5 sc&s5-sewerage work

8/10/2019 5 Sc&s5-Sewerage Work

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CSS5-SEWERAGE WORK/1

Section 5 - SEWERAGE WORK

5.1 STANDARDS OF CONSTRUCTION

Refer to Clause 1.1.1 of this specification, which applies to this section.

Generally all materials, workmanship and construction for sewerage works shall conform to the Standardset out by the relevant authorities for which all sewerage works and to whom the sewers constructed underthis Contract will be handed over to.

5.2 NON-CONFORMANCE WITH STANDARDS

Refer to Clause 1.1.2 of this specification, which applies to this section. Any Site Instruction that requires

the removal all unsuitable material with this project will require Corrective Action Reporting.

5.3 CONCRETE WORKS

Ordinary reinforced concrete works shall comply with the Section 3- Reinforced Concrete in thisSpecification.

5.4 BENCH MARK

The Contractor shall establish substantial bench marks and fixed points on the Site to the Engineer'sdirection and shall ensure 'hat these are not damaged or disturbed. All such bench marks and fixed Points

must be referred to a Master Bench Mark to be given by the Owner's Surveyor.

The Contractor shall ensure that his qualified surveyor verity the value of the bench mark against the invert

level of the manhole or sewer into which this sewer will be connected and shall inform the Engineer shoulda discrepancy be detected.

5.5 SETTING OUT

Before any work commences the sewer trace shall be set out. The manhole centre shall be marked by a

centre peg whose location shall be tied to 'three pegs situated outside the working area. For sewer lines onexisting roads the sewer trace shall be marked on the surface by paint.

The Contractor shall submit a copy of the setting out plan, duly endorsed by his Qualified Surveyor, to theEngineer for verification and record. The plan shall show clearly the reference bench mark and datum.

5.6 ORDER OF SEWER PIPES, FITTINGS & MANHOLE PARTS

For the construction of sewers, the Contractor shall place order for the supply of all the required pipes andmanhole parts within 7 days of awarding the tender and notify the Engineer of this in writing The ordershall stipulate the specified times of delivery to the site after all the necessary tests required by the

Engineer.

5.7 EXCAVATING SEWER TRENCH

Excavation shall be carried out carefully to the line gradient and level as shown.

If required, the excavated materials shall be carted to a temporary storage and returned subsequently forbackfilling to allow for a free flow of traffic.

Should any of the sewer trenches be excavated to a depth greater than necessary, the Contractor shall berequired to fill in the same at his own expense with concrete or other approved hard materials


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If any slip, fall, upheaval of earth or settlement etc shall occur, the Contractor shall make good the same.including surface restoration, at the Contractor's own expense.

5.8 RATE OF EXCAVATION AND PIPE LAYING

The Contractor shall so arrange his work that the rate of laying pipeline keeps pace with the rate ofexcavation.

5.9 SAFEGUARDING PROPERTIES ADJACENT TO SITE

Where work is undertaken near or adjacent to properties, structures or buildings and it is likely that thestability of such buildings and structures is liable to be affected as a result of the Works, the Contractor

shall, for his own protection. arrange to have such building inspected and to have on record any cracks orany other defects Which may be affected by the Works.

The Contractor shall be held full responsible for the damage to the public, private or other propertiesadjacent to the Site of the Works which is caused as a direct or indirect result of the Contractor's Work. TheContractor shall be required to carry out such preventive measures or rectification immediately or when

directed by the Engineer

5.10 METHOD OF WORKING

The Contractor is required to carry out the Works in the manner detailed, shown on the Drawings and

normally adopted in good sewerage work practice. He is at liberty to supply with his ender suchmodification as he proposes for consideration and shall seek approval from the Engineer before he isallowed to apply new or changed methods of construction

5.11 SEQUENCE OF CONSTRUCTION

The Contractor snail schedule the excavation and laying of sewer lines in such a way that the sewer linebetween the last manhole and the connection to the existing manhole is the last to be excavated and laid.

The Contractor shall not break open or attempt any connection to the existing manhole until writtenapproval is obtained from the Engineer.

5.12 SUPPORT TO EXISTING WORK

When any excavation is carried out near, or under any existing works including buildings, services, mains,cables and surfaces such as roads etc liable to be affected by subsidence, the Contractor shall take action toensure proper support, backfilling and compaction to prevent damage by subsidence whether such existing

work is shown on the Drawings or not.

