Foundation Method Statement: Uganda Electricity Transmission Corporation Limited. Uetcl

Foundation Work Method Statement for the proposed 220KV Over Head Transmission Line Project: Nkenda - Hoima (226km) Client:

Uganda Electricity Transmission Corporation Limited. UETCL Consultant:

Contractor:

KEC International Ltd.,

Foundation Method Statement DESIGNATION

NAME

SIGNATURE

DATE

AUTHORISED FOR IMPLEMENTATION PROJECT MANAGER

MR. P.K.DAS CLIENT ACCEPTANCE

PROJECT MANAGER

MRS. ANNA CONSULTANT ACCEPTANCE

PROJECT MANAGER

Rev

Date

00 12/07/2015

MR. MARIN

Checked By

Description

Document No.

Pages

MR

Issued for Approval

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20

Status

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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TABLE OF CONTENTS 1.0

SCOPE OF DOCUMENT AND FIELD OF APPLICATION...........................3

2.0

REFERENCE DOCUMENTS............................................................................3

3.0

METHODOLOGY FOR FOUNDATION INSTALLATION.............................3 3.1 3.2 3.3 3.3.1 3.3.2 3.3.3 3.3.4 3.3.5 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.10.1 3.10.2 3.11 3.12 3.13 3.14 3.15 3.15.1 3.15.2 3.16 3.16.1 3.16.2 3.17 4.0 4.1 4.2 4.3 4.4 4.5

OBJECTIVE..................................................................................................3 SITE PREPARATION...................................................................................3 EXCAVATION..............................................................................................3 GENERAL....................................................................................................3 ROCK FOUNDATION EXCAVATION:......................................................5 BLASTING...................................................................................................6 ROCK ANCHOR DRILLING......................................................................6 DEWATERING FOUNDATION EXCAVATIONS......................................7 FOUNDATION SETTING OUT AND ORIENTATION.............................7 FOUNDATION TOLERANCES..................................................................8 REINFORCEMENT PLACEMENT..........................................................10 FORMWORK.............................................................................................11 BATCHING AND MIXING.......................................................................11 FIELD CONTROL OF CONCRETE STRENGTH....................................12 PLACING CONCRETE.............................................................................13 PREPARATIONS........................................................................................13 GENERAL..................................................................................................14 REPAIR OF DEFECTIVE CONCRETE....................................................14 CONCRETE FINISHING...........................................................................15 CONCRETE CURING...............................................................................15 PROTECTION OF FOUNDATIONS AND STUBS..................................15 BACKFILL.................................................................................................15 GENERAL..................................................................................................15 COMPACTION...........................................................................................16 EMBANKMENTS......................................................................................16 GENERAL..................................................................................................16 EXCAVATION FROM BORROW FOR EMBANKMENTS.....................17 SITE CLEAN UP AND EROSION CONTROL........................................17 ANNEXURES - QUALITY CONTROL BOOK....................................17 SURVEY REPORT.....................................................................................17 EXCAVATION INSPECTION....................................................................17 STUB SETTING RECORD SHEET..........................................................17 MATERIALS INSPECTION......................................................................17 CASTING RECORD SHEET.....................................................................17

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Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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4.6.............................................CASTING PLACING CONTROL ......................................................................................................17 4.7....................CURING, BACKFILLING AND COMPACTION 4.8

1.0

17 CONCRETE CUBE TEST DATAS............................................................17

SCOPE OF DOCUMENT AND FIELD OF APPLICATION

The aim of this document is to define the methodology for the activities that shall be performed in implementation of the Tower Foundation for the proposed 220kV transmission line for Nkenda - Hoima (226km), in order to meet the Contractual requirements. 2.0

REFERENCE DOCUMENTS Contract Technical Specification S2 Foundations.



3.0

METHODOLOGY FOR FOUNDATION INSTALLATION

3.1

OBJECTIVE

To define the operations involved during foundation construction and the procedures for each activity to ensure compliance with the technical specification and safety to plant and personal. 3.2

SITE PREPARATION



The permitted area of working shall be verified. Care shall be taken to ensure no damage occurs to land or property outside this area. If additional space is required then permission from the landowners /employer shall be obtained prior to commencing the activity.



The work site shall be cleared of all materials and obstruction that may impede the site activities. This requires the clearing of tree stumps and bushes and any other materials to keep the area suitable for safe and proper placement of construction material and provide a safe area for performing the foundation activities.



