SPECIFICATION FOR

PLANT LOCATION

NAOC PH BASE - NIGERIACode:3217.46.BASG.36912

PROJECT/UNIT

NEW PORT-HARCOURT BASE POWER GENERATION PROJECTPage 1 of 25Rev

0

SPECIFICATION FOR

CONCRETE WORKS

AT

NAOC PORT-HARCOURT BASE, NIGERIA

21/06/120Issued for ReviewH. DORDORD.AKANOR.OMIETIMI

DateRevDescription of RevisionPreparedCheckedApproved

CONTENTS

1.GENERAL1.1SCOPE

1.2REFERENCE DOCUMENTS

1.21 AGIP GENERAL SPECIFICATIONS

1.22 CODES AND STANDARDS

2.CLASS OF CONCRETE

2.1CLASS OF CONCRETE

2.2 USE OF CLASS OF CONCRETE

3.MATERIALS3.1 SPECIAL REQUIREMENTS

4.AGGREGATE GRAIN SIZE COMPOSITION4.1 SPECIAL REQUIREMENTS

5.MINIMUM QUANTITY OF CEMENT5.1 SPECIAL REQUIREMENTS

6.PRELIMINARY TESTS AND CHECKS OF THE SPECIFIED CONCRETE MIXES

6.1 PRELIMINARY TESTS

6.2 CHECKING OF THE CHARACTERISTIC COMPRESSIVE ,STRENGTH

7.REINFORCEMENT AND FORMWORK

7.1SPECIAL REQUIREMENTS FOR REINFORCEMENT

7.2 SPECIAL REQUIREMENTS FOR FORMWORK

8.CONCRETING PROCEDURES

8.1CONCRETE MIXING

8.2CONCRETING IN HOT WEATHER

8.3TRANSPORTION OF CONCRETE

8.4BLINDING CONCRETE

8.5CONCRETE POURING

8.6TOLERANCES FOR FORMED SURFACES

8.6.1 Variations from plumb and alignment

8.6.2 Variations from the level or from the grade specified in the drawings

8.6.3 Variations from plan alignment in relation to the established . lines

8.6.3 Variations in sizes and location for sleeves

9.EXPANSION JOINTS

9.1PLAIN JOINTS FOR PAVING

9.2WATERTIGHT JOINTS

10.REINFORCED CONCRETE PITS

10.1SPECIAL REQUIREMENTS

11.TIGHTNESS TESTS FOR TANKS AND PITS

11.1SPECIAL REQUIREMENTS FOR TANKS

11.2SPECIAL REQUIREMENTS FOR PITS

1.0GENERAL

1.1 Scope

This document defines the specifications for concrete strengths, classes of materials, strength tests, mixing and concreting procedures for concrete work with reference to European Codes or British Codes and Standards.

1.2Reference documents

1.2.1 AGIP General Specifications

27550.VAR.CIV.FUNSite Clearing and Excavation

27551.VAR.CIV.FUNFill

27552.VAR.CIV.FUNGeneral Concrete

27563.VAR.CIV.FUNSewers and Drainage

1.2.2 Codes and Standards

Unless otherwise stated, the latest editions of the following codes and standards shall apply for all work to be carried out in accordance with this Specification:

BS 12Specification for Portland cement

BS 146Specification for Portland blast furnace cement

BS 410Specification for test sieves

BS 412Testing aggregates

BS 812 VariousMethods of sampling and testing of mineral aggregates from natural resources for concretes

BS 882Specification for aggregates from natural sources for concrete

BS 1370Specification for low heat Portland cement

BS 1881Testing concrete

BS 3148Methods of test for water for making concrete (including notes on the suitability of water)

BS 4027Specification for sulfate-resisting Portland cement

BS 4246Specification for high slag blast furnace cement

BS 4449Specification for carbon steel bars for the reinforcement of concrete

BS 4483Specification for steel fabric for the reinforcement of concrete

BS 4550Methods of testing cement

BS 5075Concrete admixture

BS 5080Structural fixings in concrete and in masonry

BS 5328Concrete

BS 5606Guide to accuracy in building

BS 5975Code of Practice for False work

BS 6588Specification for Portland pulverized-fuel ash cement

BS 6651Code of practice for protection of structures against lightning

BS 8004Code of practice for foundations

BS 8007Code of practice for design of concrete structures for retaining aqueous liquids

BS 8110Structural use of concrete

CP 102Code of practice for protection of buildings against water from the ground

CP 2012 Part 1Foundation for reciprocating machines

Building Research Establishment Digest 250 Concrete in sulphate-bearing soils and groundwater.

