Manjung Power Station - Malaysia

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Manjung Power Station CW Intake Culvert End of Contract Report – Volume 1

Leighton-LAMA Joint Venture Section 1: Page 1 of 4

MANJUNG POWER STATIONMALAYSIA

Offshore Cooling Water Intake Culvert

Leighton LAMA Joint Venture

END OF CONTRACT REPORTJuly 2000 to October 2001


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Table of Contents

VOLUME 1 – MAIN REPORT

SECTION 1. INTRODUCTIONSECTION 2. JOINT VENTURE RELATIONSHIPSECTION 3. PRE CONTRACT AWARDSECTION 4. BRIEF PROJECT DESCRIPTIONSECTION 5. DESIGN OF THE COOLING WATER INTAKESECTION 6. GEOTECHNICAL CONDITIONS ENCOUNTERED ON

THE CULVERT ROUTESECTION 7. PRODUCTION RATES, PLANT UTILISATION AND

CREW SIZES

SECTION 8. COST VS BUDGETSECTION 9. RISKS/LESSONS LEARNEDSECTION 10. STAFFING LEVELSSECTION 11. SUBCONTRACTORS & SUPPLIERSSECTION 12. TEMPORARY WORKSSECTION 13. PRECASTING OPERATIONSSECTION 14. IN-SITU CULVERT & COFFERDAMSECTION 15. MARINE WORKSSECTION 16. DOSING LINESECTION 17. NAVIGATION STRUCTURESECTION 18. FINANCIALSECTION 19. SITE PHOTOGRAPHSSECTION 20. APPENDICES – CD OF DRAWINGS


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SECTION 1. INTRODUCTION

1.1. SCOPE

The contract is for the construction of a Cooling Water Intake System as part of the ManjungPower Station. The plant is coal fired, utilizing available sea water for cooling purposes. Theproject is constructed on a joint venture design and construct basis between Leighton

Contractors (main civil subcontractor for the Manjung Power Station Project) and LAMAInternational Contractors (Design and specialist Marine Works Contractors.)

The purpose of the structure is to draw and deliver seawater, from 1500 metres offshore, tothe power station cooling system on land, at a rate of 88.2m3/sec when in full operation. Thisrequirement is being achieved by the construction of a sub-sea triple celled culvert, 1500meters long. This culvert was constructed over a period of 13 months, involving land andmarine construction operations, including a substantial amount of underwater work usingdivers. The locations of the seawater intake points have been carefully selected based on thetight specifications for minimum depth of water, water temperature, and the turbidity of theseawater.The project has been carefully designed and constructed to ensure that the clients’requirements are met in full, with due consideration for the environment, local authoritiesrequirements, constructability, programme and budget.

1.2. PROJECT DESCRIPTION

Name of Client: Leighton Contractors (Malaysia) SDN BHDJoint Venture Partner: Leighton Contractors (Malaysia) SDN BHDLocation: Lekir, Perak Darul Ridzuan, Peninsular MalaysiaType of contract: Design and Construct Lump SumInitial Budget: Design - MYR 1 677 000.00

Construction - MYR 60 000 000.00Final Cost: Design - MYR 1 883 998.47

Construction - MYR 63 250 000.00Planned Programme: Completion - July 2001

Actual programme: Completion - October 2001


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SECTION 2. PRE CONTRACT AWARD

This section deals with the contractual process prior to award of contract. The first contact tookplace in October 1999 with Leighton (Malaysia) requesting LAMA to assist them with thepreparation of a price which was to be submitted to Peremba for the construction of an intake andoutlet conduit for a new power station to be constructed at Manjung in Malaysia.

Various alternative designs were considered, including steel, HDPE and concrete pipes, all in aburied trench, concrete pipes above sea level supported on a piled structure and concrete culvertsin a trench on the seabed.

A budget price was submitted by LLJV to Peremba on 18 October 1999 based on steel pipes withan HDPE alternative. The price was developed further to exclude the outlets and an option of steelpipes on trestles above water was also priced and a budget price was submitted on the 1st November 1999.

In January 2000 negotiations moved from Peremba to Alstom (who had been presumably awardedthe Main Contract at that stage). No pre-bid agreement between ourselves and Leighton was put inplace at this stage due to the nature of the discussions being around budget pricing etc. rather thanthe submission of a formal tender. Leighton were now also in negotiations with Alstom regardingthe Main Civil Works Contract.

At this stage Alstom produced their first Design and Construct Specification, which was to be usedfor the design of the intake conduits, whichever option was selected. At this stage, however,

Alstom had still not decided whether the contract would go out as a D&C or whether they woulddesign it themselves to their own design, or thirdly whether they would carry out the design basedon the contractors chosen type of conduit.

During the month of January 2000, various options based on a steel pipe in a trench on the seabedwere priced in order to reduce the contract sum. A presentation was made by the Leighton-LAMAteam to Alstom on the proposed scheme at that time. Leighton had also requested prices fromVan Oord and See Yong & Sons.

A further alternative, that of precast concrete culverts was developed, which started looking likebeing the most cost effective solution. The development of the preliminary design of the culvertthen commenced in more detail, in order to further refine the costs of this system. The basic sizingwas taken from Alstom layout drawings showing an internal cell size of 3.42m square. A budgetprice based on precast concrete culverts was submitted on 29th January 2000. This price wasdeveloped and reduced further during the month of February 2000. The price which Leightonsubmitted for the overall Civils Works included the offshore work based on a price and submissionfrom See Yong (assumed immersed tube construction) as LAMA were not prepared to agree to afixed price at that stage due to the short time given to price the works. Leighton was awarded theCivil Works Contract including the offshore works as an option to be taken up before end May2000.

At this stage pricing of the culvert system based on Alstom doing the design as well as the projectbeing carried out as a design and construct contract, were carried out in parallel, as there was stillno confirmation from Alstom as to which way they were intending to go.

In February an internal Tender review report states that Alstom have indicated that they wouldconsider a EPC type of contract in order to advance this part of the works but might still insist oncompleting the design themselves. This report also discusses two possible bid strategies being:

1. Alstom doing the design and2. EPC type of contract.


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Both options were priced assuming different design fees as well as variable contingencies to caterfor the design risk.

By mid-March 2000, there was still no confirmation that LAMA would be responsible for thepermanent works design.

During the week ending the 19th May, we were informed by Leighton that Alstom required the JV todo a presentation on the proposed culvert design with a view to awarding the offshore contract ona design and construct basis by the beginning of June. This was the first time that Alstom hadconfirmed their intention to go the D&C route. A LAMA team travelled to Kuala Lumpur on the 20

th

May to make the presentation to Alstom and then spent the next 10 days finalising the design andprice. A revised Performance Specification was issued by Alstom as the basis on which the D&Ccontract was to be awarded.

The main issue at that time was the interface between the offshore works and the waterpool, and asolution was arrived at by the Leighton-LAMA team based on a pipe-jacking operation. LAMA’sdesign fee was adjusted during the final pricing and was based on the scope of work as defined atthat time. Discussions were also held with Nelson Borch of TerraGeotechnics (through PeterFurness) for them to assist in both the design approval process as well as providing specialistgeotechnical advice. After submission of the price, various negotiations took place betweenLeighton and Alstom and a final price of RM 63.25M for the Offshore Works was agreed to,although at this stage it was still not clear what our involvement would be.

Leighton notified LAMA during the first week of June that they (Leighton) had been awarded theoffshore contract. A LAMA team then travelled to KL to finalise LAMA’s involvement, the JVagreement, and to discuss staffing and the programme for the contract. It was at this stage that arevised JV agreement and consultancy agreement appeared for the first time and LAMA wasasked to sign it as a basis of LAMA’s design responsibility to Leighton. During this visit in Junediscussions were held with the site team (including the Project Director) and a decision was madeto change from pipe-jacking to a cofferdam for the inshore tie-In to the waterpool.

A potential standoff position developed on this visit between Leighton and LAMA around issues ofrepresentation in the JV, the JV Agreement, Indirect Cost split, sponsors fees and profit.Leighton’s view was that the marine work had been secured by Leighton as LAMA had notappeared willing to commit themselves at the time of the original price submission. Leightonthreatened to ‘drop’ LAMA if no agreement could be reached on the outstanding issues which wereonly finally resolved at the first JV EXCO meeting.

Leighton’s initial requirement was that the responsibility for the design of the works be directlybetween Leighton as the Main Civil Works Contractor and LAMA. After discussions at the first JVExco meeting on 5 September 2000, it was agreed that if there was going to be a formalagreement, then the agreement should be between the LAMA and the LLJV and not directlythrough Leighton.


