part b substation civil works -...

PART B

SUBSTATION CIVIL WORKS

CONTENTS SUB-SECTION 1 - SPECIFICATION FOR PARTICULAR

REQUIREMENTS FOR CIVIL WORKS SUB-SECTION 2 - GENERAL SPECIFICATION FOR MATERIALS

AND WORKMANSHIP FOR CIVIL WORKS

Technical Specifications – Civil Works 132

__________________________________________________________________________________________________ SUPPLY EXTENSIONS TO BURKINA FASO

SUB-SECTION 1

SPECIFICATION FOR PARTICULAR REQUIREMENTS

FOR

CIVIL WORKS



TABLE OF CONTENTS 1.0 GENERAL DESCRIPTION OF PROJECT................................................................................134 2.0 DETAILED SCOPE OF SUBSTATION CIVIL WORKS ............................................................135 2.3 STATUTORY REQUIREMENTS, CODES AND STANDARDS ................................................136 2.4 SITE CONDITIONS...................................................................................................................137 2.5 SOIL INVESTIGATION.............................................................................................................137 2.6 METEOROLOGICAL DATA .....................................................................................................137 2.7 SITE PREPARATION ...............................................................................................................138 2.8 SITE DATUM AND SETTING OUT...........................................................................................140 2.9 DESIGN REQUIREMENTS.......................................................................................................140 2.10 FOUNDATIONS........................................................................................................................145 2.11 DRAINAGE SYSTEM ...............................................................................................................146 2.12 WATER SUPPLY......................................................................................................................146 2.13 DRIVEWAYS WITHIN THE SUBSTATION YARD....................................................................146 2.14 YARD SURFACING & FENCING .............................................................................................147 2.15 CABLE TRENCHES & DUCT BANKS .....................................................................................147 2.16 SITE OFFICES AND FACILITIES FOR ENGINEERS ..............................................................149 2.17 SITE SECURITY & SAFETY ....................................................................................................149



1.0 GENERAL DESCRIPTION OF PROJECT 1.1 Introduction

The works covered by this Technical Specifications and forming the Supply Extensions to Burkina Faso – Bittou & Hamélé involves the design, manufacturing, testing, supply, transportation to site, off-loading, erection and commissioning of plant and equipment for the supply of power to Bittou and Hamele in Burkina Faso.

1.2 Scope of Project

The project has been packaged into two (2) sections as follows: Section 1: Power Supply to Bittou (Burkina Faso) Under this section, it is intended to construct a 20km line using 120mm2 ACSR on steel towers, same as the subtransmission lines in the Northern Ghana. The sending end of the line will be connected to the VRA network at Bawku Substation, through outdoor 34.5kV switchyard and the receiving end will be terminated at the switching/metering station to be constructed close to the CEPS check point in the Upper East border. The Bawku Substation has indoor 34.5kV metal-clad switchgear panels. This comprises an incoming line from Bolgatanga and then outgoing feeders to Dapaong (in Togo), Garu, and then to a 34.5/11.5kV power transformer. The station also has 11.5kV distribution panels for the networks in the Bawku Township and its environs and Auxiliary supplies. Under this project, the Bawku Substation will be modified by constructing outdoor 34.5kV switchyard complete with an incoming feeder, bus bars, outgoing feeders, and protection and control panels. The incoming to the outdoor bus bar will be via an underground cable from the existing panel that currently supplies communities located between Bawku and Danvonga, all in the Upper East region including Garu. The outgoing feeders will serve Garu (and the other communities), Bittou and provision of a spare breaker for future 34.5kV supplies from Bawku.

The detailed scope of the works comprises:

• Detailed design, manufacture, testing, delivery to site, installation and

commissioning of outdoor 34.5kV switchyard at Bawku Substation. This will involve the provision of line terminal equipment made up of circuit breakers, disconnect switches, CVT’s, CT’s, post insulators, buswork, underground cable, substation grounding, control equipment and protective relaying.

• Construction of about 20km of 34.5kV subtransmission line on steel towers from

Bawku Substation to the metering station. This will involve the supply of steel towers, conductors and line accessories, civil works, erection and stringing.

• Construction of an outdoor 34.5kV metering/switching station at the CEPS check

point in Ghana equipped with 1No. incoming feeder from Bawku Substation and 1No. outgoing feeder to Bittou. This will involve the provision of 34.5kV feeder equipment made up of outdoor disconnect switches, instrument transformers, fuses, buswork, metering equipment and protective relaying complete.

• Civil works associated with the above works including site survey, substation site

clearing, leveling, filling and compaction, equipment plinths, foundations, etc.

• The provision of single band radio communication equipment at Bawku Substation.



Section 2: Power Supply to Hamélé (Burkina Faso)

Nandom in Upper West region is served by a 34.5kV steel tower subtransmission line from Wa. Approximately 15km, 34.5kV steel tower line using 120mm2 ACSR will be constructed from the last steel tower line in Nandom to terminate at the switching/metering station to be located close to the Ghana CEPS check post in the Upper West border. The detailed scope of the works comprises:

• Detailed design, manufacture, testing, delivery to site, installation and commissioning of about 15km of 34.5kV line on steel tower lattice from Nandom to the metering station. This will involve the supply of steel towers, conductors and line accessories, erection of steel towers and stringing of 120mm2 ACSR conductors, etc.

• Construction of an outdoor 34.5kV metering/switching station at the CEPS check

point in Ghana equipped with 1No. incoming feeder from Nandom and 1No. outgoing feeder to Hamélé. This will involve the provision of 34.5kV feeder equipment made up of outdoor disconnect switches, instrument transformers, fuses, buswork, metering equipment and protective relaying complete.

• Civil works associated with the above works including site survey, substation site

clearing, leveling, filling and compaction, equipment foundations, etc.

• Decommissioning of existing wood pole between Nandom and Hamile.

• The provision of single band radio communication equipment in Nandom. 2.0 DETAILED SCOPE OF SUBSTATION CIVIL WORKS

The work comprises the turnkey execution of all civil, structural and architectural works and services necessary for the construction, completion, testing and commissioning of the proposed project of Extending Power Supply to Burkina Faso – Bittou & Hamélé. This Specification has been drawn up to cover the supply of all materials, the execution of all works, including all design and investigative work and all commissioning, necessary for the satisfactory completion and operation of the Project. However, should there be any details of construction or materials which have not been referred to in the Specification, but the necessity for which are usual or essential to the completion of all works in all trades, the same shall be deemed to be included in the Contract Price. The Contractor's attention is drawn to the general requirements for materials and workmanship contained in sub-section 2. The particular requirement contained in this sub-section 1 shall take precedence over where there is a conflict and/or augment sub-section 2. The work scope shall be, but not necessarily limited to, the following:

2.1 Bawku Substation

· Additional site surveys necessary for detailed designs and erection of all works

under the project scope. · Detailed geotechnical investigations necessary for the design and construction of all



relevant items under the project scope. · Provision of construction site services, including but not limited to temporary water

supply, electric power, telephone and fax services, and sewerage system and site toilets.

· Provision of covered storage accommodation and site offices required for the

Contractor's plant, equipment and staff. The Contractor shall keep the sites clean and tidy and shall remove all waste and surplus material daily to a location designated by the Engineer.

· Layout, supply, construct, equip and service accommodation for Engineer's staff. · Identification and relocation of existing underground services if any, including

telephone, electricity, water, foul and fresh water pipelines, storm drainage, etc. · Clearing and levelling of the site to the designed formation level. · Anti-termite treatment of the site and embankment. · Earthworks required for the construction of the station embankment including site

sterilization against weed growth and protection of embankment slopes. · Design and construction of the foundations for the 34.5kV outdoor equipment

including but not limited to switchgear and support structures. · Design and construction of all cable trenches and ducts, pits, tunnels and duct

banks. · Design and construction of a substation perimeter drainage system. · Design and construction of embankment boundary works including fencing. · Installation of substation yard surfacing/finishing.

2.2 Switching/Metering Station at Hamélé (Ghana Side) and Bittou

· Design and construction of the foundations and steel support structures for the

switching/metering and other related devices to include site survey necessary for the erection works.

2.3 STATUTORY REQUIREMENTS, CODES AND STANDARDS

The Contractor shall assume full professional liabilities with regard to fulfilment of any statutory requirements and shall be deemed to have acquainted himself fully with the local statutory regulation and requirements before Tendering. All costs associated with obtaining approvals from local bodies and authorities shall be deemed to be included in the Contract Price. The civil works shall comply with the standards and codes specified in this Specification. However, the Contractor may propose alternative equivalent and internationally recognized standards or codes of practice, provided approval from both the relevant Ghanaian statutory authority and the Employer, can be obtained by the Contractor. The Contractor shall submit two copies of an English translation of such standards or codes of practice to the Engineer and one copy to the Employer. The civil works shall comply with the current standards and codes 30 days prior to the



submission of the Tender.

2.4 SITE CONDITIONS 2.4.1 Site Visit

The Contractor is deemed to have visited the site prior to submission of Tender and examined the existing site conditions under which the Contract is to be executed. The Contractor is deemed to have acquainted himself fully with local conditions and constraints, means of access to and from the site, services, the arrangement and condition of the proposed Contractor's working and storage space accommodation requirements and all other requirements for the proper completion of the Contract. Failure to have fully investigated the site shall not relieve the Contractor of the responsibility for estimating properly the difficulty or cost of successfully performing the Works. Failure to have visited the site or to have obtained necessary information is at the Contractor's own risk and responsibility and any claim for such failure will not be considered.

2.4.2 Site Survey

The extent and existing levels of the Site for the new substation are shown on the relevant drawings included in the Appendices to the Contract Documents. The Contractor shall carry out any additional but relevant surveys that may be required for the design and construction of the Project.

2.5 SOIL INVESTIGATION

Any reputable competent company to be tasked to carry out the Soil Investigations shall do so with the approval of the Engineer. The Contractor shall be responsible for acquainting himself with local standards regarding Geotechnical criteria. The soil investigation shall be carried out in accordance with BS 5930 or other approved standard. A copy of the soil investigation report shall be submitted to the Engineer. Acceptance by the Engineer of the soil investigation report shall in no way relieve the Contractor of his sole responsibility with regard to the stability and safety of his design.

2.6 METEOROLOGICAL DATA General meteorological data for the site is summarized below. The Employer does not accept any responsibility for the accuracy and correctness of the data supplied and it shall be the responsibility of the Contractor to establish all the meteorological data deemed necessary for the satisfactory design and construction of the facilities. The climate at the site is tropical and semi arid. The following data is indicative of the climatic conditions.

Ambient air temperature 400C maximum 100C minimum 300C average (annual) Relative Humidity 70 - 95% Maximum Barometric Pressure 1034.6 mbar maximum 1000.5 mbar minimum



1010.4 mbar average Wind Velocity 34 m/sec maximum

Rainfall (normally occurs during the wet season) Maximum 1414.3 mm/year Minimum 333.1 mm/year Average 799.6 mm/year Maximum No. of Rainfall Days per year: 126 days occurring mainly in the wet season. Maximum No. of Thunder Storm Days per year: 129 days occurring mainly in the wet season

2.7 SITE PREPARATION 2.7.1 Site Clearance

The Contractor shall be responsible for all clearance and other work required for preparation of the site. The Contractor shall clear the entire substation site of all trees and shrub. In addition the Contractor shall grub up tree stumps and roots from the site completely and burn or otherwise disposed off as directed by the Engineer. Following site clearance, the site shall be excavated throughout, down to at least 150mm below existing natural levels or as otherwise directed by the Engineer. Excavations resulting from grubbing and uprooting big trees shall be filled with approved material in layers not more than 250mm loose thickness and each layer shall be compacted to the same density as that of the adjoining ground but in any case not less than 95% of the materials, optimum dry density.

2.7.2 Anti-Termite Treatment

Visible Termite Presence Where the presence of termites is indicative, termite nests shall be searched for, and if any is found, it shall be opened at the top, the Queen extracted and destroyed. The nests shall then be treated with an anti-termite chemical approved by the Engineer and the Environmental Protection Agency, (EPA). The chemical shall be applied strictly according to the directives of the manufacturer. Nests and surrounds shall be removed 2 to 3 days after treatment and the area excavated and material removed to a depth not more than 500mm. This treatment shall be carried out in addition to the treatment for ‘No Termite Presence’ as specified below. No Termite Presence (Termite presence not indicative) After removal of the vegetative top soil, the resultant top soil of the entire project site shall be loosened to a depth not less than 250mm and the loose soil treated with an anti-termite chemical approved by the Engineer and the Environmental Protection Agency (EPA). The chemical shall be applied strictly according to the directives of the manufacturer. The loose soil shall then be compacted back into place before the formation of embankment commences.



2.7.3 Substation Embankment

The embankment shall be constructed as specified in the General Specification for Materials and Workmanship and shall be finished to the lines and levels determined by the embankment design drawings to be submitted by the contractor and approved by the Engineer. The embankment shall be constructed to include but not limited to the following characteristics and to the approval of the Engineer: The embankment, its slopes and drainage facilities shall all be within the boundaries

of the site depicted by the benchmarks provided on the site plan included in the enquiry drawings.

For the purpose of pricing for the embankment works the contractor shall assume

the substation grade level to be 200mm below existing ground levels. Depending on the soil conditions on site the Engineer may direct the contractor to excavate below the grade level to provide a sub-grade course. The cost of such additional works shall be paid for under a provisional sum based on unit rates provided in the contract.

The embankment shall have layers of sub-base and/or base materials compacted in

accordance with clause 2.2 of General Specification for Materials and Workmanship as follows:

Hardfill Type I material or suitably approved laterite as sub-base.

300mm thick approved laterite base course well compacted on top of the sub-

base.

Apart from taking geotechnical considerations of stability and strength into accounts, the thickness of the sub-base shall be such that the final level of the compacted base course of the embankment shall not be less than 300mm above the existing natural ground level at any point.

Starting from the centre-line along the longer side, the top of the embankment shall

be given a 1% slope towards the side drains. The side slopes of embankment shall not be steeper than 1:2 (vertical: horizontal)

and shall be protected from erosion by stone pitching. The stone pitching shall be separated at 25 meter intervals by the introduction of

25mm wide thermal expansion gaps aligned on the side slopes and appropriately filled with approved bituminous material. It shall also be provided with weep-holes appropriately sized with a granular filter, spaced and located to ensure adequate drainage and stable side slopes.

The top and bottom peripheral edges of the embankment shall be protected with

250mm thick concrete strip and toe respectively. The yard shall be finished with 100mm thick 25 - 50mm broken stone or chippings.

The embankment shall be designed for the more onerous effects of:

- HS-20 AASHO/40 Tonnes vehicle axle loading

- Construction and in-service abnormal vehicle loading



The contractor shall submit a detailed geometric and geotechnical design of the substation embankment, based on the requirements of this specification, for approval by the engineer before starting the construction.

The contractor shall arrange for continuous field geotechnical testing of each layer of

the embankment to ensure compliance with the requirements of this specification and the approved geotechnical designs.

2.7.4 Site Sterilization

The top surface and side slopes of the embankment shall be sterilized by the application of a chemical mixture to prevent weed growth. The sterilization mixture shall be subject to the approval of the Engineer and the Contractor shall provide an approval letter from the Environmental Protection Agency (EPA) – Ghana, authorizing its use. The area to be treated shall be uniformly covered with the mixture at the rate indicated by the manufacturer. The area treated shall be wetted immediately following the application so as to cause penetration into the surface or as directed by the manufacturer. All surfaces of the embankment shall be sterilized as specified above, and in the case of the side slopes, before stones are pitched thereon.

2.8 SITE DATUM AND SETTING OUT

The Contractor shall be wholly responsible for the true and proper setting out of the Works in accordance with the approved working drawings and the setting out shall emanate from base points indicated by the Engineer. The site datum and levels shall be based on data shown on the relevant drawings included in the Appendices to the Contract Documents. Measuring and setting out shall be done with calibrated measuring tapes and adjusted levelling instruments and angle gauges. The Contractor shall provide permanent survey monuments on site at locations of setting out point, benchmarks and base line, to the approval of the Engineer. All boundary points, measuring points, fire and water hydrants and comparable facilities located underground shall be either relocated or protected from damage. Any such damage shall be made good by the contractor.

2.9 DESIGN REQUIREMENTS

2.9.1 Design Criteria

Design of the works shall be based on the following standards or their equivalent:

Foundations: Design and construction of foundations shall be in accordance with BS 8004 and this Specification.

Structural Concrete: Structural concrete work shall be in accordance with BS

8110.

Structural Steelworks: Design, fabrication and erection of structural steelworks shall be in accordance with BS 5950.



Liquid Retaining Design and construction of concrete liquid retaining Structures (Concrete) shall be in accordance with BS 8007. Blockwork/Brickwork: Design and Construction of blockwork/brickwork shall be in

accordance with the requirements of BS 5628. Seismic Design: Design for seismic loading shall be in accordance with this

Specification. Sound Insulation: All roof and wall cladding systems including ventilators,

openings, windows, doors, etc., shall be designed and constructed such that noise level emissions at the site boundary do not exceed 60 dBA.

2.9.2 Loads

General Buildings, equipment foundations, support and ancillary structures shall be designed for the worst combination of dead loads, construction loads, live loads, plant loads, impact and dynamic effects due to operation of plant, crane loads, short circuit forces, maintenance loads, earth pressure, wind loads, seismic loads, temperature effects, etc. Dead Loads: Dead loads shall include all loading due to the self-weight of all

permanent structural and non-structural components such as columns, beams, foundations, floor slabs, walls, partitions, finishes, cladding, etc. This shall include loading due to installation of plant equipment Loads:

Live Loads: All live load values proposed for the design shall be subject to the

approval of the Engineer.

Live loads in equipment areas shall include plant/equipment loads and circulation/access loading. Plant/equipment loading conditions associated with assembly and maintenance activities in combination with circulation/access loading shall be considered and the worst condition adopted for design. Stairs and access platforms not subject to assembly /maintenance loads shall be designed for a live loading of 3kN/m

2.

Tunnels and covers to trenches, pits, manholes in roads, loading bays, etc., shall be designed for the more onerous effects of: - HS-20 AASHO/40 Tonnes vehicle axle loading - Construction and in-service abnormal vehicle loading Trench covers not accessible to heavy-wheeled traffic shall be designed for a live loading of 2kN/m

2.

Plant/Equipment Plant/equipment loads shall be determined by the weight of the Loads: manufacturer's equipment supplied and by the dynamic or impact effects,

in the case of switchgear and rotating/ reciprocating machinery.



A static equivalent analysis may be adequate for all structures subject to dynamic loading. The support structures shall be designed for the maximum dynamic loading resulting from all plant, in any one zone, operating simultaneously. The derivation of static and dynamic loading used in the design shall be in line with the recommendations given in Part 1 of CP2012 or similar approved standard.

Wind Loads: Wind loads and the distribution of wind pressure on buildings and structures shall be determined in accordance with the recommendations BS CP.3 Chap. V Part 2 or equivalent approved standard.

Seismic Loads: All structures shall be designed for seismic loads in accordance with the

Uniform Building Code published by International Conference of Buildings Officials, California, USA.

