Method Statement for Construction of North Stormwater Retention Pond and Overtopping Spillway

CONTENTS

1. Purpose

• Scope of Work

• Definitions

• References

• Materials

• Plant  & Equipment

• Safety

• Prior Activities

• Procedure

1. Responsibilities

1. Attachments

1. Purpose

1.1       To ensure that the North Stormwater Retention Pond and Overtopping Spillway are 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 construction of North Stormwater Retention Pond and Overtopping Spillway.

• 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

• Material         

• Concrete Grades 40/20/S , 40/20/SF and Pavement Quality Concrete
  • Quarried Rock 125mm thick
  • 150 X 305 mm Precast Half Batter Kerb
  • 200 mm Diameter UPVC Perforated Pipe (as per RFI 32 and RFI 111)
  • 10 mm to 20 mm Gravel
  • Filter Fabric (Geotextile Fabric)
  • A393 Mesh or Equivalent Rebar.
  • Cement
  • Sand
  • Water
  • Polythene Sheet
  • Hessian Cloth
  • Polyethylene Joint Filler
  • Joint Sealant
  • Backing Cord
  • Formwork/Shuttering
  • Warning Tapes
  • Traffic Cones
  • Traffic Lights
  • Safety Barrier

• Tools, Plant & Equipments:

• Excavator
  • Wheel Loader
  • Dumper Truck
  • Water Tanker
  • Plate Compactor
  • Hand Tamping Tools
  • Spirit Level
  • Measuring Tape
  • Hammer
  • Hand Planer
  • Concrete Chisel
  • Carpenter Chisel
  • Plastic Trowel
  • Steel Trowel
  • Broom
  • Personal Protective Equipment
  • Wire Nails
  • Air Compressor
  • Generator
  • Electric Saw
  • Concrete Vibrator

• 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 North Stormwater Retention Pond and Overtopping Spillway details should be obtained from the Engineer, through the shop drawings submittal process.

• The surveyor will locate and mark all live services that are present in the site (this includes above ground services as well as buried services).  These services (electric, telephone, gas, oil, chemical, water, etc.) will be clearly marked using stakes and warning tapes.  Near these services, special precautions will be undertaken and coordination with the Engineer will be carried out to avoid any damages during the excavation and compaction process.  Any existing service, if exposed during previous excavation, will be clearly marked, protected, and properly supported during all activities.

• Procedure

9.1       Excavation

• North Stormwater Retention Pond shall be excavated to the lines and grades indicated on the approved shop drawings by using an excavator and in accordance with sub-clause 201.2 of the contract specifications.

• The excavated material shall be removed by dumper trucks and heaped or disposed off according to sub-clause 201.2.1 of the contract specifications.

• The excavated sloped sides and bottom shall be watered, levelled and compacted.

• Compaction shall be conducted by using plate and cylinder compactor at the pond’s bottom and hand tamping tools at the sides, to the satisfaction and approval of the Engineer.  Testing at formation level shall be carried out in accordance with Clause 201.2.8 of the Project Specifications.

• All excavation and filling activities will be in accordance with the previously approved Method Statement for General Excavation and Filling (1008-OAJ-MS-1002-R2).

• Construction of the Land Drain

• The land drain trench shall be excavated to the lines and grades indicated on the approved shop drawings by using an excavator and in accordance with sub-clause 201.2 of the contract specifications.

• Compaction shall be done by using hand tamping tools, to the satisfaction and approval of the Engineer.

• Approved geotextile fabric shall be laid and 200mm diameter UPVC perforated pipe shall be installed with 10mm to 20mm gravel surrounding, and then closed with the approved geotextile fabric.

            9.3       Casting of Concrete Grade 40/20/SF

• Approval of the excavation and compaction of the formation level of the retention pond by the Engineer shall be followed by 150mm thick surface preparation as shown in the contract drawings and erection of the side formwork and laying of 1000 gauge polythene sheets.
  • Concrete grade 40/20/SF (150mm thick at the base and 125mm at the sides, to the limits shown) shall be poured, levelled, and trowel finished.

• Construction and expansion joints shall be provided as shown in the shop drawings.

• 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.

9.4       Placing of 125mm thick Quarried Rock at the top 1.5m of the Pond

• Quarried rock (125mm thick) shall be placed in such a manner as to  produce a reasonable well graded mass of rock with the minimum practicable percentage of voids, and shall be constructed to the lines and grades indicated on the shop drawings.

• Quarried rock shall set in 50mm thick 4:1 sand/cement mortar.  Placing of rock shall begin from the bottom and progress up the slopes.

• The finished quarried rock shall be free from pockets of small stones and clusters of larger stones.

• Expansion and construction joints shall be provided as shown in the approved shop drawings.

            9.5       Fixing of Precast Kerb

9.5.1       The kerb blinding grade 40/20/S, 200mm minimum thickness, shall be cast to the lines and grades indicated on the approved shop drawings.

9.5.2       Precast half batter kerb (150X305 mm), conforming to BS 7263, shall be laid on 15mm thick 3:1 sand/ cement mortar bed.

9.5.3       A10mm compressible waterproof joint filler shall be provided at every tenth joint, or as directed on site, to accommodate expansion.

9.5.4       After checking of kerb by the Engineer, the hunching shall be cast by using concrete grade 40/20/S.  The blinding and hunching of the kerb shall have expansion joints with 10mm joint filler at agreed intervals.

• Casting of the Spillway

• The spillway foundation shall be prepared to the lines and grades indicated in the approved shop drawings, compacted by the contractor and inspected by the Engineer.

• Polythene sheet (1000 gauge) shall be laid and 100mm blinding concrete of Grade 40/20/S shall be cast.  Concrete for spillway structure, excluding Patrol Road slab, shall be of Grade 40/20SF.

• Construction joints shall be provided every 5mx5m bay and expansion joints at every 25m as shown in the shop drawings.

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

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

• Pavement quality concrete for Patrol Road slab shall be cast to the lines, grades and thickness indicated on the approved shop drawings.

• For concrete thickness of 150mm and less, one layer of A393 Mesh (or equivalent rebar) will be provided.  For thickness greater than 150mm thick, one layer of A393 mesh at top and bottom will be provided, as per response to RFI 0093.

• Construction and expansion joints shall be provided as mentioned above.

• The curing shall be done as mentioned above for blinding concrete.

.

10.0  Responsibilities

1. The CM will coordinate with SE and ensure that 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.