Method Statement: Building Gridline Setting Out and Control Transfer Prior to Excavation, Piling, and Foundation Works – Method Statement

Overview

This method covers the complete survey workflow for building gridline setting out works prior to excavation, piling, and foundation construction. It includes verification and establishment of primary/secondary control, transfer of control to working levels, total station operations, dimensional verification, offset marking for excavation and pile locations, independent survey checks, QA/QC inspections, as-built records, and release procedures.

Inclusions

• Review of coordinate reference system, benchmarks (TBMs), and design grid data
• Establishment/verification of primary horizontal and vertical control
• Creation of working (secondary) control network
• Total station setup, orientation, and instrument checks
• Building gridline computation and on-site setting out
• Offset marking for excavation boundaries, profile boards, and pile set-out
• Transfer of control to basements and elevated floors
• Dimensional verification and tolerances
• Independent survey check (ISC) and ITP hold/witness points
• Deliverables: setting-out reports, control network diagrams, coordinates registers, redlines/as-built

Exclusions

• Topographic surveys beyond work limits (unless specifically instructed)
• Utility detection surveys (refer to separate method; coordinate tie-ins included where provided)
• Temporary works design for edge protection, access platforms, or scaffolding

Key Tolerances [Verify per project specifications]

• Primary horizontal control positional tolerance: ±5 mm to ±10 mm
• Primary vertical control closure: ≤4 mm × √km (digital leveling loop)
• Working/secondary control positional tolerance: ±8 mm
• Gridline position at intersection: ±5 mm (relative to control)
• Gridline on level transfer (storey-to-storey): ≤±6 mm
• Pile set-out positional tolerance: typically ±10 mm (horizontal) and top level ±5 mm
• Excavation offset pegs relative to design cut: ±20 mm (horizontal) and ±10 mm (vertical)

All values are typical benchmarks and must be confirmed against the project specifications and Engineer’s requirements.

• Approved Method Statement and ITP.
• Issued-for-Construction (IFC) drawings with confirmed grid coordinates, reference system, and vertical datum.
• Confirmed coordinate reference system (CRS), site calibration/transform parameters (e.g., 7-parameter Helmert) and grid-to-ground scale factor application plan. [Verify per project]
• Benchmarks (TBMs) and any existing control provided by the Employer verified by level run.
• Instrument calibration certificates valid and field verification per ISO 17123 completed.
• Permits to Work: working at height, night works, drilling/anchoring, hot works if applicable. [Verify per project HSE plan and local regulations]
• Pre-Task Briefing (PTB) / Toolbox Talk conducted; roles and communication protocols defined.
• Utilities/constraints identified; exclusion zones agreed; temporary works/edge protection in place if needed for elevated transfers.
• Approved marking legend, color codes, and drawings for set-out sketches.
• Weather and light conditions suitable for precise survey; wind thresholds for pole work defined [Verify].

Principal Hazards and Controls

• Hazard: Working near open excavations/edges during set-out and level transfer
• Likely consequence: Falls from height, serious injury/fatality
• Engineering/procedural control: Install edge protection, guardrails, and toe boards; maintain 2 m exclusion from edges unless protected; use fall arrest only as last resort
• Required PPE: Helmet with chin strap, high-vis, safety boots, fall arrest if required
• Collective preventive measure: Physical barriers and temporary works certified

• Inspection/permit/supervision: Permit to Work for work at height; daily edge protection inspection; supervisor present

• Hazard: Traffic/plant interface (dumpers, excavators, piling rigs)

• Likely consequence: Struck-by injuries
• Engineering/procedural control: Segregated walkways; banksman control; agreed radio channels; exclusion zones around rigs
• Required PPE: High-vis, safety boots, gloves, hearing protection in active plant zones
• Collective preventive measure: Physical barriers, traffic management plan

• Inspection/permit/supervision: Daily TM inspection; banksman competency; permit for plant movement in survey areas

• Hazard: Laser/EDM exposure from total station

• Likely consequence: Eye injury
• Engineering/procedural control: Use Class 1/2 EDM only; do not aim at personnel/reflective surfaces; place warning signs
• Required PPE: Safety glasses as needed
• Collective preventive measure: Site induction on laser hazards

• Inspection/permit/supervision: Equipment compliance per manufacturer; HSE inspections

• Hazard: Manual handling of tripods, profiles, pegs

• Likely consequence: Strains/sprains
• Engineering/procedural control: Team lifts; use lightweight carbon poles; plan carry routes
• Required PPE: Gloves, safety boots
• Collective preventive measure: Mechanical aids where practical

• Inspection/permit/supervision: Manual handling training; spot checks by HSE

• Hazard: Drilling/fixing control points into concrete/structures

• Likely consequence: Striking embedded services/rebar; dust and flying fragments
• Engineering/procedural control: Scan or review drawings for rebar/services; drill stops set; dust extraction and eye protection; hot works permit if coring generates sparks
• Required PPE: Eye/face protection, dust mask (P2/P3), gloves, hearing protection
• Collective preventive measure: Use pre-cast sleeves/approved zones for targets where possible

