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Infrastructure Development Code

DS-5.8 Collection

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City Plan Performance Standard: Appendix 12B 
  1. Inlet structures (that shall comprise a network of sumps, service connections and inlet headwalls) will be provided to enable stormwater to enter the primary stormwater management system.
  2. Any individual lot connection shall be designed and located to:
    1. Provide for the existing or proposed development of the site; 
    2. Be at a depth that will drain the area being serviced;
    3. Be sized to convey the design flow for the allotment, designated building platform or area being serviced;
    4. Be within the allotment boundary; and
    5. Be free of obstruction and accessible for future maintenance.

This section describes the requirements for structures or methods for collection of stormwater run off. These are categorised as:

  1. Inlet structures (e.g. wingwalls).
  2. Sumps.
  3. Property service connections.
  4. Alternative collection methods.

The selection of a suitable location for these structures may influence the pipe alignment. Generally a minimum clearance of 1.0m shall be provided clear of the opening around any structure that may allow entry for maintenance and rescue equipment. Council may determine other specific requirements subject to individual site characteristics.

DS-5.8.1   Inlet Structures

Drawing Ref: T523, T524

City Plan Performance Standard: Appendix 12B 
  1. Inlet structures (that shall comprise a network of sumps, service connections and inlet headwalls) will be provided to enable stormwater to enter the primary stormwater management system.

The following shall apply:

  1. Inlet structures (such as wingwalls) shall be provided at the inlets of pipelines to the detail shown on Standard Drawings. 
  2. A grill shall be installed on all inlet structures of 500mmØ or larger. This grate shall be specifically designed and submitted to Council for approval.
  3. Where the consequences of a grating blockage are likely to be severe, a backup overflow system that allows runoff to enter the pipe or a clearly defined secondary flowpath shall be provided.
  4. Where a pipe is to be installed in a swale or open drain to allow for access over the drain, an inlet structure may be required to prevent erosion around the pipe entry.

DS-5.8.2   Sumps

Drawing Ref: T425, T426, T427, T525

City Plan Performance Standard: Appendix 12D 
  1. Roads required to incorporate kerb and channel shall include sumps are installed to allow surface water to enter the primary stormwater management system;

Sumps are an integral part of both the stormwater and transportation networks. The following shall apply:

  1. DS-5.8.2.1 Sump Design.
  2. DS-5.8.2.2 High Capacity Sumps.
  3. DS-5.8.2.3 Sump Connection.
  4. DS-5.8.2.4 Retrospective Sumps.

DS-5.8.2.1   Sump Design

Road and right-of-way sumps shall be designed to suit the environment that they will be placed in and to achieve the performance outcome that they are designed to achieve. It shall be demonstrated by the designer that the following has been considered for the design of sumps:

  1. Flow rates.
  2. Water quality.
  3. Environmental exposure conditions i.e. the ground condition it will be placed within.
  4. Applied loadings e.g. trafficking.
  5. Design life.
  6. Design storm event.
  7. Frequency and degree of traffic interference.
  8. Secondary flowpaths.
  9. Debris flow / grades e.g. the surrounding environment, trees, parks etc and the type of debris they produce.
  10. Operation, maintenance, cleaning, upgrade and replacement of the sump throughout its operational life.
  11. Safety of carriageway users e.g. cyclists, pedestrians, motorised traffic.

The design flow rates for sumps are shown in the following table:

Sump Type Design Flow Rate (Inlet Capacity)
Single sump 20-30 l/s
Double sump 30-50 l/s
High Capacity Sump 50-800 l/s

Road Sump designers shall also refer to DS-4.5.7 Sumps.

Yard sumps shall be provided as a means of capturing run-off from private land, swales and any other grassed areas where applicable and shall also consider the above design considerations where appropriate. 

Refer to AM-5 Stormwater for approved products.

DS-5.8.2.2   High Capacity Sumps

High Capacity sumps are required in circumstances where additional capacity is required to direct and manage stormwater, where excessive debris may be an issue or where the carriageway longitudinal gradient is very steep (e.g. ≥12%) or very flat  0-3%).
Refer to AM-5 Stormwater for approved products.

DS-5.8.2.3   Sump Connection

The following shall apply:

  1. All sumps shall be connected to the primary stormwater system by a 300mmØ minimum connection (lead) to an adjacent manhole.
  2. If the adjacent stormwater system is larger than 600mmØ and the manhole is not conveniently located, the sump lead may be saddled directly to the pipe. This connection shall be a minimum of 300mmØ.
  3. Individual sumps or interconnected double sumps shall be connected separately to a manhole and not through a second sump system.