Levelling of the site is not permitted without permission from the Employer’s Engineer prior to performing the work. Page 3 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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The centre peg shall be checked to ensure it is in place and suitably protected and marked to prevent accidental damage during construction. If not in place the surveyor shall re-establish the centre peg. 3.3

EXCAVATION

3.3.1 GENERAL Foundation excavation shall include: all requirements for installation of each tower or pole foundation type, including levelling ground around individual tower leg or pole foundations; other grading or preparation for construction; and where necessary, adequate drainage. Excavated materials shall be laid aside and used for backfill and embankment (mounding) over the foundation area of each the tower or pole site. Any excess materials shall be spread evenly around the site. Where excavation is on farm or cultivated land, the top soil should be stripped and laid aside, separate from other excavated soil, and spread evenly on top of the final backfill layer. While levelling work of tower site and individual legs or pole is required,this does not include benching shall not do into steeply sloping hill sides in lieu of use of proper tower leg extensions requirements, as determined through the engineering check and profile survey and its cross-section/transverse level survey, sub-task except where expressly approved by the Project Manager. The Surplus material shall not dispose from such levelling work in the slope area. Such material shall be used where practicable in backfill, embankment, or mounding appropriate to the given tower site. Foundation excavation shall be kept to a minimum and not more than 150mm over the foundation dimensions. Foundation stub embedment dimensions shall be strictly maintained in an excavation, and particularly on sloping ground. The excavation shall extend a sufficient distance from the foundation edge to allow inspection, placement, and removal of forms, except where foundation concrete is cast directly against an excavated surface; particular care shall be taken not to disturb soil at the bottom of an excavation and no over excavation will be made. Any over excavation shall be made good by replacing of the over excavation with concrete fill to the correct foundation formation level in a given tower leg’s excavation. In case of over excavation, the correct required foundation base level shall be re-established using blinding concrete over the whole excavation base. In no case, shall over excavation be reinstated employing excavated material. Final preparation of an excavation’s final level shall be made just before concrete is to be placed. Grading or other work, including temporary measures, shall be Page 4 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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undertaken to ensure prevention of surface water flowing into an excavation. Excavations more than 1.5m deep or less, where hazardous ground movement may be reasonably anticipated, shall be adequately shored to protect workers and restrain the excavation collapse. Shoring is to be in place before entry of workmen to advance excavation beyond 1.5m depth. Shoring shall be progressively removed as the hole is backfilled. Any mud, silt, or other objectionable material which accumulates in the bottom of the excavation shall be removed prior to pouring of concrete. During excavation, if it is discovered that the underground water level is different from that indicated by the soils investigations, the Project Manager shall be notified and change the foundation type according to Client’s advice. Foundation excavations when unattended shall be covered to prevent injury to the public at large and local human, livestock or wildlife. Excavation shall be executed manually or by use of an excavator / JCB Backhoe. Excavation shall be done by hand particularly on steep slopes, marshy or inundated ground. Where rock is encountered compressors shall be used for excavation. Suitable pumps shall be used for pumping out water which encounter in the excavation. Manual de-watering shall only be employed where the quantity of water ingress is minimal. Due care shall be taken to ensure that the water removed does not re-enter the pit. During the process of excavation, care shall be taken to place the excavated soil at the safe distance from the pit so that the excavated material shall not re-enter the pit (during rains, for example) or exert any additional pressure on the sides of the pit thereby causing collapse of excavation. When excavation is completed, the levels of the excavated pits shall be checked and entered in the Record Sheet. 3.3.2 ROCK FOUNDATION EXCAVATION: Where required, furnish all materials and equipment to perform all work required for the excavation of rock for the foundation. Rock excavation shall be made by drilling, barring, wedging, or pneumatic/air tools. Use of explosive blasting shall comply with the requirements of CTS: 13.2.3. Weathered rock shall be excavated with mechanical excavator and/or combination of manual excavation together with Page 5 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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some use of pneumatic/air tools or small hand-held petrol engine drill. The extent of rock encountered shall be sound, un-detached, competent rock or any type of rock occurring in a mass or bedded deposit. Such characteristics and extent shall be proposed for Rock type foundation design. Weathered rock or other types of rock such as soluble limestone, soft shale, slate, hard pan and organic rocks may not be suitable for construction of rock type foundations. Where any doubt exists in selecting the type of foundation when such types of rock encountered, the Client shall be informed to approve and/or select the suitable type of foundation. The surface of all rock foundations where concrete is to be placed, shall be prepared to provide for an adequate bond between the rock and concrete. All loose or unsound rock, dirt or the undesirable materials shall be removed from the prepared rock surfaces. Bearing planes shall be predominantly horizontal. 3.3.3 BLASTING Blasting shall be carried out where Ugandan regulations permit, and all precautions shall be taken for the protection of persons, work, public and private property to the satisfaction and prior approval of the relevant Ugandan authorities and the Client. All needed arrangements shall be made, including permits, approved explosives magazine and the highest order of security with the responsible Ugandan authorities, for the use of blasting for transmission line construction. Hauling, storage and handling of explosives shall be carried out in strict compliance with the requirements of the applicable Ugandan laws and regulations. Plans and methods of operation for blasting including sites and schedule shall be submitted to the Client for approval prior to implementation; with due notification provided a minimum of 48 hours prior to each use of blasting. Cap detonators and fuses shall not be kept or transported in the same place as dynamite or other explosives. An inventory of all explosive materials shall be kept and the appropriate Ugandan authorities and the Client shall be notified immediately of any loss or theft. 3.3.4 ROCK ANCHOR DRILLING During drilling, the rate of penetration shall be recorded on a per minute basis at metre intervals for subsequent comparison with other drill holes at the concerned anchor site under drilling and/or other implemented rock anchor sites. Page 6 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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The depth of any soil strata, badly weathered rock, or floaters encountered within the rock shall be recorded and added to the design depth of rock anchor. Upon reaching the correct depth, the hole shall be cleaned and plugged to prevent the entry of any foreign material. Compaction of the grout shall be by vibration of the inserted reinforcement. Sufficient grout shall be used to ensure an overflow at the surface of the rock layer. The grout overflow shall be smoothed off and sloped away from the reinforcement, and shall be left for seven days. The bottom of the rock anchor cap shall be cleaned out before concreting. Anchor holes shall be drilled in proper positions at required diameter, depth and required qty as per the tower schedule and given drawing. Make sure Steel bars have proper dimensions and diameter. Spacers shall be used to make proper alignment of the Steel Bars. Approved grout shall be used for grouting. Grout and Water mixing ratio shall maintain as per the approved specification. Other activities shall be carried out after completion of mentioned curing period. 3.3.5 DEWATERING FOUNDATION EXCAVATIONS All required materials and equipment shall be arranged to perform all work required for dewatering the foundation excavations required to permit construction of the foundations. During the placing of any concrete for the foundations, the water level in the excavation shall be kept below the base of the excavation. 3.4

