METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
Method statement for
Dislocation and protection of the existing hydro-engineering
installations on the E-763 Highway
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
Sadržaj
1.SCOPE OF THE WORKS AND TECHNICAL SOLUTION ......................................................................... 3
2. METHOD OF CONSTRUCTION FOR TRENCHING AND PIPE LAYING WORKS .................................... 4
2.1. Setting out of the pipeline route ............................................................................................................. 4
2.2 Trench excavation strutting .......................................................................................................................... 4
2.3
Trench de-watering if necessary ............................................................................................................. 5
2.4
Compaction of the trench bottom after excavation ............................................................................... 6
2.5
Laying the sand bedding up to the level of pipe and thumping.............................................................. 6
2.6
Pipe laying, levelling and connecting of the pipes (General) .................................................................. 6
3. INSTALLATION OF WATER SUPPLY - HDPE PIPES ....................................................................................... 7
3.1
Granular bedding ................................................................................................................................... 12
3.2
Backfilling ............................................................................................................................................... 13
3.3 Testing ......................................................................................................................................................... 13
3.4 Cleaning and disinfection of pipelines ........................................................................................................ 14
4 HEALTH AND SAFETY........................................................................................................................ 14
4.1 General requirements to health and safety .............................................................................................. 14
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
1.SCOPE OF THE WORKS AND TECHNICAL SOLUTION
The scope of the project, and this method statement is a part of the new built E-763 highway that connects
Belgrade with the South Adriatic. The dislocation of the hydro-engineering installations is a part of the
subsection 4 (out of total of 5 subsections) of the project. With the construction of this sub-section of the
highway, there is a need to protect the existing water supply networks that were on its way according to the
projected route ot the highway. This volume deals with the protection or relocation of the hydraulic
installations. The position of hydraulic installations (water supply) was determined exclusively according to the
data obtained in the conditions of utility company `Komunalac` Lucani.
The intersections are at the following highway stations:
Municipality of Lucani
- km 135+700 water pipe PEHD DN140;
- km 137+847 water pipe PEHD DN110;
- km 140+680 - km 141+093 water pipe PEHD DN40;
- km 141+221 water pipe PVC O300;
- km 142+038 water pipe PEHD DN40.
The pipe material of the existing installations is mainly plastic - high density polyethylene PEHD and polyvinyl
chloride PVC. All pipelines are for nominal pressures of 10 bar.
The designed solution for all pipelines is similar: it is planned to lay a pipeline that will be moved to a protective
pipe perpendicular to the route of the highway (the shortest crossing). On both sides of the highway,manholes
are planned at 1 m outside the highway fence, and the stretch of the new water supply system in the part
below the highway is in a protective pipe. The manholes contain shutters and a drain in case the section is
emptied. The water from the outlet is poured into the sewer-type inspection
descent, which is 0.5 m lower than the level of the discharge pipe, from where the water can be evacuated by
a mobile pump. For the relocated installations, the stations of their crossing with the highway are given. In
order to determine the position of the protective pipe comparations of the existing
pipeline and the new pipeline are given in parallel.
The levels of the dislocated waterwork pipes were determined in such a way as to maintain the direction of
slope of the existing pipes, in order to avoid new drains or air valves. The direction of the slope was determined
according to the elevations of the terrain. The levels of the displaced water mains were made so that the layer
of earth above the pipe was not less than 1m. The direction of the pipe slope was determined according to the
elevations of the terrain, but in such a way as to fit in with the existing waterwork slopes.
All designed displaced pipes are made of polyethylene (PEHD) for working pressures of 10 bar, of appropriate
nominal diameters. Protective pipes for water supply are intended to be made of polypropylene, DN110 mm DN500 mm designed for heavy traffic (SN16).
Of the facilities at the waterworks, only manholes are planned in front of and behind the highway. Securing
with anchor blocks and concrete plinths is planned at the pipeline turns and under the einforcement in the
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
manholes. On the sections of the pipeline under the highway, the backfilling of the pipes is with gravel, and
on the sections in green areas it is with excavated material.
