk of liquid spillage from process or storage is low. All site drainage leaves site via interceptors allowing more time to take remedial action in the vent of a spillage. Most chemicals are purchased and handled in solid form – easier to contain and clean up in an emergency.
Overall Risk: Low likelihood, but significant impact
Precautions: All plating tanks are bunded, draining into the Surface Finishes Shop sump. Procedure in place for dealing with chemical spillage into the basement sump (COMAH/EMS Emergency Procedure 4.4.7.4). All chemical additions are in solid form aiding clean up in the event of a spillage. Concentrate waste tanks are bunded.
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All tanker-loading operations are supervised by a member of the effluent plant staff so that emergency action can be taken quickly in the event of an accident. Chemical storage and transport precautions are contained in EMS Operational Procedure 4.4.6.1.
Emergency Planning: HCN detection systems are provided in the Surface Finishes Shop and bund areas linked to a cyanide gas alarm system. A cyanide alarm evacuation procedure is in place and all plating shop staff has been trained in its operation. Records are held in Surface Finishes Shop. A risk card for this area of the factory is held at security for emergency services attending an incident at site. A written procedure is in place for evacuation of the Surface Finishes Shop and for dealing with an emergency in this area. Spillage containment kits available around the site. Emergency procedures in place to shut off interceptors and prevent escape of chemical spillages to the environment. Procedures are contained in the fire and emergency procedures (Company Procedure Instruction No. 245). Emergency response co-ordinated through the security department (24 hour cover). All staff trained in emergency spillage procedures in the EMS training package. Risk cards for significant risk areas of the factory are held at security for emergency services attending an incident at site.
Monitoring The cyanide alarm system is maintained and calibrated every six months. Records are kept in Plating Shop. The cyanide alarm system is tested weekly Records are kept in Surface Finishes Shop. A full cyanide evacuation drill is held every six months. Records are kept in Surface Finishes Shop. Bunding in the basement area is inspected for integrity every fortnight (COMAH/EMS Operational Procedure 4.4.6.7). LEV is tested annually; records are kept by the Facilities Department. Sampling of main interceptor outlet discharges are carried out on a daily basis. Spillage kits checked monthly and following use.
Audit All reported significant spillages are visited by the either the Facilities Manager and HS&E department to advise on effective controls and remedial action if necessary.
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Surface Finishes Shop is visited by Environmental Agency Officers as part of ‘Part A’ authorisation site visits. Procedures are audited at least annually by an external auditor.
11 Effluent Treatment Plant Organisation
Facilities manager
Team leader
Effluent Plant
Operators
Significant Hazards and Precautions Hazardous situation:
Spillage due to treatment tank rupture. Spillage due to treatment chemical tank rupture. Spillage during tanker unloading/loading.
Precautions: Treatment plant floor bunded and fitted with impermeable membrane. Membrane proving pipes fitted to show if membrane leaks. Treatment tanks fitted with high-level alarms. Treatment chemical tanks are bunded. All tanker-loading operations are supervised by a member of effluent plant staff so that emergency action can be taken quickly in the event of an accident.
Emergency Planning Spillage containment kit is available at the Effluent Plant treatment chemicals filling location. Emergency procedures in place to shut off (gate valves) interceptors and prevent escape of chemical spillages to the environment. EMP 4.4.6.3 controls discharge
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to brook from interceptors. (For fire and evacuation- Company Procedure Instruction No. 245) Emergency response co-ordinated through security lodge (24 hour cover). All staff trained in emergency spillage procedures in the EMS training package. Risk cards for significant areas of the factory are held at security for emergency services attending an incident at site.
Monitoring The treatment of solutions process is monitored by the operators of the plant. In addition monitoring equipment such as high level alarms are fitted to treatment chemical holding tanks.
Audit The procedures are reviewed and audited within the department as circumstances require. Visits by Environmental Agency Officers are carried out as part of ‘Part A’ Permit visits. Independent audit by external auditor.
