Product Overview

Summary: This Subgrade Preparation and Compaction SOP sets out a clear, step-by-step method for constructing safe, stable and compliant foundations for roads, pavements and structures. It integrates WHS obligations with quality and geotechnical requirements, helping civil contractors deliver durable subgrades while protecting workers, plant and underground services.

Subgrade preparation and compaction is a critical activity in civil construction, directly influencing the long-term performance of roads, car parks, pavements and building platforms. Poorly prepared subgrades can lead to differential settlement, pavement failure, drainage issues and costly rework. This Safe Operating Procedure provides a structured, easy-to-follow process that combines geotechnical best practice with robust WHS controls, ensuring that every stage—from stripping topsoil to final proof rolling—is completed safely and to specification.

Developed for Australian civil and infrastructure projects, this SOP addresses the practical realities of working with variable ground conditions, heavy compaction plant and buried services. It clarifies responsibilities, standardises pre-start inspections, and details how to manage moisture conditioning, layer thickness, compaction passes and testing requirements. By adopting this procedure, businesses can demonstrate due diligence under WHS legislation, improve on-site coordination between supervisors, operators and testers, and reduce the risk of failures that can damage reputations and margins. The result is safer crews, more predictable outcomes and compliant, long-lasting subgrades.

The document is designed to integrate seamlessly into existing project management systems, quality plans and SWMS/JSA frameworks. It can be used as a training and onboarding tool for new staff, a reference for subcontractors, and supporting evidence during client audits, third‑party certifications and regulatory inspections.

Key Benefits

• Ensure consistent, compliant subgrade construction that meets project specifications and geotechnical requirements.
• Reduce safety risks associated with working around heavy compaction equipment, unstable ground and underground services.
• Minimise rework, delays and defects by standardising inspection, testing and acceptance criteria.
• Streamline communication between supervisors, plant operators, surveyors and laboratory technicians.
• Demonstrate due diligence and compliance with Australian WHS legislation, road authority specifications and relevant standards.

Who is this for?

• Civil Site Supervisors
• Project Engineers
• Construction Managers
• Plant Operators (Rollers, Graders, Excavators)
• Surveyors and Engineering Technicians
• WHS Managers and Safety Advisors
• Quality Assurance Managers
• Forepersons and Leading Hands
• Subcontractor Supervisors
• Local Government Works Supervisors

Hazards Addressed

• Plant–person interaction and struck-by incidents involving rollers, graders, water carts and excavators
• Ground instability, soft spots and potential for slips, trips, falls or plant bogging
• Contact with or damage to underground utilities (electricity, gas, water, sewer, telecommunications)
• Exposure to dust, noise and vibration from earthmoving and compaction activities
• Manual handling injuries from handling test equipment, survey gear and small compaction tools
• Working on or near roadways with live traffic and mobile plant movements
• Fatigue and reduced situational awareness during repetitive compaction operations
• Environmental hazards such as sediment runoff, erosion and poor water management on site

Included Sections

• 1.0 Purpose and Scope
• 2.0 References, Standards and Definitions
• 3.0 Roles and Responsibilities
• 4.0 Required Competencies, Licences and Training
• 5.0 Tools, Plant, Equipment and Materials
• 6.0 WHS and Environmental Requirements
• 7.0 Pre-Start Planning and Site Assessment
• 8.0 Service Locating and Protection of Underground Utilities
• 9.0 Site Preparation, Clearing and Stripping Topsoil
• 10.0 Subgrade Trimming, Proof Rolling and Identification of Soft Spots
• 11.0 Treatment of Unsuitable Material and Soft Areas
• 12.0 Moisture Conditioning and Layer Thickness Control
• 13.0 Compaction Methodology and Roller Patterns
• 14.0 Survey Control, Levels and Tolerances
• 15.0 Inspection, Testing and Acceptance Criteria (QA/Compaction Testing)
• 16.0 Traffic Management and Plant–Person Interface Controls
• 17.0 Dust, Noise and Vibration Control Measures
• 18.0 Housekeeping, Environmental Controls and Runoff Management
• 19.0 Non-Conformance Management and Corrective Actions
• 20.0 Documentation, Records and Sign-Off
• 21.0 Review, Audit and Continuous Improvement

Legislation & References

• Work Health and Safety Act 2011 (Cth) and relevant state and territory WHS Acts
• Work Health and Safety Regulations 2011 (Cth) and relevant state and territory WHS Regulations
• Safe Work Australia – Code of Practice: Construction Work
• Safe Work Australia – Code of Practice: Managing the Risk of Plant in the Workplace
• AS 3798: Guidelines on earthworks for commercial and residential developments
• AS 1289: Methods of testing soils for engineering purposes (for density and moisture testing)
• AS/NZS 1170: Structural design actions (for site classification context)
• Austroads Guides and local road authority specifications for pavement and subgrade construction