2. METHOD OF CONSTRUCTION FOR TRENCHING AND PIPE LAYING WORKS
2.1. Setting out of the pipeline route
Setting out will be performed by speciliezed survey teams by the Contractor and make all the necessary
surveying preparations for setting out the rout for the subcontractor to start with the works.
2.2 Trench excavation strutting
After the surveying works and all the necessary setting out is done, the excavation works will start. "Excavation"
will for the purpose of this method statement be deemed to refer to the excavation of all the materials of
whatever geological formation, quality, consistency. The excavation will be performed according to the
longitudinal profiles and cross sections, levels and dimensions of the design and instructed by the Engineer.
Excess excavation beyond the specified lines and levels will be limited to an absolute minimum making due
allowance for working space and the necessary Temporary Works.
CONTACTOR will take all possible precautions to prevent slips in excavations and embankments and to protect
and support structures, which may be endangered.
The following routes of pipelines are expected while constructing the pipeline:
•
Individual installation of pipelines – one trench
Strutting will not be used for consolidated land and where there are no ground waters, if the depth of the
trench is less than 1,25 m in accordance with the necessities.
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
Width of the trench is determined in accordance with the technical regulations for pipe-laying. Width of the
trench for the pipe laying will be in accordance with Technical Specifications and drawings i.e. pipe diameters
plus 40 cm on each side of the trench, but minimum 0.80m. Trenching for pipe laying will be done both manually
and mechanically. Bottom of the trench will be flat without stones and will be levelled before pipe laying.
Depending on the land stability, depth of the trench, gauge of the pipes that will be laid and the level of ground
waters, the corresponding system of strutting can be applied, in accordance with the necessities.
Steel/Timber support
System of strutting (steel/wooden) will be used when necessary to maintain the trench stability, or the system
of the wide excavation will be used, according to the preference of the subcontractor or instructed by the
Engineer.
2.3 Trench de-watering if necessary
De-Watering of the trench will be performed using the sub-merged pumps and/or well-point system depending
of the soil conditions when necessary. Pipes will be placed in water-free trenches only.
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
2.4 Compaction of the trench bottom after excavation
Trench bottom will be compacted after excavation of the trench with hand vibrating-compactor (vibrating
plate).
2.5 Laying the sand bedding up to the level of pipe and thumping
Trench will be filled in with the suitable material (sand) in order to enable the undisturbed and continued laying.
Pipes will be laid on the sand or granulated fine grained gravel (grain size to 10 mm) bedding in the layers of
10cm below the pipe and 30 cm above the crown of the pipe. Sand will be thumped manually. In the case of
using the mechanical gauge, thumping will be performed in accordance with the producer's instruction.
2.6 Pipe laying, levelling and connecting of the pipes (General)
Laying and jointing of the pipes will be carried out strictly in accordance with the manufacturer's instructions.
All pipes will be carefully handled during stringing out and laying operations. Pipes will be moved by lifting,
and will not be dropped, dragged or rolled. Suitable lifting appliances will be used, and the passing of slings
through the barrel of the pipe will not be allowed. Where pipes with an internal lining or external protective
coating are used, the lifting appliance or slings will be of a type, which does not damage the lining or coating.
All pipes will be laid in straight lines and to the levels and gradients shown on the Drawings unless otherwise
directed by the Engineer. Within the distribution network, house connections will be placed on the high points
of the secondary pipelines if possible.
Except where otherwise indicated on the Drawings or as directed by the Engineer, all pipes will be laid with a
minimum cover from ground level to the top of the pipe of 0.8 m or as directed by the Engineer. The trench
will be backfilled with suitable materials in 30 cm thick layers.
Pipeline levelling will be performed in accordance with design and with the help of the instruments for levelling
and total stations.
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
3. INSTALLATION OF WATER SUPPLY - HDPE PIPES
•
Pipes installation
o Pipe preparation – Cleaning
Pipe and fittings will be inspected before exposed piping is installed or buried piping is lowered into the trench.
The following activities will be carried out:
-
cleaning of the ends of pipes;
-
cleaning from foreign matters of pipe with brush before installation
-
removal of foreign matter and dirt from inside of pipes,
-
keep piping clean during and after laying.