12 Material Processing (Heat Treatment, Shot Peen, and NDT)
Processes Manager
Team Team Leader Process Team Leader Leader Technicians
Process Engineers Thermal Shot Peening Technicians Operators Processing Operators Operators
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Significant Hazards and Precautions Hazardous situation: Oil fire in quench tanks. Flammable atmospheres escaping from furnaces. Salt bath explosion.
Risk Discussion: See site fire risk assessments.
Precautions:
CO2 flood systems installed on all quench tanks. Excess gas flared off at furnace entrances. Salt bath under hood to protect from water.
Emergency Planning Evacuation procedure in place (procedures are contained in the fire and emergency procedures - Company Procedure Instruction No. 245) and all personnel trained - records held in Material Processing. Fire / Emergency Evacuations logged at in Security Control and Safety and Environmental Office (drills and auto fire alarms). Emergency response co-ordinated through the security department (24 hour cover). Information for emergency services held at the security department (including instructions not to use water to fight fires in this department and importance of not extinguishing excess gas flares at furnaces).
Monitoring Evacuation drills carried out for each building at least annually. Audit The Site Fire and Emergency procedure is independently reviewed by the HS&E department as circumstances require. Procedures are audited at least annually by external auditor.
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Appendix A - Cyanide Dispersion Model
1.0: Introduction
Safran Landing Systems’ Surface Finishing at its Cheltenham Road site employs a range of materials which could theoretically combine to cause a release of hydrogen cyanide. The potential for releases of hydrogen cyanide and the subsequent impact has been assessed using atmospheric dispersion modelling within the site’s Major Accident Prevention Policy. A similar assessment was undertaken in 2001 and this needed to be reviewed and reissued with the inclusion of a different worst-case scenario for hydrogen cyanide release.
Within the Surface Finishing department the principal route to production of hydrogen cyanide is the combination of sodium cyanide, used in cadmium plating, with sulphuric acid employed in chromium plating. The purpose of this dispersion model was to examine the potential release of hydrogen cyanide in a worst-case scenario, its dispersion and the subsequent impact on ambient air quality both within the Safran Landing Systems site and further afield in the vicinity of the site. The significance of the resulting ambient air quality impact is assessed in the context of applicable workplace and ambient air quality guidelines.
The worst-case scenario considered was where a failure of several vats and bunds containment resulted in the mixing of the total inventory of the four vats associated with chromium and cadmium plating and the production of hydrogen cyanide. Assuming that the Surface Finishes Department is evacuated and the air within extracted to atmosphere via the existing ventilation systems serving the vats, the resulting dispersion of hydrogen cyanide releases is predicted to have maximum impact within the site boundary. A maximum concentration of around double the workplace exposure limit is expected to occur 100m to the north east of the Surface Finishes Department. The hydrogen cyanide concentration on most of the site is predicted to be below the workplace exposure limit.
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2.0 Dispersion Modelling Approach
The approach taken for this assessment comprised the following main stages:
Determine a suitable modelling tool for the assessment. Collect appropriate representative plant operational data for input to the model. Establish the location of the release relative to existing buildings (including nearby public and commercial buildings and residential properties). Obtain information on local background concentrations of hydrogen cyanide. Obtain 5 years’ recent meteorological data from a measurement station appropriate to the location. Model the dispersion of potential releases of hydrogen cyanide from the surface finishing shop to determine the process contribution to ambient concentrations of hydrogen cyanide over the Safran Landing Systems site and the neighbouring area with particular attention to locations of human exposure.
Assess the predicted process contributions and established background concentrations with reference to applicable workplace and air quality standards to determine compliance.
3.0 Context of Assessment
Many people are exposed to a variety of substances at work, which can, under some circumstances, have a harmful effect on their health. Hydrogen cyanide is recognised as a hazardous substance in this regard with a specified workplace exposure limit (WEL) set in order to help protect the health of workers. Substances that have been assigned a WEL are subject to the requirements of Control of Substances Hazardous to Health (COSHH) regulations, which require employers to prevent or control exposure to hazardous substances
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 significantly to any threat to the attainment of air quality standards. It is in this context that, as part of the environmental permitting process operated by the Environment Agency, it is necessary to demonstrate the impact of site operations on local air quality in the context of the Environment Agency’s published guidance.
