NNPC GAS INFRASTRUCTURE COMPANY LIMITED
ENGINEERING, PROCUREMENT AND CONSTRUCTION
(EPC) OF PIPELINE INFRASTRUCTURE FOR
ESCRAVOS ENVIRONS POWER SUPPLY PROJECT
WORK METHOD STATEMENT FOR CROSSING USING
THRUST
BORING METHOD
DOCUMENT NO:
R01
16/04/2023
Issued for Review
REV.
DATE
DESCRIPTION
I.
Mathew
BY
Client
Project Contractor Discipline
NGC
EEPSP
O.
Charles
CHECKED
A.
Abiodun
APPROVED
Doc. Type
Sequence- Rev.
Sheet
Doc. Control No.
YNL
PIP
WMS
0002
R01
This document contains information, which is for company use only. This information is to be held in confidence. Disclosure,
reproduction, or other use of this document is prohibited without the prior written consent of CLIENT
ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
Revision
Date
Description
Remarks
REVISION HISTORY
Work Method Statement Civil Works
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ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
TABLE OF CONTENTS
1.0
PROJECT OVERVIEW
4
2.0
1.1 Project Objective
1.2 Scope
DEFINITIONS / ABBREVIATIONS
4
4
4
3.0
2.1 REFERENCE DOCUMENTS
ROLES AND RESPONSIBILITIES
5
5
4.0
MATERIAL REQUIRED FOR CIVIL AND STRUCTURAL WORKS
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defined.
5.0
EQUIPMENT’S AND TOOLS AS PER SITE REQUIREMENT Error! Bookmark not defined.
6.0
WORK PROCEDURE
5
6.1
7.0
SURVEYING, WORK SEQUENCE FOR EXCAVATION.
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defined.
6.2 SETTING OUT.
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6.3 FORM WORKS
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6.4 BLINDING WORKS.
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6.5 CONCRETE PROCESS
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6.6 CURING CONCRETE.
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6.7 SITE CLEARANCE
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6.8 SEQUENCE OF WORKS
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DEVIATIONS
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8.0
QUALITY CONTROL
10
9.0
SAFETY
10
Work Method Statement Civil Works
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ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
1.0
PROJECT OVERVIEW
Nigerian National Petroleum Corporation NNPC through its Subsidiary Nigerian Gas
Company (NGC) Limited intends to construct 6" x 5km and 4”X 2km gas pipelines that will
transport lean gas from Chevron Escravos Gas Plant (CNL-EGP) and NPSC Utility
pipelines respectively to EEPSP Plant within PPMC tank farm at Escravos. To this end
invited competent contractors to bids for the EPC works for gas supply to the power
generation plant at NPSC tank farm.
1.1
Project Objective
The primary objective of the project is to supply gas by tie in at the 16” pipeline using the
valve connection and 24” pipeline via hot tapping and construct a 6” spur line from the tiein point and also 4” at the 8” utility pipeline at NPSC Tank farm via hot tapping for the early
gas phase, provide facility for filtering/separating any liquid and debris, heat and reduce
the gas pressure ((PRMS) to (2- 4)bar that will be further reduced by the regulator to be
provided for the gas driven generator.
1.2
Scope
This Work Methods Statement (WMS) details the general requirements, applicable to sitespecific tasks, necessary to perform the thrust boring necessary for the crossing which is
part of EEPSP LOT III project (pipeline).
2.0
DEFINITIONS / ABBREVIATIONS
FATC…………………. First Aid Treatment Cases
SM…………………. Site Manager
PM…………………. Project Manager
ITP…………………...Inspection & Test Plan
QC…………………...Quality Control
PQP…………………Project Quality Plan
PPE…………………Personnel Protective Equipment
Work Method Statement Civil Works
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ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
HSE…………………Health & Safety Environment
2.1
3.0
REFERENCE DOCUMENTS
•
Client’s Project Specifications
•
Relevant Project Drawings
•
Contractor/Company’s Project Quality Plan
•
Contractor/Company’s Field HSE Plan
ROLES AND RESPONSIBILITIES
Crossing using thrust boring method will be performed with all appropriate and certified
equipment that will be managed under the supervision of an experienced and qualified
Superintendent, according to this WMS. The qualified supervisor will coordinate and
control the works during it realization.
The following list include the personnel will be present during the activity, but not limited
to this:
•
•
•
•
•
•
•
Supervisor
Welders
Grinders
QC inspector (when necessary)
HSSE supervisor
Operators
Helpers
4.0
WORK PROCEDURE
4.1
Preliminary works
All necessary permissions and authorization shall be obtained from the relevant
Authorities concerned before starting any work, including Permits to Work. All
restrictions and provisions accompanying this approval shall be respected.