5.13 VENTILATION

The Contractor shall provide adequate ventilation and efficient apparatus to keep all excavations trenches,tunnels and headings, structures, sewers and manholes free from all gases whether generated in the strata,arising from the use of explosives for blasting, sewage gases or otherwise and he shall take precautions toascertain they are in a safe gas free condition before allowing his workmen to proceed.

5.14 APPROVAL OF EXCAVATION

The Contractor shall report to the Engineer for an inspection when the excavation has reached the requireddepth or secure bottom and are ready to receive the sealing coat. Any concreting or other works put inbefore the excavations have been inspected and approved shall, if so directed be removed and new workssubstituted, all at the Contractor's own expense.

5.15 BACKFILLING TRENCHES


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The Contractor shall obtain the approval of the Engineer before commencing backfilling of trenches. Inbackfilling, only selected hard dry materials free from large stones or lump shall be used in the initialbackfilling and shall lie carefully placed next to the permanent works and well packed and well rammed inlayers of 150mm for a depth of at least 300mm over the top of the work. Particular attention must be paid tofilling and ramming around and above pipes in trench to thoroughly compact the filling around structuresand to the completed filling of the voids created by the withdrawal of timbering.

The remaining of the excavation shall be filled in with the best and most suitable portions Of the excavatedmaterials, in layers not exceeding 600 mm thick. Each layer shall be thoroughly rammed using mechanical

rammers before the next layer is placed. The Contractor shall maintain all refilled surfaces until reinstated.The Contractor shall bear full responsibility for claims arising from accidents due to the subsidence orinadequate maintenance.

Where ground condition is poor, the Contractor shall pay special attention to the backfilling around pipesand haunch and in particular around deep manholes. Care must be taker, to fill around the structure andensure that it is being backfilled uniformly with minimum difference in levels.

The Contractor shall be responsible for any tilting of manhole, shifting of pipelines, crack of any kind,howsoever caused, and shall made good any damage at his own expense.

5.16 DISPOSAL OF SURPLUS EXCAVATED MATERIALS

Any suitable surplus earth left after the backfilling of the excavation and consolidation shall be removedand used to top up the surrounding low lying areas approved by the Engineer, or in area specified in the siteplan. In topping up the low lying areas, the Contractor shall grade such areas in a systematic manner and insuch a way that there is no stagnation of water.

However, if instructed by the Engineer, the Contractor shall cart away any surplus earth, suitable orotherwise to his own dumping ground.

The Contractor shall be deemed to have included for filling or carting of surplus earth in the Lump Sum

Tender Price.

5.17 DE-WATERING OF EXCAVATION

The Contractor shall provide, operate and maintain a system of temporary drains, intercepting ditches, cutoff drains, sub-drains, sumps, well points, de-watering equipment and all other things necessary for keepingthe subsoil or accumulated water out of the excavation or at a level at the bottom of the excavation for sucha period as the Engineer may direct or necessary all at the Contractor's expenses.

5.18 SEALING COAT

Where indicated on the drawings and immediately a sufficient length of trench has been piled and/or

approved by the Engineer, a sealing coat of lean concrete shall be laid across the complete width of thetrench.

5.19 PIPE BEDDING

The bedding for the pi pipes shall be thoroughly compacted. There shall be no hollows, voids or foreign

materials under the pipe and the bedding shall be compacted to the Correct profile as shown on theDrawings.

Particular care must be taken to ensure that proper bedding is obtained at and on either side of the pipejoints Where pipe jointing holes are left in the bedding, particular care must be taken to ensure compete andproper tilling of the holes after pipe testing.

5.20 CONCRETE BED, HAUNCH TO PIPES


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In all cases the concrete haunch shall be provided for pipes crossing roads. No concrete shall be placedaround the pipes until the pipe joints have been inspected and approved.

In placing the concrete in surround the Contractor is required to concrete right against the side of trenchexcavation. Where excavation has been carried out to greater width than required, the Contractor will berequired to provide additional concrete necessary to concrete to the sides of the excavation all at his own

expense.

5.21 HANDLING PIPES

At every point of loading or unloading, pipes or castings must be handled by approved tackle. Unloading byrolling down planks or any other form of inclined ramp will not be allowed unless prior written approval isobtained from the Engineer. Pipes are to be carefully stacked on Site, with timber packing under andbetween the pipes. The height of stacked pipes should not exceed 2m.

