excavation method statement.pdf

8/13/2019 Excavation Method Statement.pdf

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Hydro Agricultural Development of South LebanonIrrigation and Water Supply SchemeConveyor 800

Water Resources & Development Co.S.a.r.l

Construction Method Excavation

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Excavation

1. Introduction

This method statement serves as a guideline for the excavation works undertaken during theconstruction of the Qelia Canal in the Hydro Agricultural Development of South LebanonIrrigation and Water Supply Scheme CONVEYOR 800 Project.

The process will include methods to carry out the excavation and surface preparation underwhich the Canal foundation will be placed, in compliance with the environmental and safetymeasures required.

2. Scope

This procedure is applicable to the excavation works and surface preparation for the QeliaCanal of about 6KM length.

In order to achieve the required locations and levels of the canal foundation, excavation willbe carried out to a width of 8.5m and an average depth of 3m. Excavation will continue atstages to reach the formation level, where the preparation of the surface will be executedprior to placing the 100mm blinding concrete.

This method statement intends to describe the tasks briefly to ensure the smooth running ofall the excavation activities that are undertaken during the construction of Qelia Canal.

3. Definitions

The following words used in the development of this procedure are explained below:

Barricade: Any object or structure that creates a barrier obstacle to control, blockpassage or force the flow of traffic in the desired direction.

Battering: To form the face, side or wall of an excavation to an angle to prevent earthslippage.

Benching: The horizontal stepping of the face, side or wall of an excavation. Competent Person: A person who has acquired through training, qualification or

experience the knowledge and skills to carry out the task. Face: An exposed sloping or vertical surface resulting from the excavation of material. Safe Slope: The steepest slope, at which an excavated face is stable against slips and

slides, having regard to the qualities of the material in the face, the height of the face, theload above the face and the moisture conditions.


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Sheet Piling: Vertical, close spaced or interlocking planks of steel, reinforced concrete orother structural material driven to form a continuous wall ahead of the excavation and

supported either by tie backs into solid ground structural members from within theexcavation as the work proceeds.

Shoring: The use of timber, steel or other structural material to support an excavation inorder to prevent collapse so that construction can proceed.

All other terms are defined in Item Specifications.

4. Responsibilities

The construction manager is responsible in ensuring the implementation of constructionprocedure and method statement, supervising the work and reporting the progress of workto the planning engineer.

The QA / QC engineer is responsible in monitoring the execution and performance of theworks in relation to this method statement, approved drawings and technical specifications.

The site engineer is responsible for organizing all the works on site in a safe manner,ensuring it is in accordance with the schedule and the construction drawing. He must alsoassure the method statement procedure is followed and must notify the consultant for

inspection.

The safety officer is responsible in ensuring that all activities are carried out safely at site,establishing the site safety plan, conducting continuous safety inspection and stopping anyunsafe work.

The worker is responsible to properly wear the protective equipment provided and obey allthe safety rules. He must also perform the work as described in the method statement.

5. Methodology

5.1 Prior Activities:

1. Prepare, check and submit verified construction drawings of excavation areasincluding setting out, levels and service drawings for the approval of the Engineer.

2. Upon obtaining all the necessary survey data, carry out a survey to obtain originalground levels and submit for the approval of the Engineer.

3. Set out the coordinates of excavation using steel rods driven into the ground and

indicate on these rods the required depth to be excavated, where the maximumdistance between rods is 20 meters.


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4. Prepare access to the working area and plan for the dump truck and plant movementavoiding any close approach to the edge of excavation. Access shall be approved by

the Engineer taking into account the site traffic management plan and the storagearea for materials.5. Carry out a survey with the coordination with the relevant authorities to identify any

existing services and use cable detection tools and hand digging measures to clearlymark these services on the ground.

6. It has been identified that the ground conditions will allow for the excavated faces tostand within a slope of 1/2 without the use of supports, however if this is not the case,obtain more information about ground conditions to determine the appropriatesupport system such as benching, battering or using steel sheets driven into the

ground.7. There is no significant groundwater problems anticipated on this site, but if ingress of

water occurs during any time the excavation is open, install adequate dewateringsystem through suction pumps to dispose water in accordance with the methodstatement for dewatering excavations, to be submitted when required.

5.2 Excavation:

1. Strip and store topsoil within the working width as indicated in the site clearance

method statement.2. Carry out the excavation of the Canal in accordance with the relevant approveddrawings and cross sections, to the widths and slopes shown thereon:


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3. Where the excavation is to be done starting from less than 1.2m from the top designlevel of the left canal wall to the drainage ditch, carry out the excavation at two stages

to achieve the required slopes as indicated below:

4. Recheck the excavated elevations and locations at the end of stage one to ensure thatthe face of excavation is finished to the required slope.

5. Carry out excavation works using a bulldozer with ripper and / or a 360 excavatorassisted at all times by a competent banks man.

6. As the excavation progresses, use a combination of 360 excavator fitted with ahydraulic breaker and a JCB or excavator with a small bucket attachment, to excavatethe side ditch of dimensions in accordance to the drawings and a distance from theleft wall of the canal to be agreed with the Engineer, to prevent the flow of water intothe excavation or behind the canal wall during the construction period.

7. It is the intention to excavate rocky areas by mechanical methods, however shouldthe occasion arise, carry out controlled blasting technique.

8. Execute drilling by hydraulic rock drill with the sides of the excavation to be smoothlyblasted in order to form straight lines.

9. Saw cut all the edges of excavated areas on concrete or bituminous footways androadways to form trimmed edges and minimise damages.

10. Stockpile the excavated materials that are justified by the Engineer as suitablebackfilling material, at the lower side of the excavation far away from the arearetained for maintenance road construction, but ensure not to exceed the limit of LRAproperty as indicated on the drawings.

