10 HAZARD TO LIFE ASSESSMENT

10.1 Introduction

This section of the Report presents the findings of the hazard assessment for the Tung Chung to Ngong Ping Cable Car System as stipulated in the Environmental Impact Assessment (EIA) Study Brief No. ESB-068/2001 ~~Section 2.1 ‘Objective of the EIA Study’ part (viii) –~~ to identify the risk to the passengers and workers of the cable car should there be an incident at Hong Kong International Airport (HKIA) fuel storage tank farm ~~and Section 3.3.10 of the Study Brief~~.

10.1.1 Objectives

The objective of the risk assessment is to quantify the potential risk to site workers and passengers on the cable car, during and following construction, should there be incidents in the aviation fuel storage area at HKIA (hereafter referred to as the tank farm). The risks are evaluated against the established criteria in Annex 4 of the Technical Memorandum on Environmental Impact Assessment Process (TM).

As defined in the Study Brief the scope of this assessment is to:

· identify all potentially hazardous scenarios associated with the aviation fuel storage at HKIA that will impose risk to cable car passengers and workers during construction and operational phases;

· conduct Quantitative Risk Assessment to assess the associated risk and express the risks in both individual and societal terms;

· identify practicable and cost effective risk mitigation measures if required.

This study brief deals with Dangerous Goods Storage in accordance with EIAO Technical Memorandum, Section 12, Annex 4 and Annex 22.

The following sections present the background information used in the assessment, define potential hazard scenarios, develop the consequence analyses and quantify risks and provide recommendations and mitigations measures where appropriate.

10.1.2 Context of the Cable Car System in Relation to the Aviation Fuel Tank Farm

The relative location of the cable car with respect to the Aviation Fuel Tank Farm on the airport island is illustrated on Figure 10.1, from which it can be seen that the closest distance between the facilities is about 270m. Potential concerns associated with these two facilities being located in the same general vicinity relate to the risks to passengers or workers in the event of a fire, or a spillage of fuel which could ignite. The events triggering fires at the tank farm are described in detail in the subsequent sections.

10.1.3 Potential Scenarios to be Examined

For the construction phase the concerns relate to the number of cable car workers (up to 100 number) involved in construction of the Angle Station and towers. For the operational phase both the cable car workers (3-6 number) at the Angle Station and the passengers (refer to Section 10.2.4) need to be considered.

The scenario of spillage of fuel being released to the drainage system and thereafter discharging to the Sea Channel has been discounted as the drainage system at the airport was specifically designed to avoid drainage from around the tank farm discharging into the Sea Channel. From the tank farm area the stormwater drains discharge to Tung Chung Bay (to the east of the Airport) as shown in Figure 10.2. There are a series of measures in place at the Airport to minimize the risks of discharge of fuel to sea such as flap valves and shut down mechanisms for the drainage outlets as reported in the New Airport Master Plan EIA Update (1998). The stormwater system drains via a “Spill Trap Containment System” to the Outfall No. 10 which is located, approximately 700m from the tank farm to the east of the Airport Island as indicated in Figure 10.2.

~~As described in Section 10.~~32,, the tank farm is enclosed within inner and outer bunds. This is to ensure that there is no direct discharge of any spilled fuel or stormwater run-off from the area which could be contaminated by fuel without the run-off first passing through an oil-water separator. Valves are provided on the stormwater discharge pipes from the tank farm and will be normally kept closed. These are only opened for discharge of stormwater to the airport drainage system under close supervision of the tank farm operations staff. The provision of oil separators, free swinging gates and outfall penstocks in the “Spill Trap Containment System” further reduces the potential of a fuel oil draining to the sea from the tank farm area.

As a fire in the tank farm would generate smoke plumes containing toxic gas such as CO and CO₂ and heat which may pose certain risks to the cable car passengers, this study has assessed the risk to the users of the cable car system in the context of fire (heat and smoke) scenarios.

Figure 10.1 Location of Tank Farm

Figure 10.2 Drainage Basins and Outfalls

10.2 Background Data

10.2.1 Aviation Fuel Tank Farm

Aviation fuel, Jet A-1, is stored in tanks above the ground at in the south ~~side support area~~ of HKIA at ~~with~~ a distance of 1.32 km from the southern runway ~~of the HKIA~~ (refer to Figure 10.3). The tank farm maintains an uninterrupted aviation fuel supply even during typhoons.