5.22 PIPE LAYING

All pipes shall be carefully brushed out and cleaned inside and shall be visually tested for soundness before

being laid. The pipes shall be laid separately to true inverts straight lines and falls, each pipe beingseparately boned between sight rails and bearing evenly upon the solid ground or concrete for its full length.

5.23 JOINTING PIPE

Pipes shall be jointed by heat welding with approved equipment provided by Contractor

5.24 TESTING GRAVITY PIPELINE.

All gravity pipeline and sewers of 525mm or less in diameter before being surrounded and covered shall betested by filling with water in a manner approved by the Engineer and in the presence of his representativeand the relevant authorities. The pressure shall be measured from the highest point of the pipe line undertest and shall be 1.2m head Of Water. Pipelines will net be accepted until they have withstood the required

pressure for 30 minutes without a loss in excess of 1.5 liters for 100m for each 300mm in diameter. TheEngineer reserves the right to carry out air testing if necessary

Gravity pipelines exceeding 525mm In diameter shall not D2 hydraulically tested but the joints will beinspected and shall be made to the satisfaction of the Engineer.

The pipes shall net be covered until they have been inspected and passed.

5.25 INSPECTION AND REPLACEMENT OF DEFECTIVE WORKS

The Contractor can cover up any completed works only after the work had been inspected and found to be

satisfactory. The Engineer reserves the right to request the Contractor or others to open up any work overup before his inspection or satisfactory rectification for ins inspection and checking. The Contractor shallmake the necessary allowance for this in his Lump Sum Tender Price.

Wherever in the opinion of the Engineer the work done is inadequate or of poor workmanship or interiormaterial or in any way substandard, such works shall be demolished, cut out and removed from the worksimmediately and replaced with new materials of the required standard and quality. Action will be takenagainst the Contractor for irregularities committed.

5.26 WATER TIGHTNESS

All water retaining structures must be absolutely watertight showing no leakage or dampness through any

concrete or joint in wall, floor or roof slabs. Any leakage or dampness evident on completion of the workmust be remedied by the approved method at the Contractor's expense.


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5.27 PREVENTION OF FLOTATION

The Contractor is to note that the proposed structure may not be heavy enough to resist the possible upliftdue to water pressure until the structures, soil cover and backfilling have been completed. The Contractorshall make adequate arrangements to keep the excavation dry until the structure and filling are completed orshall adept other approved means of ensuring the stability of the temporary or permanent works. The

proposed method must be submitted for approval prior to the commencement of the work and adequatestandby plant and attendance must be available at all times.

For pipelines laid in wet, waterlogged or ground subject to flooding all necessary precautions must be taken

to prevent the floatation or movement of pipelines whilst laying, laid or under test.

5.28 BUILT-IN -PIPES

At all points where pipes are built into concrete walls or floors, great care shall be taken that the joint iswatertight. If found to be otherwise, the concrete shall be cut away and replaced, at the Contractor's

expense, with concrete to make a watertight joint to the satisfaction of the Engineer.

5.29 JUNCTIONS AND CONNECTIONS

The junctions where provided shall be securely stopper, such temporary stopper being secured with cementmortar.

5.30 CONCRETE AROUND PIPES

After each length of pipes has been tested and passed, the road crossing pipes shall be haunch up withGrade 23 concrete as shown on the Drawings.

5.31 MANHOLES

Where indicated, reinforced concrete manholes are to be built in the positions shown on and in accordancewith the details on the Drawings.

The reinforced,concrete slabs covering the chamber and the shafts of the manholes snail be set and pointed

in cement mortar to form watertight joints.

At all points where pipes are built into the concrete wall or floors, great care shall be taken that the joint iswatertight. if found to be otherwise, the concrete shall be cut away and replaced with fresh concrete, tomake a watertight joint to the satisfaction of the Engineer.

Channels and benching to the concrete floors of the manholes are to be formed in Ordinary PortlandCement concrete and trowel smooth to the satisfaction of the Engineer.

Manhole covers and frames shall be set in Ordinary Portland Cement mortar and surround with Grade 30concrete and the covers left flush with the surrounding ground or road/driveway surfaces or be directed asthe case may be and shall be set on two courses of 225mm brick. Care shall be taken to ensure that thecover is level with and sloped to any fall or grade in the surrounding surfaces.