Before joining, and before any special surface preparation, surfaces will be clean and dry. General dust and
light soil will be removed by wiping the surfaces with clean, dry, lint-free cloths.
o Field Handling
Polyethylene pipe is tough, lightweight, and flexible. Installation does not usually require high capacity lifting
equipment.
WARNING: To prevent injury to persons or property, safe handling and construction practices must be
observed at all times.
Pipe up to about 219/315 mm diameter and weighing roughly 20 kg per m or less can usually be handled or
placed in the trench manually. Heavier, larger diameter pipe will require appropriate handling equipment to
lift, move and lower the pipe. Pipe must not be dumped, dropped, pushed, or rolled into a trench.
WARNING: Appropriate safety precautions must be observed whenever persons are in or near a trench.
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
Coiled lengths and long strings of heat-fused polyethylene pipe may be cold bent in the field. Field bending
usually involves sweeping or pulling the pipe string into the desired bend radius, then installing permanent
restraint such as embedment around a buried pipe, to maintain the bend.
WARNING: Considerable force may be required to field bend the pipe, and the pipe may spring back forcibly if
holding devices slip or are inadvertently released while bending. Observe appropriate safety precautions during
field bending.
o Joining by Electro-fusion
Method used to joint HDPE pipes is by electro-fusion welding. For this method it is necessary the skilled
personnel, equipment and materials. This technique produces a permanent, economical and flow-efficient
connection. Only a qualified welding specialist will weld and connect the pipes.
Surfaces to be welded will be sufficiently clean, to avoid deterioration of weld quality by any dirt, oil, grease or
other contamination. Vibration inducing operations carried out in the vicinity of welding machine are
prohibited during welding operations.
After welding, the joint will be checked visually. In case of any of the following imperfections, the pipe ends
will be cut and welded again:
•
different high welding beads on pipe end;
•
welding beads too narrow and too tall;
•
welding beads too small;
•
crack on the centre of welding beads;
•
offset too high (10% of pipes wall thickness is tolerated).
There is a barcode label on each of the Electro-fusion fittings. This label includes fusion parameters (such as
welding voltage and duration). Fusion parameters are transferred to the machine from this label either
manually or by using the barcode reader.
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
Photo by the electro-fusion welding on site.
Joining by Butt Fusion
One method that can be used for joining individual lengths of polyethylene pipe and pipe to polyethylene
fittings is by heat fusion of the pipe butt ends as illustrated in the following figure. This technique produces a
permanent, economical and flow-efficient connection. Quality butt fusion joints are produced by using trained
operators and quality butt fusion machines in good condition.
The butt fusion machine should be capable of:
−
Aligning the pipe ends
−
Clamping the pipes
−
Facing the pipe ends parallel with each other
−
Heating the pipe ends
−
Applying the proper fusion force that results in fusion
Standard Butt Fusion Joint
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
The pipes to be jointed are to be held in clamps which grip and re-round the pipe. Clamps are hydraulically
operated by electrically driven pumps. Clamp movement is controlled by the automatic of the welding unit.
The pipe surfaces inside and outside, pipe ends and clamps have to be cleaned (with suitable cleaner and
smooth patch) before inserting into the machine. Pipe ends are to be squared up by planing with an electrically
driven trimmer. Always check visually that both pipe ends are completely trimmed and check pipes for
alignment and gaps around the entire circumference of the abutted pipes. Then heated using an electrically
powered non-stick heater plate. When molten, the pipe ends are brought together and held under pressure
until cooled.
The butt welding machine should be placed on a suitable clean dry base board or ground sheet, probably inside
a tent/ shelter to minimise contamination. The butt welding machine should have been regularly serviced and
has to be in good condition. Only well-skilled workers, who have been trained on the operation of the machine,
should operate it.
The next six steps involved in making a butt fusion joint are as follow:
1. Clamp and align the pipes to be joined
2. Face the pipe ends to establish clean, parallel surfaces
3. Align the pipe profile
4. Melt the pipe interfaces
5. Join the two profiles together by applying the proper fusion force
6. Hold under pressure until the joint is cool
Photo of the butt-fusion welding on site
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
o Polyethylene Flange Adapters and Stub Ends
When joining to metal or to certain other piping materials, or if a pipe section capable of disassembly is
required, polyethylene flange adapters, as depicted in following figure, can be used if necessary.