It is necessary to examine the impact of potential hydrogen cyanide releases both within the general workplace, as regulated under COSHH, and in the wider area beyond the site boundary where environmental standards relevant to human health apply.
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4.0 Hydrogen Cyanide Release from Surface Finishes
The Surface Finishing operations at Safran Landing Systems’ Cheltenham Road include both chromium plating using sulphuric acid and cadmium plating employing sodium cyanide. While stringent measures are in place to prevent the combination of these materials, there are abnormal circumstances where accidental or deliberate mixing could occur.
On mixing the following reaction can occur:
2NaCN + H2SO4 2HCN + Na2SO4 Sodium cyanide Sulphuric acid Hydrogen Sodium cyanide sulphate
5.0 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) and the Fourth Daughter Directive (relating to metals and hydrocarbons). 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 and 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 2010 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.
There are no air quality standards which are specific to the ambient concentration of hydrogen cyanide, however for the purposes of assessing the significance of pollutants in the ambient atmosphere the Environment Agency publish Environmental Assessment Levels (EALs) for the protection of human health. The EAL relevant to this study is summarised in the following Table 1 below.
Table 1: Environment Assessment Level
Pollutant Basis Concentration Hydrogen cyanide Hourly mean 220 µg/m3
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6.0 Workplace Exposure Limit
The WEL for hydrogen cyanide is on a short-term limit, which is generally set for substances that have an acute affect rather than a chronic affect. Affects may occur following exposure for a few minutes. Hydrogen cyanide is also noted as a substance, which can be absorbed through the skin.
The WEL for Hydrogen Cyanide is shown in the following Table 2 below.
Table 2: Environment Assessment Level
Pollutant Basis Concentration Hydrogen cyanide 15 minute reference period 11000 µg/m3
7.0: Assessment Criteria
The Environment Agency provides a methodology for assessing the impact and determining the acceptability of emissions to atmosphere on ambient air quality for 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) i.e. 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
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8.0 Modelling Methodology
The process contributions to ambient concentrations of hydrogen cyanide from the worst-case scenario has been modelled using the Atmospheric Dispersion Modelling System (ADMS) version 5.1. The use of this modelling tool is widely accepted by UK Local Authorities and the Environment Agency.
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 particular they both employ a characterization of the boundary layer structure using the Monin Obuhkov length and boundary layer height, and Gaussian profiles for the concentration distribution. In this case ADMS 5.1 has been employed for the assessment
9.0 Assessment Area
Two assessment areas were considered, each with the Surface Finishes Department (388010 222180) located approximately at the centre. Figure 1 illustrates the location of the site within the local area, while Figure 2 details the Safran Landing Systems site.
Figure 1 Location of the Safran Landing Systems site
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Figure 2 Safran Landing Systems site arrangement
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The assessment area in Figure 1 is a 2 km x 2 km region which encompasses nearby local business premises and the closest residential locations and is intended as the area, with the exception of the Safran Landing Systems site, which would be assessed based on the EAL.
Figure 2 is a 400 m x 400 m area largely covering the Safran Landing Systems site where the WEL might be expected to apply. 10.0 List of Residential Receptors (Refer to Figure 1)
The list of local businesses and residential building considered for this model are shown in Table 3 below.