FOUNDATION SETTING OUT AND ORIENTATION

The foundation orientation of each tower shall be placed in such a manner that the position of the longitudinal axis of the cross-arm or insulator attachment shall lie: i. in a plane perpendicular to the traverse of the line for the foundation of each tower in a straight line section; ii.in a plane bisecting the interior angle formed by the intersection of the adjacent line traverses for the foundations of each angle tower; iii. in a plane perpendicular to the traverse of the line route Page 7 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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(regardless of the traverse of the slack span) for foundations at each dead end tower except where otherwise advised by the Project Manager. Where angle towers are fitted with inner and outer cross-arms of unequal length, or a mix of square and pointed cross-arms, the tower centre shall be offset to ensure that the conductors are located as nearly as possible equidistant either side of the route centre line. The Tower Placement can be marked with Pegs at Site. iv. The centre peg together with adjacent line pegs shall be used as the reference for all setting out at site. The surveyor shall check the centre peg remains in place. If the centre peg is not in place or there is any evidence that it might have been moved or displaced reference shall be made to the surveyor who shall re-establish the centre peg. The Centre peg shall be suitably protected. v. Line or offset Reference pegs shall be established outside the working area and be suitably protected and marked to prevent accidental damage. A minimum of two points in one KM as the reference points all along the route and be suitably protected to prevent accidental damage. These shall be employed as reference for all setting out and, if necessary, to permit the centre peg to be re-established if lost or damaged during the foundation works. The Surveyor shall be responsible for maintaining a record of the level and controls for each of the reference pegs. vi.Pit Marking. The limits of excavations shall be marked by the placement of excavation pegs by the surveyor. As per approved classification. The dimensions of placement of the excavation pegs shall be determined by reference to the appropriate and approved stub setting and excavation drawing cross referred to the approved structure list (for foundation type, setting level, leg and chimney extensions). The Supervisor shall record all setting out dimensions. 3.5