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SECTION 3. JOINT VENTURE RELATIONSHIP

3.1. BACKGROUND

Referring to Section 2 it will be noted that Leighton played the major role in securing thisproject. This was largely due to the fact that Leighton had already secured the main civilscontract and the CW Inlet was to be a sub-contract to the civils package. Because of this

existing relationship with the client, all pre -award negotiations were through Leighton, withtechnical and pricing backup being provided by LAMA.

At the first JV meeting held in Malaysia in June, just after the contract award, a new format of joint venture agreement and joint venture exco was proposed by Leighton. This differed tothose previously used and clearly the intention of Leighton was to reduce the role of LAMA in

joint venture decision-making. This was considered to be unacceptable to LAMA andeventually it was agreed by the parties to revert to the standard Leighton LAMA JVagreement previously used on the JV projects.

3.2. DURING THE CONTRACT EXECUTION

The relationship between the Leighton and LAMA Staff on site during execution of the projectwas generally good, but between the Parties was complicated by two factors:

• The JV was executing the work as a subcontractor to Leighton, and the project director ofthe Civils contract (a Leighton’s contract employee) also acted as the Joint VentureProject Manager.

• LAMA was carrying out the design works on a lump sum basis for the joint venture. Onprevious projects generally the design was carried out by LAMA within the Joint Ventrureand at the JV’s risk.

3.2.1. Subcontract to Leighton

Contractual issues

LAMA commenced work on the project only having seen a generic Leighton’s Sub -contract agreement. The proposed agreement was only prepared after the detailsof the CW Inlet subcontract were concluded between Leighton and the Client, whichwas some months after the start of the project. The proposed conditions wereunacceptable to LAMA, but Leighton refused to accept any changes to their“standard subcontract agreement” The result is that this subcontract agreementremains unsigned.

Management issues

Leighton had, at the start of the works stated that the main civil works tookprecedence over the CW Inlet and they would not permit a disagreement between

the parties to jeopardise progress on the main contract.

All negotiations with the Client which were of a commercial nature were dealt withby Leighton as they were the Main Contractor, and LAMA was generally excludedfrom these discussions. Very little in the way of correspondence between the maincontractor and client which was of a commercial nature was made available toLAMA or the JV management on site. Agreements on issues such as incentives,bonus’s, penalties and commercial issues surrounding the geotechnical problemswere only received second-hand from Leightons.


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It was agreed at the start of the contract that the Leighton’s Project Director on theCivil Works would also act as the JV’s Project Manager for the CW Inlet, despiteLAMA having placed a very experienced Project manager on site. The commercialsupport to the JV was provided by the Leighton’s Commercial Manager on site.Some of the Leighton staff found it difficult to be even-handed in their dealings withthe two JV Partners and in particular their approach taken in regard to LAMA’s claimfor additional design costs and the resolution of the Geotechnical problems were

questionable. LAMA were treated as sub -contractors by the Leightons Managementalthough they were also JV Partners.

3.2.2. Design Works

The decision by the Client to award the CW Inlet on a Design & Construct basiswas only made at a very late stage in the contract negotiation stage. With the verytight program, and the impact that the CW Works had on the Main Civil works, thedesign team were put under pressure from the start of the project.

In particular, the design of the cofferdam at the waterpool, and later the revisedfounding to the culvert units consumed a much greater design effort than waspreviously assessed.

Leighton at an early stage raised a number of issues with regard to their perceptionthat the design which LAMA was carrying out was overly conservative and moreexpensive to construct than tendered. These perceptions were largely unfounded.

The greatest influence on the JV relationship was brought about by the geotechnicalproblems encountered with the culvert foundations (elsewhere detailed). Theseproblems led to a change in design in the foundations, with the resultant increase incost. Although the decision to change the foundation system was made relativelyquickly it resulted in a polarisation between the parties which was never completelyrepaired.

There was a large amount of additional design work carried out for the project as aresult of, amongst other things:

• Cofferdam design, as a result of the variable ground conditions, and to suit pilingmethods and materials.

• Redesign of various plant items to suit the requirements of the site team.• Redesign of the “Temporary Jetty” in order that it satisfy the requirements of a

permanent structure.• Change of the culvert foundation to a piled solution• Design of the navigation structure.• Dosing line change

Although the design work was done as a Lump Sum, additional compensation was

requested for some of the additional work, especially where the additional work wasdone to suit the site requirements.

An agreement was reached on payment for certain of the minor additional work, butdespite lengthy submissions and discussions with Leighton on the balance, theyargued that much of this redesign was merely design development; no additionalstructures were built than were tendered, and therefore there were no grounds foradditional payment to the designers.


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In fact, in the final negotiations with Leighton on the settlement of the pilingfoundation claim, all design variation costs (including those agreed to be paid) wereforfeited by LAMA.

3.3. LESSONS LEARNT

• ‘Conflict of interest’ issues must be identified and dealt with in appropriately wordedagreements.

• The potentially disastrous arrangement of sub -contracting to your Joint Venture Partnercan severely stress the Joint Venture, particularly when technical or financial problemsare encountered on the project. Similar joint venturing arrangements were in place onSha Chau (with Leighton) and on the Natal Pipelines (with Pentow Marine). The ShaChau project had no technical problems and was financially very successful so therelationship was never tested and remained good. The Natal Pipelines project hadtechnical and financial problems and led to a breakdown in the Joint Venture relationship.

• Ideally, the design risk and the cost of producing the design should be shared by thepartners in the JV and not transferred to one of the partners. In this way the cost vs.

benefit of design development can best be managed.


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SECTION 4. BRIEF PROJECT DESCRIPTION

The cooling water intake culvert is approximately 1490m in length, extending from the intakestructures at the seaward end to the diaphragm wall of the pump station water pool onshore. Thetriple cell culverts have interior barrel dimensions of 3.750m vertically and 3.450m horizontally,

with 0.300m chamfers. The culvert consists of an in-situ section, 142 pre-cast sections with 6intake towers towards the end, 3 x 225mm HDPE dosing lines on top of the culvert and a

navigation structure 50m offshore of the end of the culvert. These items are described in moredetail below.

4.1. IN-SITU CONCRETE CULVERTS

The in-situ concrete culvert is 70m long, which was constructed in three sections i.e. one

10m and two 30m long sections, from the open trench through the island revetment to theconnection to the water pool diaphragm wall. Each section was constructed within a sheet-

piled cofferdam. All the sheet piles were removed after construction with the exception ofthe sheet piles up against the diaphragm wall of the water pool. The diaphragm wall of the

water pool in the region of the tie-in to the in-situ culvert, was cast prior to the constructionof the in-situ concrete culvert. A reinforced concrete chimney, which provides access to all

three barrels, is positioned towards the end of Section 1. This concrete chimney allows thethree interior structural steel bulkheads to be installed into the barrels of the in-situ culvert.The bulkheads were required to retain the water in the culvert during the construction of the

opening in the diaphragm wall of the water pool. The existing VIB wall surrounding the bulkof the power station civil works cuts across Section 1 of the culvert.

There are movement joints between each section of the in-situ culvert and at the connectionto the external face of the cooling water pool. Heavy-duty water bars were installed at the

movement joints between the in-situ culvert sections as well as the connection to the waterpool wall. The reinforcement in the concrete culvert is not continuous across these joints.

The poor soil conditions in the area where the cofferdam was constructed, as well as thelarge future settlements predicted for this area, dictated that the in-situ culvert needed to besupported on pre -cast concrete bearing piles. Pre-cast reinforced concrete piles providesupport to the culverts, positioned in four rows longitudinally under the culvert walls. Thelongitudinal pile spacing varies along the length of the in-situ culvert. The in-situ concrete

Water ool O enin into In -Situ Culvert Cofferdam for In-situ Culvert


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culvert is underlain by a 75mm concrete blinding layer. The piles penetrate the 75mmblinding layer to tie into the reinforced concrete culvert base slab.

The culverts are founded at approximately –7,680m ACD (underside concrete floor), withthe top of the concrete roof at –3,070m ACD. Over Section 1, fill is placed to a level of+4,650m ACD. The fill slopes down through the revetment over the length of Section 2 to

meet the general seabed level of –1,600m ACD. This level is maintained over the full lengthof Section 3.

4.2. PRE-CAST CONCRETE CULVERT UNITS

The cooling water intake consists of 142 Pre -cast Concrete units extending from the in-situ

culvert to the end of the intake culvert, which are divided into 11 different types as follows:

Pre -cast Culvert Units Type A and B.

