2                         DESCRIPTION OF PROJECT AND ASSUMPTIONS

 

2.1                   Background

 

2.1.1              It is proposed that the PAFF will be located at an undeveloped reclaimed shoreline site at Tuen Mun Area 38.  It will consist of the following major elements: 

 

¨      a jetty with two berths, which together will accommodate a full range of vessels from 10,000 to 80,000 dwt vessels;

¨      a tank farm with gross aviation fuel tankage capacity of 264,000m3 on commissioning and an ultimate tankage of about 388,000m3 as well as pumps and associated facilities;

¨      on site operational facilities including offices;

¨      500mm diameter twin subsea pipelines to transfer the fuel to the aviation fuel system at the airport.

 

2.1.2              The planning, design and construction of the project is programmed to take in the region of 3-4 years, with the commissioning date estimated to be in 2009.

 

2.1.3              The overall study area showing the location of the proposed site and the proposed pipeline alignment is provided in Figure 1.1.  The details of each of the key elements of the facility are discussed below. 

 

2.2                   Tank Farm and Onshore Facilities

 

2.2.1             About 6.75 ha of land is required to accommodate the aviation fuel tank farm and associated facilities.  The proposed site for the tank farm at Tuen Mun Area 38 has been reclaimed by Government and is zoned for industrial use.  The site is situated at Siu Lang Shui just southeast of the Castle Peak Power station and is adjoined on the west by the Shui Wing Steel Mill and on the south-east by the proposed EcoPark and adjacent to that is land earmarked for industrial use in keeping with the other land uses in the area.  Further east is the River Trade Terminal. The allocated plot has a short length of sea frontage of 60m in width which extends inland for about 140m before widening out to a square area of about 217m in length by 278m in width, see Figure 2.1c.

 

2.2.2             No residential developments are present in the area and the closest substantial development, Melody Garden in Tuen Mun, is at least 3 kilometres from the proposed site.  The villages at Lung Kwu Tan are closer at about 2km away but are screened from the site by the Castle Peak topography.  However, there is a planned Holiday Camp to the North-East of the site along Lung Man Road at over 500m away.

 

2.2.3             It should be noted that the previous EIA study (April 2002) was undertaken based upon the project layout detailed in Figure 3.2a and a tank design capacity of 420,000m3.   However, changes were made to the detailed layout and an application for a variation (Application No. VEP-133/2004) to the then valid Environmental Permit EP-139/2002 was made.  However, during the development of the detailed design, FSD placed a restriction on the height of the storage tanks above the emergency access.  Thus, in order to comply with FSD’s requirement on the tank height (requested in April 2003), the height of the tanks were reduced from 32.0m to 24.7m and the volume of the largest tanks reduced from 39,000m3 to 35,000m3.  As a result, the ultimate capacity of the facility was reduced to 388,000m3 from 420,000m3, resulting in variation to the environmental permit (EP-139/2002/A) which was granted by EPD in February 2004.  Details of the revised layout approved by the VEP are provided in Figure 3.2b and details of the improvements made to the tank farm layout are detailed in EP Variation Application No. VEP-133/2004 and summarized in Table 3.2 below.   Also, as part of the changes made, and as shown in Figure 3.2b, the whole site has been shifted 10m to the southeast from that proposed in the original EIA of April 2002, to accommodate Lands Department’s commitment of a land extension to Shiu Wing Steel Mill. 

 

               Table 2.1      Summary of Tank Farm Improvements

 

Item

Previous EIA Report (April 2002)

Current Design

Improvement / Neutral

Change Initiated By

Dimension

1

Volume (largest tank)

39,000 cu.m.

35,000 cu.m.

Improvement

FSD

2

Tank height (highest)

32.0 m

24.7 m

Improvement

FSD

3

Distance from tank to bund

10.0 m

10.0 m

Neutral

--

4

Distance from bund to security wall

8.0 m

8.5 m

Improvement

FSD

5

Distance from bund to boundary

16.5 m (minimum)

18.5 m

Improvement

AA

Bunding

1

Bund with wave wall

None

Included

Improvement

AA

2

Height of bund wall (average)

4.6 m

4.8 m

Improvement

FSD

3

Height of inner security wall

2.0 m

2.0 m

Neutral

--

4

Drainage ditch

Included

Included

Neutral

--

5

Earth bund in landscaped area

None

1.5 m high

Improvement

Planning/EP

6

Outer security fence/wall

Open mesh fence

Impervious wall

Improvement

AA

 

2.2.4             In addition to these changes, the phasing of the tanks has changed with 8 (eight) to be constructed initially as shown in Figure 2.1c.  While Figures 2.1b and 2.1c show the current layout for the site and phasing for the construction of the tanks, indicative cross sections between the tanks and the lot boundaries with Shiu Wing Steel and the EcoPark are provided in Figures 2.1d and 2.1e respectively with the location of the cross-sections shown in Figure 2.1c.

