COPEDEC VI, 2003, Colombo, Sri Lanka

DAMIETTA LNG-NGL PROJECT : MARINE TERMINAL PLANNINGBy

Mannion1, M B, & Fidler, M A2

1Mr, Associate Director, Halcrow, mannionmb@halcrow.com2Mr, Senior Engineer, Halcrow, fidlerma@halcrow.com

ABSTRACT

BP is seeking to develop a natural gas complex on the Egyptian Mediterranean coast. As part of thedevelopment, a harbour was required. At an early stage, the approximate harbour location was identified at anexisting port facility. The possible scales of liquified natural gas (LNG) and liquified petroleum gas (LPG)production were also determined.

Alternative basin and jetty locations were considered. These looked at a range of possible LNG and LPGshipping scenarios. Minimising land use was a priority. This impacted on jetty design, possible bertharrangement, approach and turning circle requirements. Cost estimates were derived, including a risk-basedcontingency analysis.

Possible locations were dependent on the interaction of the marine location with on-land process plantefficiency. A Quantitative Risk Assessment was undertaken, parameters included risk of ship collision,emissions, and proximity to potential impact areas.

Coastal conditions were numerically modelled to assess the influence of wave disturbance, siltation andshoreline accretion/erosion on different layouts. Other considerations included the possibility of shippingdelays due to existing port traffic. Use of new layouts by gas carriers was assessed and existing portoperations reviewed, to identify future management needs.

Commercial considerations were a key driver throughout. Advantages and disadvantages of each option wereidentified and balanced against the wider impacts of the overall development, to select the preferreddevelopment option.

The paper focuses on the port planning factors involved and how these have been addressed and integrated,to ensure that the best option is taken forward.

1 INTRODUCTION

BP Egypt (BP) is seeking to develop a natural gas complex on the Egyptian Mediterranean coast. As part ofthe development, a harbour was required.

Halcrow was commissioned by BP in June 2000 to undertake a feasibility study of the civil/marine aspects ofa proposed LNG/NGL (natural gas liquids) terminal at Damietta Port on the Egyptian Mediterranean coast.The study involved conceptual layouts for marine facilities, preliminary design, cost estimates, programme andconstruction risk evaluation.

Previous studies by BP had identified Damietta as their preferred export location on the EgyptianMediterranean coast. It would benefit from the existing port facilities, compared to the significantly higher costof greenfield developments. Alternative locations with high wave exposure and susceptibility to siltation wouldinvolve greater cost and take longer to construct.

COPEDEC VI, 2003, Colombo, Sri Lanka

Figure 1 – Satellite image of Damietta Port area

2 TERMINAL PLANNING

The following marine factors were considered :

� Proposed traffic levels at the facility� Proposed range of ships� LNG/LPG carrier characteristics such as manifold position, vessel draft� Wave disturbance, siltation, tidal currents� Effect of existing port traffic (risk of delay & ship collision)� Ease of marine access, allowable downtime, acceptable ship motion� Constructability, programme duration� Cost estimates (capital, maintenance)

At the same time, non-marine factors had a large bearing on harbour position and the form of marine facilities.Marine traffic levels are based on the proposed export volumes for LNG & LPG. The on-land process plant ispreferably located away from habitation, aligned to match prevailing wind directions and with an efficientlayout within the available land plot.

At Damietta Port (Figure 1 & 2), the study focussed on an undeveloped plot of land on the western side of thePort. Damietta Port was formed in the early 1980’s by dredging out a large port basin with a depth of –14mCD(ref. 1), protected by long breakwaters and with an 11km long access channel maintained to –15mCD. ThePort has a mix of container, grain and bulk cargo berths. Over 1800 vessels visited it during 2000.

COPEDEC VI, 2003, Colombo, Sri Lanka

Figure 2 – Damietta Port existing features

4 EXISTING PORT CHARACTERISTICSThe existing channel is some 11km long and allows one way traffic at a maximum speed of 5 knots. Thechannel width provides more than 5 times maximum beam and meets the maximum draft requirement as well.