Table 3: – Residential Receptors
Receptor Positiona Easting Northing (see Figure 1) Residential locations R1 Terncourt 480 m W 387557 222395 R2 The Channings 690 m W 387348 222428 R3 Woodfold Farm 930 m W 387146 222579 R4 Wood Farm 880 m NW 387414 222893 R5 Mobile Home Park 970 m NE 388936 222498 R6 Poplar Cottage 400 m S 387899 221855 R7 Blenheim House 610 m SW 387742 221698 R8 Boxtrees 740 m SW 387651 221599 R9 Snowdon Gardens 1020 m SW 387392 221425 R10 Orchard Way 1075 m SW 387676 221219 Commercial locations C1 Ambulance Station 160 m E 388165 222224 C2 Ashville Business Park 130 m NE 388126 222287 C3 Mitsubishi 220 m SE 388121 222045 C4 Completely Motoring 230 m SE 388169 222077 C5 Vernon Court 300 m SE 388128 221959 C6 Jupiter Court 330 m SE 388174 221953 C7 Anson Business Park 750 m E 388761 222262 C8 Sports Club 270 m N 388050 222499 C9 Kennels 620 SW 387773 221665 C10 Gloucestershire Airport 1 740 m SE 388665 221901 C11 Gloucestershire Airport 2 560 m S 388163 221692 C12 Gloucestershire Airport 3 1060 m SE 388879 221631
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11.0 List of Building and Building Parameters within the Safran Landing System Site. (Refer to Figure 2)
The list of on site buildings considered for this model is shown in Table 4 below.
Table 4: – On Site Buildings
Building centre grid Building Height Length Width reference (see Figure2) (m) (m) (m) Easting Northing A Surface Finishes section 1 388052 222216 10.2 39.8 32.3 B Surface Finishes section 2 388022 222212 10.2 19.8 56.3 C Machine shop 2 387960 222255 9.6 122.2 42.6 D Restaurant 387928 222159 6.0 47.4 48.2 E Paint shop 387972 222206 6.5 62.0 37.5 F Laboratory 387999 222185 7.2 32.1 26.7 G Heat treatment 387983 222099 8.8 101.4 85.4 H Machine shop 1 388093 222158 8.8 124.2 91.6 I OE assembly 388081 222244 10.2 39.5 69.8 J Goods inwards 388043 222247 10.2 25.2 16.4
12.0 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 Pershore station and covered the 5-year period 2011 to 2015. The Pershore station is around 23 km north east of the Safran Landing Systems site at an elevation of 35 m, compared with the site elevation of around 22 m.
On the basis of the general location and surface characteristics, the Pershore station was considered to provide measurements most representative of the conditions around the Safran Landing Systems site area.
The data included, among other parameters, hourly measurements of wind speed and direction. Figure 3 illustrates a composite wind rose for the Pershore station for the period considered within this modelling (2011 to 2015). It may be seen that the wind is predominantly from the southwest.
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Fig 3 : Wind Direction and Speed from Pershore Weather Station 2011 – 2105
NORTH
10%
8%
6%
4%
2%
WEST EAST
WIND SPEED (m/s)
>= 11.10 8.80 - 11.10 Resultant Vector 5.70 - 8.80 220 deg - 26% SOUTH 3.60 - 5.70 2.10 - 3.60 0.50 - 2.10 Calms: 0.30%
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13.0 Release of Hydrogen Cyanide
The generation of hydrogen cyanide is considered to arise from the combination of sulphuric acid and sodium cyanide in the various parts of the plating process in the Surface Finishes Department. As shown in Figure 4, there are 4 vats containing material, which has the potential to combine to produce hydrogen cyanide. The assumed contents of these vats are summarised in Table 5.
Fig 4 : Vat Arrangement of those Vats assessed during this Dispersion Model
A5 A4 A3
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Table 5 : Cadmium and Chromium Vat Inventory
W10 W6 V6 X6 Low hydrogen Vat Hard chromium Hard chromium Passivation for embrittlement plating plating cadmium cadmium plating Working volume 4644l 3444l 7096l 2352l 2.25-2.9 g/l 2.25-2.9 g/l 5-8 g/l Sulphuric acid 13.5 kg 10.0 kg 18.8 kg 225-290 g/l 225-290 g/l Chromic acid 1347 kg 999 kg 90-120 g/l Sodium cyanide 852 kg 7.5-24 g/l Sodium hydroxide 170 kg 60 g/l max Sodium carbonate 426 kg 135-175 g/l Sodium dichromate 412 kg
For this scenario It was assumed that all substances are present at the top of their respective chemical control limits. Worst Case Hydrogen Cyanide Release Scenario
Vats W10, W6 and X6 mix with the contents of V6 following a failure of all four vats and the associated bunds.
