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Foul Drainage and Sewer Line

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FOUL DRAINAGE AND SEWER LINE 1. GE GENE NER RALL ALLY  The foul drainage and sewer line system shall be carried out strictly in accordance with the relevant by-laws and if the work fails to satisfy the Local Authority concerned, the Contractor shall rectify the defects at his own expense. The Contractor shall provide suitable qualified personnel to do the section of the work.  The pipes shall be laid to even falls to gradients shown on the drawings. 2. MA MATE TER RIA IAL LS Cement, sand, aggregates, steel reinforcement reinforcement and piles to be as previously described under the appropriate trade specification sections. 3. CAS CAST T IRON IRON PIPES PIPES AND FITT FITTING INGS S Cast iron drain pipes shall comply with BS 437 and shall be with spigot and socket ends. Cast iron bends, branches, traps, gullies and other fitting shall be of the pattern and dimensions stated in BS 1130 and shall be sound, free form cracks and other defects. defects. All cast iron pipes and and fittings shall be co coated ated inside and outside with an approved bituminous solution.  Joints between cast iron pipes and fittings shall be with molten lead and tarred yarn wound round and well caulked in unless otherwise stated elsewhere. 4. LAYI LAYING NG OF DRAI DRAIN N PIPE PIPES S Cast iron drain pipes shall be laid on properly prepared beds in straight lines and to even gradients. gradients. Great care shall be exercised exercised in setting out and determining the levels of the pipes for which the Contractor shall provide suitable instruments instruments and set up and maintain all sight rails, boning rods and bench marks, etch, necessary for the purpose. Pipes shall be laid with the sockets leading up-hill and shall rest on solid and even foundations for the full length of the barrel. 5. PIPELINE Setting out Excavation for the trenches shall be to straight lines and gradients required for the pipes and and beds as specified specified.. The trench bottom shall shall be of sufficient width to allow adequate working space for the pipe layers and


 jointers but beyond these requirements the width must be kept to a minimum. Before any work commences commences the sewer sewer trace sha shall ll be set out. The manhole centres shall be marked by a centre peg whose location shall be tied to 3 pegs situated outside the working area. Sight rails shall be set up painted black and white to mark the centre line of the sewer, and boning rods shall be used to give the distance from the sight rails to the invert invert of the sewer. It is desirable that no fewer than than 3 sight rails be set up on each line so that if one is disturbed it would be obvious. The maximum distance between sight rails should be 23m.  The Contractor shall maintain the setting up of pipelines not less than 460m in advance of pipelying and shall carry such exploratory excavation as may be required by Employer. For the length of the pipelines which are curved on plan or in elevation the curve shall be obtained by deflecting the pipes at each joint. Strongly constructed, clearly painted boning rods shall be provided at each length where work is in progress. Such boning rods shall be designed to show the pipeline invert level below the sight rails. When excavation is complete and before any further work commences wooden pegs are to be driven into the formation at not more than 5 m centres the level of each peg being adjusted to the proposed sewer invert by the use of the sight rails and boning rods. 6. PIPE BEDDING BEDDING WITH WITH GRANULAR GRANULAR MATERIAL MATERIAL  The bedding for the pipes pipes shall be thoroughly thoroughly compacted. The pipes shall be laid evenly on the barrel at the required level. There should be no hollows, voids or foreign foreign material under under the pipe. Any concrete blocks or or wedges should should be removed on completion of bedding. The bedding should be completed to the correct profile as shown in the drawing.

 The bedding should at all stages of the construction be well compacted. Water shall be added to the granular material as laid to obtain optimum moisture content for compaction and sufficient mechanical tampers, vibrators or other approved method of compaction shall be employed at all times.


Particular care must be taken to ensure that proper bedding is obtained at and on either side of the pipe pipe joints. Where pipe jointing jointing holes are left the bedding particular care must be taken to ensure complete and proper filling of the holes after pipe testing. 7. CONCR CONCRETE ETE BED, BED, HAUNCH HAUNCHING ING AND AND SURROUND SURROUND TO TO PIPE  The concrete bed foundation and Type Section for the pipes shall consist of the concrete or reinforced concrete as shown in details on the Contract drawings.

In all cases the concrete shall be well rammed or vibrated and worked under and around the the pipes. No concrete shall be placed placed around the pipes until the pipe joints have been inspected and approved.

