Staged Excavation Under Retention Checklist

Definition: Staged Excavation Under Retention checklist for contractors and inspectors ensures sequenced excavation, intermediate supports, monitoring updates, and hold points for retained digs, explicitly excluding any mass grading activities.

Confirms excavation sequence, stage boundaries, and mandatory hold points.
Verifies struts, walers, or anchors installed and preloaded to design.
Updates survey and instrumentation readings against trigger thresholds.
Interactive, commentable, export ready; authenticate records via QR code.

Start Interactive
Checklist

Staged Excavation Under Retention is the controlled, sequenced removal of soil behind a temporary works system while maintaining stability. This checklist supports retained excavation operations, including props, walers, struts, and anchors, focusing on excavation staging, monitoring updates, and formal hold points. It excludes mass grading and broad earthworks. By confirming the sequence and installing intermediate supports at defined depths, teams maintain performance of the retention system, limit wall movement, and reduce risks such as collapse, base heave, and service strikes. The checklist aligns supervision, survey, and monitoring teams on trigger levels, preload requirements, tolerances, and documentary evidence. Acceptance cues—such as RLs within tolerance, preload within ±5%, and verified clearances—provide objective go/no‑go criteria before work advances. Use this tool to coordinate daily briefings, inspection test plans, and sign-offs with the engineer, keeping records organized and traceable. Start in interactive mode to tick items, add comments, and export PDF/Excel with a QR-secured audit trail.

Coordinate sequenced excavation beneath temporary retention with defined stage limits, hold points, and verified intermediate supports. This checklist provides practical tolerances, evidence requirements, and sign-off flow so teams can proceed safely while controlling wall movements and groundwater during each controlled dig stage.
Integrate survey and instrumentation updates at each stage to track deflection, pore pressure, and excavation level against trigger thresholds. Document preloads, torque, calibrations, and baseline readings to create a defensible record for engineers, clients, and authorities without slowing production on constrained sites.
Interactive online checklist with tick, comment, and export features secured by QR code.

Pre-Excavation Controls

1. Confirm latest IFC staging plan and temporary works drawings; cross-check revision numbers and dates with document control. Acceptance: no superseded drawings. Evidence: uploaded cover sheets and document register sign-off.
2. Set out stage boundaries with total station; mark paint at 5 m intervals and tag corners. Tolerance: ±25 mm from design grid. Evidence: survey report, marked-up plan, geotagged photos.
3. Verify services isolation/protection using cable locator and permits. Acceptance: no live utilities within the stage footprint. Evidence: permit-to-dig, isolation certificates, locator scan records.
4. Conduct toolbox talk on sequence, supports, triggers, and exclusion of mass grading. Acceptance: all attendees briefed. Evidence: signed attendance sheet and uploaded JSA/SWMS.

Sequence and Hold Points

5. Brief excavation sequence and identify hold points at each design RL before advancing. Acceptance: HPs logged as HP1, HP2, etc. Evidence: supervisor sign-off and engineer approval record.
6. Establish plant access/egress routes clear of walers and anchors; delineate with barriers. Acceptance: routes continuous and protected. Evidence: site logistics plan and daily photos.
7. Schedule third-party inspections at hold points per approved project specifications and authority requirements. Acceptance: ITP/IWPs issued. Evidence: inspection requests and clearance notices.
8. Install temporary edge protection along excavation crest. Method: guardrails rated 0.6 kN/m. Acceptance: continuous coverage. Evidence: inspection checklist and photos.

Intermediate Supports Installation

9. Position walers to survey marks using laser level. Tolerance: level within ±5 mm and alignment within ±10 mm. Evidence: level readings and photos.
10. Fit hydraulic struts to design bay spacing; preload to design load ±5% with calibrated gauge. Evidence: gauge photo with timestamp and calibration certificate.
11. If ground anchors specified, drill, grout, and proof-test to acceptance load; creep ≤2 mm over 10 min. Evidence: test graphs, grout batch records, engineer sign-off.
12. Torque waler connections with calibrated wrench. Tolerance: ±10% of specified torque. Evidence: torque log, fastener lot numbers, wrench calibration certificate.

Monitoring and Survey

13. Install monitoring targets on wall and struts; label IDs and coordinates. Acceptance: register complete. Evidence: monitoring register and target photos.
14. Capture baseline readings pre-excavation for prisms, inclinometers, and piezometers. Acceptance: zero set established. Evidence: signed baseline report and raw data files.
15. During each stage, measure wall deflection and strut load; classify triggers (green/amber/red) against design. Evidence: daily monitoring sheet signed by surveyor and engineer.
16. Survey excavation RL at hold points using staff and level. Tolerance: design RL ±20 mm. Evidence: survey extract, marked pegs, and photo with staff reading.

Excavation Stage Execution

17. Excavate in 200–300 mm passes with narrow bucket; maintain 1 m standoff from wall. Acceptance: no overbreak beyond limits. Evidence: progress photos and foreman log.
18. Trim to line using hand tools/small plant; avoid undercutting behind retention. Tolerance: horizontal overbreak ≤100 mm. Evidence: supervisor sketch and photos.
19. Maintain bench width between stages as designed; measure with tape. Tolerance: ±50 mm. Evidence: measurement record and geotagged photos.
20. Control groundwater per temporary works plan using sump pumps; discharge per approved project specifications and authority requirements. Evidence: pump logs, discharge permits, water quality results.