FOUNDATION TOLERANCES

The Stubs for tower foundations may only be installed with the use of approved templates or by using the lower sections of the tower with suitable temporary bracing to ensure correct spacing. The method selected shall be such that all four stubs are supported and interconnected by a rigid steel framework. The main members of templates shall be in the form of trussed beams. The stubs shall be held Page 8 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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in correct position by the template while the concrete is placed. The templates shall not be removed until at least 48 hours after the foundations have been completed excluding backfilling. Stub setting templates shall be of an approved type with sufficient rigidity to ensure correct setting of the stubs having regard to the steeply sloping nature of the ground and necessity for packing at low spots where using hill side extensions. The spacing and levels of the stubs after the templates have been removed within the tolerances specified below: The centre peg of a foundation shall not depart from the longitudinal position shown on the approved profile by more than 300mm. The centre peg shall not depart from the central axis of a section by more than 25mm. i.

the face dimensions between the tops of stubs shall not vary by more than 5mm from the approved foundation drawings. The diagonals between any two stubs shall not differ from the equivalent dimension shown on approved foundation drawings by more than 20mm.

ii.

the slope of stubs either on the face or diagonal directions shall not differ from the equivalent approved dimension by more than 5mm/metre of the stubs.

iii.

the maximum misalignment of the foundation centreline and the stub centreline at the bottom of the excavation shall be 50mm for rock anchor foundations.

Two copies of the actual elevation and horizontal distance from centre of tower to each stub angle shall be recorded after completion of each tower foundation and submitted to the Client for reference. These foundation records shall be included in final records to be hand over as part of Operational Acceptance. Work which falls outside specified tolerance limits shall be inspected by the Client, who shall determine what effect the deviations may have upon the operational functioning of the structure and who shall determine what remedies may be necessary. Stub setting using Probes for unequal Leg Extensions: Stubs shall set according to given leg extensions mentioned in the tower schedule and Soil Classifications. Using theodolite and Distance measuring meter stubs shall set as required Slope angle and height.

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Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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Turn buckles shall used on both sides to hold stub in proper position upto completion of all foundation activities and make sure it shall not displaced while pouring concrete. Stubs shall be placed on cover block on required height as per given drawing. Secure the cleats by tightening the bolts, nuts and washers with required threads out. Make sure the marks and reference holes are in the proper position as per the approved drawings. Stubs shall be checked on back to back & diagonal distances from the centre peg. Stub setting Template shall be assembled on ground as per the type of tower, body extension, leg extension and formation level. Template shall be assembled on adjustable template jacks to maintain the required ground clearance with reference to centre peg as per approved drawings. Template shall be aligned along the line and transversally, as per the pegs provided. Template shall be checked diagonally, back to back and height of template from centre peg at the following stages: -

After template is assembled. After fixing stubs to template and before reinforcement is placed. Before concrete work starts. After concrete work finishes. After back filling is completed.

All details of back to back, diagonally distance shall be entered into Record Sheets. 3.6

REINFORCEMENT PLACEMENT

Reinforcing bars shall be placed in the concrete as shown on the approved drawings. Bending of all bars shall be made to smooth curves. Standard hooks shall have 180° bends and extend 4 bar diameters parallel to the main leg of the bar. Kinked bars shall not be used. Splicing of reinforcing bars not shown on the drawings will be permitted only with prior approval of the Client, and shall be placed at points of minimum stress. All Page 10 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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reinforcing bar splices shall meet the requirements of the relevant British Standard. Before the reinforcing bars are placed, the surfaces of the bars and any bar supports shall be clean and clear of heavy or flaky rust, loose mill scale, dirt, grease, or other objectionable foreign substances. Heavy or flaky rust which cannot be removed by firm rubbing with burlap or equivalent treatment is considered objectionable. After being placed, the reinforcing bars shall be maintained in a clean condition until they are completely embedded in the concrete. Reinforcing bars shall be accurately placed on concrete, plastic spacers will be used, to secure in position so that they will not be displaced during the placing of the concrete. Special care shall be exercised to prevent any disturbance of the reinforcement in concrete that has already been placed. All bars, dowels, spacers and stirrups shall be securely tied at all intersections with an appropriate tie wire, approved by the Client. Reinforcing bars will be inspected in compliance with the requirements as to size, shape, grade, length, position and amount after they have been placed and prior to the placing of concrete. All reinforcing bars shall be placed and spaced in the foundations such that the concrete cover indicated on the drawings is maintained within a tolerance of plus or minus 7mm and the centre-to-centre bar spacing is maintained within a tolerance of plus or minus 25mm. After placement the reinforcement the same shall be checked and the appropriate observations entered in the foundation Record Sheet. Earth Strip shall be connected to stubs and reinforcement bars and then laid into the ground as per approved earthing drawing. Cover blocks shall be tied on top of reinforcement and along the sides. 3.7