 

2.2.5             The tank farm will initially house 8 storage tanks, 6 tanks of 43.5m diameter by 24.7m in height, one of 41.5m diameter by 24.7m in height and one of 35m diameter by 24.7m in height.  The tank heights refer to the total tank height but it should be noted that part of the tank will be positioned in the ground and as such only 23m will protrude above ground level.  The tanks provide a storage capacity of between 35,000m3 to 22,000m3.   It is intended that the tankage capacity would be increased once the initial capacity of 264,000m3 has been reached around 2025 to 2030. It is intended that the remaining 4 tanks would be built all together between 2025 and 2030 to increase the tankage capacity to the ultimate design tankage capacity of PAFF i.e. 388,000m3.  The heights of 3 of the remaining tanks would be 24.7m, with one tank of 23m and their capacities would vary accordingly between 35,000m3 and 19,000m3.  The 4 remaining tanks will be built according to the latest technology, industrial standards and statutory requirements at that time.  The height of the tanks has been reduced from that previously proposed in the April 2002 EIA in compliance with FSD’s specific requirements (Table 2.1), whereas the diameters of most tanks have been increased as a consequence of compliance with FSD’s tank height reduction requirement in order to maintain the designed fuel storage capacity of the tank farm. Each tank will be designed with a fixed cone roof.

 

2.2.6             The tank farm would be provided with bundwalls and contained drainage.  There are 2 main bunds (designed to contain any spills from the tank or tank piping), each containing 6 tanks in future but 4 tanks initially.  The height of the bundwalls has also been increased from previous April 2002 EIA in order to improve the retention of any fuel spillage from the tanks within the PAFF boundary.  The initial bund containment with 4 tanks in each bund would amount to at least 180% of the volume of the largest tank (well exceeding the required 110%) and ultimately (2040) this would be at least 150% of the volume of the largest tank with 6 tanks in each bund. Each tank is also separated by intermediate bund walls to hold minor spills.  There are also 2 emergency shutdown valves on the pipeline inlet to the tank farm from jetty and another 2 on the pipeline outlet of the tank farm to the Airport.  These valves are operated via motorized electric actuators.  The tank bunds and the pump platform are contained areas and drain to the interceptor via bund drain valves.  Other leakage prevention devices include fuel tank high-high level alarm and leak detection system for the pipeline.  The storm water drain will also have a remotely operated block valve to contain any oil spill on site.

 

2.2.7             Other shore based facilities would include office buildings for administrative and security control, leak detection instrumentation, fire fighting and emergency spill equipment, workshops and basic infrastructure including roads, drains, telecommunications, power supply and lighting.

 

2.3                   Berthing Jetty

 

2.3.1             The PAFF requires the construction of a twin berth jetty.  This will be sited approximately 200m offshore with no direct access to shore.  The two end to end berths would run approximately parallel to the quay wall and fuel tanker berthing would be provided on the sea facing side. The main activity at the jetty will be unloading of the tankers to the storage tanks in the tank farm.  Two unloading arms on one berth and three unloading arms at the other berth will be provided to unload the fuel at each berth.  Fuel lines and services will run to shore through submarine pipes and cabling protected by rock armour not protruding above the existing seabed, so as to provide marine access to other facilities adjoining the tank farm. Details of the jetty are provided in Figure 2.1c.

 

2.3.2             The sea bed level at the site lies between –17 and –18m PD indicating that water depths can reach 19.5-20.5m during the highest high tides.  As the berthing jetty would be built on piles, 100 tubular steel piles of diameter 800mm to 1000mm have already been driven into the seabed from 29 November 2005 to 29 March 2006 (with 59 days for actual pile driving time) using hydraulic hammers.  A key consideration in the design and construction was how to mitigate noise.

 

2.3.3             A particular consideration for this project is the need to protect marine mammals from disturbance during the piling.  Similar issues were raised when the temporary AFRF was constructed near Sha Chau in 1995.  At that time the Airport Authority were advised by a panel of international cetacean experts that percussively driven piles would be preferred over in-situ bored piles, as was the original intention at that time, based upon the decreased time required for this technique, although it would be important to strive to mitigate noise. (ERM 1996).  A similar approach was adopted in the piling of the PAFF.  This issue is examined in more detail in Section 7. 

 

2.3.4             Two defensive fender piles have already been installed on the on shore side of the jetty to prevent any possible collision from small craft straying into the prohibited area.  Coupling points on the ship would be provided with slop trays to catch occasional minor spills of unloaded fuels during coupling and de-coupling and the vessels will deal with the spills.

 

2.4                   Pipeline

 

2.4.1             A short buried submarine twin pipeline will connect the reception jetty to the onshore tank farm, together with the utilities required for the jetty.  The fuel from the jetty to the tank farm will be transferred at a rate of 3,500m3 per hour.  It is proposed that the fuel would then be delivered to the airport site by means of further buried twin subsea pipelines which would connect to the existing facility at Sha Chau.  The total length of the pipelines would be about 4.8km including a 400m stretch within the Lung Kwu Chau and Sha Chau Marine Park in the approach to the existing AFRF pipeline.