The “Flange Adapter” and its shorter version, the “Stub End,” are designed so that one end is sized the same
as the plastic pipe for butt fusion to the plastic pipe. The other end has been especially made with a flangetype end that provides structural support, which nullifies the need for a stiffener and, with a metal back-up
ring, permits bolting to the non-plastic segment of a pipe line.
The procedures for joining would be:
1. Slip the metal ring onto the plastic pipe section, far enough away from the end to not interfere with operation
of the butt fusion equipment.
2. If a stub end is used, first butt-fuse a short length of plastic pipe to the pipe end of the stub end. If a “flange
adapter” is used, the plastic pipe-sized end is usually long enough that this step is unnecessary.
3. Butt-fuse the flange adapter to the plastic pipe segment.
4. Position the flanged face of the adapter at the position required so that the backup ring previously placed on
the plastic pipe segment can be attached to the metal flange.
5. Install and tighten the flange bolts in an alternating pattern normally used with flange type connections,
drawing the metal and plastic flange faces evenly and flat. Do not use the flanges to draw the two sections of
pipe together.
At lower pressure, typically 80 psi (5.52 bar) or less, a gasket is usually not required. At greater pressure, the
serrated surface of the flange adapter helps hold the gasket in place.The flange face serration should be
individual closed concentric serration’s as opposed to a continuous spiral groove which could act as a leak path.
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
Back-up ring materials are steel, primer coated steel, epoxy coated steel, hot galvanized steel. In below ground
service, coatings will be appropriate to protect metal back-up rings from corrosion.
One edge of the back-up ring bore must be radiuses or chamfered. This edge fits against the back of the sealing
surface flange.
An all-polyethylene flange without a back-up ring is not recommended because polyethylene flanges require
uniform pressure over the entire sealing surface.
Absent a back-up ring, a polyethylene flange will leak between the bolts.
Flange adapters differ from stub-ends by their overall length. A flange adapter is longer allowing it to be
clamped in a fusion machine like a pipe end. The back-up ring is fitted to the flange adapter before fusion, so
external fusion bead removal is not required.
A stub end is short and requires a special stub-end holder for butt fusion. Once butt fused to the pipe, the
external bead must be removed so the back-up ring can be fitted behind the sealing surface flange.
o Pipe Surface Damage
Surface damage may occur during construction handling and installation. Significant damage may impair the
future performance of the pipeline. The following guidelines may be used to assess surface damage
significance.
For polyethylene pressure pipelines, damage or butt fusion misalignment should not exceed 10% of the
minimum wall thickness required for the pipeline’s operating pressure. Deep cuts, abrasions or grooves cannot
be field repaired by hot gas or extrusion welding. Excessive damage may require removal and replacement of
the damaged pipe section, or reinforcement with a full encirclement repair clamp.
Severely misaligned butt fusions (>10% wall offset) should be cut out and redone.
If damage is not excessive, the shape of the damage may be a consideration. Sharp notches and cuts should be
dressed smooth so the notch is blunted. Blunt scrapes or gouges should not require attention. Minor surface
abrasion from sliding on the ground or insertion into a casing should not be of concern.
3.1 Granular bedding
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
The bedding will be evenly spread and carefully compacted up to the level of the underside of the pipe barrel
and the surface worked to the correct gradient. After laying the pipe the bedding will be brought up evenly on
each side of the pipe in carefully compacted layers, not exceeding 100 mm thickness, to the required level.
The bedding for pipes will be brought up to the horizontal diameter of the pipe, compacted and finished level
to the full width of the trench prior to placing the specified cover and backfill.
3.2 Backfilling
The backfill material will be uniform readily compactable material. Fill above pipes shall be made of layers
not thicker than 25cm, tamped appropriately with machine. Filling material shall be taken from a site
stockpile area or a borrow pit if suitable. Only inorganic material without humus or silty ingredients may be
used.
Backfilling of trenches will not take place until the Engineer's permission has been obtained. Excavation will
be carried out in such a manner that material which is unsuitable for backfilling will be separated and removed
from the site. Trenches in the right-of-way of a road will be backfilled with selected material placed in layers
not exceeding 100mm in thickness after compacting, wetted and compacted.
