Concrete Chasing Safe Work Method Statement

Concrete chasing generates higher silica dust concentrations than any other common construction cutting activity due to combination of continuous cutting action, confined work spaces, extended operation duration, and difficulty implementing effective dust controls on hand-held equipment. Wall chasers and angle grinders create fine dust particles through high-speed abrasion as diamond cutting discs rotating at 9,000-13,000 RPM grind through concrete aggregate, with dust generation rate proportional to cutting speed and material removal rate. Typical electrical chasing work installing conduits throughout a residential unit might involve cutting 50-100 linear metres of chase over 6-8 hour work shift, creating continuous dust exposure throughout entire shift. The dust particles containing crystalline silica are less than 10 micrometres diameter enabling deep penetration into lung tissue where they cause irreversible scarring, inflammation, and progressive respiratory impairment characteristic of silicosis. Without dust controls, operators and workers in same room receive silica exposure exceeding 8-hour workplace exposure standard within 15-30 minutes of chasing work commencement. Enclosed spaces including bedrooms, bathrooms, and plant rooms lack natural ventilation causing dust accumulation, with concentrations building throughout work shift and remaining elevated for hours after cutting ceases. Workers often underestimate silica exposure risk from chasing because dust is not always visible and no immediate symptoms provide warning, with serious lung damage occurring before workers recognize exposure is harmful. Young workers in first years of trade apprenticeships receive highest cumulative exposure as they are assigned extensive chasing tasks, creating risk of silicosis diagnosis in mid-20s after only 3-5 years exposure.

Consequence: Silicosis causing progressive respiratory failure and premature death with no cure available, lung cancer development from carcinogenic silica exposure, chronic obstructive pulmonary disease reducing work capacity and quality of life, kidney disease and autoimmune conditions linked to silica exposure, permanent respiratory disability ending construction careers

Concrete chasing equipment operates with exposed diamond cutting blades rotating at peripheral speeds exceeding 70 metres per second creating severe laceration and amputation hazard if operators contact spinning blades. Wall chasers have twin blades spaced 25-50mm apart with front sections exposed during cutting to engage concrete surface, while rear blade sections are typically guarded. Angle grinders used for chasing have single exposed blade with only upper hemisphere guarded, leaving lower blade section exposed during cutting. Hand placement during chasing work positions fingers and palms within 50-100mm of rotating blades throughout operation, with momentary loss of concentration, equipment kickback, or loss of grip bringing hands into contact zone. Kickback occurs when blades bind in cuts from hitting reinforcement steel, blade pinching in closing cuts, or material wedging between twin blades on wall chasers, causing equipment to thrust violently backward toward operator without warning. The reaction time between kickback initiation and blade contact with operator hands or body is typically less than 0.3 seconds, insufficient for conscious avoidance response. Operators sometimes remove or modify blade guards attempting to achieve greater cutting depth or improved visibility of cutting line, eliminating primary protection against blade contact. Cutting overhead or at awkward angles reduces equipment control and increases contact risk, particularly when operators must work from ladders or scaffolding rather than stable floor positions. Blade breakage from excessive speed, inadequate blade specification for concrete hardness, or manufacturing defects causes blade fragments to project at high velocity toward operators and bystanders. Clothing or glove entanglement in rotating blades drags hands into cutting zone, with loose sleeves, gloves, or dangling lanyards catching on blade creating entrapment scenarios.

Consequence: Traumatic finger or hand amputation requiring surgical reconstruction, deep lacerations to hands, arms, and face requiring extensive suturing and resulting in permanent scarring, penetrating injuries from blade fragment projection, nerve damage causing permanent loss of hand function and sensation

Concrete walls and floors contain embedded electrical cables, conduits, plumbing pipes, and data cabling creating service strike risk during chase cutting operations. Electrical cable strikes energize cutting equipment and operator through blade contact with live conductors, with voltage ranging from 240V lighting circuits to 415V three-phase power creating electrocution hazard. The risk is particularly acute when chasing in walls adjacent to existing electrical services, cutting near switch positions or power outlets, or working in plant rooms and service areas with concentrated service penetrations. Building plans often do not show embedded services accurately, particularly in older buildings where services have been added or modified over decades without plan updates. Electronic cable detection provides imperfect service location as cables deeper than 75-100mm may not be detected reliably, inactive cables do not energize cable locators relying on electromagnetic field detection, and cables running perpendicular to chase path may be missed if scanning is inadequate. Plumbing pipe strikes cause water release flooding work areas, creating electrical hazards if water contacts energized equipment or cables, damaging building finishes and contents, and requiring emergency plumbing repairs. Gas pipe strikes in buildings with reticulated gas create fire and explosion risk from gas accumulation in confined spaces. Fiber optic data cable strikes cause expensive telecommunications infrastructure damage with liability for service interruption affecting multiple building occupants. Operators working under time pressure sometimes proceed with chasing based on visual inspection alone without systematic service detection, particularly for small chasing quantities or when working in areas assumed to be free of services. The shallow depth of most chasing work (25-40mm) increases probability that cables and pipes at typical embedment depths of 20-50mm will be struck.

