Excavation Method Statement.pdf

Hydro Agricultural Development of South Lebanon Irrigation and Water Supply Scheme Conveyor 800

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

Construction Method – Excavation

Contents 1. Introduction .................................................................................................................................................. 2 2. Scope ................................................................................................................................................................ 2 3. Definitions...................................................................................................................................................... 2 4. Responsibilities............................................................................................................................................ 3 5. Methodology ................................................................................................................................................. 3 5.1

Prior Activities ..................................................................................................................................... 3

5.2

Excavation ............................................................................................................................................. 4

5.3

Surface Preparation ........................................................................................................................... 6

5.4

Reinstatement...................................................................................................................................... 6

6. Risk Assessment .......................................................................................................................................... 6 7. Health and Safety Requirements........................................................................................................... 7 8. Environmental Requirements ................................................................................................................ 8 9. Quality Assurance and Quality Control Requirements ................................................................. 9 10.

Resource Allocations ............................................................................................................................. 9

11.

Document References ........................................................................................................................ 10

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Excavation 1. Introduction This method statement serves as a guideline for the excavation works undertaken during the construction of the Qelia Canal in the Hydro Agricultural Development of South Lebanon Irrigation and Water Supply Scheme CONVEYOR 800 Project. The process will include methods to carry out the excavation and surface preparation under which the Canal foundation will be placed, in compliance with the environmental and safety measures required.

2. Scope This procedure is applicable to the excavation works and surface preparation for the Qelia Canal of about 6KM length. In order to achieve the required locations and levels of the canal foundation, excavation will be carried out to a width of 8.5m and an average depth of 3m. Excavation will continue at stages to reach the formation level, where the preparation of the surface will be executed prior to placing the 100mm blinding concrete. This method statement intends to describe the tasks briefly to ensure the smooth running of all 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, block passage 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 earth slippage.



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, the load above the face and the moisture conditions.

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

Sheet Piling: Vertical, close spaced or interlocking planks of steel, reinforced concrete or other 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 the excavation as the work proceeds.



Shoring: The use of timber, steel or other structural material to support an excavation in order 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 construction procedure and method statement, supervising the work and reporting the progress of work to the planning engineer. The QA / QC engineer is responsible in monitoring the execution and performance of the works 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 also assure 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 any unsafe work. The worker is responsible to properly wear the protective equipment provided and obey all the 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 areas including 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 original ground 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 maximum distance between rods is 20 meters.

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4. Prepare access to the working area and plan for the dump truck and plant movement avoiding 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 storage area 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 clearly mark these services on the ground. 6. It has been identified that the ground conditions will allow for the excavated faces to stand 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 appropriate support 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 dewatering system through suction pumps to dispose water in accordance with the method statement 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 approved drawings 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 design level 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 that the face of excavation is finished to the required slope. 5. Carry out excavation works using a bulldozer with ripper and / or a 360° excavator assisted at all times by a competent banks man. 6. As the excavation progresses, use a combination of 360° excavator fitted with a hydraulic breaker and a JCB or excavator with a small bucket attachment, to excavate the side ditch of dimensions in accordance to the drawings and a distance from the left wall of the canal to be agreed with the Engineer, to prevent the flow of water into the excavation or behind the canal wall during the construction period. 7. It is the intention to excavate rocky areas by mechanical methods, however should the occasion arise, carry out controlled blasting technique. 8. Execute drilling by hydraulic rock drill with the sides of the excavation to be smoothly blasted in order to form straight lines. 9. Saw cut all the edges of excavated areas on concrete or bituminous footways and roadways to form trimmed edges and minimise damages. 10. Stockpile the excavated materials that are justified by the Engineer as suitable backfilling material, at the lower side of the excavation far away from the area retained for maintenance road construction, but ensure not to exceed the limit of LRA property as indicated on the drawings. 11. Transport the surplus of such materials using dump trucks to approved stockpile area for future use, or to a recycling area for crushing and screening into reusable course materials. 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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5.3



Surface Preparation:

1. Trim the finished surface of formation to the required profiles and levels within the specified design. 2. If the surface is other than rock, apply water spray and compact using a vibratory roller, immediately prior to placing the 100 mm blinding concrete. 3. Where instructed by the Engineer, establish a site investigation to identify the properties of the ground on which the structure will be founded and provide details on bearing capacity. 4. Replace any removed loose soil encountered at formation level, or any excess depth excavated below the formation level, with soil-cement mix or with approved imported fill material compacted in accordance to specification. 5. Wash the rocky foundation surface using water or air compressor and clean it from dust, mud, loose or fractured material and other debris, immediately prior to placing the 100mm blinding concrete. 6. Where rock surfaces reach high temperatures under the influence of the sun, carry out washing at night or in the early morning, to avoid fracturing due to thermal shock.

5.4

Reinstatement:

1. Upon completion of work, reinstate all occurring damages or deficiencies to channeling, kerbing or paving consisting of dressed stone, bricks, precast concrete slabs or the like, to its original condition.

6. Risk Assessment Works shall be carried out in line with the detailed project procedures below that shall be used in conjunction with this method statement: 

Health, Safety and Environment Plan



Inspection Plan



Contractor's Emergency Management and Monitoring Plan



Pollution Prevention Plan



Reinstatement Plan



Waste Management Plan



Cultural Heritage Management Plan



Training Procedure

Risk Assessment sheet of each activity shall be prepared by our specialist before commencing any activity.

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The process of hazard identification, risk assessment and control is made up of the following steps: 1. 2. 3. 4. 5.

Identify the nature and level of hazards. Assess the health and safety risk arising from the hazard. Eliminate human exposure to the threat or hazard. Determine the suitable safeguard and systems of work that shall be implemented. 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 the public and ensure a safe working environment during the entire construction period. A survey shall be carried out on areas on the site that may require specific Health and Safety attention to moderate and remove any hazards or risks. The following safety measures shall be implemented on site during the execution of the canal excavation works, along with the measures undertaken in the ‘Site Clearance’ and ‘Backfilling’ 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 competent person.

7.2

Existing Utilities:

1. Use cable detector to identify and locate the underground utilities and ensure it is protected. 2. Where overhead lines cannot be diverted or quarantined, ensure that plant is selected or 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 a safe slope or provide shoring using steel sheeting, rails or props as directed by the Geotechnical Engineer.

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2. Lower the underground water table if encountered to below the invert of the canal and 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 where there 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 leaving the 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 with requirements of the Contractor's Environmental Management and Monitoring Plan as described 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 activities in rainy seasons. 2. Take appropriate measures to minimize the effect of oil/diesel spill in case of machine failure. 3. Reduce noise from machineries to avoid disturbing the surrounding. Machines shall be 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 to undertake 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 construction and erection to the drawings, specifications and regulations. Develop Test and Inspection Plan in line with the work to be constructed showing 'Hold and Inspection' 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 per the 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 for approval. 3. Follow up on the Engineer's site inspection and comments, until the IR form is approved. 4. Circulate the approved IR form to the Corporate Quality Department for records keeping, 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: Operators:

01 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:

04

10.2.2

Excavation by Blasting:



Bulldozer:

01



Excavator:

01



Rock Breaker:

01



Wheel loader:

01



Tipper Trucks:

03



Wagon Drill:

01



Compressor (2 Jack Hammer):

01

10.2.3

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 the above.

11.

Document References

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

Section 1.3 - Excavation



Section 5.3.2 - Construction of Cuts and Fills

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Excavation Method Statement.pdf

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