Excavation Near Assets Safe Work Method Statement

Dial Before You Dig enquiries are legally mandatory before excavating in most Australian jurisdictions under state and territory work health and safety regulations and specific utilities legislation. Requirement applies to all excavation work including small hand excavations for fence posts or garden work, not just major civil works. Enquiries must be submitted minimum 2 business days before planned excavation commencement allowing service authorities time to respond. Submit enquiries online at 1100.com.au providing detailed site location, work description, excavation areas shown on plan, expected depths, and contact information. Service authorities respond within 2 business days either providing service plans, advising no services in area, or directing you to contact them directly for location assistance. Responses remain valid for 60 days - if work delayed beyond this period, new enquiries must be submitted as service information may have changed. Contractor remains responsible for locating all services identified in responses through physical investigation - Dial Before You Dig provides information but does not physically locate services. If service strike occurs without Dial Before You Dig enquiry, this constitutes automatic breach of due diligence with prosecution likely and invalidation of insurance coverage for resulting damage. Even with Dial Before You Dig enquiry, contractor remains liable for damage from inadequate physical location or unsafe excavation methods. Maintain copies of all Dial Before You Dig enquiries and responses as evidence of proper investigation - these documents are first items requested by investigators after service strikes.

Safe clearance distances for mechanical excavation depend on service type and criticality, with regulatory requirements and service authority specifications setting minimum distances. General principle: transition to hand excavation or non-destructive methods well before reaching service to account for location uncertainty and equipment precision limitations. Typical requirements: high-voltage electrical cables (above 1kV) and high-pressure gas mains (above 200 kPa) require cessation of mechanical excavation minimum 1 metre from marked service location, transition to non-destructive vacuum or hydro excavation for final exposure. Other services including low-voltage electrical, telecommunications, water, sewer, and stormwater require hand excavation within 500mm of marked locations. Australian Standard AS 5488 for service location recommends Quality Levels: QL-A (±50mm accuracy) requires vacuum excavation for verification, QL-B (±300mm accuracy) from electromagnetic detection requires hand excavation for final exposure, QL-C (±1000mm accuracy) from plans only requires investigation over wider area before mechanical excavation. These are minimum requirements - many service authorities impose stricter clearances particularly for critical assets. For example, some electricity distributors prohibit mechanical excavation within 3 metres of high-voltage transmission cables requiring hand excavation for entire exposure. Always check service authority specific requirements provided in Dial Before You Dig responses. Remember that service locations shown on plans and marked from detection have inherent uncertainty - actual positions may vary by several hundred millimetres. This uncertainty is reason for conservative clearances preventing strikes even when services not exactly where indicated.

Striking electrical cable creates immediate life-threatening hazard requiring urgent protective actions. If cable strike suspected from sparking, electrical smell, or visible cable damage: stop excavation immediately turning off equipment engine if safe to do so. If you are equipment operator and suspect cable strike, do NOT exit equipment as stepping to ground can create electrical circuit through body causing fatal electrocution. Remain in cab with all body parts inside, call emergency services on mobile phone explaining situation, wait for electricity authority to isolate cable and confirm safe before exiting. If you are ground worker and cable strike occurs, move away rapidly using shuffle steps keeping feet together and on ground preventing step potential shock from voltage gradient in ground. Move minimum 10 metres from strike location. Prevent other personnel approaching strike area establishing exclusion zone - electrified equipment or ground can remain deadly for extended period. Call 000 reporting electrical emergency and provide location details. Contact electricity distributor emergency line (number on Dial Before You Dig response) reporting cable strike and requesting urgent attendance for isolation. Do not allow anyone to approach equipment or cable until electricity authority confirms isolation - good Samaritan instinct to check on operator causes secondary electrocutions. If fire develops from cable strike, evacuate area and allow fire brigade to respond - never fight electrical fires without confirmation of isolation. After electricity authority attends and isolates cable, document incident thoroughly including photographs, witness statements, and chronology of events. Report incident to WHS regulator within required timeframe (usually 24 hours for dangerous incidents). Engage electrical specialist to assess equipment for damage before returning to service as electrical faults may have developed. Review investigation findings and implement corrective actions preventing recurrence - most cable strikes are foreseeable and preventable with proper service location and excavation procedures.

Excavation near structures (within distance equal to excavation depth, typically 3-5 metres) requires comprehensive monitoring detecting settlement before structural damage occurs. Before excavation commences, conduct detailed condition survey of all structures within potential settlement zone. Photograph comprehensively documenting existing cracks, distortion, and defects establishing baseline condition. Install survey monitoring points on structures - precision survey marks allowing measurement of vertical and horizontal movement to ±1mm accuracy. Points typically installed at building corners, mid-walls, and significant features like window sills. Establish baseline measurements recording initial elevations and positions of all monitoring points before excavation begins. During excavation, monitor structure elevations and positions daily using precision surveying equipment (total station or digital level). Plot measurements on charts showing movement trends over time. Establish trigger levels for intervention based on structure type and condition: 5mm movement typically triggers investigation and increased monitoring frequency, 10mm movement triggers work cessation and implementation of additional support measures, 15mm movement requires emergency intervention and possible evacuation if progressive movement continuing. If triggers exceeded, immediately cease excavation and implement remedial measures - these may include installation of additional support systems, reduction of excavation depth, or changes to excavation sequence reducing stress on adjacent ground. Engage geotechnical and structural engineers to assess situation and design remedial works. Monitor groundwater levels if dewatering undertaken as lowering water table can cause settlement over wide area affecting structures beyond immediate excavation zone. Continue monitoring for minimum 4 weeks after excavation completion as settlement can continue after backfilling particularly in compressible soils. If monitoring reveals significant movement, notify building owners immediately providing regular updates on monitoring results and remedial actions being implemented. Maintain all monitoring records for minimum 5 years as settlement-related issues can manifest months or years after excavation completed.

Confined space classification depends on multiple factors beyond just depth, but many excavations exceeding 1.5 metres do qualify as confined spaces requiring specific entry controls. Under WHS regulations, space is confined space if: it is substantially enclosed, it is not designed for continuous human occupancy, and it has restricted entry or exit, and it may present atmospheric hazards or engulfment risks. Typical excavations exceeding 1.5 metres with vertical or near-vertical sides meet these criteria - substantially enclosed by earth, not designed for occupancy, restricted egress requiring climbing or ladder use, and potential atmospheric hazards from oxygen depletion, toxic gases, or combustible gases. Shallow wide excavations with gentle sloped sides allowing easy egress may not classify as confined spaces despite exceeding 1.5 metres depth. Excavations near sewers or gas services have higher likelihood of atmospheric hazards. When excavation qualifies as confined space, full confined space entry procedures required: classify space and conduct risk assessment, obtain confined space entry permit before each entry period, conduct atmospheric testing before entry and continuously during occupation measuring oxygen (must be 19.5-23.5%), combustible gases (must be below 5% LEL), hydrogen sulphide (must be below 10 ppm), and carbon monoxide (must be below 30 ppm), provide mechanical ventilation if atmospheric testing reveals unsafe conditions, assign trained standby person remaining outside space throughout entry period, provide emergency retrieval equipment allowing rescue without entering space, establish communication between entrants and standby person with regular check-ins, train workers in confined space hazards and emergency procedures. Penalties for non-compliance with confined space regulations are severe particularly if incidents occur. When in doubt, treat excavation as confined space and implement full controls - this provides higher safety standard than assuming space is not confined space based on ambiguous criteria.