Trenches not in a right-of-way may be backfilled without tamping.
3.3 Testing
Testing of the constructed water system is performed by testing the installed water pipes of projected diameter
according to the valid Serbian standard SRPS EN 1610: 2006, which is identical to EN 1610: 1997. For testing,
rubber blinds are placed at the beginning and end of the test section. Due to shallow trenches the contractor
would perform the test at a lower pressure because the pipes cannot be sufficiently loaded with temporary
backfilling. The leak testing method would be adapted to the conditions on the construction site, in accordance
with standard EN 1610: 1997. The overpressure is achieved by blowing compressed air into the section under
test. During the test, all pipe joints on the test section are checked. After the examination of the section, a
record of the performed examination is made. If impermissible pressure drops are observed, the pipe joints
will be checked first and then the complete test section. After the damage is detected, it will be repaired and
the section will be re-examined.
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
3.4 Cleaning and disinfection of pipelines
All pipelines will be chlorinated before being put into service. Prior to chlorination the pipeline will be flushed
with clear water flowing at a velocity of about 1.5 - 2.0 metre per second. Chlorination of pipes will be effected
by introducing a chlorine solution in a concentration of 30 to 50 mg/l into the pipeline so that a chlorine residual
of not less than 10 mg/l remains in the water after 24 hours standing in the pipes.
The chlorine solution will be obtained from a mixture of water and a chlorine bearing compound of known
chlorine content such as calcium hypochlorite or chlorinated lime, also called "bleaching power" or liquid
sodium hypochlorite (commercially known as "liquid laundry bleach"). The chlorination will be done by or will
be advised by the sanitary office who will be responsible for disinfection and its consequences.
After chlorination the pipeline will be flushed with clean water until the replacement water has a chlorine
residual of not more than 1 mg/l and the water upon test meets the required health standards for drinking
water to the satisfaction of the Engineer.
The sanitary officer in charge shall ensure safety of workers engaged in disinfection job since chlorine is
dangerous for health if not handled carefully. Officer in user’s division shall ensure (by public announcement)
that nobody uses water intended for disinfection.
4 HEALTH AND SAFETY
4.1 General requirements to health and safety
Contactor will adhere to the concerning environment, health and safety standards and practices. Any other
local regulations will be observed as well. Contactor will ensure observance of such laws, provisions and
regulations by its personnel, and its suppliers.
Construction practices which do not take into account standards of compliance with environment, health
and safety norms may lead to undesirable consequences at the working site, directly cause damage to the
environment and local society. Therefore, it is very important, during construction works, to adopt
construction methods and relevant standards and rules. To achieve this goal Contactor will assign one
persons at the site to be responsible for safety, management and supervision of guidance on environmental
protection.
METHOD STATEMENT FOR DISLOCATION AND PROTECTION OF THE EXISTING HYDRO-ENGINEERING
INSTALLATIONS
Safety of workers shall be provided by trench strutting. Harmful and danger matters shall not be used during
work on pipelines. Excavation of earth up to depth of 125 cm (for foundations, channels, and similar) can
be performed without strutting if soil consistency it allows. Excavation deeper than 150 cm may be allowed
only if sides are properly secured. Strutting shall not be required if excavation sides are made at angle of
internal friction of the soil (natural ground sloping) or in multileveled excavation up to depth of 200 cm at
angle of 60 degrees. Width of trenches/channels shall be adequate to allow sufficient room for safe work
on strutting the trench/channel sides.
Timber and other material planned to be used for strutting of trench sides shall be firm and adequately
sized for the specific purpose according to applicable technical regulations and/or Serbian standards.
-
Dependent on work type, danger and hazardous elements, the following personal protective equipment
shall be provided for work:
- Head protection: Safety helmet
- Eye and face protection:
Shields for eyes and face, eye shield, safety spectacles with side shields. Googles with triplex glass
- Hearing protection
- Protection of respiratory system against rough, non-aggresive and non-toxic dust
- Gloves for hands protection, self reflecting vest
Safety shoes, safety belt or ropes etc..