The following criteria shall apply:

Analysis Quasi-static approach

Acceleration 0.2g (m/sec2)

Loading Combinations 1. Dead Load + Live

2. Dead Load + Wind Load + 50% Live Load. 3. Dead Load + 50% Wind Load + Short Circuit

Forces 4. Dead Load + Seismic Load without Wind.

Temperature The actual temperatures and temperature ranges for which buildings, structures, etc., are designed shall be to the approval of the Engineer. The location, type and purpose of the building/structure shall be taken into account when defining temperature criteria.

Allowance shall be made for the stresses induced in any structure due to differences in temperature between the surfaces of a member or between parts of a structure/building. Expansion joints shall be located and spaced, where necessary, so as to minimize strains in the structure/building, cladding, finishes, fixings, plant, etc.

2.9.3 Design by Tenderer

The Tenderer shall submit with his Tender a design portfolio, which shall include at least the following items:

. An account of the design method proposed for use for each part of the Works; design criteria used (loading, permissible stresses and such like); assumptions in respect of foundations.

· A listing of the standards, codes of practice, references and design data

proposed for use in respect of design and construction of the works and equipment to be supplied.

· A listing of materials to be used with brief technical descriptions. Where

proprietary products or materials are proposed, manufacturers' brochures and technical literature shall be submitted. Where these are not in the English language the Tenderer shall provide a translation.



Tenderers shall submit with their Tender, details of the qualifications and experience of the senior staff to be employed on the design. The Contractor shall notify the Engineer and obtain his approval of any change of designer during the course of the Contract.

2.9.4 Design by Contractor

Experienced and competent engineers shall carry out the design of the Works. The design shall be consistent with the highest professional standards of skill, care and diligence. The Contractor shall be entirely responsible for the adequacy of the design of the Works, notwithstanding any approvals given or comments made by the Engineer in respect of the designs, drawings and calculation submitted by the Contractor.

2.9.5 Calculations

Calculations shall be produced in accordance with the relevant procedures as described in the Contractor's Quality Control/Assurance Manual approved by the Engineer. All design calculations shall be submitted to the Engineer for his approval. Calculations shall be in English and submitted in duplicate and shall be accompanied, if requested, by two English language copies of Standards and Codes of Practice used and approved by the Engineer. Approval by the Engineer of any calculations shall not relieve the Contractor of responsibility for that calculation or for the safety, suitability and adequacy of any part of the Works designed in accordance with that calculation. The Contractor is at liberty to use any software/programme in the design of the works. However, the contractor shall clearly explain the design procedure (input, output, parameters etc) used in the calculations by the software /programme to enable checking of the designs. Computer printouts that do not allow interpretation of results or explain the design procedure will be rejected and the calculations considered as not submitted. Before being submitted to the Engineer for approval, all calculations, including computer printouts, shall be checked by an engineer in the design office of the Contractor, who shall be of similar competence to the originator of the calculations. The originator shall not act as the checker of his own work.

2.9.6 Drawings

All drawings shall be produced in accordance with the relevant procedures as described in the Contractor's Quality Control/Assurance Manual approved by the Engineer. All drawings shall be submitted to the Engineer for his approval before construction commences either in part or whole. Drawings shall be in English and shall be submitted in duplicate, together with a reproducible copy. Approval by the Engineer shall not relieve the Contractor of responsibility for the safety, suitability and adequacy of any part of the Works. Drawings and other documents shall satisfy the following requirements, where appropriate, before they are submitted to the Engineer for review: The contractor shall ensure that all drawings submitted to the Engineer for review



shall constitute a set as follows: 1. Plans 2. Elevations 3. Sections 4. Details 5. Design calculation Reports 6. Other relevant Reports e.g. soil test, etc.

All drawings shall show legends, notes, title block, drawing scale and dimensions correctly and relevantly presented to ensure comprehensive and clear presentation of information. All structural drawings shall show details of structural reinforcements, bending schedule, and dimensions correctly and relevantly presented to ensure comprehensive and clear presentation of information. All design calculation reports shall be submitted together with the relevant/appropriate drawings. Any set of drawings that do not satisfy these conditions shall be rejected outright without being reviewed and such submissions shall be considered as null and void.

2.9.7 Submissions

The detailed design, including calculations and drawings, for all the works to be carried out, shall be submitted to the Engineer for approval. Such submissions shall be in accordance with an approved programme. Submissions shall be made in an orderly and timely manner, during the periods shown for design approval in the Works Programme, such that the Engineer shall have adequate time for their detailed examination and for checking and approving any necessary revisions. A period of one month shall be allowed for the Engineer's checking and approval of any design submission from date of receipt of submission to date of notification of approval or comments. In programming submissions the Contractor shall allow for the possibility that a resubmission may be necessary before the start of any part of the Works. Each design submission shall be serially numbered and dated and shall refer to one subject matter only. Each submission shall be accompanied by a summary sheet, which lists the documents comprising the submission. Where a submission includes revisions of documents previously submitted the summary sheet shall include a reference to the original submission number.

2.9.8 Site Records & Facilities

· Site Document File

The Contractor shall maintain at the site a Site Document File incorporating all changes and modifications as they occur. The file shall include a Drawing/Document List, a Master Drawing File and a Master Technical Instruction File. The Contractor's proposal for the Site Document File shall be submitted for the approval of the Engineer. The Drawing/Document List shall be prepared and updated regularly at periods to be decided by the Engineer. The first issue shall be made within 30 days of award of the Contract and shall indicate the various types of drawing and documents,



which will be prepared during the period of the Contract and the anticipated numbers thereof. The list shall be updated as necessary and the status of each drawing/document shall be indicated under one or other of the following heading: - Issued for review - Approved - Not Approved - Approved with comments - Issued for construction - Issued "as built" All changes and modifications to the Master Drawing Files and the Master Technical Instruction Files shall be highlighted in red markings.

2.10 FOUNDATIONS 2.10.1 General

Foundations and support structures shall be provided for buildings, transformers, switchgear, and other equipment specified for the project as appropriate. All foundations shall be designed in accordance with BS 8004 or similar approved standard. The detailed design of all foundations shall be the responsibility of the Contractor. Foundations shall be designed based on the stress resultants obtained from analysis of the worst combinations of loading and on the serviceability requirement of the plant and buildings. The Contractor shall submit design calculations and working drawings for all foundations to the Engineer for review and approval prior to commencement of construction. Acceptance by the Engineer shall in no way relieve the Contractor of his sole responsibility for the adequacy of the foundations. The derivation of static and dynamic loading used in the design shall be in line with the recommendations given in Part 1 of CP 2012 or similar approved standard. All precautions for limiting and isolating vibrations shall be taken. Vibrations shall not have any harmful effects on adjacent structures or processes. For all equipment foundations subject to vibration the foundation shall be cast in a continuous single pour with no cold joints. The Contractor shall include for approval, methods of curing such foundations. Where the ground is excavated, for any reason, below the underside of the proposed foundation the void shall be filled with concrete to the approval of the Engineer. The depth of foundations shall be determined based on the recommendations of the geotechnical investigations conducted by the contractor and approved by the engineer but in any case shall not be less than 700mm from the top of the compacted base course. All foundations shall be reinforced with steel and where not required on the basis of the calculations, nominal reinforcement shall be provided.



2.11 DRAINAGE SYSTEM 2.11.1 Substation Yard Drainage

Rainfall run-off and general drainage of the substation yard shall be carried by appropriately sized reinforced concrete perimeter open channel drains to an appropriate outfall not less than 15m from the edge of the substation embankment and as shall be approved by the Engineer. To prevent possible flooding of the station in extreme precipitation conditions, e.g. 50-year return period flood, the final level of the compacted laterite base course of the substation yard embankment shall be at least 0.3m above existing ground levels of the adjoining areas. Cable trenches shall be provided with adequate slopes and their invert levels shall be such that the trenches can drained through an appropriately sized uPVC pipes into the nearest point in the perimeter drains where gravity flow can be achieved. In order to prevent flow of water into the control buildings, cable trenches shall be sloped and drained away from the control building. In addition, the design of the cable entry into the control room shall be such that they are as much as possible, water and air tight. Appropriately designed french-drains to direct run-off to the perimeter drains shall be provided to drain off substation yard areas cut-off by cable trenches.

2.11.2 Catchment Drainage The engineer in conjunction with the contractor shall study the project site and determine the need to provide additional drainage to divert runoff from the catchment area away from the substation. When it is determined that catchment drainage is required to minimize the risk of the substation against flooding the engineer shall liaise with the local planning authority and provide a suitable design for construction by the contractor. The cost of construction shall be paid using the provisional sum earmarked for such work based on the unit prices provided by the contractor in its Tender price.

2.12 WATER SUPPLY

Only potable water shall be used for construction and shall be supplied to the site by the Contractor in tankers and kept in water storage facilities which shall be provided on site to meet constructional requirements at all times.

2.13 DRIVEWAYS WITHIN THE SUBSTATION YARD

The layouts of driveways shall be determined by the arrangement of buildings, transformer and other foundations and shall be to the approval of the Engineer. Such driveways shall have a width of 5 metres. The Contractor shall provide suitable access driveways up to the off-loading bays of the control building. In addition, provision must be made for other access roads necessary for the proper movement, installation and post construction maintenance of all the major installed plant indicated on the conceptual drawings. The Contractor shall provide adequate access and facilities for the delivery and removal of transformers. These shall be designed to safely withstand all jacking point loads, etc., and adequate haulage bollards or rings shall be provided where necessary. Where driveways or transformer accesses pass over services like cables trenches or



duct banks, special designs shall be incorporated to prevent damage to such services. The design and construction of driveways shall take full account of the information provided by the Site Investigation and embankment soil test results. There shall be no special treatment required for areas earmarked for driveways other than that which is required for the general finishing of the entire substation yard. The conceptual layout of the roads is shown on the conceptual drawings. The final layout shall be determined by the Contractor in accordance with this Specification and to the approval of the Engineer.

2.14 YARD SURFACING & FENCING 2.9.1 Yard Surfacing

The yard surface is defined, as any area of the site not occupied by buildings, foundations, cable ducts, or by other structures or equipment. The substation embankment shall be restored to its level of compaction /consolidation and design slope after equipment foundations and grounding mat have been backfilled and well compacted. The yard shall then be finished with a 100mm thick course of 25-50mm broken stones or chippings.

2.9.2 Fencing

The boundary fence and entrance gates shall be made of galvanized steel chain-link fencing and galvanized steel pipes as specified in the General Specification for Materials and Workmanship. The height of the fence and the gates shall be 1.90m vertical with a further 0.5m extended outwards from the site at 450 on to which 3 No. rows of barbed wire shall be fixed as specified in this specification. The mid-sections of the fence shall be kept taut by the introduction of steel stiffeners. Fence posts shall be of galvanised tubular steel of diameter 50mm for intermediate posts and 75mm for angle and tensioned posts, 3.0 metres apart, on the average centres. The fence posts shall have concrete foundations projecting 100mm above the finished laterite level but flushing with the top level of the crush rock. The top of the concrete foundations of the steel pipes shall be cambered to prevent water stagnations that might lead to rusting. The vehicular and pedestrian gates shall be plastic coated chainlink with galvanized steel frames/posts of type, size and strength to be approved by the Engineer. The widths of the vehicular and pedestrian gates in fully opened position shall be 5.0m and 1.0m respectively. Where, feasible, vehicular gates shall be provided at both the entrance and exit points of the fence with respect to the substation access road.

2.15 CABLE TRENCHES & DUCT BANKS 2.15.1 Ducts, Trenches, Tunnels and Pits

All ducts, trenches, tunnels and pits within the substation yard and buildings shall have sufficient drainage slopes and drainage outlets such that standing water cannot collect.

Cable trenches shall be of two types as follows:



Primary Cable trench serving as the main cable collector to the control building. Secondary Cable trench normally feeding cables at right angles into the primary

trench. Cable trenches shall be of reinforced concrete, and in order to provide adequate capacity for future expansion works, the trenches shall not be less than 900mm wide by 800mm deep and 700mm wide by 500mm deep for primary and secondary trenches respectively. All cable trenches shall be provided with approved cable support system capable of preventing cable contact with the invert of the trenches. Trenches shall be provided with removable, suitably sized galvanized steel chequered cover plates 3.5mm thick minimum. Galvanized steel angle irons shall be welded onto the underside of the plates along the edges of the cable trenches and shall have 2 No. lifting holes fitted with collapsible lifting handles.

Subject to the approval of the Engineer, trenches, ducts, tunnels and pits shall be of size, adequate to facilitate cable and other installation and maintenance works. Edges of cable trenches and pits shall be provided with suitably sized galvanized steel angles. At road crossings, precast R.C. cover slabs or their equivalence as approved by the Engineer, shall be provided over trenches. Pits and manholes in driveways shall be provided with heavy-duty cast iron covers. The minimum size of reinforced concrete walls shall be 150mm and precast covers shall be 150mm. Proprietary troughs or alternative proposals shall be submitted for approval.

2.15.2 Duct Banks

2.15.2.1 Materials

Pipes shall be in accordance with the following standards:

uPVC Pipes BS 3505, BS 4660 2.15.2.2 Installation

Ducting shall be by 100mm diameter pipes minimum laid on sand bedding at least 450mm deep from the compacted laterite level from equipment to the nearest secondary cable trench. Separation between the pipes shall be 80mm minimum. They shall be laid true to line and level, and all joints shall be accurately formed in accordance with manufacturer's instructions. After installation, each duct shall be thoroughly cleaned by water, air, rodding or other approved method. The duct shall also be proved by drawing a mandrel through it. The diameter of the mandrel shall be 95 % of the internal diameter of the duct.

2. 15.2.3 Inspection and Testing

All ducting systems shall be inspected before being finally enclosed. They shall be inspected for accuracy of line and level, adequacy of joining and resistance to ingress of water. The Engineer will decide the form of test. Installations, which have failed the tests, shall be re-laid to the Engineer's satisfaction and shall be re-tested. Before being finally enclosed, all ducts shall be inspected to ensure that they are entirely free from obstructions. The ends shall then be temporarily sealed until the



ducts are required for use.

2.16 SITE OFFICES AND FACILITIES FOR ENGINEERS

The Contractor shall supply, erect and service complete office accommodation for the Project Management team of the engineer. The offices shall be well ventilated, air conditioned, weatherproof and security proof. The accommodation shall be complete with all services including lighting, telephone and telefax, water supply, sanitary services, furniture, fridge, etc., to the satisfaction of the Engineer. In particular, the accommodation shall include, but shall not be limited to the following partitioned units: - Reception - Conference room that can provide seating for 10 persons furnished with one (1)

No. large Conference Desk, size 3000(L) x 900(W) x 750(H), Fifteen (10) No. office chairs size 400(W) x 400(L) x 800(H).

- An office that can accommodate three (3) persons furnished with one (1) Air-conditioner, one (1) Refrigerator 100 litres. It shall also be furnished with three (3) No. Normal desks size 1500(L) x 800(W) x 750(H) with two (400 x200) right side drawers and three (3) No. Office Chairs size 600(L) x 500(W) x 900(H) with arm rests.

- Kitchenette - Toilet Facilities The Contractor shall be deemed to have included in his Tender, a sum for the purpose of supplying equipment to the Engineer's office and for supplying logistics for holding site meetings and refreshing participants during and after each meeting. The total sum allocated shall be approved and expended by the Engineer.

2.17 SITE SECURITY & SAFETY

The Contractor shall submit within thirty days from the date of Award of Contract the following documents for the Engineer's approval, provided, however, that the Engineer's approval of such documents shall not relieve the Contractor of his duties and obligations under the Contract: - Site Security Plan - Fire Prevention and Protection Plan - Site Sanitation Plan - Site Safety Plan These plans shall be filed with the Engineer and shall be revised and updated periodically as required by the Engineer. The requirements of these plans are set out in various clauses of this section of the Specification.

2.17.1 Site Security

The Contractor shall submit for the Engineer's approval a Site Security Plan showing how he proposes to comply with the provisions of the Contract. The Contractor shall comply with the Employers Security Regulations for the time being in operation and shall instruct all persons employed on the Works regarding same.



2.17.2 Fire Prevention and Protection

The Contractor shall take all reasonable precautions to prevent outbreaks of fire in the Works, temporary works, or in offices, stores and other places and things connected therewith and shall have special regard to the safe storage of petroleum products, paints, explosives and all other dangerous or hazardous goods. He shall comply with all rules, regulations and orders, which have been or may be made by the Government, the Local Authorities or the Employer and he shall provide and maintain in good order and hold available at all times and in all places connected with the Works a sufficiency of efficient fire fighting equipment together with personnel trained in the usage of these facilities. The Contractor shall submit for the Engineer's approval a Fire Prevention and Protection Plan showing how he proposes to comply with the provisions of the Contract.

2.17.3 Site Sanitation

The Contractor shall provide and maintain to the satisfaction of the Engineer's and the Statutory Authorities, adequate latrines and wash places for his employees on various parts of the site, together with arrangements for sewage disposal and drainage. When no longer required, the Contractor shall remove such latrines and wash places, disinfect and fill in all pits, sumps and trenches and restore the sites to a clean and sanitary condition. The Contractor shall pay any charges, which may be levied by the Statutory Authorities.

The Contractor shall submit for the Engineer's approval a Site Sanitation Plan showing how he proposes to comply with the provisions of the Contract.

2.17.4 Site Safety

The Contractor shall administer and control his site activities in a manner conducive to the achievement and maintenance of adequate safety for the public, his employees, his Sub-Contractors and their employees, the Employer and his employees and the Engineer and his employees. This shall include regular inspection of all temporary installations and portable tools and equipment. Particular attention shall be paid to safe storage of combustible and explosive materials. The Contractor shall submit a Site Safety Plan setting out the Contractor's safety policy and the proposals of the Contractor to ensure that such a policy is put into effect during the period of the Contract. The Contractor shall inform himself of the Employer's safety procedures and shall furnish a statement of his commitment to work according to these procedures. In particular, the contractor shall provide all the required safety ware and identification tags for all his employees, his Sub-Contractors and their employees, the Employer and his employees and the Engineer and his employees. The Engineer shall have power to stop the works if in his opinion they are being undertaken in an unsafe manner. All expenditure required and necessary for carrying out the works in a safe manner approved by the engineer shall be deemed to be included in the lump sum price provided in the schedule of prices.



2.17.5 Safety Regulations

The Contractor shall instruct all persons employed on the Works regarding the safety regulations of the Volta River Authority (VRA) and any other applicable authority for the time being in operation on the site and all warnings issued regarding operating plant, towers and the overhead lines and cables. He shall take all necessary precautions and actions to comply with the regulations and shall provide all necessary barriers and height gauges in such approved forms and positions as directed by the Engineer. It is recommended that the Contractor pay particular attention to these procedures, which will require detailed planning and co-ordination of site works by the Contractor and will involve certain restrictions on the Contractor's method of working.

2.17.6 Work in Operational Areas

Before the Contractor undertakes any work in any area or areas where operating plant, pipes, cables, switchgear or other electrical or mechanical apparatus are in use, he shall obtain from the Employer through the Engineer a written permit to work or limitation of access or sanction for test as required by the Safety Regulations. All work in operational areas shall be carried out strictly in accordance with the Employer's operational procedures and the Engineer's instructions.