Units type A and B are installed in a dredged trench and are supported on 4 concrete pilecaps which are supported on 4 No. 1m diameter, class C, grade 80N/mm2 concrete spun

piles. The cooling water intakes consist of 54 No intake culvert type A & 71 No intake

culvert type B units, which are each 10m long, 11.810m wide by 4.610m high overall. Unittype A and B’s are triple cell pre -cast culvert units, which have interior barrel dimensions of3.750m vertically and 3.450m horizontally, with 0.300m chamfers. Unit type B’s areidentical to unit type A’s except that they have more reinforcement in them to cater for a

greater cover of seabed material due to their location in the length of the intake culvert.

Pre -cast Culvert Units Type F.

Units type F’s are installed in a dredged trench and are supported on 4 concrete pile caps,which are supported on 4 No. 1m diameter, class C, grade 80N/mm2 concrete spun piles.

The cooling water intakes consist of 6 No intake culvert type F units, which are each 10mlong, 11.810m wide by 4.610m high overall. Unit type F’s are triple cell pre-cast culvert

units, which have interior barrel dimensions of 3.750m vertically and 3.450m horizontally,

Unburied Unit 54 Type ABuried Unit 71 Type B

Access Unit 6 T e F

T ical Pre-Cast Unit Pre-Cast Unit bein laced b Gantr


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with 0.300m chamfers. Unit type F’s are the units that have the 3 manhole covers in them inorder to access the inside of each of the 3.750m x 3.450m barrels.

Pre -cast Culvert Units Type H

The transition unit type H is the first pre -cast unit that will be placed in front of Section 3 ofthe in-situ concrete culvert. The north end is cast at an angle to match the south end ofSection 3 of the in-situ culvert. The transition unit Type H is 8.180 m long along the centreline and is 11.810 m wide x 4.610 m high overall. Reinforced concrete piles provide support

to the transition pre-cast unit Type H as follows:

• 2 No. 1000 mm diameter concrete spun piles, positioned longitudinally under the

external culvert walls, on the offshore end of unit Type H as per the typical pre-cast unitand;

• 2 No. 700mm diameter concrete spun piles, positioned under the internal walls of theculvert, at the joint between Section 3 of the in -situ culvert and the transition pre-cast

unit Type H. A continuous crosshead beam and 2 no. rectangular pile caps are cast

over the 2 No. 700mm diameter concrete spun piles to support the pre-cast transitionunit Type H.

Pre -cast Culvert Units Type J&K

Units type J&K are installed in a dredged trench and are supported on 8 concrete pile capswhich are supported on 8 No. 1m diameter, class C, grade 80N/mm2 concrete spun piles.

The cooling water intakes consist of 3 No intake culvert type J & K units, which are each

10m long, 11.810m wide by 4.610m high. The triple cell pre-cast culvert units have interiorbarrel dimensions of 3.750m vertically and 3.450m horizontally, with 0.300m chamfers.

They are similar to a typical unit except that they have a 3.450m square opening in the topslab, which incorporates an up stand beam cast around the opening which caters for the in -

situ connection of the pre -cast Intake towers to the pre-cast units. The unit types J&K alsohave internal walls for diverting and channelling the water flow into the culverts. Units J & K

support the 6 No. Intake Tower Structures at the end of the intake culvert.

Pre -cast Culvert Units Type L&M

Units type L&M are installed in a dredged trench and are supported on 4 concrete pile capswhich are supported on 4 No. 1m diameter, class C, grade 80N/mm 2 concrete spun piles.The cooling water intakes consist of 1 No intake culvert type L and 1 No intake culvert type Munits, which are each 9.5m long, 11.810m wide by 4.610m high. The triple cell pre-castculvert units have interior barrel dimensions of 3.750m vertically and 3.450m horizontally,with 0.300m chamfers. Units L & M are the Side Units Left and Right. Units L & M aresimilar to the typical 10m pre-cast units. Unit L & M consists of one additional interior wall(over part of the 9.5m length), with two interior walls angled to direct flow.

Transition Unit 1 T e H

Intake Unit 3 T e J Intake Unit 3 T e K

Unit Right 1 Type L Unit Left T e M


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Access GratingDosin Line Rin

Intake Tower Structure

Pre -cast Culvert Unit Type N

Units type N is the last pre -cast unit at the end of the intake culvert and it is installed in adredged trench and is supported on 4 concrete pile caps which are supported on 4 No. 1mdiameter, class C, grade 80N/mm2 concrete spun piles. There is only 1 No intake culverttype N, which is 9.5m long, 11.810m wide by 4.610m high. It is also a triple cell pre-castculvert unit with interior barrel dimensions of 3.750m vertically and 3.450m horizontally, with

0.300m chamfers. Unit type N is similar to unit type F in that it has three access manholeopenings in it, except that it has an end wall, which closes the unit off.

Pre -cast Culvert Units Type P

Unit type P is the same as a typical unit type B and it is the unit that is situated adjacent tothe transition unit type H. There is only 1 No intake culvert type P, which is 10m long,11.810m wide by 4.610m high with the same interior barrel dimensions as all the otherculverts.

The pre-cast culverts units all have grout socks between each unit and they will form the jointseal between two consecutive units.

Each pre-cast unit has a concrete housing structure on top of it, which contains the threedosing line pipes.

4.3. INTAKE TOWERS

The intake tower structure is supported on the pre-cast unit types J (or K) by a monolithic in-situ connection between the pre -cast elements i.e. unit J & K and the intake tower. Thereare 6 No intake towers, which consist of a concrete roof slab supported on 8 concretecolumns. There is an opening all the way around which is closed off by a stainless steelgrating. There is a diver access gate provided in the grating on one of the splayed corners ofthe intake tower. The intake towers are funnel-shaped structures which end in a 3.45msquareopening inthe top of unittype J (or K).Thehypochloritedosing ring isattached tothe intaketowerstructures.The intaketowers are

indicated inthephotograph.

End Unit 1 T e N

Unit Ad acent to Transition Unit 1 T e P


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4.4. DOSING LINES

The dosing line pipes, which supply a hypochlorite solution to the cooling water intakeculverts via the 6 intake towers, consists of three separate 225mm diameter, class 10, HDPEpipes which are continuously butt welded together in 12m lengths as indicated in thephotograph below.

The dosing line pipes areapproximately 1500mlong with a dosing ringand nozzles distributedaround the intake towers.

The chlorine dosing linepipes are housed in asmall closed concretecavity structure locatedon the top of the intakeculverts. All three dosingline pipes are locatedwithin this housing, whichcomprises two slopingpre-cast concrete kerbsfixed to the top of theculvert, each with a

recess at the top, into which a pre-cast concrete cover slab is positioned. The dosing linepipes will thus not be subject to significant wave forces, and will be protected from directsnagging dangers.

The pipes were pulled out through HDPE sleeves that are cast into pre-cast concretediaphragm walls, which are located at 5.0m c/c on the top of the pre-cast units. The housingand diaphragm walls are indicated in the photograph below.

The dosing lines come ashore through the revetment. The 225mm diameter pipes arecontained in a 355mm diameter class 10 HDPE sleeve above the in-situ culverts in the

ButtWelding

Station

225mm diameterclass 10 HDPE

dosing line pipes

Dia hra m Wall

Concrete Dosin Line Housin on to of re-cast units.


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revetment to protect the dosing lines from the backfill material and they end in a junctionbox where they will be connected to the pipe work from the chlorine dosing building. Theonshore pipes and connection box is indicated in the photographs below.

4.5. NAVIGATION STRUCTURE

A south cardinal navigation structure marks the cooling water intake culvert. The navigationstructure is situated approximately 50m south of the end pre-cast culvert type N at Latitude4008’30.93318” and Longitude 100038’27.03496” with reference to the WGS 84 system. Itconsists of a structural steel tower structure, which supports the Tideland ML-300 MaxluminaLantern. The tower is supported on a 1m thick concrete slab, which in turn is supported by 3No. 900mm diameter raking pre-cast concrete spun piles. The concrete slab and equipmentplatform are fitted with steel handrails, access ladders and a small craft berthing fenderstructure. The structure is fitted with warning signs in English and Bahasa. The navigationstructure is indicated in the photograph below.

Junction

Box

355mm

sleeve

255mmdosing

line pipe

Dosing Line Land Section

Dosin Line Junction Box

South Cardinal Marker

ML-300 Maxlumina Lantern

Access Ladder and Fender

Lightning Conductor

Warnin si n

Navi ation Structure


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4.6. PROJECT ORGANISATION AND RESOURCES

4.6.1. Overall Organigram

Client

TNB

Contractor ALSTOM

Sub Contractor – Civil Works

Leighton Contractors (Malaysia) SDN BHD

Sub Contractor – Cooling Water Intake SystemLeighton - LAMA Joint Venture

Sub Contractor - Design and Engineering ConsultantMurray & Roberts Engineering Solutions Ltd

Main Contractor ALSTOM-PEREMBA J.V.


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4.6.2. Murray & Roberts Engineering Solutions Organigram.