The current edition of the building regulations and all amendments thereto.

Standard method of detailing reinforced concrete published by the Concrete Society and the Institution of Structural Engineers.

2.0CLASS OF CONCRETE2.1Class of ConcreteThe class of concrete will depend on the compressive cube strength determined at 28 days tested to BS 1881.

2.1.1Compressive strength:15N/mm2(C15) -Blinding

2.1.2Compressive strength:20N/mm2(C20) - Road Crossings, Cable Sleeves and Mass Concrete

2.1.3Compressive strength:25N/mm2(C25) -Structures and Foundations

2.2Use of Class of Concrete The Class of concrete to be used in the works shall be as shown on the relevant construction drawings.

3.0 mATERIALS3.1 Special Requirements

3.1.1 Cement

Cement characteristics shall conform to BS 12, BS 146, BS 1370, BS4027, BS 4246, BS 6588.

The type of cement to be used and the relevant strength shall be specified on the design drawings and/or in other contract documents.

3.1.2 Water

The water used for making concrete or cleaning out shuttering, curing concrete or similar purposes shall be taken from the mains supply wherever possible, and shall comply with the requirements of BS3148: Where water is not available from the mains the Employers approval shall be obtained before use.

3.1.3 Sand (Fine Aggregate)

Sand shall be in accordance with BS882 and come from rivers, quarries, from natural sources or crushing of compact siliceous, quartz, granitic or calcareous rock. The sand shall be clean, free from silt and any other foreign matter that may affect the strength and/or the normal curing time of the concrete.

The grain size shall be well graded within the following range:

Sieve (BS410)% Passing

(by mass)

10mm100

5mm95-100

2.36mm80-100

1.18mm50-85

600(m25-60

300(m10-30

150(m2-10

The content in fines (passing through a sieve of 75(m) shall not exceed the following values:

-3% by mass for natural sand

-5% by mass for sand produced by crushing.

Sand obtained by crushing can be added to natural sand in suitable proportion in order to attain the above-mentioned values.

Crushed-sand alone cannot be used unless previously approved by the Employer.

Sea-sand if obtained from a quarry whose elevation is above the maximum highest tide level can be used (subject to Employers approval) providing the grain size is within the above-mentioned range, and the salt content meets the requirements of BS812 and BS1881.

3.1.4 Gravel or Crushed Stone (Coarse Aggregate)

Gravel shall be in accordance with BS 882 and come from a river bed, quarry, or from a natural source of siliceous, quartz, granitic or calcareous rock which is chemical inert, strong, hard, durable and of limited porosity.

Gravels which come from the crushing of compact rock shall comply with the requirements of BS 882.

All gravel and crushed stone shall be clean, free from silt or any other foreign matter that may affect the strength and/or the normal curing time of cement.

The limits of aggregate size are given in BS882 together with the flakiness index and shall be strictly adhered to during the selection and controlling of aggregates for a specific concrete use.

3.1.5 Reinforcement

The characteristics of reinforcement shall conform to the requirements of the BS4449. In particular, it shall be free from apparent defects such as laminar separation, cracks, debarring and burning, besides being clean and free from substances such as oil, greases or earth that may impair its adhesion properties.

The type of steel to be used shall be specified on the relevant design drawing.

Bar samples shall be subjected to tensile and bending tests by an approved licensed laboratory in accordance with the requirements of BS4449.

The use of a guaranteed strength reinforcement releases the Contractor from the obligation of carrying out the above-mentioned tests.

