YT-MF-G-06-02061

CONTRACTOR'S STAMP:

A FOR APPROVAL KSMU PNAN/HSV JJU 25-07-2011

REV. DESCRIPTION PREPARED CHECKED APPROVED DATE

EMPLOYER:

P.M.C.:

CONTRACTOR:

SAUDI ARCHIRODON LTD

DESIGNER:

PROJECT TITLE:

YANBU II POWER AND WATER PROJECT PACKAGE 2 - MARINE FACILITIES

Project No:

7200018815

DOCUMENT TITLE:

Intake Channel Layout Study (Flow Modelling) Location:

YANBU

No. of Pages 32

Including this page

DOCUMENT NO.:

YT-MF-G-06-02061 REV.: A


Intake Channel Layout Study

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CONTRACT Nº. 7200018815

YANBU II POWER AND WATER PROJECT - PACKAGE 2 - MARINE FACILITIES

Revision History

Rev. Section Description of change



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Saudi Archirodon Ltd.

Yanbu II Power and Water Project, Package 2 - Marine Facilities


July 2011

COWI A/S

Parallelvej 2

DK-2800 Kongens Lyngby

Denmark

Tel +45 45 97 22 11

Fax +45 45 97 22 12

www.cowi.com

COWI Project No. A017621 / P-75406

Prepared KSMU

Checked HSV/PNAN

Approved JJU



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YT-MF-G-06-02061 - Intake Channel Layout Study - Rev B.docx .

Table of Contents

1 Introduction 5

1.1 Project Location 5

1.2 Proposed Marine Facility 7

1.3 Scope of Work 8

1.4 Intake channel requirements and criteria. 9

2 Intake Channel Modelling 10

2.1 Modelling Approach 10

2.2 Model Description (MIKE 21 HDFM) 11

2.3 Model Bathymetry 11

2.3.1 Reference datum: 11

2.3.2 Bathymetry 11

2.3.3 Tendered Layout and Bathymetry: 13

2.4 Model Set-up 19

2.4.1 Water level Forcing 19

2.4.2 Intake conditions 21

2.4.3 Simulation time 21

2.4.4 Additional model parameters 21

2.5 Results 23

2.5.1 Flow Pattern 23

2.5.2 Maximum Current Velocities 26

3 References 32



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1 Introduction

The power and water utility for Jubail and Yanbu (MARAFIQ) will construct a

new 850 MW (net to the grid) power and water plant for Yanbu II Industrial

City (YIC II) which will satisfy a growing demand for power, process / potable

water and seawater cooling. The project will be located at YIC II on a new plot

which is currently vacant other than an existing, operational switch-yard locat-

ed at the Northern end [ref. (COWI, 2011)].

The site will be developed in several phases. The present project includes Phase

1 of the site development only.

Saudi Archirodon has been awarded the engineering procurement and construc-

tion (EPC) contract for the marine facilities and has engaged COWI to carry out

the detailed design of this part of the project. The marine facilities comprise a

seawater intake facility and associated pumping station, tunnels, thrust blocks

and a seawater outfall. The seawater intake facility will draw water from an in-

take basin. Dredging will be required to create this facility, with suitable

dredged material being used for land reclamation and to construct the cause-

way. The pumping station will be located on the reclaimed land. Seawater will

flow in GRP pipes from the pumping station to the battery limits of the P&W

contract, where the Power & Water Contractor takes over.

Return water will be discharged at the reef edge via two GRP pipelines. The

interface between the P&W contract and the MF contract is at the intersection

between the Eastern main site boundary and the P&W discharge channel.

1.1 Project Location

The Yanbu 2 Industrial City is located in Western Province of the Kingdom of

Saudi Arabia, approximately 280 km north of Jeddah, (see Figure 1.1). Figure

1.2 and Figure 1.3, shows the project location in the Admiralty chart no 326

and satellite imagery, dated 21-June-2010, respectively.



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Figure 1.1 Project location in the Red Sea. (courtesy: Google Earth).

Figure 1.2 Yanbu 2 project site in the Admiralty chart No 326.

Jeddah

Yanbu 2 Project

Area



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Figure 1.3 Yanbu 2 project site in the Satellite image (dated:21-June-2010).