Early discussions with the Port Authority indicated that LNG/LPG ships would be provided priority access,thus avoiding expensive ship delays. Traffic simulation was therefore not required.

For future LNG/LPG operation within the port, the pilots will need to become familiar with the handlingcharacteristics of LNG/LPG carriers, the safety requirements and there will need to be sufficient allowance forand availability of tugs. For 135,000m3 LNG carriers, 3 to 4 tugs will be required with a combined bollard pullof the order of 120 tons.

The existing port turning circle provides an alternative for turning of incoming LNG/LPG carriers.

5 LNG/LPG CARRIER CHARACTERISTICSLNG carriers can vary in capacity from 20,000m3 to 135,000m3. LNG carriers of up to 135,000m3 capacitywere considered. This meant that an upper envelope of maximum overall length of 300m and beam of 50mwere allowed for (ref. 2). Tug manoeuvring room at either end was set at 125m. A maximum vessel draft of13.4m was allowed for.

A minimum LPG size of 24,000m3 was catered for (length 155m, beam 26.5m, draft 11.7m). Critically, it wasdecided that the facility should be able to accept a wide range of possible LNG and LPG vessels, rather thana restricted number of identified gas carriers. Many previous facilities have been designed to suit a limitednumber of vessels, however the gas market has an increasing trend in provision of more flexible facilitiescapable of dealing with spot trade.

COPEDEC VI, 2003, Colombo, Sri Lanka

6 JETTY CAPACITYInitially, a two-phase development was planned, as set out below :

Phase 1 Phase 2LNG capacity (mtpy) 6.5 13LPG capacity (mtpy) 0.37 0.74Ships/year 113 226Frequency (days) 3.5 1.8

Table 1 : Shipping frequency

This was based on 2 train production of 6,459,000 tonnes/year LNG and 367,000 tonnes/year propane, andthe use of 135,000m3 LNG and 70,000m3 LPG carriers.

Therefore Phase 1 required one jetty, a second would be needed for Phase 2. Each jetty would providecombined LNG and NGL loading.

At a later stage, the amount of land available to BP and partners at Damietta for development of LNG andNGL facilities decreased, so that a single jetty was considered.

7 BASIN SIZE AND SAFETY DISTANCEBasin size depends on a combination of

� Safety distance between jetty manifold and edge of existing dredged channel� Design vessel length & beam� Turning circle� Tug manoeuvring requirements

Safety distance is a key consideration, particularly for LNG cases. The consequences of damage to LNGcarriers is well known, whilst damage to the jetty or loading facilities can have major economic cost impact.The LNG industry has a remarkable safety record to date.

The fairway between berthed vessels for the two jetty case was kept at least three times beam. The basinentrance matched the adjacent turning circle, jetty and therefore basin preferred alignment is towards opensea – to allow rapid exit in case of emergency.

8 LAYOUT OPTIONSA range of harbour positions was considered, then narrowed down to three options, based on the combinationof considerations given above. These options were then considered in more detail (ref. 3).

Layout 1 (Inset Harbour) is based on a 500m safety distance from jetty manifold position to edge of dredgedchannel. The basin is located south of the western breakwater spur, aligned towards NE. It provides less landfor process plant.

Layout 2 (Outer Harbour) is very similar to Layout 1, except that the basin has been moved north so that it isnorth of the western breakwater spur. This would give more land, but requires a new breakwater section andpartial demolition of the existing breakwater.

Layout 3 (Layby) reduces the safety distance to 200m, with the jetty or jetties aligned due North. It is cheaperto build than Layouts 1 or 2, with a different risk profile.

Data necessary for evaluation of the layout options was collected. This included a topographic survey, existinggeotechnical data, a preliminary ground investigation and met data (wind, waves, temperature, currents,suspended sediment, shoreline change, bathymetry). Materials sourcing, constructability, programmeincluding permissions were considered, taking account of recent local and regional experience.