The characteristics of welded steel wire fabric shall conform to the BS4483.

3.1.6 Admixtures

Any chemical admixtures use shall conform to the requirements of BS5075.

The use of admixtures may be used to improve the workability of the concrete provided that the approval of the Employer is obtained and that the use of such admixtures does not impair the quality of the concrete.

4.0 AGGREGATE GRAIN SIZE COMPOSITION

4.1 Special RequirementsThe grain size composition of concrete aggregates shall be expressed as a percentage by mass of each component passing through square mesh sieves, and shall normally range between the maximum and minimum values indicated in the BS882.

Before transporting the aggregate supplies to the site, the Contractor shall submit for agreement with the Employer the grain size values to be used in the concrete mixes.

Aggregates shall be from approved sources and test certification shall be provided for each source.

Coarse aggregate shall be limited to 20mm nominal size.

5.0 MINIMUM QUANTITY OF CEMENT

5.1Special RequirementsUnless otherwise specified in the Design, the minimum quantity of cement refers to one (1) m3 of concrete mix for each grade of concrete, shall be as follows:

Characteristic compressive strengthMinimum Cement Content

kg/m3

20 N/mm2220

25 N/mm2255

35 N/mm2300

These minimum quantities of cement stated above shall always be complied with.

Should it be necessary to increase the quantities of cement from those specified, to achieve the characteristic compressive strength, the mix shall be redesigned in accordance with BS8110 with due regard for the placing, workability and shrinkage, etc. of the concrete mix.

Any changes to the concrete mix shall be submitted to the Employer for his approval in writing before use on site, but this approval does not relinquish the Contractor from his responsibility and/or costs for providing the characteristic compressive strength.

6.0 PRELIMINARY TESTS AND CHECKS OF THE SPECIFIED CONCRETE MIXES

6.1Preliminary TestsPreliminary tests shall be carried out by the Contractor prior to casting, and according to the schedule submitted to and approved by the Employer.

For each grade of concrete, and according to the required consistency and workability requirements, the Contractor shall carry out preliminary tests to establish the optimum design mix with regard to the required strength and workability.

The tests therefore shall be made to check the following in accordance with BS5328.

-aggregates with different mechanical characteristics

-aggregates with different grain size composition

-quantity of water

-quantity of cement

-density of fully compacted concrete.

It should be noted that, with the same quantity of cement, the highest strength within any given grade is attained by a concrete where:

-total water (including aggregate water) to cement ratio is 0.50 or less);

-the hardest aggregates are incorporated;

-the highest density is attained by a good aggregate distribution, reducing voids to a minimum.

In the case of a low water concrete having poor workability, for its intended use, the quantity of cement can be increased provided that the initial water to cement ratio remains unchanged.

Following the Manufacturers recommendations concrete workability can be improved by using liquefying admixtures.

The use of such products shall in no way impair the strength properties of the concrete; in this connection, a series of strength tests using the liquefying admixture shall be performed.

The optimum mix shall be determined by preliminary tests performed not later than 30 days before the start of the casting of concrete and shall be constantly monitored and checked throughout the casting operation.

The preliminary determination of the strength of each class of concrete only has the purpose of defining the optimum mix.

The final acceptability of the concrete however shall depend upon its characteristic compressive strength, which shall be determined on test samples obtained during the casting operation and in accordance with the requirements of BS1881.

The preliminary tests shall be carried out on a series of cubes subjected to 7 and 28 days of curing, 1 tested at 7 days, 2 tested at 28 days, 1 spare to be tested at 56 days in the event of failure at 28 days.

The cube test results shall prove the quality of the concrete obtained regarding its density and workability, etc., and shall ensure that the concrete mix used will reach the required characteristic compressive strength specified.

6.2 Checking of the Characteristic Compressive Strength

Checking shall be carried out in accordance with the requirements of BS1881.

The check shall be carried out on four samples at a time.

The type of samples, their preparation and curing shall conform to the requirements of the previous chapter 6.1. of this Specification.