1.2 Proposed Marine Facility

The proposed marine facilities comprise of seawater intake channel and outfall

structures. The seawater intake structure consists of two curved breakwaters.

The breakwaters are approximately 800-1000m long with roundheads located

close to the reef edge. The mouth defines the entrance to the channel, whereas

the pumping station located along the shoreline defines the end of the channel.

The seawater outfall consists of two 4m diameter GRP pipes buried in the sea-

bed. The tendered layout of the proposed cooling water intake and outfall facili-

ty for the Yanbu 2 project is presented in Figure 1.4 [ref. (ARCHIRODON, Sep

2010)].

Yanbu 2 Project

Area

Yanbu 2 Project Area

Comment [ksmu1]: Comment 8.SBAS� sentence to be reframed ??

HGLN?



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Figure 1.4 Sketch of Tendered layout of Yanbu 2 marine facilities.

1.3 Scope of Work

COWI’s scope of work is structured as follows:

• Task A Project and Interface Management

• Task B Project Definition and Planning

• Task C Data Collection and Desk Studies

• Task D Hydraulic and Coastal Engineering

• Task E Layout Confirmation/Optimization

• Task F Seawater Intake Channel Design

• Task G Pumping Station Design

• Task H Seawater Outfall Design

• Task I Buildings

• Task J Infrastructure

• Task K Hydraulic Tests

The scope of the present study as a part of TASK E [ref. (COWI, 2011)] is to

evaluate the overall layout of the marine facilities. Initially, flow modelling will

be carried out and subsequently wave penetration modelling based on design

wave conditions at the intake mouth will be carried out.

1.4 Intake channel requirements and criteria.

The layout shall comply with the requirements of the Civil/Structural Design

Basis of Marafiq/Jacobs R214-00/C.02a/0001 [ref. (Jacobs/Marafiq, Saudi

Comment [ksmu2]: 9.SBAS� Image changed/Incorporated



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Arabia: May 2011)] The following requirements are stated in the tender docu-

ments:

1 The intake channel bed level shall be at least -10.0m MYAS and the veloci-

ty must not exceed 0.2m/sec for a distance of 100m from the mouth for a

flow rate as required in document R214-00/P.02a/0002.

2 After this 100m from the mouth point it can become shallower at an incline

of 5% to a level that keeps the velocity at 0.3m/sec or less for the ultimate

development.

3 Seawater intake currents shall not exceed 0.3m/s through the trash screens

of the Phase I pumping stations

The above requirements translate into the following operational criteria:

1 For an intake volume of 1,200,000 m3/hr (Phase IV) during lowest astro-

nomical tide [ref. (COWI, 2011)] the sectional average current velocity

shall not exceed 0.2 m/s for a distance of 100 m from the mouth of the in-

take channel.

2 For an intake volume of 1,200,000 m3/hr (Phase IV) during lowest astro-

nomical tide [ref. (COWI, 2011)] the sectional average current velocity

shall not exceed 0.3 m/s in the part of the intake channel which will be

shared by multiple pumping stations once future phases are implemented.

3 For an intake volume of 280,000 m3/hr during lowest astronomical tide[ref.

(COWI, 2011)] the sectional average current velocity shall not exceed 0.3

m/s at the screening wall of the pumping station.

Compliance with criteria 1 and 2 is demonstrated analytically (Q/A < 0.2 m/s,

Q/A < 0.3 m/s respectively). Criterion 3 will be tested with the numerical mod-

el study, which is described in the subsequent sections of this report. Comment [ksmu3]: Comment 4.TZ & 10.SBAS� HGLN?? How are we going to

include the section?



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2 Intake Channel Modelling

The purpose of the intake channel modelling is to study in details the flow in

the intake channel, and to optimese the layout of the channel, so that the flow

into the pumping station is steady and uniform, and meet with the above men-

tioned criteria.

2.1 Modelling Approach

The modelling approach adopted is listed in the following [ref. (COWI, 2011)]:

1. The study is performed numerically with a 2D hydrodynamic flow model

(MIKE 21 HDFM model).

2. Three layouts are tested in the MIKE 21 HD/FM model: (1) The tendered

channel layout, (2) Flow optimized channel layout 1 and (3) Flow opti-

mized layout 2.

