Excavation is the process of creating space by removing earth (soil or rock) to place a utility or structure. Several methods are available to achieve excavation. In all methods, excavation safety plays a crucial role. Some popular methods of excavation are:
- Open excavations.
- Thrust boring
- Horizontal Directional Drilling
- Microtunneling for Pipe Jacking
- Pile foundations and diaphragm walls
- Vibro stone columns
- Raise boring
Open excavation is a surface excavation suitable up to 6.0 meter deep. Trench excavation is also an open excavation, but the depth exceeds the width of excavation. Open excavation is mainly used for foundations, placing pipes and cables for utility services, test pits, borrow pits and road formations.
Open excavation is one of the most hazardous construction operations. Among excavation related dangers, cave-ins pose the greatest risk. Many constructions fatal accidents occurred during excavation. Therefore it’s vital to prepare a safe work method statement for carrying any excavation activity.
Any open excavation deeper than 1.5 meter requires side protection by sloping, benching or shoring. This method statement describes the excavation safety requirements and safe work procedure for all open excavations. It summarizes suggested method of executing works safely within any constraints. This method statement offers advice and guidance to the personnel involved in this activity to:
a) Carry works in a manner that’s safe at all times;
b) Know the hazards involved in the activity;
c) Ensure controls to steer clear of hazard exposure are in place.
Use any other resources and methods not referred to in this method statement to suit the project requirement. Always execute the work safely complying with the required standard.
The sequence of activities is a repetitive process and many hazards are common to distinct sites. Include with detail, any crucial information specific to the project. Always follow the approved checklists prior to the start of the activity.
What this Method Statement covers
The scope of this document covers:
- Safe work method and procedure for carrying open excavation works
- Materials, equipment, and tools needed to carry out the excavation activity
- Applicable standards throughout the execution of the project
Standards for excavation safety
- OSHA 2226-10R 2015: Trenching and Excavation Safety (download PDF)
- IS 3764: Indian Standard for Excavation work – Code of safety
- IS/ISO 20474-1: Indian Standard for Earth moving machinery – Safety
- IS 10386 (Part 8): Indian Standard for construction operation, operation, and maintenance of river valley projects (Part 8: Open excavation) – Safety code
- IS 3696 (Part 2): Indian Standard for scaffolds and ladders – Code of safety
- IS 4081: Indian Standard for blasting and related drilling operation – Code of safety
Personal Protective Equipment and Safety Gear
Below are the suggested PPE for excavation:
Refer standard operating procedure of PPE for further PPE details
Procedure for excavation
- Get relevant data of subsurface soil and water table location
- Design excavation sides and protective system based on the size of excavation and type of soil. Three popular methods to protect excavation sides are:
- Sloping the walls
2) Bench Excavation
3) Supported excavation by shoring up the walls with wood or metal supports
- Finalize excavation and soil removal method namely mechanically or manual
- Locate underground utilities like electric cables, Optical fiber cables (OFC), Pipeline etc. with cable detector and pipe detector.
- Assess for a chance of chemical hazard or low oxygen levels
- Intimate or take permission as needed from the underground utility operator
- Get work permit for excavation work
- Barricade the excavation area to keep vehicles, equipment, and personnel away from the excavation
- Make proper lighting arrangements
- Inspect the arrangements with a competent person before the start of excavation work
- Carry manual excavation until exposure of underground utilities. Allow mechanical excavation only after exposure of underground utilities
- Make safe access and egress arrangements for personnel and equipment at least from two sides
- Excavation should be kept free from water. Water in an excavation can weaken the surfaces of the excavation. Dewater whenever water accumulates. If required, put essential shoring to protect persons working.
- Carry the balance excavation with excavators
Precautions for safe excavation
- Within 2.0 meters of excavation edge, permit only excavation equipment. Don’t allow any other equipment near excavation edge since the weight of the machines can fall trench walls.
- Cranes should maintain a safe distance equal to the depth of excavation from the edge of the excavation
- Deposit excavated soil along with other materials at least 0.61 meters from the edge. Place soft barricades for pedestrians at least 1.0 meter from the edge. Scaffold posts, loose materials along with any loads shall be at a distance of 1.5 times excavation depth away from the edge. Provide hard barricades for vehicles at least 2.0 meter from the edge.
- Only authorized persons should enter the excavation
- Keep flagman with a red flag in busy and risky locations to guide vehicular traffic
- Keep signalman to guide equipment operation safely
- Use blinking warning lights where the pedestrian or vehicular traffic is expected.
- Provide additional bracing and shoring in the vicinity of the source of vibration such as Pile driving rigs to prevent slides, slips or cave-in where excavations.
- Provide one ladder per 15 meters of length. Extend the ladder for one meter above the top of the cut
- Prohibit persons in the path of an excavator turning bucket
- Prohibit lone workers without a supervisor
- Wherever presence of insects, leeches, and snakes is possible, make arrangements for repellents, fumigation and first aid as needed.
- Carry earth work inspection daily
Common excavation safety hazards
- Quicksand condition
- Side walls become highly unstable following rainfall due to water content
- Vibrations from nearby machinery, railroad, blasting, and other sources
- The surcharge imposed by nearby buildings
Excavation safety checklist
- Approved excavation drawing available
- Presence of underground utilities located and marked
- Barricades, safety signs, and lighting are in place
- Excavation slope protection system finalized like sloping, shoring or benching
- Entry and exit means for personnel and equipment
- Dewatering arrangements made wherever water is expected.
- Flagmen are positioned to guide vehicular traffic
- Emergency rescue equipment is in place
- Excavation permit available
Please follow the standard practice of daily checklist, weekly inspection and monthly audit for safe excavation.