The sampling frequency shall comply with the requirements set out in the Project specification; however, not less than 1 set (one) of samples per 50m3 and/or for each day of casting shall be taken, unless otherwise agreed upon with the Employer.

If ready mixed concrete is used one set of samples per delivery shall be taken.

7.0 REINFORCEMENT AND FORMWORK

7.1Special Requirements for Reinforcement

The requirements of the standard concerning carbon steel bars used for reinforcement shall be complied with in respect of construction, tolerances, joints, bends and spacers.

The minimum covering thickness of concrete shall comply with recommendations of BS8110 and/or be as shown on the detail drawings.

Bars shall be installed in accordance with the number, size, shape and position specified in the detail drawings and/or design documents.

Bars shall be tied together using annealed iron wires at all intersection points, to form rigid cages that will maintain their position without distortion or twisting during the placing and compaction of the concrete.

Prefabricated spacers of concrete or plastic type approved by the Employer, shall be inserted between the bars and internal surfaces of the formwork, so that the required concrete cover thickness is maintained during the placing and compaction of the concrete.

Contractor shall attach certified manufacturers material data sheet for reinforcement bars to be used on this project. Characteristic strength test will also be carried out on samples of reinforcement bars.

7.2Special Requirements for Formwork1)Timber or steel may be used for formwork at the Contractors convenience or according to the material he has available and shall comply with BS5975.

Formwork shall be able to withstand the weights of the structure, of the workers, and fixed and mobile equipment for the placing and compaction of the concrete, as well as any other loads or stresses.

Moreover, formwork shall be erected to prevent distortion or misalignment during concreting, and shall be built to allow the striking of the formwork in accordance with the provisions of BS8110. Care shall be taken in the design, erection and dismantling of the formwork and its supports when heavy loads, wide spans, or similar unusual features are involved.

The formwork surface in contact with the concrete shall be smooth and free from projections, indentations, undercuts or unevenness, care being taken to accurately mate the boards so that the required finished surfaces may be obtained.

Unless otherwise specified, all edges and corners of exposed concrete shall be chamfered using timber fillets (25mm).

2)PVC or fibre cement pipes of either round or square section may be used to provide anchoring pockets for bolts and similar items. Their outside surfaces shall be greased before concreting to facilitate their removal after the concrete has set.

Inserts shall be provided with holes for fixing anchor bars together with bottom plugs, when necessary. The pockets so formed shall be thoroughly cleaned before the anchor is installed; pockets shall be filled with polystyrene foam or similar to prevent any damage to the concrete.

3)The dismantling of formwork shall only be effected after the concrete has been sufficiently cured, and shall be carried out with appropriate care, avoiding shocks or sudden stresses.

In particular, before any formwork is dismantled a check should be made of the concrete pouring records to ascertain the weather conditions that existed when the concrete was cast in order to ensure that the concrete has sufficiently cured and that all the other appropriate conditions have been fulfilled.

Concrete strength checks may also be advisable prior to dismantling, by performing tests with a portable sclerometer, even though such tests shall not be regarded as final.

Formwork shall not be removed unless the correct number of days has elapsed since the date of the last casting, as specified in the BS8110 for each type of structure, considering a day to be a 24 hour unit.

4)The time of concrete curing and the dismantling dates shall be those adopted for normal pouring and curing conditions; otherwise they shall be extended in accordance with the requirements of BS8110.

5)In addition to the precautions already indicated for dismantling, care shall be taken to avoid chipping or otherwise damaging the concrete surface.

Upon completion of the formwork removal, all protruding iron stays shall be removed.

Any damage or unevenness in the structural finish, shall be reviewed by the Contractor and a recommendation for the remedial work involved, shall be presented to the Employer for his approval. This shall not in any way relieve the Contractor of his responsibility to the contracted works, and all the remedial works agreed, shall be at the Contractors expense.

8.0 CONCRETING PROCEDURES

8.1Concrete MixingNormally, mechanical means shall be used for concrete mixing, and hand mixing shall only be allowed for small works, if approved by the Employer.