A total of 42.3 kg (0.43 kg moles) of sulphuric acid mixes with an excess of sodium cyanide (852 kg) producing a hydrogen cyanide release of 23.3 kg (0.86 kg moles).
It is assumed in the above calculations that any sodium cyanide present will react with the available sulphuric acid to form hydrogen cyanide. The cadmium plating solution in V6 also contains sodium hydroxide and sodium carbonate and some reaction with the available sulphuric acid would be expected and as such in practice the amount of hydrogen cyanide produced would be less than that assumed as in most cases sulphuric acid would not be present in excess. Similarly the amount of sulphuric acid and sodium cyanide assumed to be present in the solutions is at the top of the chemical control limits. In practice a somewhat lower content would be expected also leading to a somewhat lower release of hydrogen cyanide.
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14.0 Release Conditions
It is assumed that in the event of a significant release of hydrogen cyanide the high level cyanide alarm would be triggered and the Surface Finishes Department evacuated and all doors closed. The local exhaust ventilation systems serving the chromium and cadmium plating are expected to remain operating and will therefore exhaust hydrogen cyanide ladened air to atmosphere via ventilations exhaust flues A3, A4 and A5 (see Figure 4).
The throughput of these ventilation systems was most recently measured in December 2015. Table6 below summarises the measured conditions in each exhaust flue.
Table 6: – Exhaust Flue Characteristics
Exhaust flue A3 A4 A5 Velocity m/s 10.7 12.2 10.6 Temperature oC 24 23 24 m3/h 8844 7644 9418 Volume flow rate m3/s 2.46 2.12 2.62
Measurements indicate a total volume extraction rate for the cadmium and chromium plating area of 7.20 m3/s (25906 m3/h).
The cadmium and chromium plating area has a footprint of around 532 m2 and with a building height of 10.2 m the total volume is 5427 m3. If it is assumed that the hydrogen cyanide released does not disperse beyond the plating area then at the measured extraction rate a complete air change of the plating area and hence total discharge of the hydrogen cyanide produced will take around 12 minutes and 34 seconds.
Table 7 below presents the release rates of hydrogen cyanide for each flue for this worst-case scenario. The assessment assumes that there is uniform mixing of the hydrogen cyanide produced within the volume of the cadmium and chromium plating area. Based on the assumptions made a release of hydrogen cyanide will persist for 12 minutes and 34 seconds, however the environmental standards, which are being considered, have averaging periods of 15 minutes and one hour. The average release rates for each of these standards are also calculated and are used in the modelling as appropriate to recognise the average release rate over the averaging period of the environmental standard benchmark.
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Table 7 : Hydrogen Cyanide Release from Ventilation Stacks
Total hydrogen cyanide release 23.3 kg Concentration at source 4299 mg/m3
Hydrogen cyanide release rate over averaging period (g/s) Flue Full extraction 15 minutes 1 hour A3 10.56 8.85 2.21 A4 9.13 7.65 1.91 A5 11.25 9.43 2.36
15.0 Modelling Scenarios
ADMS 5.1 has been employed to estimate process contributions to ambient concentrations of hydrogen cyanide. For the assessment the model has been run using meteorological data for each of five years (2011 to 2015).
16.0 Modelling Results
ADMS 5.1 has been run for the worst-case release scenario. The results of the modelling are discussed below. In sections 17.0 and 18.0 the results are presented in tabular form and in section 19.0 contour plots are provided which illustrate the estimated process contribution to ambient concentrations of hydrogen cyanide over the assessment areas.