2.17.7 Notification of Accidents/Fires or Similar Incidents

In the event of an accident, fire or similar incident occurring on, or associated with the site, the Contractor shall immediately notify the Engineer or his representative who will notify the necessary authorities in accordance with procedures approved by the Employer.

2.17.8 Safety Officer

During the erection phase, the Contractor shall employ a personnel qualified in safety and familiar with the type of work being performed, whose assignment shall include initiation of measures for the protection of health and the prevention of accidents and who shall see by personal inspection, that all safety rules and regulations are enforced.



SUB-SECTION 2

GENERAL SPECIFICATION FOR MATERIALS AND WORKMANSHIP

FOR

CIVIL WORKS



CONTENTS 2.1 EARTHWORKS........................................................................................................................154 2.2 STATION EMBANKMENTS .....................................................................................................159 2.3 CONCRETE WORKS ...............................................................................................................159 2.4 STRUCTURAL STEELWORK..................................................................................................179 2.5 WATER SUPPLY......................................................................................................................189 2.6 DRAINAGE WORKS ................................................................................................................190 2.7 MASONRY................................................................................................................................193 2.8 CARPENTRY AND JOINERY ..................................................................................................199 2.9 METALWORK ..........................................................................................................................202 2.10 BOUNDARY WORKS...............................................................................................................204 2.11 LIGHTING AND LOW VOLTAGE POWER ..............................................................................205



2.1 EARTHWORKS 2.1.1 Excavation 2.1.1.1 General

Unless stated otherwise in this Specification, earthworks shall be in accordance with BS 6031. Before any particular excavation is commenced, the Contractor shall submit his proposals with regard to the outline thereof to the Engineer for approval. The Contractor shall ascertain the location and nature of any existing buried services/structures services, and shall take any necessary precaution required against damaging or interfering with them during excavation for the works.

2.1.1.2 Excavation Level

Foundations for structures shall be carried down to sound and undisturbed material, to levels not higher than shown on or inferred from the Contract Drawings. The drawings shall show, as near as it is possible and practicable to determine beforehand, the depths for the proposed excavations, but such limits shall be finally determined during construction.

2.1.1.3 Foundation on Rock

The excavated rock surface at foundation level shall be free of shattered or loose particles of rock and shall be washed free of clay, silt and rock chippings etc., with an air and water jet immediately before concreting begins.

2.1.1.4 Foundation on Material other than Rock

When the depth of excavation has reached to not less than 150mm above the invert level shown on the drawings, the approval of the Engineer shall be obtained as to the suitability of the material for the foundation in question. Should the material be suitable, the excavation shall then be cleaned down to the correct foundation level, the Engineer's approval obtained and concrete placed on the invert of the excavation without delay. No excavated material shall be filled in to the bottom of excavations. Any material disturbed at the approved foundation level shall be removed and replaced by concrete. In the event of the approved invert being covered by water before concrete is placed, the excavation shall be pumped out and the excavation carried down to sound undisturbed material.

2.1.1.5 Excavation of Foundations, Pits and Trenches

Before any particular excavation is commenced, the Contractor shall submit his proposals with regard to the outline thereof to the Engineer for approval. The Contractor may carry out these excavations by any method he considers most suitable, subject to the stipulations in the Contract. The sides of pits, trenches and other excavations shall be adequately supported at all times to the satisfaction of the Engineer until backfilling is complete. Sound and durable material shall be used for supports and the Contractor shall ensure that the supports are installed, maintained, and removed by men experienced in such work.



Exposed faces of the excavations shall be cleared of all material (including rock fragments), which are liable to cause injury or damage by falling during the course of the work. The Contractor shall take all precautions necessary for the safety of adjoining structures by shoring, opening in short lengths, or otherwise. Excavations shall be kept free from water until, in the opinion of the Engineer, the works therein (including backfilling) will not be damaged by water, and the Contractor shall construct any sumps or temporary drains which the Engineer may deem necessary for this purpose. The excavations shall be of sufficient size to enable the work therein to be properly executed, and shall allow for the supports, drainage facilities, and other things required for this purpose. In the event of excavations being carried out wider or deeper than approved they shall be filled in to the required dimensions or levels with concrete or with other suitable material, to the satisfaction of the Engineer.

2.1.1.6 Excavation for Sewers, Drains, Gullies and Manholes

Excavation for sewers, drains, gullies and manholes shall be carried out to the lines and levels shown on the Contractor's Drawings or otherwise approved by the Engineer. In areas of general excavation or filling, these excavations and the subsequent construction shall not be commenced until the areas are completed to the grade unless the Engineer permits otherwise. The Contractor shall maintain pipe trenches pumped out, protected with safety barriers and well supported where necessary and shall not open up trenches and leave them to fill with water. Where solid rock is encountered at invert level, it shall be removed to a depth of 150mm below the bottom of the pipe and replaced with 150mm of compacted granular fill.

2.1.1.7 Disposal of Excavation Material

The disposal of all materials arising from excavations shall be to the approval of the Engineer. Material which is suitable for re-use as filling or for other purposes required under the Contract shall not be disposed of until it has been agreed by the Engineer that it is not required for re-use. The Contractor shall not dispose of materials outside the site or to another person, organisation body or authority without the approval of the Engineer. Materials, which, by agreement, are to be disposed to spoil, shall be removed to approved spoil dumps or otherwise as directed by the Engineer. In all cases spoil dumps shall be filled in orderly sequence and kept free from standing water or pools or areas dangerous to persons or animals. The cost of compliance with these requirements shall be deemed to be included in the Tender Price.

2.1.2 Fill 2.1.2.1 Fill Classification

Fill shall be obtained from locations suitable for winning such material. The Contractor shall inform the Engineer of the source from which he proposes to obtain fill matter. Prior to approval of the source of the material, the Contractor shall carry out such tests on samples of material as the Engineer may require ensuring that the material is in accordance with this Specification. Only fill approved by the Engineer shall be used. Fill shall be classified as follows:



a) Soft Fill b) Rock Fill c) Rock Armouring d) Hard Fill Type I

Hard Fill Type II e) Hard-core f) Fill for Transformer Pits

(a) Soft fill shall be classified as plastic or non-plastic. Non-plastic materials shall be

those described as “coarse soils or very coarse soils” in Table 6 of BS 5930. Plastic materials shall be all other materials described as "fine soils” in the above-mentioned table. Soft fill shall be placed at moisture content, which shall be to the approval of the Engineer.

(b) Rock fill shall be hard durable rock free from dirt, earth loam, clay or organic

matter of such size and properties that it can be placed in layers as described in this Specification. Soundness of won rock shall be tested by water absorption test.

The stones shall not be more than 300mm or less than 50mm in any direction; 60% of the stone shall be between 200mm and 300mm in size.

(c) Rock armouring shall be quarried and shall be hard dense stone of the best

quality obtainable, tested in accordance with the slake durability test specified by the international Society for Rock Mechanics and shall be obtained from quarry faces approved by the Engineer. The stone shall be prismoidal in shape and the maximum dimension of any stone shall not be more than three times the minimum dimension. Stone which has a tendency to fracture when dropped on stone already placed shall be rejected.

(d) Hard fill Type I shall be selected hard well graded material screened and

crushed as necessary to lie within the following grading of percentage by weight when tested in accordance with BS 1377: Test 7A:

0 - 20% shall pass 75-micron aperture sieve 8 - 45% shall pass 600-micron aperture sieve 20 - 65% shall pass 5mm-aperture sieve 45 - 100% shall pass 10mm aperture sieve 85 - 100% shall pass 37.5mm-aperture sieve 100% shall pass 1 00mm aperture sieve Free of stone over 75mm gauge. Hard fill Type II shall be selected hard granular material with not more than 7% by weight water soluble and shall be within the following grading of percentage by weight: Not more than 10% shall pass 90-micron aperture sieve. Not more than 28% shall pass 355-micron aperture sieve. Not more than 50% shall pass 4mm-aperture sieve. Free of stone over l50mm gauge.

(e) Hard core shall consist of broken stone, concrete brick or coral varying in size

from 100 to 25mm. It shall be free of clay, soft material and deleterious matter and shall be chemically inert.

(f) Fill for transformer pits shall be broken stone graded 50 to 75mm with a

minimum of 40% voids when placed.



2.1.2.2 Filling 2.1.2.2.1 General

Fill under all foundations and slabs shall be mechanically compacted at the optimum moisture content. The minimum degree of compaction shall be of the maximum dry density at the optimum moisture content. In situ density testing shall be carried out in accordance with BS 1377 Test 15.

Backfilling of foundation pits and trenches shall be carried out only after the foundation and structural works within the excavations have been inspected and approved by the Engineer. All filling shall consist of approved materials, which shall be deposited and compacted, in layers not exceeding 250mm loose depth. All filling shall be carried out in a manner approved by the Engineer. Filling of pipe trenches and associated excavations shall not commence until the permission of the Engineer has been obtained. Fragments of rock not exceeding 200mm in any dimension may be permitted in the fill, provided that they are surrounded by fine material graded so as to ensure the compaction of the fill without voids.

2.1.2.2.2 Soft Fill

Soft fill shall be placed at moisture content, which shall be to the approval of the Engineer. In the case of plastic material, this moisture content shall be not more than 2 percent above the plastic limit for the material and in the case of non-plastic material, it shall be within 2 percent of that of the material as excavated above the water table. Soft fill shall be spread in layers of 200mm loose thickness and compacted by eight passes of a 10 ton roller or such other approved plant and methods to give 95% maximum dry density as determined in accordance with BS 1377, Test No.13 or 14.

2.1.2.2.3 Rock Fill

Rock fill shall (except where otherwise required near formation level or at external surfaces) be of such size that it can be spread and levelled in layers not exceeding 450mm loose depth by a tractor weighing not less than 15 tonnes. Voids in each layer shall be filled with rock fragments before placing the next layer. Each layer shall be compacted after spreading by at least 12 passes of a towed vibratory roller with a static mass per metre width of roll of at least 1800kg or other equivalent plant approved by the Engineer.

Where material consisting of a mixture of rock and soft fill if used as filling, the material shall contain sufficient soft fill for satisfactory compaction of the filling to the satisfaction and approval of the Engineer.

2.1.2.2.4 Hard Fill

Hard fill Type I and Type II shall be placed in layers not exceeding l50mm and 300mm respectively at optimum moisture content and compacted to 95% maximum dry density as determined in accordance with BS 1377, Test No. 13 or 14. Hard core shall be compacted in layers not exceeding 200mm thick.



2.1.2.2.5 Backfilling Pipe Trenches

Filling of pipe trenches and associated excavations shall not commence until the permission of the Engineer has been obtained.

Pipe trenches shall be backfilled and compacted in layers 150mm thick, the filling to 300mm above the crown of the pipe shall be approved sandy material free from stones, etc., well packed by hand evenly around both sides of the pipe, care being taken not to disturb the pipe. Backfilling over this level shall be carried out using approved material and may be compacted by mechanical means.

2.1.2.2.6 Fill in Standing Water

Fill shall not be deposited in standing water without the Engineer's permission. This permission will not normally be granted for soft fill or for fill of a kind where the standing water can, in the opinion of the Engineer, be pumped out, drained or diverted. Permission may be granted to place rock fill by random tipping in areas where the depth of water is greater than 600mm but the methods and quality of the fill material shall be subject to approval. When the fill level is 600mm above the water surface, it shall be compacted until there is no discernible movement under the plant placing or compacting the fill, before normal filling and compacting is resumed.

2.1.2.2.7 Settlement

The Contractor shall be responsible for making good all settlements, which may occur to the satisfaction of the Engineer.

2.1.2.2.8 Blasting and Use of Explosives

If the Contractor wishes to use blasting techniques, he shall ascertain details of the regulations applying to the use of explosives in Ghana, and obtain permission from the appropriate Authority. The Engineer or Employer shall not be liable for any claims arising out of damage or alleged damage due to blasting. The Contractor shall be liable for all such claims and shall insure with an approved Insurance Company against all claims in respect of damages and injury arising from blasting. No blasting shall take place without the written approval of the Engineer. A licensed Sub-Contractor who is approved by the Employer and who specialises in blasting shall carry out blasting. Blasting shall be carried out at specified times to be agreed upon by the Contractor and the Engineer. Sufficient notices and barriers shall be erected and, immediately before blasting is due, an adequate warning shall be given to workers on the site and to the public so that no one may come within the danger zone until blasting is finished. On finishing the blasting, an “all clear” signal shall be given. Drilling and blasting shall be arranged and where necessary, the rock being blasted shall be protected so as to prevent any scattering of rock likely to cause injury to the public or damage to the Works, dwelling houses, buildings and other property.



2.2. STATION EMBANKMENTS

Embankments shall be constructed in accordance with Clause 1 - Earthworks. Fill material shall be strictly in accordance with the Engineer's direction and approval. Embankments shall be constructed according to the lines and levels indicated, with machines of the proper type and weight. Compaction shall be carried out in layers of 200mm maximum thickness and no layer shall be placed until the preceding one has attained the specified compaction ratio, i.e. 95% maximum dry density at Optimum Moisture Content. Compaction shall be tested both on site and on samples taken from the embankment. Tests shall be carried out in the number of three per 1000m

2, points of testing being

chosen at random by the Engineer.

2.3. CONCRETE WORKS 2.3.1 Codes and standards

Concrete works shall be designed constructed and tested in accordance with the requirements of BS 8110. Other internationally recognised standards may also be used for concrete works. See Clause 2.3.

2.3.2 Cement

Cement used in the works shall be in accordance with the following standards, BS 12 Ordinary Portland Cement, BS 4027 Sulphate Resisting Cement. Cement shall be from a source approved by the Engineer.

2.3.2.1 Certificates

Each consignment of cement shall be delivered in sealed branded bags, barrels or other approved container and shall be accompanied by a certificate from the manufacturer showing that the cement has been tested and analysed and the date of such tests and analysis and that such analysis complies in all respects with the Standard and if required, the bags from each consignment shall be given a distinctive seal.

2.3.2.2 Tests after Delivery

After delivery of each consignment of cement to the site, the Contractor shall supply samples of the cement for testing. The samples, in sufficient quantity for testing in accordance with the requirements of the Standard and not less than 5kg in weight, shall be supplied and handled at the Contractor's expense.

2.3.2.3 Stock of Cement

In order to ensure due progress of the Works, the Contractor shall at all times maintain on the Site a stock of cement sufficient to ensure continuity of work. No cement shall be used in the Works until the Engineer has accepted it as satisfactory.

2.3.2.4 Returns

The Contractor shall make a monthly return to the Engineer showing the quantities of



cement received and used during the month and in stock at the end of the month. 2.3.2.5 Storage on the Site

The Contractor shall arrange that cement imported for use on the Works is delivered to the Site with a minimum of delay and that it is stored under suitable conditions during transit. All cement kept on the Site shall be stored in watertight and well-ventilated covered sheds on platforms clear of the ground. Each consignment of cement shall be identified with a batch number including date of delivery and shall be stored separately. The Contractor shall ensure that cement is used in order of delivery to Site and that different brands of cement are kept in entirely separate stores. The use of bulk cement shall be subject to the Engineer's approval of the source, methods of transport, unloading and storage on Site and arrangements for delivery to the mixer.

2.3.2.6 Rejection

The Engineer may reject any cement as the result of any test thereof notwithstanding the manufacturer's certificate. He shall also reject cement, which has deteriorated owing to inadequate protection or other causes or in any other case where the cement is not to his satisfaction. The Engineer may reject cement, which has been stored on site for a period greater than one month. The Contractor shall remove all reject cement from the Site without delay and replace at his own expense.

2.3.3 Aggregates for Concrete Works 2.3.3.1 General

Except as may be modified hereunder, the aggregate (fine and coarse) for all types of concrete shall comply in all respects with BS882 "Concrete Aggregates from Natural Source" or other approved standard. They shall be hard, strong and durable and shall contain no harmful material in sufficient quantity to affect adversely the strength or durability of the concrete, to attack the reinforcement. The maximum size of coarse aggregate shall be 20mm for all concrete mixes.

2.3.3.2 Source of Aggregates

The source of aggregates shall be approved by the Project Manger and shall be open to his inspection before the start of the Works and during their progress. Aggregates shall be naturally occurring materials.

2.3.3.3 Physical Requirements

Fine and coarse aggregates shall comply with the following physical requirement: (a) The weight of voided shells in fine aggregates shall not exceed 5%

(b) The clay, fine salt and dust content shall not exceed the following limits:

Coarse Aggregates 1% by weight Natural Sands 3% by weight Crushed Stone Sand 6% by weight

(c) The flakiness index and elongation index of coarse aggregates measured in



accordance with BS 812 shall not exceed 25% and 35% respectively. (d) The absorption of fine and coarse aggregates as measured in accordance with

BS 812 shall not exceed 2%. (e) The aggregate impact value for coarse aggregates as measured in accordance

with BS 812 shall not exceed 30%. (f) Fine aggregates shall be clean, sharp, coarse sand and shall be within Zones 2,

3 and 4 only of Table 2 of BS 882. (g) Coarse aggregates shall be single sized aggregates obtained by mechanical

crushing and screening. 2.3.3.4 Chemical Requirements

Aggregates shall comply with the following chemical requirements: (a) Fine and coarse aggregates shall not contain more than 0.10% and 0.04% by

weight of chlorides (as NaCI) respectively. If either material exceeds the above limits, the material shall still be acceptable in this respect provided the total sodium chloride concentration is not greater than 0.50% by weight of cement in the mix for reinforced concrete, irrespective of the origin of the chloride.

(b) Fine and coarse aggregates shall not contain more than 0.4% by weight of acid

soluble sulphates (as SO3). (c) Fine and coarse aggregates shall not be potentially reactive with alkalis.

2.3.3.5 Aggregates to be washed

If necessary all aggregates, both fine and coarse, shall be washed mechanically by the Contractor to remove clay, silt, dust and adherent coatings to the satisfaction of the Engineer.

2.3.3.6 Sampling and Testing

Sampling and testing of aggregates shall be carried out in accordance with BS 812 "Sampling and Testing of Mineral Aggregates, Sands and Fillers" where applicable. Chemical analysis shall be by normally accepted methods. Sampling and testing shall be at the Contractor's expense. Petrographic examination shall be carried out in accordance with the American Society for Testing Materials Standard C295 'Recommended Practice for Petrographic Examination of Aggregates for Concrete". An approved testing laboratory shall carry out an accelerated test for potential alkali reactivity. If this test indicates the possibility of alkali reactivity, further testing in accordance with the following American Society for Testing Materials Standards shall be necessary: C 227 Test for potential alkali reactivity of cement aggregate combinations

(mortar bar method) for long term testing. C 289 Standard Method of test for potential volume change of cement



aggregate combinations C 586 Standard Method of test for potential alkali reactivity of carbonate rock for

concrete aggregates (rock cylinder method).

2.3.3.7 Approval of Aggregates

As soon as practicable after commencement of the Contract and well in advance of commencing concreting, the Contractor shall submit to the Engineer test results on samples of all aggregates he proposes to use in the Works. The Engineer shall require inspecting the sources of the proposed aggregates to be satisfied that the proposed methods of working, the sources and the arrangements for washing shall produce aggregates of regular quality complying with this Specification. No aggregates for use in the Works shall be delivered to Site until the Engineer has approved the aggregates to be used and the arrangements for washing, storage and such like. Thereafter, the Contractor shall take samples from every 100 cubic metres of each type of aggregate delivered to the site and submitted to the Engineer for routine control tests. Aggregates, which fail to comply with this Specification, or which have become contaminated, defective or otherwise unsatisfactory, shall be removed from Site or otherwise disposed of to the Engineer's satisfactions.