11. Transport the surplus of such materials using dump trucks to approved stockpile areafor future use, or to a recycling area for crushing and screening into reusable coursematerials.

12. Dispose unsuitable excavated materials to spoil areas approved by the Engineer.13. Upon completion of excavation, verify set out locations and check the edge slope and

the bottom founding level of excavation.


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The process of hazard identification, risk assessment and control is made up of the followingsteps:

1. Identify the nature and level of hazards.2. Assess the health and safety risk arising from the hazard.3. Eliminate human exposure to the threat or hazard.4. Determine the suitable safeguard and systems of work that shall be implemented.5. Monitor and evaluate any new control measures to ensure that they are effective and

safe and that new hazards are not created by them.

7. Health and Safety Requirements

Safety precautions shall be of paramount importance in order to prevent danger to thepublic and ensure a safe working environment during the entire construction period. Asurvey shall be carried out on areas on the site that may require specific Health and Safetyattention to moderate and remove any hazards or risks.

The following safety measures shall be implemented on site during the execution of the canalexcavation works, along with the measures undertaken in the Site Clearance andBackfilling method statements and the approved HSE plan:

7.1 Personnel and Equipment:

1. Prevent persons to enter a work area where there is a risk of injury.2. Control all activities involving moving plant using nominated banks man.3. Ensure that defective or suspect equipment, which has been withdrawn from service,

does not get back into service without the inspection and approval of a competentperson.

7.2 Existing Utilities:

1. Use cable detector to identify and locate the underground utilities and ensure it isprotected.

2. Where overhead lines cannot be diverted or quarantined, ensure that plant is selectedor modified so that it cannot reach the lines.

7.3 Protection of Excavated Face:

1. Considering soil condition and depth of excavation, batter sides of the excavation to asafe slope or provide shoring using steel sheeting, rails or props as directed by theGeotechnical Engineer.


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2. Lower the underground water table if encountered to below the invert of the canaland always check the pumps to ensure its workability.

7.4 Fall into Excavation:

1. Establish a barricaded zone, 2m back from the left excavation face, in areas wherethere is a risk of falling and where the depth of excavation exceeds 2m.

2. Ensure that all barriers, cones and flagging warning tapes are in place prior to leavingthe site.

7.5 Excavation by Blasting:

1. Hire licensed hot firer prior to commencing any blasting works.2. Ensure that the use of explosives is limited to competent, licensed personnel who

have experience in the work to be undertaken.3. Check that all safety measures are being taken else blasting will be prohibited.4. Secure all areas affected by blasting by flagmen to avoid any intrusions.5. Relocate any vehicles and equipment parked within the blasting zone to safer

locations.6. Stop any influenced traffic prior to blasting.7. Limit the use of blasting in built up areas.8. Control ground vibration by limiting the blast size and the use of delays.9. Take special care in order to avoid over breaks other than geological ones.

8. Environmental Requirements

Canal excavation and surface preparation works shall be carried out in accordance withrequirements of the Contractor's Environmental Management and Monitoring Plan asdescribed in the Site Clearance and Backfilling method statement.

In addition, the following precautions are essential and must be considered:

1. Undertake the suitable procedures to avoid the slit of soil during excavation activitiesin rainy seasons.

2. Take appropriate measures to minimize the effect of oil/diesel spill in case ofmachine failure.

3. Reduce noise from machineries to avoid disturbing the surrounding. Machines shallbe turned off when not in use.

4. Set up the lighting needed for night works in such a manner that neighboring

residents are not disturbed. However, the light should be sufficient for the crew toundertake their works safely.


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9. Quality Assurance and Quality Control Requirements

Quality assurance and quality control covers the records formed from site inspections,examinations and tests that serve as documentation of the conformance of site constructionand erection to the drawings, specifications and regulations.

Develop Test and Inspection Plan in line with the work to be constructed showing 'Hold andInspection' points.

Refer to the Project Quality Plan for all quality assurance issues.

The following steps shall be followed by the engineer in charge before proceeding with the

next activities:

1. Fill the inspection check list to ensure that all activates are being performed as perthe expected quality. The inspection check list shall include the specific requirements,safety and environmental measures.

2. Prepare inspection request, as per QA/QC Plan, and submit to the Engineer forapproval.

3. Follow up on the Engineer's site inspection and comments, until the IR form isapproved.

4. Circulate the approved IR form to the Corporate Quality Department for recordskeeping, and issue order to proceed with next activities.

10. Resource Allocations

10.1 Man Power:

Site Engineer: 01 Licensed Blasting Engineer: 01 (If Required) Safety Manager: 01

Supervisor: 01 Flagman: 01 Unskilled Labors: 04 Plant Mechanic: 01 Operators: As Required

10.2 Equipment/Machinery Required:

10.2.1 Mechanical Excavation:

Bulldozer: 01 Excavator: 02


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Rock Breaker: 01 Wheel loader: 01

Tipper Trucks: 0410.2.2 Excavation by Blasting:

Bulldozer: 01 Excavator: 01 Rock Breaker: 01 Wheel loader: 01 Tipper Trucks: 03 Wagon Drill: 01

Compressor (2 Jack Hammer): 0110.2.3 Surface Preparation:

Bob Cat or JCB: 02 Wheel loader: 01 Tipper Trucks: 02 Water tank: 01 Vibratory Steel Roller: 01

The major equipment used for the canal excavation works include, but are not limited to theabove.

11. Document References

All canal excavation works on the project shall be executed as per the following sections ofthe technical Specification - Volume 2.2:

Section 1.3 - Excavation Section 5.3.2 - Construction of Cuts and Fills

excavation method statement.pdf

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