Earthworks for residential development

Earthworks are a necessary part of preparing land for residential development, but if the right practices aren’t used, soil can be lost to water bodies. 

This sediment can have a range of negative impacts on water quality and ecosystems. Soil can be contaminated, or soil loss can cause stability issues and water runoff with lots of sediment can also be a nuisance to neighbouring landowners.

Proposed changes to the Water Plan (PC8) mean discharges of sediment from earthworks associated with residential development need to be avoided as a first priority, then best practice methods need to be used to minimise sediment loss if avoidance is not achievable.

 

What qualifies as ‘residential’ earthworks*

The regional provisions under PC8 are applied in a broad sense and are not ‘bound’ by any underlying District Plan zoning as ‘residential’ or any definitions of ‘residential activity’ or ‘residential development’ in any District Plans.

Examples that may require a consent from us include earthworks to establish building platforms, driveways and infrastructure (such as pipes, local roads) for residential dwellings or subdivisions in any zone.

PC8 excludes earthworks associated with business activities or developments, such as farm tracks, quarrying, construction of dams, works associated with plantation forestry

*Note: These examples are not an exhaustive list. Please contact ORC to confirm whether you will need to apply for consent under PC8

 

Definitions

Earthworks: The alteration or disturbance of land, including by moving, removing, placing, blading, cutting, contouring, filling or excavation of earth (or any matter constituting the land including soil, clay, sand and rock). This excludes gardening, cultivation, and disturbance of land for the installation of fence posts.

Landholding: For land subject to the Land Transfer Act 1952, land in: (i) A single certificate of title; or (ii) Two or more adjoining certificates of title, with a common occupier. For land not subject to the Land Transfer Act 1952, all contiguous land last acquired under one instrument of conveyance and occupied by a common occupier.

     

Download this information as factsheets below

Earthworks for residential development - consent requirements

Earthworks for residential development - good practice

Do you need a resource consent?

PC8 has been developed to manage the discharge of sediment from earthworks resulting in adverse effects on water quality. Rules 14.5.1.1 and 14.5.2.1 set out the specific requirements for earthworks. You will need a resource consent if you can’t meet the below criteria:

  • The area of exposed earth is no larger than 2,500m² per landholding in a 12-month period,
  • Works are not within ten metres of a water body (such as a river, stream, wetland or lake), drain, water race or the coast
  • Exposed earth is stabilised when works are completed
  • Works are not on (potentially) contaminated land
  • Soils and debris are not placed where sediment can enter waterways or the coastal marine area
  • Works will not result in flooding, erosion, land instability, subsidence or property damage

If you cannot meet one or more of these criteria, you will need both a regional land use consent under section 9(2) RMA and a discharge consent under s15 RMA.

 

If you need consent, we’ll need to know:

  • Where and how much land will be exposed
  • What you will do to minimise the risk of sediment loss
  • The extent to which your proposal complies with the Erosion and Sediment Control Guidelines for Land Disturbing Activities in the Auckland Region 2016 (Auckland Council Guideline Document GD2016/005). These guidelines contain a comprehensive set of potential measures that can be used to avoid sediment loss from your site and/ or into
  • Whether there will be adverse effects on water bodies, ecological values, other properties, human use or Kāi Tahu values

Note: Look out for discharges into District or City Council networks (such as stormwater and/ or sewer lines). You may require affected party approval from them.

 

How you can minimise the risk of sediment loss

The best measures to manage the effects of earthworks depend on the type and scale of the activity and site characteristics that affect the risk associated with an activity. Factors influencing the amount of soil loss from earthworks sites are:

  • Soil type and characteristics
  • Topography of the area of earthworks
  • Proximity to sensitive receivers, such as receiving waters to any sediment run-off
  • Area of works
  • Land stability
  • Duration of soil exposure
  • Weather and climate (including rainfall, season etc)

Types of mitigation measures include:

  • Sediment control, including simple silt and sediment barriers, diversions of run-off, chemical treatment, decanting earth bunds
  • Soil stabilisation (including battering, engineered structures, revegetation, waterproof covers, staging with progressive stabilisation)
  • Limiting works during wetter months/ days
  • Limiting the time bare soil is exposed
  • Monitoring during works whether measures are working properly and adapt if necessary

We strongly encourage the submission of management plans (such as erosion and sediment control plans) as part of an application so we can ensure that you are using the best options to control sediment run-off.

 

Good practice examples​

 

Well maintained silt fencing

Well maintained silt fencing

Artificial covers may be used to filter sediment and cover exposed soils

Artificial covers may be used to filter sediment and cover exposed soils

Pre existing waterways may be diverted through or around work sites

Pre existing waterways may be diverted through or around work sites

Covering exposed soils and silt fences to stop sediment entering water and creation of coffer dam (yellow device in water), to limit area sediment can travel to if it does reach water

Covering exposed soils and silt fences to stop sediment entering water and creation of coffer dam (yellow device in water), to limit area sediment can travel to if it does reach water

Settling pond with decanting structure in the middle, allows sediment to sink to bottom while taking clean water from top

Settling pond with decanting structure in the middle, allows sediment to sink to bottom while taking clean water from top

 

When it goes wrong

 

Sediment controls only work if they are regularly maintained.

Sediment controls only work if they are regularly maintained.

Monitoring to ensure that sediment that has been mobilised is not overwhelming the controls.

Monitoring to ensure that sediment that has been mobilised is not overwhelming the controls.

The water through this catchment has overwhelmed the sediment controls.

The water through this catchment has overwhelmed the sediment controls.

Good intentions to cover disturbed land, however no work has been done  to manage sediment from the channel itself

Good intentions to cover disturbed land, however no work has been done to manage sediment from the channel itself

 

Other resource consents that may be required

Depending on its nature and location an application involving earthworks for residential development may require other resource consents, for example:

  • Diversion and discharges of contaminated water
  • Natural hazards
  • Dust – air discharges
  • Contamination Discharges/ Contaminated land
  • Coastal consent (where outfall installed for discharge of sediment/ stormwater to the coast )
  • Defence against water (where earthen bunds are proposed to mitigate sediment run-off)

Note: You may also need bylaw approval from ORC for this.

  • Local council consents: Earthworks are managed by district and city councils as well as Otago Regional Council. You will need to check whether your earthworks also require resource consent from your district or city council.

 

Find out more:

More information about our resource consent process is available by calling 0800 474 082 or emailing customerservices@orc.govt.nz

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