CONTENTS
- Scope of Work
- Definitions
- References
- Subcontractors
- Materials
- Plant & Equipment
- Safety
- Prior Activities
- Procedure
- Responsibilities
- Attachments
1. Scope:
| 1.1 | This Method Statement covers the following activities related to Storm Water and Drainage works |
| Site cleaning and grading Trench excavation and backfill Structural excavation and Backfill |
2. Definitions:
| 2.1 | MS: STM Method Statement : Storm Water and Drainage Work |
| 2.2 | ITR Inspection and Testing Request |
| 2.3 | PS-GCMI Project Specifications-General, Civil and Mechanical Infrastructure |
| 2.4 | UG Underground |
| 2.5 | MDD Maximum Dry Density |
| 2.6 | TPS Technical Project Specification |
3. Reference
| 3.1 | GPS General Project Specifications Section107: Clause 107.3.3 Excavation and Trenches. |
| 3.2 | PS-GCMI Section 200 : Clause 200.3: Excavation |
| 3.3 | PS-GCMI Section 901, Clause 901.3: Trench Excavation Clause 901.3.8 & 901.3.9: Backfilling to pipes and Standards of compaction |
| 3.4 | PS-GCMI Section 200: Clause 201.3.3: Backfilling to structures |
| 3.4 | PS-GCMI Section 901 Clause 901.5: Testing. |
4. Subcontractors:
| N/A |
5. Products:
| 5.1 | Pipe bedding and surround material (dependent upon pipe dia. and depth, see TPS—Section 901- Clause 901.3.6 & Clause 901.3.7and Clause 901.3.10). |
| 5.2 | Backfill material for trench and around structure, Technical Project Specification Section 901 Clause 901.3.8 & Clause 901.3.9: Backfilling and Testing. |
| 5.3 | Borrow material |
6. Tools & Equipments:
| 6.1 | Dewatering equipments & pumps (If required). |
| 6.2 | Excavators/ JCB |
| 6.3 | Front end loader (Shovel) |
| 6.4 | Tipper trucks |
| 6.5 | Small vehicles |
| 6.6 | Soil compactor (Plate roller’s) |
| 6.7 | Motor graders |
| 6.8 | Surveying instruments |
| 6.9 | Bull dozers |
| 6.10 | Ladders |
| 6.11 | Concrete barricades and safety equipments. |
| 6.12 | Flagging tape/warning tape |
| 6.13 | Water tanker |
| 6.14 | Sheet piling & shoring materials (If required). |
| 6.15 | Personnel protection equipments. |
7. Safety
| 7.1 | PPS Section 100: Clause 100.2 Airport Emergency and Safety. |
| 7.2 | TPS Technical Project Specification Section 901 Clause 901.3 : Trench Excavation and Backfill. |
| 7.3 | Construction Safety Manual. |
| 7.4 | Safety Hazards and Precautions |
| a )- Strike UG Services: Use Locator and/or hand excavation (trial holes) b)- Excavation Collapse: Batter sides to safe slope or provide shoring (as directed by Geotechnical Consultant) and subject to Engineer’s approval. Keep vehicles/equipment safely away from excavation edge Keep spoil at least 2.0 meter away from edges c)- Fall into excavation: Provide fencing, guardrails, night-time lighting and flagging tape around edges. Provide safely fixed ladder (every 50m) Provide banks man when operating equipment near excavation. d)-Crane Accidents: All cranes checked and certified Operators professional and well experienced Provide banks man when operating near excavation Check load indicator, slings and wire ropes daily e)- Falling Objects: Stand clear during lifting operations Wear hard hats f)- Equipment & Vehicles: Use Safety belts Slow down and obey speed limits Provide “back-ups” alarms Provide banks man when operating equipment near excavation. g)- Confined Space: Check air with gas monitor before entering assembled pipeline or manholes Check air in deep narrow trenches or excavated before entry. Check excavations for snakes and scorpions before entry Take precautions against flooding Develop rescue procedures | |
8. Prior Activities:
| 8.1 | Drawings will be checked for existing underground utilities or obstructions. |
| 8.2 | A site survey will be conducted to record existing ground level conditions, mark UG utility locations, excavation limits and note obstructions. |
| 8.3 | All necessary work permits will be obtained prior to excavation (such as Notice of Intent). |
| 8.4 | Haul roads and designated disposal areas will be established. |
| 8.5 | Trial holes will be dug by hand to expose UG utilities and verify exact locations. |
| 8.6 | Additional trial holes may be dug to verify soil conditions and allow sampling and inspection by a Geotechnical Engineer where needed. |
| 8.7 | Detailed drawings and calculations will be provided by a qualified engineer before commencing excavations which require a bracing and/or shoring system. |
9. Procedure:
| 9.1 | Clearing & Grading | |
| a. | After the site survey is conducted and all utilities are located and required work permits are obtained, site cleaning and grading will proceed. | |
| b. | Any vegetation, rubbish, debris and other objectionable materials will be cleared away and hauled to designated disposal areas. | |
| c. | The Site will then be graded to allow vehicle and equipment access. | |
| Note: | In some cases a temporary haul road or working platform may be constructed to provide better access for vehicle and equipments. | |
| 9.2 | Dewatering | |