2.3.3.8 Storage of Aggregates

The Contractor shall at all times maintain on the Site such quantities of each type of aggregate as are considered by the Engineer to be sufficient to ensure continuity of work. Each type and grading of aggregate shall be stored separately in bins, the floors of which shall be of concrete or other approved material, having sufficient slope to ensure adequate drainage. Wet aggregate delivered to the Site shall be kept in storage for at least 24 hours, to ensure adequate drainage, before being used for concreting. Aggregates, which have been in storage for a long period, shall be removed from the bins and rewashed by the Contractor, if required by the Engineer, to remove any accumulation of dust, silt and deleterious substances.

2.3.4 Water The mixing water shall have a pH value of between 6.5 and 8. Water shall be tested in accordance with BS 3148 - the following limits shall not be exceeded:

Total Dissolved Solids Not greater than 2,000 ppm Suspended Solids Not greater than 2,000 ppm Chloride as NaCl Not greater than 800 ppm Chloride as Cl Not greater than 500 ppm Sulphates as SO3 Not greater than 1,000 ppm Alkali HCO3/CO3 Not greater than 1,000 ppm

The methods of delivery and storing the water shall be to the approval of the Engineer.

2.3.5 Admixtures Admixtures may only be used in concrete mixes with the prior approval of the



Engineer. The use of admixtures, where permitted, shall be in accordance with the provisions of BS 8110, Part 1. Admixtures shall comply with ASTM Standard C 494, BS 5075 or other Standard approved by the Engineer. Admixtures for which no approved standard exists shall be identified by type and proprietary brand name. The Contractor with his Tender shall submit proposal for the use of such admixtures. Admixtures shall be stored and handled so as to avoid contamination or damage to their properties and in accordance with the manufacturer's recommendations.

2.3.6 Production of Concrete

2.3.6.1 Concrete Grades

Grade A All concrete above ground level Grade B All concrete below ground level Grade C All blinding and mass concrete

For the purposes of the above, the ground level in the concrete structure shall be as designated by the Engineer.

2.3.6.2 Concrete Grade Requirements

Concrete (As Defined in Clause 2.3.6.1)

A B C

Cement Type to ASTM C150-83a

(Ordinary Portland)

(Sulphate Resisting)

(Sulphate Resisting)

Minimum Cement Content 350kg/m3 370kg/m3 220kg/m3 Nominal Maximum Size of Aggregate 20mm 20mm 20mm Maximum Water Cement Ratio 0.45 0.42 0.42 Characteristic Cube Strength at 28 days

25N/mm2 30N/mm2 15N/mm2

The concrete grades to be used in various parts of the Works shall be stated on the Drawings and approved by the Engineer. Concrete grade and cover to reinforcement shall be appropriate for the environmental conditions to which the concrete will be exposed.

2.3.7 Mix Proportions & Trial Mixes

Concrete mix constituents shall be selected and proportioned taking account of all design requirements including the environmental conditions to which the concrete will be exposed. Unless he proposes to use ready-mix concrete, the Contractor shall submit his proposals regarding mix proportions, with samples of cement and aggregate, at least 28 days before any concrete, incorporating those materials, is to be placed in the



Works. The requirements to perform trial mixes as described below may be relaxed by the Engineer on production of satisfactory evidence of trial mixes previously approved using the same materials in the same proportions. When the proposed mixes have been approved, they shall not be altered without the written permission of the Engineer. If the Contractor shall apply for such permission, the Engineer may require a repetition of the trial mix procedure. The proportions of fine to coarse aggregate, cement to combined aggregate and the water/cement ratio shall be determined by tests carried out in accordance with the recommendations set out in "Design of Normal Concrete Mixes" published by HM Stationery Office, London, or any other equivalent Standard to be approved by the Engineer, so as to give concrete of the required strength and of the highest possible density. In all cases, the water/cement ratio shall be the minimum practical, having regard to the conditions of handling and placing and the necessity of achieving proper compaction. The Contractor shall make trial mixes using the approved material, the plant used for these trials being, if possible, the plant which shall be used in the Works. Three 150mm test cubes shall be made from each of three consecutive batches of each mix proposed for the various grades of concrete and maximum sizes of aggregate. The cubes shall be made, stored and tested at 28 days in accordance with BS 1881. A further three cubes shall be taken from each batch for tests at 7 days. The trial mix proportions shall be approved for strength if the average crushing strength of each group of nine cubes exceeds the values for 7 day and 28 day (characteristic) strength given in Table 7.1 BS 8110: by minimum of 35%. The workability of trial mixes shall be tested in accordance with IBS 1881 using samples obtained from the batch used for the test cubes. In addition concrete from each trial mix, taken from the batches used for the test cubes, shall be placed and compacted by the methods proposed for the Works. in a trial section of formwork having a capacity of not less than 0.5m3 and representative of the sections to be employed in the Works. The Contractor shall submit full details of the trial mixes and test results and of the mixes proposed for use in the Works, which must be based on the satisfactory results of these preliminary tests and on the methods of mixing and placing the concrete in the Works. The Contractor shall be responsible for ensuring that the concrete conforms in all respects with these Specifications, notwithstanding any approval given by the Engineer to any mix proportions. If during the progress of the Works the Engineer is not satisfied with the strength, workability or other properties of the concrete, he may order the Contractor to provide additional cement, change the aggregates or vary the grading and the Contractor shall immediately comply with such order and shall have no claim for any expense or loss of time, occasioned by compliance with these provisions. The cost of all sampling and testing associated with this clause shall be borne by the Contractor.

2.3.8 Mixing of Concrete

Aggregates shall be weighed in their separate sizes in accordance with the approved mix design and the weights shall be corrected to allow for the free water contained in



the aggregates. This shall be determined by an approved method before mixing commences each day and more frequently if the Engineer so requires. The water to be added to the mix shall be similarly corrected. Cement shall be added as a number of whole bags or weighed separately in a separate weighing device. Details of the equipment, which is to be used on the Works, shall be submitted for approval before construction commences. Weighing and water dispensing equipment shall be maintained clean, properly lubricated and in good working order. When checked by standard weights and volumes, its accuracy shall be within I 3% of the quantity of cement, water or total aggregates being measured and within I 5% of the quantity of any admixture being used, and the approved mix proportions shall be accurate as an average over each day's work. The Contractor shall make provision for regular checking of “weighing and water dispense Equipment” at intervals not exceeding 1 month or as directed by the Engineer. Concrete shall be mixed in the power driven batch mixer, complying with the requirements of BS 1305, which has been approved by the Engineer and which shall be kept clean and in proper working order. The mixing blades in the drum shall be replaced when worn by 10% of their dimensions. The quantity of material in each batch shall not exceed the normal continuous rated capacity of the mixer and the speed of rotation shall be within 1 rpm of the manufacturer's recommended speed. Ingredients shall be fed into the mixing drum so as to ensure the most efficient use of the mixing period and to avoid the loss of material, particularly cement. The mixing time shall be not less than used by the manufacturer in assessing the mixer performance or otherwise as directed by the Engineer. Mixing shall continue until the concrete is homogeneous and of uniform appearance. In the case of mixes of low workability or high cement content, a satisfactory mixing time shall be determined by comparing the strength of samples mixed for different times. Aggregates may be batched by volume with the approval of the Engineer, but this shall not normally be granted for Grade C and above. The volume of the aggregates shall be adjusted to allow for the effect of moisture content on the bulking of fine aggregates, and the ingredients shall be measured separately in approved containers. Mixing of concrete shall not commence without ensuring that the stocks of ingredients are adequate (with a reasonable safety margin) for the completion of the particular pour of concrete. In the case of pours, which cannot be interrupted once commenced, the Contractor shall provide adequate standby plant and labour to the satisfaction of the Engineer. Retarding and workability agents may be added to the concrete mixer if the Engineer approves such agents. Admixtures shall be used in accordance with the manufacturer's recommendation and shall be dispersed by approved automatic dosing equipment, which feeds a fixed quantity of admixture into the mixing water before it is discharged into the mixer; the equipment shall provide a visible means of checking each dose. When more than one admixture is to be used in a mix, the compatibility of the various admixtures shall have been ascertained and certified by the manufacturers.

2.3.9 Ready-Mixed Concrete

Subject to the approval of the Engineer, the Contractor may elect to use ready-mixed concrete.



The name and address of the Works of the proposed Supplier shall be submitted to the Engineer at least 6 weeks before concrete is scheduled for delivery, together with a copy of the agreement between the Contractor and Supplier, details of the mixes proposed, specifications and all other documents relating to the supply of concrete and details of alternative supply arrangement in the event of failure of supply from the proposed Supplier. Details of the quality control procedures in operation at the ready-mix depot shall be submitted to the Engineer for approval at the time of stating the intention to use ready-mixed concrete. Facilities shall be provided at the ready-mix depot for the Engineer to inspect the batching and mixing of the concrete, the materials used, and samples of materials shall be provided for any tests which the Engineer may wish to carry out. Any inspection or testing carried out by the Engineer shall not relieve the Contractor of his obligation to provide concrete fully in accordance with this Specification.

Ready-mixed concrete shall comply in all respects with BS 5328. The cement, aggregates, admixtures and water shall comply with the requirement of this Specification and the Engineer may require the Contractor to produce evidence of compliance. Notwithstanding any approval by the Engineer, the Contractor shall be responsible for ensuring that ready-mixed concrete complies in all respects with the requirements of this Specification. In respect of each grade of concrete to be supplied, the Contractor shall provide the Engineer with a statement, certified by the ready-mixed concrete Supplier, giving the following information: (i) The nature and source of each constituent material.

(ii) The proposed quantity of each constituent material per m3 of supply

compacted concrete. Details of any proposed change in the source or nature of any constituent material and of any proposed change in the cement content from that last declared and agreed. This information shall be given not less than two weeks prior to the date of the proposed change, and the change shall not be made without the Engineer's approval.

Where a central or plant mixer is used, it shall comply with BS 1305 in so far as this applies. The Contractor shall consult with the Engineer if any ambient conditions such as high temperatures, traffic congestion etc. are likely to affect the quality of the concrete as delivered

Before discharging the concrete at the point of delivery, the Supplier shall provide the Contractor with a delivery note for each batch of concrete on which is printed, stamped or written the following minimum information: (a) Name of ready-mix concrete depot. (b) Series number of ticket. (c) Date.

(d) Truck number. (e) Name of purchaser. (f) Name and location of job. (g) Specified grade of concrete including, where specified, minimum cement content



per cubic metre of concrete. (h) Specified workability.

(i) Type of cement. (j) Type and weight of aggregate. (k) Maximum size of aggregate. (1) Type and name of admixture. (m) Amount of concrete in cubic metres.

(n) Time of loading. (o) Extra water added at the request of the Contractor and his signature. The Contractor in respect of each delivery of concrete shall also record the following information: - Position in the structure where the concrete is placed. - Results of workability tests, if any. - Details of test cubes taken, if any.

The concrete shall be compacted and in its final position within 2 hours of the introduction of cement to the aggregates, unless a longer time is agreed by the Engineer. The time of such introduction shall be recorded on the delivery note. When truck mixed concrete is used, water shall be added under supervision either at the Site or at the central batching plant as agreed by the Engineer, but in no circumstances shall water be added in transit. Sampling and testing of the ready-mixed concrete after delivery to Site shall be in accordance with this Specification.

2.3.10 Commencement of Concreting

No concreting shall be commenced in any portion of the Works until the preparations have been approved and written permission given by the Engineer that concreting in such portion of the Works may commence. Adequate notice shall be given to the Engineer when work is ready for concreting to enable him to attend all tests, inspections, checks, etc. as may be necessary.

2.3.11 Transporting of concrete

Concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods, which shall prevent the segregation or loss of the ingredients. It shall be placed as nearly as practicable in the final position to avoid rehandling.

2.3.12 Placing of Concrete

The concrete shall be placed in uniform layers as soon as possible after mixing and before the initial set has taken place. Vibrators shall not be used to spread the concrete in layers from heaps but shall be used for compacting once the concrete is in layers. Once the initial set has taken place, concrete shall not be subsequently disturbed.



The depth of lift to be concreted shall be determined by the Contractor and to the approval of the Engineer. Concrete shall not be thrown or deposited from a height greater than two metres. Where chutes are used in the placing of concrete, they shall be of a design and used at slopes approved by the Engineer. The timetable for the depositing of concrete between construction joints shall be so arranged that no face of concrete shall be left more than 15 to 20 minutes before fresh concrete is deposited against it.

Pause for meals, changes of shifts, etc. and the distribution of the concrete among the positions where work may be proceeding simultaneously must, therefore, be carefully organised to ensure that the above-mentioned interval shall not be exceeded.

The method of depositing concrete underwater shall be to the approval of the Engineer. Concrete shall not be dropped from any height through water. Where bottom-opening skips are used they shall be of such a design that the bottom doors open as the skip is lifted from the surface on which the concrete is being deposited. The skips shall be full and covered with a woven canvas cover. Concrete shall be placed evenly over the whole area enclosed by the shuttering and the order of placing shall be approved by the Engineer. The size of shutters for underwater concreting shall be such that a pour of concrete finishes level with the top of the shutter. Once placed, the concrete shall not be subsequently disturbed and shall not be vibrated or rammed.

All pours of concrete between tide levels shall be carried out in the dry and with such celerity and in such a manner that the top may be blanketed to the approval of the Engineer before being covered by the rising tide. In the case of construction joints, the blanketing shall be replaced immediately after the joint has been cleaned and roughened as specified unless depositing of further concrete follows on the same low tide. Not withstanding the need for speed, all projecting reinforcement, shuttering and joint faces shall be cleaned as specified and the concrete thoroughly compacted.

2.3.13 Compaction

All concrete shall be thoroughly compacted by vibrators during operation of placing to ensure that it is homogeneous. It shall be thoroughly worked around the reinforcement, around embedded fixtures and into the corners of the shuttering. The method of carrying out this work and the number of vibrators to be employed on any particular section of the work shall be to the satisfaction of the Engineer. All vibration shall be carried out under the direction of a specialist supervisor and to a plan approved by the Engineer. No workman shall be allowed to operate a vibrating tool without having received instruction and training in its use. Vibrators shall be immersion-type of approved pattern; they may be electrically or pneumatically driven. Care shall be taken to avoid segregation and excessive vibrating.

2.3.14 Screeding

All surfaces of slabs or other members not required to be shuttered shall be screeded in an approved manner to a smooth and dense finish by means of a wood float or steel shod tamp, unless otherwise specified.



2.3.15 Construction Joints

Construction joints shall be as shown on the Contractor's Drawings or as approved by the Engineer. No additional construction joints shall be provided without the approval of the Engineer, which approval shall only be granted in special circumstances. Kickers and nibs, 150mm depth, shall be formed upon horizontal and vertical surfaces respectively where subsequent lifts and bays of walls or columns are required. On exposed surfaces, construction joints shall be carefully formed to produce a neat straight flush line or, where required, shall be formed with a recessed joint feature. Grout checks 25mm wide and 40mm deep shall be provided at all horizontal construction joints where recessed joint features are not specified. Suitable bonding chases shall be formed in the ends of other surfaces of sections exceeding 200mm thick for the purpose of keying such section to those adjoining. The chases shall be formed over the full length of the joint and shall have sloping sides.

Unless otherwise specified, no slopes shall be allowed in connection with the deposition of concrete. Where it is necessary for any reasons to terminate a bed, such termination shall be against vertical timber shutter stepped as requested and as approved by the Engineer. At construction joints, the shutter shall, whenever practicable, be stripped as soon as possible after pouring, subject to the approval of the Engineer and any skin or laitance removed and the tops of the larger stones exposed by means of brushing and washing. At horizontal construction joints removal of laitance and exposure of the larger stones shall be accomplished, whenever practicable, by means of washing and brushing shortly after pouring, care being taken to obviate undue erosion of the mortar. After cleaning, excess water shall be removed immediately to limit absorption by the concrete. In cases where the concrete has set, but not yet hard, the removal of the laitance and roughening shall be accomplished by wire brushing and washing or by compressed air, care being taken not to damage the underlying mass. Where at either vertical or horizontal joints the concrete has set hard, any skin or laitance shall be removed and the surface roughened by hammering with an approved power-operated "bush" hammer followed by wire brushing to remove all loose particles. When using this procedure, care shall be taken to avoid breaking off the arises of the joint face and loosening the stones from the mortar matrix. Whichever of the above treatments has been given to the exposed surface, it shall be cleaned from foreign matter by further wire-brushing if necessary and shall then be thoroughly washed with clean fresh water and the surplus water blown off immediately before depositing the fresh concrete. Fresh concrete shall be forced hard onto the set faces. To this end, the compacting tools and vibrators where appropriate shall be worked right up to the old faces and into angles and corners formed between them and the shutters.

2.3.16 Movement Joints

Where it is calculated that movement joints are required in a structural reinforced concrete frame, these shall be continuous across the entire cross-section of the frame. That is, wherever the plane of the joint intersects with a member of the frame,



a space for movement shall be created. The space shall be formed by attaching an expanded polystyrene sheet of the appropriate thickness for the required movement of the face of the concrete on the side of the joint cast first and then casting the other side in contact with the polystyrene. The sheet shall fully cover the whole surface of the cast concrete and shall not be penetrated by reinforcement, concrete or anything else. Where possible, the frame on either side of the joint will rest on separate foundations. If this provision brings about a situation where twin columns have a space between them, horizontal members of the frame shall be cantilevered across this space. The joint shall be continued through any element of the building, which might otherwise bridge it, including, masonry walls, floor and roof slab and internal walls, partitions or slabs. The purpose of this shall be firstly to ensure that free movement at the joint is not impaired and secondly to prevent any damage to these elements caused by movement of the joint, which might impair the function, or aesthetics of the building. Where the joint cuts the external weathering of the building, either walls or roof, an approved special treatment shall be devised to ensure that the external skin is completely weather tight and shall remain so for the life of the building. In walls this may mean cutting back the polystyrene to leave a groove to be filled with an elastic sealant which will adhere to both concrete surfaces. In roofs the treatment shall ensure that felt or other waterproof membrane shall not be either torn or crumpled by movement at the joint. This may also involve the introduction of an upstand at the joint. Where the joint cuts tiled flooring or plastered walls, it shall be covered with an approved decorative masking strip which shall be fixed to the floor or wall at one side of the joint only so as to be undamaged by joint movement. The Contractor may propose an alternative material for the joint filler for approval.

2.3.17 Standby Plant

At all times when concreting is being carried out the Contractor shall have readily available on Site sufficient standby plant to cover the operations of mixing, transporting, placing and compaction of concrete in the event of breakdown of plant.