• Inspection/permit/supervision: Permit to drill; tool inspection; supervision during drilling

• Hazard: Night/low-light surveying

• Likely consequence: Slips/trips/struck-by incidents
• Engineering/procedural control: Temporary lighting to 50–100 lux on workface [Verify]; illuminated signage; reflective PPE
• Required PPE: Headlamp, high-vis
• Collective preventive measure: Lighting towers with backup

• Inspection/permit/supervision: Night work permit; electrical inspection of lighting

• Hazard: Weather (heat, rain, lightning, wind)

• Likely consequence: Heat stress; electrical storm strikes; unstable poles/tripods
• Engineering/procedural control: Stop work during lightning per policy; wind thresholds for pole work [e.g., >10 m/s stop – Verify]; heat rest cycles and hydration
• Required PPE: Weather-appropriate PPE, sunscreen
• Collective preventive measure: Shelters and scheduled breaks

• Inspection/permit/supervision: Supervisor weather monitoring; toolbox brief updates

• Hazard: Confined/partially enclosed basements during control transfer

• Likely consequence: Poor access, low oxygen, slips
• Engineering/procedural control: Adequate ventilation and lighting; access/egress routes maintained; atmospheric testing if required
• Required PPE: Gas monitor if required, hard hat, boots
• Collective preventive measure: Access control and rescue plan

• Inspection/permit/supervision: Confined space assessment and permit where applicable [Verify per project HSE plan and local regulations]

• Hazard: Data/coordination errors

• Likely consequence: Rework, structural misplacement
• Engineering/procedural control: Independent check of coordinate uploads; use check points; hold points prior to works
• Required PPE: N/A
• Collective preventive measure: QA process and supervision sign-offs
• Inspection/permit/supervision: ITP hold/witness points and record reviews

Emergency Preparedness

• First aid kits and trained first aiders on shift; emergency contact list posted.
• Incident reporting per site protocol; stop-work authority for Survey Manager.
• Spill kits for small fuel/paint spills if used near survey area.

• Material selection: Use low-VOC marking paint; avoid solvent-rich products indoors. [Verify]
• Noise and light: Aim lights away from public/neighboring properties; restrict night works per permit; maintain silencers on generators.
• Dust control: Use dust extraction when drilling; wet methods where acceptable; collect slurry.
• Waste: Collect spent targets, nails, chalk cans; segregate recyclable metals and dispose per waste plan.
• Surface protection: Do not mark on heritage finishes or outside agreed zones; use removable tape/targets where required.
• Water protection: Prevent washdown/paint overspray into drains; use drip trays for plant.
• Ecology: Avoid fixing markers to trees or habitats; respect buffer zones if applicable.
• Energy and batteries: Use rechargeable batteries; charge in designated areas; avoid generator idling.
• Records: Maintain an Environmental Checklist for each shift; non-conformances logged and closed out. [Verify per project EMS]

QA System

• Calibration: Maintain valid calibration certificates; perform field checks per ISO 17123 at mobilization and weekly thereafter or after impact.
• Data control: Single source of truth maintained by CAD/BIM; naming convention for points (e.g., GRID_A1_INT), version control for coordinates files; backups daily to server.
• Transformations: Document CRS, grid-to-ground strategy (combined scale factor), and 7-parameter site calibration if used; apply consistently in instrument and software; log parameters in the Coordinates Register.
• Redundancy: Use redundant observations for control (two-face, multiple resection points); avoid single-point orientations.
• Acceptance criteria: As listed in Method and ITP; project-specific values supersede typical benchmarks.
• Nonconformance: If tolerance exceeded, cease release to works, investigate (instrument, setup, data), re-observe, submit NCR/CAR with corrective action.
• Records and deliverables:
• Control Network Adjustment Report (least squares), including residuals
• TBM/Control Coordinates Register with protection notes
• Daily Survey Reports and Photos
• Stakeout Reports with deltas and instrument setups
• ISC Reports and approvals
• As-built/Set-out sketches (PDF/DWG) with legend and CRS
• IRs/ITRs, approvals, and correspondence
• Testing frequency: ISC on ≥10% of set-out points per area or per level; control re-check weekly or after major events.
• Training/competency: Surveyors competent with instruments/software; records of training/authorizations kept.
• Release: Works (excavation/piling/foundations) shall not commence until Engineer issues approval following ITP inspections and ISC sign-off.

• Sample: Daily Survey Report template
• Sample: Coordinates Register (Primary/Secondary Control)
• Sample: Stakeout/Offset Register
• Sample: TBM Level Book format
• Example: Control Network Diagram with redundancies
• Example: Grid Set-out Sketch with legend and CRS notes
• Checklists: Instrument Field Verification (ISO 17123), Edge Protection Inspection
• Risk Assessment & PTB records for survey works
• Manufacturer data sheets for instruments and anchors/epoxy [if used]
• Calibration certificates (Total Station, Digital Level, GNSS)