Preparing an Auckland site for construction can involve several connected activities, depending on the project: clearing, topsoil stripping, excavation, cut and fill, removal of material, imported fill, formation preparation, drainage, retaining wall interfaces, and testing or inspections where required. Not every project needs every activity.
The actual scope depends on the design, levels, ground conditions, site access, consent conditions and the intended development. This guide explains how the work fits together so it can be planned with the right information.
What does site preparation include?
A site cut is the reshaping of existing ground to create a platform at the levels in the design. Depending on the project, site preparation can include:
- Site establishment and erosion and sediment controls
- Clearing and topsoil stripping
- Bulk excavation and cut and fill
- Removal of surplus or unsuitable material, and imported fill where required
- Benching on sloped ground where the design calls for it
- Formation and subgrade preparation
- Drainage and retaining wall interfaces
- Testing and inspections where specified
Bromley Group's role is construction delivery and coordination within the agreed scope. Design, survey, consent and certification remain with the engineers, surveyors, planners and Council involved in the project.
Information needed before earthworks
Useful project information can include:
- Site survey
- Existing and proposed levels
- Civil drawings
- Architectural drawings where relevant
- Geotechnical information
- Retaining wall drawings
- Drainage drawings
- Resource consent conditions
- Building consent information where relevant
- Known service information
- Proposed programme
What is needed varies with the project. Sequencing earthworks with the survey, engineering, drainage and building work early helps the programme hold together.
Survey & design levels
Existing site levels and the proposed design levels (RLs) set out how much ground is cut or filled. Construction set-out then marks the formation and finished levels on site so the work can be built to the design.
Survey involvement depends on the project, the design and the construction controls required. It does not necessarily mean a registered surveyor is on site at every stage.
Geotechnical information
Geotechnical information can influence excavation, fill suitability, ground improvement, foundation preparation, retaining walls, drainage, subgrade treatment and testing requirements.
Not every site needs a new geotechnical investigation, and ground conditions differ from site to site. Where geotechnical requirements exist, Bromley Group constructs to the relevant project requirements and coordinates inspections or testing where these form part of the project.
Erosion & sediment controls
Erosion and sediment controls may be required before or during earthworks, depending on the project scale, consent conditions, site conditions and the surrounding environment. Examples include stabilised entrances, silt fencing, decanting earth bunds, temporary drainage and other approved erosion and sediment measures. Not every project needs every measure.
Resource-consent requirements for earthworks vary across Auckland. The applicable thresholds depend on the site zone, earthworks area and volume, slope, overlays and proximity to sensitive environments. If the consent position is unclear, it should be checked against the Auckland Unitary Plan or confirmed with a planner before work begins.
Site clearing & topsoil
Early works can include removing vegetation where it is part of the scope, stripping and stockpiling suitable topsoil where required, removing unsuitable material, and preparing the site for bulk earthworks.
Cut & fill
Excavation takes the ground down to the required formation. Cut and fill are balanced where practical, and excavated material is assessed for reuse. Where more material is needed, fill is imported, and surplus or unsuitable material is removed. Plant access and site logistics shape how this is done, and levels and falls are maintained throughout.
On sloped ground the design may call for benching so that new fill is tied into the existing ground.
Material reuse, import & disposal
Material movements can materially affect cost, truck movements, programme and site logistics. Suitable excavated material may be reused on site. Where it cannot be, fill or aggregate is imported and surplus soil or unsuitable material is removed to an appropriate disposal point.
Whether excavated material, including clay, is suitable for reuse depends on its condition, moisture, material properties, intended use, the project specification and geotechnical requirements where applicable. See our earthworks cost guide for how these movements affect pricing.
Subgrade & engineered fill
Bulk excavation leads into formation, fill placement, compaction, testing where specified, and final subgrade preparation. Compaction acceptance criteria depend on the material, intended use, geotechnical recommendations and project specification.
The technical detail sits in our guide to subgrade preparation in Auckland.
Drainage
Earthworks and drainage often need to be coordinated, because site levels and excavation can affect surface runoff, subsoil water, retaining walls, pavement areas, building platforms and temporary site drainage. Depending on the project, relevant works can include temporary site drainage, subsoil drainage, retaining wall drainage, surface falls, stormwater infrastructure and erosion and sediment controls.
Drainage requirements depend on the site and the design. See our drainage services and drainage cost guide for more detail.
Retaining wall interfaces
Site cuts and retaining walls often interact where level differences need to be supported. Coordination can include excavation, wall foundation preparation, pole or footing locations, drainage, backfill and surrounding levels.
The wall type and any consent or engineering requirements depend on the design and the site. See our retaining wall services and retaining wall consent guide.
Testing & inspections
Inspection and testing requirements depend on the project specification, geotechnical recommendations, consent conditions, engineered fill requirements and intended use. Testing may be required for fill, subgrade, pavement layers or other specified earthworks.
Where inspections or testing form part of the project, Bromley Group coordinates construction around the required hold points and makes the relevant work available for inspection. Geotechnical and engineering assessment is carried out by the appropriate professionals.
Completion information
Depending on the project, completion information associated with earthworks can include testing results, inspection information, survey information, drainage as-built information, construction records and consultant documentation. Which of these apply depends on the project requirements and the agreed scope.
Formal engineering, surveying, Council or consultant certification remains with the appropriate party.
Common site constraints
Practical factors that can affect Auckland earthworks projects include:
- Restricted access and truck access
- Neighbouring properties
- Live sites
- Existing services
- Weather
- Unsuitable ground
- Groundwater
- Steep sites
- Limited spoil storage
- Interfaces with builders or other trades
Not every project experiences all of these. Weather and timing are covered in our guide to earthworks season and winter works.
Bromley Group is an Auckland earthworks contractor delivering residential, commercial and subdivision earthworks. Discuss Your Project.
Frequently asked questions
What is included in a site cut?
A site cut reshapes existing ground to the levels in the design. Depending on the project it can include clearing, topsoil stripping, excavation, filling, removal of surplus or unsuitable material, formation preparation and the drainage and erosion and sediment controls that go with them.
What information is needed before earthworks start?
Useful information can include a site survey, existing and proposed levels, civil and architectural drawings where relevant, geotechnical information, retaining wall and drainage drawings, consent conditions and known service locations. What is needed depends on the project.
Can excavated material be reused?
Sometimes. Whether excavated material is suitable for reuse depends on its condition, moisture, material properties, intended use, the project specification and any geotechnical requirements.
How are cut and fill volumes determined?
Volumes are generally worked out from the existing and proposed levels shown on the survey and design. Material that is loose takes up a different volume from material in place, which affects truck numbers and imported fill.
Does my project need geotechnical testing?
It depends on the project, the design and the consent conditions. Where geotechnical information exists, construction follows the project requirements. Whether new investigation is needed is a question for the engineer or project team.
What happens if unsuitable ground is found?
The engineer or project team decides how it is treated, which can include removing or replacing it, depending on the design. Unexpected ground conditions can affect cost and programme.
Can earthworks continue during winter?
Often, subject to the project's consent conditions and the weather. Some consented projects contain winter-earthworks conditions. Our guide to earthworks season and winter works explains what to check.
How much do earthworks cost?
Cost depends on volume, ground conditions, access, disposal, imported material and the project scope. Our earthworks cost guide sets out indicative pricing and what to include in a quote.