DS-5.8.2.4   Retrospective Sumps

Retrospective sumps are those that are installed (in part or as full replacement) within existing transportation networks or reserves where flooding or ponding has become an issue.

When designing these types of sump, designers shall ensure that the sump design provides optimal functionality and fits into the operating environment without causing further issues, whether practical or aesthetic. Designers shall pay particular attention to:

  1. The crossfall of the road carriageway.
  2. The gradient of the road channel.
  3. The height and condition of the kerb.
  4. The requirements of DS-5.8.2.1 Sump Design.

DS-5.8.3   Property Service Connections

City Plan Performance Standard: Appendix 12B 
  1. Any individual lot connection shall be designed and located to:
    1. Provide for the existing or proposed development of the site; 
    2. Be at a depth that will drain the area being serviced;
    3. Be sized to convey the design flow for the allotment, designated building platform or area being serviced;
    4. Be within the allotment boundary; and
    5. Be free of obstruction and accessible for future maintenance.

The point of connection is the junction between a property’s private drain and the public stormwater network. Private drainage generally extends through to the property boundary at which point Council accepts responsibility for the downstream pipelines.

DS-5.8.4   Minimum Requirements

Property service connections shall be designed to the following minimum requirements:

  1. Each lot shall have one service connection (except where internal ground soakage is provided and appropriate). 
  2. All lots shall be connected to a piped reticulation system or a specifically designed stormwater mechanism (including soakage devices if appropriate).
  3. Specific Council approval is required to connect to the following: 
    1. An open drain.
    2. A public roadside kerb & channel connection.
    3. A road or bubble up sump.
  4. Any individual lot/property connection shall be designed and located to suit the existing and future development scenarios and where possible sized, located and designed to service the whole property (land parcel), but as a minimum, to service the building platform and impermeable area.
  5. Any connections shall be located to service the lowest practical building platform on the property.
  6. The design shall specify the requirements for the property connections including plan location, lot contours and invert level at property boundary or junction with the main as applicable.

DS-5.8.5   Private Drainage

Generally all stormwater pipes installed between a building and the point of connection to Council’s stormwater network are private assets. The Building Act requires that a Building Consent shall be obtained for their installation or alteration and that this work must be carried out only by a registered drainlayer.  

The following shall apply:

  1. Further approval must also be obtained from Council before these drains may be connected to the stormwater network. Application for this shall be on Council's Water Supply / Drainage / Vehicle Crossing Connection Application Form. 
  2. All connections to Council infrastructure can be carried out only by a Council Licensed Contractor.

DS-5.8.6   Connection Locations

Connections shall be:

  1. Clear of obstructions, e.g. tree, tree roots, paved areas.
  2. Easily accessible for future maintenance.
  3. Clear of any known future developments e.g. swimming pools or driveways.

DS-5.8.7   Connection Depth

Drawing Ref: T530, T531

The following shall apply:

  1. Connection depths shall be set to drain the whole serviced area recognising the following factors:
    1. Any connection points shall have a minimum cover of 600mm and be no deeper than 1.5m. (Deeper connections may be installed in some circumstances but only with the prior approval of Council).
    2. Surface level at plumbing fixtures of buildings (existing or proposed).
    3. Depth to the invert of pipe at plumbing fixture or intermediate points.
    4. Invert of the public main at junction point.
    5. Allowance for crossing other services.
    6. Allowance for minimum gradients of laterals and private drainage.
    7. Lateral junctions installed at minimum of 45° (vertical) to main.
  2. The designed invert level at the connection shall be no higher than the lowest calculated level consistent with these factors.

DS-5.8.8   Installation of Connections

Drawing Ref: T530, T531, T532, T533, T534, T535, T536 

The following shall apply:

  1. The end of each connection pipe shall be sealed with a solvent welded cap painted blue if the connection does not occur immediately.
  2. Where the inspection is to a property servicing multiple residential units then a surface accessible inspection chamber such as a manhole, rodding eye or other Council approved structure shall be installed.
  3. Each connection point shall be marked with a 50mm x 50mm timber stake painted blue which shall extend from the invert to a minimum of 300mm above finished ground level. A blue PVC marker tape shall be attached to the connection pipe, brought up and tied to the top of the stake.
  4. Where larger sized capping is required or a factory supplied cap is not available, specific design of these shall be required for approval.

DS-5.8.9   Connection Destinations

Where practicable and where connection is to be within 5m of a manhole, the connection shall be to the manhole.

