Method Statement for Sub base and Gravel Base

CONTENTS

1. Purpose

• Scope of Work

• Definitions

• References

• Materials

• Plant  & Equipment

• Safety

• Prior Activities

• Procedure

1. Responsibilities

1. Attachments

1.0    Purpose

To ensure that sub base and gravel base, and related activities 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.

2.0    Scope of Work

This procedure is applicable to the following works associated with the project titled, New 2k Runway – Main Runway Works”- contract number xxx

– Sub-bases and flexible road bases

3.0    Definitions

CM               Construction Manager

PE / SE        Project Engineer / Site Engineer

CS                Chief Surveyor

ME                Material Engineer

ES&H           Environmental, Safety, and Heath    

• References

Specifications:          Civil Specification Sections 331.

Drawings:                 Vol 2 – Section 8 – Part A – General and Topographic Survey

                                             Vol 2 – Section 8 – Part B – Civil, Mechanical and Navaids

                                  Vol 2 –  Section 8 – Part C  – Surface Profiles and Pavement Geometry

• Materials

• Warning tapes
• Temporary signs
• Safety Barriers
• Traffic Cones
• Grade Stakes

• Plant & Equipment

• Mixing Plant for gravel base
• Wheel Loaders
• Dumper Trucks
• Graders
• Vibrating Rollers
• Pneumatic-Tyred Roller
• Water Tankers
• Air compressors

7.0    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.

Where possible hazards may arise from filling activities, the necessary safety measures will be taken to prevent accident or injury at all times. This may include barriers, warning tape/ net, signage, watchman, and proper lighting.

Where work upon existing services may be required, the necessary work permits and safety equipment should be obtained prior to the activity commencement.

ES&H will enforce that Personal Protective Equipment be worn by site personnel at all times during construction activities.

Heat Stress Training will be provided.

Provisions of adequate cool drinking water, shade, and salt water tablets will be in place.

Plant & Equipment will be provided 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.

8.0    Prior Activities

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 filling 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 Sub base

9.1.1 The materials to be used for Sub base will originate mainly from excavated selected materials (local) and/or from Buraimi and Al Dahira Quarry in Al Ain as well as Khadra, Al Hail and Adlah quarries located in Ras Al Khaimah, Fujairah, and Sweihan respectively.

9.1.2 Mxing of material will take place in a suitable area to be defined.

9.1.3 The material shall comply with section 331.1 through 331.14 of the Specifications and the ME will inspect and test the material accordingly and periodically as per inspection and test plan no.1008 OAJ –ITP-1007 already submitted for approval.

9.1.4 Prior to commencement of any sub base filling, the grade checkers will check formation levels and mark fill levels as required The existing formation completed up to sub-grade level and proof rolled according to table 331.7.1 of the Specifications will be pre-wetted to increase bonding with the new layer.

9.1.5 The sub base material will be mixed with water that will comply with clause 200.12A, and prepared in the stockpile area (local and/or borrow) to the optimum moisture content. Then it will be transported to site via dump trucks where it will be spread and leveled by graders, and compacted initially by steel drum roller.

9.1.6 Should the need arise to adjust the moisture content, water will be sprayed uniformly using water tanker equipped with sprinkler bars.

9.1.7 The grader will have a second and third run (if required) accompanied by the steel roller till levels are reached. Thickness of each layer will conform to the Contract drawing “Typical Pavement Details” but in no case exceed 200mm. The finished surface will be moistened not damped and compacted with a PTR to have a better cohesive layer and achieve the required compaction of 100% of laboratory Maximum Dry Density.

9.1.8 Preliminary trials will be conducted at the start of the works to determine the optimum number of passes of compaction plant and control the pre-wetting and water spraying for optimum moisture content.

9.1.9 Maximum Dry Density testing and CBR Testing will be performed in accordance with clause 331.1 and 331.9 and approved QA/QC Plan. Additional layer of sub base material will be placed in the same method as described above, up to the required elevation. The Surveyor will verify that final levels are within -20/+10mm tolerance as specified in clause 331.12.

9.1.10 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.  

9.1.11 Caution will be taken in order not to cause any disturbances to surrounding existing installations and/or structures.

9.1.12 If DBM is the next pavement layer to follow, a prime coat will be applied. Finished primed surfaces will be kept free from all non-essential traffic.

9.2 Gravel Base

9.2.1 The materials to be used for gravel base, will be sourced from Buraimi and Al Dahira Quarry in Al Ain as well as Khadra, Al Hail and Adlah quarries located in Ras Al Khaimah, Fujairah, and Sweihan respectively.

The material shall comply with section 331.1 through 331.14 of the Specifications and the ME will inspect and test the material accordingly and periodically as per inspection and test plan no.1008 OAJ –ITP-1007 already submitted for approval.

9.2.2 The sequence of works will be the same as for the sub-base. However, prior to placing any additional layer, the base shall be mechanically swept and cleaned with compressed air.

9.2.3 Final levels will be within -10/+10mm tolerance as specified by table 331.12.1 of the specifications.

9.2.4 The final base layer shall be sealed by applying the prime coat to avoid its drying out.

    9.2.5 Finished primed surface to be kept free from all non-essential traffic.

10.0 Responsibilities

10.1 The CM will coordinate with SE and ensure that the necessary resources to implement the approved method statement and ITP have been allocated to the task.

10.2 The SE will ensure that the site preparation activities are conducted according to the approved method statement and all in-situ tests according to the ITP are implemented.

10.3 The ME will ensure that the materials being used are in accordance to the project specifications, the approved method statement and the ITP. 10.4 The ES&H officer along with his team will ensure implementation of all ES&H procedures related to the nature of the works being carried out and in accordance with the ES&H Plan.