Edited Excavation, Shoring, Dewatering & Construction Ms[1]

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1.0 Scope This method statement describes the shoring, excavation, dewatering and construction methodology for the type 1A FW box culvert trench on Jamal Abdul Nasser Street. A Separate method statements will be submitted for the post-excavation processes for the concrete structures and utilities. 2.0 Materials to be required for the completion of the specified job. Page2 of 6

• Shoring system (As required) • 150mm pvc pipes (dewatering) • Concrete – blinding K250 type V, structural K350 1B (submittal 298) • Reinforcement steel 3.0 Resources Superintendent Site Engineer QA/QC Engineer Foreman Surveyor Safety Officer Operators for Equipment. Dewatering Technicians Shoring Team/Technicians General operatives Plant Excavators (various sizes) Diesel engine dewatering pumps Water tanker/Water tank with hose connection to tap water Cranes Compressor Tower lights Installation of the Shoring System 1. Prior to starting the works, the surveyor will submit a WIR for setting out of the structure to be excavated. 2. The underground utilities within the excavation area will be detected. All known existing utilities will be marked. 3. The limits of excavationwill be set out on both sides of the trench, and painted lines will be marked on the ground for the shoring team. 4. Excavation will be done to the level of the first walers, whilst installing the timber lagging as the excavation depth increases. The space behind the lagging will be backfilled with soil and hand-packed. 5. The buried utilities underneath the earth will be exposed which needs protection during the excavation process(use of hand-excavation within 1m of existing utilities), providing temporary support to the utilities whilst securing them as described below

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6. Utilities crossing the excavation will be supportedon rectangular brackets (made from angle iron sections welded together)suspended from horizontal H beams fixed to waters. 7. For utilities that run within and parallel to the trenches and cannot be suitably supported because of the length of runs involved, arrangements will be made for their diversion by other contractors before commencement of trench excavation. 8. Dewatering system will be installed and the pumping of water will be started (refer to dewatering works below). 9. Install the waler beams at the specified design depth for bracing and place the bracing struts in the correct position. Where struts are used, extendthe struts to push the walers tightly against the soldier piles. Installation of the Dewatering System 10. The trench will be dewatered using a well point system, if excavation depths extends below the water table. The proposed dewatering method will be submitted together with the shoring proposals. Depending on the trench width, working area and site conditions for the trench,well points may be made outside or inside the trench. 11. Holes will be drilled for the well points to a sufficient depth to enable the ground water table to maintained at 0.5m below the formation level of the excavation (bottom of the excavation).The dewatering pipes will be inserted into the well points and the space around the pipes filled with 10mm drainage stone. The dewatering pipes will be connected to a 6” header pipe system. 12. Dewatering pumps powered by diesel will be installed and connected to the header system at an appropriate location. All pumps will be placed on steel drip trays that will be periodically emptied by a registered approved waste contractor who will dispose the contaminated effluent. 13. The environmental consultant will analyse the water and determine if it needs treatment prior to discharge. If deemed safe the water will be pumped to the nearest storm sewer manhole. 14. The dewatered water table level will be maintained at a minimum of 0.5m below the excavation level. 15. The dewatering system will be disconnected once the uplift pressure is neutralized and upon the appropriate level of backfilling being reached. 16. For safe operations, all personnel not directly involved with the shoring and dewatering operations will be kept clear of the working area. A demarcated observation area will be established to enable safe monitering and observation of the works without encroaching into the working zone. All personnel needing to enter the working area (e.g for inspections) will need to first inform the available foreman/supervisor in charge of the operation and ensure that prior to entering the works, the banksman is alerted. Excavation Works 17. Excavation of the trench will start once the installation of the shoring system is completed. Page4 of 6

18. The trench will be dug using excavators upto the required level. 19. On the designated areas on site, the excavated soil will be stockpiled for reuse later as backfill material for the excavated trench. Soil stockpiles will be kept well away from the edges of the excavation to prevent surchaging the excavation while also maintaining a clear access to work areas. 20. To check for the suitability as backfill material, samples of the excavated soil will be sent to the laboratory (it is the intention to re-use the native soil as backfill unless the soil is deemed to be unsuitable for use as backfill material). 21. The trench will be excavated to the formation level or if necessary to the next level of walers. If walers are required, the shoring system will be installed as per shoring design for the particular trench. 22. To prevent exceeding the design surcharge loading on the shoring, the minimum distance from the edge of excavation will be 900mm (for 20T excavators), increasing with heavier machines (the safe minimum clearance will be simply calculated for the excavators based on their operating weight and track dimensions and assume an applied load transferred into the ground at an angle of 45O). Any proposed decreasing of the minimum safe clearance must be justified by design calculations. 23. After the excavation reaches the required formation level, the site engineer will submit a WIR for approval of the formation and excavation. 24. All the excavated trench will be fenced off and secured when not attended for the sake of safety. There will be instances when barriers may need to be temporarily remove to enable the excavation to be carried out. A banksman will direct operations and the area will be cordoned off from all non-essential personnel. Barriers will be restored as soon as practical or at the end of the shift to ensure that no open excavations are left unsafe. Concrete Works 1. All the reinforcement for the walls will be fixed to full height, fix 50mm spacer blocks to the external faces of the walls and 75mm spacer blocks to the internal faces of the walls. 2. After fixing the reinforcement for each wall, the Engineer will inspect the wall reinforcement prior to closing the walls with formwork. 3. After inspection and approval of the reinforcement, the wall formwork will then be lifted into position (using a crane) and erected to the full height of the box culvert walls for the external faces of the walls and to the underside of the chamfer on the internal faces. At the construction provide an approved external waterstop. 4. After erection of the wall formwork, the roof slab formwork will be laid in position to the correct line and level. 5. The Engineer will then inspect the formwork and reinforcement and if satisfied give permission for casting concrete. 6. When the Engineer has passed the walls and top slab, the concrete will be called off from the batching plant. 7. The concrete shall be place into the forms from the concrete pump via a flexible hose. The concrete will be placed in even layers, between 150mm and 300mm depth. As the next layer of concete is placed, the layer beneath will be vibrated Page5 of 6

with internal vibrators to ensure that there is a homogenous mix of the concrete and avoidance of ‘layered’ concrete finish. 8. The concrete will be cast during the night shift or early morning shift, provided the shade air temperature is less than 40oC, the temperature of concrete when placed shall not exceed 32oC.

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