3. The model extends approximately 150 m outside the mouth of the channel

and covers the entire intake channel.

4. At the offshore boundaries of the model (at the intake mouth) the water lev-

el is defined as LAT, which is -0.40m MYAS.

5. Along the pumping station an open discharge boundary is generated with a

constant flux of 280,000 m3/hr.

6. A bottom friction of M=32 m1/3/s (Manning Number) is applied in the open

channel and along dredged sloped. A bottom friction of M=25 m1/3/s is ap-

plied on rock slopes to simulate higher roughness on rock armoured slopes.

7. The results are presented in terms of 2D colour plots with flow vectors.

Furthermore, the flow is extracted along cross sections in the channel 10 m

and 50 m from the pumping station and compared with criteria 3 in terms of

velocity sections and directional sections for the various layouts.



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In the present report the results of channel modeling for the tendered channel

layout and the flow optimized layout 1 are presented.

2.2 Model Description (MIKE 21 HDFM)

The numerical flow model applied in the present study is the MIKE 21 HDFM

(Hydrodynamic Flexible Mesh) module of the comprehensive 2-dimensional

MIKE 21 modelling system from DHI, Denmark. MIKE 21 HDFM is a model-

ling system for 2D free-surface flows. It can be applied to a wide range of hy-

draulic and related phenomena. This includes modelling of tidal hydraulics,

wind and wave generated currents, storm surges and flood waves. The HDFM

module is the basic module of the system and is used in the simulation of hy-

draulics and related phenomena in lakes, estuaries, bays, coastal areas and seas

where the flexibility inherited in the unstructured meshes can be utilized.

The applied MIKE 21 HDFM model requires the following main input for flow

simulations:

• Bathymetry of the area

• Hydrographic boundary conditions (water levels and/or fluxes)

• Wind and/or barometric pressure of the area

• Eddy Viscosity and Bed Resistance (Manning number)

2.3 Model Bathymetry

2.3.1 Reference datum:

The horizontal [ref. (Marafiq, Minutes of Meeting, 25.06.2011)] and vertical

[ref. (Jacobs/Marafiq, Saudi Arabia: May 2011)] datum are in MYAS

(YANBU) datum, [ref. (Jacobs, 2009)].

2.3.2 Bathymetry

Flexible mesh model bathymetries are prepared based on the drawings of the

intake channel for tendered layout and of the flow optimized channel layout 1

and 2, and the data from the bathymetric survey by Saudi Archirodon Ltd in

June 2011. The survey data is utilised from the reef edge upto a distance of ap-

proximately 150m from the mouth of the channel. The extent of the survey is

show in Figure 2.1, and the data from AREA A is used in the present study.



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Figure 2.3 shows the tendered layout, where as Figure 2.4 show the flow opti-

mised layout 1 and 2, respectively, and corresponding flexible mesh bathyme-

try used for the channel modelling simulations in the MIKE 21 HDFM model.

The area of the triangular meshes have been decreased from 50m² at boundaries

to 25m² near the study region to have a sufficiently resolved bathymetry close

to the breakwaters and in the dredged channel. To resolve the breakwater slopes

adequately a quadrangular mesh has been applied on the slopes of the breakwa-

ters.

The intake channel is protected by two curved breakwaters on each side ap-

proximately 800-1000m long as shown in Figure 2.2. The natural water depth

outside the channel mouth is deeper than -10m.

Fot the tendered layout and optimised layout , the inner channel is dredged to a

depth of -10 m MYAS from mouth to the pumping station as shown in the Fig-

ure 2.3 and Figure 2.4. where as for flow optimised layout 2 the depth of the

intake channel is varying between 6.5m to 10m. The width of the dredged

channel is varying from 130-150m and the breakwaters slopes are of varying

width. The width of the pumping station is approximately 60m for tendered

layout and ~70m for both the flow optimised layout 1 and 2.

Figure 2.1 Survey areas for Yanbu 2 project.

Comment [ksmu4]: 11.SBAS� sen-

tence to be reframed ?? HGLN?



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Figure 2.2 Survey data overlayed on the tendered plan layout of Yanbu 2 project.

