Method Statement for Sub-Surface Deglottalization of Infrastructure

CONTENTS

1. Purpose

• Scope of Work

• Definitions

• References

• Materials

• Tools, Plant  & Equipment

• Safety

• Prior Activities

• Procedure

1. Responsibilities

1. Attachments

1. Purpose

1.1       To ensure that the sub-surface delethalisation of all infrastructure within the graded portion of the runway strip that constitutes a buried upstand less than 400mm below ground level is executed safely and in accordance with the contract requirements and that all quality assurance/ control activities are conducted in a systematic manner, works are inspected and conformance is verified and documented.

• Scope of Work

• This procedure is applicable to the following works associated with the Project titled, “New 2K Runway – Main Runway Works” – Contract Number NRTW-1008-CN.

• This method statement outlines the procedures to be followed in the sub-surface delethalisation of infrastructure.  Please refer to RFI 173 for the extent of sub-surface delethalisation.

Note:   For the subgrade drainage inspection chambers, those located along the edge of the runway shoulders and fall within the delethalisation area, sub-surface delethalisation is not required on the side that is towards the runway.

• Definitions

• CM                  Construction Manager
  • SE                   Site Engineer
  • ME                   Material Engineer
  • ITP                  Inspection and Testing Plan
  • AHA                 Activity Hazard Analysis
  • JHA                 Job Hazard Analysis

• References

• Specifications:             Volume 3 – Section 9 – Part A – General, Civil and Mechanical Infrastructure

• Drawings:                    Volume 2 – Section 8 – Part B – Civil, Mechanical and Navaids.  Drawing No. PGAD 745/1008/C/731, Rev. A

• BOQ:                           Bill Nos. 3 & 18
• Materials       

• Water (complying to Clauses 200.12A and 331.11 of contract specifications)
  • Sub-Base Material
  • Lean Concrete (Concrete Grade 15/20/S)
  • Formwork
  • Polythene Sheet
  • Hessian Cloth
  • Suitable Fill (complying to Clause 201.3.6 of contract specifications)
  • Surface Protection Material
  • Bituminous Prime Coat
  • Warning Tapes
  • Temporary Signs
  • Safety Barrier
  • Traffic Cones
  • Traffic Lights

• Tools, Plant & Equipments:

• Mixing Plant for Sub-Base and Surface Protection Material
  • Wheel Loaders
  • Dumper Trucks
  • Plate Compactor
  • Water Tanker (equipped with sprinkler bars)
  • Concrete Plant
  • Transit Mixer
  • Concrete Vibrator
  • Steel Trowel
  • Small Generator
  • Air Compressor
  • Personal Protective Equipment

• Safety

• Prior to the commencement of any activities, the workforce will receive an induction talk on the project site safety requirements. This induction talk will include both activity safety issues, as well as general safety requirements.

• Front line supervisor will ensure that Personal Protective Equipment is worn by site personnel at all times during construction activities.

• Heat Stress Training will be provided.
  • Adequate cool drinking water, shade, and salt water tablets will be in place.

• Plant and Equipment will be provided with back-up alarms, lights, and all other applicable safety devices.

• For AOA work, safety requirements as defined per Section 107 will be implemented. Specific safety training will be provided to personnel for AOA work.

• Prior Activities

• Final approval for the waterproofing system, backfilling to 525mm below finished level, levels, alignments, grouting, pipe installation and infrastructure installation should be obtained from the Engineer through the checking inspectionrequests before commencement of any sub-surface delethalisation works.

• Procedure

• Placing of 125mm thick Sub-Base Material

• The materials to be used for sub-base will be as per the approved material submittal and will originate from approved sources.  The material shall comply with Clauses 331.2, 331.5 and 331.6 of the contract specifications, and the ME will inspect and test the material accordingly and periodically as per the previously approved ITP No. 1008-OAJ-ITP-1007.

• The sub-base material will be mixed with water, in a mechanical mixer, to obtain the optimum moisture content.  The sulphate and chloride ion contents of the water used for adjusting the moisture content shall not exceed the limits specified in Clause 331.11 of the contract specifications.  After mixing, the material shall be removed and transported to the placing locations, via dump trucks, without delay.

• Prior to the commencement of sub-base material placing operations, it should be ensured that the backfilling of the infrastructure units is completed, up to 525mm below the finished level, as per the relevant approved method statements and to the satisfaction of the Engineer

• The pre-mixed sub-base material shall be spread by wheel loader and labourers.  The sub-base material shall be spread evenly and compacted by plate compactors, in a layer not exceeding 125mm compacted finished thickness, with a well-bound surface finish.  The extent of placement of sub-surface material is as shown in the attached contract drawing PGAD 745/1008/C/731 Rev. A.

• Should the need arise to adjust the moisture content, water complying with Clause 200.12A of the contract specifications will be sprayed uniformly using water tanker equipped with sprinkler bars.

