foul drainage and sewer line

8/8/2019 Foul Drainage and Sewer Line

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jointers but beyond these requirements the width must be kept to a

minimum.

Before any work commences the sewer trace shall 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 of the sewer. It is desirable that no fewer 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 invertby the use of the sight rails and boning rods.

6. PIPE BEDDING WITH GRANULAR MATERIAL

The bedding for the pipes shall be thoroughly compacted. The pipes shall

be laid evenly on the barrel at the required level. There should be no

hollows, voids or foreign material under the pipe. Any concrete blocks or

wedges 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.


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Particular care must be taken to ensure that proper bedding is obtained at

and on either side of the pipe joints. Where pipe jointing holes are left the

bedding particular care must be taken to ensure complete and proper

filling of the holes after pipe testing.

7. CONCRETE BED, HAUNCHING AND SURROUND 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 pipes. No concrete shall be 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, timber or other approved material. The shuttering

material shall be left in to form a permanent joint. Where the 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 concreteright against the side of the trench excavation. Where the 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. HANDLING PIPES

At every point of loading or unloading pipes or castings must be handle by

approved lifting tackle. Unloading by rolling down planks or any other

form of inclined ramp will not be allowed. Pies are to be carefully stacked

on site with timber packings under and between the pipes. Where pipesare stacked, the height shall never exceed 2m.

9. PIPELAYING

All pipes shall be carefully brushed out inside and shall be tested for

soundness before being laid. The pipes shall be laid separately to true

inverts, straight lines and falls, each pipe being separately boned between


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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 solidground 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 pieces of rock on which the pipe 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 free from water until the pipes

are laid, jointed and surrounded with 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 pipe lines. The stoppers are only to be 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 not exceeding 1.0m deep from cover toinvert are to be 450mmx690mm on plan internally and those exceeding

915mm deep are to be 600mmx1000mm, the length being increased of

necessary to accommodate the branch drains. All reinforced concrete

bases, walls and cover slabs shall be 150mm thick as shown and

reinforced with mild steel rod reinforcement.


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Form rebated opening in cover slab for 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 bedded on. Provide galvanized 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 with lifting holes. The joints between the

sections shall be of an ogee joint with cement mortar to form a watertight

joint. Before completion of the manhole all the 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 is watertight joint. If found to be 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 ground or road surface as the case may be and shall be set

on two courses of 225mm brickwork. The fine adjustment of cover levels

shall be effected by creasing courses of hard 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.


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Special spigot and socket, tumbling bay, or backdrop junctions shall be

used in the junction between the two lines of pipes.

Tumbling bay 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 mortar. The joint shall be finished flushwith 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 size, weight and pattern. The heavy duty 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 and shall be accordance with the drawings. The

cover and frame shall be cast from a mixture of cast iron scrap and a

suitable grade of pig iron. The mixture of the resultant metal shall be free

from air and sand holes and from cold shuts. They shall be neatly dressed

and carefully fettled. All casting shall be free from voids, whether due to

shrinkage, gas inclusion or other causes.

Manhole covers and frames shall be supplied coated with a black

bituminous composition. They shall be well fitted, 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 of inner surface. Any sewers

inaccurately laid to grade, line and depth, or if the interior shows open

joints, ragged edges or protruding mortar, or which are not alignment,

shall be made good and relaid so as to conform to the drawings and

specification and at the Contractors 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 testingapparatus, including expanding plugs, flexible bag stoppers, smoke

cartridges, etc. together with any other apparatus and labour which may

be required for the proper testing of the sewers. These tests shall be

carried out before backfilling and again after completion of backfilling and

reinstatement.


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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 end but no more than 2.4m at the low 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 added for sewers or drains 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 manholes, and the air pumped in with an

approved air testing machine until a pressure of 100mm head of water is

indicated in U-tube connected to the system. The air pressure shall not

fall to less than 75mm head of water during a period of 5 minutes, without

further pumping, after a period for requisite stabilization drains which

incorporate 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 testshall 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.


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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. The loose plug shall 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 Contractors 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 theEmployer.

foul drainage and sewer line

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