The necessary traffic control measures for excavations left open during day and night,
shall be implemented as required by the Risk Assessment and in conjunction with local
Authority regulations.
Work Method Statement Civil Works
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ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
Surveyor shall fix the center line of crossing prior to actual construction.
4.2
Pits construction
The area for the Launching pit and receiving pit (if necessary) will be marked out, as
per equipment dimensions
or pipe installation.
Ground levels may be reduced, stepped or battered to reduce pit depths.
Temporary fences to limit the pits area will be placed by CONTRACTOR.
4.3
Boring operation
4.3.1 Installation of Boring Equipment
The Thrust Boring equipment consists of a Thrust / Auger Boring Machine, base frame
with rails, steel jacking shield, rotating cutting head, augers, jacking frame and
hydraulic power pack.
Once the excavation base is completed and the rails for the boring machine will be
installed, a surveyor will check the exact alignment before the installation of the boring
machine.
The boring machine elements will be rigged up, lifted, and set up in the thrust pit.
Suitable mobile crane or excavator with adequate lifting capacity to be utilized for the
works.
The boring machine and supporting structure including jacking frame are to be
installed on the correct level under supervision of boring subcontractor.
All the certificates of the Trust Boring equipment shall be provided to Company for
approval prior to start the boring activity.
4.3.2 Thrust Boring Operation
The Cutting head is installed at the front of the pilot pipe and the boring operation
proceeds by rotating the augers and cutting head, and simultaneously moving the
boring machine forward via hydraulically operated jacks.
Pilot pipe, with an open face, with the same diameter of the casing pipe, will be
progressively loaded into the boring machine The boring operation will start pushing
the first pilot pipe gently forward and once the first section of the pipe has been
installed, the next section is lowered into the pit, using a crane or excavator with
adequate lifting capacity, allocated inside the thrust machine, levelled, aligned with the
first pipe welded and painted securely together. The operation then begins again,
boring and pushing the casing pipe forward. The activity will continue until all sections
Work Method Statement Civil Works
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ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
of pilot pipe have been installed and all the sacrificial string has protruded from the
launch pit at the other side of the crossing.
The excavated spoil from the cutting face is carried through the augers inside the pilot
pipe and is extracted from the side of the boring machine, (see figure 1).
During the boring operation, elevation and alignment of the pipe shall be regularly
monitored to ensure the correct level and alignment is maintained throughout the entire
boring operation.
When the bore has been completed, the cutting head and the shield will be removed
from the front of the pipe and the augers are continuously rotated clockwise until all
the spoil has been removed from inside of the pipes.
Before the start of the pull-in activity, the receiving pit will be enlarged to a sufficient
size to provide ample working space for the equipment and prepared with a gentle
slope on the external side to receive with elastic bend the carrier pipe string. The String
will be sustained during the pulling operation by a sufficient number of side-booms or
manually by labor depending on the length of the crossing Excavator will be utilized to
remove the spoil from the thrust pit to an approved temporary stockpile area,
outside of the property easements. The stockpile locations will be chosen inside the
RoW, without using additional areas.
4.4 Cased pipeline
4.4.1 General
All construction work shall be carried out in accordance with the Contract Documents.
Due care and consideration will be given to any overhead power lines and property in
the vicinity.
Pit launcher and receiving shall be excavated to the depth in accordance with the
relevant drawing of the particular crossings and also the cover that is the height from
the crown of pipe to the surface, a minimum of 2,00 m shall be maintained.
Excavated materials shall be preserved beside the trench.
4.4.2 Crossing string preparation
Work Method Statement Civil Works
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ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
The adequate pipe string length, shall be prefabricated and welded by using
COMPANY approved welding procedures with qualified welders.
All these carrier pipe welded joints, shall be tested with the adequate NDT method, if
any defect detected, same shall be repaired and radiographed.
Prior to lowering-in of prefabricated string, a holiday test shall be carried out on the full
string. If any defective coating noted, it shall be repaired and re-tested.
While carrier pipe inserting in casing, adequate safety precautions shall be
implemented to ensure that the pipe section doesn't hit or drop over the existing
utilities. This is ensured by the following:
Providing adequate room for insertion of the pipe section;
Guiding the pipe section carefully under or over the utility;
Use of trained rigging personnel.
The carrier pipe to insert in casing section shall be properly centered and positioned.