Project Leader

Grei Wolfe

Project EngineerEngineering Manager

Derek Paul (MRES)

On - Site Design Co-Ordinator

Project Design Team

Dra wing OfficeRolf Aebischer

(MRES)

External Consultants

• Ninham Shand• ZLH• Soil & Rock

(Malaysia)• Terra Geotechnics

(Malaysia)

• Knight Hall Hendry

In-house Design Engineers

• Chris Michau• Hamied Mohammed• Stephan Hock

• Pierre Botha• Simon Meyer• Richard WegenerCAD Operators

• Nadeema Amlay• Guillame Du Toit• Adrian Julie• Theo Nel

Quality Assurance Mike Quarmby (MRES)

Document Controller • Cindy Feldman

• Monica Mbusi


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4.6.3. Cooling Water Intake Leighton LAMA Joint Venture Site Management Team

Section EngineerPre-Cast Yard

Dean Pearson(LLJV (MRES))

Section EngineerMarine

Barry Hofmeyrand later

Dean Pearson(LLJV (MRES))

Project ManagerRick Moore (LLJV)

CWIC Construction ManagerRudi Voerman (LLJV (MRES))

Design Coordinator

Alec Dixon(LLJV (MRES))

Section EngineerDosing Lines

Francois Labuschagne(LLJV (MRES))

General Superintendent

George Salmon(LLJV)

Leighton-LAMAJoint Venture Exco


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Manjung Power Station CW Intake Culvert End of Contract Repor t – Volume 1


SECTION 5. DESIGN OF THE COOLING WATER INTAKE

5.1. BACKGROUND TO THE DESIGN OF THE COOLING WATER INTAKE CULVERT

The permanent and temporary works design were carried out by Murray & RobertsEngineering Solutions in Cape Town with some of the detailed design and analysis beingcarried out by external consultants.

The purpose of the Cooling Water Intake System is to draw and deliver seawater from1500m offshore to the power station cooling system on land at a flow of 88.2m³ per second.The proposed design concept was to use pre-cast reinforced concrete triple cell culverts,each having a dry mass of 400 tonnes. The culverts were to be pre-cast on land,transported offshore and placed on a stone foundation bed in a pre-dredged trench, thensealed underwater against the previous culvert unit using a filter fabric grout sock asindicated in figure 1 below.

The cooling water intake culvert extends from a 56m-diameter cooling water pond onshorethrough the island revetment to the 6 intake tower structures 1500m offshore. The reinforcedconcrete culvert consists of a 68.5m long in-situ culvert, connecting into the 56m-diametercooling water pond, 142 no. pre-cast culvert sections, 6 pre -cast intake tower structures, 3 x225mm HDPE dosing lines on top of the culvert and a south cardinal piled navigationstructure 50m south of the end of the last pre -cast culvert as indicated in figure 2 below.

Dred ed Trench

Sand BackfillStone Bed

Rock Armour

Fi ure 1. Pro osed Desi n Conce t


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To optimise the culvert dimensions and minimise the head losses through the intakestructures, a model of the proposed intake structure was constructed at the University ofStellenbosch in Cape Town, South Africa.

To optimise the structural design, and minimize the mass, 3-D finite element structuralanalyses of the pre-cast culvert units were carried out, taking into account all the variousload cases. The load cases modelled included the transportation of the units on heavy lifttrailers to the load-out jetty, the lifting of the units off the load-out jetty using a speciallydesigned 400 tonne floating gantry, the transportation of the units in the sea to its finalposition taking into account surge loads and wave loads.

The intake tower structures were also modelled using 3-D finite element structural analyses.1:50 and 1:20 models of the intake structures were constructed in the 1m wide wave flumeat the University of Stellenbosch in order to measure the wave forces on the intake towers,to check overall stability and to optimise the design of the connection between the intaketower and the culvert.

Two distinct soil layers were evident from the borehole logs. A 25m thick upper layercomprising highly plastic grey, silty clays and a 15m to 18m thick grey fine to coarse -grainedsand layer below the grey, silty clay upper layer.

The culvert was set below the seabed in a 1500m long dredged trench. During the dredgingoperation, however, it was found that a firm founding material on which to place the stonefoundation bed could not be established. Probes by divers found firm materialapproximately 1m below the surface of the very soft clay. However, when the dredgerremoved this soft layer, it disturbed the firmer material below, preventing a firm foundinglayer from being established. Four additional boreholes with laboratory testing of coresamples were carried out during January 2001 and it was found that the moisture content ofthe very soft clay was often greater than the liquid limit, causing the soil to liquefy duringdredging.

In order to reduce the risk of excessive differential settlements between the culverts, it wasdecided to change the foundation design. After a careful time, risk and cost evaluation, a

NavigationStructure

6 No. Pre-Cast

Intake Structures

142 No. Pre-Cast Culverts

3 HDPE Dosing Lines In-Situ

Culvert

Connection to the

Cooling Water Pond

Figure 2. Cooling Water Intake


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decision was taken to construct a piled foundation for the culvert units. The design change,due to the unforeseen founding conditions, occurred seven months after the start of theproject. While a piling barge was sourced, the piled foundation design was carried out andall the approvals and testing requirements were put in place. As the pre -cast culvertconstruction was already well advanced the original structural design of the units had to bechecked for the piled support condition. The first working pile was driven eight weeks afterthe decision to change the foundation design was taken.

28m long, 1m diameter, 80Mpa, hollow pre-stressed concrete piles were driven down to thebottom of the dredged trench with a follower to a specified level, to a tolerance of –50mm.Three to four piles were installed on site per day. Two piles were placed at each jointbetween the pre-cast culvert units. Pre-cast pile caps were constructed, then placed andgrouted into the top of the hollow concrete piles as indicated in figure 3 below.

The 142 no culvert units, each with a mass of 400 tonne, were pre -cast on land undercontrolled conditions and transported by heavy lift trailers to a specially designed load-out- jetty for placement offshore. The units were placed on the piled foundation by a speciallydesigned 400 tonne capacity, floating gantry. Grout bags were then placed between theunderside of the units and the top of the pile cap and pumped full of grout to take up anyrelative movement.

This operation progressed extremely well and any time lost due to the change in design ofthe foundation was made up and even improved upon. The works were handed over within15 months in October 2001 at a final cost of US$16 million.

Pile Cap

1000mm dia hollow pre-

stressed concrete piles

Figure 3. Piled Foundation

Intake Tower StructurePre-cast Culvert Unit


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The successful completion of this project required innovative engineering and theinvolvement of experienced marine personnel throughout all phases of the project. Designsimulations, including physical and computer modelling, as well as on site testing formed amajor part of the success of this design and construct project.

Both the permanent and temporary works were designed by Murray & Roberts Engineering

Solutions. The various elements required permanent works design and temporary worksdesign were as follows:

5.2. PERMANENT WORKS

5.2.1. Hydraulic Assessment of the Cooling Water Intake Culverts

Professor Basson of the University of Stellenbosch wa s appointed to calculate theexpected friction losses in the main culverts.

Manning friction factors of 0,0116 and 0,0162 for "new and clean" and "old andfouled" roughness conditions respectively were used to calculate the total expectedhead losses. The head losses for "new and clean" conditions and "old and fouled"conditions were calculated to be about 1,6m and 2,6m respectively, both less thanthe specified corresponding maximum losses of 2,3m and 2,8m.

Energy losses through the intakes into the culverts were difficult to quantifytheoretically, due to the many changes in flow direction, and contraction andexpansion of flow. It was therefore decided that a model study should be carried outin order to verify the design assumptions. In view of the complex geometry of theintake structure, it was decided to construct a 1 in 15 scale hydraulic model of one ofthe two sets of intakes discharging into the outer barrel culverts. The model wasbuilt and tested at the Hydraulics Laboratory of the Department of Civil Engineeringof the University of Stellenbosch, South Africa, under the supervision of ProfessorGR Basson during November-December 2000.

The total energy losses across two intakes and the bend was less than waspredicted theoretically. The square layout of the intakes with their relatively largethroat areas therefore assisted in reducing losses.

The maximum local velocities through the screen openings at Intake 1 under stillwater conditions was 0.49 m/s, which was less than the specified maximum velocityof 0,5 m/s. Velocities through a significant proportion of the screens at Intake 1were lower and maximum velocities at all other intakes were also slightly lower.

The model tests and results are fully described in Appendix D of the Report on theHydraulic Assessment of the cooling water Intake Culverts Report No.MNJ/99/W/UPA/---/CA/06 rev 04. The model is indicated in the photograph below.