2.3.18 Precautions during Inclement Weather

When the air temperature rises above +300C, special precautions shall be taken, to the satisfaction of the Engineer, to cool aggregates and mixing water and to maintain the correct water/cement ratio, e.g. shading aggregate stockpiles, laying water supply main underground, adding crushed ice to mixing water. Reinforcement and shuttering shall be cooled by shading from the direct rays of the sun and by spraying with water, care being taken to remove surplus water before commencing concreting. Concreting shall not be carried out when the air temperature rises above +380C, or if the temperature of the concrete when placed rises above +300C. During windy weather, approved protection shall be provided to prevent the cement from being blown away during the process of apportioning and mixing. During wet weather, approved precautions shall be taken to protect the cement and to ensure proper mixing. No concreting shall be carried out during periods of continuous



heavy rain.

2.3.19 Curing

(a) Method statements for the curing of all concrete shall normally comply with the following minimum requirements and shall propose effective means of preventing premature drying and the resulting effects of plastic shrinkage.

Where small quantities of concrete are being used, the Engineer may relax the requirements of the following clauses. The Contractor's intentions in this instance shall be clearly indicated in his method statements and approved by the Engineer.

(b) Exposed Surfaces

(i) Exposed surfaces of concrete shall be completely covered with polythene

sheeting with substantial close fitting laps within 20 minutes of placing and compaction, and within two or three hours of this shall quickly be replaced by wet hessian covered with polythene. Polythene sheeting may be temporarily removed for surface finishing where required.

(ii) The hessian shall be kept damp continuously using water of the quality

specified for concreting for a period of at least seven days or such longer period as the Engineer may direct.

(iii) Approved curing compounds may be applied to supplement the use of wet

hessian and polythene.

(iv) In addition to the above measures, shading from direct sunlight and windbreaks may be proposed or may be required by the Engineer to give added protection.

(c) Formed Surfaces (i) Formed surfaces shall be completely covered by wet hessian and polythene

within half an hour of stripping the formwork and shall then be treated in accordance with the requirements for exposed surfaces.

(ii) Formwork shall be shaded and/or continuously wetted to prevent high

temperature accelerating cure.

(iii) For formed surfaces which are to be exposed, effective approved measures shall be taken to prevent concrete surfaces from drying out and to ensure adequate curing whilst rubbing down is taking place and before application of any approved curing membranes or other curing methods.

(d) When shade temperatures exceed 300C in any part of the day or when lower

temperatures in combination with high wind speeds are likely to lead to premature drying, the Engineer may instruct any combination of the foregoing methods to be used.

(e) Curing Compounds

(i) Curing compounds shall be stored and used strictly in accordance with the

manufacturer's instructions.

(ii) Curing compounds shall not be applied to surfaces to which further



concrete or a surface finish is subsequently to be bonded.

2.3.20 Sampling and Testing of Concrete

The sampling, preparation, curing, transport and testing of concrete cubes to ascertain the minimum crushing strengths at 7 days and 28 days shall be carried out in accordance with BS 1881; “Methods of Testing Concrete”.

2.3.21 Works Cube Tests

The Contractor shall be held responsible for ensuring that the crushing strength of the concrete is not less than that specified for the respective qualities. Samples of concrete shall be taken by the Contractor during each major pour where and when directed by the Engineer and six 150mm cubes made therefrom. The cubes shall be cured by the Contractor and then transferred by him to the Site laboratory for testing, 3 cubes at 7 days and 3 cubes at 28 days. The cubes shall be indelibly marked with the Contract identification, serial numbers and the date cast. The cost of operation, curing, marking, handling and transport of cubes shall be deemed to be included in the Contract Price. The cubes shall be tested at the expense of the Contractor. Should the crushing strength prove to be below the figures specified, the Contractor shall make such changes in the proportion or in the method of mixing or in the materials as the Engineer may approve so as to bring the concrete up to the required strength.

2.3.22 Concrete Cores

Where the quality of the finished concrete is considered by the Engineer to be suspect, he may order 100mm or 150mm nominal diameter cores to be cut from the hardened concrete for the purpose of examination and testing. The coring equipment shall be subject to the approval of the Engineer. If the estimated cube strength of any core as determined in accordance with BS 1881 is less than the appropriate specified minimum crushing strength or if in the opinion of the Engineer the concrete fails to meet the specified requirements in other respects, the concrete in that part of the Works shall be deemed not to comply with the Specification. The cost of cutting of the core specimen, preparing it for testing and making good the cored hole shall be borne by the Contractor irrespective of the result of the test.

2.3.23 Reconstruction of Faulty Work

The Contractor, on the written instruction of the Engineer, shall remove and reconstruct at his own cost, any portion of the work, which in the opinion of the Engineer, gives evidence of any fault, defect or injury from any cause whatsoever, which in the opinion of the Engineer may prejudice the strength or durability of the construction. No repairing of any concrete shall be done without the permission in writing of the Engineer and then only in such manner as he shall direct or approve. All concrete surfaces shall be smooth and true. All fins, which may occur between boards or panels, shall be removed and air holes filled with mortar of approved composition and colour. Any area requiring treatment after stripping as outlined above shall afterwards be rubbed down with a carborundum block and washed perfectly clean. No surface treatment shall be carried out until the Engineer has inspected the surface.



2.3.24 Concrete Protection

Concrete protection provided shall be agreed with the Engineer and shall be based on the results of the Site Investigation. The following is the Specification for concrete protection. Concrete surfaces to be protected shall be free from pinholes and other surface defects. The Engineer's approval shall be obtained for any method of repairing surface defects. Any preparatory filling required shall normally be carried out using an approved non-shrinking mortar. Surfaces to be coated with bituminous-based coating shall be wire brushed, either by hand or with power tools. All dust and other loose materials shall be removed. Concrete protection shall be provided for all concrete below ground level. Protection shall consist of a 50mm layer of compacted sand and bitumen mix being cast on the Grade C blinding concrete prior to pouring the foundation concrete. Two coats of bitumastic paint shall be applied to the exposed faces of concrete below ground level in contact with soil. Where spaces are to be left between the underside of suspended ground floor slabs and the ground level below, the underside of slabs and beams and the internal faces of walls enclosing this space shall be painted with 2 coats of approved bitumastic paint. All traces of loose material, laitance, shutter oil, grease, wind blown deposits and other contaminants, which could prevent the proper adhesion of, or result in adverse reaction with the protective system shall be removed from the concrete surfaces to be protected. Blinding concrete prepared for receiving base slab protection shall be free from sharp edges and projections. The surface shall be cleaned by an oil free air blast where practicable or as otherwise directed by the Engineer.

2.3.25 Concrete Finishes 2.3.25.1 General

Where uniformity of colour is required in the surface finish of concrete, each material shall be obtained from a single consistent source. Where surfaces are to be formed using large formwork panels made up from individual plywood or timber sheets, the individual sheets shall have uniform properties of absorption and surface texture. Where a concrete surface is to be permanently exposed, only one release agent from the formwork shall be used throughout the entire area. Release agents shall be applied evenly and contact with reinforcement avoided. Where the surface is to receive an applied finish, care shall be taken to ensure the compatibility of the release agent with the finish. If the Engineer so requires, a trial pour shall be made to test the suitability of the materials and techniques to be used.

2.3.25.2 Classification of Finishes

Finished concrete surfaces shall be classified in accordance with the class listed below. The class of finish required shall be shown on the Drawings.



Class Ul - Unformed Finish ("Screeded") This finish shall be required for the surface of roads, foundation, bases, slabs and structural units to be covered by backfill, subsequent stages of construction, bonded concrete toppings or mortar beds, and also for exposed surfaces of pavings where a superior finish is not required and as the first stage for finishes U2 or U3. It shall be obtained by levelling and screeding the concrete to produce an even, uniform, plain or slightly ridged surface without laitance, surplus concrete being struck off by a straight edge immediately after compaction. Class U2 - Unformed Finish (“Floated”)

This finish shall be required for the surface of beds and slabs intended to receive further finishes or for exposed surfaces where a steel-trowelled finish is not required. Floating shall be done only after the concrete has hardened sufficiently and shall not be continued to the extent of bringing excessive fine material to the surface, but only so as to produce a uniform surface free from screed marks, and within any tolerance stated or implied for the thickness of bedding or bonding material. Class U3 - Uniformed Finish (“Steel Trowelled") This is a hard smooth finish which shall be required for surfaces of high quality concrete pavings, tops of walls coping and unformed surfaces of architectural features (including precast units), for surfaces of beds and slabs to receive thin flexible sheet and tile pavings bedded in adhesive, and seatings for metal items where the metal is in direct contact with the concrete. Trowelling shall not commence until the moisture film has disappeared and the concrete is sufficiently hard to prevent the working of excess laitance to the surface. The surface shall be trowelled firmly and left free from trowel marks. Class U3 finish may be produced by power floating of concrete subject to the requirement that such work is carried out by experienced and skilled workmen.

2.3.25.3 Tolerances

The permissible tolerances in finished surfaces shall not exceed the limits shown in Appendix A to this Clause or as otherwise specified by the Engineer.

2.3.26 Formwork 2.3.26.1 Formwork Generally

Formwork shall include all temporary or permanent moulds and shutters for forming the concrete, together with all construction required for their support.

2.3.26.2 Design and Construction

Formwork shall comply with the requirements of BS 5975, "Code of Practice for Falsework".

The Contractor shall provide such details of the formwork and supports as the Engineer may require in sufficient time to permit the design to be checked before the formwork is used.



The use of proprietary type shuttering systems shall be subject to the Engineer's approval. Full details of the proposed use of such systems shall be submitted to the Engineer. Through struts or ties shall not be permitted in water retaining structures. Formwork (including supports) shall be sufficiently rigid to maintain the forms in their correct position and to correct shape and profile so that the final concrete structure is within the limits of the dimensional tolerances specified. Formwork shall be designed and constructed so that concrete can be properly placed and compacted by vibration or otherwise without loss of material and so that the concrete shall set and harden without injury.

2.3.26.3 Preparation

Formwork shall be cleaned before each use. Form release agent shall be to the approval of the Engineer. They shall be applied carefully and sparingly and shall not be allowed to come in contact with concrete surfaces or with items (including reinforcement), which are to become bonded to the concrete. Formwork with damaged edges or faces shall not be used until repaired to the approval of the Engineer. Open joints in timber forms shall be sealed. Plywood surfaces and cut edges shall be sealed to prevent the absorption of moisture. Immediately before concreting, the forms and all other surfaces which shall be in contact with the fresh concrete shall be cleaned of loose materials and debris including shavings, woods chips, sawdust, piece of wire, nails, foamed plastic, fragments of hardened concrete and mortar. Adequate clean-out holes shall be provided for this purpose and subsequently securely closed so as to restore the required formwork quality. The use of compressed air for cleaning shall be subject to approval or precautions to avoid the deposition of suspended oil on construction joint surfaces, reinforcement, or other items, which are to be bonded to concrete.

2.3.26.4 Striking and Removal

The removal of formwork shall be subject to the permission of the Engineer. Striking of formwork shall be in accordance with BS 8110.

2.3.27 Permanent Formwork

The use of proprietary type permanent shuttering system for suspended slabs shall be subject to the Engineer's approval. The erection and use of such system shall be in strict accordance with the manufacturer's instruction. Permanent shuttering will normally have a ribbed profile and manufactured from galvanised steel. Temporary propping where required shall be in accordance with the manufacturer's instructions and the Engineer's consent shall be sought before removal. Care shall be taken in the use of such system to ensure that the appropriate fire resistance rating is provided. The steel sheets shall be placed in bundles at the manufacturer's work and wrapped with a waterproof cover. Care shall be taken to ensure that this cover is not punctured there or damaged in any way during transport to the Site of the work and that it remains intact until the sheets are to be used. In general, the use of profiled steel sheets in concrete slabs shall be in accordance



with BS 5950, Part 4.

2.3.28 Holding Down Bolts and Embedded Fixtures

Holding down bolts and holding bolt assemblies shall be provided with bottom nut welded to the bolt shank and fixed to the anchor plate, channel or angle. Threads of holding down bolts shall be protected with a cold applied petroleum based anti-corrosion and sealed tape or similar material approved by the Engineer, during delivery and storage. After concreting, the bolt projections with attached nuts and washers shall be protected against corrosion with similar sealing tape and protected against mechanical damage with a timber shield or as otherwise approved until the erection of the steel works or other plant or fixtures commences. Holding down bolts, embedded fixtures and recesses shall be located in the correct position by means of timber templates or as otherwise approved and shall be held rigidly in position during concreting. Particular attention shall be directed to the placing of reinforcement around bolt assemblies and embedded fixtures. Holding down bolts and holding down bolt assemblies shall be located in the position shown on the Contractor's Drawings, and in the absence of locating tolerances on the Drawings, shall be located to the following accuracy:

Bolt Diameter Tolerances Up to l2mm +5mm l3mm to32mm +7mm 33mm and over +10mm 2.3.29 Reinforcement 2.3.29.1 Reinforcement Steel

All reinforcement shall comply with BS 4449, 4482 and 4483 or other approved Standards, and shall be tested as required by Engineer. Type of reinforcement shall be denoted by suffix in accordance with BS 4466.

2.3.29.2 Storage

Reinforcement shall be stacked on the Site, separated into the various sizes on timbers so that the steel is kept clear of the ground and free from mud, oil, grease and other contamination.

2.3.29.3 Bending

Reinforcement shall be bent in accordance with BS 4466 “Bending Dimensions and Scheduling of Bar for the Reinforcement of Concrete”. Bars shall be bent cold in such a manner that the material is not injured in any way. Bent bars ready for fixing shall be stored in bundles marked with a number corresponding to the bar list on the bending schedule. Bars shall be bent accurately and checked from time to time. Temporary bending and subsequent straightening of reinforcement shall be avoided whenever possible. When permitted by the Engineer, this shall be carried out at the ambient temperature and the internal radius of such bends shall be in accordance with BS 4466. Reshaped steel shall be inspected for signs of fracture. Steel showing signs of fracture shall be rejected and removed from Site.



2.3.29.4 Fixing

Concrete cover to reinforcement shall be as follows and as agreed with the Engineer.

Foundations 40mm Columns External 40mm Beams External 50mm Beams Internal 35mm

Columns Internal 35mm Slabs External 40mm Slabs Internal 35mm

The suffit of all ground floor slabs whether or not in contact with the ground shall be deemed an external surface and cover to the reinforcement shall be 40mm. In no case shall the cover be less than specified or exceed the specified cover by more than 5mm for concrete up to 300mm thick or not more than 10mm for concrete over 300mm thick. Bars, which intersect or pass over each, shall be securely wired together at the point of intersection with 18 or 20 SWG soft iron wire. Small concrete blocks specially precast to give the correct cover shall be used to ensure cover on ground centring and slab shuttering and elsewhere as considered necessary. They shall be made of mortar not leaner than 1 part of cement to 2 parts sand. Other suitable methods approved by the Engineer may be permitted. Support chairs for reinforcement shall be designed by the Contractor and approved by the Engineer. The use of proprietary type spacers or couplers shall be subject to the Engineer's approval, and full details of proposals for their use shall be submitted at least 4 weeks in advance of fixing reinforcement. Welding of reinforcement shall be subject to the Engineer’s approval. The Contractor shall submit to the Engineer complete details of proposals to weld reinforcement at least eight weeks in advance of fixing reinforcement. All reinforcement shall be cleaned free of salt depositions, loose mill scale and rust, grease, set mortar or other harmful matter, by power brushing or acid dipping if necessary. In particular the Contractor shall ensure that such reinforcement is protected against chemical deposits at all stages of the work until the concrete is poured. Placed reinforcement shall be checked against the relevant Drawings before concreting is permitted.

2.3.30 Precast Concrete

Units shall be provided by an approved Supplier, who shall submit details of the design and manufacture for approval by the Engineer. The quality of the finish shall be U3 and comply with Clause 2.3. of this Specification and as required by the Engineer. Precast kerbs, bricks, blocks, sills and lintels shall comply with BS 6073 or BS 7263. The concrete ingredients, grades, mixes, strengths, general quality, testing, mixing, placing and curing shall be generally as described in the Specification. The surface of



the finished units shall be smooth, dense and hard with clean sharp arises (except where otherwise indicated), and shall be free from cracks, crazing, discolouration, holes, fins, honey-combing, water-marks, dusting or shutter-marks. Units shall be manufactured and cured in a properly equipped casting yard or shop and the arrangements shall be subject to the inspection and approval of the Engineer. The Contractor shall give adequate notice to the Engineer before dispatching precast units to the Site, and if the Engineer so requires, shall provided facilities for inspection, test - loading and dimensional checking of the units before they are dispatched. In the case of units constructed in a factory or yard remote from the Site, details of the concrete ingredients, mix design, and compression test cube results shall be made available to the Engineer.

TOLERANCES

TOLERANCES mm TYPE OF

STRUCTURE TYPE OF

IRREGULARITY TYPE OF FINISH

FORMED UNFORMED 1 2 3&4 1 2 3&4

Departure from line and level

+20-10

- -

-

+10

-

-

Variation in cross section dimensions

+10-5

-

-

-

-

Abrupt ±10 - - ±10 - -

Buried Concrete in foundations, culverts, retaining walls, etc.

*Deviation from template in long dimensions

±10

-

-

±10

-

-

Departure from line and level

±10

±10

±10

-

±5

±3

Variation in cross section dimensions

±10 -5

±10 -5

±10 -5

-

-

-

Abrupt ±5

±5

±3

-

±5

±3

Exposed concrete in columns, pipes, retaining walls, abutments, etc.

*Deviation from template in long dimensions

±10

±10

±5

-

±5

±3

Departure from line ±10 - - - - -

Departure from longitudinal level

-

-

-

±3

-

-

* Departure from transverse cross section template

-

-

-

±3

-

-

Deviation from md straight edge on longitudinal section

-

-

-

±3

-

-

Roads and Paving

* Template for Formed Finishes shall be 1.5m long. Template for Unformed Finishes shall be 3.0m long.



2.4. STRUCTURAL STEELWORK 2.4.1 Materials

Except where noted or agreed otherwise the particular grade of steel used shall be determined in accordance with the design standard BS 5950 or approved equivalent standard. All steel in plates and sections shall comply with BS 4360 or similar approved standard. Structural hollow sections shall be hot rolled in Grade 43C to BS 4360. Welded cold-formed structural hollow sections shall not be used unless agreed by the Engineer. Identifying marks for the different grades of steel shall be provided in accordance with BS 4360. Except in the case of special plate with through thickness properties guaranteed by the manufacturer all plates and sections 40mm or over in thickness shall be ultrasonically tested for laminations and shall meet the requirements of grade L4 of BS 5996. The Engineer may specify that other plates be ultrasonically tested and unless otherwise specified they shall meet the requirements of grade L4 of BS 5996. Dimensional tolerances of (i) rolled sections shall comply with BS 4, BS 4848 and (ii) plates and flats shall comply with BS 4360. Electrodes for metal arc welding shall comply with the requirements of BS EN 4910. Ordinary bolts and nuts shall comply with BS 3692, BS 4190. Unless otherwise agreed with the Engineer ordinary bolts and nuts shall be grade 8.8. High strength friction grip bolts, nuts and washers shall comply with BS 4395 Part 1.

2.4.2 Certification

Two copies of manufacturers test certificates and mill certification verifying that the materials comply with the relevant British Standards or approved equivalent standards shall be submitted to the Engineer for all structural steel, bolting materials and welding consumables.