At approximately every four pipes or 6m whichever is the less interval the Contractor shall form a joint in the concrete bed or surround with 25mm thick fibreboard, fibreboard, timber or other approved approved material. The shuttering shuttering material shall be left in to form form a permanent joint. Where the concrete concrete bed is required to be reinforced all reinforcement shall stop on either side of the joint. In placing the concrete in surround the Contractor is required to concrete right against against the side of the trench trench excavatio excavation. n. Where the excavation excavation has been carried out to a greater width than the required Type Section or approved width, the Contractor will be required to provide the additional concrete necessary to the sides of the excavation. 8. HAND HANDLI LING NG PIP PIPES ES At every point of loading or unloading pipes or castings must be handle by approved lifting tackle. tackle. Unloading by rolling rolling down planks or any other other form of inclined ramp will not be allowed. Pies are to be carefully stacked on site with timber packings packings under and between between the pipes. Where pipes are stacked, the height shall never exceed 2m. 9. PI PIPE PEL LAYIN ING G All pipes shall be carefully brushed out inside and shall be tested for soundness before before being laid. The pipes shall be laid separately separately to true inverts, straight lines and falls, each pipe being separately boned between


sight rails and bearing evenly upon the solid ground or concrete for its full length. Where pipes are laid without a concrete bed, holes shall be cut in the bottom of the trench os such size and depth as to allow the joints to be properly made and the barrel of the pipe to bear evenly on the solid ground for its full length. Where pipes are to be laid on rock formation the excavation shall be taken down to 1.2 m below bed level and great care shall be taken to ensure that there are no projecting projecting pieces of rock on which the p pipe ipe will ride. The bed will then be made up to its true line and level by refilling with either 100mm of consolidated selected material from the excavation well rammed, and watered if necessary, or with 100 mm of concrete 1:3:6 or as per contact drawings.  The Contractor shall be responsible for ensuring that all blocks and wedges are of sufficient size and strength to prevent settlement of the pipes.  The excavation of the bottom 150mm of the trench and laying of screed or any other surface preparation shall be done immediately in advance of  pipe laying but no pipes shall be laid until a distance of at least 10m along the trench has been prepared and bottomed up to the receive the pipes.  The trenches and joint holes shall be kept k ept free from water until the pipes are laid, jointed and surrounded surrounded with concrete. concrete. No water from the trenches shall be allowed to endter the new pipes and no re-filling of  trenches will be allowed until the joints of the pipes have been tested, inspected and approved. Properly fitted stoppers shall be provided and constantly used to close the ends of all uncompleted uncompleted pipe lines. The stoppers are only to be removed removed when necessary. 10.REINFORCED CONCRETE MANHOLES Reinforced concrete (Grade 30-20 mm aggregates) manholes shall each be of the internal plan sizes and depths indicated on the drawing. Unless otherwise specified, manholes manholes not exceeding 1.0m deep from cover to invert are to be 450mmx690m 450mmx690mm m on plan internally and those exceeding 915mm deep are to be 600mmx1000mm, 600mmx1000mm, the length being increased of  necessary to accommodate accommodate the branch drains. drains. All reinforced reinforced concrete bases, walls and cover slabs shall be 150mm thick as shown and reinforced with mild steel rod reinforcement.


Form rebated opening opening in cover slab for manhole manhole cover and frame. The manhole shall be benched with plain concrete (Grade 25) by using sulphate resisting cement and with half round or three quarter section salt-glazed ware channels channels bedded on. Provide galvanized malleable malleable step irons to all man holes exceeding 915mm deep. 11.MANHOLE Where detailed R.C manholes are to be built in the positions shown on in accordance with the details in the approved Drawings.  The chamber and shaft rings may be supplied in different lengths and each section will be provided provided with lifting holes. holes. The joints between the sections shall be of an ogee joint with cement mortar to form a watertight  joint. Before completion completion of the manhole all the lifting lifting holes, ogee and other joints shall be neatly pointed.

 The reinforced concrete slabs covering the chambers and the shafts of the manholes shall be set and pointed in cement mortar to form watertight  joints.  The reinforced concrete slabs covering the chambers and the shafts of the manholes shall be set and pointed in cement mortar to form watertight  joints. At all points where pipes are built into walls, or floors, great care shall be taken that the joint joint is watertight watertight joint. If found to be otherwise, otherwise, the concrete shall be cut away and replaced with concrete, to make a watertight joint. Manhole covers and frames are to be set in cement mortar and surrounded with Grade B concrete and covers left flush with the surrounding surroundin g ground or road surface as the case may be and shall be set on two courses of 225mm 225mm brickwork. The fine adjustment adjustment of cover levels shall be effected by creasing creasing courses of hard burnt burnt tile. Care shall be taken to ensure that the cover is level with and sloped to any fall or grade to the surrounding surfaces. 12.BACKDROPS AND TUMBLING BAY Where detailed, tumbling bay, or backdrop are to be constructed in accordance with the details on the approved drawings.