COPEDEC VI, 2003, Colombo, Sri Lanka

Figure 3 – Layout 1

COPEDEC VI, 2003, Colombo, Sri Lanka

Figure 4 – Layout 2 (Outer Harbour)

COPEDEC VI, 2003, Colombo, Sri Lanka

Figure 5 – Layout 3 (Layby)

COPEDEC VI, 2003, Colombo, Sri Lanka

9 MET OCEAN STUDY9.1 General To assist port planning, a preliminary met ocean study was undertaken, following collection of available wave,water level, sediment and current data (ref. 4, 5). The extent of shoreline change along the northern boundarywas also assessed.

9.2 Wave modellingHalcrow’s MWAVE wave refraction model takes account of wave diffraction, refraction, breaking and seabedfriction. It transformed offshore data to nearshore positions, for the existing situation and each of the threelayouts. This allowed consideration of wave downtime at each berth and preliminary design of shorelineprotection and (for Layout 2) breakwater amendments.

The results of the wave modelling showed that all three layouts were acceptable. Significant wave height atthe berth was less than 2m for the 1 in 50 year extreme event, for ships alongside. Achieving wave height lessthan 1.5m for loading was therefore not a concern.

The most critical direction is for waves from the north west. This illustrates the benefits of the shelter providedby the existing breakwaters. Design wave heights for shoreline protection were less than 1m south of thewestern breakwater spur.

Figure 6 – Tidal modelling output

9.3 Tidal modellingHalcrow’s DAWN three dimensional hydrodynamic model generated tidal currents inside and outside the Port,for the existing situation and three options. This assisted assessment of ease of navigation, consideration ofhandling characteristics of gas carriers being provided by BP Shipping.

COPEDEC VI, 2003, Colombo, Sri Lanka

The model was then used to consider sediment transport (and therefore siltation and dredging impacts) byaddition of wave driven currents, typical seabed grain sizes and suspended sediment concentration.

Given the limited tidal range at Damietta, it was found that wind generated currents from the north west werethe most significant for navigation, effecting passage at the end of the western breakwater.

The modelling shows that the existing port basin layout is not liable to siltation and that the three layouts willnot alter this pattern. The Port Authority indicates no maintenance dredging to date south of the westernbreakwater spur whilst near the end of the western breakwater, maintenance dredging of 1 to 1.5 millionmetre cubed is required per annum, in order to maintain the entrance channel declared depth.

9.4 Shoreline changeThe shoreline to the west of the western breakwater (i.e. the northern boundary of the development site) isgenerally accreting. Since port construction, the northern beach has accreted 9 to 15 metres per year.Therefore the feasibility study did not allow for shoreline protection on the northern edge of the development.

10 RISK OF MARINE COLLISIONThe risk and consequence of marine collision was assessed for the layouts (ref. 6). The possible marinehazards during harbour transits and whilst at berth were identified and include grounding, collision (vessel tovessel) and impact (vessel to object, such as jetty).

The consequence of striking of typical LNG or LPG carriers by existing port traffic (container vessels, bulkcarriers or Ro-Ro vessels) was assessed, for different angles of collision and speeds. Data for a range ofother ports worldwide was used, to make a qualitative assessment for LNG/LPG carriers. The studyhighlighted that insufficient data exists on the LNG specific risks.

Layout 3 was deemed to have twice the level of marine risk compared to Layout 2. BP undertook an overallQuantitative Risk Assessment, taking into account the full range of risks at the site, for each layout.

11 PRELIMINARY DESIGN OF JETTY

11.1 Jetty LayoutDue to the range of LNG and LPG ships being considered, six mooring and four breasting dolphins wererecommended. The layout of the jetty and dolphins was based on standard guidance (ref. 7, 8, 9), with theadditional consideration that manifolds will not necessarily be centrally located on the LNG/LPG carriers.