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Hydraulic Model of Intakes


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5.2.2. Assessment of the Wave Loading on Intake Towers

The wave climate for the design of the intake structures was determined, asrecommended in Report No ZLH-554-02 Rev 01, November 2000, Manjung PowerStation Project, Cooling water Intake Culverts and Jetty, Design Wave Conditionsand Report No ZLH-554-03 Rev 01, November 2000, Manjung Power Station

Project, Wave Conditions for Calculation of Fatigue Loads for the Manjung ColdWater Intake Structures.

Wave loads were computed using diffraction theory combined with Morrison dragforces where appropriate. Allowance was made for up to 50mm marine growth onthe intake towers, when calculating the drag components of the forces. However,no information was available on the expected thickness of the marine growth.

The wave and current loads on the structure were computed using WIFS (WaveInteraction with Fixed Structures), C J Garrison, 2000 and API RP2A,Recommended Practice for Planning, Designing and Constructing Fixed OffshorePlatforms, Nineteenth Edition, 1991. Wave and current loads were computed forextreme conditions, as well as for fatigue design purposes.

The theoretical hydrodynamic loads calculated for the design of the structures wascompared with model tests that were carried out at scales of 1:20 and 1:50 for bothbroken and unbroken waves. The main purpose of the model study was to serve asa control on the numerical models that were used to calculate the forces andmoments on the structure. The models were built and tested at the HydraulicsLaboratory of the Department of Civil Engineering of the University of Stellenbosch,to establish the wave induced moments on the intake structures.

A comparison of the numerical wave force analysis results with those from themodel tests resulted in the numerical results being used for design purposes, for the6.3m design wave height.

The model tests are described in the Appendix of design report no.MNJ/99/W/UPA/---/CA/021 rev 01. The model is indicated in the photograph below.

1:20 Wave Model 1:50 Wave Model


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5.2.3. Structural Analysis and Design

The reinforced concrete in the culverts had the following properties:

• 45Mpa, 28 day characteristic strength• Total cementitious content 485kg• PFA content 30% of the total cementitious content• Water/cement ratio 0.33• Reinforcement cover 60mm

5.2.3.1. In-situ Culverts

The in-situ culvert consists of three sections of lengths 30m, 30m and 8.7mrespectively. Movement joints are provided at the diaphragm wall andbetween the sections of the culvert, allowing full relative rotation across the

joint. The joint design is described in document no. MNJ/99/W/UPA/---/CA19.1.

A reinforced concrete chimney, which provides access to all three barrels,

is positioned towards the end of Section 1. This concrete chimney allowedtemporary interior bulkheads to be installed into the in-situ culvert. Thebulkheads were required to provide a dry interior when the water pooldiaphragm wall was broken out to connect to the in-situ culverts.Reinforced concrete piles provide support to the culverts, positioned in fourrows longitudinally under the culvert walls. The longitudinal pile spacingvaries along the length of the in-situ culvert.

No further detailed analysis or calculations were carried out for Section 2.Section 2 was detailed using the design carried out for Section 1 as theloads for Section 2 are the same as or less than Section 1.

Reinforced concrete piles provide support to Section 3 of the Cooling Water

Intake in-situ culvert. One row of 4 No. 400mm square pre-cast concretepiles, positioned longitudinally under the culvert walls, 1.5m from themovement joint between Section 2 and Section 3 and, 2 No. 700mmdiameter concrete spun piles, under the internal walls of Section 3 of thein-situ culvert, at the joint between Section 3 of the in-situ culvert and thetransition pre-cast unit. A continuous crosshead beam and 2 no.rectangular pile caps are cast over the 2 No. 700mm diameter concretespun piles to support the pre-cast transition unit on.

Finite elements analyses were carried out using LUSAS Ver 13, with preand post processing using LUSAS Modeller Ver 13. The floor, walls androof of the culvert were modeled to the mid-surface using 8 noded thickshell elements (QTS8 element type). The piles were modeled using

engineering thick beam elements (type BMS3), with a single vertical springelement at the base of each pile to simulate the foundation stiffness. Theinterface between the piles and the culvert floor was modeled locally using20 noded solid confinuum elements (type HX20), to simulate the loadtransfer from the beam elements (piles) to the shell elements (culvert floor).

Ultimate Limit State (U.L.S.) structural design of the culvert section hasbeen carried out using ultimate bending moments and shear forcesextracted from contour plots for the worst load combinations.


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Connection to Water Pool

Concrete Chimney

Steel Bulkheads

Section 1

Pre-Cast

Concrete Units

Section 2Section 3

400mm square Pre-Cast Concrete Piles700mm dia Piles

1000mm dia Piles

Figure 4. In-situ Culvert

The Serviceability Limit State (S.L.S.) cracking checks have been carriedout using the worst service bending moments, and a maximum permissibledesign crack width of 0,2mm. The design of Section 1 and 3 of the in-situculvert is described in document no’s. MNJ/99/W/UPA/---/CA 04, Ca04.1and CA 04.2.

5.2.3.2. Pre-cast Culverts

The pre-cast culvert section of the cooling water intake consists of approx.142 No., 10m long, 11.810m wide by 4.610m high units supported on aconcrete pile cap which is supported on 1m diameter, class C, grade80N/mm 2 concrete spun piles. The triple cell pre-cast culverts have interiorbarrel dimensions of 3.750m vertically and 3.450m horizontally, with0.300m chamfers.

Figure 5. Pre-cast Culvert Lusas Computer Model


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The 10m long pre-cast culvert with three interior cells has been modeledusing the LUSAS finite element software. The bottom slab, walls and topslab of the culvert unit was modeled to the mid-surface using 8-noded thickshell elements (QTS8 element type). The piles were modeled using beamelements (type BMS3) and the pile caps as 3-D solids (type HX20). Thecontact between the pile caps and the bottom slab thick shell elementswas modeled using 3-D joint elements (type JNT4), in order to simulate the

contact over the correct area on the pile caps. Axial joint elements (typeJSH4) were used at the bottom of the piles to simulate the long term load-settlement behavior of the piles. The computer model is indicated inFigure 5.

The position of the piles and pile caps relative to the culvert unit wasvaried. In each case the pile cap joint elements were revised such that thecontact area was correctly approximated.

Full fixity boundary conditions were applied to the bottom of the piles. Allnodes on the piles were given horizontal spring stiffnesses in the twoglobal horizontal directions, based on the horizontal coefficient of subgradereaction determined by Soil & Rock Engineering for the 1,0m diameterspun concrete piles. The magnitude of the spring stiffnesses used for thelateral soil restraint was increased until the horizontal deflection of the pileswas approximately the same as that obtained by Soil & Rock Engineeringin the full geotechnical analysis. The detailed geotechnical and structuraldesign calculations for the piled foundation are contained in:

• Design report No. MNJ/99/W/UPA/---/CA/24• Design report No. MNJ/99/W/UPA/---/CA/24.1• Design report No. MNJ/99/W/UPA/---/CA/24.2• Design report No. MNJ/99/W/UPA/---/CA/25.

5.2.3.3. Intake Structures

The cooling water intakes consist of 6 intake culvert units, which haveinternal walls for diverting and channeling the water flow and intake towerstructures which are fixed in-situ to the top of the culvert units which aresupported on 8 concrete pile caps on 8 No. 1m diameter, class C, grade80N/mm² concrete spun piles. The layout of the intakes is indicated infigure 6.

The pre -cast culvert units supporting the intake towers were constructedonshore on a number of prepared casting beds. The units were cast onplinths in an elevated position to allow the heavy-lift trailers to move inunderneath the units in order to lift and load the units. Each unit’s dryweight was approximately 400t. The culverts were then transported by

heavy-lift trailers onto a specially constructed temporary load-out jetty. Thisallowed a floating gantry to straddle the jetty and unit, to lift it off totransport it out to a temporary stone foundation bed offshore

The intake tower structures were constructed onshore on a number ofprepared casting beds. The intake tower structures were cast separatelyfrom the intake culvert units supporting them. Each intake tower’s dryweight was approximately 156t. The heavy-lift trailers then transported theintake tower structures onto the specially constructed temporary load-out

jetty. The floating gantry then straddled the jetty and intake tower, and


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lifted it off for transport out to the culvert unit, which had already beenplaced on the temporary stone foundation bed offshore. The intake towerstructures were then fixed to the submerged culvert units by means of anin-situ concrete connection at low tide.

The floating gantry then moved the completed intake culvert units includingthe intake towers to their final positions on the piled foundations.