FORMWORK

Forms shall be used, wherever necessary, to confine the concrete and shape it to the required lines. Forms shall have sufficient strength to withstand the pressure resulting from placement and vibration of the concrete, and shall be maintained rigidly in position. Forms shall be sufficiently tight to prevent loss of mortar from the concrete. Forms may be removed after 24 hours of placing of concrete provided the concrete is sufficiently strong enough not to be damaged thereby. The use of forms will not be required where the character of the in-situ material is such that it can be Page 11 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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trimmed to the prescribed lines and will stand without caving or sloughing until the concrete has been placed. At the time the concrete is placed in the forms, the surfaces of the forms shall be free from encrustations of mortar, grout, loose rust, or other foreign material, and oiled with commercial form oil that will effectively prevent sticking and will not stain the concrete surfaces. Steel /wooden formwork shall be employed with firm connections at the corners to prevent mortar from flowing out of the base portion. The thickness of form work shall be suitable for the intend purpose and of such a size to prevent any sagging that might result in the specified concrete cover being infringed at any point. As soon as the base/ frustum concrete is laid and after the required initial setting time, the form boxes for the chimney portion shall be fixed in position. In the event that concrete has not set adequately, protection over the pad concrete shall be provided to have a suitable working platform. Where the chimney form work is longer than1.5 M they shall be installed and concrete in sections. Care shall be taken to ensure a clean cover to the reinforcing steel is maintained on all the four sides along the length of the chimney and the form is centred about the stub leg. 3.8

BATCHING AND MIXING

All the materials such as fine and coarse aggregates, water, cement, reinforcement required source should be approved from an approved laboratories as per employer. After that a design mix concrete shall be done and obtain Engineer’s approval for use at site. Further any change in source shall be intimated to employer and new materials shall be tested again if required. All material aggregate, cement and reinforcement shall be checked, prior to commencement of concreting. Volumetric steel gauge boxes will be used at site to measure all coarse of concrete materials like Cement, Sand, water and aggregates for every batch of concrete as per approved by the Client. Batching equipment shall be carefully operated so that the combined inaccuracies in feeding and measuring the materials will not exceed 1.5% for water or weighted cement and 2% for each size of aggregate. Periodic checking will carried out for its operational accuracy of the gauge boxes in use for concrete batching, in the Page 12 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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presence of the Client’s Supervisor, at such intervals as directed and at minimum, once every month. It will be recorded each of these gauge box checks including the methods by which the required volumes and/or weights are proved and provide copies of these batching equipment checks to the Client. Also maintain a written record of any adjustments, repairs or replacements as may be necessary to batching equipment to ensure specified requirements for accuracy of concrete batch measurements. The concrete ingredients shall be mixed in a batch mixer for not less than 1.5 minutes after all the ingredients, except the full amount of water, are in the mixer. The Client reserves the right to increase the mixing time when the charging and mixing operations fail to produce a concrete batch wherein the ingredients are uniformly distributed and consistency is uniform, when discharged from the mixer; except where changes in composition or consistency are required. Excessive overmixing requiring the addition of water to preserve the required concrete consistency will not be permitted. In locations where Mixture Machine cannot reach, hand mixing shall be done with prior approval of Client. 



The quantity of water added shall be as per design mix. The aggregate together with the cement shall be first added to the mixer without water and mixed for a minimum of one minute or as long is necessary to ensure a homogenous mix. When a homogeneous mix has been obtained the water then shall be added after which the mixing shall continue for not less than 1 minute. After mixing the concrete slump test shall taken immediately to ensure the mixing ratio of the concrete and noted on the record sheet.



Temperature of the concrete shall be tested by thermometer for every batch of concrete mixer to ensure the temperature shall not exceeds the limits given in the approved design.