DS-5.8.10   Lateral Configurations

Drawing Ref: T537, T538, T539, T540, T541, T542

To provide a service connection to each lot, a minimum 100mmØ line shall be extended from the main reticulation system to terminate within the property boundary at a minimum distance of 1.0m from the front and side boundaries whether created by cross-lease, unit title or fee-simple subdivision.
These connections shall also form part of the public system to the site boundary and be brought up to within 1.2m of the final ground surface level.

In addition the following shall apply:

  1. For a lateral providing a service connection for 1 lot connecting to a manhole refer to Standard Drawing T537.
  2. For a lateral providing a service connection for 2-6 lots connecting to a manhole refer to Standard Drawing T538.
  3. For a lateral providing a service connection for 1 lot connecting to a main refer to Standard Drawing T539.
  4. For a lateral providing a service connection for 2 lots connecting to a main refer to Standard Drawing T540.
  5. Where lateral is over 50m long or the number of connections exceeds 6 lots, normal stormwater reticulation conditions apply.
  6. Where practicable and where the connection is within 5m of a manhole the connection shall be to the manhole.
  7. Where the main is within the property boundary a separate connection shall be provided to each lot.
  8. The following connections can be connected directly to the main. These connections are all to be factory manufactured:
    1. 100mmØ or 150mmØ connection can connect to 150mmØ line or greater.
    2. Above diameter and 200mmØ connection can connect to 600mmØ line or greater.
    3. A factory made 300mmØ connection can connect to 900mm line or greater.
    4. Any combinations outside the following shall connect via a manhole.
  9. For major land use development where significant privately owned reticulation works (i.e. not being vested with Council) are being constructed and are connecting into Council infrastructure, any watercourse or the sea, all works shall be designed and constructed in accordance with the IDC requirements, however the reticulation will remain private.

DS-5.8.11  Infill Subdivision – 3 Lots or Less (Excludes Existing Lot)

It is recognised that infill subdivisions require flexibility in their reticulation layout. However, normal trade practices and standards are needed to ensure that the desired service life is achieved.

  1. Reticulation of infill subdivisions shall comply with the following criteria:
    1. Stormwater drainage within the parent lot shall remain private and be protected by an appropriate easement.
    2. Stormwater drainage lines shall be separated at the point of connection to the Council’s reticulation system and remain separate for each lot unless specific approval is gained from Council.
    3. Infill subdivisions shall be reticulated on a site-by-site basis.
    4. For minor infill subdivision type works, all private Stormwater works shall be constructed in accordance with the NZ Building Code regulations.
  2. Infill subdivisions shall be reticulated on a site by site basis to the approval of Council.
  3. Lateral connections shall be constructed or upgraded in accordance with the IDC. This lateral can be vested in Council and provide each lot with the same standard of individual connection as new ‘greenfields’ lots.
  4. Where this is considered impractical or unnecessary, the Consent Holder may make application to Council for the lateral to remain private within an appropriate easement. However common private reticulation is not encouraged so as to alleviate the friction that sometimes occurs between neighbours when shared services are involved.
  5. Lateral connections shall be separated at the point of connection to Council’s reticulation system and remain separate for each lot unless specific approval is granted by Council. Where the main is within a neighbour's property, the new junction may be installed immediately within the property being subdivided.

DS-5.8.12   Multi-Unit Properties (Such as Apartment Buildings and Body Corporate Developments)

For multiple occupancies (unit title, cross lease or company lease) service of the whole property shall be achieved by providing a single point of connection to the stormwater system. Connection of the individual units is by joint service pipes owned and maintained by the body corporate, tenants in common or the company as the case may be. In this instance the whole of the multiple occupancy shall be regarded as a single lot. All drainage within the development boundary would be private.

DS-5.8.13   Commercial and Industrial Connections

The following shall apply:

  1. All commercial and industrial lots shall be provided with a stormwater connection. 
  2. The connection and accepting reticulation mains shall be sized to cater for the maximum potential impermeable area of the site. All paved areas shall be reticulated for piped stormwater disposal. 
  3. Pollutants and contamination issues shall be identified and managed to the satisfaction of Council though the Building Consent Process.

DS-5.8.14   Connection to Existing Council Reticulation

Approval shall be obtained from Council before connection can be made to the stormwater network. Application for this shall be on Council's Water Supply / Drainage / Vehicle Crossing Connection Application Form

All connections to Council infrastructure shall be carried out only by a Council Licensed Contractor.


Definitions in this section

Council

Design

IDC

Road

Stormwater

Sump

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