| a. | Dewatering if required will be conducted according to MS-1004. | |
| 9.3 | Trench Excavation | |
| a. | Trench Excavation will be carried out to the lines, grades and levels as shown on the drawings but shall not exceed 50 metres in advance of pipelaying unless approved by the Engineer. | |
| b. | Equipment used for excavation will depend on the type of material to be excavated, method of hauling and site limitations. | |
| c. | Unsuitable material will be hauled away to designated disposal areas. | |
| d. | Suitable excavated material will be stockpiled at least 2.0 meter away from the edge of the excavation, if possible, or to an area designated by the Engineer. | |
| e. | If necessary, the bottom of the excavation will be sloped to aid dewatering. | |
| f. | The widths of trenches shall ensure a minimum of 150mm between the barrel of the pipe and the side of the excavation. | |
| g. | Shop drawings and calculations for any bracing and shoring if required for excavation will be submitted for the Engineer’s approval. | |
| h. | Final excavation (last 150mm) to required grade will only be conducted shortly before bedding material or blinding concrete is placed and will be accomplished by using thin cuts with suitable equipment to avoid disturbing the formation level. | |
| Note: | Excess excavation will be replaced with selected excavated material in properly compacted layers as instructed by the Engineer. | |
| 9.4 | Formation or Base Preparation | |
| a. | Any soft, spongy, unstable or unsuitable materials encountered at formation level will be removed and replaced with selected material in properly compacted layers. | |
| b. | The bottom of all trenches (formation) will be compacted to at least 98% MDD. | |
| c. | The base of all structures will be compacted to at least 98% MDD at formation level. | |
| Note | Formation inspection and compaction is a Hold Point and will be confirmed by the Consultants Inspector before proceeding with blinding concrete or bedding material. | |
| 9.5 | Pipe Bedding and Surround | |
| a. | Pipe bedding and surround will be placed in accordance to the drawings and pipe manufacturers recommendation. | |
| b. | Material will comply with the requirements of Section 901 Clause 901.3.6 | |
| 9.6 | Trench Backfill | |
| a. | Backfilling of trenches will comply with Clauses 901.3.8 & 901.3.9 | |
| b. | After the pipe surround has been placed and checked by the Consultants Inspector general backfill will proceed. | |
| c. | Backfill material will be compacted to 98% MDD in max.200mm maximum loose lifts and trenches with pipeline laid shall be backfilled and hand compacted to a level of 300mm above the crown of the pipe with selected excavated material. Trenches adjacent or under roads, will be backfilled compacted to 100% of MDD and consolidated before the sub-base and pavement are laid. | |
| Note: | Lifts greater than 250mm may be utilized when trials demonstrate the required compaction can be achieved. | |
| c. | Suitable backfill materials will be as described in (PS-GCMI) Section 901. | |
| d. | Approved marker tapes will be installed if required. | |
| 9.7 | Structure Backfill | |
| a. | Backfill adjacent to structures will proceed only after the external protective membrane or coating has been placed, protected and checked by the Consultants Inspector. Backfilling to Structures will comply with Clause 201.3.3 | |
| Note: | Inspection of the structure and exterior protective membrane or coating is a Hold Point and backfilling will not proceed unless approved by the Consultant’s Inspector. | |
| b. | Backfill will be placed around all sides of the structure simultaneously in order to maintain approximately the same fill height. | |
| c. | Backfilling materials will be approved selected excavated material compacted in layers not exceeding 200mm thick to achieve a to 95% MDD. | |
10. Responsibilities:
| 10.1 | It is the Manager’s duty to ensure that all necessary safety and protective equipment are provided along with properly trained and qualified personnel. |
| 10.2 | It is the Site Supervisor’s duty to organize the work in a safe manner to ensure that safety and protective equipment are being properly utilized. He must also assure the method statement procedure is followed and must observe the Hold-points and notify the Consultant for inspection. |
| 10.3 | It is the worker’s duty to properly wear the protective equipment provided and obey all safety rules. He must also perform the work as described in the method statement procedure. |
| 10.4 | The Contract Manager will coordinate with Safety Engineer and ensure that the necessary resources to implement the approved method statement have been allocated to the task. |
| 10.5 | The Site Engineer will ensure that the site preparation activities are conducted according to the approved method statement. |
| 10.6 | The Material Engineer will ensure that the materials being used are in accordance to the project specifications and the approved method statement. |