The tank farm comprises nine tanks: six large tanks, each with 20,000 nominal cubic metres of storage capacity (39m in diameter and 20m in height) and three small tanks with 10,000 nominal cubic metres of storage capacity (27.5m in diameter and 20m in height).

The tanks are enclosed by two bunds as illustrated on Figure 10.1 and the outer containment bund has a capacity of 75,000m³, which is equivalent to half of the total nominal storage capacity of the tank farm. Details of the site, inner bund and outer bund are shown in Annexes G-1 and G-2.

The drainage system at the airport was specifically designed to avoid drainage from around the tank farm discharging into the Sea Channel. From the tank farm area the stormwater drains discharge to Tung Chung Bay (to the east of the Airport) as shown in Figure 10.2. There are a series of measures in place at the Airport to minimize the risks of discharge of fuel to sea such as flap valves and shut down mechanisms for the drainage outlets as reported in the New Airport Master Plan EIA Update (1998). The stormwater system drains via a “Spill Trap Containment System” to the Outfall No. 10 which is located, approximately 700m from the tank farm to the east of the Airport Island as indicated in Figure 10.2.

There is no direct discharge of any spilled fuel or stormwater run-off from the area which could be contaminated by fuel without the run-off first passing through an oil-water separator. Valves are provided on the stormwater discharge pipes from the tank farm and will be normally kept closed. These are only opened for discharge of stormwater to the airport drainage system under close supervision of the tank farm operations staff. The provision of oil separators, free swinging gates and outfall penstocks in the “Spill Trap Containment System” further reduces the potential of a fuel oil draining to the sea from the tank farm area.

Air eliminators in the pipeline/tank farm fuel flow system remove entrained air and thereby minimize risk of explosion within the filters.

The area within 15m of the storage tanks is classified as an area in which ignition sources must be controlled and where safety procedures are being implemented by HKIA for operators working in the area. ~~All areas beyond 15 metres from the storage~~ ~~tanks are safe in normal operations.~~

For security and safety reasons, stringent controls on personnel access has been implemented at the tank farm area and CCTVs and microwave security system have been installed.

Of particular significance to this assessment are the automatically controlled Emergency Shut Down Valves which are provided at the inlets/outlets of the pipework of the storage tanks and pumps control system for use in case of emergency. Fire fighting systems have been installed including a fresh water fire hydrant system, storage tanks spray water-cooling system and base foam injection system.

Figure 10.3 Layout of HKIA Island

10.2.2 Cable Car System Information

The 5.7km long Bi-cable Cable Car System will convey up to 16 passengers in each of the gondolas/cabins between the two terminals, at Tung Chung and Ngong Ping, with a journey time of 17 minutes (in one direction). Initial capacity of the cable car system per direction per hour is 1500 passengers and can be increased to 3500. A total of 25 cabins will be operating in the initial stages of the Project. The height of the cable car at the Airport Island Angle Station is 50mPD (i.e. 43m from the ground). The Cable Car System should comply with the Aerial Ropeway (Safety) Ordinance (Cap. 211) and the Code of Practice of the Design, Manufacture and Installation of Aerial Ropeways (2002 edition) issued by the Electrical and Mechanical Services Department and any other amendments and existing ordinances in force.

10.2.3 Cable Car Workforce Estimation

Since details of the staffing of the cable car operation are not yet available, an estimation of the workforce employed during construction and operational phases is based on experience of similar systems as summarized in Table 10.1.

Table 10.1 Workforce estimation in Construction and Operation Stage

	Construction Phase	Operation Phase
	Cable Car site on airport island	Angle Station
		Day	Night
Quantity	100^#	3^*	6^*

* Information of workforce from Future Cable Car Operator.

# Estimated Figure.

10.2.4 Cable Car Passenger Estimation

The estimated number of passengers exposed to hazards associated with the operation of the tank farm is outlined in this section. Table 10.2 shows the estimated daily patronage of the cable car system extracted from the Tourism Commission, Economic Services Bureau.