Concrete mixing equipment shall be sufficient for the size of the structures to be constructed and the concreting schedules, taking into account the need to ensure a continuous supply of concrete for each structure.

Generally, a mechanical means shall be used for measuring the concrete materials, and the concrete composition shall be constant and identical with those that proved to be the optimum during the preliminary tests for each class of concrete.

8.2 Concreting in Hot Weather

The temperature of concrete at the time of placement shall not exceed 30C, but for concrete items in excess of 30m3 and/or 900mm thickness, the temperature of concrete at the time of placement shall not exceed 25C. Any concrete with a temperature in excess of the above figures shall not be used. All mixing and curing shall be in accordance with ACI 305R-91.

The Contractor shall make adequate provision before normal production concrete commences for the means of keeping within this temperature limit, taking into account the anticipated site temperatures during the period of concrete production.

Normal provisions for reducing the concrete temperature are as follows:

a)Shading of mixing plant and trucks.

b)Shading of aggregates and water tank.

c)Painting white the mixing plant, trucks, water tank and cement silo.

d)Insulating the water tank and supply piping.

e)Using flaked ice in lieu of mixing water.

f) Concreting at night.

8.3 Transportion of Concrete

The transportation of concrete to the pouring areas shall be effected by the most suitable, and usually mechanical means, to avoid segregation of the concrete.

Unless the means of transport is equipped with a mixer, no longer than 15minutes shall elapse from the time concrete is loaded to the time it is placed (dumpers, chutes, buckets or the like) concrete shall never be unloaded from a height exceeding 1.5 metres.

Concrete may also be poured using mechanically driven pumps, in which case liquefying additives may be added, subject to the Employers written approval, provided the procedure and requirements of paragraph 6.2. are adhered to.

After each interruption of the work, the pump and piping shall be flushed with pressurized air and water. Care should be taken to ensure that excess water does not enter the areas to be concreted.

On arrival at the delivery area the temperature of the concrete shall be taken to check that it complies with sub-clause 8.2.

8.4 Blinding Concrete

All foundations, whatever the nature of the soil, shall be laid on a bed of blinding concrete (grade C15) with a minimum content of 220kg of Portland cement for one m3 of mixture.

The minimum thickness of the concrete blinding shall be 50mm and it shall be laid to the specified levels.

It shall extend 50mm beyond the edge of the foundation perimeter, unless otherwise specified on the construction drawings.

8.5 Concrete Pouring

8.5.1Prior to concreting, checks shall be carried out to determine that:

-the steel reinforcement fully complies with the construction drawings with regards to the number, location and diameter of the bars, their bending, joints, offsets, laps, spacing, cover and tying, and that the cages are fastened so as to ensure their stability during concreting;

-all the formwork has been thoroughly cleaned and all foreign matter has been removed;

-all inserts, as indicated on the construction drawings, have been correctly located inside the shuttering;

-that all bolts, stays, sleeves, plates, pipes, etc. have been correctly positioned to the proper levels, position and alignment, on both horizontal and vertical structures, above and below ground, as required for the subsequent erection of any permanent or other temporary equipment;

-the formwork and any other tiling and cement material is kept damp, especially during hot weather;

-all flaws, distortions, cracks, etc., caused by board shrinking and/or settling have been properly eliminated from timber formwork, particularly during hot weather;

-all appropriate, mobile and stationary equipment has been properly installed for concrete lifting, conveying and distribution, to ensure concreting as scheduled without interruption; avoid shock loading and/or vibration from this equipment which could affect concrete stability and curing;

-where large pours are involved, requiring several days to complete, the limit of the daily pour shall be scheduled so that the construction joint occurs in the most appropriate location, depending on the type of structure.

8.5.2The Contractor shall submit for approval to the Employer a precise pouring schedule. The Employer may also issue specific pouring instructions.

8.5.3Concrete shall be laid in layers and shall be compacted using vibrators, without displacing the steel reinforcement.

