Method Statement for Backfilling of Precast Units

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 backfilling of precast units such as subgrade drainage inspection chambers, communication pits, and electrical pits 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 backfilling of precast units.

• Definitions

• CM                  Construction Manager
  • SE                   Site Engineer
  • CS                   Chief Surveyor
  • ME                   Material Engineer
  • ESHO              Environmental, Safety, and Health Officer
  • 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

• BOQ:                           Bill No. 7, & 20

• Materials       

• Water (complying to Clause 200.12A of contract specifications)
  • Sand (uniform particle size)
  • Suitable Fill (complying to Clause 200.4 of contract specifications)
  • Warning Tapes
  • Safety Barrier
  • Traffic Cones

• Tools, Plant & Equipments:

• Wheel loader
  • Dumper truck
  • Water tanker
  • Cylinder Compactor
  • Plate compactor
  • Hand tamping tools
  • 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, levels, alignments, grouting, pipe installation and precast unit installation should be obtained from the Engineer through the checking inspectionrequests before commencement of any backfilling works.

• Procedure

• For Electrical & Communication Pits:

• Approved sand shall be delivered to the backfilling location by dumper trucks and spread by wheel loaders and labourers.

• Sand shall be hydraulically compacted, by flooding with water, in 300mm lifts up to the top surface of the precast units.  Compacted surfaces will be tested as directed by the Engineer, on site.

• The use of sand as a backfill material, and its subsequent hydraulic compaction, eliminates the use of heavy vibratory compaction equipment in the vicinity of the precast unit. This in turn complies with the requirements of Clause 201.3.3 of the contract specifications, which restricts the use of heavy compaction plant within one (1) meter of a structure.

• Extreme care shall be taken to avoid any damage to the waterproofing system of the structures during the backfilling operations.

• For Subgrade Drainage Inspection Chambers and Manholes:

• The pre-mixed suitable fill material shall be delivered to the backfilling location by dumper trucks.

• The pre-mixed suitable material shall be spread by wheel loader and labourers. It shall be then compacted by using plate and cylinder compactors.

• The suitable backfill material shall be compacted and tested to 95% MDD in 200mm compacted lists, in accordance with Clause 201.3.3 of the contract specifications.

• Extreme care shall be taken to avoid any damage to the waterproofing system of the structures during the backfilling operations.

Note:

1. AGL Pits Backfilling Method Statement shall be submitted separately.

• Box culvert and associated structures backfilling procedures will be as per the approved Method Statement No. 1008-OAJ-MS-1035 R1.

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.