Table 10.2 Estimated Daily Patronage

Year	High Scenario		Medium Scenario		Low Scenario
Year	Average Day	Peak Day	Average Day	Peak Day	Average Day	Peak Day
2006	7000	25300	5300	19100	3800	13600
2011	8100	29200	5900	21100	4200	15100
2016	9600	34800	6400	23000	4600	16500

Based on the assumption that the cable car operates 16 hours per day, the incoming patronage per hour is shown in Table 10.3 below:

Table 10.3 Calculated Hourly Patronage

Year	High Scenario		Medium Scenario		Low Scenario
Year	Average (/hr)	Peak (/hr)	Average (/hr)	Peak (/hr)	Average (/hr)	Peak (/hr)
2006	438	1581	331	1194	238	850
2011	506	1825	369	1319	263	944
2016	600	2175	400	1438	288	1031

When the Cable Car operator receives notification of a fire or suspected incident at the tank farm, he will immediately cease boarding passengers. Any passengers on the system at such times will continue their journey until all passengers are cleared from the system. It must be stressed that it takes 17 minutes to clear all passengers from the system. Thus the number of passengers on the system in each direction can be estimated [i.e. (Hourly Patronage / 60) x 17 minutes] and the results are given in Table 10.4 below:

Table 10.4 No. of Patronage in System per Direction

Year	No. of passengers in system in a Tank Fire Hazardous Event
	High Scenario		Medium Scenario		Low Scenario
	Average	Peak	Average	Peak	Average	Peak
2006	124	448	94	338	67	241
2011	143	517	104	374	74	267
2016	170	616	113	407	81	292

10.2.5 Properties of Aviation Fuel

Aviation fuel is a mixture of aliphatic hydrocarbons with 10-16 carbon atoms and some aromatic hydrocarbons and naphthalene derivatives. It is a colourless/pale yellow oily liquid with a “fuel” odour. It is flammable and toxic if inhaled at high concentrations or ingested. According to Dangerous Goods Regulations, aviation fuel is classified as Category 5, Class 2 Dangerous Goods. The Institute of Petroleum has produced a code for area classification (IP, 1990a) which includes a system for classifying petroleum liquids including crude oil and its products into Classes 0, 1, II(1), II(2), III(1), III(2) and Unclassified based on their flash points. Under this system, the aviation fuel is classed as II(1) as its flash point is a minimum of 38°C .

The physical and chemical properties of aviation fuel are summarised in Table 10.5 below:

Table 10.5 Physical and Chemical Properties of Aviation Fuel (Jet A-1)

Property	Value
Molecular Weight	156 g/mole
Liquid density	800 kg/m3
Boiling Point	200-260^oC
Specific Gravity at 15^oC	0.8 (liquid)
Flash Point	38^oC or above
Flammable Limits	0.7-5% vol.
Burning Rate	0.04 mm/sec

10.3 Hazardous Scenarios

10.3.1 Hazardous Scenarios from the Tank Farm

An inspection of the EIA Report (Ref. 1) for Permanent Aviation Fuel Facility (PAFF) ~~for Hong Kong International Airport~~ was undertaken to draw out information by which to determine whether the construction or operation of the cable car system could be affected by the tank farm. All the data and assumptions used were compared and contrasted to identify differences. Table 10.6 summarizes the hazard scenarios considered in both the PAFF and this study and highlights the differences. Further details of each of the scenarios are given in the subsequent sections.

Table 10.6 Comparison of Hazard Scenarios

Scenario	Considered in PAFF	Considered in Tung Chung Cable Car Hazard Assessment
Tank fire	Yes	Yes
Tank to tank escalation	Yes	Yes
Bund fire	Yes	Yes
Bund fire escalation	Yes	Yes
Catastrophic failure leading to failure of the top plate of tank	Yes	Yes
Aircraft incident	No (as the tank farm is not under the flight path)	Yes (although as for the PAFF it was considered that the system is not under the flight path, this scenario is addressed later in this section)
Hazards from Submarine Pipeline	Yes	Pipeline leakage is outside the scope of the EIA study brief. However this scenario has been assessed and the conclusion is that there is no impact to cable car passenger, staff and workers.
Hazards due to Marine Transport	Yes	No (Not applicable )
Hazards at the Jetty	Yes	No (Not applicable)
Tank fire caused by Cable Car Operations	No (Not applicable)	Yes
Tank fire caused by activities during construction of cable car	No (Not applicable)	Yes

A comparison of the fuel tanks assumed in the PAFF and those at the tank farm at HKIA is summarized in Table 10.7.