Consequence: Operator electrocution from striking live electrical cables with potential fatality, electrical burns causing severe tissue damage, building water damage from plumbing strikes with associated repair costs and business interruption, fire risk from gas line rupture, telecommunications infrastructure damage with contractual liability for service interruption

Wall chasers and angle grinders generate significant vibration transmitted through equipment handles to operator hands and arms, classified as Hand-Arm Vibration creating risk of vibration white finger, carpal tunnel syndrome, and reduced manual dexterity. Vibration magnitude varies with equipment design, cutting conditions, and concrete hardness, with typical exposure levels 8-15 m/s² substantially exceeding the exposure action value of 2.5 m/s² requiring health surveillance and risk reduction. Extended chasing operations common during electrical and plumbing installation can involve 4-6 hours continuous or intermittent equipment operation throughout work shifts, creating cumulative vibration dose exceeding exposure limit values. Cutting through reinforced concrete generates impulsive vibration spikes when blades strike reinforcement steel, contributing to accelerated vibration injury development. Operators must maintain firm grip pressure on equipment throughout chasing to control equipment and maintain cutting alignment, preventing grip relaxation that would reduce vibration transmission. Cold weather common during winter construction exacerbates vibration injury symptoms through reduced blood flow to extremities, worsening numbness and pain in affected workers. Vibration white finger causes permanent numbness and reduced sensation in fingers affecting ability to perform fine manipulation tasks, with symptoms including finger blanching and pain triggered by cold exposure or vibration. Apprentices and young workers performing extensive chasing during early career years accumulate high vibration exposure potentially causing permanent vibration injury by late 20s or early 30s, affecting career longevity in construction trades.

Consequence: Vibration white finger causing permanent numbness and pain in hands and fingers, carpal tunnel syndrome requiring surgical treatment, reduced grip strength and manual dexterity affecting ability to perform trade tasks, tingling and loss of sensation interfering with quality of life and work capacity

Concrete chasing equipment generates noise levels typically 105-115 dB(A) measured at operator position from combination of high-speed motor operation, blade engagement with hard concrete and aggregate, and equipment vibration. Wall chasers with twin blades produce slightly higher noise than single-blade angle grinders due to dual cutting action and increased power. The sustained nature of chasing work creates cumulative noise exposure substantially exceeding daily exposure limits, with typical chasing task durations ranging from 30 minutes for small repairs to 6-8 hours for extensive electrical or plumbing installations. Enclosed spaces including bedrooms, bathrooms, and corridors where much chasing occurs lack noise absorption materials and feature hard reflective surfaces amplifying noise through reverberation, increasing operator exposure by 5-10 dB compared to outdoor cutting. Workers in adjacent rooms and on same floor receive elevated noise exposure even without directly operating equipment, affecting multiple trades working simultaneously on renovation projects. Communication between workers becomes impossible during chasing operations preventing verbal warning of hazards or coordination of tasks, requiring work stoppages for any necessary communication. Many operators work without adequate hearing protection due to discomfort during extended use, inability to hear equipment performance changes indicating binding or problems, or communication difficulties with supervisors and other workers when hearing protection prevents verbal interaction. The high-frequency noise component from concrete cutting creates particular damage risk to hearing at speech frequencies, causing communication difficulties beyond measured hearing loss thresholds.

Consequence: Permanent noise-induced hearing loss affecting speech comprehension and quality of life, tinnitus causing constant ear ringing and sleep disruption, difficulty understanding speech in noisy environments affecting social interaction and workplace communication, accelerated hearing loss progression with continued unprotected exposure

Concrete chasing removes structural material from walls, floors, and beams potentially reducing load-bearing capacity if chase depth, length, or spacing is excessive relative to element thickness and reinforcement configuration. Australian Standard AS 3600 Concrete Structures and building codes limit permissible chasing depth in structural elements, typically restricting chases to maximum one-third of wall thickness and requiring minimum spacing between parallel chases preventing excessive material removal. Walls less than 100mm thick generally should not be chased at all as any significant material removal compromises structural integrity, while 150-200mm walls can accommodate shallow chases 25-40mm deep subject to spacing and location restrictions. Chasing over door and window openings, near slab edges, or in highly stressed structural zones creates particular concern requiring engineering assessment. Cutting through reinforcement steel during chasing eliminates structural capacity provided by severed bars, potentially creating immediate structural instability or progressive deterioration if corrosion initiates at cut bar ends. Operators cannot visually determine whether cutting has struck reinforcement without removing concrete from chase, and may not recognize significance of hitting steel during cutting. Post-tensioned slabs contain high-strength steel cables under enormous tension, with cable strike during chasing causing violent cable release, serious operator injuries, and potentially slab collapse. The challenge is that operators performing chasing work are typically electrical or plumbing contractors without structural engineering knowledge, making assessment of chase structural impact difficult. Time and cost pressures encourage completion of chasing work quickly without structural consultation, even when chase depths or locations may compromise structural elements.

Consequence: Structural element failure from excessive material removal causing building damage or collapse, reinforcement corrosion from exposed cut steel bars leading to long-term structural deterioration, expensive structural repairs strengthening elements weakened by chasing, building evacuation and business interruption during emergency structural assessment and repairs