It is considered that over the area of the Safran Landing Systems site workplace exposure limits will be applicable, while beyond the site boundary it is more likely that Environmental Assessment Levels relevant to human health will need to be considered.
At each location considered the maximum hydrogen cyanide concentration resulting from the releases considered are determined based on a 15 minute or 1 hour averaging period. The maximum concentrations represent the maximum determined for the averaging period over the five meteorological years considered.
17.0 Impact of Hydrogen Cyanide Releases within Site Boundary
As shown in Figures 5 the location of maximum process contribution to ambient hydrogen cyanide concentrations for this scenario is within the site boundary and is in a north east to North West arc at approximately 100 m from the exhaust flues.
At the locations considered in Figure 2 the maximum hydrogen cyanide concentrations determined are summarised in Table 8 in terms of the workplace exposure limit.
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Table 8: Work Place Exposure Limit for Worst Case Scenario on site
Location Maximum process contribution of hydrogen cyanide (% WELa) (see Figure 3.2) Worst Case Scenario Maximum 209 1 63 2 40 3 61 4 62 5 61 6 57 7 62 8 58 9 48 10 70 11 51 12 56 13 58 14 44
The Short term WEL for hydrogen cyanide is 11000 µg/m3 averaged over a 15 minute period.
For this scenario, which is considered a highly unlikely worse case condition, the maximum concentration within the site boundary is equivalent to around 209% of the WEL. Most locations within the site boundary are subject to maximum concentrations, which are below the WEL. In the event of a release from the Surface Finishes Department via the ventilation exhausts A3 to A5, it would be most appropriate to evacuate towards the south (Cheltenham Road) or south west (Down Hatherley Lane) where maximum concentrations are below the WEL.
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18.0 Impact of releases beyond the site boundary
As shown in Figure 5 the highest concentrations of hydrogen cyanide resulting from this release scenario is generally confined to within the site boundary. The Ashville Business Park and in particular the Ambulance Station and warehouse bordering the site boundary on Commerce Road are located in the direction of the prevailing wind and are the most affected of all locations beyond the site boundary as shown in Figure 6.
Table 9 summarises the maximum process contributions of hydrogen cyanide at the off-site locations considered in Figure 1. Process contributions are reported as a proportion of the Environmental Assessment Level.
For this scenario the area of exceedance of the Environmental Assessment Level extends to around 500 m in all directions from the exhaust flues. The Ambulance Station and warehouse to the north east of the site on the Ashville Business Park are most affected with exceedances of 4 times and 6 times the EAL respectively. Commercial locations to the southeast beyond Cheltenham Road also experience significant exceedances. Only the two closest of the residential locations considered (Terncourt and Poplar Cottage) experience an exceedance of the EAL.
Table 9: Process contributions of hydrogen cyanide at off site locations
Location Maximum process contribution of hydrogen (see Figure 3.1) cyanide (% EALa) Worst Case Scenario R1 Terncourt 107 R2 The Channings 63 R3 Woodfold Farm 43 R4 Wood Farm 43 R5 Mobile Home Park 38 R6 Poplar Cottage 153 R7 Blenheim House 83 R8 Boxtrees 66 R9 Snowdon Gardens 39 R10 Orchard Way 37 C1 Ambulance Station 444 C2 Ashville Business Park 637 C3 Mitsubishi 288 C4 Completely Motoring 348 C5 Vernon Court 221 C6 Jupiter Court 171 C7 Anson Business Park 59 C8 Sports Club 223 C9 Kennels 81 C10 Gloucestershire Airport 1 60 C11 Gloucestershire Airport 2 86 C12 Gloucestershire Airport 3 34
The short term EAL for hydrogen cyanide is 220 µg/m3 averaged over a one hour period.
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On the basis of Environmental Agency assessment criteria the process contribution of hydrogen cyanide would be considered significant at all residential and commercial locations considered in this worst-case scenario.