• Maximum Dry Density testing and CBR testing will be performed in accordance with Clauses 331.1 and 331.9 of the contract specifications, and as per the approved ITP 1008-OAJ-ITP-1007.

• Extreme care shall be taken to avoid any damage to the waterproofing system of the infrastructure units during the sub-base placing operations.

• Placing of Lean Concrete (Concrete Grade 15/20/S)

• Once the placement of the sub-base material is approved by the Engineer, formwork shall be fixed and inspected by the Engineer’s Inspector.  Formwork shall be placed to facilitate the placement of lean concrete to the levels and extents shown in Section A-A of contract drawing PGAD 745/1008/C/731 Rev. A.

• Polythene sheet of 1000 gauge shall be laid and lean concrete of grade 15/20/S shall be poured, vibrated and levelled to the levels and grades shown in Section A-A of contract drawing PGAD 745/1008/C/731 Rev. A.

• The concrete shall be protected by polythene sheet after finishing and wet Hessian cloth covered with polythene sheet after final set.

• Concrete surface shall be kept continuously and thoroughly wet for a curing period of seven days.

• Extreme care shall be taken to avoid any damage to the waterproofing system of the infrastructure units during the concreting operations.

• Placing of Suitable Fill

• The placement of suitable fill material can commence once the concrete has achieved the desired strength and upon the approval of the Engineer.

• Approved suitable fill material shall be delivered to the placing locations by dumper trucks.

• Just prior to placing the suitable fill material, the concrete surface will be wetted to increase bonding with the suitable fill material.

• The suitable fill material shall be spread by wheel loader and labourers.  It shall be then compacted by using plate compactors.

• The suitable fill material shall be compacted and tested to 95% MDD in one compacted lift, varying in thickness from 100mm to 200mm as shown in Section A-A of contract drawing PGAD 745/1008/C/731 Rev. A, in accordance with Clause 201.3.3 of the contract specifications.

• The placement of suitable fill material beyond the extents of infrastructure sub-surface delethalisation will be in accordance with the approved method statement 1008-OAJ-MS-1002 – General Excavation and Filling (Revision 2) and the relevant ITP.

• Placing of Surface Protection Material

• The placement of Surface Protection Material can commence upon the completion of the placement of suitable fill material and the approval of the Engineer.

• The Surface Protection Material shall comply with Clause 200.13 of the contract specifications and the ME will inspect and test the material accordingly and periodically as per the requirements of the approved ITP 1008-OAJ-ITP-1042.

• Just prior to placing the Surface Protection Material, the surfaces of concrete and the suitable fill material will be wetted to increase bonding with the Surface Protection Material.

• The Surface Protection Material will be mixed with water at a designated approved stockpile area.  The water used for mixing the material will comply with Clause 200.12A of the contract specifications, and moisture will be kept within the range of -0% to +2% of the optimum moisture content.

• The Surface Protection Material will then be transported, via dump trucks, to the placement areas where it will be spread and levelled by wheel loaders and labourers.

• Should the need arise to adjust the moisture content again, water will be sprayed uniformly using water tanker equipped with sprinkler bars. It shall be then compacted by using plate compactors.

• Maximum Dry Density and in-situ CBR testing will be performed in accordance with Clause 200.13 of the contract specifications, at a specified frequency of one test each per 500 m² and 25,000 m² respectively.

• The surveyor will verify that the top of design surface of the Surface Protection Material is of such smoothness that, when tested with a 4.80 m straightedge applied parallel and at right angles to the centreline, it shall not show any deviation in excess of 25 mm, or shall not be more than +50/-0 mm from true grade as established by grade pins, in accordance with Clause 200.13 of the contract specifications, prior to the submission to the Engineer for approval.

• In all areas of fill, the SE will verify that no visible voids are formed within the fill.  If necessary, materials will be mixed to ensure an overall grading which will not result in visible voids being present in the fill.  The SE will ensure that all surfaces are well-closed and free from cracks and loose material.

• Where indicated on the contract drawings the Surface Protection Material layer shall be applied with a prime coat of MC 30 petroleum bitumen as described in Clause 331.31 of the contract specifications, except that the application shall be up to 1.60 litres per square meter.

• The placement of Surface Protection Material beyond the extents of infrastructure sub-surface delethalisation will be in accordance with the approved method statement 1008-OAJ-MS-1042 – Placing of Surface Protection Material (Revision 1) and the relevant ITP.

1. Responsibilities

1. The CM will coordinate with SE and ensure that all necessary resources to implement the approved method statement, JHA, and AHA have been allocated to the task.
   1. The SE will ensure that the site preparation activities are conducted according to the approved method statement, JHA and AHA.  The SE will also ensure that all in-situ tests, as required by the ITP, are implemented.

1. The ME will ensure that the materials being used are in accordance with the project specifications and the approved material submittals.

1. It is the site supervisor’s responsibility to organize the work in a safe manner to ensure that safety and protective equipment are being properly utilized.  He must also ensure that the AHA and JHA are implemented and the approved method statement procedure is followed and the ITP is applied.