Table 10.7 Comparison of Tank Design of PAFF and HKIA

Feature	PAFF Tank Farm	HKIA Tank Farm
Diameter	40m	39 m and 27.5m
Height	Between 23m to 32m	20m
Volume of the largest tank	39,000 cubic meters	20,000 cubic meters
Height of Inner Bund	4.6m	~1.5m
Height of Outer Bund	2m	~1.2m
Distance between tank and inner bund wall	10m	Min. 10m
Distance between inner and outer bund walls	8m	12 – 75m
ESD valves	On the inlet and outlet pipeline of the tank farm	Both on inlet and outlet with Nitrogen backup in case of electrical failure.
ESD initiating	Manual push-buttons actuation of the fire alarm system fuel tank high high level sudden drop in pressure in the delivery pipelines.	Manual push-buttons actuation of fuel tank high high level a sudden drop in pressure in the delivery pipeline.
Leak detection system	Provided for the delivery pipeline	Provided for the delivery pipeline (for testing purpose). The leakage test for each section of pipe to be performed fortnightly.
Fire Fighting Facility	Sea water pumps to provide fire water for tank cooling	Fresh Water fire fighting system
Tank Spray Cooling	Yes	Yes
Base foam injection facilities	Yes	Yes
Bund	110% of the contents of the largest tank in the bund and secondary bund wall	110% of the contents of the largest tank in the bund together with a outer bund that can hold 50% of the total volume
Drainage discharge Manual Shut Off Valve	Yes	Yes
Interceptor.	Yes	Yes

Tank fire

Fixed cone roof tanks are generally used for flammable liquids and combustible liquids as is the case for aviation fuel, which is flammable with a flashpoint of 38^°C or above. Tank fires are essentially treated as pool fires, in which the liquid surface and hence the base of the flame is elevated and is surrounded by a metal wall.

Tank-to-Tank Escalation

The Tank-to-Tank Escalation can result in an adjacent tank fire. However all storage tanks at HKIA are installed with a water spray cooling system and the adjacent tanks (in the sector opposite the tank on fire) will be cooled in the event of a tank fire.

As mentioned in the PAFF report (Ref. 1),, ~~Purdy’s~~ studies on tank fire escalation modelling have provided some general observations regarding the escalation potential for non-volatile fuels (such as aviation fuel). A relatively long response time was found for tank escalation to occur. The radiation level on the adjacent tanks was approximately 13-15kW/m² given the distance between tanks was 15m. At this level the heat is not sufficient to threaten the structural integrity of the adjacent tanks particularly when cooled by water spray. The studies also suggested that escalation potential was greater for smaller diameter tanks (around 10m) and less for larger diameter tanks, as in the case of this study (the diameters of the tanks at HKIA are 27.5m and 39m).

In summary, the time required to develop an escalation condition depends upon a number of factors such as tank separation, water cooling, tank fire extinguishing system, wind speed/direction as well as the emergency response time of Fire Services. In a tank farm fire drill it was demonstrated that Fire Services could arrive the tank farm within three minutes from the nearest Fire Station at HKIA. .~~Therefore the~~ The time ~~required~~ scale for a tank-to-tank escalation~~, with cooling,~~ will be much greater than the time ~~sufficient~~ for cable car passengers to be evacuated (noting that the entire evacuation procedure for cable car passengers requires 17 minutes). With reference to the above studies, detailed analysis of tank-to-tank escalation fire hazard is deemed unnecessary in this assessment because of the length of time taken for the escalation to develop. However, emergency plan for cable car passenger evacuation in the event of tank fire needs to be developed (see Section 10.7).

Bund fire

A bund fire can result from release of liquid fuel from a tank caused by catastrophic failure, overfilling or pipe failures together with a subsequent ignition of the released fuel. There are a number of potential ignition sources such as hot works, vehicles, lightning, etc. Although there is a very stringent procedure to control the ignition source within the tank farm and the chance of ignition is small, the bund fire scenarios are addressed below.