19.0 Dispersion Modelling Contour Plots
The results of the modelling of the impact of hydrogen cyanide releases on ambient ground level concentrations are presented in tabular form in Sections 17 and 18. In this section the results are presented as contour plots of the process contribution to ambient concentrations. All results are presented as the maximum contribution of the process (excluding existing background concentrations), expressed as a percentage of the applicable environmental benchmark. All plots are based on dispersion during 2014, which provided the maximum process contribution to ambient concentrations over the five years (2011 to 2015) considered in the assessment.
The plots are considered over an area of 400 m x 400 m (2) which essentially covers the immediate site where the workplace exposure limit (WEL) for hydrogen cyanide is considered to apply. Plots are also provided for a wider area (2 km x 2 km, see Figure 1) which covers the area in the immediate vicinity of the site and includes the closest commercial/industrial neighbours and residential locations. In this area, excluding the Safran Landing Systems site, the Environmental Assessment Level (EAL) for human health is considered to apply.
Exceedances of the WEL or EAL are illustrated as the 100% contour for display purposes. Areas in red therefore indicate a concentration exceeding the benchmark.
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Fig 5 : Worst Case Scenario Predicted concentrations of hydrogen cyanide (maximum 15 minutes mean - WEL) at 1.5 m for 2014
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Fig 6: Worst Case Scenario Predicted concentrations of hydrogen cyanide (maximum 1 hour mean - EAL) at 1.5 m for 2014
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20.0 Conclusions
Safran Landing Systems placed a contract with Environmental Scientifics Group Limited (ESG) to undertake an assessment of the impact on local air quality of an abnormal release of hydrogen cyanide from the surface finishing operations at its Cheltenham Road site. Four release scenarios were considered.
A worst case condition was considered where a failure of vat and bund containment resulted in the mixing of the total inventory of the four vats associated with chromium and cadmium plating and the production of hydrogen cyanide. Assuming that the Surface Finishes Department is evacuated and the air within extracted to atmosphere via the existing ventilation systems serving the vats, the resulting dispersion of hydrogen cyanide releases is predicted to have maximum impact within the site boundary. A maximum concentration of around double the workplace exposure limit is expected to occur 100m to the north east of the Surface Finishes Department. The Hydrogen cyanide concentration on most of the site is predicted to be below the workplace exposure limit.
For the scenario where the worst case condition occurred, but the building was sealed and the extraction system shutdown with only fugitive releases to atmosphere, concentrations within the site boundary were predicted to be reduced to below the WEL at all locations. This appears to be a somewhat more effective control measure for the protection of site workers following a release than the continued use of the extraction systems.
For the remaining scenarios considered, where the resulting hydrogen cyanide release was considerably lower than the worst case, the workplace exposure limit was not exceeded within the site boundary.
Beyond the site boundary the locations most affected by potential releases of hydrogen cyanide are the Ambulance Station and warehousing in Commerce Road which border the site boundary. For the worst case scenario maximum ambient concentrations of hydrogen cyanide were predicted to be around 4 to 6 times the Environmental Assessment Level for human health at these locations. Other commercial locations to the south beyond the Cheltenham Road and the two closest residential properties were also predicted to experience maximum concentrations in exceedance of the Environmental Assessment Level. Shutting down the extraction system and allowing the release to dissipate from the building by natural leakage does not appear to have the same beneficial effect for locations beyond the site boundary as for those on site. Predicted concentrations at the nearby commercial and residential locations were similar whether or not the extraction system was employed.
For the other scenarios exceedances in the Environmental Assessment Level were predicted at the Ambulance Station and warehousing in Commerce Road, although at much reduced levels compared with the worst case. No exceedances were predicted at the remaining commercial locations considered or at any residential location.
Necessary assumptions made to undertake the modelling are considered to have the effect of overestimating the process contribution to ambient concentrations of hydrogen cyanide. It is therefore considered that the predicted process impact on ambient concentrations 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.
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Appendix B – Site Map Showing Major Risk Locations
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