Sequencing Under Retention and Clear Stage Boundaries

Sequenced excavation under retention depends on disciplined depth increments, reliable set-out, and formal hold points before proceeding. Crews must treat each stage as its own operation: excavate in thin passes, verify reduced level (RL), and obtain approvals before advancing. This approach limits wall movement, reduces basal instability risk, and avoids damaging utilities or undermining adjacent assets. Align your team on the latest temporary works drawings and ITPs; superseded data is a frequent root cause of nonconformances. Clear stage boundaries, marked at 5 m intervals with coordinate tags, keep machines within the dig envelope and away from walers and anchors. Plant access routes must be planned to prevent impact loads on supports. Acceptance cues include RL within ±20 mm, benches within tolerance, and hold-point sign-offs in sequence. Evidence is crucial: combine survey extracts, geotagged photos, and digital approvals for a defensible record and efficient audits.

Treat each stage as a standalone, approved operation.
Confirm latest drawings and ITPs before soil removal.
Mark stage limits and access routes clearly.
Verify RLs within ±20 mm at hold points.
Capture photos and survey files for evidence.

Intermediate Supports: Walers, Struts, and Anchors

Intermediate supports sustain the retained excavation as depth increases. Walers must be level and aligned; struts need correct bay spacing and preload; anchors require proof testing and creep checks. Use calibrated tools and record serial numbers to validate results. Preloading struts to the design load ±5% reduces initial deflection when the next soil layer is removed. Bolted or pinned connections should be torqued to specification with a calibrated wrench, and hydraulic gauges photographed at peak and locked values. Where anchors are used, follow the anchor schedule precisely, documenting grout batches and test curves. Physical protection—scaffold fans or bumpers—prevents plant contact with supports. Only proceed to the next stage when all support criteria pass and the engineer clears the hold point.

Level walers within ±5 mm before locking.
Preload struts to design load ±5%.
Proof-test anchors and check creep limits.
Torque-check connections with calibrated tools.
Protect supports from plant contact.

Monitoring, Triggers, and Responsive Actions

Monitoring converts risk into measurable trends. Establish targets and baseline readings before digging. During each stage, capture wall deflection, strut loads, and groundwater levels. Compare results with design trigger bands: green indicates proceed, amber requires review and mitigation, and red demands stop-work and engineer direction. Survey RLs at hold points and reconcile against the model. When triggers are exceeded, typical responses include increasing strut preload, installing additional props, adjusting excavation sequence, or pausing to allow pore pressure to stabilize. Always log actions, time, and personnel. Data integrity matters: maintain instrument calibration certificates and keep raw files with timestamps. Consistent, verifiable monitoring enables safe advancement while preserving the performance of the retention system.

Baseline instruments before any excavation.
Use green/amber/red trigger bands.
Record readings and actions daily.
Retain calibration and raw data files.
Stop and escalate on red triggers.

How to Use This Staged Excavation Under Retention Checklist

Preparation: assemble staging plan, temporary works drawings, ITPs, calibrated gauges, laser levels, total station, measuring tapes, pumps, and PPE; brief team on sequence, supports, triggers, and hold points.
Project setup: create a checklist instance per stage, assign roles (supervisor, surveyor, temporary works engineer), and preload drawing revisions and reference RLs.
Start interactive mode: tick items as completed, attach geotagged photos, upload survey extracts, instrument logs, and calibration certificates.
Comment in context: use the commentable fields to flag nonconformances, propose corrective actions, and request engineer decisions at hold points.
Monitor progress: update readings at defined frequencies, classify triggers, and document applied mitigations before proceeding to the next stage.
Export and sign: generate PDF/Excel with embedded evidence; obtain digital signatures from supervisor, surveyor, and engineer.
Archive and share: store the signed pack; distribute via QR-authenticated link to client and authorities.

Start Interactive Checklist

Staged Excavation Under Retention

Call to Action

Tatiana Ivanova Tatiana Ivanova

Dec 13, 2025

553

100

FAQ

Question: What is the difference between staged excavation under retention and mass grading?

Staged excavation under retention removes soil in controlled layers inside a supported excavation, advancing only after supports are installed, monitored, and approved at hold points. Mass grading moves large volumes over broad areas without temporary retention. This checklist excludes mass grading to focus on stability, monitoring, and approvals.

Question: How often should I take monitoring readings during staged excavation?

At minimum, capture baseline before digging, then read instruments and survey RLs at each stage hold point. During active excavation, take daily readings or as specified by the design. Increase frequency if amber triggers occur, after heavy rain, or when support adjustments or preloads are made.

Question: What actions are required if trigger levels are exceeded?

Stop and stabilize the excavation. Notify the temporary works engineer, review data, and implement mitigations such as increasing strut preload, adding props, adjusting sequence, or pausing excavation to allow pore pressure to recover. Document actions, retest, and resume only after formal approval at the hold point.

Question: Which evidence is essential at each hold point sign-off?

Provide survey extracts showing RL within tolerance, photos of support installation, preload or torque logs with calibration certificates, monitoring readings against trigger bands, and signed inspection or approval records. These create an auditable trail that demonstrates compliance with the design and project specifications.