5.32 MANHOLE COVER AND FRAME

The manhole covers and frames shall be of the pre-cast concrete type.

5.33 TUMBLING BAYS AND BACKDROPS

When required, tumbling bays and backdrops are to be constructed in accordance with the details of theDrawings.


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5.34 CLEARING PIPELINE OF OBSTRUCTION

After testing the pipelines as specified and when directed by the Engineer, the interior of the pipelines shallbe inspected to ascertain that the pipes are entirely clear of obstruction and that the invert is smooth. In thecase of pipes which cannot be inspected from the inside, generally under 600mm diameter, a loose plugshall be passed through each pipeline. The loose plug shall be in the form of a cylinder with solid ends

made of timber not less than 25mm in thickness or of any other material approved by the Engineer.

The outside diameter of the ends of the plugs shall not be smaller by 25mm less man the diameter of thepipe through which it is to be passed and its length shall not, be less than its diameter.

The Engineer will not apply this test until he is satisfied that the lengths concerned are complete and readyfor operation.

Any obstruction in the pipelines shall be removed and any unevenness of the invert shall be made good.

If, as a result of the removal of any obstruction, the Engineer considers that damage may have been causedto the pipelines, he shall be entitled to order the length to be retested at the expense of the Contractor.Should such re-test prove unsatisfactory, the Contractor shall at his own expense amend the work and carry

out such furrier tests as are required by the Engineer.

5.35 FRACTURE OF PIPE

If at any time during the Contract Period or Defects Liability Period or any extension of such periodresulting from the Contractor's fault, cracks, fractures or any defects be found in the pipeline, it shall be theContractor's responsibility to make good such defects at his own expenses as and when directed by theEngineer.

Any pipe or length of pipes found to be defective shall be immediately removed and replaced at theContractors expense and leaking joints shall be remade; the inspections and tests shall then be repeated asoften as necessary until the whole line under inspection or test is accepted by the Engineer and handed over

to the relevant authorities.

5.36 SEWER CONNECTION TO EXISTING MANHOLES

The Contractor shall carry out the necessary connection to the existing manhole only when directed by theEngineer.

The Contractor shall ensure that extreme caution is exercised and avoid any damage to the existing sewer.All construction debris and excess materials must be removed from the manhole and inspected by theEngineer's representative before disposal as directed.

Prior snangements must be made with the relevant authorities for the inspection of the connection

(supervision of connection if necessary and Contractor is to allow for the supervision and inspection fees inhis Tender Once the connection is inspected and found to be satisfactory, the Contractor shall immediatelyplug it in the manner as directed to the satisfaction of the Engineer.

5.37 CONNECTION OF HOUSE DRAINS AND SANITARY LINES TO NEW SEWER

No final connection may be made from the house drain or sanitary line to the new sewer until the sewer linehas been passed and commissioned after the final inspection.

5.38 CLEANING OF SEWERS

All sewer lines and manholes must be thoroughly cleaned to the requirements of relevant Authorities before

any inspection. The Contractor shall be required to clean out all dusts and water etc from the sewer linesand manholes at his own expense and as often as necessary irrespective of the cause of the dirt etc until thewhole line under inspection or test is accepted by the Engineer,


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The Contractor shall when required by the Engineer, provide without charge the necessary aluminumladder, power torchlight of at least six battery cells, keys for the lifting of manhole covers and spirit levelsas well as a minimum of two numbers appropriate mirrors all to the approval of the Engineer.

5.39 ARRANGEMENTS FOR SEWER INSPECTION

Upon completion of the works, the Contractor shall arrange for the whole works to be thoroughly cleanedup and defects rectified. A request shall then be made to the Engineer to inspect the Works.

The Engineer shall only request for Joint inspection by the relevant authorities if all defects detected by hisinspection are satisfactorily rectified.

The Contractor shall clean the sewers and attend to all necessary inspections.

5.40 RECTIFICATION OF DEFECTS

In the event that the inspection is not satisfactory, the Contractor shall be required to carry out at his ownexpenses, all the rectification works as listed by the relevant authorities inspection report such as repair or

replacement of defective or missing parts manhole covers, and where necessary the sinking of additionalmanholes to correct kinks, bends (horizontally or vertically) on levels due to incorrect construction,settlement or whatever causes and to raise the manhole cover level to flush with the ground etc as may bedirected by the relevant authorities.