2.4.3 Drawings

For all structural steelwork the Contractor shall prepare the necessary arrangement drawings and shop drawings for fabrication and shall be fully responsible for checking the accuracy of these drawings. The general arrangement drawings shall be to such a scale that identifying numbers for each member are clearly shown. Shop drawings shall indicate all connections, welds, fabrication details, identifying mark numbers and other pertinent data. Four weeks in advance of fabrication three copies of checked shop drawings and connection design calculations shall be submitted to the Engineer for approval. Such approval shall not relieve the Contractor of the responsibility for the accurate detailing and fabrication of members and for proper assembly at the time of erection.

2.4.4 Inspection

The Contractor shall afford all facilities for the inspection of the work at all stages by the Employer at the fabrication works.



2.4.5 Fabrication

Construction and fabrication shall be in accordance with the requirements of BS 5950 or similar approved standard. The fabrication and workmanship shall be to the best modern practices and shall comply to the requirements of BS 5950 Part 2 or similar approved. Only qualified fabricators shall be engaged for the work. All measurement shall be made by a steel tape related to a standard tape, which has been certified to be correct at 200C. The tape and the steel to be measured shall be at the same temperature and proper precautions shall be taken to tension the tape correctly. All plates, bars and sections shall be flat, straight and free from twist within the tolerances specified in the relevant approved standard, unless more stringent tolerances are specified. Any flattening or straightening necessary to achieve the required tolerances or to satisfy fit-up requirements shall be carried out before any other work is done on that item. Flattening or straightening shall be done by approved mechanical means and shall be carried -out such as not to deface or weaken the material.

Steel may be sawn, sheared, cropped or machine flame cut. Sheared member shall be free from distortion. The Contractor shall carry out procedure trials for machine flame cutting; such procedures shall be to the approval of the Engineer. Where it is impractical to use machine flame cutting, the use of hand cutting shall be subject to the approval of the Engineer, who may require dressing or other treatment of the cut edges, depending on the details of the joint or member. Where notches are necessary they shall have smooth radial internal corners, produced by drilling holes not less than 20mm diameter before cutting the rest of the notch or by carefully controlled flame cutting. All burrs left by sawing, cropping or shearing shall be removed before fabrication or assembly. All sharp arises shall be removed by light grinding. The Contractor shall inform the Engineer of members on which he will be using shearing or flame cutting and in cases where steel so cut is specified as being subject to dynamic or fatigue loading or liable to brittle fracture, the sheared or flame cut edges shall be machined to a depth to be agreed by the Engineer. The ends of compression members at splices, caps or bases dependent on contact for the transmission of compressive stress shall be prepared so that butting faces fully satisfy the design requirements. Base and cap plates and other bearing surfaces shall also be prepared to the same standard. For parts -to be machined at least 3mm in excess of the finished size or thickness shall be allowed for machining. The ends of all members shall be truly square, where required. Members shall be adequately supported in both the vertical and horizontal planes during cutting or machining to ensure that the prepared ends are square to the axis of the member. All plates 25mm thick and over which are to be connected using H.S.F.G. fasteners shall be checked for "bowing" or "ripple": if these defects are present they shall be eliminated before despatch to site.



In H.S.F.G. connections all surfaces, which have been machined, shall be grit blasted in such a way as to provide the design slip factor. The ends of fitted plates and stiffeners shall be accurately sawn or sheared and ground to fit tightly between the flanges or parts to be stiffened. The maximum gap shall not exceed 0.25 mm. Any structural connection shall be either welded or bolted and no mixed connections shall be allowed. Drainage holes shall be provided in members where water could collect during and after erection. To facilitate grouting, holes shall be provided in stanchion bases for the escape of air.

2.4.6 Holes

Holing shall be in accordance with BS 5950 Part 2 or equivalent approve standard. Holes for friction grip bolts shall be in accordance with BS 4604 Part 1 or equivalent approved standard. All burrs and rags shall be removed. All holes shall preferably be drilled but punching of holes in accordance with procedures to the satisfaction of the Engineer shall be permitted. Circular holes for bolts and rivets shall not be flame cut. Slotted holes shall either be punched in one operation or else formed by punching or drilling two round holes and completed by high quality flame cutting and dressing to ensure that the bolt can travel the full length of the slot freely. Holes through more than one thickness of material in built-up sections shall, where possible, be drilled after the members are assembled and tightly clamped or bolted together. Punching may be permitted before assembly, providing the holes are punched 2mm less than the required diameter and reamed after assembly to the full diameter. Holes in members built up by welding shall be drilled after welding has been completed.

2.4.7 Welding

Metal arc welding of steel to BS 4360 shall be in accordance with the requirements of BS 5135 or other equivalent approved standard. All welders shall be suitably qualified and experienced for the work on which they are employed and shall have satisfied the relevant requirements of BS EN 287-1 or BS 4872 Part 1 as appropriate. The Contractor shall provide to the Engineer valid certification that all welders working on the Contract have passed the appropriate test. The Engineer and Employer reserve the right to have any welding operator tested at any time. Welding shall be carried out under the supervision of a competent and experienced welding superior. The Contractor shall keep records to enable all main welds, in particular butt welds, to be identified with the welder responsible for production. Such records shall be made available to Engineer, immediately on demand. Fillet welds shall be continuous to form a complete seal where two members join. All butt welds shall be complete penetration butt welds. Full throat thickness at the ends of main butt welds shall be obtained by the use of run on/run off pieces on either



side of the main plates. Welding electrodes shall give a weld deposit with mechanical properties not less than the minimum specified for the parent metals in the joint. The Contractor shall agree with the Engineer testing procedures and the quantity of testing to be carried out.

2.4.8 Bolting

The use of bolts, including permissible stresses, size and pitch of bolts shall comply with the requirements of BS 5950 or equivalent standard. All bolts, nuts, and washers other than H.S.F.G. bolts shall comply with the requirements of Grade 8.8 to BS 3692. Ordinary bolts shall be provided with a washer under the nut, unless otherwise agreed. Washers shall be tapered or otherwise suitably shaped to give nuts and heads of bolts a satisfactory bearing. The threaded portion of bolts shall be outside the parts bolted together and the ends shall protrude by not less than 2 full threads through the nut after tightening. H.S.F.G. bolts shall be used for site connections as shown on the drawings and in accordance with B5 4604 or equivalent approved standard. Only one system of H.S.F.G fastening shall be used in the Works.

Particular attention shall be directed to the correct sequence of tightening bolts in large connections. Bolts provided with load indicating devices shall be tightened in accordance with the manufacturer's instructions using power-operated spanners, equipped with torque limiters. H.S.F.G. bolts shall not be used as service or temporary bolts or in any connections bolted in the fabricator's yard. Any H.S.F.G. bolts, which have to be loosened, shall in no circumstances be re-used.

2.4.9 Local Marking/ Delivery

All steelwork shall be marked with identification marks in accordance with the number marking plans, before leaving the Contractors Works. The marks shall include the building/structure, the location within the building/structure and the serial number of the member. Erection marks shall be painted on in a visible position. Before despatch for galvanising fabricated steel shall be die stamped with the erection mark. All members weighing over 5 Tonnes shall have the weight marked thereon. The centreline of all compound columnS, trusses, beam bearings, etc., shall be scribed on the steel to ensure correct alignment and assembly. Steelwork shall be transported, handled and stacked (clear of the ground) in an approved manner so as not to overstress or in any way damage the members.

2.4.10 Erection

Steelwork erection shall be in accordance with BS 5950 or equivalent approved standard. Erection of steelwork shall be carried out in a safe manner in accordance with all relevant Safety, Health and Welfare legislation and taking account of the recommendations of BS 5531 or equivalent approved standard.



The steelwork erector shall employ on erection only such persons as are skilled and experienced in steelwork erection. A competent Engineer shall supervise them on the site. Steelwork in course of erection shall be securely bolted or otherwise connected together and if necessary provided with temporary bracing or effectively anchored steel guy ropes to resist all dead loads, loads due to erection equipment and the operation thereof and all lateral loads including wind. Temporary bracing and guy ropes shall be left in position and maintained for as long as is necessary to ensure the safety of the structure. Each part of the structure shall be aligned as soon as practicable after it has been erected. No permanent bolting or welding shall be carried out until as much of the structure as will be stiffened thereby has been brought into correct alignment. No straining into position will be allowed after the permanent connections have been made. The Contractor shall be responsible for the correct alignment and level of all steelwork and for the accurate plumbing of stanchions. The alignment, level and plumb of the steelwork shall be in accordance with the following tolerances unless superseded by more stringent tolerances dictated by installation and operation e.g. overhead maintenance cranes. (i) Position - permissible deviation of the erected +5mm column/support member from its specified position (ii) Level - permissible deviation between erected + 3 mm column base, column cap, beam, truss and specified level. (Level of beam should be taken on top of upper flange)

(iii) - -Plump permissible deviation from vertical +5mm

per 15m of height.

Maximum deviation in 45m or over + l5mm 2.4.11 Inspection

Contract Price shall be deemed to include for providing the necessary access ladders and facilities therefore and attendance on Engineers staff engaged in inspection work.

2.4.12 Protective Coatings 2.4.12.1 General

All structural steel work shall have approved corrosion protection systems applied to give a life to first maintenance of 20 years (minimum). Corrosion protection systems shall be appropriate for the environmental conditions.

The Tenderer shall include in the Technical Schedules its proposed corrosion protection system and procedures for structural steelwork, for the different environments.



2.4.12.2 Materials

Paints used shall be of the best quality suitable for tropical use and of a proprietary brand approved by the Engineer. The Contractor shall forward technical data sheets for all materials to the Engineer. These technical data shall give product information as listed in Appendix A to this Specification. All paint products and thinners shall be delivered to the place of application in sealed containers, clearly labelled, identifying the manufacturer, formulation, colour, batch number, date of manufacture, shelf life, pot life, mixing instructions and method of use.

Paints shall only be thinned in accordance with the manufacturer's instructions. All products shall be stored in properly ventilated and temperature controlled premises in accordance with the manufactures instruction. When the shelf life limit is reached the materials shall be removed from the place of application and discarded. Products shall be stored in such a manner that the material stored longest will be used first. Products, which have livered, gelled or deteriorated in any way during storage, shall not be used. Materials, which can be restored to normal consistency by stirring, will be accepted, provided that they have not exceeded the recommended shelf life. Immediately prior to application products shall be thoroughly stirred with a power mixer for a time sufficient to thoroughly remix the constituents, except where this would be contrary to the manufacturer's instructions (for example with thixotropic paints). If the product is a two-pack system then the manufacturer's instructions shall be strictly adhered to in respect of mixing and the maximum length of time the material may be in the pot before application. Under no circumstances may materials be used after the recommended pot life has elapsed.

2.4.12.3 Working Conditions/Safety

It shall be the responsibility of the Contractor to ensure that all relevant statutory legislation is complied with and that all precautions required to avoid risk to health and safety are carried out in the application of protective coatings, painting and all associated activities.

2.4.12.4 Surface Preparation

All surfaces to be coated shall be free of scale, rust, grease, oil, dust and other deleterious materials. Steelwork shall be blast cleaned to remove all miliscale and other contamination to BS 70710. The surface finish shall be to visual standard SA 21/2 in accordance with SIS 055900. The abrasive used during blast cleaning shall be steel, malleable iron or chilled iron shot of a grading suitable to give maximum surface amplitude of 100 microns. Abrasive shall be selected in accordance with BS 2451 and BS 7079 Table 2. Sand blasting shall not be used. All surface defects likely to be detrimental to the protective system such as cracks, surface laminations and deep pitting, shall be removed in accordance with BS 4360. Fabrication surface defects such as fins at saw cuts and burrs shall be similarly removed. All dirt and debris shall be removed from surfaces after blasting, by vacuum cleaner, airline or brush. If residues are trapped in the paint the affected area shall be re-blasted and recoated. All shop weld areas and shop bolted or riveted connections shall be blast cleaned to the same standard as adjacent steel. All weld slag and spatter shall be removed. Blast cleaned surfaces shall be over coated within four hours of the start of cleaning,



and the steel shall not be exposed out of doors during this period.

2.4.12.5 Connections using H.S.F.G Bolts

Under no circumstances shall the friction contact surfaces be painted, greased etc. Friction contact surfaces shall have an approved robust masking material securely applied before the application of any priming, painting coats.

Prior to erection all friction surfaces shall be thoroughly cleared with an approved solvent and shot blasted to give the design slip factor.

2.4. 12.6 Structural Steelwork Components Encased in Concrete

Steelwork to be encased in concrete and other surfaces in contact with concrete shall be unpainted. Such surfaces shall be cleared to remove oil, grease and chemicals, which may be adhering to the surfaces. The surfaces shall be blast cleaned or wire brushed to remove loose mill scale, rust and dust particles.

2.4.12.7 Painting Procedures

Before the work commences the Contractor shall supply the Engineer with samples, if required, of all paints for testing by an approved testing laboratory and painting shall not commence until paints have been approved. During the course of the Contract the Engineer shall have the power to take samples from paint in use on any part of the job for testing by an approved testing laboratory.

Paint shall be stored in a lock-up store where the temperature shall be between 50C and 300C. Any storage conditions specified by the manufacturer shall be observed, and all materials shall be used as delivered and within 12 months from date of manufacture. All paint shall be applied in accordance with the manufacturer's instructions and to the Engineer's approval. Paint may be applied by brush, roller, or airless spray equipment, provided the specified dry film thickness of the coating system is obtained and the manufacturer's instructions are observed. Spraying equipment shall be so designed and operated as to achieve a coat of specified minimum thickness and free from surface defects especially craters, pinholes, ravelling, sagging, dry patches, etc., with an even and uniform appearance and complete adhesion. The Engineer may require to witness a demonstration of the proposed procedures before work commences. The dry film thickness shall be checked by the use of an approved thickness tester. Where practicable, tracer coats shall be used in priming coats and undercoats. The convention and specification for the various coats shall be agreed before painting commences and shall comply with the paint manufacturer's recommendations. The build up of paint in boltholes shall be avoided by good painting practice. The surface shall be dry immediately before primer or coating is applied and shall be protected from moisture for as long as it is necessary for the coating to harden, set or cure to such an extent that it can be wetted without adverse effect. If heating or ventilation is employed by the Contractor to secure suitable conditions to allow work to proceed, care shall be taken to ensure that treatment of a local surface



area does not cause adverse conditions on other surfaces.

Painting shall not be carried out when:

(1) The humidity in the vicinity of the surfaces is such that condensation could readily occur on the surfaces either immediately, before or during application or when the humidity could have a detrimental effect on the work or when the relative humidity is above 90%.

(2) The wet paint film could be damaged by wind-blown sand or dust; and

(3) Conditions obtain which in the opinion of the Engineer are detrimental to good

workmanship.

2.4.12.8 Painting

Except for galvanised surfaces all steelwork shall be blast cleaned to BS 4232 (1967), second quality finish with amplitude not exceeding 50 microns. Before priming, surface defects such as cracks, surface laminations, deep pitting, fins at saw cuts, burrs, sharp edges, etc, shall be removed. Where extensive grinding has been necessary the dressed areas shall be re-blasted to remove all rust and provide an adequate paint key. The required paint treatment is:

(i) Within one hour of blast cleaning all surfaces shall be primed with one coat of

two-component epoxy/polyamide primer containing zinc phosphate with solids by column and specific gravity or not less than 48% and 1.3 respectively, to a dry film thickness of 50 microns.

After priming if any abrasive particles are found under or embedded in the paint film the affected area shall be re-blasted and re-primed. After priming, rough surfaces shall be filled with approved two component filler and rubbed down to a smooth finish. The affected area shall be re-primed if necessary.

A two-component polyamide cured epoxy high build intermediate coat with a solids by volume and specific gravity of not less than 55% and 1.3 respectively, shall then be applied to a dry film thickness of 80 microns.

Finally two coats of two-component epoxy/polyamide enamel finishing paint with high resistance to impact and abrasion with solids by volume and specific gravity of not less than 40% and 1.0, respectively, shall be applied to a dry film thickness per coat of 40 microns.

2.4.12.9 Galvanising

All galvanising shall be carried out by the hot dip process and shall conform to BS 729 or equivalent approved standard. Attention shall be paid to the detail design of members in accordance with BS 44710. Adequate provision for filling, venting and draining shall be made for assemblies fabricated from hollow sections. Vent holes shall be suitably plugged after galvanising. All surface defects in the steel including cracks, surface laminations, laps and folds shall be removed in accordance with BS 4360. All drilling, cutting, welding, forming and final fabrications of unit members and assemblies shall be completed before the



structures are galvanised. The surface of the steelwork to be galvanised shall be free from welding slag, paint, oil, grease and similar contaminants.

The minimum average coating weight shall be as specified in Table 1 of BS 7210. Structural steel items shall be initially grit blasted to BS 7079, second quality (SA 2.5). On removal from the galvanising bath the resultant coating shall be smooth, continuous, free from gross surface imperfections such as bare spots, lumps, blisters and inclusions of flux, ash or dross. During off-loading and erection the use of nylon slings shall be employed. Galvanised work, which is to be stored in works or on site shall be stacked so as to provide adequate ventilation to all surfaces to avoid wet storage staining (white rust). Any areas of the galvanised coating damaged in any way shall be repaired by: (i) Cleaning the area of any weld slag and thoroughly wire brushing to give a clean

surface. (ii) The application of two coats of zinc-rich paint, or the application of low melting

point zinc alloy repair rod or powder to the damaged area, which shall be heated to 3000C.

After fixing, bolt heads and nuts shall receive two coats of zinc-rich paint. In connections where galvanic corrosion may occur, suitable isolating membranes to the approval of the Engineer shall be used.

2.4.12.10 Bolts Nuts and Washers

Bolts, nuts and washers shall be hot dip galvanized, and subsequently centrifuged, in accordance with BS 7210. Nuts shall be tapped oversize such that after galvanizing the nut can be hand turned on the bolt for the full depth of the nut. The bolt manufacturer shall carry out galvanizing of high strength friction grip (H.S.F.G) bolts nuts and washers.



STRUCTURAL STEELWORK SPECIFICATION

APPENDIX A (Paint system proposed)

The Contractor shall submit the data requested on the sheet following for the Project Manager’s approval. Failure to submit the data in full will result in delay in obtaining approval for the paint system proposed. Information to be included in Contractor's submission for approval of any paint system.

1. Scope of use

2. Type of product

3. Composition with % of solids

4. Mixing ratio for two-pack materials

5. Pot life

6. Method of application

7. Covering capacity

8. Thickness of dry and wet films

9. Drying time

10. Flash point

11. Colours

12. Packing

13. Solvent type

14. Final appearance (gloss, matt, etc.)

15. Health and safety precautions

16. Storage conditions and shelf life 17. Spay application: nozzle characteristics

(diameter and spray-angle), pressure.

18. Minimum and maximum application temperatures

19. Resistance to heat



2.5 WATER SUPPLY

2.5.1 Quality

All materials and equipment to be incorporated into the finished work shall be new, undamaged, free of defects, and fully operational as applicable. No damaged, defective or inoperable materials or equipment shall be installed or allowed to remain in the finished work if discovered after installation. Where required by the specifications or when requested by the Engineer, the Contractor shall submit certified test results showing that the materials to be incorporated into the work meet the Specification requirements. Certifications or test results so required by the Specifications shall be submitted prior to installation of the materials into the work.