The intake units on which the towers are supported were analysed as perthe typical pre-cast units using the LUSAS finite element software. Theintake tower structure was also modeled using the LUSAS finite elementsoftware. All components of the structure were modeled to the mid-surface using 8 noded thick shell elements (QTS8 element type). Thetower model was provided with a continuous support at the bottom, withfixity in all global axis directions to model the connectivity to the pre-castunit. The wave pressures on each component of the structure werecalculated using the maximum resultant horizontal and vertical loads onthe structure as determined from the model tests and numerical analysescarried out using MORA. This previous study determined that the worstextreme wave conditions anticipated will be unbroken waves (Waves onpoint of breaking) with Hmax = 6.0m and a period of 8 seconds. A typicalcontour plot from the Lusas software is indicated in figure 7. The detailed geotechnical and structural design calculations for the intakestructures are contained in Design report No. MNJ/99/W/UPA/---/CA/25.1..

Fi ure 6. La out of Pre-Cast Intake Towers


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5.2.3.4. Navigation Structure

The Navigation Light Structure has been modeled as a space frame onStaad Pro 2001, using shell elements to model the pile caps and the pileswere modeled as 900 mm diameter x 130 mm thick concrete beamelements. The horizontal loads on the piles are applied as trapezoidalbeam loads and the horizontal loads on the slab are applied through aspecial dummy beam element at the slab perimeter. Horizontal springsupports were calculated to simulate fixity of the structure. Lateral soilsprings were provided at different depths along the length of the piles,which were based on a lateral modulus of subgrade reaction as determinedby Soil & Rock Engineering.

Vessel berthing loads were calculated based on the recommendations ofBS 6349 : Part 4 : 1994 Section 4.7. A berthing velocity of 0.5 m/sec wasused in the calculations. An EXCEL spreadsheet was developed fordetermining the wave particle velocities and wave forces based on Linear

Airy wave theory using Morisons equation.

The detailed geotechnical and structural design calculations for thenavigation structure are contained in Design repo rt No. MNJ/99/W/UPA/---/CA/03. The navigation structure is indicated in the photograph below.

-


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5.2.4. Geotechnical Analysis of the Piled Foundations

The PIES computer program was used to estimate the geotechnical safe workingloads for the concrete piles which support the in-situ, pre -cast and intake structureculverts. The PIES software was developed by Professor Poulos at the Universityof Sydney. The software uses a simplified boundary element formulation andmodels the interface between the pile and soil in a hyperbolic manner. Theprogramme calculates the down drag load of a pile embedded in settling marineclays and the pile head settlement for different applied pile head loads. In this way,a complete load vs settlement curve was derived.

The safe working load of the piles was also calculated using theoretical models

provided by Professors Fleming and Randolph. The safe working loads(geotechnical) of the concrete piles were calculated for different pile penetrations.These static analyses were carried out using the computer program PILER.Soil and Rock Engineering, Geotechnical Consultants in Kuala Lumpur, carried outthe PIES and PILER analyses referred to above.

Soil & Rock Engineering evaluated horizontal spring stiffnesses in the two globalhorizontal directions at all the nodes on the piles. These horizontal springstiffnesses where based on the horizontal coefficient of subgrade reaction of thesoil profile. These spring stiffnesses were used in the structural analyses.


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5.2.5. Hydraulic, Installation and Design of the Dosing Lines

5.2.5.1. Hydraulic Design.

The hydraulic assessment for the dosing lines for the cooling water intakeculverts from the skid to the intake was modelled with the nozzles, withoutany backpressure or non-return valve. The design parameters were as

follows: Maximum flow in pipes 186 m3/hr per pipe, Nominal flow 62 m3/hr,Minimum flow (one pump) 10 m3/hr, Head from pump curve for 51,66 l/s =28.4m, Head loss on shore to battery limit (Max flow) = 6.7m, Elevation ofpumps (above sea level) = 4.15m.

We did not have information of the actual pump curves, and we assumedthat the losses of -6.7m in the pipe work and control valves were correctfor the high flow condition. We used the PIPEN software to analyse thedosing line system.

Wave action will create a dynamic affect in the system, this may influencethe short term dosing at the individual intakes, but the general level of

chlorination in the line should not be affected.The output from the PIPEN analysis software for the various runs arecontained in design report No. MNJ/99/W/UPA/---/CA/05. The analysiswas based on a 140 ∅ dosing ring pipe, but this was subsequentlychanged to a 160 ∅ dosing ring pipe as this size was more readilyavailable than the 140 ∅ pipe. Please note that there is not a significantdifference in the analysis between the 140 ∅ and 160 ∅ pipe for thedosing ring line as most of the losses occur in the main 225 mm ∅ line.

Wave action will create a dynamic effect in the system, this may influencethe short term dosing at the individual intakes, but the general level ofchlorination in the line should not be affected.

5.2.5.2. Installation Design

The pipes were pulled out through HDPE sleeves that were cast intoconcrete diaphragm walls located at 5.0m c/c on the top of the pre-castunits. The pipes are located in a closed cavity (covered with concretecover slabs), and were thus not subject to significant wave forces, and willalso be protected from direct snagging dangers.

The pipes were assembled on land in lengths of 24m and then joinedbefore being pulled out by a suitable barge or vessel, through the sleeves.There were three different pulling lengths i.e. 1315m, 1375m and 1435m.

The pipe was designed to overcome the following forces during installation(pulling): inertia, friction at sleeves from buoyancy, affects of mis-alignmentof the sleeves from placing tolerances in the pre -cast units or settlementsand launching friction on the land rollers. A pulling nose was designed andattached to the front of each pipe. An opening was provided in the pullingnose to allow water to enter the pipe to flood it as it was being launched.


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The calculation of the installation forces and the pipe stresses in the HDPEPE80 225 ∅ Class PN 10 dosing line pipe are contained in design reportno. MNJ/99/W/UPA/---/CA/05.1

5.2.5.3. Pre -cast concrete housing design

The chlorine dosing lines are housed in a small concrete structure locatedon the top of the intake culverts. All three dosing lines are located withinthis housing, which comprises two sloping kerbs fixed to the top of theculvert, each with a recess at the top, into which a pre-cast cover slab ispositioned. These pre-cast concrete housings are subject to variousforces, the most significant of these forces is uplift on the slabs and dragforces on the kerbs, due to the action of waves and current.

A model test is the most reliable method to obtain the forces and uplift onthe units, but time and cost constraints prevented this. The analyticalmethods used to calculate the design uplift on the top of the culverts wastherefore an approximation The analytical calculations were based on thebest estimates for the combined effects of a depth limited wave for 10m ofseawater over the culvert and an allowance for up to 2m scour next to theculvert, together with the design current of 1.0 m/sec.

Linear wave theory was used to estimate the wave induced water velocitiesin the region of the housing units. Drag and lift pressures were calculatedusing Morison’s equation. The resulting pressures with 2% included foradded mass were calculated as 35 KPa Lift and 17.7 kPa Drag. The lift

force was applied to the top of the pre -cast element, and the drag forceshave been applied as 79% to the front kerb as a pressure, and theremaining 21% to the back kerb as a suction force.

Bolts were recommended to hold down the pre-cast concrete covers butthe JV chose not to use holding down bolts. The calculations for the pre-cast concrete housing are contained in design report no. MNJ/99/W/UPA/---/CA/05.2


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5.3. TEMPORARY WORKS

The temporary works elements requiring detailed design were as follows:

5.3.1. Load Out Jetty

A reinforced concrete jetty, supported on concrete spun piles, was designed to

provide a structure over the water where the pre -cast units could be positioned andlifted off the jetty using a floating gantry, before being towed to the dredged trenchand lowered onto the foundation bed in their final position.

The full jetty was modeled using an assemblage of beam elements and analysedusing the PROKON software package. The pre -cast deck slabs were modeledusing beam elements, with each beam having a width equal to half the width of apre-cast slab panel.

Horizontal supports for the piles were provided at -4.40m ACD, which correspondsto a point about 2,5 pile diameters below the scoured seabed level. A scour of1,0m was taken into account. At the pile toe (taken at – 14,40m ACD) horizontalsupports were provided, as well as a vertical spring with a stiffness of 70 000kN/m,which corresponds to the lower bound pile spring stiffness as calculated by Soil &Rock Engineering. Towards the rear of the jetty the horizontal restraints werepositioned higher up the pile to take account of the sloping landfill embankment andrevetment.

The detailed structural design was carried out in accordance with BS6349, BS5400

and BS8110. Bending moment and shear force envelopes at Ultimate Limit Statewere extracted from the PROKON analysis, for the primary elements of thestructure, namely the pre -cast deck slabs, the longitudinal deck beams near theend of the jetty, the crosshead beams and the piles. Reinforced concrete designcalculations based on the formulae in BS8110 were carried out for the peak forceson each primary element, using spreadsheet calculations. These weresupplemented with additional hand calculations where necessary. Spreadsheetcalculations were used to check the Serviceability Limit State crack widths, basedon the crack width formulae in BS5400.