Bund Fire Escalation

In the case where a bund fire occurs at the tank farm following release of fuel into a bund, the water spray cooling system would be activated. The water spray cooling system would effectively reduce the amount of heat generated by the fire that may result in an increase in the liquid temperature of the tank contents of the adjacent storage tanks and correspondingly increase in the evaporation rate and eventually lead to a tank fire. The operator of the tank farm would also report the fire to the Fire Services Department. Under normal circumstances, the Fire Services would arrive at the tank farm within 35 minutes to reach the site and handle the fire. In addition, ~~API 650~~BS 2654 tanks are designed to withstand fire engulfment for a considerable period before failure occurs by means of relief of vapours in the event of fire by failing along the roof to shell connection. Therefore failure due to flame engulfment is expected to take a significant time, and by the time it occurred, all passengers would have been evacuated (i.e. 17 minutes to clear the system). As such, further analysis is not necessary provided an emergency plan is developed for cable car passengers (see Section 10.7).

Fire Following Overtopping of Bund

In the PAFF EIA Report the conservative scenario in which the top plate of the tank ruptures, is considered, releasing a quantity of fuel from the top of the tank instantaneously. This case is also relevant to the HKIA tank farm. Part of the released fuel could potentially overtop the bund wall due to momentum and initial surge or splashing of the liquid, even though a bund wall as well as a secondary containment earth bund is provided. It can be seen in Figure 10.4 (which indicates that the minimum distance between Tank T-11-006 and the outer bund wall is 32m and that for Tank T-11-008 is 22m) that spillage from tanks T-11-006 and T-11-008 are considered to be the worst case for overtopping the secondary containment bund with respect to the cable car.

The PAFF report assumed that the top most plate of the tank wall may fail resulting in spillage onto the bund. Each plate is about 3m high which represents about 10% of the tank height. Therefore it is assumed in the PAFF report that 10% of the total contents of a storage tank would spill out and fall vertically onto the bund like a waterfall and 10% of this spillage could further splash over the bund and fall onto the secondary bund. It was also assumed that 10% of the fuel falling onto the secondary bund would further overtop the secondary bund. The height of the tank ranged from 23 to 32m.

The height of the bund wall in the PAFF is 4.6m and the distance between the tank and the bund wall is 10m. The distance between the bund wall and the security wall (secondary bund) is 7.5m. Beyond the security wall, there is boundary fence which is 4m from the security wall and a drainage ditch to be provided to trap any liquid splashed over the security wall.~~. (i.e. the splashing is completed and all liquid would be contained within 22m from the tank)~~

By comparison, tanks at HKIA are 20m high with a top plate of 2.81m high. The maximum fuel level is at 19m. Therefore in the event of roof failure, about 1.8m of fuel could be released which is equivalent to about 10% of total contents of the tank.

It can be seen in Figure 10.4 that the minimum distance between a tank and the inner bund is 10m and the minimum distance between the inner and outer bund is 12m. The inner bund is 1.2m high which is lower than that in the PAFF. In view of the fact that there are uncertainties associated with estimating the volume of fuel splashed and the HKIA tanks are less high and have a wider distance between bund walls, it is appropriate to adopt the same assumptions used in the PAFF report, i.e. 10% of the fuel may splash over the inner bund and 10% of this may splash over the outer bund. As a result, about 100-200m³ (depending on the size of the tank) fuel will spread over the emergency access road up to the gulley (the distance from this gulley to the Angle Station is about 200m but still within the tank farm). This assumption has been supported by a demonstration, andpictures presented in Annex G3 show that liquid will collect near and drain into the gulley provided along the emergency access road within the tank farm. Thus, none of the fuel will reach the public road and most of the fuel will enter the stormwater drain provided in the tank farm. As described in Section 10.2.1~~1.3~~ these drains connect to outfall number 10 on the east of the Airport Island. In the extremely unlikely case that if the fuel drain to sea via outfall no. 10, the fuel would move to the surface and then if ignited a pool fire could occur at sea. The pool fire would be 700m away from the Angle Station and will not, therefore, affect the cable car.

The fuel remaining on the emergency access road (within the tank farm) could be ignited to form a pool fire if an ignition source were present, although the probability of ignition is small within the site boundary. The minimum distance from such a fire to the Angle Station is around 200m.