Special spigot and socket, tumbling bay, or backdrop junctions shall be used in the junction between the two lines of pipes.  Tumbling bay backdrop backdrop pipes are to be built in the walls of the man hle by cutting a neat hole in the precast concrete rings sufficient for building in the pipes and pointed in cement cement mortar. The joint shall be finished finished flush with the inside of the manhole and neatly splayed on the outside to form a watertight joint. 13.MANHOLE COVERS AND FRAMES  The manhole covers and frames shall be of the cast iron machines type and of approved approved size, weight and and pattern. The heavy duty type type shall be used in roadways and paved area. Manhole covers and frames shall comply with BS 497 and be of the standard type and size size and shall be accordance accordance with the drawings drawings.. The cover and frame shall be cast from a mixture of cast iron scrap and a suitable grade of pig iron. iron. The mixture of the resultant resultant metal shall be free free from air and sand holes holes and from cold shuts shuts.. They shall be neatly dressed dressed and carefully fettled. All casting shall shall be free from voids, whether due due to shrinkage, gas inclusion or other causes. Manhole covers and frames shall be supplied coated with a black bituminous composition. composition. They shall be well fitted, flush flush at the top and should not rock. 14.TESTING TO BRITISH CODE OF PRACTICE 301:1971 After the sewers have been laid they shall be inspected by the Employer for grade, line and level and appearance appearance of inner surface. surface. Any sewers inaccurately laid to grade, line and depth, or if the interior shows open  joints, ragged edges or protruding mortar, mortar, or which are not alignment, shall be made good and relaid so as to conform to the drawings and specification and at the Contractor’s expenses. Sewers shall then be subjected to water or air test, at the discretion of the Employer, for which the Contractor shall provide all necessary testing apparatus, including expanding plugs, flexible bag stoppers, smoke cartridges, etc. together with any other apparatus and labour which may be required for the proper proper testing of the sewers. These tests shall be carried out before backfilling and again after completion of backfilling and reinstatement.


Sewer with caulked joints shall not be tested until at least 24 hours after  jointing.  The sewer or drain shall be tested in sections consisting of the length of  pipe between two adjacent manholes. Water test  The test before backfilling shall be commenced as soon as practical after laying but the sewer or drain shall have been filled for approximately one hour before test readings are taken. A test pressure of 1.2m head above the soffit of sewer or drain shall be applied at the high high end but no more than 2.4m at the low end. end. Steeply graded sewers or drains shall be tested in stages where the above maximum head would be exceeded if the whole section were tested at once.  The loss of water over a period of 30minutes shall be measured by adding water from a measuring vessel at regular intervals of 10 minutes and noting the quantity required to maintain the original water level in the stand pipe. The average quantity of water water added for sewers or dra drains ins up to 300mm nominal bore shall not exceed 0.1 gallon per hour per 30 linear metre per 25mm of nominal bore of the sewer and drain.  The test after completion of backfilling shall be described above.  The length of sewer or drain shall be effectively plugged with suitable expanding plugs between between manholes, and and the air pumped in with an approved air testing machine until a pressure of 100mm head of water is indicated U-tube conhead connected nected the system. The airof pressu pressure re shallwithout not fall to lessin than 75mm of to water during a period 5 minutes, further pumping, after a period for requisite stabilization drains which incorporate incorporat e traps shall be tested to 50mm head of water and the permissible loss shall be 12mm head of water in 5 minutes. Should the pressure not be maintained for the required time a smoke test shall applied for the purpose of locating the fault. 15.CLEARING PIPELINE OF OBSTRUCTION After testing of the pipelines as specified, the interior of the pipelines shall be inspected to ascertain that the pipes are entirely clear of obstruction and that the invert is smooth.


In the case of pipes which cannot be inspected from the inside, generally under 600mm in diameter, a loose plug shall be passed through each pipeline to ensure that the pipes are entirely clear of obstruction and that the invert is smooth. smooth. The loose plug shall be be in the form of a cylinder with solid ends made of timber not less than 25mm in thickness.  The outside diameter of the ends of the plug shall not be smaller than 25mm less than the diameter of the pipe through which it is to be passed and its length shall not less than its diameter. Any obstruction in the pipelines shall be removed and any unevenness of  the invert shall be made good. 16.FRACTURE OF PIPE In the event of pipes being fractured after properly laid whether due to imperfect beds having been formed or the material for refilling having been improperly selected or to any other causes, the Contractor in every instance, will be held responsible and he will be called upon to replace such defective pipes at his won cost, if such defect appears before the expiration of the period of maintenance. Any pipe or length of pipes found to be defective shall be immediately removed and replaced at the Contractor’s expense and leaking joints shall be remade; the inspections and test shall then be repeated as often as necessary until the whole lines under inspection or test is accepted by the Employer.

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