The manifold variation allowed for in this case was +5m to –33m off centre, based on a defined set of possiblevessels. The mooring dolphins must be capable of adequately restraining vessel movement whilst at berth,taking account of wind, waves and currents. The mooring dolphins would be fitted with quick releasesliphooks.

A jetty head of 30m wide by 25m deep permitted space for an LNG/LPG loading platform for loading arms andassociated topside facilities (transfer pipelines, valves, fire fighting equipment, navigation equipment, vesselaccess, lighting, services and space for maintenance crane access). The approach trestle width was 15m, thetrestle being short at this location. The distance from LNG berth to top of slope was circa 75m, using thesteepest achievable slopes based on site soil conditions and slope stability.

COPEDEC VI, 2003, Colombo, Sri Lanka

Figure 7 – Jetty Layout

11.2 Jetty Design FormThe jetty design is partly dictated by site soil conditions. At Damietta, these typically included a 12m upperlayer of sand (loosely compacted in the top 5m, denser with depth) above compressible Nile clays to circa30m, with lower layers becoming more competent with depth.

The alternatives can be divided into two main groups, gravity retaining structures and suspended deckstructures.

The following gravity retaining options were considered

� Solid blockwork wall (sits on rockfill to spread load, heavy 80 to 100 tonne blocks required)� Hollow blockwork wall (lighter load)� Concrete caisson structure (large monolithic structure floated into position)� Sheet piled cofferdam (interlocked web piles in closed 20m diameter cell, centre filled, high settlement

unless ground treated with surcharging and/or drains)

These rely on self-weight to resist overturning and sliding forces, more suited to sites with competentfoundations (not Damietta).

Suspended deck options were :

� Driven tubular piles (large diameter, hollow, precast, cost competitive over water or in poor soils)� Prestressed concrete driven (high end resistance, more expensive if two different forms of piling are used)� Bored cast in situ (more suited to hard ground where other methods are not feasible)

COPEDEC VI, 2003, Colombo, Sri Lanka

This form is more suitable for structures over water or in poor ground conditions. Vertical forces are taken byend bearing and/or pile skin friction (for Damietta, skin friction predominates). Lateral forces (berthing ormooring) are typically taken by raking piles.

Of the above, the hollow blockwork, caisson, cofferdam and driven tubular pile options were considered indetail. The driven tubular pile solution was chosen, considering a combination of cost, technical performance(particularly settlement criteria) and constructability.

12 COST ESTIMATES AND PROGRAMMEThe marine works cost estimates included dredging, site preparation, shoreline protection, and jetty.Estimates were prepared initially for the three options for two jetties, then later revised to allow for a singlejetty facility.

The option of LPG only jetties was also considered, especially as the NGL facilities would come on streamearlier than the LNG facilities at Damietta. Such a facility would have lower dolphin loads and thereforereduced size, also the number of dolphins would reduce. In the end, the focus was on providing a jetty toserve both needs. For all options, maintenance dredging was not a concern.

The dredging element made up 30 to 60% of the cost, with the jetty typically at 25%. The Layout 2 cost wasroughly double the Layout 3 cost, but did have the advantage of allowing sufficient dredged space for thefuture addition of a second jetty.

13 OVERALL HARBOUR LAYOUT SELECTIONOn comparison of programme, Layout 2 had the longest duration, at 17 months, due to the need to build thenew breakwater section first before dredging and jetty construction. Layout 3 had the shortest duration, at 11months. The final harbour selection had to take into account the following factors.

� Layout 1 uses too much of the available land and was therefore not favoured

� Layout 2 has a lower marine collision risk, but longer construction programme and higher cost. It providedgreater opportunity for expansion to a second jetty.

� Layout 3 has a higher marine collision risk, but shorter construction programme and lower cost There ishowever little room for expansion.