About 10-20m³ of liquid may overtop the outer bund and splashes onto the lawn area which is a 28m wide open dished grassed area. A cross section showing the details of bund walls and the lawn is given in Figure 10.5. A trial has been carried out to assess how the far the fuel can reach when the liquid splashes on the lawn area. The result shows that the fuel would reach approximately half width of the grassed area (demonstration pictures are attached in Annex G3). The fuel will then drain into an open drainage channel, which parallels the tank farm boundary fence within and along the grassed strip (about 1.2m depth and 35cm width and 150m long). No fuel will reach the public roadway. If an ignition source is present, fire could develop along the channel. The closest distance from the open channel drain to the Angle Station is about 230m.

Aircraft Incident

The site is located at the most southern part of the airport island with a perpendicular distance of 1.32km to the southern runway of the airport, 3.24km and 1.45km from the ends of the southern runway. The site is further protected by a hill 68m high on the southeast quadrant and is surrounded by a number of buildings. The physical environment provides shielding which reduces the chance of a direct hit on the tanks farm by aircraft.

In addition, aircraft movements at HKIA are carefully controlled by air traffic controllers who will not permit any low flying aircraft from flying over or close to the tank farm, thus further reducing the possibility of aircraft striking the tanks. Aircraft taking off and landing are confined to the runways which are more than 1km away from the tank farm and the directions of taking off and landing will not take the aircrafts towards the direction of the tank farm. In accordance with the PAFF, aircraft crash is the only conceivable incident that can result in more than 10% of tank contents spilling instantly. However, as discussed above and shown in Annex G4, the estimated frequency of such accident is less than 1x10^-9 per year, which is below the Societal Risk guideline frequency as stipulated in the TM, and therefore further consideration is not necessary.

Hazard of Cable Car to Tank Farm

As shown in Figure 10.1, the nearest alignment of the cable car system is about 270m from the tank farm. This separation distance is sufficient to prevent the tank farm being affected by any ignition sources that may arise during the operations of the cable car within the Angle Station. Even in the very rare case that a hill fire starts around the Angle Station, it will not affect the tank farm as it is separated by Scenic Road which serves as a fire break. In addition, fire protection systems and procedures are also in place to control fire risk and fire services will arrive the site within a few minutes.

During the construction of the cable car the work boundary will be 20m from the location of the Angle Station and Tower T2B, and activities within the construction site would be mainly at ground level and will be strictly controlled by method statements and procedures. Further, the separation distance is such that construction activities will not cause any hazards at the tank farm.

Therefore, the hazards arising from cable car construction activities need no further consideration.

Other Hazards

Other hazards such as landslide, subsidence, typhoon, wind and earthquake, which could cause damage to the tanks, have been addressed in the design in accordance with the relevant engineering codes and standards adopted and therefore not considered further.

Summary of Hazard Scenario

In summary, the hazard assessment in this report covers the following potential scenarios.

· Tank Fire;

· Fire within Inner Bund;

· Fire within Outer Bund;

· ~~Grass /~~ Ditch Fire; and

· Pool fire at Sea Surface. .

Figure 10.4 Tank Layout

Figure 10.5 Indicative Cross Section

10.4. Consequence Analysis

10.4.1 General

~~Flammable liquid in the tank farm has such low vapour pressures that any hazards from drifting vapour can be ignored.~~ The only possible sources of off-site risk are thermal radiation and toxic smoke from fires.

The thermal radiation model used in the PAFF report has been adopted for this study. Aviation fuel fire is extremely smoky and the clear flame is only a few metres high at ground and most is obscured by smoke. As stated in the PAFF EIA report, modelling of pool fires incorporates the effects of the smoke in the flame. This shows that there is a significant reduction of transmissitivity which effectively shields persons near to the flame. This drastically reduces the fatal effect distance beyond the edge of the burning pool, particularly for large pools. The heat radiation from a smokye flame is 20KW/m². Sensitivity studies show that persons beyond 3m away from the fire are able to move away from fire and will survive. Hence, there is no fatality beyond 3m away from the fire.

The smoke plume trajectories are assessed using full scale fire data(Ref. 2).

10.4.2 Heat Radiation Effect

10.4.2.1Consequence of Tank Fire Events

Tank fires are treated as pool fires and the base of the flame is elevated and surrounded by a metal wall. The effect of tank fire is limited to the tank radius plus 3m (i.e. 22.5m from the centre of a large tank and 16.75m from the centre of a small tank) which is confined to the site boundary. Therefore, tank fires do not impose any risk to either cable car passengers or workers.