2.3.3 Tendered Layout and Bathymetry:

The tendered layout is based on the drawing 0132.TD.CAT.0004 dated Sep,

2010. Figure 2.3 shows the tendered layout and flexible mesh bathymetry for

tendered layout used in the modelling.



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Figure 2.3 Tendered Layout drawing (above) and corresponding Flexible mesh

bathymetry used for the Channel modelling (depths relative to MYAS).

Flow Optimized Channel Layout 1 and Bathymetry:

Based on the results of flow pattern in the tendered layout, a revised flow opti-

mised intake channel layout 1 drawing was prepared on 08 july 2011. Figure

2.4 shows the layout plan and flexible mesh bathymetry for flow optimised lay-

out 1.

Figure

2.8



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Figure 2.4 Flow optimised layout 1 drawing and corresponding Flexible mesh ba-

thymetry used for the Channel modelling (depths relative to MYAS).

Flow Optimized Channel Layout 2 and Bathymetry:

Based on the results of flow pattern in the flow optimised layout 1, a revised

flow optimised layout 2 drawing was prepared on 25 August 2011. The depths

near the channel entrance and at the pumping station dredged to 10m and rest

of the channel is dredged to 6.5m. The width of the channel slopes depends on

Figure

2.9

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Formatted: Highlight



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the channel depth. Figure 2.5, shows the layout plan and flexible mesh bathym-

etry for flow optimised layout 2.

Figure 2.5 Flow optimised layout 2 drawing and corresponding Flexible mesh ba-

thymetry used for the Channel modelling (depths relative to MYAS).

Fig-

ure

2.10



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The intake channel basin is protected by breakwaters of dredged material, quar-

ry rock and concrete armour units if required by the final design. Tentative

cross sections of the intake breakwaters roundheads and of the breakwater

trunks are shown in Figure 2.6 and Figure 2.7.

The roundheads of the breakwaters are located near the reef edge at a water

depth of approximately -0.5m MYAS. The slopes of the breakwaters are well

resolved in the bathymetry as shown in the Figure 2.8 to Figure 2.8Figure 2.10

Figure 2.6 Intake Breakwater, tentative section at roundhead.

Figure 2.7 Intake Breakwater, tentative section at breakwater bend.

Field Code Changed

Comment [PNAN5]: Tese are the fig-ures in the latest design basis. However, we

now have new c/s which bhaskar is making

without accropodes



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Figure 2.8 Fleximesh bathymetry at the breakwater bend in the Tendered Layout.

Figure 2.9 Fleximesh bathymetry at the breakwater bend in the Flow optimised

layout 1.



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Figure 2.10 Fleximesh bathymetry at the breakwater bend in the Flow optimised

layout 2.

2.4 Model Set-up

The model is driven by the intake flux at the pump station end and tides at the

mouth of the channel. The tide are applied as water level boundary condition.

Furthermore, the model is influenced by friction in the model in terms of bed

friction and eddy viscosity. Each of these parameters used for the HDFM simu-

lations are described below.

2.4.1 Water level Forcing

The most critical condition is assumed to arise when the pump station is func-

tioning at its full capacity during the Lowest Astronomical Tide(LAT). Accor-

ing to Admiralty Tide Tables, the combined effect of seasonal variations and

tide defines LAT as being 0.56 m below MSL [ref. (Office, 2009)] (i.e., -0.40

m MYAS). A constant water levels of LAT is applied on the open east, west

and south boundaries outside the channel, as shown in the Figure 2.11. The

boundary to the south is located at a distance of approximately 150m from the

mouth of the channel, to minimise boundary instabilities in the model.



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Figure 2.11 Boundaries defined in the channel modeling for the Tendered layout

(abovetop),Flow optimised layout 1 (middle)) and Flow optimised lay-

out 2 (bottom)..



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2.4.2 Intake conditions

The inflow and discharge rates at the pumping station are summarised in Table

2.1 [ref. (COWI, 2011)]. The intake sinks are modelled as discharge boundary

near the pumping station, the discharge boundary acts as line sinks with con-

stant flow out of the model. The line sink boundary near the pumping station

for tendered layout and flow optimised layouts 1 & 2 are shown in the Figure

2.11.