2.5.2 Handling of Pipes and Accessories

The Contractor shall unload, handle and distribute the materials at locations opposite or near the places along the trench where they are to be installed. The materials shall be handled with care at all times to avoid damage, and whether moved by hand, skidway or hoist, the materials shall not be dropped or bumped. Pipe shall be handled so as not to damage the machined ends. Pipe damaged such that it cannot be repaired to the Engineer’s satisfaction shall be removed from the Site and replaced at the Contractor's expense. The interior and machined ends of pipe and fittings shall be kept free of dirt and foreign matter at all times and shall be drained and stored prior to installation in a manner to protect them from damage.

2.5.3 Pipes and Fittings

Pipes and fittings for water supply shall be in accordance with the following Standards: Polyethylene Pipes BS 1972 Cold Water uPVC Pipes B5 3505, BS 4346 Asbestos Cement Pressure Pipes BS 78, BS 1211, BS 2035 BS 4772, B5 143 Steel Pipes and Fittings BS 534 Cast Iron Valves BS 5163

2.5.4 Excavation

Trenches for water mains shall be excavated in accordance with the provisions of Section 1 of this Specification.

2.5.5 Laying and Jointing

Pipes shall be laid and jointed in accordance with BS 830l. Pipes for water mains shall be laid true to line and level. Pipes shall be carefully cleaned of all foreign matter before laying, and ends, which are not connected immediately, shall be kept plugged until the joints are made. Any coating or sheathing, which has been damaged, shall be made good and shall be continued over joints if required. Steel, cast-iron or spun-iron pipes shall have spigot and socket joints and shall be joint



systems comprising of jointing rings compressed inside an enclosed sleeve. Flanged joints shall be made with jointing rings of approved materials and the nuts on the joint bolts shall be tightened carefully and symmetrically so as to compress the ring only sufficiently to withstand the test pressure.

2.5.6 Testing

All pipes and fittings shall be tested at the works before dispatch to ensure compliance with this Specification and, after laying and jointing, the main shall be carefully filled with water so as to expel all air and then tested under pressure appropriate to the class of pipe in accordance with BS 8301.

2.5.7 Backfilling

When the permission of the Engineer has been obtained the trench shall be carefully backfilled in accordance with this Specification.

2.5.8 Cleaning

Before the main is placed in service, it shall be thoroughly flushed with clean water to the approval of the Engineer.

2.5.9 Anchor Blocks

Anchor blocks comprising Grade C concrete shall be provided at bends where required, or as directed by the Engineer. They shall be so located as not to impair the flexibility of joints, where affording adequate restraint to the pipe.

2.6. DRAINAGE WORKS 2.6.1 General

The Contractor shall be fully responsible for the design and installation of all drainage systems. All drainage work and discharge quality shall be in accordance with national and local statutory requirements of Ghana. The Contractor shall be responsible at all times during the construction and up to the end of the Maintenance Period for ensuring that all drainage work is kept in working condition at all times. All pipes shall be cleaned inside and tested for soundness and inspected for defects before being laid. Any defective, damaged or unsound pipes shall be rejected. Pipes shall be laid true to design gradients and in straight lines. Each pipe shall bear evenly on the prepared bedding material, for the full length of the barrel. The bedding material shall be in accordance with the design requirements and the pipe manufacturer’s instruction.

2.6.2 Drains and Sewers 2.6.2.1 Pipes and Fittings

Pipes and fittings shall be in accordance with the following standards: Asbestos-cement pipes BS3656, Clayware sewer and drain pipes BS65



Concrete sewer pipes BS5911 Concrete surface water pipes BS5911 Cast Iron S & S pipes BS437 Vertically cast iron pipes and fittings BS7 Chemically resistant clayware pipes BS65 Fittings for clay pipes BS65 Clay drain pipes and fittings BS65 Prestressed concrete pipes BS5911 Concrete pipes and fittings with ogee joints BS5911 Unplasticised PVC underground drain pipes and fittings BS5481 GRP pipes and fittings BS5480 Unplasticised P.V.C. pipes and fittings for gravity sewers BS4660 Pitch fibre pipes BS2760

All pipes and fittings shall be checked for soundness before laying. Pipes shall be delivered, handled and stored in accordance with manufacturers' recommendations or, in the absence of any recommendations, in such a manner as to protect them from damage, distortion or deterioration. The use of pipes and fittings containing asbestos shall be subject to the Engineer's written approval, and shall comply with all relevant safety regulations.

2.6.2.2 Excavation

All excavation for pipe trenches shall be in accordance with this Specification. Excavations for sewers, drains, gullies and manholes shall be carried out to the lines and levels shown on the drawings. The Contractor shall maintain pipe trenches pumped out, protected with safety barriers and well supported where necessary and shall not open up trenches and leave them to fill with water without the written permission of the Engineer. Where solid rock is encountered at invert level it shall be removed to a depth of 150mm below the bottom of the pipes and replaced with 150mm of compacted granular fill to the approval of the Engineer.

2.6.2.3 Laying and Jointing

Earthenware and concrete pipes shall be laid true to line and level with the sockets leading uphill and each pipe shall be separately boned between sight rails in accordance with British Standard BS 8301: Building drainage pipes shall be jointed in accordance with BS 8301. The same pipe manufacturer shall supply rubber rings used for jointing pipes. The use of special joints shall be subject to the approval of the Engineer. Cast iron pipes shall be laid and jointed in accordance with BS 8301. The use of special joints shall be subject to the approval of the Engineer.



Pitch-fibre pipes shall be laid and jointed in accordance with BS 2760. PVC pipes shall be laid and jointed in accordance with BS 8301. Other types of pipes shall be laid and jointed in accordance with the manufacturer's recommendations as approved by the Engineer. Connections to existing sewers and manholes shall be carried out in accordance with 8301.

2.6.2.4 Testing

No work shall be covered or surrounded with concrete without having given timely notice to the Engineer. All sewers and drains shall be tested for water-tightness by means of water pressure maintained for not less than ten minutes in accordance with BS 8301. Care should be taken to avoid damage due to unequal temperature of the pipes and the test water; for example, pipes exposed to hot sun should not be tested with cold water. Sewers and drains may be tested by air pressure or for straightness and obstruction in accordance with BS 8301. Pressure tests shall be repeated when backfilling is completed. Timely notice of all testing shall be given to the Engineer.

2.6.2.4 Protection

Where indicated on the drawings, or otherwise as directed by the Engineer, pipes shall be bedded, haunched, or surrounded with concrete. The concrete shall be mixed and placed in accordance with the provisions of the clauses of this Specification dealing with concrete. Concrete shall not be thrown directly on the pipes. The upper surface shall be struck off with a template or screed and neatly finished.

Flexible pipes shall be bedded or surrounded by approved granular material in accordance with the manufacturer's instructions, or as directed by the Engineer. Cast iron pipes shall have external protection by application of a factory coating and wrapping as follows:

(a) All material shall be suitable for application in the environmental conditions at

the Work Site and for use with a pipe temperature of up to 980C.

(b) Exterior wrappings shall be shop applied. The pipe shall be cleaned, primed and wrapped as per the manufacturer's recommendations. Wrap shall be heavy-duty, self-adhesive PVC or Polyethylene backed carrier strips and applied to a minimum thickness of 1 .78mm

2.6.2.6 Manholes & Catch pits

Manholes, catch pits, gullies and similar items shall be constructed and inspected in accordance with BS 8301. Concrete manholes, inspection chambers and gullies shall comply with BS 5911. Cast-iron manhole covers, road gully gratings, and frames shall comply with BS 497. The load classification of all manhole covers, road gully gratings, etc., shall be to the satisfaction of the Engineer.

Cast iron manhole step irons shall comply with BS 1247. They shall be checked for soundness before building in to manhole walls.



2.6.3 Rainwater Goods 2.6.3.1 Materials

Gutters, down pipes and fittings shall be in accordance with the following standards: Aluminium rainwater goods BS 2997 Asbestos cement rainwater goods BS569 Cast iron rainwater goods BS 460

Precast concrete eaves gutters Unplasticised PVC rainwater goods BS 4576 Pressed steel rainwater goods BS 1091

Wrought copper and zinc Rainwater goods BS 1431

All materials shall be checked for soundness before erection. 2.6.3.2 Erection

Gutters, down pipes and fittings shall be erected in accordance with BS 6367. During erection, care shall be taken to ensure that no damage is caused to existing buildings and structures. The Contractor shall ensure that his work does not interfere with other building work, which may be proceeding during erection of rainwater goods.

2.6.3.3 Protection

Steel and iron shall be protected from corrosion in accordance with BS 5493. Any protective coatings, which may have been damaged before or during erection, shall be made good immediately.

2.6.3.4 Inspection and Testing

All materials shall be inspected after erection and those parts of the work, which will be concealed, shall be tested, before being finally enclosed, in accordance with BS 6367.

2.7. MASONRY 2.7.1 General

Masonry shall preferably be constructed of locally manufactured brick/block units which shall comply with the requirements BS 3921 and BS 6073 or other equivalent of BS 3921 and BS 6073 or other equivalent standard approved by the Engineer.

Trial panels of all masonry types included in the works shall be constructed by the Contractor for approval by the Engineer. These trial panels shall be erected prior to building construction on site: The costs associated with all trial panels shall be deemed included in the Tender.



2.7.2 Materials 2.7.2.1 Bricks

Clay bricks shall be in accordance with BS 3921 calcium silicate bricks shall be in accordance with BS 187; concrete-building bricks shall be in accordance with BS 6073. Facing bricks shall be to the dimensions of standard common bricks and shall be supplied by a manufacturer approved in writing by the Engineer. The bricks are to be first quality and of uniform size and selected so as to give a slight mottled effect in colour on the finished wall.

2.7.2.2 Blocks

Concrete building blocks shall be in accordance with BS 6073. Concrete blocks and bricks shall be from an approved manufacturer whose products shall be examined and approved by the Engineer before work commences.

2.7.2.3 Mortar

The mortar shall be composed of cement, lime and sand in the ratios of 1:1/2:4 giving a minimum compressive strength at 28 days of 14N/mm2.

Sand shall be clean sharp natural sand, well graded and entirely free from loam, clay, dust or organic matter. Water and cement shall comply with this Specification. Lime shall be high calcium containing not less than 90% by weight of calcium oxide. Plasticisers shall be free from calcium chloride or similar salts and shall be to the Engineer's approval.

2.7.2.4 Sand

Sand shall be clean sharp river sand or pit sand, well graded and entirely free from loam, clay, dust or organic matter. (a) The clay/silt content shall not exceed 3% by weight.

(b) The chloride and sulphate contents shall not exceed the limits given in

Clause on aggregates for concrete. 2.7.2.5 Plasticiser

Plasticisers shall be free from calcium chloride or similar salts.

2.7.2.6 Colour Agents

Colouring agents when used in mortar shall be in accordance with BS 1014 and shall not exceed 10% by mass of the cement in the mortar.

2.7.2.7 Pre-Mixed Mortars

Shall comply with the general requirements for materials and mix proportions shall be as given in this Specification.



2.7.2.8 Damp-Proof Courses

Flexible damp-proof course materials shall comply with BS 743 where applicable and shall be:

(i) Bituminous Type C - Asbestos based (4.4 kg/m2). (ii) Black low-density polythene 0.48 kg/m2 (iii) Pitch Polymer having a minimum thickness of 1.27mm and a minimum

weight of 1.45 kg/m2 2.7.2.9 Bonding Ties

Bonding ties shall be expanded metal strips or woven mesh.

2.7.2.10 Wall Ties

Wall ties shall comply with BS 1243 and shall be hot-dip galvanised steel or stainless steel as specified.

2.7.2.11 Preformed Joint Filler

Compressible preformed expansion joint filler shall be cork or bitumen impregnated fibre boarding of the thickness specified within a tolerance of +1.5mm and of such a width that it complies with the specified joint details. The joint material shall meet the requirements of Clause 2630/4 of the Department of the Environment Specification for Roads and Bridges, UK or equivalent.

2.7.2.12 Joint Sealer

Joint sealer shall be polysulphide liquid sealant complying with BS 4254 and applied in accordance with the manufacturer's recommendations.

2.7.2.13 Joint Reinforcement

Joint reinforcement where specified shall comply with BS 1369 Figure 1. The width of reinforcement shall match the width of brick/block.

2.7.2.14 Masonry Reinforcement

Reinforcement shall comply with BS 4449, 4483 or BS 405 as appropriate.

2.7.2.15 Insulation

Cavity wall insulation shall be Extruded Expanded Polystyrene to required thickness and from an approved manufacturer.

2.7.3 Workmanship

2.7.3.1 Weather-tight Exterior Walls

The Contractor shall be entirely responsible for weather-tightness of the exterior masonry walls. The workmanship shall be such that no leaks to the interior shall occur in the exterior walls because of defective workmanship or materials, from failure to fill completely all joints or to properly install all flashings and weep holes.



2.7.3.2 Mortar

Mortar generally shall be machine mixed, mixed dry and then water added until the correct consistency and uniform distribution of materials is obtained. It shall be made in small quantities only. All mortar shall be used within half an hour of the addition of water to the dry mix and any mortar, which has begun to set, shall not be used. Before mixing a fresh series of batches, the mixer drum shall be thoroughly cleaned. Hand mixing shall be done on a clean watertight platform, first dry and then with added water until the correct consistency and uniform distribution of materials is obtained. Mortars shall be used within 35 minutes of the addition of water; any mortar not then used shall be discarded.

2.7.3.3 Masonry

All masonry delivered to Site shall be unloaded by hand and carefully stacked and protected from rain, frost and inclement weather all to the satisfaction of the Engineer. Masonry shall be stored on the Site on a drained surface clear from the ground and located away from roadways and mixing sites to avoid splashing with mud, lime or cement. Masonry shall be adequately wetted prior to use. Masonry with one frog only shall be laid frog uppermost and shall be fully and carefully bedded, all joints being filled and flushed with mortar. No joint shall exceed 10mm thickness. Every third course of masonry shall be truly levelled and laid accurately by line and kept true and square, the whole of the masonry being properly bonded together. The masonry shall be carried up uniformly and no part of the work raised more than 900mm above another unless approved by the Engineer. At the commencement of each day's work the receiving beds shall be brushed to remove all loose particles or debris and well wetted before laying proceeds. The tops of walls shall be adequately protected during construction against the effects of inclement weather and to prevent water entering the walls. Concentrated loads shall not be applied for at least 3 days after building masonry walls or columns. Staining: Grout or mortar or soil shall be prevented from staining the face of masonry to be left exposed. Remove immediately grout or mortar in contact with such masonry. Protect base of walls from rain-splashed mud and mortar splatter by means of coverings spread on ground and over wall surface. Sills, ledges and projections shall be protected from droppings of mortar.

2.7.3.4 Joints

All joints between bricks/blocks shall be as specified and shall be solidly filled to a general thickness of l0mm. All cross-joints shall be filled by well buttering the end of the brick/block and then pushing it into position against its neighbour.

2.7.3.5 Pointed Joints

Joints on external walls, which are to be pointed, shall be raked out 20mm deep as the work proceeds.



Outer surfaces of external walls are to be pointed in a cement mortar with a weather struck joint or other specified joint. The colour of this pointing shall first be determined and approved by the Engineer from a number of samples of pointing, each sample to cover an area of about one square metre. Joints between facing brick/block and precast concrete units shall be treated in a like manner. As an alternative to raking and pointing, the wall may be constructed with mortar to the colour required and to the strength required for that location. Where such coloured mortar is used, the joint is finished to the specified design.

2.7.3.6 Fairfaced Joints

Where a fairfaced finish is specified, the joints shall be rubbed with a rounded tool to give a concave finish to the mortar. This must be done when the mortar has stiffened sufficiently for working. The finished joint shall be smooth with the mortar making good contact with both masonry units.

A fairfaced finish may be required in walling of fairfaced blocks or of standard blocks.

All such blockwork shall be left free of excess mortar or droppings.

2.7.3.7 Joints in Walls to be Plastered or Tiled

Where walls are to receive a plaster or tiled finish, the joints shall be raked to a depth not exceeding 10mm to form a keyed joint or the later coating.

2.7.3.8 Flush Joints

Unless otherwise specified, joints on all other walls are to be neatly struck flush, as the work proceeds and care shall be taken to ensure that there is no raggedness and that no mortar encroaches upon the faces of the blocks or bricks. The surfaces of walls, which are to be painted, are to be cleaned down thoroughly and left clean for the painters. The face of all masonry and precast concrete products shall be left clean.

2.7.3.9 Bonding of Masonry to Structural Frame

Where masonry is bonded to a structural steel or concrete frame, the type and method of such bonding shall be detailed on the Contractor's Drawings.

2.7.3.10 Built-in Items

All items of the various trades to be built into the masonry work shall be installed as the work progresses. Other trades shall be consulted in advance and provisions made for the installation of their work to avoid unnecessary cutting and patching. All sleeves for pipes, anchors, plates and supports shall be built in. Plates and lintels shall be solidly bedded in mortar, true and level with the bedding joints not less than 10.0mm thick. Columns shall have a pre-moulded filler. Mason shall assist in setting all window, door and louver frames occurring in masonry work, fill in the joint in exterior work between masonry and frames with mortar to within 12.0mm of face of frame and rake out the joint to provide space for caulking not less than 20mm deep. Hollow metal doorframes shall be filled solid with mortar.

2.7.3.11 Embedded and Abutting Metals



All steel and aluminium surfaces, which are to be built against or embedded in masonry, shall be cleaned and given two coats of bituminous paint. The coating shall be of uniform thickness without voids. Metal surfaces not embedded or in contact with the masonry shall be protected against soiling by the bituminous paint.

2.7.3.12 Caulking

All joints of exterior masonry at the perimeter of door, window and louver frames shall be not less than 10mm nor more than 12mm wide, shall be raked out and cleaned to a minimum uniform depth of 20mm and shall be filled with caulking compound forced into place with a pressure gun and the face of joint neatly finished.

2.7.3.13 Weep Holes

Weep holes shall be provided over thru-wall flashing in wall, at bottom of quall and elsewhere as required for proper drainage. Weep holes shall be spaced at 600mm centres, and shall be formed with plastic tubing extending into the cavity and left in place.

2.7.3.14 Connection of New Work

When starting masonry work after work has been stopped for the night or other reasons, the exposed bearing surface of the masonry shall be cleaned with a wire brush, all loose mortar removed to obtain the best possible bond between new work and the previously installed work.

2.7.3.15 Connecting to Existing Masonry

Where new masonry work must be connected to existing masonry work, the Contractor shall remove all existing masonry so noted, shall do all cutting and fitting of the existing work as required to make satisfactory connections and complete the work in a finished and workmanlike manner. In general, the connection of new masonry work to existing work shall be made by cutting and toothing in such a manner that no through continuous vertical mortar joint is made and the new work is thoroughly anchored into the existing work.

2.7.3.16 Cutting and Patching

The Contractor shall leave out or cut all chases and openings shown or as required for the installation of the work of other trades, and make tight around same if required. Only masons shall perform cutting and patching of masonry. Masons shall build in or cut out all rebates for flashing as shown or evidently required. Cutting and raking shall be avoided as far as possible by co-operation with the trades involved.