10.4.2.2Consequence of inner and outer Bund Fire Event

For a bund fire, the effective distance will be limited to 3m from the bund wall which again is within the site boundary. Thus, bund fires do not impose any risk to either cable car passengers or workers.

10.4.2.3Consequence of Ditch Fire

As shown in Annex G3.4, fuel will be contained in the open drainage which will go to underground at a point which is 230m from the Angle Station. Although ~~there is unlikely to be~~ an ignition source near the drainage channel is unlikely, fire may still occur along the ditch (length of the ditch is approximately 130 metres ~~fire would be about 20m~~). Therefore, the closest distance from the possible fire in the ditch ~~this location~~ to the Angle Station is 230m. Applying the r+3 model again shows that no risk is posed to cable car passengers, staff and workers.

10.4.2.4Consequence of Pool Fire on Sea Surface Event

The pool fire would be is about 700m from the Angle Station and would not impose any risk to either cable car passengers, staff or workers.

10.4.3 Smoke Effect

10.4.3.1Distance from Fire/Smoke

A smoke plume generated from the fire will initially follow the tilt angle of the flame due to its high temperature. An illustration of the flame tilt angle is shown in Figure 10.6. In the study report by HSE (Ref. 2),~~Research Report No. 96/1996) Development of Pool Fire Thermal Radiation Model,~~ a number of full scale fire experiments were used for model validation. These provide a good reference on the actual tilt angles and flame length under different scenarios. The data set contained different type of fuels and pool diameters. Data relevant to this study havebeen extracted from the HSE report and tabulated in Annex G5. It can be seen in Annex G5 that the maximum recorded tilt angle is 60^o and any fire at distance greater than 75m the smoke should pass over the cable cabin. A summary of the distance from fire from cable cabin is summarized in Table 10.8.

Figure 10.6 Illustration of Tilt Angle

Table 10.8 Summary of Distance from Fire

Fire Scenario	Minimum Distance from Cable Car (m)	Safer Distance (m)
Tank Fire	280	75
Inner Bund Fire	270	75
Outer Bund Fire	200	75
Ditch Fire	230	75
Sea Fire	700	75

According to Annex G5, the maximum recorded tilt angle of a flame is 60^o.and the safe distance from the fire is 75m. By comparing with Table 10.8, it is concluded that the smoke plume will pass over the cable car and the passengers will not be engulfed by the smoke.

10.5 Risks Determination

10.5.1 General

As shown in the previous section, no scenario is expected to result in any harm to passengers, workers or staff. Therefore, the risk to passengers, staff and workers are zero, lying below the lowest frequency of the acceptable region of the TM Annex 4..

10.6 Conclusions

Hazards associated with the Fuel Storage facilities on the HKIA adjacent to the alignment of the Cable Car System have been identified and analysed.

~~Four major hazards~~ Fivre scenarioss- tank fire, inner bund fire, ~~and~~ outer bund fire, ditch fire and pool fire on the sea ~~surface~~ have been considered.

In all scenarios, the distance from the fire to the cable car cabin are all over 200m and based on the heat radiation model developed for the PAFF, the resulting risk to life is zero. In regard to the smoke effect, the plume will rise well above the cable car cabin and therefore has no impact on passengers, staff or workers. In conclusion, the tank farm will pose no individual and societal risk to passengers, staff or workers. Therefore, the risks are acceptable when compared with the Risk Guidelines in the EIAO - TM (Annex G-16).

10.7 Recommendations

Any emergency plan ~~Effective communication channels~~ should be ~~established~~ developed between the cable car operators, the ~~and~~ tank farm operator, the Airport Authority and emergency services to ensure passengers can be evacuated from the cable car ~~that the former be immediately informed of any tank farm events so that emergency procedures can be carried out~~ in a timely manner in the event of an tank farm incident.

Communication andeEvacuation procedures should be agreed between the cable car operator, ~~developed with~~ the tank farm operator, the Airport Authority and emergency services.

The emergency plan should be tested and reviewed annually.

10.8 References.

1. Environmental Impact Assessment Report for Permanent Aviation Fuel Facility, Mouchel, 2002.

2. Development of Pool Fire Thermal Radiation Model, HSE Contract Research Report No. 96/1996.