The concrete, particularly in cases where the water-cement ratio is lower than 0.45, and in cases where concrete with higher characteristics are used, shall be vibrated within 15 minutes of placing, using compressed air, electrical or mechanical equipment working at frequencies ranging between 8000-12000 vibrations per minute, taking into account the fact that vibrating frequency is a function of aggregate particle size and reinforcement density.

Vibrators shall be inserted and drawn out slowly, at a speed not exceeding 80 to 100mm per second, to prevent the formation of voids inside the concrete. Furthermore, contact between vibrators and any reinforcing rods shall be avoided.

The depth of each layer to be vibrated shall not exceed 40mm, which shall include 10mm of the previous layer.

Vibration shall cease as soon as a cement grout appears on the surface. Any further vibration may result in the segregation of the concrete constituents.

Where closely spaced reinforcing bars are found, blade vibrators shall be used, the blade length being 200mm or less.

Pouring shall be continuous and fill the whole section both vertically and horizontally, so that no curing occurs at any of the contact surfaces of the concrete sections during the pour.

This provision shall be strictly complied with until each structural unit shall have been completed, or at least until the pre-determined interruption limits have been reached.

To comply with this provision, concrete mixing, transportation and casting capacity shall, if necessary, be temporarily increased wherever large or otherwise unusual structures are to be cast.

All horizontal surfaces shall be flat and float finished in accordance with that specified. Surfaces in contact with the formwork shall be smooth, compact, uniform, free from colour patches, voids or burrs, after the formwork has been dismantled.

8.5.4Normally no interruption of concreting operation shall be allowed.

Any interruption which should become necessary shall be authorized by the Employer.

Any surfaces affected by the resumption of concreting shall be carefully chiselled, washed and grouted.

8.5.5During and/or after concreting, care shall be taken to ensure that:

a)No person or equipment is allowed on any structure, or part thereof, before it has adequately cured.

b)Excessively high temperature conditions do not prevent proper curing.

c)Since the daily ambient temperatures are normally going to exceed the allowable concrete temperatures in sub-clause 8.2 strict curing control shall be applied in accordance with ACI305R-91 Concreting in Hot Weather.

For large pours in particular the Contractor shall provide calculations to Employer to show that the method of curing will control the temperature and gradients within the concrete mass.

All concreting shall be carried out wherever possible during the coolest period of the day. Any temporary protection shall not be removed until the curing process is almost complete and/or that specified in BS8110.

Concrete shall be protected from heat and wind by any such means as may adequately lower the temperature, whether directly or otherwise, over the concreted surfaces.

In addition, as soon as sufficient hardness has been attained to prevent washing out, all finished surfaces shall be continuously wetted throughout the day, particularly where intense heat prevails. Insulation shall be used on the appropriate surfaces where necessary.

d)Concreting records shall be kept up-to-date by the Contractor, stating when each structure, or part thereof, is undertaken and completed, the grade of concrete used, and the weather conditions prevailing during concreting up to completion of the curing.

A copy of these records shall be delivered daily to the Employer.

8.6Tolerances for Formed Surfaces

Unless otherwise specified in the contractual documents, concrete works shall conform to the tolerance limits as stated in BS5606.

8.6.1Variations from plumb and alignment

To the arises and surfaces of columns, pillars and walls:

in any 3m of length

6mm

maximum for the entire length

25mm

8.6.2Variations from the level or from the grade specified in the drawings

To the surfaces and arises of slabs, ceilings and beam soffits:

in any 3m of length

6mm

maximum for the entire length

18mm

8.6.3Variations from plan alignment in relation to the established lines

To buildings (or supporting structures) as a whole and to the related pillars, walls and partitions:

in any 3m of length

12mm

maximum for the entire length

25mm

8.6.4Variations in sizes and location for sleeves

For floor and wall openings 6mm

9.EXPANSION JOINTS9.1Plain Joints for PavingJoints shall be 15mm wide and shall extend the full length of the concrete paving.

Polystyrene foam shall be used to fill the joint up to 25mm below the upper concrete surface, the remaining 25mm shall be sealed with a hydrocarbon-proof sealant or equivalent, approved by the Employer.