Table 2.1 Yanbu 2 Power and desalination plant cooling water systems intake

operating conditions.

Properties Tendered Layout Flow Optimised Lay-

out-1

Flow Optimised Lay-

out-2

Flow rate

(inflow/outflow)

77.778 m3/s

(280,000 m3/h)

77.778 m3/s

(280,000 m3/h)

77.778 m3/s

(280,000 m3/h)

Location E 32900, N 27555 E 32875, N 27579 E 32875, N 27579

Pumping Station

Width

~60m ~70m ~70m

Water Depth -10m (MYAS) -10m (MYAS) -6.5 to -10m (MYAS)

2.4.3 Simulation time

Initial trail runs showed that the flow stabilized after 1hour of the simulation

period and attaining a steady state condition approximately after 3 hours. To

make the model more conservative the simulations for tendered layout and flow

optimised layout 1 were carried out for 24 hours.

2.4.4 Additional model parameters

The bed resistance in the model varies in the channel. Along the natural seabed

and dredged channel a normal friction of 32m⅓/s (Manning number) is used.

On the breakwater rock slopes a friction of 25 m⅓/s is used and near the bound-

aries to attain the stability a friction of 5-10 m⅓/s is used. Figure 2.12 shows the

bed resistance maps for tendered layout and for both flow optimised layouts 1

& 2.

A constant eddy viscosity based on the Smagorinsky formulation with a propor-

tionality constant of 0.28m2/s is used in the simulation (model default). A sensi-

tivity test has been carried out with and without eddy viscosity forcing to check

the formation of eddies in the model. The results showed no effect on the for-



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mation of eddies in the tendered layout, hence a default value of 0.28m2/s is

used in the simulations.

Figure 2.12 Bed Resistance Map of Intake channel for Tendered Layout (abovetop),

flow optimised layout 1(middle) and flow optimised layout 2 (belowbot-

tom) showing various manning numbers used in MIKE 21 HDFM model

Various input parameters are summarised in Table 2.2.



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Table 2.2 MIKE 21 HDFM model parameters used in calibrated local flow model.

Parameter Value

Start date 12/12/2008

End date 12/13/2008

Timestep 5s

Drying and flooding, drying depth 0.1m

Drying and flooding, flooding depth 0.2m

Drying and flooding, wetting depth 0.3m

Eddy viscosity, Smagorinsky coefficient 0.28 m2/s (default)

Bed friction, Manning number M = 32 m1/3

/s(natural seabed )

M = 25 m1/3

/s(Breakwater Armour)

2.5 Results

2.5.1 Flow Pattern

The flow patterns and the current velocities in the channel during the LAT for

the tendered layout and for flow optimised layouts 1 & 2 are shown in Figure

2.13 and Figure 2.12, respectively. The simulations show that for both tendered

layout and for both flow optimised layouts 1& 2 the highest current velocities

occur near the pumping station mouth end of the intake channel. In the tendered

layout, formation of vortices/eddies is seen at the west breakwater slope near

the pumping station, while the flow is smooth in the flow optimised layouts 1 &

2 (see Figure 2.14 & Figure 2.15). In most parts of the channel the current ve-

locity does not exceed 0.1 m/s in the case of tendered layout and 0.12m/s for

flow optimised layouts 1 & 2.



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Figure 2.13 Flow pattern and current velocity during LAT in the tendered layout

(abovetop), and Flow optimised layout 1(middle) and Flow optimised

layout 2 (bottom)(below).



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Figure 2.14 Flow vectors near the pumping station during LAT in the tendered Lay-

out (abovetop) and Flow optimised layout 1(belowbottom).



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Figure 2.15 Flow vectors near the pumping station during LAT in the tendered Lay-

out (above) and Flow optimised layout 12(below).

2.5.2 Maximum Current Velocities

Figure 2.16 and Figure 2.14 shows the simulated maximum current velocity

during the 1day simulation period for tendered layout and for flow optimised

layouts 1 & 2, respectively. In the tendered layout the maximum current veloci-

ties of 0.14-0.16m/s are observed near the pumping station and 0.08-0.10m/s in

some areas inside the channel. In the flow optimised layouts 1& 2, the maxi-

mum current velocities are of the order of 0.10-0.12m/s near the pumping sta-

tion and near the west breakwater bend. These higher velocities are observed

across the rock armoured slopes and are thus not expected to stir up sediments.