After completion of carrier pipe string insertion, a tie-in will be realized in order to
assure the pipeline continuity.
7.4.3 Casing Pipe – inspection of pipe
Before welding, CONTRACTOR shall inspect the casing pipe in order to detect any
possible out of roundness or dents. Such defects shall be eliminated by suitable
methods.
7.4.4 Casing Pipe - Vent and Drain Pipes
Vent and drain pipes, shall be welded to casing pipe. Vent / drain pipes shall be coated,
including a length of 400 mm above grade.
The remaining section shall be painted. A final check shall be made to verify the air is
free to circulate on the vent / drain pipes.
The welding operations of vents and drains can be arranged after the lowering-in of
the prefabricated arrangement of carriers pipes already inserted in casing pipe.
7.4.5 Carrier pipe - Installation of Collar spacers / Insulator Rings
Collars spacers / insulator rings, shall be fastened and secured to the carrier pipe with
fixtures and according the procedure provided by collars spacers / insulator rings,
manufacturer.
Collars spacers / insulator rings shall be fixed by spacing of 1,00 m while, at both ends
of casing a double set of collars spacers / insulator rings shall be installed, as per
typical drawing checked and approved by COMPANY.
Materials used for the manufacturer of collars spacers / insulator rings shall ensure
electrical insulation between the carrier pipe and the casing pipe and which ensures
permanent resistance to chemical corrosion. No metal
Work Method Statement Civil Works
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ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
bolts or attachments are required. Collars spacers / insulator rings guarantee an easy
insertion of the carrier into the casing pipe preventing damage of carrier pipe coating.
Collars spacers / insulator rings will permit to be tightly fastened onto carrier pipes in
order to avoid horizontal movements during insertion and are resistant to mechanical
and thermal shocks and stresses, particularly those that occur during both the
installation and the inserting operation.
7.4.6 Sealing of Cased Pipe
The casing end seal can be arranged after the tie-in operation with pipeline.
7.4.7 Carrier Pipe - Installation into the casing
Prior to installation of carrier pipe in the casing pipe, the casing shall be cleaned and
inspected. Carrier pipe shall be pushed / pulled into the casing pipe with constant force
and maximum care shall be taken to not damage the collars spacers / insulator rings
during this operation.
7.5 Backfilling
At the conclusion of thrust / auger boring operation, both receiving pit, launching pit
and slip trench will be backfilled with an acceptable original sub soil.
Padding and backfilling operation will be realized according project documents WMS
for bedding, padding and backfilling”. The pipe shall be backfilled across the extent of
the road in accordance with the requirements and specifications stated on the
Approved for Construction (AFC) Drawings.
A casing for FOC shall be laid alongside the carrier pipe. FOC will be installed by
CONTRACTOR during FOC installation.
Surveyor engineer shall collect all data pertaining the preparation of “as built”
drawings.
QA/QC Engineer shall carry out all inspection activities and record all parameters in
the inspection formats.
Care shall be taken at all times when backfilling around existing foreign services in
order to ensure that they are fully supported by the backfill material prior to the removal
of any temporary supporting structures.
7.6 Crossing restoration and pipeline signage
All repair works necessary to restore facilities to the original condition, cut or damaged
by crossing activities, will be carry out.
All restoration work shall be to the requirements, in order to restore the area within the
crossing to its previous condition and shape. Area of construction shall be cleared off
Work Method Statement Civil Works
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ENG I NEERI NG , PRO CUREMENT AND CO NST RUCT IO N (EPC) OF PI PEL I NE
I NF RAST RUCT URE FO R ESCRAVO S ENVI RO NS PO WER SUPPL Y PRO JECT
WORK MET HOD ST AT EMENT FOR
CROSSING USI NG T HRUST
BORING MET HOD
all materials including obstruction and rubbish disposed to a suitable place as per
project specifications and COMPANY instruction.
The shoulders, ditches, banks, and slopes of all roads and railroads crossed will be
restored to their former condition.
Construction debris, surplus material and left-over pipe pup pieces shall be collected
and disposed of as appropriate. Existing facilities and installation shall be restored to
original condition.
Pipeline warning signs will need to be installed after the crossing is completely
restored.
5.0
LIST OF EQUIPMENT AND MATERIALS
The equipment defined herein shall be considered as standard and could be substituted by
equipment with equivalent function, characteristics and skills.
The following equipment and tools will be used for relevant operations:
- Excavator or backhoe
- Truck
- Thrust Auger machine (TAM)
Work Method Statement Civil Works
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