Bulk Excavations Safe Work Method Statement

Bulk excavations exceeding 4 metres depth require supervision by a competent person as defined in WHS regulations. This typically means a geotechnical engineer or engineering geologist with qualifications and experience in excavation stability. The competent person must assess excavation design, specify batter angles and support requirements, and conduct regular inspections during excavation (minimum weekly, daily for critical excavations). Additionally, site supervisors should have vocational qualifications in civil construction and experience managing earthworks projects. Plant operators require high-risk work licences for excavators (CV class) and trucks (appropriate driving licence class). Surveyors performing level control should hold qualifications in surveying or civil engineering. Principal contractors must verify all personnel hold appropriate qualifications before allowing them to perform these critical roles.

Safe batter angles depend on multiple factors and require professional geotechnical assessment - never rely on rules of thumb or previous experience alone. Engage a qualified geotechnical engineer to conduct soil investigation including boreholes or test pits determining soil type, strength parameters, and groundwater conditions. The geotechnical engineer analyzes data using slope stability software considering soil properties, excavation depth, groundwater, surcharge loads, and seismic factors. Common batter angles: 1:1 (45 degrees) for very stable rock or cemented soils for limited depths; 1:1.5 (33 degrees) for clayey soils with favorable moisture content; 1:2 (26 degrees) for sandy or loose soils; 1:3 or flatter for saturated sands or very weak soils. Angles are steeper for short-term excavations than permanent cuts. Geotechnical recommendations must be followed exactly - steepening batters to reduce excavation volume creates extreme risk. If conditions encountered during excavation differ from those assumed in design, stop work and obtain revised geotechnical advice.

If unexpected groundwater is encountered during excavation, stop excavation immediately and assess the situation before proceeding. Observe the nature of inflow: slow seepage through batter faces may be manageable with sumps and pumps; rapid inflow or artesian conditions (water flowing without pumping) indicates pressure head requiring immediate action. Contact the project geotechnical engineer to report conditions - they may need to visit site to assess implications for excavation stability. Do not deepen excavation into saturated ground without geotechnical approval as this can trigger rapid collapse. Implement temporary dewatering using sumps excavated in excavation base with pumps to remove water, but be aware that pumping without engineering design can cause ground settlement or instability. For more than minor seepage, install proper dewatering system (wellpoints, deep wells, or ejector wells) designed to lower water table minimum 500mm below excavation depth. Monitor groundwater levels continuously once dewatering operating. If artesian conditions encountered, specialized dewatering design required - do not attempt to manage with standard pumping. Adjust excavation sequence potentially battering slopes flatter or installing support systems if groundwater reduces soil strength.

Material stockpiling near excavation edges creates surcharge loading that can trigger batter collapse. Australian Standard AS 2187.1 and geotechnical engineering principles require maintaining adequate setback distances. General rule: stockpile no closer than 3 metres from excavation edge for small stockpiles (less than 2 metres high), increasing to 5+ metres for larger stockpiles. The required distance depends on stockpile height and weight, excavation depth, soil type, and batter angle. Geotechnical engineer should specify allowable surcharge loads and required setback distances in excavation design. Stockpiling 50 tonnes on a 2-metre-high pile creates significant pressure extending into ground - this load transmitted to excavation batter can reduce factor of safety below acceptable levels. For deep excavations in weak soils, stockpiling within 10 metres can affect stability. Vehicle traffic near edges creates dynamic loading compounding surcharge effects. If material must be stockpiled temporarily before haulage, keep piles low and spread over wider area rather than concentrated. Install barriers preventing vehicles from accessing areas within 3 metres of edges. Monitor batters closely for distress if stockpiling occurs nearby.

Bulk excavations must comply with environmental protection legislation preventing off-site impacts. Key requirements include: erosion and sediment control preventing soil-laden water entering waterways (install sediment fencing, silt curtains, sediment basins, and stabilize disturbed areas progressively); dust management to prevent visible dust leaving site (water cart operation, covering stockpiles, cessation during extreme wind); contaminated soil management if contamination discovered (stop work, engage environmental consultant, classify contamination, handle per regulations including notification to EPA); noise management for excavations near residential areas (comply with noise limits, restrict noisy activities to daytime hours, notify residents in advance); vegetation clearing controls if native vegetation present (obtain required permits, engage ecologist to identify threatened species, install tree protection zones); archaeological protocol if historical or Aboriginal artifacts discovered (stop work immediately, notify relevant authority, engage archaeologist before disturbing). Most states require preparation of Environmental Management Plan for significant excavations showing how impacts will be prevented. Non-compliance can result in EPA prosecution with penalties exceeding $1 million for serious breaches. Beyond regulatory requirements, implementing effective environmental controls protects business reputation and maintains community relationships critical for securing future projects.