The Manufacturers recommendations shall be carefully followed for the application of the sealant.

9.2Watertight JointsWhen the joint is required to be watertight (water tanks, basins, etc.), water stops buried in concrete shall be used so as to allow for expansion or shrinkage of the structure.

Water stops shall be used for the full length of the joint.

If non-aggressive fluids are used, joints shall be filled with a soft material (polystyrene or equivalent) up to 25mm below the concrete surface inside the tank, basin or the like, and shall be subsequently sealed with either sand-cement mortar or similar approved.

When aggressive fluids are involved, such as hydrocarbons, etc. special joints sealers shall be used for sealing tanks, basins, ducts and the like.

The joint seat shall be properly cleaned, Moltoprene or equivalent inserted and sealed all in accordance with Manufacturers recommendations.

All joints shall be 20 x 15mm in section.

9.0 REINFORCED CONCRETE PITS

10.1 Special Requirements

The casting of reinforced concrete pits for surface water, sanitary water, oily and semi-oily water sewers shall conform to the requirements of this specification.

Sealing shall be carried out to ensure that the piping inlets and outlets are watertight.

The covering slab support surfaces shall be levelled with mortar.

Where expressly required by the Employer, inside walls shall be rendered with cement mortar.

When rendering is specified, the surface finish and sealing around pipes shall be such as to ensure compliance with this specification.

No rendering shall be applied until the Employer has inspected and approved the structure.

11.0 TIGHTNESS TESTS FOR TANKS AND PITS

11.1 Special Requirements for Tanks

All basins shall be submitted to a water tightness test, if this is expressly requested by the Employer.

Water-tightness shall be tested by completely filling the basins with water.

Water level shall remain constant throughout the period required for completing the test.

-Level checks shall commence 24 hours after filling, to allow for the saturation of the walls.

-Basins shall be tested after fitting inlet and outlet pipes, and prior to backfilling.

-Test shall be commenced after the water level has been brought to the original level to offset soaking.

-All basin walls and piping intersection points shall be carefully inspected for leaks.

-Water shall not be added to restore the original level until the test is completed.

All defects that are shown up by tests shall be made good by the Contractor, even though this may require demolishing, remaking, replastering or treatment using special materials, all at the Contractors expense and at no cost to the Employer.

In the case of bottom leakage in basins, either buried or above-ground, for which correction would be a problem, the Contractor shall ensure a thorough waterproofing of the bottom using the most appropriate systems and materials on the basis of the basin construction and operational requirements.

-Defective basins, if any, shall be re-tested after all defects have been repaired or removed until completely satisfactory results are attained.

-All tests shall be attended by the Contractors and Employers representatives.

-No backfilling shall be allowed unless all specified tests have been completed in a satisfactory manner.

11.2 Special Requirements for Pits

All the pits for rain water, sanitary, oily and semi-oily water collection to a sewer system shall be submitted to tightness test, if this is expressly requested by the Employer.

Aniline-coloured water shall be used for testing pits so that leaks, if any, may be more easily detected.

-Each pit shall be tested by filling with water and shall not be classified as acceptable unless the original water level remains constant for at lest 30minutes.

-Tightness test shall be commenced 12 hours after filling to allow for the saturation of the walls; should it be required to offset the saturation, the water level shall be brought to the original level.

-Pits shall be tested after connecting all inlet and outlet pipes, and prior to backfilling.

-Pit inlets and outlets shall be sealed by airtight plugs inserted into inlet and outlet pipes, or by any equivalent method.

-All pit walls and piping intersection points shall be carefully checked for leaks.

-Further water shall not be added to restore the original level until the test is completed.

-All defects found during testing shall be made good by the Contractor.

-Defective pits, if any, shall be re-tested after all defects have been repaired or removed until complete satisfactory results are attained.

-All tests shall be attended by the Contractors and Employers representatives.

-No backfilling shall be allowed unless all specified tests have been completed in a satisfactory manner.

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