6.4 Excavation work and directional drilling Purpose This instruction provides the minimum requirements for: All Horizon Power workers who work in and around excavations. All Horizon Power workers who undertake directional drilling. Any process that displaces soil. Scope Applies to all excavation work and directional drilling. This only provides the key points relevant to Horizon Power worksites, and does not attempt to replicate the Work Safe WA Code of Practice- Excavations 2005, or any detailed work practices included in any training manuals. Safety Before commencement of work, a risk assessment must be carried out using the Risk Analysis Procedure (OSH-3.6-1-02), to identify and document the hazards and risks associated with the task and ensure appropriate control measures are implemented. It is important that, appropriate control measures must be identified, documented and implemented to lessen or control the identified hazards. Training A person performing any of the functions described in this instruction must have the relevant training and competencies. Install Trench Support (RIICCM210A) if depth of trench is deeper than 1.5 meters Basic Worksite Traffic Management (RIIOHS302A) Cable jointers (trench / pit rescue) Induction in the safe use of directional drilling rig ( i.e. Vermeer plant induction ) If there are technical issues involved in a specific excavation, then an appropriately trained and experienced engineer or a competent person acting on their behalf must be on site. Instruction For all excavations and directional drilling use the four Ps, Plan, Pothole, Protect and Proceed. Plan Conduct a job briefing and JRA (job risk assessment) before work commences. Ensure that all relevant tools and equipment are checked for condition before use. All PPE / PPC must be inspected and used for all relevant work tasks. CS10 # 2244897 FI 6.4 Excavation work and directional drilling Page 1 of 8
Contact Dial before You Dig (Dial1100) request and obtain all data for other utilities that may be a foreseeable hazard during your excavation or drilling work. Check all work plans and drawings thoroughly to ensure they relate to the work being carried out. If the scope of work changes or the plan validity date expires, submit a new Dial before You Dig enquiry before work commences. Other work permits may be required from other utilities before work can commence, i.e. high pressure gas or water. Observe and maintain all exclusion zones around and near other hazardous utilities such as high pressure mains. If the excavation or drilling associated with the project has a possible impact on local government infrastructure, they must be contacted and asked about the conditions necessary to allow work to continue. Traffic control must be considered if work is to impact on local roads, footpaths and infrastructure. Where there is a probability of excavation or drilling work damaging underground utilities or undermining a structure, contact the utility or structure owner and request implementation of appropriate risk control. Contact land owner if you are excavating or drilling on privately owned land, if land owner is not available for permission, contact your formal leader. Refer to section 9 of Network Instruction Manual for any environmental issues including ESA, s (environmentally sensitive areas) and any other environmental hazards or incidents. Note: Never assume that Dial Before You Dig plans and project documentation will represent all underground assets in your excavation area. Plans and documentation do not pinpoint the exact location they only provide information about asset general proximity. Pothole On the existing JRA, identify and document the appropriate means of potholing and reassess the hazards and risks. Utilise all reasonable techniques for advanced location of existing services and utilities in the vicinity of the proposed excavation or drilling path, this can be achieved by, hand digging, vacuum excavation, location through the use of metal detectors and ultra sound imaging. CS10 # 2244897 FI 6.4 Excavation work and directional drilling Page 2 of 8
Indicate all existing services and utilities and their routes with such measures as, spray paint, pegs or flagging tape. At five meter intervals, mark the ground to identify the underground service / utilities depth. If potholes are to be left open, the appropriate safety barriers and signs must be used to protect the public, workers and contractors. Comply with all safe approach distances (SADs) for all underground utilities, for more information on SADs, see Table 1 Safe Approach Distances in FI 2.17 Protect On the existing JRA, re-assess the risk and hazards, communicate and document if required. Install all appropriate temporary safety barriers and signs. Earth any excavating or drilling machinery according to manufactures recommendations. All drilling rigs are to be earthed at all times, and must be fitted with a strike detector in the event it strikes an energised electrical asset. The drilling rig earth is to be in the form of an earth spike, tracks are not an acceptable form of earthing. A competent safety observer must be appointed and noted on the JRA to monitor all machinery used to excavate around any underground or overhead utilities. Whenever it is possible install trench or excavation shoring, this may be needed if the soil is unstable and could possibly collapse. This may happen due to ground instability, water ingress, fine sand or vibration from machinery. Trenches and excavations deeper than 1.5 meters will require shoring, an engineer or a delegated person to act for the engineer will be required to oversee the installation of the shoring. Reinforce any structure that is likely to fall into a trench or excavation by the appropriate means, such as sheet pilling, shoring, bracing or guying. When trenching or excavation work is near a power pole, see FI 5.2 Poles-Inspection and Support Prior to Commencement of Work, for approved supporting methods. Prevent all sediment, drilling slurry and loose soil from entering drains and waterways. CAUTION IF THE HAZARD OR RISK CANNOT BE CONTROLLED, STOP WORK AND RE-ASSESS Proceed On existing JRA, re-assess the risks and hazards, communicate and document if required. Observe minimum depths and clearances as stated from information on plans provided by asset owner. CS10 # 2244897 FI 6.4 Excavation work and directional drilling Page 3 of 8