Such rectification shall be carried out diligently and expeditiously to enable a inspection to be carried out assoon as possible and to be repeated where necessary until the whole sewers and manholes can be certifiedfor taking over by the relevant authorities.

The Contractor may be charged for the inspections if more than one re-inspection is necessary.

5.41 CERTIFICATION OF COMPLETION AND USE

No sewers or part of a sewer may be put into use until the final inspection has been carried out and thesewer and manholes found to be satisfactory. The Works shall only be certified satisfactory when both theOwner and the relevant authorities have approved all the sewers and manholes.

5.42 TEST CERTIFICATES FOR MATERIALS USED IN SEWERAGE WORKS

The Contractor upon completion of the Works will have to submit the relevant test, certificates and/or testresults to the relevant authorities.

5.43 SEALING OF THE SEWER

Normally. upon satisfactory inspection by the relevant authorities ,will grant permission for the sewer to becommissioned.

In the event that the sewer is not to be commissioned until a later date, the Contractor shall be instructed toplug the upstream end of the last manhole before the existing manhole in addition a 100mm thick concrete

(Grade 30) is to be cast over the last manhole cover as shown on the Drawings and directed by theEngineer.

For manhole within the road carriageway, the manhole cover shall be constructed lower such that theconcrete sealing cover is flush with the road level or as directed by the Engineer.

The Contractor shall allow for the cost of the above in his Tender.

5.44 COMMISSIONING OF THE SEWER


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If at any time the sewer is to be commissioned before the expiry of the maintenance period, the Engineershall give written notice and the Contractor shall hack off the concrete slab over the manhole cover andclean up the whole sewer for inspection including raising the manhole cover to the final level as requiredand made good any defects found during the inspection.

The plugs can only be removed as directed by the Engineer for the sewer to be commissioned. The

Contractor is to allow for all these costs in the Lump Sum Tender Price.

5.45 CLEANING UP AT THE END OF THE CONTRACT

All water retaining and other structures shall be pumped dry and washed and swept free of all debris, mud,dirt and to construction materials.

All equipment and fittings shall be cleaned, greased and oiled and all necessary adjustment made to ensuretheir full working efficiency.

A11 site roads, paths and drains shall be swept clean and dry and all construction plants and materialsremoved from Site.

5.46 FINAL INSPECTION

At the end of the maintenance period the Contractor shall arrange to clean up the sewer and rectify alldefects before the Engineer requests the relevant authorities for an inspection of the Works. The Contractorshall comply with the comments from the relevant authorities and rectify all defects for re-inspections untilthe sewer is certified satisfactory and 'taken over by the relevant authorities.

In the case where the sewer was commissioned before or during the in maintenance period, the Contractor'sobligation shall be deemed to be discharged if the sewer after rectification and inspection as described

above is certified to be satisfactory and taken over by the relevant authorities.

Where the sewer is yet to be commissioned, the Contractor shall break the concrete slab, clean up the sewer

and rectify all defects for inspection by the relevant authorities until certified to be satisfactory, If the seweris to be commissioned then the Contractor shall raise the manhole to the final level and made good,otherwise the Contractor shall concrete over the manhole cover, again to the satisfaction of the Engineer.The sewer will then be handed over to the Owner and contractor's obligation shall be deemed to bedischarged.

The Contractor shall allow for all costs in the Lump Sum Tender Price.

5.47 DEFECTS DURING MAINTENANCE PERIOD

The Contractor shall note that the levels, limits and lines as shown on the Drawings shall be final levels,

limits and lines at the time of the expiry of the maintenance and Defects Liability Period. The Contractor is

deemed to have included in his Lump Sum Tender Price for all rectifications necessary for the sewer tines,manholes and fixtures to be inspected and handed over to the relevant authorities.

A final inspection by the relevant authorities inspectors will be carried out before the end of themaintenance period and the Contractor shall be required to carry out the clearing and rectification beforeand attendance to this inspection.

The Contractor shall be required to carry out all rectification works as listed out in the inspection reportsuch as repairs and replacement of defective or missing parts e.g. manhole covers, desalting and removal ofany foreign materials such as mud, sand or stagnant water etc in the sewer whatsoever and howsoevercaused, as the Engineer may direct in writing during the maintenance period wherever necessary all to the

satisfaction of the Engineer and the relevant authorities for the final take over.

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