Prior to commencement of concreting activities the following shall be available on site :Mixer in good condition Vibrator Water (required quantity) Fine Aggregate (required quantity) Coarse Aggregate (required quantity) Cement (required quantity) and protection for the same. Aggregate measuring boxes as per approved design mix Cube test Moulds Page 13 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

3.9

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Slump Cone and Thermometer. Concrete chutes /Slides / Elephant Trunks De-watering pumps (if necessary for site)

FIELD CONTROL OF CONCRETE STRENGTH

Tests will be carried out on Samples of Concrete from the foundation Facilities, as required by the Client. The test specimens shall be a standard 150mm cube type, cast in metallic moulds with inner faces accurately machined that ensure opposite sides of the cube specimen are smooth and in true parallel. Each mould shall be provided with a metal base having a smooth machined surface. The interior surfaces of the mould and base shall be lightly oiled before concrete is placed in the mould. Test specimens shall be prepared by placing the fresh concrete in the mould in 50mm layers, each layer being thoroughly compacted with a smooth steel bar or rod. This rod shall be 380mm long and with a ramming face 25mm square and weight of 2.8kg. The concrete shall be subjected to at least 35 strokes per layer. Concrete for the test specimens shall be taken at the point of its placement; shall be representative of the concrete in the foundations; shall consist of a number of samples taken from different points of a foundation pour, with each sample sufficient to produce a complete test cube, from a given point in a tower foundation pour. Test specimens shall be stored at Site in a place free from vibration, under damp sacks for 24±0.5 hours, after which time they should be removed from their moulds, marked and stored in water at a temperature between 10 0C and 210C until the test date. Specimens which are to be sent to a laboratory for testing shall be packed for transit in damp sand, or other suitable damp material and shall reach the laboratory at least 24 hours before test. On arrival at the laboratory they shall be similarly stored in water until the date of the test. 4 nos.of Concrete Specimens shall be taken in the cube moulds for each and every stage of concrete and marked with tower no, leg no, stage of concrete and dated. Concrete specimen tests shall be made at time intervals that correspond to 7 through to 28 day specified strengths. Compression tests shall be made between smooth plane steel plates without end packing and a load applied axially at the rate of approximately 13.8N/mm2 per minute. One compression plate of the testing machine shall be provided with a ball seating in the form of a portion of a sphere, the centre of which coincides with the central point of the face of the place. Test specimens shall be placed in the machine in such a manner that the load is applied Page 14 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

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to the sides of the specimens as cast. Test results shall be provided in a formal record format duly certified by the testing laboratory, in duplicate, to the Client as soon as possible after testing. Test results which indicate the quality of concrete materials, other defects, or compressive strength of concrete are not as compliant with specified requirements, the following check tests may be carried out as directed by the C: a)

a rebound hammer test may be used to obtain approximate indications of the strength of the concrete;

b)

coring, using the procedure for cutting cores compliant with BS 1881, Part 4;

c)

electromagnetic cover measuring device may be used to verify the position of the reinforcement, in accordance with BS 4409, Part 1.

If the result of any of the above tests a) through c) is not satisfactory, the Plant or Facilities concerned will remove or cut out that part and reconstruct to comply with Client’s Requirements, or other measures may be taken to make the Plant or Facilities secure. 3.10

PLACING CONCRETE

3.10.1 PREPARATIONS No concrete shall be placed until all formwork, reinforcement, installation of parts to be embedded, and preparation of surfaces involved in the placing have been approved by the Client. All surfaces of foundations upon or against which concrete is to be placed shall be free from standing water, mud, and debris. The surfaces of absorptive foundations, against which concrete are to be placed, shall be moistened thoroughly so that moisture will not be drawn from the freshly placed concrete. All rock surfaces of foundations upon which concrete is to be placed shall be prepared by roughening, where necessary, and through cleaning. Loose and drummy rock, dried grout, flaky and scaly coatings, organic deposits, and other foreign material must be removed. Cleaning shall be accomplished by the use of stiff brooms, picks, jets of water and air applied at high velocity, wet sandblasting, or other effective means, followed by thorough washing. Construction joints shall be cleaned thoroughly of all loose or defective surface concrete, coatings, sand, sealing compound if used, and other foreign material, by approved means and shall be thoroughly moist before concrete Page 15 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