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The calculations for the load out jetty are contained in design report no.MNJ/99/W/UPA/---/CA/02.

Lateral load analyses for the concrete spun piles were carried out using thegeotechnical software, DEFPIG 6XB (1999), which was developed by ProfessorPoulos at the University of Sydney. The programme analyses the behaviour ofsingle piles and pile groups when subjected to axial and horizontal forces and

moments. The piles were divided into 50 elements and limiting pile- soil stresses(ultimate skin friction values) and elastic moduli were assigned to each element.The pile head reactions determined from PROKON software were applied to the700mm spun piles and lateral deflections and bending moments were calculated forsingle piles driven through the revetment and offshore. The lateral deflection at thepile head level ranged from < 2mm to about 10mm. The maximum bendingmoments ranged from about 30kNm to 150kNm. The effects of a 2 No x 760kNberthing force on the 39 piles supporting the load out jetty was modelled usingDEFPIG. The maximum lateral deflection at pile head level was estimated to be14mm and the maximum bending moment was estimated to be 1860kNm. Thecalculations for the loadout jetty are contained in design report No.MNJ/99/W/UPA/---CA/02.1.

5.3.2. Cofferdam

A 53.2m long by 14.4m wide cofferdam was required in order to construct in-situsection of the concrete culvert for the connection of the cooling water intakes to thecooling water pond. The cofferdam was a multi-propped type with three layers ofprops at +1.50m, -2.70m. and –5.50m ACD respectively. The excavation depthinside the cofferdam was approximately –8.00m ACD. The ground surface of theexisting island was about +4,65m ACD. The ground level for a distance ofapproximately 8m around the cofferdam was reduced to a level of +3m ACD toreduce the soil loads on the sheet piles. A second row of Lx 16 sheet piles wasdriven around the cofferdam and the water table inside this area was reduced toapproximately 0.0m ACD, in order to reduce the water pressure on the cofferdam.

Boreholes were drilled, SPT’s, hand shear vane tests, and later CPT’s were carriedout to determine the properties of the soil in the area to enable an analysis of thecofferdam to take place.

The ground conditions varied significantly over the Cofferdam area. The cofferdamwas therefore divided into 3 distinct sections for design, referred to as Sections 1, 2and 3 respectively. Section 1 – Onshore - from 20m to 33m from the DiaphragmWall, Section 2 - Revetment - from 33m to 52.2m from the Diaphragm Wall (Section2a - from 33m to 42m, Section 2b – from 42m to 52.2m), Section 3 – Offshore -from 52.2m to 73.2m from the Diaphragm Wall. The ground conditions for Section1 (Onshore) were better than for Section 2 (Revetment) and Section 3 (Offshore)as they were surcharged by the reclamation.

The 3 Sections of the cofferdam consisted of 4 different types of sheet pilesections. Section 1 (Onshore) - 13m of 18m long PU25 sheet piles driven to –15m

ACD, Section 2 (Revetment) - Section 2a - 9m of 24m long PU25 sheet pilesdriven to –21.0m ACD plus Section 2b - 10.2m of 24m long reinforced PU25 sheetpiles driven to –21.0m ACD, Section 3 (Offshore) - 21m of 24m long reinforced Lx32 (or equivalent 24m long reinforced PU 25) sheet piles driven to –21.0m ACD.


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The WALLAP and PLAXIS finite element computer programs were used to performthe stage-by-stage analyses of the structure, in order to determine the stability ofthe cofferdam, the waler loads and the bending moments and shear forces in thesheet-piles, during the construction process. The programs can be used to modela braced excavation in layered soil deposits.

PLAXIS is a finite element program that is capable of analysing excavationproblems in 2-dimensional continuum under plain strain conditions. A 6-nodeisoparametric element was used to model the soil medium. Underneath the firmclay layer was the sand stratum and a fixed base was assumed. The phreatic linewas assumed to be at +1.0m ACD. Beam elements were used to model the walland struts. The problem was symmetrical and therefore only half of the crosssection was analysed.

The sequence of construction involving the excavation of a soil layer, theinstallation of sheet piles and struts, and ground dewatering can readily be modeledby the programs. The construction sequence generally consisted of: i) Installingconcrete piles for the culvert foundation, ii) Installing sheet piling to toe elevations

of -15m and –21m ACD, iii) Excavation for the cofferdam, iv) Installing the threelayers of struts and walers and de-watering as the excavation proceeded, v)Casting the in-situ culvert base slab hard up against the sheet piles and vi)Removing layer 3 of the struts and walers, vii) Completing the in-situ culvertconstruction and, viii) Removing layers 2 and 1 of the struts and walers as thebackfilling proceeded.

WALLAP carries out two (2) separate types of analysis: i) Limit equilibrium analysiswhere factors of safety are calculated in accordance with recognised and codifiedprocedures; and ii) Bending moment and displacement analysis. This is carried out


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by modeling the stage -by-stage development of forces and wall movements asexcavation proceeds. The results of the WALLAP analyses were not included inthe report as they were only used as a design check. The client would also notaccept designs carried out using WALLAP.

• The calculations for the cofferdam are contained in design report no.MNJ/99/W/UPA/---/CA/13.2.

• Tied back cantilever sheet pile walls were designed at the end of the cofferdamto enable the placing of the first pre-cast unit next to the in-situ culvert.

• The calculations for the wing walls are contained in design report no.MNJ/99/W/UPA/---/CA/13.3

5.3.3. 400 tonne Floating Gantry

The floating gantry was a space frame structure consisting primarily of Grade 43Asteel (or equivalent) tubular members. The structure spanned between two 120’ x40’ x 8’ barges in order to straddle the load out jetty on which the culvert unit wasplaced. The function of the gantry was to lift the unit at two lift points on the gantrystructure and transport the unit while hanging from the gantry to the offshore

location where the unit was lowered into its final position in a pre -dredged trench.The gantry was towed out from the load out jetty to the final placement location.The geometric configuration was determined by the following factors : Clearanceover the culvert unit placed on the loadout jetty, Barge dimensions and locations ofbulkheads for gantry support placement, Tidal ranges relative to jetty levels, Culvertunit dimensions and lifting corbel locations and the Space provision for rigging andlifting equipment.


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In order to assist the structural efficiency of the system, two tie members wereincluded at a level around 5.5m above the deck of the barge in order to prevent theseparation action of the two barges while the unit is hanging from the gantry. Thismeant that the relative outward displacement of the barges was not only resisted bythe portal framing of the gantry. The tie members needed to be placed after thegantry was moved over the unit prior to lifting due to clearance considerations.

The structural analysis of the framing was performed using STAAD – Pro 2000 finiteelement analysis software. Simple beam elements were used for member modelingwith tubular section properties. Member offsets at the tubular connections wereincluded in the model with additional members around the intersection points. Theoverall geometry and more specifically the tubular intersection geometry weredeveloped with the assistance of a 3-D CAD model assembled with AutoCAD software. Offset geometry coordinates were then imported as input for the STAADmodel. The 3-D model was also used for rigging and sheave block clearancechecks especially around the lift point node. Boundary conditions were applied atthe bases of the four legs on each side of the gantry (4 x 2 = 8 locations). Thebarge was not included in this structural model. Vertical springs with stiffnessesrepresenting the barge buoyancy were used at all 8 locations. One side of the gantrybase was released in the horizontal plane in order to accommodate the outwardrelative displacement of the barges.

The following loadings were considered for the structural analysis:

• Dead Load : Applied as a uniformly distributed load throughout the structureself-generated by the STAAD software. This was factored up by 5% to includeappurtenances like walkways and ladders.

• Live Load : Hanging weight of the concrete culvert unit together with associatedrigging. This hanging load was applied as a point load at the lift point node. Theload factor used is explained below.

• Environmental Loads : The environmental data used for adopting a designwave is contained in the design report.

• Wind : the magnitude of the wind loading on the gantry is insignificant comparedto the other loadings and hence was ignored.• Wave and Current : The 10 year return period maximum wave height is between

0.75 and 1.0m and hence a 1m wave height was used for the design togetherwith 0.5m (1 knot) current. The effect of the wave and current on the barges wascalculated and applied to the base of the gantry legs to represent transfer ofenvironmental load into the gantry via the barge.

By far the most critical load condition was the case of the unit hanging prior tosubmergence in the water (i.e. the dry weight of the unit).

For wave loading effects on the barges the following wave directions have beenconsidered : Beam wave (across the two barges) in order to model the effect of

barge separation in addition to differential heave and Quartering (diagonal) wave tomodel the torsional loading effects on the gantry due to anti-symmetric rotation ofthe barges about the transverse gantry axis.

The STAAD program has an API code check facility and this was used for memberdesign. In addition, the API punching shear requirements are included in the APIcode check. Hence the tubular connection design is also part of the STAADstructural analysis.