 

2.4.2             The twin pipelines would each have an outside diameter of 500mm. The pipelines will be operated at a pressure of 30 barg (gauge pressure) and have a pumping rate of 30,000m3 per day or 1,500m3 per hour based upon 20 hours per day of pumping.  It is assumed that these would be continuously welded, encased in concrete and lowered into a trench of 3m depth to protect against 6 to 22 tonne anchors.   Future dredging activities are planned along the pipeline route for a coal berth for CLP in Urmston Road and, therefore, in this section of the alignment, the pipeline depth will be increased to about 6.5m below seabed.  In both cases, the trench would then be backfilled with graded stones and rock armour to protect the pipelines.  Schematic illustrations of the proposed pipelines and utilities from the jetty to shore and from the tank farm to the connection with the AFRF at Sha Chau are provided in cross sections (A) and (B) respectively in Figure 2.2.

 

2.4.3             The pipeline from the PAFF to the existing AFRF would be connected by being brought up one of the existing dolphin piles and flanged together with the existing pipeline using a new valve arrangement incorporated in-between.

 

2.4.4             The trench is assumed to be formed by a combination of trailer suction hopper dredger for the deeper areas in Urmston Road and by grab dredging for the remaining length.  Graded stone and rock armour would be placed by bottom dumping from barges.   Graded rock would be subsequently placed either down pipe directly into the trench or lowered by grab. The proposed outline construction method for the placing of the rock armor is provided below:

 

¨            The submarine pipelines are protected from dragging anchors by layers of large crushed rock up to 700mm in size. The crushed rock will be quarry rock without clay or silt contamination minimising any release of additional sediment load to the surrounding waters;

¨            It is proposed to use a target barge, hopper barges, and derrick lighters for the backfilling work;

¨            Position of the target barge will be controlled by DGPS (Differential Global Positioning System). The barge will be held in position with 4 mooring lines;

¨            The first layer of material over the submarine pipelines will be Grade 200mm bedding layer.  This layer of rock will be placed by hopper barge in shallow (less than 10 metres) water depth areas. A derrick lighter will be used for placing the protection layer at section where the water depth exceeds 10metres;

¨            When the target barge is set to correct position, the hopper barge or derrick lighter will be moored to the target barge and backfill of rock will commence;

¨            The protection berm will be checked by echo sounding to ensure sufficient rock cover is provided before placement of Grade 700mm rock fill layer in a similar manner;

¨            A derrick lighter will trim the rock to the required profile, to ensure no rock protrudes above the original seabed level;

¨            Intermediate surveys by echo and chain soundings will be conducted to verify the rock profile; and.

¨            On completion of rock dumping work, a hydrographic survey will be carried out to verify the profile of the rock armour complies with the design requirements. A copy of final survey will be transmitted to the Marine Department and the Lands Department for their records.

 

2.4.5             A possible alternative to dredging a trench for the pipelines would be horizontal directional drilling, tunnel and ploughing.  These techniques have been discussed in Section 2 of this report and dismissed on engineering, programming, environmental and cost constraints. 

 

2.5                   Tanker Visit Frequency

 

2.5.1              The fuel reception jetty will provide two berths to allow flexibility to accommodate a full range of vessels within the size range 10,000 to 80,000dwt.  Fuel would typically be received at a frequency of three times per week rising to a forecasted average of 3.6 occasions per week at the 2040 planning horizon.

 

2.5.2              A detailed breakdown of the expected tanker offloading frequency assumptions is provided in Table 2.2 below.

 

               Table 2.2      Tanker Frequency Estimate

 

Year

Volume in tonnes

Source/

Frequency

No. of vessels

Parcel size

Volume in tonnes

Market share

2010

 6,000,000

China

60

20000

1,200,000

20%

Singapore

64

45000

 2,880,000

48%

Middle East

32

60000

 1,920,000

32%

Total volume

Vessels/ Year

Vessels/ Week

 

 

 6,000,000

100%

156

 

 

 

3.0

 

 

 

2040

8,740,000

China

70

30000

2,100,000

24%

Singapore

80

45000

3,600,000

41%

Middle East

38

80000

3,040,000

35%

Total volume

Vessels/ Year

Vessels/ Week

 

 

8,740,000

100%

188

 

 

 

3.6

 

 

 

 

2.6                   Emergency Backup Facilities

 

2.6.1       In order to ensure the security of fuel supply to the airport, it will be necessary to maintain the existing aviation fuel reception facilities and associated pipeline as an emergency backup following commissioning of the PAFF.  This strategic need was recognised at the time that the temporary facility was gazetted.  The existing temporary AFRF could not be abandoned because of need to safeguard supply in the event that that the new PAFF ever became damaged or inoperable for whatever reason.  This eventuality is considered to be remote but nonetheless must be guarded against given the strategic and economic necessity of guaranteeing constant fuel supply to the airport.  For this reason it will continue to be necessary to maintain the dredged access channel and also to maintain the existing pipeline. Based upon the selected pipeline option, regular flushing of the existing pipeline at a frequency of approximately once every 6 weeks to avoid stagnation of the sitting pipe volume and potential contamination of the down stream fuel supply is not required.