However, for most areas in the middle and outer parts of the channel, the intake

velocities does not exceed 0.1m/s in both layouts. The inflow velocities close to

the mouth of the channel are about 0.02m/s for both tendered layout and also

for both flow optimised layout 1 & 2. The velocities in the flow optimised lay-

out 2 are slightly higher than that of flow optimised layout 1, due to reduced

depth in the middle of the channel and less cross sectional area of the channel

in flow optimised layout 2.



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Figure 2.16 Maximum current velocities in the Tendered layout (top), flow opti-

mised layout 1 (middle) and flow optimised layout 2 (bottom) during the

simulation period.



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The flow across the channel has been extracted along cross sections in the

channel at a distance of 10m and 50 m away from the pumping station as

shown in the Figure 2.17, for both the tendered layout and also for flow opti-

mised layout 1 & 2. The cross sectional flow velocities and directions of simu-

lation after a steady state condition attained in the model are presented in Fig-

ure 2.18 and to Figure 2.20Figure 2.17.

Figure 2.17 10m and 50m cross section lines extracted in the channel layouts.

Figure 2.18 Cross section flow velocities and direction at 10m and 50m from the

pumping station in tendered layout during the simulation.



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Figure 2.19 Cross section flow velocities and directions at 10m(Top) and

50m(Bottom) from the pumping station in flow optimised layout

1(below)& 2 during the simulation.

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Figure 2.20 Cross section flow directions at 10m(Top) and 50m(Bottom) from the

pumping station in flow optimised layout 1& 2 during the simulation.


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The results of the cross section flow velocities shows that:

1. Speed 10m from the pumping station is higher than the speed 50m from

the pumping station, for both the tendered layout and for both the flow

optimised layouts 1 & 2. The tendered layout shows a flow velocity of

0.14m/s and 0.09m/s at 10m and 50m cross section, respectively.

Whereas the flow optimised layout 1 & 2, shows slightly lower veloci-

ties of 0.11m/s and 0.09m/s at 10m and 50m cross sections, respective-

ly, though the velocities in the later beingare slightly higher. in the flow

optimised layout 2.

2. The flow velocities are more symmetrical in the flow optimised layouts

1& 2 compared to the tendered layout.

3. The flow in the tendered layout is spread over a wider area compared to

the flowthat in the optimised layouts 1 & 2, due to the reduced channel

width close to the pump house in the two flow optimised layouts 1&2.

4. Flow directions close to the pump house are nearly the same in both the

flow optimised layouts, though they are more variable in the tendered

layout.

5. The flow criteria 3 (Section 1.4), i.e. the cross section flow velocities

should be less than 0.3m/s during LAT for a flow volume of 280,000

m3/s, is met by both the tendered layout and flow optimised layouts 1

and 2.

5. The flow pattern of the flow optimised layout 2 are considerably good

with reduced channel depths of 6.5m in middle of the channel and with

narrow channel and breakwater slopes.



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3 References

ARCHIRODON. (Sep 2010). Marine Facilities Plan View.

COWI. (2010). Rabigh Power Plant No. 2 - Design Sheet.

COWI. (2011). Preliminary Design Basis, Marine Structures. Doc No: YT-

MF-G-06-02023, YANBU II POWER AND WATER PROJECT

PACKAGE 2 - MARINE FACILITIES.

Jacobs. (2009). Yanbu 2 Power And Water Project - Overall Site Datum Plan

(Rev. E).

Jacobs/Marafiq. (Saudi Arabia: May 2011). Drawing No: R214-00/C.02a/0001

Civil/ Structural Basis of Design, 0th edition.

Marafiq. (17.05.2011). Agreement between Saudi Archirodon and Marafiq:

Confirmation of Water Quantities.

Marafiq. (25.06.2011). Minutes of Meeting.

Office, U. K. (2009). Admiralty Tide Tables (vol 3) - Indian Ocean and South

China Sea.

YT-MF-G-06-02061

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Transcript of YT-MF-G-06-02061