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The lift point, tie member connection to the 500 mm diameter gantry legs and bargesupport grillage were designed in accordance with the AISC steel design code.

In order to lift the unit from the load out jetty from two lift points on the gantry to fourlift locations on the typical culvert unit, a spreader beam was required to spread thelift load from a single line to the two lifting corbels on each side of the unit. The unitwas lifted by Macalloy bars attached to the culvert corbels. The bars were attached

to the lift beam which was connected to the lower sheave block by slings.

The calculations for the floating gantry are contained in design report no.MNJ/99/W/UPA/---/CA/13.3

5.4. EXTERNAL CONSULTANTS

The following external consultants were appointed to carry out the following detailed designand analysis.

Ref. Design ElementDesigner

1.Structural Analysis and Reinforcement Design ofIn-situ culverts, Pre-cast culverts and IntakeTower Structures

2. Computer Modelling of Wave Forces on theIntake Towers

3.Dosing Line Hydraulic Analysis and StructuralDesign

Zietsman Lloyd andHemsted Inc.

4. Geotechnical Design of the piled foundations

5. Geotechnical Analysis of CofferdamSoil & Rock Engineering

6. Hydraulic Analysis and Head Loss Calculations Ninham Shand

7. Physical Hydraulic Model of the Intake Towers

8. Physical Wave Model of the Intake Towers

University ofStellenbosch


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SECTION 6. GEOTECHNICAL CONDITIONS ENCOUNTERED ON THE CULVERT ROUTE

6.1. GEOTECHNICAL INVESTIGATIONS

The initial geotechnical data was obtained during the offshore site investigations, which werecarried out by Strata Drill Sdn. Bhd. on behalf of Alstom Export Sdn. Bhd. during December1999 and January 2000.

The site investigation information, which was provided by the client at tender stage, includedthe following:

• Six, 50m deep, exploratory boreholes drilled using rotary washboring with SPT testingand undisturbed Shelby tube sampling. Three boreholes (103, 104 and 105) were drilledalong the intake route. In-situ, field vane testing was undertaken at 1,5m to 2m intervalsin the boreholes until refusal.

• Laboratory testing of undisturbed samples from the boreholes, included Atterberg limits,particle size distribution, UU and CU triaxial compression tests, oedometer, naturalmoisture content and chemical testing.

• Twenty-five, 20m deep, marine piezocone penetration tests (CPT) were undertaken to

measure cone resistance, sleeve friction and porewater pressure. Dissipation tests werealso conducted. Fifteen of the CPT tests (CPT110 to CPT 124) were undertaken alongthe intake route.

6.2. THE SOIL PROFILE

The intake route is underlain by more than 50m of unconsolidated sediments, which aredescribed, in part, in the borehole logs as alluvium. However, references in the boreholelogs to shells suggest that, at least, the upper parts of the sedimentary layers have a marineorigin or a reworked marine origin.

Two distinct soil layers were evident from the borehole logs.

The upper 25m comprising grey, silty clays with minor sandy clays. Sandy or silty lenses,shell fragments and traces of organic material and decomposed wood also occur. Grey tolight grey, lenses of slightly silty, fine to coarse sand with some angular to sub rounded, fineto medium quartz gravel was recorded, in places. The thickness of these occurrencesranges up to 1,5m. These clayey soils were highly plastic, with the natural moisture contentof the upper 4m of soil approaching, but not exceeding the liquid limit. The undrainedcohesion varied from 5kPa to 13kPa at seabed level with a typical increase of 1.25kPa/mdepth.

A sandy layer that generally ranges in thickness from 15m to 18m occurs approximately 25mbelow sea floor (about -30m to -35m CD). These light grey sands are fine to coarse grainedand frequently contain sub angular sub rounded, fine to medium gravel. In places, the sandsare silty, and thin silty and clayey layers also occur.

6.3. GEOTECHNICAL CONDITIONS ENCOUNTERED DURING DREDGING

During November 2000, whilst trimming the excavated trench in the seabed to final level,diving inspections showed that a layer of between 500mm and 2.0m of soft disturbedmaterial continuously remained in the bottom of the trench.

After removal of further material to reach the firmer underlying layers identified by diverprobes, the thickness of this layer of poor material did not diminish but remained fairlyconstant.


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As a result the crushed stone foundation bed could not be placed in accordance with theoriginal design requirements and there was concern about being able to develop the required10 kPa bearing capacity.

It was initially unclear as to the source of the poor material as it could not be identified in thesoils data supplied at tender stage. The possibility was that it flowed in from the surrounding

seabed or that it arose from the disturbance of the seabed materials during the dredgingoperations. It is now generally accepted that the material which was marginal as a foundinglayer tended to liquefy when disturbed by the dredging operations.

6.4. REVISED COOLING WATER INTAKE FOUNDATION DESIGN

The LLJV requested the designers (LAMA) to investigate the cause of the problem andrevise the design to accommodate the seabed materials encountered. At the beginning ofDecember 2000 LAMA personnel travelled to the site to meet with the LLJV site personneland local Malaysian geotechnical engineers. The purpose of this visit was to discuss and todetermine the cause of the problem, and if necessary to institute remedial actions oralternative designs. Samples of the excavated material were viewed and tested, and theavailable borehole cores were investigated. A specification was issued for further boreholedrilling along the trench alignment and four additional exploratory boreholes were drilledduring December 2000 to supplement the investigations conducted by Strata Drill Sdn. Bhd.

Meetings were held in Malaysia with local geotechnical consultants, the Client, Powergenand the LLJV site personnel to discuss and agree on an alternative foundation design whichwould allow construction to continue with as little delay as possible. As a solution it wasproposed that instead of attempting to remove the poor material, large sized graded rock fillwould be dumped in order that it would penetrate the soft underlying material and form abase for the stone bed. A drop test was carried out to ascertain to what depth a rock wouldsink to in the deleterious material. A granite rock (approximate dimensions 0.3m x 0.5m)supported on a graduated tape was dropped into the soft material. It sank to a depth of about1.5m. Hand probing at this location refused at a depth of about 2m.

LAMA prepared an initial report on their findings and the proposed revised design. In orderto verify the proposed design, a finite element model was set up using the Sage Crisp finiteelement software to calculate and predict the long -term settlement of this foundationproposal. Rock dumping commenced on site to the revised design in order to carry out in-situ testing. The intention was to place a culvert unit on a foundation constructed to therevised design in order that the actual short-term settlement could be measured and used tocalibrate the FE model. This would improve the accuracy of the model’s long-term settlementpredictions. The results of both the model and the prototype gave very encouraging andacceptable levels of settlement. The relevant drawings were changed and design reportsprepared for the revised foundation deta ils.

At the February 2001 JV Exco meeting, the decision was taken to rather consider using a

piled foundation than the dumped rock solution that had been proposed. The reason for thisselection was that it was felt that there was less risk of differential settlement between culvertunits in the long-term with a piled structure and that Alstom were in favour of this change. Allwork on the rockfill alternative was then stopped and the test unit removed from the seabed.

6.5. CONCLUSIONS

The problems encountered with the seabed materials in the trench were considered byLAMA to be unforeseen ground conditions, as the soil investigation information provided to


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LAMA at the time of the final design being carried out did not indicate that these materialswould behave in this way during dredging.

This view has been well documented in the report submitted for the revised design, as wellas in reports by independent geotechnical consultants. The original design was found to beacceptable to our appointed local (Malaysian) geotechnical consultants, the Clientsgeotechnical engineer, as well as Powergen’s Chief Engineer.

At no stage during the design and design approval process (which was by then largelycomplete) did anyone, including the local engineers involved, foresee problems with thismaterial.

6.6. RELATED DOCUMENTS ISSUED

Design Reports:

• Doc. No. MNJ/99/W/UPA/---/CA/16, Interpretation of Geotechnical Data For The CoolingWater Intake Culverts, Rev 03, 16/11/00.

• Doc. No. MNJ/99/W/UPA/---/CA/22, Report on Unforseen Ground Conditions Resulting in

the Redesign of the Dredge Pocket Between CH300m and 500m, Rev 02, 15/01/01.• Doc. No. MNJ/99/W/UPA/---/CA/16.1, Revised Geotechnical Design Report – ForFoundation Type B, Rev 03, 06/02/01.

• Doc. No. MNJ/99/W/UPA/---/CA/30, SRK Consulting Review of Existing GeotechnicalData for the Cooling Water Intake Culvert, Rev 01, 13/02/01.

• Knight Hall Hendry report – Review of Geotechnical Data ref LAMA01C\RWH\ms dated6th March 2001


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Manjung Power Station CW Intake Culver

Manjung Power Station - Malaysia

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