N602/........... Method Statement 00 12/07/2015

is placed against them. Where concrete is permitted to be placed in water, the excavation within the required neat lines shall be free of all mud and debris immediately before placing of concrete, and all such mud and debris shall be kept out of the excavation during the placing of concrete. 3.10.2 GENERAL The Client will be informed in advance about the placement of the concrete will be performed. Unless inspection of concrete is waived in each specific case, placing of concrete shall be performed only in the presence of the Client. The methods and equipment used for transporting concrete and the time that elapses during transportation shall be such as not to cause appreciable segregation of coarse aggregate, or slump loss in excess of 25mm in the concrete as it is delivered into the work. After the surfaces have been cleaned and dampened immediately before concrete is placed, construction joints shall be covered, wherever practicable, with a layer of mortar approximately 10mm thick. Re-tempering of concrete will not be permitted. Any concrete which has become so stiff that proper placing cannot be assured shall be wasted. Concrete shall be directly deposited in all cases as nearly as practicable in its final position and shall not be caused to flow such that the lateral movement will permit or cause segregation of the coarse aggregate, mortar or water from the concrete mass. Concrete shall not be allowed to fall freely more than 2m. Formed concrete shall be placed in continuous horizontal layers of approximately 0.50m or less. The Client reserves the right to require lesser depths of layers where concrete in 0.50m layers cannot be placed in accordance with these Engineer’s Requirements. Concrete shall be consolidated to the maximum practicable density so that it is free from pockets of coarse aggregate, and closes snugly against all surfaces of forms and embedded materials. Consolidation of concrete shall be by electric or pneumaticdriven, immersion type vibrators operating at speeds of at least 7,000rpm when immersed in concrete. Layers of concrete shall not be placed until the layers previously placed have been worked and vibrated thoroughly as specified. Care shall be exercised to avoid excessive contact of the vibrating head with surfaces of the forms. 3.11

REPAIR OF DEFECTIVE CONCRETE

Repair of defective concrete shall be performed only by skilled workmen. The Client will be advised as to when repair of defective concrete will be performed. Repair of imperfections in formed concrete shall be completed within 24 hours after removal Page 16 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

N602/........... Method Statement 00 12/07/2015

of forms. Concrete that is damaged from any cause such as fractured and honey-combed shall be cut out to a depth at which sound concrete is exposed and filled within dry pack, mortar or concrete matching the structure. All concrete used for patching shall be bonded tightly to the surface of the sound concrete and shall be sound and free from shrinkage cracks and rough areas after curing and drying. All areas to be patched shall be coated with an approved concrete bonding agent in accordance with the manufacturers printed instructions. 3.12

CONCRETE FINISHING

Finishing of concrete surfaces shall be performed only by skilled workmen. The Client will be advised as to when finishing of concrete will be performed. Exposed unformed surfaces of concrete shall be brought to uniform surfaces and worked with suitable tools to a reasonable smooth wood float finish. Concrete on the top of pedestals shall be sloped to provide drainage away from the steel stub angles. Excessive floating or trowelling of surfaces while the concrete is plastic will not be permitted. Edges that will be exposed to view shall be chamfered 20mm. 3.13

CONCRETE CURING

Concrete shall be cured by water or membrane curing. If concrete is cured by water curing, the concrete shall be kept continuously moist for at least the first 7 days after being placed, by sprinkling or spraying or by other methods approved by the Client. Membrane curing of concrete shall be made by the application of a sealing compound which forms a water-retaining membrane on the surfaces of the concrete. The sealing compound shall conform to ASTM C31, and its method of application shall be approved or as directed by the Client. Any sealing membrane that is damaged or that peels from concrete surfaces within 7 days after application shall be repaired without delay and in an approved manner. 3.14

PROTECTION OF FOUNDATIONS AND STUBS

All stubs shall be coated with two coats of an approved bituminous paint from at least 300mm below the top of the concrete extending up to at least 300 mm above the top of the concrete along the steelwork. 3.15

BACKFILL

3.15.1 GENERAL

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Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

N602/........... Method Statement 00 12/07/2015

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Backfill shall be placed in and over tower foundations where required by foundation design and shown accordingly on foundation drawings. Materials used for backfill, the quantity required, and the manner of depositing the material shall be approved by the Client. Where required, foundation excavations shall be kept dewatered during the placement and compaction of backfill. Material removed during excavation, which is not suitable or is not required for backfill shall be removed from Site. Only suitable borrow material, as approved by the Client, shall be used as backfill replacing unsuitable soil removed during excavation. Care shall be taken to avoid damage to the concrete when depositing backfill, which shall not be placed until after concrete placement, has set for a minimum of 2 days. Backfill material shall be clean and free from vegetation and all foreign matter e.g. pieces of timber, large stones >100mm, empty cement bags or other deleterious materials. Backfill shall be placed in a manner to ensure original ground contours are restored as closely as possible. Any subsidence of backfill shall be made good before the issue of the Operational Acceptance Certificate. Back filling shall not commence until a minimum of 24 hours after form work removal. Back filling shall not commence until the concreting work has been inspected by the Engineer and recorded in Record Sheet. Prior to commencement of back filling all temporary timbering, shuttering, etc., and all decomposable or perishable material shall be removed from the excavations. Organic matter, silt and oversize rocks shall not be employed to backfill. Compaction of the back fill shall be conducted evenly throughout the excavation area. Compaction from one corner or one side of an excavation hole shall not be allowed. When the back filling for all legs is completed the stub setting dimensions and levels shall be rechecked and the results entered in the Record Sheet. The stub setting template shall be removed after compaction of back filling has been completed. By evenly spreading the excess around the work site. Care shall be taken not to obstruct the natural drainage of the site. 3.15.2 COMPACTION The backfill of all types of foundations shall be thoroughly rammed in layers not greater than 200mm to ensure thorough compaction, and compacted to 95% maximum dry density (60% relative density). Backfill material to be compacted shall be well-graded and shall contain no stones greater than 100mm in any of its dimensions. Page 18 of 20

Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

N602/........... Method Statement 00 12/07/2015

The distribution of materials shall be such that the compacted material is homogeneous, free from clods, void pockets streaks or other imperfections. The excavation and fill placing operations shall be such that the materials when compacted are homogenous and can demonstrate the required degree of compaction, impermeability and stability. Prior to and during compaction operations, the backfill material shall have the optimum practicable moisture content required for the purpose of compaction, as determined through the soil investigations of the concerned tower site. The moisture content shall be uniform throughout the layers of backfill, as far as practicable, with any moistening of material carried out at any given site subject to Client approval and be limited to sprinkling type addition of water only during the layered deposit of backfill to achieve required compaction as may be necessary with all fill compacted to the excavation’s original surface elevation, with special care taken to prevent any wedging action against the foundation. Carrying out regular backfill soil density tests to ensure that its backfill operations are achieving the required degree of backfill compaction. Any foundation backfill so determined to be inadequately compacted, shall be removed and re-backfilled. 3.16

EMBANKMENTS

3.16.1 GENERAL Carrying out embankment or soil surcharge works for tower sites where foundations are located in standing water of seasonal sloughs, pot holes or marshy ground, subject to the approval of the Client. No ploughing or scarifying of the ground surface under any embankment work will be required. As needed, embankments may be placed in water. Embankments shall consist of suitable material, obtained from foundation excavations or from borrow. If there is a choice of material placed in the embankments, the coarse material shall be placed in the outer slopes of the embankments. The slope of the face of the embankments shall not be less than 3.0 horizontal to 1.0 vertical and stable. Compaction will be done on the entire embankment area by travel the heavy equipments on all sides. Where this is achievable, no other compaction of the embankment will be required. And it will be maintain the embankment until acceptance of the portion of the work under the Contract. Unless otherwise determined by the Client, embankments shall be levelled after acceptance and the borrow material returned to the borrow area or disposed off in a manner acceptable to the Client. 3.16.2 EXCAVATION FROM BORROW FOR EMBANKMENTS

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Document No: Document Type: Revision No: CONTRACT NO: UETCL /WRKS/2013/00009 – LOT-01 Revision Date: TITLE: FOUNDATION CONSTRUCTION METHODOLOGY 220 KV NKENDA-HOIMA TRANSMISSION LINE PROJECT, UGANDA

N602/........... Method Statement 00 12/07/2015

The location of borrow areas for suitable embankment material shall be identified and be subject to approval of the Client. Strip the borrow area of all unsuitable materials, to obtain the required quantities of borrow materials, as approved by the Client. The surface of borrow areas shall be left in reasonable, smooth and even condition and re-vegetated. 3.17

SITE CLEAN UP AND EROSION CONTROL

After completion of all foundation activities the site shall be cleared of all surplus excavated material and construction materials. The work site shall be reinstated, wherever possible, to the original ground contours. The site shall be checked to ensure the foundations are not exposed to possible erosion problems from either natural surface water drainage and or that resulting from the construction activities. Where ever required, with approval of employer foundation protection to be established.

4.0

ANNEXURES - QUALITY CONTROL BOOK

4.1

SURVEY REPORT

4.2

EXCAVATION INSPECTIONREPORT

4.3

STUB SETTING RECORD SHEET

4.4

MATERIALS INSPECTION

4.5

CASTING RECORD SHEET

4.6

CASTING PLACING CONTROL

4.7

CURING, BACKFILLING AND COMPACTION

4.8

CONCRETE CUBE TEST DATAS

4.9

FOUNDATION SUMMARY SHEET

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