2.7.3.17 Adverse Weather Conditions

No masonry work shall be performed when the ambient temperature is below 50C (400C F) or above 400C (1040F), or is likely to fall below the minimum or rise above the maximum during the 24 hour period after laying, unless the approval of the Manager is received and adequate protection is provided. At temperature below 50C (400F), adequate equipment shall be provided for heating the materials and completed masonry.

Temperature of air on both sides of the wall shall be maintained at 50C-(400F) minimum. Temperature of the separate materials, including mixing water, when placed in the mixer shall not exceed 600C (1400F). When the mortar is being used, it shall have a temperature above 100C (500F) and the mortar shall be maintained at



this temperature until it has been placed in the masonry. No masonry units having a film of water on their surfaces shall be laid in the work.

2.7.3.18 Protection of Work

Top of new work shall be covered with suitable waterproof covering, turned down at the edges and held in place by plank or other suitable means when work is topped. The staging plank next to the walls shall be turned back from the face of the masonry work when work is stopped, to prevent spattering and staining of masonry in the event of rain. The Contractor shall protect all sills and projecting members with suitable and sufficient boxing as a protection against mortar dropping and damage. Bases of walls shall be protected from soil staining by covering adjacent soil.

2.7.3.19 Cleaning and Repairs

All masonry shall be cleaned and defects repaired as follows before acceptance of the work.

Masonry shall be cleaned with trisodium phosphate and detergent, 0.24 litres of each to each 3.9 litres of water. Before cleaning, all dirt, excess loose mortar shall be scraped or brushed off and masonry saturated with clean water. The cleaning solution shall be scrubbed on with still brushes as required and rinsed off thoroughly with clean water until all mortar, dirt and cleaning solutions are removed. As the cleaning progresses, all joints shall be examined for cracks, holes and imperfect pointing. Defective joints shall be cut out and pointing repaired. Sandblasting or use of commercial cleaners shall be used only with approval and only after a test demonstration, of the suitability of the method, are acceptable to the Engineer.

2.7.3.20 Inspection

Erected steelwork will be inspected by the Engineer and the tender price shall be deemed to include for providing the necessary access ladders, facilities and attendance of the Engineer when engaged in inspection work.

2.8 CARPENTRY AND JOINERY 2.8.1 Materials

2.8.1.1 Structural Timber

Timber grading for structural use shall comply with BS 4978 and BS 5756 and shall be used in accordance with the recommendations contained in BS 4169, BS 6446 and BSEN 26891.

2.8.1.2 Carpentry Timber

Non-structural carpentry timber shall comply with BS 1186 and shall be properly seasoned and shall be sawn square, straight and true and shall be free from the following:

Splits, ring shakes, soft pith; checks exceeding 300mm long or 1.5mm wide or one half thickness of timber in depth; knots exceeding 38mm diameter or one half the width of the surface; decayed or dead knots unless cut out and plugged; pitch



pockets; decay and insect attack.

2.8.1.3 Joinery Timber

Joinery timber shall be sound, well conditioned, properly seasoned to suit the particular use and free from the defects listed under carpentry timber.

Softwood and hardwood joinery timbers shall comply with BS 1186.

2.8.1.4 Manufactured Boards

a) Blockboard shall comply with BS 3444, Grade 2. b) Chipboard shall be resin-bonded wood chipboard complying with BS 56610. c) Fibre building boards shall comply with BS 1142. d) Plywood generally shall comply with BS 6566. Those from sources not included

in BS 6566 shall be subject to the Engineer's approval and shall be of equivalent grades of veneer and types of bonding. External quality plywood shall have Grade 2 veneer with WBP bonding and internal quality plywood shall have Grade 2 veneer with MR bonding.

2.8.1.5 Asbestos Cement

Asbestos Cement sheets shall be fully compressed sheets complying with BS 690. Sheets shall be sized to suit the location in which they are to be used.

2.8.1.6 Decorative Plastic Laminate

Decorative laminate plastic sheeting shall be 1.5mm thick complying to BSEN 438.

2.8.1.7 Polystyrene Boards

Expanded polystyrene boards shall comply with BS 3837, Grade SD, Type A cut boards.

2.8.1.8 Suitable Timbers

Unless otherwise specified or approved by the Engineer, timber shall be used in the locations as follows:

Location Timber Handrails and Midrails Teak Window Frames Teak Door Frames, External Teak Door Frames, Internal Teak Louvers Teak Architraves Teak Skirting Teak Beads, Fillets Teak Cupboard Doors 19mm Thick Blockboard Hardwood lipped all round



2.8.1.9 Pressure Impregnation

Preservative for timber shall be pressure or immersion impregnation complying with BS 1282. The Contractor shall treat cut ends and notches, etc. made on Site with a brush-applied preservative recommended by the manufacturer.

2.8.1.10 Fixing

Nails shall comply with BS 1202, screws with BS 1210, bolts with BS 916 and timber connectors with BS 15710.

2.8.1.11 Building Paper

Waterproof building paper shall comply with BS 1521, Class Al. 2.8.1.12 Priming

Priming paint shall comply with BS 5082 or BS 5358.

2.8.1.13 Storage

Timber shall be stored under cover clear of the ground and protected form dampness.

2.8.2 Workmanship

2.8.2.1 General

a) The term 'plugging' shall mean the provision and fixing of hardwood or approved proprietary plugs or, at the contractor's option fixing by means of a cartridge operated rivet gun or other approved mechanical means.

b) The term 'selected' shall be deemed to include keeping the material so described

clean for staining, varnishing or any similar finish. c) Framed work shall be properly morticed and tenoned, wedged, glued and

crimped together and dowelled where necessary. The use of nails for fixing or framing any items of joinery will not be permitted. Sprigs may be used for glazing beads only.

d) All mouldings shall be worked true to details and all joinery shall be dressed and

sand papered. e) The surface of all joinery work shall be wrought and finished so that the plane

marks do not show. f) All nailing to joinery shall be done with fine wire nails and concealed as possible.

All framed joints to joinery in timber 32mm thick and upwards to be double morticed and tenoned except where otherwise described.

g) The Contractor shall allow for: i) Priming all joinery with a coat of priming paint either before leaving the works or

within three days of delivery on to Site. All cut ends, mortices and tenons, etc. to both internal and external joinery to be primed before fixing.



ii) Pencil rounding all exposed arises on joinery. iii) Balancing veneers on all veneered or plastic covered plywoods, blockwork, etc.

2.8.2.2 Skirtings

Skirtings shall be fixed to timber grounds plugged to concrete or blockwork. Nailing through plaster will not be permitted.

2.8.2.3 Jointing

a) All necessary morticing, tenoning, grooving, matching, tongueing, housing, rebating and all other necessary for correct jointing shall be executed in a first class manner.

b) Where joints are not specifically indicated, they shall be the recognised forms of joints for each position. The joints shall be made so as to comply with BS 1186.

2.8.2.4 Veneering

Veneering shall be carried out in an approved manner and to the satisfaction of the Engineer.

2.8.2.5 Inspection

Facilities shall be given to the Engineer to inspect all work in progress in the shop and on Site.

2.8.2.6 Making Good all Defects in Work

Should any shrinkage or warping occur or any other defects appear in the joinery before the end of the defects liability period, all defective work shall be taken down and renewed to the entire satisfaction of the Engineer and any work disturbed made good at the Contractor's expense.

2.9. METALWORK

2.9.1 Crane Rails

Crane rails shall comply with BS 105 Light and Heavy Bridge Type Railway Rails or be to other approved profile and shall also comply with the general requirements of BS 11 - Flat Bottom Railway Rails. Rails shall be cold straightened and free from twist. They shall be substantially free from pitting, laminations and other defects. The supplier in accordance with these standards shall furnish manufacturers test certificates. Insofar as they are not over-ruled by this Clause, crane rails shall conform to the requirements of Clause 2.4 herein. Rails shall receive the same protective paint treatment as specified in Clause 2.4. After erection of the crane girders the rails shall be accurately aligned on the girders and fixed in position using proprietary expansion type clips approved by the Engineer. The clips shall be bolted down with high tensile bolts tightened in accordance with the manufacturer’s specification. Crane rails shall be aligned within the tolerances set out in: Federation European de la Manutention



Section 1: Heavy Lifting Equipment Appliances Additive Sheet, Tolerances of Cranes and Tracks

Location of rail joints shall be shown on the Contractor's drawings and shall be positioned to avoid joints in crane girders and be located between pairs of clips.

2.9.2 Chequer Plate

Chequer Plate flooring shall be galvanised raised pattern, self-draining type to BS 4360 Class 43A.

2.9.3 Hand railing Hand railing shall consist of galvanised tubular steel standards and tubular steel railing and bevelled where necessary. Blisters or uneven portion of welds shall be ground off. The tubing shall be in accordance with BS 1387 or BS 1775.

2.9.4 Inspection

Facilities shall be given to the Engineer to inspect all work in progress in the shop and on Site.

2.9.5 Making Good all Defects in Work

Should any shrinkage or warping occur or any other defects appear in the joinery before the end of the defects liability period, all defective work shall be taken down and renewed to the entire satisfaction of the Engineer and any work disturbed made good at the Contractor's expense.

2.9.6 Ironmongery

(a) Hinges shall be housed into the door or windows and the frames.

(b) All locks catches, etc. shall be properly cleaned tested and oiled and all keys shall be clearly labelled.

2.9.7 Materials

(a) Steel

Structural steel shall comply with the requirements of this Specification for structural steel.

(b) Galvanising

See Structural steelwork Section of this Specification.

(c) Nuts, Bolts and Screws

(i) Nuts and bolts, etc. shall comply with BS 4190 and BS 1494 and shall have ISO metric thread complying with BS 3643.

(ii) Stainless steel bolts are to be set bolts and shall comply with BS

4190. The stainless steel for bolts, nuts and washers shall comply with BS 970, quality EN 58 AM.



(iii) Self-tapping screws shall comply with BS4174

(d) Aluminium

(i) Aluminium extruded sections shall comply with DIN 1748, Part 4 or BS 1474.

(ii) Brush anodised finish to aluminium shall comply with BS 3987. (iii) Aluminium shall be supplied with the following finishes:

· Mill finish. · Matt anodised. · Brush anodised. · Brush anodised with bronze, gold or black finish.

The finish required shall be given on the Drawings or Schedules. (e) Chequer Plate

See Structural Steelwork Section of the Specification.

2.9.8 Roller Shutter Doors

(a) Design

The doors shall be designed to withstand the wind forces of the area in accordance with CP3, Chapter V, Part 2. The basic wind speed for the Site is given in the General Requirements Section of this Specification.

(a) Laths

Door laths shall be steel laths of l.6mm thickness galvanised in accordance with BS 729 and interlocking over their entire length to form a continuous hinge. Lateral movement shall be prevented by wind locks riveted to the lath ends.

(b) Ancillary Door Parts

The roller shall be of adequate diameter to resist deflection. All guides shall be of adequate depth to prevent laths slipping out under wind loading.

2.10. BOUNDARY WORKS 2.10.1 General

A minimum clearance of 3.0m shall be maintained throughout the site between the innermost face of the boundary works and any structure above ground within the substation boundary.

Adequate provision shall be made by means of uPVC pipes or openings approximately 1 metre below finished ground level to allow the ultimate development of the outgoing feeder cables of all voltages and the associated pilot cables to pass through the boundary works. uPVC pipes which pass under the boundary foundations and perimeter drain shall be encased in a concrete duct bank to the approval of the Engineer.



2.10.2 Fencing 2.10.2.1 General

Chain link fencing, gates and gateposts shall be in accordance with BS 1722, Part 1, 1972 and Supplement 1, 1974 unless otherwise specified herein.

Security chain link fence, gates and gateposts shall be in accordance with BS 1722, Part 10, 1972 unless otherwise specified herein.

2.10.2.2 Materials

(i) Wire

The plastic coated wire for the fencing mesh, line wire, straining wire and tying wire shall be in accordance with BS 4102, Grade A. Minimum diameter of wire core shall be 3.5mm. Ultimate tensile strength shall be 250N/mm2. Wire shall be galvanised in accordance with BS 443.

(ii) Framing and Gates

All framing and gates shall consist of structural steel sections. Sections shall be in accordance with BS 4848 or BS 4. Circular Hollow Section (CHS) for gateposts shall be sealed top and bottom by means of welded steel plates of same thickness as the CHS. All sections shall be hot dip galvanised in accordance with BS 7210.

(iii) Vinyl Coating

Chain link fence mesh shall have a vinyl coating of not less than 0.5mm. Colour of coating shall be dark green.

(iv) Concrete

Concrete shall be in accordance with this Specification.

2.10.2.3 Erection

Fences shall be erected without sudden steps of changes in level. If the existing ground is uneven, it shall be levelled to a uniform slope prior to fence erection.

2.10.2.4 General Levelling

Fences shall be erected without sudden steps of changes in level. If the existing ground is uneven, it shall be levelled to a uniform slope prior to fence erection.

2.11 LIGHTING AND LOW VOLTAGE POWER 2.11.1 Classification

The complete installation shall comply with a standard approved by the Local Authority and/or any Wiring Codes that are mandatory in the country of the installation. Where no codes exist, the lighting system shall be in accordance with IEC 598.

This Specification covers electric light fittings, cables, switches, contractors, L.V.



transformers, socket outlets and accessories and all other plants necessary for the completion of all lighting systems indoor and outdoor and all sockets and power supplies required within the building.

2.11.2 Design 2.11.2.1 Requirements

The lighting installation shall be designed to give adequate illumination levels for the respective area of the station. The installation shall also meet the limiting glare index as set out by the approved Code. All outdoor lighting shall be controlled by photo-electric cells and contactors shall be suitably located. Provision shall be made for over riding remote control from the control room. Lighting of all rooms shall be locally controlled. All outlets, terminals, cables, boxes etc. shall be adequately rated for the load they are supplying. A reasonable number (15%) of spare outlets shall be provided on distribution boards for unforeseen loads. A system of 415V 3-phase 40A sockets of approved type shall be provided indoor and outdoor at suitable locations. These sockets shall be suitable for welding sets and other heavy-current transportable equipment.

2.11.2.2 Coding Systems

The Contractor shall when preparing drawings showing the respective designs use a code to identify each lighting fitting and socket outlet.

2.11.2.3 Cables

Cables shall be PVC, PVC/PVC or SWR (steel wire reinforced) depending on application and shall be manufactured and tested to the requirements of the appropriate standard. Flexible type cables for pendant cords and final connections to fixed apparatus shall be butyl or silicone rubber isolated and sheathed, manufactured and tested in accordance with the requirements of the appropriate Code or Standard.

2.11.2.4 Cables Terminations

Termination for SWR cables shall be comprised of compression type glands with armour and bonding clamps to meet the requirements of the appropriate Code of Standard. Terminations for PVC/PVE insulated and rubber insulated cables shall be comprised of compression type glands where the function of the gland is to secure the outer sheath of the cable, in accordance with the requirements of the appropriate Code of Regulation. A watertight seal shall be provided between the outer sheet and the gland.

2.11.2.5 Conduit and Fittings

Conduits shall be manufactured in accordance with appropriate Code of Standard and shall be high impact heave gauge polyvinyl chloride.



2.11.2.6 Cable Trays

Cable trays, where required to be supplied as part of the Contract supply, shall be perforated galvanised sheet type.

2.11.2.7 Trunking

PVC trunking is preferred and shall be supplied in lengths suitable for erection in the areas concerned. Alternatively, trunking manufactured from good quality hot dip galvanised mild steel sheet not less than 1.22mm thick for sizes up to 100mm wide and not less than 1.63mm thick for size up to 150mm wide will be permitted.

2.11.2.8 Lighting Fittings

Lighting fittings for interior and exterior use shall be manufactured and tested in accordance with the appropriate Code of Standard and together with all components shall be suitable for service and operation in the climate stated. The lamp casing shall be resistant to corrosion and shall be of type IP65 enclosure. All lights shall be suitable for an ambient temperature of 450C. Particular importance is attached to easy services and low maintenance requirements. Outdoor fittings shall be completely weather proof. Fluorescent luminaries shall have dispersive reflectors. The fittings shall be furnished with high-pressure sodium discharge lamps for flood lighting and low-pressure sodium discharge lamps for road lighting. They shall be constructed of vitreous enamelled steel or equivalent. The outdoor lighting systems shall be fed through sub-distribution boards at suitable locations.

2.11.2.9 Switches

Switches shall be rated for 6 Amp and shall be provided with an earth terminal. Switches for use in areas designated for surface installation shall be quick-make-quick-break fixed grid industrial types mounted in galvanised malleable iron boxes with protected dolly and arranged where necessary for multigang switching. Switches for use in areas designated for flush installation shall be micro-break types fixed to white plastic cover plates and mounted in PVC flush-type box. Switches or Switch/Socket outlet combinations shall be mounted approximately 1.20 metres above finished floor level.

2.11.2.10 Socket Outlets

All single-phase socket outlets shall be mounted at approximately 0.3 metres above floor level with the exception of those for use with clocks, which shall be mounted at 2 metres above floor level. Each socket shall have two terminals live and neutral. Each terminal shall be capable of accepting two 4mm2 conductors. The sockets shall be rated at 16A or higher.

Each plug and outlet shall have two terminals generally identified as (L.N.). The live conductor terminates on terminal (L), neutral conductor on terminal (N). Provision for an earth conductor shall be made also. Colouring coding of conductor insulation for flexible shall be in accordance with the following standards:



Live (L) : brown or red Neutral (N) : blue or white

Or, otherwise with local standards.

2.11.2.11 Interior and Exterior Installations

Wiring in the power station and other like buildings shall be comprised of PVC cables drawn into conduits, which are attached to walls, ceilings or steelwork by an approved fixing. Where straight runs of lighting fittings occur cable trunking attached to building structure may be used.

2.11.2.12 Earthing and Bonding

All equipment being supplied, fittings, socket outlets, etc. shall be effectively bonded to ensure earth continuity throughout the system. If available, and allowable, the armouring of cables may be used for this purpose.

2.11.2.13 Emergency Lighting

An emergency lighting system using lighting fitting with integrated Ni-Cd batteries shall be provided in case of failure of the AC lighting system. The emergency system shall provide illumination at all exits and entrances and in all operational areas.

2.11.2.14 Safety Requirements

Where discharge lighting is used in areas containing rotating or reciprocating machinery, the fitting shall be allocated between the three phases and neutral in such a manner as to avoid stroboscopic effects. In an enclosed area where there is a risk of the accumulation of inflammable gases (e.g. in battery rooms) lighting fittings and other accessories shall be provided in accordance with IEC 710.

2.11.2.15 Lighting Sub-Distribution Boards

The lighting sub-distribution boards shall be of robust sheet metal flush fronted design. Dependent on their size and location they shall either be of freestanding or flush mounting type. The sub-distribution boards shall be designed in accordance with the relevant items of this Specification.

2.11.2.16 Drawings

The Contractor shall provide detailed drawings of the plant showing:

(a) Location of all lighting fittings and sockets throughout the site, showing the different types of equipment used.

(b) Location of sub-boards and what fittings are sockets are fed from each board. (c) Location of masts etc. and route of underground cables to sub boards. (d) Location of emergency lights at exits etc.