Some underground assets may be as little as 500mm below finished ground level. Install covers or an approved barrier to prevent damage to other underground utilities during the excavation process. Ensure private vehicles are not parked on the work site. Do not use mechanical excavators until you have located and identified all underground utilities. Excavator operators must comply with the SADs for underground utilities. Mechanical excavation is not permitted within 500mm in any direction of any underground electrical cables or gas pipe. Locate and keep clear of overhead conductors (SADs FI 2.17) where applicable. Backfill all open trenches / excavations at the end of each shift, if not barricade as per FI 2.15 Temporary Barriers and or Warning Signs. If damage has occurred as a result of excavation or drilling, ensure all appropriate risk controls are initiated, and isolate the area around the damaged utility. All damage must be reported to a nominated Horizon Power representative, and request they attend the work site. Remove all waste spoil and rubbish from work site. Leave the work site safe and in clean condition according to the risk assessment. Mechanical excavation Mechanical excavators must not be used until all underground utilities have been located, identified and marked. Mechanical excavator operators must comply with SADs for all underground utilities, and are not permitted within 500mm in any direction of any underground cables or gas pipes. When using a mechanical excavator it must be fitted with a smooth edge bucket or rounded tooth bucket. For clay / rock excavating, only layers of a maximum of 50mm may be removed at a time. Directional drilling Ensure drill rig is earthed at all times when in use, and check strike detector is operational before using the drill rig, (see manufactures operating instructions) Identify and expose any underground utility within the drill route that may be potentially damaged as a result of drilling process. A safety observer must monitor any exposed utility during the drilling process. Stability and Shoring of Structures Before any trenching, excavation or drilling work can commence, a risk assessment must be completed to determine the following: The condition and stability of soil or ground to be excavated. CS10 # 2244897 FI 6.4 Excavation work and directional drilling Page 4 of 8
The collapsible area alongside the proposed excavation, and the soundness of the structure and surrounding material. The depth of the structures footings. Where the risk assessment determines that the structure is unstable, then consideration must be given to carry out any excavation, trenching or directional drilling outside the risk area. When excavation, trenching or directional drilling cannot be undertaken, then work must not commence until the structure or surrounding material has been stabilised by bracing the structure, shoring the surrounding material, or a combination of both. Shoring must be used when there is a risk of material that forms the excavated area falling into the excavation, or the risk of any adjacent material falling or dislodging into the excavation. Where the risk assessment determines the structure is stable, or there is no risk of the material at the base of the structure falling or dislodging into the excavation, work can proceed without shoring and bracing. Shoring must be used when a person is working in an excavation 1.5 meters or deeper. Excavations Where possible excavations spoil is to be set back 1 meter from the edge of excavation. Safety helmets must be worn in excavations deeper than 1.2 meters deep. All static and dynamic loads near the excavation must be managed appropriately. A competent person must monitor the excavation during works to ensure there is no sign of excavation collapse. Access and egress from all excavations is provided. Emergency rescue plan is to be documented on JRA and tested prior to work commencing. All spoil piles must not encroach onto roads, footpaths and any other trafficable area. If this is unavoidable then sufficient signage, barricading or traffic control must be used. In the event of damage to another utility asset, the person responsible for causing the damage shall immediately contact their formal leader, who is then responsible for reporting the incident to Horizon Power Control Centre (HPCC). HPCC will then inform the relevant utility owner and the Horizon Power personal, as per the HPCC incident work instruction. CS10 # 2244897 FI 6.4 Excavation work and directional drilling Page 5 of 8
Fig. 1 Structure and Footings inside the Collapsible area If the structure and footings are inside the collapsible area and are less than 1000 mm above F.G.L., it must be either shored, braced or both. If the structure and footings are inside the collapsible area and are higher than 1000 mm above F.G.L., it must be shored and braced. Fig. 2 Structure and Footings deeper than the Collapsible area If the structure and footings are deeper than the collapsible area work may proceed if: The structure is less than 1000 mm above F.G.L. It is not retaining soil and the structure and footings are deemed safe. If the structure such as a retaining wall, fence, street furniture etc., is higher than 1000 mm above F.G.L., it must be braced. Fig. 3 Excavation less than Angle of Repose CS10 # 2244897 FI 6.4 Excavation work and directional drilling Page 6 of 8
Fig. 4 Excavation greater than Angle of Repose Fig. 5 Collapsible Area The collapsible area (set back from edge of trench) is determined by multiplying the depth of excavation, for example: 1.7m x 1.0m = 1.7m from the edge of the excavation. CS10 # 2244897 FI 6.4 Excavation work and directional drilling Page 7 of 8
References Occupational Safety & Heath Act 1984 Occupational Safety & Health Regulations 1996 SHMS OSH-3.6-1-02 Job Risk Analysis (JRA) Procedure SHMS OSH-3.6-1-26 Personal Protective Equipment Field Instruction 2.6 Worksite Clothing / Personal Protective Equipment Requirements Field Instruction 2.15 Temporary Safety Barriers and/or Warning Signs Field Instruction 2.17 Safe Approach Distances Field Instruction 2.20 Traffic Management (RIIOHS302A) Field Instruction 2.23 Job Hazard and Risk Management (JRA) Field Instruction 5.2 Poles Inspection and Support Prior to Commencement of Work Field Instruction 9.2 Environmentally Sensitive Areas Course: Trench and Pit Rescue Course: Install Trench Support (RIICCM210A) Worksafe WA Code of Practice - Excavations 2005 http://www.commerce.wa.gov.au/worksafe/pdf/codes_of_practice/code_excavation.pdf CS10 # 2244897 FI 6.4 Excavation work and directional drilling Page 8 of 8