The preferred option for LNG development was Layout 3. Mitigation to reduce marine risk to acceptable levelsincluded provision of a guard tug. Confirmation of preferred option relied on consideration of integration ofNGL and LNG facilities, balancing commercial considerations with layout risks and consequences, the effectof mitigation and overall schedules. The preferred option for a combined LNG-NGL facility was also Layout 3.

As of July 2003, due to delays in commercial finalisation of the LNG development, an NGL only option hasbeen progressed, with a single jetty in the Layout 3 position. For NGL only, the shipping frequency decreasessignificantly and therefore the marine risk reduces to an acceptable level. The preferred option for NGL onlydevelopment was therefore Layout 3. Halcrow prepared design & build tender documents for a variation onLayout 3. Dredging and reclamation are in progress, with jetty construction due to commence shortly. Halcroware acting as client’s technical advisor. LNG facilities continue to be considered, dependant on commercialconsiderations. If progressed, then Layout 2 will be favoured for an LNG focused development. Theopportunity for a combined LNG-NGL facility has now passed.

COPEDEC VI, 2003, Colombo, Sri Lanka

Figure 8 – Layout 2 Detail

COPEDEC VI, 2003, Colombo, Sri Lanka

Figure 9 – Layout 3 Detail

COPEDEC VI, 2003, Colombo, Sri Lanka

14 CONCLUSIONSThe planning of marine terminal facilities for the export of LNG and NGL can involve a complex mix ofparameters, from ship sizes and projected throughput to jetty location, cost and construction duration. Land-side process plant layouts and commercial considerations must also be included.

Due to the nature of the investigations required, the provision of a sea berth can often become a criticalactivity in the development of an LNG or NGL project, and early consideration of the location and form of theberth is recommended.

Typical examples of activities with a long lead-time are site investigation surveys and coastal processmodelling, such as wave penetration and sediment movement studies.

Early investigation of the various options for a sea berth can provide the opportunity to devise layouts that aresympathetic to the natural environmental processes with a view to reducing both construction andmaintenance costs. Typical aims would be the optimisation of breakwater heights and lengths and thereduction of maintenance dredging. There is also the opportunity to research underlying problems morerigorously and devise more imaginative and cost effective solutions.

New berths located within existing ports can produce considerable cost savings; however interaction withexisting shipping movements and the division of responsibilities for operations and maintenance should beclearly agreed between all parties.

The Damietta project illustrates the operational flexibility now demanded by the promoters of such projects. Afacility was designed to accommodate a wide range of both LNG and LPG carriers to respond to changingmarket demands and structures, but with the penalty of a marginal increase in capital costs.

15 REFERENCES[ 1 ] Admiralty Chart No. 2578

[2 ] CLARKSON (1999) ‘The Liquid Gas Carrier Register’

[3] HALCROW (November 2000) ‘Egypt LNG Infrastructure Study. Final Infrastructure Study Report’

[ 4 ] COASTAL RESEARCH INSTITUTE (2000) ‘Damietta Met Data Report’

[ 5 ] HALCROW (November 2000) ‘Egypt LNG Infrastructure Study. Data Collection Report’

[ 6 ] EAGLE LYON POPE (May 2001) ‘Damietta Draft Marine Risk Assessment’ Report No. ELP-55025-0401-57008-Rev 0 for BP

[ 7 ] SIGGTO (January 1997) ‘Information Paper No. 14. Site Selection and Design for LNG Ports and Jetties’

[ 8 ] OCIMF (1978) ‘Guidelines and Recommendations for the Safe Mooring of Large Ships at Piers and SeaIslands’ Witherby & Co. Ltd.

[ 9 ] BRITISH STANDARDS INSTITUTION (1988) ‘British Standard Code of Practice for Maritime Structures –Parts 1 to 6 – BS6349’

COPEDEC VI, 2003, Colombo, Sri Lanka

KEYWORDS

Damietta, harbour, planning, LNG, NGL