Method Statement for Placing Sub-Base and Gravel Base by Pavers

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 placing of sub-base and gravel base by pavers, 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 NRTW-1008-CN.

This method statement outlines the procedures to be followed in placing of sub-base and gravel base, by pavers, at locations shown in the contract drawings and as directed by the Engineer.

3.0    Definitions

CM               Construction Manager

PE / SE        Project Engineer / Site Engineer

CS                Chief Surveyor

ME                Material Engineer

ES&H           Environmental, Safety, and Heath    

ITP               Inspection and Testing Plan

AHA              Activity Hazard Analysis

JHA              Job Hazard Analysis

• 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
• Personal Protective Equipment

• Plant & Equipment

• Mixing Plant for sub-base and gravel base
• Wheel Loaders
• Dumper Trucks
• Pavers
• Vibrating Rollers
• Pneumatic-Tyred Roller
• Water Tankers

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.

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.

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.

Prior to commencement of any sub-base filling, the grade checkers will check top levels of compacted select fill and mark sub-base 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. Filling and compaction of selected fill will be carried out as per the method statement 1008 OAJ-MS-1028.

Sub -base and gravel base levels will be determined from the finished pavement surface as shown on the approved shop drawings and will be submitted for the Engineer’s approval.

Preliminary trials will be conducted at the start of the works to determine the optimum number of passes of compaction plant and to control the pre-wetting and water spraying for optimum moisture content.  Compaction methods will be subject to approval by the Engineer. Demonstrative trials will be undertaken in areas to be agreed upon with the Engineer.

• Procedure

9.1 Sub-base

9.1.1 The materials to be used for sub-base will be as per the material submittal and will originate from approved sources. 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 ITP no.1008 OAJ –ITP-1007already approved.

9.1.2 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 specifications. After mixing, the material shall be removed and transported to the placing location, via dump trucks, without delay.

9.1.3 Spreading of sub-base shall be done by automatic controlled pavers. ABG pavers will be used in this job. The ABG pavers are equipped with automatic sensors that control the grades and cross slopes. The sensors are mounted on either side of the paving legs and are individually controlled. Crowns or continuous grades can be established on an ABG Finisher. All machines involved in laying operation shall be in good condition and will be checked before and during the operation.

9.1.4 The strip width shall not be less than 3 meters unless approved by the Engineer. Paver’s guideline levels will be set using steel lines stretched and adequately supported to prevent any sagging on both sides.

9.1.5 Initial compaction will be undertaken by steel drum rollers.

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 Thickness of each layer will conform to the contract drawings. 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 Maximum Dry Density testing and CBR Testing will be performed in accordance with clause 331.1 and 331.9 and as per ITP 1008-OAJ –ITP-1007. Additional layers 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.

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

9.2 Gravel Base

9.2.1 The materials to be used for gravel base will be from approved sources and 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 ITP 1008-OAJ –ITP-1007.

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, JHA, and AHA 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, JHA and AHA.  The SE will also ensure that all in-situ tests, as required by the ITP, are implemented.

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

10.4 It is the Front line supervisor’s responsibility to organize the work in a safe manner to ensure the safety and that 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. 10.5 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.